• Nuclear Engineering and Technology
• /
• v.29 no.1
• /
• pp.7-14
• /
• 1997

Grain boundary diffusion plays a significant role in fission gas release, which is one of the crucial processes dominating nuclear fuel performance. Gaseous fission produce such as Xe and Kr generated during nuclear fission have to diffuse in the grain lattice and the boundary inside fuel pellets before they reach the open spaces in a fuel rod. These processes can be studied by 'tracer diffusion' techniques, by which grain boundary diffusivity can be estimated and directly used for low burn-up fission gas release analysis. However, only a few models accounting for the both processes are available and mostly handle them numerically due to mathematical complexity. Also the numerical solution has limitations in a practical use. In this paper, an approximate analytical solution in case of stationary grain boundary in a polycrystalline solid is developed for the tracer diffusion techniques. This closed-form solution is compared to available exact and numerical solutions and it turns out that it makes computation not only greatly easier but also more accurate than previous models. It can be applied to theoretical modelings for low bum-up fission gas release phenomena and experimental analyses as well, especially for PIE (post irradiation examination).

• Tunnel and Underground Space
• /
• v.4 no.2
• /
• pp.102-118
• /
• 1994

Thermomechanical analysis is conducted on the radioactive repository in deep rock mass considering the in-situ stress, excavation and thermal loading of a radioactive waste. Thermomechanical properties of a discontinuous rock mass are estimated by a theoretical method so called sequential analysis. Using the estimated properties as input for finite element analysis, the influence on temperature distribution and thermal stress is analyzed within the scope of 2-dimensional steady state and transient heat transfer and coupled thermal elastic plastic behaviour. Granitic rock mass is taken for this analysis. The analysis is done for two different rock mass conditions, i.e. continuous-homogeneous and highly jointed conditions, for the purpose of comparison. In the case of steady state, the extent of disturbed zone around the storage tunnel due to the heat production of the spent-fuel canister varies depending on the thermomechanical properties of the rock mass. In the case of transient analyses, the response of the jointed rock mass to the thermal loading after radioactive waste disposal varies significantly with time, resulting in dramatic changes in the both size and location of disturbed zone.

• Textile Coloration and Finishing
• /
• v.19 no.3
• /
• pp.6-11
• /
• 2007

The indigoid-type dyes based on isatin $\alpha-chloride$ were synthesized and the dyes were discussed with relevance to the "H-chromophore" or "cross-conjugated chromophore". The color-changed properties of the dyes were also investigated by means of visible absorption spectra. The novel dyes from isatin $\alpha-chloride$ are of theoretical interest and such dyes can be used as continuous pH indicators in acid/base titrimetric analyses.

• Journal of Bio-Environment Control
• /
• v.2 no.1
• /
• pp.1-8
• /
• 1993

Experimental and theoretical analyses were carried out to investigate the heat exchange characteristics of the nutrient solution cooling system utilizing ground water. The material of heat exchanger used in the experiment was polyethylene and the cross-flow type was adapted in which nutrient solution was mixed and ground water unmixed. For the exchanger surface area of 0.33$m^2$ and flow rates of ground water of 1-6$\ell$/min, NTU(number of transfer units) and effectiveness of experimental heat exchanger were 0.1-0.45 and 10-35％, respectively. Therefore these results showed that the hydroponic greenhouse of 1,000$m^2$(300 pyong) with the ground water of 10$m^2$/day could cover about 55-70％ of maximum cooling load in summer.

• Structural Engineering and Mechanics
• /
• v.8 no.2
• /
• pp.181-191
• /
• 1999

This paper presents an investigation of the mode localization and frequency loci veering phenomena in an aircraft with disordered external stores. Two theoretical analyses are carried out to study the occurring mechanism of the two phenomena: condensation technique in the subspace spanned by modes of interest and geometric mapping theory in the complex plane. Two simple criteria for predicting the occurrence of the mode localization and frequency loci veering are put forward. The prediction of the phenomena by our theoretically proposed criteria is in good agreement with that obtained through numerical calculations of characteristic solutions of the disordered system.

