• Journal of applied mathematics & informatics
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• 제23권1_2호
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• pp.345-352
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• 2007

In this paper, cone-valued Lyapunov functions are employed to study the impulsive control system with variable times. The stability criteria on the non-zero solution of the impulsive control system are given by the cone-valued Lyapunov functions and the results of the controllability on the control system are also obtained.

• 한국농공학회지
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• 제45권3호
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• pp.65-72
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• 2003

The objective of this study is to evaluate the stability of the design criteria recommended by Betram and Terzaghi as compared with the experimental result. A series of NEF tests was conducted to determine the loss of volume in base soils. The three kinds of base soils classified as CL, SC and SM are used for the NEF tests with various hydraulic pressures and filters following upper and lower bond of the criteria. Volume loss characteristics of the base soils was examined closely by the results of the test successfully. Firstly, it was found that the loss of base soils was mostly eroded at the first stage of seepage. Secondly, the amount of loss volume was ranked CL > SM > SC in order of their amounts for upper criteria, and SM > CL > SC orderly for lower criteria. Thirdly, the volume loss of all soils was increased with increasing the hydraulic pressures. And lastly, the needs of the new design criteria was proved for the control of seepage and piping.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 봄 학술발표회 논문집
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• pp.681-688
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• 2003

Rock damage induced by blasting can not be avoided during tunnel construction and may affect tunnel stability. But the mutual interaction between tunnel blasting design and tunnel stability design is generally not considered. Therefore this study propose a methodology to take into considration the results of the blasting damage in tunnel stability design. Rock damage is evaluated by dynamic numerical analysis for the most common blasting pattern adopted in road tunnel. Damage zone is determined by using the continuum damage model which is expressed as a function of volumetric strain. And the damage effect is taken into account by the damaged rock stiffness and the damaged failure criteria in tunnel stability assessment. The extend of plastic zone and deformation increase compared to the case of not considering blast-induced rock damage.

• Structural Engineering and Mechanics
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• 제4권4호
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• pp.365-381
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• 1996

Stability equations that evaluate the elastic critical axial load of columns in any type of construction with sidesway uninhibited, partially inhibited, and totally inhibited are derived in a classical manner. These equations can be applied to the stability of frames (unbraced, partially braced, and totally braced) with rigid, semirigid, and simple connections. The complete column classification and the corresponding three stability equations overcome the limitations and paradoxes of the well known alignment charts for braced and unbraced columns and frames. Simple criteria are presented that define the concept of partially braced columns and frames, as well as the minimum lateral bracing required by columns and frames to achieve non-sway buckling mode. Various examples are presented in detail that demonstrate the effectiveness and accuracy of the complete set of stability equations.

• 수산해양기술연구
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• 제52권2호
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• pp.79-87
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• 2016

Mobile fish-cage was developed assuming a cage net with an enclosed area, which and estimated the hydrodynamic characteristics of the cage through the model experiment. Flux-shielding plates, installed in the bow were compared with the resistance test carried out by making a hole, bilge keel and stud, and basic block flow rate consisting of the results to a flat surface plate. The experimental results confirmed the improved resistance performance effect of 3~6% in the bilge keel and the stud form. To assess the stability of the fish-cage, evaluation of the stability in accordance with the stability criteria for determining the floating docks had confirmed that it satisfied the static stability performance under operating conditions at sea.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.549-556
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• 2002

Geotextile tubes hydraulically or mechanically filled with dredged materials have been applied in hydraulic and coastal engineering in recent years(shore protection structure, detached breakwater, groins and jetty). It can also be used to isolate contaminated material from harbor, detention basin dredging, and to use this unit as dikes for reclamation work. Recently, new preliminary design criteria supported by model and prototype tests, and some stability analysis calculations have been studied. The stability analysis of geotextile tube is composed geotechnical and hydrodynamic analysis. The stability check points are sliding failure, overturning, bearing capacity failure against the wave attack. In this paper presented the construction procedure and in-situ measurement(properties of filling material, effective height variation, stress variation at geotextile tube bottom) of geotextile tube at Young-Jin Bay and stability analysis by theoretical method and hydraulic model tests

