Preparation and Properties of Spray Polyurea Elastomer for Aquaculture Foam Floating Balls

[Objectives] This study was conducted to develop a polyurea elastomer which can be sprayed on the surface of expanded polystyrene (EPS) floating balls, so as to improve the surface strength and service life of the floating balls. [Methods] The effects of the types and amounts of isocyanate, chain extenders and polyether polyols on the gelation rate, adhesion and wear resistance of polyurea elastomer were investigated, and it was finally determined the preparation process of polyurea elastomer using liquid isophorone diisocyanate (IPDI) and amino-terminated polyether (D2000) as the main raw materials, dimethylthiotoluene diamine (E300) as the chain extender and silica as the wear resistance modifier through two-step solution polymerization of prepolymerization and chain extension. [Results] The physical properties and chemical resistance tests of spray polyurea elastomer showed that it had good physical properties and acid and alkali resistance, and could meet the requirements of spraying and protection of EPS floating ball surface in marine environment. [Conclusions] Polyurea elastomer coating can improve the aging resistance, wear resistance and acid and alkali resistance of EPS floating balls, and prevent them from being fragile and floating randomly to form marine floating garbage which results in "white pollution".

Changes in Activities of the Key Enzymes Related to Starch Synthesis in Rice Grains During Grain Filling and Their Relationships with the Filling Rate and Cooking Quality

With 10 rice cultivars (lines) as materials, the changes in activities of adenosine diphosphoglucose pyrophosphorylase(ADPGPase), starch synthase (SSase) and starch branching enzyme (Q-enzyme) in the grains during grain filling, and theirrelationships with the filling rate, gel consistency (GC), alkali spreading value (ASV) and amylose content (AC) werestudied. The results showed that changes in activities of ADPGPase, SSase and Q-enzyme exhibited a single peak duringgrain filling, and the time of the activity peaks for the former two enzymes was earlier than that of the maximum grain-fillingrate (Tmax), and the time reaching the peak for Q-enzyme was synchronous with Tmax. The activities at early grain fillingstage, and the mean and maximum activities of each enzyme during grain filling period were positively and significantly orvery significantly correlated with the mean and maximum grain filling rate and starch content (mg grain-1) in the grains.Activities of ADPGPase at all grain filling stages and those of Q-enzyme at the early and mid filling stages were notsignificantly correlated the cooking quality (GC, ASV and AC). SSase activities at the early filling stage were significantlyand negatively correlated with GC and ASV, and positively correlated with AC. Activities of SSase at mid and late grainfilling stages and Q-enzyme at the late filling stage were significantly and positively correlated with GC and ASV, andnegatively correlated with AC. Spraying zeatin or abscisic acid at early grain filling stage could obviously regulate theactivities of ADPGPase, SSase and Q-enzyme in the grains.

New Method to Measure the Fill Level of the Ball Mill I——Theoretical Analysis and DEM Simulation

The accurate measurement of the fill level in the ball mill has not been resolved because of the interplay of many variable factors, which led the mill to be operated under the uneconomical condition and lost a lot of energy. At present, some methods, such as vibration method and acoustic method, have been applied for measuring the fill level by the researchers. Aiming at the problem of the traditional methods for measuring the fill level, that is, the feature variables of the fill level suffer the influences of the ball load and the water content of the coal, a novel method to measure the fill level is proposed and a possible relation between the fill level and the angular position of the maximum vibration point on the mill shell is investigated. The angular positions of the maximum vibration point on the mill shell for different fill level cases are calculated theoretically under two assumptions, respectively. Meanwhile the charge motions of the mill for different fill level cases are simulated with the discrete element method （DEM）. And the simulation results are verified by comparing the motion trajectories of steel balls and power draft of the mill. The simulated movement trajectories of the outmost layer steel balls in the mill are monitored and analyzed to obtain the angular positions of the maximum vibration point on the mill shell. Both the results of the theoretical calculation and the 3D DEM simulation show that the position of the maximum vibration point on the mill shell moves to a lower angular positions as the fill level decreasing, which provides a new idea for measuring the filllevel accurately.

