Widening Cracks Research Articles

AN APPROACH TO SUBPIXEL ACCURACY WIDENING CRACK WIDTH DETERMINATION IN IMAGE SEQUENCES

Abstract. As an extension to existing work on crack detection and subpixel accuracy crack width determination as a tool for civil engineering material testing, the paper shows an algorithmic approach to handle widening cracks with relative rotations between related crack borders. In the first time step under zero-load, a set of points to be tracked through consecutive frames of an image sequence is defined. Then, subpixel-precise displacement fields are computed for the image data of the following time steps using an 8-parameter least-squares matching approach. The points are triangulated into a mesh, and the changes of the inner geometry of the triangles are considered with a mathematical model assuming a split of each triangle. With this model, subpixel-precise deformation vectors are derived. Crack candidates are determined by a thresholding applied to the vectors’ lengths. After an estimation of the crack normal, a decomposition of the deformation vectors is applied, allowing to compute crack widths and shear movements. As a novel contribution to the technique, a model extension is proposed for the case of a relative rotation between the crack borders in order to reduce systematic errors. The model includes two separate rigid transformations for each crack side.

Answering the call: Offering and analyzing civil discourse opportunities in undergraduate public affairs education

ABSTRACT The widening cracks in the foundations of American democracy are leading to appeals for higher educational institutions generally, and public affairs programs specifically, to offer more courses on civil discourse. In this paper, we conduct a curriculum scan to evaluate the extent to which public affairs programs have answered these calls at the undergraduate level. The findings indicate that civil discourse-themed courses are essentially absent in the largest undergraduate public affairs programs, leaving the calls woefully unanswered. Then, analyzing students’ pre-post survey responses from a new course that offered content on the intersection of civil discourse and public policy making, we find that a civil discourse-themed course can simultaneously answer the calls and ensure that students meet the objectives of baccalaureate public affairs education recommended by the National Association of Schools of Public Affairs and Administration. The results are encouraging for public affairs education and democratic governance alike.

East African Community’s Response to Coronavirus: Old Habits Die Hard

The coronavirus response divulged how EAC partner states prioritize national interests over regional ones and exposed widening cracks within the community. After detecting the virus in the region, individual countries deployed varied approaches against the pandemic despite the indication of a joint response from the EAC secretariat. On the outset, the secretariat called for harmonized surveillance and reporting of the pandemic at all border points, control and prevention materials distribution, and joint training of the EAC mobile laboratory experts. Contrarily, each country acted unilaterally by imposing restrictions and border checks. Some concealed Covid-19 cases and issued non-harmonized Covid-19 certificates at regional border points. While the absence of regional solidarity might have been motivated by the need to contain the spread of the virus, lack of collective action was greatly influenced by simmering differences among EAC member countries. Before Covid-19, tensions revolved around Burundi, Rwanda, Uganda, Tanzania, and Kenya. No wonder the region’s responses to the pandemic laid bare the simmering disagreement within the community. This paper employs discourse analysis to examine how Covid-19 revealed cracks in the community reminiscent of the one leading to the collapse of EAC I.

Mechanical response and strain localization in coal under uniaxial loading, using digital volume correlation on X-ray tomography images

A comprehensive analysis of crack initiation and propagation in coal is critical for understanding its mechanical behavior and its impact on permeability. The finite element-based digital volume correlation (DVC) of time-resolved X-ray tomography images under cleat-parallel uniaxial compression provides 3D incremental strain fields to understand the evolution and propagation of cracks. In this study, DVC coupled with quantitative image analysis was used to understand the role of cleats in guiding and initiating cracks in coal. Simulation of fluid flow through coal at different loading segments provides dynamic quantification of evolution in permeability. After each loading stage, quantification of strain eigen vectors and image analysis indicates appearance, coexistence, and coalescence of tensile and shear cracks guided by the organic matter in coal. We established that constructive interference between tensile and shear crack systems enhances permeability and decreases tortuosity by almost 3x and 7x respectively in coal by widening crack aperture, however, destructive interference is likely to lead to matrix pulverization and clogging of larger crack apertures. During compression, while one part of the coal matrix shows extension perpendicular to the loading direction, another part shows slippage parallel to the loading direction. Based on the variation in crack propagation behavior, four distinct crack morphology zones were identified and discussed. We found that the tortuosity of the cracks decreases exponentially, while permeability and crack volume fraction increase exponentially up to 2.8 μm2 and 28.6% respectively with increasing load. The box-counting-based fractal dimension for the cracks shows a steady increase from 1.58 to 1.78 with loading due to the evolution of existing cracks, and the formation of new cracks.

