• 한국가시화정보학회지
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• 제19권1호
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• pp.3-11
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• 2021

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 2020년도 정기학술대회 발표논문집
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• pp.94-94
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• 2020

• 방사선산업학회지
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• 제9권3호
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• pp.137-141
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• 2015

A single-shot dual-energy x-ray imaging technique has been developed using a sandwich detector by stacking two detectors, in which the front and rear detectors respectively produce relatively lower and higher x-ray energy images. Each detector layer is composed of a phosphor screen coupled with a photodiode array. The front detector layer employs a thinner phosphor screen, whereas the rear detector layer employs a thicker phosphor screen considering the quantum efficiency for x-ray photons with higher energies. We have applied the proposed method into the inspection of printed circuit boards, and obtained dual-energy images with background clutter suppressed. In addition, the single-shot dual-energy method provides sharper-edge images than the conventional radiography because of the unsharp masking effect resulting from the use of different thickness phosphors between the two detector layers. It is promising to use the single-shot dual-energy x-ray imaging for high-resolution nondestructive testing. For the reliable use of the developed method, however, more quantitative analysis is further required in comparisons with the conventional method for various types of printed circuit boards.

• 한국표면공학회지
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• 제53권6호
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• pp.330-342
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• 2020

Since the original report on ferroelectricity in Si-doped HfO2 in 2011, fluorite-structured ferroelectrics have attracted increasing interest due to their scalability, established deposition techniques including atomic layer deposition, and compatibility with the complementary-metal-oxide-semiconductor technology. Especially, the emerging fluorite-structured ferroelectrics are considered promising for the next-generation semiconductor devices such as storage class memories, memory-logic hybrid devices, and neuromorphic computing devices. For achieving the practical semiconductor devices, understanding polarization switching kinetics in fluorite-structured ferroelectrics is an urgent task. To understand the polarization switching kinetics and domain dynamics in this emerging ferroelectric materials, various classical models such as Kolmogorov-Avrami-Ishibashi model, nucleation limited switching model, inhomogeneous field mechanism model, and Du-Chen model have been applied to the fluorite-structured ferroelectrics. However, the polarization switching kinetics of fluorite-structured ferroelectrics are reported to be strongly affected by various nonideal factors such as nanoscale polymorphism, strong effect of defects such as oxygen vacancies and residual impurities, and polycrystallinity with a weak texture. Moreover, some important parameters for polarization switching kinetics and domain dynamics including activation field, domain wall velocity, and switching time distribution have been reported quantitatively different from conventional ferroelectrics such as perovskite-structured ferroelectrics. In this focused review, therefore, the polarization switching kinetics of fluorite-structured ferroelectrics are comprehensively reviewed based on the available literature.

• 소성∙가공
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• 제33권4호
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• pp.285-290
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• 2024

Electropulsing treatment (EPT) has been developed as an alternative to furnace heat treatment (FHT) to exploit its engineering advantages in rapidly annealing metallic materials. Conventionally, the separation of thermal and athermal effects of EPT has been attempted by comparing EPT and FHT specimens processed under identical temperature and duration. However, this method inherently introduces experimental and measurement errors. This study proposes a novel approach to distinguish the thermal and athermal effects of EPT-processed metals using T-shaped specimen with two observation points, namely 'C' and 'D'. For verification, the thermal gradient of T-shaped Mg alloys was examined under various EPT conditions. The points C exhibited higher temperatures compared to those at points D at a given electric current density, because only the former received both thermal and athermal effects. It was confirmed from twelve specimens that the point C at an electric current density of 65 A·mm^-2 and point D at 70 A·mm^-2 exhibited similar temperatures. This developed method is expected to reduce measurement errors in distinguishing thermal and athermal effects, thus providing a deeper understanding of their quantitative contributions in future studies.

• 대한금속재료학회지
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• 제46권6호
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• pp.382-389
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• 2008

To manufacture Al MMCs, in-situ melt mixing process is used because it is free from contamination, and it makes reinforcements homogeneously dispersed. Large eddy simulation method is used to find the optimum melt mixing condition. At the Re 3000, the most suitable mixing is occurred between Al-Ti and Al- B melts. The in-situ formed $TiB_2$ particles has the size varying from 40 nm to 130 nm, due to the increase of cooling rate, and exhibits a homogeneous dispersion. And the interface between reinforcement and matrix is clean. Both hardness and Young's modulus of this composite are improved with increasing the cooling rate.

