In this study, the length scaling for the boundary layer separation induced by two incident shock waves is experimentally and analytically investigated. The experiments are performed in a Mach 2.73 flow. A double-wedge shock generator with two deflection angles ($\alpha _1$ and $\alpha _2$) is employed to generate two incident shock waves. Two deflection angle combinations with an identical total deflection angle are adopted: ($\alpha _1 = 7^\circ$, $\alpha _2 = 5^\circ$) and ($\alpha _1 = 5^\circ$, $\alpha _2 = 7^\circ$). For each deflection angle combination, the flow features of the dual-incident shock wave–turbulent boundary layer interactions (dual-ISWTBLIs) under five shock wave distance conditions are examined via schlieren photography, wall-pressure measurements and surface oil-flow visualisation. The experimental results show that the separation point moves downstream with increasing shock wave distance ($d$). For the dual-ISWTBLIs exhibiting a coupling separation state, the upstream interaction length ($L_{int}$) of the separation region approximately linearly decreases with increasing $d$, and the decrease rate of $L_{int}$ with $d$ increases with the second deflection angle under the condition of an identical total deflection angle. Based on control volume analysis of mass and momentum conservations, the relation between $L_{int}$ and $d$ is analytically determined to be approximately linear for the dual-ISWTBLIs with a coupling separation region, and the slope of the linear relation obtained analytically agrees well with that obtained experimentally. Furthermore, a prediction method for $L_{int}$ of the dual-ISWTBLIs with a coupling separation region is proposed, and the relative error of the predicted $L_{int}$ in comparison with the experimental result is $\sim$10 %.

Interactions between the boundary layer and two successive incident shock waves (ISWs) often occur in the supersonic mixed-compression inlets. However, the flow mechanism involved in such interactions has been studied rarely. In this study, we investigate experimentally and analytically the turbulent boundary layer separation flow induced by the single ISW and dual ISWs at the identical total deflection angles in a Mach 2.73 flow. Schlieren photography, wall pressure measurement and surface oil-flow visualisation are employed to diagnose the flow field. Experiments with the impingement points of the two ISWs intersecting on the bottom wall exhibit a separated flow with a triangle-like separation bubble, namely the first kind of dual-ISW/turbulent boundary layer interaction (ISWTBLI). Comparative studies show that various flow features of this kind of dual-ISWTBLI, including the extent of the separation region, pressure distribution and surface-flow topological structures, are nearly identical to those of the single-ISWTBLI with an identical total deflection angle. As the distance between the two ISWs increases, the shape of the separation region in the dual-ISWTBLI changes from triangle-like to quadrilateral-like, and the height of the separation region decreases accordingly, forming the second kind of dual-ISWTBLI. Furthermore, an inviscid model is developed for the dual-ISWTBLI to describe the complex shock wave system and elucidate the cause of a quadrilateral-like separation bubble in the second kind of dual-ISWTBLI. Moreover, based on a previous work by Souverein et al. (J. Fluid Mech., vol. 714, 2013, pp. 505–535) on the single-ISWTBLI, a modified scaling method is established for the first kind of dual-ISWTBLI.

Little is known about the impact of modifiable risk factors on blood pressure (BP) trajectories and their associations with hypertension (HTN). We aimed to identify BP trajectories in normotensive Chinese adults and explore their influencing factors and associations with HTN. We used data from 3436 adults with at least four BP measurements between 1989 and 2018 in the China Health and Nutrition Survey, an ongoing cohort study. We measured BP using mercury sphygmomanometers with appropriate cuff sizes in all surveys. We used group-based trajectory modelling to identify BP trajectories between 1989 and 2009 and multiple logistic and Cox regression models to analyse their influencing factors and associations with HTN in 2011–2018. We identified five systolic blood pressure (SBP) trajectories, ‘Low-increasing (LI)’, ‘Low–stable (LS)’, ‘Moderate-increasing (MI)’, ‘High-stable (HS)’ and ‘Moderate-decreasing (MD)’, and four diastolic blood pressure (DBP) trajectories classified as ‘Low-increasing (LI)’, ‘Moderate–stable (MS)’, ‘Low-stable (LS)’ and ‘High-increasing (HI)’. People with higher physical activity (PA) levels and lower waist circumferences (WC) were less likely to be in the SBP LI, MI, HS and MD groups (P < 0·05). People with higher fruit and vegetable intakes, lower WCs and salt intakes and higher PA levels were less likely to be in the DBP LI, MS and HI groups (P < 0·05). Participants in the SBP HS group (hazard ratio (HR) 2·01) or the DBP LI, MS and HI groups (HR 1·38, 1·40, 1·71, respectively) had higher risks of HTN (P < 0·05). This study suggests that BP monitoring is necessary to prevent HTN in the Chinese population.

