• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1933-1938
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• 2004

Nucleate boiling experiments with constant wall temperature of heating surface were performed using R113 for almost saturated pool boiling conditions. A microscale heater array and Wheatstone bridge circuits were used to maintain a constant wall temperature condition and to measure the heat flow rate with high temporal and spatial resolutions. Bubble images during the bubble growth were taken as 5000 frames a sec using a high-speed CCD camera synchronized with the heat flow rate measurements. The geometry of the bubble during growth time could be obtained from the captured bubble images. The bubble growth behavior was analyzed using the new dimensionless parameters for each growth regions to permit comparisons with previous results at the same scale. We found that the new dimensionless parameters can describe the whole growth region as initial and later respectively. The comparisons showed good agreement in the initial and thermal growth regions. The required heat flow rate for the volume change of the observed bubble was estimated to be larger than the instantaneous heat flow rate measured at the wall. Heat, which is different from the instantaneous heat supplied through the heating wall, can be estimated as being transferred through the interface between bubble and liquid even with saturated pool conditions. This phenomenon under a saturated pool condition needs to be analyzed and the data from this study can supply the good experimental data with the precise boundary condition (constant wall temperature).

• Journal of the Korean Chemical Society
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• v.18 no.2
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• pp.126-131
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• 1974

Trioctylamine-and tricaprylylmethylammonium chloride-tungstate salts have been prepared by solvent extraction from the sodium tungstate solution of various acidities(pH = 2, 4, 6). The molecular weights of the amine-tungstate salts thus obtained could be cryoscopically measured in benzene by means of a home-built Wheatstone bridge utilizing thermistor with sensitivity of 1/$4000^{\circ}C$. The cryoscopic data along with the results of chemical analysis and infrared spectra of the salts indicate that the amine-tungstates prepared at pH = 2 and 4 are all metatungstate whereas the salt obtained at pH = 6 is an unknown form quite different from the expected paratungstate.R = 0.14. By hydrogen bonding a guanidyl nitrogen of a sulfaguanidine molecule is linked to the sulfonyl oxygens of the other molecules indirectly through two different water molecules. The role of water molecule is both a .
nor and an acceptor in hydrogen-bonding formation and these hydrogen bonds are tetrahedrally o？ented. The hydrogen-bonding networks form infinite molecular layers parallel to (001) plane.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.578-583
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• 2017

This paper presents a 3D touch pad technology that uses force touch sensors as a next-generation method for mobile applications. 3D touch technology requires detecting the location and pressure of touches simultaneously, as well as multi-touch function. We used metal foil strain gauges for the touch recognition sensor and detected the weak touch signals using Wheatstone bridge circuit at each strain gauge sensor. We also developed a touch recognition system that amplifies touch signals, converts them to digital data through a microprocessor, and displays the data on a screen. In software, we designed a touch recognition algorithm with C code, which is capable of recognizing two-point touch and differentiating touch pressures. We carried out a successful experiment to display two touch signals on a screen with different forces and locations.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.5
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• pp.29-36
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• 2019

In modern society in which the fourth industrial revolution has come to the fore and rapid technology innovations are taking place, a phenomenon of making and selling small quantities of various products that consumers want instead of mass producing one item has emerged. As the market is moving toward the multi-item small-sized production system, there is a need for a system in which a machine independently judges and carries out machining and post-processing. In order for a machine to judge processing on its own, it is necessary to measure the force applied to a product. This study aimed to develop a large-scale dynamometer that enables three-axis measurement using octagonal ring load cells. As for the device's configuration, four octagonal ring load cells, which were previously researched, were used to enable three-axis measurement. It was reconfigured by modifying the attachment position of the octagonal ring load cells' strain gauge and the Wheatstone bridge of each axis, and a system was set up to allow the monitoring of data measured through the monitor. The configured device calculated a strain rate by an experiment, and this rate was compared with the theoretical strain rate to find a correction value. The correction value was entered into a formula, deriving a modified formula. The modified formula was entered into the device, which completed the large-scale dynamometer.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.3
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• pp.352-362
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• 2005

Statement of problem. Accurate impression is essential to success of implant prostheses. But there have been few studies about the accuracy of fixture-level impression techniques in internal connection implant systems. Purpose. The purpose of this study was to compare the accuracy of two fixture-level impression techniques in two conditions (parallel and divergent) and to assess the effect of tightening sequences and forces on stresses generated on superstructures in internal connection implant system (Astra Tech). Material and methods. Two metal master frameworks made from two abutments (Cast-to Abutment ST) each and a corresponding, passively fitting, dental stone master cast with four fixture replicas (Fixture Replica ST) were fabricated. Ten dental stone casts for each impression techniques (direct unsplinted & splinted technique) were made with vinyl polysiloxane impressions from the master cast. Strain gauges for each framework were fixed midway between abutments to measure the degree of framework deformation on each stone cast. Pairs of strain gauges placed opposite each other constituted one channel (half Wheatstone bridge) to read deformation in four directions (superior, inferior, anterior, and posterior). Deformation data were analyzed using one-way ANOVA and the Tukey test at the .01 level of significance. And the effect of tightening sequences (right-to-left and left-to-right) and forces (10 Ncm and 20 Ncm) were assessed with ten stone casts made from parallel condition by the splinted technique. Deformation data were analyzed using paired t-test at the .01 level of significance. Conclusions. Within the limitations of this study, the following conclusions could be drawn. 1. Frameworks bent toward the inferior side on all casts made by both direct unsplinted and splinted impression techniques in both parallel and divergent conditions. 2. There was no statistically significant difference of accuracy between the direct unsplinted and splinted impression techniques in both parallel and divergent conditions (P>.01). 3. There was no statistically significant difference of stress according to screw tightening sequences in casts made by the splinted impression technique in parallel condition (P>.01). 4. Greater tightening force resulted in greater stress in casts made by the splinted impression technique in parallel condition (P<.01).