• Geomechanics and Engineering
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• 제19권1호
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• pp.93-104
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• 2019

Anomalies and/or fractured grounds not detected by the surface geophysical and geological survey performed during design stage may cause significant problems during tunnel excavation. Many studies on prediction methods of the ground condition ahead of the tunnel face have been conducted and applied in tunneling construction sites, such as tunnel seismic profiling and probe drilling. However, most such applications have focused on the drill and blast tunneling method. Few studies have been conducted for mechanized tunneling because of the limitation in the available space to perform prediction tests. This study aims to predict the ground condition ahead of the tunnel face in TBM tunneling by using an electrical resistivity tomography survey. It compared the characteristics of each electrode array and performed an investigation on in-situ tunnel boring machine TBM construction site environments. Numerical simulations for each electrode array were performed, to determine the proper electrode array to predict anomalies ahead of the tunnel face. The results showed that the modified dipole-dipole array is, compared to other arrays, the best for predicting the location and condition of an anomaly. As the borehole becomes longer, the measured data increase accordingly. Therefore, longer boreholes allow a more accurate prediction of the location and status of anomalies and complex grounds.

• Journal of Audiology & Otology
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• 제23권3호
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• pp.145-152
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• 2019

Background and Objectives: The present study aims to investigate whether the cochlear implant electrode array design affects the electrophysiological and psychophysical measures. Subjects and Methods: Eighty five ears were used as data in this retrospective study. They were divided into two groups by the electrode array design: lateral wall type (LW) and perimodiolar type (PM). The electrode site was divided into three regions (basal, medial, apical). The evoked compound action potential (ECAP) threshold, T level, C level, dynamic range (DR), and aided air conduction threshold were measured. Results: The ECAP threshold was lower for the PM than for the LW, and decreased as the electrode site was closer to the apical region. The T level was lower for the PM than for the LW, and was lower on the apical region than on the other regions. The C level on the basal region was lower for the PM than for the LW whereas the C level was lower on the apical region than on the other regions. The DRs on the apical region was greater for the PM than for the LW whereas the DR was narrower on the apical region than on the other regions. The aided air conduction threshold was not different for the electrode design and frequency. Conclusions: The current study would support the advantages of the PM over the LW in that the PM had the lower current level and greater DR, which could result in more localized neural stimulation and reduced power consumption.

• 대한청각학회지
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• 제23권3호
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• pp.145-152
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• 2019

Background and Objectives: The present study aims to investigate whether the cochlear implant electrode array design affects the electrophysiological and psychophysical measures. Subjects and Methods: Eighty five ears were used as data in this retrospective study. They were divided into two groups by the electrode array design: lateral wall type (LW) and perimodiolar type (PM). The electrode site was divided into three regions (basal, medial, apical). The evoked compound action potential (ECAP) threshold, T level, C level, dynamic range (DR), and aided air conduction threshold were measured. Results: The ECAP threshold was lower for the PM than for the LW, and decreased as the electrode site was closer to the apical region. The T level was lower for the PM than for the LW, and was lower on the apical region than on the other regions. The C level on the basal region was lower for the PM than for the LW whereas the C level was lower on the apical region than on the other regions. The DRs on the apical region was greater for the PM than for the LW whereas the DR was narrower on the apical region than on the other regions. The aided air conduction threshold was not different for the electrode design and frequency. Conclusions: The current study would support the advantages of the PM over the LW in that the PM had the lower current level and greater DR, which could result in more localized neural stimulation and reduced power consumption.

• 한국정밀공학회지
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• 제21권2호
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• pp.177-185
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• 2004

The machining performance of wire electrical discharge machining(WEDM), such as cutting speed, surface roughness and straightness depend on the electrode, and the machining parameters are diverse and affect each other. Therefore operator must have a lot of experiences of the parameter for the better machining performance in WEDM. An approach to minimize the time for determining of parameters setting is proposed. Based on the Taguchi method, the significant factors affecting the machining performance are determined. Types of electrodes are arranged at inner array in tables of orthogonal arrays so that we can estimate machining performances of each electrode. Coating wire shows better performances than brass wire in cutting speed but it produces poor surface roughness, and two wires shows similar performance in straightness

• Advances in Energy Research
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• 제3권1호
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• pp.45-57
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• 2015

This article is addressed to define a new composite electrode constituted by porous nickel and an array of highly ordered $TiO_2$ nanotubes obtained by a previous galvanostatic anodization treatment in an ethylene glycol solution. The electrochemical performances of the composite anode were evaluated in a photo-electrolyser, which showed good solar conversion efficiency with respect to the UV irradiance together with a reduction of energy consumption. Such a combination of materials makes our system simple and able to work both in dark and under solar light exposure, thus opening new perspectives for industrial-scale applications.

• 한국재료학회지
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• 제14권8호
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• pp.587-594
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• 2004

Three-dimensionally ordered macroporous (3DOM) structures of the $LiCoO_2$ electrode materials for Li secondary batteries were fabricated by using the close-packed arrays of PMMA spheres served as templates. In order to successfully fabricate the cathode materials with highly ordered array form, the metal citrates were applied to new precursors. The precursor/template composites were prepared by the infiltration with metal citrate precursors into the voids of template. By removing the PMMA templates, then, the inverse opal structures with the uniform pores of narrow size distribution were resulted. It was confirmed that the 3DOM $LiCoO_2$ material is to take a single phase of rocksalt (R3m) structure. In addition, 3DOM $LiNiO_2$ and $LiMn_{2}O_4$ cathode materials were fabricated using an identical preparation procedure. Also, the morphology of the 3DOM cathode materials calcined at $500^{\circ}C\;to\;700^{\circ}C$ was observed by scanning electron microscope.

