Effect of length-width ratio of rounded rectangle aquaculture tank in dual-diagonal-inlet layout on hydrodynamics

To adapt to the change of aquaculture workshop site,optimize the shape of aquaculture tanks and improve the utilization rate of breeding space,it is necessary to determine the appropriate length width ratio parameters of aquaculture tanks.In this paper,computational fluid dynamics(CFD)technology is adopted to study the flow field performance of aquaculture tanks with different L/B ratios(L:the length;B:the width,of aquaculture tank)and different jet direction conditions(lengthways jet and widthways jet).A three-dimensional numerical calculation model of turbulence in rounded rectangle aquaculture tanks in dual-diagonal-inlet layout was established.Jet directions are arranged lengthways and widthways,and the water flow velocity,resistance coefficient change,vorticity,etc.are analyzed under two working conditions.Results show that the flow field performance in aquaculture tank decreases with the increase of the L/B ratio.The flow field performed well when L/B was 1.0-1.3,sharply dropped at 1.4-1.6,and poor at 1.7-1.9.The results provided a theoretical basis for the design and optimization in flow field performance of the industrialized circulating aquaculture tanks.

Effect of natural and synthetic fibers reinforcement on California bearing ratio and tensile strength of clay

Use of environmentally friendly approaches with the purpose of strengthening soil layers along with finding correlations between the mechanical characteristics of fiber-reinforced soils such as indirect tensile strength(ITS)and California bearing ratio(CBR)and as well as the evaluation of shear strength parameters obtained from the triaxial test would be very effective at geotechnical construction sites.This research was aimed at investigating the influence of natural fibers as sustainable ones including basalt(BS)and bagasse(BG)as well as synthetic polyester(PET)fibers on the strength behavior of clayey soil.To this end,the effects of various fiber contents(0.5%,1%and 2%)and lengths(2.5 mm,5 mm and 7.5 mm)were experimentally evaluated.By conducting ITS and CBR tests,it was found that increasing fiber content and length had a significant influence on CBR and ITS values.Moreover,2%of 7.5 mm-long fibers led to the largest values of CBR and ITS.The CBR values of soil reinforced with PET,BS,and BG fibers were determined as 19.17%,15.43%and 13.16%,respectively.The ITS values of specimens reinforced with PET,BS,and BG fibers were reported as 48.57 kPa,60.7 kPa and 47.48 kPa,respectively.The results of the triaxial compression test revealed that with the addition of BS fibers,the internal friction angle increased by about 100%,and with the addition of PET fibers,the cohesion increased by about 70%.Moreover,scanning electron microscope(SEM)analysis was employed to confirm the findings.The relationship between CBR and ITS values,obtained via statistical analysis and used for the optimum design of road pavement layers,demonstrated that these parameters had high correlation coefficients.The outcomes of multiple linear regression and sensitivity analysis also confirmed that the fiber content had a greater effect on CBR and ITS values than fiber length.

Rare Earth Doped Optical Fibers for Temperature Sensing Utilizing Ratio-Based Technology

A new and practical fluorescence temperature detecting system based on fluorescence intensity ratio was proposed . The background theory of fluorescence intensity-ratio method was presented simply. And the characters of rare earth doped samples were detailed. The erbium-doped fiber was chosen as the sensing element. The energy levels of 2H11/2 and 4S3/2 are responsible for the emission of radiation at approximately 530 and 555 nm. The erbium-doped (960 ppm) fiber of length 20 cm and core diameter 3.2μm was used as the sensing part. A silica photodiode transfers the fluorescence signal to electric signal, then the ratio of the average of the two different signals was calculated by the computer and the temperature was obtained. The ratio R of the intensity resulting from the transition between the two levels varies proportionly with temperature interval from 293 K to 373 K. The sensitivity of the sensor is approximately 0.05 K-1.

