Compact beam expander with linear gratings

Novel compact beam expanders that could be useful for applications such as providing light to flat panel displays are presented. They are based on a planar configuration in which three spatially linear gratings are recorded on one transparent substrate, so as to expand a narrow incoming beam in two dimensions. We present the design and recording procedures along with results, showing a relatively uniform intensity of the wide output beam. Such expanders can serve for illuminating flat panel displays.     

Effects of foam on ocean surface microwave emission inferred from radiometric observations of reproducible breaking waves

WindSat, the first satellite polarimetric microwave radiometer, and the NPOESS Conical Microwave Imager/Sounder both have as a key objective the retrieval of the ocean surface wind vector from radiometric brightness temperatures. Available observations and models to date show that the wind direction signal is only 1-3 K peak-to-peak at 19 and 37 GHz, much smaller than the wind speed signal. In order to obtain sufficient accuracy for reliable wind direction retrieval, uncertainties in geophysical modeling of the sea surface emission on the order of 0.2 K need to be removed. The surface roughness spectrum has been addressed by many studies, but the azimuthal signature of the microwave emission from breaking waves and foam has not been adequately addressed. Recently, a number of experiments have been conducted to quantify the increase in sea surface microwave emission due to foam. Measurements from the Floating Instrumentation Platform indicated that the increase in ocean surface emission due to breaking waves may depend on the incidence and azimuth angles of observation. The need to quantify this dependence motivated systematic measurement of the microwave emission from reproducible breaking waves as a function of incidence and azimuth angles. A number of empirical parameterizations of whitecap coverage with wind speed were used to estimate the increase in brightness temperatures measured by a satellite microwave radiometer due to wave breaking in the field of view. These results provide the first empirically based parameterization with wind speed of the effect of breaking waves and foam on satellite brightness temperatures at 10.8, 19, and 37 GHz.     

Macrocrack interaction with semi-infinite microcrack array

The collinear periodical array of microcracks ahead of a semi-infinite crack (macrocrack) is considered. A close form solution in terms of complex stress potentials is given, assuming that a remote, macroscale, stress intensity factor is given. The exact solution of the interaction of a macrocrack with a single microcrack is given.Results demonstrate that for relatively close location (with respect to crack length) of microcracks to the macrocrack tip, the microcrack spacing becomes important. For microcrack spacing (period) greater than 10 crack lengths the interaction can be taken as for a single microcrack, and, for distance greater than two microcrack lengths, the local stress intensity factor can be taken as equal to that remotely applied (for cases with crack spacing greater than two crack lengths).In other cases the macro-microcrack interaction is significant.

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Résumé On prend en considération le cas d'une rangée de fissures périodiques et colinéaires qui se forment en avant d'une fissure macroscopique semi-infinie. On propose une solution de forme fermée, exprimée en potentiels complexes de contraintes, et qui suppose l'existence d'un facteur d'intensité de contrainte s'exerçant à une échelle macroscopique. On fournit la solution exacte à l'interaction entre une macro-fissure et une simple microfissure.Les résultats présentés démontrent que, pour les micro-fissures relativement proches de l'extrémité de la macro-fissure, c'est leur espacement qui est important. Lorsque la période caractérisant l'espacement entre deux micro-fissures est supérieure ou égale à dix fois la longueur de la microfissure, l'interaction peut être assimilée à celle d'une micro-fissure simple. Lorsque la distance qui sépare la première micro-fissure de l'extrémité de la fissure est supérieure à deux fois la longueur de cette micro-fissure, et que la période entre deux micro-fissures successives excède deux fois leur longueur, l'interaction entre micro et macro-fissure peut être négligée pour le calcul du facteur d'intensité de contrainte à extrémité de la macro-fissure.Dans les autres configurations, l'interaction devient significative et ne peut être négligée.

     

Experimental verification for stability improvement of sensorless vector control system of induction motor using real‐time tuning of observer gain

This paper proposes a method for the design of the adaptive rotor flux observer gain to improve stability at low speed and in regenerating mode. The method is based on stability analysis, which utilizes a linearized model considering all systems, including each control loop. Therefore, the proposed method considers the effects of motor constants and control circuit constants. The stability analysis using the transfer function for the rotor speed considers the arrangement of poles and zeros and the steady‐state error. The rotor flux observer gain which improves the stability for each operating condition is ascertained. This paper also proposes a real‐time tuning method for the observer gain. The validity of the proposed method was confirmed by simulation using Matlab Simulink and by experiment. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(1): 67–81, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20715     

A New Method of Stereoscopic Viewing

A new kind of Stereoscopic Viewer is described which produces the illusion that the object viewed is actually in the room.     

The use of RO to remove emerging micropollutants following CAS/UF or MBR treatment of municipal wastewater

The removal of various organic micropollutants (OMPs), including six antibiotics (ERY, ROX, CLA, SMX, SMZ, and TMP), three pharmaceuticals (ibuprofen, salicylic acid, and diclofenac), one industrial product (BPA), and one hormone (cholesterol), was investigated in two pilot plants treating the same raw sewage of the Tel-Aviv WWTP. The effluent production by CAS-UF was 45 m³/h while that of MBR was 40 L/h. Each system's effluent constituted the feed for its RO, which comprised three RO steps after the CAS/UF and a semi-batch RO system after the MBR. Despite significant molecular differences between the selected OMPs, high removal rates were achieved after the RO stage (> 99% for macrolides, pharmaceuticals, cholesterol, and BPA, 95% for diclofenac, and > 93% removal of sulfonamides). However, low antibiotics concentrations and 28–223 ng/L residuals of ibuprofen, diclofenac, salicylic acid, cholesterol, and BPA in the MBR/RO and CAS-UF/RO permeates showed that although RO is an efficient removal solution, it cannot serve as an absolute barrier to OMPs. Therefore, additional treatment techniques should be considered to be incorporated aside the RO to ensure complete removal of such substances.     

Comparing objective and subjective learning curves: Judgments of learning exhibit increased underconfidence with practice.

When participants studied a list of paired associates for several study-test cycles, their judgments of learning (JOLs) exhibited relatively good calibration on the 1st cycle, with a slight overconfidence. However, a shift toward marked underconfidence occurred from the 2nd cycle on. This underconfidence-with-practice (UWP) effect was very robust across several experimental manipulations, such as feedback or no feedback regarding the correctness of the answer, self-paced versus fixed-rate presentation, different incentives for correct performance, magnitude and direction of associative relationships, and conditions producing different degrees of knowing. It was also observed both in item-by-item JOLs and in aggregate JOLs. The UWP effect also occurred for list learning and for the memory of action events. Several theoretical explanations for this counterintuitive effect are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociations of Personally Significant and Task-Relevant Distractors Inside and Outside the Focus of Attention: A Combined Behavioral and Psychophysiological Study.

Studies of attentional capture by personally significant stimuli have reached inconsistent results, possibly because of improper control of the participants' attention. In the present study, the authors controlled visual attention by using a Stroop-like task. Participants responded to a central color and ignored a word presented either centrally (i.e., at the focus of attention) or peripherally (i.e., outside the focus of attention). Central words led to slower reaction times and larger orienting responses for significant items than for neutral items. These effects largely disappeared when the words appeared in a peripheral location. The peripheral words interfered with performance when they were relevant to task demands. These results indicate that there is a fundamental difference between task-relevant words and personally significant words: The former capture attention even when presented peripherally, whereas the latter do not. (PsycINFO Database Record (c) 2010 APA, all rights reserved)