This article provides a comprehensive and critical synthesis of the methods utilized in studies investigating the role of language aptitude in second language acquisition (SLA). The synthesis is informed by sixty-five studies generated by a thorough search of the literature, three meta-analyses (Li, 2015, 2016, 2017), and a thematic issue of Studies in Second Language Acquisition (Li & DeKeyser, in press). The synthesis starts by identifying three categories of research investigating the role of aptitude in naturalistic learning, aptitude's associations with instructed learning, and the nature of aptitude pertaining to whether it increases with age and learning experience and how it is connected to other individual difference variables. The synthesis then presents an overview and critique of major measures of aptitude and discusses the construct validity of aptitude measures based on the principles of psychometric assessments. Specifically, the measures are scrutinized along the dimensions of reliability, content validity, divergent/convergent validity, and predictive validity. The content and measurement of implicit aptitude—a newly emerged construct in SLA—are highlighted. The synthesis proceeds to summarize and vet the measures of the outcome variable of aptitude research—L2 proficiency. Throughout the synthesis, methodological features are summarized, issues are identified, and remedies are proposed.

Fractal features of the turbulent/non-turbulent interface (TNTI) in shock wave/turbulent boundary-layer interaction (SWBLI) flows are essential in understanding the physics of the SWBLI and the supersonic turbulent boundary layer, yet have received almost no attention previously. Accordingly, this study utilises a high spatiotemporal resolution visualisation technique, ice-cluster-based planar laser scattering (IC-PLS), to acquire the TNTI downstream of the reattachment in a SWBLI flow. Evolution of the fractal features of the TNTI in this SWBLI flow is analysed by comparing the parameters of the TNTI acquired in this study with those from a previous result (Zhuang et al.J. Fluid Mech., vol. 843, 2018a).

Tensile properties of different directions of X70 pipeline steel plate were tested, and microstructural evolutions of different zones along the transverse direction (TD) were also investigated using electron backscatter diffraction. The highest strength values (yield strength and ultimate strength) appear at TD, and the diagonal direction shows the largest uniform elongation. The elongations of the polygonal ferrite and quasi polygonal ferrite grains increase with the decrease in the distance to the fracture zone. The ratio between high-angle grain boundaries and low-angle grain boundaries in the as-received steel is about 7/3 and starts to decrease from the fillet zone to the fracture zone. The refinement of grains occurs adjacent to the fracture section with the formation of subgrains. With the increase in tensile strain, the intensities of cube and γ-fiber textures increase sharply, and the reinforcement of the (111)$\left[ {\bar{1}\bar{1}2} \right]$ component was obviously larger than the (111)$\left[ {1\bar{2}1} \right]$ component in the γ-fiber texture during tensile deformation.

Previous studies have demonstrated adverse mental health effects of Pb exposure. The purpose of this study is to investigate the relationship between consumption of preserved egg (PE), a high-Pb-containing food and depressive symptoms among adults in China. A sample of 25 213 adults (mean age 41·4 (sd 11·8) years; males, 53·9 %) in Tianjin, China, was studied in a cross-sectional analysis. Dietary intake including PE was assessed using a valid self-administered FFQ. Depressive symptoms were assessed using the Self-Rating Depression Scale (SDS). The association was estimated by OR using logistic regression models adjusted for multiple confounders. The prevalence of elevated depressive symptoms was 6·6 % (SDS≥50). Compared with the least frequent PE consumption (<once/week), multivariable adjusted OR for elevated depressive symptoms were 1·52 (95 % CI 1·28, 1·81), 2·24 (95 % CI 1·76, 2·81) and 3·31 (95 % CI 2·52, 4·30) for consumption of once, 2–3 times and ≥4 times/week, respectively (Pfor trend<0·0001), indicating a clear dose–response relationship. The results suggested that higher consumption of PE was strongly associated with depressive symptoms among adults in China. These findings underscore the need to consider dietary Pb exposure as a risk factor for psychological distress.

The hot deformation behavior of Nb–V–Ti microalloyed ultra-high strength steel was investigated by isothermal compression at 900–1200 °C with strain rates from 0.01 to 10 s−1. The microstructure evolution and precipitation behavior were studied using an optical microscope and a transmission electron microscope Results indicate that the peak stress of experimental steel increases with increasing the strain rate and decreasing the deformation temperature. The constitutive equation of hot deformation was developed with the activation energy Q being about 407.29 kJ/mol. The processing maps were also obtained to identify the instable regions of the flow behavior and to evaluate the efficiency of hot deformation. The size of dynamically recrystallized grains increases gradually with a decrease in the strain rate. Three types of carbides were identified, namely M3C, rich-Ti MC, and rich-Nb MC. With the increase of the deformation rate, the amounts of carbides increase, and the average sizes of the carbides decrease gradually.

