• Animal Bioscience
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• 제36권9호
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• pp.1435-1444
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• 2023

Objective: This study was conducted to evaluate Raman spectroscopy technique as a noninvasive tool to predict meat quality traits on Braford longissimus thoracis et lumborum muscle. Methods: Thirty samples of muscle from Braford steers were analyzed by classical meat quality techniques and by Raman spectroscopy with 785 nm laser excitation. Water holding capacity (WHC), intramuscular fat content (IMF), cooking loss (CL), and texture profile analysis recording hardness, cohesiveness, and chewiness were determined, along with fiber diameter and sarcomere length by scanning electron microscopy. Warner-Bratzler shear force (WBSF) analysis was used to differentiate tender and tough meat groups. Results: Higher values of cohesiveness and CL, together with lower values of WHC, IMF, and shorter sarcomere were obtained for tender meat samples than for the tougher ones. Raman spectra analysis allows tender and tough sample differentiation. The correlation between the quality attributes predicted by Raman and the physical measurements resulted in values of R² = 0.69 for hardness and 0,58 for WBSF. Pearson's correlation coefficient of hardness (r = 0.84) and WBSF (r = 0.79) parameters with the phenylalanine Raman signal at 1,003 cm^-1, suggests that the content of this amino acid could explain the differences between samples. Conclusion: Raman spectroscopy with 785 nm laser excitation is a suitable and accurate technique to identify beef with different quality attributes.

• 한국음향학회지
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• 제29권2호
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• pp.148-153
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• 2010

음성 신호처리 환경에서 잡음이 섞인 신호를 개선할 목적으로 음성향상 기법이 많이 이용되고 있다. 잡음추정 알고리즘은 변화하는 환경에 빠르게 적응할 수 있어야 하며 음성신호의 영향을 줄이기 위해 음성신호가 존재하지 않는 구간에서만 잡음의 파워를 갱신한다. 이러한 방법은 음성구간검출이 선행되어야 한다. 그러나 잡음에 열화된 음성신호에 묵음구간이 존재하지 않을 경우, 위와 같이 음성검출을 통한 묵음구간에서의 잡음 추정 방법 및 SNR 추정 방법이 적용될 수 없다. 본 논문에서는 묵읍구간이 존재하지 않는 연속음성신호에서 SNR을 추정하는 기법을 제안한다. 음성신호는 MBE(Multi-Band Excitation) 발성 모델에 따라 유 무성음으로 구분할 수 있다. 그리고 에너지가 유성음에 대부분 분포하기 때문에, 부가성 잡음환경에서 유성음의 에너지를 음성신호의 에너지로 근사화하여 SNR을 추정할 수 있다. 제안하는 방식은 연속음성신호를 IMBE (Improved Multi-Band Exciation) 보코더를 이용해 유 무성음 대역으로 구분하고, 각각 대역의 에너지 정보를 아용하여 단구간 음성신호의 SNR을 계산한다. 전체 음성구간의 SNR은 단구간 SNR의 평균값을 통해 추정한다.

• 한국항공우주학회지
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• 제46권8호
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• pp.639-651
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• 2018

본 논문은 인공위성의 자세명령을 해석적으로 생성하는 기법을 제안한다. 실제 위성에서는 1) 구동기 성능, 2) 위성체 유연구조, 3) 원격명령 데이터크기 등과 같은 제한조건들이 존재하고, 이로 인해 해석적인 자세명령 해를 구하기 어렵다. 따라서 본 논문에서는 고유축 회전, 프로파일 형상화를 통해 문제를 단순화하는 방법을 제안하고, 최종적으로 해석적 해를 유도하였다. 생성된 자세명령은 온-보드 자세제어기의 피드포워드 입력 형태로 사용되어 위성의 기동성을 높일 수 있다. 각속도 경계조건에 따라 rest-to-rest 기동과 spin-to-spin 기동으로 나누어 자세명령 해를 유도하였다. 시뮬레이션 예제를 통해 제안된 자세명령생성 기법이 구동기 제한조건을 지키면서 초기/최종 시간에서의 경계조건도 잘 만족하는 것을 확인하였다. 제안된 해석 해는 자세명령을 비교적 적은 수의 파라미터로 구현할 수 있어 원격명령 데이터크기 측면에서 경쟁력이 있다. 또한, 해석 해로 반복계산이 필요없어 온-보드 자세명령생성 자동화에도 기여할 수 있을 것으로 판단된다.

• 대한기계학회논문집A
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• 제29권2호
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• pp.270-276
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• 2005

This paper develops the flexible computational model of a heavy truck by interfacing the frame modeled as a flexible body to the heavy truck's computational model composed of rigid bodies. The frame is modeled by the finite element method. Three torsional modes and three bending modes of the frame are considered for the interface of the heavy truck's computational model. The actual vehicle test is conducted off road with a velocity of 20km/h. The vertical accelerations at the cab and front axle are measured in the test. For the verification of the developed computational model, the measured vertical acceleration profiles are compared with the simulation results of the heavy truck's flexible computational model. E grade irregular road profile of ISO is used as an excitation input in the simulation. The verified flexible computational model is used to compare the vibration characteristics of a front suspension system having a multi-leaf spring and that having a tapered leaf spring. The comparison results show that the front suspension having a tapered leaf spring has a higher vertical acceleration at the front axle but a lower vertical acceleration at the cab than the suspension system having a multi-leaf spring.

