bluuebunny/crossref_metadata_2025 huggingface dataset:
Improving the directional stability of a traction control system without additional sensors
Authors: Jung H , Kwak B , Park Y
Published: April 2011

The traction control system (TCS) comprises a slip control subsystem and a directional stability subsystem. The slip controller can enhance the traction performance by maintaining the slip ratio within an appropriate range. Additional information about the lateral behaviour of the vehicle is necessary to enhance the directional stability during cornering or lane change on slippery roads. With an assumption of slowly varying steering input, a new method to measure the mixture of yaw rate and lateral acceleration, using the speed difference of non-driven wheels, is proposed. Using this measurement, the controller imposes independent pressure to each driven wheel and improves the stability during cornering on slippery roads or acceleration on split-μ roads without additional sensors such as yaw rate and lateral acceleration sensors. The proposed method is verified through simulation based on a 15-degrees-of-freedom (15 DOF) passenger car model.
Fracture tolerance of the male forearm: The effect of pronation versus supination
Authors: Duma S M , Schreiber P H , McMaster J D , Crandall J R , Bass C R
Published: April 2011

This paper presents the dynamic injury tolerance of the male forearm, derived from dynamic three-point bending tests using ten male cadaver upper extremities. The impact loading conditions were chosen to be representative of those observed during upper extremity interaction with frontal air bags. Using matched forearm pairs, it was determined that the forearm is significantly ( p = 0.01) stronger in the supinated position, 126±13 N m, than in the pronated position, 108 ± 8 N m. Two distinct fracture patterns were seen for the pronated and supinated groups. In the supinated position the average difference in fracture time between the radius and ulna was not significantly different ( p = 0.24); however, the pronated tests yielded an average difference in fracture time that was significantly different ( p = 0.05), with the ulna breaking before the radius in every test. This trend implies that in the pronated position the ulna and radius are loaded independently, while in the supinated position the ulna and radius are loaded together as a combined structure. To produce a conservative injury criterion, only the data from the pronated tests were included for an average failure tolerance of 108 N m. It is anticipated that these data will provide injury reference values for the male forearm during driver air bag loading.
The design of overlapped crankshafts. Part 2: Web shape
Authors: Warrior N A , Sime A P , Hyde T H , Fessler H
Published: April 2011

The boundary element (BE) technique was used to analyse nine widely different shapes to investigate the effects of crankweb shape on the peak stresses in the crankpin/web and journal/web fillets and on the crankshaft. Under radial three-point bending, pure radial bending and torsion, increasing the web thickness or increasing the overlap reduces the peak fillet stresses and stiffens the crankshaft. Empirical equations are presented for the maximum stresses in both types of bending, torsion, web spread and twist.
Bouncing of the diesel injector needle at the closing stage
Authors: Lee J H , Cho S , Lee S Y , Bae C
Published: April 2011

An experiment has been performed to examine the phenomenon of the after-injection (secondary injection) of diesel fuel at the closing stage of needle motion in a single-spring diesel injector. A simplified analytical model has been proposed to describe needle bouncing. Needle bouncing was confirmed by spray visualization to be the primary cause of after-injection. The needle motion was well simulated by the proposed model. A series of parametric studies have been performed to find the effects of injector design parameters and operating conditions. Needle bouncing becomes small with a larger damping force by fluid shear at the needle surface. It can also be reduced by decreasing the material stiffness and installation displacement of the needle spring, the equivalent stiffness of the needle seat and the injector body and the maximum needle lift. The possibility of optimizing the injector design to reduce after-injection is discussed.
Fifth percentile female dummy upper extremity interaction with a deploying side air bag
Authors: Duma S M , Crandall J R , Pilkey W D , Seki K , Aoki T
Published: April 2011

This paper presents the results from experiments designed to characterize the upper extremity response of the small female during side air bag loading. A seat-mounted thoracic side air bag was deployed statically using three different inflators. The aggressivity of the inflators varied in peak pressure and pressure onset rate. The fifth percentile female HIII dummy was utilized in three positions, which were chosen to maximize loading of the humerus and elbow joint. Two had the dummy positioned outboard with the forearm on the armrest, and the third had the dummy inboard such that the humerus was positioned horizontally in front of the air bag module with the forearm supported above the armrest. Instrumentation for the fifth percentile female dummy included the fully instrumented SAE upper extremity with six axis load cells in the humerus and forearm as well as accelerometers and angular rate sensors attached to each segment. All inflators produced resultant humerus moments below published injury tolerance values for the small female, with the more aggressive air bags producing higher responses. The upper extremity proved useful in evaluating injury risk relative to side air bag design.
On car steering torques at parking speeds
Authors: Sharp R S , Granger R
Published: April 2011

