• Structural Engineering and Mechanics
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• v.68 no.4
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• pp.475-483
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• 2018

Square tubular columns are commonly used in moment resisting frames, while through-diaphragm connection is the most typical configuration detail to connect the H-shaped beam to the column. However, brittle fracture normally occurs at the complete joint penetration weld between the beam flange and the through-diaphragm due to the stress concentration caused by the geometrical discontinuity. Accordingly, three improved types of through-diaphragm are presented in this paper to provide smooth force flow path comparing to that of conventional connections. Tensile tests were conducted on four specimens and the results were analyzed in terms of failure modes, load-displacement response, yield and ultimate capacity, and initial stiffness. Furthermore, strain distributions on the through-diaphragm, the beam flange plate, and the column face were comprehensively evaluated and discussed. It was found that all the proposed three types of improved through-diaphragm connections were able to reduce the stress concentration in the welds between the beam flange and the through-diaphragm. Furthermore, the stress distribution in connection with longer tapered through-diaphragm was more uniform.

• Structural Engineering and Mechanics
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• v.32 no.4
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• pp.477-488
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• 2009

A slip critical joint has various values to adopt the proper slip coefficient in various conditions of faying surfaces in the following codes: AISC, AIJ and Eurocode 3. However, the Korean Building Code still regulates the unique slip coefficient, 0.45, regardless of the diverse faying conditions. In this study, the slip resistance test, including five kinds of surface treatments were conducted to obtain the proper slip coefficients available to steel plate KS SM490A. The faying surfaces were comprised of a clean mill, rust, red lead paint, zinc primer, and shot blast treatment. The candidates for high strength bolts were torque-shear bolts, torque-shear bolts with zinc coating, and ASTM A490 bolts. Based on the test results, the specimens with a shot blasted surface and rusted surface exhibited $k_s$, 0.61, and 0.5, respectively. It is recommended that the specimens with zinc primer exhibit $k_s{\geq}0.40$. The clean mill treated surface had prominently lower values, 0.27. For red lead painted treatment, the thickness of the coating affects the determinant of slip coefficient, so it is necessary to establish a minimum $k_s$ of 0.2, with a coating thickness of 65 ${\mu}m$. During 1,000 hours of relaxation, the uncoated surfaces exhibited the loss of clamping force behind 3%, while the coated surfaces within a certain limited thickness exhibited the loss of clamping within a range of 4.71% and 8.37%.

• Journal of Powder Materials
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• v.20 no.5
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• pp.355-358
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• 2013

Micro trench structures are applied in gratings, security films, wave guides, and micro fluidics. These micro trench structures have commonly been fabricated by micro electro mechanical system (MEMS) process. However, if the micro trench structures are machined using a diamond tool on large area plate, the resulting process is the most effective manufacturing method for products with high quality surfaces and outstanding optical characteristics. A nonferrous metal has been used as a workpiece; recently, and hybrid materials, including polymer materials, have been applied to mold for display fields. Thus, the machining characteristics of polymer materials should be analyzed. In this study, machining characteristics were compared between nonferrous metals and polymer materials using single crystal diamond (SCD) tools; the use of such materials is increasing in machining applications. The experiment was conducted using a square type diamond tool and a shaper machine tool with cutting depths of 2, 4, 6 and 10 ${\mu}m$ and a cutting speed of 200 mm/s. The machined surfaces, chip, and cutting force were compared through the experiment.

• Journal of Korean Physical Therapy Science
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• v.9 no.3
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• pp.97-106
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• 2002

Purpose. This study was tried to compare the effect of the change in postural deviation caused by the pain side Subjects and Methods. Inpatients and outpatients (n=71) were selected from I hospital who have a musculoskeletal low back pain and shoulder pain without any history of the central nervous system (CNS) lesions, orthopaedic problems of the both lower extremities, or the vestibular and the visual default. For the control group, normal and healthy subjects (n=30) were selected without any history of weight bearing disorders. the weight bearing was rated by the computerized force plate. Results. 1) Postural deviation was not significant difference between patients and control group(p<0.01). But postural deviation in patients was more pronounced than control group. 2) There was significant difference of postural deviation between in patients according to the pain side(p<0.01). When the pain side was on the left side, postural deviation tended to the right. When the pain side was on the right side and vertebral body, postural deviation tended to the left. 3) There was no significant difference of postural deviation between regional pain in shoulder and regional pain in low back(p<0.01). Discussions and Conclusion. As a result, the pain, for sure, affected the good posture and its keeping process directly or/and indirectly. Therefore, as the postural deviation increases, the additional energy consumption increased by the works of the muscles to keep the good posture. Preponderated postural deviation, furthermore, could load too much to the musculoskeletal system, leading to increase the pain. The postural deviation, a result of the pain, can cause a secondary deformity of the distal area as a compensatory reaction, and this compensation actually become a cause of the musculoskeletal symptom back in a cycle. Therefore, the appropriate treatment of the musculoskeletal problem and the education of the posture correction should be given to decrease the pain, preventing the secondary deformities, and increasing muscle energy efficiency of the posture remaining muscles.

• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.2
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• pp.52-62
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• 2015

This study aims at developing a new seismic resistant method by using precast concrete wall panels for existing low-rise, reinforced concrete beam-column buildings such as school buildings. Three quasi-static hysteresis loading tests were performed on one unreinforced beam-column specimen and two reinforced specimens with U-type precast wall panels. Top shear connection of the PC panel was required to show the composite strength of RC column and PC wall panel. However, the strength of the connection did not influence directly on the ultimate loading capacities of the specimens in the positive loading because the loaded RC column push the side of PC wall panel and it moved horizontally before the shear connector receive the concentrated shear force in the positive loading process. Under the positive loading sequence(push loading), the reinforced concrete column and PC panel showed flexural strength which is larger than 97% of the composite section because of the rigid binding at the top of precast panel. Similar load-deformation relationship and ultimated horizontal load capacities were shown in the test of PR1-LA and PR1-LP specimens because they have same section dimension and detail at the flexural critical section. An average of 4.7 times increase in the positive maximum loading(average 967kN) and 2.7 times increase in the negative maximum loading(average 592.5kN) had resulted from the test of seismic resistant specimens with anchored and welded steel plate connections than that of unreinforced beam-column specimen. The maximum drift ratios were also shown between 1.0% and 1.4%.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.757-762
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• 2002

Many reports have been shown that the buoyancy, electromagnetic force, surface tension, and gas shear stress are the driving forces of weld pool circulation in arc welding. Among them, the surface tension of molten metal plays an important role in the flow in weld pool, which are clarified by the specially designed experiments with small particles as well as the numerical simulations. The surface tension is also related to the penetration in arc welding. Therefore, a quantitative evaluation of surface tension is demanded for the development of materials and arc process control. However, there are few available data published on the surface tension of molten metals, since it depends on the temperature and the composition of materials. In this study, a new method was proposed for the evaluation of surface tension and its temperature dependence, in which it is evaluated by the equilibrium condition of acting forces under a given surface geometry, especially back surface. When this method was applied to the water pool and to the back surface of molten pool in the stationary gas tungsten arc welding of thin plate, following results were obtained. In the evaluation of surface tension of water, it was shown that the back surface geometry was very sensitive to the evaluation of surface tension and the evaluated value coincided with the surface tension of water. In the measurement of molten pool in the stationary gas tungsten arc welding, it was also shown that the comparison between the surface tension and temperature distribution across the back surface gave the temperature dependent surface tension. Applying this method to the mild steel and stainless steel plates, the surface tension with negative gradient for temperature is obtained. The evaluated values are well matched with ones in the published papers.

• Journal of International Academy of Physical Therapy Research
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• v.3 no.1
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• pp.391-396
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• 2012

The purpose of this study is to identify which width of the base of support(BOS) is safer and more effective in lifting by comparing muscle activations and body sways when lifting objects under the width variation of the BOS. A total of fifteen healthy adults participated in this study. For the width variation of the BOS, the participants changed the width between their feet into three different types(10cm, 32cm, 45cm) and lifted a 10kg four times in each type after going up on a force plate. In order to measure body sways according to the width variation of the BOS, a motion analysis system was used. In addition, in order to measure the muscle activations of lower extremities, including the erector spinae, gluteus maximus, rectus femoris, and tibialis anterior, an electromyogram(EMG) analysis was employed. In addition, the Borg's scale was drawn by quantifying the subjective discomfort levels felt from each width of the BOS. In conclusion, no statistically significant differences according to the width variation of the BOS were observed(p=.295, .308)(p>.05). However, a statistically significant difference was exhibited between the Borg's scale, which indicates the discomfort levels from lifting performances, and the width variation of the BOS (p=$.000^*$).

• Maxillofacial Plastic and Reconstructive Surgery
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• v.23 no.4
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• pp.338-347
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• 2001

