Ionization of liquids by radiation: measurement by charge scavenging

Pulse radiolysis of dilute solutions of triphenylcarbinol in saturated hydrocarbon gives spectra of the triphenylmethyl free radical, (C(6)H(5))(3)C., and cation, (C(6)H(5))(5)C(+). The yield of the ion is independent of the carbinol concentration, and is thought to measure the yield of free ions generated in the solvent. The relative yields of ions thus found in cyclohexane and 2,2,4-trimethylpentane agree with measurements made by the clearing-field method.     

Apollo 12 magnetometer: measurement of a steady magnetic field on the surface of the moon

The Apollo 12 magnetometer has measured a steady magnetic field of 36 +/- 5 gammas on the lunar surface. Surface gradient measurements and data from a lunar orbiting satellite indicate that this steady field is localized rather than global in its extent. These data suggest that the source is a large, magnetized body which acquired a field during an epoch in which the inducing field was much stronger than any that presently exists at the moon.     

Soil-water potential: direct measurement by a new technique

Current methods of measuring the potential of water in soil are inadequate. It is proposed to depress the reference free energy of water by a predetermined amount from the standard level of pure free water at atmospheric pressure by use of a solute. The specific free-energy difference of soil water from the depressed reference can be measured as a pressure.     

Time measurement in insect photoperiodism: reversal of a photoperiod effect by chilling

Spectacular reversals of the photoperiodic control of diapause are obtained if females of Nasonia vitripennis are chilled for 4 hours in certain lightdark cycles. Experiments in which chilling is combined with short light breaks (night interruptions) show that the first peak of diapause inhibition moves in response to the chilling. This result provides an explanation for the photoperiodic reversal; it is also circumstantial evidence for the participation of circadian rhythms in photoperiodism.     

Short interval time measurement by a parasitoid wasp

The number of eggs laid by the parasitoid wasp Trichogramma varies with host volume. The duration of the wasp's initial transit across the host surface during host examination is used to determine the number of eggs laid. A 2.5-second reduction in initial transit resulted in a 30% reduction in eggs oviposited, demonstrating that these wasps measure short time intervals. This measure is used for progeny allocation independent of host body size.     

Milankovitch radiation variations: a quantitative evaluation

A quantitative determination of changes in the surface temperature caused by variations in insolation calculated by Milankovitch has been made through the use of the thermodynamic model of Adem. Under extreme conditions, mean coolings of 3.1 degrees and 2.7 degrees C, respectively, at latitudes 25 degrees and 65 degrees N are obtained for Milankovitch radiation cycles. At the sensitive latitude 65 degrees N, a mean cooling below the present temperature for each of the times of radiation minimum is only 1.4 degrees C. This result indicates that the Milankovitch effect is rather small to have triggered glacial climates.     

Light-driven motion of liquids on a photoresponsive surface

The macroscopic motion of liquids on a flat solid surface was manipulated reversibly by photoirradiation of a photoisomerizable monolayer covering the surface. When a liquid droplet several millimeters in diameter was placed on a substrate surface modified with a calix[4]resorcinarene derivative having photochromic azobenzene units, asymmetrical photoirradiation caused a gradient in surface free energy due to the photoisomerization of surface azobenzenes, leading to the directional motion of the droplet. The direction and velocity of the motion were tunable by varying the direction and steepness of the gradient in light intensity. The light-driven motion of a fluid substance in a surface-modified glass tube suggests potential applicability to microscale chemical process systems.     

太阳辐射作用下冻结期衬砌渠道温度场分析

【目的】对季节性冻土区衬砌渠道在太阳辐射作用下的温度场进行数值模拟,分析太阳辐射对渠道温度分布的影响。【方法】利用Hottel太阳辐射模型,结合热传导理论和有限元分析方法,考虑渠道自身的遮蔽作用,对太阳辐射作用下的梯形衬砌渠道的温度场进行计算。【结果】提出了梯形渠道太阳辐射的计算方法;衬砌渠道表面太阳辐射的日变化表现为早晚最小、中午最大;渠道阴、阳坡接受到的太阳辐射差异明显,阴坡太阳总辐射约为阳坡的20%;渠道表面温度的日变化趋势与大气温度相同,近似为正弦分布,其温度变幅小于大气温度变幅,变化滞后于太阳辐射约2.5h,阴、阳坡温度最大相差4℃左右,阳坡温度值与日间温度增加速率均大于阴坡。【结论】渠道温度变化与太阳辐射有密切关系,阴、阳坡接受到的太阳辐射量不同是渠道温度存在较大差异的原因,太阳辐射是渠道冻融循环的动力,在渠道冻胀研究中必须考虑太阳辐射的影响。     

Seeing with a new light: synchrotron radiation

The special properties of synchrotron light are leading to a rapid increase in its utilization for both research and technology. At wavelength in the ultraviolet region of the broad spectrum in these beams a number of atomic, molecular, and solid-state spectroscopies are being pursued; soft x-rays are being used for spectroscopy, lithography, microscopy, and topography; at still shorter wavelengths, advantage is taken of scattering properties to probe the structure of matter. Characteristics of synchrotron radiation and of the sources which produce it are described, and some typical investigations and applications are presented to suggest the versatility of these sources.     

