• Elastomers and Composites
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• v.56 no.4
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• pp.209-216
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• 2021

In this study, we observed the mechanical properties, thermal stability, and low temperature sealing performance of fluorosilicone elastic composites. When the blend ratio of Phenyl vinyl methyl silicone (PVMQ) was increased, the tensile strength, modulus at 100%, and compression set were decreased. The thermal stability of fluorosilicone elastic composites showed a similar tendency. These were caused by poorer green strength of PVMQ than Fluorosilicone rubber (FVMQ). The change in the tensile strength and elongation at -40℃ showed a decreasing tendency with increasing PVMQ blend ratio. By increasing the PVMQ blend ratio, low-temperature performance was improved. The Dynamic mechanical analysis (DMA) results showed that T_g was decreased and low-temperature performance was improved with increasing PVMQ blend ratio. However tanδ was decreased becaused of the poor green strength and elasticity of PVMQ. From a hysteresis loss at -40℃, the hysteresis loss value was increased and fluorosilicone elastic composites showed the decreasing tendency of elasticity with increasing PVMQ blend ratio. From the TR test, TR10 was decreased with increasing PVMQ blend ratio. FS-4 (45% PVMQ blended composites) showed a TR10 of -68.0℃ that was 5℃ lower than that of FS-1 (100% FVMQ). The gas leakage temperature was decreased with increasing PVMQ blend ratio. The gas leakage temperature of FS-4 was -69.2℃ that was 5℃ lower than that of FS-1. Caused by the polymer chain started to transfer from a glassy state to a rubbery state and had a mobility of chain under T_g, the gas leakage temperature showed a lower value than T_g. The sealing performance at low temperature was dominated by T_g that directly affected the mobility of the polymer chain.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.12
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• pp.1667-1674
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• 2018

Recently, speeding up real time calculation using the specialized hardware accelerator is often used in the various engineering and science area, and the accelerators are required to include PCI express interconnection between FPGA and a host computer. The implementation of the high speed PCIe for the multi-giga bytes per second transmission is one of the most difficult issue in the development of the accelerators. There are several commercialized IP solutions and research results in the literature, but these solutions are required extra cost and design period to analyze the detailed implementation method. For the hardware accelerator on Xilinx FPGA, utilizing Xilinx's XDMA PCIe IP, which is provided without extra charge, can be the best solution in terms of the development period and cost. Consequently, this paper presents the evaluation system on Zynq-7000 FPGA and Windows 10 host computer, and analyze the performance of the PCIe IP with various configuration parameters.

• Mass Spectrometry Letters
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• v.15 no.2
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• pp.79 -94
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• 2024

Over the past few decades, new psychoactive substances (NPS) have become prevailing. With the widespread emergence of NPS, phenethylamines (PEAs) have become one of the groups abused most which PEAs, along with other stimulants, make up the majority of stimulants. When determining the NPS, the methods for screening and confirmation are crucial which assesses the reliability of testimony. In this study, a set of GC/MS methods employing two derivatizing agents for determining 76 target PEAs in urine was established and further applied for authentic sample analysis. Five PEAs (N,N-DMA, PMMA, 4-CA, amphetamine, and methamphetamine) with contents over their LLOQs were detected in thirteen of the twenty tested samples. In order to compare the result from the GC/MS methods with the previously established LC-MS/MS method, Cohen's kappa coefficient and McNemar's test were applied for statistical analysis. Perfect agreement between GC/MS and LC-MS/MS techniques for determining target PEAs is demonstrated by the Kappa coefficient for each of the five detected targets.

• Journal of Food Hygiene and Safety
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• v.23 no.1
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• pp.6-14
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• 2008

