Search

This paper proposes a novel switch fault-tolerant operation for switched-mode power conversion. The switch fault-tolerant scheme is implemented on the boost converter operates with a redundant switch. The redundant/secondary switch is driven by a delayed version of primary switching pulses. Both the switches provide charging paths to the inductor when individually turned-on. Thus, the inductor experiences doubled operating frequency than individual switches. Since the operating switching frequency is shared by two switches the control scheme allows the switches to share equal currents in healthy conditions. If one of the switches gets failed, the closed-loop control reconfigures the switching pulse width such that the healthy switch could provide the required power. The key features of the proposed schemes are low component count, continuous operation of the redundant switch, and less circuit complexity. For evidence of the proposed control scheme, MATLAB/Simulink results are presented. The simulation results of 600 W Boost Converter show promising operation in faulty conditions.

An azimuth tree-based network algorithm is proposed on a uniform random distribution of scattered points which is actually graph-based. In the proposed azimuth on a tree-based network, first tree is established through the algorithm for finding the weight function of the tree would constrain the number of points to be considered during azimuth routing, thereby limiting the search space, reducing time complexities, and inducing further optimizations. The idea behind our paper would be applying the azimuth algorithm on a selected number of points, which would be achieved through the efficient tree-based routing protocol. So, firstly, we would apply our tree-based protocol on the uniform random distribution of points. The limited number of points output by this algorithm would be fed as input to azimuth routing. And in the protocol proposed by us, the aggregation of data in this tree-based network helps in reducing the network load and the energy consumption. And this research work mainly revolves around the criteria to be taken into consideration for balancing factors like these and construct a tree-based network which is better in terms of both lifetime of the network and the successful routing of protocols. With the help of simulation implemented using C++ and then constructing its corresponding graph, we have shown how considering all the factors possible has improved the performance of tree-based network. And finally, a comparative analysis is done where our proposed model is compared to the already existing traditional routing protocols namely AODV, DSDV, LEACH, Azimuth-based algorithm.

This paper presents an application of optical character recognition(OCR) which can extract information from images of bills and receipts; store it as machine-processable text; in an organized manner for ease of access. It can do this efficiently even in the presence of watermarks on the bills or any shadows in the images of the bills. In developing this application, OpenCV has been used for the processing of the images and the Tesseract OCR engine has been used for optical character recognition and text extraction. The image is first processed using OpenCV for the removal of any shadows or watermarks present in it. For longer invoices, by employing the image bifurcation process, the data can be easily extracted which was not possible earlier. Furthermore, the processed image is passed on to the Tesseract OCR engine for the retrieving of text present in it. The text is then searched for important information, such as the total amount spent and the date on the receipt, using string processing.

We demonstrate a benign and straightforward method to modify the chitosan (CH) by carbamoylation. The free amines on CH are converted into carbamyl functionalities by reacting with potassium cyanate (KCNO). One wt% CH solution, when reacted with KCNO ⩾ 0.1 M, leads to the sol–gel transition of CH through the hydrogen bonding to form carbamoylated chitosan (CCH) hydrogel. Gelation time of CCH decreases with an increase in the KCNO concentration and an interconnected porous network is formed as observed under SEM. Rheological studies show that while one wt% CH solution is a viscous liquid, the CCH hydrogel with 0.5 M KCNO has a storage modulus (G') of 104 Pa. The CCH hydrogel is proved to be non-cytotoxic and promotes the attachment and growth of the small lung cancer model A549, and the neuroblastoma SH-SY5Y cell lines. CCH hydrogel also promotes the differentiation of SH-SY5Y cells into neuronal cells, as supported by immunostaining and thus demonstrating its utility as a versatile scaffold for three-dimensional cell-culture systems.

The application of DC microgrid is increasing due to the elevation of renewable energy (especially solar energy) practice. Increasing reliance on the DC microgrid seeks more reliable or faultless operation for impeccable control over the DC grids. The concept of reliability enhancement is at its verge since none of the electronic devices can be operated forever. Therefore, the idea of fault tolerance in the presence of redundancy has emerged. This paper proposes the review on fault phenomenon and reliability of the power electronics converters from various aspects such as performance, application, efficiency, etc. Different fault-tolerant schemes reported in the literature have been critically reviewed, compared, and explained in detail to have insight into the prominent solutions. This paper aims a bridge between the inference of reliable and fault-tolerant ability of power electronic converters for DC microgrid`s application. The ability to diagnose and intimate such faults in real-time has also been discussed in addition to various fault-tolerant converter topologies.

