bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural and Aerodynamic Influences to Airfoil Forced Response: Does a Thicker Airfoil Have Reduced Vibratory Response?
Authors: Tatakis Spiros , Stockton Richard J.
Published: February 2015

The influence of airfoil geometric and aerodynamic parameters on the vibratory response of low frequency modes subjected to low order excitations was investigated. The predicted vibratory response of a thicker airfoil was compared to the response of a baseline thickness design. Two types of forcing mechanisms were analyzed. It was found that force-controlled response, that may originate from mechanical input or surge, can be managed by increasing the airfoil thickness and providing sufficient margin below the endurance limit of the material. Velocity-controlled response, mainly from aerodynamic interactions, depend on the airfoil excitation placement. The aerodynamic forcing function and damping were determined using flat plate unsteady aerodynamic solutions integrated with an MSC/NASTRAN structural finite element model of the airfoil. Thickening appears to reduce blade response in a velocity-controlled situation provided the modal stress has been reduced by the thickening. However, the response reduction is greater for the force-controlled situation. The modal parameter model provides a quick assessment of either possibility.
Influence of Surface Heating Condition on Local Heat Transfer in Enclosed Corotating Disks With Axial Throughflow
Authors: Kim S. Y. , Han J. C. , Morrison G. L. , Elovic E.
Published: February 2015

Local heat transfer in a rotating cavity with axial throughflow was experimentally investigated. The rotating cavity was bounded by two plane disks and a cylindrical rim (shroud). The ratio of the rim span to the disk outer radius was 0.4 and the ratio of the disk inner radius to outer radius was 0.25. This study investigated the effects of axial coolant flow rate, rotation speed, and disk surface heating condition on the local heat transfer coefficient distributions inside the cavity. Three cavity surface heating conditions were tested: case 1 - upstream and downstream disks with radially increasing temperature but colder than rim; case 2 - upstream and downstream disks at uniform temperature but colder than rim; and case 3 - upstream and downstream disks and rim at uniform temperature. Tests were systematically performed for the axial flow Reynolds numbers between 2500 and 25,000, the rotational Reynolds numbers between 0 and 5.11 × 105, and the rotational Grashof numbers between 5 × 106 and 1.3 × 1010, respectively. The results show that the local heat transfer coefficients for the non-rotating cavity increase with increasing axial flow Reynolds number. However, the local heat transfer coefficients initially decrease and then increase with increasing rotational Reynolds number. In general, the heat transfer coefficients on the rim for case 2 surface heating condition are higher than those for case 1 and case 3 whereas the heat transfer coefficients on the upstream and downstream disks for case 3 surface heating condition are higher than those for case 1 and case 2.
Optimum Design of Rotating Laminate Blade With Dynamic Behavior Constraints
Authors: Shiau Ting Nung , Yu Yung Dann , Kuo Chun Pao
Published: February 2015

The optimum design of rotating laminated blade subject to dynamic behavior constraint is investigated. The dynamic behavior constraints consist of restrictions on multiple natural frequencies as well as on maximum dynamic deflections of rotating laminated blade. The harmonic excitations are considered to simulate the aerodynamic forces acting on the blade. The optimization techniques of optimality criterion method and modified method of feasible directions have been successfully developed and applied to minimize the weight of rotating laminated blade. The effect of setting angles and rotating speed on the system dynamic behaviors as well as on the optimum design are also studied. The dynamic analysis shows that most of the bending modes can be significantly affected by rotating speed, setting angle, and the radius of disc. The results also indicate that the optimum weight will decrease with the increase of rotating speed for the multiple frequency constraints. The similar phenomena is also obtained for the dynamic response constraints. Moreover, the optimum weight of the dynamic response constraints case is higher than that of multiple frequency constraints case. This study presents that the weight of rotating laminated blade can be greatly reduced at optimum stage.
Durability Surveillance of Advanced Gas Turbines: Performance and Mechanical Baseline Development for the GE Frame 7F
Authors: Meher-Homji Cyrus B. , Lakshminarasimha A. N. , Mani G. , Dohner Clark V. , Ondryas Igor , Boehler Pierre D. , Lukas Holger , Cincotta G. A. (Tom)
Published: February 2015

This paper describes the methodology and approach of baseline development as part of a comprehensive Durability Surveillance Study Program of an Advanced Gas Turbine (AGT) sponsored by the Electric Power Research Institute (EPRI) on a GE Frame 7F gas turbine operating in peaking service. The gas turbine is an advanced technology 156 MW (ISO), 955 lb/sec machine operating at a turbine inlet temperature of 2300° F (rotor inlet temperature) and a pressure ratio of 13.5:1. The turbine is located at Potomac Electric Power Company (PEPCO) Station H plant in Dickerson, Maryland. In order to facilitate the durability surveillance, the turbine has a data acquisition and analysis system which obtains data from the control system (via serial port) as well as from special sensors such as proximity probes, dynamic pressure sensors, strain gauges and hot section pyrometers. With the GE Frame 7F and FA machines becoming very popular in utility applications worldwide, the EPRI Durability Surveillance Program and baseline generation methodology will be of considerable practical interest to gas turbine users. The basic methodology presented for baseline development can be used for any single shaft gas turbine. We believe the base-line to be of considerable importance in evaluating future condition of the machine as well as for maintenance planning. The paper also briefly describes the status and future plans of the EPRI durability surveillance program.
Prediction of Surface Roughness and Incidence Effects on Turbine Performance
Authors: Boyle R. J.
Published: February 2015

