• Design & Manufacturing
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• v.2 no.1
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• pp.33-38
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• 2008

As consumer in optics, electronics, aerospace and electronics industry grow, the demand for ultra precision aspherical surface lens increases higher. Precision turning with single-diamond tools has a long history of development for fabrication of optical quality surfaces since the advent of aerostatic rotary spindles and precise linear motion guide ways. To enhance the precision and productivity of ultra precision aspherical surface micro lens, the following specification of ultra precision grinding system is required: the highest rotational speed of the grinder is 100,000rpm and its turning accuracy is $0.1{\mu}m$, positioning accuracy is $0.1{\mu}m$. The development process of the grinding system for the ultra precision aspherical surface micro lens for optoelectronics industry is introduced. In the work reported in this paper, an intelligent grinding system for ultra precision aspherical surface machining was designed by considering the factors affecting the surface roughness and profiles accuracy. An aerostatic form was adopted to build the spindle of the workpiece and the spindle of grinder and ultra precision LM guide way was adopted in this system. And this paper deals with mirror grinding of an aspheric surface micro lens by resin bonded diamond wheel and spherical lens of BK7. It results was that a form accuracy of $0.6{\mu}m$ P-V and a surface roughness of $0.006{\mu}m$ Rmax.

• Journal of Biosystems Engineering
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• v.32 no.6
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• pp.440-447
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• 2007

In this study, a biosensor was developed using an enzyme-linked immunosorbent assay (ELISA) to rapidly measure the fungicide iprovalicarb residues in agricultural products. The biosensor was designed to include micro-pumps and solenoid valves for fluid transport, a spectrophotometer cuvet as a reaction chamber, a photodiode with a light-emitting diode for optical density measurement, and a control microcomputer to implement assay. The rate of change in optical density of the cuvet was read as final signal output. Micro-pumps were evaluated to investigate their delivery capability, the highest values of the error and the coefficient of variation were 4.3% and 4.6% respectively. As the incubation period was reduced from 15 minutes to 11 minutes to shorten the total processing time, the sensor sensitivity was decreased as the antibody dilution ratio was reduced to a half. The maximum usable period of the coated cuvet was found to be two days with 1% error limit. To predict the concentration of the iprovalicarb residue in agricultural products, a linear calibration model was obtained with r-square values of 0.992 for potato and 0.985 for onion. In validation test for the samples of potatoes and onions against the high performance liquid chromatography, very high correlation values were obtained as 0.996 and 0.993 respectively. Using the cuvet immobilized with antigen, it took 21-minutes for the biosensor to complete the measuring process of the iprovalicarb residues.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.6
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• pp.59-66
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• 2006

Acoustic cavity as a stabilization device to control high-frequency combustion instabilities in liquid rocket engine is adopted and its damping capacity is verified in atmospheric temperature. First, harmful resonant frequency in a modeling chamber can be damped effectively by the installation of properly-tuned acoustic cavity. Besides, geometric effects of acoustic cavity on damping characteristics are analyzed and compared quantitatively. Satisfactory agreements have been achieved with linear acoustic analysis and experimental approach. Results show that the acoustic cavity of the largest orifice area or the shortest orifice length was the most effective in acoustic damping of the harmful resonant frequency. Finally, it is proved that an optimal design process is indispensable for the effective control of combustion instabilities.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.3
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• pp.247-255
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• 2016

The purpose of this study is to investigate unsteady-state characteristics of a pintle thruster with various pintle speed. Based on steady state experimental results, non-linear pintle stroke equation is obtained and applied to the unsteady state experimental system. For the unsteady state experiments, three different pintle speeds are used: 3.10 mm/s, 5.65 mm/s, 10.83 mm/s, respectively. Results show that backward pintle stroke results in faster convergence time because of high chamber pressure during backward pintle stroke sequence. During the forward and backward process, thrust curve shows singular points. These phenomenons is caused by variation of mass flow rate, which is mainly due to changes of both chamber pressures and nozzle throat area. This behavior becomes distinctive for a faster pintle speed case.

• International Journal of Highway Engineering
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• v.2 no.1
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• pp.147-156
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• 2000

Compaction is known to critically affect pavement performance. Due to its importance, a theoretical modelling of compacted density in the term of number of roller coverages is attempted by assuming compaction process essentially identical to pavement rutting. Excellent data fittings by the developed equation may prove the validation of assumptions made as well as justification of its use. According to the derived equation, a plot of density difference with respect to number of roller coverages in the logarithmic scale Produces a linear relationship. However, this linearity is turned out to be deviated by cooling effect, change of amplitude and frequency. Investigation of these three factors proposes a new generalized compaction density equation, which shows a promising future. By applying this general formula, the equations for the number of roller coverages required and the final compaction density obtained for a particular compaction project is derived first time in compaction research.

