• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.81-81
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• 2010

유리기판위에 큰 결정입자를 갖는 실리콘 (폴리 실리콘) 박막을 제조하는 것은 가격저가화 및 대면적화 측면 같은 산업화의 높은 잠재성을 가지고 있기 때문에 그동안 많은 관심을 가지고 연구되어 오고 있다. 다양한 방법을 이용하여 다결정 실리콘 박막을 만들기 위해 노력해 오고 있으며, 태양전지에 응용하기 위하여 연속적이면서 10um이상의 큰 입자를 갖는 다결정 실리콘 씨앗층이 필요하며, 고속증착을 위해서는 (100)의 결정성장방향 등 다양한 조건이 제시될 수 있다. 다결정 실리콘 흡수층의 품질은 고품질의 다결정 실리콘 씨앗층에서 얻어질 수 있다. 이러한 다결정 실리콘의 에피막 성장을 위해서는 유리기판의 연화점이 저압 화학기상증착법 및 아크 플라즈마 등과 같은 고온기반의 공정 적용의 어려움이 있기 때문에 제약 사항으로 항상 문제가 제기되고 있다. 이러한 관점에서 볼때 유리기판위에 에피막을 성장시키는 방법으로 많지 않은 방법들이 사용될 수 있는데 전자 공명 화학기상증착법(ECR-CVD), 이온빔 증착법(IBAD), 레이저 결정화법(LC) 및 펄스 자석 스퍼터링법 등이 에피 실리콘 성장을 위해 제안되는 대표적인 방법으로 볼 수 있다. 이중에서 효율적인 관점에서 볼때 IBAD는 산업화측면에서 좀더 많은 이점을 가지고 있으나, 박막을 형성하는 과정에서 큰 에너지 및 이온크기의 빔 사이즈 등으로 인한 표면으로의 damages가 일어날 수 있어 쉽지 않는 방법이 될 수 있다. 여기에서는 이러한 damage를 획기적으로 줄이면서 저온에서 결정화 시킬 수 있는 cold annealing법을 소개하고자 한다. 이온빔에 비해서 전자빔의 에너지와 크기는 그리드 형태의 렌즈를 통해 전체면적에 조사하는 것을 쉽게 제어할 수 있으며 이러한 전자빔의 생성은 금속 필라멘트의 열전자가 아닌 Ar플라즈마에서 전자의 분리를 통해 발생된다. 유리기판위에 흡수층 제조연구를 위해 DC 및 RF 스퍼터링법을 이용한 비정질실리콘의 박막에 대하여 두께별에 따른 밴드갭, 캐리어농도 등의 변화에 대하여 조사한다. 최적의 조건에서 비정질 실리콘을 2um이하로 증착을 한 후, 전자빔 조사를 위해 1.4~3.2keV의 다양한 에너지세기 및 조사시간을 변수로 하여 실험진행을 한 후 단면의 이미지 및 결정화 정도에 대한 관찰을 위해 SEM과 TEM을 이용하고, 라만, XRD를 이용하여 결정화 정도를 조사한다. 또한 Hall효과 측정시스템을 이용하여 캐리어농도, 이동도 등을 각 변수별로 전기적 특성변화에 대하여 분석한다. 또한, 태양전지용 흡수층으로 응용을 위하여 dark전도도 및 photo전도도를 측정하여 광감도에 대한 결과가 포함된다.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.80-80
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• 2010

