• Journal of the Korea Society for Simulation
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• v.1 no.1
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• pp.48-54
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• 1992

This study discusses the performance evaluation of queueing network methodologies as used for the planning of FMS production systems. The possibility of applications and utilities of queueing network models is investigated for FMS producton plans. Experimental results by queueing network models such as CAN-Q, MVAQ and results by detailed simulation models written in SIMAN are compared and some propositions are presented based on the results of the experiments.

• Biotechnology and Bioprocess Engineering:BBE
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• v.7 no.5
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• pp.281-288
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• 2002

Recombinant Escherichia coli strain harboring the ${\lambda}$pR-pL promotor and heterologus poly-${\beta}$-hydroxybutyrate (PHB) biosynthesis genes was used to investigate the effect of culture conditions on the efficient PHB production. The expression of phb genes was induced by a temperature upshift from $33^{\circ}C\;to\;38^{\circ}C$. The protein expression levels were measured by using two-dimensional electrophoresis, and the enzyme activities were also measured to understand the effect of culture temperature, carbon sources, and the dissolved oxygen (DO) concentration on the metabolic regulations. AcetylCoA is an important branch point for PHB production. The decrease in DO concentration lowers the citrate synthase activity, thus limit the flux toward the TCA cycle, and increase the flux for PHB production. Since NADPH is required for PHB production, the PHB production does not continue leading the overproduction of acetate and lac-tate. Based on these observations, a new operation was considered where DO concentration was changed periodically, and it was verified its usefulness for the efficient PHB production by experiments.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.33 no.3
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• pp.48-54
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• 2010

S plastic injection molding factory located at Namdong Industrial Complex in Incheon produces plastic parts for semiconductor, vacuum cleaners, office furniture, etc. It produces the parts to customers' order and delivers them directly to customers at due dates using the trucks of freight company. In recent years, it has been suffered from the excessive production cost, high lost sales rate, rigid response to customers' order, and high delivery cost, which affect negatively on its profit. This paper introduces a case study on the profit increase through a newly proposed production and distribution method which applies a make-to-stock and multi-visit delivery strategy at S plastic injection molding factory. The proposed method is evaluated by comparing with the current method with respect to sales profit using the historical data of customer demand. It is confirmed through the computational experiments that the proposed production and distribution method yields almost double increase in profit resulted from the increased production, reduced lost sales, reduced production cost, and reduced delivery cost.

• Journal of Korean Institute of Industrial Engineers
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• v.37 no.4
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• pp.367-381
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• 2011

Reducing waste for the efficiency of production is becoming more important because of the rapidly changing market circumstances and the rising material and oil prices. The dispatching also has to consider the characteristic of production circumstance for the efficiency. The production circumstance has the non-identical parallel machines with rework rate since machines have different capabilities and deterioration levels in the real manufacturing field. This paper proposes a dispatching method, FTLR (Flow Time Loss Index with Rework Rate) for production efficiency. The goal of FTLR is to minimize flow time based on such production environments. FTLR predicts the flow time with rework rate. After assessing dominant position of expected flow time per each machine, FTLR performs dispatching to minimize flow time. Experiments compare various dispatch methods for evaluating FTLR with mean flow time, mean tardiness and max tardiness in queue.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.43 no.3
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• pp.61-67
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• 2020

The fourth industrial revolution encourages manufacturing industry to pursue a new paradigm shift to meet customers' diverse demands by managing the production process efficiently. However, it is not easy to manage efficiently a variety of tasks of all the processes including materials management, production management, process control, sales management, and inventory management. Especially, to set up an efficient production schedule and maintain appropriate inventory is crucial for tailored response to customers' needs. This paper deals with the optimized inventory policy in a steel company that produces granule products under supply contracts of three targeted on-time delivery rates. For efficient inventory management, products are classified into three groups A, B and C, and three differentiated production cycles and safety factors are assumed for the targeted on-time delivery rates of the groups. To derive the optimized inventory policy, we experimented eight cases of combined safety stock and data analysis methods in terms of key performance metrics such as mean inventory level and sold-out rate. Through simulation experiments based on real data we find that the proposed optimized inventory policy reduces inventory level by about 9%, and increases surplus production capacity rate, which is usually used for the production of products in Group C, from 43.4% to 46.3%, compared with the existing inventory policy.

