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玉米精播机漏播补偿系统设计 总被引:21,自引:2,他引:21
目前玉米免耕播种机的播种质量仍低于常规播种。本文讨论了微机控制的排种监测及漏播补偿装置,通过机电结合手段解决漏播问题。台架试验表明本装置能够准确发现漏播,并通过采取的措施实现及时补种,补种成功率可达90%以上。 相似文献
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在内蒙古锡林郭勒盟镶黄旗蝗灾发生区,采集了严重危害草原的4龄期、5龄期及成虫的亚洲小车蝗,分别对它们的活体、死体的悬浮速度进行了测定,为草地蝗虫吸捕机的设计与改进提供了理论依据。 相似文献
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储训 《扬州大学学报(农业与生命科学版)》1986,(1)
本文采用数学分析的方法,建立了大型泵站肘形进水流道过水断面面积与内外壁边界几何参数之间的方程,并给出了方程的数值解法。与以往所采用的图解法相比,免除了繁琐的作图和校核修改过程,对应于一定的流速分布给出唯一的结果。 相似文献
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Background, aim, and scope Contaminated mine drainage water has become a major hydrogeological and geochemical problem. Release of soluble metal contaminants
and acidity from mining sites can pose serious chemical risks to surface and groundwater in the surrounding environment, and
it is an important socio-economic factor addressed by working groups like SUITMA Morel and Heinrich (J Soils Sediments 8:206–207,
2008). The release of Zn and Pb from sulfide-bearing flotation residues of a small scale mine in Western Germany is investigated
with focus on metal transfer to soil solution. Total contents of the soil material as well as soil water sampled with suction
cups were analyzed. The influence of pH on leaching behavior was investigated with pHstat tests. Isotopic analyses helped assessing seepage water velocity. The aim of this study was the assessment of the environmental
behavior of zinc and lead caused by the weathering of sulfide-bearing mine tailings. Especially, we address in this paper
the dissolution of sphalerite (ZnS) in contrast to the well-known dissolution processes of pyrite (FeS2).
Materials and methods Total metal contents of the soil samples were analyzed by energy-dispersive X-ray fluorescence spectroscopy, total C concentration
was measured using a CHNS elemental analyzer. X-ray diffraction (XRD) spectra were recorded from powdered soil samples. Soil
water was sampled in nylon suction cups. Electrical conductivity (EC), pH, and temperature of the soil water samples were
measured in the field immediately after sampling. Major anions (F, Cl, NO2, NO3, SO4) were analyzed by ion chromatography, major cations (Ca, Na, K, Li) were analyzed by flame photometry, heavy metals (Zn,
Pb, Fe, Mn, and Mg) by flame atomic absorption spectrometry. Tritium was analyzed by liquid scintillation counting (LSC),
18O and 2H were analyzed by isotope ratio mass spectrometry (IRMS). pHstat tests were performed at four different pH values between 2 and 5.
Results Total Zn contents of the soil samples averaged 10 g kg−1, Pb contents averaged 2.5 g kg−1, Fe 22 g kg−1, S 8.0 g kg−1, and total carbon 4.0 g kg−1. Below 2-m depth, soil samples had neutral pH values. Toward the surface, pH decreased down to pH 5.4 in P1 and P3, and to
pH 5.9 in core P2, respectively. Dissolved contents of major ions (Mg, Ca, K, SO4, and HCO3) in the soil solution increased with depth. Metal concentrations (Fe, Mn, Zn) decreased with depth. The solution pH was neutral
to slightly alkaline in samples below 2 m and slightly acidic (pH 6) at 1 m depth. Tritium values are around 7 TU and correspond
to modern rain, i.e., after 1975. Stable isotope values plot on the global meteoric water line. The pHstat tests provide two kinds of information, the acid neutralization capacity after 24 h (ANC24) and the release of metals depending
on pH. The ANC24 increases linearly with decreasing pH from about 60 mmol(eq) kg−1 at pH 5 to about 460 mmol(eq) kg−1 at pH 2. Zn and Fe release show a strong increase with decreasing pH to 126 and 142 mmol(eq) kg−1, respectively. Pb release increases at pH <4 and Mn release at pH <5, both to about 10 mmol(eq) kg−1.
