• Composites Research
• /
• v.16 no.5
• /
• pp.45-53
• /
• 2003

The experimental and numerical investigations on the failure characteristics of the secondary bonded composite single-lap joints were performed. The initiations and growths of cracks were observed using CCD camera and acoustic emission sensor during the tension tests of the joint specimens. The structural behaviors of the specimens were predicted by the geometric nonlinear two-dimensional finite element analysis. The three types of observed initial cracks were included in each finite element models and the strain energy release rates of each specimen models were calculated by VCCT(Virtual Crack Closure Technique) technique. The tension tests showed that the initial cracks occurred in the 60∼90% of final failure loads and the major failure modes of the specimens were adhesive failure and the delamination between the 1st and 2nd ply of laminate. The specimens with the thicker bondline had earlier crack initiation loads but higher crack propagation resistance and eventually better loading capability. The delaminations were mostly observed in the thicker bondline specimens. The mode I values of calculated strain energy release rates were higher than the mode II values in the all specimen models considering the three types of initial cracks. The mode I and total strain energy release rates were calculated as higher values in the order of initial crack in the edge interface, comer interface and delamination between the plies of laminate.

• Journal of the Korean Electrochemical Society
• /
• v.6 no.1
• /
• pp.1-5
• /
• 2003

[ $LiNi_{1-x}Co_xO_2\;(x=0.0\~1.0)$ ] powders were synthesized by citrate method, and their crystal structures and electrochemical performance as the cathode material in Li secondary batteries were analyzed. X-ray diffraction analysis revealed that all the samples carry a single phase regardless of the Co substitution. The results of Rietveld refinement suggested that the crystal structure of solid solutions varies according to the Co substitution. When the Co substitution is low $(x=0.3\~0.5)$, the solid solutions carry a cubic-like structure with a relatively small value in the ratio of lattice parameters (c/a). The solid solutions made with a higher Co substitution (x=0.7), however, exhibit a layered structure with a higher c/a ratio. This difference was also observed in the electrochemical voltage spectroscopy (EVS) profiles, whereby the Co component in scarcely substituted materials shows a charging reaction at $3.7V\;(vs.\;Li/Li^+)$, but in the heavily substituted ones at 3.92V.

• Membrane Journal
• /
• v.19 no.2
• /
• pp.96-103
• /
• 2009

A series of organic-inorganic composite membranes from poly(vinyl chloride) (PVC) graft copolymer electrolyte and heteropolyacid (HPA) were prepared for proton conducting membranes. First, poly(vinyl chloride)-g-poly(styrene sulfonic acid) (PVC-g-PSSA) was synthesized by atom transfer radical polymerization (ATRP) using direct initiation of the secondary chlorines of PVC. HPA nanoparticles were then incorporated into the PVC-g-PSSA graft copolymer though the hydrogen bonding interactions, as confirmed by FT-IR spectroscopy. The proton conductivity of the composite membranes increased from 0.049 to 0.068 S/cm at room temperature with HPA contents up to 0.3 weight traction of HPA, presumably due to both the intrinsic conductivity of HPA particles and the enhanced acidity of the sulfonic acid of the graft copolymer. The water uptake decreased from 130 to 84% with the increase of HPA contents up to 0.45 of HPA weight traction, resulting from the decrease in number of water absorption sites due to hydrogen bonding interaction between the HPA particles and the polymer matrix. Thermal gravimetric analysis (TGA) demonstrated the enhancement of thermal stabilities of the composite membranes with increasing concentration of HPA.

