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        검색결과 685

        181.
        2017.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This research was conducted to investigate the effects of feeding high and low forage diets with different forage sources on rumen fermentation characteristics and blood parameters of Holstein cows during the dry period. Eight Holstein cows were completely randomized assigned to two groups and repeated measurement was utilized in the analysis. Cows in two treatments were fed with diets with high (F:C = 70:30, 70F; forage source: mixed-sowing whole crop barley and Italian ryegrass silage, BIRG) and low (F:C = 55:45, 55F; forage source: tall fescue hay, TF) forage level. Rumen fluid pH was higher in 70F group. Levels of acetic acid, propionic acid, and butyric acid showed a similar pattern: from the lowest value at 07:30 h to the highest at 10:30 h and then decreased in both groups. The ratio of acetic acid to propionic acid was significantly higher (p < 0.05) in 55F group at 09:30 and 10:30 h. Rumen fluid NH3-N concentrations were significantly higher (p < 0.05) in 70F group at 09:30 and 10:30 h. Blood urea nitrogen was significantly higher (p < 0.05) in 70F group. It was concluded that BIRG based diet with a high forage level had no adverse effects on rumen fermentation, some blood chemical parameters, and immune system in dry Holstein cows and could be used as a forage source instead of imported TF.
        4,000원
        182.
        2016.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Incremental sheet forming (ISF) is a highly versatile and flexible process for rapid manufacturing of complex sheet metal parts. Compared to conventional sheet forming processes, ISF is of a clear advantage in manufacturing small batch or customized parts. ISF needs die-less machine alone, while conventional sheet forming requires highly expensive facilities like dies, molds, and presses. This equipment takes long time to get preparation for manufacturing. However, ISF does not need the full facilities nor much cost and time. Because of the facts, ISF is continuously being used for small batch or prototyping manufacturing in current industries.However, spring-back induced in the process of incremental forming becomes a critical drawback on precision manufacturing. Since sheet metal, being a raw material for ISF, has property to resilience, spring-back would come in the case.It is the research objective to investigate how geometrical shaping parameters make effect on shape dimensional errors. In order to analyze the spring-back occurred in the process, this study experimented on Al 1015 material in the ISF. The statistical tool employed experimental design with factors. The table of orthogonal arrays of L8 (27) are used to design the experiments and ANOVA method are employed to statistically analyze the collected data. The results of the analysis from this study shows that the type of shape and the slope of bottom are the significant, whereas the shape size, the shape height, and the side angle are not significant factors on dimensional errors. More error incurred on the pyramid than on the circular type in the experiments. The sloped bottom showed higher errors than the flat one.
        4,000원
        183.
        2016.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The sol-gel method is the simplest method for synthesizing monodispersed silica particles. The purpose of this study is to synthesize uniform, monodisperse spherical silica nanoparticles using tetraethylorthosilicate (TEOS) as the silica precursor, ethanol, and deionized water in the presence of ammonia as a catalyst. The reaction time and temperature and the concentration of the reactants are controlled to investigate the effect of the reaction parameters on the size of the synthesized particles. The size and morphology of the obtained silica particles are investigated using transmission electron microscopy and particle size analysis. The results show that monodispersed silica particles over a size range of 54-504 nm are successfully synthesized by the sol-gel method without using any additional process. The nanosized silica particles can be synthesized at higher TEOS/H2O ratios, lower ammonia concentrations, and especially, higher reaction temperatures.
        4,000원
        184.
