• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.5 s.51
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• pp.49-61
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• 2006

The floor impact sound insulations are installed frequently for reducing the floor impact sound into the floor slab of the residential buildings in recent years. Therefore the analytical FE model considering the insulation is needed for the sound and vibration analysis of the floor and it is necessary to use a refined finite element model fer considering the large number of modes involved dynamic responses. So it is very difficult to use FE model because of the tiresome task for constructing the FE model, taking a lot of times for analysis and the impossibility of using the proportional damping. The efficient analysis and modeling method are proposed to the dynamic analysis for the floor with damping layer in this study. The floor slabs and finished layers are modeled individually and the spring elements that mean damping layers used to connect two parts. The dynamic analysis by the $Newmark-{\beta}$ method is performed to solve the non-proportional damping problem due to the damping coefficient of insulations.

• Journal of Environmental Science International
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• v.11 no.6
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• pp.519-528
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• 2002

This study was to evaluate the impact of river runoff and salt intrusion by tide on nutrient balance of estuary during a complete tidal cycle. 24 hours time series survey was carried out during a spring tide July 2001 on a tidal estuary in the Keum river. Three stations(A,B,C) were set along a transect line of about 10km, which linked the lower part of estuary dyke to the subtidal zone. Surface water was sampled simultaneously at each station every hours f3r the determination of nutrients. Water temperature, pH and dissolved oxygen were measured in situ. Riverine input of silicate and nitrate during ebb tide significantly increased the concentration of all stations. Conversely, during high tide, nutrient concentration were lowered by the mixing of fresh water with sea water Ammonium nitrogen concentration were higher at intertidal zone(Stn.B) due to sewage inflow to Kyeongpo stream and ammonium release under anaerobic conditions. Also, these results was discussed as a biological component that influences the processes of nutrient regeneration within the estuary. Best correlations were found at lower part of estuary dyke(Stn.A) for salinity against DIN(Y=0.121 Sal.+4.97, r2=0.956) and silicate(Y=0.040 Sal.+2.62, r2=0.785). But no significant correlation was found between salinity and ammonium. Unbalanced elemental ratio(N/P, Si/N and Si/P) depended significantly on the import of nutrients (silicate & nitrate nitrogen) from river and stream. The effect of the tidal cycle and river runoff is important that in determining the extend of the variations in nutrient concentrations at all station.

• Korean Journal of Food Science and Technology
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• v.24 no.3
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• pp.294-299
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• 1992

This study was to examine the effect of functional properties of soy protein isolate(SPI) and qualities of soybean curd upon proteolytic hydrolysis. SPI was hydrolyzed using proteolytic enzyme, bromelain. The protein content of SPI by microkjeldahl method was 84% and the degree of hydrolysis in modified soy protein isolate(MSPI) was 2.7%. The solubility of MSPI was higher than that of control at various pH tested and proteolytic hydrolysis was increased emulsion formation and foam expansion while decreased emulsion stability, foam stability and calcium precipitation. Modified soybean curdI, standard soybean milk: Modified soybean milk=3:1, was soft and springy soybean curd when the texture properties of soybean curd were tested by texture profile analysis using Instron and sensory evaluation. The rheological model of soybean curds was investigated by stress relaxation test. The analysis of relaxation curve revealed that the rheological behavior of soybean curds could be expressed by 7-element generalized Maxwell model. The equilibrium modulus and modulus of elasticity decreased as the ratio of modified soybean milk was increased.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.3
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• pp.1091-1097
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• 2011

This study aims to develop the plastic suspension assembly which is installed on inside of vehicle seat and supports passenger's back to provide the comfortable feeling. This design is the suspension structure to support the back equally and assemble seat back frame and plastic suspension effectively. The parts of suspension are designed by considering the property of body pressure distribution. As analysis values are approached to measured values by comparing the deformations in the cases of existed spring suspension and developed plastic suspension, the optimum design can be established.

