• Journal of Astronomy and Space Sciences
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• 제25권4호
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• pp.335-346
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• 2008

Using the global total electron contents (TEC) measured by the TOPEX satellite from Aug. 1992 to Oct. 2005, we investigate the variations of the longitudinal wavenumber-4 (LW-4) structure in the equatorial anomaly (EA) crests with season, local time, and solar activity. Our study shows that the LW-4 structure in the EA crests ($5{\sim}20^{\circ}$ MLAT in both hemispheres) has clear four peaks at fixed longitude sectors during the daytime for both equinoxes and June solstice. In spite of being called a wavelike structure, however, the magnitudes and spatial intervals of the four peaks are far from being the same or regular. After sunset, the four-peak structure begins to move eastward with gradual weakening in its amplitude during equinoxes and this weakening proceeds much faster during June solstice. Interestingly, the longitudinal variations during December solstice do not show clear four-peak structure. All these features of the LW-4 structure are almost the same for both low and high solar activity conditions although the ion densities are greatly enhanced from low to high solar activities. With the irrelevancy of the magnetic activity in the LW-4, this implies that the large changes of the upper atmospheric ion densities, one of the important factors for ion-neutral interactions, have little effect on the formation of the LW-4 structure. On the other hand, we found that the monthly variation of the LW-4 is remarkably similar to that of the zonal component of wavenumber-3 diurnal tides at low latitudes, which implies that the lower atmospheric tidal forcing, transferred to the upper atmosphere, seems to have a dominant role in producing the LW-4 structure in the EA crests via the E-region dynamo.

• 한국초등과학교육학회지:초등과학교육
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• 제33권2호
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• pp.207-216
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• 2014

Understanding the nature of science (NOS) has been a major component of scientific literacy and an important learning goal in science education (American Association for the Advancement of Science, 1990, 1993; Millar & Osborne, 1998; National Research Council, 1996, 2013). To achieve this goal, it is necessary to include appropriate views of the nature of science in science curriculum such as a textbook. The aim of this study was to conduct a content analysis of the elementary science textbooks to examine the presentation of the nature of science (NOS) using the four themes of scientific literacy, which are (1) nature of scientific knowledge, (2) nature of scientific inquiry, (3) nature of scientific thinking, and (4) nature of interactions among science, technology, and society (STS). Findings show while $3^{rd}$ and $4^{th}$ grade levels of science textbooks heavily emphasize on the Theme I, nature of scientific knowledge and the Theme II, the nature of scientific inquiry, the upper grade levels such as $5^{th}$ and $6^{th}$ grades of science textbooks are well balanced with the four themes of the nature of science. In addition, most of elementary science textbooks little focus on the Theme IV, nature of interactions among science, technology, and society (STS) among the four themes of the nature of science. It might be a shortcoming because the understanding the nature of interacions among science, technology and society (STS) is one of the key components in order for students to be a scientific literate person.

• 성인간호학회지
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• 제28권2호
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• pp.191-201
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• 2016

Purpose: The purpose of this methodological study was to examine the validity and reliability of a translated Korean version of The Oncology Patients' Perception of the Quality of Nursing Care Scale. Methods: The translated scale was pilot tested and then administered to 360 patients with cancer. Exploratory and confirmatory factor analyses were utilized to assess the factor structure. Internal consistency reliability was determined using coefficient ${\alpha}$. Results: Two of the 40 items were deleted with a principal component method of exploratory factor analysis because they did not meet the factor-loading criterion. The 38 items were again analyzed and, four factors were validated (KMO=.96, Bartlett ${\chi}^2=10809.81$, df=780, p<.001). The four factors accounted for 60.9% of the variance. Factor loadings of the scale on the four subscales ranged from .65 to .91. The scale showed reliable internal consistency with a Cronbach's ${\alpha}$, total 38 items (${\alpha}=.96$) in four subscales: individualization (18 items, ${\alpha}=.96$), proficiency (10, .91), responsiveness (7, .90), and coordination (3, .80). Conclusion: The findings of this study demonstrate that the scale has satisfactory construct validity and reliability to measure quality of cancer nursing care from the patient's perspective in Korea.