• Applied Science and Convergence Technology
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• 제24권4호
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• pp.111-116
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• 2015

The graphene oxide (GO) and graphene oxide quantum dots (GOQDs), which have gained research interest as new types of light-emitting materials, were synthesized by the modified Hummers method for oxidation of graphite flake and graphite nanoparticle. The optical properties of GO and GOQDs have been compared by mean of photoluminescence (PL), PL excitation (PLE), UV-vis absorbance, and time-resolved PL. The GO have an absorption peak at 229 nm and shoulder part at 310 nm, whereas the GOQDs show broad absorption with a gradual change up without any absorption peaks. The PL emission of GOQDs and GO showed the green color at 520 nm and the red color at 690 nm, respectively. The red emission of GO showed faster PL decay time than the green emission of GOQDs. In particular, the temporal PL profile of the GO showed redshift from 560 nm to 660 nm after the pump event.

• Wind and Structures
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• 제11권4호
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• pp.303-321
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• 2008

When first commissioned, the 1.6 km span 275kV Severn Crossing Conductor experienced large amplitude vibrations in certain wind conditions, but without ice or rain, leading to flashover between the conductor phases. Wind tunnel tests undertaken at the time identified a major factor was the lift generated in the critical Reynolds number range in skew winds. Despite this insight, and although a practical solution was found by wrapping the cable to change the aerodynamic profile, there remained some uncertainty as to the detailed excitation mechanism. Recent work to address the problem of dry inclined cable galloping on cable-stayed bridges has led to a generalised quasi-steady galloping formulation, including effects of the 3D geometry and changes in the static force coefficients in the critical Reynolds number range. This generalised formulation has been applied to the case of the Severn Crossing Conductor, using data of the static drag and lift coefficients on a section of the stranded cable, from the original wind tunnel tests. Time history analysis has then been used to calculate the amplitudes of steady state vibrations for comparison with the full scale observations. Good agreement has been obtained between the analysis and the site observations, giving increased confidence in the applicability of the generalised galloping formulation and providing insight into the mechanism of galloping of yawed and stranded cables. Application to other cable geometries is also discussed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 학술대회 논문집 정보 및 제어부문
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• pp.270-272
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• 2005

In this paper, we proposed a new method detecting actions of some components driven by the coil excitation. Nuclear power reactors are typically controlled by the movement of several neutron-absorbing control rods into or out of the reactor core. For moving control rods, we use an electromagnetic-jack-typed mechanism, which is called Control Rod Drive Mechanism. This mechanism moves control rods by the step composed of sequential actions of components. In case any mechanical problems happen in the mechanism, the orders for the control rod movement from the higher system cannot be performed properly. This abnormal state must be monitored and the sequential actions of the components can be the monitoring target. The actions of components generate some deviations in the profiles of the currents flowing into the coils in the mechanism. We focused on this phenomena and devised a new method of detecting the actions of the components in Control Rod Drive Mechanism by using the wavelet transform for observing the current profile.

• JSTS:Journal of Semiconductor Technology and Science
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• 제6권3호
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• pp.162-168
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• 2006

To fabricate nanometer scale InGaAs HEMTs, we have successfully developed various novel nano-patterning techniques, including sidewall-gate process and e-beam resist flowing method. The sidewall-gate process was developed to lessen the final line length, by means of the sequential procedure of dielectric re-deposition and etch-back. The e-beam resist flowing was effective to obtain fine line length, simply by applying thermal excitation to the semiconductor so that the achievable final line could be reduced by the dimension of the laterally migrated e-beam resist profile. Applying these methods to the device fabrication, we were able to succeed in making 30nm $In_{0.7}Ga_{0.3}As$ HEMTs with excellent $f_T$ of 426GHz. Based on nanometer scale InGaAs HEMT technology, several high performance millimeter-wave integrated circuits have been successfully fabricated, including 77GHz MMIC chipsets for automotive radar application.

• 한국기계가공학회지
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• 제11권3호
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• pp.116-121
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• 2012

In recent years, world is faced with a transportation energy dilemma, and the transportation is dependent on a single fuel - petroleum. However, Hybrid Electric Vehicle(HEV) technology holds more advantages to reduce the demand for petroleum in the transportation by efficiency improvements of petroleum consumption. Therefore, there is a trend that lower gear noise levels are demanded in HEV for drivers to avoid annoyance and fatigue during operation. And meshing transmission error(T.E.) is the excitation that leads to the tonal noise known as gear whine, and radiated gear whine is also the dominant source of noise in the whole gearbox. This paper presents a method for the analysis of gear tooth profile and lead modification, and the predictions of transmission error and load distribution are shown under one loaded torque for the 1st gear pair of HEV gearbox. The test is also obtained before tooth micro-modification under the torque. At last, the appropriate tooth modification is used to minimize the transmission error and load distribution under the loaded torque. It is a good approach which the simulated result is used to improve the design in order to minimize the radiation gear whine noise.

• Journal of Advanced Marine Engineering and Technology
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• 제34권8호
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• pp.1057-1067
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• 2010

다단 기어연쇄, 베어링, 축, 로터로 구성되는 함포용 synchro system의 구동장치를 개발하기 위하여, AGMA규격에 의한 기어 굽힘강도, 면압강도해석, 기어치형설계를 포함한 정적설계를 수행하였다. 또한 전달행렬법을 효과적으로 적용시킬 수 있는 Hibner's branch법과 자유도가 큰 경우에도 계산 오차 없이 고유특성치를 빠뜨리지 않고 산출할 수 있는 ${\lambda}$-matrix법을 도입하여 함포용 Synchro system의 좌우 선회용과 상하 고각형의 위험속도 해석 및 평가를 하였고, 운전속도 범위 내에 위험속도가 존재하지 않았다.