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Triple Modular Redundancy (TMR) is a common reliability technique for mitigating single event upsets (SEUs) in FPGA designs operating in radiation environments. For FPGA systems that employ configuration scrubbing, majority voters are needed in all feedback paths to ensure proper synchronization between the TMR replicates. Synchronization voters, however, consume additional resources and impact system timing. This work introduces and contrasts seven algorithms for inserting synchronization voters while automatically performing TMR. The area cost and timing impact of each algorithm on a number of circuit benchmarks is reported. The work demonstrates that one of the algorithms provides the best overall timing performance results with an average 8.5% increase in critical path length over a triplicated design without voters and a 29.6% area increase. Another algorithm provides far better area results (an average 3.4% area increase over a triplicated design without voters) at a slightly higher timing cost (an average 14.9% increase in critical path length over a triplicated design without voters). In addition, this work demonstrates that restricting synchronization voter locations to flip-flop output nets is an effective heuristic for minimizing the timing performance impact of synchronization voter insertion.

Miscommunication between controllers and pilots, potentially resulting from a high pilot cognitive load, has been a causal or contributing factor in a large number of aviation accidents. In this context, failure to communicate can be attributed, among other factors, to an inadequate human-system interface design, the related high cognitive load imposed on the pilot, and poor performance reflected by a higher error rate. To date, voice radio remains in service without any means for managing pilot cognitive load by design (as opposed to training or procedures). Such an oversight is what prompted this dissertation. The goals of this study were (a) to investigate the utility of a voice-to-text transcription (V-T-T) of ATC clearances in managing pilot's cognitive load during controller-pilot communications within the context of a modern flight deck environment, and (b) to validate whether a model of variable relationships which is generated in the domain of learning and instruction would "transfer", and to what extend, to an operational domain. First, within the theoretical framework built for this dissertation, all the pertaining factors were analyzed. Second, by using the process of synthesis, and based on guidelines generated from that theoretical framework, a redundant verbal display of ATC clearances (i.e., a V-T-T) was constructed. Third, the synthesized device was empirically examined. Thirty four pilots participated in the study – seventeen pilots with 100-250 total flight hours and seventeen with > 500 total flight hours. All participants had flown within sixty days prior to attending the study. The experiment was conducted one pilot at a time in 2.5-hour blocks. A 2 Verbal Display Redundancy (no-redundancy and redundancy) X 2 Verbal Input Complexity (low and high) X 2 Level of Expertise (novices and experts) mixed-model design was used for the study with 5 IFR clearances in each Redundancy X Complexity condition. The results showed that the amounts of iii reduction of cognitive load and improvement of performance, when verbal display redundancy was provided, were in the range of about 20%. These results indicated that V-T-T is a device which has a tremendous potential to serve as (a) a pilot memory aid, (b) a way to verify a clearance has been captured correctly without having to make a "Say again" call, and (c) to ultimately improve the margin of safety by reducing the propensity for human error for the majority of pilot populations including those with English as a second language. Fourth, the results from the validation of theoretical models "transfer" showed that although cognitive load remained as a significant predictor of performance, both complexity and redundancy also had unique significant effects on performance. Furthermore, these results indicated that the relationship between these variables was not as "clear-cut" in the operational domain investigated here as the models from the domain of learning and instruction suggested. Until further research is conducted, (a) to investigate how changes in the operational task settings via adding additional coding (e.g., permanent record of clearances which can serve as both a memory aid and a way to verify a clearance is captured correctly) affect performance through mechanisms other than cognitive load; and (b) unless the theoretical models are modified to reflect how changes in the input variables impact the outcome in a variety of ways; a degree of prudence should be exercised when the results from the model "transfer" validation are applied to operational environments similar to the one investigated in this dissertation research.

Herbivorous fishes include a diverse assemblage of species that target primarily benthic autotrophs. This is perhaps one of the most well-studied groups of coral reef fishes, often reputed to be key components of coral reef communities, contributing to coral reef health in numerous ways. Through their feeding ecology and benthic interactions, they help mediate algae-coral interactions which can allow for improved coral survival and health. Despite the wealth of literature documenting the prominent roles of these fishes in coral reef ecosystems, studies from the Red Sea are surprisingly lacking. The Red Sea is a marginal reef environment, with a host of unique environmental and biological characteristics making it a unique environment where dynamics of herbivory may differ. This dissertation aims to fill key gaps in our knowledge of herbivorous fishes through the study of their distribution and trophic ecology. Herein, I describe habitat-specific partitioning of Red Sea herbivorous fish assemblages, discovering higher diversity and abundance found in reefs closer to shower, dissimilar to findings from other regions. Cross-shelf variation in assemblage structure seems to be quite robust through time, indicating short-term stability in herbivore assemblages. Through the use of stomach contents and stable isotope analyses, I then investigate the trophic ecology of browsing herbivores across the same shelf-gradient. I found higher trophic redundancy on nearshore reefs through time, with increased variation in diet and high levels of complementarity on offshore reefs where macroalgae are scarce. Stable isotope analyses of both liver and muscle revealed the stability of this resource partitioning through time, demonstrating for the first-time temporal stability of resource partitioning within this group. This dissertation broadens our knowledge of herbivorous fishes, filling important gaps. It offers new insight into the role of habitat in structuring trophic ecology and how flexible the diets of browsing species can be. Together, this information creates a foundation where improved knowledge of herbivorous fish ecology could be incorporated into future management plans of ongoing giga projects within the Kingdom. Incorporating herbivores into these plans could allow for increased resiliency for Red Sea coral reefs in the face of future development and shifting climatology.

