bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative Assessment of Myocardial Acceleration in Normal Left Ventricle with Velocity Vector Imaging
Authors: Zhang Haibin , Li Jun , Liu Liwen , Qian Yunqiu , Zhu Ting , Wei Zhangrui , Zhu Yongsheng , Zhang Jun , Zhou Xiaodong
Published: April 2008

Background: Application of two‐dimensional myocardial acceleration map derived from tissue Doppler imaging is limited by inherent angle dependency and substantial reader variability in the visualization of the origin of ventricular activation site. In this study we investigated the characteristics of myocardial acceleration in normal left ventricular (LV) walls with velocity vector imaging (VVI). Methods: VVI was applied to the parasternal short‐axis two‐dimensional echocardiographic images at basal, mid, and apical levels of the LV in 30 normal volunteers. Peak acceleration during early systole (ACCs) and time to ACCs (TACCs) were calculated for each segment of the standard 16‐segment model. Results: The time point of onset of active myocardial contraction corresponding to the QRS complex could not be determined in 409 (85.21%) of all 480 segments. No significant differences were found in TACCs among different LV levels and walls. In LV‐free walls, there were no significant differences in ACCs among different LV levels and walls. Conclusions: The time point of onset of myocardial active contraction during early systole cannot be determined in most of normal myocardial segments. Also, there is homogeneity of the time to early systolic peak acceleration in the whole normal LV walls. Myocardial acceleration seems to have limited potential in the assessments of the site of initial electrical stimulation and the sequence of ventricular depolarization.
Winnowing in Environmental Policy: Jurisdictional Challenges and Opportunities
Authors: Krutz Glen S. , Jorgensen Paul D.
Published: April 2008

While scholars developed an understanding of the processes moving issues from the systemic to the institutional agenda, we know little about the inner workings of the institutional agenda. Winnowing theory addresses this gap by examining the leadership, bill sponsor, and contextual factors helping bills move through the institutional agenda. By expanding winnowing theory to incorporate a fragmented policy domain, the environment, we find that multiple referral status actually helps a bill's chances of receiving attention and passing through the committee.
Urban Government Innovation: Identifying Current Innovations and Factors that Contribute to Their Adoption
Authors: Franzel Joshua M.
Published: April 2008

This article presents two new sets of information regarding local government innovation. Using survey techniques, the research establishes a list of 22 modern local government innovations and identifies what are considered by local government professionals to be the top three mainstream local government innovations and cities leading in their usage. The research uses statistical techniques and previous research on the topic to test what effect factors related to the 100 most populated U.S. cities have on innovation usage. Among other variables, consistency, the population size, size of the advantaged population, and number of Democratic voters are found to be positively related to innovation on usage by cities.
Mesenchymal stem cells and platelet‐rich plasma enhance bone formation in sinus grafting: a histomorphometric study in minipigs
Authors: Pieri Francesco , Lucarelli Enrico , Corinaldesi Giuseppe , Iezzi Giovanna , Piattelli Adriano , Giardino Roberto , Bassi Massimo , Donati Davide , Marchetti Claudio
Published: April 2008

Objectives: Autologous, allogenic, and alloplastic materials for sinus augmentation have specific drawbacks, which has stimulated an ongoing search for new materials and tissue‐engineering constructs. We investigated whether mesenchymal stem cells (MSCs) and platelet‐rich plasma (PRP) seeded on a fluorohydroxyapatite (FH) scaffold can improve bone formation and bone‐to‐implant contact (BIC) in maxillary sinus grafting.

Material and Methods: Bilateral sinus augmentation procedures were performed in eight minipigs. MSCs, PRP, and FH scaffold (test site) or FH alone (control site) were grafted in each maxillary sinus. Distal to the osteotomy, one dental implant per sinus was placed in the grafting material through the facial sinus wall. The animals were killed 3 months after grafting, and block sections of the implant sites were harvested and prepared for histomorphometric analysis.

Results: After 12 weeks, a significant increase in bone formation occurred in the test sites compared with the control sites (42.51%versus 18.98%; p=0.001). In addition, BIC was significantly greater in the test sites compared with the control sites in the regenerated area (23.71%versus 6.63%; p=0.028).

Conclusions: These findings show that sinus augmentation with MSCs–PRP, combined with FH may enhance bone formation and osseointegration of dental implants compared with FH alone in minipigs.
Cutaneous histopathological findings of Aicardi–Goutières syndrome, overlap with chilblain lupus
Authors: Kolivras Athanassios , Aeby Alec , Crow Yanick J. , Rice Gillian I. , Sass Ursula , André Josette
Published: April 2008

