Equivalent Loadings Research Articles

3D modeling of residual stresses induced in finish turning of an AISI304L stainless steel

This paper addresses the development of a new methodology predicting residual stresses induced in finish turning of a AISI304L stainless steel. A hybrid approach combining experimental results and a numerical model is applied. The model simulates the residual stresses generation by applying equivalent thermo-mechanical loadings onto the machined surface without modeling the chip removal process, which enables rapid calculation. The shape and the intensity of equivalent thermo-mechanical loadings are identified through experimental measurements. Friction tests enable to model the thermal and mechanical loadings along the tool–workmaterial interface. Orthogonal cutting tests provide thermal and mechanical loadings below the primary and third shear zone. This model has already been presented in several papers, but only in a 2D configuration. The objective of this paper is to transfer this hybrid approach into a 3D configuration, which is closer to a concrete longitudinal turning operation. Based on this new model, the paper aims at investigating the interactions between each revolution. It is shown that around five revolutions are necessary to reach a steady state. Finally numerical results are compared with experimental measurements obtained by X-Ray diffraction. It is shown that residual stresses cannot be considered as homogeneous over the surface due to tool's feed. Additionally, the X-Ray beam is much too large to be able to quantify this heterogeneity. Based on average numerical values coherent with average values obtained by X-Ray diffraction, it is shown that the numerical model provides consistent results compared to experimental measurements for a large range of cutting speed and feed.

A Study on the Equivalent Static Wind Loadings on the Arched Roof Frames of Low-Rise Buildings in Atmospheric Boundary Layers

A series of wind tunnel aerodynamic experiments were conducted to investigate the wind loads on the low-rise buildings with arched roofs. The wind loadings were calculated from the simultaneous measured wind pressures data over all of the models surfaces in a simulated open terrain exposure atmospheric boundary layer. With these data the equivalent static wind loads (ESWL) of fluctuating wind pressures acting on buildings frames were evaluated and the results of equivalent static wind loads were compared with the 2006 version design codes of wind loadings on buildings in Taiwan. The design codes suggested the direction of wind acting on the low-rise buildings roofs were normal to the ridges of roofs. In this study results shown, the equivalent static wind loads caused by the approaching turbulent flow may exceed the suggested values by codes. So the peak response of structural frames should be considered carefully.

Interrogation of a Sonogashira Cross-Coupling of 8-Bromoguanosine with Phenylacetylene on Amberlite: Evidence for Pd/Cu Ion Binding and Propagation of Pd/Cu Nanoparticles

The reactivity of Amberlite (IRA-67) base “heterogeneous” resin in Sonogashira cross-coupling of 8-bromoguanosine 1 with phenylacetylene 3 to give 2 has been examined. Both 1 and 2 coordinate to Pd and Cu ions, which explains why at equivalent catalyst loadings, the homogeneous reaction employing triethylamine base is poor yielding. X-ray photo-electron spectroscopy (XPS) has been used to probe and quantify the active nitrogen base sites of the Amberlite resin, and postreaction Pd and Cu species. The PdCl2(PPh3)2 precatalyst and CuI cocatalyst degrade to give Amberlite-supported metal nanoparticles (average size ∼2.7 nm). The guanosine product 2 formed using the Amberlite Pd/Cu catalyst system is of higher purity than reactions using a homogeneous Pd precatalyst, a prerequisite for use in biological applications.

Drift optimization of high‐rise buildings in earthquake zones

AbstractThis paper presents a Drift Design Structural Model (DDSM) for the design optimization of high‐rise buildings in seismic zones. The model is formulated as a Generalized Single Degree of Freedom System subjected to equivalent static seismic loadings. The model objectives are: (a) the minimization of the structure weight; (b) the minimization of the structure top drift; and (c) the uniform distribution of the inter‐story drifts over the building height in order to minimize earthquake damage through the increase in plastic ductility. Seven high‐rise buildings were analysed in order to validate the model, to illustrate its use and to demonstrate its capabilities in structural design optimization in earthquake zones. The results obtained show that the DDSM performed well and consequently can be of practical value to structural designers. Copyright © 2009 John Wiley & Sons, Ltd.

