• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.3
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• pp.799-818
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• 2014

Spectrum sensing is a key technical challenge for cognitive radio (CR). It is well known that multi-cycle cyclostationarity (MC) detector is a powerful method for spectrum sensing. However, conventional MC detector is difficult to implement due to its high computational complexity. This paper pays attention to the fact that the computation complexity can be reduced by simplifying the test statistic of conventional MC detector. Based on this simplification process, an improved MC detector is proposed. Compared with the conventional one, the proposed detector has the low-computational complexity and sufficient-accuracy on sensing performance. Subsequently, the sensing performances are further investigated for the cases of Rayleigh, Nakagami-m, Rician, composite Rayleigh fading-lognormal shadowing and composite Nakagami fading-lognormal shadowing channels, respectively. Furthermore, the square-law combining (SLC) is introduced to improve the detection capability over fading-shadowing channels. The corresponding closed-form expressions of average detection probability are derived for each case by the moment generation function (MGF) approach. Finally, illustrative and analytical results show that the efficiency and reliability of proposed detector and the improvement on sensing performance by SLC over composite fading-shadowing channels.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.11
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• pp.5375-5379
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• 2012

Introduction: Published studies on the association between Nijmegen breakage syndrome 1(NBS1) gene polymorphisms and breast cancer risk have been inconclusive, and a meta-analysis was therefore performed for clarification. Methods: Eligible articles were identified by a search of MEDLINE and EMBASE bibliographic databases for the period up to March 2012. The presence of between-study heterogeneity was investigated using the chi-square-based Cochran's Q statistic test. When there was statistical heterogeneity, the random effects model was chosen; otherwise, fixed effects estimates were reported as an alternative approach. Results: A total of 11 eligible articles (14 case-control studies) were identified, nine case-control studies were for the 657del5 mutation (7,534 breast cancer cases, 14,034 controls) and five case-control studies were for the I171V mutation (3,273 breast cancer cases, 4,004 controls). Our analysis results indicated that the 657del5 mutation was associated with breast cancer risk (carriers vs. non-carriers: pooled OR =2.63, 95% CI: 1.76-3.93), whereas the I171V mutation was not (carriers vs. non-carriers: pooled OR =1.52, 95% CI: 0.70-3.28). Conclusion: The present meta-analysis suggests that the 657del5 gene mutation in the NBS1 gene plays a role in breast cancer risk, while the I171V mutation does not exert a significant influence.

• Journal of Elementary Mathematics Education in Korea
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• v.20 no.4
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• pp.677-694
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• 2016

Storycrafting is a creative educational technique in Finland. Since 2011, storytelling approach of mathematics textbooks in South Korea can be regarded as opportunities for interesting learning of mathematics as well as its improper application to mathematics lessons. We need to revise and improve the storytelling method. The purpose of this study is to make a storycrafting program that encourages students to make mathematical stories for themselves and to analyze the effect of the storycrafting program on mathematical creativity and communication. To do so, we developed a storycrafting program of mathematics for sixth graders, which is composed of 33 lessons. And we applied them to one sixth class as experimental group. Through pre-test and post-test, their mathematical creativity and communication were tested. Based on the result of t-test, we can verify the statistical meaningful effect of the storycrafting program. This study contains some conclusions and suggestions.

• Journal of Korea Water Resources Association
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• v.33 no.6
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• pp.733-744
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• 2000

Due to the randomness of reservoir inflow and supply demand it is not easy to establish an optimal reservoir operation rule. However, the operation rule can be derived by the implicit stochastic optimization approach using synthetic inflow data with some demand satisfied. In this study the optimal reservoir operation which was reasonably formulated as Linear Tracking model for maximizing the hydro-energy of seven reservoirs system in the Han river was performed by use of the optimal control theory. Here the operation model made to satisfy the 2001st year demand in the capital area inputted the synthetic inflow data generated by multi-site Markov model. Based on the regressions and statistic analyses of the optimal operation results, monthly reservoir operation rules were developed with the seasonal probabilities of the reservoir stages. The comparatively larger dams which would have more controllability such as Hwacheon, Soyanggang, and Chungju had better regressions between the storages and outflows. The effectiveness of the rules was verified by the simulation during actually operating period.period.

• The Korean Journal of Applied Statistics
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• v.23 no.6
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• pp.1103-1113
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• 2010

An extensively used approach for family based association test(FBAT) is compared with the sib transmission/disequilibrium test(S-TDT), and in particular the adjusted S-TDT, in which the covariance among related siblings is taken into consideration, can provide a more sensitive test statistic for association. A simulation study comparing the three test statistics demonstrates that the type I error rates of all three tests are larger than the prespecified significance level and the power of the FBAT is lower than those of the other two tests. More detailed studies are required in order to assess the influence of the assumed conditions in FBAT on the efficiency of the test.

