• 한국컴퓨터그래픽스학회논문지
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• 제6권1호
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• pp.11-17
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• 2000

본 논문에서는 강체와 변형 객체 사이에서 발생할 수 있는 자체관통을 포함한 충돌처리 방법을 제시한다. 충돌은 객체간 계층구조 교차검사를 통해 감지된다. 연속된 프래임 사이에서 발생하는 충돌을 감지하기 위해 객체간 교차검사 외에 모조객체와 상대 객체 사이의 교차검사를 수행한다. 모조객체는 두 프래임 사이의 객체 움직임을 기반으로 구성된다. 일단 충돌이 발생되면, 객체간 관통은 허용되지 않으며 객체의 변형이 유발된다. 변형과정에서 발생 가능한 자체관통은 또 다른 종류의 모조객체와 객체 사이의 교차검사에 의해 빠르게 감지된다. 이때의 모조객체는 연속된 두 프래임간의 변형된 영역을 나타낸다. 객체 변형은 자체 접촉이 발생한 때까지로 제한된다. 제안 방법은 객체 형태와 무관하게 적용될 수 있다.

• 방송공학회논문지
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• 제21권4호
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• pp.493-505
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• 2016

컴퓨터 비전이나 감시영상 시스템에서 유동인구 수 측정은 안전, 스케줄링, 광고효과 측면에서 중요한 과제 중 하나이다. 유동인구 수 측정은 조명변화, 부분적인 폐색, 중첩, 사람검출과 같은 다양한 어려움을 겪고 있다. 가장 큰 문제점은 혼잡한 상황에서 추적되는 객체에 대한 폐색과 중첩이다. 정확한 유동인구 수 측정을 위해 폐색과 중첩은 반드시 해결해야 할 과제이다. 본 논문에서는 기존의 보행자 추적 방법을 개선한 효율적인 유동인구 수 측정 시스템을 제안한다. 기존의 보행자 추적과 달리, 제안된 방법은 평균 필터 추적방법을 적용하여 성능을 향상시킬 수 있음을 보인다. 또한 객체 추적의 성능향상을 위한 프레임 보상, 아웃라이어 제거를 통해서 추적을 개선한다. 그와 동시에 제안된 시스템은 추적된 객체의 다양한 정보를 저장한다. 데이터 셋 S6와 데이터 셋 S7에 대하여 유동인구 수 측정 정확도를 향상시키고 에러율을 줄인다. 또한 제안된 방법은 실시간으로 평균 80fps의 검출을 제공한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권6호
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• pp.1881-1900
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• 2014

Since 802.11 wireless LANs are so widely used, it has become common for numerous access points (APs) to overlap in a region, where most of those APs are managed individually without any coordinated control. This pattern of wireless LAN usage is called the private OBSS (Overlapping Basic Service Set) environment in this paper. Due to frame collisions across BSSs, each BSS in the private OBSS environment suffers severe performance degradation. This study approaches the problem from the perspective of congestion control rather than noise or collision resolution. The retry limit, one of the 802.11 attributes, could be used for traffic control in conjunction with TCP. Reducing the retry limit causes early discard of a frame, and it has a similar effect of random early drops at a router, well known in the research area of congestion control. It makes the shared link less crowded with frames, and then the benefit of fewer collisions surpasses the penalty of less strict error recovery. As a result, the network-wide performance improves and so does the performance of each BSS eventually. Reducing the retry limit also has positive effects of merging TCP ACKs and reducing HOL-like blocking time at the AP. Extensive experiments have validated the idea that in the OBSS environment, reducing the retry limit provides better performance, which is contrary to the common wisdom. Since our strategy is basically to sacrifice error recovery for congestion control, it could yield side-effects in an environment where the cost of error recovery is high. Therefore, to be useful in general network and traffic environments, adaptability is required. To prove the feasibility of the adaptive scheme, a simple method to dynamically adjust the value of the retry limit has been proposed. Experiments have shown that this approach could provide comparable performance in unfriendly environments.

