• Journal of the Korean Chemical Society
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• v.40 no.9
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• pp.640-648
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• 1996

Crosslinked chitosan was prepared from chitin after reaction with epichlorohydrin followed by deacetylation at C2-position. Epidermal releasing polymeric matrix was prepared after swelling crosslinked chitosan with distilled water and adding silver sulfadiazine and glycerine as a plasticiser. The release behavior of silver sulfadiazine from polymeric matrix was studied in pH 7.4 phosphate buffer solution by varing the drug content, glycerine concentration, and the thickness of the matrix. The drug release time was delayed by increasing the content of silver sulfadiazine and the thickness of the matrix, whereas decreased as glycerine concentration increased. The apparent constant(K) of release rate was independent upon the matrix thickness, but was proportional to the content of drug or glycerine of crosslinked chitosan matrix. These results indicated that chitosan matrix showed some potential as a drug delivery system for transdermal therapeutic application.

• Korean Journal of Materials Research
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• v.11 no.6
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• pp.492-497
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• 2001

We report the characteristics and the dependence of sputter-deposited Ta films on the process parameters. The properties of as-deposited Ta films such as deposition rate, resistivity, Rs uniformity, reflectivity, and stress were investigated and analyzed as a function of process parameter using a statistical experimental method. The functional relationships between the independent and dependent variables were predicted by surface response. The optimal deposition condition of DC magnetron sputtered Ta films was obtained at the chamber pressure of 2 mTorr, power density of 8 W/$\textrm{cm}^2$, and substrate temperature of 2$0^{\circ}C$ by means of resistivity and Rs uniformity. The fitness value for quadratic model as evaluated by the R- square was 0.85~ 0.9 without pooling. The as-deposited Ta films exhibited the resistivity of ~180$\mu$$\Omega$cm with Rs uniformity of ~2%. The transmission electron microscopy and x-ray diffractometry identified that the phase of as-deposited film was $\beta$-Ta having the grain size of 100~200.

• Archives of Pharmacal Research
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• v.24 no.6
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• pp.568-571
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• 2001

The purpose of this work was to study the effect of storage time and temperature on the in vitro release kinetics of a commercial sustained-release dosage form of theophylline, at different pHs of the dissolution medium. The formulation was stored at $35^{\circ}C$ for 16 months and at $45^{\circ}C$ for 8 months, with a relative humidity of 60%. The in vitro release tests were performed at pHs 2, 4, 6 and 7.4. The mean values of the transport coefficient n, were close to 0.5 in all the conditions tested, which indicates that the transport system is not modified after storage of the formulation at $35^{\circ}C$ and $45^{\circ}C$. The mean values of the dissolution rate constant ranged from 0.036 to 0.043 $min^{-n}$, under all the conditions tested. Significant differences (${\alpha}=0.05$) were found between pHs 2, 4 and 6, 7.4 for all the model-independent parameters studied. When the formulation was kept at $35^{\circ}C$ for 16 months, the mean percentage of drug dissolved at 8 hours was 25.61% (pHs 2, 4) and, 36.12% (pHs 6, 7.4), representing a 26% and 24% reduction, respectively. Simitar results were obtained after storing the formulation at $45^{\circ}C$ for 8 months, corresponding to 33.3% (pHs 2, 4) and, 22.5% (pHs 6, 7.4) diminution, respectively. The values of the similarity factory $f_2$, obtained were lower than 50, which indicates the lack of similarity among the dissolution profiles, after storing the formulation under the experimental Conditions tested.

