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Polymer-based dielectrics have attracted much attention in flexible electronics due to their excellent flexibility and dielectric and mechanical properties. However, the rational design of a nanofiller–polymer nanocomposite for improving dielectric and mechanical properties remains challenging. Herein, layered dielectric nanocomposites filled with high-κ Ca2Nb3O10 perovskite nanosheets were fabricated via shear-flow-induced alignment of nanosheets. The hierarchical structure and good dispersion of nanosheets endowed the layered nanocomposites with an outstanding modulus of 12.7 GPa and toughness of 1.8 MJ/m3. Meanwhile, the layered nanocomposites exhibited a high dielectric constant of 14.7, a low dielectric loss of 4.2%, and low leakage current density of <1 × 10–7 A/cm2. The layered dielectric nanocomposites designed in this work have broad application prospects in flexible electronics. [ABSTRACT FROM AUTHOR]

Hydraulic fracturing is one of the most effective stimulation methods for unconsolidated sandstone reservoirs. However, the design of hydraulic fracturing must take into account the mechanical and stress properties of different geological formations between layers. In this paper, a three-dimensional coupled fluid-solid model using the finite element method is developed to investigate multiple vertical fractures at different depths along a vertical wellbore under different geological and geomechanical conditions. The finite element model does not require further refinement of any new cracks, requiring much smaller degrees of freedom and higher computational efficiency. In addition, new elements were used to account for local pressure drop due to perforation entry friction along the vertical wellbore. Numerical simulation results indicate that hydraulic fracture connections are observed from adjacent layers. Furthermore, the low stress contrast and high Young's modulus between the layers increases the likelihood of multiple fracture connections. Higher fluid leakage rates increase the likelihood of fracture branching, but decrease the area of fracture coverage near the wellbore. Increasing fluid viscosity is effective in improving the area of fracture coverage near the wellbore. These findings are useful for the design of hydraulic fracturing in multi-layered formations in unconsolidated sandstone formations. [ABSTRACT FROM AUTHOR]

The production of high temperature and high pressure gas wells fluctuates with time, which makes the pressure in the string fluctuate obviously and affects the service security of tubing string. In this paper, a pressure fluctuation model of the complete production process (including well opening, production and shut-in) is established, which is suitable for the multiphase flow of gas well. The pressure fluctuation in the tubing string is simulated. Influence of different well depth and average production on the fluctuating pressure of gas well are analyzed. According to the research results, if the well opening time top is 50 s, a transient pressure fluctuation is generated at wellhead and drops gradually. After the production starts, a pressure fluctuation will occur at wellhead 10~15 s after top, which is small and attenuates quickly. Pressure increases quickly in the shut-in moment and reaches the peak at tsh. Although pressure increases gradually with the well depth, fluctuation flattens out. The hysteresis phenomenon in appearance of pressure wave becomes more and more obvious with the well depth. The greater the production of gas well, the greater the pressure fluctuation in tubing string during well opening and production, but the value may not be very high. During well shut-in, the greater the production, the greater the pressure fluctuation and the value. Amplitude, angular frequency and value of phase are in direct proportion to pressure fluctuation degree and valve radix is in inverse proportion to pressure, which means that the greater the valve radix, the smaller the pressure.

The Y oilfield reservoir is characterized by ultra-depleted reservoir and multiple pressure systems in each well section. If conventional PLUS/KCL drilling fluid is used in directional drilling, the following problems are found: the rheological stability of drilling fluid is not sufficient, resulting in increased viscosity and thickening after aging, and the single plugging material may cause loss-circulation when the drilling differential pressure is more than 26 MPa, resulting in poor reservoir protection effects. To solve the above problems, based on the conventional PLUS/KCL drilling fluid formula, a PLUS/KCL drilling fluid system suitable for directional drilling in multi-pressure systems was formed by optimizing the addition of a treating agent to improve the rheological stability of the drilling fluid, optimizing the plugging agent and compound combination to improve plugging ability, and optimizing the particle size distribution of a temporary plugging agent to improve the reservoir protection effect. The laboratory test evaluation showed that the optimized PLUS/KCL drilling fluid had fine plugging pressure capacity, and the intrusion depth was only 4.1 cm on the natural core at 120 °C/35 MPa/12 h, effectively reducing the risk of loss-circulation. The permeability recovery rate of the core after cutting off the polluted end was more than 90%, indicating that the reservoir protection effect was good. The drilling fluid performance was stable, and the cuttings rolling recovery rate was over 90%. Field application showed that the optimized PLUS/KCL drilling fluid was used without any loss-circulation or wellbore instability, and the production of all wells was over-matched, effectively solving the problem of ensuring drilling safety and reducing reservoir damage under the differential pressure of multiple pressure systems. [ABSTRACT FROM AUTHOR]

