• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.36 no.12
• /
• pp.1151-1159
• /
• 2012

Spray visualization and computer simulation of a DME injector have been conducted to investigate the enlarged injection hole diameter effect. To increase the reliability of the computational result, simulation results have been compared with the visualization test results, and the behaviors of a DME spray under various high-pressure and -temperature conditions have been computed. This study shows a discrepancy of 3.57% between the experimental and the computational results of penetration length for an injection pressure of 35 MPa and ambient pressure of 5 MPa. When simulating the engine conditions, the maximum penetration length of a fully developed DME spray is 42 mm when the temperature to pressure ratio is 300 K/MPa. The DME spray behavior is dominantly affected by the ambient pressure under the condition that the ratio is less than 300 K/MPa, and by the ambient temperature under the condition that the ratio is more than 300 K/MPa.

• Health Policy and Management
• /
• v.22 no.2
• /
• pp.207-224
• /
• 2012

This study estimates the total health expenditure of ambulatory dental care and explores the factors related to disbursements. The study used two waves of a 2008 Korea Health Panel (KHP) survey, of which each wave is composed of 7866 households and 24,659 persons. The KHP includes missing expanses of reimbursement data of the National Health Insurance (NHI), such as out-of-pocket, drugs, and private health insurance. The study estimates total monthly ambulatory dental expenditure and the sub-special categories of dental care. For influential factors analyses, the study exploits log-linear model with age, gender, education, job, equivalence income, the status of chronic diseases, means-tested benefit recipients, private insurance, and the composite deprivation index as independent variables. The total monthly outpatient health spending is estimated to be 102,468 won per household, and for dental, each household spends 31,115 won per month. Older age, means-test recipients, non-regular workers are more likely to spend less money on dental care, whereas private insurers, high income, and those who live in less deprived areas are more likely to spend more money for dental services. From the study we found that the KHP data are more suitable to estimate the total amount of health care markets, especially when the NHI coverage is low, such as for dental care in Korea.

• Geophysics and Geophysical Exploration
• /
• v.7 no.1
• /
• pp.14-18
• /
• 2004

High levels of ambient noise and safety factors often limit the use of 'active-source' seismic methods for geotechnical investigations in urban environments. As an alternative, shear-wave velocity-depth profiles can be obtained by treating the background microtremor wave field as a stochastic process, rather than adopting the traditional approach of calculating velocity based on ray path geometry from a known source. A recent field test in Melbourne demonstrates the ability of the microtremor method, using only Rayleigh waves, to resolve a velocity inversion resulting from the presence of a hard, 12 m thick basalt flow overlying 25 m of softer alluvial sediments and weathered mudstone. Normally the presence of the weaker underlying sediments would lead to an ambiguous or incorrect interpretation with conventional seismic refraction methods. However, this layer of sediments is resolved by the microtremor method, and its inclusion is required in one-dimensional layered-earth modelling in order to reproduce the Rayleigh-wave coherency spectra computed from observed seismic noise records. Nearby borehole data provided both a guide for interpretation and a confirmation of the usefulness of the passive Rayleigh-wave microtremor method. Sensitivity analyses of resolvable modelling parameters demonstrate that estimates of shear velocities and layer thicknesses are accurate to within approximately $10\%\;to\;20\%$ using the spatial autocorrelation (SPAC) technique. Improved accuracy can be obtained by constraining shear velocities and/or layer thicknesses using independent site knowledge. Although there exists potential for ambiguity due to velocity-thickness equivalence, the microtremor method has significant potential as a site investigation tool in situations where the use of traditional seismic methods is limited.

• Tuberculosis and Respiratory Diseases
• /
• v.81 no.1
• /
• pp.6-12
• /
• 2018

The role of the treatment for latent tuberculosis infection (LTBI) has been underscored in the intermediate tuberculosis (TB) burden countries like South Korea. LTBI treatment is recommended only for patients at risk for progression to active TB-those with frequent exposure to active TB cases, and those with clinical risk factors (e.g., immunocompromised patients). Recently revised National Institute for Health and Care Excellence (NICE) guideline recommended that close contacts of individuals with active pulmonary or laryngeal TB, aged between 18 and 65 years, should undergo LTBI treatment. Various regimens for LTBI treatment were recommended in NICE, World Health Organization (WHO), and Centers for Disease Control and Prevention guidelines, and superiority of one recommended regimen over another was not yet established. Traditional 6 to 9 months of isoniazid (6H or 9H) regimen has an advantage of the most abundant evidence for clinical efficacy-60%-90% of estimated protective effect. However, 6H or 9H regimen is related with hepatotoxicity and low compliance. Four months of rifampin regimen is characterized by less hepatotoxicity and better compliance than 9H, but has few evidence of clinical efficacy. Three months of isoniazid plus rifampin was proved equivalence with 6H or 9H regimen in terms of efficacy and safety, which was recommended in NICE and WHO guidelines. The clinical efficacy of isoniazid plus rifapentine once-weekly regimen for 3 months was demonstrated recently, which is not yet introduced into South Korea.

• Magazine of the Korea Concrete Institute
• /
• v.7 no.5
• /
• pp.172-178
• /
• 1995

Concrete contains numerous microcracks at initially poured. The growth and propagation of nicrockacsk are believed tc finally incur the faiure of concrete. These processings are understood as a damage. Damage IS represented as a second-order tensor and crack is treated as a con tinuum phenomenon. In this paper, damage is characterized through the effective stress concept together with the hypothesis of elastic energy equivalence, and damage evolution law and constitutive equation of a damage model are derived by using the Helmholtz frte eriergy and the dissipation potential by means of the thermodynamic principles. The constitutive equation of the model includes the effects of elasticity, anisotropic damage and plasticity of concrete. There are two effective tangent stiffness tensors in this model : one is for elastic-darnage and the other for plastic damage. For the verification of the model, finite element analysis was performed for the analysis of concrete subjec:t to uniaxial and biaxial loading and the results obtained were compared with test results.

