Characterization of the contribution of inertial parameters to the dynamics of multibody systems

In this paper, an approach is developed for sensitivity analysis of inertial parameters. It is based on the reformed equations of motion linear in terms of the inertial parameters, which are transformed to dimensionless inertial parameters. Based on an eigenvalue analysis, directions of the parameter space are found along which maximum/minimum changes are achieved on the generalized forces, i.e., on the dynamics of the system. Directional derivatives of the generalized force vector in these directions characterize how each inertial parameter contributes to the system dynamics.     

Proposed soil classification based on the experiences of soft-ground tunneling in Iran

Bulletin of Engineering Geology and the Environment - An essential step in successful mechanized and conventional tunneling operations is a thorough characterization of ground conditions and...     

Introducing spectral moment features in analyzing the SpecTex hyperspectral texture database

Hyperspectral imaging provides more information than conventional RGB images. However, its high dimensionality prevents its adaptation to the existing image processing techniques. Defining full-band spectral feature is the first missing step, which is currently dealt with indirectly by band selection or dimension reduction. This article proposes a spectral feature extraction method using the mathematical moments to quantify the shape of the reflectance spectrum from different aspects. A whole family of features is presented by changing the moment attributes. All the features and their combinations are extensively tested in texture analysis of a new hyperspectral image database from textile samples (SpecTex). Two supervised experiments are performed: image patch classification and pixel-wise mosaic image segmentation. The proposed features are compared to four other features: the grayscale intensity, the RGB and CIELab values, and the principal components. Also, three analysis methods are tested: co-occurrence matrix, Gabor filter bank, and local binary pattern. In all cases, the moment features outperformed the opponents. Notably, combining the moment features with complementary attributes remarkably improved the performance. The most discriminative combinations are studied and formulated in this article.     

A force analogy method (FAM) assessment on different static condensation procedures for frames with full Rayleigh damping

In this paper, influence of different static condensation methods on nonlinear time history response of structures in presence of full Rayleigh damping matrix has been studied. Equation of motion is derived in details for 2 newly introduced cases; Full Static Condensation Model and Reduced Static Condensation Model (RSCM or RSCM‐1). Nonlinear analyses are performed with state‐space form of equation of motion along with force analogy method. A novel aspect of this study in comparison with previous researches is to consider full Rayleigh damping in formulations for static condensation in nonlinear structural analysis. Numerical examples are presented for the proposed methods. In addition, the same structure was modeled in finite element method and analyzed by the OpenSEES program. Comparisons demonstrate that results, which are obtained from introduced methods in this article, are in good agreement with the finite element method results. In addition to explaining the equation derivations in main article, proofs for some equations have been demonstrated in appendices. The comparisons show that both RSCM and Full Static Condensation Model lead to almost the same results but in case of using RSCM‐1, the responses have some deviation from other condensation methods.     

A fast-locking low-jitter digitally-enhanced DLL dynamically controlled for loop-gain and stability

Conventional structure of delay locked loops (DLLs) is modified to achieve better jitter and smaller lock time. In the proposed structure, analog charge pump is eliminated, to remove the problems of leakage current on output capacitance, and is replaced by combination of a digital accumulator (ACC) and a digital-to-analog converter. A programmable ACC is also proposed, to dynamically control the loop gain and lock time. When the loop enters to lock region at the first time, a lock detector block disables ACC and equivalent digital code is stored on a latch array. So, a fixed control voltage controls delay elements and the systematic jitter, due to periodic discharge of control voltage. RMS jitter of less than 33.5 and 1.6 ps are achieved at 20 and 625 MHz operating frequencies, respectively, when the supply is subject to 110 mV random noise and also 40 mV periodic noise, related to generated clock signals. Lock time is reduced from 38 to 2 µs at 20 MHz, and also from 900 to 45 ns at 600 MHz, when the proposed dynamic control mechanism is applied on the loop. Total power consumption for the main core of DLL is 7.85 mW at 1.8 V supply in 0.18 µm CMOS process.     

Developing a multi-objective, multi-item inventory model and three algorithms for its solution

We develop a multi-objective model in a multi-product inventory system.The proposed model is a joint replenishment problem (JRP) that has two objective functions.The first one is minimization of total ...     

An accurate and power-efficient period-modulator-based interface for grounded capacitive sensors

A low-power and high-resolution capacitance-to-period converter (CPC) based on period modulation (PM) for subnanometer displacement measurement systems is proposed. The presented circuit employs the interface developed in a previous work, “a grounded capacitance-to-voltage converter (CVC) based on a zoom-in structure,” further improving its performance through a symmetrical design of the applied autocalibration technique. The scheme is based on the use of a relaxation oscillator. To minimize the error contributed by the CPC circuitry, different precision techniques such as chopping, autocalibration, and active shielding are applied. The proposed CPC is realized in a 0.18-μm complementary metal-oxide-semiconductor (CMOS) technology, occupies an area of 0.5 mm², and consumes 135 μA from a 2-V power supply. In order to achieve optimal performance and avoid overdesigning, a noise estimation of various parts of the CPC has been done. Accordingly, for a 10-pF sensor capacitance, the overall CPC demonstrates a capacitance resolution of 0.5 fF for a latency of 128 microseconds, corresponding to an effective number of bits (ENOB) of 12.5 bits and an energy efficiency of 6 pJ/step. The nonlinearity error has been evaluated as well, resulting in a less than 0.03% full-scale span (FSS).     

Topological aspects of meshless methods and nodal ordering for meshless discretizations

The meshless element‐free Galerkin method (EFGM) is considered and compared to the finite‐element method (FEM). In particular, topological aspects of meshless methods as the nodal connectivity and invertibility of matrices are studied and compared to those of the FE method. We define four associated graphs for meshless discretizations of EFGM and investigate their connectivity. The ways that the associated graphs for coupled FE‐EFG models might be defined are recommended. The associated graphs are used for nodal ordering of meshless models in order to reduce the bandwidth, profile, maximum frontwidth, and root‐mean‐square wavefront of the corresponding matrices. Finally, the associated graphs are numerically compared. Copyright © 2001 John Wiley & Sons, Ltd.     

最先进的IC：超声波装置收发器

由于应用物理及电子学的研究及发展，医疗成像领域受益极多．尤其在仪器、影像撷取及建模等方面。由于超声波本身完全无侵人性．因此在各种成像模式中占有特殊地位．为内脏研究提供了可靠的方法。超声波技术用于医疗用途已逾半世纪之久．然而．这类的必要设备不仅体积庞大，而且价格昂贵．直到最近才特别以离散式部件进行制作。