Browsing by Author "Tsai, Chih-Hung"

Now showing 1 - 15 of 15

A Multitheragnostic Nanobubble System to Induce Blood-Brain Barrier Disruption with Magnetically Guided Focused Ultrasound
(2015-01-27)
Huang, Hsin-Yang
;
Liu, Hao-Li
;
Hsu, Po-Hung
;
Chiang, Chih-Sheng
;
Tsai, Chih-Hung
A study of developing an input-oriented ratio-based comparative efficiency model
(2011-03-01)
Wei, Ching-Kuo
;
Chen, Liang-Chih
;
Li, Rong-Kwei
;
Tsai, Chih-Hung
;
工業工程與管理學系
Data envelopment analysis (DEA) is a representative method to estimate efficient frontiers and derive efficiency. However, in a situation with weight restrictions on individual input-output pairs, its suitability has been questioned. Therefore, the main purpose of this paper is to develop a mathematical method, which we call the input-oriented ratio-based comparative efficiency model, DEA-R-I, to derive the input-target improvement strategy in situations with weight restrictions. Also, we prove that the efficiency score of DEA-R-I is greater than that of CCR-I, which is the first and most popular model of DEA, in input-oriented situations without weight restrictions to claim the DEA-R-I can replace the CCR model in these situations. We also show an example to illustrate the necessity of developing the new model. In a nutshell, we developed DEA-R-I to replace CCR-I in all input-oriented situations because it sets a more accurate weight restriction and yields a more achievable strategy. (C) 2010 Elsevier Ltd. All rights reserved.
A study of optimal weights of Data Envelopment Analysis - Development of a context-dependent DEA-R model
(2012-03-01)
Wei, Ching-Kuo
;
Chen, Liang-Chih
;
Li, Rong-Kwei
;
Tsai, Chih-Hung
;
Huang, Hsiao-Ling
The weight is one of the main issues of Data Envelopment Analysis (DEA), and relevant theoretical research indicates that many DEA mathematical models include redundant restraints on weight, resulting in underestimated efficiency, pseudo inefficiency, and difficulty in representing specific Input/Output relationships. This study proposes a context-dependent DEA-R model to address shortcomings resulting from redundant restraints on the weights of an efficient decision making unit (DMU), and converts the optimal weight to analyze the influences of redundant restraints on weights. The evaluation results of Taiwan medical centers show that the efficiency of the DMU is underestimated and pseudo inefficiency may occur due to redundant restraints on weight. Moreover, optimal weights are used as variables to conduct cluster analysis in order to determine the information of the weights. The results of cluster analysis indicate that it can assist DMUs in understanding the relationships between DMUs, and contribute to the development of a unique survival strategy for hospitals. (C) 2011 Elsevier Ltd. All rights reserved.
Controlled mechanical cleavage of bulk niobium diselenide to nanoscaled sheet, rod, and particle structures for Pt-free dye-sensitized solar cells
(2014)
Ibrahem, Mohammed Aziz
;
Huang, Wei-Chih
;
Lan, Tian-wey
;
Boopathi, Karunakara Moorthy
;
Hsiao, Yu-Chen
In this study, we report a one-step process for the preparation of NbSe2 nanosheets, nanorods and nanoparticles from pristine materials under the effects of shear and friction forces. Nevertheless, simple and facile methods for the large-scale syntheses of well-defined NbSe2 nanostructures in high yield have yet to be realized and that will have a great impact in a wide range of applications. For example, developing platinum (Pt)-free and highly efficient counter electrodes is meaningful and necessary for the cost reduction of dye-sensitized solar cells (DSSCs). By integrating this approach with a simple method of thin film preparation (spray coating) allowed us to prepare large-area, conductive, semitransparent flexible thin films of NbSe2. We have used microscopic and macroscopic methods to examine the morphologies, compositions, crystallinity, and electrical and optical properties of the converted NbSe2 nanostructures. DSSCs with NbSe2 nanosheet counter electrodes (CEs) achieved a conversion efficiency of 7.73%, superior to an efficiency of 7.01% for Pt-based CEs. Our NbSe2 nanostructure provides a cost-effective CE alternative to the noble metal Pt in DSSCs.
