• Steel and Composite Structures
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• v.47 no.5
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• pp.569-585
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• 2023

This paper proposes an efficient approach for the structural topology optimization of bi-directional functionally graded structures by incorporating popular radial basis functions (RBFs) into an implicit level set (ILS) method. Compared to traditional element density-based methods, a level set (LS) description of material boundaries produces a smoother boundary description of the design. The paper develops RBF implicit modeling with multiquadric (MQ) splines, thin-plate spline (TPS), exponential spline (ES), and Gaussians (GS) to define the ILS function with high accuracy and smoothness. The optimization problem is formulated by considering RBF-based nodal densities as design variables and minimizing the compliance objective function. A LS-RBF optimization method is proposed to transform a Hamilton-Jacobi partial differential equation (PDE) into a system of coupled non-linear ordinary differential equations (ODEs) over the entire design domain using a collocation formulation of the method of lines design variables. The paper presents detailed mathematical expressions for BiDFG beams topology optimization with two different material models: continuum functionally graded (CFG) and mechanical functionally graded (MFG). Several numerical examples are presented to verify the method's efficiency, reliability, and success in accuracy, convergence speed, and insensitivity to initial designs in the topology optimization of two-dimensional (2D) structures. Overall, the paper presents a novel and efficient approach to topology optimization that can handle bi-directional functionally graded structures with complex geometries.

• Journal of Korean Neurosurgical Society
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• v.50 no.3
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• pp.166-172
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• 2011

Objective : The intralaminar screw (ILS) fixation technique offers an alternative to pedicle screw (PS) and lateral mass screw (LMS) fixation in the C7 spine. Although cadaveric studies have described the anatomy of the pedicles, laminae, and lateral masses at C7, 3-dimensional computed tomography (CT) imaging is the modality of choice for pre-surgical planning. In this study, the goal was to determine the anatomical parameter and optimal screw trajectory for ILS placement at C7, and to compare this information to PS and LMS placement in the C7 spine as determined by CT evaluation. Methods : A total of 120 patients (60 men and 60 women) with an average age of $51.7{\pm}13.6$ years were selected by retrospective review of a trauma registry database over a 2-year period. Patients were included in the study if they were older than 15 years of age, had standardized axial bone-window CT imaging at C7, and had no evidence of spinal trauma. For each lamina and pedicle, width (outer cortical and inner cancellous), maximal screw length, and optimal screw trajectory were measured, and the maximal screw length of the lateral mass were measured using m-view 5.4 software. Statistical analysis was performed using Student's t-test. Results : At C7, the maximal PS length was significantly greater than the ILS and LMS length (PS, $33.9{\pm}3.1$ mm; ILS, $30.8{\pm}3.1$ mm; LMS, $10.6{\pm}1.3$; p<0.01). When the outer cortical and inner cancellous width was compared between the pedicle and lamina, the mean pedicle outer cortical width at C7 was wider than the lamina by an average of 0.6 mm (pedicle, $6.8{\pm}1.2$ mm; lamina, $6.2{\pm}1.2$ mm; p<0.01). At C7, 95.8% of the laminae measured accepted a 4.0-mm screw with a 1.0 mm of clearance, compared with 99.2% of pedicle. Of the laminae measured, 99.2% accepted a 3.5-mm screw with a 1.0 mm clearance, compared with 100% of the pedicle. When the outer cortical and inner cancellous height was compared between pedicle and lamina, the mean lamina outer cortical height at C7 was wider than the pedicle by an average of 9.9 mm (lamina, $18.6{\pm}2.0$ mm; pedicle, $8.7{\pm}1.3$ mm; p<0.01). The ideal screw trajectory at C7 was also measured ($47.8{\pm}4.8^{\circ}$ for ILS and $35.1{\pm}8.1^{\circ}$ for PS). Conclusion : Although pedicle screw fixation is the most ideal instrumentation method for C7 fixation with respect to length and cortical diameter, anatomical aspect of C7 lamina is affordable to place screw. Therefore, the C7 intralaminar screw could be an alternative fixation technique with few anatomic limitations in the cases when C7 pedicle screw fixation is not favorable. However, anatomical variations in the length and width must be considered when placing an intralaminar or pedicle screw at C7.

