Prediction of short fatigue crack growth of Ti‐6Al‐4V

It is observed that the short fatigue cracks grow faster than long fatigue cracks at the same nominal driving force and even grow at stress intensity factor range below the threshold value for long cracks in titanium alloy materials. The anomalous behaviours of short cracks have a great influence on the accurate fatigue life prediction of submersible pressure hulls. Based on the unified fatigue life prediction method developed in the authors' group, a modified model for short crack propagation is proposed in this paper. The elastic–plastic behaviour of short cracks in the vicinity of crack tips is considered in the modified model. The model shows that the rate of crack propagation for very short cracks is determined by the range of cyclic stress rather than the range of the stress intensity factor controlling the long crack propagation and the threshold stress intensity factor range of short fatigue cracks is a function of crack length. The proposed model is used to calculate short crack propagation rate of different titanium alloys. The short crack propagation rates of Ti‐6Al‐4V and its corresponding fatigue lives are predicted under different stress ratios and different stress levels. The model is validated by comparing model prediction results with the experimental data.     

The low process yield of some PNP power transistors

A study is presented of the symptoms of the devices in a slice of PNP power transistors with a poor yield. The failure modes over the slice are analysed. In specific areas the electrical characteristics and optical appearance of the devices were studied and failure statistics are presented. The low yield is ascribed to cracks in the phosphosilicate glass used for the base diffusion. The effect of these cracks is just visible in the optical and scanning electron microscope.     

Suggestion Mining from Opinionated Text of Big Social Media Data

Social media data are rapidly increasing and constitute a source of user opinions and tips on a wide range of products and services. The increasing availability of such big data on biased reviews and blogs creates challenges for customers and businesses in reviewing all content in their decision-making process. To overcome this challenge, extracting suggestions from opinionated text is a possible solution. In this study, the characteristics of suggestions are analyzed and a suggestion mining extraction process is presented for classifying suggestive sentences from online customers’ reviews. A classification using a word-embedding approach is used via the XGBoost classifier. The two datasets used in this experiment relate to online hotel reviews and Microsoft Windows App Studio discussion reviews. F1, precision, recall, and accuracy scores are calculated. The results demonstrated that the XGBoost classifier outperforms—with an accuracy of more than 80%. Moreover, the results revealed that suggestion keywords and phrases are the predominant features for suggestion extraction. Thus, this study contributes to knowledge and practice by comparing feature extraction classifiers and identifying XGBoost as a better suggestion mining process for identifying online reviews.     

Magnetic resonance imaging of the pelvic floor in the postpartum patient

Magnetic resonance imaging (MRI) was used to assess anatomical changes in the pelvic floor after childbirth. Six women underwent serial MRI examination within 30 hours and at 1 week, 2 weeks, 6 weeks and 6 months after delivery; 8 additional women were studied only within 30 hours of delivery. T-1 and T-2-weighted images of the pelvis in the transverse and sagittal planes with a 1.5-T MR imager were obtained. In the sagittal section we assessed the urethrovesical angle, urethral length, distance from the symphysis to the proximal and distal vagina, vaginal length, width and length of the sphincters, and the presence of sphincter defects. Axial sections were assessed for sphincter defects for the distance between the symphysis and midurethra, vagina and rectum. Only one parameter (distance between symphysis and distal vagina) changed significantly over time, without a clear trend in direction. Interobserver variation was reasonable (<15%) except for anal canal length, urethral length and distance between symphysis and anus. There were no significant correlations between birthweight and MRI parameters. There was a non-significant association (P = 0.09) between the sole combined sphincter defect and rectal injury, but not with episiotomy or parity. We concluded that it is feasible to determine multiple measurements on MR images to evaluate structures of the pelvic floor.     

Technetium-99m-MIBI myocardial SPECT: supine versus right lateral imaging and comparison with coronary arteriography

Myocardial perfusion SPECT using the prone position improves inferior wall counts and decreases motion problems as compared with the usual supine position. Nonetheless, it is not suitable for women. In addition, it is associated with artifactual anteroseptal defects and hot spots. METHODS: The right lateral (RL) position was evaluated instead of the prone position in 72 patients (26 women). RL imaging was performed immediately after the supine imaging during a routine 2-day 99mTc-sestamibi exercise protocol. The SPECT images were scored semiquantitatively by three physicians. Moreover, regional myocardial counts, as well as extent and severity of defects, were assessed by quantitative polar map analysis. RESULTS: All patients tolerated the RL position well and there was no significant patient movement in either position. Higher inferior myocardial counts per pixel were observed in the RL than in supine images. Inferior wall defects (especially mild ones) were more common in the supine than the RL images, whereas defects in other regions were not different. Quantitative analysis confirmed these findings. Analysis of 34 patients with recent coronary arteriography revealed an overall coronary artery disease (CAD) supine- and RL-imaging specificity of 50% and 75%, respectively, and the sensitivities of both were 93%. Right CAD sensitivity, specificity and normalcy rates for the supine position were 100%, 44% and 55%, whereas those of the RL position were 94%, 75% and 90%, respectively. CONCLUSION: The RL position improves CAD diagnostic accuracy, particularly right CAD, without significant artifacts in other myocardial regions. Unlike the prone position, the RL position is well tolerated by both women and men.     