The steering torque at the handwheel, necessary to steer a car at zero speed, is discussed. Measurements made on a tyre alone on a static rig and measurements made on a car in normal trim are complemented by a mathematical system model. The model uses parameter values deriving partly from the tyre rig results, partly from the car specification and partly from the car results. It provides simulated behaviour matching that from the car experiments. It therefore provides a basis for understanding the results obtained and for predicting the results of design and operating changes. The various physical mechanisms involved in the steering torque are identified and their relative magnitudes, for the case considered, are established. The role of steering offset receives particular attention.
Improvement of perceived vehicle performance through adaptive electronic throttle control
Authors: Tuplin S , Best M C , Passmore M A
Published: April 2011

With the advent of production electronic throttle control there is scope for increased customer satisfaction through the optimization of the throttle pedal demand map to individual drivers. The aim of this study is to develop algorithms to identify, from variables measured in real time on a test vehicle, the requirement for and the direction of adaptation of throttle pedal progression. An on-line appraisal procedure has been developed to identify the individual ‘ideal’ progression (IIP) for any driver. During the appraisal the subject is exposed to a series of pedal progressions, and their verbal response to each change is used to converge to their optimal setting. Vehicle data acquired on these appraisal drives have been regressed against IIP in a full factorial study, and the most statistically significant driver model established. A preliminary implementation of the model is used to demonstrate that throttle progression adapts appropriately towards IIP, thereby matching vehicle performance feel to driver expectations.
Multidisciplinary design optimization of engine mounts with consideration of the driveline
Authors: Suh M-W , Shim M-B , Kim M-S , Hong S-K
Published: April 2011

This paper discusses the multidisciplinary design optimization of an engine system to improve the idle refinement of the vehicle and to remove the possibility of interaction between the powertrain system and vehicle systems. The driveline model attempts to provide practical support to engine mount development by providing sufficient detail for design modification assessment in a stable and efficient modelling environment. By applying forced vibration analysis for vehicle systems and mode decouple analysis for the engine mount system to the design of the engine mount, it is shown that an improved optimization result is obtained.
A three-dimensional kinematic model for compound crank axle suspension mechanism
Authors: Mántaras D A , Luque P , Vera C
Published: April 2011

A three-dimensional model is presented of the kinematic behaviour of a compound crank axle suspension system. A general approach is put forward to determine the main parameters (camber, steer angle, toe in/out) that influence the handling of the vehicle as a function of the operational factors of the system. The input data are the suspension geometry and the travel of the struts. The model has been applied to a standard vehicle, and the validity of the results has been proven.
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.
A generic fuzzy electrohydraulic steering controller for off-road vehicles
Authors: Zhang Qin
Published: April 2011

A fuzzy controller, unlike most other mathematical model-based controllers, incorporates human heuristic knowledge on how to control a plant. Since the representation of the heuristic knowledge for controlling similar plants is often the same, it is possible to design a generic fuzzy controller to control those plants. This paper presents a method for designing a generic fuzzy electrohydraulic steering controller usable for various types and/or models of wheel-type off-road vehicle. This research found that it was possible to design one generic fuzzy controller to steer different types and/or models of wheel-type vehicle having similar steering mechanisms. The only required modification was to redefine the domain of fuzzy values to make them represent the controllable range of the particular steering actuating system. Validation tests verified that this generic fuzzy controller was capable of accomplishing satisfactory steering control on five types and/or models of agricultural vehicle.
An operation algorithm with state of charge recovery for a parallel-type hybrid vehicle
Authors: Choi Dookhwan , Im Moonhyuk , Kim Hyunsoo
Published: April 2011

In this work, an algorithm for the operation of a hybrid powertrain is proposed for a parallel hybrid electric vehicle (HEV). The operation algorithm suggested in this work yields the operating points where the operational cost of the HEV is minimal at each state of charge (SOC). The operational cost of an HEV is calculated considering both the cost of fossil fuel consumed by the engine and the cost of electricity consumed by the electric motor. A weighting function of SOC, which is inversely proportional to the SOC, is applied to the estimation of electricity cost. By the effect of a weighting function of the SOC, it is expected that the algorithm has the property of SOC recovery. Computer simulations are carried out in order to test the suggested algorithm, and simulation results show that the final SOC is recovered to the middle band of the SOC as the operation of the HEV is continued, regardless of initial SOC values.
Performance of a direct injection diesel engine fuelled with a dimethyl ether/diesel blend
Authors: Hewu Wang , Longbao Zhou
Published: April 2011