• Journal of the Korean Society for Railway
• /
• v.7 no.1
• /
• pp.65-69
• /
• 2004

In reference to this study, Part Ⅰ showed how the system respond to the harmonics originated from electric locomotives. That is, the system response to the harmonics was derived by computational algorithm with numerical formulas in theoretical aspects. However, Real catenary system has complex configuration of conductors and it is an important point that if we can consider the circuit element of catenary conductors as an uniformly distributed RLC element. Moreover, harmonic characteristics in electric locomotive depend on its operational modes. From these point of view, measurements of harmonics are performed for real railway power supply systems under the various operational modes, and spectrum and distortion analyses in measurement data are described.

• Structural Engineering and Mechanics
• /
• v.25 no.6
• /
• pp.753-765
• /
• 2007

The response histories and distribution of dynamic interlaminar stresses in composite laminated plates under free vibration and thermal load is studied based on a thermoelastodynamic differential equations. The stacking sequence of the laminated plates may be arbitrary. The temperature change is considered as a linear function of coordinates in planes of each layer. The dynamic mode of displacements is considered as triangle series. The in-plane stresses are calculated by using geometric equations and generalized Hooke's law. The interlaminar stresses are evaluated by integrating the 3-D equations of equilibrium, and utilizing given boundary conditions and continuity conditions of stresses between layers. The response histories and distribution of interlaminar stress under thermal load are presented for various vibration modes and stacking sequence. The theoretical analyses and results are of certain significance in practical engineering application.

• Journal of Broadcast Engineering
• /
• v.26 no.7
• /
• pp.862-867
• /
• 2021

Although Deep Neural Networks (DNNs) have shown remarkable performance in various artificial intelligence fields, it is well known that DNNs are vulnerable to adversarial attacks. Since adversarial attacks are implemented by adding perturbations onto benign examples, increasing the sparsity of DNNs minimizes the propagation of errors to high-level layers. In this paper, unlike the traditional pruning scheme removing low magnitude weights, we eliminate high magnitude weights that are usually considered high absolute values, named 'reverse pruning' to ensure robustness. By conducting both theoretical and experimental analyses, we observe that reverse pruning ensures the robustness of DNNs. Experimental results show that our reverse pruning outperforms previous work with 29.01% in Top-1 accuracy on perturbed CIFAR-10. However, reverse pruning does not guarantee benign samples. To relax this problem, we further conducted experiments by adding a regularization term for the high magnitude weights. With adding the regularization term, we also applied conventional pruning to ensure the robustness of DNNs.

• Steel and Composite Structures
• /
• v.30 no.6
• /
• pp.577-589
• /
• 2019

In this study, on-site testing was carried out to investigate the vibration performance of a composite steel-bar truss slab with steel girder system. Ambient vibration was performed to capture the primary vibration parameters (natural frequencies, damping ratios, and mode shapes). The composite floor possesses low frequency (< 10 Hz) and damping (< 2%). Based on experimental, theoretical, and numerical analyses on natural frequencies and mode shapes, the boundary condition of SCSC (i.e., two opposite edges simply-supported and the other two edges clamped) is deemed more reasonable for the composite floor. Walking excitations by one person (single excitation), two persons (dual excitation), and three persons (triple excitation) were considered to evaluate the vibration serviceability of the composite floor. The measured acceleration results show a satisfactory vibration perceptibility. For design convenience and safety, a crest factor ${\beta}_{rp}$ describing the ratio of peak acceleration to root-mean-square acceleration induced from the walking excitations is proposed. The comparisons of the modal parameters determined by ambient vibration and walking tests reveal the interaction effect between the human excitation and the composite floor.

• Journal of Power Electronics
• /
• v.19 no.2
• /
• pp.602-611
• /
• 2019

The major drawbacks of magnetic resonant coupled wireless power transfer (WPT) to the embedded sensors on spindles are transmission instability and low efficiency of the transmission. This paper proposes a novel double-loop coil design for wirelessly charging embedded sensors. Theoretical and finite-element analyses show that the proposed coil has good transmission performance. In addition, the power transmission capability of the double-loop coil can be improved by reducing the radius difference and width difference of the transmitter and receiver. It has been demonstrated by analysis and practical experiments that a magnetic resonant coupled WPT system using the double-loop coil can provide a stable and efficient power transmission to embedded sensors.