• 대한전기학회논문지:전력기술부문A
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• 제51권6호
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• pp.255-261
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• 2002

Recently, traction motors in trains are supplied with single phase a.c. power. After this power is converted to d.c. power, it is inverted to three phase power to operate traction motors. As going through the process of the conversion, harmonic current is generated in train. The method of conventional analysis on harmonics, studied by RTRI, is modeled with equivalent circuit of ac AT-fed electric railroad system using by the distributed constant circuit. However, this circuit as two-port network model has some difference in comparison with real system. The reason why the conventional method is different from the real system is that the conventional method dose not include three conductor groups, that is catenary, rail, and feeder, and admittance between the conductors for line capacitance. Therefore, this method has a little error. This paper proposes new method to more effectively estimate Harmonic current. In this method, numerous components in electric railway are categorized and each component is defined as a four- port network model. The equivalent circuit for the entire power supply system is also described into a four-port network model with connections of these components. In order to evaluate the efficiency and the accuracy of a proposed method, it is compared with values measured in Kyung-Bu high speed line and ones calculated by the conventional method.

• Journal of Crop Science and Biotechnology
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• 제10권4호
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• pp.223-230
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• 2007

Vitellaria paradoxa commonly called shea is an important agro forestry and fruit-bearing species present in four agro-ecological zones of Cameroon. The goal of this work was the morphological characterization of certain populations of V. paradoxa which will serve as a necessary step for a subsequent genetic study of the species. Morphological observations related to 20 agronomic traits, studied on 8-13 trees selected from each of the eight shea populations across four different agro-ecological zones located in four provinces of Cameroon were studied. The study showed that there was a variation between the populations, related to the traits measured on the trunk, fruit, nut, and leaf. Three shapes of the tree(ball, broom, and trained), five shapes of the fruit(round, oblong, reversed pear, ovoid, and oblong), three colors of the nut(clear brown, dark brown, and blackish brown) were identified. The principal component analysis(PCA) carried out on the quantitative characters revealed 72% of the total variance expressed on the first and second main axis. This variation was essentially explained by the traits measured on the fruits and on the nuts. The analyses showed that only the traits of the fruits and the nuts were discriminative. The shea populations studied were structured into two distinct groups using these discriminative traits.

• 한국군사과학기술학회지
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• 제7권2호
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• pp.81-87
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• 2004

Semiconductor thick film gas sensors based on tin oxide are fabricated and their gas response characteristics are examined for four simulant gases of chemical warfare agent (CWA)s. The sensing materials are prepared in three different sets. 1) The Pt or Pd $(1,\;2,\;3\;wt.\%)$ as catalyst is impregnated in the base material of $SnO_2$ by impregnation method.2) $Al_2O_3\;(0,\;4,\;12,\;20\;wt.\%),\;In_2O_3\;(1,\;2,\;3\;wt.\%),\;WO_3\;(1,\;2,\;3\;wt.\%),\;TiO_2\;(3,\;5,\;10\;wt.\%)$ or $SiO_2\;(3,\;5,\;10\;wt.\%)$ is added to $SnO_2$ by physical ball milling process. 3) ZnO $(1,\;2,\;3,\;4,\;5\;wt.\%)$ or $ZrO_2\;(1,\;3,\;5\;wt.\%)$ is added to $SnO_2$ by co-precipitation method. Surface morphology, particle size, and specific surface area of fabricated sensing films are performed by the SEM, XRD and BET respectively. Response characteristics are examined for simulant gases with temperature in the range 200 to $400^{\circ}C$, with different gas concentrations. These sensors have high sensitivities more than $50\%$ at 500ppb concentration for test gases and also have shown good repetition tests. Four sensing materials are selected with good sensitivity and stability and are fabricated as a sensor array A sensor array Identities among the four simulant gases through the principal component analysis (PCA). High sensitivity is acquired by using the semiconductor thick film gas sensors and four CWA gases are classified by using a sensor array through PCA.

• Journal of Electrical Engineering and Technology
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• 제7권1호
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• pp.1-8
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• 2012

The current paper presents a novel control strategy of a three-phase, four-wire Unified Power Quality (UPQC) to improve power quality. The UPQC is realized by the integration of series and shunt active power filters (APF) sharing a common dc bus capacitor. The realization of shunt APF is carried out using a three-phase, four-leg Voltage Source Inverter (VSI), and the series APF is realized using a three-phase, three-leg VSI. To extract the fundamental source voltages as reference signals for series APF, a zero-crossing detector and sample-and-hold circuits are used. For the control of shunt APF, a simple scheme based on the real component of fundamental load current (I $Cos{\Phi}$) with reduced numbers of current sensors is applied. The performance of the applied control algorithm is evaluated in terms of power-factor correction, source neutral current mitigation, load balancing, and mitigation of voltage and current harmonics in a three-phase, four-wire distribution system for different combinations of linear and non-linear loads. The reference signals and sensed signals are used in a hysteresis controller to generate switching signals for shunt and series APFs. In this proposed UPQC control scheme, the current/voltage control is applied to the fundamental supply currents/voltages instead of fast-changing APF currents/voltages, thus reducing the computational delay and the required sensors. MATLAB/Simulink-based simulations that support the functionality of the UPQC are obtained.

