Adaptive Delay and Synchronization Control for Wi-Fi Based Mobile AV Conferencing

The tremendous success of the IEEE 802.11b technology and the popularity of portable computing units (e.g., PDAs) have led to a surge of Wi-Fi based real-time multimedia applications. However, due to the unpredictable and often fluctuating channel behavior, it is rather difficult to configure an appropriate de-jitter buffer to maintain a satisfactory perceived quality for end users. Motivated by this problem, we propose in this paper an adaptive delay and synchronization control scheme for Wi-Fi based AV conferencing applications. We target at campus-wide IEEE802.11b WLANs that are generally capable of supporting low-latency multimedia applications. The proposed scheme employs a distributed timing mechanism and performs localized control at the receiver side. The scheme can also be configiured flexibly with either one of the two inter-stream synchronization control options. Based on real-time monitored synchronization errors, Media Data Unit (MDU) loss, and real-time statistical estimation of the delay jitter among adjacent MDUs, the scheme is able to piece-wisely adjust the equalization delay to compensate for the delay jitter and control the MDU loss effectively. We investigate the performance of the proposed scheme using trace-driven approach. Through simulations, we show that the proposed scheme is capable of dynamically balancing between synchronization and latency requirements and effectively control the MDU loss as well. In particular, compared to the solutions using a static setting, the proposed scheme is able to provide the same MDU loss performance with a significant reduction in resultant latency. Haining Liu is currently a graduate student researcher in the Donald Bren School of Information and Computer Sciences at the University of California, Irvine. He received the B.E. degree and M.S.E. degree in Electrical Engineering from Tianjin University (China) in 1994 and 1997, respectively. After that, he was with the Beijing Posts and Telecommunications Design Institute of Ministry of Information Industry (China) as a telecommunications design engineer from 1997 to 1999. He received another M.S.E. degree in Systems Engineering from the University of Pennsylvania in 2000. His research interests include multimedia networking, wireless networks and real-time systems. Magda El Zarki received the B.E.E. from Cairo University, Cairo, Egypt in 1979 and the Ph.D. degree in Electrical Engineering from Columbia University, New York City, NY in 1981 in December 1987. Currently she holds the position of Professor in the Donald Bren School of Information and Computer Sciences at the University of California, Irvine, where she is involved in the telecommunication networks program. Prior to that she was an Associate Professor in the Department of Electrical Engineering at the University of Pennsylvania in Philadelphia where she also held the position of Director of the Telecommunications Program. From 1992–1996 she held the position of Professor of Telecommunications at the Technical University of Delft, Delft, The Netherlands. Ms. El Zarki is the co-author of a new text: Mastering Networks: An Internet Lab Manual. She is also on the editorial board of several journals in the telecommunications area, and is actively involved in many international conferences.     

Effect of Molybdate Ions on the Corrosion Behaviour of Ti Alloys

1. IntroductionTitanium alloys are most often specified for industrial and chemical process service due to theirrelatively superior corrosion performance in chlorideand other -halide--containing' environments[1]. Moreoverl Ti-alloys are candidate materials for containersof high-level nuclear waste suitable for deep underground burial for geological formations for extremelylong periods of timelZ]. This is because Ti-alloys canmailltain passivation in the ranges of temperatures,PH and chloride…     

Patterns and correlates of agreement between parent, teacher, and male adolescent ratings of externalizing and internalizing problems.

The authors examined how well 394 triads of male youths, caregivers, and teachers agreed about youth problems reported on the Achenbach checklists. Dyadic agreement was measured through difference scores (subtracting the raw score of youth self-report from the caregiver's or teacher's score for shared items), q correlations between pairs of raters across items, and D2 (generalized distance between item profiles) for both externalizing and internalizing items. Teachers reported fewer internalizing and externalizing problems than did caregivers or youths. Teacher–youth disagreement was higher for African American than European American males about externalizing criteria. Caregiver depression and stress (but not paternal antisocial behavior or maternal substance abuse) correlated with higher disagreement with other informants about all criteria. These factors appear to increase disagreement about the level of problems but not about specific symptom patterns. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cannulation and vascular access-related complications in hemodialysis: Factors determining successful cannulation

Little is known about cannulation of the vascular access (VA), such as the number of successful cannulation procedures, frequency of complications caused by cannulation, and VA failure. Incident patients were followed for 6 months, from the first successful cannulation with 2 needles—both used for the hemodialysis treatment. Data included patient characteristics, comorbidities, and medication. Vascular access characteristics included: type of VA and location, vein diameter assessed by Duplex ultrasound, length of the cannulation route, and maturation period. Longitudinal data were collected by dialysis nurses, using identical questionnaires, and a standardized method to register data from each dialysis session. Among 10 Dutch dialysis facilities, clinical data from 120 patients were collected from June 2005 to March 2007. The use of autogenous arteriovenous fistulae (P<0.001) and limited length of the cannulation route (P<0.003) negatively affect the outcome of cannulation and complications such as use of single-needle (SN) dialysis and central vein catheters (CVC). Previous use of CVC and SN hemodialysis were significant predictors for VA failure (P<0.0001). The present study demonstrated that during the first 6 months of a newly placed VA, a huge number of cannulation-related complications such as miscannulation, use of CVC, and SN dialysis are encountered. Despite the fact that guidelines recommended the arteriovenous fistulae as the preferred VA, cannulation-related complications can lead to increased morbidity. The length of the cannulation route positively correlates with successful cannulation. Therefore, adjusted cannulation techniques might be indicated to improve VA outcome.     

