bluuebunny/crossref_metadata_2025 huggingface dataset:
“Words tickle me, thoughts caress me”: Gombrowicz on the Point of Interpretation
Authors: Chrostowska S. D.
Published: March 2011

This article focuses on Witold Gombrowicz’s most challenging drama, The Marriage (1948).1 Based on the creation and manipulation of meaning it stages, I tease out the play’s implicit semiotics and relate this to the difficulty of interpreting the text as a whole. The Marriage, I argue, indicates an unorthodox direction for literary analysis, one overlooked in the exegetical search for deeper significances and the application of external theoretical models. An outlier in the crop of postmodern readings of Gombrowicz, my article develops considerably the most recent and still sparse work in this area.

The fragmented body of what scholars have dubbed “Gombrowiczian Man” is the principal metaphor of man’s participation in form, the fragmentation of self, and the multiplicity of meaning. In my reading, Gombrowicz’s use of the metaphor in TheMarriage– and specifically of the finger to which it grants such prominence – challenges the traditional method of interpretation interested in extracting from signs (words, gestures) a stable meaning. Utilizing the dramatic topos of the dream, the frame of drunkenness, and the figure of the extended finger (touching, pointing, cuing, designating, and so on), the play presents its author’s anti‐essentialist stand on meaning, language, and reality, placing the interpretation of form before that of content.
Transient DNA / RNA‐protein interactions
Authors: Blanco Francisco J. , Montoya Guillermo
Published: March 2011

The great pace of biomolecular structure determination has provided a plethora of protein structures, but not as many structures of nucleic acids or of their complexes with proteins. The recognition of DNA and RNA molecules by proteins may produce large and relatively stable assemblies (such as the ribosome) or transient complexes (such as DNA clamps sliding through the DNA). These transient interactions are most difficult to characterize, but even in ‘stable’ complexes captured in crystal structures, the dynamics of the whole or part of the assembly pose great technical difficulties in understanding their function. The development and refinement of powerful experimental and computational tools have made it possible to learn a great deal about the relevance of these fleeting events for numerous biological processes. We discuss here the most recent findings and the challenges that lie ahead in the quest for a better understanding of protein–nucleic acid interactions.
Glycomics‐based analysis of chicken red blood cells provides insight into the selectivity of the viral agglutination assay
Authors: Aich Udayanath , Beckley Nia , Shriver Zachary , Raman Rahul , Viswanathan Karthik , Hobbie Sven , Sasisekharan Ram
Published: March 2011

Agglutination of red blood cells (RBCs), including chicken RBCs (cRBCs), has been used extensively to estimate viral titer, to screen glycan‐receptor binding preference, and to assess the protective response of vaccines. Although this assay enjoys widespread use, some virus strains do not agglutinate RBCs. To address these underlying issues and to increase the usefulness of cRBCs as tools for studying viruses, such as influenza, we analyzed the cell surface N‐glycans of cRBCs. On the basis of the results obtained from complementary analytical strategies, including MS, 1D and 2D‐NMR spectroscopy, exoglycosidase digestions, and HPLC profiling, we report the major glycan structures present on cRBCs. By comparing the glycan structures of cBRCs with those of representative human upper respiratory cells, we offer a possible explanation for the fact that certain influenza strains do not agglutinate cRBCs, using specific human‐adapted influenza hemagglutinins as examples. Finally, recent understanding of the role of various glycan structures in high affinity binding to influenza hemagglutinins provides context to our findings. These results illustrate that the field of glycomics can provide important information with respect to the experimental systems used to characterize, detect and study viruses.
Modulatory effect of a complex fraction derived from colostrum on fibroblast contractibility and consequences on repair tissue
Authors: Doillon Charles J , Lehance Frédéric , Bordeleau Louis‐Jean , Laplante‐Campbell Marie‐Pier , Drouin Réjean
Published: March 2011

A complex compound (immune (’IM’) fraction) from colostrum‐derived whey was investigated for its potential wound healing properties. One of its most intriguing in vitro abilities was to significantly inhibit the contraction of collagen gel while fibroblast density remained as in control gels. This antagonist effect was dose dependent and fibroblasts in these gels did not exhibit any stress fibres. Subsequently, in vivo studies have been conducted in two wound models in guinea pigs. Daily application on full‐thickness wounds of a liquid formulation of the IM fraction (first model) significantly delayed wound closure by contraction compared to what normally occurred in control wounds. In another wound model, a gel formulation of the IM fraction was applied on scar tissues, which resulted in a minimised residual scar on 5/8 wounds compared to corresponding wound areas seen prior to treatment. Conversely, most control wounds exhibited scar tissue from which 3/8 resembled hypertrophic scar tissue. Wound tissue treated with IM fraction covered a significantly larger area than in the control wounds, whereas the collagen deposition was unchanged as in the presence of α‐smooth muscle actin. Thus, IM fraction may act by modulating the contraction rate and wound remodelling.
Microbial diversity in Calamita ferromagnetic sand
Authors: Perfumo Amedea , Cockell Charles , Elsaesser Andreas , Marchant Roger , Kminek Gerhard
Published: March 2011

