• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.9 no.1
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• pp.112-124
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• 1999

The purposes of this study were to provide the data for composition of ethylene glycol ethers and 2-ethoxyethyl acetate(EEA) exposure assessment of workers in various industrial operations. In this study, 80 thinners were analyzed to identify their composition and the air concentration of 2-ethoxyethyl acetate(EEA) and urinary 2-ethoxyacetic acid(EAA) were measured. In this study the subjects were the total of 183 drawn from 98 workers who were occupationally exposed to EEA and 85 workers who were not. The results were as follows: 1. There were found average 4.2 components in each thinner. 2. There were 90 components(26.9%) in ethylene glycol ethers of total of 334 detected organic solvents 3. Ethoxyethyl acetate, ethoxyethanol, buthoxyethanol, methoxy-ethanol were found in 30(37.5%), 27(33.8%), 19(23.8%), 2thinners(2.5%), respectively and their contents were average 18.5%. 4. Benzene was found 8 thinners(10.0%) of the total 80 surveyed. 5. In the electronic painting workers EEA exposure concentration was the highest, as showed 2.88ppm(0.01~15.1ppm), cases of exceeded threshold limit value(TLV=5ppm) were 7(10.6%) workers among the total of 98 exposed workers. 6. The geometric mean of urinary EEA in exposed workers was 1.61 mg/gcreatinine, and was higher than that of workers who were not exposed. In the electronic painting workers and offset printers, the geometric mean of urinary EAA was the highest showing 2.8 mg/gcreatinine. 7. The correlation coefficient between urinary concentration of EAA and air concentration of EEA was 0.90(P<0.05). The present results suggest that composition of ethylene glycol ethers in thinners must be evaluated when industrial hygiene surveys and biological monitoring are performed.

• Transactions of the Korean Society of Automotive Engineers
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• v.25 no.2
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• pp.179-189
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• 2017

This paper is the fifth investigation on the methods of evaluating flow characteristics in a steady flow bench. In previous studies, several assumptions used in the steady flow bench were examined and it was concluded that the assumption of the solid rotation may lead to serious problems. In addition, though the velocity profiles were improved as the measuring position went downstream, the distributions were far from ideal regardless of the valve angle and evaluation position. The eccentricities were also not sufficiently small to disregard the effect on impulse swirl meter (ISM) measurement. Therefore, the effect of these distribution and eccentricity changes according to the positions needs to be analyzed to discuss the method of flow characteristics estimation. In this context, the effects of evaluation position on the steady flow characteristics were studied. For this purpose, the swirl coefficient and swirl ratio were assessed and compared via measurement of the conventional ISM and calculation based on the velocity by particle image velocimetry(PIV) from 1.75B, 1.75 times bore position apart from the cylinder head, to the 6.00B position. The results show that the swirl coefficients by ISM strictly decrease and the curves as a function of the valve lift become smooth and linear as the measuring position goes downstream. However, the values through the calculation based on the PIV are higher at the farther position due to the approach of the tangential velocity profile to ideal. In addition, there exists an offset effect between the velocity distribution and eccentricity in the low valve lift range when the coefficients are estimated based on the swirl center. Finally, the curve of the swirl ratio by ISM and by PIV evaluation as a function the measuring position intersect around 5.00B plane except at $26^{\circ}$ valve angle.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.381-381
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• 2010

$(ZrO_2)_{0.66}(HfO_2)_{0.34}$ thin films as gate dielectrics have been proposed to overcome the problems of tunneling current and degradation mobility inachieving a thin equivalent oxide thickness. An extremely thin $SiO_2$ layer is used in order to separate the carrier in MOSFET channel from the dielectric field fluctuation caused by phonons in the dielectric which decreases the carrier mobility. The electronic and optical properties influenced the device performance to a great extent. $(ZrO_2)_{0.66}(HfO_2)_{0.34}$ dielectric films on p-Si (100) were grown by atomic layer deposition method, for which the conduction band offsets, valence band offsets and band gapswere obtained by using X-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy. The band gap, valence and conduction band offset values for $(ZrO_2)_{0.66}(HfO_2)_{0.34}$ dielectric thin film, grown on Si substrate were about 5.34, 2.35 and 1.87 eV respectively. This band alignment was similar to that of $ZrO_2$. In addition, The dielectric function (k, $\omega$), index of refraction n and the extinction coefficient k for the $(ZrO_2)_{0.66}(HfO_2)_{0.34}$ thin films were obtained from a quantitative analysis of REELS data by comparison to detailed dielectric response model calculations using the QUEELS-$\varepsilon$(k, $\omega$)-REELS software package. These optical properties are similar with $ZrO_2$ dielectric thin films.

