The impact of aviation checkpoint queues on optimizing security screening effectiveness

Passenger screening at aviation security checkpoints is a critical component in protecting airports and aircraft from terrorist threats. Recent developments in screening device technology have increased the ability to detect these threats; however, the average amount of time it takes to screen a passenger still remains a concern. This paper models the queueing process for a multi-level airport checkpoint security system, where multiple security classes are formed through subsets of specialized screening devices. An optimal static assignment policy is obtained which minimizes the steady-state expected amount of time a passenger spends in the security system. Then, an optimal dynamic assignment policy is obtained through a transient analysis that balances the expected number of true alarms with the expected amount of time a passenger spends in the security system. Performance of a two-class system is compared to that of a selective security system containing primary and secondary levels of screening. The key contribution is that the resulting optimal assignment policies increase security and passenger throughput by efficiently and effectively utilizing available screening resources.     

Situvis: A sensor data analysis and abstraction tool for pervasive computing systems

Pervasive systems are large-scale systems consisting of many sensors capturing numerous types of information. As this data is highly voluminous and dimensional, data analysis tasks can be extremely cumbersome and time-consuming. Enabling computers to recognise real-world situations is an even more difficult problem, involving not only data analysis, but also consistency checking. Here we present Situvis, an interactive visualisation tool for representing sensor data and creating higher-level abstractions from the data. This paper builds on previous work, Clear et al. (2009) [8] through evolved tool functionality and an evaluation of Situvis. A user-trial consisting of 10 participants shows that Situvis can be used to complete the key tasks in the development process of situation specifications in over 50% less time than an improvised alternative toolset.     

Onset of convection in a horizontal porous layer driven by catalytic surface reaction on the lower wall

The onset of convection in a horizontal layer filled with a fluid-saturated porous medium is studied in this paper. On the lower wall there is an exothermic surface reaction, described by the Arrhenius kinetics, while the upper wall is subjected to uniform temperature and concentration. The problem, cast in dimensionless form, is governed by three dimensionless parameters pertaining to the exothermic reaction and the Lewis number. Once the basic state is solved, a linearized stability analysis is then performed and the resulting eigenvalue problem is solved using a conventional shooting method. One determines numerically the critical Rayleigh and wave numbers at the onset of convection, for various values of the problem parameters.     

Charged-Spray Deposition Characteristics Within Cereal Crops

Fluorescent tracer studies experimentally quantified the spatial distribution of droplet mass transfer and charge transfer characterizing three modes of electrostatic pesticide spraying onto barley-weed-soil target arrays. Droplet charging in the 1.5-4.5 mC/kg range provided significant deposition increases on all plant surfaces while beneficially reducing residues on underlying soil. With the intense space-charge spray clouds utilized (e.g., 10 μC/m3), externally applied driving fields as great as 37 kV/m provided no significant deposition increases but instead exacerbated gaseous charge exchange between the spray cloud and the target via undesirable leaf-tip coronas. Nonuniformity characterized deposition of both uncharged and charged sprays throughout the target array, with no improvement provided by spray-entrainment air velocities as great as 2 m/s. Results will guide prototype design by establishing the relative importance of the space charge, the applied field, and the aerodynamic force components for selectively targeting specific sites within living-plant arrays.     

Determination of polybrominated diphenyl ethers and polychlorinated biphenyls in human adipose tissue by large-volume injection-narrow-bore capillary gas chromatography/electron impact low-resolution mass spectrometry

A new analytical method has been developed for the quantification of polybrominated diphenyl ethers (PBDEs) in human adipose tissue samples. After Soxhlet extraction and a cleanup procedure using two successive solid-phase extraction cartridges containing acid silica and acid silica: neutral silica:deactivated basic alumina (from top to bottom), detection can been achieved by narrow-bore (0.10-mm i.d.) capillary gas chromatography/electron impact low-resolution mass spectrometry using a large-volume injection technique. Using narrow-bore capillaries, it is possible to analyze complex mixtures in a short time (up to 10 min), saving 50% or more of the analysis time of conventional columns while maintaining a similar resolution power. The method allows the determination of five major PBDE congeners (BDE 28, 47, 99, 100, and 153) at concentrations below 1 ng/g lipid weight. Detection limits in the selected ion mode varied between 0.05 and 0.30 ng/g lipid weight, depending on the degree of bromination. The sensitivity of this method can compete with low-resolution mass spectrometry with electron capture ionization, while a much better selectivity is obtained. Levels of PBDEs in 20 Belgian human adipose tissue samples ranged between 2.18 and 11.70 ng/g lipid weight and were similar to previously reported values from Europe.     

