bluuebunny/crossref_metadata_2025 huggingface dataset:
A Measurement Procedure for the Sound Emission of Railway Sources Including Source Separation
Authors: Wunderli J M
Published: November 2005

A measurement method for railway noise, which yields spectral source levels for rolling noise including three-dimensional directivity information, is presented. Additionally, emission values for secondary sources as traction noise or aerodynamic noise are gathered. The method is based on two microphones and an intensity probe. The latter is placed in a way to suppress sound intensity stemming from the rail-wheel area and therefore allows secondary sources to be measured that are masked by rolling noise in the overall sound exposure.

The method has been tested with a loudspeaker placed on a freight train. Various combinations of train speeds and amplitudes of the loudspeaker signal showed the ability of the method to identify secondary sources that were up to 15 dB below rolling noise with high accuracy. In a further step, traction noise from a high power traction unit was identified and the results were compared with array measurements.

The tests proved the method's ability to yield input information for complex railway noise models. The fact that the method can be applied at comparably modest expense in comparison with other elaborated measurement procedures seems to be promising for further applications.
Influence of Short-Pitch Wheel/Rail Corrugation on Rolling Contact Fatigue of Railway Wheels
Authors: Nielsen J C O , Ekberg A , Lundén R
Published: November 2005

A numerical procedure to integrate simulation of high-frequency dynamic train-track interaction and prediction of rolling contact fatigue (RCF) impact is presented. Features of the included models and possibilities of applications are outlined. The influence of short-pitch rail corrugation and wheel out-of-roundness (OOR) on RCF of a high-speed passenger train is investigated. It is shown how the corrugation and the OOR will have a profound effect in that levels of wheel and rail irregularities that have been measured in the field may be sufficient to generate subsurface-initiated RCF. In particular, the high-frequency content of the contact forces is of importance. Errors induced by neglecting such high-frequency components in measurements and/or simulations are investigated by comparing RCF indices based on contact forces that have been low-pass filtered with various cut-off frequencies. To avoid cracking due to RCF, a maximum roughness level in the wavelength interval up to 10 cm is sought. To limit the effects of corrugation, grinding practices have been altered leading to a significant decrease in RCF.
A Study on Dynamic Behaviour of Pantographs by Using Hybrid Simulation Method
Authors: Zhang W H , Mei G M , Wu X J , Chen L Q
Published: November 2005

To study the dynamic behaviour of pantographs, a hybrid simulation method has been used. A special test facility, which is used to simulate the dynamic performance of a pantograph when it runs through the overhead line, is established and described in this paper. As the catenary is difficult to be modelled by a hardware test facility indoor, a mixed theoretical-experimental technique is used in test facility. On the basis of the set-up of hybrid simulation test device of the pantograph-catenary system, the dynamic behaviours of four types of pantographs running along the overhead equipment at different running speeds are examined and compared. Meanwhile, the dynamic parameters such as mass, stiffness, and damping of four pantographs are measured using the hybrid simulation test facility. On the basis of these parameters, the dynamic behaviours of the four pantographs are analysed.
Experimental investigation of applying miller cycle to reduce NOx emission from diesel engine
Authors: Wang Y , Zeng S , Huang J , He Y , Huang X , Lin L , Li S
Published: November 2005

An experimental investigation of nitrogen oxides (NOx) emission reduction from a diesel engine using the Miller cycle was carried out. A Lister-Petter diesel engine, type TS2, was used for the experiments. Three versions of Miller cycles were designed and realized on a diesel engine. A series of tests were carried out on the test rig to compare the performances and emissions of the original engine (standard dual cycle) with those of the three versions of Miller cycles. The test results from the standard dual cycle and from the three versions of Miller cycles showed that applying Miller cycle to the diesel engine could reduce the NOx emission from the diesel engine. The reduction ratios of NOx for the Miller cycles are from 4.4 to 17.5 per cent. The best reduction effect is Miller cycle 1 and the reduction rates of NOx are from 11.0 to 17.5 per cent.
Optimization of a stator blade using response surface method in a single-stage transonic axial compressor
Authors: Jang C-M , Kim K-Y
Published: November 2005

