Evaluation of Two Homogenization Techniques for Modeling the Elastic Behavior of Granular Materials

This paper discusses the capabilities of two homogenization techniques to accurately represent the elastic behavior of granular materials considered as assemblies of randomly distributed particles. The stress-strain relationship for the assembly is determined by integrating the behavior of the interparticle contacts in all orientations, using two different homogenization methods, namely the kinematic method and the static method. The numerical predictions obtained by these two homogenization techniques are compared to results obtained during experimental studies on different granular materials. Relations between elastic constants of the assembly, interparticle properties, and fabric parameters are discussed, as well as the capabilities of the models to take into account inherent and stress-induced anisotropy for different stress conditions.     

E-Society Portal: Integrating Urban Highway Construction Projects into the Knowledge City

Community involvement is an important factor for sustainable highway construction. Information and communication technologies provide a new and more effective approach to facilitate community involvement. However, there are too many parameters with conflicting and subjective definitions related to sustainability and too many stakeholders with varying degrees of interest and sophistication. There is a need for an effective tool to communicate project impacts on sustainability to local communities. This paper presents an ontology for stakeholder management and sustainability in highway construction. An ontology is a conceptual semantic model that attempts to capture human knowledge (both explicit and tacit) in a consistent manner. Ontologies include three main elements: a taxonomy (common vocabulary presented in concept trees), set of relationships (linking concepts across trees), and axioms (limitation/constraints on the behavior of concepts). The ontology was used to develop a portal for broadcasting highway design features to local communities. By browsing through the portal, a user can learn about project elements, the impacts of each element on sustainability issues, who is sponsoring such element, and what efforts have been made to reduce any impacts of such elements on local communities.     

Observations of Aggressive Children During Peer Provocation and With a Best Friend.

Observational methods were used to examine aggressive children's peer relations in 2 contexts: when being teased by a peer and when interacting with a best friend. Because aggressive children may have more difficulty than nonaggressive children in both peer contexts, the authors also examined whether relations between behaviors across contexts varied as a function of aggression. Results indicated that aggression was related to children's behavior when provoked. Children's behavior when provoked was associated with fewer positive and more negative interactions with their best friend, particularly for aggressive children. Results are discussed with respect to social norms in middle childhood and informing interventions for aggressive children. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reciprocal Associations Between Adolescent Sexual Activity and Quality of Youth-Parent Interactions.

The authors examined differences in adolescents' relationships with their parents before and after adolescent first sexual activity. Participants were 13,570 members of the core sample of the National Longitudinal Survey of Adolescent Health (Add Health) Waves 1 and 2. Path analyses examined changes in parent-adolescent closeness, shared activities, and problem-focused interactions associated with changes in sexual activity separately for sons and daughters and for mothers and fathers. Race, religion, age, urbanicity, and parents' education were controls. Results confirm that increased problem-focused interactions and decreased parental closeness and shared activities both precede and follow adolescent sexual activity. Maintaining positive parental relations after adolescent first sexual activity is discussed as a means to reduce risks associated with sex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

平均应变对0Cr18Ni10Ti钢随机循环应力-应变关系的影响规律

试验研究了平均应变对0Cr18Ni10Ti管道钢随机循环应力．应变关系的影响规律从节约试样和试验费用角度，提出了改进的极大似然疲劳试验法，以应变比分别为-1、-0．52、-0．22、0．029．0．18和0．48完成了104个试样的应变控制疲劳试验。揭示出材料具有Masing行为和完全平均应力松弛特征，现有平均应变理论无法表征其影响。因此．首先基于Ramberg-Osgood方程，应用广义极大似然法有效地测定出各应变比的材料随机循环应力-应变关系。通过比较各应变比的循环应力幅均值、循环应力幅均方差和概率循环应力幅，揭示出高可靠性管理时．平均应变具有降低循环应力幅作用，应变比接近0时最显著．偏离逐渐减弱，说明了研究平均应变效应．仅考虑均值．可能给出错误评价；必须综合考虑均值、均方差和样本量3因素才能给出合理评价。     

New design relations for 2-DOF PID-like control systems

Self-regulating processes can be controlled by internal model control systems where the usual three-parameter model of the process is transformed into a rational model via a parametrized first-order approximant of the apparent dead time. Using feedback and feedforward compensators leads to 2-DOF PID controllers whose time constants cancel that of the rational model. To obtain the desired sensitivity of the actual control loop, the model adaptation parameter and a gain tuning factor in the control system are determined by functions of the normalized dead time. The response to setpoint changes is selected by means of the feedforward compensator or via a prefilter. Plots of the sensitivity and the simulation of step responses to changes in the controller setpoint or to disturbances, show the validity of these design relations for transfer functions representative of typical industrial processes.     

Direction relations and two-dimensional range queries: optimisation techniques

This paper defines direction relations (e.g., north, northeast) between two-dimensional objects and shows how they can be efficiently retrieved using B-, KDB- and R- tree-based data structures. Essentially, our work studies optimisation techniques for 2D range queries that arise during the processing of direction relations. We test the efficiency of alternative indexing methods through extensive experimentation and present analytical models that estimate their performance. The analytical estimates are shown to be very close to the actual results and can be used by spatial query optimizers in order to predict the retrieval cost. In addition, we implement modifications of the existing structures that yield better performance for certain queries. We conclude the paper by discussing the most suitable method depending on the type of the range and the properties of the data.     

Stress Dilatancy and Fabric Dependencies on Sand Behavior

A stress dilatancy model with embedded microstructural information, originally developed by the writers, is used to illustrate the pivotal importance of dilatancy and fabric on the behavior of sand. Fabric, as a second-order tensor, enters into the stress dilatancy equation obtained from a microscopic analysis of an ensemble of rigid particles. Model simulations of sand behavior are carried out in triaxial stress conditions along strain paths with varying degrees of controlled dilation (or compaction) including isochoric deformations as a particular case. Under particular strain paths and fabric conditions, it is shown that a relatively dense sand can succumb to instability or liquefaction under other than isochoric (undrained) conditions. This phenomenon is in accord with laboratory experiments in which dilation or compaction is controlled by modulating the amount of water flowing in or out of a sand specimen during shearing. Mixed drained–undrained loading paths are also simulated with particular reference to fabric dependence at a fixed void ratio. Model simulations capture most of the observed characteristics of sand response, such as instability and asymptotic behavior under various conditions.     

Concordance in Attachment States of Mind and Styles With Respect to Fathers and Mothers.

It is believed that by adulthood, independent attachments to the mother and the father coalesce into a single state of mind with respect to attachment. If true, states of mind with respect to mothers and fathers should be concordant. Fifty-six young adults were administered two versions of the Adult Attachment Interview, each of which asked about their relationship with one parent. State of mind with respect to the father was significantly related to state of mind with respect to the mother, as were attachment styles regarding the two parents. Perceptions of attachment styles were not very related to corresponding states of mind but were related to inferred loving from a parent. (PsycINFO Database Record (c) 2010 APA, all rights reserved)