268 research outputs found
Stochastic optimization of product-machine qualification in a semiconductor back-end facility
Full text linkabstract: In order to process a product in a semiconductor back-end facility, a machine needs to be qualified, first by having product-specific software installed and then running test wafers through it to verify that the machine is capable of performing the process correctly. In general, not all machines are qualified to process all products due to the high machine qualification cost and tool set availability. The machine qualification decision affects future capacity allocation in the facility and subsequently affects daily production schedules. To balance the tradeoff between current machine qualification costs and future potential backorder costs due to not enough machines qualified with uncertain demand, a stochastic product–machine qualification optimization model is proposed in this article. The L-shaped method and acceleration techniques are proposed to solve the stochastic model. Computational results are provided to show the necessity of the stochastic model and the performance of different solution methods.This is an Author's Accepted Manuscript of an article published as Fu, Mengying, Askin, Ronald, Fowler, John, & Zhang, Muhong (2015). Stochastic optimization of product-machine qualification in a semiconductor back-end facility. IIE TRANSACTIONS, 47(7), 739-750. DOI: 10.1080/0740817X.2014.964887. Copyright Taylor & Francis, available online at: http://www.tandfonline.com/doi/abs/10.1080/0740817X.2014.96488
A Preclinical Study on Brugada Syndrome with a CACNB2 Variant Using Human Cardiomyocytes from Induced Pluripotent Stem Cells
No full textAims: Some gene variants in the sodium channels, as well as calcium channels, have been associated with Brugada syndrome (BrS). However, the investigation of the human cellular phenotype and the use of drugs for BrS in presence of variant in the calcium channel subunit is still lacking. Objectives: The objective of this study was to establish a cellular model of BrS in the presence of a CACNB2 variant of uncertain significance (c.425C > T/p.S142F) using human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and test drug effects using this model. Methods and results: This study recruited cells from a patient with Brugada syndrome (BrS) and recurrent ventricular fibrillation carrying a missense variant in CACNB2 as well as from three healthy independent persons. These cells (hiPSC-CMs) generated from skin biopsies of healthy persons and the BrS patient (BrS-hiPSC-CMs) as well as CRISPR/Cas9 corrected cells (isogenic control, site-variant corrected) were used for this study. The hiPSC-CMs from the BrS patient showed a significantly reduced L-type calcium channel current (ICa-L) compared with the healthy control hiPSC-CMs. The inactivation curve was shifted to a more positive potential and the recovery from inactivation was accelerated. The protein expression of CACNB2 of the hiPSC-CMs from the BrS-patient was significantly decreased compared with healthy hiPSC-CMs. Moreover, the correction of the CACNB2 site-variant rescued the changes seen in the hiPSC-CMs of the BrS patient to the normal state. These data indicate that the CACNB2 gene variant led to loss-of-function of L-type calcium channels in hiPSC-CMs from the BrS patient. Strikingly, arrhythmia events were more frequently detected in BrS-hiPSC-CMs. Bisoprolol (beta-blockers) at low concentration and quinidine decreased arrhythmic events. Conclusions: The CACNB2 variant (c.425C > T/p.S142F) causes a loss-of-function of L-type calcium channels and is pathogenic for this type of BrS. Bisoprolol and quinidine may be effective for treating BrS with this variant
Why do Chinese firms go public abroad and how do they perform?
