• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.7
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• pp.663-668
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• 2003

In this paper, a CPW fed slot antenna with novel broadband feed structure is presented. To enhance the impedance bandwidth of the slot antenna we proposed the broadband feed structure of new bow-tie slot which is combined with four λ/2 rectangular radiation slot and inductively coupled. The measured 10 dB impedance bandwidth is about 60 %(5.2∼9.4 GHz) and the simulated antenna gain is about 6 dBi at 7.36 GHz.

• Journal of IKEEE
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• v.21 no.4
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• pp.331-337
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• 2017

In this paper, we present the design of a 20MHz bandwidth 3rd-order continuous-time low-pass sigma-delta modulator with low-noise and low-power consumption. The bandwidth of the system is sufficient to accommodate LTE and other wireless network standards. The 3rd-order low-pass filter with feed-forward architecture achieves the low-power consumption as well as the low complexity. The system uses 3bit flash quantizer to provide fast data conversion. The current-steering DAC achieves low-power and improved sensitivity without additional circuitries. Cross-coupled transistors are adopted to reduce the current glitches. The proposed system achieves a peak SNDR of 65.9dB with 20MHz bandwidth and power consumption of 32.65mW. The in-band IM3 is simulated to be 69dBc with 600mVp-p two tone input tones. The circuit is designed in a 0.18-um CMOS technology and is driven by 500MHz sampling rate signal.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.3
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• pp.285-295
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• 2001

The transport phenomena in a wedge-shaped pool of twin-roll continuous caster are affected by the various operating parameters such as the melt-feed pattern, roll-gap thickness, melt-superheat, and casting speed. A computer program has been developed for analyzing the two-dimensional, steady conservation equations for transport phenomena during twin-roll continuous casting process in order to estimate the turbulent melt-flow, temperature fields, and solidification in the wedge-shaped pool. The turbulent characteristics of the melt-flow were considered using a low-Reynolds-number K-$\xi$ turbulence model. Based on the computer program, the effects of the different melt-feed patterns, roll-gap thicknesses, and superheats of melt on the variations of the velocity and temperature distributions, and the mushy solidification were examined. The results show that the liquidus line is located considerably at the upstream region, and in the lower region appear the well-mixed melt-flow and most widely developed mushy zone. Besides, the variation of melt-flow due to varying melt-feed patterns, affects mainly the liquidus line, and scarcely has effects on the solidus line in the outlet region.

• The Korean Journal of Community Living Science
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• v.23 no.3
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• pp.255-263
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• 2012

Polybrominated diphenyl ethers (PBDEs) are a group of brominated flame retardants (BFRs), which are used in a variety of consumer products. Several of those are produced in large quantities. Their chemical structure similarities to polychlorinated dibenzo-p-dioxins and polychlorinated biphenyls (PCBs), as well as their toxicity, has been studied. PBDEs are persistent and lipophilic, which results in their bioaccumulation in the fatty tissues of organisms and enrichment throughout food chains. In addition, a number of studies also reported high levels of PBDEs in animals and food resulting from the use of contaminated animal feed Public concern about PBDEs levels in animals and food has been raised. Feed contamination by toxic chemicals has been the cause of the contamination of poultry products. The purpose of this study was to evaluate PBDEs in pig feed to search the origin chase of POPs in pigs. Feed samples were obtained wheat from East Europe, corn from South America and America, soybean meal from Korea, America, South America and India and tallow from Korea. The preparation of samples was based on the EPA method 1614. Instrumental analysis was based on the use of high resolution gas chromatography coupled to high resolution mass spectrometry (HRGC/HRMS). Quantification was carried out by the isotopic dilution method. The analysis of ${\Sigma}PBDEs$ involved 22 PBDE congeners, including BDE-17, 28, 47, 49, 66, 71, 77, 85, 99, 100, 119, 126, 138, 153, 154, 156, 183, 184, 190, 191, 196 and 197.

