• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.131-131
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• 2003

The advent of photonic technologies in the field of communications and data transmission has been heavily increasing the demand in integrated optical (IO) circuits capable of accomplishing not only simple tasks like signal, but also more sophisticated functions like all-optical signal routing or active multiplexing/demultiplexing. In the last decade, sol-gel technology has been widely used to prepare optical materials. Sol-gel processes show many promises for the development of low-loss, high-performance glass integrated optical circuits. However, crack formation is likely to occur during heat treatment in thick gel films. In order to overcome the critical thickness limitation, the organic-modified silicate has been widely used. In this case coating matrices have been prepared from the organo-silanes of T structures, acidic catalyst and the as-prepared gel films have been heat-treated below 200$^{\circ}C$ to avoid the crack formation and the degradation of organic components. However, the films prepared in the acidic condition and the low heat temperature make the films contain high OH groups which is the major optical loss function. In this work, C$\sub$6/H$\sub$5/SiO$\sub$1.5/ films were prepared on silicon substrate by sol-gel method using base catalyst in a PTMS/NH$_4$OH/H$_2$O/C$_2$H$\sub$5/OH system. The sol showed spinable viscosity at 50 wt% of solid content, and neglectable viscosity change with time. The films were crack-free and transparent after curing at 450 $^{\circ}C$, and highly condensed to minimize OH content in C$\sub$6/H$\sub$5/SiO$\sub$1.5/ networks. The effects of heat treatment of the films are characterized on the critical thickness, the chemical composition and the refractive indices by means of SEM, FT-IR, TGA, prism coupler, respectively.

• Analytical Science and Technology
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• v.21 no.5
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• pp.397-402
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• 2008

Uranium dioxide was dissolved with nitric acid and a trace amount of HF. The analytical conditions of a spectrophotometer were investigated to determine a trace amount of silicon in the uranium matrices without a separation process. The effects of a trace amount of HF on the determination of silicon were examined. Boric acid was used to eliminate HF the interference in the colorimetric process. The recovery of silicon in the presence of a trace amount of HF in uranium solutions with or without saturated boric acid was $103.3{\pm}0.8$ and $76.6{\pm}6.8%$, respectively. The amount of saturated boric acid did not affect the recovery of the silicon. Therefore it was possible for this procedure to measure a trace amount of silicon in a uranium matrix without a separation by a UV-VIS spectrophotometry.

• Food Science of Animal Resources
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• v.44 no.4
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• pp.873-884
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• 2024

Flunixin is a veterinary nonsteroidal anti-inflammatory agent whose residues have been investigated in their original form within tissues such as muscle and liver. However, flunixin remains in milk as a metabolite, and 5-hydroxy flunixin has been used as the primary marker for its surveillance. This study aimed to develop a quantitative method for detecting flunixin and 5-hydroxy flunixin in milk and to strengthen the monitoring system by applying to other livestock and fishery products. Two different methods were compared, and the target compounds were extracted from milk using an organic solvent, purified with C₁₈, concentrated, and reconstituted using a methanol-based solvent. Following filtering, the final sample was analyzed using liquid chromatography-tandem mass spectrometry. Method 1 is environmentally friendly due to the low use of reagents and is based on a multi-residue, multi-class analysis method approved by the Ministry of Food and Drug Safety. The accuracy and precision of both methods were 84.6%-115% and 0.7%-9.3%, respectively. Owing to the low matrix effect in milk and its convenience, Method 1 was evaluated for other matrices (beef, chicken, egg, flatfish, and shrimp) and its recovery and coefficient of variation are sufficient according to the Codex criteria (CAC/GL 71-2009). The limits of detection and quantification were 2-8 and 5-27 ㎍/kg for flunixin and 2-10 and 6-33 ㎍/kg for 5-hydroxy flunixin, respectively. This study can be used as a monitoring method for a positive list system that regulates veterinary drug residues for all livestock and fisheries products.

