• Proceedings of the Korea Information Processing Society Conference
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• 2015.10a
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• pp.383-386
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• 2015

Ad Hoc 네트워크는 단말간 채널 경쟁을 통해 데이터 패킷을 전송하는 DCF(Distributed Coordination Function)에 기반을 둔다. DCF는 단말의 수가 많아질수록 충돌 확률이 증가하여 성능이 급격하게 감소한다. 성능 향상을 위해 DPCF(Distributed Point Coordination Function) 방법이 제안되었다. 이 방법에서 단말은 기본적으로 DCF로 동작하고 채널 접근 권한을 얻었을 때 이웃 단말들에게 PCF(Point Coordination Function)를 이용하여 채널 경쟁 없이 데이터 패킷을 전송하도록 한다. 그러나 이 방법은 히든 노드 문제를 더 가중시키고 데이터 패킷이 없는 단말도 폴링을 하기 때문에 채널 낭비를 초래한다. 본 논문에서는 이 문제점을 해결하기 위한 새로운 방법을 제안한다. 제안된 방법은 PCF로 동작할 때 전송 범위 내 모든 단말이 아닌 제한된 영역에 있는 단말을 대상으로만 동작한다. 또한 데이터 패킷이 있는 단말에 대해서만 폴링을 수행한다. 이를 통해 제안된 방법은 Ad Hoc 네트워크에서 충돌 확률을 낮추고 성능을 향상시킨다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.05a
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• pp.547-549
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• 2014

In RFID systems, the performance for the tag identification is closely related with the tag collision, which is caused by the simultaneous transmission. The PS algorithm divides the tags within the identification range of reader into smaller groups by increasing the transmission power incrementally and identifies them. This algorithm uses the fixed frame size at every scan. Therefore, it is anticipated that the performance of PS algorithm can be variously shown according to the number of tags, frame size, and power level increase. In this paper, we analize the performance of PS algorithm according to the frame length and power level increase.

• 한국HCI학회:학술대회논문집
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• 2008.02a
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• pp.451-455
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• 2008

In this paper, we present how we implement the low-level, triangle intersection routine in a massively parallel fashion using n VIDIA's new GPGPU language, CUDA. Triangle intersection often becomes a computational bottleneck in the collision detection problem. Due to the relatively low bandwidth between CPU and GPU, it has been challenging to implement efficient, object-space collision detection between triangle sets. However, thanks to the improved data transmission rates in CUDA architecture, in this paper, we improved the performance of triangle intersection substantially better than the optimized CPU counterpart.

• Composites Research
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• v.29 no.6
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• pp.363-368
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• 2016

This study performed a nonlinear finite element crash analysis of guardrail structures using supports made of composite materials. In this study, we used a new [0/90/90/0] laminated Boron fiber composite for resisting the crash effects. Based on the improved ground-structure interaction model, appropriate ground properties to the support were determined. In particular, the complex crash mechanism of guardrails was studied using various parameters. The parametric studies are focused on the various effects of car crash on the structural performance and thickness of supports. The numerical results for various parameters are verified by comparing those using existing steel materials.

• Journal of Internet Computing and Services
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• v.12 no.5
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• pp.101-111
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• 2011

Most researches in WSN-based parking management system used wireless sensors to monitor the events in a car parking area. However, the problem of car collisions in car parks was not discussed by previous researches. The car position details over time are vital in analyzing a collision event. This paper proposes a collision verification method to detect and to analyze the collision event in the parking area, and then notifies car owners. The detection uses the information from motion sensors for comprehensive details of position and direction of a moving car, and the verification processes an object tracking technique with a fast OBB intersection test. The performance tests show that the location technique is more accurate with additional sensors and the OBB collision test is faster compared to a normal OBB intersection test.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.8
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• pp.120-125
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• 2002

