• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.11
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• pp.788-797
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• 2010

This study examines the influence of fluctuating daylight illuminance on daylight dimming control systems. Field measurements were performed for a full-scale mocked-up model under various daylight conditions in winter. Fluctuating ranges for a partially-shielded photosensor were great when the variation of sky ratio was great. When solar altitude was lower the illuminance and fluctuating range of illuminance were great due to the influence of direct components of daylight and the interrefelction between surfaces in rear area of space. It implies that daylight dimming system would not function effectively, unless the desktop illuminance by daylight is enough. Fluctuation ranges of photosensor illuminance were lower than 50 lx under clear sky conditions, but they were greater than 100 lx under partly-cloudy sky conditions. It means that the fluctuation range of electric light output of lighting fixture would greater under the partly-cloudy conditions and cause potential visual annoyance to occupants. Outdoor vertical illuminance reaching the windows would be an effective factor that can be used to predict the fluctuation of photosensor signals for effective controls of daylight dimming system.

• Health Policy and Management
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• v.13 no.1
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• pp.23-45
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• 2003

This study was performed to evaluate economic effect of the water fluoridation program in Cheong-Ju City from 1982 to 2010. To study this economic effect, this study used cost-benefit analysis methodology from eight years old to fourteen years old in Cheong-Ju City. Major findings were as follows; First, total cost of fluoridation program in Cheong-Ju City was 1,384,164,734 korean won and total benefit was 15,057,426,621 Korean won from 1982 to 2010. Second, total cost which was converted by present value 2000 year was 1,687,412,718 won and total benefit which was converted by present value 2000 year was 14,582,548,519 Korean won. Cost-benefit ratio was 8.64. Net present value which happened from 1982 to 2000 was 7,990,710,155 Korean won and cost benefit ratio was 7.47. In conclusion, by the above result, economic impact of the water fluoridation program was very effective for children in some area of Cheong-Ju city.

• Asian-Australasian Journal of Animal Sciences
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• v.7 no.2
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• pp.255-260
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• 1994

Calving records of 107 heifers from two breed groups were used to identify the major factors contributing to calving difficulty (dystocia) and compare the influence of pelvic diameters, weight and height of heifers measured after breeding and before calving on dystocia. The horizontal and vertical pelvic diameters, hip height and weight of heifers were measured two months after breeding and again two months before calving. Snell transformed calving difficulty scores (0 = normal to 100 = surgical intervention) were used in analyzing the data by analysis of covariance. Body condition score of the heifer, sire birth weight of the calf, birth weight of the calf, and ratio of calf birth weight to pelvic area all had significant effects on dystocia. Calf birth weight, ratio of calf birth weight to pelvic area, and heifer's condition score were especially important. However, sex of calf did not have a significant influence on dystocia. Generally, the variables measured before calving accounted for a higher proportion of variation in dystocia than those measured after breeding. Thus, based on the relative importance of the major factors affecting dystocia, it is suggested that selection of bulls with low birth weight for breeding on normal size heifers with optimum body condition score, and well developed pelvic opening, would be effective in reducing the incidence and severity of dystocia in beef heifers.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.11
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• pp.1007-1013
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• 2005

In this study, a step-down piezoelectric transformer was fabricated to utilize as an adapter for charging batteries of mobile electronic appliances. The ceramic part of the transformer is $Pb[(Mn_{1/3}Sb_{2/3})_{_0.05}Zr_{0.475}Ti_{0.475}]O_3$ with mechanical quality factor of 1600, electromechanical coupling coefficient $59\%$, and piezoelectric constant $d_{33}$ 1300, which can be utilized as a piezoelectric transformer. A simply fabricated disk-typed test pattern of diameter 28 mm and thickness 2 mm was used to characterize output voltage, step-down ratio as a function of electrode area with the input remained constant, and power, efficiency as a function of input voltage, and temperature-dependent electric characteristics were evaluated. The sample APT1 showed the best properties. The highest admittance, effective electromechanical coupling coefficient and an appropriate mechanical quality factor were obtained at the sample with the input/output area ratio of 1:1.5 at the common electrode, and the condition of 20 $V_{rms}$, $50\;\Omega$ made the maximum efficiency of $95\%$. The temperature was increased by 14.7'E as the input voltage was increased for $50\;V_{rms},\;50\;\Omega$.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.5
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• pp.33-41
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• 1994

