• Title/Summary/Keyword: Dynamic System Simulation

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Recent Progress in Air Conditioning and Refrigeration Research - A Review of papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 1998 and 1999 - (공기조화, 냉동 분야의 최근 연구 동향 - 1998년 1999년 학회지 논문에 대한 종합적 고찰 -)

  • 이재헌;김광우;김병주;이재효;김우승;조형희;김민수
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.12 no.12
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    • pp.1098-1125
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    • 2000
  • A review on the papers published in the Korean Journal of Air-Conditioning and Refrigerating Engineering in 1998 and 1999 has been done. Focus has been put on current status of research in the aspect of heating, cooling, ventilation, sanitation and building environment. The conclusions are as follows. 1) A review of the recent studies on fluid flow, turbomachinery and pipe-network shows that many experimental investigations are conducted in applications of impingement jets. Researches on turbulent flows, pipe flows, pipe-networks are focused on analyses of practical systems and prediction of system performance. The results of noise reduction in the turbomachinery are also reported. 2) A review of the recent studies on heat transfer analysis and heat exchanger shows that there were many papers on the channel flow with the application to the design of heat exchanger in the heat transfer analysis. Various experimental and numerical papers on heat exchanger were also published, however, there were few papers available for the analysis of whole system including heat exchanger. 3) A review of the recent studies on heat pump system have focused on the multi-type system and the heat pump cycle to utilize treated sewage as the heat source. The defrosting and the frosting behaviors in the fin-tube heat exchanger is experimentally examined by several authors. Several papers on the ice storage cooling system are presented to show the dynamic simulation program and optimal operation conditions. The study on the micro heat pipes for the cooling of high power electronic components is carried out to examine the characteristics of heat and mass transfer processed. In addition to these, new type of separate thermosyphon is studied experimentally. 4) The recent studies on refrigeration/air conditioning system have focused on the system performance and efficiency for new alternative refrigerants. New systems operating with natural refrigerants are drawing lots of attention. In addition to these, evaporation and condensation heat transfer characteristics of traditional and new refrigerants are investigated for plain tubes and also for microfin tubes. Capillary tubes and orifice are main topics of research as expansion devices and studies on thermophysical properties of new refrigerants and refrigerant/oil mixtures are widely carried out. 5) A review of the recent studies on absorption cooling system shows that numerous experimental and analytical studies on the improvement of absorber performance have been presented. Dynamic analysis of compressor have been performed to understand its vibration characteristics. However research works on tow-phase flow and heat transfer, which could be encountered in the refrigeration system and various phase-change heat exchanger, were seemed to be insufficient. 6) A review of recent studies on duct system shows that the methods for circuit analysis, and flow balancing have been presented. Researches on ventilation are focused on the measurement of ventilation efficiency, and variation of ventilation efficiency with ventilation methods by numerous experimental and numerical studies. Furthermore, many studies have been conducted in real building in order to estimate indoor thermal environments. Many research works to get some information for cooling tower design have been performed but are insufficient. 7) A review on the recent studies on architectural thermal environment and building mechanical systems design shows that thermal comfort analysis is sitting environment, thermal performance analysis of Korean traditional building structures., and evaluation of building environmental load have been performed. However research works to improve the performance of mechanical system design and construction technology were seemed to be insufficient.

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Performance Evaluation of a Dynamic Bandwidth Allocation Algorithm with providing the Fairness among Terminals for Ethernet PON Systems (단말에 대한 공정성을 고려한 이더넷 PON 시스템의 동적대역할당방법의 성능분석)

