그레디언트 스피커 배열을 이용한 저주파 지향성 제어

최찬규,박천일,노정규,이선희 사단법인 한국위성정보통신학회 2013 한국위성정보통신학회논문지 Vol.8 No.4

최근 미디어 컨텐츠 산업의 세계화로 예술분야에 다양한 활동이 이루어지고 있으며, 이러한 예술분야의 하나인 음향에서 스피커의중요성은 매우 높다. 스피커의 지향 특성은 음을 방사한 경우에 어느 특정 방향으로 방사되는 특성을 말하며, 공간에서 사용되는스피커의 가장 중요한 특성중 하나이다. 현재 사용되고 있는 라우드스피커(loudspeaker, 이하 스피커)의 지향 특성을 모든 주파수에서 동일하게 유지되도록 설계하는 것은 음파의 길이와 혼(horn)이나 트랜스듀서(transducer)의 크기 때문에 어려운 문제이다. 이에본 논문에서는 전기음향 설비에 있어서 실내 음향 특성에 영향을 미치는 전대역 스피커의 저주파수 지향 특성을 개선하기 위한 그레디언트 배열(gradient array) 방법을 제안하였다. Recently the globalization of the media content industry, various activities have been made in the field of art and the speakersystem is very important in the sound industry which is one of the arts. The directional characteristics of a loudspeaker referto the radiation of sound in certain directions and are among the most important features of a loudspeaker. Designing aloudspeaker that can keep all of its constant directivity at all frequencies is difficult due to the wavelengths of audiofrequencies and the size of horns and transducers. This study proposed gradient array methods to improve low frequencypattern control of full-range speakers to maximize Direct to Reverberant Ratios at the listeners.

Manufacturing yield and cost estimation of a MEMS accelerometer based on statistical uncertainty analysis

최찬규,김용일,유홍희 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.2

Manufacturing yield maximization to minimize the production cost is one of the most important objectives of manufacturing. Themanufacturing yield is the probability to manufacture products that satisfy multiple performance requirements. For a given set of productperformance requirements, its manufacturing yield can be estimated based on the system parameter uncertainties including manufacturingtolerances, which are related to the production cost. We employ three performance indices for the design of a MEMS accelerometer,and the manufacturing yield and cost are estimated using statistical uncertainty analysis methods. The effects of the MEMS accelerometerparameter uncertainties on the manufacturing yield and cost are investigated.

Precision Fault Diagnosis Procedure for a Structural System Having a Defect Employing Hidden Markov Models

최찬규,유홍희 한국정밀공학회 2014 International Journal of Precision Engineering and Vol. No.

Condition-based maintenance (CBM) is one of the most effective maintenance methods since it can minimize operation shutdownsfor maintenance. In CBM, a fault diagnosis is conducted using vibration signals caused by various fault types. To analyze signalvariations automatically and efficiently, pattern recognition methods are usually employed. Typical pattern recognition methodsemployed for CBM include the Artificial Neural Network (ANN) and the Hidden Markov Model (HMM). Among them, HMMs wereemployed in this paper to identify the size and location of a crack in a structural system. In CBM employing HMMs, feature vectorextraction is the most important step for reliable diagnosis. In this paper, Fast Fourier Transform (FFT) was employed for featurevector extraction. Even though it is relatively easy to identify the fault type, it is difficult to identify the size and location of a defectsince signal variation due to defect size or location variation is extremely small. In this paper, a diagnosis procedure to identify thesize and location of a defect is proposed. The effectiveness of the proposed method is validated using a numerical analysis model ofa rotating blade having a crack.

환경차이에 따른 밭토양중 살균제 myclobutanil 의 잔류 및 토양미생물상 변화

최찬규,정재훈,백승화,한성수 한국응용생명화학회 1994 한국응용생명화학회 학술발표회 Vol.1994 No.1

Residue level of myclobutanil[2-p-chlorophenyl-2-(1H-1,2,4-trizol-l-yl-methyl) hexane nitril] and number of soil microorganism were investigated at different environmental conditions such as the sterile and the non-sterile soils, moisture content, pH, temperature, application rate, and soil types under laboratory and field to study the effect of those factors on degradation characteristics of this fungicide and change of microflora in soil. Decomposition rate of myclobutanil was 3.9 times faster in the non-sterile soil than in the sterile soil, 1.6 times in the field than in the laboratory, 1.4 times in the concentration of 10ppm than in that of 20ppm, and 1.2 times in the clay loam soil than in the silty loam soil. Degradation rate of myclobutanil was the fastest at pH 9.0 among the tested pHs and the latest at pH 5.5. Degradation rate of myclobutanil was in order of 27℃ > 37℃ > 17℃. Otherwise, the effect of soil water content on myclobutanil degradation was found not clear. Number of microorganism in the non-sterile soil was remarkedly more than that in the sterile soil. Numbers of microbes were not significantly different between treatment plot and non-treatment plot of myclobutanil at the different conditions of soil moisture content, pH, temperature and soil type. Numbers of fungi and total microbes were more in the treatment than in the non-treatment of myclobutanil at field test but the same trends were not found at laboratory test. Within non-treatment of myclobutanil, numbers of microbes were not significantly different under the various condition of pH, application rate, and soil type in laboratory and upland field. The number of bacteria were more in 60% moisture content of water holding capacity than in 40% and the number of fungi were more in 17℃ of soil temperature than in 37℃. Within the application plot of myclobutanil, numbers of microbes were not significantly different at various pH in laboratory and upland field. The number of bacteria and total microbes were more in 80% moisture content of water holding capacity than in 40% and 60% and actinomycetes were more at 27℃ in the clay loam soil than at 17℃ in the silty loam soil.

