• Journal of the Korean Society of Marine Environment & Safety
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• v.16 no.2
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• pp.201-207
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• 2010

Recently, about 600 cases of marine accidents occur annually in Korea. According to many studies and analyses on occurrence of marine accidents, 70~80% of marine accidents were caused by human factors. Among the human factors, navigation officers' fatigue is very important factor. Although navigation officers' fatigue serves as an important role in marine accidents, there is no method to exactly examine the degree of officers' fatigue. Accordingly, this study analyzed human factors according to types of marine accidents and extracted important five factors affecting navigation officers' fatigue through the questionnaire survey by means of literatures and 5-point scale. In addition, evaluation factors of marine accident risks caused by fatigue factors were divided and structured by using ISM. Lastly, it found out the importance of each fatigue factor drawn by AHP and decided marine accidents that were most highly caused by navigation officers' fatigue in order. At the result, weights were high as sleep time 0.385, stress 0.302, health condition 0.139, rest time 0.099, alcohol and drug 0.074 in fatigue factors, and death and injury 0.328, collision 0.308, grounding 0.195, sinking 0.094, fire accident 0.075 in evaluation factors of marine accident risks. Therefore, the control plan to lower marine accident risks should be prepared on the basis of high weight factors.

• The Journal of the Convergence on Culture Technology
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• v.6 no.2
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• pp.55-70
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• 2020

This study aims to identify the influence of risk-inducing factors and safety inspection on the measures of reducing accidents among workers of building structures in small construction sites. The result can be summarized as follows: First, as for the influence of risk-inducing factors on human factors, preparation for work, disintegrating molds, taking follow-up measures, and keeping records, have statistically significant influences. Therefore, it can be said that safety inspection has a partial mediating effect in the relationship between risk-inducing factors and human factors. Second, as for the influence of risk-inducing factors on facility factors, preparation for work, and taking follow-up measures influenced significantly. This indicates that safety inspection has a partial mediating effect in the relationship between risk-inducing factors and facility factors. Third, as for the influence of risk-inducing factors on management factors, the installation of shores and risk assessment are found to have significant effects. This shows that safety inspection has a partial mediating effect in the relationship between risk-inducing factors and management factors. Fourth, the influence of risk-inducing factors on work factors was significant only in the installation of shores. This indicates that safety inspection has a completely mediating effect in the relationship between risk-inducing factors and work factors. Finally, in the relationship between risk-inducing factors and accident reduction measures, preparation for work, installation of shores, and taking follow-up measures showed significantly positive influences. In contrast, keeping records has a significant negative influence. Thus, safety inspection has a partial mediating effect in the relationship between risk-inducing factors and management factors.

• Journal of the Korea Concrete Institute
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• v.23 no.3
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• pp.321-330
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• 2011

Recently, the effects of high temperature and fiber content on the residual mechnical properties of high-strength concrete were experimentally investigated. In this paper, residual mechanical properties of concrete with water to cement (w/c) ratios of 0.55, 0.42 and 0.35 exposed to high temperature are compared with those obtained in fiber reinforced concrete with similar characteristics ranging from 0.05% to 0.20% polypropylene (PP) fiber volume percentage. Also, factors including pre-load levels of 20% and 40% of the maximum load at room temperature are considered. Outbreak time, thermal strain, length change, and mass loss were tested to determine compressive strength, modulus of elasticity, and energy absorption capacity. From the results, in order to prevent the explosive spalling of 50 MPa grade concretes exposed to high temperature, more than 0.05 vol. % of PP fibers is needed. Also, the cross-sectional area of PP fiber can influence the residual mechanical properties and spalling tendency of fiber reinforced concrete exposed to high temperature. Especially, the external loading increases not only the residual mechanical properties of concrete but also the risk of spalling and brittle failure tendency.

