22,000 research outputs found
Gamma-Ray Burst Afterglows with Energy Injection: Homogeneous Versus Wind External Media
Assuming an adiabatic evolution of a gamma-ray burst (GRB) fireball
interacting with an external medium, we calculate the hydrodynamics of the
fireball with energy injection from a strongly magnetic millisecond pulsar
through magnetic dipole radiation, and obtain the light curve of the optical
afterglow from the fireball by synchrotron radiation. Results are given both
for a homogeneous external medium and for a wind ejected by GRB progenitor. Our
calculations are also available in both ultra-relativistic and non-relativistic
phases. Furthermore, the observed R-band light curve of GRB{000301C} can be
well fitted in our model, which might provide a probe of the properties of GRB
progenitors.Comment: revised version for publication in Chin. Phys. Let
Semileptonic B decays into excited charmed mesons from QCD sum rules
Exclusive semileptonic decays into excited charmed mesons are studied
with QCD sum rules in the leading order of heavy quark effective theory. Two
universal Isgur-Wise functions \tau and \zeta for semileptonic B decays into
four lowest lying excited mesons (, , , and ) are
determined. The decay rates and branching ratios for these processes are
calculated.Comment: RevTeX, 17 pages including 2 figure
Convergence of Blockchain and Edge Computing for Secure and Scalable IIoT Critical Infrastructures in Industry 4.0
This is the author accepted manuscript. The final version is available from IEEE via the DOI in this recordCritical infrastructure systems are vital to underpin
the functioning of a society and economy. Due to ever-increasing
number of Internet-connected Internet-of-Things (IoTs) / Industrial IoT (IIoT), and high volume of data generated and collected,
security and scalability are becoming burning concerns for
critical infrastructures in industry 4.0. The blockchain technology
is essentially a distributed and secure ledger that records all
the transactions into a hierarchically expanding chain of blocks.
Edge computing brings the cloud capabilities closer to the
computation tasks. The convergence of blockchain and edge
computing paradigms can overcome the existing security and
scalability issues. In this paper, we first introduce the IoT/IIoT
critical infrastructure in industry 4.0, and then we briefly present
the blockchain and edge computing paradigms. After that, we
show how the convergence of these two paradigms can enable
secure and scalable critical infrastructures. Then, we provide a
survey on state-of-the-art for security and privacy, and scalability
of IoT/IIoT critical infrastructures. A list of potential research
challenges and open issues in this area is also provided, which
can be used as useful resources to guide future research.Engineering and Physical Sciences Research Council (EPSRC
Research on relationship between charging principle and hearth activity of blast furnace (BF)
The relationship between charging principle and hearth activity of blast furnace has been clarified in this research. The voidage and diameter of coke in deadman which are related to charging principle serve as two pivotal factors for hearth activity. Discrete element method (DEM) analog simulation illustrates that both central and non-central coke charging result in the stratified structure of coke and ore in BF center. It is suggested to take non-central coke charging to promote central gas flow if the quality of raw materials meets the corresponding requirements. For the BF with poor raw materials, it is reasonable to employ central coke charging to keep the long-term stability of the production
Research on relationship between charging principle and hearth activity of blast furnace (BF)
The relationship between charging principle and hearth activity of blast furnace has been clarified in this research. The voidage and diameter of coke in deadman which are related to charging principle serve as two pivotal factors for hearth activity. Discrete element method (DEM) analog simulation illustrates that both central and non-central coke charging result in the stratified structure of coke and ore in BF center. It is suggested to take non-central coke charging to promote central gas flow if the quality of raw materials meets the corresponding requirements. For the BF with poor raw materials, it is reasonable to employ central coke charging to keep the long-term stability of the production
Verifying Policy Enforcers
Policy enforcers are sophisticated runtime components that can prevent
failures by enforcing the correct behavior of the software. While a single
enforcer can be easily designed focusing only on the behavior of the
application that must be monitored, the effect of multiple enforcers that
enforce different policies might be hard to predict. So far, mechanisms to
resolve interferences between enforcers have been based on priority mechanisms
and heuristics. Although these methods provide a mechanism to take decisions
when multiple enforcers try to affect the execution at a same time, they do not
guarantee the lack of interference on the global behavior of the system. In
this paper we present a verification strategy that can be exploited to discover
interferences between sets of enforcers and thus safely identify a-priori the
enforcers that can co-exist at run-time. In our evaluation, we experimented our
verification method with several policy enforcers for Android and discovered
some incompatibilities.Comment: Oliviero Riganelli, Daniela Micucci, Leonardo Mariani, and Yli\`es
Falcone. Verifying Policy Enforcers. Proceedings of 17th International
Conference on Runtime Verification (RV), 2017. (to appear
Particle-hole symmetry in the antiferromagnetic state of the cuprates
In the layered cuprate perovskites, the occurence of high-temperature
superconductivity seems deeply related to the unusual nature of the hole
excitations. The limiting case of a very small number of holes diffusing in the
antiferromagnetic (AF) background may provide important insights into this
problem. We have investigated the transport properties in a series of crystals
of , and found that the temperature dependences of the Hall
coefficient and thermopower change abruptly as soon as the AF phase
boundary is crossed. In the AF state at low temperatures , both and
are unexpectedly suppressed to nearly zero over a broad interval of . We
argue that this suppression arises from near-exact symmetry in the
particle-hole currents. From the trends in and , we infer that the
symmetry is increasingly robust as the hole density becomes very small
(). We discuss implications for electronic properties both within
the AF state and outside.Comment: 8 pages, 7 figure
- …