• Title/Summary/Keyword: percent frequency effect

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Size-dependent forced vibration response of embedded micro cylindrical shells reinforced with agglomerated CNTs using strain gradient theory

  • Tohidi, H.;Hosseini-Hashemi, S.H.;Maghsoudpour, A.
    • Smart Structures and Systems
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    • v.22 no.5
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    • pp.527-546
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    • 2018
  • This article presents an analysis into the nonlinear forced vibration of a micro cylindrical shell reinforced by carbon nanotubes (CNTs) with considering agglomeration effects. The structure is subjected to magnetic field and transverse harmonic mechanical load. Mindlin theory is employed to model the structure and the strain gradient theory (SGT) is also used to capture the size effect. Mori-Tanaka approach is used to estimate the equivalent material properties of the nanocomposite cylindrical shell and consider the CNTs agglomeration effect. The motion equations are derived using Hamilton's principle and the differential quadrature method (DQM) is employed to solve them for obtaining nonlinear frequency response of the cylindrical shells. The effect of different parameters including magnetic field, CNTs volume percent and agglomeration effect, boundary conditions, size effect and length to thickness ratio on the nonlinear forced vibrational characteristic of the of the system is studied. Numerical results indicate that by enhancing the CNTs volume percent, the amplitude of system decreases while considering the CNTs agglomeration effect has an inverse effect.

Heart Response Effect by 1/f Fluctuation Sounds for Emotional Labor on Employee (1/f 수준 별 음악 자극이 감정 노동 종사자의 심장 반응에 미치는 효과)

  • Jeon, Byung-Mu;Whang, Min-Cheol
    • Science of Emotion and Sensibility
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    • v.18 no.3
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    • pp.63-70
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    • 2015
  • This study identified heart response of participants while listening to sounds which have 1/f fluctuations with exponent ${\alpha}$ gradient. The participants were engaged in emotional stress work. Prior studies related to 1/f fluctuation sound have reported that sound source can alleviate psychological and physiological state of users. Subjects of this study were exposed to sound with three levels of ${\alpha}$ gradient. Heart response of subjects were measured with Photoplethysmography(PPG) sensor simultaneously. The dependent variables of this study were beat per minute(BPM), very low frequency percent of pulse rate variability (VLF percent), the standard deviation of all normal RR intervals (SDNN), and high frequency power(HF power). Subject showed arousal response when exposed to sound with exponent ${\alpha}$ gradient of 3 whereas the sound with exponent ${\alpha}$ gradient of 1 and 2 resulted in relax effect. The characteristic of 1/f fluctuation sounds can be applied to alleviate stress for employers under emotional labor.

A Study on the Induced Abortion Behavior of Currently Married Women in Korea (우리나라 유배우부인의 인공임신중절에 관한 연구)

  • 오영희
    • Korea journal of population studies
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    • v.9 no.2
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    • pp.42-52
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    • 1986
  • An attempt had been made to obtain current information on induced abortion among currently married women aged 15 to 44. The source of data was 1985 National Fertility and Family Planning Survey conducted by Korea Institute for Population and Health in may 1985. 1. At the time of the survey, 53 percent of currently married women aged 15 to 44 had experienced induced abortion: 25.5 percent of the respondents who had experienced induced abortion only one time and another 27.6 percent more than two times. 2. The proportion of women who had experienced induced abortion seemed to increase according to the advance in age. It seemed that there was no significant difference in the experience rate of induced abortion by academic career, and there was inverse relationship between the experience rate of induced abortion and the age at first marriage. The experience rate if induced abortion by the number of living children was highest among those who had three children as 65.6 percent. 3. To analyze the effect of induced abortion on fertility, this study employed multiple regression analysis as a statistical technique. Instead of index representing fertility level the number of living children served as dependent variable. Independent variables used in analysis included age, age at first marriage, education level, ideal number of children, religion, frequency of induced abortion, total number of pregnancies and participation in labor force. Standardized partial regression coefficient of induced abortion was no less than -0.61. So, it can be concluded that induced abortion offered the great contribution on the birth control. A consistant health education and efficient management of family planning program would be essential for effectiveness of contraceptive practice.

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The Effect of Neglecting Own Weight on The Natural Frequency of Vibration of Laminated Composite Plates with Attached Mass/Masses (첨가질량이 작용하는 적층복합판의 고유진동수에 대한 자중 무시효과)

  • Kim, Duk-Hyun;Sim, Do-Sik;Lee, Jung-Ho
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 1996.04a
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    • pp.127-134
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    • 1996
  • In this paper, the effect of neglecting the own weight of the composite plate on the natural frequency of vibration of the laminated plates is presented. The method used has been developed by the author since 1974. This method is very effective for the plates with arbitrary boundary conditions and irregular sections. When the attached mass is equal to the weight of the plate, the effect of neglecting the plate weight is 9.26 percent

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Climatological Spatio-Temporal Variation of Strong Wind in Korea (우리나라 강풍의 기후학적 시공간 변화 특성)

