Orientation Data Research Articles

Penentuan Orientasi dan Translasi Gerakan UAV menggunakan Data Fusion berbasis Kalman Filter

In an unmanned aircraft vehicle, a navigation system is needed to calculate its orientation and translation. The navigation system can utilize data from the accelerometer, gyroscope, magnetometer, and GPS. The orientation can be precisely calculated from the accelerometer and magnetometer data when the sensor is in a static state. Meanwhile, under dynamic conditions, the orientation can be more precisely calculated from the gyroscope data. In order to obtain the robust navigation system, a data fusion based on Kalman filter is built to calculate the orientation from the accelerometer, gyroscope, and magnetometer. The Kalman filter trusts more in the data from the accelerometer and magnetometer when the UAV is static and trusts more in to the gyroscope data when the UAV is in dynamic conditions. Meanwhile, the UAV translation is obtained by performing data fusion of the accelerometer data with location data from the GPS sensor. The Kalman filter combines data from the accelerometer and GPS when available, otherwise trusts in data from the accelerometer only. The trust level shifting is done by changing the measurement noise covariance. The data fusion based on Kalman filter provides more accurately the orientation and translation data. The orientation as a result of the calculation from the gyroscope has an average error of 18.12%, while the orientation as a result of the accelerometer and magnetometer has an error of 1.3%. By using Kalman filter-based data fusion, the error of the orientation decreases to 0.87%

Life under COVID-19 for LGBT+ people in the UK: systematic review of UK research on the impact of COVID-19 on sexual and gender minority populations

ObjectiveTo systematically review all published and unpublished evidence on the impact of the COVID-19 pandemic on the health and well-being of UK sexual and gender minority (LGBT+; lesbian, gay, bisexual,...

Mechatronics Design and Kinematic Analysis of SMA Spring Actuated Parallel Manipulator

Flexible parallel manipulators can be used as an orienting device because of their precise positioning ability and better stiffness. The flexibility to the manipulator induces challenges in the selection of actuator, sensors and control. The paper presents a novel mechatronics design of a flexible symmetric parallel manipulator with minimum number of actuators used as an orienting device. Shape memory alloy springs (SMA) are used as an actuator because of ease of integration and higher deflection. In order to avoid any contact type sensor which could affect the compliance of the manipulator, the position of SMA spring is calculated indirectly from the kinematic model with the end effector orientation data measured from IMU sensor. The complete experimental set up design including electrical and control circuitry is explained in detail in the work. Preliminary open loop test is conducted on the prototype to understand the SMA response to various current input and to verify the effectiveness of the kinematic model in the actuator length measurement. Closed loop control based on ON/OFF control is implemented in the controller and is tested for step input.

Validity and reliability of a player-tracking device to identify movement orientation in team sports

ABSTRACT The purpose of this study was to determine the validity and reliability of the GPExe pro2 device to identify movement orientation in team-sport locomotion. Part A involved a series of discrete movement tasks of varying direction and orientation at two speeds (walk, run); Part B involved a continuous Simulated Game Circuit (SGC). For validity, distance in each orientation quadrant (forward, backward, left, right) and two aggregated sectors (lateral, non-forward), was compared to the known distance and calculated as the standard error of estimate (SEE). Inter-unit reliability was assessed in the SGC and reported as typical error (TE) and coefficient of variation (CV). In total, 256 trials were collected for validity (Part A 232, Part B 24), and 17 trials for reliability. Validity improved with faster and more continuous movement (SEE: walk 6.2–8.7%; run 4.4–8.2%; SGC 1.0–6.2%), was better for forward and backward (1.0–2.8%) compared to left and right orientation (3.8–6.2%), and for aggregated sectors (2.4–5.1%) rather than specific quadrants. Reliability was good (CV<5%) for forward and backward quadrants and both aggregated sectors, but poor (CV>10%) for left and right quadrants. These devices provide valid and reliable movement orientation data for team-sport locomotion, particularly in differentiating between forward and non-forward movement.

