Antenna Selection for MIMO-OFDM Systems in Correlated Channels

Chia-Chang Hu,Hao-Yun Yang 대한전자공학회 2009 ITC-CSCC :International Technical Conference on Ci Vol.2009 No.7

In the paper, the joint transceiver antenna selection schemes for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems are addressed in the broadband correlated channels. Modified antenna selection methods for frequency-selective fading channel are proposed and analyzed in this paper. Consequently, the use of the proposed modified antenna selection algorithms achieve a substantial saving in system-hardware complexity of the multiple radio frequency (RF) chains associated with multiple antennas without compromising overall system-capacity performance.

The coupled vibration in a rotating multi-disk rotor system with grouped blades

YiJui Chiu,Chia-Hao Yang 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.5

The influence on coupling vibrations among shaft-torsion, blade-bending and lacing wire coupling vibrations of a multi-disk rotor systemwith grouped blades was investigated analytically. The natural frequencies and the mode shapes of the system were solved for onetofour-disk cases as examples. First, numerical results showed how the natural frequencies varied by lacing wires and disks in a multidiskrotor system. The diagrams of the coupling mode shapes were drawn. From the results, the inter-blade (BB) modes, the shaft-blade(SB) modes and the lacing wires-blade (LB) modes change rules were given in this paper. Numerical calculation also revealed three interestingresults that the natural frequencies were affected by lacing wire constant, lacing wire location and the disk distance. In the rotationeffects, the multi-disk has drawn three important phenomena. The times of instability will due to the number of disk, the more diskrotor causes instability earlier than the less disk case and the lacing wires could not affect the system instability.

Research on heat-elastic coupled vibration in a rotating rigid disk rotor system

Ya-Zheng Zhao,Yi-Jui Chiu,Chia-Hao Yang,Guo-Fei Yu 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.4

The operation of a real aircraft engine is affected by heat. After an initial comprehensive coupled vibration study of a shaft-disk-blades rotor, the authors added heat to explore heat-elastic coupled vibrations. The assumed mode and finite element methods were applied in this study. In addition, a new material, the nickel-based super alloy K409, was also considered. Two new coupling-mode types were defined. These are the blade-heat (BH) and shaft-blade-heat (SBH) modes. The qualitative variation behaviors showed that the 1a mode changed from the SB mode to the SBH mode, and the 1b modes with four repeated eigenvalues changed from the BB mode to the BH mode. However, the process is not a simple variation, but a variety of mode change phenomena occurred. The thermal variation behaviors from 0 to 1300 °C were explored quantitatively. Steel and K409 yielded similar results. Finally, the effect of the rotational speed was explored.

Negative effects on medical students’ scores for clinical performance during the COVID-19 pandemic in Taiwan: a comparative study

Eunice Jia-Shiow Yuan,Shiau-Shian Huang,Chia-An Hsu,Jiing-Feng Lirng,Tzu-Hao Li,Chia-Chang Huang,Ying-Ying Yang,Chung-Pin Li,Chen-Huan Chen 한국보건의료인국가시험원 2023 보건의료교육평가 Vol.20 No.-

Purpose Coronavirus disease 2019 (COVID-19) has heavily impacted medical clinical education in Taiwan. Medical curricula have been altered to minimize exposure and limit transmission. This study investigated the effect of COVID-19 on Taiwanese medical students’ clinical performance using online standardized evaluation systems and explored the factors influencing medical education during the pandemic. Methods Medical students were scored from 0 to 100 based on their clinical performance from 1/1/2018 to 6/31/2021. The students were placed into pre-COVID-19 (before 2/1/2020) and midst-COVID-19 (on and after 2/1/2020) groups. Each group was further categorized into COVID-19-affected specialties (pulmonary, infectious, and emergency medicine) and other specialties. Generalized estimating equations (GEEs) were used to compare and examine the effects of relevant variables on student performance. Results In total, 16,944 clinical scores were obtained for COVID-19-affected specialties and other specialties. For the COVID-19-affected specialties, the midst-COVID-19 score (88.51–3.52) was significantly lower than the pre-COVID-19 score (90.14–3.55) (P<0.0001). For the other specialties, the midst-COVID-19 score (88.32–3.68) was also significantly lower than the pre-COVID-19 score (90.06–3.58) (P<0.0001). There were 1,322 students (837 males and 485 females). Male students had significantly lower scores than female students (89.33–3.68 vs. 89.99–3.66, P=0.0017). GEE analysis revealed that the COVID-19 pandemic (unstandardized beta coefficient=-1.99, standard error [SE]=0.13, P<0.0001), COVID-19-affected specialties (B=0.26, SE=0.11, P=0.0184), female students (B=1.10, SE=0.20, P<0.0001), and female attending physicians (B=-0.19, SE=0.08, P=0.0145) were independently associated with students’ scores. Conclusion COVID-19 negatively impacted medical students' clinical performance, regardless of their specialty. Female students outperformed male students, irrespective of the pandemic.