유리기판위에 큰 결정입자를 갖는 실리콘 (폴리 실리콘) 박막을 제조하는 것은 가격저가화 및 대면적화 측면 같은 산업화의 높은 잠재성을 가지고 있기 때문에 그동안 많은 관심을 가지고 연구되어 오고 있다. 다양한 방법을 이용하여 다결정 실리콘 박막을 만들기 위해 노력해 오고 있으며, 태양전지에 응용하기 위하여 연속적이면서 10um이상의 큰 입자를 갖는 다결정 실리콘 씨앗층이 필요하며, 고속증착을 위해서는 (100)의 결정성장방향 등 다양한 조건이 제시될 수 있다. 다결정 실리콘 흡수층의 품질은 고품질의 다결정 실리콘 씨앗층에서 얻어질 수 있다. 이러한 다결정 실리콘의 에피막 성장을 위해서는 유리기판의 연화점이 저압 화학기상증착법 및 아크 플라즈마 등과 같은 고온기반의 공정 적용의 어려움이 있기 때문에 제약 사항으로 항상 문제가 제기되고 있다. 이러한 관점에서 볼때 유리기판위에 에피막을 성장시키는 방법으로 많지 않은 방법들이 사용될 수 있는데 전자 공명 화학기상증착법(ECR-CVD), 이온빔 증착법(IBAD), 레이저 결정화법(LC) 및 펄스 자석 스퍼터링법 등이 에피 실리콘 성장을 위해 제안되는 대표적인 방법으로 볼 수 있다. 이중에서 효율적인 관점에서 볼때 IBAD는 산업화측면에서 좀더 많은 이점을 가지고 있으나, 박막을 형성하는 과정에서 큰 에너지 및 이온크기의 빔 사이즈 등으로 인한 표면으로의 damages가 일어날 수 있어 쉽지 않는 방법이 될 수 있다. 여기에서는 이러한 damage를 획기적으로 줄이면서 저온에서 결정화 시킬 수 있는 cold annealing법을 소개하고자 한다. 이온빔에 비해서 전자빔의 에너지와 크기는 그리드 형태의 렌즈를 통해 전체면적에 조사하는 것을 쉽게 제어할 수 있으며 이러한 전자빔의 생성은 금속 필라멘트의 열전자가 아닌 Ar플라즈마에서 전자의 분리를 통해 발생된다. 유리기판위에 다결정 실리콘 씨앗층을 제조하기 위하여 전자빔을 조사하는 방법과 Al을 이용한 씨앗층 제조법이 비교되어 공정 수행이 이루어진다. 우선, 전자빔 조사를 위해 DC 및 RF 스퍼터링법을 이용하여 ${\sim}10^{20}cm^{-3}$이상의 농도를 갖는 $p^+^+$ 비정질 실리콘 박막을 제조한다. Al의 증착은 DC 스퍼터링법을 이용하여 제조하고 그 두께는 실리콘 박막의 두께와 동일한 조건(350nm)으로 제조한다. 제조된 샘플은 E-beam gun이 달린 챔버로 이동하여 1.4keV의 세기를 가지고 각각 10, 20, 50, 100초를 조사한 후 단면의 이미지를 SEM으로, 결정화 정도를 Raman으로, 결정화 방향 등에 대한 조사를 XRD로 분석 측정한다. 그리고 Hall effect를 통해 전자빔의 조사 전후의 캐리어 농도, 이동도 및 비저항 등에 대한 조사가 이루어진다. 동시에 Al을 촉매로 한 layer교환에 대하여 마찬가지로 분석을 통하여 최종적으로 비교분석이 이루어 진다. 전자빔을 조사한 샘플에 대하여 빠른 시간 및 캐리어농도 제어 등의 우수성이 보이며, 특히 ~98%이상의 결정화율을 보일 것으로 예상된다.

• Journal of the Korean Geosynthetics Society
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• v.18 no.4
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• pp.151-165
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• 2019

In this study, the four types of improvement methods (increase self weight and reducing sliding force etc.) were proposed depending on install location with compaction grouting to improve seismic performance of existing port structure and optimal methods by analyzing the effects of improvement (stability, constructability and economy) by theoretical and numerical methods. From the dynamic time history analysis for artificial seismic waves, the results indicated that the horizontal displacement after improvement decreased compared to before improvement, however the displacement reduction effect among improvement methods was not significantly different. Slope stability based on the strength reduction method and the limit equilibrium analysis method, it is confirmed that the passive pile method is more safe than other methods. It is due to the shear strength at the failure surface is increased. In addition, the analysis of constructability and economy showed that the reduction of earth pressure method (type 02) and the passive pile method (type 03) are excellent. However, in the case of the passive pile method is concerned that there is a shortage of design cases and the efficiency can be reduced depend on various constraints such as ground conditions.