Implementation of Gender Identity and Assigned Sex at Birth Data Collection in Electronic Health Records: Where Are We Now?

In 2015, the United States Department of Health and Human Services instantiated rules mandating the inclusion of sexual orientation and gender identity (SO/GI) data fields for systems certified under Stage 3 of the Meaningful Use of Electronic Health Records (EHR) program. To date, no published assessments have benchmarked implementation penetration and data quality. To establish a benchmark for a U.S. health system collection of gender identity and sex assigned at birth, we analyzed one urban academic health center’s EHR data; specifically, the records of patients with unplanned hospital admissions during 2020 (N = 49,314). Approximately one-quarter of patient records included gender identity data, and one percent of them indicated a transgender or nonbinary (TGNB) status. Data quality checks suggested limited provider literacy around gender identity as well as limited provider and patient comfort levels with gender identity disclosures. Improvements are needed in both provider and patient literacy and comfort around gender identity in clinical settings. To include TGNB populations in informatics-based research, additional novel approaches, such as natural language processing, may be needed for more comprehensive and representative TGNB cohort discovery. Community and stakeholder engagement around gender identity data collection and health research will likely improve these implementation efforts.

Towards semi-automatic discontinuity characterization in rock tunnel faces using 3D point clouds

Searching for an efficient and reliable method to reduce manual intervention and subjective parameter selection during the discontinuity characterization process of rock tunnel faces is an important task. This paper presents a new method for semi-automatic discontinuity characterization in rock tunnel faces using 3D point cloud data, which consists of the following five procedures: (1) regions of interest selection, (2) octree-based local curvature calculation, (3) automatic discontinuity sets classification, (4) cluster analysis for point cloud data, and (5) visualization of classified discontinuity sets. To evaluate the performance of the proposed method, the point cloud data of three rock tunnel faces are collected and established using a photogrammetry-based scheme. Experiments are carried out to identify the optimized parameter values (point cloud density, plane radius, and discontinuity set number) for discontinuity characterization in a typical rock tunnel face. Using the optimized parameter values, the proposed method showed excellent performance and the statistical discontinuity orientation data were in good agreement with those obtained through in situ measurements. In comparison with the other two state-of-the-art methods (the Discontinuity Set Extractor (DSE) method and the qfacet fast marching (qfacet FM) method), the proposed method demonstrates improved processing efficiency and reasonable accuracy for discontinuity characterization using 3D point clouds. Overall, this study provides a step forward towards automatic 3D discontinuity characterization and visualization in the field for rock tunnel engineers.

Sources of Missing Sexual Orientation and Gender Identity Data in the Behavioral Risk Factor Surveillance System

This paper describes the sources, magnitude, and correlates of missing data in the Behavioral Risk Factor Surveillance System Sexual Orientation and Gender Identity module. Missing data from the Behavioral Risk Factor Surveillance System Sexual Orientation and Gender Identity module fielded from 2014 to 2019 were ascribed to 4 sources: the optional nature of the Sexual Orientation and Gender Identity module, out-of-state cell phone respondents, interview termination, and item nonresponse. The prevalence of missingness from these 4 sources was examined in relation to sociodemographic factors and survey process factors. Data were analyzed in 2018-2020. From 2014 to 2019, of 2,698,738 Behavioral Risk Factor Surveillance System respondents, 1,330,025 (44.8%, weighted) were in states that did not administer the Sexual Orientation and Gender Identity module. Among 723,301 cell phone interviews in states administering the module, 12.5% (weighted) were out of state. Among 1,316,174 otherwise potential respondents, 9.4% (weighted) terminated the interview before Sexual Orientation and Gender Identity module administration. Among 1,205,177 administered the module, item-level missingness was 3.4% for sexual orientation and 1.3% for gender identity. Correlates of missingness varied considerably at each stage. Missing the Behavioral Risk Factor Surveillance System Sexual Orientation and Gender Identity data is much more prevalent than item nonresponse alone would suggest. Analytic techniques that consider only item nonresponse, such as complete case analysis, risk producing biased findings. Including the Sexual Orientation and Gender Identity module in the required core demographics section is the only feasible method to reduce the amount and complexity of missing data.