Laminate sheets attract increasing attention from researchers and engineers. In this paper, Al/Ti/Al laminate sheets were fabricated by using cryogenic roll bonding for first time. The edge defects, mechanical properties, and interface bonding of laminate sheets by cryogenic roll bonding technique were compared with these by room-temperature roll bonding technique. Results show that there are some edge cracks in laminate sheets by room-temperature roll bonding while they do not appear when subjected to cryogenic roll bonding. The ultimate tensile stress of laminate sheets by cryogenic roll bonding increases up to 36.7% compared to that by room-temperature roll bonding. When laminate sheets are rolled to 0.125 mm from 2.025 mm, the interfaces between Al and Ti layers are bonded well for both cryogenic roll bonding and room-temperature roll bonding. Finally, we discussed the improvement in edge quality and mechanical properties and the mechanism of interface bonding of Al/Ti/Al laminate sheets during cryogenic roll bonding.

The Figure 4 in the original version has a stylistic error.

It ought to use the figure as follows: The authors apologise for this error.

Previous studies have supported the theory that there is a positive association between ferritin and carotid atherosclerosis in Western people. Diet plays an important role in determining serum ferritin concentration. Asian dietary patterns are different from Western dietary patterns, implying that there may be a difference in the association of ferritin with carotid atherosclerosis between Asian and Western people. However, few studies focus on the association between ferritin and carotid atherosclerosis among Asians. The aim of this study was to investigate how serum ferritin levels are associated with carotid atherosclerosis in an Asian adult population. A cross-sectional assessment was performed in 8302 adults in Tianjin, China. Carotid intima-media thickness (IMT) and plaques were assessed using ultrasonography, and serum ferritin was measured using the protein chip-chemiluminescence method. Multiple logistic regression analysis was used to examine the association between quartiles of serum ferritin concentration and carotid atherosclerosis. In the present study, the overall prevalence of IMT and carotid plaques in participants is 29·2 and 22·7 %, respectively. In women, after adjustments for potentially confounding factors, the OR of IMT and carotid plaques by increasing serum ferritin quartiles were 1·00, 1·39 (95 % CI 0·98–1·99), 1·39 (95 % CI 0·99–1·97), 1·81 (95 % CI 1·30–2·55) (Pfor trend<0·001) and 1·00, 1·24 (95 % CI 0·89–1·73), 1·18 (95 % CI 0·85–1·65), 1·59 (95 % CI 1·15–2·20) (Pfor trend<0·01), respectively. However, no association was found between serum ferritin and carotid atherosclerosis in men. The study demonstrated that increased serum ferritin levels are independently associated with IMT and carotid plaques in Asian women but not in Asian men.

The constitutive equation was established based on the consideration of strain compensation to describe the hot deformation behavior of low carbon reduced activation ferritic/martensitic (RAFM) steels at the temperatures of 850–1050 °C and the strain rates of 0.01–10 s−1. The result indicates that the flow stress is increased with the increase of strain rate but decreased with increase of deformation temperature. During the hot deformation process, the increase of temperature is beneficial to attain the complete dynamic recrystallization (DRX). However, excessively high temperature leads to grow up of dynamic recrystallized grain. Higher strain rate leads to finer recrystallized grains. The material constants (α, n, A) and deformation activation energy (Q) are calculated by the regression analysis. The increase of strain caused the decrease of Q, indicating the DRX occurred more easily. In addition, the developed constitutive equation could accurately predict the hot deformation behavior of the low carbon RAFM steel.

The dwarfing wheat (Triticum aestivum L.) breeding has promoted a dramatic increase in yields. Since the utilized dwarfing genes in wheat are very limited, identification of novel dwarfing genes is necessary for improving the genetic diversity of wheat. In this study, more than 300 dwarfing wheat lines from induced mutation were screened by kompetitive allele-specific PCR and gibberellin (GA) treatment. The 17.49% of Rht-D1b and 1.37% of Rht-B1b dwarfing mutants were identified in this mutant group. Additionally, Rht-D1b mutants showed more effective in reduction of plant height and higher 1000-grain weight comparing with that of Rht-B1b mutants. By combing with comparison of yield components and expression profile of GA biosynthetic genes with wild-type, the GA-responsive mutant dm15 without directly involvement in GA metabolism, significantly increased 1000-grain weight but no change of other yield components in two locations of field experiments. Meanwhile, another elite mutant dm11 with change of GA biosynthetic genes expression was also identified. These mutants will be promising candidates for dwarfing wheat breeding.

Microstructures of new heat-resistant steel grade T23 welded joint without PWHT and its corresponding mechanical properties including creep were investigated to clarify its premature failure mechanisms in the large water wall panel of the advanced power plant boiler. The results show that the T23 steel GTAW welded joint in a wall thickness of 6.5 mm without PWHT exhibits high tensile strength, good ductility, and sufficient impact toughness, while the hardness of the WM is higher than the maximum permitted value of 350 HV due to the large amount of un-tempered martensite formed during the cooling process of welding. This WM in as-welded condition has higher creep rupture strength but poorer rupture ductility than the tempered BM. Poor rupture ductility taken place in the WM results from inter-granular cracking during creep exposure and is not related to the second hardening because no hardness rise occurs in the fractured WM compared with as-welded condition. The paper does not specifically investigate the effect of service exposure but simulates the failure of WM by a creep test. The main point is that the WM has low creep ductility, especially at a stress concentration.