bluuebunny/crossref_metadata_2025_split huggingface dataset:
MERRA: NASA’s Modern-Era Retrospective Analysis for Research and Applications
Authors: Rienecker Michele M. , Suarez Max J. , Gelaro Ronald , Todling Ricardo , Bacmeister Julio , Liu Emily , Bosilovich Michael G. , Schubert Siegfried D. , Takacs Lawrence , Kim Gi-Kong , Bloom Stephen , Chen Junye , Collins Douglas , Conaty Austin , da Silva Arlindo , Gu Wei , Joiner Joanna , Koster Randal D. , Lucchesi Robert , Molod Andrea , Owens Tommy , Pawson Steven , Pegion Philip , Redder Christopher R. , Reichle Rolf , Robertson Franklin R. , Ruddick Albert G. , Sienkiewicz Meta , Woollen Jack 
Published: April 2011

Abstract
The Modern-Era Retrospective Analysis for Research and Applications (MERRA) was undertaken by NASA’s Global Modeling and Assimilation Office with two primary objectives: to place observations from NASA’s Earth Observing System satellites into a climate context and to improve upon the hydrologic cycle represented in earlier generations of reanalyses. Focusing on the satellite era, from 1979 to the present, MERRA has achieved its goals with significant improvements in precipitation and water vapor climatology. Here, a brief overview of the system and some aspects of its performance, including quality assessment diagnostics from innovation and residual statistics, is given.
By comparing MERRA with other updated reanalyses [the interim version of the next ECMWF Re-Analysis (ERA-Interim) and the Climate Forecast System Reanalysis (CFSR)], advances made in this new generation of reanalyses, as well as remaining deficiencies, are identified. Although there is little difference between the new reanalyses in many aspects of climate variability, substantial differences remain in poorly constrained quantities such as precipitation and surface fluxes. These differences, due to variations both in the models and in the analysis techniques, are an important measure of the uncertainty in reanalysis products. It is also found that all reanalyses are still quite sensitive to observing system changes. Dealing with this sensitivity remains the most pressing challenge for the next generation of reanalyses.
Production has now caught up to the current period and MERRA is being continued as a near-real-time climate analysis. The output is available online through the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC).
SUNCT syndrome successfully treated by gamma knife radiosurgery: Case report
Authors: Effendi Khaled , Jarjoura Samir , Mathieu David 
Published: April 2011

Background: The SUNCT syndrome (short-unilateral neuralgiform headache with conjunctival injection and tearing) can be very disabling for affected patients and is often refractory to medical management. We report the first case of SUNCT with a successful response to stereotactic radiosurgery without any adverse effect. Case: After failing optimal medical treatment, a 82-year old male patient suffering from SUNCT syndrome was treated with Gamma knife radiosurgery. The trigeminal nerve and sphenopalatine ganglion were targeted with a maximum dose of 80 Gy each. The patient had complete pain cessation 2 weeks after the treatment, and remains pain-free with no medication at the latest follow-up 39 months after radiosurgery. He did not have any side effect from the procedure. Conclusion: Gamma knife radiosurgery is an option for medically refractory SUNCT patients.
Biomechanical Analysis of Chlorhexidine Power Irrigation to Disinfect Contaminated Anterior Cruciate Ligament Grafts
Authors: Han Yung , Giannitsios Demetri , Duke Kajsa , Steffen Thomas , Burman Mark 
Published: April 2011

