• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.78.1-78.1
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• 2014

An ionization front (IF) surrounding an H II region is a sharp interface through which a cold neutral gas makes transition to a warm ionized phase by absorbing UV photons from central massive stars. We investigate the structure and instability of a plane-parallel D-type IF threaded by magnetic fields parallel to the front. We find that magnetic fields increase the maximum propagation speed of the IFs, while reducing the expansion factor, defined as the density ratio of neutral to ionized phases. IFs become unstable to distortional perturbations due to gas expansion across the fronts, exactly analogous to the Darrieus-Landau instability of ablation fronts in terrestrial flames. The growth rate of the IF instability is proportional linearly to the perturbation wavenumber as well as the upstream flow speed. The IF instability is stabilized by gas compressibility and becomes completely quenched when the front is D-critical. The instability is also stabilized by magnetic pressure when the perturbations propagate in the direction perpendicular to the fields. When the perturbations propagate in the direction parallel to the fields, on the other hand, it is magnetic tension that reduces the growth rate, completely suppressing the instability when ${\beta}$ < 1.5, with ${\beta}$ denoting the square of the ratio of the sound speed to the Alfven speed in the pre-IF region. When the front experiences an acceleration, the IF instability cooperates with the Rayleigh-Taylor instability to make the front more unstable. We discuss potential effects of IF instability on the evolution and dynamics of IFs in the interstellar medium.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.16 no.1
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• pp.1-4
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• 2010

The compression strength of corrugated fiberboard containers for packaging the agricultural products rapidly decreases because of various environmental conditions during distribution of unitized products. Among various environmental conditions, the main factors affecting the compression strength of corrugated fiberboard are absorption of moisture, long-term accumulative load, and fatigue caused by shock and vibration. An estimated rate of damage for fruit during distribution is about 30~40% owing to the shock and vibration. This study was carried out to characterize the durability of corrugated fiberboard containers for packaging the fruits and vegetables under simulated transportation environment. After the packaging freight was vibrated at various experimental conditions, the compression test for the packaging was performed. The compression strength of corrugated fiberboard containers decreased with loading weight and vibration time. The multiple nonlinear regression equation ($R^2$ = 0.9198) for predicting the decreasing rate of compression strength of corrugated fiberboard containers were developed using four independent variables such as input acceleration level, input frequency, loading weight and vibration time.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.30B no.5
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• pp.62-72
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• 1993

The phased array antenna has the ability to perform adaptive sampling by directing the radar beam without inertia in any direction. The adaptive sampling capability of the phased array antenna allows each sampling time interval to be varied for each target, depending on the acceleration of each target at any time. In this paper we design a three dimensional adaptive target tracking algorithm for the phased array radar system with a given set of measurement parameters. The tracking algorithm avoids taking unnecessarily frequent samples, while keeping the angular prediction error within a fraction of antenna beamwidth so that the probability of detection will not be degraded during a track updata illuminations. In our algorithm, the target model and the sampling rate are selected depending on the target range and the target maneuver status which is determined by a maneuver level detector. A detailed simulation is conducted to test the validity of our tracking algorithm for target trajectories under various conditions of maneuver.

• Journal of Electrical Engineering and Technology
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• v.3 no.4
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• pp.576-583
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• 2008

In this study, we attempt to design a real-time autonomic nervous system(ANS) evaluation system usable during exercise using heart instantaneous frequency(HIF). Although heart rate variability(HRV) is considered to be a representative signal widely used ANS evaluation system, the R-peak detection process must be included to obtain an HRV signal, which involves a high sampling frequency and interpolation process. In particular, it cannot accurately evaluate the ANS using HRV signals during exercise because it is difficult to detect the R-peak of electrocardiogram(ECG) signals with exposure to many noises during exercise. Therefore, in this study, we develop the ground for a system that can analyze an ANS in real-time by using the HIF signal circumventing the problem of the HRV signal during exercise. First, we compare the HRV and HIF signals in order to prove that the HIF signal is more efficient for ANS analysis than HRV signals during exercise. Further, we performed real-time ANS analysis using HIF and confirmed that the exerciser's ANS variation experiences massive surges at points of acceleration and deceleration of the treadmill(similar to HRV).

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.2
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• pp.332-337
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• 2004

The use of gas absorption refrigeration machine has considerably increased because of the shortage of the electric power in the summer and the regulation of freon refrigerant. Gas absorption refrigeration machine consists of a condenser, a heat exchanger. supplying pipes, a radiator etc, This system is likely to be corroded by acid. dissolved oxygen and gases, Cavitation erosion-corrosion by flow velocity of cooling water may happen in absorption refrigeration machine. In these cases. erosion and corrosion occur simultaneously. Then, it makes a serious damage with synergy effect. Therefore, this paper was studied on the cavitation damage of cupronickel(70/30) tube for gas absorption refrigeration machine, In the $30^{\circ}C$ tap water, linear polarization test and anodic polarization test were carried out for copper(C1220T-OL) and cupronickel(70/30) tube. Also, cavitation erosion-corrosion behavior of cupronickel (70/30) tube was considered, The main results are as following: (1) In the linear test, the corrosion current density of cupronickel(70/30) is higher than that of copper. (2) The erosion-corrosion rate of cupronickel(70/30) displayed later tendency than that of copper by vibratory cavitation in cooling water. (3) In cooling water, the progress mechanism of erosion-corrosion rate of copper and cupronickel(70/30) follows a pattern of incubation, acceleration, attenuation and a steady state period.

