The inefficiency of Consensus-based Atomic Broadcast protocols in the presence of collisions (concurrent proposals) harms their adoption in the implementation of State Machine Replication. Proposals that are not decid...
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ISBN:
(纸本)9781538621950
The inefficiency of Consensus-based Atomic Broadcast protocols in the presence of collisions (concurrent proposals) harms their adoption in the implementation of State Machine Replication. Proposals that are not decided in some instance of Consensus (commands not delivered) must be re-proposed in a new instance, delaying their execution. The CFABCast (Collision-Fast Atomic Broadcast) algorithm uses M-Consensus to decide and deliver multiple values in the same instance. However, CFABCast is not Byzantine fault-tolerant, a requirement for many systems. Our first contribution is a modified version of CFABCast to handle Byzantine failures. Unfortunately, the resulting protocol is not collision-fast due to the possibility of malicious failures. In fact, our second contribution is to prove that there are no Byzantine collision-fast algorithms in an asynchronous model as traditionally extended to solve Consensus. Finally, our third contribution is a Byzantine collision-fast algorithm that bypasses the stated impossibility by means of a USIG (Unique Sequential Identifier Generator) trusted component.
We present, in this paper, a new overlay network design that is suited for large scale peer-to-peer networks requiring fast message transmission. We particularly address the problem of designing an overlay communicati...
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ISBN:
(纸本)9781538621950
We present, in this paper, a new overlay network design that is suited for large scale peer-to-peer networks requiring fast message transmission. We particularly address the problem of designing an overlay communication network that spans across a set of data centres located in multiple geographic locations with the necessity of requiring locality properties for applications. Our design for the overlay network is motivated by the social network structures and we use different operators as found in evolutionary computing to emulate a semi-structured *** present the network structure and the various algorithms required for basic communication and maintenance. We also study the proposed network by simulation and compare with existing overlay networks. The simulated results show that on an average there are at most six hops required for a message originated at any node in the network to be transferred to any other node in the network. The network so designed is scalable, and resilient to failure and, can include node of arbitrary in processing capacity, network bandwidth and storage.
At the Naval Research Laboratory Optical Sciences and Remote Sensing Divisions, a compact hyperspectral imaging sensor has been in development using a method of multi-order spectroscopy using Fabry-Perot etalon arrays...
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ISBN:
(数字)9781510617902
ISBN:
(纸本)9781510617902
At the Naval Research Laboratory Optical Sciences and Remote Sensing Divisions, a compact hyperspectral imaging sensor has been in development using a method of multi-order spectroscopy using Fabry-Perot etalon arrays. This has allowed for the first broadband, ultra compact spectrometer. A prototype hyperspectral imaging system is now in development for use with an unmanned aerial vehicle. This system will be a "push-broom system" that scans ground data line by line in a row of pixels forming the hyperspectral datacube and will be georeferenced onto a Digital Surface Model of the ground with location (latitude, longitude, altitude) and attitude (azimuth, pitch, roll) GPS-INS 6-degree of freedom parameters. These parameters will be collected through the use of a high end modern smartphone with its GPS, accelerometer, gyroscope, barometric pressure, and digital compass sensors. In this paper, we discuss the various sensors and systems being utilized with a smartphone for use with the hyperspectral imaging sensor in development.
Curved image sensors offer a new degree of freedom in optical system design that promise low-cost, small-volume solutions for wide field-of-view imaging. Stretchable polymer backplanes can provide the high-density of ...
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ISBN:
(数字)9781510618244
ISBN:
(纸本)9781510618244
Curved image sensors offer a new degree of freedom in optical system design that promise low-cost, small-volume solutions for wide field-of-view imaging. Stretchable polymer backplanes can provide the high-density of interconnects and tolerate the large deformations needed to transform planar, wafer-based image sensors into shapes with large non-zero Gaussian curvature. Here we demonstrate a thermoformable backplane based on glycolated polyethylene terephthalate (PETg) that can be deformed to a 98 degrees spherical cap with 0.5 '' radius. We introduce a process to integrate such backplanes with a CMOS image sensor and release the circuit from the wafer to form a monolithically integrated image sensor that can be thermoformed to the desired shape.
The emergence of microfluidic techniques coupled with flow-induced electrification has advanced the development of innovative self-powered sensors. However, selective detection of target substances using these sensors...
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The emergence of microfluidic techniques coupled with flow-induced electrification has advanced the development of innovative self-powered sensors. However, selective detection of target substances using these sensors is extremely challenging, owing to the lack of recognition elements in the flow pathway. To overcome this, catalytic enzymes are immobilized on the microfluidic channel and the concentration of targets is measured via monitoring the streaming current. As an example, a urease equipped self-powered microtubular sensor is developed to selectively detect urea, a physiologically and industrially important molecule. The urease catalyzes the hydrolysis of urea into ions, increasing the pH of the fluid, which serves as the basis of the sensing mechanism. Remarkably, high sensitivity, wide detection range, short response time, and superior selectivity are reported for urinary urea detection. The accuracy and reliability of sensing in artificial urine are validated with the standard spectrophotometric method. The microtubular sensor features facile fabrication and operation and circumvents the need for sophisticated peripherals, highlighting its enormous potential in chemical and biomedical applications, such as pollutant detection, food quality assessment, disease diagnosis, and point-of-care testing.