• Journal of Korean Neurosurgical Society
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• v.43 no.3
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• pp.131-134
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• 2008

Objective: The surgical approach for anterior choroidal artery (AChA) aneurysm is typically similar to those used for other supraclinoid internal carotid artery (ICA) lesions. However, the surgical clipping of this aneurysm is complicated and as a result. can result in postoperative ischemic complications. The purpose of this study was to clarify the risk of clip-induced ischemic complication in AChA aneurysm and to get the benefits for helping decision making. Methods: We retrospectively investigated 53 cases (4.0%) of AchA aneurysm treated surgically. We divided the AChA aneurysm to 3 subtype according to the origin of aneurysmal neck; A type originating from the AChA itself. J type from junction of AChA and ICA and I type from the ICA itself. We evaluated brain CT about 1 week post-operative day to confirm the low density in AChA territory. Results: Ruptured aneurysm was 26 cases and unruptured aneurysm 27 cases. The aneurysmal subtype of A, J, and I was 13, 17, and 23 cases. Of the 53 cases who performed surgical neck clipping, twelve (22.6%) had postoperative AChA distribution infarcts. Increased infarct after neck clipping had statistic significance in non-I subtype (r=0.005) Conclusion: AChA aneurysm surgery carries a significant risk of postoperative stroke. Don't always stick to clipping only, especially in non-I type of incidental small aneurysm, which has high risk of post-clip ischemic complications.

• Journal of Korean Society of Transportation
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• v.22 no.1 s.72
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• pp.63-72
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• 2004

In conducting traffic safety programs, it is very important to identify hazardous sites in appropriate manner. The rate qualify control method is generally used in identifying hazardous sites since it can interpret the sites in the statistic aspects. The rate qualify control method is based on the assumption that the occurrences of traffic crashes follow the Poisson's distribution in which the expected value of traffic crashes equals the variance of those. However, there is greater variability than expected statistically, we call this phenomenon over dispersion. This study analyzed the problem related to the rate quality control method under the over dispersed data, and established a methodology to solve the problem. As a result of test on the basis of the field data, the new approach produced more reasonable results than those of the Poisson based rate quality control method.

• Journal of The Korean Astronomical Society
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• v.52 no.6
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• pp.217-225
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• 2019

We apply a modified Convolutional Neural Network (CNN) model in conjunction with transfer learning to predict whether an active region (AR) would produce a ≥C-class or ≥M-class flare within the next 24 hours. We collect line-of-sight magnetogram samples of ARs provided by the SHARP from May 2010 to September 2018, which is a new data product from the HMI onboard the SDO. Based on these AR samples, we adopt the approach of shuffle-and-split cross-validation (CV) to build a database that includes 10 separate data sets. Each of the 10 data sets is segregated by NOAA AR number into a training and a testing data set. After training, validating, and testing our model, we compare the results with previous studies using predictive performance metrics, with a focus on the true skill statistic (TSS). The main results from this study are summarized as follows. First, to the best of our knowledge, this is the first time that the CNN model with transfer learning is used in solar physics to make binary class predictions for both ≥C-class and ≥M-class flares, without manually engineered features extracted from the observational data. Second, our model achieves relatively high scores of TSS = 0.640±0.075 and TSS = 0.526±0.052 for ≥M-class prediction and ≥C-class prediction, respectively, which is comparable to that of previous models. Third, our model also obtains quite good scores in five other metrics for both ≥C-class and ≥M-class flare prediction. Our results demonstrate that our modified CNN model with transfer learning is an effective method for flare forecasting with reasonable prediction performance.

• Journal of the Economic Geographical Society of Korea
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• v.16 no.3
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• pp.344-358
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• 2013

Vietnam's growth as the second largest coffee producer in the world has been fueled by domestic migration into central highlands. However, the detail migration processes have not been explicitly discussed. In particular, the existing literatures tend to describe the migration flow in a framework of planned migration versus spontaneous migration, paying less attention to the linkage between them. With a case study of Dak Lak province which is the leading robusta producer in Vietnam, this research investigates the linkage between planned and spontaneous migration in a multiscalar approach. The statistic data allow the researcher to know temporal association between the two type of migration in a provine scale. The survey and interview about two coffee-producing communes - Ea H'Ding in Cu M'gar district and Doan Ket in Krung Buk district - inform us that the linkage between planned and spontaneous migration is contingent to the local contexts including ethnic composition, timing of settlements, governement's development program, and timing of a large flow of in-migration.

• International Commerce and Information Review
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• v.7 no.3
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• pp.269-286
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• 2005

The exchange rate volatility has been increased since the time when the floating exchange rate system was introduced in Korea. As a result, the increase of the exchange rate volatility raised the risk in international trades in Korea. The purpose of this study in to study the feature of exchange rate volatility and the main sources of its increase and to confirm whether the exchange rate volatility influence export volume and price of Korea. In the first place, I measured exchange rate volatility with two methods. The one is descriptive statistic method such as the width of daily exchange rate fluctuation and the rate of exchange rate devaluation. The other is the time varying conditional variance of exchange rate. Then, I studied the sources of exchange rate volatility. In the second place, I defined the exchange rate volatility as the time varying conditional variance and estimated it by using elastic a approach model which shows exchange rate is affected by itself and its conditional variance, I estimated its effects on export volumes and prices of electric home appliances, information & communication equal and semi-conductor. The result of this study is as follows. With presumed result EU and Korea because is not the goods which is to substantial competition relationship, The effect where the relative value change of presumed result expression anger and the dollar of import and export function goes mad to the import and export of Korea the income compared to is to export and it is appearing a lot. The EU goods is sold more expensively the Korean goods than from about length being caused by American market of the dollar and the balance of trade of Korea is visible like being visible the improvement of single breadth. Because the relationship of competition is weak but substantially there is to a short term and expression - the effect where the dollar rate fluctuation is big in Korean trade there is a possibility of saying that widely known it is not.