• Journal of the Korean Society of Visualization
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• v.20 no.3
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• pp.49-57
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• 2022

The interaction of planar shock wave with rectangular water column is investigated numerically. The flow phenomenon like reflection, transmission, cavitation, recirculation of shock wave, and large negative pressure due to expansion waves was discussed qualitatively and quantitatively. The numerical simulation was performed in a shock tube with a water column, and planar shock was initiated with a pressure ratio of 10. Three cases of the water column with different thicknesses, namely 0.5D, 1D, and 2D, were installed and studied. Water naturally has a higher acoustic impedance than air and mitigates the shock wave considerably. The numerical simulations were modelled using Eulerian and Volume of fluids multiphase models. The Eulerian model assumes the water as a finite structure and can visualize the shockwave propagation inside the water column. Through the volume of fluids model, the stages of breakup of the water column and mitigation effects of water were addressed. The numerical model was validated against the experimental results. The computational results show that the installation of a water column significantly impacts the mitigation of shock wave.

• Asia-Pacific Journal of Business
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• v.13 no.1
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• pp.141-152
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• 2022

Purpose - This study attempts to explore the factors that affect the consumer's response to the influencer's "backdoor advertisement" which has been a social media controversy recently. Accordingly, this study focuses on the importance of the information source's characteristics in influencer marketing, and demonstrates the impact of influencer credibility, attractiveness, and expertise on consumer responses after the influencer's sponsorship controversy. Design/methodology/approach - To this end, a study was conducted on adults who subscribed to one or more channels of influencers, and a virtual newspaper article was used in the survey. 196 sample data were collected and SPSS PROCESS Macro was used for data analysis. Findings - As a result, there was a negative impact on the credibility of the influencer which carried over to a negative reception of their shared content, while the attractiveness of the influencer had a positive impact on the reception of their shared content, even after the controversy over the influencer's backdoor advertisement. Research implications or Originality - This study contributes to the expansion of research on influencer marketing. Also, it provides insight into understanding and interpreting the phenomenon of influencers' backdoor advertisements and consumer reactions.

• Progress in Superconductivity and Cryogenics
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• v.9 no.1
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• pp.86-90
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• 2007

The cryoprobe used in cryosurgery should be fabricated in milimeter-order size for its practical usage. In general a miniature J-T(Joule-Thomson) refrigerator is applied to a cryoprobe. In case of the miniature J-T refrigerator, the mass flow rate of working fluid is small due to considerable friction in a minute flow path. For that reason, the miniature J-T refrigerator has a limited cooling power. To obtain the large cooling power from the J-T refrigerator, the refrigerator should have large mass flow rate and effective J-T temperature drop. These quantities are closely related to the geometry of the heat exchanger and the expansion nozzle in a cryoprobe, and are contradictory. The large mass flow rate leads to the small J-T temperature drop and vice versa in the miniature J-T refrigerator. Therefore, the optimal design of a cryoprobe to achieve maximum cooling power at fixed tube size and fixed operating temperature is required. This paper presents the design procedure of such case.

• Journal of Chest Surgery
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• v.36 no.6
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• pp.404-410
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• 2003

Different treatment options are available according to the stage and duration of the empyema. Stage I empyema (exudate stage) is treated concurrently by the administration of appropriate antibiotics and chest tube drainage. Stage III empyema (organized stage) is considered for decortication through an open thoracotomy. However, the treatment of fibrinopurulent, stage II empyema remains controversial. Recently, debridement with the use of Video-Assisted Thoracoscopic Surgery (VATS) has been proposed for the treatment of stage II empyema. We analyzed and report our initial experience of 5 cases of stage II empyema, treated with the use of VATS. Material and Method: Between June 2001 and February 2002, 5 patients with fibrinopurulent empyema that did not respond to antibiotics, chest tube drainage or Percutaneous Catheter drainage (PCD), and instillation of fibrinolytic agent were treated by debridement and irrigation with the use of VATS. A CT scan was performed in all patients before the operation to confirm the diagnosis of loculated empyema and to detect additional lung parenchymal diseases. Result: All 5 patients underwent successful debridement and irrigation with the use of VATS and the chest tube was inserted properly. And no patients needed conversion to open thoracotomy. The ratio of sex was 4 : 1 (male : female), the mean age was 53 years old (range, 26~73 years), the mean operative time was 73.4 minutes (range, 52~95 minutes), the mean duration of postoperative chest tube placement was 12.4 days (range, 6~19 days), and the mean duration of postoperative hospital stay was 20.8 days (range, 10~36 days). In all patients, clinical symptoms such as pain and fever subsided and simple chest PA view revealed satisfactory lung expansion. No major postoperative complication was observed during the hospital course and no patient suffered from the recurrence of empyema in the follow-up period. Conclusion: We think that early operation with the use of VATS is safe and efficient for stage II empyema which did not respond to medical treatment(antibiotics and chest tube drainage), therefore, it can prevent stage II empyema from advancing to stage III, organized empyema.

