• Title/Summary/Keyword: Cycle time

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Dynamic Right Sizing of Maximum-windows for Efficient Bandwidth Allocation on EPON (EPON에서 효율적 대역폭 할당을 위한 최대전송윈도우 크기의 동적변화기법)

  • Lee, Sang-Ho;Lee, Tae-Jin;Chung, Min-Young;Lee, You-Ho;Choo, Hyun-Seung
    • Journal of Internet Computing and Services
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    • v.8 no.4
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    • pp.41-49
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    • 2007
  • Ethernet passive optical network(EPON) is the next-generation technology for supporting services of high-quality at low-cost. In the EPON, all optical network units(ONUs) have to share a limited uplink channel for upstream data. In order to satisfy bandwidth demands of users on high-capacity local access networks(LANs), the optical line terminal(OLT) efficiently divides and allocates time slots of uplink channel to all ONUs. We discuss previous schemes for dynamic bandwidth allocation(DBA), such as interleaved polling with adaptive cycle time(IPACT) and sliding cycle time(SLICT). In this paper, dynamic right sizing of maximum-windows(DRSM), as a novel bandwidth allocation service, is proposed for more effective and efficient time slot allocation of the uplink channel. DRSM which is based on past information of bandwidth allocated by OLT calculates maximum available bandwidth and dynamically alters the maximum window size for the next ONU. This scheme does not only exert every effort to meet bandwidth demands of ONUs with the possible scope, it also seeks fairness of bandwidth allocation among ONUs.

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An Integrated Production and Inventory Model in a Single-Vendor Multi-Buyer Supply Chain (단일 공급자 다수 구매자 공급체인에서 통합 생산 및 재고 모형)

  • Chang, Suk Hwa
    • Journal of the Society of Korea Industrial and Systems Engineering
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    • v.38 no.3
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    • pp.117-126
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    • 2015
  • This paper is to analyze an integrated production and inventory model in a single-vendor multi-buyer supply chain. The vendor is defined as the manufacturer and the buyers as the retailers. The product that the manufacturer produces is supplied to the retailers with constant periodic time interval. The production rate of the manufacturer is constant for the time. The demand of the retailers is constant for the time. The cycle time of the vendor is defined as the elapsed time from the start of the production to the start of the next production, while the cycle times of the buyer as the elapsed time between the adjacent supply times from the vendor to the buyer. The cycle times of the vendor and the buyers that minimizes the total cost in a supply chain are analyzed. The cost factors are the production setup cost and the inventory holding cost of the manufacturer, the ordering cost and the inventory holding cost of the retailers. The cycle time of the vendor is investigated through the cycle time that satisfies economic production quantity with the production setup cost and the inventory holding cost of the manufacturer. An integrated production and inventory model is formulated, and an algorithm is developed. An numerical example is presented to explain the algorithm. The solution of the algorithm for the numerical examples is compared with that of genetic algorithm. Numerical example shows that the vendor and the buyers can save cost by integrated decision making.

A Study on the Process Simulation Analysis of the High Precision Laser Scriber (고정밀 레이저 스크라이버 장비의 공정 시뮬레이션 분석에 관한 연구)

  • Choi, Hyun-Jin;Park, Kee-Jin
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.18 no.7
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    • pp.56-62
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    • 2019
  • The high-precision laser scriber carries out scribing alumina ceramic substrates for manufacturing ultra-small chip resistors. The ceramic substrates are loaded, aligned, scribed, transferred, and unloaded. The entire process is fully automated, thereby minimizing the scribing cycle time of the ceramic substrates and improving the throughput. The scriber consists of the laser optical system, pick-up module of ceramic substrates, pre-alignment module, TH axis drive work table, automation module for substrate loading / unloading, and high-speed scribing control S/W. The loader / unloader unit, which has the greatest influence on the scribing cycle time of the substrates, carries the substrates to the work table that carries out the cutting line work by driving the X and Y axes as well as by adsorbing the ceramic substrates. The loader / unloader unit consists of the magazine up / down part, X-axis drive part for conveying the substrates to the left and right direction, and the vision part for detecting the edge of the substrate for the primary pre-alignment of the substrates. In this paper, the laser scribing machining simulation is performed by applying the instrument mechanism of each component module. Through this study, the scribing machining process is first verified by analyzing the process operation and work area of each module in advance. In addition, the scribing machining process is optimized by comparing and analyzing the scribing cycle time of one ceramic substrate according to the alignment stage module speed.

A Study for Optimal Phase Design of Traffic Signal Using Fuzzy Theory (퍼지 논리를 이용한 최적교통신호 현시설계에 관한 연구)

  • 진현수;홍유식;김성환
    • Journal of Korean Society of Transportation
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    • v.14 no.1
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    • pp.117-133
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    • 1996
  • In the paper a superior performance algorithm compared to the existing vehicle actuated controller and time fixed controller and the additional controller is described through realization of fuzzy traffic phase controller. Fuzzy theory is encouraging since the application is similar to human's decision ability that is approately coped with uncertain conditions. The paper presents that selection of the phase adequated the variable traffic conditions through the fuzzy theory algorithm and decision of optimal cycle time approated the uncertain traffic volume are predominant in traffic jam solution compared to the existing Webster's cycle time decision method and the sequential traffic phase design method and dual-ring phase operation system.

