• Smart Structures and Systems
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• 제1권1호
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• pp.63-82
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• 2005

This paper introduces a technology for robust and low maintenance cost sensor network capable to detect accelerations below a micro-g in a wide frequency bandwidth (above 1,000 Hz). Sensor networks with such performance are critical for navigation, seismology, acoustic sensing, and for the health monitoring of civil structures. The approach is based on the fabrication of an array of high sensitivity accelerometers, each utilizing Fabry-Perot cavity with wavelength-dependent reflectivity to allow embedded optical detection and serialization. The unique feature of the approach is that no local power source is required for each individual sensor. Instead one global light source is used, providing an input optical signal which propagates through an optical fiber network from sensor-to-sensor. The information from each sensor is embedded onto the transmitted light as an intrinsic wavelength division multiplexed signal. This optical "rainbow" of data is then assessed providing real-time sensing information from each sensor node in the network. This paper introduces the Fabry-Perot based accelerometer and examines its critical features, including the effects of imperfections and resolution estimates. It then presents serialization techniques for the creation of systems of arrayed sensors and examines the effects of serialization on sensor response. Finally, a fabrication process is proposed to create test structures for the critical components of the device, which are dynamically characterized.

• Bulletin of the Korean Chemical Society
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• 제24권2호
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• pp.183-188
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• 2003

The micro-patterning of multi-layered thin films containing CdS and $Ta_2O_5$ layers on ITO substrate with various structures was successfully obtained by combining three different techniques: chemical solution depositions, sol-gel, and microcontact printing (μCP) methods using octadecyltrichlorosilane (OTS) as the organic thin layer template. $Ta_2O_5$ layer was prepared by sol-gel casting and CdS one obtained by chemical solution deposition, respectively. Parallel and cross patterns of multi-layers with $Ta_2O_5$ and CdS films were fabricated additively by successive removal of OTS layer pre-formed. This study presents the designed architectures consisting of the two types of feature having horizontal dimensions of 170 ㎛ and 340 ㎛ with constant thickness ca. 150 nm of each deposited materials. The thin film lay-out of the cross-patterning is composed of four regions with chemically different layer compositions, which are confirmed by Auger electron microanalysis.

• Journal of Welding and Joining
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• 제29권3호
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• pp.76-81
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• 2011

Recently, the structural failures due to fatigue occur frequently with the increase of size of ships and offshore structures. In this respect, the assessment of fatigue life and the residual strength are very important. Currently, the smart materials technology has demonstrated a variety of possibilities for a diagnosis of structural strength and structural health condition for large structures. The benefits and feature of the MFC sensor are more flexible, durable and reliable than conventional smart material. In this study, Micro Fiber Composite (MFC) sensor for the measurement of stress intensity factor (SIF) of two dimensional cracks induced in a structure is developed. Two MFC sensors are placed in the vicinity of the crack tip close to each other with the crack tip in between them. The SIFs of Mode I($K_I$) as well as of Mode II($K_{II}$) based on the piezoelectric constitutive law and fracture mechanics are calculated. In this study, the SIF values measured by MFC sensors are compared with the theoretical results and measured value.

• 비파괴검사학회지
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• 제29권3호
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• pp.214-218
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• 2009

The occlusal force of the tooth leads to loss of tooth tissue owing to attrition and abrasion, and may cause abfraction and pathological change of the dentin. Thus, we developed finite element models, examined them by applying ordinary occlusal force, and analyzed the stress distribution. Specimens used were mandibular first premolars from 15 Korean males and 13 females and were made into finite element models from medical images that were obtained using a Micro-CT. We have found that the irregular feature of the tooth is not only useful to masticating and pronouncing as well known, but it is also suitable for protecting inner tissue by dispersing stress and delivering proper pressure to periodontal tissue to continue a physiological action. Also, image analysis could let us know the factor that is the cause of a disorder due to stress concentration in the cervical line. These results are expected to support the field of dental treatment planning, operating procedure and clinical trial, and the advance of technical expertise to develop implants and dentures.

• 소성∙가공
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• 제13권3호
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• pp.262-267
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• 2004

Ultrasonic machining has been known as one of the conventional machining methods in the glass fabrication processes. In ultrasonic machining, typically, glass is removed by the impulse energy of the abrasive generated by the ultrasonic power. However, when the machining feature decrease under hundreds of micrometers, as conventional ultrasonic machining uses only the impulse energy of the abrasive, the speed of ultrasonic machining decreases significantly and the surface roughness becomes deteriorated. To overcome this size effect, the chemicals which can erode glasses, such as HF, XF, etc, are added to the slurry. The chemical-assisted ultrasonic machining method, so called, is another alternating effective way for micro machining of glasses. In previous work, we used the hydrofluoric acid (HF) as an additive chemical. But, as the HF solution is too poisonous to be used as a ultrasonic process additive, it is needed to be substituted by other safe chemicals. As results of the machinability comparison of several chemicals, the GST-500F was selected to replace the HF. The GST-500F (pH $4.0{\pm}1.0$) is non-volatile, odorless. During experimental works, it was shown that the machining rate increases 1.5 times faster than the conventional ultrasonic machining. The machining load also decreases. However, the enlargement of the hole diameter and significant tool wear are still the problems to be solved.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.176-183
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• 2005

