Effects of finite strains in fully coupled 3D geomechanical simulations

Numerical modeling of geomechanical phenomena and geo-engineering problems often involves complex issues related to several variables and corresponding coupling effects. Under certain circumstances, both soil and rock may experience a nonlinear material response caused by, for example, plastic, viscous, or damage behavior or even a nonlinear geometric response due to large deformations or displacements of the solid. Furthermore, the presence of one or more fluids (water, oil, gas, etc.) within the skeleton must be taken into account when evaluating the interaction between the different phases of the continuum body. A multiphase three-dimensional (3D) coupled model of finite strains, suitable for dealing with solid-displacement and fluid-diffusion problems, is described for assumed elastoplastic behavior of the solid phase. Particularly, a 3D mixed finite element was implemented to fulfill stability requirements of the adopted formulation, and a permeability tensor dependent on deformation is introduced. A consolidation scenario induced by silo filling was investigated, and the effects of the adoption of finite strains are discusse

Unemployment in Latin America and the Caribbean

This study constructs a new data set on unemployment rates in Latin America and the Caribbean and then explores the determinants of unemployment. We compare different countries, finding that unemployment is influenced by the size of the rural population and that the effects of government regulations are generally weak. We also examine large, persistent increases in unemployment over time, finding that they are caused by contractions in aggregate demand. These demand contractions result from either disinflationary monetary policy or the defense of an exchange-rate peg in the face of capital flight. Our evidence supports hysteresis theories in which short-run changes in unemployment influence the natural rate.

Pour une sociologie culturelle foucaldienne... de la peur

Nous exposons trois dimensions complémentaires d’une sociologie culturelle d’inspiration foucaldienne : l’analyse de la culture comme incarnation subjective ; l’analyse des modes d’objectivation et des processus de subjectivation ; et l’analyse textuelle comme lecture productrice de sens. Nous démontrons comment ces trois dimensions peuvent être mises au service d’une sociologie culturelle de la peur. La sociologie culturelle proposée comprend la culture à travers les jeux de vérité et leurs effets de réalité — effets concrets mais non obligatoires de la création culturelle, dont les effets de pouvoir, de savoir et de subjectivité. Nous suggérons une exploration plus poussée des dimensions émotionnelles et affectives de la culture. En conclusion, nous entamons une réflexion sur l’exercice de la peur dans l’époque contemporaine.We present three complementary dimensions of a cultural sociology inspired by the works of Foucault : analysis of culture as a subjective incarnation ; analysis of the methods of objectifying and processes of subjectifying ; and textual analysis as meaningful reading. We show how these three dimensions may be applied in a cultural sociology of fear. The cultural sociology proposed includes culture through the play of truths and their reality effects — concrete but non-obligatory effects of cultural creation, including those of power, knowledge and subjectivity. We propose a more in-depth exploration of the emotional and affective dimentions of culture. In conclusion, we initiate a reflection on the exercise of fear in the present era.Exponemos tres dimensiones complementarias de una sociología cultural de inspiración foucauldiana : el análisis de la cultura como encarnación subjetiva ; el análisis de los métodos de objetivación y los procesos de subjectivación ; y el análisis textual como lectura productora de sentido. Demostramos cómo estas tres dimensiones pueden ponerse al servicio de una sociología cultural del miedo. La sociología cultural propuesta incluye la cultura a través de los juegos de verdad y sus efectos de realidad — efectos concretos pero no obligatorios de la creación cultural, incluidos los efectos de poder, de saber y de subjetividad. Sugerimos una exploración más avanzada de las dimensiones emocionales y afectivas de la cultura. En conclusión, iniciamos una reflexión sobre el ejercicio del miedo en la época contemporánea

On Hirth Ring Couplings: Design Principles Including the Effect of Friction

Rings with Hirth couplings are primarily used for the accurate positioning of axial-symmetric components in the machine tool industry and, generally, in mechanical components. It is also possible to use Hirth rings as connection tools. Specific industries with special milling and grinding machines are able to manufacture both tailor made and standard Hirth rings available on stock. Unfortunately, no international standard (for instance ISO, DIN or AGMA) is available for the production and the design of such components. In the best-case scenario, it is possible to find simplified design formulae in the catalogue of the suppliers. The aim of this work is to provide some accurate formulae and computational methods for design to provide better awareness on the limitations and the potential of this type of connection. The work consists of five parts: (i) a review of the base calculation derived mainly from the catalogues of manufacturers; (ii) an improved calculation based on a new analytical method including the friction phenomenon; (iii) an experimentation run for validating the method; (iv) a case study applied to a machine tool; and, (v) a closed form formulation to determine an upper threshold for friction, thus ensuring the Hirth coupling regular performance