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Effects of nucleating agents and plasticizers on the crystallinity and crystal structure of PLA(PolyLactic Acid) (핵제 및 가소제 첨가에 따른 PLA(PolyLactic Acid)의 결정화도 개선 및 결정구조에 관한 연구)

  • Park, Eun-Jo;Park, Hern-Jin;Kim, Dong-Hak
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.1
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    • pp.914-920
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    • 2015
  • In this paper, the crystal structure and the crystallinity of PLA(PolyLactic Acid) were studied. PLA is a eco-friendly thermoplastic which completely decomposed by microorganisms, but has low thermal stability and low degree of crystallinity. The low crystallization rate makes the cycle time of injection molding longer and the degree of crystallinity lower. It is a very big disadvantage comparing the other thermoplastics. We improved the degree of crystallinity and the crystallization rate by introducing nucleating agents and plasticizer, and discussed the mechanism.

Optimal Working Cycles for Minimal Repair Policy (정기교체 및 최소수리를 고려한 작업주기 횟수 최적화)

  • Lee, Jinpyo
    • Journal of Korean Society for Quality Management
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    • v.48 no.1
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    • pp.201-214
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    • 2020
  • Purpose: The purpose of this paper is to determine an optimal number of cycle times for the replacement under the circumstance where the system is replaced at the periodic time and the multiple number of working cycles whichever occurs first and the system is minimally repaired between the replacements if it fails. Methods: The system is replaced at periodic time () or cycle time, whichever occurs first, and is repaired minimally when it fails between successive replacements. To determine the optimal number of cycle times, the expected total cost rate is optimized with respect to the number of cycle times, where the expected total cost rate is defined as the ratio of the expected total cost between replacements to the expected time between replacements. Results: In this paper, we conduct a sensitivity analysis to find the following results. First, when the expected number of failures per unit time increases, the optimal number of cycle times decreases. Second, when the periodic time for replacement becomes longer, the optimal number of cycle times decreases. Third, when the expected value for exponential distribution of the cycle time increases, the optimal number of cycle times increases. Conclusion: A mathematical model is suggested to find the optimal number of cycle times and numerical examples are provided through the sensitivity analysis on the model parameters to see the patterns for changes of the optimal number of cycle times.

Experimental Study on PSA Process for High Purity CH4 Recovery from Biogas (바이오가스로부터 고순도 CH4 회수를 위한 PSA 공정의 실험적 연구)

  • Kim, Young-Jun;Lee, Jong-Gyu;Lee, Jong-Yeon;Kang, Yong-Tae
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.23 no.4
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    • pp.281-286
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    • 2011
  • The objective of this study is to optimize the four-bed six-step pressure swing adsorption(PSA) process for high purity $CH_4$ recovery from the biogas. The effects of P/F(purge to feed) ratio and cycle time on the process performance were evaluated. The cyclic steady-states of PSA process were reached after 12 cycles. The purity and recovery rate of product gas, pressure and temperature changes were constant as the cycle repeated. It was shown that the P/F ratio gave significant effect on the product recovery rate by increasing the amount of purge gas in purge and regeneration step. The optimal P/F ratio was found to be 0.08. As the cycle time increased, the product purity decreased by increasing the feed gas flow rate. It was found that the optimal operating conditions were P/F ratio of 0.08 and total cycle time of 1,440 seconds with the purity of 97%.

An analysis of excavation cycle time for Korean tunnels and the comparison with the Standard of Construction Estimate (국내터널 굴착 사이클타임에 대한 분석결과와 표준품셈과의 비교)

  • Kim, Yangkyun;Kim, Hyung-Mok;Lee, Sean S.
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.21 no.1
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    • pp.137-153
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    • 2019
  • Estimating tunnel construction time and costs are the most fundamental part of a tunnel project planning, which has been generally assessed on a deterministic basis until now. In this paper, excavation cycle time was investigated for two road tunnels and one subway tunnel, and the results were compared with the Standard of Construction Estimate (SE), which is made for the estimation of construction time and cost in a design stage. The results show that the difference in cycle time between SE and actual cycle time is 50%, 7% and 31% respectively for the three tunnels, which means that SE does not reflect practical operation time. The major reasons of the difference are skilled level of tunneling workers, the change of operation sequences for more effective operations, much more complicated working atmosphere in a tunnel than the assumption of SE etc. Finally, even though the results can not be generalized since investigated tunnels are only 3, but it is thought that SE needs to be upgraded into the model able to consider quite common situations through additional tunnel investigation and studies in the future.