A three-dimensional dynamic posture prediction model for simulating in-vehicle seated reaching movements: development and validation

A three-dimensional dynamic posture prediction model for simulating in-vehicle seated reaching movements is presented. The model employs a four-segment 7-degrees-of-freedom linkage structure to represent the torso, clavicle and right upper extremity. It relies on an optimization-based differential inverse kinematics approach to estimate a set of four weighting parameters that quantify a time-constant, inter-segment motion apportionment strategy. In the development phase, 100 seated reaching movements performed by 10 subjects towards five typical in-vehicle targets were modelled, resulting in 100 sets of weighting parameters. Statistical analysis was then conducted to relate these parameters to target and individual attributes. In the validation phase, the generalized model, with parameter values statistically synthesized, was applied to novel data sets containing 700 different reaching movements (towards different targets and/or by different subjects). The results demonstrated the model's ability to generate close representations in prediction: the overall mean time-averaged error in joint angle was 5.2 degrees, and the median was 4.7 degrees, excluding reaches towards two extreme targets (for which modelling errors were excessive). The model's general success in prediction and its unique characteristics led to implications with regard to the performance and underlying control strategies of human reaching movements.     

Development of physical selection procedures for the British Army. Phase 2: relationship between physical performance tests and criterion tasks

This paper is the second in a series of three to describe the development of physical selection standards for the British Army. The first paper defined criterion tasks (single lift, carry, repetitive lift and carry, and loaded march tasks) and set standards on the criterion tasks for all British Army trades. The principal objective was to determine which combination of physical performance tests could be best used to predict criterion task performance. Secondary objectives included developing so-called 'gender-free' and 'gender-unbiased' models. The objectives were met by analysing performance data on the criterion tasks and a large battery of physical performance tests collected from 379 trained soldiers (mean age 23.5 (SD 4.45) years, stature 1734 (SD 79.5) mm, body mass 71.4 (SD 10.58) kg). Objective 1 was met: the most predictive physical performance tests were identified for all criterion tasks. Both single lift tasks were successfully modelled using muscle strength and fat free mass scores. The carry model incorporated muscle endurance and body size data, but the errors of prediction were large. The repetitive lift models included measures of muscle strength and endurance, and body size, but errors of prediction were also large. The loaded march tasks were successfully modelled incorporating indices of aerobic fitness, supplemented by measures of strength, endurance or body size and composition. The secondary objectives were partially fulfilled, though limitations in the data hampered the process. Although only one model (a loaded march) was gender-free, three models were gender-related (i.e. contained 'gender' explicitly in the model). The remaining six were gender-specific (i.e. were appropriate for men or for women). Owing to both a lower accuracy of prediction in women's scores and a greater tendency for the women's scores to be distributed around the pass standards, a greater percentage of women than men were misclassified as passing or failing, resulting in indirect discrimination. A validation of the models in a separate sample of the user population of recruits is reported in the third paper in this series.     

Fleet study evaluation of an advance brake warning system

The advance brake warning system (ABWS) is a mechanism that activates the brake lights in response to a rapid disengagement of the gas pedal, before the driver's foot reaches the brake pedal. Two previous studies showed that (a) such rapid releases of the gas pedal are typically followed by brake activation, and (b) the ABWS can prevent a high percentage of rear-end collisions in which an attentive following driver maintains a headway of 1.0 s or less from the vehicle ahead. In the present study the crash involvement of 764 government cars and light trucks was tracked over an average period of 35 months. The vehicles were matched in pairs--one of each pair with the ABWS and one without it. Data analyses focused on collisions in which the government vehicles were rear-ended. Overall, ABWS-equipped vehicles were not significantly less involved in rear-end collisions. However, an examination of the struck vehicles only showed that the ABWS-equipped vehicles were involved in fewer rear-end collisions per kilometer driven than were the vehicles without the ABWS. In conclusion, despite the theoretical appeal and the results of earlier studies, the fleet study failed to demonstrate that such a system is a cost-effective safety device for the prevention of rear-end crashes. Actual or potential applications include the evaluation of new in-vehicle technologies by a hierarchy of multiple validation studies prior to consideration.     

An automatic method for the evaluation of xenobiotic toxicity on haematopoietic progenitors

Culture of haematopoietic progenitors is used in toxicology to evaluate the effects of xenobiotic contaminants on humans. One of the most important parts of this analysis is the quantification of cell aggregates in the culture. These aggregates can have different sizes and shapes, which reflect the category of cells (granulocyte or monocyte), and the growth percentage reflects the toxic effect of the contaminant. A proposal for an automatic method based on image analysis is described in this work. Algorithms able to solve the basic problems are proposed and tested, and the problem concerning a tridimensional analysis is exposed and discussed.     

TEODOLINDA. A communication architecture for hospital information systems

This paper is focused on a system for the release and distribution of messages and services among hospital units, which extends hospital information systems features in the field of communication and supports hospital organisation to fulfil healthcare commitments.     

