Contour Variations Research Articles

Autonomous Crop Row Guidance Using Adaptive Multi-ROI in Strawberry Fields

Automated robotic platforms are an important part of precision agriculture solutions for sustainable food production. Agri-robots require robust and accurate guidance systems in order to navigate between crops and to and from their base station. Onboard sensors such as machine vision cameras offer a flexible guidance alternative to more expensive solutions for structured environments such as scanning lidar or RTK-GNSS. The main challenges for visual crop row guidance are the dramatic differences in appearance of crops between farms and throughout the season and the variations in crop spacing and contours of the crop rows. Here we present a visual guidance pipeline for an agri-robot operating in strawberry fields in Norway that is based on semantic segmentation with a convolution neural network (CNN) to segment input RGB images into crop and not-crop (i.e., drivable terrain) regions. To handle the uneven contours of crop rows in Norway’s hilly agricultural regions, we develop a new adaptive multi-ROI method for fitting trajectories to the drivable regions. We test our approach in open-loop trials with a real agri-robot operating in the field and show that our approach compares favourably to other traditional guidance approaches.

Neural dynamics of cue reliability in perceptual decisions.

To extract meaningful information from scenes, the visual system must combine local cues that can vary greatly in their degree of reliability. Here, we asked whether cue reliability mostly affects visual or decision-related processes, using visual evoked potentials (VEPs) and a model-based approach to identify when and where stimulus-evoked brain activity reflects cue reliability. Participants performed a shape discrimination task on Gaborized ellipses, while we parametrically and independently, varied the reliability of contour or surface cues. We modeled the expected behavioral performance as a linear function of cue reliability and established at what latencies and electrodes VEP activity reflected behavioral sensitivity to cue reliability. We found that VEPs were linearly related to the individual behavioral predictors at around 400 ms post-stimulus, at electrodes over parietal and lateral temporal cortex. The observed cue reliability effects were similar for variations in contour and surface cues. Notably, effects of cue reliability were absent at earlier latencies where visual shape information is typically reported, and also in data time-locked to the behavioral response, suggesting the effects are not decision-related. These results indicate that reliability of visual cues is reflected in late distributed perceptual processes.

Relationship Between Presunset Wave Structures and Interbubble Spacing: The Seeding Perspective of Equatorial Plasma Bubble

AbstractIn this paper, we study on the precursor seed structures well before the prospective occurrence of equatorial plasma bubble (EPB). We use the scanning mode observations made by the 30‐MHz Gadanki Ionospheric Radar Interferometer for estimating interbubble spacing and high time resolution observations made by a collocated digisonde for inferring horizontal wavelength of wave‐like variations prior to the onset of EPB. Horizontal wavelength of wave‐like variations has been inferred from plasma density variations and height variations of isodensity contours; both show consistent results. Remarkable agreement has been found between the estimated horizontal wavelength and interbubble spacing, which demonstrates the potential of digisonde in providing relevant seed structure for a prospective EPB formation. Further analysis based on observational results and numerical simulation of collisional interchange instability shows that while the eventual formation of EPB has a strong bearing on the height of the F layer and density gradient scale length, the growth perspective of the EPB depends on the seed wavelength. These results are presented and discussed keeping the future prospective of EPB forecasting/nowcasting.

A novel cardiac SPECT system and imaging method

ABSTRACT A novel SPECT model with an elliptical orbit and multiple detectors is proposed for detecting the metabolism of the human heart. Under the structure of the proposed model, the distance between the detector and the patient becomes smaller, which can effectively improve the SNR. The slit-slat collimator is used to collimate the emitted photons. Modified iterative reconstruction algorithm is proposed to reconstruct a small centre field with severe truncation data under the constraints of body contour and total variation (TV). Simulations for the proposed SPECT are implemented to access the image reconstruction quality. The simulation results show that proposed imaging system with appropriate reconstruction methods can provide significant improvements in the spatial resolution and the image quality. The geometric efficiency of the proposed SPECT is about twice that of the conventional SPECT system, but the scanning time is only about one tenth.

Developing an All-Digital Workflow for Dental Skills Assessment: Part II, Surface Analysis, Benchmarking, and Grading.

