• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6B
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• pp.875-887
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• 2010

The workgroup of IEEE 802 proposed the IEEE 802.16 standard, also known as WiMAX, to provide broadband wireless access (BWA). The standard specifies two operational modes, one is popular PMP mode, and the other is optional mesh mode. In the mesh mode, the network entry process-NetEntry is the pivotal procedure for mesh network topology formulation and thus, influences the accessibility of whole mesh network. Unfortunately, the NetEntry process suffers from the hidden neighbor problem, in which new neighborship emerges after a new node comes in and results in possible collisions. In this paper, we propose a new SN-protected NetEntry process to address the problem. Simulation results show that the new proposed NetEntry process is more stable compared with the standard-based NetEntry process.

• Journal of Satellite, Information and Communications
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• v.8 no.4
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• pp.142-149
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• 2013

As we, human expand its everyday life boundary to the geosynchronous orbit, we have experienced frequent chance of the atmospheric re-entry and surface impact of space objects(satellite and space debris). Recently a satellite re-entry monitoring room in Korea has been operated to predict the time and the location of the re-entry of space objects. However, we do not have a domestic version of a numerical re-entry model for normal operation using TLE (Two line Element) information from the United States Strategic Command yet. The space information from the several space operation centers has been used to analyse the re-entry situations. In this paper, the re-entry time is calculated with TLE based on the several atmosphere models, the result is comprehensively analyzed, a new re-entry case model fitted from the result of the predicted satellite re-entry times by a new Rubber Sheet Shift Method used by the domestic satellite re-entry room is suggested.

• The Korean Journal of Pain
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• v.25 no.2
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• pp.81-88
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• 2012

Background: In discography performed during percutaneous endoscopic lumbar discectomy (PELD) via the posterolateral approach, it is difficult to create a fluoroscopic tunnel view because a long needle is required for discography and the guide-wire used for consecutive PELD interrupts rotation of fluoroscope. A stereotactic system was designed to facilitate the determination of the needle entry point, and the feasibility of this system was evaluated during interventional spine procedures. Methods: A newly designed stereotactic guidance system underwent a field test application for PELD. Sixty patients who underwent single-level PELD at L4-L5 were randomly divided into conventional or stereotactic groups. PELD was performed via the posterolateral approach using the entry point on the skin determined by premeasured distance from the midline and angles according to preoperative magnetic resonance imaging (MRI) findings. Needle entry accuracy provided by the two groups was determined by comparing the distance and angle measured by postoperative computed tomography with those measured by preoperative MRI. The duration and radiation exposure for determining the entry point were measured in the groups. Results: The new stereotactic guidance system and the conventional method provided similarly accurate entry points for discography and consecutive PELD. However, the new stereotactic guidance system lowered the duration and radiation exposure for determining the entry point. Conclusions: The new stereotactic guidance system under fluoroscopy provided a reliable needle entry point for discography and consecutive PELD. Furthermore, it reduced the duration and radiation exposure associated with determining needle entry.

• Journal of Korean Neurosurgical Society
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• v.50 no.4
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• pp.341-347
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• 2011

Objective : The purpose of this retrospective study was to evaluate the efficacy and safety of atlantoaxial stabilization using a new entry point for C2 pedicle screw fixation. Methods : Data were collected from 44 patients undergoing posterior C1 lateral mass screw and C2 screw fixation. The 20 cases were approached by the Harms entry point, 21 by the inferolateral point, and three by pars screw. The new inferolateral entry point of the C2 pedicle was located about 3-5 mm medial to the lateral border of the C2 lateral mass and 5-7 mm superior to the inferior border of the C2-3 facet joint. The screw was inserted at an angle $30^{\circ}$ to $45^{\circ}$ toward the midline in the transverse plane and $40^{\circ}$ to $50^{\circ}$ cephalad in the sagittal plane. Patients received followed-up with clinical examinations, radiographs and/or CT scans. Results : There were 28 males and 16 females. No neurological deterioration or vertebral artery injuries were observed. Five cases showed malpositioned screws (2.84%), with four of the screws showing cortical breaches of the transverse foramen. There were no clinical consequences for these five patients. One screw in the C1 lateral mass had a medial cortical breach. None of the screws were malpositioned in patients treated using the new entry point. There was a significant relationship between two group (p=0.036). Conclusion : Posterior C1-2 screw fixation can be performed safely using the new inferolateral entry point for C2 pedicle screw fixation for the treatment of high cervical lesions.

• Asia Marketing Journal
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• v.17 no.3
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• pp.73-103
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• 2015

According to Resource Dependence theory, an organization's behavior and strategy is affected by external resources. An organization has diverse resources interacting with environment. Because organization cannot focus on all those resources, it concentrates on its critical resources. In market environment, firm responds to other firms by controlling their internal critical resources or manages interdependency with environment to get market share. Thus Firm should choose best behavior and strategy when internal and external resources are change. When new brand enters, incumbents might change their strategy to protect their market share depending on critical value. More precisely, incumbents sharing market with entrant respond, but incumbents having competitive internal resources do not. In this article, we study incumbent's responses to a new brand entry and long-term effect. We show that how incumbents change their price strategy in reaction to the new brand' entry and also show these responses vary depending on interdependency of internal resources and external environments and ownership.

