• Research in Community and Public Health Nursing
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• v.33 no.3
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• pp.312-320
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• 2022

Purpose: This study was performed to explore the effect of the delivery format on teaching presence, learning presence, and learning outcomes in distance learning of nursing students. Methods: A descriptive survey was conducted to understand teaching presence, learning presence, and learning outcomes depending on the delivery format of distance learning. Quota sampling methodology was used to recruit 295 nursing students from all over the country, and data collection was done from July 27 to September 10, 2020. The first delivery format for distance learning was synchronous learning in which communication between the instructor and students occurred simultaneously. The second delivery format was asynchronous learning in which prerecorded videos were provided and communication did not occur simultaneously. Results: In synchronous learning, teaching presence (especially direct facilitation) and learning presence (especially emotional expression) had a statistical significance that was higher than in asynchronous learning. However, in learning outcomes, there was no statistically significant difference. There were significant positive correlations between teaching presence, learning presence, and learning outcomes, and there were significant positive correlations. Conclusion: It can be suggested that learning outcomes can be improved if presence is improved in the distance learning environment based on the results of this study. It is necessary to add contact with nursing students and instructors to improve teaching presence in the asynchronous learning, and it is necessary to help students express their emotions to improve learning presence.

• Membrane and Water Treatment
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• v.14 no.2
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• pp.77-83
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• 2023

As a result of algal bloom, algal organic matters (AOMs) are rapidly increased in surface water. AOMs can act as precursors for the formation of harmful disinfection by-products (DBPs), which are serious problems in water treatment and human health. The main aim of this study is to characterize the formation of DBPs from AOMs produced by three different algae such as Oscillatoria sp., Anabaena sp., and Microcystis aeruginosa under different algal growth phases. In an effort to examine formation of DBPs during chlorination, chloroform (TCM), dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) were determined under various CT (product of disinfectant concentration and contact time, mg·min/L) values. Generally, the amounts of DBPs tended to increase with increasing CT values at the most growth phases. However, there was a significant difference between the amounts of DBPs produced by the three algal species at different growth phases. This result is likely due to the chemical composition variability of AOM from different algae at different growth phases. In addition, the effect of pre-ozonation on coagulation for the removal of AOMs from three algal species was investigated. The pre-ozonation had a positive effect on the coagulation/flocculation of AOMs.

• Journal of Korea Society of Digital Industry and Information Management
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• v.20 no.1
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• pp.47-58
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• 2024

The serving robot is defined as a robot that carries cooked food to a customer table or collects and carries bowls after eating. This study presented a research model to find out the causal relationship between customer satisfaction and continuous use intention through the three factors of serving robot service quality. In addition, in order to empirically verify the above research model, a survey was conducted on customers using serving robots within the last 5 months. 300 copies were analyzed using SPSS 20 as the final analysis, excluding unfaithful responses. The main findings of this study are as follows. First, serving robot service quality (typical) found to have significant effect on customer satisfaction and continuous use intention. Second, it was found that serving robot service quality (reliability) had a significant effect on customer satisfaction and continuous use intention. Third, it was found that serving robot service quality (ease) did not significantly affect customer satisfaction and continuous use intention.

• The Plant Pathology Journal
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• v.40 no.2
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• pp.192-204
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• 2024

In this study, the efficacy of the essential oil of Mentha longifolia, Achillea arabica and Artemisia absinthium plants were evaluated against important soil-borne fungal pathogens as Verticillium dahliae, Rhizoctonia solani, and Fusarium oxysporum. Essential oils were obtained from plants by hydrodistillation method and the chemical components of essential oils were determined by analyzing by gas chromatography-mass spectrometry. The main components found as piperitone oxide (13.61%), piperitenone oxide (15.55%), pulegone (12.47%), 1-menthone (5.75%), and camphor (5.75%) in M. longifolia, á-selinene 13.38%, camphor 13.34%, L-4-terpineneol 8.40%, (-)-á-Elemene 7.01%, 1,8-cineole 4.71%, and (-)-spathulenol 3.84% in A. arabica, and á-thujone (34.64%), 1,8-cineole (19.54%), pulegone (7.86%), camphene (5.31%), sabinene (4.86%), and germacrene-d (3.67%) in A. absinthium. The antifungal activities of the oils were investigated 0.05, 0.1, 0.25, 0.5, 1.00, and 2.00 μl/ml concentrations with the contact effect method. M. longifolia oil (1.00 and 2.00 μl/ml) has displayed remarkable antifungal effect and provided 100% inhibition on mycelial growth of V. dahliae, R. solani and F. oxysporum. The results obtained from this study may contribute to the development of new alternative and safe methods against soil-borne fungal pathogens.

