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Purpose In this paper, a novel and unified method for geometry configuration simulation of flexible cable under certain boundary conditions is presented. This methodology can be used to realize cable assembly verification in any computer-aided design/manufacturing system. The modeling method, solution algorithm, geometry configuration simulation and experimental results are presented to prove the feasibility of this proposed methodology. The paper aims to discuss these issues. Design/methodology/approach Considering the gravity, bending and torsion, modeling of cable follows the Kirchhoff theory. For this purpose, Euler quaternions are used to describe its spatial geometry configuration by a carefully chosen set of coordinates. Then the cable is discretized by the FEM, and the equilibrium condition per element is computed. In this way, the global static behavior is independent of the discretization. The static evolution of the cable is obtained by numerical integration of the resulting Kirchhoff equations. Then the manner is demonstrated, in which this system of equations can be decoupled and efficiently solved. Geometry configuration simulation examples with different boundary conditions are presented. Finally, experiment validation are given to describe the effectiveness of the models and algorithms. Findings The method presented in this paper can be adapted to computer-aided assembly verification of flexible cable. The experimental results indicate that both of the model and algorithm are efficient and accurate. Research limitations/implications The method should be extended to flexible cables with multiple branches and more complex constraints (holes, curved surfaces and clamps) and non-circular sections. Dynamic assembly process simulation based on the Kirchhoff theory must be considered in the future. Originality/value Unlike in previous approaches, the cable behavior was independent of the underlying discretization, and the finite element approach enables physically plausible cable assembly verification.

In the experiment, the filtrate loss of synthetic fluid loss control fluid was recorded in room temperature and high temperature in the composite brine base and sodium chloride brine base slurry, and compared with the filtrate loss before base polymer addition. In this way, the effect of filtration loss and salt resistance and temperature resistance of synthetic polymers were evaluated. The influence of the synthesized polymer on the rheological properties of the composite brine was also evaluated by determining the viscosity of the drilling fluid added to the base slurry and polymer. In the end, the structure of the synthetic polymers was characterized through the infrared spectrum, which initially analyzed through the mechanism of its function in reducing the filter loss. Finally, the products produced according to the recipe are given to the site and added to the two wells to record the drilling fluid performance data.

Pulse hydraulic fracturing is a promising stimulation technology to enhance the effectively permeability of coal seams. The fundamental of pulse hydraulic fracturing is that fracturing fluids with a certain frequency are injected into coal, resulting in the rupture of coal and forming a well-distributed fracture network due to the pulse loading. Better effects of gas extraction using pulse hydraulic fracturing had been gotten compared with that of hydraulic fracturing. Accordingly, how to apply pulse hydraulic fracturing technology to improve the fracturing effect of tight and shale reservoirs is a question worth thinking about, although this is very challenging due to the totally different downhole operating conditions. In this paper, experimental apparatus for fatigue damage of quasi-triaxial rock under alternating loads was established. The maximum injection pressure is 50MPa, while the pulse pressure amplitude is greater than 5MPa, and the pulse frequency is adjustable from 0 to 50Hz. Rock failure experiments under pulsating load were carried out and the effects of different hydraulic pulse parameters and rock properties on rock damage were studied. Experimental results show that hydraulic pulse has different effects on rock compressive strength and fracture pressure of different properties. With the increase of hydraulic pulse frequency, the influence on rock compressive strength increases firstly and then decreases. With the increase of pulse pressure amplitude, the influence on rock strength increases. With the increase of hydraulic pulse processing time, the influence on rock fracture pressure increases firstly and then tends to stabilize. Hydraulic pulse has the greatest influence on the compressive strength and fracture pressure of He 8 reservoir, followed by Chang 8 and Chang 6 reservoir of Changqing Oilfield in China. Based on the experimental results, hydraulic pulse frequency is preferred to be about 18-20Hz, accordingly, a downhole hydraulic pulse generator is designed and manufactured. The indoor test results show that the generator performance meets the design requirements. Field tests of pulse hydraulic fracturing were carried out in 3 wells in Changqing tight oil reservoir. Encouraging results were obtained, the average construction pressure was reduced obviously and average daily production per well increased significantly compared to adjacent wells.

