Determination of Specimen Geomery for Estimation of the Complex Modulus of Viscoelas the Materials by the Lumped Mass Model

In order to use viscoelastic materials efficiently for noise and vibration control, or th qualify newly developed materials, knowledge of the Young s modulus and loss factor is essemtial. These material properties, the so-called complex Young s modulus, are frequently treated as dynamic charicteristics because of their dependence upon the frequency. Many techniques have been developed and verified for measuring complex Young s modulus of viscoelastic materials. Among them, the impedance method is preferable in order to obtain the frequency information in detail. In this method, a cylindrical or prismatic specimen is excited into longitudinal harmonic vibration at one end, the other being fixed, and the resulting force is measured at the driving or fixed end. The amplitude ratio of the two signals and phase angle between them are then used to compute the material properties using various mathematical models. In this paper, the impedance method is investigated theoretically and experimentally. A way to determine the specimen geometry which is most appropriate for the identification of complex Young s modulus using the lumped mass model is presented and discussed. Then experimental results supporting the theoretical predictions are presented

Vibration analysis of beam and plate structures with viscoelastic boundary supports

학위논문(박사) - 한국과학기술원 : 기계공학과, 1996.8, [ x, 152 p. ]한국과학기술원 : 기계공학과

Flora of Mt. Choryong, Mt.Baekhwa and Mt.Gunja in Kwesangun, Chungchongbukdo

This study was carried out to investigate flora and vegetation of Mts. Choryoung, Baekhwa and Gunja in Kwesangun, Chungcungbookdo form May to September 1992. The results obtained from this study were as follows: 1. Total numbcr of vascular plants distributed at the particular investigated area were 86 families, 255 genera and 428 kinds (including 356 species, 69 varieties and 3 formas) in Mt. Choryoung, 70 families, 218 genera and 319 kinds (including 276 species, 40 varieties and 3 formas) in Mt. Baekhwa and 81 families, 210 genera and 319 kinds (including 274 species, 43 varieties and 2 formas) in Mt. Gunja. 2. Leontopodium japonicum Miq., Lilium cernum Kom., Rhododendron micranthum Turcz., Monotropa h3popithys L. and Phacellanthus tubiflorus S. et Z. were identified as important species. It makes this study worthwhile that L. japonicum Miq. distributed to this area (Mt. Choryoung) was at southern border and L. cernum Kom. was found as a new element in this area(Mts. Gunja and Baekhwa). R. micranthum Turcz. must be protected because of it's limited rare distribution. And it is important that the distribution of M. hrpopithys L. and P. tubiflows S. et Z. was proved in this area

Influences of specimen geometry on the identification of the complex young's modulus of viscoelastic materials by impedance method

학위논문(석사) - 한국과학기술원 : 생산공학과, 1991.2, [ [v], 56 p. ]한국과학기술원 : 생산공학과

Effects of Duration and Time Distribution of Probability Rainfall on Paddy Fields Inundation

The objective of this study was to analyze the effect of the duration and time distribution of probability rainfall on farmland inundation for the paddyfields in the drainage improvement project site. In this study, eight drainage improvement project sites were selected for inundation modeling. Hourlyrainfall data were collected, and 20- and 30-year frequency probability rainfalls were estimated for 14 different durations. Probability rainfalls weredistributed using Intensity-Duration-Frequency (IDF) and Huff time distribution methods. Design floods were calculated for 48 hr and critical duration,and IDF time distribution and Huff time distribution were used for 48 hr duration and critical duration, respectively. Inundation modeling was carriedout for each study district using 48 hr and critical duration rainfalls. The result showed that six of the eight districts had a larger flood discharge usingthe method of applying critical duration and Huff distribution. The results of inundation depth analysis showed similar trends to those of design floodcalculations. However, the inundation durations showed different tendencies from the inundation depth. The IDF time distribution is a distribution inwhich most of the rainfall is concentrated at the beginning of rainfall, and the theoretical background is unclear. It is considered desirable to applycritical duration and Huff time distribution to agricultural production infrastructure design standards in consideration of uniformity with other designstandards such as flood calculation standard guidelines.N