• Solar Energy
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• v.15 no.1
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• pp.53-71
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• 1995

Experiments have been conducted on a planar, free surface jet of water to investigate the effects of aspect ratios(AR=6.67, 15, 26.67), average nozzle velocity($V_0=3.3m/s{\sim}78m/s$) and nozzle-to-plate spacings($Z/W=6{\sim}40$) on the characteristics of heat transfer, when 3 rectangular waterjets impinging on a flat plate which has the uniform heat flux. the scondary peaks which produced by circular jets also produced by rectangular water jets. The position of the scondary peaks depends upon the aspect ratio of nozzle. The heat transfer coefficient was subjected to the influence of aspect ratio. The heat transfer correlations and best position of nozzles which produced maximum heat transfer coefficient at stagnation point are provided.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.3
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• pp.181-187
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• 2009

To estimate the status and volume of artificial reefs(ARs) deployed at the sea bottom in fishing grounds, this study assessed the initial volume of ARs, the cubic volume of AR groups, and the porosity of each AR using image data collected during a survey using a multi-beam echo sounder(MBES) and a side scan sonar(SSS). These results were compared with data collected during diver surveys and used to develop a new method and prediction formulas for countermeasures, facility volume, and efficient use of volume for deployed ARs(cubic concrete). The field survey results for nine ARs deployed in the Busan Sea region were calculated, and the average value of coefficient k(indicating the efficient use of volume ratio) among ARs was 0.753, and the correlation between coefficient k and year(Yr) of deployment was calculated as k=0.0023Yr+0.725. The relationship between these two factors was poor. In years following the deployment of artificial reefs, coefficient k and year of deployment were not correlated, in spite of the hardening ground due to subsidence and the reduced distance between ARs. Consequently, it is reasonable to suppose that coefficient k was defined by bottom surface conditions and initial deployment conditions.

• Journal of Information Display
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• v.3 no.1
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• pp.17-21
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• 2002

Measurement of the ion-induced secondary electron emission coefficient (${\gamma}_i$) for insulating films is hampered by an unavoidable charging problem. Here, we demonstrate that a pulsed ion beam technique is a viable solution to the problem, allowing for accurate measurement of ${\gamma}_i$ for insulating materials. To test the feasibility of the pulsed ion beam method, the secondary electron emission coefficient from n-Si(100) is measured and compared with the result from the conventional continuous beam method. It is found that the ${\gamma}_i$ from n-Si(100) by the ion pulsed beam measured to be 0.34, which is the same as that obtained by continuous ion beam. However, for the 1000 A $SiO_2$ films thermally deposited on Si substrate, the measurement of ${\gamma}_i$ could be carred out by the pulsed ion method, even though the continuous beam method faced charging problem. Thus, the pulsed ion beam is regarded to be one of the most suitable methods for measuring secondary electron coefficient for the surface of insulator materials without experiencing charging problem. In this report, the dependence of ${\gamma}_i$ on the kinetic energy of $He^+$ is presented for 1000 ${\AA}$ $SiO_2$ films. And the secondary electron emission coefficient of 1000 ${\AA}$ MgO e-beam-evaporated on $SiO_2/Si$ is obtained using the pulsing method for $He^+$ and $Ar^+$ with energy ranging from 50 to 200 eV, and then compared with those from the conventional continuous method.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1989-1991
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• 1999

This paper presents characteristics of CrN thin-film strain gauges, which were deposited on glass by DC reactive magnetron sputtering in an argon-nitrogen atmosphere(Ar-$(5{\sim}25%)N_2$). The physical and electrical characteristics of these films investigated with the thickness range $3500{\AA}$ of CrN thin films, annealing temperature $(100{\sim}300^{\circ}C)$ and annealing $(24{\sim}72hr)$. The optimized condition of CrN thin-film strain gauges were thickness range of $3500{\AA}$ and annealing condition($300^{\circ}C$, 48 hr) in Ar-10 %$N_2$ deposition atmosphere. Under optimum conditions, the CrN thin-films for strain gauge is obtained a high resistivity, ${\rho}=1147.65{\mu}{\Omega}cm$, a low temperature coefficient of resistance, TCR=$-186ppm/^{\circ}C$ and a high temporal stability with a good longitudinal, 11.17. And change in resistance after annealing for the CrN thin-films were quitely linear and stable.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.1
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• pp.36-40
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• 2003

The diamond-like nanocomposite (DLN) thin films were deposited on Si substrates using $CH_4/(C_2H_5O)_4Si/H_2$/Ar gas mixtures as source gases by the plasma enhanced chemical vapor deposition (PECVD). The chemical structure and microstructure of grown films were investigated and their tribological properties were evaluated by a ball-on-plate type tribometer. The deposited DLN films mainly consisted of diamond-like a-C:H and quartz-like a-Si:O networks. The DLN films had a good agreement with tribological coating applications due to their extremely low friction coefficients and low wear rates.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.2
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• pp.907-923
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• 2020

