Find Theses

Theses
  • All
  • Scholar Profiles
  • Research Units
  • Research Output
  • Theses

1.Towards a theory of sharing economy-based service triad

Author:Dun Li 2020
Abstract:The sharing economy is a fast-growing phenomenon that has significantly disrupted traditional businesses. Sharing-economy businesses are involved in many sectors, such as the transportation, accommodation, labour, financial and food sectors. Thus, these companies have been considered important by both industrial and academic areas. Sharing-economy platform companies in different sharing-economy industries seek to constantly improve their “sharing” business to provide better services to users. Fundamentally, the nature of the sharing economy consists of three actors, the platform, service supplier and customer, forming a triadic structure within one specific sharing economy context. Among the main streams of service operations management research, it is surprising that, with a few exceptions, the role of platform service operations management in the sharing economy context has been ignored by researchers. Little is known about how sharing-economy platforms carry out their daily operations management in different sectors. To address this gap in the literature, four papers have been developed, including one literature review paper (conceptual paper) and three empirical papers. Seven unicorn level sharing-economy platform companies from three sharing-economy industries were selected for investigation in this research. They are DiDi and Uber China (ridesharing industry), OfO, Mobike and Hellobike (bike-sharing industry) and Huochebang and Yunmanman (logistics-sharing industry). By adopting different theories, such as balance theory, social capital theory, contingency theory, social exchange theory, information processing theory and the knowledge-based view, this study investigates different aspects of operations management under the sharing-economy context accordingly, such as the role of different platform strategies in sustainability, the influence of contingent factors on platform stickiness, bike-sharing platforms’ operations management and information management of the sharing-economy platform, and thus makes a significant theoretical contribution to the service operations management literature, providing insightful practical implications for sharing-economy platforms.

3.Development of Low Cost CdS/CdTe Thin Film Solar Cells by Using Novel Materials

Author:Jingjin WU 2016
Abstract:cadmium Telluride (CdTe) thin film solar cells are one of the most promising solar cell technologies and share 5% of the photovoltaics market. CdTe thin film solar cells are expected to play a crucial role in the future photovoltaics market. The limitations of terawatt-scale CdTe solar cells deployment are scarcity of raw materials, low power conversion efficiency, and their stability. During the last few decades, intensive studies have been made to further understand the material properties, explore substitute materials, and get insight into the defect generation and distribution in solar cells. Yet, these problems are still not fully resolved. One of these significant topics is replacement of indium tin oxide (ITO). Following the introduction of aluminum doped zinc oxide (ZnO:Al or AZO) into thin film solar cells application, zinc oxide based transparent conducting oxides attract the attention from academic research institutes and industry. Zinc oxides are commonly doped with group III elements such as aluminium and gallium. Some researchers introduced group IV elements, including titanium, hafnium, zirconium, and obtained good properties. In our work, deposited zirconium doped zinc oxide (ZnO:Zr or ZrZO) by atomic layer deposition (ALD). Based on the advantage of precisely controlling of chemical ratio, the nature of ZrZO could be revealed. It is found that the ZrZO thin film has good thermal stability. By increasing zirconium concentration, the energy bandgap of ZrZO film follows the Burstein – Moss effect. Another issue of CdTe solar cells is the doping of CdTe thin films, low carrier concentration in CdTe thin films hinders the open circuit voltage and thus power conversion efficiency. Copper is a compelling element that is used as a CdTe dopant; however, high concentration of copper ions results in severe solar cell degradation. One approach was to evaporate a few nm thick copper on CdTe thin film followed with annealing. Another approach was to introduce a buffer layer in between the CdTe thin film and back metallic electrode. Numerous works have been shown that Sb2Te3 layer performs better than copper-based buffer layer, and the stability of carbon-based buffer layers, such as Graphene and single wall carbon nanotubes showed excellent permeability.

4.Depth-Map-Assisted Texture and Depth Map Super-Resolution

Author:Zhi JIN 2016
Abstract:With the development of video technology, high definition video and 3D video applications are becoming increasingly accessible to customers. The interactive and vivid 3D video experience of realistic scenes relies greatly on the amount and quality of the texture and depth map data. However, due to the limitations of video capturing hardware and transmission bandwidth, transmitted video has to be compressed which degrades, in general, the received video quality. This means that it is hard to meet the users’ requirements of high definition and visual experience; it also limits development of future applications. Therefore, image/video super-resolution techniques have been proposed to address this issue. Image super-resolution aims to reconstruct a high resolution image from single or multiple low resolution images captured of the same scene under different conditions. Based on the image type that needs to be super-resolved, image super-resolution includes texture and depth image super-resolutions. If classified based on the implementation methods, there are three main categories: interpolation-based, reconstruction-based and learning-based super-resolution algorithms. This thesis focuses on exploiting depth data in interpolation-based super-resolution algorithms for texture video and depth maps. Two novel texture and one depth super-resolution algorithms are proposed as the main contributions of this thesis. The first texture super-resolution algorithm is carried out in the Mixed Resolution (MR) multiview video system where at least one of the views is captured at Low Resolution (LR), while the others are captured at Full Resolution (FR). In order to reduce visual uncomfortableness and adapt MR video format for free-viewpoint television, the low resolution views are super-resolved to the target full resolution by the proposed virtual view assisted super resolution algorithm. The inter-view similarity is used to determine whether to fill the missing pixels in the super-resolved frame by virtual view pixels or by spatial interpolated pixels. The decision mechanism is steered by the texture characteristics of the neighbors of each missing pixel. Thus, the proposed method can recover the details in regions with edges while maintaining good quality at smooth areas by properly exploiting the high quality virtual view pixels and the directional correlation of pixels. The second texture super-resolution algorithm is based on the Multiview Video plus Depth (MVD) system, which consists of textures and the associated per-pixel depth data. In order to further reduce the transmitted data and the quality degradation of received video, a systematical framework to downsample the original MVD data and later on to super-resolved the LR views is proposed. At the encoder side, the rows of the two adjacent views are downsampled following an interlacing and complementary fashion, whereas, at the decoder side, the discarded pixels are recovered by fusing the virtual view pixels with the directional interpolated pixels from the complementary downsampled views. Consequently, with the assistance of virtual views, the proposed approach can effectively achieve these two goals. From previous two works, we can observe that depth data has big potential to be used in 3D video enhancement. However, due to the low spatial resolution of Time-of-Flight (ToF) depth camera generated depth images, their applications have been limited. Hence, in the last contribution of this thesis, a planar-surface-based depth map super-resolution approach is presented, which interpolates depth images by exploiting the equation of each detected planar surface. Both quantitative and qualitative experimental results demonstrate the effectiveness and robustness of the proposed approach over benchmark methods.

