Development of underwater electric manipulator based on interventional autonomous underwater vehicle (AUV)

In applications such as marine rescue,marine science,archaeology,and offshore industries,autonomous underwater vehicles(AUVs)are frequently used for survey missions and monitoring tasks,with most operations being performed by manned submersibles or remotely operated vehicles(ROVs)equipped with robotic arms,as they can be operated remotely for days without problems.However,they require expensive marine vessels and specialist pilots to operate them.Scientists exploring oceans are no longer satisfied with the use of manned submersibles and ROVs.There is a growing desire for seabed exploration to be performed using smarter,more flexible,and automated equipment.By improving the field operation and intervention capability of AUVs,large-scale and long-range seafloor exploration and sampling can be performed without the support of a mother ship,making it a more effective,economical,convenient,and rapid means of seafloor exploration and sampling operations,and playing a critical role in marine resource exploration.In this study,we explored the integration technology of underwater electric robotic arms and AUVs and designed a new set of electric manipulators suitable for water depths greater than 500 m.The reliability of the key components was analyzed by finite element analysis and,based on the theory of robot kinematics and dynamics,simulations were performed to verify the reliability of the key components.Experiments were conducted on land and underwater,trajectory tracking experiments were completed,and the experimental data in air and water were compared and analyzed.Finally,the objectives for further research on the autonomous control of the manipulator underwater were proposed.

Bifurcation control of solid angle car-following model through a time-delay feedback method

In order to alleviate unstable factor-caused bifurcation and reduce oscillations in traffic flow,a feedback control with consideration of time delay is designed for the solid angle model(SAM).The stability and bifurcation condition of the new SAM is derived through linear analysis and bifurcation analysis,and then accurate range of stable region is obtained.In order to explore the mechanism of the influence of multiple parameter combinations on the stability of controlled systems,a definite integral stabilization method is provided to determine the stable interval of time delay and feedback gain.Numerical simulations are explored to verify the feasibility and effectiveness of the proposed model,which also demonstrate that feedback gain and delay are two key factors to alleviate traffic congestion in the SAM.

Biomaterial types,properties,medical applications,and other factors:a recent review

Biomaterial research has been going on for several years,and many companies are heavily investing in new product development.However,it is a contentious field of science.Biomaterial science is a field that combines materials science and medicine.The replacement or restoration of damaged tissues or organs enhances the patient’s quality of life.The deciding aspect is whether or not the body will accept a biomaterial.A biomaterial used for an implant must possess certain qualities to survive a long time.When a biomaterial is used for an implant,it must have specific properties to be long-lasting.A variety of materials are used in biomedical applications.They are widely used today and can be used individually or in combination.This review will aid researchers in the selection and assessment of biomaterials.Before using a biomaterial,its mechanical and physical properties should be considered.Recent biomaterials have a structure that closely resembles that of tissue.Antiinfective biomaterials and surfaces are being developed using advanced antifouling,bactericidal,and antibiofilm technologies.This review tries to cover critical features of biomaterials needed for tissue engineering,such as bioactivity,self-assembly,structural hierarchy,applications,heart valves,skin repair,bio-design,essential ideas in biomaterials,bioactive biomaterials,bioresorbable biomaterials,biomaterials in medical practice,biomedical function for design,biomaterial properties such as biocompatibility,heat response,non-toxicity,mechanical properties,physical properties,wear,and corrosion,as well as biomaterial properties such surfaces that are antibacterial,nanostructured materials,and biofilm disrupting compounds,are all being investigated.It is technically possible to stop the spread of implant infection.

Numerical study on ethylene-air continuous rotating detonation in annular combustors with different widths

To investigate the impact of combustor width on continuous rotating detonation(CRD)fueled by ethylene and air,a series of 3 D simulations are conducted by changing the inner cylinder radius of an annular combustor while retaining the same outer cylinder radius.The results show that the CRD wave propagates more steadily and faster as the combustor width increases.The high-temperature zone at the backward-facing step preheats the propellants and contributes to the steady propagation of the CRD wave in 25-and 30-mm wide combustors.The highest and the lowest velocities are obtained in the30-and 15-mm wide combustors at,respectively,1880.27 and 1681.01 m/s.On the other hand,the average thrust decreases as the combustor width increases.The highest thrust is obtained in the 15-mm wide combustor while the lowest is in the 30-mm wide combustor,at 758.06 and 525.93 N,respectively.Nevertheless,the thrust is much more stable in the 25-and 30-mm wide combustors than in the 15-and 20-mm wide combustors.

