Browsing by Author "Chen, Y. S."

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Abnormal Early Gamma Responses to Emotional Faces Differentiate Unipolar from Bipolar Disorder Patients
(2014)
Liu, T. Y.
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Chen, Y. S.
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Su, T. P.
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Hsieh, J. C.
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Chen, L. F.
This study investigates the cortical abnormalities of early emotion perception in patients with major depressive disorder (MDD) and bipolar disorder (BD) using gamma oscillations. Twenty-three MDD patients, twenty-five BD patients, and twenty-four normal controls were enrolled and their event-related magneto encephalographic responses were recorded during implicit emotional tasks. Our results demonstrated abnormal gamma activity within 100 ms in the emotion-related regions (amygdala, orbitofrontal (OFC) cortex, anterior insula (AI), and superior temporal pole) in the MDD patients, suggesting that these patients may have dysfunctions or negativity biases in perceptual binding of emotional features at very early stage. Decreased left superior medial frontal cortex (smFC) responses to happy faces in the MDD patients were correlated with their serious level of depression symptoms, indicating that decreased smFC activity perhaps underlies irregular positive emotion processing in depressed patients. In the BD patients, we showed abnormal activation in visual regions (inferior/middle occipital and middle temporal cortices) which responded to emotional faces within 100 ms, supporting that the BD patients may hyperactively respond to emotional features in perceptual binding. The discriminant function of gamma activation in the left smFC, right medial OFC, right AI/inferior OFC, and the right precentral cortex accurately classified 89.6% of patients as unipolar/bipolar disorders.
COMPARISON OF THE PROPULSION PERFORMANCE OF AEROSPIKE AND BELL-SHAPED NOZZLE USING HYDROGEN PEROXIDE MONOPROPELLANT UNDER SEA-LEVEL CONDITION
(2019-06-01)
Lai, A.
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Wei, S. S.
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Lai, C. H.
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Chen, J. L.
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Liao, Y. H.
This study investigates numerically the performance of applying aerospike nozzle in a hydrogen peroxide mono-propellant propulsion system. A set of governing equations, including continuity, momentum, energy and species conservation equations with extended k-epsilon turbulence equations, are solved using the finite-volume method. The hydrogen peroxide mono-propellant is assumed to be fully decomposed into water vapor and oxygen after flowing through a catalyst bed before entering the nozzle. The aerospike nozzle is expected to have high performance even in deep throttling cases due to its self-compensating characteristics in a wide range of ambient pressure environments. The results show that the thrust coefficient efficiency (C-f,C-eta) of this work exceeds 90% of the theoretical value with a nozzle pressure ratio (PR) in the range of 20 similar to 45. Many complex gas dynamics phenomena in the aerospike nozzle are found and explained in the paper. In addition, performance of the aerospike nozzle is compared with that of the bell-shape nozzle.
Electron transport and electroluminescent efficiency of conjugated polymers
(2009-01-01)
Tseng, S. R.
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Chen, Y. S.
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Meng, H. F.
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Lai, H. C.
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Yeh, C. H.
The relation between charge balance and electroluminescent efficiency for polymers is studied systematically in this work. Light-emitting diodes of several kinds of polymers with very different efficiency are compared. The electron and hole currents are measured in the uni-polar devices and fitted by the theoretical model to get carrier mobilities. The universal features of the high efficiency polymers are that the electron and hole mobilities are comparable and the electron current is larger than the hole current due to the higher hole barriers. The electron current is more crucial than hole current to determine the efficiency in the bipolar light-emitting diode. The purity of polymers and low electron injection barriers both play significant roles in producing stronger electron currents. These results give the physical rules for designing new polymers and the device structures to achieve highly electroluminescent devices. Crown Copyright (C) 2008 Published by Elsevier B.V. All rights reserved.
High-temperature magnetoresistance study of a magnetic tunnel junction
(2006-09-01)
Chen, D. C.
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Yao, Y. D.
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Chen, C. M.
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Hung, James
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Chen, Y. S.
