유압구동식 버터플라이 밸브의 개폐속도 제어장치 개발

김도석,김윤철 한국특허학회 2004 특허학연구 : 한국특허학회지 Vol.6 No.3

서보 모터용 듀얼 리드 웜 감속기 설계 및 성능 평가

김도석 한국기계기술학회 2019 한국기계기술학회지 Vol.21 No.5

In case of worm reducer, the worm and worm wheel are the significant design elements. Most of the worm and worm wheel are being importer and assembled because that the localization is inadequate. As the demand increases and the necessity of localization and precision grows, to develop them is now more important things. In this study, we conducted the design, manufactured prototype and performance evaluation for worm reducer for dual lead 5.2:1 servo motor. The worm reducer is analyzed design reliability by finite element method. The performance evaluation for manufactured prototype worm reducer was conducted on the backlash, operation temperature and contact efficiency with/without load and satisfied for the all test items.

가중 거리 개념이 도입된 HCNN을 이용한 화자 독립 숫자음 인식에 관한 연구

김도석,이수영 한국통신학회 1993 韓國通信學會論文誌 Vol.18 No.10

HCNN(Hidden Control Neural Network)은 신경회로망에 의한 비선형 예측과 HMM의 segmentation 기능을 접합시킨 신경회로망 모델로서, 시간에 따라 입출력 사상 함수를 변화시킴으로써 음성 신호를 잘 모델링할 수 있도록 되어 있다. 본 논물에서는 첫째, HCNN의 성능이 HMM보다 우수함을 보이고, 둘째로, HCNN에서의 예측 오차 측정에 적절한 거리 측도를 이용하기 위해 가중거리가 도입된 HCNN을 제안하여, 화자 독립 음성 인식에 있어 그 성능이 우수함을 보였다. 여기서 가중거리는 음성 특징 벡터 각 구성 성분의 분산도 차이를 고려한 거리이다. 화자 독립 숫자음 인식 실험 결과, 유클리드 저리를 이용한 HCNN에 대해 95%의 인식율을 얻었는데, 이는 HMM에 비해 1.28% 높은 결과로서, 확률적인 제한이 가해진 HMM에 비해 시스템의 동작인 모델링을 이용한 HCNN이 더 우수함을 알 수 있다. 또한 가중거리를 이용한 CNN에 대해서는 97.35%의 인식율을 얻었는데, 이는 유클리드 거리를 이용한HCNN에 비해 2.3%가 향상된 결과이다. 가중 거리를 도입한 HCHN의 경우에 더 높은 인식율을 얻은 이유는, 오인식이 많이 되는 화자의 인식율을 높임으로써 화자간의 인식율차가 감소하게 되기 때문임을 알 수 있었고, 따라서 화자 독립 음성인식에 가중거리를 도입한 HCNN이 보다 적합합을 알 수 있다. Nonlinear mapping function of the HCNN( Hidden Control Neural Network ) can change over time to model the temporal variability of a speech signal by combining the nonlinear prediction of conventional neural networks with the segmentation capability of HMM. We have two things in this paper. first, we showed that the performance of the HCNN is better than that of HMM. Second, the HCNN with its prediction error measure given by weighted distance is proposed to use suitable distance measure for the HCNN, and then we showed that the superiority of the proposed system for speaker-independent speech recognition tasks. Weighted distance considers the differences between the variances of each component of the feature vector extraced from the speech data. Speaker-independent Korean digit recognition experiment showed that the recognition rate of 95%was obtained for the HCNN with Euclidean distance. This result is 1.28% higher than HMM, and shows that the HCNN which models the dynamical system is superior to HMM which is based on the statistical restrictions. And we obtained 97.35% for the HCNN with weighted distance, which is 2.35% better than the HCNN with Euclidean distance. The reason why the HCNN with weighted distance shows better performance is as follows : it reduces the variations of the recognition error rate over different speakers by increasing the recognition rate for the speakers who have many misclassified utterances. So we can conclude that the HCNN with weighted distance is more suit-able for speaker-independent speech recognition tasks.