New Method to Measure the Fill Level of the Ball Mill Ⅱ-Analysis of the Vibration Signals

The exact measurement of the fill level is the key and basic problem for automatic control and optimized operation of the coal pulverizing system. Because the ball mill pulverizing system is non-linearity, long time delay and time-varying, the reliable and effective method for measuring the fill level was lacked at present. In order to reduce the influence by various factors on measuring the fill level and improve the measuring accuracy of the fill level, a novel characteristic variable is proposed. A set of wireless transmission device was designed to record vibration signals, and an accelerometer with high accuracy and large measuring range was mounted directly on the mill shell to pick up the vibration signals from the mill shell. A series of data acquisition experiments under various ball load and water content of coal conditions were conducted in an industrial mill to investigate the relationship between the fill level and the angular position of the maximum vibration point of the mill shell through the analysis of the vibration signals. The analytical result of test data clearly show that the angular position of the maximum vibration point on the mill shell decreases as the fill level increases. At the same time, comparing with the traditional characteristic variable, the feature variable of the fill level proposed in this paper is not subject to the effect of the ball load and water content of coal, which provides a new solution and reliable basis for the accurate measurement of the fill level.

Enhanced mechanical properties and degradation rate of Mg-Ni-Y alloy by introducing LPSO phase for degradable fracturing ball applications

In this work,as-cast Mg-Ni-Y alloys were proposed to develop a feasible material for fracturing balls,and their mechanical performance and corrosion behavior were systematically investigated.Long period stacking order(LPSO)phase was firstly introduced to improve both the mechanical properties and degradation rate of magnesium alloys.With the increase of LPSO phase,the compressive strength was improved significantly,while the elongation of the alloys decreased owing to the relatively brittle nature of LPSO phase.Due to the higher corrosion potential of LPSO phase,the LPSO phase can accelerate the corrosion process by providing more micro-couples.However,the LPSO phase would serve as the corrosion barrier between the corrosion medium and the matrix when the contents of LPSO phase are too high in Mg92.5Ni3Y4.5 and Mg87.5Ni5Y7.5 alloys.As-cast Mg97.5Ni1Y1.5 alloy with satisfactory mechanical properties and rapid degradation rate was successfully developed,exhibiting a high degradation rate of 6675 mm/a(93℃)in 3 wt.%KCl solution and a favorable ultimate compressive strength of 410 MPa.The degradation rate of Mg97.5Ni1Y1.5 alloy is 2-5 times of the current commercial magnesium alloy fracturing materials.

Effects of Nitrogen Fertilizer Treatments on Caryopsis Filling and Respiratory Rate of Rice

An experiment was conducted to study the effects of nitrogen （N） rate and application time on grain filling and respiratory trait of caryopsis in two rice varieties, IR36 and Dali. The treatments were consisted of no N application topdressing at both tillering and booting stages （CK）, 6 g/pot of N topdressing at the tillering stage and 2 g/pot of N topdressing at the booting stage, 2 g/pot of N topdressing at the tillering stage and 6 g/pot of N topdressing at the booting stage. The results showed that the proper utilization of N fertilizer can be helpful to maintain the higher water content, higher respiratory rate and higher dehydrogenase activity of rice caryopsis in late filling phase, and prolong the course for filling and maintaining higher respiratory rate and dehydrogenase activity of rice caryopsis. More N application at booting was more effective compared to more N application at tillering.

Study of the Effect of Operating Temperatures (1320 K, 1420 K and 1520 K) on the Vacant Sites of TiN Alloy in B2 Structure at 45%, 50% and 55% N by MEAM Method

In this work, we have studied the vacancy formation energy of TiN alloy of structure B2 of size 10 × 10 × 10 for nitrogen percentages of 45%, 50% and 55% under the influence of temperature at 1320 K, 1420 K and 1520 K using the Modified Embedded Atom Method MEAM under the calculation code LAMMPS version 2020. This study has enabled us to understand the behavior of the TiN alloy under different nitrogen percentages in terms of total energy, vacancy formation energy, crystalline parameter, occupancy rate and order parameter. For total energy, we have shown that as temperature increases, total energy decreases, making it easier to obtain TiN at higher temperatures;reaching the value of -7344.9169 eV for the 55% nitrogen structure for the temperature of 1420 K. For the energy of formation, we have shown that the compounds obtained at 1320 K and 1520 K have a more considerable energy of formation than that obtained at 1420 K. The study of fractions and the order parameter showed us that the structure of TiN with 55% nitrogen is less likely, as the composition obtained is at most 53.35%.