The use of a Navier-Stokes analysis to predict the change in turbine efficiency resulting from changes in blade surface roughness or incidence flow angles is discussed. The results of a midspan Navier-Stokes analysis are combined with those from a quasi-three-dimensional flow analysis code to predict turbine performance. A quasi-three-dimensional flow analysis code was used to determine turbine performance over a range of incidence flow angles. This analysis was done for a number of incidence loss models. The change in loss due to changes in incidence flows computed from the Navier-Stokes analysis is compared with the results obtained using the empirical loss models. The Navier-Stokes analysis was also used to determine the effects of surface roughness using a mixing length turbulence model, which incorporated the roughness height. The validity of the approach used was verified by comparisons with experimental data for a turbine with both smooth and rough blades tested over a wide range of blade incidence flow angles.
Spanwise Transport in Axial-Flow Turbines: Part 1 — The Multistage Environment
Authors: Lewis K. L.
Published: February 2015

Selected experimental results, obtained from a detailed investigation into the flowfields within two low speed multistage turbines, are presented. A repeating stage condition occurred typically after two stages, with the secondary flows an important factor in the low aspect ratio geometry. A tracer gas technique was employed to identify the dominant mechanisms of spanwise transport and their relative significance. In the first stages of both machines, tracer transport was more intense near the endwalls than at mid-span whilst in the multistage environment the transport was approximately constant across the whole span. The convective influence of classical secondary flow, shroud leakage and wake passage through a downstream blade was identified and shown to be as significant as turbulent diffusion in effecting cross-passage and spanwise transport. The data show that spanwise transport should be included within any throughflow model and are used to calibrate two scaling models. These models are presented in Part 2 where the influence of incorporating spanwise transport into a throughflow model is investigated.
Experimental and Theoretical Investigations of Heat Transfer in Closed Gas-Filled Rotating Annuli
Authors: Bohn D. , Deuker E. , Emunds R. , Gorzelitz V.
Published: February 2015

The prediction of the temperature distribution in a gas turbine rotor containing closed, gas-filled cavities, for example in between two discs, has to account for the heat transfer conditions encountered inside these cavities. In an entirely closed annulus forced convection is not present, but a strong natural convection flow exists, induced by a non-uniform density distribution in the centrifugal force field.

Experimental investigations have been made to analyze the convective heat transfer in closed, gas-filled annuli rotating around their horizontal axis. The experimental set-up is designed to establish a pure centripedal heat flux inside these annular cavities (hot outer, and cold inner cylindrical wall, thermally insulated side walls). The experimental investigations have been carried out for several geometries varying the Rayleigh number in a range usually encountered in cavities of turbine rotors (1007 < Ra < 1012). The convective heat flux induced for Ra = 1012 was found to be a hundred times larger compared to the only conductive heat flux. By inserting radial walls the annulus is divided into 45° sections and the heat transfer increases considerably.

A computer programme to simulate flow and heat transfer in closed rotating cavities has been developed and tested successfully for annuli with isotherm side walls with different temperatures giving an axial heat flux. For the centripedal heat flux configuration, three-dimensional steady state calculations of the sectored annulus were found to be consistent with the experimental results. Nevertheless, analysis of unsteady calculations show that the flow can become unstable. This is analogous to the Bénard problem in the gravitational field.
Active Vibration Control of Rotating Machinery Using Piezoelectric Actuators Incorporating Flexible Casing Effects
Authors: Barrett Timothy S. , Palazzolo Alan B. , Kascak Albert F.
Published: February 2015

The modern trend toward lighter and more flexible designs in rotating machinery brings with it increasing demands for ways to dissipate the excess energy transferred to such structures by the action of dynamic forces. The present study incorporates the use of active feedback control mechanisms to suppress this unwanted vibration. The basic active damping scheme involves the introduction of a control force on the structure from a feedback network whose input is dictated by the motion of the structure. The control force is applied to the rotor bearing support housing via a piezoelectric actuator attached to the rotor casing. The current research extends previous electromechanical simulations by incorporating a flexible finite element shell model of the casing to support the actuator and sensors. Actuator and feedback loop dynamics are included in the stability and response simulation.
Temperatures in a Gas Turbine Vaporizer at Near Idle Engine Conditions
Authors: Vaskopulos Theodore , Polymeropoulos Constantine E. , Sernas Valentinas
Published: February 2015