Purpose: This is to review the cases of posterior maxillary segmental osteotomies to regain the interarch spaces for dental implants in the posterior mandible. Materials & Methods: Seven patients who presented with alveolar extrusion of upper posterior molars underwent segmental osteotomies by single-stage Kufner's buccal approach under the intravenous sedation and local anesthesia. The posterior maxillary cento-alveolar segments were repositioned upward using pre-fabricated palato-occlusal resin splints and immobilized with osteosynthesis microplates and screws. Dental implants were installated simultaneously. The regained spaces, tooth vitality, periodontal healing, relapse, tenderness on function, and complications including maxillary sinus involvements were evaluated periodically for over one year after the surgeries. Results: The single-tage procedures were completed within 80 minutes without any surgical complications. The posterior maxillary segments were repositioned upward to regain the interarch spaces ranging from 2.5 to 5.5mm. All teeth involved in the procedures keep their vitalities. The repositioned segments were maintained showing neither evidence of periodontal break-down nor tenderness to function. One patient whose segments had not been immobilized by osteosynthesis plate resulted in 2mm down-ward relapse in post-operative 8 months. A case of postoperative nasal bleeding from the posterior-lateral wall resulted in oroantral fistula and chronic maxillary sinusitis later. Conclusion: The extruded dento-alveolar segments of the posterior maxilla were repositioned properly by Kufner's one-stage segmental osteotomies. One microplate can be of help to keep the position until the osseous healing enough to support the masticatory force.

• Physical Therapy Korea
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• v.8 no.4
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• pp.17-29
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• 2001

발목에 대한 유착성 테이핑의 적용은 물리치료 분야와 운동 트레이닝 분야에서의 일반적인 치료 접근 방법이라 할 수 있다. 즉 발목 염좌 같은 손상을 예방하기 위한 방법과 재활의 부가적인 치료 형태로 이용될 수 있는 것이다. 본 연구는 발목의 테이핑과 트레드밀에서의 30분간 보행이 수직 착지 동작 동안 하지의 운동 역학적 요소들에 어떠한 영향을 주는지 알아보기 위해 시행되었다. 14명의 신체 건강한 대상자들 (남:10, 여:4)이 본 연구에 참여하였다. 한발로 서있는 동안 40 cm의 높이로 뛰게 하였다. 가자미근, 전경골근, 안쪽넓은근, 넙다리 두갈래근에 근전도 전극이 부착되었다. 테이핑된 신체 부위로 착지하는 동안 근전도와 힘판(force plate) 자료가 500 Hz의 주파수로 수집되었다. 대상자들의 우세쪽 하지 발목에 테이핑을 하였고, 대상자는 한발로 뛰어 내리는 동작을 반복하였다. 트레드밀에서 30분 동안 발목에 테이핑을 한 채로 보행하였고 이후 한발로 뛰어 내리는 동작을 반복하여 수행하였다. 테이핑을 적용한 상태와 테이핑한 채로 30분 동안 트레드밀에서 걷기 운동을 한 조건에서 수직 지면 반발력의 통계학적으로 유의미한 증가가 있었다. 착지 동안에 네 가지 상황에서의 최대 내측 가속도의 유의한 차이가 있었고, 그 차이는 테이핑 전과 테이핑을 한 채로의 운동 조건에서 유의한 차이가 있었다. 테이핑한 상태에서 가자미근은 접촉되는 착지 순간부터 최대 수직 지면 반발력이 나타나는 동안의 평균 근전도의 수치에 있어서 유의한 감소가 있었다. 반면에 다른 근육들에서는 아무런 변화를 보이지 않았다. 비록 발목 테이핑이 발목 손상의 위험을 줄이는데 효과적이라고 일반적으로 인식되고 있으나 이번 실험의 결과는 30분 동안의 트레드밀에서의 보행 후 테이핑은 발목의 움직임을 제한하는 효과는 있지만 한편으로는 가자미근의 활동을 감소시키는 것을 보여주었다. 따라서 이 연구의 결과는 테이핑을 하면 점프와 착지로 이어지는 동작 중에 발목관절 손상 위험을 증가시킬 가능성이 있음을 보여주었다.

• The korean journal of orthodontics
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• v.50 no.5
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• pp.346-355
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• 2020

The treatment of skeletal Class III malocclusion in adolescents is challenging. Maxillary protraction, particularly that using bone anchorage, has been proven to be an effective method for the stimulation of maxillary growth. However, the conventional procedure, which involves the surgical implantation of mini-plates, is traumatic and associated with a high risk. Three-dimensional (3D) digital technology offers the possibility of individualized treatment. Customized mini-plates can be designed according to the shape of the maxillary surface and the positions of the roots on cone-beam computed tomography scans; this reduces both the surgical risk and patient trauma. Here we report a case involving a 12-year-old adolescent girl with skeletal Class III malocclusion and midface deficiency that was treated in two phases. In phase 1, rapid maxillary expansion and protraction were performed using 3D-printed mini-plates for anchorage. The mini-plates exhibited better adaptation to the bone contour, and titanium screw implantation was safer because of the customized design. The orthopedic force applied to each mini-plate was approximately 400-500 g, and the plates remained stable during the maxillary protraction process, which exhibited efficacious orthopedic effects and significantly improved the facial profile and esthetics. In phase 2, fixed appliances were used for alignment and leveling of the maxillary and mandibular dentitions. The complete two-phase treatment lasted for 24 months. After 48 months of retention, the treatment outcomes remained stable.