• The Korean Journal of Physiology
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• v.29 no.1
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• pp.81-89
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• 1995

The effects of prolactin and vasopressin on the regulation of amniotic fluid (AF) volume and its $Na^{+}$ concentration $([Na^{+}])$ through the membrane surrounding the AF during increase in AF volume due to fetal urination were studied. About 70% of AF volume was replaced with normal isotonic saline solution. Isotonic saline solution (0.5 ml) containing Censored and LiCl was introduced into each amniotic sac. Vasopressin (25 ng/ml) or prolactin (1 mg/ml) of AF was then injected into experimental amniotic sac. The concentrations of Congored, $Li^{+}$, and $Na^{+}$ were measured at 30 and 60 min intervals after injection. Af samples with decreased Censored concentration ([CR]) during the period of 30 - 60 min were analyzed. The percentage change of $[Na^{+}]$ and the rate of $Li^{+}$ movement during this period were calculated, and the effects of vasopressin and prolactin on them were evaluated. Fellowing results were obtained: 1. The rate of reduction of [CR] in the AF was retarded by vasopressin or prolactin injection. 2. The rate of reduction of $[Li^{+}]$ in the AF was also retarded by vasopressin or prolactin injection. 3. The rate of reduction of $[Li^{+}]$ in the AF was less retarded by vasopressin than that of [CR]. 4. $[Na^{+}]$ changed to approach to the normal level, but this was markedly retarded by prolactin injection. 5. Direction of $Li^{+}$ movement was correlated with the change in $[Na^{+}]$ but it always moved out of the amniotic sac even when the $[Na^{+}]$ increased in vasopressin injected AF. From the above results, it is suggested that vasopressin in the AF triggers the fetus to urinate, and then the membranes surrounding the AF regulate osmolarity by efflux of $Na^{+}$. We suggest that prolactin facilitates water outflow across the amniotic membrane during increase in AF volume, in contrast to a constant volume, whereas regulation of $[Na^{+}]$ is partly restricted by prolactin.

• Journal of Electrical Engineering and Technology
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• v.13 no.3
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• pp.1294-1303
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• 2018

This study optimises the no-load voltage waveform of tubular hydro-generators by a simple design scheme. For different centerlines of the pole shoe and damper bar, the optimisation effects on the no-load voltage waveform are investigated in two tubular hydro-generators with different weighted powers (34 MW and 18 MW). The results are compared with those of the traditional stator-slots skewed design. The quality of the no-load voltage waveform was related to the shifting degree, and the different optimisation effects between the integer slot generator (q = 2) and the fractional slot generator (q = 11/2) were analysed. This research can improve the quality of the power output and no-load voltage waveform, and provide an effective reference for improving the industrial design and manufacture level of tubular hydro-generators.

• Progress in Superconductivity and Cryogenics
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• v.23 no.4
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• pp.56-60
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• 2021

The microwave Radar used for special purposes in the past is being applied in various areas due to the technological advancement and cost reduction, and is particularly applied to autonomous driving in the automobile field. The FMCW (Frequency Modulated Continuous Wave) Radar can acquire level information of liquid in vessel based on the beat frequency obtained by continuously transmitting and receiving signals by modulating the frequency over time. However, for cryogenic fluids with small impedance differences between liquid medium and gas medium, such as liquid nitrogen and liquid hydrogen, it is difficult to apply a typical Radar-based level meter. In this study, we develop an 80 GHz FMCW Radar for level measurement of cryogenic fluids with small impedance differences between media and analyze its characteristics. Here, because of the low intrinsic impedance difference, most of the transmitted signal passes through the liquid nitrogen interface and is reflected at the bottom of the vessel. To solve this problem, a radar measurement algorithm was designed to detect multiple targets and separate the distance signal to the bottom of the vessel in order to estimate the precise position on the liquid nitrogen interface. Thereafter, performance verification experiments were performed according to the liquid nitrogen level using the developed radar level meter.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.12
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• pp.6993-6997
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• 2014

The aim of this study was to experimentally investigate the sound quality characteristics, such as sound deflection, sound pressure level and frequency characteristics of a magnetic type speaker in an anechoic chamber to overcome the sound quality and voice-coil temperature problems. To accomplish this, the sound quality performance of the magnetic type speaker was tested according to the magnetic fluid amount and magnetic field intensity. The sound deflection, sound pressure level, and frequency characteristics were measured using the Smarrt program. As a result, at a magnetic fluid amount of 2.4 ml, the sound deflection and the sound pressure level of the magnetic type speaker were enhanced by comparing with those of the general type speaker. The frequency characteristics and the sound pressure level of the magnetic type speaker were enhanced greatly with increasing magnetic field intensity from 8.06 mT to 9.10 mT. In addition, the sound deflection of the magnetic type speaker was 0.01% lower than that of the general type speaker.

