• Journal of the Korean Society for Nondestructive Testing
• /
• v.29 no.5
• /
• pp.473-478
• /
• 2009

The purpose of this study is to evaluate the behaviour of the plastic deformed zone at crack tip on the standard Charpy specimens which were taken from the multi-passed weld block of the pressure vessel steel. Notch was machined on the standard Charpy test specimens and pre-crack which was located around the fusion line was made under the repeat load. Four point bend and acoustic emission tests were carried out simultaneously. The size of plastic region at crack tip was calculated using stress intensity factor. Relationships between characteristics of acoustic emission and plastic zone size at crack tip were discussed through the cumulative AE energy. Regardless of the specimens, AE signals were absent within the elastic region almost and most of AE signals were produced at the plastic deformation region from yield point to the mid-point between yield and maximum load. More AE signals for the weldment were produced compared with the base-metal and PWHT specimen. Relations between plastic deformed zones at crack tip and cumulative AE energy for the weldment and PWHT specimen were different quietly from the base-metal. Besides, number of AE counts for the weldment was the larger than those of the base-metal and PWHT specimen.

• Tuberculosis and Respiratory Diseases
• /
• v.39 no.5
• /
• pp.392-399
• /
• 1992

Background: Despite dyspnea is a predominant complaint of patients with respiratory disease, the mechanisms contributing to the sensation of breathlessness are poorly understood. Traditionally, physicians have measured objective pulmonary function to assess severity of dyspnea. But it will be also useful to measure subjective dyspnea index because dyspnea probably depends on a complex interplay of mechanical, experimental, emotional and other factors. Method: We measured breathlessness at rest, after Methacholine challenge and then bronchodilator inhalation using a Visual Analogue Scale (VAS) and Borg Scale Dyspnea Index (BSDI) in stable asthmatic patients. Spirometry was performed concomittently. Results: There was no correlation between dyspnea index and FEV1. There was also no correlation between the change in dyspnea index and change in FEV1. The change in dyspnea index after methacholine and bronchodilator was greater in clinically mild asthmatic patients than clinically severe symptomatic group. Conclusion: In asthmatic patients, there was a wide variation in sensory response for any given FEV1, and the change in perception of dyspnea was greater in those with clinically mild symptoms. The measurement of dyspnea index may yield information complementary to that obtained by spirometry.

• 대한공업교육학회지
• /
• v.35 no.2
• /
• pp.1-24
• /
• 2010

The purpose of this study is to investigate provedly the effectiveness of the practice for the arts and crafts by machine for project based learning upon improving industrial high school students' key competency for vocation, and to provide the incumbent teachers and future teachers who want to conduct research, a similar study with the basic reference materials. The vocational key competencies interested in this study are communication ability, information usage skills, team work skills, problem solving skills, tool usage skills, and responsibility and confidence areas. Because the result of pre and post testing over these six areas has insignificant differences statistically, we reach a conclusion which project based learning is more effective than traditional practice methods at improving the vocational key competencies of industrial students. On the basis of the results of this study, I would like to suggest some kinds of things needed to improve the vocational key competencies of industrial high school students. First, we require the diverse research to investigate the best teaching and learning methods to cultivate people of ability with the vocational key competencies Second, it is required that to measure the extent of the improvement of the vocational key competencies of industrial high school students, we have to develop a more objective test tool than that used in this study. Third, in the light of facts that project based learning influences on improving the vocational key competencies of the industrial high school student, we will have to make an effort actively to find the best teaching and learning methods, like project based learning. Therefore, we need to give diverse training opportunities and financial support so that teachers can conduct research to find the best teaching and learning method at improving the vocational key competencies for industrial high school students.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.11
• /
• pp.747-754
• /
• 2017

The Concrete-Filled Tube (CFT) system was developed for its excellent structural performance, such as its good stiffness, stress and ductility, which is derived from the mechanical advantages of its composite structure. However, it is known that the flat type of reinforcing plates need stiffeners placed at a certain distance from each other to avoid buckling failure, which increases the cost accordingly. This paper investigates the contribution of the rib elements placed inside the steel tube for the purpose of increasing the bond strength between the steel and concrete and fire performance with no additional protection. The test results also demonstrate the effectiveness of the corrugated rib's shape against fire. The results of this study showed that the buckling prevention and fire resistance performance criteria were satisfied by the application of the inner surface attachment rib, due to the resulting increase in the strength of the CFT column. Therefore, it is considered that the CFT method using the corrugated rib structure reinforcement developed through this study satisfies the structural and fire resistance performance criteria without the need for a refractory coating. Future studies will be needed to make the process efficient and economical for factory production.

