• Title/Summary/Keyword: Gap Size Ratio

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The Effects of Fertility and Strong Son Preference on Korean Society - On the basis of the changes of age and sex structure - (저출산수준과 강한 남아선호관이 사회에 미치는 영향 -성.연령별 인구 구조의 변화를 중심으로-)

  • 김태헌
    • Korea journal of population studies
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    • v.16 no.2
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    • pp.1-23
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    • 1993
  • Korea fertility level has dropped since the 1960's and speed of decline has accelerated in the 1980's. In the resuls, the growth rate reached to less then 1 percent in 1990 and will be $\ulcorner$0 $\lrcorner$ percent growth in 2021. The total population will increase to 50, 586 thousand persons in 2021 then will decrease. With the rapid fertility decline the age structure of Korean population has changed : while the proportion of child population aged 0-14 is decreasing sharply, that of old-age population aged 65 and over is increasing. Because of the recent increase of sex ratio at birth, the sex structure among the young generation has been destorted; the sex ratio at age 0-4 was as high as high as 112.0 in 1990. The effects of these population phenomena on Korean society are the followings: 1) Old age dependency ratio is increasing rapidly and continuously and will be about 40.0 from the 2050's. 2) Because of the rapid decline of the number of births, the absolute number of the major labour force at age 25-34 will decrease after around 2000 and then from the 2010's become less than that in 1990. 3) Since the large fertility defferentials by womens's educational level have continued and the relation between the educational levels of mothers and children are very strong, level has dropped among higher educated women first when the average fertility level has declined in Korea, the average educational level of the children is may be expected to be relatively low and then the future productivity is will be also low, which causes the decline of 'quality of population. 4) When the high sex ratio at birth (over 110 since 1986) continues, number of brides will be short by over 20 percent from the 2010s, which will bring various kinds of social prblems. Therefore, the counter measures in concrete to relieve the heavy problems are recommended as follows: 1) The extention of the birth intervals, which helps to drop the population growth rate at the same level of number of children per women. 2) The positive supports for out-migrants, which helps to reduce the population size without any destortion of age-sex structure. 3) The defferent supports of family planning for the higher and lower classes, which helps to reduce the gaps between different ferility levels of the classes and to keep and improve the quality of population. 4)population education for both students and adults, which helps to minimize the gap between the private and public requirements.

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Hexagonal Boron Nitride Monolayer Growth without Aminoborane Nanoparticles by Chemical Vapor Deposition

  • Han, Jaehyu;Yeo, Jong-Souk
    • Proceedings of the Korean Vacuum Society Conference
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    • 2014.02a
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    • pp.409-409
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    • 2014
  • Recently hexagonal boron nitride (h-BN), III-V compound of boron and nitrogen with strong covalent $sp^2$ bond, is a 2 dimensional insulating material with a large direct band gap up to 6 eV. Its outstanding properties such as strong mechanical strength, high thermal conductivity, and chemical stability have been reported to be similar or superior to graphene. Because of these excellent properties, h-BN can potentially be used for variety of applications such as dielectric layer, deep UV optoelectronic device, and protective transparent substrate. Ultra flat and charge impurity-free surface of h-BN is also an ideal substrate to maintain electrical properties of 2 dimensional materials such as graphene. To synthesize a single or a few layered h-BN, chemical vapor deposition method (CVD) has been widely used by using an ammonia borane as a precursor. Ammonia borane decomposes into hydrogen (gas), monomeric aminoborane (solid), and borazine (gas) that is used for growing h-BN layer. However, very active monomeric aminoborane forms polymeric aminoborane nanoparticles that are white non-crystalline BN nanoparticles of 50~100 nm in diameter. The presence of these BN nanoparticles following the synthesis has been hampering the implementation of h-BN to various applications. Therefore, it is quite important to grow a clean and high quality h-BN layer free of BN particles without having to introduce complicated process steps. We have demonstrated a synthesis of a high quality h-BN monolayer free of BN nanoparticles in wafer-scale size of $7{\times}7cm^2$ by using CVD method incorporating a simple filter system. The measured results have shown that the filter can effectively remove BN nanoparticles by restricting them from reaching to Cu substrate. Layer thickness of about 0.48 nm measured by AFM, a Raman shift of $1,371{\sim}1,372cm^{-1}$ measured by micro Raman spectroscopy along with optical band gap of 6.06 eV estimated from UV-Vis Spectrophotometer confirm the formation of monolayer h-BN. Quantitative XPS analysis for the ratio of boron and nitrogen and CS-corrected HRTEM image of atomic resolution hexagonal lattices indicate a high quality stoichiometric h-BN. The method presented here provides a promising technique for the synthesis of high quality monolayer h-BN free of BN nanoparticles.

