Can the age discrepancies of neutron stars be circumvented by an accretion-assisted torque?

It is found that 1E 1207.4-5209 could be a low-mass bare strange star if its small radius or low altitude cyclotron formation can be identified. The age problems of five sources could be solved by a fossil-disk-assisted torque. The magnetic dipole radiation dominates the evolution of PSR B1757-24 at present, and the others are in propeller (or tracking) phases.Comment: ApJL accepted, or at http://vega.bac.pku.edu.cn/~rxxu/publications/index_P.ht

Quantum state engineering with flux-biased Josephson phase qubits by Stark-chirped rapid adiabatic passages

In this paper, the scheme of quantum computing based on Stark chirped rapid adiabatic passage (SCRAP) technique [L. F. Wei et al., Phys. Rev. Lett. 100, 113601 (2008)] is extensively applied to implement the quantum-state manipulations in the flux-biased Josephson phase qubits. The broken-parity symmetries of bound states in flux-biased Josephson junctions are utilized to conveniently generate the desirable Stark-shifts. Then, assisted by various transition pulses universal quantum logic gates as well as arbitrary quantum-state preparations could be implemented. Compared with the usual PI-pulses operations widely used in the experiments, the adiabatic population passage proposed here is insensitive the details of the applied pulses and thus the desirable population transfers could be satisfyingly implemented. The experimental feasibility of the proposal is also discussed.Comment: 9 pages, 4 figure

Behavior modelling and individual recognition of sonar transmitter for secure communication in UASNs

It is necessary to improve the safety of the underwater acoustic sensor networks (UASNs) since it is mostly used in the military industry. Specific emitter identification is the process of identifying different transmitters based on the radio frequency fingerprint extracted from the received signal. The sonar transmitter is a typical low-frequency radiation source and is an important part of the UASNs. Class D Power Amplifier, a typical non-linear amplifier, is usually used in sonar transmitters. The inherent nonlinearity of power amplifiers provides fingerprint features that can be distinguished without transmitters for specific emitter recognition. Firstly, the non-linearity of the sonar transmitter is studied in depth, and the nonlinearity of the power amplifier is modeled and its non-linearity characteristics are analyzed. After obtaining the nonlinear model of an amplifier, a similar amplifier in practical application is obtained by changing its model parameters as the research object. The output signals are collected by giving the same input of different models, and then the output signals are extracted and classified. In this paper, the memory polynomial model is used to model the amplifier. The power spectrum features of the output signals are extracted as fingerprint features. Then the dimensionality of the high-dimensional features is reduced. Finally, the classifier is used to recognize the amplifier. The experimental results show that the individual sonar transmitter can be well identified by using the non-linear characteristics of the signal. By this way, this method can enhance the communication safety of UASNs

The use of product scarcity in marketing

Purpose: as a frequently observed business phenomenon, the use of product scarcity to improve a product’s market performance has received increasing attention from both academics and practitioners. The resulting literature has covered a wide variety of issues based on various theories, using different research methods, in a diverse range of settings. However, this diversity also makes it difficult to grasp the core themes and findings, and to see the outstanding knowledge gaps. This paper reviews previous studies on the use of product scarcity in marketing, and identifies new directions for future research. Design/methodology/approach: a systematic review was conducted to identify and analyse 66 research papers published in business and management journals between 1970 and 2017. Findings: we examined the underlying theories of scarcity-based marketing, and developed a conceptual framework that describes the key factors of product scarcity and how they influence both consumers and the market. We also highlighted some key achievements in modelling the processes involved in using product scarcity in marketing. Originality/value: our analysis of the identified papers suggests that there are substantial gaps in our knowledge of this field, which opens up new paths for future research. For future research, we identified three directions aimed at: addressing the practical needs of firms in understanding product scarcity; guiding the implementation of scarcity-based strategies; and measuring, monitoring, and predicting the level of product scarcity and its impacts during implementation