Comparison of the Fluorescence Characteristics of Dye Molecules in Liquid Crystal and Conventional Solvents

김도석,심태규,김성현,Masahito Oh-e 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.4

We investigated the fluorescence characteristics of hemicyanine dye molecules in conventional solvents and in the isotropic phase of liquid-crystal 4-pentyl-4'-cyanobiphenyl. Fluorescence decay lifetime of hemicyanine in liquid crystal decreased monotonically as the temperature was increased. As compared to glycerol, the fluorescence decay lifetime of hemicyanine in the isotropic phase of liquid crystal was appreciably longer. This longer decay lifetime of hemicyanine in liquid crystal can be explained by a restricted internal rotational motion of the hemicyanine molecule due to strong interaction between the dye molecule and the liquid crystal molecules as compared to other solvents. We investigated the fluorescence characteristics of hemicyanine dye molecules in conventional solvents and in the isotropic phase of liquid-crystal 4-pentyl-4'-cyanobiphenyl. Fluorescence decay lifetime of hemicyanine in liquid crystal decreased monotonically as the temperature was increased. As compared to glycerol, the fluorescence decay lifetime of hemicyanine in the isotropic phase of liquid crystal was appreciably longer. This longer decay lifetime of hemicyanine in liquid crystal can be explained by a restricted internal rotational motion of the hemicyanine molecule due to strong interaction between the dye molecule and the liquid crystal molecules as compared to other solvents.

Direct Imaging of a Collapsed Langmuir Monolayer and Multilayer Formation

김도석,석상준,김태중,김영동,David Vaknin 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.3

Imaging ellipsometry was used to investigate the collapsed region of arachidic-acid monomolecular layers spread on the surfaces of pure water and a CaCl2 solution. We could observe the domain image of a collapsed region caused by over-compressing the Langmuir monolayers beyond the minimal closely-packed molecular area. The thicknesses of the layers obtained from the analysis were approximately integer multiples of the molecular lengths, accounting for the small tilt from the surface normal direction. The thickness of the collapsed region is proposed to depend sensitively on the existence of salt in the water subphase.

합주파수 발생 현상을 이용한 표면 분광학

김도석,Kim, Do-Seok 한국광학회 2005 광학과 기술 Vol.9 No.4

Viscosity of Sucrose Aqueous Solutions Measured by Using Fluorescence Correlation Spectroscopy

김도석,Seoncheol Cha,Sung Hyun Kim 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.4

Fluorescence correlation spectroscopy (FCS) is a technique for investigating diffusion phenomena from fluorescence fluctuation in a small volume. As the diffusion coefficient of fluorescent dye is governed by the properties of surrounding liquids, essential properties, such as the viscosity can be measured by using FCS, provided enough care is taken to account for subtle changes in the experimental conditions. We characterized the performance of FCS as a micro-viscometer by monitoring the diffusional motion of dye molecules in aqueous sucrose solutions. The viscosity values of the sucrose solutions determined by using the Stokes-Einstein relations were reliable, and their variations under different experimental conditions, such as excitation beam power and data acquisition scheme, could be clarified, demonstrating that FCS is an suitable tool for determining the viscosity of liquid systems.

Particles Size Measurements of Silole Nano-clusters by Using Fluorescence Correlation Spectroscopy

김도석,심태규,Sung Hyun Kim,Ben Zhong Tang 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.4

Fluorescence correlation spectroscopy (FCS) is a powerful tool in fundamental and applied science to measure the properties of particles diffusing in a liquid. Important parameters of the diffusive particles, such as the diffusion coefficient, particle size, and viscosity, can be directly measured by using FCS with high accuracy. Here, we used FCS to study nano-clusters of silole molecules formed by aggregation in acetone-water mixtures. The analysis of the auto-correlation of the intensity fluctuation from fluorescing nanoaggregates freely diffusing in a solution allowed the determination of the size of the clusters on a nanometer scale. Aggregate formation of silole molecules was investigated systematically by measuring the cluster sizes made at different silole concentrations and water contents.