Potential of a combination of entomopathogenic fungal strains and a non-ionic surfactant to control the fall armyworm (Spodoptera frugiperda)

Wu Sing-Shan,Tseng Ching-Tzu,Yang Yu-Hung,Liu Yao-Chia,Chang Ju-Chun,Gyawali Purushottam,Li Yi-Hsuan,Yang Tzu-Hao,Tsai Yi-Fang,Tang Li-Cheng,Nai Yu-Shin 한국응용곤충학회 2022 Journal of Asia-Pacific Entomology Vol.25 No.4

The fall armyworm, Spodoptera frugiperda, is an emerging invasive pest in Taiwan that feeds on a wide range of crops and causes serious damage. Herein, an entomopathogenic fungal library (EFLib) was constructed to identify potential microbes to control FAW. Twenty-eight indigenous entomopathogenic fungi (EPF) were iso lated and investigated for their potential pathogenicity, with Metarhizium pinghaense (Mp-NCHU-124) and Beauveria bassiana (Bb-NCHU-157) exerting dose-dependent effects on the 4th instar FAW larvae. The non-ionic surfactant Silwet L-77 rapidly killed FAW larvae after spraying at a concentration of 300 mg/kg and the toxic effect of Silwet L-77 on FAW larvae was dose-dependent. When the EPF isolates (10 6 conidia/mL) were applied to FAW larvae in combination with the non-ionic surfactant Silwet L-77 (30–90 mg/kg), the mortality rate dramatically increased and the LT 50 reduced, with increased fungal mycosis (Mp-NCHU-124: 38% to 72% and Bb-NCHU-157: 20 to 62%), indicating the high compatibility of EPF with the non-ionic surfactant. Thus, the Silwet L-77+EPF combined formulation has potential for practical field application for FAW pest control and sustainable agriculture in the future.

An assumed mode method and finite element method investigation of the coupled vibration in a flexible-disk rotor system with lacing wires

Shui-Ting Zhou,YiJui Chiu,Guo-Fei Yu,Chia-Hao Yang,Hong-Wu Huang,Sheng-Rui Jian 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.2

The Assumed mode method (AMM) and Finite element method (FEM) were used. Their results were compared to investigate the coupled shaft-torsion, disk-transverse, and blade-bending vibrations in a flexible-disk rotor system. The blades were grouped with a spring. The flexible-disk rotor system was divided into three modes of coupled vibrations: Shaft-disk-blade, disk-blade, and blade-blade. Two new modes of coupled vibrations were introduced, namely, lacing wires-blade and lacing wires-disk-blade. The patterns of change of the natural frequencies and mode shapes of the system were discussed. The results showed the following: first, mode shapes and natural frequencies varied, and the results of the AMM and FEM differed; second, numerical calculation results showed three influencing factors on natural frequencies, namely, the lacing wire constant, the lacing wire location, and the flexible disk; lastly, the flexible disk could affect the stability of the system as reflected in the effect of the rotational speed.

A Password and Smart Card Based User Authentication Mechanism for Multi-Server Environments

Chun-Ta Li,Cheng-Chi Lee,Hsing Mei,Chia-Hao Yang 보안공학연구지원센터 2012 International Journal of Future Generation Communi Vol.5 No.4

Three methods for studying coupled vibration in a multi flexible disk rotor system

YiJui Chiu,Xiao-Yun Li,Yi-Cheng Chen,Sheng-Rui Jian,Chia-Hao Yang,I-Hsiang Lin 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.11

This paper improved and developed Shaft-disk-blade (SDB) rotor system based on the previous studies of the authors in the last decade from Yang and Huang (2005) to Chiu et al. (2017). This paper also explored blade-bending, disk-transverse, and shaft-torsion coupling vibration of a multi flexible disk rotor system. Unlike the previous studies of the authors, this paper adopted three methods: (a) Assumed mode method (AMM), (b) Finite element method (FEM), and (c) experimental method. The first approach is the main method, and the two other methods are complementary. Results generated from the three methods were then compared and analyzed. Based on the previous definition of the authors, a flexible disk rotor system displays three types of coupling vibrations: Inter-blade, SDB, and diskblade modes. The system changes the rules of natural frequencies and mode shapes. This paper presents several interesting results. First, the author determined the change rules of the mode shapes and natural frequencies using the AMM, FEM (including three kinds of software), and the experimental method. Second, numerical calculation results also revealed that two phenomena regarding the distance of disk and flexible disk would be affected by the natural frequencies. Third, the experimental results would be explored in this paper. Last, the flexible disk could affect the system instability in the case study of rotation effects.

Research on effect of rings on coupling vibration in a rigid-disk rotor

YiJui Chiu,Xiao-Yun Li,Guo-Fei Yu,Chia-Hao Yang,Jeng-Shyang Pan,ChinLing Chen 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.2

This paper uses new deductions of the equation of motion and obtains new modes of change that differ from the authors’ previous research. The blade-bending, shaft-torsion and ringbending coupled vibration influence of a single-disk rotor whose blade subsystem was coated with a ring is investigated. In the last two years, the authors adopted two methods, the assumed mode method and finite element method, and compared both parties results. This article continues that work. In this paper, the phenomena of ring joint coupling vibrations are different and interesting. The authors defined two new types, the shaft-blade-ring (SBR) and blade-ring (BR) modes. These two coupling modes can be mutually affected by the shaft, blade, and ring, and no single subsystem predominates. The new change rules of natural frequencies of rotors with two to 15 blades and those of mode shapes are discussed. The influence of the ring thickness and rotational speed are also studied in this paper.