Enhancement of coherent energy transfer by disorder and temperature in light harvesting processes

We investigate the influence of static disorder and thermal excitations on excitonic energy transport in the light-harvesting apparatus of photosynthetic systems by solving the Schr\"{o}dinger equation and taking into account the coherent hoppings of excitons, the rates of exciton creation and annihilation in antennas and reaction centers, and the coupling to thermally excited phonons. The antennas and reaction centers are modeled, respectively, as the sources and drains which provide the channels for creation and annihilation of excitons. Phonon modes below a maximum frequency are coupled to the excitons that are continuously created in the antennas and depleted in the reaction centers, and the phonon population in these modes obeys the Bose-Einstein distribution at a given temperature. It is found that the energy transport is not only robust against the static disorder and the thermal noise, but it can also be enhanced by increasing the randomness and temperature in most parameter regimes. Relevance of our work to the highly efficient energy transport in photosynthetic systems is discussed.Comment: 21 pages, 6 figure

Vibration Induced Non-adiabatic Geometric Phase and Energy Uncertainty of Fermions in Graphene

We investigate geometric phase of fermion states under relative vibrations of two sublattices in graphene by solving time-dependent Sch\"{o}dinger equation using Floquet scheme. In a period of vibration the fermions acquire different geometric phases depending on their momenta. There are two regions in the momentum space: the adiabatic region where the geometric phase can be approximated by the Berry phase and the chaotic region where the geometric phase drastically fluctuates in changing parameters. The energy of fermions due to vibrations shows spikes in the chaotic region. The results suggest a possible dephasing mechanism which may cause classical-like transport properties in graphene.Comment: 9 pages, 5 figure

Statistical Properties of Interacting Bose Gases in Quasi-2D Harmonic Traps

The analytical probability distribution of the quasi-2D (and purely 2D) ideal and interacting Bose gas are investigated by using a canonical ensemble approach. Using the analytical probability distribution of the condensate, the statistical properties such as the mean occupation number and particle number fluctuations of the condensate are calculated. Researches show that there is a continuous crossover of the statistical properties from a quasi-2D to a purely 2D ideal or interacting gases. Different from the case of a 3D Bose gas, the interaction between atoms changes in a deep way the nature of the particle number fluctuations.Comment: RevTex, 10pages, 4 figures, E-mail: [email protected]

Topology Control Algorithm considering Antenna Radiation Pattern in Three-Dimensional Wireless Sensor Networks

Topology control is a key issue of wireless sensor network to reduce energy consumption and communication collision. Topology control algorithms in three-dimensional space have been proposed by modifying existing two-dimensional algorithms. These algorithms are based on the theoretical assumption that transmission power is radiated equally to the all directions by using isotropic antenna model. However, isotropic antenna does not exist, which is hypothetical antenna to compare the real antenna performance. In the real network, dipole antenna is applied, and because of the radiation pattern, performance of topology control algorithm is degraded. We proposed local remapping algorithm to solve the problem and applied it to existing topology control algorithms. Simulation results show that our algorithm increases performance of existing algorithms and reduces power consumption

Internet of Things Cloud: Architecture and Implementation

The Internet of Things (IoT), which enables common objects to be intelligent and interactive, is considered the next evolution of the Internet. Its pervasiveness and abilities to collect and analyze data which can be converted into information have motivated a plethora of IoT applications. For the successful deployment and management of these applications, cloud computing techniques are indispensable since they provide high computational capabilities as well as large storage capacity. This paper aims at providing insights about the architecture, implementation and performance of the IoT cloud. Several potential application scenarios of IoT cloud are studied, and an architecture is discussed regarding the functionality of each component. Moreover, the implementation details of the IoT cloud are presented along with the services that it offers. The main contributions of this paper lie in the combination of the Hypertext Transfer Protocol (HTTP) and Message Queuing Telemetry Transport (MQTT) servers to offer IoT services in the architecture of the IoT cloud with various techniques to guarantee high performance. Finally, experimental results are given in order to demonstrate the service capabilities of the IoT cloud under certain conditions.Comment: 19pages, 4figures, IEEE Communications Magazin

A Tri-band-notched UWB Antenna with Low Mutual Coupling between the Band-notched Structures

A compact printed U-shape ultra-wideband (UWB) antenna with triple band-notched characteristics is presented. The proposed antenna, with compact size of 24×33 mm2, yields an impedance bandwidth of 2.8-12GHz for VSWR<2, except the notched bands. The notched bands are realized by introducing two different types of slots. Two C-shape half-wavelength slots are etched on the radiating patch to obtain two notched bands in 3.3-3.7GHz for WiMAX and 7.25-7.75GHz for downlink of X-band satellite communication systems. In order to minimize the mutual coupling between the band-notched structures, the middle notched band in 5-6GHz for WLAN is achieved by using a U-slot defected ground structure. The parametric study is carried out to understand the mutual coupling. Surface current distributions and equivalent circuit are used to illustrate the notched mechanism. The performance of this antenna both by simulation and by experiment indicates that the proposed antenna is suitable and a good candidate for UWB applications

Non-linear amplification of small spin precession using long range dipolar interactions

In measurements of small signals using spin precession the precession angle usually grows linearly in time. We show that non-linear interactions between particles can lead to an exponentially growing spin precession angle, resulting in an amplification of small signals and raising them above the noise level of a detection system. We demonstrate amplification by a factor of greater than 8 of a spin precession signal due to a small magnetic field gradient in a spherical cell filled with hyperpolarized liquid $^{129}$Xe. This technique can improve the sensitivity in many measurements that are limited by the noise of the detection system, rather then the fundamental spin-projection noise.Comment: 4 pages, 4 figure

Vibration problem of a spherical tank containing jet propellant: numerical simulations

This document is the final report on the joint research project on vibration problem of a spherical tank containing jet propellant between IHI, Japan and SES, University of Southampton, UK. The background of the project is described. The fundamental principles and numerical method used in numerical simulations are presented. The detailed FEA models for each studied cases are given. The calculation results are presented using tables, curves, figures as well as the attached data files. The available experiment results are listed to compare with the numerical calculations. The calculation results show a fundamental agreement with the experiment results. The numerical analysis confirms that:1)Due to water – tank interaction, the natural frequencies of the water – tank system are decreased with the water level increase. For the 25% water level, the natural frequencies, especially heave mode frequency, shows a significant decrease compared with the empty case. However, with continuing increase the filed water more than 25% level, the decrease gradient of the natural frequencies gradually tends to zero. In the 100% water case, the natural frequency of heave mode is about 200 Hz which can not equal zero.2)Considering free surface wave effect produces a lot of sloshing modes of very low frequencies compared with the natural frequencies of the dry tank structure. Therefore, for dynamic response analysis with high frequency excitations, the free surface wave may be neglected. However, to assess loads caused by sloshing modes, the free surface waves have to be considered.3)There exist relative big deformations at the four tank support places in several vibration modes, which may produce a large local stress at support places to cause the product fail in vibration environment. A strengthen local design at the support places is needed.4)The dynamic response results are affected by damping coefficients of all modes used in the dynamic response analysis. The damping coefficients are approximately presented and therefore, the numerical results are good reference for practical designs.The report confirms that the original purpose of this joint research project has well completed by IHI and SES