Calamita is a black ferromagnetic sand from a marine iron ore on Elba Island (Italy). Its total iron content is approximately 80% and a major fraction (63% w/w) has magnetic properties. Desiccation, ultraviolet irradiation and the high temperature induced by the thermal conductivity of iron make Calamita sand an extreme biotope. We report, for the first time, the geomicrobiological characterization of Calamita sand, which showed a low bacterial biodiversity as determined by denaturing gradient gel electrophoresis and 16S rRNA gene clone library analysis. We retrieved sequences closely affiliated with uncultured bacteria inhabiting the harshest deserts on Earth. Radiation‐ and desiccation‐tolerant bacteria from the phyla Proteobacteria, Actinobacteria and Deinococcus‐Thermus dominated the community. Heavy metal‐resistant organisms, for example Variovorax sp. were also abundant. Sequences of organisms with an inferred metabolism based on lithotrophic iron oxidation were detected. The sands also contained thermophilic bacilli, which were cultivated at 60°C. These data provided important insights also into the biogeographical distribution of these organisms in the Mediterranean region. In summary, this study on Calamita helps to expand our knowledge of the biodiversity in extreme, iron‐rich, environments.
Cost Allocation in Manufacturing–Remanufacturing Operations
Authors: Toktay L. Beril , Wei Donna
Published: March 2011

For firms remanufacturing their products, the total life‐cycle costs and revenues from new and remanufactured products determine their profitability. In many firms, manufacturing/sales and remanufacturing/remarketing operations are carried out in different divisions. Each division is responsible for only part of the product's life cycle. Practices regarding transfer pricing across divisions vary significantly among companies, affecting the life‐cycle profit performance of the product. In this research, we identify characteristics of transfer prices that achieve the firm‐wide optimal solution. To this end, we consider a manufacturer who also undertakes remanufacturing operations and we focus on price (quantity) decisions. We determine that a cost allocation mechanism that allocates a portion of the initial production cost to each of the two stages of the product life cycle should be used. We also conclude that cost allocation should be implemented as a fixed cost allocation, where charges to the remanufacturing division should be determined independently of the actual quantity of units remanufactured.
Container Scheduling: Complexity and Algorithms
Authors: Choi Byung‐Cheon , Lee Kangbok , Leung Joseph Y.‐T. , Pinedo Michael L. , Briskorn Dirk
Published: March 2011

We consider the transport of containers through a fleet of ships. Each ship has a capacity constraint limiting the total number of containers it can carry and each ship visits a given set of ports following a predetermined route. Each container has a release date at its origination port, and a due date at its destination port. A container has a size 1 or size 2; size 1 represents a 1 TEU (20‐foot equivalent unit) and size 2 represents 2 TEUs. The delivery time of a container is defined as the time when the ship that carries the container arrives at its destination port. We consider the problem of minimizing the maximum tardiness over all containers. We consider three scenarios with regard to the routes of the ships, namely, the ships having (i) identical, (ii) nested, and (iii) arbitrary routes. For each scenario, we consider different settings for origination ports, release dates, sizes of containers, and number of ports; we determine the computational complexity of various cases. We also provide a simple heuristic for some cases, with its worst case analysis. Finally, we discuss the relationship of our problems with other scheduling problems that are known to be open.
Supportive periodontal therapy for high‐ and low‐risk patients
Authors: Carollo‐Bittel Barbara , Persson Rigmor E. , Persson Gösta Rutger , Lang Niklaus P.
Published: March 2011

Aim:  The validity of the risk assessment in predicting tooth loss due to periodontitis or disease progression was explored.

Methods:  Systemic factors, smoking status, bleeding on probing (BoP) percentage, number of residual pockets (probing pocket depth ≥6 mm), tooth loss, and alveolar bone loss in relation to age were the variables of the risk assessment. Based on an improving or deteriorating risk assessment in 2005 compared with 1999, 89 patients were divided into either a high‐ or low‐risk group. Findings were compared with the 2008 outcome.

Results:  Using BoP ≤ 20% as the cut‐off, the relationship between BoP and interleukin‐1 genotype status was neither significant in 2005 nor in 2008. Neither the high‐ nor low‐risk group was predictive for tooth loss. Patients displayed similar proportions of probing pocket depths ≥6 mm in 2005 and in 2008. Linear stepwise regression analysis demonstrated that only the number of supportive periodontal therapy visits explained the number of teeth lost due to periodontitis (P < 0.01).

Conclusions:  The categorization of patients into high‐ and low‐risk groups, according to the periodontal risk assessment model applied within a supportive periodontal therapy period of 3 years, had limitations in predicting future tooth loss.
Histological evaluation of the peri‐implant tissues of three human‐retrieved Straumann implants
Authors: Dellavia Claudia , Carmagnola Daniela , Storelli Stefano , Rossi Alessandro , Canciani Elena , Romeo Eugenio
Published: March 2011

The most frequently‐used histological parameters to define dental implant osseointegration include bone‐to‐implant contact and quantitative and qualitative assessments of the surrounding tissue (rate of mineralized/non‐mineralized tissue and proportion of lamellar and woven bone compared to soft tissue or bone marrow). The aim of this paper was to present the histological features of the bone tissue surrounding three well‐functioning Straumann SLA and SLActive implants placed in two patients after 12 and 60 months of loading. The percentage of osseointegration ranged from 66.4% and 71.9% for SLA surfaces, to 88.3% for the SLActive implant. Such results confirm that osseointegration occurs with high rates of bone‐to‐implant contact in humans, and that implants can be similarly clinically successful, although they show different bone‐to‐implant contact values.
Actual proliferating index in oral squamous cell carcinoma and leukoplakia
Authors: Chandak Abhay R. , Gadbail Amol Ramchandra , Chaudhary Minal S. , Chandak Shweta A. , Wadhwani Ritesh
Published: March 2011

Aim:  To examine the possible association between epithelial proliferation and disease progression in the oral mucosa using the actual proliferation index.

