Velocity limiting safety system Patent

Velocity limiting safety system for motor driven research vehicl

A comparison of Manchester symbol tracking loops for block 5 applications

The linearized tracking errors of three Manchester (biphase coded) symbol tracking loops are compared to determine which is appropriate for Block 5 receiver applications. The first is a nonreturn to zero (NRZ) symbol synchronizer loop operating at twice the symbol rate (NRZ x 2) so that it operates on half symbols. The second near optimally processes the mid-symbol transitions and ignores the between symbol transitions. In the third configuration, the first two approaches are combined as a hybrid to produce the best performance. Although this hybrid loop is the best at low symbol signal to noise ratios (SNRs), it has about the same performance as the NRZ x 2 loop at higher SNRs (greater than 0-dB E sub s/N sub 0). Based on this analysis, it is tentatively recommended that the hybrid loop be implemented for Manchester data in the Block 5 receiver. However, the high data rate case and the hardware implications of each implementation must be understood and analyzed before the hybrid loop is recommended unconditionally

Critique of a Hughes shuttle Ku-band data sampler/bit synchronizer

An alternative bit synchronizer proposed for shuttle was analyzed in a noise-free environment by considering the basic operation of the loop via timing diagrams and by linearizing the bit synchronizer as an equivalent, continuous, phased-lock loop (PLL). The loop is composed of a high-frequency phase-frequency detector which is capable of detecting both phase and frequency errors and is used to track the clock, and a bit transition detector which attempts to track the transitions of the data bits. It was determined that the basic approach was a good design which, with proper implementation of the accumulator, up/down counter and logic should provide accurate mid-bit sampling with symmetric bits. However, when bit asymmetry occurs, the bit synchronizer can lock up with a large timing error, yet be quasi-stable (timing will not change unless the clock and bit sequence drift). This will result in incorrectly detecting some bits

Critique of the Hughes Aircraft shuttle Ku band leading edge bit synchronizer

A bit synchronizer is analyzed via timing diagrams in a noise-free environment. It is believed that this new bit synchronizer will track the rising edge of the data bits with 25% asymmetry and up to a 90 deg phase shift between the received clock and data bit timing. In addition, the data bits will be demodulated correctly. It is not true that phase shifts larger than 90 deg will necessarily be corrected by this bit synchronizer. However, the specifications currently require the loop to operate over only a + or - 75 deg phase shift between the received data stream leading edges and the bit synchronizer leading edges; consequently, there should be no problem

Isospin quantum number of D_{s0}^+(2317)

The D_s^+ pi^0 and D_s^{*+} gamma decays of the D_{s0}^+(2317) are studied by assigning it to various charmed strange scalar mesons. As a result, it is found that its assignment to an iso-triplet four-quark meson is favored by the severest experimental constraint on the ratio of the rates for these decays, while assigning it to an I=0 state (a four-quark or a conventional {c\bar{s}}) is inconsistent with this constraint.Comment: 6 pages, no figure, RevTeX4, references added and clarification of tex

Crossflow vorticity sensor

A crossflow vorticity sensor for the detection of crossflow vorticity characteristics is described. The sensor is comprised of crossflow sensors which are noninvasively adhered to a swept wing laminar surface either singularly, in multi-element strips, in polar patterns, or in orthogonal patterns. These crossflow sensors are comprised of hot-film sensor elements which operate as a constant temperature anemometer circuit to detect heat transfer rate changes. Accordingly, crossflow vorticity characteristics are determined via cross-correlation. In addition, the crossflow sensors have a thickness which does not exceed a maximum value h in order to avoid contamination of downstream crossflow sensors

A study of the education welfare officer working to improve school attendance

Truancy is currently (DfElS, 2001) right at the top of the government's list of educational issues to be addressed. On any one day, 400,000 pupils who should be in school are absent.That is 5% of the school population. The education welfare officer (EWO) has a very specific role in supporting a school to maintain high levels of attendance but these figures indicate there is clearly a need to examine ways in which different Education Welfare Services (EWSs) and their officers tackle school non-attendance. The research documented in this study set out to examine the working practice of EWOs engaged to improve school attendance. The methodology employed to do trIis comprised of a postal questionnaire, 16 in-depth interviews over a six-month period and a two-year action research investigation in one 'failing' secondary school. The lead methodological approach has been the interview technique that has enabled the researcher to pursue the collection of data as part of a social process. The research strategy involved a survey of 90 EWOs and from this sample 16 volunteers were sought to take part in the next phase of the research. The research findings strongly suggest the status and position of the EWS within education hierarchy is not at all clear. Issues regarding practitioner's title, training, supervision, skills required, qualifications and interventions have all been discussed leading to a conclusion that the EWS needs to be professionalised, the role of the EWO needs to be specialised and basic administrative tasks need to be undertaken by an administrator. The findings from this study are entirely in keeping with evidence from other research in that there are no national guidelines; staff tend to disagree with the fundamentals of their job; some staff do not work in partnership with schools; others try to change what happens in a school without the position and authority to succeed. However, this investigation has taken matters a stage further by extending this knowledge through interviews with EWOs and managers to develop a model of effective practice that has been tried and tested