Anisotropic characterization of crack growth in the tertiary flow of asphalt mixtures in compression

Asphalt mixtures exhibit primary, secondary, and tertiary stages in sequence during a rutting deterioration. Many field asphalt pavements are still in service even when the asphalt layer is in the tertiary stage, and rehabilitation is not performed until a significant amount of rutting accompanied by numerous macrocracks is observed. The objective of this study was to provide a mechanistic method to model the anisotropic cracking of the asphalt mixtures in compression during the tertiary stage of rutting. Laboratory tests including nondestructive and destructive tests were performed to obtain the viscoelastic and viscofracture properties of the asphalt mixtures. Each of the measured axial and radial total strains in the destructive tests were decomposed into elastic, plastic, viscoelastic, viscoplastic, and viscofracture strains using the pseudostrain method in an extended elastic-viscoelastic correspondence principle. The viscofracture strains are caused by the crack growth, which is primarily signaled by the increase of phase angle in the tertiary flow. The viscofracture properties are characterized using the anisotropic damage densities (i.e., the ratio of the lost area caused by cracks to the original total area in orthogonal directions). Using the decomposed axial and radial viscofracture strains, the axial and radial damage densities were determined by using a dissipated pseudostrain energy balance principle and a geometric analysis of the cracks, respectively. Anisotropic pseudo J-integral Paris' laws in terms of damage densities were used to characterize the evolution of the cracks in compression. The material constants in the Paris' law are determined and found to be highly correlated. These tests, analysis, and modeling were performed on different asphalt mixtures with two binders, two air void contents, and three aging periods. Consistent results were obtained; for instance, a stiffer asphalt mixture is demonstrated to have a higher modulus, a lower phase angle, a greater flow number, and a larger n1 value (exponent of Paris' law). The calculation of the orientation of cracks demonstrates that the asphalt mixture with 4% air voids has a brittle fracture and a splitting crack mode, whereas the asphalt mixture with 7% air voids tends to have a ductile fracture and a diagonal sliding crack mode. Cracks of the asphalt mixtures in compression are inclined to propagate along the direction of the external compressive load. © 2014 American Society of Civil Engineers.

Shortest node-disjoint paths on random graphs

A localized method to distribute paths on random graphs is devised, aimed at finding the shortest paths between given source/destination pairs while avoiding path overlaps at nodes. We propose a method based on message-passing techniques to process global information and distribute paths optimally. Statistical properties such as scaling with system size and number of paths, average path-length and the transition to the frustrated regime are analyzed. The performance of the suggested algorithm is evaluated through a comparison against a greedy algorithm. © 2014 IOP Publishing Ltd and SISSA Medialab srl.

On a Hypersingular Equation of a Problem, for a Crack in Elastic Media

Mathematics Subject Classification 2010: 45DB05, 45E05, 78A45.

On a 3D-Hypersingular Equation of a Problem for a Crack

MSC 2010: 45DB05, 45E05, 78A45

A Linear Time Algorithm for Computing Longest Paths in Cactus Graphs

ACM Computing Classification System (1998): G.2.2.

Crack Theory with Singularities at the Boundary

2002 Mathematics Subject Classification: 35S15, 35J70, 35J40, 38J40

Dynamic Determination of Personalized Educational Paths

Report published in the Proceedings of the National Conference on "Education and Research in the Information Society", Plovdiv, May, 2014

Automatized Generation of Personalized Learning Paths through Aspects in Multidimensional Spaces

Report published in the Proceedings of the National Conference on "Education and Research in the Information Society", Plovdiv, May, 2016

Impact of the carrier relaxation paths on two-state operation in quantum dot lasers

We study InGaAs QD laser operating simultaneously at ground (GS) and excited (ES) states under 30ns pulsed-pumping and distinguish three regimes of operation depending on the pump current and the carrier relaxation pathways. An increased current leads to an increase in ES intensity and to a decrease in GS intensity (or saturation) for low pump range, as typical for the cascade-like pathway. Both the GS and ES intensities are steadily increased for high current ranges, which prove the dominance of the direct capture pathway. The relaxation oscillations are not pronounced for these ranges. For the mediate currents, the interplay between the both pathways leads to the damped large amplitude relaxation oscillations with significant deviation of the relaxation oscillation frequency from the initial value during the pulse.

