In this paper, an alternative method to predict the noise of a submersible Axial Piston Pump (APP) for different valve seat materials is presented. The proposed method is composed of an Artificial Neural Network (ANN) model trained using experimental data and integrated with a hybrid algorithm consists of Cat Swarm Optimization (CSO) and Firefly Algorithm (FA) algorithms. The hybrid CSFA algorithm is used as a subroutine in the ANN model to estimate the ANN weights. The FA is used as local operator to improve the exploitation ability of CSO. The obtained results prove the excellence of the proposed method in predicting the noise of APP considering four different valve seat materials (Polytetrafluoroethylene (PTFE), Polyetheretherketone (PEEK), Aliphatic polyamides (NYLON), and stainless steel (316 L)), five speed levels, and six system pressures. Moreover, the effects of different mechanical properties of the valve seat materials as well as operating conditions (speed and system pressure) have been investigated.

Noise prediction of axial piston pump based on different valve materials using a modified artificial neural network model

Layered two-dimensional materials can potentially be utilized for organic solvent nanofiltration (OSN) membrane fabrication owing to their precise molecular sieving by the interlayer structure and excellent stability in harsh conditions. Nevertheless, the extensive tortuosity of nanochannels and bulky solvent molecules impede rapid permeability. Herein, nanoporous graphene (NG) with a high density of sp2 carbon domain was synthesized via sequential thermal pore activation of graphene oxide (GO) and microwave-assisted reduction. Due to the smooth sp2 carbon domain surfaces and dense nanopores, the microwave-treated nanoporous graphene membrane exhibited ultrafast organic solvent permeance (e.g., IPA: 2278 LMH/bar) with excellent stability under practical cross-flow conditions. Furthermore, the membrane molecular weight cut-off (MWCO) is switchable from 500 Da size of molecule to sub-nanometer-size molecules depending on the solvent type, and this switching occurs spontaneously with solvent change. These properties indicate feasibility of multiple (both binary and ternary) organic mixture separation using a single membrane. The nanochannel structure effect on solvent transport is also investigated using computation calculations. 

/pdf/microwave-assisted-design-of-nanoporous-graphene-membrane-252iaje6.pdf

Microwave-assisted design of nanoporous graphene membrane for ultrafast and switchable organic solvent nanofiltration

Graphene oxide has aroused significant interest for a range of applications owing to their outstanding physico-chemical properties. Specifically, the presence of a large number of reactive chemical moieties such as hydroxyl, carboxyl, epoxide, and sp2 carbon allows these novel materials to be tailored with additional functionalities with the purpose of tuning intrinsic properties. There has been a vivid discussion on the non-covalent modification of GO; however, a comprehensive summary of the chemical functionalization which enables forming a stable particle is still elusive. Hence, in this study, we summarize recently advanced methodologies used for designing the functional GO for their use in specific applications. Together with a brief discussion on the essential characterization techniques, this study will provide fundamental insight into the latest developments in the preparation of covalently modified GO derivatives, thereby leading to their broader utilization in future.

Functional groups in graphene oxide.

Effect of materials on the noise of a water hydraulic pump used in submersible

Simulation and analysis of a seawater hydraulic relief valve in deep-sea environment

Natural water is widely used as working or lubricating medium instead of the traditional oil. Hard materials have potential application to solve the abrasive wear caused by the silt suspending in natural water and poor lubrication of water. As the candidate materials can worked in water, the tribological characteristics of the tribological properties of high velocity oxy-fuel (HVOF) spraying WC–10Co–4Cr coating combined with sintered Si 3 N 4 were investigated under different natural water lubrication, including natural silt-laden and filtered water from sea and river. In addition, distilled water was used as typical water lubricants to study the effect on the tribological behaviours. The tribological results of the tribopair exhibit excellent friction and wear resistance behaviours under the natural waters. The average steady-state friction coefficients of the tribopair under natural water are below 0.009, whilst the average wear rates under all natural waters are below 9 × 10 − 12  cm 3 /(N·m) for both materials. The results indicate that the WC–10Co–4Cr/Si 3 N 4 tribopair owns wider applicability to different natural waters. The water hydraulic components with this tribopair can work in different water areas in word, even unfiltered natural waters as pressure medium.