The thermal stability and the spin transportation phenomenon at room temperature and 140 degrees C of a series of magnetic tunneling junctions with the structure of bottom electrode/PtMn/Pinned layer/ AlO(x)/CoFe/NiFe/top electrode have been investigated. The MR ratio decreases from 33.5% at room temperature to 29% at 140 degrees C. The MR ratio at room temperature increases roughly 0.8% after thermal treatment at temperatures above 60 degrees C. This is related to the thermal relaxation of the strains existing in the samples. (C) 2006 Elsevier B.V. All rights reserved.
Highly Scalable Hafnium Oxide Memory with Improvements of Resistive Distribution and Read Disturb Immunity
(2009)
Chen, Y. S.
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Lee, H. Y.
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Chen, P. S.
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Gu, P. Y.
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Chen, C. W.
A 30x30 nm(2) HfOx resistance random access memory (RRAM) with excellent electrical performances is demonstrated for the scaling feasibility in this work. A 1 Kb one transistor and one resistor (1T1R) array with robust characteristics was also fabricated successfully. The device yield of the 1 Kb array is 100%, and the endurance for these devices can exceed 10(6) cycles by a pulse width of 40 ns. Two effective verification methods, which make a tight distribution of high resistance (R-HIGH) and low resistance (R-LOW) are proposed for the array to ensure a good operation window. A thin A1O(x) buffer layer under the HfOx layer was adopted to enhance the read disturb immunity. Without large parasitic capacitance, the 1T1R RRAM devices exhibit excellent program(PGM)/erase(ERS) disturb immunity.
Mixing Effectiveness Study in Scramjet Combustion
(2013-01-01)
Chen, Y. S.
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Lian, Y. Y.
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Chou, T. H.
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Lai, Alfred
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Wu, J. S.
Scramjet propulsion provides promising opportunities for high-speed transportation and cost reduction for satellite and spacecraft launch operations. This paper provides some selected numerical examples among the abundance of available test cases for the purpose of demonstrating to what extends the current computational models can do in assisting the design and test programs of scramjet combustors. Numerical examples that cover a wide range of flight speeds are investigated with benchmark data validations. Ideas of mixing enhancement and flame holding mechanisms in scramjet combustion is analyzed and planned for the future experimental investigations. (C) 2013 The Authors. Published by Elsevier Ltd.
New Observations on the Regular and Irregular Noise Behavior in a Resistance Random Access Memory
(2014-01-01)
Chen, Scott C. H.
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Huang, Y. J.
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Chung, S. S.
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Lee, H. Y.
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Chen, Y. S.
In this paper, a new type of noise, different from the conventional Random Telegraph Noise (RTN), has been found and analyzed in a resistance random access memory (RRAM). The regular RTN signal is governed by the trapping and detrapping of the electrons. It will appear regularly with a two-level current and the amplitude of the RTN is smaller. However, an abnormal noise, called giant noise, was observed from the oxygen migration. The amplitude of the giant noise is much larger than the RTN one. Also, two different types of giant noise were observed depending on the movement of the oxygen vacancies. All of the above various types of noise might play an important role in the readout error in an RRAM. Therefore, these noise effects need further attention in the design of RRAM.
NUMERICAL INVESTIGATION OF A N2O/HTPB HYBRID ROCKET MOTOR WITH A DUAL-VORTICAL-FLOW (DVF) DESIGN
(2017-12-01)
Lai, A.
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Lin, Y. C.
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Wei, S. S.
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Chou, T. H.
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Lin, J. W.
A compact hybrid rocket motor design that incorporates a dual-vortical-flow (DVF) concept is proposed. The oxidizer (nitrous oxide, N2O) is injected circumferentially into various sections of the rocket motor, which are sectored by several solid fuel "rings" (made of hydroxyl-terminated polybutadiene, HTPB) that are installed along the central axis of the motor. The proposed configuration not only increases the residence time of the oxidizer flow, it also implies an inherent "roll control" capability of the motor. Based on a DVF motor geometry with a designed thrust level of 11.6 kN, the characteristics of the turbulent reacting flow within the motor and its rocket performance were analyzed with a comprehensive numerical model that implements both real-fluid properties and finite-rate chemistry. Data indicate that the vacuum specific impulse (Isp) of the DVF motor could reach 278 s. The result from a preliminary ground test of a lab-scale DVF hybrid rocket motor (with a designed thrust level of 3,000 N) also shows promising performance. The proposed DVF concept is expected to partly resolve the issue of scalability, which remains challenging for hybrid rocket motors development.
