• 한국경영과학회지
• /
• 제29권3호
• /
• pp.111-127
• /
• 2004

We consider a supply chain model with a make-to-order production facility and a single supplier. The model we treat here is a special case of a two-echelon inventory model. Unlike classical two-echelon systems, the demand process at the supplier is affected by production process at the production facility as well as customer order arrival process. In this paper, we address that how the demand variability impacts on the optimal replenishment policy. To this end, we incorporate Erlang and phase-type demand distributions into the model. Formulating the model as a Markov decision problem, we investigate the structure of the optimal replenishment policy. We also implement a sensitivity analysis on the optimal policy and establish its monotonicity with respect to system cost parameters.

• Industrial Engineering and Management Systems
• /
• 제8권3호
• /
• pp.155-161
• /
• 2009

We focus on discrete event systems with a structure of parallel processing, synchronization, and no-concurrency. We use max-plus algebra, which is an effective approach for controller design for this type of system, for modeling and formulation. Since a typical feature of this type of system is that the initial schedule is frequently changed due to unpredictable disturbances, we use a simple model and numerical examples to examine the possibility of applying the concepts of the feeding buffer and the project buffer of critical chain project management (CCPM) on max-plus linear discrete event systems in order to control the occurrence of an undesirable state change. The application of a CCPM-based framework on a max-plus linear discrete event system was proven to be effective.

• 한국컴퓨터산업학회논문지
• /
• 제4권12호
• /
• pp.975-983
• /
• 2003

본 연구에서는 정보화 기반에서 취약한 우리 나라의 중소기업체가 공급망 관리 체계를 구축하기 위한 접근 방법을 살펴보고자 한다. 우리 나라 기업들의 공급망 성과에 대한 분석과 함께 중소기업의 공급망 관리 시스템 구축 사례를 검토하여 향후 공급망 관리 시스템을 도입하고자 하는 중소기업을 위한 전략적 방향을 제시하고자 한다.

• 한국정보통신학회:학술대회논문집
• /
• 한국정보통신학회 2018년도 춘계학술대회
• /
• pp.507-509
• /
• 2018

최근 사물인터넷 기술에 관한 연구가 활발히 이루어지고 있는 가운데, 기존 중앙 집중형 운영에서의 문제점으로 지적되는 사물인터넷 서버 측 부하와 보안의 취약성을 극복하고자 블록체인의 도입에 관한 연구가 요구되고 있다. 본 논문에서는 사물인터넷의 진화에 따른 네트워크의 구조 변화와 이로 인한 문제점을 분석하고, 이를 해결하기 위한 방안으로 블록체인과의 융합을 제안하기 위해 융합을 위한 네트워크 도메인을 제시한다. 또한 사물인터넷과 블록체인의 융합으로 얻어지는 장점과 다양한 응용분야에 대해서도 기술한다.

• Journal of Information Display
• /
• 제12권4호
• /
• pp.223-227
• /
• 2011

Electrophosphorescent devices with ionomer-type hole transport layers were investigated. On top of the 3,4-ethylenedioxy thiophene:poly(4-styrene sulfonate) [PEDOT:PSS] structures, fluoropolymer interfacial layers (FPIs) with different side chain lengths were introduced. Both for the PEDOT:PSS/FPI (layered) and PEDOT:PSS (mixed) structures with soluble phosphorescent emitters, the short-side-chain FPIs showed higher efficiency. The difference in the electrical properties of the two FPIs for bipolar (light-emitting) devices was not clear, but the hole-only device clearly showed the favored hole injection at the PEDOT:PSS/FPI structure with a shorter side chain, a copolymer of tetrafluoroethylene and sulfonyl fluoride vinyl ether.

• Journal of Advanced Marine Engineering and Technology
• /
• 제27권2호
• /
• pp.238-245
• /
• 2003

To overcome the weakness in the load capacity of conventional robot manipulators actuated by motors with the speed reducer such as the harmonic driver, we proposed a new closed-chain type of the robot actuator which is composed of the four-bar-link mechanism driven by the ball screw. The robot manipulator is revolute-jointed and composed of four axes. The base axis is actuated by the lineal actuator such as the ball screw, and the others are actuated by the proposed actuator. We analyzed the mechanism of the actuators of the robot joints, and developed the dynamics model. The dynamics are expressed in the joint coordinates and then they are mapped into the sliding coordinates of the ball screw. We performed fundamental tests on the structure of the robot.

• 대한기계학회논문집A
• /
• 제20권11호
• /
• pp.3398-3407
• /
• 1996

In this paper, we derive an algorithm and develope a computer program which analyze rapidly and precisely the inverse kinematics of robotic mechanism with spatial complex chain structure based on the relative coordinates. We represent the inverse kinematic problem as an optimization problem with the kinematic constraint equations. The inverse kinematic analysis algorithm, therefore, consists of two algorithms, the main, an optimization algorithm finding the motion of independent joints from that of an end-effector and the sub, a forward kinematic analysis algorithm computing the motion of dependent joints. We accomplish simulations for the investigation upon the accuracy and efficiency of the algorithm.

• 한국경영과학회지
• /
• 제39권2호
• /
• pp.97-109
• /
• 2014

This paper considers a reverse supply chain with simultaneous recovery of used products and manufacturing of brand-new ones. Recovered products are downgraded and have to be sold in a market different from that of brand-new products at a different price. In case of a shortage of recovered product inventory, a brand-new item, if available, can be offered at the price of a recovered product. In other words, one-way demand substitution is allowed. We address the joint decision of when to manufacture brand-new product, when to recover returned product, and how to control demand substitution to maximize the hybrid production system's profits. To this end, we propose a Markov decision Process model and investigate the structure of the optimal policy. Performance comparison is numerically implemented between the models with and without downward demand substitution option under different operating conditions of the system parameters.

• 한국미생물·생명공학회지
• /
• 제30권1호
• /
• pp.21-25
• /
• 2002

토양으로부터 분리한 Bacillus sp. YJ-63으로부터 항진균성 항생물질을 분리하여 그 구조를 분석한 결과는 다음과 같다. 항생물질은 7개의 $\alpha$-amino acid와 1개의 $\beta$-amino acid가 결합한 환상구조를 가지는 iturin E 계에 속하며 특히. $\beta$-amino acid의 methylene 수가 기존의 iturin E 보다 더 많은 것으로 나타났다.

• Applied Microscopy
• /
• 제48권4호
• /
• pp.126-127
• /
• 2018

Carbon has numerous allotropes and various crystalline forms with full dimensionalities such as diamond, graphite, fullerenes, and carbon nanotubes leading a wide range of applications. Since the emerge of graphene consisting of a single atomic layer of carbon atoms, a fabrication of all-carbon-based device with combination of one-, two-, and three-dimensional carbons has become a hot issue. Here, we introduce an ultimate one-dimensional carbon atomic chain. Carbon atomic chains were experimentally created by removing atoms from monolayer graphene sheet under electron beam inside transmission electron microscope (TEM). A series of TEM images demonstrate the dynamics of carbon atomic chains over time from the formation, transformation, and then breakage.