• 제목/요약/키워드: reversibility

검색결과 304건 처리시간 0.039초

두 단계로 구성된 순환대기네트워크의 설계 (A Design Problem of a Two-Stage Cyclic Queueing Network)

  • 김성철
    • 한국경영과학회지
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    • 제31권1호
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    • pp.1-13
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    • 2006
  • In this paper we consider a design problem of a cyclic queueing network with two stages, each with a local buffer of limited capacity. Based on the theory of reversibility and product-form solution, we derive the throughput function of the network as a key performance measure to maximize. Two cases are considered. In case each stage consists of a single server, an optimal allocation policy of a given buffer capacity and work load between stages as well as the optimal number of customers is identified by exploiting the properties of the throughput function. In case each stage consists of multiple servers, the optimal policy developed for the single server case doesn't hold any more and an algorithm is developed to allocate with a small number of computations a given number of servers, buffer capacity as well as total work load and the total number of customers. The differences of the optimal policies between two cases and the implications of the results are also discussed. The results can be applied to support the design of certain manufacturing and computer/communication systems.

아조벤젠을 함유한 장쇄 지방산의 광재현성과 안정성에 관한 연구 (The Photo-reproducibility and Stability of Long Chain Fatty Acid Containing Azobenzene)

  • 박근호;박태곤
    • 한국응용과학기술학회지
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    • 제12권1호
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    • pp.109-114
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    • 1995
  • The Synthesis of long chain fatty acid containing azobenzene and $(C_{n}-Azo)$ was optimized, starting from p-(p'-hydroxy phenyl azo)-benzoic acid and the product of reaction containing azobenzene chromophores was investigated by ultraviolet spectrophotometery in chloroform solvent at the various temperature. In addition, Reversibility and stability of azo compounds have been measured by means of Ultraviolet and the structure of these compound were ascertained by means of FT-IR and NMR. Recrystallization of reaction product in the solvent results the experimental yield obtained about 62.93% p-(p'-octadecyloxy phenyl azo)-benzoic acid. Long chain azobenzene derivatives in chloroform solution are induced photoisomerization by u. v. and visible light irradiation. The solution of long chain fatty acids$(C_{n}-Azo)$ containing azobenzene are possible of being applied to functional molecular devices such as photomemory and light switching.

PAS 전극에 관한 전기화학적 특성 측정 (Electrochemical Property Measurement on Flyacenic Semiconductor(PAS))

  • 김한주;박수길;손원근;이홍기;이주성
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 1999년도 춘계학술대회 논문집
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    • pp.197-200
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    • 1999
  • The polyacene materials prepared from phenol resine at relatively low temperature(550~75$0^{\circ}C$) show a highly Li-doped state up to $C_2$Li state without liberation of Li cluster. We prepared each polyacenic materials various temperature and investigated electrochemical property. We tried to change the mole ratio of [H]/[C] that was 0.24~0.4 range and finally found that the further discussion of improvements of battery materials. The X-ray structural analyses have shown that this material is essentiallly amorphous with loose structure in molecular size order. This structure ensures that the PAS battery has both reliability on repetitive doping-undoping processes and higher energy density than other batteries. The PAS electrode has been confirmed to show good stability and reversibility.

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리튬이차전지용 Polyacenic Semiconductor Material의 전기화학적 특성

  • 박수길;박종은;;이주성
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 1998년도 춘계학술대회 논문집
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    • pp.407-410
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    • 1998
  • During the past decade, substantial research effort has been directed into the development of rechargeable lithium batteries. Although some improvements in cycle life and efficiency have been achieved, the reversibility of the lithium electrode remains as a significant problem in aprotic solvent based electrolyte. The major problems limiting cycle life are short circuits resulting from growth of lithium dendrites, and macroscopic shape changes during the recharge process. As an anode material of lithium rechargeable battery, amorphous carbon materials have been studied extensively because of their high electrochemical performance. The polyacene materials prepared from phenol refine at relatively low temperature(550∼750$^{\circ}C$) show a highly Li-doped state up C$_2$Li state without liberation of Li cluster. So it has largely layered distance 4${\AA}$. The Li storage mechanism as well as the large hysterisis observed in the voltage-capacity profile of the amorphous carbone materials are still the subjects of controversy. We prepared each polyacene material various temperature and investigated electrochemical property. The mole ratio of [H]/[C] is 0.027∼0.015 range.

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섬유층을 이용한 단백질의 크로마토그래피적 분리에 관한 연구(I) -흡착성 섬유제조 및 자료처리- (A Study on the Chromatographic Separation of Proteins Using Fibrous Beds(I) -Adsorbent Fiber Manufactures and Data Handling-)

  • 박돈희;박주정
    • KSBB Journal
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    • 제9권2호
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    • pp.98-103
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    • 1994
  • 본 연구는 크로마토그래피적 방법에 의한 단백질 분리를 규모화시키기 위한 기초적인 실험을 행한 것이다. 단백질 분리를 위해서 화학적 처리된 폴리에틸렌섬유를 미국 Millipore사의 여과 Cartridge에 장착시키고, 그 시스템에서 단백질인 5%의 Bovine Serum Albumin을 통과시켜 섬유 표면의 단백질 흡착능력과 결합 가역성 등을 관찰하였다. 또한 실험자료들을 Omega 프로그램이 내장된 컴퓨터와 맥킨토시의 Kaleidagraph로 자료처리 한 것을 보여주었다.