An automatic workflow for orientation of historical images with large radiometric and geometric differences

AbstractThis contribution proposes a workflow for a completely automatic orientation of historical terrestrial urban images. Automatic structure from motion (SfM) software packages often fail when applied to historical image pairs due to large radiometric and geometric differences causing challenges with feature extraction and reliable matching. As an innovative initialising step, the proposed method uses the neural network D2‐Net for feature extraction and Lowe’s mutual nearest neighbour matcher. The principal distance for every camera is estimated using vanishing point detection. The results were compared to three state‐of‐the‐art SfM workflows (Agisoft Metashape, Meshroom and COLMAP) with the proposed workflow outperforming the other SfM tools. The resulting camera orientation data are planned to be imported into a web and virtual/augmented reality (VR/AR) application for the purpose of knowledge transfer in cultural heritage.

Tuning critical resolved shear stress ratios for bcc-titanium Ti21S via an automated data analysis approach

We introduce a novel method for automated slip trace detection and analysis based on the Hough transform algorithm and apply it to electron channeling contrast imaging micrographs. This is further augmented with an automation procedure for the determination of slip-trace crystallography in conjunction with orientation data acquired via electron backscattered diffraction. Automation is required for faster indexation of the slip traces and for more reliable statistical studies. The automation procedure was applied to different regions of interest on a β-Ti21S sample loaded in situ in tension. β-Ti21S is a bcc alloy with 48 slip systems available to accommodate plastic deformation, including all complexities associated with pencil glide. Multiple regions of interest were analyzed using the automation procedure. The acquired slip distribution statistics reveals that the majority of the slip traces belong to the {112} and {123} slip families. The deformation response of the observed regions of interest was also simulated using a full-field crystal plasticity model implemented in DAMASK, based on a phenomenological power law based constitutive formulation, incorporating all potentially active 48 slip systems. The slip system activity distribution from modelling is compared with the slip distribution statistics observed experimentally. The plasticity parameters for β-Ti21S were taken from the literature and the critically resolved shear stress (CRSS) values were adjusted to match the experimentally observed yield stress value. We begin with uniform CRSS ratios for all three potential slip system families and tune the CRSS ratios to match the slip-distribution statistics experimentally, keeping the average CRSS value the same for all cases. Thus, a method has been introduced to tune average CRSS values and ratios by considering both the macroscopic stress–strain response and the locally observed slip-distribution statistics, obtained via automated slip trace detection procedure.

Symposia

The COVID-19 pandemic enhances and accelerates an inevitable paradigm shift in interactions between health care providers and patient: from physician guided intermittent clinical visits and assessments towards remote active and passive monitoring and provision of care and education (E-health). The broad availability of electronic/ digital tools like smartphones and smartwatches, that have become indispensable in more and more areas of daily life, provides the technological basis for this transformation. Smartphones or smartwatches already contain sensors like accelerometers (acceleration), gyroscopes (angular velocity) and magnetometers (compass level orientation data) that can provide frequent or even continuous, objective, real-world information about qualitative and quantitative aspects of human performance enabling a comprehensive remote assessment. The realization of such obvious advantages and opportunities is not trivial: We need to develop appropriate signal processing and data analysis tools and algorithms to derive informative and reliable features that may be used as digital biomarkersout of a nearly indefinite quantity of data. We will discuss challenges and opportunities in the context of ongoing projects that aim at validating digital biomarkers such as our own project dreaMS. In Multiple Sclerosis (MS), a complex and chronic disease, the additional challenge is to complement established clinical and innovative digital biomarkers by laboratory and imaging features that access the underlying pathological processes in the immune and nervous system. Only such comprehensive approaches will allow real progress towards personalized MS care.