5.Development of Nanomaterial-based Gas Microsensors for Environmental Application

Author:Lin Liu 2020
Abstract:Air pollution is a serious environmental problem that jeopardizes human’ health. Inhalation of gas pollutants can cause many health problems such as respiratory disease, lung cancer, leukemia, or even death. Thus, development of new technologies and novel portable miniaturized sensors to detect trace gas pollutants has received significant attention. This study aims to develop high performance gas sensors by designing hierarchical nanostructured materials and new device structures. In Chapter 2, novel brush-like (B-) ZnO@SnO2 n-n hierarchical nanostructures (HNSs) were successfully synthesized by using a simple two-step hydrothermal method. The growth mechanism of the B-ZnO@SnO2 HNSs was studied. The B-ZnO@SnO2 HNS-based NO2 sensor showed high sensing performance including high sensitivity (response value: 25.5 to1 ppm NO2), fast response (< 60 s), and low detection limit (5 ppb). The enhanced sensing mechanism was attributing to the unique structure of B- ZnO@SnO2 HNSs, which can provide large specific surface area and can induce synergism effect due to the formed multi-junctions. In Chapter 3, NiO nanowalls decorated by SnO2 nanoneedles (NiO@SnO2) were directly grown on ceramic chips via a chemical bath deposition method to obtain uniform sensing materials without aggregation instead of using slurry-coating method, which is used in the Chapter 2. The morphologies and compositions of the NiO@SnO2 HNSs were well tuned by varying the growth time to optimize the sensing performance. The response of the NiO@SnO2 HNSs (2 h) to 1 ppm H2S was over 23 times higher than that of the pure NiO nanowalls and 17 times higher than that of the pure SnO2 nanosheets. This dramatic enhancement is mainly due to the large surface area of the NiO@SnO2 HNSs and the p-n heterojunction at the hetero-interface of SnO2 and NiO. The variation in the depletion layers (WSnO2 and WNiO) at the interface of SnO2 and NiO greatly depends on the properties of the target gases (e.g., electron-withdrawing property (NO2) or electron-donating property (H2S)). In Chapter 4, based on the in situ growth method (“bottom-up”) which was reported in Chapter 3, a “top-down” and “bottom-up” combined strategy was proposed to manufacture wafer-scale miniaturized gas sensors with high-throughput by growth of patterned Ni(OH)2 nanowalls at specific locations. First, micro-hotplates were fabricated on a two-inch (2”) silicon wafer by micro-electro-mechanical-system (MEMS) techniques (“top-down” strategy). Then a template-guided controllable de-wetting method was used to assemble a thermoplastic elastomer (TPE) thin film with uniform micro-sized holes (relative standard deviation (RSD) of the size of micro-holes < 3.5 %, n >300), which serves as the mask for growing Ni(OH)2 nanowalls (“bottom up” strategy). The obtained sensors based on these strategies showed great reproducibility of electric properties (RSD < 0.8%, n=8) and sensing performance toward H2S (RSD <3.5%, n=8). Different from the chemiresistive gas sensors reported in this thesis, which are driven by external power source, a novel device structure was proposed to construct photovoltaic self-powered H2S sensor based on p-type single-walled carbon nanotubes (SWNTs) and n-type silicon (n-Si) heterojunction. The energy from visible light suffices to drive the device owing to a built-in electric field (BEF) induced by the differences between the Fermi energy levels of SWNTs and n-Si. Under 600 nm illumination (1.8 mW/cm2), linearly self-powered detecting H2S in the range of 100 ppb to 800 ppb was implemented, with fast response time (57 s) and recovery time (110 s) at room temperature. Compared with conventional chemiresistive sensor based on SWNTs, the response time and response of the photovoltaic self-powered device were significantly enhanced. When exposing to 400 ppb H2S, the sensing response increased more than 4 times attributed to the BEF. Overall, three different heterostructure-based gas sensors were studied to enhance their performance and the sensing mechanisms of the sensors were also investigated. Moreover, a novel “top-down” & “bottom-up” strategy was proposed for wafer-scale fabrication of miniaturized gas sensor.

6.The impact of margin-trading and short-selling reform on liquidity: Evidence from the Chinese stock market

Author:Shengjie Zhou 2021
Abstract:Margin-trading and short-selling activities in the Chinese stock market are unique in that only part of stocks are eligible for margin-trading and short-selling and the list of stocks that are eligible for margin-trading and short-selling changes over time. In addition, daily data on margin trading and short selling activities are available for each individual stock. Taking advantage of this market design and using daily data from March 2010 to the end of 2016, I firstly show that stocks’ eligibility on margin trading and short selling contributes to improvement in stock liquidity as measured by effective spread and Amihud’s (2002) Illiquidity Ratio. Secondly, to differentiate the impacts of margin trading and short selling, I find that margin-trading enhances liquidity while short selling impairs liquidity. In addition, I prove that the detrimental effect of short-selling on liquidity is due to it increases the adverse selection risk of the relevant stocks. Results suggest that short-sellers are informed traders as short-selling have predictive power on returns. In addition, short-selling in stocks with highest information asymmetry level tend to have the strongest negative impact on stock liquidity. Thirdly, I also demonstrate the asymmetry impacts of margin-trading and short-selling in different market conditions. At poor market conditions, stocks eligible for margin-trading and short-selling tend to have lower liquidity rather than higher liquidity. Furthermore, margin-trading activity hinders liquidity but short-selling improves liquidity. Hence, the impacts of margin trading and short selling on liquidity reversed during the market downturns. My finding helps to reconcile the discrepancy between many literature findings and regulators’ policy of short selling ban during market crisis period. I also examine the impacts of margin trading and short selling on the lead-lag relations in liquidity and return between stocks eligible for margin-trading and short selling and other stocks. Firstly, applying the Vector Autoregression (VAR) models on minute data, I find a strong lead-lag relation in both liquidity and return between eligible stocks and ineligible stocks. That is, liquidity and returns for eligible stocks lead those of the ineligible stocks. This lead-lag effect persists under different market conditions. In addition, the lead-lag effect in liquidity is stronger when investors are facing constrained funding liquidity which supports the theoretical model of Brunnermeier and Pedersen (2009) which suggests the interaction between funding liquidity and stock liquidity. Secondly, only margin trading has significant impacts on the lead-lag relations. To explain why the margin trading would have impact on lead-lag effects, I proposed three possible mechanisms (i.e., deleverage channel, cross-asset learning channel, and information diffusion channel) and use mediation analysis to test the importance of each mechanism. I found that the deleverage channel accounts for 58.24% (70.73%) of the impacts from margin trading on lead-lag effect in liquidity (return). The information diffusion channel only explains 2.28% (0.86%) of total effect that margin trading has on lead-lag effect in liquidity (return). The cross asset learning channel can explain 39.58% (28.41%) of the impacts of margin trading on lead-lag in liquidity (return). Our study provides the first empirical evidence in literature on the lead-lag relation in liquidity. In addition, it is the first paper that demonstrates the existence of return lead-lag relation at intraday level. Finally, it highlights the role that margin trading played in forming such lead lag relations in both liquidity and return.