The work is a laboratory investigation of the effect of different liquids and liquid flow rates on the metal temperature of a gas turbine T vaporizer. Most of the experimentation was carried out using JP5. A limited number of runs using Diesel Fuel Marine and calibration runs using water provided additional data for different fluids. Conditions that approach local liquid depletion inside the vaporizer were identified by monitoring local overheating of the vaporizer metal. Because of apparatus limitations, testing was carried out only at vaporizer pressure and liquid flow rates approaching idle engine operation. An experimental correlation was developed allowing estimation of the mean vaporizer temperature as a function of input conditions and fluid properties.
Stiffness Degradation in Metal Matrix Composites Caused by Thermomechanical Fatigue Loading
Authors: Aksoy Sait
Published: February 2015

Damage during thermomechanical fatigue loading of a metal matrix composite is represented by a vector. The undamaged material is characterized by the generalized Hooke’s law for transversely isotropic materials. The residual elastic properties of metal matrix composite are related to the initial elastic properties by the damage vector. The residual stiffness properties are then correlated with the number of fatigue cycles to failure. The ability to use this concept to determine the safe strength requirement for a given cyclic life is discussed.
Simulating Indirect Thrust Measurement Methods for High Bypass Turbofans
Authors: Stevenson J. D. , Saravanamuttoo H. I. H.
Published: February 2015

As yet, there is no known reliable method for directly measuring the thrust of a turbofan in flight. Manufacturers of civil turbofans use various indirect thrust measurements to indicate performance of an engine to the flight deck. Included among these are: Engine Pressure Ratio (EPR), Integrated Engine Pressure Ratio (IEPR), Fan mechanical speed (N1), and various Turbine Gas Temperatures such as ITT or EGT. Of key concern is whether these thrust indicators give an accurate account of the actual engine thrust. The accuracy of these methods, which are crucial at take-off, may be compromised by various types of common engine deterioration, to the point where a thrust indicator may give a false indication of the health and thrust of the engine. A study was done to determine the effect of advanced engine cycles on typical values of these parameters. A preliminary investigation of the effects of common kinds of turbofan deterioration was conducted to see how these faults can affect both actual engine performance and the indirect thrust indicators.
Advanced Turbine Systems Program and Coal Applications
Authors: Webb H. A. , Parsons E. L. , Bajura R. A.
Published: February 2015

The U.S. Department of Energy (DOE) is conducting a program to develop ultra high-efficiency, cost-effective, environmentally benign gas turbine systems for industrial and utility applications. The Advanced Turbine Systems (ATS) Program, jointly managed by the DOE’s Office of Fossil Energy (DOE/FE) and Office of Conservation and Renewable Energy (DOE/CE), will lead to the commercial offering by industry of systems meeting full program goals by the years 2000–2002. It is expected that some advanced technology will already have been commercialized in intermediate systems before that time. Teams, led by U.S. turbine manufacturers, will conduct most of the development work in the ATS Program. However, a substantial technology base element of the program will see universities and others conduct significant research and development (R&D) on generic technology issues relevant to the program.

The program is primarily aimed at developing natural gas-fired turbine systems. Although the conversion of ATS to firing with coal or biomass fuels will be addressed in the analysis of ATS, tests will not be conducted in the program to verify conversion to alternate fuel firing. The program will, however, include work to transfer advanced technology to the coal- and biomass-fueled systems being developed in other DOE programs.
Application of RQL Coal Combustor Technology to Large Utility Gas Turbines
Authors: Wilkes C. , Wenglarz R. A. , Hart P. J. , Mongia H. C.
Published: February 2015

This paper describes the application of Allison’s rich-quench-lean (RQL) coal combustor technology to large utility gas turbines in the 100 MWe+ class. The RQL coal combustor technology was first applied to coal derived fuels in the 1970s and has been under development since 1986 as part of a Department of Energy (DOE)-sponsored heat engine program aimed at proof of concept testing of coal-fired gas turbine technology. The 5 MWe proof of concept engine/coal combustion system was first tested on coal water slurry (CWS); it is now being prepared for testing on dry pulverized coal. A design concept to adapt the RQL coal combustor technology developed under the DOE program to large utility-sized gas turbines has been proposed for a Clean Coal V program. The engine and combustion system modifications required for application to coal-fueled combined cycle power plants using 100 MWe+ gas turbines are described. Estimates for emissions and cycle performance are given. Included are comparisons with a conventional pulverized coal plant that illustrates the advantages of incorporating a gas turbine on cycle efficiency and emission rate.
Ceramic Gas Turbine Technology Development and Applications
Authors: Smyth J. R. , Morey R. E. , Schultze R. W.
Published: February 2015

Under the ongoing DOE/NASA-funded Advanced Turbine Technology Applications Project (ATTAP), Garrett Auxiliary Power Division (GAPD) is continuing to address the issues of developing and applying structural ceramics to production gas turbine engines. Several critical technologies are being developed to advance this issue, including design methods development, component design, component fabrication, material characterization, and engine testing. The brittle nature of structural ceramics highlights concerns regarding impact damage. Through analysis and experimentation, design methods are being developed to improve the resistance of ceramic components to impact damage. Ceramic component designs now integrate these design methods into practice and proof testing methods are being developed to verify the results for actual engine components. Ceramic component fabrication processes are being optimized by selected subcontractors, resulting in deliveries of high-quality ceramic components which fully meet engine test needs. Verification of the component material properties is being achieved through comparisons of material property data from test bars cut from actual engine components with data generated from ceramic material test specimens. All these efforts are aimed at demonstrating endurance of the AGT101 all-ceramic turbine engine at the maximum operating temperature conditions up to 2500F (1371C).

