• Analytical Science and Technology
• /
• v.11 no.4
• /
• pp.271-280
• /
• 1998

Rice flour reference materials were prepared from the unpolished rice grown in Korea and certified for elemental composition. The reference materials consist of two samples containing normal and high level. The reference material at elevated level was prepared by spiking to the normal rice flour six toxic elements of As, Cd, Cu, Cr, Hg, Pb with $1.0{\mu}g/g$ on a dry weight basis. Homogeneity of the prepared materials was evaluated through the determination of Ca, Cu, Fe, Mn, Zn by instrumental neutron activation analysis (INAA) and atomic absorption spectrometry (AAS). Small variance of elemental composition among interbottled samples assured homogeneity of the prepared materials. The materials were decomposed by high pressure digestion and microwave digestion method. INAA, AAS, inductively coupled plasma-atomic absorption spectrometry (ICP-AES), ICP-mass spectrometry (MS) and vapour generation techniques were employed to analyze the reference materials. From this independent analytical results, the certified or reference values are determined for As, Ca, Cd, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, Na, P, Pb, Se, Zn.

• Proceedings of the Korean Society of Crop Science Conference
• /
• 2017.06a
• /
• pp.287-287
• /
• 2017

The objective of this study was to evaluate difference of quality properties of between fresh cooked rice and re-heated cooked rice after retrogradation. Nine rice varieties raised by NICS were compared the properties of physicochemical, texture, sensory evaluation, toyo glossiness value, pasting properties. Among nine rice cultivars, the changes of weight and length-width ratio of after soaking as well as cooking showed how water absorbed in each rice granule. The amount of water absorption after soaking was highest in Wolback (semi-waxy), Hiami and lowest in Samgwang, Seonpum, Ilpum. After cooking, the amount of water absorption was high in Dasan 1 and Andabyeo, however low in Ilpum. In the length-width ratio after soaking, Wolback (semi-waxy cultivar) and Anda (indica cultivar) increase their volume relatively as their shape are while others increased more in length than width. Among cooked rice, the highest value of length-width ratio shows in Anda, Dasan1, Hiami and Seonpum, the Wolbak was similar to that of non-glutinous rice. After cooking, the others stored at $10^{\circ}C$ for 16 hours for retrogradation (imitated at convenience store). Then re-heated using by microwave. Pasting properties were considerably affected by storage temperature and periods of rice. The setback showed in the following order: Wolback (-92.25 RVU, the lowest retrogradation) < Seonpum (-35.20) < Chindle (-22.08) < Jungsanggold (-21.98). Toyo glossiness value of cooked rice showed in the following order: Chindle (82.40) > Samgwang (79.43) > Hiami (79.23). Sensory evaluation of re-heated rice of Jungsanggold, Samgwang, and Chindle were 78.97, 78.36, and 77.35, respectively. Hardness, elasticity, and toughness of re-heated rice ware increased compared to cooked rice, whereas cohesiveness was decreased. Hardness and elasticity is higher in Seonpum, Dasan1 and Hiami, toughness is higher in Jungsanggold, Samgwang and Wolbak. Cohesiveness of Jungsanggold and wolbak showed higher than others.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.41 no.2
• /
• pp.55-63
• /
• 2009

This study was performed to evaluate the heavy metal contents in various packaging board. Domestic and foreign OCC (old corrugated containers) and old duplex boards were used as raw materials. Tests were made for the printed and unprinted parts of the sample. Heavy metal contents of old food packaging boards made from virgin pulp fibers were also evaluated. The contents of heavy metals including lead (Pb), cadmium (Cd), barium (Ba), arsenic (As), antimony (Sb), selenium (Se), and mercury (Hg) were determined using ICP-AES (Inductively Coupled Plasma - Atomic Emission Spectrometer), and CV-AAS (Cold vapor-atomic absorption spectrometer) after digesting the samples in a microwave oven. The contents of heavy metals contained in domestic packaging board were higher than those in overseas samples, and OCC showed higher contents of heavy metals than old duplex boards. Printed parts gave greater heavy metal contents than unprinted parts. Results indicate that recycling of paper and paperboard products increases the heavy metal contamination of the paper packaging products and this derives mostly from the heavy metals contained in printing inks. Recycling processes that decrease heavy metals in recycled fibers and new printing inks that contains less heavy metals should be developed to solve the problem associated with the heavy metals in packaging paper products.

