• The Journal of the Acoustical Society of Korea
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• v.35 no.6
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• pp.491-500
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• 2016

The present study describes the acoustical characteristics of the new noise barriers which can control not only noise but also wind pressure by allowing air flow through barriers. In order to investigate the sound reduction index of the air transparent noise barrier, 17 models in total were examined with various size of openings and the volume of the resonators. As a result, it was found that the sound reduction index varies with the volume of the resonator and the area of the openings. Also, it was revealed that double layer of units has more sound reduction index than the single layer of unit at the frequency band from 400 Hz to 1250 Hz. This denoted that physical features of openings and resonators affect the sound reduction index of the air transparent noise barrier.

• Corrosion Science and Technology
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• v.9 no.2
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• pp.57-66
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• 2010

Since nuclear power plants are being operated under high temperature and high pressure, on-line monitoring technique to detect corrosion could be more effective than off-line method in shut-off period. In this operating condition, electrochemical noise method may be suitable to monitor the corrosion. This paper aims the analysis on the relation between the cracking and electrochemical noise signal of Alloy 600 under U-bending. When electrochemical noise monitoring technique was used during SCC test, it was judge to be obvious that if cracks generate, its generation can be detected by electrochemical current noise. Cracking-related noise was defined as the noise showing 5~10 times greater than the average value of background noise bands. On the base of crack noise, crack initiation time was determined. From SCC test and electrochemical noise monitoring in $25^{\circ}C$, 0.1 M $Na_2S_4O_6$ solution (Reverse U-Bended Alloy 600 SE+), average crack initiation time was obtained as 9,046 seconds and from its initiation time, it could be defined that net crack propagation rate is the crack length divided by ${\Delta}T$(= total test period - crack initiation time). Therefore, average net crack propagation rate was obtained to be $1.18{\times}10^{-9}\;m/s$.

• Journal of Digital Convergence
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• v.13 no.9
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• pp.323-332
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• 2015

This paper examines the level of the primary care continuity for patients with high blood pressure and the effects of the primary care continuity on their convergence health outcomes. We conducted a retrospective cohort study. A total of 315,791 patients who had received new diagnoses of hypertension. We determined standard indices of continuity of care-MFPC, MMCI, and COC and evaluated their association with study outcomes over three years of follow-up. Outcome measures included hospitalization and emergency room visits. The result of the primary care continuity levels and hazard ratios of health outcome showed that, comparing continuity group, non-continuity group had higher rates of hospitalization by 1.655(95% CI: 1.547-1.771) and emergency room visits by 1.669(95% CI: 1.465-1.903). This paper argues that medical costs of chronic diseases will reduce if low continuity of care turns into high continuity of care.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3C
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• pp.113-120
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• 2012

An actual slope failure was analyzed in residual soils at Jinju. Due to rainfall infiltration, the safety factor decreases in the unsaturated layers, since the effective stress and shear strength decrease. In this study, the effective stress is based on suction stress using soil water retention curve. Unsaturated properties were evaluated on soil water retention curve, hydraulic conductivity and shear strength with samples from the site. After infiltration analysis of unsaturated flow under the actual rainfall, the distribution of pore water pressure could be calculated in the slope layers. In the stress field of finite elements, an elastic analysis calculated total stress distribution in the layers and also shear stresses on the slip surface using elastic model. On the slip surface, suction stress and effective stress evaluated the shear strength. As a result, the factor of safety was calculated due to rainfall, which could simulate the actual slope failure. In particular, it was found that the suction stress increases and both the effective stress and the shear strength decrease simultaneously on the slip surface.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.72-76
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• 2010

To research and develop a high performance injector for LRE, it needs not only cold flow test, but also investigations of combustion performance, optimization of cyclogram and thermo-fluid dynamical characteristics of combustion flow field through hot-fire test. In this study, hot-fire test of LOX-CH4 coaxial swirl injector has been carried out using lab-scale hot fire test stand which can supply and control cryogenic propellant. Ignition and continuous combustion for LOX-$GCH_4$ propellant of 0.19 kg/s total mass flowrate and 2.80 O/F Ratio was achieved through cyclogram optimization. The mean combustion chamber pressure and thrust were measured as approximately 1.43 MPa and 38.7 kgf respectively.

• Membrane and Water Treatment
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• v.9 no.4
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• pp.221-231
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• 2018

A new procedure to produce poly(vinylidene fluoride)/boron nitride hybrid membrane is presented for application in membrane distillation (MD) process. The influence of hexagonal boron nitride (h-BN) incorporation on the performance of the polymeric membranes is studied through the present investigation. For this aim, h-BN nanopowders were successfully synthesized using the simple chemical vapor deposition (CVD) route and subsequent solvent treatments. The resulting h-BN nanosheets were blended with poly(vinylidene fluoride) (PVDF) solution. Then, the prepared composite solution was subjected to phase inversion process to obtain PVDF/h-BN hybrid membranes. Various examinations such as scanning electron microscopy (SEM), wettability, permeation flux, mechanical strength and liquid entry pressure (LEP) measurements are performed to evaluate the prepared membrane. Moreover, Air gap membrane distillation (AGMD) experiments were carried out to investigate the salt rejection performance and the durability of membranes. The results show that our hybrid PVDF/h-BN membrane presents higher water permeation flux (${\sim}18kg/m^2h$) compared to pristine PVDF membrane. In addition, the experimental data confirms that the prepared nanocomposite membrane is hydrophobic (water contact angle: ${\sim}103^{\circ}$), has a porous skin layer (>85%), as well competitive fouling resistance and operational durability. Furthermore, the total salt rejection efficiency was obtained for PVDF/h-BN membrane. The results prove that the novel PVDF/h-BN membrane can be easily synthesized and applied in MD process for salt rejection purposes.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.5
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• pp.405-414
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• 2015

