• Nuclear Engineering and Technology
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• v.23 no.2
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• pp.174-182
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• 1991

Effects of human error relevant to the periodic test are incorporated in the evaluations of the unavailability and optimal test interval of a safety system. Two types of possible human error with respect to the test and maintenance are considered. One is the possibility that a good safety system is inadvertently left in a bad state after test（Type A human error) and the other is the possibility that a bad safety system is undetected upon the test（Type B human error). An event tree model is developed for the steady-state unavailability of a safety system in order to determine the effects of human errors on the system unavailability and the optimal test interval. A reliability analysis of the Safety Injection System (SIS) was peformed to evaluate the effects of human error on the SIS unavailability. Results of various sensitivity analyses show that ; (1) the steady-state unavailability of the safety system increases as the probabilities of both types of human error increase and it is far more sensitive to Type A human error, (2) the optimal test interval increases slightly as the probability of Type A human error increases but it decreases as the probability of Type B human error increases, and (3) provided that the test interval of the safety injction pump is kept unchanged, the unavailability of SIS increases significantly as the probability of Type A human error increases but slightly as the probability of Type B human error increases. Therefore, to obtain the realistic result of reliability analysis, one should take shorter test interval (not optimal test interval) so that the unavailability of SIS can be maintained at the same level irrespective of human error. Since Type A human error during test & maintenance influeces greatly on the system unavailability, special efforts to reduce the possibility of Type A human error are essential in the course of test & maintenance.

• Journal of the Korea Computer Graphics Society
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• v.8 no.2
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• pp.1-7
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• 2002

The fast extraction of the silhouettes of a model is very useful for many applications in computer graphics and animation. In this paper, we present an efficient algorithm to compute a sequence of perspective silhouettes for a polyhedral model from a moving viewpoint. The viewpoint is assumed to move along a trajectory q(t), which is a space curve of a time parameter t. Then, we can compute the time-intervals for each edge of the model to be contained in the silhouette by two major computations: (i) intersecting q(t) with two planes and (ii) a number of dot products. If q(t) is a curve of degree n, then there are at most of n + 1 time-intervals for an edge to be in a silhouette. For each time point $t_i$ we can extract silhouette edges by searching the intervals containing $t_i$ among the computed intervals. For the efficient search, we propose two kinds of data structures for storing the intervals: an interval tree and an array. Our algorithm can be easily extended to compute the parallel silhouettes with minor modifications.

• Journal of Internet Computing and Services
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• v.12 no.4
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• pp.157-172
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• 2011

The latest active studies on distributed OLAP to adopt a distributed environment are mainly focused on DHT P2P OLAP and Grid OLAP. However, these approaches have its weak points, the P2P OLAP has limitations to multidimensional range queries in the cloud computing environment due to the nature of structured P2P. On the other hand, the Grid OLAP has no regard for adjacency and time series. It focused on its own sub set lookup algorithm. To overcome the above limits, this paper proposes an efficient central managed P2P approach for a cloud computing environment. When a multi-level hybrid P2P method is combined with an index load distribution scheme, the performance of a multi-dimensional range query is enhanced. The proposed scheme makes the OLAP query results of a user to be able to reused by other users' volatile cube search. For this purpose, this paper examines the combination of an aggregation cube hierarchy tree, a quad-tree, and an interval-tree as an efficient index structure. As a result, the proposed cloud P2P OLAP scheme can manage the adjacency and time series factor of an OLAP query. The performance of the proposed scheme is analyzed by a series of experiments to identify its various characteristics.

• Journal of Internet Computing and Services
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• v.16 no.1
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• pp.75-82
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• 2015

Major corporations and portals have implemented a link server that connects Content Management Systems (CMS) to the physical address of content in a database (DB) to support efficient content use in web-based environments. In particular, a link server automatically connects the physical address of content in a DB to the content URL shown through a web browser screen, and re-connects the URL and the physical address when either is modified. In recent years, the number of users of digital content over the web has increased significantly because of the advent of the Big Data environment, which has also increased the number of link validity checks that should be performed in a CMS and a link server. If the link validity check is performed through an existing URL-based sequential method instead of petabyte or even etabyte environments, the identification rate of dead links decreases because of the degradation of validity check performance; moreover, frequent link checks add a large amount of workload to the DB. Hence, this study is aimed at providing a link server that can recognize URL link deletion or addition through analysis on the B-tree-based Information Identifier count per interval based on a large amount of URLs in order to resolve the existing problems. Through this study, the dead link check that is faster and adds lower loads than the existing method can be performed.

• Korean Journal of Environment and Ecology
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• v.27 no.5
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• pp.571-578
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• 2013

This study generated regression models through a direct harvesting method to estimate carbon storage and uptake by Pinus densiflora and Pinus koraiensis, the major evergreen tree species in urban landscape, and established essential information to quantify carbon reduction by urban trees. Open-grown landscape tree individuals for each species were sampled reflecting various diameter sizes at a given interval. The study measured biomass for each part including the roots of sample trees to compute the total carbon storage per tree. Annual carbon uptake per tree was quantified by analyzing radial growth rates of stem samples at breast height. The study then derived a regression model easily applicable in estimating carbon storage and uptake per tree for the two species by using diameter at breast height (DBH) as an independent variable. All the regression models showed high fitness with $r^2$ values of higher than 0.98. While carbon storage and uptake by young trees tended to be greater for P. densiflora than for P. koraiensis in the same diameter sizes, those by mature trees with DBH sizes of larger than 20 cm showed results to the contrary due to a difference in growth rates. A tree of P. densiflora and P. koraiensis with DBH of 25 cm stored 115.6 kg and 130.0 kg of carbon, respectively, and annually sequestered 9.4 kg and 14.6 kg. The study has broken new grounds to overcome limitations of the past studies which quantified carbon reduction of the study species by substituting, due to a difficulty in direct cutting and root digging of landscape trees, coefficients from forest trees such as biomass expansion factors, ratios of below ground/above ground biomass, and diameter growth rates.