• Clinical and Experimental Reproductive Medicine
• /
• v.28 no.2
• /
• pp.79-86
• /
• 2001

Objective: Mouse pre-antral follicles require the addition of gonadotropins (Gns) to complete maturation and ovulation of oocyte and antrum formation in vitro. However, we tried examination of in vitro growth of mouse pre-antral follicles in medium without Gns and/or phygiological factors. And also, pre-antral follicles were isolated from ovaries by mechanical method. Our present studies were conducted to evaluate on the growth of follicles and intra-follicular oocytes and antrum formation in vitro of mouse pre-antral follicles in two different media. Methods: Pre-antral follicles ($91{\sim}120{\mu}m$) were isolated mechanically by fine 30G needles not using enzymes from ovaries of 3-6 week-old female ICR mice. Isolated pre-antral follicles were cultured in $20{\mu}l$ droplets of TCM (n=17; follicles: $107.8{\pm}1.58{\mu}m$; oocytes: $57.9{\pm}1.2{\mu}m$) or MEM (n=12; follicles: $109.3{\pm}2.53{\mu}m$; oocytes: $55.4{\pm}1.6{\mu}m$) under mineral oil on the 60 mm culture dish. All experimental media was supplemented with 10% FBS without Gns and/or physiological factors. Pre antral follicles were individually cultured for 8 days. Antram formation and growth of pre-antral follicles and intra-follicular oocytes were evaluated using precalibrated ocular micrometer at X200 magnifications during in vitro culture. Results were analyzed using combination of Student's t-test and Chi-square, and considered statistically significant when p<0.05. Results: Antrum formation had started in two culture media on day 2. On day 8, antrum formation had occurred in 58.3% of pre-antral follicles cultured in DMEM, but only in 23.5% of those cultured in TCM (p=0.0364). Growth of pre-antral follicles and intra-follicular oocytes were observed on day 4 and 8. On day 4, follicular diameter was similar (p=0.1338) in TCM ($119.4{\pm}2.58{\mu}m$) and MEM ($125.4{\pm}4.52{\mu}m$). However, on day 8, diameters of pre-antral follicles cultured in MEM ($168.9{\pm}17.29{\mu}m$) were significantly bigger (p=0.0248) than that in TCM ($126.7{\pm}4.28{\mu}m$). On day 4 and 8, diameters of intra-follicular oocytes were similar in TCM ($67.1{\pm}1.3$ and $72.4{\pm}0.9{\mu}m$) and MEM ($65.2{\pm}1.7$ and $73.3{\pm}1.5{\mu}m$), respectively. Conclusion: We can conform that medium without Gns and/or physiological factors can be used for in vitro antrum formation and growth of pre-antral follicles and intra-follicular oocytes in mouse. In conclusion, MEM supplemented with FBS can be used for growth in vitro of mouse pre-antral follicles isolated mechanically.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.11a
• /
• pp.473-476
• /
• 2008

Due to the pursuit of high function and international price increase in the field of construction, the application of the secondary product using cement is on the increase gradually in the construction industry in the pursuit of economic cost reduction by the shortening of the construction time like Expediting and the dry construction method at the same time. However, it is in very urgent situation of measures to improve the structural performance or durable performance because it is limited for use in terms of panel in interior exterior building or functional repair reinforce as yet. Accordingly, this study is to investigate applicability of permanent Formwork like mould with the structural performance or excellent durable performance in the field of construction, and to derive optimum mixture in the performance and quality of manufacture. As a result of analysis comparison with the dynamic and durable properties of vacuum extrusion molding high toughness cement panel according to the mixture of four conditions, this study has found that the test body of mixing ECC-DP3 using small filler and large granulated blast furnace slag and powder flame retardant had excellent relative hardness and bending stress strain. The durable performance has shown excellent tendency by the decrease of porosity and enhancement of water-tightness.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.51 no.3
• /
• pp.164-173
• /
• 2014

In underwater robotics, vision would be a key element for recognition in underwater environments. However, due to turbidity an underwater optical camera is rarely available. An underwater imaging sonar, as an alternative, delivers low quality sonar images which are not stable and accurate enough to find out natural objects by image processing. For this, artificial landmarks based on the characteristics of ultrasonic waves and their recognition method by a shape matrix transformation were proposed and were proven in Part 1. But, this is not working properly in undulating and dynamically noisy sea-bottom. To solve this, we propose a framework providing a selection phase of likelihood candidates, a selection phase for final candidates, recognition phase and tracking phase in sequence images, where a particle filter based selection mechanism to eliminate fake candidates and a mean shift based tracking algorithm are also proposed. All 4 steps are running in parallel and real-time processing. The proposed framework is flexible to add and to modify internal algorithms. A pool test and sea trial are carried out to prove the performance, and detail analysis of experimental results are done. Information is obtained from tracking phase such as relative distance, bearing will be expected to be used for control and navigation of underwater robots.

