• 제목/요약/키워드: Technological defects

검색결과 36건 처리시간 0.028초

미래주의 관점에서 본 론 아라드의 공간 표현에 관한 연구 (A Study on Futuristic Aspects of Ron Arad's Interior Design)

  • 고자경;심은주
    • 한국실내디자인학회논문집
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    • 제17권4호
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    • pp.50-57
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    • 2008
  • Futurism can be defined as a movement in the early 20th century founded by Italian writer Marinetti apposing to traditional and conservative art. Though its life as a movement seemed to be fairly short, it can be said that the very essence of futurism can be seen whenever there is radical change in our society such as the information revolution. Even though the information revolution has brought us many positive improvements our life including art and design, lately there are also discussions about the defects in our life. Ron Arad may be considered as a designer and artist whose intentions and expressions are very similar to those of futurism. This study investigates concepts, meanings, and expressions of futurism in art history and then those of Ron Arad's shown in interior design projects. By examining selected project examples the author defined that rather than optimistic viewpoints, avant-garde and technological aspects were found to be strong in symbolic qualities. As for expressive qualities, dynamism and continuity appeared to be Ron Arad's unique expressions, very similar to those of futurism on the other hand, purity and temporarily were found less. It is hoped that the study may be a help in better understanding futuristic qualities of Ron Arad, one of the radical and experimental designers of our age.

Comparative review and interpretation of the conventional and new methods in blast vibration analyses

  • Uyar, G. Gulsev;Aksoy, C.O.
    • Geomechanics and Engineering
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    • 제18권5호
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    • pp.545-554
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    • 2019
  • The customary approach used in the blast vibration analysis is to derive empirical relations between the peak particle velocities of blast-induced waves and the scaled distance, and to develop patterns limiting the amounts of explosives. During the periods when excavations involving blasting were performed at sites far from residential areas and infrastructure works, this method based on empirical correlations could be effective in reducing vibrations. However, blasting procedures applied by the fast-moving mining and construction industries today can be very close to, in particular cities, residential areas, pipelines, geothermal sites, etc., and this reveals the need to minimize blast vibrations not only by limiting the use of explosives, but also employing new scientific and technological methods. The conventional methodology in minimizing blast vibrations involves the steps of i) measuring by seismograph peak particle velocity induced by blasting, ii) defining ground transmission constants between the blasting area and the target station, iii) finding out the empirical relation involving the propagation of seismic waves, and iv) employing this relation to identify highest amount of explosive that may safely be fired at a time for blasting. This paper addresses practical difficulties during the implementation of this conventional method, particularly the defects and errors in data evaluation and analysis; illustrates the disadvantages of the method; emphasizes essential considerations in case the method is implemented; and finally discusses methods that would fit better to the conditions and demands of the present time compared to the conventional method that intrinsically hosts the abovementioned disadvantages.

Interface structure and anisotropic strain relaxation of nonpolar a-GaN on r-sapphire

