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Most interaction control formulations focused on electrically driven parallel mechanism. In this paper, the combining practice applications of compliant motion control technique on six degrees of freedom (6-DOF) hydraulic parallel mechanism (HPM) are investigated. According to the manipulation task specification and hydraulic control system characteristics, three different compliant motion control schemes are presented in three typical application scenarios, respectively: a parallel position/force control scheme in the joint space coordinate for train curve negotiation performance test, a hybrid position/force control scheme with the internal force suppression for shaking table with actuation redundancy, and a hybrid impedance control scheme for auto-docking mechanism based on force and vision. The feasibility and effectiveness of the proposed schemes were verified through a series of experiments. It showed that the 6-DOF HPM achieves good compliant behavior by applying the proposed compliant motion control techniques. These schemes could also be extended to other applications where the compliant motion of the 6-DOF HPM is required.

Microbial enhanced oil recovery (MEOR) is a unique technique but remains relatively marginal. However, trials of MEOR in Chinese oil fields are still active. This paper briefly discusses the mechanisms of MEOR, then reports more than twenty MEOR field projects carried out in China since 2000. Those field cases were not well known due to language barrier. The cases were implemented over months or even years. According to field experiences in China, MEOR achieved good success rates, with around 70% of treated wells showing positive responses. Besides, all of the projects were profitable. Traditionally, high temperature and high salinity have been obstacles for field applications of MEOR, but the field cases in China extended the method to more challenging reservoir conditions. MEOR has been tried in tight formations, high-salinity reservoirs, high-temperature reservoirs, and heavy-oil fields. MEOR proved effective for challenging reservoir conditions with careful selection of microbes and proper project execution.

This study aimed to present the characteristics of and to predict subclinical hypocalcemia in dairy cows during the transition period using blood analytes. We examined fluctuations in plasma calcium (Ca), phosphorus (P), bone metabolic markers carboxy-terminal telopeptide of type I collagen (CTX), fibroblast growth factor (FGF23), 1,25(OH)2D3, parathyroid hormone, and other blood biochemical analytes from prepartum week 2 to postpartum day 14 in 116 multiparous high-producing Holstein cows from a free-stall barn dairy farm. With a plasma concentration of Ca 0 considered as an indication of increased risk of subclinical hypocalcemia after calving. The scoring rule had an accuracy of 79.3%, sensitivity of 76.9%, and specificity of 81.3%. The plasma concentrations of FGF23, CTX, and Ca were ideal predictors of postpartum subclinical hypocalcemia in dairy cows.

The effects of bleomycin and rapamycin on cellular senescence and differentiation of rabbit annulus fibrosus stem cells (AFSCs) were investigated using a cell culture model. The results showed that bleomycin induced cellular senescence in AFSCs as evidenced by senescence-associated secretory phenotype. The morphology of AFSCs was changed from cobblestone-like cells to pancake-like cells. The senescence-associated β-galactosidase activity, the protein expression of P16 and P21, and inflammatory-related marker gene levels IL-1β, IL-6, and TNF-α were increased in bleomycin-treated AFSCs in a dose-dependent manner. Rapamycin treatment decreased the gene expression of MMP-3, MMP-13, IL-1β, IL-6, TNF-α, and protein levels of P16 and P21 in bleomycin-treated AFSCs. Furthermore, neither bleomycin nor rapamycin changed the ribosomal S6 protein level in AFSCs. However, the phosphorylation of the ribosomal S6 protein was increased in bleomycin-treated AFSCs and decreased in rapamycin-treated AFSCs. AFSCs differentiated into adipocytes, osteocytes, and chondrocytes when they were cultured with respective differentiation media. Rapamycin inhibited multi-differentiation potential of AFSCs in a concentration-dependent manner. Our findings demonstrated that mammalian target of rapamycin (mTOR) signaling affects cellular senescence, catabolic and inflammatory responses, and multi-differentiation potential, suggesting that potential treatment value of rapamycin for disc degenerative diseases, especially lower back pain.

In order to promote the research and development on evaluating the seismic performance of structures, China State Construction Engineering Corporation (CSCEC) planned to construct a large-scale loa...

Purpose The purpose of this paper is to propose a hybrid position/force control scheme using force and vision for docking task of a six degrees of freedom (6-dof) hydraulic parallel manipulator (HPM). Design/methodology/approach The vision system consisted of a charge-coupled device (CCD) camera, and a laser distance sensor is used to provide globe relative position information. Also, a force plate is used to measure local contact forces. The proposed controller has an inner/outer loop structure. The inner loop takes charge of tracking command pose signals from outer loop as accurate as possible, while the outer loop generates the desired tracking trajectory according to force and vision feedback information to guarantee compliant docking. Several experiments have been performed to validate the performance of the proposed control scheme. Findings Experiment results show that the system has good performance of relative position tracking and compliant contact. In whole docking dynamic experiment, the amplitudes of contact forces are well controlled within 300 N, which can meet perfectly the requirement of the amplitude being not more than 1,000 N. Originality/value A hybrid position/force control scheme using force and vision is proposed to make a 6-dof HPM dock with a moving target object compliantly.

