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Ionospheric diurnal double maxima (DDM) is a twin-peak pattern in the ionospheric electron density/total electron content (TEC) during the daytime. Understanding the characteristics of DDM is essential to study the physical mechanisms of the ionosphere. In this paper, the vertical TEC data (VTEC) in 2019–2020 derived from 537 globally distributed GPS stations were used to investigate the DDM phenomenon. The results reveal that the occurrence rate of DDMs is roughly quasi-symmetrical about the magnetic equator. In the northern hemisphere, it first increases, then decreases, and finally increases with the increase of magnetic latitude. The DDM phenomenon also exhibits significant seasonal variation. It mainly appears in summer/winter in the northern/southern hemisphere, and the valley and the second peak usually appear earlier in winter and later in summer. According to the difference in the magnitude of the two peaks of DDM, the DDM phenomenon is mainly manifested as the front peak significant type or the posterior peak significant type. The probability of the former shows an M-shaped variation with increasing longitude in the middle and high latitudes of the northern hemisphere and an inverted V-shaped variation in the high latitudes of the southern hemisphere within 180°W~60°W. The probability of the posterior peak significant type shows a trend opposite to the front peak significant type in each area. The occurrence time of DDM structures is usually about one hour later in low-latitude regions than in other regions, and the duration is usually shorter than in other regions. The relative magnitude of the DDM’s twin peaks in low-latitude regions is usually smaller than in other regions.

Grinding balls in wet ball mill are important consumables in mine grinding equipment, which have poor wear resistance and large consumption. It is imperative to find excellent wear-resistant materials for the grinding balls. Carbidic Austempered Ductile Iron (referred to as CADI) was used as small and medium-sized wet ball mills. This grinding ball has the advantages of less wear, low crushing rate, power saving and low noise. However, the CADI grain boundaries are distributed with net-like eutectic carbides, which seriously damage the continuity of the matrix. In addition, the mechanism of corrosion wear and impact fatigue is lack of research due to complex phase composition and unclear mechanism of phase properties on improving performance. So CADI can’t be applied to the grinding balls in large wet ball mill. Based on the above problems, this paper first analyzed the heteronucleation mechanism and adsorption mechanism of M3C type carbides by using the first principle of microalloying elements, and then verified it by combining with experimental results. Then the thermodynamics and kinetics of austenite homogenization and isothermal transformation of ductile iron containing carbides were analyzed by means of modeling calculation and experiment. On this basis, a new type heat treatment process comprising super-high temperature pretreatment and austempering treatment (S&A treatment) was used to process CADI, which provides a new idea for further improving toughness of CADI. Finally, the CADI corrosion wear and impact fatigue failure mechanism were revealed by analyzing the change rule of the sample surface and cross section after corrosion wear and impact fatigue.

In order to study the characteristics of thermal environment and comfort of residential buildings during winter in hot summer and cold winter (HSCW) climate zone of China, this study conducted a questionnaire survey and field test. It was found that 70.9% of residential buildings in HSCW climate zone had space heating equipment, among that the percentage of air conditioning, electric equipment (electric oil-filled radiator and fan heater) and other were 56.0%, 27.6% and 16.4%, respectively. Furthermore, 77.3% (48.7%) of residents only heat their bedrooms (living rooms), and 76.5% of residents heat their rooms only in cold weather, which shows the “part-space” and “part-time” space heating characteristics in HSCW climate zone. For rooms with space heating, the thermal environment is category I in general, but more than 30% of these residents hope a higher indoor temperature. For rooms without space heating, the indoor temperature is below the hygiene limit of 12°C, which belongs to category II, but thermal feeling for 55% of residents is cold and 90.9% of residents hope a warmer indoor environment. The results indicated that the existing evaluation criteria in HSCW climate zone are inconsistent with the thermal sensation and expectation, and an advanced evaluation criterion is needed.

