bluuebunny/crossref_metadata_2025 huggingface dataset:
Unique Renal Tubule Changes Induced in Rats and Mice by the Peroxisome Proliferators 2,4-Dichlorophenoxyacetic Acid (2,4-D) and WY-14643
Authors: Ozaki Keisuke , Mahler Joel F. , Haseman Joseph K. , Moomaw Cindy R. , Nicolette Matthew L. , Nyska Abraham
Published: January 2003

Peroxisome proliferators are non-mutagenic carcinogens in the liver of rodents, acting both as initiators and promoters. The National Toxicology Program (NTP) conducted a study of several peroxisome proliferators (PPs), including Wyeth (WY)-14643 as a prototypical PP and 2,4-dichlorophenoxyacetic acid (2,4-D) as a weak PP, in Sprague-Dawley rats, B6C3F1 mice, and Syrian hamsters. In the kidney, an unusual change was observed in the outer stripe of the outer medulla, especially in rats treated with 2,4-D or WY-14643. This change was characterized by foci of tubules that were partially or completely lined by basophilic epithelial cells with decreased cytoplasm and high nuclear density. Changes typical of chronic nephropathy such as interstitial fibrosis or basement membrane thickening were not associated with these foci. Results of immunohistochem- ical staining for catalase and cytochrome P-450 4A in the kidney indicated increased staining intensity in renal tubular epithelial cells primarily in the region where the affected tubules were observed; however, the altered cells were negative for both immunohistochemica l markers. Ultrastructurally, affected cells had long brush borders typical of the P3 tubule segment. The most distinguishing ultrastructural change was a decreased amount of electronlucent cytoplasm that contained few differentiated organelles and, in particular, a prominent reduced volume and number of mitochondria; changes in peroxisome s were not apparent. In addition to the lesion in rats, mice treated with the highest dose of 2,4-D, but not WY-14643, manifested similar renal tubular changes as seen by light microscopy. Neither chemical induced renal tubular lesions in hamsters. Hepatocellular changes characteristic of PPs were present in all 3 species treated with WY-14643, but not 2,4-D. These results indicate that the rat is the species most sensitive to the nephrotoxic effects of PPs and there is a site specificity to this toxicity related to areas of PP-related enzyme induction. Although 2,4-D is considered a weak PP for the liver, it was the most effective at inducing renal lesions, indicating that the toxic potency of various PPs will depend on the target organ.
Toxicosis Associated with Dual Oral Exposure of Rats to Lead and Trichloroethylene
Authors: Nunes Jack , Ehrich Marion , Robertson John
Published: January 2003

To determine if additive or synergistic toxic effects would occur, adult male rats were exposed orally to lead carbonate (2,000 mg/kg) for 9 days before trichloroethylene (TCE), 2,000 mg/kg, was given concurrently for an additional 7 days. Comparisons were made with groups of vehicle-treated rats and rats given only lead or only TCE. Potential neurotoxicity was evaluated by using the Functional Observational Battery (FOB) recommended for neurotoxicity screening. Rats were sacrifi ced on day 16, and brain, testes, spleen, kidney/adrenals, heart, and liver weighed and observed for pathological changes. Results of the FOB indicated that lead carbonate was more responsible than TCE for changes observed. Additive or synergistic neurotoxicities were not noted. Histological examination of the kidney from lead-treated rats revealed inclusions, an increased incidence of coagulated proteins, and tubular dilation that was generally more severe in the medullary segments. Gastric and testicular necrosis were found in rats given lead carbonate both with and without TCE (15/20 and 6/20 treated, respectively). The results suggest that, even when given concurrently, the toxicities of lead carbonate and TCE are expressed only as though one toxicant was given.
Analysis of Toxic Effects of Alternaria Toxins on Esophagus of Mice by Light and Electron Microscopy
Authors: Yekeler Hayreddin , Bitmiş Kazim , Ozçelik Nurten , Doymaz Mehmet Z. , Çalta Metin
Published: January 2003

In this study, the possible toxic effects of Alternariol Methyl Ether ( AME) and Tenuazonic Acid ( TeA) produced by Alternaria species on esophagus of mice were investigated by using light and electron microscopy techniques. Mice were orally fed daily with AME or TeA for 10 months and at the end of this period, the effects of these chemicals on the esophageal mucosa were determined. By light microscopic examination, moderate and severe dysplasia characterized by loss of polarity, nuclear pleomorphism, and hyperchromasi a were observed in TeA-treated animals. Electron-microscopi c examination of TeA-treated mucosal epithelial cells revealed pyknosis in some nuclei, granulation and increase in chromatin mass, irregularities in the nuclear contours, vacuolization in nucleoplasms, and marked pleomorphism in the nuclei. In conclusion, our results suggested that TeA has higher toxicity as evidenced by dysplastic transformation.
Is p53 Haploinsufficient for Tumor Suppression? Implications for the p53+/- Mouse Model in Carcinogenicity Testing
Authors: Venkatachalam Sundaresan , Tyner Stuart D. , Pickering Curtis R. , Boley Scott , Recio Leslie , French John E. , Donehower Lawrence A.
Published: January 2003

