柱后衍生法测定食用油中黄曲霉毒素B_1含量的研究

通过使用柱后衍生系统,建立柱后碘衍生法测定食用油中黄曲霉毒素B_1含量的方法。结果表明:黄曲霉毒素B_1在0.5~55.0 ng/mL浓度范围内具有良好的线性相关性,相关系数为0.999;对黄曲霉毒素B_1浓度0.4、2.0、20.0ng/mL的标准品进行6次平行分析,重复性结果良好,回收率范围为85.8%~106.2%,方法检出限为0.050μg/kg。     

How costly are debt crises?

The aim of this paper is to assess the short and medium-term impact of debt crises on GDP. Using an unbalanced panel of 154 countries from 1970 to 2008, the paper shows that debt crises produce significant and long-lasting output losses, reducing output by about 10 percent after 8 years. The results also suggest that debt crises tend to be more detrimental than banking and currency crises. The significance of the results is robust to different specifications, identification and endogeneity checks, and datasets.     

“北斗一号”卫星信标不同通道信号互扰分析和解决方法

分析了“北斗一号”信号强弱信号码自干扰对弱信号捕获所构成的影响,并将在GPS 中行之有效的一种连续干扰取消（SIC）方法应用于“北斗”。模拟及实测结果表明：强弱 信号强度相差高于15 dB时,“北斗一号”信号码自干扰已经不可忽视;当强弱信号强度相差超 过一定程度,弱信号会陷于完全的失捕或是误捕。采用SIC方法通过去除强信号解除码自干扰影响 ,使强信号下弱信号捕获得以实现且效果明显。     

传统观光景区发展模式创新研究——以沙家浜旅游度假区为例

在国内休闲旅游总体呈现观光旅游向非观光主题旅游过渡的趋势下,传统观光景区常常处在保护与发展的两难境地,"1+X"发展模式为传统观光景区转型升级提供了全新视角。在阐释其内涵和构架的基础上,以沙家浜旅游度假区为例进行了实证分析,探讨了传统景区从观光游发展为休闲游的实践路径,并为完善和运用这一模式提出了对策建议。     

The influence of direct payments on farmers’ hail insurance decisions

We analyze determinants of hail insurance use of Swiss farmers, using FADN panel data covering the period 1990–2009. Mixed effect logistic regression models are estimated to identify the most important farm and farmer characteristics that trigger insurance use. In addition, information on local hail risk is taken into account in these models. It shows that larger farms, with specialization in crop production, and with larger local hail risks are more likely to adopt the hail insurance. Moreover, insurance users are usually older and better educated. Since the early 1990s, Swiss agricultural policy has reduced price support and introduced general and ecological direct payments. This has led to a much higher importance of direct payments for farmers’ incomes. Our analysis shows that this development has contributed to decreasing hail insurance adoption rates in Switzerland over the period considered. Our results indicate that the larger the share of direct payments for total farm revenue, the less attractive is insurance as a risk management strategy for farmers. This interdependency should be explicitly considered by agricultural policy in the design of support mechanisms.     

泡沫剂室内优选及其在调剖工艺中的应用

TFP-1高温发泡剂是以石油磺酸盐为主剂的耐高温泡沫剂。室内试验分别测试在油藏温度(50℃)下发泡剂溶液表面张力、发泡体积、半衰期和阻力因子,以确定发泡剂的最佳浓度。发泡剂浓度在0.5%时泡沫各项性能达到最佳,在高温加热的条件下,发泡剂热稳定性能较好。现场气液比设计优选为1:1,实验证明氮气泡沫能够对高含水层、高渗透层具有较好的封堵能力。针对某区边水淹井现场试验共28井次,泡沫剂浓度按注入蒸汽量的0.5%～0.6%设计,应用后排水期缩短,综合含水下降;同时峰值产油增加,油气比增加。     

高透氧性纤维素包装膜的制备

鲜果蔬保鲜包装中包装膜的阻隔性能对于果蔬的保鲜具有重要影响,本研究利用不同种类的凝固浴制备LiCl/DMAc工艺再生纤维素包装膜,并考察了甲醇、乙醇、异丙醇、LiC l/DMAc和去离子水对纤维素包装膜的断面结构、表面结构、透氧和透湿性能以及机械性能的影响。结果表明,使用醇类凝固浴制备的纤维素包装膜的断面呈松散结构,尤其是以乙醇凝固浴制备的包装膜出现了指状孔;包装膜的透氧性能明显提高,乙醇凝固浴制备的纤维素包装膜的透氧系数为15%LiCl/DMAc凝固浴制备的纤维素包装膜的50倍,并且其机械性能达到12.7Mpa,可以满足日常包装性能要求。     

