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        검색결과 121

        83.
        2003.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Granular Activated Carbon (GAC) has been proven to be an excellent material for many industrial applications. A systematic study has been carried out of the kinetics of physical as well as chemical activation of phenolic resin chars. Physical activation was carried out using CO2 and chemical activation using KOH as activating agent. There are number of factors which influence the rate of activation. The activation temperature and residence time at HTT varied in the range 550~1000℃ and ½~8 hrs respectively. Kinetic studies show that the rate of chemical activation is 10 times faster than physical activation even at much lower temperature. Above study show that the chemical activation process is suitable to prepare granular activated carbon with very high surface area i.e. 2895 m2/g in short duration of time i.e. 1 to 2 hrs at lower temperature i.e. 750℃ from phenolic resins.
        4,000원
        84.
        2002.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The catalytic activities of several metalloporphyrin, wherein the porphyrins are TPP(5,lO,l5,20-Tetraphenyl-21H,23H-porphyrin) and (p-X)TPP (X =CH3O, CH3, F, Cl), are reported for the oxidation of styrene and it's derivatives. The electronic effects of substrates and porphyrins on the catalytic activity of metalloporphyrin containing the transition metal ion such as Mn(III) was discussed. Investigating the correlation between the Michaelis-Menten's rate parameters and the substituent constants, we are going to analyze the influences on the changes of catalytic activity or rate determining step during the processes of the formation and the dissociation of the M-oxo-olefin.
        4,000원
        86.
        2001.11 KCI 등재 구독 인증기관 무료, 개인회원 유료
        본 연구는 보행주기 동안 정상인과 당뇨병성 족부궤양 환자의 족관절 운동역학적 변수와 족관절 근육들의 근활성도에 차이가 있는지 알아보기 위하여 실시하였다. 본 연구의 대상자는 당뇨병성 족부궤양이 있는 환자 9명(남자: 6명, 여자: 3명)과 성, 연령, 체중으로 짝짓기(matching)시킨 대조군 9명이었다. 3차원 동작분석기, 힘판, 표면 근전도를 이용하여, 보행주기 동안 족관절의 관절가동범위, 모멘트(moment), 일률(power), 그리고 내측가자
        5,100원
        88.
        2000.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        염화철(Ferrous Choloride) 증기의 고온 수소환원 반응을 통한 미립질 철분말의 생성속도에 대한 이론적인 해석돠 실험을 수행하였다. 철분말의 생성기구는 염화철이 증발하여 생성된 증기와 운반가스인 알곤을 혼합하여 반응부로 유입시키고 수소에 의한 고온환원반을을 통하여 철분말과 함께 부산물인 염화수소(HCI) 가스를 얻게 된다. 생성된 반응부 후미에 설치한 유기용매 포집기를 이용하여 회수하였으며, 염화수소는 가성소다 수용액에 흡수시키고 이를 적정함으로써 초기 반응물인 염화철의 전환율을 계산하였다. 반응속도식의 반응물에 대하여 1차반응(1st-order reaction)이고 염화철 증가와 운반체인 알곤가스가 평형상태일 때의 속도상수는 k=7,879exp(-53,840/RT)dm3/mole.sec으로 표시되며, 이때의 활성화에너지는 53.84kJ/mole이었다. 철분말의 TEM 사진에 의하면 입도범위는 0.1~1.0μm이며, 반응온도 및 가스유량에는 크게 영향을 받지 않는것으로 나타났다.
        4,000원
        89.
        2000.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Physical therapists have been using balance and weight shifting training to induce improvements in standing and walking. This study compared the effects of kinetic feedback frequency and concurrent kinetic feedback on the performance and learning of a weight shifting skill in young, nondisabled adults. Sixteen young adults without known impairment of the neuromusculoskeletal system volunteered for the study. Subjects in each of three kinetic feedback groups performed a weight shifting task in an attempt to minimize error between their effort and a center of pressure (COP) template for a 12 second period. Feedback was provided: 1) concurrently (concurrent feedback), 2) after each trial (100% feedback), 3) after every other trial (50% feedback). Immediate and delayed (24 hour) retention tests were performed without feedback. During acquisition phase, the concurrent feedback group exhibited less error than either of the post response feedback group. For the immediate retention test, the 50% feedback group exhibited less error than did the 100% feedback and concurrent feedback. During the delayed retention, 50% feedback group displayed less error than did the other groups. But no significant differences were found between groups. These results suggest that practice with concurrent feedback is beneficial for the immediate performance, but not for the learning of this weight shifting skill. Lower frequency of feedback resulted in more permanent changes in the subject's ability to complete the task.
        4,000원
        92.
