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961.
Jian Ni Lap Keung Chu Feng Wu Domenic Sculli Yuan Shi 《European Journal of Operational Research》2012
This paper addresses the problem of mitigating procurement risk that arises from volatile commodity prices by proposing a hedging strategy within a multi-stage time frame. The proposed multi-stage hedging strategy requires a commodity futures position to be correctly initialised and rebalanced with adequate volumes of short/long positions, so as to reduce the volatility in the total procurement cost that would otherwise be generated by varying commodity spot prices. The novelty in the approach is the introduction of the rebalancing of commodity futures position at defined intermediate stages. To obtain an efficient or near optimal multi-stage hedging strategy, a discrete-time stochastic control model (DSCM) is developed. Numerical experiments and Monte Carlo simulation are used to show that the proposed multi-stage hedging strategy compares favourably with the minimal-variance hedge and the one-stage hedge. A close-form optimal solution is also presented for the case when procurement volume and price are independent. 相似文献
962.
Synthesis of multi‐functionalized carbonyl compounds by palladium–catalysed γ‐substitution of MBH adducts with activated amides
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Gao Pei‐Sen Zhang Jin‐Lei Li Ning Zheng Zhan Jiang Yuan Yang Gao Zi‐Wei Zhang Weiqiang Xu Li‐Wen 《应用有机金属化学》2018,32(3)
Catalytic allylic γ‐substitution with Morita‐Baylis‐Hillman (MBH) adducts for creating a new family of unsymmetrical dicarbonyl compounds was presented in this work, in which a variety of allylated amide products were achieved in good yields and high regioselectivity with excellent linear‐to‐branched ratios. Especially, it was found that the Pd/HZNU‐Phos complex exhibited remarkably high activity (with a TON up to 16800) in this transformation between dicarbonyl amides and MBH adducts. In addition, the possibly multisite interaction between multifunctional Pd/HZNU‐Phos catalyst system and substrates might responsible for its exceptionally high efficiency in this reaction. 相似文献
963.
A novel inorganic-organic hybrid supramolecular compound,[(3-nitroanilinium~+)(18-crown-6)][IO_4](CH_3OH)(1),was discovered as phase-transition materials displaying dielectric anomalous behaviors.The yellow block crystal formed by N-H…O hydrogen bonding that made contact through the cavity of 18-crown-6 was characterized by single-crystal X-ray diffraction,elemental analysis,infrared analysis,thermogravimetric analysis,differential scanning calorimetry,and potential-energy calculations.Differential scanning calorimetry measurements indicate that the compound experiences a reversible phase transition at around 220 K.Temperature-dependent dielectric measurements further confirm the phase transitions.Potential-energy calculations demonstrate that the phase transition occurs due to the molecular order-disorder rotation of CH_3OH,whereas the space grouping of the crystal remains unchanged. 相似文献
964.
Liping Yang Hanbang Liu Jiacheng Xing Dr. Danhua Yuan Prof. Dr. Yunpeng Xu Prof. Dr. Zhongmin Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(20):6187-6190
Xylene isomer separation is considered one of the seven separation challenges that changed the world. In addition, the high-energy demand of xylene separation highlights the need for efficient novel adsorbents. Herein, the liquid-phase separation potential of the anion-pillared hybrid material SIFSIX-1-Cu was studied for preferential adsorption of o-xylene and m-xylene over p-xylene, which was inspired by a previous complexation crystallization method for separating m-xylene. We report detailed experimental liquid-phase adsorption experiments, yielding selectivities of 3.0 for o-xylene versus p-xylene and 2.6 for m-xylene versus p-xylene. Our theoretical calculations thus provide a reasonable explanation that the xylene adsorption selectivity is attributed to the C−H⋅⋅⋅F interaction, and the host–guest interaction order agrees with the adsorption priority: o-xylene > m-xylene > p-xylene. 相似文献
965.
966.
A rapid real-time polarization measurement system was designed and implemented in this paper. The system is centered round a computer running application developed for the purpose. The paper illustrates how to build such an excellent application with National Instruments’ graphical programming language LabVIEW, a synchronized high speed multi-channels data acquisition card and some photoelectric conversion module in detail. With simple and friendly user interface, the experimental result shows that the measurement system has high computational efficiency, high precision calibration matrix, which can be efficiently utilized in experiments relating to the measurement of polarization. 相似文献
967.
968.
969.
"文革"时期的期刊传播由于时代的特殊性而呈现与前后截然不同的传播范式,而在"文革"时期"如火如荼"的科学史研究,尤其是中国古代科学技术史的研究,是这个时代的"副产品"。虽然处于政治高压之下,"批林批孔"、批儒尊法是主要目的,但这一时期的科学史研究承上启下,为之后中国第二次科学史研究高潮的出现作了重要铺垫。 相似文献
970.
采用伪势两相格子玻尔兹曼方法(LBM)研究了非增湿条件下碳纸和碳布气体扩散层(GDL)的流体流动状态。通过随机方法和X射线扫描法构建了气体扩散层样本。为确保模型中表面张力和接触角计算的准确性,采用玻璃微珠模型进行验证,随后通过调整气体扩散层的亲疏水特性,分析流体在气体扩散层中流动的实时状态,得到了亲疏水特性对孔隙结构内水饱和度的影响规律。结果表明:疏水性气体扩散层中的水分布与亲水性气体扩散层中的水分布明显不同,较大的疏水性更有利于气体扩散层内水的排出;疏水性更强的气体扩散层显著提高了液态水进入气体扩散层的入口压力,导致催化剂层(CL)更容易受到水渗透的影响。 相似文献