Evolution of Biofilm and Its Effect on Microstructure of Mortar Surfaces in Simulated Seawater

To explore the role of biofilm formation on the corrosion of marine concrete structures, we investigated the attachment of biofilm on mortar surfaces in simulated seawater and the influence of biofilm on the microstructure of mortar surfaces. The results show that the evolution of biofilm on mortar surfaces in simulated seawater is closely related to the corrosion suffered by the mortar, and the process of biofilm attachment and shedding is continuous and cyclical. It is found that the specimens in the absence of biofilm attachment are more severely eroded internally by the corrosive medium in simulated seawater than those in the presence of biofilm attachment. For the specimens without biofilm attachment, after 60 days, gypsum forms,and after 120 days, the number of pores in the mortar is reduced. In contrast, for the specimens in the presence of biofilm attachment, gypsum could only be detected after 90 days, and fewer pores are filled. Therefore, the formation of biofilm could delay the invasion of the corrosive medium into the interior of mortar during the evolution of biofilm on mortar surfaces, mitigating the corrosion of mortars in seawater.

Effect of rare earths on corrosion resistance of Cu-30Ni alloys in simulated seawater

Cu-30Ni-xRE(x=0–0.213 wt.%) alloy was prepared by adding rare earths(RE) in melted Cu-30Ni alloy using metal mould casting method.The effects of RE on corrosion resistance of the alloy in simulated seawater were investigated using optical microscope,scanning electronic microscope with energy-dispersive spectrometer and electrochemical measurement system.The results showed that the corrosion resistance of Cu-30Ni alloy was greatly improved by adding proper amount of RE,whereas excess addition of RE worsened ...

Deformation simulation of low-temperature high-speed extrusion for 6063 Al alloy

The hot compression test of 6063 Al alloy was performed on a Gleeble-1500 thermo-simulation machine, and the forming of 6063 rod cxtrudate in low-temperature high-speed extrusion was simulated with extrusion ratio of 25 on the platform of DEFORM 2D successfully. From the compression experimental results, the flow stress model of this Al alloy is obtained which could be the constitutive equation in the simulation of low-temperature high-speed extrusion process. From the numerical simulation results, there is a higher strain concentration at the entrance of the die and the exit temperature reaches up to 522 ℃ in low-temperature high-speed extrusion, which approaches to the quenching temperature of the 6063 Al alloy. The results show that the low-temperature high-speed extrusion method as a promsing one can reduce energy consumption effectively.

Determination of ion quantity by using low-temperature ion density theory and molecular dynamics simulation

In this paper, we report a method by which the ion quantity is estimated rapidly with an accuracy of 4%. This finding is based on the low-temperature ion density theory and combined with the ion crystal size obtained from experiment with the precision of a micrometer. The method is objective, straightforward, and independent of the molecular dynamics （MD） simulation. The result can be used as the reference for the MD simulation, and the method can improve the reliability and precision of MD simulation. This method is very helpful for intensively studying ion crystal, such as phase transition, spatial configuration, temporal evolution, dynamic character, cooling efficiency, and the temperature limit of the ions.

PREDICTING THE CONSEQUENCES OF SEAWATER INTRUSION AND PROTECTION PROJECTS

The simulation of this process and the effects of protection projects lays the foundation of its effective control and defence. The mathematical model of the problem and upwind splitting alternating direction method were presented. Using this method, the numerical simulation of seawater intrusion in Laizhou Bay Area of Shandong Provivce was finished. The numerical results turned out to be identical with the real measurements, so the prediction of the consequences of protection projectects is reasonable.

Parametric optimization and performance comparison of organic Rankine cycle with simulated annealing algorithm

Taking the ratio of heat transfer area to net power and heat recovery efficiency into account, a multi-objective mathematical model was developed for organic Rankine cycle （ORC）. Working fluids considered were R123, R134a, R141b, R227ea and R245fa. Under the given conditions, the parameters including evaporating and condensing pressures, working fluid and cooling water velocities were optimized by simulated annealing algorithm. The results show that the optimal evaporating pressure increases with the heat source temperature increasing. Compared with other working fluids, R123 is the best choice for the temperature range of 100--180℃ and R141 b shows better performance when the temperature is higher than 180 ℃. Economic characteristic of system decreases rapidly with the decrease of heat source temperature. ORC system is uneconomical for the heat source temperature lower than 100℃.