How education should link with career paths

How good is your pharmacy practice? And what does “good” look like? Take a look back at the education and training you have received in your career to date. Has it stood you in good stead? Certainly there is a need to establish a model of professional education and development that produces good pharmacists — you should be able to demonstrate your competence regardless of your sector of work. It may help if we move away from the view that excellence in pharmacy practice is primarily defined by where you practise and the kind of job that you do. The Modernising Pharmacy Careers programme’s aspirations to integrate the undergraduate degree with the preregistration training year are bold and to be applauded — provided the outcome delivers changes that are more than superficial. The new model needs to deliver greater integration of education with practice, while retaining an adequate science base. Theory should be put into the context of practice-based, cross-sector learning needs and opportunities. For example, is the classroom really the best environment in which to learn dispensing? Pharmacokinetic theory could be put into context through creatively designed work placements. And it might make more sense to learn patient counselling in a community pharmacy, and so on. Is it resources we lack to make this happen? Or do we lack the collective will to be imaginative, to be radical and to conceive new approaches to professional education? Implicit in this new approach to education is the expectation that pharmacists should teach and mentor and, conversely, that those who teach should also engage in relevant practice. University education must produce graduates whose knowledge and competence are useful to employers. Moreover, graduates must be adequately prepared to enter any area of the profession endowed with professional self-confidence (something, arguably, that needs further development within the pharmacy psyche). Of course, becoming qualified is just the beginning. Post-qualification, pharmacists need structured career paths that foster this professional confidence, support learning and ensure recognition. To this end, the Royal Pharmaceutical Society-led professional curriculum group is working to define knowledge, skills and experience for all areas of advanced practice. More than ever, the profession needs to adopt a culture of learning, teaching and practice research that is unified. The question is: how do we move away from merely collecting qualifications (trophies) to developing meaningful careers? Pharmacists in all areas and at all levels of the profession need to consider their own willingness to make this shift. The RPS and MPC are leading the way, but are we following?

Identifying the configurational paths to innovation in SMEs:a fuzzy-set qualitative comparative analysis

Using fuzzy-set qualitative comparative analysis (fsQCA), this study investigates the conditions leading to a higher level of innovation. More specifically, the study explores the impact of inter-organisational knowledge transfer networks and organisations' internal capabilities on different types of innovation in Small to Medium size Enterprises (SMEs) in the high-tech sector. A survey instrument was used to collect data from a sample of UK SMEs. The findings show that although individual factors are important, there is no need for a company to perform well in all the areas. The fsQCA, which enables the examination of the impacts of different combinations of factors, reveals that there are a number of paths to achieve better incremental and radical innovation performance. Companies need to choose the one that is closest to their abilities and fits best with their resources.

Optimal redistricting under geographical constraints: Why "pack and crack" does not work

We show that optimal partisan redistricting with geographical constraints is a computationally intractable (NP-complete) problem. In particular, even when voter's preferences are deterministic, a solution is generally not obtained by concentrating opponent's supporters in \unwinnable" districts ("packing") and spreading one's own supporters evenly among the other districts in order to produce many slight marginal wins ("cracking").