• Journal of applied mathematics & informatics
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• v.16 no.1_2
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• pp.115-123
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• 2004

A recursive tree is constructed by starting with a root node and repeatedly adjoining new nodes to one node of the tree already constructed. Such a tree can represent, for example, the heirarchy of a workforce of a company that grows via recruiting. At times of economic depression, the company may decide to layoff participants, and in some cases it is a fair policy to relieve the last senior worker (most recent entry in the tree). If we remove an edge from such a tree then it falls into two subtrees one of which contains the most recent entry. If we continue to remove edges from the successively smaller subtrees that contain the most recent entry, we eventually isolate the most recent entry. We consider how many randomly selected edges must be removed in average before isolating the most recent entry by this procedure.

• International Journal of Ocean System Engineering
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• v.2 no.1
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• pp.32-36
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• 2012

This paper presents a comparison of potential and viscous computational codes for the water entry problem. A po-tential code was developed which adopted the boundary element method to solve the problem. A nonlinear free surface boundary condition was integrated to find new locations of free surface. The dynamic boundary condition was simplified by taking constant potential values for every time steps. The simplified dynamic boundary condition was applied in the new position of the free surface not at the mean level, which is the usual practice for linearized theory. The commercial code FLUENT was used to solve the water entry problem from the viscosity point of view. The movement of the air-liquid interface is traced by distribution of the volume fraction of water in a computational cell. The pressure coefficients were compared with each other, while experimental results published by other researchers were also examined. The characteristics of each method were discussed to clarify merits and limitations when they were applied to the water entry problems.

• Journal of the Korean Home Economics Association
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• v.42 no.1
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• pp.69-79
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• 2004

This study has examined factors of young married women's new entry in labor market after the birth of their first child. For the dynamic analysis, the Cox Regression Hazard Model is applied. The following results are obtained： First, about 33％ of married women who did not have a job at the pre-birth enter in labor market at the post-birth. Second, compared to those out of the labor force, women who succeeded in finding their first jobs after the birth of their first child are more likely to be younger, have baby-sitters, have working experiences in the past, and have lower level of household income. Third, age, having baby-sitter and the experience of job transition are vital factors in entering the labor market after the first child birth.

• Journal of the Ergonomics Society of Korea
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• v.36 no.5
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• pp.355-372
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• 2017

Objective: The aim of this study is to investigate the performance and usability of ten-finger text entry on Tablet PCs. Background: Generally a soft keyboard is used on Tablet PCs. However, the soft keyboard's performance is usually worse than physical keyboard's performance. In this study, we proposed a modified keyboard for tablet PCs to improve the performance of ten-finger text entry and evaluated the performance and subjective ratings of the keyboard. Method: The modified soft keyboard that is suggested in this study was compared with current Google and Samsung soft keyboards on Tablet PCs. Results: The three keyboards were not significantly different in terms of typing speed, error rate, and mental workload and showed bad performance. Also, the subjective ratings were not shown positively. Conclusion: Based on our results, ten-finger text entry using soft keyboards on Tablet PCs seems to be very difficult. However, we need to research the possibility continuously since ten-finger text entry can improve typing speed. Application: Our study can be a starting point of research that explores ten-finger text entry on Tablet PCs. The new soft keyboard design can be one of the soft keyboard alternatives. However, the key factors to improve the performance and usability of the soft keyboard will not be 'key size' or 'convenience to typing special characters or numbers', but other factors (e.g., 'tactile feedback').

• Journal of the Ergonomics Society of Korea
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• v.26 no.3
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• pp.117-124
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• 2007

A few people are frequently using Korean text entry function in the mobile phone. To make matters worse, too many kinds of Korean text entry methods exist in the market, compelling mobile phone users to learn how to input texts all over again, whenever they purchase a new mobile phone. The purpose of this study is to propose a universal design of Korean text entry method for mobile phones. Several experiments and several questionnaire surveys were conducted in order to induce design factors for the universal design. Participants were mobile phone users with the diverse levels of text entry expertise and with the diverse ages. The results of this investigation were identical, irrespective of participants' age and expertise. The efficiency of the text entry method was not more important factor than memorability. The layout of vowels to keypad was preferred to map just 3 strokes to the 3 buttons so that users can make for themselves vowels that they want to input. The preference on the consonants layout was different according to investigation methods. According to the survey, it was preferred that consonants were arranged by alphabet order. However, the result of text entry speed measurement was that the arrangement by alphabet order was not superior to the typical arrangement. Such results may be used to design mobile phones for diverse users.