• 정보처리학회논문지A
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• 제14A권1호
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• pp.73-76
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• 2007

단위원의 내부로부터 Jordan 영역으로의 등각사상을 구하는 것은 일반적으로 비선형방정식인 Theodorsen 방정식을 푸는 것으로 귀결된다. 저자는 이 비선형 방정식의 수치적 해법 중 가장 효율적인 방법으로 알려진 Wegmann의 해법에 저주파 필터를 적용하여 개선하고 새로운 산법의 수렴성을 이론적으로 증명한 바 있다[1, 2]. 또한 이 해법에 있어 참값을 모르더라도 오차평가가 가능한 방법을 제안하였다[3]. 본 논문에서는 참값을 모르더라도 오차평가가 가능한 연구결과를 이용하여 주어진 문제영역과 허용오차에 따라 자동으로 수치등각사상이 결정되는 알고리즘을 제안한다. 이 알고리즘에서는 지금까지 경험에 의존했었던 표본수와 저주파 필터 파라메터가 주어진 문제영역에 따라 자동으로 결정된다. 이것은 문제의 난이도가 문제영역의 변형에 의존한다는 전제로 문제영역의 모양을 결정하는 함수를 Fourier 급수로 전개, 분석하여 얻을 수 있다. 수치실험을 통해 그 유효성을 입증한다.

• The Journal of Advanced Prosthodontics
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• 제1권1호
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• pp.26-30
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• 2009

STATEMENT OF PROBLEM. Qualitative and semi-quantitative methods have been developed for TMJ sound classification, but the criteria presented are completely inhomogeneous. Thus, to develop more objective criteria for defining TMJ sounds, electroacoustical systems have been developed. We used Joint vibration analysis in the BioPAK system(Bioresearch Inc., Milwaukee, USA) as the electrovibratography. PURPOSE. The aim of this study was to examine the TMJ sounds with repect to frequency spectra patterns and the integral > 300 Hz /< 300 Hz ratios via six-months follow-up. MATERIAL AND METHODS. This study was done before and after the six-months recordings with 20 dental school students showed anterior disk displacement with reduction. Joint vibrations were analyzed using a mathematical technique known as the Fast Fourier Transform. RESULTS. In this study Group I and Group II showed varied integral > 300 /< 300 ratios before and after the six-months recordings. Also, by the comparative study between the integral > 300 /< 300 ratios and the frequency spectrums, it was conceivable that the frequency spectrums showed similar patterns at the same location that the joint sound occurred before and after the six-months recordings. while the frequency spectrums showed varied patterns at the different locations that the joint sound occurred before and after six-month recordings, it would possibly be due to the differences in the degree of internal derangement and/or in the shape of the disc. CONCLUSIONS. It is suggested that clinicians consider the integral > 300 /< 300 ratios as well as the frequency spectrums to decide the starting-point of the treatment for TMJ sounds.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2003년도 Proceeding
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• pp.223-230
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• 2003

Feature-based similarity retrieval has become an important research issue in multimedia database systems. The features of multimedia data are useful for discriminating between multimedia objects (e 'g', documents, images, video, music score, etc.). For example, images are represented by their color histograms, texture vectors, and shape descriptors, and are usually high-dimensional data. The performance of conventional multidimensional data structures(e'g', R- Tree family, K-D-B tree, grid file, TV-tree) tends to deteriorate as the number of dimensions of feature vectors increases. The R＊-tree is the most successful variant of the R-tree. In this paper, we propose a SOM-based R＊-tree as a new indexing method for high-dimensional feature vectors.The SOM-based R＊-tree combines SOM and R＊-tree to achieve search performance more scalable to high dimensionalities. Self-Organizing Maps (SOMs) provide mapping from high-dimensional feature vectors onto a two dimensional space. The mapping preserves the topology of the feature vectors. The map is called a topological of the feature map, and preserves the mutual relationship (similarity) in the feature spaces of input data, clustering mutually similar feature vectors in neighboring nodes. Each node of the topological feature map holds a codebook vector. A best-matching-image-list. (BMIL) holds similar images that are closest to each codebook vector. In a topological feature map, there are empty nodes in which no image is classified. When we build an R＊-tree, we use codebook vectors of topological feature map which eliminates the empty nodes that cause unnecessary disk access and degrade retrieval performance. We experimentally compare the retrieval time cost of a SOM-based R＊-tree with that of an SOM and an R＊-tree using color feature vectors extracted from 40, 000 images. The result show that the SOM-based R＊-tree outperforms both the SOM and R＊-tree due to the reduction of the number of nodes required to build R＊-tree and retrieval time cost.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 금형가공,미세가공,플라스틱가공 공동 심포지엄
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• pp.35-40
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• 2005