We report a 2‐year‐old girl with developmental delay who, from the age of 1 year, developed perniotic lesions of the hands and feet initially diagnosed as chilblain lupus. Histological examination showed features of epidermal necrosis with intraepidermal bulla formation, interface dermatitis, lymphocytic vasculitis with fibrinoid necrosis and thrombi formation, both superficial and deep dermal lymphocytic infiltrate, lymphocytic eccrine hidradenitis and absence of marked dermal edema. Subsequent investigations suggested a clinical diagnosis of Aicardi–Goutières syndrome (AGS), a rare genetic leukoencephalopathy. Recently, both AGS and familial chilblain lupus, an autosomal dominant form of systemic lupus erythematosus (SLE), have been shown to be allelic thus suggesting a common pathogenic basis. In addition, a phenotypic overlap is apparent between SLE and AGS. To our knowledge, this is the first comprehensive dermatopathological report of the cutaneous lesions seen in AGS, and our paper highlights the importance of considering AGS in the differential diagnosis of perniosis and chilblain lupus.
Metastatic myoepithelial carcinoma in a child
Authors: Law Robert M. , Viglione Michael P. , Barrett Terry L.
Published: April 2008

Cutaneous myoepithelial tumors are rare entities, with few reported malignant variants in the literature. The majority of these tumors are reported in the head and neck region of the adult population, with few examples in the literature arising in young patients. We present a case of myoepithelial carcinoma in a 13‐year‐old girl, with documented metastatic disease. Reproducible predictors of malignant behavior have yet to be clarified.
A single lesion showing features of pigmented eccrine poroma and poroid hidradenoma
Authors: Chiu Hsiu‐Hui , Lan Cheng‐Che E. , Wu Chieh‐Shan , Chen Gwo‐Shing , Tsai Kun‐Bow , Chen Po‐Hung
Published: April 2008

Poroid hidradenoma (PH) is a variant of poroma. This entity was defined by Abenoza and Ackerman in 1990. This neoplasm shows architectural characteristics of hidradenoma (tumor cells confined entirely within the dermis in both solid and cystic components) and cytologic characteristics of poroid neoplasm (poroid and cuticular cells, the latter showing ductal differentiation). We herein document a case of single poroid lesion with the features of both eccrine poroma and PH. The patient was a 55‐year‐old woman with a pigmented nodular lesion on her upper back for 7 years. The histopathologic features of the lesion were consistent with those of eccrine poroma and PH. Unlike most eccrine poromas, this case was pigmented, clinically and microscopically.
Cultural Wounds and Physical Scarring in Once Were Warriors
Authors: Bryden Rachel
Published: April 2008

This essay won the 2007

Literature Compass

Graduate Essay Prize, Twentieth Century & Contemporary Section.

How does the wounding and healing of the Maori body in the book and film versions of Once Were Warriors work to construct a national narrative for New Zealand race relations? This essay compares the book and film versions of Once Were Warriors, examining how they work to construct a national narrative for New Zealand race relations. It looks at the popularity of Lee Tamahori's film adaptation of Alan Duff's novel and argues that New Zealanders have incorporated the story of Pine Block as a certain kind of national narrative, arguably a national narrative that works against constructions of a mutually beneficial settlement process. To read or watch this particular construction of national identity is an experience that New Zealanders find almost unbearably painful, yet Once Were Warriors became the most successful film in New Zealand box office history. It is interesting that as a nation we feel prepared to take on these representations, rather than dismissing them as the reactionary perspectives of a specific group of people as so often happens with Maori portrayals of oppression and colonial violence. The trauma in Once Were Warriors arguably acts as a form of collective cultural catharsis, allowing New Zealanders to work through a somewhat repressed history of forceful settlement. The book and the film resolve these issues in different ways, but both incorporate physical trauma, domestic trauma, and trauma associated with marginalisation which allows us to experience the pain of that particular form of violence and then take pleasure from the healing of that wound. These wounds are created in both narratives through tattooing, gang violence, domestic violence and rape. However, the book and film construct and heal these wounds in very different ways and, in doing so, perhaps create different narratives of national identity. This essay examines whether these dual narratives deposit the viewer/reader back at the site of conventional racial unity or suggest a new way of representing ourselves as a nation.
Crystal structure of highly thermostable glycerol kinase from a hyperthermophilic archaeon in a dimeric form
Authors: Koga Yuichi , Katsumi Ryota , You Dong‐Ju , Matsumura Hiroyoshi , Takano Kazufumi , Kanaya Shigenori
Published: April 2008

The crystal structure of glycerol kinase from the hyperthermophilic archaeon Thermococcus kodakaraensis (Tk‐GK) in a dimeric form was determined at a resolution of 2.4 Å. This is the first crystal structure of a hyperthermophilic glycerol kinase. The overall structure of the Tk‐GK dimer is very similar to that of the Escherichia coli glycerol kinase (Ec‐GK) dimer. However, two dimers of Ec‐GK can associate into a tetramer with a twofold axis, whereas those of Tk‐GK cannot. This may be the reason why Tk‐GK is not inhibited by fructose 1,6‐bisphosphate, because the fructose 1,6‐bisphosphate binding site is produced only when a tetrameric structure is formed. Differential scanning calorimetry analyses indicate that Tk‐GK is a highly thermostable protein with a melting temperature (Tm) of 105.4 °C for the major transition. This value is higher than that of Ec‐GK by 34.1 °C. Comparison of the crystal structures of Tk‐GK and Ec‐GK indicate that there is a marked difference in the number of ion pairs in the α16 helix. Four ion pairs, termed IP1–IP4, are formed in this helix in the Tk‐GK structure. To examine whether these ion pairs contribute to the stabilization of Tk‐GK, four Tk‐GK and four Ec‐GK derivatives with reciprocal mutations at the IP1–IP4 sites were constructed. The determination of their stabilities indicates that the removal of each ion pair does not affect the stability of Tk‐GK significantly, whereas the mutations designed to introduce one of these ion pairs stabilize or destabilize Ec‐GK considerably. These results suggest that the ion pairs in the α16 helix contribute to the stabilization of Tk‐GK in a cooperative manner.
Geraniol dehydrogenase, the key enzyme in biosynthesis of the alarm pheromone, from the astigmatid miteCarpoglyphus lactis(Acari: Carpoglyphidae)
Authors: Noge Koji , Kato Makiko , Mori Naoki , Kataoka Michihiko , Tanaka Chihiro , Yamasue Yuji , Nishida Ritsuo , Kuwahara Yasumasa
Published: April 2008

