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Ensuring Access to Safe and Nutritious Food for All Through the Transformation of Food Systems
Joint Activity Detection, Channel Estimation, and Data Decoding for Grant-free Massive Random Access
In the massive machine-type communication (mMTC) scenario, a large number of
devices with sporadic traffic need to access the network on limited radio
resources. While grant-free random access has emerged as a promising mechanism
for massive access, its potential has not been fully unleashed. In particular,
the common sparsity pattern in the received pilot and data signal has been
ignored in most existing studies, and auxiliary information of channel decoding
has not been utilized for user activity detection. This paper endeavors to
develop advanced receivers in a holistic manner for joint activity detection,
channel estimation, and data decoding. In particular, a turbo receiver based on
the bilinear generalized approximate message passing (BiG-AMP) algorithm is
developed. In this receiver, all the received symbols will be utilized to
jointly estimate the channel state, user activity, and soft data symbols, which
effectively exploits the common sparsity pattern. Meanwhile, the extrinsic
information from the channel decoder will assist the joint channel estimation
and data detection. To reduce the complexity, a low-cost side information-aided
receiver is also proposed, where the channel decoder provides side information
to update the estimates on whether a user is active or not. Simulation results
show that the turbo receiver is able to reduce the activity detection, channel
estimation, and data decoding errors effectively, while the side
information-aided receiver notably outperforms the conventional method with a
relatively low complexity
Quantum Mechanics Lecture Notes. Selected Chapters
These are extended lecture notes of the quantum mechanics course which I am
teaching in the Weizmann Institute of Science graduate physics program. They
cover the topics listed below. The first four chapter are posted here. Their
content is detailed on the next page. The other chapters are planned to be
added in the coming months.
1. Motion in External Electromagnetic Field. Gauge Fields in Quantum
Mechanics.
2. Quantum Mechanics of Electromagnetic Field
3. Photon-Matter Interactions
4. Quantization of the Schr\"odinger Field (The Second Quantization)
5. Open Systems. Density Matrix
6. Adiabatic Theory. The Berry Phase. The Born-Oppenheimer Approximation
7. Mean Field Approaches for Many Body Systems -- Fermions and Boson
Effects of 3 MeV Proton Irradiation on Superconductivity and CDW in 2H-NbSe2 Single Crystals
Interplay between superconductivity and charge-density wave (CDW) in 2H-NbSe2
single crystals irradiated by 3 MeV protons is studied. Both Tc and TCDW are
found to decrease monotonically with the increase in irradiation dose. This
behavior is different from electron-irradiated NbSe2, where TCDW is suppressed
monotonically with the increase in dose, while Tc shows an initial enhancement
before it starts to decrease. We attempt to explain this difference based on
the negative pressure effect which has been reported in our previous study on
NbSe2 irradiated by heavy ions
Aero-thermal analysis of a laminar separation bubble subjected to varying free-stream turbulence: Large Eddy Simulation
A quantitative analysis illustrating salient features of a Laminar Separation
Bubble (LSB), its transition forming coherent structures, and associated heat
transfer has been performed on a flat plate for varying free stream turbulence
(fst) between 1.2% to 10.3%. A well-resolved Large Eddy Simulation (LES)
developed in-house is used for the purpose. Flow separation has been induced by
imposing an adverse pressure gradient on the upper boundary of a Cartesian
domain. Isotropic perturbations are introduced at the inlet to mimic grid
turbulence. With an increase of fst, an upstream shift in the mean reattachment
point has been observed while the onset of separation remains almost invariant,
shrinking the bubble length significantly. The transition of the shear layer is
triggered by the Kelvin-Helmholtz (K-H) instability for fst of less than 3.3%,
while Klebanoff modes (Kmodes) dictate the flow transition at fst greater than
6.5%. Further, a mixed mode, i.e., both K-H and K-modes, contribute to the flow
transition at a moderate level of fst, lying between 3.3% and 6.5%. Thus, the
roll-up of the shear layer appears in the second half of the bubble shedding
large-scale vortices that keep their identity far downstream at low fst levels.
On the contrary, the streamwise streaks via K-modes prior to the separation are
found to interact with the LSB, resulting in an earlier breakdown of the shear
layer with abundant small-scale vortices downstream at the moderate to high fst
levels. However, higher surface-normal heat flux is associated with large-scale
energetic coherent vortices
AutoTAB: Automatic Tracking Algorithm for Bipolar Magnetic Regions
Bipolar Magnetic Regions (BMRs) provide crucial information about solar
magnetism. They exhibit varying morphology and magnetic properties throughout
their lifetime, and studying these properties can provide valuable insights
into the workings of the solar dynamo. The majority of previous studies have
counted every detected BMR as a new one and have not been able to study the
full life history of each BMRs. To address this issue, we have developed an
Automatic Tracking Algorithm (AutoTAB) for BMRs, that tracks the BMRs for their
entire lifetime or throughout their disk passage. AutoTAB uses the binary maps
of detected BMRs to automatically track the regions. This is done by
differentially rotating the binary maps of the detected regions and checking
for overlaps between them. In this first article of this project, we provide a
detailed description of the working of the algorithm and evaluate its strengths
and weaknesses. We also compare its performance with other existing tracking
techniques. AutoTAB excels in tracking even for the small features and it
successfully tracks 9152 BMRs over the last two solar cycles (1996-2020),
providing a comprehensive dataset that depicts the evolution of various
properties for each tracked region. The tracked BMRs follow familiar properties
of solar cycles except for these small BMRs that appear at all phases of the
solar cycle and show weak latitudinal dependency, which is represented through
the butterfly diagram. Finally, we discuss the possibility of adapting our
algorithm to other datasets and expanding the technique to track other solar
features in the future.Comment: 14 pages including 9 figures; Submitted in ApJS; Comments are welcom
NSC++: Non-Standard Cosmologies in C++
We introduce NSC++, a header-only C++ library that simulates the evolution of
the plasma and a decaying fluid in the early Universe. NSC++ can be used in C++
programs or called directly from python scripts without significant overhead.
