Investigation of hydraulic fracture propagation using a post-peak control system coupled with acoustic emission

This study investigates the fracture mechanism of fluid coupled with a solid resulting from hydraulic fracture. A new loading machine was designed to improve upon conventional laboratory hydraulic fracture testing and to provide a means of better understanding fracture behavior of solid media. Test specimens were made of cement mortar. An extensometer and acoustic emission (AE) monitoring system recorded the circumferential deformation and crack growth location/number during the test. To control the crack growth at the post-peak stage the input fluid rate can be adjusted automatically according to feedback from the extensometer. The complete stress-deformation curve, including pre- and post-peak stages, was therefore obtained. The crack extension/growth developed intensively after the applied stress reached the breakdown pressure. The number of cracks recorded by the AE monitoring system was in good agreement with the amount of deformation (expansion) recorded by the extensometer. The results obtained in this paper provide a better understanding of the hydraulic fracture mechanism which is useful for underground injection projects. © 2014 Springer-Verlag Wien.

Extension ladders - synthesis and characterisation of new spacer-bridged tetraorganodistannoxanes

Preliminary results are described on the synthesis and characterization of novel spacer-bridged tetraorganodistannoxanes, {[[R(Cl)Sn]₂(CH₂)₂]O}₄ (n = 5 – 8, 10, 12; R = CH₂SiMe₃) containing particularly long organic spacers. In the solid state, these compounds reveal typical double-ladder structures with eight tin atoms per molecule, whereas in solution a partial and reversible rearrangement takes place to form tetraorganodistannoxanes, {[[R(Cl)Sn]₂(CH₂)_n]O}₂ (n = 5 – 8, 10, 12; R = CH₂SiMe₃), having four tin atoms per molecule.

Combining extension matrix and integer programming for optimal concept learning

This paper proposes two integer programming models and their GA-based solutions for optimal concept learning. The models are built to obtain the optimal concept description in the form of propositional logic formulas from examples based on completeness, consistency and simplicity. The simplicity of the propositional rules is selected as the objective function of the integer programming models, and the completeness and consistency of the concept are used as the constraints. Considering the real-world problems that certain level of noise is contained in data set, the constraints in model 11 are slacked by adding slack-variables. To solve the integer programming models, genetic algorithm is employed to search the global solution space. We call our approach IP-AE. Its effectiveness is verified by comparing the experimental results with other well- known concept learning algorithms: AQ15 and C4.5.

Correlates of sexual assault in a sample of male African American crack cocaine users

Although numerous studies have reported an association between substance use and sexual assault, little is known about the impact of sexual assault on male African American crack cocaine users. This study found that from a sample of 137 respondents from Houston, Texas, one-third reported having been sexually assaulted at least once during their lifetime. Respondents who reported sexual assault were using cocaine more often and were more likely to be physically dependent on drugs and to report greater numbers of physical health problems due to their drug use. However, no differences were identified in respect of reported mental health problems, or problems with family, friends or the workplace associated with drug use. The findings suggest further research as to the impact of sexual assault on male crack cocaine users is warranted and that clinical staff working with male substance users require some awareness of the impacts of sexual assault.

Frequency distribution of TATA box and extension sequences on human promoters

TATA box is one of the most important transcription factor binding sites. But the exact sequences of TATA box are still not very clear yet. In this study, we conducted a dedicated analysis on the frequency distribution of TATA Box and its extension sequences on human promoters. Sixteen TATA elements derived from TATA Box motif, TATAWAWN, were classified into three distribution patterns: peak, bottom-peak and bottom. Fourteen TATA extension sequences (up to two base extensions) were predicted to be the new TATA Box elements because of their high motif factors, which indicate their statistical significance. Statistical analysis on the promoters of mouse, zebrafish and drosophila melanogaster verified seven of these elements. It was also observed that the distribution of TATA elements on the promoters of housekeeping genes are very similar with their distribution on the promoters of tissue specific genes in human.

The impact of religious affiliation while growing up on substance use by African-American crack cocaine users

This paper explores the relationship between church attendance while growing up and the substance use issues reported by 159 African American crack cocaine users in Houston Texas. It was found that more frequent juvenile attendance at church was associated with being less likely to suffer withdrawal symptoms or to take drugs to avoid withdrawal. However/ there were no differences between regular/ irregular and non-attendees in respect of number of substance use issues reported or attendance at a self help group for substance use/ even though these are often faith-based. The relevance of including questions on religious participation when young in screening instruments to be used with adult substance abusers is questioned.

Medication compliance and satisfaction with treatment for HIV disease in a sample of African-American crack cocaine smokers

The development of treatment regimes for African-American HIV-infected crack cocaine users has often been based on assumptions about compliance with medication regimes rather than evidence. This study sought to obtain baseline information on the adherence to antiretroviral medications by members of this important risk population in Houston, Texas. It was found that for only 5 of a range of 16 antiviral medications was there a significant correlation between levels of compliance reported by respondents and their beliefs as to how effective these medications are. Medication compliance was also found not to be associated with frequency of crack cocaine use in the month prior to interview. Furthermore, irrespective of both gender and their reported extent of medication compliance, the respondents tended to report positive relationships with their treating physician, with higher levels of satisfaction reported by women. These results suggest that the majority of African-American crack cocaine users are able to comply with HIV treatment regimes, with more than half (53%) claiming full compliance for one or more medications, and a further one third (31%) claiming compliance more than half the time. Moreover, these findings suggest that they will continue to take antiretroviral medications even if they have doubts about the effectiveness of these medications.

