• International Journal of Highway Engineering
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• v.6 no.2 s.20
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• pp.47-59
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• 2004

The temperature variation of concrete pavement at early-age significantly affects the initiation and propagation of its early-age cracks. This implies that the measurement and analysis of early age temperature trend are necessary to examine the causes of early age cracks in the concrete pavement. In this study, it is investigated how the early age temperature trend in concrete pavement affects the random crack initiation and behaviors of saw-cut joints using the actual construction site which is located at the KHC test road. During 72 hours after placing the concrete pavement, the ambient air temperature and temperatures at the top, middle, and bottom in concrete pavement were measured and the random crack initiation in concrete slabs and early age behaviors in the joints were surveyed. The investigation results indicate that the first random crack was initiated at one of the slabs placed in the early morning which have higher temperature changes during early 72 hours. The movement of slab was influenced by the early-age crack in the joint. It suggested that the different occurrence time of the cracks in the joint had an influence on the behavior of the cracks. Besides, the slab constructed In the morning had higher possibility of crack initiation than that in the afternoon. The rarely occurred cracks had bigger gap than other cracks.

• Journal of the Korean Society of Radiology
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• v.8 no.2
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• pp.57-63
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• 2014

This study aims to find out the standardized test criteria regarding patients with the anterior cruciate ligament damage by identifying the degree of the flexion gap of femur and tibia upon bending of the anterior cruciate ligament in order to carry out the accurate test of such impairment. On the standardized test method and judgement criteria upon the anterior cruciate ligament test using Telos, it has been shown that there was no significant difference in the results according to the position of a fixed roller in the anterior cruciate ligament test for normal patients. However, in a test for patients who had undergone the anterior cruciate ligament reconstruction, it has been shown that the measured values of the anterior cruciate ligament tended to be pushed when the position of a fixed roller was less than 1cm in the test according to the position of a fixed roller of Telos (less than 1cm, more than 3cm), and this was statistically significant. The anterior cruciate ligament test (knee stress test) is a limited method used in orthopedics and rehabilitation medicine, and there have been no standardized test guidelines available yet although numerous ligament measurement tests have been performed. In addition, since the measured values are often different depending on testers even on the test that is expected to give the same result, the reproducibility of the test is still low. Accordingly, it is considered that the criteria for the anterior cruciate ligament test need to be established, and this would contribute to the accuracy of the diagnosis through the accurate test and standardized measurements.

• Journal of Technology Innovation
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• v.28 no.2
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• pp.63-100
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• 2020

This study analyzes the effectiveness of government supported R&D program for SMEs by measuring TFP improvements. We estimate TFP for Korean companies from 2011 to 2018 using Levinsohn and Petrin (2003) method which reduces endogenous problem. Then government R&D beneficiary companies were extracted from the NTIS and linked to TFP estimates. The empirical results are as follows. First, as a result of estimating production function, the contribution of TFP to value-added is more important than in the past. Second, the TFP gap between large firms and SMEs continues to wide and there is no sign of easing.(from 3.72 times in 2011 to 5.23 times in 2018). Third, SMEs beneficiaries show higher TFP level than non-beneficiaries. However their TFP was on the decline until government support. After government supported R&D program, it reverses upward. Fourth, although one-year TFP improvement of beneficiaries is bigger than non-beneficiaries, it is smaller than the control group through PSME. Because SMEs participating in government R&D programs had showed downward trend of TFP until R&D program, it is necessary to examine whether there is a fundamental discordance between the demand of SMEs for R&D program and governments policy goal. More sophisticated program design will be required to escape the recognition that government R&D programs for SMEs are just charity.

• School Mathematics
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• v.15 no.2
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• pp.289-314
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• 2013

Achievement profile by attribute in Korean students' mathematics was analyzed by applying cognitive diagnostic model, which is the newest measurement theory, to 2011 NAEA(National Assessment of Educational Assessment) results. The results are as follows. As the level of school is higher from 6th grade, 9th grade to 11th grade, the percentage of students mastering cognitive attribute 9(expressions using picture, table, graph, formula, symbol, writing, etc) drastically declined from 78%, 35% to 26%. It is necessary to have learning strategies to reinforce their abilities of expressing table, graph, etc. that higher graders in mathematics are more vulnerable to. Next, the property of mastering cognitive attributes according to gender, multi-cultural family was analyzed. In terms of mathematics, the percentage of girls mastering most of the attribute generally is higher than that of boys from 6th grade to 9th grade, however, boys show higher mastery in almost attributes than girls in the 11th grade. Compared to boys, the part where girls have the most trouble is attribute 9 in mathematics(expressions using picture, table, graph, formula, symbol, writing, etc). As international marriage, influx of foreign workers, etc. increase, the number of students from Korea's multi-cultural families is expected to be higher, therefore, identifying the characteristics of their educational achievement is significant in reinforcing Korea's basic achievement. In mathematics, gap of mastery level of attributes between multi-cultural group and ordinary group is more severe in higher grade and the type of multi-cultural group that needs supports for improving achievement most urgently changed in 6th grade, 9th grade and 11th grade respectively. In the 6th and 11th grade, migrant students from North Korea show the lowest level of mastering attributes, however, in the 9th grade, the mastery rate of immigrant students is lowest. Therefore, there is an implication that supporting plans for improving achievement of students from multi-cultural family should establish other strategies based on the characteristics of school level.

