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Analytical Study on Strength Safety of LPG Mini Tank with Column for Level Gauge (레벨게이지용 컬럼을 설치한 LPG 미니탱크의 강도안전성에 관한 해석적 연구)

  • Kim, Chung Kyun
    • Journal of the Korean Institute of Gas
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    • v.23 no.3
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    • pp.46-50
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    • 2019
  • In this study, the strength stability of an LPG mini tank with a storage capacity of about 250 kg was analyzed by FEM. According to the results of the FEM analysis, it is preferable that the corner radius of the LPG mini tank having a storage capacity of 250 kg is designed to be 175 to 205 mm. Generally, the larger the corner radius of the end plate of the gas storage tank, the higher the safety of the strength, but the volume or capacity of the tank is reduced. Therefore, it is important to derive the optimum design data. Further, in order to securely design the strength of the gas tank, the thickness of the tank is designed to be thick. However, when the thick steel sheet is used, the material and the transportation costs are increased. The result shows that it is preferable to select the optimum thickness of the steel sheet from 4.5 to 5.5 mm. Using the level gauge type of column on the central axis of the gas tank, the safety strength of the LPG tank can be enhanced as much as twice, compared with the tank of the existing level gauge to measure the liquid level by piercing the side wall of the tank.

Effect of addition of Tl+ and Pd2+ on the texture and hardness of the non-cyanide gold plating layer (논시안 금도금층의 조직과 경도에 미치는 Tl+ 과 Pd2+ 이온첨가의 영향)

  • Heo, Wonyoung;Son, Injoon
    • Journal of Surface Science and Engineering
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    • v.55 no.6
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    • pp.460-468
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    • 2022
  • Due to its high electrical conductivity, low contact resistance, good weldability and high corrosion resi-stance, gold is widely used in electronic components such as connectors and printed circuit boards (PCB). Gold ion salts currently used in gold plating are largely cyan-based salts and non-cyanic salts. The cya-nide bath can be used for both high and low hardness, but the non-cyanide bath can be used for low hardness plating. Potassium gold cyanide (KAu(CN)2) as a cyanide type and sodium gold sulfite (Na3[Au(SO)3]2) salt as a non-cyanide type are most widely used. Although the cyan bath has excellent performance in plating, potassium gold cyanide (KAu(CN)2) used in the cyan bath is classified as a poison and a toxic substance and has strong toxicity, which tends to damage the positive photoresist film and make it difficult to form a straight side-wall. There is a need to supplement this. Therefore, it is intended to supplement this with an eco-friendly process using sodium sulfite sodium salt that does not contain cyan. Therefore, the main goal is to form a gold plating layer with a controllable hardness using a non-cyanide gold plating solution. In this study, the composition of a non-cyanide gold plating solution that maintains hardness even after annealing is generated through gold-palladium alloying by adding thallium, a crystal regulator among electrolysis factors affecting the structure and hardness, and changes in plating layer structure and crystallinity before and after annealing the correlation with the hardness.

Effects of Bed Insert Geometry and Shape of WGS Catalysts on CO Conversion in a Fluidized Bed Reactor for SEWGS Process (SEWGS 공정을 위한 유동층 반응기에서 내부 삽입물의 모양 및 WGS 촉매의 형상이 CO 전환율에 미치는 영향)

  • Ryu, Hojung;Kim, Hana;Lee, Dongho;Bae, Dalhee;Hwang, Taeksung
    • Journal of Hydrogen and New Energy
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    • v.24 no.2
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    • pp.150-159
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    • 2013
  • To enhance the performance of SEWGS system by holding the WGS catalyst in a SEWGS reactor using bed inserts, effects of insert geometry and shape of WGS catalysts on CO conversion were measured and investigated. Small scale fluidized bed reactor was used as experimental apparatus and WGS catalyst (particle and tablet) and sand were used as bed materials. The parallel wall type and cross type bed inserts were used to hold the WGS catalysts. The CO conversion with steam/CO ratio was determined based on the exit gas analysis. The measured CO conversion using the bed inserts showed high value comparable to physical mixing cases. Moreover, gas flow direction was confirmed by bed pressure drop measurement for each case. Most of input gas flowed through the catalyst side when we charged tablet type catalyst into the bed insert and this can cause low CO2 capture efficiency because the possibility of contact between input gas and CO2 absorbent is low in this case. New bed insert geometry was proposed based on the results from this study to enhance contact between input gas and WGS catalyst and CO2 absorbent.

