A mixture-model approach to linking ADHD to adolescent onset of illicit drug use.

Prior research findings have been mixed as to whether attention-deficit/hyperactivity disorder (ADHD) is related to illicit drug use independent of conduct problems (CP). With the current study, the authors add to this literature by investigating the association between trajectories of ADHD symptoms across childhood and adolescence and onset of illicit drug use, with and without controlling for CP. In a longitudinal panel study of a community sample of 754 girls and boys recruited in kindergarten, this research question was examined with a combination of growth mixture modeling (to model parent-reported ADHD symptom trajectories) and survival analysis (to model youth-reported initiation of illicit drug use). Results revealed a 3-class model of ADHD trajectories, with 1 class exhibiting no or minimal symptoms throughout childhood and adolescence, another class showing a convex shape (an increase, then a decrease in symptoms) across time, and a third class showing a concave shape (a decrease, then a slight increase in symptoms) over time. The concave-trajectory class demonstrated significantly earlier onset of illicit drug use than the minimal-problem class, with the convex-trajectory class falling between (but not significantly different from either of the other two classes). These results did not change when the authors added CP to the model as a covariate. Implications of findings for theory and practice are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Using Finite Element Simulation to Optimize the Heat Treatment of Tire Protection Chains

The heat treatment of tire protection chains has a major influence on the final product because the high local stresses that arise during quenching may lead to material failure, i.e., quench cracks. The investigations presented in this paper aim at the identification of critical areas in the design of a tire chain link made of 50CrV4 (DIN 1.8159) steel. Parametric studies were conducted by means of finite element (FE) simulation. The FE model enables the calculation of the stress evolution in the chain link during heat treatment. The position of the cracks produced in laboratory quench experiments coincided with the position where the FE simulation model predicted the maximum tensile stress at the end of the quench. Hence, geometry optimization of the chain links is now possible by means of parametric FE studies aiming to minimize these tensile stresses. To identify the influence of the various input parameters on the calculated stress evolution during the quenching, a sensitivity analysis was performed. The influence of the mesh size, the heat transfer at the surface, and the thermo-mechanical properties of the material phases on the stress calculation was evaluated and trends were identified. Temperature measurements during quenching experiments were used to determine the heat transfer parameters. X-ray residual stress measurements on pre-defined positions after an instrumented laboratory quenching were used to validate the simulation results.     

Purpose and function in a collaborative CAD environment

In a multidisciplinary design environment, such as the architecture, engineering and construction (AEC) domain, the various designers will have their own concepts and representations of the design object making communication in such an environment a complex task. Computer-aided design (CAD) modelling is seen as the vehicle for interdisciplinary communication and integration. However, this paper stresses the need for a multiple view approach based upon an assumption that different views of an object are based on different functional contexts. The paper demonstrates that an understanding of concepts such as function, purpose and intent is critical since the representation of the functional properties of design objects is the underlying basis for the formation of different representations and the coordination of these representations. The paper puts forward definitions for function and purpose which allow for the representation of these properties of a design object and the communication of intent and effects.     

Agent-Based Interoperability without Product Model Standards

Abstract:   This article describes using agents in the exchange of industrial product data when predefined translators are not available. A major problem with standard translators is that a seamless data transfer instantly fails when not every translator implements a mapping into or from the standard format. This is frequently the case for large design projects that involve the use of a multitude of heterogeneous tools, possibly in evolving configurations over time. The agent-based approach developed and presented in this article aims to flexibly provide product models in a form adapted to the needs of the particular tools when there is no prior agreement on a common data format. Experiments show the feasibility of this approach as well as its efficacy and efficiency.     

Untersuchung der Verockerungsneigung von Vertikalfilterbrunnen im Modellversuch

Operating wells are often influenced by performance losses which increase over time. These losses can be caused by clogging of system elements due to oxidation and precipitation of diluted Fe(II)- and Mn(II)-ions to Fe(III)- and Mn(IV)-hydroxides. The influence of iron clogging on the conductivity of the gravel pack??in particular on the hydraulic gradient in the gravel pack??is analyzed with a combined hydraulic and hydrogeochemical model of a vertical well in which the clogging process is accelerated by hydrochemical modifications. Over 295 h, the iron concentration in the filter gravel increased up to 15 g Fe per kg gravel. According to the preliminary findings, these incrustations induce an increase of the pressure loss in the filter gravel pack of nearly 30?%. After defining a test termination criterion, the model will be used for tests concerning different well material (screen and gravel pack) and methods for reduction of the incrustation (operation and regeneration) as well as for parametric studies.     

Operational status of the Magnum-PSI linear plasma device

The construction phase of the linear plasma generator Magnum-PSI at the FOM institute DIFFER has been completed and the facility has been officially opened in March 2012. The scientific program to gain more insight in the plasma–wall interactions relevant for ITER and future fusion reactors has started.In Magnum-PSI, targets of a wide range of materials and shapes can be exposed to high particle, high heat flux plasmas (>10²⁴ ions m^?2 s^?1; >10 MW/m²). For magnetization of the plasma, oil-cooled electromagnets are temporarily installed to enable pulsed operation until the device is upgraded with a superconducting magnet. The magnets generate a field of up to 1.9 T close to the plasma source for a duration of 6 s. Longer exposure times are available for lower field settings.Plasma characterizations were done with a variety of gases (H, D, He, Ne and Ar) to determine the machine performance and prepare for subsequent scientific experiments. Thomson scattering and optical emission spectroscopy were used to determine the plasma parameters while infrared thermography and target calorimetry were used to determine the power loads to the surface.This paper reports on the status of Magnum-PSI and its diagnostic systems. In addition, an overview of the plasma parameters that can be achieved in the present state will be given.     

The place of expert systems in civil engineering

Engineering is concerned with much more than calculation and numeric analysis. It is concerned with ideas, concepts, judgement and deploying experience which cannot be represented numerically. All of these appear to be outside the realm of traditional engineering computing. Engineers make use of knowledge about objects, events and processes and make declarative statements about them which are often written down symbolically. These limitations of traditional computing in civil engineering can be overcome by expert systems. In this paper we present a number of expert systems dealing with analysis, design and knowledge acquisition in the field of civil engineering.     

Pesticide residue variability--implications for Codex MRLs and world trade.

A number of developments have taken place in addressing consumer risk to pesticide residues. Progress is being made to harmonize an international database to allow short exposure assessments to be carried out on a routine basis and a number of initiatives have been arranged to support this process. Since Codex Alimentarius Commission has adopted these proposals, they will become an integral part of the process for assessing and accepting Codex MRLs in the future.     

From Synthesis to Formulation and Final Application

Meeting the requirements for insensitive munitions remains a complex route, where all the steps of the production process have to be addressed. NTO is a choice component, especially for large munitions. Various compositions have been optimized, which are now available, in pressed or cast PBX as well as melt cast formulations. Standard products such as RDX have been improved by the synthesis or crystallization methods, giving reduced sensitivity formulations. Some cast PBX can sustain severe shaped charge jet impacts, thanks to their large critical diameter, and are candidates as main filling of large munitions such as IM Mk82. The formulation step is addressing not only new binder principles, allowing an increase in the filler and thus energy contents, but also a bi‐component innovative method to get a semi continuous filling process where the pot life is no longer an issue. Finally a partial toolset for designing IM features is proposed with a recent example of successful application.     

深入了解赛灵思System Generator中的时间参数

针对基于模型的设计,本文提出了采用赛灵思为DSP提供的SystemGenerator工具的系统化解决方案,详细介绍和分析了其中的比例-积分-微分(PID)控制器以及各时间参数的定义和选择.