• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.3
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• pp.1-8
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• 2011

Stainless steel sheets are widely used as the structure material for the railroad cars and the commercial vehicles. These kinds structures used stainless steel sheets are commonly fabricated by using the gas welding. Gas welding is very important and useful technology in fabrication of an railroad car and vehicles structure. However fatigue strength of the gas welded joints is considerably lower than parent metal due to stress concentration at the weldment, fatigue strength evaluation of gas welded joints are very important to evaluate the reliability and durability of railroad cars and to establish a criterion of long life fatigue design. In this paper, ${\Delta}-N_f$ curve were obtained by fatigue tests. Using these results, the accelerated life test (ALT) is conducted. From the experimental results, an acceleration model is derived and acceleration factors are estimated. So it is intended to obtain the useful information for the fatigue lifetime of plug and ring gas welded joints and data analysis by statistical reliability method, to save time and cost, and to develop optimum accelerated life prediction plans.

• Korean Journal of Microbiology
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• v.3 no.2
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• pp.9-14
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• 1965

The enzyme-producing potentials of industrially important strains of Aspergillus spp. were studied. Irradiation of three original isolates of Aspergillus oryzae to ultra-violet rays resulted in the production of mutants which differed from the parent riboflavin and vitamin $B_{12}$ in culture media. 1. Irradition three strains of Aspergillus oryzae to ultraviolet light produced mutants and two strains of them were selected for soy sauce brewing. 2. The two strains are the physiological mutants of Aspergillus oryzae. Both were found to have superior enzyme activity to their relatives. 3. Aspergillus oryzae UV-induced mutant 172-722 and 569-713 were more powerful than others in the production of riboflavin and vitamin $B_{12}$. The enzyme activity of these strain were high and decreased only slightly even in 20 percent solution of NaCl. 4. Aspergillus oryzae UV-induced mutant 172-722 had more powerful protease producibility in wheat bran media than in modified Czapek's solution. On the contrary, Aspergillus oryzae UV-induced mutant 569-713 had more powerful producibility of saccharogenic and dextrinogenic amylase in modified Czapek's solution than in mold bran. 5. Aspergillus oryzae UV-induced mutant 172-722 formed the spore rapidly and Aspergillus oryzae UV-induced mutant 569-713 did ordinarily. 6. It is found from the results that Aspergillus oryzae UV-induced mutant 172-722 is valuable material for the manufacture of soy sauce because of its high protease activity in 20 percent solution of NaCl. Aspergillus oryzae UV-induced mutant 569-713 is suitable for soy bean mash and for fermented red pepper sauce for its high saccharogenic and dextrinogenic amylase activity in 20 percent solution of sodium chloride.

• The Korean Journal of Emergency Medical Services
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• v.14 no.1
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• pp.19-29
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• 2010

Purpose : This study was conducted to examine the degree of recognition of safety education and its execution for child-care teachers at daycare center for the disabled children in Jeollanam-do. Ninety six child care teachers filled out the questionnaire and the results were as follows. Results : 1. The possibility of accident prevention by the day care teachers was a little higher in case of nearby education institution. The most appropriate period of safety education was within one month. 2. Majority of child care teachers had received safety and first-aid educations before and the education was done for less than 2 hours. 3. The best educational method was practice-centered education of off-duty time. The contents of first-aid education were bleeding, fall, shock, and burn. 4. The education material and book should be available to the teachers when they need the knowledge. 5. By the annual schedule, safety education should be conducted and provided to the parents. Conclusion : This study suggested that reinforcement of contents related to emergency situation and actual first-aid as well as theory education in the process of parent and teacher education should be conducted on the basis of information of general conditions related to safety and first-aid education at the daycare center for the disabled children.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.2
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• pp.134-138
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• 1999

Eggs and larval development of Chelon affinis were reared and observed in the laboratory with parent fishes obtained in the Minrak fish market Pusan on March, 1997. The spawned eggs of the species are transparent, round, separated, floated, and their diameters were varied within 0.95$\~$1.06 mm. Hatching began about 73 hours after spawning at $16.0^{\circ}C$. The newly hatched larvae were 1.72$\~$1.92 mm in total length with 19 myomeres, mouth and unopened anus, rod shape melanophores distributed in body. The larvae absorbed yolk material completely in 5 days after hatching and became postlarvae.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.4
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• pp.511-520
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• 2010

