• Proceedings of the KWS Conference
• /
• 2010.05a
• /
• pp.29-29
• /
• 2010

레이저 용접은 고밀도 에너지빔을 이용하는 용접방법으로 아크용접에 비해 빠른 용접과 깊은 용입이 가능하며, 낮은 열이력을 가지는 장점이 있다. 때문에 열에 의해 연화되는 고강도강의 용접에 큰 이점을 가지고 있다. 차체경량화 추세와 더불어 차량에 고강도강의 적용이 늘어나고 있는데 충돌시 차량 구조를 유지시켜주는 범퍼나 B-필러와 같은 부품에 적용되는 무도금 보론 합금강과 알루미늄 코팅 보론 합금강은 핫스템핑(Hot Stamping) 기술에 의해 제조된 소재로 약 1.5GPa의 인장강도를 가진다. 알루미늄 코팅 보론 합금강의 경우 제조공정과 이송 중 소재 표면산화에 의한 산화철발생 또는 표면 탈탄 현상을 방지하기 위해 알루미늄 코팅 처리를 하는데 이러한 코팅층이 용접시 용접부의 물성을 저하시키는 역할을 한다고 보고되어 있다. 본 연구에서는 1.5GPa급 무도금 보론 합금강과 알루미늄 코팅 보론 합금강을 대상으로 레이저 용접을 적용하여 용접부 특성을 파악하고자 하였다. 실험은 겹치기 형상으로 Fiber Laser, Disk Laser를 적용하여 진행하였으며 빔Size, 용접속도, Gap등을 변경하며 해당조건에서의 용입특성, 파단모드, 기계적특성 등을 알아보았다.

• East Asian mathematical journal
• /
• v.24 no.5
• /
• pp.527-545
• /
• 2008

One of the education purpose of the section "Figures" in the eighth grade is to develop students' deductive reasoning ability, which is basic and essential for living in a democratic society. However, most or middle school students feel much more difficulty or even frustration in the study of formal arguments for geometric situations than any other mathematical fields. It is owing to the big gap between inductive reasoning in elementary school education and deductive reasoning, which is not intuitive, in middle school education. Also, it is very burden for students to describe geometric statements exactly by using various appropriate symbols. Moreover, Usage of the same symbols for angle and angle measurement or segments and segments measurement makes students more confused. Since geometric relations is mainly determined by the measurements of geometric objects, students should be able to interpret the geometric properties to the algebraic properties, and vice verse. In this paper, we first compare and contrast inductive and deductive reasoning approaches to justify geometric facts and relations in school curricula. Convincing arguments are based on experiment and experience, then are developed from inductive reasoning to deductive proofs. We introduce teaching methods to help students's understanding for deductive reasoning in the textbook by using stepwise visualization materials. It is desirable that an effective proof instruction should be able to provide teaching methods and visual materials suitable for students' intellectual level and their own intuition.

• The Journal of Korean Physical Therapy
• /
• v.30 no.5
• /
• pp.173-180
• /
• 2018

Purpose: This study examined the effects of sling exercise therapy on vertebral alignment, VAS, muscle activity, and multifidus of patients with chronic low back pain. Methods: Simple random sampling was used to divide the patients (n=116) into the sling exercise therapy group (SETG) and conservative physical therapy group (CPTG), with each group provided a intervention program in 3 sessions a week for 12 weeks. The lumbar lordosis angle (LLA), lumbar intervertebral disc angle (LIVDA) for vertebral alignment, lumbar muscle activity, and multifidus atrophy were measured before and after the intervention. Results: SETG showed significant changes in LLA, LIVDA of rate of change (delta score), and in relieving pain. The right-left balance gap for the lumbar dynamic muscle activity decreased after the intervention. The SETG showed significant changes in the grade of lumbar multifidus atrophy. Conclusion: The sling exercise therapy program is an effective exercise therapy method on vertebral alignment, muscle activity, recovery from multifidus atrophy, and pain relief for patients with chronic low back pain.

• Journal of the Korean Society of Earth Science Education
• /
• v.2 no.1
• /
• pp.41-47
• /
• 2009

This study examined the difference for the ability of self-directed learning and information literacy(the ability to use information) between small group-cooperative instruction of ICT practical environment and explanatory instruction using ICT of general classroom in middle school science education. The 138 students(7th grade) participated in this study were classified in two group, experimental group(68) and controlled group(70). Experimental small group consisted of 5-6 students who had different levels and the ability of each the group was equal. The teaching of experimental group was made in the science lab which was equipped with computers to connect super high-speed Internet. The teaching of control group was made in general classroom. Under these two environment, this study was executed during 10 weeks. As the result, Small group-cooperative learning using ICT was more effective in diminishing the gap of information literacy in middle school students. And in the ability of self-directed learning, the small group learning using ICT was also more effective than general classroom instruction.

• Journal of Information Technology Services
• /
• v.16 no.3
• /
• pp.47-65
• /
• 2017

The reference guide for the cost of establishing the digital documents has been used as a basis for establishing the budget for the construction of the knowledge information resource. However, due to the abolition of the nominal unit price notification in terms of IT projects, it is necessary to conduct research to convert the standard of the current labor force grade standard to the national incompetency standard (NCS). In this study, we investigate and revise the system and contents of the current knowledge information cost estimation model. In specific, i) we conducted gap analysis of cost estimation model and existing NCS model. As the contents conforming for the construction of the knowledge information resource were not adoptable, we define the description of the construction of the knowledge information resource and to identify the core elements of NCS prior to the improvement of the cost model. ⅱ) then we proposed improve the cost model considering integration with newly proposed NCS model for knowledge information construction job. In order to ensure the validity of the application of NCS development and cost estimation model, the experts reviewed relevant contents and made plans for improvement by using experts from supply and demand groups of various fields of national knowledge informatization projects.

