A comparative study of tribological behavior of microarc oxidation and hard-anodized coatings

Microarc oxidation (MAO), a novel coating technique capable of depositing dense, hard ceramic composite coatings on aluminium and its alloys, has the potential to replace conventional hazardous anodizing techniques. However, the emergence of such a scenario depends strongly on the properties and performance of MAO coatings in comparison to hard-anodized coatings. In order to facilitate such a comparative investigation, a 6061 T6 aluminium alloy was employed as the substrate and the coatings were deposited through microarc oxidation (MAO) and hard anodizing techniques. The tribological performance of the coatings was evaluated using dry-sand abrasive wheel tests at different normal loads and solid-particle erosion wear tests at different particle velocities and impact angles by employing silica as erodent. The hard-anodized coatings reduced the abrasive wear rate of 6061 Al alloy by a factor of 2, while the MAO coatings reduced the wear rate by a factor of 12-30. Under erosion conditions, the overall wear rate of MAO coatings is identical to that of bare alloy, whereas the hard-anodized coatings exhibit 10 times higher erosion rate.     

Structure from planar motion.

Planar motion is arguably the most dominant type of motion in surveillance videos. The constraints on motion lead to a simplified factorization method for structure from planar motion when using a stationary perspective camera. Compared with methods for general motion, our approach has two major advantages: a measurement matrix that fully exploits the motion constraints is formed such that the new measurement matrix has a rank of at most 3, instead of 4; the measurement matrix needs similar scalings, but the estimation of fundamental matrices or epipoles is not needed. Experimental results show that the algorithm is accurate and fairly robust to noise and inaccurate calibration. As the new measurement matrix is a nonlinear function of the observed variables, a different method is introduced to deal with the directional uncertainty in the observed variables. Differences and the dual relationship between planar motion and planar object are also clarified. Based on our method, a fully automated vehicle reconstruction system has been designed.     

Pesticide exposure and cholinesterase levels among farm workers in the Republic of South Africa.

A preliminary survey was undertaken to establish the extent of pesticide exposure in a farming community. The area under investigation included a coffee plantation in the northern region of South Africa. Cholinesterase levels in red blood cells and plasma were used as markers to monitor the extent of organophosphate and carbamate exposure. Sixty-nine farm workers with specific pesticide exposure were selected for the study, and the frequency of the different symptoms which may be related to pesticide exposure was determined by interview and questionnaire. Of the workers, 77% had their red blood cell cholinesterase levels below the normal reference range, while 27% of the workers had depressed plasma cholinesterase levels.     

Acute toxicity oftrans-5-hydroxy-2-nonenal in fisher 344 rats

The potential toxicity oftrans-4-hydroxy-2-nonenal (HNE), a product formedin vivo during lipid peroxidation, which is also present in foods, was investigated in Fisher 344 rats. Five groups of five male rats each were given by gavage 1000, 300, 100, 30 or 10 mg/kg body weight HNE dissolved in 0.5 mL corn oil. The sixth group, the control, received corn oil alone. Two rats died 6 and 8 hr after being treated with 1000 mg/kg HNE. These two rats showed extensive acute tubular necrosis of the kidney, but had very little liver damage. Diffuse liver cell necrosis was observed in a dose dependent manner in all the rats killed 14 days after treatment, whereas renal change was mild. Interestingly, body weight of the lowest dosage group was significantly higher than that of the control group at termination of the experiment. The results of this study show that HNE has almost the same toxicity as other enals, such astrans-2-heptenal, and that kidney and liver are the main organs affected by toxicity of HNE. Although animals may have efficient defense systems, such as glutathione, to detoxify low to moderate dosages of HNE, at high doses of HNE this defense system is overwhelmed, resulting in serious renal and hepatic damage.     