• Journal of Information Technology Services
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• v.17 no.4
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• pp.101-117
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• 2018

Companies are responding appropriately to the rapidly changing business environment and striving to lead those changes. As part of that, we are meeting our strategic goals through IT projects, which increase the number of simultaneous projects and the importance of project portfolio management for successful project execution. It also strives for efficient deployment of human resources that have the greatest impact on project portfolio management. In the early stages of project portfolio management, it is very important to establish a reasonable manpower plan and allocate performance personnel. This problem is a problem that can not be solved by linear programming because it is calculated through the standard deviation of the input ratio of professional manpower considering the uniformity of load allocated to the input development manpower and the importance of each project. In this study, genetic algorithm, one of the heuristic methods, was applied to solve this problem. As the objective function, we used the proper input ratio of projects, the input rate of specialist manpower for important projects, and the equal load of workload by manpower. Constraints were not able to input duplicate manpower, Was used as a condition. We also developed a program for efficient application of genetic algorithms and confirmed the execution results. In addition, the parameters of the genetic algorithm were variously changed and repeated test results were selected through the independent sample t test to select optimal parameters, and the improvement effect of about 31.2% was confirmed.

• Korean Journal of Labor Studies
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• v.23 no.2
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• pp.141-167
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• 2017

This study carries out an empirical analysis of how workplace innovation affects employment growth. The theoretical model and hypotheses of this study are drawn from the previous research on the employment effects of innovation. I use the data on Workplace Innovation Indicators(2013-14) collected by Labor Foundation. As the regression models for this study, I adopt OLS models whose dependent variable is employment growth rate, and whose main independent variables are the adoption and the intensity(standardized values) of three innovative work practices such as TQM, employee suggestion plans and multi-skill training programs. The results of this study indicate that the adoption of workplace innovation does not have significant effects on employment growth, but that the intensity of workplace innovation has weakly positive effects on employment growth. Besides, the results of this demonstrate show that government-subsided organizational innovation consulting and training hours per capita have positive employment effects, but that wage level and prior employment size have negative ones. Finally the empirical results are outlined, and their limitations and the future direction of research on this topic are discussed.

• Nuclear Engineering and Technology
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• v.55 no.11
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• pp.3973-3982
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• 2023

As for two-phase flow in rectangular channels, the flow regimes especially like churn-turbulent and annular flow are significant for the physical problem like Countercurrent Flow Limitation (CCFL). In this study, the rectangular channels with cross-sections of 4 × 66 mm, 6 × 66 mm, 8 × 66 mm are adopted to investigate the flow regimes of air-water vertical upward two phase flow under adiabatic condition. The gas and liquid superficial velocities are 0 ≤ j_g ≤ 20m/s and 0.25 ≤ j_f ≤ 3m/s respectively which covering bubbly to annular flow. The flow regimes are identified by random forest algorithm and the flow regime maps are obtained. As the results, the transitional void fraction from slug to churn turbulent flow fluctuate from 0.47 to 0.58 which is significantly affected by the dimensional size of channel and flow rate. Besides, the void fraction at transitional points from churn-turbulent (slug) to annular flow are 0.66-0.67, which are independent with the gap size. Furthermore, a new criteria of slug to churn-turbulent flow is established in this study. In addition, by introducing the interfacial force model, the criteria of churn-turbulent (slug) flow to annular flow is verified.

• Applied Chemistry for Engineering
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• v.35 no.4
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• pp.329-334
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• 2024

To improve the UV absorbance and emulsion stability of sunscreen creams prepared using refined seabuckton oil, experimental conditions were designed utilizing the central composite design model-response surface methodology (CCD-RSM). The amount of surfactant, emulsification time, and thickener amount were chosen as independent variables, and the experiment was carried out after the reaction values of ESI, MDS, and UV absorbance at 290 nm were determined. The main effect and interaction effect, which have the most influence on the response value, were analyzed through the F-value and P-value of the regression equation coefficient calculated through RSM, and the statistical significance of the coefficient was evaluated through the P-value. The optimal emulsification conditions using RSM were calculated as follows: amount of surfactant (4.39 wt%), emulsification time (25.42 min), and amount of thickener (1.24 wt%). At these conditions, the reaction value was calculated as ESI (98.5%), MDS (32.9 nm), and UV absorbance (2.73). As a result of conducting an actual experiment under the calculated optimal conditions, the average error rate was measured as ± 2.7%

• Korean Circulation Journal
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• v.52 no.12
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• pp.878-886
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• 2022

