排序方式: 共有13条查询结果,搜索用时 15 毫秒
1.
A variety of quantitative techniques (such as capital budgeting or linear programming) may be understood more fully by students when they are able to work through relatively simple applications of the techniques by hand. Unfortunately, such manual computations are inherently susceptible to arithmetic errors. The authors propose that students use the electronic spreadsheet to work out these types of problems during their initial learning stage. An advantage of the electronic spreadsheet for this purpose is the automatic calculation of data by the program thereby eliminating the usual arithmetic errors. As long as appropriate formulas are correctly entered into the spreadsheet, the results should be correct.The method presented by the authors does not yield general solutions to capital budgeting or to linear programming problems. Rather, the methodology requires the student to think through the solution process while removing some of the usual drudgery and potential inaccuracies of manual solutions. 相似文献
2.
The interaction between molten gallium and the hydrocarbon medium induced by ultrasonic energy—can gallium carbide be formed?
下载免费PDF全文
![点击此处可从《Journal of the American Ceramic Society》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Vijay Bhooshan Kumar Manuel Monte Olivier Mathon Sakura Pascarelli Ze'ev Porat Aharon Gedanken 《Journal of the American Ceramic Society》2017,100(7):3305-3315
Ultrasonic irradiation of molten gallium in organic liquids (decane, dodecane, etc.) results in dispersion of the gallium into nanometric spheres. These were examined by several analytical methods XRD, DSC, Raman and IR spectroscopy) as well as electron microscopy (SEM, TEM) and found to be composed of Ga and C. The DSC analysis indicates that the Ga has possibly reacted with carbon, while the Raman spectrum of the product demonstrates a strong additional peak that could not be identified. This work explores the possibility that the product is gallium carbide or another gallium‐carbon complex. To investigate the nature of the product, we performed detailed extended X‐ray absorption fine structure (EXAFS) and X‐ray absorption near‐edge structure (XANES) analyses. On the basis of DSC, IR, and Raman it appear to be formation of GaC, whereas the analysis by EXAFS and XANES demonstrated that the gallium is found to be in a higher reduced state (almost metallic), supported by carbon. The question that remains open in addition to the one related to the formation of galium carbide is whether a complex structure, including oxygen contamination is involved in the layers surrounding the Ga as indicated by the EXAFS results. 相似文献
3.
Silver nanoparticles were deposited spontaneously from their aqueous solution on a porous silicon (PS) layer. The PS acts both as a reducing agent and as the substrate on which the nanoparticles nucleate. At higher silver ion concentrations, layers of nanoparticle aggregates were formed on the PS surface. The morphology of the metallic layers and their SERS activity were influenced by the concentrations of the silver ion solutions used for deposition. Raman measurements of rhodamine 6G (R6G) and crystal violet (CV) adsorbed on these surfaces showed remarkable enhancement of up to about 10 orders of magnitude. 相似文献
4.
Ron Shaoul Dov Tiosano Ze'ev Hochberg 《Critical reviews in food science and nutrition》2016,56(6):887-895
Homo sapiens are unique in having a life history phase of childhood, which follows infancy, as defined by breastfeeding. This review uses evolutionary life history theory in understanding child growth in a broad evolutionary perspective, using the data and theory of evolutionary predictive adaptive growth-related strategies for transition from infancy to childhood. We have previously shown that a delayed infancy–childhood transition has a lifelong impact on stature. Feeding practices during infancy are fundamental elements of nutrition as they program for future growth and body composition. A relationship between the duration of breastfeeding and the nature of weaning has been suggested as a possible cause for later obesity and growth patterns. This review highlights the role that breast milk feeding and variations in the weaning age have on transition to childhood, growth, and body composition. 相似文献
5.
Ze'ev Schmilovitch Aharon Hoffman Haim Egozi Rachel Ben‐Zvi Zvi Bernstein Victor Alchanatis 《Journal of the science of food and agriculture》1999,79(1):86-90
In Israel, fresh dates are normally harvested unripe and stored in a controlled environment until marketed. Proper ripening depends on maturity at harvest time. Sugar and water contents of the dates are considered important maturity attributes. Decision‐making on the harvesting schedule for each section in a plantation of fresh dates (variety Hayani) is one of the major problems for the growers. In order to estimate the optimum harvest time, conventional laboratory methods have been used to assess the maturity of samples of dates; methods which by nature are destructive, manual and time consuming. A semi‐automatic system for maturity determination of fresh dates has been developed, tested and operated. It combines a near infrared (NIR) spectrometer with a step‐wise cell conveyor, both of which are controlled by a PC. The NIR models were based on measuring the water and total soluble solids (TSS) contents. The calibration models and the prediction results had a standard error of prediction (SEP) of 1% for TSS and water contents. The correlation coefficient R between TSS and water contents as predicted by NIR models and as measured in routine laboratory destructive tests was 0.9. The system was capable of testing 100 dates in 3 min. © 1999 Society of Chemical Industry 相似文献
6.
