An improved positioning model of deep-seafloor datum point at large incidence angle

The inhomogeneous sound speed in seawater causes refraction of sound waves,and the elimination of the refraction effect is essential to the accuracy of underwater acoustic positioning.The raytracing method is an indispensable tool for effectively handling problems.However,this method has a conflict between localization accuracy and computational quantity.The equivalent sound speed profile(ESSP)method uses a simple sound speed profile(SSP)instead of the actual complex SSP,which can improve positioning precision but with residual error.The residual error is especially non-negligible in deep water and at large beam incidence angles.By analyzing the residual error of the ESSP method through a simulation,an empirical formula of error is presented.The data collected in the sailing circle mode(large incidence angle)of the South China Sea are used for verification.The experiments show that compared to the ESSP method,the improved algorithm has higher positioning precision and is more efficient than the ray-tracing method.

Development of New Green Feed for Large Water Surface Ecological Fishery

In view of the fact that cages and bait are not allowed in large water surface aquiculture,1-2 kinds of new green feeds"plankton+microecologics"were developed to solve the problems of yield reduction,slow growth and difficulty in fishing of aquatic organisms caused by extensive mode.The new green feed is ecological,environmentally friendly and residue-free,which not only supplements nutrition but also meets the requirements of environmental protection.

Spatial and Temporal Variation and Trend Analysis of Water Quality in Large Reservoirs in Ji’an City

Based on the water quality monitoring data of 5 large reservoirs in Ji’an City,Jiangxi Province from 2015-2021,the temporal and spatial variation characteristics and trends of water quality of the reservoirs were analyzed by single-factor evaluation method and seasonal Kendall test to evaluate the trophic status of the reservoirs and explore the influencing factors of characteristic pollutants.The results showed that:①the water quality of the reservoirs was good and could meet the water needs of various functions;②the water quality of the reservoirs had generally changed from bad to good in recent years,indicating that the implementation of“river chief system”has achieved certain results;③Kendall test analysis showed that,except for individual projects which showed an upward trend in water quality,other projects showed no obvious change trend or downward trend,indicating that the water quality of the reservoirs is indeed improving;④the causes of water pollution in reservoir area were further analyzed by exploring the natural and human factors of the characteristic pollutant total phosphorus.It is recommended to strengthen supervision in the later stage to control point and non-point source pollution.