GCC at Crossroads: Challenges Amidst Unrest in the Arab World

The Arab unrest had a severe impact on the GCC, as it uncovered the existing internal fissures and limitations of the organization. Despite their success in integrating themselves on vital economic, security and political issues, divergent policies adopted by the individual member states on a number of regional issues in the aftermath of the Arab unrest was the main reason for the widening cracks within the organization. Failure to establish consensus and often contrarian positions adopted by the members over sensitive regional issues amid the regional turbulence have raised questions over the unity and relevance of the organization.

Citrate-modified biochar for simultaneous and efficient plant-available silicon release and copper adsorption: Performance and mechanisms

Silicon (Si) deficiency and heavy metals (HMs) pollution are common for farmland soil because of long-term intensive farming. In this study, a novel citrate-modified biochar (C-BC) was introduced as a soil conditioner to simultaneously increase the amount of plant-available Si (PASi) and immobilize HMs. The maximum amount of PASi released was 33.00 mg⋅g−1 from C-BC pre-treated with 0.1 mol⋅L−1 citrate (C-BC0.1). A formation–transport coupling mechanism for increasing the amount of PASi released was developed. Stable Si in the biomass was pyrolyzed to give silicate that was relatively mobile via nucleophilic attack of citrate and hydrolysis of amorphous Si. Silicate species were then released through the porous surface and widening cracks caused by pyrolysis. At citrate concentrations >0.1 mol⋅L−1, the surface and cracks were easily blocked by precipitates formed during pyrolysis. The ability of C-BC to remove HMs was assessed using Cu as an example. C-BC0.1 was optimal for adsorbing Cu, and the maximum adsorption capacity was 271.73 mg⋅g−1. The Cu adsorption mechanism mainly involved surface precipitation, surface complexation, electrostatic attraction and hydrogen bonding. Our research provides important implications for simultaneously addressing Si deficiency and HMs contaminant problems by these materials for soil amendment in agro-ecosystem.

Plague Journal.

Given a strong family history of early heart attacks, the future has always been an iffy proposition. Miraculously, I have bypassed the early off-ramps and find myself approaching 80, stents in place, considering the very real but previously unimaginable possibility of still more. But what kind of more? With dopamine on the wane and no longer supercharged by the push and shove of unbridled ambition and pride, bigger and grander are out of the question. Tired clichés poke through the widening cracks in my thinking to become uninvited bulletins of compromise and consolation. Be grateful. Relax, reminisce, enjoy sunsets, learn the backyard birds' names, maybe even sing to them, and count blessings.

Covid-19 as a ‘breaching experiment’: exposing the fractured society

ABSTRACT In this brief paper, I argue that the coronavirus pandemic is functioning like an ethnomethodological ‘breaching experiment’. In short, it is putting a gigantic spanner in the works of neoliberal governance, in the process exposing the widening cracks and fissures of what I have called the ‘fractured society’. I begin by recalling Garfinkel’s notion of the breaching experiment and by listing the principal attributes of the fractured society. I then explore the response to the coronavirus in the UK, from the government’s initial commitment to ‘herd immunity’ to its present policy of ‘muddling through’. The bulk of the remainder of this contribution addresses precisely how this global health crisis shines a harsh and unforgiving searchlight on the strategies and policies pursued by governments in the UK since 2010, and most especially after the passing of the Health and Social Care Act of 2012. In the closing paragraphs, I examine possible scenarios for a post-fractured society, making particular use of Fraser’s concepts on ‘reactionary’ versus ‘progressive populism’, and conclude with a comment on sociology and engagement.

A novel elastic-body-rotation model for concrete cover spalling caused by non-uniform corrosion of reinforcement

Abstract A novel elastic-body-rotation model is proposed to analyze the mechanism and the process of cover cracking and spalling caused by the non-uniform corrosion of widely spaced reinforcements. The width of the cover surface cracks, bulging of the concrete surface and maximum thickness of the corroded steel can be predicted by using the proposed model. The predicted bulging of the concrete cover has been validated by the experimental and numerical results. Using the validated model, the effects of the diagonal crack angle, tensile strength of concrete and cover thickness on the bulging of the cover surface and the thickness of the corroded steel for initiating and widening cracks are investigated with a parametric study. It is found that the diagonal cracking angle has a major influence on the cover surface crack width. In addition, the degree of corrosion in rebars and the width of internal diagonal cracks can be evaluated by simply measuring the width of surface cracks or the bulging of cover surface.