A methodology for the lightweight design of modern transfer machine tools

This paper deals with a modern design approach via finite elements in the definition of the main structural elements (rotary table and working unit) of an innovative family of transfer machine tools. Using the concepts of green design and manufacture, as well as sustainable development thinking, the paper highlights the advantages derived from their application in this specific field (i.e., the clever use of lightweight materials to allow ruling out high-consumption hydraulic pump systems). The design is conceived in a modular way, so that the final solution can cover transfers from four to 15 working stations. Two versions of the machines are examined. The first one has a rotary table with nine divisions, which can be considered as a prototype: this machine has been studied in order to set up the numerical predictive model, then validated by experimental tests. The second one, equipped with a rotary table with 15 divisions, is the biggest of the range: this machine has been entirely designed with the aid of the previously developed numerical model. The loading input forces for the analyses have been evaluated experimentally via drilling operations carried out on a three-axis CNC unit. The definition of the design force made it possible to accurately assess both the rotary table and the working units installed in the machine

INFLUENCE OF THE STIFFNESS AND FRICTIONAL CHARACTERISTICS ON THE SHANK TORQUE OF SCREWS IN BOLTED JOINTS

This work aims at determining the influence of tribological and stiffness characteristics of a bolted joint on the residual shank torque of the screw. Even if it is commonly accepted to consider such a residual torque equal to half the torque at the thread, the literature lacks experimental data about the topic. The residual shank torque combines with the axial preload and the external loads to bring about the overall stress on the screw. Hence, the higher the residual torque, the lower the admissible external load for given size and class of the screw. From there stems the need for an analytical tool allowing the designer to calculate the residual torque as a function of the key parameters of the joint

An adaptive thermal comfort model for hot humid South-East Asia

The present paper presents a full procedure to develop an adaptive comfort model for South-East Asia. Meta-analysis on large number of observations from field surveys which were conducted in this region was employed. Standardization and bias control of the database were fully reported. Statistical tests of significance and weighted regression method applied in the analyses strengthened the reliability of the findings. This paper found a great influence of ‘Griffiths constant’ on the establishment of adaptive comfort equation and proposed an appropriate value. The adaptive comfort model generated is applicable to naturally ventilated building under hot and humid conditions of South-East Asia. The mean neutral comfort temperature (operative temperature, effective temperature, standard effective temperature) in naturally ventilated and air-conditioned building was compared and the differences have been discussed. The similar neutral standard effective temperature in both naturally ventilated and air-conditioned building proposes a new idea to implement SET* into building simulation tools to assess thermal comfort without the attention of building classification. Through the analysis, the effectiveness of behavioral adaptive actions on occupant’s thermal perception has been argued. The extended PMV-PPD model for hot humid conditions was examined and its applicability was recommended. Other comfort related issues, the differences and similarities between various adaptive comfort models were also addressed.Peer reviewe

Considering the impact of situation-specific motivations and constraints in the design of naturally ventilated and hybrid buildings

A simple logical model of the interaction between a building and its occupants is presented based on the principle that if free to do so, people will adjust their posture, clothing or available building controls (windows, blinds, doors, fans, and thermostats) with the aim of achieving or restoring comfort and reducing discomfort. These adjustments are related to building design in two ways: first the freedom to adjust depends on the availability and ease-of-use of control options; second the use of controls affects building comfort and energy performance. Hence it is essential that these interactions are considered in the design process. The model captures occupant use of controls in response to thermal stimuli (too warm, too cold etc.) and non-thermal stimuli (e.g. desire for fresh air). The situation-specific motivations and constraints on control use are represented through trigger temperatures at which control actions occur, motivations are included as negative constraints and incorporated into a single constraint value describing the specifics of each situation. The values of constraints are quantified for a range of existing buildings in Europe and Pakistan. The integration of the model within a design flow is proposed and the impact of different levels of constraints demonstrated. It is proposed that to minimise energy use and maximise comfort in naturally ventilated and hybrid buildings the designer should take the following steps: 1. Provide unconstrained low energy adaptive control options where possible, 2. Avoid problems with indoor air quality which provide motivations for excessive ventilation rates, 3. Incorporate situation-specific adaptive behaviour of occupants in design simulations, 4. Analyse the robustness of designs against variations in patterns of use and climate, and 5. Incorporate appropriate comfort standards into the operational building controls (e.g. BEMS)