• Journal of the Korean Society of Industry Convergence
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• v.7 no.1
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• pp.19-24
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• 2004

An experimental investigation was performed to study the characteristics of laminar water flow in a horizontal circular tube by using liquid crystal. A simultaneous measurement technique has been employed to measure the velocity field in a two-dimensional cross section of fluid flow. This study found the velocity distributions for Re = 1,594 ~ 2,510 along longitudinal sections and the results appear to be physically reasonable. To determine some characteristics of the laminar flow, 2D PIV technique is employed for velocity measurement by using liquid crystal in water. The experimental rig was manufactured from an acryle tube. The test tube diameter of 25mm, and a length of 1200mm. The used algorithm is the gray level cross-correlation method by using Kimura et al. in 1986.

• Journal of the Korean Society of Clothing and Textiles
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• v.16 no.2
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• pp.169-180
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• 1992

The purpose of this study is to investigate the effects of type of clothing microclimate and exercise condition on ventilation. The experimental system employed a trace gas technique of the previous research. Clothing microclimate volume measurement was based on the substitution water technique for inter-clothing air volume. The experimental variables were tested at four levels of clothing microclimate spacing, microclimate shape of the previous research and two levels of exercise conditions. 2, 4, 6 cm ease were added to B/2+4 of basic blouse pattern for the microclimate spacing variable. Each combination of three variables were tested in triplicate. Analysis of variance of experimental variables on vetilation, such as oxygen exchange rate, half time of first order model was conducted. Oxygen exchange rate and half time of first order model are affected by the shape of microclimate air and exercise condition.

• Journal of ILASS-Korea
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• v.15 no.4
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• pp.202-207
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• 2010

Mist cooling is widely employed as a cooling technique of high temperature surfaces, and it has heat transfer characteristics similar to boiling heat transfer which has the convection, nucleate and film boiling regions. In the present study, mist cooling heat transfer was experimentally investigated for the mist flow impacting on the heated surfaces of mico-fins. The mist flow was generated by supersonic vibration. Experiments were conducted under the test conditions of droplet flow rate, $Q=6.02{\times}10^{-9}{\sim}3.47{\times}10^{-8}\;m^3/s$ and liquid temperature, $T_f=30{\sim}35^{\circ}C$. From the experimental results, it is found that an increase in the droplet flow rate improves mist cooling heat transfer in the both case of smooth surface and surfaces of micro-fins. Micro-fins surfaces enhance the mist cooling heat transfer. Besides, the experimental results show that an increase in the droplet flow rate decrease the heat transfer efficiency of mist cooling.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.10 no.1
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• pp.43-48
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• 2010

This article presents the experimental studies of controlling angle and position of the inverted pendulum system using neural network to compensate for errors caused due to fuzzy controller. Although fuzzy control method can deal with nonlinearities of the system, fixed fuzzy rules may not work and result in tracking errors in some cases. First, a nominal Takagi-Sugeno (TS) type fuzzy controller with fixed weights is used for controlling the inverted pendulum system. Then the neural network is added at the reference input to form the reference compensation technique (RCT)control structure. Neural network modifies the input trajectories to improve system performances by updating internal weights in on-line fashion. The back-propagation learning algorithm for neural network is derived and used to update weights. Control hardware of a DSP 6713 board to have real time control is implemented. Experimental results of controlling inverted pendulum system are conducted and performances are compared.

• Wind and Structures
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• v.16 no.5
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• pp.491-515
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• 2013

Wind pressure characteristics on a double tower high-rise structure, which is disturbed by surrounding buildings, were investigated using large eddy simulation (LES) and 1:300 scale wind tunnel experiments. The computational simulation technique and wind tunnel experimental technique were described in detail initially. Comparisons of computational results with the experimental data have subsequently been carried out to validate the reliability of LES. Comparisons have been performed in detail for the mean and fluctuating pressure coefficients. Detailed explanations of each comparison were given in the paper. To study further on the pressure coefficients on the building surfaces, parametric studies on shape coefficient and spatial correlation were performed and investigated. The numerical and experimental results presented in this paper advance understanding on wind field around buildings and the application of LES and wind tunnel tests.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1111-1113
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• 2005

This paper deals with optimal design technique to reduce torque of IPM BLDC motor having concentrated winding. Optimization process using experimental design method which is one of the design technique is explained. Finally, the validity of experimental design method is proved by the results between prototype and optimization model.

