Biologically-Inspired Collective Control for an Autonomous Robotic Arm

Biological collective control architectures and simple control principles used in nervous systems provide novel alternative approaches for the design of fault-tolerant, adaptable real-world robotic systems that have traditionally relied on centralized control. In this research, a robotic arm composed of multiple identical segments in a collective computational architecture was tested for its ability to produce adaptive pointing and reaching behavior. The movement rules for these robotic arm segments were derived from reflex arc principles in the human nervous system. These arm segments received no central directions and used no direct informational exchange, but rather the arm was sensor-driven at its leading segment in a way that maximized pointing accuracy of the arm. The remaining non-leading segments in the arm were moved in a sequential order using only sensed locally-available movement information about neighboring segments.Pointing and reaching behavior was observed in experiments with and without obstacles to movement. Because such behavior was not specified within each segment, the overall limb behavior emerged due to the interaction and coordination of all segments, rather than due to any single segment, centrally controlled influence, or explicit inter-segmental method of communication.     

Femorotibial bypass in the elderly for revascularization of the severely ischemic lower extremity

In the elderly, revascularization of a severely ischemic lower extremity with occlusion of both femoral and popliteal arteries often can be achieved by surgical construction of a distal bypass to the tibial or peroneal arteries. An aggressive diagnostic and therapeutic approach is necessary, in an attempt to prevent recourse to primary amputation. Femoroperoneal or femorotibial bypass can be performed safely and is recommended in elderly patients with advanced ischemia of a lower extremity with absolute indications for surgical intervention, e.g., gangrene, gangrenous ulceration or rest pain. A significant number of limbs can be salvaged by this method. Although the mortality rate in the older age groups is predictably higher, the overall rate for this operation compares favorably with that for primary amputation.     

Statistical analysis of the effect of side-grooving on the measurement of brittle fracture toughness

Fracture mechanics specimens are commonly side-grooved to promote uniformity of the crack tip stress field, but this practice may affect the fracture toughness measured because of changes in the net thickness and in the constraint. This study, based on Weibull statistics, shows that, for brittle fracture, the difference between the fracture toughness measured with plain-sided and 20 percent side-grooved specimens results essentially from the difference in net thicknesses. It is also shown that the effect of constraint should not be evaluated from the load arrying capacity of the specimen, but rather from the distribution of stress intensity factor along the crack front.

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Résumé Il est courant de nantir d'une entaille de bord les éprouvettes de mécanique de rupture pour provoquer un champ de contraintes uniforme à l'extrémité de la fissure. Cette pratique peut néanmoins affecter la ténacité à la rupture en raison des modifications dans l'épaisseur nette et dans le bridage.La présente étude, que est basée sur l'approache probabilistique de Weibull, montre que dans une rupture fragile la différence entre les ténacités à la rupture mesurées avec des éprouvetes sans entailles et avec un entaillage à 20% résulte essentiellement de la différence qui caractérise les épaisseurs nettes:On montre également que l'effet du bridage ne peut être déduit de la capacité qu'a l'éprouvette de supporter la charge, mais bien plutôt de la distribution du facteur d'intensité des contraintes le long du front de la fissure.

     

Alignment of nucleotide or amino acid sequences on microcomputers, using a modification of Sellers' (1974) algorithm which avoids the need for calculation of the complete distance matrix

A program to calculate optimum alignment between two sequences, which may be DNA, amino acid or other information, has been written in PASCAL. The Sellers' algorithm for calculating distance between sequences has been modified to reduce its demands on microcomputer memory space by more than half. Gap penalties and mismatch scores are user-adjustable. In 48 K of memory the program aligns sequences up to 170 elements in length; optimum alignment and total distance between a pair of sequences are displayed. The program aligns longer sequences by subdivision of both sequences into corresponding, overlapping sections. Section length and amount of section overlap are user-defined. More importantly, extension of this modification of Sellers' algorithm to align longer sequences, given hardware and compilers/languages capable of using a larger memory space (e.g. 640 K), shows that it is now possible to align, without subdivision, sequences with up to 700 elements each. The increase in computation time for this program with increasing sequence lengths aligned without subdivision is curvilinear, but total times are essentially dependent on hardware/language/compiler combinations. The statistical significance of an alignment is examined with conventional Monte Carlo approaches.     

