• 콘크리트학회지
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• 제8권3호
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• pp.209-218
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• 1996

프리캐스트 프리스트레스트 콘크리트 구조물의 정착부에 프리스트레스트 힘이 도입되면, 과다한 국부 집중 하중으로 인하여 균열이 발생할 수 있으며, 최근 이러한 구조물 건설시 텐던을 따라가며 심각한 균열이 발생한 경우가 있다. 본 논문은 프리캐스트 프리스트레스트 콘크리트 구조물의 정착부에 발생하는 국부집중응력의 분포 특성을 규명하고, 정착부 보강 형태에 따른 국부응력 효과를 규명하여 합리적인 정착부 설계 개념을 제시함에 목적이 있다. 이를 위하여 정착부 형태에 따른 역학적 거동 실험 및 해석연구가 수행되었다. 위의 연구 결과 나선형 보강철근이 극한 및 균열하중에 대한 저항능력이 가장 우수함이 집중응력 분포 특성을 고찰함으로서 나타났으며, 정착부의 파괴기구, 정착부 보강설계를 위한 기본 개념 및 그 방법이 제시되었다.

• 대한기계학회논문집A
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• 제25권11호
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• pp.1863-1872
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• 2001

In this Paper, we suggest the precision stage using a novel non-contact planar actuator that utilizes an interaction between an array type of air-core solenoids and permanent magnets. The former with axes arranged in the mutually orthogonal direction is fixed on the stator and the latter with the same polar direction is attached below the stage. The promising magnetic structure has little uncertainty such as hysteresis loss caused by ferromagnetic material, then it is simple to quantify the magnetic phenomenon. And all the magnetic forces are transmitted through narrow air-gap between the coil and the permanent magnet, therefore the structure can be highly compacted. Furthermore, the stage or plate can be perfectly isolated from the stator without any wire connection, leading to diminish the generating possibility of wear particles due to mechanical contact. Then. it is estimated that the proposed operating principle is very suitable for work requiring high accuracy and cleanness. or general-purpose nano stage. The main issues rebated to the plate driving are discussed here.

• 한국전산유체공학회지
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• 제2권1호
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• pp.46-53
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• 1997

The flow field around a three dimensional minivan-like body has been simulated. This study solves 3-D unsteady incompressible Navier-Stokes equations on a non-orthogonal curvilinear coordinate system using second-order accurate schemes for the time derivatives, and third/second-order scheme for the spatial derivatives. The Marker-and-Cell concept is applied to efficiently solve continuity equation. A H-H type of multi-block grid system is generated around a three dimensional minivan-like body. Turbulent flows have been modeled by the Baldwin-Lomax turbulent model. To validate present procedure, the flows around the Ahmed body with 12.5° of slant angle are simulated. A good agreement with other numerical results is achived. After code validation, the flows around a mimivan-like body are simulated. The simulation shows three dimensional vortex-pair just behind body. The flow separation is also observed on the rear of the body. It has concluded that the results of present study properly agreed with physical flow phenomena.

• 한국의류학회지
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• 제34권12호
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• pp.2062-2072
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• 2010

This research evaluates the change of the water absorbency and drying speed of a quick-drying knit fabric by repeated laundering and laundering conditions and investigates the influence of laundering conditions on the functional properties of the knit fabric. Four factors of laundering conditions were studied: detergent, water hardness, water temperature, and frequency of rotation. Knit fabrics were washed for 25 laundering cycles in a drum-type washing machine with nine different laundering conditions derived from an orthogonal array. The properties of knit fabrics were measured with a drop absorption test, a strip test, and a drying time test. Relaxation shrinkage pointed to a change in the structural characteristics of the knit fabric. Wetting time was faster and wickability was greater in the knit fabrics that underwent 5 laundering cycles; in addition, there were no obvious changes in wetting time and wickability. The detergent was the most important factor in wetting time (40.4%) and wickability (60% or above). Water hardness, water temperature and RPM had less of an effect on wetting time and wickability. There were no significant differences between the levels of laundering conditions (except for detergent) on wetting time and wickability. Drying times with neutral and alkali were slower by repeated laundering; however, there was no obvious change in drying time. Hardness, water temperature and RPM had less of an impact on drying time.

• 품질경영학회지
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• 제39권4호
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• pp.507-515
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• 2011

MIL-HDBK-217 has played a pivotal role in reliability prediction of electronic equipments for more than 30 years. Recently, RIAC developed a new methodology $217Plus^{TM}$which officially replaces MIL-HDBK-217. Sensitivity analysis of the 217Plus component models to various parameters has been performed and meaningful observations have been drawn in this study. We first briefly reviewed the $217Plus^{TM}$ methodolog and compared it with the conventional model, MIL-HDBK-217. We then performed sensitivity analysis $217Plus^{TM}$ component models to various parameters. Based on the six parameters and an orthogonal array selected, we have performed indepth analyses concerning parameter effects on the model. Our result indicates that, among various parameters, operating temperature and temperature rise during operation have the most significant impacts on the life of a component, and thus a design robust to high temperature is the most importantly required. Next, year of manufacture, duty cycle, and voltage stress are weaker but may be significant when they are in heavy load conditions. Although our study is restricted to a specific type of diodes, the results are still valid to other cases. The results in this study not only figure out the behavior of the predicted failure rate as a function of parameters but provide meaningful guidelines for practical applications.

