• Title/Summary/Keyword: Constrained condition

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Cosmic Dawn III: Simulating the Reionization of the Local Group

  • Ahn, Kyungjin
    • The Bulletin of The Korean Astronomical Society
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    • v.46 no.1
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    • pp.47.1-47.1
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    • 2021
  • Cosmic Dawn III (CoDa III) is the last of the series of simulations of the reionization of the Local Group, the galaxy cluster including the Milky Way and the M31. The simulation is based on the constrained initial condition, N-body and hydrodynamic simulation of structure formation, modelling of galaxy formation, calculation of radiation transfer, and calibration against the observed high-redshift galaxy luminosity function. We present various physical properties we observed and important lessons that could stimulate future observations.

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Reliability Evaluation of a Microgrid Considering Its Operating Condition

  • Xu, Xufeng;Mitra, Joydeep;Wang, Tingting;Mu, Longhua
    • Journal of Electrical Engineering and Technology
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    • v.11 no.1
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    • pp.47-54
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    • 2016
  • Microgrids offer several reliability benefits, such as the improvement of load-point reliability and the opportunity for reliability-differentiated services. The primary goal of this work is to investigate the impacts of operating condition on the reliability index for microgrid system. It relies on a component failure rate model which quantifies the relationship between component failure rate and state variables. Some parameters involved are characterized by subjective uncertainty. Thus, fuzzy numbers are introduced to represent such parameters, and an optimization model based on Fuzzy Chance Constrained Programming (FCCP) is established for reliability index calculation. In addition, we present a hybrid algorithm which combines scenario enumeration and fuzzy simulation as a solution tool. The simulations in a microgrid test system show that reliability indices without considering operating condition can often prove to be optimistic. We also investigate two groups of situations, which include the different penetration levels of microsource and different confidence levels. The results support the necessity of considering operating condition for achieving accurate reliability evaluation.

Long-term Prediction of Speech Signal Using a Neural Network (신경 회로망을 이용한 음성 신호의 장구간 예측)

  • 이기승
    • The Journal of the Acoustical Society of Korea
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    • v.21 no.6
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    • pp.522-530
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    • 2002
  • This paper introduces a neural network (NN) -based nonlinear predictor for the LP (Linear Prediction) residual. To evaluate the effectiveness of the NN-based nonlinear predictor for LP-residual, we first compared the average prediction gain of the linear long-term predictor with that of the NN-based nonlinear long-term predictor. Then, the effects on the quantization noise of the nonlinear prediction residuals were investigated for the NN-based nonlinear predictor A new NN predictor takes into consideration not only prediction error but also quantization effects. To increase robustness against the quantization noise of the nonlinear prediction residual, a constrained back propagation learning algorithm, which satisfies a Kuhn-Tucker inequality condition is proposed. Experimental results indicate that the prediction gain of the proposed NN predictor was not seriously decreased even when the constrained optimization algorithm was employed.

A Receiver-driven TCP Flow Control for Memory Constrained Mobile Receiver (제한된 메모리의 모바일 수신자를 고려한 수신자 기반 TCP 흐름 제어)

  • 이종민;차호정
    • Journal of KIISE:Information Networking
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    • v.31 no.1
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    • pp.91-100
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    • 2004
  • This paper presents a receiver-driven TCP flow control mechanism, which is adaptive to the wireless condition, for memory constrained mobile receiver. A receiver-driven TCP flow control is, in general, achieved by adjusting the size of advertised window at the receiver. The proposed method constantly measures at the receiver both the available wireless bandwidth and the packet round-trip time. Depending on the measured values, the receiver adjusts appropriately the size of advertised window. Constrained by the adjusted window which reflects the current state of the wireless network, the sender achieves an improved TCP throughput as well as the reduced round-trip packet delay. Its implementation only affects the protocol stack at the receiver and hence neither the sender nor the router are required to be modified. The mechanism has been implemented in real environments. The experimental results show that in CDMA2000 1x networks the TCP throughput of the proposed method has improved about 5 times over the conventional method when the receiver's buffer size is limited to 2896 bytes. Also, with 64Kbytes of buffer site, the packet round-trip time of the proposed method has been reduced in half, compared the case with the conventional method.

Real-Time Seam Tracking System Using a Visual Device with Vertical Projection of Laser Beam (레이저빔 수직투사 구조의 시각장치를 이용한 실시간 용접선추적 시스템)

  • Kim, Jin-Dae;Lee, Jeh-Won;Shin, Chan-Bai
    • Journal of the Korean Society for Precision Engineering
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    • v.24 no.10
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    • pp.64-74
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    • 2007
  • Because of the size and environment in the shipbuilding process, the portable type robot is required for the automatic seam tracking. For this reason, the structure of laser sensor should be considered in the initial design step and the coordinate transformation between welding robot and laser sensor, which is joint finder, must be identified exactly and the real time tracking algorithm based on these consideration could be developed. In this research, laser displacement sensor in which its structure is laser beam's vertical projection, is developed to recognize the location of weld joint. In practical applications, however, images of weld joints are often degraded because of the surface specularity or spatter. To overcome the problem, the constrained joint finding algorithm is proposed. In the approach of coordinate conversion rule for the visual feedback control among welding torch, robot body and laser sensor is applied by the same reference point method. In the real time seam tracking algorithms we propose constrained sampling method which uses look ahead distance. The RLS(Recursive Least Square) filter is applied to obtain the smooth tracking path from the sensitive edge data. From the experimental results, we could see the possibility that the developed laser sensor with proposed processing algorithm and real time seam tracking method can be used as a welding under the shipbuilding condition.