构筑非晶/晶体NiFe-MOF@NiS异质结构催化剂增强大电流密度下水/海水氧化

电化学水分解作为一种生产高纯度氢气的绿色技术,虽然前景广阔,但阳极析氧反应(OER)动力学缓慢,严重制约了其能量转换效率.目前,电化学水分解系统主要以淡水作为原料.然而,大规模使用淡水进行分解无疑会给淡水资源带来沉重负担.相比之下,占水资源总量96%以上的海水,因其丰富的储量,成为替代淡水的理想选择.然而,由于海水中含有大量的氯离子,会引发与OER的竞争性氯析出反应(ClER)形成次氯酸盐(ClO^(–)),导致活性位点失活,严重降低催化剂的活性和稳定性.因此,如何在利用海水进行电化学水分解的同时,有效抑制ClER的发生,是当前亟待解决的科学问题.在最新催化剂研究中,金属有机框架(MOF)凭借其高孔隙率、大比表面积和分散的活性位点,在电化学水分解中展现出良好的性能.然而,MOF的电子导电性和OER反应能垒受限于氧原子p轨道与金属原子d轨道间的电子云重叠.因此,设计MOF活性位点的电子结构,促进自发电子转移,对于提升导电性和OER效率至关重要.界面工程能优化MOF活性位点的电子结构,增强局部电荷再分配,从而提高OER活性.为满足工业高电流密度需求,构建富含缺陷的异质结构是关键,其能暴露更多OER活性位点,优化质量传递,缩短电子迁移路径.结合高导电、可调电子结构的NiS晶体相,构建MOF非晶/NiS晶体异质界面,可调控电子结构并加速电荷转移.目前,关于MOF基非晶/晶异质界面催化剂用于海水氧化的报道尚少,这一方向具有巨大潜力.本文通过两步法耦合策略,成功在泡沫镍基底上制备了NiFe-MOF@NiS异质结构催化剂.首先,利用硫温和改性腐蚀方法在泡沫镍基体生长晶相NiS纳米片;随后,通过电沉积处理在NiS表面生长非晶相NiFe-MOF纳米颗粒.理论计算结果表明,NiFe-MOF和NiS之间的电子相互作用可以加速电荷转移,有效调节金属位点的d带中心,从而优化含氧中间体的吸附能力.与NiFe-MOF和NiS相比,NiFe-MOF@NiS/NF催化剂对OOH*中间体的吸附能力更为突出,这大大降低了速率决定步骤(O*→OOH*)的反应能垒,为高效催化OER提供了理论支撑.实验结果表明,在1 mol L^(‒1)KOH和碱性海水电解液中,NiFe-MOF@NiS/NF催化剂仅需要346和355 mV的低过电位,即可驱动500 mA cm^(–2)的大电流密度.Tafel斜率和电化学阻抗谱的结果表明,该催化剂具有较好的OER动力学特征.此外,质量活性和转换频率结果表明,NiFe-MOF@NiS/NF催化剂展现出良好的本征催化活性.多步恒电流阶梯曲线以及在100和500 mA cm‒2电流密度下的计时电位曲线结果表明,NiFe-MOF@NiS/NF催化剂具有出色的长期稳定性.通过对在碱性海水电解液OER反应后的NiFe-MOF@NiS/NF催化剂进行表征发现,在OER过程中,NiS物种会在阳极电压下自重构形成硫酸盐膜,可以显著抑制Cl–离子在催化剂表面的吸附,使NiFe-MOF@NiS/NF催化剂在海水电解质中具有强大的耐腐蚀性.这一特性使得NiFe-MOF@NiS/NF催化剂在碱性KOH和碱性海水中均能保持较好的OER活性和稳定性,性能超过了商业RuO_(2)以及大多数报道的其他MOF基的催化剂.综上所述,本文通过简便易行的合成策略,制备了高性能的NiFe-MOF@NiS异质结催化剂,其表现出高效电解海水性能和稳定性.本工作为合理设计高活性、稳定性、选择性的MOF基抗氯腐蚀催化剂以提高碱性海水的OER性能提供了新视角.

Strong electronic coupling of CoNi and N-doped-carbon for efficient urea-assisted H2 production at a large current density

Exploiting efficient urea oxidation reaction(UOR)and hydrogen evolution reaction(HER)catalysts are significant for energy-saving H2 production through urea-assisted water electrolysis,but it is still challenging.Herein,carbon-encapsulated CoNi coupled with CoNiMoO(CoNi@CN-CoNiMoO)is prepared by solvothermal method and calcination to enhance the activity/stability of urea-assisted water electrolysis at large current density.It exhibits good activity for UOR(E10/1,000=1.29/1.40 V)and HER(E-10/-1000=-45/-245 mV)in 1.0 M KOH+0.5 M urea solution.For the UOR||HER system,CoNi@CN-CoNiMoO only needs 1.58 V at 500 mA cm-2 and shows good stability.Density functional theory calculation suggests that the strong electronic interaction at the interface between NiCo alloy and N-doping-carbon layers can optimize the adsorption/desorption energy of UOR/HER intermediates and accelerate the water dissociation,which can expedite urea decomposition and Volmer step,thus increasing the UOR and HER activity,respectively.This work provides a new solution to design UOR/HER catalysts for H2 production through urea-assisted water electrolysis.

Effects of Ultra-drying Treatment on Large Amounts of Four Kinds of Crop Seeds

This study was to understand the physiological changes of four kinds of crop seeds including baby corn, cowpea, radish and rape- seed, under the treatment of ultra-drying. Large amounts of seeds as experimental materials （ 10 kg for each material） were respectively dried to the suitable water content consistent with the ultra-dried seed criterion via heating at 50 ~C; then the physiological indices of these ultra-dried seeds such as water content, seed germination, dehydrogenase activity and SOD activity were measured. The results showed that except cowpea seeds, whose ultra-drying treatment should be controlled between two and four days, other three kinds of seeds were tolerant to high tem- perature and low water content. The ultra-dried seeds assumed similar or even higher activities than CKs, but showed no damage symptom. Our result proves that ultra-drying treatment via heating at 50 ℃ is safe and efficient to experimental seeds.

