• Korean Journal of Materials Research
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• v.21 no.2
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• pp.95-99
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• 2011

The microstructure and Cu diffusion barrier property of Ta-Si-N films for various Si and N compositions were studied. Ta-Si-N films of a wide range of compositions (Si: 0~30 at.%, N: 0~55 at.%) were deposited by DC magnetron reactive sputtering of Ta and Si targets. Deposition rates of Ta and Si films as a function of DC target current density for various $N_2/(Ar+N_2)$ flow rate ratios were investigated. The composition of Ta-Si-N films was examined by wavelength dispersive spectroscopy (WDS). The variation of the microstructure of Ta-Si-N films with Si and N composition was examined by X-ray diffraction (XRD). The degree of crystallinity of Ta-Si-N films decreased with increasing Si and N composition. The Cu diffusion barrier property of Ta-Si-N films with more than sixty compositions was investigated. The Cu(100 nm)/Ta-Si-N(30 nm)/Si structure was used to investigate the Cu diffusion barrier property of Ta-Si-N films. The microstructure of all Cu/Ta-Si-N/Si structures after heat treatment for 1 hour at various temperatures was examined by XRD. A contour map that shows the diffusion barrier failure temperature for Cu as a function of Si and N composition was completed. At Si compositions ranging from 0 to 15 at.%, the Cu diffusion barrier property was best when the composition ratio of Ta + Si and N was almost identical.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.47 no.2
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• pp.39-47
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• 2010

In Wireless Sensor Network, transmission errors are frequently occurred due to the node failure, battery discharge, and interference by objects. Although Directed Diffusion has been considered as a prominent Data-centric routing algorithm, it revealed some weaknesses at this kind of unexpected network errors. In order to address the problem, we proposed a radio-aware routing algorithm for improving reliability of Directed Diffusion in Wireless Sensor Networks. The proposed algorithm is aware of the network status based on the radio information of MAC and PHY layers using a cross-layer approach. The link quality and the node failure information from the acquired network status were used to decide an alternative path to provide a reliable data transmission in error-prone sensor networks. The proposed algorithm showed its effectiveness of the data delivery rate and data ratio with several simulations consisting of various error rates and the number of nodes.

• Journal of the Korean Society for Marine Environment & Energy
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• v.11 no.2
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• pp.92-97
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• 2008

Salt wedge into the river from the sea or fresh water flume (fresh wedge) in the ocean from the sea has density current characteristics. However, when temperature and salinity simultaneously determine the density of wedges, one of salinity and temperature can distributed in the reversed profiles against gravity, even though the density profile is stable. In this case, the double diffusive process is critical in determining mixing rate. The present work studies relative contribution of shear driven mechanical mixing component and double diffusive layering process, when warm salty denser water is introduced into the cold fresh lighter water column. Laboratory experiment releases warm salty denser water into cold fresh lighter water controlling discharge amount to achieve the steady state of density current. When longitudinal density rate becomes 15, the released amount ratio of salt and heat changes sharply and in the releasing point, vigorous mixing occurs with increase of discharged amount due to double diffusion. Double diffusion distabilizes gravitational stability and enhances the mixing rate up to $6{\times}10$ times at the lower density ratio comparing to the higher density ratio.

• Journal of Korean Neurosurgical Society
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• v.38 no.5
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• pp.331-337
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• 2005

