Rigid Cylinder Model Research Articles

Effect of Submerged Artificial Vegetation on Flow and Trapping Sediment

This study is about the effect of flow and trapping sediment using submerged artificial vegetation. The purpose of this study is to analyse the velocity of vegetation layer and upper layer, global flow resistance and determine the relationship between Total Suspended Solid (TSS) with flow velocity and vegetation density. Rigid cylinder model with diameter of 8 mm was used to simulate the artificial vegetation. The flow velocity on vegetation layer is found to be lowered compare to upper layer which result S-curve of vertical velocity profile. Besides, comparison of estimated and measured data of flow velocity and global flow resistance with previous researcher in term of Root Mean Square Error (RMSE) also provided in this study. It is shown that at the lowest flow velocity, more sediment was trapped at the channel bed, where the TSS were increased from slow, moderate to fast velocity. The increment percentage of TSS value from slow to fast velocity were within 13.04% to 36.11% for vegetation density (m) of 1056 m−2. Next, for m of 1533 m−2, the increment percentage of TSS value from slow to fast velocity were within 5.55% to 5.26%. while m for 2756 m−2, the increment percentage of TSS value from slow to fast velocity were 6.67% and 6.25%. Slower flow velocity and higher vegetation density give the best performance in trapping sediment. It proves that the flow velocity and vegetation density play the key role for trapping sediment.

Pressure Pulse Distortion by Needle and Fiber-Optic Hydrophones due to Nonuniform Sensitivity.

Needle and fiber-optic hydrophones have frequency-dependent sensitivity, which can result in substantial distortion of nonlinear or broadband pressure pulses. A rigid cylinder model for needle and fiber-optic hydrophones was used to predict this distortion. The model was compared with measurements of complex sensitivity for a fiber-optic hydrophone and three needle hydrophones with sensitive element sizes ( ) of 100, 200, 400, and . Theoretical and experimental sensitivities agreed to within 12 ± 3% [root-mean-square (RMS) normalized magnitude ratio] and 8° ± 3° (RMS phase difference) for the four hydrophones over the range from 1 to 10 MHz. The model predicts that distortions in peak positive pressure can exceed 20% when and spectral index (SI) >7% and can exceed 40% when and SI >14%, where is the wavelength of the fundamental component and SI is the fraction of power spectral density contained in harmonics. The model predicts that distortions in peak negative pressure can exceed 15% when . Measurements of pulse distortion using a 2.25 MHz source and needle hydrophones with , 400, and agreed with the model to within a few percent on the average for SI values up to 14%. This paper 1) identifies conditions for which needle and fiber-optic hydrophones produce substantial distortions in acoustic pressure pulse measurements and 2) offers a practical deconvolution method to suppress these distortions.

Conformational change from rigid rod to star: a triple-helical peptide with a linker domain at the C-terminal end.

Small-angle X-ray scattering and circular dichroism measurements were made for a triple-helical peptide of which one end was linked by the thermally stable trimerization domain of type XIX collagen. The radius of gyration decreased steeply around the transition temperature while the scattering intensity at zero angle did not significantly change, indicating no molar mass change through the conformational transition. Thus, the data were analyzed in terms of the rigid cylinder model for the data at low temperatures and the wormlike star model at high temperatures. It was confirmed that the peptide molecules behave as a rod-like cylinder at low temperature and a semi flexible three-arm star-like chain at high temperature of which the single-coil peptide chain is appreciably extended by the high segment density nearby the linking domain.

Flexibility and Cross-Sectional Structure of an Anionic Dual-Surfactant Wormlike Micelle Explored with Small-Angle X-ray Scattering Coupled with Contrast Variation Technique

The contrast variation technique by adding sucrose to aqueous solvents as an electron density adjusting reagent was applied to small-angle X-ray scattering (SAXS) from a dual surfactant wormlike micelle consisting of sodium lauryl ether sulfate and coconut fatty acid amido propyl betaine in order to evaluate the flexibility and the cross-sectional structure of the micelle. The salt concentration dependence of the zero-shear and dynamic viscosities were found not to be affected by the cation species nor the presence of sucrose in the solution. SAXS showed that the scattering profile [I(q)] can be fitted a double layer cylinder model. By systematically changing the sucrose concentration (CS), a "matching composition" was found in which the shell layer can become invisible in SAXS for each sodium cation concentration ([Na+]). From this composition, the electron densities of the shell (rhoS) and core (rhoC) layers were evaluated to be 370 and 216 e/nm(-3), respectively. These values were consistent with the chemical structure of the surfactant. At these matching compositions, I(q) was measured at low q range (0.03 nm(-1)<q<4 nm(-1)) and the data points were perfectly fitted with a single layer rigid cylinder model, except for [Na+]>1.02 M. In these larger [Na+], the I(q) showed an up-turn deviation from the rigid rod limit (i.e., I(q) proportional, variant q(-1)) at low q, indicating appearance of the flexibility of the cylinder. By applying a wormlike cylinder theory, the Kuhn statistical segment length was evaluated as a function of [Na+]. At the infinite limit of [Na+], the intrinsic Kuhn length (excluding of the electrostatic interactions) can be evaluated to be about 20-40 nm. This value was comparable with that of the wormlike micelles made of nonionic surfactants.