An educational tool to illustrate cost-effectiveness in diagnostic pathways for coronary artery disease

Rapid increases in healthcare costs have led to increased interest in the cost-effectiveness of medical interventions. Coronary artery disease is responsible for a significant share of total healthcare spending, and therefore economic evaluations of medical procedures to treat the condition are potentially very important. We have developed a spreadsheet model as an educational tool that can be used to illustrate cost-effectiveness in the selection of diagnostic pathways (a "work-up" strategy of tests designed to reach a final diagnosis) for coronary artery disease. The model, in Microsoft Excel, is easy to use, requiring no specialist computer knowledge. It is menu-driven and the user navigates the model via a number of on-screen buttons. A data entry screen allows the user to customize the data for the key model parameters, making it possible to take into account location-specific features. The data entry screen also allows the user to undertake sensitivity analysis and rate "what if" scenarios. The model demonstrates how sensitive the cost-effectiveness of different diagnostic pathways is to the pretest probability of disease. This package could also be used as a decision support tool, although it is important to recognize some of its limitations for this purpose.     

Synchrony in heterogeneous networks of spiking neurons

The emergence of synchrony in the activity of large, heterogeneous networks of spiking neurons is investigated. We define the robustness of synchrony by the critical disorder at which the asynchronous state becomes linearly unstable. We show that at low firing rates, synchrony is more robust in excitatory networks than in inhibitory networks, but excitatory networks cannot display any synchrony when the average firing rate becomes too high. We introduce a new regime where all inputs, external and internal, are strong and have opposite effects that cancel each other when averaged. In this regime, the robustness of synchrony is strongly enhanced, and robust synchrony can be achieved at a high firing rate in inhibitory networks. On the other hand, in excitatory networks, synchrony remains limited in frequency due to the intrinsic instability of strong recurrent excitation.     

Effects of delay on the type and velocity of travelling pulses in neuronal networks with spatially decaying connectivity

We study a one-dimensional model of integrate-and-fire neurons that are allowed to fire only one spike, and are coupled by excitatory synapses with delay. At small delay values, this model describes a disinhibited cortical slice. At large delay values, the model is a reduction of a model of thalamic networks composed of excitatory and inhibitory neurons, in which the excitatory neurons show the post-inhibitory rebound mechanism. The velocity and stability of propagating continuous pulses are calculated analytically. Two pulses with different velocities exist if the synaptic coupling is larger than a minimal value; the pulse with the lower velocity is always unstable. Above a certain critical value of the constant delay, continuous pulses lose stability via a Hopf bifurcation, and lurching pulses emerge. The parameter regime for which lurching occurs is strongly affected by the synaptic footprint (connectivity) shape. A bistable regime, in which both continuous and lurching pulses can propagate. may occur with square or Gaussian footprint shapes but not with an exponential footprint shape. A perturbation calculation is used in order to calculate the spatial lurching period and the velocity of lurching pulses at large delay values. For strong synaptic coupling, the velocity of the lurching pulse is governed by the tail of the synaptic footprint shape. Moreover, the velocities of continuous and lurching pulses have the same functional dependencies on the strength of the synaptic coupling strength gsyn: they increase logarithmically with gsyn for an exponential footprint shape, they scale like (In gsyn)1/2 for a Gaussian footprint shape, and they are bounded for a square footprint shape or any shape with a finite support. We find analytically how the axonal propagation velocity reduces the velocity of continuous pulses; it does not affect the critical delay. We conclude that the differences in velocity and shape between the front of thalamic spindle waves in vitro and cortical paroxysmal discharges stem from their different effective delays.     

数字线路纵差保护

本文提出的线路纵差保护结合模拟综合器，导引线及数字测量值处理的优点，央线路每端配置两台装置可保护三端线路，调试时可导引线电容及电阻，导引线监视信号电平并在运行中自动加以考虑。因此此保护用于配有导引线的架空线和电缆时容易调整。     

SiC WHISKER-TOUGHENED ALUMINIUM NITRIDE CERAMICS

Aluminium nitride ceramics containing 15-30 w/o of SiC whiskers can be sintered tofull density(by hot pressing at 1800℃)using2-3 w/o of Y_2O_3,additions.The whiskersincrease the toughness and strength of thecomposite,K_(10) increasing from 2.8 to about5.0 and flexural strength increasing by 30-50%.However,the whiskers must be welldispersed and if the dispersion is notsatisfactory,toughness may increase but thestrength decreases.The hot-pressingtemperature can be reduced by up to 100℃ ifY(NO_3)_3 .5H_20 is used as the sinteringadditive instead of Y_2O_3,but some oxidation ofthe AIN occurs during heating.Isopropan-2-01 is a better dispersing agent thancyclohexane,but again some oxidation of theAIN does occur.The best sample prepared during this work contained 20 w/o of SiC whiskers and 2 w/oY_2O_3 added as Y(NO_3)_3. 5H_2O and mixed inisopropanol.This exhibited a mean strength of453MPa(maximum 522MPa,measured bydisc flexure)and a fracture toughness of5.5MPam~(1/2).