The p53 tumor suppressor gene has been shown to be critical in preventing cancer in humans and mice. We have generated and extensively characterized p53-deficient mice lacking one (p53+/-) or both (p53-/-) p53 alleles. The p53-defi cient mice are much more susceptible to an array of different tumor types than their wild-type (p53+/+) littermates. The enhanced tumor susceptibility of the p53+/- mice has made them one of several transgenic mouse models that are being considered as substitutes for standard 2-year rodent carcinogenicity assays. In order to fully exploit this model, it will be important to understand some of the basic biological and molecular mechanisms that underlie its enhanced tumor susceptibility. With this in mind, we have explored the fate of the remaining wild-type p53 allele in spontaneously arising p53+/-tumors and have shown that over half of these tumors retain an intact, functional wild-type p53 allele. This suggests that p53 is haploinsufficient for tumor suppression and that mere reduction in p53 dosage is suffi cient to promote cancer formation. To support the idea that p53 is indeed a haploinsufficient tumor suppressor, we show here that normal p53+/-cells exhibit reduced parameters of growth control and stress response compared to their p53+/+ counterparts. We hypothesize that the reduced p53 dosage in the p53+/- cells provides an environment more conducive to the development of further oncogenic lesions and the initiation of a tumor. Finally, we have assessed p53 loss of heterozygosity (LOH) in carcinogen-induced p53+/- tumors and have found that some agents induce tumors that almost invariably exhibitp53 LOH, whereas other agents induce tumors that often retain the wild-type p53 allele. Our preliminary data suggest that LOH is dependent on both the mechanism of genotoxicity of the agent utilized and the tissue type targeted.
Iron Lactate-Induced Osteopenia in Male Sprague-Dawley Rats
Authors: Matsushima Shuuichi , Hoshimoto Mariko , Torii Mikinori , Ozaki Kiyokazu , Narama Isao
Published: January 2003

Osteopenia was induced in rats fed a diet containing 50,000 ppm (5%) iron lactate for 2 or 4 weeks. Blood chemistry, urinalysis, and bone histomorphometry of the proximal tibial metaphysis were performed. Urinary pyridinoline and deoxypyridinolin e and the osteoclast number per bone surface were selected for the measurement of dynamic resorption. The osteoclast surface, eroded surface, and osteoblast surface increased at both ends of the exposure periods, and bone resorption and formation both increased. The bone volume, trabecular thickness, and trabecular number decreased, and the secondary spongiosa of proximal metaphysis showed a marked bone loss. However, no mineralization defect was observed. At the end of the 2-week exposure period, biomarkers of osteoclasts and osteoblasts had increased the most, and the osteoblast surface, osteoclast surface, and osteoclast number per bone surface increased with prolonged exposure. The pathological changes of the bone lesion in iron lactate-overloaded rats were similar to those in rats of the osteoporotic model, because they consisted of changes reflecting the increase of bone resorption and formation without an osteomalacic change. However, the decline of serum parathyroid hormone (PTH) levels was different from that of the osteoporosi s model rat.

We concluded iron-induced bone lesions probably differ from those of low turnover bone diseases.
Antimicrobial susceptibility and pneumococcal serotypes
Authors: Fenoll A. , Asensio G. , Jado I. , Berrón S. , Camacho M. T. , Ortega M. , Casal J.
Published: January 2003

The increase in antibiotic resistance and the possible changes in serotype prevalence as a consequence of a new conjugated vaccine have contributed to renewed interest in the study of pneumococcal serotypes and their antibiotic resistances. Spain still has one of the highest penicillin resistance rates, but in the past 4–5 years a slight decrease has been observed. The level of resistance has not increased either, 12.7% of the 11 165 isolates studied showed high-level penicillin resistance but 94% of these had an MIC of only 2 mg/L. Serotypes 6, 9, 14, 19 and 23 included 83% of the penicillin-resistant pneumococci; the remaining 17% belonged to 18 different serotypes. We analysed these minor penicillin-resistant serotypes in view of their potential increase following a possible child vaccination programme. Four of these serotypes (11, 15, 21 and 35) were the most prevalent, and among them serotype 15 was particularly frequent with >50% of its strains resistant. The effective control of these minor penicillin-resistant serotypes should be based on continuous surveillance of pneumococcal epidemiology.
From ecological reservoir to disease: the nasopharynx, day-care centres and drug-resistant clones of Streptococcus pneumoniae
Authors: de Lencastre H. , Tomasz A.
Published: January 2003