At present, the formation mechanism of gas hydrate (hereinafter referred to as hydrate) plugging in the wellbore during deepwater drilling is not clear, so there are problems such as the overuse of hydrate inhibitors and the low utilization efficiency of inhibitors. Therefore, in view of the risk of hydrate formation and plugging under different working conditions during deepwater drilling, research was carried out on the wellbore hydrate formation area and wellbore hydrate deposition and plugging. Taking an atmospheric well in the South China Sea as an example, the wellbore annulus temperature field under different working conditions was combined with the hydrate formation phase curve to analyze the hydrate formation plugging risk under different working conditions during deepwater drilling, and the hydrate formation risk region of the wellbore under different working conditions was obtained. The effects of the drilling fluid circulation rate, injection temperature and drilling fluid viscosity in the wellbore annulus on the risk zone and subcooling of the wellbore hydrate formation were predicted. A deepwater drilling wellbore hydrate deposition plugging model was developed, based on which the dynamic deposition of the hydrate in the wellbore was predicted quantitatively. The results of the study showed that: (1) Increasing the circulation rate of drilling fluid, drilling fluid inlet temperature and drilling fluid viscosity during deepwater drilling can effectively reduce the hydrate formation region and subcooling, thus reducing the hydrate formation. (2) The risk of plugging by hydrate formation basically does not occur during normal drilling. (3) Under the condition of using seawater bentonite slurry drilling fluid, the safe operating time for stopping drilling is 20 h, and the safe operating time for shutting in and killing the well is 30 h. [ABSTRACT FROM AUTHOR]

A porous morph-genetic SiC/C ceramic material was fabricated using biomass-derived C template, Si powder, and Fe(NO 3) 3 ·9H 2 O as the starting materials. The effects of heating temperature, and catalyst/Si mole ratio on the formation of SiC/C ceramic were investigated. In addition, the pore size distribution was obtained through pore size analysis, and the determination of oxidation resistance of SiC/C ceramics and C template was carried out by thermogravimetric analysis. The results show that copious amounts of SiC nanowires, which were distributed on the surfaces and interiors of the C template holes, were formed at 1300 °C with 4 wt% Fe as catalyst. The SiC nanowires significantly affected the oxidation resistance and microporous structures of the prepared materials. Moreover, a possible formation mechanism for the porous SiC/C ceramic was determined. [ABSTRACT FROM AUTHOR]

VN powders were synthesized in N 2 atmosphere by using V 2 O 5 and Mg as raw materials in KCl-KF molten salt environment. The effects of reaction temperature, reaction time and the presence or absence of salts on the formation of VN powders were investigated. The results showed that when the temperature increased to 700 °C, pure phase VN powders were fabricated, along with the specific surface area of 8.428 m2 g−1. As the temperature rose from 700 to 800 °C, VN powders presented the smallest average size of 0.10 μm. The electrochemical performance test showed that the specific capacitance of VN was 25 F/g at 0.5 A/g and the internal resistance was 1.8 Ω. The VN emission peak was composed of 263, 388 and 547 nm, indicating that it has good optical properties. A possible synthesis mechanism of VN powders in molten salt environment powders is proposed. [ABSTRACT FROM AUTHOR]

Industrial robots, as a structurally sophisticated mechatronics system, have a high cost of routine maintenance and repair. Repairs after fault require the corresponding manpower and material resources, and have hysteresis. If the fault can be predicted in a timely and accurate manner, the maintenance process can be carried out in advance, and the hidden dangers can be eliminated to fundamentally solve the fault problem. Based on the self-organised critical theory (SOC theory), this article draws lessons from its self-organisation evolution model and uses the self-organised criticality of industrial robot fault to establish an autoregressive moving average model (ARMA model) for industrial robots. According to the analysis of residual value and the explanation for the faults of industrial robots, find ways and means to prevent and reduce faults. [ABSTRACT FROM AUTHOR]