• Journal of Ocean Engineering and Technology
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• v.34 no.5
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• pp.285-293
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• 2020

This study evaluated the Hook-up installation of an offshore site construction process, which is the final step in an offshore site installation process. During Hook-up installation, the offshore structure can have a detrimental effect on the work stability due to low-frequency motion. Moreover, economic costs can be incurred by the increase in available days of a tugboat. Therefore, this study developed a numerical analysis program to assess the dynamic behavior of mooring systems during hook-up installation to analyze the generally performed installation process and determine when the tugboat should be released. In this program, the behavior of an offshore structure was calculated using Cummin's time-domain motion equation, and the mooring system was calculated by Lumped mass method (LMM). In addition, a tugboat algorithm for hook-up installation was developed to apply the Hook-up procedure. The model used in the calculations was the barge type assuming FPSO (Floating production storage and off-loading) and has a taut mooring system connected to 16 mooring lines. The results of the simulation were verified by comparing with both MOSES, which is a commercial program, and a calculation method for restoring coefficient matrix, which was introduced by Patel and Lynch (1982). Finally, the offset of the structure according to the number of tugboats was calculated using the hook-up simulation, and the significant value was used to represent the calculation result.

• Journal of Korean Academy of Nursing
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• v.29 no.4
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• pp.903-916
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• 1999

The purpose of this study was to compare the ear-based rectal temperature measured with a tympanic thermometer with the rectal temperature measured with a glass mercury thermometer in order to test the accuracy of tympanic thermometer and to determine relationship among rectal, axilla, and abdominal temperature in neonates. The samples consisted of thirty four neonates admitted to the neonatal intensive care unit and nursery at an university affiliated hospital. The mean age of the subjects was 4.9 days. The ear-based rectal temperatures were taken with a tympanic thermometer in rectal mode (First Temp Genius 3000). Rectal and axilla temperatures were taken with a glass mercury thermometer, Abdominal temperature was continuously monitored with the probe connected to the servo controller of incubator. The results of the study can be summarized as follows : 1. Intrarater comparison : Agreement between the first and the second ear-based rectal temperature was 97% within 0.1$^{\circ}C$. 2. Comparison of ear-based rectal temperature and the rectal temperature from a glass mercury thermometer : ear-based rectal temperature ranged from 36.95$^{\circ}C$d to 37.95$^{\circ}C$, with a mean of 37.58$^{\circ}C$(SD＝0.22$^{\circ}C$). Rectal temperature from a glass mercury thermometer ranged from 36.2$0^{\circ}C$ to 37.2$0^{\circ}C$, with a mean 36.75$^{\circ}C$(SD＝0.29). The mean difference between both temperatures was 0.84$^{\circ}C$. The correlation coefficient between both temperatures was r＝0.77(p＝0.00). 3. Comparison of rectal and axilla temperature : Axilla temperature ranged from 35.8$0^{\circ}C$ to 37.1$0^{\circ}C$, with a mean of 36.55$^{\circ}C$. The mean absolute difference between the rectal and axilla temperature was 0.23$^{\circ}C$. The correlation coefficient between rectal and axilla was r＝0.67. 4. Comparison of axilla and abdominal temperature : Abdominal temperature ranged from 36.2$0^{\circ}C$ to 37.0$0^{\circ}C$, with a mean of 36.58$^{\circ}C$. The mean absolute difference between axilla and abdominal temperature was only -0.03$^{\circ}C$. Findings of this study suggest that ear-based rectal temperature overestimates the actual rectal temperatures in neonates. Therefore, the interchangeble use of both temperatures in clinics seems problematic. The site offset(adjustment value) programmed in rectal mode of the tympanic thermometer needs to be readjusted. Choosing one optimal site for temperature measurement for each patient, and using the specific site consistently would result in more consistent measurements of changes in body temperature, and thus can be more effective in diagnosing fever or hypothermia.

• Geophysics and Geophysical Exploration
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• v.9 no.2
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• pp.139-147
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• 2006

We had conducted a numerical modeling to investigate seismic properties of gas hydrate with field parameters acquired over the East sea in 1998. We used a 2-D staggered grid finite difference method to generate synthetic elastic seismograms for multi-channel seismic survey, OBC (Ocean Bottom Cable) survey and VCS (Vertical Cable Seismic) survey. The results of this study showed that the method using staggered grid yielded stable results and could be used to seismic imaging. We could find out the high amplitude anomaly and the phase reversal phenomenon of reflection wave at interface between the gas hydrate layer and free gas layer such a BSR (Bottom Simulating Reflector) which is the evidence for existence of gas hydrate in seismic reflection data. And we computed the reflection coefficients at the incident angles corresponding to offset distance with the synthetic seismograms. The reflection coefficients acquired from the numerical modeling were nearly consistent with the reflection coefficient computed by Shuey's equation.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.643-646
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• 2005

