1,721,975 research outputs found
Telecommunication Subsystem Design for Small Satellites
No full textSatellite design has always been considered as an extremely expensive and high risk business which not only requires vast knowledge and expertise but also extensive budget. Primarily, this concept was based on initial development and launching cost. Secondly, it was impossible to repair and substitute parts in space (this was true up to 1993: the first Hubble Space Telescope servicing mission), which made the design more tough because it required advanced fault tolerance solutions and extreme reliability. With the passage of time academic entities and small companies have also entered this market. Low cost design techniques have played an important role in the aerospace market growth over the recent years, but they can still play an important role in future developments. At present, several private companies are also providing an affordable launch services which lowers the accumulative cost. Many universities and Small and Medium Enterprises (SMEs) worldwide are trying to further reduce the satellite costs. One recent example of these efforts is the CubeSat concept: a really small satellite, built using commercial components.
This thesis work also proceeds in the same direction: the novel AraMiS (Italian acronym for Modular Architecture for Satellites) architecture and its different tiles (main subsystem) will be described. The goal of AraMiS is to progress beyond the concept of CubeSats and create a true modular architecture. The main idea of the AraMiS is modularity at mechanical, electronic and testing levels. These modules can then be assembled together to get desired requirements for the targeted mission, which allows for an effective cost sharing between multiple missions.
This thesis deals with the design and development of telecommunication subsystems for AraMiS Project and in particular for AraMiS-C1 satellite on a single CubeSat standard module called tile. The implementation of S-band transceiver over the half of telecommunication tile is not a trivial task. Several techniques were employed to make possible such a reduction interms of size, weight and power consumption while still achieving desirable performance for communication link. COTS components have been used for 1B9_CubeTCT sub modules implementation. COTS particularly for RF Front End design were selected on the basis of performance in harsh LEO environment, power losses, dimension and space occupied onboard 1B9_CubeTCT. In order to cope with such anomalies on the 1B9_CubeTCT Subsystem; different housekeeping sensors have been employed at various point of the tile.
This thesis work also elaborates on the S-band antennas design for both versions of AraMiS satellites with uses innovative technique to enhance performance while keep the size, weight and cost within acceptable margins.
The first couple of chapter presents an introduction to AraMiS project and AraMiS-C1 satellite. In chapter 3 there is a discussion of different satellite design flow configurations.
The chapter 4 comprehensively discusses the 1B9_CubeTCT, which is the CubeSat standard telecommunication tile developed for AraMiS-C1 and other CubeSat standard nano-satellites. It consists of S-band and UHF OBRF modules which provide radio communication link between satellite and the earth. It also gives an indepth explanation on the design and development of each sub-module onboard 1B9_CubeTCT that includes CubeTCT S-band transceiver, RF front end, Housekeeping Sensors, Tile Regulators, anti-latchup protection circuit and RF matching network.
Chapter 5 deals with the S-band antenna design, fabrication and testing for conventional AraMiS architecture and AraMiS C-1 satellite. It explains in detail, the design, implementation and testing of single patch antenna and AraMiS patch array that are used for AraMiS C-1 and Conventional AraMiS satellites respectively.
The chapter 6 provides link budget estimation for different scenarios, ranging for worst to the best possible case. A brief description on the Polito ground station and its key attributes is also provided. The Link budget estimates for other ground stations (GENSO members) are also performed and feasibility of developed 1B9CubeTCT hardware is verified.
Chapter 7 introduces the AraMiS protocol, developed in compliance with GENSO project which aims for providing an extended communication link for a satellite (remotely via internet), by using a GENSO member ground station around the World. A new frame format is defined which makes AraMiS satellite compatible with GENSO. Later in the chapter are presented different possible scenarios of AraMiS Protocol mechanism during normal operation case and also in case of packet loss (in both uplink and downlink communication.
Architecture level power-performance trade-offs in data-dominated designs
No full textAs the demand for feature-rich portable devices continues to increase, new techniques are needed to minimise power consumption. This thesis is concerned with the development and validation of new systematic architectural methods of determining pipeline stage insertion in data-dominated designs with the aim of reducing dynamic power consumption. The methods place special emphasis on the number of latches used in pipeline stages and voltage scaling. The first part of the thesis addresses power minimisation through systematic analysis of the number of latches in pipeline stages. A new pipeline stage insertion (PSI) method operating at the architectural level is developed which takes into account system clock period and FEs outputs and delays. A PSI algorithm based on analytical heuristic equations is formulated to ensure the successful application of this method to any given data-dominated design. The input to the algorithm is designer clock period and naively inserted pipeline stages. The output from the algorithm is a pipelined design fulfilling the timing constraint with the least dynamic power consumption. To support efficient power-performance trade-offs exploration, the algorithm was fully automated. The second part of the thesis focuses on the validation of the PSI method using two real-life case studies: triple data path floating-point adder and MPEG-1 motion compensation module. These designs are common in many portable devices and have numerous implementation challenges large number of FEs and significant power consumption. Extensive experimental results show that for the motion compensation module, the PSI is able to reduce dynamic power consumption by up-to 30% compared with other reported approaches. The final part of the thesis concentrates on voltage scaling (VS) and its impact on pipeline stages. The timing slack available in each stage is investigated, with the aim of further reducing power consumption by lowering the supply voltage. The PSI method is modified to support voltage scaling, and as a result, a new pipeline stage insertion with voltage scaling (PSI-VS) method is proposed. Experimental results show that the PSI-VS can lead to significant power saving compared with PSI without VS. For the MPEG-1 motion compensation case study, a power saving of 68% is observed. All the developed methods have linear time complexity as the number of pipeline stages increases, facilitating their application to large designs without incurring run time penalty. The results for the case studies were based on a synthesisable RTL implementation using 90nm technology together with accurate power analysis using commercial tools.</p
An insight into more factors affecting adherence to medications in the elderly
No full textSyed Maaz Tariq, Mohammad Hasan, Syed Ali Haider Department of MBBS, Jinnah Sindh Medical University, Karachi, PakistanWe read the article “Medication adherence and beliefs about medication in elderly patients living alone with chronic diseases” by Park et al1 thoroughly. They were right in stating that identification of barriers to patient adherence to a medication holds vital importance, and despite a proper plan devised by the physician, if the patient does not adhere to medication, management of a chronic illness can prove to be challenging.1 View original paper by Park et al 
Innovative Power Management, Attitude Determination and Control Tile for CubeSat Standard NanoSatellites
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
