Electrical Measurements of an AlGaN/GaN High-electron-mobility Transistor Structure Grown on Si

Zhi-Yao Zhang,Shun-Tsung Lo,Li-Hung Lin,Kuang Yao Chen,J. Z. Huang,Zhi-Hao Sun,C.-T. Liang,N. C. Chen,Chin-An Chang,P. H. Chang 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.9

We report on magnetotransport results for an Al_0.15Ga_0.85N/GaN high-electron-mobility-transistor structure grown on a p-type Si (111) substrate. Our results show that there exists an approximately temperature (<i>T</i>)-independent point, which could be ascribed to a direct transition from a weak insulator to a high Landau level filling factor quantum Hall state, exists in the longitudinal resistivity ρ_xx. The Hall resistivity decreases with increasing <i>T</i>, compelling experimental evidence for electron-electron interaction effects in a weakly-disordered two-dimensional (2D) system. We find that electron-electron interaction effects can be estimated and eliminated, giving rise to a corrected nominally temperature-independent Hall slope. By fitting the low-field magnetotransport data to conventional 2D weak localization theory, we find that the dephasing rate 1/τ_φ is proportional to <i>T</i>. Moreover, 1/τ_φ is finite as <i>T</i> → 0, evidence for zero-temperature dephasing in our system.

Development of a High-Frequency Discharge Power Source with Non-Equal Energy Relaxation Oscillator Circuit Applied to β-Ga2O3 Microstructure Array Wire Electric Discharge Machining

Shun-Tong Chen,Shih-Yao Chen 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.10 No.6

A high-frequency discharge power source with non-equal energy relaxation oscillator circuit is proposed in this study. An experiment based on gallium oxide (Ga2O3) and an aluminum alloy microstructure array is devised to verify the machining performance of the power source. Signals are sent by a field-programmable gate array (FPGA) for the control of an N-MOSFET load switch, thus determining when the power source charged and discharged to generate a discharge waveform with narrow pule width and alternating high and low peaks. Compared to a conventional RC discharge circuit, the proposed design generated a pulse train with a regular and dense pattern and created high-density and tiny-energy high-temperature plasma. The experiment was performed with a high-frequency discharge energy pulse train designed with alternating high and low-peaks to examine the machining performance of the discharge source for pyrolytic Ga2O3 material including: the best-fit capacitance combination, feed-rate of wire-electrode, material removal rate, kerf width and spark erosion capability. The experiment’s results revealed that the design high-frequency relaxation oscillator circuit successfully generated surface microstructure arrays and pillared microstructure with outstanding dimensional accuracy and consistence. Clearly, the application of the proposed high-frequency power source proposed performed admirably in spark erosion in addition to its high-efficiency, -controllability, and -stability, and it prevented thermal damage to microstructures. The workpiece’s polarity, surface roughness, material removal mechanism, surface degenerating layer and discharging performance of metal and semiconductor are analyzed both quatitatively and qualitatively.

Direct Adaptive Fuzzy Sliding Mode Control for Under-actuated Uncertain Systems

Shun-Feng Su,Yao-Chu Hsueh,Cio-Ping Tseng,Song-Shyong Chen,Yu-San Lin 한국지능시스템학회 2015 INTERNATIONAL JOURNAL of FUZZY LOGIC and INTELLIGE Vol.15 No.4

The development of the control algorithms for under-actuated systems is important. Decoupled sliding mode control has been successfully employed to control under-actuated systems in a decoupling manner with the use of sliding mode control. However, in such a control scheme, the system functions must be known. If there are uncertainties in those functions, the control performance may not be satisfactory. In this paper, the direct adaptive fuzzy sliding mode control is employed to control a class of under-actuated uncertain systems which can be regarded as a combination of several subsystems with one same control input. By using the hierarchical sliding control approach, a sliding control law is derived so as to make every subsystem stabilized at the same time. But, since the system considered is assumed to be uncertain, the sliding control law cannot be readily facilitated. Therefore, in the study, based on Lyapunov stable theory a fuzzy compensator is proposed to approximate the uncertain part of the sliding control law. From those simulations, it can be concluded that the proposed compensator can indeed cope with system uncertainties. Besides, it can be found that the proposed compensator also provide good robustness properties.

