• Title/Summary/Keyword: Hot-press

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A Study on Enhancement of MIR Transmittance of Hydrothermally Synthesized ZnS Nanoparticles with Sintering Pressure (수열합성된 황화아연 나노입자의 소결 압력에 따른 중적외선향상에 관한 연구)

  • Yeo, Seo-Yeong;Park, Buem-Keun;Paik, Jong-Hoo
    • Journal of Sensor Science and Technology
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    • v.29 no.1
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    • pp.63-67
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    • 2020
  • This study investigated the influence of various sintering pressures of ZnS nanoparticles prepared by hydrothermal synthesis performed at 220 ℃ for 20 h. The hydrothermally synthesized ZnS nanoparticles formed a cubic phase. The ZnS nanoparticles were sintered using a hot-press process at 850 ℃ for 2 h under pressures of 10, 20, 30, 40, 50, 60, and 70 MPa. The ZnS ceramics indicate the cubic phase is the major phase and the hexagonal phase is the minor phase. In the ZnS ceramics, as the sintering pressure increased, a decrement in the hexagonal phase was confirmed. When the sintering pressure equaled or exceeded 30 MPa, the transmittance and density improved with reductions in porosity and hexagonal phase. A sintering pressure of 60 MPa delivered the highest transmittance (69.7%).

Preparation of Bipolar Plate for Fuel Cell Using CNT/Graphite Nano-Composite

  • Choi, Jong-Min;Kim, Tae-Jin;Hyun, Min-Soo;Peck, Dong-Hyun;Kim, Sang-Kyung;Lee, Byung-Rok;Park, Jong-Soo;Jung, Doo-Hwan
    • Carbon letters
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    • v.6 no.3
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    • pp.181-187
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    • 2005
  • Bipolar plates require some specific properties such as electrical conductivity, mechanical strength, chemical stability, and low permeability for the fuel cell application. This study investigated the effects of carbon nanotube (CNT) contents and process conditions of hot press molding on the electrical and physical properties using CNT 3~7 wt% added graphite nano-composites in the curing temperatures range of 140~$200^{\circ}C$ and pressure of 200~300 kg/$cm^2$. Bulk density, hardness and flexural strength increased with increasing CNT contents, curing pressure and temperature. With the 7 wt% CNT added noncomposite, the electrical resistance improved by 30% and the flexural strength increased by 25% as compared to that without CNT at the temperature of $160^{\circ}C$ and pressure of 300 kg/$cm^2$. These properties were close to the DOE reference criteria as bulk resistance of 13 $m{\Omega}cm$ and tensile strength of 515 kg/$cm^2$.

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Stress concentration factors test of reinforced concrete-filled tubular Y-joints under in-plane bending

  • Yang, Jun-fen;Yang, Chao;Su, Ming-zhou;Lian, Ming
    • Steel and Composite Structures
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    • v.22 no.1
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    • pp.203-216
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    • 2016
  • To study the stress concentration factors (SCFs) of concrete-filled tubular Y-joints subject to in-plane bending, experiments were used to investigate the hot spot stress distribution along the intersection between chord and brace. Three concrete-filled tubular chords forming Y-joints were tested with different reinforcing components, including doubler-plate, sleeve, and haunch-plate reinforcement. In addition, an unreinforced joint was also tested for comparison. Test results indicate that the three different forms of reinforcement effectively reduce the peak SCFs compared with the unreinforced joint. The current research suggests that the linear extrapolation method can be used for chords, whereas the quadratic extrapolation method must be used for braces. The SCF is effectively reduced and more evenly distributed when the value of the axial compression ratio in the chord is increased. Furthermore, the SCFs obtained from the test results were compared to predictions from some well-established SCF equations. Generally, the predictions from those equations are very consistent for braces, but very conservative for concrete-filled chords.