• International Journal of Highway Engineering
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• v.4 no.2 s.12
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• pp.33-42
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• 2002

The cracks in the pavements result from drying shrinkage, temperature change, repeated traffic loadings and so on. The reduction of soil support, spatting and many local failures are caused by water and incompressible foreign materials infiltrated into the cracks. In order to reduce this kind of problems the crack width must be controlled and managed by the accurate measurement. The current method is a visual survey using a microscope, which requires traffic blocking. The purpose of this study is to find the best condition to measure accurate crack width using automated pavement condition survey equipment running at the similar speed as other vehicles. In this study pavement surfaces are filmed on an enlarged scale by the camera with a zoom lens, and then the proper focal distance is determined according to the crack width through a pilot survey. The conditions for measurement of the accurate crack width using the image processing technique are suggested by comparing crack widths surveyed using a microscope in the field with those computed by various factors in the image processing program, STADI-2. In conclusion, the camera with a focal distance of 75m could detect crack range of 0.5mm$\sim$1.2mm In width with an accuracy of 80% for CRCP. The camera with a focal distance of 12.5mm could detect crack range of 1.8mm$\sim$3.3mm in width with an accuracy of 90% for asphalt pavement.

• Journal of KIISE:Databases
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• v.30 no.1
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• pp.64-79
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• 2003

In client-server computing environments, update transactions of spatial data have the following characteristics. First, a transaction to update maps needs interactive work, and therefore it nay take a long time to finish. Second, a long transaction should be allowed to read the dirty data to enhance parallelism of executing concurrent transactions. when %he transaction is rolled back, it should guarantee the cascading rollback of all of the dependent transactions. Finally, two spatial objects may have a weak dependency constraint, called the spatial relationship, based on geometric topology. The existing recovery approaches cannot be directly applied to this environment, due to the high rollback cost and the overhead of cascading rollbacks. Furthermore, the previous approaches cannot guarantee the data integrity because the spatial relationship, which is a new consistency constraint of spatial data, is not considered. This paper presents new recovery schemes for update transactions of spatial data. To guarantee the data integrity, this paper defines recovery dependency as a rendition of cascading rollbacks. The partial-rollback is alto suggested to solve the problem of high rollback cost. The recovery schemes proposed in this paper can remove the unnecessary cascading rollbacks by using undo-delta, partial -redo and partial-undo. Finally, the schemes are performed to ensure the correctness.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.5
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• pp.421-427
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• 2014

Most of the structure of the real world is influenced under dynamic loads. However, when structure analysis and the structural optimization is performed, it is assumed that the static load acts on structure. When considering the actual load of dynamic loads in order to take into account a variety of loads, computational resources and time becomes a big burden in terms of cost. However, considering only the simple static load condition is not preferable for structural safety. For this reason, a lot of studies have been conducted trying to compensate this trouble by applying weight factor or replacing dynamic load with the equivalent static load. In this study, structural optimization techniques for structures under dynamic loads is proposed by applying the equivalent static load. From previous study, after determining the positions of equivalent static load based on primary degrees of freedom, the equivalent static load is calculated through the optimization process. In this process, the equivalent static load optimization of previous research is complemented by adding constraints to avoid excessively large load extraction. In numerical examples, dynamic load is applied to the truss structure and the plate. Then, the reliability of the proposed optimization technique is verified by carrying out size optimization with the equivalent static load.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.9
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• pp.261-268
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• 2018

The use of electric cable was limited due to the installation time and large space as the increase of power demand and load quantity in side line. In order to solve these problems, the application of busway system which can supply the large current was increasing. But it was lack of methods of performance tests to evaluate the reliability and results of test for busway system. In this paper, we presented items to evaluate the reliability test for epoxy coated busway system with reference to IEC 61349-6. In addition, we proposed items to evaluate the reliability and long term life cycle test for the epoxy coated busway system. The combined acceleration deterioration test that reflects actual conditions of the survey as much as possible was conducted considering both thermal and electrical stresses. The deterioration condition was selected to satisfy fifty years life expectation and the insulation performance verification test of the busway system confirmed the long term life prediction. Furthermore, as test items for reliability assessment of compliance with the environment for the use of temperature, humidity and load current where busway system was installed, thermal overload test, water immersion test, cold shock temperature test and thermal cycle test were performed. And we examined changes in characteristics and abnormality after tests. From results, the test items presented to evaluate performance and reliability of the epoxy insulated busway system were confirmed to be appropriate in this paper, and the performance of the product was also confirmed to be excellent for reliability tests.

