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        검색결과 121

        61.
        2011.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Bagasse fly ash (BFA) is one of the important wastes generated in the sugar industry; it has been studied as a prospective low-cost adsorbent in the removal of congo red (CR) from aqueous solutions. Chemical treatment with H2O2 was applied in order to modify the adsorbability of the raw BFA. Batch studies were performed to evaluate the influence of various experimental parameters such as dye solution pH, contact time, adsorbent dose, and temperature. Both the adsorbents were characterized by Fourier-transform infrared spectrometer, energy-dispersive X-ray spectrophotometer and nitrogen adsorption at 77 K. Equilibrium isotherms for the adsorption of CR were analyzed by Langmuir, Freundlich and Temkin models using non-linear regression technique. Intraparticle diffusion seems to control the CR removal process. The obtained experimental data can be well described by Langmuir and also followed second order kinetic models. The calculated thermodynamic parameters indicate the feasibility of the adsorption process for the studied adsorbents. The results indicate that BFA can be efficiently used for the treatment of waste water containing dyes.
        4,000원
        62.
        2010.12 구독 인증기관 무료, 개인회원 유료
        The aim of this study is to offer scientific materials and effective teaching methods of place kick motions of high school students by comparing and analyzing kinetic and motor mechanical variables of experts and beginners’ place kicks which are usually u
        5,800원
        63.
        2010.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The purpose of this study is to investigate the effects of closed and open kinetic chain exercise for increasing knee joint function on the knee position sense in the normal adults. Thirty normal adults(male 15, female 15; mean age: 22.13±2.58 years) were participated in this study into two groups, each with 15 people. The group I was trained that closed kinetic chain exercise on the knee joint and the group II was trained that open kinetic chain exercise on the knee joint. Exercise programs performed for 4 weeks, 3 times a week were using Shuttle 2000-1 closed kinetic chain exercise and Knee Extensor open kinetic chain exercise(HUR, Filand). The results of this study were as follows: 1) There were statistically significant decreasing of measuring error degree in 0-20。were found between before and after training in closed kinetic chain exercise(p<.05). 2) There were statistically significant decreasing of measuring error degree in 21-40。were found between before and after training in closed kinetic chain exercise(p<.05). 3) There were statistically significant decreasing of measuring error degree in 41-60。were found between before and after training in closed kinetic chain exercise(p<.05). 4) There were statistically significant decreasing of measuring error degree in 0- 20。were found between before and after training in open kinetic chain exercise(p<.05). 5) There were statistically significant decreasing of measuring error degree in 21-40。were found between before and after training in open kinetic chain exercise(p<.05). 6) There were statistically significant decreasing of measuring error degree in 41- 60。were found between before and after training in open kinetic chain exercise(p<.05). In conclusion, these results suggest that closed and open kinetic chain exercise has increased in the knee joint proprioception between before and after training. Especially, closed kinetic chain exercise could be more useful intervention than open kinetic chain exercise for increasing proprioceptive sense.
        4,000원
        65.
        2009.12 구독 인증기관 무료, 개인회원 유료
        This study is conducted to examine kinematic and kinetic variables influencing on vertical jump records. To this end, as the subjects of the study, three male volleyball players and three general students vertically jumped five times, and the study compar
        4,000원
        66.
        2009.12 구독 인증기관 무료, 개인회원 유료
        The purpose of this study is to analyze the kinematic variables due to the course change in the first serve of high school girl tennis athletes using three dimensional video analysis and to produce kinetic variables using ground reaction force to understa
        5,800원
        67.
        2009.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Kinetic studies on the ligand substitution reactions of cyanocomplexes were performed in several micellar solutions. It showed the observed rate constants was found to be independent of the entering ligand concentration at high concentration of cyanopyridine and pyrazinecarboxylate. We could see also that in nonionic and anionic micellar solutions no influence of changes in the surfactant concentration on the observed rate constants was found. Taking into account the hydrophilic nature of the cobalt complex, the cobalt complex molecule was expected to be located in the aqueous phase of the micellar systems, where the reaction would take place. In cationic micellar solutions, a small increase in the observed rate constant was found when the cationic surfactant concentration increased. After reaching a maximum, the rate constant decreased on increasing surfactant concentration and subsequently it reached a plateau, where the observed rate constant was independent of changes in the surfactant concentration.