7.Total Ionizing Dose Response of High-k Dielectrics on MOS Devices

Author:Yifei MU 2017
Abstract:As advanced Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) technology continues to minimize the gate oxide thickness, the exponential increase in gate leakage current poses a major challenge for silicon dioxide (SiO2) based devices. In order to reduce the gate leakage current while maintaining the same gate capacitance, alternative gate insulator materials with higher dielectric constant (high-k) became the preferred replacement of SiO2 gate dielectrics. Germanium (Ge) MOSFETs have been regarded as promising candidates for future high-speed applications because they possess higher carrier mobility when compared to silicon based devices. At present, advanced microelectronics devices and circuits are used in aerospace engineering, nuclear industry, and radiotherapy equipment. These applications are unavoidably exposed to space-like radiation, which has a relative low radiation dose rate at 10-2-10-6 rad(Si)/s. For these reasons, it is necessary to understand the low-dose-rate radiation response of high-k materials based on Si and Ge MOS devices. The radiation response of high-k materials such as radiation-induced oxide and interface trap density have been typically examined by carrying out off-site capacitance-voltage (CV) measurements. However, the conventional and off-site radiation response measurements may underestimate the degradation of MOS devices. In this study, a semi-automated laboratory-scale real-time and on-site radiation response testing system was developed to evaluate the radiationresponse. The system is capable of estimating the radiation response of MOS devices whilst the devices are continuously irradiated by ?-rays raysrays. Moreover, the complete CV characteristics of MOS capacitors were measured in a relatively short time. The pulse CV measurement reduces the impact of charge trapping behavior on the measurement results, when compared to conventional techniques. The total ionizing dose radiation effect on HfO2 dielectric thin films prepared by atomic layer deposition (ALD) has been investigated by the proposed measurement system. The large bidirectional ΔVFB of the irradiated HfO2 capacitor was mainly attributed to the radiation-induced oxide trapped charges, which were not readily compensated by bias-induced charges produced over the measurement timescales of less than 5 ms. Radiation response of Ge MOS capacitors with HfO2 and HfxZr1-xOy gate dielectrics was also investigated. It was found that radiation-induced interface traps were the dominant factor for Flat-band Voltage shift (ΔVFB) in HfO2 thin films, whereas the radiation response for Zr-containing dielectrics under positive bias was mainly affected by oxide traps. Under positive biased irradiation, the Zr-doped HfxZr1-xOy exhibited smaller ΔVFB than that of HfO2. This is attributed to the de-passivation of Ge-S bonds in capacitors incorporating HfO2 thin films, resulting in the build-up of interface traps. Under negative biased irradiation, ΔVFB was attributed to the combined effect of the net oxide trapped charges and the passivation of Ge dangling bonds at the Ge/high-k interface.

8.Investigating the Effects of Simian Retrovirus (SRV) Infection on the Autophagic Pathway, Apoptotic Pathway and m6A RNA Methylation in Jurkat Cells

Author:Jingting Zhu 2019
Abstract:Simian type D retrovirus (SRV) is an etiological agent for the fatal simian acquired immunodeficiency syndrome (SAIDS), which mainly infects Asian macaques and leads to varying degrees of immunosuppression. Until now, little was known about the underlying pathogenic mechanisms of SRV infection. Especially, the effects of SRV infection on T lymphocytes, the major host cells of SRV, are still largely unclear. Apoptosis and autophagy are two important evolutionarily conserved host immune defense pathways against viral invasion and mediate viral pathogenesis. In addition, in the last decade, a growing number of studies has revealed the emerging roles of m6A RNA modification in regulating the viral infection and virus-host cell interactions. Therefore, the aims of this thesis are to investigate the effects of SRV infection on the autophagic pathway, apoptotic pathway and m6A RNA modification in Jurkat T lymphocytes (Jurkat cells). The capacities of SRV infection and replication in Jurkat cells were also assessed. The results showed that both SRV-4 and SRV-8, the major SRV subtypes circulated in the macaque breeding colonies in China, were able to infect and replicate in Jurkat cells. In addition, both SRV-4 and SRV-8 infection have been shown to induce autophagy and apoptosis in Jurkat cells. The results demonstrated that SRV-4/SRV-8 infection was able to enhance the formation of autophagosome as well as to increase the completed autophagic flux in Jurkat cells. Moreover, the levels of activated caspase-3 and caspase-8 and apoptosis were significantly increased in Jurkat cells by SRV-4/SRV-8 infection. In addition, the SRV-8 infection-induced autophagy was shown to inhibit SRV replication and promote apoptosis in Jurkat cells. Inhibition of autophagy by knockdown of Beclin1 in SRV-8-infected Jurkat cells was shown to significantly increase the amount of SRV genome released in the culture medium, as well as to significantly decrease the levels of caspase-3/-8 activation and inhibit apoptosis. Interestingly, further investigations on the interaction between LC3 and procaspase-8 in SRV-8-infected Jurkat cells suggested that the autophagosomes was, at least partially, involve in the process of caspase-8 activation. In addition, the results in this thesis also showed that SRV-8 viral RNAs in the infected Jurkat cells contain six distinct m6A peaks. Moreover, SRV-8 infection was shown to decrease the global m6A level in Jurkat cells, as well as to reprogramme the Jurkat cellular m6A epitranscriptome. Interestingly, depletion of ALKBH5, an m6A “eraser”, or YTHDF1, an m6A “reader”, in the infected Jurkat cells was demonstrated to significantly decrease SRV-8 replication, suggesting the regulatory roles of m6A modification and the components of the cellular m6A machinery in SRV replication. The results in this thesis have revealed for the first time the effects of SRV infection on the autophagic and apoptotic pathways as well as on the m6A RNA methylation in Jurkat cells, which have the potential to provide novel insights for the development of new antiviral therapies.