Geraniol dehydrogenase (GeDH), which plays an important role in the biosynthesis of neral, an alarm pheromone, was purified from the astigmatid miteCarpoglyphus lactis. The enzyme was obtained in an apparently homogeneous and active form after 1879‐fold purification through seven steps of chromatography.Car. lactisGeDH was determined to be a monomer in its active form with a relative molecular mass of 42 800, which is a unique subunit structure in comparison with already established alcohol dehydrogenases.Car. lactisGeDH oxidized geraniol into geranial in the presence of NAD+. NADP+was ineffective as a cofactor, suggesting thatCar.lactisGeDH is an NAD+‐dependent alcohol dehydrogenase. The optimal pH and temperature for geraniol oxidation were determined to be pH 9.0 and 25 °C, respectively. TheKmvalues for geraniol and NAD+were 51.0 μmand 59.5 μm, respectively.Car. lactisGeDH was shown to selectively oxidize geraniol, whereas its geometrical isomer, nerol, was inert as a substrate. The high specificity for geraniol suggests thatCar. lactisGeDH specializes in the alarm pheromone biosynthesis ofCar. lactis.Car. lactisGeDH is composed of 378 amino acids. Structurally,Car. lactisGeDH showed homology with zinc‐dependent alcohol dehydrogenases found in mammals and a mosquito (36.6–37.6% identical), and the enzyme was considered to be a member of the medium‐chain dehydrogenase/reductase family, in view of the highly conserved sequences of zinc‐binding and NAD+‐binding sites. Phylogenetic analyses indicate thatCar. lactisGeDH could be categorized as a new class, different from other established alcohol dehydrogenases.
Synchronous early gastric cancer and gastrointestinal stromal tumor in the stomach of a patient with idiopathic thrombocytopenic purpura
Authors: VILLIAS Constantinos , GOURGIOTIS Stavros , VELOUDIS George , SAMPAZIOTIS Dimitrios , MOREAS Hercules
Published: April 2008

The synchronous occurrence of gastrointestinal stromal tumour (GIST) in the stomach and early gastric cancer is uncommon, with only a few previous reports. In particular, the collision of GIST and early gastric cancer in a patient with idiopathic thrombocytopenic purpura (ITP) has never been reported. We present the case of a 78‐year‐old male patient with ITP who was diagnosed with a synchronous development of GIST and early gastric cancer of the stomach. He underwent an elective subtotal gastrectomy with splenectomy. We discuss whether the development of GIST in the stomach in concert with early gastric cancer is an incidental coexistence or involve the same carcinogenic agents. Furthermore, it is not known whether or not such a situation is connected with ITP. To our knowledge this is the second report of a small GIST concomitant with an early gastric cancer and the first one in a patient with ITP.
Nozzle Geometry and Injection Duration Effects on Diesel Sprays Measured by X-Ray Radiography
Authors: Kastengren A. L. , Powell C. F. , Riedel T. , Cheong S.-K. , Im K.-S. , Liu X. , Wang Y. J. , Wang J.
Published: April 2008

X-ray radiography was used to measure the behavior of four fuel sprays from a light-duty common-rail diesel injector. The sprays were at 250bar injection pressure and 1bar ambient pressure. Injection durations of 400μs and 1000μs were tested, as were axial single-hole nozzles with hydroground and nonhydroground geometries. The X-ray data provide quantitative measurements of the internal mass distribution of the spray, including near the injector orifice. Such measurements are not possible with optical diagnostics. The 400μs sprays from the hydroground and nonhydroground nozzles appear qualitatively similar. The 1000μs spray from the nonhydroground nozzle has a relatively consistent moderate width, while that from the hydroground nozzle is quite wide before transitioning into a narrow jet. The positions of the leading- and trailing-edges of the spray have also been determined, as has the amount of fuel residing in a concentrated structure near the leading edge of the spray.
Study of Oscillating Flow of Viscoelastic Fluid With the Fractional Maxwell Model
Authors: Jia Jiu-hong , Hua Hong-xing
Published: April 2008