• Biomedical Science Letters
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• v.8 no.1
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• pp.47-52
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• 2002

To investigate an effect of cyclohexanone (CHO) treatment on the serum levels of xanthine oxidase (XO) in liver damaged animals, the rats were intraperitoneally pretreated with 50% carbon tetrachloride ($CCl_4$) in olive oil (0.1 mL/ 100 g body weight) 14 times every other day. To the $CCl_4$-pretreated rats, CHO (1.56 g/kg body weight) was injected once and then the animals were sacrificed at 4 hours after CHO treatment. The increasing rate of serum and liver XO activities to the control was higher in CHO-treated animals pretreated with $CCl_4$ than the $CCl_4$-pretreated those. Concomitantly CHO injection to the $CCl_4$-pretreated animals showed somewhat higher Vmax and lower Km value in the kinetics of liver XO enzyme. Furthermore, increasing rate of hepatic malonedialdehyde content to the control was also higher in CHO-treated animals pretreated with $CCl_4$ than $CCl_4$-pretreated those. On the other hand, the injection of CHO to the $CCl_4$-pretreated animals showed the more enhanced liver damage on the basis of liver function finding; liver weight per body weight (%), serum levels of alanine aminotransferase activity and hepatic glucose-6-phosphatase activity. In conclusion, injection of CHO to the $CCl_4$-pretreated rats led to more increased activity of serum XO and it may be caused by acceleration of hepatocyte membrane permeability and induction of enzyme protein.

• BMB Reports
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• v.46 no.6
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• pp.310-315
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• 2013

The gene order on the X chromosome of eutherians is generally highly conserved, although an increase in the rate of rearrangement has been reported in the rodent lineage. Conservation of the X chromosome is thought to be caused by selection related to maintenance of dosage compensation. However, we herein reveal that the cattle (Btau4.0) lineage has experienced a strong increase in the rate of X-chromosome rearrangement, much stronger than that previously reported for rodents. We also show that this increase is not matched by a similar increase on the autosomes and cannot be explained by assembly errors. Furthermore, we compared the difference in two cattle genome assemblies: Btau4.0 and Btau6.0 (Bos taurus UMD3.1). The results showed a discrepancy between Btau4.0 and Btau6.0 cattle assembly version data, and we believe that Btau6.0 cattle assembly version data are not more reliable than Btau4.0.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.3
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• pp.75-80
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• 2014

In previous study, make an attempt to estimate exhaust valve seat and seat-ring wear acceleration factor for engine durability test with measuring and consideration of wear mechanism. But found abnormal initial wear rate in exhaust valve seat-ring. And have to improve exhaust valve seat-ring wear rate for reliability reason, because next GDI/Turbo engine is based on this engine and GDI/Turbo engine have higher combustion pressure and higher thermal load. In this study, Trying to find the cause of abnormal wear factor, improve valve-train durability by change specification & design of parts and verify variant parts for improving durability of valve-train. And then I would like to propose a design guide line of valve-train system in a reliability point of view, besides make a complement of previous study.

• Journal of Biosystems Engineering
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• v.38 no.2
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• pp.163-170
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• 2013

Purpose: The purpose of this study is to provide analysis of physiological, biomechanical responses occurring from the operation to lifting or twist lifting task appears frequently in agricultural work. Methods: This study investigated the changes of physiological factors such as heart rate, heart rate variability (HRV) and biomechanical factors such as physical activity and kinetic analysis in the task of twisting at the waist while lifting. Results: Heart rates changed significantly with the workload. The result indicated that the workload of 2 kg was light intensity work, and the workload of 12 kg was hard intensity work. Physical activity increased as the workload increased both on wrist and waist. Besides, stress index of the worker increased with the workload. Dynamic load to herniated discs was analyzed using inertial sensor, and the angular acceleration and torque increased with the workload. The proposed measurement system can measure the recipient's physiological and physical signals in real-time and analyzed 3-dimensionally according to the variety of work load. Conclusions: The system we propose will be a new method to measure agricultural workers' multi-dimensional signals and analyze various farming tasks.

• Proceedings of the Korean Society for Food Science of Animal Resources Conference
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• 2002.05a
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• pp.17-25
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• 2002

Application of electrical stimulation in the red meat species (eg. beef and sheep) processing has been erratic around the world and this may reflect an incomplete knowledge of how to optimise the technology. Although it is well established that stimulation increases the rate of post-mortem glycolysis other biochemical and biophysical effects have been implicated with the use of this technology. On the basis of currently available knowledge, this mini-review seeks to examine the current theories about the effect of stimulation on post-mortem muscle. The classical view that stimulation prevents muscle from shortening excessively during rigor development has been expanded to include the possibility that it also results in physical disruption of muscle structure. The interaction of these effects with the acceleration of the rate of proteolysis through activation of the calpain protease system has not been comprehensively reviewed in the past. As a result of conclusion driven, this article highlights several areas that may prove fruitful for further research. The challenge for further development of electrical stimulation systems is optimisation of the activation of the enzyme systems in parallel with manipulation of chilling regimes so as to ensure rigor mortis is achieved at temperatures which minimise shortening. The potential of regional stimulation of sections of the carcass to achieve this outcome is worthy of study given the different fibre composition of muscles and temperature gradients.