• Textile Coloration and Finishing
• /
• v.10 no.4
• /
• pp.37-44
• /
• 1998

The purpose of this study was to elucidate the effect of weight loss of polyethylene terephthalate(PET) fabrics on the mechanical properties such as bending and shear. In order to compare the effect of treatment machine on the mechanical properies of treated PET fabrics, PET fabrics were hydrolyzed with NaOH aqueous solution using Tank machine and Liquor flow machine, respectively. The results were as follows ： 1. The bending rigidity and shear stiffness of hydrolyzed PET fabric decreased markedly up to about 10％ weight loss regardless of treatment machines. At the above 10％ weight loss, the variation of these properties is nearly unchanged. In addition, the bending hysteresis and shear hysteresis also showed similar trend. 2. Weft density change of PET fabrics treated with Liquor flow machine decreased by 1pick/inch. It is assumed that this is attributed to the tension during the treatment of Liquor flow machine. On the other hand, the weft density change of PET fabrics treated with Tank machine is scarcely influeneced by the weight loss. While warp density of PET fabrics treated with Liquor flow machine had no change with weight loss, warp density of PET fabrics treated with Tank machine decreased by 6pick/inch due to the tension. 3. The bending rigidity and shear stiffness of PET fabrics hydrolyzed with liquor flow machine slightly higher than with Tank m/c at the above 10％ weight loss. It is assumed that this is caused by the increasement of the crossing pressure of warp and weft yarn and contact points of filaments in the yarns. Also, the bending and shear hysteresis of PET fabrics treated with Tank machine were higher than that of liquor flow machine.

• Proceedings of the KIEE Conference
• /
• 1999.11d
• /
• pp.879-881
• /
• 1999

Radical and ion densities in a CF4 plasma have been calculated as a function of input power density. 9as pressure and feed gas flow rate using simple 0 dimensional global model. Fluorine atom is found to be the most abundant neutral particle. Highly fragmented species such as CF and CF+ become dominant neutral and ionic radical at the high power condition. As the pressure increases. ion density increases but ionization rate decreases due to the decrease in electron temperature. The fractional dissociation of CF4 feed gas decreases with pressure after increasing at the low pressure range. Electron density and temperature are almost independent of flow rate within calculation conditions studied. The fractional dissociation of CF4 monotonically decreases with flow rate. which results in increase in CF3 and decrease in CF density. The calculation results show that the SiO2 etch selectivity improvement correlates to the increase in the relative density of fluorocarbon ion and neutral radicals which has high C/F ratio.

• Proceedings of the KIEE Conference
• /
• 1997.07e
• /
• pp.1657-1659
• /
• 1997

Electron temperature and electron density were measured in a radio-frequency inductively coupled plasma (RFICP) using a probe measurements. Measurement was conducted in an argon discharge for pressures from 10 [mTorr] to 40 [mTorr] and input rf power from 100 [W] to 800 [W], Ar flow rate from 5 [sccm] to 30 [sccm], Spatial distribution electron temperature and electron density were measured for discharge with same aspect ratio (R/L=2). Electron temperature and electron density were discovered depending on both pressure and power, Ar flow rate. Electron density was increased with increasing input power and in creasing pressure, increasing Ar flow rate. Radial distribution of the electron density was peaked in the plasma center. Normal distribution of the electron density was peaked in the center between quartz plate and substrate. From these results, We found out the generation mechanism of Radio-Frequency Inductively Coupled Plasma.

• 한국전산유체공학회:학술대회논문집
• /
• 2004.10a
• /
• pp.161-164
• /
• 2004

A finite volume numerical model is developed for simulating non-equilibrium electroosmotic flow in micro- and nanochannels. The Guoy-Chapman model is adopted to compute the flow and electric potential. The Nernst-Planck equation is employed to trace unsteady transports of ionic species, i.e., time-dependent net charge density. A new set of boundary conditions based on surface charge density are designed rather than using the conventionally-employed zeta potential. A few issues for an efficient computation of electroosmotic flows are discussed. Representative computational examples are given to illustrate the robustness of the numerical model.