9.Investigating the effects of human Carbonic Anhydrase 1 expression in mammalian cells

Author:Xiaochen LIU 2016
Abstract:Amyotrophic Lateral Sclerosis (ALS) is one of the most common motor neuron diseases with a crude annual incidence rate of ~2 cases per 100,000 in European countries, Japan, United States and Canada. The role of Carbonic Anhydrase 1 (CA1) in ALS pathogenesis is completely unknown. Previous unpublished results from Dr. Jian Liu have shown in the spinal cords of patients with sporadic amyotrophic lateral sclerosis (SALS) there is a significant increased expression of CA1 proteins. The purpose of this study is to examine the effect of CA1 expression in mammalian cells, specifically, whether CA1 expression will affect cellular viability and induce apoptosis. To further understand whether such effect is dependent upon CA1 enzymatic activity, three CA1 mutants (Thr199Val, Glu106Ile and Glu106Gln) were generated using two-step PCR mutagenesis. Also, a fluorescence-based assay using the pH-sensitive fluorophore Pyranine (8-hydroxypyrene-1,3,6-trisulfonic acid) to measure the anhydrase activity was developed. The assay has been able to circumvent the requirement of the specialized equipment by utilizing a sensitive and fast microplate reader and demonstrated that three mutants are enzymatically inactive under the physiologically relevant HCO3- dehydration reaction which has not been tested before by others. The data show that transient expression of CA1 in Human Embryonic Kidney 293 (HEK293), African Green Monkey Kidney Fibroblast (COS7) and Human Breast Adenocarcinoma (MCF7) cell lines did not induce significant changes to the cell viability at 36hrs using the Water Soluble Tetrazolium-8 (WST8) assay. Wild-type CA1 significantly reduced cell viability in HEK293 using a virally transduced inducible stable expression system at 96hrs and 144hrs of protein induction whereas out of the two mutants used only Thr199Val induced significant toxicity at 144hrs. Wild-type CA1 has also been found to protect COS7 cells against doxycycline-induced toxicity at 96hrs and 144hrs of protein induction whereas no protective effect was seen by the mutants. Using flow cytometry analysis the results has shown wild-type CA1 expression significantly increased Caspase-3 activation and its downstream molecule Poly (ADP-Ribose) Polymerase 1 (PARP-1) cleavage at 96hrs whereas Glu106Ile only significantly increased Caspase-3 activation. In conclusion, this study marks the first time where CA1 expression has shown to directly cause significant apoptotic toxicity in HEK293 cells and protect against doxycycline-induced toxicity in COS7 cells. Although the implication of this study in ALS requires further investigation, the results here suggest in healthy cells increased levels of CA1 expression may cause onset of toxicity, whereas when cells undergo stress, increased CA1 expression can be protective to prevent further loss in cell viabilities. Despite numerous previous studies that have examined CA1 as potential diseases marker, these results represent for the first time in understanding the effect of CA1 in mammalian cells.

10.Dielectric Relaxation and Frequency Dependence of HfO2 Doped by Lanthanide Elements

Author:Chun ZHAO 2014
Abstract:The decreasing sizes in complementary metal oxide semiconductor (CMOS) transistor technology requires the replacement of SiO2 with gate dielectrics that have a high dielectric constant (k). When the SiO2 gate thickness was reduced below 1.4 nm, electron tunneling effects and high leakage currents occurred which presented serious obstacles for the reliability issue in terms of metal-oxide-semiconductor field-effect transistor (MOSFET) devices. In recent years, various alternative gate dielectrics have been researched. Following the introduction of HfO2 into the 45 nm process by Intel in 2007, the screening and selection of high-k gate stacks, understanding their properties, and their integration into CMOS technology has been a very active research area. Frequency dispersion of high-k dielectrics was commonly observed and classified into two parts: extrinsic and intrinsic causes. The frequency dependence of the dielectric constant (k-value), that is the intrinsic frequency dispersion, could not be assessed before suppressing the effects of extrinsic frequency dispersion, such as the effects of the lossy interfacial layer (between the high-k thin film and silicon substrate) and the parasitic effects. The significance of parasitic effects (including series resistance and the back metal contact of the metal-oxide-semiconductor (MOS) capacitor) on frequency dispersion was studied. The effect of the lossy interfacial layer on frequency dispersion was investigated and modeled using a dual frequency technique. The effect of surface roughness on frequency dispersion is also investigated. Several mathematical models were discussed to describe the dielectric relaxation of high-k dielectrics. Some of the relaxation behavior can be modeled using the Curie-von Schweidler (CS) law, the Kohlrausch-Williams-Watts (KWW) relationship and the Havriliak-Negami (HN) relationship. Other relaxation models were also introduced. For the physical mechanism, dielectric relaxation was found to be related to the degree of polarization, which was dependent on the structure of the high-k material. The degree of polarization was attributed to the enhancement of the correlations among polar nano-scale size domain within the materials. The effect of grain size for the high-k materials' structure mainly originated from higher surface stress in smaller grain size due to its higher concentration of grain boundary.