The Endosperm-Specific Expression of YUCCA Genes Enhances Rice Grain Filling

Grain filling is a crucial process that affects yield in rice(Oryza sativa L.).Auxin biosynthesis and signaling are closely related to rice yield;therefore,it is important to understand the effects of auxin biosynthesis on rice grain filling to improve crop yield.In this study,we used physiological and molecular strategies to identify the roles of auxin in rice grain filling.Exogenous application of auxin(IAA)or auxin analogues(2,4-D)to young spikelets and flag leaves improved the seed-setting rate and yield per spike.Furthermore,real-time quantitative PCR assays confirmed that nine members of the OsYUCCA family of auxin biosynthetic genes were upregulated during grain filling,implication that auxin biosynthesis plays a major role in grain development.The specific expression of either Arabidopsis AtYUCCA1 or OsYUCCA2 in the endosperm or leaves resulted in increased expression of OsIAA genes and auxin content of seeds,as well as increased grain filling and seed-setting rate.This result establishes that the auxin content in grains and leaves is important for grain development.Our findings further highlight the potential applications for improving rice yield by elevating targeted gene expression in specific tissues.

Characteristic of laser-MIG hybrid welding with filling additional cold wire for aluminum alloy

The weld appearance, deposition rate, welding efficiency, stability of arc, laser keyhole characteristic, and weld property were studied by using a novel laser-MIG hybrid welding process with filling wire of aluminum alloy. The results were also compared with those by conventional laser-MIG hybrid welding process. It was found that with the suitable process parameters this novel welding process for aluminum alloy was stable and final weld bead had fine appearance. Compared to conventional laser-MIG hybrid welding process, during this novel welding process the stability of arc, the laser keyhole characteristic and the weld property were similar, while the keyhole cycle frequency and keyhole opening area had differences of 1.23% and 15.34%, respectively, and the welding efficiency increased by about 31% without increasing heat input.

Physiological basis for the differences of productive capacity among tillers in winter wheat

The quality or structure of a wheat population is significantly affected by the compositions of tillers. Little has been known about the physiological basis for the differences of productive capacity among tillers. Two winter wheat cultivars, Shannong 15（SN15） and Shannong 8355（SN8355）, were used to investigate the differences of productive capacity among tillers and analyze the physiological mechanisms that determine the superior tiller group. Low-position tillers（early initiated tillers） had a higher yield per spike than high-position tillers（late initiated tillers） in both cultivars, which was due to their more grain number per spike, more fertile spikelet per spike, less sterile spikelet per spike and higher grain weight. According to cluster analysis, tillers of SN15 were classified into 2 groups： superior tiller group including main stem（0）, the first primary tiller（I） and the second primary tiller（II）; and inferior tiller group including the third primary tiller（III） and the first secondary tiller（I-p）. Tillers of SN8355 were classified into 3 groups： superior tiller group（0 and I）, intermediate tiller group（II and III） and inferior tiller group（I-p）. In comparison with other tiller groups, the superior tiller group had higher photosynthetic rate of flag leaves, higher antioxidant enzyme（SOD, POD and CAT） activities and lower levels of lipid peroxidation in leaves, higher grain filling rate in both superior and inferior grains during grain filling, higher single-stem biological yield and larger single-stem economic coefficient. Correlation analysis showed that yield per spike was positively and significantly correlated with the flag leaf photosynthetic rate, grain filling rate, the antioxidant enzyme activities and soluble protein content（except for SN15 at 5 days post-anthesis（DPA）） of flag leaf, the single-stem biological yield, and the single-stem economic coefficient. Remarkable negative correlation was also found between yield per spike and MDA content of flag leaf. These results suggested that superior tiller group had stronger leaf photosynthetic capacity, more predominance in terms of grain filling, slower senescence rate, higher biological yield and larger economic coefficient, and therefore, showed greater productive capacity than other tiller groups.