• Animal Bioscience
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• 제34권2호
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• pp.213-222
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• 2021

Objective: The metabolites that constitute the rumen fluid and milk in dairy cattle were analyzed using proton nuclear magnetic resonance (1H-NMR) spectroscopy and compared with the results obtain for other dairy cattle herds worldwide. The aim was to provide basic dataset for facilitating research on metabolites in rumen fluid and milk. Methods: Six dairy cattle were used in this study. Rumen fluid was collected using a stomach tube, and milk was collected using a pipeline milking system. The metabolites were determined by 1H-NMR spectroscopy, and the obtained data were statistically analyzed by principal component analysis, partial least squares discriminant analysis, variable importance in projection scores, and metabolic pathway data using Metaboanalyst 4.0. Results: The total numbers of metabolites in rumen fluid and milk were measured to be 186 and 184, and quantified as 72 and 109, respectively. Organic acid and carbohydrate metabolites exhibited the highest concentrations in rumen fluid and milk, respectively. Some metabolites that have been associated with metabolic diseases (acidosis and ketosis) in cows were identified in rumen fluid, and metabolites associated with ketosis, somatic cell production, and coagulation properties were identified in milk. Conclusion: The metabolites measured in rumen fluid and milk could potentially be used to detect metabolic diseases and evaluate milk quality. The results could also be useful for metabolomic research on the biofluids of ruminants in Korea, while facilitating their metabolic research.

• International Journal of Industrial Entomology and Biomaterials
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• 제45권2호
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• pp.84-92
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• 2022

White-Jade silkworm (previously also known as Baegokjam) variety is the most popular silkworm variety that produces white cocoons. In 2021, the market share of White-Jade variety in Korea is very high, accounting for 88% of the silkworm production. Daebaekjam, Dodamsilkworm, Kumkangjam, and Kumokjam varieties, which have recently been established, make white cocoons like White-Jade. In this study, we found that 5 types of HongJams produced from 5 varieties of silkworms producing white cocoons did not show any severe difference in proximate analysis. The amounts of crude proteins, the most abundant nutrient, were between 71.05 ~ 73.38%, and those of crude lipids were 13.89 ~ 14.69% in 5 types of HongJams. In addition, there was no difference between White-Jade HongJam (WJ) and Daebaekjam HongJam in amino acid compositions. The amount of unsaturated fatty acid was significantly higher in WJ than in the other four types of HongJams, but the omega-6 fatty acids/omega-3 fatty acids ratio was higher in the four types of HongJams. Most of the minerals were higher in four types of HongJams than in WJ, and three heavy metal were not detected in all 5 types of HongJams. Phytochemicals were also most abundant in WJ, but the difference in the amounts were not severe. And pepsin digestibility was the highest for Kumokjam HongJam and the lowest for Dodam-silkworm HongJam, but the difference was not severe. The nutritional component analysis results of this study suggested that four new varieties can be used for producing HongJams, and Daebaekjam can replace White-Jade the most as the protein source.

• 대한지리학회지
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• 제30권3호
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• pp.207-229
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• 1995

한반도는 중위도의 아시아대륙 동안에 위치하여 있고 지형적으로 복잡하므로 계절 을 통해 다양하게 탁월한 천후가 출현한다. 이러한 탁월천후의 특성은 일기출현율과 그 연 변화상에 잘 반영되고 있을 것으로 생각된다. 따라서 본 논문은 cybernetics의 일부로 있는 정보이론을 이용하여 남한의 탁월일기의 다소와 그 연변화형에 대해 일기의 평균정보량인 일기엔트로피를 구하고, 주성분분석기법을 응용하여 추출된 일기엔트로피의 연변화형과 그 공간 스케일에 따라 객관적인 작업에 의해 계량적으로 기후지역구분을 한 것이다. 주로 소 백, 태백산맥을 경계로 그 이서와 이동은 일기엔트로피의 출현월과 주성분분석 기법을 응용 하여 수량적으로 추출된 일기엔트로피의 연변화형이 각각 다르게 나타난다. 또한 이것은 해 안과 내륙에 위치하느냐에 따라서도 지역별로 그 정도차가 크다. 남한에서는 최소 일기엔트 로피의 출현월에 다라 8개형의 지역이 나타나며, 주성분분석에 의한 일기엔트로피의 연변화 형에 따라서는 16개형 지역으로 분류된다. 이를 종합하면 남한은 31개 지역으로 지역구분 된다.