• Science of Emotion and Sensibility
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• v.22 no.3
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• pp.3-20
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• 2019

With advancements in technology of virtual reality, it is used for various purposes in many fields such as medical care and healthcare, but as the same time there are also increasing reports of nausea, eye fatigue, dizziness, and headache from users. These symptoms of motion sickness are referred to as cybersickness, and various researches are under way to solve the cybersickness problem because it can cause inconvenience to the user and cause adverse effects such as discomfort or stress. However, there is no official standard for the causes and solutions of cybersickness at present. This is also related to the absence of tools to quantitatively measure the cybersickness. In order to overcome these limitations, this study proposed quantitative and objective cybersickness evaluation method. We measured 128-channel EEG waves from ten participants experiencing visually stimulated virtual reality. We calculated the relative power of delta and alpha in 11 regions (left, middle, right frontal, parietal, occipital and left, right temporal lobe). Multiple regression models were obtained in a stepwise manner with the motion sickness susceptibility questionnaire (MSSQ) scores indicating the susceptibility of the subject to the motion sickness. A multiple regression model with the highest under the area ROC curve (AUC) was derived. In the multiple regression model derived from this study, it was possible to distinguish cybersickness by accuracy of 95.1% with 11 explanatory variables (P_D.MF, P_D.LP, P_D.MP, P_D.RP, P_D.MO, P_A.LF, P_A.MF, P_A.RF, P_A.LP, P_A.RP, P_A.MO). In summary, in this study, objective response to cybersickness was confirmed through 128 channels of EEG. The analysis results showed that there was a clearly distinguished reaction at a specific part of the brain. Using the results and analytical methods of this study, it is expected that it will be useful for the future studies related to the cybersickness.

• Women's Health Nursing
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• v.17 no.3
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• pp.225-242
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• 2011

Purpose: The purpose of this study was to identify students' experiences of performance and their satisfaction with clinical nursing practice in Women's health nursing. Methods: Data was collected using questionnaire consisting of 104; 89,; and 82 nursing activities with 12; 10; and 7 domains for delivery floor, obstetric, and gynecologic wards retrospectively. Five hundred ninety nursing students from 10 four year and one three year colleges, were recruited and selected for data collection. Results: Site specific core nursing activities among top 15 items of performed experience were: interpreting fetal monitoring; massage for pain reduction; breathing technique; perineal pad change; non stress test; manual check for uterine contraction; and position change for the delivery floor. Experiences of clinical nursing practice for the obstetric ward and the gynecologic ward were identified and ranked as well. Observation of delivery, measurement & test during labor and observation of anesthesia and operation were the highest ranked activity domains of satisfaction for delivery floor, obstetric and gynecologic wards retrospectively. Conclusion: Discussions are needed to standardize curriculum for clinical practice in women's health nursing initiated at the level of Korean Society of Womens' Health Nursing by reflecting this result. Strategic approaches are emphasized in order to enhance a collaboration between clinical fields and colleges.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.1
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• pp.118-126
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• 2011

Ester-linked fatty acid methyl ester (EL-FAME) profiles were used to describe differences in soil microbial communities influenced by conventional farming system (CFS), and organic farming system (OFS) in controlled horticultural land. Soil physicochemical properties and soil microbial communities were determined in the experimental fields. Higher organic matter content in OFS reduced soil bulk density which in turn increased the soil porosity. Generally, soil chemical properties in OFS were higher than those of CFS, but EC value in OFS was significantly lower than that of CFS. With the exception of Fe content, other macronutrient contents and pH in both farming system decreased with the soil depth. Soil microbial biomass of OFS was approximately 1.3 times in topsoil and 1.8 times in subsoil higher than those of CFS. Lower ratios of cy17:0 to $16:1{\omega}7c$ and cy19:0 to $18:1{\omega}7c$ were found in the CFS soils than the OFS soils, indicating that microbial stress decreased. The ratio of MUFA to SFA was higher in OFS due to organic input to the soil. In principal components analysis (PCA), the first variable accounted for 54.3%, while the second for 27.3%, respectively. The PC1 of the PCA separated the samples from CFS and OFS, while the PC2 of the PCA separated the samples from topsoil and subsoil. EL-FAMEs with the positive eigenvector coefficients for PC1 were cy17: 0 to $16:1{\omega}7c$ ratio, cy19:0 to $18:1{\omega}7c$ ratio, soil pH, soil organic matter, and soil $NO_3$-N content. Our findings suggest that the shifting cy19:0 to $18:1{\omega}7c$ ratio should be considered as potential factors responsible for the clear microbial community differentiation observed between different cultivation systems and soil depth in controlled horticultural land.