npj Computational Materials, 6 (1), ISSN:2057-3960

BACKGROUND Primary CNS lymphoma (PCNSL) requires a biopsy for diagnosis. Administration of corticosteroids can lead to inconclusive results and delay diagnosis. The aim of this study was to compare outcomes of patients treated under haematology compared to radiation oncologists. METHODS Retrospective case review of patients treated under radiation oncology (2006–2010) and haematology (2011–2016). RESULTS 121 cases were identified (median age 63 years; range 19–84). Median WHO performance status (PS) was 1. Fourteen patients (11.6%) required repeat biopsy. 10 patients were managed palliatively due to poor PS. 67 cases were managed under haematology. Median symptom duration was 28 days (range 2–540). Median time from MRI to diagnosis was 18 days (range 6–232). 66 patients received chemotherapy, 1 received radiotherapy. Median overall survival (OS) was 8 months (95%CI:0.7–15.3), 5-year OS was 22.4%. 44 cases were managed under radiation oncology. Median symptom duration was 28 days (range 2–365). Median time from MRI to diagnosis was 16 days (range 6–309). 34 patients received radiotherapy first-line, 10 received chemotherapy. Median OS was 7 months (95%CI:0–21.5), 5-year OS was 15.9%. Multivariate analysis demonstrated PS (HR 2.02 (95%CI: 1.08–3.76)) and symptom duration (HR 0.63 (95%CI: 0.41–0.96)) to be significant prognostic indicators for OS. CONCLUSION The outcomes from the ‘haematology era’ are similar to those achieved by radiation oncologists. Delay in diagnosis leads to worse outcomes and highlights the ongoing need to streamline the patient pathway to improve outcomes.

Background With the increased rate of childhood cancer survivors, a marked rise in the incidence of secondary intracranial meningiomas has been established. Objective Determine the outcomes of patients diagnosed with radiation-induced meningiomas (RIM). Methods Single-centre retrospective cohort study of patients with new or recurrent RIM (2007–2018). Results 47 patients were identified (21 females). Mean age at radiation was 15 years (SD=14) and the most common indications were leukaemia (n=8) and childhood brain tumours (n=35; medulloblastoma and pilocytic astrocytoma (n=7 each)). 93 de-novo meningiomas were identified. The median latency period between radiation and diagnosis was 28.5 years (IQR 22–37). 61% were asymptomatic whilst the remainder manifested headache (20%), focal neurological deficit (12%) and epilepsy (5%). 32 operated de-novo RIM revealed WHO grade I (n=19; 59%), WHO grade II (n=11; 34%) and 2 intraosseous meningiomas (n=2; 6%). After a median of 5 years (IQR 3–10), 9 (28%) operated RIM recurred/progressed. At recurrence, 5 were operated (3 WHO grade I, 2 WHO grade II and 1 WHO grade III), 2 patients were palliated and 2 remain under active observation. By the end of the study period, 20 patients were harbouring multiple meningiomas and 8 patients were deceased. Conclusion Radiation-induced meningioma should be monitored until symptomatic. Operated RIMs have a high recurrence rate. Further radiotherapy is not effective. Further clinical and genetic analyses as part of an international multi-centre collaboration are planned.

We present a two-scale topology optimization framework for the design of macroscopic bodies with an optimized elastic response, which is achieved by means of a spatially-variant cellular architecture on the microscale. The chosen spinodoid topology for the cellular network on the microscale (which is inspired by natural microstructures forming during spinodal decomposition) admits a seamless spatial grading as well as tunable elastic anisotropy, and it is parametrized by a small set of design parameters associated with the underlying Gaussian random field. The macroscale boundary value problem is discretized by finite elements, which in addition to the displacement field continuously interpolate the microscale design parameters. By assuming a separation of scales, the local constitutive behavior on the macroscale is identified as the homogenized elastic response of the microstructure based on the local design parameters. As a departure from classical FE2 -type approaches, we replace the costly microscale homogenization by a data-driven surrogate model, using deep neural networks, which accurately and efficiently maps design parameters onto the effective elasticity tensor. The model is trained on homogenized stiffness data obtained from numerical homogenization by finite elements. As an added benefit, the machine learning setup admits automatic differentiation, so that sensitivities (required for the optimization problem) can be computed exactly and without the need for numerical derivatives – a strategy that holds promise far beyond the elastic stiffness. Therefore, this framework presents a new opportunity for multiscale topology optimization based on data-driven surrogate models., Computer Methods in Applied Mechanics and Engineering, 383, ISSN:0045-7825, ISSN:1879-2138