        4,000원
        68.
        2009.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The adsorption of phenolic compound resorcinol on activated carbons prepared from Moringa oleifera (Drumstick bark) has been investigated. Activated carbon was prepared by impregnating Moringa oleifera with 50% phosphoric acid in the ratio of 1:1 and 1:2(w/w), designated as MOAC1 and MOAC2. Equilibrium and isotherm studies were carried out. The influences of variables such as contact time, initial concentration of resorcinol, carbon dosage in the solution on percentage adsorption and adsorption capacity of the bark have been analysed. The equilibration time was found to be 4 h. Kinetics of resorcinol onto activated carbons was checked for pseudo first order and pseudo second order model. It was found that the adsorption of resorcinol follows pseudo second order kinetics for both MOAC1 and MOAC2. The isotherm data were correlated with isotherm models, namely Langmuir and Freundlich. Adsorption isotherms were satisfactorily fitted by both the Langmuir and Freundlich model for MOAC1 and MOAC2.
        4,000원
        69.
        2008.12 구독 인증기관 무료, 개인회원 유료
        The purpose of this study were to offer the scientific data of the right and left feet's kick motion of the ROK high school boy students and to seek out the effective method of instruction, througth comparing and analyzing the variation aspects of the kin
        5,400원
        71.
        2008.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Batch sorption experiments were carried out for the removal of metylene blue from its aqueous solution using H3PO4 activated Acacia arabica carbon (AAC). The prepared activated carbon was characterized and was found as an effective adsorbent material. The operating variables studied were initial metylene blue concentration, AAC concentration and solution pH. AAC activated carbon posses a maximum sorption capacity for the range of initial dye concentrations studied (60~100 mg L-1). The sorption kinetics were analyzed using reversible first order kinetics, second order, reversible first order, pseudo-first order, and pseudo-second order model. The sorption data tend to fit very well in pseudo-second order model for the entire sorption time. The average pseudo-second order rate constant, KII and regression coefficient value were determined to be 0.0174 mg g-1 min-1 and 0.9977. The biosorption process also fit well to reversible I order kinetics with a regression coefficient of 0.9878.
        4,000원
        72.
        2007.11 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The aim of the present study was to investigate age-related differences in stepping behavior in response to sensory perturbations of postural balance. The participants for this study were 2 healthy elderly adults (mean age=76.0) and 2 younger adults (mean age=25.5). Subjects were asked to step over a 10 cm high obstacle at self-paced speed with the right limb to land on the primary target (normal step length) that is 10 cm in diameter. However, if, during movement, the light was illuminated, then the subject had to step on the secondary target (long step length). It was planned that the onset of the light would be prior to peak Fx of swing limb, between swing peak Fx and swing toe-off, and after swing toe-off. In the younger adults these secondary visual cues were provided at mean times of 240 ms (standard deviation (SD)=11), 402 ms (SD=13), and 476 ms (SD=88) following the movement onset. Corresponding mean times for the healthy elderly were 150 ms (SD=67), 352 ms (SD=39), and 562 ms (SD=115). Results showed great changes in both group and visual cue condition in Fx ground reaction forces and temporal events following the swing toe-off. Swing limb acceleration force (Fx) and stance peak Fx1 was much greater in the young adults compared to the older adults. Both young and older adults increased stance peak Fx2 in the visual cue condition compared to normal stepping. There was no difference in stance peak Fx2 between the visual cue conditions in both groups. Similarly, the time to stance peak Fx2 was much longer for the visual cue condition than for the normal stepping. It was not different between the visual cue conditions in the young adults, but in the elderly mid and late cue was much greater than early cue. In addition, time to stance peak Fx2 and swing and stance time were much longer in the older adults compared to the young adults for the visual cue conditions. These results suggest that unlike young adults, elderly adults did not flexibly modify their responses to unexpected changes in step length while stepping over obstacles.
        4,000원
        73.