• Asian Journal of Turfgrass Science
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• v.23 no.1
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• pp.163-176
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• 2009

Investigating endophyte distribution, naturally occurring in native grasses, is important for understanding endophyte-grass associations and using the beneficial effects of endophytes in cultivated plants. The goal of this study was to investigate endophytes from natural Festuca spp. in Yunnan, Guizhou, and Sichuan Provinces of China, and to study the compatibility between the endophytes and turf type tall fescue (Festuca arundinacea) which is widely used for lawn and athletic fields in that region. Of 628 accessions in F. ovina, 421 had endophytes identified in leaf sheath from on-site microscopic examination. From Festuca spp, three isolates were obtained from the seeds and ninety isolates were obtained from seedlings established from the collected seeds. The isolates from F. ovina and F. stapfii were tentatively identified as Neotyphodium typhinum and Neotyphodiumstarii, respectively. We tested compatibility of the two fungal species with seven tall fescue cultivars, Little Hero, Sub Boy, Eldorado, Arid III, Millennium, Crossfire, and Fawn. N. typhinum or N. starii did not infect 'Fawn' with either seed injection or seed soaking method. The highest infection rate byboth N. typhinum and N. starii was in 'Sun Boy' and 'Eldorado'. There were significant interaction effects between tall fescue cultivar and type of endophyte on infection.

• The Journal of Engineering Geology
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• v.30 no.1
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• pp.17-30
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• 2020

An optical televiewer is a geophysical logging device that produces continuous high-resolution full-azimuth images of a borehole wall using a light-emitting-diode and a complementary metal-oxide semiconductor image sensor to provide valuable information on subsurface discontinuities. Recently, borehole imaging logging has been applied in many fields, including ground subsidence monitoring, rock mass integrity evaluation, stress-induced fracture detection, and glacial annual-layer measurements in polar regions. Widely used commercial borehole imaging logging systems typically have limitations depending on equipment specifications, meaning that it is necessary to clearly verify the scope of applications while maintaining appropriate quality control for various borehole conditions. However, it is difficult to directly check the accuracy, implementation, and reliability for outcomes, as images derived from an optical televiewer constitute in situ data. In this study, we designed and constructed a modular fractured borehole model having similar conditions to a borehole environment to report unprecedented results regarding reliable data acquisition and processing. We investigate sonde magnetometer accuracy, color realization, and fracture resolution, and suggest data processing methods to obtain accurate aperture measurements. The experiment involving the fractured borehole model should enhance not only measurement quality but also interpretations of high-resolution and reliable optical imaging logs.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.6
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• pp.528-535
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• 2004

Ultrasonic Vibrator is designed to achieve the maximum vibration amplitude at 30 kHz by in-cluding a horn (diameter, 40 mm), mechanical vibration amplifier at the top of the ultrasonic vibrator in the system and making the complete system resonate. In addition, it is experimentally visualized by particle imaging velocimetry (PIV) that the acoustic streaming velocity in the gap is at maximum when the gap between the ultrasonic vibrator and stationary plate agrees with the multiples of half-wavelength of the ultrasonic wave. This fact results from the resonance of the sound wave and the theoretical analysis of that is also accomplished and verified by experiment. It is observed that the magnitude of the acoustic streaming dependent upon the gap between the ultrasonic vibrator and stationary plate possibly changes due to the measurement of the average velocity fields of the acoustic streaming induced by the ultrasonic vibration at resonance and non-resonance. There exists extremely small average velocity at non-resonant gaps while the relatively large average velocity exists at resonant gaps compared with non-resonant gaps. It also reveals that there should be larger axial turbulent intensity at the hub region of the vibrator and at the edge of it in the resonant gap where the air streaming velocity is maximized and the flow phenomena is conspicuous than that at the other region. Because the variation of the acoustic streaming velocity at resonant gap is more distinctive than that at non-resonant gap, shear stress increases more in the resonant gap and is also maximized at the center region of the vibrator except the local position of center (r〓0). At the non-resonant gap there should be low values of vorticity distribution, but in contrast to the non-resonant gap, high and negative values of it exist at the center region of the vibrator with respect to the radial direction and in the vicinity of the middle region with respect to the axial direction. Acoustic streaming is noise-free due to the ultrasonic vibration and maintenance-free because of the absence of moving parts. Moreover, the proposed method by acoustic streaming can be utilized to the nano and micro-electro mechanical systems as a driving mechanism in addition to the augmentation of the streaming velocity.

• 한국해양학회지
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• v.19 no.2
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• pp.141-152
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• 1984

In order to investigate the circulation dynamics of the Keum River estuary, 300velocity fields obtained at six sites over two tidal cycles by using instantaneous profiling technique were analyzed in detail. In this investigation, the variability of shear velocity, bottom shear stress, drag coefficient, and roughness length scale were confirmed. The measured values of the bottom boundary drag coefficient show wide range of variations, i.e., C$\_$100/=6.78${\times}$10$\^$-5/∼1.15${\times}$10$\^$-1/, and the mean of 300 measurements is 1.6${\times}$10$\^$-2/. The relationship between U* and C$\_$100/ also show the scatter in values. However, overall mean values over two tidal cycles at 6 stations show that if U* 1cm/s, C$\_$100/ is unpredictable, if U* 1cm/s, C$\_$100/ increase with U*. The values of Re$\_$100/ and C$\_$100/ have scatter. But the overall mean values over two tidal cycles show that if Re$\_$100/ 3.6${\times}$10$\^$5/, C$\_$100/ is unpredictable, if Re$\_$100/ 3.6${\times}$10$\^$5/, C$\_$100/=1.4${\times}$10$\^$-2/. Finally the flow regime of the Keum River estuary was classified as "subcritical fully turbulent" flow.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.4
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• pp.373-388
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• 2010

