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  • Author or Editor: K. Lee x
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Abstract  

The thermal behaviors of three pentaerythritol tetranitrate (PETN) base polymer bonded explosives (PBX), Detasheet A (EL506A, red) and Datasheet C (EL506C, yellow-green) that supply by DuPont Co., PBXN-301 were investigated using thermal techniques in this work. The thermal properties of PETN base polymer bonded explosives, such as vacuum thermal stability (VTS), time to ignition, auto-ignition and shelf life of PBX that calculation from Arrhenius equation by the length of time for 5% decomposition were also examined. By comparing the thermal properties, VTS and shelf life of PETN base polymer bonded explosives, the application and storage of Datasheet C (EL506C, yellow-green) should be considered carefully, owing to the ingredients of Datasheet C (EL506 C, yellow-green) containing nitrocellulose. Binders that using in this study seems play no significant effect on the decomposition for polymer bonded explosives, because the decomposition temperature of binders is always higher than that of PETN.

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The thermal decomposition properties of primer mixture 1 with different water content can be investigated using a series of thermal analysis equipment and by its technique. By the DSC analysis in this work, although the major exothermic peak of the primer mixture 1 with different water content, at the temperature range from 250 to 350°C were gradual disappeared when increasing the water content of primer mixture 1, but this result could not indicate that the detonating ability of wetted primer mixture 1 was lost. And by TG analysis, wetted primer mixture 1 was still found possessing detonation properties under a higher heating rate condition. Although wetted primer mixture shows hard detonating character but we still need very carefully when executing a disposal mission.

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Abstract  

In order to remove the radiotoxic nuclides, Cs+ and I, from low-level liquid wastes, the adsorption characteristics have been studied using a mixed adsorbent of chabazite zeolite and activated carbon. The equilibrium data of each nuclide were well correlated with the DA equation in the wide range of equilibrium concentrations. The SEM-EDAX analysis provided precise understanding of the adsorption mechanism of each nuclide. A surface diffusion model was applied to estimate the intraparticle mass transfer and provided prediction results acceptable for practical implementation in the liquid waste treatment.

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Abstract  

Depth distribution of239,240Pu and137Cs in the soils of South Korea have been studied. The average accumulated depositions were estimated roughly to be 54.8±32.1 Bq·m–2 for239,240Pu, 1.6±1.0 Bq· ·m–2 for238Pu and 1982.8±929.1 Bq·m–2 for137Cs. The activity ratios of239,240Pu/137Cs in soils were found to be in the narrow range of 0.0153 to 0.0364 with a mean value of 0.0230±0.006. The concentrations of239,240Pu and137Cs in soils decrease exponentially with increasing the soil depth. A significant correlation was found between the concentration of239,240Pu and that of137Cs. The activity ratios of239,240Pu/137Cs tend to increase slightly with increasing soil depth.

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Abstract  

Positron annihilation lifetimes were measured for several polymers in the atmosphere of high pressure CO2 gas. At low CO2 pressured both 3 andI 3 decreased due to the Langmuir-type sorption, and at higher pressures their values recovered because the Henry-type sorption takes over. The amount of sorbed CO2 and dilation of the bulk volume were measured simultaneously, and the free volume fraction was determined at each CO2 pressure. The free volume fraction became smaller (for polyimide and polycarbonate) or slightly larger (for polyethylene) with the progress of sorption. However, the size of the o-Ps hole estimated from the 3 value increased regardless of the change of the free volume fraction. It appears that o-Ps is selectively looking at larger holes or expanding the holes in which it is accommodated. For polycarbonate, which remains to be glassy even at the largest CO2 sorption attained in the experiment, the o-Ps hole size became larger than that before sorption. This implies that, even if the polymer is glassy as bulk, the sorption site is strongly prone to molecular displacement by the pressure of the penetrating Ps. Cautious consideration is evoked about directly correlating the o-Ps lifetime and intensity with the free volume in general.

