• Title/Summary/Keyword: Defect structures

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Reconstruction of a total defect of the lower eyelid with a temporoparietal fascial flap: a case report

  • Kim, Yun-Seob;Lee, Nae-Ho;Roh, Si-Gyun;Shin, Jin-Yong
    • Archives of Craniofacial Surgery
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    • v.23 no.1
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    • pp.39-42
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    • 2022
  • The reconstruction of total lower eyelid defects is challenging to plastic surgeons due to the complicated anatomical structure of the eyelid. In addition, in the setting of cancer excision, the resection is deep, which requires some volume augmentation. However, in some cases, free tissue transfer is not applicable. We report a case of using a temporoparietal fascia flap (TPFF) for reconstructing a total lower eyelid defect. A large erythematous mass in an 83-year-old woman was diagnosed as squamous cell carcinoma by biopsy. After wide excision, the defect size was about 8×6 cm. The lower eyelid structures including the tarsus were removed. The TPFF including the superficial temporal artery was elevated and inset to the defect area. After the flap inset, a split-thickness skin graft with an acellular dermal matrix was performed on the fascial flap. There were no wound problems such as infection, dehiscence, or necrosis. After the patient's discharge, partial skin graft loss and ectropion occurred. The complications resolved spontaneously during the postoperative period. We report a case of reconstructing a lower eyelid defect using a TPFF. A TPFF can be applied to patients with large defects for whom free tissue transfer surgery is not appropriate as in this case.

The Optimization of NDT Method for Real Time X-ray Imaging (X선 실시간 영상장치를 이용한 비파괴시험 조건 최적화 연구)

  • Na, Sung-Youb;Choi, Yong-Kyu
    • Journal of the Korean Society for Nondestructive Testing
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    • v.16 no.1
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    • pp.19-28
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    • 1996
  • This study has investigated the optimization of NDT method and the minimum detectable defect size for complex structures such as the solid propellant rocket motor using real time X-ray imaging system. Test specimens were made of steel plates with various defect size, and installed with proper thickness for which solid propellant, rubber, and case converted to the steel equivalent thickness according to the radiographic equivalent theory. As the results, this examination obtained optimum magnification and X-ray energy, dose rate according to steel equivalent thickness, also, obtained the relationship between minimum detectable defect size and the ratio(defect depot/object thickness). Thus, this simulated test is the preliminary procedure before performing NDT for real objects, and is possibly applied for NDT of other complex structures.

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Point Defect Engineering Approaches to Enhance the Performance of Thermoelectric Materials (열전소재 성능 증대를 위한 점결함 제어 전략)

  • Kim, Hyun-Sik;Jeong, Hyung Mo;Choi, Soon-Mok;Lee, Kyu Hyoung
    • Journal of the Microelectronics and Packaging Society
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    • v.26 no.4
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    • pp.157-161
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    • 2019
  • Independent control of electronic and thermal transport behaviors is one of the most effective approaches to enhance the performance of thermoelectric materials. To address this, many researches on the relationship between defect structures and thermoelectric properties have been carried out since defects are intrinsic ingredients of polycrystalline materials. Recently, experimental results of simultaneously improved electronic and thermal transport properties have been reported via the formation of 0-dimensional point defects. Here, theoretical backgrounds to the engineering of electronic and thermal transport behaviors by the formation of point defects are discussed and related experimental considerations are also presented in order to provide a practical guide for the development of highperformance thermoelectric materials.

Structural Analysis of Composite Wind Blade Using Finite Element Technique (유한요소기법을 이용한 복합재 풍력 블레이드 구조해석)

  • Unseong Kim;Kyeongryeol Park;Seongmin Kang;Yong Seok Choi;Kyungeun Jeong;Soomin Lee;Kyungjun Lee
    • Tribology and Lubricants
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    • v.40 no.4
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    • pp.133-138
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    • 2024
  • This study evaluates the structural safety of wind turbine blades, analyzes the behavior of composite laminate structures with and without defects, and assesses surface erosion wear. The NREL 5 MW standard is applied to assign accurate composite material properties to each blade section. Modeling and analysis of the wind turbine blades reveal stable behavior under individual load conditions (gravity, motor speed, wind speed), with the web bearing most of the load. Surface erosion wear analysis in which microparticle impacts are simulated on the blade coating shows a maximum stress and maximum displacement of 14 MPa and 0.02 mm, respectively, indicating good initial durability, but suggest potential long-term performance issues due to cumulative effects. The study examines defect effects on composite laminate structures to compare the stress distribution, strain, and stiffness characteristics between normal and cracked states. Although normal conditions exhibit stable behavior, crack defects lead to fiber breakage, high-stress concentration in the vulnerable resin layer, and decreased rigidity. This demonstrates that local defects can compromise the safety of the entire structure. The study utilizes finite element analysis to simulate various load scenarios and defect conditions. Results show that even minor defects can significantly alter stress distributions and potentially lead to catastrophic failure if left unaddressed. These findings provide valuable insights for wind turbine blade safety evaluations, surface protection strategies, and composite structure health management. The methodology and results can inform the design improvements, maintenance strategies, and defect detection techniques of the wind energy industry.

