• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.3
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• pp.643-650
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• 2021

The purpose of this study was to evaluate the impact of lecture content on the overall academic satisfaction in non-contact online classes. The study was conducted using an online survey of 107 university students attending metropolitan, local and foreign universities for a week from August 25th, 2020 to September 2nd, 2020. The analysis methods used included descriptive statistics and chi-square distribution, Fisher's exact test, linear by linear association, and logistic regression. The result of the study showed a significant decrease in Junior by 0.025 times compared to Senior (p<.05). Furthermore, a significant decrease in the impact of recorded lectures by 0.036 times compared to a hybrid of face-to-face and online lectures (p<.05). Compared to the response 'No', the number of student's responses of 'Yes' increased significantly by 31.358 times (p<.05). Additionally, a significant increase was seen in teaching methods by 19.709 times, and academic satisfaction by 7.989 times(p<.05). In conclusion, the results imply that the quality of lecture content is also important to improve the student's satisfaction with school life, but overall management is required in the areas of appropriate teaching methods, appropriate tuition, and evaluation methods.

• Journal of Advanced Navigation Technology
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• v.24 no.6
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• pp.566-572
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• 2020

In a wireless power transmitter, the characteristics and effects of wireless power transmission between two induction coils are investigated, and a power converter circuit and a battery charger/discharger circuit using wireless power transmission technology are proposed. The advantage of wireless power transmitters and wireless chargers is that, instead of the existing plug-in-mounted wired charger (OBC; on-board charger), the user can wirelessly charge the battery without connecting the power source when charging power to the battery. There is. In addition, the advantage of wireless charging can bring about an energy efficiency improvement effect by using the secondary side rectifier circuit and the receiving coil, but the large-capacity long-distance wireless charging method has a limitation on the transmission distance, so many studies are currently being conducted. The purpose of the study is to study the transmitter circuit and receiver circuit of a wireless power transmission device using a primary coil, a secondary coil, and a half bridge series resonance converter, which can transmit power of a non-contact type power transmitter. As a result, a new topology was applied to improve the power transmission distance of the wireless charging system, and through an experiment according to each distance, the maximum efficiency (95.8%) was confirmed at an output of 3 kW at an 8 cm transmission distance.

• Membrane Journal
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• v.31 no.6
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• pp.434-442
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• 2021

Poly(vinylidene fluoride) (PVDF) membrane has a good membrane durability because of its high mechanical resistance, thermal and chemical stability. However, the strong hydrophobic property of PVDF membrane can induce a low water permeability and easy fouling by proteins and organic matters. In order to improve the anti-fouling properties of PVDF membrane, the PVDF mixed matrix asymmetric membranes impregnated with biofunctional material 𝛽-cyclodextrin (𝛽-CD) in the membrane structure were prepared by phase inversion method. The membrane filtration experiments of pure water and BSA solution were performed using the PVDF/𝛽-CD mixed matrix asymmetric membranes prepared according to the 𝛽-CD contents. The experiments showed that the introduction of 𝛽-CD into the PVDF polymer matrix contributed to increase in the hydrophilic property of the PVDF membranes, and this led to the reduction of contact angles and improvement of anti-fouling properties. The PVDF/𝛽-CD membrane which was prepared using the dope solution with a 2 wt% 𝛽-CD content represented 64 L/m²·h of pure water flux, 95% of BSA rejection and maximum 80% of flux enhancements compared to flux results of the pristine PVDF membrane.

• The Journal of the Convergence on Culture Technology
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• v.7 no.4
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• pp.325-330
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• 2021

