• ETRI Journal
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• v.32 no.2
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• pp.312-318
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• 2010

A small reconfigurable patch antenna is proposed to achieve polarization diversity for digital multimedia broadcasting systems at 2.6 GHz. To obtain polarization diversity, a pair of on-slit PIN diodes is inserted in each diagonal of a cross-shaped patch. Thus, four PIN-diodes on these slits are utilized to change the connection of the slits and thus achieve polarization. Bias circuits for the diodes are allocated in the cutting corner of the cross-shaped patch to minimize the antenna size. The antenna produces left-hand circular polarization, right-hand circular polarization, or linear polarization, depending on the PIN-diode status. Analysis of circular polarization operation is explicated. Measurements show a gain of about 1.5 dB, a cross polarization of about -20 dB, and an axial ratio of about 2.5 dB.

• Journal of The Korean Astronomical Society
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• v.25 no.1
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• pp.11-21
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• 1992

Applying mass model to disk galaxy NGC 300, since the observed rotation curve of NGC 300 is flatter than Toomre's mass model n = 1, two cases are used; obtaining parameters $a^n$ and $b^n$ from the polynomial fitting of the observed rotation curve (case A) and from the least square fitting between the observed rotation curve and model rotation curve (case B). In any case, n bas a fixed value of 1. Brandt's mass model is also discussed. which has a shape parameter n = 1.4. Calculated total mass and total mass to luminosity ratio are $3.3{\times}10^{10}M_{\odot}$, l2.1 for case A and $2.8{\times}10^{10}M_{\odot}$, 10.3 for case B. In case of Brandt's model, the values are $4.2{\times}10^{10}M_{\odot}$ and 15.4. The rise in the local mass to luminosity ratio in the outer part of NGC 300 implies existence of massive halo. Other dynamical properties are also discussed.

• Asian-Australasian Journal of Animal Sciences
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• v.16 no.1
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• pp.88-95
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• 2003

The objective of the present study was to determine the effect of exogenous bovine somatotropin on the mammary function in late lactating crossbred Holstein cows. Twelve 87.5% late lactating Holstein cows, approximately 30 weeks postpartum, were divided into two groups of 6 animals each. Animals in the control group were given sodium bicarbonate buffer by subcutaneous injection, while animals in the treated group were given recombinant bovine somatotropin (bST) by subcutaneous injection with 500 mg of bST (14 day prolonged-release bST). After bST injection, milk yield significantly increased from the control level on day 8 to day 20 (p<0.05) with a concomitant increase in mammary blood flow (p<0.01). An increase in mammary blood flow in response to bST treatment was greater than an increase in milk production. An increased plasma concentration of IGF-I coincided with an increase in mammary blood flow in animals treated with bST. There were no significant changes in the concentration of arterial plasma glucose concentration, the arteriovenous concentration difference (A-V difference) and mammary extraction ratio while the mammary glucose uptake increased when compared to the control group. The concentration of arterial plasma triglyceride decreased throughout the experimental period in animals give bST. The plasma concentration of acetate, and the mammary uptake for acetate significantly increased (p<0.05) after bST treatment. The action of bST did not affect the plasma concentration, A-V difference and extraction ratio across the mammary gland for $\beta$-hydroxybutyrate. The concentrations of milk fat and lactose tended to increase during bST treatment. Milk protein concentration initially increased in the first few days and decreased after bST injection when compared to the pretreated period. The present results indicated that bST could affect the mammary function in late lactating cows by increase in milk yield involving changes in both extra-mammary and intra-mammary mechanisms. The exogenous bST exerted its galactopoietic action through an increase in circulating IGF-I of the late lactating Crossbred Holstein cattle.

• Journal of electromagnetic engineering and science
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• v.10 no.1
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• pp.25-27
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• 2010

This paper presents a gain and phase mismatch calibration technique for an image-reject RF receiver. The gain mismatch is calibrated by directly measuring the output signal amplitudes of two signal paths. The phase mismatch is calibrated by measuring the output amplitude of the final IF output at the image band. The calibration of the gain and phase mismatch is performed at power-up, and the normal operation of the RF receiver does not interfere with the mismatch calibration circuit. To verify the proposed technique, a 2.4-GHz Weaver image-reject receiver with the gain and phase mismatch calibration circuit is implemented in a 0.18-${\mu}m$ CMOS technology. The overall receiver achieves a voltage gain of 45 dB and a noise figure of 4.8 dB. The image rejection ratio(IRR) is improved from 31 dB to 59.76 dB even with 1 dB and $5^{\circ}$ mismatch in gain and phase, respectively.