        2006.09 구독 인증기관·개인회원 무료
        The present paper is a parameter study of zinc flake production using a Simoloyer CM01 horizontal high energy rotary ball mill. The manufactured flakes have a dimension in thickness (t) < 1μm and diameters (d) 5-100 μm, consequently a ratio d/t up to 200. The flake geometry is mainly controlled by the variation of process parameters such as rotary speed of the rotor, ratio of powder/ball charge, load ratio of the system, process temperature, operating model and the quantity of process control agent (PCA). The Zn flakes were characterized by SEM, tap densitometry, laser diffraction and water coverage measurement.
        74.
        2006.09 구독 인증기관·개인회원 무료
        A new tungsten heavy alloy with hybrid structure was manufactured for the kinetic energy penetrator. The tungsten heavy alloy is composed of two parts: core region is molybdenum added heavy alloy to promote the self-sharpening; outer part encompassing the core is conventional heavy alloy to sustain severe load in a muzzle during firing. From ballistic test, it was found that the penetration performance of the hybrid structure tungsten heavy alloy is higher than that of conventional heavy alloy. This heavy alloy is thought to be very useful for the penetrator in the near future.
        75.
        2006.04 구독 인증기관·개인회원 무료
        The horizontal high energy rotor ball mill () is used to break and activate dry solids. It is used for dry-milling and in the vertical mount for wet-milling in leaching processes. Technical electric arc furnace (EAF) dust with high contents of zinc oxide, zinc ferrite and magnetite is efficiently separated by ambient temperature leaching. The process shows promise for industrial application
        78.
        2004.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        A new concept of tungsten heavy alloy composite was suggested and manufactured in this study for the kinetic energy penetrator. The composite heavy alloy was composed of two parts, the center was molybdenum added heavy alloy compositions which were designed to promote the self-sharpening effect and outside was conventional heavy alloy in order to sustain the severe stress condition in the muzzle during the firing. The center part showed an intergranular and brittle mode at tungsten/tungsten interfaces by which self-sharpening effect could be activated. On the other hand, that of outside showed conventional ductile fracture mode under high strain rate condition. From the sub-scale penetration test, the depth of penetration in heavy alloy composites showed greater values than those of conventional tungsten heavy alloys. It is suggested that the heavy alloy composite could be considered as one of the future penetrator materials.
        4,000원
        79.
        2004.08 KCI 등재 구독 인증기관 무료, 개인회원 유료
        An experimental study on the combustion of superfine aluminum powders (average particle diameter, a: ∼0.1 ) in air is reported. The formation of aluminum nitride during the combustion of aluminum in air and the influence of the combustion scenario on the structures and compositions of the final products are in the focus of this study. The experiments were conducted in an air (pressure: 1 atm). Superfine aluminum powders were produced by the wire electrical explosion method. Such superfine aluminum powder is stable in air but once ignited it can burn in a self-sustaining way due to its low bulk: density (∼0.1 g/㎤) and a low thermal conductivity. During combustion, the temperature and radiation were measured and the actual burning process was recorded by a video camera. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and chemical analysis were performed on the both initial powders and final products. It was found that the powders, ignited by local heating, burned in a two-stage self-propagating regime. The products of the first stage consisted of unreacted aluminum (-70 mass %) and amorphous oxides with traces of AlN. After the second stage the AlN content exceeded 50 mass % and the residual Al content decreased to ∼10 mass %. A qualitative discussion is given on the kinetic limitation for AlN oxidation due to rapid condensation and encapsulation of gaseous AlN.N.
        4,000원
        80.
        2004.08 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Ultrafine titanium carbide particles were synthesized by the reaction of liquid-magnesium and vaporized TiCl+CCl(x = 1 and 2) solution. Fine titanium carbide particles with about 50 nm were successfully produced by combining Ti and C atoms released by chloride reduction of magnesium, and vacuum was then used to remove the residual phases of MgCl and excess Mg. Small amounts of impurities such as O, Fe, Mg and Cl were detected in the product, but such problem can be solved by more precise process control. The lattice parameter of the product was 0.43267 nm, near the standard value. With respect to the reaction kinetics, the activation energy for the reactions of TiCl+CCland Mg was found to 69 kJ/mole, which was about half value against the use of TiCl+CCl, and such higher reactivity of the former contributed to increase the stoichiometry until the level of TiC and decrease the free carbon content below 0.3 wt.%.
        4,000원
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