• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.43 no.11
• /
• pp.998-1007
• /
• 2015

The $H_{\infty}$ control theory using LMI method is applied to design an attitude controller of radial type satellite that has strongly coupled channels due to the large product of inertia. It is observed that the cross-over frequency of open-loop with $H_{\infty}$ controller is lower than that of open-loop without controller, which is not typical phenomenon in an optimal control design result: it is interpreted that due to a large product of inertia, there is certain limit in increasing agility of satellite by just tuning weighting function. ${\mu}$-analysis is performed to verify the stability and performance robustness with the assumption of +/-5% MOI variation. ${\mu}$-analysis result shows that the variation of principal MOI degrades the stability and performance robustness more than the variation of POI does.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.22 no.3
• /
• pp.54-59
• /
• 1985

From the foregoing papers, it has been clarified that the push-pull current-fed DC-DC converter is excellent in stability as compared with the other conventional DC-DC con-verters. The relation between the stability of the converter and the capacitance of smoothing condenser is analyzed, considering the ESR of smoothing condenser and the 1 st order phase lag of the feedback circuit. From the results, it is known that when the capacitance of smoothing condenser is reduced, the stability of the converter is also excellent as compared with the conventional buck type converter, whereas there are limitations for practical use, since the ripple of output voltage increases by increasing of output current.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.14 no.5
• /
• pp.547-559
• /
• 2012

The concrete structural design in domestic has based on the allowable stress design (ASD) method and ultimate strength design (USD) method. Recently limit state design (LSD) method has issued and attempted to adopt in geotechnical design. Because ASD method and USD method have restriction in economic design. In this study, the generated member forces were calculated about high strength concrete segment lining based on japanese LSD code. And it compared with domestic USD code for identifying the economic design possibility of LSD and domestic applicability. In analysis results, the aspect of moment had generated similarly each other but the member forces of japanese LSD code were decreased (26.0% of moment and 26.7% of shear force) comparing with USD method. For that reason, possibility of economic segment design with stable condition were identified.

• Tunnel and Underground Space
• /
• v.8 no.4
• /
• pp.287-295
• /
• 1998

Limit equilibrium method is widely used for the stability analysis of soil slopes. In jointed rock slopes however, the failure of the slope is largely dependent upon the strength and deformability of the joints in the rock mass and quite often failure occurs along the joints. This paper describes the use of ubiquitous joint model for the stability analysis of the jointed rock slopes. This model is essentially an anisotropic elasto-plastic model and can simulate two sets of joint in arbitrary orientations. Validation of the developed with the factor of safety equal to unity was selected when the shape of the failure plane is assumed log spiral. Then the factor of safety of the rock slope having two perpendicular joint sets was calculated while rotating joint orientations. Rusults were compared with limit equilibrium solutions on soil slopes having equivalent soil properties when plane sliding was assumed. Developed model predicted the factor of safety of jointed rock slope in a reasonable accuracy when joint spacing is sufficiently small.

• The Journal of Engineering Geology
• /
• v.22 no.4
• /
• pp.417-425
• /
• 2012

CCTV cameras are used for surveillance and purposes of security, and can also be applied for monitoring infrastructure and equipment. In the Cut Slope Management System managed by KICT (Korea Institute of Construction Technology), cut slopes are continuously monitored using a real-time system, with CCTV cameras installed at 119 sites to detect slope activity. Here we compare CCTV images with displacement at three sites and perform a quantitative analysis. Methods for improving CCTV camera management and systems are also discussed with regard to communication, obstacles, and nighttime management.

• Journal of Wetlands Research
• /
• v.13 no.3
• /
• pp.515-522
• /
• 2011

This study examined the epiphytes using stable isotopes. Separated epiphytes should represent the water quality. In study areas, where agricultural paddies were prevailing, biomass of epiphytes can increase nitrogen isotopes(${\delta}^{15}N$) and as a result decrease in carbon isotopes(${\delta}^{13}C$). Naerin stream and Inbuk upper areas showed higher nitrogen isotopes(${\delta}^{15}N$) than in Hangye and Buk stream. Also, stable carbon isotopes(${\delta}^{13}C$) in Naerin stream and Inbuk streams tended to increase than in Hangye and Buk stream. This can indicate the epiphytes can be a good indicator for water quality pollution.