Several lines of epidemiological and microbiological studies point to the multiple and critical roles of the nasopharynx of children—particularly those of pre-school age and attending day-care centres (DCCs)—in the emergence and spread of drug-resistant Streptococcus pneumoniae (DRP). A systematic yearly surveillance of the nasopharyngeal flora of children attending DCCs has been carried out in Lisbon since 1996. Molecular typing of several hundred DRP isolates showed that the great majority of DRP were represented by a relatively few clonal types that were frequently carried by many children in geographically distant DCCs and over several years of surveillance. The same epidemic DRP clones were also frequent among pneumococci causing both paediatric and adult disease worldwide. Penicillin-resistant pneumococci carry sequences of heterologous origin in their pbp genes and also in the recently identified murM : a gene essential for expression of penicillin resistance and for the unique cell wall structure of penicillin-resistant pneumococci. Virtually all DRP express only a limited number (five or six) of the very large genetic repertoire (up to 90) of serotypes available for this bacterial species and the serotypes of drug-resistant strains happens to be the same as the serotypes of drug-susceptible pneumococci that most frequently colonize pre-school age children. These observations strongly suggest that the nasopharynx of children is an important global ecological reservoir of DRP and may also play a critical role as the favoured anatomical site for the evolution of DRP.
Evaluating a credit guarantee agency in a developing economy: a non‐parametric approach
Authors: Ong Hway‐Boon , Shah Habibullah Muzafar , Radam Alias , Azali M.
Published: January 2003

Banks are important sources of external credit but they are reluctant to lend to small and medium enterprises (SMEs) due to the high credit risk involved. Therefore, Credit Guarantee Corporation (Malaysia) Limited (CGC) was set up to assist SMEs to secure loans from financial institutions in Malaysia. Being the sole issuer of credit guarantees to SMEs, the performance of CGC directly reflects the availability of credit guarantees to SMEs. Hence, to ascertain the accessibility of credit guarantees, this study evaluates the efficiency of credit guarantee schemes provided by CGC. From a non‐parametric analysis, CGC is found to be operating at a relatively low level of overall technical efficiency. Therefore, CGC should consider reallocating its existing inputs as well as increase the amount of credit guarantees granted to SMEs in order to achieve a reasonable level of efficiency.
Theories and controversies in finance: a paradigmatic overview
Authors: Ardalan Kavous
Published: January 2003

The purpose of this paper is to provide an overview of the paradigmatic context and structure of the current theories and controversies in mainstream academic finance. It identifies the context among paradigms and the structure within the identified paradigm. The paper is based on the view that worldviews underlie theories and controversies in general, and those of finance, in particular. It notes how any worldview can be positioned on a continuum formed by four basic paradigms: functionalist, interpretive, radical humanist, and radical structuralist. Then, the paper notes that theories and controversies in mainstream academic finance, despite their apparent diversity, are founded on and associated with the functionalist paradigm. Then, the paper continues with the discussion of the hierarchical structure of paradigms. It discusses that it consists of three consecutive levels: paradigm; metaphor; and puzzle solving. It looks at a sample of prominent controversies in academic finance and notes that they belong to the substructure of the functionalist paradigm. Throughout, the paper emphasizes that, in the future, mainstream academic finance should benefit from the contributions of the other three paradigms.
The corporate communication function: how well is it funded
Authors: Dolphin Richard R.
Published: January 2003

This guest editorial article considers the extent to which the corporate communication function in the UK context is adequately funded. It concentrates on what appears to be the entirely neglected research area of whether or not organizations consider that the competitive advantage that successful communications can bring is worthy of the financial investment on which such success may well depend crucially. The article concludes that a sizeable minority receives little or no investment in the communication function. It notes that a large majority of communication executives feel that they are adequately resourced; but it questions whether their competitive advantage would be enhanced through more substantial funding. It also suggests that substantial resourcing may well go hand in hand with the controversial nature of the organization itself.
Financial reporting on the Internet by leading Japanese companies
Authors: Marston Claire
Published: January 2003

Financial reporting on the Internet is an activity that has increased in recent years. This paper reports the results of a survey of Internet reporting by the top 99 Japanese companies in 1998. It was found that the majority of these companies (78) had a Web site in English and that of these 68 reported some financial information with 57 providing detailed accounting information. Company size was significantly positively associated with the existence of a Web site but the extent of financial disclosure did not appear to be related to size. There was no significant association between profitability, industry grouping and overseas listing status and Internet disclosure. The survey was updated in 2001 by re‐evaluating those companies which had no Web site or only a Japanese Web site in 1998. It was found that the majority of these companies now have an English language Web site with full annual reports available.
Generalized Framework for Three-Dimensional Upper Bound Limit Analysis in a Tresca Material
Authors: Puzrin A. M. , Randolph M. F.
Published: January 2003

A new method is proposed for deriving kinematically admissible velocity fields (KAVFs) for three-dimensional upper bound limit analyses in a Tresca material using coordinate transformations. The method allows the incompressibility condition to be satisfied simply by imposing certain requirements on the analytical form of velocity magnitudes. This allows for new classes of velocity fields to be derived solely using standard procedures. These new classes of fields include: KAVFs with new streamline shapes; new planar but non-plane-strain KAVFs; new radial but nonaxisymmetric KAVFs. The method allows the expression of local dissipation of plastic work in any field to be derived in a closed form. The proposed method makes an attempt to expand the applicability of three-dimensional upper bound limit analysis by introducing more realistic shapes of KAVFs, while maintaining simplicity and clear engineering meaning.
Robust Optimal Positioning of Strain Gages on Blades
Authors: Mignolet Marc P. , Choi Byeong-Keun
Published: January 2003

