• Advances in Computational Design
• /
• 제7권2호
• /
• pp.129-137
• /
• 2022

Compo-casting method is one of the popular technique to produce metal based matrix composites. But, one of the main challenges in this process is un-uniform spreading of reinforced subdivisions (particles) inside the metallic matrix and the lack of desirable mechanical properties of the final produced composites due to the low bonding strength among the metal matrix and reinforcement particles. To remove these difficulties and to promote the mechanical properties of these kind of composites, the WARM ARB technique was utilized as supplementary technique to heighten the mechanical and microstructural evolution of the casted Al/Al₂O₃ composite strips. The microstructure evolution and mechanical properties of these composites have been considered versus different WARM ARB cycles by tensile test, average Vickers micro hardness test, wear test and scanning electron microscopy (SEM). The SEM results revealed that during the higher warm- ARB cycles, big alumina clusters are broken and make a uniform distribution of alumina particles. It was shown that cumulating the forming cycles improved the mechanical properties of composites. In general, combined compo-casting and ARB process would consent making Al/Al₂O₃ composites with high consistency, good microstructural and mechanical properties.

• Journal of the Korea institute for structural maintenance and inspection
• /
• 제22권6호
• /
• pp.81-88
• /
• 2018

The present study evaluated the effective arrangement approach of transverse reinforcement in the jacket section for seismic strengthening of reinforced concrete columns. To simulate the full-scale columns, the section dimensions were determined as $450{\times}450mm$ for non-seismic existing columns and $750{\times}750mm$ for section enlargement strengthening columns. Over-lapped channel-shape bars and prefabricated bar units were proposed for closed-hoops in the jacket section, and conventional cross-ties anchored into existing columns and V-ties were considered for the supplementary ties. Test results showed that the axial capacity of the existing column and section enlargement columns with over-lapped channel-shape hoops was similar to the nominal strength calculated using ACI 318-14 procedure whereas the section enlargement column with prefabricated bar units possessed 1.25 times higher axial capacity than the nominal prediction. Furthermore, the axial ductility ratio of the section enlargement column with prefabricated bar unit was 139% higher than that of the existing column despite the potential size effect on ductility of concrete. Thus, it can be concluded that the developed prefabricated bar unit technique is practically useful for preventing the premature buckling of longitudinal reinforcement and confining core concrete in the section enlargement strengthening columns.

• Tunnel and Underground Space
• /
• 제9권1호
• /
• pp.48-55
• /
• 1999

One of the major roles of concrete lining is the supplementary support of ground load. Therefore, if there are cracks or deformation found in the lining, the causes should be carefully examined. Tunnel Soundness Evaluation System (DW-TSES) was developed to meet such requirements. Main facility of the system was intended to find the probable causes on the basis of the apparent changes in lining and the environmental conditions. It also includes facilities for evaluating the soundness of a tunnel and indicating the method for repair or reinforcement. The characteristic feature of damages is used for reasoning in case of deterioration and leakage, and artificial neural network is used in external pressure. This process depends on the results of the case analyses and FDM, which have a collection of the typical features of different types of damages as well as the unusual changes caused by the external pressure. The comparison of the outputs of this system with those of expert's diagnoses draws the following conclusions. 1) Artificial neural network was a suitable tool to find to causes of damages by external pressure. 2) The environmental conditions improved the accuracy in reasoning. 3) The result of finding causes and evaluating soundness was helpful to suggest effective methods concerning tunnel maintenance.

• Structural Monitoring and Maintenance
• /
• 제2권1호
• /
• pp.35-48
• /
• 2015

The main objective of this study is to evaluate the long-term performance of various concrete composites in natural marine environment prevailing in the Gulf region. Durability assessment studies of such nature are usually carried out under aggressive environments that constitute seawater, chloride and sulfate laden soils and wind, and groundwater conditions. These studies are very vital for sustainable development of marine and off shore reinforced concrete structures of industrial design such as petroleum installations. First round of testing and evaluation, which is presented in this paper, were performed by standard tests under laboratory conditions. Laboratory results presented in this paper will be corroborated with test outcome of ongoing three years field exposure conditions. The field study will include different parameters of investigation for high performance concrete including corrosion inhibitors, type of reinforcement, natural and industrial pozzolanic additives, water to cement ratio, water type, cover thickness, curing conditions, and concrete coatings. Like the laboratory specimens, samples in the field will be monitored for corrosion induced deterioration signs and for any signs of failureover initial period ofthree years. In this paper, laboratory results pertaining to microsilica (SF), ground granulated blast furnace slag (GGBS), epoxy coated rebars and calcium nitrite corrosion inhibitor are very conclusive. Results affirmed that the supplementary cementing materials such as GGBS and SF significantly impacted and enhanced concrete resistivity to chloride ions penetration and hence decrease the corrosion activities on steel bars protected by such concretes. As for epoxy coated rebars applications under high chloride laden conditions, results showed great concern to integrity of the epoxy coating layer on the bar and its stability. On the other hand corrosion inhibiting admixtures such as calcium nitrite proved to be more effective when used in combination with the pozzolanic additives such as GGBS and microsilica.