• Journal of the Korean earth science society
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• v.38 no.2
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• pp.161-171
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• 2017

Observed ground motions are composed of three factors such as, seismic source, attenuation, and site amplification effect. Among them, the site amplification characteristics should be considered significantly when estimating seismic source and attenuation characteristics with more confidence. The site effect is also necessary when estimating not only seismic hazard in seismic design engineering but also rock mechanical properties. This study uses the method of H/V spectral ratio of observed ground motion between target site and reference site called a reference site method. In addition to using the vertical Fourier spectrum of the reference site, we try out the horizontal Fourier spectrum as a new method in this study. We analyze H/V spectral ratio of six ground motions respectively, observed at four sites close to Yedang Reservoir. We then compare site amplification effects at each site using 3 kinds of seismic energies including S waves, Coda waves energy, and background noise. The results suggest that each site showed similar site amplification patterns in S waves and Coda waves energy. However, the site amplification of background noise shows much different characteristics from those of S waves and Coda wave energy, which suggests that the background noises at each site have their own developing mechanism. Each station shows its own characteristics of specific resonance frequency and site amplification properties in low, high and specific resonance frequency ranges. Comparison of the method used in this study to the others that used different methods can provide us with more information about the dynamic amplification of a site characteristics and site classification.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.12
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• pp.1009-1015
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• 2014

The present study investigated the effects of non-equilibrium condensation with the angle of attack on the coefficients of pressure, lift, and drag in the transonic 2-D flow of NACA0012 by numerical analysis of the total variation diminishing (TVD) scheme. At $T_0=298k$ and ${\alpha}=3^{\circ}$, the lift coefficients for $M_{\infty}=0.78$ and 0.81 decreased monotonically with increasing ${\Phi}_0$. In contrast, for $M_{\infty}$ corresponding to the Mach number of the force break, $C_L$ increased with ${\Phi}_0$. For ${\alpha}=3^{\circ}$ and ${\Phi}_0=0%$, $C_D$ increased markedly as $M_{\infty}$ increased. However, at ${\Phi}_0=60%$ and ${\alpha}=3^{\circ}$, which corresponded to the case of the condensation having a large influence, $C_D$ increased slightly as $M_{\infty}$ increased. The decrease in profile drag by non-equilibrium condensation grew as the angle of attack and stagnation relative humidity increased for the same free stream transonic Mach number. At ${\Phi}_0=0%$, the coefficient of the wave drag increased with the attack angle and free stream Mach number. When ${\Phi}_0$ > 50%, the coefficient of the wave drag decreased as ${\alpha}$ and $M_{\infty}$ increased. Lowering ${\Phi}_0$ and increasing $M_{\infty}$ increased the maximum Mach number.

• Applied Chemistry for Engineering
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• v.16 no.2
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• pp.296-303
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• 2005

The co-pyrolysis characteristics of polyvinylchloride (PVC) and acrylonitrile butadiene styrene (ABS) mixtures with various mixing ratios and effect of addition of CaO and $Cu_2O$ have been studied using thermogravimetry (TG) and gas chromatograph-mass spectrometry (GC-MS). In an isothermal decomposition conducted at $500^{\circ}C$, the yields of styrene monomers and aromatic compounds increased as the mixing ratio of ABS increased, and the yield of BTX compounds reached its maximum (16.14%) when the mixing ratios of PVC and ABS was 4:1. In an isothermal decomposition added with metal oxides, the maximum yield of liquid product was 73% when CaO [CaO/(PVC+ABS)=0.4] was added and it was 70% when $Cu_2O$ [$Cu_2O$/(PVC+ABS)=0.4] was added, respectively, where HCl contained in the gaseous product was completely removed when added with CaO [CaO/(PVC+ABS)=0.5] and $Cu_2O$ [$Cu_2O$/(PVC+ABS)=1.0]. Therefore, to obtain the highest yield of liquid product it appears to be the reaction condition: the reaction temperature of $500^{\circ}C$ and mixing ratios of CaO and $Cu_2O$ are 0.5 and 1.0, respectively.

• Resources Recycling
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• v.25 no.6
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• pp.73-81
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• 2016

Geopolymers produced from aluminosilicate materials such as metakaolin and coal ash react with alkali activators and show higher fire resistance than portland cement, due to amorphous inorganic polymer. The percentage of thermal shrinkage of geopolymers ranges from less than 0.5 % to about 3 % until $600^{\circ}C$, and reaches about 5 ~ 7 % before melting. In this study, geopolymers paste having Si/Al = 1.5 and being mixed with carbon nanofibers, silicon carbide, pyrex glass, and vermiculite, and ISO sand were studied in order to understand the compressive strength and the effects of thermal shrinkage of geopolymers. The compressive strength of geopolymers mixed by carbon nanofibers, silicon carbide, pyrex glass, or vermiculite was similar in the range from 35 to 40 MPa. The average compressive strength of a geopolymers mixed with 30 wt.% of ISO sand was lowest of 28 MPa. Thermal shrinkage of geopolymers mixed with ISO sand decreased to about 25 % of paste. This is because the aggregate particles expanded on firing and to compensate the shrinkage of paste. The densification of the geopolymer matrix and the increase of porosity by sintering at $900^{\circ}C$ were observed regardless of fillers.

