Geometric Metasurface Fork Gratings for Vortex Beam Generation and Manipulation

In recent years, optical vortex beams possessing orbital angular momentum have caught much attention due to their potential for high capacity optical communications. This capability arises from the unbounded topological charges of orbital angular momentum (OAM) that provides infinite freedoms for encoding information. The two most common approaches for generating vortex beams are through fork diffraction gratings and spiral phase plates. While realization of conventional spiral phase plate requires complicated 3D fabrication, the emerging field of metasurfaces has provided a planar and facile solution for generating vortex beams of arbitrary orbit angular momentum. Here we realize a novel type of geometric metasurface fork grating that seamlessly combine the functionality of a metasurface phase plate for vortex beam generation, and that of a linear phase gradient metasurface for controlling the wave propagation direction. The metasurface fork grating is therefore capable of simultaneously controlling both the spin and the orbital angular momentum of light

Investments in green strategies improve company value

The opportunities and challenges in investing in environmental strategies have become an important issue as the world transcends into being more sustainable. Investments in green related strategies are given more importance as there is now opportunity to develop and engage in green projects. Firms are beginning to engage and involved themselves in the green marketplace at rapid pace to keep themselves on par with customers’ expectation as well as society’s expectation. These expectations include the demands for the reduction of ecological effects and the potential benefits of such actions. There has to be some sort of quantifiable meaning to these environmental actions to firms while trying to meet customers’ and societal expectations. Thus, the question of whether firms that invest in green initiatives improve their company value arises

Quantum efficiency measurement of single photon detectors using photon pairs generated in optical fibers

Using the correlated signal and idler photon pairs generated in a dispersion shifted fiber by a pulsed pump, we measure the quantum efficiency of a InGaAs/InP avalanche photodiode-based single photon detector. Since the collection efficiency of photon pairs is a key parameter to correctly deduce the quantum efficiency, we carefully characterize the collection efficiency by studying correlation dependence of photon pairs upon the spectra of pump, signal and idler photons. This study allows us to obtain quantum efficiency of the single photon detector by using photon pairs with various kinds of bandwidths.Comment: 21pages, 6figures, 4tables, accepted for publication in J. Opt. Soc. Am.

Prevalence of the metabolic syndrome in Chinese adolescents

Since national figures on the occurrence of metabolic syndrome among Chinese adolescents are lacking, this study aims to estimate its prevalence and distribution among Chinese youngsters. The 2002 China National Nutrition and Health Survey is a nationally representative cross-sectional study. Applying the criteria for US adolescents, we estimated the prevalence of metabolic syndrome among 2761 adolescents aged 15 to 19 years. The prevalence of metabolic syndrome among Chinese adolescents overall was 3·7% (10% in US adolescents). It was 35·2 %, 23·4% and 2·3% among adolescents who were overweight (BMI $95th percentile), at risk of overweight (BMI between 85th and 95th percentile) and normal weight (BMI below the 85th percentile), respectively. Urban boys had the highest rate (5·8$85th percentile and one or two parent(s) with metabolic syndrome, the prevalence was 46·4 %. A total of 96% of overweight adolescents had at least one and 74·1% overweight adolescents had at least two abnormalities of metabolic syndrome. Based on these figures, it is estimated that more than three million Chinese adolescents have metabolic syndrome. Both overweight and metabolic syndrome prevalence among adolescents are still relatively low in China, but the prevalence of metabolic syndrome among Chinese overweight adolescents is similar to those living in the USA

Rollout algorithm based duty cycle control with joint optimisation of delay and energy efficiency for beacon-enabled IEEE 802.15.4 networks

Duty cycle control is applied in IEEE 802.15.4 medium access control (MAC) protocol to reduce energy consumption. A low duty cycle improves the energy efficiency but it reduces the available transmission time, thereby increases the end-to-end delay. Thus, it is a challenge issue to achieve a good trade-off between energy efficiency and delay. In this paper, we study a duty cycle control problem with the aim of minimising the joint-cost of energy consumption and end-to-end delay. By applying dynamic programming (DP), the optimal duty cycle control is derived. Furthermore, to ensure the feasibility of implementing the control on computation limited sensor devices, a low complexity rollout algorithm based duty cycle control (RADutyCon) is proposed. The joint-cost upper bound of the proposed RADutyCon is investigated. Simulation results show that RADutyCon can effectively reduces the joint-cost of energy consumption and end-to-end delay under various network traffic. In addition, RADutyCon achieves an exponential reduction of computation complexity compared with DP optimal control

Practical applications of multi-agent systems in electric power systems

The transformation of energy networks from passive to active systems requires the embedding of intelligence within the network. One suitable approach to integrating distributed intelligent systems is multi-agent systems technology, where components of functionality run as autonomous agents capable of interaction through messaging. This provides loose coupling between components that can benefit the complex systems envisioned for the smart grid. This paper reviews the key milestones of demonstrated agent systems in the power industry and considers which aspects of agent design must still be addressed for widespread application of agent technology to occur

Efficient scheme for three-photon Greenberger-Horne-Zeilinger state generation

We propose an efficient scheme for the generation of three-photon Greenberger-Horne-Zeilinger (GHZ) state with linear optics and postselection. Several devices are designed and a two-mode quantum nondemolition (QND) detection is introduced to obtain the desired state. It is worth noting that the states which have entanglement in both polarization and spatial degrees of freedom are created in one of the designed setups. The method described in the present scheme can create a large number of three-photon GHZ states in principle. We also discuss an approach to generate the desired GHZ state in the presence of channel noise.Comment: 7pages, 3 figure

Exploring consumers' attitudes and behaviours toward online hotel room reservations

Marketers in Malaysia need to have solid understanding on consumers’ online attitude and buying behavior. This is mainly due to the shift and trend that consumers are moving fast into online purchasing. Malaysia is rank one of the ten countries in the world with the highest number of internet users. The travel market in the Asia Pacific region is fast growing and more consumers are reserving their hotel reservations via online travel agencies. Hence, the main purpose of this conceptual paper is to explore the factors that influence consumers’ attitude and purchase behaviour toward online hotel room reservations. Four factors which are information, trust, price and convenience have been identified in this study. The focus of this study will be on consumers who reserve their hotel rooms via online travel agents. The research plans to adopt a survey method using stratified random sampling and the hypotheses will be tested using structural equation modelling