• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2002년도 제18회 학술발표대회 논문초록집
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• pp.46-49
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• 2002

Three-dimensional flow characteristics in a liquid fuel ramjet combustor were investigated using the PIV method. The combustor has two rectangular inlets that loin a 90-degree angle each other. Three cases of test combustors are made in which those inlet angles are 30 degree, 45degree and 60 degree. The experiments were performed in a water tunnel test with the same Reynolds number as Mach 0.3 at the inlet. PIV software was developed to measure the characteristics of the flow field in the combustor. Accuracy of the developed PIV program was verified with a rotating disk experiment and standard data. The characteristics of the internal flows of the combustor are large swirling flows which appear symmetric with respect to the symmetric section. This is attributed to the fact that the flows introduced from the right and left intakes collide with each other, thus forming symmetrically large vortices. A large and complex three-dimensional recirculating flow was measured behind the intakes. An inlet angle of 30 degrees is the most suitable angle as a frame he]der in the performed experimental ranges.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.1032-1035
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• 1996

While Ethernet and TCP/IP are the most widely used protocol, for Real-time system, it is not applicable because it doesn't guarantee the deterministic transmission time. Furthermore, the TCP acknowledgement scheme and sliding window algorithm enforce to collide packets. Although various Collision-Free CSMA protocol was presented, it is very difficult to implement in well known OS(UNIX, WilidowsNT) because we have to modify network kernel. This paper presents another transmission protocol based on modified UDP. The colliding probability can be minimized by avoiding successive packet transmission and decreasing competition duration. The proposed algorithm can be used for the soft real-time industrial automation network.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.824-827
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• 1996

Most autonomous mobile robots view things only in front of them. As a result, they may collide against objects moving from the side or behind. To overcome the problem we have built an Active Omni-directional Range Sensor that can obtain omnidirectional depth data by a laser conic plane and a conic mirror. In the navigation of the mobile robot, the proposed sensor system makes a laser conic plane by rotating the laser point source at high speed and achieves two dimensional depth map, in real time, once an image capture. The experimental results show that the proposed sensor system provides the best potential for navigation of the mobile robot in uncertain environment.

• 대한전자공학회논문지
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• 제26권11호
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• pp.1770-1781
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• 1989

Two robots working in a common workspace may collide with each other. In this paper, a collision-free motion planning algorithm using view time concept is proposed to detect and avoid collision before robot motion. Collision may occur not only at the robot end effector but also at robot links. To detect and avoid potential collisions, the trajectory of the first robot is sampled periodically at every view time and the region in Cartesian space swept by the first robot is viewed as an obstacle during a single sampling period. The forbidden region in the joint constraint map (JCM). The JCM's are obtained in this way at every view time. An algorithm is established for collision-free motion planning of the two robot system from the sequence of JCM's and it is verified by simulations.

• 기계와재료
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• 제11권2호통권40호
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• pp.53-61
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• 1999

The paper describes a characteristics analysis for cushion pressure and cushion stroke time at hydraulic cushioning cylinder. In hydraulic cushioning cylinder, an inertia exaggerates a kinetic energy at a reciprocation that collide with an end of stroke and generate a destructive shock, noise and vibration within the structural and operating member of machine of equipment. In order to reduce which cause to undesirable noise, vibration and fatigue in hydraulic control system, it is indispensible measure a cushion parameters at cushion region of hydraulic cushioning cylinder. A cushioning device is applied to absorb high impact energy and to decelerate a fast travelling object, too. At an experimental results, it turns out that cushion pressure is mainly a function of the external load and cylinder input flowrate rather than the supply pressure.

• 한국정밀공학회지
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• 제23권4호
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• pp.83-90
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• 2006

A robot manipulator is usually operated in two modes: free and constrained motion modes, depending on whether the robot is in contact with an environment or not. At the moment of contact, an impact occurs and can exert harmful effects to the robot or the object. In case of teleoperation, since a user may give an inadequately excessive velocity command to the slave due to insufficient visual information, the robot nay collide the object with an excessive speed and it possibly deteriorates the robot's performance causing vibrations and at worst, shortens its lifetime by its fracture. In this article, a new algorithm is proposed by introducing a command signal modification method on the basis of impedance control and validity of the proposed algorithm is demonstrated by performing simulations and experiments.

• 대한기계학회논문집B
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• 제22권11호
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• pp.1499-1508
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• 1998

A numerical study is performed to investigate pressure drops, particle trajectories and erosion around orifice plates in pulverized coal pipe lines. Particle impaction rates change significantly with orifice shapes and Stokes numbers. At Reynolds number of $5{\times}10^5$, the pulverized coal flows well with streamlines and do not collide at the orifice plates at small sizes (${\sim}20{\mu}m$). However, the large particles (over $70{\mu}m$) impact on the front face of the orifice and erode the orifice surface. The pressure loss coefficients around the erode orifice are largely different from the designed original orifice.

• 한국가구학회지
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• 제12권1호
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• pp.69-79
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• 2001

The purpose of this study is to examine the characteristics of Arne Jacobsen's chair design. He was one of the few creators who inscribed his name in both the history of architecture and furniture design. His works reflected a form of "Regional Modernism" in which traditional techniques collide with functionalist beliefs. This grafting of ideas generated a person aesthetics which he used to establish a suitability of scale, detail an program for each design. In the material aspect, he had enjoyed using the plasticity of the plywood, polyurethane, tubular steel and in the formative aspect, organic form is combined with minimalization of material and simplicity. To sum up what is unique about Arne Jacobsen's chair design, it is that it is distinguished by a clear understanding and expression of beauty from nature, a complete understanding of the material used and the melding of traditional and functional techniques to generate organic form.anic form.

• 한국철도학회논문집
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• 제3권1호
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• pp.27-33
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• 2000

In this paper, numerically evaluated is the crashworthiness of the new design of the standard Korea Electric Multiple Unit Train(K-EMU)[developed by the Korea Railway Research Institute]. The 4-car consist of K-EMU is analyzed under collision conditions such as normal coupling, heavy shunting, light collision and heavy collision to collide against another stationary one at 5 kph, 10 kph, 25 kph and 32 kph, respectively. Energy absorbing capacity of its draftgear commercially available in the market and to be equipped in K-EMU is evaluated under each collision condition. Analytical results show that draftgear only is not enough to provide necessary energy absorbing capacity. It is therefore concluded that additional energy absorbers like mechanical fuses should be adopted to improve the crashworthiness of K-EMU.

• 천문학회보
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• 제38권1호
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• pp.46.1-46.1
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• 2013

High velocity clouds (HVCs) are H I clouds that move with large speed (${\mid}V_{LSR}{\mid}$ >100 km/s) in the halo of the Milky Way. It is now evident that at least some populations of HVCs originated from extragalactic sources, either primordial gas left over from the galaxy formation or gaseous material stripped off from other galaxies closely passing by the Milky Way. HVCs with extragalactic origin play an important role in the star formation of the Milky Way when they eventually collide with the disk of the Milky Way. Although it is still observationally controversial whether HVCs are surrounded by dark matter or not, it is theoretically interesting to investigate the effect of dark matter on the collision of HVCs with the disk of the Milky Way. We model this scenario by using hydrodynamic simulations and search for proper parameters that explain the currently available observations such as the Smith Cloud that is thought to have collided with the Galactic disk already.