Fluid transport is a key issue in the development of microfluidic systems. Recently, Myong (2014) has proposed a new concept for droplet transport without external power sources and numerically validated the results for a hypothetical 2D, initially having a hemicylindrical droplet. In this paper, the movement of an actual water droplet, initially having a 3D hemispherical shape, on horizontal hydrophilic/hydrophobic surfaces is simulated using a commercial computational fluid dynamics (CFD) package, Fluent, with VOF (volume of fluid) method. The results are compared with the 2D analysis of Myong (2014), and the transport mechanism for the actual water droplet is examined based on the numerical results of the time evolution of the droplet shape, as well as the total kinetic, gravitational, surface free and pressure energies inside the droplet.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.2 s.257
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• pp.188-194
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• 2007

New diesel engines equipped with common-rail injection systems and advanced engine management control allow drastic decreases in the production of particulate matters and nitrogen oxides with a significant advantage in terms of the fuel consumption and $CO_2$ emissions. Nevertheless, the contribution of exhaust gas after treatment in the ultra low emission vehicles conception has become unavoidable today. Recently the passive type DPF(Diesel Particulate Filter Trap) system for diesel passenger vehicle has been manufactured into mass production from a French automotive maker since the year of 2000. This passive DPF system fully relies on the catalytic effects from additives blended into the diesel fuel and additives injected into the DPF system. In this study, the effects of PM regeneration in the commercial diesel passenger vehicle with the passive type DPF system were investigated in chassis dynamometer CVS(constant volume sampler)-75 mode. As shown in this experimental results, the DPF regeneration was observed at temperature as low as $350^{\circ}C$. And the engine-controlled the DPF regeneration founded to be one of the most promising regeneration technologies. Moreover, the durability of this DPF system was evaluated with a season weather in terms of the differential pressure and exhaust gas temperature traces from a road test during the total mileage of 80,000km.

• Journal of The Korean Society of Clinical Toxicology
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• v.2 no.1
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• pp.7-11
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• 2004

Purpose: We would evaluate the cardiovascular manifestations of the patients with acute organophosphate and carbamate poisoning in the emergency department. Methods: This was retrospectively studied with the review of patient's charts, included total 38 patients were admitted during the past two years in the emergency department of Yeungnam university hospital with the diagnosis of organophosphate or carbamate poisoning. Results: Cardiovascular complications were variously developed in many patients. Electrocardiographic findings were as follows; 4 ($10.5\%$) cardiac arrhythmias included 1 cardiac arrest caused by ventricular fibrillation, 14 ($36.8\%$) sinus tachycardias, 3 ($7.9\%$) sinus bradycardias, and 17 ($44.7\%$) normal sinus rhythms. Conduction disturbances were 23 ($60.5\%$) like as prolonged QTc, 4 ($10.5\%$) ST-T changes, 2 (5.3%) first degree AV block, and 3 ($7.9\%$) right bundle branch block were shown. Other cardiovascular complications were 22 ($57.9\%$) hypertensives, 4 ($10.5\%$) hypotensives, 15 ($39.5\%$) tachycardias, 2 ($5.3\%$) bradycardias, 18 ($47.4\%$) hypoxemics, 12 ($31.6\%$) metabolic acidosis, and 9 ($23.7\%$) pulmonary edemas. Sixteen patients ($42.1\%$) needed ventilatory support because of respiratory paralysis. No patients died in hospital and 36 ($94.7\%$) patients were alive-discharged. Conclusion: Cardiovascular complications are variously in patients with acute organophosphate and carbamate poisoning. Especially, some findings included ventricular arrhythmias, QTc prolongation, hypoxemia, acidosis, and blood pressure changes are known as major precipitating factors to increase the mortality. So, intensive support and aggressive treatment are needed in patients shown various cardiovascular manifestations in the emergency department.

• Journal of the Korean Dietetic Association
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• v.2 no.1
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• pp.20-28
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• 1996

In Korea, nutritional services have not been included in the periodic medical examinations for employees. Naturally, the practice of individual dietary treatment, or nutrition education, has not yet been implemented, specifically for employees who are expected to encounter health problems. This study was designed to evaluate the necessity and development of nutritional consultations during medical examinations of employees and of worksite nutrition programs. One hundred and five employees from three companies were chosen as subjects for this study. As a result, the average intake of nutrients were found to be sufficient for male employees but female employees were found to be deficient in their intake of total calories, calcium, iron, vitamins A and $B_2$. Also, most of employees did not recognize their own blood cholesterol levels, blood pressure, or blood sugar level. Many employees thought that they needed nutritional consultation during periodic medical examinations and during worksite nutrition programs that also include programs for the whole family. According to the results, clinics for weight control were urgently demanded among several nutrition programs. It should be noted that weight problems, high blood cholesterol levels, diabetes, and other health problems were frequently found in companies whose employees had relatively minimal knowledge about nutrition information. In an effort to prevent disease, the worksite nutrition programs and other nutritional services for employees are critical. This study, therefore, suggests to include nutritional services in medical examinations and to develop efficient worksite nutrition programs.