No full textIn this thesis, we attempt to solve an interesting question of why Chinese firms go public abroad and how they perform. In order to fully understand this issue, we conduct three essays in this field from the institutional background, policy change, and data analysis to empirical study and result interpretation. The first essay is A Narrative on Overseas Listings by Chinese Firms. In this essay, we first document the evolution of Chinese firms’ initial public offerings (IPOs) outside Mainland China, including the institutional background of IPO process, overseas listing modes, and listing requirements. We discuss important reforms in both the Mainland and Hong Kong and the effects on the listing location choices by the Chinese firms. Next, we compare the performance of listed firms in the Hong Kong, United States, and A-share markets based on statistical analysis. The main finding is that overseas-listed companies do not perform better than A-share listed firms, but they are more likely to conduct M&A activities, financial investments, and bond issuance in currencies other than RMB. Finally, we discuss the delisting pressure on Chinese stocks from the U.S. exchanges from both the Chinese and U.S. authorities. The second essay, named Cost of Capital Market Policy Distortions: Evidence from Overseas Listed Chinese Firms, empirically studies the motivation and valuation of overseas listing. In this essay, we first conduct the two-system equation to simultaneously estimate the pre-IPO factors that have an impact on the firm’s listing location and the post-IPO factors that affect the firm’s valuation in different markets, using the control function approach. We find that there is a valuation discount of Chinese firms listed overseas compared with their
domestically listed counterparts and this valuation discount is persistent in the long run. Then, we investigate reasons for such valuation discounts by examining the impact of policy distortions on the overseas listing. When there are policy distortions such as foreign investment restrictions, administrative approval IPO system, and tighter capital outflow controls, the valuation discount of Chinese firms listed overseas further expands. The valuation discount measures the costs of policy distortions. Our third essay, Asset Pricing under Capital Controls: Evidence from A-H Price Premium, focuses on a narrowed sample that shares dual-listed in Hong Kong and mainland China to assess the impact of capital controls on asset pricing across borders. These are shares issued by the same Chinese firms listed in Shanghai (Shenzhen) stock market as A-shares and in the Hong Kong stock market as H-shares. Despite identical fundamentals, A-shares have been persistently traded with a premium to H-shares. The Shanghai-Hong Kong Stock Connect launched in 2014 is a pilot program that allows cross-border investment under certain conditions. As all the A-H dual-listed shares listed on Shanghai and Hong Kong stock exchanges are eligible for the Connect, this pilot program provides us a great opportunity to investigate the impact of capital control liberalization on asset pricing. Using a Difference-In-Differences(DID) strategy in spirit, we find on average this partial capital account liberalization reduces the A-H price premium by 47.9% under the control of other current hypotheses of the price difference. The magnitude of the impact is more pronounced for firms that face higher hurdles in bypassing capital control.Doctor of Philosoph
Reducing Inbound Logistics Costs- A Case Study in the Chinese Automobile Industry
No full textGlobalization has made company competition more intense. Supply chain management has developed to enable companies to compete effectively. Logistics supports competitiveness of the supply chain as a whole by meeting customer demand both timely and at a competitive cost and inbound logistics cost management is considered to be a priority in reducing costs.
As the Chinese automobile industry is China���������������¢��������������������������������s pillar industry, and China is believed to be a high logistics cost country, the researcher attempts to find out ways to reduce the inbound logistics costs in this industry. A case study is applied to address what aspects reflect the high logistics costs in the Chinese automotive company. The reasons which cause them are analyzed in detail and more importantly, implications on how to reduce the logistics costs are offered one by one.
Inventory control is focused on, as it is the most effective way to reduce costs. Such recommendations as VMI, reducing uncertainty of demand, increasing shipping frequency, improving communications with suppliers, reducing safety stock, etc. are made to reduce inventory. Reduction of local parts transportation costs is considered. 3PL management is addressed to reduce warehousing cost and line stoppage cost, and optimizing material flow and improvement in company management skills are considered to reduce the material handling costs
A comparative study of ports and their hinterlands : factors determining port performance and choice