• The Korean Journal of Community Living Science
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• v.23 no.2
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• pp.129-136
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• 2012

Dioxins are chemical substances that are not properly decomposed degradation under natural photochemical, biological and chemical conditions in the environment, and bio-accumulate through the food chain, so pose a risk of causing adverse effects to human health and the environment. Ninety seven percent of human exposure to dioxins comes through meat, fish, dairy consumption and so on. Pork is the largest proportion meat aspect of daily intake in the Korean food. Pigs are three times more than Cattle in terms of breeding population and production amount in the world, and the amount is increasing every year. Therefore, it is necessary to monitor the exposure level of dioxins in pig's body. Also, it is required to evaluate the presence of these chemical substances in the pig's feed grain such as corn, soybeans, and tallow. The purpose of this study was to evaluate PCDD/Fs in pig's feed to search the origin of PCDD/Fs. Feed samples obtained were wheat from East Europe, corn from South America and America, soybean meal from Korea, America, South America and India and tallow from Korea. The preparation of samples was based on the EPA method 1613. Instrumental analysis was based on the use of high resolution gas chromatography coupled to high resolution mass spectrometry (HRGC/HRMS). The concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 1,2,3,7,8-pentachlorodibenzo-p-dioxin (PCDD), which are the most toxic potent dioxins, were not observed in any of the samples. However OCDD was detected in most of the samples. The TEQs in the feed samples were ranged from 0 pg TEQ/g to 0.09841 pg TEQ/g. Especially, the high level of TEQs was observed in the samples of wheat from East Europe and soybean meal from Korea.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1664-1667
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• 2003

Aperture-coupled microstrip antenna is one type of microstrip antennas. This type of antenna has bandwidth wider than simple microstrip antenna. Herein, we use two substrates, that have the same dielectric constant 2.47 (PTFE-quartz) in which upper substrate is a rectangular patch. The microstrip patch is fed by a microstrip line which is printed on lower substrate, through an aperture or slot in the common ground plane of patch and microstrip feed. This antenna is analyzed by using Finite Difference Time Domain (FDTD) method the specific design frequency 10 GHz and match impedance is 50 ohms. The simulation results of its characteristics are input impedance, return loss, VSWR and radiation patterns respectively.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.05a
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• pp.128-131
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• 2000

This paper describes design for dual-linear polarization antenna using EMC(electromagnetic-coupled) dipole. EMC dipole has a simple element structure and it is fed by microstrip line. Vortical and horizontal polarization are determined by structure of dipole fed by microstrip line. FDTD Method is used for an analysis of antenna element. Length, width, height and offset of dipole are designed for 1-element antenna. Resonant length of diploe differs from the calculated value by a formula because of coupling effect of dipole and feed line. Radiation Power is controlled by the offset of dipole. In prectical fabrication of antenna array, a constant height of dipoles is required. Therefore, the teflon plate with height of 0.8 mm is considered in antenna element design for the vertical polarization.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.7
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• pp.1459-1467
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• 1997

The current on the thin planar structure as an element of the transversely fed electromagnetically coupled(EMC) microstrip dipole array antenna is obtained by using the integral forms of the finite difference time domain(FDTD) method. This method was applied to calculating the optimum current distribution (Doplh-Tchebyscheff distribution) of each dipole element on the feed line as a function of their offset positions for the narrow main beam width and the side beam level below -20 dB. The current on each dipole substitutes for the electric and magnetic current densities on the virtual surface of the FDTD calculation to express the far field intensity, the calculation time and the computer memeory can be reduced to about 80% and 1.3 Mbyte, respectively. The calculated radiation patterns are compared to the measured values and these are in good agreement.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.5
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• pp.738-746
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• 1999

In this paper, a microstrip $18\times2$ dual beam array antenna is designed at 10 GHz. The radiating element is an aperture-coupled patch, and it is analyzed by the transmission line model. The feed is a tapered parallel-series type to reduce the side lobe level. To obtain dual beam at $\pm45^{\circ}$, The difference in phase excitation between the elements is $180^{\circ}$. In conclusion, the side lobe level is 25 dB, and the beam width $8^{\circ}$with two main lobes at $\pm44.5^{\circ}$.

• Korean Chemical Engineering Research
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• v.46 no.5
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• pp.892-897
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• 2008

A new ethanol dehydration process utilizing a thermally coupled distillation column is proposed to reduce the energy requirement of the existing dehydration processes. An entrainer of benzene is used in the proposed system having the column profile similar to the equilibrium composition profile for the maximum distillation column efficiency, and the feed composition is arranged to close to the boundary of different distillation regions. It is found that the proposed distillation system gives some 18% of energy saving over the existing process. In addition, design guidelines are suggested for other azeotropic distillation process.