• 전자공학회논문지 IE
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• v.45 no.3
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• pp.27-35
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• 2008

In this paper, we propose a minute signal detection algorithm for a development of optical analyzer, using the non-dispersive infrared method with multi gas filter correlation wheel, that can measure various environmental air-pollution materials (CO, SO2, NOx, etc.) in real-time. The MCT(mercury cadmium telluride) sensor can detect minute signals those show and absorption characteristic of each environmental pollution materials. In the proposed method, a corresponding data of each environmental pollution materials can be separated by an external trigger and threshold values in the measured continuous signals.

• Journal of the Society of Disaster Information
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• v.16 no.2
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• pp.383-391
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• 2020

Purpose: To identify internal self ignition and ignition caused by external flames in energy storage rooms, and to analyze the difference between ignition due to overheating and ignition caused by external heat sources. Method: membrane melting point measurement, battery external hydrothermal experiment, battery overcharge experiment, comparative analysis of electrode plate during combustion by overcharge and external heat, overcharge combustion characteristics, external hydrothermal fire combustion characteristics, 3.4 (electrode plate comparison) / 3.5 (overcharge) /3.6 (external sequence) analysis experiment. Result: Since the temperature difference was very different depending on the position of the sensor until the fire occurred, it is judged that two temperature sensors per module are not enough to prevent the fire through temperature control in advance. Conclusion: The short circuit acts as an ignition source and ignites the mixed gas, causing a gas explosion. The electrode breaks finely due to the explosion pressure, and the powder-like lithium oxide is sparked like a firecracker by the flame reaction.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.62-62
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• 2015

In this study, we study the effects of CF4 plasma treatment on the characteristics of enhancement mode (E-mode) AlGaN/GaN high electron mobility transistors (HEMTs). The CF4 plasma is generated by inductively coupled plasma reactive ion etching (ICP-RIE) system. The CF4 gas is decomposed into fluorine ions by ICP-RIE and then fluorine ions will effect the AlGaN/GaN interface to inhibit the electron transport of two dimension electron gas (2DEG) and increase channel resistance. The CF4 plasma method neither like the recessed type which have to utilize Cl2/BCl3 to etch semiconductor layer nor ion implantation needed high power to implant ions into semiconductor. Both of techniques will cause semiconductor damage. In the experiment, the CF4 treatment time are 0, 50, 100, 150, 200 and 250 seconds. It was found that the devices treated 100 seconds showed best electric performance. In order to prove fluorine ions existing and CF4 plasma treatment not etch epitaxial layer, the secondary ion mass spectrometer confirmed fluorine ions truly existing in the sample which treatment time 100 seconds. Moreover, transmission electron microscopy showed that the sample treated time 100 seconds did not have etch phenomena. Atomic layer deposition is used to grow Al2O3 with thickness 10, 20, 30 and 40 nm. In electrical measurement, the device that deposited 20-nm-thickness Al2O3 showed excellent current ability, the forward saturation current of 210 mA/mm, transconductance (gm) of 44.1 mS/mm and threshold voltage of 2.28 V, ION/IOFF reach to 108. As IV concerning the breakdown voltage measurement, all kinds of samples can reach to 1450 V.

• Clean Technology
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• v.25 no.4
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• pp.316-323
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• 2019

In order to enhance combustion efficiency and reduce atmosphere pollutants, it is essential to measure carbon monoxide (CO) concentration precisely in combustion exhaust. CO is the important gas species regarding pollutant emission and incomplete combustion because it can trade off with NOx and increase rapidly when incomplete combustion occurs. In the case of a steel annealing system, CO is generated intentionally to maintain the deoxidation atmosphere. However, it is difficult to measure the CO concentration in a combustion environment in real-time, because of unsteady combustion reactions and harsh environment. Tunable Diode Laser Absorption Spectroscopy (TDLAS), which is an optical measurement method, is highly attractive for measuring the concentration of certain gas species, temperature, velocity, and pressure in a combustion environment. TDLAS has several advantages such as sensitive, non-invasive, and fast response, and in-situ measurement capability. In this study, a combustion system is designed to control the equivalence ratio. Also, the combustion exhaust gases are produced in a Liquefied Petroleum Gas (LPG)/air flame. Measurement of CO concentration according to the change of equivalence ratio is confirmed through TDLAS method and compared with the simulation based on Voigt function. In order to measure the CO concentration without interference from other combustion products, a near-infrared laser at 4300.6 cm^-1 was selected.

• Korean Journal of Materials Research
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• v.20 no.3
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• pp.111-116
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• 2010

Chloride-based fluxes such as NaCl-KCl are used in the refining of Al melt. The vapor pressure of the chloride is one of the fundamental pieces of information required for such processes, and is generally high at elevated temperatures. In order to measure the vapor pressure for chlorides, the apparatus for the transpiration method was assembled in the present study. The vapor pressure of $ZnCl_2$ and $FeCl_2$, which is related with the process of aluminum refining and the recovery of useful elements from iron and steel industry by-products, was also measured. In the measurement of vapor pressure by the transpiration method, the powder of $ZnCl_2$ or $FeCl_2$ in a alumina boat was loaded in the uniform zone of the furnace with a stream of Ar. The weight loss of $ZnCl_2$ and $FeCl_2$ after holding was measured by changing the flow rate of Ar gas (10 sccm -230 sccm), and the partial pressures of $ZnCl_2$ and $FeCl_2$ were calculated. The partial pressures within a certain range were found to be independent of the flow rate of Ar at different temperatures. The vapor pressures were measured in the temperature range of 758-901K for $ZnCl_2$ and 963-983K for $FeCl_2$. The measured results agreed well with those in the literature.

