Search results for: Dae Hoon Kwon
Commenced in January 2007
Frequency: Monthly
Edition: International
Paper Count: 163

Search results for: Dae Hoon Kwon

133 Principal Component Analysis using Singular Value Decomposition of Microarray Data

Authors: Dong Hoon Lim

Abstract:

A series of microarray experiments produces observations of differential expression for thousands of genes across multiple conditions. Principal component analysis(PCA) has been widely used in multivariate data analysis to reduce the dimensionality of the data in order to simplify subsequent analysis and allow for summarization of the data in a parsimonious manner. PCA, which can be implemented via a singular value decomposition(SVD), is useful for analysis of microarray data. For application of PCA using SVD we use the DNA microarray data for the small round blue cell tumors(SRBCT) of childhood by Khan et al.(2001). To decide the number of components which account for sufficient amount of information we draw scree plot. Biplot, a graphic display associated with PCA, reveals important features that exhibit relationship between variables and also the relationship of variables with observations.

Keywords: Principal component analysis, singular value decomposition, microarray data, SRBCT

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132 Field Emission Properties of Multi-wall Carbon Nanotube Field Emitters using Graphite Tip by Electroporetic Deposition

Authors: Gui Sob Byun, Yang Doo Lee, Kyong Soo Lee, Keun Soo Lee, Sun-Woo Park, Byeong Kwon Ju

Abstract:

We fabricated multi-walled carbon nanotube (MCNT) emitters by an electroporetic deposition (EPD) method using a MCNT-sodium dodecyl sulfate (SDS) suspension. MCNT films were prepared on graphite tip using EPD. We observe field emission properties of MCNT film after heat treatment. Consequently, The MCNT film on graphite tip exhibit good electron emission current.

Keywords: Field emission, Multi-wall carbon-nanotube (MCNT), Electrophoretic deposition (EPD)

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131 A Second Law Assessment of Organic Rankine Cycle Depending on Source Temperature

Authors: Kyoung Hoon Kim

Abstract:

Organic Rankine Cycle (ORC) has potential in reducing fossil fuels and relaxing environmental problems. In this work performance analysis of ORC is conducted based on the second law of thermodynamics for recovery of low temperature heat source from 100oC to 140oC using R134a as the working fluid. Effects of system parameters such as turbine inlet pressure or source temperature are theoretically investigated on the exergy destructions (anergies) at various components of the system as well as net work production or exergy efficiency. Results show that the net work or exergy efficiency has a peak with respect to the turbine inlet pressure when the source temperature is low, however, increases monotonically with increasing turbine inlet pressure when the source temperature is high.

Keywords: Organic Rankine cycle (ORC), low temperature heat source, exergy, source temperature.

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130 Implementation of a Reed-Solomon Code as an ECC in Yet Another Flash File System

Authors: Sungjoon Sim, Soongyu Kwon, Dongjae Song, Jong Tae Kim

Abstract:

Flash memory has become an important storage device in many embedded systems because of its high performance, low power consumption and shock resistance. Multi-level cell (MLC) is developed as an effective solution for reducing the cost and increasing the storage density in recent years. However, most of flash file system cannot handle the error correction sufficiently. To correct more errors for MLC, we implement Reed-Solomon (RS) code to YAFFS, what is widely used for flash-based file system. RS code has longer computing time but the correcting ability is much higher than that of Hamming code.

Keywords: Reed-Solomon, NAND flash memory, YAFFS, ErrorCorrecting Code, Flash File System

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129 Performance Analysis of Absorption Power Cycle under Different Source Temperatures

Authors: Kyoung Hoon Kim

Abstract:

The absorption power generation cycle based on the ammonia-water mixture has attracted much attention for efficient recovery of low-grade energy sources. In this paper a thermodynamic performance analysis is carried out for a Kalina cycle using ammonia-water mixture as a working fluid for efficient conversion of low-temperature heat source in the form of sensible energy. The effects of the source temperature on the system performance are extensively investigated by using the thermodynamic models. The results show that the source temperature as well as the ammonia mass fraction affects greatly on the thermodynamic performance of the cycle.

Keywords: Ammonia-water mixture, Kalina cycle, low-grade heat source, source temperature.

