Static fatigue of Hi-Nicalon™-S fiber at elevated temperature in air,steam, and silicic acid-saturated steam

A facility for testing SiC fiber tows in static fatigue and creep at elevated temperatures in air and steam was developed. Static fatigue of Hi-Nicalon™-S fibers was investigated at 800°C-1100°C at applied stresses between 115 and 1250 MPa in air, in Si(OH)₄(g)-saturated steam, and in unsaturated steam. Fibers tested in Si(OH)₄(g)-saturated steam and in air had silica scales throughout the test sections, but those tested in unsaturated steam did not develop scales near the steam injection point. Fiber lifetimes in static fatigue were shortest in unsaturated steam, intermediate in Si(OH)₄(g)-saturated steam, and longest in air. Failure strains did not exceed 0.3%. Steady-state strain rates and static fatigue lifetimes are modelled empirically by the Monkman-Grant relationship. Failure mechanisms are discussed.     

Length to diameter ratio of extrudates in catalyst technology I. Modeling catalyst breakage by impulsive forces

Natural or forced catalyst extrudate breakage is an important phenomenon during catalyst manufacture. Here, a two‐parameter model for predicting the reduction in the length to diameter ratio of catalyst extrudates due to breakage by impulsive forces as experienced in a laboratory drop test is developed. Part II will show how both parameters can be correlated with the strength of the extrudates and the severity of the drop test. For breakage by impulsive forces, the model reveals that extrudates are reduced in length to diameter ratio according to a pseudosecond‐order break law. Also, a tie‐in exists with the well‐known Golden Ratio that is famous for its inherent esthetic value. Applying the model to cases of “severity sequencing” and “severity conditioning” reveals the nonlinear behavior of the length to diameter ratio and yields results that are often nonintuitive and hard to get without this engineering analysis. © 2015 American Institute of Chemical Engineers AIChE J, 62: 639–647, 2016     

Estimating design reliability of composite rotor blades under ultimate loading

A probabilistic stress analysis tool predicting reliability of composite wind turbine rotor blades was developed and validated by comparing with results from a three‐dimensional shell finite element model of a blade. Stress analysis was based on thin wall multicellular Euler–Bernoulli beam theory using as input section stress resultants directly from aeroelastic simulations; a finite strip method was implemented for elastic stability calculations. Reliability analysis was performed at the ply level of the multidirectional laminates implementing various methods such as the response surface method, β‐index and crude Monte Carlo simulation. Physical and statistical uncertainties of the basic variables was taken into account while several model uncertainties related to the material properties were further introduced and quantified in the light of appropriate test results. To prove the efficiency of the code as a design tool, the effect of various probabilistic assumptions concerning the material properties was directly investigated on the estimated reliability β‐index values for two rotor blade design cases typical of stall‐regulated and pitch‐regulated wind turbines. Copyright © 2014 John Wiley & Sons, Ltd.     

Hydrologic scaling for hydrogeomorphic floodplain mapping: Insights into human‐induced floodplain disconnectivity

Hydrogeomorphic approaches for floodplain modelling are valuable tools for water resource and flood hazard management and mapping, especially as the global availability and accuracy of terrain data increases. Digital terrain models implicitly contain information about floodplain landscape morphology that was produced by hydrologic processes over long time periods, as well as recent anthropogenic modifications to floodplain features and processes. The increased availability of terrain data and distributed hydrologic datasets provide an opportunity to develop hydrogeomorphic floodplain delineation models that can quickly be applied at large spatial scales. This research investigates the performance of a hydrogeomorphic floodplain model in two large urbanized and gauged river basins in the United States, the Susquehanna and the Wabash basins. The models were calibrated by a hydrologic data scaling technique, implemented through regression analyses of USGS peak flow data to estimate floodplain flow levels across multiple spatial scales. Floodplain model performance was assessed through comparison with 100‐year Federal Emergency Management Agency flood hazard maps. Results show that the hydrogeomorphic floodplain maps are generally consistent with standard flood maps, even when significantly and systematically varying scaling parameters within physically feasible ranges, with major differences that are likely due to infrastructure (levees, bridges, etc.) in highly urbanized areas and other locations where the geomorphic signature of fluvial processes has been altered. This study demonstrates the value of geomorphic information for large‐scale floodplain mapping and the potential use of hydrogeomorphic models for evaluating human‐made impacts to floodplain ecosystems and patterns of disconnectivity in urbanized catchments.     

