Split-Capacitor Self-Balancing of Single-Phase Half-Bridge Inverters

Che-Wei Chang,Terng-Wei Tsai,Yaow-Ming Chen 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

This paper uncovers the mechanism of the unbalanced split capacitor voltage caused by the deviation of the sensing signal. For the single-phase half-bridge (SPHB) inverter, the deviation of the sensing signal will lead to an offset on the output current and further causes the deviation of split capacitor voltage. However, this unbalance capacitor voltage will help to compensate the output current offset. Consequently, the capacitor voltages will drift to a certain stable voltage level, which is commonly called the selfbalancing effect. This paper presents the precise mathematical equations by analyzing the self-balancing mechanism and accurately predict the value of capacitor voltage variations. Computer simulations and hardware experimental results of a 1kVA SPHB inverter are shown to verify the accuracy of the mathematical equations.

Phase transition and energy transfer of lead-free Cs2SnCl6 perovskite nanocrystals by controlling the precursors and doping manganese ions

Tsai-Wei Lin,Chaochin Su,Chun Che Lin 한국정보디스플레이학회 2019 Journal of information display Vol.20 No.4

Perovskite quantum dots (QDs), such as all-inorganic CsPbX3 (X = Cl, Br, and I), are novel fluorescent semiconductor nanocrystals (NCs) that have attracted tremendous attention due to their excellent optical properties and great applications (e.g. display backlights, light-emitting diodes, and photodetectors). The instability and toxicity of lead-based perovskite QDs, however, are intrinsic defects that obstruct their application and commercialization. Poison is released from the lead of the unstable CsPbX3 NCs, which are generally ascribed to the labile surface, ionic character, and metastable structure. In this work, lead-free Cs2SnCl6 perovskite NCs are successfully synthesized via hot injection. Particularly, by controlling the different precursor ratios, phase transition (CsCl to Cs2SnCl6) was clearly observed from X-ray diffraction (XRD) measurements. The Cs2SnCl6 NCs exhibited a highly efficient deep-blue emission at 425 nm, with a 55nm Stokes shift and an 84nm full width at half maximum (FWHM). After doping Mn ions, the preferred formation of CsSnCl3:Mn2+ with double-wavelength emission was demonstrated based on the XRD and photoluminescence spectra. The study showed that doping synthesis should be widely used in lead-free perovskite NCs as an important strategy for next-generation solid-state lighting.

Can Elderly Patients with Severe Mitral Regurgitation Benefit from Trans-catheter Mitral Valve Repair?

Ching-Wei Lee,Shih-Hsien Sung,Wei-Ming Huang,Yi-Lin Tsai,Hsiang-Yao Chen,Chiao-Po Hsu,Chun-Che Shih,Kuo-Piao Chung 대한심장학회 2019 Korean Circulation Journal Vol.49 No.6

Background and ObjectivesAge is a traditional risk factor for open-heart surgery. The efficacy and safety of transcatheter edge-to-edge mitral valve repair, using MitraClip (Abbott Vascular), has been demonstrated in patients with severe mitral regurgitation (MR). Since octogenarians or older patients are usually deferred to receive open-heart surgery, the main interest of this study is to elucidate the procedural safety and long-term clinical impact of MitraClip in elderly patients. MethodsPatients with symptomatic severe MR were evaluated by the heart team. For those with high or prohibitive surgical risks, transcatheter mitral valve repair was performed in hybrid operation room. Transthoracic echocardiography (TTE), blood tests, and six-minute walk test (6MWT) were performed before, 1-month, 6-months, and 1 year after index procedure. ResultsA total of 46 consecutive patients receiving MitraClip procedure were enrolled. Nineteen patients (84.2±4.0 years) were over 80-year-old and 27 (73.4±11.1 years) were younger than 80. Compare to baseline, the significant reduction in MR severity was achieved after the procedure and sustained. All the patients benefited from significant improvement in New York Heart Association functional class. The 6-minute walk test (6MWT) increased from 259±114 to 319±92 meters (p=0.03) at 1 year. The overall 1-year survival rate was 80% in the elderly and 88% in those <80 years, p=0.590. Baseline 6MWT was a predictor for all-cause mortality (odds ratio, 0.99; 95% confidence interval, 0.982–0.999; p=0.026) after the MitraClip procedure. ConclusionsTrans-catheter edge-to-edge mitral valve repairs are safe and have positive clinical impact in subjects with severe MR, even in advanced age.

Grasping the Pseudo-Cleft in the Case of a Small, Severely Tethered Posterior Mitral Leaflet

Ching-Wei Lee,Shih-Hsien Sung,Ting-Yung Chang,I-Lin Tsai,Chih-Po Hsu,Chun-Che Shih 대한심장학회 2017 Korean Circulation Journal Vol.47 No.4

Online Experts Screening the Worst Slicing Machine to Control Wafer Yield via the Analytic Hierarchy Process

( Chin Tsai Lin ),( Che Wei Chang ),( Cheng Ru Wu ),( Huang Chu Chen ) 한국품질경영학회 2006 The Asian Journal on Quality Vol.7 No.2

Online Experts Screening the Worst Slicing Machine to Control Wafer Yield via the Analytic Hierarchy Process

Lin, Chin-Tsai,Chang, Che-Wei,Wu, Cheng-Ru,Chen, Huang-Chu The Korean Society for Quality Management 2006 The Asian Journal on Quality Vol.7 No.2