  • Park Ji-won;Yoon Chong-ho;Song Jae-yeon;Lim Se-youn;Kim Jin-hee
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.11B
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    • pp.980-990
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    • 2004
  • In this paper, we propose the dynamic bandwidth allocation algorithm for the IEEE802.3ah Ethernet Passive Optical Network(EPON) system to provide the fairness among terminals, and evaluate the delay-throughput performance by simulation. For the conventional EPON systems, an Optical Line Termination (OLT) schedules the upstream bandwidth for each Optical Network Unit (ONU), based on its buffer state. This scheme can provide a fair bandwidth allocation for each ONU. However, it has a critical problem that it does not guarantee the fair bandwidth among terminals which are connected to ONUs. For an example, we assume that the traffic from a greedy terminal increases at a time. Then, the buffer state of its ONU is instantly reported to the OLT, and finally the OW can get more bandwidth. As a result, the less bandwidth is allocated to the other ONUs, and thus the transfer delay of terminals connected to the ONUs gets inevitably increased. Noting that this unfairness problem exists in the conventional EPON systems, we propose a fair bandwidth allocation scheme by OLT with considering the buffer state of ONU as welt as the number of terminals connected it. For the performance evaluation, we develop the EPON simulation model with SIMULA simulation language. From the result of the throughput-delay performance and the dynamics of buffer state along time for each terminal and ONU, respectively, one can see that the proposed scheme can provide the fairness among not ONUs but terminals. Finally, it is worthwhile to note that the proposed scheme for the public EPON systems might be an attractive solution for providing the fairness among subscriber terminals.

A System Dynamics Model for Negotiation strategy Analysis with North Korea (남북관계와 대북협상전략)

  • 곽상만
    • Korean System Dynamics Review
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    • v.1 no.2
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    • pp.5-31
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    • 2000
  • The summit meeting of the South North Korean leaders was a turning point in the relationships between the two countries. It was followed by the Red-Cross Meeting, Minister-Level Meeting, economic agreements, which have increased the relationship more colorful in both quantities and qualities. However, the half-century period for separation was too long to overcome all the problems by only one event. The two countries have quite different social systems; one politically strong person is governing the North, while many interest groups are involved in political decision making processes in the South. In short, it would take a long time to settle down all the problems residing between the two countries. A system dynamics model is developed to describe the long term dynamics of the relations between the South and North Koreas. As a first attempt, the model focuses only on the diplomatic meeting issues between the South and North. The model aggregates diplomatic issues into 5 categories; economic issues, security issues, infrastructure, cultural issues, and past problems. It assumes that there would not be any dramatic changes between the two countries. It is a conceptual model composed of around 200 variables, and should not be used as a forecast tool. However, it captures most of the logics discussed in the papers and conferences concerning the South and North Korea relations. Many sensitivity studies and Monte Carlo simulations have shown that the simulation results matches with mental models of experts; that is the model can be used as a learning tool or as a secondary opinion until the data required by the model is collected. In order to analyze the current situation, five scenarios are simulated and analyzed; the functional approach, the conditional approach, the balanced approach, the circumstantial approach, and the strategic approach. The functional approach represents that the South makes efforts in the area where the possibility of agreement is high for the next 10 years. The conditional approach is a scenario where the South impose all difficult issues as conditions for resolving other diplomatic issues. The balanced approach is resolving the five issues with the same priorities, while the circumstantial approach is resolving issues which seem to be resolved easily. Finally, another optimum approach has been seek using the system dynamics model developed. The optimum strategy (it is named as the strategic approach) was strikingly different from other four approaches. The optimum strategy is so complicated that no one could find it with mental model(or by just insights). Considering that the system dynamic model used to find the optimum is a simplifind (maybe over simplified) version of the reality, it is concluded that a well designed system dynamics model would be of great help to resolving the complicated diplomatic problems in any kind.

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Symbol Power Allocation and Channel Estimation Method for LR-WPAN System (LR-WPAN 시스템에서 심볼 전력 할당과 2개의 직교 코드를 사용한 채널 추정 기법)

  • Lee, Kyung-Tak;Lee, Sung-Jun;Sohn, Sung-Hwan;Kim, Jae-Moung
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.44 no.11
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    • pp.1-10
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    • 2007
  • In this paper, we proposed channel estimation scheme for LR-UWB system which has low data rate for WPAN in IEEE 802.15.4a. At the transmitter, we proposed dynamic power level allocation depends on channel condition in specific period when we modulate signal. We use two orthogonal code to estimate channel at once. It can estimate channel more accurately by using two code which shows good correlation characteristic then it can estimate more accurately by spreading gain. Using estimated channel condition, we synchronize symbol timing of transmitted signal. Then determined power allocation scheme and channel information is transmitted to transmiter side. Finally, using these information, transmiter side change the power level of repeated pulse to adopt to channel condition. Simulation is performed under S-V channel for LR-WPAN in IEEE 802.15.4a and we compare the performance with a different type of receiver type. We use coherent and non-coherent method at the receiver. Simulation result shows us at the NLOS channal performance evaluation is greater than that of LOS channel and the result is independent of receiver type. In the NLOS channel, as the signal delay spreading is big, performance evaluation is also increased.

