• 제어로봇시스템학회논문지
• /
• 제4권6호
• /
• pp.802-810
• /
• 1998

The purpose of this study is to find the analytic solution of determining the optimal capacity of processes and storages to meet the product demand. Recent trend to reduce product delivery time and to provide high quality product to customer requires the increasing capacity of storage facilities. However, the cost of constructing and operating storage facilities is becoming substantial because of increasing land value, environmental and safety concern. Therefore, reasonable decision making about the capacity of processes and storages is important subject for industries. The industrial solution for this subject is to use the classical economic lot sizing method, EOQ(Economic Order Quantity) model, trimmed with practical experience but the unrealistic assumption of EOQ model is not suitable for the chemical plant design with highly interlinked processes and storages. This study, a first systematic attempt for this subject, clearly overcomes the limitation of classical lot sizing method. The superstructure of the plant consists of the network of serially and/or parallelly interlinked processes and storages. A novel production and inventory analysis method, PSW(Periodic Square Wave) model, is applied. The objective function of optimization is minimizing the total cost composed of setup and inventory holding cost. The advantage of PSW model comes from the fact that the model provide a set of simple analytic solution in spite of realistic description of material flow between process and storage. The resulting simple analytic solution can greatly enhance the proper and quick investment decision for the preliminary plant design confronting diverse economic situation.

• Reproductive and Developmental Biology
• /
• 제31권2호
• /
• pp.103-108
• /
• 2007

This study was carried out to investigate the effects of cryoprotectants, warming solution and removal of lipid on open pulled straw vitrification (OPS) method of porcine embryos produced by nuclear transfer (NT) of fetal fibroblasts. All solutions used during vitrification were prepared with holding medium consisting of 25 mM Hepes buffered TCM199 medium containing 20% fetal bovine serum (FBS) at $38.5^{\circ}C$. The blastocysts derived from NT with or without lipid were vitrified in each medium of different concentrations of dimethyl sulfoxide (DMSO) and ethylene glycol (EG). Also, blastocysts after cryopreservation were warmed into different concentrations of sucrose in warming solution. The optimal concentrations of cryoprotectants in vitrification solution were 10% DMSO + 10% EG in vitrification solution 1 (VS1) and 20% DMSO + 20% EG in vitrification solution 2 (VS2). The optimal concentrations of sucrose were 0.3 M sucrose in warming solution 1 (WS1) and 0.15 M sucrose in warming solution 2 (WS2). lipid removal from oocytes before NT enhanced the viability of NT embryos after vitrification. Our results show that use of the OPS method in conjunction with lipid removal provides effective cryopreservation of porcine nuclear transfer embryos.

• Corrosion Science and Technology
• /
• 제13권1호
• /
• pp.28-35
• /
• 2014

Recently, the fuel oil of diesel engines of marine ships has been increasingly changed to heavy oil of low quality as the oil price is getting higher and higher. Therefore, the spiral gear attached at the motor of the oil purifier which plays an important role to purify the heavy oil is also easy to expose at severe environmental condition due to the purification of the heavy oil in higher temperature. Thus, the material of the spiral gear requires a better mechanical strength, wear and corrosion resistance. In this study, the heat treatment(tempering) with various holding time at temperature of $500^{\circ}C$ was carried out to the alloy of Cu-7Al-2.5Si as centrifugal casting, and the properties of both hardness and corrosion resistance with and without heat treatment were investigated with observation of the microstructure and with electrochemical methods, such as measurement of corrosion potential, cathodic and anodic polarization curves, cyclic voltammogram, and a.c. impedance. in natural seawater solution. The ${\alpha}$, ${\beta}^{\prime}$ and ${\gamma}_2$ phases were observed in the material in spite of no heat treatment due to quenching effect of a spin mold. However, their phases, that is, ${\beta}^{\prime}$ and ${\gamma}_2$ phases decreased gradually with increasing the holding time at a constant temperature of $500^{\circ}C$. The hardness more or less decreased with heat treatment, however its corrosion resistance was improved with the heat treatment. Furthermore, the longer holding time, the better corrosion resistance. In addition, when the holding time was 48hrs, its corrosion current density showed the lowest value. The pattern of corroded surface was nearly similar to that of the pitting corrosion, and this morphology was greatly observed in the case of no heat treatment. It is considered that ${\gamma}_2$ phase at the grain boundary was corroded preferentially as an anode. However, the pattern of general corrosion exhibited increasingly due to decreasing the ${\gamma}_2$ phase with heat treatment. Consequently, it is suggested that the corrosion resistance of Cu-7Al-2.5Si alloy can be improved with the heat treatment as a holding time for 48 hrs at $500^{\circ}C$.

• Bulletin of the Korean Chemical Society
• /
• 제33권2호
• /
• pp.597-600
• /
• 2012

Polyynes were formed by laser ablation of a graphite target in deionized water ($H_2O$ and $D_2O$) and various organic solvents such as acetonitrile, n-hexane, and c-hexane and were identified by analyzing ultraviolet (UV) absorption and Raman spectra. We assigned the major UV absorption peaks that coincided with the electronic transitions corresponding to linear polyyne chains. The UV absorption peak intensities of a polyyne solution decreased as the holding temperature of the solution increased. Also, the absorption spectra of polyynes obtained by laser ablation of a graphite target at different volume fractions of $H_2O$ and $D_2O$ were examined.