This article describes the shape optimization of a stator blade in a single-stage transonic axial compressor. The blade optimization has been performed using response surface method and three-dimensional Navier-Stokes analysis. Thin-layer approximation is introduced to the Navier-Stokes equations, and an explicit Runge-Kutta scheme is used to solve the governing equations. Two geometric design variables of the stator blade, which are used to define a stacking line, are introduced to increase an adiabatic efficiency. D-optimal design is employed to reduce the number of evaluation points for response surface. With the optimization of the stator blade, the adiabatic efficiency is successfully improved when compared with that of the reference shape of the stator with straight stacking line. Positive stacking line, which bends on blade pressure side, effectively suppresses the flow separation on the blade suction surface of the stator.
Analysis of a smart clutch with cooling flow using two-dimensional bingham plastic analysis and computational fluid dynamics
Authors: Ellam D J , Atkin R J , Bullough W A
Published: November 2005

Two-dimensional (orthogonal) steady isothermal flows of a Bingham plastic between two plates, one moving and the other stationary, are discussed. This is done principally to examine and quantify the concept of cooling a smart clutch by throughflow.

The fluid is modelled conventionally as an ideal Bingham plastic to verify the subsequent use of a computational fluid dynamics (CFD) package for similar flows in more complex situations but with a futuristic view to including heat transfer, electrical conductance, thermal and shear rate effects on fluid properties, and unsteady motion. The CFD (Fluent) package incorporates a user-defined subroutine facility which allows non-Newtonian constitutive models to be incorporated. Both radial and concentric geometries are considered. The two approaches (conventional analysis and CFD) are seen to complement one another.
Numerical and experimental investigation of stepped tip gap effects on a subsonic axial-flow compressor rotor
Authors: Lu X , Zhu J , Chu W
Published: November 2005

This article investigates the flow field at the tip region of compressor rotor. In particular, the effect of stepped tip gaps on the performance and flow field of axial compressor was reviewed using experimental and computational methods. An axial compressor rotor with no inlet guide vanes was tested under subsonic conditions. A parametric study of clearance levels and step profiles was performed using eight different casing geometries. This study was aimed at comparing compressor performance in specified configurations. The experimental results showed that the inclusion of stepped tip gaps with the small clearance level gave increased pressure ratio, efficiency, and stall margin throughout the mass flow range at both speeds. However, when using medium and large clearance levels, the benefits of stepped tip gaps were not noticed for all rotor operating conditions when compared with the baseline case. Steady-state Navier-Stokes analyses were performed for cases involving small clearance level and stepped tip gap geometries. They highlighted the mechanisms associated with performance improvement. The numerical procedure correctly predicted the overall effects of stepped tip gaps. Detailed numerical simulation results showed that the interaction between the stepped groove flow and the blade passage flow could entrain the blockage produced by upstream tip leakage flow into the tip gap of adjacent blades of the compressor rotor. It is through this process that stepped tip gaps can help in dissipating blockage that was caused by upstream tip leakage flow. Thus, the path and extent of the blockage in the tip region are altered to increase the passage through-flow area, and so, the rotor performance can be improved.
Experimental and numerical study of high-pressure-swirl injector sprays in a direct injection gasoline engine
Authors: Gao J , Jiang D , Huang Z , Wang X
Published: November 2005