• Structural Engineering and Mechanics
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• v.22 no.1
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• pp.17-32
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• 2006

The application of cellular materials in load-carrying and security-relevant structures requires the exact prediction of their mechanical behavior, which necessitates the development of robust simulation models and techniques based on appropriate experimental procedures. The determination of the yield surface requires experiments under multi-axial stress states because the yield behavior is sensitive to the hydrostatic stress and simple uniaxial tests aim only to determine one single point of the yield surface. Therefore, an experimental technique based on a uniaxial strain test for the description of the influence of the hydrostatic stress on the yield condition in the elastic-plastic transition zone at small strains is proposed and numerically investigated. Furthermore, this experimental technique enables the determination of a second elastic constant, e.g., Poisson's ratio.

• Journal of Mechanical Science and Technology
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• v.14 no.1
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• pp.113-120
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• 2000

This study has developed a new liquid crystal calibration technique using Neural networks with median filtering and applied this technique to heat transfer measurements. To verify the validity of this new measurement technique, the local Nusselt numbers on a flat plate surface subjected to an axisymmetric impinging jet were measured and compared with the results by the conventional Hue-temperature calibration technique under the same conditions. Because the Neural networks predict the non-linear relations between temperatures and corresponding R, G, B values, Neural networks-median filtering calibration technique can utilize a much wider color band in the experiment than the Hue-temperature calibration technique, resulting in a significant reduction in the experimental time.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.321-324
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• 2005

This paper describes the application of newly developed conducted EMI reduction technique of SVPWM in induction motor drive. The newly developed common mode voltage reduction SVPWM technique doesn't any zero-voltage vector states for inverter control. Hence it can restrict the common mode voltage better than conventional PWM technique. The proposed technique is verified through simulation and experimental results. And by applying vector-controled system, the proposed technique have superior ability of reducing EMI and equal control performance comparing conventional SVPWM technique.

• Journal of the korean academy of Pediatric Dentistry
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• v.24 no.1
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• pp.112-124
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• 1997

According to extensive use of composite resin which have superior esthetic property, every effort on improving bonding strength between a tooth and composite resin has been continued. Acid etching technique is a method that micro-etches the tooth surface which provides bonding with composite resin possible. Recently, there were several reports that mechanical treatment obtained from air-abrasion can provide similar bonding strength with acid etching technique. So, this experimental study was designed to compare the shear bonding strength between using air-abrasion technique and using acid etching technique. Initially, bovine teeth were divided into enamel and dentin experimental groups. Respectively each group was categorized into three subgroups. One subgroup was acid etched with 35% phosphoric acid, then bonded with composite resin. The other subgroup was air-abraded with $50{\mu}m$ $Al_2O_3$ particles sprayed with 160psi air pressure using air abrasion unit(KCP-1000, A.D.T., U.SA), and composite resin was bonded. In another subgroup, composite resin was bonded after acid etching following air-abrasion. So, enamel experimental groups were made of E1 (acid etched only), E2(air-abraded only), E3(acid etched following air-abraded), and dentin experimental groups were made of D1(acid etched only), D2(air-abraded only), D3(acid etched following air-abraded). Each subgroup had 10 specimens. Dentin bonding system(Scotchbond Multi-purpose, 3M Co., U.S.A.) and composite resin(Z-100, 3M Co., U.S.A.) were applied on treated surface using 5mm diameter gelatin capsule as manufacturer's direction. After 1200 times thermocycling between $5^{\circ}C$ and $55^{\circ}C$, shear bond strength was measured in 5mm/min crosshead speed with Instron(Instron Co., U.S.A.), and also treated enamel and dentin were observed with SEM(JEOL Co., Japan). The following results were obtained: 1. In the enamel experimental groups, acid etched following air-abraded group had highest shear bond strength, but there was no significant difference compared to acid etched group. Air-abraded only group had lowest shear bond strength, and there was significant difference compared to the rest of groups. 2. In the dentin experimental groups, acid etched following air-abraded group had highest shear bond strength, but there was no significant difference compared to acid etched group. Air-abraded only group had lowest shear bond strength, and there was significant difference compared to the rest of groups. 3. In the SEM study, air-abraded enamel and dentin had irregular and rough surfaces.