• 대한안전경영과학회지
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• 제9권5호
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• pp.37-41
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• 2007

There are two parts(middle and southern) according to dividing line of district in Korea. Middle part contains Kang Won, Chung Chung, Gyeong Gi, Seoul, In Cheon and Dae Jeon. Southern part contains Gyeong Sang, Jeol La, Je Ju, Bu San, Dae Gu, Ul San, and Gwang Ju. It is known that there are some differences between middle and southern part on weather. The climatic differences might affect human body. Thus, the mall objective of this study is to analyze effects of climatic differences which influence somatotype characteristics on residents in two regions. In order to compare and analyze data, $R\ddot{o}hrer$ index and drop-value were used. Also, this paper provides typical ratios according to dividing line of district.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.942-947
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• 2004

The differential equations governing free, in-plane vibrations of stepped non-circuiar arches are derived as nondimensional forms including the effects of rotatory inertia, shear deformation and axial deformation. The governing equations are solved numerically to obtain frequencies and mode shapes. The lowest four natural frequencies and mode shapes are calculated for the stepped parabolic arches with hinged-hinged, hinged-clamped, and clamped-clamped end constraints. A wide range of arch rise to span length ratios, slenderness ratios, section ratios, and discontinuous sector ratios are considered. The effect of rotatory inertia and shear deformation on natural frequencies is reported. Typical mode shapes of vibrating arches are also presented.

• Bulletin of the Korean Chemical Society
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• 제10권1호
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• pp.47-50
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• 1989

The methanolysis reactions of phenylacetyl chlorides have been investigated in methanol-acetonitrile mixtures at temperatures ranging - $15.0-0.0^{\circ}C.$ Substituent and solvent effects on the rate supported an associative $S_N2$ mechanism for the solvolysis. Activation parameters indicated that the reaction is entropy controlled, while the a/s ratios of the Taft's solvactochromic correlation proved to be remarkably constant with a typical value of 0.50 that is consistent for the reactions proceeding by a typical $S_N2$ path.

• 대한기계학회논문집B
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• 제22권11호
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• pp.1571-1581
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• 1998

A flow visualization study was carried out for the branch pipe mixing flow in which a jet was issued normally to the fully developed pipe flow. An instantaneous laser tomographic method was used for cross flow Reynolds numbers based on the cross flow diameter D ranged $Re_{cf}=5.26{\times}10^3{\sim}1.13{\times}10^4$, diameter ratios d/D = 0.1 ~ 0.2 and velocity ratios R = 0.5 ~ 10. Oil mist with the size of about $10{\mu}m$ diameter was used for the scattering particle. The main purpose of this study was to reveal the physical mechanism and the structure of vortices formation with varying the velocity ratios and diameter ratios in the branch pipe flow. It was found that the physical mechanism and the structures of vortices formation were quite different depending on the velocity ratios. Particularly in the case of R < 1, the typical vortex shows single loop shape and that for the case of R > 1 depicts mushroom-like structure in the cross flow jet.

• Tribology and Lubricants
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• 제6권1호
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• pp.99-107
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• 1990

Most of machines and structures contain the elements which contact each other directly. When these elements subjected to vibration or repeated load, local relative movement occurs between the elements in contact which results in, a kind of wear. In order to know the factors which govern fretting, we have to analyze the phenomenon of microslip which causes fretting by using a general and efficient method from a viewpoint of contact mechanics. Based on the results of analysis, it is necessary to propose the way of minizing fretting which is one of the most significant surface failure. In this report, a general and efficient algorithm is applied to analyze the contact problem of the bolted joint, which is one of the typical elements damaged by fretting, with ratios of plate thickness, the ratios of Young's moduli, the ratios of the plate thickness to bolt radius varied. Finally, the ways of minizing fretting for the boked joint are suggested.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 추계 학술논문 발표대회
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• pp.13-14
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• 2014

Ultra high performance concrete (UHPC) consists of cement, silica fume (SF), sand, fibers, water and superplasticizer. Typical water/binder-ratios are 0.15-0.20 with 20-30% of silica fume. The development off properties of hardening UHPC relates with both hydration of cement and pozzolanic reaction of silicafume. In this paper, by considering the production of calcium hydroxide in cement hydration and its consumption in the pozzolanic reaction, a numerical model is proposed to simulate the hydration of UHPC. The degree of hydration of cement and degree of reaction of silica fume are obtained as accompanied results from the proposed hydration model. The properties of hardening UHPC, such as degree of hydration of cement, calcium hydroxide contents, and compressive strength, are predicted from the contribution of cement hydration and pozzolanic reaction. The proposed model is verified through experimental data on concrete with different water-to-binder ratios and silica fume substitution ratios.

