• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.2
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• pp.22-28
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• 1998

A $g_m$-control technique using a new electronic zener diode (EZD) for CMOS rail-torail input stages is presented. A regulated CMOS inverter is used as an EZD to obtain a constant-$g_m$ input stage. The turn-off characteristic of the proposed EZD is better than that of the existing EZD using two complementarey diodes, and thus, better $g_m$-control can be achieved. With this input stage, a 3V constant-$g_m$ rail-to-rail CMOS op-amp has been designed and fabricated using a $0.8\mu\extrm{m}$single-poly, double-metal CMOS process. Measurements results show that the $g_m$ variation is about 6% over the entire input common-mode range, and the op-amp has a dc gain of 88dB and a unity-gain frequency of 4MHz for $C_L=20pF, R_L=10k\Omega$

• ETRI Journal
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• v.31 no.1
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• pp.68-70
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• 2009

In this letter, a parametric analysis of the Fresnel-field antenna measurement method is performed for a square aperture. As a result, the optimum number of Fresnel fields for one far-field point is guided as $M_{opt}=N_{opt}=D^2/{\lambda}R+5$, where D is the antenna diameter, ${\lambda}$ is the wavelength, and R is the distance between the source antenna and the antenna under test. For the aperture size 5 ${\leq}$ $L_x/{\lambda}$ ${\leq}$ 20, the tolerable distances for gain errors of 0.5 dB and 0.2 dB can be guided as $R_{0.5\;dB}$ ${\approx}$ $1.2Lx/{\lambda}$ and $R_{0.2\;dB}$ ${\approx}$ $2.0L_x/{\lambda}$, where $L_x$ is the lateral length of the square aperture. The tolerable distances for 20 ${\leq}$ $L_x/{\lambda}$ ${\leq}$ 200 are also proposed. This measurement guideline can be fully utilized when performing the Fresnel-field antenna measurement method.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.9
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• pp.384-391
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• 2003

The wideband annular ring slot antenna with concentric radiating structure and low impedance feedline has been presented. This antenna has been analyzed in compensation for FR-4 substrate with relative permittivity 4.3 and thickness 1 mm. As the measured 10 dB impedance bandwidth of the proposed antenna is 127.2%(2.17∼9.76 GHz), its bandwidth is much broader than maximum 82% bandwidth of a conventional annular ring slot antenna. Experimental results from 2 to 10 GHz are shown to be in good agreement with the simulation. And this antenna has a high gain above 4 dBi from 2 GHz to 10 GHz as well as a 24% size reduction and 42% area reduction than a circular slot antenna.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.10A
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• pp.943-951
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• 2006

Multi-input-multi-output (MIMO) systems are considered to improve the capacity and reliability of next generation mobile communication. However, the multiple RF chains associated with multiple antennas are costly in terms of size, power and hardware. Antenna selection is a low-cost low-complexity alternative to capture many of the advantages of MIMO systems. We proposed new joint Tx/Rx antenna selection algorithm with low complexity. The proposed algorithm is a method selects $L_R{\times}L_T$ channel matrix out of $L_R{\times}L_T$ entire channel gain matrix where $L_R{\times}L_T$ matrix selects alternate Tx antenna with Rx antenna which have the largest channel gain to maximize Frobenius norm. The feature of this algorithm is very low complexity compare with Exhaustive search which have optimum capacity. In case of $4{\times}4$ antennas selection out of $8{\times}8$ antennas, the capacity decreases $0.5{\sim}2dB$ but the complexity also decreases about 1/10,000 than optimum exhaustive search.

• Journal of Veterinary Clinics
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• v.14 no.2
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• pp.201-207
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• 1997

This study was carried out to investigate the changes of blood chemical values in 61 crossbred calves at 1 day, 1 week, 2 weeks, 4 weeks and 9 weeks of age, respectively. The blood chemical values of calves with diarrhea were compared with those of normal calves, and blood chemical values were compared for groups of calves with weight gain divided into four ranges; up to 0.9 kg/wk and over 7.0 kg/wk. The results obtained in this study show that the mean values and standard deviation of red blood cell (RBC) and packed cell volume (PCV) of normal calves at 1 day of age (806.7$\pm $56.5 10$^{4}$/$\mu$l and 33.8$\pm $5.2 %) decreased at 1 week of age and increased at 2 and 4 weeks of age. The PCV of normal calves at 9 weeks of age (32.6$\pm $2.3 %) was significantly lower than that at 2 and 4 weeks of age (p<0.05). Total protein of normal calves at 1 day of age (6.8$\pm $0.5 g/100 ml) decreased to 6.4$\pm $0.6 g/100ml at 1 week and increased to 7.0$\pm $ 0.7 g/100 ml at 2 weeks. After 2 weeks of age, total protein tended to decrease gradually to 9 weeks of age. Glucose of normal calves at 9 weeks of age (78$\pm $4 mg/100 ml) was significantly lower than that at 1 week (110$\pm $8 mg/100 ml) (p<0.01). At all ages, RBC, white blood cell (WBC), PCV and fibrinogen of calves with diarrhea were higher than those of normal calves. RBC and PCV of calves with diarrhea at 1 week of age (929.7$\pm $39.7 10$^{4}$/$\mu$ and 42.3$\pm $0.4 % were significantly higher than those of normal calves at 1 week (786.4$\pm $80.9 10$^{4}$/$\mu$l and 32.2$\pm $3.8 %) (p< 0.05), which suggest that diarrhea at this age can be dangerous. The weekly weight gain was an average of 4.2 kg/wk from birth to 9weeks. RBC, PCV, fibrinogen, total protein and vitamin E of calves with weight gain more than 4.0kg/wk. From the above results we obtained eledata support the importance of providing high quality feed from 4 weeks to 9 weeks of age for satisfactory weight gain of calves.