These critical ceramics technologies being developed under ATTAP are also providing a critical launch pad into production-oriented programs. GAPD has three concurrent programs underway, aimed at integrating ceramics into production Auxiliary Power Units (APUs). These include: installing and evaluating ceramic turbine nozzles under actual field conditions in a well-established product line (the 85 Series Ceramic Nozzle Demonstration Program); incorporating ceramic first-stage turbine stators and blades in a three-stage axial turbine APU (the 331-200 Ceramic Demonstration Program); and incorporation of a ceramic first-stage turbine stator in our latest APU design, the G250 Auxiliary Power Generation System (APGS) for the USAF F-22 fighter aircraft.
Hot Section Turbine Disk Lifing Philosophies
Authors: Goswami Tarun K.
Published: February 2015

The life prediction of critical gas turbine engine components is carried out using a bank of laboratory test data which is also verified by a comprehensive program on full scale fatigue tests. These tests include carcass for containment, canopy for foreign body ingestion, disks for bolt hole and dovetail/firtree root cracks and blades for thermal shock and fatigue.

The life of the majority of these components is limited by low cycle fatigue which eventually is based on ‘initiation’ concepts and first detection of a crack 0.8 mm deep. Safe life design requires a high confidence of 99.9% probability of crack free components. Using safe life design concepts there is a large number of prematurely retired disks from service which have a high potential of useful life left in them.

Damage tolerance or fracture mechanics based lifing concepts attempt to utilize this ‘useful’ life by analyzing the cracks. However, these concepts depend on the accuracy of detecting cracks by Non-Destructive Inspection (NDI) techniques. The probability of detection curves do not follow a fixed statistical distribution to give sufficient confidence level to fix the next inspection interval. Probabilistic and deterministic fracture mechanics based lifing philosophies are overviewed.
Gas Turbines in Ship Propulsion: Design Constraints in Relation to Ship Types
Authors: Bakountouzis L. N.
Published: February 2015

In recent years merchant marine propulsion has been dominated by the diesel engine (primarily the slow speed type) with fuel costs being the principal factor in favour of their selection. Fuel costs, however, constitute but one of the major constraints entering the design and operation of the marine power plant.

Following a systems approach, the design problem of the marine power plant (within the framework of the overall ship design and seaborne transport systems) is considered, with the view to properly identify and classify the complete set of machinery constraints and their interactions, in relation to different ship applications.

On this basis, the gas turbine is compared with its internal combustion rival by considering the most significant constraints, but with due reference to other factors (of a lesser importance), where appropriate. It is shown that, in this way, the predominance of one type of prime mover over the other, in different applications can be easily explained.

Finally, consideration is given to future developments in terms of high-speed marine transportation demands, possible legislation requirements for environmental protection and potential advances in prime movers themselves. It is concluded that the gas turbine could well assume a more prominent role in marine propulsion, in the near or distant future.
Computerized Design, Simulation and Feasibility Study of the Heat Recovery System at Jeddah Oil Refinery Company
Authors: Faqeeh Essam I.
Published: February 2015

Cogeneration is a very well known and important subject in the industries due to its impact in energy saving and reduction of air pollution. Jeddah Oil Refinery Company (JORC) generates its electric power demand using four industrial gas turbines for a total of 88 MW, while the process steam is produced by four Mitsubishi water tube boilers with a capacity of 50 tons per hour each. The steam condition is at 12 bars gage pressure and 188°C saturation temperature. A computer program “Cogen” has been developed to evaluate the design and off-design performance of the existing four gas turbines at JORC. Accordingly, a heat recovery combined cycle cogeneration system was proposed to utilize the exhaust energy leaving the turbines to fulfill the requirements of the refinery in both electric power and saturated steam. The output results of the computer program are presented in the form of figures. The fuel utilization efficiency of the combined plant has increased to 60% and resulted in approximately 55% reduction in fuel consumption and a payback period of 1.99 years in which the technical and economical feasibility of the proposed system is assured.
Aircraft Gas Turbine Emissions Challenge
Authors: Koff B. L.
Published: February 2015