• Journal of Korean society of Dental Hygiene
• /
• 제17권3호
• /
• pp.515-526
• /
• 2017

Objectives: This study was carried out for the purpose of examining the levels of vocational awareness and the professional ethics recognition in the clinical dental hygienists. Methods: A survey was conducted targeting 500 members who participated in the supplementary education program for dental hygienists in the first half of 2017. Total 328 subjects' materials were analyzed. Results: A reason for working in terms of the occupational identity was very high with 81.4% in 'aiming to earn money'. A goal of working was the highest with 41.5% in 'financial independence'. The professional ethics approach level was indicated to be the highest with 3.33 points in the domain of human relation. It was shown to be in order of the job satisfaction level with 3.21 points, followed by the lifelong working with 3.17 points, the vocational ethics observance with 2.95 points, the workplace satisfaction level with 2.82 points, and the job anxiety level with 2.65 points. The domain in the job anxiety level according to general characteristics was indicated to be significantly high in the higher age and work career in case of the married and in case of Seoul as a workplace. The domain in the professional ethics observance was shown to be significantly high in the higher work career in case of the married and in case of Gyeonggi Province as a workplace. The domain in the lifelong working was indicated to be significantly high in case of the married. Conclusions: For the establishment of the right professional ethics as a dental hygienist and for the securement of its practice starting from the education for the dental hygiene department, the development of educational program will be needed aiming at the approach to the professional ethics and the reinforcement in the vocational ethics recognition.

• Tunnel and Underground Space
• /
• 제12권2호
• /
• pp.120-129
• /
• 2002

Natural cavitied were found at shallow depth during construction of a huge bridge in Cambro-Ordovician Limestone Basin in the central part or Korea. The distribution patterns of cavities in this area were investigated carefully with a supplementary field job such as a structural geological survey, a geophysical survey, and a rock mechanical test in laboratory or field. A structural geological mapping produced a detail geological map focusing the route of the Proposed highway. It suggested that there were three faults in this wet and these faults had an influence on the mechanism of natural cavities. Among many kinds of geophysical surveys, an electrical resistivity prospecting was applied first on the specific area that was selected by results from the geological survey. Many evidences far cavities were disclosed from this geophysical data. Therefore, a seismic tomography was tested on the target wet which was focused by results from the electrical resistivity Prospecting and was believed to have several large cavities. A distinct element numerical simulation using the UDEC was followed on the target area after completing all of field surveys. Data from field tests were directly dumped or extrapolated to numerical simulations as input data. It was verified from numerical analysis that several natural cavities underneath the foundation of the bridge should be reinforced Based on the project result, finally, most of fecundations far the bridge were re-examined and the cement grouting reinforcement was constructed on several foundations among them.

• Land and Housing Review
• /
• 제11권4호
• /
• pp.51-65
• /
• 2020

The purpose of this study was to identify the problems related to the amendment and preservation of the lien system and to suggest a feasible and efficient improvement plan. The Analytic Hierarchy Process (AHP) and descriptive statistical analyses were used in this study. The survey subjects were divided into three groups based on their expertise: "Administrative Experts, Practical Experts, and Financial Institution Experts" and compared to find the results. The results show that 1) the procedural aspect was the most important for the large classification, 2) the supplementary disclosure system was the most important for the legislative aspect, and 3) the supplementation of the abuse of the lien report was the most important for the intermediate classification. Furthermore, the study showed that the most important finding was the reinforcement of punishment for the right of false reporting and illegal acts, followed by the registration order system (the creditor alone application), and the registration system (bond, debtor, joint application). The implications and suggestions of this study are as followed. With regard to the current lien system, illegal acts such as false liens and the misuse of multiple reporting were considered as the biggest problems. In terms of the effective improvement plan of the lien system, the misuse of reporting liens and improvement in the procedural aspects of reporting rights should be given top priority. Therefore, the most important course of action is to strengthen the punishment for false liens, improve the disclosure system and make it mandatory to report rights.

