• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.264-267
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• 2003

Pitch measurements of 150 nm pitch one-dimensional grating standards were carried out using an contact mode atomic force microscopy(C-AFM) with a high resolution three-axis laser interferometer. It was called as 'Nano-metrological AFM' In Nano-metrological AFM, Three laser interferometers were aligned well to the end of AFM tip. Laser sources of the three-axis laser interferometer in the nano-metrological AFM were calibrated with an I$_2$-stablilzed He-Ne laser at a wavelength of 633 nm. So, the Abbe error was minimized and the result of the pitch measurement using the nano-metrological AFM has a traceability to the length standard directly. The uncertainty in the pitch measurement was estimated in accordance with the Guide to the Expression of Uncertainty in Measurement(GUM). The Primary source of uncertainty in the pitch-measurements was derived from repeatability of pitch-measurement, and its value was approx 0.186 nm. Expanded uncertainty(k=2) of less than 5.23 nm was obtained. It is suggested that the metrological AFM is a useful tool for the nano-metrological standard calibration.

• Journal of the Korean Society for Heat Treatment
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• v.15 no.2
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• pp.76-81
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• 2002

The melt-spun amorphous $Fe_{77-X}P_{13}C_4B_4Al_2Mo_X$(x=4~10) and $Fe_{82-X}P_XC_4B_4Al_2Mo_8$(x=9~15) alloys were found to exhibit a large supercooled liquid region(${\Delta}T_x$) exceeding 40 K before crystallization. The largest ${\Delta}T_x$ for the glassy alloys containing Mo reaches as large as 65 K for the $Fe_{69}P_{13}C_4B_4Al_2Mo_8$ alloy. The corrosion behavior of the amorphous $Fe_{77-X}P_{13}C_4B_4Al_2Mo_X$(x=4~15) and $Fe_(82-X)P_XC_4B_4Al_2Mo_8$ (x=9~17) alloys were examined by electrochemical measurements in 9M $H_2SO_4$ solution at 303 K. The addition of Mo(or P) for replacing some portion of Fe is effective in improving the corrosion resistance of the investigated Fe-based glassy alloys. They are spontaneously passivated and have a wide passive region with low passive current density.

• Macromolecular Research
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• v.12 no.4
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• pp.342-351
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• 2004

Poly(ethylene glycol) (PEG1K) and sulfonated PEG (PEG1K-SO$_3$) methacrylate (MA) copolymers have been prepared and characterized. The structures of the synthesized copolymers were confirmed by $^1$H and $^{13}$ C NMR spectroscopy and elemental analysis. The bulk characteristics of the copolymers were evaluated by viscosity and thermal analysis. The surface properties of the copolymers were investigated using dynamic contact angle measurements and electron spectroscopy for chemical analysis. The hydrophilicity of the surfaces modified with PEG1KMA or PEG1K-SO$_3$MA increased, possibly as a result of the orientation of the hydrophilic PEG1KMA/PEG1K-SO$_3$MA chains into the water phase. Platelets adhered less to the surfaces of the copolymers than they did to a polyurethane control. In addition, adhesion of platelets to the copolymer surfaces decreased upon increasing the chain density of PEG1KMA and sulfonated PEG1KMA in the copolymers. Both bacterial adhesion and protein adsorption were significantly reduced on the copolymer surfaces and their levels differ depending on the kind of surface or media.

• Journal of Preventive Medicine and Public Health
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• v.29 no.1 s.52
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• pp.1-14
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• 1996