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실리콘 재료의 표면개질에 따른 리튬이차전지 음극 특성 (Electrochemical Properties of Surface-Modified Silicon as Anode for Lithium Secondary Batteries)

  • 박철완;도칠훈;문성인;윤문수
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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    • pp.602-606
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    • 2003
  • Silicon has been developed as an alternate anode material for lithium secondary batteries. A simple approach to improve the electrical contact of silicon powder has described. Carbon-coated and silver-coated silicon have been prepared by chemical vapor deposition and electroless plating respectively. Assembled cells, which consisted of surface modified silicon, lithium foil and $Li^+$ contained organic electrolyte, have been studied using electrochemical methods. Carbon-coated silicon was improved in the electrochemical performance such as reversibility and resistance compared to surface-unmodified silicon.

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스퍼터링으로 증착한 바나듐 텅스텐 산화물 박막의 전기화학적 거동 (Electrochemical Behavior of Vanadium Trungsten Oxide Thin Films Deposited by Sputtering)

  • 박영신;이병일;주승기
    • 한국표면공학회지
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    • 제30권2호
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    • pp.121-127
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    • 1997
  • Vanadium tungsten oxide thin films were formed by RF magnetron sputtering and the effects of tungsten addition on the crystallinity and on the electrochemical behavior were investigated. X-ray analysis revealed that amorphized films could be obtained by tungase addition. In order to investigate the electrochemical behavior of the vanadium tungsten oxide films, electrochemical insertion and extraction of lithium were out in 1m $LiCIO_4$-PC-DME electrolyte using litium metal as a counter electrode. When the tungsten was added to the $V_2O_5$ films, cycling reversibility was considerably improved. Electrochemical test showed the cell capacity of about $70\mu\;Ah/\textrm{cm}^2-\mu\textrm{m}$ when the amount of additive tungseten reached 30 atomic percent. No appreciable degradation of the cell capacity could be observed after hundred cycles of insertion and extration od Li.

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RF Sputtered $SnO_2$, Sn-Doped $In_2O_3$ and Ce-Doped $TiO_2$ Films as Transparent Counter Electrodes for Electrochromic Window

  • 김영일;윤주병;최진호;Guy Campet;Didier Camino;Josik Portier;Jean Salardenne
    • Bulletin of the Korean Chemical Society
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    • 제19권1호
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    • pp.107-109
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    • 1998
  • The $SnO_2$, Sn-doped $In_2O+3\; and \;Ce-doped\; TiO_2$ films have been prepared by RF sputtering method, and their opto-electrochemical properties were investigated in view of the applicability as counter electrodes in the electrochromic window system. These oxide films could reversibly intercalate $Li^+$ ions owing to the nanocrystalline texture, but remained colorless and transparent. The high transmittance of the lithiated films could be attributed to the prevalence of the $Sn^{4+}/Sn^{2+}\; and\; Ce^{4+}/Ce^{3+}$ redox couples having 5s and 6s character conduction bands, respectively. For the Ce-doped $TiO_2$ film, $(TiO_2)_{1-x}(CeO_2)_x$, an optimized electrochemical reversibility was found in the film with the composition of x = 0.1.

A Synthetic Study on Trans-2,5-Disubstituted Tetrahydrofurans via Phenylselenoetheriflcation

  • Kang, Sung-Ho;Hwang, Tae-Seop;Lim, Joong-Ki;Kim, Wan-Joo
    • Bulletin of the Korean Chemical Society
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    • 제11권5호
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    • pp.455-460
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    • 1990
  • 2,5-Disubstituted tetrahydrofurans 11-13 were prepared by phenylselenoetherification of 1-alkyl-4-phenyl-(3E)-butenols 8-10 under kinetic conditions. Their stereochemical outcome and reactivity were controlled by solvent, reaction temperature and the alkyl substituent. While the cyclization was stereorandom in dichloromethane, its stereoinduction was moderate to good in propionitrile and good to excellent in diethyl ether. The reaction went to completion in dichloromethane and propionitrile, but it did not in diethyl ether. The results can be rationalized by the degree of reversibility in the formation of episelenonium cation and 1,3-diaxial interactions in the transition state of the formation of tetrahydrofuranonium cation.

유한 용량의 버퍼를 가지는 대기행렬에서의 저장공간 공유방안 비교에 관한 연구 (A Study on the Comparison of Storage Sharing Schemes in Queueing System with Finite Capacity Buffer)

  • 권수태
    • 산업경영시스템학회지
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    • 제27권4호
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    • pp.15-22
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    • 2004
  • 본 논문의 목적은 유한 저장공간을 가지는 대기행렬 시스템에서 완전공유(Complete Sharing), 완전분할(Complete Partitioning), 최소할당공유(Sharing with Minimum Allocation)와 같은 다양한 저장공간 공유방안들을 비교ㆍ분석하는 것으로, 이를 위하여 먼저 각각의 공유방안에서의 대기행렬 안정상태확률을 효율적으로 구할 수 있는 방법이 제시되었다. 다음으로 각각의 저장공간 공유방안을 특징짓는데 필요한 몇 가지 성질들이 규명되었으며, 이를 토대로 각각의 저장공간 공유방안에 대하여 시스템 성능척도인 생산률들을 도출하는 한편, 이들의 대소관계를 파악하고, 수치실험을 통하여 이를 입증하였다.