In the preceding tests using the KSR-III Sub.(I) engines, it was observed that the heat resistant capability of the engines was not enough for the mission. So Sub.(I) Mod. engines were designed and tested. The Sub.(I) Mod. engines have three major design parameters - the arrangement of main injectors, the impinging angle of main injectors and thermal barrier coating. More than twenty experiments were carried on to evaluate engine performance and heat resistance capability with respect to design parameters. In this study, the test results are introduced. Analysing the result of Sub.(I) engine tests, it is found that decreasing the impinging angle, adopting the H-type arrangement(rather than radial type arrangement) and adopting the thermal barrier coating can increase heat resistance capacity substantially. Also, engine performance evaluation is conducted using specific impulse and characteristic velocity parameter. The results show that the performance variation is small(about 5%) and the performance is better in the case of radial arrangement. It is suspected that these phenomena are caused by the change of flame structure atomization mixing characteristic of sprays and the distortion of recirculation zone. Also from the low frequency instability point of view, it is observed that reducing the impinging angle and adopting the H type arrangement can increase the instability characteristics.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.29 no.1
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• pp.77-83
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• 2005

In collision avoidance problem of a ship, collision risk model is usually set up using the interview results fron experts who sit on a simulator by varying parameters, in which DCPA and TCPA are commonly used. This method, however, has the weakness in that not only it is expensive but also it shows different results depending on the inerviewees and other navigational parameters. In this study, a fuzzy inference system is designed based on own ship's maneuverability verified fron simulation instead of interviewing navigators. The time and distance corresponding to the collision risk value on which avoidance maneuver should be started are set to the minimum marginal time at which own ship starts maneuvering and the minimum marginal distance suggested by marine traffic rules respectively. This system can be recorfigured as a nonlinearity-strengthened one by increasing the number of fuzzy membership functions.

• Journal of KIISE
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• v.42 no.4
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• pp.442-450
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• 2015

This paper proposes a method for reducing false conflicts in signature-based eager hardware transactional memory (HTM). The method tracks the information on all cache blocks that are accessed by a transaction. If the information provides evidence that there are no conflicts for a given transactional request from another core, the method prevents the occurrence of a false conflict by forcing the HTM to ignore the decision based on the signature. The method is very effective in reducing false conflicts and the associated unnecessary transaction stalls and aborts, and can be used to improve the performance of the multicore processor that implements the signature-based eager HTM. When running the STAMP benchmark on a 16-core processor that implements the LogTM-SE, the increased speed (decrease in execution time) achieved with the use of the method is 20.6% on average.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.6
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• pp.497-506
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• 2015

A composite guidance law for impact angle control against nonstationary nonmaneuvering targets is proposed. The proposed law is based on the characteristics of proportional navigation and generates two kinds of guidance commands during the homing phase. The first command is to keep the desired look angle, and the second is to attack the target with impact angle constraint. The switch of guidance phases occurs when the specific light-of-sight(LOS) angle determined from the engagement information is satisfied. The calculation method of the maximum achievable impact angle is also proposed to design easily the desired impact angle within the missile capability. Numerical simulations are performed to investigate the performance and characteristics of the proposed law.

• The KIPS Transactions:PartA
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• v.16A no.4
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• pp.289-298
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• 2009

Generally, RFID systems are composed of one reader and several passive tags, and share the single wireless channel. For this reason, collisions occurwhen more than two tags simultaneously respond to the reader's inquiry. To achieve this problem, many papers, such as QT[8], HCT[10], BSCTTA[2], and QT-BCS[9], have been proposed. In this paper, we propose the tree-based anti-collision algorithm using a bit change sensing unit (TABCS) based on BSCTTA algorithm. The proposed algorithm can identify bits returned from tags through bit change sensing unit, even if multi collisions occur. So, it rapidly generates the unique prefix to indentify each tag, and reduce the total of bits. As the result, the cost of identifying all tag IDs is relatively reduced as compared with existing algorithms. It is verified through simulations that the proposed algorithm surpass other existing algorithms.