• Journal of the Korean Physical Society
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• v.81
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• pp.942-947
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• 2022

We report the electrical transport properties of a dual-gate graphene device placed on a CaF₂ substrate. A hexagonal boron nitride top-gate dielectric was introduced to confirm the electrical characteristics of the CaF₂/graphene transistor because it is difficult to inject sufficient carriers through the CaF₂ substrate owing to its thickness of 500 ㎛, and the typical ambipolar behavior of graphene with a slight n-doping effect was clearly observed. In addition, we used a polymethyl methacrylate (PMMA) film as a top-gate dielectric for large-scale graphene devices grown via chemical vapor deposition, which was transferred onto a CaF₂ substrate. We controlled the high gate leakage current caused by the breakdown of the polymer due to non-uniformity by applying the film-transfer process rather than the direct coating method on the graphene device. Furthermore, the transport properties of large-area graphene in contact with CaF₂ are discussed with respect to the effect of top-contacted PMMA.

• Korean Journal of Materials Research
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• v.1 no.3
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• pp.132-138
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• 1991

A comparision was made on the influence of BPSG flow temperatures on the electrical properties in submicron CMOS DRAMs containing two BPSG layers. Three different combinations of BPSG flow temperature such as $850^{\circ}C/850^{\circ}C,\;850^{\circ}C/900^{\circ}C,\;and\;900^{\circ}C/900^{\circ}C$ were employed and analyzed in terms of threshold, breakdown and isolation voltage along with sheet resistance and contact resistance. In case of $900^{\circ}C/900^{\circ}C$ flow, the threshold voltage of NMOS was decreased rapidly in channel length less than $0.8\mu\textrm{m}$ with no noticeable change in PMOS and a drastic decrease in breakdown voltages of NMOS and PMOS was observed in channel length less than and equal to $0.7\mu\textrm{m}$ and $0.8\mu\textrm{m}$, respectively. Little changes in threshold and breakdown voltages of NMOS and PMOS, however, were shown down to channel length of $0.6\mu\textrm{m}$ in case of $850^{\circ}C/850^{\circ}C$ flow. The isolation voltage was increased with decreasing BPSG flow temperature. A significant increase in the sheet resistance and contact resistance was noticeable with decreasing BPSG flow temperature from $900^{\circ}C$ to $850^{\circ}C$. All these observations were rationalized in terms of dopant diffusion and activation upon BPSG flow temperature. Some suggestions for improving contact resistance were made.

• Journal of Adhesion and Interface
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• v.11 no.4
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• pp.149-154
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• 2010

Interfacial evaluation was investigated for single-carbon fiber/phenolic and carbon nanotube (CNT)-phenolic composites by micromechanical technique and electrical resistance measurement combined with wettability test. Compressive strength of pure phenol and CNT-phenolic composites were compared using Broutman specimen. The contact resistance of CNT-phenolic composites was obtained using a gradient specimen by two and four-point methods. Surface energies and wettability by dynamic contact angle measurement were measured using Wilhelmy plate technique. Since hydrophobic domains are formed as heterogeneous microstructure of CNT in the surface, the dynamic contact angle exhibited more than $90^{\circ}$. CNT-phenolic composites exhibited a higher apparent modulus than neat phenolic case due to better stress transferring effect. Work of adhesion, $W_a$ between single-carbon fiber and CNT-phenolic composites exhibited higher than neat phenolic resin due to the enhanced viscosity by CNT addition. It was consistent with micro-failure patterns in microdroplet test.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.9
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• pp.480-485
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• 2017