• Science of Emotion and Sensibility
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• v.20 no.4
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• pp.89-100
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• 2017

Since smart devices are able to efficiently provide information without barriers of time and location, they are widely utilized with advent of the hyper-connected society. Especially, the smart devices have been developed in the form of wearable devices for mutual interaction between human and objects. Smart clothing, which embeds smart devices within clothes, measures and obtains a variety of bio-signals as it is in close contact with the human bodies. Conventional smart clothing generated wearers' discomfort because they were developed by simple attachment of electronic devices to clothes. Therefore, it is highly recommended to develop novel smart clothing based on smart textiles which integrate electronic devices as parts of textiles. As smart watches are currently the most available wearable devices in the market, smart watch users were selected in this study, for the purpose of investigating core needs of wearable smart device users based on the user experience and user's sensibility. Qualitative research was performed through semi-structured interview in order to obtain detailed answers about user sensibility based on smart watch user experience. After the in-depth interview, the user's sensibility was categorized into four aspects; functional, aesthetic, social, and empirical. Sensibility adjectives and key words were assigned to each aspect and their frequency was analyzed. It was the functional aspect of sensibility that the wearable device users require the most. The results of this study will be utilized as a fundamental data to develop the smart textiles required for the next generation of smart clothing which is attracting as a future wearable device.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.3
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• pp.158-169
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• 2019

A probabilistic model that can predict the residual useful lifetime of structure is formulated by using the gamma process which is one of the stochastic processes. The formulated stochastic model can take into account both the sampling uncertainty associated with damages measured up to now and the temporal uncertainty of cumulative damage over time. A method estimating several parameters of stochastic model is additionally proposed by introducing of the least square method and the method of moments, so that the age of a structure, the operational environment, and the evolution of damage with time can be considered. Some features related to the residual useful lifetime are firstly investigated into through the sensitivity analysis on parameters under a simple setting of single damage data measured at the current age. The stochastic model are then applied to the rubble-mound breakwater straightforwardly. The parameters of gamma process can be estimated for several experimental data on the damage processes of armor rocks of rubble-mound breakwater. The expected damage levels over time, which are numerically simulated with the estimated parameters, are in very good agreement with those from the flume testing. It has been found from various numerical calculations that the probabilities exceeding the failure limit are converged to the constraint that the model must be satisfied after lasting for a long time from now. Meanwhile, the expected residual useful lifetimes evaluated from the failure probabilities are seen to be different with respect to the behavior of damage history. As the coefficient of variation of cumulative damage is becoming large, in particular, it has been shown that the expected residual useful lifetimes have significant discrepancies from those of the deterministic regression model. This is mainly due to the effect of sampling and temporal uncertainties associated with damage, by which the first time to failure tends to be widely distributed. Therefore, the stochastic model presented in this paper for predicting the residual useful lifetime of structure can properly implement the probabilistic assessment on current damage state of structure as well as take account of the temporal uncertainty of future cumulative damage.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.6
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• pp.88-95
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• 2011

An embedded mobile device mostly has lower computation power than a general purpose computer because of its relatively lower system specifications. Consequently, conventional face tracking and face detection methods, requiring complex algorithms for higher recognition rates, are unsuitable in a mobile environment aiming for real time detection. On the other hand, by applying a real-time tracking and detecting algorithm, we would be able to provide a two-way interactive multimedia service between an user and a mobile device thus providing a far better quality of service in comparison to a one-way service. Therefore it is necessary to develop a real-time face and eye tracking technique optimized to a mobile environment. For this reason, in this paper, we proposes a method of tracking horizontal face position of a user on a T-DMB device for enhancing the quality of 3D DMB content. The proposed method uses the orientation of edges to estimate the left and right boundary of the face, and by the color edge information, the horizontal position and size of face is determined finally to decide the horizontal face. The sobel gradient vector is projected vertically and candidates of face boundaries are selected, and we proposed a smoothing method and a peak-detection method for the precise decision. Because general face detection algorithms use multi-scale feature vectors, the detection time is too long on a mobile environment. However the proposed algorithm which uses the single-scale detection method can detect the face more faster than conventional face detection methods.