BACKGROUND In the kidney, 5-hydroxytryptamine (5-HT) and dopamine (DA) are formed by the same enzyme, l-aromatic amino acid decarboxylase, but act on renal function and glomerular structure in an opposite direction. The present study was designed to explore whether rates of renal production of 5-HT relative to that of DA are altered in patients with essential hypertension and microalbuminuria. METHODS We measured urinary levels of 5-HT and DA, reflecting renal production of 5-HT and DA as well as 24-hour ambulatory blood pressure and urinary albumin excretion in 82 consecutive untreated, essential hypertensives without overt proteinuria. RESULTS Urinary 5-HT excretion and the ratio of urinary 5-HT to DA were significantly higher in 22 patients with microalbuminuria than in the remaining patients with normoalbuminuria, although urinary DA levels did not differ between the groups. The 24-hour systolic and diastolic blood pressures were also higher in the microalbuminuric group than in the normoalbuminuric group. Multiple regression analysis revealed that urinary 5-HT excretion and 24-hour systolic blood pressure were independently associated with urinary albumin excretion. Furthermore, urinary 5-HT excretion was positively correlated with creatinine clearance as well as blood pressure but tended to be negatively correlated with fractional excretion of sodium. CONCLUSIONS Renal production of 5-HT is enhanced compared with that of DA in essential hypertensives with microalbuminuria. This imbalance may contribute to the genesis of hypertensive glomerular damage. [ABSTRACT FROM PUBLISHER]

With the increasing exploration and development area of deep-water oil and gas fields in the South China Sea, well construction operations in the deep-water sloping seabed area become more and more frequent, so it is of great significance to accurately assess the safety of jetting well construction in the sloping seabed. Based on the characteristics of jetting well construction technology, the soil disturbance model was established and the wellhead instability mechanism in sloping seabed was studied. It was found that the jetting flow rate and fluid range were the main factors to determine the disturbance intensity and disturbance range to sloping seabed. The risk of jetting well construction in the sloping seabed was also studied based on the geologic models of various forms of sloping seabed. The finite element strength reduction method was used to analyze the influence of seabed dip angle, soil strength and soil stratification on sloping seabed stability, and the sloping seabed instability evolution law under different jetting disturbance parameters was obtained. Through the assessment of the risk of jetting well construction in the sloping seabed, the selection range of well locations was expanded, which could aid in ensuring the security of deep-water oil and gas field construction. • Combining petroleum engineering and geotechnical engineering, the influence of jetting well construction on sloping seabed stability is studied. • The law of influence of deep-water jetting well construction on sloping seabed is obtained, which fills the gap of research on deep-water sloping seabed well construction. • The study expands the scope of well site selection for deep-water drilling, and provides technical support for further development of deep-water resources. [ABSTRACT FROM AUTHOR]

Deepwater gas wells usually have high production rates, which result in high-speed sand movement along with the gas flow and acid components such as CO 2 in the gas flow. The erosion and corrosion effect intensifies the damage to sand screens and can further lead to sand control failures, which endanger the safety of production operations. In this paper, using a differential rotation device to simulate erosion, corrosion, and erosion-corrosion, experiments observing the impacts of several factors on sand screens were carried out. The factors include CO 2 partial pressure, temperature, flow velocity, sand content, and sand particle size. Their impacts on erosion, corrosion, and erosion-corrosion rate are inspected independently, and the sensitivity of factors to the erosion-corrosion rate of a sand screen was determined using the range method. Traditional erosion models involving flow rate, sand content, and sand grain size and traditional corrosion models involving CO 2 partial pressure and temperature are taken as references, and an erosion-corrosion coupled model of sand screens is established based on the experimental results using the multivariate regression analysis. With critical damage thickness taken as the failure criterion of a sand screen, a prediction method for sand screen failure is formed and is applied to the case study of the S deepwater gas field. The results show that under the experimental conditions, the screen loss rate due to erosion-corrosion is significantly higher than that of erosion only or corrosion only and is even higher than the sum of both. The erosion-corrosion rate increases with the increase of CO 2 partial pressure, temperature, flow velocity, sand content, and sand particle size. It has an exponential relationship with the negative reciprocal of temperature, a linear relationship with the partial pressure of CO 2 , and power fitting relationships with flow velocity, sand content, and sand particle size. The ranking of sensitivities to the erosion-corrosion rate of high-quality screens is as follows: sand content > flow velocity > temperature > sand particle size > CO 2 partial pressure. The error between the predicted results by the proposed model and the experimental results is in the range of 0.44-9.47%. The erosion-corrosion rate of sand screens in each production well of the S gas field is in the range of 0.0111-0.0521 mm/a, while the durability of the screens is 14-68 years. The erosion-corrosion rate model of a sand screen and the prediction method for sand screen failure proposed in this paper provide theoretical support to the durability evaluation of sand screen in deepwater gas wells, which is of great significance for ensuring the safe and efficient development of offshore oil and gas resources., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