This paper focuses on the formulation and validation of an automatic strategy for the selection of the locations and directions of strain gages to capture at best the modal response of a blade in a series of modes. These locations and directions are selected to render the strain measurements as robust as possible with respect to random mispositioning of the gages and gage failures. The approach relies on the evaluation of the signal-to-noise ratios of the gage measurements from finite element strain data and includes the effects of gage size. A genetic algorithm is used to find the strain gage locations-directions that lead to the largest possible value of the smallest modal strain signal-to-noise ratio, in the absence of gage failure, or of its expected value when gage failure is possible. A fan blade is used to exemplify the applicability of the proposed methodology and to demonstrate the effects of the essential parameters of the problem, i.e., the mispositioning level, the probability of gage failure, and the number of gages.
Shear Buckling of Sandwich, Fiber Composite and Lattice Columns, Bearings, and Helical Springs: Paradox Resolved
Authors: Bazˇant Z. P.
Published: January 2003

As shown three decades ago, in situations where the initial stresses before buckling are not negligible compared to the elastic moduli, the geometrical dependence of the tangential moduli on the initial stresses must be taken into account in stability analysis, and the stability or bifurcation criteria have different forms for tangential moduli associated with different choices of the finite strain measure. So it has appeared paradoxical that, for sandwich columns, different but equally plausible assumptions yield different formulas, Engesser’s and Haringx’ formulas, even though the axial stress in the skins is negligible compared to the axial elastic modulus of the skins and the axial stress in the core is negligible compared to the shear modulus of the core. This apparent paradox is explained by variational energy analysis. It is shown that the shear stiffness of a sandwich column, provided by the core, generally depends on the axial force carried by the skins if that force is not negligible compared to the shear stiffness of the column (if the column is short). The Engesser-type, Haringx-type, and other possible formulas associated with different finite strain measures are all, in principle, equivalent, although a different shear stiffness of the core, depending linearly on the applied axial load, must be used for each. The Haringx-type formula, however, is most convenient because it represents the only case in which the shear modulus of the core can be considered to be independent of the axial force in the skins and to be equal to the shear modulus measured in simple shear tests (e.g., torsional test). Extensions of the analysis further show that Haringx’s formula is preferable for a highly orthotropic composite because a constant shear modulus of the soft matrix can be used for calculating the shear stiffness of the column, and further confirm that Haringx’s buckling formula with a constant shear stiffness is appropriate for helical springs and built-up columns (laced or battened).
Measurement and CFD Prediction of the Flow Within an HP Compressor Drive Cone
Authors: Long Christopher A. , Turner Alan B. , Kais Guven , Tham Kok M. , Verdicchio John A.
Published: January 2003

In some gas turbine aeroengines, the HP compressor is driven by the H.P. turbine through a conical shaft or drive cone. This drive cone is enclosed by a stationary surface that forms the supporting material for the combustion chambers. Air used to cool the turbine blades is directed into the space around the drive cone, and a major concern to an engine designer is the temperature rise in this air due to frictional dissipation and heat transfer. This paper presents results from a combined experimental and CFD investigation into the flow within an engine representative HP compressor drive cone cavity. The experimental results show similarities in flow structure to that found in classic rotor-stator systems. Both 2-D and 3-D CFD simulations were carried out using the FLUENT/UNS code. The 3-D model which included the actual compressor blade tip clearance gave the best agreement with the experimental data. However, the computational resource required to run the 3-D model limits its practical use. The 2-D CFD model, however, was found to give good agreement with experiment, providing care was exercised in selecting an appropriate value of initial tangential velocity.
Predicting Bladerow Interactions Using a Multistage Time-Linearized Navier-Stokes Solver
Authors: Ning W. , Li Y. S. , Wells R. G.
Published: January 2003

A multistage frequency domain (time-linearized/nonlinear harmonic) Navier-Stokes unsteady flow solver has been developed for predicting unsteady flows induced by bladerow interactions. In this paper, the time-linearized option of the solver has been used to analyze unsteady flows in a subsonic turbine test stage and the DLR transonic counter-rotating shrouded propfan. The numerical accuracy and computational efficiency of the time-linearized viscous methods have been demonstrated by comparing predictions with test data and nonlinear time-marching solutions for these two test cases. It is concluded that the development of efficient frequency domain approaches enables unsteady flow predictions to be used in the design cycles to tackle aeromechanics problems.
An Investigation of Simple Evaporation Models Used in Spray Simulations
Authors: Yao G. F. , Abdel-Khalik S. I. , Ghiaasiaan S. M.
Published: January 2003

