PLA Navy Submarine Academy

An acidification metabolite such as volatile fatty acids (VFAs) and ethanol could be used as denitrification carbon sources for solving the difficult problem of carbon source shortages and low nitrogen removal efficiency. A proper control of environmental factors could be essential for obtaining the optimal contents of VFAs and ethanol. In this study, suspended solids (SS), oxidation reduction potential (ORP) and shaking rate were chosen to investigate the interactive effects on VFAs and ethanol production with waste sludge. It was indicated that T-VFA yield could be enhanced at lower ORP and shaking rate. Changing the SS, ORP and shaking rate could influence the distribution of acetic, propionic, butyric, valeric acids and ethanol. The optimal conditions for VFAs and ethanol production used as a denitrification carbon source were predicted by analyzing response surface methodology (RSM).

In this paper, a series of tests were conducted on the bearings of induction motors to investigate vibration signal analysis-based diagnosis of bearing faults, and a thorough analysis was also conducted. In the engineering field, the kurtosis coefficient of vibration acceleration and the root mean square of vibration velocity, as well as resonant demodulated spectrum analysis of vibration acceleration, have been widely used for bearing fault diagnosis. These are integrated in almost any commercially available device for diagnosing bearing faults. However, the unsuitable use of these devices results in many false diagnoses. In light of this, they were selected as research objects and were investigated experimentally. In three induction motors, faults of different severity in the bearing outer race and cage were modeled for tests, and the corresponding results were used to evaluate the performance of the selected diagnosis methods. Some vague information in engineering was clarified, and some instructive rules were outlined to improve the bearing fault diagnosis performance. Taking the kurtosis coefficient of vibration acceleration (Ku) as an example, in engineering, Ku = 4 is generally taken as the diagnostic threshold of bearing faults. This means the following rule applies: if Ku ≤ 4, the bearing is healthy; otherwise, the bearing is faulty. However, the test results in this paper show that even if Ku ≤ 4, the bearing might be faulty; if Ku > 4, the bearing is indeed faulty. Therefore, the diagnostic rule should be improved as follows: if Ku > 4, the bearing is faulty (which can be assured), and if Ku ≤ 4, the status of the bearing is still undetermined. Thus, this paper can be helpful for researchers to gain an experimental understanding of the selected diagnosis methods and provides some improved rules on their use for reducing false diagnoses.

A decision-making method based on fuzzy theory and Bayesian Rough sets is advanced according to the characteristics of weapon argumentation decision-making. First of all, the decision-making model is established, the comprehensive operational efficiency, cost, cycle and risk are chosen as decision-making factors, and also the evidence theory and the cloud model theory are used to optimize the comprehensive operational efficiency factor. Next, there is the redundancy problem in decision-making factors, so, Bayesian Rough sets is introduced to solve this problem. Simultaneously, there is the relation problem in decision-making factors, therefore, fuzzy measure theory is applied to obtain the weight of each decision-making factor. What's more, Choquet fuzzy integral was used to synthesize all the decision-making factors, then the ultima decision-making result is achieved. Finally, the simulation is carried out, and simulation results show that the method is reasonable and effective.

Aiming at shortcomings of the existing cooperative laying mines method in the joint blockade combat, a new method of cooperative laying mines with the submarine and reconnaissance force is advanced. In the joint blockade combat, reconnaissance forces perform different tasks at different stages of lay mines, and according to different tasks, firstly, cooperative laying mines models of reconnaissance forces for battlefield warning and battlefield guide are constructed respectively. And, the calculation model of mine lines is optimized, then, the cooperate-guide-lay mines model of reconnaissance force and submarine is improved. Finally, the constructed models are simulated, and simulation results show models are rational and effective, moreover, they are more suitable for actual laying mines.

The path planning of Unmanned Underwater Vehicle (UUV) is a crucial aspect of their operation in underwater environments, Meta-heuristic algorithms are extensively utilized for addressing UUV path planning problems. To address the limitations of the traditional dung beetle optimization algorithm (DBO), including inadequate convergence speed and precision in two-dimensional UUV path planning, and its propensity for local optima, an improved dung beetle optimization algorithm (IDBO) is introduced which employing a suite of refinement strategies. Furthermore, the solution capability of the IDBO is validated through the CEC2017 test suite and two-dimensional raster maps that replicate actual underwater environments. The simulation results demonstrate the robust problem-solving capacity of the IDBO, applicable to both benchmark functions and real-world scenarios, affirming the efficacy of the enhancement strategies in practical applications.