A method to avoid the cycle-skip phenomenon in time-of-flight determination for ultrasonic flow measurement

The double-threshold method has been widely used in ultrasonic flow measurement to determine time-of-flight(TOF)due to its low cost and ease of implementation.Performance of this method is negatively affected by the cycle-skip phenomenon which occurs frequently under inconstant working conditions,especially varied fluid temperature.This paper proposes a method to suppress the phenomenon to facilitate reliable determination of TOF in ultrasonic flow measurement.First,the double-threshold method is used to generate a feature point to segment the signal.Second,based on the correlation coefficient and signal power,judgement factors of individual signal periods are calculated to determine signal onset.Finally,a valid zero crossing which has a constant lag from the onset is selected to determine the TOF.Thus,the cycle-skip phenomenon is suppressed.Two additional modifications are proposed to eliminate the influence of varied signal frequency and low sampling rate.The proposed method was validated by an experiment based on an ultrasonic water flow sensor.Results showed that the frequently appearing cycle-skip phenomenon can be successfully suppressed by the proposed method.

土-膨润土隔离墙孔压静力触探非单调消散曲线研究（英文）

目的:土-膨润土隔离墙的水力特性可通过孔压静力触探试验进行评价。本文旨在研究土-膨润土隔离墙中孔压消散试验产生非单调孔压消散曲线的原因,并对现有计算固结系数与渗透系数的方法在土-膨润土隔离墙中的适用性进行分析。创新点:1.首次在土-膨润土隔离墙中测得非单调的孔压消散曲线;2.本文认为在土-膨润土隔离墙中测得非单调孔压消散曲线是由于探头贯入过程中在填料及其包裹的土块中产生的超孔压不一致引起的,并且由于填料的低渗透性,孔压上升的时间较长;3.比较不同方法的分析结果,并推荐结果与实测相近的计算方法作为工程应用。方法:1.通过室内一维固结试验和柔性壁渗透试验,分别获得墙体材料的固结系数和渗透系数;2.通过现场土-膨润土隔离墙的孔压静力触探试验与孔压消散试验,获得相应的力学参数与孔压消散曲线;3.分别采用不同方法对墙体材料的固结系数和渗透系数进行计算,并将计算结果与室内试验结果进行比较。结论:1.填料的非均质性导致探头贯入过程中产生的超孔压存在重分布,这使得土-膨润土隔离墙中产生了非单调孔压消散曲线,并且由于填料的低渗透性,测得孔压上升的时间较长;2.四种计算固结系数的方法中,有三种结果与室内一维固结试验结果相近,另一种结果则明显偏大;3.四种计算渗透系数的方法中,基于太沙基固结理论的关系式得到的结果与室内柔壁渗透试验结果相近,另两种经验公式得到的结果偏小,而基于探头贯入数据计算的渗透系数则偏大。