This study set out to investigate the forms, attributes, and escape methods of post-subjects projected on the investigator's works in connection with rhizomatic thinking proposed as a way of social transformation by Deleuze and Guattari and examine their social connotations. Post-subjects projected on the investigator's works are not completed wholes of some sort, but like materials whose constant premise is change and creation. In the investigator's works, post-subjects have conscious and unconscious desire. It is the desire of creation with positive attributes including Deleuze's and Guattari's pursuit of changes in a contradicting society. When desire is deployed in post-subjects, they will carry out an escape. This way of escape is rhizomatic proposed by Deleuze and Guattari. It deconstructs contradicting things and repeats connection, contact, and severance with the outside world, building a new order. Rhizomatic post-subjects appearing in the investigator's works depict the escape process and method in abstract ways through the variable installation of objets combined with a color field of repeating brushes. In this work, the goal of post-subjects is to make a safe landing in a space where beings are recognized for their values and free and creative lives. These post-subjects are nomads creating a new landscape continuously, wandering around vast plains, and also artists and literary figures resisting a contradicting society. That is, they are connected to the concept of a war machine proposed by Deleuze and Guattari as a concept of social transformation and to the concept of Nietzsche's Agon to devise and create new values and politics based on street passion. They seek after a space where they can co-exist with otherness recognized rather than the complete deconstruction of the old order.

• Journal of Korea Entertainment Industry Association
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• v.15 no.2
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• pp.83-97
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• 2021

This study started with curiosity about theatre without its three elements and would reveal its possibility through performance and experiment and promote the expansion of each element and the development of a new form at the same time. After the occurrence of COVID-19, theatre has come up against a big limitation of contact-free, untact communication due to its inherent characteristic of 'presence.' For the survival of theatre in the rapidly changing world, it is desperately necessary to check the existing performance method and to be concerned about its development for the future. Thus, this researcher started from a more fundamental exploration of theatre focused on an "experiment of theatre without its three elements" and would sort out the three elements (actors, audience, and a play) from a macroscopic perspective. Also, the researcher would investigate the impacts of these elements on the performance and the possibility of theatre even after removing the elements through performance and experiment. This study consists of one performance and two experiments and is based on the interviews and progress details conducted by the planner and experimenter and the survey with the experiment participants. The significance of this study is its reflection on the essence of the genre, theatre, and the roles of all elements constituting that, not from a narrow perspective that would simply define the concepts of the elements but through the expansion and change of them. Furthermore, hopefully, it will be connected to the discovery of a new theatrical format that has not been considered through its combination with another genre.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.6
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• pp.589-604
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• 2021

Waterjets for rocks have various advantages of the non-contact and eco-friendly excavation using only water and abrasive. To overcome the problems (e.g., dust and noise occurrence) of the conventional drilling methods, waterjet excavation methods are broadly used. It is advantageous to operate a couple of nozzles in order to increase the waterjet excavation efficiency. When multiple nozzles are used, it is essential to analyze the excavation performance and shape according to the nozzle operation method. In this study, nozzle angle, horizontal distance between nozzles, and standoff distance were defined as nozzle operating parameters and the excavation performance and shape were analyzed. As a result of the experiment, when the nozzle angle and standoff distance are increased, the excavation depth is decreased and the effective depth tends to be increased. In addition, based on the experimental results, the excavation shape criteria required for nozzle insertion were proposed and optimal nozzle operating parameters were derived according to the criteria. This study result is expected to be used as useful basic research in the future development of multiple waterjet nozzles for rock drilling.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.28 no.1
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• pp.15-21
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• 2022

The purpose of our study was to investigate the migration level of lead (Pb), cadmium (Cd), and barium (Ba) from glassware into a food simulant and to evaluate the exposure of each element. The test articles were glassware, including tableware, pots, and other containers. Pb, Cd, and Ba were analysed by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). The analytical performance of the method was validated in terms of its linearity, limit of detection (LOD), limit of quantification (LOQ), recovery, precision, and uncertainty. The monitoring was performed for 110 samples such as glass cups, containers, pots, and bottles. a food simulant. Migration test was conducted at 25? for 24 hours in a dark place using 4% acetic acid as a food simulant. Based on the data; exposure assessment was carried out to compare the estimated daily intake (EDI) to the human safety criteria. The risk levels of Pb and Ba determined in this study were approximately 1.9% and 0.3% of the provisional tolerable weekly intake (PTWI) and tolerable daily intake (TDI) value, respectively, thereby indicating a low exposure to the population.

