Perceptual learning of spatial localization: specificity for orientation, position, and context

Discrimination of simple visual attributes can improve significantly with practice. We have trained human observers to perform peripherally presented tasks involving the localization of short line segments and examined the specificity of the learning for the visual location, orientation, and geometric arrangement of the trained stimulus. Several weeks of training resulted in dramatic threshold reductions. The learning was specific for the orientation and location of the trained stimulus, indicating the involvement of the earliest cortical stages in the visual pathway where the orientation and location of stimuli are mapped with highest resolution. Furthermore, improvement was also specific for both the configuration of the trained stimulus and the attribute of the stimulus that was under scrutiny during training. This degree of specificity suggests that the learning cannot be achieved by cortical recruitment alone, as proposed in current models, but is likely to involve a refinement of lateral interactions within the cortex and possibly a gating of lower level changes by attentional mechanisms.     

Determination of gas dispersion in vapor extraction of heavy oil and bitumen

In this work, a mathematical model is developed and simulated to determine gas dispersion along with solubility during the vapor extraction (Vapex) of live oil from a laboratory scale physical model. The physical model is a rectangular block of homogenous porous medium saturated with heavy oil and bitumen. At a given temperature and pressure, the block is initially exposed on its side to a solvent gas, which diffuses into the medium and gets absorbed. The absorption of gas reduces the viscosity of heavy oil and bitumen causing it to drain under gravity. The low-viscosity “live oil” is produced at the bottom of the porous block. The production of live oil with time is accompanied by the shrinkage of oil in the block as well as its increased exposure to gas from top. These phenomena of Vapex are described by the mathematical model, which is used to calculate live oil production with various values of gas solubility and dispersion. Their optimal values are determined for the vapor extraction of Cold Lake bitumen with butane by matching calculated live oil production with its experimental values published earlier.     

Mechanical ventilation: simplifying the terminology

There is presently considerable ambiguity and confusion relating to ventilator terminology. This can be eliminated using a simple approach, visualising mechanical ventilation as an inspiratory pump, and defining trigger, limit, and cycling in this context. The trigger is the signal that starts a breath by opening the inspiratory valve, the limit is the factor which controls the way gas flows into the lung, and the cycle is the signal that stops the breath by closing the inspiratory valve and opening the expiratory valve. By identifying these three basic parameters, one can precisely dissect and interpret any of the vast ventilatory terminology.     

Synthesis and physicochemical studies of some new amphoteric ion exchangers

Some new amphoteric ion exchangers have been synthesized by condensing salicylic acid, p-hydroxybenzoic acid, sulfosalicylic acid, gallic acid, 3-hydroxy-2-naphthoic acid, β-resorcylic acid, and resacetophenone with epichlorohydrin employing ethylenediamine as a crosslinking agent. Some of the physicochemical properties, such as moisture content, true density, apparent density, void volume fraction, concentration of ionogenic groups, exchange capacity, rate of exchange, pH-titration curves, pK values, isoionic point, thermal stability, oxidation resistance, and swelling behavior in different solvents, have been investigated.     

In situ observation of phosphorous and non-phosphorous antiwear films using a mini traction machine with spacer layer image mapping

Since 1940s the principal source of an antiwear additive in crankcase applications has been due to a family of additives known as zinc dialkydithiophosphate (ZDDP). In this study, we have applied a novel technique, the mini traction machine with spacer layer image mapping (MTM SLIM), to study film formation characteristics of monoblend oils containing only basestock and ZDDP and also fully forrmulated oils containing a boron antiwear additive. The purpose of this study was initially to understand the build up of ZDDP film and then to establish whether boron compounds alone could provide significant antiwear films under mixed rolling and sliding contact.     

A comparison of mixed integer programming formulations of the capacitated lot-sizing problem

We propose a novel mixed integer programming formulation for the capacitated lot-sizing problem with set-up times and set-up carryover. We compare our formulation to two earlier formulations, the Classical and Modified formulations, and a more recent formulation due to Suerie and Stadtler. Extensive computational experiments show that our formulation consistently outperforms the Classical and Modified formulations in terms of CPU time and solution quality. It is competitive with the Suerie–Stadtler (S&S) formulation, but outperforms all other formulations on the most challenging instances, those with low-capacity slack and a dense jobs matrix. We show that some of the differences in the performance of these various formulations arise from their different use of binary variables to represent production or set-up states. We also show that the LP relaxation of our Novel formulation provides a tighter lower bound than that of the Modified formulation. Our experiments demonstrate that, while the S&S formulation provides a much tighter LP bound, the Novel formulation is better able to exploit the intelligence of the CPLEX solution engine.     

