• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.2
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• pp.46-52
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• 2009

In this paper, the timing estimator based on the principle of the best linear unbiased estimator (BLUE) is proposed in OFDMA uplink systems. The proposed timing estimator exploits the phase information of the differential correlation between adjacent subcarriers. The differential correlation can extract the information about timing offset and mitigate the distortion of the signal caused by the frequency selectivity of channel. Compared with conventional methods, the proposed estimator shows more accurate capability in estimation. In addition, the estimator is hardly affected by the distortion caused by the frequency selectivity of channel. Simulation results confirm that the proposed estimator shows a small error mean and a relatively small error variance. In addition, the performance of the estimator is evaluated by means of SNR loss. It is shown by simulations that the SNR loss of the proposed estimator by estimation errors is less than 0.4 dB for the SNR values between 0 and 20 dB. This might indicate that the proposed estimator is suitable for the timing synchronization of multiple users in OFDMA uplink systems.

• Therapeutic Science for Rehabilitation
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• v.6 no.1
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• pp.11-23
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• 2017

Spatial neglect is a neurological disorder following stroke, a lesion that usually affects the right hemisphere, fail to process or attention on the contralateral side of body and space. Functional neuroimaging studies report that spatial neglect is associated with lesions of large middle cerebral artery, perisylvian network and attention network. Spatial neglect is associated with a poor outcome. For optimal diagnosis and intervention, Types and theories of spatial neglect should be considered, in addition to clinical assessment with the conventional test and functional test. The treatment for spatial neglect could be consist of top-down approaches and bottom-up approaches. Recent trends in rehabilitation intervention for spatial neglect have reported prism adaptation.

• Spatial Information Research
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• v.19 no.6
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• pp.1-10
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• 2011

The evaluation systems on the National Spatial Information Policy(NSIP) has been changed, since the Establishment and Use of the National Geographic Information System Act(NGIS Act, 2000) was abolished and the National Spatial Data Infrastructure Act(NSDI Act, 2009) was enacted. As compared to the NGIS Act, the policy evaluation systems for National Spatial Information are regarded as unified and centralized. However, some argue that the claim of budget and the legal feasibility of the NSIP was weakened. Given the different views on the two laws, this study aims at analyzing the changes in the evaluation system by comparing the NGIS Act and the NSDI Act. A Comparative Analysis framework is employed. The subjects of the comparative analysis are evaluation mechanism, evaluator, evaluation target and range, after-assessment utilization, and agent. In order to improve the effectiveness of the evaluation system, it is recommended that the clarification of evaluation purposes, institutional enhancement for evaluation agency, the development of evaluation indexes, the combination of top-down approach and bottom -up approach, and the increased linkage between budget and evaluation result.

• Journal of KIISE:Software and Applications
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• v.31 no.2
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• pp.189-202
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• 2004

In this paper, we propose a new salient region detection method in an image. The algorithm is based on the characteristics of human's bottom-up visual attention. Several features known to influence human visual attention like color, intensity and etc. are extracted from the each regions of an image. These features are then converted to importance values for each region using its local competition function and are combined to produce a saliency map, which represents the saliency at every location in the image by a scalar quantity, and guides the selection of attended locations, based on the spatial distribution of saliency region of the image in relation to its Perceptual importance. Results shown indicate that the calculated Saliency Maps correlate well with human perception of visually important regions.

• Korean Journal of Soil Science and Fertilizer
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• v.28 no.3
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• pp.233-240
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• 1995

Fick's diffusion equation was transformed into algebraic subsidiary equation with its initial and boundary conditions through Laplace transformation, and the subsidiary equation was transformed back on the basis of Burington's table of inverse transformations so that it became the solution of Fick's equation. The initial and boundary condition was for upward diffusion of salts into flooding water of constant depth from uniform polder soil of infinite depth containing constant concentration of salt. The derived solution was tested through comparison for its conformability with other solutions of simpler initial and boundary conditions. The importance of shallow transplanting of rice seedlings and salt removing by growing rice was mentioned on the basis of very slow desalting rate by diffusion calculated from the derived solutions.

