Improved myoelectric prosthesis control using targeted reinnervation surgery: a case series.

Targeted reinnervation is a surgical technique developed to increase the number of myoelectric input sites available to control an upper-limb prosthesis. Because signals from the nerves related to specific movements are used to control those missing degrees-of-freedom, the control of a prosthesis using this procedure is more physiologically appropriate compared to conventional control. This procedure has successfully been performed on three people with a shoulder disarticulation level amputation and three people with a transhumeral level amputation. Performance on timed tests, including the box-and-blocks test and clothespin test, has increased two to six times. Options for new control strategies are discussed.     

逆变侧送极控主系统直流电压测量结果影响分析(一)

根据天广直流输电系统的基本控制策略、极控内后备保护和软件监视功能等,从理论上分析了逆变侧送极控主系统电压测量值异常对直流输电系统可能造成的影响,并指出为了提高直流输电系统的可靠性,首先应合理改进受其影响最大、对系统影响最直接迅速的换流器开路保护I段。     

Computing the internal transient voltage response of a transformerwith a nonlinear core using Gear's method. II. Verification

An EHV transformer's insulation structure must be designed to withstand the internal electrical stresses generated during system transients. Computer models are employed for predetermination of these stresses. Part I of this paper developed a detailed transformer model and solution method representing the nonlinear, saturable characteristic of tire core during transients. The resulting set of stiff nonlinear differential algebraic equations are solved by application of Gear's method. Part II presents the verification of this methodology. This is accomplished by comparing the computed and measured response of a 765/345/34.5 kV 500 MVA autotransformer during energization and transient excitation     

Permittivity measurement of disk and annular dielectric samples using coaxial transmission line fixtures. part II: experimentation and accuracy analyses

An improved permittivity measurement technique for dielectric disks involving S-parameter measurement of a two-port coaxial transmission line fixture is presented. The previous form of the method suffers from variation of the retrieved permittivity with frequency, which leads to inaccuracies that may be severe at some frequencies. An extension of the method that reduces these errors is devised. In addition, an independently developed new technique for measuring the permittivity of annular samples via quadratic curve fitting is presented. This technique also involves S-parameter measurement of a coaxial fixture and requires measurement of only three known materials (one of them may be free space, in which case the requirement is reduced to only two solid dielectrics). The permittivity of any unknown dielectric may subsequently be determined with high accuracy over a wide frequency range. The method is based on the premise that the variation of the reflection characteristics of the two-port coaxial transmission line fixture with the permittivity of the sample displays a strongly quadratic behaviour. This paper constitutes the second of two parts of this work. Part I, also appearing in this issue, presents the theoretical formulation for the moment method mode-matching treatment of the coaxial fixture for treating annular samples. In the present paper, the measurement techniques are described, and numerical simulations of the experimental procedure based on the theory of Part I are presented. In addition, comparative results of accuracy for these two approaches are given. Sensitivity analyses are also presented, along with preliminary experimental results.     

From LDPE to XLPE: Investigating the change of electrical properties. Part II. luminescence

Luminescence experiments have been used to probe the nature of trapping sites and the dynamic behavior of charge carriers in low density polyethylene (LDPE), antioxidant containing LDPE (LDPE+AO) and cross-linked polyethylene (XLPE). It is shown that deep traps of different natures are present in these materials. For example carbonyl functions provide deep traps in LDPE. New traps are seen in LDPE+AO and XLPE, associated with the anti oxidant itself or with its reaction produces, and to the by-products of the cross-linking reaction. Among those, acetophenone, cumyl alcohol and /spl alpha/-methylstyrene cannot account for the observed spectra. It is shown, in addition, that two XLPE compounds based on two different base resins exhibit the same behaviour demonstrating that the chemical and/or structural modifications introduced by the cross-linking process itself control the charge storage in XLPE. The electrical properties of the same materials are discussed in the light of the work reported in pt.I see ibid., vol.12 no.3 p.438-46, (2005).     

