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1.
畦灌糙率系数的变异规律及其对灌水质量的影响? 总被引：1，自引：0，他引：1
摘要：【目的】糙率系数是地面灌溉设计和管理的基本参数之一。为了更好地进行地面灌溉系统的设计和管理,研究了畦灌糙率系数的变异规律,并分析了其对灌水效果的影响。【方法】在110m的畦田长度上,观测了水流推进过程及沿程各点的水深,采用曼宁公式的数值解法估算了26条畦田的田面糙率系数,分析了其变异规律,评价了糙率系数对灌水质量评价指标的影响。【结果】结果表明,裸地畦田的平均糙率系数在0.038左右,其变异程度为中等强度。对试验区域内各畦田灌水模拟结果显示,当采用平均糙率系数模拟灌水效果评价指标时,与采用各畦田实际糙率系数相比,灌水效率指标最大相对误差达6.48%,灌水均匀度最大相差66.67%。【结论】因此,在实际地面灌溉设计与管理中,糙率系数的这种差异性不可忽略。 相似文献
2.
不同耕作条件下土壤表面粗糙度随时间变化规律研究 总被引：2，自引：1，他引：1
为了研究耕作后土壤表面粗糙度随时间变化的规律,通过采用3种不同耕作方式（铧式犁、浅松铲、圆盘耙）,在耕作后45天内,每隔5天利用激光土壤表面粗糙度扫描仪测量土壤表面粗糙度的方法,分别研究了耕作后45天内两种粗糙度指数（均方根RMS和自相关长度ACL）随时间变化的规律,研究结果表明,无论以RMS或ACL为土壤表面粗糙度的指标,与耕后天数均为指数模型相关,其中,3种耕作条件下,RMS与耕后天数的相关性在0.88~0.93之间,而ACL与耕后天数的相关性更高,在0.94~0.95之间,通过本实验研究揭示了耕作后短期内土壤表面粗糙度随时间变化的规律,对粗细农业的具体实施具有一定的意义。 相似文献
3.
湖州大气扩散能力变化特征及其原因探讨 总被引：1，自引：0，他引：1
为大气环境治理提供理论参考,利用1980-2013年湖州大气混合层高度、大气扩散参数和平均风速等资料,分析其多时间尺度变化特征及可能原因。结果表明：(1)湖州大气混合层高度呈现缓慢增长趋势,水平风速和大气扩散参数总体趋于减弱,风速与大气扩散参数有显著的正相关关系。(2)大气混合层高度、扩散参数和水平风速的月变化呈双峰型,3月与8月为波峰,7月和10月为波谷,且三者存在显著正相关关系,其季节变化呈现春高秋低特征。(3)城市化建设、城市热岛和干岛效应等增加了大气的垂直运动能力,使得大气混合层高度增加,而地表粗糙度的增加使得水平风速减小,导致大气的水平运动能力减弱,大气扩散能力减弱。(4)紧邻太湖水体使得湖州大气扩散能力与沿海相似,水陆热力差异、风速变化、梅雨、晴热高温等对大气混合层厚度和扩散参数的季节变化都有明显影响。 相似文献
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5.
The characteristics of work piece's surface under precision abrasive belt grinding are analyzed.A comprehensive understanding of the reason of low roughness value's surface is found out,which the edge of grain formed compact and crossed micro grinding marks that can compensate for the inconsistence of grinding mark's height in single grinding direction.The grinding test of gear shaft is done for the sake of doing research on the main factors of surface roughness in grinding quenching stainless steel.The results indicate that decreasing the vertical pressure is beneficial to(reduce) surface roughness of work piece,and the surface roughness also can reach the requirement of precision processing when steadily grinding. 相似文献
6.
Through a large number of tests of grinding the cycloidal flanks with abrasive belt, the surface roughness and residual stress exist in the complex curved parts resulting from large-curvature belt-grinding are discussed. The effect of the technical parameters on surface quality is analyzed and the empiric formula is given. This is enable to provide the grinding process with correct selecting of technical parameters. 相似文献
7.