Discussion With an average of 10 g kg−1, this field site is highly enriched in Zn. In the oxidized topsoil, Zn concentrations are significantly lower than in the
anoxic subsoil. The distribution pattern of total Zn contents and soil pH values indicate that the topsoil, which is prone
to oxidation and acidification, is already depleted in Zn. Only in soil core P2, Zn (and Fe) contents in the topsoil were
higher than in the subsoil. Oxidation of the sulfidic material leads to redistribution into mobilizable species. High soil
water concentrations (10 to 15 mg L−1) can be found at acidic pH. The dominant Zn species in the soil solution is Zn2+. At neutral pH, Zn concentrations are below 0.001 mg L−1. During the soil passage, the contaminated seepage water enters the anoxic subsoil with pH buffering carbonates. Results
indicate that Zn is immobilized there. However, when the acid neutralization capacity is exhausted, a breakthrough of dissolved
Zn to the groundwater has to be expected. Lead averages 2.5 g kg−1 inside the flotation dump. In contrast to Zn, the first centimeters of the oxidized topsoil with high TOC contents show higher
Pb contents than the anoxic subsoil. About 80% of the cation exchange capacity in the topsoil is occupied by Pb. In contrast
to Zn, Pb is not abundant as aqueous species at slightly acidic pH. Values lower than pH 4 are necessary to mobilize Pb in
higher amounts, as pHstat experiments confirm. Hence, Pb is not expected to be leached out until the buffer capacity of the soil is exhausted.
Conclusions The environmental fate and behavior of Zn and Pb in the flotation dump is strongly depending on pH and redox conditions. Oxidation
of sphalerite leads to a transfer of Zn from immobile to easily mobilizable species. Sulfide oxidation leads to an acidification
of the topsoil where the buffer capacity is already exhausted due to the leaching of carbonates. At acidic pH, Zn is transferred
to the aqueous phase and leached to the subsoil where soil pH is neutral. Electron supply and the buffer capacity of the material
are found to be the main factors controlling the mobility of Zn. In contrast, the transfer of comparable amounts of Pb to
the aqueous phase requires pH values <4. Since Pb is enriched in the topsoil, not leaching to the groundwater, but direct
uptake (e.g., children, animals) and uptake by plants is the highest environmental risk. If the acidification of the soil
proceeds with the same rate as in the last 40 years, it will reach the bottom of the tailing in about 200 years and a breakthrough
of metals to the groundwater has to be expected.
Recommendations and perspectives The behavior of the different metals and their environmental impact depends on the different metal properties as well as on
external conditions, e.g. pH, redox conditions, buffer capacity, and groundwater recharge. To assess the future release of
metals from a flotation dump it is crucial to determine the main processes leading to acidification, the buffer capacity,
and heavy metal binding forms. The release of heavy metals to the groundwater could be prevented by liming or other buffering
techniques de Andrade et al. (J Soils Sediments 8:123–129, 2008).
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
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为有效监测玉米播种质量,减少漏播、断行的发生,设计一套基于光电法原理的玉米漏播监测器。采用3 mm红外发光管和硅PIN光电二极管作为感测元件,利用光伏效应原理设计了传感器,以检测种子通过与否。以stm32F103单片机为核心,设计了主控制器。主控制器通过中断方式接收传感器的信号,种子通过时即触动内部相应定时器工作或复位,定时计数超过3 s 时就产生报警信号并在屏幕上显示。田间试验表明:在播种机正常排种频率范围内,计数误差不低于97%,漏播检测率达到95%,光照强度、机具振动对漏播监测器工作无影响。 相似文献
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