• Journal of Integrative Natural Science
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• v.8 no.2
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• pp.128-134
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• 2015

This paper focuses on the applicability of a continuous monitoring method on trace sulfur compounds in the ambient air by TD and GC/PFPD. The target compounds for monitoring include H2S(hydrogen sulfide), Methyl mercaptan, Dimethyl Sulfide, and Dimethyl disulfide. The result of QA/QC on monitoring instruments satisfies all the standards of Odor Measurement and Analysis Method, showing that the reproductivity of the compounds by concentration is within 10%, linearity is above 0.98 of a correlation efficient, method detection limit is 0.16 ppb by MM standard, and recovery rate is over 70%. Monitoring was conducted for two years from March 2006 to February 2008. As a result of the monitoring, the average concentration of H2S was 0.08 ppb, with the maximum concentration at 16.15 ppb. The result indicates that it is reasonable to do continuous monitoring as there appears a spontaneous event of high concentration by the condition of the site during monitoring odor-causing substances. Therefore, it is suggested that the continuous monitoring method used in this paper is appropriate to identify the characteristics of sudden occurrence and concentration variations of sulfur compounds.

• Journal of Hydrogen and New Energy
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• v.23 no.5
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• pp.493-502
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• 2012

Syngas laminar burning velocity measurements were carried out at atmospheric pressure and ambient temperature using the Bunsen flame configuration with nozzle burner as a fundamental study on flame stability of syngas fuel. Representative syngas mixture compositions ($H_2$:CO) such as 25:75%, 50:50% and 75:25% and equivalence ratios from 0.5 to 1.4 have been conducted. Average laminar burning velocities have been determined by the stabilized nozzle burner flames using the angle method, radical surface area method and compared with the data obtained from the other literatures. And the results of each experimental methodologies in the various composition ratios and equivalence ratios were coincided with the result of numerical simulation. Especially, it was confirmed that there was necessary to choice a more accurate measurement methodology even the same static flame method for the various composition ratios of syngas fuel including hydrogen. Also, it was reconfirmed that the laminar burning velocities gradually increased with the increasing of hydrogen content in a fuel mixture.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.781-789
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• 2008

The fluorescence ratio method for processing planar laser induced fluorescence(PLIF) data was generalized for quantitative imaging of the injectant mole-fraction in supersonic mixing flowfields. The original fluorescence ratio approach was introduced by Hartfield et al. for tests in a special closed-loop wind tunnel to eliminate the effects of thermodynamic property variations in compressible flowfields and to provide a quantitative means of mole-fraction measurement. However, they implicitly assumed that the tracer molecules were seeded at the same fraction in both main and secondary flows. In the present study, we proposed generalizing the Hartfield method by considering differences in the tracer seeding rates. We examined the generalized method in a mixing flowfield formed by sonic transverse injection into a Mach 1.8 supersonic air stream. The injectant molefraction distribution obtained from PLIF data processed by our new approach showed better agreement with the gas chromatograph than one based on the Hartfield method.

• Tribology and Lubricants
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• v.1 no.1
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• pp.46-58
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• 1985

The basic mechanism of lubrication between the piston ring and the cylinder wall is developed theoretically under the assumption of a reciprocating and dynamically loaded slider-bearing pair of parabolic form and smooth plane. A numerical computation for the prediction in cyclic variations of film thickness, net lubricant flow and frictional behaviour is attempted, and the influenec on the performance characteristics due to the ring height, ring face radius of curvature and the degree of offset, is also examined. The computational procedures develeped for a single ring system are extended and applied further to the complex problem of a ring pack system. It is well known that the ring pressure which is the total load on a ring, can be obtained from either an experimental measurement or a gas flow analysis. In this work, the latter of a gas low analysis method was used to calculate the pressures. It is remarked that the work done was focused on the role of flow continuity and lubricant starvation within the ring pack lubrication.

• Journal of Sensor Science and Technology
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• v.27 no.3
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• pp.199-203
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• 2018

In this study, we develop a methane sensor module that can detect low concentrations below 5,000 ppm and measure up to the detection limit of 50 ppm with the NDIR method, with a long lifetime and high accuracy. Methane ($CH_4$) is one of a representative greenhouse gas, which is very explosive. Thus, it is important to quickly and accurately measure methane concentration in the air. To adjust the methane sensor for industrial field applications, a NDIR-based small sensor was implemented and characterized, where its volume was $4cm{\times}4cm{\times}2cm$ and its response time ($T_{90}$) was less than 30 sec. These results demonstrate that the proposed sensor is commercially available for low-concentration measurement, low volume, and fast response application, such as IoT sensor nodes and portable devices.