• International Journal of Automotive Technology
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• 제8권3호
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• pp.337-342
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• 2007

A multi-objective optimization technique was implemented to obtain optimal topologies of the inner reinforcement for a vehicle's hood simultaneously considering the static stiffness of bending and torsion and natural frequency. In addition, a smoothing scheme was used to suppress the checkerboard patterns in the ESO method. Two models with different curvature were chosen in order to investigate the effect of curvature on the static stiffness and natural frequency of the inner reinforcement. A scale factor was employed to properly reflect the effect of each objective function. From several combinations of weighting factors, a Pareto-optimal topology solution was obtained. As the weighting factor for the elastic strain efficiency went from 1 to 0, the optimal topologies transmitted from the optimal topology of a static stiffness problem to that of a natural frequency problem. It was also found that the higher curvature model had a larger static stiffness and natural frequency than the lower curvature model. From the results, it is concluded that the ESO method with a smoothing scheme was effectively applied to topology optimization of the inner reinforcement of a vehicle's hood.

• Bulletin of the Korean Chemical Society
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• 제28권12호
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• pp.2466-2470
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• 2007

A new highly salicylate-selective PVC membrane electrode based on tripodal tris-thiourea derivatives, L1 and L2, as neutral carriers is described. The electrodes display an excellent potentiometric response to salicylate ions and an anti-Hofmeister selectivity sequence in the following order: Salicylate? > ClO4 ? > Benzoate? > I? >NO3? > NO2? > Maleate? > Acetate? > Lactate? > Fumarate?. It also exhibited a near-Nernstian potential in a linear range of 5.0 × 10?5 - 1.0 × 10?1 M with a detection limit of 9.0 × 10?5 mol/L and a slope of ?59.9 mV/decade at a pH of 7.0 in a saline buffer solution at 25 oC. The stability constant (log KS) of the anionsionophore complex was also determined at 25 oC by a conductometric titration in DMSO solution.

• 대한기계학회논문집B
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• 제29권6호
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• pp.711-721
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• 2005

In order to design of emergency ventilation systems, the smoke movements in tunnel fire with natural and forced ventilation were investigated. Reduced-scale experiments were carried out under the Froude scaling with novel fire source consisting many wicks. Temperature profiles were measured under the ceiling and vertical direction along the center of the tunnel and poisonous gases were measured at emergency exit point in the natural ventilation case. In forced ventilation, temperature profiles were measured with various flow rate to obtain critical velocity. The results showed that the interval of emergency exit having 225m was estimated reasonably through the measurements of temperature variation and poisonous gas in the natural ventilation. In the case of forced ventilation, the temperature distribution near fire source is remarkably different from that of natural ventilation. Also, the critical velocity to prevent upstream smoke flow has the range of 0.57m/s between 0.64m/s. Finally, it was also identified that although the increase of flow rate can suppress the backward flow of smoke to upstream direction, brings about the increase of flame intensity near stoichiometric fuel/air ratio.

• Natural Product Sciences
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• 제10권1호
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• pp.35-39
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• 2004

Aldose reductase (AR), the key enzyme of the polyol pathway, is known to play important roles in the diabetic complications. The inhibitors of AR, therefore, would be potential agents for the prevention of diabetic complications. In order to clarify the structural requirements of flavonoids for aldose reductase inhibitory activity, thirty flavonoids were examined. Among the thirty flavonoids, flavonols such as quercetin (5), reyneutrin (7), quercitrin (9), isoquercitrin (11), and avicularin (14) were found to exhibit much stronger AR inhibition. Lonicerin (10), amentoflavone (27) and sophoraflavanone B (30) were also showed strong inhibitory activity. Especially, quercitrin and reyneutrin exhibited the most inhibitory potency on rat lens (RL) AR. The results suggested that flavonol having the 7-hydroxyl and/or catechol moiety at the B ring exhibit strong activity. In addition, flavonols having 3-O-monosaccharide also showed stronger inhibition than free flavonols at the 3-position. These results suggested that quercitrin and reyneutrin are attributed to be the promising compounds for the prevention and/or treatment of diabetic complications.

• Structural Engineering and Mechanics
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• 제61권5호
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• pp.563-576
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• 2017

This paper is a continuation of the investigations started in the paper by Akbarov, S.D., Guliyev, H.H and Yahnioglu, N. (2016) "Natural vibration of the three-layered solid sphere with middle layer made of FGM: three-dimensional approach", Structural Engineering and Mechanics, 57(2), 239-263, to the case where the three-layered sphere is a hollow one. Three-dimensional exact field equations of elastodynamics are employed for investigation and the discrete-analytical method is employed for solution of the corresponding eigenvalue problem. The FGM is modelled as inhomogeneous for which the modulus of elasticity, Poison's ratio and density vary continuously through the inward radial direction according to power law distribution. Numerical results on the natural frequencies are presented and discussed. These results are also compared with the corresponding ones obtained in the previous paper by the authors. In particular, it is established that for certain harmonics and for roots of certain order, the values of the natural frequency obtained for the hollow sphere can be greater (or less) than those obtained for the solid sphere.

