Technique for Ecological Pond Breeding of Charybdis japonica

In 2016 and 2017,the ecological pond breeding experiment of Charybdis japonica was carried out,with a total of experimental area up to 4 ha.Through two years of experimental research,it obtained a total of 48950 kg of C.japonica,with an average output of 12237.5 kg/ha.The production output value was 2.3675 million yuan,the total production cost was 831700 yuan,the net profit was 1.5358 million yuan,the average profit was 384000 yuan/ha,and the input-output ratio was 1∶2.85.The average proportion of C.japonica population with a production weight of 150 g or more was 7.9%.The proportion of the group of 120-150 g was relatively large,with an average of 80%in two years,and the proportion of the group below 120 g was relatively small,with an average of 12%in two years.The cumulative harvest of shellfish in two years was 65700 kg,with an average output of 16425 kg/ha,the production output value of 738100 yuan,the production cost of 295500 yuan,the net profit of 442600 yuan,and the average profit of 110700 yuan/ha.

A Simple FEM for Solving Two-Dimensional Diffusion Equation with Nonlinear Interface Jump Conditions

In this paper,we propose a numerical method for solving parabolic interface problems with nonhomogeneous flux jump condition and nonlinear jump condition.The main idea is to use traditional finite element method on semi-Cartesian mesh coupled with Newton’s method to handle nonlinearity.It is easy to implement even though variable coefficients are used in the jump condition instead of constant in previous work for elliptic interface problem.Numerical experiments show that our method is about second order accurate in the L1 norm.

A Review:From Aquatic Lives Locomotion to Bio-inspired Robot Mechanical Designations

With the development of camera technology,high-speed cameras have greatly contributed to capturing the movement and posture of animals,which has dramatically promoted experimental biology research.At the same time,with the concept of bionics gradually gaining popularity among researchers,the design of robots is absorbing more and more biological features,where the interest in the bio-inspired robot is hewed out.Compared with the traditional robot,the bio-inspired robot imitates the motion pattern to achieve similar propulsion features,which may be more effective and reasonable.In this paper,the motion patterns of aquatic animals are divided into four categories according to their propulsion mechanisms:drag-based,lift-based,jet-based,and interface-based.And bio-inspired robots imitating aquatic prototypes are introduced and reviewed.Finally,the prospect of aquatic bio-inspired robots is discussed.

Unidirectional transport in amorphous topological photonic crystals

Many works on topological insulators have focused on periodic lattice systems,where short-and long-range order is considered.Here we construct a two-dimensional amorphous photonic crystal with short-range order and a controllable level of long-range order and experimentally investigate the transport of topological edge states in this amorphous system.We demonstrate that topology properties remain constant with unidirectional edge state propagation,immune to specific disorder strength.The partition phenomena of edge states are also observed at the intersection of four topological channels in microwave experiments.This proposed amorphous configuration provides new opportunities to explore the relationship between short-range order and topology and may alleviate the fabrication difficulties of topological optical devices for practical applications.

Robust RGB-D Camera and IMU Fusion-based Cooperative and Relative Close-range Localization for Multiple Turtle-inspired Amphibious Spherical Robots

In the narrow, submarine, unstructured environment, the present localization approaches, such as GPS measurement, dead?rcckoning, acoustic positioning, artificial landmarks-based method, are hard to be used for multiple small-scale underwater robots. Therefore, this paper proposes a novel RGB-D camera and Inertial Measurement Unit (IMU) fusion-based cooperative and relative close-range localization approach for special environments, such as underwater caves. Owing to the rotation movement with zero-radius, the cooperative localization of Multiple Turtle-inspired Amphibious Spherical Robot (MTASRs) is realized. Firstly, we present an efficient Histogram of Oriented Gradient (HOG) and Color Names (CNs) fusion feature extracted from color images ofTASRs. Then, by training Support Vector Machine (SVM) classifier with this fusion feature, an automatic recognition method of TASRs is developed. Secondly, RGB-D camerabased measurement model is obtained by the depth map In order to realize the cooperative and relative close-range localization of MTASRs, the MTASRs model is established with RGB-D camera and IMU. Finally, the depth measurement in water is corrected and the efficiency of RGB-D camera for underwater application is validated. Then experiments of our proposed localization method with three robots were conducted and the results verified the feasibility of the proposed method for MTASRs.

