Search

Coalbed Methane (CBM) is an unconventional form of natural gas which is self-generated and self-stored in coal seams. In order to realize the effective exploitation of CBM in Zhengzhuang block, microstructure, wettability, permeability, rock mechanics and in-situ stress of coal were studied in this research. It is found that high rank anthracite characterized by high vitrinite content and low inorganic mineral content, is abundant in CBM. More than 96% of inorganic minerals are clays dominated by kaolinite and illite. Various types of pores are developed on the coal. The wettability of coal differs from high to low to surface water, active water, and foam fracturing fluid; and contact angles of coal with active water and foam fracturing fluid decrease with the increase of burial depth. Gradients of fracture pressure and closure pressure in No.3 coal seam are higher than that of No.15 coal seam. The elastic modulus of coal is lower than that of sandstone. The construction curve of hydraulic fracturing shows that, when the construction flow rate and sand quantity are similar, the construction pressure of prepad in No.3 coal seam is lower than the pumping pressure of No.15 coal seam, but the propagated pressure is higher than that of No.15 coal seam. The drainage effect of No.3 coal seam with large pore volume, shallow burial depth and obvious fracture pressure is better than that of No.15 coal seam. The comprehensive understanding of coal physical properties and engineering practice in the block provide certain guiding significance to the CBM exploitation in Qinshui Basin.

BACKGROUND Para-Bombay phenotype is rare in ABO blood group. We describe FUT1 mutations in a Chinese woman with the para-Bombay phenotype, including her familial inheritance. METHODS ABO grouping, H antigen detection, absorptionelution test, salivary antigen substance detection, deter-mination of titer of ABH antibody, ABO genotyping, gene sequencing (FUT1,2), blood transfusion compatibility test, and pedigree investigation were performed. RESULTS The patient was confirmed as group A1 para-Bombay phenotype (Amh) in her family's investigation, revealing her FUT1 gene had c.658C>T (p.Arg220Cys) homozygous mutation and FUT2 gene had c.357C>T homozygous mutation. The patient was provided an appropriate transfusion solution. CONCLUSIONS A combination of using classical serological methods, gene sequencing methods and pedigree investigation methods can effectively analyze the genetic inheritance of patients with para-Bombay phenotype, increasing their choices of blood transfusion.

[Purpose/significance] This paper attempts to construct a model framework based on the theory of open innovation to evaluate the impact of open innovation platforms on corporate innovation performance, and provide development suggestions for builders and users of open platform communities. [Method/process] This article is based on the open innovation theory and knowledge management theory. First, it establishes the model of the impact of open innovation communities on corporate innovation performance and proposes research hypotheses. Then, Python is used to capture the data of an open innovation community for empirical research and validate the research hypothesis. [Result/conclusion] Research results are consistent with the hypothesis in that①the community organization mechanisms have significant positive effects on the community social network structure; ②the community technical mechanisms have significant positive influences on the community social network structure; ③the community social network structure positively influences corporate knowledge acquisition; ④the community social network structure positively influences the enterprise knowledge transformation; ⑤the community social network structure positively influences the activity of the community innovation source; ⑥the activity of the community innovation source positively affects the scale of the community innovation source; ⑦the scale of the community innovation source positively influences the enterprise knowledge transformation; ⑧the enterprise knowledge transformation positively affects the enterprise innovation performance; ⑨the activity of the community innovation source positively affects the enterprise innovation performance. Consequently, the strategic guidance for the construction and development of open innovation communities is provided.

Coalbed methane (CBM) is a new clean and unconventional energy that has broad space for development. In Qinshui basin, CBM reserves reach 3,97·1012m3, which is 10,8% of the total resource in China. Compared to the main coal basins of USA, Australia, Canada and Russia, coal seams in Qinshui basin have the characteristics of high metamorphism, high gas content, low porosity, low permeability and low reservoir pressure. Therefore, effective stimulation treatments must be used in Qinshui basin to realize industrial exploitation of CBM. At present, vertical wells with hydraulic fracturing are dominated in Qinshui basin. In addition, injection CO2, electric pulse, multi-stage fracturing and other technologies are also applied to the CBM exploitation.