Methods:  The actual proliferation index was measured by the Ki‐67 labeling index and argyrophilic nucleolar organizer region count per nucleus. Immunohistochemistry was carried out for Ki‐67 by using the molecular immunology borstel‐1 clone in 20 leukoplakias, 20 oral squamous cell carcinomas, and 10 normal oral mucosae.

Results:  The argyrophilic nucleolar organizer region count per nucleus, Ki‐67 labeling index, and actual proliferation index were significantly higher in oral squamous cell carcinoma, followed by leukoplakia and normal oral mucosa. Leukoplakia with dysplasia showed a significantly higher Ki‐67 labeling index and actual proliferation index, compared to leukoplakia without dysphasia. There was a significant correlation of Bryne’s histological malignancy grading with the argyrophilic nucleolar organizer region count and the Ki‐67 labeling index. There was a significant positive correlation between the argyrophilic nucleolar organizer region count and the Ki‐67 labeling index among all groups.

Conclusions:  Leukoplakia or suspected epithelial dysplasia should be stained for argyrophilic nucleolar organizer regions and Ki‐67. The actual proliferation index is not only useful as a prognostic factor, but could also be a promising treatment determining modality for patients with premalignant and malignant lesions.
Descriptive epidemiology of joint injuries in Thoroughbred racehorses in training
Authors: REED S. R. , JACKSON B. F. , MC ILWRAITH C. W. , WRIGHT I. M. , PILSWORTH R. , KNAPP S. , WOOD J. L. N. , PRICE J. S. , VERHEYEN K. L. P.
Published: March 2011

Reasons for performing study: No large scale epidemiological studies have previously quantified the occurrence of carpal, metacarpo‐ and metatarsophalangeal (MCP/MTP) joint injuries in Thoroughbred racehorses.

Objectives: To develop an objective classification system for carpal and MCP/MTP joint injuries and estimate the incidence of these injuries in young Thoroughbreds in flat race training.

Methods: In a prospective cohort study, data on daily exercise and veterinary‐diagnosed carpal and MCP/MTP joint injuries were collected from Thoroughbreds monitored since starting training as yearlings, for up to 2 years. Cases were classified in one of 4 categories: 1) localised to a carpal or MCP/MTP joint based on clinical examination and/or diagnostic analgesia; no diagnostic imaging performed; 2) localised to a carpal or MCP/MTP joint based on clinical examination and/or diagnostic analgesia; radiographs taken but no abnormalities detected; 3) evidence of abnormality of subchondral bone and/or articular margin(s) on diagnostic imaging and 4) evidence of discontinuity of the articular surface on diagnostic imaging. Incidence rates and rate ratios were estimated using Poisson regression, adjusting for trainer‐level clustering.

Results: A total of 647 horses from 13 trainers throughout England contributed 7785 months at risk of joint injury. One‐hundred‐and‐eighty‐four cases of carpal (n = 82) or MCP/MTP (n = 102) joint injury were reported in 165 horses and classified in Category 1 (n = 21), Category 2 (n = 21), Category 3 (n = 72) or Category 4 (n = 70). The overall joint injury rate was 1.8 per 100 horse months (95% CI = 1.2, 2.8); rates did not differ significantly between 2‐ and 3‐year‐olds but females sustained Category 1 injuries at triple the rate of males (P = 0.03). Joint injury rates differed significantly between trainers (P<0.001) and there was trainer variation in anatomical site and severity of injury.

Conclusions and potential relevance: Carpal and MCP/MTP joint injuries are an important cause of morbidity in Thoroughbred racehorses. Identification of modifiable risk factors for these injuries may reduce their incidence.
Estimates of Mechanical Properties and Residual Stress of Narrow Gap Weld for Leak-Before-Break Application to Nuclear Piping
Authors: Yang Jun-Seok , Park Chi-Yong , Huh Nam-Su
Published: March 2011

