• Nuclear Engineering and Technology
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• v.56 no.1
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• pp.167-179
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• 2024

This study explores the feasibility of employing (U, Th)-based accident tolerant fuels (ATFs), specifically (_0.8UO₂, _0.2ThO₂), (_0.8UN, _0.2ThN), and (_0.8UC, _0.2ThC). The investigation assesses the overall performance of these proposed fuel materials in comparison to the conventional UO₂, focusing on deep neutronic and thermal-hydraulic (Th) analyses. Neutronic analysis utilized the MCNPX code, while COMSOL Multiphysics was employed for thermal-hydraulic analysis. The primary objective of this research is to overcome the limitations associated with traditional UO₂ fuel by exploring alternative fuel materials that offer advantages in terms of abundance and potential improvements in performance and safety. Given the limited abundance of UO₂, long-term sustainable nuclear energy production faces challenges. From a neutronic standpoint, the U-Th based fuels demonstrated remarkable fuel cycle lengths, except (_0.8UN, _0.2ThN), which exhibited the minimum fuel cycle length and, consequently, the lowest fuel burn-up. Regarding thermal-hydraulic performance, (_0.8UN, _0.2ThN) exhibited outstanding performance with significant margins against fuel melting compared to the other materials. Overall, when considering the integrated performance, the most favourable results were obtained with the use of the (_0.8UC, _0.2ThC) fuel configurations. This study contributes valuable insights into the potential benefits of (U, Th)-based ATFs as a promising avenue for enhanced nuclear fuel performance.

• Journal of the Korean Chemical Society
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• v.39 no.5
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• pp.329-337
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• 1995

Energetic oxetane derivatives which undergo cationic polymerizations have been investigated theoretically by using ab initio HF/3-21G calculations. We have examined structures, charges, and molecular electrostatic potentials. The ring structure of oxetane has changed significantly due to (1) the introduction of large substituents in the ring or (2) the addition of either proton or BF3. This structural change is attributed to electrostatic interactions and/or steric repulsions. The nucleophilicity and basicity of oxetane derivatives can be explained by the negative charge and the minimum electrostatic potential value of O atom. The reactivity in the polymerization can be rationalized by (1) the basicity of O atom and (2) the difference between HOMO energy of oxetanes and LUMO energy of activated oxetane polymeric chains. Our calculations predict that 3-azidomethyl-3-methyl oxetane (AMMO) is more basic than 3-nitratomethyl-3-methyl oxetane (NMMO), and AMMO is more reactive toward both AMMO and NMMO polymeric chains. Our results are in good agreement with previous experimental data.

• Journal of Communications and Networks
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• v.14 no.4
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• pp.434-442
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• 2012

Several gateway selection schemes have been proposed that select gateway nodes based on a single Quality of Service (QoS) path parameter, for instance path availability period, link capacity or end-to-end delay, etc. or on multiple non-QoS parameters, for instance the combination of gateway node speed, residual energy, and number of hops, for Mobile Ad hoc NETworks (MANETs). Each scheme just focuses on the ment of improve only a single network performance, i.e., network throughput, packet delivery ratio, end-to-end delay, or packet drop ratio. However, none of these schemes improves the overall network performance because they focus on a single QoS path parameter or on set of non-QoS parameters. To improve the overall network performance, it is necessary to select a gateway with stable path, a path with themaximum residual load capacity and the minimum latency. In this paper, we propose a gateway selection scheme that considers multiple QoS path parameters such as path availability period, available capacity and latency, to select a potential gateway node. We improve the path availability computation accuracy, we introduce a feedback system to updated path dynamics to the traffic source node and we propose an efficient method to propagate QoS parameters in our scheme. Computer simulations show that our gateway selection scheme improves throughput and packet delivery ratio with less per node energy consumption. It also improves the end-to-end delay compared to single QoS path parameter gateway selection schemes. In addition, we simulate the proposed scheme by considering weighting factors to gateway selection parameters and results show that the weighting factors improve the throughput and end-to-end delay compared to the conventional schemes.