Evaluation of Rainwater Harvesting Methods and Structures Using Analytical Hierarchy Process for a Large Scale Industrial Area

In India, with ever increasing population and stress on natural resources, especially water, rejuvenation of rainwater harvesting (RWH) technique which was forgotten over the days is becoming very essential. Large number of RWH methods that are available in the literature are demand specific and site specific, since RWH system depends on the topography, land use, land cover, rainfall and demand pattern. Thus for each and every case, a detailed evaluation of RWH structures is required for implementation, including the analy-sis of hydrology, topography and other aspects like site availability and economics, however a common methodology could be evolved. The present study was aimed at evaluation of various RWH techniques in order to identify the most appropriate technique suitable for a large scale industrial area to meet its daily wa-ter demand. An attempt is made to determine the volume of water to be stored using mass balance method, Ripple diagram method, analytical method, and sequent peak algorithm method. Based on various satisfying criteria, analytical hierarchy process (AHP) is employed to determine the most appropriate type of RWH method and required number of RWH structures in the study area. If economy alone is considered along with hydrological and site specific parameters, recharging the aquifer has resulted as a better choice. However other criteria namely risk, satisfaction in obtaining required volume of water for immediate utilization etc. has resulted in opting for concrete storage structures method. From the results it is found that AHP, if used with all possible criteria can result in a better tool for evaluation of RWH methods and structures. This RWH structures not only meets the demand but saves transportation cost of water and reduces the dependability of the industry on irrigation reservoir. Besides monetary benefits it is hoped that the micro environment inside the industry will improve due to the cooling effect of the stored water.

Design on Vibration Monitoring and Fault Diagnosis System of Large Water Pump Motor

Large water pump motor,whose operation decides the reliability of the whole production line,plays a very important role.Therefore,its online condition monitoring can help companies better know its operation,process fault analysis and protection.The essay mainly studies and designs large water pump motor′s real time vibration monitoring and fault diagnosis system.The essay completes the systems project design,the establishment of the system and performance test.Eddy-currentsensor,XM-120 vibration module,XM-320 axial translation module,XM-362 temperature module,XM-360 process amount module and XM-500 gateway module are used to measure the axial vibration and displacement of main motors.Laboratory tests prove that the system can meet the requirements of motor vibration monitoring.

Hydrological Modeling of Large Drainage Basins Using a GIS-based Hybrid Atmospheric and Terrestrial Water Balance (HATWAB) Model

A Hydrological model is proposed to study the spatial and temporal variability of the water budget components of large drainage basin systems from atmospheric and terrestrial water balances. In order to understand the water balances that include, surface runoff, actual evapotranspiration and soil moisture, a GIS-based simple water balance model which is referred as Hydrological Model from Hybrid Atmospheric and Terrestrial Water Balances with acronym HATWAB is presented. The spatio-temporal climatology database was created from a network of climate stations from CLIMWAT data base to reconstruct the monthly primary inputs to HATWAB model, rainfall and potential evapotranspiration. The modeling principles and HATWAB model are demonstrated using the Limpopo and Congo basins in Africa. The model was used to simulate water balance components by taking rainfall-runoff processes in the basin including soil-texture controlled moisture in the terrestrial system, and the vertical integrated moisture convergence that accounts for the net water vapor flux from the basins in order to close the hydrologic water budget.