BACKGROUND Resection of meningioma leaves residual solid tumour in ~25% of patients. Selection for further treatment and follow-up strategy may benefit from knowledge of volumetric growth and associated prognostic factors. MATERIAL AND METHODS Growth rates were assessed using a linear mixed effects model, in a retrospective adult cohort that underwent subtotal resection of meningioma (2004–2018). Endpoints were re-treatment, end of follow-up or death. Cox regression analysis was used to identify prognostic factors for progression, defined using the Response Assessment in Neuro-Oncology (RANO) volumetric criteria. RESULTS 236 patients were included. Mean age at surgery was 56.3 years (SD=13.7) and 73.7% were female. WHO grades were 1 (n=195, 82.6%), 2 (n=40, 16.9%) and 3 (n=1, 0.5%). Adjuvant fractionated radiotherapy (fRT) was administered to 34 patients (14.4%), with no propensity towards higher WHO grade or residual volume. Median pre-operative meningioma and post-operative residual volumes were 34.0cm3 (IQR 16.0–63.0) and 2.0cm3 (IQR 0.8–5.2), respectively. Median follow-up was 64 months (IQR 42–104). Median absolute growth rate (AGR) and relative growth rate (RGR) were 0.1cm3/year and 4.3%/year, respectively. According to RANO criteria, 132 (55.9%) patients progressed, of which 13 (9.8%) developed symptoms. Median progression-free survival was 56 months (95% CI 43.1–69.0). Multivariable analysis identified adjuvant fRT (HR 1.7, [95% CI 1.0–2.8], P=0.046), skull base location (HR 1.5, [95% CI 1.0–2.4], P=0.047) and Ki-67 index (HR 3.7 [95% CI 1.3–10.8], P=0.017) as prognostic factors for volumetric progression. WHO grade was not significant (HR 1.0, [95% CI 0.5–1.7], P=0.905). Forty-nine patients who progressed (37.1%) underwent further treatment: fRT (n=19), re-operation (n=15), Stereotactic radiosurgery (SRS) (n=10) and surgery+adjuvant fRT (n=5). Of those, 8 (16.3%) progressed further (after re-operation [n=6] and SRS [n=2]). Seven were treated with a 2nd re-operation (n=3), fRT (n=3), and SRS (n=1). One patient progressed after a 2nd reoperation and was treated with SRS, after which they remained stable. Median survival was not reached. 5- and 10-year overall survival (OS) was 96% and 86% respectively. CONCLUSION Growth rates of a residual meningioma vary with a dichotomy observed in progression rates. Half of patients with a residual meningioma showed radiological progression requiring multiple treatment to control the tumour. The other half demonstrate a more indolent course. Skull base location and higher Ki67 are important prognostic factors for progression and therefore, should be considered to stratify patients for adjuvant radiotherapy.

We propose a new approach for data-driven automated discovery of isotropic hyperelastic constitutive laws. The approach is unsupervised, i.e., it requires no stress data but only displacement and global force data, which are realistically available through mechanical testing and digital image correlation techniques; it delivers interpretable models, i.e., models that are embodied by parsimonious mathematical expressions discovered through sparse regression of a large catalogue of candidate functions; it is one-shot, i.e., discovery only needs one experiment — but can use more if available. The problem of unsupervised discovery is solved by enforcing equilibrium constraints in the bulk and at the loaded boundary of the domain. Sparsity of the solution is achieved by ℓp regularization combined with thresholding, which calls for a non-linear optimization scheme. The ensuing fully automated algorithm leverages physics-based constraints for the automatic determination of the penalty parameter in the regularization term. Using numerically generated data including artificial noise, we demonstrate the ability of the approach to accurately discover five hyperelastic models of different complexity. We also show that, if a “true” feature is missing in the function library, the proposed approach is able to surrogate it in such a way that the actual response is still accurately predicted., Computer Methods in Applied Mechanics and Engineering, 381, ISSN:0045-7825, ISSN:1879-2138

Detailed studies on asphaltenes from Indian sources are scarce. In this study, nC7 asphaltenes were extracted from an atmospheric tower bottom and a low waxy crude oil using IP143-based method and characterised using elemental analysis, nuclear magnetic resonance, Fourier-transform infrared spectroscopy, matrix-assisted laser desorption-time of flight mass spectroscopy, X-ray diffraction, and scanning electron microscopy. Results show that both asphaltenes differ widely in structures and molecular weights. It was deduced that both asphaltenes might have formed from kerogen degradation process resulting in higher oxygen content. Lower molecular weight and structural parameters (NMR) of atmospheric tower bottom asphaltene could be due to degradation of aliphatic part during preheating before atmospheric distillation process. Although dispersed, the XRD derived aromaticity of petroleum asphaltenes seems to vary inversely with stacking height and average diameter of the aromatic sheets, possibly due to compact structure of the cluster resulting from decreased stack height. [Received: September 29, 2019; Accepted: November 9, 2019]

