• Journal of Korea Foundry Society
• /
• v.17 no.4
• /
• pp.402-410
• /
• 1997

Developing a salt core for squeeze casting process, two different salt cores(pure salt core and mixed salt core) were fabricated and investigated. Pure salt core was composed of 100% NaCl and mixed salt core was made by mixtures of NaCl with MgO(1%), $Na_2B_4O_7$(2%), and talc(1%) as a binder or a strengthening agent. Salt cores were compacted to various theoretical density, heat treated, and then squeeze-cast with molten Al alloy(AC8A). The compression strength of salt cores were measured and the squeeze-cast products were examined for shape retention, infiltration of molten metal into the cores, and microstructures. The shape of salt core compacted at above 75% of the theoretical density was maintained stably. The higher theoretical density of salt cores gave higher compression strength, and the compression strength of mixed salt core was higher than that of pure salt core. Namely at 90% theoretical density, the compression strength of mixed salt core was $6.3 kg/mm^2$, compared to $4.6 kgmm^2$ for pure salt core. At a squeeze casting pressure of $1000 kg/cm^2$, molten Al alloy was infiltrated into pure salt core of under 85% of the theoretical density. At squeeze casting pressure of $1000 kg/cm^2$, only mixed salt core above 90% of the theoretical density were valid, but the shape of the core was altered in the case of pure salt core at 90% of theoretical density. A key factor for developing a salt core for squeeze casting process was estimated as the ultimate compressive strength of salt core.

• Steel and Composite Structures
• /
• v.27 no.1
• /
• pp.49-74
• /
• 2018

Generally, beam-column joints are taken into account as rigid in assessment of seismic performance of reinforced concrete (RC) structures. Experimental and numerical studies have proved that ignoring nonlinearities in the joint core might crucially affect seismic performance of RC structures. On the other hand, to improve seismic behaviour of such structures, several strengthening techniques of beam-column joints have been studied and adopted in practical applications. Among these strengthening techniques, the application of FRP materials has extensively increased, especially in case of exterior RC beam-column joints. In current paper, to simulate the inelastic response in the core of RC beam-column joints strengthened by FRP sheets, a practical joint model has been proposed so that the effect of FRP sheets on characteristics of an RC joint were considered in principal tensile stress-joint rotation relations. To determine these relations, a combination of experimental results and a mechanically-based model has been developed. To verify the proposed model, it was applied to experimental specimens available in the literature. Results revealed that the model could predict inelastic response of as-built and FRP strengthened joints with reasonable precision. The simple analytic procedure and the use of experimentally computed parameters would make the model sufficiently suitable for practical applications.

• Proceedings of the KSME Conference
• /
• 2001.11a
• /
• pp.38-43
• /
• 2001

The interfacial adhesive joining characteristics of the foams are very important for the structural integrity of sandwich structures. Peel strength is one of the best criteria for the interfacial characteristics of the sandwich structures and peel energy is most commonly used for the interfacial characteristics. The peel strength is the first peak force per unit width of bond line required to produce progressive separation by the wedge or other crack opening type action of two adherends where one or both undergo significant bending and the peel energy is the surface active energy per unit width of bond line. In this work, to investigate the strengthening effect of resin treatment on the interfacial surface of foam material, peel strength and peel energy of epoxy resin treated polyurethane foam core sandwich structures were obtained by the cleavage peel tests and compared with those of non surface treated polyurethane foam core sandwich structures.

• Journal of Korean Physical Therapy Science
• /
• v.29 no.2
• /
• pp.14-19
• /
• 2022

Background: Plank exercise (PE) is an effective exercise to enhance lower back stability by strengthening the core and lower limb muscles. However, in patients with a shortened hamstring muscle (HAM), PE may cause abnormal movement of the pelvis and lower back due to HAM hyperactivity. Therefore, the objective of this study was to investigate the effects of PE on the core muscles and HAM in subjects with a shortened HAM. Design: Cross-sectional study. Methods: Subjects were divided into a normal length of HAM group (NHG; 9 subjects) and a shortened length of HAM group (SHG; 14 subjects). The activities of the erector spinae (ES), rectus abdominis (RA), external oblique (EO), and HAM muscles were measured using surface electromyography. Results: The results showed that RA, EO, and ES muscle activities were higher in the NHG than in the SHG; however, no significant differences were detected. Conclusion: HAM activity was significantly higher in the SHG than in the NHG. In subjects with a shortened HAM, PE may hyperactivate the HAM, adversely affecting the pelvis and lower back.