Solvent/Gelator Interactions and Supramolecular Structure of Gel Fibers in Cyclic Bis-Urea/Primary Alcohol Organogels

An organogel system consisting of trans-(1S,2S)-bis(ureidododecyl)cyclohexane (SS-BUC) and a series of primary alcohols was explored with optical polarizing microscopy (OPM), electron microscopy, circular dichroism (CD), wide-angle X-ray scattering (WAXS), and synchrotron small-angle X-ray scattering (SAXS). OPM, SAXS, and especially WAXS showed that the gel fiber of SS-BUC/methanol gels essentially consists of SS-BUC crystal itself. SAXS showed that the SS-BUC crystal in the gel takes a lamella with a domain spacing of 5.2 nm. When we left the gel at room temperature, the spacing decreased to 3.1 nm after several months. This distance change may correspond to the structural transition from a double-layer structure to an intercalated-layer structure, which was proposed by Feringa et al. (Chem.-Eur. J. 1999, 5, 937-950) as a possible arrangement of the molecular packing. When the gels in ethanol, propanol, butanol, or octanol were examined, they never showed crystalline peaks in WAXS and SAXS, indicating the amorphous nature of the gels. With increasing the alkyl chain length from ethanol to octanol, dramatic changes were observed in the CD spectrum in the 200-500-nm range. Because these CD changes are correlated to the absorbance of urea, those can be considered as the evidence that the solvents strongly relate to the spatial arrangement between the adjacent urea groups. For the amorphous gels, the cross-sectional correlation function [gammaCu] was directly obtained by the inverse Hankel transform of the SAXS data. The value of gammaCu for the gels is decreased with increasing u (distance between the two scattering bodies, see eq 5). Furthermore, it more rapidly decreases than that of the rigid cylinder model. This feature can be explained by the speculation that many solvent molecules permeate into the SS-BUC fiber. There was a clear difference between ethanol and the other gels, indicating that the solvents with a longer alkyl chain give the more permeated and diffused fiber. This permeated fiber (i.e., wet fiber) can rationalize the dramatic CD change, by presuming that the permeated solvent molecules alter the molecular stacking form.

HEISENBERG SPINS ON A CYLINDER SECTION

Classical Heisenberg spins in the continuum limit (i.e. the nonlinear σ-model) are studied on an elastic cylinder section with homogeneous boundary conditions. The latter may serve as a physical realization of magnetically coated microtubules and cylindrical membranes. The corresponding rigid cylinder model exhibits topological soliton configurations with geometrical frustration due to the finite length of the cylinder section. Assuming small and smooth deformations allows to find shapes of the elastic support by relaxing the rigidity constraint: an inhomogeneous Lamé equation arises. Finally, this leads to a novel geometric effect: a global shrinking of the cylinder section with swellings.

Plastic Buckling of Unanchored Roofed Tanks under Dynamic Loads

Cylindrical tanks that are not anchored effectively to their foundations often rock during seismic loading. Vertical compressive forces in the tank wall that are required to resist seismic overturning moments then tend to be concentrated over a small portion of the circumference of the tank, where the tank wall remains in contact with the foundation. This together with the effect of internal pressures often leads to plastic buckling of the tank wall at the base or the so-called elephant foot bulge. This paper aims at predicting not only whether elephant foot bulging will occur, but also the extent of elephant foot bulging. This is done by means of a nonlinear dynamic time history analysis on a simplified rigid cylinder model, in which equivalent springs are used to represent elastic tank deformations, as well as nonlinear effects including geometric and plastic shortening of the tank wall caused by elephant foot bulging, and the resistance to uplift provided by the hold-down action of the floor plate. A physically based approach is provided to calculate the properties and location of the equivalent springs using finite-element analyses of the tank that can be performed with minimal computational effort. This leads to a simplified model for which key aspects of the behavior (dynamic as well as static) match that of the real tank. The approach is applied to a tank that was damaged during the 1977 San Juan earthquake. Although field measurements of the amount of elephant foot bulging are not available, photographs taken after the earthquake show an amount of bulging that is consistent with the predictions.

132 柔軟な弾性表面を持つ円筒周りの流れ場の可視化

The purpose of this study is to clarify the mechanism of decreasing the drag in natural swimming of fish, whale and dolphin. A cylinder which has Elasto-flexible surface simplified marine creature was placed in a water tunnel, and using Laser Light Sheet method to visualize flow field around the model, vortex pair shedding period from the model, deformation of its cross-sectional form and hydrodynamical drag of the model were simultaneously measured. As a result, the following were found: the rigid front flexible rear cylinder model has showed about 20% higher St number than rigid cylinder model. The local deformation of the surface changed local flow pattern and wake due to some interaction between flexible surface and vortex. Time variation of the drag of the Rigid Front Flexible Rear Cylinder (RFFRC) became smaller than rigid one.