• Journal of Educational Research in Mathematics
• /
• v.18 no.1
• /
• pp.81-101
• /
• 2008

This study points out that the way of teaching varies according to the kinds of figures in explaining the volume and the surface area of solid figures in the seventh grade curriculum. Especially, the study discusses the limitation of the explanation depending on the experimental method using physical objects. Considering the study of Archimedes' research about measuring sphere, we investigate its educational implications and, based on this result, suggest the complementary approach and the considerations for applying to current school mathematics curriculum.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2006.11a
• /
• pp.117-121
• /
• 2006

This study intends to suggest the effective methods for water leakage prevention around the windows in stone works to up-grade the outdoor public space that has been taken much portion of apartment housing trends. The subjects of the study was selected among the domestic subcontractors of stone works. There are four methods for water leakage prevention around the windows; Firstly, the painting water-proof method after the masonry. Secondly, the urethane water-proof method after galvanizing panels on the gap. Thirdly, the separation method between stone and substructure and the last one is water-proof method that they put some water-proof screen between stone and substructure with the EPDM sheets. According to the analysis of the water-proof effects, constructability and planning, we could approach to conclusion that the most influent items to the water-leakage are the filling material's deformation, the state of oxygenation and deterioration of work skill. Among the water-proof methods in construction the EPDM sheet is most excellent water-proof method to meet the technical conditions. However, we have to apply it to stone works as a water-proof method for the decrease of the leakage defects after standardizing the materials, test and construction skill because there are many work skills according the subcontractors.

• Korean Journal of Child Studies
• /
• v.17 no.2
• /
• pp.79-105
• /
• 1996

The purpose of this study was to understand children's viewpoints on their fathers from a phenomenological perspective. Sixty nine elementary school children (2nd and 5th grade) were asked to write poems about their fathers. Through the poems, they described their feelings towards their fathers in their own words. Results indicated that the most prominent and popular description for the father was in terms of the provider of the family. Because of the excessive emphasis on the provider role, fathers are very busy and tired, and can not Participate actively in their children's daily life. As a result, many fathers are in an on-looker position in their homes, and their children are spoiled. On the other hand, children described their fathers as warm, kind- hearted, respectable and great images that gave everything to their children. They liked and sincerely appreciated these aspects of their fathers. Because of the gap between the ideal image of the father and the actual provider image of the father, children experience conflict and a psychological deficit of a father. We believe that this problem will be improved through the fathers' own awareness of their role which pays more attention to our children's wellbeing and a reform of the existing social system.

• Membrane and Water Treatment
• /
• v.6 no.6
• /
• pp.451-476
• /
• 2015

Membrane distillation (MD), which can utilize low-grade thermal energy, has been extensively studied for desalination. By incorporating solar thermal energy, the solar membrane distillation desalination system (SMDDS) is a potential technology for resolving the energy and water resource problems. Small-scale SMDDS (s-SMDDS) is an attractive and viable option for the production of fresh water for small communities in remote arid areas. The minimum-cost design and operation of s-SMDDS are determined by a systematic method, which involves a pseudo steady state approach for equipment sizing and the dynamic optimization using overall system mathematical models. The s-SMDDS employing three MD configurations, including the air gap (AGMD), direct contact (DCMD) and vacuum (VMD) types, are optimized. The membrane area of each system is $11.5m^2$. The AGMD system operated for 500 kg/day water production rate gives the lowest unit cost of $5.92/m^3$. The performance ratio and recovery ratio are 0.85 and 4.07%, respectively. For the commercial membrane employed in this study, the increase of membrane mass transfer coefficient up to two times is beneficial for cost reduction and the reduction of membrane heat transfer coefficient only affects the cost of the DCMD system.

• Nuclear Engineering and Technology
• /
• v.55 no.5
• /
• pp.1783-1790
• /
• 2023

Barium Bismuth Oxide Borate (BBOB) has been synthesized for the first time using solution combustion technique. SEM analysis reveal flower shape of the nanoparticles. The formation of the nanoparticles has been confirmed through XRD & FTIR studies which gives the physical and chemical structure of the novel material. The UV light absorption is observed in the range 200-300 nm. The present study highlights the radiation shielding ability of BBOB for different radiations like X/Gamma rays, Bremsstrauhlung and neutrons. The gamma shielding efficiency is comparable to that of lead in lower energy range and lesser than lead in the higher energy range. The bremsstrauhlung exposure constant is comparably larger for BBOB NPs than that of concrete and steel however it is lesser than that of lead. The beauty of BBOB nanoparticles lies in, high absorption of radiations and low emission of secondary radiations when compared to lead. In addition, the neutron shielding parameters like scattering length, absorption and scattering cross sections of BBOB are found to be much better than lead, steel and concrete. Thus, BBOB nanoparticles are highly efficient in absorbing X/Gamma rays, neutrons and bremsstrauhlung radiations.