• Journal of Environmental Health Sciences
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• v.30 no.5 s.81
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• pp.455-468
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• 2004

The purpose of this paper is to understand the time series and origin of a chemical component and to compare the difference during yellow sand episodes for analysis $PM_{10}$ chemical components in the region of west in Korean Peninsula, 1999-2001. An annual mean concentration of $PM_{10}$ is $29.1\;{\mu}g/m^3$. A monthly mean and standard deviation of $PM_{10}$ concentration are very high in spring but there is no remarkably seasonal variation. Also, water soluble ionic component of $PM_{10}$ be influenced by double more total anion than total cation, be included $NO_{3}^-\;and\;SO_{4}^{2-}$ for the source of acidity and $NH_{4}^+$ to neutralize. Tracer metals of $PM_{10}$ slowly increases caused by emitted for soil and ocean (Fe, Al, Ca, Mg, Na) and Zn, Pb, Cu, Mn for anthropogenic source. According to method of enrichment factor (E.F) and statistics, assuming that the origin of metal component in $PM_{10}$ most of element in the Earth's crust e.g. Mg, Ca, Fe originates soil and Cu, Zn, Cd, Pb derives from anthropogenic sources. The ionic component for $Na^{+}\;Cl^-,\;Mg^{2+}\;and\;Ca^{2+}$ and Mg, Al, Ca, Fe originated by soil component largely increase during yellow sand period and then tracer metal component as Pb, Cd, Zn decrease. According to factor analysis, the first group is ionic component ($Na^+,\;Mg^{2+},\;Ca^{2+}$) and metal component (Na, Fe, Mn and Ni) be influenced by soil. The second group, Mg, Cr also be influenced by soil particle.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.4
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• pp.429-435
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• 2015

A bellows is an important temperature control component in a Joule-Thomson micro-cryocooler. It is designed using a very thin shell, and the inside of the bellows is filled with nitrogen gas. The bellows is made of a nickel-cobalt alloy that maintains its strength and elastic properties in a wide range of temperatures from cryogenic to $300^{\circ}C$. The pressure of the gas and the volume within the bellows vary according to the temperature of the gas. As a result, the bellows contracts or expands in the axial direction like a spring. To explore this phenomenon, the deformation of the bellows and its internal volume must be calculated iteratively under a modified pressure until the state equation of the gas is satisfied at a given temperature. In this paper, the modified Benedict-Webb-Rubin state equation is adopted to describe the temperature-volume-pressure relations of the gas. Experiments were performed to validate the proposed method. The results of a numerical analysis and the experiments showed good agreement.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.7
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• pp.233-240
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• 2003

Recently, the world are preparing for new revolution, called as If (Information Technology), NT (Nano-Technology), and BT (Bio-Technology). NT can be applied to various fields such as semiconductor-micro technology. Ultra precision processing is required for NT in the field of mechanical engineering. Recently, together with radical advancement of electronic and photonics industry, necessity of ultra precision processing is on the increase for the manufacture of various kernel parts. Therefore, in this paper, stability of ultra precision cutting unit is investigated, this unit is the kernel unit in ultra precision processing machine. According to alteration of shape and material about hinge, stability investigation is performed. In this paper, hinge shapes of micro stage in UPCU(Ultra Precision Cutting Unit) are designed as two types, where, hinge shapes are composed of round and rectangularity. Elasticity and strength are analyzed about micro stage, according to hinge shapes, by FE analysis. Micro stage in ultra precision processing machine has to keep hinge shape under cutting condition with 3-component force (cutting component, axial component, radial component) and to reduce modification against cutting force. Then we investigated its elasticity and its strength against these conditions. Material of micro stage is generally used to duralumin with small thermal deformation. But, stability of micro stage is investigated, according to elasticity and strength due to various materials, by FE analysis. Where, Used materials are composed of aluminum of low strength and cooper of medium strength and spring steel of high strength. Through this stability investigation, trial and error is reduced in design and manufacture, at the same time, we are accumulated foundation data for unit control.