• Fisheries and Aquatic Sciences
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• v.5 no.2
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• pp.127-135
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• 2002

Twenty seafood samples, which are common edible species and commercially important items in Korea, were purchased at the local fisheries markets and were analyzed for polycyclic aromatic hydrocarbons (PAHs) using gas chromatography coupled to mass spectrometer detector (GC/MSD). The levels of sixteen PAHs in seafood from Korean coasts were 161 to 2,243 pg/g wet weight. The highest concentration was found at saury (Coloabis saira) and the lowest level was found at jacopever (Sebastes schlegeli). The concentrations of potentially carcinogenic PAHs of six species were in the range of 9 to 123 pg/g wet weight. The residues of PAHs in fishes from Korean coasts were slightly low or relatively moderate to other countries. There was no correlation between PAH residues and lipid contents in seafood samples. The predominant contributors in fish samples were lower-molecular-weight two and three ring aromatic PAHs such as naphthalene, acenaphthene, fluorene and phenanthrene. Filter-feeding organisms like shrimp, crab and topshell were dominated by three- and four-ring aromatic PAHs. The PAH profiles in marine sediments, bivalves, fishes, shrimp, crab and topshell according to exposure pathway were compared through factor analysis. The PAH profiles were clearly classified by the difference of species or environmental matrices. This result suggests that most of PAHs within the same samples behave identically in marine environment.

• Korean Journal of Optics and Photonics
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• v.25 no.5
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• pp.262-272
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• 2014

Using an ellipsometer with dual rotating quarter-wave plates, we have analyzed the relationship between Fourier coefficients and Mueller matrices in the cases of an error-free optical system and of five systematic errors (alignment errors and retardation errors in the quarter-wave plates, and alignment error in the analyzer). In the case with five systematic errors, simulation results show that retardation errors cause more error in the diagonal elements of the Mueller matrix than do alignment errors. We have found that errors in the Mueller matrix caused by initial misalignment of the dual quarter-wave plates were the same. We have chosen the rotation rates of two quarter-wave plates such that the rotational frequencies ${\omega}_1$ and ${\omega}_2$ differ by a factor of 5, i.e. ${\omega}_2=5{\omega}_1$. The simulation results show 0.18% relative error in the diagonal elements ($m_{22}$ and $m_{33}$) and 200% relative error in the off-diagonal elements ($m_{23}$ and $m_{32}$), when we compare errors caused by misalignment of the analyzer to those caused by initial misalignment of the quarter-wave plates. We can use these results in measuring accurate Mueller matrices of optical materials.

• Analytical Science and Technology
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• v.19 no.1
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• pp.1-8
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• 2006

The isotope dilution method was used for the determination of Br impurity in $1000{\mu}g/g$ Cl standard solution. Since relatively pure KCl salt was used for the preparation of the Cl standard solution, the Br impurity determination suffers from both spectral and non-spectral interferences due to the presence of a large amount of K and Cl matrices. AG2-X8 anion-exchange resin was employed to separate the Br analyte from the matrices, and RF power was raised to 1500 W and nebulizer gas flow rate was lowered to 0.77 L/min to reduce background from the $ArArH^+$ molecular ions. The Br impurity in the $1000{\mu}g/g$ Cl standard solution was determined to be 43.7 ng/g with the standard addition method. The analytical result was in good agreement with 41.2 ng/g (RSD 1.6%) determined by the isotope dilution method to lower uncertainty from poor reproducibility of the anion-exchange process.

• Korean Journal of Veterinary Service
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• v.44 no.4
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• pp.175-183
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• 2021

