873 research outputs found
The correspondence between augmentations and rulings for Legendrian knots
We strengthen the link between holomorphic and generating-function invariants
of Legendrian knots by establishing a formula relating the number of
augmentations of a knot's contact homology to the complete ruling invariant of
Chekanov and Pushkar.Comment: v2: 10 pages, 3 figures; minor revisions, to appear in Pacific J.
Mat
Sneutrino Higgs models explain lepton non-universality in CMS excesses
Recent searches for first-generation leptoquarks and heavy right-handed
bosons have seen excesses in final states with electrons and jets. A bizarre
property of these excesses is that they appear to violate lepton universality.
With these results in mind, we study the phenomenology of supersymmetric models
in which the Higgs arises as the sneutrino in an electron supermultiplet. Since
the electron is singled out in this approach, one can naturally account for the
lepton flavor structure of the excesses. In this work, we show that in such a
framework, one can significantly alleviate the tension between the Standard
Model and the data and yet evade current constraints from other searches.
Lastly we point out that correlated excesses are expected to be seen in future
multilepton searches.Comment: 17 pages, 7 figure
SEABASS: Symmetric-keychain Encryption and Authentication for Building Automation Systems
There is an increasing security risk in Building Automation Systems (BAS) in that its communication is unprotected, resulting in the adversary having the capability to inject spurious commands to the actuators to alter the behaviour of BAS. The communication between the Human-Machine-Interface (HMI) and the controller (PLC) is vulnerable as there is no secret key being used to protect the authenticity, confidentiality and integrity of the sensor data and commands.
We propose SEABASS, a lightweight key management scheme to distribute and manage session keys between HMI and PLCs, providing a secure communication channel between any two communicating devices in BAS through a symmetric-key based hash-chain encryption and authentication of message exchange. Our scheme facilitates automatic renewal of session keys periodically based on the use of a reversed hash-chain. A prototype was implemented using the BACnet/IP communication protocol and the preliminary results show that the symmetric keychain approach is lightweight and incurs low latency
Invariants of Legendrian Knots and Coherent Orientations
We provide a translation between Chekanov's combinatorial theory for
invariants of Legendrian knots in the standard contact R^3 and a relative
version of Eliashberg and Hofer's Contact Homology. We use this translation to
transport the idea of ``coherent orientations'' from the Contact Homology world
to Chekanov's combinatorial setting. As a result, we obtain a lifting of
Chekanov's differential graded algebra invariant to an algebra over Z[t,t^{-1}]
with a full Z grading.Comment: 32 pages, 17 figures; small technical corrections to proof of Thm 3.7
and example 4.
Environmental, operational and financial sustainability of packaging methods in delivery businesses
Thesis (M. Eng. in Logistics)--Massachusetts Institute of Technology, Engineering Systems Division, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 143-148).In retail delivery companies, packaging is used to transport goods to customers while preventing damage, shrinkage and loss of the contents. With consumer preferences reflecting the growing concern for the environment, retail delivery businesses are at the crossroads of implementing a sustainable operational and financial business model of delivering packages to customers. In this thesis, we will address the issue of sustainable packaging in retail delivery companies by evaluating the financial, environmental and operational viability of such strategies. The thesis will be limited to the downstream order fulfillment cycle from the retail delivery company to the customer. We will focus on three areas applicable to sustainable packaging. The first area is materials innovation where we will analyze alternative materials suitable for retail delivery packaging. The second area involves waste elimination through reducing packaging material use and reusing of packaging materials through a returnable tote program. Lastly, we will understand the implementation challenges to increase the success rate of the strategies mentioned earlier.by Joshua Ng and Kendall Chow.M.Eng.in Logistic
Critical Fidelity
Using a Wigner Lorentzian Random Matrix ensemble, we study the fidelity,
, of systems at the Anderson metal-insulator transition, subject to small
perturbations that preserve the criticality. We find that there are three decay
regimes as perturbation strength increases: the first two are associated with a
gaussian and an exponential decay respectively and can be described using
Linear Response Theory. For stronger perturbations decays algebraically
as , where is the correlation dimension of the
critical eigenstates.Comment: 4 pages, 3 figures. Revised and published in Phys. Rev. Let
Analysis of Shop Floor Performance through Discrete Event Simulation: A Case Study
Shop floor performance management is a method to ensure the effective utilization of people, processes, and equipment. Changes
in the shop floor might have a positive or negative effect on production performance. Therefore, optimal shop floor operation is
required to enhance shop floor performance and to ensure the long-term efficiency of the production process. This work presents
a case study of a semiconductor industry. The punching department is modeled to investigate the effect of changes in the shop
floor on production performance through discrete event simulation. The effects on the throughput rate, machine utilization, and
labor utilization are studied by adjusting the volume of parts, number of operators, and flow pattern of parts in a series of models.
Simulation results are tested and analyzed by using analysis of variance (ANOVA).The best model under changes in the shop floor
is identified during the exploration of alternative scenarios
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