  • 공보현;조형균;송근만;윤대호
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2010년도 하계학술대회 논문집
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    • pp.31-31
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    • 2010
  • The growth of the high-quality GaN epilayers is of significant technological importance because of their commercializedoptoelectronic applications as high-brightness light-emitting diodes (LEDs) and laser diodes (LDs) in the visible and ultraviolet spectral range. The GaN-based heterostructural epilayers have the polar c-axis of the hexagonal structure perpendicular to the interfaces of the active layers. The Ga and N atoms in the c-GaN are alternatively stacked along the polar [0001] crystallographic direction, which leads to spontaneous polarization. In addition, in the InGaN/GaN MQWs, the stress applied along the same axis contributes topiezoelectric polarization, and thus the total polarization is determined as the sum of spontaneous and piezoelectric polarizations. The total polarization in the c-GaN heterolayers, which can generate internal fields and spatial separation of the electron and hole wave functions and consequently a decrease of efficiency and peak shift. One of the possible solutions to eliminate these undesirable effects is to grow GaN-based epilayers in nonpolar orientations. The polarization effects in the GaN are eliminated by growing the films along the nonpolar [$11\bar{2}0$] ($\alpha$-GaN) or [$1\bar{1}00$] (m-GaN) orientation. Although the use of the nonpolar epilayers in wurtzite structure clearly removes the polarization matters, however, it induces another problem related to the formation of a high density of planar defects. The large lattice mismatch between sapphiresubstrates and GaN layers leads to a high density of defects (dislocations and stacking faults). The dominant defects observed in the GaN epilayers with wurtzite structure are one-dimensional (1D) dislocations and two-dimensional (2D) stacking faults. In particular, the 1D threading dislocations in the c-GaN are generated from the film/substrate interface due to their large lattice and thermal coefficient mismatch. However, because the c-GaN epilayers were grown along the normal direction to the basal slip planes, the generation of basal stacking faults (BSFs) is localized on the c-plane and the generated BSFs did not propagate into the surface during the growth. Thus, the primary defects in the c-GaN epilayers are 1D threading dislocations. Occasionally, the particular planar defects such as prismatic stacking faults (PSFs) and inversion domain boundaries are observed. However, since the basal slip planes in the $\alpha$-GaN are parallel to the growth direction unlike c-GaN, the BSFs with lower formation energy can be easily formed along the growth direction, where the BSFs propagate straightly into the surface. Consequently, the lattice mismatch between film and substrate in $\alpha$-GaN epilayers is mainly relaxed through the formation of BSFs. These 2D planar defects are placed along only one direction in the cross-sectional view. Thus, the nonpolar $\alpha$-GaN films have different atomic arrangements along the two orthogonal directions ($[0001]_{GaN}$ and $[\bar{1}100]_{GaN}$ axes) on the $\alpha$-plane, which are expected to induce anisotropic biaxial strain. In this study, the anisotropic strain relaxation behaviors in the nonpolar $\alpha$-GaN epilayers grown on ($1\bar{1}02$) r-plane sapphire substrates by metalorganic chemical vapor deposition (MOCVO) were investigated, and the formation mechanism of the abnormal zigzag shape PSFs was discussed using high-resolution transmission electron microscope (HRTEM).

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고에너지 분쇄 매체 지르코니아 Beads의 미세구조 및 기계적 특성에 따른 마모율 분석 (Analysis of Attrition Rate of Y2O3 Stabilized Zirconia Beads with Different Microstructure and Mechanical Properties)

  • 김정환;윤세중;한병동;안철우;윤운하;최종진
    • 한국재료학회지
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    • 제28권6호
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    • pp.349-354
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    • 2018
  • Particle size reduction is an important step in many technological operations. The process itself is defined as the mechanical breakdown of solids into smaller particles to increase the surface area and induce defects in solids, which are needed for subsequent operations such as chemical reactions. To fabricate nano-sized particles, several tens to hundreds of micron size ceramic beads, formed through high energy milling process, are required. To minimize the contamination effects during high-energy milling, the mechanical properties of zirconia beads are very important. Generally, the mechanical properties of $Y_2O_3$ stabilized tetragonal zirconia beads are closely related to the mechanism of phase change from tetragonal to monoclinic phase via external mechanical forces. Therefore, $Y_2O_3$ distribution in the sintered zirconia beads must also be closely related with the mechanical properties of the beads. In this work, commercially available $100{\mu}m-size$ beads are analyzed from the point of view of microstructure, composition homogeneity (especially for $Y_2O_3$), mechanical properties, and attrition rate.

식스시그마 프로젝트 사례에서 혁신효과 분석을 위한 품질척도의 특성 및 적용 (The Characteristics and Implementations of Quality Metrics for Analyzing Innovation Effects in Six Sigma Projects)