        2016.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study was conducted to estimate growth curve parameters by sex in Korean native Goat. Weight-age data from 148 male goats and 169 female goats raised at Animal Genetic Resources Research Center in Korea were used in this study. Growth curve parameters were estimated from nonlinear regression using Gompertz and Logistic models. Mature weight ( ) and growth rate () of male goats were 50.0 kg, and 0.0038, respectively, when Gompertz model was used. They were 47.9 kg and 0.0062, respectively, when Logistic model was used. In female goats, mature weight ( ) and growth rate () were 35.8 kg and 0.0030, respectively, when Gompertz model was used. They were 34.6 kg and 0.0046 when Logistic model was used. The goodness of fit determined by R2 was higher in the Gompertz model than that in the Logistic model. The growth curve functions estimated from the Gompertz model in Korean-native male and female goats were , respectively. The inflection point () showed that the maximum growth rate and the weight at inflection (  ) estimated from the Gompertz model were 234.8 days and 18.37 kg, respectively, in male goats. They were 235.7 days and 13.16 kg, respectively, in female goats. The growth pattern of Korean-native goats obtained from this study might be useful for determining their feeding and management plans by sex and design breeding strategies.
        4,000원
        185.
        2016.11 구독 인증기관·개인회원 무료
        The thermally induced phase separation(TIPS) method offers higher reproducibility with lower tendency for defect formation and narrower pore size distribution, rendering the method more suitable for microfiltration(MF) and ultrafiltration(UF) applications. PVDF is widely used in membrane technology due to their excellent chemical resistance and strong mechanical properties. In case of MF and UF applications, the stretching method has been applied for increasing the performance of membrane by extending pore size. In this work, the effects of dope and bore flow rates and dope composition on the tensile strength of membranes was investigated. A design of experiment(DOE) analysis was used to understand the effects of the stretching parameters such as temperature, stretching ratio and holding time on the membrane performance.
        189.
        2016.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Tri-isotropic (TRISO) coatings on zirconia surrogate beads are deposited using a fluidized-bed vapor deposition (FB-CVD) method. The silicon carbide layer is particularly important among the coated layers because it acts as a miniature pressure vessel and a diffusion barrier to gaseous and metallic fission products in the TRISO-coated particles. In this study, we obtain a nearly stoichiometric composition in the SiC layer coated at 1400oC, 1500oC, and 1400oC with 20 vol.% methyltrichlorosilane (MTS), However, the composition of the SiC layer coated at 1300-1350oC shows a difference from the stoichiometric ratio (1:1). The density decreases remarkably with decreasing SiC deposition temperature because of the nanosized pores. The high density of the SiC layer (≥ 3.19 g/cm2) easily obtained at 1500oC and 1400oC with 20 vol.% MTS did not change at an annealing temperature of 1900°C, simulating the reactor operating temperature. The evaluation of the mechanical properties is limited because of the inaccurate values of hardness and Young’s modulus measured by the nano-indentation method.
        4,000원
        190.
        2016.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        본 연구는 분만간격과 비유곡선 모수들 간의 상관관계를 규명하기 위하여 농협중앙회 젖소개량사업 소에서 진행하고 있는 유우군 능력검정사업에 참여하고 있는 홀스타인 젖소로부터 조사한 착유기록 36,505개를 분석하였는데, 분석에 이용된 착유기록은 모두 2011년부터 2013년 사이에 분만한 경산우 로부터 조사하였다. 비유곡선 모수는 Wood 모형을 적용하여, SAS 9.2 NLIN Procedure를 이용해 추 정하였다. 분만년도-계절(봄, 여름, 가을, 겨울)효과와 산차(2, 3, 4산차)의 효과를 고정효과로 한 다 형질 일반선형모형으로 SAS(GLM procedure)를 이용하였다. 분만간격, 305일 유량, 비유곡선모수(A, b, c), 비유지속성, Peak 일시 및 Peak기 유량에 대해 분만년도-계절과 산차의 효과는 모두 유의적 으로 나타났다(p<0.05). Wood 모형으로 추정한 비유곡선 함수는 2, 3 및 4산차에 대해 각각 yt = 24.66t0-175e-0.00302t, yt = 24.69t0-192e-0.00334t 및 yt = 24.22t0.200e-0.00341t으로 추정되었다. 분만간격과 305일 유량, 모수값 A, b, c, 비유지속성, Peak 일시 및 Peak기 유량과의 표현형상관(잔차상관)은 각 각 0.093, -0.014, 0.028, -0.046, 0.099, 0.085 및 0.052으로 나타났다. 분만간격이 길어지면 비유 곡선의 상향경사도, 비유지속성, Peak 일시, Peak기 유량은 증가하고, 비유곡선의 하향경사도는 감소 하여, 305일 유량은 증가할 것으로 판단된다.