The characteristics of free spray of a new type high-pressure-swirl injector in gasoline direct injection (GDI) engine under various injection conditions are investigated. The fuel spray with hollow-cone structure, wide spreading, and large spray angle is observed under the injection condition simulating to the GDI engine operation at full load. The study shows that a vortex structure can be clearly observed in the periphery of the spray. Meanwhile, an initial spray slug also appears at the tip of the main spray. Under the injection condition of GDI engine partial load, the structure of fuel spray changes into the more compact and solid-cone shape with decreased spray width. Moreover, the influences of the injection pressures and ambient pressures on the spray characteristics of the injector are studied. Along with the experimental studies, a general numerical model for the swirl spray is developed. Then, the model is implemented into a multi-dimensional computational fluid dynamics code (KIVA-3V) to theoretically study the pressure-swirl injector sprays. Comparisons between the computed and measured spray characteristics such as spray structure, spray tip penetration, and droplet sizes are made, and good agreement has been achieved between the model prediction and measurement.
Experimental study of an aqueous desiccant mixture system: Air dehumidification and desiccant regeneration
Authors: Al-Farayedhi A A , Gandhidasan P , Antar M A , Abdul Gaffar M S
Published: November 2005

This article presents the results of an experimental study on the performance of a structured packing dehumidifier and the regenerator system. The system is tested using different proportions of an aqueous desiccant mixture of calcium chloride and lithium chloride solutions with an overall concentration of 40 wt%. The instantaneous effectiveness and the time-average effectiveness of the dehumidification process as well as the regeneration process are defined for the hybrid cooling system. It is found that as the lithium chloride content in the solution increases, the effectiveness of the dehumidifier as well as the regenerator increases. Moreover, the regeneration of the lithium chloride solution is found to be more effective than that of calcium chloride solution. The dehumidifier effectiveness using the desiccant mixture of 20 wt% CaCl2 and 20 wt% LiCl is found to be close to that of 45 wt% solution of calcium chloride and improves by ɛ80 per cent over the 40 wt% solution of calcium chloride.
Application of exergy method to an irreversible inter-cooled refrigeration cycle
Authors: Chen C-K , Su Y-F
Published: November 2005

The exergy method, based on the maximum exergetic efficiency criterion, has been applied to an irreversible inter-cooled refrigeration cycle. The exergetic efficiency defined as the ratio of the rate of exergy output to the rate of exergy input is taken as the objective function to be maximized. Multi-irreversibilities include finite-rate heat transfer, internal dissipation of the working fluid, and heat leaks between heat reservoirs. The maximum exergetic efficiency can be determined analytically by introducing the internal irreversibility parameter, which represents the degree of internal irreversibility. The corresponding performances of the irreversible refrigeration system are obtained simultaneously. The results show that the exergy method can be used as an effective criterion in designing an irreversible inter-cooled refrigeration system.
An Engineering Tool for the Quantitative Prediction of General Roughness Deformation in EHL Contacts Based on Harmonic Waviness Attenuation
Authors: Venner C. H. , Lubrecht A. A.
Published: November 2005

The performance prediction of elastohydrodynamic lubricated contacts with rough surfaces is currently an important issue, because in many engineering applications, the ratio of film thickness to surface roughness is small and decreasing.

The classical way of introducing roughness in the lubrication equations is through the approach pioneered by Patir and Cheng. This approach treats the roughness in a statistical manner and it cannot be used to predict the behaviour of a particular surface texture. Furthermore, the main hypotheses stem from hydrodynamic lubrication and neglect the viscosity change with pressure and the elastic surface deformation.

The opposite approach uses the full transient EHL equations, introduces a real, measured roughness, and studies the lubrication of this surface. This approach has several drawbacks. First, it is difficult to analyse the precision of the results obtained. Furthermore, this direct approach of surface roughness is difficult to generalize as each roughness, or set of operating conditions is unique, and general trends are difficult to extract.

A third approach has emerged over the last decade, in which the amplitude reduction of a sinusoidal waviness is studied as a function of the amplitude, the wavelength, and the operating conditions. The simplification of the roughness to a sinusoidal waviness can be justified in several ways. The first and simplest justification points out that many engineering surface finishes have one dominant wavelength and amplitude. Even if the geometry is removed from the sinusoidal one, a first approximation of the roughness behaviour can be obtained through the study of the waviness with the same wavelength and amplitude.

A second argument is slightly more sophisticated; it argues that if the amplitude reduction is approximately linear, Fourier decomposition of the roughness into sinusoidal components is permitted. Next, the amplitude reduction of each Fourier component is computed, and finally, the deformed waviness signals are assembled to yield the deformed roughness signal.

