Carnegie Mellon University

About: Carnegie Mellon University is a education organization based out in Pittsburgh, Pennsylvania, United States. It is known for research contribution in the topics: Population & Robot. The organization has 36317 authors who have published 104359 publications receiving 5975734 citations. The organization is also known as: CMU & Carnegie Mellon.

Service disciplines for guaranteed performance service in packet-switching networks

Abstract: While today's computer networks support only best-effort service, future packet-switching integrated-services networks will have to support real-time communication services that allow clients to transport information with performance guarantees expressed in terms of delay, delay jitter, throughput, and loss rate. An important issue in providing guaranteed performance service is the choice of the packet service discipline at switching nodes. In this paper, we survey several service disciplines that are proposed in the literature to provide per-connection end-to-end performance guarantees in packet-switching networks. We describe their mechanisms, their similarities and differences and the performance guarantees they can provide. Various issues and tradeoffs in designing service disciplines for guaranteed performance service are discussed, and a general framework for studying and comparing these disciplines are presented. >

Three-dimensional printing of complex biological structures by freeform reversible embedding of suspended hydrogels.

Abstract: We demonstrate the additive manufacturing of complex three-dimensional (3D) biological structures using soft protein and polysaccharide hydrogels that are challenging or impossible to create using traditional fabrication approaches. These structures are built by embedding the printed hydrogel within a secondary hydrogel that serves as a temporary, thermoreversible, and biocompatible support. This process, termed freeform reversible embedding of suspended hydrogels, enables 3D printing of hydrated materials with an elastic modulus <500 kPa including alginate, collagen, and fibrin. Computer-aided design models of 3D optical, computed tomography, and magnetic resonance imaging data were 3D printed at a resolution of ~200 μm and at low cost by leveraging open-source hardware and software tools. Proof-of-concept structures based on femurs, branched coronary arteries, trabeculated embryonic hearts, and human brains were mechanically robust and recreated complex 3D internal and external anatomical architectures.

Coping with stress: divergent strategies of optimists and pessimists.

Abstract: Previous research has shown that dispositional optimism is a prospective predictor of successful adaptation to stressful encounters. In this research we attempted to identify possible mechanisms underlying these effects by examining how optimists differ from pessimists in the kinds of coping strategies that they use. The results of two separate studies revealed modest but reliable positive correlations between optimism and problem-focused coping, seeking of social support, and emphasizing positive aspects of the stressful situation. Pessimism was associated with denial and distancing (Study 1), with focusing on stressful feelings, and with disengagement from the goal with which the stressor was interfering (Study 2). Study 1 also found a positive association between optimism and acceptance/resignation, but only when the event was construed as uncontrollable. Discussion centers on the implications of these findings for understanding the meaning of people's coping efforts in stressful circumstances.

Efficiency Analysis for Exogenously Fixed Inputs and Outputs

Abstract: We evaluate, by means of mathematical programming formulations, the relative technical and scale efficiencies of decision making units DMUs when some of the inputs or outputs are exogenously fixed and beyond the discretionary control of DMU managers. This approach further develops the work on efficiency evaluation and on estimation of efficient production frontiers known as data envelopment analysis DEA. We also employ the model to provide efficient input and output targets for DMU managers in a way that specifically accounts for the fixed nature of some of the inputs or outputs. We illustrate the approach, using real data, for a network of fast food restaurants.

Theoretical models incorporating electron correlation

Abstract: Some methods of describing electron correlation are compared from the point of view of requirements for theoretical chemical models. The perturbation approach originally introduced by Moller and Plesset, terminated at finite order, is found to satisfy most of these requirements. It is size consistent, that is, applicable to an ensemble of isolated systems in an additive manner. On the other hand, it does not provide an upper bound for the electronic energy. The independent electron-pair approximation is accurate to second order in a Moller-Plesset expansion, but inaccurate in third order. A series of variational methods is discussed which gives upper bounds for the energy, but which lacks size consistency. Finally, calculations on some small molecules using a moderately large Gaussian basis are presented to illustrate these points. Equilibrium geometries, dissociation energies, and energy separations between electronic states of different spin multiplicities are describe substantially better by Moller--Plesset theory to second or third order than by Hartree--Fock theory.