The oscillating flow of the viscoelastic fluid in cylindrical pipes has been applied in many fields, such as industries of petroleum, chemistry, and bioengineering. It is studied using the fractional derivative Maxwell model in this paper. The exact solution is obtained utilizing a simpler and more reasonable technique. According to this velocity solution, the time-velocity profile of one kind of viscoelastic fluid is analyzed. From analysis, it is found that the flow behaves like the Newton fluid when the oscillating frequency is low, and the flow reversal occurs when the oscillating frequency is high. Moreover, two series approximations for the velocity are obtained and analyzed for different model parameters. In one series approximation, the velocity is parabolic in profile, while in the other series approximation, the velocity presents three characteristics: (1) it is independent of radius and at the centerline is smaller than that of steady Poiseuille flow, (2) the phase lags about 90deg with respect to the imposed pressure gradient, and (3) the Richardson annular effect is found near the wall.
Dynamic Response of Thin-Walled Composite Material Timoshenko Beams
Authors: Bank L. C. , Kao C.-H.
Published: April 2008

Thin-walled structural members are used extensively in the offshore industry in applications ranging from marine risers to platforms and frames. Advanced fiber composite structural members may offer advantages over their conventional steel counterparts in certain situations. Use of composite members will require modifications to existing structural analysis codes. This paper presents a beam theory for thin-walled composite beams that can be incorporated into existing codes. Timoshenko beam theory is utilized to account for shear deformation effects, which cannot be neglected in composite beams, and for the variability in material properties in different walls of the beam cross section. The theory is applied to the analysis of the free vibration problem and shows the dependence of the natural frequencies and mode shapes on the in-plane properties of the laminates that form the walls of the beam. Forced periodic and forced arbitrary problems are also discussed and the deflected shapes and maximum deflections are shown as functions of wall layups.
The Effect of Nonuniform Interfacial Pressures on the Heat Transfer in Bolted and Riveted Joints
Authors: Madhusudana C. V. , Peterson G. P. , Fletcher L. S.
Published: April 2008

In bolted or riveted joints where the interfacial pressure is not uniform, the total resistance to heat flow in a vacuum is the result of two separate components: the microscopic resistance, which arises due to the constraint of the heat flow through the actual microscopic contact spots, and the macroscopic resistance, which exists because the contact zone, over which these microscopic contact spots are located, is only a fraction of the total interfacial area. Presented here is a review of the recent literature addressing the interfacial pressure distribution and the size of the contact zone, in so far as they affect the heat transfer at these interfaces. A survey of the experimental work on contact pressure and the associated heat transfer in bolted joints is presented, along with the size of the actual contact zone which was identified as an important parameter affecting both the microscopic and the macroscopic resistances. An analysis is performed in which it is formally shown that the exact form of the stress distribution within the contact zone is immaterial for the computation of the total microscopic conductance if the available theoretical results for local solid spot conductance are used. If experimental correlations for local solid spot conductance are used, however, the computed total microscopic conductances may differ about 5 to 10 percent, depending on the type of stress distribution chosen. It is also shown that, for a given load, the total microscopic conductance may be increased by increasing the loading radius and/or the plate thickness.
A Constitutive Model for Frozen Sand
Authors: Adachi T. , Oka F. , Poorooshasb H. B.
Published: April 2008

An elasto-viscoplastic constitutive model for frozen sand is proposed based on the elasto-viscoplasticity theory incorporating the new time measure. The proposed model can describe a number of features of the mechanical behavior of the medium, such as rate sensitivity and strain softening under the triaxial compression test loading conditions. The effects of temperature, ambient pressure and the concentration of soil particles are also discussed.
The Thermodynamics of Compressed Air Exergy Storage
Authors: Osterle J. F.
Published: April 2008

The Compressed Air Energy Storage (CAES) concept is analyzed as an exergy storage concept. A thermodynamic analysis involving the application of the first and second laws of thermodynamics to both the charge and discharge processes is made. Works, heats, cavern energy changes, cavern exergy changes, and dissipations are evaluated for two designs—one idealized and the other more practical. An appropriate effectiveness based on the exergy concept is defined and evaluated.
Review of Methanol and Compressed Natural Gas (CNG) as Alternative for Transportation Fuels
Authors: Gandhidasan P. , Ertas A. , Anderson E. E.
Published: April 2008

Concern over the environment and a potential oil shortage has resulted in an intensified research for alternative fuels for the transportation sector. Two fuels given strong consideration are methanol and compressed natural gas (CNG). This paper is a comprehensive comparative study of methanol and CNG as transportation fuels. The physical properties of methanol and CNG are discussed. The various concerns, such as source and potential fuel supply, safety, toxicity and health hazards, engine performance and emissions, fuel storage, fuel tank and refueling of these alternative fuels are addressed briefly in this paper. We find that no single alternative fuel is best in all categories. The merits and drawbacks of each fuel are tabulated and the vehicle characteristics are compared with gasoline. The study concludes that the neat methanol may be considered as an alternative for passenger cars and CNG may be considered for fleets, light and heavy-duty vehicles as the best near-term solution.
Numerical Simulation of Different Types of Steam Surface Condensers
Authors: Zhang C. , Sousa A. C. M. , Venart J. E. S.
Published: April 2008