The demand for small and high-capacity optical data storage devices has rapidly increased. The areal density of optical disk is increased using higher numerical aperture objective lens and shorter wavelength source. A wafer-scale stacked micro objective lens with a numerical aperture of 0.85 and a focal length of 0.467mm for the 405nm blue- violet laser was designed and fabricated. A diffractive optical element (DOE) was used to compensate the spherical aberration of the objective lens. Among the various fabrication methods for micro DOE, the UV-replication process is more suitable for mass-production. In this study, an 8-stepped DOE pattern as a master was fabricated by photolithography and reactive ion etching process. A flexible mold was fabricated for improving the releasing properties and shape accuracy in UV-molding process. In the replication process, the effects of exposing time and applied pressure on the replication quality were analyzed. Finally, the shapes of master, mold and molded pattern were measured by optical scanning profiler. The deviation between the master and the molded DOE was less than 0.1um. The efficiency of the molded DOE was measured by DOE efficiency measurement system which consists of laser source, sample holder, aperture and optical power meter, and the measured value was $84.5\%$.

• 한국소음진동공학회논문집
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• 제12권11호
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• pp.833-839
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• 2002

As the demand for slim laptops requires low-height optical disc drives, vibration problems of optical disc drives are of great concern. Additionally, with the decrease of a track width and a depth of focus in high density drives, studies on vibration resonance between mechanical parts become more important. From the vibration point of view, the performance of optical disc drives is closely related with the relative displacement between a disc and an objective lens which is controlled by servo mechanism. In other words, to read and write data properly, the relative displacement between an optical disc and an objective lens should be within a certain limit. The relative displacement is dependent on not only an anti-vibration mechanism design but also servo control capability. Good servo controls can make compensation for poor mechanisms, and vice versa. In a usual development process, robustness of the anti-vibration mechanism is always verified with the servo control of an objective lens. Engineers partially modify servo gain margin in case of a data reading error. This modification cannot correct the data reading error occasionally and the mechanism should be redesigned more robustly. Therefore it is necessary to verify a mechanism with respect to the possible servo gain plot. In this study we propose the experimental verification method for anti-vibration mechanism with respect to the existing servo gain plot. Thismethod verifies axial vibration characteristics of optical disc drives on the basis of transmissibility. Using this method, we verified our mechanism and modified the mechanism for better anti-vibration characteristics.

• 한국음향학회지
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• 제38권4호
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• pp.467-475
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• 2019

고출력의 초음파는 매질을 진행하면 음향 흐름과 음향 방사힘을 만들어낸다. 공기를 매질로 하는 3차원 공간상에 음향 방사힘을 발생시키면 입체적인 촉감을 형성할 수 있으므로 공간적인 정보를 직접 피부에 촉각으로 전달할 수 있다. 본 논문은 40 kHz의 작은 초음파 송신자 154개를 묶어 오목한 형태로 배열시켜서 초음파를 송신하여 집속초점에서 음향 방사힘을 발생시켰다. 초음파 음장의 초점의 근처에서 음향 방사힘에 의한 촉각을 확인하였다. 촉각 감도를 올리기 위하여 송신 초음파를 60 Hz의 구형파로 진폭 변조를 하였다. 초음파 촉각의 응용으로 음향 방사힘이 형성되는 허공에 촉각이 감지되는 영역을 형성시켜서, 손의 위치를 지정하는 지시자로 사용하였다. 촉각이 감지되는 초점위치에 있는 손의 모양을 영상 입력으로 받아서 손가락의 개수를 기계에 피드백하는 시스템을 구현함으로써 초음파를 이용한 촉각의 유용성을 확인하였다.