We introduce an improved meshfree approximation scheme which is based on the local maximum-entropy strategy as a compromise between shape function locality and entropy in an information-theoretical sense. The improved version is specifically designed for severe, finite deformation and offers significantly enhanced stability as opposed to the original formulation. This is achieved by (i) formulating the quasistatic mechanical boundary value problem in a suitable updated-Lagrangian setting, (ii) introducing anisotropy in the shape function support to accommodate directional variations in nodal spacing with increasing deformation and eliminate tensile instability, (iii) spatially bounding and evolving shape function support to restrict the domain of influence and increase efficiency, (iv) truncating shape functions at interfaces in order to stably represent multi-component systems like composites or polycrystals . The new scheme is applied to benchmark problems of severe elastic and elastoplastic deformation that demonstrate its performance both in terms of accuracy (as compared to exact solutions and, where applicable, finite element simulations) and efficiency. Importantly, the presented formulation overcomes the classical tensile instability found in most meshfree interpolation schemes , as shown for stable simulations of, e.g., the inhomogeneous extension of a hyperelastic block up to 100% or the torsion of a hyperelastic cube by 200° — both in an updated Lagrangian setting and without the need for remeshing.

This paper shall emphasize on the design and development of a Type-II compensator through a detailed transfer function analysis and Pspice model of PWM IC, MOSFET, diode and BJTs, used in simulation. The simulation results thus obtained using the PSpice models shall give the clear view of the actual results which would be produced if implemented in the hardware thereby deducing the hardware errors well in advance. The explicit design considerations and detailed discussion on the controller has been done to bring out the significant difference among the practitioners with respect to some prominent controllers/ compensators used in industrial applications. The transfer function analysis has been taken into consideration; both in time and frequency domain approaches to bridge the gap between theoretical and practical aspects of boost converter control. A 600W boost converter is simulated with stated compensator having feasible stability margin as discussed in the paper. Further, a compensator performance analysis has been discussed in detail as an inference, based on the simulation results which are obtained through LTspice-XVII modeling tool.

The field of wireless sensor networks has witnessed an increasing traction among researchers in the erstwhile few decades. Since in large networks, sensors are not uniformly distributed; thus, a problem arises in low- and medium-density part of that large network which has a high probability of the packets getting stuck at a specific node due to the problem of local minima. Thus, this paper tries to solve the problem of unsuccessful routing in low–medium-density networks by implementing updated form of azimuthal routing protocol which removes the overhead of keeping the routing details and also ensures that the packets reach the sink and is not affected by the presence of holes which is normally the case in lower density network. This protocol has been compared with greedy protocol which shows that it exhibits excellent performance with around 98.78% of average successful ratio compared to 45.38% in case of greedy.

Introduction Primary CNS lymphoma (PCNSL) requires a biopsy for diagnosis but can be inconclusive when steroids are administered. Without treatment median survival is 1.5–3.3 months, improving to 10–20 months with oncological treatment. This study aimed to compare outcomes of PCNSL treated under haematology to those of clinical oncologists. Methods Retrospective casenote review of patients with PCNSL treated under oncologists (2006–2010) and haematologists (2011–2016). Results 121 cases were identified (median age 63 years; range 19–84). Median WHO performance status (PS) was 1. 11.6% required repeat biopsy. 10 patients were managed palliatively due to poor PS. 67 cases were managed under haematology. Median symptom duration was 28 days (range 2–540). Median time from MRI to diagnosis was 18 days (range 6–232). 66 patients received chemotherapy, 1 received radiotherapy. Median overall survival (OS) was 8 months (95%CI: 0.7–15.3), 5-year OS was 22.4%. 44 cases were managed under oncology. Median symptom duration was 28 days (range 2–365). Median time from MRI to diagnosis was 16 days (range 6–309). 34 patients received radiotherapy first-line, 10 received chemotherapy. Median OS was 7 months (95%CI: 0–21.5), 5-year OS was 15.9%. Multivariate analysis demonstrated PS (HR 2.02 (95%CI: 1.08–3.76)) and symptom duration (HR 0.63 (95%CI: 0.41–0.96)) to be significant prognostic indicators for OS. Discussion PCNSL carries poor prognosis and outcomes from the ‘haematology era’ are similar to those achieved by clinical oncologists. Delay in diagnosis leads to worse outcomes and highlights the ongoing need to streamline current clinical services to improve outcomes.