Spherical harmonics microwave algorithm for shape and location reconstruction of breast cancer tumor

A reconstruction algorithm to simultaneously estimate the shape and location of three-dimensional breast cancer tumor is presented and its utility is analyzed. The approach is based on a spherical harmonic decomposition to capture the shape of the tumor. We combine a gradient descent optimization method with a direct electromagnetic solver to determine the coefficients in the harmonic expansion as well as the coordinates of the center of the tumor. The results demonstrate the potential advantage of collecting data using a multiple-view/tomographic-type strategy. We show how the order of the harmonic expansion must be increased to capture increasingly "irregularly" shaped tumors and explore the resulting increase in the central processing unit (CPU) time required by the algorithm. Our approach shows accurate reconstruction of the tumor image regardless of the source polarization. This work demonstrates the promise of the algorithm when used on data corrupted with Gaussian noise and when perfect knowledge of the tumor electrical properties is not available.     

Effect of Gravitational Field and Temperature Dependent Properties on Two-Temperature Thermoelastic Medium with Voids under G-N Theory

This investigation is aimed to study the two dimensional problem of thermoelastic medium with voids under the effect of the gravity. The modulus of elasticity is taken as a linear function of the reference temperature and employing the two-temperature generalized thermoelasticity. The problem is studied in the context of Green-Naghdi (G-N) theory of types II and III. The normal mode analysis method is used to obtain the exact expressions for the physical quantities which have been shown graphically by comparison between two types of the (G-N) theory in the presence and the absence of the gravity, the temperature dependent properties and the two-temperature effect.     

Improved method for quantifying levoglucosan and related monosaccharide anhydrides in atmospheric aerosols and application to samples from urban and tropical locations

An improved analytical method was developed and validated for the determination of the monosaccharide anhydrides levoglucosan, mannosan, and galactosan in atmospheric aerosol samples. The method uses an external recovery standard, extraction in dichloromethane, trimethylsilylation, addition of an internal standard (1-phenyl dodecane), and analysis by gas chromatography with flame ionization detection (GC-FID) and gas chromatography/mass spectrometry (GC/MS). As external recovery standard, we selected 1,2,3-trihydroxyhexane, which has a similar polarity as the monosaccharide anhydrides; furthermore, it was ensured that the trimethylsilylation step leads to complete derivatization into trimethylsilyl ethers. The reproducibility of the combined trimethylsilylation and analysis of levoglucosan was about 2% for standard solutions, whereas the precision of the entire method for the sum of all three monosaccharide anhydrides (MAs) in real aerosol filter samples was about 5%. The method was applied to aerosol samples from urban and tropical locations. The atmospheric concentration of the MAs in fine (<2.5 microm) aerosols at a primary forest site in Rond?nia, Brazil, was on average 2.15 microg m(-3) during the dry season when intensive biomass burning occurs, which was almost 400 times higher than during the wet (nonburning) season. Urban total aerosols collected in Gent, Belgium, showed an average atmospheric concentration of MAs of 0.56 microg m(-3) for the winter season, which was a factor of 20 higher than for the summer season. The carbon in the MAs accounted on average for about 5.1% and 1.8% of the organic carbon in the Brazilian dry season and Gent winter aerosols, respectively. Levoglucosan was the major MA, with a relative abundance in the range of 76-93%.     

Familial risk factors to oppositional defiant disorder and conduct disorder: Parental psychopathology and maternal parenting.

In a sample of 177 clinic-referred children (aged 7–13 yrs), an association was found between a diagnosis of conduct disorder (CD) and several aspects of family functioning: maternal parenting (supervision and persistence in discipline) and parental adjustment (paternal antisocial personality disorder and paternal substance abuse). Children with oppositional defiant disorder were intermediate to families of children with CD and clinic control children on all variables, but differed from control children only in having a higher rate of paternal substance abuse and paternal antisocial personality disorder (APD). When both parental APD and deviant maternal parenting were entered into 2?×?2 logit-model analyses predicting CD, only parental APD was significantly associated with CD, and no interactions between parental adjustment and maternal parenting were found. The importance of these findings for understanding the etiology of CD and for disentangling correlated risk factors in future studies is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of juvenile aggression and violence: Some common misconceptions and controversies.

This article addresses 5 misconceptions and controversies concerning the development of aggression and violence: (a) the misconception that high stability coefficients of aggression over time imply that discontinuity of aggression from childhood to early adulthood is negligible; (b) the misconception that all serious forms of violence have an origin in aggression during early childhood; (c) the controversy about whether a single pathway or multiple pathways best represent individuals' development of antisocial behavior, including violence; (d) the controversy about whether causes of violence are similar to the causes of property offending; and (e) the assumption that the development of violence in women is very similar to that in men. Each of the points is discussed against empirical findings. Theoretical, research, and applied implications of the 5 points are discussed (PsycINFO Database Record (c) 2010 APA, all rights reserved)