The present paper addresses the mechanical characteristics of the stainless steel narrow gap weld (NGW) for the leak-before-break (LBB) application to the main loop piping of a nuclear power plant. Recently, in Korea, the connection with the reactor coolant main loop piping and the steam generator has been welded with ER308L NGW after the replacement of a steam generator of a Korean nuclear power plant. The NGW technique has many merits, for instance, the reduction of construction time and the reduction of shrinkage and deformation after welding due to its small groove angle and welding bead width compared with the conventional welds. In this paper, the tensile and fracture toughness test results of the three ER308L test coupons from NGW were presented and compared with those from conventional welds at the operating condition of the nuclear power plant. In addition, the distribution of the welding residual stress as well as the deformation behavior of the ER308L weld due to NGW was predicted through the nonlinear two-dimensional finite element analysis in which the detailed actual welding process of NGW was simulated. The results presented in this paper can be used to evaluate LBB application to nuclear piping with NGW and to provide the important information to perform the flaw evaluation as well as improve the weld procedure of NGW.
A New Method for Prediction of the Transient Force Generated by a Liquid Slug Impact on an Elbow of an Initially Voided Line
Authors: Kayhan Bülent A. , Bozkus Zafer
Published: March 2011

The aim of the present study is to predict the impact force applied by an individual transient liquid slug on an elbow at the end of a horizontal and initially empty pipeline. The liquid slug is driven by pressurized air in a tank located upstream of the pipeline. The time dependent pressure distribution along the elbow and a vertical extension segment after the elbow are solved with a 1D numerical approach along a curved line mesh. An assumed and calibrated axial turbulent velocity profile function with 3D skewed shape for the slug is also used in the solution. The impact pressures and the transient forces at the elbow are computed and also compared with those obtained experimentally and numerically from previous studies. Comparisons indicate that the new method developed in the present study predict the peak pressures and/or forces with higher accuracy than the previous method proposed by other researchers.
Computational Investigation of Liquid Spray Dispersion Modification by Conical Nozzle Attachments
Authors: Pougatch Konstantin , Salcudean Martha
Published: March 2011

Liquid spray characteristics such as the droplet size and dispersion angle are determined by the atomizer design and the physical properties of the liquid and surrounding gas. One of the options to change these characteristics is to attach an especially designed piece to the nozzle exit. While these attachments can have a variety of shapes, we chose a conical geometry to exploit its axial symmetry and, at the same time, obtain the results that can be generalized to other configurations. Thus, we investigate an addition of the conically shaped attachment to the premixed gas-assisted high-pressure atomizer with the previously developed numerical model. This is a two-fluid Eulerian-Eulerian model with a catastrophic phase inversion that was developed for compressible gas-liquid mixtures and can be applied to both the flow through the nozzle-atomizer and to the dispersion of the spray. The model also accounts for the break-up and coalescence effects of bubbles and droplets. Our investigation reveals that the conical nozzle attachments act as spray limiters by reducing the natural expansion angle of a spray. Also, the droplets produced by the nozzle with a conical addition tend to be larger than the ones obtained with a stand alone nozzle. The largest droplets are generated by the smallest attachment angle considered, 10 deg. With the increase of the angle, the spraying characteristics become closer to those of the stand alone nozzle. It can be concluded that the conical shape of the attachments with a relatively small angle may be used when higher jet penetration and lower dispersion are desirable. The attachments with larger angles do not offer a substantial difference from the stand alone nozzle. Another important conclusion is that the dispersion of the jet is determined by the radial momentum transferred to the liquid before or immediately after the phase inversion takes place. Thus, for improved dispersion, the area where the atomization is taking place should not be restricted.
Medial Axis Transform Method for Shape Design of Hub and Shroud Contours of Impellers
Authors: Wang Pengfei , Ruan Xiaodong , Zou Jun , Fu Xin
Published: March 2011

A novel method of designing hub and shroud contours is presented. The method, based on the medial axis transform theory in differential geometry, gives a uniform description of hub and shroud contours and the formula of cross section area. Through solving the formula of cross section area with an additional constraint, the hub and shroud contours can be determined numerically. The constraint is exposed through a curvature equation, which allows the medial axis or hub (shroud) contour to be a certain form. Using this method, various optimization criteria relating to the cross section area can be conveniently introduced into the design.
An Advanced Semi-Implicit Method for Two-Phase Flow Calculation
Authors: Yi Sung-Jae , Chung Moon-Sun
Published: March 2011

Introducing the interfacial pressure jump terms based on the surface tension into the momentum equations of two-phase two-fluid model, the system of governing equations is turned mathematically into the hyperbolic system. The eigenvalues of the equation system become always real representing the void wave and the pressure wave propagation speeds as shown in the present authors’ reference: Numerical Heat Transfer —Part B, vol. 40, pp. 83–97. To solve the interfacial pressure jump terms with void fraction gradients implicitly, the conventional semi-implicit method should be modified as an intermediate iteration method for void fraction at fractional time step. Owing to this modified numerical scheme with surface tension effect, the advanced semi-implicit method (ASIM) then becomes stable without conventional additive terms. As a consequence, including the interfacial pressure jump terms with the advanced semi-implicit method, the numerical solutions of typical two-phase problems can be more stable and sound than those calculated exclusively by using any other terms like virtual mass, or artificial viscosity.
The Wave Propagation Equation of Heat Conduction in Crystal
Authors: Huang Weimin
Published: March 2011

This paper advances a new statistic way for localized particles of crystal by space configuration of momentum restricting on order of position and proposes the concept of macroscopic “thermal oscillation” in gradient field of temperature. The oscillation equation of “thermal oscillaton” and the wave propagation equation in temperature field of crystal are deduced from the Hamilton function with the oscillation kinetic energy and thermal potential energy. The finite propagation velocity of heat is analytically discussed.
The Le´veˆque Analogy: Does it Work for Solid Ceramic Sponges Too?
Authors: Dietrich Benjamin , Kind Matthias , Martin Holger
Published: March 2011

