Dynamic response of a beam on elastic foundation of finite depth under a moving force

Summary In this paper, dynamic response of an infinitely long beam resting on a foundation of finite depth, under a moving force is studied. The effect of foundation inertia is included in the analysis by modelling the foundation as a series of closely spaced axially vibrating rods of finite depth, fixed at the bottom and connected to the beam at the top. Viscous damping in the beam and foundation is included in the analysis. Steady state response of the beam-foundation system is obtained. Detailed numerical results are presented to study the effect of various parameters such as foundation mass, velocity of the moving load, damping and axial force on the beam. It is shown that foundation inertia can considerably reduce the critical velocity and can also amplify the beam response.List of symbols b width of the beam - C _b coefficient of viscous damping for the beam - C _f coefficient of viscous damping for the foundation - E Young's modulus - f frequency - H foundation depth - I moment of inertia - i =(–1)^0,5 - K, k indexing variables - k _f foundation modulus - m mass per unit length of the beam - N total number of frequency points in Eqs. (25) and (26) - n indexing variable - P moving force - Q axial force on the beam - q(x, t) foundation pressure per unit length of the beam - q() foundation pressure in the moving co-ordinate system - t time variable in sec. - U _j () generalized coordinate in Eq. (4) - U _j ^*(f) Fourier transform ofU _j - u(y, t; x) axial displacement in the foundation at a particularx value - u(y, ) foundation displacement in the moving coordinate system - , nondimensionalized foundation deflection - v velocity in meters/sec. - v _cr critical velocity corresponding to massless foundation - w(x, t) beam deflection - w() beam deflection in the moving coordinate system - =w()/L nondimensionalized beam deflection - Fourier transform of - x, y coordinate axis - velocity parameter - _cr critical velocity parameter - mass parameter - moving coordinate - _b beam damping parameter - _f foundation damping parameter - (y, t, x) vertical stress in the foundation - () Dirac delta function - foundation mass per unit depth per unit length of the beam     

Effect of zeolites on thermal decomposition of ammonia borane

Chemical hydrides due to their light weight and high storage capacity are considered to be promising hydrogen storage materials for both mobile and stationary applications. Ammonia Borane (AB) is a novel material with very high hydrogen content (19.6 wt %) per mass. The decomposition of AB takes place in three steps at desorption temperatures of about 100 °C, 140 °C and above 1000 °C respectively releasing 1 mol of hydrogen in each step. The major obstacle towards the use of AB as a hydrogen store is its irreversibility and slow kinetics. With the additives the decomposition temperature could be reduced and the kinetics can be improved. Effect of addition of Zeolites on decomposition of Ammonia Borane at different temperatures is reported in this paper. It was observed that the kinetics behaviour is greatly affected by addition of Zeolites with considerable reduction in the induction or warm-up period.     

Single-channel speech enhancement using implicit Wiener filter for high-quality speech communication

International Journal of Speech Technology - Speech enables easy human-to-human communication as well as human-to-machine interaction. However, the quality of speech degrades due to background...     

Detection of Copy-Move Forgery in Digital Image Using Multi-scale,Multi-stage Deep Learning Model

Neural Processing Letters - Images are an important source of information and copy-move forgery (CMF) is one of the vicious forgery attacks. Its objective is to conceal sensitive information from...     

Coupled surface-enhanced Raman spectroscopy and electrical conductivity measurements of 1,4-phenylene diisocyanide in molecular electronic junctions

Probing the structure of molecules in a metal-molecule-metal junction under an applied voltage is critical for understanding molecular electron transport properties. We present an approach that allows recording surface-enhanced Raman spectra simultaneously with electrical measurements of a monolayer of molecules in molecular electronic junctions. 1,4-Phenylene diisocyanide in two different types of junctions was used to illustrate the approach. The results show that the molecular integrity was intact in the molecular junctions and under the applied bias. The monolayer sensitivity of the approach provides a new powerful tool for characterizing molecular structure in a molecular electronic junction.     

Adsorptive removal of water poisons from contaminated water by adsorbents

Adsorptive removal of water poisons such as Pb(II), Cu(II), Mn(II), Hg(II), CN(-), microbes, nerve and blister agents (concentration range from 100 to 1000 mg/L) were studied by using adsorbents such as active carbon, impregnated carbon and bentonite loaded fabric strip. Removal of water poisons (99.5%) could be achieved with an optimum stirring time of 5-15 min and weight of adsorbent of 0.8-8.0 g/100mL contaminated water, respectively. However, 85% bentonite loading was found to be most effective for Pb(II) removal. Effect of contaminants concentration was also studied.     

Chernoff-Type Direct Product Theorems

Consider a challenge-response protocol where the probability of a correct response is at least α for a legitimate user and at most β<α for an attacker. One example is a CAPTCHA challenge, where a human should have a significantly higher chance of answering a single challenge (e.g., uncovering a distorted letter) than an attacker; another example is an argument system without perfect completeness. A natural approach to boost the gap between legitimate users and attackers is to issue many challenges and accept if the response is correct for more than a threshold fraction, for the threshold chosen between α and β. We give the first proof that parallel repetition with thresholds improves the security of such protocols. We do this with a very general result about an attacker’s ability to solve a large fraction of many independent instances of a hard problem, showing a Chernoff-like convergence of the fraction solved incorrectly to the probability of failure for a single instance. Russell Impagliazzo: Research partially supported by NSF Awards CCR-0515332 and CNS-0716790. Views expressed are not endorsed by the NSF. Ragesh Jaiswal: Research partially supported by NSF Awards CCR-0515332, CCF-0634909, CNS-0524765 and CNS-0716790. Views expressed are not endorsed by the NSF.     

Doping optimization and surface modification of aluminum doped zinc oxide films as transparent conductive coating

Aluminum doped zinc oxide (ZnO:Al) films were grown using spray pyrolysis technique. Effect of doping on structural, electrical, optical and morphological properties was studied. Aluminum doping improved the prominence of [002] growth while maintaining the grain size ~ 48 nm. Using an intermediate Al/Zn atomic ratio in precursor (1.5:100), we could achieve a low resistivity ρ ~ 7 × 10^− 4 Ωcm. These films possessed an average visible transmittance ~ 88%, an optical gap ~ 3.7 eV and plasma wavelength at 1.87 μm. A simultaneous use of methanol and iso-propanol in the precursor lead to a moderate surface roughness ~ 12 nm. The films were surface modified using wet chemical etching in diluted hydrochloric acid, for varied time intervals (5 s-15 s) and etchant concentrations (0.125%-1%). The etching experiments could be used to know the building of the film as also to modify the surface for desired optical and morphological properties.