• Journal of the Korean Institute of Gas
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• v.12 no.3
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• pp.50-55
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• 2008

The flash points for the systems, ethlybenzene+n-butanol and ethlybenzene+n-hexanol, were measured by using Tag open-cup tester (ASTM D1310-86). These binary mixtures exhibited MFPB (minimum flash point behavior), which leads to the minimum on the flash point vs composition curve. The experimental data were compared with the values calculated by the Raoult's law, the UNIQUAC equation and the NRTL equation. The calculated values based on the UNIQUAC and NRTL equations were found to be better than those based on the Raoult's law. It was concluded that the UNIQUAC and NRTL equations were more effective than the Raoult' law at describing the activity coefficients for nonideal solution such as the ethlybenzene+n-butanol and ethlybenzene+n-hexanol systems. And the predictive curve of the flash point prediction model based on the NRTL equation described the experimentally-derived data more effectively than was the case when the prediction model was based upon the UNIQUAC equation.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.8
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• pp.1167-1177
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• 1989

In this paper, a generalized adaptive law is proposed which uses a rational function type operator for parameter adjustment. To satisfy the passivity condition of the adaptation block, we introduce a constant feedback gain into the adaptation block. This adaptation scheme is applied to the model reference adaptive control of a continuous-time, linear time-invariant, minimum-phase system whose relative degree is 1. We prove the asymptotic stability of the output error of this adaptive system by hyperstability method. It is shown that by digital computer simulations this law can give a better output error transient response in some cases than the conventional gradient adaptive law. And the output error responses for the several types of the proposed adaptation law are examined in the presence of a kind of unmodeled dynamics.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.12
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• pp.1302-1312
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• 2008

Relaxed Static Stability(RSS) has been applied to improve flight performance of modern version supersonic jet fighters. Flight control systems are necessary to stabilize an unstable aircraft and to provide adequate handling qualities. Also, flight control systems of modern aircraft employ many safety measure to cope with emergency situations such as a pilot unknown attitude flight conditions of an aircraft in night flight-testing. This situation is dangerous because the aircraft can lose if the pilot not take recognizance of situation. The system called the "Pilot Activated Recovery System" or PARS, provided a pilot initiated automatic maneuver capable of an aircraft recoveries in situations of unusual attitudes, speed and altitude. This paper addresses the concept of PARS with AARS(Automatic Attitude Recovery System), ATCS(Automatic Thrust Control System) and MARES(Minimum Altitude Recovery Estimation System), and this control law is designed by nonlinear control law design process based on model of supersonic jet trainer. And, this control law is verified by real-time pilot evaluation using an HQS(Handling Quality Simulator). The result of evaluation reveals that the these systems support recovery of an aircraft unusual attitude and speed, and improve a safety of an aircraft.

• The Korean Journal of Air & Space Law and Policy
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• v.22 no.2
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• pp.85-108
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• 2007

동북아시아지역에서 인천국제공항이 최고의 허브공항으로서 역할을 위해서는 무엇보다도 환승율에 대한 연구가 필요하다고 판단된다. 인천국제공항은 2005년도에 3,054,485만명의 환승여객을 처리하여 환승율은 11.9% 를 기록하였는데 이는 동북아시아의 경쟁허브공항의 환승율인 30-40%와 비교해보면 공항경쟁력이 상당히 뒤쳐진다고 할 수 있다. 이러한 약점을 보완하기 위하여 여러 가지 관련 인자들을 검토하는 것이 중요하다고 판단되어지는데 그중에서 인천국제공항의 비행편최소연결시간(MCT)을 개선하는 것이 필요하다. 이러한 문제를 개선하기 위해서는 항공기 스케줄, 항공사 배치, 게이트 배정방법, 수하물처리, 여객 동선 등이 함께 검토되어야 할 것이다. 그러나 이러한 인자들에 대한 세부적인 분석이 단기간에 걸쳐 해결되는 문제가 아니기 때문에 본 연구에서는 외국 허브공항의 MCT 수준, 관리방법, 국외사례 등을 고찰해 보고 동북아시아에서 허브공항을 향한 인천국제공항의 환승율 제고차원에서 정책적 방안을 제시하고자 한다.

