• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.9
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• pp.947-956
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• 2008

In this paper, miniaturized conically stepped COBRA is proposed. In order to prevent electrical breakdown, COBRA, which consists of hem and lens, has to get bigger if it is designed with conventional method. Because of the phase error increase, shortening the length of the antenna without changing the aperture size leads to the reduction of the antenna gain. To avoid this, the phase error at the aperture is compensated by transforming the COBRA lens into conically stepped form. The simulations result shows that the proposed antenna has higher gain than the conventional COBRA in spite of the size reduction from 1,300 mm to 600 mm. The fabricated and measured COBRA has the gain of 26.2 dBi.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.75-81
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• 1996

COBRA-TF is a two fluid, three field subchannel code. Three fields are continuous vapor, continuous liquid and droplet. Some assessments are conducted to validate the related models and to estimate a code ability through dryout and post-CHF experiment in a tube and DNB test in rod bundles. It turned out form dryout and post-CHF experiment that the predicted dryout locations and wall temperature profiles are in close agreement with the experiments. On the other hand, DNB prediction of COBRA-TF are performed for two kinds of rod bundles along with EPRI CHF correlation. To estimate its performance COBRA-IV of homogeneous model is also run for the same data. The results say that COBRA-TF/EPRI is better in DNB prediction than COBRA-IV/EPRI. In addition the thermal-hydraulic behaviors due to the different two-phase flow models are presented at the condition of CHF.

• Journal of the military operations research society of Korea
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• v.36 no.3
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• pp.83-93
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• 2010

In this paper, we propose a new expert system for close combat in military war game model for training. Simulation logic for damage assesment is one of the main simulation functions in military war game. In Changcho 21's model which is the war game model for Republic of Korea Army corps and division, the main function of close combat's damage assessment has not been calculated by Changcho 21's model, but by COBRA which was made by US Army and has been the expert system for close combat. Results which were calculated in COBRA were sent to Changcho 21's model through a cable network. And Changcho 21's model finally calculated the value of damage assessment with the results. In this paper, we develop an new expert system for close combat using decision tree. The experimental results show that the proposed expert system has similar performance to COBRA and has less computing complexity. And it can substitute for COBRA and be applicable to battlefield.

• Nuclear Engineering and Technology
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• v.30 no.3
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• pp.181-193
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• 1998

The COBRA-TF liquid droplet entrainment models have been assessed and improved through various experiments. The COBRA-TF code uses the Wurtz entrainment model in the film mist flow regime and the mechanistic model based on the critical Weber number and critical vapor velocity in the hot wall flow regimes, respectively. The Wurtz model has been replaced with the modified Sugawara model. The assessment against the experiments by Hewitt, Keeys, Yanai, and Whalley showed the modified Sugawara model better predicts the steam-water as well as the air-water experiments for the film mist flow regime. For hot wall flow regime, the COBRA-TF entrainment model was modified using two methods, one with an increased critical Weber number and the other with the Yonomoto's critical vapor velocity model. The modified models were assessed using the FLECHT-SEASET bottom reflood tests. The results showed that the Yonomoto model best predicts the quenching time, whereas the local maximum rod temperature was not affected much.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.10a
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• pp.591-598
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• 1997

The COBRA/RELAPS code, an integrated version of the COBRA-TF and RELAP5/MOD3 codes, has been developed for the realistic simulations of complicated, multi-dimensional, two-phase, thermal-hydraulic system transients in light water reactors. Recently, KAERA developed an unified version of the COBRA/RELAP5 code, which can run in serial mode on both workstations and personal computers. This paper provides the brief overview of the code integration scheme, the recent code modifications, the developmental assessments, and the future development plan.

• Proceedings of the Korean Nuclear Society Conference
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• 2001.05a
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• pp.147.1-147
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• 2001

• Proceedings of the Korean Nuclear Society Conference
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• 1998.10a
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• pp.126-126
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• 1998

• Proceedings of the Korean Nuclear Society Conference
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• 2002.10a
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• pp.158.1-158
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• 2002

• Journal of Animal Science and Technology
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• v.59 no.9
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• pp.20.1-20.9
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• 2017

Background: Ribonuclease (RNase) is one of the few toxic proteins that are present constantly in snake venoms of all types. However, to date this RNase is still poorly studied in comparison not only with other toxic proteins of snake venom, but also with the enzymes of RNase group. The objective of this paper was to investigate some properties of RNase from venom of Vietnam cobra Naja atra. Methods: Kinetic methods and gel filtration chromatography were used to investigate RNase from venom of Vietnam cobra. Results: RNase from venom of Vietnam cobra Naja atra has some characteristic properties. This RNase is a thermostable enzyme and has high conformational stability. This is the only acidic enzyme of the RNase A superfamily exhibiting a high catalytic activity in the pH range of 1-4, with $pH_{opt}=2.58{\pm}0.35$. Its activity is considerably reduced with increasing ionic strength of reaction mixture. Venom proteins are separated by gel filtration into four peaks with ribonucleolytic activity, which is abnormally distributed among the isoforms: only a small part of the RNase activity is present in fractions of proteins with molecular weights of 12-15 kDa and more than 30 kDa, but most of the enzyme activity is detected in fractions of polypeptides, having molecular weights of less than 9 kDa, that is unexpected. Conclusions: RNase from the venom of Vietnam cobra is a unique member of RNase A superfamily according to its acidic optimum pH ($pH_{opt}=2.58{\pm}0.35$) and extremely low molecular weights of its major isoforms (approximately 8.95 kDa for RNase III and 5.93 kDa for RNase IV).

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.284-289
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• 1996

The predictions of the COBRA-IV-I code with the modified turbulent mixing and void drift models have been compared with the diabatic two-phase flow data on equilibrium quality. The turbulent mixing model based on an equal mass exchange of the existing COBRA-IV-I code has been modified to that based on an equal volume exchange between adjacent subchannels, and a void drift model has been newly incorporated in the code. To evaluate the performance of the equal volume exchange turbulent mixing model and the effects of the void drift model, the diabatic steam-water two-phase flow data obtained for the 9-rod bundle test under the typical operating conditions of the boiling water reactor(BWR) conducted by the General Electric (GE) were analyzed by the modified COBRA-IV-I code. The analysis indicates that the equal volume exchange turbulent mixing model with void drift predicts the observed two-phase flow data trends better than the equal mass exchange model, and to predict the correct data trends a more physically based void drift model need to be developed.