• Proceedings of the Korea Contents Association Conference
• /
• 2007.11a
• /
• pp.97-100
• /
• 2007

Recently, there is developed various antenna's models due to increment of wireless communication the need of quantitative study on antenna's measuring technology gets to highlight. In this paper, we propose algorithm of antenna's edge alignment for making automatic measuring system of antenna's characteristics of near-field measurement system of antenna. The proposed algorithm gets the bottom image of antenna from camera, extracts antenna object, and finds the boundary the object. The proposed algorithm calculates distortion of the object using the extracted boundary and the angle to correct this. The proposed algorithm is applied to the standard gain horn antenna. The results show that antenna's object is efficiently extracted and the angle for correcting the error is calculated.

• Journal of Korea Multimedia Society
• /
• v.9 no.1
• /
• pp.41-50
• /
• 2006

This paper aims to improve the efficiency of a 3D-graphic software engine in a PDA platform and the performance of a rasterizer. There are many problems in implementing a software engine in a mobile platform, due to its relatively weak processing power. Taking the advantages and complementing weaknesses of the depth-sort algorithm and the Z-buffer algorithm, we implemented an adaptive Z-buffer algorithm and proved its performance on several PDA platforms. Our algorithm was evaluated to have midway speed compared with two conventional algorithms. It also removed reversal errors in comparison with the depth-sort algorithm.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2006.05a
• /
• pp.627-628
• /
• 2006

High speed milling process is emerging as an important fabrication process benefits include the ability to fabricate micro and meso-scale parts out of a greater range of materials and with more varied geometry. It also enables the creation of micro and meso-scale molds for injection molding. Factors affecting surface roughness have not been studied in depth for this process. A series of experiments has been conducted in order to begin to characterize the factors affecting surface roughness and determine the range of attainable surface roughness values for the high speed milling process. It has previously been shown that run-out creates a greater problem for the dimensional accuracy of pans created by high speed milling process. And run-out also has a more significant effect on the surface quality of milled parts. The surface roughness traces reveal large peak to valley variations. This run-out is generated by spindle dynamics and tool geometry. In order to investigate the relationship between tool alignment errors and surface roughness the scallop generating mechanism in the ball-end milling with tool alignement errors has been studied and simulated. The results indicate that tool alignment errors have no significant effects ell the dimension of scallops in for flat planes.

• The Transactions of the Korea Information Processing Society
• /
• v.4 no.11
• /
• pp.2690-2700
• /
• 1997

This paper presents parallel sorting algorithm, SHARED-MEMORY-BS and REDUCED-BS, which are implemented on shared-memory parallel computers. These algorithm sort N keys in $O(log^2N)$ time. REDUCED-BS users a parity strategy which gives an idea for the efficient usage of the local memory associated with each processor. By taking advantage of the local memory associated with each processor, the communication of REDUCED-BS is decreased by approximately half that of SHARED-MEMORY-BS. On the basis of alleviating the communication, the algorithm REDUCED-BS results in a significant improvement of performance.

• Proceedings of the KAIS Fall Conference
• /
• 2001.05a
• /
• pp.269-272
• /
• 2001

실리콘 마이크로머시닝 기술과 바이폴라 공정으로 집적화된 압력센서를 제작하고 동작특성 평가를 수행하였다. 센서부 보상파라미터를 추출하였고 트리밍 공정을 통하여 출력전압의 보상을 수행하였다. 센서 특성은 압저항 위치, 마스크 정렬 오차, 다이어프램 정밀두께제어 정도, 보호막의 과도식각 정도 등에 의하여 민감하게 좌우됨을 알 수 있었다. 웨이퍼별 샘플추출을 통하여 센서부 감도는 평균 0.653mV/kPa, 감도의 온도계수는 -2078.8ppm/℃, 옵셋 전압은 30.78mV, 옵셋전압의 온도계수는 32.11㎶/℃로 측정되었다. 추출된 샘플의 다이어프램 두께오차는 27±2.5㎛였다. 센서부 특성평가 결과를 통하여 신호처리회로의 옵셋 및 스팬보상, 온도보상을 위한 트리밍 공정을 수행한 결과 개발사양을 만족하는 결과를 얻을 수 있었다.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2009.04a
• /
• pp.523-526
• /
• 2009