For the establishment of large force standard and the accurate measurement of large force, 2MN hydraulic force standard machine which consists of loading frame, deadweight machine, two ram/cylinder systems and hydraulic control system was designed and fabricated. Measurement results of shapes for tow ram/cylinders reveal that the ratio of effective area is 200.094. The relative deviation of force stability for the machine is about .+-. 0.01% at 2MN and is less than .+-. 0.005% below 2MN. This machine may be widely used to calibrate the force measuring devices in industry and to test the force sensors.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.6
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• pp.73-83
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• 2016

Bearing stress near anchor plates is usually very high due to prestressing force in anchorage zone of concrete structure used post-tensioned prestressed method. In order to effective utilization of cross section and crack control, appropriate size of anchorage plates should be used to prevent crack initiation and failure of concrete structures eventually. This study aims to suggest equation for effective area of bearing plate of rectangle type and circular type by Highway Bridge Design Specification and PTI etc. A shape factor according to bearing plate shape is suggested based on numerical analysis, and it can be used suitability for design of special anchorage plate dimension.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.73-76
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• 2006

Acoustic cavity as a stabilization device to control high-frequency combustion instabilities in liquid rocket engine is adopted and its damping capacity is verified in atmospheric temperature. Geometric effects of acoustic cavity on damping characteristics are analyzed and compared quantitatively. Satisfactory agreements have been achieved with linear acoustic analysis and experimental approach. Results show that the acoustic cavity of the largest orifice area or the shortest orifice length was the most effective in acoustic damping of the harmful resonant frequency finally, it is proved that an optimal design process is indispensable for the effective control of combustion instabilities.

• Journal of Radiation Protection and Research
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• v.16 no.2
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• pp.17-26
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• 1991

Beta ray $(^{90}Sr+^{90}Y)$ absorbed dose at tissue surface was measured from the distance of 30cm by use of extrapolation chamber. In the measurement, following factors were considered: effective area of collecting electrode, polarity effect, ion recombination and window attenuation. The measured absorbed dose rate at tissue surface was $1.493{\mu}Gy/sec$ with ${\pm}2.9%$.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.1
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• pp.8-16
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• 2020

In this paper, a single-bit 2nd-order delta-sigma modulator with the architecture of cascaded-of-integrator feedforward (CIFF) is proposed for column-parallel analog-to-digital converter (ADC) array used in a low noise CMOS image sensor. The proposed modulator implements two switched capacitor integrators and a single-bit comparator within only 10-㎛ column-pitch for column-parallel ADC array. Also, peripheral circuits for driving all column modulators include a non-overlapping clock generator and a bias circuit. The proposed delta-sigma modulator has been implemented in a 110-nm CMOS process. It achieves 88.1-dB signal-to-noise-and-distortion ratio (SNDR), 88.6-dB spurious-free dynamic range (SFDR), and 14.3-bit effective-number-of-bits (ENOB) with an oversampling ratio (OSR) of 418 for 12-kHz bandwidth. The area and power consumption of the delta-sigma modulator are 970×10 ㎛2 and 248 ㎼, respectively.

• Journal of Mechanical Science and Technology
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• v.15 no.4
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• pp.459-464
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• 2001

The effects of internal air-pressing on deep drawability are investigated in this study to increase the deep drawability of aluminum sheet. The conventional deep drawing process is limited to a certain limit drawing ratio(LDR) beyond which failure will occur. The intention of this work is to examine the possibilities of relaxing the above limitation through the deep drawing with internal air-pressing, aiming towards a process with an increased drawing ratio. The idea which may lead to this goal is the use of special punch that can exert high pressure on the internal surface of deforming sheet during the deep drawing process. Over the ranges of conditions investigated for Al-1050, the local strain concentration at punch nose radius area was decreased by internal air-pressing of punch, and the deep drawing with internal air-pressing was proved to be very effective process for obtaining higher LDR.