This study describes a novel algorithm for optimizing the quality yield of silicon wafer slicing. 12 inch wafer slicing is the most difficult in terms of semiconductor manufacturing yield. As silicon wafer slicing directly impacts production costs, semiconductor manufacturers are especially concerned with increasing and maintaining the yield, as well as identifying why yields decline. The criteria for establishing the proposed algorithm are derived from a literature review and interviews with a group of experts in semiconductor manufacturing. The modified Delphi method is then adopted to analyze those results. The proposed algorithm also incorporates the analytic hierarchy process (AHP) to determine the weights of evaluation. Additionally, the proposed algorithm can select the evaluation outcomes to identify the worst machine of precision. Finally, results of the exponential weighted moving average (EWMA) control chart demonstrate the feasibility of the proposed AHP-based algorithm in effectively selecting the evaluation outcomes and evaluating the precision of the worst performing machines. So, through collect data (the quality and quantity) to judge the result by AHP, it is the key to help the engineer can find out the manufacturing process yield quickly effectively.

Screening Synchronously Occurred Multiple Abnormal Quality Characteristics in a Silicon Wafer Slicing Process

Lin, Chin-Tsai,Chen, Chie-Bein,Chang, Che-Wei 한국품질경영학회 2002 The Asian Journal on Quality Vol.3 No.1

Silicon wafer slicing manufacturing process exhibits several characteristics. They are: (1) the product type is small batch production, (2) saw cutting must be very precise, (3) the process run time is long, and (4) inspecting samples is difficult. Furthermore, the process involves several synchronously occurred multiple quality characteristics, such as thickness(THK), bow and warp, which must be closely monitored and controlled. Synchronously monitoring multiple quality characteristics is more expensive than monitoring a single quality characteristic in the manufacturing process. The sizes of inspected samples in the existing process are difficult to maintain the quality control chart. Grey situation decision method is used to screen the worst quality characteristic from the synchronously occurred multiple quality characteristics to monitor the process. Finally, a case study is presented to demonstrate the feasibility and effectiveness of proposed decision method. The exponential weighted moving average (EWMA) control chart is used to verify that the process quality is more reliable.

The Effect of Monetary Policies on the Relationship between Advertising and Mutual Fund Flows

Ming-Hung Wu,Wei-Che Tsai,Miao-Ling Chen 한국증권학회 2016 Asia-Pacific Journal of Financial Studies Vol.45 No.5

This paper investigates the effect of monetary policies, mainly proxied by interest rate changes, on the relationship between advertising and subsequent net cash flows for Taiwan’s mutual fund industry. Based on a comprehensive mutual fund dataset and allowing for a precise estimation of fund inflows and outflows, we find that there is a positive advertising–cash flow relation under different macroeconomic conditions. Taking into account a change in the interest rate, we document that the positive relationship between the two only exists when the interest rate is at a relatively low level regardless of restrictive and expansionary periods. Our empirical findings shed new light on marketing strategies whereby mutual fund advertising works well during relatively low interest rate environments, which are generally interpreted as exhibiting low cost of capital and a good signal of future economic conditions.

The Impact of Derivatives Hedging on Stock Market : Evidence from Taiwan Covered Warrants Market

San-Lin Chung,Wen-Ranq Liu,Wei-Che Tsai 한국재무학회 2011 한국재무학회 학술대회 Vol.2011 No.09

This paper examines the hedging impact on the underlying stock market using a comprehensive dataset of covered warrants traded in the Taiwan Stock Exchange (TWSE). Since TWSE requires the warrant issuers to conduct dynamic hedging over the life of warrants, we can estimate the number of shares bought or sold for rebalancing the hedging portfolio and measure its impact. We find significant positive abnormal returns and trading volumes before the announcement day of warrants issuance, suggesting that issuers establish their hedging portfolios before the announcement day. The magnitude of the price effect is positively related to the size of the hedging portfolio. Moreover, there is a significantly positive relationship between stock return volatility and the price elasticity of hedging demand (defined as the percentage of shares needed for rebalancing hedge portfolio when the underlying stock price changes 1%). Finally, we also observe significantly negative price effect to the underlying stock before (after) the expiration date for call warrants that are expired out-of-the-money (in-the-money). For call warrants expired in-the-money, the negative price impact is due to the fact that warrants traded in TWSE are cash settlement when exercised, and thus the issuers have to liquidate the hedging portfolio after expiration, which results in selling pressure on the underlying stock.

The impacts of day trading activity on market quality: evidence from the policy change on the Taiwan stock market

( Tun-ya Yang ),( Si-yuan Huang ),( Wei-che Tsai ),( Pei-shih Weng ) 한국파생상품학회(구 한국선물학회) 2020 선물연구 Vol.28 No.4

This paper aims to investigate the impact of day trading on market quality on the Taiwan stock market with the implementation of a unique policy change. This paper examines 396 listed stocks from June 2015 to October 2016, a period when the stock market in Taiwan officially approved selected stocks for day trading for all investors. Within the sample period, the empirical findings show that day trading increases the bid-ask spread, price depth and stock volatility, indicating that day trading activities not only cause higher transaction costs and trading risk but also raise the market’s ability to absorb price impact. This paper considers two-stage regression and tests the exogenous shock because of further relaxation for day trading to deal with the possible endogenous problem and the main findings remain consistent. Since early 2014, the Taiwan stock market has been experiencing a distinct growth in trading volume after unwinding the day trading; however, the results show that the impacts of stock day trading on market quality are not all positive.