        4,000원
        193.
        2016.10 구독 인증기관·개인회원 무료
        Asiatic apple leafminer, Phyllonorycter ringoniella Matsumura (Lepidoptera: Gracillariidae) is an important insect pest in apple orchard, however little is known about its demography and relationship with environmental factors. The effect of five constant temperatures (13.3, 15.3, 20.7, 26.1, and 30.0℃) on the demography of P. ringoniella was examined based on jackknife randomization method in the laboratory. The lowest (34.0%) and highest (63.3%) survivorship of immature stages occurred at 30.0 and 20.7℃, respectively. Sex ratio was estimated to be 0.5 and was unaffected by the temperature. Mean developmental times of immature stage were inversely related to temperature and varied from 25.9 days at 26.1℃ to 76.4 days at 13.3℃. Female adult longevity was longest at 15.3℃ (18.6 ± 0.96 days) and shortest at 30℃ (5.4 ± 0.27 days). The highest (86.24) and lowest (13.59) gross fecundity rate occurred at 15.3 and 30.0℃, respectively, while daily egg production displayed its highest (6.48) and lowest (2.12) values at 26.1 and 30.0℃, respectively. The highest net reproductive rate (R0), intrinsic rate of increase (r), and finite rate of increase (λ) obtained at 20.7℃ were 12.43, 0.064, and 1.067, respectively. Mean generation time (T) decreased with increasing temperatures from 85.24 days at 13.3℃ to 30.48 days at 30.0℃. Doubling time (DT) varied significantly with temperature and the shortest value (10.75 days) was obtained at 20.7℃. The life expectancies of female adult were estimated to be 16.2, 18.6, 10.8, 7.2, and 5.4 days at 13.3, 15.3, 20.7, 26.1, and 30.0℃, respectively. This study was the first time to report demographic biology of P. ringoniella, thus it provide potential direction for future research on P. ringoniella and its natural enemies in apple orchards.
        194.
        2016.08 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this study, the effectiveness of electrodialysis in removing inorganic arsenic from groundwater was investigated. To evaluate the feasibility of the electrodialysis, operating parameters such as treatment time, feed concentration, applied voltage and superficial velocity were experimentally investigated on arsenic removal. The higher conductivity removal and arsenic removal efficiency were obtained by increasing applied voltages and operation time. An increase of salinity concentrations in arsenic polluted groundwater exerted no effects on the arsenic separation ratios. Arsenic polluted waters were successfully treated with stack voltages of 1.8 ~ 2.4 V/cell-pair to approximately 93.4% of arsenic removal. Increase flow rate in diluate cell gave positive effect to removal rate. However, increase of superficial velocity in the concentrated cell exerted no effects on either the conductivity reduction or on the separation efficiency. Hopefully, this paper will provide direction in selecting appropriate operating conditions of electrodialysis for arsenic removal.
        4,000원
        195.
        2016.08 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We developed an Al sputtering process by varying the plasma power, process temperature, and film thickness. We observed an increase of hillock distribution and average diameter with increasing plasma power, process temperature, and film thickness. Since the roughness of a film increases with the increase of the distribution and average size of hillocks, the control of hillock formation is a key factor in the reduction of Al corrosion. We observed the lowest hillock formation at 30 W and 100 oC. This growth characteristic of sputtered Al thin films will be useful for the reduction of Al corrosion in the future of the electronic packaging field.
        4,000원
        198.