Interplay between Defect Propagation and Surface Hydrogen in Silicon Nanowire Kinking Superstructures

  • Sin, Nae-Cheol
    • Proceedings of the Korean Vacuum Society Conference
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    • 2015.08a
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    • pp.221.1-221.1
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    • 2015
  • The vapor-liquid-solid (VLS) method, where the "liquid" catalytic droplets collecting atoms from vapor precursors build the solid crystal layers via supersaturation, is a ubiquitous technique to synthesize 1-dimensional nanoscale materials. However, the lack of fundamental understanding of chemical information governing the process inhibits the rational route to the structural programming. By combining the in situ or operando IR spectroscopy with post-growth high resolution electron microscopy, we show the strong correlation between the surface chemical species concentration and nanowire structures. More specifically, the critical role of surface adsorbed hydrogen, generated from the decomposition of Si2H6 precursor on the interplay between nanowire / kinking and the defect propagation is demonstrated. Our results show that adsorbed hydrogen atoms are responsible for selecting -oriented growth and indicate that a twin boundary imparts structural coherence. The twin boundary, only continuous at / kinks, reduces the symmetry of the trijunction and limits the number of degenerate directions available to the nanowire. These findings constitute a general approach for rationally engineering kinking superstructures and also provide important insight into the role of surface chemical bonding during VLS synthesis.

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Damage assessment of linear structures by a static approach, I: Theory and formulation

  • Tseng, Shih-Shong
    • Structural Engineering and Mechanics
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    • v.9 no.2
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    • pp.181-193
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    • 2000
  • The objective of this research is to propose a new global damage detection parameter, termed as the static defect energy (SDE). This candidate parameter possesses the ability to detect, locate and quantify structural damage. To have a full understanding about this parameter and its applications, the scope of work can be divided into several tasks: theory and formulation, numerical simulation studies, experimental verification and feasibility studies. This paper only deals with the first part of the task. Brief introduction will be given to the dynamic defect energy (DDE) after systematically reviewing the previous works. Process of applying the perturbation method to the oscillatory system to obtain a static expression will be followed. Two implementation methods can be used to obtain SDE equations and the diagrams. Both results are equally good for damage detection.

A Method to Simulate Frictional Heating at Defects in Ultrasonic Infrared Thermography

  • Choi, Wonjae;Choi, Manyong;Park, Jeonghak
    • Journal of the Korean Society for Nondestructive Testing
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    • v.35 no.6
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    • pp.407-413
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    • 2015
  • Ultrasonic infrared thermography is an active thermography methods. In this method, mechanical energy is introduced to a structure, it is converted into heat energy at the defects, and an infrared camera detects the heat for inspection. The heat generation mechanisms are dependent on many factors such as structure characteristics, defect type, excitation method and contact condition, which make it difficult to predict heat distribution in ultrasonic infrared thermography. In this paper, a method to simulate frictional heating, known to be one of the main heat generation mechanisms at the closed defects in metal structures, is proposed for ultrasonic infrared thermography. This method uses linear vibration analysis results without considering the contact boundary condition at the defect so that it is intuitive and simple to implement. Its advantages and disadvantages are also discussed. The simulation results show good agreement with the modal analysis and experiment result.

The Defect Characterization of Rare-earth Intensifying Screen Material by Doppler Broadening Positron Annihilation Spectrometer (도플러 넓어짐 스펙트럼을 이용한 희토류 증감지 결함 특성)

  • Lee C. Y.;Kim C. G.;Song G. Y.;Kim J. H.
    • Korean Journal of Materials Research
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    • v.15 no.6
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    • pp.370-374
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    • 2005
  • Doppler broadening spectrometer for positron annihilation experiment(DBPAS) has been used to characterize nano size defect structures in materials. DBPAS measures the concentration, spatial distribution, and size of open volume defects in the rare-earth intensifying screen materials. The screens were exposed by X-ray varying the exposed doses from 3, 6, 9, and 12 Gy with 6 W and 15 MV respectively and also irradiated by 37 MeV proton beams ranging from 0 to $10^{12}ptls$. The S parameter values increased as the exposed time and the energies increased, which indicated the defects were generated more. The S parameters of the samples with X-rays varied from 0.5098 to 0.5108, on the other hand, as proton beams varied from 0.4804 to 0.4821.

Charateristics of defect modes in two-dimensional photonic bandgap structures (2차원 광자 밴드갭 구조의 디펙드 모드 특정)

  • 서영술;정교망
    • Korean Journal of Optics and Photonics
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    • v.11 no.3
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    • pp.198-201
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    • 2000
  • Using the Finite-Difference Time-Domain (FDTD) method that analyzes the Maxwell equations in time domain, we simulated the characteristics of optical wave propagation and defect modes in two-dimensional photonic crystals composed of dielectric cylinders located on triangular, square, and honeycomb lattices. In particular, we investigated the properties of defect modes as the permittvity of the defects is varied. aried.

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Physical issues for the next generation of nano devices (차세대 나노소자에서의 물리적 논점)

  • Cho, Mann-Ho
    • Vacuum Magazine
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    • v.1 no.3
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    • pp.21-27
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    • 2014
  • Advanced process and integration for future semiconductor devices is approaching the physical limit. The new materials with low dimensional structure have recently attracted great attention due to its expandability for the future electronic devices. In order to apply the materials to future semiconductor devices, the control of carrier scattering is critical issue. That is, the carrier scattering with physical quantity in low dimensional structure significantly modulates the device characteristics. We introduce the role of defect in several future semiconductor materials and devices. The analysis of defect in the structure becomes the most important techniques. In particular, surface defect in nano structures totally controls the device characteristics. The changes imply that the metrology field is leading the future industry for semiconductor.