Optical Properties of Ce-Doped ZnO Nanowires Directionally Grown by Hydrothermal Method
(2008-09-01)
Chen, Y. S.
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Tseng, T. Y.
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
Well directionally grown Ce-doped ZnO nanowires were successfully synthesized by a simple hydrothermal method. The Ce dopant plays a key role in evolving the morphology, affecting the crystalline size, and forming the uniform nanostructure of the ZnO nanowires. The amount of Ce dopant in the ZnO nanowires also affects the regions of blue-shift in the UV and green emission peaks and the intensities of emission peaks based on the cathodoluminescence spectra of the nanowires. Moreover, the effect of Ce doping amount on the microstructure of the nanowires is also presented.
Oxide-Based RRAM: Unified Microscopic Principle for both Unipolar and Bipolar Switching
(2011)
Gao, B.
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Kang, J. F.
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Chen, Y. S.
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Zhang, F. F.
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Chen, B.
A unified microscopic principle is proposed to clarify resistive switching behaviors of transition metal oxide based resistive random access memories (RRAM) for the first time. In this unified microscopic principle, both unipolar and bipolar switching characteristics of RRAM are correlated with the distribution of localized oxygen vacancies in the oxide switching layer, which is governed by the generation and recombination with dissociative oxygen ions. Based on the proposed microscopic principle, an atomistic simulation method is developed to evaluate critical memory performance, and successfully conduct the device optimization. The experimental data are well in line with the developed simulation method.
Pattern classification of gray matter density in unipolar, bipolar I, and bipolar II patients using voxel-based morphometry and bayesian classifier
(2012-03-01)
Su, T. P.
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Chen, L. F.
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Chen, Y. S.
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Chan, C. Y.
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Lee, P. S.
RmpA Regulation of Capsular Polysaccharide Biosynthesis in Klebsiella pneumoniae CG43
(2010-06-01)
Cheng, H. Y.
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Chen, Y. S.
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Wu, C. Y.
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Chang, H. Y.
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Lai, Y. C.
Sequence analysis of the large virulence plasmid pLVPK in Klebsiella pneumoniae CG43 revealed the presence of another mucoid factor encoding gene rmpA besides rmpA2. Promoter activity measurement indicated that the deletion of rmpA reduced K2 capsular polysaccharide (CPS) biosynthesis, resulting in decreased colony mucoidy and virulence in mice. Introduction of a multicopy plasmid carrying rmpA restored CPS production in the rmpA or rmpA2 mutant but not in the rcsB mutant. Transformation of the rmpA deletion mutant with an rcsB-carrying plasmid also failed to enhance CPS production, suggesting that a cooperation of RmpA with RcsB is required for regulatory activity. This was further corroborated by the demonstration of in vivo interaction between RmpA and RcsB using two-hybrid analysis and coimmunoprecipitation analysis. A putative Fur binding box was only found at the 5' noncoding region of rmpA. The promoter activity analysis indicated that the deletion of fur increased the rmpA promoter activity. Using electrophoretic mobility shift assay, we further demonstrated that Fur exerts its regulatory activity by binding directly to the promoter. As a result, the fur deletion mutant exhibited an increase in colony mucoidy, CPS production, and virulence in mice. In summary, our results suggested that RmpA activates CPS biosynthesis in K. pneumoniae CG43 via an RcsB-dependent manner. The expression of rmpA is regulated by the availability of iron and is negatively controlled by Fur.
The Physical Insights Into an Abnormal Erratic Behavior in the Resistance Random Access Memory
(2013)
Huang, Y. J.
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Chung, Steve S.
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Lee, H. Y.
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Chen, Y. S.
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Chen, F. T.
The voltage ramping rate during the forming and set-reset process is strongly related to the formation of soft-breakdown (SBD) paths. In this paper, we examined the effect of two different operation methods in RRAM, including sweep and pulse modes. The RTN analysis has been utilized to examine their influences on the SBD paths. For the first time, we found a different behavior of the RTN currents generated by two different modes of operation. Results show that more SBD paths are created during the pulse mode which led to the instability of switched resistance, and induced the erratic bit during the readout of RRAM.