Photocatalytic degradation of dyes using dioxygen activated by supported metallophthalocyanine under visible light irradiation

Yuyuan Yao,Zhenfu Huang,Binbin Zheng,Shun Zhu,Wangyang Lu,Wenxing Chen,Haixiang Chen 한국물리학회 2013 Current Applied Physics Vol.13 No.8

Zinc tetraaminophthalocyanine (Zn-TAPc) modified by cyanuric chloride was immobilized on silk fibers by covalent bond to obtain a supported photocatalyst (Zn-TDTAPc-SF). The photocatalytic degradation of acid orange II based on Zn-TDTAPc-SF/O2 system was investigated under visible light irradiation (λ ≥ 400 nm). The results indicated that Zn-TDTAPc-SF exhibited excellent photocatalytic performance in the presence of O2 under visible light irradiation. In 6 h, more than 93% of acid orange II (AO2) in Zn-TDTAPc-SF/O2 systemwas eliminated at initial pH 5 under visible light irradiation, and Zn-TDTAPc-SF still remained effective in repetitive fives cycles. Furthermore, NaCl played a positive role in the catalytic reaction, different from the negative one observed in homogeneous catalysis, and the reaction can proceed in a more wide pH range from acidic to alkaline. Based on the analysis of FT-IR and Gas Chromatography/Mass Spectrometry (GCeMS), AO2 was mainly converted into some small molecular biodegradable aliphatic carboxylic compounds such as maleic acid, fumaric acid, succinic acid, etc. The photodegradation mechanism for the evolution of AO2 was proposed by Electron Paramagnetic Resonance (EPR) spectra.

Direct Adaptive Fuzzy Sliding Mode Control for Under-actuated Uncertain Systems

Su, Shun-Feng,Hsueh, Yao-Chu,Tseng, Cio-Ping,Chen, Song-Shyong,Lin, Yu-San Korean Institute of Intelligent Systems 2015 INTERNATIONAL JOURNAL of FUZZY LOGIC and INTELLIGE Vol.15 No.4

The development of the control algorithms for under-actuated systems is important. Decoupled sliding mode control has been successfully employed to control under-actuated systems in a decoupling manner with the use of sliding mode control. However, in such a control scheme, the system functions must be known. If there are uncertainties in those functions, the control performance may not be satisfactory.In this paper, the direct adaptive fuzzy sliding mode control is employed to control a class of under-actuated uncertain systems which can be regarded as a combination of several subsystems with one same control input. By using the hierarchical sliding control approach, a sliding control law is derived so as to make every subsystem stabilized at the same time. But, since the system considered is assumed to be uncertain, the sliding control law cannot be readily facilitated. Therefore, in the study, based on Lyapunov stable theory a fuzzy compensator is proposed to approximate the uncertain part of the sliding control law. From those simulations, it can be concluded that the proposed compensator can indeed cope with system uncertainties. Besides, it can be found that the proposed compensator also provide good robustness properties.

How Can South Asia and Sub-Saharan Africa Gain From the Next WTO Round?

Anderson, Kym,Yao, Shunli 세종대학교 국제경제연구소 2003 Journal of Economic Integration Vol.18 No.3

If South Asia and Sub-Saharan Africa are to become constructively engaged in the next attempt by World Trade Organization(WTO) members to liveralize trade multilaterally, they need to be convinced that there will ve sufficient gains from trade reform to warrant the inevitable costs of negotiation and adjustment. This paper provides new estinates of the likely economic effects on their evonomies of further liberalizing world trade post-Uruguay Round. The results show that the developing countries of South Asia and Sub-Sanaran Africa have much to gain from taking part in the next round. However, those gains will ve far greater the more those countries are willing to embrace regorm at home so as to enable their firms to take greatest advantage of the opportunities provided by the opening up of markets abroad.

