• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.622-622
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• 2013

Piezoelectric energy harvesting (PEH) device refers to a power device for acquiring mechanical energy from the environment surrounding us which would otherwise be wasted and for converting it into usable electrical energy. While much work has been done on developing ZnO nanogenerator (NG) with nanowire arrays, there are some issues of not only scaling up its output power but also optimizing structure for operating feasibly in various conditions. Efficiency of NG is highly dependent on fixed orientation. But in many cases, it is not easy to predict where the pressure and vibration may come from. Furthermore, the direction of the applied mechanical stress is usually non-stationary and can be random in various practical applications. Therefore an omnidirectional PEH is needed.In this work, we investigate an omnidirectional PEH device consisting ZnO nanowires. We deposited spiral patterned ZnO seed layer on Kapton film. We deposited thin Cr layer on the ZnO seed layer using DC-sputter to form a passivation layer to retard un-expected growth of ZnO nanowires. We grew ZnO nanowires along the spiral arms using hydrothermal method. ZnO nanowires have been selectively grown from the ZnO sidewall without Cr layer and have the average length of$5{\mu}m$ and the average diameter of 40nm. We reduced the defect in the as-grown ZnO nanowires by O2 plasma using asher and by thermal treatment using RTA. Consequently, each nanowire has different directions to each other. This isotropic design can lead to the omnidirectional power generation. The morphology of NG is characterized with FESEM. Maximum output power of the device is measured by using a picoammeter and a nanovoltmeter.

• 대한전자공학회논문지SP
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• 제44권5호
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• pp.35-44
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• 2007

넓은 시야각을 갖는 전방향(omnidirectional) 카메라 시스템은 적은 수의 영상으로도 주변 장면에 대해 많은 정보를 취득할 수 있는 장점으로 카메라 교정(calibration), 공간의 3차원 재구성(reconstruction) 등에 널리 응용되고 있다. 실 세계에 존재하는 직선 성분들은 전방향 카메라 모델에 의해 컨투어로 사영(projection)되기 때문에, 영상간에 대응되는 컨투어 성분은 카메라의 회전 및 이동 등의 추정에 효과적으로 활용될 수 있다. 본 논문에서는 전방향 카메라의 변환 파라미터를 추정하기 위한 2단계 최소화 알고리즘이 제안된다. 제안된 알고리즘은 컨투어를 이루는 대응점에 대한 에피폴라(epipolar) 평면과 3차원 벡터간의 각도 오차함수 및 사영된 컨투어의 거리 오차를 단계별로 최소화하는 카메라 파라미터를 계산한다. 등거리(equidistance) 사영된 합성영상과 어안렌즈(fisheye lens)로 취득한 실제 영상을 대상으로 제안된 알고리즘이 카메라의 위치 정보를 정확하게 추정함을 확인하였다.

• Clinical and Experimental Otorhinolaryngology
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• 제11권4호
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• pp.267-274
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• 2018

Objectives. Two main digital signal processing technologies inside the modern hearing aid to provide the best conditions for hearing aid users are directionality (DIR) and digital noise reduction (DNR) algorithms. There are various possible settings for these algorithms. The present study evaluates the effects of various DIR and DNR conditions (both separately and in combination) on listening comfort among hearing aid users. Methods. In 18 participants who received hearing aid fitting services from the Rehabilitation School of Shahid Beheshti University of Medical Sciences regularly, we applied acceptable noise level (ANL) as our subjective measure of listening comfort. We evaluated both of these under six different hearing aid conditions: omnidirectional-baseline, omnidirectional-broadband DNR, omnidirectional-multichannel DNR, directional, directional-broadband DNR, and directional-multichannel DNR. Results. The ANL results ranged from -3 dB to 14 dB in all conditions. The results show, among all conditions, both the omnidirectional-baseline condition and the omnidirectional-broadband DNR condition are the worst conditions for listening in noise. The DIR always reduces the amount of noise that patients received during testing. The DNR algorithm does not improve listening in noise significantly when compared with the DIR algorithms. Although both DNR and DIR algorithms yielded a lower ANL, the DIR algorithm was more effective than the DNR. Conclusion. The DIR and DNR technologies provide listening comfort in the presence of noise. Thus, user benefit depends on how the digital signal processing settings inside the hearing aid are adjusted.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 C
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• pp.2046-2048
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• 2004

In this paper, we have proposed a novel omnidirectional power divider/combiner configuration. By using the even- and odd- mode analysis. we analyse the proposed power divider/combiner circuit. In order to show the validity of the presented power divider/combiner circuit. We have designed and implemented the proposed circuit of the center frequency of 2.3GHz.

