Propagation of gaseous detonation waves in a spatially inhomogeneous reactive medium

Detonation propagation in a compressible medium wherein the energy release has been made spatially inhomogeneous is examined via numerical simulation. The inhomogeneity is introduced via step functions in the reaction progress variable, with the local value of energy release correspondingly increased so as to maintain the same average energy density in the medium, and thus a constant Chapman Jouguet (CJ) detonation velocity. A one-step Arrhenius rate governs the rate of energy release in the reactive zones. The resulting dynamics of a detonation propagating in such systems with one-dimensional layers and two-dimensional squares are simulated using a Godunov-type finite-volume scheme. The resulting wave dynamics are analyzed by computing the average wave velocity and one-dimensional averaged wave structure. In the case of sufficiently inhomogeneous media wherein the spacing between reactive zones is greater than the inherent reaction zone length, average wave speeds significantly greater than the corresponding CJ speed of the homogenized medium are obtained. If the shock transit time between reactive zones is less than the reaction time scale, then the classical CJ detonation velocity is recovered. The spatio-temporal averaged structure of the waves in these systems is analyzed via a Favre averaging technique, with terms associated with the thermal and mechanical fluctuations being explicitly computed. The analysis of the averaged wave structure identifies the super-CJ detonations as weak detonations owing to the existence of mechanical non-equilibrium at the effective sonic point embedded within the wave structure. The correspondence of the super-CJ behavior identified in this study with real detonation phenomena that may be observed in experiments is discussed

Quasi-Local Energy Flux of Spacetime Perturbation

A general expression for quasi-local energy flux for spacetime perturbation is derived from covariant Hamiltonian formulation using functional differentiability and symplectic structure invariance, which is independent of the choice of the canonical variables and the possible boundary terms one initially puts into the Lagrangian in the diffeomorphism invariant theories. The energy flux expression depends on a displacement vector field and the 2-surface under consideration. We apply and test the expression in Vaidya spacetime. At null infinity the expression leads to the Bondi type energy flux obtained by Lindquist, Schwartz and Misner. On dynamical horizons with a particular choice of the displacement vector, it gives the area balance law obtained by Ashtekar and Krishnan.Comment: 8 pages, added appendix, version to appear in Phys. Rev.

Scattering of coherent states on a single artificial atom

In this work we theoretically analyze a circuit QED design where propagating quantum microwaves interact with a single artificial atom, a single Cooper pair box. In particular, we derive a master equation in the so-called transmon regime, including coherent drives. Inspired by recent experiments, we then apply the master equation to describe the dynamics in both a two-level and a three-level approximation of the atom. In the two-level case, we also discuss how to measure photon antibunching in the reflected field and how it is affected by finite temperature and finite detection bandwidth.Comment: 18 pages, 7 figure

SLUG FLOW IN LARGE DIAMETER PIPELINE-RISER SYSTEMS: PREDICTION AND MITIGATION

 Slug flow could pose serious threat to oil and gas production facility. The objective of the study was to gain better insight into the behaviour of slug flow in large pipe diameter pipeline-riser system. The influence of geometry configuration on the slug characteristics was also investigated. The understanding of these are very important in the development of effective slug control strategy. Numerical simulations were carried out on a 3.7 km long horizontal pipeline leading to a 0.13 km vertical riser using an industrial software package. The pipeline and riser are both of 17” internal diameter. Slug envelopes were developed for the pipeline-riser system and its constituents’ pipes. A total number of 572 data points were investigated, covering superficial velocities ranging from 0.01 to 44.28 m/s for gas and 0.02 and 8.25 m/s for liquid. The results showed three distinct slug flow regions: region due to horizontal pipeline slugging (H) where slugs formed in the horizontal pipeline are transported through the riser pipe nearly unchanged, region due to both horizontal and vertical pipes slug contributions (I) where the slugs formed in the horizontal pipe keeps growing even through the riser pipe and region due to vertical pipe slugging (V) where slug formation was predominantly due to the vertical pipe. The observed phenomenon is in consonance qualitatively with the experimental studies published in another paper, but quantitatively different and this may be due to diameter effect.  The results also showed that choking can indeed be used to mitigate slug flow in all the regions but at considerable cost. The valve must be choked down at various degrees depending on the regions (flow conditions). There is therefore, the need to seek a better way of stabilizing slug flow bearing in mind the distinct behaviours of the identified regions

Phase-Remapping Attack in Practical Quantum Key Distribution Systems

Quantum key distribution (QKD) can be used to generate secret keys between two distant parties. Even though QKD has been proven unconditionally secure against eavesdroppers with unlimited computation power, practical implementations of QKD may contain loopholes that may lead to the generated secret keys being compromised. In this paper, we propose a phase-remapping attack targeting two practical bidirectional QKD systems (the "plug & play" system and the Sagnac system). We showed that if the users of the systems are unaware of our attack, the final key shared between them can be compromised in some situations. Specifically, we showed that, in the case of the Bennett-Brassard 1984 (BB84) protocol with ideal single-photon sources, when the quantum bit error rate (QBER) is between 14.6% and 20%, our attack renders the final key insecure, whereas the same range of QBER values has been proved secure if the two users are unaware of our attack; also, we demonstrated three situations with realistic devices where positive key rates are obtained without the consideration of Trojan horse attacks but in fact no key can be distilled. We remark that our attack is feasible with only current technology. Therefore, it is very important to be aware of our attack in order to ensure absolute security. In finding our attack, we minimize the QBER over individual measurements described by a general POVM, which has some similarity with the standard quantum state discrimination problem.Comment: 13 pages, 8 figure

Probing the quantum vacuum with an artificial atom in front of a mirror

Quantum fluctuations of the vacuum are both a surprising and fundamental phenomenon of nature. Understood as virtual photons flitting in and out of existence, they still have a very real impact, \emph{e.g.}, in the Casimir effects and the lifetimes of atoms. Engineering vacuum fluctuations is therefore becoming increasingly important to emerging technologies. Here, we shape vacuum fluctuations using a "mirror", creating regions in space where they are suppressed. As we then effectively move an artificial atom in and out of these regions, measuring the atomic lifetime tells us the strength of the fluctuations. The weakest fluctuation strength we observe is 0.02 quanta, a factor of 50 below what would be expected without the mirror, demonstrating that we can hide the atom from the vacuum

The impact of power and relationship commitment on the integration between manufacturers and customers in a supply chain

Supply chain integration (SCI) has received increasing attention from scholars and practitioners in recent years. However, our knowledge of what influences SCI is still very limited. Although marketing and management researchers have investigated power and relationship commitment issues between organizations, few have examined their impact on SCI. This paper extends the power–relationship commitment theory established in Western marketing literature and links it with SCI in China, through examining the relationship between power, relationship commitment and the integration between manufacturers and their customers. We propose and empirically test a model using data collected from 617 manufacturing companies in China. The results show that different types of customer power impact manufacturers’ relationship commitment in different ways. Expert power, referent power and reward power are important in improving manufacturers’ normative relationship commitment, while reward power and coercive power enhance instrumental relationship commitment. We also found that normative relationship commitment had a greater impact on customer integration than instrumental relationship commitment. These findings are interpreted in light of national culture differences between China and the U.S. in terms of power distance and collectivism, which provide a new perspective on SCI