Measurement Equivalence of the Trauma Symptom Checklist-40 for Chemically Dependent African American and Caucasian Women: A Preliminary Study

The Trauma Symptom Checklist-40 (TSC-40) is a brief self-report measure of trauma-related symptoms. Using a confirmatory factor analysis framework, this preliminary study examined whether the TSC-40 provided a good fit for 50 African American and 52 Caucasian economically and educationally disadvantaged women enrolled in a residential treatment program. A 5-factor structure of the TSC-40 appeared to be more applicable for our sample than the original 6-factor model. This 5-factor model includes negative mood, interpersonal problems, sleep disturbance, dissociative-like symptoms, and sexual problems. Equivalent factor structure and factor loadings emerged for the two ethnic and racial groups. Implications pertaining to trauma assessment are discussed.

Factorial Invariance, Scale Reliability, and Construct Validity of the Job Control and Job Demands Scales for Immigrant Workers: The Multi-Ethnic Study of Atherosclerosis

Immigrants have a different social context from those who stay in their home country or those who were born to the country that immigrants now live. Cultural theory of risk perception suggests that social context influences one's interpretation of questionnaire items. We examined psychometric properties of job control and job demand scales with US- and foreign-born workers who preferred English, Spanish, or Chinese (n = 3,114, mean age = 58.1). Across all groups, the job control scale had acceptable Cronbach's alpha (0.78-0.83) and equivalent factor loadings (ΔCFI < 0.01). Immigrants had low alpha (0.42-0.65) for the job demands scale regardless of language, education, or age of migration. Two job-demand items had different factor loadings across groups. Among immigrants, both scales had inconsistent associations with perceived job stress and self-rated health. For a better understanding of immigrants' job stress, the concept of job demands should be expanded and immigrants' expectations for job control explored.

Recalibration of the Asphalt Layer Coefficient

While there is an increasing interest in mechanistic-empirical flexible pavement design, this methodology will likely not be implemented by the majority of transportation agencies for several more years. Therefore, there is a need for optimization of the current design methodology, which for many agencies, is the 1993 AASHTO design guide. This approach contains a flexible pavement design equation with inputs of soil modulus, traffic, structural number, reliability, variability, and change in serviceability. A sensitivity analysis conducted on the inputs to this equation showed that the HMA layer coefficient (a 1 ) is the most influential on the resulting HMA thickness. A recalibration of a 1 was performed using data from the National Center for Asphalt Technology Test Track. A least-squares regression was performed to minimize the error between predicted and actual equivalent single axle loadings applied to the test sections. The resulting average a 1 was 0.54 with a standard deviation of 0.08. Using 0.54 instead of the AASHTO recommended coefficient (0.44) results in a HMA thickness savings of approximately 18%.

Numerical Simulation of Liquefaction Deformation of Sand Layer around Bucket Foundations under Dynamic Loadings

Bucket Foundations under Dynamic Loadings The liquefaction deformation of sand layer around a bucket foundation is simulated under equivalent dynamic ice-induced loadings. A simplified numerical model is presented by taking the bucket-soil interaction into consideration. The development of vertical and horizontal liquefaction deformations are computed under equivalent dynamic ice-induced loadings. Firstly, the numerical model and results are proved to be reliable by comparing them with the centrifuge testing results. Secondly, the factors and the development characteristics of liquefaction deformation are analyzed. Finally, the following numerical simulation results are obtained: the liquefaction deformation of sand layer increases with the increase of loading amplitude and with the decrease of loading frequency and sand skeletonrs strength. The maximum vertical deformation is located on the sand layer surface and 1/4 times of the bucketrs height apart from the bucketrs side wall (loading boundary). The maximum horizontal deformation occurs at the loading boundary. When the dynamic loadings is applied for more than 5 hours, the vertical deformation on the sand layer surface reaches 3 times that at the bottom, and the horizontal deformation at 2.0 times of the bucket height apart from the loading boundary is 3.3% of which on the loading boundary.

Health-related quality of life and help seeking among American Indians with diabetes and hypertension

To evaluate the Health-Related Quality of Life (HRQoL) of American Indians with diabetes, hypertension, or both conditions using the SF36; and to explore how the HRQoL is associated with help seeking among American Indians with and without these chronic conditions. We analyzed data obtained from respondents with diabetes and/or hypertension who participated in a large epidemiological study of two culturally distinct American Indian tribes. Comparison data were provided by an age, gender, and tribe matched sample from the same study who did not report either condition. The respondents with both diabetes and hypertension had the lowest HRQoL on all eight subscales of SF36. Confirmatory factor analysis (CFA) showed that the assumption of equivalent factor loadings for participants with and without diabetes and/or hypertension was not satisfied. Biomedical service use was significantly associated with the SF36 physical health factor in those with hypertension only. Help seeking from traditional healers was significantly negatively related to physical factor scores for all the respondents except those with diabetes only. Participants with comorbid diabetes and hypertension had worse HRQoL. The relationships between HRQoL and different types of help seeking varied depending on the comorbidity status of the respondents.