• The Journal of Korean Academic Society of Nursing Education
• /
• v.21 no.2
• /
• pp.256-265
• /
• 2015

Purpose: The purpose of this study was to propose and test a predictive model that could explain and predict the core competencies of nursing students. Methods: A survey using a structured questionnaire was conducted with 361 nursing students. The data was analyzed using SPSS Windows 21.0 and AMOS 21.0. Results: The elements that directly influence the core competencies of nursing students were satisfaction with their academic discipline (nursing) and critical thinking disposition in which the disposition toward critical thinking directly influenced their satisfaction with nursing as an academic discipline and clinical practice. Conversely, satisfaction with clinical practice indirectly influenced core competencies through critical thinking disposition. Conclusion: This result provides the basic data for a competence-based curriculum intent on strengthening the core competencies (communication, problem-solving, and self-directed learning) by improving satisfaction with both clinical practice with their major and disposition toward critical thinking on the part of nursing students.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.12 no.1
• /
• pp.70-79
• /
• 2009

Currently, the investment on Research and Development(R&D) for defense core technology is continuously increasing to maintain advanced country's R&D level. In accordance with this trend, the national defense R&D investment management system is being more strengthening, and importance of performance evaluation is being emphasized more and more. However, the existing indicators of performance evaluation for defense core technology R&D is limited in efficient management because of the qualitative evaluation items and subjective allocation of points. In this paper, we developed a novel indicator for defense core technology R&D performance evaluation through domestic and foreign related literature and inquiry, brainstorming, and analysis techniques by Stepwise Multiple linear Regression(SMR) and Analytic Hierarchy Process(AHP). And we verified effectiveness of proposed indicators of performance evaluation by comparing with the existing evaluation indicators. Our proposed indicators for performance evaluation will create superiority performance on defense R&D fields.

• Journal of the Architectural Institute of Korea Structure & Construction
• /
• v.35 no.6
• /
• pp.121-128
• /
• 2019

There is a big move to build zero-energy buildings in the form of passive houses that reduce energy waste worldwide. Korea has set a goal of reducing its greenhouse gas emissions by 37% by 2030 through the activation of green buildings, such as strengthening the energy levels of new buildings and improving the energy efficiency of existing buildings. The use of insulation with high insulation performance is one of the key technologies to realize this, and vacuum insulation is the next generation insulation that blocks the energy flow of the building. In this study, we measured the bonding structure of dry and wet processing glass fiber core materials and compared the insulation performance of vacuum insulation panel. In addition, the insulation performance of vacuum insulation panel was measured according to the thickness of the laminated core. It can be confirmed that the lamination structure of the core and the lamination thickness are important factors for the heat insulating performance of the vacuum insulating panel.

• Journal of the Korea Society of Computer and Information
• /
• v.27 no.9
• /
• pp.169-176
• /
• 2022

This study was conducted to find out the relationship between the perception of the necessity and importance of creative teaching methods and core competencies in universities. A total of 142 people who voluntarily agreed to participate in the study were selected and surveyed using the Naver online questionnaire. It was found that the necessity and importance of creative teaching methods was related to the sub-factors of core competencies such as practical field competency, problem-solving competency, convergence competency, communication competency, job ethics, community consciousness. University education should actively introduce and apply creative teaching methods such as action learning and PBL, focusing on improving core competencies, which are actual abilities to be performed in the field.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.165-168
• /
• 2008

This paper presents the design, fabrication and performance of a reinforced concrete beam strengthened by GFRP box plate and its possibility for structural rehabilitations. The load capacity, ductility and failure mode of reinforced concrete structures strengthened by FRP box plate were investigated and compared with traditional FRP plate strengthening method. This is intended to assess the feasibility of using FRP box plate for repair and strengthening of damaged RC beams. A series of four-point bending tests were conducted on RC beams with or without strengthening FRP systems the influence of concrete cover thickness on the performance of overall stiffness of the structure. The parameters obtained by the experimental studies were the stiffness, strength, crack width and pattern, failure mode, respectively. The test yielded complete load-deflection curves from which the increase in load capacity and the failure mode was evaluated.

• Korea Journal of Hospital Management
• /
• v.28 no.2
• /
• pp.32-43
• /
• 2023

Purposes: This research is conducted to identify main features and trends of mission, vision and core values in Korean tertiary general hospitals by using text-mining. Methodology: For the study, 45 mission, 112 vision and 190 core values are collected from 45 tertiary general hospitals' homepages in 2022 and use word frequency analysis and Leyword co-occurrence analysis. Findings: In the tertiary general hospitals' mission, there are high frequency words such as 'health', 'humanity', 'medical treatment', 'education', 'research', 'happiness', 'love', 'best', 'spirit', and mission mainly includes the content of contributing humanity's health and happiness with these words. In case of vision, high frequency words are 'hospital', 'medical treatment', 'research', 'lead', 'trust', 'centered', 'patient', 'best', 'future'. By using these words in vision, it represents the definition and characteristics of vision such as ideal organizations in the future, goals and targets. As a result of the Leyword co-occurrence analysis, vision includes the content of 'high-tech medical treatment', 'special care for patients', 'leading education and research', 'the highest trust with customer', 'creative talents training'. -astly, the high frequency word-pairs in core values are 'social distribution', 'innovation pursuit', 'cooperation and harmony', and it defines standards of behavior for organizations. Practical Implication: To correct the problems of vision, mission and core values from findings, firstly, it needs for Korean tertiary general hospitals to use the words that can explain organization's identity and differentiate others in their mission. Secondly, considering strengthening the role of hospitals in their community and the importance of members in organizations, it is necessary to establish vision with considering community and members to activate vision effectively. Thirdly, because there are no specific guidelines of establishing mission, vision and core values for healthcare organizations, this research concepts and results could be utilized when other organizations establish mission, vision and core values.