• International Journal of Highway Engineering
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• v.13 no.3
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• pp.21-30
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• 2011

As well known, dowel bars are used to transfer traffic load acting on one edge to another edge of concrete slab in concrete pavement system. The dowel bars widely used in South Korea are round shape steel bar and they shows satisfactory performance under bending stress which is developed by repetitive traffic loading and environment loading. However, they are not invulnerable to erosion that may be caused by moisture from masonry joint or bottom of the pavement system. Especially, the erosion could rapidly progress with saline to prevent frost of snow in winter time. The problem under this circumstance is that the erosion not only drops strength of the steel dower bar but also comes with volume expansion of the steel dowel bar which can reduce load transferring efficiency of the steel dowel bar. To avoid this erosion problem in reasonable expenses, dowers bars with various materials are being developed. Fiber reinforced plastic(FRP) dower that is presented in this paper is suggested as an alternative of the steel dowel bar and it shows competitive resistance against erosion and tensile stress. The FRP dowel bar is developed in tube shape and is filled with high strength no shrinkage. Several slab thickness designs with the FRP dowel bars are performed by evaluating bearing stress between the dowel bar and concrete slab. To calculated the bearing stresses, theoretical formulation and finite element method(FEM) are utilized with material properties measured from laboratory tests. The results show that both FRP tube dowel bars with diameters of 32mm and 40mm satisfy bearing stress requirement for dowel bars. Also, with consideration that lean concrete is typical material to support concrete slab in South Korea, which means low load transfer efficiency and, therefore, low bearing stress, the FRP tube dowel bar can be used as a replacement of round shape steel bar.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.11
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• pp.6452-6457
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• 2014

R1234yf has been developed as an alternative refrigerant to R134a, which has been associated with global warming. The capillary tubes as expansion valves control the mass flow rate and balance system pressure in the refrigeration cycle. The present numerical model used the governing equations including the law of conservation of mass, momentum, and energy in a capillary tube. The mass flow rate of R1234yf decreased by 47.0% as the capillary tube length was increased from 1 to 4 m. As the inner diameter of the capillary tubes was changed from 1.3 to 1.7 mm, the mass flow rate of R134a and R1234yf increased by 117.9% and 121.0%, respectively. The mass flow rate of the R134a and R1234yf increased by 28.3% and 29.1% with subcooling increasing from 0 to $7^{\circ}C$. In addition, when the inlet temperature of the capillary tubes was changed from 35 to $60^{\circ}C$, the mass flow rate of R134a and R1234yf increased by 31.0% and 45.4%, respectively.

• Tuberculosis and Respiratory Diseases
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• v.72 no.5
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• pp.441-447
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• 2012

Background: Chest tube drainage (CTD) is an indication for the treatment of pneumothorax, hemothroax and is used after a thoracic surgery. But, in the case of incomplete lung expansion, and/or persistent air leak from CTD, medical or surgical thoracoscopy or, if that is unavailable, limited thoracotomy, should be considered. We evaluate the efficacy of bronchoscopic injection of ethanolamine to control the persistent air leak in patients with CTD. Methods: Patients who had persistent or prolonged air leak from CTD were included, consecutively. We directly injected 1.0 mL solution of 5% ethanolamine oleate into a subsegmental or its distal bronchus, where it is a probable air leakage site, 1 to 21 times using an injection needle through a fiberoptic bronchoscope. Results: A total of 15 patients were enrolled; 14 cases of spontaneous pneumothorax [idiopathic 9, chronic obstructive pulmonary disease (COPD) 3, post-tuberculosis 2] and one case of empyema associated with broncho-pleural fistula. Of these, five were patients with persistent air leak from CTD, just after a surgical therapy, wedge resection with plication for blebs or bullae. With an ethanolamine injection therapy, 12 were successful but three (idiopathic, COPD and post-tuberculosis) failed, and were followed by a surgery (2 cases) or pleurodesis (1 case). Some adverse reactions, such as fever, chest pain and increased radiographic opacities occurred transiently, but resolved without any further events. With success, the time from the procedure to discharge was about 3 days (median). Conclusion: Bronchoscopic ethanolamine injection therapy may be partially useful in controlling air leakage, and reducing the hospital stay in patients with persistent air leak from CTD.