The new generation of jet powered aircraft faces a significant challenge to reduce pollutant emissions while increasing fuel efficiency. Carbon monoxide (CO) and unburned hydrocarbon (HC) emissions are already very low and continued control of these pollutants is expected as engine temperatures and pressure ratios are increased. In contrast, significant system design improvements are needed to reduce oxides of nitrogen (NOx) emissions because of their harmful effect on the earth’s ozone layer. This paper discusses the prospects and technical approaches for significant NOx reductions in current and future subsonic and supersonic aircraft.
A Power Increase of 17% for the EGT Typhoon Gas Turbine
Authors: Sanders A. T. , Gallimore S. , Whitehouse P.
Published: February 2015

Following the successful introduction of the EGT Typhoon at a power rating of 4100 kW (5500 hp), planned enhancements have been introduced to increase the power to 4790 kW (6400 hp). The changes to meet the higher power requirement include an increase in rotational speed by 5% with resulting increases in mass flow and pressure ratio, thermal barrier coating of the combustion chambers, and the directional solidification of the hp rotor blade material.

The design changes are described along with the validation by rig work and engine running, building on the extensive field running of engines at the 4100 kW rating.
Gas Turbine Engine Noise Control Using Fiber Metal Lined Ducts
Authors: Clark Ray C. , Mekwinski Julius C.
Published: February 2015

Fiber metal acoustic sheet materials are used in lined duct sound absorbers for gas turbine engine noise. Duct treatment utilizes a fiber metal face sheet backed by a cavity of controlled depth. The fiber metal facing and cavity depth provide a tuned system that is broadly effective in a desired frequency band. Fiber metal lined ducts are used in engine applications such as fan ducts, inlet cowls, auxiliary power units and environmental control systems. This approach is used in engine treatments to provide effective absorption within engine limits of weight and space.

This paper discusses design methodology for fiber metal ducts. Topics include frequency tuning the absorber, treated area versus noise reduction, matching the acoustical impedance of the fiber metal to the air in the duct, the effects of flow and sound pressure level in the duct on noise reduction, and an example of noise reduction achieved in an engine application.
Paralympic Sprint Performance Between 1992 and 2012
Authors: Grobler Lara , Ferreira Suzanne , Terblanche Elmarie
Published: February 2015

The Paralympic Games have undergone many changes since their inception in 1960, one being the advances made in running-specific prostheses (RSPs) for track athletes with lower-limb amputations.

Purpose:

To investigate the sprinting-performance changes in athletes with lower-limb amputations since 1992 to assess whether the influence of developments in RSP technology is evident.

Methods:

The results of the Olympic and Paralympic Games ranging between 1992 and 2012 for the 100-m and 200-m were collected, and performance trends, percentage change in performance, and competition density (CD) were calculated.

Results:

The results indicate that the greatest performance increases were seen in athletes with lower-limb amputations (T42 = 26%, T44 = 14%). These performance improvements were greater than for Olympic athletes (<3%), as well as Paralympic athletes from other selected classes (<10%). The T42 and T44 classes also showed the lowest CD values.

Discussion:

These results suggest that although there is an overall trend for improved Paralympic sprint performances, RSP technology has played a noteworthy role in the progression of performances of athletes with amputations. It is also hypothesized that the difference in the performance improvements between the T42 and T44 classes is due to the level of disability and therefore the extent to which technology is required to enable locomotion.

Conclusion:

It is evident that RSP technology has played a significant role in the progression of performances in athletes with lower-limb amputations.
Accumulation of Domain-Specific Physical Inactivity and Presence of Hypertension in Brazilian Public Healthcare System
Authors: Turi Bruna Camilo , Codogno Jamile S. , Fernandes Romulo A. , Sui Xuemei , Lavie Carl J. , Blair Steven N. , Monteiro Henrique Luiz
Published: February 2015

Background:

Hypertension is one of the most common noncommunicable diseases worldwide, and physical inactivity is a risk factor predisposing to its occurrence and complications. However, it is still unclear the association between physical inactivity domains and hypertension, especially in public healthcare systems. Thus, this study aimed to investigate the association between physical inactivity aggregation in different domains and prevalence of hypertension among users of Brazilian public health system.

Methods:

963 participants composed the sample. Subjects were divided into quartiles groups according to 3 different domains of physical activity (occupational; physical exercises; and leisure-time and transportation). Hypertension was based on physician diagnosis.

Results:

Physical inactivity in occupational domain was significantly associated with higher prevalence of hypertension (OR = 1.52 [1.05 to 2.21]). The same pattern occurred for physical inactivity in leisure-time (OR = 1.63 [1.11 to 2.39]) and aggregation of physical inactivity in 3 domains (OR = 2.46 [1.14 to 5.32]). However, the multivariate-adjusted model showed significant association between hypertension and physical inactivity in 3 domains (OR = 2.57 [1.14 to 5.79]).