The gas hydrate exploration using seismic reflection data, the detection of BSR(Bottom Simulating Reflector) on the seismic section is the most important work flow because the BSR have been interpreted as being formed at the base of a gas hydrate zone. Usually, BSR has some dominant qualitative characteristics on seismic section i.e. Wavelet phase reversal compare to sea bottom signal, Parallel layer with sea bottom, Strong amplitude, Masking phenomenon above the BSR, Cross bedding with other geological layer. Even though a BSR can be selected on seismic section with these guidance, it is not enough to conform as being true BSR. Some other available methods for verifying the BSR with reliable analysis quantitatively i.e. Interval velocity analysis, AVO(Amplitude Variation with Offset)analysis etc. Usually, AVO analysis can be divided by three main parts. The first part is AVO analysis, the second is AVO modeling and the last is AVO inversion. AVO analysis is unique method for detecting the free gas zone on seismic section directly. Therefore it can be a kind of useful analysis method for discriminating true BSR, which might arise from an Possion ratio contrast between high velocity layer, partially hydrated sediment and low velocity layer, water saturated gas sediment. During the AVO interpretation, as the AVO response can be changed depend upon the water saturation ratio, it is confused to discriminate the AVO response of gas layer from dry layer. In that case, the AVO modeling is necessary to generate synthetic seismogram comparing with real data. It can be available to make conclusions from correspondence or lack of correspondence between the two seismograms. AVO inversion process is the method for driving a geological model by iterative operation that the result ing synthetic seismogram matches to real data seismogram wi thin some tolerance level. AVO inversion is a topic of current research and for now there is no general consensus on how the process should be done or even whether is valid for standard seismic data. Unfortunately, there are no well log data acquired from gas hydrate exploration area in Korea. Instead of that data, well log data and seismic data acquired from gas sand area located nearby the gas hydrate exploration area is used to AVO analysis, As the results of AVO modeling, type III AVO anomaly confirmed on the gas sand layer. The Castagna's equation constant value for estimating the S-wave velocity are evaluated as A=0.86190, B=-3845.14431 respectively and water saturation ratio is $50\%$. To calculate the reflection coefficient of synthetic seismogram, the Zoeppritz equation is used. For AVO inversion process, the dataset provided by Hampson-Rushell CO. is used.

• Journal of Sensor Science and Technology
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• v.9 no.1
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• pp.1-8
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• 2000

One of today's very critical and sensitive accurate accelerometer which can be used higher temperature than $200^{\circ}C$ and corrosive environment, is particularly demanded for automotive engine. Because silicon is a material of large temperature dependent coefficient, and the piezoresistors are isolated with p-n junctions, and its leakage current increase with temperature, the performance of the silicon accelerometer degrades especially after $150^{\circ}C$. In this paper, The temperature characteristic of a accelerometer using silicon on insulator (SOI) structure is studied theoretically, and compared with experimental results. The temperature coefficients of sensitivity and offset voltage (TCS and TCO) are related to some factors such as thermal residual stress, and are expressed numerically. Thermal stress analysis of the accelerometer has also been carried out with the finite-element method(FEM) simulation program ANSYS. TCS of this accelerometer can be reduced to control the impurity concentration of piezoresistors, and TCO is related to factors such as process variation and thermal residual stress on the piezoresistors. In real packaging, The avarage thermal residual stress in the center support structure was estimated at around $3.7{\times}10^4Nm^{-2}^{\circ}C^{-1}$ at sensing resistor. The simulated ${\gamma}_{pT}$ of the center support structure was smaller than one-tenth as compared with that of the surrounding support structure.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.11 s.114
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• pp.1040-1049
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• 2006

A design method for minimizing transmission loss of a broadband right-angle transition from a coaxial cable to a microstrip line is presented. The right-angle transition has been widely used where printed circuit applications need to be fed from behind the ground plane using coaxial line. To obtain the minimized transmission loss over the whole operating frequency range of the transition, design parameters such as ground aperture and probe diameters, ground aperture offset, and stub length are optimized using a commercial electromagnetic simulation software. Results are presented for the optimum right-angle transition from an SMA connector to a microstrip line on common reinforced 0.787 mm thick PTFE substrates. Measurements of a fabricated transition show that reflection coefficient is less than -22 dB and insertion loss is less than 0.45 dB over $0.05{\sim}20GHz$.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.2
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• pp.97-107
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• 2017

This study is the second investigation on the steady flow characteristics of an SI engine with a semi-edge combustion chamber as a function of the port shape with varying evaluation positions. For this purpose, the planar velocity profiles were measured from 1.75B, 1.75 times of bore position apart from the bottom of head, to 6.00B positions using particle - image velocimetry. The flow patterns were examined with both a straight and a helical port. The velocity profiles, streamlines, and centers of swirl were almost the same at the same valve lift regardless of the measuring position, which is quite different from the case of the pent-roof combustion chamber. All the eccentricity values of the straight port were out of distortion criterion 0.15 through the lifts and the position. However, the values of the helical port exceeded the distortion criterion by up to 4 mm lift, but decreased rapidly above the 3.00B position and the 5 mm lift. There always existed a relative offset effect in the evaluation of the swirl coefficient using the PIV method due to the difference of the ideal impulse swirl meter velocity profile assumption, except for the cylinder-center-base estimation that was below 4 mm of the straight port. Finally, it was concluded that taking the center as an evaluation basis and the assumption about the axial velocity profile did not have any qualitative effect on swirl evaluation, but affected the value owing to the detailed profile.