Effective reduction of the emissions of low-power wood-log fueled firing appliances is only possible, if advanced combustion air stream control concepts are applied. Such an advanced method of automated estimation and...
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Effective reduction of the emissions of low-power wood-log fueled firing appliances is only possible, if advanced combustion air stream control concepts are applied. Such an advanced method of automated estimation and control of combustion air streams is based on combustion temperature, residual oxygen concentration and content of the un-/partly combusted exhaust gas components and separate control loops for adjustment of the combustion air streams using air mass stream sensors and motor driven air stream limiting shutters. In the past lack of appropriate CO/HC gas sensors providing satisfying long-term signal stability hindered the effectuation of those control systems in the market of advanced firing systems. In this paper an electrochemical method is reported, which may solve the problem. It enables checking of the current status of CO/HC gas sensitivity of a commercial mixed potential type gas sensor and, if required, regeneration of sensitivity at the place of operation under ambient air conditions.
Various state estimation problems in dairy farm applications, like heat detection, feeding behavior, etc. are well studied by using Hidden Markov Models (HMM) to represent the sampled process. Our use-case of monitori...
ISBN:
(数字)9781728137155
ISBN:
(纸本)9781728137162
Various state estimation problems in dairy farm applications, like heat detection, feeding behavior, etc. are well studied by using Hidden Markov Models (HMM) to represent the sampled process. Our use-case of monitoring cows in remote farms in real-time and perform online state estimation/classification requires intelligent sampling of the underlying HMM. Due to the limited capacity of the sensor network at the dairy farm, and due to possible wireless errors, the central server does not always receive all the sampled data. Right value of the observation arrival rate into the parameter and state estimation algorithm running at a central server is required to ensure that a prescribed heat detection performance level is achieved. We provide a working implementation of a setup where the end devices using Bluetooth Low Energy (BLE) are provided with an online recommendation on the sampling (hence, channel access) rates so that the HMM state estimated at the central server is ( α, β)-current.
Most of the currently developed indoor localization techniques depend on some kind of sensory input, utilizing, among others, WiFi-signals (e.g. [2]), smartphone sensors (e.g. [4]) or Bluetooth beacons (e.g. [1]). How...
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ISBN:
(纸本)9781450366618
Most of the currently developed indoor localization techniques depend on some kind of sensory input, utilizing, among others, WiFi-signals (e.g. [2]), smartphone sensors (e.g. [4]) or Bluetooth beacons (e.g. [1]). However, each of these systems has its own downsides, such as a lack of infrastructure, power consumption and proneness to noise. These are the reasons no such system is currently able to be truly considered as the "GPS for the indoors", as they cannot provide worldwide coverage.
Transparent and flexible UV sensors have attracted considerable attention for use in portable/wearable optoelectronic systems. Although UV sensors based on photoactive nanomaterials have been reported for such applica...
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Transparent and flexible UV sensors have attracted considerable attention for use in portable/wearable optoelectronic systems. Although UV sensors based on photoactive nanomaterials have been reported for such applications, achieving full transparency and flexibility remains a challenge because they still rely on opaque or brittle electrodes. Here, a fully transparent, flexible, and highly sensitive UV sensor based on 1D carbon nanotubes (CNTs)-2D graphene hybrid is demonstrated. Under UV illumination, oxygen molecules on the CNT surfaces are desorbed by photoinduced plasmon energy, leading to a significant decrease in hole concentration, and correspondingly an increase in the electrical resistance of CNT. The combination of CNT and graphene minimizes the effect of contact resistance and facilitates effective charge transfer between them without potential barrier, resulting in a high photoresponse, which is 30 times as high as that of Au-electrode-based CNT sensor. Simultaneously, CNT-graphene UV sensor shows remarkable transparency (over 80% at 550 nm) and outstanding mechanical flexibility without any significant change in electrical resistance for 500 cycles at a bending radius of 5.5 mm. The integration of CNT-graphene hybrid onto flexible substrates through scalable microfabrication is expected to provide exciting opportunities for the development of high performance, optically and mechanically invisible optoelectronic devices.
Worlds first graphene-based Pirani pressure sensor is presented. Due to the decreased area and low thickness, the graphene-based Pirani pressure sensor allows for low power applications down to 0.9 mW. Using an innova...
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ISBN:
(纸本)9781538652732
Worlds first graphene-based Pirani pressure sensor is presented. Due to the decreased area and low thickness, the graphene-based Pirani pressure sensor allows for low power applications down to 0.9 mW. Using an innovative, transfer -free process, suspended graphene beams are realized. This allows for up to 100x miniaturization of the pressure sensor area, while enabling wafer -scale fabrication. The response of the miniaturized pressure sensor is similar to that of the much larger state-of-the-art Si -based Pirani pressure sensors, demonstrating the potential of graphene-based Pirani sensors.
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