Neuro-Resistive Grid approach to trainable controllers: A pole balancing example

A new neural network approach is described for the task of pole-balancing, considered a benchmark learning control problem. This approach combines Barto, Sutton and Anderson's [1] Associative Search Element (ASE) with a Neuro-Resistive Grid (NRG) [2] acting as Adaptive Critic Element (ACE). The novel feature in NRG is that it provides evaluation of a state based on propagation of the failure information to the neighbours in the grid. NRG is updated only on a failure, and provides ASE with a continuous internal reinforcement signal by comparing the value of the present state to the previous state. The resulting system learns more rapidly and with fewer computations than that of Barto et al.[1]. To establish a uniform basis of comparison of algorithms for pole balancing, both the systems are simulated using benchmark parameters and tests specified in Geva and Sitte [3].     

Social patterns in productive software development organizations

Software development is a predominantly social activity. It is important to view software development groups, departments, and corporations as social bodies. We study software organizations using a novel data-gathering approach that combines several techniques commonly used in social network analysis. Our techniques differ from those of ordinary social anthropology in that we help the organization introspect about itself; the technique is a mirror for the subject organization. We catalogued social network diagrams using a variety of visualization techniques. We have found visual patterns that correlate well to subjective measures of a good organization. We built analytical models to capture properties of the social networks, employing techniques similar to those used in established social network science. The emerging design technique based on architectural patterns provides a good vehicle for communicating organizational patterns. We have captured practices from outstanding organizations in a group of patterns that form a pattern language for productive software development.     

Hydrogels Containing Gradients in Vascular Density Reveal Dose-Dependent Role of Angiocrine Cues on Stem Cell Behavior

Biomaterials that replicate patterns of microenvironmental signals from the stem cell niche offer the potential to refine platforms to regulate stem cell behavior. While significant emphasis has been placed on understanding the effects of biophysical and biochemical cues on stem cell fate, vascular-derived or angiocrine cues offer an important alternative signaling axis for biomaterial-based stem cell platforms. Elucidating dose-dependent relationships between angiocrine cues and stem cell fate are largely intractable in animal models and 2D cell cultures. In this study, microfluidic mixing devices are leveraged to generate 3D hydrogels containing lateral gradients in vascular density alongside murine hematopoietic stem cells (HSCs). Regional differences in vascular density can be generated via embossed gradients in cell, matrix, or growth factor density. HSCs co-cultured alongside vascular gradients reveal spatial patterns of HSC phenotype in response to angiocrine signals. Notably, decreased Akt signaling in high vessel density regions led to increased expansion of lineage-positive hematopoietic cells. This approach offers a combinatorial tool to rapidly screen a continuum of microenvironments with varying vascular, biophysical, and biochemical cues to reveal the influence of local angiocrine signals on HSC fate.     

The Effects of Haptic Feedback and Visual Distraction on Pointing Task Performance

Previous research has not fully examined the effect of additional sensory feedback, particularly delivered through the haptic modality, in pointing task performance with visual distractions. This study examined the effect of haptic feedback and visual distraction on pointing task performance in a 3D virtual environment. Results indicate a strong positive effect of haptic feedback on performance in terms of task time and root mean square error of motion. Level of similarity between distractor objects and the target object significantly reduced performance, and subjective ratings indicated a sense of increased task difficulty as similarity increased. Participants produced the best performance in trials where distractor objects had a different color but the same shape as the target object and constant haptic assistive feedback was provided. Overall, this study provides insight toward the effect of object features and similarity and the effect of haptic feedback on pointing task performance.     

QoSPlan: A Measurement Based Quality of Service aware Network Planning Framework

In this article we present QoSPlan—a measurement based framework for preparing information relevant to Quality of Service (QoS)-aware IP network planning, which aims at reducing a core operational expenditure for the network operator. QoSPlan is designed to reduce the cost of deployment and maintenance of network monitoring systems. The process involves analysis of pre-existing accounting data to estimate a network-wide traffic matrix. Part of this estimation process relates to the generalization of QoS-related effective bandwidth coefficients taken from traffic analyzed on the network. We offer recommendations on how to appropriately realize QoSPlan to maximize its accuracy and effectiveness when applied to different network traffic scenarios. This is achieved through a thorough sensitivity analysis of the methods proposed using real traffic scenarios and indicative network topologies. We also provide an economic analysis of the deployment and maintenance costs associated with QoSPlan in comparison to a direct measurement approach, demonstrating cost savings of up to 60 % given different topology sizes.     