This study investigated the status and analyzed of stray dogs, stray cats admitted to the Jeju Animal Shelter during the year of 2015 to 2019, and the infection rates of specific diseases for abandoned dogs. In addition, in 2017 to 2019, the collected intake and outcome data were reviewed to analyze shelter capacity in terms of housing capacity (monthly daily average intake, required holding capacity, and adoption-driven capacity), staff capacity (staff hours required for daily care). Out of 24,557 dogs admitted to the shelter, owners of 1,808 dogs (7.4%) visited the shelter and found their lost dogs, while 3,612 dogs (14.7%) were adopted to new families. However, the number of puppies that were euthanized was the highest at 12,266 (49.9%), and 6,876 (28%) died either death from disease or natural causes because they were detained in shelters. The monthly daily average (MDA), which is one of the indicators for efficient population management of Jeju Animal Shelter, was found to be 17.4 for abandoned dogs and 1.7 for abandoned cats. Seasonal variations were observed for MDA, RHC, MDA adoptions, ADC, and RSDC, indicating that various strategies are needed for shelter management. This study was performed to analyze and interpret meaningful statistics for improving the efficiency of animal shelters in Jeju. However, inconsistent collection of animal statistics limited data compilation. Creation of a basic animal statistics matrix with reference to well-designed matrices from recognized professional animal shelters is essential.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.6 no.2
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• pp.139-149
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• 1994

In this paper, a finite element technique is applied to the prediction of the wave resonance phenomena in harbors. The mild-slope equation is used with a partial reflection boundary condition introduced to model the energy dissipating effects on the solid boundary. For an efficient modeling of the radiation condition at infinity, a new infinite element is developed. The shape function of the infinite element is derived from the asymptotic behavior of the first kind of the Hankel's function in the analytical boundary series solutions. For the computational efficiency, the system matrices of the element are constructed by performing the relevant integrations in the infinite direction analytically. Comparisons with the results from experiments and other solution methods show that the present model gives fairly good results. Numerical experiments are also carried out to determine the proper distance to the infinite elements from the mouth of the halter, which directly affect the accuracy and efficiency of the solution.

• Asian-Australasian Journal of Animal Sciences
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• v.29 no.5
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• pp.753-758
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• 2016

Moisture content influences physiological characteristics of microbes and physical structure of solid matrices during composting of animal manure. If moisture content is maintained at a proper level, aerobic microorganisms show more active oxygen consumption during composting due to increased microbial activity. In this study, optimum moisture levels for composting of two bedding materials (sawdust, rice hull) and two different mixtures of bedding and beef manure (BS, Beef cattle manure+sawdust; BR, Beef cattle manure+rice hull) were determined based on oxygen uptake rate measured by a pressure sensor method. A broad range of oxygen uptake rates (0.3 to 33.3 mg $O_2/g$ VS d) were monitored as a function of moisture level and composting feedstock type. The maximum oxygen consumption of each material was observed near the saturated condition, which ranged from 75% to 98% of water holding capacity. The optimum moisture content of BS and BR were 70% and 57% on a wet basis, respectively. Although BS's optimum moisture content was near saturated state, its free air space kept a favorable level (above 30%) for aerobic composting due to the sawdust's coarse particle size and bulking effect.

• Mycobiology
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• v.43 no.2
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• pp.93-106
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• 2015

Alternaria species are common saprophytes or pathogens of a wide range of plants pre- and post-harvest. This review considers the relative importance of Alternaria species, their ecology, competitiveness, production of mycotoxins and the prevalence of the predominant mycotoxins in different food products. The available toxicity data on these toxins and the potential future impacts of Alternaria species and their toxicity in food products pre- and post-harvest are discussed. The growth of Alternaria species is influenced by interacting abiotic factors, especially water activity ($a_w$), temperature and pH. The boundary conditions which allow growth and toxin production have been identified in relation to different matrices including cereal grain, sorghum, cottonseed, tomato, and soya beans. The competitiveness of Alternaria species is related to their water stress tolerance, hydrolytic enzyme production and ability to produce mycotoxins. The relationship between A. tenuissima and other phyllosphere fungi has been examined and the relative competitiveness determined using both an Index of Dominance ($I_D$) and the Niche Overlap Index (NOI) based on carbon-utilisation patterns. The toxicology of some of the Alternaria mycotoxins have been studied; however, some data are still lacking. The isolation of Alternaria toxins in different food products including processed products is reviewed. The future implications of Alternaria colonization/infection and the role of their mycotoxins in food production chains pre- and post-harvest are discussed.