Effects of alarms on control of robot teams

Annunciator driven supervisory control (ADSC) is a widely used technique for directing human attention to control systems otherwise beyond their capabilities. ADSC requires associating abnormal parameter values with alarms in such a way that operator attention can be directed toward the involved subsystems or conditions. This is hard to achieve in multirobot control because it is difficult to distinguish abnormal conditions for states of a robot team. For largely independent tasks such as foraging, however, self-reflection can serve as a basis for alerting the operator to abnormalities of individual robots. While the search for targets remains unalarmed the resulting system approximates ADSC. The described experiment compares a control condition in which operators perform a multirobot urban search and rescue (USAR) task without alarms with ADSC (freely annunciated) and with a decision aid that limits operator workload by showing only the top alarm. No differences were found in area searched or victims found, however, operators in the freely annunciated condition were faster in detecting both the annunciated failures and victims entering their cameras' fields of view. Copyright 2011 by Human Factors and Ergonomics Society, Inc. All rights reserved

SHORT COMMUNICATION: Agronomic effectiveness of novel phosphate fertilisers derived from an igneous Zimbabwe phosphate rock

A review of literature shows that work on non-conventional phosphate fertilisers has been done exclusively on sedimentary phosphate rocks. The potential of using novel phosphate fertiliser materials derived from unreactive igneous Dorowa (Zimbabwe) phosphate rock was investigated in a greenhouse experiment. Three phosphate fertiliser materials; (1) finely ground (0.150-mm screen) Dorowa phosphate rock (DPR), (2) partially acidulated Dorowa phosphate rock (PADPR), and (3) a compacted mixture of DPR + triple superphosphate + urea + potassium chloride (DTUK) with half of P from DPR and half from triple superphosphate (TSP) were made from Dorowa rock and their relative agronomic effectiveness compared with that of single superphosphate (SSP) on an acid Hartsells silt loam (pH 4.8) with maize (Zea mays L.) as the indicator crop. Direct application of DPR was found to be ineffective in increasing phosphorus (P) uptake and dry matter yield of maize. The relative agronomic effectiveness of DPR partially acidulated with 50% of the sulfuric acid (H2SO4) required for complete acidulation, in increasing P uptake and dry matter yield was 60% and 75%, respectively. The compacted fertiliser product, DTUK, was equally effective in increasing P uptake and dry matter yield as SSP. Key Words: Acidulation, agronomic effectiveness, fertiliser compaction, Zea mays Résumé Une revue de la littérature montre que le travail sur engrais phosphatiques non conventionels a été fait exclusivement sur les roches (substances) phosphate sedimentaires. Le potentiel d'utilisation des nouveaux matériaux fertilisants phosphatiques dérivés de réactifs éruptifs Dorowa (Zimbabwe) ont été examiné dans une serre experimentale. Trois matériaux fertilisants phosphate ; finement moulu (0, 150 mm tamis) Dorowa roche phosphatique (DRP), et 2) DRP acidulé (DRPA), et 3) un melange compacte de DRP et le triple superphosphate+ urée+ chloride de potassium (DTUK) avec la moitié de P du DRP et la moitié de triple superphosphate (TSP) était faite à partir de la roche Dorowa et leur efficacité agronomique relatives comparées avec celle du superphosphate (SSP) sur un depôt d'acide Hartsells terreau (BH 4, 8) avec le maïs (Zea mays L.) comme indicateur de plante. Une application directe du DRP était trouvée être non effective dans la croissance de l'assimilation du phosphore (P) et production de matière sèche de maïs. L'efficacité relative agronomique du DRP partiellement acidulé, avec 50%d'acide sulfurique (H2SO4) demandée pour une complète acidulation, pour l'accroissement de l'assimilation et la production de matière sèche de P était respectivement de 60% et 75%. Le produit fertilisant compacté DTUK était également effectif dans accroissement de l'assimilation et la production de matière sèche de P comme le SSP. Mots Clés: Acidulation, efficacité agronomique, compaction de fertilisants, Zea mays (Af Crop Sci J 2003 Vol 11 No 3 pp235-243

