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Rigid Structure (rigid + structure)
Selected AbstractsMODELING THE LONG TERM IMPACTS OF USING RIGID STRUCTURES IN STREAM CHANNEL RESTORATION1JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 6 2006Sue L. Niezgoda Abstract: Natural channel designs often incorporate rigid instream structures to protect channel banks, provide grade control, promote flow deflection, or otherwise improve channel stability. The long term impact of rigid structures on natural stream processes is relatively unknown. The objective of this study was to use long term alluvial channel modeling to evaluate the effect of rigid structures on channel processes and assess current and future stream channel stability. The study was conducted on Oliver Run, a small stream in Pennsylvania relocated due to highway construction. Field data were collected for one year along the 107 m reach to characterize the stream and provide model input, calibration, and verification data. FLUVIAL-12 was used to evaluate the long term impacts of rigid structures on natural channel adjustment, overall channel stability, and changing form and processes. Based on a consideration of model limitations and results, it was concluded that the presence of rigid structures reduced channel width-to-depth ratios, minimized bed elevation changes due to long term aggradation and degradation, limited lateral channel migration, and increased the mean bed material particle size throughout the reach. Results also showed how alluvial channel modeling can be used to improve the stream restoration design effort. [source] Injection of the insertion of the deep digital flexor tendon in horses using radiographic guidanceEQUINE VETERINARY EDUCATION, Issue 7 2008J. D. C. Anderson Summary Insertional tendinopathies of the DDFT have been reported both as the sole lesion and as part of a multifocal lesion (Dyson et al. 2003). Computed tomography (CT) and magnetic resonance imaging allow specific diagnosis of deep digital flexor tendon lesions within the hoof capsule; however, direct intralesional treatment of such lesions is difficult because of the hoof's rigid structure. A technique designed to mimic intralesional injection of insertional tendinopathies of the DDFT in the standing horse using radiographic guidance was assessed. Radiographic and contrast CT imaging and sectioning of the limbs confirmed accurate injection in all cases although inadvertant administration of injectate into adjacent structures was also evident. [source] Underwater shock-free surface,structure interactionINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 4 2003T. G. Liu Abstract A recently developed numerical method has been employed to evaluate the influence of free surface on shock loading in a cylindrical underwater explosion carried out near to both a free surface and a cylindrical rigid structure. In the usual simulation of underwater shock,structure interaction, the shock loading tends to accelerate/move the (rigid) structure only in the resultant force direction. The presence of a free surface and explosion bubble suggests the existence of a reverse loading and provides an additional torque (rotational moment) on the loaded structure. The numerical results also demonstrate the possible existence of a cavitation zone/region in the immediate vicinity of the free surface due to the near-surface underwater explosion. Copyright © 2003 John Wiley & Sons, Ltd. [source] Molecular structure, conformational analysis and charge distribution of pralidoxime: Ab initio and DFT studiesINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 3 2002Alexandre T. Castro Abstract A detailed structural study of pralidoxime (2-PAM), the main antidote against organophosphate intoxication, was performed using Hartree-Fock, Möller,Plesset (MP2), and density functional theory (Becke, Lee, Yang, and Paar [B3LYP]) methods. Rotational barriers, equilibrium geometries, and charge distributions were calculated, showing important differences between the two forms available in physiological conditions, namely with the oxime group protonated or unprotonated. For the protonated form, conjugation between the side chain and the pyridinium ring, although present, has little importance, resulting in a flexible structure. On the other hand, the unprotonated form has a more rigid structure and a smaller charge density on the oxime oxygen. Contrary to the common belief, those results strongly suggest that it may be the protonated form of 2-PAM, instead of the unprotonated form, that is responsible for the antidote activity of this compound. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002 [source] A Two Degree of Freedom Gripper Actuated by SMA with Flexure HingesJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 11 2003A. Manuello Bertetto A gripper prototype was designed and built. It is made by a rigid structure articulated by compliant hinges. Its kinematics consists of both parallel and angular finger motion. The movements were designed to be independent from each other and auto-adaptive as well. The motions were driven by Ni-Ti shape memory alloy (SMA) wires. The recovery position is achieved by the elastic force exerted by the flexure hinges in the case of parallel motion and by an axial spring in the case of angular motion. Both the actuators and the hinges were experimentally characterized by suitable test rigs. The gripper prototype was tested and it showed to be able to reach the design performances. © 2003 Wiley Periodicals, Inc. [source] Biomechanics of the rostrum and the role of facial suturesJOURNAL OF MORPHOLOGY, Issue 1 2003Katherine L. Rafferty Abstract The rostrum is a large diameter, thin-walled tubular structure that receives loads from the teeth. The rostrum can be conceptualized both as a rigid structure and as an assemblage of several bones that interface at sutures. Using miniature pigs, we measured in vivo strains in rostral bones and sutures to gain a better understanding of how the rostrum behaves biomechanically. Strains in the premaxillary and nasal bones were low but the adjacent maxillary-premaxillary, internasal, and intermaxillary suture strains were larger by an order of magnitude. While this finding emphasizes the composite nature of the rostrum, we also found evidence in the maxillary and nasal bones for rigid structural behavior. Namely, maxillary strain is consistent with a short beam model under shear deformation from molar loading. Strain in the nasal bones is only partially supported by a long beam model; rather, a complex pattern of dorsal bending of the rostrum from incisor contact and lateral compression is suggested. Torsion of the maxilla is ruled out due to the bilateral occlusion of pigs and the similar working and balancing side strains, although it may be important in mammals with a unilateral bite. Torsional loading does appear important in the premaxillae, which demonstrate working and balancing side changes in strain orientation. These differences are attributed to asymmetrical incisor contact occurring at the end of the power stroke. J. Morphol. 257:33,44, 2003. © 2003 Wiley-Liss, Inc. [source] ESTIMATION AND HYPOTHESIS TESTING FOR NONPARAMETRIC HEDONIC HOUSE PRICE FUNCTIONSJOURNAL OF REGIONAL SCIENCE, Issue 3 2010Daniel P. McMillen ABSTRACT In contrast to the rigid structure of standard parametric hedonic analysis, nonparametric estimators control for misspecified spatial effects while using highly flexible functional forms. Despite these advantages, nonparametric procedures are still not used extensively for spatial data analysis due to perceived difficulties associated with estimation and hypothesis testing. We demonstrate that nonparametric estimation is feasible for large datasets with many independent variables, offering statistical tests of individual covariates and tests of model specification. We show that fixed parameterization of distance to the nearest rapid transit line is a misspecification and that pricing of access to this amenity varies across neighborhoods within Chicago. [source] Actively and passively excited sinusoidal microstrip and PCB strip antennas operating at K and millimeter-wave bandsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2008A. O. Salman Abstract Actively and passively excited sinusoidal wire structure is applied to the PCB strip and microstrip structures successfully at K and millimeter-wave frequency bands. Antenna dimensions are reduced till the half value, and more rigid structure is also obtained than the sinusoidal wire antennas by this way. Actively excited PCB sinusoidal antennas are investigated at these high frequencies and passively excited ones are introduced in the literature for the first time in this study. Transversely polarized broadside radiation is obtained for both types of antenna. The measured field patterns are compared with the calculated and simulated ones. The calculated patterns, phase velocity, and attenuation constants of investigated antennas are calculated by a written MATLAB code based the analytical approach. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1302,1308, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23347 [source] (Z)-Bis{,-[1-(2-naphthylmethyloxy)propan-2-iminato- O,N:N]}bis[bromobis(tetrahydrofuran- O)magnesium] ditoluene solvateACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2000André B. Charette The title compound, [Mg2Br2(C14H14NO)2(C4H8O)4]·2C7H8, has been crystallized as a C2 -symmetric dimer and the Mg atom has a distorted octahedral geometry. The metal is chelated by the N atom of the ketiminate and the O atom of the ether moiety, giving a rigid structure. [source] Water-in-ionic liquid microemulsion-based organogels as novel matrices for enzyme immobilizationBIOTECHNOLOGY JOURNAL, Issue 8 2010Ioannis V. Pavlidis Abstract The use of water-in-ionic liquid microemulsion-based organogels (w/IL MBGs) as novel supports for the immobilization of lipase B from Candida antarctica and lipase from Chromobacterium viscosum was investigated. These novel lipase-containing w/IL MBGs can be effectively used as solid phase biocatalysts in various polar and non-polar organic solvents or ILs, exhibiting up to 4.4-fold higher esterification activity compared to water-in-oil microemulsion-based organogels. The immobilized lipases retain their activity for several hours at 70°C, while their half life time is up to 25-fold higher compared to that observed in w/IL microemulsions. Fourier-transform infrared spectroscopy data indicate that immobilized lipases adopt a more rigid structure, referring to the structure in aqueous solution, which is in correlation with their enhanced catalytic behavior observed. [source] Study on Synthesis of Thebaine DerivativesCHINESE JOURNAL OF CHEMISTRY, Issue 12 2005He