Occupied Ones Research Articles

Dynamics of nest occupation and homing of solitary bees in painted trap nests

1. The oil‐collecting bee Centris analis (Fabricius, 1804) is an important pollinator for the Neotropical region. The species can be attracted to nest in human‐made cavities. Such trap nests or insect hotels offer the opportunity to study the behaviour of populations in semifield conditions.2. We studied a newly established trap nest aggregation of C. analis in Mato Grosso do Sul, Brazil and tested the effect that differentially painted nesting options have on the rate of nest foundation, and on the ability of relocating the nest when returning from a foraging trip (homing behaviour). Moreover, we tested if the duration of foraging trips decreased with time.3. We found that females preferred to nest in painted nests compared to unpainted nests, with blue nests being the most occupied ones, followed by purple, yellow, white, and green. Furthermore, bees improved their homing behaviour with time, however, nest colour did not seem to have an effect on this process. Moreover, we found that bees reduce the duration of their foraging trips with time. This could be an indicator of improved foraging efficiency through learning.4. These findings could inform a new and fruitful line of research on the behaviour and ecology of trap nesting solitary bees.

Implementation of Cognitive Radio Network Testbed for Multimedia Communications

A cognitive radio is a form of wireless communication in which a transceiver can intelligently detect which communication channels are in use and which are not, and instantly move into vacant channels while avoiding occupied ones. This intelligently avoids interference amongst users and provides the ability to use up all available bandwidth on the RF spectrum. There are many ways in which the communication can be demonstrated. This paper examines how we have implemented a cognitive radio network testbed using software defined radios (SDRs) for multimedia communications, where components that have been traditionally implemented in hardware are instead implemented by means of software on a personal computer or embedded system to communicate and transfer a file between each other. We attempt to demonstrate potential use of SDRs for future multimedia applications.

Two-dimensional imaging of energy bands from crystal orientation dependent higher-order harmonic spectra in h−BN

High-order harmonic generation (HHG) from hexagonal boron nitride is simulated by solving extended multiband semiconductor Bloch equations under strong laser fields. By changing the angle of the laser polarization with respect to the crystal orientation, we find that harmonic spectra present a double-plateau structure and HHG is dominantly emitted along \ensuremath{\Gamma}-M direction in the first plateau, but special anisotropic distribution is observed in the secondary plateau. In-depth analyses reveal that two plateaus originate from different pair of conduction band and valence band, and the shapes of band dispersion and transition dipole moment determine anisotropic harmonic emission in $h$-BN crystal. Furthermore, we show that band energies of high-lying unoccupied bands and low-lying occupied ones can be directly extracted from laser polarization dependent high harmonic spectra. This paves a way to image the two-dimensional band information of solid materials by using laser-induced HHG.

Genetic-based optimization of temperature set-point signals for buildings with unoccupied rooms

In this paper we present a strategy, based on genetic algorithms, for the optimization of the set-point signals for the heating system of a residential building in case there are totally unoccupied rooms. In particular, the optimization algorithm determines a particular set-point signal for each room based on a simplified linear temperature model of the system. The methodology includes constraints on the temperature level in the occupied rooms based on the choice of the inhabitants. A genetic algorithm determines the optimal set-point signal that have to be applied both to the unoccupied rooms and to the occupied ones in order to minimize the energy consumption in the case of a radiators-based heating system. Simulation results demonstrates the effectiveness of the method.

A Throughput and Spectrum Aware Fuzzy Logic Based Routing Protocol for CRN

Cognitive Radio has been considered a key technology in the future wireless communication. These radio networks with their spectrum sensing capability have become one of the most reliable wireless communication networks. Basically, these networks employ two types of users PU’s (Primary Users) having licensed frequency band for their usage and SU’s (Secondary Users) that can intelligently detect which communication channels are available and move into vacant ones while avoiding occupied ones. To have communication among these users, a routing protocol is used whose basic purpose is to provide a reliable route from source to destination. An important parameter while designing a routing strategy is the consideration of overall throughput of path. In this paper we consider the same to find the most optimal throughput path using fuzzy logic theory. MATLAB-7.01 is used for implementation and results show that our proposed scheme outperforms shortest spectrum aware routing scheme.

Intelligent Wireless Communication System Using Cognitive Radio

The increasing demand for wireless communication introduces efficient spectrum utilization challenge. To address this challenge, cognitive radio (CR) is emerged as the key technology; which enables opportunistic access to the spectrum. CR is a form of wireless communication in which a transceiver can intelligently detect which communication channels are in use and which are not, and instantly move into vacant channels while avoiding occupied ones. This optimizes the use of available radio-frequency (RF) spectrum while minimizing interference to other users. In this paper, we present a state of the art on the use of Multi Agent Systems (MAS) for spectrum access using cooperation and competition to solve the problem of spectrum allocation and ensure better management. Then we propose a new approach which uses the CR for improving wireless communication for a single cognitive radio mobile terminal (CRMT).