Crack tip stress study for elastic-perfectly plastic materials with some applications

The problems of plasticity and non-linear fracture mechanics have been generally recognized as the most difficult problems of solid mechanics. The present dissertation is devoted to some problems on the intersection of both plasticity and non-linear fracture mechanics. The crack tip is responsible for the crack growth and therefore is the focus of fracture science. The problem of crack has been studied by an army of outstanding scholars and engineers in this century, but has not, as yet, been solved for many important practical situations. The aim of this investigation is to provide an analytical solution to the problem of plasticity at the crack tip for elastic-perfectly plastic materials and to apply the solution to a classical problem of the mechanics of composite materials.^ In this work, the stresses inside the plastic region near the crack tip in a composite material made of two different elastic-perfectly plastic materials are studied. The problems of an interface crack, a crack impinging an interface at the right angle and at arbitrary angles are examined. The constituent materials are assumed to obey the Huber-Mises yielding condition criterion. The theory of slip lines for plane strain is utilized. For the particular homogeneous case these problems have two solutions: the continuous solution found earlier by Prandtl and modified by Hill and Sokolovsky, and the discontinuous solution found later by Cherepanov. The same type of solutions were discovered in the inhomogeneous problems of the present study. Some reasons to prefer the discontinuous solution are provided. The method is also applied to the analysis of a contact problem and a push-in/pull-out problem to determine the critical load for plasticity in these classical problems of the mechanics of composite materials.^ The results of this dissertation published in three journal articles (two of which are under revision) will also be presented in the Invited Lecture at the 7$\rm\sp{th}$ International Conference on Plasticity (Cancun, Mexico, January 1999). ^

A phenomenology of crack abuse

The aim of this dissertation is to identify, describe, and explain the common experiences defining the crack abuser's life-world. Its method is phenomenological. Using basic cybernetic premises, a neurophysiologically oriented phenomenological framework concerning the constitution of thoughts, memories, and perceptions is first written. The framework is designed to hypothetically represent the neuropathology of crack abuse within a perspective that prescinds and describes the constitution, flow, and interdependence of experience. After the framework is written, the dissertation outlines the neuro-psychopharmacology of crack abuse and delimits crack abusers as a specific group within the more general population of cocaine users. It then represents the neuropathology of crack abuse within its phenomenological framework and uses the first-person accounts of forty-two crack dependents to actualize a phenomenological sketch of the crack abuser's life-world. The ethnographies afford the possibility of writing a “thick” description of the crack abuser's daily life—one that communicates the substance, order, and subjective and cultural dimensions of the dependent's defining experiences. ^ The dissertation's goals are successfully realized. The framework written and the ethnographies recorded and transcribed, the dissertation is able to identify, describe, and to a certain extent explain some of the common experiences defining the crack abusers life-world. The dissertation concludes that the crack abuser's life-world is organized around three primary and four secondary experiences. His primary experiences include: (1) an almost complete, yet fleeting, satisfaction of the ego's innate insufficiency and sublime, erotic-like stimulation of its core, (2) a fundamental inclination and expansion of the uniquely oriented euphoria-dysphoria dynamic that vivifies and orients the flow of consciousness, and (3) a change in the ego's innate structure. His secondary experiences include: (a) a characteristic aiming of projects, actions, and conduct toward the procurement and consumption of crack, (b) a denigration in the hold of legitimations and institutionalizations on the thematic field, (c) a strict alignment and a contraction in the scope of logical types pointing to the salient experiences within the stock of knowledge, and (d) for some crack abusers, ontological insecurity, despair, and exhaustion. ^

Venezuela and Chile: Two Opposite Paths of Democratic Consolidation and Economic Development.

In the past 20 years, Chile and Venezuela have followed divergent paths of democratic and economic development. When the Cold War ended, Venezuela was one of the few Latin American countries where democracy had survived the authoritarian wave of the 1960 and 1970s. Heralded in the late 1980s as the most stable democracy and one of the most developed and globalized economies in the region, Venezuela has since experienced deterioration of democratic institutions, political polarization, economic stagnation, and instability. In contrast, Chile has experienced a democratic renaissance since 1990. Rapid economic growth, an increasingly efficient public sector, significant reductions in poverty, and improvements in social programs have all made Chile a regional leader in democratic consolidation and sustainable development. Chile emerges as a success story and Venezuela as a country lagging behind in terms of making progress in economic development and poverty reduction. While Chile has developed a democratic system based on institutions, Venezuela has seen its democracy evolve towards increasing concentration of power on the hands of President Hugo Chávez.