A quantity of 10 per cent dimethyl ether (DME) was added to diesel fuel, and an investigation of the performance of a direct injection (DI) diesel engine fuelled with blend fuel was carried out. The test results showed that, in comparison with diesel operation, the torque at low engine speed was increased; the brake specific fuel consumption (b.s.f.c.) with speed characteristics at full load was reduced by 20 g/kW h on average; the smoke was reduced significantly, and the coeffcient of light absorption of smoke decreased by 50 per cent; the NOx and HC emissions were also clearly reduced, and the CO emission was at the same level as that of a diesel engine.
A study of heat flux in a constant-volume combustion chamber
Authors: Lee Chi-Woo , Kim Chi-Won , Kim Si-Pom
Published: April 2011

In the production of internal combustion engines, there has been a move towards the development of high-performance engines with fuel economy, lighter weights and smaller sizes. These trends help to answer problems related to thermal load and abnormal combustion, etc., in these engines. In order to clarify these problems, a thin film-type probe for instantaneous measurement of surface temperatures has been suggested. A method for manufacturing such a probe was established in this study. The instantaneous surface temperature of a constant-volume combustion chamber was measured by this probe, and heat flux was calculated and analysed with a Fourier series. For a thorough understanding of the characteristics of combustion, the authors measured the wall temperature of the combustion chamber and computed heat flux through a cylinder wall while varying the protrusion height of the probe. To achieve the above goals, an instantaneous temperature probe was developed, thereby making possible the analysis of the instantaneous temperature of the wall surface and unsteady heat flux in the constant-volume combustion chamber.
Development of compressed natural gas/diesel dual-fuel turbocharged compression ignition engine
Authors: Shenghua Liu , Ziyan Wang , Jiang Ren
Published: April 2011

A natural gas and diesel dual-fuel turbocharged compression ignition (CI) engine is developed to reduce emissions of a heavy-duty diesel engine. The compressed natural gas (CNG) pressure regulator is specially designed to feed back the boost pressure to simplify the fuel metering system. The natural gas bypass improves the engine response to acceleration. The modes of diesel injection are set according to the engine operating conditions. The application of honeycomb mixers changes the flowrate shape of natural gas and reduces hydrocarbon (HC) emission under low-load and lowspeed conditions. The cylinder pressures of a CI engine fuelled with diesel and dual fuel are analysed. The introduction of natural gas makes the ignition delay change with engine load. Under the same operating conditions, the emissions of smoke and NOx from the dual-fuel engine are both reduced. The HC and CO emissions for the dual-fuel engine remain within the range of regulation.
Dynamic contact analysis for the valvetrain dynamics of an internal combustion engine by finite element techniques
Authors: Lee Kisu
Published: April 2011

The full equations of motion of the valvetrain of an internal combustion engine formulated by finite element techniques are solved by imposing the contact conditions. Velocity and acceleration constraints as well as displacement constraints are imposed on the contact points by an iterative scheme similar to the augmented Lagrangian multiplier method for stability of the solution. The valve spring is also modelled by employing rod elements, and surging with the coil collisions is computed by the contact conditions.
Comparative analysis for bus side structures and lightweight optimization
Authors: Lan F , Chen J , Lin J
Published: April 2011

Lightweight structures in bus body design have been highlighted. In this investigation a new typical medium-sized bus body structure has been modelled and analysed using the computer aided design (CAD) package UG and finite element (FE) solver ANSYS. This paper presents a comparative analysis of two body side structures: with and without structural supporting members between the longitudinal waist beams of the side frames. Firstly, analysis of structure strength and stiffness for low-order vibration modes was carried out, and the effects of different structures on strength, rigidity and material use efficiency were examined. Corresponding experimentation was carried out to validate the simulation results. Secondly, sensitivity studies and structural optimization were performed to reduce body weight without losing overall strength and rigidity. Geometric parameters, including cross-sectional parameters and wall thickness, of large structural members are considered in the optimization. The results of the research provide a means of structural design optimization with consideration of bus body weight reduction.
Structures of flow around a full scale side mirror of a car with relevance to aerodynamic noise
Authors: Dölek Ö , Özkan G , Özdemir I B
Published: April 2011

Noise radiated from a side mirror has been studied using spatial and temporal characteristics of surface-pressure fluctuations. The relevant structures of turbulent flow were examined by visualization and by local measurements of dynamic pressure behind a full-scale side mirror, which was placed in a wind tunnel and exposed to an approach velocity of 42 m/s. The results showed that sudden changes of surface curvature and flow separations behind the mirror support led to the generation of significant pressure fluctuations. The wake vortices were strongly influenced by the curvature effects at the corners of the mirror casing, which resulted in selective amplification of naturally occurring modes. As a result, turbulent energy was transferred from large-scale vortices to smaller scales and this process was promoted by the interactions with the vortices shed from the mirror support.
Transversal tyre road characteristic estimation
Authors: Cadiou J C , El Hadri A
Published: April 2011