Evaluation of gases'molecular abundance ratio by fiber-optic laser-induced breakdown spectroscopy with a metal-assisted method

A metal-assisted method is proposed for the evaluation of gases’molecular abundance ratio in fiber-optic laser-induced breakdown spectroscopy(FO-LIBS).This method can reduce the laser ablation energy and make gas composition identification possible.The principle comes from the collision between the detected gases and the plasma produced by the laser ablation of the metal substrate.The interparticle collision in the plasma plume leads to gas molecules dissociating and sparking,which can be used to determine the gas composition.The quantitative relationship between spectral line intensity and molecular abundance ratio was developed over a large molecular abundance ratio range.The influence of laser ablation energy and substrate material on gas quantitative calibration measurement is also analyzed.The proposed metal-assisted method makes the measurement of gases’molecular abundance ratios possible with an FO-LIBS system.

Preparation and Properties of Carbon Fiber Chiral Materials

The chiral materials were prepared by using the carbon fiber helices as chiral inclusions, and the composite of Fe3O4 and polyaniline as matrix. The electromagnetic properties, including the rotation angles, the axial ratios and the complex chirality parameters, were measured by using a circular waveguide method in the 8.5-11.0 GHz frequency range. The dependence of these electromagnetic properties on the frequency and the concentration of the Fe3O4 in the composite matrix were analyzed. The results show that an appropriate concentration of Fe3O4 in the matrix is useful in improving the electromagnetic properties of the chiral material.

ESTIMATION OF BLENDING RATIO OF TWO-COMPONENT FIBER BUNDLE FROM BUNDLE LOAD-ELONGATION CURVE

In this paper, two methods were developed to assess the blending ratio of two-componentfiber bundles. They were the peak-height method and the slope method. The relationship be-tween blending ratio and testing data was analysed, and the regression curves were obtained bystepwise regression method. It was pointed out that the testing errors of both methods were lessthan two percent. The validities of both methods were verified by experiments, All calculationsof both methods were completed by computer. The blending ratio was ascertained from the test-ing data of bundle fiber strength tester which was made by the authors themselves.

Yields,growth and water use under chemical topping in relations to row configuration and plant density in drip-irrigated cotton

Background Water deficit is an important problem in agricultural production in arid regions.With the advent of wholly mechanized technology for cotton planting in Xinjiang,it is important to determine which planting mode could achieve high yield,fiber quality and water use efficiency(WUE).This study aimed to explore if chemical topping affected cotton yield,quality and water use in relation to row configuration and plant densities.Results Experiments were carried out in Xinjiang China,in 2020 and 2021 with two topping method,manual topping and chemical topping,two plant densities,low and high,and two row configurations,i.e.,76 cm equal rows and 10+66 cm narrow-wide rows,which were commonly applied in matching harvest machine.Chemical topping increased seed cotton yield,but did not affect cotton fiber quality comparing to traditional manual topping.Under equal row spacing,the WUE in higher density was 62.4%higher than in the lower one.However,under narrow-wide row spacing,the WUE in lower density was 53.3%higher than in higher one(farmers’practice).For machine-harvest cotton in Xinjiang,the optimal row configuration and plant density for chemical topping was narrow-wide rows with 15 plants m-2 or equal rows with 18 plants m-2.Conclusion The plant density recommended in narrow-wide rows was less than farmers’practice and the density in equal rows was moderate with local practice.Our results provide new knowledge on optimizing agronomic managements of machine-harvested cotton for both high yield and water efficient.

Effects of Fiber Weight Ratio, Structure and Fiber Modification onto Flexural Properties of Luffa-Polyester Composites

The effect of chemical modification, reinforcement structure and fiber weight ratio on the flexural proprieties of Luffa-polyester composites was studied. A unsaturated polyester matrix reinforced with a mat of Luffa external wall fibers (ComLEMat), a short Luffa external wall fibers(ComLEBC) and a short Luffa core fi-bers (ComLCBC) was fabricated under various conditions of fibers treatments (combined process, acetylat-ing and cyanoethylating) and fiber weight ratio. It resorts that acetylating and cyanoethylating enhance the flexural strength and the flexural modulus. The fiber weight ratio influenced the flexural properties of com-posites. Indeed, a maximum value of strength and strain is observed over a 10% fiber weight ratio. The uses of various reinforcement structures were investigated. The enhancement of elongation at break and the strain values of the composite reinforced by natural mat was proved.