Indiana University-Purdue University Indianapolis (IUPUI) / In this dissertation, a beyond-CMOS approach to Static Random Access Memory (SRAM) design is investigated using exploratory transistors including Tunnel Field Effect Transistor (TFET), Carbon Nanotube Field Effect Transistor (CNFET) and Graphene NanoRibbon Field Effect Transistor (GNRFET). A Figure-of-Merit (FOM) based comparison of 6-transistor (6T) and a modified 8-transistor (8T) single-port SRAMs designed using exploratory devices, and contemporary devices such as a FinFET and a CMOS process, highlighted the performance benefits of GNRFETs and power benefits of TFETs. The results obtained from the this work show that GNRFET-based SRAM have very high performance with a worst-case memory access time of 27.7 ps for a 16x4-bit 4-word array of 256-bitcells. CNFET-based SRAM bitcell consume the lowest average power during read/write simulations at 3.84 uW, while TFET-based SRAM bitcell show the best overall average and static power consumption at 4.79 uW and 57.8 pW respectively. A comparison of these exploratory devices with FinFET and planar CMOS showed that FinFET-based SRAM bitcell consumed the lowest static power at 39.8 pW and CMOS-based SRAM had the best read, write and hold static noise margins at 201 mV, 438 mV and 413 mV respectively. Further, the modification of 8T-SRAMs via dual wordlines for individually controlling read and write operations for uni-directional transistors TFET and CNFET show improvement in read static noise margin (RSNM). In dual wordline CNFET 8T-SRAM, an RSNM improvement of approximately 23.6x from 6 mV to 142 mV was observed by suppressing the read wordline (RWL) from a nominal supply of 0.71 V down to 0.61 V. In dual wordline TFET 8T-SRAM, an RSNM improvement of approximately 16.2x from 5 mV to 81 mV was observed by suppressing the RWL from a nominal supply of 0.6 V down to 0.3 V. Next, the dissertation explores whether the robustness of SRAM arrays can be improved. Specifically, the robustness related to noise margin during the write operation was investigated by implementing a negative bitline (NBL) voltage scheme. NBL improves the write static noise margin (WSNM) of the SRAM bitcells in the row of the array to which the data is written during a write operation. However, this may cause degraded hold static noise margin (HSNM) of un-accessed cells in the array. Applying a negative wordline voltage (NWL) on un-accessed cells during NBL shows that the NWL can counter the degraded HSNM of un-accessed cells due to NBL. The scheme, titled as NBLWL, also allows the supply of a lower NBL, resulting in higher WSNM and write-ability benefits of accessed row. By applying a complementary negative wordline voltage to counter the half-select condition in columns, the WSNM of cells in accessed rows was boosted by 10.9% when compared to a work where no negative bitline was applied. In addition, the HSNM of un-accessed cells remain the same as in the case where no negative bitline was implemented. Essentially, a 10.9% boost in WSNM without any degradation of HSNM in un-accessed cells is observed. The dissertation also focuses on the impact of process-related variations in SRAM arrays to correlate and characterize silicon data to simulation data. This can help designers remove pessimistic margins that are placed on critical signals to account for expected process variation. Removing these pessimistic margins on critical data paths that dictate the memory access time results in performance benefits for the SRAM array. This is achieved via an in-situ silicon monitor titled SRAM process and ageing sensor (SPAS), which can be used for silicon and ageing characterization, and silicon debug. The SPAS scheme is based on a process variation tolerant technique called RAZOR that compares the data arriving on the output of the sense amplifiers during the read operation. This scheme can estimate the impact of process variation and ageing induced slow-down on critical path during read operation of an array with high accuracy. The estimation accuracy in a commercially available 65nm CMOS technology for a 16x16 array at TT, and global SS and FF corners at nominal supply and testing temperature were found to be 99.2%, 94.9% and 96.5% respectively. Finally, redundant columns, an architectural-level scheme for tolerating failing SRAM bitcells in arrays without compromising performance and yield, is studied. Redundant columns are extra columns that are programmed when bitcells in the regular columns of an array are slower or have higher leakage than expected post-silicon. The regular columns are often permanently disabled and remain unused for the chip lifetime once redundant columns are enabled. In the SRRC scheme proposed in this thesis, the regular columns are only temporarily disabled, and re-used at a later time in chip life cycle once the previously awakened redundant columns become slower than the disabled regular columns. Essentially, the scheme can identify and temporarily disable the slowest column in an array until other mitigating factors slow down active columns. This allows the array to operate at a memory access time closer to the target access time regardless of other mitigating factors slowing down bitcells in arrays during chip life cycle. An approximate 76.4% reduction in memory access time was observed from a 16x16 array from simulations in a commercially available 65nm CMOS technology with respect to a work where no redundancy was employed.