This paper presents two methods for lateral tyre/road characteristic identification. The proposed methods are estimation based on simulation (EBS) and estimation based on observer (EBO). The first method is based on the development of a vehicle dynamics simulation whereas the second is based on a vehicle dynamics observation. In the EBS method, a vehicle simulator is used to replay certain road tests assuming that only the side force characteristic is unknown. The EBO method uses an observer to reconstruct vehicle dynamics and thus estimate tyre forces. For both methods a tyre characteristic described by a reduced Bakker—Pacjeka tyre model is used to characterize the tyre / road interface. The principle of the proposed procedures consists in the use of an iterative process based on the minimization of quadratic error in order to find the optimal tyre characteristic. To evaluate the proposed procedures, some experimental results were performed. The results are obtained off line on the basis of a set of test data. The originality of these approaches is to have a simple method and a less expensive technique for the characterization of the tyre/road interface.
Heat pump supplemental heating system for motor vehicles
Authors: Antonijevic D , Heckt R
Published: April 2011

The paper deals with the importance of supplemental heating of motor vehicles and the possibilities of automotive heat pump system utilization. A prototype heat pump system for motor vehicles has been developed, built in a test vehicle and tested at low-temperature working conditions. Results have been analysed and the system compared with the other current-production supplemental heating systems. The proposed automotive heat pump heating system has been found to be superior to other automotive supplemental heating solutions regarding the parameters of performance, fuel consumption and operational behaviour.
Modelling and analysis of powertrain hybridization on all-wheel-drive sport utility vehicles
Authors: Liao G Y , Weber T R , Pfaff D P
Published: April 2011

Four concepts of strong hybridization powertrains on all-wheel-drive sport utility vehicles are presented. These concepts enable conversion of conventional powertrains into strong hybrid powertrains with minimal tear-up to the existing architecture. The first concept incorporates an electric machine attached to the output side of a conventional transmission. The second concept is a strong input power-assist system, where the motor is packaged between the torque converter and the transmission. The third concept is similar to the second one, but the torque converter is replaced by a starting clutch. The fourth concept is a compound-input, power-split, electric-variable transmission (EVT). These concepts provide extensive hybrid functionality, such as motor-only drive, launch assist, and energy recuperation. Simulation results indicate that proposed strong hybrid concepts can result in fuel economy gains of 19-26 per cent over conventional powertrains.
Performance and exhaust emissions test results from a liquid propane injected engine with hydrogen enrichment
Authors: Choi Gyeung Ho , Han Sung Bin
Published: April 2011

This paper investigates the effect of performance and exhaust emissions test results from a liquid propane injected engine with hydrogen enrichment. In order to research this topic, the test engine was run at 1400 rpm with a compression ratio of eight. Relative air—fuel varied between 0.8 and 1.3. CO emissions decreased with the addition of hydrogen, but the oxygen amount decreased around the rich and stoichiometric air—fuel ratio as the hydrogen supplement rate increased. CO emissions decreased with the increase in the hydrogen supplement rate. Total hydrocarbon emissions decreased as hydrogen was added in the rich and around stoichiometic air—fuel ratio. NOx emissions were maximum at around λ = 1.2 and the addition of 20 per cent hydrogen resulted in about a 20 percent increase in the amount of NO x emissions compared to that of pure LPG combustion. Power and thermal efficiency increased with the decrease of the hydrogen supplement rate.
Modelling a variable valve timing spark ignition engine using different neural networks
Authors: Beham M , Yu D L
Published: April 2011

In this paper different neural networks (NN) are compared for modelling a variable valve timing spark-ignition (VVT SI) engine. The overall system is divided for each output into five neural multi-input single output (MISO) subsystems. Three kinds of NN, multilayer Perceptron (MLP), pseudo-linear radial basis function (PLRBF), and local linear model tree (LOLIMOT) networks, are used to model each subsystem. Real data were collected when the engine was under different operating conditions and these data are used in training and validation of the developed neural models. The obtained models are finally tested in a real-time online model configuration on the test bench. The neural models run independently of the engine in parallel mode. The model outputs are compared with process output and compared among different models. These models performed well and can be used in the model-based engine control and optimization, and for hardware in the loop systems.
Review and analysis of variable valve timing strategies—eight ways to approach
Authors: Hong H , Parvate-Patil G B , Gordon B
Published: April 2011

