In view of the high gas pressure and low permeability of deep coal seam, it is difficult to control gas, which affects the safety production of coal mine. The technical scheme of hydraulic fracturing ...to improve the permeability of coal seam is put forward, and the gas drainage technology is used to control the gas emission of coal seam. The fracturing effect under different water pressure, different gradient fracturing times, and in situ stress is analyzed by using 3DEC (3-Dimensional Distinct Element Code) discrete element software. The simulation analysis and field verification results show that the coal seam gas pressure increases linearly with the buried depth. In situ stress characteristics and hydraulic strength are the key factors affecting the effect of hydraulic fracturing. The fracturing radius increases with the increase of flow. When the construction pressure of hydraulic fracturing test is 18 MPa, the distance between fracturing hole and drainage hole is 8.5 m. The actual measurement shows that after hydraulic fracturing and gas drainage, the maximum gas emission is reduced by 51%, and the average gas emission is reduced by 58%.
Located on the Pamir Plateau in Xinjiang Province, China, the Ji'erzankale Necropolis dates back to 2500 yr BP. Many materials that have been unearthed in this cemetery, including shoo konghou ...(musical instrument), bronze mirrors and glass beads, suggest cultural transference between East and West. Furthermore, small-sized and rounded fire altars made from sweet-scented Sabina were found for the first time and regarded as implements for fire veneration. We identified 70 wooden objects from 25 tombs within the Necropolis, and found that each object had been made from one of seven tree species. Analysis revealed that the inhabitants of the region mainly used the most widely available types of wood, namely Betula and Populus. People also specifically chose inflammable Populus wood to make hearth boards and hand drills (both are used for making fire by drilling), rigid Betula wood to craft wooden plates. Salix was used for fashioning wooden sticks, while sweet-scented Sabina was the preferred choice for making fire altars. Lonicera was selected for arrow shaft manufacture and Fraxinus syriaca, which has a beautiful grain, was chosen for making musical instruments. Conscious selection of different types of wood indicates that people of the Pamir Plateau were aware of the properties of various types of timbers, and were able to exploit these properties to the full. In turn, this demonstrates their wisdom and their ability to survive in, and adapt to, their local environment.
Powder of a nickel-based superalloy, RR1000, has been hot isostatically pressed (HIPped) at a supersolvus temperature and post-HIP heat treated to produce different microstructures. Microstructures ...were investigated using a scanning electron microscope together with an energy dispersive X-ray spectrometer and a wave-length dispersive X-ray spectrometer. High cycle four-point bending fatigue and tension-tension fatigue tests have been performed on the fabricated samples. It was found that HIPped and aged samples showed the best four-point bending fatigue limit while HIPped and solution-treated and aged samples had the lowest fatigue limit. The four-point bending fatigue crack initiations all occurred from the sample surfaces either at the sites of inclusion clusters or by cleavage through large grains on the surfaces. The tension-tension fatigue crack initiation occurred mainly due to large hafnia inclusion clusters, with lower fatigue lives for samples where inclusions were closer to the surface. Crack initiation at the compact Al
2
O
3
inclusion cluster led to a much higher fatigue life than found when cracks were initiated by large hafnia inclusion clusters. The tension-tension fatigue limits were shown to decrease with increased testing temperature (from room temperature to 700 °C).
•Novel “Tβ-30°C” and “Tβ-10°C” duplex annealing was adopted, respectively.•Microstructure and mechanical properties after heat treatments were compared.•Room temperature ductility could be improved ...by 40%, from 10±1% to 14±3%.•600°C/310MPa stress rupture life could be improved by 24%, from 317±12h to 394±16h.
