• Korean Membrane Journal
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• 제3권1호
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• pp.39-50
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• 2001

The counter-diffusion of two gaseous substances permeating a polymeric membrane has been investigated both experimentally and theoretically. The aim of the study was to find mutual effects, if any, that could influence the permeability and diffusivity data. The experimental data were obtained with an isostatic permeameter operating at ambient pressure and 303 K: helium, nitrogen, carbon dioxide methane were used as permeating gas at different partial pressure; helium or nitrogen as equilibrating or carrier gas. No evident mutual effect of the counter-diffusing gas was observed. The theoretical analysis gave some insight into the phenomena and it was concluded that at near-atmospheric pressures, and in the absence of swelling phenomena no mutual interaction exists. On a theoretical basis any mutual interaction between diffusing and counter-diffusing gases could only occur: i) at high pressures , when the free movement of permeating gas molecules within the polymer is hindered by the counter-diffusing gas; ii) when a large part of the free volume fraction is occupied by the counter--diffusing gas; iii) swelling phenomena modify the structure and free volume fraction of the polymer.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.507-511
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• 2008

LTCC (Low Temperature Co-fired Ceramic) has been successfully applied to ceramic substrates for circuits and micro-fluidic systems and has proven its superior performance in a variety of applications. The prediction of shrinkage in LTCC process is an important for dimensional control of micro LTCC products which has influences on electronic characteristics. For avoiding the unpredictable shrinkage of LTCC during the sintering which makes accurate placement of the circuit devices difficult, pre-processes such as WIP (Warm Isostatic Pressing) and lamination must be modified. The objective of the present investigation is to establish a proper WIP conditions for near net shape fabrication of LTCC products. This paper discusses the influence of WIP conditions on the dimensional change of LTCC sheet. In the investigation, it is shown that the shrinkage values of sheets depend on WIP conditions and sheet directions. This work is a quantitative evaluation of the effect of WIP pressure on shrinkage of LTCC sheet. Additionally, the results show anisotropic shrinkage behaviour of sheet during LTCC process.

• 대한원격탐사학회지
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• 제21권1호
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• pp.51-57
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• 2005

The currently operating NASA/GFZ Gravity Recovery and Climate Experiment (GRACE) mission is designed to measure small mass changes over a large spatial scale, including the mapping of continental water storage changes and other geophysical signals in the form of monthly temporal gravity field. The European Space Agency's Gravity field and steady state Ocean Circulation Explorer (GOCE) space gravity gradiometer (SGG) mission is anticipated to determine the mean Earth gravity field with an unprecedented geoid accuracy of several cm (rms) with wavelength of 130km or longer. In this paper, we present a summary of present GRACE studies for the recovery of hydrological signals in the Amazon basin using alternative processing and filtering techniques, and local inversion to enhance the temporal and spatial resolutions by two-folds or better. Simulation studies for the potential GRACE detection of slow deformations due to Nazca-South America plate convergence and glacial isostatic adjustment (GIA) signals show that these signals are at present difficult to detect without long-term data averaging and further improvement of GRACE measurement accuracy.

• International Journal of Precision Engineering and Manufacturing-Green Technology
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• 제5권5호
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• pp.605-612
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• 2018

This work investigates the relationships between the static mechanical properties of Ti-6Al-4V manufactured through selective laser melting (SLM) and post-process heat treatments, namely stress relieve, annealing and hot isostatic pressing (HIP). In particular, Ti-6Al-4V parts were fabricated in three different build orientations of X, Z, and $45^{\circ}$ to investigate the multi-directional mechanical properties. The results showed that fully densified Ti-6Al-4V parts with densities of up to 99.5% were obtained with optimized SLM parameters. The microstructure of stress relieved and mill annealed samples was dominated by fine ${\alpha}^{\prime}$ martensitic needles. After HIP treatment, the martensite structure was fully transformed into ${\alpha}$ and ${\beta}$ phases (${\alpha}+{\beta}$ lamellar). Within the realm of tensile properties, the yield and ultimate strength values were found statistically similar with respect to the built orientation for a given heat treatment. However, the ductility was found orientation dependent for the HIP samples, where a lower value was observed for samples built in the X direction.

• Nuclear Engineering and Technology
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• 제54권5호
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• pp.1535-1540
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• 2022

A solid tungsten target was used at the China Spallation Neutron Source (CSNS) with 100 kW proton beam power. To improve the lifetime, hot isostatic pressing (HIP) process was selected to bond tantalum cladding with tungsten plates. Radioactive isotope ¹⁸²Ta, an activation product of tantalum, was found in the cooling water after a period of operation, however, no radioactive isotopes of ¹⁸⁷W was found, which shows the tantalum layer remained mostly intact. The CSNS Target-1 had been operating safely for three years and was replaced by Target-2 in August 2020.