Background and Objectives: Moderate aortic stenosis (AS) confers a surprisingly adverse prognosis, approaching that of severe AS. The objective of this study was to describe the clinical course of patients with moderate AS with evidence of concomitant heart failure manifesting as elevated brain natriuretic peptide (BNP) levels. Methods: This is a single-center, retrospective cohort study of 332 patients with elevated BNP. 165 patients with moderate AS were compared with 167 controls with none-mild AS. The Median follow-up duration was 3.85 years. The primary outcome was a composite endpoint of all-cause hospitalizations and all-cause mortality. Results: BNP levels were 530 and 515 pg/mL in the study and the control groups, respectively. Moderate AS had significantly higher rates of primary composite endpoint in both univariate analysis (hazard ratio [HR], 1.50; 95% confidence interval [CI], 1.14-1.97; p=0.004) and adjusted analysis (HR, 1.45; 95% CI, 1.05-2.01; p=0.02). Moderate AS had 1.41 (95% CI, 1.18-1.69; p<0.001) times more all-cause hospitalization per patient-year of follow-up compared to controls in the univariate model. After adjustment for significant covariates, moderate AS remained an independent predictor of all-cause hospitalizations (incidence rate ratio [IRR], 1.45; 95% CI, 1.18-1.79; p=0.005). Furthermore, moderate AS was significantly associated with higher all-cause hospitalization rates in both heart failure with reduced ejection fraction (IRR, 1.33; 95% CI, 1.02-1.75; p=0.038) and heart failure with preserved ejection fraction [IRR], 1.31; 95% CI, 1.03-1.67; p=0.026). Conclusions: Moderate AS in conjunction with elevated BNP portends a significantly worse prognosis than those without moderate AS and should be followed closely.

• Journal of Intelligence and Information Systems
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• v.9 no.1
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• pp.227-249
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• 2003

Prediction of corporate failure using past financial data is a well-documented topic. Early studies of bankruptcy prediction used statistical techniques such as multiple discriminant analysis, logit and probit. Recently, however, numerous studies have demonstrated that artificial intelligence such as neural networks can be an alternative methodology for classification problems to which traditional statistical methods have long been applied. In building neural network model, the selection of independent and dependent variables should be approached with great care and should be treated as model construction process. Irrespective of the efficiency of a teaming procedure in terms of convergence, generalization and stability, the ultimate performance of the estimator will depend on the relevance of the selected input variables and the quality of the data used. Approaches developed in statistical methods such as correlation analysis and stepwise selection method are often very useful. These methods, however, may not be the optimal ones for the development of neural network model. In this paper, we propose a genetic algorithms approach to find an optimal or near optimal input variables fur neural network modeling. The proposed approach is demonstrated by applications to bankruptcy prediction modeling. Our experimental results show that this approach increases overall classification accuracy rate significantly.

• Applied Chemistry for Engineering
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• v.29 no.4
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• pp.446-451
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• 2018

Effective ingredients were extracted using wheat sprout with high levels of flavonoids, and the extraction process was optimized with a central composite design model. The response value of the central composite design model establishes the extraction yield and the content of the flavonoids. The main and interactive effects were then analyzed depending on independent variables such as the extraction time, the volume ratio of alcohol to ultrapure water, and the extraction temperature. The extraction time and temperature were relatively large for the extraction yield. For the total flavonoids, the extraction time was most significantly affected. Considering both the extraction yield and the content of the total flavonoids, optimal extraction conditions were as follows: the extraction time (2.44 h), volume ratio of alcohol to ultrapure water (50.00 vol%), extraction temperature ($54.41^{\circ}C$). Under these condition, the extraction yield was 30.14 wt% and the content of the total flavonoids was $35.37{\mu}g\;QE/mL\;dw$. From the actual experimental result, the extraction yield under this condition was 29.92 wt% and the content of the total flavonoids was $35.32{\mu}g\;QE/mL\;dw$, which had an error rate of 0.39% and 0.74%, respectively. This is a multi-analysis comprehensive analysis that analyzes two simultaneous values of responses, but is considered to be highly accurate and also provides an excellent reliability of the optimization process in this study.