http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
In-process Truing of Metal-bonded Diamond Wheels for Electrolytic In-process Dressing(ELID) Grinding
Tanveer Saleh,Indraneel Biswas,Han Seok Lim,Mustafizur Rahman 한국정밀공학회 2008 International Journal of Precision Engineering and Vol.9 No.4
Electrolytic in-process dressing(ELID) grinding is a new technique for achieving a nanoscale surface finish on hard and brittle materials such as optical glass and ceramics. This process applies an electrochemical dressing on the metal-bonded diamond wheels to ensure constant protrusion of sharp cutting grits throughout the grinding cycle. In conventional ELID grinding, a constant source of pulsed DC power is supplied to the ELID cell, but a feedback mechanism is necessary to control the dressing power and obtain better performance. In this study, we propose a new closed-loop wheel dressing technique for grinding wheel truing that addresses the efficient correction of eccentric wheel rotation and the nonuniformity in the grinding wheel profile. The technique relies on an iterative control algorithm for the ELID power supply. An inductive sensor is used to measure the wheel profile based on the gap between the sensor head and wheel edge, and this is used as the feedback signal to control the pulse width of the power supply. We discuss the detailed mathematical design of the control algorithm and provide simulation results that were confirmed experimentally.
Combustion of Coal and Solid Waste using a Horizontal Combustor
( Tanveer Ahmad ),( Sang-sup Lee ) 한국폐기물자원순환학회(구 한국폐기물학회) 2017 한국폐기물자원순환학회 춘계학술발표논문집 Vol.2017 No.-
The aim of this work to investigate the distribution of mercury in the gas phase, bottom ash and fly ash during the combustion of coal and solid waste such as dried sludge and solid refuse fuel (SRF) because the solid waste can be used as alternative fuel. In our study, we used two types of continuous combustors including vertical and horizontal combustor at the same conditions. In vertical combustor, we can get only the bottom ash while in horizontal combustor we get both fly ash and bottom ash. For both combustors, the gaseous mercury was measured by using the Ontario Hydro Method. The results showed that a significant amount of emission of gas phase mercury occurs during the combustion of coal, dried sludge, and SRF. Among the fuels, SRF showed high mercury oxidation while dried sludge showed a high level of gaseous mercury emission in the flue gas.
( Tanveer Ahmed Khan ),( Hyun-joong Kim ) 한국목재공학회 2018 한국목재공학회 학술발표논문집 Vol.2018 No.1
The medium density fiber boards(MDF) provide an alternative to structural materials from furniture to flooring to crown molding. It is made from a slurry containing wood fibers and a thermoset resin usually urea formaldehyde (UF) bonded under heat and pressure. An MDF board should have high dimensional stability and high mechanical strength under adverse atmospheric conditions of temperature and humidity; these requirements strongly depend on the board processing conditions. Wood fibers have low thermal conductivity thereby imposing severe inhomogeneity during the curing process and leads to low internal bonding, poor modulus of rupture and low dimensional stability. The thermal conductivity of the wood fiber could be increased by nano/micro structured fillers. It is hypothesized that carbon materials, such as carbon black, carbon nanotubes, carbon fibers would offer high thermal conductivity considering the carbon-carbon bonding between wood fibers and carbon materials. In this work, the carbon material was synthesized by pyrolysis of rubber wood fibers and characterized by CHNOS analyzer, X-ray diffraction (XRD), Brunauer, Emmett and Teller (BET) and scanning electron microscope (SEM). The prepared carbon materials were used as fillers in urea-formaldehyde adhesive in different weight concentration up to 5%. The dispersion of carbon materials into UF resin matrix were evaluated using Thermo gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Fourier Transform Infrared (FTIR), X-ray diffraction (XRD) and solution rheology. The MDF was prepared by mixing of rubber wood fibers and UF/carbon material, resin at different weight percentages, i.e. 1, 2.5, 3.5 and 5. The mixing of carbon materials enhanced the heat transfer during the hot pressing of MDF. The core temperature reached 100 °C in 72 seconds on the board made using carbon material control board made without carbon material i.e., 84 seconds. The internal bonding (IB) strength and the modulus of rupture (MOR) estimated for the MDF is observed to have a maximum of 1 wt. % concentration of carbon material i.e., 0.71MPa and 37.63MPa respectively which are significantly higher than the boards made without carbon material i.e, IB and MOR values are 0.56 MPa and 32.31 MPa respectively.
Particle size dependence of relaxivity for silica-coated iron oxide nanoparticles
Tanveer Ahmad,배홍섭,이일수,장용민,이재준,홍성욱 한국물리학회 2012 Current Applied Physics Vol.12 No.3
We investigate the particle size dependence of the relaxivity of hydrogen protons in an aqueous solution of iron oxide (Fe3O4) nanoparticles coated in silica for biocompatibility. The T1 and T2 relaxation times for various concentrations of silica-coated nanoparticles were determined by a magnetic resonance scanner. We find that the relaxivity increased linearly with increasing particle size. The T2 relaxivity (R2) is more than 50 times larger than the T1 relaxivity (R1) for the nanoparticle contrast agent, which reflects the fact that the T2 relaxation is mainly influenced by outer sphere processes. The high R2/R1 ratio demonstrates that silica-coated iron oxide nanoparticles may serve as a T2 contrast agents in magnetic resonance imaging with high efficacy. We investigate the particle size dependence of the relaxivity of hydrogen protons in an aqueous solution of iron oxide (Fe3O4) nanoparticles coated in silica for biocompatibility. The T1 and T2 relaxation times for various concentrations of silica-coated nanoparticles were determined by a magnetic resonance scanner. We find that the relaxivity increased linearly with increasing particle size. The T2 relaxivity (R2) is more than 50 times larger than the T1 relaxivity (R1) for the nanoparticle contrast agent, which reflects the fact that the T2 relaxation is mainly influenced by outer sphere processes. The high R2/R1 ratio demonstrates that silica-coated iron oxide nanoparticles may serve as a T2 contrast agents in magnetic resonance imaging with high efficacy.
Tanveer, Waqas Hassan,Ji, Sanghoon,Yu, Wonjong,Cha, Suk Won Korean Society for Precision Engineering 2015 International Journal of Precision Engineering and Vol.16 No.10
Electrolyte thin films of yttria-stabilized- zirconia (YSZ) for low temperature solid oxide fuel cell applications are investigated. Films of same thickness and composition are fabricated by using two distinct thin film deposition techniques, atomic layer deposition (ALD) and radio frequency (RF) sputtering. Scanning electron microscopic images indicate that both methods form uniform, polycrystalline films on amorphous matrix. Deposition rates of ALD and sputtered YSZ electrolyte films are easily controllable. In-plane ionic conductivity of <TEX>$O^{2-}$</TEX> ions for YSZ is measured using electrochemical impedance spectroscopy. Experimental results show that, at a low temperature of <TEX>$250^{\circ}C$</TEX>, ALD YSZ thin films exhibit considerably lower resistance to the conduction of oxygen ions as compared to the sputtered films. This lower resistance results in better ionic conductivity of ALD YSZ thin films.