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Analysis and Improvement Strategies of Academic Achievement of Middle School in Changwon City (창원시 중학교 학력수준 분석 및 개선 방안 모색)

  • Kim, SeongYul;Kwon, Eun-Kyoung
    • Journal of Digital Convergence
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    • v.16 no.12
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    • pp.153-162
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    • 2018
  • This paper analyzed the current level of the middle school academic achievement in Changwon City and explored the ways for improving academic achievement of the middle school in Changwon City. The data used in the analysis were the results of National Assessment of Educational Achievement of middle school students from 2013 to 2016 which was released on the school's information website(www.schoolinfo.go.kr) First, the analysis found that the academic achievement level of the middle school in Changwon City was not higher than those of Gwangju, Daejeon, and Ulsan, where the population size is similar. Second, the level of academic achievement among middle schools in Changwon City differed by year. Third, the level of academic achievement of middle school in Changwon City differed by district. Fourth, the educational achievement gap among middle schools in Changwon City existed by public and private school, as well as by male school, female school, and male and female Middle School. The paper suggested that schools with low ratio of proficient and above achievement levels should look for ways to raise the percentage of proficient and above achievement levels, and schools with higher rates of below basic achievement should make efforts to solve the problem.

Effect of Methodologies for Laser-Induced Plasma Creation on Hydrogen Sensing (레이저 유도 플라스마 생성 방법이 수소 검출에 미치는 영향)

  • Jang, Jung-Ik;Kim, Ki-Bum
    • Transactions of the KSME C: Technology and Education
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    • v.3 no.4
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    • pp.291-297
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    • 2015
  • As promising future energy source, hydrogen has been drawing much attention; however, it is easily leaked from the small gap in any storage container due to its find molecule size. In this study, Laser induced breakdown spectroscopy(LIBS) was used for hydrogen leak detection, and feasibility of the scheme was evaluated based on different way for plasma generation. Laser power of 295 mW was required for generating plasma on metal surface to measure hydrogen atomic emission while approximately 2.5 times higher laser power was needed for plasma formation directly in the hydrogen gas stream. It was shown that peak to base ratio increased linearly with increasing the concentration of hydrogen. It can be concluded that LIBS is a viable technique for hydrogen sensing when the concentration of hydrogen is less than 5%.

Adaptive Group Loading and Weighted Loading for MIMO OFDM Systems

  • Shrestha, Robin;Kim, Jae-Moung
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.5 no.11
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    • pp.1959-1975
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    • 2011
  • Adaptive Bit Loading (ABL) in Multiple-Input Multiple-Output Orthogonal Frequency-Division Multiplexing (MIMO-OFDM) is often used to achieve the desired Bit Error Rate (BER) performance in wireless systems. In this paper, we discuss some of the bit loading algorithms, compare them in terms of the BER performance, and present an effective and concise Adaptive Grouped Loading (AGL) algorithm. Furthermore, we propose a "weight factor" for loading algorithm to converge rapidly to the final solution for various data rate with variable Signal to Noise Ratio (SNR) gaps. In particular, we consider the bit loading in near optimal Singular Value Decomposition (SVD) based MIMO-OFDM system. While using SVD based system, the system requires perfect Channel State Information (CSI) of channel transfer function at the transmitter. This scenario of SVD based system is taken as an ideal case for the comparison of loading algorithms and to show the actual enhancement achievable by our AGL algorithm. Irrespective of the CSI requirement imposed by the mode of the system itself, ABL demands high level of feedback. Grouped Loading (GL) would reduce the feedback requirement depending upon the group size. However, this also leads to considerable degradation in BER performance. In our AGL algorithm, groups are formed with a number of consecutive sub-channels belonging to the same transmit antenna, with individual gains satisfying predefined criteria. Simulation results show that the proposed "weight factor" leads a loading algorithm to rapid convergence for various data rates with variable SNR gap values and AGL requires much lesser CSI compared to GL for the same BER performance.

