• Korean Chemical Engineering Research
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• v.61 no.2
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• pp.322-327
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• 2023

A design of experiments was evaluated in optimizing MOF-5 synthesis for acetylene adsorption. At first, mixture design was used to optimize precursor concentration, terephthalic acid, zinc acetate dihydrate and N,N-dimethylformamide. More specifically, 13 conditions with various molar ratios were designed by extreme vertices design method. After preparing the samples, XRD, N₂ physisorption and SEM analysis were performed for their characterization. Moreover, acetylene adsorption experiments were carried out over the samples under identical conditions. The optimal precursor composition for MOF-5 synthesis was predicted on a molar basis as follows: terephthalic acid : acetate dihydrate : dimethylformamide = 0.1 : 0.4 : 0.5. Thereafter, multi-level factorial design was designated to investigate the effect of synthesis reaction conditions such as temperature, time and stirring speed. By the statistical analysis of 18 samples designed, 4 reaction parameters were determined for additional adsorption experiments. Therefore, MOF-5 prepared under the synthesis time and temperature of 100 ℃ and 12 h, respectively, showed the maximum adsorption capacity of 15.1 mmol/g.

• Journal of the Korean Society of Food Culture
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• v.24 no.3
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• pp.321-330
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• 2009

This study was conducted to develop a recipe for a nutritional cookie containing chungkukjang powder that had a composition of ingredients and a texture that resulted in a high preference by all age groups. Wheat flour was partially substituted with chungkukjang powder to reduce its content. Response surface methodology was then used to analyze the measured results, which showed 16 experimental points including 2 replicates for chungkukjang powder, butter and sugar. The compositional and functional properties were then measured, after which these values were applied to a mathematical model. A canonical form and perturbation plot revealed the influence of each ingredient on the final mixture. The results of the sensory evaluation showed significant values with respect to color (p<0.01), texture (p<0.05) and overall quality (p<0.05). Taken together, the results of this study indicated that the optimal ratio was 26.57 g of chungkukjang powder, and 82.08 g of butter for every 52.36 g of sugar. The physical and chemical sensory measurements were then evaluated by a t-test, and the results revealed significant differences in the flavor of the optimized cookie when compared to the control cookie.

• Tribology and Lubricants
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• v.40 no.3
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• pp.71-77
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• 2024

Hydrogen has emerged as an eco-friendly and sustainable alternative to fossil fuels. However, the utilization of hydrogen requires high-pressure compression, storage, and transportation, which poses challenges to the durability of compressor components, particularly the diaphragm. This study aims to improve the durability of 304 stainless steel diaphragms in hydrogen compressors by optimizing their surface roughness and corrosion resistance through wet etching. The specimens were prepared by immersing 304 stainless steel in a mixture of sulfuric acid and hydrogen peroxide, followed by etching in hydrochloric acid for various durations. The surface morphology, roughness, and wettability of the etched specimens were characterized using optical microscopy, surface profilometry, and water contact angle measurements. The friction and wear characteristics were evaluated using reciprocating sliding tests. The results showed that increasing the etching time led to the development of micro/nanostructures on the surface, thereby increasing surface roughness and hydrophilicity. The friction coefficient initially decreased with increasing surface roughness owing to the reduced contact area but increased during long-term wear owing to the destruction and delamination of surface protrusions. HCl-30M exhibited the lowest average friction coefficient and a balance between the surface roughness and oxide film formation, resulting in improved wear resistance. These findings highlight the importance of controlling the surface roughness and oxide film formation through etching optimization to obtain a uniform and wear-resistant surface for the enhanced durability of 304 stainless steel diaphragms in hydrogen compressors.

