• Journal of Photoscience
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• v.6 no.1
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• pp.5-6
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• 1999

Solar ultraviolet-B (UV-B) irradiances incident on a horizantal surface at Taegu of Korea during 1995-1998 were calculated with 5 min averges of measuremets taken every 30 seconds by a broadband UV-B sensor. The maximum and minimum of monthly averages of daily UV-B dose were 15.89 KJ m-2 day-1 in April and 3.91KJm-2 day-1 on May 22, 1998 and 1.230W m-2 at 12 : 45, July 13, 1998, respectively. Increasing trend in annual maximum of instantaneous UV-B radiation was averaged to 12.0% per year during 1995-1998 of observation period.

• Journal of applied mathematics & informatics
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• v.28 no.5_6
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• pp.1185-1202
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• 2010

In this paper, we have studied the dynamical behaviour such as boundedness, local and global stabilities, bifurcation of a single species population affected by environmental toxicant and population toxicant. We have also studied the effect of discrete delay of the environmental toxicant on the instantaneous growth rates of the population biomass and population toxicant due to incubation period. The length of delay preserving the stability is also estimated. Computer simulations are carried out to illustrate our analytical findings.

• Nuclear Engineering and Technology
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• v.23 no.1
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• pp.30-40
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• 1991

For automatic power control of KMRR, a new method, Reactivity Constraint Method, is applied for time optimal control. This method limits the net reactivity to the amount that can be offset by instantaneous control rod action. The reactivity to be constrained for the constant reactor period should be obtained by the dynamic period equation. A new formulation of the dynamic period equation for 2-point kinetics model is presented. A methematical controller model was applied to the plant simulator, KMRSIM to test this control law. The performance test showed that reactivity constraint approach is also a reliable means for reactor power change control.

• Journal of Energy Engineering
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• v.23 no.4
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• pp.41-48
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• 2014

Leak of liquid has been categorized conventionally into instantaneous release and continuous release. In this study, the spread of cryogenic liquid due to limited period of release is investigated for the first time to establish a new classification method with recognizing the irrationality of the conventional one. Such physical phenomena are governed by simultaneous equations concerning volume, radius and height of pool of the cryogenic liquid, and major parameters are evaporation rate per unit area, time of release, and spill quantity. The simultaneous governing equations is decoupled to get efficiently perturbation solutions. As the results, for the same spill quantity, in view of release model, combined release model that consists of continuous and consecutive instantaneous model is necessary with small time of release, while continuous model is solely required with large time of release. Also, the combined model is necessary for small spill quantity with the same time of release. These two regimes of release are clearly distinguished using the perturbation solution to provide a clear basis for the new classification of release models.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.3
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• pp.191-198
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• 2007

This paper proposes the instantaneous source voltage and phase current control for torque ripple reduction of a high speed miniature BLDC motor. As compared with general BLDC motor, a high speed miniature BLDC motor has a fast electrical time-constant. So the current and torque ripple are very serious in a conventional PWM switching during conduction period. In order to reduce the switching current ripple, instantaneously controlled source voltage is supplied to the inverter system according to the motor speed and load torque. In addition, the fast hysteresis current controller can keep the phase current In the limited band. The proposed method is verified by the computer simulation and experimental results.

• The Journal of the Korea Contents Association
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• v.21 no.12
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• pp.302-309
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• 2021

The section speed enforcement system measures the starting instantaneous speed, the The section speed enforcement system measures the starting instantaneous speed, the ending instantaneous speed, and the section average speed, and imposes fines only for the portion that has been speeding the most. However, according to the Road Traffic Act, most of the systems are installed on highways, so existing research has been conducted on highway sections. In this study, it is expected that the installation of section speed enforcement systems on general national roads will be expanded according to the revision of related laws. ITS collection and operation data targeting the section speed enforcement system installed on National Road 3 Seongnam Icheon-ro was used to analyze traffic speed, standard deviation of traffic speed, and reduction in traffic accidents by dividing it into before installation, trial operation period, and after crackdown. As a result of the analysis, the traffic speed, standard deviation, and traffic accidents decreased by 13%, 25%, and 70%, respectively, after installation, confirming that the installation of the section speed enforcement system greatly contributed to the reduction of accidents.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.6
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• pp.141-148
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• 2008

