• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.10 no.12
• /
• pp.2258-2263
• /
• 2006

In this parer, hump characteristics of short-channel nMOSFETs induced by moistures of the ILD(inter-layer dielectric) layer in the shallow trench isolation (STI) process are investigated and the method for hump suppression is proposed Using nMOSFETs with various types of the gate and a measurement of TDS-APIMS (Thermal Desorption System-Atmospheric Pressure ionization Mass Spectrometry), hump characteristics were systematically analyzed and the systemic analysis based hump model was presented; the ILD layer over poly-Si gate of nMOSFET generates moistures, but they can't diffuse out of the SiN layer due to the upper SiN layer. Consequently, they diffuses into the edge between the gate and STI and induces short-channel hump. In order to eliminate moisture in the ILD layer by out-gassing method, the annealing process prior to the deposition of the SiN layer was carried out. As the result, short-channel humps of the nMOSFETs were successfully suppressed.

• Nuclear Engineering and Technology
• /
• v.47 no.7
• /
• pp.924-933
• /
• 2015

The correlation of the isotopic composition of uranium, plutonium, neodymium, and cesium with the burnup for high burnup pressurized water reactor fuels irradiated in nuclear power reactors has been experimentally investigated. The total burnup was determined by Nd-148 and the fractional $^{235}U$ burnup was determined by U and Pu mass spectrometric methods. The isotopic compositions of U, Pu, Nd, and Cs after their separation from the irradiated fuel samples were measured using thermal ionization mass spectrometry. The contents of these elements in the irradiated fuel were determined through an isotope dilution mass spectrometric method using $^{233}U$, $^{242}Pu$, $^{150}Nd$, and $^{133}Cs$ as spikes. The activity ratios of Cs isotopes in the fuel samples were determined using gamma-ray spectrometry. The content of each element and its isotopic compositions in the irradiated fuel were expressed by their correlation with the total and fractional burnup, burnup parameters, and the isotopic compositions of different elements. The results obtained from the experimental methods were compared with those calculated using the ORIGEN-S code.

• Mycobiology
• /
• v.43 no.3
• /
• pp.272-279
• /
• 2015

To screen molecular chaperones similar to small heat shock proteins (sHsps), but without ${\alpha}$-crystalline domain, heat-stable proteins from Schizosaccharomyces pombe were analyzed by 2-dimensional electrophoresis and matrix assisted laser desorption/ionization time-of-flight mass spectrometry. Sixteen proteins were identified, and four recombinant proteins, including cofilin, NTF2, pyridoxin biosynthesis protein (Snz1) and Wos2 that has an ${\alpha}$-crystalline domain, were purified. Among these proteins, only Snz1 showed the anti-aggregation activity against thermal denaturation of citrate synthase. However, pre-heating of NTF2 and Wos2 at $70^{\circ}C$ for 30 min, efficiently prevented thermal aggregation of citrate synthase. These results indicate that Snz1 and NTF2 possess molecular chaperone activity similar to sHsps, even though there is no ${\alpha}$-crystalline domain in their sequences.

• The Journal of the Petrological Society of Korea
• /
• v.13 no.4
• /
• pp.238-243
• /
• 2004

Duwon meteorite was fallen on 23 November 1943 in Duwonmyeon, Goheung, Jeolanam-Do. We measured rare earth element abundance of Duwon meteorite by isotope dilution thermal ion mass spectrometry (ID-TIMS) and ICP-MS. As a result, except La and Ce, abundance of other rare earth element show a correspondence within 10％ of error range. However, La and Ce show more than 70％ in abundance, which is considered due to 1) experimental procedure or 2) inhomogeneity of sample. Leedey meteorite was fallen on 25 November 1943 in Dewey County, Oklahoma, USA. which suggested that fallen difference between Leedey and Duwon meteorites is only 2 days. Leedey and Duwon meteorites are classified as ordinary chondrite of L6 type. In Leedey chondrite-normalized REE pattern, Duwon meteorite shows nearly flattened, which suggests close relationship between Leedey and Duwon meteorites meteoritically or cosmochemically.

