MODE I AND MIXED-MODE STABLE CRACK EXTENSIONS THROUGH STIFFENED THREE-POINT BEND SPECIMENS

Abstract Both experimental and theoretical results on stable crack extensions are presented for symmetrically stiffened and unstiffened three point bend specimens subjected to mode I or mixed mode loading systems. Results concerning load-displacement variation, growth of plastic zones, instantaneous crack edge profiles, tunnelling, etc., are presented. There is good agreement between the experimental and theoretical results. The whole of stable crack growth can be characterized by the crack opening angle criterion. The stiffening helps to increase substantially both the initiation load and the maximum fracture load.     

Lack of association between renin-angiotensin system, gene polymorphisms, and wall thickness of the radial and carotid arteries

To investigate the relationship between polymorphisms of the angiotensin-converting enzyme (ACE) and the angiotensin II type 1 receptor (AT1R) genes and structural phenotypes of arteries, we studied a cohort of 340 subjects (aged 49+/-12 years) without evidence of cardiovascular disease and who had never been treated previously with any cardiovascular treatments. Structural phenotypes (wall thickness and internal diameter) were evaluated for the common carotid and the radial arteries using high-resolution echo-tracking devices (NIUS-02 and Wall Track System). The influence of ACE insertion/deletion (I/D) and AT1R A/C1166 polymorphism genotypes on structural parameters was tested by ANOVA and logistic regression analysis. For the radial artery, mean wall thickness among subjects according to the ACE I/D or AT1R A/C1166 genotypes was not different. This lack of association persisted in a logistic regression analysis or when the comparison was restricted to a subgroup of subjects potentially at high genetic risk (DD and CC or AC) compared with subjects at low genetic risk (AA and II or ID). Also, no association was observed between the carotid artery intima-media thickness and the 2 polymorphisms. In conclusion, the ACE I/D and the AT1R A/C1166 gene polymorphisms are not markers of vascular hypertrophy in subjects with no evidence of cardiovascular disease. These results suggest that these gene polymorphisms have an undetectable role in the geometry of the radial and carotid arteries compared with usual determinants such as blood pressure and age.     

Balancing of an inverted pendulum with a SCARA robot

The balancing act of an inverted pendulum with a robotic manipulator is a classical benchmark for testing modern control strategies in conjunction with fast sensor-guided movements. From the control design perspective, it presents a challenging and difficult problem, as the system is open-loop instable and includes nonlinear effects in the actuators, such as friction, backlash, and elasticity. In addition, the necessity of a sensor system that can measure the inclination angles of the pendulum contributes to the complexity of the balancing problem. The pendulum is projected onto the xz and yz planes of the inertial coordinate system. These projections are treated independently from each other and are controlled individually by a state-space controller in the x and y axes, respectively. The nonlinearities of the robot are compensated by using inverse dynamics and inverse kinematics. A specially developed sensor system allows the contactless measurement of the inclination angles of the pendulum. This system consists of a small magnet, placed at the bottom of the pendulum, and Hall-effect sensors placed inside the end effector     

Some notes on fusion of uncertain information

This article attempts to analyze the combination of uncertain pieces of information, particularly, given several pieces of information, each of which is assigned a certainty factor. The problem then is whether it is possible to find the certainty factor associated with the combination result. This problem, even if it has been widely commented on in probability literature from various viewpoints, sounds less analyzed in the framework of possibility or evidence theories. This study investigates various proposals for quantifying certainty qualification and then constructs the certainty assigned for the combination result of initial inputs. First, we shall consider some basic combination modes and then attempt to generalize the result for more general combination modes. © 2004 Wiley Periodicals, Inc.     

Query Processing and Optimization on the Web

The advent of the Internet and the Web and their subsequent ubiquity have brought forth opportunities to connect information sources across all types of boundaries (local, regional, organizational, etc.). Examples of such information sources include databases, XML documents, and other unstructured sources. Uniformly querying those information sources has been extensively investigated. A major challenge relates to query optimization. Indeed, querying multiple information sources scattered on the Web raises several barriers for achieving efficiency. This is due to the characteristics of Web information sources that include volatility, heterogeneity, and autonomy. Those characteristics impede a straightforward application of classical query optimization techniques. They add new dimensions to the optimization problem such as the choice of objective function, selection of relevant information sources, limited query capabilities, and unpredictable events. In this paper, we survey the current research on fundamental problems to efficiently process queries over Web data integration systems. We also outline a classification for optimization techniques and a framework for evaluating them.     

Finite element analysis of gradient coil deformation and vibration in NMR microscopy

Resolution degradation due to gradient coil deformation and vibration in NMR microscopy is investigated using finite element analysis. From the analysis, deformations due to the Lorentz force can be as large as 1-10 mum depending on the gradient strength and coil frame material. Thus, these deformations can be one of the major resolution limiting factors in NMR microscopy. Coil vibration, which depends on the input current waveform and resolution degradation due to time-variant deformation and time-invariant deformation are investigated by numerical simulations.     

Precoding and power allocation algorithms for device-to-device communication in massive MIMO networks

Device-to-device communication (D2D) and massive multiple input multiple output (MIMO) systems are two emerging technologies that are being considered to improve the performance of next generation wireless cellular systems. In D2D, two mobile nodes communicate directly without traversing the base station (BS). Consequently, interference management, coordination, and/or cancellation techniques have to be adopted to target the problem of mutual interference between the D2D devices and the BS (or the normal mobiles nodes connected to the BS). In this paper, we investigate the problem of BS precoder design and D2D devices power allocation in the downlink of a single-cell network assuming existence of D2D devices as well as massive MIMO at the BS. We propose algorithms to maximize the sum of the achievable data rates of the D2D pairs while maintaining quality of service constraints on the cellular user equipment, which communicate normally with the BS. We also propose two algorithms for the precoding problem; the first is based on semi-definite programming while the second is based on gradient descent algorithms. Moreover, we investigate two solutions for the power allocation problem; the first solves an approximate convex optimization problem iteratively while the second is a suboptimal, but far less complex, heuristic. Finally, we propose a technique to apply the mentioned solutions when only partial channel state information is available at the BS. Simulation results show that the proposed solutions are superior to the conventional precoding and power allocation schemes.     

A 0.5-bit step multi-resolution adjustable-input range reconfigurable noise-shaping TDC using multi-step quantizer gated-ring oscillators

A reconfigurable noise-shaping time-to-digital converter (TDC) with adjustable resolution and input range is presented as a solution to nonlinear multi-input readout systems. By varying the frequency of a multi-step quantizer gated-ring oscillator (MSQ-GRO), the resolution and input range are adjusted without affecting the acquisition time. A prototype of a standalone second-order MASH MSQ-GRO-TDC operating over a 34 μs adjustable input range and covering five resolution modes is presented. The MSQ-GRO frequency changes by a factor of approximately \(\sqrt 2\), thus adjusting the resolution in steps of 0.5-bit. With a 12 MHz sampling frequency, the MSQ-GRO-TDC consumes 0.85 mW from a 1.2 V supply and achieves integrated noise of 42.8 and 1.9 ps_rms in 500 and 1 kHz bandwidths, respectively. The measured resolution is 13.3-to-15.3 bits with a sampling signal of 200 kHz in a 5 kHz bandwidth. The input range/resolution optimization allows up to 51% of power saving under the same supply voltage, thus extending the battery lifetime in portable devices. The MSQ-GRO-TDC is used as a data converter for a nonlinear pressure sensor. It achieves a worst-case resolution of 24.5 μbar_rms. It is realized in a standard 0.13 μm CMOS technology and occupies an area of 0.145 mm².