Computational design of mould sprue for injection moulding thermoplastics

  • Lakkannan, Muralidhar;Mohan Kumar, G.C.;Kadoli, Ravikiran
    • Journal of Computational Design and Engineering
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    • v.3 no.1
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    • pp.37-52
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    • 2016
  • To injection mould polymers, designing mould is a key task involving several critical decisions with direct implications to yield quality, productivity and frugality. One prominent decision among them is specifying sprue-bush conduit expansion as it significantly influences overall injection moulding; abstruseness anguish in its design criteria deceives direct determination. Intuitively designers decide it wisely and then exasperate by optimising or manipulating processing parameters. To overwhelm that anomaly this research aims at proposing an ideal design criteria holistically for all polymeric materials also tend as a functional assessment metric towards perfection i.e., criteria to specify sprue conduit size before mould development. Accordingly, a priori analytical criterion was deduced quantitatively as expansion ratio from ubiquitous empirical relationships specifically a.k.a an exclusive expansion angle imperatively configured for injectant properties. Its computational intelligence advantage was leveraged to augment functionality of perfectly injecting into an impression gap, while synchronising both injector capacity and desired moulding features. For comprehensiveness, it was continuously sensitised over infinite scale as an explicit factor dependent on in-situ spatio-temporal injectant state perplexity with discrete slope and altitude for each polymeric character. In which congregant ranges of apparent viscosity and shear thinning index were conceived to characteristically assort most thermoplastics. Thereon results accorded aggressive conduit expansion widening for viscous incrust, while a very aggressive narrowing for shear thinning encrust; among them apparent viscosity had relative dominance. This important rationale would certainly form a priori design basis as well diagnose filling issues causing several defects. Like this the proposed generic design criteria, being simple would immensely benefit mould designers besides serve as an inexpensive preventive cliché to moulders. Its adaption ease to practice manifests a hope of injection moulding extremely alluring polymers. Therefore, we concluded that appreciating injectant's polymeric character to design exclusive sprue bush offers a definite a priori advantage.

Growth Properties of Sputtered ZnO Thin Films Affected by Oxygen Partial Pressure Ratio (산소분압비에 따른 ZnO 박막의 성장특성)

  • Kang, Man-Il;Kim, Moon-Won;Kim, Yong-Gi;Ryu, Ji-Wook;Jang, Han-O
    • Journal of the Korean Vacuum Society
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    • v.17 no.3
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    • pp.204-210
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    • 2008
  • ZnO thin films were grown on a glass by RF sputtering system with RF power 100W and oxygen partial pressure of $0%{/sim}30%$. Elliptic constants were measured by using a phase modulated spectroscopic ellipsometer and analyzed with the Tauc-Lorentz dispersion formula and best fit method in the range of 1.5 to 3.8eV. Also, scanning electron microscope(SEM) was used for the analysis of surface crystallization condition. From elliptic constants spectra, optical constants, thickness and roughness of ZnO films were evaluated. Total thickness of ZnO films obtained by ellipsometry showed good agreement with SEM data. It was found that the grain size of the films were getting smaller with increasing oxygen partial pressure. Band-gap of ZnO films increase with the oxygen partial pressure. These findings clearly indicate that optical properties of ZnO films are strongly dependent on the oxygen partial pressure. It could be explained that increasing the oxygen partial pressure induced high crystalline imperfection in the ZnO films.

