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81.
Debojyoti Das Vaneet Bhatia Jayarethanam Pillai Aviral Kumar Tiwari 《Energy Sources, Part B: Economics, Planning, and Policy》2018,13(1):37-45
The authors revisit the relationship between US economic growth and crude oil prices considering Industrial Production Index and West Texas Intermediate crude oil spot prices as respective proxies for a period spanning over January 1986 to June 2017. To capture the asymmetric and time-varying relationship, the authors employ maximum overlap discrete wavelet transform (MODWT)-based quantile regression (QR) analysis. Interestingly, MODWT-based QR analysis provides evidence of supply-driven link between crude oil prices and economic growth in the short run. However, in the medium to long run a demand-driven link is dominant. In addition, the QR results without MODWT also advocate a demand-driven link. Overall, the result of this study adds a new dimension to the literature on the relationship between crude oil prices and economic growth by focusing upon the time-frequency varying business cycle fluctuations. 相似文献
82.
Experimental study of the combustion characteristics of methanol‐gasoline blends pool fires in a full‐scale tunnel 下载免费PDF全文
The combustion characteristics of methanol‐gasoline blends pool fires were studied in a series of full‐scale tunnel experiments conducted with different methanol and gasoline blends. The parameters were measured including the mass loss rate, the pool surface temperature, the fire plume centerline temperature, the ceiling temperature, the smoke layer temperature profile, the flame height, and the smoke layer interface height. The gasoline components were analyzed by GC‐MS. The effects of azeotropism on the combustion characteristics of the different blends were discussed. On the basis of the results of the fire plume centerline temperature, the ceiling temperature, and the flame height, it shows that the tunnel fire regime gradually switches from fuel controlled to ventilation controlled with increasing gasoline fractions in the blends. The fire plume can be divided into 3 regions by the fire plume centerline temperature for the different blends. The N‐percentage rule to determine the smoke layer interface height is found to be applicable for tunnel fires with different blends for N = 26. 相似文献
83.
An economic evaluation of management strategies to mitigate the negative effect of twinning in dairy herds 总被引:1,自引:0,他引:1
R. Mur-Novales F. Lopez-Gatius P.M. Fricke V.E. Cabrera 《Journal of dairy science》2018,101(9):8335-8349
Our objectives were to develop an economic model to estimate the economic impact of twinning in dairy cows and to evaluate management strategies to mitigate the negative economic impact of twinning in dairy herds. A probabilistic tree considering spontaneous embryo reduction, early pregnancy loss, abortion, metritis, retained placenta, and culling rate at 120 d of the second, at the end of the second, and at the end of the third lactation was developed for a single pregnancy; we also developed 3 management options upon diagnosis of a twin pregnancy: (1) do nothing, (2) induce abortion using PGF2α, or (3) attempt manual embryo reduction. A value was given to each branch of the tree by simulating cow states on a farm for 1,400 d to encompass 4 consecutive lactations. The incomes considered in the simulations included milk income over feed cost, income from calves, and slaughter value upon culling. The expenses taken into account depending on each branch included additional inseminations and synchronization protocols, embryo reduction, induction of abortion, replacement heifers, and costs due to metritis and retained placenta. The gross value for a singleton pregnancy and the 3 management options upon diagnosis of a twin pregnancy were calculated by adding the value of all braches multiplied by their probability. The costs for the 3 management options were calculated by subtracting its gross value minus the gross value of a singleton pregnancy. The negative economic impact of a twin pregnancy ranged from $97 to $225 depending on the type of twin pregnancy (unilateral vs. bilateral), parity, and DIM when the twin pregnancy occurred. The overall negative economic impact of twinning on dairy farm profitability in the United States was estimated to be $96 million per year. Attempting manual embryo reduction early during gestation upon diagnosis of a twin pregnancy was the optimal management strategy for mitigating the negative economic impact of twinning under a wide variety of scenarios. 相似文献
84.
Amlan Paul 《先进材料力学与结构力学》2018,25(12):982-994
For thermally postbuckled configurations, the free vibration behavior of functionally graded (FG) Timoshenko beams are investigated. The postbuckling configurations are obtained through a geometrically nonlinear static problem. The free vibration problem around the postbuckled configuration is formulated using its tangent stiffness. The energy based governing equations are solved following the Ritz method. The elements of the tangent stiffness matrix are obtained using the Ritz coefficients. The results are shown to exhibit the effects of FG material, material profile parameter, and length-thickness ratio. The comparative results are presented for both the cases of the physical neutral surface and the geometrical neutral surface. 相似文献
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This paper is focusing on the numerical simulation of a swirling flame, resulting from the interaction of multiple fires, evolving in a free and unlimited environment. A typical system, formed by a central fire source surrounded by four heat sources, is used. Since the thermal characteristic of the surrounding sources is the main engine for the rotation of flame, a detailed study is performed by varying the heating flux of these sources. This study shows that an increase of the heating flux of surrounding sources has as a result an intensification of the penetrating air puffs through the openings between the surrounding four heat sources. These puffs tangentially drive the central flame, thus producing a marked improvement on the angular momentum. Moreover, this study shows that the flame height is strongly affected by the flame rotation. Moreover, two different aspects of the flame height evolution are observed from the flow visualization and the thermal and dynamic fields for the different cases studied. 相似文献
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目的研究Q235碳钢在静止和流动条件下腐蚀程度和主要腐蚀区域的差异。方法使用丝束电极(WBE)技术和电化学阻抗谱(EIS)技术分别研究了WBE在静止和流动条件下的电流密度分布、电荷转移电阻以及腐蚀形貌的变化和差异,同时分析了电极的极性转换现象。结果流动条件下Q235碳钢的电荷转移电阻明显降低。在静止条件下,Q235碳钢表面阳极电流区域所占的最大比例为47%,且阳极电流峰集中出现在WBE的中间区域,而四周边缘处的阳极电流峰较少。在流动条件下,Q235碳钢表面的阳极电流区域所占的最大比例为58%,阳极电流峰随机分布在整个WBE表面,且电流分布区间明显变窄。浸泡在静止条件下的58~#电极和流动条件下的39~#电极发生了多次极性转换现象。结论 Q235碳钢在静止和流动条件下均发生了明显的不均匀腐蚀现象。流动条件加剧了Q235碳钢的腐蚀且降低了腐蚀不均匀性。静止条件下Q235碳钢的腐蚀区域集中在中间区域,流动条件下Q235碳钢的腐蚀区域随机分布在整个碳钢表面。静止和流动条件下的钢电极均发生了电流的极性转换现象。 相似文献