  • 최성운
    • 대한안전경영과학회지
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    • 제16권1호
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    • pp.169-176
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    • 2014
  • This research discusses the characteristics and the implementation strategies for two types of quality metrics to analyze innovation effects in six sigma projects: fixed specification type and moving specification type. $Z_{st}$, $P_{pk}$ are quality metrics of fixed specification type that are influenced by predetermined specification. In contrast, the quality metrics of moving specification type such as Strictly Standardized Mean Difference(SSMD), Z-Score, F-Statistic and t-Statistic are independent from predetermined specification. $Z_{st}$ sigma level obtains defective rates of Parts Per Million(PPM) and Defects Per Million Opportunities(DPMO). However, the defective rates between different industrial sectors are incomparable due to their own technological inherence. In order to explore relative method to compare defective rates between different industrial sectors, the ratio of specification and natural tolerance called, $P_{pk}$, is used. The drawback of this $P_{pk}$ metric is that it is highly dependent on the specification. The metrics of F-Statistic and t-Statistic identify innovation effect by comparing before-and-after of accuracy and precision. These statistics are not affected by specification, but affected by type of statistical distribution models and sample size. Hence, statistical significance determined by above two statistics cannot give a same conclusion as practical significance. In conclusion, SSMD and Z-Score are the best quality metrics that are uninfluenced by fixed specification, theoretical distribution model and arbitrary sample size. Those metrics also identify the innovation effects for before-and-after of accuracy and precision. It is beneficial to use SSMD and Z-Score methods along with popular methods of $Z_{st}$ sigma level and $P_{pk}$ that are commonly employed in six sigma projects. The case studies from national six sigma contest from 2011 to 2012 are proposed and analyzed to provide the guidelines for the usage of quality metrics for quality practitioners.

Online condition assessment of high-speed trains based on Bayesian forecasting approach and time series analysis

  • Zhang, Lin-Hao;Wang, You-Wu;Ni, Yi-Qing;Lai, Siu-Kai
    • Smart Structures and Systems
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    • 제21권5호
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    • pp.705-713
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    • 2018
  • High-speed rail (HSR) has been in operation and development in many countries worldwide. The explosive growth of HSR has posed great challenges for operation safety and ride comfort. Among various technological demands on high-speed trains, vibration is an inevitable problem caused by rail/wheel imperfections, vehicle dynamics, and aerodynamic instability. Ride comfort is a key factor in evaluating the operational performance of high-speed trains. In this study, online monitoring data have been acquired from an in-service high-speed train for condition assessment. The measured dynamic response signals at the floor level of a train cabin are processed by the Sperling operator, in which the ride comfort index sequence is used to identify the train's operation condition. In addition, a novel technique that incorporates salient features of Bayesian inference and time series analysis is proposed for outlier detection and change detection. The Bayesian forecasting approach enables the prediction of conditional probabilities. By integrating the Bayesian forecasting approach with time series analysis, one-step forecasting probability density functions (PDFs) can be obtained before proceeding to the next observation. The change detection is conducted by comparing the current model and the alternative model (whose mean value is shifted by a prescribed offset) to determine which one can well fit the actual observation. When the comparison results indicate that the alternative model performs better, then a potential change is detected. If the current observation is a potential outlier or change, Bayes factor and cumulative Bayes factor are derived for further identification. A significant change, if identified, implies that there is a great alteration in the train operation performance due to defects. In this study, two illustrative cases are provided to demonstrate the performance of the proposed method for condition assessment of high-speed trains.

근사알고리즘을 적용한 금형온도 제어 방법 (Mold temperature control method using Approximation Algorithm)

  • 박성수;구형일
    • 한국정보통신학회:학술대회논문집
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    • 한국정보통신학회 2017년도 추계학술대회
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    • pp.270-273
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    • 2017
  • 플라스틱 사출물의 불량 감소 및 사이클 타임 축소를 통한 생산성 향상은 사출업계의 오랜 숙원 사항이다. 특히 중국 등 후발 주자의 추격과 좁혀지지 않는 독일, 일본과의 기술격차 사이에 끼어 있는 국내 사출업계에게 생산성 향상은 매우 절실하다. 30여년 국내 사출업계의 연구와 경험을 통해 금형 내 사출물 표면 온도 제어가 품질 관리의 핵심임을 알게 되었고 PID 제어 등 고급제어 기법을 활용한 다양한 시도가 있었으나 독일, 일본의 유수 업체의 생산성에는 아직 부족하다. 이에 근사알고리즘 중 "Knapsack"개념과 "Minimum Makespan Scheduling"기법을 활용하여 PID 제어로 풀기 어려운 수렴하지 않고 주기적인 반복 데이터 패턴을 지닌 대상을 효율적으로 제어할 수 있는 방법을 소개하고 또한 실제 사출 현장에서 추출한 데이터 분석으로 사출품의 생산성 향상에 근사알고리즘을 이용한 제어가 충분히 효과적임을 제시하고자 한다.