Background: Ischemic spinal cord injury (ISCI) results in the motor sensory dysfunction of the limbs below the injury site. In response to the injury, astrocytes develop into neuroprotective astrocytes (A2s) to mitigate the damage. Methods: We used the abdominal aortic occlusion model in vivo. Immunohistochemistry was used to detect the distribution of A2s in the spinal cord. We used an Oxygen Glucose Deprivation(OGD) method to model astrocytes ischemia in vitro, and tested proliferation, migration, and excitability of A2 astrocytes using an Edu, wound scratch assay, and a calcium-ion probe. After adjustment miR-21, we detected the model and target genes of A2s using polymerase chain reaction, Western blot, immunofluorescence, and chromatin immunoprecipitation. Findings: These results showed that miR-21 could regulate the conversion between A1s and A2s and that A2s mediated synapsis by targeting gpc6 and neurite growth by means of gdnf via the STAT3 pathway. Interpretation: miR-21 is a switch to regulate the polarization of reactive astrocyte, and promoted synapsis formation and nerites growth after acute ISCI. Funding Statement: Grant support was provided by the National Natural Science Funds of China (Nos. 81401014, 81771346), the Chinese Postdoctoral Science Foundation (No. 2014M561935), and the Chinese Postdoctoral Science Foundation (No. 2015T80725), Technology Research and Development Program of Jinan City(No. 201704133). Declaration of Interests: All authors: No reported conflicts. Ethics Approval Statement: All procedures were performed in accordance with the animal care standards of the Chinese National Institute of Health(CNIH) and regulations of the Taishan medical university Committee for the Care and Use of Laboratory Animals.

Adaptive inverse control (AIC) is an advanced control technology which can efficiently learn and control the severely nonlinear and real-time plant, such as the electrohydraulic shaking table (EST). The foundation of AIC is the system identification of the plant via an adaptive filer. The traditional adaptive filter theory is known as a fixed tap-length (length of the weight vector) FIR (Finite impulse response) filter whose weights change by adaptive algorithm automatically. The mismatch between plant and the fixed tap-length will cause inaccuracy or compute complexity. This paper introduce a variable tap-length NLMS(VTLNLMS) algorithm to find the optimum tap-length (OPTL) of the model of multi-DOF EST, then use AIC to improve the accuracy of time wave replication. The dynamics response nonlinear model of the EST is built to reflect the experimental situation. The nonlinear EST model and referred algorithm are simulated in MATLAB/Simulink. Results show the AIC with OPTL is effective in the EST.

With the depletion of light oil, heavy oil is becoming one of the most promising resources for meeting future energy consumption. Heavy oil resources are abundant, but the traditional water flooding method can only achieve less than 20% of heavy oil recovery. Thermal recovery has proven effective in producing heavy oil, but not suitable for many heavy oil formations that are either thin or buried deep underground. Carbon Dioxide injection is a ‘win-win’ enhanced oil recovery (EOR) technique for many heavy oil fields. Injected CO2 not only increases heavy oil output, but also traps injected CO2 underground. Carbon dioxide effectively recovers heavy oil thanks to several mechanisms, including oil swelling, viscosity reduction, and blow-down recovery. This review discusses the advances of CO2 flooding at both laboratory scale and field scale. Laboratory tests show that CO2 can significantly improve heavy oil recovery. Several field cases in the USA, Turkey, Trinidad, and China are reviewed. Field experiences show that CO2 flooding is a successful EOR method for heavy oil fields. However, some issues were encountered in field applications, such as early gas breakthrough, corrosion, CO2 availability, and high costs.

The strong dynamic coupling exists in each channel of 6-DOF motion simulator. Aiming at this problem, singular value decomposition is used to transform coupling physical space to decoupling space of motion simulator. PID controller of decoupling space for each channel of motion simulator is designed, which realizes dynamic decoupling of motion simulator and optimal regulation of control parameter of each channel. The experiment results verify the effectiveness of the proposed dynamic decoupling control strategy.

In order to improve the accuracy performance of a six degree-of-freedom (DOF) redundantly actuated parallel mechanism (RAPM), a self-calibration method based on sensor redundancy is presented. The kinematic model of the RAPM is built and its 44 identifiable parameters are determined by QR decomposition of the identification matrix. Consequently, the self-calibration algorithm is formulated and the least-squares method is used to correct kinematic parameters. A guideline for selection of measurement configurations is presented. Numerical simulations are performed to confirm the validity of the proposed calibration algorithm. Simulation results show that the average parameter error of 2.23 mm is reduced to 0.12 mm, and the position and orientation accuracy of the platform can reach 0.05 mm and 0.16 mrad after calibration.

