带扩散系数的拟线性时滞脉冲现象的振动性

研究了一类带扩散系数的拟线性脉冲时滞抛物型方程组的振动性,利用振动的定义、Green公式和Newmann边值条件将这类脉冲时滞抛物方程组的振动问题转化为脉冲时滞微分不等式正解的不存在性问题,并利用最终正解的定义和脉冲时滞微分不等式,获得了该类方程组所有解(强)振动的充分条件.     

MEMS传感器技术在汽车上的应用研究与展望

为了满足汽车电子化、智能化的需要,越来越多的MEMS(微机电系统)传感器应用到汽车上。本文对主要的几种汽车MEMS传感器的应用状况和研究现状进行简述,并且对压力传感器和微加速度计的设计缺陷进行研究。同时,结合MEMS传感器的特点和车载传感器的要求,对汽车MEMS传感器的发展提出几点建议和展望。     

规模化猪场粪污处理工艺的研究

在国内外猪场粪污处理工艺调研的基础上，通过对粪污粒径分布、沉降性能和气浮工艺适用性的试验研究，确定了一种先进实用、可靠、易行的猪场粪污达标排放的处理工艺。     

农资仓储脉冲超宽带室内定位系统设计与试验及误差分析

针对仓储环境下农资物品与自动导引运输车(automated guided vehicle,AGV)的定位精度低的问题,开发了适用于农资仓储环境下的脉冲超宽带技术(impulse radio-ultra wide band,IR-UWB)室内定位系统。采用双面双程测距(symmetric double sided-two way ranging,SDS-TWR)方法,建立了考虑时钟频偏等因素的到达时间(time of arrival,TOA)定位系统模型。研究表明定位系统计算所带来的误差主要来源于距离测算方法和节点位置计算方法 2方面,在这2方面提出了相应的解决办法,包括测距算法的选择,基站的布置等。最后,以DW1000射频芯片为硬件基础,设计了定位系统移动站和基站节点,并在农资仓库的环境中分别进行了静态测距试验、静态定位试验、以及动态定位试验。试验表明:静态测距精度优于50 mm,静态定位精度优于50 mm,动态定位试验精度优于85 mm。综合结果表明,该文搭建的系统可满足农资物品定位的实际应用要求,可为室内农资仓储环境下AGV的定位和导航提供参考。     

农业与生产性服务业互动关系的实证研究——以广东为例

运用脉冲响应函数方法,考察了广东省农业与生产性服务业的长期动态影响特征。冲击响应结果表明,改革开放以来,广东省农业与生产性服务业之间存在相互促进的关系;两者对冲击的反应均存在一定的滞后期。方差分解结果显示,生产性服务业是解释农业发展的重要变量;但农业对生产性服务业预测性方差贡献度则相对较小,农业对生产性服务业的促进机制仍需改善。最后,提出相关的政策建议。简要补充说明在哪几个主要方面提出建议。     

The feasibility of using an industrial sewage sludge produce in Pakistan as agricultural fertilizer used for cultivation of Sorghum bicolor L

Abstract

In the present study we evaluate the feasibility of using untreated industrial sewage sludge by liming before use as a fertilizer, produced in Pakistan. In a pots experiment, limed industrial sewage sludge (LSW) and non-limed sewage sludge (NLSW), were amended with soil separately and grown sorghum. After maturity, the sorghum grains were analysed for total contents of potentially toxic metals (TPTM), As, Cd, Cr, Cu, Ni, Pb and Zn. The proportion of different mobility fractions of each element in LWS and NLSW, a modified BCR sequential extraction procedure (Community Bureau of Reference) and single extractions with mild extractants (deionized water and CaCl₂) were used. In LSW, the availability of most of the elements under study was reduced, probably due to the increased pH of soil, while this was the reverse in the cases of Cd and Cu, their mobility was slightly increased by lime-treated sludge. The sorghum grains grown in LSW have low level As, Cr, Ni, Pb and Zn as compared to grains grown in NLSW, except Cu and Cd, which, however, never exceeded legal limits. Thus the research showed that liming, by augmenting soil alkalinity, allows a safe agricultural use even of industrial sludge, which is environmentally hazardous for its great content of heavy metals.     

浅谈大型浮选机的研制与设计

文章分析了KYF系列和JJF-130系列浮选机研制过程中要解决的关键技术,详细阐述了在设计过程中整机的主要结构和参教的选择,以及槽体、叶轮、定子等关键部件的结构和参数选择.     

HPFL加固混凝土结构斜截面承载力计算及工程应用

根据企业集群与生物种群有着一定的相似性，借鉴种群生态学中的种群竞争模型建立了网状型企业集群模式下企业间竞争关系的数学模型 —— 一类具脉冲效应和反馈控制的非自治企业竞争模型系统，并通过脉冲微分方程的比较性定理，建立了该系统持久性生存的充分条件，并做经济学解释.     

农村劳动力转移动因实证研究--以宁夏为例

以宁夏为例,将农村劳动力转移数量、城市化水平、城乡期望收入差距、劳动力转移成本作为内生变量,建立一个向量自回归模型,同时进行协整检验、基于误差修正模型的脉冲响应函数分析。研究发现,农村劳动力对自身有强的带动作用。市场化程度与农村劳动力转移正相关,收入差距和城市化水平与农村劳动力转移基本负相关。因此,应在发展农村经济的同时鼓励劳动力密集型产业发展、改革户籍制度来增加劳动力流动性。     

Physical characteristics of reticuloruminal contents of oxen in relation to forage type and time after feeding

The stratification of reticulorumen (RR) contents has been described in domestic ruminants, but suspected to be absent in certain wild ruminant species. To investigate how such stratification could be quantified, we tested variables indicating stratification in three oxen with rumen cannulae, fed once daily for 3 h, one of three different forages (fresh grass FG, grass hay GH, lucerne hay LH). Ingesta samples from dorsal rumen (DR), ventral rumen (VR) and reticulum (RET) were taken at 0, 3, 6, 12 and 24 h after the last meal and analyzed for dry matter (DM) concentration, mean particle size and proportion of floating/sedimenting particles. Viscosity was measured in centrifuged RR fluid. There was no relevant variation in rumen fluid viscosity over time or with feeding regime. Dry matter content in DR was always higher than in VR or RET and increased after feeding. When LH and FG were fed, DR always contained larger particles than VR, except at 6 and 12 h of feeding GH. The proportion of floating particles was higher in DR than VR except at GH 6 h and GR between 6 and 12 h. The floating particle fraction mostly contained larger particles, except for GH 3 h in both DR and VR and for FG 3–12 h in DR. Changes in the distribution of particle size and proportion of floating particles over time comply with the theoretical course of fermentative digestion for different forages, but make these variables unreliable indicators of stratification in less controlled settings, such as investigations in wild ruminants. In contrast, viscosity of rumen fluids appears constant over time and feeding regime and might be used as a species‐specific variable. The difference in DM content in DR and VR is a reliable indicator for RR contents stratification characterized by an oversaturation of the contents with fluid, leading to lower VR DM contents.