• Transactions on Electrical and Electronic Materials
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• v.16 no.2
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• pp.86-89
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• 2015

Uniform ZrO₂ nanoballs were synthesized at 700℃ using the inverse replication method through a colloid-imprinted carbon (CIC) template. The structural, dielectric, and conducting properties of the ZrO₂ nanoballs were investigated and compared with those of ZrO₂ film prepared by sol-gel method and powdered ZrO₂ chemical. Both the monoclinic and cubic phases were found in the ZrO₂ balls and film but the ZrO₂ chemical showed a monoclinic phase, where the cubic structure is known to be formed at above 2,300℃. ZrO₂ nanoballs showed the lower dielectric property of k = 21.2 at 1 MHz because the 8-coordinated cubic phase in the ZrO₂ nanoball produced lower polarization than the polarization of the 7-coordinated monoclinic ZrO₂ chemical (k = 23.6). The dielectric stability was maintained in each ZrO₂ ball, film, and chemical under the applied forward and reverse voltage range (−5 to +5 V) at 1 MHz. The ionic conductivities were 7.86 × 10⁻⁸/Ω·cm for ZrO₂ nanoballs, 3.29 × 10⁻⁸/Ω·cm for ZrO₂ chemical, and 6.70 × 10⁻⁵/Ω·cm for the thickness of 1,053 nm ZrO₂ film at room temperature with the electronic contribution being less than 0.006%.

• Journal of Powder Materials
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• v.15 no.5
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• pp.371-377
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• 2008

This paper deals with the phase analysis of $MgB_2$ bulk using spark plasma sintering process after ball milling. Mg and amorphous B powders were used as raw materials, and milled by planetary-mill for 9 hours at argon atmosphere. In order to confirm formation of $MgB_2$ phase, DTA and XRD were used. The milled powders were fabricated to $MgB_2$ bulk at the various temperatures by Spark Plasma Sintering. The fabricated $MgB_2$ bulk was evaluated with XRD, EDS, FE-SEM and PPMS. In the DTA result, reaction on formation of $MgB_2$ phase started at $340^{\circ}C$. This means that ball milling process improves reactivity on formation of $MgB_2$ phase. The $MgB_2$ MgO and FeB phases were characterized from XRD result. MgO and FeB were undesirable phases which affect formation of $MgB_2$ phase, and it's distribution could be confirmed from EDS mapping result. Spark Plasma Sintered sample for 5 min at $700^{\circ}C$ was relatively densified and it's density and transition temperature showing super conducting property were $1.87\;g/cm^3$ and 21K.

• The Journal of Engineering Geology
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• v.19 no.4
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• pp.493-499
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• 2009

Recently, the construction of Concrete Faced Rockfill Dam (CFRD) is increasing because rock material resources are plenty in Korea. Bedding zone in the CFRD is necessary enough bearing capacity to support the concrete face slab uniformly and enough impermeability to prevent the loss of fine soils in case of leakage from the concrete slab face. Therefore, cut-off the water leakage in bedding zone securely is the key factor influencing the safety of CFRD. Tested materials satisfied with the specification of particle size distribution at the Bedding Zone area are chosen for conducting permeability tests, which are done to evaluate the property of cut off the materials. Based on the test results, the effects of cut off the materials are investigated by considering the coefficient of permeability, the soil particle distribution, and the dry unit weight. Especially, the relationships between coefficient of permeability with effective size(D10), dry unit weight, and weight passing percent the No.4 sieve are suggested, and also the variation of coefficient of permeability with time are proposed.

• Applied Chemistry for Engineering
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• v.21 no.4
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• pp.430-434
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• 2010

The sheet for electromagenetic interference (EMI) shielding was prepared with slurry made by the mixture of binder, methyl ethyl ketone, cyclohexanone and metal powder. We tried to enhance the shielding efficiency by adding carbon nanotube (CNT), which has known as highly conducting material. Surface and component analyses were carried out with SEM and EDS, respectively. The electric characteristics and EMI shielding efficiencies were measured with 4-point probe measurement and EMI efficiency measurement equipment. The sheet with 2% CNT addition showed the lowest electrical resistance, $13.13{\Omega}}{\cdot}cm$. It also showed the highest EMI shielding efficiency of 63 dB.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.167-177
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• 2002

A test method has been attempted to estimate the soil stiffness by measuring and analyzing dynamic signals of stress waves reflected at the bottom end of the SPT rod contacting a soil deposit. Before conducting a real size testing, a series of parametric studies were conducted in this paper to examine the applicability and the theoretical adequacy of the test method. As a result of these studies, it has been shown that the most significant influence factor affecting the amplitude ratio of the reflected wave to the incident wave at the rod-soil interface was the variation of soil stiffness. Also, the variation of the amplitude ratio was found to be closely related with the variation of impedance ratio of the soil deposit to the SPT rod. As a result, a potential of the test method could be proved to estimate the impedance and the elastic modulus of the soil deposit interfaced with the SPT rod using the test method.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.6 no.6
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• pp.1-13
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• 2003

