• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.1
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• pp.50-58
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• 2000

Experiments were carried out to obtain the effects of nozzle configuration and jet to jet spacing on the heat transfer characteristics of single line of circular water jets impinging on a constant heat flux plane surface. The nozzle configurations are Cone type, Reverse cone type and Vertical circular type, and the nozzle arrays are single jet(nozzle dia. 8 mm), 1 row of 3 jets and 1 row of 5 jets. Jet velocities ranging from 3m/s to 8m/s were investigated for the nozzle to target plate spacing of 80 mm. For the Cone and Reverse cone type nozzle arrays, the average Nusselt number of 1 row of 5 jets was larger than that of 1 row of 3 jets at Re$_{D}$<45000, but that of 1 row of 3 jets was larger than that of 1 row of 5 jets at $Reo\le45000$. For the Vertical circular type nozzle, however, the average Nusselt number of 1 row of 3 jets was larger than that of 1 row of 5 jets at all jet velocities. In the condition of fixed mass flow rates, the maximum heat transfer augmentation was obtained for 1 row of 5 jets and was over 2 times larger than that of the single jet for all nozzle configurations. The nozzle configurations that produce the maximum average Nusselt number are as follows: For 1 row of 3 jets, the Vertical circular type at $Reo\le45000$ and the Reverse cone type at $Reo\le45000$. But, they are the Reverse cone type at Re$_{D}$<55000 and the Vertical circular type at$Reo\le55000$ for 1 row of 5 jets.

• Biomolecules & Therapeutics
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• v.27 no.2
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• pp.168-177
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• 2019

Dysregulation of excitatory neurotransmission has been implicated in the pathogenesis of neuropsychiatric disorders. Pharmacological inhibition of N-methyl-D-aspartate (NMDA) receptors is widely used to model neurobehavioral pathologies and underlying mechanisms. There is ample evidence that overstimulation of NMDA-dependent neurotransmission may induce neurobehavioral abnormalities, such as repetitive behaviors and hypersensitization to nociception and cognitive disruption, pharmacological modeling using NMDA has been limited due to the induction of neurotoxicity and blood brain barrier breakdown, especially in young animals. In this study, we examined the effects of intraperitoneal NMDA-administration on nociceptive and repetitive behaviors in ICR mice. Intraperitoneal injection of NMDA induced repetitive grooming and tail biting/licking behaviors in a dose- and age-dependent manner. Nociceptive and repetitive behaviors were more prominent in juvenile mice than adult mice. We did not observe extensive blood brain barrier breakdown or neuronal cell death after peritoneal injection of NMDA, indicating limited neurotoxic effects despite a significant increase in NMDA concentration in the cerebrospinal fluid. These findings suggest that the observed behavioral changes were not mediated by general NMDA toxicity. In the hot plate test, we found that the latency of paw licking and jumping decreased in the NMDA-exposed mice especially in the 75 mg/kg group, suggesting increased nociceptive sensitivity in NMDA-treated animals. Repetitive behaviors and increased pain sensitivity are often comorbid in psychiatric disorders (e.g., autism spectrum disorder). Therefore, the behavioral characteristics of intraperitoneal NMDA-administered mice described herein may be valuable for studying the mechanisms underlying relevant disorders and screening candidate therapeutic molecules.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.12
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• pp.24-29
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• 2021

Recently, owing to the high demand for eco-friendly cars in the automotive industry, noise and vibrations have become major challenges. The use of laminated damping steel is increasing in response to these demands. Laminated damping steel is primarily used in sound insulation plates. The vibration energy is converted into thermal energy due to the viscoelastic resin being located between two steel sheets and being able to damp the vibrations when an external force, such as, noise or vibration is applied to the steel plate. Laminated damping steel is chiefly applied to dash panels in automotive body parts, and because of its structure, junction technology for bonding with other components is necessary. However, there has not been sufficient research conducted on junctions. In this study, regardless of the electrode shape, in the range of 4.0 ~ 8.0 kA welding current, the same welding force and welding time were applied which were 2.8 kN and 200 m/s (12 cycles) and the tensile shear load and nugget size were analyzed after the resistance spot welding between different materials of laminated damping steel with a thickness of 1.035 mm. The results show that in the range of 5 ~ 8 kA welding current, 1.035 mm laminated damping steel meets the MS181-15 standard, which is the technical standard of Hyundai-Kia Motors.