• Analytical Science and Technology
• /
• v.33 no.6
• /
• pp.245-251
• /
• 2020

Lead (Pb) has been shown to be a useful tracer of contamination sources and geochemical processes such as age dating and crustal evolution. These studies require a chromatographic technique for Pb separation from geological samples. This paper presents a comparison study on the effect of eluent concentration between 6M HCl and 8M HCl on the separation of Pb from Pb resin. The results showed that the separation of Pb using 6M HCl as the eluent was not effective compared to the separation using 8M HCl. To verify this method, we measured the Pb isotopic compositions of the Pb isotopic standard (NIST NBS981) and geological reference materials (BCR-2, GSP-2, and JG-1a) using a thermal ionization mass spectrometer (TIMS). The results correspond well with the reported values within the error range, implying that this method can be useful.

• Nuclear Engineering and Technology
• /
• v.21 no.4
• /
• pp.277-286
• /
• 1989

Destructive methods are used for the turnup determination of an irradiated PWR fuel. One of the methods includes U, Pu, Nd-148 and Nd-(145+146) determination by an isotope dilution mass spectrometry using triple spikes (U-233, Pu-242 and Nd-150). The method involves two sequential ion exchange resin separation procedures. Pu is eluted from the first anion exchange resin column (Dowex AG 1$\times$8) with 12 M HCl-0.1 M HI mixed solution, followed by U elution with 0.1 M HCl. Nd is isolated from other fission products on the second anion exchange resin column (Dowex AG 1$\times$4) with a nitric acid-methanol eluent. Each fraction is analysed by thermal ionization mass spectrometry. The difference between Nd-148 and Nd-(145+146) method is found with an average 2.07%. The results are compared with those by the heavy element method using U and Pu isotopes and by the destructive y-spectrometric measurement of Cs-137. The dependences of isotope composition of U and Pu on burn-up, and correlation between those isotopes are illustrated graphically.

• Journal of Radiation Protection and Research
• /
• v.43 no.3
• /
• pp.120-123
• /
• 2018

Background: Analysis of enrichment of $UO_2$ is important to verify the information declared by the license-holders. The redundancy methods are required to guarantee the analysis result. Korea Institute of Nuclear Nonproliferation and Control (KINAC) used to analyze it with alpha spectrometry and consign to Korea Basic Science Institute (KBSI) Thermal Ionization Mass Spectrometry (TIMS). This article evaluated the similarity of the results with two methods and derive correlation equation. It could be compared to the results measured by TIMS running by KBSI. Materials and Methods: There are not many certified materials for the uranium enrichment value. Therefore, 34 uranium pellets, which have the wide range of uranium enrichment from 0.21 to 4.69 wt%, were used for the experiments by the alpha spectrometry and the TIMS. Results and Discussion: The study shows there are the tendency of analyzed enrichment by each equipment. It shows uranium enrichment with alpha spectrometry evaluated 17% higher than that with TIMS on average. The regression equations were also derived in case the similarity between the two results with two methods is lower than predicted. Two experiments were designed to compare the effect of number of samples. The $R^2$ was 0.9977 with 34 pellets. It shows the equation is appropriate to predict the enrichment values by TIMS with that of alpha spectrometry. The $R^2$ was 0.9858 with four pellets for ten times. The $R^2$ decreased while the number of samples increased. The discrepancy between the lowest and highest enrichment seems to be one of the reason for it. Conclusion: KINAC expects the first equation with 34 samples is useful to predict the result with TIMS, the redundancy method, based on the alpha spectrometry. The extra samples are necessary to collect if the enrichment value analyzed by TIMS is lower than the value predicted with the equation. Further study would be followed related to the impact of the peak counts for each uranium isotopes, sample amount and number of experiments when TIMS established in KINAC by the end of 2018.