Development of an Amphibious Turtle-Inspired Spherical Mother Robot

Robots play an important role in underwater monitoring and recovery operations, such as pollution detection, submarine sampling and data collection, video mapping, and object recovery in dangerous places. However, regular-sized robots may not be suitable for applications in some restricted underwater environments. Accordingly, in previous research we designed several novel types of bio-inspired microrobots using Ionic Polymer Metal Composite （IPMC） and Shape Memory Alloy （SMA） ac- tuators. These microrobots possess some attributes of compact structure, multi-functionality, flexibility, and precise positioning. However, they lack the attributes of long endurance, stable high speed, and large load capacity necessary for real-world appli- cations. To overcome these disadvantages, we proposed a mother-son robot system, composed of several microrobots as sons and a newly designed amphibious spherical robot as the mother. Inspired by amphibious turtles, the mother robot was designed with a spherical body and four legs with two Degrees of Freedom （DOF）. It is actuated by four vectored water-jet propellers and ten servomotors, and it is capable of walking on land and cruising underwater. We analysed the mother robot＇s walking and underwater cruising mechanisms, constructed a prototype, and carried out a series of experiments to evaluate its amphibious motions. Good motion performance was observed in the experiments.

A Fuzzy PID Algorithm for a Novel Miniature Spherical Robots with Three-dimensional Underwater Motion Control

We proposed and developed a small bionic amphibious spherical robot system for tasks such as coastal environment monitoring and offshore autonomous search and rescue.Our third-generation bionic small amphibious spherical robots have many disadvantages,such as the lack of maneuverability and a small operating range.It is difficult to accomplish underwater autonomous motion control with these robots.Therefore,we proposed a fourth-generation amphibious spherical robot.However,the amphibious spherical robot developed in this project has a small and compact design,with limited sensors and external sensing options.This means that the robot has weak external information collection capabilities.We need to make the real time operation of the robot's underwater motion control system more reliable.In this paper,we mainly used a fuzzy Proportional-Integral-Derivative(PID)control algorithm to design an underwater motion control system for a novel robot.Moreover,we compared PID with fuzzy PID control methods by carrying out experiments on heading and turning bow motions to verify that the fuzzy PID is more robust and exhibits good dynamic performance.We also carried out experiments on the three-dimensional(3D)motion control to validate the design of the underwater motion control system.

Design, Implementation and Control of an Amphibious Spherical Robot

We proposed and implemented a leg-vector water-jet actuated spherical robot and an underwater adaptive motion control system so that the proposed robot could perform exploration tasks in complex environments.Our aim was to improve the kinematic performance of spherical robots.We developed mechanical and dynamic models so that we could analyze the motions of the robot on land and in water.The robot was equipped with an Inertial Measurement Unit(IMU)that provided inclination and motion information.We designed three types of walking gait for the robot,with different stabilities and speeds.Furthermore,we proposed an online adjustment mechanism to adjust the gaits so that the robot could climb up slopes in a stable manner.As the system function changed continuously as the robot moved underwater,we implemented an online motion recognition system with a forgetting factor least squares algorithm.We proposed a generalized prediction control algorithm to achieve robust underwater motion control.To ensure real-time performance and reduce power consumption,the robot motion control system was implemented on a Zynq-7000 System-on-Chip(SoC).Our experimental results show that the robot’s motion remains stable at different speeds in a variety of amphibious environments,which meets the requirements for applications in a range of terrains.

AN IMPROVED NON-TRADITIONAL FINITE ELEMENT FORMULATION FOR SOLVING THE ELLIPTIC INTERFACE PROBLEMS

We propose a non-traditional finite element method with non-body-fitting grids to solve the matrix coefficient elliptic equations with sharp-edged interfaces. All possible situations that the interface cuts the grid are considered. Both Diriehlet and Neumann boundary conditions are discussed. The coefficient matrix data can be given only on the grids, rather than an analytical function. Extensive numerical experiments show that this method is second order accurate in the L∞ norm.

A Bilinear Petrov-Galerkin Finite Element Method for Solving Elliptic Equation with Discontinuous Coefficients

In this paper,a bilinear Petrov-Galerkin finite element method is introduced to solve the variable matrix coefficient elliptic equation with interfaces using nonbody-fitted grid.Different cases the interface cut the cell are discussed.The condition number of the large sparse linear system is studied.Numerical results demonstrate that the method is nearly second order accurate in the L^(∞)norm and L^(2) norm,and is first order accurate in the H^(1) norm.

A decoupling three-dimensional motion control algorithm for spherical underwater robot

Underwater spherical robots are good assistants for ocean exploration,where motion control algorithms play a vital role.Conventional motion control algorithms cannot eliminate the coupling relationship between various motion directions,which will cause the motion control of various directions to interfere with one other and significantly affect the control effect.This study proposes a new decoupling motion control algorithm based on the robot attitude calculation for an underwater spherical robot designed for offshore,shallow water,and narrow terrain.The proposed method uses four fuzzy proportional-integral-derivative(PID)controllers to independently control the robot’s movement in all directions.Experiments show that the motion control algorithm proposed in this study can significantly improve the flexibility and accuracy of the movement of underwater spherical robots.