Energy Detector with Baseband Sampling for Cognitive Radio: Real-Time Implementation

Cognitive radio (CR) is a technology that provides a promising new way to improve the efficiency of the use of the electromagnetic spectrum that available. Spectrum sensing helps in the detection of spectrum holes (unused channels of the band), and instantly move into vacant channels while avoiding occupied ones. An energy detector with baseband sampling for CR is presented with mathematical analyses for an additive white Gaussian noise (AWGN) channels. A brief overview of the energy detection based spectrum sensing for CR technology is introduced. Practical implementation issues on Texas Instruments TMS320C6713 floating point DSP board are presented. Novelties of this work came from a derivation of probability of detection and probability of false alarm for the baseband energy detector without including the sampling theorems and the associated approximation.

Electronic structures and spectroscopic properties of promising highly efficient red phosphorescent Os(II)(LR)2(PH3)2 complexes: a theoretical exploration

The red phosphorescent osmium(II) complexes [Os(LR)2(PH3)2] (L = 2-pyridyltriazole (ptz): R = H (1a), CF3 (1b), t-Bu (1c)); L = 2-pyridylpyrazole (ppz): R = H (2a), CF3 (2b), t-Bu (2c)); L = 2-phenylpyridine (ppy): R = H (3a)) were explored using density functional theory (DFT) methods. The ground- and excited-state geometries of the complexes were optimized at the B3LYP/LANL2DZ and UB3LYP/LANL2DZ levels, respectively. The absorption and phosphorescence of the complexes in CH2Cl2 media were calculated based on the optimized ground- and excited-state geometries using time-dependent density functional theory method with the polarized continuum model. The optimized geometry structural parameters of the complexes in the ground state agree well with the corresponding experimental values. The lower-lying unoccupied molecular orbitals of the complexes are dominantly localized on the L ligand, while the higher-lying occupied ones are composed of Os(II) atom and L ligand. The low-lying metal-to-ligand and intraligand charge transfer (MLCT/ILCT) transitions and high-lying ILCT transitions are red-shifted with the increase in the π-donating ability of the L ligand and the π electron-donating ability of R substituent. The calculation revealed that the phosphorescence originated from 3MLCT/3ILCT excited state. However, the complex 3a displayed different types of MLCT/ILCT excited state compared with that of 1a–2c, and the different types of transition were also found in the absorption. In addition, we found that the phosphorescence quantum efficiency of Os(II) complexes is related to the metal composition in the high-energy occupied molecular orbitals, it will be helpful to designing highly efficient phosphorescent materials.

Equivalent orbitals for multiconfigurational spin‐tensor electron propagator method (MCSTEP): The vertical ionization potentials of B, NO, CF, and OF

AbstractThe multiconfigurational spin tensor electron propagator method (MCSTEP) was developed as an implementation of electron propagator/single particle Green's function methods for ionization potentials (IPs) and electron affinities (EAs). MCSTEP was specifically designed for open shell and highly correlated (nondynamically correlated) initial states. For computational efficiency the initial state used in MCSTEP is typically a small complete active space (CAS) multiconfigurational self‐consistent field (MCSCF) state. If in a molecule there are some degenerate orbitals which are not fully or half occupied, usual MCSCF calculations will make these orbitals inequivalent, i.e., the occupied ones will be different from the nonoccupied ones, so that the degeneracy is broken. In this article, we use a state averaged MCSCF method to get equivalent orbitals for the initial state and import the integrals into the subsequent MCSTEP calculations. This gives, in general, more reliable MCSTEP vertical IPs. © 2008 Wiley Periodicals, Inc., 2008

Normalized differential conductivity and surface density of states in simulated tunneling spectroscopy

Tunneling spectroscopy is often used to study electronic properties of metal and semiconductor surfaces. The normalized differential conductivity of tunneling was considered to be an invariant quantity showing the surface density of states (DOS). This understanding is critically examined in this paper using known tunneling theory. We assume a number of possible surface DOS distributions to simulate the I- V characteristics and the normalized differential conductivity. The obtained results show that this conductivity does provide quite a good invariant quantity and it indicates some features of the surface state distributions. In particular, it shows empty state features of samples more strikingly than occupied ones. A sign reversion of the conductivity may occur in the positive sample-voltage range related to a decrease in DOS. An explanation is given in terms of electron tunneling probability depending on electron energy.

Diagonalization of the Hartree–Fock Hamiltonian for Occupied States

A variational principle is found which implies that the Hartree-Fock (HF) single-particle Hamiltonian for occupied states is diagonal. The Brillouin condition is recovered by stipulating that the arbitrary unoccupied orbitals be orthogonal to the occupied ones. When it is further stipulated that the unoccupied orbitals be orthonormal, the HF equation for occupied states is determined uniquely and no off-diagonal Lagrangian multipliers occur.