Absorption of solar radiation by clouds: observations versus models

There has been a long history of unexplained anomalous absorption of solar radiation by clouds. Collocated satellite and surface measurements of solar radiation at five geographically diverse locations showed significant solar absorption by clouds, resulting in about 25 watts per square meter more global-mean absorption by the cloudy atmosphere than predicted by theoretical models. It has often been suggested that tropospheric aerosols could increase cloud absorption. But these aerosols are temporally and spatially heterogeneous, whereas the observed cloud absorption is remarkably invariant with respect to season and location. Although its physical cause is unknown, enhanced cloud absorption substantially alters our understanding of the atmosphere's energy budget.     

太阳辐射作用下浮顶油罐温度场的数值模拟

为了研究太阳辐射对浮顶油罐温度场的影响,有必要掌握受太阳辐射影响原油在浮顶油罐中的温度变化规律.通过分析浮顶油罐与环境换热过程,建立2×104 m3 浮顶油罐的三维模型,对一天内浮顶油罐油品及罐壁的温度变化进行数值模拟.结果表明:在以太阳辐射为主的环境变化影响下,浮顶油罐的近壁面和浮盘处会产生温度梯度较大的高温油层,深...     

水田除草关键部件扭矩测试试验研究

苗间除草装置是水田除草机的核心部件,其工作时的功率消耗为该机具总功消耗的主要部分.利用自制扭矩传感器测取除草机工作过程中除草刀轴上产生的扭矩.选取影响除草机功率消耗的刀盘转速、机具前进速度、除草作业深度三因素为试验因子,采用二次正交旋转设计方法进行试验研究.运用minitab15.1软件处理扭矩测试结果,根据田间试验分析,得出苗间除草刀在最佳工作状况下产生的扭矩值,该数值可为机具关键部件可靠性分析和寿命估算等提供重要的理论参考     

Gravity field of venus: a preliminary analysis

The line-of-sight gravity field for Venus has been mapped by tracking the Pioneer Venus spacecraft in the vicinity of periapsis for a 45 degrees swath of longitude eastward of 294 degrees . There are consistent and systematic variations in the gravity signature from orbit to orbit, attesting to the reality of observed anomalies. Orbit 93 passes over a large positive topographic feature, the "northern plateau," for which there is no corresponding gravity signature. If this region has no isostatic compensation, the gravity signal would exceed the noise level by a factor of 7. The results of simulation modeling indicate that the northern plateau must be compensated at depths of about 100 kilometers or less. The long-wavelength anomalies seen in the Venus gravity data have been Fourier-decomposed along the orbital tracks and compared to analogous spectra for Earth. The gross power in the two mean spectra is approximately, the same, but systematic variations among the harmonics suggest differences in dynamic processes or lithospheric behavior, or both, for the two planets.     

农田土壤水分测定与模拟研究进展

土壤水分不仅是农业生产中影响产量的重要调控因子,而且还影响环境污染物质的迁移和土壤的持续利用。本文对土壤水分各测定方法的优缺点进行了评述。提高土壤水分监测传感器精确性和观测数据自动采集、区域土壤水分的遥感监测是当前和未来的主要发展方向。对国内外应用较多的土壤水分模型做了概括和总结,其模拟方法主要以土壤水动力学方法、土壤水分平衡方法为主,随机模型受到关注。本文还对土壤水分的未来研究进行了展望。     

Propagation of positional measurement errors to agricultural field boundaries and associated costs

It has been argued that the upcoming targeted approach to managing field operations, or precision farming, requires that field boundaries are measured with cm level accuracy, thus avoiding losses such as wasted inputs, unharvested crops and inefficient use of the land. This paper demonstrates a method for verification of such claims, based on a statistical model that accounts for temporal correlation in positional measurement errors. Our implementation employs the Data Uncertainty Engine (DUE), which is free software that aids the user in defining probability distributions for uncertain spatial objects, and draws random samples from these distributions. A case study concerning the financial consequences of uncertain geometry for a farmer who uses a digital map to optimise field operations for 15 ha of a potato crop is presented. The error model was parameterised on measurement scenarios representing (1) the Dutch registry of agricultural fields; (2) differential GPS-based field checks for verification of area declarations; and (3) special purpose Real Time Kinematic (RTK)-GPS surveys. We found that a farmer who has a manually digitised map of the study area would benefit from a RTK-GPS survey in a single crop year if the survey would cost less than € 442. An independent test case showed that the results of the error model were consistent with field data.     

基于GPS-OEM的车载农田面积测量系统的设计

根据GPS定位信息的采集、测量实际农田试验数据,得出的农田面积测量简易算法,设计出一种基于GPS-OEM的车载田间面积测量系统。该系统在农业机械作业时,利用GPS-OEM模块实时接收GPS定位信息,能够算出农业机械的动态作业面积。系统拥有常用的CAN总线通信接口和存储设备,方便与其他设备实现信息共享和数据存储。并具有测量准确,价格低廉等特点,适合于各种农业机械作业面积的测量。