• Analytical Science and Technology
• /
• v.23 no.1
• /
• pp.24-35
• /
• 2010

To learn more about the calibration properties of reduced sulfur compounds (RSCs) by the combination of gas chromatography(GC)-pulsed flame photometric detector (PFPD) and thermal desorption method, a series of calibration experiments were conducted on the basis of both internal and external calibration approaches. For these experiments, gaseous standards of 4 RSCs ($H_2S$, $CH_3SH$, DMS, and DMDS) were prepared at two different concentration levels of both low (10, 20, 50,and 100 ppb) and high ranges (100, 200, 500, and 1000 ppb) along with $CS_2$ as an internal standard. First, the external calibration results were compared between fixed standard volume (FSV) and fixed standard concentration (FSC) method. Secondly, FSV-based calibration results were compared between external and internal calibration results. As FSV method suffers from sensitivity variations less significantly than FSC, the former is recommended to maintain the consistency in GC-TD sensitivity for RSC analysis. In addition, when the calibration data were examined in terms of RSE between external and internal calibration data, the results were not consistent enough to show improvements in internal method. Hence, diverse efforts are desirable to optimize the reproducibility in terms of GC-TD sensitivity for RSC analysis.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2002.10a
• /
• pp.799-804
• /
• 2002

This paper is mainly Intended to show an effect of foundation depth on heat of hydration in mass concrete. From the analysis, it was found that the foundation depth which is not affected by the heat conduction is more than 5 m. But this study shows that, an optimum foundation depth for the FEM analysis for heat of hydration in mass concrete is approximately 1 m from this study. And in order to study tile significance of various parameters, a sensitivity analysis of heat transfer in mass concrete is performed and the amount of heat liberated at complete hydration of unit weight of cement and the reaction velocity of hydration are the most sensitive parameters factors of other various parameters.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.28 no.6
• /
• pp.709-716
• /
• 2004

In order to prevent the interface delamination of an plastic IC package in the infrared (IR) soldering process, we tried to reduce stress by parameterization, sensitivity analysis and unconstraint optimization. The design variables of dimensions and material properties are determined among all the possible variables from the parametric study. Their optimized values are determined by applying the unconstraint optimization to the parameterized IC package. The maximum von-Mises stress value decreases greatly by optimum design.

• Proceedings of the IEEK Conference
• /
• 1998.10a
• /
• pp.981-982
• /
• 1998

We fabricated sampled fiber grating by double-exposure method. First, a short-period grating was written into the hydrogen-loaded single mode fiber and then the refractive index was modulated over it by an amplitude mask. It was observed that several transmission dips appear due to the index modulation. The thermal and strain responses were measured over $40-180^{\circ}C$ and $0-1800\mu\varepsilon,$ respectively. The dips have the same and linear sensitivity to both physical quantities over the range of measurement.

• Journal of Sensor Science and Technology
• /
• v.16 no.2
• /
• pp.91-96
• /
• 2007

The characteristic of tellurium thin films was studied for detecting nitrogen dioxide gas at room temperature. The film was deposited on $Al_{2}O_{3}$ substrate by using thermal evaporator. The subsequent process was heat treatment by several conditions. (temperature, flowed gases) Surface and grain boundary was investigated using SEM. The results showed that resistance of the tellurium film decreases reversibly in the presence of nitrogen dioxide. The sensitivity of this device depends on the gas concentration and detect lower concentrations less than 10 ppm.

• Korean Journal of Microbiology
• /
• v.24 no.2
• /
• pp.161-167
• /
• 1986

Some of the physiological properties of Sp816 bacteriophage of Bacillus subtilis SNU816 were characterized. It could form plaques on either B. subtilis SNU816 or B. natto 8102, but not on any other bacillus strains investrgated. Its plaque morphology was circular with a diameter of less than 1.0mm and had a narrow halo surrounding the clear center. Its latent period was 34-36 min and had a burst size of 547. It was most stable at pH 6.0, and rapidly inactivated at $60^{\circ}C$ with a initial deaty rate of -0.216 $min^{-1}$. Host range, thermal inactivation rate at $60^{\circ}C$, pH stability, and UV sensitivity revealed that SP816 was quite different from any other phages investigated together but seemed to be rather related to B. natto phages.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2001.11a
• /
• pp.303-308
• /
• 2001

Recently, concrete structures have become larger and higher and are demanding high performance concrete with lower heat to prevent thermal cracking, far greater workability, high strength and durability, Application of low heat portland(Type IV) cement for the high performance concrete is the best solution to satisfied those requirements. Here are explained the effect on the properties of high flowing concrete using low heat portland cement by material and mixing variations. Variables for sensitivity test were selected items like finess modulus of aggregates, particle size of limestone powder, unit water, superplasticizer, viscosity agent and concrete temperature. The results of this study were be applied to slurry wall of #215 and #216 of underground LNG tank in Inchon.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2005.05a
• /
• pp.426-430
• /
• 2005

The fiber-optic interferometer which is a powerful application for nondestructive measurement techniques has many advantages such as capability of making portable system, easy optical arrangement, low optical loss. In spite of these advantages, this system has an environmental sensitivity of thermal drifts and vibrations. Against environmental perturbations and nonlinear characteristic of phase modulator, the accurate and fast ${\pi}/2$ phase stepping has been achieved by using zero-crossing detection. CCD camera trigger signal is generated at the 4 zero-crossing points. Our System has achieved up to 100 Hz of image capture speed and 0.6 mrad of accuracy of phase stepping, accuracy.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.05a
• /
• pp.46-50
• /
• 2007

The nuclear power plant's turbine-generator system had been suffered form some problems, such as high shaft vibration, generator casing crack, stator coil water leakage, high $H_2$ gas consumption rate. Those kinds of problems were related to high vibration. So nuclear plant decided to replace generator in order to reduce rotor high vibration and high thermal sensitivity. A series of effort to reduce turbine-generator vibration was carried out as followings, first of all, replacement of generator, analysis of turbine-generator vibration, LP B rotor shop balancing, improvement of LP B/Gen coupling run-out, improvement of Generator basement and field balancing. Finally the nuclear turbine-generator's shaft vibration was reduced below $60{\mu}m$ from over $200{\mu}m$ which is very excellent vibration in nuclear turbine-generator in Korea.

• Computers and Concrete
• /
• v.19 no.1
• /
• pp.33-39
• /
• 2017

In this study, two types of aggregate were used for making self-compacting concrete. Standard cubic specimens were exposed to different temperatures. Seventy-two standard cylindrical specimens ($150{\times}300mm$) and Seventy-two cubic specimens (150 mm) were tested. Compressive strengths of the manufactured specimens at $23^{\circ}C$ were about 33 MPa to 40 MPa. The variable parameters among the self-compacting concrete specimens were of sand stone type. The specimens were exposed to 23, 100, 200, 400, 600, and $800^{\circ}C$ and their mechanical specifications were controlled. The heated specimens were subjected to the unconfined compression test with a quasi-static loading rate. The corresponding stress-strain curves and modulus of elasticity were compared. The results showed that, at higher temperatures, Scoria aggregate showed less sensitivity than ordinary aggregate. The concrete made with Scoria aggregate exhibited less strain. The heated self-compacting concrete had similar slopes before and after the peak. In fact, increasing heat produced gradual symmetrical stress-strain diagram span.