Effect of SiO2 Buffer Layer Thickness on Performance and Reliability of Flexible Polycrystalline Silicon TFTs Fabricated on Polyimide
(2016-12-01)
Chen, Bo-Wei
;
Chang, Ting-Chang
;
Hung, Yu-Ju
;
Huang, Shin-Ping
;
Chen, Hua-Mao
This letter investigates flexible polycrystalline silicon thin film transistor performance variation due to different buffer layer thicknesses. In flexible electronics, thermal expansion stress during device fabrication is inevitable. A thicker SiO2 buffer demonstrates better endurance to thermal expansion stress from the polyimide substrate during device annealing. However, if the SiO2 buffer thickness is above a critical point, its weak heat dissipation capability causes the optimal ELA crystallization condition to shift. A thermal expansion stress simulation and TEM photos were utilized to verify performance variation. Furthermore, a similar trend was observed in electrical characteristics after negative bias temperature instability.
Efficiency evaluation of a hybrid miniaturized concentrated photovoltaic for harvesting direct/diffused solar light
(2019-03-01)
Tsao, Wei-Chen
;
Zeng, Qiu-Chun
;
Yeh, Yu-Hsiang
;
Tsai, Chih-Hung
;
Hong, Hwen-Fen
In this paper, a miniaturized concentrator photovoltaic (CPV) system is experimentally demonstrated based on a hot embossing silicone lens array with a size of 2 cm x 2 cm. Owing to the small size of the lens array, the total track of the CPV system can be as small as 4 cm. Consequently, the weight of the CPV system can be much lower than conventional bulky CPV system. For harvesting the diffuse solar radiation, perovskite solar cells are mounted adjacent to a multi junction solar cell. Theoretically, the short-circuit current of the CPV system can be enhanced from 48.1 to 85.5 mA for gamma = 0.7. The enhancement can be much higher for off-normal incident light. This kind of hybrid CPV system will be useful for cloudy weather and also useful for compensating the loss caused by the miss-alignment of the tracking module.
Exploration of efficiency underestimation of CCR model: Based on medical sectors with DEA-R model
(2011-04-01)
Wei, Ching-Kuo
;
Chen, Liang-Chih
;
Li, Rong-Kwei
;
Tsai, Chih-Hung
;
工業工程與管理學系
Data Envelopment Analysis (DEA) is one of the best-known efficiency evaluation methods due to its advantages in selection of weights. Many research papers have extensively discussed the issue of weight restrictions, rather than those implied in the model itself. However, this often leads to a failure to represent the relations of certain weights, as well as underestimation of the efficiency of Decision Making Units (DMUs). When analyzing the medical sectors of Taiwan with the developed models and CCR, it is found that efficiency underestimation by efficient DMUs is more serious than that of inefficient DMUs. In addition, underestimation occurs when weights are concentrated in the same output, however, every output of referenced DMU is the same times of corresponding output of targeted DMU. (C) 2010 Elsevier Ltd. All rights reserved.
Highly stable organic light emitting devices based on uniformly mixed hole transport layer
(2005)
Tsai, Chih-Hung
;
Liao, Chi-Hung
;
Chen, Chin-H.
;
友訊交大聯合研發中心
;
D Link NCTU Joint Res Ctr
High stable organic light emitting devices (OLEDs) can be achieved by using an Uniformly Mixed Hole transport layer (UM-HTL) composed of a mixture of 2-methyl-9,10-di(2-naphthyl)anthracene (MADN) with N,N'-bis(1-naphthyl)-N,N'-diphenyl, 1,1'-biphenyl-4, 4'-diamine (NPB) in a 4:6 ratio of MADN:NPB. Compared to OLEDs using the conventional structure (t(90) = 1500 h) the lifetime of green tris(8-hydroxyquinoline) aluminum (Alq(3)) device using the UM-HTL can be improved to about 3 times (t(90) = 4420 h). Consequently utilizing the UM-HTL in OLEDs can effectively depress device degradation without impacting on the driving voltage and the color saturation significantly.