Discovery of novel thienopyrimidine derivatives as LRRK2 inhibitors

최찬규,Jiwon Park,장소연,Jihyung Kim,이소희,Kyung Hoon Min 대한화학회 2022 Bulletin of the Korean Chemical Society Vol.43 No.2

Leucine-rich repeat kinase 2 (LRRK2) is considered a promising therapeutic target for Parkinson's disease, Crohn's disease, and cancer. Despite considerable research, none of these inhibitors are available for clinical application. Herein, we designed and synthesized novel thienopyrimidine derivatives by a bioisosteric replacement and investigated their structure?activity relationships. Thieno[3,2-d]pyrimidine derivative 22 showed the most potent inhibitory activity and inhibited both wild-type and G2019S mutant LRRK2 with IC50 values of 30 and 14?nM, respectively.

[Letter 5] 아날로그도, 디지털도 다 좋아!

최찬규 샘터사 2021 월간 샘터 Vol.616 No.-

Identification of location and size of a defect in a structural system employing active external excitation and hybrid feature vector components in HMM

최찬규,Jong Su Kim,Hong Hee Yoo 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.6

For the fault diagnosis of a mechanical system, various kinds of methods have been developed so far. For a structural system having a defect, pattern recognition methods such as Hidden Markov model (HMM) and Artificial neural network (ANN) are widely used in engineering fields. A statistical model can be constructed with one of the methods using various signals that are extracted from the structural system of interest. In the present study, a HMM employing hybrid feature vector measures is proposed for the fault diagnosis of a structural system having a defect. To obtain the hybrid feature vector components, five frequency response peaks obtained with FFT and two additional components obtained with ANN are employed. For the proposed method, an active external excitation having some specific frequency components is also applied to the structure to overcome the noise effect. To verify the effectiveness of the proposed method, a numerical model of a rotating blade having a crack is employed. Acceleration signals extracted from the structural system are employed to develop the proposed model so that the location and size of the crack can be identified. Using the proposed method, the diagnostic accuracy of the identification is significantly improved even with high level of noise in the system.

Micro SIM Card Socket에 사용된 Push-Push Type 기구의 다물체동역학 해석

최찬규,김주철,윤주영,심정길,유홍희,Choi, Chan Kyu,Kim, Ju Chul,Yun, Ju Young,Sim, Jung Kil,Yoo, Hong Hee 대한기계학회 2013 대한기계학회 논문집. Transactions of the KSME. C, 산업기술과 혁신 Vol.1 No.1

SIM card socket은 USIM 카드를 휴대폰에 고정시키기 위하여 많이 사용되며 사용자의 편의를 위하여 push-push 기구를 많이 사용하고 있다. Push-push 기구는 하트-캠 구조에 의해 작동되며 사용자가 USIM 카드를 한번 눌러주면 삽입이 되면서 locking, USIM 카드를 다시한번 눌러주면 토출이 되면서 unlocking이 되는 기구이다. Push-push 기구는 주 스프링에 의해 구동되는데 주 스프링에 의해 캠 슬라이더와 캠 스틱에 응력이 발생하여 기구가 파손되기도 한다. 따라서 push-push 기구 동작 시 발생하는 응력을 반드시 고려한 기구 설계가 필요하다. 기존의 기구 설계 방식은 정적인 응력해석 결과만 사용한 방식을 사용하였다. 하지만 기구 특성상 동작 시 충격력이 반드시 발생하기 때문에 충격력에 의해 발생하는 동응력을 해석하고 기구 설계에 반영하여야 한다. 본 논문에서는 push-push 기구 동작 시 발생하는 동응력 해석을 위하여 push-push 기구의 유연 다물체 동역학 모델을 개발하고 기구 동작 시 발생하는 동응력을 해석하였다. A SIM card socket is used for a cell phone to fix an USIM card and a push-push mechanism is typically employed in the SIM card socket for a user convenience. A SIM card is inserted with locking when a user pushes the card once and a SIM card is removed with unlocking when a user pushes the card again. A push-push mechanism is operated by a heart-cam structure and a main spring. A cam slider and a cam stick consisting a push-push mechanism may be broken because of the main spring. So, dynamic stress at a cam slider and a cam stick which is generated by a main spring during operating should be analyzed and considered in the push-push mechanism design. In this paper, a flexible multibody model of a push-push mechanism was developed to analyze dynamic stress at a cam slider and a cam stick.

Uncertainty analysis of nonlinear systems employing the first-order reliability method

최찬규,유홍희 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.1

In most mechanical systems, properties of the system elements have uncertainties due to several reasons. For example, mass, stiffness coefficient of a spring, damping coefficient of a damper or friction coefficients have uncertain characteristics. The uncertain characteristics of the elements have a direct effect on the system performance uncertainty. It is very important to estimate the performance uncertainty since the performance uncertainty is directly related to manufacturing yield and consumer satisfaction. Due to this reason, the performance uncertainty should be estimated accurately and considered in the system design. In this paper, performance measures are defined for nonlinear vibration systems and the performance measure uncertainties are estimated employing the first order reliability method (FORM). It was found that the FORM could provide good results in spite of the system nonlinear characteristics. Comparing to the results obtained by Monte Carlo Simulation (MCS), the accuracy of the uncertainty analysis results obtained by the FORM is validated.

Micro SIM socket 에 사용된 push-push 기구의 동작 패턴에 따른 동응력 및 진동해석

최찬규(Chan Kyu Choi),김주철(Ju Chul Kim),김도준(Do Jun Kim),윤주영(Ju Young Yun),유홍희(Hong Hee Yoo) 한국소음진동공학회 2013 한국소음진동공학회 학술대회논문집 Vol.2013 No.4