Barriers and facilitators to sexual orientation and gender identity (SOGI) data collection.

e18520 Background: Lack of sexual orientation and gender identity (SOGI) data collection is a barrier to inclusion of sexual and gender minority (SGM) patients in oncology. ASCO, NIH, and other groups have called for collection of SOGI data and documentation of SGM health disparities as a priority for clinical care and research. However, SOGI data are not routinely collected in most cancer care settings. The purpose of this study was to examine perceived barriers and facilitators to SOGI data collection among oncology professionals and researchers. Methods: An anonymous 54-item web-based survey was distributed to ASCO members which included two opened-ended items on barriers and facilitators to SOGI data collection. The survey was also promoted on listservs (Association of Community Cancer Centers, Association of Oncology Social Workers) and social media (e.g., Twitter, LinkedIn, Facebook professional groups). Responses to the open–ended items (n = 152) were coded by three coders using content analysis and constant comparison methods. Inter-rater reliability was 0.95. Results: The majority of respondents noted individual and organizational barriers to collecting SOGI data, including Culture (no support, expressed value or awareness of need from institution); Electronic Health Record (no location for SOGI or workflow challenges); Provider Discomfort (lack of knowledge on how/why to collect SOGI data, concerns about expressed bias); Patient Discomfort (privacy concerns, mistrust, refusal); Lack of Training or Resources; and Time (insufficient time to collect). Facilitators included a need for Protocols (intake process, patient-initiated disclosure); Training (how to collect and what to do with data); Culture change (institutional and/or provider priority); and improving Community Trust (patient trust, particularly in conservative areas of the country). A few respondents were concerned about patient safety in disclosure and some respondents noted culture change would require more representation of SGM staff and “safe spaces” in oncology settings. Three respondents made negatively biased comments about SGM patients. Conclusions: Overall, specific feedback from oncology providers identified barriers to SOGI data collection and suggested facilitators to resolve them, although not all respondents expressed value for SOGI data collection. Conservative culture and lack of leadership prioritization were cultural barriers; culture change (organizational and social) was noted as a potential facilitator for SOGI data collection. While workflow challenges and lack of a place to document SOGI in the EHR were barriers, protocols for documentation and patient-led disclosure were suggested facilitators. The study supports the need for leadership, processes, structured data fields, implicit bias and cultural humility training, and reduction of stigma to respond to the ASCO and NIH call to action.

Individual and institutional predictors of sexual orientation and gender identity data collection in oncology practice: An ASCO survey.

6520 Background: Most oncology practices do not collect patients’ sexual orientation (SO) or gender identity (GI) (SOGI), prohibiting assessment of sexual and gender minority (SGM) patients’ cancer disparities and identification of such patients in cancer care or research. Studies report that 90% of SGM patients would disclose their SOGI, while 78% of clinicians believe that patients would not. Preliminary evidence indicates that SOGI disclosure improves health outcomes. Organizations, including ASCO and NIH, have called for routine SOGI data collection, but institutional barriers, e.g. lack of SOGI fields in EMRs, hinder progress. This study aimed to delineate institutional and individual-level factors related to SOGI data collection in oncology. Methods: From Oct to Nov 2020, an anonymous 54 item online survey was distributed to ASCO members via direct outreach, listservs and social media. The survey assessed whether respondents’ institutions collect SOGI data, factors related to SOGI data collection, respondents’ attitudes about SOGI data and SGM patients, and demographics. Simple and multiple logistic regression modeling determined factors associated with respondents’ reports of SOGI data collection at their institutions. Results: Nearly half of 257 respondents reported their institutions collect SO and GI data (42%, 48%, respectively); over a third reported their institutions did not collect SO or GI data (36%, 34%, respectively); and a fifth were unsure (22%, 18%, respectively). Collection of both SO and GI was associated in unadjusted models with leadership support and having resources for SOGI data collection. SO collection was also associated with type of institution, having an SGM family member, and belief that knowing SO is important for providing quality care. GI collection was associated with the respondent’s role, SO, political leaning, past SGM training, and belief that knowing GI is important for providing care. Odds ratios (OR) from adjusted models with 95% confidence intervals (CI) comparing respondents who reported SO or GI collection as “Yes” vs. “No” are reported (comparisons to “Unsure” not presented). Most respondents (79%) felt it was important to know both SO and GI to provide quality care, while 14% felt neither was important. Conclusions: Whether or not institutions collect SOGI data is related to many factors. Despite limited statistical power, the same three factors emerged as drivers of data collection: leadership support, resources and individuals’ attitudes. These are critical and possibly self-reinforcing elements for collecting SOGI data.[Table: see text]