        1997.04 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        회전 불밀에 있어서 볼의 운동을 비선형 spring과 비선형 deshpot로 구성된 Kelvin모델을 사용한 DEM(Distinct Element Method;개별요소법)에 의하여 2차원으로 해석하였다. 모델에 있어서 점성계수는 볼과 밀벽사이의 반발실험 데이타로 부터 결정하였다. 각볼의 동적인 운동은 비선형 점탄성과 Newton의 운동법칙를 기초로하여 모사되었다. 밀이 회전하는 동안 볼의 궤적과 동적인 운동은 실제 실험에 의한 밀내에서의 볼의 운동고 잘 일치하였다. 본 연구에서 제안된 모델 시뮬레이션은 회전 볼밀내의 실제의 3차원인 볼의 운동에 대한 해석에 중요한 단서가 될 수 있었다. 볼의 운동고 운동에너지는 회전 볼밀의 속도와 볼의 충진율에 의해 크게 영향을 받았다.
        4,000원
        94.
        1990.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study investigated the effects of variations in the kinetic structure on the science knowledge acquisition and analyzed the kinetic structure of a sience classroom communication. According to the rationale of the kinetic structure theory, a communication with high structure would facilitate greater knowledge acquisition than that with low structure. To testify that hypothesis, a modified non-equivalent pretest-posttest control group design was used. Four classes(8th grade), two classes for each sex, were selected. On the topic of 'Moon and Macs', two tape-recorded lessons differing in the kinetic structure were developed. Each lessons played 14 minutes long. One of them was high structure(B ̄₁ = 0.48) and the other was low structure(B ̄₁ = 0.19). The results showed that the students with high structure lesson achieved greater than those with low structure lesson(F = 7.03, p $lt; .01). But when the results were analyzed by sex, only boy students' achievement showed a significant difference between low and high structure groups(F = 9.54, p $lt;.01). The results of this study suggest that a high structure communication will facilitate the science learning in the case of boy students. On the other hand, an actual classroom communication on the topic of `Moon and planets' was tape-recorded from a middle school science class(9th grade) and lasted 45 minutes long. It was analyzed by Anderson's and Kim's methods of the kinetic structure analysis. The grand mean fundamental coefficient of the whole communication was 0.20, and the grand mean weighted coefficient was 0.84. This communication showed high mean progression density(D ̄s= 0.88 with (NAC) ̄=1.14). Thus, in general, this verbal communication had low structure and high progression. Therefore, it can be concluded that this classroom communication will give the students some difficulties in their learning.
        4,000원
        95.
        1989.12 구독 인증기관 무료, 개인회원 유료
        대표적인 재료로서 바나나를 선정하여 건조방법과 조건에 따른 최적화에 사용할 수 있는 Ascorbic acid 저하속도와 비효소적 갈변속도에 대한 반응속도 예측 모델식을 결정하였다. Ascorbic acid 저하 속도와 비 효소적 갈변속도를 각각 1차반응, 0차반응으로, 두반응의 온도 의존성은 Arrhenius식으로 나타내어 SPSS Computer Program을 이용하여 실제 측정된 Ascorbic acid와 비효소적 갈변의 data에 가장 접근하도록 Parameter를 반복계산하여 찾았다. 얻어진 반응속도식에서의 Parameter값들은 R. SQUARE값이 평균 0.99이상이므로 살험치를 잘 예측하였으며 건조공정의 최적화에 이용될 수 있을 것으로 생각되어진다. Ascorbic acid 저하속도와 비효소적 갈변속도는 건조초기에 낮고 건조가 진행되어 수분함량의 감소와 함께 최대속도를 보이다가 서서히 감소하였다. 이때 동결건조의 경우가 가장 안정된 품질변화를 나타냈음을 알 수 있었다.
        4,000원
        96.
        2020.08 KCI 등재 서비스 종료(열람 제한)
        Zeolite material having XRD peaks of Na-A zeolite in the 2θ range of 7.18 to 34.18 can be synthesized from the waste catalyst using a fusion/hydrothermal method. The adsorption rate of Mn ions by a commercial Na-A zeolite and the synthesized zeolitic material increased as the adsorption temperature increased in the range of 10 ~ 40℃. The adsorption of Mn ion were very rapid in the first 30 min and then reached to the equilibrium state after approximately 60 min. The adsorption kinetics of Mn ions by the commercial Na-A zeolite and the zeolitic material were found to be well fitted to the pseudo-2nd order kinetic model. Equilibrium data by the commercial Na-A zeolite and the zeolitic material fit the Langmuir, Koble-Corrigan, and Redlich-Peterson isotherm models well rather than Freundlich isotherm model. The removal capacity of the Mn ions by the commercial Na-A zeolite and the zeolitic material obtained from the Langmuir model was 135.2 mg/g and 128.9 mg/g at 30℃, respectively. The adsorption capacity of Mn ions by the synthesized zeolitic material was almost similar to that of commercial Na-A zeolite. The synthesized zeolitic material could be applied as an economically feasible commercial adsorbent.
        97.
        2018.01 KCI 등재 서비스 종료(열람 제한)
        Biomass as a renewable energy source has several limitations in terms of the potential for steady supply and its thermal characteristics. This study conducted a thermal weight change analysis and determined its kinetics to address this problem. Sawdust was chosen as the biomass, and PE and PP were the plastics used. Based on the result of thermogravimetric analysis (TGA), the kinetic characteristics were analyzed using Kissinger, Ozawa, and Friedman methods, which are the most common methods used to obtain reaction coefficients and activation energy. The methods used to determine the thermal degradation kinetics were considered feasible for evaluating the pyrolytic behavior of the materials tested. The experimental results of this study provided insights into mixed biomass/plastics pyrolysis kinetics and their optimal operation conditions.