Time-Lag Effect of Dietary Fiber and Fat Intake Ratio on Japanese Colon Cancer Mortality

The daily intake of total dietary fiber (TDF) was evaluated from data of the National Nutrition Survey (NNS) in Japan for 41 years since 1947. An interrelationship between the nutrient intake, including TDF, and the mortality from colon cancer in Japanese people was calculated by a simple correlation coefficient and time-series correlation coeffcient.TDF intake per capita decreased rapidly from 27.4 g in 1947 to 15.8 g in 1963, and subsequently decreased by a lesser rate to 15.3 g in 1987. Fat intake increased rapidly from 18.0 g in 1950 to 56.6 g in 1987.The age-adjusted mortality from colon cancer shows a significant positive correlation with both the intakes of animal protein and of total fat, and the fat energy ratio. A time-series analysis indicates that the mortality from colon cancer was negatively correlated with TDF with a 15-27 year delay, the maximum correlation existing with a 23-year lag (r = -0.947). The TDF intake was less than 17.9 g in 1965. At the same time, the mortality from colon cancer increased rapidly. A fat/TDF ratio above 3.0 resulted in a rapid increase in colon cancer mortality.The non-adjusted mortality from colon cancer has much the same interrelationship with TDF and fat intake as the adjusted figures. It is suggested that the cause of the increased mortality from colon cancer in Japan is positively related to the increased intake of fat and protein. In addition, the decrease in TDF intake has accelerated the mortality of colon cancer after a delay of 23-24 years. The importance of fat/TDF as a nutritional criterion for the incidence of colon cancer needs to be better recognized

Effect of Fiber Weight Ratio and Fiber Modification on Flexural Properties of Posidonia-Polyester Composites

The main objective of this research is to study the effect of fiber weight ratio and chemical fiber modification on flexural properties of composites reinforced with Posidonia fiber. An unsaturated polyester matrix reinforced with untreated and treated Posidonia fibers was fabricated under various fiber weight ratios. Results showed that the combined chemical treatment provided better mechanical properties of composites in comparison with untreated fiber. The fiber weight ratio influenced the flexural properties of composites. Indeed, a maximum value of flexural modulus was observed for 10% fiber weight ratio for composites reinforced with treated fibers. SEM photographs revealed a different fracture surface between Posidonia fibers reinforced polyester composites.

Experimental Investigation on Vibration Reduction Performance of Fiber Metal Laminate Beams with MRE Core

The vibration reduction characteristics of composite beams filled with magnetorheological elastomer core are studied experimentally.The fiber metal laminates with magnetorheological elastomers core is self-designed and prepared.Internal magnetic field is applied to the beam to explore its action of damping vibration performance under the magnetic field for the first time.The composite elements test system with controllable magnetic field intensity is designed and the function of each part is introduced.Then,a set of reasonable and standard vibration test flow of this type of composite beam under different magnetic field intensity is clarified,and the practical test is conducted.It has been found that the composite beam has excellent damping performance with the first 4 damping ratios being greater than 10%.Moreover,after the magnetic field is applied,its damping results can be further improved to meet the active control purpose.