시계열 데이터에서 패턴을 분석하는 기법은 많은 발전이 이루어져 오고 있으나 주식시장의 경우 패턴 분석 및 예측에 관련되어 많은 연구가 이루어져 있지 않고 있다. 이는 주가의 등락 자체가 본질적으로 무작위하다고 생각되어지고 있기 때문이다. 본 연구에서는 주가의 등락이 보여주는 무작위성의 정도를 Kolmogorov Complexity로 측정, 그 무작위성의 정도와 본 논문에서 제시한 반전역정렬로 예측하는 주가의 예측 간의 상관관계를 보인다. 이를 위하여 KOSPI 주식 데이터 28년 690개의 데이터를 수집하여 이들 주식 데이터의 등락을 양자화된 문자열로 변환하여 본 논문에서 제시한 방법의 의미를 평가하였다. 그 결과 Kolmogorov Complexity가 높은 경우에는 주가 변동 예측이 어려우며, Kolmogorov Complexity가 낮은 경우에는 주식 변동 예측은 가능하나 등락 예측 율은 단기 예측은 12%이상의 예측율을 보일 수 없으며, 장기 예측의 경우 54%의 예측율로 수렴함을 확인하였다.

• Journal of the Korean Magnetics Society
• /
• v.11 no.5
• /
• pp.184-188
• /
• 2001

Using a DC-sputter and changing the substrate temperature to room temperature and 200$\^{C}$, we manufactured each Co-22%Cr alloy thin-films, which has a uniform micro-structure at room temperature, and a fine self-organized nato structure (SONS) at the inside of the grain at the elevated temperature. We also investigated the microstructure and domain structure using a transmission electron microscope (TEM) and a magnetic force microscope (MFM). We managed to corrode selectively Co-enriched phase, then investigate the microstructure using a TEM. We found that it has a uniform composition when it is manufactured at room temperature, but, we found that it has a unique microstructure, which has a plate-like fine Co-enriched phase, with the formation of SONS at the inside of the grain at the elevated temperature. In MFM characterization, we found maze-type domains at the period of 5000 when the substrate temperature maintains at room temperature. We define that the maze-type domain has a disadvantage at the high density recording because it generates noises easily as the exchange coupling energy between the grains is big. On the other hand, there is only a fine domain structure at the period of 500 when the substrate temperature maintains at 200 $\^{C}$. We define that the fine domain structure has an advantage at the high density magnetic recording because it has thermal stability due to small exchange coupling energy.

• Proceedings of the Korean Vacuum Society Conference
• /
• 1999.07a
• /
• pp.93-93
• /
• 1999

