降雨作用下土石混合体边坡力学参数弱化规律与稳定性分析

土石混合体边坡地质灾害是中国最为常见的地质灾害之一,而降雨是其主要诱发因素,降雨条件下边坡劣化机理研究是防灾减灾领域的重要研究方向.通过分析不同含水率条件下土石混合体力学性质试验数据,建立抗剪强度参数随含水率的演化方程;以此为基础,针对西南地区典型土石混合体边坡,考虑降雨条件下力学参数弱化的影响,采用Geostudio软件开展边坡稳定性分析.结果表明:演化方程能有效反映含水率增大对土石混合体抗剪强度具有显著的弱化效应;降雨强度的增大会显著降低边坡稳定性,降雨持时只是降雨过程中某一时刻值的体现,对边坡稳定性影响不大;降雨量与边坡安全系数呈明显线性负相关.研究成果可为土石混合体边坡地质灾害预测与防治提供技术支撑.     

Innovation,agile project management and firm performance in a public sector-dominated economy: Empirical evidence from high-tech small and medium-sized enterprises in China

While agile project management has become increasingly important for high-tech small and medium-sized enterprises (SMEs), firm performance varies greatly due to companies’ different degrees of innovation capability and internal and external environmental dynamics. Drawing on the resource-based view – as well as innovation capability and agile project management theories – a comparative analysis was conducted of two high-tech SMEs. The results were used to develop a theoretical model based on six hypotheses. Empirical research was carried out that included measurement of key variables, data collection and analysis, validity and reliability tests, regression analysis, and structural equation modeling, which confirmed five of the six initial hypotheses. The proposed model incorporates different innovation capability roles, considers project agility enhancement of firm performance, and takes into account interactions between companies’ innovation atmosphere and environmental dynamics in a public sector-dominated economy (i.e., China). The results contribute to project agility management’s theoretical development and refinement by presenting new findings on innovation and environmental dynamics. The results also provide guidelines for project agility practices in high-tech SMEs in China, with the potential to improve these firms’ performance. Implications and limitations are also discussed.     

Is marketing agility important for emerging market firms in advanced markets?

Marketing agility has recently gained the attention of international marketing managers and scholars. However, scholars have not examined how this capability directly and indirectly influences firm performance and how the effects change under the complex market conditions facing emerging market (EM) firms in advanced economy (AE) markets. Hence, underpinned by the dynamic capability and complexity theories, this study investigates the direct effect of marketing agility—a dynamic meta-capability involving market sensing, speed, flexibility and responsiveness—on firm performance and its indirect effect via marketing program adaptation. Moreover, it explores changes in these direct and indirect relationships under varying market complexity levels. EM firms are often disadvantaged owing to AE market complexity, such as the presence of low-cost advantage of local AE firms. Hence, investigating this framework in this context is valuable. Using data on Pakistani firms exporting to AE markets, the study finds that marketing agility influences firm performance, and the influence is stronger under high market complexity. When market complexity is low, the influence is mediated by the firms’ ability to adapt their marketing program to meet AE market requirements. Supporting theoretical and managerial implications are offered.     

Option pricing with orthogonal polynomial expansions

We derive analytic series representations for European option prices in polynomial stochastic volatility models. This includes the Jacobi, Heston, Stein–Stein, and Hull–White models, for which we provide numerical case studies. We find that our polynomial option price series expansion performs as efficiently and accurately as the Fourier‐transform‐based method in the nested affine cases. We also derive and numerically validate series representations for option Greeks. We depict an extension of our approach to exotic options whose payoffs depend on a finite number of prices.     

Detecting passengers' heterogeneity on airlines’ services using SP data

In this paper, the heterogeneity in passengers' perceptions of airlines' services has been investigated by using a Random Parameter Mixed logit model. To calibrate and validate the proposed model, data from a Stated Preferences choice experiments was used. The survey was conducted online and involved the whole population of the University of Calabria (Italy). The experiments were designed by considering the main service attributes characterizing air travellers’ experience in its entirety: before, during, and after the flight. Differently from the previous studies using Stated Preferences survey, two different groups of choice experiments were designed: the former referring to before/after the flight stages, and the last referring to during the flight experience. For each group, specific attributes were considered.Final findings remark that flyers' perceptions on airline's services vary among the different service aspects and among individuals. Specifically, we found that curtesy of cabin crew, space available, temperature, cleanliness, service on board and ticket cost are attributes referring to the during the flight stage of the travel that showed heterogeneity in passenger's perceptions. On the contrary, the attributes referring to the before/after the flight stages for which we detected heterogeneity in passengers' perceptions are waiting time at check-in, delay of flight departure, and ticket cost.     

带阻尼器拉索结构的索力识别研究

为解决带多个阻尼器索结构的索力识别问题,依据动力学相关理论,建立带3个减振器的拉索-减振器动力学模型,推导其频率方程,构造相应的无量纲参数并进行参数分析.结果表明:随着减振器支撑刚度的增加,无量纲振动频率逐渐增大,但这种增大趋势随支撑刚度的继续增加而趋于平缓;随着减振器安装距离的增加,无量纲振动频率逐渐增大,且这种趋势接近线性变化.最后利用有限元分析软件ANSYS并分别采用LINK单元与BEAM单元对其结论进行验证.     

Identification with latent variables

This is an essay on a unified approach to the identifiability problem in static models with and without hidden endogenous variables. As is well known, when some of these variables are unobserved, the prior information requirements for models when all endogenous variables are observed, are still there. In addition, extra prior information that takes the place of the means and covariances of the missing variables will have to be supplied directly or indirectly by the statistical researcher. In the paper we characterize the quality and quantity of the required information for the general linear static model and apply it when the model is i) an econometric demand and supply model with missing observations on the quantity transacted, ii) a factor analysis model with observed characteristics of the test takers and iii) a LISREL Model without fixed exogenous variables. With unknown true parameters, the exact rank conditions are seldom verifiable but we do recommend an implementable check-list that is adequate for almost all parameters.     

线性回归模型参数线性约束检验的Eviews实施

线性回归模型是计量经济模型的主要形式,其参数除了需要显著性检验和方程显著性检验外,有时还需要对其参数线性约束条件的检验。本文介绍运用Eviews软件对模型参数线性约束的F检验、沃尔德检验与t检验三种方法。     

Minimax estimation under convex loss when the parameter interval is bounded

In the present paper families of truncated distributions with a Lebesgue density forx=(x ₁,...,x _n ) ε ℝ ⁿ are considered, wheref ₀:ℝ → (0, ∞) is a known continuous function andC _n (ϑ) denotes a normalization constant. The unknown truncation parameterϑ which is assumed to belong to a bounded parameter intervalΘ=[0,d] is to be estimated under a convex loss function. It is studied whether a two point prior and a corresponding Bayes estimator form a saddle point when the parameter interval is sufficiently small.     

信息共享下绿色供应链价格协调问题研究

在信息共享前提下建立了绿色供应链中制造商、零售商的博弈模型,分别讨论了非合作博弈与合作博弈下的利润模型,制定了该绿色供应链在合作博弈下的内部价格协调机制,以及给出了价格协调参数的两种求解方法。最后,验证了信息共享下该绿色供应链的制造商与零售商进行合作时,不仅能极大的提高消费者对该绿色产品的需求,而且按照对联盟的贡献协调内部价格时,该供应链系统的稳定性与整体效率都得到提高。