Analysis of vibration attenuation characteristics of large thickness carbon fiber composite laminates

The vibration attenuation and damping characteristics of carbon fiber reinforced composite laminates with different thicknesses were investigated by hammering experiments under free boundary constraints in different directions.The dynamic signal testing and analysis system is applied to collect and analyze the vibration signals of the composite specimens,and combine the self-spectrum analysis and logarithmic decay method to identify the fundamental frequencies of different specimens and calculate the damping ratios of different directions of the specimens.The results showed that the overall stiffness of the specimen increased with the increase of the specimen thickness,and when the thickness of the sample increases from 24mm to 32mm,the fundamental frequency increases by 35.1%,the vibration showed the same vibration attenuation and energy dissipation characteristics in the 0°and 90°directions of the specimen,compared with the specimen in the 45°direction,which was less likely to be excited and had poorer vibration attenuation ability,while the upper and lower surfaces of the same specimen showed slightly different attenuation characteristics to the vibration,the maximum difference of damping capacity between top and bottom surfaces of CFRP plates is about 70%.

聚甲醛纤维对超高性能混凝土力学性能影响研究

先选择适宜的养护条件,再对比研究了掺入不同纤维对UHPC抗压强度、弹性模量、弯曲性能、冲击性能、劈裂抗拉强度的影响。结果表明:90℃蒸汽养护3 d为研究较优养护方式,单掺聚甲醛(POM)纤维会导致UHPC抗压强度降低,在较优养护方式下,各组UHPC抗压强度约为120 MPa,较未掺组降低了约9%。但掺入POM纤维能明显提升UHPC的弯曲性能、冲击性能及劈裂抗拉强度,当POM纤维直径为0.2 mm,长度为18 mm时,UHPC的抗冲击性能最好,延性系数为0.94,劈裂抗拉强度最高,达到14.80 MPa。

高韧性水泥基复合材料配合比优化研究

为探究高韧性水泥基复合材料(Engineered Cementitious Composite,ECC)合理配合比,减少配合比对ECC性能的不利影响从而改善ECC的工作表现,在保持聚乙烯纤维(PE纤维)体积掺量2%的基础上,以砂胶比、粉煤灰替代率和减水剂掺量为基本参数设置9组正交试验进行流动指标、抗压、抗拉性能以及极限应变测试,并对实验结果中的影响参数进行分析。试验分析结果表明,在满足试验强度设计要求前提下,当选择0.3、35%、0.003比例的砂胶比、粉煤灰替代率和减水剂掺量配合比时,所得到PE-ECC流动性能、抗压强度、抗拉强度以及极限应变最佳,相比基础配合比显著改善了ECC的工作表现。

沙漠砂纤维陶粒混凝土力学性能试验研究

为研究沙漠砂纤维轻骨料混凝土(DPFLWC)的力学性能,通过不同掺量的聚丙烯纤维混凝土进行28 d抗压强度、劈拉强度的试验研究。探讨了劈拉强度、抗压强度在不同纤维掺量下的变化规律;构建了劈拉强度与抗压强度关系的计算模型。结果表明:其抗压强度、劈拉强度均随纤维掺量的增加呈先增后减的规律,当纤维掺量较高时,其强度增长率降低;能量耗散分析表明聚丙烯纤维起到了增韧作用,提高了耗能能力;结合现有文献数据验证了劈拉强度与抗压强度的换算关系的可靠性;其结果可为沙漠砂纤维陶粒混凝土在工程上的应用提供参考。

PK预应力混凝土叠合板抗裂混凝土试验研究

为了研究PK预应力混凝土叠合板用抗裂混凝土,提高混凝土在预应力叠合板中应用前景,通过室内试验,开展相关试验研究。采用单因素试验方法并借助混凝土试验设备主要研究了水胶比、玄武岩纤维、减水剂、粉煤灰、矿粉对混凝土流动性能、力学性能、抗裂性能的影响。结果表明:(1)水胶比对混凝土流动性能、力学性能均会产生一定影响,且影响规律近似相同;试验得出最优水胶比0.39。(2)玄武岩纤维掺加会减少混凝土28 d内收缩率、延缓混凝土开裂时间,减小混凝土裂缝宽度,对混凝土抗裂性能有较大影响;试验得出玄武岩纤维最优体积掺量0.3%。(3)正交试验得到各因素对混凝土初始扩展度、28 d抗压强度影响顺序均依次为减水剂、矿粉、粉煤灰;试验得出各因素最佳掺量为减水剂12.25 kg/m^(3)、粉煤灰35 kg/m^(3)、矿粉44 kg/m^(3)。(4)最优配合比性能测试表明,混凝土具备较高的流动性能、力学性能、抗裂性能,满足PK预应力混凝土叠合板抗裂混凝土应用要求,具有较高的应用价值。