There is no special installation process or external dependencies. Furthermore,
there are example programs that can be modified to handle several cases.Comment: 18 pages; 3 figures; 4 tables; The stable version of the library can
be found at https://github.com/dkaramit/NSCpp/tree/stable. v2: Added
reference; Minor corrections to text. v3: Minor corrections, matches
published versio
Corporate Social Responsibility: the institutionalization of ESG
Understanding the impact of Corporate Social Responsibility (CSR) on firm performance as it relates to industries reliant on technological innovation is a complex and perpetually evolving challenge. To thoroughly investigate this topic, this dissertation will adopt an economics-based structure to address three primary hypotheses. This structure allows for each hypothesis to essentially be a standalone empirical paper, unified by an overall analysis of the nature of impact that ESG has on firm performance. The first hypothesis explores the evolution of CSR to the modern quantified iteration of ESG has led to the institutionalization and standardization of the CSR concept. The second hypothesis fills gaps in existing literature testing the relationship between firm performance and ESG by finding that the relationship is significantly positive in long-term, strategic metrics (ROA and ROIC) and that there is no correlation in short-term metrics (ROE and ROS). Finally, the third hypothesis states that if a firm has a long-term strategic ESG plan, as proxied by the publication of CSR reports, then it is more resilience to damage from controversies. This is supported by the finding that pro-ESG firms consistently fared better than their counterparts in both financial and ESG performance, even in the event of a controversy. However, firms with consistent reporting are also held to a higher standard than their nonreporting peers, suggesting a higher risk and higher reward dynamic. These findings support the theory of good management, in that long-term strategic planning is both immediately economically beneficial and serves as a means of risk management and social impact mitigation. Overall, this contributes to the literature by fillings gaps in the nature of impact that ESG has on firm performance, particularly from a management perspective
People make Places
For centuries Glasgow, as a bucolic fishing village and ecclesiastical centre on the banks of the River Clyde, held little of strategic significance. When success and later threats came to the city, it was as a consequence of explosive growth during the industrial era that left a significant civic presence accompanied by social and environmental challenges. Wartime damage to the fabric of the city and the subsequent implementation of modernist planning left Glasgow with a series of existential threats to the lives and the health of its people that have taken time to understand and come to terms with.
In a few remarkable decades of late 20th century regeneration, Glasgow began to be put back together. The trauma of the second half of the 20th century is fading but not yet a distant memory. Existential threats from the climate emergency can provoke the reaction “what, again?” However, the resilience built over the last 50 years has instilled a belief that a constructive, pro-active and creative approach to face this challenge along with the recognition that such action can be transformational for safeguarding and improving people’s lives and the quality of their places. A process described as a just transition that has become central to Glasgow’s approach.
Of Scotland’s four big cities, three are surrounded by landscape and sea only Glasgow is surrounded by itself. Even with a small territory, Glasgow is still the largest of Scotland’s big cities and by some margin. When the wider metropolitan area is considered, Glasgow is – like Birmingham, Manchester and Liverpool – no mean city.
People make Places begins with a review of the concept and complexities of place, discusses why these matter and reviews the growing body of evidence that place quality can deliver economic, social and environmental value. The following chapters focus on the history and evolution of modern Glasgow in four eras of 19th and early 20th century industrialisation, de- industrialisation and modernism in mid 20th century, late 20th century regeneration and a 21st century recovery towards transition and renaissance, and document the process, synthesis and the results of a major engagement programme and to explore systematic approaches to place and consensus building around the principal issues.
The second half of the work reflects on a stocktaking of place in contemporary Glasgow, looking at the city through the lenses of an international, metropolitan and everyday city, concluding with a review of the places of Glasgow and what may be learned from them revealing some valuable insights presented in a series of Place Stories included.
The concluding chapter sets out the findings of the investigation and analysis reviewing place goals, challenges and opportunities for Glasgow over the decades to 2030 and 2040 and ends with some recommendations about what Glasgow might do better to combine place thinking and climate awareness and setting out practical steps to mobilise Glasgow’s ‘place ecosystem’
Worldtube excision method for intermediate-mass-ratio inspirals: scalar-field model in 3+1 dimensions
Binary black hole simulations become increasingly more computationally
expensive with smaller mass ratios, partly because of the longer evolution
time, and partly because the lengthscale disparity dictates smaller time steps.
The program initiated by Dhesi et al. (arXiv:2109.03531) explores a method for
alleviating the scale disparity in simulations with mass ratios in the
intermediate astrophysical range (), where
purely perturbative methods may not be adequate. A region ("worldtube") much
larger than the small black hole is excised from the numerical domain, and
replaced with an analytical model approximating a tidally deformed black hole.
Here we apply this idea to a toy model of a scalar charge in a fixed circular
geodesic orbit around a Schwarzschild black hole, solving for the massless
Klein-Gordon field. This is a first implementation of the worldtube excision
method in full 3+1 dimensions. We demonstrate the accuracy and efficiency of
the method, and discuss the steps towards applying it for evolving orbits and,
ultimately, in the binary black-hole scenario. Our implementation is publicly
accessible in the SpECTRE numerical relativity code.Comment: 19 pages, 10 figure
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