To evaluate the health risk of the workplace environment of a general hospital toward the hospital workers, a questionnaire survey on the perception of risk at the workplace environment and environmental measurements at 27 locations with 240 workers in the hospital were made from October 25th, 1993 to October 30th, 1994. The results were as follows ; 1. By the environmental measurements, 86 workers(36%) were found to be exposed to poor or harmful degree of general illumination, 193 workers(80%) were exposed to poor or harmful local illumination, 34 workers(14%) were exposed to poor or harmful degree of thermal condition and 180 workers(75%) were exposed to poor or harmful noise level, but nobody was exposed to poor or harmful dust and toluene concentration. Also nobody was exposed to poor or harmful level of radiation or anticancer/antibiotic agents. 2. The subjective perceptions on the environmental conditions felt by the workers were different from the objective findings by the environmental measurements. The workers underscored the poor illumination state and overscored the dust concentrations. Also workers oversensitized about the thermal condition, the noise level, the radiation level, the toluene concentration and anticancer/antibiotic agents 3. The sources of noise were the dialogue(179 workers) and the office instruments(131 workers). The sources of dust came from the clothes(108 workers) and the building materials(79 workers). 4. The questionnaire survey showed that the 28 workers were exposed to poor or harmful level of the antibiotics, 10 workers to alkali or acid and 6 workers to drug dust in the pharmacy but the above findings could not be proved by the environmental measurements.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.2
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• pp.201-208
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• 2011

With the increase in the number of smartphone users, precise 3D positional information is required by various applications. The positioning accuracy using civilian single-frequency pseudoranges is at the level of 10 m or so, but most applications these days are asking for a sub-meter level Therefore, instead of an absolute positioning technique, the VRS-based differential approach is applied along with the correction of the double-differenced (DD) residual errors using FKP (Flachen-Korrektur-Parameter). The VRS (Virual Reference Station) is located close to the rover, and the measurements are generated by correcting the geometrical distance to those of the master reference station. Since the unmodeled errors are generally proportional to the length of the baselines, the correction parameters are estimated by fitting a plane to the DD pseudorange errors of the CORS network. The DD positioning accuracy using 24 hours of C/A code measurements provides the RMS errors of 37 cm, 28 cm for latitudinal and longitudinal direction, respectively, and 76 cm for height. The accuracy of the horizontal components is within ${\pm}0.5m$ for about 90% of total epochs, and in particular the biases are significantly decreased to the level of 2-3 cm due to the network-based error modeling. Consequently, it is possible to consistently achieve a sub-meter level accuracy from the single-frequency pseudoranges using the VRS and double-differenced error modeling.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.80-80
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• 2000

Surface acoustic wave (SAW) devices have become more important as mobile telecommunication systems need h호-frrequency, low-loss, and down-sized components. Higher-frequency SAW divices can be more sasily realized by developing new h호-SAW-velocity materials. The ZnO/diamond/Si multilasyer structure is one of the most promising material components for GHz-band SAW filters because of its SAW velocity above 10,000 m/sec. Silicon carbide is also a potential candidate material for high frequency, high power and radiation resistive electronic devices due to its superior mechanical, thermal and electronic properties. However, high price of commercialized 6- or 4H-SiC single crystalline wafer is an obstacle to apply SiC to high frequency SAW devices. In this study, single crystalline 3C-SiC thin films were grown on Si (100) by MOCVD using bis-trimethylsilymethane (BTMSM, C7H20Si7) organosilicon precursor. The 3C-SiC film properties were investigated using SEM, TEM, and high resolution XRD. The FWHM of 3C-SiC (200) peak was obtained 0.37 degree. To investigate the SAW propagation characteristics of the 3C-SiC films, SAW filters were fabricated using interdigital transducer electrodes on the top of ZnO/3C-SiC/Si(100), which were used to excite surface acoustic waves. SAW velocities were calculated from the frequency-response measurements of SAW filters. A generalized SAW mode. The hard 3C-SiC thin films stiffened Si substrate so that the velocities of fundamental and the 1st mode increased up to 5,100 m/s and 9,140 m/s, respectively.

• Journal of the Korean Electrochemical Society
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• v.3 no.1
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• pp.25-30
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• 2000

