Influence of the transition section shape on the cavitation characteristics at the bottom outlet

The hydraulic characteristics of the lock chamber section in a bottom outlet are complex. Particularly, cavitation is a prominent problem when the flow in the tunnel transitions from pressurized to unpressurized conditions. As a countermeasure, sidewall contractions are often installed at the end of the pressurized section. In this paper, with numerical simulations and vacuum tank experiments, we analyzed the design parameters of several prototype projects and studied the flow properties and cavitation characteristics of the transition section. The four main factors that influence cavitation risks are the contraction ratio of the transition section, the top press slope, the length of the transition section, and the shape of the orifice. The study of a real-world project demonstrates that by implementing a severe constriction degree, the top press slope can be slowed down, and the pressurized transition section can be extended, thereby reducing cavitation risks and improving flow patterns. These research results provide a reference for the optimal design of hydraulic structures. HIGHLIGHTS This paper analyses four factors that affect the cavitation of the bottom discharge tunnel.; This paper collects the design parameters of 23 lock chambers and summarizes the value range and design law of these design parameters.; The cavitation and flow pattern of the LW hydropower station are verified through the vacuum tank experiment and numerical simulation.

Maternal Stress in Gestation: Birth Outcomes and Stress-Related Hormone Response of the Neonates

Relatively few studies have been made on neurobehavioral outcomes of prenatal maternal stress during the newborn period, and little research has focused on umbilical cord stress hormones including cortisol, adrenocorticotropic hormone (ACTH), norepinephrine, and epinephrine. Our objective was to investigate the effects of prenatal maternal life stressors on neonatal birth outcomes, neurobehavioral development, and stress-related hormones levels. Methods: Participants were 142 mothers and their infants; 71 were selected as the prenatal life stressor exposed group and 71 as the control group matched on maternal age, gestational week, delivery type, socioeconomic and education status, and newborns' sex. Maternal life stressors during pregnancy were determined using the Life Events Scale for Pregnant Women. Neonatal neurobehavioral development was assessed with the Neonatal Behavioral Neurological Assessment. Umbilical cord plasma stress-related hormones, including ACTH, cortisol, norepinephrine, and epinephrine were measured using an enzyme-linked immunosorbent assay. Results: In the prenatal life stressors exposed group, newborns had significantly lower birth weight, smaller head circumference (p < 0.01, p < 0.01, respectively). Scores of Neonatal Behavioral Neurological Assessment were significantly reduced (p < 0.001). Cord plasma ACTH, norepinephrine, and epinephrine levels were significantly increased (p < 0.001), but cortisol levels were reduced (p < 0.001). Conclusion: Prenatal maternal stress may negatively affect fetal birth outcomes, neurobehavioral development and affect neonates' cord plasma ACTH, cortisol, norepinephrine, and epinephrine

A novel digital tomosynthesis (DTS) reconstruction method using a deformation field map

We developed a novel digital tomosynthesis (DTS) reconstruction method using a deformation field map to optimally estimate volumetric information in DTS images. The deformation field map is solved by using prior information, a deformation model, and new projection data. Patients’ previous cone-beam CT (CBCT) or planning CT data are used as the prior information, and the new patient volume to be reconstructed is considered as a deformation of the prior patient volume. The deformation field is solved by minimizing bending energy and maintaining new projection data fidelity using a nonlinear conjugate gradient method. The new patient DTS volume is then obtained by deforming the prior patient CBCT or CT volume according to the solution to the deformation field. This method is novel because it is the first method to combine deformable registration with limited angle image reconstruction. The method was tested in 2D cases using simulated projections of a Shepp–Logan phantom, liver, and head-and-neck patient data. The accuracy of the reconstruction was evaluated by comparing both organ volume and pixel value differences between DTS and CBCT images. In the Shepp–Logan phantom study, the reconstructed pixel signal-to-noise ratio (PSNR) for the 60° DTS image reached 34.3 dB. In the liver patient study, the relative error of the liver volume reconstructed using 60° projections was 3.4%. The reconstructed PSNR for the 60° DTS image reached 23.5 dB. In the head-and-neck patient study, the new method using 60° projections was able to reconstruct the 8.1° rotation of the bony structure with 0.0° error. The reconstructed PSNR for the 60° DTS image reached 24.2 dB. In summary, the new reconstruction method can optimally estimate the volumetric information in DTS images using 60° projections. Preliminary validation of the algorithm showed that it is both technically and clinically feasible for image guidance in radiation therapy