Background: Coronavirus disease 2019 (COVID-19) is a new viral respiratory disease and whether pregnant women are at increased risk of infection is unknown. Viral pneumonia is an important indirect cause of maternal death. Little is known about the effects of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) during pregnancy. Objective: To describe the clinical characteristics of COVID-19 in pregnancy and their newborn infant, and we sought to explored whether the SARS-CoV-2 can be intrauterine vertically transmitted. Study Design: The study was a case series study conducted in the obstetric ward of Tongji Hospital affiliated to Huazhong University of science and technology, Wuhan, China. Demographic, clinical, laboratory and radiological profiles of the SARS-CoV-2 infection case series. A systematic testing procedure for SARS-CoV-2 infection using oropharyngeal swab, placenta tissue, vaginal mucus, and breast milk of mothers. and oropharyngeal swab, umbilical cord blood, and serum of newborns was conducted. Results: We have conducted the most thorough virological assessment to date, and we include a longer clinical observation in mother-infant dyads during hospitalization. The clinical course and outcomes of three pregnant women who acquired SARS-CoV-2 infection late pregnancy are described in mother-infant dyads. Two had caesarean delivery in their third trimester. All patients showed an uneventful perinatal course, and a successful outcome. No infants became infected by vertical transmission or during delivery. Conclusion: No evidence to suggest the potential risk of intrauterine vertical transmission in the case series and further in-depth study is needed. Both the pregnancy woman and infant showed fewer adverse maternal and neonatal outcomes.

To improve the efficiency of wafer fabrication, this work addresses the scheduling and control problems of mixed-processing with multiple wafer types in cluster tools. Then, based on a developed Pe...

It is difficult for mechanical machining to fabricate concave micro-array due to size limit and micro-tool wear. Hence, electro discharge micro-machining is proposed to fabricate concave micro-arra...

High temperature steam gasification experiments were conducted to gasify sludge in an electrically heated tubular furnace at 650, 750, 850, 950, and 1050?C. The obtained results develop a mechanistic understanding on steam gasification of sludge from starting constituents to final products. The introduction of steam led to a steam reforming of the tar and CnHm compounds, and a partial gasification of the solid char and CH4, which contributed to the generation of rich H2 and CO. The steam gasification process can be divided into three significant stages. As temperature increased, a decreasing absorbance amount of C-Har and C-O and a large reduction of C = O were accompanied with an evident reduction of tar yield and an increasing gas yield, especially the increase of H2 and CO contents. The H2 and CO were the indicator for the occurrence of tar and CnHm steam reforming. In addition, more micro-pores generated in solid char and a sharp increase of Brunauer-Emmett-Teller (BET) surface from 24.2 m2g?1 to 75.4 m2g?1 showed the occurrence of char decomposition. An increasing content of polycyclic aromatic hydrocarbons (PAH) with 2 and 3 rings and a significant decrease of PAH with 4-6 rings in tar showed the tar cracking and reforming of non-condensable intermediates.

The functional performance and the product life of micro-milled Inconel 718 parts highly depend on their mechanical properties such as excessive work hardening, which will reduce fatigue life, and the corrosion resistance of micro Inconel 718 parts. Also, work hardening can accelerate tool wear. Therefore, investigation of work hardening caused by micro-milling is important if we are to improve the functional performance and extend the life of microproducts such as Iconel718. However, few studies have developed methods of predicting the surface hardness of micro-milled parts. Thus, this paper uses 3D finite element analysis (FEA) based on ABAQUS to simulate the process of micro-milling Inconel 718. We simulated clamping, micro-milling, tool retracing, and constraint conversation stages with surface residual strains as output. Then, after identifying the relationship among Vickers hardness, the flow stress, and the flow strain of Inconel 718, we built the surface micro-hardness prediction model of micro-milled Inconel 718 and confirmed the accuracy and validity of the surface hardness prediction model by experiments. From the model, the influences of spindle speed, feed per tooth, and axial cutting depth on surface micro-hardness were determined.

The application and development of metal ceramic composites have been restricting due to its low grinding efficiency and ground quality. In this paper, the hybrid machining technology combined mechanical with electrolytic grinding based on dressed coarse diamond grinding wheel is proposed to perform efficient and precise grinding of metal ceramic composites. First, the dry electrical discharge dressing technology was used to dress coarse diamond grinding wheel to obtain high grain protrusion and sharp micro-grain cutting edges. Next, the mechanical and electrolytic hybrid grinding process using dressed coarse diamond wheel was developed to grind metal ceramic. Finally, the effects of different process parameters on ground surface topographies and surface roughness were investigated. It is shown that the proposed hybrid grinding method was feasible and can effectively improve the ground surface quality. The experimental results show that the optimal process parameters including the depth of cut, open-circuit voltage and impulse width were 5 μm, 20 V and 400 ns, respectively. Compared with traditional mechanical grinding, the ground surface roughness by the proposed hybrid machining method was improved by about 25%.

In view of the traditional PID control algorithm for the control of the quad-rotor attitude angle, the control parameters are difficult to change with the change of environment. Thus, the fast stability problem of the quad-rotor is affected, and an improved single neuron adaptive control algorithm is proposed. The algorithm of single neuron by changing the value of K in size, which increases the speed of response, and to limit the overshoot, compared with incremental PID, the simulation results show that the improved algorithm has fast dynamic response, high control precision, strong anti-interference ability, can achieve of the Quad-rotor attitude control is better.