A numerical procedure is developed to simulate the fluid flow and heat transfer processes in the shell-side of steam surface condensers. The governing equations are solved in primitive variable form using a semi-implicit consistent control-volume formulation in which a segregated pressure correction linked algorithm is employed. The procedure is applied to three different types of surface condenser. The numerical predictions are critically assessed by comparison to available experimental data for condensers, and in general, the solutions are in good agreement with the experimental data.
Performance of the Wells Turbine With Variable Pitch Rotor Blades
Authors: Gato L. M. C. , Ec¸a L. R. C. , Falca˜o A. F. de O.
Published: April 2008

The Wells turbine is an axial-flow air-turbine designed to extract energy from the ocean waves. The turbine is self-rectifying, i.e., produces an unidirectional time-averaged torque from a reciprocating flow. The paper describes an experimental investigation on the aerodynamic performance of a modified version of the Wells turbine, whose rotor blades can be set at varying angle (as in a Kaplan turbine) while the turbine is in motion. The purpose of the work is to investigate whether, and to what extent, the modification to the turbine can enable it to achieve phase control—a method of tuning the energy-absorbing device to the incident waves—and avoid aerodynamic stall on the turbine rotor blades at peaks of air flow rate under conditions of real irregular ocean waves. Experimental results obtained with a model turbine are compared with predicted values from a quasi-three-dimensional computational method of flow analysis.
Entrainment Limitations in Thermosyphons and Heat Pipes
Authors: Peterson G. P. , Bage B. K.
Published: April 2008

The isothermal characteristics and high effective thermal conductivity of heat pipes and thermosyphons make them particularly useful in air to air and process to air heat recovery systems. Although previous investigations have developed successful techniques for predicting many of the transport limitations, entrainment remains the least understood. Current entrainment modeling techniques have resulted in a large range in the predicted axial heat flux required for the onset of entrainment. Included here is a review of the present analytical methods used to predict the liquid entrainment as a function of the pipe’s physical parameters and working fluid properties, for both thermosyphons and heat pipes. The results of the models are compared with existing experimental data in an effort to determine the accuracy of the predictive techniques. Using a sample copper/water thermosyphon and a similar screen wicked heat pipe, comparisons of the experimental entrainment limit and those predicted by seven thermosyphon and four heat pipe models were made. The results of this comparison can provide insight for designers developing heat pipe exchangers and will provide a basis for further understanding the phenomena which govern this limit.
A Study of Impact Response of Composite Pipe
Authors: Pang S. S. , Kailasam A. A.
Published: April 2008

The objective of this study was to gain a better understanding of the low-velocity impact phenomena of composite pipe. The focus was on test method development, and material and damage characterization. A drop weight tower tester was designed in this investigation. The dynamic tests were conducted using three different impactor geometries, velocities, and masses. It was found that the damage was localized and on the outer surface of the pipe in the case of the conical and wedge tip impactors. On the other hand, the damage zone was larger than the impact zone for the hemispherical impactor, and cracks were first seen within the inner surface of the pipe. This implies that the hemispherical tip impactor caused more damage to the pipe than the conical or wedge tips. The energy absorbed slightly increased with an increase in velocity or in mass. The contact period for the conical impactor was the longest. The velocity and mass of the impactor had only a slight effect on that period. The wedge impactor generated the largest peak force. The energy absorbed by the two composite pipes under low-velocity impact was studied. The specimen-1, Derakane 411-45 resin with less glass fiber, seemed to absorb more energy compared to the specimen-2, Derakane 470-36 resin with more glass fiber. In addition, the specimen-2 exhibited a slightly higher maximum impact force. Therefore, impact response is sensitive to fiber content.
Toughening Behavior and Interfacial Properties of Fiber-Reinforced Ceramic Composites
Authors: Hsueh C. H.
Published: April 2008

Toughening of ceramics by incorporating strong fibers has become an established technology, resulting in the creation of a new generation of tough ceramic composites. This toughening effect is primarily due to bridging of the crack surfaces by intact fibers when the composite is subjected to tension. The fiber bridging mechanisms, which are contingent upon the stress transfer phenomena between the fiber and the matrix, are reviewed in this paper. The critical role of the properties at the fiber/matrix interface in controlling the stress transfer phenomena is examined. Finally, evaluations of the interfacial properties of the composite by the indentation technique and the corresponding analysis are presented.
Design of Composite Cylindrical Panels for Maximum Axial and Shear Buckling Capacity
Authors: Kumar N. , Tauchert T. R.
Published: April 2008

Response of a cylindrical panel made of layers of composite material and subjected to in-plane loads is investigated. Prebuckling deformations are determined for antisymmetric angle-ply and cross-ply panels having simply supported boundary conditions. Buckling solutions are obtained via the Rayleigh-Ritz method. Nonlinear programming is used to optimize the designs. Design variables are taken as fiber orientations and/or thicknesses of different layers. Numerical results are presented for different materials and different geometrical parameters, including aspect ratio and curvature-to-length ratio.
Stochastic Models Related to Fatigue Damage of Materials
Authors: Ihara C. , Misawa T.
Published: April 2008