Generating a multiplicity of policies for agent steering in crowd simulation

Pedestrian steering algorithms range from completely procedural to entirely data‐driven, but the former grossly generalize across possible human behaviors and suffer computationally, whereas the latter are limited by the burden of ever‐increasing data samples. Our approach seeks the balanced middle ground by deriving a collection of machine‐learned policies based on the behavior of a procedural steering algorithm through the decomposition of the space of possible steering scenarios into steering contexts. The resulting algorithm scales well in the number of contexts, the use of new data sets to create new policies, and in the number of controlled agents as the policies become a simple evaluation of the rules asserted by the machine‐learning process. We also explore the use of synthetic data from an “oracle algorithm” that serves as an as‐needed source of samples, which can be stochastically polled for effective coverage. We observe that our approach produces pedestrian steering similar to that of the oracle steering algorithm, but with a significant performance boost. Runtime was reduced from hours under the oracle algorithm with 10 agents to on the order of 10 frames per second (FPS) with 3000 agents. We also analyze the nature of collisions in such a framework with no explicit collision avoidance. Copyright © 2014 John Wiley & Sons, Ltd.     

Packet Spacing: An Enabling Mechanism for Delivering Multimedia Content in Computational Grids

Streaming multimedia with UDP has become increasingly popular over distributed systems like the Internet. Scientific applications that stream multimedia include remote computational steering of visualization data and video-on-demand teleconferencing over the Access Grid. However, UDP does not possess a self-regulating, congestion-control mechanism; and most best-effort traffic is served by congestion-controlled TCP. Consequently, UDP steals bandwidth from TCP such that TCP flows starve for network resources. With the volume of Internet traffic continuing to increase, the perpetuation of UDP-based streaming will cause the Internet to collapse as it did in the mid-1980's due to the use of non-congestion-controlled TCP. To address this problem, we introduce the counter-intuitive notion of inter-packet spacing with control feedback to enable UDP-based applications to perform well in the next-generation Internet and computational grids. When compared with traditional UDP-based streaming, we illustrate that our approach can reduce packet loss over 50% without adversely affecting delivered throughput.     

Sample size required to estimate a parameter in the power function distribution

The purpose of this paper is to establish a two step sampling procedure for estimating the parameter θ of the power function distribution to within givend units of its true value with a given probability 1—α;(0<α<1). The density of the power function distribution is a function of two parameters, the second of whichk is assumed known. Given a preliminary sample sizem, tables and formulas are presented by which one may establish the sizen of the second sample such thatP(|y _n —θ|<d)>1—α is true, wherey _n is the largest observation in the second sample. The method used is deriving the results of this paper is similar to that given by Graybill and Connell (1964) and since the power function density reduces to the uniform density whenk=0, their results can be derived from the formulas given here. Also a table of comparisons between the expected second sample size in this paper and two other solutions is given.

---

Sumario El propósito de este escrito es el de establecer un procedimiento de muestreo de dos pasos, para estimar el parámetro de la distribución de funciones de potencia cerca ded unidades de su valor verdadero con una probabilidad 1—α;(0<0<α<1). la densidad de la distribución de funciones de potencia es una función de dos parámetros, el segundo de los cualesk se supone es conocido. Dado un tama?o de muestra preliminarm, se presentan tabulaciones y fórmulas con las cuales se puede establecer el tama?on de la segunda muestra, de tal manera queP(|y _n —θ|<d)>1—α sea cierto, dondey _n es la observación más grande en la segunda muestra. El método usado en la derivación de los resultados de este escrito es similar al dado por Graybill y Connell (1964, Journal of the American Statistical Association) y ya que la densidad de funciones de potencia se reduce a la densidad uniforme cuandok=0, sus resultados pueden ser derivados a partir de las fórmulas dadas aquí. Además, se presenta una tabulación de comparaciones entre el segundo tama?o de muestra dado en este escrito y otras dos soluciones. Lafdp de la distribución de funciones de potencia es de la formaf(u)=(k+1)θ ^−(k+1) u ^k ,0<u<θ, θ>0 y cero en cualquiera otra parte.

---

---

Research supported under ONR contract N00014-68-A-0515.