Isolation and characterization of cellulose degrading ability in Paenibacillus isolates from landfill leachate

Aims: Cellulases are enzymes that convert cellulose into glucose molecules, and are produced by various microorganisms in the environment. Due to their importance to the biofuel industry, there is a need to screen for more efficient varieties of cellulases. In this study, leachate samples from a landfill site were screened for cellulolytic bacteria. Methodology and results: Leachate samples obtained from a landfill collection pond were cultured in an enriched cellulose medium. Two cellulolytic isolates, designated MAEPY1 and MAEPY2, were isolated and further characterized. Phenotypic profiles and phylogenetic analyses using sequences of 16S rRNA, gyrB and whole genome suggested that these isolates are new strains of the Paenibacillus genera. The crude enzyme extracts from both isolates have cellulose degradation activity at approximately 0.1-0.2 IU/mg under working conditions of pH 6 and 55 °C. Assays using other lignocellulosic substrates showed that the crude enzyme extracts also have high xylan degradation activity. Conclusion, significance and impact of study: Paenibacillus sp. are known to produce multiple enzymes for lignocellulolytic degradation and the present results suggest that isolates described in this study, MAEPY1 and MAEPY2, are excellent candidates deserving further study as potential producers of efficient cellulases for use in industries associated with cellulosic biomass

Feynman Rules in the Type III Natural Flavour-Conserving Two-Higgs Doublet Model

We consider a two Higgs-doublet model with $S_3$ symmetry, which implies a $\pi \over 2$ rather than 0 relative phase between the vacuum expectation values $$and$$. The corresponding Feynman rules are derived accordingly and the transformation of the Higgs fields from the weak to the mass eigenstates includes not only an angle rotation but also a phase transformation. In this model, both doublets couple to the same type of fermions and the flavour-changing neutral currents are naturally suppressed. We also demonstrate that the Type III natural flavour-conserving model is valid at tree-level even when an explicit $S_3$ symmetry breaking perturbation is introduced to get a reasonable CKM matrix. In the special case $\beta = \alpha$, as the ratio $\tan\beta = {v_2 \over v_1}$ runs from 0 to $\infty$, the dominant Yukawa coupling will change from the first two generations to the third generation. In the Feynman rules, we also find that the charged Higgs currents are explicitly left-right asymmetric. The ratios between the left- and right-handed currents for the quarks in the same generations are estimated.Comment: 16 pages (figures not included), NCKU-HEP/93-1

On Existence and Properties of Approximate Pure Nash Equilibria in Bandwidth Allocation Games

In \emph{bandwidth allocation games} (BAGs), the strategy of a player consists of various demands on different resources. The player's utility is at most the sum of these demands, provided they are fully satisfied. Every resource has a limited capacity and if it is exceeded by the total demand, it has to be split between the players. Since these games generally do not have pure Nash equilibria, we consider approximate pure Nash equilibria, in which no player can improve her utility by more than some fixed factor $\alpha$ through unilateral strategy changes. There is a threshold $\alpha_\delta$ (where $\delta$ is a parameter that limits the demand of each player on a specific resource) such that $\alpha$-approximate pure Nash equilibria always exist for $\alpha \geq \alpha_\delta$, but not for $\alpha < \alpha_\delta$. We give both upper and lower bounds on this threshold $\alpha_\delta$ and show that the corresponding decision problem is ${\sf NP}$-hard. We also show that the $\alpha$-approximate price of anarchy for BAGs is $\alpha+1$. For a restricted version of the game, where demands of players only differ slightly from each other (e.g. symmetric games), we show that approximate Nash equilibria can be reached (and thus also be computed) in polynomial time using the best-response dynamic. Finally, we show that a broader class of utility-maximization games (which includes BAGs) converges quickly towards states whose social welfare is close to the optimum