• 한국터널지하공간학회 논문집
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• 제22권1호
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• pp.91-105
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• 2020

본 연구는 Shield TBM의 챔버 내 교반봉의 영향범위 및 배토효율 향상을 위한 기초연구이다. 현재 국내Shield TBM의 연구에 있어 디스크 커터, 커터 비트, 세그먼트에 관한 연구는 많이 이루어져 있다. 하지만 Shield TBM 굴착 시 막장면에서 유입되는 토사 및 암반들을 교반시켜 스크류 컨베이어로 배토시키는 연구는 해외에 비해 미비하다. 본 연구에서는 기존 Shield TBM 챔버를 축소모형으로 제작하여 실험을 진행하였다. 챔버 내부는 크기(4 mm, 6 mm, 8 mm, 10 mm)와 색(검은색, 흰색, 빨간색, 파란색)이 다른 시료를 사용해 층을 형성하였다. 이에 대하여 RPM과 교반봉의 형상 및 크기에 차이를 두어 실험을 진행하였다. 또한 중력의 방향이 교반 효율에 끼치는 영향을 파악하기 위하여 축소모형을 세웠을 때와 눕혔을 때의 교반 차이를 확인해 보았다. 이는 중력방향의 차이 외의 다른 조건은 모두 동일하게 진행하였다. 본 실험을 통해 챔버모형의 설치 방향, 내부의 교반봉 크기 및 형상, RPM에 따른 교반효과 및 Torque를 파악하였다. 교반효과 및 Torque를 비교 검토한 결과 교반봉의 형상 및 크기는 시료의 교반에 영향을 끼치며, 중력방향은 Torque에 영향을 끼치는 것을 확인하였다.

• 한국자기학회지
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• 제13권4호
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• pp.182-186
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• 2003

펄스자장종축성형법(pulse die press, PDP)을 이용하여 32 wt%RE-67 wt%TM-1 wt%B(RE: 희토류원소, TM: 30천이금속)조성을 갖는 소결자석을 제조함에 있어서 자장성형시 분말의 탭밀도, 성형밀도, 인가자장세기 및 인가방법의 변화에 따라 얻어지는 자석의 배향율과 감자곡선상의 각형성 변화를 조사하였다. 출발합금 제조방법으로서 strip casting process에 의하여 $\alpha$-Fe 편석없이 미세하고 균일한 조직을 갖는 합금 flake가 얻어졌고, 합금 flake를 수소처리한 후 고압가스를 이용한 건식분쇄방법(jet mill)에 의하여 평균입도, 표준편차가 각각 3.65 $\mu\textrm{m}$, 1.39인 미세하고 균일한 입도의 분말로 제조하였다. 제조된 분말은 30-50 kOe치 고펄스자장에 의하여 분말을 배향시키고 동일한 펄스자장을 인가하면서 종축성형을 실시함으로써 배향율을 향상시킬 수 있었다. 결과적으로 32 wt%RE조성의 분말을 이용하여 종전의 자장성형방법인 TDP(transverse die press)와 본 연구에서 제안된 PDP에 의하여 제조된 자석의 최대자기에너지적은 각각 42.0 MGOe 및 44.8 MGOe가 얻어져, PDP가 분말의 배향율과 감자곡선상의 각 형성을 향상시키는데 효과적인 자장성형방법임을 알 수 있었다.

• 천문학회지
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• 제29권spc1호
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• pp.63-64
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• 1996