In Part I of this study, evidence was presented that visual inspection (VI) of dental student waxups exhibited low precision (ICC=0.332) and accuracy, resulting in questionable grade validity. VI inappropriately assesses morphology in part due to oversimplified grading rubrics and inappropriate application of ratio measurement to ordinal data. The aim of Part II of this study was to develop, apply, and compare with VI a digital assessment workflow and report the outcomes. After inclusion criteria were met, 67 (83%) student waxups were scanned with an intraoral scanner and analyzed using open source surface comparison software. Each was digitally compared to the homologous standard typodont tooth. Percentage contour variation within a stipulated tolerance was computed. The acceptable tolerance was derived from clinical literature reporting how contour deviations impact the biological and biomechanical stability of teeth and periodontium. Surface roughness of each waxup was also computed and compared with the reference teeth. A formula for digital assessment was developed and applied to each waxup. On average, digital grades exceeded the VI assessments, while correcting individual errors for greater accuracy and precision (ICC=0.866). Students were able to easily apply the digital workflow for visualization and accurate self-evaluation. In this study, a digital grading workflow was developed that used portable data formats and freely available open source analysis software, so the method could be introduced at any dental school where intraoral scanning is available.

Protracted Development on Native Tone Interpretation: Evidence From Mandarin-Learning Infants' Novel Word Learning.

Studies have shown that infants from cultures with tone languages develop categorical perception of their native lexical tone before their first birthday, but few studies have explored whether, and when, they interpret the phonemic function of lexical tone in word learning. Two habituation-switch experiments were conducted to explore whether Mandarin-learning infants could exploit tonal cues during their word learning, and detect a change when the association of two word-object pairs was switched. In Experiment 1, two words were solely differentiated by their lexical tones (/fāi/ vs. /făi/), and Mandarin-learning infants failed to detect the switch of tones at 14 months, but succeeded at 18 months. In Experiment 2, two words were markedly distinct (/fāi/ vs. /bǒu/), and infants could detect the change of words as early as 14 months. The results indicate that infants may not refer to the lexical function of tone during their novel word learning until 18 months, even though infants from birth are able to distinguish the Tone 1 vs. Tone 3 contrast. Given that lexical tone is expressed by variations of the pitch contours, which are also related to intonation, infants’ increasing knowledge of both tone and intonation may contribute to their misinterpretation of pitch contours in word learning at 14 months and, further, to their development of a sophisticated use of the phonemic function of lexical tone at 18 months of age.

New shape descriptor in the context of edge continuity

The object contour is a significant cue for identifying and categorising objects. The current work is motivated by indicative researches that attribute object contours to edge information. The spatial continuity exhibited by the edge pixels belonging to the object contour make these different from the noisy edge pixels belonging to the background clutter. In this study, the authors seek to quantify the object contour from a relative count of the adjacent edge pixels that are oriented in the four possible directions, and measure using exponential functions the continuity of each edge over the next adjacent pixel in that direction. The resulting computationally simple, low-dimensional feature set, called as ‘edge continuity features’, can successfully distinguish between object contours and at the same time discriminate intra-class contour variations, as proved by the high accuracies of object recognition achieved on a challenging subset of the Caltech-256 dataset. Grey-to-RGB template matching with City-block distance is implemented that makes the object recognition pipeline independent of the actual colour of the object, but at the same time incorporates colour edge information for discrimination. Comparison with the state-of-the-art validates the efficiency of the proposed approach.

Does magnetic resonance imaging improve soft tissue sarcoma contouring for radiotherapy?

Objective:Soft tissue sarcomas (STS) are a rare, heterogeneous tumour group. Radiotherapy improves local control. CT is used to plan radiotherapy, but has poor soft tissue definition. MRI has superior soft tissue definition. Contour variation amongst oncologists is an important factor in treatment failure. This study is the first to directly compare STS tumour contouring using CT vs MRI.Methods:Planning CT and T 2 weighted MR images of eight patients with STS were distributed to four oncologists. Gross tumour volume was contoured on both imaging modalities using in-house software. Images were recontoured 6 weeks later. The mean distance to agreement (DTA), standard deviation of the DTA, dice similarity coefficient (DSC) and contour volume were calculated for each oncologist and compared to a median contour volume. Results for CT and MRI were compared using a pairwise Student's t-test.Results:When comparing MRI to CT, tumour volumes were significantly smaller, with a difference of 21.4 cm3 across all patients (p = 0.008). There was not a statistically significant difference in the mean distance to agreement or dice similarity coefficient, but the standard deviation of the DTA showed a statistically significant improvement ( p = 0.04). For intraobserver variation, there was no statistically significant improvement using MRI vs CT.Conclusion:Oncologists contour smaller tumour volumes using MRI, with reduced interobserver variation. Improving the reliability and consistency of contouring is needed for improved quality assurance.Advances in knowledge:With further experience, the use of MRI in STS radiotherapy planning may reduce variation between oncologists and contribute to improved local control and reduced treatment toxicities.