Semantic memory in Alzheimer's disease and the frontotemporal dementias: A longitudinal study of 236 patients.

Using semantic dementia (SD) as a reference point, the authors assessed semantic memory in four other neurodegenerative disorders: progressive nonfluent aphasia (PNFA), frontal variant frontotemporal dementia (fvFTD), Alzheimer's disease (AD), and posterior cortical atrophy (PCA). Individuals with SD were more impaired than other groups on semantic measures and showed a characteristic pattern across tasks: category fluency (CF) worse than letter fluency (LF), naming worse than comprehension, and visual and verbal comprehension equally affected, suggesting disruption to an amodal semantic system. Individuals with AD demonstrated a similar pattern to a milder degree. Although PNFA, fvFTD, and PCA groups had abnormal scores (relative to controls) on most semantic measures, their differing patterns across measures indicate that the apparent semantic impairment in these conditions is largely secondary to other factors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recursion Engineering for Reduction Incorporated Parsers

Reduction Incorporated (RI) recognisers and parsers deliver high performance by suppressing the stack activity except for those rules that generate fully embedded recursion. Automaton constructions for RI parsing have been presented by Aycock and Horspool [John Aycock and Nigel Horspool. Faster generalised LR parsing. In Compiler Construction, 8th Intnl. Conf, CC'99, volume 1575 of Lecture Notes in Computer Science, pages 32 – 46. Springer-Verlag, 1999] and by Scott and Johnstone [Adrian Johnstone and Elizabeth Scott. Generalised regular parsers. In Gorel Hedin, editor, Compiler Construction, 12th Intnl. Conf, CC'03, volume 2622 of Lecture Notes in Computer Science, pages 232–246. Springer-Verlag, Berlin, 2003] but both can yield very large tables. An unusual aspect of the RI automaton is that the degree of stack activity suppression can be varied in a fine-grained way, and this provides a large family of potential RI automata for real programming languages, some of which have manageable table size but still show high performance. We give examples drawn from ANSI-C, Cobol and Pascal; discuss some heuristics for guiding manual specification of stack activity suppression; and describe work in progress on the automatic construction of RI automata using profiling information gathered from running parsers: in this way we propose to optimise our parsers' table size against performance on actual parsing tasks.     

Seismic Site Response for Near-Fault Forward Directivity Ground Motions

Forward directivity effects in the near-fault region produce pulse-type motions that differ significantly from ordinary ground motions that occur at greater distances from the causative fault. Current code site factors are based on empirical observations and analyses involving less intense nonpulse ordinary ground motions. Nonlinear site response analyses with bidirectional shaking are performed using representative site profiles to quantify seismic site response effects for intense near-fault motions resulting from forward directivity. Input rock motions are represented with simplified velocity pulses that characterize the amplitude and period of forward directivity motions. Results indicate that site response affects both the amplitude and period of forward directivity pulses, and hence, local site conditions should be considered when evaluating seismic designs in the near-fault region. Stiff soil sites tend to amplify the peak ground velocity and increase the period of pulse-type motions, particularly, when the period of the rock motion coincides with the degraded period of the site. Amplification is limited at soft soil sites by the dynamic strength of the weak soil, so attenuation occurs for intense input motions. This nonlinearity is not reflected in the site factors in current building codes. Guidance is provided for estimating the amplitude and pulse period for velocity pulses at soil sites.     

Touch-Space: Mixed Reality Game Space Based on Ubiquitous, Tangible, and Social Computing

This paper presents a novel computer entertainment system which recaptures human touch and physical interaction with the real-world environment as essential elements of the game play, whilst also maintaining the exciting fantasy features of traditional computer entertainment. Our system called ‘Touch-Space’ is an embodied (ubiquitous, tangible, and social) computing based Mixed Reality (MR) game space which regains the physical and social aspects of traditional game play. In this novel game space, the real-world environment is an essential and intrinsic game element, and the human’s physical context influences the game play. It also provides the full spectrum of game interaction experience ranging from the real physical environment (human to human and human to physical world interaction), to augmented reality, to the virtual environment. It allows tangible interactions between players and virtual objects, and collaborations between players in different levels of reality. Thus, the system re-invigorates computer entertainment systems with social human-to-human and human-to-physical touch interactions. Correspondence to: Professor A. Cheok, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260. Email: adriancheok@nus.edu.sg