• Journal of the Korean Wood Science and Technology
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• 제46권4호
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• pp.380-392
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• 2018

The importance of polysaccharides is increasing globally due to their role as a significant source of dietary prebiotics in the human diet. In the present study, in order to maximize the yield of crude polysaccharides from Pinus densiflora, response surface methodology (RSM) was used to optimize a two-stage extraction process consisting of steam explosion and water extraction. Three independent main variables, namely, the severity factor (Ro) for the steam explosion process, the water extraction temperature ($^{\circ}C$), and the ratio of water to raw material (v/w), were studied with respect to prebiotic sugar content. A Box-Behnken design was created on the basis of the results of these single-factor tests. The experimental data were fitted to a second-order polynomial equation for multiple regression analysis and examined using the appropriate statistical methods. The data showed that both the severity factor (Ro) and the ratio of water to material (v/w) had significant effects on the prebiotic sugar content. The optimal conditions for the two-stage process were as follows: a severity factor (Ro) of 3.86, a water extraction temperature of $89.66^{\circ}C$, and a ratio of water to material (v/w) of 39.20. Under these conditions, the prebiotic sugar content in the extract was 332.45 mg/g.

• Computers and Concrete
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• 제19권2호
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• pp.133-142
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• 2017

Two-stage concrete (TSC), also known as pre-placed aggregate concrete, is characterized by its unique placement technique, whereby the coarse aggregate is first placed in the formwork, then injected with a special grout. Despite its superior sustainability and technical features, TSC has remained a basic concrete technology without much use of modern chemical admixtures, new binders, fiber reinforcement or other emerging additions. In the present study, an experimental database for TSC was built. Different types of cementitious binders (single, binary, and ternary) comprising ordinary portland cement, fly ash, silica fume, and metakaolin were used to produce the various TSC mixtures. Different dosages of steel fibres having different lengths were also incorporated to enhance the mechanical properties of TSC. The database thus created was used to develop fuzzy logic models as predictive tools for the grout flowability and mechanical properties of TSC mixtures. The performance of the developed models was evaluated using statistical parameters and error analyses. The results indicate that the fuzzy logic models thus developed can be powerful tools for predicting the TSC grout flowability and mechanical properties and a useful aid for the design of TSC mixtures.

• 전력전자학회논문지
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• 제19권3호
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• pp.276-282
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• 2014

In a single-phase grid-connected power system consisting of a dc-dc converter and a dc-ac converter, the current drawn from renewable energy sources has a tendency to be pulsated and contains double-fundamental frequency ripple components, which results in several drawback such as a power harvesting loss and a shortening of the energy source's life. This paper presents a new double-fundamental current reduction-scheme with a fast dc-link voltage loop for two-stage dc-dc-ac grid connected systems. In the frequency domain, an adequate control design is performed based on the small-signal transfer function of a two-stage dc-dc-ac converter. To verify the effectiveness of proposed control algorithm, a 1 kW hardware prototype has been built and experimental results are presented.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권2호
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• pp.100-105
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• 2006

In this paper, a low noise amplifier(LNA) in a receiver of a low noise block down converter (LNB) for direct broadcasting service(DBS) is implemented using GaAs HEMT. The LNA is designed for the bandwidth of 11.7 GHz-12.2 GHz. The two-stage LNA consists of a input matching circuit, a output matching circuit, DC-blocks and RF-chokes. Experimental results of the LNA show the noise figure less than 1.4 dB, the gain greater than 23 dB and the flatness of 1 dB in the bandwidth of 11.7 to 12.2 GHz.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집 특별세미나,특별/일반세션
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• pp.183-188
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• 2009

The High speed electrical multiple train having a distributed electrical motor system has just been developing to aim the experimental maximum speed at 400km/h since August, 2007. This project comes in stage of basic design and so, it needs to take some review and analysis the characteristics of suspensions on the view of basic design. The vehicle model for dynamic analysis is made from the concept design model that used for the preliminary design review with Vampire program and it is modeled with three linear secondary dampers and two shear springs separated from the bush elements in previous model. The optimization technique is applied to search the proper range of linear characteristics for the suspension elements to satisfy the stability performance at speed 130m/s (about 460km/h). The results shows there are some optimum points according to the variation of primary and secondary suspension characteristics and it would be useful to make a decision to select the proper suspension elements in the precision design that will be done by the manufacturing company.

• Structural Engineering and Mechanics
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• 제52권1호
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• pp.19-33
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• 2014

Structural robustness refers to the ability of a structure to avoid disproportionate consequences to the original cause. Currently attentions focus on the concepts of structural robustness, and discussions on methods of robustness based structural design are rare. Firstly, taking basis in robust $H_{\infty}$ control theory, structural robustness is assessed by $H_{\infty}$ norm of the system transfer function. Then using the SIMP material model, robustness based design of grid structures is formulated as a continuum topology optimization problem, where the relative density of each element and structural robustness are considered as the design variable and the optimization objective respectively. Generalized elitist genetic algorithm is used to solve the optimization problem. As examples, robustness configurations of plane stress model and the rectangular hyperbolic shell model were obtained by robustness based structural design. Finally, two models of single-layer grid structures were designed by conventional and robustness based method respectively. Different interference scenarios were simulated by static and impact experiments, and robustness of the models were analyzed and compared. The results show that the $H_{\infty}$ structural robustness index can indicate whether the structural response is proportional to the original cause. Robustness based structural design improves structural robustness effectively, and it can provide a conceptual design in the initial stage of structural design.