We present a novel scheme to derive nonlinearly elastic constitutive laws for special Cosserat rod modeling of nano and continuum rods. We first construct a 6-parameter (corresponding to the six strains in the theory of special Cosserat rods) family of helical rod configurations subjected to uniform strain along their arc-length. The uniformity in strain then enables us to deduce the constitutive laws by just solving the warping of the helical rod’s cross-section (smallest repeating cell for nanorods) but under certain constraints. The constraints are shown to be critical in the absence of which, the 6-parameter family reduces to a well known 2-parameter family of uniform helical equilibria. An explicit formula for the 6-parameter helical map is derived which maps atoms in the repeating cell of a nanorod to their images for the purpose of repeating cell energy minimization. A scheme for the passage from nano to continuum scale is also presented to derive the constitutive laws of a continuum rod via atomistic calculations of nanorods. The bending, twisting, stretching and shearing stiffnesses of diamond nanorods and carbon nanotubes are computed to demonstrate our theory. We show that our scheme is more general and accurate than existing schemes allowing us to deduce shearing stiffness and several coupling stiffnesses of a nanorod for the first time.

This paper presents the effective design and analysis of a DC-DC Boost converter in continuous, discontinuous and boundary condition modes. The converter is designed on an LTspice XVII simulation tool using the design values/parameters obtained from the PSpice/SPICE model provided by the supplier. This PSpice/SPICE model parameters are those values of the model which are available practically and are used as hardware components for the development of a prototype model. The simulation results thus obtained is not the ideal simulation results but is according to the non-ideal values used for the design. The hardware boost converter prototype is then developed using the same components as were used for the simulation and the results were acquired. This paper then further investigates on the comparison of the simulation and hardware results obtained which includes switching operations of the MOSFET switch, output voltage (capacitor), inductor voltage and current, and further draws an inference of reducing the error and improving the design effectiveness of the converter if the hardware prototype set up is developed using the identical values as used in the simulation for the converter.

Cloud environment is highly prone to failures due to its distributed nature and inherent complexity. Proactive identification of failures aids the service providers to avert these failures by taking corrective actions before they actually happen. In this paper, we analyze the resource usage patterns to identify failures due to resource contention in cloud. The resource usage and performance metrics of the working system are analyzed at regular time instants to model the normal and anomalous working behaviors. A two stage framework has been implemented where a hybrid of long short term memory (LSTM) and bidirectional long short term memory (BLSTM) is used to predict the future resource usage and performance metric values in the first stage. In the second stage, the hybrid model is used to classify the expected state as either normal or abnormal. We evaluate the proposed anomaly detection model in a virtual environment set up using Docker containers. The experimental results show that the proposed algorithm outperforms state-of-the-art algorithms.

Severe plastic deformation (SPD), occurring ubiquitously across metal forming processes, has been utilized to significantly improve bulk material properties such as the strength of metals. The latter is achieved by ultra-fine grain refinement at the polycrystalline mesoscale via the application of large plastic strains on the macroscale. We here present a multiscale framework that aims at efficiently modeling SPD processes while effectively capturing the underlying physics across all relevant scales. At the level of the macroscale boundary value problem, an enhanced maximum-entropy (max-ent) meshless method is employed. Compared to finite elements and other meshless techniques, this method offers a stabilized finite-strain updated-Lagrangian setting for improved robustness with respect to mesh distortion arising from large plastic strains. At each material point on the macroscale, we describe the polycrystalline material response via a Taylor model at the mesoscale, which captures discontinuous dynamic recrystallization through the nucleation and growth/shrinkage of grains. Each grain, in turn, is modeled by a finite-strain crystal plasticity model at the microscale. We focus on equal-channel angular extrusion (ECAE) of polycrystalline pure copper as an application, in which severe strains are generated by extruding the specimen around a 90 ° -corner. Our framework describes not only the evolution of strain and stress distributions during the process but also grain refinement and texture evolution, while offering a computationally feasible treatment of the macroscale mechanical boundary value problem. Though we here focus on ECAE of copper, the numerical setup is sufficiently general for other applications including SPD and thermo-mechanical processes (e.g., rolling, high-pressure torsion, etc.) as well as other materials systems.