Arbetet beskrivet i denna rapport har utförts på AstraZeneca AB:sproduktionsanläggning i Gärtuna, Södertälje. Företaget vill öka redundansen på sin tryckluftsanläggning för att höja driftsäkerheten i produktionen. I sin tillverkning av läkemedel används stora mängder tryckluft för bland annat produktionsprocesser. Vid haveri av till exempel en kompressor riskerar produktionen att bli stillastående tills dess att problemet åtgärdats eller att en hyrd kompressor har kopplats in. Produktionsbortfall är en av de största indirekta kostnaderna ett tillverkningsföretag kan råka ut för. Då AstraZeneca tillverkar läkemedel uppstår även konsekvenser för samhället då viktiga läkemedel inte når ut till kunden. Det är därför av stor vikt att de stöttande systemen, som till exempel tryckluftssystemet, designas med inbyggd redundans för att klara av haverier eller läckage. Målet med projektet har varit att föreslå en lösning för att sammankoppla ett mindre tryckluftssystem med det centrala systemet för att öka redundansen på anläggningen. Det mindre systemet förser produktionen i byggnad B833 med tryckluft. Systemets tryck i denna byggnad är för närvarande högre än trycket i det centrala systemet och kan därför inte kopplas samman. Det har genomförts försök att sänka trycket i B833, men tyvärr har det lägre trycket lett till att problem i produktionen uppstått. I projektets genomförande har orsaken till att problemen uppstår undersökts genom att kartlägga alla brukare av tryckluft i byggnaden, analysera produktions- och tryckluftsloggar samt kartläggning av rörsystemet och dess dimensioner. Teori har insamlats genom litteratursökning och intervjuer med personal från produktion och driftorganisation. Grundorsaksanalys har genomförts med verktygen Ishikawa och 5-varför metoden. Resultatet verifierades med en FTA, felträdsanalys. För att kunna sänka trycket i B833 till 6,5 bar krävs det att vissa ledningar ersätts med rör med större dimensioner. På vissa delar av rörnätet uppstår ett för högt tryckfall på grund av för små dimensioner. 6,5 bar vid kompressorn reduceras till 3,3 bar längst ut i systemet på plan 3, vid normalflöde. Många maskiner i byggnaden fungerar inte med ett sådant lågt tryck. Lösningen består av att byta ut 4 stycken rörledningar och öka dessa från 25, 20, 20, och 15 mm till 50, 40, 40 och 32 mm respektive. Dessa ledningar befinner sig både på plan 1, plan 3 och i schaktet mellan våningsplanen. Ökade dimensioner på dessa rör kommer att möjliggöra en trycksänkning i B833 och sammankopplingen med det centrala systemet kan driftsättas. Detta leder till ökad redundans och högre driftsäkerhet, både i B833 så väl som i hela anläggningen. / The project summarized in this report was executed at AstraZeneca’s production facilityin Gärtuna, Södertälje. The company wants to increase redundancy in their compressed air system in order to achieve higher operational reliability. In their manufacture of pharmaceuticals, large amounts of compressed air are used for, among other things, production processes. In case of a breakdown of, for example, a compressor, the production is at risk of becoming stagnant until the problem has been rectified or arental compressor has been connected to the system. Production loss is one of the largest indirect costs for a manufacturing company. And perhaps more importantly, medicines will not reach the customer in time. It is therefore of great importance that the supporting systems, such as the compressed air system, are designed with built-in redundancy to cope with breakdowns or leaks. The goal of the project has been to find a solution to connect a smaller compressed air system with the central system to increase the redundancy at the facility. The smaller system supplies the production in building B833 with compressed air. The pressure of the system in this building is currently higher than the pressure in the central system, and therefore they cannot be connected. Attempts have been made to reduce the pressure in B833, which has led to problems in the production. In this project, the cause of the problems that occur when pressure is reduced has been investigated by mapping all users of compressed air in the building, analyzing logs from production and compressed air systems, and mapping the pipe system and its dimensions. The theory necessary for solving the task has been gathered through a literature study as well as interviewing personnel from the production and the operating organization. Root cause analysis has been performed, using the tools Ishikawa and 5-why-method. The results were verified with a FTA, Fault tree analysis. To be able to decrease the pressure in B833 to 6,5 bar, it will require the distribution pipes to be replaced with pipes in larger dimensions. In some parts of the piping system, the pressure drop will be too high because of too small dimensions. 6,5 bar from the compressor is reduced to 3,3 bar at the far end of the system on floor level 3, while the consumption is at a normal level. Many of the machines will not work on that low level of pressure. The solution is to change the dimensions of four pipes from 25, 20, 20 and 15 mm to 50, 40, 40 and 32 mm respectively. The pipes considered are located at level 1, level 3 and in a shaft located between these levels. With larger dimensions, it will be possible to reduce the pressure, and this will enable the pipes that are connected to the central system to be taken into operation. This will lead to an increase in redundancy and reliability in B833 as well as the whole production site.