The major results of this amplitude reduction work are reviewed in this article.
Elastohydrodynamic Lubrication in Biological Systems
Authors: Jin Z. M. , Dowson D
Published: November 2005

Elastohydrodynamic lubrication (EHL) appears to be an important mechanism in various biological systems. In this paper, a few examples will be selected to illustrate the biological applications of EHL: microcirculation of red blood cells in capillaries, blinking of eye and contact lens, and respiratory motion between pleural surfaces and articulation in synovial joints. It is shown that the relatively large elastic deformation of the bearing surfaces associated with relatively compliant biological tissues is responsible for the major contribution of fluid film action to the lubrication at both tissue and cellular levels. Under unfavourable lubrication conditions, the articulating surfaces can be protected by the powerful effect of micro-EHL in smoothing out surface asperities and further by the glycocalyx present on the biological surfaces.
The Application of Ultrasonic NDT Techniques in Tribology
Authors: Dwyer-Joyce R. S.
Published: November 2005

The use of ultrasonic reflection is emerging as a technique for studying tribological contacts. Ultrasonic waves can be transmitted non-destructively through machine components and their behaviour at an interface describes the characteristics of that contact. This paper is a review of the current state of understanding of the mechanisms of ultrasonic reflection at interfaces, and how this has been used to investigate the processes of dry rough surface contact and lubricated contact. The review extends to cover how ultrasound has been used to study the tribological function of certain engineering machine elements.
Nitrogenous Chemicals from Carbon Based Materials
Authors: Demirbas M. Fatih
Published: November 2005

Coal and biomass consist carbon-based materials can be used as a source of chemicals. There are four widespread processes allow for making chemicals from coals and biomass: Gasification, liquefaction, direct conversion, and co-production of chemicals and fuels along with electricity. The carbon-based materials are gasified to produce synthesis gas (syngas) with a gasifier which is then converted to parafinic liquid fuels and chemicals by Fischer-Trops synthesis. The humus substances can be recovered from brown coal by alkali extraction. Ammonium sulfate from coal tar by pyrolysis can be converted to ammonia. Nitrogenous biomass materials such as animal and municipal wastes are nitrogen-rich materials. All natural systems include ammonia concentrations below 2 ppm.
Underpressured and Overpressured Tight Gas Sands: II. Spatially and Temporally Varying Conditions
Authors: Lerche Ian
Published: November 2005

This paper investigates the behavior of gas in tight sand aquifers when the shape of the aquifer, its cross-section, permeability, and temperature can all vary along the length of the aquifer. The basic response equation is steady state input of gas under pressure at the lower end of the aquifer and uses Darcy's law for fluid motion in association with buoyancy drive on the gas to determine the gas pressure variations along the aquifer as the lower end aquifer conditions are changed. Both overpressured and underpressured situations can arise, and are sensitive to the variation of parameters describing both the geometry and the physical conditions in the aquifer. Several illustrations are given to show how simple changes can cause different pressure conditions along the aquifer, making it difficult ahead of drilling to know which conditions prevail in a given tight gas sand aquifer.
Current Status of Fuel Cell Technologies
Authors: Ni Meng
Published: November 2005

A fuel cell is an electrochemical energy conversion device for electricity generation using hydrogen fuel. The principal characteristic of a fuel cell is that it can convert chemical energy directly into electrical energy with higher efficiencies than conventional mechanical systems. The emission of fuel cells using hydrogen as a fuel is only water vapour. Fuel cells are currently under development for both stationary and mobile applications in response to the need for sustainable energy technology. This paper reviews current status of fuel cell technologies, compares different types of fuel cells. The potential applications of fuel cells are discussed.
Economic Exploration Assessment of Hydrocarbon Leakage across a Fault. III. Hydrocarbon Leaks and Fault Locations
Authors: Lerche Ian
Published: November 2005