The stochastic models for the fatigue damage phenomena are proposed. They describe the uncertainty caused by inhomogeneity of materials for fatigue crack propagation of metals and fatigue damage of carbon fiber composite (CFRP). The models are given by the stochastic differential equations derived from the randomized Paris-Erdogan’s fatigue crack propagation law and Kachonov’s equation of fatigue damage. The sample paths and life distribution of fatigue crack propagation in metals or of damage accumulation in CFRP are obtained by using the solution of the stochastic differential equation and the probability density function, respectively. These theoretical results are compared with the actual experiments—fatigue crack propagation of high tensile strength steel APFH 60 and fatigue test for a carbon eight-harness-satin/epoxy laminate—through numerical experiments.
Nonlinear Behavior of Plain Woven G. F. R. P. Under Repeated Biaxial Tension/Torsion Loading
Authors: Amijima S. , Fujii T. , Sagami T.
Published: April 2008

Fatigue tests on a plain woven glass composite at room temperature under biaxial (tension/torsion) loading were conducted. Nonlinear stress-strain (S-S) response especially in shear, was found and focused. Under pulsating shear stress loading, the S-S relation during loading periods became linear just before final failure, while the unloading S-S curve kept its nonlinear relation. According to the cyclic stress profile, the S-S curve was much affected and changed. It was found that preferential cracks due to the shear stress component occurred and might affect the fatigue failure as well as the nonlinear stress-strain response.
Influence of Downstream Distance on the Drop Size Characteristics of an Evaporative Liquid Spray in a Convective Gaseous Medium
Authors: Sengupta S. P. , Mitra A. K. , Dash S. K. , Som S. K.
Published: April 2008

Numerical studies have been made to evaluate the interdependence of drop size characteristics and evaporation histories of an atomized liquid spray in a convective medium of uniform free stream at high temperature. With the help of a discrete droplet evaporation model, both the actual drop size distribution and the apparent one, that could have been obtained in practice by light-scattering technique, have been determined numerically at different downstream locations perpendicular to the spray axis. Variations of actual and apparent mass mean diameter and the evaporation rate with the axial distance of the spray have been established. Finally, the influences of pertinent input parameters, namely, the initial Reynolds number of the spray, the ratio of free stream to initial drop temperature and the ratio of free stream to initial drop velocity on the mean diameter and evaporation histories have been recognized.
Experimental Study of Self-Ignition and Smoldering of Moist Cellulosic Materials
Authors: Badr O. , Karim G. A.
Published: April 2008

The self-ignition and smoldering characteristics of cellulosic materials, as exemplified by cotton fibers, when subjected to convective low-velocity heated air stream were studied experimentally at atmospheric pressure. The effects of the content of moisture in the raw cotton on its ignition delay and smolder front propagation rates were established. Some comparative tests were also conducted on dry cotton samples containing instead of moisture, various concentrations of n-hexane or an alcohol mixture.
An Analytical Examination of the Partial Oxidation of Rich Mixtures of Methane and Oxygen
Authors: Karim G. A. , Hanafi A. S.
Published: April 2008

The uncatalyzed partial oxidation of rich mixtures of methane and oxygen is examined analytically, primarily with the view of hydrogen and/or synthesis gas (hydrogen plus carbon monoxide) production while employing a detailed chemical kinetic scheme of 108 simultaneous reactions and 28 species. The role of various operating conditions in establishing the yield of hydrogen and other products, the corresponding ignition delay periods and reaction rates is examined over a wide range of temperature, equivalence ratio and pressure. Correlations in terms of simple overall Arrhenius expressions are also provided.
Natural Convection in Porous Media Induced by the Centrifugal Body Force: The Solution for Small Aspect Ratio
Authors: Vadasz P.
Published: April 2008

The analytical solution to the natural convection problem in a rotating rectangular porous domain is presented for a small aspect ratio of the domain. The convection results from differential heating of the horizontal walls leading to temperature gradients orthogonal to the centrifugal body force. The solution to the nonlinear set of partial differential equations was obtained through an asymptotic expansion of the dependent variables in terms of a small parameter representing the aspect ratio of the domain. The convection regime is apparent in the results, although it has a weak effect on the mean heat flux.
Thermal Stresses Under Engine Heat Flux—Part 1: Ceramic Coating on Metal Substrate
Authors: Sheets B. E. , Kokini K.
Published: April 2008

The thermal stresses in a ceramic coating bonded to a metal substrate generated by heat flux conditions in an engine were studied. Edge delamination of the coating was related to the displacements of an interface crack between the ceramic and the metal. The effects of varying the thermal expansion coefficients of the ceramic, the bond coat and the metal, thin moduli of elasticity, their thicknesses and the initial stress-free temperature were determined.
Exergy Costing in Exergoeconomics
Authors: Tsatsaronis G. , Lin L. , Pisa J.
Published: April 2008

