• International Journal of Highway Engineering
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• v.8 no.1 s.27
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• pp.77-87
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• 2006

Dynamic stability (DS) in the wheel tracking (WT) test is used as a basic index of rut-resistance for asphalt mixtures. In general, the deeper rut depth is obtained from the weaker mixture, resulting in the lower DS value. On the other hand, the shallower rut depth is obtained from the stronger mixture, resulting in the higher DS. However, it is not always the case when the DS is calculated by the existing method because the DS is simply determined based on the slope at the final stage of the rut depth-cycle curve. Specifically, in the case of the depth-cycle curve showing a steeper slope in the early part but flatter slope in last part, the DS is calculated to be higher than the curve showing a ever-increasing slope throughout the test. As long as the last part of slope is flatter, the deeper final rut depth is evaluated to show a higher DS than the little final rut depth. Therefore, a reasonable method for DS evaluation need to be established. Several new methods were suggested by considering the early, middle and final parts of rut depth to determine a reasonable DS. The results have shown that those new methods have demonstrated a significant improvement in distinguishing similarly performing mixtures. The result also showed that $DS_2$ had better correlation with SD than any other methods , representing the rutting resistance of asphalt mixture very well. The new DS calculation method is relatively simple and easy to follow. More validatin study is required for practical application.

• Journal of the Korean Geotechnical Society
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• v.18 no.2
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• pp.123-136
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• 2002

The infiltration of prolonged rainfall causes shallow slope failures on surficial slopes. Experiments performed on soil-water characteristic curves in weathered soils of three different types(SW, SP, SM) were used to construct a general equation for the soil-water characteristic curve. Based on this, the saturated depth by Green & Ampt model was compared with the results of numerical analyses and the range of application of Green & Ampt model was evaluated. It was found that the saturated depth occurred by infiltration on the surface of slopes has an inf1uence on the surficial stability of slopes md, the stability analysis of unsaturated soils calculated by using the soil-water characteristic curve of weathered soils was found to be a proper analysis for shallow slope failures due to rainfall.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.1
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• pp.96-104
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• 1989

The behaviors of acoustic emission emitted in the tests of the fracture toughness and fracture stability are observed by using the specimens of aluminum 2024-T351 and 7039-T6 alloys. The empirical eqution of J-R curve is derived. It is demonstrated from the comparison of the fracture toughness obtained from J-R curve with that from ASTM standard E813-81 that the latter is larger than the former. The discontinuous point in the log-log graph of J-integral vs. total acoustic emission count is observed in between the two offset lines referred from ASTM standard E813-81, but it's physical meaning is uncretain. An empirical material tearing modulus is derived in terms of the total acoustic emission count and proved to be valid in fracture instability test.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1124-1125
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• 2007

클린룸의 규모가 커짐에 따라 물류 이송 장비의 사이즈가 커지고 길이가 장거리화 되고 있다. 이에 이송대차(Vehicle)의 수가 증가하는 추세이다. 같은 클린룸 공간에서 물류 이송 시스템의 공간 활용 밀도를 높이면 생산수율을 높일 수 있다. 따라서 OHS(Over Head Shuttle) 시스템은 여러 대의 이송대차간 독립제어가 가능하고, 물류 이송 장비의 구조가 직선구간과 곡선구간이 혼용되어진 구조를 가지며, OHS 시스템의 이송대차에 전원을 안정적으로 공급하기 위한 비접촉 전원장치에 관한 연구가 활발히 이루어지고 있다. 따라서 본 논문은 직선구간과 곡선구간에서 비접촉 전원장치를 안정적인 전원을 공급하기 위한 방법을 제시하고, 기존 방법과 비교 검토하기 위해 시작품을 제작하여 이동대차 2대를 대상으로 실험을 행하여 검증하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6C
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• pp.249-257
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• 2012

The reinforced earth method is financially viable. Furthermore, it overcomes environmental limitations and is therefore employed in retaining walls, slopes, foundations, roads, embankments, and other structures. However, in some cases, reinforced retaining walls are not strong enough in the curved sections and can collapse. Such mishaps are believed to occur because of an unsatisfactory analysis of the curved sections of a reinforced retaining wall. Accordingly, with the aim of investigating the workability and structural safety of curved sections of various types, this study investigates the differences in the estimated horizontal displacements of curved sections of various types and subsequently uses this information to study and analyze preliminary data so that appropriate measures can be taken to resolve alignment issues. The results of an experiment reveal that when a load is applied to curved sections of both concave and convex types, the largest horizontal displacement occurs at the center of the section. In the concave form, the earth pressure force is directed inward, whereas in the convex form, this force is directed outward. As a result, the horizontal displacement in convex forms is larger than that in concave forms. Convex reinforced earth structures are subjected to earth pressures as well as lateral earth pressure, therefore horizontal displacements in convex curved sections is larger than that of concave curved sections.