Contour variation is a primary source of error when delivering post prostatectomy radiotherapy: Results of the Trans-Tasman Radiation Oncology Group 08.03 Radiotherapy Adjuvant Versus Early Salvage (RAVES) benchmarking exercise.

Variation in target volume delineation from clinical trial protocols has been shown to contribute to poorer patient outcomes. A clinical trial quality assurance framework can support compliance with trial protocol. Results of the TROG 08.03 RAVES benchmarking exercise considering variation from protocol, inter-observer variability and impact on dosimetry are reported in this paper. Clinicians were required to contour and plan a benchmarking case according to trial protocol. Geometric pjmirometers including volume, Hausdorff Distance, Mean Distance to Agreement and DICE similarity coefficient were analysed for targets and organs at risk. Submitted volumes were compared to a STAPLE and consensus 'reference' volume for each structure. Dosimetric analysis was performed using dose volume histogram data. Benchmarking exercise submissions were received from 96 clinicians. In total 205 protocol variations were identified. The most common variation was inadequate contouring of the CTV in 84/205 (41%). The CTV volume ranged from 65.3 to 193.1cm3 with a median of 113.2cm3 . The most common dosimetric protocol variation related to rectal dosimetry. The mean submitted rectal volume receiving 40Gy and 60Gy, respectively, was 56.14%±5.55% and 30.25%±6.15%. When corrected to the protocol defined length the mean rectal volume receiving 40Gy was 60.8%±7.92%, while the volume receiving 60Gy was 33.86%±8.21%. Variations from protocol were found in the RAVES benchmarking exercise, most notably in CTV and rectum delineation. Inter-observer variability was evident. Incorrect delineation of the rectum impacted on dosimetric compliance with protocol.

Creating Robust Predictive Radiomic Models for Data From Independent Institutions Using Normalization

Purpose: The distribution of a radiomic feature can differ between two institutions due to, for example, different image acquisition parameters, imaging systems, and contouring (i.e., tumor delineation) variations between clinicians. We aimed to develop effective statistical methods to successfully apply a radiomics-based predictive model to an external dataset. Theory: Two common feature normalization methods, rescaling and standardization, were evaluated for suitability in reducing feature variability between institutions. Standardization was chosen as the preferred approach, since rescaling was more sensitive to statistical outliers, and potentially reduced the discrimination power of a feature. It was also demonstrated why a dataset needs to be balanced between positive and negative outcomes before standardization is applied to it. Methods: In this paper, the novelty and power of the developed method for improved application of radiomics models on external datasets is tied to finding the normalization transformations separately for each independent set. The clinical effectiveness of the normalization method was shown using magnetic resonance images of primary uterine adenocarcinoma. Feature selection was done using 94 samples (Institution X), and feature testing was done using 63 samples (Institution Y). The outcomes studied were lymphovascular space invasion and cancer staging. Logistic regression was used to obtain the prediction accuracy of a feature. Promising radiomic features were defined as those with AUC > 0.75 in the training set. Results: When comparing the prediction accuracy, ${F}$ -score, and Matthews correlation coefficient (MCC) of promising radiomic features in the testing set with and without standardization, there was an improvement due to standardization. For cancer stage prediction, average accuracy for all promising features rose from 0.64 to 0.72, average ${F}$ -score from 0.48 to 0.71, and average MCC from 0.34 to 0.44 ( ${p}\,\, { ). Furthermore, when applying standardization, the ratio of sensitivity to specificity was close to unity in the testing set, comparable to the ratio in the training set. Without standardization, this ratio deviated significantly from unity in the testing set. Conclusions: Applying feature standardization separately for each independent set using imbalance adjustments was shown to improve the predictive ability of radiomic models when applied to a dataset from an external institution.

18F] FDG Positron Emission Tomography (PET) Tumor and Penumbra Imaging Features Predict Recurrence in Non-Small Cell Lung Cancer.