Based on CFD method and dynamics mesh method, the transient flow simulation model of dry scroll vacuum pump was established. Numerical calculation was carried out under three kinds of typical working conditions of viscous flow state including under-compression, slightly over-compression and over-compression. Simulation results are in line with the results of experiment or theoretical calculation on the whole. The maximum error of pumping speed between the simulation and the experiment is about 30%, and the minimum is close to 10%. The predicted compression power accords with the theoretical prediction of approximate polytropic process. The simulation pressure inside the pump also has a consistent change process with experimental results. The contrast and analysis of the simulation model and the physical experiments suggest that the further correctly modified geometric parameters and boundary conditions according to practical situations can significantly improve the accuracy of the numerical calculation. Further analysis of the main flow phenomena and characteristics of scroll compression chamber at the discharge side during the discharge process confirms that under-compression and over-compression lead to the large variation of gas pressure and dramatic fluctuation of compression torque.

Coalbed methane (CBM) is clean unconventional energy that can be exploited with stimulation treatment to realize commercial value, and hydraulic fracturing is the key technology for increasing CBM production. The simulation of hydraulic fractures is an important research content that can guide the engineering practice to achieve the purpose of increasing production. Based on the distribution characteristic of cleats in coal, the research on the propagation of hydraulic fractures is carried out via Discrete element method (DEM). The simulated results show that: hydraulic fractures mainly propagate along the cleats towards the maximum principal stress. The fracture network can be formed due to the intersection of face cleats and butt cleats that can propagate at certain pressure. During the injection process of fracturing fluid, the pressure at injection point decreases with the fracture propagation until the pressure tends to be stable. With the increase of injection rate and fracturing fluid viscosity at the same condition, the maximum aperture of hydraulic fracture increases, while the length of principal hydraulic fracture shortens. Therefore, to achieve the purpose of forming hydraulic fracture network in coal seams with cleats, low viscosity fracturing fluid and low injection rate need be applied to the fracturing technology. As the cleat density increases, the number of branch fractures increases, but the length of principal hydraulic fracture becomes short. Long and narrow hydraulic fractures are easily formed in coal seams with lower cleat density.

An adaptive controller is necessary for a quadrotor to deal with the different flight cases, this paper presents a scheme of design and implementation of a fuzzy self-tuning PD controller for stable attitude. The transfer function simplified from a nonlinear dynamic model of a quadrotor is obtained to design a PD controller for the pitch, roll, yaw rate channels, however for a performance improvement a fuzzy self-tuning unit is added for the adjustment of PD controller's parameters. The simulation based on Matlab/Simulink software is used to evaluate the controller. Meanwhile a quadrotor control system platform, based on the STM32F405 MCU and MPU6500, AK8975, MS5611 Sensors, is designed and built, and the follow-up flight tests at the cases of hovering and level flight give some comforting results, which show that the fuzzy self-tuning PD controller is practical and effective, and gives a better performance than a simple PD controller.

Increasing evidence suggests that FOXO1, one critical gene related to the human immune system, probable is closely to the human infection. In the present study we aimed to investigate genetic association of FOXO1 with bacteremia in Han Chinese. 188 patients with bacteremia diagnosed with blood culture and 250 healthy blood donors without signs of infection were studied, two tagging SNPs of FOXO1 (rs9532571, rs3751436) were selected and genotyped using predesigned TaqMan allelic discrimination assays. The results showed that the allele frequency of rs9532571 and rs3751436 in FOXO1 was not associated with an increased risk of bacteremia (P=0.762, OR=1.05, 95% CI 0.77-1.43; P=0.059, OR=1.34, 95% CI 0.99-1.81 respectively), the genotype distribution of these two SNPs was also not significantly different between bacteremia patients and control groups (P=0.9; P=0.16). Haplotypes in this block were not significantly associated with bacteremia risk. Conclusion: the association between FOXO1 genetic polymorphism and bacteremia has not been observed in the study, maybe a larger sample population and more SNPs in the FOXO1 need to reveal the role in bacteremia in the future.

In this paper, a surface roughness prediction model of micro-milling Inconel 718 by applying response surface methodology (RSM) is presented. The experiments based on centre composite rotatable design (CCRD) are designed to conduct the experiments. The cutting parameters considered are depth of cut, spindle speed and feed rate. Statistical methods, analysis of variance (ANOVA), are used to analyse the adequacy of the predictive model. The influence of each micro-milling parameter on surface roughness is analysed; also the magnitude order of parameters is determined. Depth of cut is found to be the critical influence factor. At last, the parameters interaction on surface roughness of micro-milling Inconel 718 is discussed by graphical means through MATLAB.