• Journal of the Korean Society for Railway
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• v.13 no.3
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• pp.309-316
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• 2010

When the horizontal and vertical curves are superimposed in railway alignments, which affects the running stability, ride comfort, and track maintenance costs. However, when designing new lines or realigning existing ones, there are many cases of superimposition caused by the existing fixed points (bridge, tunnel, turnout, and catenary system, etc) on the conventional lines and undesirable impacts on the environment, etc. In this study, when the horizontal and vertical curves are superimposed, in order to optimize the horizontal curve in aspect of the ride comfort, the object function was developed and verified by vehicle dynamic analysis. Also, the solution algorithm for simplified evaluation method was presented.

• International Journal of Highway Engineering
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• v.10 no.2
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• pp.135-143
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• 2008

According to the present highway design criteria, there are minimum standards which re ade from special design speeds. If some highways are satisfied the standards, it regards he highway as safety. In reality, however, most drivers drive a car at different speed compared with design speed. It is very dangerous for drivers especially at transition sections between curve and horizontal curve sections. Hence, this study calculated the rate of changing and horizontal acceleration at each section. Moreover, this study evaluated thesafety of design at curve transition sections and then calculated lateral acceleration and curve radii. This study found the minimum standards which are using as basic safety standards are not appropriate for measuring driver's safety.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.600-601
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• 2011

국가 경제활동에서의 에너지 역할이 점차 증대함에 따라 이를 안정적으로 확보하는 것이 중요한 과제로 부각되고 있다. 에너지원의 대부분을 수입하고 있는 우리나라의 경우 안정적이고도 저가의 에너지원을 확보하는 것은 매우 중요한 문제이다. 전력측면에서의 이와 같은 문제는 적정전원 구성문제로 귀결된다. 이에 대한 개념적 해법으로는 심사곡선법이 주로 사용되고 있으며, 실질적으로는 발전설비의 건설 및 운전기간을 고려한 동태적 최적화기법이 사용되고 있다. 본 논문에서는 투자자산의 포트폴리오 기법에 의한 적정전원 구성을 도출하고 심사곡선법에 의한 결과와 비교하였다.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.948-954
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• 2004

This study deals with the Evaluation of track system, when Newly developed Korea High Speed Train(KHST) by KRRI and KTX trains are running pass curved track of conventional line. In order to evaluate stability of track and vehicle running safety. the effect of curve radius, the field tests were performed at sharply curved track.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.245-245
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• 2011

$BiFeO_3$ (BFO)박막에 전위금속 Pb와 Co를 각각 치환환 박막을 chemical solution deposition 방법으로 Pt/Ti/SiO2/Si(100) 기판위에 증착하였다. Bi 자리에 Pb와 Co를 20 at.% 치환하였으며, 치환된 $Bi_{0.8}Pb_{0.2}FeO_3$ (BPFO), $Bi_{0.8}Co_{0.2}FeO_3$ (BCFO) 박막의 구조적, 자기적 특성 변화를 BFO 박막과 비교하여 조사하였다. XRD 패턴을 분석한 결과 BPFO, BCFO 박막들은 모두 rhombohedrally distorted perovskite 구조였으며 불순물인 pyrochlore 상이 약하게 관측되었다. 치환이 이루어진 BPFO, BCFO 박막들의 자기 이력곡선은 안정된 포화곡선을 나타냈으며 BFO의 포화값(5 emu/$cm^3$)에 비해 크게 증가된 55 emu/$cm^3$, 35 emu/$cm^3$의 값을 나타냈다. 또한 보자력장(coercive field, Hc)값도 BFO의 500 Oe보다 크게 증가된 1,200 Oe, 800 Oe의 값을 보였다.