Higher-order elliptical bevel gear is a typical form of the noncircular bevel gear transmission.Space spherical coordinate system of the bevel gear meshing is set up based on the meshing theory of space transmission.The varying relationship among the pitch curve,tooth profile and mesh lines are analyzed,and the equation of the gear tooth surface is developed with matrix method based on space coordinate transformation.The basic parameters of the noncircular bevel gear such as transmission ratio,modulus and the number of teeth are designed,and detailed analysis of the influence of the eccentricity on the relevant parameters is carried out as well.By using discrete numerical method and three-dimensional software,the mathematical model of the tooth profile and virtual physical model of the noncircular bevel gear are established,and then simulation on its motion and interference checking are performed.Finally,the approach for design,calculation and generation of the tooth profile is obtained and its correction has been verified by experiment. 相似文献
8.
The 2D motif method is a surface characterization method promising to separate roughness and waviness from a profile and is adopted by ISO,so is meaningful to extend this method to 3D.Vincent's watershed algorithm is employed for the generation of 3D-motif.A smallest area selecting criteria is proposed for the use of clearing the small motifs which are concerned as noise.As there are no manipulating factors as 2D-method,a multi-scale analysis is employed based on area and depth criteria,the use of depth criteria is to prevent the combination of two adjacent motifs if there is a significant peak on the border of them.Finally the surface of C(100) are analyzed by the presented method,the texture of this surface has been characterized. 相似文献
9.
Bridge surface roughness is usually considered to be the main Influencing factors of vehicle-bridge coupled vibrations.The way that obtaine Bridge surface roughness by the transformation of power spectral density is effective and rapid.The Bridge surface roughness is obtained by Fourier inverse transform method and trigonometric series method respectively. It can be concluded from the comparision that the precision of Fourier inverse transform method is higher than trigonometric series method. The vibration functions for 4-dofs Vehicle and bridge were derived with the employment of d'Alembert principle and computational procedures for vehicle-bridge coupled vibration were compiled. The dynamic response of a simply supported beam and vehicle was analyzed considering bridge surface roughness which was obtained by Fourier inverse transform method.The research shows that the influence due to the bridge surface roughness is significiant and vehicle speed also effects the bridge vibrations by changing the frequency of the force acting on the bridge due to vehicle and the force acting on the vehicle due to bridge deformation. 相似文献
10.
Hydraulic system pressure, contact surface between grinding roller and materials and grinding roller force of roller mill are analyzed. A new roller pressure calculation method named average surface roller pressure calculation method is proposed,and the corresponding theoretical formula is derived from three different perspectives, including roller pressure numerical calculation, stress and strain of main components and mill power through the calculation of real samples. The average surface roller and traditional average material roller pressure are compared to verify the correctness and accuracy of the proposed method. Design parameters such as the grinding roller structure, material maximum size, layer height and working pressure of the hydraulic system on the influence of roller are analyzed according to the formula of roller pressure. The research results provide theoretical basis for the selection of design parameters and the design calculation of structural strength for roller mill. 相似文献
11.
《Soil Technology》1993,6(3):273-286
The main objective of this study was to investigate how the interactions between rainfall energy and microrelief affect soil surface sealing and runoff. Furthermore, several roughness indices and geostatistical procedures were tested for their ability to characterize microrelief.Runoff boxes filled with soil from the plough layer of a silty Luvisol were subjected to simulated rainfall. Two types of microrelief (rough and fine) were tested at two rainfall intensities (30 and 60 mm/h). A photogrammetric technique was used to develop digital elevation models (DEMs) of the soil surface before and after rainfall with a resolution in height of 0.2 mm and a grid spacing of 2 mm.The random roughness coefficient according to Currence & Lovely (1970) was found to be sensitive to surface microrelief variations. Semivariograms of the data indicated that big clods were the main elements determining microrelief and the ratio of total surface are to map area. The observed variations in runoff as a function of microrelief were best explained by rainfall energy per total surface area and by the relative contribution of the effective normal component of kinetic energy with respect to the impact angle of raindrops. Microdepression storage was only 0.6 mm or less and was found to be negligible in terms of runoff. 相似文献
12.