• Radiation Oncology Journal
• /
• v.16 no.2
• /
• pp.139-145
• /
• 1998

Purpose : The purpose of this study was to evaluate the efficacy of curative radiotherapy in the management of supralottic cancer. Materials and Methods : Twenty-one Patients with squamous cell carcinoma of the supralottis were treated with radiotherapy at Gyeongsang National University Hospital between 1590 and 1994. Median follow-up period was 36 months and 95% were observed for at least 2 years. Results : Actuarial survival rate at 5 years was 39.3% for 21 patients. The 5-rear actuarial survival rate was 75.0% in Stage I, 42.9% in Stage II, 33.3% in Stage III and 28.6% in Stage IV(p=0.54), The 5-year local control rate was 52.0% for 21 patients. The 5-rear local control rate was 75.0% in Stage I, 57.1% in Stage II, 66.7% in Stage III, and 28.6% in Stage IV(p=0.33). Double primary cancer was developed in 3 patients and those were all esophageal cancers. Conclusion : In early stage(Stage I and II) supralottic cancer, curative radiotherapy would be a treatment of choice and surgery would be better to be reserved for salvage of radiotherapy failure. In advanced stage(Stage III and IV), radiotherapy alone is inadequate for curative therapy and combination with surgery should be done in operable patients. This report emphasizes the importance of esophagoscopy and esophagogram at the follow-up of patients with supralottic cancer.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.25 no.1
• /
• pp.27-35
• /
• 2005

Ultrasonic inspection methods are widely used for detecting flaws in materials. The signal analysis step plays a crucial part in the data interpretation process. A number of signal processing methods have been proposed to classify ultrasonic flaw signals. One of the more popular methods involves the extraction of an appropriate set of features followed by the use of a neural network for the classification of the signals in the feature spare. This paper describes an alternative approach which uses the least mean square (LMS) method and exportation maximization (EM) algorithm with the model based deconvolution which is employed for classifying nondestructive evaluation (NDE) signals from steam generator tubes in a nuclear power plant. The signals due to cracks and deposits are not significantly different. These signals must be discriminated to prevent from happening a huge disaster such as contamination of water or explosion. A model based deconvolution has been described to facilitate comparison of classification results. The method uses the space alternating generalized expectation maximiBation (SAGE) algorithm ill conjunction with the Newton-Raphson method which uses the Hessian parameter resulting in fast convergence to estimate the time of flight and the distance between the tube wall and the ultrasonic sensor. Results using these schemes for the classification of ultrasonic signals from cracks and deposits within steam generator tubes are presented and showed a reasonable performances.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.02a
• /
• pp.227-227
• /
• 2012

Cryopump는 반도체 임플란타 공정, OLED분야, 신소재 개발, 표면분석 및 처리, 의료분야, 입자가속기, 핵융합 등 다양한 진공분야에 응용되는 고진공용 극저온펌프이다. 특히 향후로의 산업구조는 디스플레이, 반도체, IT 산업분야로 집중 재편될 것이기에, 이에 따른 핵심제조장비인 고진공 펌프의 수요가 급증할 것으로 판단된다. 그리고 이를 위한 핵심부품과 장비들의 국산화가 시급한 실정이다. 기술적인 측면에서 보자면 GVT는 미국의 Varian과 일본Ebara의 Cryopump 제조기술을 원천으로 한 회사로써 현재는 국내 유일의 G-M냉동기와 Cryopump 제조기술을 보유한 업체이다. 그리고 최근 오랫동안 정체되었던 관련 기술을 발전시켜 최적화된 한국형 G-M 냉동기 및 이를 장착한 다양한 사이즈의 고성능 Cryopump를 출시하게 되었다. 가장 큰 수확은 Cryopump의 성능을 크게 향상시켰으며 무엇보다 고객맞춤형으로 디자인할 수 있을 정도의 기술력을 확보하게 되었다는 점이다. Cryopump의 성능은 장착되는 Cryocooler(G-M냉동기)의 성능과 밀접한 관련이 있기 때문에 일차로 Cryocooler의 성능을 개선하고 이차로 이를 장착한 Cryopump의 성능을 개선하였다. 본 연구는 일차로 진행된 HP Series 2단 Cryocooler 4가지 모델 중 가장 범용인 HPM 모델과 HPS모델에 대한 제작과 성능시험에 관한 것이다. 이는 각각 기존의 ICP Series 펌프에 장착되던 Expander 535 모델 및 Expander 855 모델에 대한 설계 최적화의 결과물로써 내용은 Cryocooler에 대한 'Typical Performance Test(1st STG와 2nd STG의 온도가 각각의 Stage에 인가되는 Heat Load에 의해 그물망 형태의 그래프가 되도록 수행하는 시험법)'의 절차를 따라 수행되었다. HPM Cryocooler의 성능은 2nd STG Temp. 20K 와 1st STG Temp. 80K를 Heat Load 기준으로 하였을 경우, 각각 8.2W, 55.0W의 성능을 나타내었고 HPS Cryocooler의 성능은 2nd STG Temp. 20K 와 1st STG Temp. 72K를 Heat Load기준으로 하였을 경우, 각각 14.0W, 90.0W의 성능을 나타내었다. 1st STG Temp.를 72K로 정한 이유는 Power Supply의 용량 한계로 인해 90W이상의 Heat Load를 인가할 수 없었기 때문이다. 만약 성능 그래프의 경향성을 고려하여 1st STG Temp. 80K로 가정한다면, 각각 약 13W, 100W 정도의 성능을 가질 것으로 추정된다. 단, 본 시험에 사용된 Compressor는 GVT의 HC80Plus 모델로 내부에는 Helium용 5HP급 Scroll Type의 Compressor가 장착되어 있으며, 봉입압력 250Psig에 저압 100Psig기준, 65scfm의 유량을 가지는 압축기이다. 압축기와 Cryocooler의 조합은 1:1이었고 시험방법은 Cryocooler에 대한 GVT 자체규정에 따라 진행되었으며 밤과 낮 및 공장전체의 부하변동에 따른 냉각수 온도변화에 따른 펌프의 성능변화는 고려되지 않았다.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.02a
• /
• pp.118-118
• /
• 2012

