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In this present investigation, we developed a new category of rhodanide anion based ternary gel polymer electrolytes (TILGPEs) with high electrochemical and thermal stability, which advantageously use the harmonizing properties of a temperature-responsive polymer poly vinylidene fluoride-co-hexafluoropropylene (PVdF-co-HFP) and room temperature ionic liquid (1-ethyl-3-methylimiazolium rhodanide (thiocyanate), (EMImSCN)). TILGPEs were fabricated using a facile solution cast method by incorporating EMImSCN and lithium rhodanide (LiSCN) into PVdF-co-HFP based membranes. Among the series of electrochemical tests including electrochemical impedance spectroscopy, cyclic voltammetry, linear sweep voltammetry and chronoamperometry, the membrane with 80 wt% electrolyte mixtures (EMImSCN/LiSCN) showed better performance in all aspects. The maximum ionic conductivity was found to be in the order of 2.8 × 10−4 S cm−1 at 298 K. The LiFePO4/TILGPE3/Li cell offered a maximum discharge capacity of 149.8 mA h g−1 at C/10 rate. The inimitable properties allowed the effective use of the rhodanide TILGPEs as active separators for the development of advanced lithium ion batteries.

Pb-free ferroelectric (Na0.5Bi0.5)TiO3 (NBT) thin films were prepared by a modified sol-gel process. Their structural, dielectric and pyroelectric properties were investigated as a function of the excess Na/Bi ratio and the annealing temperature. In the case of thin films containing no excess Na and Bi, only partial amounts of the perovskite NBT were crystallized, where the films consisted mainly of the pyrochlore phase of Bi2Ti2O7 for annealing conditions of 600~800 o C. With increasing excess Na/Bi ratio, the proportion of the perovskite phase effectively increased due to the compensation of the volatile Na and Bi components. For a Na/Bi ratio of 2.0, the thin film with single NBT perovskite phase was obtained within XRD detection limit after annealing at 700 o C for 10 min and it showed the excellent dielectric properties, er of ~550 and tan δ of 0.03. While these properties were degraded for Na/Bi ratio of 2.5 despite the existence of pure perovskite phase. The NBT thin film with Na/Bi ratio of 2.0 are also promising candidates for applications requiring pyroelectric devices because it was found to have pyroelectric coefficients of 1.3~7 nC/cm 2 K in the temperature range of 30~100 o C.

The International Astronomy Olympiad (IAO) was established by the Euro-Asian Astronomical Society in order to disseminate astronomical knowledge, promote international cooperation in astronomical education area and recognize the importance of astronomy in far-reaching field of science and human culture. The first IAO competition was held at the Special Astrophysical Observatory of the Russian Academy of Sciences located in the north Caucasus of Russia in 1996. Since then, it has been held every year. This paper describes the present status of the IAO main regulations regarding its operation and major results by year, related institutions, and organizations. We created a scientific inquiry framework to analyze past IAO problems in the recognitive aspect in order to measure levels of the scientific knowledges and the scientific thinking abilities. Through this analysis, we can understand the current status of the IAO, and examine the future direction of Korea Astronomy Olympiad. Also, we can make preparation for the IAO competition and the education of delegates.

This study was aimed to understand the structures of preservice secondary school teachers` alternative conceptions on radioactive isotopes in the interior of earth. The structure of their conceptions were analyzed by the suggestions of Niaz (1988) based on the Lakatosian frameworks. The survey was carried out on a group of seventeen students who were major in science education. The research method was open-ended written questionnaire. The results of this study show that students had apparent alternative conceptions. The high temperature and pressure` explanation for radioactive decay in earth`s interior had most import effects on their alternative conceptions. It was also intended to survey their conceptional change by our teaching strategies of the philosophy of science in order to construct science concepts.

This study was to understand the components that influence preservice elementary teachers' mental models about `astronomical phenomena' such as the Seasons of the year, and the Lunar Phases of the month. We selected university of education students among whom 23 were in the second year. The data collected from the paper-pencil test and individual interview with students. The results of this study show that the students had apparent synthetic Mental models, and that the 'distance theory, and occultation theory' had most important effects on their Mental Models. It can be said that preservice elementary teachers' initial mental models of the `astronomical phenomenon' have their origin in their belief sets (specific theory) related to `astronomical phenomenon', on the basis of which they can interpret their observations and cultural information with the constraints of a naive framework of physics. The structures and possible sources of their mental models for overcoming these synthetic mental models were also discussed.