Passive building energy efficiency refers to utilizing ecological building design principles with natural climate resources to realize building energy efficiency, which is greener, more conducive to the sustainable development of the human living environment, and will actively advocate building energy efficiency. This paper will analysis the adaptability of six passive building energy efficiency technologies including passive solar heating, natural ventilation, thermal storage wall, induced and night ventilation, direct evaporative cooling and indirect evaporative cooling in typical cities of Shenzhen and Guangzhou in hot summer and cold winter region. In addition, this paper will establish adaptability model of passive building energy efficiency technology. According to the adaptability model, appropriate passive building energy efficiency technologies can be analyzed in typical cities in hot summer and cold winter region.

Unmanned aerial vehicle(UAV) often flies in close proximity to terrain. The expansion in the number of low-altitude flight operations, along with increased operator workload, have made controlled flight into terrain the number one cause of loss of UAV. This paper is to give an overview of the Automatic Ground Collision Avoidance System (Auto-GCAS) program attempt to provide a system to eliminate that cause of UAV loss. The Auto-GCAS utilizes a digital terrain system with a terrain referenced navigation algorithm to locate the aircraft spatially with respect to the terrain. The terrain database around the aircraft is scanned, and a terrain profile is created. This paper presents a new compression algorithm called bubble terrain compression algorithm for Auto-GCAS of UAV. In this paper, optimal trajectory is considered as a minimax optimal control problem, which is solved using direct transcription of the continuous optimal control problem. Within a very general framework for solving such problems, we transform the non-smooth cost function into a constrained nonlinear programming problem. In the formulation, we solve for optimal collision avoidance manoeuvres. To ensure smooth derivatives of general two dimensional terrain, it is approximated using the optimal trajectories with disturbances in the initial conditions. Simulation results show that the UAV with the proposed methodology successfully achieves autonomous recovery maneuvers in MATLAB environment.

Nowadays, there are urgent demands of micro structure/parts which have high strength in high temperature environment in the fields such as aerospace, energy, power, bio-medical, etc. Nickel-based superalloy Inconel 718 is the suitable material for manufacturing the kind of micro parts. Micro-milling can be applied to manufacture Inconel 718 micro components. Different processing conditions lead to different residual stress on workpiece surface, which has a significant effect on reliability and working life of product. To study the residual stress problem in micro-milling of Inconel 718, the investigation of micro-milling Inconel 718 process was implemented based on ABAQUS simulation. The model based on the input of cutting parameters and the output of surface residual stress was developed. At last, the experiments of micro-milling Inconel 718 were conducted to verify the validity of model. The work offers reference for selecting cutting parameters in micro-milling of Inconel 718.

Air Data Computer, referred to ADC, is an important on-board electronic equipment of Aircraft, and the performance of ADC directly affects the safety and efficiency of an Aircraft's flight. In this paper, we let ARM as the core of Air Data Computer, and use some real objects, such as airspeed tube and the related sensor, etc. And then adopt the design ideas of modular to give the overall scheme of designing Analog Air Data Computer. This paper clearly illustrates the constitutes of Analog Air Data Computer systems and the realization process of software and hardware. And then realizing the acquisition, processing and display function of air data parameters of Air Data Computer, and providing good ideas for the design and development of Air Data Computer on small aircraft and Unmanned Aerial Vehicle (UAV).

Rub is a common fault of rotating machinery. It will bring serious damage to mechanical equipment. A new diagnosis method based on empirical mode decomposition (EMD) and support vector machine (SVM) is proposed. Firstly, signals are decomposed into a finite number of intrinsic mode functions (IMFs).Then, the maximal singular values of the every single of IMF are defined as the feature vectors and served as input parameters of SVM classifiers to classify fault patterns of rotating machinery. Meanwhile the way was used on the rub impact fault identification of dual-disk over-hung rotor-bearing system. Experimental results show that the way can be more effectively and accurately than conventional BP and RBF neural networks, and has high robustness, good generalization ability as well.

This paper carries out numerical simulation for pressure driven microscale gas flows in transition flow regime. The relaxation time of LBM model was modified with the application of near wall effective mean free path combined with a combination of Bounce-back and Specular Reflection (BSR) boundary condition. The results in this paper are more close to those of DSCM and IP-DSCM compared with the results obtained by other LBM models. The calculation results show that in transition regime, with the increase of Knudsen number, the dimensionless slip velocity at the wall significantly increases, but the maximum linear deviation of nonlinear pressure distribution gradually decreases.