Grain-filling characteristics and yield differences of maize cultivars with contrasting nitrogen efficiencies

To investigate the effect of nitrogen management on the grain-filling characteristics and yield formation of maize cultivars with contrasting nitrogen efficiencies,and to identify differences in grain-filling characteristics and yield of maize cultivars in response to nitrogen management,a two-year field experiment was conducted in southwest China in2015–2016.The grain-filling rate and duration of the N-inefficient cultivar XY 508 were higher than those of the N-efficient cultivar ZH 311.The 100-kernel weight of XY 508 was significantly higher than that of ZH 311.The kernel number per ear of ZH 311 was significantly higher than that of XY 508,making the population filling rate of ZH 311 significantly higher than that of XY 508.The higher population filling rate of the N-efficient maize cultivar led to a significant yield advantage over the N-inefficient maize cultivar.Nitrogen management effectively improved maize grain yield,but the response of maize cultivars with contrasting nitrogen efficiencies to nitrogen management was inconsistent.A basal fertilizer ratio 60.43%with a topdressing ratio 39.57%effectively increased grainfilling rate,delayed the time to maximum filling rate,prolonged the active filling period and effective grain-filling time,increased the 100-kernel weight,and maintained higher kernels per ear,thereby improving the population filling rate and maximizing the yield advantage of the N-efficient cultivar.A 100%basal fertilizer ratio not only increased the number of kernels per ear,but also maintained high grain filling characteristics to obtain a higher 100-kernel weight and increased the population filling rate,leading to a high grain yield in the N-inefficient cultivar.Thus,the 100%basal fertilizer ratio partially compensated for the deficient grain yield of the N-inefficient cultivar.

Differences in Chlorophyll Fluorescence Parameters, Yield and Its Components Between Different Genotypes of Wheat Under Waterlogging Conditions at Anthesis

Waterlogging is one of the most factors limiting wheat production in the middle and lower reaches of the Yangtze River Plain of China,especially in the middle and late stages of wheat.Wheat varieties‘Jingmai102’(JM102)and‘Yangmai158’(YM158)were planted to study the dynamic changes of photosynthetic characteristics in flag leaf and the influence of waterlogging at anthesis on the yield and components and dry matter accumulation and remobilization of winter wheat in above ground.The results showed that the SPAD values slightly increased at 1 day after anthesis(d),and then kept decreasing with the increase of waterlogging time.The decrease in SPAD value was more remarkably in YM158 than that in JM102.As for the chlorophyll fluorescence parameters,the photochemical efficiency(Fv/Fm),potential activity(Fv/Fo)of photosystem II,and electronic transmission(Fm/Fo)on photosystem II increased first and then decreased with the increase of waterlogging days after anthesis.The quantum ratio of heat dissipation(Fo/Fm)had a tendency opposite to that of Fv/Fm,and the change range of JM102 was lower than that of YM158.For the grain yield and components,waterlogging at anthesis decreased the dry weight of single stem,grain yield,1 000-kernel weight,spikelet per panicle,and harvest index,and the reduction of JM102 was smaller than that of YM158.As for the accumulation and remobilization of dry matter,the accumulation of dry matter after anthesis decreased significantly under waterlogging condition(WL),and the reduction of JM102 was smaller than that of YM158.In conclusion,waterlogging at anthesis significantly affected the photosynthetic characteristics,yield and components in both varieties,but different varieties exhibited different tolerances to waterlogging stress and YM158 was more sensitive to water stress than JM102.

