Flight-measured laminar boundary-layer transition phenomena including stability theory analysis

Flight experiments were conducted on a single-engine turboprop aircraft fitted with a 92-in-chord, 3-ft-span natural laminar flow glove at glove section lift coefficients from 0.15 to 1.10. The boundary-layer transition measurement methods used included sublimating chemicals and surface hot-film sensors. Transition occurred downstream of the minimum pressure point. Hot-film sensors provided a well-defined indication of laminar, laminar-separation, transitional, and turbulent boundary layers. Theoretical calculations of the boundary-layer parameters provided close agreement between the predicted laminar-separation point and the measured transition location. Tollmien-Schlichting (T-S) wave growth n-factors between 15 and 17 were calculated at the predicted point of laminar separation. These results suggest that for many practical airplane cruise conditions, laminar separation (as opposed to T-S instability) is the major cause of transition in predominantly two-dimensional flows

Natural laminar flow experiments on modern airplane surfaces

Flight and wind-tunnel natural laminar flow experiments have been conducted on various lifting and nonlifting surfaces of several airplanes at unit Reynolds numbers between 0.63 x 10 to the 6th power/ft and 3.08 x 10 to the 6th power/ft, at Mach numbers from 0.1 to 0.7, and at lifting surface leading-edge sweep angles from 0 deg to 63 deg. The airplanes tested were selected to provide relatively stiff skin conditions, free from significant roughness and waviness, on smooth modern production-type airframes. The observed transition locations typically occurred downstream of the measured or calculated pressure peak locations for the test conditions involved. No discernible effects on transition due to surface waviness were observed on any of the surfaces tested. None of the measured heights of surface waviness exceeded the empirically predicted allowable surface waviness. Experimental results consistent with spanwise contamination criteria were observed. Large changes in flight-measured performance and stability and control resulted from loss of laminar flow by forced transition. Rain effects on the laminar boundary layer caused stick-fixed nose-down pitch-trim changes in two of the airplanes tested. No effect on transition was observed for flight through low-altitude liquid-phase clouds. These observations indicate the importance of fixed-transition tests as a standard flight testing procedure for modern smooth airframes

Fiscal Transparency, Accountability and Corporate Collapse: A Post-Mortem Analysis of Failure of State-Owned Enterprises (SOEs) in Nigeria

The study investigated through a post mortem research paradigm the extent to which lack of fiscal transparency and accountability accounted the collapse of SOEs in Nigeria without prejudice to other variables identified in previous studies. The study adopted the fiscal transparency and accountability code of good conduct as evolved by the IMF in building the model tested in the study. The paper observed that institutionalization of the tripod of: clarity of roles and responsibilities (which is a cardinal principle of internal control); public availability of information; and open preparation and proper of implementation of budget would have contributed significantly to foreclosing the collapse of SOEs in Nigeria. The paper also observed that assurances of integrity which revolved around proper engagement of external audit services could not have prevented the failure of SOEs. The paper concludes that the non enshrinement of fiscal transparency and accountability in the management of SOEs is a recipe not only for their poor performance but eventual failure. This conclusion is firmly collocated within the current push for greater transparency and answerability on the part of government and her institutions as evidenced in the ongoing public service reforms. Therefore, the paper recommends the imperative of institutionalizing fiscal transparency and accountability in all public institutions as a critical service delivery success factor and the enthronement of good governance. Keywords: Fiscal transparency, accountability, state-owned enterprises, corporate collapse, post mortem, national development

Digestão de tecido vegetal em forno de micro-ondas via sistema aberto.

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Status report on a natural laminar-flow nacelle flight experiment

The natural laminar flow (NLF) nacelle experiment is part of a drag reduction production program, and has the dual objectives of studying the extent of NLF on full scale nacelles in a flight environment and the effect of acoustic disturbance on the location of transition on the nacelle surface. The experiment is being conducted in two phases: (1) an NLF fairing was flown on a full scale Citation nacelle to develop the experiment technique and establish feasibility; (2) full scale, flow through, NLF nacelles located below the right wing of an experimental NASA OV-1 aircraft are evaluated. The measurements of most interest are the static pressure distribution and transition location on the nacelle surface, and the fluctuating pressure levels associated with the noise sources. Data are collected in combinations of acoustic frequencies and sound pressure levels. The results of phase 2 tests to date indicate that on shape GE2, natural laminar flow was maintained as far aft as the afterbody joint at 50 percent of the nacelle length. An aft facing step at this joint caused premature transition at this station. No change was observed in the transition pattern when the noise sources were operated

Influence of Selected Alternative Extension Approaches on the Acquisition of Knowledge, Skills for Agricultural Productivity in the Lake Victoria Region, Kenya

