Efficient compensation for frequency-dependent errors in analog reconstruction filters used in IQ modulators

In a direct-conversion transmitter system, the nonideal transfer characteristics of practical analog subsystems can have significant adverse effects on the performance of the transmitter system. While a significant body of research exists on correcting static errors (including gain imbalance, phase errors, and DC offsets) in the analog subsystems, relatively little attention has been paid to the impact of nonideal frequency-dependent characteristics in the analog reconstruction filters that are employed in direct-conversion structures. This paper presents a new computationally efficient and numerically robust method for automatic digital compensation for nonideal frequency-dependent characteristics in the signal reconstruction filters of a quadrature (IQ) modulator structure. The new compensation technique is used in conjunction with existing compensation approaches that compensate for static errors.     

Automated three-dimensional US frame positioning computed from elevational speckle decorrelation

For ultrasonographic B-scan images collected by means of a handheld transducer moving in the elevational direction, frame spacings are computed with a speckle-decorrelation algorithm, without additional positioning hardware. Fully developed speckle volumes are automatically segmented and spacing computed from the decorrelation curves. Position accuracy is within 10% for phantoms and 15% for breast studies. The algorithm provides image-based registration, which allows accurate three-dimensional volume rendering.     

Height perception: A function of social distance.

Investigated the effects of (a) status-related ethnic membership, and (b) the prejudice of the O on height perception. Ss were 126 undergraduates who were shown slides of various objects and people in a counter-balanced fashion. It was found that height-equated individuals rated high on the Bogardus Social Distance Scale were perceived as taller than height-equated individuals rated low on the Bogardus Social Distance Scale. The implications of these findings are discussed. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modeling Ice Passage at Navigation Locks

Physical and numerical models were used to assess ice passage at navigation locks, focusing on key factors such as the design of the lock filling and emptying system and the intakes to the lock filling culverts. Unconventional ice passage techniques such as manifolds in the miter gates were also evaluated. Physical model results were compared to field observations and to a parallel series of tests using the DynaRICE ice-hydraulic numerical model. The study focused on three general ice processes at locks: (1) ice accumulating near culvert intakes during lock filling; (2) drawing ice into the lock chamber; and (3) flushing ice out of the lock. Ice accumulation thickness in the upper lock approach was found to be the most important parameter affecting ice passage into the lock chamber. Physical and numerical model results compared reasonably well, proving DynaRICE to be a useful tool for assessing ice passage for new lock designs.     

Structural Ice Control Alternatives for Middle Mississippi River

The middle Mississippi River, which extends from the mouth of the Missouri River near St. Louis to the confluence with the Ohio River at Cairo, Ill., is a critical navigation route throughout the year. During cold periods, the ice accumulations and ice jams that form on this reach can delay or suspend winter navigation, incurring great costs to industry as well as cities and towns whose economies depend on river commerce. Much of this ice originates in the Missouri River. With the onset of warmer air temperatures, the rapid release of these ice accumulations can result in substantial damage to river structures such as dikes, revetments, and levees. This study analyzed historical data and used numerical hydraulic models to assess the possibility of structural solutions to these ice problems. The study identified reach locations where structural ice control might be possible. A simple computer model then simulated the upstream progression of ice covers on the middle Mississippi to assess the feasibility of various ice control alternatives. An ice retention structure located on the Missouri River near its mouth was found to be the most favorable of the structural ice control options considered.     

Ice Adhesion to Locks and Dams: Past Work; Future Directions?

Adhesion of ice to surfaces creates problems for many industries, including aviation, hydropower, telecommunications, navigation, electrical distribution, and all forms of transportation. Specific problems at locks and dams include ice buildup on lock walls and miter gates, and spillway gate freeze up, preventing opening on short notice. At present, ice removal techniques are both costly and time-consuming. In an effort to reduce the cost, time, and physical labor associated with ice removal, much research on ice adhesion has been done. This work ranges from theoretical studies to microscopic investigations and full-scale field tests. The main focus of all of these studies is how to lower ice’s adhesive strength, thus easing ice removal. Three principal methods to lower ice’s adhesive strength have been pursued—electrical, chemical, and mechanical. Of the three methods, the mechanical removal of ice has received the least amount of attention. Three approaches have been taken with regard to electrical methods. They are using heaters, creating an electrical pulse that mechanically breaks the ice, and applying a direct current bias to change the ice’s adhesion. The search for a low adhesive coating or material has by far received the most attention of any method pursued for lowering ice’s adhesive strength. A class of chemicals containing polysiloxanes has shown promise in providing a low adhesion surface. Based on this review, we recommend that an electroexpulsion method developed for the space shuttle and a newly formulated polysiloxane be tested as to their feasibility in the lock and dam environment.     

The influence of elevated levels of sodium in drinking water on elementary and high school students in Massachusetts

Continuing epidemiologic studies at the University of Massachusetts have examined the hypothesis that elevated levels of sodium (Na) in drinking water contribute to elevations of blood pressure (BP). Comparing tenth graders from a town with 107 mg Na/L in the drinking water to those from a town with 8 mg, Na/L, revealed statistically significant and medically important higher BP distributions among the high Na town students relative to their low Na town peers for both systolic and diastolic BP in both boys and girls. The differences were upheld when potentially confounding factors, including dietary Na intake and other water factors occurring differentially in the two water supplies, were controlled in the analysis. A replication study among third graders in the same communities showed similar results.Most recently, an experimental bottled water study assessed the effect on bloodpressure of lowering Na concentration in the water of some of the high sodium community fourth graders. For three months trios of children matched by sex, school, and baseline BP each used different water for all cooking and drinking purposes, with BP monitored bi-weekly. Pupils were randomly allocated to the three water conditions: 1) high sodium water bottled from their own community distribution system, 2) low sodium water bottled from the distribution system of the comparison community with sodium added to the level of the high sodium community water and 3) low sodium water bottled from the distribution system of the low sodium community but with no sodium added.Preliminary results indicate the BP levels of the girls on the low sodium waterexhibited marked decreases in BP over the test period when compared to the other two groups.