Full text linkAs a consequence of globalisation, port performance has become increasingly important for international trade. Different port regions perform differently. The aim of this research is to identify factors that determine port performance and choice in a comparative study between two case ports in Europe and Asia. Specifically, this research aims to examine factor differences between two European and Asian ports‘ contexts; to identify the key factors that drive port performance and choice; to investigate the differences in importance and performance among the factors; to analyse how the importance and performance of factors varies for different ports; to analyse the role a port hinterland plays in port performance and choice; and to illustrate the usefulness of key findings for port stakeholders. The construct of importance factors is based on the literature. The research methodology was that of mixed methods to collect both qualitative and quantitative data in two port regions (China and UK) and was carried out in two phases. Phase one comprised semi-structured in-depth interviews. Phase two consisted of questionnaire-based surveys to validate the factors influencing port performance. The questionnaire surveys were distributed to port experts from 500 organisations and had a 50.8% response rate. Thematic analysis was used for qualitative data analysis of the data from the interviews. Methods for analysis of the data from the questionnaires included descriptive analysis, factor analysis, t-test, Kruskal-Wallis H test, importance-performance analysis and other statistical validation and significance tests. The findings of this research suggest that ports wishing to outperform competitors can do so by improving the factors that are of high importance but currently perform poorly. This could also be achieved by improving performances on shipping services, shipping prices, overall logistics cost, logistics services and government support in descending order which is based on factor evaluation in this research. The thesis further analyses this result within the context of urgent, salient and basic factors based on IPA, including explicit & implicit importance. Shipping services and cost have a critical effect on port performance. Differences in port charges are the most significant differences in factor importance at the case ports of the Humber and Xiamen. Government support has the most significant differences in factor performance between the two case ports. This research is not without limitations. The analysis was restricted to two port regions in China and the UK and data used in this research were mainly generated from interviews and questionnaire surveys, responses to which are to some extent subjective
A comparative study of ports and their hinterlands : factors determining port performance and choice
Full text linkAs a consequence of globalisation, port performance has become increasingly important for international trade. Different port regions perform differently. The aim of this research is to identify factors that determine port performance and choice in a comparative study between two case ports in Europe and Asia. Specifically, this research aims to examine factor differences between two European and Asian ports' contexts; to identify the key factors that drive port performance and choice; to investigate the differences in importance and performance among the factors; to analyse how the importance and performance of factors varies for different ports; to analyse the role a port hinterland plays in port performance and choice; and to illustrate the usefulness of key findings for port stakeholders. The construct of importance factors is based on the literature. The research methodology was that of mixed methods to collect both qualitative and quantitative data in two port regions (China and UK) and was carried out in two phases. Phase one comprised semi-structured in-depth interviews. Phase two consisted of questionnaire-based surveys to validate the factors influencing port performance. The questionnaire surveys were distributed to port experts from 500 organisations and had a 50.8% response rate. Thematic analysis was used for qualitative data analysis of the data from the interviews. Methods for analysis of the data from the questionnaires included descriptive analysis, factor analysis, t-test, Kruskal-Wallis H test, importance-performance analysis and other statistical validation and significance tests. The findings of this research suggest that ports wishing to outperform competitors can do so by improving the factors that are of high importance but currently perform poorly. This could also be achieved by improving performances on shipping services, shipping prices, overall logistics cost, logistics services and government support in descending order which is based on factor evaluation in this research. The thesis further analyses this result within the context of urgent, salient and basic factors based on IPA, including explicit & implicit importance. Shipping services and cost have a critical effect on port performance. Differences in port charges are the most significant differences in factor importance at the case ports of the Humber and Xiamen. Government support has the most significant differences in factor performance between the two case ports. This research is not without limitations. The analysis was restricted to two port regions in China and the UK and data used in this research were mainly generated from interviews and questionnaire surveys, responses to which are to some extent subjective.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Reducing Inbound Logistics Costs- A Case Study in the Chinese Automobile Industry
No full textGlobalization has made company competition more intense. Supply chain management has developed to enable companies to compete effectively. Logistics supports competitiveness of the supply chain as a whole by meeting customer demand both timely and at a competitive cost and inbound logistics cost management is considered to be a priority in reducing costs.
As the Chinese automobile industry is China���������������¢��������������������������������s pillar industry, and China is believed to be a high logistics cost country, the researcher attempts to find out ways to reduce the inbound logistics costs in this industry. A case study is applied to address what aspects reflect the high logistics costs in the Chinese automotive company. The reasons which cause them are analyzed in detail and more importantly, implications on how to reduce the logistics costs are offered one by one.
