Full-dimensional quantum calculations of ground-state tunneling splitting of malonaldehyde using an accurate ab initio potential energy surface

Quantum calculations of the ground vibrational state tunneling splitting of H-atom and D-atom transfer in malonaldehyde are performed on a full-dimensional ab initio potential energy surface (PES). The PES is a fit to 11 147 near basis-set-limit frozen-core CCSD(T) electronic energies. This surface properly describes the invariance of the potential with respect to all permutations of identical atoms. The saddle-point barrier for the H-atom transfer on the PES is 4.1 kcal/mol, in excellent agreement with the reported ab initio value. Model one-dimensional and "exact" full-dimensional calculations of the splitting for H- and D-atom transfer are done using this PES. The tunneling splittings in full dimensionality are calculated using the unbiased "fixed-node" diffusion Monte Carlo (DMC) method in Cartesian and saddle-point normal coordinates. The ground-state tunneling splitting is found to be 21.6 cm(-1) in Cartesian coordinates and 22.6 cm(-1) in normal coordinates, with an uncertainty of 2-3 cm(-1). This splitting is also calculated based on a model which makes use of the exact single-well zero-point energy (ZPE) obtained with the MULTIMODE code and DMC ZPE and this calculation gives a tunneling splitting of 21-22 cm(-1). The corresponding computed splittings for the D-atom transfer are 3.0, 3.1, and 2-3 cm(-1). These calculated tunneling splittings agree with each other to within less than the standard uncertainties obtained with the DMC method used, which are between 2 and 3 cm(-1), and agree well with the experimental values of 21.6 and 2.9 cm(-1) for the H and D transfer, respectively. (C) 2008 American Institute of Physics.

Condensation and moisture transport in cold roofs: effect of roof underlay

Cold pitched roofs, with their form of construction situating insulation on a horizontal ceiling, are intrinsically vulnerable to condensation. This study reports the results derived from using a simulation package (Heat, Air and Moisture modelling tool, or HAM-Tools) to investigate the risk of condensation in cold pitched roofs in housing fitted with a vapour-permeable underlay (VPU) of known characteristics. In order to visualize the effect of the VPUs on moisture transfer, several scenarios were modelled, and compared with the results from a conventional bituminous felt with high resistance (200 MNs/g, Sd = 40 m). The results indicate that ventilation is essential in the roof to reduce condensation. However, a sensitivity analysis proved that reducing the overall tightness of the ceiling and using lower-resistance VPUs would help in controlling condensation formation in the roof. To a large extent, the proposed characteristic performance of the VPU as predicted by manufacturers and some researchers may only be realistic if gaps in the ceiling are sealed completely during construction, which may be practically difficult given current construction practice.

The art of conversation is coordination: common ground and the coupling of eye movements during dialogue

When two people discuss something they can see in front of them, what is the relationship between their eye movements? We recorded the gaze of pairs of subjects engaged in live, spontaneous dialogue. Cross-recurrence analysis revealed a coupling between the eye movements of the two conversants. In the first study, we found their eye movements were coupled across several seconds. In the second, we found that this coupling increased if they both heard the same background information prior to their conversation. These results provide a direct quantification of joint attention during unscripted conversation and show that it is influenced by knowledge in the common ground.

Cooperative transport of extended payloads

In this paper we present experimental results for the dual robot transport of an extended payload. Two robotic rovers that were designed specifically for the extended payload transport task are described. Each rover incorporates a 4-DOF robot arm incorporating three active joints (one of which is a gripper), a passive wrist, and a mobile base which employs a rocker-bogie design. A set of behaviours has been developed to support the performance of the task, integrating simple sensing with controls. We describe the behaviours and their integration within the overall task structure. The experimental results presented focus on the manipulation elements of the task, but incorporate a complete cycle of pick-up, traversal, and putdown.

Offering 802.11 MAC frame transport over multiband OFDM for consumer devices

A method to map all the variants of the IEEE 802.11 MAC frames into the Multiband OFDM based ECMA-368 Physical standard is proposed, without contravening the standard. The transportation of IEEE 802.11 MAC frames over ECMA-368 allows for the migration current of Wireless LAN applications towards a Wireless Personal Area Network (WPAN) solution. This system benefits the Consumer Electronics Market as the high data-rate WPAN is capable of transporting broadcast-quality video while the same system can also transport existing applications available today, maintaining existing effort, products and backward-compatibility(1).

Case study: object and ground point separation on a river bank using airborne based LIDAR data

In the past decade, airborne based LIght Detection And Ranging (LIDAR) has been recognised by both the commercial and public sectors as a reliable and accurate source for land surveying in environmental, engineering and civil applications. Commonly, the first task to investigate LIDAR point clouds is to separate ground and object points. Skewness Balancing has been proven to be an efficient non-parametric unsupervised classification algorithm to address this challenge. Initially developed for moderate terrain, this algorithm needs to be adapted to handle sloped terrain. This paper addresses the difficulty of object and ground point separation in LIDAR data in hilly terrain. A case study on a diverse LIDAR data set in terms of data provider, resolution and LIDAR echo has been carried out. Several sites in urban and rural areas with man-made structure and vegetation in moderate and hilly terrain have been investigated and three categories have been identified. A deeper investigation on an urban scene with a river bank has been selected to extend the existing algorithm. The results show that an iterative use of Skewness Balancing is suitable for sloped terrain.

Modeling of carrier transport in nanowires

We consider a physical model of ultrafast evolution of an initial electron distribution in a quantum wire. The electron evolution is described by a quantum-kinetic equation accounting for the interaction with phonons. A Monte Carlo approach has been developed for solving the equation. The corresponding Monte Carlo algorithm is NP-hard problem concerning the evolution time. To obtain solutions for long evolution times with small stochastic error we combine both variance reduction techniques and distributed computations. Grid technologies are implemented due to the large computational efforts imposed by the quantum character of the model.