• Journal of Plant Biotechnology
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• 제36권3호
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• pp.236-243
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• 2009

The halophyte Leymus chinensis (Trin.) is a perennial rhizome grass (tribe Gramineae) that is widely distributed throughout China, Mongolia and Siberia. This study was conducted to investigate an optimal condition for plant regeneration from mature seeds, leaf base segments, and root segments in L. chinensis. Plant growth regulators affecting embryogenic callus induction and plant regeneration were investigated by four-factor-three-level [L9 (34)] orthogonal test in this study. The effects of explants types (mature seeds, leaf base segments and root segments), callus types, medium types were examined in this study. Wild type (WT) and Jisheng No. 1 plants (JS) were used for primary callus induction. A clear explants difference was seen during callus induction; mature seeds were considered as the preferred explants; and the highest frequency of callus induction was obtained in Medium 6 using mature seeds as explants in WT. Plant regeneration ability was evaluated by frequencies of green callus forming, shooting, rooting, and shooting with roots. Effect of α-naphthalene acetic acid (NAA) on shoot regeneration was remarkable with the highest frequency of 70.8% in WT after 2-month culture. The medium with 0.2- 0.5 mg/L NAA was found to have the highest shoot induction. All regenerated shoots were successfully rooted when transferred on half-strength Murashige and Skoog (MS) basal medium. The acclimatized plantlets were grown to mature with flowering and seeds setting in green house conditions.

• 한국소음진동공학회논문집
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• 제20권11호
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• pp.995-1000
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• 2010

With the development of the auto industry, the automobile manufacturers demand to shorten development period and reduce the cost. Compared with the traditional method, applying the virtual prototype is more economical. This paper presents a method for parameters sensitivity analysis and optimizing the performance of vehicle noise and vibration. The existing design processes were repeatedly analyzed with a focus on vehicle performance to decide the design parameters of dimension, thickness, mounting type of body and chassis systems in the vehicle development period. This paper describes the prediction technique of vehicle performance using L18 orthogonal array layout, quality deviation analysis and parameter sensitivity analysis for robust design. This paper analyzed the performance correlation equation through the frequency and sensitivity database according to a design factor change. The new concept is that the performance prediction is possible without repeated activities of test and analysis. This paper described the parameter analysis applications such as bush dynamic stiffness and bush void direction of rear suspension. Design engineer could efficiently decide the design variable using parameter analysis database in early design stage. These improvements can reduce man hour and test development period as well as to achieve stable NVH performance.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.177-178
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• 2014

This work proposes a two-dimensional (2-D) laser scanning mirror actuator with a simple structure composed of one magnet and four coils. The mirror-actuating device generates 2-D scanning motions about two orthogonal axes by combining electromagnetic actuators of the conventional moving-magnet types. The magnet is attached to back side of the mirror placed inside of the moving frame. The four coils is placed on the base frame in a cross shape. We implement a finite element analysis to calculate magnetic flux in the electromagnetic system with the overall size of $20mm(W){\times}20mm(D){\times}13mm(H)$ for the mirror size of $8mm{\times}8mm$. The each moving-magnet type electromagnetic actuator has the motor constant 3.41 mNm/A and the restoring constant 1.75 mNm/rad and the resonance frequency of 58 Hz and the bandwidth of 80 Hz. The proposed compact and simple 2-D scanning mirror predicted advantages of large 2-D angular deflections, wide frequency bandwidth and low manufacturing cost.

• Applied Microscopy
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• 제27권4호
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• pp.483-488
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• 1997

A misfit dislocation generation in InAs epilayers grown on (001) InP substrates (oriented $2^{\circ}$ off (001) toward the [110] direction) using metalorganic chemical-vapor deposition was studied. The InAs film of 17 nm thickness grown at $405^{\circ}C$ showed the three different arrays of dislocations: a straight orthogonal array to the <110> direction, an array to the >100> direction, and an array tilted by a degree of $5\sim45^{\circ}$ from the [110] direction. All of the dislocations had a/2<101> Burgers vectors inclined $45^{\circ}$ to the interface. Upon annealing at $660^{\circ}C$ the InAs films with 60, 140 and 220 nm thicknesses, most of the misfit dislocations became the Lomer type $(\sim100%)$ oriented exactly along the >110> direction. These misfit dislocation spacings were decreased with increasing the InAs thickness up to 220 nm thickness. This phenomena was interpreted by the relationship between the dislocation interaction energy among parallel misfit dislocations and the opposite remnant InAs epilayer strain energy. The distance between misfit dislocations was measured by transmission electron microscopy.

• 한국자동차공학회논문집
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• 제17권1호
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• pp.176-181
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• 2009

The passenger airbag(PAB) designed for standard sized adults may induce unexpected results to children in out-of-position(OOP) postures. In this work, using MADYMO software, simulations of the OOP injury of children have been performed with respect to PAB design parameters and child dummy positions. The attention is focused on some details with respect to the injury of 3 and 6 year old children in two OOP postures. Among the various design parameters of the passenger airbag systems, four parameters are selected for the sensitivity analysis of the injury with the Taguchi method: bag folding pattern, vent hole size, position of the cover tear seam and the type of door tear seam. An optimal combination of the parameters is suggested.