• Journal of Advanced Marine Engineering and Technology
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• v.38 no.3
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• pp.276-284
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• 2014

The purpose of this study is to establish the designing method of ORC(Organic Rankine Cycle) radial inflow turbines. RTDM(Radial Turbine Design Modeler) Ver.2.1 which is a preliminary design program of radial inflow turbines was developed to achieve this purpose. The 200kW-class radial inflow turbine for OTEC(Ocean Thermal Energy Conversion) was designed by using the RTDM Ver.2.1 and CFD(Computational Fluid Dynamics) simulation was performed to verify the accuracy of RTDM Ver.2.1. With the result of simulation, the accuracy of RTDM Ver.2.1 was almost 94.6% based on the designed total enthalpy drop of the radial inflow turbine. Strategy of adjusting the mass flow rate was adopted on this study to satisfy the requirements of its power and rotor outlet's conditions for the designed radial inflow turbine. The mass flow rate was consequently increased to 21.2 kg/s for the designed 200kW-class radial inflow turbine for OTEC, and then Total to total and Total to static efficiency are 89.8% and 85.36% respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.27-36
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• 2018

A significant amount of studies were performed on evaporation heat transfer and pressure drop in microfin tubes. Most studies, however, focused on the refrigerants used in air-conditioners or heat pumps, and very limited information is available on R-404A, which is used in low temperature refrigeration. In this study, the evaporation heat transfer and pressure drop characteristics of R-404A in a 9.5 mm O.D. microfin tube were investigated for the mass flux range from $80kg/m^2s$ and $200kg/m^2s$. A smooth tube of the same outer dimeter was also tested for comparison. The results showed that the heat transfer enhancement ratio of the microfin tube increased with increasing mass flux and the heat flux decreased. The relative contribution of the convective heat transfer and the heat flux on total heat transfer was attributed to the observed trend. The pressure drops of the microfin tube were slightly (maximum 28%) larger than those of the smooth tube. Existing correlations do not adequately predict the measured heat transfer coefficients of pressure drops, probably due to the test range of the present study, which is outside of the existing correlations.

• Resources Recycling
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• v.8 no.4
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• pp.11-19
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• 1999

Fly ash generated from (he pulverized coal power plant have caused the serious ocean pollution due to the disposal in the ash pond, the life reduction of a power plant and the waste of re-utilizable resource The research to reuse the unburned carbon and mineral composing of the ash has been progressed. In this study. the physical and chemical characteristics of high grade ash and unburned carbon particles obtained from countercurrent column flotation are investigated. The cleaned ash of the less 0,5% loss on Ignition(LOI) in carbon content is a spherical sphere and 39.8${\mu}m$ in size of MMD(Mass Median Diameter). 2.22 $m^2/g$ of specific area. The morphology of high LOI carbon particles is a amorphousness, 76.6 ${\mu}m$ of particle size and 15.2 $m^2/g$ of specific The high grade cleaned ash and the high LOI ash have some difference in the light of physical. chemical and morphological characteristics

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.5
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• pp.11-21
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• 2007

Currently in the country, the necessity of seismic analyses is increasing due to the increase of demand and interest in seismic design. Especially, shear wall apartments are constructed mostly for a residental building so seismic analyses for the apartment are actively executed. For the seismic analysis of the shear wall apartment, it may be not efficient in time and effort to model the entire structure by a finite element mesh. Therefore, an equivalent model is needed to simulate the dynamic behavior of the structure by decreasing the number of degrees of freedom. In this study, a method to form an equivalent model that is simple and easy to use was proposed utilizing effective mass coefficient that is highly correlated to mode shape of the structure. This equivalent model was obtained by replacing a shear wall structure with an equivalent frame structure having beams and columns. This model can be used very effectively when excessive seismic analyses are necessary in a short period because it can be operated in any commercial program and reduce the analysis time. Also, it can model floor slabs so it can represent the actual behavior of shear wall apartments. Furthermore, it is very excellent since it can represent the asymmetry of the structure.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.14 no.2
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• pp.90-101
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• 2009