Conclusions:

The results suggest an unequal prevalence of hypertension according to physical inactivity across different domains and increasing the promotion of physical activity in the healthcare system is needed.
Characteristics of groundwater seepage with cut-off wall in gravel aquifer. I: Field observations
Authors: Wu Yong-Xia , Shen Shui-Long , Xu Ye-Shuang , Yin Zhen-Yu
Published: February 2015

This paper presents a case history of the leakage behavior during dewatering tests in the gravel strata of an excavation pit of a metro station in Hangzhou, China. The groundwater system at the test site is composed of a phreatic aquifer underlain by an aquitard and a confined aquifer with coarse sand and gravel. The sandy gravel stratum has very high hydraulic conductivity. The maximum depth of the excavation is 24 m below the ground surface, which reaches the middle of the aquitard strata, where the thickness of the clayey soil is insufficient to maintain the safety of the base of the excavation. To understand the hydrological characteristics of gravel strata, single- and double-well pumping tests were conducted, where a cut-off wall was installed 43 m deep with its base penetrating 2 to 3 m into the aquifer. Test results show that this partial cut-off of the aquifer cannot effectively protect the base of the excavation from the upward seepage force of the groundwater during excavation. Therefore, a new cut-off wall (second phase) was constructed to a depth of 54 m to cut off the confined aquifer. A second pumping test was conducted after the construction of the second phase cut-off wall, and test results show that this full cut-off combined with dewatering can control groundwater effectively during excavation. This finding indicates that when a deep excavation is conducted in a confined aquifer with high hydraulic conductivity, determination of the depth of the retaining wall should be based on three factors: the stability of the base, the upward seepage stability, and settlement control.
LANGUAGES WITH A FINITE ANTIDICTIONARY: SOME GROWTH QUESTIONS
Authors: SHUR ARSENY M.
Published: February 2015

We study FAD-languages, which are regular languages defined by finite sets of forbidden factors, together with their “canonical” recognizing automata. We are mainly interested in the possible asymptotic orders of growth for such languages. We analyze certain simplifications of sets of forbidden factors and show that they “almost” preserve the canonical automata. Using this result and structural properties of canonical automata, we describe an algorithm that effectively lists all canonical automata having a sink strong component isomorphic to a given digraph, or reports that no such automata exist. This algorithm can be used, in particular, to prove the existence of a FAD-language over a given alphabet with a given exponential growth rate. On the other hand, we give an example showing that the algorithm cannot prove non-existence of a FAD-language having a given growth rate. Finally, we provide some examples of canonical automata with a nontrivial condensation graph and of FAD-languages with a “complex” order of growth.
Some bidouble planes with pg= q = 0 and 4 ≤ K2≤ 7
Authors: Rito Carlos
Published: February 2015

We give a list of possibilities for surfaces of general type with pg= 0 having an involution i such that the bicanonical map of S is not composed with i and S/i is not rational. Some examples with K2= 4, …, 7 are constructed as double coverings of an Enriques surface. These surfaces have a description as bidouble coverings of the plane.
An elementary proof of a non-triviality of the E8subfactor planar algebra
Authors: Okazaki Kenta
Published: February 2015

In this paper, we show in a combinatorial way that the 0-box space of the E8subfactor planar algebra is 1-dimensional. In the proof, we improve on Bigelow's relations for the E8subfactor planar algebra and give an efficient algorithm to reduce any planar diagram to the empty diagram.
Spherically symmetric solutions in a FRW background
Authors: Moradpour H. , Riazi N.
Published: February 2015

We impose perfect fluid concept along with slow expansion approximation to derive new solutions which, considering non-static spherically symmetric metrics, can be treated as Black Holes (BHs). We will refer to these solutions as Quasi BHs. Mathematical and physical features such as Killing vectors, singularities, and mass have been studied. Their horizons and thermodynamic properties have also been investigated. In addition, relationship with other related works (including McVittie's) are described.
Using Skew for Classification
Authors: DeBonis Mark J.
Published: February 2015

One classic example of a binary classifier is one which employs the mean and standard deviation of the data set as a mechanism for classification. Indeed, principle component analysis has played a major role in this effort. In this paper, we propose that one should also include skew in order to make this method of classification a little more precise. One needs a simple probability distribution function which can be easily fit to a data set and use this pdf to create a classifier with improved error rates and comparable to other classifiers.
Exploring the Uncertainty Space of Ensemble Classifiers in Face Recognition
Authors: Fernández-Martínez Juan Luis , Cernea Ana
Published: February 2015

In this paper, we present a supervised ensemble learning algorithm, called SCAV1, and its application to face recognition. This algorithm exploits the uncertainty space of the ensemble classifiers. Its design includes six different nearest-neighbor (NN) classifiers that are based on different and diverse image attributes: histogram, variogram, texture analysis, edges, bidimensional discrete wavelet transform and Zernike moments. In this approach each attribute, together with its corresponding type of the analysis (local or global), and the distance criterion (p-norm) induces a different individual NN classifier. The ensemble classifier SCAV1 depends on a set of parameters: the number of candidate images used by each individual method to perform the final classification and the individual weights given to each individual classifier. SCAV1 parameters are optimized/sampled using a supervised approach via the regressive particle swarm optimization algorithm (RR-PSO). The final classifier exploits the uncertainty space of SCAV1 and uses majority voting (Borda Count) as a final decision rule. We show the application of this algorithm to the ORL and PUT image databases, obtaining very high and stable accuracies (100% median accuracy and almost null interquartile range). In conclusion, exploring the uncertainty space of ensemble classifiers provides optimum results and seems to be the appropriate strategy to adopt for face recognition and other classification problems.
Time-dependent particle production and particle number in cosmological de Sitter space
Authors: Greenwood Eric
Published: February 2015