A new approach for computing the bandwidth statistics of avalanchephotodiodes

A new approach for characterizing the avalanche-buildup-time-limited bandwidth of avalanche photodiodes (APD's) is introduced which relies on the direct knowledge of the statistics of the random response time. The random response time is the actual duration of the APD's finite buildup limited random impulse response function. A theory is developed characterizing the probability distribution function (PDF) of the random response time. Recurrence equations are derived and numerically solved to yield the PDF of the random response time. The PDF is then used to compute the mean and the standard deviation of the bandwidth. The dependence of the mean and the standard deviation of the bandwidth on the APD mean gain and the ionization coefficient ratio is investigated. Exact asymptotics of the tail of the PDF of the response time are also developed to aid the computation efficiency. The technique can be readily applied to multiplication models which incorporate dead space and can be extended to cases for which the carrier ionization coefficient is position dependent     

Generalized algebraic scene-based nonuniformity correction algorithm

A generalization of a recently developed algebraic scene-based nonuniformity correction algorithm for focal plane array (FPA) sensors is presented. The new technique uses pairs of image frames exhibiting arbitrary one- or two-dimensional translational motion to compute compensator quantities that are then used to remove nonuniformity in the bias of the FPA response. Unlike its predecessor, the generalization does not require the use of either a blackbody calibration target or a shutter. The algorithm has a low computational overhead, lending itself to real-time hardware implementation. The high-quality correction ability of this technique is demonstrated through application to real IR data from both cooled and uncooled infrared FPAs. A theoretical and experimental error analysis is performed to study the accuracy of the bias compensator estimates in the presence of two main sources of error.     

Formation of the beef flavour precursors and their correlation with chemical parameters during the controlled thermal oxidation of tallow

Thermal oxidation of tallow was assayed by peroxide value (PV), p-anisidine value (p-AV), and acid value (AV), and the volatile compounds produced at different oxidation conditions were analysed by SPME-GC/MS. The accumulation of characteristic beef flavour precursors, such as hexanal, 1-octen-3-ol, (E,E)-2,4-decadienal and (E,E)-2,4-heptadienal, reached a maximum value when heated at 140 °C for 2 h with an air flow of 75 l/h per 100 g tallow, whereas at the same temperature PV and p-AV were both at high levels, and AV was relatively low. A correlation analysis of chemical parameters and volatile compounds showed that the beef flavour precursors were positively related to PV, and the off-flavour compounds were highly correlated to AV. Therefore, a moderate oxidation of tallow could be achieved via controlled thermal treatment.     

Morphology and release profile of microcapsules encapsulating peppermint oil by complex coacervation

The gelatin/gum Arabic microcapsules encapsulating peppermint oil were prepared by complex coacervation using transglutaminase as hardening agent. The release of microcapsules was investigated in different dispersing media. The release of microcapsules separately followed first order release kinetics model in hot water and zero order release kinetics model in high-temperature oven. The release of microcapsules in hot water exhibited initial rapid release phase and following slow release phase, where effect of core/wall ratio on the release rate was different due to the increase of loading and particle size with the core/wall ratio. The release kinetics rate constant, K, was analyzed by an Arrhenius plot and found to fit well with a linear relation between in ln(K) and 1/T. The activation energy was evaluated to be 32.6 kJ mol⁻¹. The microcapsules were only release about 7% of peppermint oil during the storage of 40 days in cold water, exhibiting excellent storage stability.     

Nonlinear convective flow with variable thermal conductivity and Cattaneo-Christov heat flux

An analysis is introduced to investigate the salient features of nonlinear convective flow of thixotropic fluid in the version of Cattaneo-Christov heat flux theory. The stagnation point flow is present. The flow phenomenon is by an impermeable stretching sheet. The energy expression is modeled through the theory of Cattaneo-Christov heat flux. Characteristics of heat transfer phenomenon are described within the frame of variable thermal conductivity. Suitable variables reduced to the nonlinear partial differential expressions to the ordinary differential expressions. Series solutions of resulting systems are acquired within the frame of homotopy theory. Convergence analysis is achieved and suitable values are determined by capturing the so-called ℏ−curves. Graphical results for velocity and temperature are displayed and argued for sundry physical variables. Expression of skin friction coefficient is calculated through numerical values. Higher values of mixed convection parameter, Prandtl number, and thermal relaxation time lead to decay the temperature and layer thickness.