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128 PSRR Enhanced LDO Regulator Using Noise Sensing Circuit

Authors: Min-ju Kwon, Chae-won Kim, Jeong-yun Seo, Hee-guk Chae, Yong-seo Koo

Abstract:

In this paper, we presented the LDO (low-dropout) regulator which enhanced the PSRR by applying the constant current source generation technique through the BGR (Band Gap Reference) to form the noise sensing circuit. The current source through the BGR has a constant current value even if the applied voltage varies. Then, the noise sensing circuit, which is composed of the current source through the BGR, operated between the error amplifier and the pass transistor gate of the LDO regulator. As a result, the LDO regulator has a PSRR of -68.2 dB at 1k Hz, -45.85 dB at 1 MHz and -45 dB at 10 MHz. the other performance of the proposed LDO was maintained at the same level of the conventional LDO regulator.

Keywords: LDO regulator, noise sensing circuit, current reference, pass transistor.

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127 Thermodynamic Analysis of Ammonia-Water Based Regenerative Rankine Cycle with Partial Evaporation

Authors: Kyoung Hoon Kim

Abstract:

A thermodynamic analysis of a partial evaporating Rankine cycle with regeneration using zeotropic ammonia-water mixture as a working fluid is presented in this paper. The thermodynamic laws were applied to evaluate the system performance. Based on the thermodynamic model, the effects of the vapor quality and the ammonia mass fraction on the system performance were extensively investigated. The results showed that thermal efficiency has a peak value with respect to the vapor quality as well as the ammonia mass fraction. The partial evaporating ammonia based Rankine cycle has a potential to improve recovery of low-grade finite heat source.

Keywords: Ammonia-water, Rankine cycle, partial evaporating, thermodynamic performance.

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126 Influence of Flash Temperature on Exergetical Performance of Organic Flash Cycle

Authors: Kyoung Hoon Kim, Chul Ho Han

Abstract:

Organic Flash Cycle (OFC) has potential of improving efficiency for recovery of low temperature heat sources mainly due to reducing temperature mismatch in the heat exchanger. In this work exergetical performance analysis of ORC is conducted for recovery of low grade heat source. Effects of system parameters such as flash evaporation temperature or heating temperature are theoretically investigated on the exergy destructions (anergies) at various components of the system as well as exergy efficiency. Results show that exergy efficiency has a peak with respect to the flash temperature, and the optimum flash temperature increases with the heating temperature. The component where the largest exergy destruction occurs varies with the flash temperature or heating temperature.

Keywords: Organic flash cycle (OFC), low grade heat source, exergy, anergy, flash temperature.

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125 Study on Rupture of Tube Type Crash Energy Absorber using Finite Element Method

Authors: Won Mok. Choi, Tae Su. Kwon, Hyun Sung. Jung, Jin Sung. Kim

Abstract:

The aim of this paper is to confirm the effect of key design parameters, the punch radius and punch angle, on rupture of the expansion tube using a finite element analysis with a ductile damage model. The results of the finite element analysis indicated that the expansion ratio of the tube was mainly affected by the radius of the punch. However, the rupture was more affected by the punch angle than the radius of the punch. The existence of a specific punch angle, at which rupture did not occur, even if the radius of the punch was increased, was found.

Keywords: Expansion tube, Ductile damage, Shear failure, Stress triaxiality.

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124 Delay-Dependent Stability Criteria for Linear Time-Delay System of Neutral Type

Authors: Myeongjin Park, Ohmin Kwon, Juhyun Park, Sangmoon Lee

Abstract:

This paper proposes improved delay-dependent stability conditions of the linear time-delay systems of neutral type. The proposed methods employ a suitable Lyapunov-Krasovskii’s functional and a new form of the augmented system. New delay-dependent stability criteria for the systems are established in terms of Linear matrix inequalities (LMIs) which can be easily solved by various effective optimization algorithms. Numerical examples showed that the proposed method is effective and can provide less conservative results.

Keywords: Neutral systems, Time-delay, Stability, Lyapunovmethod, LMI.