In this paper experimental results of pressure drop and heat transfer for different ceramic sponges (variables: material, ppi number and porosity) are presented. The pressure drop data is correlated using an Ergun-type equation, which yields to an accuracy of 20%. The heat transfer coefficients were determined by a transient method and correlated in dimensionless form (Nusselt number) by a power law of Reynolds and Prandtl number. Furthermore the applicability of the well known Generalized Le´veˆque Equation (GLE) on solid ceramic sponges is checked. The GLE provides a correlation between pressure drop and heat transfer. The investigation shows that the tendency observed for the data corresponds with that of the theoretical model.
Research on Mechanisms and Applications of Catalytic Combustion of Natural Gas
Authors: Zhang Shihong , Li Ning
Published: March 2011

This article discussed the thermal efficiency, stability, and pollutant emissions characteristics of the combustion of lean natural gas-air mixtures in Pd metal based honeycomb monoliths by means of experiments on a practical burner V. The chemistry at work in the monoliths was then investigated using fundamental experimental reactors, namely the stagnation point flow reactor or SPFR. It was found that catalytic combustion inhibited the extent of gas-phase oxidation and increased the surface temperature of homogeneous ignition. According to the applications of catalytic combustion in the condenser boiler, the data of catalytic combustion condenser boiler V were measured at atmospheric temperature and pressure. The study also showed that more than 100% of its thermal efficiency was found possible while preserving near zero pollutant emissions. For all the catalysts tested, flow rates, and mixture compositions of natural gas and air used here, no CO, unburned fuel nor NOx were detected as long as surface combustion was taking place.
Experimental Investigation on the Anti-Fouling and Heat Transfer Performance of the Coated Surfaces
Authors: Xu Zhi-ming , Chen Ling , Gao Ying-lun , Zhang Zhong-bin
Published: March 2011

The main purpose of this investigation was to study the anti-fouling and heat transfer performance of coated surfaces (ECTFE, FEP, PTFE and PFA). In the present investigation, the heat transfer performance of the coated surfaces was compared to base metal surfaces, and crystallization fouling experiments of coated surfaces were carried out under various operating parameters such as solution temperature, solution concentration and hydrodynamics of the system. The characteristic parameters of the coated surface, such as surface roughness, surface contour, contact angle and surface energy were measured and calculated, which were used to analyze the anti-fouling performances of the coated surface. The results show that compared with the base metal surface, Nusselt number of coated surfaces decrease. But coated surfaces have advantage on anti-fouling ability.
Heat Transfer Augmentation by Two-Phase Impinging Jet
Authors: Choo Kyo Sung , Kim Sung Jin
Published: March 2011

Heat transfer and fluid flow characteristics of air-water impinging jets were experimentally investigated under a fixed pumping power condition. The effects of dimensionless pumping power and the volumetric fraction on the Nusselt number were considered. The results showed that the Nusselt number had an optimum point at around 0.2 ∼ 0.3 of the volumetric fractions.
Development of a Profiled Multilayer Tube for High Temperature Solar Receivers and Heat Exchangers
Authors: Jedamski Jens , Amsbeck Lars , Buck Reiner , Couturier Raphael , Heller Peter , Tochon Patrice , Uhlig Ralf , Vasquez Felipe
Published: March 2011

In solar tower plants absorber tubes are the main components of various solar receivers, e.g. steam receivers, salt receivers, pressurized air receivers. The solar radiation on the absorber tube causes an inhomogeneous temperature distribution because most of the solar radiation along the tube circumference is one-sided. The resulting internal stresses of the tube and the maximum fluid temperature decrease the lifetime significantly. Within the projects SOLHYCO and FUTUR a profiled multilayer tube (PML) is currently under development in order to reduce this problem. It consists of three metallic layers: a high temperature nickel-based alloy at the outer side, a copper layer as intermediate layer and another high temperature nickel-based alloy at the inner side of the tube. The outer layer provides the structural strength while the copper is used to conduct the heat from the irradiated side to the opposite side. The inner layer protects the copper from corrosion and oxidation at high temperatures. In addition, a wire coil is inserted (profiled) to increase the heat transfer on the inside. The PML is manufactured in a hydro-forming process by deforming the tube composite with water under high pressure. To demonstrate the performance and to determine the heat transfer, the pressure loss and the temperature distribution, a test loop was built to simulate the different loads under laboratory conditions. The thermo hydraulic measurements and finite element calculations show that the temperature gradient and the maximum temperature can be reduced significantly. Based on these studies the advantages of the PML in comparison to common tubes will be presented as well as several possibilities for future improvements.
A Distributed Model for Air-to-Refrigerant Fin-and-Tube Evaporators With Special Emphasis on Two-Phase Zone
Authors: Li Haiyan , Tong Lige , Sun Xinxing , Wang Li , Yin Shaowu
Published: March 2011