Numerical analysis of steady and transient processes in a directional solidification system

  • Lin, Ting-Kang;Lin, Chung-Hao;Chen, Ching-Yao
    • Coupled systems mechanics
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    • v.5 no.4
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    • pp.341-353
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    • 2016
  • Manufactures of multi-crystalline silicon ingots by means of the directional solidification system (DSS) is important to the solar photovoltaic (PV) cell industry. The quality of the ingots, including the grain size and morphology, is highly related to the shape of the crystal-melt interface during the crystal growth process. We performed numerical simulations to analyze the thermo-fluid field and the shape of the crystal-melt interface both for steady conditions and transient processes. The steady simulations are first validated and then applied to improve the hot zone design in the furnace. The numerical results reveal that, an additional guiding plate weakens the strength of vortex and improves the desired profile of the crystal-melt interface. Based on the steady solutions at an early stage, detailed transient processes of crystal growth can be simulated. Accuracy of the results is supported by comparing the evolutions of crystal heights with the experimental measurements. The excellent agreements demonstrate the applicability of the present numerical methods in simulating a practical and complex system of directional solidification system.

Experimental and numerical assessment of beam-column connection in steel moment-resisting frames with built-up double-I column

  • Dehghan, Seyed Mehdi;Najafgholipour, Mohammad Amir;Ziarati, Seyed Mohsen;Mehrpour, Mohammad Reza
    • Steel and Composite Structures
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    • v.26 no.3
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    • pp.315-328
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    • 2018
  • Built-up Double-I (BD-I) columns consist of two hot rolled IPE sections and two cover plates which are welded by fillet welds. In Iran, this type of column is commonly used in braced frames with simple connections and sometimes in low-rise Moment Resisting Frames (MRF) with Welded Flange Plate (WFP) beam-column detailing. To evaluate the seismic performance of WFP connection of I-beam to BD-I column, traditional and modified exterior MRF connections were tested subjected to cyclic prescribed loading of AISC. Test results indicate that the traditional connection does not achieve the intended behavior while the modified connection can moderately meet the requirements of MRF connection. The numerical models of the connections were developed in ABAQUS finite element software and validated with the test results. For this purpose, moment-rotation curves and failure modes of the tested connections were compared with the simulation results. Moreover to avoid improper failure modes, some improvements of the connections were evaluated through a numerical study.

Experimental investigation and numerical analysis of optimally designed composite beams with corrugated steel webs

  • Erdal, Ferhat;Tunca, Osman;Ozcelik, Ramazan
    • Steel and Composite Structures
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    • v.37 no.1
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    • pp.1-14
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    • 2020
  • Composite beams with corrugated steel webs represent a new innovative system which has emerged in the past decade for medium span in the construction technology. The use of composite beams with corrugated steel webs results in a range of benefits, including flexible spaces and reduced foundation costs in the construction technology. The thin corrugated web affords a significant weight reduction of these beams, compared with hot-rolled or welded ones. In the current research, an optimal designed I-girder beam with corrugated web has been proposed to improve the structural performance of continuous composite girder under bending moment. The experimental program has been conducted for six simply supported composite beams with different loading conditions. The tested specimens are designed by using one of the stochastic techniques called hunting search algorithm. In the optimization process, besides the thickness of concrete slab and studs, corrugated web properties are considered as design variables. The design constraints are respectively implemented from Eurocode 3, BS-8110 and DIN 18-800 Teil-1. The last part of the study focuses on performing a numerical study on composite beams by utilizing finite element analysis and the bending behavior of steel girders with corrugated webs experimentally and numerically verified the results. A nonlinear analysis was carried out using the finite element software ANSYS on the composite beams which were modelled using the elements ten-node high order quadrilateral type.

Microstructure and Strength Property of Liquid Phase Sintered $SiC_f$/SiC Composites (액상소결 $SiC_f$/SiC 복합재료의 미세조직 및 강도특성)

  • Lee, Moon-Hee;Cho, Kyung-Seo;Lee, Sang-Pill;Lee, Jin-Kyung
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.234-238
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    • 2008
  • The efficiency of fiber reinforced CMC(ceramic matrix composite) on the SiC materials have been investigated, in conjunction with the fabrication process by liquid phase sintering and the characterization. LPS-$SiC_f$/SiC composites was studied with the detailed analysis such as the microstructure, sintered density, flexural strength and fracture behavior. The applicability of carbon interfacial layer has been also investigated in the LPS process. Submicron SiC powder with the constant total amount and composition ratio of $Al_2O_3,\;Y_2O_3$ as sintering additives was used in order to promote the performance of the SiC matrix material. LPS-$SiC_f$/SiC composites were fabricated with hot press under the sintering temperature and applied pressure of $1820^{\circ}C$ and 20MPa for 1hr. The typical property of monolithic LPS-SiC materials was compared with LPS-$SiC_f$/SiC composites.