Sensitivity of Electrical Appliances to Harmonics and Fractional Harmonics of the Power System's Voltage. Part II: Television Sets, Induction Watthour Meters and Universal Machines

The sensitivity of television sets, induction watthour meters and universal motors to harmonics and fractional harmonics, as they occur in home appliances, is derived analytically and experimentally. This study shows that television sets are very sensitive to fractional harmonics. Calculations and measurements performed with single-phase watthour meters show that the harmonic torques within the aluminum disk are always positive and accelerate the disk. Universal machines are not as sensitive to voltage harmonics as compared with induction machines. The work described has been supported by the U.S. Department of Energy.     

Pattern recognition as a tool to support decision making in the management of the electric sector. Part II: A new method based on clustering of multivariate time series

This work presents a new method for the clustering and pattern recognition of multivariate time series (CPT-M) based on multivariate statistics. The algorithm comprises four steps that extract essential features of multivariate time series of residential users with emphasis on seasonal and temporal profile, among others. The method was successfully implemented and tested in the context of an energy efficiency program carried out by the Electric Company of Alagoas (Brazil) that considers, among others, the analysis of the impact of replacing refrigerators in low-income consumers’ homes in several towns located within the state of Alagoas (Brazil). The results were compared with a well-known method of time series clustering already established in the literature, the Fuzzy C-Means (FCM). Unlike C-means models of clustering, the CPT-M method is also capable to obtain directly the number of clusters. The analysis confirmed that the CPT-M method was capable to identify a greater diversity of patterns, showing the potential of this method in better recognition of consumption patterns considering simultaneously the effect of other variables in additional to load curves. This represents an important aspect to the process of decision making in the energy distribution sector.     

Brain-computer interfaces for 1-D and 2-D cursor control: designs using volitional control of the EEG spectrum or steady-state visual evoked potentials.

We have developed and tested two electroencephalogram (EEG)-based brain-computer interfaces (BCI) for users to control a cursor on a computer display. Our system uses an adaptive algorithm, based on kernel partial least squares classification (KPLS), to associate patterns in multichannel EEG frequency spectra with cursor controls. Our first BCI, Target Practice, is a system for one-dimensional device control, in which participants use biofeedback to learn voluntary control of their EEG spectra. Target Practice uses a KPLS classifier to map power spectra of 62-electrode EEG signals to rightward or leftward position of a moving cursor on a computer display. Three subjects learned to control motion of a cursor on a video display in multiple blocks of 60 trials over periods of up to six weeks. The best subject's average skill in correct selection of the cursor direction grew from 58% to 88% after 13 training sessions. Target Practice also implements online control of two artifact sources: 1) removal of ocular artifact by linear subtraction of wavelet-smoothed vertical and horizontal electrooculograms (EOG) signals, 2) control of muscle artifact by inhibition of BCI training during periods of relatively high power in the 40-64 Hz band. The second BCI, Think Pointer, is a system for two-dimensional cursor control. Steady-state visual evoked potentials (SSVEP) are triggered by four flickering checkerboard stimuli located in narrow strips at each edge of the display. The user attends to one of the four beacons to initiate motion in the desired direction. The SSVEP signals are recorded from 12 electrodes located over the occipital region. A KPLS classifier is individually calibrated to map multichannel frequency bands of the SSVEP signals to right-left or up-down motion of a cursor on a computer display. The display stops moving when the user attends to a central fixation point. As for Target Practice, Think Pointer also implements wavelet-based online removal of ocular artifact; however, in Think Pointer muscle artifact is controlled via adaptive normalization of the SSVEP. Training of the classifier requires about 3 min. We have tested our system in real-time operation in three human subjects. Across subjects and sessions, control accuracy ranged from 80% to 100% correct with lags of 1-5 s for movement initiation and turning. We have also developed a realistic demonstration of our system for control of a moving map display (http://ti.arc.nasa.gov/).     

Solving the problems concerned with modernization of power unit monitoring and control systems using the distributed facilities and technologies available in the SARGON computerized automation system. Part 2: Standard solutions for problems relating to modernization of power unit monitoring and control systems

Typical problems encountered in modernizing control and monitoring systems of the main thermal power equipment used at power stations are considered, and ways of solving them through the use of distributed tools available in the SARGON computerized automation system for control of essential equipment are discussed.