• 복식문화연구
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• 제24권6호
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• pp.777-787
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• 2016

This study was carried out in order to provide useful data for planning fabrics of summer eco-friendly fashion products. The fabrics used in this study were four cellulose fibers: cotton, cotton/mulberry blended, flax, and flax/lyocell blended. Dyeing with natural indigo was carried out under three different reducing conditions (i.e., general, eclectic, and eco-friendly) that have different reducing agent and pH levels, and hydrosulfite and glucose were used as a reducing agent. The dye uptake (K/S value) of fabrics dyed with natural indigo by a reducing condition was the highest at 660nm. Regardless of the fabrics, dye uptake was the highest under the general reducing condition and the lowest under the eco-friendly reducing condition. Under different reducing conditions, the dye uptake of natural indigo fabrics with the maximum absorption wavelength indicated a difference. The colorfastness of cellulose fabrics that were dyed with natural indigo had a rate of 4 to 5 except for rubbing fastness, which indicated good colorfastness. Additionally, natural indigo-dyed cotton and flax fabrics had good antibiosis. When the color characteristics of fabrics dyed with natural indigo were measured, all of the three reducing conditions created purple blue (PB) colors, and the color characteristics of dyed fabrics by reducing condition and fabric showed significant differences.

• 한국환경과학회지
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• 제23권12호
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• pp.2107-2120
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• 2014

Natural environmental protection system in North Korea is rarely understood mainly because of lack of information in scientific and legislative fields. Legislation is very important to achieve goal for protected areas, which are described in "Natural Protected Area Law(NPAL)". Cabinet of North Korea has authorities to lead the Central Agency for Land and Environment Conservation(CALEC). Designation and managements of natural protected areas are regarded as CALEC and local governments responsibilities. There are many differences between South and North Korea. Especially legislation system has many differences. North Korea's Labor Party is superior to the Government and Labor Party's order has at least the same authority to regulate and manage the national policy and means. With NPAL, CALEC organizes the national plan for natural protected area and regulate the activities of the Agencies for Land and Environment Conservation in the aspects of action plan, budget and other resources. For the reunification in the future, legislation system of North Korea should be understood.

• 한국조경학회지
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• 제33권6호
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• pp.1-11
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• 2006

The purpose of this study was to investigate the influence of natural landscapes in the context of work environments. The study examined the impact of natural landscapes on urban office workers' stress reduction and cognitive performance, using physiological, psychological, and cognitive measures. One-hundred-twenty urban office workers participated in the experiments. The physiological measures used were GSR (galvanic skin response) and IBI (interbeat interval), and the psychological measure was ZIPERS (Zucherman Inventory of Personal Reactions). Cognitive performance was measured using a mental arithmetic test that had been developed by a pretest. The results from the physiological, psychological, and cognitive measures converged to indicate that the natural landscape had more beneficial effects in relieving both psychological and physiological stress and in enhancing cognitive performance of the of office workers than the city landscape. The results suggest wide applications in the fields of workers' well-being and landscape research. First, the results can provide reliable information for promoting natural landscaping in work places in order to relieve worker stress and enhance cognitive performance. Second, the results provide an example for future empirical landscape research using multiple measurements, such as psychological, physiological, and cognitive tests. Third, they can foster experimental research to investigate the relationship between stress reduction and natural landscapes.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.467-471
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• 2014

The natural frequencies of a mechanical system are determined by the system parameters such as masses and stiffness of the system. Since material irregularities and manufacturing tolerances always exist in most of practical engineering situations, the system parameters always have uncertainties. As the uncertainties of the parameters increase, the uncertainties of the system natural frequencies also increases. Then, the reliability of the system deteriorates. So, the uncertainty of the system natural frequencies should be analyzed accurately and considered in the design of the system. In order to analyze the uncertainty of the system natural frequencies employing most of existing uncertainty analysis methods, the probability distributions of the uncertain system parameters should be identified. In most practical situations, however, identification of the probability distributions is almost impossible because of limited time and cost. For that case, the reliability should be estimated based on finite samples of the system parameters. In this paper, sample based reliability estimation method employing extreme value theory was proposed. Using the proposed estimation method, sample based reliability design of the system natural frequencies was conducted.

• 태양에너지
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• 제16권2호
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• pp.15-37
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• 1996

Most of the world's energy demand is met by fossil fuels, mainly petroleum and natural gas. Even though their production is not keeping up with the demand, there are many options before us-solar energy in its direct and indirect forms, nuclear breeders, thermonuclear power, geothermal energy, synthetic fluid fuels, and hydrogen as energy carrier to complement the nonfossil energy sources. But, before these energy alternatives can be utilized, in most cases, it is necessary to conduct extensive research and development work. In order to solve global energy and environmental issues, it is very important to develop and install energy supply systems which utilizes natural energy. The installation of these systems brings the following merits from the viewpoints of energy saving or environmental protection-(a) the positive use of natural energy reduces fossil fuel consumption; and (b) it also prevents environmental degradation. In this paper, the types of natural energy considered is confined to the solar, wind, hydraulic, geothermal and ocean-wave energy. And, the objective of the paper is to describe the state of the art of natural energy and future utilization prospect of them.