• Journal of Hydrogen and New Energy
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• v.23 no.4
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• pp.397-403
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• 2012

Galactose, an isomer of glucose with an opposite hydroxyl group at the 4-carbon, is a major fermentable sugar in various promising feedstock for hydrogen production including red algal biomass. In this study, hydrogen production characteristics of galactose-glucose mixture were investigated using batch fermentation experiments with heat-treated digester sludge as inoclua. Galactose showed a hydogen yield compatible with glucose. However, more complicated metabolic steps for galactose utilization caused a slower hydrogen production rate. The existence of glucose aggravated the hydrogen production rate, which would result from the regulation of galactose-utilizing enzymes by glucose. Hydrogen produciton rate at galactose to glucose ratio of 8:2 or 6:4 was 67% of the production rate for galactose and 33% for glucose, which could need approximately 1.5 and 3 times longer hydraulic retention time than galacgtose only condition and glucose only condition, respectively, in continuous fermentation. Hydrogen production rate, Hydrogen yield, and organic acid production at galactose to glucose ratio of 8:2 or 6:4 were 0.14 mL H2/mL/hr, 0.78 mol $H_2$/mol sugar, and 11.89 g COD/L, respectively. Galactose-rich biomass could be usable for hydogen fermenation, however, the fermentation time should be allowed enough.

• Journal of the Korean Solar Energy Society
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• v.37 no.5
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• pp.27-37
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• 2017

In this study, an artificial solar simulator composed of a 2.5 kW Xe-Arc lamp and mirror reflector was used to carry out the solar thermal two step thermochemical water decomposition cycle which can produce high efficiency continuous hydrogen production. Through various operating conditions, the change of hydrogen production due to the possibility of a dual-zone reactor and heat recovery were experimentally analyzed. Based on the reaction temperature of Thermal-Reduction step and Water-Decomposition step at $1,400^{\circ}C$ and $1,000^{\circ}C$ respectively, the hydrogen production decreased by 23.2% under the power off condition, and as a result of experiments using heat recovery technology, the hydrogen production increased by 33.8%. Therefore, when a thermochemical two-step water decomposition cycle is conducted using a dual-zone reactor with heat recovery, it is expected that the cycle can be operated twice over a certain period of time and the hydrogen production amount is increased by at least 53.5% compared to a single reactor.

• Journal of the Korea Safety Management & Science
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• v.22 no.4
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• pp.65-74
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• 2020

Many of companies have made significant improvements for globalization and competitive business environment The supply chain management has received many attentions in the area of that business environment. The purpose of this study is to generate realistic production and distribution planning in the supply chain network. The planning model determines the best schedule using operation sequences and routing to deliver. To solve the problem a hybrid approach involving a genetic algorithm (GA) and computer simulation is proposed. This proposed approach is for: (1) selecting the best machine for each operation, (2) deciding the sequence of operation to product and route to deliver, and (3) minimizing the completion time for each order. This study developed mathematical model for production, distribution, production-distribution and proposed GA-Simulation solution procedure. The results of computational experiments for a simple example of the supply chain network are given and discussed to validate the proposed approach. It has been shown that the hybrid approach is powerful for complex production and distribution planning in the manufacturing supply chain network. The proposed approach can be used to generate realistic production and distribution planning considering stochastic natures in the actual supply chain and support decision making for companies.

• MALSORI
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• no.62
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• pp.51-68
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• 2007

Two experiments were conducted to determine the exact locus of the frequency effect in speech production. Experiment 1 addressed the question as to whether the word frequency effect arise from the stage of lemma selection. A picture-word interference task was performed to test the significance of interactions between the effects of target frequency, distractor frequency and semantic relatedness. There was a significant interaction between the distractor frequency and the semantic relatedness and between the target and the distractor frequency. Experiment 2 examined whether the word frequency effect is attributed to the lexeme level which represent phonological information of words. A methodological logic applied to Experiment 2 was the same as that of Experiment 1. There was no significant interaction between the distractor frequency and the phonological relatedness. These results demonstrate that word frequency has influence on the processes involved in selecting a correct lemma corresponding to an activated lexical concept in speech production.

• KSBB Journal
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• v.26 no.4
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• pp.341-346
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• 2011

This work is focused on the possibility of marine biomass Codium fragile as renewable resources for production of levulinic acid. In an effort to optimize the reaction conditions of levulinic acid production from Codium fragile, response surface methodology was applied. A total of 18 individual experiments were designed to investigate the effect of reaction temperature, catalyst amount, and reaction time. As a result, 4.26 g/L levulinic acid from Codium fragile was produced in the condition of $160.7^{\circ}C$ of reaction temperature, 3.9% of sulfuric acid, and 39.1 min of reaction time. This result will provide the useful information for chemical production from marine resource.