• Bulletin of the Korean Chemical Society
• /
• v.31 no.2
• /
• pp.275-280
• /
• 2010

Actinobacillus actinomycetemcomitans is a gram-negative, nonmotile coccobacillus bacterium that is associated with several human diseases, including endocarditis, meningitis, osteomyelitis, subcutaneous abscesses and periodontal diseases. A full-length Omp1-like protein gene from A. actinomycetemcomitans was cloned into a pQE30 vector and overexpressed in Escherichia coli BL21(DE3) cells. The protein revealed sequence homologies to Seventeen kilodalton proteins (Skp) from Pasteurella multocida and E. coli that have been characterized as periplasmic chaperones. This soluble Omp1-like protein was successfully purified to homogeneity for further folding and functional studies. The purity, identity, and conformation of the protein were determined using sodium dodecyl sulfate polyacrylamide gel electrophoresis, matrix-assisted laser desorption ionization mass spectrometry, circular dichroism, fluorescence spectroscopic, and differential scanning calorimetric studies. We showed that the protein formed an oligomer larger than a tetramer. We found, further, that it is comprised of mostly $\alpha$-helices and boasts high thermal stability.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.19 no.3
• /
• pp.367-386
• /
• 2021

The overestimation and underestimation of the radioactivity concentration of difficult-to-measure radionuclides can occur during the implementation of the scaling factor (SF) method because of the uncertainties associated with sampling, radiochemical analysis, and application of SFs. Strict regulations ensure that the SF method as an indirect method does not underestimate the radioactivity of nuclear wastes; however, there are no clear regulatory guidelines regarding the overestimation. This has been leading to the misuse of the SF methodology by stakeholders such as waste disposal licensees and regulatory bodies. Previous studies have reported instances of overestimation in statistical implementation of the SF methodology. The analysis of the two most popular linear models of the SF methodology showed that severe overestimation may occur and radioactivity concentration data must be dealt with care. Since one major source of overestimation is the use of minimum detectable activity (MDA) values as true activity values, a comparative study of instrumental techniques that could reduce the MDAs was also conducted. Thermal ionization mass spectrometry was recommended as a suitable candidate for the trace level analysis of long-lived beta-emitters such as iodine-129. Additionally, the current status of the United States and Korea was reviewed from the perspective of overestimation.

• Analytical Science and Technology
• /
• v.21 no.6
• /
• pp.487-494
• /
• 2008

An experiment was performed for zone refined Re-filament and normal (nonzone refined) Re-filament to reduce the background effect on the measurement of low level uranium samples. From both filaments, the signals which seemed to come from a cluster of light alkali elements, $(^{39}K_6)^+$, $(^{39}K_5+^{41}K)^+$ and $PbO_2$ were identified as the isobaric effect of the uranium isotopes. The isobaric effect signal was completely disappeared by heating the filament about $2000^{\circ}C$ at < $10^{-7}$ torr of vacuum for more than 1.5 hour in zone refined Refilaments, while that from the normal Re-filaments was not disappeared completely and was still remained as 3 pg. of uranium as the impurities after the degassing treatment was performed for more than 5 hours at the same condition of zone refined filaments. A threshold condition eliminating impurities were proved to be at 5 A and 30 minutes of degassing time. The uranium content as an impurity in rhenium filament was checked with a filament degassing treatment using the U-233 spike by isotope dilution mass spectrometry. A 0.31 ng of U was detected in rhenium filament without degassing, while only 3 pg of U was detected with baking treatment at a current of 5.5 A for 1 hr. Using normal Re-filaments for the ultra trace of uranium sample analysis had something problem because uranium remains to be 3 pg on the filament even though degassed for long hours. If the 1 ng uranium were measured, 0.3% error occurred basically. It was also conformed that ionization filament current was recommended not to be increased over 5.5 A to reduce the background. Finally, the contents of uranium isotopes in uranium standard materials (KRISS standard material and NIST standard materials, U-005 and U-030) were measured and compared with certified values. The differences between them showed 0.04% for U-235, 2% for U-234 and 2% for U-236, respectively.