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Critical node identification, one of the key issues in social network analysis, is addressed in this article with the development of a new centrality metric termed graph energy centrality (GEC). The fundamental idea underlying this GEC measure is to give each vertex a centrality value based on the graph energy that results from vertex elimination. We show that the GEC of each vertex is asymptotically equal to two for cycle graphs and exactly equal to two for complete graphs. We further demonstrate that star graphs can be ranked using only two GEC values, whereas path graphs can be ranked using a maximum of n+12values. The proposed algorithm takes O(n3) time complexity to rank all vertices; hence an optimised algorithm is also being proposed considering only a few classes of graphs. The proposed algorithm ranks the nodes based on the collaborative measure of eigenvalues.

The propagation of the new pandemic COVID-19 is more likely linked to human social relations and activities. A social network can be used to describe these human relationships and activities. Understanding the dynamic properties of disease dissemination through diverse social networks is critical for effective and efficient infection prevention and control. With the frequent emergence and spread of infectious diseases and their impact on large areas of the population, there is growing interest in modelling these complex epidemic behaviour. Such an approach could provide a stronger decision-making method to tackle and control disease. In this paper, a transmission network is developed using the South Korean data, and the study of the network is carried out using graph energy centrality. This measure of centrality allows us to recognise the primary cause of the spread of the virus within the established network by ranking the nodes of the network based on graph energy. The identified primary cause can then be isolated, which can prevent further spread of infection. We have also considered the Novel_Corona_Virus_2019_Dataset from Johns Hopkins University to analyse epidemiological data around the world.

The incidence of endocarditis produced by the so-called 'opportunists' as a complication of prosthetic valve surgery is progressively increasing in frequency and gradually transforming the clinical picture habitually associated with [...]

Here we report the discovery of cold-seep ecosystem and shallow methane hydrates (2–3 mbsf) associated with methane gas flares in the water column from the Indian EEZ for the first time. The seep-sites are located in the Krishna–Godavari (K–G) basin at water depths of 900–1800 m and are characterized by gas flares in the water-column images. The occurrence of methane gas hydrates at very shallow depths (2–3 mbsf) at some of the seep-sites is attributed to high methane flux and conducive P–T conditions, necessary for the stability of methane hydrate. Chemosymbiont bearing Bivalves (Vesicomidae, Mytilidae, Thyasiridae and Solemyidae families); Polychaetes (Siboglinidae family) and Gastropods (Provannidae family) are also identified from seep-sites.

Prostate-specific membrane antigen (PSMA) positron emission tomography (PET) can be used to locate lesions based on PSMA avidity, however guidelines on its use are limited by its infancy. We aimed to compare multiparametric magnetic resonance imaging (mpMRI) and PSMA PET/CT to prostatectomy histopathology. We conducted a chart review from February 2015 to January 2017 of 50 male patients staged for prostate cancer using PSMA PET/CT and mpMRI who then underwent radical prostatectomy. Pre-operative PSMA PET/CT and mpMRI were paired with corresponding histopathology. Correlations, sensitivity, and specificity were used for comparisons. A total of 81 lesions were confirmed by histopathology. Fifty index lesions were detected by histopathology, all of which were detected by PSMA PET/CT (100% detection), and 47 by mpMRI (94% detection). Thirty-one histologically confirmed secondary lesions were detected, 29 of which were detected by PSMA PET/CT (93.5% detection), and 16 by mpMRI (51.6% detection). PSMA had better sensitivity for index lesion localization than mpMRI (81.1 vs. 64.8%). Specificity was similar for PSMA PET/CT and mpMRI (84.6 vs. 82.7%). SUVmaxof index lesions ranged from 2.9 to 39.6 (M= 9.27 ± 6.41). Index lesion SUVmaxwas positively correlated with PSA (rho = 0.48, p< 0.001) and ISUP grade (rho = 0.51, p< 0.001). PSMA-PET/CT provided superior detection of prostate cancer lesions with better sensitivity than mpMRI. PSMA-PET/CT can be used to enhance locoregional mpMRI to provide improved detection and characterization of lesions.

