| 1. |
- Abate, F., et al.
(författare)
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Smart meters and water leakage detection : A preliminary study
- 2019
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Ingår i: I2MTC 2019 Proceedings. - 9781538634608
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Konferensbidrag (refereegranskat)abstract
- The paper deals with water leakage beyond the meter at household level. The automatic leakage detection is emerging as priority task for scientists and technicians. Each possible solution must include the use of smart meters for the continuous survey of domestic water consumption. Water smart meters aren't widespread yet, and the few either are prototypes or exhibit not adequate battery and communication performance. The authors, participants to the EMPIR 17IND13 Metrowamet project, propose an embedded system that can work with different water sensors, whose characteristics have been suitably designed for respecting stringent requirements of energy efficiency, computational burden and wireless transmission capability.
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| 2. |
- Abbas, Q., et al.
(författare)
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A Markovian Model for the Analysis of Age of Information in IoT Networks
- 2021
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Ingår i: IEEE Wireless Communications Letters. - : Institute of Electrical and Electronics Engineers Inc.. - 2162-2337 .- 2162-2345. ; 10:7, s. 1596-1600
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Tidskriftsartikel (refereegranskat)abstract
- Age of Information (AoI) is a critical metric in status update systems as these systems require the fresh updates. This letter investigates the uplink of an Internet-of-Thing (IoT) network where L nodes transmit their information packets to a base station. The effects of the arrival rate of packets at the nodes, the number of nodes in the system, and queue length of each node have been studied by devising a discrete time Markov chain (MC) model. This model helps in predicting the values of AoI and probability of packet drops in such systems. The notion of first-in first-out is used for queuing, which transmits the oldest packet first, resulting in decreasing the overall AoI of the system. The results show that AoI increases with the increase in queue length, number of nodes and arrival rate and we quantify the aforementioned metrics using the MC model. The results found using the MC model are also validated using extensive simulations. © 2012 IEEE.
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| 3. |
- Abbas, Q., et al.
(författare)
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Age of Information in Backscatter Communication
- 2021
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Ingår i: Internet Things. - Cham : Springer. ; , s. 67-80
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Konferensbidrag (refereegranskat)abstract
- Age of Information (AoI) has been introduced to characterize the newness of data which is observed in real time. In other words, it is the measure of time elapsed since the generation of last received update about a process and is a vital metric in networks such as Internet of things (IoTs), especially when the application demands fresh updates. Most of the applications require fresh data e.g., applications related to environmental monitoring, smart agriculture, body area networks etc. On the other hand backscatter communication promises to resolve one of the most challenging issues of IoT devices, i.e., making them capable for communication without the batteries. The importance of AoI in backscatter communication is paramount to gauge performance of backscatter IoT networks. This chapter addresses the significance of AoI in backscatter communication and suggests some techniques to design a communication system with minimum AoI, maximum energy efficiency, and minimum outage. © 2021, Springer Nature Switzerland AG.
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| 4. |
- Abbaszad Rafi, Abdolrahim, et al.
(författare)
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A facile route for concurrent fabrication and surface selective functionalization of cellulose nanofibers by lactic acid mediated catalysis
- 2023
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322 .- 2045-2322. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Celulose nanofibers are lightweight, recycable, biodegradable, and renewable. Hence, there is a great interest of using them instead of fossil-based components in new materials and biocomposites. In this study, we disclose an environmentally benign (green) one-step reaction approach to fabricate lactic acid ester functionalized cellulose nanofibrils from wood-derived pulp fibers in high yields. This was accomplished by converting wood-derived pulp fibers to nanofibrillated “cellulose lactate” under mild conditions using lactic acid as both the reaction media and catalyst. Thus, in parallel to the cellulose nanofibril production, concurrent lactic acid-catalyzed esterification of lactic acid to the cellulose nanofibers surface occured. The direct lactic acid esterification, which is a surface selective functionalization and reversible (de-attaching the ester groups by cleavage of the ester bonds), of the cellulose nanofibrils was confirmed by low numbers of degree of substitution, and FT-IR analyses. Thus, autocatalytic esterification and cellulose hydrolysis occurred without the need of metal based or a harsh mineral acid catalysts, which has disadvantages such as acid corrosiveness and high recovery cost of acid. Moreover, adding a mineral acid as a co-catalyst significantly decreased the yield of the nanocellulose. The lactic acid media is successfully recycled in multiple reaction cycles producing the corresponding nanocellulose fibers in high yields. The disclosed green cellulose nanofibril production route is industrial relevant and gives direct access to nanocellulose for use in variety of applications such as sustainable filaments, composites, packaging and strengthening of recycled fibers.
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| 5. |
- Abbaszad Rafi, Abdolrahim, et al.
(författare)
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Photo-Switchable Nanomechanical Systems Comprising a Nanocontainer (Montmorillonite) and Light-Driven Molecular Jack (Azobenzene-Imidazolium Ionic Liquids) as Drug Delivery Systems; Synthesis, Characterization, and in Vitro Release Studies
- 2018
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Ingår i: ACS Biomaterials Science & Engineering. - : American Chemical Society. - 2373-9878. ; 4:1, s. 184-192
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Tidskriftsartikel (refereegranskat)abstract
- In this work, photoresponsive nanomechanical systems were prepared through the intercalation of positively charged photoswitching molecular jacks (azobenzene ionic liquids, Azo-ILs) within montmorillonite (MMT) layers (MMT@Azo-ILs). The study shows that MMT@Azo-ILs are photosensitive and the synthesized molecular jacks could change the basal distances of MMT layers upon UV irradiation. These changes come from changes in the structure and geometry of Azo molecules (i.e., cis-trans isomerization) between clay layers upon UV irradiation. The prepared photoresponsive nanomechanical systems were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDX), field-emission scanning electron microscope (FE-SEM). Moreover, the in vitro release studies were performed in different conditions (upon UV irradiation and darkness) in pH 5.8 at 34 ± 1 °C, and it was found that the release rates from drug loaded MMT@Azo-ILs were higher upon UV irradiation in comparison with the release rates in darkness. According to the release studies, the prepared photoresponsive carriers might be considered as an excellent potential candidate in order to formulate smart sunscreens. © 2017 American Chemical Society.