• Journal of the Korean association of regional geographers
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• v.10 no.2
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• pp.407-427
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• 2004

The rapid innovation of information and communication technology and its sharp falling prices have brought about the expansion of the Internet, integrating the world as one space under converged space and time. This rapid expansion of the Internet and its application in the economy have spurred the emergence of the digital economy. The Internet has influenced strongly on the changes of not only economic activities but also political, social and cultural activities. In this context, a rapidly increasing Internet expansion renders the rhetoric about the death of distance and about the meaningless of geographical place. However, the development and expansion of Internet induces a growing digital divide among nations and also a spatial inequality in a nation as the supply of the Internet has concentrated towards demand-affluent large cities. A large gap of digital access has been occurred between high income and low income countries according to a measurement of the international digital access index. In a national level, the Internet backbone has been built around large cities which favor a large amount of the Internet demand, and the affordable accessibility of these cities for the Internet services has influenced strongly on the agglomeration of Internet related industries, further inducing the construction and investment of the Internet backbone into large cities as cumulative causation effects. As a result, the expansion of the Internet affects immensely on the changes of spatial structure in a nation resulting in the new spatial phenomena such as centralization, concentration and splintering in the digitalized space-economy.

• Proceedings of the KIEE Conference
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• 1988.11a
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• pp.372-375
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• 1988

The III-V ternary alloy semiconductor $In_{l-x}Ga_{x}As$ were grown by the temperature Gradient of $0.60{\leq}x{\leq}0.98$. The electrical properties were investigated by the Hall effect measurement with the Van der Pauw method in the temperature range of $90{\sim}300K$. $In_{l-x}Ga_{x}As$ were revealed n-type and the carrier concentration at 300K were in the range of $9.69{\times}10^{16}cm^{-3}{\sim}7.49{\times}10^{17}cm^{-3}$. The resistivity was increased and the carrier mobility was decreased with increasing the composition ratio. The optical energy gap determined by optical transmission were $20{\sim}30meV$ lower than theoretical valves on the basis of absorption in the conduction band tail and it was decreased with increasing the temperature by the Varshni rule. In the photoluminescence of undoped $In_{l-x}Ga_{x}As$ at 20K, the main emission was revealed by the radiative recombination of shallow donor(Si) to acceptor(Zn) and the peak energy was increased with increasing the composition, X. The diffusion depth of Zn increases proportionally with the square root of diffusion time, and the activation energy for the Zn diffusion into $In_{0.10}Ga_{0.90}As$ was 2.174eV and temperatures dependence of diffusion coefficient was D = 87.29 exp(-2.174/$K_{B}T$). The Zn diffusion p-n $In_{x}Ga_{x}As$ diode revealed the good rectfying characteristics and the diode factor $\beta{\approx}2$. The electroluminescence spectrum for the Zn-diffusion p-n $In_{0.10}Ga_{0.90}As$ diode was due to radiative recombation between the selectron trap level(${\sim}140meV$) and Zn acceptor level(${\sim}30meV$). The peak energy and FWHM of electroluminescence spectrum at 77K were 1.262eV and 81.0meV, respectively.

• Journal of Internet Computing and Services
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• v.18 no.4
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• pp.109-119
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• 2017

This paper is to analyse empirically using the data collected from Korea portal Naver's ad management system and show online ad platform may not be two-sided market. It is aim of this study to propose the appropriate approach to define the market, based on the empirical result. Here are two research questions to be reviewed. First, is there any consistency between business model of search advertising and definition of two-sided market which Rochet-Tirole proposed in 2006? Second, do indirect network externalities exist significantly in search advertising market? if so, this study is going to estimate the level of it through empirical measurement. Based on Luchetta's paper which suggested that google may be one-sided market, it performed the correlation & regression analysis to prove his suggestion. The result is that online search advertising costs increased by more than 50 won when advertisers increased by one unit. However, there was no significant correlation and regression between the search frequency and online search advertising cost. It means that there is little possibility to identify two-sidedness in online search advertising service(market) because of no(or little) indirect network externalities which are a necessary condition for two-sided market. This result has three implications, such as the availability to adapt traditional market definition tools to online search advertising market, the possibility enhancement to find the fundamental competition elements in defined market and promotion of the powers of persuasion in competitive market reality. It is significant that the gap between legal scholars including regulatory practitioners and economists can be overcome to some extent. who have shown the different perspective on the two-sided market.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.11
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• pp.923-932
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• 2002