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상변태 예측 및 열응력 해석에 의한 CrMoSC1 강의 열처리 공정 설계 (Heat Treatment Process Design of CrMoSC1 Steel by Prediction of Phase Transformation and Thermal Stress Analysis)

  • 최봉학;곽시영;김정태;최정길
    • 열처리공학회지
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    • 제18권4호
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    • pp.247-255
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    • 2005
  • Although heat treatment is a process of great technological importance in order to obtain desired mechanical properties such as hardness, the process was required a tedious and expensive experimentation to specify the process parameters. Consequently, the availability of reliable and efficient numerical simulation program would enable easy specification of process parameters to achieve desired microstructure and mechanical properties without defects like crack and distortion. In present work, the developed numerical simulation program could predict distributions of microstructure and thermal stress in steels under different cooling conditions. The computer program is based on the finite difference method for temperature analysis and microstructural changes and the finite element method for thermal stress analysis. Multi-phase decomposition model was used for description of diffusional austenite decompositions in low alloy steels during cooling after austenitization. The model predicts the progress of ferrite, pearlite, and bainite transformations simultaneously during quenching and estimates the amount of martensite also by using Koistinen and Marburger equation. To verify the developed program, the calculated results are compared with experimental ones of casting product. Based on these results, newly designed heat treatment process is proposed and it was proved to be effective for industry.

몰드 두께에 의한 팬 아웃 웨이퍼 레벨 패키지의 Warpage 분석 (Analysis of Warpage of Fan-out Wafer Level Package According to Molding Process Thickness)

  • 문승준;김재경;전의식
    • 반도체디스플레이기술학회지
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    • 제22권4호
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    • pp.124-130
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    • 2023
  • Recently, fan out wafer level packaging, which enables high integration, miniaturization, and low cost, is being rapidly applied in the semiconductor industry. In particular, FOWLP is attracting attention in the mobile and Internet of Things fields, and is recognized as a core technology that will lead to technological advancements such as 5G, self-driving cars, and artificial intelligence in the future. However, as chip density and package size within the package increase, FOWLP warpage is emerging as a major problem. These problems have a direct impact on the reliability and electrical performance of semiconductor products, and in particular, cause defects such as vacuum leakage in the manufacturing process or lack of focus in the photolithography process, so technical demands for solving them are increasing. In this paper, warpage simulation according to the thickness of FOWLP material was performed using finite element analysis. The thickness range was based on the history of similar packages, and as a factor causing warpage, the curing temperature of the materials undergoing the curing process was applied and the difference in deformation due to the difference in thermal expansion coefficient between materials was used. At this time, the stacking order was reflected to reproduce warpage behavior similar to reality. After performing finite element analysis, the influence of each variable on causing warpage was defined, and based on this, it was confirmed that warpage was controlled as intended through design modifications.

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크랩랜딩(Crab Landing) QAR(Quick Access Recorder) 비행 데이터 통계분석 모델 (Crab Landing QAR (Quick Access Recorder) Flight Data Statistical Analysis Model)

  • 전제형;김현덕
    • 한국항행학회논문지
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    • 제28권2호
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    • pp.185-192
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    • 2024
  • 항공산업은 기술적인 혁신을 통해 안전성을 향상했으며, 항공 당국의 안전 규제와 감독을 통해 비행안전을 강화해 왔다. 항공산업의 안전 접근 방식이 항공기 시스템 전체에 대한 체계적인 접근 방식으로 발전함으로써 항공사는 새로운 안전 관리시스템을 구축하게 되었다. 항공기의 기술적 결함이나 비정상적인 데이터는 사고로 이어질 수 있는 전조 징후가 될 수 있으며, 이러한 징후를 조기에 식별하고 대처함으로써 사고 발생의 위험을 감소시킬 수 있다. 따라서 비정상적인 전조 징후의 관리는 데이터 기반 의사결정을 촉진하고, 항공사의 운영 효율성 및 안전수준을 강화하는 데 있어 필수적인 요소이다. 본 연구에서는 항공기 착륙 시에 활주로 이탈로 이어질 수 있는 크랩랜딩 이벤트의 패턴과 원인 분석을 위한 사전적 분석 단계에서 QAR (quick access recorder) 비행 데이터 통계 분석 모델을 제시하여 착륙 이벤트의 전조 징후와 원인을 식별 및 제거하는 안전관리의 효율성을 제고하고자 한다.