Towards a super-resolution based approach for improved face recognition in low resolution environment

Multimedia Tools and Applications - The video surveillance activity generates a vast amount of data, which can be processed to detect miscreants. The task of identifying and recognizing an object...     

多阶模态瑞利面波频散曲线的BP神经网络反演

瑞利面波勘探已经广泛应用于工程地质勘探和工程质量检测等领域中。瑞利面波勘探频散曲线反演解释时主要考虑基阶模态面波。当地层中含有软弱层以及表层为高速层时,在高频段高阶模态面波相对基阶模的能量更占优势。在瑞利面波勘探频散曲线反演解释中,必须考虑高阶模态面波的信息;在高阶模态面波占优势时,同时利用多阶模态组合频散曲线（包括基阶、二阶、三阶、四阶等）进行反演解释。本文通过对软夹层型和地表为高速层两种高阶模态面波能量较强的地层结构的理论和实测多阶组合模态频散曲线的反演研究,获得了比仅利用基阶模态面波解释更好的效果。     

Element free galerkin study of steady quasi-static crack growth in plane strain tension in elastic-plastic materials

Employing an extension of the convective mesh technique, an Element Free Galerkin (EFG) based formulation for steady quasi-static crack growth in elastic-plastic materials undergoing small scale yielding is established. In accordance with the steady state condition, a parallel path constitutive law integration scheme is implemented into the formulation and a body force type term is introduced for the contribution of crack tip plasticity. A detailed numerical analysis is performed for steady quasi-static growth of a mode I crack under plane strain conditions in elastic-perfectly plastic materials. The numerical solutions to this problem confirm the existence of an elastic unloading wedge. The computed near-tip stress distributions and the crack opening displacements for this problem provide good agreements with the corresponding asymptotic solutions and demonstrate the validity of the EFG based formulation. A rough estimate of the range of validity of the asymptotic solutions is also made based on the numerical solutions. In addition, the effect of strain hardening on the steady quasi-static crack growth is investigated. Both power hardening and linear hardening models are considered.     

Combination of modal responses: A closed-form formulation for rigid response coefficient

Recent studies conducted by US Nuclear Regulatory Commission (USNRC) for combining modal responses in a response spectrum method of seismic analysis and design have emphasized that each modal response quantity should be separated into damped-periodic and rigid parts before combining the contributions from different modes. The damped-periodic parts of modal responses are combined using the double-sum equation whereas the rigid parts are combined algebraically. A particular modal response quantity is separated into damped-periodic and rigid parts using the “rigid response coefficient”. The USNRC sponsored study recommends the calculation of rigid response coefficient by either the Lindley–Yow approach or Gupta method. While Lindley–Yow's method has a heuristic basis and gives incorrect results in low frequency region, Gupta's method is based on numerical studies of free-field earthquake motions and works well in the frequency regions of interest for a free-field ground motion. A closed-form solution was developed by Hahn and Valenti in 1997 using a frequency domain approach. With appropriate simplifications, their work can be shown to result in an expression which is very similar to that given by Gupta. It must be noted that the earthquake input to the secondary systems such as piping and equipment is defined by a floor motion and not a free-field ground motion. The frequency characteristics of a floor motion are very different from those of a free-field ground motion. In this paper, we study the validity of existing formulations for the case of floor motions and develop a closed-form solution based on a time domain approach to explain the behavior of rigid response coefficient. The formulation is then used to explain the nature of variation in rigid response coefficient for ground as well as floor motions. It is shown that the proposed formulation and its simplified form gives results that are identical to those evaluated numerically in the complete frequency region of interest.     

Fuzzy Reliability Assessment of Distribution System with Wind Farms and Plug-in Electric Vehicles

Abstract

The equipment failures are highly uncertain in nature and simple average failure rate will not reflect this uncertainty. The uncertainty level further increases in reliability evaluation due to the integration of wind farm (WF) because of the intermittent nature of wind speed and random charging patterns of plug-in electric vehicles (PEVs). In this work, the uncertain variables in the distribution system (failure rate, repair time, WF output, PEVs charging and system load factor) are represented as fuzzy numbers to handle the uncertainty. The available uncertain data are used to find the probability distribution function (PDF) of that parameter and is converted into fuzzy membership function using transformation techniques. Failure rate of equipment is converted into failure probability using Monte Carlo simulation (MCS) method. Sampling method is applied to create the PDF of a variable which has average value. Fuzzy severity index (FSI) is proposed to find the importance of an equipment on reliability and is evaluated by measuring the fuzzy distance between the fuzzy reliability indices. The proposed assessment method is validated on modified RBTS bus 2 by comparing with analytical and MCS methods. The proposed method has been tested with integration of WFs and PEVs.     

