• Nuclear Engineering and Technology
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• v.53 no.9
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• pp.2953-2959
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• 2021

A new practical modeling of the Norton's power law creep is proposed and implemented to analyze the high temperature behaviors of Alloy 690 SG tube material. In the model, both the stress exponent n and the rate constant B are simply treated as the temperature dependent parameters. Based on the two-step optimization procedure, the temperature function of the rate constant B(T) was determined for the data set of each B value after fixing the stress exponent n value by using the prior optimized function at each temperature. This procedure could significantly reduce the numerical errors when using the power law creep equations. Based on the better description of the steady-state creep rates, the experimental rupture times could also be well predicted by using the Monkman-Grant relationship. Furthermore, the difference in tensile strengths at high temperatures could be very well estimated by assuming the imaginary creep stress related to the given strain rate after correcting the temperature effects on the elastic modulus.

• Journal of the Semiconductor & Display Technology
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• v.21 no.1
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• pp.33-38
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• 2022

This study investigates the outlet temperature of coolant heater based on heat and flow volume conditions. Through computer simulation, the coolant temperature at the outlet was analyzed to investigate the heat and flow volume conditions of the coolant heater, and the optimal conditions were derived. Results show that heat and flow volume conditions, it was confirmed that heat condition is 0.424 W/mm³, and flow volume condition is 500 l/h, demonstrates optimal conditions. The results of this study can be utilized to efficiently control the coolant temperature through various heat and flow volume conditions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.1
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• pp.51-60
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• 2012

Optimization procedures of performance analysis for ORC(Organic Rankine Cycle) system are established to the characteristics of low temperature heat sources such as open-type and closed-type. Effective heat recovery and heat extraction related to maximum power of the cycle as well as heat quality and thermal efficiency must be considered in the case of the open-type low temperature heat source. On the other hand, in the case of the closed-type low temperature heat source, only thermal efficiency is important due to constant heat input. In this study, thermal efficiency and exergy efficiency representing a level of close to Carnot cycle are studied, as useful index for the optimization of the ORC system. To validate the results of cycle analysis, those are compared with appropriate experimental data of ORC system as a thermal efficiency point of view.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.581-584
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• 2005

A district heating(DH) system supplies environmentally-friend heat and is appropriate for reduction of energy consumption and/or air pollutions. The objectives of this paper are to systematize data processing of transition temperature, investigate its effects on fatigue life of DH pipes and optimization for size of DH pipes. A relational database management system as well as reliable fatigue life evaluation procedures is established for Korean DH pipes. Also, since the prototypal evaluation results satisfied both cycle-based and stress-based fatigue criteria. Through the optimum design process, the cross section diminished 18.64% and the CUF diminished 23.35%. So, it can be used as useful information in the future for optimal design, operation and energy saving via setting of efficient condition and stabilization of water temperature.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.7
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• pp.521-528
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• 2007

The desiccant rotor is the most essential component of desiccant cooling system, but its design relies on manufacturer's experience and principles are not yet clear in spite of a lot of theoretical/experimental work published. The mathematical modeling of desiccant rotor needs solution of coupled partial differential equations of heat and mass transfer. In this study, numerical program is developed and validated using a real desiccant rotor. The calculation results are in reasonable agreement with the experimental data and other available numerical results. Optimization of desiccant rotor on the condition of low regeneration temperature are investigated. The optimal rotor speed at which the process outlet humidity becomes minimized, shows same as that of the system optimization. Compared to high regeneration temperature, broad is the range of optimal speed of low regeneration temperature. Systematic analysis on the optimal area ratio of regeneration to dehumidification section has also been conducted.