• Journal of Communications and Networks
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• 제13권1호
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• pp.32-42
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• 2011

Frequency reuse among relay stations (RSs) in a down-link access zone is widely adopted for throughput enhancement in IEEE 802.16j relay networks. Since the areas covered by the RSs or the base station (BS) may overlap, some mobile stations (MSs) at the border between two neighboring transmitting stations (RS or BS) using an identical frequency band may suffer severe interference or outage. This co-channel interference within the cell degrades the quality of service (QoS) fairness among the MSs as well as the system throughput. Exclusive use of a frequency band division (orthogonal resource allocation) among RSs can solve this problem but would cause degradation of the system throughput. We observe a trade-off between system throughput and QoS fairness in the previously reported schemes based on frequency reuse. In this paper, we propose a new frequency reuse scheme that achieves high system throughput with a high fairness level in QoS, positioning our scheme far above the trade-off curve formed by previous schemes. We claim that our scheme is beneficial for applications in which a high QoS level is required even for the MSs at the border. Exploiting the features of a directional antenna in the BS, we create a new zone in the frame structure. In the new zone, the RSs can serve the subordinate MSs at the border and prone to interference. In a 3-RS topology, where the RSs are located at points $120^{\circ}$ apart from one another, the throughput and Jain fairness index are 10.64 Mbps and 0.62, respectively. On the other hand, the throughput for the previously reported overlapped and orthogonal allocation schemes is 8.22 Mbps (fairness: 0.48) and 3.99 Mbps (fairness: 0.80), respectively. For a 6-RS topology, our scheme achieves a throughput of 18.38 Mbps with a fairness of 0.68; however, previous schemes with frequency reuse factors of 1, 2, 3, and 6 achieve a throughput of 15.24 Mbps (fairness: 0.53), 12.42 Mbps (fairness: 0.71),8.84 Mbps (fairness: 0.88), and 4.57 Mbps (fairness: 0.88), respectively.

• 한국주거학회:학술대회논문집
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• 한국주거학회 2006년도 추계학술발표대회 논문집
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• pp.366-369
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• 2006

Multi Housing design has not considered the remodeling even at the beginning of the construction. This severely hindered systematic maintenance, providing fundamental causes of consuming society. In general, in about 20 years when the buildings become too old, they are brought down or removed with a trail of waste left behind. In addition, since the current remodeling or future remodeling type is a general remodeling that leaves only a frame, some question the role of the remodeling as a solution to the reconstruction from economically and environmentally efficient aspects. This study intends to find a solution for long-life span multi-family housing design, promoting sequential remodeling by stating the life cycle of components. Problems were identified by analyzing joints, design and construction of multi-family housing based on the previous researches. Conclusion from characterization of the design plan according to joint parts can be summarized as the following firstly, the problem of the wet was seen in joints between the structure and a finishing materials and ones between separate finishing materials. Secondly, the problem of overlap was frequently seen in joints between the structure and a door/window, ones between a door/window and a finishing materials, and ones between a finishing materials and an electrical/mechanical device.

• Journal of Electrical Engineering and Technology
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• 제11권2호
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• pp.519-528
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• 2016

In order to achieve fast computational speed with good visual quality of output video, we propose a frequency domain based new fractal video compression scheme. Normalized cross correlation is used to find the structural self similar domain block for the input range block. To increase the searching speed, cross correlation is implemented in the frequency domain using FFT with one computational operation for all the domain blocks instead of individual block wise calculations. The encoding time is further minimized by applying rotation and reflection DFT properties to the IFFT of zero padded range blocks. The energy of overlap small size domain blocks is pre-computed for the entire reference frame and retaining the energies of the overlapped search window portion of previous adjacent block. Quadtree decompositions are obtained by using domain block motion compensated prediction error as a threshold to control the further partitions of the block. It provides a better level of adaption to the scene contents than fixed block size approach. The result shows that, on average, the proposed method can raise the encoding speed by 48.8 % and 90 % higher than NHEXS and CPM/NCIM algorithms respectively. The compression ratio and PSNR of the proposed method is increased by 15.41 and 0.89 dB higher than that of NHEXS on average. For low bit rate videos, the proposed algorithm achieve the high compression ratio above 120 with more than 31 dB PSNR.