• 대한임베디드공학회논문지
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• 제3권2호
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• pp.74-81
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• 2008

This paper describes a low-cost omnidirectional camera system designed for the intruder detection capability of a security robot. Moving targets on sequential images are detected first by an adaptive background subtraction technique, and the targets are identified as intruders if they fail to enter a password within a preset time. A warning message is then sent to the owner's mobile phone. The owner can check scene pictures posted by the system on the web. The system developed worked well in experiments including a situation when the indoor lighting was suddenly changed.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.2356-2361
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• 2005

In this paper, we present a complete isotropy analysis of a caster wheeled omnidirectional mobile robot(COMR) with nonredundant/redundant actuation. The motivation of this work is that the omnidirectional mobility loses significance in motion control unless the isotropy characteristics is maintained well. First, with the characteristic length introduced, the kinematic model of a COMR is obtained based on the orthogonal decomposition of the wheel velocities. Second, a general form of the isotropy conditions of a COMR is given in terms of physically meaningful vector quantities which describe the wheel configurations. Third, for all possible nonredundant and redundant actuation sets, the algebraic expressions of the isotropy conditions are derived to completely identify the isotropic configurations of a COMR. Fourth, the number of the isotropic configurations and the characteristic length required for the isotropy are discussed.

• 한국HCI학회:학술대회논문집
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• 한국HCI학회 2007년도 학술대회 1부
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• pp.994-999
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• 2007

전방향(omnidirectional) 카메라 시스템은 보다 적은 수의 영상으로부터 주변 장면(scene)에 대한 많은 정보를 취득할 수 있는 장점이 있기 때문에 전방향 영상을 이용한 자동교정(self-calibration)과 3차원 재구성 등의 연구가 활발히 진행되고 있다. 본 논문에서는 기존에 제안된 교정 방법들을 이용하여 추정된 사영모델(projection model)의 정확성을 검증하기 위한 새로운 방법이 제안된다. 실 세계에서 다양하게 존재하는 직선 성분들은 전방향 영상에 컨투어(contour)의 형태로 사영되며, 사영모델과 컨투어의 양 끝점 좌표 값을 이용하여 그 궤적을 추정할 수 있다. 추정된 컨투어의 궤적과 영상에 존재하는 컨투어와의 거리 오차(distance error)로부터 전방향 카메라의 사영모델의 정확성을 검증할 수 있다. 제안된 방법의 성능을 평가하기 위해서 구 맵핑(spherical mapping)된 합성(synthetic) 영상과 어안렌즈(fisheye lens)로 취득한 실제 영상에 대해 제안된 알고리즘을 적용하여 사영모델의 정확성을 판단하였다.

• Journal of electromagnetic engineering and science
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• 제15권3호
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• pp.194-198
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• 2015

Magnetic resonant coupling is more efficient than inductive coupling for transferring power wirelessly over a distance. However, a conventional resonant wireless power transfer (WPT) system requires a transmitter and receiver pair in exactly coaxial positions. We propose a resonator that can serve as an omnidirectional WPT system. A magnetic field will be generated by the current flowed through the transmitter. This magnetic field radiates omnidirectionally in the x-y plane because of the crisscross structure characteristic of the transmitter. The proposed resonator is demonstrated by using a single port. To check the received S21 and transfer efficiency, we moved the receiver around the transmitter at different distances (50-350 mm). As a result, the transmission efficiency is found to be 48%-54% at 200 mm.

• 제어로봇시스템학회논문지
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• 제18권6호
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• pp.571-578
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• 2012

In the paper, we proposed a ring type structured light image based embedded ranging sensor for a mobile robot. Since the proposed ranging sensor obtains omnidirectional object distance, it is useful for autonomous navigation of a mobile robot. By matching the local omnidirectional distance map with a given global object map, it is possible to get position and heading angle of mobile robot in the global coordinates. Experiments for matching and navigation were carried out to verify the performance of the proposed ranging sensor.

• 제어로봇시스템학회논문지
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• 제4권1호
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• pp.88-99
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• 1998

In assembly, misalignment must be detected and compensated for during the mating period, regardless of the complexity of the cross-sectional shape. To this end, we propose a novel omnidirectional image sensing system for assembling parts with complicated shapes(OISSA) and its feasibility for detecting the misalignment between mating parts is shown by a series of simulations. This system encompasses a camera with an optical unit attached to the front of the camera. The optical unit consists of a pair of plane mirrors and a pair of conic mirrors. Utilizing the proposed sensing system, a 2$\pi$ coaxial image of the misalignment along the mating boundary interface between mating parts can be immediately obtained without experiencing self-occlusion.