• ETRI Journal
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• v.38 no.6
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• pp.1052-1063
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• 2016

We propose a millimeter wave (MMW)-based mobile hotspot network (MHN) system for application in high-speed railways that is capable of supporting a peak backhaul link throughput of 1 Gbps per train at 400 km/h. The MHN system can be implemented in subways and high-speed trains to support passengers with smart devices and provide access to the Internet. The proposed system can overcome the inherent high path loss in MMW through system designs and high antenna gains. We present a simulation of the system performance that shows that a fixed beamforming strategy can provide high signal-to-interference-plus-noise-ratio similar to those of an adaptive beamforming strategy, with the exception of 15% of the train path in which the network can use link adaptation with low-order modulation formats or trigger a handover to maintain the connection. We also demonstrate the feasibility of the MHN system using a test bed deployed in Seoul subway line 8. The backhaul link throughput varies instantaneously between 200 Mbps and 500 Mbps depending on the SNR variations while the train is running. During the field trial, the smartphones used could make connections through offloading.

• Bulletin of the Korean Chemical Society
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• v.19 no.5
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• pp.569-575
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• 1998

Investigation of the structure of the gangliosides has proven to be very important in the understanding of their biological roles. We have determined the tertiary structure of asialoganglioside GM1 $(GA_1)$ using NMR spectroscopy and distance geometry calculations. All of the structures are very similar except the glycosidic torsion angles in the ring IV and ring III linkages. There are two low-energy structures for GA1, G1 and G2. G1 differs from G2 only in the IV-III glycosidic linkages and the orientation of acetamido group in ring III. There is a stable intramolecular hydrogen bond between the third hydroxyl group in ring I and the ring oxygen atom in ring II. Also, there may be a weak hydrogen bond between the second hydroxyl group in ring IV and the acetamido group in ring III. Small coupling constants of $^3J_{IH3,IOH3}\; and\; ^3J_{IVH2,IVOH2}$ support this result. Overall structural features of $(GA_1)$ are very similar to those of $(GM_1)$. It implicates that specificities of the sugar moieties in GM1 are caused not by their tertiary foldings, but mainly by the electrostatic interactions between the polar sialic acid and its receptors. Since it is evident that $(GA_1)$ is more hydrophobic than $(GA_1)$, a receptor with a hydrophobic binding site can recognize the $(GA_1)$ better than $(GA_1)$. Studies on the conformational properties of $(GA_1)$ may lead to a better understanding of the molecular basis of its functions.

• Journal of the Korea Society of Computer and Information
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• v.25 no.3
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• pp.229-234
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• 2020

The purpose of this study is to empirically analyze the structural relationship between parental rearing attitude, social support for teenagers and the mobile phone dependency. In this paper, we survey for teenagers in Gmetropolitan city and the collected data were analyzed using Amos 18.0. The results showed that the parental rearing attitude had a significant influence on social support for teenagers and also the parenting attitude and social support had a important effect on teenagers' mobile phone dependency. In addition, social support was found to have a mediating effect on the relationship between parental rearing attitude and teenagers' mobile phone dependency. Therefore, we resulted that parental rearing attitude and social supports were important variable factors to lower the teenagers' mobile phone dependency.

• Journal of the Korean Society of School Health
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• v.30 no.2
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• pp.113-123
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• 2017

Purpose: The purpose of this study was to examine and compare the academic engagement, academic burnout, stress, and social support among undergraduate nursing students by grade. Methods: The study is a descriptive comparative survey. The participants were 247 undergraduate nursing students enrolled in 3 universities located in G city. The collected data was analyzed with descriptive statistics, $x^2$ tests, and analysis of covariance, using SPSS/WIN 21.0 program. Results: The students showed significant differences in academic engagement, academic burnout, and stress according to their grade. The post-hoc analysis results showed that sophomores and juniors had lower academic engagement and higher academic burnout and stress than others (i.e., freshmen, or seniors). There was no significant difference in social support among nursing students. Academic engagement had a positive correlation with social support and a negative correlation with academic burnout and stress. Also, academic burnout had a positive correlation with stress and a negative correlation with academic engagement and social support. Conclusion: The findings indicate that nursing students in second and third grade were at risk of academic burnout and under severe stress. Therefore, sophomores and juniors need more attention and care to help them relieve and control stress and burnout and to improve their academic engagement. Also, the findings should be considered when developing plans and/or interventions for nursing students' major adjustment and academic achievement.