  • Kim, Hyun Uk;Kim, Baek-Jo;Nam, Hyoung-Gu;Jung, Jong Hyeok;Shim, Jae-Kwan
    • Atmosphere
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    • v.30 no.1
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    • pp.47-57
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    • 2020
  • In this study, the climatological spatio-temporal variation of strong wind and gust wind in Korea during the period from 1993 to 2018 was analyzed using daily maximum wind speed and daily maximum instantaneous wind speed data recorded at 61 observations. Strong wind and gust wind were defined as 14 m s-1 and 20 m s-1, which are the same as the KMA's criteria of special weather report. The frequency of strong wind and gust wind occurrence was divided into regions with the higher 25 percent (Group A) and the lower 75 percent (Group B). The annual frequency of strong wind and gust wind occurrence tended to be decreased in most parts of the Korean peninsula. In Group A with stations located at coastal region, strong wind and gust wind occurred most frequently in winter with higher frequency at 1200~1600 LST and 2300~2400 LST due to influence of East Asian winter monsoon. In addition, a marked decreasing trend throughout the four seasons was shown at Daegwallyeong, Gunsan and Wando observations. In contrast, it can be found in Group B that the monthly frequency of strong wind and wind gust occurrence was higher in August and September by effect of typhoon and hourly frequency was higher from 1200 LST to 1800 LST.

The effect of voltage and nanoparticles on the vibration of sandwich nanocomposite smart plates

  • Farokhian, Ahmad
    • Steel and Composite Structures
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    • v.34 no.5
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    • pp.733-742
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    • 2020
  • Vibration analysis in nanocomposite plate with smart layer is studied in this article. The plate is reinforced by carbon nanotubes where the Mori-Tanaka law is utilized for obtaining the effective characteristic of structure assuming agglomeration effects. The nanocomposite plate is located in elastic medium which is simulated by spring element. The motion equations are derived based on first order shear deformation theory and Hamilton's principle. Utilizing Navier method, the frequency of the structure is calculated and the effects of applied voltage, volume percent and agglomeration of Carbon nanotubes, elastic medium and geometrical parameters of structure are shown on the frequency of system. Results indicate that with applying negative voltage, the frequency of structure is increased. In addition, the agglomeration of carbon nanotubes reduces the frequency of the nanocomposite plate.

Application of Strain Energy for Determining the Location of Damping Material (스트레인 에너지를 이용한 제진재 위치 결정)

  • Kim, Joong-Bae;Ryu, Kuk-Hyun;Park, Sang-Kyu;Lee, Sang-Jo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.18 no.11
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    • pp.1199-1205
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    • 2008
  • The vehicle design engineers have studied the method of applying damping materials to the vehicle bodies by computer simulations and experimental methods in order to improve the vibration and noise characteristics of the vehicles. The unconstrained layer damping, being concerned with this study, has two layers(base layer and damping layer) and proyides vibration control of the base layer through extensional damping. Generally this kind of surface damping method is effectively used in reducing structural vibration at frequencies beyond 150Hz. The most important thing is how to apply damping treatment with respect to location and size of the damping material. To solve these problems, the current experimental methods have technical limits which are cumbersome, time consuming, and expensive. This Paper proposes a method based on finite element method and it employes averaged ESE(element strain energy) percent of total of dash panel assembly for 1/1 octave band frequency range by MSC/NASTRAN. The regions of high ESE percent of total are selected as proposed location of damping treatment. The effect of damping treatment is analyzed by comparing the frequency response function of the SPCC bare Panel and the damping treated panels.

Forced vibration response in nanocomposite cylindrical shells - Based on strain gradient beam theory

  • Shokravi, Maryam
    • Steel and Composite Structures
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    • v.28 no.3
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    • pp.381-388
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    • 2018
  • In this paper, forced vibration of micro cylindrical shell reinforced by functionally graded carbon nanotubes (FG-CNTs) is presented. The structure is subjected to transverse harmonic load and modeled by beam model. The size effects are considered based on strain gradient theory containing three small scale parameters. The mixture rule is used for obtaining the effective material properties of the structure. Based on sinusoidal shear deformation theory of beam, energy method and Hamilton's principle, the motion equations are derived. Applying differential quadrature method (DQM) and Newmark method, the frequency curves of the structure are plotted. The effect of different parameters including, CNTs volume percent and distribution type, boundary conditions, size effect and length to thickness ratio on the frequency curves of the structure is studied. Numerical results indicate that the dynamic deflection of the FGX-CNT-reinforced cylindrical is lower with respect to other type of CNT distribution.

