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Spintronics-based microwave devices, such as oscillators and detectors, have been the subject of intensive investigation in recent years owing to the potential reductions in size and power consumption. However, only a few concepts for spintronic amplifiers have been proposed, typically requiring complex device configurations or material stacks. Here, we demonstrate a spintronic amplifier based on two-terminal magnetic tunnel junctions (MTJs) produced with CMOS-compatible material stacks that have already been used for spin-transfer torque memories. We achieve a record gain (|S11 | > 2) for input power on the order of nW (

Torpedoes play an irreplaceable role in naval warfare; therefore, it is significant to study the dynamic response of the direct navigation of torpedoes. In order to study the dynamic response of torpedoes under different Munk moment coefficients, the dynamic equation of torpedoes is established based on the momentum theorem and the momentum moment theorem. The linear motion mathematical model of torpedoes is obtained. The relationship between the torpedo and the Munk moment coefficient is derived. The straight-line motion model of the torpedo under different Munk moments is established, and the dynamic properties of the space motion of the torpedo are analyzed. It is found that the Munk moment coefficient increase will lead to an increase in the deflection of the torpedo’s direct motion on each degree of freedom, and the Munk moment coefficient is related to the additional mass matrix. During the design of the torpedo, the added mass should be reduced by changing the shape of the torpedo as much as possible so as to reduce the pitch moment, yaw, and roll moments of the torpedo.

The configuration of marine towing cable changes significantly during the turning process, with the rotating procedure with fixed cable length being the most frequent. To overcome these challenges, the configuration and dynamic properties of the marine towing cable must be addressed. However, under some particular operating situations, the tugboat must release the marine towed cable during rotation, resulting in a constant change in the length of the marine cable. In view of this, the towed cable is discretized into a lumped mass model based on the lumped mass method, and the dynamic analysis model of the rotation process of towed cable with variable length under different release speeds and different depths is established. This is done with reference to the specific parameters of a towed system, combined with the specific sea conditions of a particular sea area. Time-domain coupling analysis is used to determine the dynamic changes in configuration and stress of marine towing cable at various release speeds and depths. The results of the calculations have some guiding relevance for a certain engineering practice.

Waves have an important influence on the motion performances of offshore crane vessels. The floating crane vessel in waves gives rise to the motion of the lifted object which is connected to the hoisting wire. Based on the geometric parameters of a revolving offshore crane vessel, combined with the specific process of the floating crane vessel at work, a model of the offshore crane vessel under full-circle swing hoisting has been established by OrcaFlex. With the change in wave direction, the dynamic response of the system is made and the impact force between the support vessel and the hanging object and the tension of the crane wire under different wave directions is obtained. At the same time, the minimum impact forces between the support vessel and the hanging object and the tension of the crane wire and their wave directions are obtained. According to the calculated result, the optimal design of the full-circle swing hoisting operation of large revolving offshore crane vessel has been determined.

The trawl system plays an irreplaceable role in deep-sea fishing. In the towing process of the trawl system, many complex mechanical phenomena occurs, so it is necessary to analyze the dynamic response of the deep-sea trawl system during the towing process. In this paper, an equivalent mathematical model for predicating the movement of the ocean trawl system is established based on the equivalent net theory. In the proposed method, the lumped mass method is used to simulate the towed cable and some lines with hydrodynamic characteristics are used to simulate the fishing net. The effects of towing speeds on the dynamic characteristics of a rigid truss trawl system and a flexible trawl system during straight-line towing and rotation towing are studied. The results show that it is possible to simulate trawl motion, and the trawling process is well-presented using this equivalent mathematical model. The disadvantage of this method is also obvious, that is, it cannot simulate trawls with a large number of meshes because the proliferation of mesh numbers can lead to difficult computational convergence. The results also demonstrate that during straight-line towing, the higher the speed, the greater the tension of the cable. Due to the rigid truss, the shape of the rigid truss trawl under different towing speeds is not much different, while the shape of the flexible trawl system changes greatly. During rotating towing, the tension of the cable changes abruptly in the initial stage, and then fluctuates periodically in the time domain. With the increase of towing speed, the overall outward floating distance of the trawl increases gradually. This study has a certain reference and guiding role for deep-sea fishing operations.