One of the critical constraints for lifetime and operability of sensor networks is the limited amount of available energy. Reducing the interference is one of the important positive steps towards this as high interference number increases the probability of packet loss and hence forces the sender node to retransmit the packets resulting in more energy consumption. Minimum Interference Strong Bidirectional Topology (MISBT) problem is to assign transmit power to each sensor in a sensor network such that the maximum/average node interference of a sensor is minimised subject to the constraint that the induced topology containing bidirectional links only is strongly connected. In this paper we propose two new models for measuring the interference, namely the MAX model and SUM model. We present algorithms for minimising maximum and average node interference under these models. The average interference obtained by our algorithms for MAX and SUM models is at most twice the optimal. The simulation results show that the total power consumptions by the solution produced by our algorithm under the SUM model is less than the solution produced by the existing algorithm under the OR model. Furthermore, our algorithms under different models are 2–approximation algorithms for the average receiver–centric interference as well.

Recent efforts to produce and separate neutron-rich rare isotopes in peripheral collisions below the Fermi energy are presented. The experiments have been performed at the Cyclotron Institute of Texas A&M University employing beams from the K500 Superconducting Cyclotron. Two magnetic separators were used: the MARS recoil separator and the Superconducting Solenoid Line (BigSol Line). An enhanced production of neutron-rich nuclides in comparison with high-energy fragmentation mechanisms has been observed and attributed to the role of the N/Z and the nuclear periphery of the target. From a practical viewpoint, these reactions below or around the Fermi energy offer a novel way to access very neutron-rich rare isotopes. The experience obtained in the production of rare isotope beams (RIB) below the Fermi energy will be exploited in the ongoing RIB upgrade of the Cyclotron Institute that will involve production, stopping and reacceleration of rare isotopes.

A novel method was developed for the extraction of short emission times of light particles from the projectile-like fragments in peripheral deep-inelastic collisions in the Fermi energy domain. We have taken an advantage of the fact that in the external Coulomb field particles are evaporated asymmetrically. It was possible to determine the emission times in the interval 50–500 fm/c using the backward emission anisotropy of α-particles relative to the largest residue, in the reaction 28Si + 112Sn at 50 MeV/nucleon. The extracted times are consistent with predictions based on the evaporation decay widths calculated with the statistical evaporation model generalized for the case of the Coulomb interaction with the target.

New highly exclusive experiments in the field of formation and decay of composite systems in heavy ion reactions are presented. Dynamical effects are reviewed in the light of recent works on the role of the N/Zasymmetry between projectile and target. The possibility of extracting directly from the experimental data the emission barrier of alpha particles emitted from highly excited nuclei is discussed. Finally, the first experimental evidence of double giant resonance excitation in fusion-evaporation reaction is presented.

Study of heavy ion induced fusion-fission reactions at near and below barrier energies has attracted a great deal of attention in recent years, due to the observations of anomalous features in the fragment angular distributions for many target-projectile systems. Additionally there are also measurements of the fragment spin distributions and time-scales of the fusion-fission reactions, which have provided important information on the dynamics of these processes. In the present paper, the emphasis would be to highlight some of the recent experimental findings and their implications on the dynamics of the fusion-fission reactions in heavy ion collisions at near and above barrier energies.

The advantages of the stress-relaxation technique can be effectively realized by applying the procedure to conventional four-point bend tests usually employed in the deformation studies of ceramic materials. A test system and procedure for determining plastic strain rate-stress relationships at elevated temperatures (up to 1600° C) by the stress-relaxation method is described. An analysis to calculate true plastic strains and stresses from measured deflections and loads is presented and it is shown that such an analysis requires minimum assumptions regarding the materials behaviour. Preliminary results obtained on an iron-doped MgO specimen are discussed and compared with the constant load test results obtained on identical specimens. Sources of error in the four-point bend stressrelaxation tests and the methods to minimize them are also discussed.