We identified computational imaging features on 18F-fluorodeoxyglucose positron emission tomography (PET) that predict recurrence/progression in non–small cell lung cancer (NSCLC). We retrospectively identified 291 patients with NSCLC from 2 prospectively acquired cohorts (training, n = 145; validation, n = 146). We contoured the metabolic tumor volume (MTV) on all pretreatment PET images and added a 3-dimensional penumbra region that extended outward 1 cm from the tumor surface. We generated 512 radiomics features, selected 435 features based on robustness to contour variations, and then applied randomized sparse regression (LASSO) to identify features that predicted time to recurrence in the training cohort. We built Cox proportional hazards models in the training cohort and independently evaluated the models in the validation cohort. Two features including stage and a MTV plus penumbra texture feature were selected by LASSO. Both features were significant univariate predictors, with stage being the best predictor (hazard ratio [HR] = 2.15 [95% confidence interval (CI): 1.56–2.95], P < .001). However, adding the MTV plus penumbra texture feature to stage significantly improved prediction (P = .006). This multivariate model was a significant predictor of time to recurrence in the training cohort (concordance = 0.74 [95% CI: 0.66–0.81], P < .001) that was validated in a separate validation cohort (concordance = 0.74 [95% CI: 0.67–0.81], P < .001). A combined radiomics and clinical model improved NSCLC recurrence prediction. FDG PET radiomic features may be useful biomarkers for lung cancer prognosis and add clinical utility for risk stratification.

Fracture Segmentation Method Based on Contour Evolution and Gradient Direction Consistency in Sequence of Coal Rock CT Images

The coal rock exhibits obvious heterogeneity and anisotropy after a long-term geological evolution in nature. Therefore, the coal rock CT (computed tomography) image shows uneven grey scale, low contrast, and the fractures with weak boundaries. The accurate segmentation of the coal rock fracture networks is challenging. In this paper, a segmentation method of fractures based on contour evolution and gradient direction consistency is proposed to accurately segment the fracture networks in the sequence of coal rock CT images. According to the contour variation rule of the fractures in the discrete 3D (three dimensional) space formed by the sequence of CT images, the fracture contour evolution model (FCEM) is constructed and the preliminary segmentation results of fractures are obtained from FCEM. A 3D adaptive median filtering (3DAMF) and a 3D bilateral filtering (3DBF) are proposed. The high density miscellaneous point noises in the coal rock CT images are filtered by the 3DAMF. And the boundaries of fractures are enhanced by 3DBF. According to the similarity of the preliminary segmentation results of fractures and the real contours of fractures, the preliminary segmentation results of fractures are optimized based on the gradient direction consistency model (GDCM) proposed in this paper to obtain the accurate boundaries of fractures. The fracture segmentation method proposed in this paper can obtain accurate boundaries of fractures with weak boundaries, and the experimental results show that the segmentation efficiency for sequence is high and adaptability is strong.

Heat Transfer and Friction Measurement in Pin-Fin Arrays Under Mist Flow Condition

Abstract Effects of air/water mist flow on endwall heat transfer in a square channel were experimentally investigated using infrared thermography. The purpose was to study the detailed heat transfer contour variation caused by the generation of the liquid films. The surface was roughened with staggered partial pin-fin arrays to enhance flow mixing and liquid entrainment. Two streamwise spacings (Xp/d = 3 and 6) of the fin array were investigated. The gas Reynolds number ranged from 7900 to 24,000. The calculated droplet deposition velocity was comparable to the literature results and was not substantially affected by the gas Reynolds number or fin spacing. For the pin-fin array, heat transfer was dominated by the water accumulation and liquid film formation, which was dependent on the carrier gas flow rate and fin spacing. Furthermore, thick liquid fragments entrained between the fins substantially enhanced local convective heat transfer coefficients. The average heat transfer enhancement on the finned surfaces using mist flow was four times as high as the air flow. The pressure drop from the mist flow was two times as high as the air flow.