• The Journal of Engineering Geology
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• v.5 no.1
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• pp.75-93
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• 1995

This study investigates the adsorption capacity of the gibbsite and the clay on the development of admixed liner. The gibbsite is produced as a by-product in the pretreatment process for cleaning and coloring of Alurninurn sash. From the study, following conclusions were obtained: 1) The adsorption of metals such as Cu(II), Cd(II), and Ni(II) and phenol on gibbsite and l:entonite was equilibrated rather quickly(12 ~48 hrs ). 2) The rate and extent of adsorption is a function of surface area the adsorbent having. 3) The Larigmuir isotherm is found to be more suitable than Freundlich isotherm for the adsorption analysis of heavy metals on gibbsite and bentonite. 4) In case of phenol, Freundlich isotherm, whose N value is close to 1, i.e., close to linear isotherm, is more fit to describe the adsorption on gibbsite and bentonite. 5) The amount of metals and phenol adsorbed is found to be in the following order : Adsorbent : $2{\mu}m-Al(OH)_3$ > Mixed Solid > $12{\mu}m-Al(OH)_3$ > Na-Bentonite > $30{\mu}m-Al(OH)_3$

• Journal of Sensor Science and Technology
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• v.24 no.1
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• pp.41-46
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• 2015

In this work, pure hierarchical ZnO structure was prepared using a simple hydrothermal method, and Ag nanoparticles doped hierarchical ZnO structure was synthesized uniformly through photochemical route. The reduced graphene oxide (rGO) has been synthesized by typical Hummer's method and reduced by hydrazine. Prepared Ag/ZnO nanostructures are uniformly dispersed on the surface of rGO sheets using ultrasonication process. The synthesized samples were characterized by SEM, TEM, EDS, XRD and PL spectra. The average size of prepared ZnO microspheres was around $2{\sim}3{\mu}m$ and showed highly uniform. The average size of doped-Ag nanoparticles was 50 nm and decorated into ZnO/rGO network. The $C_2H_2$ gas sensing properties of as-prepared products were investigated using resistivity-type gas sensor. Ag/ZnO-rGO based sensors exhibited good performances for $C_2H_2$ gas in comparison with the Ag/ZnO. The $C_2H_2$ sensor based on Ag/ZnO-rGO had linear response property from 3~1000 ppm of $C_2H_2$ concentration at working temperature of $200^{\circ}C$. The response values with 100 ppm $C_2H_2$ at $200^{\circ}C$ were 22% and 78% for Ag/ZnO and Ag/ZnO-rGO, respectively. In additions, the sensor still shows high sensitivity and quick response/recovery to $C_2H_2$ under high relative humidity conditions. Moreover, the device shows excellent selectivity towards to $C_2H_2$ gas at optimal working temperature of $200^{\circ}C$.

• Journal of Physiology & Pathology in Korean Medicine
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• v.22 no.5
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• pp.1057-1061
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• 2008

For the purpose of investigating the reasonable logics contained in physiognomy of east and old western medicine. hypothetical researches based on hydromechanics theory were performed concerning facial types of form and pathologic features, especially 4 types of Dr. Jisan-Essence, Qi energy. Emotional Activity and Blood(EQAB). In order to infer the functional relation between facial type forming and EQAB factors, EQAB were supposed as fluid grounded on their continual flowing or periodical change and pressure effect from its congestion. and a premise that there's a linear corresponding relationship between the appearance of organ and its physical conditions of its inner vessels is formed too. Through this work, the unit fluid model(UFM) of Essence can be assumed as circle shape formed by the high viscosity and surface tension, the UFM model of Qi energy as quadrangular shape by the scattering features to outer four directions, and the UFM of emotional activity as inverted triangular shape by the flippant and uprising features, and the UFM of blood as ellipsoid triangle by the heavy and descending features in spite of circulation. The shapes made from each UFM are reproduced in the process of human development and manifest respective facial shape through the self-reproduction method like fractal theory in the last. Conclusively. it is said that the facial form analysis method like EQAB type theory can be the useful methodology to understand the human pathological and physiological features in view of hydromechanics.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.3
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• pp.187-192
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• 2017

This paper presents an ongoing study to develop a novel pressure sensor by means of a Nano Carbon Piezoresistive Composite (NCPC). The sensor was fabricated using the 3D printing process. We designed a miniaturized cantilever-type sensor electrode to improve the pressure sensing performance and utilized a 3D printer to build a small-sized body. The sensor electrode was made of 2 wt％ MWCNT/epoxy piezoresistive nano-composite, and the sensor body was encapsulated with a pipe plug cap for easy installation to any pressure system. The piezoresistivity responses of the sensor were converted into stable voltage outputs by using a signal processing system, which is similar to a conventional foil strain gauge. We evaluated the pressure-sensing performances using a pressure calibrator in the lab environment. The 3D-printed cantilever electrode pressure sensor showed linear voltage outputs of up to 16,500 KPa, which is a 200％ improvement in the pressure sensing range when compared with the bulk-type electrode used in our previous work.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.4
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• pp.575-594
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• 2010

In this study, we propose a space search algorithm (SSA) and then introduce a hybrid optimization of fuzzy inference systems based on SSA and information granulation (IG). In comparison with "conventional" evolutionary algorithms (such as PSO), SSA leads no.t only to better search performance to find global optimization but is also more computationally effective when dealing with the optimization of the fuzzy models. In the hybrid optimization of fuzzy inference system, SSA is exploited to carry out the parametric optimization of the fuzzy model as well as to realize its structural optimization. IG realized with the aid of C-Means clustering helps determine the initial values of the apex parameters of the membership function of fuzzy model. The overall hybrid identification of fuzzy inference systems comes in the form of two optimization mechanisms: structure identification (such as the number of input variables to be used, a specific subset of input variables, the number of membership functions, and polyno.mial type) and parameter identification (viz. the apexes of membership function). The structure identification is developed by SSA and C-Means while the parameter estimation is realized via SSA and a standard least square method. The evaluation of the performance of the proposed model was carried out by using four representative numerical examples such as No.n-linear function, gas furnace, NO.x emission process data, and Mackey-Glass time series. A comparative study of SSA and PSO demonstrates that SSA leads to improved performance both in terms of the quality of the model and the computing time required. The proposed model is also contrasted with the quality of some "conventional" fuzzy models already encountered in the literature.