Background: Accidental graft contamination is a likely complication to occur in an orthopaedic sports medicine surgeon’s career. There are no clinical outcome studies to direct management, and a recent survey showed that preferred management varied. Three liters of 2% chlorhexidine power irrigation has been shown to be an efficient and effective disinfection protocol; however, the biomechanical sequelae of this disinfection protocol to the graft are unknown. Purpose: The purpose of this study was to determine if 3 L of 2% chlorhexidine power irrigation used to disinfect contaminated anterior cruciate ligament (ACL) grafts significantly weakens the graft at time zero. Study Design: Controlled laboratory study. Methods: Eight fresh bovine superficial digital flexor tendons underwent disinfection protocol with 3 L of 2% chlorhexidine power irrigation. Contralateral tendons served as the control. Tendons were preconditioned and loaded to failure. Results: The average ultimate failure load for the control tendons and disinfected tendons was 4081 ± 654.4 N and 4146 ± 723.2 N, respectively. The average ultimate failure stress for the control tendons and disinfected tendons was 97.10 ± 12.03 MPa and 95.18 ± 11.79 MPa, respectively. The average stiffness for the control tendons and disinfected tendons was 546.20 ± 28.16 N/mm and 539.2 ± 25.93 N/mm, respectively. The P values for ultimate failure load, ultimate failure stress, and stiffness showed no statistically significant difference between the chlorhexidine and control tendons. Conclusion: Disinfecting tendons with 3 L of 2% chlorhexidine power irrigation does not adversely weaken the tendon’s tensile mechanical properties. Clinical Relevance: Three liters of 2% chlorhexidine power irrigation can effectively disinfect a contaminated ACL graft without weakening the graft.
A comparison of the experimental and computational modelling of the fluidic turn-up vortex amplifier at full and zero swirl conditions
Authors: Woolhouse R. J. , Tippetts J. R. , Beck S. B. M. 
Published: April 2011

The design and operation of a novel type of fluidic vortex amplifier have been investigated experimentally using model tests with ambient air, and using computationally time-dependent computational fluid dynamics (CFD) simulation. The ultimate objective is to develop a no-moving-part variable air distribution device for implementation within gas turbine combustors using the fuel flow as the controlling agent. Although both liquid and gaseous fuels are ultimate goals of this device, this paper describes the first stage of the work involving operation with nominally uniform density fluid (air). There is some discrepancy between the simulation and test data, but design and performance trends were usefully simulated. An important feature of the CFD was the occurrence of a weak time dependent flow structure, particularly with the Reynolds stress model (RSM). Flow modulation within the desired range (4.5 compared with 2.6) was demonstrated, and these are shown, along with some general points concerning computational modelling convergence and turbulence models.
Monitoring wood decay in poles by the vibroacoustic response method
Authors: Craighead I. A. , Thackery S , Redstall M , Thomas M. R. 
Published: April 2011

Despite recent advances in the development of new materials, wood continues to be used globally for the support of overhead cable networks used by telecommunications and electrical utility companies. As a natural material, wood is subject to decay and will eventually fail, causing disruption to services and danger to public and company personnel. The traditional method of testing poles for decay involves hitting them with a hammer and listening to the sound that results. However, evidence suggests that a large number of poles are replaced unnecessarily and a significant number of poles continue to fail unexpectedly in service. Therefore, a more accurate method for assessing the structural integrity of wooden poles is required. The underlying physical principles behind the ‘pole tester's approach’ have been identified and used in the development of a decay meter to enable objective monitoring of decay in wooden poles.
An artificial neural network module for simulation of the energy storage system of a hybrid electric vehicle
Authors: Bhatikar S. R. , Mahajan R. L. , Wipke K , Johnson V 
Published: April 2011

A hybrid electric vehicle (HEV) is a complex system integrating interactive subsystems of disparate degrees of complexity. The simulation of an HEV thus poses a challenge. An accurate simulation requires highly accurate models of each subsystem. Without these, the system has a poor overall performance. Typically, modelling problems are not amenable to physical solutions without simplifying assumptions that impair their accuracy. Conventional empirical models, on the other hand, are time consuming and data intensive and falter where extensive non-linearity is encountered. An artificial neural network (ANN) approach to simulation of an HEV is presented in this paper. An ANN model of the energy storage system (ESS) of an HEV was deployed in the ADVISOR simulation software developed by the National Renewable Energy Laboratories (NREL) of the US Department of Energy. The ANN model mapped the state of charge (SOC) and the power requirement of the vehicle to the voltage and current at the ESS output An ANN model was able accurately to capture the complex, non-linear phenomena underlying the ESS. A novel performance-enhancing technique for design of ANN training data, Smart Select, is described here. It resulted in a model of 0.9978 correlation (R2 error) with data. ANNs can be data hungry. The issue of knowledge sharing between ANN models to save development time and effort is also addressed in this paper. The model transfer technique presents a way of levering the expertise of one ANN into the development of another for a similar modelling task. Lastly, integration of the ANN model of the ESS into the ADVISOR software, on the MATLAB software platform, is described.
The stability of motorcycles under acceleration and braking
Authors: Limebeer D. J. N. , Sharp R. S. , Evangelou S 
Published: April 2011