• The korean journal of orthodontics
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• v.30 no.3 s.80
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• pp.343-355
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• 2000

The purpose of this study was to evaluate the amount and interrelationship of hard and soft tissue changes after mandibular setback osteotomy and reduction genioplasty in mandibular prognathism with long anterior facial height. The control group (Group A) consisted of 20 patients who had severe horizontal discrepancy. They experienced Presurgical orthodontic treatment and orthognathic surgery via mandibular setback. The experimental group (Group B) consisted of 20 patients who had severe horizontal and vertical discrepancy. They experienced presurgical orthodontic treatment and orthognathic surgery via mandibular setback and reduction genioplasty. The presurgical and postsurgical lateral cephalograms were evaluated. The computerized statistical analysis was tarried on with EXCEL 97 program. The results were as follows : 1. The correlation of hard and soft tissue horizontal changes in lower 2/3 of lower anterior facial height were high for both groups. The correlation coefficients of hard tissue changes and Ls, Stm, Li changes in Group B were moderately higher than Group A. 2. The correlation of hard and soft tissue vortical changes in Group B were lower than Group A. (except for pointB-Ils, Me-Me') 3. The ratio for soft tissue to Pog in Group B was lower than Group A. The ratios of hard and soft tissue vertical changes were 32% at Ils, 54% at Pog', and 60% at Me'. 4. The ratio of lower anterior facial height to total anterior facial height was reduced for both groups. But ratio of upper 1/3 of lower anterior facial height to total anterior facial height did not changed significantly in Group B. 5. Reduction genioplasty combined with mandibular setback procedure showed no change in upper one third(Sn-Stm) and significant decrease(Stm-Me') in the lower two thirds of the soft-tissue anterior lower facial height

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.214-222
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• 2016

As information becomes more sophisticated with the advancing technology of our times, the usability of software is considered an important factor. However, the research on usability of weapons system software graphical user interfaces (GUIs) remains insufficient. For this reason, this paper focuses on developing checklists for the usability of GUIs in weapons systems. In the first step, design principles are collected from various design guidelines on usability and from career soldiers. In the second step, a survey is conducted for factor analysis, and in the third step, factor analysis is conducted on 12 principles, with two principles excluded, as a result, due to less correlation with weapons system usability. In Step 4, the weights for design characteristics and design principles are derived using AHP. In the final step, the checklists are developed by mapping the GUI design factors and from the results of factor analysis. This research could be utilized as a foundation for usability evaluation of GUIs in weapons systems.

• Journal of Navigation and Port Research
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• v.39 no.1
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• pp.15-21
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• 2015

In high precision positioning systems based on GNSS, ambiguity resolution is an important procedure. Correct ambiguity leads to positioning results which have high precision between millimeters and centimeters. However, when the ambiguity is determined incorrectly, ensuring accuracy and precision of the positioning result is impossible. An ambiguity validation test is required to obtain correct ambiguity when ambiguity resolution is performed based on the ILS (Integer Least Squares), which shows the best performance in point of theory and experiment when compared with other methods such as IR (Integer Rounding) and IB (Integer Bootstrapping). Comparison between the candidates of the validation test is needed to judge ambiguity correctly, because ILS searches for candidates of integer ambiguity, unlike other methods which calculate only one integer ambiguity. We analyzed the experimental performance of ambiguity validation tests. R-ratio, F-ratio and W-ratio were adopted for analysis. The performance of validation tests was evaluated by classifying normal operation, detection, missed detection and false alarm. As a result, strengths and weaknesses of validation tests was showed to experimental. we concluded that validation tests must be selected according to environment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.1
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• pp.190-196
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• 2020