• 한국분말재료학회지
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• 제31권1호
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• pp.1-7
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• 2024

This study explores the profound impact of varying oxygen content on microstructural and mechanical properties in specimens HO and LO. The higher oxygen concentration in specimen HO is found to significantly influence alpha lath sizes, resulting in a size of 0.5-1 ㎛, contrasting with the 1-1.5 ㎛ size observed in specimen LO. Pore fraction, governed by oxygen concentration, is high in specimen HO, registering a value of 0.11%, whereas specimen LO exhibits a lower pore fraction (0.02%). Varied pore types in each specimen further underscore the role of oxygen concentration in shaping microstructural morphology. Despite these microstructural variations, the average hardness remains consistent at ~370 HV. This study emphasizes the pivotal role of oxygen content in influencing microstructural features, contributing to a comprehensive understanding of the intricate interplay between elemental composition and material properties.

• 자원환경지질
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• 제51권5호
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• pp.463-471
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• 2018

서해안에서 보고되고 있는 다수의 해수면 변동 곡선들은 모두 상대해수면(Relative sea-level) 변동곡선으로 사료된다. 서해안의 상대해수면 변동곡선들은 크게 1) 홀로세 해수면은 현 해수면보다 높은 적이 없었다는 학설과 2) 중기 홀로세에 해수면은 현재 해수면보다 수m 높았으며, 이 후 서서히 하강하면서 현해수면에 도달하였다는 학설로 대표된다. 전자는 절대해수면 곡선과 대비되는 반면, 후자는 빙하로부터 원거리에 위치하고 있는 대륙의 연안 역에서 나타나는 상대해수면곡선과 대비된다. 해수면 곡선 복원도에 활용된 자료들을 검토하여 보았을 때, 대부분 기 발표된 논문의 자료들을 인용하였으나, 그 인용에 있어 분석자료의 선택적 사용으로 서로 다른 결과들이 도출되었다. 그럼에도 불구하고, 후자의 자료들은 모두 군산이북지역으로부터 얻어진 것으로, 중기 홀로세 이후 서서히 하강하는 해수면 변동곡선이 군산 이북지역을 대표하고 있는 것으로 생각된다. 서해안 상대해수면 곡선은 빙하평형조절(GIA:Glacio isostatic adjustment)과 이에 수반된 중력 끌림(Gravitational attraction)에 의한 요인뿐만 아니라 그 이외의 지엽적으로 발생하는 지구조 운동 등에 의하여 변동될 수 있다. 그러므로, 서해안역의 상대해수면곡선 양상이 원거리 지역에서 나타나는 것과 대비 되지만, 서해안의 활발한 지진활동과 한반도에 분포하는 다수의 단층 존재를 미루어 볼 때, 지역적으로 발생하는 지구조 운동이 상대해수면 변동에 영향을 끼칠 수 있었을 것으로 예상된다.

• 한국재료학회지
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• 제10권4호
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• pp.312-316
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• 2000

HIP처리가 가스터빈 고정익 등 고온부품에 적용되는 열차폐 코팅층의 접착강도 및 고온특성에 미치는 영향을 조사하였다. 시편은 IN738LC 초합금 표면에 8wt%Y$_2$O$_3$-$ZrO_2$분말을 플라즈마 용사법으로 코팅한 후 $1200^{\circ}C$, 100MPa의 고온, 고압에서 4시간 동안 HIP 처리하여 준비하였다. 실험결과 HIP 처리된 코팅의 경우 미세균열과 기공이 상당량 감소하였으며 EDX분석을 통해 계면에서 원자간 상호확산이 발생한 것을 확인하였다. 이러한 코팅층의 치밀화 및 상호확산으로 인해 HIP처리된 코팅층의 접착강도는 48% 이상 크게 증가하였으며 조직 또한 균질화 되었다. 반면 가열과 냉각이 반복되는 환경에서 코팅층의 내구력은 HIP 처리된 경우가 다소 저하되었다. 이는 코팅과 모재와의 열팽창 차이로 인한 변형을 완화시켜주는 기공과 미세균열이 감소되었기 때문으로 판단된다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2007년도 추계학술대회 논문집
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• pp.381-382
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• 2007

• 한국세라믹학회지
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• 제24권3호
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• pp.223-226
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• 1987

Among many densification routes for silicon nitride, HIP(hot isostatic pressing) is becomming more popular these days, mainly due to the fact that it can produce highly reliable products with superior mechanical properties. This study involves in sintering of silicon nitride followed by HIP which requires no canning. Various property changes curing sintering and HIP are observed and analyzed in terms of microstructural changes. Porosity decrease and enhanced interlocking of grains by HIP are considered to be the major causes for improved mechanical properties of silicon nitride.