• Smart Structures and Systems
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• v.23 no.6
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• pp.641-651
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• 2019

The stochastic stability control of the parameter-excited vibration of an inclined stay cable with multiple modes coupling under random and periodic combined support disturbances is studied by using the direct eigenvalue analysis approach based on the response moment stability, Floquet theorem, Fourier series and matrix eigenvalue analysis. The differential equation with time-varying parameters for the transverse vibration of the inclined cable with control under random and deterministic support disturbances is derived and converted into the randomly and deterministically parameter-excited multi-degree-of-freedom vibration equations. As the stochastic stability of the parameter-excited vibration is mainly determined by the characteristics of perturbation moment, the differential equation with only deterministic parameters for the perturbation second moment is derived based on the $It{\hat{o}}$ stochastic differential rule. The stochastically and deterministically parameter-excited vibration stability is then determined by the deterministic parameter-varying response moment stability. Based on the Floquet theorem, expanding the periodic parameters of the perturbation moment equation and the periodic component of the characteristic perturbation moment expression into the Fourier series yields the eigenvalue equation which determines the perturbation moment behavior. Thus the stochastic stability of the parameter-excited cable vibration under the random and periodic combined support disturbances is determined directly by the matrix eigenvalues. The direct eigenvalue analysis approach is applicable to the stochastic stability of the control cable with multiple modes coupling under various periodic and/or random support disturbances. Numerical results illustrate that the multiple cable modes need to be considered for the stochastic stability of the parameter-excited cable vibration under the random and periodic support disturbances, and the increase of the control damping rather than control stiffness can greatly enhance the stochastic stability of the parameter-excited cable vibration including the frequency width increase of the periodic disturbance and the critical value increase of the random disturbance amplitude.

• Geomechanics and Engineering
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• v.25 no.3
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• pp.233-243
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• 2021

Rib spalling is a major issue affecting the safety of steeply inclined coal seam. And the failure coal face and support system can be affected with each other to generate a vicious cycle along with inducing large-scale collapse of surrounding rock in steeply inclined coal seam. In order to analyze failure mechanism and propose the corresponding prominent control measures of steeply inclined coal working face, mechanical model based on coal face-support-roof system and mechanical model of coal face failure was established to reveal the disaster mechanism of rib spalling and the sensitive analysis of related factors was performed. Furthermore, taking 3402 working face of Chen-man-zhuang coal mine as engineering background, numerical model by using FLAC3D was built to illustrate the propagation of displacement and stress fields in steeply inclined coal seam and verify the theory analysis as mentioned in this study. The results show that the coal face slide body in steeply inclined working face can be observed as the failure height of upper layer smaller than that of lower layer exhibiting with an irregular quadrilateral pyramid shape. Moreover, the cracks were originated from the upper layer of sliding body and gradually developed to the lower layer causing the final rib spalling. The influence factors on the stability of coal face can be ranked as overlying strata pressure (P) > mechanical parameters of coal body (e.g., cohesion (c), internal fraction angle (φ)) > support strength (F) > the support force of protecting piece (F') > the false angle of working face (Θ). Moreover, the corresponding control measures to maintain the stability of the coal face in the steeply inclined working face were proposed.

• Journal of Industrial Convergence
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• v.21 no.6
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• pp.73-80
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• 2023

The purpose of this study was to identify the stress, social support, and happiness in undergraduate nursing students who experienced the COVID-19 pandemic, and to identify factors affecting happiness. The survey was conducted from December 18, 2022 to January 5, 2023. The subjects were 195 first and second grades nursing students attending two universities located in G city. Data were analyzed by t-test, ANOVA, Scheffe test, Games-Howell test, Pearson's correlation, and multiple regression. Statistically, happiness showed a significantly negative correlation stress(r=-.17, p=.017) and positive correlation with social support(r=.68, p<.001). Influencing factors on happiness were social support(β=.63, p<.001) and department satisfaction(β =.30, p<.001) accounting for 49.7% of the total change. In order to improve the happiness of nursing students based on the results of this study, strategies and programs that can increase social support and department satisfaction are needed.

