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排序方式: 共有311条查询结果,搜索用时 15 毫秒
101.
Hirbod Assa Hossein Sharifi Andrew Lyons 《European Journal of Operational Research》2021,288(3):918-934
This study examines how managing risk by introducing commodity price insurances may improve the likelihood of increased investment in agri-food supply chains. A model is introduced which shows how insurance products on index prices can reduce the uncertainty of the impact of investment, and also how lower investment can generate the same impact as a higher investment. To show our results, we use two different frameworks which include total profit (Pareto optimal) and Stackelberg game setups. The results demonstrate that in both frameworks the investment will have a greater impact when an insurance product is present. By implication, the study presents an encouraging message to the insurance industry to introduce products to secure supply chain actors’ revenue leading to an increase in investment rate. Consequently, the study offers insight into how the role of traditional government subsidies for protecting farmers, particularly the small to medium-sized farms, may be revisited by replacing some of the existing subsidisation policies with revenue insurance. 相似文献
102.
Vu T. Nguyen Viet D. Nguyen Graham C. Haug Ngan T. H. Vuong Hang T. Dang Hadi D. Arman Oleg V. Larionov 《Angewandte Chemie (International ed. in English)》2020,59(20):7921-7927
The development of efficient and selective C?N bond‐forming reactions from abundant feedstock chemicals remains a central theme in organic chemistry owing to the key roles of amines in synthesis, drug discovery, and materials science. Herein, we present a dual catalytic system for the N‐alkylation of diverse aromatic carbocyclic and heterocyclic amines directly with carboxylic acids, by‐passing their preactivation as redox‐active esters. The reaction, which is enabled by visible‐light‐driven, acridine‐catalyzed decarboxylation, provides access to N‐alkylated secondary and tertiary anilines and N‐heterocycles. Additional examples, including double alkylation, the installation of metabolically robust deuterated methyl groups, and tandem ring formation, further demonstrate the potential of the direct decarboxylative alkylation (DDA) reaction. 相似文献
103.
N. Asadi R. Naderi M. Saremi S. Y. Arman M. Fedel F. Deflorian 《Journal of Sol-Gel Science and Technology》2014,70(3):329-338
The effects of dipping duration in the silane solution and the sol pH on the protective performance of an eco-friendly silane sol–gel coating consisting a mixture of tetraethoxysilane, methyltriethoxysilane and glycidyloxypropyltrimethoxysilane applied on mild steel substrate were studied in this paper using electrochemical techniques and surface analysis. In consistency with the data obtained from electrochemical impedance spectroscopy and polarization curves, electrochemical current noise fluctuation analysis, appearance of the power spectral density plots and noise resistance indicated the most efficient sol pH and immersion time in the silane solution. In this regard, field emission type scanning electron microscopy images and water contact angle values revealed impact of the sol pH on the film structure. The enhancement in protective performance of the hybrid coating resulting from optimum immersion in the silane solution with appropriate pH was connected to the film homogeneity and higher cross linking and thickness as well. Moreover, a good trend correlation was observed between the noise resistance and low-frequency impedance modulus data. 相似文献
104.
A. Sharifi M. S. Abaee M. Mirzaei R. Salimi 《Journal of the Iranian Chemical Society》2008,5(1):135-139
This room-temperature Darzens condensation of α-chloroacetophenone with various aromatic aldehydes mediated by [bmim][BF4] ionic liquid in the presence of sodium tert-butoxide resulted in the sole formation of good to excellent yields of trans-α,β-epoxy ketones in short time periods. In contrast, tert-butyl 2-chloroacetate underwent Darzens reactions with aldehydes giving mixtures of both cis and trans products with low selectivity. In all reactions, the ionic liquid was recovered and reused in the subsequent reactions without significant loss of activity. 相似文献
105.
Ali Sharifi Hossein Farhangian Farshid Mohsenzadeh M. R. Naimi-Jamal 《Monatshefte für Chemie / Chemical Monthly》2002,133(2):199-204
Summary. Terminal alkynes, secondary amines, and formaldehyde undergo a Mannich reaction at room temperature in the presence of CuCl on Al2O3 without any organic solvent as reaction medium. The reaction can be promoted by microwave irradiation and is complete within
one minute.