Analysis of multi-channel seismic reflection data from the Southern Ulleung Basin reveals that Plio-Quaternary section in the area consists of nine stacked sedimentary units separated by erosional unconformities. On the southern slope, these sedimentary units are acoustically characterized by chaotic seismic facies without distinct internal reflections, interpreted as debris-flow bodies. Toward the basin floor, the sedimentary units are defined by well-stratified facies with good continuity and strong amplitude, interpreted as turbidite/hemipelagic sediments. The seismic facies distribution suggests that deposition of Plio-Quaternary section in the area was controlled mainly by tectonic movement and sea-level fluctuations. During the Pliocene, sedimentation was mainly controlled by tectonic movements related to the back-arc closure of the East Sea. The back-arc closure that began in the Miocene caused compressional deformation along the southern margin of the Ulleung Basin, resulting in regional uplift which continued until the Pliocene. Large amounts of sediments, eroded from the uplifted crustal blocks, were supplied to the basin, depositing Unit 1 which consists of debris-flow deposits. During the Quaternary, sea-level fluctuations resulted in stacked sedimentary units (2-9) consisting of debris-flow deposits, formed during sea-level fall and lowstands, and thin hemipelagic/turbidite sediments, deposited during sea-level rise and highstands.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.1
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• pp.33-42
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• 1987

Grid structures are extensively used in bridge and slab strucures. When the elements are assembled for the entire structure the number of degree of freedom may be very large and thus, the stiffness, mass, and damping matrices become of large dimension. Undoubtedly, determining natural frequencies and mode shapes of such structures are complicated and require large computer costs. For these reasons various eigenvalue economizer procedures have been developed, which serve to reduce the number of degree of freedom. This paper proposes an economic method of dynamic analysis of grid stuctures using static and dynamic condensation techniques. The accuracy and economy of this method are investigated by comparing some results of model analysis of N-degree of freedom. It has been shown that the method achieves remarkable economy at only a little cost of accuracy.

• Journal of the Korean Society of Physical Medicine
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• v.15 no.1
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• pp.95-104
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• 2020

PURPOSE: A prospective study was conducted to investigate the correlation between the inspiration ability, bone mineral density, lumbar muscle strength, and muscular endurance for the national softball athletes in the national training center. METHODS: The general characteristics of study subjects, inspiration ability, bone mineral density, muscle strength, and muscular endurance data were analyzed using descriptive statistics. In addition, the Pearson product moment correlation was performed to investigate the correlation between the inspiratory capacity, bone mineral density, muscle strength, and muscular endurance. RESULTS: The inspiration, flow rates, and volume were not correlated with the bone mass and bone mineral density. Inspiration and the flow rates and volume were not correlated with the bone mass and bone mineral density. On the other hand, inspiration was correlated with the Extensor muscles (r=.464, p=.006) at an angular velocity of 60°/s and the flexors (r=.463, p=.006) and extensor muscles (r=.615, p<.001) at an angular velocity of 180°/s. The flow rate was also correlated with the extensor muscles (r=.444, p=.009) at an angular velocity of 60°/s and with flexor muscles (r=.432, p=.011) and extensor muscles (r=.589, p<.001) at an angular velocity of 180°/s. Finally, the volume was correlated at the extensor muscles at an angular velocity of 180°/s (r=.534, p=.001). CONCLUSION: The correlation between the inspiratory capacity, bone mineral density, muscle strength, and muscular endurance of softball athletes did not correlate with the bone mass and bone density. On the other hand, the lumbar muscle strength increased with increasing inspiratory capacity.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.2
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• pp.449-454
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• 2010

In this paper, flow characteristics of R600a in an adiabatic capillary tube were investigated employing the homogeneous flow model. The model is based on fundamental equations of mass, energy and momentum which are solved simultaneously. Two friction factors(Churchill) and viscosity(McAdams) are comparatively used to investigate the flow characteristics. Thermodynamic and transport properties of R600a are calculated employing EES property code. Flow characteristics analysis of R600a in an adiabatic capillary tube is presented to offer the basic design data for the operating parameters. The operating parameters considered in this study include condensation temperature, evaporation temperature, subcooling degree and inner diameter tube of the adiabatic capillary tube. The main results were summarized as follows: condensation and evaporation temperature, inlet subcooling degree and inner diameter tube of an adiabatic capillary tube using R600a have an effect on length of an adiabatic capillary tube. The length of an adiabatic capillary tube using R600a is expressed to the correlation shown in Eq. (15).