The World’s Largest Lakes Water Level Changes in the Context of Global Warming

The article is focused on the assessment of changes in the average annual water levels of large lakes of the planet in the changing climate conditions characteristic of the recent decades. Eight large lakes, i.e.Baikal, Balkhash, Superior, Issyk-Kul, Ladoga, Onega, Ontario, and Erie, located on the territory of Eurasia and North America, were chosen as the research objects. They were selected because of the availability of a long-term observations series of the water level. As is known, long-term changes in the lakes water level result from variation in the water volume. The latter depends on the?ratios between the water balance components of the lake that have developed during a given year, which, in turn, reflect the climatic conditions of the respective years. The features of the water balance structure of the above-mentioned?lakes and the intra-annual course of the water level are considered. The available long-term records of observational data on all selected lakes and their stations were divided into two periods: from 1960 to 1979 (the period of stationary climatic situation) and from 1980 to 2008 (the period of non-stationary climatic situation). The homogeneity and significance of trends in the long-term water level series of records have been estimated. It has been established that over the second period the nature and magnitude of the lakes water levels variations differ significantly. For lakes Balkhash, Issyk-Kul, Ladoga, Superior, and Erie, there is a general tendency for a decrease in water levels. For the remaining three lakes (Baikal, Onega, and Ontario), the opposite tendency has been noted: the levels of these lakes increased. Quantitatively, the range of changes in water levels on the lakes in question over the period of 1980-2008 ranged from -4 cm to +26 cm.

Large post-liquefaction deformation of sand:Mechanisms and modeling considering water absorption in shearing and seismic wave conditions

Large deformation of sand due to soil liquefaction is a major cause for seismic damage.In this study,the mechanisms and modeling of large post-liquefaction deformation of sand considering the significant influence of water absorption in shearing and seismic wave conditions.Assessment of case histories from past earthquakes and review of existing studies highlight the importance of the two factors.Based on the micro and macro scale mechanisms for post-liquefaction shear deformation,the mechanism for water absorption in shearing after initial liquefaction is revealed.This is aided by novel designed constant water-absorption-rate shear tests.Water absorption in shearing can be classified into three types,including partial water absorption,complete water absorption,and compulsory water absorption.Under the influence of water absorption in shearing,even a strongly dilative sand under naturally drained conditions could experience instability and large shear deformation.The mechanism for amplification of post-liquefaction deformation under surface wave load is also explained via element tests and theoretical analysis.This shows that surface wave–shear wave coupling can induce asymmetrical force and resistance in sand,resulting in asymmetrical accumulation of deformation,which is amplified by liquefaction.A constitutive model,referred to as CycLiq,is formulated to capture the large deformation of sand considering water absorption in shearing and seismic wave conditions,along with its numerical implementation algorithm.The model is comprehensively calibrated based on various types of element tests and validated against centrifuge shaking table tests in the liquefaction experiments and analysis projects(LEAP).The model,along with various numerical analysis methods,is adopted in the successful simulation of water absorption in shearing and Rayleigh wave-shear wave coupling induced large liquefaction deformation.Furthermore,the model is applied to high-performance simulation for large-scale soil-structure interaction in liquefiable ground,including underground structures,dams,quay walls,and offshore wind turbines.

Behavior of large post-liquefaction deformation in saturated Nanjing fine sand

Laboratory tests on the large post-liquefaction deformation of saturated Nanjing fine sand were performed by using a hollow cylinder apparatus. The stress-strain responses and the characteristics of excess pore water pressure after liquefaction were studied. It was found that the relationship between deviatoric stress and axial strain presented a sigmoid curve, and there was a good linearity relationship between normalized pore water pressure and deviatoric stress. On this basis, a constitutive model of stress-strain responses and a dissipation model of excess pore water pressure were established. It was found that the results predicted by the two models were in good agreement with the experimental data. The influence of relative densities and confining pressure on the characteristics of liquefied soil were studied, The results showed the relative densities and initial effective confining pressure all had an important influence on the stress-strain responses of liquefied saturated Nanjing fine sand. However, the dissipation model of excess pore water pressure after liquefaction was only affected by the confining pressure.

Study on inhomogeneous cooling behavior of extruded profile with unequal and large thicknesses during quenching using thermo-mechanical coupling model

The interfacial heat transfer coefficient between hot profile surface and cooling water was determined by using inverse heat conduction model combined with end quenching experiment. Then, a Deform-3 D thermo-mechanical coupling model for simulating the on-line water quenching of extruded profile with unequal and large thicknesses was developed. The temperature field, residual stress field and distortion of profile during quenching were investigated systematically. The results show that heat transfer coefficient increases as water flow rate increases. The peak heat transfer coefficient with higher water flow rates appears at lower interface temperatures. The temperature distribution across the cross-section of profile during quenching is severe nonuniform and the maximum temperature difference is 300 ℃ at quenching time of 3.49 s. The temperature difference through the thickness of different parts of profile first increases sharply to a maximum value, and then gradually decreases. The temperature gradient increases obviously with the increase of thickness of parts. After quenching, there exist large residual stresses on the inner side of joints of profile and the two ends of part with thickness of 10 mm. The profile presents a twisting-type distortion across the cross-section under non-uniform cooling and the maximum twisting angle during quenching is 2.78°.