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| 6. |
- Abdalla, Munir A, et al.
(författare)
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A CMOS APS for dental X-ray imaging using scintillating sensors
- 2001
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - 0168-9002 .- 1872-9576. ; 460:1, s. 197-203
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we present an integrating CMOS Active Pixel Sensor (APS) circuit to be used with scintillator type X-ray sensors for intra oral dental X-ray imaging systems. Different pixel architectures were constructed to explore their performance characteristics and to study the feasibility of the development of such systems using the CMOS technology. A prototype 64 x 80 pixel array has been implemented in a CMOS 0.8 mum double poly n-well process with a pixel pitch of 50 mum. A spectral sensitivity measurement for the different pixels topologies, as well as measured X-ray direct absorption in the different APSs are presented. A measurement of the output signal showed a good linearity over a wide dynamic range. This chip showed that the very low sensitivity of the CMOS APSs to direct X-ray exposure adds a great advantage to the various CMOS advantages over CCD-based imaging systems,
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| 7. |
- Abdalla, Munir A, et al.
(författare)
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A new biasing method for CMOS preamplifier-shapers
- 2000
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Ingår i: ICECS 2000: 7TH IEEE INTERNATIONAL CONFERENCE ON ELECTRONICS, CIRCUITS & SYSTEMS, VOLS I AND II. ; , s. 15-18
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Konferensbidrag (refereegranskat)
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| 8. |
- Abdalla, Munir A, et al.
(författare)
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An integrating CMOS APS for X-ray imaging with an in-pixel preamplifier
- 2001
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - 0168-9002 .- 1872-9576. ; 466:1, s. 232-236
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Tidskriftsartikel (refereegranskat)abstract
- We present in this paper an integrating CMOS Active Pixel Sensor (APS) circuit coated with scintillator type sensors for intra-oral dental X-ray imaging systems. The photosensing element in the pixel is formed by the p-diffusion on the n-well diode. The advantage of this photosensor is its very low direct absorption of X-rays compared to the other available photosensing elements in the CMOS pixel. The pixel features an integrating capacitor in the feedback loop of a preamplifier of a finite gain in order to increase the optical sensitivity. To verify the effectiveness of this in-pixel preamplification, a prototype 32 x 80 element CMOS active pixel array was implemented in a 0.8 mum CMOS double poly, n-well process with a pixel pitch of 50 mum. Measured results confirmed the improved optical sensitivity performance of the APS. Various measurements on device performance are presented.
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| 9. |
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| 10. |
- Abdalla, Suliman A
(författare)
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Architecture and circuit design of photon counting readout for X-ray imaging sensors
- 2007
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Hybrid pixel array detectors for X-ray imaging are based on different technologies for sensor and readout electronics. The readout electronics are based on standard CMOS technologies that are experiencing continuously rapid improvements by means of down-scaling the feature sizes, which in turn lead to higher transistor densities, lower power consumption, and faster circuits. For pixel-array imaging sensors the improvements in CMOS technology opens up new possibilities of integrating more functionality in the pixels for local processing of the sensor data. However, new issues related to the tight integration of both analog and digital processing circuits within the small area of a pixel must also be evaluated. The advantages of down-scaling the CMOS technology can be utilized to increase the spatial resolution by reducing the pixel sizes. Recent research indicates however that the bottleneck in reaching further spatial resolution in X-ray imaging sensors may not be limited by the circuit area occupied by the functions necessary in the pixels, but are instead related to problems associated with charge-sharing of charges generated by the sensor which are distributed over a neighbourhood of pixels and will limit the spatial resolution and lead to a distortion of the energy spectrum. In this thesis a mechanism to be implemented in the readout circuits is proposed in order to suppress the charge-sharing effects. The proposed architecture and its circuit implementation are evaluated with respect to circuit complexity (area) and power consumption. For a photon-counting pixel it is demonstrated that the complete pixel, with charge-sharing suppression mechanism, can be implemented using 300 transistors with an idle power consumption of 2.7μW in a 120nm CMOS technology operating with a 1.2V power supply. The improvements in CMOS technology can also be used for increasing the range of applications for X-ray imaging sensors. In this thesis, an architecture is proposed for multiple energy discrimination, called color X-ray imaging. The proposed solution is the result of balancing the circuit complexity and the image quality. The method is based on color sub-sampling with intensity biasing. For three-level energy discrimination, that corresponds to color imaging systems for visible light with R, G, and B color components, the increase in circuit complexity will be only 20% higher than that for the Bayer method but results in significantly better image quality. As the circuit complexity in the digital processing within each pixel is increased, the digitally induced noise may play an increasingly important role for the signal-to-noise ratio in the measurements. In this thesis an initial study is conducted regarding how the digital switching noise affects the analog amplifiers in the photon-counting pixel.
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