Brain–computer interfacing: more than the sum of its parts

The performance of non-invasive electroencephalogram-based (EEG) brain–computer interfaces (BCIs) has improved significantly in recent years. However, remaining challenges include the non-stationarity and the low signal-to-noise ratio of the EEG, which limit the bandwidth and hence the available applications. Optimization of both individual components of BCIs and the interrelationship between them is crucial to enhance bandwidth. In other words, neuroscientific knowledge and machine learning need to be optimized by considering concepts from human–computer interaction research and usability. In this paper, we present results of ongoing relevant research in our lab that addresses several important issues for BCIs based on the detection of transient changes in oscillatory EEG activity. First, we report on the long-term stability and robustness of detection of oscillatory EEG components modulated by distinct mental tasks, and show that the use of mental task pairs “mental subtraction versus motor imagery” achieves robust and reliable performance (Cohen’s κ > 0.6) in seven out of nine subjects over a period of 4 days. Second, we report on restricted Boltzmann machines (RBMs) as promising tools for the recognition of oscillatory EEG patterns. In an off-line BCI simulation we computed average peak accuracies, averaged over ten subjects, of 80.8 ± 7.2 %. Third, we present the basic framework of the context-aware hybrid Graz-BCI that allows interacting with the massive multiplayer online role playing game World of Warcraft. We show how a more integrated design approach that considers all components of BCIs, their interrelationships, other input signals and contextual information can increase interaction efficacy.     

Biologischer Abbau chlorierter Kohlenwasserstoffe

Biological Degradation of Chlorinated Hydrocarbons . Chlorinated hydrocarbons (CHC) have been produced on an industrial scale since the 1920's and 1930's and are frequently used as solvents, extractants, and disinfectants. Because their low biodegradability they are often enriched in the food chains of animals, resulting in high mortality. It is therefore necessary to prevent the discharge of CHC's into water, air, and soil. They are often not biodegraded in municipal or industrial activated sludge plants or in trickling filters. Until harmless substitutes become widely available, CHC's will continue to pose a threat and must be eliminated from all effluents before entering wastewater treatment plants. Information about specific conditions for anaerobic and aerobic biodegradation of selected CHC's is given below. Two topics will be discussed in greater detail: the kinetics of dechlorination and mineralization and some examples of the reaction engineering process in lab and pilot scale.     

Effects of thermal history on the polymerisation mechanism and network development in aromatic polybenzoxazines

The effect of heating rate (2, 8 and 15 K min^-1) during the initial stages of cure of 2,2-bis(3,4-dihydro-3-phenyl-2H-1,3-benzoxazine)propane is examined. The rate of heating has a marked effect on the observed modulus, measured by DMTA, with the higher heating rate giving rise to an increase in storage modulus of ca. 1000 MPa, although this is not accompanied by an increase in glass transition temperature. The thermal stability of the resulting polybenzoxazines also differs with the slower heating rate giving rise to less thermally stable structures. Data obtained from Raman spectroscopy (when combined with principal components analysis) suggest subtle changes in the mechanism during the early stages of reaction associated C–N–C and C–O moieties, some of which persist following a higher temperature postcure step leading to a crosslinked network with higher aliphatic character.     

Material Evidence for Multiple Firings of Ancient Athenian Red‐Figure Pottery

The production of Athenian fine ware pottery, produced between the 6th and 4th centuries B.C., required alternating the high‐temperature kiln between oxidative and reductive environments during a single firing to create the iconic red and black decorative scenes. Here, we show that the production of this pottery was even more complex, with vessels subjected to two, or possibly more, firings in the kiln, with applications of slip between each firing. On a representative sherd, we compared three painted black decorative features—relief line, contour line, and background slip. Scanning transmission electron microscopy (STEM) of the slips revealed that the relief line had a more melted microstructure than either the contour line or background slip. By characterizing the chemistry and micromorphology of the slips, we find that the relief line microstructure could only be produced through a separate firing, at a hotter temperature, than the other two decorative features.