This paper addresses the concerns of potential hydrocarbon leakage through a fault when there are changes in the location of the fault, its orientation, and its length in relation to a given sand body of known width. The probability that hydrocarbons interact with the fault is expressed in terms of the overlap length of the fault in the sand, and in terms of the sand width as well. When the probability that the fault is open or shut to hydrocarbon flow is added to the geometric probabilities as a basic variable, the uncertainties of the five parameters (fault length, sand body width, fault orientation, fault location in relation to the sand body, and probability the fault is open to hydrocarbon escape) are addressed in terms of Monte Carlo representations of the chances of retaining or losing hydrocarbons. The dominant contributions to the uncertainties of the fraction of hydrocarbons most likely lost or retained are also given so that one can determine which of the five basic parameters need to have their ranges of uncertainty narrowed first in order to improve on the probable estimates of hydrocarbon retention. Numerical illustrations are given to show how one goes about assessing these factors for a sand cut by a fault, and to illustrate the chances that the sand is hydrocarbon bearing or not due to possible loss through the fault.
The Relevance of the Dynamic Stall Effect for Transient Fault Operations of Active-Stall Wind Turbines
Authors: Jauch Clemens , Sørensen Poul , Jensen Birgitte Bak
Published: November 2005

This article describes a methodology to quantify the influence of dynamic stall on transient fault operations of active-stall turbines. The model of the dynamic stall effect is introduced briefly. The behaviour of the dynamic stall model during a transient fault operation is described mathematically, and from this its effect quantified. Two quantities are chosen to describe the influence of the dynamic stall effect: one is active power and the other is time delay. Subsequently a transient fault scenario is simulated with and without the dynamic stall effect and the differences discussed. From this comparison, the conclusion is drawn that the dynamic stall effect has some influence on the post-fault behaviour of the wind turbine, and it is hence suggested that the dynamic stall effect is considered if an active-stall wind turbine is to be modelled realistically.
Fault Recovery of a Wind Farm with Fixed Speed Induction Generators Using a STATCOM
Authors: Aten M. , Martinez J. , Cartwright P. J.
Published: November 2005

This paper describes a feasibility study for a wind farm with Fixed Speed Induction Generators and having a STATCOM, combined with Mechanically Switched Capacitors, for reactive power control and fault recovery. The turbine blade and generator inertia, coupled with a shaft of finite stiffness, are modelled to represent torsional oscillation. This is important to represent the dynamic behaviour of the system adequately.

Dynamic simulations show that fault ride-though capability of a wind farm can be met by using a STATCOM, and switching in shunt capacitors, when the overspeed protection is set at 1.1 pu. However, the wind turbine must be designed to cope with the mechanical stress resulting from a fault in the AC system with a large magnitude of voltage dip. Successful fault recovery is demonstrated for symmetrical and asymmetrical faults. The control strategy proposed here can be adopted for different grid code requirements and various wind farms.
Characterising Turbulence Intensity for Fatigue Load Analysis of Wind Turbines
Authors: Hansen Kurt S. , Larsen Gunner Chr.
Published: November 2005

Turbulence in wind velocity presents a major factor for modern wind turbine design as cost reduction as are sort for the dynamic structures. Therefore this paper contains a parametrisation of the turbulence intensity at given sites, relevant for the calculation of fatigue loading of wind turbines. The parameterisation is based on wind speed measurements extracted from the “Database on Wind Characteristics” ( www.winddata.com ). The parameterisation is based on the LogNormal distribution, which has proven to be suitable distribution to describe the turbulence intensity distribution.
Noise from Air-Cooled Chillers
Authors: Brown Peter
Published: November 2005

The use of air-cooled chillers in external locations requires careful assessment of the level of noise generated. Peter Brown gives an acoustic consultant's view of some of the potential pitfalls associated with noise levels and equipment selection.
Analysis of Coupled Lateral-Torsional-Pounding Responses of One-Storey Asymmetric Adjacent Structures Subjected to Bi-Directional Ground Motions Part II: Spatially Varying Ground Motion Input
Authors: Hao H. , Gong L.
Published: November 2005