In this paper, we consider the occupation number of induced quasi-particles which are produced during a time-dependent process using three different methods: Instantaneous diagonalization, the usual Bogolyubov transformation between two different vacua (more precisely the instantaneous vacuum and the so-called adiabatic vacuum), and the Unruh–DeWitt detector methods. Here we consider the Hamiltonian for a time-dependent Harmonic oscillator, where both the mass and frequency are taken to be time-dependent. From the Hamiltonian we derive the occupation number of the induced quasi-particles using the invariant operator method. In deriving the occupation number we also point out and make the connection between the Functional Schrödinger formalism, quantum kinetic equation, and Bogolyubov transformation between two different Fock space basis at equal times and explain the role in which the invariant operator method plays. As a concrete example, we consider particle production in the flat FRW chart of de Sitter spacetime. Here we show that the different methods lead to different results: The instantaneous diagonalization method leads to a power law distribution, while the usual Bogolyubov transformation and Unruh–DeWitt detector methods both lead to thermal distributions (however the dimensionality of the results are not consistent with the dimensionality of the problem; the usual Bogolyubov transformation method implies that the dimensionality is 3D while the Unruh–DeWitt detector method implies that the dimensionality is 7D/2). It is shown that the source of the descrepency between the instantaneous diagonalization and usual Bogolyubov methods is the fact that there is no notion of well-defined particles in the out vacuum due to a divergent term. In the usual Bogolyubov method, this divergent term cancels leading to the thermal distribution, while in the instantaneous diagonalization method there is no such cancelation leading to the power law distribution. However, to obtain the thermal distribution in the usual Bogolyubov method, one must use the large mass limit. On physical grounds, one should expect that only the modes which have been allowed to sample the horizon would be thermal, thus in the large mass limit these modes are well within the horizon and, even though they do grow, they remain well within the horizon due to the mass. Thus, one should not expect a thermal distribution since the modes will not have a chance to thermalize.
Structural Damage Detection Using Sensitivity-Enhanced Autoregressive Coefficients
Authors: Wang Zhen , Liu Fang , Yu Lian Qing , Chen Shuang Hong
Published: February 2015

This paper presents an innovative technique for structural damage detection based on time series analysis with feedback controllers incorporated into the structure. The sensitivity of autoregressive (AR) coefficients to element stiffness is first derived, and it is proposed that the sensitivity of the AR coefficients can be enhanced by intentionally assigning the poles of the detection system. Finally, an [Formula: see text] control chart is constructed based on the sensitivity-enhanced AR coefficient. Identification of the occurrence of damage is achieved by monitoring statistically significant changes in the control chart. The proposed methodology is validated by examples including a cantilever Euler beam and Phase I of the IASC-ASCE benchmark structure. The simulation results show that by utilizing the sensitivity-enhanced AR coefficients, the control charts are more sensitive to damage and are capable of detecting small levels of structural damage even in the presence of measurement noise.
Comparing Ranking Methods for Tensor Components in Multilinear and Concurrent Subspace Analysis with Applications in Face Images
Authors: Filisbino Tiene A. , Giraldi Gilson A. , Thomaz Carlos E.
Published: February 2015

In the area of multi-dimensional image databases modeling, the multilinear principal component analysis (MPCA) and concurrent subspace analysis (CSA) approaches were independently proposed and applied for mining image databases. The former follows the classical principal component analysis (PCA) paradigm that centers the sample data before subspace learning. The CSA, on the other hand, performs the learning procedure using the raw data. Besides, the corresponding tensor components have been ranked in order to identify the principal tensor subspaces for separating sample groups for face image analysis and gait recognition. In this paper, we first demonstrate that if CSA receives centered input samples and we consider full projection matrices then the obtained solution is equal to the one generated by MPCA. Then, we consider the general problem of ranking tensor components. We examine the theoretical aspects of typical solutions in this field: (a) Estimating the covariance structure of the database; (b) Computing discriminant weights through separating hyperplanes; (c) Application of Fisher criterium. We discuss these solutions for tensor subspaces learned using centered data (MPCA) and raw data (CSA). In the experimental results we focus on tensor principal components selected by the mentioned techniques for face image analysis considering gender classification as well as reconstruction problems.
MECHANICAL CHARACTERIZATION OF ABDOMINAL AORTIC ANEURYSM WALL IN RAT MODEL TREATED BY MESENCHYMAL STEM CELLS
Authors: ASSOUL NABILA , MOHAND-KACI FAÏZA , ALLAIRE ERIC , ZIDI MUSTAPHA
Published: February 2015