11.Essays on Consumer Choice for Electric Vehicles and Potential Adoption of Autonomous Vehicles in China

Author:Youlin Huang 2020
Abstract:To address global sustainability challenges such as air pollution and energy shortage, massive attention has been paid to the research and development of low-carbon innovations. Electric vehicles (EVs), powered by electricity, are one of the most promising low-carbon innovations for helping reduce carbon emission and achieve sustainable developmental goals. EVs are also more likely to achieve partial or full autonomous driving in near future. Drawing on multi-level perspective (MLP), which views sustainable transition as a non-linear process, this thesis presents four empirical studies to examine the adoption and diffusion of EV, as well as the adoption of autonomous vehicles (AVs) in China. These four studies (i.e. Working Paper 1~4) were conducted from 2017 to 2019 by collecting three waves of stated preference (SP) experiment and surveys from a group of nationwide households in China. Specifically, Working Paper 1 studies the effect of generation and city in the EV transition. Inspired by findings of Working Paper 1, Working Paper 2 examines consumer preferences for adopting EVs in innovative business models, which addresses consumers’ concerns related to technology immaturity of EVs that Working Paper 1 identifies. As an extension of Working Paper 1, Working Paper 3 integrates the three waves of SP data to examine the dynamic consumer preferences for EVs over time. The last working paper explores antecedents and mechanism of potential adoption of AV, as another pathway of future diffusion of EV and a future direction of automobility. Overall, this thesis identifies not only critical monetary, service and policy attributes that influence consumer preferences for EVs, but also the dynamic consumer preferences for EVs and a range of EV attributes over time, as well as the mechanism behind consumers’ potential adoption of AV. The analyses unveil that (1) the young generation is not more inclined to adopt EV than the old generation as expected, but consumers in small cities show stronger preferences for EVs and such preferences are even growing over time; (2) battery-leasing business model is perceived as a substitute of EV-buying business model, while EV-leasing and EV-sharing business models are perceived independent; (3) individuals’ reasoning process affects their attitude and adoption intentions towards AVs, and two psychological traits (i.e., need for uniqueness and risk aversion) are antecedents to consumers’ reasoning process. Therefore, this thesis contributes to sustainable transition literature by empirically analysing the dynamic consumer preferences for sustainable innovations along with market development in the MLP. This research is also one of the first studies to quantitatively analyse the role of business models in influencing consumers’ adoption for sustainable innovations, and to analyse the effect of psychological traits on adopting AVs. This research offers policy and business implications for driving EV transition by contextualising public policies and marketing strategies, promoting collaborations among automakers, governments and service providers, communicating relevant policies, implementing alternative business models for EV adoption, and providing more experiential opportunities of EVs and AVs to potential adopters.To address global sustainability challenges such as air pollution and energy shortage, massive attention has been paid to the research and development of low-carbon innovations. Electric vehicles (EVs), powered by electricity, are one of the most promising low-carbon innovations for helping reduce carbon emission and achieve sustainable developmental goals. EVs are also more likely to achieve partial or full autonomous driving in near future. Drawing on multi-level perspective (MLP), which views sustainable transition as a non-linear process, this thesis presents four empirical studies to examine the adoption and diffusion of EV, as well as the adoption of autonomous vehicles (AVs) in China. These four studies (i.e. Working Paper 1~4) were conducted from 2017 to 2019 by collecting three waves of stated preference (SP) experiment and surveys from a group of nationwide households in China. Specifically, Working Paper 1 studies the effect of generation and city in the EV transition. Inspired by findings of Working Paper 1, Working Paper 2 examines consumer preferences for adopting EVs in innovative business models, which addresses consumers’ concerns related to technology immaturity of EVs that Working Paper 1 identifies. As an extension of Working Paper 1, Working Paper 3 integrates the three waves of SP data to examine the dynamic consumer preferences for EVs over time. The last working paper explores antecedents and mechanism of potential adoption of AV, as another pathway of future diffusion of EV and a future direction of automobility. Overall, this thesis identifies not only critical monetary, service and policy attributes that influence consumer preferences for EVs, but also the dynamic consumer preferences for EVs and a range of EV attributes over time, as well as the mechanism behind consumers’ potential adoption of AV. The analyses unveil that (1) the young generation is not more inclined to adopt EV than the old generation as expected, but consumers in small cities show stronger preferences for EVs and such preferences are even growing over time; (2) battery-leasing business model is perceived as a substitute of EV-buying business model, while EV-leasing and EV-sharing business models are perceived independent; (3) individuals’ reasoning process affects their attitude and adoption intentions towards AVs, and two psychological traits (i.e., need for uniqueness and risk aversion) are antecedents to consumers’ reasoning process. Therefore, this thesis contributes to sustainable transition literature by empirically analysing the dynamic consumer preferences for sustainable innovations along with market development in the MLP. This research is also one of the first studies to quantitatively analyse the role of business models in influencing consumers’ adoption for sustainable innovations, and to analyse the effect of psychological traits on adopting AVs. This research offers policy and business implications for driving EV transition by contextualising public policies and marketing strategies, promoting collaborations among automakers, governments and service providers, communicating relevant policies, implementing alternative business models for EV adoption, and providing more experiential opportunities of EVs and AVs to potential adopters.

12.Determinants of Asymmetric Cost Behavior

Author:Yuxin Shan 2019
Abstract:Asymmetric cost behavior describes a non-linear association between the change of costs and change of sales. This dissertation consists of three papers identifying different determinants of the asymmetric cost behavior. In terms of the economic theory of sticky costs, the institutional theory and the “grabbing hand” theory, the first paper identifies three factors in China that increase the level of cost stickiness, including state ownership, the five-year government plan and the density of skilled labor. Using data from 34 OECD countries, the second paper provides empirical evidence showing that companies in high tax rate jurisdictions are more likely to have a greater level of cost stickiness than companies in low tax rate jurisdictions. Using the U.S. data, the third paper explores the association between high-quality information technology (IT) and the level of cost stickiness. Consistent with my expectation, empirical results show that high-quality IT weakens the asymmetric cost behavior. In addition, the third paper investigates the relationship between high-quality IT and audit efficiency, showing that high-quality IT enhances the audit quality and decreases audit fees. This study contributes to cost accounting literature by suggesting additional determinants affecting resource adjustment decisions of managers. Meanwhile, this study sheds light on the tax avoidance literature by providing empirical evidence for the effect of country-level statutory tax rates on “real” corporate decisions. This study also contributes to extant literature about the return to IT investments, showing that the quality of IT affect managers’ resource adjustment decisions and audit efficiency. Additionally, this study provides guidance for policymakers about how managers react to the change of government plans and regulations.