An utility voltage information, including the frequency, phase angle and amplitude is very important in many industrial systems. The grid-connected photovoltaic system in the limelight as alternative energy needs utility voltage information such as frequency, phase angle and magnitude to connect the grid-line. In this paper, it proposes the instantaneous phase-tracking in PLL that uses the frequency from the utility voltage as a sync signal and locks the phase with compensation for phase difference from DPT algorithm. It also proposes not only DFT algorithm execution by every sample not by one period, but also phase-tracking method in a wide range of frequency not a fixed one. This paper shows the feasibility and the usefulness of the proposed methods through the computer simulation and the experiment.

• Ocean and Polar Research
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• v.37 no.1
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• pp.11-22
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• 2015

In-situ measurements are labor-intensive, time-consuming, and limited in their ability to observe currents with spatial variations in the surf zone. This paper proposes an optical image-based method of measurement of currents in the surf zone. This method measures nearshore currents by tracking in time wave breaking-induced foam patches from sequential images. Foam patches in images tend to be arrayed with irregular pixel intensity values, which are likely to remain consistent for a short period of time. This irregular intensity feature of a foam patch is characterized and represented as a keypoint using an image-based object recognition method, i.e., Scale Invariant Feature Transform (SIFT). The keypoints identified by the SIFT method are traced from time sequential images to produce instantaneous velocity fields. In order to remove erroneous velocities, the instantaneous velocity fields are filtered by binding them within upper and lower limits, and averaging the velocity data in time and space with a certain interval. The measurements that are obtained by this method are comparable to the results estimated by an existing image-based method of observing currents, named the Optical Current Meter (OCM).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.39 no.4
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• pp.344-348
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• 2006

The ecological characteristics and stock biomass of the Shiba shrimp, Metapenaeus joyneri, in Korean waters were determined, using fishery data from the Ministry of Maritime Affairs and Fisheries (MOMAF) and available length frequency data. The instantaneous coefficient of total mortality (Z) of M. joyneri was estimated to be 4.191year, and the annual survival rate (S) was 0.015. The estimated instantaneous coefficient of fishing mortality (F) for recent years was calculated to be 1.94/year. The age at first capture of M. joyneri was 0.71 years. Based on these parameters, the annual biomass of the M. joyneri stock was estimated using a biomass-based cohort analysis and data on the annual catch in weight at age for 1993-2004 in Korean waters. During the study period, the biomass of the shrimp peaked in 1994 at about 9,082 metric tons. Subsequently, it decreased to 500 metric tons in 1998.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.62.2-62.2
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• 2017

We have made an investigation on the radial and azimuthal wave modes of full halo coronal mass ejections (HCMEs). For this, we consider 24 HCMEs which are simultaneously observed by SOHO and STEREO A & B from August 2010 to August 2012 when they were roughly in quadrature. Using the SOHO/LASCO C3 and STEREO COR2 A & B running difference images, we estimate the instantaneous apparent speeds of the HCMEs at 24 different position angles. Major results from this study are as follows. First, there are quasi-periodic variations of the instantaneous radial velocity with the periods ranging from 24 to 48 mins. Second, the amplitudes of instant speed variations are about a third of the projected speeds. Third, the amplitudes are found to have a weak anti-correlation with period. Our preliminary identification from SOHO observations shows that there are several distinct radial and azimuthal wave modes: m=0 (radial) for five events, m=1 for eleven events, m=2 for three events, and unclear for the other events. In addition, we are making a statistical investigation on the oscillation of 733 CMEs to understand their physical origins.