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Purpose As the excessive lifting force can lead to catwalk rollover and well site accidents, the lifting process boundary conditions and structural parameters have a significant effect lifting force, it is important to analysis the structural parameters on the maximum lifting force in the lifting process of power catwalk. Design/methodology/approach A new model is proposed to analyze the influence of structure parameters on its lifting force for lifting power catwalk in this paper, and the geometric and dynamic equations are established according to the different boundary conditions in different stages. In addition, the establishment of dynamics equations is based on D'Alembert's principle. To solve the model, dynamic analysis software is developed, which uses c # call MATLAB to solve the geometric and dynamic equations. The maximum lifting force is analyzed and optimized according to the software, the influence of structural parameters on the maximum lifting force is obtained and the correctness of the optimization is proved by experiments. Findings The best value of offset e is 0. The length of L22 should as small as possible while the installation size of the end of the conveying arm are guaranteed. The length of L1 should as small as possible while ensuring the not exceed the maximum value. The maximum lifting force remain the same in the second phase, the maximum lifting force decreases with the increase of Lcp, Lcpshould as small as possible. The maximum pressure of the hydraulic oil dropped by an average of 13.62% under optimized parameters. Practical implications This paper provides a theoretical basis for the selection of hydraulic winch, which also provides the theoretical basis and data support for the design and optimization of the structural parameters of the power catwalk. Social implications This research has industrial applications in SJ Petroleum Machinery CO.LTD, SINOPEC (China) .CANRIG, North Rig, TESCO, Sichuan HONGHUA petroleum equipment CO.LTD of CNPC., Baoji Oil field Machinery CO.LTD, SJ Petroleum Machinery Co. LTD of SINOPEC, Yantai Jereh Oilfield Services Group CO.LTD, Nanyang clips oil equipment (group) CO. LTD, etc are the likely users. Originality/value A new model is proposed to analyze the lifting force of lifting power catwalk. The model takes into account the inertia force of the structure, development of dynamics software and analysis and optimization of structural parameters. The maximum lifting force is analyzed and optimized according to the software, the influence of structural parameters on the maximum lifting force is obtained and the correctness of the optimization is proved by experiments.

Supercapacitors with high power density, ultralong lifespan and wide range operating temperature have drawn significant attention in recent years. However, monitoring the state of charge in supercapacitors in a cost-effective and flexible way is still challenging. Techniques such as transmission electron microscopy and X-ray diffraction can analyze the characteristics of supercapacitor well. But with large size and high price, they are not suitable for daily monitoring of the supercapacitors’ operation. In this paper, a low cost and easily fabricated fiber-optic localized surface plasmon resonance (LSPR) probe is proposed to monitor the state of charge of the electrode in a supercapacitor. The Au nanoparticles were loading on the fiber core as LSPR sensing region. In order to implant the fiber in the supercapacitor, a reflective type of fiber sensor was used. The results show that this tiny fiber-optic LSPR sensor can provide online monitoring of the state of charge during the charging and discharging process in situ. The intensity shift in LSPR sensor has a good linear relationship with the state of charge calculated by standard galvanostatic charging and discharging test. In addition, this LSPR sensor is insensitive to the temperature change, presenting a great potential in practical applications.

To obtain a high quantum efficiency transmission-mode GaAlAs photocathode, a photocathode with a graded Al composition structure is designed, in which the Al composition of the emission layer is decreased gradually from bulk to surface, and the outermost layer is GaAs. Based on the graded Al composition structure, GaAlAs photocathodes with different thicknesses of GaAs layers are prepared. The experimental results show that the quantum efficiency of the GaAlAs photocathode in blue-green light significantly increased when the thickness of the outermost GaAs achieves a dozen nanometers. The peak quantum efficiency of a GaAlAs photocathode with a nanoscale GaAs layer could achieve 31%, which appears at 620 nm. The nanoscale surface structure has a quantum confinement effect, which is the main factor in the increased quantum efficiency of the GaAlAs photocathode.

Spacecraft attitude and momentum management aims to slow down the accumulation of control momentum gyro (CMG) momentum through active attitude adjustments. This paper is a systematical discussion of the momentum management problem in the inertial space. The paper can be mainly divided into two parts, as follows: (1) dynamical/constraints analyses, and (2) optimal controller design. In the analysis part, the stable momentum equilibrium attitudes and the constraints for successful momentum management are presented. The analyses show that inertial oriented spacecraft with momentum management consideration is required to keep one of its principal axes of inertia perpendicular to the orbital plane. Due to the uncertainty of the inertia property, the requirement of absolute perpendicularity is difficult to obtain. To solve this problem, the second part of the paper presents an optimal momentum management controller, in which CMG momentum is feedback controlled to avoid momentum accumulation. Theoretical...

Based on the studies of the GaAs photocathode, the surface model of the Ga0.37Al0.63As photocathode is investigated and the energy distributions of electrons reaching the surface charge region, reaching the surface and emitting into vacuum are calculated. The (Cs, O) adsorption and photoemission characteristics of the Ga0.37Al0.63As photocathode are studied according to the experiments. We use the quantum efficiency formula to fit the experimental curve, and obtain the performance parameters of the photocathode and the surface barrier parameters. The results show that the surface barrier of the Ga0.37Al0.63As photocathode is similar to that of the GaAs photocathode. The prepared reflection-mode Ga0.37Al0.63As photocathode responds to the blue-green light, while the transmission-mode Ga0.37Al0.63As photocathode is sensitive to the 532 nm light.