• Title/Summary/Keyword: reduction of pressure

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A Study on the Echo Reduction Performance of Underwater Acoustic Material (수중 음향재료의 반향음 감소성능 연구)

  • Seo, Young Soo;Ham, Il Bae;Jung, Woo Jin
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.24 no.11
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    • pp.868-875
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    • 2014
  • The requirement of acoustic material which is used in underwater environment more increases. The material is used to reduce acoustic signature and radiate noise for underwater vehicle. Underwater acoustic material was made by viscoelastic material such as rubber and polyurethane etc. The mechanical and acoustic characteristics of these material change with hydrostatic pressure. In order to improve an acoustic performance according to hydrostatic pressure, several kinds of scatterers were added to viscoelastic material. In this paper, acoustic modelling and analysis techniques of underwater acoustic material with hydrostatic pressure were introduced and proposed. The specimens for pulse tube test were made and echo reductions were calculated and measured with hydrostatic pressure. Also the characteristics of echo reduction of the specimens with hydrostatic pressure were obtained and discussed.

Development of Tight-fitting Upper Clothing for Measuring ECG -A Focus on Weft Reduction Rate and Subjective Assessment- (심전도 측정을 위한 밀착 의복 연구 -패턴 축소 및 주관적 평가를 중심으로-)

  • Jeong, Yeonhee;Yang, YoungMo
    • Journal of the Korean Society of Clothing and Textiles
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    • v.36 no.11
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    • pp.1174-1185
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    • 2012
  • This study develops tight-fitting upper clothing to measure electrocardiography (ECG) data. Taking into consideration the elasticity of the clothing, we made 4 experimental clothes by applying to each a weft reduction rate of 40%, 50%, 60%, and 70%. The 4 experimental clothes were used to measure resting ECG, exercise ECG, and post-exercise ECG for 4 men in their 20s. We compared clothing pressures using sensors on the human body and on a dressform. Subjective wear sensations of the 4 experimental clothes were evaluated using a subjective 7-point scale (with 7 being most excellent). We measured clothing pressures by using the air type pressure (AMI 3037-2) for upper and lower chest sensors in the developed tight-fitting upper clothing. The lower chest sensor showed that the clothing pressure on a human body and dressform changed consistently as the weft reduction rate decreased. The upper chest sensor showed inconsistent changes in clothing pressure as the weft reduction rate decreased. The wearing-test result for preliminary subjects showed that the lower chest sensor was more stable than the upper chest sensor; therefore, we inserted the sensor at the lower chest position before performing ECG. Except for Subject 4, the resting ECGs were stably measured for 3 subjects (Subject 1, Subject 2, and Subject 3) in all the developed clothes (A clothing, B clothing, C clothing, and D clothing). However, D clothing showed stable ECG values after exercise. The results of the experiment showed that we could measure ECG without difficulty using clothes with a weft reduction rate of 40% when the movement was not intense; however, tight-fitting upper clothing with a weft reduction rate of 70% was necessary to measure exercise ECG and post-exercise ECG values.

Effect of High Pressure on Polarographic Parameters of Metal Complex Ion (金屬錯이온의 폴라로그래피的 파라미터에 미치는 壓力의 影響)

  • Heung Lark Lee;Zun Ung Bae;Jong Hoon Yun
    • Journal of the Korean Chemical Society
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    • v.31 no.5
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    • pp.444-451
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    • 1987
  • The dependence of polarographic parameters on the pressure for the reduction of copper(II), cadmium(II), and zinc(II) complex ions with ethylenediamine, propylenediamine, and diethylenetriamine has been studied. In this study the dropping mercury electrode, the mercury pool electrode, and helix type of platinum wire were used as the working, the reference, and the auxilary electrode, respectively. With increasing the pressure from 1 atmosphere to 1,500 atmospheres, the reduction half-wave potentials of metal complex ions are shifted to the negative values and the diffusion currents become considerably larger, in keeping with the theory on the change of the physical properties of the electrolytic solution such as the density, the viscosity, the dielectric constant, and the electrical conductance, etc. The slope values of the logarithmic plot are increased with increasing the pressure, which indicates the more irreversible reduction. The temperature coefficients of diffusion current observed over the range of the temperature from 25$^{\circ}$C to 35$^{\circ}$C are about two percentage with increasing the pressure, therefore the polarographic reduction under the high pressure is controlled by diffusion. The linear relationships between diffusion current and concentration of metal complex ions are established over all pressure range.