A Study on Balanced -type Oseillating Mole-Drainer(III)-Model Test for Draft Force, Torque, Power and Moment (평행식 진동탄환 암거 천공기의 연구(III)-견인력, 토크, 동력 및 모멘크에 관한 모형시험-)

  • 김용환
    • Journal of Biosystems Engineering
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    • v.1 no.1
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    • pp.1-6
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    • 1976
  • This paper is the third one of the study on balanced type oscillating mole-drainer, the first one was presented in No 9. Gyeongsang College Report and the second one in Vol. 17, No.4 of the KSAE. In the first part of this study, the characteristics of traction forces between the nonoscillating earth working equipments and oscillating ones was compared. A model of the balanced type oscillating mole-drainer, which composed of a mechanism that may reduce the machine vibration, was designed following the dimensional analysis and similitude technique. The model test was carried out to clarify the balancing mechanism of the oscillating parts and other parts of the machine. In the light of the results from the model tests, a prototype machine was made for experimental purpose. Results from the field test by a reported in the near future. In the second report, the model tests were carried out under the same soil conditions, i.e, . oscillating frequency, running velocity, and oscillating amplitude, etc. It was clear that use of balanced type oscillating model could substantially reduce the vibration of the whole system of the machine, when compared with the nonoscillating type model. In this paper(the third report), results of investigation on the traction force, power requirement, and moment. etc, is presented. Analysis of variance technique was used for analyzing the effect of the frequency, amplitude, and running velocity on the draft force, torque, power requirements, and moments. The results obtained from the model tests are as follows, 1) By practicing a balanced-type oscillating mole-drainer, it was possible to reduce the traction resistance by 55.1-61. 2 percent of traction resistance, however, was 1.75 - 1.95 times greater than the value of resistance which was induced by use of a mole-drainer with single bullet. The resistance of rear shank against soil was considered as a main causing factor of the above results. 2) As the oscillation frequency was increased, the traction resistance was decreased. Considering on the effect of oscillation the greater the amplitude, and the slower the running velocity was, the greater the reduction ratio of traction resistance was. 3) The ratio of the traction resistance of oscillating mole-drainer to that of non-oscillating one could be represented as a function of dimensionless variable (V/$Af$). The results from the tests were well agreed with the reported results from the experim ents on oscillation plow or hoe. 4) By taking a lower value of (V/$Af$), reducing the traction resistance was possible. This fact meant, however, that the efficiency of mole drain practice would be lower. 5) It was experimentally confirmed under the same condition of soil that the variable (R/$rD1^3$) could be represented as a function of a variable($V^2/gD$) when a non\ulcornerocillating mole-drainer was used. 6) When a oscillating mole-drainer was used, the variable(R/$rD_1^{3}$) could be represented as a function of two variables ($v^2/gD_1$) and (V^2/gD_1$). 7) The torque was not affected by a change of frequency. However, a relation of proportionality existed between torque and amplitude, running velocity, and ratio of bullet diameter. When a balanced type oscillating mole-drainer with two bullets was used, torque was increased by 52.8-78. 4 percent and total power requirement was also increased. 8) Total power requirement was increased linearly in accordance with the increasing frequency, 41.96 percent of total power was used for oscillating action. The magnitude of total power requirement was 1. 8-9. 4 times greater than that of a non-oscillating mechanism. In the view point of power requirement, it was not advisable to increase the frequency, amplitude, running velocity, and ratio of bullet diameter at the same time. 9) Only the positive moment occured in the rear shank. Change of the diameter of a rear bullet, could not affect the balancing against the soil resistance. It was necessary for rear bullet to have a large resistance against soil only when the rear bullet was in backward motion. 10) Within an extent of the experimental base, optimum limits for several design factors were A=0.5cm, $f$=22.5Hz, V=O. 05m/sec, and $\lambda$=1.0 By adapting these values traction resistance was reduced by 40 percent and vibration acceleration wa s reduced by 60 percent. Even though the total , power requirements for operating a balanced type oscillation mechanism was greater ~than that of non-oscillating one, using a oscillating mechanism would be more effective. Because a balanced type oscillating mechanism is used, tractive resistance will be reduced and then the lighter . tractive equipment could be used.

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An Experimental Study on Heat Transfer in the Pulsating Pipe Flow (원관내 맥동유동의 열전달에 관한 실험적 연구)

  • Kim, Hi Yong;Kim, Chang Kee
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.3 no.1
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    • pp.78-85
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    • 1991
  • An experimental result for heat transfer of pulsating turbulent pipe flow was presented under the condition of fully developed dynamic regime and uniform wall heat flux. Experiments were performed at following conditions ; Inlet time-averaged Reynolds number varied from 5000 to 11000; The peak pressure fluctuation were 1.3, 2.3 and 3.5 percent of the mean pressure; Pulsating frequency ranged from 53 Hz to 320 Hz The measurements showed that the effect of pulsation on local heat transfer is greater at downstream, in which pulsating source exists, than upstream and the heat transfer rate, averaged over the pipe length, was higher or lower than in an equivalent non-pulsating flow according to the pulsating conditions. In addition, the significant change of heat transfer rate was observed in acoustically resonant conditions, when the pulsating frequency of the flow corresponded to the pipe natural frequency.

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