A stoichiometric mixture of evaporating materials for CdIn$\_$2/S$\_$4/ single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films, CdIn$\_$2/S$\_$4/ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by hot wall epitaxy(HWE) system. The source and substrate temperatures were 630 $\^{C}$ and 420 $\^{C}$, respectively. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction(DCXD). The carrier density and mobility of CdIn$\_$2/S$\_$4/ single crystal thin films measured from Hall effect by van der Pauw method are 9.01$\times$10$\^$16/ cm$\^$-3/ and 219 ㎠/V$.$s at 293 K, respectively. From the optical absorption measurement, the temperature dependence of energy band gap on CdIn$\_$2/S$\_$4/ single crystal thin films was found to be Eg(T) ＝ 2.7116 eV - (7.74 $\times$ 10$\^$-4/ eV) T$\^$2//(T＋434). After the as-grown CdIn$\_$2/S$\_$4/ single crystal thin films was annealed in Cd-, S-, and In-atmospheres, the origin of point defects of CdIn$\_$2/S$\_$4/ single crystal thin films has been investigated by the photoluminescence(PL) at 10 K. The native defects of V$\_$cd/, V$\_$s/, Cd$\_$int/ and S$\_$int/ obtained by PL measurements were classified as donors or accepters type. And we concluded that the heat-treatment in the S-atmosphere converted CdIn$\_$2/S$\_$4/ single crystal thin films to an optical p-type. Also, we confirmed that In in CdIn$\_$2/S$\_$4/GaAs did not from the native defects because In in CdIn$\_$2/S$\_$4/ single crystal thin films existed in the form of stable bonds.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.2
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• pp.117-126
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• 2005

A stoichiometric mixture of evaporating materials for $AgGaS_2$ single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, $AgGaS_2$ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the hot wall epitaxy (HWE) system. The source and substrate temperatures were $590^{\circ}C\;and\;440^{\circ}C$, respectively The temperature dependence of the energy band gap of the $AgGaS_2$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=2.7284 eV-(8.695{\times}10^{-4}eV/K)T^2/T(T+332K)$. After the as-grown $AgGaS_2$, single crystal thin films was annealed in Ag-, S-, and Ga-atmospheres, the origin of point defects of $AgGaS_2$ single crystal thin films has been investigated by the photoluminescence(PL) at 10K. The native defects of $V_{Ag},\;V_s,\;Ag_{int},\;and\;S_{int}$, obtained by PL measurements were classified as a donors or acceptors type. And we concluded that the heat-treatment in the Ag-atmosphere converted $AgGaS_2$ single crystal thin films to an optical n-type. Also, we confirmed that Ga in $AgGaS_2$ crystal thin films did not form the native defects because Ga in $AgGaS_2$ single crystal thin films existed in the form of stable bonds.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.3
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• pp.43-49
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• 2010

Direct printing technology is an attractive metallization method, which has become immerging as "Green technology" to the conventional photolithography, on account of low cost, simple process and environment-friendliness. In order to commercialize the printed electronics in industry, it is essential to evaluate the electrical properties of conductive circuits using direct printing technology. In this contribution, we focused on the electrical characteristics of inkjet-printed circuits. A Cu nanoink was inkjet-printed onto a Bisaleimide triazine(BT) substrate with parallel transmission line(PTL) and coplanar waveguide(CPW) type, then was sintered at $250^{\circ}C$ for 30 min. We calculated the resistivity of printed circuits through direct current resistance by the measurement of I-V curve: the resistivity was approximately 0.558 ${\mu}{\Omega}{\cdot}cm$ which is about 3.3 times that of bulk Cu. Cascade's probe system in the frequency range from 0 to 30 GHz were employed to measure the Scattering parameter(S-parameter) with or without a gap between the substrate and the probe station chuck. The result of measured S-parameter showed that all printed circuits had over 5 dB of return loss in the entire frequency range. In the curve of insertion loss, $S_{21}$, showed that the PTL type circuits had better transmission of radio frequency (RF) than CPW type.