Inventory control is focused on, as it is the most effective way to reduce costs. Such recommendations as VMI, reducing uncertainty of demand, increasing shipping frequency, improving communications with suppliers, reducing safety stock, etc. are made to reduce inventory. Reduction of local parts transportation costs is considered. 3PL management is addressed to reduce warehousing cost and line stoppage cost, and optimizing material flow and improvement in company management skills are considered to reduce the material handling costs
A 2.1MHz PWM Based Class D Audio Amplifier
No full textThis work presents a fully differential Class D audio amplifier using 2.1MHz pulse-width modulation (PWM) frequency and 425kHz LC filter cut-off frequency to decrease the cost of off-chip components. Moreover, feedback after LC filter structure is used to attenuate LC filter nonlinearities
A Framework for On-the-fly Energy Calculation of BIM Models
No full textResearches have been conducted to involve the sustainability of energy in the building's early design stage. The methods used include the IEF-based method, the BIM-API-based method, and other approaches. However, these methods have not helped architects out in the early design stage since the complexity of the assessment is not decreased.The contradiction of increasingly complex energy simulations and early conceptual designs forms a research gap in energy optimization. As changes in the early design stage have more effect on the buildings and make less cost, the introduction of on-the-fly energy assessment in the early stages is of great importance.This thesis developed a framework to help boost energy efficiency in building design. The framework aims to improve the efficiency of energy assessment by providing simultaneous and on-the-fly energy performance assessment of the design. BIM software Revit and the visual programming environment Grasshopper were integrated via Rhino.Inside, a bridge between the BIM environment and others to perform the assessment. The workflow of the framework contains three parts: data input from BIM models and the determination method NTA 8800, the connection by Rhino.Inside and the computation of the Grasshopper script, the final results, and the report produced by the Grasshopper script.A script in Grasshopper as a demonstration of the framework was developed as such that Revit models can be directly linked to the energy analysis, and the results can be returned simultaneously. The script was created based on a preliminary case study and two sets of studies were conducted to validate it. The case study of a tiny house was first investigated to test and validate the developed tool. The energy demand result of the developed tool has only a 3% difference for the case study calculated via Uniec 3, a verified software used in the Netherlands. The developed tool was also validated through 4 variants with different configurations to find out if the tool is accurate and robust enough concerning dimensions and physical properties. The comparison of the results shows that the developed tool can produce steadily accurate results that vary within 5% from the standard outcome. In addition, the study indicates the framework's potential of optimizing the building's performance on energy efficiency as the proposed framework significantly shortens the time and workload compared to Uniec 3 which requires a body of manual input.The study in this thesis integrates the BIM models and energy analysis to enhance the sustainability concept in the building design industry. It fills the gap in the application of semi-automated BIM to the BEM framework in the early design stage of buildings. The developed framework provides a useful tool and practical benefits to the field of energy efficiency. This study investigated the potential of applying on-the-fly energy assessment in early design stage, which could be developed further in future work to explore more or better solutions.Civil Engineering | Building Engineerin
Improving the osteogenesis of human bone marrow mesenchymal stem cell sheets by microRNA-21-loaded chitosan/hyaluronic acid nanoparticles via reverse transfection
No full textZhongshan Wang,1 Guangsheng Wu,2,3 Mengying Wei,4 Qian Liu,1 Jian Zhou,1 Tian Qin,1 Xiaoke Feng,1 Huan Liu,1 Zhihong Feng,1 Yimin Zhao1 1State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Oral Diseases, Department of Prosthodontics, 2State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Engineering Research Center for Dental Materials and Advanced Manufacture, Department of Periodontology, School of Stomatology, The Fourth Military Medical University, Xi’an, 3Qingdao First Sanatorium, Jinan Military Region, Qingdao, Shandong Province, 4Department of Biochemistry and Molecular Biology, The Fourth Military Medical University, Xi’an, People’s Republic of China Abstract: Cell sheet engineering has emerged as a novel approach to effectively deliver seeding cells for tissue regeneration, and developing human bone marrow mesenchymal stem cell (hBMMSC) sheets with high osteogenic ability is a constant requirement from clinics for faster and higher-quality bone formation. In this work, we fabricated biocompatible and safe chitosan (CS)/hyaluronic acid (HA) nanoparticles (NPs) to deliver microRNA-21 (miR-21), which has been proved to accelerate osteogenesis in hBMMSCs; then, the CS/HA/miR-21 NPs were cross-linked onto the surfaces of culture plates with 0.2% gel solution to fabricate miR-21-functionalized culture plates for reverse transfection. hBMMSC sheets were induced continuously for 14 days using a vitamin C-rich method on the miR-21-functionalized culture plates. For the characterization of CS/HA/miR-21 NPs, the particle size, zeta potential, surface morphology, and gel retardation were sequentially investigated. Then, the biological effects of hBMMSC sheets on the miR-21-functionalized culture plates were evaluated. The assay results demonstrated that the hBMMSC sheets could be successfully induced via the novel reverse transfection approach, and miR-21 delivery significantly enhanced the in vitro osteogenic differentiation of hBMMSC sheets in terms of upregulating calcification-related gene expression and enhancing alkaline phosphatase production, collagen secretion, and mineralized nodule formation. The enhanced osteogenic activity of hBMMSC sheets might promisingly lead to more rapid and more robust bone regeneration for clinical use. Keywords: human bone marrow MSCs, cell sheets, microRNA, chitosan, nanoparticles, osteogenic differentiatio
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