Twin studies in behavioral research : a skeptical view

behavioural science

Acoustical properties of double porosity granular materials

Granular materials have been conventionally used for acoustic treatment due to their sound absorptive and sound insulating properties. An emerging field is the study of the acoustical properties of multiscale porous materials. An example of these is a granular material in which the particles are porous. In this paper, analytical and hybrid analytical-numerical models describing the acoustical properties of these materials are introduced. Image processing techniques have been employed to estimate characteristic dimensions of the materials. The model predictions are compared with measurements on expanded perlite and activated carbon showing satisfactory agreement. It is concluded that a double porosity granular material exhibits greater low-frequency sound absorption at reduced weight compared to a solid-grain granular material with similar mesoscopic characteristics

A computerized symbolic integration technique for development of triangular and quadrilateral composite shallow-shell finite elements

Computerized symbolic integration was used in conjunction with group-theoretic techniques to obtain analytic expressions for the stiffness, geometric stiffness, consistent mass, and consistent load matrices of composite shallow shell structural elements. The elements are shear flexible and have variable curvature. A stiffness (displacement) formulation was used with the fundamental unknowns consisting of both the displacement and rotation components of the reference surface of the shell. The triangular elements have six and ten nodes; the quadrilateral elements have four and eight nodes and can have internal degrees of freedom associated with displacement modes which vanish along the edges of the element (bubble modes). The stiffness, geometric stiffness, consistent mass, and consistent load coefficients are expressed as linear combinations of integrals (over the element domain) whose integrands are products of shape functions and their derivatives. The evaluation of the elemental matrices is divided into two separate problems - determination of the coefficients in the linear combination and evaluation of the integrals. The integrals are performed symbolically by using the symbolic-and-algebraic-manipulation language MACSYMA. The efficiency of using symbolic integration in the element development is demonstrated by comparing the number of floating-point arithmetic operations required in this approach with those required by a commonly used numerical quadrature technique

MODELING THE DEMAND FOR DURABLE INPUTS: DISTRIBUTED LAGS AND CAUSALITY

Vector-autoregressive-moving-average (VARMA) modeling was used to identify distributed lag relationships among farm tractor derived demand variables and to provide a basis for formally testing the hypothesis that the price of new tractor horsepower is exogeneous to its quantity demanded. Similar causality tests were used for a number of other explanatory variables, including the interest rate, price of diesel fuel, and price of used tractors. Results indicate that several lagged variables are significant causal factors and that the dynamic nature of the demand structure cannot be ignored when explaining tractor demand.Demand and Price Analysis,

Utility Analysis for Multiple Selection Devices and Multiple Outcomes

Traditional utility analysis only calculates the value of a given selection procedure over random selection. This assumption is not only an inaccurate representation of staffing policy but leads to overestimates of a device\u27s value. This paper generates a new utility model that accounts for multiple selection devices and multiple criteria. The model is illustrated using previous utility analysis work and an actual case of secretarial employees with eight predictors and nine criteria. A final example also is provided which includes these advancements as well as other researchers\u27 advances in a combined utility model. Results reveal that accounting for multiple criteria and outcomes dramatically reduces the utility estimates of implementing new selection devices

Inefficient Policies and Incumbency Advantage

We study incumbency advantage in a dynamic game with incomplete information between an incumbent and a voter. The incumbent knows the true state of the world, e.g., the severity of an economic recession or the level of criminal activities, and can choose the quality of his policy. This quality and the state of the world determine the policy outcome, i.e., the economic growth rate or the number of crimes committed. The voter only observes the policy outcome and then decides whether to reelect the incumbent or not. Her preferences are such that she would reelect the incumbent under full information if and only if the state of the world is above a given threshold level. In equilibrium, the incumbent is reelected in more states of the world than he would be under full information. In particular, he chooses ine±cient policies and generates mediocre policy outcomes whenever the voter's induced belief distribution will be such that her expected utility of reelecting the incumbent exceeds her expected utility of electing the opposition candidate. Hence, there is an incumbency advantage through ine±cient policies. We provide empirical evidence consistent with the prediction that reelection concerns may induce incumbents to generate mediocre outcomes.Elections; Incumbency Advantage; Political Economics

Thousand Aviator Study - Nonvestibular Contributions to Postural Equilibrium Functions

Psychomotor performance and postural equilibrium functioning defined by quantitative ataxia test battery, and relation to pilot selection and gerontolog