• International Journal of Automotive Technology
• /
• v.8 no.6
• /
• pp.761-769
• /
• 2007

The configuration of the flow channel on a bipolar plate of a proton exchange membrane fuel cell(PEMFC) for efficient reactant supply has great influence on the performance of the fuel cell. Recent demand for higher energy density fuel cells requires an increase in current density at mid voltage range and a decrease in concentration overvoltage at high current density. Therefore, an interdigitated flow channel where mass transfer rate by convection through a gas diffusion layer is greater than the mass transfer by a diffusion mechanism through a gas diffusion layer was recently proposed. This study attempts to analyze the i-V performance, mass transfer and pressure drop in interdigitated flow channels by developing a fully three dimensional simulation model for PEMFC that can deal with anode and cathode flow together. The results indicate that the trade off between performance and pressure loss should be considered for efficient design of flow channels. Although the performance of the fuel cell with interdigitated flow is better than that with conventional flow channels due to a strong mass transfer rate by convection across a gas diffusion layer, there is also an increase in friction due to the strong convection through the porous diffusion layer accompanied by a larger pressure drop along the flow channel. It was evident that the proper selection of the ratio of channel and rib width under counter flow conditions in the fuel cell with interdigitated flow are necessary to optimize the interdigitated flow field design.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.8 no.1
• /
• pp.37-44
• /
• 2009

Density is the most important congestion indicator among the three fundamental flow variables, flow, speed and density. Measuring density in the field has two different ways, direct and indirect. Taking photos with wide views is one of direct ways, which is not widely used because of its cost and lacking of proper positions. Another direct density measuring method using two spot detectors has been introduced with the concept of instantaneous density, average density and measurement interval. The relationship between accuracy and measurement interval has been investigated using the simulation data produced by Paramics API function. Finally, density measurement algorithm has been suggested including exponential smoothing for device development.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.22 no.4
• /
• pp.61-67
• /
• 2008

In this papar, the flow meter system for pulverized coal is developed for the pulverizer-burner system of the boiler or the blast furnace. The sensor of the system a lied the capacitance with a pair of electrode on the outer wall of the electric insulator pipe. The circuit is designed for the measurement of the granule flow density combining as a measuring electrode and a reference. In order to measure granule-flow density, the calibration curve between the weight measured from loadcell and the voltage from the circuit is created. It is verified that the flow meter system has reliability and accuracy using on-line test.

• Journal of Mechanical Science and Technology
• /
• v.16 no.5
• /
• pp.683-695
• /
• 2002

The objective of the present study is to analyze the fluid flow with moving boundary using a finite element method. The algorithm uses a fractional step approach that can be used to solve low-speed flow with large density changes due to intense temperature gradients. The explicit Lax-Wendroff scheme is applied to nonlinear convective terms in the momentum equations to prevent checkerboard pressure oscillations. The ALE (Arbitrary Lagrangian Eulerian) method is adopted for moving grids. The numerical algorithm in the present study is validated for two-dimensional unsteady flow in a driven cavity and a natural convection problem. To extend the present numerical method to engine simulations, a piston-driven intake flow with moving boundary is also simulated. The density, temperature and axial velocity profiles are calculated for the three-dimensional unsteady piston-driven intake flow with density changes due to high inlet fluid temperatures using the present algorithm. The calculated results are in good agreement with other numerical and experimental ones.

• Journal of Ocean Engineering and Technology
• /
• v.14 no.2
• /
• pp.106-111
• /
• 2000

Recently it was reported that the life of Al Sacrifical anode is being used in port piers has been significantly shortened compared with the original design life (e.g. average life shortened from 20 years to 13-15 year) Those factors involving these problems mentioned above were seemed to be a quality of anode material and diverse environmental factors such as pH flow rate temperature Dissolved oxygen Chemical oxygen demand and resistivity etcm In this study flow rate and contamination degree(pH) of sea water affecting to sacrificial anode life hve been investigated in terms of electrochemical characteristics of Al alloy sacrificial anode It was known that the lifetime of Al alloy anode was shortened not only by increasing of self-corrosion quantity by varying flow rate of sea water but also by increasing corrosion current density due to the potential difference increment between Al anode and steel structure cathode by varying contamination degree of sea water. Especially when anode current density is from 1mA/cm2 to 3mA/cm2 and flow rate of sea water is under 2m/s anode current efficiency is 90% above However flow rate is over 2m/s anode current efficiency fell down sharply due to erosion corrosion as well as galvanic corrosion.

• Journal of the Korean institute of surface engineering
• /
• v.37 no.2
• /
• pp.92-98
• /
• 2004

The current efficiency and the microstructure of the trivalent Cr deposits plated in flow cell system were investigated according to additives in sulfate bath and current density. The current efficiency of the deposits plated in the formic acid complexed bath was noticeably higher than that of the deposits from glycine complexed bath. The current efficiency of the deposits from the complexed baths with boric acid buffer increased linearly with current density in the range of 60-100 A/dm$^2$, while that of the deposits from the baths with both Al sulfate and mixed buffers increased parabolically with current density. The nodular crystallite size of the deposits increased with current density, and the deposits plated in low current density region had relatively smooth surface appearance with fine grains. The structure of the deposits from the complexed baths with boric acid buffer changed from amorphous structure to crystalline one with strong (110)peak with increasing current density. The deposits from the baths with both Al sulfate and mixed buffers had generally amorphous structure.