Construction of a macromolecular structural model of Chinese lignite and analysis of its low-temperature oxidation behavior

The aim of this paper is to analyze the change in the active structure of lignite during the process of lowtemperature oxidation by constructing a molecular structure model for lignite. Using quantum computation combined with experimental results of proximate analysis, ultimate analysis, Fourier transform infrared spectroscopy(FTIR) and X-ray photoelectron spectroscopy(XPS), a structural model for the large molecular structure was constructed. By analyzing the bond lengths in the model molecule, the evolution law for the active structure of lignite was predicted for the process of low-temperature oxidation. In low-temperature oxidation,alkanes and hydroxyls are the primary active structures observed in lignite, though ether may also react. These active functional groups react with oxygen to release heat, thereby speeding up the reaction between coal and oxygen. Finally, the content of various functional groups in the process of lignite low-temperature oxidation was analyzed by infrared analysis, and the accuracy of the model was verified.

Distribution Performance Analysis and Experimental Research on the Port Plate Pairs of Low Speed High Torque Seawater Hydraulic Motor

The current research of seawater hydraulic motor mainly focused on piston motor and vane motor, but seldom regarded low speed high torque seawater hydraulic motor. Low speed high torque seawater hydraulic motor as a kind of energy conversion device and actuator plays an important role in seawater hydraulic transmission system. However, the physical and chemical properties of seawater, such as low viscosity, high causticity and poor lubrication, result in numerous problems. In this paper, the flow distribution characteristics of port plate pairs for the seawater hydraulic motor are investigated, and the leakage flow and power loss models of port plate pairs are established. Numerical simulations are carried out to examine the effects of water film, inlet pressure and rotating speed on the pressure distribution and leakage flow. And the friction and wear tests of port plate pairs are also carried out. Moreover, the test system of the seawater hydraulic motor is constructed and the performance of prototype with no-load or loading is conducted. The results indicate that the clearance of port plate pairs and inlet pressure have a significant effect on distribution characteristics, but the effect of rotating speed is not very obvious. The experimental results show that the minimum error rate can be maintained within 0.3% by the proposed flow model and the counter materials of 316 L against carbon-fiber-reinforced polyetheretherketone(CFRPEEK) are suitable for the port plate pairs of seawater hydraulic motor. Finally, based on the seawater hydraulic experiment platform, the volumetric efficiency of no-load and loading are obtained that the maximum can achieve 94.71% and 90.14%, respectively. This research work may improve the flow distribution performance, lubrication and the friction and wear properties, enhance energy converting efficiency of port plate pair and provide theoretical and technical support for the design of highperformance water hydraulic components.

Distribution Characteristics of Mean Seawater Temperature Related to the Thermocline in the Deep-Water Area of Nansha

On the bisis of determining the there elements of thermocline ( depth [upper bound depth ], thickness and intensity ) and the maximum vertical temperature gradient of the surveying station, the paper calculates the mean temperature of the Nansha deep-water surveying station within the upper-bound depth layer of thermocline and the mean temperature below the lower-bound depth of thermocline between the 300m and 800m layers,respectively. Analysis indicates that the horizontal distribution of mean seawater temperature shows a distinct trend of the low-temperature seawater slowly moving from the northeast to the southeast of Nansha,which seems to have been driven by the Northeast Monsoon. The larger the vertical temperature radient is, the greater is its capability of preventing the heat of the upper seawater from diffusing into the deeper layers on the vertical direction.

The Theory and Application of Upwind Finite Difference Fractional Steps Procedure for Seawater Intrusion

Numerical simulation and theoretical analysis of seawater intrusion is the mathematical basis for modern environmental science. Its mathematical model is the nonlinear coupled system of partial differential equations with initial-boundary problems. For a generic case of a three-dimensional bounded region, two kinds of finite difference fractional steps pro- cedures are put forward. Optimal order estimates in norm are derived for the error in the approximation solution. The present method has been successfully used in predicting the consequences of seawater intrusion and protection projects.

Controlled Growth of NiMoO_(4) Nano-rods on Carbon Cloth:A Novel Electrode for the Hydrogen Evolution Reaction in Alkaline Media and Simulated Sea Water

A series of NiMoO_(4)-nano rod/carbon cloth composite electrodes with different loadings(x)of NiMoO_(4)-NRs was synthesized with a view to implementing an efficient hydrogen evolution reaction(HER).The NiMoO_(4) nano-rods(NRs)were prepared by growing them directly on carbon cloth(CC)via a simple hydrothermal reaction coupled with an annealing treatment.The resulting NiMoO_(4)-NR/CC-x composites served directly as electrodes for electrolysis of an alkaline medium and a simulated sea water.The results indicated that among the NiMoO_(4)-NR/CC-x composites,the NiMoO_(4)-NR/CC-10 composite possessed the highest HER activity with an overpotential of 244.8 mV at 10 mA/cm^(2),a Tafel slope of 95 mV/dec,the fastest charge transfer rate(R_(ct)<1Ω)and good stability in alkaline media.Even in simulated seawater,the NiMoO_(4)-NR/CC-10 composite showed good stability.The outstanding HER activity and stability may originate from the strong interaction between Ni and Mo in the NiMoO_(4) NRs as well as the efficient charge transfer process and the rate of the HER due to the synergistic effect involving the CC and NiMoO_(4) NRs.