In the present work, an unified derivation of simple evaporation models used in spray simulation is described and a new evaporation model is formulated. In the model, the Nusselt number, Sherwood number, and evaporation mass flux are derived using the traditional film theory. However, instead of determining the film thicknesses using the Nusselt and Sherwood numbers derived in the absence of high mass transfer rate, the film thicknesses are calculated from those derived from the fully numerical solutions which represent the realistic heat and mass transfer processes around a droplet. The model predictions are compared with the fully numerical solutions.
A Mathematical Confirmation for Higher LMTD Value of Counter Flow Versus Parallel Flow Heat Exchangers
Authors: Kowsary Farshad , Biglarbegian Mohammad
Published: January 2003

A rigorous argument based on the characteristic of a monotonously increasing function is presented to establish the well-known fact of higher LMTD value of counter flow heat exchangers as compared to parallel flow ones.
Mitigation of Particulate Fouling by Ozonation
Authors: Wu Bang-Yenn , Chan S. H.
Published: January 2003

Heat transfer surface fouling introduces a major uncertainty into the design and operation of cooling water systems. Fouling caused by calcium carbonate CaCO3 typically occurs on heat transfer surfaces. Ozone has been successfully used for more than 90 years as a disinfectant in drinking water. Recently, it has been proposed to use ozone for cooling tower water treatment. In this research, the effectiveness of mitigation of calcium carbonate particulate fouling by ozone was studied systematically. The experimental results show that, at low Reynolds numbers, though the ozonation retards the initial calcium carbonate particulate fouling rate, the retardation led to a non-porous deposit layer and a higher asymptotic fouling resistance. However, at high Reynolds numbers, ozonation was found to reduce the asymptotic fouling resistance.
Experimental Study on Frost Structure on Surfaces With Different Hydrophilicity: Density and Thermal Conductivity
Authors: Shin Jongmin , Tikhonov Alexei V. , Kim Cheolhwan
Published: January 2003

An experimental study has been conducted to investigate the effects of surface energy on frost formation. Test samples with three different surfaces of which dynamic contact angles (DCA) were 23, 55, and 88 deg were installed in a wind tunnel and exposed to a humid airflow. The airflow Reynolds number, humidity, the air and the cold plate temperatures were maintained at 9000, 0.0042 kg/kg′, +12 and −22°C, respectively. The thickness and the mass of frost layer were measured and used to calculate frost density while heat flux and temperature profile were measured to obtain thermal conductivity. Exact positions of thermocouple junctions were verified by means of visualization system in order to increase accuracy. Results showed that frost density and thermal conductivity increase with time. The surface with a lower DCA showed a higher frost density and thermal conductivity during a two-hour test, but minor differences have been found after two hours of frost generation. Empirical correlations for thickness, mass deposition, density and thermal conductivity were proposed as the functions of test time and surface energy.
Blade Row Interaction in a High-Pressure Steam Turbine
Authors: Chaluvadi V. S. P. , Kalfas A. I. , Hodson H. P. , Ohyama H. , Watanabe E.
Published: January 2003

This paper presents a study of the three-dimensional flow field within the blade rows of a high-pressure axial flow steam turbine stage. Compound lean angles have been employed to achieve relatively low blade loading for hub and tip sections and so reduce the secondary losses. The flow field is investigated in a low-speed research turbine using pneumatic and hot-wire probes downstream of the blade row. Steady and unsteady numerical simulations were performed using structured 3-D Navier-Stokes solver to further understand the flow field. Agreement between the simulations and the measurements has been found. The unsteady measurements indicate that there is a significant effect of the stator flow interaction in the downstream rotor blade. The transport of the stator viscous flow through the rotor blade row is described. Unsteady numerical simulations were found to be successful in predicting accurately the flow near the secondary flow interaction regions compared to steady simulations. A method to calculate the unsteady loss generated inside the blade row was developed from the unsteady numerical simulations. The contribution of various regions in the blade to the unsteady loss generation was evaluated. This method can assist the designer in identifying and optimizing the features of the flow that are responsible for the majority of the unsteady loss production. An analytical model was developed to quantify this effect for the vortex transport inside the downstream blade.
Finite Element Analysis of Brittle Cracking due to Single Grit Rotating Scratch
Authors: Subhash G. , Zhang W.
Published: January 2003

Finite element analysis of single grit rotating scratch on brittle materials was conducted using an “elastic-plastic-cracking” (EPC) model. The brittle material removal mechanism was modeled based on a critical crack-opening displacement criterion. It was found that the tangential and normal force profiles as well as the damage morphology observed in scratch experiments were fully captured by the EPC model. The results revealed that the induced damage zone size increases linearly with a brittleness parameter EY/σf21/3 as well as the maximum depth of cut.
Effect of Pressure, Subcooling, and Dissolved Gas on Pool Boiling Heat Transfer From Microporous Surfaces in FC-72
Authors: Rainey K. N. , You S. M. , Lee S.
Published: January 2003