The applicability of WC–10Co–4Cr/Si3N4 tribopair to the different natural waters

Angstrom-confined solvents in 2D laminates can travel through interlayer spacings, through gaps between adjacent sheets, and via in-plane pores. Among these, experimental access to investigate the mass transport through in-plane pores is lacking. Our experiments allow an understanding of this mass transport via the controlled variation of oxygen functionalities, size and density of in-plane pores in graphene oxide membranes. Contrary to expectations, our transport experiments show that higher in-plane pore densities may not necessarily lead to higher water permeability. We observed that membranes with a high in-plane pore density but a low amount of oxygen functionalities exhibit a complete blockage of water. However, when water-ethanol mixtures with a weaker hydrogen network are used, these membranes show an enhanced permeation. Our combined experimental and computational results suggest that the transport mechanism is governed by the attraction of the solvents toward the pores with functional groups and hindered by the strong hydrogen network of water formed under angstrom confinement.

/pdf/mass-transport-via-in-plane-nanopores-in-graphene-oxide-2u533g64.pdf

Mass Transport via In-Plane Nanopores in Graphene Oxide Membranes.

2-Dimensional materials-based membranes have been considered as promising candidates for water purification. Here, we report that graphene oxide (GO) membrane can reject aquatic humic acid (HA) up to 94.2% in a 2-bar pressurized filtration process. In-depth analysis indicated that the filtration performances such as water flux and rejection rate depend on the thickness and physical structure of the membranes. The experimental study reveals that the GO membrane with a mass loading of 0.58 mg/cm^2, which is approximately equivalent to 3 μm thickness, is required to reach the rejection rate of HA at 94% using 2 bar pressurized filtration method. We further confirmed the membranes’ integrity by over 98% rejection of methylene blue (MB). For practicality, we tested our membrane in tubular form by coating GO on PVDF hollow fibres, which presented similar rejection performances using vacuum filtration method while maintaining the water flux around 100 L m^−2 h^−1 bar^−1. Graphical abstract

/pdf/graphene-oxide-membranes-for-effective-removal-of-humic-acid-3kdvq4lh.pdf

Graphene oxide membranes for effective removal of humic acid

The tribopairs of water hydraulic plunger pumps are usually operated under severe conditions, due to the poor lubrication of water and silt suspended in natural water. It is essential to identify the desired engineering materials and material combinations for designing water pumps. As the candidate materials of tribopairs, the tribological characteristics of different Al2O3-TiO2 coatings combined with Si3N4 ceramics under silt-laden water and tap water lubrication were investigated. The Al2O3-TiO2 coatings with different weight percentages of TiO2 in a wide range from 3 to 100% were tested. The tribological characteristics of the various couple pairs were researched using a ring-on-ring test rig. The microstructures of the contact surfaces were analyzed with a scanning electron microscope before and after the test to study the wear mechanism. The experimental results indicate that the friction coefficient of the Al2O3-TiO2/Si3N4 tribopairs increases with an increase in the percentage of TiO2 conte...

The Tribological Behaviors of Different Mass Ratio Al2O3-TiO2 Coatings in Water Lubrication Sliding against Si3N4

The invention discloses a semi-active heave compensation system for a cabled underwater robot. The semi-active heave compensation system for the cabled underwater robot comprises a passive heave compensation unit, an active heave compensation unit and an underwater armoured cable unit, wherein the passive heave compensation unit is used for compensating for static loads of the underwater armoured cable unit; the active heave compensation unit is used for compensating for dynamic loads of the underwater armoured cable unit; and the underwater armoured cable unit comprises an armoured cable, a relay, a mooring cable and the underwater robot. According to the semi-active heave compensation system for the cabled underwater robot, on the basis that the passive heave compensation unit compensates for the static loads, the active heave compensation unit plays an auxiliary compensation role so as to overcome the dynamic loads, the armoured cable of the underwater armoured cable unit moves in the direction opposite to the direction of heave movement of a mother ship, and thus tension fluctuation of the armoured cable and the oscillation amplitude of the relay are reduced. Through the mode of mechanically combining passive heave compensation and active heave compensation, the heave compensation efficiency of the system is further improved on the basis of reducing the energy consumption of the system, and the system is suitable for large-depth, large-load, long-time and high-efficiency heave compensation occasions of the cabled underwater robot.

Semi-active heave compensation system for cabled underwater robot

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