• Fire Science and Engineering
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• v.22 no.4
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• pp.65-69
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• 2008

An accurate knowledge of the flash point is important in developing appropriate preventive and control measures in industrial fire protection. The lower flash points for the n-propanol+formic acid system were measured by Pensky-Martens closed cup apparatus. This binary mixture exhibited MFPB (minimum flash point behavior), which leads to the minimum on the flash point vs composition curve. The Raoult's law and optimization method using Wilson equation were used to predict the lower flash points and were compared with experimental data. The calculated values based on the optimization method were found to be better than those based on the Raoult's law.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.6
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• pp.485-493
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• 1990

Timing recovery for recently proposed nonlinear minimum-bandwidth systems is of concern since most conventional methods fail for these systems. As a method to surmount this retiming difficulty, this paper proposes the fourth-power-law method. The feasibility of the proposed method for minimum-bandwidth systems is shown through a rigorous analysis. Furthermore, extensive computer simulations are used to determine the best configurational strategy for various filters around the fourth-power nonlinear process. It is found that no intermediate filtering is necessary in general and even the pre-filtering can be omitted for systems having symmetric power spectral densities.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.52 no.4
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• pp.189-197
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• 2003

The problem of designing a parallel feedforward compensator (PFC) is considered for a class of non-square linear systems such that the closed-loop system is strictly passive. If a given square system has (vector) relative degree one and is weakly minimum phase, the system can be rendered passive by a state feedback. However, when the system states are not always measurable and the given output is considered, passivation (i.e. rendering passive) of a non-minimum phase system or a system with high relative degree cannot be achieved by any other methodologies except by using a PFC. To passivate a non-square system we first determine a squaring gain matrix and design a PFC such that the composite system has relative degree one and is minimum phase. Then the system is rendered strictly passvie by a static output feedback law. Necessary and sufficient conditions for the existence of the PFC and the squaring gain matrix are given by the static output feedback formulation, which enables to utilize linear matrix inequality (LMI). As an application of the scheme, an alternative way of replacing the role of velocity measurements is provided for the PD-control law of a convey-crane system.

• Geomechanics and Engineering
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• v.7 no.3
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• pp.233-246
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• 2014

Estimation of fracture initiation pressure is one of the most difficult technical challenges in hydraulic fracturing treatment of vertical or horizontal oil wells. In this study, the influence of in-situ stresses and pore pressure values on fracture initiation pressure and its profile in vertical and horizontal oil wells in a normal stress regime have been investigated. Cohesive elements with traction-separation law (XFEM-based cohesive law) are used for simulating the fracturing process in a fluid-solid coupling finite element model. The maximum nominal stress criterion is selected for initiation of damage in the cohesive elements. The stress intensity factors are verified for both XFEM-based cohesive law and analytical solution to show the validation of the cohesive law in fracture modeling where the compared results are in a very good agreement with less than 1% error. The results showed that, generally by increasing the difference between the maximum and minimum horizontal stress, the fracture pressure and its profile has been strongly changed in the vertical wells. Also, it's been clearly observed that in a horizontal well drilled in the direction of minimum horizontal stress, the values of fracture pressure have been significantly affected by the difference between overburden pressure and maximum horizontal stress. Additionally, increasing pore pressure from under-pressure regime to over-pressure state has made a considerable fall on fracture pressure in both vertical and horizontal oil wells.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.12
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• pp.1256-1263
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• 2004

Output feedback passivation problem is studied when the given system is not minimum-phase or does not have relative degree one. Using a parallel connection with an additional dynamics, the authors provide a dynamic output feedback control law which renders the composite system passive. Sufficient conditions are presented under which the composite system is output feedback passive. As an application of the dynamic passivation scheme, a point-to-point control law for a flexible joint robot is presented when only the position measurements are available. This provides an alternative way of replacing the role of the velocity measurements for the proportional-derivative (PD) feedback law. The performance of the proposed control law is illustrated in the simulation studies of a manipulator with three revolute elastic joints.

• The Korean Society of Law and Medicine
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• v.14 no.1
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• pp.275-302
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• 2013

The Unites States has been plagued with soaring health care costs and an alarmingly large number of uninsured population. The Patient Protection and Affordable Care Act of 2010 ushered in the most sweeping health care reform in the United States since the introduction of Medicare and Medicaid in 1965 to address these issues. The law's requirement for individuals to purchase health insurance (the so-called "individual mandate"), however, not only caused a political stir but also prompted constitutional challenges. Some questioned whether the federal government, lacking general police power, could require its citizens to buy unwanted insurance based on its enumerated powers under the U.S. Constitution. This paper summarizes the decision of the U.S. Supreme Court on the constitutionality of individual mandate, and explores how the decision relates to Korea's own universal health care.