Melting and floating processes of inorganic materials in molten steel:Visualization physical simulation and mathematical modelling

It has been demonstrated that heat absorption method by using the inorganic material rod to cool the molten steel can significantly reduce the macrosegregation level of the large steel ingot.However,owing to the opacity of the molten steel,the physical mechanism of the heat absorption method is not clear.In this work,a transparent hydraulic physical model with water and paraffin wax was built to simulate the melting and floating processes of inorganic materials in the molten steel.A mathematical simulation was also carried out to analyze the connection between the actual ingot and the physical model.Results show that it is feasible to simulate the molten steel and inorganic materials with water and paraffin wax.With the help of the physical model,the process of the melting of paraffin wax and its floating to the surface of water were clearly observed,during which the temperature of water at some characteristic positions in the mold was recorded.The visualization findings demonstrate that the melting and floating processes of paraffin wax can help to bring the heat from the center of the mold to the top surface more quickly,which reduces the superheat and significantly accelerates the cooling rate of water.The experimental results show that for the water with a certain superheat,the use of a larger mass of paraffin wax can accelerate the cooling of the water,but there is a risk of incomplete melting of the paraffin wax.A higher superheat of water will lead to a quicker melting rate for a given mass of paraffin wax,while a lower superheat leads to the incomplete melting of paraffin wax as well.

Failure mechanism and control technology of water-immersed roadway in high-stress and soft rock in a deep mine

Aiming at soft rock ground support issues under conditions of high stress and long-term water immersion, the ground failure mechanism is revealed by taking the deep-water sumps of Jiulong Mine as the engineering background and employing field investigation, tests of rock structure, mechanical properties and mineral composition. The main factors leading to the surrounding rock failure include the high and complex stress state of the water sumps, high-clay content and water-weakened rock, and the unreasonable support design. In this paper, the broken and fractured rock mass near roadway opening is considered as ground small-structure, and deep stable rock mass as ground large-structure. A support technology focusing on cutting off the water, strengthening the small structure of the rock and transferring the large structure of the rock is proposed. The proposed support technology of interconnecting the large and small structures, based on high-strength bolts, high-stiffness shotcrete layer plugging water,strengthening the small structure with deep-hole grouting and shallow-hole grouting, highpretensioned cables tensioned twice to make the large and small structures bearing the pressure evenly,channel-steel and high-pretensioned cables are used to control floor heave. The numerical simulation and field test show that this support system can control the rock deformation of the water sumps and provide technical support to similar roadway support designs.

Temperature Tolerance of Large Yellow Croaker,Pseudosciaena Crocea(Richardson)Associated with Summer Season

L ethal temperature tolerance was determined for about 8 cm, age 0 Pseudosciaena crocea using both slow heating and rapid transfer protocol. The acclimatization temperature was 28 ℃ with summer season, lethal temperature ( LT50 value ) of slow heating protocol ( CTMax ) was 35.0 ℃, and the upper and lower incipient lethal temperatures of rapid transfer protocol were 34.2 ℃ and 17.5 ℃ respectively.

Prompt Electrodeposition of Ni Nanodots on Ni Foam to Construct a High-Performance Water-Splitting Electrode:Efficient, Scalable,and Recyclable