Microprocessor Control of Cycloconverter: Techniques for Implementation and Testing

Since the 1930's, cycloconverter control circuits have been designed with vacuum tubes, transistors, and integrated circuits. With the advent of microprocessors, much more logical and computational power became available in much less space and cost. This led to the design of converter control circuits using microprocessors [2]-[9]. Each of these papers describes a specific implementation. Advancements in microprocessor technology are still going at full steam. To take full advantage of this technology and its continued advancements, a systematic and broad-based study of techniques that can be used for cycloconverter control-on microprocessor-based systems-is required. This paper reports the findings of such a study [10]. In this study a few general techniques were developed for cycloconverter control. In developing the various Techniques, accuracy of trigger timing and the system's speed of response were used as performance criteria. The techniques developed were tested on a system based on the 8085 CPU. Each technique was tested qualitatively by recording the cycloconverter waveforms produced by using it. For quantitative testing, first, the theoretical trigger timings were found by a digital computer simulation of the cycloconverter. These timings were then compared with those produced on the microprocessor-based system. From the test results it was concluded that an 8 bit data width suffices for cycloconverter control. The main bottleneck in achieving the desired performance is the execution time of the processor. In one of the techniques, when improvement in trigger timing accuracy was achieved it lead to reduction in the speed of response.     

On improved hybrid finite elements with rotational degrees of freedom

A set of three new hybrid elements with rotational degrees-of-freedom (d.o.f.'s) is introduced. The solid, 8-node, hexahedron element is developed for solving three-dimensional elasticity problems. This element has three translational and three rotational d.o.f.'s at each node and is based on a 42-parameter. three-dimensional stress field in the natural convected co-ordinate system. For two-dimensional, plane elasticity problems, an improved triangular hybrid element and a quadrilateral hybrid element are presented. These elements use two translational and one rotational d.o.f. at each node. Three different sets of five-parameter stress fields defined in a natural convected co-ordinate system for the entire element are used for the mixed triangular element. The mixed quadrilateral element is based on a nine-parameter complete linear stress field in natural space. The midside translational d.o.f.'s are expressed in terms of the corner nodal translations and rotations using appropriate transformations. The stiffness matrix is derived based on the Hellinger–Reissner variational principle. The elements pass the patch test and demonstrate an improved performance over the existing elements for prescribed test examples.     

Natural Frequencies of Stable Griffith Cracks

A quasi-statically growing stable crack, if perturbed from its equilibrium position, will accelerate back towards it. Within quasi-static, ideal, Griffith fracture theory, vibrations of the crack and the structure have characteristic natural frequencies. We explore this feature of Griffith fracture theory in two simple geometries: a crack between a bar and a substrate, and a crack in a double-cantilever beam (DCB) specimen. For small perturbations about the stable quasi-static configuration, the dynamic equations of motion reduce to simple eigenvalue problems, leading to exact expressions for natural frequencies and mode shapes. An interesting feature of the mode shapes is that they correspond to force-free or moment-free conditions at the crack tip. Using an extended form of Hamilton's principle, we have developed a variable-length finite element technique to calculate natural frequencies and mode shapes of deformations perturbed from the stable equilibrium state. Its accuracy is demonstrated by application to the two problems analyzed previously. The possibility of crack tip oscillations in real brittle materials with irreversibility in crack tip decohesion is discussed in light of Rice's generalization of the Griffith theory.     

Economics of producing hydrogen as transportation fuel using offshore wind energy systems

Over the past few years, hydrogen has been recognized as a suitable substitute for present vehicular fuels. This paper covers the economic analysis of one of the most promising hydrogen production methods—using wind energy for producing hydrogen through electrolysis of seawater—with a concentration on the Indian transport sector. The analysis provides insights about several questions such as the advantages of offshore plants over coastal installations, economics of large wind-machine clusters, and comparison of cost of producing hydrogen with competing gasoline. Robustness of results has been checked by developing several scenarios such as fast/slow learning rates for wind systems for determining future trends. Results of this analysis show that use of hydrogen for transportation is not likely to be attractive before 2012, and that too with considerable learning in wind, electrolyzer and hydrogen storage technology.     

Simulation model for sizing of stand-alone solar PV system with interconnected array

Solar PV arrays made of interconnected modules are comparatively less susceptible to shadow problem and power degradation resulting from the aging of solar cells. This paper presents a simulation model for the sizing of stand-alone solar PV systems with interconnected arrays. It considers the electricity generation in the array and its storage in the battery bank serving the fluctuating load demand. The loss of power supply probability (LPSP) is used to connote the risk of not satisfying the load demand. The non-tracking (e.g., fixed and tilted) and single-axis tracking aperture arrays having cross-connected modules of single crystalline silicon solar cells in a (6×6) modular configuration are considered. The simulation results are illustrated with the help of a numerical example wherein the load demand is assumed to follow uniform probabilistic distribution. For a given load, the numbers of solar PV modules and batteries corresponding to zero values of LPSP on diurnal basis during the year round cycle of operation are presented. The results corresponding to the surplus and deficit of energy as a function of LPSP are also presented and discussed to assess the engineering design trade offs in the system components.Furthermore, a simple cost analysis has also been carried out, which indicates that for Delhi the stand-alone solar PV systems with fixed and tilted aperture arrays are better option than those with single-axis tracking aperture (with north–south oriented tracking axis) arrays.