In internal combustion engines, particularly for spark ignition (SI) engines, valve events and their timings have a major influence on the engine's overall efficiency and its exhaust emissions. Because the conventional SI engine has fixed timing and synchronization between the camshaft and crankshaft, a compromise results between engine efficiency, performance, and its maximum power. By using variable valve timing (VVT) technology it is possible to control the valve lift, phase, and valve timing at any point on the engine map, with the result of enhancing the overall engine performance. To get full benefits from VVT, various types of mechanisms have been proposed and designed. Some of these mechanisms are in production and have shown significant benefits in improving engine performance. During the last two decades, remarkable developments have been seen in the field of VVT. This paper reviews the literature in the technology of intake and exhaust philosophies of VVT and their effects on the pressure—volume (PV) cycle of the engine. A single-cylinder engine is simulated by the GT-Power software. The effects of different VVT philosophies from the simulations are analysed and compared to those of the literature reviewed.
Simulation for high efficiency liquefied petroleum gas engine development
Authors: Lee Seang-Wock , Daisho Yasuhiro
Published: April 2011

It has been recognized that alternative fuels, such as liquid petroleum gas (LPG), have less polluting combustion characteristics than diesel fuel. Furthermore, when LPG direct-injection, stratified-charge combustion can be adopted in the spark-ignition engine in place of the conventional premixed spark-ignition combustion, it will be possible to achieve less polluting and more efficient combustion characteristics. However, the physical properties of LPG, such as boiling point (—40-0°C) and viscosity, differ largely in comparison with current fuels. Therefore, there are many unknown phenomena in the behaviour of spray, mixture formation, and combustion of LPG in the cylinder. These issues make the development of a high-efficiency LPG engine difficult. Thus, in this study, a numerical method has been adjusted to predict the mixture formation and combustion of LPG. KIVA-3 code was used for this purpose, and tuning factors were adjusted by comparing them with the measurements. In the combustion model, the eddy-dissipation combustion model proposed by Magnussen and Hjertager [1] is adopted. The predicted results show favourable agreement with the measurements and the possibility of useful methods to improve engine performance.
Catalyst regeneration via chemical treatment and emission tests at idle speeds
Authors: Arapatsakos C. I. , Sparis P. D.
Published: April 2011

The present paper examines the possibility of chemical treatment of used catalysts for the purpose of improving catalytic efficiency. The proposed method inserts the catalyst in a bath of a strong organic solvent that dissolves oil, soot and fuel residues, cleaning the active surface of the catalyst. The tests were conducted at low (750 r/min) and high (3100 r/min) idle speeds. The experimental results based on CO, HC and catalyst inlet-outlet temperature difference measurements indicate that after treatment the catalytic efficiency improves considerably (>25 per cent) at low idle (750 r/min). The improvement is even higher at high idle (3100 r/min), exceeding 40 per cent. Therefore, there are strong indications that, if car catalysts underwent a similar treatment at regular service intervals, e.g. every 20 000 km, engine emissions could be considerably reduced and catalyst operational life extended.
Non-linear simulation of coupled rotor-fuselage response using symbolically derived equations of motion. Part 1: Derivation
Authors: Robinson C S , King R L , Wood E R
Published: April 2011

This paper presents a new simulation method for ground and air resonance stability analysis of helicopter rotor systems. The method presented is based on the formulation of the full non-linear equations of motion of three rigid offset blades with degrees of freedom in the flap and lead/lag and a hub that has two translational degrees of freedom for the body. The set of non-linear equations of motion is developed by the Lagrangian method using symbolic processing software for expanding the equations. In addition, the symbolic software automatically converts the equations of motion into a source code that is optimized for numerical integration. Part 1 of this paper addresses the derivation of the equations of motion for the rotor-body combination. Part 2 of this paper addresses the comparison of simulation output to referenced works and includes several unique applications that take advantage of the non-linear capability of the resulting simulation.
Non-linear simulation of coupled rotor-fuselage response using symbolically derived equations of motion. Part 2: Confirmation and illustrative cases
Authors: Robinson C S , King R L , Wood E R
Published: April 2011

This paper presents a unique simulation method for the ground and air resonance of helicopter rotor systems; the derivation of the full non-linear equations of motion for a rotor-body combination with three rigid blades was discussed in Part 1 of this paper. This section, Part 2, addresses the confirmation of the simulation and includes several unique applications that take advantage of the non-linear capability of the resulting simulation. The symbolic processing software that performed the derivation converted the equations of motion into a high-level language. This code is then incorporated into an interactive numerical methods environment. The modelling method includes all terms, including non-linear and trigonometric functions, and produces inherently highly reliable code results from eliminating manual coding of the equations of motion.
Effect of angle-of-turn on the performance of divided intake ducts
Authors: Bharani S , Singh S N , Seshadri V , Chandramouli R
Published: April 2011

