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31.
通过单因素及正交实验,比较高产米曲霉在摇床培养与发酵罐培养中生产曲酸的发酵工艺参数。结果表明,在温度为23℃、发酵天数为9 d、接种量为25%、菌龄为96 h时,摇床发酵的曲酸产量达到最高,最高可达98.6 g·L-1;而发酵罐培养的最佳工艺条件是温度23℃、发酵天数4 d,接种量15%,菌龄96 h时,此条件下曲酸产量可达到99.6 g·L-1。本研究为工业化生产曲酸提了供理论依据。 相似文献
32.
运用SWOT方法对上海市大力发展农村金融服务进行分析。分析结果可知上海在大力发展农村金融服务时存在政策、地理位置优势;但在法律和农户金融意识方面存在劣势;此外,上海市既面临"互联网+"与金融合作、潜在需求大的机遇,也面临违约和诈骗风险的威胁。 相似文献
33.
34.
This paper examines the correlation and the dependence patterns of the Qatar stock market with other markets using copula statistical theory and exploiting new datasets covering the period August 1998 to June 2018. To examine the crisis –specific change in the average degree of dependence we decomposed the data into the time periods before and after oil price shocks and the 2017 political crisis among the Gulf Cooperation Council members (i.e. the Qatari blockade). Our findings from the static copula modelling show that the correlations between the Qatari and the other stock markets significantly change after the oil price and the blockade crisis as well. The degree of change in the correlation is time varying and differs from county-group to another. Moreover, our findings reveals that the 2008 global financial crisis has a stronger impact than the price shocks and political crisis. The findings of the paper are of interest and allow for formulating a reliable and dynamic portfolio design framework for investors and risk managers. 相似文献
35.
为了快速直接测定蜂蜜中多种矿物元素的含量,采用电感耦合等离子体发射光谱(ICP-AES)法建立了同时测定蜂蜜中钙、钾、镁、钠、锌、铁、铜7种矿物元素含量的方法,考察了方法的标准曲线线性关系、检出限、精密度和准确度,讨论了前处理方法、不同产地以及蜜源植物种类对各元素含量的影响。结果表明:线性相关系数达到0.999 9以上,方法检出限为0.003~0.030 mg/L,相对标准偏差低于2%,回收率为88.66%~105.31%;不同产地的洋槐蜜中,河北洋槐蜜的钙、钾含量明显高于其他地区,广西洋槐蜜的钠、铁含量最高;不同蜜源植物的蜂蜜中,河北枣花蜜的铁含量最高,野生蜜中各种矿物元素都较为丰富。电感耦合等离子体发射光谱法可以快速、同时测定蜂蜜中多种矿物元素含量,方法简便易行,结果准确可靠,可为蜂蜜品质鉴定以及人们对蜂蜜的合理选择提供参考。 相似文献
36.
《Food Policy》2019
This article tests the hypotheses of convergence to a single level of total factor productivity (TFP), and a steady state of TFP growth rate in China’s agricultural sector. Based on multilateral TFP estimates we found that China’s agricultural sector has rebounded in recent years from a slower TFP growth in the 2005–2007 period. While convergence test results confirm a “catch-up” effect that provinces with lower TFP levels tend to grow faster than others, estimated rates of β convergence are conditional on how we capture the heterogeneity effect across regions. The rates of β convergence range from 0.016 to 0.039 under different model specifications. Estimates show that higher growth rates of educational attainment, R&D, and intermediate goods density (per unit of labor) can enhance TFP growth. Unfortunately, there is no evidence of an overall σ convergence, indicating that TFP levels are not converging except in the South region. It implies that to catch up with leading provinces, it would require extra efforts for those lagging behind by increasing their region-specific research investment, promoting rural educational attainment, and enhancing embodied technical change. 相似文献
37.
The short‐time behavior of VIX‐implied volatilities in a multifactor stochastic volatility framework
We consider a modeling setup where the volatility index (VIX) dynamics are explicitly computable as a smooth transformation of a purely diffusive, multidimensional Markov process. The framework is general enough to embed many popular stochastic volatility models. We develop closed‐form expansions and sharp error bounds for VIX futures, options, and implied volatilities. In particular, we derive exact asymptotic results for VIX‐implied volatilities, and their sensitivities, in the joint limit of short time‐to‐maturity and small log‐moneyness. The expansions obtained are explicit based on elementary functions and they neatly uncover how the VIX skew depends on the specific choice of the volatility and the vol‐of‐vol processes. Our results are based on perturbation techniques applied to the infinitesimal generator of the underlying process. This methodology has previously been adopted to derive approximations of equity (SPX) options. However, the generalizations needed to cover the case of VIX options are by no means straightforward as the dynamics of the underlying VIX futures are not explicitly known. To illustrate the accuracy of our technique, we provide numerical implementations for a selection of model specifications. 相似文献
38.
Wiebke Pirsich 《国际粮食与农业综合企业市场学杂志》2019,31(2):150-174
Several consumer studies have shown considerable market potential for sustainable meat products, however, their markets shares are still marginal. In Germany, the sustainable aspects “organic,” “local origin,” and “animal welfare” are of special interest. To obtain a precise overview of potential target groups for these meat categories and their choice of store format, 620 German consumers were surveyed on their attitudes toward sustainable meat production and their shopping behavior. First, target groups based on consumers’ attitudes were identified by cluster analysis, taking into account possible overlaps. Consumers were also clustered by their store format choice and their preferred type of meat packaging. A cross tabulation of the results then provided insights into which store format and type of meat packaging is preferred by the target groups for sustainable meat products. Due to overlaps found in the target groups, the existence of important subgroups was shown. Amongst the target groups, only a slight preference for unpackaged meat products was found. Basically, the offer of sustainable meat products appears of interest for all store formats, with particular emphasis on supermarkets. The results of this study can support producers and retailers developing new and tailored marketing strategies for sustainable meat products. 相似文献
39.
Freddy Cepeda-López Carlos León Hernán Rincón-Castro 《The journal of international trade & economic development》2019,28(4):452-485
This paper employs network analysis to study world trade from 1995 to 2014. We focus on the main connective features of the world trade network (WTN) and their dynamics. Results suggest that countries’ efforts to attain the benefits of trade have resulted in an intertwined network that is increasingly dense, reciprocal, and clustered. However, these features do not correspond to a linear aggregation of the characteristics of its constituents (trade sectors). Trade linkages are distributed homogeneously among countries, but their intensity (i.e. their value) is highly concentrated in a small set of countries. The main connective features of the WTN were not affected by the 2007–2008 international financial crisis. However, we find that the crisis marks a turning point in the evolution of the WTN from a two-group (led by the US and Germany) to a three-group (led by the US, Germany, and China) hierarchical structure. 相似文献
40.
运用熵权灰色关联分析法对黑龙江省森工林区所辖4个林业管理局2012—2017年养殖业、绿色食品等5个接替产业综合发展水平进行评价,并运用耦合协调度模型测算接替产业的均衡水平。结果表明:不同林业管理局的5个接替产业均呈波动发展状态;伊春林业管理局的优势接替产业是养殖业、绿色食品、北药开发和工业,牡丹江林业管理局的优势接替产业是绿色食品,合江林业管理局的优势接替产业是服务业,松花江林业管理局没有显著的优势接替产业;接替产业的综合发展水平偏低导致其均衡水平不高,总体上由初步协调向中度协调发展。因此,各林业管理局应继续发展具有优势的接替产业,同时扶持相对薄弱的接替产业,并开发与引进新的接替产业。 相似文献