The relation between the phase-shift profile for the intermediate frequencies and the Langmuir adsorption isotherm at the poly-$Pt/0.1\;M\;H_2SO_4$ aqueous electrolyte interface has been studied using ac impedance measurements, i.e., the phase-shift methods. The suggested interfacial equivalent circuit consists of the serial connection of the electrolyte resistance ($R_S$), the faradaic resistance $(R_F)$ and the equivalent circuit element $(C_P)$ of the adsorption pseudocapacitance $(C_\varphi)$. The delayed phase shift $(\varphi)$ depends on both the cathode potential (E) and frequency (f), and is given by $\varphi=-tan^{-1}[1/2{\pi}f(R_s+R_F)C_p]$. The phase-shift profile $(\varphi\;vs.\;E)$ for the intermediate frequency (ca. 6Hz) can be used as an experimental method to determine the Langmuir adsorption isotherm (9 vs. E). The equilibrium constant (K) for H adsorption and the standard free energy $({\Delta}G_{ads})$ of H adsorption at the poly-$Pt/0.1\;M\;H_2SO_4$ electrolyte interface are $1.8\times10^{-4}\;and\;21.4kJ/mol$, respectively. The H adsorption is attributed to the over-potentially deposited hydrogen (OPD H).

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.67-69
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• 2006

Capacitance and loss values of pentacene MIS capacitors with different thicknesses are measured as a function of frequency for the modeling of the devices. The equivalent circuit for the ideal MIS capacitor is adopted to model the obtained admittance, so the values of $C_i,\;C_d,\;C_b$, and $R_b$ are determined for each pentacene thickness. In the loss curve, broader loss peaks are observed in measurement than the modeling results regardless of the pentacene thickness. By considering the effects of dispersive charge transport in bulk semiconductor, more accurate modeling results are obtained.

• Macromolecular Research
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• v.12 no.6
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• pp.559-563
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• 2004

Both the ultrasonic velocity at 3 MHz and the absorption coefficient in the frequency range from 0.2 to 2 MHz were measured for aqueous solutions of poly(sodium 4-styrenesulfonate) over the concentration range from 5 to $25\%$ (by weight). The pulse echo overlap method was employed to measure the ultrasonic velocity over the temperature range from 10 to $90^{\circ}C;$ the high-Q ultrasonic resonator method was used for the measurement of the absorption coefficient at $20^{\circ}C.$ The velocities exhibited their maximum values at ca. 55, 59, 63, 67, and $71^{\circ}C.$ for the 25, 20, 15, 10, and $5\%$ solutions, respectively. The velocity increased with respect to the poly(sodium 4-styrene-sulfonate) concentration at a given temperature. A study of the concentration dependence of the both the relaxation frequency and amplitude indicated that the relaxation at ca. 200 kHz is related to structural fluctuations of the polymer molecules, such as the segmental motions of the polymer chains and that the relaxation at ca. 1 MHz resulted from the proton transfer reactions of the oxygen sites of $SO_3.$ Both the absorption and the shear viscosity increase upon increasing the polymer concentration, but they decrease upon increasing the temperature.

• Journal of Nutrition and Health
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• v.40 no.1
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• pp.69-77
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• 2007

The study was conducted to investigate the factors associated with bone mineral content (BMC) changes among early pubertal aged girls. Two hundred and thirty girls between 9 to 11 years of age participated in (our surveys over 2 year period. During each survey, dietary intakes were collected with 3-day food records, BMC of left leg's calcaneus were measured by PIXI (Lunar Ltd.) and body composition was measured by bioimpedance method (Inbody 3.0 Biospace Co. Ltd, Seoul, Korea). Mean values of BMC increased in consecutive measurements -1.48 g, 1.54 g, 1.61 g and 1.66 g. The change of BMC between the first and last measurements was significantly positively correlated with % body fat, negatively correlated with BMC at the baseline (p < 0.05). Change of BMC was also significantly positively correlated with % change of lean mass and mineral mass between the first and last measurements. Nutrient intakes during the study period were calculated as mean daily intakes from all surveys. Mean daily intakes of Vit. C and Vit. $B_6$ were positively and isoflavone intake was negatively correlated with changes of BMC (p < 0.05). In stepwise regression of BMC change with body composition and nutrient intakes, baseline values of BMC, weight, BMI and age, % change of mineral mass during the study period, mean intakes of isoflavone, Vit. $B_6$, protein, carotene and zinc were significant explanatory variables ($R^2=0.38$, p <.001, F = 32.39). The results imply that the change of BMC among early pubertal aged girls are associated with some body composition and intakes of certain nutrients.