Experience of Campylobacter gastroenteritis in Korean children: Single-center study

  • Seo, Seung Hyeon;Lee, Yeoun Joo;Mun, Sang Wook;Park, Jae Hong
    • Kosin Medical Journal
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    • v.33 no.2
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    • pp.150-158
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    • 2018
  • Objectives: Although Campylobacter is the main cause for bacterial acute gastroenteritis (AGE), there has been no notable clinical research into it, especially for Korean children. In this study, we share our experience of clinical, laboratory and image findings with Campylobacter AGE. Methods: Between May 2013 and June 2016, children diagnosed as having Campylobacter AGE were retrospectively enrolled in our study. Campylobacter AGE was considered diagnosed when a patient had symptoms of bacterial AGE and a positive Campylobacter result in stool using multiplex PCR. Results: Among 539 patients with suspected bacterial AGE, 31 (5.8%) patients had a positive result for Campylobacter. The average age of the 31 patients was 10.2±5.0 years with a range between 1.1 and 16.9 years. Eighteen (58%) of the total patients were hospitalized between June and August. Diarrhea (93.5%), abdominal pain (83%) and fever (83%) were common symptoms. For 20 patients (65%), diarrhea lasted for less than three days, and fever lasted for 2.1 days on average. Among the 20 patients subjected to imaging studies, 12 patients (60%) showed bowel wall thickening on the right side of colon. In blood tests of 30 patients, 22 (73%) and 29 (97%) patients exhibited leukocytosis and elevated C-reactive protein, respectively. During treatment for Campylobacter AGE, prediagnostic empirical antibiotics were used for 6 (19%) patients. All patients recovered without complications. Conclusions: Among the children with suspected bacterial AGE, 5.8% had a positive result on Campylobacter in stool using multiplex PCR. Therefore, we observe that Campylobacter AGE should be considered in school-age children who have diarrhea, fever, and abdominal pain.

Research on the anti-seismic performance of composite precast utility tunnels based on the shaking table test and simulation analysis

  • Yang, Yanmin;Li, Zigen;Li, Yongqing;Xu, Ran;Wang, Yunke
    • Computers and Concrete
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    • v.27 no.2
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    • pp.163-173
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    • 2021
  • In this paper, the parameters of haunch height, reinforcement ratio and site condition were evaluated for the influence on the seismic performance of a composite precast fabricated utility tunnel by shaking table test and numerical simulation. The dynamic response laws of acceleration, interlayer displacement and steel strain under unidirectional horizontal seismic excitation were analyzed through four specimens with a similarity ratio of 1:6 in the test. And a numerical model was established and analyzed by the finite element software ABAQUS based on the structure of utility tunnel. The results indicated that composite precast fabricated utility tunnel with the good anti-seismic performance. In a certain range, increasing the height of haunch or the ratio of reinforcement could reduce the influence of seismic wave on the utility tunnel structure, which was beneficial to the structure earthquake resistance. The clay field containing the interlayer of liquefied sandy soil has a certain damping effect on the structure of the utility tunnel, and the displacement response could be reduced by 14.1%. Under the excitation of strong earthquake, the reinforcement strain at the side wall upper end and haunches of the utility tunnel was the biggest, which is the key part of the structure. The experimental results were in good agreement with the fitting results, and the results could provide a reference value for the anti-seismic design and application of composite precast fabricated utility tunnel.