• Polymer(Korea)
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• v.31 no.6
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• pp.479-484
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• 2007

In this study, the hybrid ion exchange fibers (HIEF) were prepared by using web spraying muthod with hot melt adhesive. Characteristics of HIEF and their adsorption properties for ammonia gas were investigated. The ion exchange capacity (IEC) of HIEF was increased with increasing the resin contents and their values were higher than those of pure resin and ion exchange fabrics. The removal efficiency for ammonia gas increased with an increase in packing density of hybrid ion exchange fabrics in the column. The adsorption breakthrough time was 270 min, which was slower than those of the resin and fibers. The maximum value of adsorption for ammonia gas was 94%. The breakthrough time was also increased with increasing the concentration and flow rate of ammonia gas. The reaction constant(k) for ammonia gas was increased with increasing the concentration and flow rate of the gas, while it was decreased an the mass was increased.

• Physical Therapy Korea
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• v.10 no.4
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• pp.43-59
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• 2003

보행 종료(gait termination)는 인간의 보행개시(gait initiation)나 율동성 보행(rhythmical walking)에 비해 관심을 적게 받고 있다. 파킨슨 환자들이 보행종료와 방향전환 시 가지는 어려움은 이들 환자들이 보행 시 넘어지게 되는 노출 요인으로 보고되어져 왔다. 보행종료에 대한 기전의 이해는 효과적으로 걸음을 멈추지 못해 넘어지게 되는 위험요인을 가진 사람들에게 적용되어질 수 있다. 이 논문에서 우리는 보행종료에 대한 최근문헌을 고찰하고 우리 실험실에서 진행되어온 파킨슨환자의 보행종료에 관한 일련의 실험들의 결과를 요약하였다. 본 연구는 율동적인 보행상태에서 완전한 멈춤으로의 전환에서 일어나는 동역학의 변화를 검사하기위해 시행되었다. 보행속도가 증가함에 따라 따르는 다리(trailing limb; 보행종료시점에서 뒤에 위치하는 다리)의 유의한 가속력 감소가 나타나고 멈출 때 이끄는 다리(leading limb; 보행종료시점에서 앞에 위치한 다리)에서 유의한 감속력의 증가가 나타난다. 보행종료 시, 이끄는 다리의 뒤쪽에 질량중심(center of mass) 을 유지시키기 위해 하지 신전근의 활성도가 오래 지속되어져야 한다. 예측하지 못한 상황에서 보행종료 시, 보행 중이나 예측되어진 상황에서 멈출 때보다 이끄는 다리 아래에서 감속력이 빠르게 발생하는 경향을 보였다. 대상자들을 보행속도에 따라 두 군으로 나눌 때, 계획되지 않은 보행종료를 하는 동안 보행속도가 느린 군이 빠른 군보다 전방 가속력을 급속하게 증가시키는 것으로 나타났다. 이러한 결과들은 보행속도가 느린 대상자들이 따르는 다리로 힘을 생성하기 보다는 주로 이끄는 다리에 의존하여 보행종료를 하는 것을 보여준다. 따르는 다리에서 발생되는 힘과 근육활성도의 조절을 측정하기 위하여, 파킨슨 환자와 연령에 의해 짝짓기된 정상 환자군에게 표적 조건(target condition)을 추가하였다. 파킨슨 환자군은 표적에 다리를 정확히 놓기 위해 몇 발자국 전부터 보행 속도를 줄였다. 파킨슨 환자들은 보행종료를 촉진하기 위해 필요한 근육들의 활성도를 증가시키는데 큰 어려움을 가지고 있다고 생각되어진다.