This is the second paper presenting numerical results of a parametric study of seismic induced lateral-torsional-pounding responses of an asymmetric and a symmetric one-storey adjacent structure. The accompany paper (Part I) (Gong and Hao 2004) assumed ground motion input at all structural supports as uniform. Torsional responses are generated because of inherent structural eccentricity and eccentric pounding. In reality, seismic ground motion at different structural supports inevitably varies owing to wave propagation. Spatially varying ground motion will induce torsional responses of structures, and generate out-of-phase responses between adjacent structures. Thus it might have a significant effect on coupled lateral-torsional-pounding responses. This paper studies the ground motion spatial variation effect. For comparison purpose, same adjacent structure models and impact element used in Part I of this study are adopted here again. 20 sets of spatially varying ground motion time histories are stochastically simulated. All the time histories are compatible with the Newmark-Hall design response spectrum with 5% damping and normalized to 0.5g. The spatial variation of any two simulated time histories is compatible with an empirical coherency loss function. Coupled lateral-torsional-pounding responses of the two structures to the simulated ground motions are calculated. Discussions on the ground motion spatial variation effects are made.
A Locking Free Mortar Method for Coupling of Fourier Models and 3D Non-Axisymetric Shell Structures
Authors: Combescure A. , Baillis C. , Bauruelle J. C.
Published: November 2005

In this paper a new method is introduced for the coupling of sub-domains some of them being axisymetric and others being fully 3D. A dedicated “mortar” method is presented and a number of examples are presented for linear, buckling, and non linear geometrical and material cases. The method presented uses the COMU shell element which permits non linear computation of axisymetric structures either with non axisymetric initial imperfections or non axisymetrically loaded. This element is combined with usual 3D DKT shell element via a special mortar method.
Analysis of Horizontal Reactions Due to Moving Vehicle Loads in Curved Bridges with Varied Support Conditions
Authors: Kim Sang-Hyo , Lee Yong-Seon , Cho Kwang-Yil
Published: November 2005

A curved bridge can have two different bearing directions: chordal and tangential direction. This may bring differences of load distribution due to moving vehicles and structural behavior of a curved bridge. This study presents a 3D numerical model that can demonstrate the dynamic responses of a curved bridge to moving vehicles more precisely. The dynamic response induced by the centrifugal rolling motion of a vehicle is identified according to the variations of the superelevation and the radius of curvature of the deck. Dynamic characteristics of the curved bridge with the moving vehicle are analyzed under the condition of the support types and two different support systems. In general, while the vehicle is passing over the curved bridge, the negative reaction occurs in the inside of the girder. The final result shows that the support system located outside the girder is more advantageous than other systems, and the characteristics of load distributions differ from the others in the various conditions of support systems.
Medication Utilization Patterns and Methods of Suicidality in Borderline Personality Disorder
Authors: Makela Eugene H , Moeller Karen E , Fullen Jennifer E , Gunel Erdogan
Published: November 2005

Background:

Borderline personality disorder (BPD) is a psychiatric disorder characterized by suicidal thoughts/attempts and instability of mood, interpersonal relationships, and self-image. Patients with BPD engage in manipulative acts in apparent attempts to exert control in their interpersonal relationships. This issue of control may also be exhibited in their manner of self-medication.

Objective:

To examine the medication utilization patterns of patients with BPD versus patients without personality disorders in a control group and to compare methods of suicidality between the groups.

Methods:

A randomized, retrospective, chart review study was conducted at an academic medical center psychiatric hospital. The study examined the medication utilization patterns and methods of suicidality displayed over a one-year period for 29 patients hospitalized with BPD versus 29 patients in a control group.

Results:

The number of psychotropic, non-psychotropic, and total drugs on admission and discharge was significantly greater for patients with BPD compared with patients in the control group. There was no significant difference between the 2 groups with respect to overdose and cutting methods of suicidality. The mean number of Axis III discharge diagnoses in the control group upon discharge was significantly less than that in the study group. Approximately 25% of patients with BPD considered overdosage as a means to end their life.