• 조명전기설비학회논문지
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• 제24권10호
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• pp.21-25
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• 2010

This paper explains hybrid method that combines Time domain simulation technique with the direct method of Transient stability analysis. First, it calculate trajectory of real system by Time domain Simulation using OOP(Object Oriented Programming method) and evaluate Transient Energy Function to induce stability index to calculate Transient stability margin. Once the status of system(stable or unstable) has been identified, proper criteria are proposed to stop time-domain simulation to reduce CPU time.

• 한국지반공학회논문집
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• 제19권4호
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• pp.167-178
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• 2003

발파설계가 터널 굴착 시 암반손상 및 여굴에 미치는 영향을 분석하고 암반손상 및 여굴이 터널 안정성에 미치는 영향을 분석함으로서 발파설계가 터널 지보설계에 미치는 영향을 연구하였다. 도로터널의 일반적인 발파패턴에 대해 동적발파 수치해석을 시행하고 연속체 손상역학(continuum damage mechanics)의 손상변수(damage variable)를 이용하여 여굴과 암반손상 정도를 분석함으로서 터널 굴착면 주위의 암반손상 정도와 영역을 구분하였다. 또한 발파하중 같은 동적하중이 암반내를 전파할 때 변화하는 암반의 동적파괴기준에 대한 연구를 수행하였다. 발파 암반손상 영향을 터널 안정성 해석에 반영하기 위하여 손상된 암반강성과 파괴기준을 적용하였다. 손상된 암반강성은 손상역학의 강도감소 모델을 이용하여 감소시켰다. 손상된 암반의 파괴기준은 암반강성과 지질강도지수의 관계식에서 도출한 손상된 지질강도지수(GSI$GSI_d$)를 적용함으로서 산출한 수정 Hoek-Brown 파괴기준을 적용하였다. 암반손상을 고려하여 터널안정성을 해석한 결과, 암반손상을 고려하지 않는 경우와 비교하여 소성영역 범위가 확대되고 변위량이 증가하였다. 이는 발파암반손상을 고려하지 않고 터널설계를 하는 경우 단기적 혹은 장기적으로 터널안정성이 위협받을 수 있음을 나타내었다.

• 한국산학기술학회논문지
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• 제14권5호
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• pp.2207-2214
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• 2013

본 연구는 지역 간 고용격차를 파악하고, 고용경쟁력 평가지표를 통해 지역현황 및 특성을 분석하기 위한 연구이다. 첫째, 지역 간 고용격차는 심화되고 있는 것으로 나타났으며, 질적 측면과 안정성 측면에서의 격차가 더욱 심각한 것으로 나타났다. 둘째, 지역별 고용경쟁력은 충남, 서울, 울산, 경북, 대전 등의 순으로 나타났으며, 부산은 고용위험 지역으로 분류되었다. 셋째, 고용경쟁력에 가장 많은 영향을 미치는 요인은 안정성 측면의 지표들인 것으로 분석되었다. 따라서 지역 간 고용격차를 완화하고 고용경쟁력을 강화하기 위해서는 양질의 안정적인 일자리를 창출하기 위한 노력이 필요하며, 특히 고용위험 지역의 경우에는 지속적인 모니터링이 요구된다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 추계학술대회 논문집
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• pp.301-304
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• 2001

Hot-compression tests were carried out to investigate the hot workability of Ti64 and Ti6246 alloys at different temperatures and strain rates. Processing maps were developed on the basis of the dynamic material model unifying the relationship among constitutive behavior, hot workability and microstructure development. Stable regions, defined on the basis of four stability criteria 0${\delta}log(m)/\frac{\bot}{\varepsilon})<0$, s<1 and ${\delta}log(s)/\frac{\bot}{\varepsilon})<0$, were found to be associated with dynamic recovery and recrystallization.