• The Journal of Korean Academy of Prosthodontics
• /
• v.44 no.5
• /
• pp.642-653
• /
• 2006

Purpose : The purpose of this study was to investigate the effect of the output energy(voltage) of laser welding on the strength and properties of joint of cast titanium(CP Gr II) and titanium alloy(Ti-6Al-4V). Material and method : Cast titanium and its alloy rods(ISO6871) were prepared and perpendicularly cut at the center of the rod. After the cut halves were fixed in a jig, and the joints welded with a laser-welding machine at several levels of output voltage of $200V{\sim}280V$. Uncut specimens served as the non-welded control specimens The pulse duration and pulse spot size employed in this study were 10ms and 1.0mm respectively. Tensile testing was conducted at a crosshead speed of 0.5mm/min. The ultimate tensile strength(MPa) was recorded, and the data (n=6) were statistically analyzed by one-way analysis of variance(ANOVA) and Scheffe's test at ${\alpha}$=0.05. The fracture surface of specimens investigated by scanning electron microscope (SEM). Vickers microhardness was measured under 500g load of 15seconds with the optimal condition of output voltage 280V. Results : The results of this study were obtained as follows, 1. When the pulse duration and spot size were fixed at 10ms and 1.0mm respectively, increasing the output energy(voltage) increased UTS values and penetration depth of laser welded to titanium and titanium alloy. 2. For the commercial titanium grade II, ultimate tensile strength(665.3MPa) of the specimens laser-welded at voltage of 280V were not statistically(p>0.05) different from the non-welded control specimens (680.2MPa). 3. For the titanium alloy(Ti-6Al-4V), ultimate tensile strength(988.3MPa) of the specimens laser-welded at voltage of 280V were statistically(p<0.05) different from the non-welded control specimens (665.0MPa). 4. The commercial titanium grade II and titanium alloy(Ti-6Al-4V) were Vickers microhardness values were increased in the fusion zone and there were no significant differences in base metal, heat-affected zone.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.10
• /
• pp.283-290
• /
• 2020

In this study, a floater was developed for a frame-type solar power plant. The floater supports the frame and the solar panels. A finite element analysis was performed to design its shape and thickness, and the floater was manufactured by a rotational molding method using linear low-density polyethylene. It was found that the floater did not cause collapse and it maintained its stiffness even at 4 times the maximum load of 322.7 kgf. To perform a long-term compression test, a weight-type load application device that uses gravity was designed and manufactured. The amount of compressive deformation was measured for 7 days, and a long-term deformation equation was obtained. Even under small loads, continuous deformation was observed. However, the 10-year deformation amount for a constant load of 100 kgf was predicted to be small at about 4.64 mm. As a result, it was found that the developed floater could be used in a solar power plant on a body of water.

• Archives of Plastic Surgery
• /
• v.36 no.4
• /
• pp.380-384
• /
• 2009

Purpose: Autologous vessels remain the gold standard for vascular grafts in microanastomoses. However, they are sometimes unavailable and have a limited long - term patency. Synthetic vessels have high success rates in large - diameter reconstructions but failed when used as small - diameter grafts due to graft occlusion. It has been proved that endothelial cell seeding improves prosthesis performance and long - term patency. Among polyurethane, PET and ePTFE, polyurethane has the best affinity to endothelial cells and mechanical properties closest to human vessels. We examined the ability of endothelial cells to attach to a polyurethane graft manufactured by the electrospinning method. Methods: Endothelial cells, which were cultured from porcine internal jugular veins, were attached to polyurethane grafts with an internal diameter of 3 mm. The same cells were attached to allogeneic decellularized porcine internal carotid artery grafts as controls. Both of the 10 mm - long grafts were exposed to endothelial cells in a well for 1 hour. Each well contained $2{\times}10^5$ endothelial cells. The graft materials were rotated through 90 degrees every 15 minutes in order to minimize the effect of gravity. The extent of cell attachment was examined with the MTT assay. Results: The MTT assay showed good incorporation of endothelial cells into both grafts. For the evaluation of affinity, the number of attached cells was counted at 10 fields of microscopic examination with ${\times}40$ magnification. Endothelial cells adhered more to polyurethane grafts (mean, $127.4{\pm}6.2cells$) compared to porcine artery grafts (mean $45.8{\pm}5.1cells$)(p<0.05,Mann - Whitney test). Conclusion: In this study, we attached porcine endothelial cells to polyurethane grafts, manufactured by electrospinning. The grafts exhibited a better affinity to endothelial cells than allogeneic decellularized porcine internal carotid artery grafts. It is suggested that the time required for endothelial cells to attach to decellulized artery grafts may be longer than that which is required for attachment to polyurethane grafts.