In general, spot welding is used at no welding rod or flux for the process, low welding point temperature compared to arc welding, short heating time, less damage to the parent material, and low deformation and residual stress, relatively. Also, because of the pressurization effect, better mechanical qualities of the welding parts are obtained. Therefore, in various fields of industry its rapid operation speed can make mass production possible such as motor industry. In FEM analysis for the spot welding process, it is effective to use simple modeling rather than complicated one because of its numerous number of spots and reduction of analysis time. Therefore, this study provides with not only simplification of modeling analysis by using beam component composition of structure without re-compositing the spot welding point mesh but also modeling analysis of which property of fracture strength is reflected. In addition complete spot welding model is examined at rectangular post shape (hat shape) by impact test, compared the results, and verified its validity. As a result, it is possible to optimize the welding position and to recognize the strength of structure and the proposed equal distance model shows the effect of welding point reduction and improvement of stiffness.

• Journal of Welding and Joining
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• v.7 no.4
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• pp.56-67
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• 1989

In this study, the possibility of evaluating the peculiar fracture strength of weldment in high strength steels was investigated by means of a small punch(SP) test. In order to obtain the ductile-brittle transition temperature(DBTT) of SP energy by which the fracture strength of weldment in structural steels such as SS41 and SM53B steels had been evaluated in our preceding publication, the effects of notches and loading rates on SP energy were discussed. It was found that the correspondence of SP energy to critical COD at test temperature -196.deg. C showed a linear relation with some deviation. The empirical correlation with scatter band, Esp/(Esp)p = 1.67[.delta./(.delta./sub c//(.delta./sub c/)/sub p/]-0.55, was developed between the SP energy ratio and critical COD ratio of each weld structure compared with parent material at test temperature -196.deg. C. In addition, there did not appear to be a significant effect of test materials and specimen size etc. on the correlation.

• Journal of Welding and Joining
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• v.16 no.1
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• pp.77-87
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• 1998

This paper deals with the effect of laser welding parameters on the weld formation. Thin steels for automotive application were prepared so as to be welded with high power carbon dioxide laser system. Major process parameters were position of focus and travel speed. The effect of shielding gas was also discussed by employing the high speed photometry. Test results showed that the optimal position of focus varied in accordance with the joint configuration; bead-on-plate, butt or lap welding. It was recommended that the position of focus for the lap welding be located at slightly inner part of the material to be welded. In this case, however, it was noticeable that the weld penetration ratio, d/t$_{0}$ dropped drastically at the critical region. Results also demonstrated that both the bead width and penetration reduced as the travel speed increased. The penetration ratio showed two distinct regions; stabilized zone at the lower range of the travel spped and sudden drop zone at the higher range of travel speed. Lower limit of the penetration for acceptable weld was proved to be about 90% of the parent metal thickness based on the physical properties of the weld. Mixed gas application for both the shielding of molten metal and laser induced plasma control was recommended as far as the penetration was concerned.d.

• Smart Structures and Systems
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• v.26 no.6
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• pp.721-733
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• 2020

The present study investigates the employing of piezoelectric patches in active control of a sandwich plate. Indeed, the active control and optimal patch distribution on this structure are presented together. A sandwich plate with honeycomb core and composite reinforced by carbon nanotubes in facesheet layers is considered so that the optimum position of actuator/sensor patches pair is guaranteed to suppress the vibration of sandwich structures. The sandwich panel consists of a search space which is a square of 200 × 200 mm with a numerous number of candidates for the optimum position. Also, different dimension of square and rectangular plates to obtain the optimal placement of piezoelectric actuator/senor patches pair is considered. Based on genetic algorithm and LQR, the optimum position of patches and fitness function is determined, respectively. The present study reveals that the efficiency and performance of LQR control is affected by the optimal placement of the actuator/sensor patches pair to a large extent. It is also shown that an intelligent selection of the parent, repeated genes filtering, and 80% crossover and 20% mutation would increase the convergence of the algorithm. It is noted that a fitness function is achieved by collection actuator/sensor patches pair cost functions in the same position (controllability). It is worth mentioning that the study of the optimal location of actuator/sensor patches pair is carried out for different boundary conditions of a sandwich plate such as simply supported and clamped boundary conditions.