This study aims at conducting an awareness survey of three parties, namely, citizens, government officials, and developers for improvement of urban landscape and, based on the survey result, to suggest a direction to develop a landscape plan for improvement of urban landscape of Yong-in city in the future. The summary of this study is as follows. First, in case of Yong-in, the main drivers of forest landscape destruction were "residential complexes developed for apartment buildings" and "golf courses", the driver of river landscape damage was "the status of cleanliness of riverside and poor facilities", the driver of roadside landscape damage was "construction sites" that completely eliminate original natural landscape in both citizen and government official groups. When granting development-related approvals in the future, appropriate actions should be prepared such as developing a landscape management guideline or including a landscape plan in advance to assure plans and designs fully reflecting landscape. Second, citizens' commitment to participate in urban landscape creation and improvement was rated high at even willing to tolerate regulations including restriction of property rights. In the future, landscape improvement programs allowing resident participation should be developed proactively. The roles of government officials include preparing various criteria at a city level and convincing and guiding citizens to initiate landscape improvement project together with citizens and developers through proactive efforts by government officials. Third, the role of developers would be to realize development projects conserving local environment and/or harmonizing with local natural environment before preparing a development plan or launching construction rather than offering various considerations after executing development projects.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1377-1384
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• 2010

The objective of this study is to determine the best material model that represents the deformation behavior of the Sn37Pb solder alloy accurately. First, a specimen is fabricated and subjected to a thermal cycle with temperatures ranging from the room temperature to $125^{\circ}C$. An experiment is conducted to examine deformation by Moire interferometry. Three different constitutive equation models are used in the finite element analysis (FEA) of the thermal cycle. In order to minimize the difference between the FEA results and the experimental results, the material parameters of the solder alloy are considered to be unknown and are determined by conducting optimization. As a result of the study, the Anand model is found to represent the deformation behavior of the solder most accurately.

• The Journal of the Korea Contents Association
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• v.16 no.10
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• pp.533-545
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• 2016

It is well known that international technology transfer(ITT) is relatively more difficult than the domestic technology transfer because of the difference in interest, technology level, culture and other various macro-environmental conditions. This study aims to derive recommendations for ITT of National Science and Technology Information Service(NTIS) of Ministry of Science, ICT and Future Planning(MSIP) by conducting case study of ITT in domestic public information systems. The cases are the national agencies that performed successfully in ITT. The cases are Korea Customs Service(KCS)'s customs administration system(UNI-PASS), Public Procurement Service(PPS)'s Korea On-Line E-Procurement System(KONEPS), and Korean Intellectual Property Office(KIPO). After studying on how the cases proceeded ITT, this paper suggests proper preparation strategies in the view point of information marketing.

• Microbiology and Biotechnology Letters
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• v.45 no.2
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• pp.143-148
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• 2017

Ten Bacillus strains possessing amine oxidase activity were selected from 126 Bacillus isolates from meju and doenjang (two traditional Korean soybean foods). Among the isolates, two B. licheniformis strains (8MI05 and 8MS03) harbored the amine oxidase gene yobN. By conducting a gene search against published B. licheniformis genomes, the possession of yobN was proved to be a strain-specific property. Both strains degraded four types of biogenic amines (cadaverine, histamine, putrescine, and tyramine) supplemented in tryptic soy broth during their culture. A recombinant harboring yobN also degraded the four types of biogenic amines during cultivation. Both Bacillus strains could grow at a NaCl concentration of 14% and exhibited strain-specific protease and lipase activities.

• Journal of the Mineralogical Society of Korea
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• v.27 no.4
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• pp.293-299
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• 2014

The bentonite, a buffer material, is essential for the deep geological disposal of HLW (high-level radioactive waste), and it is important to know its characteristic long-term evolution in the underground environment. With an assumption that the concentration of aqueous copper ions will increase if copper-coated materials on a metal canister are corroded, we examined some characteristic ion-exchanges and cation release phenomena occurring in the bentonite clay (montmorillonite) interacted with aqueous Cu cations. During the interaction between dissolved copper and bentonite, Na rather than Ca cations in the expandable clay were preferentially replaced by Cu ions in the experiment. In addition, the Cu-exchanged montmorillonite was characterized by an asymmetric X-ray diffracted pattern with relatively collapsed interlayers compared to the raw sample. These results indicate that the gradual change of the original bentonite property may occur in a underground disposal condition. We are going to further study the characteristic chemical and mineralogical changes of the bentonite buffer to be used for the disposal site by conducting additional experiments.