The coupling effect between the offshore platform and the riser in the offshore platform-riser multi-body system might be greatly increased under heavy external maritime stresses. The system will become significantly more nonlinear. The partial secondary development of OrcaFlex is carried out considering the strong non-linearity of the dynamic positioning (DP) offshore platform-riser multi-body system, combined with the actual offshore construction engineering background and the lumped mass method, based on Python-language embedded programming with the basis of the operation principle of the application program interface (API) and the composition of its modules. To regulate the dynamic positioning of the offshore platform-riser multi-body coupling system, a UKF-PID control approach based on an unscented Kalman filter is presented. Based on the procedures described above, a classical calculation model is created, and the model’s calculation results are compared to those of relevant references, confirming the method’s validity and viability. Finally, the model of the PID-controlled dynamic positioning offshore platform-riser rigid–flexible multi-body system is developed, and a dynamic simulation is performed under specified sea conditions. The findings have implications for engineering practice.

Different burial depths have different effects on the mechanical characteristics of the horizontal lifting of subsea pipelines. With the consideration of the soil resistance to subsea pipelines, combined with the specific sea condition parameters of a certain sea area, and based on the lumped mass method, the subsea pipeline is discretized into a lumped mass model, the dynamic analysis model of the three-point horizontal lifting of subsea pipelines with different burial depths is established. The stress and bending of the pipelines with different burial depths are analyzed. The calculation results with different burial depths are compared. The variation of mechanical characteristics of the process of lifting horizontal pipelines with different buried depths is obtained. The results show that the change of burial depth has a significant influence on the effective tension of the pipeline. With the increase of the burial depth, the maximum degree of stretching of the pipeline first decreases and then increases. Within a certain depth range, burying the pipeline in the seabed can reduce both the effective tension and the intensity of the fluctuation of the effective tension when the pipeline is lifted. The change of burial depths for the shear action is mainly reflected in the numerical values of the shear force. There is no significant impact on the degree and variation fluctuation of the shear force. The conclusions can provide a certain theoretical reference for the design of the process of horizontal pipeline lifting.

A dam breaking is a major flood catastrophe. The shape, depth, and wave Doppler effect of initial water flow are all modified as a result of the interaction of the water body with downstream structures after a dam breach, forming a diffraction and reflection flow field. This study investigates the dam breaking problem of a single liquid, by creating a two-dimensional simplified numerical model using the VOF approach, analysing the interaction and effect between barriers of various forms and the dam failure flow, and explains the problem of a complex flow mechanism involving significant deformation of the free surface of a medium. According to the findings, obstacles of varying forms could obstruct the dam break’s water flow to various degrees, and the viscous dissipation characteristic of the water body at the edge of the obstacle is closely related to the slope of the site. The numerical simulation presented in this study is validated, demonstrating its accuracy for both the gate-pulling and downstream wet-bed scenarios.

When analyzing the dynamic characteristics of marine cables, the static equilibrium state must first be calculated; a dynamic analysis can then be carried out based on the static equilibrium. Since the calculation of the static equilibrium is the basis of dynamic calculation, different methods for the calculation of the static equilibrium will have important impacts on the dynamic response characteristics of cables, which result in cables having different dynamic characteristics. This paper summarizes the research progress in the effects of different methods for the calculation of the static equilibrium on the dynamic response of marine cables during the releasing process, and current methods for their static calculation are more comprehensively developed as well as being more accurate. To study the influence of different static equilibrium calculation methods, with the reference of some specific parameters of a mooring cable, combined with specific sea conditions, through the necessary simplification of the cable releasing process, based on the lumped mass method, mooring cables are discretized into the lumped mass model, and dynamic analysis models of the releasing process of mooring cables under three methods for the calculation of the static equilibriums (the fast static equilibrium calculation method, the analytic catenary calculation method, and the catenary calculation method) are established. The dynamic characteristics of the spatial configurations of mooring cables based on different static equilibrium calculation methods are obtained through time domain coupling analyses. It was found that if the static equilibrium of a cable is calculated, taking into account gravity, buoyancy, wave current resistance, inertia forces, and the axial stiffness of a cable, then the characteristics of a cable during dynamic descent are closest to that of a real situation. The calculation results have a certain guiding significance for specific engineering practices.

The ocean towing system plays an important role in the ocean development process. The motion of a towed body is closely coupled with the motion of a towing cable. In this paper, the lumped mass method is used to discrete a towing cable into a lumped mass model. At the same time, on the basis of some assumptions, the relationship between the expression of Munk moments in the classical towed body kinematics and the expression of the Munk moments in the hydrodynamic analysis software OrcaFlex is established. Based on the above assumptions and the derivation, combined with the specific parameters of a certain sea state and a certain towing system, the dynamic simulation of the towing system is made by OrcaFlex. By changing the different Munk moment coefficients, the real-time response of the cable tension and the towed underwater body under different Munk moments is achieved. The effects of different Munk moment coefficients on the change of the tension are obtained; the six degrees of freedom of the towed body under the action of different Munk moment coefficients are shown. To obtain the spectral density of the six degrees of freedom of the towed body under the action of different Munk moment coefficients, Fast Fourier Transform is performed on the calculated results of the towed body in the time domain. The results provide a theoretical basis for the optimal design of a cable and towed body.

