• 한국포장학회지
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• 제7권2호
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• pp.25-30
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• 2001

Corrugated board is composed of cellulose fibers which are arranged with the same direction as the board manufactured. The direction is classified with machine direction (MD) and cross-machine direction (CD). Therefore, corrugated board is orthotropic material that has totally different strength properties at each direction and especially, at machine direction, the mechanical properties of fiberboard is superior. The compression strength of the corrugated fiberboard boxes is very important information to the manufacturers and the end users. This study was carried out to design the optimum pattern, size, and location of ventilating hole for ventilating container through the finite element analysis. The optimum pattern and location of ventilating and hand hole were vertical oblong, a short distance to the right and left from the center of panel, and center or a short distance to the top of both sides, respectively. We identified the effect on both stress dispersion and stress level from the analysis of redisigned hand hole.

• 한국태양에너지학회 논문집
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• 제31권5호
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• pp.1-8
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• 2011

In this study, we performed a sensitivity analysis to see how the true north error of a wind direction vane installed to a meteorological mast affects predictions of the annual-average wind speed and the annual energy production. For this study, two meteorological masts were installed with a distance of about 4km on the ridge in complex terrain and the wind speed and direction were measured for one year. Cross predictions of the wind speed and the AEP of a virtual wind turbine for two sites in complex terrain were performed by changing the wind direction from $-45^{\circ}$ to $45^{\circ}$with an interval of $5^{\circ}$. A commercial wind resource prediction program, WindPRO, was used for the study. It was found that the prediction errors in the AEP caused by the wind direction errors occurred up to more than 20% depending on the orography and the main wind direction at that site.

• 제어로봇시스템학회논문지
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• 제16권5호
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• pp.463-468
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• 2010

An obstacle avoidance method for a mobile robot is proposed in this paper. Our research was focused on the obstacles that can be found indoors since a robot is usually used within a building. It is necessary that the robot maintain the desired direction after successfully avoiding the obstacles to achieve a good autonomous navigation performance for the specified project mission. Sensors such as laser, ultrasound, and PSD (Position Sensitive Detector) can be used to detect and analyze the obstacles. A PSD sensor was used to detect and measure the height and width of the obstacles on the floor. The PSD sensor was carefully calibrated before measuring the obstacles to achieve better accuracy. Data obtained from the repeated experiments were used to plot an error graph which was fitted to a polynomial curve. The polynomial equation was used to navigate the robot. We also obtained a direction-error model of the robot after avoiding the obstacles. The prototypes for the obstacle and direction-error were modeled using a neural network whose inputs are the obstacle height, robot speed, direction of the wheels, and the error in direction. A mobile robot operated by a notebook computer was setup and the proposed algorithm was used to navigate the robot and avoid the obstacles. The results showed that our algorithm performed very well during the experiments.

• 방송공학회논문지
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• 제27권1호
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• pp.91-103
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• 2022

음원의 음량, 방향 및 음원까지의 거리와 같은 음원의 특성을 인식하는 것은 자율주행차, 로봇 시스템, AI 스피커 등 무인 시스템에서 중요한 기술 중의 하나이다. 음원의 방향이나 거리를 인식하는 방법은 레이다, 라이더, 초음파 및 고주파와 소리를 이용하는 방법이 있다. 그러나 이러한 방법은 신호를 발신하여야 하며, 장애물에 의한 비가시 영역에서 발생하는 음원은 정확하게 인식할 수 없다. 본 논문에서는 비가시 영역을 포함한 주변에서 발생하는 음원의 음량, 방향 및 음원까지의 거리를 인식하는 방법으로 가청 주파수 대역의 소리를 검출하여 인식하는 방법을 구현하고 평가하였다. 음원을 인식하기 위하여 주로 사용하는 교차형 기반의 음원인식 알고리즘은 음원의 음량과 방향을 인식할 수 있으나 사각영역이 발생하는 문제가 있다. 뿐만아니라 이 알고리즘은 음원까지의 거리를 인식할 수 없다는 제약이 있다. 이러한 기존 방법의 한계를 탈피하기 위하여, 본 논문에서는 교차형 기반의 알고리즘보다 더 발전된 직사각형 기법을 사용한 QRAS 기반의 알고리즘으로 음원의 음량, 방향 및 음원까지의 거리를 인식하여 음원의 특성을 파악할 수 있는 음원인식 알고리즘을 제안한다. 전방향 음원인식을 위한 QRAS 기반의 알고리즘은 직사각형으로 배치된 4개의 음향센서에 의하여 도출되는 6쌍의 음향 도착 시간차를 사용한다. QRAS 기반의 알고리즘은 기존 교차형 기반의 알고리즘으로 음원을 인식할 때 발생하는 사각영역과 같은 문제점을 해결할 수 있으며, 음원까지의 거리도 인식할 수 있다. 실험을 통하여 제안된 전방향 음원 인식을 위한 QRAS 기반의 알고리즘은 사각영역없이 음원의 음량, 방향 및 음원까지의 거리를 인식할 수 있음을 확인하였다.

