275 research outputs found
Design, development and thermal analysis of reusable Li-ion battery module for future mobile and stationary applications
The performance, energy storage capacity, safety, and lifetime of lithium-ion battery cells of different chemistries are very sensitive to operating and environmental temperatures. The cells generate heat by current passing through their internal resistances, and chemical reactions can generate additional, sometimes uncontrollable, heat if the temperature within the cells reaches the trigger temperature. Therefore, a high-performance battery cooling system that maintains cells as close to the ideal temperature as possible is needed to enable the highest possible discharge current rates while still providing a sufficient safety margin. This paper presents a novel design, preliminary development, and results for an inexpensive reusable, liquid-cooled, modular, hexagonal battery module that may be suitable for some mobile and stationary applications that have high charge and or discharge rate requirements. The battery temperature rise was measured experimentally for a six parallel 18650 cylindrical cell demonstrator module over complete discharge cycles at discharge rates of 1C, 2C and 3C. The measured temperature rises at the hottest point in the cells, at the anode terminal, were found to be 6, 17 and 22 °C, respectively. The thermal resistance of the system was estimated to be below 0.2 K/W at a coolant flow rate of 0.001 Kg/s. The proposed liquid cooled module appeared to be an effective solution for maintaining cylindrical Li-ion cells close to their optimum working temperature
A Study of Coronary Artery Disease in Type 2 Diabetic Women
1. Incidence of CAD,including myocardial infarction,in type 2 diabetic women was 37.6%.
2. Incidence of myocardial infarction was 9.5%.
3. Incidence of CAD in post menopausal type 2 diabetic women was 79.7%.Incidence in pre menopausal women was 20.3%.
4. Incidence of CAD was maximum in age group 50-60
years(40.6%).
5. Incidence of hypertension was maximum in age group 50-60 years(39.3%).
6. A significant percentage of CAD (23.4%) with p value <0.05 were observed among patients with systolic BP in the range of 140-160 mm of Hg.
7. Incidence of CAD among patients with sedentary occupations was (40.6%).
8. In the study a significant proportion (28 out of the 64 patients) reported 'high' levels of subjective stress in the 2-4 week period preceding acute
coronary events.
9. In the study of 64 CAD patients 59.4% were overweight and 15.6% were obese.
10. 67.2% of the CAD patients had waist circumference >88 cm.
11. In the study of PPBS and the incidence of CAD,maximum incidence was found in 200-250 mg% range(34.4%)and 20.3% in 250-300mg % range.
12. Maximum incidence of CAD was found in patients with FBS>125 mg % (78.1%).
13. Moderate hypercholesterolemia (210-250 mg% ) was observed in 67.2% of coronary artery disease patients and hypercholesterolemia(>250mg %) in 9.4%.
14. In the study 60.9% of the CAD patients had triglycerides >150mg%
A random fiber bundle with many discontinuities in the threshold distribution
We study the breakdown of a random fiber bundle model (RFBM) with
-discontinuities in the threshold distribution using the global load sharing
scheme. In other words, different classes of fibers identified on the
basis of their threshold strengths are mixed such that the strengths of the
fibers in the class are uniformly distributed between the values
and where . Moreover, there
is a gap in the threshold distribution between and class. We
show that although the critical stress depends on the parameter values of the
system, the critical exponents are identical to that obtained in the recursive
dynamics of a RFBM with a uniform distribution and global load sharing. The
avalanche size distribution (ASD), on the other hand, shows a non-universal,
non-power law behavior for smaller values of avalanche sizes which becomes
prominent only when a critical distribution is approached. We establish that
the behavior of the avalanche size distribution for an arbitrary is
qualitatively similar to a RFBM with a single discontinuity in the threshold
distribution (), especially when the density and the range of threshold
values of fibers belonging to strongest ()-th class is kept identical in
all the cases.Comment: 6 pages, 4 figures, Accepted in Phys. Rev.
Landau-Zener problem with waiting at the minimum gap and related quench dynamics of a many-body system
We discuss a technique for solving the Landau-Zener (LZ) problem of finding
the probability of excitation in a two-level system. The idea of time reversal
for the Schrodinger equation is employed to obtain the state reached at the
final time and hence the excitation probability. Using this method, which can
reproduce the well-known expression for the LZ transition probability, we solve
a variant of the LZ problem which involves waiting at the minimum gap for a
time t_w; we find an exact expression for the excitation probability as a
function of t_w. We provide numerical results to support our analytical
expressions. We then discuss the problem of waiting at the quantum critical
point of a many-body system and calculate the residual energy generated by the
time-dependent Hamiltonian. Finally we discuss possible experimental
realizations of this work.Comment: 6 pages including 3 figures; significantly expanded -- this is the
published versio
Dynamical delocalization of Majorana edge states by sweeping across a quantum critical point
We study the adiabatic dynamics of Majorana fermions across a quantum phase
transition. We show that the Kibble-Zurek scaling, which describes the density
of bulk defects produced during the critical point crossing, is not valid for
edge Majorana fermions. Therefore, the dynamics governing an edge state quench
is nonuniversal and depends on the topological features of the system. Besides,
we show that the localization of Majorana fermions is a necessary ingredient to
guaranty robustness against defect production.Comment: Submitted to the Special Issue on "Dynamics and Thermalization in
Isolated Quantum Many-Body Systems" in New Journal of Physics. Editors:M.