Existing methods of exergoeconomic analysis and optimization of energy systems operate with single average or marginal cost values per exergy unit for each material stream in the system being considered. These costs do not contain detailed information on (a) how much exergy, and (b) at what cost each exergy unit was supplied to the stream in the upstream processes. The cost of supplying exergy, however, might vary significantly from one process step to the other. Knowledge of the exergy addition and the corresponding cost at each previous step can be used to improve the costing process. This paper presents a new approach to exergy costing in exergoeconomics. The monetary flow rate associated with the thermal, mechanical and chemical exergy of a material stream at a given state is calculated by considering the complete previous history of supplying and removing units of the corresponding exergy form to and from the stream being considered. When exergy is supplied to a stream, the cost of adding each exergy unit to the stream is calculated using the cost of product exergy unit for the process or device in which the exergy addition occurs. When the stream being considered supplies exergy to another exergy carrier, the last-in-first-out (LIFO) principle of accounting is used for the spent exergy units to calculate the cost of exergy supply to the carrier. The new approach eliminates the need for auxiliary assumptions in the exergoeconomic analysis of energy systems and improves the fairness of the costing process by taking a closer look at both the cost-formation and the monetary-value-use processes. This closer look mainly includes the simultaneous consideration of the exergy and the corresponding monetary values added to or removed from a material stream in each process step. In general, the analysis becomes more complex when the new approach is used instead of the previous exergoeconomic methods. The benefits of using the new approach, however, significantly outweigh the increased efforts. The new approach, combined with some other recent developments, makes exergoeconomics an objective methodology for analyzing and optimizing energy systems.
A Compound Effect of Cutting Depth and Bit Dull on Cutters’ Temperature for Polycrystalline Diamond Compact Bits
Authors: Kuru E. , Wojtanowicz A. K.
Published: April 2008

This paper presents a simulation study to evaluate the combined effect of cutting depth (drilling rate) and wear (bit dull) on the thermal response of polycrystalline diamond compact (PDC) cutters under downhole drilling conditions. A new understanding of frictionally generated heat between rock and PDC cutter is introduced from the analysis of forces active on the wearflat and the cutting (leading) surfaces of a cutter. Then this new concept is used to predict PDC bit performance with the controlled temperature of its cutters. Previous concepts, largely based on the laboratory drilling tests (with low drilling rate and under atmospheric conditions), recognize only one source of heat—the wearflat surface. However, this study, using field data, shows that the heat generated at the cutting surface may significantly contribute to the total heat flux in the cutter. As a result, the distribution of temperature within the cutter is changed, which particularly affects the maximum value of temperature at the cutting edge. A simplified 2-D finite difference numerical code is used to quantify the difference in cutter wearflat temperatures calculated with and without the additional heat flux generated at the cutting surface. The numerical analysis reveals that neglecting the cutting surface effect results in underestimation of the actual wearflat temperature by 10 to 530 percent, depending upon bit dull and downhole hydraulics. Also demonstrated is the actual impact of these findings on field drilling practices. The example comparison is made by calculating the optimal-control procedures for PDC bit with and without the effect of cutting surface. In these procedures, wearflat temperature becomes a mathematical constraint which limits weight on bit and rotational speed. The comparison includes calculation of the maximum bit performance curves which represent maximum drilling rate attainable for a bit to drill a predetermined length of a borehole (footage). The curves show an up to 18 percent reduction of drilling rate when the new and more rigorous temperature limitation is used. In addition, the example calculations show that the actual temperature of the bit cutters can be 460°C (860°F), and exceeds by almost 30 percent its maximum acceptable value of 350°C (660°F). For practical applications, the study reveals that many field failures of PDC bits may have been caused by lack of understanding of operational limits imposed by heat considerations.
Integrated Resource Planning
Authors: Kreith F.
Published: April 2008

This article presents the essential features of an integrated resource planning (IRP) process designed to provide energy for societal and industrial needs at least cost. Use of renewable energy sources and energy conservation measures, as well as consideration of social costs, are described. Available data of social costs and estimates for energy cost of conservation measures and renewable energy systems are included.
Numerical Modeling of Rock-Bit Interaction in Laminated Formations
Authors: Karfakis M. G. , Ouyang H.-J.
Published: April 2008

Numerical modeling of the rock-bit interaction process in laminated formation has been performed using a finite element approach. A finite element program was developed with the assumption of plane strain. Anisotropic elements, dynamic, loading, progressive failure, and variable stiffness were used to represent the actual penetration process. The Hoek and Brown failure criterion was used in the failure analysis. An interation method, using an incremental approach, has been applied for the continuous tooth penetration process where displacements, axial loads, strength and stiffness of elements are modified after each iteration. The program provides quantitative information on stress, displacement, and rock failure for each iteration. Furthermore, deviation due to laminated formation can be inferred and the effects of changing bit geometry can be assessed. The model also shows good quantitative agreement with laboratory wedge indentation tests.
An Optimal Operational Advisory System for a Brewery’s Energy Supply Plant
Authors: Ito K. , Shiba T. , Yokoyama R. , Sakashita S.
Published: April 2008