In this work, we study the mechanical properties of abdominal aortic aneurysms (AAAs) treated by cell therapy. Based on the xenograft model in rats, we analyze the effects of the injection of bone marrow mesenchymal stem cells (MSCs) on the stiffness of the arterial wall. Uniaxial tests performed on control, treated and untreated samples, have led to the identification of a nonlinear behavior law, using a mechanical model based on a stress-stretch exponential relation. The comparison of the mechanical behavior shows the benefits of the proposed cell therapy which improves the mechanical strength of the aneurysmal vessel wall. A histological study has shown the favorable change expression of elastin and collagen which are involved in the mechanical behavior of repaired arterial tissue. Thus, this work is part of MSCs biological understanding and it contributes to evaluate the approaches used in cell therapy and regenerative medicine to treat AAAs.
Large-Scale Numerical Simulation of an RC Tunnel Junction Member Using Particle Discretization Scheme FEM
Authors: Sun Fangtao , Tanaka Seizo , Hori Muneo
Published: February 2015

This paper presents a large-scale numerical simulation of a reinforced concrete (RC) tunnel junction member using solid FEM. Particle discretization scheme (PDS), which uses two sets of non-overlapping characteristic functions to discretize displacement field and strain/stress field respectively, is employed to represent the multiple-cracking configurations of concrete. An efficient parallel FE program, called ADVENTURE, is used to implement PDS as well as a reformulated nonlinear concrete constitutive relation. A simplified tunnel junction member, in order to reveal its multiple-cracking behavior under the static load, is studied and the stochastic behavior of cracking is investigated; good agreements are achieved between the simulation results and experimental observations regarding the multiple cracking configurations.
Peristaltic transport of a MHD Carreau fluid in a tapered asymmetric channel with permeable walls
Authors: Kothandapani M. , Prakash J. , Srinivas S.
Published: February 2015

The effect of permeable walls and magnetic field on the peristaltic flow of a Carreau fluid in a tapered asymmetric channel is studied. The tapered asymmetric channel is normally created due to the intra-uterine fluid flow induced by myometrial contractions and it was simulated by asymmetric peristaltic fluid flow in a two-dimensional infinite non-uniform channel. The analysis has been performed under long wavelength and low-Reynolds number assumptions to linearize the governing flow equations. A series solution in respect of a small Weissenberg number is obtained for the stream function, axial pressure gradient and shear stress. Time average of pressure rise and frictional force on the upper wall has also been computed using numerical integration. The results have been presented graphically for the various interested physical parameters. It is observed that for Carreau fluids the peristalsis works as a pump against a greater pressure rise compared with a Newtonian fluid, while there exists no significant difference in free pumping flux for Newtonian and Carreau fluids in the tapered asymmetric channel.
Mathematical modeling of micropolar fluid flow through an overlapping arterial stenosis
Authors: Haghighi Ahmad Reza , Asl Mohammad Shahbazi
Published: February 2015

In this study a mathematical model for two-dimensional pulsatile blood flow through overlapping constricted tapered vessels is presented. In order to establish resemblance to the in vivo conditions, an improved shape of the time-variant overlapping stenosis in the elastic tapered artery subject to pulsatile pressure gradient is considered. Because it contains a suspension of all erythrocytes, the flowing blood is represented by micropolar fluid. By applying a suitable coordinate transformation, tapered cosine-shaped artery turned into non-tapered rectangular and a rigid artery. The governing nonlinear partial differential equations under the imposed realistic boundary conditions are solved using the finite difference method. The effects of vessel tapering on flow characteristics considering their dependencies with time are investigated. The results show that by increasing the taper angle the axial velocity and volumetric flow rate increase and the microrotational velocity and resistive impedance reduce. It has been shown that the results are in agreement with similar data from the literature.
Valuations of skew quantum polynomials
Authors: Acosta Cristian Arturo Chaparro
Published: February 2015

In this paper, we extend some results obtained by Artamonov and Sabitov for quantum polynomials to skew quantum polynomials and quasi-commutative bijective skew Poincaré–Birkhoff–Witt (PBW) extensions. Moreover, we find a counterexample to the conjecture proposed in [V. A. Artamonov, Quantum Polynomial, Advances in Algebra and Combinatorics (World Scientific, 2008)].
Rings with (x, y, z) – (z, y, x) in the right nucleus
Authors: Jayalakshmi K. , Nageswari G.
Published: February 2015

Let R be a semiprime nonassociative ring satisfying (x, y, z)–(z, y, x) ∈ Nr then Nl = Nr where Nl and Nr are Lie ideals of R, the set {x ∈ Nr : (R, R, R)x = 0} = {x ∈ Nl : x(R, R, R) = 0} is an ideal of R, and it is contained in the nucleus. Further if [R, R]Nr ⊂ Nr and R is a prime ring with Nr ≠ 0 then R is either associative or commutative.