Modern and Old-fashioned Homonegativity Among Samples of Canadian and American University Students

The viability of modern homonegativity was examined in two studies using Canadian ( N = 374) and American ( N = 608) university students as participants. Results suggest that negativity toward sexual minorities grounded in contemporary assertions such as gay men and lesbian women no longer experience discrimination and possess all the rights they need, appears to be distinguishable from old-fashioned negativity, which reflects traditional, moral, and/or religious objections to homosexuality. Invariance analysis revealed that a majority of items designed to assess modern homonegativity had equivalent loadings across the two samples. Results also indicated that American participants were more homonegative than their Canadian counterparts, though this difference was most apparent with old-fashioned homonegativity. The limitations associated with the current series of studies are discussed and directions for future research are articulated.

Multi-input Markov chain equivalent fatigue loadings

The equivalent fatigue approach is a method for transforming complicated loadings into simpler ones, equivalent in terms of damage, without information about the geometry of the structure. It has been used for the design specifications of metallic structures, for the conditions of their tests trials, and finally for the characterization of customers and markets. The case of the one input equivalent fatigue approach has been thoroughly investigated at PSA. The current work treats the extension of the equivalent fatigue approach to the case of multi-input loadings. Especially the aim of this paper is to develop Markov chain models for the equivalent fatigue loadings.

A Simple Method To Improve the Clarity and Rheological Properties of Polymer/Clay Nanocomposites by Using Fractionated Clay Particles

We present a simple method to improve the transparency and rheological properties of polystyrene/organoclay nanocomposites. Such composites are typically prepared using organophilic derivatives of commercial montmorillonite (MMT) clays that contain a wide range of particle sizes. Our approach is to fractionate the native MMT clay to exclude large aggregates and then modify the fractionated clay (FMT) by a surfactant treatment (the resulting organoclay is termed o-FMT). Polystyrene nanocomposites made from the o-FMT are then compared with those made from a commercial organoclay having the same surfactant treatment. The o-FMT-based composites exhibit much better rheological properties (e.g., their elastic moduli at low frequencies are approximately 10 times higher) at equivalent mass loadings. Moreover, the o-FMT-based materials also have better transparency: e.g., a 10% o-FMT sample transmits as much light as a sample with 5% commercial clay. Transmission electron microscopy confirms that these differences in properties are related to microstructural differences; i.e., large aggregates are generally absent in the o-FMT samples. Clay fractionation may thus be a general strategy to enhance the properties of polymer/clay nanocomposites.

Nanostructured fly ash–styrene butadiene rubber hybrid nanocomposites

AbstractHybrid nanocomposites of styrene butadiene rubber (SBR) with nanostructured fly‐ash (NFA) were prepared in the laboratory by melt blending technique in an internal mixer. Curatives were added on a laboratory two‐roll mill. Curing characteristics as well as physico‐mechanical properties of the composites were evaluated. A comparison on SBR composites filled with fresh fly‐ash (FFA); carbon black (CB) and precipitated silica (PS) has been reported. In general, SBR‐NFA composites exhibit higher state of cure and higher strength properties as compared with HAF black‐filled and fresh fly‐ash‐filled SBR composites at equivalent loadings. This may be attributed to the higher reinforcing ability of NFA. This fact has also been supported by the swelling studies and Kraus' plot. Tear strength and abrasion resistance of the SBR‐NFA composites were superior to FFA‐filled and precipitated silica‐filled vulcanizates, but were inferior to carbon black‐ filled SBR vulcanizates. The SBR‐NFA composites showed lower hardness as compared with both the carbon black‐filled and silica‐filled composites. Transmission electron microscopy and scanning probe microscopy studies revealed that the NFA particles are well dispersed in the SBR matrix. These results were further supported by fracture surface analysis under the SEM, which revealed the role of NFA in the prevention of fracture propagation. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers

Retrospective Dosimetric Comparison of Low-Dose-Rate and Pulsed-Dose-Rate Intracavitary Brachytherapy Using a Tandem and Mini-Ovoids

The purpose of this study was to compare the dose distribution of Iridium-192 ( 192Ir) pulsed-dose-rate (PDR) brachytherapy to that of Cesium-137 ( 137Cs) low-dose-rate (LDR) brachytherapy around mini-ovoids and an intrauterine tandem. Ten patient treatment plans were selected from our clinical database, all of which used mini-ovoids and an intrauterine tandem. A commercial treatment planning system using AAPM TG43 formalism was used to calculate the dose in water for both the 137Cs and 192Ir sources. For equivalent system loadings, we compared the dose distributions in relevant clinical planes, points A and B, and to the ICRU bladder and rectal reference points. The mean PDR doses to points A and B were 3% ± 1% and 6% ± 1% higher than the LDR doses, respectively. For the rectum point, the PDR dose was 4% ± 3% lower than the LDR dose, mainly because of the 192Ir PDR source anisotropy. For the bladder point, the PDR dose was 1% ± 4% higher than the LDR dose. We conclude that the PDR and LDR dose distributions are equivalent for intracavitary brachytherapy with a tandem and mini-ovoids. These findings will aid in the transfer from the current practice of LDR intracavitary brachytherapy to PDR for the treatment of gynecologic cancers.

Effects of aspect ratio of MWNT on the flammability properties of polymer nanocomposites

The effects of the aspect ratio of multi-walled carbon nanotubes (MWNTs) on the rheology and flammability of polystyrene/MWNT nanocomposites are studied using two MWNTs having average aspect ratios (length to outer diameter) of 49 and 150. Dynamic rheological experiments show that the particles with the larger aspect ratio impart much higher storage moduli and complex viscosities to the nanocomposites compared to equivalent mass loadings of particles with the smaller aspect ratio. Additionally, in flammability experiments, the larger aspect ratio particles lead to a greater reduction in mass loss rate, i.e., they are more effective at reducing flammability. These results demonstrate that the aspect ratio of MWNTs is a key parameter in controlling the rheology and flammability of polymer nanocomposites.

TU-EE-A1-01: Capabilities of a CT-Suitable, Patient-Adaptive HDR/PDR Intracavitary Brachytherapy Applicator for the Treatment of Cervical Cancer

Purpose: To demonstrate the capability of a prototype, high-dose-rate/pulsed-dose-rate (HDR/PDR) intracavitary brachytherapy cervical applicator to be (a) imaged using computed tomography (CT) with minimal artifacts as compared to current, clinically-utilized applicators and (b) deliver dose to a simulated disease plane that is at least equivalent to that delivered by the FW applicator while delivering less dose to multiple, simulated rectal planes for equivalent loadings. Capability (b) demonstrates the prototype applicator's ability to adapt to varying patient anatomies utilizing a remotely adjustable shield contained within the colpostat. Method and Materials: CT image sets were acquired of the Fletcher-Suite-Delclos (FSD), Fletcher-Williamson (FW), and prototype applicators (utilizing a step-and-shoot technique) and artifacts generated by each were compared qualitatively. Images were acquired of the applicators positioned parallel to the table and in positions that simulated applicator placement during treatment. Using film validated MCNPX Monte Carlo (MC) models of the prototype and FW applicators, dose comparisons (min, max, average, and dose-surface histograms) were made in simulated disease (1cm medial to colpostat) and multiple rectal (1cm distal and 0, 0.5, and 1cm medial to the colpostat) planes. Results: Preliminary results indicate that the prototype applicator is CT-friendly; qualitatively minimizing anatomy-obscuring artifacts compared to equivalent FW and FSD image sets. Additionally, the prototype applicator is able to deliver comparable dose levels (within +/− 5%) to a simulated disease plane while reducing dose (32% average) to varying simulated rectal planes when compared to equivalent FW treatments. Conclusion: The prototype applicator is able to be CT imaged with minimal artifacts and substantially reduce dose delivered to the rectum while maintaining dose delivered to disease when compared to current ICBT technologies. Currently, the model is being extended to include two prototype applicators and a 15° tandem so that dose-volume histograms can be generated using specific-patient cases of varying anatomical geometries.