Experimental analysis of the abrasive belt follow-up grinding of Zirconium-4 alloys tubes and pipes 总被引：1，自引：1，他引：0
Abrasive belt grinding experiments of Zr-4 nuclear power tube are carried out by using three different abrasive belts with same size, and the interactive generating mechanism between abrasive and workpiece is analyzed, the main factors of material removal rate and surface roughness of Zr-4 alloys are obtained. With the help of the advanced test facilities, the abrasive grain abrasion and surface topography of the workpiece are observed. The metallographic structure and microhardness of the layer of burnt surface during Zr-4 alloys Grinding are analyzed. Some conclusions are given as follows: the material removal rate and surface roughness are mainly affected by the factors of belt speed, grinding pressure, hardness of the contact wheel and abrasive type, of which, the belt speed is the strongest factor. The adhesion wear of the Zirconium corundum and aluminium oxide abrasive grit is more serious, the most important wear form of silicon carbide is abrasion wear. With the onset of grinding burn, the mechanical properties of Zr-4 alloys are deteriorated obviously. The results provide a theoretical and experimental basis for technical optimization in the grinding of Zr-4 alloys with efficiency and high quality. 相似文献
13.
Steel-plastic composite geogrid enjoys greater reinforcement effect than other types of geogrid due mainly to its special design and structure,such as deliberately roughed rib surface to enhance its surface roughness and friction coefficient.Hence,engaging force together with interface friction raises the reinforced soil's stability.Tests of pull-out on varied size of steel-plastics composite geogrid have been performed with copper tailing as filling soil,and interaction parameters of shearing intensity and pseudo-friction coefficient between geogrid and copper tailing are obtained.In addition,other influence factors have been discussed. 相似文献
14.
Based on the formal solutions of the buckling eigen equation,the probability density evolution equation for the random buckling eigenvalue is derived considering the random wind loading.Taking the averaged wind speed at 10m height and roughness length as the random factors,the random buckling bearing capacity for a super-high cooling tower is then analyzed.Furthermore,both the mean and the standard deviations of the capacity are calculated.It is indicated that there exhibits a general shape for the probability density function of the random buckling capacity.And the mean of the random buckling bearing capacity is close to that one computed by the averaged parameter.However,the variation of the random buckling bearing capacity is between the corresponding values of averaged wind speed at 10m height and roughness length. 相似文献
15.
Liao Xiaoyun Lei Wenyu 《保鲜与加工》1999,(1):18-23
A new analysis method for machining surface profile error is presented in this paper.The linear regression and nonlinear regression are first applied respectively,and then the Weierstrass Mandebrot fractal function is used to obtain the fractal parameters of machining profiles.A minimal parameter set which depicts the machining surface geometric precision is set up,and the surface profile can be reconstructed using these parameters,and an analysis method for part performance and its tolerance structure is proposed.Examples are provided to illustrate the method is feasible and effective. 相似文献
16.
以红地球葡萄果实为试料,采用质构分析法（TPA）研究了不同高度跌落机械损伤对葡萄果粒感官品质及质地变化的影响,并分析各指标相互关系。结果表明：葡萄果实经不同高度机械跌落后,随着跌落高度的增加,其感官品质发生很大变化;当跌落高度小于60 cm时,外观观察无明显差异,当跌落高度≥80 cm后,外观差异明显,损伤的果粒数量和损伤级数均增加明显;损伤指数与跌落高度回归拟合度高（R2=0.985）,100 cm和160 cm高度跌落时,损伤指数分别是60 cm处理的4倍和8倍之多;随跌落高度的增加,果实硬度和咀嚼性值呈下降趋势,80~160 cm处理下降幅度明显大于其他处理;果实弹性、凝聚性和回复性呈增加趋势,80~160 cm处理均与对照呈极显著差异（P＜0.01）,100 cm和160 cm处理凝聚性分别增加了24.5%和31.0%,回复性大于其他3个处理;机械损伤指数与硬度、咀嚼性、胶黏性呈负相关性,与凝聚性和弹性、回复性呈正相关。 相似文献
17.