Cryopump는 반도체 임플란타 공정, OLED분야, 신소재 개발, 표면분석 및 처리, 의료분야, 입자가속기, 핵융합 등 다양한 진공분야에 응용되는 고진공용 극저온펌프이다. 특히 향후로의 산업구조는 디스플레이, 반도체, IT 산업분야로 집중 재편될 것이기에, 이에 따른 핵심제조장비인 고진공 펌프의 수요가 급증할 것으로 판단된다. 그리고 이를 위한 핵심부품과 장비들의 국산화가 시급한 실정이다. 기술적인 측면에서 보자면 GVT는 미국의 Varian과 일본Ebara의 Cryopump 제조기술을 원천으로 한 회사로써 현재는 국내 유일의 G-M 냉동기와 Cryopump 제조기술을 보유한 업체이다. 그리고 최근 오랫동안 정체되었던 관련 기술을 발전시켜 최적화된 한국형 G-M 냉동기 및 이를 장착한 다양한 사이즈의 고성능 Cryopump를 출시하게 되었다. 가장 큰 수확은 Cryopump의 성능을 크게 향상시켰으며 무엇보다 고객맞춤형으로 디자인할 수 있을 정도의 기술력을 확보하게 되었다는 점이다. Cryopump의 성능은 장착되는 Cryocooler (G-M냉동기)의 성능과 밀접한 관련이 있기 때문에 일차로 Cryocooler의 성능을 개선하고 이차로 이를 장착한 Cryopump의 성능을 개선하였다. 본 연구는 일차로 진행된 HP Series 2단 Cryocooler 4가지 모델 중 가장 범용인 HPM 모델과 HPS모델에 대한 제작과 성능시험에 관한 것이다. 이는 각각 기존의 ICP Series 펌프에 장착되던 Expander 535 모델 및 Expander 855 모델에 대한 설계 최적화의 결과물로써 내용은 Cryocooler에 대한 'Typical Performance Test(1st STG와 2nd STG의 온도가 각각의 Stage에 인가되는 Heat Load에 의해 그물망 형태의 그래프가 되도록 수행하는 시험법)'의 절차를 따라 수행되었다. HPM Cryocooler의 성능은 2nd STG Temp. 20K와 1st STG Temp. 80K를 Heat Load기준으로 하였을 경우, 각각 8.2W, 55.0W의 성능을 나타내었고 HPS Cryocooler의 성능은 2nd STG Temp. 20K 와 1st STG Temp. 72K를 Heat Load기준으로 하였을 경우, 각각 14.0W, 90.0W의 성능을 나타내었다. 1st STG Temp.를 72K로 정한 이유는 Power Supply의 용량 한계로 인해 90W이상의 Heat Load를 인가할 수 없었기 때문이다. 만약 성능 그래프의 경향성을 고려하여 1st STG Temp. 80K로 가정한다면, 각각 약 13W, 100W 정도의 성능을 가질 것으로 추정된다. 단, 본 시험에 사용된 Compressor는 GVT의 HC80Plus 모델로 내부에는 Helium용 5HP급 Scroll Type의 Compressor가 장착되어 있으며, 봉입압력 250Psig에 저압 100Psig기준, 65scfm의 유량을 가지는 압축기이다. 압축기와 Cryocooler의 조합은 1:1이었고 시험방법은 Cryocooler에 대한 GVT 자체규정에 따라 진행되었으며 밤과 낮 및 공장전체의 부하변동에 따른 냉각수 온도변화에 따른 펌프의 성능변화는 고려되지 않았다.

