DSpace at AUS
https://dspace.aus.edu:443/xmlui
The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Sun, 09 Aug 2020 08:52:37 GMT2020-08-09T08:52:37ZHighly variable upper and abyssal overturning cells in the South Atlantic
http://hdl.handle.net/11073/19569
Highly variable upper and abyssal overturning cells in the South Atlantic
Kersale, Marion; Meinen, Christopher S.; Perez, Renellys C.; Le Henaff, Matthieu; Valla, Daniel; Lamont, Tarron; Sato, Olga; Dong, Shenfu; Terre, Thierry; van Caspel, Mathias; Chidichimo, Maria Paz; van den Berg, Marcel; Speich, Sabrina; Piola, Alberto; Campos, Edmo; Ansorge, Isabelle; Volkov, Denis; Lumpkin, Rick; Garzoli, Silvia
The Meridional Overturning Circulation (MOC) is a primary mechanism driving oceanic heat redistribution on Earth, thereby affecting Earth's climate and weather. However, the full-depth structure and variability of the MOC are still poorly understood, particularly in the South Atlantic. This study presents unique multiyear records of the oceanic volume transport of both the upper (<~3100 meters) and abyssal (>~3100 meters) overturning cells based on daily moored measurements in the South Atlantic at 34.5°S. The vertical structure of the time-mean flows is consistent with the limited historical observations. Both the upper and abyssal cells exhibit a high degree of variability relative to the temporal means at time scales, ranging from a few days to a few weeks. Observed variations in the abyssal flow appear to be largely independent of the flow in the overlying upper cell. No meaningful trends are detected in either cell.
Wed, 05 Aug 2020 00:00:00 GMThttp://hdl.handle.net/11073/195692020-08-05T00:00:00ZOn the dot product graph of a commutative ring II
http://hdl.handle.net/11073/18297
On the dot product graph of a commutative ring II
Abdulla, Mohammad Ahmad; Badawi, Ayman
In 2015, the second-named author introduced the dot product graph associated to a commutative ring A. Let A be a commutative ring with nonzero identity, 1 ≤ n < ∞ be an integer, and R = A × A × · · · × A (n times). We recall that the total dot product graph of R is the (undirected) graph T D(R) with vertices R∗ = R \ {(0, 0, . . . , 0)}, and two distinct vertices x and y are adjacent if and only if x·y = 0 ∈ A (where x·y denotes the normal dot product of x and y). Let Z(R) denote the set of all zero-divisors of R. Then the zero-divisor dot product graph of R is the induced subgraph ZD(R) of T D(R) with vertices Z(R)∗ = Z(R) \ {(0, 0, . . . , 0)}. Let U(R) denote the set of all units of R. Then the unit dot product graph of R is the induced subgraph UD(R) of T D(R) with vertices U(R). In this paper, we study the structure of T D(R), UD(R), and ZD(R) when A = Zn or A = GF(pn), the finite field with pn elements, where n ≥ 2 and p is a prime positive integer.
Wed, 01 Jan 2020 00:00:00 GMThttp://hdl.handle.net/11073/182972020-01-01T00:00:00ZDevelopment and Characterization of Novel Composite and Flexible Electrode Based on Titanium Dioxide
http://hdl.handle.net/11073/16732
Development and Characterization of Novel Composite and Flexible Electrode Based on Titanium Dioxide
Alatoom, Aseel Dirar; Al-Othman, Amani; Al-Nashash, Hasan; Al-Sayah, Mohammad
Flexible implantable bioelectrodes have the potential to advance neural sensing and muscle stimulation, especially in peripheral nerve injuries. In such cases, the application of electrical stimulation to muscles prevents muscular atrophy and helps to bridge the gap between the injured nerve and the corresponding muscle. This work investigates the fabrication and characterization of a novel, cost effective, flexible bioelectrodes, based on silicone polymer (polysiloxane) and titanium (IV) dioxide. Samples were synthesized and evaluated for their electrochemical and mechanical properties. The bioelectrodes fabricated in this work exhibited promising electrical and mechanical characteristics. The ductile properties for the samples showed an elongation of 293% ± 27.1% before breaking and an elastic modulus of 32.9 ± 5.01 kPa. The impedance at 1 kHz (a standard frequency value to measure the neural activity) was equal to 198 kΩ. The lowest electrode impedance found at 7 MHz was 0.35 kΩ. Thus, supporting its' potential to be employed in implantable electrode applications.
Thu, 11 Jun 2020 00:00:00 GMThttp://hdl.handle.net/11073/167322020-06-11T00:00:00ZSelf-Powered Balun Low Noise Amplifier with Degeneration Balancing and Thermal Noise Analysis
http://hdl.handle.net/11073/16731
Self-Powered Balun Low Noise Amplifier with Degeneration Balancing and Thermal Noise Analysis
Mohammad Abubaker, Qusai
The Balun low noise amplifier (LNA) is an LNA that exploits a combination of a common-source (CS) and a common-gate (CG) transistor, which cancels the noise and distortion of the CG stage. And since the CG is known to be linear, only the CS needs to be carefully designed and optimized. In this thesis, the CS section will be fully analyzed, and shown how the condition set in the literature review still satisfies the balancing output and cancels the CS stage thermal noise as well as the CG thermal noise. Also, forward body biasing (FBB) is used to reduce the threshold voltage and in addition, CS degeneration resistor will be studied to balance the output and cancel the
thermal noise of the transistors. The circuit is tested using UMC180nm on Cadence. The LNA achieves a gain of 19-16dB, NF<3.6 dB over the bandwidth 0.2-1.9GHz without a CS degeneration. A 17.8-14.8dB gain, a NF<3.8 dB over the bandwidth 0.2- 2.1GHz and power consumption of 12mW in both cases. Although outside the bandwidth, at ISM 2.4GHz a gain of 14.5dB and a NF of 3.8 is achieved, making it suitable for wireless sensor node (WSN) applications. According to the authors’ knowledge, this is the first time the degeneration resistor noise analysis on a Balun LNA is derived and simulated. Also, an RF harvester will be studied and used to power the Balun LNA. A two stage Dickson charge pump using MOSFET connected diode is chosen for this application. Although the efficiency is around 40%, the harvester was successfully integrated to the LNA, and its noise figure added to the output of the LNA.
A Master of Science thesis in Electrical Engineering by Qusai Mohammad Abubaker entitled, “Self-Powered Balun Low Noise Amplifier with Degeneration Balancing and Thermal Noise Analysis”, submitted in May 2020. Thesis advisors is Lutfi Albasha. Soft copy is available (Thesis, Approval Signatures, Completion Certificate, and AUS Archives Consent Form). Embargo expires February 25, 2021.
Fri, 01 May 2020 00:00:00 GMThttp://hdl.handle.net/11073/167312020-05-01T00:00:00Z