Investigations using computational fluid dynamics (CFD) have been carried out on divided intake ducts having angles-of-turn as 22.5°/22.5°, 30°/30° and 458/458 and area ratios of 2 and 3. It is observed that the core flow in the duct remains towards the convex walls up to the outlet plane with lower magnitudes in the centre of plane. Cross-velocity magnitudes are found to be less than 10 per cent of the longitudinal velocity at the outlet plane. Pressure recovery is found to decrease with the increase in the angle-of-turn for both area ratios.
The application of laser measurement techniques to aerospace flows
Authors: Lawson N J
Published: April 2011

Laser measurement techniques are becoming more commonly applied to many areas of thermofluids and heat transfer. An area of their application, which presents highly challenging requirements, is in the measurement of aerospace flows. In this case the experimentalist may encounter high mass flowrates, high-speed flows and in some cases high temperatures, and the measurements may also have to be taken with restricted optical access. Such types of flow have already been measured using established laser techniques such as particle image velocimetry, laser Doppler anemometry, laser-induced fluorescence and liquid crystal thermography. Other more recent techniques which have seen application include Doppler global velocimetry and molecular tagging velocimetry for velocity measurement and thermographic phosphor thermometry for surface temperature measurement. This paper reviews the most recent advances in laser techniques and their application to aerospace environments.
Oxidation of high-temperature coatings
Authors: Evans H E , Taylor M P
Published: April 2011

Nickel-based superalloys used in stressed situations at high temperatures tend to be optimized for mechanical properties and have insufficient aluminium to form a continuous surface layer in service to provide long-term protection against oxidation. This deficiency can be met through the use of coatings that have higher aluminium contents and which form a protective alumina layer during service. These can take the form of metallic overlays or diffusion coatings, both of which can also form a bondcoat layer within thermal barrier coatings (TBCs). Factors which lead to loss of aluminium through oxidation and interdiffusion are discussed in this article. A consequence of excessive aluminium depletion is the formation of non-protective oxides which can be particularly deleterious in TBCs.
Unsteady flow around suction elbow and inlet guide vanes in a centrifugal compressor
Authors: Cui M M
Published: April 2011

Suction elbow and inlet guide vanes (IGVs) are typical upstream components in front of the first-stage impeller in a centrifugal compressor. As the flow field in the front of the impeller is subsonic, the flow motion induced by the rotating impeller interacts with the elbow and IGVs. These interactions induce turbulent unsteady flows inside compressors. The resulting unsteadiness affects efficiency, vibration, and noise generation of the compressor. To understand the mechanism controlling the interactions between upstream components and to optimize the compressor design for better efficiency and reliability, the turbulent unsteady flow inside the first stage of the compressor was simulated. The model included the suction elbow, IGV housing, and firststage impeller. HFC 134a was used as the working fluid. The thermodynamic and transport properties of the refrigerant gas were modelled by the Martin-Hou equation of state and power laws, respectively. The three-dimensional unsteady flow field was numerically simulated. The overall performance parameters were obtained by integrating the field quantities. The force, torque, and the arm of moments acting on the IGVs were then calculated. The results can be used to design IGVs and their motion control system to achieve higher efficiency and improve reliability.
Fault diagnosis of inertia sensor in missile control systems
Authors: Liu X C , Pan Q , Liang Y , Cheng Y M , Zhang H C , Yuan Q
Published: April 2011

Because the magnitude of each order of oscillation signals in the yaw and roll channels of missile control systems varies with various influences, it is impossible to diagnose faults in the sensors of these channels using modelbased fault diagnosis. Based on the characteristics of the systems, a method of fault diagnosis with adjacent wavelet coefficient algorithm is given. Further, based on the difference between the characteristics of the Mallat wavelet coefficients and that of Coilflets wavelet, different algorithms are given. Then, thresholds can be properly selected and abrupt faults diagnosed. A method to diagnose disconnection or short circuit faults is also proposed according to the zone of the current and the zone of voltage when the fault occurs gradually. The combination of these two methods effectively solves fault diagnosis problems of sensors in missile control systems.
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.
Low-cost orbit manoeuvres for minisatellites using novel resistojet thrusters
Authors: Sweeting M N , Lawrence T , Leduc J
Published: April 2011