Normalized Mode I stress intensity factors,N1(a/R), for symmetrical radial cracks in diametral compression test specimens were experimentally evaluated using disc specimens of polymethyl methacrylate and the method of caustics. The method of caustics was first employed with precracked three-point bend specimens to assess the optical constant for the test material. This material property and the diameters of the caustics as a function of the applied load at different relative crack lengths (a/R) yielded the non-dimensional stress intensity factors using equations presented by Theocaris. These experimental values agreed closely with the theoretical solutions reported in the literature. Disc specimens of a polycrystalline alumina were also tested in diametral compression at temperatures up to 1000° C and the measured fracture toughness values were compared to those measured with chevron-notched bend specimens. It is shown that the centre-cracked diametral compression specimens give very reproducible fracture toughness measurements, and the specimen and the test technique can be usefully employed to assess the fracture toughness of structural ceramics at both ambient and elevated temperatures.

Erosion rates of SiC-Al2OC ceramics, with Al2OC content varying from 5 to 75wt%, were assessed using 240-grit alumina abrasive particles accelerated to a velocity estimated at 120msec-1 and impacting the target at normal incidence. The target ceramics varied in hardness from 27.1 GPa for SiC-5wt% Al2OC to 10.8 GPa for SiC-75wt% Al2OC, but the fracture toughness was essentially independent of composition (Klc ã 3.5 MPa m1/2). The erosion weight loss varied linearly with the test duration for all the ceramics and the erosion rate decreased systematically with increasing target hardness; the hardness dependence of the erosion rate was, however, much greater than the predictions of the currently available erosion models.

Rising-crack-growth resistance or R-curves evaluated by direct measurements of crack lengths associated with indentation flaws in a sintered silicon nitride and a sintered and isostatically hot pressed (HIPed) SiC (whisker)-reinforced alumina were used to predict the corresponding indentation-load dependence of fracture strengths. Two empirical R-curve functions, a power law and an exponential function, were fitted to the R-curve data for the analysis. Fracture strengths were calculated by a combined numerical and graphical procedure that determined the point of tangency between crack-driving forces and the R-curves. The results revealed that the exponential function gave a better prediction of the measured log fracture-strength versus log indentation-load relation than the power law. The exponential function also predicted a nearly linear relation between log fracture-strength and log indentation-load, thus indicating that the apparent linearity of this plot is not adequate evidence to assume a power-law R-curve function. This study, therefore, reinforces the case for R-curve evaluations to be based on direct crack-length measurements rather than strength measurements, because the indentation-load dependence of the fracture strength is not sufficiently sensitive to discriminate between potential R-curve functions.

Bend-test curves were calculated for materials obeying three very different damage laws. One result of the calculations is that the neutral axis migrates towards the compression face as the load-point displacement increases. For the three damage laws investigated, there is a simple relationship between the location of the neutral axis and the secant modulus derived from the bend-test record; this relationship is quite insensitive to the exact form of the damage law. The stress at a point 20 per cent of the beam depth from the tensile outer fibre is also fairly insensitive to the form of the damage law. Combining these two observations, it is possible to use bend-test data to make a good estimate of the tensile stress-strain curve of a material subject to damage.

Indentation fracture of a series of well-characterized WC-Co cermets was studied with a Vickers diamond pyramid indenter. The resulting crack length-indentation load data were analysed in terms of relations characteristic of radial (Palmqvist) and fully developed radial/median (half-penny) crack geometries. The radial crack model gave a better fit to the data on all the alloys studied. Crack shapes determined by repeated surface polishing confirmed the radial nature of the cracks. An indentation fracture mechanics analysis based on the assumption of a wedge-loaded crack is shown to be consistent with the observed linear relation between the radial crack length and the indentation load. The analysis also predicts a simple relation among the fracture toughness (Klc), the Palmqvist toughness (W) and the hardness (H) of the WC-Co alloys.

Critical components in coal-liquefaction system, like letdown value trim and valve seats, are subject to severe wear from the erosive coal slurries. The slurry-erosion behavior of candidate valve trim and seat materials, like WC-Co cermets and hard ceramics (SiC, B4C), was studied by measuring the wear rates in a slurry-jet impingement test and by examining the wear craters in a scanning electron microscope. The erosion rates of the WC-Co cermets decreased monotonically with decreasing cobalt volume fraction in the range 36.9 to 5.1 Percent. The mechanism of erosion changed systematically from one involving preferential removal of binder and release of undamaged WC grains in high-binder alloys to a uniform transgranular wear of WC grains in the low-binder alloys. A sintered grade of SiC and a hot-pressed grade of B4C showed wear rates less than those of the cermets.

