• Korean Chemical Engineering Research
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• v.51 no.2
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• pp.208-213
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• 2013

Zirconium hydroxide was synthesized by varying the aging time of the zirconyl chloride octahydrate at $100^{\circ}C$ in aqueous solution and the resulting hydroxides were calcined at $700^{\circ}C$ for 6 h to obtain the crystalline $ZrO_2$. The materials used in this study were characterized by differential thermal analysis (DTA), X-ray diffraction (XRD), $N_2$-sorption, transmission electron microscopy (TEM), $NH_3$ temperature-programmed desorption ($NH_3$-TPD), $CO_2$-TPD and iso-propanol TPD analyses to correlate with catalytic activity for the dehydration of iso-propanol. The pure tetragonal $ZrO_2$ phase was obtained after 24 h aging of zirconium hydroxide and successive calcination at $700^{\circ}C$. The increase of aging time showed the production of smaller particle size $ZrO_2$ resulting that the higher specific surface area and total pore volume. $NH_3$-TPD results revealed that the relative acidity of the catalysts increased along with the increase of aging time. On the other hand, the results of $CO_2$-TPD showed the reverse trend of $NH_3$-TPD results. The best catalytic activity for the dehydration of iso-propanol to propylene was shown over $ZrO_2$ catalyst aged for 168 h which had the highest $S_{BET}$ ($178\;m^2\;g^{-1}$). The catalytic activity could be correlated with high surface area, relative acidity and easy desorption of iso-propanol.

• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.541-547
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• 2011

Nanorod-clustered $MnO_2$ precursors with ${\alpha}$-, ${\beta}$-, and ${\gamma}$-phases are synthesized by hydrothermal reaction of $MnSO_45H_2O$ and $(NH_4)S_2O_8$. The formation of nanorod-clustered ${\beta}-MnO_2$ is particularly confirmed under the conditions of high reactant concentration and hydrothermal reaction at $150^{\circ}C$. The spinel $LiMn_2O_4$ nanorod-clusters are also prepared by lithiating the $MnO_2$ precursors, varying the concentration of lithiating agent ($LiC_3H_3O_2{\cdot}2H_2O$) and heat treatment temperature, and characterized for use as cathode material of lithium-ion batteries. As a result, the nanorod-clustered $LiMn_2O_4$ prepared from the ${\beta}-MnO_2$ at higher $LiC_3H_3O_2{\cdot}2H_2O$ concentration and the annealing at $800^{\circ}C$ is proven to show the cubic spinel structure and to achieve the high initial discharge capacity of 120 mAh/g.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.5
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• pp.1054-1065
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• 1993

A computer simulation is performed on the effectiveness of the active minimization of harmonically excited enclosed sound fields for producing global reduction in the amplitude of the pressure fluctuations. In this study for the appreciable reductions in total time averaged acoustic potential energy, $E_{pp}$, the transducer location strategies for three dimensional active noise control is presented based on a state space modal which approximates the closed acoustic field.In this study, the above theoretical basis is used to investigate the application of active control to sound fields of low modal density. By the used of room-like 3-dimensional rectangular enclosure it is demonstrated that the reductions in $E_{pp}$ can be achieved by using a single secondary source, provided that the source is placed within the half a wavelength from the primary source and placed away from nodal line of the sound field. Concerning the reductions in $E_{pp}$ by minimzing the pressure in sound fields by the use of 3-dimensional rectangular enclosure, the effects of the number of sensors and the locations of these sensors are investigated. When a few modes dominate the response it is found that if only a limited number of sensors are located away from nodal line and located at the pressure maxima of the sound field such as at each corner of a rectangular enclosure.

• Journal of Food Hygiene and Safety
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• v.22 no.3
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• pp.137-144
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• 2007

Koji is steamed rice that has had koji-kin, or koji mold spores, cultivated onto it. The isolation, culture, and microscopic examination of molds in the koji require the use of the selective media and special microscopic slide techniques. If simple wet mount slides of molds were attempted, it became apparent that wet mount slides made from mold colonies usually don't reveal the arrangement of spores that is so necessary in identification. The process of merely transferring hyphae to a slide breaks up the hyphae and sporangiophores in such a way that identification becomes very difficult. The slide culture method is superior to wet mounts in that the hyphae, sporangiophores, and spores remain more or less intact when transferred. The procedure that will be used to produce a mold culture on a slide that can be observed directly on the slide. We investigated the contamination rate of penicillium spp. on the 21 kinds of koji distributed at Korea. The contamination rate of Penicillium spp. were not detected at 21 products by slide culture method. These results will be used to reestablish a mold determination of koji and food in Food Additives Code.