• 동아시아경상학회지
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• 제11권3호
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• pp.37-45
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• 2023

Purpose - This research contributes to the existing literature by shedding light on a unique intersection of creativity and leadership, carving out a niche that calls for further exploration. Thus, this study addresses the questions regarding how creative leadership manifests within the context of art education and what the distinct types of business leadership from applying creative leadership principles are in art education? Research design, data, and methodology - This research is made up of two stages to collect textual data from the literature. The first stage involves screening titles and abstracts to weed out studies that overtly lack alignment with the research's focus. The second stage involves a full-text review of the remaining studies to ascertain their suitability based on the research objectives. Result: There are four types of business leadership on Creative Leadership in Art Education, such as Visionary Artistic Leadership, Collaborative Expressionist Leadership, Adaptive Impressionist Leadership, Experimental Abstract Leadership, Experimental Abstract Leadership. Conclusion - The research could conclude that 'Visionary Artistic Leadership' offers practitioners a compelling strategy for igniting innovation within their teams and organizations. HR practitioners can foster a culture of daring creativity by encouraging leaders to embrace visionary thinking. To implement this style, HR professionals can nurture individuals strongly inclined towards innovative ideation.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1993년도 추계학술대회 논문집
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• pp.249-254
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• 1993

In order to respond to the increasing demands of ultraprecision positioning mechanism in the field of precision engineering, more accurate stages are needed whose positioning uncertainty should be in the unprecedented level of nanometers, while maintaining a long travek range. For this application, most conventional stage mechanisms are found not suitable, so the concept of dual servo, which uses two different servos, is one of the new design and control strategies being extensively investigated these days, This paper presents a fine motion mechanism as a part of research on the dual servo control. The stage is made of a single structure of elastic flexure, whose xy .theta. motions are induced in the form of elastic deformation activated by three piezoelectric actuators. Experimental results show that the translational and rotational motions of the stage can be controlled with resolutions of 5 nm and 0.1 arcsec, respectively.

• 대한간호학회지
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• 제42권3호
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• pp.322-332
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• 2012

Purpose: This study was conducted to examine effects of a small group-based cardiocerebrovascular disease (CVD) prevention education program on knowledge, stage of change and health behavior among male bus drivers with CVD risk factors. Methods: A non-equivalent control group pretest-posttest design was used. Participants were 68 male bus drivers recruited from two urban bus companies. Participants from the two groups were selected by matching age, education and risk factors. Experimental group (n=34) received a small group-based CVD prevention education program 8 times over 6 weeks and 3 times through telephone interviews at 2-week intervals. Data were collected between December, 2010 and March, 2011, and were analyzed using chi-square test, t-test, and repeated measure analysis of variance with SPSS/Win18.0. Results: Experimental group showed significantly higher scores in CVD prevention knowledge (p<.001) and health behavior (p<.001) at 6 and 12 weeks after intervention. Participants in pre-contemplation and contemplation stages made progress to contemplation and action. This was significantly better at 6 and 12 weeks after intervention (p<.001). Conclusion: Results suggest that small group-based education programs for CVD prevention are effective in increasing knowledge, stage of change, and health behavior to prevent CVD among male bus drivers with CVD risk.

• 한국산업융합학회 논문집
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• 제23권1호
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• pp.83-91
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• 2020

The evaluation of the compression behavior of the cushioning material is of importance to achieve appropriate packaging design. In order to change packaging design from polymeric-based to more eco-friendly cellulose-based nire effectively, comparative study on the compression behavior between these two packaging materials is crucial. In this study, the stress-strain behavior, hysteresis loss, and response characteristics for cyclic loading were analyzed through compression tests on multi-layered corrugated structure (MLCS) and expanded polystyrene (EPS) packaging materials. MLCS produced in Korea is produced by winding a certain number of single-faced corrugated paperboard, and the compression behavior of this material was turned out to be 6 stages: elastic stage, first buckling stage, sub-buckling stage, densification stage, last buckling stage and high densification stage. On the other hand, EPS's compression behavior was in 3 stages: linear elastic stage, collapse plateau, and densification stage. The strain energy per unit volume (strain energy density) of MLCS did not differ depending on the material thickness, but it showed a clear difference depending on the raw material and flute type. Hysteresis loss of MLCS ranged from 0.90 to 0.93, and there were no significant differences in the raw material and flute type. These values were about 5 to 20% greater than the hysteresis of the EPS (about 0.78 to 0.87).