In order to improve the thermal environment of residential buildings in winter for Xinjiang, this research conducted a field test and a survey of residential buildings under typical heating methods. The results show that the indoor temperature and humidity are dynamically changing, and the variation of central heating and gas wall-mounted furnace fluctuated less than that of coal heating. Furthermore, the thermal environment evaluation shows that the thermal comfort level under gas wall-mounted furnace heating are the highest, which belongs to category Ⅰ. For the central heating and coal stove, only 12% and 26% of buildings achieve to category Ⅱ. Moreover, it is found that the acceptable temperature range of coal furnace heating residents can be as low as 19.5°C, while that of central heating and gas wall-mounted furnace heating is 20.3°C~25.7°C, which relate to the clothing insulation of residents under different heating methods. In addition, all residents almost have the same habit of window opening behaviour during heating period, and 72% of residents open windows for ventilation. Correspondingly, 62% of residents feel dry during heating season, which induce xerosis cutis, dry mouth and other uncomfortable symptom, and can be improved by using humidifier, planting plants and so on.

The Zr-1Nb alloy was treated by laser melting and vacuum annealing in order to improve the high temperature corrosion resistance. The morphology of the melting layer was observed by scanning electron microscopy,phase compositions and quantities were determined by X-ray diffraction and Raman; surface roughness was determined by profile meter; and hardness was measured by the micro-hardness tester. In order to characterize the corrosion resistance,autoclave experiments were conducted for 70 days in an aqueous steam condition of 360℃ under 18.6MPa in 0.01mol/L LiOH solutions. The results show that the surface roughness of Zr-1Nb cladding tubes is improved by laser melting; the laser melted layer is mainly composed of α-Zr phase and a small amount of m-ZrO2,and the phase composition of laser melted layer does not change after heat-treatment; under high power condition,laser melting can reduce the high temperature corrosion resistance of Zr-1Nb alloy. However,the high temperature corrosion resistance of Zr-1Nb alloy can be improved significantly under the condition of low power laser melting and auxiliary heat treatment process. By laser melting treatment,microhardness of zirconium alloy can be increased by 50-80HV0.1. And after heat treatment,microhardness of zirconium alloy is decreased compared with the laser melted sample,but it is still higher than the origin sample.

The effect of pressure of squeeze casting on the microstructure and mechanical properties of Mg-6Zn-1Al-0.5Mn-0.5Ca alloy has been systematically studied using XRD. SEX. TEM and tensile test. The results show that the microstructure of the as-cast alloy consists of α-Mg matrix with τ(Mg32(Al, Zn)49) and some Al8Mn5 second phase particles. The imposed pressure dose not change the composition of alloy phase precipitation. With the increase of squeeze casting pressure, the second phase particles of the as-cast ZAMX6100 alloy becomes more and fine, and more uniformly distributed. Simultaneously, ZAMX6100 alloy solidified under pressure improves the uniform distribution of micro-elements Mn, Ca, which decreases the extent of interdendritic segregation. When pressure is increased from 0 MPa to 100 MPa, the tensile strength, yield strength, elongation and hardness of ZAMX6100 alloy are all improved by 27%, 14%, 31% and 9% respectively. The fine ZAMX6100 alloy microstructure is mainly caused by the atom spread activation energy decreasement under pressure during the solidification, which decreases the crystal growth velocity, and at the same time the high pressure squeeze casting causes an entire contact of magnesium alloy with the mold inside, which causes the increase of cooling rate and refinement of microstructure.

K4536 alloy formed by SLM was treated by HIP, and the effects of HIP on the microstructure and high-temperature mechanical properties were studied. The results show that the surface of sample manufactured by SLM has cracks, and the longitudinal and horizontal microstructures are different. After HIP processing, the cracks in the sample is repaired to some extent, the microstructure of the sample also is changed, and many second phase particles are dissolved out from the matrix. We know that the precipitation is M23C6 phase by TEM diffraction analysis. Furthermore, the surface of sample has “white bright layer” with the thickness of about 30 μm, the “white bright layer” is resulted by the decrease of Cr by EDS energy spectrum analysis. The K4536 alloy sample formed by SLM has different high-temperature tensile properties in the vertical and horizontal, and the vertical performance is better than that of horizontal. After HIP processing, the vertical and horizontal performances have little difference, and the high-temperature strength of the sample is reduced, the high-temperature plasticity is increased.

For low accuracy of face tracking applying active shape model(ASM) in condition of sudden change of illumination and contaminated and covered miner face in underground coal mine, an improved ASM was proposed. Firstly, mirror sample set is formed by definition of mirror image with selected special training sample set. Then, the mirror sample set is processed by logarithmic scale. Finally, related block model is used as ASM learning model for training. The experimental results show that the method can effectively improve accuracy of underground face tracking.