Damage Characterization and Real-Time Health Monitoring of Aerospace Materials Using Innovative NDE Tools

The objective of this work is to characterize the damage and monitor in real-time aging structural components used in aerospace applications by means of advanced nondestructive evaluation techniques. Two novel experimental methodologies are used in this study, based on ultrasonic microscopy and nonlinear acoustics. It is demonstrated in this work that ultrasonic microscopy can be successfully utilized for local elastic property measurement, crack-size determination as well as for interfacial damage evaluation in high-temperature materials, such as metal matrix composites. Nonlinear acoustics enables real-time monitoring of material degradation in aerospace structures. When a sinusoidal ultrasonic wave of a given frequency and of sufficient amplitude is introduced into a nonharmonic solid, the fundamental wave distorts as it propagates, and therefore the second and higher harmonics of the fundamental frequency are generated. Measurements of the amplitude of these harmonics provide information on the coefficient of second- and higher-order terms of the stress–strain relation for a nonlinear solid. It is shown in this article that the material bulk nonlinear parameter for metallic alloy samples at different fatigue levels exhibits large changes compared to linear ultrasonic parameters, such as velocity and attenuation.     

A new microcontroller-based technique for generating variable voltage/frequency sinusoidal PWM signals

This paper presents a flexible and robust microcontroller-based technique for generating the control signals of any sinusoidal pulse width modulation (SPWM) scheme for variable voltage/frequency output. The proposed technique exploits the fully static design of a high-speed microcontroller and generates the PWM control signals by varying the controller's clock, while keeping the number of the algorithm processing states constant. As the experimental results show, the technique can be used for transient-free frequency and/or voltage changes with very good resolution and a wide range of applications.     

A biosocial developmental model of borderline personality: Elaborating and extending linehan’s theory.

Over the past several decades, research has focused increasingly on developmental precursors to psychological disorders that were previously assumed to emerge only in adulthood. This change in focus follows from the recognition that complex transactions between biological vulnerabilities and psychosocial risk factors shape emotional and behavioral development beginning at conception. To date, however, empirical research on the development of borderline personality is extremely limited. Indeed, in the decade since M. M. Linehan initially proposed a biosocial model of the development of borderline personality disorder, there have been few attempts to test the model among at-risk youth. In this review, diverse literatures are reviewed that can inform understanding of the ontogenesis of borderline pathology, and testable hypotheses are proposed to guide future research with at-risk children and adolescents. One probable pathway is identified that leads to borderline personality disorder; it begins with early vulnerability, expressed initially as impulsivity and followed by heightened emotional sensitivity. These vulnerabilities are potentiated across development by environmental risk factors that give rise to more extreme emotional, behavioral, and cognitive dysregulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of water content on the glass transition,caking and stickiness of protein hydrolysates

Abstract

Protein hydrolysates play an important function in many special dietary foods, e.g. for infants, those with genetic disorders, athletes and geriatrics. Because of hydrolysis these materials are more hygroscopic than the initial intact protein. In this reset the moisture sorption isotherms and the glass transition profile as a function of moisture content for fish protein hydrolysates (FPH), whey protein hydrolysates (WPH) and casein hydrolysates (CH) were determined. The properties of each hydrolysates were related to molecular weight with a lower glass transition curve at lower molecular weight, the Tg was proportional to degree of hydrolysis. These hydrolysates may be as important as sugars in lowering Tg. Fish moisture sorption was related to hydrolysis. CH was less susceptible to caking than FPH and WPH.