Performance of a compact adaptive-optics system

The design of an adaptive-optics system for correction of a beam propagating through high-speed, unpredictable optical turbulence required the use of a robust controller rather than a conventional least-squares controller. We describe the 37-channel, 50-Hz adaptive-optical system and its performance (lambda/75 rms).     

Microelectromechanical system programmable aberration generator for adaptive optics

Adaptive optics systems and control algorithms can be tested in the laboratory with controlled disturbances. We have a micromachined deformable mirror that we use as a programmable aberration generator. We present a method of programming the actuator amplitudes so that the wave front reflecting from the surface will simulate atmospheric turbulence. We present experimental results that show that we can simulate the Kolmogorov spatial spectrum within the constraints of the useful region of the deformable mirror.     

FMS™ scores and low-back loading during lifting – Whole-body movement screening as an ergonomic tool?

Background

Previous research suggests that a general whole-body movement screen could be used to identify personal movement attributes that promote potentially injurious low-back loading patterns at work. The purpose of this study was to examine the relationship between Functional Movement Screen™ (FMS) composite scores and the low-back loading response to lifting.

Methods

Fifteen men who scored greater than 14 on the FMS (high-scorers) and 15 height- and weight-matched low-scorers (FMS < 14) performed sagittally symmetric and asymmetric laboratory-based lifting tasks. A three-dimensional dynamic biomechanical model was used to calculate peak low-back loading levels, and the angle of the lumbar spine was captured at the instant when the peak compressive force was applied.

Results

Regardless of the lifting task performed, there were no differences in peak low-back compression (p ≥ 0.4157), anterior/posterior reaction shear (p ≥ 0.5645), or medial/lateral reaction shear (p ≥ 0.2581) forces between the high- and low-scorers. At the instant when peak compressive forces were applied, differences in the lumbar spine angle between high- and low-scores were not statistically significant about the lateral bend (p ≥ 0.4215), axial twist (p ≥ 0.2734), or flexion/extension (p ≥ 0.1354) axes, but there was a tendency for the lumbar spine to be more deviated in the low-scorers.

Conclusions

Using the previously established injury prediction threshold value of 14, the composite FMS score was not related to the peak low-back loading magnitudes in lifting. Though not statistically significant, the tendency for the lumbar spines of low-scorers to be more deviated when the peak low-back compression force was imposed could be biomechanically meaningful because spinal load tolerance varies with posture. Future attempts to modify or reinterpret FMS scoring are warranted given that several previous studies have revealed links between composite FMS scores and musculoskeletal complaints.     

Evaluating the Effects of Predicated Execution on Branch Prediction

As microprocessor designs move towards deeper pipelines and support for multiple instruction issue, steps must be taken to alleviate the negative impact of branch operations on processor performance. One approach is to use branch prediction hardware and perform speculative execution of the instructions following an unresolved branch. Another technique is to eliminate certain branch instructions altogether by translating the instructions following a forward branch into predicate form. Both these techniques are employed in many current processor designs. This paper investigates the relationship between branch prediction techniques and branch predication. In particular, we are interested in how using predication to remove a certain class of poorly predicted branches affects the prediction accuracy of the remaining branches. A variety of existing predication models for eliminating branch operations are presented, and the effect that eliminating branches has on branch prediction schemes ranging from simple prediction mechanisms to the newer more sophisticated branch predictors is studied. We also examine the impact of predication on basic block size, and how the two techniques used together affect overall processor performance.     

A bibliometric analysis of publications in computer networking research

Scientometrics - Computer networking is a major research discipline in computer science, electrical engineering, and computer engineering. The field has been actively growing, in terms of both...