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  • Author or Editor: J. Hong x
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Abstract  

When an equivalent dose value (D e) is estimated by using a conventional OSL-SAR method, it is necessary to make growth curves of all the aliquots used for D e estimation. However, the technique using standardized growth curve (SGC) has an advantage in that, once a standardized growth curve is defined, an equivalent dose value can be quickly obtained by using information from the natural luminescence signal only. In this study, we investigate the SGC technique with naturally dosed quartz samples from Korea that were originally zeroed by heating. Our study reveals that quartz samples from the same location appear to have very similar growth curve parameters, regardless of the sampling points in an outcrop, but quartz aliquots from different locations (i.e., sample locations that are a long distance apart) show significant inter-aliquot variations in growth curve shapes. In addition, for samples from the same location, the equivalent doses obtained by SGC technique were consistent with those estimated by SAR protocol.

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Abstract  

The curing and adsorption behaviors of an epoxy/amidoamine system under the influence of iron, aluminum, and zinc oxides are studied by using differential scanning calorimetry (DSC) and diffuse reflectance infrared spectroscopy (DRIFT). From DRIFT, it is obtained that the amidoamine curing agent is preferentially adsorbed on the three metal oxide surfaces. The amount of amidoamine adsorbed is in the order of iron oxide>zinc oxide>aluminum oxide. Moreover, the iron and zinc oxides adsorb resins more firmly than the aluminum oxide. The results of DSC analyses indicate that more amine related exotherms are found in the specimen filled with the iron oxide but more amide related exotherms are found in the zinc oxide added specimens and they are related to the difference in the preferential adsorption found on three metal oxides. The curing characteristics are also changed in the presence of metallic fillers and the greatest change is obtained from the specimen containing the iron oxide.

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Lycopene content (LC) and soluble solid content (SSC) are important quality indicators for cherry tomatoes. This study attempted simultaneous analysis of inner quality of cherry tomato by Electronic nose (E-nose) using multivariate analysis. E-nose was used for data acquisition, the response signals were regressed by multiple linear regression (MLR) and partial least square regression (PLS) to build predictive models. The performances of the predictive models were tested according to root mean square and correlation coefficient (R2) in the training set and prediction set. The results showed that MLR models were superior to PLS model, with higher value of R2 and lower values of for RMSE firmness, pH, SSC, and LC. Together with MLR, E-nose could be used to obtain firmness, pH, soluble solid and lycopene contents in cherry tomatoes.

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Summary  

A small X-ray irradiator (Varian VF-50J X-ray tube) has some advantages over the conventional radioactive sources for equivalent dose determination, as required for example in the process of luminescence dating of sediments and sherds. One advantage of the X-ray irradiator is that the photon energies below a few keV, which may cause an error in the equivalent dose value, can be eliminated by an aluminum absorber. Data is presented to establish the optimum thickness of the aluminum absorber, found to be about 50 μm.

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Abstract

The interventional treatment of diffuse coronary artery disease often requires the placement of long lengths of intracoronary stents. We have anecdotally observed that target vessel failure rates seem high in these patients. Therefore, we examined long-term angiographic and clinical outcomes in patients treated with long lengths of intracoronary stent. A total of 312 consecutive patients who received ≥30 mm of stent(s) in a single coronary vessel were identified. Bare metal stents (BMS) were placed in 118 of these patients and drug eluting stents (DES) were used in 175 patients. Nineteen patients who received both BMS and DES were excluded from comparative analysis. The mean number of stents placed was 2.4±0.92 and the mean stent length was 45.7±18.2 mm. For the entire cohort, the restenosis rate was 20.8%. Restenosis rates were significantly higher in the BMS group compared to the DES group (34.7% vs. 11.4%; p<0.0001). The rates of major adverse cardiac events were significantly lower in the DES group compared to the BMS group. In conclusion, the treatment of diffuse coronary artery disease by placement of long lengths of intracoronary stent is a durable therapeutic option when DES are utilized.

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Abstract  

A (D3C)2O (d6-acetone) target was irradiated with semi-monoenergetic neutrons generated from 9Be(p,n)9B reaction with 20 MeV protons to convert 13C and oxygen nuclides in the target into 14C. With both liquid scintillation counting (LSC) and accelerator mass spectrometry (AMS) we measured the (D3C)2O (d6-acetone) liquid targets, which were combustible and easy to afford CO2 for the AMS measurements. The 14C yield measured by the LSC method turned out to be 80 times larger than that by the AMS method. This large discrepancy may be attributed to the loss of 14C atoms during the sample pretreatment in the AMS method such as combustion and cryogenic trapping of CO2. It means that 14C newly produced by nuclear reactions can exist in various chemical forms, i.e., C3D6O, CO, CO2, hydrocarbons, etc., and a simple sample pretreatment right after production can cause serious isotopic fractionation. Therefore, using the AMS method, extreme caution in sample pretreatment should be exercised when the 14C yield produced immediately by nuclear reaction is measured.

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Abstract  

We have measured the cross sections of the 16O(n,t) reactions above 18.1 up to 33.1 MeV in an neutron activation method. H2O (water) as an 16O target was irradiated with semi-monoenergetic neutrons generated from the 9Be(p,n)9B reaction with 25–35 MeV protons. The neutron flux was obtained with the aid of previous study by Uwamino et al. (Nucl Instr Methods A 271:546, 1988). The tritium activities were measured by using the liquid scintillation counting (LSC) method. The present value for the cross section of 16O(n,t) reaction agrees with previous values measured by using the same LSC method at similar neutron energy ranging from 18.1 up to 33.1 MeV.

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Abstract  

A nanosecond proton bunching system has been constructed at Korea Institute of Geoscience and Mineral Resources (KIGAM). This pulsed ion beam will be converted into corresponding duration of neutron pulse, which can reduce the scattered neutron background during neutron spectroscopy. The pulsed beam is obtained by deflection and double bunching by RF field. RF fields are applied to deflection and bunching electrodes as 2 kV p-p, 4 MHz and 2 kV p-p, 8 MHz, respectively. A push-pull RF amplifier has been designed and constructed with a maximum output power of 300 W continuous wave (CW) between 2 and 30 MHz. The main parameters of bunching beam were as follows: 8 MHz repetition rate, 2 ns FWHM, approximately 20% of duty factor and the maximum energy spread of 2 keV within a pulse.

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Abstract  

The Eu tris(dibenzoylmethanato)phenanthroline complex doped xerogel has been synthesized by a catalyst-free sol-gel roure. The non-isothermal kinetic analysis is calculated by Friedman isoconversional method and multivariate non-linear regression method. The overall decomposition process below 600C is fitted by an Fn model (n order reaction), corresponding to the dehydration of the matrix, and a two-step consecutive reaction of Cn model (n order autocatalytic reaction), corresponding to the decomposition of organic complex. Correlation coefficient is 0.99986. The lifetime values of xerogel, defined as the 5% decomposition of europium organic complex, indicate that the xerogel can find application at near room temperature.

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