Improved stability of C-545T doped green OLEDs
(2005)
Lee, Meng-Ting
;
Liao, Chi-Hung
;
Tsai, Chih-Hung
;
Chen, Chin-H.
;
應用化學系
The stability of C-545T doped green organic electroluminescent device (OLED) has been improved by doping styrylamine derivate, p-bis(p-N,N-diphenyl-aminostyryl)benzene (DSA-Ph) benzene (DSA-Ph) in hole transporting layer, the device configuration abbreviated as BHTL. Compared with the undoped device, the stability of the BHTL device has increased by a factor of 1.3 without affecting the electroluminescence (EL) efficiency of 11 cd/A and color (CIEx,y = 035, 0.61). The enhanced stability is believed to derive from the hole trapping nature of DSA-Ph which can reduce the residual hole carriers in tris(8-hydroquinolinato)aluminum (Alq(3)) and suppress the formation of florescent quencher of Alq(3) cationic species.
Intriguing field-effect-transistor performance of two-dimensional layered and crystalline CrI3
(2020-03-01)
Patil, Ranjit A.
;
Tu, Hao-Wei
;
Jen, Ming-Hsing
;
Lin, Jing-Jia
;
Wu, Ching-Cherng
There are many candidate materials that can be used as channel materials for the next-generation field effect transistors (FETs). CrI3 is one of the particular candidates for application in FET, because it is a two-dimensional (2D) ferromagnet and has giant tunneling magnetoresistance. The ferromagnetic nature extends to not only electronics but also spintronics. In this study, the large-area, layered, and crystalline 2D CrI3 were synthesized by horizontal Bridgman method. The suspended CrI3 FETs were fabricated for explorations of intrinsic electron transport in the CrI3 channel and of electrical contact problems. The suspended FET structure lets the CrI3 channel free from trapping charges in the SiO2-capped Si substrate. The oneoff ratio of the suspended CrI3 FET is up to 10(4), making the 2D layered CrI3 potential for future FETs. The investigations of the mobility and the interface-trap density at various temperatures reveal that the trapping charges as well as the interface-trap densities are increased with further gas adsorption on the surface of the CrI3 flake. The performance of the suspended CrI3 FET can be improved, if the gas adsorption problem can be carefully treated. (c) 2020 Elsevier Ltd. All rights reserved.
Reliability improvement of InGaZnO thin film transistors encapsulated under nitrogen ambient
(2012-04-09)
Wu, Chun-Yu
;
Cheng, Huang-Chung
;
Wang, Chao-Lung
;
Liao, Ta-Chuan
;
Chiu, Po-Chun
The nitrogen ambient encapsulation (NAE) technique is introduced to improve the reliability issue for the amorphous InGaZnO (a-IGZO) thin-film transistors under positive gate bias stress (PGBS). For the NAE devices, the threshold voltage (Vth) shift is significantly decreased from 1.88 to 0.09 V and the reduction of saturation drain current is improved from 15.75 to 5.61 mu A as compared to the bare a-IGZO counterparts after PGBS. These improvements are attributed to the suppression of negatively charged oxygen adsorption on the a-IGZO backsurface and thereby well maintain the channel potential of NAE devices, which in turn sustain the Vth during PGBS. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3702794]
Research on enhancement of TOC Simplified Drum-Buffer-Rope system using novel generic procedures
(2010-05-01)
Lee, Jun-Huei
;
Chang, Jia-Ging
;
Tsai, Chih-Hung
;
Li, Rong-Kwei
;
工業工程與管理學系
The Theory of Constraints (TOC) Simplified Drum-Buffer-Rope (SDBR) system works effectively in typical job shop environments. However, according to the experiences implementing SDBR system in local companies, such environments have the following characteristics, which may block SDBR implementation: (1) capacity constraint resources (CCR) is not always located in the middle of the routing as assumed in SDBR. The CCR can be located in either the front or back end of routing; (2) multiple or interactive CCRs can exist rather than the assumption of just one CCR; (3) order insertion, including urgent orders, change in due-date (especially bringing it forward) is common. Two ways may be applied to overcome these characteristics: (1) move back to a traditional DBR; (2) address problems through the buffer management process. However, both these ways have limitations and complexities. This paper presents an alternative method enhancing SDBR system performance. With the enhancement, we expect that SDBR can be adopted by more companies, especially those that have the same characteristics. (C) 2009 Elsevier Ltd. All rights reserved.
