A graphics simulator for a robotic arm

A graphics robot simulator designed for an IBM PC/XT/AT or PS/2 personal computer is presented. The simulator is a terminate-and-stay resident (TSR) program that runs in the background and intercepts commands that would normally go to the robot controller through the COM1 serial communication device. With the use of the simulator, students can develop and test robot control programs offline without a physical robot present, using the language of their choice. The status of the simulated robot is available through a 3-D graphics display and a one-line text window, each of which can be activated from the keyboard or from within a user program. Data files are used to specify the robot to be simulated and the environment or workcell within which it is to operate. Currently supported robots include the Rhino XR-3 educational robot and the Adept One and Inteledex 660 industrial robots. The workcell features an overhead camera and objects that can be sensed by the camera and manipulated by the robot.<>     

Method for three-dimensional data registration from disparate imaging modalities in the NOGA Myocardial Viability Trial

Region-by-region comparison of data concerning left ventricular (LV) status is difficult to perform quantitatively if the data was acquired from disparate imaging modalities. We validated a method for comparing measurements obtained by electromechanical mapping (EMM) catheter with dobutamine stress echocardiography (DSE) via biplane contrast ventriculography, with the assistance of three-dimensional (3-D) echocardiographic data. The ventriculograms were traced and the borders were used to reconstruct the LV in 3-D with the aid of a database of 3-D echocardiographic studies. The 3-D LV was oriented to the EMM data based on the body coordinates and then manually scaled and translated to fit. The EMM data were mapped to the 3-D surface. The 3-D surface was divided into the 16 regions defined for echocardiographic assessment. The mean EMM value for local linear shortening, a parameter of function, was computed in each segment. The EMM and semiquantitative echocardiographic assessments of regional myocardial function were compared by segment, and the volume of the 3-D LV was compared with the volume computed from the ventriculogram. The volume of the 3-D surface correlated closely with that of the ventriculogram (r = 0.97, SEE = 27.4 ml) but with a significant overestimation of 63 +/- 35 ml. There was a highly significant (p < 0.0001) agreement in regional function between EMM and echo. Local linear shortening correlated significantly (p < 0.0001) with echocardiographic severity of wall motion, averaging 9.5 +/- 6.5, 8.1 +/- 5.4, 5.9 +/- 4.8, and 6.2 +/- 3.3 in segments read as normal, hypokinetic, akinetic, and dyskinetic, respectively. The method presented is valid for comparing cardiac parameters derived from disparate image data on a region-by-region basis by employing anatomic landmarks on 3-D reconstructions of the LV endocardial surface.     

Frequency response of fiber-optic multilayer hydrophones: experimental investigation and finite element simulation

The frequency response of a fiber-optic hydrophone that uses a dielectric multilayer system as the sensing element for ultrasound detection is investigated. A primary interferometric calibration technique is applied to determine by experiment the frequency-dependent pressure-voltage transfer function up to 45 MHz. The interaction between an incident pressure wave and the fiber end is analyzed by finite element methods. The simulation yields the response of the sensor to a short Gaussian impulse in the time domain from which the transfer function is calculated. The results of the model simulations allowed the transfer function obtained to be interpreted as the result of the superposition of longitudinal, edge diffraction and lateral waves with a resonant vibration mode of the fiber body representing an elastic rod     

UML specification of access control policies and their formal verification

Security requirements have become an integral part of most modern software systems. In order to produce secure systems, it is necessary to provide software engineers with the appropriate systematic support. We propose a methodology to integrate the specification of access control policies into Unified Modeling Language (UML) and provide a graph-based formal semantics for the UML access control specification which permits to reason about the coherence of the access control specification. The main concepts in the UML access control specification are illustrated with an example access control model for distributed object systems.     