Realization of Forward Real-time Decoder using Sliding-Window with decoding length of 6 (복호길이 6인 Sliding-Window를 적용한 순방향 실시간 복호기 구현)

  • Park Ji woong
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.30 no.4C
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    • pp.185-190
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    • 2005
  • In IS-95 and IMT-2000 systems using variable code rates and constraint lengths, this paper limits code rate 1/2 and constraint length 3 and realizes forward real-time decoder using Sliding-Window with decoding length 6 and PVSL(Prototype Vector Selecting Logic), LVQ(Learning Vector Quantization) in Neural Network. In comparison condition to theoretically constrained AWGN channel environment at $S/(N_{0}/2)=1$ I verified the superiority of forward real-time decoder through hard-decision and soft-decision comparison between Viterbi decoder and forward real-time decoder such as BER and Secure Communication and H/W Structure.

Security Constrained Optimal Power Flow Incorporating Load Curtailment Schedule (부하차단량을 고려한 상정사고 절약 최적조류계산 알고리즘 개발)

  • Chung, Koo-Hyung;Kang, Dong-Joo;Kim, Bal-Ho
    • Proceedings of the KIEE Conference
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    • 2005.07a
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    • pp.801-803
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    • 2005
  • Fundamentally, success of the competitive electricity market is dependent on efficient market design. However, since electricity incorporates various physical constraints as other commodities, the resource assignment (i.e., dispatch scheduling) is also one of requisites for the successful operation of electricity market. Therefore, efficient dispatch scheduling is an important issue to succeed in the deregulated electricity market and the efficiency of this electricity market may be considerably increased by systematic studies on dispatch scheduling algorithm and corresponding constraints, especially system security. Moreover, contrary to traditional vertically-integrated electric power industry condition, since various decision-makings in deregulated electricity market are directly connected with market participants' benefits, only rational dispatch scheduling algorithm can convince these participants. Therefore, it can provide a basis of grievance prevention. In this paper, we propose an algorithm for security constrained dispatch scheduling with respect to load curtailment. Proposed algorithm decomposes the dispatch problem into a master problem corresponding to basecase optimal power flow (OPF) and several subproblems corresponding a series of contingencies using two-stage optimization technique.

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A fast full search algorithm for multiple reference image motion estimation (다중 참조 영상 움직임 추정을 위한 고속 전역탐색법)

  • Kang Hyun-Soo;Park Seong-Mo
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.43 no.1 s.307
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    • pp.1-8
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    • 2006
  • This paper presents a fast full search algorithm for motion estimation applicable to multiple reference images. The proposed method is an extended version of the rate constrained successive elimination algorithm (RSEA) for multiple reference frame applications. We will show that motion estimation for the reference images temporally preceding the first reference image can be less intensive in computation compared with that for the first reference image. for computational reduction, we will drive a new condition to lead the smaller number of candidate blocks for the best matched block. Simulation results explain that our method reduces computation complexity although it has the same quality as RSEA.

An Embedded Multi-Agent Based Healthcare Service with Two-way Handshaking Mode (무선 및 유선환경에서 임베디드 멀티에이전트 기반의 쌍방향 건강관리 서비스)

  • Md, Amiruzzaman;Kim, Hyoung-Joong
    • Journal of the Institute of Electronics Engineers of Korea CI
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    • v.45 no.5
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    • pp.155-161
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    • 2008
  • An automated healthcare monitoring is demand of time, lot of problems occurring just because of less monitoring of patients health condition on time. In this paper an embedded healthcare service is proposed by an iSCSI protocol on an automated multi-agent coordination by resource-constrained devices controlled system for healthcare service. The coordination between the resource constrained devices (e.g. PDA, SmartPhone, Tablet PC), and automated agents are maintained by a two-way handshaking mode iSCSI protocol. The automated health care control could be useable, and beneficial in the repetitive way. A fully centralized control is not applicable for this kind of approach.

Dynamic Analysis of Constrained Mechanical System Moving on a Flexible Beam Structure(II) : Application (유연한 보 구조물 위를 이동하는 구속 기계계의 동력학 해석(II) : 응용)

  • Park, Chan-Jong;Park, Tae-Won
    • Journal of the Korean Society for Precision Engineering
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    • v.17 no.11
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    • pp.176-184
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    • 2000
  • Recently, it becomes a very important issue to consider the mechanical systems such as high-speed vehicle and railway train moving on a flexible beam structure. Using general approach proposed in the first part of this paper, it tis possible to predict planar motion of constrained mechanical system and elastic structure with various kinds of foundation supporting condition. Combined differential-algebraic equations of motion derived from both multibody dynamics theory and Finite Element Method can be analyzed numerically using generalized coordinate partitioning algorithm. To verify the validity of this approach, results from simply supported elastic beam subjected to a moving load are compared with exact solution from a reference. Finally, parameter study is conducted for a moving vehicle model on a simply supported 3-span bridge.

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