A Gendered View of Risk Taking in Venture Philanthropy

Relying on gender-role congruity theory, this paper investigates the relationship between the gender of the top management teams of venture philanthropy firms and their business risk-taking orientation. The research also assesses if and how experience moderates this relationship. Using a combination of survey data to capture the venture philanthropy firm’s risk orientation and biographical data to identify managers’ gender and experience, it finds that only gender affects business risk-orientation in these firms. Surprisingly, this is the opposite direction than expected, whereby teams with a higher proportion of women have a higher risk-taking profile. This suggests the need to revise the applicability of gender role congruity theory, the existence of a gender-bind dilemma, and the relevance of context in venture philanthropy.

Episodes of fissure formation in the Alps: connecting quartz fluid inclusion, fissure monazite age, and fissure orientation data

Fluid assisted Alpine fissure-vein and cleft formation starts at prograde, peak or retrograde metamorphic conditions of 450–550 °C and 0.3–0.6 GPa and below, commonly at conditions of ductile to brittle rock deformation. Early-formed fissures become overprinted by subsequent deformation, locally leading to a reorientation. Deformation that follows fissure formation initiates a cycle of dissolution, dissolution/reprecipitation or new growth of fissure minerals enclosing fluid inclusions. Although fissures in upper greenschist and amphibolite facies rocks predominantly form under retrograde metamorphic conditions, this work confirms that the carbon dioxide fluid zone correlates with regions of highest grade Alpine metamorphism, suggesting carbon dioxide production by prograde devolatilization reactions and rock-buffering of the fissure-filling fluid. For this reason, fluid composition zones systematically change in metamorphosed and exhumed nappe stacks from diagenetic to amphibolite facies metamorphic rocks from saline fluids dominated by higher hydrocarbons, methane, water and carbon dioxide. Open fissures are in most cases oriented roughly perpendicular to the foliation and lineation of the host rock. The type of fluid constrains the habit of the very frequently crystallizing quartz crystals. Open fissures also form in association with more localized strike-slip faults and are oriented perpendicular to the faults. The combination of fissure orientation, fissure quartz fluid inclusion and fissure monazite-(Ce) (hereafter monazite) Th–Pb ages shows that fissure formation occurred episodically (1) during the Cretaceous (eo-Alpine) deformation cycle in association with exhumation of the Austroalpine Koralpe-Saualpe region (~ 90 Ma) and subsequent extensional movements in association with the formation of the Gosau basins (~ 90–70 Ma), (2) during rapid exhumation of high-pressure overprinted Briançonnais and Piemontais units (36–30 Ma), (3) during unroofing of the Tauern and Lepontine metamorphic domes, during emplacement and reverse faulting of the external Massifs (25–12 Ma; except Argentera) and due to local dextral strike-slip faulting in association with the opening of the Ligurian sea, and (4) during the development of a young, widespread network of ductile to brittle strike-slip faults (12–5 Ma).

