Dual frequency receiver system for Mariner 1967 to Venus Final engineering report

Dual frequency receiver system for inclusion in Mariner 1967 spacecraft payload for use in measuring Venusian ionosphere and atmosphere by radio occultatio

Effect of time delay on feedback control of a flashing ratchet

It was recently shown that the use of feedback control can improve the performance of a flashing ratchet. We investigate the effect of a time delay in the implementation of feedback control in a closed-loop collective flashing ratchet, using Langevin dynamics simulations. Surprisingly, for a large ensemble, a well-chosen delay time improves the ratchet performance by allowing the system to synchronize into a quasi-periodic stable mode of oscillation that reproduces the optimal average velocity for a periodically flashing ratchet. For a small ensemble, on the other hand, finite delay times significantly reduce the benefit of feedback control for the time-averaged velocity, because the relevance of information decays on a time scale set by the diffusion time of the particles. Based on these results, we establish that experimental use of feedback control is realistic.Comment: 6 pages, 6 figures, to appear in Europhysics Letter

Engineering handbook on the atmospheric environmental guidelines for use in wind turbine generator development

The guidelines are given in the form of design criteria relative to wind speed, wind shear, turbulence, wind direction, ice and snow loading, and other climatological parameters which include rain, hail, thermal effects, abrasive and corrosive effects, and humidity. This report is a presentation of design criteria in an engineering format which can be directly input to wind turbine generator design computations. Guidelines are also provided for developing specialized wind turbine generators or for designing wind turbine generators which are to be used in a special region of the United States

Children's brain injury : a postal follow-up of 525 children from one health region in the UK

Primary objectives: to follow-up a population of children admitted to one Hospital Trust with traumatic brain injury (TBI), and compare outcomes following mild TBI with outcomes following moderate or severe TBI. Research design: population-based postal questionnaire survey. Methods and procedures: questionnaires were mailed to parents of all 974 surviving children on a register of paediatric TBI admissions, 525 completed questionnaires were returned (56.2%). Most children (419) had suffered mild TBI, 57 moderate, and 49 severe. Main outcomes and results: Thirty percent of parents received no information on post-injury symptoms, and clinical follow-up was limited. Statistically significant differences were observed between mild and moderate/severe groups for cognitive, social, emotional, and mobility problems. Nevertheless, approximately 20% of the mild group suffered from poor concentration, personality change, and educational problems post-injury. Few schools (20%) made special provision for children returning after injury. Conclusions: children can have long lasting and wide ranging sequelae following TBI. Information should be routinely given to parents and schools after brain injury

Outcomes following childhood head injury : a population study

Objectives: To identify outcomes following head injury (HI) amongst a population of children admitted to one hospital centre and compare outcomes between different severity groups. Methods:A postal follow-up of children admitted with HI to one NHS Trust, between 1992-1998, was carried out. Children were aged 5-15 years at injury (mean 9.8), followed-up at a mean of 2.2 years post-injury. Parents of 526 injured children (419 mild, 58 moderate, 49 severe) and 45 controls completed questionnaires. Outcomes were assessed using the King’s Outcome Scale for Childhood Head Injury (KOSCHI). Results:Frequent behavioural, emotional, memory and attentional problems were reported by one third of the severe group, one quarter of the moderate, and 10-18% of the mild. Personality change since HI was reported for 148 children (28%) (21% mild HI, 46% moderate, 69% severe). There was a significant relationship between injury severity and KOSCHI outcomes. Following the HI, 252(48%) had moderate disability (43% mild HI, 64% moderate, 69% severe), 270(51%) made a good recovery (57% mild HI, 36% moderate, 22% severe). There was a significant association between social deprivation and poor outcome (p=0.002). Only 30%(158) of children received hospital follow-up after the HI. All children with severe disability received appropriate follow-up, but 64% of children with moderate disability received none. No evidence was found to suggest a threshold of injury severity below which the risk of late sequelae could be safely discounted. Conclusions:Children admitted with mild HI may be at risk of poor outcomes, but often do not receive routine hospital follow-up. A postal questionnaire combined with the KOSCHI to assess outcomes after HI may be used to identify children who would benefit from clinical assessment. Further research is needed to identify factors which place children with mild HI at risk of late morbidity