• Progress in Medical Physics
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• v.27 no.3
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• pp.162-168
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• 2016

Proton therapy is increasingly being actively used in the treatment of cancer. In contrast to photons, protons have the potential advantage of delivering higher doses to the cancerous tissue and lower doses to the surrounding normal tissue. However, a range shifter is needed to degrade the beam energy in order to apply the pencil beam scanning technique to tumors located close to the minimum range. The secondary neutrons are produced in the beam path including within the patient's body as a result of nuclear interactions. Therefore, unintended side effects may possibly occur. The research related to the secondary neutrons generated during proton therapy has been presented in a variety of studies worldwide, since 2007. In this study, we measured the magnitude of the secondary neutron dose depending on the location of the detector and the use of a range shifter at the beam nozzle of the proton scanning mode, which was recently installed. In addition, the production of secondary neutrons was measured and estimated as a function of the distance between the isocenter and detector. The neutron dose was measured using WENDI-II (Wide Energy Neutron Detection Instruments) and a Plastic Water phantom; a Zebra dosimeter and 4-cm-thick range shifter were also employed as a phantom. In conclusion, we need to consider the secondary neutron dose at proton scanning facilities to employ the range shifter reasonably and effectively.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.19 no.1
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• pp.79-84
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• 1983

The test specimen, designated the double cantilever beam, was employed for a fracture mechanics study of stress corrosion cracking (SCC) of type 5083 Al-alloy in seawater. Stress intensities for this DCB specimen were calculated by using compliance, strain energy release rate and relation between stress intensity and strain energy release rate. Analytical expression for compliance as a function of crack length was obtained by applying beam theory. It was investigated that the polarization potentials affected the growth rate and surface of stress corrosion cracking. The results are as follows, The critical stress intensity was 134.81-148.38kg/mm super(3/2) and K sub(Ii) under polarization potentials was 75.92-145.78kg/mm super(3/2). The minimum stress corrosion crack growth rate was occurred at-987mV SCE. Insoluble compound on $\beta$ phase was looked into through SCC. The greater anodic potential is, the larger insoluble compound on $\beta$ phase becomes.

• Steel and Composite Structures
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• v.29 no.6
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• pp.785-802
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• 2018

In this paper, two different computational methods, called Rayleigh-Ritz and collocation are developed to estimate the ultimate strength of composite plates. Progressive damage behavior of moderately thick composite laminated plates is studied under in-plane compressive load and uniform lateral pressure. The formulations of both methods are based on the concept of the principle of minimum potential energy. First order shear deformation theory and the assumption of large deflections are used to develop the equilibrium equations of laminated plates. Therefore, Newton-Raphson technique will be used to solve the obtained system of nonlinear algebraic equations. In Rayleigh-Ritz method, two degradation models called complete and region degradation models are used to estimate the degradation zone around the failure location. In the second method, a new energy based collocation technique is introduced in which the domain of the plate is discretized into the Legendre-Gauss-Lobatto points. In this new method, in addition to the two previous models, the new model named node degradation model will also be used in which the material properties of the area just around the failed node are reduced. To predict the failure location, Hashin failure criteria have been used and the corresponding material properties of the failed zone are reduced instantaneously. Approximation of the displacement fields is performed by suitable harmonic functions in the Rayleigh-Ritz method and by Legendre basis functions (LBFs) in the second method. Finally, the results will be calculated and discussions will be conducted on the methods.

• Tribology and Lubricants
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• v.38 no.5
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• pp.191-198
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• 2022

With the world's fast expanding energy usage comes a slew of new issues. Because one-third of energy is lost in overcoming friction, tremendous effort is being directed into minimizing friction. Surface texturing is the latest surface treatment technology that uses grooves and dimples on the friction surface of the machine to significantly reduce friction and improve wear resistance. Despite the fact that many studies on this issue have been conducted, most of them focused on parallel surfaces, with relatively few cases of converging films, as in most sliding bearings. This study investigated the lubrication performance of surface-textured inclined slider bearings. We analyzed the continuity and Navier-Stokes equations using a commercial computational fluid dynamics code, FLUENT. The results show the pressure and velocity distributions and the lubrication performance according to the number and orientation of rectangular dimples. Partial texturing somewhat improves the lubrication performance of inclined slider bearings. The number of dimples with the maximum load-carrying capacity (LCC) and minimum friction is determined. When the major axis of the dimple is arranged in the sliding direction, the LCC and friction reduction are maximized. However, full texturing significantly reduces the LCC of the slider bearing and increases the flow rate. The results have the potential to improve the lubrication performance of various sliding bearings, but further research is required.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.44 no.1
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• pp.64-70
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• 2007