13.Temperature-based Weather Derivatives Modeling and Contract Design in Mainland China

Author:Lu ZONG 2015
Abstract:In the presented thesis, we build the theoretical framework for the development of temperature-based weather derivatives market in China. Our research is divided into two separate studies due to their di erent scopes. In the rst study, we focus on the determination of the most precise model for temperature-based weather derivative modeling and pricing in China. To achieve this objective, a heuristic comparison of the new stochastic seasonal variation (SSV) model with three established empirical temperature and pricing models, i.e. the Ala-ton model [1], the CAR model [2] and the Spline model [3] is conducted. Comparison criteria include residual normality, residual auto-correlation function (ACF), Akaike information criterion (AIC), relative errors, and stability of price behaviors. The re- sults show that the SSV model dominates the other three models by providing both a more precise tting of the temperature process and more stable price behaviors. In the second study, novel forms of temperature indices are proposed and an- alyzed both on the city level and the climatic zone level, with the aim to provide a contract-selecting scheme that increases the risk management e ciency in the agricultural sector of China. Performances of the newly-introduced indices are in-vestigated via an e ciency test which considers the root mean square loss (RMSL),the value at risk (VaR) and the certainty-equivalent revenues (CERs). According to the results, agricultural risk management on the city scale can be optimized by using the absolute-deviation growth degree-day (GDD) index. On the other hand, it is suggested that climatic zone-based contracts can be more e cient compared with city-based contracts. The recommended contract-selection scheme is to purchase climatic zone-based average GDD contracts in climatic zone II, and to purchase climatic zone-based optimal-weighted GDD contracts in climatic zone I or III.

14.Model Checking the Reliability of Smart Grid

Author:Kai Zheng 2019
Abstract:In recent years, air pollution in China become more serious than before. Thermal power generation is one of the main pollution sources, so the Chinese government wants to develop distributed energy systems (DESs) to solve the problem. However, the monitoring and control of the DESs become a challenge. In order to solve the problem, the concept of smart microgrid is introduced. Smart microgrid can monitor and optimize the running of DESs in an intelligent way. Smart microgrid systems usually include the following components: DESs, converters, inverters, sensors, gateways, and servers. The control algorithms are imported into the inverters and converters to realize the optimal control of DESs. The internet of things (IoT) network in a smart microgrid is used for monitoring the operation of the DESs. However, the reliability of smart microgrid is still a challenge. In recent years, some of the researchers also focus on the reliability of smart microgrid[53]. But the research about the reliability of the smart microgrid is still not enough. Most of the researchers focus on the power quality reliability of the microgrid. However, few research concentrates on optimizing the structure design of smart microgrid. In this project, we will optimize the architecture design of smart microgrid. Continuous- time Markov chain (CTMC) models will be used to evaluate the reliability of smart micro- grid. The architectures of the IoT system and DC microgrid will be evaluated respectively. Then the analysis results will show our optimized architecture is better. The optimized design of smart microgrid in this project will help the designer to improve the architecture design of smart microgrid in real cases. In this project, Monte Carlo method, reliability block diagram (RBD) method and case study system are used as benchmarks.

15.Dual-functional carbon–based Interlayers towards high-performance Li-S batteries

Author:Ruowei Yi 2020
Abstract:For reducing carbon emission and alleviating pollution, people are gradually replacing the fossil fuel-employing combustion engines with new energy devices. The secondary batteries with high energy storage have become a hot alternative to power sources due to its zero emission during their operation. In recent years, as the most popular energy storage equipment in the battery market for mobile devices, lithium-ion battery is gradually showing a decline in the field of power battery, because its energy density (~ 150 Wh kg-1) has been unable to meet the demands of power equipment, and the current research has almost reached the theoretical capacity of lithium-ion battery electrode materials, and leaves little space for improvement. Therefore, academic research began to seek a variety of new battery systems to meet the needs of the industry. As a battery system based on the non-topological reaction between lithium anode and sulfur anode, lithium sulfur battery has a very high theoretical energy density (2567 Wh kg-1) and theoretical specific capacity (1672 mAh g-1), which is good enough to meet the energy density requirements (500-600 Wh kg-1) of power battery. Meanwhile, sulfur is of low cost and environmentally friendly, which is suitable for large-scale commercialization. Therefore, it is considered as a strong competitor of the next generation power supply. However, a series of shortcomings of lithium sulfur battery limit its large-scale application at present stage; for examples, the sluggish reaction kinetics of active sulfur and the degraded cyclic stability from shuttle effect. The improvement of both can ameliorate the rate performance and cycle stability of lithium sulfur battery, which are crucial to the practical application of power battery. In this thesis, in order to solve the above problems, the author first used a facile and scalable method to prepare carbon black/ PEDOT:PSS. The modified separator was applied to lithium sulfur battery as an improved interlayer of the cathode. The principle of improving sulfur cathode by the interlayer was studied by the electrochemical analysis. The high conductivity and polysulfide adsorption ability of the coating delivers an initial specific capacity of 1315 mAh g-1 at 0.2 C current, and 699 mAh g-1 at a high rate of 2 C current; secondly, for the purpose of reducing the density of the cathode interlayer, a three-dimensional graphene foam was chosen as the conductive substrate of the interlayer, and modified with the zinc oxide by atomic layer deposition (ALD), creating the self-standing three-dimensional graphene foam / nano zinc oxide interlayer. This interlayer leads to an initial specific capacity of 1051 mAh g-1 at a 0.5 C rate. Its low area density (0.15 mg cm-2) also reduces the influence on the energy density of the cathode. As a step forward, the two-dimensional Ti3C2Tx nanosheet (MXene) with high conductivity and polysulfide adsorption characteristics was selected as an alternative material of zinc oxide to modify the graphene foam (GFMX), which simplifies the synthesis process and enhances the electronic conductivity of the interlayer. After 120 cycles at 0.2 C, the lithium sulfur batteries still maintain a specific capacity of 867 mAh g-1 and 755 mAh g-1 at 2 C high rate current with the GFMX interlayer. In light of the significant improvement of the interlayer by MXene, the modified the MXene by an in-situ growth of nitrogen and nickel doped carbon nanosheets has been studied. Results show that the stacking of MXene is greatly reduced and the specific surface area of the material is increased, moreover, the adsorption capacity of polysulfides has been largely improved by the nitrogen doping. When using the obtained composite material as the separator coating, the lithium sulfur batteries exhibit 943 mAh g-1 specific capacity after 100 cycles at 0.2 C current, and 588 mAh g-1 specific capacity after 500 cycles at 1 C. The average cycle capacity decay rate is 0.069%, and the specific capacity of the high sulfur loading cathode (3.8 mg cm-2) is 946 mAh g-1, highlighting its potential applications in the high-performance lithium sulfur batteries.