• Journal of Chest Surgery
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• v.24 no.4
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• pp.421-427
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• 1991

Atrial fibrillation[Af] is closely related to thrombus in left atrium, systemic embolism, and loss of the contribution of atrial contraction to cardiac output. Therefore maintenance of sinus rhythm[SR] is undoubtedly hemodynamically superior to Af in the clinical course of mitral valvular disease especially in the unstable period immediately after surgery. In this article, the conversion rate and the factors influencing the conversion of Af to SR after surgery were studied. Ninety-three patients with mitral valvular replacement at Chungnam National University Hospital were analysed with electrocardiography before and after surgery during the period from June 1985 to June 1990. Eighty patients presented Af before surgery. Twenty-four[30Yo] of the patients were converted to SR[A group] and fifty six presented continuous Af after surgery[B group]. The duration of preoperative Af, preoperative left atrial dimension[LAD], preoperative functional status[NYHA classification] and cardiothoracic[CT] ratio were factors influencing the conversion of Af to SR after surgery. The mean preoperative duration of Af was 3.5$\pm$2.6yr in group A and 7.6$\pm$4.9yr in group B. The mean preoperative LAD was 53. 7$\pm$9.4mm in group A and 62.5$\pm$11.2mm in group B. Before surgery, eleven patients[46%] were belong to NYHA class I, II in group A and eight[14%] in group B. The preoperative CT ratio was 62$\pm$6% in group A and 69$\pm$8% in group B.

• Journal of Magnetics
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• v.21 no.1
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• pp.148-152
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• 2016

The main goal was to evaluate effectiveness of a modified TSE sequence compared with DIR (double inversion recovery) sequence in acquisition of fast flow brain vessel images using signal void effect. 32 healthy volunteers (10 men and 22 women; mean age of 31 years; ranging between 28-43 years) who underwent black blood DIR sequence (group A) and the modified TSE sequence (group B) were enrolled in our study. Signal to Noise Ratio (SNR) and Contrast to Noise Ratio (CNR) of the internal carotid arteries' lumen were compared in T1 and T2 weighted images for both group A and B. The images obtained from group B showed lower SNR values in internal carotid artery than the group A in both of the T1 and T2 weighted images (11.49% and 13.66% respectively). While the CNR values were higher in the group B than the group A in both of the T1 and T2 weighted images (8.69% and 7.55 % respectively). The qualitative score of all categories were not significantly different between the two groups. Furthermore approximately 49% of the total scan time was reduced from group B. Our study is to shorten the scanning time and minimize the inconveniences of the patients in acquisition of the black blood images of brain by using the signal void effect in the modified TSE technique while keeping the diagnostic value of the test.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.4
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• pp.486-492
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• 2004

Flow patterns around a rotating circular cylinder having square dimpled surface were visualized by the hydrogen bubble technique at velocity ratios from a=0 to 4.8 and Reynolds number of Re=1.0${\times}$10$^4$. The wake region of the cylinder was reduced as the velocity ratios increase and was smaller than that of the smooth cylinder without dimples at the same velocity ratio. The hydrodynamic characteristics on the cylinder was investigated by measuring of lift and drag at velocity ratios from a=0 to 4.1 and Reynolds number from Re=1.2${\times}$10$^4$ to Re=2.0${\times}$10$^4$. As the velocity ratios increase, the average lift and drag coefficients were increased and at the same velocity ratio, the average lift was larger but the average drag was smaller than that of the smooth cylinder.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.5
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• pp.640-647
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• 2002

An experimental investigation or the sonic and supersonic air ejector systems has beer conducted to develop design and prediction programs for practical ejector system. Five different primary nozzles have been employed to operate the ejector systems in the ranges of low and moderate operating pressure ratios. The ejector operating pressure ratio for the secondary chamber pressure to be minimized has a strong influence of the ejector throat ratio. The pressure inside the ejector diffuser is not dependent on the primary nozzle configurations employed but only a function of the ejector operating pressure ratio. Experimental results show that a supersonic ejector system is more desirable for obtaining high vacuum pressure of the secondary chamber than a sonic ejector system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.9
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• pp.1351-1359
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• 2003

This study presents a numerical procedure to optimize shape of streamwise periodic ribs mounted on both of the principal walls to enhance turbulent heat transfer in a rectangular channel flow. The response surface method is used as an optimization technique. The optimization is based on Navier-Stokes analysis of flow and heat transfer with $k-{\varepsilon}$ turbulence model. The width-to-height ratio of a rib, rib height-to-channel height ratio and rib pitch to rib height ratio are chosen as design variables. The object function is defined as a function of heat transfer coefficient and friction drag coefficient with weighting factor. Optimum shapes of the rib have been obtained for the range of 0.02 to 0.1 of weighting factor.

• Journal of Aerospace System Engineering
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• v.14 no.4
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• pp.40-46
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• 2020

Recently, the aviation industry has sought to reduce its carbon usage in aircraft operations. Specifically, the industry is proceeding with the development of ultra-large turbofan engines and the development of hybrid electric engines to reduce the fuel consumption of aircraft. In one case, Airbus is developing as its future goal an aircraft with a short take-off distance that uses a catapult. In this study, when a b747-400 aircraft with two of the four engines removed was tested using a catapult, its fuel consumption was compared with that of the original aircraft. Fuel consumption was calculated using the mass flow consumption formula. Further, the aircraft L/D ratio caused by engine removal was interpreted using the CFD Tool, Ansys Fluent. The results showed that the lift ratio was improved by about 7% and that the fuel efficiency was improved by about 14%.