Symbolic Compression and Processing of Document Images

In this paper, we describe a compression and representation scheme which exploits the component-level redundancy found within a document image. The approach identifies patterns which appear repeatedly, represents similar patterns with a single prototype, stores the location of pattern instances, and codes the residuals between the prototypes and the pattern instances. Using a novel encoding scheme, we provide a representation that facilitates scalable lossy compression and progressive transmission and supports document image analysis in the compressed domain. We motivate the approach, provide details of the encoding procedures, report compression results, and describe a class of document image understanding tasks that operate on the compressed representation.     

Using learning communities to teach technical communication inaccounting

The paper describes the implementation of a learning community involving a technical communication course and an accounting course. Students are simultaneously registered in all the courses constituting the learning community. The learning community approach to writing instruction can be viewed as one way to implement writing across the curriculum with the following distinguishing features. First, students are registered simultaneously for both courses; the communication skills taught in one course are simultaneously reinforced in another course. Second, the faculty of the two courses interact extensively to deliver skills (e.g., communication skills) in a coherent manner across the two courses. We describe the development of a theoretical framework for connecting the two courses. This theoretical framework guided implementation decisions such as the choice of communication skills to be covered in the accounting course, the design of assignments, and the design of evaluation criteria. While we focus on the integration of an accounting course with a communication course, the learning community approach and the implementation steps are applicable to other disciplines     

Frozen storage affects the compressive creep behavior of the porcine intervertebral disc

STUDY DESIGN: A biomechanical study of the compressive creep behavior of the porcine intervertebral disc before and after frozen storage. OBJECTIVE: To determine whether frozen storage alters the creep response, hydration, and nuclear swelling pressure of the intact intervertebral disc. SUMMARY OF BACKGROUND DATA: The mechanical response of the disc is dominated by swelling and fluid flow, whose effects are time-dependent. Because fluid content, which may change during storage, plays a significant role in the disc's time-dependent behavior, changes in mechanical response due to freezing may have been missed in previous studies that focused on time-independent behavior only. METHODS: Porcine intervertebral discs were tested in repeated cycles of compressive creep either immediately postmortem or after 3 weeks of frozen storage. Swelling pressure and nuclear hydration were also measured in fresh and frozen discs. A fluid transport model was used to analyze the creep data. RESULTS: The creep behavior of the intact porcine intervertebral disc is dramatically affected by frozen storage. The apparent permeability of the frozen discs was 82% higher than that of the fresh discs, and the swelling pressure of frozen discs was 25% lower in frozen discs (P < 0.01). The behavior of fresh and frozen discs became more dissimilar with repeated cycles of creep. CONCLUSIONS: In vitro tests of frozen porcine intervertebral discs do not represent fresh behavior. Frozen storage appears to permanently alter disc behavior. The precise nature of any freezing-induced damage, and whether frozen storage similarly affects human discs, remains to be seen.     

Rare earth cobaltite catalysts: Relation of activity to spin and valence states of cobalt

Catalytic activities of rare earth cobaltites and related compounds are shown to be related to the spin and valence states of cobalt.     

An information system for village handpumps

The need for a computerised information system for handpumps installed in any state is brought out. A system with organisational and software aspects is presented. The organisational aspect covers the generation and transmission of data on handpumps at the users’ and the government level. The software consists of a Fortran program, data files, an updating program and a transaction file. The periodic updating of data files is discussed. The system output covers many items of vital information needed for formulating maintenance and research and development policies. A test run of the program with an arbitrarily selected data base is discussed.     

Adiabatic gas absorption in packed columns with large thermal effects

The performance of packed bed adiabatic gas absorbers has been analyzed using the enthalpy and material balance equations incorporating a new parameter, f_r, defined as the fraction of the heat of absorption that is accounted for in the gas stream. An experimental programme to evaluate f_r was carried out and the data correlated. It was found that f_r was dependent on the thermo-physical properties and the hydrodynamic conditions. It is postulated that the mechanism by which this heat transfer occurs is by turbulence at the interface and by entrainment.