• Tribology and Lubricants
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• 제14권2호
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• pp.35-41
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• 1998

The $WS_2$ solid lubricant synthesized through the vapour phase transport method was coated on the commercial bearing steel (SUJ 2) substrate, and the tribological behaviour of the lubricant was investigated using a ball-on-disk type tester. The $WS_2$ powder was spray-coated at room temperature using compressed air, and the change of friction coefficient was examined in various conditions, i.e., specimen configuration, atmosphere (air and nitrogen), applied load and rotating speed. $WS_2$ coated ball and disk showed the optimum friction coefficient of 0.07 and wear life of 45,000 cycles in the nitrogen atmosphere under 0.3 kgf and 100 rpm, whereas relatively high coefficient of 0.13 and reduced wear life of 4,000 cycles were observed in air atmosphere. The effect of rotating speed on the friction coefficient was not observed both in nitrogen and in air atmospheres. This confirmed that the spray-coated $WS_2$ solid lubricant was effective in reducing the friction coefficient and improving wear life in nitrogen atmosphere, and the oxygen and moisture existing in air could seriously deteriorate the lubrication effect of $WS_2$ coating layer.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 Proceedings of the Korea Automatic Control Conference, 11th (KACC); Pohang, Korea; 24-26 Oct. 1996
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• pp.324-327
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• 1996

This paper describes the robust controller design methods applied to the problem of an automatic system for tow-vehicle/trailer combinations. This study followed an inverse Linear Quadratic Regulator(LQR) approach which combines pole assignment methods with conventional LOR methods. It overcomes two concerns associated with these separate methods. It overcomes the robustness problems associated with pole placement methods and trial and error required in the application of the LQR problem. Moreover, a Kalman filter is used as the observer, but is modified by using the loop transfer recovery (LTR) technique with modified transmission zero assignment. The proposed inverse LQG,/LTR controllers enhances the forward motion stability and maneuverability of the combination vehicles. At high speeds, where the inherent yaw damping of the vehicle system decreases, the controller operates to maintain an adequate level of yaw damping. At backward moton, both 4WS (2WS tow-vehicle, 2WS trailer) and 6WS (4WS tow-vehicle, 2WS trailer) control laws are proposed by using inverse LQG/LTR method. To evaluate the stability and robustness of the proposed controllers, simulations for both forward and backward motion were conducted using a detailed nonlinear model. The proposed controllers are significantly more robust than the previous controllers and continues to operate effectively in spite of parameter perturbations that would cause previous controllers to enters limit cycles or to loose stability.

• Tribology and Lubricants
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• 제13권4호
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• pp.60-65
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• 1997

The tungsten disulfide $(WS_2)$ solid lubricant was synthesized by two different reaction processes, i.e., the reaction between $CS_2$ gas phase and solid $WO_3$powder, and the vapour phase transport method of tungsten and sulfur in a high vacuum. The chemical and physical characteristics of synthesized $WS_2$powder were analyzed in terms of the average particle size, morphology, crystalline phase etc. in comparison with those of commercial $WS_2$powder. The solid $WO_3$ powder with the average size of 0.2 ${\mu}{\textrm}{m}$ was reacted with $CS_2$gas flowed with$N_2$or 96%$N_2{\times}4%H_2$forming gas for 36 h and 24 h at 90$0^{\circ}C$ respectively. $WS_2$ crystalline phase was then formed through the intermediate phase of .$W_{20}O_{58}$ In the case of vapour phase transport method, the 3.5 wt% iodine was added as a vapour transport reagent into the composition of tungsten and sulfur powders maintaining a constant molar ratio of W:S=1:2.2. The mixture was then heat treated at 85$0^{\circ}C$ for 2 weeks in vacuum. The reaction product obtained showed the average size of 12 ${\mu}{\textrm}{m}$ and the hexagonal plate shape of typical solid lubricant with 2H-$WS_2$crystalline phase.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회/대한산업공학회 2003년도 춘계공동학술대회
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• pp.772-779
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• 2003

In the real world, business processes are very complex and composed or heterogeneous business activities. As the advent or the Web services enables business processes to be Integrated and to be automated. It makes enterprises integrate heterogeneous business processes from different business partners as well as their internal business processes. To support recent trends in integration of business processes, BPEL, WS-E and WS-T specipications have been established since 2002 WS-C and WS-T describe the reliable business environment including compensation (undo) or completed business processes. The compensation of business processes is a basic requirement for automation or business processes among business partners. Systems implementing these specifications, however, very rarely exist. It's not only because those specifications are developed recently. but also because they are not perfect yet. In this paper, a new business process transaction management, which complements the deficiency of WS-E and WS-T, is suggested. Furthermore, the new approach proposes the business logics for supervisory coordinators which manage serial and parallel business gates The modification or traditional WS-T specification and the simplification or WS-E specification make business processes managed effectively.