Heat transfer performance of a helical heat exchanger depending on coil distance and flow guide for supercritical cryo-compressed hydrogen

  • Cha, Hojun;Choi, Youngjun;Kim, Seokho
    • Progress in Superconductivity and Cryogenics
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    • v.24 no.3
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    • pp.62-67
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    • 2022
  • Liquid hydrogen (LH2) has a higher density than gaseous hydrogen, so it has high transport efficiency and can be stored at relatively low pressure. In order to use efficient bulk hydrogen in the industry, research for the LH2 supply system is needed. In the high-pressure hydrogen station based on LH2 currently being developed in Korea, a heat exchanger is used to heat up supercritical hydrogen at 700 bar and 60 K, which is pressurized by a cryogenic high-pressure pump, to gas hydrogen at 700 bar and 300 K. Accordingly, the heat exchanger used in the hydrogen station should consider the design of high-pressure tubes, miniaturization, and freezing prevention. A helical heat exchanger generates secondary flow due to the curvature characteristics of a curved tube and can be miniaturized compared to a straight one on the same heat transfer length. This paper evaluates the heat transfer performance through parametric study on the distance between coils, guide effect, and anti-icing design of helical heat exchanger. The helical heat exchanger has better heat transfer performance than the straight tube exchanger due to the influence of the secondary flow. When the distance between the coils is uniform, the heat transfer is enhanced. The guide between coils increases the heat transfer performance by increasing the heat transfer length of the shell side fluid. The freezing is observed around the inlet of distribution tube wall, and to solve this problem, an anti-icing structure and a modified operating condition are suggested.

Damage Proxy Map over Collapsed Structure in Ansan Using COSMO-SkyMed Data

  • Nur, Arip Syaripudin;Fadhillah, Muhammad Fulki;Jung, Young-Hoon;Nam, Boo Hyun;Kim, Yong Je;Park, Yu-Chul;Lee, Chang-Wook
    • The Journal of Engineering Geology
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    • v.32 no.3
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    • pp.363-376
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    • 2022
  • An area under construction for a living facility collapsed around 12:48 KST on 13 January 2021 in Sa-dong, Ansan-si, Gyeonggi-do. There were no casualties due to the rapid evacuation measure, but part of the temporary retaining facility collapsed, and several cracks occurred in the adjacent road on the south side. This study used the potential of synthetic aperture radar (SAR) satellite for surface property changes that lies in backscattering characteristic to map the collapsed structure. The interferometric SAR technique can make a direct measurement of the decorrelation among different acquisition dates by integrating both amplitude and phase information. The damage proxy map (DPM) technique has been employed using four high-resolution Constellation of Small Satellites for Mediterranean basin Observation (COSMO-SkyMed) data spanning from 2020 to 2021 during ascending observation to analyze the collapse of the construction. DPM relies on the difference of pre- and co-event interferometric coherences to depict anomalous changes that indicate collapsed structure in the study area. The DPMs were displayed in a color scale that indicates an increasingly more significant ground surface change in the area covered by the pixels, depicting the collapsed structure. Therefore, the DPM technique with SAR data can be used for damage assessment with accurate and comprehensive detection after an event. In addition, we classify the amplitude information using support vector machine (SVM) and maximum likelihood classification algorithms. An investigation committee was formed to determine the cause of the collapse of the retaining wall and to suggest technical and institutional measures and alternatives to prevent similar incidents from reoccurring. The report from the committee revealed that the incident was caused by a combination of factors that were not carried out properly.