A comprehensive study of the effects of acceleration and braking on motorcycle stability is presented. This work is based on a modified version of a dynamic model presented earlier, and is thought to be the most comprehensive motorcycle dynamic model in the public domain. Extensive use is made of both non-linear and linearized models. The models are written in LISP and make use of the multibody modelling package AUTOSIM. There is novelty in the way in which control systems have been used to control the motorcycle drive and braking systems in order that the machine maintains desired rates of acceleration and deceleration. The results show that the wobble mode of a motorcycle is significantly destabilized when the machine is descending an incline or braking on a level surface. Conversely, the damping of the wobble mode is substantially increased when the machine is ascending an incline at constant speed, or accelerating on a level surface. This probably accounts for the pleasingly stable ‘feel’ of the machine under firm acceleration. Except at very low speeds, inclines, acceleration and deceleration appear to have little effect on the damping or frequency of the weave mode. Non-linear simulations have quantified the known difficulties to do with rear tyre adhesion in heavy braking situations that are dominated by rear wheel braking.
Image sequences and wavelets for vibration analysis: Part 2: Extraction of modal dampings and modeshapes
Authors: Patsias S , Staszewski W J , Tomlinson G R 
Published: April 2011

The paper presents the extraction procedure for modal damping and modeshapes from image sequences obtained through the use of optical measurements. The modal dampings are extracted from the image sequence used to identify a cantilever's natural frequencies through the use of the continuous wavelet transform. The identification of the first five vibration modeshapes of the cantilever is attempted. The differences between the theoretical and experimental modeshapes are tracked back to the experimental set-up and a procedure that compensates for this effect is introduced and proved to be successful. The modal assurance criterion (MAC) is computed for the five modes, indicating high correlation for the first four modes, while the fifth was not possible to identify, due to insufficient spatial resolution. The wavelet transform plays a central role, since it is involved in every stage of the analysis: image edge detection, modeshape extraction, natural frequencies identification and modal damping extraction from multi-degree-of-freedom (MDOF) decays. This paper discusses the issues that need to be tackled with optical measurements, such as temporal and spatial resolution of the image sequence acquisition.
Pressure loss and heat transfer mechanisms in a lattice-frame structured heat exchanger
Authors: Kim T , Hodson H P , Lu T J 
Published: April 2011

A novel heat exchanger medium, a high-porosity (0.938) lattice-frame material (LFM), has been introduced for possible use in mechanically and thermally loaded heat exchanger applications. The LFM is made up of circular cylinders, forming tetrahedral unit cells. This paper describes the results of experiments and numerical simulation leading to a detailed understanding of the flow structure, pressure loss and heat transfer mechanisms. It is shown that the circular LFM struts are responsible for approximately 85 per cent of the overall pressure losses in the unit cell by means of form drag at high Reynolds number. The LFM causes heat removal from the substrate by promoting flow mixing and also contributes to the overall heat transfer by convection from the strut surfaces. If a high thermal conductivity material is used, the strut and substrate contribute 57 and 43 per cent respectively of the total heat transfer. Steady numerical simulations show that a porosity of approximately 0.8 provides the best heat transfer performance for a fixed mass flowrate. However, the pressure loss monotonically increases as the porosity decreases within a range of porosity, 0.7 ≤ ε ≤ 0.938.
Heat flux measurement techniques
Authors: Childs P R N , Greenwood J R , Long C A 
Published: April 2011