Numerical Analysis of Conjugated Heat and Mass Transfer of Helical Hollow Fiber Membrane Tube Bank for Seawater Distillation

A numerical study on the conjugated heat-mass transfer of helical hollow fiber membrane tube bank(HFMTB)for seawater desalination was carried out.Physical and mathematical models of fluid flow,temperature and humidity distribution were constructed to investigate the influences of flow type,Reynolds number,and temperature on the conjugated heat-mass transfer performance of hollow fibers in the distillation membrane module.The conjugated heat-mass transfer characteristics of HFMTB were discussed by utilizing the friction coefficient,Nusselt number(Nu),and Sherwood number(Sh).Results demonstrate that a distillation efficiency enhancement of 29%compared to the straight HFMTB has been detected for four-helical HFMTB configuration,though the friction coefficient of such a module is about 4 times of their straight counterparts.The values of average Nu and Sh numbers are increasing with tube number,which improves distillation efficiency.The effect of flow type has been studied by employing the upstream and downstream flows to the double-helical HFMTB,demonstrating upstream flow type is more conducive to the heat-mass transfer process.Both the outlet air humidity(ω)and distillation efficiency(η)decrease with the air-side Reynolds number(Rea)and inlet air temperature in the helical HFMTB while increasing with the solution-side Reynolds number(Re_(S))and inlet solution temperature.Overall,the obtained results indicate that helical HFMTB applying upstream flow has great potential to achieve high-performance SGMD for seawater desalination.It is anticipated that the present work can assist in a better understanding of the membrane desalination process in HFMTB and thus provide theoretical suggestions for further optimization and development.

基于SEAWAT的海水入侵数值模拟

基于三维有限差分理论,运用地下水模拟软件Visual MODFLOW中的SEAWAT模块,模拟了大连海洋大学新校区变密度条件下的海水入侵。模拟中考虑了有防渗墙和无防渗墙两种工况,并分析和比较了这两种工况下,新校区的地下水位和盐分浓度,其分布及变化规律。模拟结果表明:防渗墙对新校区地下水位和盐分浓度的分布及变化,影响都很小;盐分最终侵入校园区域,并且随着时间的增长,浓度上升至较高水平。

SIMPLE SIMULATION OF THE ANNUAL VARIATION OF THE SPECIFIC PHOTOSYNTHESIS RATE IN JIAOZHOU BAY

A simple diagnostic simulation of the annual cycling of the surface specific photosynthesis rate (SPR) in Jiaozhou Bay is described in this paper. Light intensity, temperature and nutrients (nitrate + ammonia, phosphate) were considered as main factors controlling photosynthesis of phytoplankton and were introduced into the model by different function equations. The simulated variation of specific photosynthesis rate coincided with the measured data. Analysis of the effect of every factor on photosynthesis indicated that the variation of photosynthesis rate was controlled by all these three factors, while temperature showed good correlation with SPR as measurement showed. This diagnostic simulation yielded the values of some parameter relating with the photosynthesis in Jiaozhou Bay.

Simulation of Multi-stage Flash(MSF)Desalination Process

MSF seawater desalination has become an important technology to solve the scarce of fresh water resources in the world. But the high energy cost is the bottle-neck of extendibility and application. In this paper, the principle of MSF is analyzed and the single flash stage is divided into several elementary unit operations. The Aspen Plus is adopted to simulate MSF desalination process. The effect factor of MSF system, such as the feed seawater temperature, the top brine temperature(TBT) and the stage number, is investigated and the optimum operation condition is obtained.