• The Korean Journal of Applied Statistics
• /
• v.28 no.2
• /
• pp.289-294
• /
• 2015

Linear mixed models are commonly used in the clinical pharmaceutical studies to analyze repeated measures such as the crossover study data of bioequivalence studies. In these models, random effects describe the correlation between repeated outcomes and variance-covariance matrix explain within-subject variabilities. Bioequivalence analysis verifies whether a 90% confidence interval for geometric mean ratio of Cmax and AUC between reference drug and test drug is included in the bioequivalence margin [0.8, 1.25] performed using linear mixed models with period, sequence and treatment effects as fixed and sequence nested subject effects as random. A Levofloxacin study is referred to for an example of real data analysis.

• Journal of the Korean Society of Industry Convergence
• /
• v.20 no.2
• /
• pp.105-113
• /
• 2017

Recently the direct injection diesel engine is the most efficient one available for road vehicles, so this fundamental advantage suggests the compression injection diesel engine are a wise choice for future development efforts. The compression ignition diesel engine, with its bigger compression ratios if compared to the SI engine, offers a higher thermodynamic efficiency, also additionally the diesel engine with its less pumping losses due to the throttled intake charge as in a SI engine has higher fuel economy. But the largest obstacle to the success of this engine is meeting emission standards for Nitric oxides and particulate matter while maintain fuel consumption advantage over currently available engines. Thus its use should be largely promoted, however, diesel engine emits more Nitric oxides and particulate matter than other competing one. There has been a trade-off between PM and NOx, so efforts to reduce NOx have increased PM and vice versa, but trap change this situation and better possibility emerge for treating NOx emission with engine related means, such as injection timing, equivalence ratio, charge composition, and engine speed. The common rail direct injection system is able to adjust the fuel injection timing in a compression ignition engine, so this electronically controlled injection system can reduce the formation of NOx gas without increase in soot. In this study it is designed and used the engine test bed which is installed with turbocharge and intercooler. In addition to equipped using CRDI by controlling injection timing with mapping modulator, it has been tested and analyzed the engine performance, combustion characteristics, and exhaust emission as operating parameters.

• Journal of the Korea Society of Computer and Information
• /
• v.20 no.8
• /
• pp.121-128
• /
• 2015

This study aimed to investigate the effects of an unplugged robot education system capable of computerless coding education. Specifically, this study compared this education system with PicoCricket, an educational robot that can also be used with elementary students in lower grades, using assessment tools on perceived usefulness and ease. Using random sampling and randomized assignment for more objective validation, 30 participants were assigned to the unplugged robot education system group (experimental group) and 30 participants were assigned to the PicoCricket group (control group), for a total of 60 study participants. The research procedure included verification of the equivalence of the two groups by conducting a pretest after a 2-hour basic training session on algorithms and programming. The experimental and control groups learned the same content using different educational tools in accordance with software training guidelines for a total of 12 hours. Then, the difference in perceived usefulness and ease between the two groups was examined using a post-treatment test. The study results showed that scores on both dependent variables, perceived usefulness and perceived ease, were significantly higher in the experimental group than the control group. Moreover, scores on all sub-variables of the dependent variables were significantly higher in the experimental group than the control group. These results suggest that learners using the unplugged robot education system found it more useful and easier to use than learners using the existing educational robot, PicoCricket. This study's findings are significant, as according to the technology acceptance model, the perceived usefulness and ease of an educational tool are important variables that determine the acceptance of the tool (i.e., persistence of learning).

• Korean Journal of Culture and Social Issue
• /
• v.26 no.4
• /
• pp.501-524
• /
• 2020

This study was conducted to validate the Korean Love addiction Questionnaire-Short Form (K-LAQ-SF) applicable to Korean society. As a result of exploratory factor analysis for Love addiction 40 Questions(Peabody, 2005), the final 5 factors and 15 questions appeared, and the model fit of the final scale was confirmed through confirmatory factor analysis. The results of the equivalence test showed that the theoretical structure of the abbreviated scale works in the same way for each gender. The results of correlation analysis between K-LAQ-SF and original scale showed that the abbreviated scale represented the original scale relatively faithfully. Finally, the results of correlation analysis between this scale and relationship addiction, love type and depression showed that convergence, discrimination and criterion validity were secured. K-LAQ-SF is significant in that it can be usefully used to easily measure the characteristics of Korean adults' love addiction in a short time based on stable reliability and validity.

• School Mathematics
• /
• v.13 no.2
• /
• pp.307-321
• /
• 2011

Recognizing the importance of affective factors in mathematical learning and achievement, international comparative assessment as PISA and TIMSS survey affective achievement as well as scholastic achievement. On the affective survey those items of PISA are categorized by 5 factors ; interest of mathematics, instrumental motivation, Mathematics self-efficacy, mathematics anxiety, mathematics self-concept) and those of TIMSS are categorized by 3 factors; Positive affect toward mathematics (PATM), Students' Self-Confidence in Learning Mathematics(SCM), and Students' Valuing Mathematics(SVM). In this study we carried out Exploratory Factor Analysis, Confirmatory Factor Analysis and Measurement Equivalence/Invariance to find whether the constructs are well defined and divided. As a result of our analysis, some factors were overlapped in PISA whereas the items of TIMSS were categorized as intended in TIMSS study. Based on these results, it is confirmed that the questionnaire items need to be developed to understand our students affective characteristics. Also, how questionnaire of large-scaled international assessment can give implication to the development of the questionnaire of Korean specific.