Conclusions:

As patients with BPD receive more medications than patients without the disorder and often exhibit suicidal thoughts/attempts, clinicians should closely monitor the use of all medications.
Pharmacist-Provided Quantitative Heel Ultrasound Screening for Rural Women at Risk of Osteoporosis
Authors: Naunton Mark , Peterson Gregory M , Jones Graeme
Published: November 2005

Background:

Osteoporosis is underdiagnosed, and rural communities often have limited technical resources for the assessment of osteoporosis.

Objective:

To evaluate the impact of a pharmacist, trained in the use of a portable heel ultrasound device, in screening elderly rural women for risk of osteoporosis and determine whether those found to be at risk seek further help and treatment from their general practitioner (GP) following screening.

Methods:

Following promotion of the service, 345 women were recruited from 6 rural community pharmacies in Tasmania, Australia, and underwent quantitative heel ultrasound screening. Women were comprehensively educated on risk factors for osteoporosis and completed a calcium intake questionnaire. Results were forwarded to each woman's GP, and the participants were followed up 3 months later to assess outcomes from the screening procedure.

Results:

Approximately 20% of women were shown to be at high risk for osteoporosis; 201 (58%) of these were referred to their GP for further assessment. Sixty-eight percent of women who were screened discussed their results with their GP, and 11% underwent further investigation. Over one-third of women screened began medication (30% calcium, 6% bisphosphonate, 6% vitamin D) for osteoporosis.

Conclusions:

Pharmacist-provided screening for osteoporosis in rural areas is a potentially useful method to identify women at risk for fracture and a convenient time point for discussion of preventive therapy.
Effects of Siderophores on Pb and Cd Adsorption to Kaolinite
Authors: Hepinstall Sarah E. , Turner Benjamin F. , Maurice Patricia A.
Published: November 2005

Siderophores are low molecular weight organic ligands synthesized by aerobic microorganisms to acquire Fe. In addition to Fe(III), siderophores may complex other metals such as Pb and Cd. This study compared the effects of the trihydroxamate siderophores desferrioxamine-B (DFO-B), desferrioxamine-D1 (DFO-D1), desferrioxamine-E (DFO-E), and the monohydroxamate siderophore-like ligand acetohydroxamic acid (aHA) on Pb and Cd (except for DFO-E) adsorption to kaolinite (KGa-1b) at pH 4.5 to 9, in 0.1 M NaClO4, at 22°C, in the dark. At pH >6, all of the studied ligands decreased Pb adsorption to kaolinite: aHA by 5–40% and DFO-B, DFO-D1 and DFO-E by 30–75%; the greater effects were at higher pH. The studied ligands decreased Cd adsorption to kaolinite at pH >8: aHA by 5–20% and the trihydroxamates by as much as 80%. We also observed enhancement of Pb adsorption in the presence of DFO-B at pH ≈5–6.0, probably due to adsorption of the doubly positively charged H3Pb (DFO-B)2+ complex, although spectroscopic evidence is needed.
Performance Characteristics of a Novel Tandem Mass Spectrometry Assay For Serum Testosterone
Authors: Kushnir Mark M , Rockwood Alan L , Roberts William L , Pattison Elizabeth G , Bunker Ashley M , Fitzgerald Robert L , Meikle A Wayne
Published: November 2005

Background: Commercial immunoassays for testosterone (Te) may give inaccurate results for samples from women and children, leading to misdiagnosis and inappropriate treatment. We developed a sensitive and specific tandem mass spectrometric assay for measurement of Te at the concentrations encountered in women and children.

Methods: Te was extracted with methyl tert-butyl ether from 100 μL of serum or plasma, derivatized to form an oxime, and reextracted by solid-phase extraction. Instrumental analysis was performed on an API 4000 HPLC tandem mass spectrometer in the multiple-reaction monitoring (MRM) mode. The MRM transitions (m/z) were 304→124 and 304→112 for Te and 307→124 and 307→112 for d3-Te.