Reliability of diaphragm wall in serviceability limit states

The paper describes a procedure using serviceability limit state equations to calculate the reliability index for a laterally loaded diaphragm wall. The reliability indices related to the serviceability limit state have been obtained by creating two response surfaces: one based on the maximum lateral displacements of wall head and the other one using the maximum values of bending moments widening cracks in the wall concrete. The global reliability index has been obtained by using the appropriate system reliability formulae proposed by structural reliability theory.

Evidence of recent fault movements in the Tungnafellsjökull fissure swarm in the Central Volcanic Zone, Iceland

he volcanic system of Tungnafellsjökull lies in the Central Iceland volcanic zone near the center of the hot spot and the triple junction where the Eurasian Plate, the North-American Plate and the Hreppar Microplate meet. Holcene activity in the Tungnafellsjökull system has been very low, only two small lavas are associated with the system. The Tungnafellsjökull fissure swarm is rather short and wide compared with fissure swarms of other volcanic systems at the divergent plate boundary, 40 km long and 20 km wide. Earthquakes are not common, with usually fewer than 10 being registered per year. Due to these facts, it came as a surprise when InSAR measurements detected movements on faults in the fissure swarm of Tungnafellsjökull during the Gjálp eruption in Vatnajökull in 1996 at a distance of around 37 km from the eruption site. Ground check in 2009 and 2010 revealed evidence of recent movements on faults in the area in the form of fresh sinkholes and fractures, some of which had moved as recently as the spring of 2010. Fresh sinkholes are known to form mostly during faulting events. They are formed when surface soil is washed into underlying, widening cracks in the bedrock. Based on earthquake data and InSAR images these fault movements occurred during three tectonic events, in October 1996 during the Gjálp eruption, in August 2008 and in November 2009. The events are expressed by increased seismicity in the Tungnafellsjökull area, both in terms of number of recorded earthquakes as well as rate of seismic moment release. The earthquakes were all small. The total released seismic moment is equivalent to that of a single earthquake of magnitude 3.4.The widespread evidence of recent fault movements and the small magnitude of the earthquakes suggests that the fault activity is related to magma movements rather than tectonic faulting.

The EU and Africa since the Lisbon summit of 2007: Continental drift or widening cracks?

This article, by providing an overall assessment of the relations between Africa and the EU since the adoption of the Joint Africa Europe Strategy in Lisbon in 2007, tests the hypothesis of a ‘continental drift’. It looks in particular at four key variables in the relationship: economy, development, governance and politics, and multilateralism. A continental drift is in the making, associated with widening cracks in economic blocks: most of the trade between the two continents is concentrated on a dozen countries on each side. Although the EU has lost some of its leadership in development policies, its funding capacities are still attractive for countries in need: the donor–recipient relation is largely maintained. Both sides have agreed to disagree or to remain quiet about their reciprocal political inconsistencies: the management of governance and political dialogue is thus carried out in a pragmatic manner. The continent-to-continent relationship remains largely a vision.

The Israeli Peace Movement: A Shattered Dream (review)