The effect of amylose on kernel phenotypic characteristics,starch-related gene expression and amylose inheritance in naturally mutated high-amylose maize

High-amylose maize starch has great pote ntial for widespread in dustrial use due to its ability to form strong gels and film and in the food processi ng field,thus servi ng as a resista nt starch source.However,there is still a substa ntial shortage of high-amylose maize due to the limitation of natural germplasm resources,although the well-known amylose extender(ae)gene mutants have bee n found to produce high-amylose maize lines since 1948.In this con text,high-amylose maize lines(13 inbreds and 18 hybrids)originating from a natural amylose mutant in our testing field were utilized to study the correlation between amylose content(AC)and phenotypic traits(kernel morphology and endosperm glossiness),grain filling characteristics,gene expression,and amylose inheritanee.Our results showed that AC was negatively correlated with total starch con tent but was not correlated with grain phe no types,such as kernel full ness,kernel morphology and endosperm glossiness.Maize lines with higher amylose had a greater grain filling rate than that of the controI(B73)during the first 20 days after pollination(DAP).Both starch debranching enzyme(DBE)groups and starch branching enzyme lib(SBEIIb)groups showed a greater abundance in the control(B73)than in the high-amylose maize lines.Male parents directly predicted AC of Fv which was moderately positively correlated with the F2 generation.

Microscopic Pore and Filling Performance of Coal Gangue Cementitious Paste

To obtain the influence laws of the fine gangue rate on the properties of coal gangue cementitious paste, the slump, divergence, stratification, bleeding, setting time and mechanical strength with the change of fine gangue rate were studied on the basis of keeping the amount of cementing material and slurry concentration unchanged. The porosity and the distribution of pore diameter of the filling specimen for curing 28 d were tested by a mercury injection instrument under different fine gangue rate conditions. It was shown that the slump, divergence, setting time and compressive strength of the paste firstly increased and then decreased with increasing fine gangue rate. The stratification and bleeding rate decreased with increasing fine gangue rate. The smaller the critical pore size of the paste was, the smaller the porosity was, the smaller the average pore size was. When the fine gangue rate was 40%, the maximum critical pore diameter of the paste was 55.79 μm, and the corresponding porosity was 17.54%, and the properties of filling paste were the best. When the fine gangue rate further increased, the aggregate surface area increased, and the reaction product of cementitious materials could not effectively fill the pores. It weakened the agglomeration effect. The particles surface of coal gangue was fragmental and flake deposit with irregular shape and uneven fold morphology. It was easy to be bonded with the surface of other filling material. The hydration products of coal gangue cementitious material were a large number of C-S-H gel with fibrous shape and ettringite（AFt） with compact block structure. The theoretical reference was provided for the preparation of low cost gangue cemented filling materials in coal mines.

WORST SUBCARRIER AVOIDING WATER-FILLING SUBCARRIER ALLOCATION SCHEME FOR OFDM-BASED CRN

Efficient and reliable subcarrier power joint allocation is served as a promising problem in cognitive OFDM-based Cognitive Radio Networks (CRN). This paper focuses on optimal subcarrier allocation for OFDM-based CRN. We mainly propose subcarrier allocation scheme denoted as Worst Subcarrier Avoiding Water-filling (WSAW), which is based on Rate Adaptive (RA) criterion and three constraints are considered in CRN. The algorithm divides the assignment procedure into two phases. The first phase is an initial subcarrier allocation based on the idea of avoiding selecting the worst subcarrier in order to maximize the transmission rate; while the second phase is an iterative adjustment process which is realized by swapping pairs of subcarriers between arbitrary users. The proposed scheme could assign subcarriers in accordance with channel coherence time. Hence, real time subcarrier allocation could be implemented. Simulation results show that, comparing with the similar existing algorithms, the proposed scheme could achieve larger capacity and a near-optimal BER performance.

Investigation of Upstream Near-Far Problem in VDSL Systems via Complete Adaptive Iterative Water Filling Algorithm

Crosstalk is the main degrading factor in Digital Subscriber Line (DSL) systems which are the result of electromagnetic coupling between two adjacent twisted pairs in a cable. Very-high bit-rate Digital Subscriber Line (VDSL) systems which use higher frequencies for data transmission than the other DSL systems, this effect is more considerable in Bit Error Rate (BER) degradation. This paper considers a complete adaptive iterative water-filling (IWF) algorithm for Resolving Upstream Near-Far Problem in VDSL Systems. The new distributed dynamic spectrum management algorithm is proposed, which improve achievable bit rate of iterative water-filling algorithm. The paper proffers a new power back-off strategy of the spectral mask at the near-end users, in order to protect the far-end users. Simulation of the proposed algorithm indicates that the bit rate is increased considerably rather the IWF and adaptive water-filling (AIWF) algorithms by keeping their low complexity. Furthermore, by adding the number of users in network, the new algorithm achieves performance gains over the AIWF, completely adaptive.