Environmental factors predicting the orientation of sea turtle hatchlings on a naturally lighted beach: A baseline for light-management goals

On sea turtle nesting beaches, artificial lighting associated with human development interferes with hatchling orientation from nest to sea. Although hatchling disorientation has been documented for many beaches, data that managers can use in understanding, predicting, and managing the issue are of limited detail. The present study provides baseline hatchling orientation data that can be compared to those from beaches with artificial lighting to prioritize light-management efforts there. In 2014, the precision of hatchling orientation was quantified for 87 nests on a naturally lighted beach that had little to no artificial lighting. Precision of hatchling orientation was regressed against seven environmental variables: beach slope, distance from nest to dune, dune height, apparent dune silhouette height relative to nest site, moon illumination percentage, cloud cover percentage, and relative humidity. Results favored a regression model that included distance from nest to dune, with shorter distances from the dune predicting a narrower angular range (i.e., greater precision) of hatchling orientation. The study confirmed findings of an earlier laboratory experiment that highlighted the importance to accurate hatchling orientation of a dark silhouette (dune) on the side of the nest site opposite the ocean side. Reducing artificial light and promoting the planting of pioneer plants that assist dune formation can increase hatchling survival.

Data enriched lubrication force modeling for a mechanistic fiber simulation of short fiber-reinforced thermoplastics

The simulative prediction of fiber orientation for injection-molded short fiber-reinforced thermoplastics is an important step in prediction warpage and failure of injection molded parts. There exists a variety of phenomenological macroscopic fiber orientation models, which are computationally very efficient but strongly dependent on phenomenological parameters. This research focuses on a mechanistic fiber orientation model for concentrated short fiber-reinforced thermoplastics. A fully coupled computational fluid dynamics particle simulation is used to estimate the lubrication forces between two fibers in different configurations (angles between fibers, velocities) with varying fiber length and surrounding fluid viscosity. Based on these data, a calibrated lubrication model is developed and implemented in a mechanistic fiber orientation simulation. In addition, the fiber orientation estimated by the enhanced mechanistic fiber model is compared to experimental fiber orientation data obtained with a glass fiber-reinforced thermoplastic industrial grade, which showed an improvement over a simulation that did not include the lubrication force.

Development and Evaluation of a Low-Drift Inertial Sensor-Based System for Analysis of Alpine Skiing Performance

In skiing it is important to know how the skier accelerates and inclines the skis during the turn to avoid injuries and improve technique. The purpose of this pilot study with three participants was to develop and evaluate a compact, wireless, and low-cost system for detecting the inclination and acceleration of skis in the field based on inertial measurement units (IMU). To that end, a commercial IMU board was placed on each ski behind the skier boot. With the use of an attitude and heading reference system algorithm included in the sensor board, the orientation and attitude data of the skis were obtained (roll, pitch, and yaw) by IMU sensor data fusion. Results demonstrate that the proposed IMU-based system can provide reliable low-drifted data up to 11 min of continuous usage in the worst case. Inertial angle data from the IMU-based system were compared with the data collected by a video-based 3D-kinematic reference system to evaluate its operation in terms of data correlation and system performance. Correlation coefficients between 0.889 (roll) and 0.991 (yaw) were obtained. Mean biases from −1.13° (roll) to 0.44° (yaw) and 95% limits of agreements from 2.87° (yaw) to 6.27° (roll) were calculated for the 1-min trials. Although low mean biases were achieved, some limitations arose in the system precision for pitch and roll estimations that could be due to the low sampling rate allowed by the sensor data fusion algorithm and the initial zeroing of the gyroscope.

Veterans' Reported Comfort in Disclosing Sexual Orientation and Gender Identity.

The Veterans Health Administration (VHA) does not routinely collect and document sexual orientation and gender identity (SOGI) data despite research on health disparities among sexual and gender minority (SGM) veterans. Due to the legacy of previous Department of Defense policies that prohibited disclosure of sexual or gender minority identities among active-duty personnel, minority veterans may be reluctant to respond to SOGI questions on confidential VHA surveys and in discussions with their VHA providers. Veterans may generally find SOGI questions uncomfortable and may not appreciate their relevance to health care. The purpose of this research was to examine veterans' comfort in reporting identity characteristics on confidential VHA surveys and in discussion with their VHA providers and whether comfort differed by sociodemographic characteristics. The project involves the secondary analysis of quantitative data from a quality improvement survey project. A total of 806 veterans were surveyed. Overall, 7.15% endorsed sexual or gender minority identity which is a higher rate than the 4.5% noted in the general US population. Cisgender and heterosexual veterans were more comfortable reporting identity characteristics both on VHA confidential surveys and in discussion with VHA providers compared with SGM veterans. These data suggest that the majority of veterans feel comfortable reporting their identities both on surveys and in the context of health care. Understanding these perceptions can assist VHA programs in implementing SOGI data collection and disclosure in clinical care, creating a welcoming environment of care for SGM veterans that does not make veterans from other backgrounds feel uncomfortable.