A general and simple model for simulating the steady behavior of air-to-refrigerant fin-and-tube evaporators, which accounts for detailed flow state inside the tubes, is introduced. To account for the heat transfer between air and the working fluid, the evaporator is divided into a number of control volumes. Space dependent partial differential equations group is obtained from the mass, energy and momentum balances for each one. The corresponding discretized governing equations are solved afterwards. Empirical correlations are also required to estimate the void fraction, the internal and external heat transfer coefficients, as well as the pressure drops. According to the phase of refrigerating fluid, the evaporator can be divided into two distinct zones on the refrigerant-side: the vapor zone and the two-phase zone, while special emphasis is performed on the treatment of the two-phase zone. The distribution of flow pattern has been evaluated with the aim of improving the calculation accuracy. The model prediction is validated against experimental data for an evaporator using R22 as the working fluid, which shows a reasonable level of agreement: the cooling capacity is predicted within the error band of 3%. The developed model will have wide applications in operational optimization, performance assessment and pipeline design.
Gaseous Conductivity Study on Silica Aerogel and Its Composite Insulation Materials
Authors: Wei Gaosheng , Liu Yusong , Du Xiaoze , Zhang Xinxin
Published: March 2011

This paper presented theoretical and experimental study on gaseous conductivity of silica aerogel and it’s composite insulation materials. The samples of silica aerogel, xonotlite-type calcium silicate, xonotlite-aerogel composite and ceramic fibre-aerogel composite insulation materials were prepared firstly. The gaseous conductivities of the prepared samples were measured from 0.045 Pa to atmospheric pressure with the transient hot-strip (THS) method. The gaseous conductivity expressions based on the kinetic theory were then compared with the experimental results. It is shown that both the gaseous conductivity of xonotlite-type calcium silicate and silica aerogel decreases significantly with the drop of pressure. The gaseous conductivity of xonotlite-type calcium silicate reaches to zero at about 100 Pa and the gaseous conductivity of silica aerogel reaches to zero at about 104 Pa. The theoretical gaseous conductivity expressions match well with the experimental results of xonotlite-type calcium silicate and silica aerogel respectively, but do not match with the experimental results for the composite insulation materials. It indicates that the aerogel does not fill the two kinds of composite insulation materials entirely, and some micro level pores still exist in them.
CFD Modelling of the Gasification of Coal Particles in Fluidised Beds
Authors: Armstrong Lindsay-Marie , Gu Sai , Luo Kai H.
Published: March 2011

In this paper, two-fluid modelling is used to model a bubbling fluidised bed gasifier (BFBG) introducing two solid phases namely, sand and coal. The devolatilisation model and heterogeneous reactions are implemented and the gases produced are compared to experimental results, which shows a good agreement. The production of fuel gases is strongly influenced by the distribution of the solid phases, which requires accurate modelling of the multiphases involved.
Non-Homogeneous Radiation Characteristic in Carbon-Ash Composite Particle Cloud of Coal Char
Authors: Itaya Yoshinori , Kosaka Fumiya , Kobayashi Nobusuke , Tanabe Yasuhiro
Published: March 2011

This study is to evaluate the radiation properties of coal char and ash particles. Char in coal-firing and gasification processes exists in a form of heterogeneous composite particles consisting of nano-order fine particle made mainly of soot and micron-order particle of carbon and ash components. The radiation properties were discussed by a term of apparent extinction efficiency determined from spectra of transmissivity of a particle-liquid paraffin wax dispersion film as an independent parameter of particle dispersion density. Extinction efficiency measured directly from the original char gave unacceptably great magnitude. However, if the original char was classified into a narrow particle size distribution by a pretreatment with a wet method, extinction efficiency of each particle showed a reasonable magnitude and deduced successfully extinction coefficient of the original char dispersion with a certain content from combining that of each particle with accounting for the fraction. The effect of carbon content in char particle excluding soot on extinction efficiency could be also correlated empirically by a simple function using the properties of carbon-free ash burnt out and ash-free carbon treated by hydrofluoric acid. Additionally the value of apparent extinction efficiency measured from transmissivity of ash dispersion was compared with the properties estimated by applying the known refractive index into Mie’s theory, and noted to be close to rather absorption efficiency than extinction efficiecny analyzed theoretically although scattering albedo was as large as over 0.9. This fact may result in that a strong forward scattering pointed out in the past work was acceptable and the ash particle cloud can be assumed as an absorbing-emitting medium having the properties obtained here ignoring the effect of scattering at least.
Mechanism of Dropwise Condensation on Ion Implanted Metallic Surfaces
Authors: Rausch Michael H. , Leipertz Alfred , Fro¨ba Andreas P.
Published: March 2011

In this work a model for the mechanism of dropwise condensation on ion implanted metallic surfaces is proposed. Considering experimental results for respective surfaces, the model is based on droplet nucleation and growth on preferably wetted, elevated precipitates, resulting in short-term steam entrapment after droplet coalescence. According to wetting theory this transition state yields increased macroscopic contact angles enabling dropwise condensation. Open condensation phenomena like enlarging dropwise condensation areas in spite of increasing condensation rate become comprehensible by our approach. Furthermore, the model points out that contact angles and surface free energies measured under ambient air conditions are not usable for predicting the condensation form of steam on the modified surfaces. Although the suggested microscopic mechanism cannot be directly proved by experiment, its capability of explaining experimental observations colliding with previous theoretical approaches supports its validity. The results also reveal that dropwise condensation of steam can originate from microscopically different mechanisms.
Unsteady Forced Convection Heat Transfer for Power Law Fluids in a Pipe
Authors: Li Botong , Zheng Liancun , Zhang Xinxin
Published: March 2011