Objective : The purpose of this study is to identify correlations between diffusion tensor imaging[DTI] and motor improvement by quantifying and visualizing the corticospinal tract on DTI to predict motor impairment in patients with hypertensive intracerebral hemorrhage[ICH]. Methods : Fifteen normal subjects and 7 patients with hypertensive ICH were examined and the latter were treated surgically. DTI was performed with a 3.0 T MRI. The region of interest[ROI] from the posterior limbs of both internal capsules was measured on a fractional anisotropy[FA] map, and the ratios of ROIs were calculated. Tractography, 3-dimensional DTI was then constructed. Motor impairment was assessed on admission and 2weeks after stroke by the Motricity Index[MI]. The FA ratio, tractography and score on MI were analyzed for correlations. Results : The FA ratio from the initial DTI did not show a linear correlation with motor impairment. However, after 2weeks, patients with high FA ratios showed high degrees of motor recovery, regardless of the initial severity, and patients with low FA ratios showed low recovery rates. Otherwise, a relationship between the amount of hematoma and the degree of motor recovery could not be determined. On tractography, injury of the corticospinal tract could be visualized and estimated 3-dimensionally. Conclusion : FA ratio analysis and tractography constructed from DTI may be useful in understanding corticospinal tract injury and in predicting the recovery from motor impairment in patients.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.1
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• pp.75-84
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• 2007

The effects of hydrogen enrichment to methane on NOx formation have been investigated with swirl stabilized pre-mixed hydrogen enriched methane flame in a laboratory-scale pre-mixed combustor(nominally of 5,000 kcal/hr). The hydrogen enriched methane fuel and air were mixed in a pre-mixer and introduced to the combustor through different degrees of swirl vanes. The flame stability was examined for different amount of hydrogen addition to the methane fuel, different combustion air flow rates and swirl strengths by comparing equivalence ratio at the lean flame limit. The hydrogen addition effects and swirl intensity on the combustion characteristics of pre-mixed methane flames were examined using gas analyzers, and OH chemiluminescence techniques to provide information about species concentration of emission gases and flowfield. The results of NOx and CO emissions were compared with a diffusion flame type combustor. The results show that the lean stability limit depends on the amount of hydrogen addition and the swirl intensity. The lean stability limit is extended by hydrogen addition, and is reduced for higher swirl intensity at lower equivalence ratio. The addition of hydrogen increases the NOx emission, however, this effect can be reduced by increasing either the excess air or swirl intensity. The NOx emission of hydrogen enriched methane premixed flame was lower than the corresponding diffusion flame under the fuel lean condition.

• Geomechanics and Engineering
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• v.34 no.2
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• pp.155-171
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• 2023

Aiming at the grouting treatment of water inflow in karst conduits, a visualized experiment system for conduit-type grouting blocking was developed. Through the improved water supply system and grouting system, and the optimized multisource information monitoring system, the real-time observation of diffusion and deposition of slurry, and the data acquisition of pressure and velocity during the whole process of grouting were realized, which breaks through the problem that the monitoring element is easy to fail due to slurry adhesion in conventional test system. Based on the grouting experiments in static and flowing water, the diffusion and deposition behavior of the quick-setting slurry under different working conditions were analyzed. The temporal and spatial variation behavior of the pressure and velocity were studied, and the blocking mechanism of the grouting were further revealed. The results showed that: (1) Under the flowing water condition, the counter-flow diffusion distance of slurry was negatively correlated with the flow water velocity and the volume ratio of cement and sodium silicate (C-S ratio), and positively correlated with the grouting volume. The slurry deposition thickness was negatively correlated with the flowing water velocity, and positively correlated with the grouting volume and C-S ratio. (2) The pressure increased slowly before blocking of the flowing water and rapidly after blocking in karst conduits. (3) With the continuous progress of grouting, the flowing water velocity decreased slowly first, then significantly, and finally tended to be stable. According to the research results, some engineering recommendations were put forward for the grouting treatment of the conduit-type water inflow disaster, which has been successfully applied in the treatment project of the China Resources Cement (Pingnan) Limestone Mine. This study provided some guidance and reference for the parameter optimization of grouting for the treatment projects of water inflow in karst conduits.