实现异步冲击的自动冲击装置:一种针对操作过程中模态测试的实用方案（英文）

目的:目前手动冲击锤设备缺乏对冲击时间的控制,容易引起冲击相位和周期荷载的周期性响应的相位同步问题。本文旨在通过使用异步自动冲击激励的自动冲击装置代替同步冲击模态分析中传统手动冲击锤的方法来解决上述问题。创新点:1.引入具有可调冲击参数的自动冲击装置;2.该装置可通过控制施加冲击的时间步来确保冲击和来自循环载荷组件的响应异步;3.当周期性响应的相位与装置所施加的冲击信号不一致时,加速响应中未知力源的影响会被降到最小。方法:1.分别使用数字方波信号的波峰和波谷来控制自动冲击装置的"开"和"关"状态;2.通过调控样本大小(1024个)、采样率(50 000个/秒)、占空比(0.5%)和冲击频率(97.78 Hz)(或周期)等参数得到不同的冲击图形。结论:1.使用可实现异步冲击的自动冲击装置可以估算第3阶自然模态;2.前3种自然模态可以被成功确定并与基准实验模态分析结果具有良好的相关性,表现为低于1.67%的自然频率差异,1.79%~12.54%的阻尼比差异以及介于0.893和0.925之间的模态置信度。3.针对谐波干扰对相位的影响,相比于使用手动冲击锤来增强频率响应函数估计和模态提取数据,使用可实现异步冲击的自动冲击装置是一种更可行的选择。

考虑受损基元承载影响的岩石统计损伤本构模型及工程应用（英文）

目的:建立三轴压缩作用下考虑受损基元承载影响的岩石材料损伤本构关系,并将其应用于工程实际。创新点:1.进行岩石损伤机理分析,探讨损伤阈值存在的原因,提出损伤修正系数,确定受损基元与无损基元的应力分配关系;2.建立能够反映岩石破裂全过程的损伤本构模型,验证模型的合理性并实现其程序化。方法:1.通过数值计算探讨岩石在初始缺陷下的损伤劣化机理,将不同初始状态的岩石定义为不同岩性的无损材料,建立合理的损伤模型;2.基于Mohr-Coulomb准则,结合连续损伤和统计理论,推导基于受损基元承载影响的岩石材料本构方程;3.与前人试验数据及理论成果进行对比,验证本构模型的合理性,最后利用C++语言编译的动态链接库(DLL)实现有限差分软件FLAC3D的二次开发,实现模型的工程应用。结论:1.岩体损伤劣化是无损基元发生物理性状改变导致材料刚度变小的结果,受损基元与无损基元的应力分配关系与岩体的瞬时损伤状态和应力状态有关;2.建立的岩石损伤本构模型与试验数据的拟合精度较高,能够准确地描述岩石的应力-应变关系;3.数值模拟结果与现场监测数据的吻合程度较高,表明该模型能够合理反映软弱岩体的损伤劣化效应。

Numerical investigation of the power generation of a ducted composite material marine current turbine

In the hostile and highly corrosive marine environment,advanced composite materials can be used in marine current turbines due to their high strength-to-weight ratios and excellent resistance to corrosion.A composite material marine current turbine(CMMCT),which has significant advantages over traditional designs,has been developed and investigated numerically.A substantial improvement in turbine performance is achieved by placement of a duct to concentrate the energy.Computational fluid dynamics(CFD) results show that the extracted power of a ducted CMMCT can be three to four times the power extracted by a bare turbine of the same turbine area.The results provide an insight into the hydrodynamic design and operation of a CMMCT used to shorten the design period and improve technical performance.

3D analysis for pit evolution and pit-to-crack transition during corrosion fatigue

This paper presents a deterministic model to predict the pit evolving morphology and crack initiation life of corrosion fatigue.Based on the semi-ellipsoidal pit assumption,the thermodynamic potential including elastic energy,surface energy and electrochemical energy of the cyclically stressed solid with an evolving pit is established,from which specific parameters that control the pit evolution are introduced and their influence on the pit evolution are evaluated.The critical pit size for crack nucleation is obtained from stress intensity factor criterion and the crack nucleation life is evaluated by Faraday's law.Meanwhile,this paper presents a numerical example to verify the proposed model and investigate the influence of cyclic load on the corrosion fatigue crack nucleation life.The corrosion pit appears approximately as a hemisphere in its early formation,and it gradually transits from semicircle to ellipsoid.The strain energy accelerates the morphology evolution of the pit,while the surface energy decelerates it.The higher the stress amplitude is,the smaller the critical pit size is and the shorter the crack initiation life is.