For the severe haze situation in the Beijing-Tianjin-Hebei region, conventional fine particulate matter (PM2.5) concentration prediction methods based on pollutant data face problems such as incomplete data, which may lead to poor prediction performance. Therefore, this paper proposes a method of predicting the PM2.5 concentration based on image analysis technology that combines image data, which can reflect the original weather conditions, with currently popular machine learning methods. First, based on local parameter estimation, autoregressive (AR) model analysis and local estimation of the increase in image blur, we extract features from the weather images using an approach inspired by free energy and a no-reference robust metric model. Next, we compare the coefficient energy and contrast difference of each pixel in the AR model and then use the percentages to calculate the image sharpness to derive the overall mass fraction. Furthermore, the results are compared. The relationship between residual value and PM2.5 concentration is fitted by generalized Gauss distribution (GGD) model. Finally, nonlinear mapping is performed via the wavelet neural network (WNN) method to obtain the PM2.5 concentration. Experimental results obtained on real data show that the proposed method offers an improved prediction accuracy and lower root mean square error (RMSE).

• Journal of Welding and Joining
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• v.20 no.2
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• pp.109-115
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• 2002

In the case of using high temperature by coating ceramic/metal, large stress was produced due to difference of thermal expansion coefficient between those. And then lead to delamination. In order to relaxation of the stress A1$_2$O$_3$/SS316 composite powders with $10wt.%Al_2O_3$ compositional gradient and $10wt.%Al_2O_3$ agglomerated powder were made by spray drying method. These powders were sintered to improve the strength and to be plasma sprayed in order to fabricate the FGC(functionally graded coating). The influence of gun power, working distance and Ar pressure on the microstructure of the coating layer was studied in order to optimize the plasma spray conditions. It was proven that the optimum conditions were 40kw gun power, 5cm working distance and $100ft^3/h$ Ar flow for both powders. FGC with 10 compositional steps was fabricated and the total thickness was 1.3mm. FGC was heat treated at $1100^{\circ}C$for 10hours to evaluate the heat resisting characteristics.

• KSTLE International Journal
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• v.4 no.2
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• pp.56-59
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• 2003

Boron carbide thin coatings were deposited on silicon wafers by DC magnetron sputtering using a ${B}_4$C target with Ar as processing gas. Various amounts of methane gas (${CH}_4$) were added in the deposition process to better understand their influence on tribological properties of the coatings. Reciprocating wear tests employing an oscillating friction wear tester were performed to investigate the tribological behaviors of the coatings in ambient environment. The chemical characteristics of the coatings and worn surfaces were studied using X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES). It revealed that ${CH}_4$addition to Ar processing gas strongly affected the tribologcal properties of sputtered boron carbide coating. The coefficient of friction was reduced approximately from 0.4 to 0.1, and wear resistance was improved considerably by increasing the ratio of ${CH}_4$gas component from 0 to 1.2 vol %. By adding a sufficient amount of ${CH}_4$(1.2 %) in the deposition process, the boron carbide coating exhibited lowest friction and highest wear resistance.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1375-1377
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• 2001

This paper describes the fabrication and characteristics of CrN thin-film type pessure sensors, in which the sensing elements were deposited on SUS. 630 diaphragm by DC reactive magnetron sputtering in an argon-nitride atmosphere(Ar-(10%) $N_2$). The optimized condition of CrN thin-film sensing elements was thickness range of 3500$\AA$ and annealing condition($300^{\circ}C$, 3 hr) in Ar-10 %$N_2$ deposition atmosphere. Under optimum conditions, the CrN thin-films for strain gauges is obtained a high resistivity, $\rho$=1147.65 ${\mu}{\Omega}$cm, a low temperature coefficient of resistance, TCR=-186 ppm/$^{\circ}C$ and a high temporal stability with a good longitudinal, 11.17. The output sensitivity of fabricated CrN thin-film type pressure sensors is 2.36 mV/V, 4$\sim$20 mA and the maximum non-linearity is 0.4 %FS and hysteresis is less than 0.2 %FS..

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2002.05a
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• pp.13-22
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• 2002

This paper presents characteristics of CrOx thin-film Strain gauge pressure sensors, which were deposited on SUS630 diaphragm by DC reactive magnetron sputtering in an argon-Oxide atmosphere(Ar-(10%)$O_2$). The optimized condition of CrOx thin-film strain gauges were thicknessrange of 2500$\AA$ and annealing condition ($350^{\circ}C$, 3 hr) in Ar-10 %$O_2$deposition atmosphere. Under optimum conditions, the CrOx thin-films for strain gauge is obtained a high resistivity, $\rho$=156.7$\mu$$\Omega$cm, a low temperature coefficiect of resistance, TCR=-86 ppm/$^{\circ}C$ and a high temporal stability with a good longitudinal, 15. The output sensitivity of pressure sensor obtained is 2.46㎷/V and the maximum non-linearity is 0.3%FS and hysteresis is less than 0.2%FS. The output characteristics of pressure transmitter obtained is 4~20㎃ and total accuracy is less than $\pm$0.5%FS. In those conclusions, CrOx thin film pressure sensors is quite satisfactory for many applications in industrial electronics.