基于AdaGrad+的自适应Heavy-Ball动量法及其最优个体收敛性

自适应策略与动量法是提升优化算法性能的常用方法。目前自适应梯度方法大多采用AdaGrad型策略,但该策略在约束优化中效果不佳,为此,研究人员提出了更适用于处理约束问题的AdaGrad+方法,但其与SGD一样在非光滑凸情形下未达到最优个体收敛速率,结合NAG动量也并未达到预期的加速效果。针对上述问题,文中将AdaGrad+调整步长的策略与Heavy-Ball型动量法加速收敛的优点相结合,提出了一种基于AdaGrad+的自适应动量法。通过设置加权动量项、巧妙选取时变参数和灵活处理自适应矩阵,证明了该方法对于非光滑一般凸问题具有最优个体收敛速率。最后在l∞∞范数约束下,通过求解典型的hinge损失函数优化问题验证了理论分析的正确性,通过深度卷积神经网络训练实验验证了该方法在实际应用中也具有良好性能。

粉煤灰浆液氨吹脱及其膏体制备特性

为改善含氨粉煤灰对充填膏体性能带来的不利影响,提高粉煤灰的利用率,实验采用空气吹脱粉煤灰浆液的方式进行脱氨,探究吹脱时间、气浆比、固液比、温度和加碱量等影响因素对粉煤灰脱氨率的影响.结果表明,通过响应面优化吹脱条件,控制吹脱时间1h、气浆比900、固液比0.219、温度26.785℃和加碱量1.802%,预测总脱氨率最高达97.178%,与实际误差率在2%以内.经优化吹脱后所制备的粉煤灰充填膏体,仅在养护前期有少量的氨气释放,其泵送性能和微观结构相较于原含氨粉煤灰膏体都得到改善,且在养护28d后,抗压强度提升高达57%.

施氮量对不同夏玉米品种籽粒灌浆特性、产量和品质的影响

以脱水速率不同的2个夏玉米品种迪卡517(DK 517,脱水速率较快)和郑单1002(ZD 1002,脱水速率较慢)为材料,研究施氮量[0 kg/hm^(2)(N0)、180 kg/hm^(2)(N1)、300 kg/hm^(2)(N2)]对夏玉米籽粒灌浆特性、脱水速率、产量和品质的影响,以期为黄淮海夏玉米优质高效生产提供理论依据。结果表明,随着施氮量的增加,DK 517和ZD 1002籽粒干质量总体上均逐渐增加,行粒数和产量先增加后降低,籽粒粗蛋白含量增加,粗淀粉含量降低。N1处理总体上籽粒灌浆速率最大时的生长量和最大灌浆速率最高,活跃灌浆期最长,行粒数最多,进而产量最高,分别为9694.60 kg/hm^(2)和11204.56 kg/hm^(2),且籽粒粗蛋白含量较高。不同施氮量处理对不同脱水类型夏玉米品种籽粒灌浆特性影响不同。授粉后15~24 d,不同处理夏玉米籽粒含水量之间差异显著,授粉后58 d,DK 517籽粒含水量表现为N2>N1>N0,ZD 1002籽粒含水量表现为N1>N0>N2。授粉后49~58 d,N0处理籽粒脱水速率最高。与ZD 1002相比,DK 517籽粒灌浆速率最大时的生长量和最大灌浆速率较高,到达最大灌浆速率的时间较早,活跃灌浆期较短,籽粒含水量较低,灌浆前期籽粒脱水速率较低,中后期较高,行粒数、百粒质量和产量较低,籽粒粗脂肪含量较低,粗蛋白和粗淀粉含量较高。籽粒脱水速率与穗粗、秃尖长呈显著或极显著负相关,与穗长和粗淀粉含量呈显著或极显著正相关。综上,施氮180 kg/hm^(2)可促进夏玉米籽粒灌浆,提高产量和籽粒粗蛋白含量。