잡음 환경에서의 음성 인식을 위한 청각 표현

김도석,이수영,길이만,Kim, Doh-Suk,Lee, Soo-Young,Kil, Rhee-M. 한국음향학회 1996 韓國音響學會誌 Vol.15 No.5

본 논문에서는 잡음 환경에서의 음성 인식을 위한 전처리기로서 청각 모델을 제안하였다. 제안된 청각 모델은 와우각 대역 통과 필터와 비선형단으로 구성되어 있으며, 잡음 환경에서도 신호의 주파수 정보와 강도 정보를 효과적으로 표현할 수 있다. 주파수 정보는 신호의 영교차 간격에 의해서, 또 강도 정보는 피크 검출기와 포화 비선형 함수에 의해서 구해진다. 영교차 간격이 교란되는 양의 분산을 교차 레벨 값의 함수로 표현함으로써 영교차 간격을 사용하는 것이 레벨 교차간격에 비해 잡음에 둔감한 특성이 있음을 보였다. 제안된 청각 모델은 다른 청각 모델에 비해 계산량이 적고, 미리 많은 파라미터를 정해줄 필요가 없다. 화자 독립 격리단어 인식 실험 결과 제안된 방법은 잡음 환경에서 우수한 성능을 보였다. An auditory model is proposed for robust speech recognition in noisy environments. The model consists of cochlear bandpass filters and nonlinear stages, and represents frequency and intensity information efficiently even in noisy environments. Frequency information of the signal is obtained by zero-crossing intervals, and intensity information is also incorporated by peak detectors and saturating nonlinearities. Also, the robustness of the zero-crossings in estimating frequency is verified by the developed analytic relationship of the variance of the level-crossing interval perturbations as a function of the crossing level values. The proposed auditory model is computationally efficient and free from many unknown parameters compared with other auditory models. Speaker-independent speech recognition experiments demonstrate the robustness of the proposed method.

반도체 패키지 기술 동향 분석과 시소타입 솔더 볼 로더에 대한 실험적 연구

김도석,이준환,우영환,이종원 중앙대학교 생산공학연구소 2000 생산공학연구소 논문집 Vol.9 No.1

전자 패키지는 반도체 산업에 있어서는 미세회로가 설계된 칩을 실제 전자기기에 실장하여 최종 제품화하는 과정이라고 볼 수 있다. 반도체 패키지는 소형화, 경량화 추세에 따라 삽입실장에서 표면실장으로 변화되었다. 대표적으로 BGA/CSP 기술은 리드프레임을 대신해 솔더볼을 면배열하는 형식의 기술이다. 볼을 면에 탑재하는 장치를 볼 마운터라고 한다. 기존에 진공흡입식의 볼마운터가 사용되었으나 CSP용 솔더볼에는 한계점을 가진다. 이에 대해 시소타입 로더는 솔더볼의 산화, 정전기, 변형에 있어 장점을 가지고 있다. 본 연구에서는 반도체 패키지의 발전동향을 분석, 검토하고 실제 솔더볼 로딩장치를 개발하여 실험을 통해 최적의 작업 조건을 알아 보았다. Electronic packaging is the art and process of creating a physical electronic product in the semiconductor industry, where integrated circuits are molded by EMC(Epoxy Mold Compound) and mounted on common base board. With the trends of miniaturing and light-weighting the package, insertion mounting is replaced by surface mounting. BGA/CSP is representative of area array package and solder balls are bumped on the die pad array. Ball mounter is solder ball bumping machine. Conventional vacuum suction type ball mounter has a limitation for bumping CSP solder ball. Seesaw type ball loader has some, advantages in oxidation, static electricity and deformation of solder ball.