Ding, Z.; Zhang, Y.; Wang, Y., and Zhao, Q., 2022. Determining the structural frame damage mechanisms of deep-sea manned submersibles. Journal of Coastal Research, 38(1), 77–85. Coconut Creek (Florida), ISSN 0749-0208. Deployment and recovery data describing the service life of the Jiaolong-manned submersible and its structural frame damage inspection records suggest that the damage sustained by the structural frame could be related to wave loads when the manned submersible is recovered in rough seas. The computational fluid dynamics simulation was used to calculate the wave loads acting on the manned submersible in this article, and the results were used as inputs for a finite element analysis of the structural frame to evaluate the stress in and displacement of the structural frame during manned submersible recovery in rough seas. The results of this analysis indicated that some of the nodes in the structural frame experienced stresses considerably in excess of the permitted limits and approached the yield strength of the material, representing a severe threat to the safety of the Jiaolong-manned submersible when recovered in rough seas.

Haptics is a new and important interaction method for virtual reality. As an important haptic interaction device, force feedback device can improve the reality of interactive operation. In this paper, the force feedback interface (OpenHaptics) is fully analyzed. Physical models are constructed with physical attributes such as friction, stiffness, inertia and gravity added. The principle of simulated physical properties of force feedback device is discussed in detail. The principle of simulated physical properties by force feedback device is described. Taking reducer as an example and using Visual Studio 2008 as a development platform, combined with OpenHaptics library, complete the integration of physical attributes with geometric models and interactive operation simulation of force feedback device.

The Triangular Model of Interpretive Theory put forward by Paris School is one of the most significant theories nowadays, with which the interpreter can fully comprehend the communicative sense of source language by integrating language knowledge and cognitive complement and re-express the sense in a more acceptable way after deverbalization. Therefore, under the guidance of this theory, this paper mainly revolves around difficulties during interpreting in terms of culturally-loaded terms, redundancy, colloquial expressions, logical fuzziness and paratactic-prominent feature in Chinese and put forward some strategies to tackle those difficulties, including free translation, amplification, omission, sentence reorganization and combination. Each of these strategies can be applied to solve several problems.

This study investigates the issue of the three-dimensional deployment for blended-wing-body underwater gliders (BWBUGs) at deep depths. Initially, an underwater three-dimensional deployment optimisation model is formulated, considering factors such as the three-dimensional coverage ratio and the balance of node communication energy consumption. Subsequently, a sine-logistic chaos strategy with excellent ergodicity is proposed. Thereafter, the dynamic decision-assisted heuristic method (DDHM) is proposed based on the dynamic decision framework, sine-logistic chaos strategy, and opposition-based learning. The well-designed dynamic decision framework effectively avoids the premature convergence and local optimum of the algorithm. Additionally, the multi-objective variant of DDHM, referred to as MDDHM, is established utilising the archival mechanism. Lastly, the performance of the DDHM and MDDHM is evaluated by simulation experiments. Statistical analysis demonstrates that DDHM is highly effective for the underwater three-dimensional deployment of the multi-BWBUG cooperative system. Furthermore, its overall performance surpasses that of other comparative methods.

On the bases of nonlinear dynamics theory of phase space reconstruction,the methods for selecting dimension and delay time of reconstructed phase space were analyzed.The similar sequence repeatability(RPT) characters among Lorenz,one ship noise and Gauss noise were contrasted,which indicated that the RPT curve of ship noise had different geometry feature from that of random noise and determinate signal.By improving the definition of nonlinear RPT character,then applying it to ocean target noise analyses,a model for ocean target noise nonlinear RPT character extraction was built.Application on experimental data implied that the nonlinear RPT character could distinguish underwater targets and waterborne targets,underwater low-speed targets and underwater high-speed targets,waterborne large,mid and small targets effectively.So this model for ocean noise nonlinear RPT character extraction can detect different type ocean targets,thus offer a new idea and method for underwater acoustics target detection.