Sentiment Analysis Engine for Cambodian Music Industry Re-building (캄보디아 음악 산업 재건을 위한 감정 분석 엔진 연구)

  • Khoeurn, Saksonita;Kim, Yun Seon
    • Journal of the Korea Society for Simulation
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    • v.26 no.4
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    • pp.23-34
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    • 2017
  • During Khmer Rouge Regime, Cambodian pop music was completely forgotten since 90% of artists were killed. After recovering from war since 1979, the music started to grow again in 1990. However, Cambodian popular music dynamic and flows are observably directed by the multifaceted socioeconomic, political and creative forces. The major problems are the plagiarism and piracy which have been prevailing for years in the industry. Recently, the consciousness of the need to preserve Khmer original songs from both fans and artist have been increased and become a new trend for Cambodia young population. Still, the music quality is in the limit state. To increase the mind-set, the feedbacks and inspiration are needed. The study suggested a music ranking website using sentiment analysis which data were collected from Production Companies Facebook Pages' posts and comments. The study proposed an algorithm which translates from Khmer to English, doing sentiment analysis and generate the ranking. The result showed 80% accuracy of translation and sentiment analysis on the proposed system. The songs that rank high in the system are the songs which are original and fit the occasion in Cambodia. With the proposed ranking algorithm, it would help to increase the competitive advantage of the musical productions as well as to encourage the producers to compose the new songs which fit the particular activities and event.

Study on a Spin Stabilization Technique Using a Spin Table (스핀테이블을 이용한 스핀안정화 기법 연구)

  • Kim, Dae-Yeon;Suh, Jong-Eun;Han, Jae-Hung;Seo, Sang-Hyeon;Kim, Kwang-Soo
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.46 no.5
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    • pp.419-426
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    • 2018
  • For an orbit transfer in a space exploration mission, a solid or liquid rocket booster is included at the last stage of the launch vehicle. During the orbit transfer, thrust misalignment can cause a severe orbit error. Three axis attitude control or spin stabilization can be implemented to minimize the error. Spin stabilization technique has advantages in structural simplicity and lightness. One of ways to apply the spin stabilization to the payload is to include a spin table system in the launch vehicle. In this paper, effect of the spin table system on separation dynamics of the payload is analyzed. Simple model of the spin table to mimic basic functions is designed and simulation environment is established with the model. Effect of the spin table is tested by evaluating separation dynamics of a payload with and without the spin table. Analysis on tolerance effect of separation spring constant on separation dynamics of a payload is conducted.

3-Dimensional Numerical Analysis of Air Flow inside OWC Type WEC Equipped with Channel of Seawater Exchange and Wave Characteristics around Its Structure (in Case of Irregular Waves) (해수소통구를 구비한 진동수주형 파력발전구조물 내 공기흐름과 구조물 주변에서 파랑특성에 관한 3차원수치해석(불규칙파의 경우))

  • Lee, Kwang Ho;Lee, Jun Hyeong;Jeong, Ik Han;Kim, Do Sam
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.30 no.6
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    • pp.253-262
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    • 2018
  • Oscillating Water Column (OWC) Wave Energy Converters (WEC) harness electricity through a Power-Take-Off (PTO) system from the induced-airflow by seawater oscillating inside a chamber. In general, an air chamber with a relatively small cross-sectional area is required compared to seawater chamber to obtain high-velocity air in the PTO system, and in order to simulate an accurate air flow rate in the air chamber, a three-dimensional study is required. In this study, the dynamic response of OWC-WEC that is equipped with the channel of seawater exchange for the case of irregular waves has been numerically studied. The open source CFD software, OLAFLOW for the simulation of wave dynamics to the openFOAM and FOAM-extend communities, was used to simulate the interaction between the device and irregular waves. Based on the numerical simulation results, we discussed the fluctuation characteristics of three dimensional air flow in the air-chamber, wave deformation around the structure and the seawater flow inside the channel of seawater exchange. The numerical results the maximum air flow velocity in the air-chamber increases as the Ursell value of the significant wave increases, and the velocity of airflow flowing out from the inside of air chamber to the outside is greater than the speed of flowing into the air chamber from the outside.