In past decades,Ni-based catalytic materials and electrodes have been intensively explored as low-cost hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)catalysts for water splitting.With increasing demands for Ni worldwide,simplifying the fabrication process,increasing Ni recycling,and reducing waste are tangible sustainability goals.Here,binder-free,heteroatom-free,and recyclable Ni-based bifunctional catalytic electrodes were fabricated via a one-step quick electrodeposition method.Typically,active Ni nanodot(NiND)clusters are electrodeposited on Ni foam(NF)in Ni(NO3)2 acetonitrile solution.After drying in air,NiO/NiND composites are obtained,leading to a binder-free and heteroatom-free NiO/NiNDs@NF catalytic electrode.The electrode shows high efficiency and long-term stability for catalyzing hydrogen and oxygen evolution reactions at low overpotentials(10ηHER= 119 mV and 50ηOER=360 mV)and can promote water catalysis at 1.70 V@ 10mA cm-2.More importantly,the recovery of raw materials(NF and Ni(NO3)2)is quite easy because of the solubility of NiO/NiNDs composites in acid solution for recycling the electrodes.Additionally,a large-sized(S^70 cm2)NiO/NiNDs@NF catalytic electrode with high durability has also been constructed.This method provides a simple and fast technology to construct high-performance,low-cost,and environmentally friendly Ni-based bifunctional electrocatalytic electrodes for water splitting.

Responses of Vertical Structures in Convective and Stratiform Regions to Large-Scale Forcing during the Landfall of Severe Tropical Storm Bilis (2006)

The responses of vertical structures, in convective and stratiform regions, to the large-scale forcing during the landfall of tropical storm Bilis （2006） are investigated using the data from a two-dimensional cloud-resolving model simulation. An imposed large-scale forcing with upward motion in the mid and upper troposphere and downward motion in the lower troposphere on 15 July suppresses convective clouds, which leads to -100% coverage of raining stratiform clouds over the entire model domain. The imposed forcing extends upward motion to the lower troposphere during 16-17 July, which leads to an enhancement of convective clouds and suppression of raining stratiform clouds. The switch of large-scale lower-tropospheric vertical velocity from weak downward motion on 15 July to moderate upward motion during 16-17 July produces a much broader distribution of the vertical velocity, water vapor and hydrometeor fluxes, perturbation specific humidity, and total hydrometeor mixing ratio during 16-17 July than those on 15 July in the analysis of contoured frequency-altitude diagrams. Further analysis of the water vapor budget reveals that local atmospheric moistening is mainly caused by the enhancement of evaporation of rain associated with downward motion on 15 July, whereas local atmospheric drying is mainly determined by the advective drying associated with downward motion over raining stratiform regions and by the net condensation associated with upward motion over convective regions during 16-17 July.

Hydrologic modeling of the Heihe watershed by DLBRM in Northwest China

Water shortage is a chronic problem in arid Northwest China.The rapid population growth and expanding urbanization as well as potential climate change impacts are likely to worsen the situation,threatening domestic,irrigation,and industrial supplies and even the survival of the ecosystems in Northwest China.This paper describes the preliminary work of adapting the Distributed Large Basin Runoff Model(DLBRM) to the Heihe watershed(the second largest inland river in arid Northwestern China,with a drainage area of 128,000 km2) for understanding distribution of glacial-snow melt,groundwater,surface runoff,and evapotranspi-ration,and for assessing hydrological impacts of climate change and glacial recession on water supply in the middle and lower reaches of the watershed.Preliminary simulation results show that the Qilian Mountain in the upper reach area produces most runoff in the Heihe watershed.The simulated daily river flows during the period of 1990-2000 indicate that the Heihe River dis-charges about 1×109 m3 of water from the middle reach(at Zhengyixia Station) to lower reach,with surface runoff and interflow contributing 51 and 49 percent respectively.The sandy lower soil zone in the middle reach has the highest evapotranspiration rate and also contributes nearly half of the river flow.Work underway focuses on the DLBRM model improvement and incorporation of the climate change and management scenarios to the hydrological simulations in the watershed.

Study on the Embedded Mode of Large Diameter Steel Tube and Concrete Combined Pile

As the stiffness discontinuous of large diameter steel tube and concrete combined pile, the complicated stress state is caused by the combination of the pile foundation and the base rock, the steel casing and the bedrock structure. It is needed to put forward a scientific basis to determine the pile foundation effective depth of embedded. For this purpose, the physical model and the numerical model of single pile with large diameter steel tube and reinforced concrete combined force are established. Through numerical simulation and contrast test of a large number of variable parameters, the various factors that affect the lateral bearing capacity of the embedded piles are discussed in detail, the mechanical properties of the foundation under the action of the steel tube and the pile foundation are obtained.