Epoxy−Silica Mesocomposites with Enhanced Tensile Properties and Oxygen Permeability

As-made and calcined forms of large-pore (5.3 nm) mesostructured silica with a wormhole framework structure, denoted MSU-J, have been used to form rubbery epoxy mesocomposites containing 1.0−12% (w/w) silica. The tensile modulus, strength, toughness, and extension-at-break for the mesocomposites formed from as-made and calcined forms of MSU-J silica are systematically reinforced by up to 4.8, 5.7, 1.6, and 8.5 times, respectively, in comparison to the pure epoxy polymer. The composites represent the first examples wherein the reinforcement benefits provided by mesostructured silica particles are comparable to those provided by exfoliated organoclay nanolayers at equivalent loadings. Moreover, the reinforcement benefits are realized without the need for organic modification of the silica surface, and the increases in tensile properties occur with little or no sacrifice in optical transparency or thermal stability. The oxygen permeability of the mesocomposites prepared from as-made MSU-J silica increases dr...

Different factor loadings for SF36: The Strong Heart Study and the National Survey of Functional Health Status

Background To increase our understanding of the psychometric characteristics and factor structure of the SF36® in older American Indian populations. Methods Between 1993 and 1995, SF36® data were collected from 3,488 Phase II participants of the Strong Heart Study (SHS) between the ages of 48 and 81. Comparison data were provided by an age- and gender-matched sample ( n = 695) from the National Survey of Functional Health Status (NSFHS) conducted in 1989 and 1990. Results Generally, the basic psychometric analyses showed that the SF36® performed adequately in these older American Indians. Exploratory factor analyses indicated that a one-factor model best fit the data for both older groups. On the other hand, confirmatory factor analyses showed that a two-factor model with correlated factors provided a superior fit to the data than a one-factor model. An assumption of equivalent factor loadings for the SHS and NSFHS groups was untenable. Conclusion These analyses demonstrate that use of summary scores assuming a differentiated physical/mental functioning structure is likely improper in at least some populations. The SF36® provides an important opportunity to understand cultural differences in the conceptualization and measurement of health-related quality of life.

Autoantibodies to Redox-modified Oligomeric Aβ Are Attenuated in the Plasma of Alzheimer's Disease Patients

Accumulation of Abeta protein in beta-amyloid deposits is a hallmark event in Alzheimer's disease (AD). Recent findings suggest anti-Abeta autoantibodies may have a role in AD pathology. However, a consensus has yet to emerge as to whether endogenous anti-Abeta autoantibodies are elevated, depressed, or unchanged in AD patients. Whereas experiments to date have used synthetic unmodified monomeric Abeta (Abetamon) to test autoimmunity, up to 40% of the Abeta pool inB AD brain consists of low molecular weight oligomeric cross-linked beta-amyloid protein species (CAPS). Recent studies also suggest that CAPS may be the primary neurotoxic agent in AD. In the present study, AD and nondemented control plasma were analyzed for immunoreactivity to CAPS and Abetamon. Plasma of both nondemented and AD patients were found to contain autoantibodies specific for soluble CAPS. Nondemented control and AD plasmas demonstrated similar immunoreactivity to Abetamon. In contrast, anti-CAPS antibodies in AD plasma were found to be significantly reduced compared with nondemented controls (p=0.018). Furthermore, age at onset for AD correlated significantly (p=0.041) with plasma immunoreactivity to CAPS. These data suggest that autoantibodies to CAPS are depleted in AD patients and raise the prospect that immunization with anti-CAPS antibodies might provide therapeutic benefit for AD.

Internet-based attitude assessment: does gender affect measurement equivalence?

As researchers and practitioners increasingly turn to the Internet as a data collection medium, investigating the differential effects of administration mode on data quality becomes increasingly important. To date, no research has investigated whether data gathered from differing subgroups demonstrate measurement equivalence across Internet and paper-and-pencil administration modes despite the large literature suggesting that males and females differ in terms of computer anxiety. The present study, employing a repeated measures design, investigated systematic cross-mode differences in responding as a function of gender. Results demonstrate that both sexes use the same psychological metric when providing satisfaction ratings regardless of Internet or paper-and-pencil administration (equivalent factor structure and factor loadings). Furthermore, there were no statistically significant differences in scale/item means over the modes of administration according to gender. These results suggest that gender does not lead to a negative impact on cross-mode measurement equivalence for self-report ratings.