        98.
        2017.06 서비스 종료(열람 제한)
        본 연구는 총 여덟 가지 실외원예활동 동작의 운동학 및 운동역학적 특성을 분석하기 위해 수행되었다; 땅고르기, 땅파기, 종자파종, 모종 심기, 근거리 잡초뽑기, 원거리 잡초뽑기, 저위치 수확하기, 고위치 수확하기. 20대 남자 대학생 총 24명(평균 연령 : 23.4 ± 2.93세)이 본 연 구에 참여하였다. 삼차원 동작분석 시스템(Qualisys Track Manager 2.7 build 783)과 지면반력기기(Kistler Instruments)를 이용하여 무게 중심, 관절각도와 같은 운동학적 요인과 지면반력, 압력중심, 관절모멘트와 같은 운동역학적 요인을 측정하였다. 또한 표면 근전도기기 (Desktop DTS)를 이용하여 총 16개 양측 몸통과 하지근육의 근육활성도를 측정하였다. 그 결과 총 여덟 가지의 실외원예활동 동작은 1) 한 발 내딛기(예 : 땅고르기, 땅파기), 2) 쭈그려 앉기(예 : 종자파종, 모종심기, 근거리 잡초뽑기, 원거리 잡초뽑기), 3) 허리 구부리기(예 : 저위 치 수확하기, 고위치 수확하기)로 구분되었다. 각 동작은 다시 세 개 또는 네 개의 구간으로 세분화되었다. 원예활동 동작 수행 시 무게중심 은 전·후 방향과 상·하 방향으로 이동하였다. 전·후 방향으로 무게중심 이동이 가장 많은 원예활동은 땅고르기였고, 상·하 방향으로 가장 많은 무게중심 이동이 나타나는 원예활동은 종자파종이었다(p = 0.001). 무게중심 이동으로 불안정해진 신체균형을 유지하기 위한 보상적 움직임으로 지면반력 발생, 압력중심 이동, 하지 관절과 근육의 결합운동이 발생했다. 총 여덟 가지 실외원예활동은 원예활동 수행방법에 따라 운동학 및 운동역학적 특성의 차이를 보였다(p = 0.05). 따라서 본 연구의 결과는 노인과 재활환자의 균형감 향상을 위한 원예치료 프 로그램 개발 시 유용한 기초자료로서 활용되어 질 것이다.
        99.
        2016.11 서비스 종료(열람 제한)
        Anaerobic digestion is one of the most economical ways to treat organic wastes; the production of excessive sludge is limited; aeration is not required; operation cost is low; valuable energy resource (methane) is produced. However, propionate, an intermediate substance during the process, is known to inhibit biochemical process at high concentration; but it is difficult to be degraded biologically as its oxidation is thermodynamically unfavorable (△G>0). However, there are several microorganisms which could oxidize propionate fully by their syntrophic association. Therefore, in this research, the propionate enrichment culture was produced in large amount (~1L), and the main players which are responsible for utilizing propionate are identified. Furthermore, the kinetic parameter was obtained from this research. Seed came from two different full-scale anaerobic digesters which is located in Joongrang (JR) and Sincheon (SC). 16s rRNA gnee based metagenomics results indicated that Smithella propionica and Methanobacterium beijingense were the most dominant species in all seeds. The fact that bacterial family Syntrophomonadaceae and archaeal genus Methanosaeta were also found significantly in all seeds means that there might be symbiotic relationship among propionate oxidizing bacteria, butyrate oxidizing bacteria, hydrogenotrophic methanogens and acetotrophic methanogens in complete oxidation of propionate. Based on the first order kinetic which indicated propionate degrading rate, k (1/day) on JR and SC was represented 0.0243 and 0.0223, respectively. Also, based on Modified-Gompertz model, umax on JR and SC was represented as 0.024 and 0.016, respectively.
        100.
        2016.11 서비스 종료(열람 제한)
        The re-emission of mercury (Hg), as a consequence of the formation and dissociation of the unstable complex HgSO3, is a problem encountered in flue gas desulphurization (FGD) treatment in coal-fired power plants. A model following a pseudo-second-order rate law for Hg2+ reduction was derived as a function of [SO32-], [H+] and temperature and fitted with experimentally obtained data to generate kinetic rate values of (0.120 ± 0.04, 0.847 ± 0.07, 1.35 ± 0.4) mM-1 for 40°, 60°, and 75℃, respectively. The reduction of Hg2+ increases with a temperature increase but shows an inverse relationship with proton concentration. Plotting the model-fitted kinetic rate constants yields ΔH = 61.7 ± 1.82 kJ mol-1, which is in good agreement with literature values for the formation of Hg0 by SO32-. The model could be used to better understand the overall Hg2+ re-emission by SO32- happening in aquatic systems such as FGD wastewaters.
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