        2016.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This experimental study was conducted to identify the correlation between speaker design factors and T/S parameters. For experiments to be conducted in the study, the sample speakers modified the damper, sub-cone, and mass of diaphragm of woofer speaker for vehicles were made to find characteristics of mechanical factors of speaker and non-linear factors; and the sound pressure characteristics were investigated. The correlation between design factors and T/S parameters showed that the strength of suspension system and the mass of motor part increased with the increase of mass of cone paper; and the force factor and resonance frequency tended to exhibit different behaviors according to the changes of damper.
        4,000원
        199.
        2016.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The present study investigated the effects of processing parameters such as time (10, 20, 30, 40 min), pressure (25, 50, 75, 100 MPa), and the salinity of brine (0~10%(w/v)) on jacopever (Sebastes schlegeli Hilgendorf) in order to establish optimization of the three factors using a high hydrostatic pressure (HHP) machine. To do so, it analyzed the quality characteristics of volatile basic nitrogen (VBN), trimethylamine (TMA), total bacterial counts, dynamic viscoelasticities, and differential scanning calorimetry (DSC) properties. First, when the time increased to 40 mins, by 10 min intervals, the total bacterial counts in HHP groups under 25℃, 100 MPa, and 4%(w/v) brine were significantly decreased except for the first 10 min in comparison to the control group. In regards to DSC properties, the onset temperature (TO) of the first endothermal curve was significantly reduced. Second, when the pressure level increased up to 100 MPa by 25 MPa increments, the total bacterial counts in the HHP samples significantly decreased for 20 min at 50 MPa or higher. As the pressure increased, G′, G″ and the slope of tan δ decreased (except for 50 MPa). Third, in regards to the salinities of brine, when the HHP processing was treated at 100 MPa, 25℃ for 20 min, the total bacterial counts of all the HHP groups significantly decreased in comparison to those of the control group. A significant difference was found in the enthalpy of the second endothermic curve in the 6~10%(w/v) (except 7%(w/v)) HHP groups. Therefore, the salinity of the immersion water under the HHP condition was appropriate when it was lower than 6%(w/v). The present study demonstrated that the optimum parameter condition according to/under the condition of the microbial inhibition and economic effects using an HHP would be the reaction time for 20 min, reaction pressure at 100 MPa, and the salinity of 4%(w/v) brine.
        4,200원
        200.
        2016.05 구독 인증기관 무료, 개인회원 유료
        본 연구의 목적은 사회복지사의 개인환경 요인인 신체적 요인, 정서적 요인, 사회적 요인이 직 무열정 및 직무만족에 미치는 영향과 직무열정의 매개효과를 분석하여 사회복지사의 직무만족을 높일 수 있는 정책적 함의를 모색할 수 있는 기초자료를 제공하는데 있다. 이를 해결하기 위한 연구문제는 다음과 같다. 첫째, 사회복지사의 개인환경 요인이 직무만족에 직·간접적인 영향을 미치는가. 둘째, 사회복지사의 직무열정이 직무만족에 직접적으로 영향을 미 치며 매개효과를 가지는가 이며, 통계프로그램인 PASW(SPSS) Ver. 22.0 프로그램을 이용하여 분석을 실시하였다. 분석기법으로는 신뢰도 분석, 회귀분석 등을 실시하였다. 매개효과 검증을 위 해 다중회귀분석을 실시하였으며, 연구의 결과와 결론은 다음과 같다. 첫째, 사회복지사의 개인환경 요인인 신체적 요인, 정서적 요인, 사회적 요인이 모두 직접 또는 간접적으로 직무만족에 중요하고 긍정적인 영향이 있는 것으로 나타났다. 둘째, 직무열정은 직무 만족에 긍정적 영향을 미치는 요인으로 나타났다. 사회복지사의 개인환경 요인인 신체적, 정서적, 사회적 요소를 반영하여 직무열정과 직무만족을 높일 수 있는 다양한 프로그램 개발과 정책의 시행이 필요하다.
        6,400원