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The role of the electrode in electric discharge machining (EDM) performance is crucial because it has an impact on the geometrical accuracy, machining efficiency and surface finish of the machined components. In the present work, a new technical approach combining equal channel angular pressing (ECAP) and deep cryogenic treatment (DCT) was put forward to manufacture copper electrodes for enhancing the machining characteristics of electric discharge machining (EDM). Effects of the ECAP, the ECAP + DCT on the EDM performances including the electrode wear rate (EWR), the workpiece corner sharpness (WCS), the surface roughness (Ra) and the surface characteristics of EDM workpieces have been investigated. The EWR after the ECAP and the ECAP + DCT was reduced to the minimum after two passes of ECAP. The EWR and WCS after the ECAP + DCT were less than that after the ECAP due to the higher hardness and electrical conductivity. The Ra of EDM workpieces using electrodes processed by the ECAP + DCT was slightly less than that after ECAP. An analogous Hall–Petch relation between the Ra of EDM workpieces and the grain size of electrodes was observed, indicating that ultrafine-grained electrodes processed by ECAP and the additional DCT would enhance the surface finish. The surface finish of EDM workpieces was discussed based on the features of the surface morphology.

This study is to obtain precise data on iron physiological requirements in Chinese children using single stable isotope tracer technique.Thirty boys (10.6 ± 0.2 years) and 27 girls (10.4 ± 0.2 years) were received oral 6 mgThe iron physiological requirement was significantly lower in boys than those values in girls (16.88 ± 7.12This study indicate that iron physiological requirement could require more daily iron intake in girls as compare with the values in boys having the same body weight. These findings would be facilitate to the new revised dietary reference intakes.

In recent years, people’s demand for cool climate environment has promoted the vigorous development of summer tourism activities. Xining is the largest city on the Qinghai-Tibet Plateau, and has great advantages in developing summer tourism. In this paper, several popular summer tourism cities in China in 2019 are selected. By comparing the development conditions of summer tourism between Xining and these cities quantitatively and qualitatively, the advantages and disadvantages of developing summer tourism in Xining are analyzed, and targeted suggestions are put forward for the development of summer tourism.

Turbine blades operate under a harsh environmental condition, and the inlet temperature of gas turbines is increasing with requirement of high engine efficiency. Some cooling schemes are adopted to prevent these blades from the thermal erosion of the hot mainstream. Film cooling technology is used widely and effectively in gas turbines. The coolant air is suppressed to the wall by the mainstream after jetting out of the film hole. A new hole configuration is first proposed to improve the film cooling characteristics in this paper. Comparison between a conventional cylindrical hole and a new combined hole is conducted by computational fluid dynamics, and effects of various blowing ratios and droplet sizes are also investigated. Results show that the combined hole configuration provides a wider coverage than that in the cylindrical hole configuration case at high blowing ratios (M = 1.0 and M = 1.5). In addition, the film cooling with mist injection also provides a significant enhancement on cooling performance especially for the combined hole case with a small droplet size (10−5 m).

To analyze the rate of erythrocyte iron incorporation and provided guidance for the iron nutrition for prepubertal children.Fifty-seven prepubertal children of Beijing were involved in this study and each subject was orally administered 3 mg ofThe percentage of erythrocyteThe oral administration of

Atomic gravimetry measures the gravitional acceleration of an ensemble of identical neutral atoms through the atom interferometry based on Raman two-photon transition, where the Raman lasers are used as “optical ruler" and the identical neutral atoms play the role of test mass and quantum storage of gravity field information. As the novel gravimetry system suffers no mechanical wear and works at a higher repetition rate, atom gravimetry can reach a much better short-term sensitivity than the classical falling-corner-cube counterpart, and the accuracy is reasonably well. Since the very first in-laboratory device built over 30 years ago, atomic gravimetry has matured to a versatile tool that offers both precise and accurate absolute gravity measurement to fundamental research and metrology, such as testing the weak equivalence principle or linking the mass and weight of the test mass in Watt (Kibble) balance. As the current rapid development of compact cold-atom gravimeters, atomic gravimetry is moving out of the laboratory to be used as a quantum enhancement of classical devices in dynamical measurement, such as geophysics survey, inertial navigation and space mission. We review the roadmap for the development of cold-atom absolute gravimetry, highlight recent advances in the dynamical measurement using compact cold atom gravimeters and discuss the associated technological challenges. In the future, with the maturity of its application in dynamical measurement or civil engineering and the innovation in atom interferometry theory, atomic gravimetry could play a more and more important role in our life.

The trajectory of the spray is studied theoretically and experimentally when a round liquid jet is injected into a supersonic crossflow vertically. A solid model of continuous liquid column is established in three-dimensional space. The cross-section deformation equation of the continuous liquid column along the injection direction is established using a method of micro-element analysis. The stress analysis of cross section is simplified into a two-dimensional droplet. The shape of the cross section is considered to continuously change from circular to elliptical shape. And the bow shock wave in front of the jet column is simplified into an oblique shock wave with a known shock angle. Based on this, the calculation of aerodynamic force is greatly simplified. A dimensionless parameter named effective deformation time of liquid column (the logogram is \begin{document}${t_{\rm valid}}$\end{document}) is defined and used to judge the end point of the liquid column quantitatively. The liquid jet trajectory and cross-section deformation can be calculated using MATLAB software. The instantaneous images of continuous liquid columns in supersonic crossflow are captured using high-spatial-resolution microscopic imaging methods. The microscopic imaging system is composed of a double pulse solid-state laser, computer, CCD camera, synchronous controller, microscope lens and laser diffuser. After passing through the laser diffuser, a plane background light with uniform distribution is formed on the scattering plate. The mean filtering method is used to filter the original image. After filtering, the range of gray distribution in the background area is obviously reduced. The distribution of gray value is more concentrated, and the background of the image is more uniform. Then the image edge detection function is used to obtain the near-field jet trajectory. The parameter variables studied include liquid injection pressure drop (1–2 MPa), liquid nozzle diameter (0.5 mm/1.0 mm), and liquid gas momentum ratio (3.32–7.27). The results show that the continuous liquid column model can better predict the jet trajectory on the center plane and the shape of the liquid column in three-dimensional space. It is indicated that the predictive result matches well with the experimental result. This study is of great significance for establishing the solid-particle coupling model of liquid jet in supersonic crossflows.