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123 Exact Evaluation Method for Error Performance Analysis of Arbitrary 2-D Modulation OFDM Systems with CFO

Authors: Jaeyoon Lee, Dongweon Yoon, Hoon Yoo, Sanggoo Kim

Abstract:

Orthogonal frequency division multiplexing (OFDM) has developed into a popular scheme for wideband digital communications used in consumer applications such as digital broadcasting, wireless networking and broadband internet access. In the OFDM system, carrier frequency offset (CFO) causes intercarrier interference (ICI) which significantly degrades the system error performance. In this paper we provide an exact evaluation method for error performance analysis of arbitrary 2-D modulation OFDM systems with CFO, and analyze the effect of CFO on error performance.

Keywords: Carrier frequency offset, Probability of error, Inter-channel interference, Orthogonal frequency division multiplexing

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122 The Effect of Pulsator on Washing Performance in a Front-Loading Washer

Authors: Eung Ryeol Seo, Hee Tae Lim, Eunsuk Bang, Soon Cheol Kweon, Jeoung-Kyo Jeoung, Ji-Hoon Choic

Abstract:

The object of this study is to investigate the effect of pulsator on washing performance quantitatively for front-loading washer. The front-loading washer with pulsator shows washing performance improvement of 18% and the particle-based body simulation technique has been applied to figure out the relation between washing performance and mechanical forces exerted on textile during washing process. As a result, the mechanical forces, such as collision force and strain force, acting on the textile have turned out to be about twice numerically. The washing performance improvement due to additional pulsate system has been utilized for customers to save 50% of washing time.

Keywords: Front-loading washer, mechanical force, fabric movement, pulsator, time saving.

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121 A Novel Tracking Method Using Filtering and Geometry

Authors: Sang Hoon Lee, Jong Sue Bae, Taewan Kim, Jin Mo Song, Jong Ju Kim

Abstract:

Image target detection and tracking methods based on target information such as intensity, shape model, histogram and target dynamics have been proven to be robust to target model variations and background clutters as shown by recent researches. However, no definitive answer has been given to occluded target by counter measure or limited field of view(FOV). In this paper, we will present a novel tracking method using filtering and computational geometry. This paper has two central goals: 1) to deal with vulnerable target measurements; and 2) to maintain target tracking out of FOV using non-target-originated information. The experimental results, obtained with airborne images, show a robust tracking ability with respect to the existing approaches. In exploring the questions of target tracking, this paper will be limited to consideration of airborne image.

Keywords: Tracking, Computational geometry, Homography, Filter

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120 Self-Assembling Hypernetworks for Cognitive Learning of Linguistic Memory

Authors: Byoung-Tak Zhang, Chan-Hoon Park

Abstract:

Hypernetworks are a generalized graph structure representing higher-order interactions between variables. We present a method for self-organizing hypernetworks to learn an associative memory of sentences and to recall the sentences from this memory. This learning method is inspired by the “mental chemistry" model of cognition and the “molecular self-assembly" technology in biochemistry. Simulation experiments are performed on a corpus of natural-language dialogues of approximately 300K sentences collected from TV drama captions. We report on the sentence completion performance as a function of the order of word-interaction and the size of the learning corpus, and discuss the plausibility of this architecture as a cognitive model of language learning and memory.

Keywords: Linguistic recall memory, sentence completion task, self-organizing hypernetworks, cognitive learning and memory.

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119 Mechanical Equation of State in an Al-Li Alloy

Authors: Jung-Ho Moon, Tae Kwon Ha

Abstract:

Existence of plastic equation of state has been investigated by performing a series of load relaxation tests at various temperatures using an Al-Li alloy. A plastic equation of state is first developed from a simple kinetics consideration for a mechanical activation process of a leading dislocation piled up against grain boundaries. A series of load relaxation test has been conducted at temperatures ranging from 200 to 530oC to obtain the stress-strain rate curves. A plastic equation of state has been derived from a simple consideration of dislocation kinetics and confirmed by experimental results.

Keywords: Plastic equation of state, Dislocation kinetics, Load relaxation test, Al-Li alloy, Microstructure.

