• Structural Engineering and Mechanics
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• v.52 no.2
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• pp.239-260
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• 2014

Non-stationary random vibration of linear structures with uncertain parameters is investigated in this paper. A time-domain explicit formulation method is first presented for dynamic response analysis of deterministic structures subjected to non-stationary random excitations. The method is then employed to predict the random responses of a structure with given values of structural parameters, which are used to fit the conditional expectations of responses with relation to the structural random parameters by the response surface technique. Based on the total expectation theorem, the known conditional expectations are averaged to yield the random responses of stochastic structures as the total expectations. A numerical example involving a frame structure is investigated to illustrate the effectiveness of the present approach by comparison with the power spectrum method and the Monte Carlo simulation method. The proposed method is also applied to non-stationary random seismic analysis of a practical arch bridge with structural uncertainties, indicating the feasibility of the present approach for analysis of complex structures.

• Korean Journal of Biological Psychiatry
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• v.15 no.2
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• pp.92-100
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• 2008

Objectives : The purpose of this study was to investigate 1) the neuropsychological deficits with major depressive disorder(MDD) in depressed state and 2) the changes of neuropsychological dysfunctions during depressed episodes and remitted periods in the MDD group. Methods : 12 patients with MDD and 70 normal controls who were diagnosed and classified by DSM-IV and SCID-IV interview participated in this study. The psychopathology was measured using the Hamilton rating scale for depression(HAM-D) and Brief Psychiatric Rating Scale(BPRS). The memory function, executive function, and sustained attention were measured by a trained psychologist using the Korean version of Memory Assessment Scale(K-MAS), Wisconsin Card Sorting Test(WCST), and Vigilance(VIG) and Cognitrone (COG) in Vienna Test System. After 6 weeks of treatment, we retested the cognitive tests in order to measure the cognitive functions in remitted states. Results : Patients with MDD achieved significantly lower score in sentence immediately recall, verbal memory score and total memory score of the K-MAS, total errors of the WCST, response time of Vigilance and response time at "Yes" response of Cognitrone than normal controls at baseline. After 6 weeks of medication, the psychiatric symptoms in the patient group were attenuated, and most of the neuropsychological functions including attention, memory, and frontal/executive function were improved except for response time of Cognitrone. Conclusions : This study provides evidence for distinct neuropsychological deficits in patients with MDD on their depressed states and remitted periods. The impairment on response time remains after remission, and this would be a trait marker of major depressive disorder.

• Korean Journal of Organic Agriculture
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• v.20 no.1
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• pp.91-99
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• 2012

This study was conducted to develop a functional feed additive for pig with spent $Lycium$ $chinense$ Mill fruit. We investigated the optimum conditions for the extraction of polyphenol from spent $Lycium$ $chinense$ Mill using methanol. Methanol concentration as a solvent for extraction, extraction time and the volume of solvent per a gram of solid (ground spent Lyceum chinense Mill) were selected as parameters. Three levels of parameters were configured according to Box Behnken experiment design, a fractional factorial design, and total 15 trials were employed. Total polyphenol concentration from each trial was used as response from experiment system and effects of parameters on total polyphenol extraction efficiency were determined using response surface model. As a result, all terms in analysis of variance, regression ($p$ = 0.001), linear ($p$ = 0.002), square ($p$ = 0.017) and interaction ($p$ = 0.047) was significant and adjusted determination coefficient ($R^2$) was 94.7%. Total polyphenol extraction efficiency was elevated along increased methanol content and decreased solvent to solid ratio. However extraction time did not affect the efficiency. This study provides a primary information for the optimum extraction conditions to maximize total polyphenol recovery from spent Lycium chinens Mill fruit and this result could be applied to re-use of argo-industrial by-products and to develop of functional feed additives in organic farming.

• The Korean Journal of Emergency Medical Services
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• v.22 no.3
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• pp.177-187
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• 2018

Purpose: The purpose of the study was to investigate the causes of non-transport in 119 ambulance services and to describe the difference in response time according to the reason for non-transport. Methods: This study analyzed 42,415 non-transport cases out of 123,158 cases using prehospital care reports in a metropolitan city. The Kruskal-Wallis test and the Wilcoxon-Mann-Whitney test were used to 6,857 cases for which time was recorded. Results: Non-transportation in 20${\bigcirc}{\bigcirc}$ comprised 33.1% of all ambulance services. The reason for non-transport were other reasons (25.5%), cancellation (23.8%), and moving to other vehicles (21.7%). There were differences in ambulance service times according to the reasons for non-transport. The activation interval was the longest (2.68 minutes) in the absence of the patient, and the response interval was the shortest (4.96 minutes) among the cancelled case. The total interval was the shortest time (21.97 minutes) in the cancellation cases and the longest time among the death cases (32.23 minutes). Conclusion: It is important to suggest the direction of development of emergency services by identifying the reasons for non-transport by ambulance services and describing the response time according to the reason for non-transport.