• Korean Journal of Optics and Photonics
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• v.12 no.3
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• pp.200-204
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• 2001

The structural design and the measured characteristics of optical signal amplification unit for 640 Gbps (10 Gbps$\times$64 ch.) WDM transmission systems are reported. The unit is composed of two sub gain block units for the amplification of C-band (1530-1560 nm) and L-band (1570-1600 nm), respectively. Programmable microprocessors monitor the states of operation and optimize the optical output conditions. Each sub gain block unit can maintain total optical output power of +21 dBm with gain flatness of < 1 dB and noise figure of <7.2 dB for the input power in the dynamic range from-5 to +1 dBm.+1 dBm.

• Journal of The Korean Society of Grassland and Forage Science
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• v.36 no.2
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• pp.115-123
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• 2016

In this study, the effect of energy and protein ratio on the nutrient availability and body weight gain was determined to find the proper nutrient level for the stage of replacement dairy heifers before fertilization at approximately 12~24 months old after birth. Dry matter intake showed that the TDN/CP rate of T1 (5.0:1), T2 (4.5:1) and T3 (4.0:1) resulted in similar values. Among feces, the ash content of T1 was 11.07%, which was significantly (p < 0.05) higher than that of T3 (9.69%). It was also significantly (p < 0.05) higher than that of T2 (10.32%). When the TDN/CP rate was increased, the ash content in the feces was also increased. Regardless of the initial weight, weight gain was increased significantly as the CP rate in the feed was increased on the $30^{th}$ day. On the $60^{th}$ day, T2 showed the highest rate of gain (p < 0.05). As the TDN rate was decreased or the protein rate was increased, weight gain was significantly (p < 0.05) increased. Regarding GPT level in the blood after finishing the test, T1 and T3 (112.6, 88.3 u/l) showed significantly (p < 0.05) higher value than T2 (50.9 u/l). For phosphorus level, T1 (46.3 mg/dl) showed significantly (p < 0.05) higher value than other treatments. For HDL cholesterol level, T2 (145.2 mg/dl) had significantly (p < 0.05) higher level than T1 (121.0 mg/dl) or T3 (132.3 mg/dl). For triglyceride levels, T3 (40.6 mg/dl) had significantly (p < 0.05) higher value than T1 (20.7 mg/dl) and T2 (29.0 mg/dl). For other blood parameters including BUN concentration, there were no significant (p > 0.05) difference among treatments. As a result, although feed intake and weight gain with TDN/CP rate of 4:1 showed best results, considering the excess body fat accumulation possibilities or blood metabolism, it seems 4.5:1 ratio is most appropriate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.7
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• pp.1191-1202
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• 1994

We numerically investigate a stable propagation regime of soliton pulse trains in fibers with periodically copensated loss by lumped optical amplifiers. When amplification solition pulses is 1.2~1.5 and the minimum soliton separation normalized by the soliton width becomes about 6. In cases of L=50[km], the allowable range of A is 1.5~1.7 under =6. The maximum allowable variation of the loss compensation in each lumped amplifier becomes +-2% of the fiber loss when L=50[km], A=1.6, and =6. Generally, the allowable rages of the soliton amplitude A and amplifier gain are inversely proportional to the amplification period L.

• Journal of the Korean Institute of Telematics and Electronics
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• v.13 no.5
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• pp.1-8
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• 1976

Microwave GaAs Metal Semiconductor Field effect Transistors (MESFET) with the gate-length of two micrometers are investigated. The scattering parameters of the transistors have been measured from 1GHz to 2GHz by Hp8545 Automatic network analyzer. From the measured data, an equivalent circuit is established which consists of an ntrinsic and. extrinsic transistor elements. In this paper, GaAb MESFET Amplifier is used in conjunction with conventional microstrip techniques to match into a 50 ohms high input/output impedances system. We found that Power gain is less than 8dB and VSWR is less than 1.5 in L-Band.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.2
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• pp.173-180
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• 2014

The development process of a L-Band microwave radiometer for remote sensing of soil-moisture are described in this paper. Achieving the development aim of the measurement accuracy within 2% for soil moisture content of 0~50%, the requirements and specifications of the microwave radiometer and its receiver are drawn. The receiver with high gain, high sensitivity is designed and implemented to satisfy these requirements and specifications. The receiver has the bandwidth of 40 MHz, the system gain of 50 dB and the sensitivity of average value 0.19 K, maximum value 0.313K at 1390 MHz.