The present research is an experimental study of the effects of pressure, subcooling, and non-condensable gas (air) on the pool nucleate boiling heat transfer performance of a microporous enhanced and a plain (machine-roughened) reference surface. The test surfaces, 1-cm2 flat copper blocks in the horizontal, upward facing orientation, were immersed in FC-72. The test conditions included an absolute pressure range of 30–150 kPa, a liquid subcooling range of 0 (saturation) to 50 K, and both gas-saturated and pure subcooling conditions. Effects of these parameters on nucleate boiling and critical heat flux (CHF) were investigated. Results showed that, in general, the effects of pressure and subcooling on both nucleate boiling and CHF were consistent with the prevailing trends in the literature. For the present heater geometry, the effects of dissolved gas on the boiling performance were generally small, however, as the dissolved gas content increased (through either increased pressure or subcooling) more of the nucleate boiling curve was affected (enhanced). The enhancement of CHF from increased liquid subcooling was greater for the microporous surface than the plain surface. Correlations for both nucleate boiling and CHF were also presented.
Surface Energy Variation Effect on the Onset of Thermocapillary Instability of a Thin Liquid Layer Heated from the Side
Authors: Wu Lin , Chen Kang Ping
Published: January 2003

A general interfacial energy balance equation taking into account surface energy variation is derived for viscous two-layer flows. Application of this interfacial energy equation to a thin liquid layer heated from one side using a one-layer model shows that thermocapillary induced surface energy variation has a tendency to stabilize the system, resulting in an increase in the critical Marangoni number for the onset of thermocapillary instability. Thermocapillary induced surface energy variation tends to decrease the temperature of hot surface spots and increase the temperature of cold surface spots through an absorb-release mechanism. This absorb-release mechanism increases the free surface’s capability to convect thermal energy from hot spots to cold spots and thus redistributes the disturbance energy evenly across the free surface. This new stabilizing effect becomes stronger at high surface temperature and at high surface dilatation rate.
Solar Powered Water Pumps: The Past, the Present—and the Future?
Authors: Short T. D. , Oldach R.
Published: January 2003

Solar (photovoltaic) powered water pumps could be a real instrument for the alleviation of water related deaths and illnesses in developing countries through the provision of clean water. However, despite the benefits that access to sustainable potable water supplies can bring, solar powered water pumps have a long way to go before they even begin to meet the needs of those who could use them. This paper addresses some of the complex, inter-related social and technical issues that have prevented solar powered water pumping from reaching its full potential and shows how future efforts should be directed in order to respond to these issues.
Indirectly Irradiated Solar Receiver-Reactors for High-Temperature Thermochemical Processes
Authors: Wieckert Christian , Meier Anton , Steinfeld Aldo
Published: January 2003

A solar receiver-reactor concept for high-temperature thermochemical applications involving gas and condensed phases is presented. It features two cavities in series. The inner cavity is an enclosure, e.g., made of graphite, with a small aperture to let in concentrated solar power. It serves as the solar receiver, radiant absorber, and radiant emitter. The outer cavity is a well-insulated enclosure containing the inner cavity. It serves as the reaction chamber and is subjected to thermal radiation from the inner cavity. The advantages of such a two-cavity reactor concept are outlined. A radiation heat transfer analysis based on the radiosity enclosure theory is formulated and results are presented in the form of generic curves that indicate the design constraints. High energy absorption efficiency can be achieved by minimizing the aperture area, by maximizing the size of the inner cavity and by constructing it from a material of high emissivity.
Effects of Tip Geometry and Tip Clearance on the Mass/Heat Transfer From a Large-Scale Gas Turbine Blade
Authors: Papa M. , Goldstein R. J. , Gori F.
Published: January 2003

An experimental investigation has been performed to measure average and local mass transfer coefficients on the tip of a gas turbine blade using the naphthalene sublimation technique. The heat/mass transfer analogy can be applied to obtain heat transfer coefficients from the measured mass transfer data. Flow visualization on the tip surface is provided using an oil dot technique. Two different tip geometries are considered: a squealer tip and a winglet-squealer tip having a winglet on the pressure side and a squealer on the suction side of the blade. Measurements have been taken at tip clearance levels ranging from 0.6 to 3.6% of actual chord. The exit Reynolds number based on actual chord is approximately 7.2×105 for all measurements. Flow visualization shows impingement and recirculation regions on the blade tip surface, providing an interpretation of the mass transfer distributions and offering insight into the fluid dynamics within the gap. For both tip geometries the tip clearance level has a significant effect on the mass transfer distribution. The squealer tip has a higher average mass transfer that sensibly decreases with gap level, whereas a more limited variation with gap level is observed for the average mass transfer from the winglet-squealer tip.
Numerical Solutions of Cauchy-Riemann Equations for Two and Three-Dimensional Flows
Authors: Hafez M. , Housman J.
Published: January 2003