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118 Distributed Frequency Synchronization for Global Synchronization in Wireless Mesh Networks

Authors: Jung-Hyun Kim, Jihyung Kim, Kwangjae Lim, Dong Seung Kwon

Abstract:

In this paper, our focus is to assure a global frequency synchronization in OFDMA-based wireless mesh networks with local information. To acquire the global synchronization in distributed manner, we propose a novel distributed frequency synchronization (DFS) method. DFS is a method that carrier frequencies of distributed nodes converge to a common value by repetitive estimation and averaging step and sharing step. Experimental results show that DFS achieves noteworthy better synchronization success probability than existing schemes in OFDMA-based mesh networks where the estimation error is presented.

Keywords: OFDMA systems, Frequency synchronization, Distributed networks, Multiple groups.

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117 Thermodynamic Performance Assessment of Steam-Injection Gas-Turbine Systems

Authors: Kyoung Hoon Kim, Giman Kim

Abstract:

The cycles of the steam-injection gas-turbine systems are studied. The analyses of the parametric effects and the optimal operating conditions for the steam-injection gas-turbine (STIG) system and the regenerative steam-injection gas-turbine (RSTIG) system are investigated to ensure the maximum performance. Using the analytic model, the performance parameters of the system such as thermal efficiency, fuel consumption and specific power, and also the optimal operating conditions are evaluated in terms of pressure ratio, steam injection ratio, ambient temperature and turbine inlet temperature (TIT). It is shown that the computational results are presented to have a notable enhancement of thermal efficiency and specific power.

Keywords: gas turbine, RSTIG, steam injection, STIG, thermal efficiency.

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116 Sampled-Data Model Predictive Tracking Control for Mobile Robot

Authors: Wookyong Kwon, Sangmoon Lee

Abstract:

In this paper, a sampled-data model predictive tracking control method is presented for mobile robots which is modeled as constrained continuous-time linear parameter varying (LPV) systems. The presented sampled-data predictive controller is designed by linear matrix inequality approach. Based on the input delay approach, a controller design condition is derived by constructing a new Lyapunov function. Finally, a numerical example is given to demonstrate the effectiveness of the presented method.

Keywords: Model predictive control, sampled-data control, linear parameter varying systems, LPV.

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115 A Talking Head System for Korean Text

Authors: Sang-Wan Kim, Hoon Lee, Kyung-Ho Choi, Soon-Young Park

Abstract:

A talking head system (THS) is presented to animate the face of a speaking 3D avatar in such a way that it realistically pronounces the given Korean text. The proposed system consists of SAPI compliant text-to-speech (TTS) engine and MPEG-4 compliant face animation generator. The input to the THS is a unicode text that is to be spoken with synchronized lip shape. The TTS engine generates a phoneme sequence with their duration and audio data. The TTS applies the coarticulation rules to the phoneme sequence and sends a mouth animation sequence to the face modeler. The proposed THS can make more natural lip sync and facial expression by using the face animation generator than those using the conventional visemes only. The experimental results show that our system has great potential for the implementation of talking head for Korean text.

Keywords: Talking head, Lip sync, TTS, MPEG4.

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114 Object Detection based Weighted-Center Surround Difference

Authors: Seung-Hun Kim, Kye-Hoon Jeon, Byoung-Doo Kang, I1-Kyun Jung

Abstract:

Intelligent traffic surveillance technology is an issue in the field of traffic data analysis. Therefore, we need the technology to detect moving objects in real-time while there are variations in background and natural light. In this paper, we proposed a Weighted-Center Surround Difference method for object detection in outdoor environments. The proposed system detects objects using the saliency map that is obtained by analyzing the weight of each layers of Gaussian pyramid. In order to validate the effectiveness of our system, we implemented the proposed method using a digital signal processor, TMS320DM6437. Experimental results show that blurred noisy around objects was effectively eliminated and the object detection accuracy is improved.