This paper studied the problem of forced convection heat transfer for power law fluids in a pipe which was affected by the varying inlet temperature. The fluid flow was hydrodynamically fully-developed and laminar while the effects of viscous dissipation and the power law kinematic viscosity on heat transfer were considered. A control volume technique based on the finite difference model coupled with the LU decomposition method was adopted and the least squares polynomial was introduced to approximate the non-linear items. The results show that the heat transfer behaviors are strongly depending on the value of the power law index. It is found that the thermal wave of the inlet temperature has less penetration with the increasing axial coordinate, and the effect of heat transfer is dominant away from the wall. The temperature profile is flatter as the power law index increases, which is implies that the shear-thickening non-Newtonian flows are affected easier by the inlet temperature than the shear-thinning fluids.
A Molecular Dynamics Study on the Effects of Nanostructural Clearances on Thermal Resistance at a Liquid-Solid Interface
Authors: Shibahara Masahiko , Takeuchi Kiyoshi
Published: March 2011

The effects of the surface structures and the surface structural clearances at the nanometer scale on the thermal resistance at a liquid water-solid interface, as well as the self-diffusion behaviors of liquid molecules, were investigated directly by the non-equilibrium classical molecular dynamics simulations. When the potential parameter between liquid molecules and nanostructure atoms is equal to that between liquid molecules and solid wall atoms, the geometric surface area change depending on the nanostructures as well as their clearances and the self-diffusion coefficient change of the liquid molecules at the interface depending on the nanostructural clearances cause the thermal resistance change depending on the nanostructures at the liquid-solid interface. When the potential parameter between liquid molecules and nanostructure atoms is different from that between liquid molecules and solid wall atoms, the interfacial thermal resistance is dependent on the potential parameter between liquid molecules and nanostructure atoms itself rather than the geometric surface area in a molecular scale.
Horizontal Tube Side Convective Condensation Under an Applied DC Voltage
Authors: Sadek H. , Cotton J. , Ching C. Y.
Published: March 2011

An experimental study was performed to investigate the tube side convective condensation under an applied DC high voltage. Experiments were performed in a horizontal, single-pass, counter-current heat exchanger with a rod electrode placed along the centre of the tube. A 8 kV DC voltage was applied across the annular gap between the central electrode and the pipe wall. The experiments were performed for mass flux in the range 45 to 156 kg/m2s and average quality of 45 percent. The application of the high voltage electric field results in electric body forces at the liquid-vapor interface which extracts the liquid from the bottom stratum towards the vapour core. The application of the 8 KV DC voltage increased heat transfer and pressure drop by factor 3 and 4.5 respectively at the lowest mass flux of 45 kg/m2s. The results show that liquid extraction from the bottom liquid stratum changed the mode of heat transfer at the bottom of the tube from convective condensation into film condensation.
Transient Two-Phase Flow Patterns by Application of a High Voltage Pulse Width Modulated Signal and the Effect on Condensation Heat Transfer
Authors: Ng K. , Ching C. Y. , Cotton J. S.
Published: March 2011

The objectives of this study are (i) to determine the transient phase redistributions of a two-phase flow in a smooth horizontal annular channel by applying high voltage pulses to induce electric fields and (ii) to quantify the resultant changes in the condensation heat transfer. The experiments were performed using refrigerant R-134a flowing in a tube that was cooled on the outside by a counter-current flow of water. The electric fields are established by applying high voltage to a concentric rod electrode inside a grounded tube. The effect of the electrohydrodynamic (EHD) forces on the changes to the initial stratified/stratified wavy flow pattern was visualized using a high speed camera. The EHD effect results in the redistribution of the liquid-vapour phase within the channel and unique flow structures, such as twisted liquid cones and entrained droplets, are observed. These structures only appear during the initial application of EHD and are absent in the steady state flow pattern. Experiments were performed using a 8kV pulse width modulated (PWM) signal with duty cycles ranging from 0–100% to evaluate the heat transfer and pressure drop characteristics of the transient EHD flow patterns. The resultant heat transfer increased with the duty cycle to approximately 2.7-fold at a low mass flux (45–55kg/m2s) and 1.2-fold at a high mass flux (110kg/m2s). The enhancement was higher as the pulse width was increased.
Convection Heat Transfer Analysis for Darcy Flow in Porous Media: A New Two-Dimensional Solution
Authors: Dukhan Nihad , Ratowski Jeff
Published: March 2011

The two-equation energy equations are solved analytically for the temperature of the solid phase inside a two-dimensional rectangular porous media subjected to constant heat flux on one side. The fluid conduction is neglected in the governing equations and the Darcy flow model is used. Several simplifying assumptions are made regarding the boundary layers. The solid temperature decays in what looks like an exponential fashion as the distance from the heated base increases. Applications of such solution may be found in porous media with high solid phase conductivity cooled by low-conductivity fluids, e.g., open-cell metallic and graphite foams cooled by air.
On a Numerical Model of Laser Cladding Process
Authors: Esmaeelpanah J. , Passandideh-Fard M.
Published: March 2011