• Journal of Korean Society of Forest Science
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• v.106 no.4
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• pp.465-472
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• 2017

In this study, containerized seedlings of Pinus densiflora (2-0) were planted in Iso-ri, Hwadong-myeon, Sangju-si, Gyeongbuk on April, 2015. It was planted by lightweight planting auger that Kyungpook University has developed and mattock which is the general planting method of containerized seedlings. With the square planting method ($1.8{\times}1.8m$), 225 trees were planted respectively and about 2 years of initial growth, survival rate and seedling quality index (SQI) were analyzed and investigated. According to the analysis result, the average root collar diameter (mm) of planted containerized seedlings that used lightweight planting auger and mattock reached 3.77 and 3.94 in 2015, 18.73 and 15.32 in 2016, and 27.8 and 23.9 in 2017 respectively. In addition, the average height of containerized seedlings rated 33.4 and 33.4 in 2015, 89.8 and 74.7 in 2016 and 120.7 and 97.9 in 2017. It turns out that the height of initial growth of containerized seedlings that are planted by lightweight planting auger were much higher than mattock. The survival rate of the containerized seedlings that used lightweight planting auger was also higher by 10% than that used mattock. Also, H/D rate (healthiness) and T/R rate were almost the same, however, for the SQI, 0.60 was for lightweight planting auger and 0.24 for mattock. It seems like the lightweight planting auger is more advantageous than mattock in initial growth.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2003.09a
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• pp.52-52
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• 2003

악성종양을 치료하는 방법중 방사선과 온열요법은 가장 강력한 치료방법으로 연구되어왔으며 이를 병용함으로 서 상승효과를 얻을 수 있다. 인체조직에 41$^{\circ}C$ 이상의 열을 가하면 세포질의 단백질변성으로 세포에 손상을 주어 세포가 사멸하게 되며 세포의 생존율은 가열시간 즉 열량에 따라 지수적으로 감소한다. 온열은 세포주기중 방사선 저항성이 매우 큰 DNA 합성시기와 산도가 높을 때 감수성이 매우 크기 때문에 방사선과 병용요법은 상호 상승효과를 가져온다. 이와 같이 온열을 이용한 악성종양의 치료가능성은 생물학적 기초연구와 임상시험에서 경이적인 효과를 얻을 수 있었으나 아직 까지 가열방법과 온도분포측정이 큰 과제로 남아있으며 주위건강조직의 가열을 피하면서 인체 깊은 곳에 존재하는 종양에만 집중 가열하는 방법인 삽입형 온열치료방법에 대한 연구가 집중되었다. 한편 방사선 치료방법은 주위 건강조직의 피폭을 최소로 줄이고 종양에만 집중 조사가 요구되며 자궁암, 유방암, 뇌암등 부피가 작고 집중적 치료를 요하는 종양은 방사성동위원소를 이용한 근접 삽입치료 (Brachyradiotherapy)가 큰 효과를 나타내고 있다 방사선과 온열의 병행 치료를 위하여 방사선 삽입 치료에 사용한 선원 삽입관을 그대로 두고 삽입관 속에 방사성 동위원소 대신 온열 전극을 넣어 열을 가하는 방사선 온열 병용치료방법을 고안하였으며 방사선과 온열병용에 사용할 최적 삽입관의 제작과 이에 따른 온도분포의 측정과 최적삽입방법을 결정하였다. 방사선 삽입치료용 폴리에찌렌 삽입관의 외부에 금박을 입혀 라디오파 첨극을 삽입할 때 서로 연결되도록 고안 제작함으로서 방사선 삽입치료와 자입식 온열치료를 동시에 만족하게 수행할 수 있는 병용삽입관 (Flexible thermoradiotherapy probes)을 제작하였다. 전도율이 큰 금박부위가 직접 조직에 접촉됨으로 라디오파의 전달이 용이하며 금박의 길이를 2 cm 에서 5 cm 로 구분제작 함으로서 종양의 크기와 모양에 따라 선택할 수 있도록 하였다. 라디오파를 이용한 온열분포의 측정은 인체조직과 전기적 특성이 비슷한 물질인 한천 팬텀 제작하여 사용하였으며 온도분포 측정은 열전대와 서머그람으로 시행하였다. 생체조직 내에서의 온도분포와 온열효과를 관찰하기 위하여 직접 개의 뇌를 이용하여 시행하였으며 4 개의 전극을 이용하여 43$^{\circ}C$로 50분간 가열하고 일주일후 개를 회생시켜 개 뇌에 대한 조직학적 검사를 시행하였다. 한편 팬텀 표면에서 중앙부로 안테나 길이가 2 cm 인 4 개의 전극을 1 cm 간격으로 정사각형이 되도록 삽입하여 가열하였을 때 90% 등온곡선이 반경 1.25의 원형으로 균일하게 분포되었고 종단면상 삽입관의 길이에 따라 균일한 온도분포가 이루어졌다. 전극을 2 cm 간격으로 삽일 하였을 때 90% 등온곡선이 1.75 반경으로 거의 4 각형의 균일한 분포를 얻었으나 전극의 간격이 증가하면 전도율이 떨어져서 전극 중심부에 불균일한 온도분포를 형성하였다. 동물실험에서 정상 개의 뇌 실질에 자입하여 직접 정방형의 중심을 43$^{\circ}C$로 유지하며 50분간 온열 요법을 시행한 후 관찰한 조직병리학적 소견은 liquefactive necrosis, pyknosis of neuronal element 및 polymorphonuclear leukocytes들의 회백질에서 급성기에 관찰되었고 liquefactive necrosis 주위에 lipid-laden macrophage들이 관찰됨이 공통적인 특정이었으며 후기변화로 괴사조직 주위로 신경교세포의 증식이 관찰되었다.