Structural and Electrical Properties of Zn-Mn-O System Ceramics for the Application of Temperature Sensors (온도센서로의 응용을 위한 Zn-Mn-O계 세라믹의 구조적, 전기적 특성)

  • Kim, Kyeong-Min;Lee, Sung-Gap;Lee, Dong-Jin;Park, Mi-Ri;Kwon, Min-Soo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.29 no.8
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    • pp.470-475
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    • 2016
  • In this study, $Zn_xMn_{3-x}O_4$ (x=0.95~1.20) specimens were prepared by using a conventional mixed oxide method. All specimens were sintered in air at $1,200^{\circ}C$ for 12 h and cooled at a rate of $2^{\circ}C/min$ to $800^{\circ}C$, subsequently quenching to room temperature. We investigated the structural and electrical properties of $Zn_xMn_{3-x}O_4$ specimens with variation of ZnO amount for the application of NTC thermistors. As results of X-ray diffraction patterns, all specimens showed the formation of a complete solid solution with tetragonal spinel phase. And, the second phase was observed by the solubility limit of Zn ions in $x{\geq}1.10$ composition. The average grain size was increased from $2.72{\mu}m$ to $4.18{\mu}m$ with increasing the compositional ratio of Zn ion from x=0.95 to 1.20, respectively. $Zn_{1.10}Mn_{1.90}O_4$ specimen showed the minimum electrical resistance of $57.5k{\Omega}$ at room temperature and activation energy of 0.392 eV.

A Study on the Preparation of PBAST/PVA Double Layered Hollow Microspheres (PBAST/PVA 이중층 중공미세구의 제조에 관한 연구)

  • Song, Myung-Sook;Woo, Je-Wan
    • Clean Technology
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    • v.14 no.4
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    • pp.256-264
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    • 2008
  • In this study, using PBAST (poly(butylene adipate-co-succinate-co-terephthalate)) which was eco-friendly biodegradable aliphatic polyester, PBAST/PVA (poly(vinyl alcohol)) double-layered hollow microspheres were prepared with the water/oil/water multiple emulsion ($W_1/O/W_2$) method. The double-layered hollow microspheres were manufactured with the yield of 30.92% when the concentration of polymer PBAST in organic phase was 5 wt%, the concentration of PVA in inner aqueous phase was 5 wt%, the volume ratio of $W_1/O$ emulsion to outer aqueous phase was 1:4.5, and when co-surfactants that had large gap in HLB (hydrophile-lipophile balance) value were used. The bulk density of prepared hollow microsphere was 0.180 g/ml and particle size was $1.5{\sim}3\;{\mu}m$.

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Self-Assembled ZnO Hexagonal Nano-Disks Grown by RF Sputtering

  • Jeong, Eun-Ji;Kim, Ji-Hyeon;Kim, Su-Jin;Gang, Hyeon-Cheol
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.02a
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    • pp.461-461
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    • 2013
  • Over the last decade, zinc oxide (ZnO) thin films have attracted considerable attention owing to large band gap of 3.37 eV and large exciton binding energy of 60 meV at room temperature [1-3]. Recent interest in ZnO related researches has been switched into the fabrication and characterization of low-dimensional nanostructures, such as nano-wires and nano-dots that can be applicable to manufacture the optoelectronic devices such as ultraviolet lasers, light-emitting-diodes and detectors. Since the optical properties of ZnO nano-structures might be distinct from those of bulk materials or thin films, the low-dimensional phenomena should be examined further. In order to utilize such advanced optoelectronic devices, one of the challenges is how to control the surface state related emissions that are drastically increased with increasing the density of the nano-structures and the surface-to-volume ratio. This paper reports the synthesis and characterization of self-assembled ZnO hexagonal nano-disks grown by radio-frequency magnetron sputtering. X-ray diffraction data and scanning electron microscopy data showed that ZnO hexagonal nano-disks were nucleated on top of the flat surfaces as the film thickness reached to 1.56 ${\mu}m$ and then the number of nano-disks increased with increasing the film thickness. The lateral size of hexagonal nano-disks was ~720 nm and height was ~74 nm. The strong photo luminescence spectra obtained at 10 K was also observed, which was assigned to a surface exciton emission at 3.3628 eV arising from the surface sites of hexagonal nano-disks.

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