玄武岩纤维增强材料对建筑抗震性能的影响

探讨了玄武岩纤维增强材料对建筑抗震性能的影响,特别关注了纤维质量分数如何系统地改变混凝土的结构性能。研究结果显示,混凝土的抗压强度和抗拉强度随着玄武岩纤维质量分数的增加呈现出先上升后下降的趋势,抗压强度在玄武岩纤维质量分数为1.0%时达到最大,抗拉强度在质量分数为1.5%时达到最高,此时7d和28d的抗拉强度分别为5MPa和6.5MPa。阻尼比分析表明,随着玄武岩纤维质量分数从0增至2.5%,阻尼比上升至最大值0.045。振动台测试进一步证实,抗震性能评分在玄武岩纤维质量分数为1.0%时达到峰值8.4,但超过此质量分数后,评分逐渐下降并趋向平稳。

玄武岩纤维增强乳化沥青冷再生混合料性能研究

采用室内试验研究玄武岩纤维掺量对乳化沥青冷再生混合料力学性能的增强规律,优化玄武岩纤维掺量。基于控制应力四点弯曲疲劳试验、控制应变三点加载疲劳试验及MMLS3加速加载试验,研究玄武岩纤维增强乳化沥青冷再生混合料的抗疲劳性能与高温长期荷载作用下的稳定性。结果表明:随着玄武岩纤维掺量增大,乳化沥青冷再生混合料的力学性能呈二次函数关系变化,推荐最佳玄武岩纤维掺量为0.40%;掺加玄武岩纤维显著提高了乳化沥青冷再生混合料的力学性能、抗疲劳耐久性能与抗永久变形性能。

掺加复合纤维的硬质高模量沥青混合料性能研究

将木质素纤维与玄武岩纤维复合纤维添加到硬质沥青混合料中制备高模量沥青混凝土,基于动态压缩模量试验、高低温与水稳定性试验、四点弯曲疲劳试验,分析掺加玄武岩纤维、木质素纤维及其复合纤维对硬质沥青混合料动态模量、高低温与水稳定路用性能及疲劳性能的增强作用。结果表明:掺加木质素与玄武岩复合纤维明显增大了硬质高模量沥青混合料的油石比,硬质高模量沥青混合料具有优异的抗车辙性能、高低温路用性能、水稳定性及抗疲劳性能。

Reinforcement effect of fiber and deoiled asphalt on high viscosity rubber/SBS modified asphalt mortar

In this paper we investigate the reinforcement mechanism of high viscosity rubber/SBS modified asphalt mortar mixed with fiber （mineral, lignin or carbon fiber） and deoiled asphalt （DOA）. The softening point, penetration and viscosity tests were conducted to characterize the engineering properties of asphalt-fiber mortar. The microstructure of fiber was observed using scanning electron microscopy （SEM）, and the results indicated that fiber can effectively improve the toughness of asphalt matrix through forming a spatial network structure, and then adhesion and stabilization of asphalt binder. The cone penetration test was designed to study the rheological property of fiber modified asphalt. The results indicated that the reinforcement effect increased with fibers and DOA fraction increasing to a certain threshold, and the optimal fiber content was dependent on the fiber type and its length. Fiber content and filler-asphalt ratio had significant effects on the softening point, penetration, viscosity and cone penetration of asphalt mortar.