• Nuclear Engineering and Technology
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• 제55권11호
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• pp.4159-4166
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• 2023

Laser decontamination of radioactive surfaces is an innovative technology. Our contribution to improving this technology includes studies on laser beam decontamination with a pulsed laser of an average power of 150 W, equipped with a hand guided working head. Our investigations are focused on metallic surfaces typical in nuclear power plants, such as stainless steel, bright and rusted mild steel, galvanized steel, and painted steel. As typical nuclides of contaminated surfaces we chose Co-60 and Cs-137, the most frequently occurring nuclides in many nuclear plant components; Sr-85 as a representative of Sr-90, the potentially most harmful fission nuclide; and Am-241 as a representative of the minor alpha-radiation emitting actinides. Here, we present our results of decontamination and recovery ratios. Decontamination ratios of 90-100% were achieved on different surfaces.

• Steel and Composite Structures
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• 제49권4호
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• pp.441-456
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• 2023

Aiming at the development trend of light weight and high strength of engineering structures, this paper experimentally investigated the seismic performance of circular-in-square high-strength concrete-filled double skin steel tubular (HCFDST) stub columns with out-of-code width-to-thickness (B/t) ratios. Typical failure mode of HCFDST stub columns appeared with the infill material crushing, steel fracture and local buckling of outer tubes as well as the inner buckling of inner tubes. Subsequently, the detailed analysis on hysteretic curves, skeleton curves and ductility, energy dissipation, stiffness degradation and lateral force reduction was conducted to reflect the influences of hollow ratios, axial compression ratios and infill types, e.g., increasing hollow ratio from 0.54 to 0.68 and 0.82 made a slight effect on bearing capacity compared to the ductility coefficients; the higher axial compression ratio (e.g., 0.3 versus 0.1) significantly reduced the average bearing capacity and ductility; the HCFDST column SCFST-6 filled with concrete obviously displayed the larger initial secant stiffness with a percentage 34.20% than the column SCFST-2 using engineered cementitious composite (ECC); increasing hollow ratios, axial compression ratios could accelerate the drop speed of stiffness degradation. The out-of-code HCFDST stub columns with reasonable design could behave favorable hysteretic performance. A theoretical model considering the tensile strength effect of ECC was thereafter established and verified to predict the moment-resisting capacity of HCFDST columns using ECC. The reported research on circular-in-square HCFDST stub columns can provide significant references to the structural application and design.

• 동아시아식생활학회지
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• 제23권3호
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• pp.341-348
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• 2013

The Rubus coreanus Miquel concentrate was added in 0 (control), 10, 20, 30, and 40% substitution ratios by weight per sugar. The specific gravity and water content in pound cake batter tended to increase specific gravity according to the added Rubus coreanus Miquel concentrate. The volume, weight, and specific loaf volume in pound cake tended to decrease by according to the addition Rubus coreanus Miquel concentrate. Moisture contents in pound cake tended to increase long the addition Rubus coreanus Miquel concentrate. Brix and pH also decreased. 'L' and 'b' along with the increase in 'a' values were followed in proportion to the substitution ratio. Typical textural parameters like hardness, gumminess, and chewiness were increased in proportion to the substitution ratios, but springiness decreased. Adhesiveness and cohesiveness did not show any considerable differences between the pound cakes. The sensory evaluation showed a high preference for pound cake made with 30% Rubus coreanus Miquel concentrate.

• 한국기계가공학회지
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• 제3권1호
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• pp.59-65
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• 2004

Hollow flange-shaped parts rue widely used in transportation systems. For good quality products, in general, design of preforms and die shapes for a progressive forging process is an important issue. For the design of die shapes for the forging process of a hollow flange, computer simulations Were earned out using the rigid-plastic finite element method. Forging defects like folding were seen in the vicinity of die corners at the typical shape ratios of upper and lower dies Die shape ratios at which the forging defect could occur during the extrusion-forging process of the hollow flange were investigated. The results might be efficiently used for the proper design of perform shapes, die shapes, and forging processes.