• Journal of the Korean Chemical Society
• /
• v.34 no.5
• /
• pp.404-412
• /
• 1990

The time resolved electron spin resonance spectroscopy are used to two measurement methods of chemically induced dynamic electron polarization (CIDEP) and absorption ESR. The spectra of the semiquinone radical anion were successively detected in the laser flash photolysis of anthraquinone in the mixtures of 2-propanol and triethylamine. The semiquinone radical anion was fairly stable and its cw ESR could be observed. The rate constant (T1$^{-1}$) of the spin-depolarization of polarized semiquinone radical anion was 2.6 ${\times}\;1-^5$ sec$^{-1}$ and the decay of the radical anion was the first order with the rate constant (K$_1}$) of 300.0 sec$^{-1}$. The intensity of CIDEP spectra increased with the increasing the microwave power, but the Torrey wiggles appeared following with decay curves.

• Journal of the Korean Chemical Society
• /
• v.48 no.1
• /
• pp.46-52
• /
• 2004

The effect of crystallinity on the structural stability of layered manganese oxide has been systematically investigated. While well-crystalline manganate was prepared by solid-state reaction-ion exchange method, nanocrystalline one was obtained by Chimie-Douce reaction at room temperature. According to micro-Raman and Mn K-edge X-ray absorption spectroscopic results, manganese ions in both the manganese oxides are stabilized in the octahedral sites of the layered lattice consisting of edge-shared MnO6 octahedra. The differential potential plot clarifies that the layered structure of nanocrystalline material is well maintained during electrochemical cycling, in contrast to the well-crystalline homologue. From the micro-Raman results, it was found that delithiation-relithiation process for well-crystalline material gives rise to the structural transition from layered to spinel-type structure. On the basis of the present experimental findings, it can be concluded that nanocrystalline nature plays an important role in enhancing the structural stability of layered manganese oxides.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.28 no.2
• /
• pp.123-130
• /
• 2015

This paper presents a new formulation for transient simulations of microwave propagation in heterogeneous unbounded domains. In particular, perfectly-matched-layers(PMLs) are introduced to allow for wave absorption at artificial boundaries used to truncate the infinite extent of the physical domains. The development of the electromagnetic PML targets the application to engineering mechanics problems such as structural health monitoring and inverse medium problems. To formulate the PML for plane electromagnetic waves, a complex coordinate transformation is introduced to Maxwell's equations in the frequency-domain. Then the PML-endowed partial differential equations(PDEs) for transient electromagnetic waves are recovered by the application of the inverse Fourier transform to the frequency-domain equations. A mixed finite element method is employed to solve the time-domain PDEs for electric and magnetic fields in the PML-truncated domain. Numerical results are presented for plane microwaves propagating through concrete structures, and the accuracy of solutions is investigated by a series of error analyses.