• IMMUNE NETWORK
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• v.22 no.5
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• pp.38.1-38.24
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• 2022

Exosomes, which are well-known nanoscale extracellular vesicles, are multifunctional biomaterials derived from endosomes and perform various functions. The exosome is a critical material in cell-cell communication. In addition, it regulates the pathophysiological conditions of the tumor microenvironment in particular. In the tumor microenvironment, exosomes play a controversial role in supporting or killing cancer by conveying biomaterials derived from parent cells. Innate immunity is a crucial component of the host defense mechanism, as it prevents foreign substances, such as viruses and other microbes and tumorigenesis from invading the body. Early in the tumorigenesis process, the innate immunity explicitly recognizes the tumor via Ags and educates the adaptive immunity to eliminate it. Recent studies have revealed that exosomes regulate immunity in the tumor microenvironment. Tumor-derived exosomes regulate immunity against tumor progression and metastasis. Furthermore, tumor-derived exosomes regulate polarization, differentiation, proliferation, and activation of innate immune cells. Exosomes produced from innate immune cells can inhibit or support tumor progression and metastasis via immune cell activation and direct cancer inhibition. In this study, we investigated current knowledge regarding the communication between tumor-derived exosomes and innate immune cell-derived exosomes (from macrophages, dendritic cells, NK cells, and neutrophils) in the tumor microenvironment. In addition, we discussed the potential development of exosomal immunotherapy using native or engineered exosomes against cancer.

• Research in Community and Public Health Nursing
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• v.5 no.2
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• pp.181-202
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• 1994

This study was conducted in order to grasp the condition of the student's knowledge and attitude about tuberculosis. And to offer the basic materials for the prevent tuberculosis in elementary school. The objects were comprised 395 of volunteered 6th grade students who study in two elementary schools. The material of this study was the questionaire(chronbach $\alpha=.9016$) suited to the purposed of this research which has been made through studying references. All the questionaire were collected immediately without explanation. The data was collected from 13rd to 25th of May on 1994. Analysis of the data was done utilizing SPSS for percentage, mean, ANOVA and pearson-Correlation Coefficient. The Result are as follows; 1. General features of the objects of study. Sex distribution was similar. Salary of 1000-1500 thousand won were highest (40.2%), nuclear family was highest (87.1%), fathers of graduated high school were the highest(44.0%), mothers of graduated high school were the highest(56.8%). And there was nobody about tuberculosis patient in one's close relatives were highest(95.4%). 2. The conditions of attitude about tuberculosis. Having experience of tuberculin test were highest(59.0%). Less than 9mm indulation among the tuberculin tested group were 85.1%, more than indulation were 14.9%. Have a B. C. G. injection among the less than 9mm indulation were 83.2%. Leave alone among the more than 10mm indulation were 56.0%. Think it too much trouble to do not tuberculine test were 63.0%. Do not take a chest X-ray in the past were 60.3%. And take a chest X-ray in the past were 39.7%. Health educated group was 74.3%. If tuberculosis sign was developed, notified to parent was 73.8%. 3. The condition of knowledge about tuberculosis. When 5 points was given to 'very affiming' and 1 point was given to 'very deny', the total average was 3.54. And symptom of tuberculosis secion was 3.67, vaccination of tuberculosis section was 3.66, tuberculine test section was 3.56, epidemiology of tuberculosis section was 3.54, infection of tuberculosis section was 3.38. And every section showed affirmative correlation(P<.001). 4. Correlation between the general features and attitude variables. High incomed group may have more attitude on tuberculin test than low incomed group($x^2=16.$ 190, P<.01). High educated group may have more attitude on tuberculin test than low educated group(Father : $x^2=28.530$, P<.001, Mother: $x^2=26.060$, P<.001). High educated group may have more attitude on health education than low educated group(Father: $x^2=20.$ 767, P<.000, Mother: $x^2=10.639$, P<.05). Nuclear family may have more attitude on notify to parent than others($x^2=51.45$, P<.000). Tuberculosis patient in one's close associates have more attitude on notify to parent than others($x^2=51.$ 45, P<.000). 5. Difference between the general features and knowledge of tuberculosis. High incomed group were highest score in knowledge (F=3.99, P<.01). High educated group were highest score in knowledge(Father : F=8.81, P<.000, Mother: F=9.09, P<.000). 6. Difference between the attitude and knowledge of tuberculosis. Tuberculin tested group were highest score in knowledge(t=9.88, P<.000). Taken chest X-ray group were highest score in knowledge (t=2.07, P<.05). Received health education group were highest score in knowledge(t=6.83, P<.000). Notified symptoms to teachers and parent group were highest score in knowledge(F=3.89, P<.01).