• Korean Journal of Food Science and Technology
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• v.26 no.1
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• pp.37-43
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• 1994

Optimization study was conducted for preparation of uncompressed soy protein isolate(SPI) tofu in the aspects of water addition ratio, second heating temperature and amounts of oil and dextrin added. The SPI tofu was prepared without compression step with SPI-oil-dextrin mixture and $CaSO_4-GDL$ mixed coagulants. The data were statistically analyzed by multiple regresstion and response surface methodology(RSM). Addition of dextrin increased the hardness of tofu, particularly for the second heating at $85^{\circ}C$ and 8 times of water to SPI. RSM figure showed that the effect of dextrin on hardness became to be less as the heating temperature increased. The hardness increase effect was no significant except addition of 25% oil and 8 times of water and second heating at $85^{\circ}C$. The addition of 25% oil and $10{\sim}15%$ dextrin and second heating at $90^{\circ}C$ for $45{\sim}60$ minutes resulted hardness and cohesive tofu. The optimal method proposed for uncompressed SPI tofu on the basis of textural and sensory properties was first heating of homogenized SPI-oil-dextrin(100:25:15) with addition of 8 times of water(on the basis of SPI) at $100^{\circ}C$ for 6 minutes, cooling to $40^{\circ}C$, additon of mixed coagulants of $CaSO_{4}-GDL$(0.07 g, 0.0075 g/SPI) and second heating at $90^{\circ}C$ for 45 minutes.

• KIPS Transactions on Computer and Communication Systems
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• v.3 no.7
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• pp.219-230
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• 2014

In the cloud computing environment, cloud service users purchase and use the virtualized resources from cloud resource providers on a pay as you go manner. Typically, there are two billing plans for computing resource allocation adopted by large cloud resource providers such as Amazon, Gogrid, and Microsoft, on-demand and reserved plans. Reserved Virtual Machine(VM) instance is provided to users based on the lengthy allocation with the cheaper price than the one of on-demand VM instance which is based on shortly allocation. With the proper mixture allocation of reserved and on-demand VM corresponding to users' requests, cloud service providers are able to reduce the resource allocation cost. To do this, prior researches about VM allocation scheme have been focused on the optimization approach with the users' request prediction techniques. However, it is difficult to predict the expected demands exactly because there are various cloud service users and the their request patterns are heavily fluctuated in reality. Moreover, the previous optimization processing techniques might require unacceptable huge time so it is hard to apply them to the current cloud computing system. In this paper, we propose the cloud brokering system with the adaptive VM allocation schemes called A3R(Adaptive 3 Resource allocation schemes) that do not need any optimization processes and kinds of prediction techniques. By using A3R, the VM instances are allocated to users in response to their service demands adaptively. We demonstrate that our proposed schemes are able to reduce the resource use cost significantly while maintaining the acceptable Quality of Service(QoS) of cloud service users through the evaluation results.

• Journal of the Korean Society of Food Science and Nutrition
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• v.46 no.9
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• pp.1081-1090
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• 2017

The purpose of this study was to develop a functional porridge prepared with mulberry leaf and mulberry fruit powder, which can ameliorate hypertension. The experiment was designed according to the central composite design. For optimization of the mixture ratio of mulberry leaf powder (MLP) and mulberry fruit powder (MFP), the independent variables were defined as MLP (X1) and MFP (X2) and the dependent variables were defined as K (Y1), Na (Y2), ${\gamma}$-aminobutyric acid (GABA) (Y3), cyanidin-3-glycoside (C3G) (Y4), rutin (Y5), and flavonoid (Y6). The optimal MLP to MFP mixture ratio according to the response surface method were 5.41 g of MLP and 2.65 g of MFP. The amounts of K, Na, GABA, C3G, rutin, and flavonoid in the optimal MLP and MFP mixture were 1,844.22 mg/100 g, 52.74 mg/100 g, 139.98 mg/100 g, 1,134.89 mg/100 g, 101.56 mg/100 g, and 201.28 mg/100 g, respectively. The amounts of Ca, K, Mg, and Na in the functional porridge at this optimal point were 27.66 mg/100 g, 131.32 mg/100 g, 19.57 mg/100 g, and 3.59 mg/100 g, respectively. Overall, this functional porridge can help reduce hypertension.

• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.11
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• pp.1708-1714
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• 2015

Fermented red ginseng concentrate is known as a healthy food source, whereas it has off-flavor such as bitterness and sour flavor based on fermentation. ${\beta}$- and ${\gamma}$-cyclodextrin (CD) were used to encapsulate the off-flavor of fermented red ginseng concentrate by using response surface methodology design on ${\beta}$- and ${\gamma}-CD$ combination. The reducing effects were analyzed by sensory evaluation for bitter and sour tastes, ginsenoside Rb1, and total acidity. The optimized mixing ratio of ${\beta}$- and ${\gamma}-CD$ for reducing bitterness was the least expected value of 2.07 at ${\beta}-CD$ 3.74% versus the soluble solid content of fermented red ginseng concentrate and the ${\gamma}-CD$ 20.63% mixture. The encapsulation effects of ginsenoside Rb1 were the most expected value of 96.75% at ${\beta}-CD$ 3.47% and ${\gamma}-CD$ 19.89% mixture. The encapsulation effects of sour taste were the least expected value of 5.63 at ${\beta}-CD$ 9.34% and ${\gamma}-CD$ 9.96% mixture. The encapsulation effects of lactic acid were the most expected value of 67.73% at ${\beta}-CD$ 16.0% and ${\gamma}-CD$ 13.18% mixture. Based on encapsulation and each optimized combination, the most effective entrapping ${\beta}$-and ${\gamma}-CD$ combination ratio was ${\beta}-CD$ 10% and ${\gamma}-CD$ 13%.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.3
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• pp.229-235
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• 2011

This research aims todevelopa compression/absorption hybrid heat pump system using an $NH_3/H_2O$ as working fluid.The heatpump cycle is based on a combination of compression and absorption cycles. The cycle consists of two-stage compressors, absorbers, a desorber, a desuperheater, solution heat exchangers, a solution pump, a rectifier, and a liquid/vapor separator. The compression/absorption hybrid heat pump was designed to produce hot water above $90^{\circ}C$ using high-temperature glide during a two-phase heat transfer. Distinct characteristics of the nonlinear temperature profile should be considered to maximize the performance of the absorber. In this study, the performance of the absorber was investigated depending on the capacity, shape, and arrangementof the plate heat exchangers with regard tothe concentration and distribution at the inlet of the absorber.

• Korean Chemical Engineering Research
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• v.43 no.5
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• pp.595-602
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• 2005

In order to purify diethylene glycol as main impurity included in p-dioxanone, SLE (solid-liquid equilibria) and mixture density on two components system of p-dioxanone and diethylene glycol were measured and a layered melt crystallization with seed has been applied. The SLE of p-dioxanone and diethylene glycol were a simple eutectic system and the temperature and PDX concentration at eutectic point were 0.08 and 246 K, respectively. Densities of their binary mixtures were well fitted by the best correlation equation, ${\rho}_l=0.405+1.361x+0.002T-0.004xT$. In the melt crystallization, the growth rate (G) was proportional to the 1.5th power of the subcooling degree. The effective distribution coefficient ($K_{eff}$) as the degree of impurity removal was observed to increase with increasing the growth rate and initial p-dioxanone concentration. And also, $K_{eff}$ was correlated with Z function using Wintermantel's model such as $K_{eef}=-0.0604+6.392{\times}Z$. Finally, PDX purity through the optimization of this process can be obtained over 99%.

• Journal of Korea Multimedia Society
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• v.5 no.5
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• pp.512-522
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• 2002

In this paper, we propose a hybrid method which is mixed with frame selection and weighting model rank method, based on GMM(gaussian mixture model), for real-time text-independent speaker recognition system. In the system, maximum likelihood estimation was used for GMM parameter optimization, and maximum likelihood was used for recognition basically Proposed hybrid method has two steps. First, likelihood score was calculated with speaker models and test data at frame level, and the difference is calculated between the biggest likelihood value and second. And then, the frame is selected if the difference is bigger than threshold. The second, instead of calculated likelihood, weighting value is used for calculating total score at each selected frame. Cepstrum coefficient and regressive coefficient were used as feature parameters, and the database for test and training consists of several data which are collected at different time, and data for experience are selected randomly In experiments, we applied each method to baseline system, and tested. In speaker recognition experiments, proposed hybrid method has an average of 4% higher recognition accuracy than frame selection method and 1% higher than W method, implying the effectiveness of it.