• 지구물리와물리탐사
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• 제18권3호
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• pp.115-124
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• 2015

수변 콘크리트 구조물의 누수 탐지를 위해 변형된 배열을 이용하여 전기비저항 탐사를 실시하였다. 전극을 수면에 설치하여 콘크리트 구조물에 대한 새로운 전기비저항 탐사 방식을 제안하였으며, 해석의 단순화를 위해 선형 전류 송신원을 전류전극으로 사용하였다. 마지막으로 전위차를 얻는 방법에 따라 변형된 3가지 전극 배열을 제안하였고, 동일열전위 배열(direct potential array), 평행열 전위 배열(parallel potential array), 횡단 전위 배열(cross potential array)로 명명하였다. 변형된 전기비저항 탐사법을 수치해석, 실내 모형실험, 현장탐사에 적용한 후 그 결과를 비교 분석하여 수변 콘크리트 구조물의 누수 탐지 기술로서의 적합성을 알아보았다. 비교 분석 결과 동일열 전위 배열, 평행열 전위 배열, 횡단전위 배열 모두 누수가 일어날 때, 누수지점에서 뚜렷한 전위차의 변화 양상을 보여 수변 콘크리트 구조물의 누수 탐지에 유용한 방법임을 확인하였다.

• 지구물리와물리탐사
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• 제5권4호
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• pp.250-256
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• 2002

전기비저항 토모그래피는 지하의 전기비저항 분포를 영상화할 수 있는 매우 중요한 정밀 물리탐사법으로 지반조사 및 환경 오염대의 조사에 널리 사용되고 있다. 전기비저항 토모그래피 탐사의 경우 다양한 전극배열법이 사용될 수 있으며 각 배열법은 나름대로의 장단점을 가지고 있다. 예를 들어 단극배열의 경우에는 신호대 잡음비는 높으나 분해능이 벌어지며, 쌍극자배열의 경우에는 분해능은 높지만 신호대 잡음비가 너무 낮다. 단극-쌍극자 배열의 경우에는 중간정도의 분해능과 신호대 잡음비를 갖는다. 최근 개발된 변형된 단극-쌍극자 배열의 경우에는 단극-쌍극자 배열 수준의 신호대 잡음비와 분해능을 갖는다. 그러나 단극배열을 제외한 이들 전극배열법은 전류 및 전위 전극의 위치에 따라서는 겉보기 비저항이 발산할 수도 있다는 단점을 갖는다. 또한 단극배열의 경우에는 측정된 겉보기 비저항이 이상체의 전기비저항을 그대로 반영하지 못한다는 단점이 있다. 본 연구에서는 전류전극과 전위전극의 상대적인 위치에 따라 단극-쌍극자 배열과 변형된 단극-쌍극자 배열을 혼용하는 소위 혼합배열이라는 새로운 전극배열법을 제안하고자 한다. 이 새로운 전극배열법은 신호대 잡음비 및 분해능은 단극-쌍극자 배열의 수준을 유지하며, 측정 시추공상에서 겉보기 비저항이 발산하지 않는 특성을 갖는다. 또한 측정되는 겉보기 비저항은 항상 이상체의 전기비저항을 잘 반영한다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권7호
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• pp.521-524
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• 1999

Nb silicide was formed on the Si micro-tip arrays in order to improve field emission properties of Si-tip field emitter array. After silicidization of the tips, the etch-back process, by which gate insulator, gate electrode and photoresist were deposited sequentially and gate holes were defined by removing gradually the photoresist by $O_2$ plasma from the surface, was applied. Si nitride film was used as a protective layer in order to prevent oxygen from diffusion into Nb silicide layer and it was identified that the NbSi2 was formed through annealing in $N_2$ ambient at $1100^{\circ}C$ for 1 hour. By the Nb silicide coating on Si tips, the turn-on voltage was decreased from 52.1 V to 32.3 V and average current fluctuation for 1 hour was also reduced from 5% to 2%. Also, the fabricated Nb silicide-coated Si tip FEA emitted electrons toward the phosphor and light emission was obtained at the gate voltage of 40~50 V.

• JSTS:Journal of Semiconductor Technology and Science
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• 제1권2호
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• pp.132-139
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• 2001

We considered the uniformity of fabricated micromirror arrays by characterizing the fabrication process and calculating the appropriate driving voltages of micromirrors used as virtual photomask in maskless photolithography. The uniformity of the micromirror array in terms of driving voltage and optical characteristics is adversely affected by factors, such as the air gap between the bottom electrode and the mirror plate, the spring shape and the deformation of the mirror plate or torsion spring. The thickness deviation of the photoresist sacrificial layer, the misalignment between mirror plate and bottom electrode, the aluminum deposition condition used to produce the spring and the mirror plate, and initial mirror deflection were identified as key factors. Their importance lies in the fact that they are related to air gap deviations under the mirror plate, asymmetric driving voltages in left and right mirror directions, and the deformation of the Al sring or mirror plate after removal of the sacrificial layer. The plasma ashing conditions used for removing the sacrificial layer also contributed to the deformation of the mirror plate and spring. Driving voltages were calculated for the pixel operation of the micromirror array, and the non-uniform characteristics of fabricated micromirrors were taken into consideration to improve driving performance reliability.