• Journal of the Korean Applied Science and Technology
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• v.40 no.6
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• pp.1363-1372
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• 2023

This study is concerned with the optimization of the manufacturing process of a hot water extract containing antioxidant activity from Lycium barbarum, traditionally known to have various physiological activities. For the establishment of the optimization process, the central composite design of response surface methodology(RSM) was used. Thirteen extraction processes were performed by encoding the independent variables, extraction temperature (65.9℃-94.1℃) and extraction time (2.59 hr-5.41 hr). As a result of the experiment, the optimal manufacturing conditions for the extract were 340.0 mg/100 g of GAE at an extraction temperature of 94.1℃ and an extraction time of 5 hr. The maximum yield of flavonoids was 22.44 mg/100 g of HES at an extraction temperature of 94.1℃ and an extraction time of 4 hr. The conditions for producing the extract with the maximum antioxidant capacity (DPPH 92.12%) were 90℃ and 4.5 hr extraction time. Therefore, the optimal manufacturing process conditions for extracts containing total phenol content, flavonoid content, and DPPH radical scavenging activity, which are dependent variables, were extraction temperature of 90-95℃ and extraction time of 4 hr, which were not significantly different from the actual values. Therefore, Lycium barbarum extract rich in total phenol and flavonoid content related to antioxidant function is expected to be used as a functional food and cosmetic material.

• Food Science and Biotechnology
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• v.17 no.5
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• pp.904-911
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• 2008

Covalent cross-links between a number of proteins and peptides explain why transglutaminase may be widely used by food processing industries. The objective of this work was optimization of the fermentation process to produce transglutaminase from a new microbial source, the Streptomyces sp. P20. The strategy adopted to modify the usual literature media was: (1) fractional factorial design (FFD) to elucidate the key medium ingredients, (2) central composite design (CCD) to optimise the concentration of the key components. Optimization of the medium resulted in not only an 86% increase in microbial transglutaminase activity as compared to the media cited in the literature, but also a reduction in the production cost. Optimal fermentation conditions - namely temperature and agitation rate - were also studied, using CCD methodology. Usual conditions of $30^{\circ}C$ and 100 rpm were within the optimal area. All other parameters for enzyme production were experimentally proven to be optimum fermentation conditions.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.1
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• pp.124-130
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• 2012

An injection mold cooling circuit for an automotive front bumper was optimally designed in order to simultaneously minimize the average of the standard deviations of the temperature and the difference in mean temperatures of the upper and lower molds for uniform cooling. The temperature distribution for a specified design was evaluated by Moldflow Insight 2010, a commercial injection molding analysis tool. For efficient design, PIAnO (Process Integration, Automation and Optimization), a commercial PIDO tool, was used to integrate and automate injection molding analysis procedure. The weighted-sum method was used to handle the multi-objective optimization problem and PQRSM, a function-based sequential approximate optimizer equipped in PIAnO, to handle numerically noisy responses with respect to the variation of design variables. The optimal average of the standard deviations and difference in mean temperatures were found to be reduced by 9.2% and 56.52%, respectively, compared to the initial ones.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.10
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• pp.381-386
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• 2016

An optimization algorithm is developed based on a simulation case of a single family house model equipped with PV arrays. To increase the nationwide use of PV power generation facilities, a market-competitive electricity price needs to be introduced, which is determined based on the time of use. In this study, quadratic programming optimization was applied to minimize the electricity bill while maintaining the indoor temperature within allowable error bounds. For optimization, it is assumed that the weather and electricity demand are predicted. An EnergyPlus-based house model was approximated by using an equivalent RC circuit model for application as a linear constraint to the optimization. Based on the RC model, model predictive control was applied to the management of the cooling load and electricity for the first week of August. The result shows that more than 25% of electricity consumed for cooling can be saved by allowing excursions of temperature error within an affordable range. In addition, profit can be made by reselling electricity to the main grid energy supplier during peak hours.

• Journal of the Korean Society of Systems Engineering
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• v.1 no.1
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• pp.14-19
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• 2005

High temperature vacuum furnaces or high standard electric furnaces demand high technology level and high production cost. Therefore, an iterative design process and the optimization approach under integrated computing environment are required to reduce the development risk. Moreover, it also required to develop an integrated design software that can manage the centralized database system between factory and design department, and the automated furnace design and analysis. The developed software is dedicated to the development of the vacuum (electric) furnaces. Based on the distribute middleware system, the GUI module, the CAD module, the thermal analysis module and the optimization module are integrated. For the DBMS, Microsoft Access is employed, the GUI is developed using Visual Basic language, and AutoCAD is utilized for the configuration design. By investigating the analysis code interface, the analysis and optimization process, and the data communication method, the overall system architecture, the method to integrate the optimizer and ana lysis codes, and the method to manage the data flow are proposed and verified through the optimal furnace design.