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This article addresses the potential effectiveness of blind review in selecting and funding research proposals in a “scientifically small” country. By analyzing 474 responses of the blinded reviewers ever worked for Korea Science and Engineering Fund, it was found that blind review is fairly effective. About two thirds of the blinded reviewers were unable to recognize the applicants accurately. The applicant detection was affected by (1) physical age, (2) professional experience, and (3) geographical location of doctoral education of the applicant, (4) review experience, (5) rank of employing universities of the reviewers, and (6) similirity of research interest between an applicant and a reviewer. It was also found that blind review was more strongly advocated by those who had made a wrong guess or who had given up guessing. Implications of the findings and future research directions were discussed.

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Abstract  

Thermogravimetric analysis (TG) provides information regarding mass changes in the sample resulting from heat treatment under controlled environment. However, it does not provide any chemical information regarding the gases evolved during the thermal degradation. Using FT-IR spectrometry in combination with TG, it is often possible to identify the evolved gases, and also monitor their evolution profiles during thermal degradation. In this study, we present the TG/FT-IR combined analysis of incineration and pyrolysis of some common plastics such as high density polyethylene (HDPE), polyvinyl chloride (PVC), polyethylene terephthalate (PET), and polystyrene (PS). This study demonstrates the utility of such combined analysis in providing useful information regarding the use of thermal treatment for recycling or incineration.

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This paper presents a rapid and quantitative radiochemical separation method for the Pu, Am and Cm isotopes with an anion exchange resin and a TRU resin. After the Pu isotopes were purified with an anion exchange resin method and the Am and Cm isotopes were purified with the TRU resin method, micro-coprecipitation method was applied for an alpha-source preparation. The activity concentrations and activity ratios for the Pu, Am and Cm isotopes in a radioactive sample were measured by radiation counting methods such as an alpha-spectrometry and a liquid scintillation counting as well as by a mass spectroscopic method such as a thermal ionization mass spectrometry.

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The effects of red grape, wild grape and black raspberry wines on the quality of ground pork during a 15 days refrigerated storage period were investigated. The levels of phenolic compounds were the highest in black raspberry wine (P<0.05). In contrast, the antioxidant capacities according to ferric reducing antioxidant potential (FRAP) and trolox equivalent antioxidant capacity (TEAC) were not significantly different among the wines (P>0.05). The addition of 5% and 10% wine influenced the quality of ground pork by decreasing pH, inhibiting the progression of lipid oxidation and the formation of total volatile basic nitrogen (TVB-N), and stabilizing the red colour of the ground pork compared to control samples to which no wine was added. In ground pork, addition of red grape wine led to lower concentrations of thiobarbituric acid reactive substances (TBARS, 0.19–0.39 mg kg−1) and TVB-N values (69.1–119.9 mg kg−1) than wild grape (0.16–0.43 mg kg−1 and 72.0–194.1 mg kg−1, respectively) or black raspberry wine (0.33–0.58 mg kg−1 and 81.7–225.4 mg kg−1, respectively) up to 10 days of storage. Results from the present study suggested that the quality of ground pork was affected by wine type and storage period. These effects could be due to phenolic compounds as well as other chemical components of the wines.

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Abstract  

The new polycyclic nitramine 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (HNIW) has been focused as a considerable amount of research recently on investigating its polymorphs, relative stability, and respective reaction chemistry. It is known as CL-20 popularly, CL-20 is a very high-energy and relatively high oxygen balance value crystalline compound whose method of synthesis and detailed performance data are still classified. 5-oxo-3-nitro-1,2,4-triazole (NTO, or nitrotriazolone) was an insensitive molecule comparison general explosives, and the NTO based polymer bonded explosives (PBX) was a low vulnerability explosive. Both energetic materials are all very important high explosives, which is used in a variety of military formulations widely owing to the properties of high energy and desensitization of PBX, many researchers have demonstrated the usefulness of above two energetic materials in explosive component. In this work, the thermal decomposition characteristics of explosives CL-20 and NTO were studied using thermal analytical techniques (TG, DSC), then the compatibility of above two explosives with silicone rubber, and the decomposition kinetic parameters such as activation energies of decomposition, the frequency factor of the decompose reaction are also evaluated by non-isothermal DSC techniques.

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