• The Journal of the Acoustical Society of Korea
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• v.28 no.8
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• pp.768-773
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• 2009

This paper demonstrates the digital communication in air using the parametric array. The stepped-plate transducer which is suitable for high-power and high-efficient radiation is used to generate the difference frequency wave with the parametric array. The primary frequencies are selected to 83 kHz and 122 kHz and the resulting difference frequency wave at the frequency of 39 kHz is used for the communication. The modulation method is selected to On-Off Keying method. The waveform and signal-to-noise ratio (SNR) is measured and analyzed to see the characteristics of the digital communication using the parametric array. The proper distance for the communication using parametric array is about 3 m. The measured beam width of the 3dB SNR reduction was $14^{\circ}$. The possibility of the communication in air using the parametric array is confirmed and the high directional characteristic of the communication using the parametric array is expected to have the advantages for the multi path and the security problems.

• Korean Journal of Applied Biomechanics
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• v.17 no.2
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• pp.113-121
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• 2007

The purpose of this study was to determine the effect of three different plates($0^{\circ}$, $10^{\circ$}, $20^{\circ}$)under heels on the lower limb muscles and erector spinae during squat exercise. Ten high school korean traditional wrestling players(age: $18.5{\pm}0.7$, weight: $1972.2{\pm}128.5N$, height: $177.8{\pm}6.0cm$, weight of barbell: $1004.5{\pm}132.4N$) performed squat exercise using three different tilting plates under heels at a cadence of 40beats/sec with 80% one repetition maximum load. Surface electrodes were placed on the participants' left and right erector spinae, and rectus femoris, vastus medialis, vastus lateralis, tibialis anterior, biceps femoris, medial gastrocnemius, and lateral gastrocnemius in the right lower extremity. One S-VHS camcorder(Panasonic AG456, 60fields/s) was placed 10m to the side of the participant. To synchronize the video and EMG data, a synchronization unit was used for this study. Average and Peak IEMG values were determined for each participant. For each variable, a one-way analysis of variance was used to determine whether there were significant differences among three different tilting plates under heels. When a significant difference was found in plates type, post hoc analyses were performed using the Tukey procedure. A confidence level of p<.05 was used to determine statistical significance. As a result of this study, maximum nEMG values of the tibialis anterior in $0^{\circ}$ plates was significantly higher than the corresponding values for the other plates during the knee extension. This increased activation in the tibialis anterior muscle indicates an increase in displacement of center of gravity of body. It is very likely that additional muscle activation are needed to stop the forward and backward movement. The results also showed that muscular activities of quadriceps femoris and erector spinae were decreased with increasing angle of plates. This suggests that increasing angle of plate may help to sustain the balance and posture of squat exercise. It is considered that very few significant differences were found among three different plates($0^{\circ}$, $10^{\circ}$, $20^{\circ}$) since elite players with much experience in squat exercise, were chosen as a participant of this study. In order to obtain meaningful results regarding the tilting angle of heel plates in squat exercise, kinetic and 3D kinematic analysis will be needed in the future study.