16.Online Shopping Adoption and Quality of Life Among Older Consumers in China

Author:Xue Bai 2021
Abstract:The development of online shopping in China is accelerating quickly, but the usage is primarily amongst younger people. The adoption of online shopping among older consumers (50+) is still under researched. This study identifies the factors that influence the adoption of online shopping among older consumers in China and evaluates the effects of adoption on their quality of life and wellbeing. This thesis contributes to the existing technology adoption and marketing literature in the following ways. First, besides adopters and non-adopters of online shopping, this research identifies a third category of users among older consumers in China, and this consists of people who ask younger family members (i.e. their adult children or children-in-law) to shop online for them. This phenomenon of supported adopters occurs not only because older consumers lack confidence or seek for convenience, but it is also because younger family members employ this approach to show their filial piety to their parents or parents-in-law. Second, this study develops an extended Technology Acceptance Model (TAM) that incorporates anxiety, autonomy, and cognitive age, and it examines their relationships across the three user groups (i.e. adopters, supported adopters, and non-adopters). The findings show that perceived usefulness and perceived ease of use are facilitators for all users, whereas rising cognitive age is a barrier. Autonomy is only perceived as a facilitator among adopters, whereas anxiety as a perceived barrier matters only for supported adopters and non-adopters. Besides the factors that are examined in the quantitative analysis, this thesis further reveals that reverse socialization is a key process for Chinese older consumer to adopt online shopping themselves. The practical implications of reverse socialization provides a solution for encouraging older consumers to adopt online shopping, and the theoretical implications of supported adopters in the context of online shopping are explained and discussed.

17.Growth, Dielectrics Properties, and Reliability of High-k Thin Films Grown on Si and Ge Substrates

Author:Qifeng Lu 2018
Abstract:With the continuous physical size down scaling of Metal Oxide Semiconductor Field Effect Transistors (MOSFETs), silicon (Si) based MOS devices have reached their limits. To further decrease the minimum feature size of devices, high-k materials (with dielectric constants larger than that of silicon dioxide (SiO2), 3.9) have been employed to replace the SiO2 gate dielectric. However, there are higher densities of traps in high-k dielectrics than in the near trap free SiO2. Therefore, it is important to comprehensively investigate the defects and electron trapping/de-trapping properties of the oxides. Also, germanium (Ge) has emerged as a promising channel material to be used in high-speed metal-oxide-semiconductor (MOS) devices, mainly due to its high carrier mobility compared with that of silicon. However, due to the poor interface quality between the Ge substrate and gate dielectrics, it is difficult to fabricate high-performance germanium based devices. Therefore, an effective passivation method for the germanium substrate is a critical issue to be addressed to allow the fabrication of high quality Ge MOSFETs. To solve the above problems, the study of high-k materials and the passivation of germanium substrates was carried out in this research. In the first part of this work, lanthanide zirconium oxides (LaZrOx) were deposited on Si substrates using atomic layer deposition (ALD). The pulse capacitance-voltage (CV) technique, which can allow the completion of the CV sweep in several hundreds of microseconds, was employed to investigate oxide traps in the LaZrOx. The results indicate that: (1) more ii traps are observed in the LaZrOx when compared with measurements using the conventional CV characterization method; (2) the time-dependent trapping/de-trapping is influenced by edge times, pulse widths and peak to peak voltages (VPP) of the gate voltage pulses applied. Also, an anomalous behavior in the pulse CV curves, in which the relative positions of the forward and reverse CV traces are opposite to those obtained from the conventional measurements, was observed. A model relating to interface dipoles formed at the high-k/SiOx is proposed to explain this behavior. Formation of interface dipoles is caused by the oxygen atom density difference between the high-k materials and native oxides. In addition, a hump appears in the forward pulse CV traces. This is explained by the current displacement due to the pn junction formed between the substrate and inversion layer during the pulse CV measurement. Secondly, hafnium titanate oxides (TixHf1-xO2) with different concentrations of titanium oxide were deposited on p-type germanium substrates by ALD. X-ray Photoelectron Spectroscopy (XPS) was used to analyze the interface quality and chemical structure. The current-voltage (IV) and capacitance-voltage (CV) characteristics were measured using an Aglient B1500A semiconductor analyzer. The results indicate that GeOx and germinate are formed at the high-k/Ge interface and the interface quality deteriorates severely. Also, an increased leakage current is obtained when the HfO2 content in the TixHf1-xO2 is increased. A relatively large leakage current density (~10-3 A/cm2) is partially attributed to the deterioration of the interface between Ge and TixHf1-xO2 caused by the oxidation source from HfO2. The small band gap of iii the TiO2 also contributes to the observed leakage current. The CV characteristics show almost no hysteresis between the forward and reverse CV traces, which indicates low trap density in the oxide. Since deterioration of the interface quality was observed, an in-situ ZnO interfacial layer was deposited in the ALD system to passivate the germanium substrate. However, a larger distortion of the as-deposited sample was observed. Although the post deposition annealing (PDA) has a positive effect on the CV curves, there is an increase in frequency dispersion and the leakage current after PDA. Therefore, the ZnO interfacial layer is not an effective passivation layer for the germanium substrate. In addition, GeO is formed due to the reaction and GeO desorption from the gate oxide/Ge interface occurs, which also leads to the deterioration of the device performance. In the final part of this work, to circumvent the problems explored above, 0.1 mol/L propanethiol solution in 2-propanol, 0.1 mol/L octanethiol solution in 2-propanol, and 20% (NH4)2S solution in DI water were used to passivate the n-type germanium substrates before HfO2 dielectric thin films were deposited by ALD. The results show that an increase in the dielectric constant and a reduction in leakage current are obtained for the samples with chemical treatments. The sample passivated by octanethiol solution has the largest dielectric constant. The lowest leakage current density is observed for the sample passivated by (NH4)2S solution followed by the one passivated by octanethiol solution. In addition, effects of a TiN cap layer on the formation and suppression of GeO were investigated. It was found that the formation of GeO and iv desorption of the GeO form gate oxides/Ge interface are suppressed by the cap layer. As a result, an increase in dielectric constant from 8.2 to 13.5 and a lower leakage current density for a negatively applied voltage are obtained. Therefore, the passivation of the substrates by octanethiol or (NH4)2S solutions followed by the TiN cap layer is a useful technique for Ge based devices.