양자점(Quantum dot : QD)를 이용한 소자를 만들기 위해서는 수직방향으로의 적층이 필수적이다. 양자점의 적층은 수직적으로 같은 위치에 정렬하므로, 고려되어야 할 요소로는 양자점간의 파동함수의 중첩(coupling)에 의한 특성변화, 적층의 진행에 따른 변형(strain)의 증가로 기인되는 volcano 모양으로 나타나는 결함등이 있다. 이러한 결함은 nonradiative recombination center로 작용하여 오히려 효율이 떨어지게 되는 현상이 발생하게 되므로 본 연구에서는 적층횟수에 따른 발광효율의 변화를 조사하여 소자응용에 적절한 적층 조건을 조사하였다. 시료성장은 molecular beam epitaxy (MBE) 장치를 이용하여 GAs(100) 기판위에 GaAs buffer를 58$0^{\circ}C$에서 150nm 성장후 InAs/GaAs 양자점과 50$0^{\circ}C$에서 적층회수 1, 3, 6, 10, 15, 20회로 하였으며 적층성장 이후 GaAs cap layer를 성장하였다. GaAs spacing과 cap layer의 성장온도 역시 50$0^{\circ}C$이며 시료의 분석은 photoluminescence (PL)과 scanning transmission electron microscope (STEM)으로 하였다. 적층횟수를 바꾸어 시료를 성장하기 전에 적층횟수를 10회로 고정하고 spacing 두께를 2.8nm, 5.6nm, 11.2nm로 바꾸어 성장하여 PL 특성을 관찰하여본 결과 spacing이 2.8nm인 경우 수직적으로 정렬된 양자점 간에 coupling이 매우 커서 single layer QD의 PL peak에 비해 약 100nm 정도 파장이 증가하였고, spacing의 두께가 11.2nm 일 경우는 single layer QD와 거의 같은 파장의 빛을 방출하여 중첩이 거의 일어나지 않지만 두꺼운 spacing때문에 PL세기가 감소하였다. 한편, 적층회수에 따른 광학적 특성을 PL로 조사하여 본 결과 peak 파장은 적층횟수가 1회에서 3회로 증가했을 때는 blue shift 하다가 이후 적층이 증가함에 따라 red shift 하였다. 그리고 10층 이상의 적층에서는 excited state에서 기인된 peak이 검출되었다. 이렇나 원인은 적층수가 증가함에 따라 carrier life time이 증가하여 exciter state에 carrier가 존재할 확률이 증가하기 때문으로 생각된다. 또한 PL 세기가 다소 증가하다가 10층 이상의 경우는 다시 감소함을 알 수 있었다. 반치폭도 3층과 6층에서 가장 적은 값을 보였다. 이와 같은 결과는 결함생성과 관련하여 STEM 분석으로 해석되어질 수 있는데 6층 적층시는 양자점이 수직적으로 정렬되어 잘 형성됨을 관찰할 수 있었고 적층에 따른 크기 변화도 거의 나타나지 않았다. 그러나 10층 15층 적층시 몇가지 결함이 형성됨을 볼수 있었고 양자점의 정렬도 완전하게 이루어지지 않음을 볼 수 있었다. 그러므로 수직적층된 InAs 양자점의 광학적 특성은 성장조건에 따른 결함생성과 밀접한 관련이 있으며 상세한 논의가 이루어질 것이다.

• Journal of the Korean Orthopaedic Association
• /
• v.54 no.1
• /
• pp.1-8
• /
• 2019

Globally, the elderly population is increasing rapidly, which means that the number of deformity correction operations for elderly spine deformity patient has increased. On the other hand, for aged patients with deformity correction operation, preoperative considerations to reduce the complications and predict a good clinical outcome are not completely understood. First, medical comorbidity needs to be evaluated preoperatively with the Cumulative Illness Rating Scale for Geriatrics or the Charlson Comorbidity Index scores. Medical comorbidities are associated with the postoperative complication rate. Managing these comorbidities preoperatively decreases the complications after a spine deformity correction operation. Second, bone densitometry need to be checked for osteoporosis. Many surgical techniques have been introduced to prevent the complications associated with posterior instrumentation for osteoporosis patients. The preoperative use of an osteogenesis inducing agent - teriparatide was also reported to reduce the complication rate. Third, total body sagittal alignment need to be considered. Many elderly spine deformity patients accompanied degenerative changes and deformities at their lower extremities. In addition, a compensation mechanism induces the deformed posture of the lower extremities. Recently, some authors introduced a parameter including total body sagittal alignment, which can predict the clinical outcome better than previous parameters limited to the spine or pelvis. As a result, total body sagittal alignment needs to be considered for elderly spine deformity patients after a deformity correction operation. In conclusion, for elderly spine deformity patients, medical comorbidities and osteoporosis need to be evaluated and managed preoperatively to reduce the complication rate. In addition, total body sagittal alignment needs to be considered, which is associated with better clinical outcomes than the previous parameters limited to the spine or pelvis.

• Progress in Medical Physics
• /
• v.17 no.4
• /
• pp.192-200
• /
• 2006

We evaluated the positional accuracy of the delivered beams to the target in a phantom by simulating the whole process of the radiation treatments Including CT scanning, planning and beam exposures with MLCs. For this purpose, a phantom was made to calibrate the alignment between the CT and the attached laser system. A new, convenient method was also devised to align the setup lasers in the treatment room. Film was used for the Identification of the delivered beam and analyzed with a homemade computer program. The positional differences between the target and the beam centers varied with the couch rotations. The accelerator we used showed a maximum discrepancy of 2.0 mm at the table angle of $295^{\circ}$. The same measurements based on the new isocenter from the Winston-Lutz test resulted in the maximum of 1.35 mm for all rotation angles. The evaluation of the differences between the target and the beam centers is useful for the treatment planning.