Estimation of total above-ground phytomass production using remotely sensed data

Remote sensing potentially offers a quick and nondestructive method for monitoring plant canopy condition and development. In this study, multispectral reflectance and thermal emittance data were used in conjunction with micrometeorological data in a simple model to estimate above-ground total dry phytomass production of several spring wheat canopies. The fraction of absorbed photosynthetic radiation (PAR) by plants was estimated from measurements of visible and near-infrared canopy reflectance. Canopy radiation temperature was used as a crop stress indicator in the model. Estimated above-ground phytomass values based on this model were strongly correlated with the measured phytomass values for a wide range of climate and plant-canopy conditions.     

The use of crack layer theory to predict the lifetime of the fatigue crack growth of high density polyethylene

In the case of high density polyethylene (HDPE), the fatigue crack propagates in a discontinuous manner, which can be observed by distinct striations. In this article, fatigue crack growth (FCG) experiments were conducted on two grades of HDPE pipe with compact‐tension (CT) and cracked round bar (CRB) specimens. The effects of the stress ratio (R‐ratio) which is defined as the ratio of minimum stress and maximum stress of fatigue loadings and the frequency on FCG behavior were experimentally studied. Although FCG rates showed a great dependence on the R‐ratio in terms of the range of the stress‐intensity factor, the effect of the frequency may be considered to be significant in the low crack growth region. In addition, these experimental data were employed for predicting the lifetime on the basis of the crack layer (CL) theory. Only a few steps of FCG are needed to determine all necessary parameters for CL theory, and the FCG behavior can be reconstructed based on a computer program that has been developed for the application of CL theory. The predictions from this program accord with experimental data. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Unifying Principles in Zeolite Chemistry and Catalysis

In recent years molecular sieve catalysts have assumed an increasingly important role in industrial catalysis, Applications of zeolite catalysts are expanding from the traditional petroleum refining to new and improved fuel processing applications, and to new roles in both the petrochemical and chemical industries. Up to the present, all commercial applications of zeolite catalysts have been carried out with aciaic zeolites. Recent investigations of zeolite chemistry revealed several important features which appear common to both alkali and acidic zeolites. This new chemical evidence raises the possibility that the underlying physicochemical features of both types of zeolites play a role in catalysis.     

高浓度活性染料溶液的电导率

通过测定活性染料溶液的电导率,探索了活性染料在溶液中的状态及聚集情况。考察了染料浓度、介质温度及添加剂对染料溶液电导率的影响。结果表明:活性染料溶液的电导率与染料的浓度和温度存在正向递增关系;实验所用各染料溶液的电导率的变化存在一定的临界区间,染料的浓度区间为30~40 mmol/L,温度为50℃左右;电导率在该区间前后的变化率存在着差异,提高温度将有利于染料的解聚;在浓度为40 mmol/L活性橙13染料溶液中添加硫酸钠产生的同离子效应使染料聚集情况加剧,但是染液中硫酸钠的质量浓度低于3 g/L时可促进染液的电离;阴离子表面活性剂十二烷基苯磺酸钠在50℃时对提高活性橙13染料溶液稳定性有显著效果。     

低温季节大体积混凝土基础的裂缝控制

由于采取了有效的管理措施和施工技术 ,防止了低温季节大体积混凝土基础施工时混凝土裂缝的产生。     

Computational and experimental investigation of delamination in L-shaped laminated composite components

Formation of initial delaminations and growth of existing delaminations in L-shaped laminates made of plies of a unidirectional carbon fiber reinforced epoxy resin is investigated computationally and experimentally. For this purpose an experimental test is designed which allows to realize load states for which delamination is the dominant failure mechanism. Two types of test specimens, with and without initial delaminations, are investigated and good agreement is obtained between the computational predictions and the experimental results concerning delamination emergence, delamination growth, growth stability, the structural response, and the maximum principal strains.     

View angle effects in the radiometric measurement of plant canopy temperatures

The thermal infrared sensor response from a wheat canopy was extremely non-Lambertian because of spatial variations in energy flow processes; the effective radiant temperature of the sensor varied as much as 13°C with changing view angle. This variation of sensor response was accurately quantified (root-mean-square of deviations between theoretical and measured responses reduced to 1.1°C) as a function of vegetation canopy geometry, vertical temperature distribution of canopy components, and sensor view angle. The results have important implications for optimizing sensor view angles for remote sensing missions.     

An array language for data parallelism: Definition,compilation, and applications

The programming of SIMD machines that strongly support data parallelism, such as the Connection Machine, ¹ presents new challenges for language, compiler, and algorithm designers. We propose an array language that captures many of the abstractions that are necessary for the effective programming of such machines, thereby liberating the user from having to specify low-level details. Consequently, this new language, ALP, allows for efficient compilation using state-of-the-art techniques, achieving hand-code quality. We demonstrate the effectiveness of our approach by two examples which show that despite being an array language, ALP does not restrict expressiveness to rigidly regular computational structures.Work supported in part by ONR grant number N00014-89-J-1906 while on sabbatical leave at the Department of Computer Science, Yale University.Work supported in part by NSF grant number DCR-8405478 while on sabbatical leave at the Department of Computer Science, Yale University.     

Detection and Evaluation of Plant Stresses for Crop Management Decisions

The ability to quantitatively assess crop conditions using remotely sensed data would not only improve yield forecasts but would also provide information that would be useful to farm managers in making day-to-day management decisions. Experiments were conducted using ground-based radiometers to relate spectral response to crop canopy characteristics. It was found that radiometrically measured crop temperature, when compared with a reference temperature, was related to the degree of plant stress and could indicate the onset of stress. Reflectance based vegetation indices, on the other hand, were not sensitive to the onset of stress but were useful in evaluating the consequences of stress as expressed in changing quantities of green phytomass. Anatomical and physiological changes occur within plant cells when plants are stressed and increase the amount of reflected radiation. However, canopy geometrical changes may alter the amount of radiation that reaches a radiometer, complicating the interpretation of spectral response to stress. Timeliness, frequency of coverage, andresolution are three factors that must be considered when satellite-based sensors are used to evaluate crop conditions for farm management applications.     

Progesterone receptors: expression and regulation in the mammalian ovary

The authors have briefly discussed the molecular structure, regulation, and function of progesterone receptors in the mammalian ovary. Particularly important is the contrast in the regulatory mechanisms of PR induction in the ovary (gonadotropins/membrane receptor mediated) and other well-known progesterone target tissues, such as the uterus and mammary gland (estrogen/nuclear receptor mediated). Future research will focus on how the PR gene responds to these hormonal regulatory signals in this cell-specific manner. Equally important in this discussion has been the mounting evidence indicating that PRs are an essential component of the ovulatory process. The observation that PR-/- knockout mice are incapable of undergoing ovulation, even in response to gonadotropin challenge, further supports the previous physiological evidence indicating that PRs in preovulatory follicles are induced before, and are necessary for, ovulation. Further studies are required to determine the identity of PR-regulated target genes during the periovulatory period. Although our knowledge of PR structure, regulation, and function has increased dramatically during the past decade, many exciting questions remain related to the regulation and function(s) of PRs in the ovary and other tissues.