Exact and asymptotic tests for possibly non-regular hypotheses on stochastic volatility models

We study the problem of testing hypotheses on the parameters of one- and two-factor stochastic volatility models (SV), allowing for the possible presence of non-regularities such as singular moment conditions and unidentified parameters, which can lead to non-standard asymptotic distributions. We focus on the development of simulation-based exact procedures–whose level can be controlled in finite samples–as well as on large-sample procedures which remain valid under non-regular conditions. We consider Wald-type, score-type and likelihood-ratio-type tests based on a simple moment estimator, which can be easily simulated. We also propose a C(α)-type test which is very easy to implement and exhibits relatively good size and power properties. Besides usual linear restrictions on the SV model coefficients, the problems studied include testing homoskedasticity against a SV alternative (which involves singular moment conditions under the null hypothesis) and testing the null hypothesis of one factor driving the dynamics of the volatility process against two factors (which raises identification difficulties). Three ways of implementing the tests based on alternative statistics are compared: asymptotic critical values (when available), a local Monte Carlo (or parametric bootstrap) test procedure, and a maximized Monte Carlo (MMC) procedure. The size and power properties of the proposed tests are examined in a simulation experiment. The results indicate that the C(α)-based tests (built upon the simple moment estimator available in closed form) have good size and power properties for regular hypotheses, while Monte Carlo tests are much more reliable than those based on asymptotic critical values. Further, in cases where the parametric bootstrap appears to fail (for example, in the presence of identification problems), the MMC procedure easily controls the level of the tests. Moreover, MMC-based tests exhibit relatively good power performance despite the conservative feature of the procedure. Finally, we present an application to a time series of returns on the Standard and Poor’s Composite Price Index.     

Semiparametric binary regression models under shape constraints with an application to Indian schooling data

We consider estimation of the regression function in a semiparametric binary regression model defined through an appropriate link function (with emphasis on the logistic link) using likelihood-ratio based inversion. The dichotomous response variable Δ$\Delta$ is influenced by a set of covariates that can be partitioned as (X,Z)$(X,Z)$ where Z$Z$ (real valued) is the covariate of primary interest and X$X$ (vector valued) denotes a set of control variables. For any fixed X$X$, the conditional probability of the event of interest (Δ=1$\Delta =1$) is assumed to be a non-decreasing function of Z$Z$. The effect of the control variables is captured by a regression parameter β$\beta$. We show that the baseline conditional probability function (corresponding to X=0$X=0$) can be estimated by isotonic regression procedures and develop a likelihood ratio based method for constructing asymptotic confidence intervals for the conditional probability function (the regression function) that avoids the need to estimate nuisance parameters. Interestingly enough, the calibration of the likelihood ratio based confidence sets for the regression function no longer involves the usual χ²${\chi }^2$ quantiles, but those of the distribution of a new random variable that can be characterized as a functional of convex minorants of Brownian motion with quadratic drift. Confidence sets for the regression parameter β$\beta$ can however be constructed using asymptotically χ²${\chi }^2$ likelihood ratio statistics. The finite sample performance of the methods are assessed via a simulation study. The techniques of the paper are applied to data sets on primary school attendance among children belonging to different socio-economic groups in rural India.     

Semiparametric tests of conditional moment restrictions under weak or partial identification

We propose two new semiparametric specification tests which test whether a vector of conditional moment conditions is satisfied for any vector of parameter values θ₀. Unlike most existing tests, our tests are asymptotically valid under weak and/or partial identification and can accommodate discontinuities in the conditional moment functions. Our tests are moreover consistent provided that identification is not too weak. We do not require the availability of a consistent first step estimator. Like Robinson [Robinson, Peter M., 1987. Asymptotically efficient estimation in the presence of heteroskedasticity of unknown form. Econometrica 55, 875–891] and many others in similar problems subsequently, we use k-nearest neighbor (knn) weights instead of kernel weights. The advantage of using knn weights is that local power is invariant to transformations of the instruments and that under strong point identification computation of the test statistic yields an efficient estimator of θ₀ as a byproduct.