The determination of the local conditions for void initiation in front of a crack tip for materials with second-phase particles

A procedure is proposed to determine, for second-phase particles near a crack tip, the maximum particle stresses at the moment of void initiation by either particle fracture or particle/matrix interface separation. A digital image analysis system is applied to perform a quantitative analysis of corresponding fracture surface regions from stereo image pairs taken in the scanning electron microscope. The fracture surface analysis is used to measure, for individual particles, the crack tip opening displacement at the moment of void initiation and the particle location with respect to the crack tip. From these data, the stress tensor at the moment of void initiation is calculated from the Hutchinson–Rice–Rosengren (HRR) field theory. The corresponding average local stresses within the particle are evaluated by a non-linear Mori–Tanaka-type approach. These stresses are compared to estimates according to the models by Argon et al. [A.S. Argon, J. Im, R. Safoglu, Metall. Trans. 6 (1975) 825] and Beremin [F.M. Beremin, Metall. Trans. 12 (1981) 723]. The procedure is demonstrated on an Al6061–10% Al2O3 metal matrix composite.

Numerical modeling of interactions between a macro-crack and a cluster of micro-defects

The interactions between a macro-crack and a cluster of micro-defects are studied numerically by using a series of special finite elements each containing a defect. These special finite elements, which contain defects such as holes, cracks, and inhomogeneities, are developed based on the hybrid displacement, complex potential and conformal mapping techniques. These hybrid-type elements can be used together with the conventional finite elements without any difficulty. Thus, simple finite element models can be devised to study the interactions between a macro-crack and a cluster of micro-defects. In this paper, the mathematical and finite element modeling procedures for the study of the above-mentioned problems are presented.

Cause-related marketing : an extension of the congruity concept

This paper considers the concept of congruity or 'fit' in a cause-related marketing (CRM) context. At present, there is a gap in the literature that explores how nonprofit-forprofit pairings affect a consumer's response to and evaluation of CRM campaigns. This paper develops the concept of 'fit' with particular attention being paid to three dimensions, namely, cognitive, emotional and behavioural congruity and the role these concepts play in determining consumers’ perception of the 'relatedness' of products and causes.

Into the protecting arms: the League of Nations and the extension of international assistance to unprotected persons in the Middle East and Europe, 1926 - 1928

The refugee dilemma in Europe in the years between the two world wars had a number of aspects: humanitarian, political, and diplomatic. It raised questions of migration, questions of international law, and questions of the fate of hundreds of thousands of individuals. Refugees were visible from the very last days of the war and remained a matter of serious international concern even beyond the outbreak of war again in September 1939. The refugee dilemma in Europe was, firstly, a humanitarian crisis because the size of the refugee population was without precedent. It was also a political problem because national governments had to contend with questions about the refugees' legal status and their legitimacy under national and international law, as well as balance humanitarian concerns with national political interests. The humanitarian and political aspects together created a crisis for the international community newly united in the League of Nations. One of its first great acts-to take these refugees into its protective care-was not even prescribed for it in its Covenant. But the refugee crisis facing Europe was so great that member states were united in the belief that the League had been established precisely to undertake a task of this kind.

Kant, or the crack in the universal : Slavoj Zizek's politicising the transcendental turn

This paper examines Slavoj Zizek’s reading of Immanuel Kant. Its undergirding argument is that Zizek’s work as a whole- up to and including his politically radical statements, which have become more and more prominent since 1997- is conceivable as a project in the rereading of the Kantian ‘Copernican Revolution’ via Lacanian psychoanalysis. Critics now agree that Zizek’s orienting aim is to write a philosophy of politics, as more recent texts, like The Ticklish Subject make clear. (Kay, 2003; Sharpe, 2004; Dean 2006) If Zizek’s philosophy is ultimately a philosophy of politics, however, Zizek’s political philosophy is grounded in a wider post or ‘neo’-Kantian philosophy of subjectivity.
The essay has three major parts. Part I gives Zizek’s reading of Kant on the subject of apperception. Part II recounts Zizek’s pivotal reading of Kant on the sublime, which he ties closely to the problematics of the ‘Transcendental Dialectic’ of the first Critique. Part III then examines Zizek’s conception of subjectivity in terms of the faculties (and especially the faculty of imagination) that Kant argues are involved in the transcendental constitution of objects in the first half of The Critique of Pure Reason.
In the Conclusion, the force of the paper’s subtitle—‘Politicising the Transcendental Turn’—will become manifest. I lay out three principles of Zizek’s ‘neoKantian/Hegelian’ ontology. These also make clear how his philosophy of political agency is grounded in this apparently suprapolitical or solely philosophical reading of Kant.

Quantitative assessment of through-thickness crack size based on Lamb wave scattering in aluminium plates

The interaction of Lamb wave modes at varying frequencies with a through-thickness crack of different lengths in aluminium plates was analysed in terms of finite element method and experimental study. For oblique-wave incidence, both numerical and experimental results showed that the wave scattering from a crack leads to complicated transmission, reflection and diffraction accompanied by possible wave-mode conversion. A dual-PZT actuation scheme was therefore applied to generate the fundamental symmetrical mode (S0) with enhanced energy to facilitate the identification of crack-scattered wave components. The relationship between crack length and the reflection/transmission coefficient obtained with the aid of the Hilbert transform was established, through which the crack length was quantitatively evaluated. The effects of wavelength of Lamb waves and wave diffraction on the properties of the reflection and transmission coefficients were analysed.

Range extension of the Millewa Skink Hemiergis millewae in the Murray-Sunset National Park, Victoria

This article reports a range extension for the critically endangered Millewa Skink Hemiergis millewae in Victoria. An individual H. millewae was found approximately 85 km east of its former known range in mature mallee vegetation, near the eastern edge of the Murray-Sunset National Park on 27 March 2007. Site characteristics are described, and a list of other reptile species found at the same site is provided. Further research into the habitat associations and distribution of H. millewae is recommended in order to guide the management of this species.