Paleostress and outcrop fracture analysis along Himalayan Foothills (Eastern Salt Range), Potwar Plateau, NW Himalaya, Pakistan

The Salt Range (SR) is an ENE-WSW trending fault bend fold that form the range front of the Himalayan fold and thrust belt in Pakistan. The research is carried out in the Eastern Salt Range (ESR) with the objective to determine the paleostress inversion from reduced stress tensors by using fracture data. The surface morphology of the fold is predominantly shaped by Eocene limestone that provide best exposure of joint surfaces that can be used for kinematic and dynamic analysis. We adopted a classical circle inventory method in the field and collected orientation data (dip amount, direction, and strike) from 7 localities (outcrop stations) of the Eocene Sakesar Limestone. Three prominent fracture trends are present in the study area namely, FS-1; (E-W), FS-2; (ENE-WSW) and FS-3; (NNE-SSW). For stress analysis and data processing we used the Tensor Program of Delvaux and Sperner (2003) and calculated seven stress fields by the Right Dihedron Method. The orientations of the principal stress axes (ϭ1, ϭ2, ϭ3) and Stress Ratio (R) depicts ϭ1(Shmax) and ϭ2 are sub-horizontal while ϭ3 is vertical in all stress tensors. The paleostress results show that ϭ1(Shmax) oriented NNE-SSW belonging to a compressive regime. It is suggested that ϭ1 developed more or less perpendicular to the trend of SRT and other relevant structures in the Potwar Plateau.

A Multi-Scale Approach for Phase Field Modeling of Ultra-Hard Ceramic Composites.

Diamond-silicon carbide (SiC) polycrystalline composite blends are studied using a computational approach combining molecular dynamics (MD) simulations for obtaining grain boundary (GB) fracture properties and phase field mechanics for capturing polycrystalline deformation and failure. An authentic microstructure, reconstructed from experimental lattice diffraction data with locally refined discretization in GB regions, is used to probe effects of local heterogeneities on material response in phase field simulations. The nominal microstructure consists of larger diamond and SiC (cubic polytype) grains, a matrix of smaller diamond grains and nanocrystalline SiC, and GB layers encasing the larger grains. These layers may consist of nanocrystalline SiC, diamond, or graphite, where volume fractions of each phase are varied within physically reasonable limits in parametric studies. Distributions of fracture energies from MD tension simulations are used in the phase field energy functional for SiC-SiC and SiC-diamond interfaces, where grain boundary geometries are obtained from statistical analysis of lattice orientation data on the real microstructure. An elastic homogenization method is used to account for distributions of second-phase graphitic inclusions as well as initial voids too small to be resolved individually in the continuum field discretization. In phase field simulations, SiC single crystals may twin, and all phases may fracture. The results of MD calculations show mean strengths of diamond-SiC interfaces are much lower than those of SiC-SiC GBs. In phase field simulations, effects on peak aggregate stress and ductility from different GB fracture energy realizations with the same mean fracture energy and from different random microstructure orientations are modest. Results of phase field simulations show unconfined compressive strength is compromised by diamond-SiC GBs, graphitic layers, graphitic inclusions, and initial porosity. Explored ranges of porosity and graphite fraction are informed by physical observations and constrained by accuracy limits of elastic homogenization. Modest reductions in strength and energy absorption are witnessed for microstructures with 4% porosity or 4% graphite distributed uniformly among intergranular matrix regions. Further reductions are much more severe when porosity is increased to 8% relative to when graphite is increased to 8%.