Objective of this study was to investigate the residual levels of mercury (Hg) in soil for "Top-rice" area and its uptake into rice plant for making sure food safety as compared to "Top-rice" & common rice produced from 2005 to 2006. Hg was analyzed with the direct mercury analyzer (DMA 80, Milestone, Italy), which implements the US/EPA method 7473. The average concentration of Hg in paddy soil was 0.031 mg/kg, which was below at 1/25-1/65 fold of the threshold levels (concern level 4 mg/kg, action level 10 mg/kg) for soil contamination designated by "The Soil Environment Conservation Law" in Korea. The maximum residue level (MRLs) for Hg residue in the polished rice is not designated in Korea. Therefore, Hg contents in the polished rice of "Top-rice" brand and common rice were compared to other country's criteria. Hg contents in the polished rice of "Top-rice" brand was 0.0018 mg/kg, which was lower at 1/10-1/30 fold than the MRLs, 0.02 mg/kg of China criteria and 0.05 mg/kg of Taiwan criteria, respectively. Hg were 0.02788, 0.00896, 0.00182, 0.00189, 0.00166, 0.00452 and 0.00145 mg/kg in soil, rice straw, unhulled rice, rice hulls, brown rice, rice bran, and polished rice produced in 2006 "Top-rice" area, respectively. For the ratio of Hg as compared to Hg contents in soil, there were 0.321 of rice straw ${\gg}$ 0.162 of rice bran ${\gg}$ 0.068 of rice hulls > 0.065 of unhulled rice > 0.060 of brown rice> 0.052 of polished rice. And, the slope of Hg uptakes was steeped as following order; rice straw ${\gg}$ rice bran ${\gg}$ rice hulls > unhulled rice > brown rice > polished rice. It means that the more slope steeped was the more uptakes. For the distribution of Hg uptaken, there was 83.8% into rice straw, and 16.2% into unhulled rice, 2.8% into rice hulls, 12.4% into brown rice, 3.5% into rice bran and 9.7% into polished rice. Consequently, it was appeared that the Hg contamination in the polished rice should not be worried in Korea.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.57 no.2
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• pp.188-194
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• 2012

This study was carried out to evaluate the quality properties, fatty acid composition and amino acid composition of major Korean inbred lines and hybrids of maize for corn breeding. Protein content of $F_2$ seeds was 9.0%, which was slightly lower than those of inbred lines, 11.4%, and $F_1$ seeds, 10.9%. in hybrid maizes. Lipid content of $F_2$ seeds of hybrid maizes was 4.2%, slightly higher than those of inbred lines, 3.3%, and $F_1$ seeds, 3.6%. However, there was no significant difference in ash content. The amount of linoleic acid in inbred lines, $F_1$ and $F_2$ seeds of hybrid maizes was highest among all fatty acids and followed by oleic acid, palmitic acid, stearic acid and linolenic acid. The composition of saturated fatty acid of $F_2$ seeds was 17.6%, similar to $F_1$ seeds but it was lower than that of inbred lines. The composition of unsaturated fatty acid of $F_2$ seeds was 82.4%, similar to $F_1$ seeds but was higher than inbred lines. The content of leucine of $F_2$ seeds was lower than inbred lines and $F_1$ seeds. The content of valine, serine, threonine, cysteine, aspartic acid, lysine, arginine, histidine of $F_2$ seeds was higher than inbred lines and $F_1$ seeds. MMA (monoamino monocarboxylic acid) in inbred lines, $F_1$ and $F_2$ seeds of hybrid maizes was highest among all amino acids and followed by DMA (diamino monocarboxylic acid) and AAA (aromatic amino acid).

• Korean Journal of Ecology and Environment
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• v.41 no.2
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• pp.188-197
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• 2008

This research was a preliminary case study to determine the levels of total mercury in the tissues of sentinel species (Zacco platypus) and ecological health in relation to habitat characteristics and chemical conditions. We collected fishes in Gap Stream during June$\sim$October 2007 and analyzed the total mercury from five types of tissues such as liver, kidney, gill, vertebrae and muscle of Zaceo platypus using Direct Mercury Analyzer (DMA-80, US EPA Method 7473). Mean concentrations of total [Hg], based on all tissues, was 67.2 and $20.7\;{\mu}g\;kg^{-1}$, in the upstream and downstream site, respectively, indicating 3 times greater level in the upstream. In other words, the levels were higher in the pristine upstream than the downstream influenced by the wastewater disposal plant. Chemical water quality, based on BOD, COD and nutrients (TN, TP) showed that severe degradation occurred in the downstreams than the upstreams. Index of Biological Integrity (IBI) using fish multi-metric model averaged 32, indicating a "good$\sim$fair" condition and varied from 42 (excellent$\sim$good) at S2 to 22 (fair$\sim$poor) at S5 depending on the sites sampled. Qualitative Habitat Evaluation Index (QHEI) in the all sites averaged 142, which was judged as "good" habitat health, but showed a high variation (181 in Site 2 vs. 67 in Site 5). Overall data suggest that health conditions, based on IBI and QHEI, was better in the upstream sites but the mercury bioaccumulation levels in the fish tissues were opposite. We believe that measurements of various parameters are required for a diagnosis of integrative ecosystem health.