To develop a new method for separating the residual liquid of peroxide urea production by the formation of gas hydrate, the equilibrium of the system water + hydrogen peroxide + urea + carbon dioxide was studied under the conditions of P ) (1.2 to 1.9) MPa and T ) (272.15 to 275.15) K. The equilibrium pressure and temperature of gas hydrate formation were investigated at the different concentrations of hydrogen peroxide and urea with the anionic surfactant sodium dodecyl sulfate (SDS) and the sodium dodecyl benzene sulfonate (SDBS) in the system and without either. It was found that the equilibrium pressure of gas hydrate formation increased with the increase of temperature and the mass fraction of hydrogen peroxide and urea. The addition of anionic surfactant SDBS and SDS lowered the equilibrium pressure of the gas hydrate formed. The equilibrium pressure of the gas hydrate formed was calculated by Chen-Guo thermodynamic model, and the calculated values were in accord with the experimental results.

Keywords: Motion simulator; Dynamic model; Movement decomposition; Model simplification Abstract. Highly nonlinearity and strong dynamic coupling exist in 6-DOF motion simulator. Usually, in order to make the system has good dynamic and static quality, a good controller need to be designed according to the nature of the dynamic model. Therefore, the research about the simplified dynamic model used for real-time solution will be very meaningful. First, KANE method is used to build complete compact multi-rigid-body dynamic model. Second, rigid body and movement decomposition method are used to split dynamic model. On this basis, simplified strategy of the dynamic model of 6-DOF motion simulator based on dynamic contribution factor is proposed. Finally, the simulation verifies that the simplified dynamic model can be real-time calculated with high efficiency.

In this paper, a novel embedded servo controller is design and implemented for 6-DOF motion system which adopts the multi-agent concept and rapid control prototyping technology. Through using multi-agent concept, the control system of 6-DOF motion system is divided into several cooperated controller agents with natural hierarchy. And the embedded servo controller is designed as an agent controller corresponding to the unique role for actuator's position control. Through transforming agent controllers to cooperated agent tasks, the modularization design object for hardware and software levels of 6-DOF motion system is easily achieved. Furthermore, by using simulink and real-time workshop based on RCP technology, the agent tasks are efficiently implemented which accelerate and simplify the development process of embedded controller. The validation test and analysis results show that the designed servo controller achieved desired functions and performance.

The copolymerization of styrene with N-phenyl maleimide in the presence of organomodified montmorillonite or Na+ montmorillonite was investigated. The conversion of the monomer was determined dilatometrically or gravimetrically. The copolymerization rate was accelerated and the polymerization activation energy in bulk and solution copolymerization decreased in the presence of montmorillonite. The tendency of alter-copolymerization was enhanced for bulk and solution polymerization, but not affected for emulsion polymerization, by the addition of organomodified montmorillonite or Na+ montmorillonite. X-ray diffraction studies showed that the methods of emulsion and bulk intercalative polymerization were more appropriate techniques for preparing nanocomposites with good dispersibility of clay. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1932–1937, 2005

With the depletion of light oil, heavy oil is becoming one of the most promising resources to meet future energy consumption. It is estimated that total resources of heavy oil are 3396 billion barrels worldwide. Water flooding can only achieve less than 20% of heavy oil recovery. Thermal recovery has been proven as a feasible method to recover heavy oil. But it is not suitable for thin layers and deep reservoirs due to excessive heat loss. Polymer flooding and CO2 flooding are potential EOR techniques for the heavy oil reservoirs not suitable for thermal recovery. However, polymer degradation and high costs seriously hinder its field applications. Carbon Dioxide immiscible flooding effectively recovers heavy oil thanks to several mechanisms, such as oil swelling, viscosity reduction and blow-down recovery. This paper discusses the developments in CO2 immiscible flooding at laboratory scale as well as field scale. Laboratory tests show that CO2 can significantly improve heavy oil recover by 30%. Several field cases in USA, Turkey and Trinidad are reviewed. Field experiences show that CO2 flooding is a successful EOR method for heavy oil fields. However, some issues are encountered in field applications, including early gas breakthrough, corrosion, CO2 availability and high costs.

Welan gum (WLG) has been widely used in food industry as thickener. This paper studies its potential applications in upstream petroleum industry. Welan gum was added to drilling mud, and rheology tests were conducted to evaluate mud performance. Experiments demonstrate welan gum effectively boosts mud viscosity. WLG mud also shows strong stability under high temperature and high concentrations of salts. Welan gum has good potential as mud thickener. Rheology tests were also carried out for the aqueous solution of welan gum. Viscosity of WLG solution remained high after addition of sodium chloride and calcium chloride. Long term heating has limited effect on its viscosity. Recovery tests show welan gum can improve oil recovery, and speed up recovery process. Welan gum has good potential for enhanced oil recovery.