Immobilization of heavy metals in sludge using phosphoric acid and monobasic calcium phosphate

The purpose of this research is to investigate the potential of pre-treatment with phosphoric acid(PA) and monobasic calcium phosphate(MCP) for the stabilization of heavy metals in sludge and its bottom ash.The tannery sludge samples were collected in Wenzhou,China and heavily contaminated with heavy metals,such as Pb,Cr and so on.The samples were pre-treated with PA or MCP.Then XRD and TCLP tests were adopted as the evaluating methods to characterize the Pb,Cr,Cu,Zn and Cd immobilization in the pre-treated sludge and its bottom ash.The results showed that this treatment effectively immobilized Pb and Cd in the sludge,lightly stabilized the metal Cu,and adversely,enhanced the leachability of Zn.After incineration at 900℃,Pb and Cr in the bottom ash of pre-treated sludge were significantly stabilized due to the formation of their highly thermostable phosphates and pyromorphite-like minerals during the incineration process.However,an increase of Cu and Zn solubility was observed which might be attributable to the acidification of sludge due to the addition of PA or MCP.

Mechanical and electronic properties of diamondlike BC_5

The structural properties,mechanical behavior,and electronic structure of the newly developed diamondlike BC5 (d-BC5) was investigated using density functional theory (DFT) calculations.The results indicate that d-BC5 has great bulk modulus of 393 GPa,large shear modulus of 398 GPa,and high hardness of 62 Pa,and thus support the fact that d-BC5 is an ultra-incompressible and superhard material.Remarkably,the superhard d-BC5 exhibits metallic features.Furthermore,the trend that the mechanical behavior falls with the increase of boron content was revealed.The combination of huge stiffness,high hardness,and good metallicity makes series of diamondlike BCx (d-BCx) valid for wider applications in comparison with pure diamond.

A sensorless and simple controller for VSC based HVDC systems

Voltage source converter high-voltage direct current (VSC-HVDC) is a new po0wer transmission technology pref- erable in small or medium power transmission. In this paper we discuss a new control system based on space vector modulation (SVM) without any voltage line sensors. Using direct power control (DPC) SVM and a new double synchronous reference frame phase-locked loop (DSRF-PLL) approach, the control system is resistant to the majority of line voltage disturbances. Also, the system response has accelerated by using a feed forward power decoupled loop. The operation of this control strategy was verified in a SIMULINK/MATLAB simulation environment. To validate this control system, a 5 kV·A prototype system was constructed. Compared to the original controllers, the current total harmonic distortion (THD), the active and reactive deviations and the DC voltage overshoot were lowered by 2.5%, 6.2% and 8%, respectively. The rectifier power factor in the worst condition was 0.93 and the DC voltage settling time was 0.2 s.

Optimized algorithm for balancing clusters in wireless sensor networks

Wireless sensor networks consist of hundreds or thousands of sensor nodes that involve numerous restrictions in-cluding computation capability and battery capacity.Topology control is an important issue for achieving a balanced placement of sensor nodes.The clustering scheme is a widely known and efficient means of topology control for transmitting information to the base station in two hops.The automatic routing scheme of the self-organizing technique is another critical element of wireless sensor networks.In this paper we propose an optimal algorithm with cluster balance taken into consideration,and compare it with three well known and widely used approaches,i.e.,LEACH,MEER,and VAP-E,in performance evaluation.Experimental results show that the proposed approach increases the overall network lifetime,indicating that the amount of energy required for com-munication to the base station will be reduced for locating an optimal cluster.

Liquid film dryout model for predicting critical heat flux in annular two-phase flow

Gas-liquid two-phase flow and heat transfer can be encountered in numerous fields, such as chemical engineering, refrigeration, nuclear power reactor, metallurgical industry, spaceflight. Its critical heat flux (CHF) is one of the most important factors for the system security of engineering applications. Since annular flow is the most common flow pattern in gas-liquid two-phase flow, predicting CHF of annular two-phase flow is more significant. Many studies have shown that the liquid film dryout model is successful for that prediction, and determining the following parameters will exert predominant effects on the accuracy of this model: onset of annular flow, inception criterion for droplets entrainment, entrainment fraction, droplets deposition and entrainment rates. The main theoretical results achieved on the above five parameters are reviewed; also, limitations in the existing studies and problems for further research are discussed.