The main reason for the heat induced accidents occurring at the after stern tube journal bearing is the excessive local pressure caused by the deflection of the propulsion shaft due to the propeller loads. It is expected that the contact area could beenlarged and the local pressure reduced accordingly by using a lining material having alow Young's modulus instead of the existing white metal. The purpose of this work is to investigate the characteristics of the pressure distribution and determine the allowable pressure value in the case where bearing products made of materials having a low Young's modulus are used. In this study, the propeller loads, heat effect, and hull deflection are considered in the evaluation of the local pressure of the ship propulsion shaft. Also, the Hertzian contact condition was applied. From the analysis results in the case where a lining material with a low Young's modulus was used, it was found that a robust design could be achieved and the local pressure could be reduced effectively independent of the load conditions. It will be possible to producenew products made of materials having a low Young's modulus if the manufacturer confirms the performance specifications drawn by this study.

• Korean Journal of Applied Biomechanics
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• v.12 no.1
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• pp.15-30
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• 2002

The purpose of this study was analyzed the effect of kinematical and kinetical factors of lower extremity of form change in the cause of growth an unborn child during in pregnancy. Three pregnant women were selected from pregnant 24 weeks as subjects. Each subjects were required to walk with usual walking speed. Cinematographic and GRF data were collected during walking, and the kinematical and kinetical variables were calculated using Kwon3d. Based on the results of the study, the following conclusions were drawn : 1. Step width and Step length The change of form during the period of pregnancy was not statistically found significant in the step width and the step length. 2. Angle of lower extremity 1) The change of form during the period of pregnancy was not statistically found significant in the hip angle at right heel contact, mid stance, but it was statistically found significant in the hip angle at toe off on p<.05. 2) The change of form during the period of pregnancy was not statistically found significant in the knee angle at right heel contact, mid stance, but it was statistically found significant in the knee angle at toe off on p<.05. 3) The change of form during the period of pregnancy was not statistically found significant in the ankle angle at right heel contact, mid stance, but it was statistically found significant in the ankle angle at toe off on p<.05. 3. Ground reaction force 1) The change of form during the period of pregnancy was statistically found significant in medial-lateral force(Fx) on p<.001. 2) The change of form during the period of pregnancy was not statistically found significant in post-anterior force(Fy). 3) The change of form during the period of pregnancy was statistically found significant in impulse force and minimum peak of vertical reaction force on p<.001, p<.01 but it was not statistically found significant in second maximum force.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.34 no.3
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• pp.163-172
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• 2012

Purpose: Diabetes mellitus (DM) has been shown to alter the properties of the bone and impair bone healing around a titanium implant. The aim of this study is to investigate whether the low-intensity pulsed ultrasound (LIPUS), which has been known to stimulate the bone healing, improve the osseointegration of the titanium implant in tibia of DM-induced rats. Methods: 16 rats were received streptozotocin (60 mg/kg) for inducing diabetes. A total number of 32 titanium implants were placed bilaterally into both tibiae of these rats. The right tibia of each rat received LIPUS application (10 min/day) during 7 days post-operation, while the left side received no treatment. The study was carried on for six weeks and the rats were sacrificed at 1, 2, 4, and 6 weaks postoperatively (4 rats for each week) for histomorphometric and histologic analysis. Bone-implant contact and bone area were measured. Comparisons between the groups were made using statistical analysis on histomorphometric analysis. Results: The histomorphometry parameters showed that the bone-implant contact and the bone area values have decreased in the late osseointegration periods (4, 6 weeks) compared to the early osseointegration periods (1, 2 weeks) in both two groups. The bone-implant contact values of the LIPUS group were somewhat higher than those of controls at 1, 2 weeks, but the difference was not statistically significant. The bone area values of the LIPUS group were also higher than those of controls at 1, 2 weeks, but the difference was not statistically significant as well. Conclusion: Results of this study indicate that LIPUS may have positive effects on early osseointegration but could not improve the long term stability of dental implants.