Absorption of ammonia in a batch bubble column

The batch neutralization of dilute hydrochloric acid by ammonia in a 10.16 cm i.d. bubble column has been examined. Experimental results agree with a diffusion-type mixing model when 5.08 cm disc baffles are present, but agreement is only approximate with 7.62 cm diameter baffles. Axial dispersion coefficients have been determined and compared with published data. A simple batchwise procedure for evaluating bubble columns is suggested.     

Nano- and meso-measurement methods in the study of dielectrics

Measurements of the physical form and morphology of dielectrics and of their chemical characteristics and physical properties have become increasingly important at micron and sub-micron length scales. Such length scales are accessible by different forms of microscopy but scanning probe methods allow both chemical and physical measurements to be made, in addition to morphological and typographical imaging, at nanoscopic and mesoscopic length scales. These measurements are described in this paper with examples drawn from many areas of dielectric research and applications, including polymer morphology, surface and subsurface charge measurements along with the dynamics of charge-decay, surface potential and work function, microelectronics, ferroelectrics, photocharging, dielectric response and nanoscopic relaxation and nanoscopic Raman spectroscopy. The future of scanning probe methods for dielectric measurements is assured but more effort is required to both develop and consolidate this form of nano-metrology.     

Positive DC Coronas with Arbitrary Outer-Conductor Geometries

The two-dimensional Poisson's equation for a positive dc corona in air with arbitrarily-shaped boundaries-is solved using numerical methods. Solutions to the problem give the potential, electric field, space charge density, ion trajectories, and current density for all points in the field of interest, and the corona current flowing to any boundary. Good agreement is obtained between the theory and experimental measurements.     

Issues in the design and use of wearable computers

Wearable computers are fully functional, self-powered, self-contained computers that allow the user to access information anywhere and at any time. In this paper, design issues for wearable computers are discussed, including power considerations, use of input devices, image registration, and the use of wearable computers for the design of smart spaces. Application areas for wearable computers are presented, including medicine, manufacturing, maintenance, and as personal assistants. Finally, future research directions for wearable computers are indicated.     

Evaluating the effectiveness of augmented reality displays for a manual assembly task

The focus of this research was to examine how effectively augmented reality displays, generated with a wearable computer, could be used for aiding an operator performing a manual assembly task. Fifteen subjects were asked to assemble a computer motherboard using four types of instructional media: paper manual, computer-aided, opaque augmented reality display, and see-through augmented reality display. The time of assembly and assembly errors were measured for each type of instructional media, and a questionnaire focusing on usability was administered to each subject at the end of each condition. The results of the experiment indicated that the augmented reality conditions were more effective instructional aids for the assembly task than either the paper instruction manual or the computer-aided instruction. The see-through augmented reality display resulted in the fastest assembly times, followed by the opaque augmented reality display, the computer-aided instruction, and the paper instructions respectively. In addition, subjects made fewer errors using the augmented reality conditions compared to the computer-aided and paper instructional media. However, while the two augmented reality conditions were a more effective instructional media when time for assembly was the response measure, there were still some important usability issues associated with the augmented reality technology that were not present in the non-augmented reality conditions.     

An analytical framework for local feedforward networks

Interference in neural networks occurs when learning in one area of the input space causes unlearning in another area. Networks that are less susceptible to interference are referred to as spatially local networks. To obtain a better understanding of these properties, a theoretical framework, consisting of a measure of interference and a measure of network localization, is developed. These measures incorporate not only the network weights and architecture but also the learning algorithm. Using this framework to analyze sigmoidal, multilayer perceptron (MLP) networks that employ the backpropagation learning algorithm on the quadratic cost function, we address a familiar misconception that single-hidden-layer sigmoidal networks are inherently nonlocal by demonstrating that given a sufficiently large number of adjustable weights, single-hidden-layer sigmoidal MLPs exist that are arbitrarily local and retain the ability to approximate any continuous function on a compact domain.     

The experiences of Sudanese unaccompanied minors in foster care.

Sudanese unaccompanied minors were separated from their parents in childhood and lived apart from their families in refugee camps for close to a decade before being resettled in the United States. This phenomenological study examines the refugees’ experiences of living in American foster families after living in peer groups in the camps. Interviews with 18 young adults, 7 years after resettlement, revealed that nearly all of the youth struggled with parental authority initially, and nearly half of them changed placements because of relationship difficulties with their foster parents. Misunderstandings based on cultural differences often exacerbated conflicts. However, 15 of 18 youth currently had a positive relationship with at least 1 foster parent, sometimes with a parent from their second or third placement. Changing foster families is often considered a failure in the child welfare system, but several Sudanese youth reported that having supportive relationships helped them during the acculturation process whether those relationships developed during the first or last placement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reading and arithmetic in adolescents with autism spectrum disorders: Peaks and dips in attainment.

In describing academic attainment in autism spectrum disorders (ASD), results are typically reported at the group mean level. This may mask subgroups of individuals for whom academic achievement is incommensurate with intellectual ability. The authors tested the IQ, literacy, and mathematical abilities of a large group (N = 100) of adolescents (14–16 years old) with ASD. Seventy-three percent of the sample had at least one area of literacy or mathematical achievement that was highly discrepant (approximately 14 standard score points) from full-scale IQ (FSIQ). The authors focused on four subgroups with either word reading (“Reading Peak” and “Reading Dip”) or arithmetic (“Arithmetic Peak” and “Arithmetic Dip”) higher or lower than FSIQ. These subgroups were largely mutually exclusive and were characterized by distinct intellectual profiles. The largest was the “Arithmetic Peak” subgroup of participants, who presented with average intellectual ability alongside superior arithmetic skills and who were predominantly in a mainstream educational setting. Overall, the most pervasive profile was discrepantly poor reading comprehension, which associated with severity of social and communication difficulties. The high rate of uneven academic attainment in ASD has implications for educational practice. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adaptive sidelobe nulling using digitally controlled phase-shifters

Adaptive null-steering arrays which use phase-only weights are examined. The optimal phase weightings are developed and the mathematical equations are reduced to a simplified computational form. Approximations for low sidelobe arrays allow more efficient computations and demonstrate the decomposition of the antenna pattern into a sum of patterns which place gain towards each directional emitter. Computer simulations and breadboard array measurements substantiate the mathematical development and indicate the practicality of the method.