Machining characteristics of USV-MF complex assisted WEDM-LS based on multi-physical coupling

Yan Wang,Shun-wen Yao,Zi-jun Ding,Chen-zhen Wu,Wei Xiong 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.2

Ultrasonic vibration (USV) and magnetic field (MF) complex assisted techniques are combined with low speed wire electrical discharge machining (USV-MF complex assisted WEDM-LS) to improve the machining performance of conventional WEDM-LS. Firstly, the simulation results of multi-physical coupling simulation model show that under the influence of ultrasonic vibration, the working fluid fluidity is greatly enhanced and its temperature is significantly decreased. Then, a three-phase flow model of bubble, working fluid and debris in the machining area is established to investigate the effects of ultrasonic vibration on bubble and debris, and the process of bubble rupture is simulated. The simulation results show that with the increase of ultrasonic frequency, the movement of bubble and debris becomes fiercer and fiercer, when ultrasonic frequency is 30 kHz and ultrasonic amplitude is 10 μm, the bubble is collapsed. Finally, comparison of the experimental results of conventional WEDM-LS, USV assisted WEDM-LS, MF assisted WEDM-LS and USV-MF complex assisted WEDM-LS in machining TiNi-01 shape memory alloy reveals that the ratio of normal discharge and the material removal rate are both increased, the workpiece surface roughness value is decreased and the workpiece surface quality is improved in the process of USV-MF complex assisted WEDM-LS.

How Can South Asia and Sub-Saharan Africa Gain From the Next WTO Round?

( Kym Anderson ),( Shun Li Yao ) 세종대학교 경제통합연구소 (구 세종대학교 국제경제연구소) 2003 Journal of Economic Integration Vol.18 No.3

If South Asia and Sub-Saharan Africa are to become constructively engaged in the next attempt by World Trade Organization (WTO) members to liberalize trade multilaterally, they need to be convinced that there will be sufficient gains from trade reform to warrant the inevitable costs of negotiation and adjustment. This paper provides new estimates of the likely economic effects on their economies of further liberalizing world trade post-Uruguay Round. The results show that the developing countries of South Asia and Sub-Saharan Africa have much to gain from taking part in the next round. However, those gains will be far greater the more those countries are willing to embrace reform at home so as to enable their firms to take greatest advantage of the opportunities provided by the opening up of markets abroad.

THE ROLE OF REAL-TIME ULTRASONOGRAPHIC UNIT IN NUCLEAR MEDICINE DIVISION TO IMPROVE THE DIAGNOSTIC ACCURACY OF THE INTRAHEPATIC MASS LESION - A PROPOSAL

Liao, Sun Quinn,Yao, Wei Jen,Wu, Chih Shun 대한핵의학회 1984 핵의학 분자영상 Vol.18 No.1

A snapback‑free reverse‑conducting IGBT with multiple extraction channels

Weizhong Chen,Xuwei Lin,Shun Li,Yao Huang,Yi Huang,Zhengsheng Han 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.2

A novel Reverse-Conducting Insulated Gate Bipolar Transistor (RC-IGBT) with Multiple Extraction Channels (MEC) is proposed and investigated. The MEC is characterized by two transistors NPN1 (Nbuffer/Pbarrier/Ncollector), NPN2 (Nbuffer/Pfloat/Npoly) and short Rgap in the collector. The P-Collector, N-Collector, polysilicon and Rgap are shorted together, thus the NPN1, NPN2 and Rgap are parallel with the PNP transistor (Pbody/Nbuffer/Pcollector). At the forward conduction, the unipolar mode is effectively suppressed by the electron barriers P-barrier (the base of the NPN1) and P-float (the base of the NPN2), thus the snapback effect can be completely eliminated. At the turn-off, the electrons are quickly extracted by three channels of the NPN1, NPN2 and Rgap, thus the Eoff can be remarkably decreased. Results show at the same Von of 2.8 V, the Eoff of the MEC RC-IGBT is reduced by 20%, 37%, 45% and 59% compared to AB, FPL, DFS and TOC RC-IGBT, respectively. Therefore the excellent trade-off characteristics with snapback free are achieved.