Surface Engineering of Polycrystalline Silicon for Long-Term Mechanical Stress Endurance Enhancement in Flexible Low Temperature Poly-Si Thin-Film Transistors
(2017-04-05)
Chen, Bo-Wei
;
Chang, Ting-Chang
;
Chang, Kuan-Chang
;
Hung, Yu-Ju
;
Huang, Shin-Pin
The surface morphology in polycrystalline silicon (poly-Si) film is an issue regardless of whether conventional excimer laser annealing (ELA) or the newer metal-induced lateral crystallization (MILC) process is used. This paper investigates the stress distribution while undergoing longterm mechanical stress and the influence of stress on electrical characteristics. Our simulated results show that the nonuniform stress in the gate insulator is more pronounced near the polysilicon/gate insulator edge and at the two sides of the polysilicon protrusion. This stress results in defects in the gate insulator and leads to a nonuniform degradation phenomenon, which affects both the performance and the reliability in thin-film transistors (TFTs). The degree of degradation is similar regardless of bending axis (channel-length axis, channel-width axis) or bending type (compression, tension), which means that the degradation is dominated by the protrusion effects. Furthermore, by utilizing long-term electrical bias stresses after undergoing long-tern bending stress, it is apparent that the carrier injection is severe in the subchannel region, which confirms that the influence of protrusions is crucial. To eliminate the influence of surface morphology in poly-Si, three kinds of laser energy density were used during crystallization to control the protrusion height. The device with the lowest protrusions demonstrates the smallest degradation after undergoing long-term bending.
USING GAME AND STATISTICAL ANALYSIS TO CONFIRM GOLDRATT'S LOGICAL ANALYSIS OF POOR DELIVERY IN A MULTI-PROJECT ENVIRONMENT
(2011-11-01)
Huang, Chia-Ling
;
Chang, Hao-Ging
;
Li, Rong-Kwei
;
Tsai, Chih-Hung
;
工業工程與管理學系
The objective of this study is to confirm Goldratt's logical analysis of poor delivery in a multi-project environment. Two hundred and ten experienced managers were invited to participate in a multi-project management game that simulates reality. A statistical analysis of the experimental data of this study indicates that the mode of project planning and execution (unrealistic project planning, a lack of clear working priorities, misuse of safety time, and bad multi-tasking), not uncertainty, is the root cause of poor delivery, and should therefore be improved first. The result confirmed Goldratt's logical analysis of poor delivery in project management.
Using the DEA-R model in the hospital industry to study the pseudo-inefficiency problem
(2011-03-01)
Wei, Ching-Kuo
;
Chen, Liang-Chih
;
Li, Rong-Kwei
;
Tsai, Chih-Hung
;
工業工程與管理學系
Because of the unreasonable and unnecessary weight restriction assumption, a barely noticeable deficiency in pseudo-inefficiency occurs at times when applying a CCR model. The CCR was the first model designed for Data Envelopment Analysis (DEA); it remains its most popular model. To detect this type of unobvious deficiency, this study compared the following; the efficiency score and optimal weight set of an input oriented CCR model (CCR-I); the model with a weight restriction assumption; an input-oriented ratio-based DEA model (DEA-R-I); and the model without it. In this case study of hospitals, pseudo-inefficiency was discovered and the reason behind it determined. Further, this study proved that the DEA-R-I is a valid model. Because DEA-R-I is valid and without a weight restriction assumption, this study puts forward the DEA-R-I as a capable substitutive model for CCR-I in order to avoid pseudo-inefficiency. (C) 2010 Elsevier Ltd. All rights reserved.