A nonlinear large deformation cable equation system based on arc length is employed to determine the configuration of the cable under current and buoyancy loads. Different from a traditional initial method and a shooting method, we have solved this nonlinear problem as a boundary value problem with nonlinear and global boundary conditions directly. A finite difference scheme is proposed to solve the large deformation cable equation, and the Newton–Raphson iteration is used to search for numerical approximate solution. We demonstrate that this system degenerates into the catenary equation in the case of vanishing bending stiffness for the first time. The solution of the catenary equation serves as the initial guess for the three-section cable problem. This method overcomes the disadvantages of the initial value method and step method, avoiding the need to adjust the boundary location. The spatial shapes of the large deformation cable and the effects of the length and position of the buoyancy section are discussed. The impact of ocean currents is also analyzed using Morison's formula.

To address the issue of evaluating learning quality in virtual assembly teaching systems, an evaluation program that combines Petri nets and the fuzzy comprehensive evaluation method has been designed. First, a systematic learning quality evaluation indicator system is established by integrating the operational mode of the virtual assembly teaching system. Next, a Petri net model of the equipment assembly process is created by analyzing the real assembly process of the equipment. Based on this model, a quantitative scheme for the relevant evaluation indicators is formulated. Subsequently, a course-oriented learning quality evaluation model is developed using the fuzzy comprehensive evaluation method. Finally, a student is used as an evaluation object for example analysis. The constructed fuzzy comprehensive evaluation model processes the data to obtain the student’s overall rating. Practice has shown that this model can effectively assess the quality of student learning, achieving an organic combination of qualitative judgment and quantitative analysis, and providing a reference for evaluating student learning quality.

Purpose The purpose of this paper is to present an algorithm for determining the inner and outer loops of arbitrary parametric surfaces. Design/methodology/approach The algorithm considers two sub-algorithms: one for non-closed surfaces and another one for closed surfaces. The first sub-algorithm named by area positive and negative method (APNM), combines a curve discretization algorithm with the polygon direction judgment algorithm to judge the inner and outer loops of non-closed surfaces. The second sub-algorithm, called by cross-period number method (CPNM), combines a curve discretization algorithm with the periodicity of closed surfaces to judge the type of boundary loops. Findings The APNM can use less CPU time to determining the inner and outer loops of the non-closed parametric surfaces. The CPNM can also determine the inner and outer loops of closed parametric surfaces effectively. The judgment results of loops can ensure that the direction of meshes generated on these surfaces is right. And finally ensure the correctness of the numerical simulation results. Originality/value Several numerical examples presented have verified the robustness and efficiency of the proposed algorithm. Compared with the conventional algorithm, the more complex the model, the more time the APNM saves in the process of determining the inner and outer loops for non-closed surfaces. The CPNM is also a new method to determining the inner and outer loops for closed parametric surfaces. The single run-time of CPNM is very small and can reach the level of microseconds.

Abstract The installation error of an acoustic transceiver array is one of the important error sources in an ultra-short baseline (USBL) system. In a USBL system with a positioning accuracy of 0.5%, an installation error angle of 1° will lead to a positioning error of 1.7% times the slant distance. In this paper, a dual transponder-based installation angle error calibration method for USBL is proposed. First, the positioning errors induced by various installation angles are deduced and analysed using the linear measurement of seafloor targets. Then, an iterative algorithm is proposed that estimates the rolling alignment error, pitching alignment error, and heading alignment error, in that order. The simulation and experienced results show that, after three iterations, the estimates of the three alignment errors can converge quickly, all of the estimates converge to within 0.001° and the estimated values are very close to the true values. The horizontal positioning error caused by the installation error angle can be reduced by nearly 75%. The method has good effectiveness and robustness, and can greatly improve the positioning accuracy of the USBL system.

In order to analyze the interactions among various components of hybrid contra-rotating shaft pod (HCRSP) propulsor and effects of test devices, the model test of HCRSP propulsor was conducted in a cavitation tunnel. In the present study, the interactions among fore propeller, aft propeller, and the pod of HCRSP propulsor are analyzed with the influence of a long-axis dynamometer. It was found that the long-axis dynamometer shows great influence on the pod propulsor, which is made up of a pod and an aft propeller, but little influence on the fore propeller. Especially, under the condition of using a long-axis dynamometer or not, the difference of thrust coefficient and torque coefficient of the aft propeller with a high advance coefficient reached 10%. Also, the fore propeller could accelerate the flow of the pod propulsor. In detail, the pod and aft propeller show blocking and suction effects, respectively, and these impacts could cancel each other out within a certain range.