• Journal of the Mineralogical Society of Korea
• /
• v.25 no.3
• /
• pp.131-141
• /
• 2012

The guano formed from the bat excrement in a cave contains various sulfate and phosphate minerals formed from the reaction of bat excrement with surrounding rocks and clastic minerals. Therefore, the mineral compositions in the guano provide basic informations on the geochemical environments affecting mineral formation in a cave. This study was conducted to study the mineral compositions of guano and the factors affecting those compositions by comparing mineralogical and chemical compositions in three different limestone caves in Korea. The guano samples in Gossi Cave contain detrital minerals such as illite, quartz and feldspar and relatively large amount of gypsum. The contents of gypsum increase with increasing depth, which is different from the samples collected in other caves. The samples collected from Baekryong Cave have the similar mineral compositions to those in Gossi Cave, but they also contain additional kaolinite and very small amount of gypsum. The samples in Sungryu Cave have similar mineralogical compositions to those in Gossi Cave, but contian bassanite instead of gypsum. The mineralogical compositions are well correlated with the chemical compositions of guano. The mineral compositions indicate that, in Gossi Cave, the minerals were formed by the reaction of large amount of bat excrement with surrounding rocks in high humidity condition or in the condition of frequent floods. In the case of Sungryu Cave, bassanite which can be formed in a dry condition indicates that minerals were formed in a relatively low humidity condition.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.28 no.5
• /
• pp.303-311
• /
• 2016

From having an experimental study of physical and consolidation characteristics of soft clay in Nakdong river lower basin, we come to the conclusion as follow. Clay minerals in Nakdong river lower basin are classified into Kaolinite and Illite. Water content($W_n$) is similarly distributed in a range of 50.4% to 92.8% in Noksan and 46.6% to 99.0% in Jangyu, and liquid limit(LL) of both areas appears lower than water content. In the case of compression index, the index of jangyu is a little higher than that of Noksan because Jangyu is in a range of 0.67 to 1.94 and Noksan in a range of 0.44 to 1.5. The second compression index of Jangyu in a range of 0.027 to 0.092 is also higher than Noksan in a range of 0.024 to 0.075. As a result of regression analysis, a relation between water content and compression index is linear, and between initial void ratio and compression index is shown to $C_c=0.80e_o-0.58$. The ratio of $C_{\alpha}/C_c$ in a range of 0.03 to 0.08 expresses a wide range.

• Korean Journal of Environmental Agriculture
• /
• v.36 no.1
• /
• pp.22-28
• /
• 2017

BACKGROUND: There is very limited knowledge of the effects of biochar derived from exhausted coffee residue on metal adsorption processes. Furthermore, only limited information is available on the adsorption mechanism of copper. The aim of this study was to evaluate the absorption behaviors of copper by biochar derived from exhausted coffee residue. METHODS AND RESULTS: Biochars produced by pyrolysis of exhausted coffee residue at $300^{\circ}C$(CB300) and $600^{\circ}C$(CB600) were characterized and investigated as adsorbents for the removal of copper from aqueous solution. The results indicated that the adsorption equilibrium was achieved around 2 h and the pseudo-second-order kinetic model fit the data better than the pseudo-first-order kinetic model. The maximum Cu adsorption capacities of CB600 by Freundlich and Langmuir isotherms were higher than those of CB300. The adsorption data were well described by a Langmuir isotherm compare to Freundlich isotherm. CONCLUSION: Our results suggest that exhausted coffee residue can be used as feedstock materials to produce high quality biochar, which could be used as adsorbents to removal copper.