Keywords: Saliency Map, Center Surround Difference, Object Detection, Surveillance System

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113 Effect of Y Addition on the Microstructure and Mechanical Properties of Sn-Zn Eutectic Alloy

Authors: Jung-Ho Moon, Tae Kwon Ha

Abstract:

The effect of Yttrium addition on the microstructure and mechanical properties of Sn-Zn eutectic alloy, which has been attracting intensive focus as a Pb-free solder material, was investigated in this study. Phase equilibrium has been calculated by using FactSage® to evaluate the composition and fraction of equilibrium intermetallic compounds and construct a phase diagram. In the case of Sn-8.8Zn eutectic alloy, the as-cast microstructure was typical lamellar. With addition of 0.25wt.%Y, a large amount of pro-eutectic a phase have been observed and various YZnx intermetallic compounds were expected to successively form during cooling. Hardness of Sn-8.8Zn alloy was not affected by Y-addition and both alloys could be rolled by 90% at room temperature.

Keywords: Sn-Zn eutectic alloy, Yttrium, FactSage®, microstructure, mechanical properties.

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112 Sampling Effects on Secondary Voltage Control of Microgrids Based on Network of Multiagent

Authors: M. J. Park, S. H. Lee, C. H. Lee, O. M. Kwon

Abstract:

This paper studies a secondary voltage control framework of the microgrids based on the consensus for a communication network of multiagent. The proposed control is designed by the communication network with one-way links. The communication network is modeled by a directed graph. At this time, the concept of sampling is considered as the communication constraint among each distributed generator in the microgrids. To analyze the sampling effects on the secondary voltage control of the microgrids, by using Lyapunov theory and some mathematical techniques, the sufficient condition for such problem will be established regarding linear matrix inequality (LMI). Finally, some simulation results are given to illustrate the necessity of the consideration of the sampling effects on the secondary voltage control of the microgrids.

Keywords: Microgrids, secondary control, multiagent, sampling, LMI.

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111 Kinematic Optimal Design on a New Robotic Platform for Stair Climbing

Authors: Byung Hoon Seo, Hyun Gyu Kim, Tae Won Seo

Abstract:

Stair climbing is one of critical issues for field robots to widen applicable areas. This paper presents optimal design on kinematic parameters of a new robotic platform for stair climbing. The robotic platform climbs various stairs by body flip locomotion with caterpillar type main platform. Kinematic parameters such as platform length, platform height, and caterpillar rotation speed are optimized to maximize stair climbing stability. Three types of stairs are used to simulate typical user conditions. The optimal design process is conducted based on Taguchi methodology, and resulting parameters with optimized objective function are presented. In near future, a prototype is assembled for real environment testing.

Keywords: Stair climbing robot, Optimal design, Taguchi methodology, Caterpillar, Kinematic parameters.

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110 A Cooperative Transmission Scheme Using Two Sources Based On OFDM System

Authors: Bit-Na Kwon, Dong-Hyun Ha, Hyoung-Kyu Song

Abstract:

In wireless communication, space-time block code (STBC), cyclic delay diversity (CDD) and space-time cyclic delay diversity (STCDD)are used as the spatial diversity schemes and have been widely studied for the reliablecommunication. If these schemes are used, the communication system can obtain the improved performance. However,the quality of the system is degraded when the distance between a source and a destination is distant in wireless communication system. In this paper, the cooperative transmission scheme using two sources is proposed and improves the performance of the wireless communication system.

Keywords: OFDM, Cooperative communication, CDD, STBC, STCDD.

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109 Dissipation of Higher Mode using Numerical Integration Algorithm in Dynamic Analysis

Authors: Jin Sup Kim, Woo Young Jung, Minho Kwon

Abstract:

In general dynamic analyses, lower mode response is of interest, however the higher modes of spatially discretized equations generally do not represent the real behavior and not affects to global response much. Some implicit algorithms, therefore, are introduced to filter out the high-frequency modes using intended numerical error. The objective of this study is to introduce the P-method and PC α-method to compare that with dissipation method and Newmark method through the stability analysis and numerical example. PC α-method gives more accuracy than other methods because it based on the α-method inherits the superior properties of the implicit α-method. In finite element analysis, the PC α-method is more useful than other methods because it is the explicit scheme and it achieves the second order accuracy and numerical damping simultaneously.

Keywords: Dynamic, α-Method, P-Method, PC α-Method, Newmark method.