海水泵站流道非对称引水流态特性数值模拟分析

为探讨海水泵站流道非对称引水流态特性,基于OpenFOAM建立了某液化天然气接收站海水泵站流道数值模型,在利用实测数据验证的基础上,模拟计算与分析了对称和非对称引水时,流道内流速与紊动动能分布特征。模拟结果表明:海水泵站非对称引水时,水流进入前池后流速较大,在低水位下水流无法充分扩散,在流道入口处形成偏流,行进至海水泵前断面水流分布已基本均匀;非对称引水时,海水泵所在进水池各断面均匀性指数平均值高于对称引水工况,且各海水泵进水池的紊动动能平均值也小于对称引水工况;从过水断面流速分布均匀性以及紊动量级来看,非对称引水对水泵运行更有利。

模拟海水对Q235钢腐蚀性能的影响分析

以Q235碳素钢为研究对象,借助旋转式挂片腐蚀试验仪,考察转速、温度、酸碱度等因素对其在模拟海水中腐蚀性能的作用。结果表明,腐蚀速度随温度的变化呈现两个阶段:第一阶段,当温度小于45℃时,腐蚀速度随温度的增大而不断升高;第二阶段,在温度大于45℃时,曲线斜率最大,腐蚀速度达到最大值;腐蚀速度随转速的变化呈现两个阶段:第一阶段,当转速小于60 r/min时,腐蚀速度基本保持不变,维持恒定;第二阶段,当转速大于60 r/min时,曲线斜率增大,腐蚀速度急剧升高,腐蚀速度随转速的增大而不断升高,并出现60 r/min的临界值;腐蚀速度随酸碱度的增大而不断降低。所得结论对Q235钢在海洋环境中的腐蚀和防护具有一定的参考价值。

Ni含量对CrN涂层抗磨蚀性能的影响研究

目的探究在模拟海洋环境下,Ni的掺入对CrN涂层耐磨性能的影响,研究不同Ni含量的CrNiN涂层的磨蚀行为。方法采用磁控溅射方法对CrNiN涂层中的Ni含量进行调控,制备CrN涂层、Ni掺杂含量分别为15.85%(原子数分数)和39.06%的CrNiN涂层。通过干摩擦试验和模拟海水磨蚀试验,对3种涂层的力学性能和磨蚀行为进行研究对比,并分析其摩擦损伤机理。结果在干摩擦试验条件下,CrNiN涂层的摩擦学性能主要由涂层的力学性能决定,Ni原子数分数为15.85%的CrNiN涂层兼具高硬度和良好韧性,磨痕最浅,其磨损率在3种涂层中最低,为9.1×10^(-7)mm^(3)/(N·m),而在模拟海洋磨蚀的开路电位(OCP)下,Ni原子数分数为15.85%的CrNiN涂层的磨损率大于CrN涂层,CrN涂层具有最低的摩擦因数以及最低的磨损率。3种涂层在正电位(+0.6 V)时的磨损率显著大于开路电位(OCP)下的磨损率,说明腐蚀降低了涂层的耐磨性。通过对腐蚀产物进行分析,表明CrN的腐蚀产物主要是CrO_(2)以及Cr_(2)O_(3),具有一定的润滑作用,而含Ni的CrNiN涂层在腐蚀过程中产生了NiO,对涂层的耐磨性产生了不利影响。结论在干摩擦试验条件下,CrNiN涂层的摩擦学性能主要由涂层的力学性能决定,Ni原子数分数为15.85%的CrNiN涂层兼具高硬度和良好韧性,从而更耐磨。在模拟海洋磨蚀试验条件下,CrNiN涂层的腐蚀产物严重影响其磨蚀性能。

核电厂海水循环泵肘形进水流道优化设计

为提高核电厂海水循环泵运行的稳定性,基于CFD数值模拟对海水循环泵肘形进水流道进行优化设计。以国内某核电厂的进水流道为研究对象,建立全新坐标系,通过理论推导得出肘形流道控制参数之间的函数关系,根据流道性能评判指标等参数,通过数值模拟研究肘形进水流道4个重要控制参数对流道水力性能的影响,优选出最佳方案并进行试验验证。结果表明,在设计流量下优化后的流道出口平均流速提高了0.026 m/s,流速分布均匀度降低0.13%,水流平均角度提高0.034°,水力损失降低11.2%。本文的研究结果显示提出的肘形流道优化设计方法快速、可靠,具有出口流态较好、水力损失较小等优点,可为工程建立提供一定的参考。

超大型海水冷却塔塔群飘滴及盐沉积数值模拟研究

针对核电项目大型海水冷却塔,采用三维数值模型,结合厂址气象数据、冷却塔设计参数、总图布置以及周围环境特征,研究了超大型自然通风海水冷却塔在建筑物、环境风相互作用下的冷却塔飘滴扩散迁移特征和盐沉积量。结果表明,当环境风向与塔排平行时,出口热空气相互叠加形成一股气流,有利于减少飘滴和盐沉积对环境的影响,粒径大于550μm的飘滴不能从高位冷却塔出口逸出,6台核电机组正常运行工况时,盐沉积量一般不会对植物造成严重损坏。