Aimed at the problems of high frictional resistance, lots of residue after gel breaking and the difficulty in recycling for Guanidine fracturing fluids used in Changqing Oilfield. By combining the surface colloid chemistry with oilfield chemistry to develop a kind of oil displacement recyclable clean fracturing fluids system to replace guanidine gum. The clean fracturing fluid consisted of 1.5% thickener (XYZC-6) and 0.5% conditioner (XYTJ-3). The thickener XYZC-6 is a composed of viscoelastic surfactant with a near peptide chain structure and multi-component organic solvent, it can be mixed continuously in real time and can be reused. The conditioner XYTJ-3 could form various water-soluble complexes with the ions in the return liquid, reducing the effect of the degree of mineralization on the performance of the fracturing fluid. The results showed the fracturing fluid has a good temperature resistance at 90 °C, a salt resistance of up to 100,000 mg/L, good sand-carrying performance and low damage, the interfacial tension of the broken glue can reach 10−2 to 10−3 mN/m. It has been successfully applied in the Jing’an block of the Changqing oilfield and the production of single well is two times than adjacent well. Besides, the returning liquid treated with separation and settlement could be reconfigured the fracturing fluid and used for oil displacement which realize zero emissions and zero pollution, reduced greatly the risk of environmental pollution, and provided technical support of fracturing fluid.

Changqing oilfield is a typical low permeability, low porosity sandstone reservoir, and most wells drilled in the field have to be fractured before production. Nevertheless, the fracturing scales were relatively small. With the number increase and rapid production decrease of old fractured well, study and application of re-fracturing technologies to restore or improve old oil wells productions become necessary. In this paper, we break through traditional re-fracturing ideas in sandstone reservoirs (such as old fractures re-extending or deflection fracturing), and put forward SRV fracturing technology to increase the stimulated reservoir volume by increasing fracturing scale, injecting base fluid / cross-linked fluid alternately, and using temporary plugging agents. Firstly, applicable conditions of this technology were studied, such as reservoir properties, rock brittleness, natural fractures and horizontal stress difference. Then, two kinds of temporary plug agents were selected and evaluated, also technological parameters and construction processes were optimized in lab. Finally, pre-fracturing evaluation of old oil wells was carried out and field tests of 3 wells were conducted. Field tests results showed that the selected plugging agents could realize temporarily plugging of the fractures by measuring downhole pressures. Microseismic fracture monitoring result indicated that SRV fracturing, by means of fluid alternate injection and plugging agent, could really increase SRV of the old oil well. After stimulation, average daily oil production of the 3 wells increased 72%. Laboratory researches and field tests results indicate that increase stimulated reservoir volume for old oil wells in low perm sandstone reservoir is technically feasible, and this technology has a good application prospect, which benefits the traditional re-fracturing methods significantly.

The dynamic behaviors of a pilot control valve have been studied using the pseudo bond graph approach. The pseudo bond graph model can synchronously retain the mathematical structure and the physical structure of the research object. State equations are deduced from the pseudo bond graph model and been numerically solved with MATLAB-SIMULINK. The simulation results show that the pilot control valve can work well in despite of an unexpected response. The profiles of the gas pressure in different chambers and the displacement of the valve spool are obtained. The pseudo bond graph model can predict the dynamic behaviors of the pilot control valve, thereby providing reference for further optimization.

In order to make sure what factors have an effect on condensation, a mathematical model has been established for the discharging process of a pneumatic system using the fluid grid theory, an analytic equation has been derived to determine the maximum humidity of air during discharging of pneumatic system, and an analytic equation has been established as the first necessary condition for the determination of internal condensation in a pneumatic system. Flowing air may produce water droplets in a pneumatic system when the system satisfies the first necessary condition. An analytic equation has been developed as the second necessary condition for determination of internal condensation in a pneumatic system by introducing stroke and establishing an analytic equation for the stroke. The water droplets produced by satisfaction of the first necessary condition form drops of water inside the system when the system satisfies the second necessary condition. Internal condensation does not occur when the system does not satisfy the first necessary condition, and internal condensation occurs only when the system satisfies both conditions at the same time. The experimental results indicate that the points of internal condensation, external condensation and no condensation exhibit a regular distribution on the plane formed by the dimensionless volume of the discharging pipe and the average velocity of air, and the plane can then be divided into regions, providing a graphic discrimination method for determination of condensation in a pneumatic system.