湖南典型土壤磷素剖面分布特征及其流失风险 总被引：3，自引：1，他引：2
为了明晰不同土壤类型、利用方式土壤磷素分布特征,评估其流失风险的大小,研究了湖南3种典型土壤（红壤、潮土、紫色土）磷素含量特征及其剖面分布。野外采集3种母质发育土壤的旱地和水田土壤剖面样品进行室内分析,按张守敬等提出的酸性土壤无机磷形态的分级测定方法,对土壤无机磷进行分级。结果表明,不同土壤中磷素含量和形态分布有明显差异：磷素含量由高到低依次为潮土>红壤>紫色土;红壤发育的土壤以磷酸铝和磷酸铁占优势,潮土和紫色土的Ca-P含量占优势较高。土壤磷素在剖面中的分布均为表层最高,且随剖面深度的增加而减少,而后趋于相对稳定;无机磷中的Al-P、Fe-P以及O-P主要集中在0~20 cm的土层中,其剖面分布于全磷类似,而Ca-P剖面分布上相对变化不大。土地利用方式的不同导致全磷的差异：水田均大于旱地。土壤类型及利用方式均对磷素含量和形态特征有明显影响,应根据不同的土壤类型和利用方式控制其流失风险。 相似文献
18.
缺磷胁迫对不同玉米幼苗生长的影响 总被引：4，自引：2，他引：4
营养液砂培4种不同玉米自交系材料,设置0.25mol/LKH2PO4全磷(对照)、0mol/LKH2PO4(缺磷)两种处理,于5、7、9、11d时考察幼苗生长指标。对缺磷胁迫下4种不同基因型玉米自交系生长的研究表明,低磷胁迫对040651、044191地上部分的抑制大于根系,根系的相对干生物量明显高于地上部分的相对干生物量;从相对株高和相对叶面积的研究显示,编号为040651的自交系受缺磷胁迫的影响小于其他3个自交系材料。缺磷胁迫下4种不同基因型玉米自交系根系形态的研究显示:缺磷胁迫诱导玉米根伸长,根系表面积增大,根冠比显著增加。 相似文献
19.
Wind induced responses of a single steel circular antenna with an asymmetric brace were computed considering wind speed and direction joint distribution function at location of the structure, and then wind induced fatigue life of the structure was estimated in frequency domain and time domain, respectively. Some parameters, including wind direction, surface roughness, vortex induced resonance and mean wind speed, which would have effects on the wind induced fatigue life of the structure,were discussed. It is found that 1) wind direction has great effects on wind induced fatigue damage, that is, significant fatigue can occur in wind direction of high probability; 2) the more roughness the surface of structure is, the shorter the wind induced fatigue life is; 3) the effects of vortex resonance on wind induced fatigue life should not be neglected; 4) the mean velocity has slight impact on the wind induced fatigue life of the structure. 相似文献
20.
利用3个直立穗型和3个弯曲穗型粳稻品种研究了两种不同穗型水稻穗上不同粒位籽粒淀粉RVA谱特征的差异。结果表明:穗内不同粒位间籽粒的淀粉黏滞特性的差异幅度和变异系数大小因品种而异,与穗型特征无关。淀粉黏滞特性好坏与其颖花在穗上的开花顺序有密切联系,早开花籽粒的淀粉黏滞特性强于晚开花籽粒。一次枝梗上的6个粒位的RVA谱特征值排列顺序以第1,6,5粒位较高,第2粒位最低;二次枝梗上的3个粒位排序为第1粒位>第3粒位>第2粒位。从空间上看,整穗粒位间从上到下,淀粉黏滞特性有逐渐变劣的趋势。 相似文献