We assessed the prevalence of non- communicable diseases (NCDs) risk factors with a focus on their clustering among healthy adults in Shenzhen, China. Data from the 2011 China Health and Nutrition Survey, comprising a regionally representative sample of 806 healthy adults aged 35 years or older, were obtained to determine the prevalence of five risk factors for NCDs. The prevalence of current smoking, central obesity, impaired fasting glucose, borderline hypertension, and borderline high total cholesterol was 19.97%, 28.29%, 4.47%, 10.55%, and 36.10%, respectively. A total 63.77% of participants had at least one risk factor. Upon examination of risk factor clustering, we observed that 7.57% of participants had at least three risk factors. Using this threshold as a cutoff, clustering of risk factors was associated with sex [odds ratio (OR) = 3.336, 95% confidence interval (CI): 1.782 to 6.246], physical activity (OR = 1.913, 95% CI: 1.009 to 3.628), and BMI (OR = 7.376, 95% CI: 3.812 to 14.270). The prevalence of risk factors for NCDs is fairly high among healthy adults in Shenzhen, with a clustering tendency.

The spray characteristics of a liquid-liquid pintle injector under different momentum ratios are investigated experimentally in this paper. Water is used as a simulant medium for both the fuel and the oxidizer. By increasing the mass flow rate of the oxidizer or reducing the mass flow rate of the fuel, the local momentum ratio is increased from 0.16 to 0.99, wherein the responding total momentum obtained by the former throttling method is relatively high due to the higher mass flow rate of the fluid. The outer and inner spray boundary, droplet size distribution and the velocity field are studied by high-speed camera and phase Doppler anemometry (PDA). It is indicated that the spray pattern is affected by the operating conditions directly. The spray pattern is divided into the solid cone and the hollow-solid cone, generally. Furthermore, the spray pattern influences the other spray characteristics. Under the same local momentum ratio with different throttling methods, the spray angle is almost consistent, while the spray boundary in the far field is wider under the higher total momentum. With the increase of the mass flow rate of the outer injector, a hollow structure is generated in the near field of the spray, and its range expands with the increase of the local momentum ratio. The value of SMD increases with the local momentum ratio increasing. Under the same local momentum ratio, the variation range of SMD is wider under the higher total momentum. The variation trend of SMD in the radial direction differs from the spray pattern, too. The SMD of the hollow-solid spray displays as an " N” shape along the radial direction, and reaches its peak at the outer boundary. By contrast, the SMD of the solid spray decreases slightly in the radial direction and varies on a small scale. The value of the resultant velocity is determined by the total momentum, and the curves of all the resultant/axial/radial velocity display as an inverted " V” in the radial direction. Nevertheless, the trend of axial velocity in the radial direction is mainly decreasing, and the increasing stage only exists at the central spray. However, the radial velocity undergoes a slight decrease or levels off directly after reaching the peak. The higher the local momentum ratio, the larger the radial velocity is, while the lower the axial velocity. In addition, the velocity field below the hollow field is dominated by the liquid film, which is explained by analyzing the impinging process of the neighboring cloaks in this paper.

Iron deficiency anemia is one of the most prevalent nutritional deficiency worldwide. The commonly used cut-off values for identifying iron deficiency are extrapolated from older children and may not be suitable for infants. Therefore, our study aimed to establish appropriate cut-off values for the evaluation of iron status in Chinese infants. Pregnant women who delivered at ⋝37 gestational weeks with normal iron status were recruited. Later, infants with normal birth weight and who were breastfed in the first 4 months were selected. Blood samples were collected to assess hemoglobin, serum ferritin, soluble transferrin receptor, mean corpuscular volume and free erythrocyte protoporphyrin. Cut-offs of all iron indices were determined as the limit of 95% confidence interval.

In this paper, Taguchi method is applied to optimize ultrasound thermal process for extracting caffeine and flavor from coffee. The use of ultrasound can abridge experiments in cost, energy loss and time; the different operating conditions for extraction experiments are executed and the results are also compared. The results show that the best design factors for caffeine are 95? of extraction temperature, 28 kHz of operating frequency and 30 s of extraction time. The proposed optimized extraction method is efficient and energy-saving compared with the general process for making coffee

The purpose of this study was to apply a skin suspension to accelerate wound healing at the skin donor site.A small fragment of skin was collected after skin transplantation had been performed. The skin suspension was prepared by mixing the small fragments of skin tissue with the same volume of normal saline. The suspension was then applied to the donor site. Donor sites without skin suspension were employed as controls.Faster healing was found at the donor sites that had been covered with skin suspension and with less scar formation compared to controls.Skin suspension prepared from residual graft skin can ameliorate donor site wound healing.