The nature of distant faint blue field galaxies remains a mystery, despite the fact that much attention has been devoted to this subject in the last decade. Galaxy counts, particularly those in the optical and near ultraviolet bandpasses, have been demonstrated to be well in excess of those expected in the 'no-evolution' scenario. This has usually been taken to imply that galaxies were brighter in the past, presumably due to a higher rate of star formation. More recently, redshift surveys of galaxies as faint as B$\~$24 have shown that the mean redshift of faint blue galaxies is lower than that predicted by standard evolutionary models (de-signed to fit the galaxy counts). The galaxy number count data and redshift data suggest that evolutionary effects are most prominent at the faint end of the galaxy luminosity function. While these data constrain the form of evolution of the overall luminosity function, they do not constrain evolution in individual galaxies. We are carrying out a series of observations as part of a long-term program aimed at a better understanding of the nature and amount of luminosity evolution in individual galaxies. Our study uses the luminosity-linewidth relation (Tully-Fisher relation) for disk galaxies as a tool to study luminosity evolution. Several studies of a related nature are being carried out by other groups. A specific experiment to test a 'no-evolution' hypothesis is presented here. We have used the AUTOFIB multifibre spectro-graph on the 4-metre Anglo-Australian Telescope (AAT) and the Rutgers Fabry-Perot imager on the Cerro Tolalo lnteramerican Observatory (CTIO) 4-metre tele-scope to measure the internal kinematics of a representative sample of faint blue field galaxies in the red-shift range z = 0.15-0.4. The emission line profiles of [OII] and [OIII] in a typical sample galaxy are significantly broader than the instrumental resolution (100-120 km $s^{-l}$), and it is possible to make a reliable de-termination of the linewidth. Detailed and realistic simulations based on the properties of nearby, low-luminosity spirals are used to convert the measured linewidth into an estimate of the characteristic rotation speed, making statistical corrections for the effects of inclination, non-uniform distribution of ionized gas, rotation curve shape, finite fibre aperture, etc.. The (corrected) mean characteristic rotation speed for our distant galaxy sample is compared to the mean rotation speed of local galaxies of comparable blue luminosity and colour. The typical galaxy in our distant sample has a B-band luminosity of about 0.25 L$\ast$ and a colour that corresponds to the Sb-Sd/Im range of Hub-ble types. Details of the AUTOFIB fibre spectroscopic study are described by Rix et al. (1996). Follow-up deep near infrared imaging with the 10-metre Keck tele-scope+ NIRC combination and high angular resolution imaging with the Hubble Space Telescope's WFPC2 are being used to determine the structural and orientation parameters of galaxies on an individual basis. This information is being combined with the spatially resolved CTIO Fabry-Perot data to study the internal kinematics of distant galaxies (Ing et al. 1996). The two main questions addressed by these (preliminary studies) are: 1. Do galaxies of a given luminosity and colour have the same characteristic rotation speed in the distant and local Universe? The distant galaxies in our AUTOFIB sample have a mean characteristic rotation speed of $\~$70 km $s^{-l}$ after correction for measurement bias (Fig. 1); this is inconsistent with the characteristic rotation speed of local galaxies of comparable photometric proper-ties (105 km $s^{-l}$) at the > $99\%$ significance level (Fig. 2). A straightforward explanation for this discrepancy is that faint blue galaxies were about 1-1.5 mag brighter (in the B band) at z $\~$ 0.25 than their present-day counterparts. 2. What is the nature of the internal kinematics of faint field galaxies? The linewidths of these faint galaxies appear to be dominated by the global disk rotation. The larger galaxies in our sample are about 2"-.5" in diameter so one can get direct insight into the nature of their internal velocity field from the $\~$ I" seeing CTIO Fabry-Perot data. A montage of Fabry-Perot data is shown in Fig. 3. The linewidths are too large (by. $5\sigma$) to be caused by turbulence in giant HII regions.

• 농약과학회지
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• 제16권4호
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• pp.282-287
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• 2012

본 실험은 배부식 분무기 노즐 종류를 달리하여 농약을 살포하였을 경우 작물 중 농약잔류량에 미치는 영향을 구명하기 위해 수행하였다. 배부식 인력분무기의 2구 디스크형 노즐과 배부식 동력분무기의 2구 선형노즐을 분구형상에 따라 I형은 분구가 하나, II형은 분구가 둘, III형은 분구가 셋으로 3가지 유형으로 구분하여 분무입경과 시간당 분무량을 조사하였다. 선형노즐 II형(상표명: D-3)이 압력 $1.1{\pm}0.2$ MPa에서 분무입경 $76{\mu}m$, 단위 시간당 약제 살포량 2.4 L/min.으로, 선형노즐 II형 (상표명: D-35)가 압력 $1.0{\pm}0.2$ MPa에서 분무입경 $90{\mu}m$, 단위 시간당 약제 살포량 2.6 L/min.으로 적정하다고 판단되었다. D-3의 분구 크기는 0.65 mm length ${\times}$ 0.45 mm width이고 D-35의 분구 크기는 0.62 mm length ${\times}$ 0.46 mm width 이였다. 들깻잎을 대상으로 노즐별 imidacloprid의 잔류량 차이를 비교하여 유의수준 5%에서 잔류량의 차이가 있었다. 디스크형 노즐과 선형노즐 I형이 $3.76{\sim}3.92mg\;kg^{-1}$으로 선형노즐 II형과 III형의 $4.52{\sim}4.92mg\;kg^{-1}$보다 잔류량이 적었다. 분무 노즐을 달리하여 농약살포시 들깻잎 중 잔류량의 차이가 있다고 판단되었다.