• 한국정보통신학회논문지
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• 제11권8호
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• pp.1612-1618
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• 2007

유비쿼터스 환경으로 발전하면서 이종의 디바이스들을 자연스럽게 연동시킬 수 있는 기술에 대한 요구가 크게 증가하고 있으며, 이를 해결하기 위한 하나의 대안으로 웹서비스가 주목받고 있다. 최근 디바이스 연동을 선언적인 ECA(Event-Condition-Action) 룰로 정의하고 이를 이용하여 디바이스 연동을 수행할 수 있는 웹서비스 기반의 WS-ECA(Web Services-ECA) 프레임워크가 제안되었다. 본 논문에서는 WS-ECA 프레임워크에 대한 구체적인 모듈 단위의 설계 부분을 제안하고, 이를 기반으로 WS-ECA 프레임워크를 구현하였다.

• Journal of Electrochemical Science and Technology
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• 제10권1호
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• pp.89-97
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• 2019

As a promising candidate for anode materials in lithium ion battery (LIB), tungsten trioxide ($WO_3$) and tungsten disulfide ($WS_2$) nanocrystals were synthesized, and their electrochemical properties were comprehensibly studied using a half cell. One-dimensional $WO_3$ nanowires with uniform diameter of 10 nm were synthesized by hydrothermal method, and two-dimensional (2D) $WS_2$ nanosheets by unique gas phase sulfurization of $WO_3$ using $H_2S$. $WS_2$ nanosheets exhibits uniformly 10 nm thickness. The $WO_3$ nanowires and $WS_2$ nanosheets showed maximum capacities of 552 and $633mA\;h\;g^{-1}$, respectively, after 100 cycles. Especially, the capacity of $WS_2$ is significantly larger than the theoretical capacity ($433mA\;h\;g^{-1}$). We also examined the cycling performance using a larger size $WO_3$ and $WS_2$ nanocrystals, showing that the smaller size plays an important role in enhancing the capacity of LIBs. The larger capacity of $WS_2$ nanosheets than the theoretical value is ascribed to the lower charge transfer resistance of 2D nanostructures.

• 오토저널
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• 제12권3호
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• pp.21-29
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• 1990

Equipments of passenger cars with modern technologies are gaining their importance. Related with such developments, the four-wheel steering system (4WS) was introduced recently to a few passenger cars in the market. The most important research goal on this new steering system is improvement of active safety, in other words, improvement of handling characteristics of vehicle stability and maneuverability. This paper presents a computer-based study about the effects of 4WS system on the vehicle handling characteristics. A simple bicycle model of 2 d.o.f. is used for the development of four wheel control algorithms of 4WS system, and the rear wheel control strategies are applied to a complex vehicle model of 16 d.o.f. for simulation of selected ISO-driving tests. The 4WS systems, which reduce the sideslip angle at the mass center of vehicle to almost zero, show much improved handling characteristics compared to that of the conventional 2WS system. These 4WS systems, however, result in vehicles with eigen-steer characteristics of extreme understeer behaviour.

• 한국생산제조학회지
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• 제8권1호
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• pp.150-157
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• 1999

In this study, the loader was completed that has 4-wheel gear driven drivetrain of study (Ⅰ), the 4-wheel steering with power wheel type, all-wheel traction system, and joy-stick type lever for hydraulic control valve. From driving test of the developed 4WD and 4WS type loader, we obtained that the minimum circling radius and the necessary width in circling motion reduced about 40% and 33% compared with 2WS type loader. Also, all-wheel traction system could keep the tires glued to the ground with greater stability, the power steering allowed a smoother operation, and the joy-stick type lever offered easily to control. Thus, the developed loader having these functions was very fit in a small cattle shed or rugged ground.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2007년도 춘계종합학술대회
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• pp.869-871
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• 2007

최근 유비쿼터스 환경으로 발전하면서 이종의 하드웨어와 소프트웨어 플랫폼을 가지고 있는 디바이스들 간의 연동 기술이 점점 중요해지고 있다. 이에 대한 연구 중의 하나로 웹서비스를 이용한 이벤트 기반 다바이스 연동 프레임워크가 있으며, 이는 XML을 기반으로 이벤트 기반의 다바이스 연동을 정의하는 룰 언어인 WS-ECA를 제안하고 있다. 그러나, 아직까지 WS-ECA를 효과적으로 작성할 수 있는 방법이 제시되지 않고 있다. 따라서, 본 논문은 비즈니스 프로세스에 대한 로직을 표현하는 데 가장 활용이 많이 되고 있는 BPEL을 WS-ECA로 변환하는 방법을 제안하며, 이는 BPEL 저작 툴을 이용하여 기본적인 디바이스 연동을 정의할 수 있으므로 효과적으로 WS-ECA을 생성할 수 있는 방법을 제공할 수 있다.

• 한국지능시스템학회논문지
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• 제11권7호
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• pp.628-632
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• 2001

We propose time-frequency (TF) tools for analyzing linear time-varying (LTV) systems and nonstationary random processes. Obtained warping the narrowband Weyl symbol (WS) and spreading function (SF), the new TF tools are useful for analyzing LTV systems and random processes characterized by generalized frequency shifts, This new Weyl symbol (WS) is useful in wideband signal analysis. We also propose WS an tools for analyzing systems which produce dispersive frequency shifts on the signal. We obtain these generalized, frequency-shift covariant WS by warping conventional, narrowband WS. Using the new, generalized WS, we provide a formulation for the Weyl correspondence for linear systems with instantaneous of linear signal transformation as weighted superpositions of non-linear frequency shifts on the signal. Application examples in signal and detection demonstrate the advantages of our new results.