Liu Abstract The reaction of 7, -acetyl-6,14-endoethano-6,7,8,14-tetrahydrothebaine with 2-(thien-2-yl)ethylmagnesium bromide was investigated. The tertiary alcohol derivative 7, -[R-1-hydroxyl-1-methyl-3-(thien-2-yl)propyl])-6,14-endoethano-6,7,8,14-tetrahydrothebaine (3) and a by-product 4 were isolated. The structure of 4 was elucidated by X-ray analysis. The Grignard reaction shows high degree of stereoselectivity according with Cram rule. The crystal structure of 4 indicates that dihydrofuran ring was opened to form a phenolic hydroxyl group and a three-membered ring structure. It maintains the main rigid structure of morphine and contains a C(6)-C(14) enthano bridge. The 1-hydroxyl-1-methyl-3-(thien-2-yl)propyl group at C(7) position adopted S -configuration. [source] Silica Hybrid Containing (R)-2,2,-Binaphtho-20-crown-6 Moieties via the Sol-Gel ProcessCHINESE JOURNAL OF CHEMISTRY, Issue 8 2003Cheng, Yi-Xiang (R) -6,6,-Bis (triethoxysilylethen-2-yl)-2,2,-binaphtho-20-crown6 (precursor, R -2) derived from (R)-2,2,-BINOL derivative was synthesized by Pd-catalyzed Heck reaction of (R)-6,6,-dibromo-2, 2,-binaphtho-20-crown-6 (R -1) intermediate with vinyltriethoxysilane. The hydrolysis and polycondensation of the precursor gave rise to the corresponding xerogel. Both precursor and xerogel were analysed by NMR, FT. IR, UV, CD spectra, fluorescent spectroscopy, polarimetry and elemental analysis. The precursor and xerogel can emit strong blue fluorescence and are expected to have the potential application in the separation of chiral molecules as fluorescent sensor. The precursor exhibits strong Cotton effect in its circular dichroism (CD) spectrum indicating that it is a highly rigid structure. [source] Discrimination of enantiomers of ,-amino acids by chiral derivatizing reagents from trans -1,2-diaminocyclohexane,CHIRALITY, Issue 3-4 2008Magdalena Kaik Abstract New chiral derivatizing reagents (CDAs) derived from trans -1,2-diaminocyclohexane, having an electron-deficient aromatic substituent (either an aromatic imide or 3,5-dinitrobenzamide) and rigid structure (either an amide or a urea linker), are reported. Significant shift differences of diastereotopic protons in the 1H NMR signals are observed for enantiomers of suitably protected ,-amino acids, linked to CDA by a covalent bond. A simple, general model rationalizing the observed enantiomer discrimination and based on semiempirical conformational search is presented. Chirality, 2008. © 2007 Wiley-Liss, Inc. [source] MODELING THE LONG TERM IMPACTS OF USING RIGID STRUCTURES IN STREAM CHANNEL RESTORATION1JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 6 2006Sue L. Niezgoda Abstract: Natural channel designs often incorporate rigid instream structures to protect channel banks, provide grade control, promote flow deflection, or otherwise improve channel stability. The long term impact of rigid structures on natural stream processes is relatively unknown. The objective of this study was to use long term alluvial channel modeling to evaluate the effect of rigid structures on channel processes and assess current and future stream channel stability. The study was conducted on Oliver Run, a small stream in Pennsylvania relocated due to highway construction. Field data were collected for one year along the 107 m reach to characterize the stream and provide model input, calibration, and verification data. FLUVIAL-12 was used to evaluate the long term impacts of rigid structures on natural channel adjustment, overall channel stability, and changing form and processes. Based on a consideration of model limitations and results, it was concluded that the presence of rigid structures reduced channel width-to-depth ratios, minimized bed elevation changes due to long term aggradation and degradation, limited lateral channel migration, and increased the mean bed material particle size throughout the reach. Results also showed how alluvial channel modeling can be used to improve the stream restoration design effort. [source] Response analysis of rigid structures rocking on viscoelastic foundationEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 7 2008Alessandro Palmeri Abstract In this paper the rocking response of slender/rigid structures stepping on a viscoelastic foundation is revisited. The study examines in depth the motion of the system with a non-linear analysis that complements the linear analysis presented in the past by other investigators. The non-linear formulation combines the fully non-linear equations of motion together with the impulse-momentum equations during impacts. The study shows that the response of the rocking block depends on the size, shape and slenderness of the block, the stiffness and damping of the foundation and the energy loss during impact. The effect of the stiffness and damping of the foundation system along with the influence of the coefficient of restitution during impact is presented in rocking spectra in which the peak values of the response are compared with those of the rigid block rocking on a monolithic base. Various trends of the response are identified. For instance, less slender and smaller blocks have a tendency to separate easier, whereas the smaller the angle of slenderness, the less sensitive the response to the flexibility, damping and coefficient of restitution of the foundation. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||||||||