The role of agricultural extension is vital to the diffusion of new technologies, but extension is currently not very effective in many African nations, with traditional extension approaches having minimal impact. In Kenya, there have been gaps on the availability of studies and documentation of the specific extension approaches and their influence on the acquisition of knowledge, skills and productivity for household food security despite the various extension efforts and resources put in place in many parts of the country. This study therefore investigated the influence of three selected alternative extension approaches on the acquisition of knowledge, skills and productivity for household food security in the Lake Victoria region, Kenya. The main objective of the study was to compare the individual and collective influence of Farmer Field Schools, On-Farm Research and Focal Area approaches on the acquisition of knowledge, skills and farm productivity for enhanced household security in the Lake Victoria region of Kenya. A cross sectional survey design was adopted in order to develop a detailed account of the effect of the three approaches. The total population of the study area was 188,661 households from which a random sample of 396 was selected comprising of small-scale farmers from three sub counties: Bondo, Rachuonyo and Nyamira. Data was analyzed using both descriptive and inferential statistics with the aid of Statistical Package for Social Sciences (SPSS 18.0) at 5 percent level of significance. Findings revealed that Farmer Field School contributed to the acquisition of knowledge and skills in various agricultural production activities and an increase in farm productivity. Results on On-Farm Research revealed that it contributed to knowledge and skills as well as improvement of farm productivity. However, a hypothesis test showed no significant influence on knowledge, skills and productivity for household food security. Findings about Focal Area approach revealed that it contributed to the acquisition of knowledge, skills and productivity for household food security. Focal Area approach proved to be the most effective of the three approache

Influence of Farmer FFS Approach on the Acquisition of Knowledge, Skills for Agricultural Productivity in the Lake Victoria Region, Kenya

The role of agricultural extension is vital to the diffusion of new technologies, but extension is currently not very effective in many African nations, with traditional extension approaches having minimal impact. In Kenya, there have been gaps on the availability of studies and documentation of the specific extension approaches and their influence on the acquisition of knowledge, skills and productivity for household food security despite the various extension efforts and resources put in place in many parts of the country. This study therefore investigated the influence of Farmer Field Schools extension approaches on the acquisition of knowledge, skills and productivity for household food security in the Lake Victoria region, Kenya. The main objective of the study was to compare the influence of Farmer Field Schools and Conventional extension on the acquisition of knowledge, skills and farm productivity for enhanced household security in the Lake Victoria region of Kenya. A cross sectional survey design was adopted in order to develop a detailed account of the effect of the three approaches. The total population of the study area was 188,661 households from which a random sample of 236 was selected comprising of small-scale farmers from three sub counties: Bondo, Rachuonyo and Nyamira. Data was analyzed using both descriptive and inferential statistics with the aid of Statistical Package for Social Sciences (SPSS 18.0) at 5 percent level of significance. Findings revealed that Farmer Field School contributed to the acquisition of knowledge and skills in various agricultural production activities and an increase in farm productivity. Results on On-Farm Research revealed that it contributed more in the acquisition of knowledge and skills as well as improvement of farm productivity as compared to Conventional Extension. Furthermore a hypothesis test showed a significant difference between the two approaches. It is hoped that the findings of this study will contribute to greater understanding of agricultural extension approaches especially in policy formulation and design of the provision of extension services to communities in Kenya

The impact of skull bone intensity on the quality of compressed CT neuro images

International audienceThe increasing use of technologies such as CT and MRI, along with a continuing improvement in their resolution, has contributed to the explosive growth of digital image data being generated. Medical communities around the world have recognized the need for efficient storage, transmission and display of medical images. For example, the Canadian Association of Radiologists (CAR) has recommended compression ratios for various modalities and anatomical regions to be employed by lossy JPEG and JPEG2000 compression in order to preserve diagnostic quality. Here we investigate the effects of the sharp skull edges present in CT neuro images on JPEG and JPEG2000 lossy compression. We conjecture that this atypical effect is caused by the sharp edges between the skull bone and the background regions as well as between the skull bone and the interior regions. These strong edges create large wavelet coefficients that consume an unnecessarily large number of bits in JPEG2000 compression because of its bitplane coding scheme, and thus result in reduced quality at the interior region, which contains most diagnostic information in the image. To validate the conjecture, we investigate a segmentation based compression algorithm based on simple thresholding and morphological operators. As expected, quality is improved in terms of PSNR as well as the structural similarity (SSIM) image quality measure, and its multiscale (MS-SSIM) and informationweighted (IW-SSIM) versions. This study not only supports our conjecture, but also provides a solution to improve the performance of JPEG and JPEG2000 compression for specific types of CT images

Evolution of Electronic Circuits using Carbon Nanotube Composites

Evolution-in-materio concerns the computer controlled manipulation of material systems using external stimuli to train or evolve the material to perform a useful function. In this paper we demonstrate the evolution of a disordered composite material, using voltages as the external stimuli, into a form where a simple computational problem can be solved. The material consists of single-walled carbon nanotubes suspended in liquid crystal; the nanotubes act as a conductive network, with the liquid crystal providing a host medium to allow the conductive network to reorganise when voltages are applied. We show that the application of electric fields under computer control results in a significant change in the material morphology, favouring the solution to a classification task