• Journal of the Korea Society for Simulation
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• v.26 no.3
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• pp.115-123
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• 2017

Dispite the fact that our military has outwardly made notable accomplishments such as the development of weapon systems like tanks, self-propelled artillery, and missiles, there has been a lack of attention to producing weapon effectiveness data that suggests a standard as to what effects the developed weapons will demonstrate on the battlefield. For such reasons, most of the weapon effectiveness data utilizes JMEM data introduced by the United States and as for the rest of the data that cannot be acquired, respective branches create and utilize their own data through research. This research aims to develop a reliable methodology that can meet the requirements of the requesting branches in a short span of time and at a low cost by studying the existing weapon effectiveness data production methodologies such as that of JMEM. As a result I have developed a method that calculates the vulnerable area and the probability of kill of the weapon system that one wants to calculate by applying statistical technique and simulation technique based on weapon effectiveness data of similar weapon systems in JMEM and live test data.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.216-223
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• 2019

This study was conducted to identify the effects of patient safety competency on patient safety management practice by nursing students and provide basic data for the development of the program to improve patient safety management practice. Participants were 293 fourth year nursing students who had clinical practice as student nurses for more than one year. Data were collected from April 26 to May 9, 2018. Collected data were analyzed for frequency, percentage, mean, standard deviation, t-test, ANOVA, Pearson' s correlation coefficient, and multiple regression with SPSS/WIN 24.0 computer program. Nursing students' patient safety competency was an average $2.90{\pm}0.38$ points (patient safety knowledge $2.68{\pm}0.65$; patient safety skills $3.26{\pm}0.56$; patient safety attitudes $2.75{\pm}0.40$). The average core of management practices to patient safety recorded $4.13{\pm}0.57$ points. In terms of the correlation among subjects' patient safety knowledge, skills, attitudes and patient safety management practices, significant correlation existed between skills and management practices (r=.337, p<.001), attitudes and management practices (r=-.150, p =.010), knowledge and management practices (r=.171, p=.003). Regression analysis revealed that 15.7% of the variance in patient safety management practice by nursing students could be explained by patient safety skills (${\beta}=.307$, p<.001), patient safety accident experience of Fire (${\beta}=-.127$, p=.026), patient safety attitudes (${\beta}=-.121$, p=.026), and patient safety accident experience of patient education (${\beta}=-.119$, p=.034). Additional studies to determine the various factors affecting patient safety management practice of nursing students and to develop educational program for increasing patient safety management practice should be conducted.

• Journal of the Korea Convergence Society
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• v.10 no.1
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• pp.371-380
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• 2019

Electromygram was measured in three different cases; not wearing of a helmet, wearing of a 920g helmet, and wearing of a 1310g helmet, and it was revealed that there was a high level of muscle activities on the opposite side (sternocleidomastoid muscle) while the head and the neck were moving right and left and muscle activities of the curve and of the hyperextension were found to be not significant. Especially, the presence of a helmet seemed to cause a difference in a level of muscle activities on the deltoid and erector spine muscles while lifting or lowering with a weight placed on the deniz backboard. Therefore, it would be possible to assume that this newly developed smart helmet would not affect muscles around the necks of paramedics if they do not move their necks and heads right and left while lowering or lifting a patient using the deniz backboard. In addition, in case of the deltoid and erector spine muscles, it is shown that an increase in the degree of movement could lead to an increase in the level of muscle activities on the muscles controlling of the corresponding action, which are waist and back muscles. Despite it, it would be possible to prevent possible injuries and/or muscular and skeletal diseases around the lumbar by fully complying with a basic rule of straightening of the waist while making a power-lifting motion.