A laser deposited near α titanium alloy Ti60A (Ti–5.54Al–3.38Sn–3.34Zr–0.37Mo–0.46Si) was annealed near Tβ at different temperatures for 1h, followed by 700°C annealing for 2h. The effect of duplex annealing on microstructure, room temperature and 600°C tensile properties and stress rupture life at 600°C/310MPa was investigated. Fractography and microstructural characterisation were performed by optical microscopy, electron backscattered diffraction, scanning electron microscopy and transmission electron microscopy. Results indicate that as-deposited Ti60A alloy has a fine basket-weave microstructure. In the “Tβ-30°C” state (1020°C/1h/AC+700°C/2h/AC), the alloy has 65vol.% coarsened lamellar α and transformed β. In the “Tβ-10°C” state (1040°C/1h/AC+700°C/2h/AC), the alloy has 25vol.% “crab-claw-like” α and fine lamellar transformed β. Moreover, there are Ti3Al precipitates described by 011¯1α//011¯2Ti3Al occurring without silicides in all three states of the alloy. The room-temperature tensile ductility and stress rupture life at 600°C/310MPa is improved obviously in the “Tβ-10°C” state, but the ductility at 600°C/310MPa is reduced. The effect of near Tβ duplex annealing on mechanical properties of laser deposited alloy Ti60A is discussed in detail as related to α morphology, continuous colony boundary α, fine lamellar transformed β and Ti3Al precipitates.
Additive manufacturing (AM) of nickel superalloys typically leads to large columnar grains forming along the build direction, resulting in poor and anisotropic tensile performance. In this work, a ...novel AM process involving directed energy deposition (DED) combined with in-situ rolling was applied to fabricate a typical nickel superalloy – Inconel 718. The results revealed hierarchical layered refined grains formed in the microstructure, due to the unique dynamic and meta-dynamic recrystallization induced by the in-situ rolling during DED. Through this, an average grain size of ∼8 µm and much weaker texture was achieved for the in-situ rolled samples. Tensile test showed that a significant increase of over 50% in the yield strength was achieved for the in-situ rolled samples at both room temperature and 650°C, while maintaining a good uniform elongation above 10%.
•A rolling-assisted DED process has been applied to fabricate Inconel 718 superalloy.•Columnar to equiaxed transition of grains is achieved.•The refined grains (∼8 µm in size) exhibited hierarchical layered distribution.•Over 50% yield strength increment is achieved at both room temperature and 650°C.
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Conflicting reports support or refute an association between vitamin D deficiency with high levels of parathyroid hormone (PTH) and raised blood pressure or hypertension.
To explore the associations ...of serum vitamin D and PTH levels with blood pressure and risk of hypertension in a Chinese population.
A population-based cross-sectional study was conducted among 1,420 Chinese participants, aged 20-83 years, in 2010. Anthropometric phenotypes and blood pressure were evaluated. Serum lipids, 25-hydroxyvitamin D 25(OH)D and PTH were measured.
One thousand four hundred and twenty participants, including 566 women (39.9%), were evaluated in 2010. Four hundred and eighty seven were hypertensive (34.3%), of whom 214 (43.9%) received antihypertensive treatment. The median concentrations of serum 25(OH)D and PTH were 22.0 ng/ml and 2.83 pmol/l, respectively. Serum 25(OH)D and natural log of PTH levels were not independently associated with blood pressure in a multivariable adjusted linear regression analysis of 1,206 participants not receiving antihypertensive treatment (P>0.05). In logistic regression analyses, serum 25(OH)D levels were not associated with risk of hypertension in single and multiple regression models. One unit increments of natural log of PTH levels were significantly associated with risk of hypertension in the crude model (OR = 1.78, 95% confidence interval 1.38-2.28, P<0.0001) and model adjusted for age and sex (OR = 1.41, 95% confidence interval 1.08-1.83, P = 0.01). However, these associations were attenuated and became nonsignificant (OR = 1.29, 95% confidence interval 0.98-1.70, P = 0.07) after further adjustment for body mass index, current alcohol intake, current smoking, glomerular filtration rate and family history of hypertension.
Serum vitamin D and PTH levels are not independently associated with blood pressure or risk of hypertension in a Chinese population.