• Korean Journal of Radiology
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• v.25 no.1
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• pp.43-54
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• 2024

Objective: To evaluate the added value of diffusion-weighted imaging (DWI)-based quantitative parameters to distinguish uterine sarcomas from atypical leiomyomas on preoperative magnetic resonance imaging (MRI). Materials and Methods: A total of 138 patients (age, 43.7 ± 10.3 years) with uterine sarcoma (n = 44) and atypical leiomyoma (n = 94) were retrospectively collected from four institutions. The cohort was randomly divided into training (84/138, 60.0%) and validation (54/138, 40.0%) sets. Two independent readers evaluated six qualitative MRI features and two DWI-based quantitative parameters for each index tumor. Multivariable logistic regression was used to identify the relevant qualitative MRI features. Diagnostic classifiers based on qualitative MRI features alone and in combination with DWI-based quantitative parameters were developed using a logistic regression algorithm. The diagnostic performance of the classifiers was evaluated using a cross-table analysis and calculation of the area under the receiver operating characteristic curve (AUC). Results: Mean apparent diffusion coefficient value of uterine sarcoma was lower than that of atypical leiomyoma (mean ± standard deviation, 0.94 ± 0.30 10^-3 mm²/s vs. 1.23 ± 0.25 10^-3 mm²/s; P < 0.001), and the relative contrast ratio was higher in the uterine sarcoma (8.16 ± 2.94 vs. 4.19 ± 2.66; P < 0.001). Selected qualitative MRI features included ill-defined margin (adjusted odds ratio [aOR], 17.9; 95% confidence interval [CI], 1.41-503, P = 0.040), intratumoral hemorrhage (aOR, 27.3; 95% CI, 3.74-596, P = 0.006), and absence of T2 dark area (aOR, 83.5; 95% CI, 12.4-1916, P < 0.001). The classifier that combined qualitative MRI features and DWI-based quantitative parameters showed significantly better performance than without DWI-based parameters in the validation set (AUC, 0.92 vs. 0.78; P < 0.001). Conclusion: The addition of DWI-based quantitative parameters to qualitative MRI features improved the diagnostic performance of the logistic regression classifier in differentiating uterine sarcomas from atypical leiomyomas on preoperative MRI.

• 한국연소학회:학술대회논문집
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• 2004.11a
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• pp.124-129
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• 2004

The ratio pyrometry has been investigated experimentally for the measurement of soot particle temperatures in a diffusion flame. A tungsten lamp calibration system was constructed and used in order to calibrate the ratio pyrometry and two-color pyrometry using a KL-factor method. Once the ratio pyrometry is properly calibrated, temperatures measured using a ratio pyrometry were virtually identical to those obtained from a KL-factor method. The effect of soot volume fraction on temperature measurement was almost negligible, and therefore, the ratio pyrometry could provide the useful temperature information of sooting flames. The potential application of a ratio pyrometry to a 2-D temperature measurement without sacrificing the accuracy was demonstrated.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.665-670
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• 2001

The studies on chloride diffusion of concrete have been done so far by many researchers. However, there are few studies that present the effects of other attacks on chloride diffusion properties. Therefore, in this study the experiments are carried out to show the effects of combined attacks, such as carbonation, sulfate attacks, on chloride diffusivity in concrete. The specimens are made by varying cement type and replacement ratio of fly ash. The results show that cement type and replacement of fly ash do not affect greatly chloride diffusion properties. And concrete treated by combined attacks show a little higher chloride content than those treated by chloride solution only. Therefore, the effects of these factors should be taken into account in predicting the penetration of chloride ion in concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.196-199
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• 2004

Metakaolin is a cementitious material for producing high-strength concrete. This material is now used as substitute for silica-fume. In this paper, we tested the compressive strength of concrete according to the substitute ratio of metakaolin, silica-fume. And we did the durability test such as chloride ion diffusion and chemical attack. In the compressive strength test, the result shows that $10\%$ substitute of metakaolin & silica-fume for binder is optimum. In the chloride ion diffusion test, according to the increase of substitute of metakaolin & silica-fume for binder, the diffusion coefficient is more reduced. And in the chemical attack test, according to the increase of substitute, the resistance is more excellent. In the durability test, we recognized that metakaolin is able to used as a substitute for silica-fume.