To maximize the number of planet detections, current microlensing follow-up observations are focusing on high-magnification events which have a higher chance of being perturbed by central caustics. In this paper, we investigate the properties of central caustics and the perturbations induced by them. We derive analytic expressions of the location, size, and shape of the central caustic as a function of the star-planet separation, $s$, and the planet/star mass ratio, $q$, under the planetary perturbative approximation and compare the results with those based on numerical computations. While it has been known that the size of the planetary caustic is \propto \sqrt{q}, we find from this work that the dependence of the size of the central caustic on $q$ is linear, i.e., \propto q, implying that the central caustic shrinks much more rapidly with the decrease of $q$ compared to the planetary caustic. The central-caustic size depends also on the star-planet separation. If the size of the caustic is defined as the separation between the two cusps on the star-planet axis (horizontal width), we find that the dependence of the central-caustic size on the separation is \propto (s+1/s). While the size of the central caustic depends both on $s$ and q, its shape defined as the vertical/horizontal width ratio, R_c, is solely dependent on the planetary separation and we derive an analytic relation between R_c and s. Due to the smaller size of the central caustic combined with much more rapid decrease of its size with the decrease of q, the effect of finite source size on the perturbation induced by the central caustic is much more severe than the effect on the perturbation induced by the planetary caustic. Abridged., Comment: 5 pages, 4 figures, ApJ accepted

The problem of the collapse of a self gravitating disk is here considered. We show self-similar solutions for the above problem under a modified viscous parameter. Surface density depends on r in the inner region, where m is -1.6. Therefore growing central mass goes on without mass inflow to the system.

Five contemporary pre-main sequence (PMS) evolution model grids are compared with the photo-metric data for a nearly complete sample of low-mass members in NGC 2264. From amongst the grids compared, the models of Baraffe et al. (1998) prove to be the most reliable in mass-age distribution. To overcome the limited mass range of the models of Baraffe et al. we derived a simple transformation relation between the mass of a PMS star from Swenson et al. (1994) and that from Baraffe et al., and applied it to the PMS stars in NGC 2264 and the Orion nebula cluster (ONC). The resulting initial mass function (IMF) of the ONC shows that the previous interpretation of the IMF is not a real feature, but an artifact caused by the evolution models adopted. The IMFs of both clusters are in a good agreement with the IMF of the field stars in the solar neighborhood. This result supports the idea proposed by Lada, Strom, & Myers (1993) that the field stars originate from the stars that are formed in clusters and spread out as a result of dynamical dissociation. Nevertheless, the IMFs of OB associations and young open clusters show diverse behavior. For the low-mass regime, the current observations suffer from difficulties in membership assignment and sample incompleteness. From this, we conclude that a more thorough study of young open clusters is necessary in order to make any definite conclusions on the existence of a universal IMF.

UBVRI and Hα CCD photometry has been performed in the southern region of NGC 2264 around the Cone Nebula. A nearly complete list of pre–main-sequence (PMS) members in the cluster has been made from the compilation of Hα emission stars identified in this study plus those selected in previous investigations, together with stars with X-ray emission. Using the H-R diagram, we tested a set of four PMS evolution models based on the PMS age and age spread estimate for the cluster and the mass-age relationship among individual stars. The resultant initial mass function (IMF) is in good agreement with the field star IMF of the solar neighborhood, with an IMF slope Γ = -1.7 in the mass range 0.3 ≤ log m ≤ 0.8.

All-in-one adhesives were recently developed for reducing the technique sensitivity and chair time, but lots of concerns were made on bondability, longevity, and microleakage. The object of this study was to evaluate microleakage and marginal quality of all-in-one adhesives using electrochemical method and SEM analysis quantitatively. After making Class V cavities, they were bulk filled with Heliomolar(#A1 after surface treatment with three adhesives: Adper Prompt (Group A), One up bond F (Group O), Xeno III (Group X) Electrical conductivity (microamphere, ) was checked two times: before and after cavity filling. Percentage of leaky margin was estimated from SEM image (). The data were statistically analysed: ANOVA and Paired T test for electrical conductivity, Kruskal-Wallis and Mann-Whitney test for marginal quality, Spearman s rho test for checking of relationships between 2 methods. The result were as follows: 1. There was no difference in microleakage between adhesive systems and every specimen showed some of microleakage after filling. 2. Microleakage was reduced about 70% with composite resin filling. 3. Marginal quality was the best in group A. decreasing among groups in the following order: group O, followed by group X. There were significant differences between group A and group X (p=0.015), and between group 0 and group X (p=0.019). 4. There was no relationship between the microleakage measured by electrochemical method and marginal quality measured by SEM analysis. Within the results of this study, there was no difference in microleakage among groups by electrical conductivity. However, significant difference in marginal quality was seen among groups. It was believed that these dissimilar results might be induced because of their own characteristics. Analysis of microleakage needs various methods for accuracy.