For two-dimensional flows, the conservation of mass and the definition of vorticity comprise a generalized Cauchy-Riemann system for the velocity components assuming the vorticity is given. If the flow is compressible, the density is a function of the speed and the entropy, and the latter is assumed to be known. Introducing artificial time, a symmetric hyperbolic system can be easily constructed. Artificial viscosity is needed for numerical stability and is obtained from a least-squares formulation. The augmented system is solved explicitly with a standard point relaxation algorithm which is highly parallelizable. For an extension to three-dimensional flows the continuity equation is combined with the definitions of two vorticity components, and are solved for the three velocity components. Second-order accurate results are compared with exact solutions for incompressible, irrotational, and rotational flows around cylinders and spheres. Results for compressible (subsonic) flows are also included.
Hierarchical Divergence-Free Bases and Their Application to Particulate Flows
Authors: Sarin V. , Sameh A. H.
Published: January 2003

The paper presents an algebraic scheme to construct hierarchical divergence-free basis for velocity in incompressible fluids. A reduced system of equations is solved in the corresponding subspace by an appropriate iterative method. The basis is constructed from the matrix representing the incompressibility constraints by computing algebraic decompositions of local constraint matrices. A recursive strategy leads to a hierarchical basis with desirable properties such as fast matrix-vector products, a well-conditioned reduced system, and efficient parallelization of the computation. The scheme has been extended to particulate flow problems in which the Navier-Stokes equations for fluid are coupled with equations of motion for rigid particles suspended in the fluid. Experimental results of particulate flow simulations have been reported for the SGI Origin 2000.
Aerodynamic Interactions Between Parachute Canopies
Authors: Stein K. , Tezduyar T. , Kumar V. , Sathe S. , Benney R. , Thornburg E. , Kyle C. , Nonoshita T.
Published: January 2003

Aerodynamic interactions between parachute canopies can occur when two separate parachutes come close to each other or in a cluster of parachutes. For the case of two separate parachutes, our computational study focuses on the effect of the separation distance on the aerodynamic interactions, and also focuses on the fluid-structure interactions with given initial relative positions. For the aerodynamic interactions between the canopies of a cluster of parachutes, we focus on the effect of varying the number and arrangement of the canopies.
Evaluation of a New Photodiode Sensor for Measuring Global and Diffuse Irradiance, and Sunshine Duration
Authors: Wood John , Muneer Tariq , Kubie J.
Published: January 2003

A new integrated device (called the BF3) has been developed, which enables the simultaneous measurement of horizontal global and diffuse irradiance as well as sunshine presence at any time. The sensor needs no specific polar alignment or routine adjustment, and works at any latitude. To evaluate the performance of this new device, a BF3 sensor was installed on the roof of a six-story building in the Merchiston Campus of Napier University, Edinburgh from February 22–July 3, 2001. Horizontal global and diffuse irradiance data were collected from the BF3. To enable a cross check, two Kipp and Zonen CM11 sensors, one with a shade ring, have also been installed beside the BF3 sensor on the same roof. These were used to give a reference measure of the horizontal global and diffuse irradiance. To evaluate the BF3 sunshine duration performance, the direct beam normal irradiance was calculated from the CM11 global and diffuse readings, and compared with a threshold of 120W.m−2 to give sunshine presence according to the WMO definition. This was compared against the BF3 output, and also with data from two Campbell-Stokes sunshine recorders on the same site. The results show a stable performance on the part of the BF3 sensor for the measurement of horizontal global and diffuse irradiance. The global irradiance measured by the BF3 showed values 4.7% high, with a standard error of 16.5W.m−2 compared to the Kipp and Zonen sensors. Diffuse values were 1.4% high with a standard error of 13.4W.m−2. The BF3 sunshine duration was within 2% of that calculated from the WMO definition over the study period, with a typical daily error of less than 20 min. This is well within the WMO requirements for a sunshine recorder. In comparison, the Campbell-Stokes recorders gave readings up to 7% different from the WMO values, with a typical daily error of almost an hour.
Investigation on Convective Heat Transfer and Flow Features of Nanofluids
Authors: Xuan Yimin , Li Qiang
Published: January 2003

An experimental system was built to investigate convective heat transfer and flow features of the nanofluid in a tube. Both the convective heat transfer coefficient and friction factor of the sample nanofluids for the turbulent flow are measured, respectively. The effects of such factors as the volume fraction of suspended nanoparticles and the Reynolds number on the heat transfer and flow features are discussed in detail. A new type of convective heat transfer correlation is proposed to correlate experimental data of heat transfer for nanofluids.
Temperature Gradient in the Unfrozen Liquid Layer for Multiphase Energy Balance With Incoming Droplets
Authors: Naterer G. F.
Published: January 2003

Phase change heat transfer with impinging supercooled droplets on an ice surface is examined. Partial solidification of incoming droplets leads to an unfrozen water layer above the ice. The significance of temperature variations within the water layer is considered. The multiphase energy balance is shown to approach the measured rate of ice growth when the surface heat input is lowered sufficiently. This asymptotic behavior is essential for establishing the proper role of heat conduction in the solid and liquid (unfrozen water) layers. Predicted results are successfully validated by comparisons with experimental data involving ice buildup on heated circular conductors.
Investigation of a Two-Equation Turbulent Heat Transfer Model Applied to Ducts
Authors: Rokni and Masoud , Sunde´n Bengt
Published: January 2003

