Positively Verifying Mating of Previously Unverifiable Flight Connectors

Current practice is to uniquely key the connectors, which, when mated, could not be verified by ground tests such as those used in explosive or non-explosive initiators and pyro valves. However, this practice does not assure 100-percent correct mating. This problem could be overcome by the following approach. Errors in mating of interchangeable connectors can result in degraded or failed space mission. Mating of all flight connectors considered not verifiable via ground tests can be verified electrically by the following approach. It requires two additional wires going through the connector of interest, a few resistors, and a voltage source. The test-point voltage V(sub tp) when the connector is not mated will be the same as the input voltage, which gets attenuated by the resistor R(sub 1) when the female (F) and male (M) connectors are mated correctly and properly. The voltage at the test point will be a function of R(sub 1) and R(sub 2). Monitoring of the test point could be done on ground support equipment (GSE) only, or it can be a telemetry point. For implementation on multiple connector pairs, a different value for R(sub 1) or R(sub 2) or both can be selected for each pair of connectors that would result in a unique test point voltage for each connector pair. Each test point voltage is unique, and correct test point voltage is read only when the correct pair is mated correctly together. Thus, this design approach can be used to verify positively the correct mating of the connector pairs. This design approach can be applied to any number of connectors on the flight vehicle

State-space average modelling of converters with parasitics and storage-time modulation

The State-Space Averaging approach to modelling switching converter power stages is used to extend the analytical descriptions of the buck, boost, buck-boost, and Cuk converters to included the effects of all parasitic resistances and transistor storage-time modulation. The analysis reveals for the first time a new and unexpected term in the line to ouput response of the Cuk converter. The new term contains a right half-plane zero produced by the energy transfer capacitance in combination with the duty-ratio-weighted sum of the on-resistances of the transistor and diode plus a non-dissipative ac resistance term due to transistor storage-time modulation. The conventional circuit model of the converter is modified to include the effects of the new term. The improved model permits an eas physical interpretation of the new zero, which has been observed only the in Cuk converter. An extended analysis of storage-time modulation in bipolar transistor switches shows that the ac small-signal performance of a switching converter is highly dependent on the nature of the base drive. It is demonstrated that storage-time modulation in conjunction with a proportional base drive can produce instability in switching converters, even open-loop. The results of these analyses are verified experimentally and their impacts on practical converters are discussed

Review of the radiographic modalities used during dental implant therapy - A narrative

The introduction of digital x-ray receivers which replaced conventional films was a significant radiographic development that is commonly used in daily dental practice. Dental implant therapy (DIT) is a sought after dental therapeutic intervention and dental radiography is an essential component contributing to the success of treatment. Dental radiographs taken in daily practice are generally conventional two-dimensional images and/or three-dimensional images. Ideally, the choice of radiographic technique should be determined after a thorough clinical examination and comprehensive consideration of the advantages, indications, and drawbacks. Digital three-dimensional modalities that have emerged over the last decade have been incorporated into DIT with the assumption that treatment outcomes will be improved. These modalities are constantly being reassessed and improved but there is a paucity of published information regarding the assessment of variables such as dosages and dimensional accuracy, suggesting that further research in these matters is necessary. This is crucial in order to obtain evidence-based information that may influence future radiographic practices. In this narrative, the authors present the most commonly used dental radiographic modalities currently used in DIT

Physical Activity Sensing via Stand-Alone WiFi Device

WiFi signals for physical activity sensing shows promising potential for many healthcare applications due to its potential for recognising various everyday activities, non-invasive nature and low intrusion on privacy. Traditionally, WiFi-based sensing uses the Channel State Information (CSI) from an offthe- shelf WiFi Access Point (AP) which transmits signals that have high pulse repetition frequencies. However, when there are no users on the communication network only beacon signals are transmitted from the WiFi AP which significantly deteriorates the sensitivity and specificity of such systems. Surprisingly WiFi based sensing under these conditions have received little attention given that WiFi APs are frequently in idle state. This paper presents a practical system based on passive radar technique which does not require any special setup or preset firmware and able to work with any commercial WiFi device. To cope with the low density of beacon signal, a modified Cross Ambiguity Function (CAF) has been proposed to reduce redundant samples in the recorded. In addition, an external device has been developed to send WiFi probe request signals and stimulate an idle AP to transmit WiFi probe responses thus generate usable transmission signals for sensing applications without the need to authenticate and join the network. Experimental results prove that proposed concept can significantly improve activity detection and is an ideal candidate for future healthcare and security applications

Causal Factors of Breeding Success and Frequency in Threatened Grassland Birds on the Ingula Nature Reserve, South Africa

The high-altitude grasslands covering the eastern escarpment of South Africa is one of the country’s most valuable habitats for biodiversity, livestock and water production. The habitat hosts several threatened bird species including endangered species such as the Rudd\u27s Lark (Heteromirafra ruddi) and Grey Crowned Crane (Balearica regulorum), and vulnerable species such as the Blue Crane (Grus paradisea), Wattled Crane (Bugeranus carunculatus), Southern Bald Ibis (Geronticus calvus), and Yellow-breasted Pipit (Anthus chloris). Avian research and monitoring have been ongoing within the recently declared Ingula Nature Reserve for more than 15 years as part of the activities of the Ingula Partnership - a partnership between BirdLife South Africa, Eskom Holdings SOC Ltd and the Middelpunt Wetland Trust - with the objective of effectively conserving birds and their habitat surrounding the Ingula Pumped Storage Scheme development. Avian monitoring on Ingula refocused in 2014 to confirm the presence of threatened species on site, followed by the determination of the breeding status of these species. An initiative was then launched to assess the breeding frequency and success of each identified species. Breeding monitoring for 13 out of the 24 occurring threatened species commenced in 2014 and was conducted for five consecutive seasons. Breeding success per season was measured in relation to the grassland management regime of that season (including both fire and grazing), as well as weather data, adjusting for dry and wet seasons. Results confirm that various grassland management regimes directly influenced the initiation of breeding activities and density of several of the species studied, while others’ breeding success and frequency were more dependent on macro-weather patterns (including climate change) and fire frequency and timing. These results have direct implications for the management of highland grasslands and associated species in the given region