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Vibration and instability analysis of pipes reinforced by SiO2 nanoparticles considering agglomeration effects

  • Golabchi, Hadi;Kolahchi, Reza;Bidgoli, Mahmood Rabani
    • Computers and Concrete
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    • v.21 no.4
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    • pp.431-440
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    • 2018
  • Fluid velocity analysis on the instability of pipes reinforced by silica nanoparticles ($SiO_2$) is presented in this paper. Mori-Tanaka model is used for obtaining the effective materials properties of the nanocomposite structure considering agglomeration effects. The well known Navier-Stokes equation is used for obtaining the applied force of fluid to pipe. Based on the Reddy higher-order shear deformation theory, the motion equations are derived based on energy method and Hamilton's principal. The frequency and critical fluid velocity of structure are calculated using differential quadrature method (DQM) so that the effects of different parameters such as volume fractions of SiO2 nanoparticles, SiO2 nanoparticles agglomeration, boundary conditions and geometrical parameters of pipes are considered on the nonlinear vibration and instability of the pipe. Results indicate that increasing the volume fractions of SiO2 nanoparticles, the frequency and critical fluid velocity of the structure are increased. Furthermore, considering SiO2 nanoparticles agglomeration, decreases the frequency and critical fluid velocity of the pipe.

An experimental study on the development and verification of NCC(new concrete cutting) system

  • Park, Jong-Hyup;Han, Jong-Wook
    • Structural Engineering and Mechanics
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    • v.65 no.2
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    • pp.203-211
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    • 2018
  • This paper introduces the development process of NCC(New Concrete Cutting) system and analyzes first verification test. Based on the first verification test results, some problems of NCC system have been newly modified. We carry out the second verification test. We tried to verify cutting performance and dust control efficiency of NCC system through the cutting test of concrete bridge piers. In particular, this verification test strives to solve the problem of concrete dust, which is the biggest problem of dry cutting method. The remaining dust problems in cutting section tried to solve through this verification test. This verification test of the NCC system shows that the dust problem of dry cutting method is closely controlled and solved. In conclusion, the proposed NCC method is superior to the dry cutting method in all aspects, including cutting performance, dust vacuum efficiency and cooling effect. The proposed NCC system is believed to be able to provide eco-friendly cutting technology to various industries, such as the removal of the SOC structures and the dismantling of nuclear plants, which have recently become a hot issue in the field of concrete cutting.

Effect of Dewaxing Ratio of Beeswax-treated Hanji by Heat and Pressure Method on Aging Behavior of Dewaxed Hanji (가온 가압법에 의한 밀랍도포한지의 탈랍율이 탈랍지의 열화 거동에 미치는 영향)

  • Cho, Byoung-Uk;Choi, Do-Chim;Jo, Byoung-Muk
    • Journal of Korea Technical Association of The Pulp and Paper Industry
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    • v.44 no.3
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    • pp.15-21
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    • 2012
  • The optimum dewaxing ratio in dewaxing treatment by the heat and pressure method was investigated by considering aging stability of dewaxed Hanji. Commercial Hanji was coated with beeswax and thermally aged at $150^{\circ}C$ for 24 hours. Then it was dewaxed using the laboratory sheet press equipped with hot plates on both top and bottom sides. Dewaxing ratio was controlled by pressing temperature and time. Four type of dewaxed Hanji samples with different dewaxing ratio were prepared and thermally aged at $150^{\circ}C$. Then the aging stability of dewaxed Hanji samples was evaluated in terms of optical and strength properties. It was found that the aging stability of dewaxed Hanji was superior with higher dewaxing ratio. The result concluded that, in the aspect of aging stability, the coated beeswax in beeswax-treated Hanji shall be completely removed if the coated wax would be dewaxed.