A New Technique:Research and industrial application of a novel compound permanent magnet synchronous machine

We propose a novel kind of compound permanent magnet synchronous machine (CPMSM), which is applicable in low-speed and high-torque situations. We first explain the structure of the CPMSM. Based on theoretically deducing the calculation formulae of the CPMSM electromagnetic parameters, we analyze the operating characteristics of the CPMSM, and obtain the power-angle curves and working curves. The no-load magnetic field distribution and the cogging torque are analyzed by applying the finite element method of three-dimensional (3D) magnetic fields, to determine the no-load leakage coefficient and the waveform of the cogging torque. Furthermore, the optimal parameters of the permanent magnet for reducing the cogging torque are determined. An important application target of the CPMSM is in directdrive pumping units. We have installed and tested a direct- drive pumping unit in an existing oil well. Test results show that the power consumption of the direct-drive pumping unit driven by CPMSM is 61.1% of that of the beam-pumping unit, and that the floor space and weight are only 50% of those of a beam-pumping unit. The noise output does not exceed 58 dB in a range of 1 m around the machine when the machine is 1.5 m from the ground.

A network-aware error-resilient method using prioritized intra refresh for wireless video communications

We propose a novel prioritized intra refresh method for the wireless video communication.The proposed method considers the characteristics of the human visual system,the error-sensitivity of the bitstream,and the state of the time-varying wireless channel jointly.An expected perceptual distortion model was used to adjust the intra refresh rate adaptively.This model consists of the perceptual weight map based on an attention model,the bit error probability map based on bitstream size,and the dynamic channel state information(CSI).Experimental results indicate that,compared with other intra refresh methods that consider only the content of the video or the CSI,the proposed method improves the average peak signal-to-noise ratio(PSNR) of the whole frame by about 0.5 dB,and improves the average PSNR of the attention-area by about 0.8 dB.

Novel algorithm for complex bit reversal:employing vector permutation and branch reduction methods

We present novel vector permutation and branch reduction methods to minimize the number of execution cycles for bit reversal algorithms.The new methods are applied to single instruction multiple data(SIMD) parallel implementation of complex data floating-point fast Fourier transform(FFT).The number of operational clock cycles can be reduced by an average factor of 3.5 by using our vector permutation methods and by 1.1 by using our branch reduction methods,compared with conventional im-plementations.Experiments on MPC7448(a well-known SIMD reduced instruction set computing processor) demonstrate that our optimal bit-reversal algorithm consistently takes fewer than two cycles per element in complex array operations.

Research on cubic polynomial acceleration and deceleration control model for high speed NC machining

To satisfy the need of high speed NC (numerical control) machining, an acceleration and deceleration (acc/dec) control model is proposed, and the speed curve is also constructed by the cubic polynomial. The proposed control model provides continuity of acceleration, which avoids the intense vibration in high speed NC machining. Based on the discrete characteristic of the data sampling interpolation, the acc/dec control discrete mathematical model is also set up and the discrete expression of the theoretical deceleration length is obtained furthermore. Aiming at the question of hardly predetermining the deceleration point in acc/dec control before interpolation, the adaptive acc/dec control algorithm is deduced from the expressions of the theoretical deceleration length. The experimental result proves that the acc/dec control model has the characteristic of easy implementation, stable movement and low impact. The model has been applied in multi-axes high speed micro fabrication machining successfully.

Investigation on the temperature distribution and strength of flat steel ribbon wound cryogenic high-pressure vessel

By analyzing heat transfer on the wall of flat steel ribbon wound vessel (FSRWV), a numerical model of temperature distribution on the entire wall (including inner core wall, flat steel ribbons, outside cylinder of jacket and insulating layer) was established by the authors. With the model, the temperature distribution and the length change in the vessel walls and flat steel ribbons in low temperature are calculated and analyzed. The results show that the flat steel ribbon wound cryogenic high-pressure vessel is simpler in structure, safer and easier to manufacture than those of conventional ones.