STUDY OF MORPHOLOGY OF THE ETHMOIDAL ROOF ON CT SCAN IN PATIENT WITH NASOSINUSAL SYNDROMES

Background: The ethmoidal roof is the thinnest bone of the skull base. Study of morphology of the ethmoidal roof on sinus CT Scan to avoid damaging the ethmoidal roof during sinus surgery. Objective: Describe the shape of the ethmoidal roof and some adjacent structures on computed tomography. Survey the relation between the shape of the ethmoidal roof and some adjacent structures. Patients and methods: Including 177 patients with nasosinusal syndromes who examined and underwent sinus CT scan at Hue University of Medicine and Pharmacy. Result: The mean hight of the lateral lamella of the cribrifom plate is 4.27 ± 1.96 mm on the right and 4.64 ± 1.92mm on the left. Keros type 1 accounted for 41.5%, type 2 accounted for 47.2% and type 3 accounted for 11.3%. Keros classification on the left was significantly higher than that on the right side. The hight of the nasal cavity was lowest in the Keros type 1 group and highest in type 3 (p=0.001). For more than 2 mm asymmetry of the hight of the lateral lamella of the cribrifom plate, the Keros 3 group showed a statistical more common when compared to the other groups (X2=15.62, p=0.004). The hight of the lateral lamella of the cribrifom plate at the ipsilateral side (deviated side) was higher than that of the contralateral side, but the difference is not statistically significant. Conclusion: Understanding potential asymmetries and variations of the skull base contour may assist the surgeons in avoiding complications in sinus surgery. Key words: The ethmoid roof, sinus surgery

Calculation of air gaps between bolus and skin on the dose received from the skin

Introduction: In the last few decades, a lot of monte carlo codes have been introduced for medical applications. For close - to - surface tumors, the surface of the skin can be used to increase the surface dose so that all or part of the bunch area can fall into bolus, thereby increasing the dose of the skin. The air gaps between bolus and skin can affect the dose of skin, especially if the skin is only the target of treatment. For this purpose, the effect of energy, bolus thickness, the amount of air gap, field dimensions and angle of field contact angle will be evaluated. Materials and Methods: In this study, the MCNPX calculation code is used to simulate the linear accelerator of Siemens to determine the effects of air gaps between bolus and skin. The studied fields were chosen in this study with dimensions 4×4 and 10×10 cm2. it also simulated a water phantom at SSD=100 cm and bolus thickness 0.5,1 cm in distances 0, 0.5 cm. Results: For field sizes 4×4 cm2 with 6 photon beam The bolus was as thick as 0.5 cm in the distance of 0 and 0.5 cm from the phantom level with a percent of surface dose to the maximum dose in the absence of the air gaps with %104.615 in the presence of air gaps %101.866 and the bolus thickness of 1cm in a same distance from the phantom level with a percent of surface dose to the maximum dose in the absence of the air gaps with %106.89 in the presence of air gaps %100.47. Also for field sizes 10×10 cm2, thickness of 0.5 cm in distance of 0 and 0.5 cm, from the phantom level with a percent of surface dose to the maximum dose in the absence of the air gaps with %99.62 in the presence of air gaps %97.74. Conclusion: For field size 10×10 cm2 Dsurf is largely unaffected by air gaps. However, smaller air gap results in shallower dmax for 6 MV photon beams at all fields sizes. Special consideration should be taken to reduce air gaps between bolus and skin for field sizes smaller than 10×10 cm2 or when surface contour variations are greater or when the bolus covers small area and at the border of the field.

Clinically Oriented Contour Evaluation Using Dosimetric Indices Generated From Automated Knowledge-Based Planning

Geometric indicators of contouring accuracy suffer from lack of clinical context in radiation therapy. To provide clinical relevance, treatment plans should be generated from the candidate contours, but manual planning could introduce confounding variations. Therefore, our objectives in this study were as follows: (1) determine the feasibility of using automated knowledge-based planning as an objective tool to generate dosimetric parameters for contour evaluation, (2) evaluate the correlation between geometric indices and dosimetric endpoints, and (3) report the dosimetric impact of multiple observations of head and neck target and organ-at-risk (OAR) volumes contoured by resident physicians. Twenty-two resident physicians contoured the clinical target volumes, parotids, and cochleae for a nasopharyngeal cancer case, and expert-generated contours were defined as the gold standard for this study. A validated knowledge-based planning routine generated 67 treatment plans with various resident/gold-standard and target/OAR combinations. Dosimetric indices (dose to hottest 98% volume of planning target volume, and mean dose of OAR) were calculated on gold-standard contours. Commonly used geometric indices (Dice coefficients, Hausdorff maximum/mean/median distances, volume differences, and centroid distances) were also calculated. R2 quantified the correlation between geometric and dosimetric indices. The correlation between geometric and dosimetric indices was weak (R2<0.2 for 61% of the correlations studied-77 of 126) and inconsistent (no single geometric index consistently exhibited superior/inferior correlation with dosimetric endpoints). The lack of consistent correlations between geometric and dosimetric indices resulted in the inability to define any geometric index thresholds for clinical acceptability. Geometric indices also exhibited a high propensity for false positives and false negatives as a classifier of dosimetric impact. Finally, we found substantial interresident contour variation, whether quantified using geometric or dosimetric indices, with significant negative dosimetric impact should these contours be used clinically. Contour variation among resident physicians significantly affected dosimetric endpoints, highlighting the importance of resident education in head and neck anatomy delineation. Whenever available, dosimetric indices generated from automated planning should be used alongside geometric indices in radiation therapy contouring studies.