• 대한기계학회논문집
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• 제13권5호
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• pp.991-998
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• 1989

본 연구에서는 충돌각을 변수로 한 실험적 연구를 수행하기 위하여 여타의 변수를 고정하였으며, 유속은 R$_{e}$=5.2*$10^{4}$의 결과를 제시하였다.

• International Journal of Precision Engineering and Manufacturing
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• 제2권1호
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• pp.87-93
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• 2001

A reliable analytic model that determines the exit cross sectional shape a workpiece(material) in round-oval (oroval-round) pass sequence has been developed. The exit cross sectional shape of an outgoing workpiece is predicted by using the linear interpolation of the radius of curvature of an incoming workpiece and that of roll groovw to the roll axis direction. The requirements placed on the choice of the weighting function were to ensure boundary conditions specified. The validity of the analytic model has been examined by not rod rolling experiment with the roll gap and specimen size changed. The exit cross sectional shape and area of the workpiece predicted by the proposed analytic model were good agreement with those obtained experimentally. We found that the analytic model has not only simplicity and accuracy for practical usage but also save a large amount of computational time compared with finite element method.

• 로봇학회논문지
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• 제9권4호
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• pp.206-215
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• 2014

Acoustic signal is crucial for the autonomous navigation of underwater vehicles. For this purpose, this paper presents a method of acoustic source localization. The proposed method is based on the probabilistic estimation of time delay of acoustic signals received by two hydrophones. Using Bayesian update process, the proposed method can provide reliable estimation of direction angle of the acoustic source. The acquired direction information is used to estimate the location of the acoustic source. By accumulating direction information from various vehicle locations, the acoustic source localization is achieved using extended Kalman filter. The proposed method can provide a reliable estimation of the direction and location of the acoustic source, even under for a noisy acoustic signal. Experimental results demonstrate the performance of the proposed acoustic source localization method in a real sea environment.

• 대한음성학회지:말소리
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• 제67호
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• pp.121-133
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• 2008

To estimate directions of multi-sound sources, we consider an approach based on zero crossings which provided more robust results to diffuse noise than the conventional cross-correlation-based method [6][7]. In reverberant environments, the performance of source direction estimation can be improved by using signal components through direct paths from sources to microphones. Since a cepstral prefiltering technique [8] removes the effect of reverberation, we propose a source direction estimation method which can find out intervals of the direct-path components by comparing original and cepstral-prefiltered envelopes. Simulations demonstrate that the proposed method can improve the performance of source direction estimation in reverberant environments.

• 말소리와 음성과학
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• 제3권3호
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• pp.109-114
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• 2011

To estimate sound direction of arrival with a pair of microphones, a method based on Time Difference of Arrival (TDOA) estimation using the Cross Power Spectrum Phase (CPSP) function is largely used due to its simplicity and good performance. In this paper, we investigate CPSP maximum values for various SNRs and adverse environments, and propose a novel method to improve the estimation performance of sound direction of arrival. The proposed method applies a threshold to the CPSP values and increases the reliability of the estimated sound direction. Through computer simulation for various SNRs, we validate the effectiveness of the proposed method. When the threshold was set to 0.1, more than 90% of success rate of sound direction of arrival estimation has been achieved for directions of $10^{\circ}$, $40^{\circ}$, $70^{\circ}$ from the source location even with reverberation times of 0.1s.

• 대한기계학회논문집B
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• 제24권2호
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• pp.280-287
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• 2000

Laboratory measurements were made of wall pressure fluctuations in a separated and reattaching flow over a backward-facing step. An array of 32 microphones along the streamwise direction was utilized. Various statistical properties of pressure fluctuations were scrutinized. The main emphasis was placed on the flow inhomogeneity along the streamwise direction. One point statistics such as the streamwise distribution of rms pressure and autospectra were shown to be generally consistent with other studies. The coherences and wavenumber spectra in the streamwise directions were indicative of the presence of dual modes in pressure; one is the large-scale vortical structure in low frequency and the other is the boundary-layer-like decaying mode in high frequency.