• 한국경영과학회:학술대회논문집
• /
• 대한산업공학회/한국경영과학회 2004년도 춘계공동학술대회 논문집
• /
• pp.421-424
• /
• 2004

This paper focuses on the problem of determining the quantity and timing of disassembling used products while satisfying the demand of their parts or components over a planning horizon. The case of multiple product types with parts commonality is considered for the objective of minimizing the sum of setup, disassembly operation, and inventory holding costs. A heuristic is suggested, in which an initial solution is obtained using a linear programming relaxation method, and then improved by perturbing the given solution using a dynamic programming approach and a look-ahead check while considering the trade-offs among different cost factors.

• 산업경영시스템학회지
• /
• 제17권31호
• /
• pp.115-123
• /
• 1994

Group scheduling, which is a kind of operations scheduling based on the GT concept is analyzed in a multi-stage manufacturing system. The purpose of this research is to develop and evaluate a heuristic algorithm for determining gro up sequence and job sequence within each group to minimize a complex cost function, i.e. the sum of the total pe-nalty cost for tardiness and the total holding cost for flow time, in a multi-stage manufacturing system with group setup time dependent upon group sequence. A heuristic algorithm for group sc heduling is developed, and a numerical example is illustrated. For the evaluation of the pro-posed heuristic algorithm, the heuristic solution of each of 63 problems is compared with that of random scheduling. The result shows that the proposed heuristic algorithm provides better solution in light of the proposed cost function.

• 한국경영과학회지
• /
• 제14권2호
• /
• pp.67-74
• /
• 1989

This paper considers single-product production and inventory management problem where cumulative demands up to each time period are mutually independent random variables(known) having continuous probability distributions and the associated cost-minimizing production schedule (when to produce and how much to produce) need be determined in rolling horizon environment. For the problem, both the production cost and the inventory holding and backlogging costs are included in the whole system cost. The probability distributions of these costs are expressed in terms of random demands, and utilized to exploit a solution procedure for a production schedule which minimizes the expected unit time system cost and also reduces the probability of rist that, for the first-period of each production cycle (rolling horizon), the cost of the "production" option will exceed that of the "non-production" one. Numerical examples are presented for the solution procedure illustration.cedure illustration.

• 산업기술연구
• /
• 제25권B호
• /
• pp.229-239
• /
• 2005

Dietary powder from Plantaginis ovatae testa was prepared by mechnical milling/grinding of the outer layer of the seed. The crystalline/surface structures of its powder (100 mesh) were examined, and several physical functionalities including, water capacity, oil holding capacity, emulsion/foam properties and physiological functionality such as in-vitro glucose and bile acid retarding effects were also investigated. Water holding capacity(WHC) of psyllium powder was $33.71{\pm}0.10g$ water retained/g solid at room temperature, whileas oil holding capacity(OHC) for soybean or rice bran oil were about 1.80g oil retained/g solid. These values of WHC and OHC were about 5.6 times higher and 2.8 times lower than those of commercial ${\alpha}$-cellulose, respectively. Changes of pH showed a small effect on WHC, but WHC increased with temperature. Emulsion capacity of 2%(w/v) psyllium was about 60% level of 0.5%(w/v) xanthan gum but emulsion stability after incubation of 24 hours showed about 1.4 times improvement of xanthan gum(0.5%,w/v). Also, psylliume(above 2%, w/v) alone had higher foam capacity than that of xanthan(1.1 times) and especially, 1 or 2% addition of psyllium improved the foam stability of protein solution(1% albumin+0.5% $CaCl_2$) by factor of 3.3 and 6.0 times, respectively. The glucose and bile acid retarding effects of psyllium powder were relatively very excellent suggesting the prevention from diabetes and arteriosclerosis. Especially, psyllium showed the 3.7 and 3.3 times higher effect on in-vitro glucose and bile acid retardation than those of commercial ${\alpha}$-cellulose, respectively.

• Elastomers and Composites
• /
• 제34권4호
• /
• pp.360-365
• /
• 1999

2-에틸헥실아크릴레이트(2-EHA), n-부틸아크릴레이트(BA), 에틸아크릴레이트(EA) 및 비닐아세테이트(VAc)의 네 가지 단량체를 사용하여 제조한 아크릴4원공중합체(PEBEV)와 염화비닐-비닐프로피오네이트 공중합체 (PVCVP)를 용액 블렌드하고 이들의 점착물성을 조사하여 PEBEV/염화비닐-비닐아세테이트 공중합체(PVCVAc) 블렌드계와 비교하였다. 블렌드계의 상용성은 PEBEV/PVCVP계가 PEBEV/PVCVAc계 보다 우수하였다. 블렌드계의 점착성은 두계 모두 비슷하였으나, 유지력의 경우 PEBEV/PVCVAc계는 PVCVAc 함량이 15%를 넘어서면서 감소하는데 반해 PEBEV/PVCVP계는 PVCVP 함량이 증가할수록 계속 증가하는 경향을 보여주었다. 박리 유형을 살펴보면, PEBEV/PVCVP 블렌드계중 PVCVP의 함량이 5%인 블렌드가 부분응집파괴 형태를 보이는 것을 제외하면, 모든 블렌드계가 계면파괴의 형태를 보였다.

• 산업경영시스템학회지
• /
• 제38권3호
• /
• pp.117-126
• /
• 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.