23,967 research outputs found
Pedersen ideals of tensor products of nonunital C*-algebras
We show that positive elements of a Pedersen ideal of a tensor product can be
approximated in a particularly strong sense by sums of tensor products of
positive elements. This has a range of applications to the structure of tracial
cones and related topics, such as the Cuntz-Pedersen space or the Cuntz
semigroup. For example, we determine the cone of lower semicontinuous traces of
a tensor product in terms of the traces of the tensor factors, in an arbitrary
C*-tensor norm. We show that the positive elements of a Pedersen ideal are
sometimes stable under Cuntz equivalence. We generalize a result of Pedersen's
by showing that certain classes of completely positive maps take a Pedersen
ideal into a Pedersen ideal. We provide theorems that in many cases compute the
Cuntz semigroup of a tensor product.Comment: circulated as preprint 2017
Silicon active microvalves using buckled membranes for actuation
Design considerations and experiments have been made for obtaining a new type of active microvalves using silicon buckled membranes. The properties of the buckled membranes permitting to obtain high deflections and to actuate them more convenient are demonstrated. A thermal actuation using an aluminium ring layer heated with a polysilicon resistor is analysed. The polysilicon and the aluminium ring layers have been deposited in the region of the membrane having the minimum internal stress. The fabrication process consist of photolithography, LPCVD depositions, diffusion, AI sputtering. isotropic, anisotropic etching and anodic bonding. The design and experiments show a convenient low temperature range necessary to actuate the microvalve.\ud
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Energy-aware Load Balancing Policies for the Cloud Ecosystem
The energy consumption of computer and communication systems does not scale
linearly with the workload. A system uses a significant amount of energy even
when idle or lightly loaded. A widely reported solution to resource management
in large data centers is to concentrate the load on a subset of servers and,
whenever possible, switch the rest of the servers to one of the possible sleep
states. We propose a reformulation of the traditional concept of load balancing
aiming to optimize the energy consumption of a large-scale system: {\it
distribute the workload evenly to the smallest set of servers operating at an
optimal energy level, while observing QoS constraints, such as the response
time.} Our model applies to clustered systems; the model also requires that the
demand for system resources to increase at a bounded rate in each reallocation
interval. In this paper we report the VM migration costs for application
scaling.Comment: 10 Page
Clustering Algorithms for Scale-free Networks and Applications to Cloud Resource Management
In this paper we introduce algorithms for the construction of scale-free
networks and for clustering around the nerve centers, nodes with a high
connectivity in a scale-free networks. We argue that such overlay networks
could support self-organization in a complex system like a cloud computing
infrastructure and allow the implementation of optimal resource management
policies.Comment: 14 pages, 8 Figurs, Journa
Quantum Error Correction of Time-Correlated Errors
The complexity of the error correction circuitry forces us to design quantum
error correction codes capable of correcting a single error per error
correction cycle. Yet, time-correlated error are common for physical
implementations of quantum systems; an error corrected during the previous
cycle may reoccur later due to physical processes specific for each physical
implementation of the qubits. In this paper we study quantum error correction
for a restricted class of time-correlated errors in a spin-boson model. The
algorithm we propose allows the correction of two errors per error correction
cycle, provided that one of them is time-correlated. The algorithm can be
applied to any stabilizer code when the two logical qubits and
are entangled states of basis states in
.Comment: 14 pages, 3 figure
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