With the increasing using temperature, the magnetic performance of high temperature stable Sm 2 Co 17 type permanent magnet will be decreased. In order to explore the effect of the high temperature on microstructure of the alloy, the differential thermal analysis (DTA) was made and three distinct phase transformation temperature 254 °C, 342 °C and 540 °C were obtained. Then X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray energy dispersive spectrometer equipped (EDS) were used to analyze the phase information, microstructure and composition of the samples treated at the above temperatures. The results suggested that the oxidation and precipitation of Cu and Fe are the key reason to result in the failure of the material, which provides an important reference for the research of the magnet.

Abstract For the shortcomings of the fracturing fluid at president, the paper commenced from several aspects which are the salinity of the fracturing fluid, the ingredients of Inorganic ions, acidic or alkaline, surface or interfacial tension, insolubles and gel breaking residues, then combined them to form the ionic equilibrium fracturing fluid system. The pH and salinity have little influence on the system and there are no insolubles or gel breaking in the fracturing fluid. The pH of the liquid system is 6–6.5 which belongs to the weak acid. The fracturing fluid is the high salinity formation water which is compound with the 4% of KCl and its performance of crosslinking is good. The system has a good performance of heat and shear resistance in the environment of weak acidity and high salinity. The temperature of its heat resistance can be up to 85 ?. Introduction At present more than 90% of the fracturing fluid is water-based fracturing fluid and because of the good comprehensive economic, the water-based crosslinking fracturing fluid whose thickener is polymer plant gum occupies the dominant position. The field application of water-based fracturing fluid will go through four main processes: the compound of the fracturing fluid before being put into the well; the support of fracturing construction; contact and react with the formation; flow back after the fracturing. Among them, the first process not only determines the intuitive quality of the fracturing fluid on the ground, but also plays a decisive role in the second stage of fracturing construction; the stand or fall of the second process determines the effect of fracturing transformation.

To compensate for the domestic space of the basic theory on large-scale wind power bearing, a large-scale wind power yaw bearing test rig control system is put forward. Through the analysis of load calculation and bearing running condition, design a hydraulic loading system and test devices; According to the operation requirement, design a control system and supervisory control and data acquisition system based on PLC control system. The tester for all the design can satisfy the wind bearing rig each index of requirements. It has a vital significance for large wind bearing test research.

It is known that for an external push a humanoid robot can take three strategies, i.e. ankle strategy, hip strategy and step strategy, to recover balance. For the limited joint torque, the response strategy depends on the external push applied. This paper proposes a criterion for balance recovery based on initial phase plane by using inverted pendulum mode including angular moment. The step length and step amount are especially considered in step strategy. Furthermore step-one-out strategy is presented for balance recovery planning based on analytical method, which is divided into four phase and takes vertical CoM (Center of Mass) motion into account. The simulation results verify the effectiveness of the proposed method under strong external push.

This paper describes a study of data transformation from CAD systems to virtual assembly (VA) environment based on STEP intended for simulation the assembly and disassembly process. This includes two steps. First export CAD data as STEP format file. Then translate STEP file into VA environment built with WTK toolkit. The transformation is realized based on the analysis of the STEP neutral file which includes the description of geometry information, attribute information, topology information. Step neutral file is composed with EXPRESS language. Because most CAD systems could export STEP format, this method realized the translation from different CAD systems to VA environment.

It is difficulty to get the most reasonable project artificially when the number of the encoding sequences is bigger so a method of computer simulation is introduced. Base on the mathematics model of the zero-coding, the reciprocal of the contrast D, the general number of bright lines, the general number of reticles, and the influence on the zero-coding due to differ photoelectric devices are considered. The project of zero-coding sequences with higher contrast and light-passing efficiency or higher signal-to-noise ratio is achieved via the optimized non-symmetric encoding.