Parental stress and burden following traumatic brain injury amongst children and adolescents

Primary objectives: to assess parental stress following paediatric traumatic brain injury (TBI) and examine the relationship between self-reported problems and parental stress and general health. Research design: controlled interview study Methods and procedures: Parents of ninety-seven children admitted with a TBI (49 mild, 19 moderate, 29 severe) were identified from a case register of all paediatric admissions from 1992-1998. Parents of 31 uninjured children acted as controls. Structured interviews were carried out with families, and parents assessed on the Parenting Stress Index (PSI/SF) and General Health Questionnaire (GHQ-12) at recruitment, and repeated 12 months later. Main outcomes and results: regardless of injury severity, parents of injured children suffered greater stress than control parents as measured by the PSI/SF (p = 0.001). There was a highly significant relationship between number of problems reported and level of parental stress (p = 0.001). Financial burden was related to severity of TBI. Conclusions: improved information, follow-up, and support is likely to reduce parental stress and family burden

A New Linear Inductive Voltage Adder Driver for the Saturn Accelerator

Saturn is a dual-purpose accelerator. It can be operated as a large-area flash x-ray source for simulation testing or as a Z-pinch driver especially for K-line x-ray production. In the first mode, the accelerator is fitted with three concentric-ring 2-MV electron diodes, while in the Z-pinch mode the current of all the modules is combined via a post-hole convolute arrangement and driven through a cylindrical array of very fine wires. We present here a point design for a new Saturn class driver based on a number of linear inductive voltage adders connected in parallel. A technology recently implemented at the Institute of High Current Electronics in Tomsk (Russia) is being utilized[1]. In the present design we eliminate Marx generators and pulse-forming networks. Each inductive voltage adder cavity is directly fed by a number of fast 100-kV small-size capacitors arranged in a circular array around each accelerating gap. The number of capacitors connected in parallel to each cavity defines the total maximum current. By selecting low inductance switches, voltage pulses as short as 30-50-ns FWHM can be directly achieved.Comment: 3 pages, 4 figures. This paper is submitted for the 20th Linear Accelerator Conference LINAC2000, Monterey, C

Single Z' production at CLIC based on e^- gamma collisions

We analyze the potential of CLIC based on e- gamma collisions to search for new $Z'$ gauge boson. Single Z' production at e-gamma colliders in two SU(3)_C X SU(3)_L X U(1)_N models: the minimal model and the model with right-handed (RH) neutrinos is studied in detail. Results show that new Z' gauge bosons can be observed at the CLIC, and the cross sections in the model with RH neutrinos are bigger than those in the minimal one.Comment: 11 pages, 4 figures, To appear in JET

A quantitative evaluation of metallic conduction in conjugated polymers

As the periodicity in crystalline materials creates the optimal condition for electronic delocalization, one might expect that in partially crystalline conjugated polymers delocalization is impeded by intergrain transport. However, for the best conducting polymers this presumption fails. Delocalization is obstructed by interchain rather than intergrain charge transfer and we propose a model of weakly coupled disordered chains to describe the physics near the metal-insulator transition. Our quantitative calculations match the outcome of recent broad-band optical experiments and provide a consistent explanation of metallic conduction in polymers.Comment: 4 pages incl. 3 figure

The interpretation of the field angle dependence of the critical current in defect-engineered superconductors

We apply the vortex path model of critical currents to a comprehensive analysis of contemporary data on defect-engineered superconductors, showing that it provides a consistent and detailed interpretation of the experimental data for a diverse range of materials. We address the question of whether electron mass anisotropy plays a role of any consequence in determining the form of this data and conclude that it does not. By abandoning this false interpretation of the data, we are able to make significant progress in understanding the real origin of the observed behavior. In particular, we are able to explain a number of common features in the data including shoulders at intermediate angles, a uniform response over a wide angular range and the greater discrimination between individual defect populations at higher fields. We also correct several misconceptions including the idea that a peak in the angular dependence of the critical current is a necessary signature of strong correlated pinning, and conversely that the existence of such a peak implies the existence of correlated pinning aligned to the particular direction. The consistency of the vortex path model with the principle of maximum entropy is introduced.Comment: 14 pages, 7 figure