• The KSFM Journal of Fluid Machinery
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• v.12 no.3
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• pp.19-25
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• 2009

InThe purpose of this work is to analyze the flow characteristics and aerodynamic noise generated from a shroud fan at a constant 2,100 rpm using LES and FW-H noise model provided in the commercial code, FLUENT. Velocity distributions around the shroud fan obtained by using FLUENT code show good agreement with experimental results. The sound pressure level is decreased by about 6 dB as the distance from the fan increases twice. The directivity at 1st BPF shows a tendency of increasing SPL toward the axis of rotation.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.5
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• pp.148-156
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• 2001

Computational Fluid Dynamics (CFD) analysis was carried out to investigate exhaust gas flow and acoustic characteristics in the exhaust system of a passenger car. Transient 3-dimensional flow field in the front and rear mufflers was simulated by CFD and far-field sound pressure was modeled by a simple monopole source method. Engine performance simulation was also performed to obtain the boundary condition of instantaneous fluid flow variation at the inlet of the exhaust system. Detailed exhaust gas flow characteristics such as velocity and pressure distribution inside the mufflers were presented and the pulsating pressure amplitude was compared at several positions in the exhaust system to deduce sound pressure level. The present method of the acoustic analysis coupled with CFD techniques would be very effective for the prediction of sound noise from vehicle exhaust systems although the effects of the inlet boundary condition and heat transfer on the accuracy of the prediction have to be validated through further studies.

• The KSFM Journal of Fluid Machinery
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• v.9 no.2 s.35
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• pp.13-18
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• 2006

This paper was studied to design Process considered flexibility and reliability of suction and discharge valves. Flexibility and reliability of valves are main important factors in compressor valves design. And they are incompatible with efficiency of compressor. In this study, we have performed the optimal design of CO2 compressor valves to consider these factors. At first, we analyzed performance simulation of compressor to obtain optimal flexibility level of valves. From this simulation, we could get some important data at valve design like the optimal natural frequency and the height of retainer. After that we studied to reliability of valves corresponding to optimal flexibility level by finite element method. For each case bending stress and natural frequency were obtained by it. Also we investigated the fatigue stability to obtain optimal valve shape that ensured to reliability.

• Journal of KSNVE
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• v.9 no.4
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• pp.693-702
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• 1999

We study the characteristics of airflow and sound noise induced by disk rotation in optical disk drives. The characteristics of airflow around a rotating disk surrounded by various tray structures are numerically investigated using a commercial CFD program and then compared with experimental results. Sound pressure and intensity caused by the fluid-structure interactions in the CD/DVD-ROM drive are measured, and the effect of the ariflow on the sound noise and disk vibration is discussed. In order to reduce airflow-induced noise and vibration around the rotating disk, tray geometry is modified. Both numerical and experimental studies implemented with different tray models show that the improved tray model alters the characteristics of the disk-induced airflow, causing the reduction of the airflow-induced sound level.

• The KSFM Journal of Fluid Machinery
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• v.6 no.3 s.20
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• pp.7-14
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• 2003

It is addressed that the turbulent broadband sound power from a sirocco fan can be modeled by the trailing edge noise. The trailing edge noise is usually influenced by inflow turbulence, separation, and boundary layer thickness on the blade. The design parameters such as solidity (c/s) and stagger angle are specified to predict performance and noise level because the separation and slip velocity are strongly affected by them along with the flow coefficient. This paper reports the effects of the stagger angle upon the trailing edge noise for various trailing edge shapes. It is believed that the serrated trailing edge provides break-up mechanism for organized convecting vortices, thereby reduce the overall noise level for every case of stagger angle.

• International Journal of Fluid Machinery and Systems
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• v.7 no.1
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• pp.7-15
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• 2014

In the present study, a computational analysis of the flow in a centrifugal blower is carried out to predict a performance and to explain noise characteristics of the blower. Unsteady, 3D Navier-Stokes equations were solved with k-${\varepsilon}$ turbulence model using CFX software. CFD results were compared with the experimental data that is acquired from an experiment conducted with the same blower. The pressure fluctuation in the blower was transformed into the frequency domain by Fourier decomposition to find the relationship between flow behaviors and noise characteristics. Sound pressure level (SPL) which is obtained from wall pressure fluctuation at impeller outlet represents relative overall sound level of the blower well. Sound spectra show that there are some specific peak frequencies at each mass flow rate and it can be explained by flow pattern.