Voltage-time characteristics for steep-front impulse voltages ofparticle-contaminated spacers in SF6 gas-insulated switchgear

The voltage-time characteristics of spacer surfaces for steep-front impulse waves are investigated under a particle-contaminated condition in SF₆ gas. The characteristics are measured as a function of particle length, particle position, and space shapes. Flashover voltages monotonically increase in the submicrosecond region as time to flashover is shorter, and are a minimum in the 1 μs region. Applicability of the equal voltage-time area criterion for estimating the voltage-time characteristics is discussed and the estimation is clarified. Moreover, it is demonstrated that an optimized spacer with ribs greatly improves flashover voltages in the submicrosecond region as well as in the 1 μs and power frequency region     

Screening demand-side management programs with a value-based test

A value-based test is presented for economic screening of electric utility demand-side management (DSM) programs. The widely used least cost test is valid if the programs do not alter the amount or value of energy services provided to customers. But, in general, DSM programs have such effects and, as a result, the value consumers receive is changed. A more general economic efficiency test, the most value test, provides a practical method for considering the effects of DSM on customer value. The version presented allows for multiple load periods and can account for rate impacts on several customer classes. Four typical DSM programs are evaluated as illustrations     

Medical technology development: limiting regulation

The medical technology industry is one of the most innovative sectors of the US economy. The paper considers how the US federal government, in a variety of roles as promoter, protector and payer, is involved in every stage of the innovative process for medical technology. It discusses the influence of government policies on medical innovation     

Diarrhea in young children associated with Escherichia coli non-O157 organisms that produce Shiga-like toxin

The aim of this study was to evaluate the way in which short-term protection declines and is eventually lost in preconditioning and to determine the efficacy of a second preconditioning at various reperfusion intervals. Male rabbits were divided into six groups. Forty-five minutes (sustained) ischemia followed by 120 minutes reperfusion was applied 60, 65, 70, 75, and 80 minutes after a 5 minute preconditioning (groups A, B, C, D, and E) and in a control group (F) after no preconditioning. The infarct to risk ratio (I/R) was 38.3 +/- 3.5% in group A, 46.0 +/- 7.8% in B, 61.6 +/- 9.7% in C, 68.1 +/- 4.2% in D, 64.5 +/- 7.8% in E, and 61.0 +/- 7.7% in F. Group A had a smaller I/R compared with groups C, D, E, and F (p < 0.05). In another series, groups G, H, and I were exposed to two 5-minute preconditioning stimuli, separated, respectively, by 45, 60, and 75 minutes of reperfusion; 10 minutes after the last preconditioning, the animals were exposed to 45-minutes ischemia and 120 minutes reperfusion. Groups A and D (with the smaller and higher I/R ratio) were also incorporated into this protocol in order to compare the effect of the additional preconditioning with the single one. The I/R ratio was 25.4 +/- 8.5% in group G, 22.8 +/- 7.0% in group H, and 14.7 +/- 4.0% in group I (p = NS). Group D showed a higher I/R compared with groups G, A, and H (p < 0.01), and group I had a smaller I/R compared with groups A (p < 0.01) and D (p < 0.001). Cardioprotection after a first preconditioning declines gradually and is eventually lost. An additional preconditioning is always effective, and the longer the interval from the first preconditioning, the more potent is the effect.     

Neurocontrol for lateral vehicle guidance

A solution to autonomous lateral vehicle guidance using a neurocontroller that can learn from measured human-driving data without knowledge of the physical car parameters is discussed. Simulations and practical tests confirm that a small-size feedforward autonomous neural network (21 neurons) can learn to steer a vehicle at high speeds only from looking at human-driving examples. In this way, the network learns the total closed-loop behavior, including the nonlinear dynamics of the vehicle and the driver's individual driving style. The main result of practical investigations is that the neutral controller trained on human-driving examples exhibits an aperiodic behavior that does not vanish at higher speeds (tests performed up to 130 km/h) and produces fewer lateral deviations than the linear state controller