Reviewed by: The Israeli Peace Movement: A Shattered Dream Benjamin Gidron The Israeli Peace Movement: A Shattered Dream, by Tamar S. Hermann. New York, Cambridge University Press, 2009. 310 pp. $85.00. The long and protracted conflict between the Israelis and the Palestinians had almost a full decade of hope during the 1990s. It started with the election of Yitzhak Rabin to the post of Prime Minister in 1992, it continued with the 1993 Oslo Agreements between Israel and the PLO, to be followed by a smear campaign of the Right which led to Rabin's assassination in November 1995, and it ended abruptly with the failure of the Camp David talks between Israeli Prime Minister Ehud Barak and PLO Chairman Yasser Arafat and the outbreak of the Al-Aksa Intifada in 2000. Despite the murder of Prime Minister Rabin, this decade raised a lot of expectations that, in a similar manner to the long Northern Irish and South African conflicts, which experienced breakthroughs that led to their resolution in the 1990s, a similar process could and would take place around the Israeli-Palestinian conflict as well. The breakthrough of the Oslo Agreements (exactly like the Good Friday Agreement in Northern Ireland and the move towards democratic elections in South Africa) did not happen by a stroke of a pen; it was preceded by a concerted effort of a whole array of citizens' groups and organizations that [End Page 180] advocated a negotiated rather than a military solution to the conflict. This is the focus of Hermann's book, which not only analyzes such groups and their roles before the Oslo Accord but takes a much longer view of the Israeli Peace Movement, from the Pre-State era till the end of the first decade of the twenty-first century. Hermann characterizes the Israeli peace movement as "peripheral" and analyzes the reasons for such a depiction—both contextual-societal reasons and internal reasons. But she argues that despite that fact, "the movement has been a significant factor in influencing the climate of opinion in Israel by persistently putting forward some unconventional and much-contested alternative readings of the conflict, thereby cultivating the ground for the transformation from armed conflict to peace negotiations" (p. 7). As has already been shown in other studies on that subject, the role of preparing the public for the transformation from an armed conflict to the stage of negotiation is probably the most important role of non-governmental citizens' peace groups and organizations. In the height of the conflict, when the country's leadership and media used inflammatory rhetoric to characterize the "enemy" and advocated a strategy of violence to deal with it, a different characterization was heard and a different strategy proposed to deal with the conflict. This was a slowly widening crack that later served as a legitimization of the negotiations. It gave a human face to the "enemy" and actually showed that the other side also wanted to end the conflict and that negotiations were possible. Is this all the Israeli Peace Movement, composed of dozens of groups and organizations, did? Was it not a major factor to push the government towards negotiations? Even if it was, it is not possible to prove it; politicians involved in transformations tend to take the credit for such breakthroughs for themselves and are reluctant to admit that they were "pushed" by outsiders to take those bold steps. But even if the politicians are right and they were not "pushed" by citizens' groups, the role of preparing the public opinion for negotiations should not be belittled. Meeting with representatives of the "enemy," discovering willingness on the other side to negotiate, creating dialog groups or joint planning groups of Israelis and Palestinians, preparing to solve together common problems such as the environment or water—all this shows the public that peace is not only possible but a much preferred option. Without their activity the move from armed conflict to negotiations would be too abrupt and hard to accept by the population. The role of these organizations is often forgotten, and the book is partly meant to compensate for this "collective amnesia." A second focus of the book is...

Strain response of C/SiC composite to thermal and mechanical load cycling in oxidising atmosphere

Strain response of a C/SiC composite simultaneously subjected to thermal cycling (1173–1473 K) and mechanical cycling (60±20 MPa) in an oxygen–argon mixture: 10·4%O2–89·6%Ar was investigated. Thermal strain with maximum value of ∼0·117% and mechanical strain with maximum value of ∼0·029% were directly measured on a progressively increasing baseline strain from 0·354 to 0·670%. The thermal strain and mechanical strain were found to have an approximately linear relationship with the temperature and stress respectively; and to be in quantitative agreement with the calculated results using the proposed semiempirical formulas. The baseline strain was considered to be damage dependent and could increase with accumulated damage. It is observed that the thermal and mechanical load cycling in an O2–Ar mixture could cause the coating/matrix cracks, the degradation of the interfaces, fibre oxidation, and an increase in the baseline strain of the composites by widening crack opening displacement due to larger interfacial debonding and fibre sliding, and reducing effective load bearing area of the fibres.

Feux et Signaux de Brume: Virginia Woolf’s Lighthouse

We are told that Virginia Woolf was reading Proust when she was writing To the Lighthouse. Indeed, she entitled the second part of her novel Time Passes. To measure the passage of time she needed a clock; she used a house. The way an abandoned country house grows old is something everyone has seen and understands. Little airs pry their way in; water leaks through widening cracks; rats invade; spiders stubbornly weave their webs; dust thickens on floor boards beginning to shrink apart?until that brief moment when the balance is tipped by something as light as a feather, the roof caves in, and the house suddenly collapses. Lovers then seek shelter in its ruins, and campers make their beds among the invading brambles. Just as the faces and hands of old men become wrinkled, so the rooftop and walls of the house come to bear the marks of bad weather and passing weeks, that is, of tempests and time. Tomorrow we will go to the Lighthouse if the weather is fine. No, we will not, the wind is blowing from the wrong direction. Romance languages employ a single word (temps, tempo, tiempo) for two meanings that English and German distinguish: the first, chaotic, is registered on a barometer, and the second, oscillating, on a chronometer: time and weather, Zeit and Wetter. Aligned in aleatory fashion, the intemperate weather (rains, winds, and snow) of temperate latitudes calculated on the barometer accelerates the work of temporality calculated on the chronometer to the rhythm of winters and springs, months and weeks, and the yellow flashes that sweep windows and walls of the house with light. Furthermore, all Indo-European languages assimilate two temps, times that the roots of the word, derived from two Greek verbs, distinguish: teino and temno. The first is continuous, a stretching out (at least ten years of absence), the second is discontinuous, intermittent?the flashing of the revolving lamp marks the rhythmic measure, the ten-second beat, let us say, of a process that never ceases, be its tempo fast or slow.