7.
E. Ben‐Ze'ev N. Agam Y. Kaufman B. Holben 《International journal of remote sensing》2013,34(15):3203-3221
Vegetation indices (VIs) such as the Normalized Difference Vegetation Index (NDVI) are widely used for assessing vegetation cover and condition. One of the NDVI's significant disadvantages is its sensitivity to aerosols in the atmosphere, hence several atmospherically resistant VIs were formulated using the difference in the radiance between the blue and the red spectral bands. The state‐of‐the‐art atmospherically resistant VI, which is a standard Moderate Resolution Imaging Spectroradiometer (MODIS) product, together with the NDVI, is the Enhanced Vegetation Index (EVI). A different approach introduced the Aerosol‐free Vegetation Index (AFRI) that is based on the correlation between the shortwave infrared (SWIR) and the visible red bands. The AFRI main advantage is in penetrating an opaque atmosphere influenced by biomass burning smoke, without the need for explicit correction for the aerosol effect. The objective of this research was to compare the performance of these three VIs under smoke conditions. The AFRI was applied to the 2.1 µm SWIR channel of the MODIS sensor onboard the Earth Observing System (EOS) Terra and Aqua satellites in order to assess its functionality on these imaging platforms. The AFRI performance was compared with those of NDVI and EVI. All VIs were calculated on images with and without present smoke, using the surface‐reflectance MODIS product, for three case studies of fires in Arizona, California, and Zambia. The MODIS Fire Product was embedded on the images in order to identify the exact location of the active fires. Although good correlations were observed between all VIs in the absence of smoke (in the Arizona case R 2 = 0.86, 0.77, 0.88 for the NDVI–EVI, AFRI–EVI, and AFRI–NDVI, respectively) under smoke conditions a high correlation was maintained between the NDVI and the EVI, while low correlations were found for the AFRI–EVI and AFRI–NDVI (0.21 and 0.16, for the Arizona case, respectively). A time series of MODIS images recorded over Zambia during the summer of 2000 was tested and showed high NDVI fluctuations during the study period due to oscillations in aerosol optical thickness values despite application of aerosol corrections on the images. In contrast, the AFRI showed smoother variations and managed to better assess the vegetation condition. It is concluded that, beneath the biomass burning smoke, the AFRI is more effective than the EVI in observing the vegetation conditions. 相似文献
8.
The long Syrian Arc belt in the Middle East consists of tens of folds and monoclines with their associated faults. The structure of one monocline of this belt, the Hebron monocline in Israel, is analyzed by construction of accurate structural traverses, measurement of the internal strain of the rocks, and geological mapping. The surface structure indicates that three modes of monocline development, draping, buckling and kinking, operated in the Hebron monocline. The subsurface structure, which includes a steep reverse fault, is deduced through mechanical and tectonic models, and structural similarity with other monoclines in Israel. 相似文献
9.
Ze'ev V. I. Zaretskii 《Israel journal of chemistry》1978,17(3):198-201
The relative stabilities of stereoisomers in the vitamin D3 series were established using the appearance — ionization energies differences obtained for the main fragmentation processes characteristic of these compounds. The influence of (Z)-and (E)-configurations of the 5,6-double bonds in vitamin D3 stereoisomers on the previtamin D - vitamin D equilibrium in gas phase, have been also studied. 相似文献
10.
Giora Kimmel Roni Z. Shneck Witold Lojkowski Ze'ev Porat Tadeusz Chudoba Dmitry Mogilyanski Stanislaw Gierlotka Vladimir Ezersky Jacob Zabicky 《Journal of the American Ceramic Society》2019,102(7):3829-3835
Rare earth oxides are important materials due to their chemical and physical properties. The rare earth sesquioxides (RESOXs) possess a cubic, monoclinic, or hexagonal structure, depending on pressure, temperature and ionic radius. When RESOXs take the form of single crystalline grains with diameter in the nanoscale range (nanocrystals), it is suspected that the grain size determines the phase stability as well. RESOXs with medium ionic radius such as Gd2O3, Eu2O3 and Sm2O3 in the low temperature range up to 900°C may take the monoclinic structure or the cubic structure, depending on the synthesis process. The structure determining factor can be, besides temperature, also the grain size. In order to determine the stable structure taking into account grain size as a parameter, we produced Gd2O3 and Sm2O3 nanocrystals embedded in a neutral MgO matrix. This way, we prevented grain growth during annealing. For comparison, we annealed pure Gd2O3 and Sm2O3 nanocrystals in which temperature increase caused grain growth, as in traditional experiments for phase stability determination. We have shown that for coarse grained materials at low temperature monoclinic is the stable structure. For nano-sized crystallites, cubic is the stable structure. This explains the controversial results as far as which phase is the stable one below 900°C and permits to program the needed structure by controlling crystallization kinetics and grain growth. 相似文献