Cazalilla, M. Rigol. New references and some typos correcte
Effect of discontinuity in threshold distribution on the critical behaviour of a random fiber bundle
The critical behaviour of a Random Fiber Bundle Model with mixed uniform
distribution of threshold strengths and global load sharing rule is studied
with a special emphasis on the nature of distribution of avalanches for
different parameters of the distribution. The discontinuity in the threshold
strength distribution of fibers non-trivially modifies the critical stress as
well as puts a restriction on the allowed values of parameters for which the
recursive dynamics approach holds good. The discontinuity leads to a
non-universal behaviour in the avalanche size distribution for smaller values
of avalanche size. We observe that apart from the mean field behaviour for
larger avalanches, a new behaviour for smaller avalanche size is observed as a
critical threshold distribution is approached. The phenomenological
understanding of the above result is provided using the exact analytical result
for the avalanche size distribution. Most interestingly,the prominence of
non-universal behaviour in avalanche size distribution depends on the system
parameters.Comment: 6 pages, 4 figures, text and figures modifie
Building a Climate Movement Through Relational Organizing
Community organizing is a process for achieving social change through the mobilization of resources and the formation of collective identity. Relational community organizing is a particular approach to developing new leaders and building organizational capacity for sustaining a powerful movement, and is especially relevant in the climate justice movement because relationships serve to bring actors from isolation and despair toward communal identity and hopeful action. Minnesota Interfaith Power & Light (MNIPL) is a community organization that is using relational organizing to activate faith communities to take action on climate change. This paper describes the design and first phase of evaluation of MNIPL’s Movement Builder Program, a networked distributed leadership model that uses peer mentors to increase the efficacy of new organizers. Can a peer-to-peer network increase the leverage of organizers? Will supportive relationships move people to increased action and to develop the leadership of others? We provide an introduction to this inquiry as well as the foundational frameworks and historical context of this new approach
Quantum Discord in a spin-1/2 transverse XY Chain Following a Quench
We report a study on the zero-temperature quantum discord as a measure of
two-spin correlation of a transverse XY spin chain following a quench across a
quantum critical point and investigate the behavior of mutual information,
classical correlations and hence of discord in the final state as a function of
the rate of quenching. We show that though discord vanishes in the limit of
very slow as well as very fast quenching, it exhibits a peak for an
intermediate value of the quenching rate. We show that though discord and also
the mutual information exhibit a similar behavior with respect to the quenching
rate to that of concurrence or negativity following an identical quenching,
there are quantitative differences. Our studies indicate that like concurrence,
discord also exhibits a power law scaling with the rate of quenching in the
limit of slow quenching though it may not be expressible in a closed power law
form. We also explore the behavior of discord on quenching linearly across a
quantum multicritical point (MCP) and observe a scaling similar to that of the
defect density.Comment: 6 pages, 5 figure
Time Evolution within a Comoving Window: Scaling of signal fronts and magnetization plateaus after a local quench in quantum spin chains
We present a modification of Matrix Product State time evolution to simulate
the propagation of signal fronts on infinite one-dimensional systems. We
restrict the calculation to a window moving along with a signal, which by the
Lieb-Robinson bound is contained within a light cone. Signal fronts can be
studied unperturbed and with high precision for much longer times than on
finite systems. Entanglement inside the window is naturally small, greatly
lowering computational effort. We investigate the time evolution of the
transverse field Ising (TFI) model and of the S=1/2 XXZ antiferromagnet in
their symmetry broken phases after several different local quantum quenches.
In both models, we observe distinct magnetization plateaus at the signal
front for very large times, resembling those previously observed for the
particle density of tight binding (TB) fermions. We show that the normalized
difference to the magnetization of the ground state exhibits similar scaling
behaviour as the density of TB fermions. In the XXZ model there is an
additional internal structure of the signal front due to pairing, and wider
plateaus with tight binding scaling exponents for the normalized excess
magnetization. We also observe parameter dependent interaction effects between
individual plateaus, resulting in a slight spatial compression of the plateau
widths.
In the TFI model, we additionally find that for an initial Jordan-Wigner
domain wall state, the complete time evolution of the normalized excess
longitudinal magnetization agrees exactly with the particle density of TB
fermions.Comment: 10 pages with 5 figures. Appendix with 23 pages, 13 figures and 4
tables. Largely extended and improved versio
Adiabatic dynamics of an inhomogeneous quantum phase transition: the case of z > 1 dynamical exponent
We consider an inhomogeneous quantum phase transition across a multicritical
point of the XY quantum spin chain. This is an example of a Lifshitz transition
with a dynamical exponent z = 2. Just like in the case z = 1 considered in New
J. Phys. 12, 055007 (2010) when a critical front propagates much faster than
the maximal group velocity of quasiparticles vq, then the transition is
effectively homogeneous: density of excitations obeys a generalized
Kibble-Zurek mechanism and scales with the sixth root of the transition rate.
However, unlike for z = 1, the inhomogeneous transition becomes adiabatic not
below vq but a lower threshold velocity v', proportional to inhomogeneity of
the transition, where the excitations are suppressed exponentially.
Interestingly, the adiabatic threshold v' is nonzero despite vanishing minimal
group velocity of low energy quasiparticles. In the adiabatic regime below v'
the inhomogeneous transition can be used for efficient adiabatic quantum state
preparation in a quantum simulator: the time required for the critical front to
sweep across a chain of N spins adiabatically is merely linear in N, while the
corresponding time for a homogeneous transition across the multicritical point
scales with the sixth power of N. What is more, excitations after the adiabatic
inhomogeneous transition, if any, are brushed away by the critical front to the
end of the spin chain.Comment: 10 pages, 6 figures, improved version accepted in NJ
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