Bring Out Yer Dead

This article reviews three recent books about challenges facing contemporary labor movements. Clawson’s argument that U.S. labor unions ought to seek a fusion with 1960s social movements to build a broad challenge to neoliberal politics reflects the seriousness of labor’s crisis in the United States; his argument is an important one but does not adequately explore the obstacles and difficulties involved in such a fusion. The contributors to Michael Gold’s volume are much more optimistic aboutlabor’s future in Europe, but the contributionof neoliberal restructuringto widening cracks in Europe’s social pacts and a gradual weakening of labor’s position there are evident. Contributors to Cornfield and McCammon’s volume raise doubts about European labor movements’long-term ability to resist neoliberal pressures and demonstrate how in the global South neoliberalism has paralyzed some countries’ labor movements and sparked grassroots resistance in others.

Cost-Effectiveness of Paving Fabrics Used to Control Reflective Cracking

The Illinois Department of Transportation (IDOT) spends $2 million annually on reflective crack control treatments; however, the cost-effectiveness of these treatments had not been reliably determined. A recent study evaluated the cost-effectiveness of IDOT reflective crack control System A, which consists of a nonwoven polypropylene paving fabric, placed either in strips longitudinally over lane-widening joints or over the entire pavement (area treatment). The study was limited to projects constructed originally as rigid pavements and subsequently rehabilitated with one or more bituminous overlays. Performance of 52 projects across Illinois was assessed through crack mapping and from distress and serviceability data in IDOT’s condition rating survey database. Comparisons of measured reflective cracking in treated and control sections revealed that System A retarded longitudinal reflective widening crack development, but it did not significantly retard transverse reflective cracking, which agrees with earlier studies. However, both strip and area applications of these fabric treatments appeared to improve overall pavement serviceability, and they were estimated to increase rehabilitation life spans by 1.1 and 3.6 years, respectively. Reduction in life-cycle costs was estimated to be 4.4 and 6.2 percent when placed in medium and large quantities, respectively, and to be at a break-even level for small quantities. However, life-cycle benefits were found to be statistically insignificant. Limited permeability testing of field cores taken on severely distressed transverse joints suggested that waterproofing benefits could exist even after crack reflection. This was consistent with the observation that, although serviceability was generally improved with area treatment, crack reflection was not retarded relative to untreated areas.

Markov based correlations of damage cycles in Gaussian and non-Gaussian loads

The sequence of peaks and troughs in a load process acting on a material, contains important information about the damage caused by the load, e.g. on the growth rate of a widening crack. The stress range, i.e. the difference between a peak and the following trough, is one of the variables that is used to describe e.g. fatigue life under random loading. The moments, in particular the mean and variance, of the load range are important variables that determine the total damage caused by a sequence of stress cycles, and they give the parameters in the distribution of the time to fatigue failure. However, for many random load processes, the successive stress ranges can show considerable correlation, which affects the failure time distribution. In this paper we derive the modified failure time distribution under correlated stress ranges, under a realistic approximation that the sequence of peaks and troughs forms a Markov chain. We use the regression method to calculate the transition probabilities of the Markov chain for Gaussian load processes with known spectral density. Simulations of Gaussian processes with Pierson-Moscowitz spectrum, and linear and the Duffing oscillators driven by Gaussian white noise, show very good agreement between observed correlations and those calculated from the Markov approximation. Also the numerically calculated transition probabilities lead to good agreement with simulation.

Landslides on Pillar Mountain

Scars from past landslides on Pillar Mountain above the harbor of Kodiak, Alaska, serve as reminders of the past—a past that could herald the future, according to a recent U.S. Geological Survey report. Reuben Kachadoorian and Willard H. Slater cite several factors as being indicative of landslide movement in the area. These include widening cracks seen from aerial and field observations, subsurface movement noted in two observation holes, and surface movement showing a range of downslope movement from 1.3 to 165 mm between 1972 and 1976. There is also geologic evidence, they add, that ‘the current earth movement on the Pillar Mountain landslide appears to be part of an ancient landslide on the mountain that has been reactivated.’