Development of Attack Intention Extractor for Soccer Robot system (축구 로봇의 공격 의도 추출기 설계)

  • 박해리;정진우;변증남
    • Journal of the Institute of Electronics Engineers of Korea CI
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    • v.40 no.4
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    • pp.193-205
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    • 2003
  • There has been so many research activities about robot soccer system in the many research fields, for example, intelligent control, communication, computer technology, sensor technology, image processing, mechatronics. Especially researchers research strategy for attacking in the field of strategy, and develop intelligent strategy. Then, soccer robots cannot defense completely and efficiently by using simple defense strategy. Therefore, intention extraction of attacker is needed for efficient defense. In this thesis, intention extractor of soccer robots is designed and developed based on FMMNN(Fuzzy Min-Max Neural networks ). First, intention for soccer robot system is defined, and intention extraction for soccer robot system is explained.. Next, FMMNN based intention extractor for soccer robot system is determined. FMMNN is one of the pattern classification method and have several advantages: on-line adaptation, short training time, soft decision. Therefore, FMMNN is suitable for soccer robot system having dynamic environment. Observer extracts attack intention of opponents by using this intention exactor, and this intention extractor is also used for analyzing strategy of opponent team. The capability of developed intention extractor is verified by simulation of 3 vs. 3 robot succor simulator. It was confirmed that the rates of intention extraction each experiment increase.

A Study on the Effectiveness Analysis of Freeway Traffic Management Strategy Based on exTMS (exTMS기반의 고속도로 교통관리방안 효과분석에 관한 연구)

  • Sung, Ji-Na;So, Jae-Hyun;Oh, Young-Tae
    • The Journal of The Korea Institute of Intelligent Transport Systems
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    • v.8 no.5
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    • pp.38-47
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    • 2009
  • This paper aims to evaluate the freeway traffic management Strategy based on exTMS according to traffic situation of freeway. As freeway user's demands increase, we thus need future-oriented and optimized traffic management. So, through improving the existing system and introducing the advanced system, these systems evaluate for not only preparing the application in real world but also preliminary feasibility. To evaluate effects of the traffic management based on exTMS, in this study, shoulder LCS, advanced VMS(assumption in it is improving next-generation system which it can be offering diverse dynamic traffic information), Ramp-metering system are applicated in simulation. In addition, this study evaluates the effect when all proposed systems are applicated, and compare the individual effect of when independent system is applicated, through considering about traffic condition of V/C=0.5, V/C=0.8, V/C=1.2. The study results show that all assumed cases, the travel speed were improved according to the increasing V/C. Furthermore, the results of evaluated the individual system show that the shoulder LCS was found to be the largest effect, and the effect of VMS(detour rate is 11%) is larger than the other cases.

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Study on a Propulsion Control of the Roller Coasters Train based on Air Cored Linear Synchronous Motor (공심형 선형동기전동기 기반의 궤도열차 추진제어에 관한 연구)

  • Jo, Jeong-Min;Han, Young-Jae;Lee, Jin-Ho
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.12
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    • pp.8187-8194
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    • 2015
  • To accelerate a heavy roller coaster train with over 1G force, a lot of thrust is required and linear synchronous motor(LSM) as propulsion method is suitable for this kind of system. To increase the propulsion efficiency of LSM, precise and real-time position information of vehicle is required for accurate phase control. However, the discontinuous position information with relatively long time interval is usually transmitted from the hall-sensors on the track every magnet length. In this paper, the basic motor model based on traditional dq-axis equations is described and the motor dynamic model is produced by considering the cogging force and friction loss. To improve the position accuracy, the position estimator is also proposed for LSM control system. Simulations were performed to check the characteristics of the torque control system which includes the position estimator based on the motor model. Simulation results based on the linearized model show that this control system has an enough bandwidth and phase margin and the executed algorithm achieves an ideal effect to follow the real-time position signal. Therefore, the feasibility of position estimator is also confirmed.