FRACAS(Failure Reporting, Analysis and Corrective Action System) has been applied in various industries to improve the reliability of the systems. FRACAS is effective in improving reliability by repeating failure analysis, proper corrective action, and result verification for identified failures. However, FRACAS has many limitations in terms of process, data collection and management to be integrated into the existing development environment. In the domestic defense industry, studies on the development of FRACAS system and process improvement have been conducted to solve the difficulties of applying FRACAS, but most of them are concentrated in the operation/maintenance phase. Since FRACAS should be conducted in consideration of TLCSM(Total Life Cycle System Management), it is necessary to study the reference architecture so that FRACAS can be applied from the early design phase. In this paper, we studied the TLCSM-based integrated architecture considering the system life cycle phases, FRACAS closed-loop process, and FRACAS essentials in order to effectively apply FRACAS throughout the life cycle of defense systems. The proposed architecture was used as a reference model for FRACAS in a shipboard combat system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.2
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• pp.76-82
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• 2019

This study has done to search for a solution to remove risk limitedly caused by separating weapon system acquisition from operation and maintenance at the view point of Logistic Commander who's responsible for stable operation and maintenance after acquiring weapon system. At the System development stage, unverified overhaul development plan may cause additional manpower and costs after the development, and furthermore it is likely to have risk to lower reliability of the military. Thus, research and development agency should write overhaul development plan at the System development stage, and it should be verified through evaluation and verification test. Secondly, during research and development, institutional supplementation is needed to calculate human and material resources writing overhaul development plan. Thirdly, it should be able to analyze proper operation & maintenance plan and cost for overhaul plan at the pre-investigation stage. Fourthly, the base which can develop overhaul concept and overhaul factors should be included in the need and need determination document. Lastly, for the weapon system which has small amount of high power figure, project management should be performed to be able to specify at the each acquisition level of weapon system to realize Article 28, clause 3 and 4 of Defense business law.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.759-767
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• 2021

Most weapons systems that are Force Integration are expensive equipment that reflects the latest technology, and the operation and maintenance cost is increasing continuously. Factors that efficiently operate and maintain these weapon systems include maintenance plans, economic costs, and repair part requirements. Among them, predicting the repair parts requirements during the life cycle in advance is an important way to increase operation and maintenance cost efficiency and operating availability. The start of requirement analysis for repair parts is a calculation of the CSP (CSP: Concurrent Spare parts, CSP hereafter) that is distributed when the weapon system is deployed. The CSP is an essential component of achieving the operating availability during this period because the weapon system aims to successfully perform a given operation mission without resupply for an initial set period. In the present study, the CSP calculation method was analyzed, reflecting the failure rate and operating time of items, but the analyzed CSP was aimed at preparing for technical failure, but in the initial operating environment, it is limited in coping with unexpected failures caused by human error. The failure is not included in the scope of free maintenance and is a serious factor in making the weapon system inoperable during the initial operation period. To prevent the inoperable status of a weapon system, CSP that considers human error is required in the initial operating environment, and the calculation criteria and measures are proposed.

• Defense and Technology
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• no.10 s.164
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• pp.14-17
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• 1992

방산기술 자립을 위해서는 정부와 업체의 효과적인 역할분담이 절실히요구되고 있습니다. 먼저 정부는 방위산업에 대한 활성화 대책 수립과 업체주도 연구개발체제의 조기 정착및 확대, 기술개발제품의 양산사업 보장과 함께 종합군수지원(ILS)의 중요성에 대한 재인식이 요구되고있습니 다. 또한 업체는 장기적 차원에서 핵심 기술 확보전략을 수립 하고, 장기적 안목의 기술인력 확보, 양성에 주력해야 하겠으며, 방산시장의 한계 극복을 위한 수요창출 노력을 다각적으로 전개해 나가야 하겠습니다

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.1
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• pp.91-98
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• 2010

At present, advanced countries are focusing on the study of Demilitarization Method of Conventional Ammunitions. In this paper, we will report the current trends of Demilitarization of Conventional and Guided Missile ammunitions, and present the efficient Demilitarization Methods of new development of Guided Missile ammunitions in Korea.