• KSBB Journal
• /
• v.25 no.2
• /
• pp.130-136
• /
• 2010

Astaxanthin is an unsaturated compound with a double bond. So it is easily decayed by heat and oxidation (light) during its storage and processing of it. Nanoliposome formulation technology was utilized to improve the stability of astaxanthin. Nanoliposome preparation conditions were established and the stability of astaxanthin encapsulated nanoliposome and free astaxanthin was investigated. Thermal stability and UV-stability of astaxanthin encapsulated nanoliposome increased up to two times and tree times, respectively. Astaxanthin encapsulated nanoliposome could be used as a stable functional material for industrial purposes.

• Journal of the Korean Geotechnical Society
• /
• v.39 no.7
• /
• pp.5-15
• /
• 2023

The evaluation of passive earth pressure plays a crucial role in the design of earth-retaining structures such as retaining walls and temporary earth-retaining walls to withstand horizontal earth pressure. In the earth pressure theory, active and passive earth pressures represent the earth pressures at the limit state, where the wall displacement reaches the maximum allowed displacement. In the design of earth-retaining structures, the passive earth pressure is considered as the resisting force. In this context, the limit displacement at which passive earth pressure occurs is significantly greater than that associated with the active earth pressure. Therefore, it is irrational to apply this displacement directly to the calculation of passive earth pressure. Instead, it is necessary to consider the mobilized passive earth pressure exerted at the allowable horizontal displacement to evaluate the structural stability. This study proposes an allowable wall displacement, denoted as 0.002 H (where H represents the excavation depth), based on a literature review that focuses on sandy soils. To calculate the mobilized passive earth pressure from the wall displacement, a semi-empirical equation is proposed. By analyzing the obtained data on mobilized passive earth pressure, a reduction factor applicable to Rankine's passive earth pressure is proposed for practical application in sandy soils under different wall movement types.

• Tunnel and Underground Space
• /
• v.20 no.6
• /
• pp.475-490
• /
• 2010

The analysis of slope stability was performed from seven sites among total eleven sites of waste rock which are divided into two objects (mullock-pile and rock mass) according to the location of dumping-dropping point in L limestone Mine. The analysis of circular failure using Bishop's simplified method and the finite element method for mullock-pile slopes were adopted. For rock mass slopes, identification of failure modes on stereonet projection was determined, thereby limit equilibrium analysis was applied to obtain the safety factor of slopes and the finite element method was used to understand overall behavior of slope. Phi-c reduction method was used to calculate the safety factor of slopes through the finite element method. In mullock-pile slope of zone D and rock slopes of zone F and G, the assurance of slope stability was difficult, and the plans to assure the stability of slopes were proposed on the basis of the analysis of slopes at disposal sites of waste rock. Therefore, the method of piling with waste rock by dozer pushing after dumping for mullock-pile slope of zone D is required, and the method of piling after moving to the place which has no fault zone for rock slope of zone F and G is recommended.

• Proceedings of the Korean Information Science Society Conference
• /
• 2005.11a
• /
• pp.379-381
• /
• 2005

Ad hoc 네트워크에서 노드의 한정된 에너지 용량은 개설 경로의 수명과 안정성에 많은 영향을 미치는 요소이다. 따라서 이러한 에너지 한계를 극복하기 위한 다양한 power-aware 라우팅 프로토콜들이 네트워크 계층에서 제안되고 있으며, 이들 라우팅 프로토콜들은 기본적으로 노드의 배터리 잔량 에너지와 전송 전력량을 경로 탐색 과정에서 반영한다. 본 논문에서는 기존의 power-aware 라우팅 프로토콜보다 개설 경로의 동작시간을 높이고 전체 네트워크의 부하균등을 이를 수 있도록 하는 새로운 라우팅 프로토콜을 제안하며 TPR(Traffic load based power-aware routing protocol)로 명명한다. TPR은 NS-2를 이용한 성능 평가를 통해 전체 네트워크의 부하 균등과 개설 경로의 수면, 안정성 측면에서의 개선점을 확인한다.