Heat flux measurement is used in the field of fluid mechanics and heat transfer to quantify the transfer of heat within systems. Several techniques are in common use, including: differential temperature sensors such as thermopile, layered resistance temperature devices or thermocouples and Gardon gauges; calorimetric methods involving a heat balance analysis and transient monitoring of a representative temperature, using, for example, thin-film temperature sensors or temperature sensitive liquid crystals; energy supply or removal methods using, for example, a heater to generate a thermal balance; and, finally, by measurement of mass transfer which can be linked to heat transfer using the analogy between the two. No one method is suitable to all applications because of the differing considerations of accuracy, sensitivity, size, cost and robustness. Recent developments including the widespread availability and application of thin-film deposition techniques for metals and ceramics, allied with advances in microtechnology, have expanded the range of devices available for heat flux measurement. This paper reviews the various types of heat flux sensors available, as well as unique designs for specific applications. Critical to the use of a heat flux measurement technique is accurate calibration. Use of unmatched materials disturbs the local heat flux and also the local convective boundary layer, producing a potential error that must be compensated for. The various techniques in common use for calibration are described. A guide to the appropriate selection of a heat flux measurement technique is provided according to the demands of response, sensitivity, temperature of operation, heat flux intensity, manufacturing constraints, commercial availability, cost, thermal disturbance and acceleration capability for vibrating, rotating and reciprocating applications.
Technical Note: Neural network modelling of the emissions and performance of a heavy-duty diesel engine
Authors: Thompson G. J. , Atkinson C. M. , Clark N. N. , Long T. W. , Hanzevack E 
Published: April 2011

Internal combustion engines are being required to comply with increasingly stringent government exhaust emissions regulations. Compression ignition (CI) piston engines will continue to be used in cost-sensitive fuel applications such as in heavy-duty buses and trucks, power generation, locomotives and off-highway applications, and will find application in hybrid electric vehicles. Close control of combustion in these engines will be essential to achieve ever-increasing efficiency improvements while meeting increasingly stringent emissions standards. The engines of the future will require significantly more complex control than existing map-based control strategies, having many more degrees of freedom than those of today. Neural network (NN)-based engine modelling offers the potential for a multidimensional, adaptive, learning control system that does not require knowledge of the governing equations for engine performance or the combustion kinetics of emissions formation that a conventional map-based engine model requires. The application of a neural network to model the output torque and exhaust emissions from a modern heavy-duty diesel engine (Navistar T444E) is shown to be able to predict the continuous torque and exhaust emissions from a heavy-duty diesel engine for the Federal heavy-duty engine transient test procedure (FTP) cycle and two random cycles to within 5 per cent of their measured values after only 100 min of transient dynamometer training. Applications of such a neural net model include emissions virtual sensing, on-board diagnostics (OBD) and engine control strategy optimization.
Performance evaluation of non-edible vegetable oils as substitute fuels in low heat rejection diesel engines
Authors: Prasad C. M. V. , Krishna M V S M , Reddy C. P. , Mohan K. R. 
Published: April 2011

Search for renewable fuels such as vegetable oils, in particular non-edible vegetable oils, has become more pertinent in the context of the fossil fuel crisis and vehicle population explosion. The drawbacks associated with vegetable oils for use in diesel engines call for a hot combustion chamber. The concept of the low heat rejection diesel engine is gaining prominence for adopting vegetable oils as substitute fuels for conventional diesel fuel. Non-edible vegetable oils such as Pongamia oil and Jatropha curcas oil are found to be efective substitute fuels in the low heat rejection diesel engine. EsteriRcation, preheating and increase in injection pressures have been tried for efective utilization of the vegetable oils. Performance parameters such as the brake specific energy consumption (b.s.e.c.) and exhaust gas temperature (EGT) have been reported for varying magnitudes of brake mean efective pressure (b.m.e.p.) with diferent non-edible vegetable oils as substitute fuels. The pollution levels of black smoke and NOx have been recorded. Combustion diagnosis is also carried out with the aid of a miniature piezoelectric pressure transducer and TDC (top dead centre) encoder.
Gear oil influences on efficiency of gear and fuel economy of cars
Authors: Bartz W. J. 
Published: April 2011