• Journal of Korean Society of Forest Science
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• v.89 no.2
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• pp.167-172
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• 2000

Inter-simple sequence repeat (I-SSR) markers were analyzed from diploid genomes of 95 nutmeg trees (Torreya nucifera Siev. et Zucc.) in 5 populations. A total of 62 I-SSR amplicons were observed and 7 of them were monomorphic in 95 individuals. DNA fingerprint of each tree was verified by pooling the observed I-SSR amplicons. Most of the genetic diversity was allocated within population (90.65%) and all the populations revealed similar level of I-SSR amplicon diversity within population. Degree of population differentiation (${\phi}_{ST}=9.35%$) was moderate on the basis of criteria obtained from isozyme analysis. Based on the results of the cluster analysis of UPGMA, genetic relationships among 5 populations were not coincided with the pattern of geographic distribution. Non-significant confidence interval at each node also suggests that all the nutmeg populations are genetically not much differentiated.

• Korean Journal of Radiology
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• v.22 no.5
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• pp.751-758
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• 2021

Objective: Preoperative differentiation between inverted papilloma (IP) and its malignant transformation to squamous cell carcinoma (IP-SCC) is critical for patient management. We aimed to determine the diagnostic accuracy of conventional imaging features and histogram parameters obtained from whole tumor apparent diffusion coefficient (ADC) values to predict IP-SCC in patients with IP, using decision tree analysis. Materials and Methods: In this retrospective study, we analyzed data generated from the records of 180 consecutive patients with histopathologically diagnosed IP or IP-SCC who underwent head and neck magnetic resonance imaging, including diffusion-weighted imaging and 62 patients were included in the study. To obtain whole tumor ADC values, the region of interest was placed to cover the entire volume of the tumor. Classification and regression tree analyses were performed to determine the most significant predictors of IP-SCC among multiple covariates. The final tree was selected by cross-validation pruning based on minimal error. Results: Of 62 patients with IP, 21 (34%) had IP-SCC. The decision tree analysis revealed that the loss of convoluted cerebriform pattern and the 20th percentile cutoff of ADC were the most significant predictors of IP-SCC. With these decision trees, the sensitivity, specificity, accuracy, and C-statistics were 86% (18 out of 21; 95% confidence interval [CI], 65-95%), 100% (41 out of 41; 95% CI, 91-100%), 95% (59 out of 61; 95% CI, 87-98%), and 0.966 (95% CI, 0.912-1.000), respectively. Conclusion: Decision tree analysis using conventional imaging features and histogram analysis of whole volume ADC could predict IP-SCC in patients with IP with high diagnostic accuracy.

• Journal of the Korean Data and Information Science Society
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• v.23 no.5
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• pp.881-893
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• 2012

This paper proposes to develop system trading strategy using rough set, decision tree in futures market. While there is a great deal of literature about the analysis of data mining, there is relatively little work on developing trading strategies in futures markets. There are three objectives in this paper. The first objective is to analysis performance of decision tree in rule-based system trading. The second objective is to find proper profitable trading interval. The last objective is to find optimized training period of trading rule training. The results of this study show that proposed model is useful trading strategy in foreign exchange market and can be desirable solution which gives lots of investors an important investment information.

• Korean journal of applied entomology
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• v.42 no.3
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• pp.233-240
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• 2003

The effect of density suppression of Amblyseius fallacis (Garman) against Panonychus citri (McGregor) on citrus tree introduced with some different ratio was investigated. When it was introduced with over 16:1 (Panonychus citri: A. fallacis) ratio, Panonychus citri was suppressed very effectively. And in case of introduced once or two times with 20: 1 ratio when the density of Panonychus citri was reached 0.5 and 1.0 per leaf, the density of A. fallacis was formed highly, but the suppression effect against Panonychus citri was not effective. Also, the density changes of P. citri and A. fallacis on the citrus tree released with 10: 1 ratio (P. citri: A. fallacis) when the density of P. citri was reached about 0.1 per leaf in plastic film house were investigated. In case of released twice at the interval of 10 days, the density of A. fallacis was high and P. citri was suppressed so effectively over two month. On the inside of canopy of the citrus tree planted in plastic film house, the air temperature was much lower than on the outside of canopy, while relative humidity was much higher.

• Korean Journal of Environmental Agriculture
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• v.17 no.4
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• pp.358-361
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• 1998

This study was carried out to develop a short term hardening method of tree seedlings of Rhus chinensis Mill., Evodia daniellii Hemsley and Parthenocissus tricuspidata(Sieb. et Zucc.) Planck for afforestation on a concave and a crack of cut-rock slope. The seedlings were grown in a cylinder shaped pot made of polyvinyl net with the soil media of peatmoss, vermiculite, clay, compost, fertilizer, and absorbant(40:25:19:15:1:0.1, v:v). They were cultivated in a greenhouse for four months and in field condition for two months. During the last three months of the growing period the seedlings were hardened by periodic desiccation and irrigation in 4 to 10 days interval. The hardened seedlings showed lower leaf water potential, higher leaf osmotic pressure, and lower T/R ratio than those before the hardening. The hardened seedlings survived well on the soil medium in the concave of cut-rock slope.