• Women's Health Nursing
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• v.28 no.1
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• pp.27-37
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• 2022

Purpose: The purpose of this study was to investigate the association between maternal knowledge and social support on pregnancy stress among pregnant women in Korea. Methods: The participants in this study were 148 pregnant women in Korea, recruited from online communities on pregnancy and/or childbirth, from June 2019 to April 2020. The collected data were analyzed using the independent t-test, one-way analysis of variance, Pearson correlation coefficient, and multiple regression. Results: Participants were at average 18.25±8.28 weeks gestation, 56% were in the second trimester, 31% had one or more health issues in the current pregnancy (e.g., hyperemesis gravidarum), and 76% were first-time mothers. Participants had moderate levels of pregnancy stress (mean, 23.09±7.11 points out of 48) and maternal knowledge (mean, 14.42±4.67 points out of 21), whereas social support was somewhat high (mean 45.88±7.81 points out of 60). Pregnancy stress was weakly negatively correlated with social support (r=-.37, p<.001). Main source of pregnancy information (β=-.21, p=.011), marital satisfaction (β=-.18, p=.036), and social support (β=-.19, p=.038) were identified as significant factors affecting pregnancy stress, and these variables had an explanatory power of 22.7% for pregnancy stress. Conclusion: Based on these findings, nurses should assess pregnancy-related stress during pregnancy and consider main source of pregnancy information and marital satisfaction when providing education or counseling. Moreover, strategies to reduce pregnancy stress through social support are needed to improve the quality of life for pregnant women.

• Korean Journal of Applied Biomechanics
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• v.26 no.2
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• pp.221-228
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• 2016

Objective: The purpose of this study was to investigate differences in gait parameters and symmetry between walking speed by using the Froude number and preferred walking speed. Method: Fifty adults (age: $21.0{\pm}1.7years$, body weight: $71.0{\pm}9.2kg$, height: $1.75{\pm}0.07m$, leg length: $0.89{\pm}0.05m$) participated in this study. Leg length-applied walking speed was calculated by using the Froude number, defined as Fr = ${\upsilon}^2$/gL, where v is the velocity, g is the gravitational acceleration, and L is the leg length. Video data were collected by using eight infrared cameras (Oqus 300, Qualysis, Sweden) and the Qualisys Track Manager software (Qualisys, Sweden), with a 200-Hz sampling frequency during two-speed walking (preferred walking speed [PS] and leg length-applied walking speed [LS]) on a treadmill (Instrumented Treadmill, Bertec, USA). The step length, stride length, support percentage, cadence, lower joint angle, range of motion (ROM), and symmetry index were then calculated by using the Matlab R2009a software. Results: Step and stride lengths were greater in LS than in PS (p < 0.05). The right single-support percentage was greater in LS than in PS (p < 0.05). The hip joint angle at heel contact and toe-off were greater in LS than in PS (p < 0.05). The hip and knee joint ROM were greater in LS than in PS (p < 0.05). Conclusion: Based on our findings, we suggest that increased walking speed had a significant effect on step length, stride length, support percentage, and lower joint ROM.

• Physical Therapy Korea
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• v.26 no.4
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• pp.70-76
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• 2019

Background: An excessive pronated foot is defined as a flattening or complete loss of the medial longitudinal arch. Excessive foot pronation is considered to have high risk factors of overuse injuries in the lower limb. Various treatments have been investigated in attempts to control excessive pronation. Objects: This meta-analysis identifies the effects of an anti-pronation taping technique using different materials. Methods: The electronic databases used include MEDLINE, the Physiotherapy Evidence Database (PEDro), Science Direct, the Korean Studies Information Service System (KISS), the Research Information Sharing Service (RISS), the Korea National Library, and the Korean Medical Database (studies published up to July 31, 2019). The database search used the following keywords: "foot drop" OR "foot arch" OR "foot pronation" OR "flat foot (pes planus)" AND "taping" OR "support." Eight eligible studies were analyzed to determine the effectiveness of anti-pronation taping in study and control groups. Results: The overall random effect size (Hedges'g) of the anti-pronation taping technique was 0.147 (95% confidence interval [CI]: -.214 to .509). When the effect (Hedges' g) was compared by the type of tape material, rigid tape (RT; Lowdye taping) was .213 (95% CI: -.278 to .704) and kinesiotape (KT; arch support taping) was -.014 (95% CI: -.270 to .242). Based on this meta-analysis, it was not possible to identify the extent to which anti-pronation taping was effective in preventing navicular drop, improving balance, or changing foot pressure. Only three of the eight eligible studies applied KT on excessive pronated feet, and the outcome measure areas were different to those of the RT studies. The KT studies used EMG data, overall foot posture index (FPI) scores, and rear foot FPI scores. In contrast, the RT studies measured navicular heights, various foot angles, and foot pressure. Conclusion: This review could not find any conclusive evidence about the effectiveness of any taping method for patients with pronated feet. Future studies are needed to develop the anti-pronation taping technique based on the clinical scientific evidence.