There is a large proportion of pool fire occurrence on the upper part of offshore platforms. In order to reduce the occurrence of fire disasters, the fire risk assessment of FPSOs should be carried out. According to the temperature characteristics of offshore platform fires based on computational fluid dynamics, the temperature field of the superstructure of the offshore platform under pool fire has been analyzed, the regularities of the distribution of the wall temperature of the platform of FPSO under different wind speeds are studied, and research on the distribution of heat radiation flux of different fire is made. Based on the finite element method, the structural response of the platform structure in different fire scenarios has been made. In consideration of the pool fires caused by liquid leakage of the upper part of the platform structure, with the basis of the changes of temperature field and radiation field being obtained by CFD, a structural response analysis of the offshore platform structure using the finite element method and a risk assessment method based on quantitative analysis for pool fires caused by liquid leakage is proposed.

In the actual process of the submarine cable laying, there are problems of excessive cost and long time spent on the project. Therefore, it is necessary to predict the process to improve the safety...

In consideration of the bend moment and torque, the lumped mass method was derived. Based on the lumped mass method, the umbilical cable was discretised into a lumped mass model and the interferenc...

Subsea pipelines are being installed in the Arctic or deeper water. There is an increased interest in improving leak detection system capabilities throughout the pipeline industry. In this paper, a...

Biomass is an important parameter in fermentation processes. The estimation of biomass during fermentation usually uses an off-line method, such as optical density at 600 nm (OD600) or the determination of dry cell weight (DCW). Online measurement of biomass via mid-infrared (MIR) spectroscopy has also been published. However, no strict demonstration has been given that biomass measurement by MIR is due to the specific absorption of infrared radiation by cells. Three factors are analyzed about cell absorption, which being: optical sampling theory, spectral absorbance intensity inspection, and PLS regression of cells model. Three aspects lead to the conclusion that the measurement of biomass by MIR is not due to specific absorption by bacteria but rather to a chance correlation with the substrate glutamate in this study. If a chance correlation is present, the biomass can be measured by this indirect method. The most reliable measurement method is still by DCW or OD600. It is frustrating that the online measurement of biomass still remains uncertain.

As the demand of marine resources is continuously growing, more and more people are focusing on the study of underwater towed system for marine survey, in which mastering and predicting the dynamic characteristic of the system is the key problem. Based on the parameters of a certain underwater system, combined with the lumped mass method, the underwater cable-body 3D motion mathematical model has been established by OrcaFlex, in which the variation of the tension of the towed cable and the variation of the depth of the towed body have been given and the effect of the towed speed on critical radius in the process of the 360° rotary motion has been discussed. The results show a good agreement with previous research results. At the same time, we also make a research on the effects of the change of the hydrodynamic coefficients and the parameters of towed cable on variation of the tension and towed depth. These studies can provide a basis for the selection of cable in the system.

The new continuum model mentioned in this paper is developed based on optimal velocity car-following model, which takes the drivers’ anticipation effect into account. The critical condition for traffic flow is derived, and nonlinear analysis shows density waves occur in traffic flow because of the small disturbance. Near the neutral stability line, the KdV–Burgers equation is derived and one of the solutions is given. Numerical simulation is carried out to show the local cluster described by the model.

Flow interference between an upstream stationary cylinder and an inline oscillating cylinder is studied with the lattice Boltzmann method. With a fixed Reynolds number Re = 100 and pitch ratio L/D = 4, the effects of oscillation amplitude A/D = [0.25, 1] and frequency f e/f s = [0.5, 2] are investigated. The wake response state is categorized into lock-in and non-lock-in. The lock-in zone in the bifurcation diagram of amplitude versus frequency is discontinuous. Response states of upstream and downstream wakes are similar under the conditions of small amplitude or low frequency. However, with large oscillating parameters, the two wakes are prone to be in different states as the flow field becomes irregular. Two distinct flow regimes have been identified, i.e., single-cylinder and two-cylinder shedding regimes. The presence of single-cylinder shedding regime is attributed to the low shedding frequency of the downstream cylinder at large amplitude. Hydrodynamic forces of the oscillating tandem system are discussed. The results reveal that forces on the two cylinders behave differently and that the absence of vortices in the gap flow significantly reduces the forces exerting on the tandem system.