• Clean Technology
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• v.21 no.1
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• pp.76-82
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• 2015

Volatile organic compounds (VOC) free adhesives have been interested by many scientists and engineers due to environmental regulations and the safety of industrial workers. In this work, a series of composites composed with bisphenol A epoxy resin used as solvent, dicyandiamide, and promoter were prepared to investigate the most appropriate molar ratio for steel-steel adhesion. The cured test specimen of each composite were measured with universal testing machine (UTM) to figure out mechanical properties such as tensile strength, Young’s modulus, and elongation. Furthermore, the lap shear strength of the specimen was tested with UTM while impact resistance was measured with Izod impact tester. The composite whose molar ratio of epoxy resin to curing agent is 1 : 0.9 (sample 3), showed better tensile strength, coefficient of elastic modulus, elongation, and impact strength than other composites did. The highest tanδ from dynamic mechanical analysis (DMA) was observed from sample 2 (epoxy resin: dicy = 1 : 0.7) while sample 3 showed slightly lower tanδ than that of 2. The morphology of the fracture surface of the cured composites from SEM showed that the number of subtle lines on the surface caused by impact increase as the contents of amine curing agent accrete. Furthermore, the viscosity change of sample 5 (epoxy resin: dicy = 1 : 1.3) was observed to confirm its storage stability.

• Analytical Science and Technology
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• v.36 no.3
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• pp.135-142
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• 2023

The total arsenic and 6 arsenic species were investigated in 56 fish collagen products using ICP-MS (Inductively coupled plasma-mass spectrometer) and HPLC-ICP-MS(High performance liquid chromatography-Inductively coupled plasma-mass spectrometer). The mean concentrations of total arsenic and arsenic species were 40.103±81.133 ㎍/kg (N.D.~586.686) and 30.070±50.378 ㎍/kg (N.D.~313.871), respectively. The mean concentration of inorganic arsenic was 24.610±32.706 ㎍/kg (N.D.~129.331), and the As(V) (Arsenate) was the most dominant. The standards and specifications of arsenic have not been established for fish collagen products. Our study presents that arsenic levels are relatively safe compared with not only previous studies but also domestic and international standards. However, in one sample, the total arsenic concentration was 586.686 ㎍/kg, showing the inorganic was 8.119 ㎍/kg, and the DMA was 305.752 ㎍/kg, which was high than the Canadian standard for organic arsenic. In conclusion, it is necessary to monitor arsenic levels consistently and establish standards and specifications of arsenic in fish collagen products to assure consumer safety.

• Polymer(Korea)
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• v.32 no.2
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• pp.163-168
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• 2008

Biomedical scaffold for tissue regeneration was fabricated by one of rapid prototyping processes, bioplotting system, with a biodegradable and biocompatible poly($\varepsilon$-carprolactone)(PCL). Through dynamic mechanical test, it was observed that the PCL scaffold manufactured by the bioplotting process has the superior mechanical properties compared to the conventional scaffold fabricated by a salt-leaching process, and the plotted scaffold could be employed as a potential scaffold to regenerating hard and soft tissue. The plotted scaffold was consisted of porous structures. which were interconnected with each pore to help cells be easily adhered and proliferated in the wall of pore tunnels, and metabolic nutrients can be transported within the matrix. By using the plotting system, we could adjust the pore size, porosity, strand pitch, and, strand diameter of PCL scaffolds, which were important parameters to control mechanical properties of the scaffolds, and consequently we could determine that the mechanically controlled scaffolds could be used as a matching scaffold for any required mechanical properties of the target organ. The fabricated 3D PCL scaffold showed enough possibility as a 3D biomedical scaffold, which was cell-cultured with chondrocytes.

• The korean journal of orthodontics
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• v.35 no.4 s.111
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• pp.312-319
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• 2005

Streptococcus mutans and Streptococcus sobrinus are major etiological agents in enamel demineralization around orthodontic appliances. This study was designed to examine the prevalence of these streptococci on orthodontic brackets in vivo using polymerase chain reaction. Four incisor brackets in the upper and lower arches were removed and collected from 80 patients at the time of debonding. The genomic DMA of adhered bacteria was extracted and each dextranase gene of S. mutans and S. sobrinus was amplified using the specific oligonucleotide primers. The results showed that the maxillary incisor brackets were colonized by both cariogenic streptococci to a somewhat higher degree than that taken from the mandible. The prevalence of S. mutans was $50.0\%$ on the maxillary incisor brackets and $33.8\%$ on the mandibular incisor brackets, and that of S. sobrinus was $17.5\%$ and $15.0\%$, respectively. Both species were detected on the maxillary incisor brackets of 7 patients $(8.8\%)$ and the mandibular incisor brackets of 5 patients $(6.3\%)$. These results suggest that cariogenic streptococci can adhere to the incisor brackets and may be resident species on the incisor brackets.