Predictors of early high school dropout: A test of five theories.

This study compared the adequacy of 5 theories to predict dropping out of high school before the 10th grade. These theories include full mediation by academic achievement and direct effects related to general deviance, deviant affiliation, family socialization, and structural strains. Nested latent variable models were used to test these theories on prospective data from an ethnically diverse urban sample. Poor academic achievement mediated the effect of all independent factors on school dropout, although general deviance, bonding to antisocial peers, and socioeconomic status also retained direct effects on dropping out. Therefore, none of the theories tested was fully adequate to explain the data, although partial support was obtained for each theory. Implications for prevention of early high school dropout are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Liquid Crystals as Multifunctional Interfaces for Trapping and Characterizing Colloidal Microplastics

Identifying and removing microplastics (MPs) from the environment is a global challenge. This study explores how the colloidal fraction of MPs assemble into distinct 2D patterns at aqueous interfaces of liquid crystal (LC) films with the goal of developing surface-sensitive methods for identifying MPs. Polyethylene (PE) and polystyrene (PS) microparticles are measured to exhibit distinct aggregation patterns, with addition of anionic surfactant amplifying differences in PS/PE aggregation patterns: PS changes from a linear chain-like morphology to a singly dispersed state with increasing surfactant concentration whereas PE forms dense clusters at all surfactant concentrations. Statistical analysis of assembly patterns using deep learning image recognition models yields accurate classification, with feature importance analysis confirming that dense, multibranched assemblies are unique features of PE relative to PS. Microscopic characterization of LC ordering at the microparticle surfaces leads to predict LC-mediated interactions (due to elastic strain) with a dipolar symmetry, a prediction consistent with the interfacial organization of PS but not PE. Further analysis leads to conclude that PE microparticles, due to their polycrystalline nature, possess rough surfaces that lead to weak LC elastic interactions and enhanced capillary forces. Overall, the results highlight the potential utility of LC interfaces for rapid identification of colloidal MPs based on their surface properties.     

High Performance Microstrip Low Pass Filter for Wireless Communications

A microstrip low-pass filter using T-shaped resonators is designed to achieve an ultra-sharp transition band and high suppression level. The performance of the resonators is investigated based on an LC equivalent circuit and a transfer function to compute the equations of the transmission zeros. This filter has an acceptable stopband with high insertion loss (28 dB) by adopting a rectangular suppressor. Also, the width of the transition band is 0.09 GHz (with – 3 and ? 40 dB attenuation levels), that exhibits a very high sharpness (ξ = 411 dB/GHz). The proposed filter with a 3 dB cut-off frequency (f_c) of 1.32 GHz presents a high return loss in the passband (17 dB) and high figure of merit of 57,073. The designed filter is fabricated and measured, demonstrating sufficient agreement between the simulation and experimental results.

     

Furnace water-wall slag deposition testing in a 0.5 MWt combustion pilot plant

This article presents combustion pilot-plant test results obtained using newly developed ash deposition probes (ADPs) designed to measure both the thermal and mechanical properties of furnace ash deposits. The ADP measurements are obtained at multiple elevations in the furnace to provide detailed heat absorption and ash deposition time constant profiles for 8 h soot-blowing cycles. Profiles of incident radiation are also presented. Results are presented for four different coal types representing major steam-coal-producing regions in the United States. The furnace heat absorption profiles are distinctly different for each coal type and also vary significantly with furnace elevation. Combined furnace heat absorption and time constant data are used to recommend optimal use of soot-blowing resources, or to specify soot blower and water-wall surface addition and location according to coal type.     

Optimization of the sulfuric acid-catalyzed estolide synthesis from oleic acid

The production of estolide from oleic acid with sulfuric acid as a catalyst was optimized for minimal acid concentration and temperature. Commercial oleic acid forms estolide optimally when reacted at 55°C with 5% vol/vol concentrated sulfuric acid for 24 h under vacuum. The extent of oligomerization was 1.2 estolide units under these reaction conditions. Temperature plays a critical role in the rate of estolide formation as well as in the overall yield, with higher temperatures providing faster rates but lower yields. The ratio of sulfuric acid to oleic acid equivalents also plays a role, where higher acid concentrations gave faster rates and higher yields of estolide. Vacuum had a minor effect on oligomerization and estolide yield.     

De-noising techniques for terahertz responses of biological samples

Signal processing techniques may be used to improve the speed, resolution and noise robustness of pulsed terahertz (T-ray) imaging systems. Such systems have a wide range of applications and much recent interest has focussed on several promising biomedical fields. There are a number of significant challenges to be overcome before a commercial biomedical terahertz system can be realised. Recent research is focussed on the implementation of a high speed, compact and portable T-ray imaging system. This system will draw heavily on MOEMS technology. One of the major stages in the development of such a system is the design of efficient software algorithms to perform signal recognition and imaging operations in real time.

This paper considers a number of signal processing techniques suitable for de-noising and extracting information from the data obtained in a terahertz pulse imaging system. Two main de-noising techniques are considered. Wavelet de-noising and Wiener deconvolution algorithms are applied to the terahertz responses of biological samples including Spanish Serrano ham and an oak leaf.     

2-D Wavelet Segmentation in 3-D T-Ray Tomography

In this letter, segmentation techniques for terahertz (T-ray) computed tomographic (CT) imaging are investigated. A set of linear image fusion and novel wavelet scale correlation segmentation techniques is adopted to achieve material discrimination within a 3-D object. The methods are applied to a T-ray CT image dataset taken from a plastic vial containing a plastic tube. This setup simulates the imaging of a simple nested organic structure, which provides an indication of the potential for using T-ray CT imaging to achieve T-ray pulsed signal classification of heterogeneous layers     

Four-wave mixing penalties in long-haul WDM transmission links

We show computationally and experimentally that large resonances in signal variance due to four-wave mixing can occur in wavelength-division-multiplexed transmission systems. These resonances are the result of periodic amplifier spacing and distribution in dispersions and lengths of the fiber spans     

Multiple target tracking with lazy background subtraction and connected components analysis

Background subtraction, binary morphology, and connected components analysis are the first processing steps in many vision-based tracking applications. Although background subtraction has been the subject of much research, it is typically treated as a stand-alone process, dissociated from the subsequent phases of object recognition and tracking. This paper presents a method for decreasing computational cost in visual tracking systems by using track state estimates to direct and constrain image segmentation via background subtraction and connected components analysis. We also present a multiple target tracking application that uses the technique to achieve a large reduction in computation costs.