Nonconservative Nature of the Stresses Developed in a Continuum.

The stresses in an elastic continuum (i.e. a continuum with zero strains after unloading) are classically deemed to be conservative (i.e. their total work all over the continuum is a single-valued function of only the displacement distribution in the continuum). So, internal damping in an elastic continuum appears to be a contradiction in itself. Actually, the total work of the internal stresses all over a continuum does not coincide with the strain energy of the continuum, but also includes the work of the internal body forces formed by the stress derivatives, which only con-tributes to the kinetic energy of the continuum. Owing to this inclusion, the total work of the internal stresses cannot be a single-valued function of only the displacement distribution in the continuum, and hence, the internal stresses must be nonconservative, which indicates internal damping inherent in any continuum whether elastic or not. Only statically deforming continua may possess conservative internal stresses

Bernoulli's Transformation of the Response of an Elastic Body and Damping

Bernoulli's transformation and the related separation of variables method or modal analysis as classically applied to the partial differential equation of motion of an elastic continuum will always conclude an undamped response. However, this conclusion lacks reliability, since the underlying analysis assumes either integrandwise differentiability (i.e. differentiation and integration signs are interchangeable) or termwise differentiability (i.e. the derivative of an infinite series of terms equals the sum of the derivatives of the terms) for Bernoulli's transformation, which not only is responsible for the undamped response but also is arbitrary. This paper using Bernoulli's transformation examines an elastic uniform column ruled by the generalized Hooke’s law and subjected to axial surface tractions at its free end or a free axial vibration, and shows that the above differentiability assumptions underlying classical analysis are equivalent and actually constitute a limitation to the class of the response functions. Only on this limitation, damping appears to be inconsistent with the elastic column response. Removing the limitation through nontermwise differentiability of Bernoulli’s transformation results in a damped response of the elastic column, which indicates that damping actually complies with the generalized Hooke’s law as applied to elastic continua

E-Procurement Framework for Shipping

The existing procurement process in shipping is paper-based and labor-intensive. Looking to cut costs and improve delivery times, while simultaneously enabling companies to take a more strategic approach to their jobs, an eprocurement framework is proposed to automate and streamline its procurement process by bringing it online. In this paper we present an intranet Web-based electronic procurement infrastructure. The shipping organizational process requirements was fully analyzed and evaluated. The ships as end-users were provided with access to the application taking into account the existing communication cost and restrictions. The logical Architecture is presented including the schema of the databases, the catalog management, the workflow of the purchase order plus the end-users interaction with the procurement system through Web browser. Then the physical architecture is described when security, load simulation and several well known technologies are applied. In all step the shipping environment and its specific characteristics are fully assessed. The application in its pilot implementation (marine engines spare parts procurement) shows that is scaleable, has a supplier integration strategy that met the shipping company’s core requirement, is relatively eas y to install, configure and use and can be integrated with ERP

Systems thinking for the transition of existing technologies to blockchain technologies

The 4th Industrial evolution has brought along a lot of technological achievements which can change the form of humanity. Peer-to-peer networks (Distributed networks), network of sensors (Internet of Things), algorithms capable to take decisions (Artificial Intelligence), computers with the ability of self-learning (Machine Learning), more complex queries for analyzing the data, that we are collecting since the birth of internet (Data Science) and new electronic money(cryptocurrencies) are some of the characteristics of those new technologies. But the adoption of those achievements (known as Digital Transformation or Digitization) demands Managers open-minded, well-educated on those technologies and ready to trace the new possible Risks. They must also be capable to use the Systems Thinking, as the Blockchain Technologies have created an Ecosystem (Sociotechnical Systems); the combination of Social Systems (Organizations - Companies), whose behavior is not predictable, and Mechanical Systems (technical equipment) with a predefined way of function. So, this kind of Systems (Sociotechnical) need a more delicate approach using a combination of, not only Systemic methodologies and technics, but also other theories and proper tools. We are going to publish a series of articles in which we are going to specify the proper theories and methodologies in each phase of the digital transformation. Thus, the purpose of this study is to explain to the new generation of Managers how the Systems Thinking, DCSYM Methodology and VSM Model, are applied on those Ecosystems

Selectivity, Market Timing and the Morningstar Star-Rating System

This paper evaluates the Morningstar mutual fund ranking system. We find that indeed higher Morningstar ratings are associated with higher returns on the portfolios including respectively five-, four-, three-, two- and one-star funds only (STAR5 to STAR1). We then perform an unconditional and conditional portfolio performance evaluation. In both cases the evidence suggests that the better performance of the STAR3, STAR4 and STAR5 categories reflects superior stock selection rather than market timing abilities. Overall, the implication for the Morningstar ranking system is that this is most effective in identifying the worst-performing funds (STAR1 or STAR2) rather than the best-performing ones.mutual fund, Morningstar Star-Rating System, CAPM, conditional and unconditional portfolio performance evaluation