In this paper, a 2D transient numerical model for the simulation of a laser cladding process with a coaxial powder injection is developed. The model is based on the enthalpy method integrated into a liquid/solid volume fraction approach which can simulate the phase change phenomenon. The physical governing equations solved in the model are: the Navier-Stokes equations for fluid flow, and the energy equation including phase change for heat transfer within the powder, clad and substrate. A Volume-of-Fluid (VOF) algorithm is used to obtain the solution of the free surface. The model is capable of predicting the clad height, dilution depth and final shape of the clad. The simulations were performed for titanium particles on a titanium substrate. The simulations show that the clad height is decreased with the laser power, the scan speed, and the substrate and particle temperature.
Analysis of Liquid-Cooled Heat Sink Used for Power Electronics Cooling
Authors: Hu Hemin , Zhang Jiahui , Du Xiaoze , Yang Lijun
Published: March 2011

In the paper, liquid-cooled heat sink (cold plate) used for power electronic cooling is numerically studied. Thermal and hydraulic performances are analyzed, with the emphasis on geometrical construction of cooling channels. Two heat transfer enhancing channel shapes are investigated, such as alternating elliptical channel (AE-C) and alternating rectangular channel (AR-C). Their performances are compared with that of three traditional straight channel shapes, as straight circular channel (SC-C), straight elliptical channel (SE-C), and straight rectangular channel (SR-C). Coolant pressure drop and heat sink surface temperature are calculated using computational fluid dynamics (CFD) approach, with water as coolant. It is found that, when channel hydraulic diameter and coolant volumetric flow rate are fixed, the heat sinks with alternating rectangular channel have the highest thermal performance with a little penalty on pressure drop. Geometry optimization is studied for AR-C. The effects of channel density are investigated, and it is found that higher channel density can improve both thermal and hydraulic performances. A case study is conducted for a heat sink with uniform and discrete heat sources. It is concluded that alternating channels provide excellent thermal performance and should be taken into application for cold plate.
Heat Transfer and Flow Instabilities in Ethanol Sessile Drops Under Evaporation
Authors: Sobac Benjamin , Brutin David
Published: March 2011

Thanks to a recent increase in space resolution and temperature accuracy of infrared camera device, it’s now possible to perform thermal visualizations of sessile drops under evaporation. Using infrared techniques, we can access local thermal motions inside millimetric drops without perturbing the internal mechanisms. In the full paper, we will provide a literature review of experimental, numerical simulation and theoretical work recently perform on sessile drop evaporation. We will also detail the experimental setup which has been elaborated to realize these thermal observations. Using infrared and visible video recording, we can follow respectively the evolution of the motion inside the drop and the drop shape during evaporation. Using a heat fluxmeter placed below the drop, we can analyze the heat transfer between the substrate and the drop. We will completely describe the evaporation process based on a reference experiment and evidence the existence of several phases during this process. Then, we will dwell on the heat flux transferred to the drop during each step of the evaporation process to obtain very important information about the coupling between flow motion and heat transfer coefficient. Finally, we will present the influence of substrate temperature and drop size on the evaporation process which leads us to build a scaling law and better understand drop evaporation process.
Explosive Crystallization in Thin Amorphous Layers on Heat Conducting Substrates
Authors: Buchner Christoph , Schneider Wilhelm
Published: March 2011

The self-sustaining process of transformation from an amorphous state to the crystalline state is considered. The crystallizing layer, which is mounted on a substrate, is assumed to be very thin. Thus the energy balance for the layer reduces to the equation of one-dimensional heat diffusion with a source term due to the local liberation of latent heat and a heat loss term due to thermal contact with the substrate. The crystallization rate is determined by a rate equation based on the crystallization theory due to A.N. Kolmogorov and M. Avrami. Heat conduction in the substrate is described by introducing a continuous distribution of moving heat sources at the interface. The problem is solved numerically with a collocation method. The propagation speed of the crystallization wave is obtained as an eigenvalue. Dual solutions are found below a critical value of a non-dimensional heat-loss parameter, whereas no solution exists above that value.
Tomography-Based Determination of Effective Transport Properties for Reacting Porous Media
Authors: Haussener Sophia , Jerjen Iwan , Wyss Peter , Steinfeld Aldo
Published: March 2011

The effective heat and mass transport properties of a porous packed bed of particles undergoing a high-temperature solid-gas thermochemical transformation are determined. The exact 3D geometry of the reacting porous media is obtained by high-resolution computer tomography. Finite volume techniques are applied to solve the governing conservation equations at the pore-level scale and to determine the effective transport properties as a function of the reaction extent, namely: the convective heat transfer coefficient, permeability, Dupuit-Forchheimer coefficient, tortuosity and residence time distributions. These exhibit strong dependence on the bed morphological properties (e.g. porosity, specific surface area, particle size) and, consequently, vary with time as the reaction progresses.