Electric propulsion using resistojets operating at low power (~100 W) and using liquid propellants have re-emerged as attractive propulsion options for small satellites. Compared to low-power pulsed plasma thrusters (PPT), the resistojet achieves 50 times the increase in thrust (~1–50 mN), which is necessary to overcome drag at solar maximum for small satellites in high drag obits (~200 km). Two resistojet thrusters have been developed at the Surrey Space Centre (SSC), which utilize a packed bed of silicon carbide (SiC) particles for the heat exchanger. A thermodynamic model has been developed to study and optimize the thruster design and a series of practical performance tests with both nitrous oxide and water as propellants has been completed at the USAF Research Lab (Edwards AFB) using the NASAJPL inverted pendulum thrust stand. Endurance tests (~300 h duration) were conducted to determine possible lifetime limitations or failure modes. The results are very encouraging and resistojet thrusters are now proposed as options for future USAF and SSC minisatellite missions. This paper describes the complete resistojet system, test results for the USAF Mighty Sat II. I and its flight performance, its performance and integration on the UoSAT-12 minisatellite and its launch in April 1999 where this novel technique was demonstrated for the first time in low Earth orbit on 26 July 1999.
Development of the STRV 1c and 1d mission based on the experiences of STRV 1a and 1b
Authors: Wells N S
Published: April 2011

Following the successful launch in June 1994 and subsequent operations in the geosynchronous transfer orbit of the space technology research vehicle (STRV 1a and STRV 1b) spacecraft, the Defence Evaluation and Research Agency conducted a feasibility study and project definition phase for a follow-on mission. Having successfully completed these phases, the detailed design and construction of the STRV 1c and 1d spacecraft are now well advanced and a launch date is planned in early 2000. The mission objectives for the follow-on spacecraft are the same as they were for the initial mission, i.e. to enable international governments and industry to enhance operational space missions by proving new technologies in the highly stressing environment of the orbit aboard a low-cost, short time-scale series of small (>100 kg) satellites.

The author provides a description of the design of the STRV 1c and 1d spacecraft and ground segment and discusses the necessary evolution from the first mission design.
Robot- and computer-assisted craniotomy (CRANIO): From active systems to synergistic man—machine interaction
Authors: Cunha-Cruz V , Follmann A , Popovic A , Bast P , Wu T , Heger S , Engelhardt M , Schmieder K , Radermacher K
Published: April 2011

Computer and robot assistance in craniotomy/craniectomy procedures is intended to increase precision and efficiency of the removal of calvarial tumours, enabling the preoperative design and manufacturing of the corresponding implant. In the framework of the CRANIO project, an active robotic system was developed to automate the milling processes based on a predefined resection planning. This approach allows for a very efficient milling process, but lacks feedback of the intra-operative process to the surgeon. To better integrate the surgeon into the process, a new teleoperated synergistic architecture was designed. This enables the surgeon to realize changes during the procedure and use their human cognitive capabilities. The preoperative planning information is used as guidance for the user interacting with the system through a master—slave architecture. In this article, the CRANIO system is presented together with this new synergistic approach. Experiments have been performed to evaluate the accuracy of the system in active and synergistic modes for the bone milling procedure. The laboratory studies showed the general feasibility of the new concept for the selected medical procedure and determined the accuracy of the system. Although the integration of the surgeon partially reduces the efficiency of the milling process compared with a purely active (automatic) milling, it provides more feedback and flexibility to the user during the intra-operative procedure.

Editor's note: This paper was commissioned for this Image Guided Surgery special issue, but has been published in an earlier issue. It can be found in Proc. IMechE, Part H: J. Engineering in Medicine, 2010, 224(H3), 441–452. DOI: 10.1243/09544119JEIM596.
A Dissociation Between Judged Causality and Imagined Locations in Simple Dynamic Scenes
Authors: Levillain Florent , Bonatti Luca L.
Published: April 2011

To mentally extrapolate the trajectory of a moving object that disappears from sight, different sources of information can be exploited: memory of its last visible position, its inferred movement through time, and general understanding of the causal structure of the scene. It is often assumed that these cues are integrated into unified analog mental representations. In our experiment, participants predicted the position of an object that disappeared behind an occluder and estimated the degree to which the movement was caused by another object. They made considerable errors in predicting imagined displacements. Moreover, their predictions were misaligned with their judgments of causality. They predicted the positions of the invisible moving objects better in events that they judged less causally correct than in events that they judged more causally correct. These results suggest that physical and cognitive parameters of imagined dynamic events do not merge into unitary mental models simulating actual states of the world.
The Use of Definite References Signals Declarative Memory
Authors: Duff Melissa C. , Gupta Rupa , Hengst Julie A. , Tranel Daniel , Cohen Neal J.
Published: April 2011