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108 Thermal Fatigue Behavior of 400 Series Ferritic Stainless Steels

Authors: Seok Hong Min, Tae Kwon Ha

Abstract:

In this study, thermal fatigue properties of 400 series ferritic stainless steels have been evaluated in the temperature ranges of 200-800oC and 200-900oC. Systematic methods for control of temperatures within the predetermined range and measurement of load applied to specimens as a function of temperature during thermal cycles have been established. Thermal fatigue tests were conducted under fully constrained condition, where both ends of specimens were completely fixed. It has been revealed that load relaxation behavior at the temperatures of thermal cycle was closely related with the thermal fatigue property. Thermal fatigue resistance of 430J1L stainless steel is found to be superior to the other steels.

Keywords: Ferritic stainless steel, automotive exhaust, thermal fatigue, microstructure, load relaxation.

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107 Microstructure and Aging Behavior of Nonflammable AZ91D Mg Alloy

Authors: Seok Hong Min, Tae Kwon Ha

Abstract:

Phase equilibria of AZ91D Mg alloys for nonflammable use, containing Ca and Y, were carried out by using FactSage® and FTLite database, which revealed that solid solution treatment could be performed at temperatures from 400 to 450oC. Solid solution treatment of AZ91D Mg alloy without Ca and Y was successfully conducted at 420oC and supersaturated microstructure with all beta phase resolved into matrix was obtained. In the case of AZ91D Mg alloy with some Ca and Y; however, a little amount of intermetallic particles were observed after solid solution treatment. After solid solution treatment, each alloy was annealed at temperatures of 180 and 200oC for time intervals from 1 min to 48 hrs and hardness of each condition was measured by micro-Vickers method. Peak aging conditions were deduced as at the temperature of 200oC for 10 hrs.

Keywords: Mg alloy, AZ91D, nonflammable alloy, phase equilibrium, peak aging.

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106 An Empirical Formula for Seismic Test of Telecommunication Equipments

Authors: Young Hoon Lee, Bong Jin Kang, Won Ho Kang

Abstract:

Antiseismic property of telecommunication equipment is very important for the grasp of the damage and the restoration after earthquake. Telecommunication business operators are regulating seismic standard for their equipments. These standards are organized to simulate the real seismic situations and usually define the minimum value of first natural frequency of the equipments or the allowable maximum displacement of top of the equipments relative to bottom. Using the finite element analysis, natural frequency can be obtained with high accuracy but the relative displacement of top of the equipments is difficult to predict accurately using the analysis. Furthermore, in the case of simulating the equipments with access floor, predicting the relative displacement of top of the equipments become more difficult. In this study, using enormous experimental datum, an empirical formula is suggested to forecast the relative displacement of top of the equipments. Also it can be known that which physical quantities are related with the relative displacement.

Keywords: Empirical formula, First natural frequency, Seismic test, Telecommunication equipments.

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105 Entropy Generation Analysis of Heat Recovery Vapor Generator for Ammonia-Water Mixture

Authors: Chul Ho Han, Kyoung Hoon Kim

Abstract:

This paper carries out a performance analysis based on the first and second laws of thermodynamics for heat recovery vapor generator (HRVG) of ammonia-water mixture when the heat source is low-temperature energy in the form of sensible heat. In the analysis, effects of the ammonia mass concentration and mass flow ratio of the binary mixture are investigated on the system performance including the effectiveness of heat transfer, entropy generation, and exergy efficiency. The results show that the ammonia concentration and the mass flow ratio of the mixture have significant effects on the system performance of HRVG.

Keywords: Entropy, exergy, ammonia-water mixture, heat exchanger.

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104 New Dynamic Constitutive Model for OFHC Copper Film

Authors: Jin Sung Kim, Hoon Huh

Abstract:

The material properties of OFHC copper film was investigated with the High-Speed Material Micro Testing Machine (HSMMTM) at the high strain rates. The rate-dependent stress-strain curves from the experiment and the Johnson−Cook curve fitting showed large discrepancies as the plastic strain increases since the constitutive model implies no rate-dependent strain hardening effect. A new constitutive model was proposed in consideration of rate-dependent strain hardening effect. The strain rate hardening term in the new constitutive model consists of the strain rate sensitivity coefficients of the yield strength and strain hardening.

Keywords: Rate dependent material properties, Dynamic constitutive model, OFHC copper film, Strain rate.

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