• Applied Chemistry for Engineering
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• v.34 no.1
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• pp.69-74
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• 2023

As a chemical de-icing method, propylene glycol de-icing fluid is applicable for melting ice caused by snow and ice adhering to the lower part of high-speed rail rolling stock and bogie parts in winter. By spraying propylene-glycol de-icing fluid on high-speed rail rolling stock and bogie parts in advance to minimize snow adhesion, ice-melting efficiency can be further improved. In the case of high-speed rail rolling stock, even if propylene-glycol de-icing fluid is sprayed, the anti-icing performance is poor because the fluid is almost lost on the surface of the vehicle when operating at high speed. In this study, in order to prevent freezing caused by snow and ice adhering to the lower part of high-speed rail rolling stock and bogie parts, we have investigated the properties of propylene-glycol de/anti-icing fluid containing water-repellent agents that prevent surface freezing. We tried to find the optimal component for de/anti-icing fluid for high-speed rail rolling stock by evaluating the ice melting performance, contact angle, and anti-icing performance according to the types of water-repellent agent. As a result of the evaluation, it was confirmed that an de/anti-icing fluid containing an ethoxysilane-type water repellent agent was most suitable.

• Journal of the Korean Society of Food Culture
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• v.37 no.1
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• pp.1-12
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• 2022

This qualitative study analyzed various environmental factors and difficulties faced by school foodservices during the COVID-19 pandemic. Focus group interviews were conducted by enrolling 12 nutrition teachers and nutritionists. Data collected were subsequently analyzed for changes implemented during the pandemic, in hygiene management, diet management, and distribution management of the school meal. The content and method of delivery of information related to diet guidance and school foodservice by related organizations were also examined. Results of the survey show that personal hygiene (such as maintaining student-to-student distance, checking students for a fever, and hand disinfection) was duly applied, installation of table coverings and distancing between school cafeteria seats were conducted, and mandatory mask-wearing to prevent droplet transmission was enforced. Depending on the COVID-19 situation, the number of students having school meals was limited per grade, and time-spaced meals were provided. To prevent infection, menus that required frequent hand contact were excluded from the meal plan. Overall, it was difficult to manage the meal plan due to frequent changes in tasks, such as the number of orders and meal expenses. These changes were communicated by nutrition teachers and nutritionists wherein the numbers of school meals were adjusted, depending on situations arising from each COVID-19 crisis stage. Furthermore, in some schools, either face-to-face nutrition counseling was stopped entirely, or nutrition education was conducted online. Parent participation was disallowed in the monitoring of school meals, and the prohibition on conversations inside the school cafeteria resulted in the absence of communication among students, nutrition teachers, and nutritionists. Additionally, confusion in meal management was caused by frequent changes in the school meal management guidelines provided by the Office of Education and the School Health Promotion Center in response to COVID-19. In anticipation of the emergence of a new virus or infectious diseases caused by mutations in the years to come, it is suggested that a holistic, well-thought-out response manual for safe meal operation needs to be established, in close collaboration with schools and school foodservice-related institutions.

• Journal of the Society of Disaster Information
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• v.18 no.3
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• pp.581-588
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• 2022

Purpose: This study is about offering ways of improving existing technical standards in order to propose how to deal with coal deep-seated fire and to increase effectiveness of wetting agent. Method: This study conducts infiltration experiment using eight tons of coal, three types of wetting agents and fire water. And this study analyzes domestic and international technical standards, overseas experimental cases. Result: It is found that two findings are identified; one is fire water cannot infiltrate into the coal due to high level of surface tension, and the other is three types of wetting agent can infiltrate into the coal to the depth of 5~25cm. Also, domestic wetting agent technical standards include measuring surface tension only and testing wood on extinguishing capacity test. On the other hand, this study found that deep-seated fire experiment using cotton, B-class fire test using heptane are used from abroad. Besides it is analyze that capillary rise test, sink test, contact angle measurement are conducted to increase effectiveness of wetting agent at the U.S. Bureau of Mines. Conclusion: Based on standards and cases of U.S. NFPA and Bureau of Mines, this study suggests that domestic technical standards should include adding a new test standard which measures infiltration directly.