Dislocation-based continuum models of crystal plasticity on the micron scale

The miniaturization trends on electronic components manufacturing, have challenged conventional knowledge on materials strength and deformation behavior. ”The smaller the stronger” has become a commonplace expression summarizing a multitude of experimental findings in micro-scale plasticity, and modelling tools capable of capturing this distinctive reality are in urgent demand. The thesis investigates the ubiquitous size effects in plastic deformation of micron-scale specimens. Tracing the source of such a behavior to the constituent elements of plastic deformation, we use as starting point the dynamics of discrete dislocations and try to embody them into a continuum framework. The thesis is structured in two independent parts. In the first part the question why size effects occur in constrained geometries is addressed. A systematic investigation of the connection between internal and external length scales is carried out in a system where dislocations, in the form of continuous lines embedded in a threedimensional isotropic medium, move, expand, interact, and thus create plastic distortion on the deforming body. Our modelling strategy utilizes a set of deterministic evolution equations on dislocation densities for describing the stress-driven evolution of the material’s internal state. These transport-like equations simultaneously serve the role of constitutive laws describing the deformation of the stressed body. Subsequent application to three benchmark problems is found to give good agreement both with experiment and discrete dislocation dynamics simulation. The second part of this thesis focuses on the heterogeneity and intermittency of deformation processes on the micro scale. Recent experimental results question the concept of smooth and homogeneous plastic flow with fluctuations that average out above a certain scale. Bursts of activity, which follow power-law size distributions and produce long-range correlated deformation patterns, seem to pertain even on scales far greater than the atomic one. In short, plasticity in this view appears as a ’crackling noise’ phenomenon similar to other irregular and burst-like processes such as earthquakes or granular avalanches. But then why do we witness smooth stress-strain curves on macroscopic sample testing? Concepts originating from Self Organized Criticality and pinning theories are employed for producing an efficient continuum description which is then used to study the effect of intrinsic and extrinsic deformation parameters on the fluctuation phenomena. It is deduced that hardening, load driving and specimen size, are all decisive on constraining fluctuating behavior, and limits of classical theory’s applicability can be drawn

Statistical modeling of stock returns: explanatory ordescriptive? A historical survey with some methodologicalreflections

The purpose of this paper is twofold: first, to survey the statistical models of stock returns that have been suggested in the finance literature since the middle of the twentieth century; second, to examine under the prism of the contemporary philosophy of science, which of the aforementioned models can be classified as explanatory and which as descriptive. Special emphasis is paid on tracing the interactions between the motivation for the birth of statistical models of stock returns in any given historical period and the concurrent changes of the theoretical paradigm in financial economics, as well as those of probability theory

A System Dynamics Model to Identify the Impact of the Economic Crisis on Crime Rate and on Security Sensation in European Societies

Modern society is a Complicated System, in which the interaction between its essential parts is affected in a daily basis by: (a) the Economic Crisis, (b) the Feeling of Xenophobia, (c) the Interweaving of the Political System and (d) the Degeneration of Human Interpersonal Relationships. Two important facts that have been excessively observed in the European Union over the last few years are the increase of Crime Rate, and at the same time the decrease of Security Sensation. The model that we have developed simulates the way that particular social phenomena such as: (a) the taxation, (b) the reduction of the State Expenditure on Equipment and (c) the conflicts of interest caused by the Economic Crisis, affect the Crime Rate. Therefore, this study can be the starting point for identifying other social phenomena that should be taken into account in the Strategic Plan of Crime and Violence treatment in member countries of the European Union

A Risk Assessment Framework For Interconnected And Interdependent Surface Transport Networks

The functioning and viability of modern societies is heavily depended upon the continuous and uninterruptible operation of critical infrastructures. Surface transportation systems are in the heart of the daily lives of millions of citizens globally. As such, they are open and freely accessible by design and in the past have been exploited for terrorism attacks. Like many critical infrastructures, different multimodal and heterogeneous transportation networks are interconnected as integral part of larger synergistic systems forming a “network of networks”. These underlying and often concealed interconnections between network assets enable adverse effects to manifest at assets that are initially unaffected by a security incident. The present paper introduces a holistic Risk Assessment Framework for heterogeneous, transportation networks that is applicable at a strategic level, where risk is propagated between interconnected networks through an “Incident Propagation Matrix” taking into account the nature of the interconnection and the type of threat. The proposed methodology views and models the risk analysis process from the perspective of the network operator and emergency responders and emphasizes the reduction of the impacts on business continuity

Application of a 245 metric ton Dual-Use Active TMD System

The slender design of a 245 m tall tower structure requires additional structural damping to reduce vortex shedding induced vibrations. Wind tunnel tests indicate that wind speeds can produce critical accelerations at the observation deck on the tower’s top level. The resulting displacements not only raise concern regarding the fatigue capacity at the concrete core of the tower, but would also lead to the discomfort of its visitors. To mitigate critical displacements, a state of the art passive Tuned Mass Damper (TMD) system was chosen to be implemented. The primary use of the tower is not only to give visitors access to its observation deck but to also serve as a test facility for equipment susceptible to building sway. To test the equipment under real life conditions the TMD system is required to be either in passive or in active mode, where in the latter it could excite the tower in its fundamental mode of vibration and cause a significant, yet controlled, building sway in any direction. To satisfy these requirements a novel dual purpose active/passive TMD system was developed. This hybrid TMD is capable of even suppressing the occurring vibrations in one direction while, with the aid of active control, synchronously exciting the tower’s perpendicular direction. The following paper reports on the design approach of the passive system and describes the control strategy when switched into excitation mode. The initial optimization approach will be presented as well as the in-situ results of vibration tests during a monitoring campaign on the tower. In addition, the safety concept to avoid excessive displacements of the tower will be presented