A numerical simulation of single bubble growth in subcooled boiling water

Water-cooling blanket is closely related to system safety in future fusion reactor for it can cooling down the reactor. The process of cooling in water-cooling blanket may involve bubble generation under subcooled boiling condition. Although many researchers have investigated bubble generation numerically, the details of bubble generation in subcooled boiling remain unclear. In this paper a two-dimensional bubble growth simulation under subcooled nucleate boiling condition has been conducted using VOF (Volume of Fluid) method in ANSYS FLUENT. A phase change model was adopted by adding extra mass source term and energy source term to the Navier-Stokes equations in the cells adjacent to vapor-liquid interface. The variations of bubble contour before bubble departure, temperature fields, velocity fields and contribution of heat flux from superheated layer and subcooled fluid can be obtained by simulation. The results were compared with existing datum of visual experiment in previous literature to verify the validity of the simulation.

Impact of Natural Variations in Freeze-Drying Parameters on Product Temperature History: Application of Quasi Steady-State Heat and Mass Transfer and Simple Statistics.

Inter- and intra-batch variability in heat and mass transfer during the drying phase of lyophilization is well recognized. Heat transfer variability between individual vials in the same batch arise from both different positions in the vial array and from variations in the bottom contour of the vials, both effects contributing roughly equally to variations in the effective heat transfer coefficient of the vials, Kv. Both effects can be measured in the laboratory, and variations in average Kv values as a function of vial position in the array for lab and production can be calculated by use of the simple steady-state heat and mass transfer theory. Typically, in the laboratory dryer, vials on the edge of the array, "edge vials," run 2-4°C warmer than "center vials," but differences between laboratory and manufacturing temperatures are modest. The variability in mass transfer can be assigned to major variations in ice nucleation temperature (both intra-batch and inter-batch), including major differences between laboratory and manufacturing. The net effect of all random variations, for each class of vial, can be evaluated by a simple statistical model-propagation of error, which then allows prediction of the distribution in product temperatures and drying times, and therefore prediction of percent of vials dry and percent of vials collapsed and proximity to the edge of failure for a given process. Good agreement between theoretical and experimentally determined maximum temperatures in primary drying and percent collapsed product demonstrates the calculations have useful accuracy.

Creep-fatigue crack growth rate assessment using ductility damage model

In this study, we analyzed the behavior of creep damage and fracture resistance parameters in a 3D finite thickness compact specimen by employing damage-evolution equations. A damage model for the fracture process zone is represented using a ductility-based formulation. Following the ductility model, a new multi-axial failure strain condition is derived. Both damage-free and defective creeping solids are analyzed. The variations in the creep damage contour and crack tip governing parameters in terms of the creep In-integral with respect to time, as well as the crack size, are considered using full-field finite element model solutions. Creep-fatigue crack growth rate tests are performed on a specially designed program test cycle. The application of the previously introduced creep stress intensity factor, as a creep-damage-sensitive parameter for creep-fatigue interaction, is discussed.

Mixed convection in a two-sided lid-driven cavity containing heated triangular block for non-Newtonian power-law fluids

In this work, we have presented the numerical results for 2D, steady, laminar and incompressible flow in a square, two-sided, lid-driven cavity with a decentered heated triangular block (maintained at the isothermal thermal condition, TH) for non- Newtonian power-law fluids. The range of flow governing parameters considered for the numerical experimentations are Reynolds number (100 ≤ Re ≤ 1000), Richardson Number (Ri = 0.01, 1, 10) power law index; (0.2 ≤ n ≤ 1.8), blockage (10% and 30% of the height of cavity) and Prandtl number of Pr = 1. The upper and lower walls of the square cavity are kept moving in the opposite directions along –x axis (u−ux) and are thermally insulated. The left and right stationary walls are exposed to ambient condition (Tc). The governing flow equations are solved by using the finite volume approach and SIMPLE algorithm. Heat transfer characteristics and flow kinematics are revealed by systematic variation of streamlines and temperature contours. The effect of mixed convection parameter, i.e., Ri, found to have a negligible impact on fluid and thermal structure inside the cavity for fluids with n = 0.2.Heat transfer rate found to be lower for Ri = 0.01 for both blockages.