Productivity rise can be realized at high-speed welding, but in a practice, the constraints emanate from the tolerance welding speed limit beyond which generate humping defects and the likes. These defects are undesirable in welding as they undermined the weld bead integrity and decrease productivity. In this study, an investigation on a lap joint welding using a hybrid Laser-GMAW (L-GMAW) welding process on a carbon steel sheet was undertaken to examine the mechanisms involved in the arc behavior, the droplet transfer, and the weld pool flow dynamics in a hump defect formation at high-speed welding. A variation of the process parameters in the hybrid welding system such as the wire feed speed (WFS), the traveling speed (TS) and the oscillation of the laser beam were used as input signals. A high-speed video camera was used with different viewing positions to capture the sequence of events during the hybrid welding process. The high-speed images of the arc behavior, the weld pool flow pattern with the use of tracer particles in arriving at the root mechanisms were acquired. Based on the experimental resultant, the occurrence mechanisms of the weld defects were proposed. In this study, the key factors in the humping defect formation are the two dominant lateral flows toward the top and bottom sheets, the collision between the weld pool back- and rear-flow and the interruption of the weld pool flow channel. Also, the generation of copious spatter due to the two lateral flows and the swollen buildup towards the hump closure were responsible for the next hump initiation formation. The beam oscillation applied to wet the weld toe angle to delay the outset of the humping defect occurrence was insignificant at higher travel speed. Furthermore, the force of gravity and surface tension were the key forces in this study. Keywords: Hybrid L-GMAW, Lap joint, Arc behavior, Droplet transfer, Hump formation, High travel speed

PurposeThe incidence of Ewing sarcoma varies according to race and ethnicity, and genetic susceptibility is known to affect disease risk. Apart from these factors, the etiology of Ewing sarcoma is largely unknown.MethodsWe compared the birth characteristics of a population-based series of 556 Ewing sarcoma cases born in California in 1978-2015 and diagnosed in 1988-2015 with those of 27,800 controls selected from statewide birth records and frequency-matched to cases on the year of birth, using multivariable logistic regression models. We also assessed whether Ewing sarcoma clustered within families.ResultsCompared to non-Hispanic White subjects, Black (odds ratio [OR] = 0.07, 95% confidence interval [CI] 0.03-0.18), Asian (OR = 0.57, 95% CI 0.41-0.80), and Hispanic (OR = 0.73, 95% CI 0.62-0.88) individuals had a significantly lower risk of Ewing sarcoma. Race and ethnicity differences were more profound for metastatic Ewing sarcoma. Birthweight was also identified as a significant risk factor (OR = 1.09, 95% CI 1.00-1.18 for each 500 g increase in birthweight). A separate family-based cancer clustering analysis did not suggest any strong role for familial predisposition alleles.ConclusionsThis population-based study with minimal selection bias provides support for a role of accelerated fetal growth in the etiology of Ewing sarcoma in addition to more precise estimates of racial and ethnic variations in disease risk. This comparatively large analysis of birth characteristics and Ewing sarcoma in a multiethnic population should stimulate further investigations into genetic and environmental causes.

Angiogenesis plays crucial roles in the progress of tumor growth, progression and metastases. The new tumor blood vessel tracer RRL can be targeted to the VEGFR-2 receptor on tumor vascular endothelial cells, Tracing with radioisotopes different types of tumor and angiogenesis in malignant tumor tissues with different invasive ability will provide the important information on the diagnosis, treatment and evaluated prognosis of malignant tumor. In this review, the recent study and progresses on molecular imaging with the peptide RRL in tumor angiogenesis will be summarized.

At present, the development of rural tourism in China is faced with the embarrassment of "small scale, flat resources" and the lack of creative planning methods, which leads to the serious problem of the simplification and homogeneity of rural tourism products. From the perspective of cultural creativity, this paper puts forward TAIM model of rural tourism product development, and takes "Guangxi district-level rural tourism poverty alleviation village" Xintian village of Quanzhou county as an example to make an empirical analysis of this model, in order to provide some inspiration for the development of rural tourism products in China.