497,780 research outputs found

    Endogeneity in quantile regression models: a control function approach

    Get PDF
    This paper considers a linear triangular simultaneous equations model with conditional quantile restrictions. The paper adjusts for endogeneity by adopting a control function approach and presents a simple two-step estimator that exploits the partially linear structure of the model. The first step consists of estimation of the residuals of the reduced-form equation for the endogenous explanatory variable. The second step is series estimation of the primary equation with the reduced-form residual included nonparametrically as an additional explanatory variable. This paper imposes no functional form restrictions on the stochastic relationship between the reduced-form residual and the disturbance term in the primary equation conditional on observable explanatory variables. The paper presents regularity conditions for consistency and asymptotic normality of the two-step estimator. In addition, the paper provides some discussions on related estimation methods in the literature and on possible extensions and limitations of the estimation approach. Finally, the numerical performance and usefulness of the estimator are illustrated by the results of Monte Carlo experiments and two empirical examples, demand for fish and returns to schooling

    Efficient semiparametric estimation of a partially linear quantile regression model

    Get PDF
    This paper is concerned with estimating a conditional quantile function that is assumed to be partially linear. The paper develops a simple estimator of the parametric component of the conditional quantile. The semiparametric efficiency bound for the parametric component is derived, and two types of efficient estimators are considered. Asymptotic properties of the proposed estimators are established under regularity conditions. Some Monte Carlo experiments indicate that the proposed estimators perform well in small samples

    Estimating panel data duration models with censored data

    Get PDF
    This paper presents a method for estimating a class of panel data duration models, under which an unknown transformation of the duration variable is linearly related to the observed explanatory variables and the unobserved heterogeneity (or frailty) with completely known error distributions. This class of duration models includes a panel data proportional hazards model with fixed effects. The proposed estimator is shown to be n1=2-consistent and asymptotically normal with dependent right censoring. The paper provides some discussions on extending the estimator to the cases of longer panels and multiple states. Some Monte Carlo studies are carried out to illustrate the finite- sample performance of the new estimator

    Estimating panel data duration models with censored data

    Get PDF
    This paper presents a method for estimating a class of panel data duration models, under which an unknown transformation of the duration variable is linearly related to the observed explanatory variables and the unobserved heterogeneity (or frailty) with completely known error distributions. This class of duration models includes a panel data proportional hazards model with fixed effects. The proposed estimator is shown to be n1/2-consistent and asymptotically normal with dependent right censoring. The paper provides some discussions on extending the estimator to the cases of longer panels and multiple states. Some Monte Carlo studies are carried out to illustrate the finite-sample performance of the new estimator

    Identification of a competing risks model with unknown transformations of latent failure times

    Get PDF
    This paper is concerned with identification of a competing risks model with unknown transformations of latent failure times. The model in this paper includes, as special cases, competing risks versions of proportional hazards, mixed proportional hazards, and accelerated failure time models. It is shown that covariate effects on latent failure times, cause-specific link functions, and the joint survivor function of the disturbance terms can be identified without relying on modelling the dependence between latent failure times parametrically nor using an exclusion restriction among covariates. As a result, the paper provides an identification result on the joint survivor function of the latent failure times conditional on covariates

    Reduction of porosity in aluminum weldments

    Get PDF
    Method is described for elimination of porosity of aluminum weldments by replacing polyvinyl chloride tubing (used to connect welder to gas source, and is permeable to moisture at high humidity) with copper tubing. In addition liquid argon gas is used at weld stations

    On the nonexistence of Smith-Toda complexes

    Full text link
    Let p be a prime. The Smith-Toda complex V(k) is a finite spectrum whose BP-homology is isomorphic to BP_*/(p,v_1,...,v_k). For example, V(-1) is the sphere spectrum and V(0) the mod p Moore spectrum. In this paper we show that if p > 5, then V((p+3)/2) does not exist and V((p+1)/2), if it exists, is not a ring spectrum. The proof uses the new homotopy fixed point spectral sequences of Hopkins and Miller.Comment: 10 pages, AMSLate

    Method of neutralizing the corrosive surface of amine-cured epoxy resins

    Get PDF
    The corrosive alkaline surface layer of an epoxy resin product formed by the curing of the epoxy with an aliphatic amine is eliminated by first applying a non-solvent to remove most or all of the free unreacted amine and then applying a layer of a chemical reagent to neutralize the unused amine or amine functional groups by forming a substituted urea. The surface then may be rinsed with acetone and then with alcohol. The non-solvent may be an alcohol. The neutralizing chemical reagent is a mono-isocyanate or a mono-isothiocyanate. Preferred is an aromatic mono-isocyanate such as phenyl isocyanate, nitrophenyl isocyanate and naplthyl isocyanate

    An Assessment of the ICC Statute

    Get PDF
    The large number of signature States together with the current speed of ratification from various regions of the world seems to indicate the general acceptance of the treaty; many of the problems first identified have since been clarified and resolved. It seems reasonable to expect the Rome Statute to come into operation as early as next summer. While it is necessary to ensure effective criminal investigation and prosecution to counter serious human rights violations, we need also to develop additional ways and means for addressing the root causes that led to violations and impunity. Justice is important but justice alone cannot bring peace. We need both justice and peace. Criminal prosecution through courts and tribunals will not and cannot suit all situations, bring justice to all, or, still less, end all conflicts. Accountability and criminal responsibility are important and necessary. But the tribunals cannot deal adequately when massive cases are involved. Massive trials require large resources and are time-consuming, particularly when there are large numbers of defendants. In recent years, various measures of accountability have been employed for managing situations involving past serious violations of human rights. These measures include acknowledging and publicizing responsibility through truth commissions, dismissing or suspending officials connected with the abuses of the previous regimes, seizure of property and assets of the perpetrators, blocking financial sources of rogue organizations, and compensation for victims and their families. All these are intended to demonstrate that a sense of sanctions has been applied to misdeeds, though such sanctions may not be sufficient in all cases. The parties concerned must work out by themselves the best solution to suit their need

    Mass loading effects on vibrated ring and shell structures

    Get PDF
    Efficient methods for predicting the effects of attached masses on the vibration characteristics of ring and shell structures have been developed and substantiated with experimental data
    corecore