• Corrosion Science and Technology
• /
• v.12 no.2
• /
• pp.65-78
• /
• 2013

The present investigation deals with the corrosion inhibition of mild steel in 1M $H_2SO_4$ with 1, 4-dihydro pyridine and its derivatives prepared using microwave activation method. The synthesis of inhibitor was confirmed by IR spectra. The effect of 1, 4-dihydropyridine derivatives on the corrosion inhibition of mild steel in 1M $H_2SO_4$ was studied using weight loss and electrochemical polarization techniques. Influence of temperature (303-333K) and synergistic effect of halide ions ($I^-$, $Br^-$ and $Cl^-$) on the inhibition behaviour was also studied. Corrosion products on the metal surface were analyzed by scanning electron microscopy (SEM) and a possible mechanism of inhibition by the compounds is suggested. Thermodynamic parameters were calculated using weight loss data in order to elaborate the mechanism of corrosion inhibition. Polarization measurements revealed that the studied compounds acted as mixed type inhibitor but slightly anodic in nature. Electrochemical impedance measurements revealed that the compounds were adsorbed onto the carbon steel surface and the adsorption obeyed the Langmuir adsorption isotherm. The synergistic effect of halide ions on the IE increases with increase in concentration. The IE obtained from atomic absorption spectrophotometric studies was found to be in good agreement with that obtained from the conventional weight loss method. SEM revealed the information of a smooth, dense protective layer in presence of the inhibitors.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.25 no.3
• /
• pp.339-347
• /
• 2014

In this paper, the authors present a new design for a broad-band metamaterial(MTM) absorber that utilizes flexible substrate. The proposed MTM unit cell is constructed by a electric-inducive-capacitive(ELC) resonator and a cut-wire on the same side of the flexible polyimide substrate. To reduce the radar cross section at frequencies other than the targeted frequency bands, the metallic pattern layer of the proposed structure is placed facing toward the incident wave propagation direction. A prototype absorber was fabricated with a planar array of $33{\times}45$ unit cells. Our experiments showed that the proposed absorber exhibits a peak absorption rate of 92 % and 93 % at 9.06 GHz and 15.0 GHz, respectively, and 75 % of the full-width at half-maximum(FWHM) bandwidth is achieved. The proposed backplane-less MTM structure can be used for a broad-band microwave absorber and irregular surface applications.

• Journal of Korean Society for Atmospheric Environment
• /
• v.21 no.4
• /
• pp.423-430
• /
• 2005

This study was investigated with sample digestion techniques and a reliability of the analytical results for a quantitative analysis of a standard reference material ('urban particulate matter', SRM 1648). The metallic elements were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) with closed vessel microwave acid digestion method and atomic absorption spectroscopy (AAS). Quality control of the overall analytical procedures for metallic element determinations of standard reference material were estimated by analysis of a SRM 1648. Three digestion solutions $(type\;1:\;HNO_3,\;type\;2:\;HNO_3\;and\;H2O_2(4'1)\;mixture,\;type\;3:5.55\%\; HNO_3\;and\;16.75\%\;HCI\;mixture)$ were applied to SRM 1648. As a result, three digestion solutions used in this study are completely unable to digest Cr of SRM 1648. Reliability of Cr and As showed some errors in the digestion with digestion solution type (3) due to the influence of chlorides. Type (3) digestion solutions are sufficient to fulfill the digestion of As as well as Se in SRM 1648. ICP-MS results showed the improvement in accurate and precise determination of some trace elements like Cd, V and Pb in SRM 1648. It is important to use the proper digestion solution for each element to qualify analytical precision.

• Journal of the Korean Chemical Society
• /
• v.44 no.6
• /
• pp.563-572
• /
• 2000

The analysis of coal ash is very important to predict some factors, such as slagging and fouling in the boiler, and to determine optimum mixing ratios of the each coals used. In ASTM, the analysis of coal ash is clarified to use lithium metaborate (LiBO$_2$) as a fluxing agent and then to analyze the pre-treated samples using AAS. However, it takes too much time and efforts to analyze many samples by ASTM method, as a result, this method is not proper in our laboratory in charge of analyses of all power plants. So we tried to establish more convenient and accurate analytical method of coal ash by 3 different methods which are 2 different pre-treatment methods (fusion dissolution and microwave digestion) and XRF analysis method using a clear pellet. Although all 3 methods can be utilized to analyze the major elements of coal ash, each method has its own characteristics, therefore, each method should be chosen according to its own purpose.