• 대한중풍순환신경학회지
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• 제15권1호
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• pp.50-56
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• 2014

The prevalence rate of plant poisoning is growing up gradually. However, it could be difficult to get proper treatment without detail medical history taking due to the diversity of poisonous plants and their various symptoms. Scopolia Japonica, which grows naturally in Korea, is reported to cause severe toxicity which could be lethal. A few therapeutic measures have been reported in Traditional Korean Medicine (TKM), but it has not been reported yet that those measures have been successfully proven in the clinical practice in modern times. This is a case report of toxicity caused by scopolia japonica ingestion. A 65years-old male patient with cognitive impairment, behavioral disorder, gait difficulty, dysarthria, dysphagia and abnormal pupil reflex recovered from those symptoms during taking Gamigamdu-tang and getting acupuncture. This study shows the clinical aspects of Scopolia Japonica toxicity and the possibility of TKM treatments as one of plant poisoning treatments.

• 소성∙가공
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• 제32권5호
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• pp.276-286
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• 2023

The field of sheet metal forming using press technology has become essential in modern mass production systems. Draw bead is often used to enhance formability. However, optimal draw bead design often requires excessive time and cost due to iterative experimentation and sometimes results in some defects. Given these challenges, there is a need to enhance formability by introducing segmented blank holders without draw beads. In this paper, the feasibility of a localized holding strategy using segmented blank holders is evaluated without the use of draw beads. The possibility for improving the formability was evaluated by utilizing a combination of the forming limit diagram and the wrinkle pattern-based defect indicators. Artificial neural networks were used for predicting defect indicators corresponding to arbitrary input holding forces and the NSGA-II optimization algorithm is used to find optimum blank holder forces yielding better defect indicators than the original process with drawbeads. Using optimum holding forces obtained from the proposed procedure, the stamping process with the segmented blank holders can yield better formability than the conventional process with drawbeads.

• 소성∙가공
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• 제28권1호
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• pp.27-33
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• 2019

The effect of hardening methods and process parameters on surface hardening of a Ti-6Al-4V Alloy has been investigated in this study. To characterize the effectiveness of the respective surface hardening methods, samples of a Ti-6Al-4V alloy were self-quenched, laser-nitrided, laser-carburized, laser-carbonitrided at the same laser irradiation conditions. This experimental procedure was followed by comparing the microstructural evolutions and mechanical properties of the respective samples after the laser surface hardenings. The hardening characteristics of the respective laser surface hardenings were well defined in this study, and the hardness was significantly influenced by the reaction compounds and laser energy density.

• 한국기록관리학회지
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• 제16권2호
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• pp.143-172
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• 2016

전통적으로 부산 일대에서 전통적인 정치 행정의 중심지는 정주공간인 동래이고, 부산은 동래부 동평현 부산포라는 어촌이었다. 개항 이후 일본과의 연이은 조약으로 일본인의 조선 내에서의 활동범위가 넓어지고 조선에서 일본인의 상업행위가 허용됨에 따라 일본인의 이주가 급증하였다. 일본은 조차나 임대, 매입 또는 매축을 통해 전관거류지와 서쪽 방면 일대, 북항 일대의 부지를 확보하고, 북항 일대에 공공시설과 상공업시설, 철도 항만시설을 구비하여 경부철도와 관부연락선이 바로 연결되도록 하였다. 이처럼 부산이 한일간 교통의 요충지가 되자 부산은 통상 중심의 상업이 발달하고, 부산항은 조선 최대의 무역항으로 자리매김 하였다. 조선이 일본에 병합된 이후 조선총독부는 토지조사사업을 통해 조선의 임야와 거대한 농지를 확보하고, 소작농이 도시 임금노동자로 전락하게 되었다. 회사령을 통해 조선 자본의 성장을 억제하고 일본 자본이 침투하여 일본인 기업이 대거 설립되었다. 1914년에 시가지는 부(府)로, 농촌은 군(郡)으로 지방행정조직이 개편됨에 따라 부산포 일대의 일본인이 개발한 지역은 부산부로, 그 외의 농촌지역은 동래군으로 바뀌었다. 새로 신설되는 공공시설과 상공업시설, 철도 항만시설은 부산부에 집중적으로 들어섬에 따라 변방이었던 이곳이 정치 행정의 중심지로 탈바꿈하였다. 부산이 교통과 교역의 중심지로 성장함에 따라 경상남도의 도청이 진주에서 부산으로 이전하였다. 이로써 부산이 경상남도의 정치와 행정의 중심지로 역할이 확대되었다. 토지조사사업으로 대규모 노동력을 확보하고, 회사령 철폐로 일본이 대자본이 식민지로 진출하였다. 부산진 방면의 매립으로 조선방직 등 대규모 공업시설이 설립되었다. 이런 과정을 통해 부산의 도시 정체성, 즉 로컬리티도 어촌에서 통상 위주의 상업도시로, 나아가 상공업 도시로 변모하게 되었다.