Experiments on Passive Hypervelocity Boundary-Layer Control Using an Ultrasonically Absorptive Surface

Recently performed linear stability analyses suggested that transition could be delayed in hypersonic boundary layers by using an ultrasonically absorptive surface to damp the second mode (Mack mode). Boundary-layer transition experiments were performed on a sharp 5.06-deg half-angle round cone at zero angle of attack in the T5 Hypervelocity Shock Tunnel to test this concept. The cone was constructed with a smooth surface around half the cone circumference (to serve as a control) and an acoustically absorptive porous surface on the other half. Test gases investigated included nitrogen and carbon dioxide at M∞ ≃ 5 with specific reservoir enthalpy ranging from 1.3 to 13.0 MJ/kg and reservoir pressure ranging from 9.0 to 50.0 MPa. Comparisons were performed to ensure that previous results obtained in similar experiments (on a regular smooth surface) were reproduced, and the results were extended to examine the effects of the porous surface. These experiments indicated that the porous surface was highly effective in delaying transition provided that the pore size was significantly smaller than the viscous length scale

Surgical management of posterior fossa metastases

The diagnosis of brain metastases is associated with a poor prognosis reflecting uncontrolled primary disease that has spread to the relative sanctuary of the central nervous system. 20 % of brain metastases occur in the posterior fossa and are associated with significant morbidity. The risk of acute hydrocephalus and potential for sudden death means these metastases are often dealt with as emergency cases. This approach means a full pre-operative assessment and staging of underlying disease may be neglected and a proportion of patients undergo comparatively high risk surgery with little or no survival benefit. This study aimed to assess outcomes in patients to identify factors that may assist in case selection. We report a retrospective case series of 92 consecutive patients operated for posterior fossa metastases between 2007 and 2012. Routine demographic data was collected plus data on performance status, primary cancer site, details of surgery, adjuvant treatment and survival. The only independent positive prognostic factors identified on multivariate analysis were good performance status (if Karnofsky performance score >70, hazard ratio (HR) for death 0.36, 95 % confidence interval (CI) 0.18–0.69), adjuvant whole brain radiotherapy (HR 0.37, 95 % CI 0.21–0.65) and adjuvant chemotherapy where there was extracranial disease and non-synchronous presentation (HR 0.51, 95 % CI 0.31–0.82). Patients presenting with posterior fossa metastases may not be investigated as thoroughly as those with supratentorial tumours. Staging and assessment is essential however, and in the meantime emergencies related to tumour mass effect should be managed with steroids and cerebrospinal fluid diversion as required

An empirical study on Retinex methods for low-light image enhancement

A key part of interpreting, visualizing, and monitoring the surface conditions of remote-sensing images is enhancing the quality of low-light images. It aims to produce higher contrast, noise-suppressed, and better quality images from the low-light version. Recently, Retinex theory-based enhancement methods have gained a lot of attention because of their robustness. In this study, Retinex-based low-light enhancement methods are compared to other state-of-the-art low-light enhancement methods to determine their generalization ability and computational costs. Different commonly used test datasets covering different content and lighting conditions are used to compare the robustness of Retinex-based methods and other low-light enhancement techniques. Different evaluation metrics are used to compare the results, and an average ranking system is suggested to rank the enhancement methods

Role of ICTs in Enhancing a Sustainable Educational Development in Selected Secondary Schools in Ilorin Metropolis

The study investigated the impact of the introduction of Information and Communication Technology (ICTs) has made on the Sustenance of Education in selected secondary schools in Ilorin metropolis. The study made use of primary data obtained through the administration of questionnaires on thirty (30) teachers and Ninety (90) students randomly selected across the six secondary schools within metropolis. The data obtained from the study were analysed using descriptive statistics and chi-square. The results reveal that Information and Communication Technology (ICT) has helped in the development of education in the study area. The findings also reveal that the students’ respondents have developed a positive attitude towards the use of ICT for the acquisition of new skills. . The study therefore recommended that government should make computer and internet facilities available at all levels of our education system as this is expected to improve the performance of students in their academic pursuit. Keywords: Sustainable Development, Information and Communication Technology.(ICT)

Is there such a thing as agile IT program management?

This paper presents early evidence of agile methods in IT enabled transformational programs of high strategic significance and substantial complexity in large organisations. Based on interviews of top management, and program and project managers, we discuss the key drivers that lead to agile IT enabled programs and some of the barriers encountered while managing IT enabled programs in an agile manner. In addition to the need for fast response to environmental changes, strong IT-business collaboration, and efficient resource use by minimising governance burden, we found that organisations are adopting agile practices in program management as transitory step towards achieving enterprise agility. In doing so agile and non-agile projects co-exist within a program thus creating new coordination challenges. Programs with high degree of agile methods adoption face similar challenges in coordinating with the rest of the organisation which operates in non-agile manner. The paper aims to contribute to fostering scholarly discussion on implementation of agile practices in major projects and programs, an emerging area of research with scarce academic literature

Ellipsometer nulling: convergence and speed

The process of nulling in ellipsometry is studied by a graphical presentation using the trajectories of two significant polarization states in the complex plane, XPC and XSA. These states are determined by (1) the polarizer and compensator (XPC) and (2) the specimen and the analyzer (XSA) in the polarizer-compensator-specimen-analyzer ellipsometer arrangement. As the azimuth angles of the ellipsometer elements are varied, XPC and XSA move closer to one another in a stepwise fashion until they coincide when a null is reached. Thus, at null, the polarization states are matched, and XPC = XSA. For an isotropic reflector, the trajectory of XSA is a straight line, which simplifies the development of a criterion for achieving the most rapid nulling for two nulling procedures

Ellipsometer nulling: convergence and speed

The process of nulling in ellipsometry is studied by a graphical presentation using the trajectories of two significant polarization states in the complex plane, XPC and XSA. These states are determined by (1) the polarizer and compensator (XPC) and (2) the specimen and the analyzer (XSA) in the polarizer-compensator-specimen-analyzer ellipsometer arrangement. As the azimuth angles of the ellipsometer elements are varied, XPC and XSA move closer to one another in a stepwise fashion until they coincide when a null is reached. Thus, at null, the polarization states are matched, and XPC = XSA. For an isotropic reflector, the trajectory of XSA is a straight line, which simplifies the development of a criterion for achieving the most rapid nulling for two nulling procedures