Raman spectroscopy is known to have strong potential for providing noninvasive dermatological diagnosis of skin cancer. According to the previous work, various well known methods including maximum a posteriori probability (MAP) and multilayer perceptron networks (MLP) showed competitive results. Since even the small errors often leads to a fatal result, we investigated the method that reduces classification error perfectly by screening out some ambiguous patterns. Those ambiguous patterns can be examined by routine biopsy. We incorporated an ambiguous pattern class in MAP, linear classifier using minimum squared error (MSE), MLP and reduced coulomb energy networks (RCE). The experiments involving 216 confocal Raman spectra showed that every methods could perfectly classify BCC by screening out some ambiguous patterns. The best results were obtained with MSE. According to the experimental results, MSE gives perfect classification by screening out 8.8% of test patterns.

• Journal of Biosystems Engineering
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• v.2 no.2
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• pp.37-45
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• 1977

Solar energy is a potential source of power that offers much promise being used for low-temperature applications like drying farm crops, space heating, and water heating for domestic uses. Already much of it are being used for those purpose in foreign countries. However, very little research has been done to determine the possibility of using the solar energy in Korea. This study was conducted to develop the general prediction equation of the total radiation on a horizontal surface in Daejeon area based on 5 years 91972, Jun.1-1976. Dec.31) meteorological data (bright sunshine hours, average total horizontal radiation), and to obtain experimentally the thermal efficiency of solar air and water collectors, which will be used as a basic data of designing flat-plate solar collector system.In addition to the thermal efficiency of the collectorsthe relationship among those factors affecting it such as weather condition, orientation factor, and tilted angle of collector was analyzed. The results of this study were as follows. 1. The general predicted equation of the total radiation on a horizontal surface in Daejeon area based on bright sunshine hours was developed as $H_{av} =(1.546\frac{n}{N}-0.582)H_o$. Predicting the total radiation on a horizontal surface by the above equation was thought to be possible because to values of 0.882 was smaller than any t values at above 0.05 level on the basis of two tailed test of the difference between the calculated and the recorded values. 2.It was observed that optimum tilt angle of the collector in the summer and the autumn drying season was 13 degrees and 51 degrees respectively, these values could be obtained by adding or substracting approximately 25 degrees from the latitude of this area $(36.3^{\circ}N)$ .The relationship between orientation factor and declination of sun at suitable tilt angle of 33 degrees $(s=0.9\O)$ was shown at Fig.4. 3.The thermal efficiency of solar wdter collector was shown 13.4-51. 6% on Aug. 15 (the minimum radiation recorded) and 43.8 ~537% Aug.20 (the maximum radiation recorded), and 13.8~ 46.6 and 44.3~ 49.7 were shown on each corresponding day. 4.The thermal efficiency of the collectors according to the weather condition was shown a big difference of about 10% between the day of the maximum radiation recorded and the minimum, but the differen of efficiency between the air and the water collector was at most 2 ~ 3%. 5. Even if the efficiency of the solar water collector was a little higher than the solar air collector, for drying farm products, the solar air collector was thought to be more effective because the air heated by collector could be directly used for drying them.

• Applied Chemistry for Engineering
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• v.7 no.2
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• pp.228-236
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• 1996

An electrolysis system with a vertically circulating mercury capillary bundle electrode was developed with a very large electrode area in a minimum space. This system was operated by forcedly feeding mercury and aqueous solution containing metal ion into a fiber bundle packed densely within a small porous glass tube. In order to test the characteristics and stability of the electrolysis system, the reduction voltammograms of uranyl and ferric ions were measured with changes of the mercury flow rate and the aqueous flow rate. The aqueous flow rate had a large effect on the electrochemical reaction of metal ion occurring at the interface between the mercury and the aqueous solution and had to be regulated as an appropriate value to have a good limiting current shape. The limiting current was linearly proportional to the aqueous flow rate, and complete reductions of uranyl and ferric ions were rapidly and continuously accomplished at the potential showing limiting current. With a mercury flow rate high enough to keep a capillary continuum of mercury in the fiber bundle, the mercury flow rate had almost no effect on the electrochemical reaction. This system was confirmed to be effective and stable enough to control rapidly and continuously the oxidation state of metal ions fed into the system under an appropriate aqueous flow rate.