• Korean Chemical Engineering Research
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• v.47 no.1
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• pp.133-140
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• 2009

This paper presents the experimental study to analyze the pressure and production behavior using depressurization and thermal methods in order to evaluate the hydrate productivity in the 2-D multi-well, plate-type apparatus which has 80 md permeability and 30% hydrate saturation. Injecting methane gas through multi-well allowed to set up the highly saturated hydrate system and combining two different sorts of sands made possible to build up the low permeability system. In this system, both depressurization and electric stimulation methods were applied. When operating pressure was low, according to the depressurization experiments results, the gas recovery was high, however strong pulses which appeared at initial stage of production would damage the operation system. Moreover, cases that hydrate reformed have occurred by endothermic reaction. We have conducted experiments four and six times for the depressurization magnitudes of 140 psi and 320 psi, respectively, to analyze production behavior for the method more in detail. For the cases that the depressurization magnitude was set as 140 psi, the unstable period appears in the results, but stabilized soon. In the experiment results for 320 psi the discontinuous and intermittent behavior has been observed. Thermal stimulation experiments was conducted with depressurizing 80 psi which is the case that shows stable behavior and low recovery. In the results, the gas recovery was high and the energy efficiency was low for long stimulating time. The energy efficiency and gas recovery increased for the soaking time of 1 minute after 2 minute-preheating. In the cases of which the soaking time exceeds 1 minute, energy loss by long soaking time caused low gas recovery and poor energy efficiency.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.163-170
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• 2011

Applicability of regenerative cooling in 2,500 N-class bipropellant thruster using hydrogen peroxide and kerosene was considered for improvement performance and application in various missions. Calculation was performed by one dimensional approach using hydrogen peroxide as a coolant. In designed regenerative cooling thruster, heat flux at nozzle throat was estimated at 18 ~ 20 $MW/m^2$. Designed cooling channel width and height were 2.5 mm and 0.5 mm, respectively. Based on designed cooling channel configuration, flat plate model was manufactured and tested for estimation of pressure drop in cooling channel, and CFD analysis was compared with the test result. The maximum error between CFD analysis and experimental result was approximately 13% and average error was approximately 5%.

• The Korean Journal of Mycology
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• v.14 no.1
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• pp.17-23
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• 1986

The mating system of monokaryotic isolates in Pleurotus sajor-caju was controlled by two incompatibility factors A and B of tetrapola mating system. The mycelia of dikaryotic isolates grew faster than those of their component monokaryons, but no correlation between dikaryotic and their component monokaryotic isolates was found. The primodia formed well on the potato dextrose agar (PDA) media not only in the dikaryotic isolates but also in the monokaryons under irradiated conditions. The dikaryotic isolates produced normal sporophores; however, the monokaryotic isolates produced abnormal sporophores when they were cultivated with sawdust substrates. Some dikaryotic isolates derived by mating between monokaryotic isolates showed high yields of sporophores more than those of parental strains. Both the dikaryotic mycelial growth rate and primodia formation number on the PDA plate showed significant correlation with its sporophore products on sawdust substrates.

• Korean Journal of Veterinary Research
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• v.9 no.1
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• pp.1-9
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• 1969