This investigation concerns numerical calculation of fully developed turbulent forced convective heat transfer and fluid flow in ducts over a wide range of Reynolds numbers. The low Reynolds number version of a non-linear eddy viscosity model is combined with a two-equation heat flux model with the eddy diffusivity concept. The model can theoretically be used for a range of Prandtl numbers or a range of different fluids. The computed results compare satisfactory with the available experiment. Based on existing DNS data and calculations in this work the ratio between the time-scales (temperature to velocity) is found to be approximately 0.7. In light of this assumption an algebraic scalar flux model with variable diffusivity is presented.
Residual Stress-Induced Center Wave Buckling of Rolled Strip Metal
Authors: Fischer F. D. , Rammerstorfer F. G. , Friedl N.
Published: January 2003

In this paper computational and analytical treatments of the center wave buckling phenomenon in thin strips under in-plane loads which typically appear during cold rolling of sheet metal, are presented. Buckling due to self-equilibrating residual stresses, caused by the rolling process, in conjunction with global tensile stresses (due to the traction force acting on the strip) is considered. The shape of the distribution of the residual stresses over the width of the strip influences the buckling mode. Furthermore, it is shown that an increasing global tension force leads not only to increased critical residual stress intensities but also to shorter buckling waves concentrated towards the center of the strip. Taking these facts into account, a proper combination of the information gained from measuring the global tensile force at which buckling appears, the wave length, and some characteristic shape parameters of the buckling pattern allows the estimation of the intensity and the type of the residual membrane force distribution in the strip. By introducing dimensionless quantities, diagrams are provided which can be used for the determination of critical loading combinations, wave lengths, and shape parameters.
Numerical investigation and electro-acoustic modeling of measurement methods for the in-duct acoustical source parameters
Authors: Jang Seung-Ho , Ih Jeong-Guon
Published: January 2003

It is known that the direct method yields different results from the indirect (or load) method in measuring the in-duct acoustic source parameters of fluid machines. The load method usually comes up with a negative source resistance, although a fairly accurate prediction of radiated noise can be obtained from any method. This study is focused on the effect of the time-varying nature of fluid machines on the output results of two typical measurement methods. For this purpose, a simplified fluid machine consisting of a reservoir, a valve, and an exhaust pipe is considered as representing a typical periodic, time-varying system and the measurement situations are simulated by using the method of characteristics. The equivalent circuits for such simulations are also analyzed by considering the system as having a linear time-varying source. It is found that the results from the load method are quite sensitive to the change of cylinder pressure or valve profile, in contrast to those from the direct method. In the load method, the source admittance turns out to be predominantly dependent on the valve admittance at the calculation frequency as well as the valve and load admittances at other frequencies. In the direct method, however, the source resistance is always positive and the source admittance depends mainly upon the zeroth order of valve admittance.
A narrow band pattern-matching model of vowel perception
Authors: Hillenbrand James M. , Houde Robert A.
Published: January 2003

The purpose of this paper is to propose and evaluate a new model of vowel perception which assumes that vowel identity is recognized by a template-matching process involving the comparison of narrow band input spectra with a set of smoothed spectral-shape templates that are learned through ordinary exposure to speech. In the present simulation of this process, the input spectra are computed over a sufficiently long window to resolve individual harmonics of voiced speech. Prior to template creation and pattern matching, the narrow band spectra are amplitude equalized by a spectrum-level normalization process, and the information-bearing spectral peaks are enhanced by a “flooring” procedure that zeroes out spectral values below a threshold function consisting of a center-weighted running average of spectral amplitudes. Templates for each vowel category are created simply by averaging the narrow band spectra of like vowels spoken by a panel of talkers. In the present implementation, separate templates are used for men, women, and children. The pattern matching is implemented with a simple city-block distance measure given by the sum of the channel-by-channel differences between the narrow band input spectrum (level-equalized and floored) and each vowel template. Spectral movement is taken into account by computing the distance measure at several points throughout the course of the vowel. The input spectrum is assigned to the vowel template that results in the smallest difference accumulated over the sequence of spectral slices. The model was evaluated using a large database consisting of 12 vowels in /hVd/ context spoken by 45 men, 48 women, and 46 children. The narrow band model classified vowels in this database with a degree of accuracy (91.4%) approaching that of human listeners.
Spectral integral representations of monostatic backscattering from three-dimensional distributions of sediment volume inhomogeneities
Authors: LePage Kevin D. , Schmidt Henrik
Published: January 2003

A theory is developed for generating short time, monostatic reverberation realizations caused by three-dimensionally distributed volume inhomogeneities in stratified media. A wave number integral approach to treating the propagation to and from the scatterers, combined with a two-dimensional spectral representation of the azimuthally averaged scatterer realizations and a novel numerical implementation, combine to yield an efficient, high fidelity reverberation simulator for predicting monostatic backscatter from horizontally stratified sediments.