Transformation yield and plasticity, transformation zone sizes at crack tips and rising crack-growth-resistance (R-curve) behaviours were studied in a commercial-grade ceria partially stabilized zirconia polycrystalline material (CeO2-TZP). The yield stresses measured in three-point bending decreased from 390 to 176 MPa when the sintering temperature was varied from 1425 to 1525° C. The corresponding total plastic strain to fracture increased with decreasing yield stress. Crack-tip transformation zones in precracked, annealed and loaded single-edge-notch-bend specimens decreased significantly in size with increasing transformation yield stress; however, the R-curves were relatively insensitive to the yield stresses or the transformation zone sizes. The measured zone sizes and R-curves were examined in terms of both crack shielding and plastic yield strip zone models.

This paper highlights a new noncontact technique to assess the differences in surface characteristics of components machined by shaping, milling, turning, and grinding processes. The method suggested here is a laboratory analysis based on the process of intensity Fourier transformation taking place on the surface under testing. The measurements are made on the spatial frequency spectrum of the ground surface as an example, using lasers, rather than on the image of the surface. The results are analyzed by using an in-process microprocessor system to evaluate the surface characteristics immediately.

Increasing use of ceramics in structural applications has led to the development of a probabilistic design methodology that combines three elements: linear elastic fracture mechanics theory that relates strengths of ceramics to size, shape, and orientation of critical flaws, a characteristic flaw size distribution function that accounts for the size effect on strength via the weakest-link concept, and a time-dependent strength caused by subcritical crack growth or other mechanisms. This paper reviews recent research that has been focused on the first of the above three elements, the investigation of fracture criteria for arbitrarily oriented flaws in ceramics, i.e., the mixed-mode fracture problem in linear elastic fracture mechanics theory. Experimental results obtained with two-dimensional through cracks and three-dimensional surface (indentation) cracks are summarized and compared to mixed-mode fracture criteria. The effects of material microstructure and the stress state on mixed-mode fractures are discussed. The application of mixed-mode fracture criteria in reliability analysis is illustrated for several simple stress states in the absence of time-dependent strength degradation.

Fracture toughness of polycrystalline alumina and ceria partially stabilized tetragonal zirconia (CeO2-TZP) ceramics were assessed in combined mode I and mode II loading using precracked disk specimens in diametral compression. Stress states ranging from pure mode I, combined mode I and mode II, and pure mode II were obtained by aligning the center crack at specific angles relative to the loading diameter. The resulting mixed-mode fracture toughness envelope showed significant deviation to higher fracture toughness in mode II relative to the predictions of the linear elastic fracture mechanics theory. Critical comparison with corresponding results on soda-lime glass and fracture surface observations showed that crack surface resistance arising from grain interlocking and abrasion were the main sources of the increased fracture toughness in mode II loading of the polycrystalline ceramics. The normalized fracture toughness for pure mode II loading, (KII/KIc), increased with increasing grain size for the CeO2-TZP ceramics. Quantitative fractography confirmed an increased percentage of transgranular fracture of the grains in mode II loading.

Chevron-notched bend specimens in three-point loading are increasingly used for evaluation of fracture toughness of structural ceramics. Its advantages include stable precracking of the specimen during loading, a simple specimen geometry, and a compressive mode of loading that is convenient for testing ceramics at elevated temperatures. Subcritical crack growth caused by environmental interactions or mass transport phenomena at elevated temperatures, however, can affect the apparent fracture toughness measured. A numerical computational study was carried out to assess the effects of subcritical crack growth on crack stability in the chevron-notched three-point bend specimens. A power-law relationship between the sub-critical crack velocity (v) and the applied stress intensity (KI) was used along with compliance and stress-intensity relationships for the chevron-notched bend specimen to calculate the load response under fixed deflection rate and a machine compliance. The results indicate that the maximum load during the test occurs at the same crack length for all the deflection rates; the maximum load, however, is dependent on the deflection rate for rates below a critical rate. The resulting dependence of the apparent fracture toughness on the deflection rate is compared to experimental results on soda-lime glass and polycrystalline alumina.