Fracture causes serious problems in many instance of prosthetic failures. But it is hard to find the definite causes when fractures occur. Fractography encompasses the examination of fracture surfaces that contain features resulting from the interaction of the advancing crack with the microstructure of the material and the stress fields. All fractured specimens(implant retaining screw) retrieved from Gangneung-Wonju national university dental hospital for 3 years(from 2007 to 2009). After pretreatment of samples, the scanning electon microscope were used for surface examination and fracture analysis. In case of most of the fractured specimens, fracture took place by fatigue fracture and fractured surface represents fatigue striation. Fatigue striation indicate the progression of the crack front under cyclic loading, are characteristic of stage 2 crack growth. The site of crack initiation and stage 1 crack growth were not easily identified in any of the failure, presumably because of the complex microstructural features of the polycrystalline sample. In case of fractured by overload, dimpled or cleavage surface were observed. Using the interpretation of characteristic markings(ratchet mark, fatigue striation, dimple, cleavage et al) in fracture surfaces, failure events containing the crack origin, crack propagation, material deficiency could be understand. Using the interpretation of characteristic markings in fracture surfaces, cause and mechanism of fractures could be analyzed.

• Journal of Korean Society of Forest Science
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• v.84 no.1
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• pp.1-9
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• 1995

This study investigates the collective aspects of hunting motivation and hunters' attitude toward natural environment. Data were collected from three different types of respondents : 148 hunters who purchased hunting license between November 1992 and March 1993 in Cholla Province. 120 university students and 260 Suwon residents. The 26 items out of 90 items were selected to develop an attitude scale toward natural environment. Results of ANOVA revealed that there were significant differences among five groups(hunters, urban residents and students from 3 major fields) in terms of their attitude values. Hunters' attitude value toward natural environment was the highest among five different types of respondents. Two major motives for hunting participation are 'exercise' and 'like out-of-doors'. Factor analysis presents eight motivational dimensions underlying hunter's involvement in the activities: 1)stewardship, 2)social contact, 3)show-off, 4)sportsmanship, 5)like to kill, 6)recreation/relax, 7)economic gain, and 8)being alone. The correlation between the motivational factor of 'economic gain' and the attitudinal item of 'relationship between man and nature' was negative(r=-0.28). There is a positive correlation(r=0.24) between the motivation of 'being alone' and the attitude of 'needs for natural environment'. These relationships indicate that individual's attitude value decreases when one perceives nature as economic goods, while it increases when one visits nature to relieve stress and to develop self-esteem.

• Toxicological Research
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• v.33 no.3
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• pp.239-253
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• 2017

Neodymium is a future-oriented material due to its unique properties, and its use is increasing in various industrial fields worldwide. However, the toxicity caused by repeated exposure to this metal has not been studied in detail thus far. The present study was carried out to investigate the potential inhalation toxicity of nano-sized neodymium oxide ($Nd_2O_3$) following a 28-day repeated inhalation exposure in male Sprague-Dawley rats. Male rats were exposed to nano-sized $Nd_2O_3-containing$ aerosols via a nose-only inhalation system at doses of $0mg/m^3$, $0.5mg/m^3$, $2.5mg/m^3$, and $10mg/m^3$ for 6 hr/day, 5 days/week over a 28-day period, followed by a 28-day recovery period. During the experimental period, clinical signs, body weight, hematologic parameters, serum biochemical parameters, necropsy findings, organ weight, and histopathological findings were examined; neodymium distribution in the major organs and blood, bronchoalveolar lavage fluid (BALF), and oxidative stress in lung tissues were analyzed. Most of the neodymium was found to be deposited in lung tissues, showing a dose-dependent relationship. Infiltration of inflammatory cells and pulmonary alveolar proteinosis (PAP) were the main observations of lung histopathology. Infiltration of inflammatory cells was observed in the $2.5mg/m^3$ and higher dose treatment groups. PAP was observed in all treatment groups accompanied by an increase in lung weight, but was observed to a lesser extent in the $0.5mg/m^3$ treatment group. In BALF analysis, total cell counts, including macrophages and neutrophils, lactate dehydrogenase, albumin, interleukin-6, and tumor necrosis factor-alpha, increased significantly in all treatment groups. After a 4-week recovery period, these changes were generally reversed in the $0.5mg/m^3$ group, but were exacerbated in the $10mg/m^3$ group. The lowest-observed-adverse-effect concentration of nano-sized $Nd_2O_3$ was determined to be $0.5mg/m^3$, and the target organ was determined to be the lung, under the present experimental conditions in male rats.