• The Journal of Engineering Geology
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• v.23 no.4
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• pp.447-455
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• 2013

A micro-mechanical pipe network model with the shape of a cube was developed to simulate the behavior of fluid flow through a porous medium. The fluid-flow mechanism through the cubic pipe network channels was defined mainly by introducing a well-known percolation theory (Stauffer and Aharony, 1994). A non-uniform flow generally appeared because all of the pipe diameters were allocated individually in a stochastic manner based on a given pore-size distribution curve and porosity. Fluid was supplied to one surface of the pipe network under a certain driving pressure head and allowed to percolate through the pipe networks. A percolation condition defined by capillary pressure with respect to each pipe diameter was applied first to all of the network pipes. That is, depending on pipe diameter, the fluid may or may not penetrate a specific pipe. Once pore pressures had reached equilibrium and steady-state flow had been attained throughout the network system, Darcy's law was used to compute the resultant permeability. This study investigated the sensitivity of network size to permeability calculations in order to find out the optimum network size which would be used for all the network modelling in this study. Mean pore size and pore size distribution curve obtained from field are used to define each of pipe sizes as being representative of actual oil sites. The calculated and measured permeabilities are in good agreement.

• Journal of Korean Society of Steel Construction
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• v.21 no.5
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• pp.451-459
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• 2009

The purpose of this study was to evaluate the in-plane bending moment for T-joints made of cold-formed square hollow steel sections. In the previous studies, the T-joint was shown not to have an obvious peak load, and the failure mode was the main chord flange failure at the branch-width-to-chord-width ratio ($\beta$) of below 0.71. Based on the experimental results, including the tests conducted by Zhao, the deformation limit of 1% B was proposed for ${16.7{\leq}2{\gamma}(=B/T){\leq}33}$ and ${0.34{\leq}{\beta}(=b_{1}/B){\leq}0.71}$. Then, the ultimate in-plane bending strength was shown to be Mu=1.5${\cdot}$M1% B. The existing strength formulae for the original T-joint were investigated and were determined to be the main chord flange failure for the branch-squared T-joint. The bending strength formulae of CIDECT and other researchers were compared with the test results. Finally, a reasonably good agreement with Zhao's formula was found. Therefore, the design guidelines were presented based on Zhao's strength formula for T-joints.

• Journal of Korea Water Resources Association
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• v.36 no.6
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• pp.925-936
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• 2003

The objective of this study is to suggest new drawing methods of isochrones using GIS. For this purpose the Unit Hydrograph (UH) of studied watershed for instantaneous rainfall suggested by Clark have been determined by routing the time-area curve through a single linear reservoir. To evaluate constructing methods of isochrones three methods has been examined; Channel Profile and Clark-kict method; Laurenson method; Average velocity method of S.C.S. Also, these methods have been recomposed by GIS in this study. To apply first method, spatial modeling, the vector based on the stream network and Route_System measuring a distance between points has been used. A raster based on the flow direction grid from burn DEM and the slope grid from original DEM has been applied for the second method. The third method has been applied by a raster based on the landuse grid and a velocity function expressed by slope. Results by these three methods have been evaluated with observed hydrograph, and the method using average velocity method of S.C.S shows more reasonable results comparatively.

• Journal of the Korean Geotechnical Society
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• v.17 no.6
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• pp.181-191
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• 2001

Granular compaction piles increase the load bearing capacity of the soft ground and reduce the settlement of fecundation built on the reinforced soil. Also the granular compaction piles accelerate the consolidation of soft ground using the granular materials such as sand, gravel, stone etc. However, this method is one of unuseful methods in Korea. In the present study, the estimation procedure for the ultimate bearing capacity of randomly installed granular compaction pile group is proposed. Also, carbon rod tests have been peformed for verifying the group effect of granular compaction piles and the behavior characteristics such as bulging failure zone on granular compaction piles. From the test results, it is found that bulging failure shape of granular compaction piles was conical shape and the ultimate bearing capacity increased as the spacing of piles became gradually narrow. Also, from the proposed method in this study, the optimal locations of granular compaction piles with various installed cases are analyzed. The results were shown that the bearing capacity was increased in the case concentrated on the central part of pile group.