1. First of all, it should be considered that the fuel consumption of a car depends on a set of parameters only partly related to tribology. Their influence is much more pronounced than that of the lubricant. 2. Only the mechanical losses can be decreased by lubricant-related measures. Therefore, the fuel economy improvement that possibly might be realized is rather limited, especially when taking into account the rather high efficiency of gears. 3. When evaluating the influence of viscosity on fuel consumption, the so-called effective viscosity must be taken into account. This is most important for non-Newtonian oils. 4. Reducing the gear oil viscosity by one SAE viscosity grade will result in fuel consumption reductions of 0.2-1.5 per cent at high temperatures and 0.4-2.5 per cent at low temperatures. 5. Using friction modifiers in gear oils, fuel consumption reductions of between 1.0 and 6.0 per cent are realistic. 6. On the basis of a 50 per cent friction reduction maximum fuel consumption reductions between 1.0 and 5.1 per cent by other gear oils are possible, considering different driving programmes. 7. Tests with a real automobile gear resulted in fuel economy improvements of the order of magnitudes of 1 per cent by other gear oils. 8. The results of measurements confirm in principle the calculated estimations.
Full-cycle firing simulation of a pent-roof spark-ignition engine with visualization of the flow structure, flame propagation and radiative heat flux
Authors: Henson J. C. , Malalasekera W 
Published: April 2011

A numerical study is made of how the complex geometry of a pent-roof spark-ignition engine influences the flow field, the flame propagation and, novelly, the instantaneous radiative heat flux. The solver integrates a generalized weighted-sum-of-grey-gases-discrete transfer method radiation model into the computational fluid dynamics code KIVA-II also modified to enable the simulation of open ports and canted valves, wave action effects in the exhaust and mixing-controlled combustion. The full-cycle mean pressure variation is in good agreement with measurements. The overall burning angle of 37° crank angle and peak radiative flux of 210 kW/m2 are also plausible on the basis of published data. Finally, remarkable insight is gained into how the head geometry and flow structure influence flame propagation and in turn how this governs the spatial and temporal variation in radiative heat flux on the cylinder walls.
Convective coolant heat transfer in internal combustion engines
Authors: Robinson K , Hawley J G , Hammond G P , Owen N J 
Published: April 2011

Simple heat transfer correlations are known to underpredict the single-phase convective heat transfer coefficient when applied to internal combustion (IC) engine cooling passages. The reasons for such underprediction were investigated using a specially designed test rig which was operated under a wide variety of test conditions relevant to IC engine operation. Data from this rig study identified that undeveloped flow (fluid dynamically and thermally), surface roughness and fluid viscosity variation with temperature were the physical reasons responsible for the mismatch. Simple empirical heat transfer models have subsequently been extended to take account of these factors and are shown to give much improved correlation with rig data, and data from an engine study. The implications of this work for predicting engine heat transfer in a three-dimensional computational fluid dynamics environment are discussed.
Small spacecraft missions—the US scene
Authors: Turner R F 
Published: April 2011

In current NASA terms a fully fuelled small spacecraft weighs less than 1000 kg. It may be recalled that the first US spacecraft (1958) weighed only 14 kg (virtually a NanoSat by today's standard) and by contrast the Hubble Space telescope (1990) is 10.8 tonnes and was carried aloft inside another spacecraft (the 80 tonne Shuttle). Since 1992 NASA has embarked upon a policy of limiting cost and schedule aspects for its smaller scientific spacecraft in order to promote a structured, but competitive, programme for more frequent research investigations. This marks a departure from the sporadic, expensive, annually reviewed missions of the past. Already this policy has met with success at a time when research budgets are shrinking. The role of these small spacecraft is often complementary to the infrequent class of large observatories and can serve to develop steadily technologies that are then made available to all US programmes. However, the development of low-cost launchers is lagging behind expectations and some short-cuts on spacecraft reliability are questioning the new philosophy. NASA is an organization consisting of many centres, which have to some extent overlapping or complementary programmes. This paper is an attempt to present the thread that runs through the everchanging NASA scene.