Wheat leaf rust (caused by Puccinia triticina ) and stripe rust (caused by Puccinia striiformis f. sp. tritici ) cause large production losses in many regions of the world. The objective of this study was to identify quantitative trait loci (QTL) for resistance to leaf rust and stripe rust in a recombinant inbred line population derived from a cross between wheat cultivars SW 8588 and Thatcher. The population and parents were genotyped with the Wheat 55K SNP Array and SSR markers and phenotyped for leaf rust severity at Zhoukou in Henan Province and Baoding in Hebei Province. Stripe rust responses were also evaluated at Chengdu in Sichuan Province, and at Baoding. Seven and six QTL were detected for resistance to leaf rust and stripe rust, respectively. Four QTL on chromosomes 1BL, 2AS, 5AL, and 7BL conferred resistance to both rusts. The QTL on 1BL and 2AS were identified as Lr46 / Yr29 and Lr37 / Yr17 , respectively. QLr.hebau-2DS from Thatcher, identified as Lr22b that was previously thought to be ineffective in China, contributed a large effect for leaf rust resistance. QLr . hebau-5AL / QYr.hebau-5AL , QLr.hebau-3BL , QLr.hebau-6DS , QYr.hebau-4BS , and QYr.hebau-6DS are likely to be new QTL, but require further validation. Kompetitive allele-specific PCR (KASP) markers for QLr.hebau-2DS and QLr.hebau-5AL / QYr.hebau-5AL were successfully developed and validated in a diverse wheat panel from Sichuan Province, indicating their usefulness under different genetic backgrounds. These QTL and their closely linked SNP and SSR markers will be useful for fine mapping, candidate gene discovery, and marker-assisted selection in breeding for durable resistance to both leaf and stripe rusts.

We report herein a 27-year-old male case of inherited distal renal tubular acidosis complicated with renal diabetes insipidus, the symptoms of which were aggravated by the occurrence of diabetes mellitus. At 2 months after birth, he was diagnosed as having inherited distal renal tubular acidosis and thereafter supplementation of both potassium and alkali was started to treat his hypokalemia and metabolic acidosis. At the age of 4 years, calcification of the bilateral renal medulla was detected by computed tomography. Subsequently his urinary volume gradually increased and polyuria of approximately 4 L/day persisted. At the age of 27 years, he became fond of sugar-sweetened drinks and also often forgot to take the medicine. He was admitted to our hospital due to polyuria of more than 10 L day, muscle weakness and gait disturbance. Laboratory tests disclosed worsening of both hypokalemia and metabolic acidosis in addition to severe hyperglycemia. It seemed likely that occurrence of diabetes mellitus and cessation of medications can induce osmotic diuresis and aggravate hypokalemia and metabolic acidosis. Consequently, severe dehydration, hypokalemia-induced damage of his urinary concentration ability and enhancement of the renin angiotensin system occurred and thereby possibly worsened his hypokalemia and metabolic acidosis. As normalization of hyperglycemia and metabolic acidosis might have exacerbated hypokalemia further, dehydration and hypokalemia were treated first. Following intensive treatment, these abnormalities were improved, but polyuria persisted. Elevated plasma antidiuretic hormone (12.0 pg/mL) and deficit of renal responses to antidiuretic hormone suggested that the polyuria was attributable to the preexisting renal diabetes insipidus possibly caused by bilateral renal medulla calcification. Thiazide diuretic or nonsteroidal anti-inflammatory drugs were not effective for the treatment of diabetes insipidus in the present case.

A 55-year-old man was admitted to our hospital because of arthralgia, purpura, abdominal pain, melena and leg edema. Laboratory findings showed an increased serum creatinine level (2.4 mg/dL), hematuria and massive proteinuria (10.7 g/day). Renal biopsy revealed diffuse endocapillary proliferation and focal mesangial proliferation with IgA deposition predominantly in the glomerular capillary walls. Based on these findings, he was diagnosed as having Henoch-Schönlein purpura nephritis and steroid therapy was started. Following steroid therapy, his nephrotic state remained unchanged, although his renal function improved concomitantly with the disappearance of arthralgia, purpura and abdominal symptoms. Therefore, cyclosporine was added to the steroid therapy to enhance immunosuppression. However, melena recurred and anemia progressed. Endoscopy revealed multiple ulcers in the duodenum and jejunum, and clipping was performed at some bleeding sites. However, he died of hemorrhagic shock. The autopsy revealed that hemorrhagic lesions having cytomegalovirus infection spread widely in the stomach, duodenum and jejunum. Recurrence of gastrointestinal bleeding during the treatment of Henoch-Schönlein purpura nephritis is usually due to severe vasculitis or steroid ulcer. However, in patients receiving strong immunosuppressive therapy, cytomegalovirus infection needs to be considered as cause of gastrointestinal bleeding.