• Nuclear Engineering and Technology
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• v.27 no.6
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• pp.811-824
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• 1995

The CANDU element bowing is attributed to actions of both the thermally induced bending moments and the bending moment due to hydraulic drag and mechanical loads, where the bowing is defined as the lateral deflection of an element from the axial centerline. This paper consider only the thermally-induced bending moments which are generated both within the sheath and the fuel and sheath by an asymmetric temperature distribution with respect to the axis of an element The generalized and explicit analytical formula for the thermally-induced bending is presented in con-sideration of 1) bending of an empty tube treated by neglecting the fuel/sheath mechanical interaction and 2) fuel/sheath interaction due to the pellet and sheath temperature variations, where in each case the temperature asymmetries in sheath are modelled to be caused by the combined effects of (i) non-uniform coolant temperature due to imperfect coolant mixing, (ii) variable sheath/coolant heat transfer coefficient, (iii) asymmetric heat generation due to neutron flux gradients across an element and so as to inclusively cover the uniform temperature distributions within the fuel and sheath with respect to the axial centerline. As the results of the sensitivity calculations of the element bowing with the variations of the parameters in the formula, it is found that the element bowing is greatly affected relatively with the variations or changes of element length, sheath inside diameter, average coolant temperature and its variation factor, pellet/sheath mechanical interaction factor, neutron flux depression factor, pellet thermal expansion coefficient, pellet/sheath heat transfer coefficient in comparison with those of other parameters such as sheath thickness, film heat transfer coefficient, sheath thermal expansion coefficient and sheath and pellet thermal conductivities.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.3
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• pp.185-190
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• 2016

Damages of the main engine aftmost bearing and the after stern tube bearing tend to increase due to misalignment. And as the shafting system becomes stiffer due to the large engine power, whereas the hull structure becomes more flexible due to optimization by using high tensile thin steel plates. And this is the reason that more sophisticated shaft alignments are required. In this study, the optimum shafting alignment calculation was carried out, considering the thermal expansion effect, exploiting the sensitivity index, which indicates the reasonable position of forward intermediate shaft bearing for shaft alignment. and as the main subject in this study, the elastic deformation on intermediate shaft and main engine bearings occurred by vertical load of shaft mass were examined thoroughly and analyzed allowable load of bearings, reaction influence numbers of all bearings. As the result, a reliable optimum shafting alignment was derived theoretically. To verify these results, they were referred to the engine maker's technical information of main engine installation and being used shafting alignment programs of both Korean Register of Shipping and Det Norske Veritas, their reliability were reviewed.

• Korean Journal of Veterinary Service
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• v.35 no.4
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• pp.263-268
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• 2012

From the end of July 2012, several cases of abortion have been happened at the Korean indigenous cattle farm with 124 heads in Chungbuk province, Korea. Serological tests such as Rose-bengal test (RBT) and standard tube agglutination test (STAT) have been performed according to the standard official protocols of bovine brucellosis and 41 cattle turned out to be brucellosis-positive simultaneously. To find out the main factors of brucellosis outbreaks and spreads, additional serological, etiological and molecular investigation were applied. Totally, 11 B. abortus were isolated from 10 cattle's specimens including lymph-nodes and/or testis, and drinking water in cowhouse. In genotyping by multi-locus VNTR assay (MLVA) using 17 loci markers, the present B. abortus isolates were shown all the same pattern, D1 genotype, which has been reported in Gyeonggi and Gangwon province, Korea. These results suggest that the input of brucellosis might come from neighboring farms directly or indirectly, even if by unknown factor and expansion within farm would accelerate by materials related with aborting cows.