Wind resource assessment from C-band SAR

Using accurate inputs of wind speed is crucial in wind resource assessment, as predicted power is proportional to the wind speed cubed. First, wind speeds retrieved from a series of 91 ERS-2 SAR and Envisat ASAR images, at moderate wind speeds (2-15 m s^− 1), were validated against in situ measurements from an offshore mast in the North Sea. The wind direction input, necessary for SAR wind speed retrievals, was obtained from the meteorological mast and from a local gradient analysis of wind streaks in the SAR images. A wind speed standard deviation of ∼ 1.1 m s^− 1 was found when in situ wind directions were used. The use of local gradient wind directions yielded a standard deviation of ∼ 1.3 m s^− 1. Wind speeds retrieved from three geophysical model functions (CMOD-IFR2, CMOD4, and CMOD5) were compared. The best approximation to the in situ measurements of wind speed was found for CMOD-IFR2, despite a bias on the order of − 0.3 m s^− 1. CMOD4 retrievals also underestimated the wind speed, whereas the bias on CMOD5 retrievals was negligible. Then, wind resource assessments were made from the SAR-based wind observations to show how errors in wind speed from the different SAR wind retrievals were reflected in the wind statistics. The mean wind speed, obtained for all of the 91 SAR scenes, was linked closely to the bias of SAR wind retrievals. Agreement to ± 15% of the in situ measurements was found for all the wind retrieval methods tested. The accuracy of power density estimates for the entire data set was evaluated by the standard deviation of SAR wind retrievals relative to the in situ measurements. SAR wind fields retrieved with CMOD-IFR2, using in situ wind direction inputs, exactly yielded the power density predicted from in situ measurements alone. The SAR-based wind resource assessment also corresponded well to predictions from longer time series of in situ measurements. This indicates that a reliable wind resource assessment may be achieved from a series of randomly selected SAR images. The findings presented here could be useful in future wind resource assessment based on SAR images.     

Finite element analysis of a shear punch test

The authors present new experimental data for shear punch tests and tensile tests using four different materials. The correlation between shear punch and tensile yield stresses must be established empirically, and the procedure for doing this is discussed. The elastic-plastic deformation in a shear punch test develops gradually with increasing punch displacement and is often assumed to be simple shear. This is examined using finite element analysis to simulate the development of plasticity during the early stages of punch displacement. The simulation results are used to rationalize the empirically established yield stress correlations.     

用MDBT分析纳米Zn及其合金

应用高能球磨机械合金化方法制备纳米Zn及Zn—Al合金体材料，采用拉伸实验和MDBT实验对这些材料的样品的机械性能进行测量分析．结果表明：球磨3～5h获得的Zn-0．6％Al含金具有很好的塑性．室温下球磨3h所得的纯Zn比液氮温度下球磨3h加室温球磨6h所得的纯Zn具有更好的塑性．     

Frequency Stabilization of a Ho:Tm:YLF Laser to Absorption Lines of Carbon Dioxide

A single-frequency Ho:Tm:YLF laser, operating at an eye-safe wavelength of 2 mum, has been developed with tuning characteristics optimized for spectroscopy of absorption features. The laser frequency was stabilized to three different absorption lines of carbon dioxide by a wavelength modulation technique. Long-term frequency drift has been eliminated from the laser, and shorter-term jitter has been reduced to within 13.5 MHz of the absorption line center. This stabilized laser is an ideal injection seed source for a differential absorption lidar system for measurement of atmospheric gases.     

Measurement of ultrasonic pressure by heterodyne interferometry with a fiber-tip sensor

A fiber-optic measurement system is described that allows ultrasound to be detected in fluids. It is based on a heterodyne interferometer, and the sensing element consists of a metal-coated fiber tip. The heterodyne technique permits direct acquisition of the sound pressure. The required ac photodetection is carried out with wide bandwidth, and the system provides high temporal and spatial resolution. For optimum performance the system parameters are matched to the sound-wave properties of the current application with the aid of theoretical and numerical calculations. The fiber-optic sensor system was applied to two problems of ultrasonic exposimetry in which the favorable features of the measurement technique were exploited. Shock waves from an electromagnetic lithotripter were investigated by use of the wide bandwidth of the system, and the subharmonic in an ultrasonic cleaner was detected, which indicates cavitation.     

Dynamic range and sensitivity adaptation in a silicon spikingneuron

We propose an adaptive procedure that enables a spiking neuron, whether artificial or biological, to make optimal use of its dynamic range and gain. We discuss an analog electronic circuit implementation of this algorithm using a biologically realistic artificial "silicon" neuron. The adaptation procedure adapts the neuron's firing threshold and the sensitivity (or gain) of its current-frequency relationship to match the DC offset (or mean) and the dynamic range (or variance) of the time-varying somatic input current. The neuron extracts the minimum and maximum levels of the reconstructed somatic current signals from the cell's own spike trains. These are used to regulate the somatic leak conductance in order to shift the somatic current-frequency relation and to adjust a calcium-activated potassium conductance to change the dynamic range of the cell's somatic current-frequency relationship. We report experimental data from a test neuron-built using analog subthreshold CMOS VLSI technology-that shows the expected behavior.