• Journal of Korean Society for Atmospheric Environment
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• v.8 no.1
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• pp.20-28
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• 1992

The x-ray fluorescence(XRF) is one of the most convenient and widely used techniques for analyzing trace elements in ambient particulate matters. The objects of the study were to estimate the optimum exposure time using the XRF, to investigate the distributions of heavy metal levels in particulate matters, and finally to study seasonal variation for the concentrations of total suspended particulate matters(TSP) and size fractionated particulate matters. The suspended particulate matters had been collected by a cascade impactor having 9 size fragnated stages for 3 years(Dec. 1988 to Nov. 1991) in Kyung Hee University-Suwon Campus. The particulate matters were then collected on each stage by membrane filters. The weight concentrations were determined by the XRF system. Thus, seasonal variations and relationship between concentration and particle size could be investigated. Resulting distribution was bimodal with the coarse and the fine particle groups minimum occurring around 2.1 to 3.3 $\mu$m as an aerodynamic diameter. To determine optimum exposure time of the XRF for various trace inorganic elements, membrane filters and the NIST standard filters were extensively studied. Using a statistical technique, optimum exposure time was estimated for each trace element and overall elements. The time was then determined as 20 seconds for the XRF system. The concentration of TSP was 123.9$\mum/m^3$ on an arithmatic average. The levels of each inorganic metal were Si 2420.0ng/$m^3$, Fe 977.1ng/$m^3$, and so on. The Pb. Zn, and Cu abounded in the fine mode group, while Ca, Fe, Si, Al, and K in the coarse group. Marked seasonal variation of TSP and metal concentrations was observed. The concentration of heavy metals in the fine mode was highest in winter : on the other hand, that in the coarse mode was highest in spring.

• Structural Engineering and Mechanics
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• v.75 no.4
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• pp.477-485
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• 2020

Finite element (FE) model based structural damage detection (SDD) methods play vital roles in effectively locating and quantifying structural damages. Among these methods, structural model updating should be conducted before SDD to obtain benchmark models of real structures. However, the characteristics of updating parameters are not reasonably considered in existing studies. Inspired by the l_∞ norm regularization, a novel anti-sparse representation method is proposed for structural model updating in this study. Based on sensitivity analysis, both frequencies and mode shapes are used to define an objective function at first. Then, by adding l_∞ norm penalty, an optimization problem is established for structural model updating. As a result, the optimization problem can be solved by the fast iterative shrinkage thresholding algorithm (FISTA). Moreover, comparative studies with classical regularization strategy, i.e. the l₂ norm regularization method, are conducted as well. To intuitively illustrate the effectiveness of the proposed method, a 2-DOF spring-mass model is taken as an example in numerical simulations. The updating results show that the proposed method has a good robustness to measurement noises. Finally, to further verify the applicability of the proposed method, a six-storey aluminum alloy frame is designed and fabricated in laboratory. The added mass on each storey is taken as updating parameter. The updating results provide a good agreement with the true values, which indicates that the proposed method can effectively update the model parameters with a high accuracy.

• Earthquakes and Structures
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• v.6 no.1
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• pp.89-110
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• 2014

Nonlinear dynamic analyses are carried out to investigate the influence of the pinching hysteretic response of the exterior RC beam-column joints on the seismic behavior of multistory RC frame structures. The effect of the pinching on the local and global mechanisms of an 8-storey bare frame and an 8-storey pilotis type frame structure is evaluated. Further, an experimental data bank extracted from literature is used to acquire experimental experience of the range of the real levels that have to be considered for the pinching effect on the hysteretic response of the joints. Thus, three different cases for the hysteretic response of the joints are considered: (a) joints with strength and stiffness degradation characteristics but without pinching effect, (b) joints with strength degradation, stiffness degradation and low pinching effect and (c) joints with strength degradation, stiffness degradation and high pinching effect. For the simulation of the beam-column joints a special-purpose rotational spring element that incorporates the examined hysteretic options developed by the authors and implemented in a well-known nonlinear dynamic analysis program is employed for the analysis of the structural systems. The results of this study indicate that the effect of pinching on the local and global responses of the examined cases is not really significant at early stages of the seismic loading and especially in the cases when strength degradation in the core of exterior joint has occurred. Nevertheless in the cases when strength degradation does not occur in the joints the pinching may increase the demands for ductility and become critical for the columns at the base floor of the frame structures. Finally, as it was expected the ability for energy absorption was reduced due to pinching effect.