An optimal operational advisory system is proposed to operate rationally a brewery’s energy supply plant from the economical viewpoint. A mixed-integer linear programming problem is formulated so as to minimize the daily operational cost subject to constraints such as equipment performance characteristics, energy supply-demand relations, and some practical operational restrictions. This problem includes lots of unknown variables and a hierarchical approach is adopted to derive numerical solutions. The optimal solution obtained by this method is indicated to the plant operators so as to support their decision making. Through the numerical study for a real brewery plant, the possibility of saving operational cost is ascertained.
Mathematical Modeling of PDC Bit Drilling Process Based on a Single-Cutter Mechanics
Authors: Wojtanowicz A. K. , Kuru E.
Published: April 2008

An analytical development of a new mechanistic drilling model for polycrystalline diamond compact (PDC) bits is presented. The derivation accounts for static balance of forces acting on a single PDC cutter and is based on assumed similarity between bit and cutter. The model is fully explicit with physical meanings given to all constants and functions. Three equations constitute the mathematical model: torque, drilling rate, and bit life. The equations comprise cutter’s geometry, rock properties drilling parameters, and four empirical constants. The constants are used to match the model to a PDC drilling process. Also presented are qualitative and predictive verifications of the model. Qualitative verification shows that the model’s response to drilling process variables is similar to the behavior of full-size PDC bits. However, accuracy of the model’s predictions of PDC bit performance is limited primarily by imprecision of bit-dull evaluation. The verification study is based upon the reported laboratory drilling and field drilling tests as well as field data collected by the authors.
A Laboratory-Scale Experimental Study of In-Situ Combustion Processes
Authors: Hubbard M. , Krehbiel D. K. , Gollahalli S. R.
Published: April 2008

A laboratory-scale experimental study of in-situ combustion for enhanced oil recovery is presented. The effects of oil saturation, preheating of the oil-sand bed, porosity of sand, and air-injection rate on both the time history of liquid yield and the total liquid yield have been determined. From the measured temperature profiles and charred length of oil-sand bed, the propagation rate of combustion front has been deduced. The volumetric concentrations of CO2 and O2 in the effluent gas have been measured. The rate of liquid yield is highest in the initial periods of insitu heating or combustion. Air-injection rate, although it has an indirect influence on the temperatures achieved in the bed, exerts only a weak effect on the liquid yield. The increase in porosity of sand increases the liquid yield rate. The relative effects of air injection rate, oil saturation, and the porosity of sand under combustion conditions are simulated well by preheating the bed.
A Thermodynamic Analysis of the Lean Flammability Limits of Fuel-Diluent Mixtures in Air
Authors: Wierzba I. , Bade Shrestha S. O. , Karim G. A.
Published: April 2008

A procedure is described for calculating the lean flammability limits of fuel-diluent mixtures in air over a wide range of fuel-diluent combinations and for different initial mixture temperatures. Good agreement is shown to exist between the predicted values of the limits with the corresponding experimental values for some common gaseous fuels that include CH4, C2H6, C2H4, C3H8, C4H10, H2, and CO and the diluents CO2, N2, He, and Ar over the temperature range of −60°C up to 400°C.
Gas Turbine Cycles With Solid Oxide Fuel Cells—Part I: Improved Gas Turbine Power Plant Efficiency by Use of Recycled Exhaust Gases and Fuel Cell Technology
Authors: Harvey S. P. , Richter H. J.
Published: April 2008

In conventional energy conversion processes, the fuel combustion is usually highly irreversible, and is thus responsible for the low overall efficiency of the power generation process. The energy conversion efficiency of the combustion process can be improved if immediate contact of fuel and oxygen is prevented and an oxygen carrier is used. In a previous paper (Harvey et al., 1992), a gas turbine cycle was investigated in which part of the exhaust gases—consisting mainly of CO2, H2O, and N2—are recycled and used as oxygen-carrying components. For the optimized process, a theoretical thermal efficiency of 66.3 percent was achieved, based on the lower heating value (LHV) of the methane fuel. A detailed second-law analysis of the cycle revealed that, although the exergy losses associated with the fuel oxidation were significantly less than those associated with conventional direct fuel combustion methods, these losses were still a major contributor to the overall losses of the system. One means to further improve the exergetic efficiency of a power cycle is to utilize fuel cell technology. Significant research is currently being undertaken to develop fuel cells for large-scale power production. High-efficiency fuel cells currently being investigated use high-temperature electrolytes, such as molten carbonates (~ 650°C) and solid oxides (usually doped zirconia, ~1000°C). Solid oxide fuel cells (SOFC) have many features that make them attractive for utility and industrial applications. In this paper, we will therefore consider SOFC technology. In view of their high operating temperatures and the incomplete nature of the fuel oxidation process, fuel cells must be combined with conventional power generation technology to develop power plant configurations that are both functional and efficient. In this paper, we will show how monolithic SOFC (MSOFC) technology may be integrated into the previously described gas turbine cycle using recycled exhaust gases as oxygen carriers. An optimized cycle configuration will be presented based upon a detailed cycle analysis performed using Aspen Plus™ process simulation software (Aspen Technology, 1991) and a MSOFC fuel cell simulator developed by Argonne National Labs (Ahmed et al., 1991). The optimized cycle achieves a theoretical thermal efficiency of 77.7 percent, based on the LHV of the fuel.