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<p>Have a nice day :)</p> / <p>This thesis presents a unified framework for coordination and control of human-in-the-loop asymmetric semi-autonomous robotic systems. It introduces a highly general teleoperation system configuration involving any number of operators, haptic interfaces, and robots with possibly different degrees of mobility. The proposed framework allows for mixed teleoperation/autonomous control of user-defined subtasks by establishing position/force tracking as well as kinematic constraints among relevant <em>teleoperation control frames</em>. Three layers of velocity-based autonomous subtasks at different priority levels with respect to human teleoperation are integrated into the control system design. The control strategy is hierarchical comprising of a high-level teleoperation coordinating controller and low-level joint velocity controllers. A Lyapunov-based adaptive joint-space velocity controller is presented as one candidate for the low-level control. The approach utilizes idempotent, generalized pseudoinverse and weighting matrices, as well as a soft-switching rank changing algorithm in order to achieve new performance objectives that are defined for such asymmetric semi-autonomous teleoperation systems. A detailed analysis of system performance and stability is presented. The proposed framework constitutes the most general formulation and solution for the teleoperation control problem to date. It yields many interesting and useful system configurations never studied before, in addition to those already considered in the literature. In particular, seven system configurations arising from the proposed teleoperation architecture are analyzed and studied in detail. Experimental results are provided to demonstrate the desired system response in these configurations. Moreover, human factors experiments are carried out to assess operator(s) performance in maneuverability and grasping under various teleoperation system configurations. The results show statistically significant performance improvement in teleoperation of a nonholonomic mobile robot and telegrasping using a twin-armed manipulator.</p> / Doctor of Philosophy (PhD)

<p>This thesis investigates two significant problems in control and coordination of complex teleoperation systems as they relate to the operation of a mobile robotic manipulator. The first part of the thesis focuses on the design of a control framework to resolve kinematic redundancy in teleoperation of a mobile robotic manipulator. Apart from the redundancy, workspace considerations for the operator and robot and asymmetry of master and slave systems pose significant design challenges in such telerobotic systems . The second part of the thesis considers psychophysical aspects of teleoperation from the operator's perspective. This part presents a method for automatic {\em optimal} positioning of a single camera for a remotely navigated mobile robot in systems with a controllable camera platform. In each part, a constrained optimization problem is formulated and solved in real time. The solution of these optimization problems are integrated seamlessly into the teleoperation control framework in order to assist the operator in accomplishing the main task. The proposed control framework in the first part allows the operator to concentrate on the manipulation task while the mobile base and arm joint configurations are automatically {\em optimized} according to the needs of the task. Autonomous control subtasks are defined to guide the base and the arms towards this optimal configuration while the operator teleoperates the end-effector(s) of the mobile arm(s). The teleoperation and autonomous control tasks have adjustable relative priorities set by the system designer. The work in the second part enables the operator to focus mainly on navigation and manipulation while the camera viewpoint is automatically adjusted. The workspace and motion limits of the camera system and the location of the obstacles are taken into consideration in camera view planning. A head tracking system enables the operator to use his/her head movements as an extra control input to guide the camera placement, if and when necessary. Both proposed controllers have been implemented and evaluated in teleoperation experiments and user studies. The results of these experiments confirm the effectiveness of these controllers and demonstrate significant improvements compared to other existing controllers from the literature included in the studies.</p> / Master of Applied Science (MASc)