4,348 research outputs found
Incorporation of Inherent Safety and Environmental Aspects in Process Design and Supply Chain Optimization
The integration of inherently safer design and environmental aspects at the early phases of supply chain selection and process design provides significant benefits. It allows the highest ability to positively influence lifecycle safety, environmental impact, and cost of the project. Because of the preliminary nature of conceptual process design, it is crucial to have a simple yet effective approach to evaluate and compare the design alternatives based on the safety and environmental aspects at the early stage of the project when available engineering information and data are limited. This work proposes a framework to incorporating life-cycle safety measures in the supply chain design and the process technologies included in the supply chain.
A hierarchical approach is developed for conceptual-phase engineering project to facilitate the inclusion of safety objectives in the process synthesis and supply chain design engineering work in a consistent manner. Design options are first generated and screened based on economic criteria. Next, safety metrics are used in addition to economic objectives to evaluate the various designs and transportation options. Findings from the hazard and risk assessment are used to generate design alternatives to improve the safety performance. Economic evaluation is updated for acceptable options to guide the decision making.
To demonstrate the approach, a case study is solved for a conceptual design of a high density polyethylene (HDPE) supply chain from shale gas. Various conceptual design options that considered different elements such as process technology, manufacturing network and capacity were screened and evaluated per proposed framework. A high-level quantitative risk assessment approach was used for assessing the safety aspects of the design options
Incorporation of Inherent Safety and Environmental Aspects in Process Design and Supply Chain Optimization
The integration of inherently safer design and environmental aspects at the early phases of supply chain selection and process design provides significant benefits. It allows the highest ability to positively influence lifecycle safety, environmental impact, and cost of the project. Because of the preliminary nature of conceptual process design, it is crucial to have a simple yet effective approach to evaluate and compare the design alternatives based on the safety and environmental aspects at the early stage of the project when available engineering information and data are limited. This work proposes a framework to incorporating life-cycle safety measures in the supply chain design and the process technologies included in the supply chain.
A hierarchical approach is developed for conceptual-phase engineering project to facilitate the inclusion of safety objectives in the process synthesis and supply chain design engineering work in a consistent manner. Design options are first generated and screened based on economic criteria. Next, safety metrics are used in addition to economic objectives to evaluate the various designs and transportation options. Findings from the hazard and risk assessment are used to generate design alternatives to improve the safety performance. Economic evaluation is updated for acceptable options to guide the decision making.
To demonstrate the approach, a case study is solved for a conceptual design of a high density polyethylene (HDPE) supply chain from shale gas. Various conceptual design options that considered different elements such as process technology, manufacturing network and capacity were screened and evaluated per proposed framework. A high-level quantitative risk assessment approach was used for assessing the safety aspects of the design options
Floquet engineering of long-range p-wave superconductivity: Beyond the high-frequency limit
It has been shown that long-range {\it p}-wave superconductivity in a Kitaev
chain can be engineered via an ac field with a high frequency [Benito et al.,
Phys. Rev. B 90, 205127 (2014)]. For its experimental realization, however,
theoretical understanding of Floquet engineering with a broader range of
driving frequencies becomes important. In this work, focusing on the ac-driven
tunneling interactions of a Kitaev chain, we investigate effects from the
leading correction to the high-frequency limit on the emergent {\it p}-wave
superconductivity. Importantly, we find new engineered long-range {\it p}-wave
pairing interactions that can significantly alter the ones in the
high-frequency limit at long interaction ranges. We also find that the leading
correction additionally generates nearest-neighbor {\it p}-wave pairing
interactions with a renormalized pairing energy, long-range tunneling
interactions, and in particular multiple pairs of Floquet Majorana edge states
that are destroyed in the high- frequency limit.Comment: 13 pages, 8 figure
Backaction of a charge detector on a double quantum dot
We develop a master equation approach to study the backaction of quantum
point contact (QPC) on a double quantum dot (DQD) at zero bias voltage. We
reveal why electrons can pass through the zero-bias DQD only when the bias
voltage across the QPC exceeds a threshold value determined by the eigenstate
energy difference of the DQD. This derived excitation condition agrees well
with experiments on QPC-induced inelastic electron tunneling through a DQD [S.
Gustavsson et al., Phys. Rev. Lett. 99, 206804(2007)]. Moreover, we propose a
new scheme to generate a pure spin current by the QPC in the absence of a
charge current.Comment: 6 pages, 4 figure
Collective quantum phase slips in multiple nanowire junctions
Realization of robust coherent quantum phase slips represents a significant
experimental challenge. Here we propose a new design consisting of multiple
nanowire junctions to realize a phase-slip flux qubit. It admits good
tunability provided by gate voltages applied on superconducting islands
separating nanowire junctions. In addition, the gates and junctions can be
identical or distinct to each other leading to symmetric and asymmetric setups.
We find that the asymmetry can improve the performance of the proposed device,
compared with the symmetric case. In particular, it can enhance the effective
rate of collective quantum phase slips. Furthermore, we demonstrate how to
couple two such devices via a mutual inductance. This is potentially useful for
quantum gate operations. Our investigation on how symmetry in multiple nanowire
junctions affects the device performance should be useful for the application
of phase-slip flux qubits in quantum information processing and quantum
metrology.Comment: 12 pages, 6 figure
Cooling a nanomechanical resonator by a triple quantum dot
We propose an approach for achieving ground-state cooling of a nanomechanical
resonator (NAMR) capacitively coupled to a triple quantum dot (TQD). This TQD
is an electronic analog of a three-level atom in configuration which
allows an electron to enter it via lower-energy states and to exit only from a
higher-energy state. By tuning the degeneracy of the two lower-energy states in
the TQD, an electron can be trapped in a dark state caused by destructive
quantum interference between the two tunneling pathways to the higher-energy
state. Therefore, ground-state cooling of an NAMR can be achieved when
electrons absorb readily and repeatedly energy quanta from the NAMR for
excitations.Comment: 6 pages, 3 figure
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