• Investigative Magnetic Resonance Imaging
• /
• 제4권1호
• /
• pp.14-19
• /
• 2000

Purpose : This study was to present the functional brain mapping of both functional magnetic resonance imaging(MRI) and transcranial magnetic stimulation(TMS) in a case of schizencephaly. Materials and methods : A 28-year-old man, who had left hemiplegia and schizencephaly in right cerebral hemisphere, was exacted with both functional MRI and TMS. Motor function of left hand was decreased whereas right hand was within normal limit. For functional MRI, gradient-echo echo planar imaging($TR/TE/{\alpha}$=1.2 sec/90 msec/90) was employed. The paradigm of motor task consisted of repetitive self-paseo hand flexion-extension exercises with 1-2 Hz periods. An image set of 10 slices was repetitively acquired with 15 seconds alternating periods of task performance and rest and total 6 cycles (three ON periods and three OFF periods) were performed. In brain mapping, TMS was performed with the round magnetic stimulator (mean diameter; 90mm). The magnetic stimulation was done with 80% of maximal output. The latency and amplitude of motor evoked potential(MEP)s were obtained from both abductor pollicis brevis(APB) muscles. Results : Functional MRI revealed activation of the left primary motor cortex with flexion-extension exercises of healthy right hand. On the other hand, the left primary motor cortex, left supplementary motor cortex, and left promoter areas were activated with flexion-extension exercises of left hand. In TMS, magnetic evoked potentials were induced in no areas of right cerebral hemisphere, but in 5 areas of left corebral hemisphere from both abductor pollicis brevis. Latency, amplitude, and contour of response of the magnetic evoked potentials in both hands were similar. Conclusion : Functional MRI and TMS in a patient with schizencephaly were successfully used to localize cortical motor function. Ipsilateral motor pathway is thought to be secondary to reinforcement of the corticospinal tract of the ipsilateral motor cortex.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• 제21권4호
• /
• pp.428-436
• /
• 2020

The purpose of this study is to analyze the needs for developing a curriculum for strengthening the long-term care service expertise and job competency. Specifically, the researchers analyzed previous studies on national long-term care services and national policy data, and conducted focus group interviews with 14 experts from related agencies. Activity theory was applied as a framework for analysis and a questionnaire about the importance and difficulty of subjects from 25 long-term service employees was administered for validating the results of the qualitative data analysis. The upper part of the subject-goal-tool of the activity system was considered the main area of action, and the following rule-community-division was divided into contextual parts for action, and the implications for demand analysis and future operation of the online curriculum are summarized. In total, six courses were required for development. These courses could be applied to as a learner-centered flip learning for long-term care service workers and various educational methods of collective education and supplementary education have been proposed. Based on the study results, implications in the educational field for effective management of courses were suggested at the end of the study.

• Journal of the Korean Society for Library and Information Science
• /
• 제41권3호
• /
• pp.165-179
• /
• 2007

This study regards the evaluation for the main contents of the 'Library Development Plan(2003-2011)' promoted by the Ministry of Culture and Tourism for the library development plan in Korea. SMART evaluation method was introduced for the evaluation of vision, objective, core project of library development plan. Following result was acquired as a result of the study. First. as a result of SMART vision, objective, core projects and main business of library development plan was presented to be 3.05, 3.09, 3.15 and 3.12 respectively. Thus, in the evaluation for components of development Plan, it was excellent in core projects. Second, as a result of SMART, concreteness, measurability, achievability, relevance and time frame of library development plan was presented to be 3.09. 2.99. 3.12. 3.24 and 3.10 respectively. Thus, in the evaluation components of development plan. it was excellent in relevance but it has been found that supplementary measures should be taken on measurability. Third, 'culture-oriented room with knowledge and information' was found to be superior to the 'information library with up-to-date technology' in evaluation of the objective. Fourth, 'substantiality in user service with the supplement of library contents' was excellent in evaluation of core projects but there is some problem with 'activation of library function through training and supplement of professional manpower.' Fifth. 'Enhancement in library information service' was presented to be excellent in evaluation of main business but there was problem in 'reinforcement in function of library for each location and type,' 'partnership of public-private enterprises' and 'promotion for book culture of the public' thus it need to be revised and supplemented hereafter.