Language function in patients with impaired declarative memory presents a compelling opportunity to investigate the inter-dependence of memory and language in referential communication. We examined amnesic patients’ use of definite references during a referential communication task. Discursively, definite references can be used to mark a referent as situationally unique (e.g., “the game,” as in the case of a recently publicized game) or as shared information (e.g., “the game,” as in one discussed previously). We found that despite showing normal collaborative learning after repeated referring—as indexed by consistent and increasingly efficient descriptive labels for previously unfamiliar tangram figures—amnesic patients did not consistently use definite references in referring to those figures. The use of definite references seems to be critically dependent on declarative memory, and the engagement of such memory is signaled by language.
Community Norms About Suppression of AIDS-Related Prejudice and Perceptions of Stigma by People With HIV or AIDS
Authors: Miller Carol T. , Grover Kristin W. , Bunn Janice Yanushka , Solomon Sondra E.
Published: April 2011

We investigated the relationship between community motivations to control AIDS-related prejudice and the experience of stigma by community members with HIV or AIDS, using self-reports from 203 New England residents with HIV or AIDS and 2,444 randomly selected residents of the same New England communities. Multilevel regression analyses revealed that the disclosure concerns of participants with HIV or AIDS were lower in communities where residents were motivated by personal values to control AIDS-related prejudice, and were higher in communities where residents were motivated by social pressure to control AIDS-related prejudice. Reported experiences with discrimination and exclusion were unrelated to community motivations. The results of our study suggest that external and internal pressures to control prejudice shape the experience of stigmatization.
Stuck in the Middle
Authors: Bonezzi Andrea , Brendl C. Miguel , De Angelis Matteo
Published: April 2011

The classic goal-gradient hypothesis posits that motivation to reach a goal increases monotonically with proximity to the desired end state. However, we argue that this is not always the case. In this article, we show that motivation to engage in goal-consistent behavior can be higher when people are either far from or close to the end state and lower when they are about halfway to the end state. We propose a psychophysical explanation for this tendency to get “stuck in the middle.” Building on the assumption that motivation is influenced by the perceived marginal value of progress toward the goal, we show that the shape of the goal gradient varies depending on whether an individual monitors progress in terms of distance from the initial state or from the desired end state. Our psychophysical model of goal pursuit predicts a previously undiscovered nonmonotonic gradient, as well as two monotonic gradients.
What It Pays to Know About a Close Other
Authors: Friesen Charity A. , Kammrath Lara K.
Published: April 2011

Researchers have debated the benefits of having accurate knowledge about a close other’s personality. However, the existing research has examined personality knowledge solely in terms of traits. Although trait knowledge may be useful during relationship selection, we hypothesize that once a relationship becomes established, accurate personality knowledge about the other person’s if-then profiles—the person’s characteristic patterns of responses to situations—may be particularly beneficial. We conducted the first study of if-then accuracy in close relationships. To do so, we developed the If-Then Trigger Profile Questionnaire, which consists of 72 descriptions of potentially bothersome interpersonal behaviors. Participants in this study selected a friend to participate with them. Both friends then rated how much each behavior tended to trigger a negative emotional reaction in themselves personally and how much each behavior might trigger a negative emotional reaction in their friend. Findings demonstrated that accurate knowledge about a friend’s if-then trigger profile is associated with reduced feelings of conflict and increased feelings of depth in the relationship.
Benefits of butyrylcholinesterase reactivability testing in organophosphate poisoning
Authors: Şorodoc Laurenţiu , Lionte Cătălina , Largu Ema , Petriş Ovidiu
Published: April 2011

Organophosphate (OP) poisoning continues to represent an important medical issue through its high prevalence among toxic pathologies and through its severity. In diagnosing this toxicological disorder, the most frequently utilized and available laboratory test remains the assessment of plasma cholinesterase – butyrylcholinesterase (BChE) – activity. Despite the reluctance of many researchers on the usefulness of serum BChE for kinetic analysis in OP intoxications, we have tested a recently proposed protocol, which is safe, non-expensive, easy to perform, appropriate to distinguish between an aged cholinesterase and a still reactivable one. Our aim was to validate the usefulness of this protocol, studying a series of 23 consecutive patients acutely intoxicated with OP, admitted in a regional Emergency Hospital, over a 1-year period. Introducing the proposed test in the routine of monitoring OP-intoxicated patients has resulted in the identification of a pattern with a funnel aspect, consequence of the initial possibility to increment the degree of BChE activity. This funnel shape defines the presence of reactivability, while its absence demonstrates the lack of obidoximes effect, due to cholinesterase’s ageing process. This method consisted in an advantage for the diagnosis, having the potential of improving prognostic evaluation and therapeutic orientation in OP intoxications.