Mitigating the effect of urban layout on torsion of buildings caused by infill walls

  • Noorifard, Azadeh;Tabeshpour, Mohammad Reza;Saradj, Fatemeh Mehdizadeh
    • Earthquakes and Structures
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    • v.23 no.2
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    • pp.151-168
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    • 2022
  • Torsion is one of the most important causes of building collapse during earthquakes. Sometimes, despite the symmetric form of the building, infill walls disturb the symmetry of the lateral resisting system. The purpose of this research is to investigate the effect of urban layout on developing torsion caused by infill walls. For this purpose, a typological study was conducted based on the conditions of perimeter walls on 364 buildings and then 9 cases were selected. The dimensions of the selected buildings are constant and the conditions of the perimeter walls including facades with openings and cantilevered facades are variable. The selected buildings with 60 different layouts of infill walls were analyzed and the behavior of each one was evaluated based on the torsional irregularity criteria of seismic codes. The results of the analyses showed that if the perimeter walls of a building are symmetric, asymmetric interior walls will not be important in developing torsion and effective parameters in symmetry of the perimeter infill walls are the number of walls, area of openings, aspect ratio, and construction details. Finally, architectural solutions to mitigate the torsional effects of infill walls were proposed for buildings with solid infill walls on some sides, for buildings where the perimeter walls of one side are on the cantilevered part, and for buildings where the perimeter walls of two adjacent sides are on the cantilevered part. In three-sided buildings, where two adjacent façades are cantilevered, it is often impossible to use the potential of the infill walls.

Investigation of the behavior of a tunnel subjected to strike-slip fault rupture with experimental approach

  • Zhen Cui;Tianqiang Wang;Qian Sheng;Guangxin Zhou
    • Geomechanics and Engineering
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    • v.33 no.5
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    • pp.477-486
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    • 2023
  • In the studies on fault dislocation of tunnel, existing literatures are mainly focused on the problems caused by normal and reverse faults, but few on strike-slip faults. The paper aims to research the deformation and failure mechanism of a tunnel under strike-slip faulting based on a model test and test-calibrated numerical simulation. A potential faulting hazard condition is considered for a real water tunnel in central Yunnan, China. Based on the faulting hazard to tunnel, laboratory model tests were conducted with a test apparatus that specially designed for strike-slip faults. Then, to verify the results obtained from the model test, a finite element model was built. By comparison, the numerical results agree with tested ones well. The results indicated that most of the shear deformation and damage would appear within fault fracture zone. The tunnel exhibited a horizontal S-shaped deformation profile under strike-slip faulting. The side walls of the tunnel mainly experience tension and compression strain state, while the roof and floor of the tunnel would be in a shear state. Circular cracks on tunnel near fault fracture zone were more significant owing to shear effects of strike-slip faulting, while the longitudinal cracks occurred at the hanging wall.

Effects of Molding Conditions on the Deflection of Rib Moldings of Fiber-reinforced Plastic Composites in Compression Molding (섬유강화 플라스틱 복합재료의 압축성형에서 리브 성형품의 휨에 미치는 성형조건의 영향)

  • Kim, Jin-Woo;Lee, Jung-Hoon;Lee, Dong-Gi
    • Journal of Advanced Engineering and Technology
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    • v.10 no.3
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    • pp.285-290
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    • 2017
  • Molding of body with ribs is the most difficult during flow molding process. The rib area is easy to be deformed at the rear side due to wall thickness variation. In this study, relationships between molding condition and deflection of rib-shaped part is investigated during the compression molding of fiber reinforced plastic composites, and the following results are derived. Polypropylene(PP), Polystyrene(PS), and stampable sheet(SS 40wt%) show the increment of deflection along with releasing temperature. For the correlation between incremental holding pressure load and deflection, stampable sheet exhibits lower deflection along with higher holding pressure, while PS shows significant increase of deflection with higher holding pressure, PP shows completely different characteristic, significant reduction of deflection along with higher holding pressure. Regarding to mold temperature and deflection, deflection amount of SS is the biggest, and PS shows the smallest. In addition, all three kinds shows the highest amount of deflection at 173C. Deflection is reduced when mold closing speed is increased. Amount of deflection in SS is larger and is not highly dependent on molding conditions like holding pressure and cooling parameters, compared with single component material like PP. This can be elucidated by anisotropic and inhomogeneous characteristics of glass fiber during filling process of stampable sheet composite.