• Journal of Internet Computing and Services
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• v.11 no.5
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• pp.81-94
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• 2010

The purpose of the study is to suggest a standardized teaching-learning model as a method for strengthening the practical effect of the information ethic education for the adolescent, which is practiced in schools as the inter-disciplinary way. A survey was put to teachers and their needs are analyzed. At the same time, in order to draw the practical teaching-learning model, the teaching examples were collected for contesting. Through this process, a bottom-up approach which tries to analyze the actual class examples and generalizes them, the teaching-learning model has been suggested. As a result, another survey was conducted for the investigation of the efficacy of the model between beneficiary group and comparison group. The results are as followings; the experiment group showed a higher index in regard with such items as Information Culture Index, Lesson Satisfaction Degree, and Practice Will than Comparison Group, and the differences are statistically significant. According to the results of the analysis.

• Journal of Navigation and Port Research
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• v.36 no.1
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• pp.9-14
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• 2012

Maritime security incidents by pirates and by terrorists increase, but maritime incidents investigation models are limited to figure out the maritime security incidents. This paper provides the analysis model for maritime security incidents. To develop this analysis model, this categorizes five threat factors, the ship, the cargo type, port system, human factor, information flow system, makes the risk assessment matrix to quantify the risk related to threat factors and classifies four priority categories of risk assessment matrix. Also, this model makes from the frameworks which include a variety of security initiatives implementing in stakeholder levels like international organizations, individual governments, shipping companies, and the ship. Therefore, this paper develops the Analysis for Maritime Security Management model based on various security initiatives responding to the stakeholder levels of maritime security management and top-bottom/bottom-up decision trees, and shows the validity through verifying the real maritime security incident of M/V Petro Ranger.

• The Journal of Korean Institute for Practical Engineering Education
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• v.3 no.1
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• pp.127-135
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• 2011

The past quantitative analysis of the demand for job skill training had mainly focused on personnel shortage and oversupply, so it has the problems of the qualitative discrepancies called skill mismatch. As a supplementary study relating to specific industries and occupations, a discussion to improve the job skills training programs through a qualitative analysis is needed. This study provide the analysis of urgency evaluation using the relative importance and gap of the job skill elements in the display industry. And renewal possibilities of the training program based on this qualitative bottom-up approach will be discussed. We carried out a job skill demand survey in the display industry as research methods. Industry related jobs and each job task, the qualitative demand for each job skills, and procurement methods for each job skills were analyzed. Adequate supply of vocational training programs have tried to find ways by illustrating some related training courses.

• Journal of the Korea Convergence Society
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• v.12 no.4
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• pp.217-228
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• 2021

After the integrated fare system has been applied, public transportation and transfer traffic increased. As a result, transfer passengers must be considered in the operation of the bus. Although previous studies have limitations due to utilizing deterministic mathematical models, which fails to reflect the stochastic movements of passengers and buses, in this study, a more realistic bus stop micro-simulation model is proposed. Based on the proposed simulation model, we represent the relationship between bus arrival interval and passenger wait time as a regression model and empirically show the differences between the cases with and without transfer passengers. Also, we propose a method converting passenger waiting time to cost and find optimal bus arrival interval based on the converted cost. It is expected the proposed method enables bottom-up decision making reflecting practical situation.

• Journal of KIISE:Databases
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• v.31 no.6
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• pp.684-698
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• 2004

The Hippocratic database model recently proposed by Agrawal et al. incorporates privacy protection capabilities into relational databases. Since the Hippocratic database is based on the relational database, it needs extensions to be adapted for XML databases. In this paper, we propose the Hippocratic XML database model, an extension of the Hippocratic database model for XML databases and present an efficient access control mechanism under this model. In contrast to relational data, XML data have tree-like hierarchies. Thus, in order to manage these hierarchies of XML data, we extend and formally define such concepts presented in the Hippocratic database model as privacy preferences, privacy policies, privacy authorizations, and usage purposes of data records. Next, we present a new mechanism, which we call the authorization index, that is used in the access control mechanism. This authorization index, which is Implemented using a multi-dimensional index, allows us to efficiently search authorizations implied by the authorization granted on the nearest ancestor using the nearest neighbor search technique. Using synthetic and real data, we have performed extensive experiments comparing query processing time with those of existing access control mechanisms. The results show that the proposed access control mechanism improves the wall clock time by up to 13.6 times over the top-down access control strategy and by up to 20.3 times over the bottom-up access control strategy The major contributions of our paper are 1) extending the Hippocratic database model into the Hippocratic XML database model and 2) proposing an efficient across control mechanism that uses the authorization index and nearest neighbor search technique under this model.