The experimental studies were performed to observe the characteristics of the myelinated nerve fibers of the tradiaphragmatic branches of phrenic nerves in dog In the work to be reported five mixed breed Korean dog were used, they were one year old and he body eights were about 12 Kgm. in average with healthy conditions. The specimens (nerve) were taken at the point of 1.5 cm posterior part from the left and right phrenic nerves entrance to the diaphragm, and the dorso-lateral and dorso-medial branches of phrenic nerves vere also, taken at the point of 0.5 cm distal part from their branching portion. The specimens were fixed for 24 hrs. in Flemming's solution, and embedded in paraffin. The paraffin section. were cut at 6 microns and stained with Walter's modification of Weigert-pal method for the myelinated fibers. Microphotographs were taken and enlarged into 750 times of the actual size, and the diameter of the photographic images of the myelinated fibers were measured by the scale on the transparent Percepex Plate. The following conclusions were made: 1. The percentage of distribution of the several intradiaphragmatic branches of phrenic nerves were as follows. Ventral branches were 34.97%, lateral branches were 37.90%, dorsal branches were 27.13%, and the dorsal branches were branched again into dorso-lateral branches(54.22%) and dorso-medial branches (45. 78%). 2. The mean value and S.D. of the total numbers of the myelinated nerve fibers at the left ventral branches were $490.80{\pm}12$, and at the right ventral branches were $486.6{\pm}13$. Total average cross sectional area on the left ventral branches were 38,000. $6{\pm}136{\mu}^2$, and the right ventral branches were $37,150.2{\pm}1.782{\mu}^2$. 3. The mean value and S.D. of the total numbers of the myelinated nerve fibers at the left lateral branches were $533.8{\pm}8$, and at the right lateral branches were $525.6{\pm}7$. Total average cross sectional area of the left lateral branches were $41,582{\pm}1,170{\mu}^2$, and the right lateral branches were $40,454.8{\pm}812{\mu}^2$. 4. The mean value and S.D. of the total numbers of the myelinated nerve fibers at the left dorsal branches were $378.2{\pm}14$, and at the right dorsal branches were $380.2{\pm}8$. Total average cross sectional area of the left dorsal branches were $27,771{\pm}1,256{\mu}^2$, and the right dorsal branches were $27,507.2{\pm}645{\mu}^2$. 5. The mean value and S.D. of the total numbers of the myelinated fibers at the left dorso-lateral branches were $205.4{\pm}15$, and at the right dorso-lateral branches were $210.6{\pm}17$. Total average cross sectional area of the left dorso lateral branches were $15,354. 8{\pm}1,519{\mu}^2$, and the right dorsal branches were $15,887{\pm}1,297{\mu}^2$. 6. The mean value and S.D. of the total numbers of the myelinated nerve fibers at the left dorso-medial branches were $175{\pm}14$, and at the right dorso-medial branches were $176.2{\pm}17$. Total average cross sectional area of the left dorso-medial branches were $13,037.4{\pm}944{\mu}^2$, and at the right dorso-medial branches were, $13,103{\pm}1,373{\mu}^2$. 7. The highest frequent distribution of the intradiaphragmatic branches of phrenic nerves were found in the $10-12{\mu}^2$ groups, and they were almost 30% of the total groups. 8. The largest fibers diameter were in the $14-16{\mu}^2$ groups, and these were shown the lowest frequent distribution. 9. The largest cross sectional area of the intradiaphragmatic branches of phrenic nerves were found in the $10-12{\mu}^2$ groups. 10. All of the intradiaphragmatic branches of phrenic nerves were unimodal which has a peak in the $10-12{\mu}^2$ groups.

• Journal of Food Hygiene and Safety
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• v.29 no.3
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• pp.217-222
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• 2014

This study was performed to evaluate the sporicidal efficacy of a fumigation disinfectant containing 20% ortho-phenylphenol against Clostridium perfringens (C. perfringens) spores. In this research, efficacy test of fumigant against C. perfringens spores was carried out according to French standard NF T 72-281. C. perfringens spores working culture suspension number (N value), all the spore numbers on the carriers exposed with the fumigant (n1, n2, and n3), the number of bacterial spore suspensions by pour plate method (N1), the number of bacterial spore suspensions by filter membrane method (N2) and the mean number of bacterial spore recovered on the control-carriers (T value) were obtained from the preliminary test. In addition, the reduction number of C. perfringens spores exposed with the fumigant (d value) was calculated using T value, the mean number of bacterial spore in recovery solution (n'1) and the mean number of bacterial spore on carriers plated in agar (n'2). N value was $4.3{\times}10^7spores/mL$, and n1, n2, and n3 were higher than 0.5N1, 0.5N2 and 0.5N1, respectively. Additionally, T value was $4.9{\times}10^5spores/carrier$. In the sporicidal effect of the fumigant, the d value was 4.52log reduction. According to the French standard for the fumigant, the d value for the effective sporicidal fumigant should be over than 3log reduction. The results indicated that Fumagari $OPP^{(R)}$ had an efficient sporicidal activity against spores of C. perfringens, then the fumigant can be applied to disinfect food materials and kitchen appliances contaminated with bacterial spores.