Abstract: The plastic deformation behavior of high purity (99.999 pct) polycrystalline and single crystal aluminum under repeated stressing was investigated by studying the creep behavior. The creep behavior under repeated stressing (cyclic creep) was compared with the static creep behavior at identical peak stresses. The influence of such experimental variables as the applied stress, the amplitude of cyclic stress, the test temperature and the static creep rate prior to stress cycling were systematically examined. The most important experimental observation in this study was that the cycling of the creep stress could either enhance or retard the creep deformation, depending upon the combination of the experimental variables. The experimental variable that had the most significant influence on the cyclic creep behavior was the applied stress; the enhancement of the creep rate was observed above a threshold stress, while the cyclic stress retarded the creep deformation at lower stresses. The threshold stress was found to depend sensitively on temperature. The implications of the threshold stress were examined by an analysis of the work-hardening behavior.

Pulmonary hypertensive crises (PHC) are a recognized cause of sudden clinical deterioration and death after the surgical correction of congenital heart disease. In this study, pulmonary artery pressure was monitored in 84 children (at high risk to develop PHC) aged nine days to five years (mean 1.4 years) using monitoring lines inserted percutaneously through the right internal jugular vein (IJV). Success rate of placement of the catheter tip in the pulmonary artery (PA) in the pre-incision period was not high (7%) but all catheter-tips were successfully placed in the PA by the surgeon before right atrial closure prior to separation from cardiopulmonary bypass. Complications related to the technique were transient ventricular/atrial arrhythmias (78.5%) during insertion and slipping or coiling (20%) of the catheter in the right ventricle. Complications relating to the IJV puncture included carotid arterial puncture1and pneumothorax1. No other complications were encountered. Monitoring lines inserted percutaneously and guided into the pulmonary artery during surgery provide a safe and practical way of monitoring pulmonary artery in infants and children at risk of postoperative pulmonary hypertensive crises.

A simple inexpensive technique to assess the sharpness of scalpel blades by laser diffraction is presented. Two of the factors that contribute to edge sharpness such as cutting angle and grinding finish of the side faces are evaluated by optical transformation techniques. One could therefore arrive at an optimum set of values of the above two factors which would in turn lead to the production of sharper blades.

This paper highlights a new, noncontact technique to assess the differences in surface characteristics of components machined by shaping, milling, turning, grinding processes. The method suggested here is a laboratory analysis based on the process of intensity Fourier Transformation taking place on the surface under test. The results are analyzed by using an in-process microprocessor system to evaluate the surface characteristics immediately.

The transfer-induced fission channel has been studied in the collision of 340 MeV 28Si on 232Th as a function of the atomic number of the projectile-like fragments (PLF) by using a 4π detector array. The average excitation energy of the target-like fragment (TLF) is derived from the measured energy loss, whereas its angular momentum has been obtained from the angular distribution of fission fragments. The measured ratio of transfer-fission yield to PLF singles, Yf, first increase up to a net charge transfer ΔZ = 4, then shows a plateau around the values Yf = 0.4 - 0.6. This ratio can be identified as the cumulative fission probability of the populated nuclei for net charge transfer ΔZ≤6, suggesting a significant survival probability against fission of these TLF nuclei, in marked disagreement with the standard statistical model predictions. The observed survival probability implies that there is a strong hindrance to fission in the early stages of the deexcitation, such effects are important in the population of nuclei in the heavy and superheavy mass region by transfer reactions. Moreover pre- and post-scission multiplicities of neutrons and alpha particles have been simultaneously measured for the fission-like channel of the same reaction. Dynamical model calculations using HICOL code predict that 90% of the observed events are of quasi-fission type while the remaining 10% are from compound nucleus fission decay. From a comparison of PACE2 Statistical Model predictions with the measured pre-scission neutron multiplicity, the fission delay is estimated to be of 5+7−3×10−20s, which overlaps with the average duration of fission-like process from the contact to the scission point (2×10-20s) as determined from HICOL-based dynamical calculations.

Al2O3‐15 vol.% ZrO2bar‐shaped ceramic specimens are prepared in the green state in such a manner that the outer regions consist of Al2O3and unstabilized ZrO2, whereas the inner region contains ZrO2partially stabilized with Y2O3.