18.A novel regulatory role of immune adaptor ADAP in TLR4-mediated macrophage inflammatory response and polarization

Author:Naiqi Yang 2020
Abstract: Liposaccharide, is a potent bacterial stimulus recognized by Toll-like receptor 4 (TLR4) and drives macrophage polarization towards classical pro-inflammatory M1 phenotype. In response to microenvironment, macrophage can reprogramme its phenotype and functions towards alternative anti-inflammatory M2 phenotype. A balance of macrophage M1-M2 polarization governs proper inflammation and its resolution. ADAP, originally identified as an essential adaptor molecule in TCR signaling and T-cell adhesion, has emerged as a critical regulator of innate immune cells such as macrophages, mast cells and dendritic cells, but its role in macrophage polarization and inflammatory responses remains elusive. In the present study, I show that ADAP plays a role in TLR4-mediated macrophage inflammatory response and M1/M2 polarization. Upon LPS stimulation, ADAP deficient macrophages exhibit a higher expression of M1 markers and pro-inflammatory cytokines IL-1, IL-6, IL-12, TNF-α, IFN-γ as well Th1-reruiting chemokines CXCL9 and CXCL11, but a lower expression of M2-skewed cytokines IL-10. Loss of ADAP augments LPS-induced NF-κB and MAPKs activation, whereas dampens STAT3 tyrosine phosphorylation and activation in macrophages which is essential for skewing macrophage towards M2 polarization. Mechanically, ADAP constitutively binds to STAT3 in macrophages, while LPS stimulation dissociates ADAP-STAT3 complex and triggers phosphorylation at Y571 in the motif YDSL of ADAP. Overexpression of ADAP enhances, whereas mutation of Y571 to F severely impairs the stimulating effect of ADAP on STAT3 activity and the ability of ADAP to inhibit M1 polarization in TLR4-activated macrophages, suggesting ADAP acts as a co-activator of STAT3 activity and M2-skew function, which mostly depends on the tyrosine phosphorylation of Y571 induced by LPS. Consequently, ADAP deficient macrophages display an enhanced ability in M1-skewed polarization and bacterial phagocytic activity, and manifest enhanced capacity in inducing Th1 responses. Collectively, my findings revealed an additional layer of regulation of TLR4-mediated macrophage plasticity whereby ADAP acts as a turn-off switch for M1 polarization via sustained activation of STAT3.  

19.End-user Centred Participatory Design for Community-based Healthcare Environments in China

Author:Qichao Ban 2019
Abstract:The national healthcare system in China is currently experiencing significant reform, which aims to establish a more accessible, affordable and equitable healthcare service for the whole society. One of the long-term key tasks is set to transform the allocation of medical resources in urban areas from a “centralised” pattern to a “decentralised” one. It intends to improve the capacity of delivering primary care for urban residents. In this research, attention is paid to the social sustainability and design process of healthcare environments at a community level, since the design quality has a significant impact upon the provision and delivery of healthcare service while there is a lack of specific building regulations or standards that are tailored to inform or assess the design of community-based healthcare facilities in China.   This research explores end-users’ satisfaction and the design strategies related to their needs. A “multi-strategy research” strategy is applied for the research framework, which consists of desktop research and field investigations. In the desktop research, the design strategies for healthcare environments are collected with relevant evidence from regulations and previous literature. A series of social studies are conducted for the field investigations, and finally, the responses of target groups in this research are cross-compared and analysed in order to shed an in-depth insight into end-users’ cognitive differences. Their preferences are used to identify the relative importance of design strategies that are related to end-users’ needs for community-based healthcare environments.   It is found that a complete consensus on the needs of end-users cannot be reached for good healthcare environment design at a community level. Evidence-based design principles can improve the efficiency of knowledge exchange in the participatory design decision-making process. Information from building regulations is expected to be used as a communication platform for stakeholders with different knowledge levels. Based on the findings regarding end-users’ preferences for the design of community-based healthcare environments, the suggestions on improving the existing building regulations from a social perspective are raised. Furthermore, a design aided tool, End-user Centred Participatory Design for Community-based Healthcare Environments Version 1.0 (ECPD), is proposed, which can be employed in conjunction with GB/T 51153 currently, in order to improve the overall design quality and social sustainability of community-based healthcare environments in China.

20.Investor horizon and corporate innovation

Author:Ruiwen An 2020
Abstract:Innovation is crucial to corporate long-run growth and competitiveness. There exist gaps in the current literature on investor horizon and corporate innovation. The relationship between institutional investor horizon and innovation is inconclusive, and the role of exit on innovation lacks examination. In this thesis, we first investigate whether longer investor horizon can lead to more innovation. Chapter 3 develops a non-linear model and estimates it using a sample of U.S. public firms. We find an inverted-U relationship between horizon and innovation. This indicates a positive effect of horizon on innovation and the effect diminishes if the horizon is too long. These results call for a study of the negative side of long investment horizon.   Chapter 4 argues that worsening price informativeness and lifting agency costs may be two disadvantages of long horizon. It then studies whether exit by investors improves stock price efficiency and whether an increase in price efficiency leads to more innovation. The positive role of exit on price efficiency is supported by empirical evidence. Also, Chapter 4 finds positive relationship between price efficiency and innovation. These findings support that exit has the potential to mitigate information asymmetry and agency costs between managers and investors. Chapter 4 also provides reasons why holding stocks too long may impede innovation.   Chapter 5 aims to tackle the contradiction between long horizon and frequent exit, both of which are important to innovation as demonstrated in Chapter 3 and 4. Chapter 5 investigates whether investors could maintain a relatively long investing period while show threat of exit to motivate managers at the same time. Using the triple differences approach, Chapter 5 finds that there is a complementary effect between long horizon and threat of exit in promoting innovation. The positive effect of long horizon on innovation could be strengthened by threat of exit of institutional investors.
Total 128 results found
Copyright 2006-2020 © Xi'an Jiaotong-Liverpool University 苏ICP备07016150号-1 京公网安备 11010102002019号