• Korean Journal of Food Science and Technology
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• v.28 no.2
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• pp.212-219
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• 1996

Four-dimensional response surface methodology was used for monitoring dynamic changes in substrates during Maillard reaction. The coefficients of determination ($R^2$) of response surface regression equations for the changes in amino acids during Maillard reaction were 0.9478 for total amino acids and above 0.90 for each amino acid. $R^2$ of regression equations for the changes in sugars during Maillard reaction were 0.9250 for glucose and 0.6490 for fructose. The contents of total amino acids gradually decreased with increasing reaction temperature and pH of the solvent. Browning color intensity increased with rising reaction temperature, showing maximum color intensity at around $145^{\circ}C$. Each amino acid showed a decreasing tendency in its contents, which was similarly found in total amino acids. Four-dimensional response surface methodology indicated that the increased temperature during Maillard reaction was the most influential factor in decreasing substrates, such as aspartic acid, threonine and glucose. While the reaction time and pH of solvent little affected the changes in the above-mentioned substrates during Maillard reaction.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.7
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• pp.719-725
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• 2009

An efficient time-domain numerical method for the analysis of broadband noise generation and propagation due to turbulence-cascade interaction is developed. The core algorithm of the present method is based on the B-periodicity of the acoustic response function of the flat-airfoil cascade to the ingesting gust(B denotes the number of airfoils in the cascade). To confirm this periodicity, gust-cascade interaction problem are solved by using the time-domain method, which shows that the incident gust with the circumferential mode number having the same remainders when divided by the airfoil number excites the same acoustic response of the cascade. Using the proposed fast algorithm with this periodicity, we show that the total computation time for the model broadband problem using the total 525 incident gust modes can be reduced to about 1/4 of that taken in using the previous time-domain program.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.477-482
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• 2009

An efficient time-domain numerical method for the analysis of broadband noise generation and propagation due to turbulence-cascade interaction is developed. The core algorithm of the present method is based on the B-periodicity of the acoustic response function of the flat-airfoil cascade to the ingesting gust (B denotes the number of airfoils in the cascade). To confirm this periodicity, gust-cascade interaction problem are solved by using the time-domain method, which shows that the incident gust with the circumferential mode number having the same remainders when divided by the airfoil number excites the same acoustic response of the cascade. Using the proposed fast algorithm with this periodicity, we show that the total computation time for the model broadband problem using the total 525 incident gust modes can be reduced to about 1/4 of that taken in using the previous time-domain program.

• Journal of the Korean Wood Science and Technology
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• v.45 no.6
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• pp.809-827
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• 2017

Steam explosion was applied to extract phenolic compounds from oak wood (Quercus mongolica). The effects of three independent factors (ethanol concentration, extraction temperature and extraction time) on the total phenolic content, DPPH radical scavenging activity, and antimicrobial activity from the steam exploded oak wood were optimized using response surface methodology (RSM). The independent variables were coded at three levels and their actual values were selected on the basis of preliminary experimental results. The following optimal extraction conditions were selected: ethanol concentration 82.0%, extraction temperature $71.7^{\circ}C$, and extraction time 60.5 min for total phenolic content; ethanol concentration 78.3%, extraction temperature $70.3^{\circ}C$, and extraction time 57.6 min for DPPH radical scavenging activity; ethanol concentration 80.6%, extraction temperature $68.4^{\circ}C$, and extraction time 59.0 min for antimicrobial activity. The experimental values agreed with those were predicted within confidence intervals indicating the suitability of RSM in optimizing the ethanol extraction of phenolic compounds from the steam exploded oak wood. Under the optimized conditions, the experimental value of the total phenolic content was 111.8 mg GAE/g dry steam exploded oak wood, DPPH free radical scavenging activity was 65.7%, and antimicrobial activity was 17.0 mm, and those are reasonably close to the predicted values (109.2 mg GAE/g dry steam exploded oak wood, 62.3% and 15.9 mm, respectively).

• 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.

• Structural Engineering and Mechanics
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• v.49 no.3
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• pp.411-425
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• 2014

This paper presents the processing of nonlinear features associated with a damage event by quadratic time-frequency distributions for damage identification in a frame structure. A time-frequency distribution is a function which distributes the total energy of a signal at a particular time and frequency point. As the occurrence of damage often gives rise to non-stationary, nonlinear structural behavior, simultaneous representation of the dynamic response in the time-frequency plane offers valuable insight for damage detection. The applicability of the bilinear time-frequency distributions of the Cohen class is examined for the damage assessment of a frame structure from the simulated acceleration data. It is shown that the changes in instantaneous energy of the dynamic response could be a good damage indicator. Presence and location of damage can be identified using Choi-Williams distribution when damping is ignored. However, in the presence of damping the Page distribution is more effective and offers better readability for structural damage detection.