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Heat Transfer Characteristics of an Annulus Channel Cooled with R-134a Fluid near the Critical Pressure (임계압력 근처에서의 환형관 채널에 대한 열전달 특성 연구)

  • Hong, Sung-Deok;Chun, Se-Young;Kim, Se-Yun;Baek, Won-Pil
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.2094-2099
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    • 2004
  • An experimental study on heat transfer characteristics near the critical pressure has been performed with an internally-heated vertical annular channel cooled by R-134a fluid. Two series of tests have been completed: (a) steady-state critical heat flux (CHF) and (b) heat transfer tests for pressure reduction transients through the critical pressure. In the present experimental range, the steady-state CHF decreases with the increase of the system pressure For a fixed inlet mass flux and subcooling, the CHF falls sharply at about 3.8 MPa and shows a trend toward converging to zero as the pressure approaches the critical point of 4.059 MPa. The CHF phenomenon near the critical pressure does not lead to an abrupt temperature rise of the heated wall because the CHF occurred at remarkably low power levels. In the pressure reduction transient experiments, as soon as the pressure passed through the critical pressure, the wall temperatures rise rapidly up to a very high value due to the occurrence of the departure from nucleate boiling. The wall temperature reaches a maximum at the saturation point of the outlet temperature, then tends to decrease gradually.

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The Effect of Meridian Massage on the Reduction of Pain and Subjective Symptoms of Myofascial Pain Syndrome (경락마사지가 근막동통 증후군의 동통과 자각증상 감소에 미치는 효과)

  • Sung, Kyung-Suk;Jung, Hyang-Mi
    • The Korean Journal of Rehabilitation Nursing
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    • v.6 no.2
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    • pp.248-256
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    • 2003
  • Purpose: This research was for checking the effect of meridian massage on the reduction of pain and subjective symptoms of myofascial pain syndrome. Method: The method of the research was interruptive time series design. The research objects are 25 hospital workers with myofascial pain syndrome at B hospital in Busan from July 22, 2002 to August 18, 2002. SPSS Win 10.0 was used for data analysis, paired t-test and repeated measures ANOVA for hypothesis test. Result: The recipients of meridian massage felt less pain than before(F=12.587, p=.000). The recipients of meridian massage felt less often than before (F=6.705, p=.001). The recipients of meridian massage got lower score on subjective symptoms of myofascial pain than before(F=12.857, p=.000). The recipients of meridian massage had lower blood pressure than before(systolic blood pressure; t=4.697, p=.000, diastolic blood pressure; t=3.426, p=.002). The recipients of meridian massage did not get the lower number of pulse than before(t=0.33, p=.744). Conclusion: The above results show that meridian massage is effective on the reduction of pain and subjective symptoms of myofascial pain syndrome and makes stable the blood pressure. Therefore meridian massage can be apply as the effective intervention for the reduction of pain and subjective symptoms of myofascial pain syndrome.

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The bonding mechanism and bond strength of cold pressure welding (엡셋팅에 의한 냉간 압접의 결합 기구와 결합강도)

  • 한인철;김재도
    • Journal of Welding and Joining
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    • v.8 no.3
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    • pp.31-38
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    • 1990
  • The bonding mechanism and bond strength were investigated for the cold pressure welding of Al to Al, Cu to Cu and Al to Cu by upsetting. A phenomenon of bonding betweenthe metallic components has been observed by a scanning electron microscope and metallurgical microscope. A modified equation for bond strength with respect to the reduction of height shows reasonably a good agreement with the experimental data. When the values of the hardening factor and threshold deformation for the given materials could be determined, the theoretical bond strength can be calculated.

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Study on the cold pressure welding by upsetting (업셋팅 을 이용한 냉간압접 에 대한 연구)

  • 안기원;김재도
    • Journal of Welding and Joining
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    • v.3 no.2
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    • pp.27-34
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    • 1985
  • The mechanical properties and bonding mechanism of aluminum, copper and mild steel have been determined in cold pressure welding. The brittle cover layer to be established by scratch-brushing plays an important role in bond strength and has an influence on the threshold of deformation. The cold pressure welding was achieved at 54% of height reduction in A1-A1, 75% in Cu-Cu, 56% in Al-Cu, and 74% in Cu-steel. The height reduction at which the bond strength of weld interface was the same as the tensile strength of base metal should be over 76% in Al-Al, 82% in Cu-Cu, and 78% in Al-Cu.