• 대한기계학회논문집A
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• 제32권3호
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• pp.209-216
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• 2008

The application of focused ion beam (FIB) depends on the optimal interaction of the operation parameters between operating parameters which control beam and samples on the stage during the FIB deposition process. This deposition process was investigated systematically in C precursor gas. Under the fine beam conditions (30kV, 40nm beam size, etc), the effect of considered process parameters - dwell time, beam overlap, incident beam angle to tilted surface, minimum frame time and pattern size were investigated from deposition results by the design of experiment. For the process analysis, influence of the parameters on FIB-CVD process was examined with respect to dimensions and constructed shapes of single and multi- patterns. Throughout the single patterning process, optimal conditions were selected. Multi-patterning deposition were presented to show the effect of on-stage parameters. The analysis have provided the sequent beam scan method and the aspect-ratio had the most significant influence for the multi-patterning deposition in the FIB processing. The bitmapped scan method was more efficient than the one-by-one scan type method for obtaining high aspect-ratio (Width/Height > 1) patterns.

• 한국통신학회논문지
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• 제33권8B호
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• pp.609-614
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• 2008

TDM-PON의 상향전송 데이터 프레임은 여러 가지 오버헤드를 포함하고 있으며, 각 ONU 전송시간 사이에는 가드밴드가 존재한다. 이들은 수신단의 동기 및 전송성능 유지를 위해 중요한 요소들이지만, 상향 대역폭 낭비의 원인이 되고 있다. 본 논문에서는 상향 전송에 두 종류의 파장을 이용해 대역폭 이용효율을 극대화하는 방식의 TDM-PON을 제안하였다. ONU들에 두 파장을 고르게 배치하고, 각 ONU는 전송 패킷의 오버헤드를 중첩하여 전송함으로써 이용 효율을 100%에 근접하도록 하였으며, 이를 위한 OLT 다중화회로를 구현하였다.

• 말소리와 음성과학
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• 제5권4호
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• pp.201-207
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• 2013

This study is a follow-up study of Han and Kang (2013) and Kang and Han (2013) which examined cross-generational changes in the Korean vowels /o/ and /u/ using acoustic analyses of the vowel formants of these two vowels, their Euclidean distances and the overlap fraction values generated in SOAM 2D (Wassink, 2006). Their results showed an on-going approximation of /o/ and /u/, more evident in female speakers and non-initial vowels. However, these studies employed non-words in a frame sentence. To see the extent to which these two vowels are merged in real words in spontaneous speech, we conducted an acoustic analysis of the formants of /o/ and /u/ produced by two age groups of female speakers while reading a letter sample. The results demonstrate that 1) the younger speakers employed mostly F2 but not F1 differences in the production of /o/ and /u/; 2) the Euclidean distance of these two vowels was shorter in non-initial than initial position, but there was no difference in Euclidean distance between the two age groups (20's vs. 40-50's); 3) overall, /o/ and /u/ were more overlapped in non-initial than initial position, but in non-initial position, younger speakers showed more congested distribution of the vowels than in older speakers.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제54권11호
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• pp.511-518
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• 2005

This paper presents the design and drive characteristics of a switched reluctance motor for an electric power pallet vehicle. The designed switched reluctance motor is redesigned by using the finite element analysis(FEA) as a variation of the pole-arc angle for the purpose of an electric power pallet vehicle performance. The output power and torque characteristics of a switched reluctance motor are variable by switching angles of the commutator. Therefor this paper is studied about relationship between the output power and torque characteristics of a switched reluctance motor according to switching angles. The output power of the characteristic point of an electric power pallet vehicle has been shown by experiment. The designed motor drive system operates with the low voltage and high current with using the battery. The core and frame temperatures were described. In this paper, the designed motor is shown better drive characteristics than the DC motor from the rated to maximum, which is verified by the finite element analysis and experimental results.