Laser heat treatment technology is used for improving the feature of fatigue resistance and wear resistance in mobile parts. The purpose of this study is to compare the characteristics of laser heat treatment and high frequency heat treatment, which is commonly used in industrial place. For the preemptive experiment, the distribution, depth and size of hardening and its micro-structural features were compared between surface heat treatment case by defocusing and variables of each process for heat treatment by exclusively manufactured heat treatment optical system. As a result, high frequency heat treatment has wide distribution of hardening depth and width about 3 times larger than laser heat treatment, however, its average hardness showed 621.4Hv which is smaller than the average hardness of laser heat treatment with 691Hv.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.322-325
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• 2005

The shrinking critical dimensions of modern technology place a heavy requirement on optimizing feature shapes at the micro- and nano scale. In addition, the use of ion beams in the nano-scale world is greatly increased by technology development. Especially, Focused ion Beam (FIB) has a great potential to fabricate the device in nano-scale. Nevertheless, FIB has several limitations, surface swelling in low ion dose regime, precipitation of incident ions, and the re-deposition effect due to the sputtered atoms. In recent years, many approaches and research results show that the re-deposition effect is the most outstanding effect to overcome or reduce in fabrication of micro and nano devices. A 2D string based simulation software AMADEUS-2D $(\underline{A}dvanced\;\underline{M}odeling\;and\;\underline{D}esign\;\underline{E}nvironment\;for\;\underline{S}putter\;Processes)$ for ion milling and FIB direct fabrication has been developed. It is capable of simulating ion beam sputtering and re-deposition. In this paper, the 2D FIB simulation is demonstrated and the characteristics of ion beam induced direct fabrication is analyzed according to various parameters. Several examples, single pixel, multi scan box region, and re-deposited sidewall formation, are given.

• 한국기계가공학회지
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• 제20권10호
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• pp.88-94
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• 2021

Machining operations require the removal of chips to keep the water-soluble cutting oil clean and fresh throughout the operation time. Water-soluble cutting oil for metal processing is diluted using a 3-8% solution in water which is generally replaced every three to six months. This study aims to develop multiple purification devices to efficiently remove fine contaminating particles from water-soluble cutting oil. The 2D concept designs were created using AutoCAD. The designs were drawn using the 3D modelling feature of CATIA. Flow analysis was performed in a bubble purifier using Ansys computational fluid dynamics (CFD). This analysis has aided in improving the design and structure of the device to create the final prototype. Experiments were conducted to check the prototype's performance. Comparisons of the effects of each process variable on the experiment was carried out using ANOVA.

• 한국자기공명학회논문지
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• 제23권3호
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• pp.61-66
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• 2019

RNAs exhibit distinct structural and dynamic features required for proper function. The hydrogen-bonded imino protons of RNAs are a probe of the conformational transition and dynamic feature. MicroRNAs originate from primary transcripts containing hairpin structures. The levels of mature miR156 influence the flowering time of plants. To understand the molecular mechanism of biological function of $miR156:miR156^*$ duplex, we performed hydrogen exchange study on the model RNAs mimicking two phenotypes of $miR156:miR156^*$, $miR156:miR156^*$ (m-miR156a) and $miR156:miR156^*$ (m-miR156g) duplexes. This study found that the internal bulge of m-miR156a destabilized the neighboring base-pairs, whereas the bulge structure of m-miR156g did not affect the thermal stabilities of the neighboring base-pairs.

• 한국전자파학회논문지
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• 제29권7호
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• pp.550-559
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• 2018

본 논문은 딥뉴럴네트워크(deep neural network: DNN)를 이용해 사람 걸음 및 배경잡음원에 의해 발생한 마이크로 도플러 신호를 탐지 및 분류 처리하는 연구를 제안한다. 기존 분류처리 연구는 경험 및 통계적인 방법을 통해 분류기 성능에 직접적으로 영향을 미치는 의미있는 특징을 추출하기 위한 복잡한 과정을 포함한다. 그러나 딥뉴럴네트워크는 다수의 레이어 층을 단계적으로 통과하는 과정을 통해 점진적으로 특징을 재구성 및 생성하므로, 별도의 특징 추출과정을 생략할 수 있으며, 자연스럽게 네트워크상에서 특징을 생성할 수 있는 이점이 있다. 따라서 본 논문에서는 마이크로 도플러 신호 인식을 위한 딥뉴럴네트워크 효과성 입증을 위해, 이진분류기와 다층클래스 분류기를 다층퍼셉트론과 딥뉴럴네트워크를 통해 설계하고 비교분석한다. 실험 결과, 다층퍼셉트론은 이진분류기의 경우 테스트세트에 대한 분류 정확도가 90.3 %로 측정되었고, 다층클래스 분류기의 경우 테스트세트에 대한 분류정확도가 86.1 %로 측정되었다. 딥뉴럴네트워크는 이진분류기의 경우 테스트세트에 대한 분류 정확도가 97.3 %로 측정되었고, 다층클래스 분류기의 경우 테스트세트에 대한 분류정확도가 96.1 %로 측정되었다.