Received May 2, 2001. Accepted (revised) June 25, 2001 相似文献
106.
Ali Asghar Hatamnia Arman Rostamzad Nasser Abbaspour Reza Darvishzadeh Parviz Malekzadeh 《Natural product research》2016,30(5):600-604
Leaves of 10 Bene genotypes were collected from six provinces (West Azerbaijan, Kurdistan, Kermanshah, Ilam, Hamedan and Lorestan) in Iran. This study was carried out to better characterise the total phenolic and flavonoid contents, antioxidant capacity and phenolic composition, as well as to evaluate the correlation between content of phenolic compounds and antioxidant activity in 10 genotypes of Bene. The antioxidant activity of leaf extracts was measured using different assays: ferric reducing antioxidant power, nitric oxide radical scavenging and 2,2-diphenyl-1-picrylhydrazyl. The results indicated that the antioxidant capacity can be related to total phenolic and flavonoid content, so that among all the genotypes studied here, the highest and the lowest phenolic content and antioxidant activity were observed in B2 and B10 genotypes, respectively. Analysing the phenolic composition using high performance liquid chromatography, caffeic acid, vanillic acid, ferulic acid and sinapic acid were found in all investigated genotypes. 相似文献
107.
Romyar T. Sharifi 《Mathematische Annalen》2008,342(2):297-308
Let p be an odd prime satisfying Vandiver’s conjecture. We consider two objects, the Galois group X of the maximal unramified abelian pro-p extension of the compositum of all Z
p
-extensions of Q(μ
p
) and the Galois group of the maximal unramified pro-p extension of Q
. We give a lower bound for the height of the annihilator of X as an Iwasawa module. Under some mild assumptions on Bernoulli numbers, we provide a necessary and sufficient condition for
to be abelian. The bound and the condition in the two results are given in terms of special values of a cup product pairing
on cyclotomic p-units. We obtain in particular that, for p < 1,000, Greenberg’s conjecture that X is pseudo-null holds and is in fact abelian. 相似文献
108.
Sharifi Omid Golmohammad Mohammad Soozandeh Mozhde Mehranjani Alireza Soleimany 《Journal of Solid State Electrochemistry》2023,27(9):2433-2444
Journal of Solid State Electrochemistry - Li7La3Zr2O12 (LLZO) is one of the most competent candidates as a solid electrolyte for next-generation Li-ion batteries. Although the stabilization of the... 相似文献
109.
A new synthetic approach is suggested for preparation of layered rare-earth oxide compounds containing [Ln2O2] slices and molecular anion sheets (CO32-, SO42-, and CrO42-). It is based on exchange reactions of rare-earth oxychlorides, [Ln2O2]Cl2, and alkali carbonates, sulfates, or chromates. Five new rare-earth oxychromates [Ln2O2]CrO4 (Ln=Pr-Gd) have been prepared which adopt a new, probably layered, structure type. In addition, significantly easier and more efficient synthetic pathways were found to the known compounds [Ln2O2]K2(CO3)2 and [La2O2]CrO4. The structure of the latter compound has been determined from neutron powder diffraction data. Factors affecting reaction pathways and products are discussed, as well as prospects for applying the approach to more complex layered compounds. 相似文献
110.
The diffusioosmosis of an electrolyte solution inside a uniformly charged rectangular channel at steady locally developed conditions is the subject of this study. Utilizing a finite element based numerical procedure, we try to estimate the errors incurred by modeling the actual rectangular geometry of typical microchannels as a slit. We demonstrate that the flow pattern and direction are generally dependent upon the width‐to‐height ratio of the channel. Such a finding, besides showing the ineffectiveness of the slit geometry in representing a rectangular channel of small aspect ratio, informs us of another mechanism of controlling the diffusioosmotic flow. Inspections of the mean velocity reveal that, although it drastically grows by increasing the aspect ratio at smaller values of this parameter, no significant change is observed when the aspect ratio is 5 or higher. The same trend is observed when EDL is shrunk and is considered as a basis for the introduction of a slip‐like velocity, similar to the concept of the Helmholtz–Smoluchowski electroosmotic velocity, which will be of high practical importance when dealing with a micronsized channel. Because of its significance, an expression is presented for this slip velocity utilizing the curve fitting of the results, assuming a typical Peclet number. 相似文献