Hot-isostatic-pressing (HIPping) of pre-alloyed powders is an effective, highly material-efficient, novel manufacturing technique for the preparation of near-to-net shape components. However, the ...effect of pressure during HIPping on the beta arrow right alpha transformation inherent in titanium alloys is not well understood. This effect on phase transformation was investigated on both powder-based and bulk-based Ti-5Al-5Mo-5V-3Cr (Ti-5553). Microstructure characterisation and phase relationships were investigated using scanning electron microscopy and X-ray diffraction methods. The results show that the modest pressure applied in HIPping (100-200MPa) can influence the alpha - beta phase transformation in Ti-5553. Possible mechanisms related to these changes in phase transformation and microstructure are discussed.
•A crack data set with various forms is constructed by manual collection.•Proposes a network model suitable for multi shape object segmentation.•Proposes a kind of boundary weighted loss function ...which is suitable for the segmentation network of small objects.•Our model has better detection effect than the existing crack segmentation network in this scene.
The existence of cracks will affect the stability of the building. It is very important to identify and deal with the cracks in time to ensure the safety and stability of the building. Based on the above background, the purpose of this paper is to study the method of building crack recognition and total quality management based on deep learning. This paper focuses on the computer vision technology in artificial intelligence, studies the image classification algorithm and semantic segmentation algorithm based on the deep learning method, and applies it to the field of building crack image analysis. In this paper, we use the deep convolution neural network to design the building image crack classification model and segmentation model, realize the identification and analysis of building cracks, and build a building crack analysis system, which can significantly improve the efficiency of building crack detection. Then, based on the image processing technology, the quantitative analysis of the fracture segmentation results is carried out. Through the basic morphological methods such as corrosion, expansion, opening and closing operations, the segmentation mark map, skeleton map and geometric parameter information of the fracture are obtained, which further provides the maintenance and judgment basis for professional engineers. The experimental results show that compared with FCN, the accuracy of rfcn-a is improved by 5.98%, the precision is improved by 6.07%, and the real and f'score are improved by 3.11% and 6.01%, respectively.
The process of staining was frequently employed to enhance or alter the color of agate beads in ancient times. One of the key challenges in studying ancient beads is comprehending the intricate ...techniques employed to color agate stones. An understanding of the staining mechanism from a mineralogical standpoint offers insights into the level of technological advancement in different civilizations. In this study, the mineral structure of eight ancient agate beads from Xinjiang Uygur Autonomous Region, NW China, was analyzed using Micro X-ray fluorescence (µXRF), Raman spectroscopy, Scanning Electron Microscope (SEM), and Fourier Transform Infrared (FTIR) techniques. The color, transparency, mineral phase, and surface roughness of the beads were examined, revealing variations ranging from colorless to light violet to dark violet. Raman and FTIR spectroscopy were employed to determine the SiO
2
phase and the changes in optical characteristics of agate beads after artificial staining. The black color of the beads was formed by carbon penetration, while the red color was produced by heating. The coexistence of α-quartz and moganite phases in the red, the dark red, the black, the idiochromatic white and the part translucent zones of the ancient beads was confirmed by the 464 cm
−1
peak of α-quartz and the 502 cm
−1
peak of moganite phase. The analyzed red, the dark red, the black, the idiochromatic white and the part translucent zones exhibited remarkably similar FTIR spectral features, with two prominent bands at ~ 1097 and ~ 1187 cm
−1
, as well as two weak bands at 798 and 778 cm
−1
, indicating the presence of moganite and α-quartz in the unetched ancient beads. In contrast to the idiochromatic white appearance of natural agate, the scattered white coloration in etched beads was generated by an etching reaction. Both Raman and FTIR spectroscopy indicated the absence of moganite in etched beads, indicating that the scattered white color was produced by the loss of moganite and a portion of α-quartz, resulting in a rough surface.
The recently emerged Al–Mn–Mg–Sc–Zr alloys were regarded as high-strength Al alloys suitable for high-temperature applications. However, the influence of laser powder bed fusion (LPBF) fabricated ...anisotropic microstructure on tensile creep performance has not been explored. In this work, we reported an anisotropic tensile creep behavior, which is superior in the vertical specimens than the horizontal counterparts. The tensile creep anisotropy was attributed to the bi-modal microstructure of columnar grains within melt pool and equiaxed grains at melt pool boundary, the “fish-scale” melt pool morphology and the resulted tortuous crack path in the vertical orientation.
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