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A Study on the Correlation Evaluation of Confining Pressure and Pile-Soil Interface Strength Reduction Factor Using Numerical Analysis (수치해석에 의한 지중 구속압과 말뚝-지반 경계면 강도감소계수 관계 분석)

  • Tae-Gyeom Lee;Jung-Geun Han;Gigwon Hong;Seung-Kyong You
    • Journal of the Korean Geosynthetics Society
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    • v.23 no.1
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    • pp.9-16
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    • 2024
  • In order to evaluate the relationship between the ground confining pressure and the shear characteristics of the pile-soil interface, this study described the comparative results of the existing experimental results and the FEA results using the strength reduction factor. The strength reduction factor was applied to simulate the shear behavior of the pile-soil interface in finite element analysis(FEA). The analysis results showed that the maximum pullout resistance decreased due to the influence of low confining pressure, as the fines content increased. This trend was similar to the previous experimental research, and this FEA model simulated with the interface strength reduction factor was evaluated as reasonable. The analysis results of the variation in the interface strength reduction factor clearly showed that the interface strength reduction factor clearly increased at a high fines content when the confining pressure was 50kPa. However, it was found that the increase rate was low when the confining pressure was 100kPa and 150kPa. Therefore, confining pressure and fines content need to be considered in FEA to evaluate the shear behavior of the pile-soil interface.

Effects of an Anti-wind Net on Wind Velocity Reduction by a Wind Tunnel Test and CFD (풍동시험과 CFD를 통한 방풍망의 풍속저감 효과)

  • Yum, Sung-Hyun;Kang, Seung-Hee;Kim, Seoung-Hee;Lee, Sang-Bong;Kim, Min-Young
    • Journal of Biosystems Engineering
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    • v.36 no.5
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    • pp.355-360
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    • 2011
  • This study was carried out to analyze the installation effect of an anti-wind net on reducing wind velocity which was used to protect orchards as well as single-span plastichouses. The pressure drop through three types of anti-wind net was measured in a subsonic wind tunnel. The wind reduction through the anti-wind facility for several sets in respect to three types of the net and heights of the facility ranging from 3 to 11 m was analyzed by using computational fluid dynamics (CFD). The measured data showed that the pressure drop increased as an equation of the second degree of the inlet wind velocity. Numerical computations exhibited that the effect of wind reduction definitely augmented as the net size became smaller and increased with the height of the facility being heightened to some extent. For the typical and widely used anti-wind facility with a height of 5 m and a net size of 4mm, the amount of wind reduction came up to 5.1 m/s for the inlet wind velocity of 20 m/s, and also 7.6 and 10.1 m/s for the inlet wind velocities of 30 and 40 m/s, respectively. In case for the orchard's longitudinal length to be within about 200 m, the appropriately effective height of the facility was predicted to be 5 m. Finally, the negative total pressure on the top face of the single-span plastichouse certainly reduced for all the cases with the anti-wind facility being installed. In particular, the reduction of the negative total pressure was more considerable as the inlet wind velocity increased.

Numerical Study on the Characteristics of Pressure Pulsations according to Design Factors of Fuel Rail with Self Damping Effect (자체 맥동 감쇠 효과를 갖는 연료레일의 설계 변수별 압력맥동 특성에 관한 수치적 연구)

  • Heo, Hyung-Seok;Bae, Suk-Jung;Song, Kyung-Suk;Kim, Bo-Kyoum
    • Transactions of the Korean Society of Automotive Engineers
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    • v.15 no.1
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    • pp.186-192
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    • 2007
  • In general, pulsation damper is installed in fuel rail for conventional MPI engine to decrease undesirable noise in vehicle cabin room. However, pulsation damper is so expensive that there are prevailing studies to reduce fuel pressure pulsations with integrated damping effect. This paper is one of basic studies for development of fuel rail to abate pulsations with self-damping effect. Primarily, the pressure pulsation characteristics was investigated with aspect ratio of cross section, wall thickness, and materials of fuel rail. A high aspect ratio or thin wall was found to absorb the pressure pulsations effectively. But volume effects on the fuel pressure pulsation reductions were not especially significant than cross section effects because volume increment rate is larger than pressure pulsation reduction rate. The fuel rail made of aluminum is effective for reduction of pressure pulsation than that of low-carbon steel. Pressure change period increases on the basis of same lengths of supply line and fuel rail as the volume is enlarged and/or the thickness of wall is thinned.