Results: Within- and between-run CVs were <12% and 7.9%, respectively. The limit of quantification was 0.0346 nmol/L (1 ng/dL). Reference intervals for sex hormone–binding globulin and total, free, and bioavailable Te were established for children of Tanner stages 1 through 5 and adult males and females.

Conclusions: The sensitivity and specificity of the method are adequate for analysis of Te in samples from women and children. The method requires small sample volumes, has adequate precision, and is not subject to interferences.
Measurement of Procarboxypeptidase U (TAFI) in Human Plasma: A Laboratory Challenge
Authors: Willemse Johan L , Hendriks Dirk F
Published: November 2005

Background: The importance of carboxypeptidase U (CPU) as a novel regulator of the fibrinolytic rate has attracted much interest during recent years. CPU circulates in plasma as a zymogen, proCPU, that can be activated by thrombin, thrombin-thrombomodulin (T-Tm), or plasmin. Given that the proCPU concentration in plasma is far below its Km for activation by the T-Tm complex, the formation of CPU will be directly proportional to the proCPU concentration. A low or high proCPU plasma concentration might therefore tip the balance between profibrinolytic and antifibrinolytic pathways and thereby cause a predisposition to bleeding or thrombosis.

Content: To measure plasma proCPU concentrations, different methods have been developed based on 2 different principles: antigen determination and measurement of CPU activity after quantitative conversion of the proenzyme to its active form by addition of T-Tm. The major drawbacks that should be kept in mind when analyzing clinical samples by both principles are reviewed.

Conclusions: proCPU is a potential prothrombotic risk factor. Evaluation of its relationship with thrombosis requires accurate assays. Many assays used in different clinical settings are inadequately validated, forcing reconsideration of conclusions made in these reports.
Clinical Analysis by Microchip Capillary Electrophoresis
Authors: Li Sam FY , Kricka Larry J
Published: November 2005

Clinical analysis often requires rapid, automated, and high-throughput analytical systems. Microchip capillary electrophoresis (CE) has the potential to achieve very rapid analysis (typically seconds), easy integration of multiple analytical steps, and parallel operation. Although it is currently still in an early stage of development, there are already many reports in the literature describing the applications of microchip CE in clinical analysis. At the same time, more fully automated and higher throughput commercial instruments for microchip CE are becoming available and are expected to further enhance the development of applications of microchip CE in routine clinical testing. To put into perspective its potential, we briefly compare microchip CE with conventional CE and review developments in this technique that may be useful in diagnosis of major diseases.
Sharing Control Between Humans and Automation Using Haptic Interface: Primary and Secondary Task Performance Benefits
Authors: Griffiths Paul G. , Gillespie R. Brent
Published: November 2005

This paper describes a paradigm for human/automation control sharing in which the automation acts through a motor coupled to a machine's manual control interface. The manual interface becomes a haptic display, continually informing the human about automation actions. While monitoring by feel, users may choose either to conform to the automation or override it and express their own control intentions. This paper's objective is to demonstrate that adding automation through haptic display can be used not only to improve performance on a primary task but also to reduce perceptual demands or free attention for a secondary task. Results are presented from three experiments in which 11 participants completed a lane-following task using a motorized steering wheel on a fixed-base driving simulator. The automation behaved like a copilot, assisting with lane following by applying torques to the steering wheel. Results indicate that haptic assist improves lane following by least 30%, p < .0001, while reducing visual demand by 29%, p < .0001, or improving reaction time in a secondary tone localization task by 18 ms, p = .0009. Potential applications of this research include the design of automation interfaces based on haptics that support human/automation control sharing better than traditional push-button automation interfaces.
Low-Back Biomechanics and Static Stability During Isometric Pushing
Authors: Granata Kevin P. , Bennett Bradford C.
Published: November 2005

Pushing and pulling tasks are increasingly prevalent in industrial workplaces. Few studies have investigated low-back biomechanical risk factors associated with pushing, and we are aware of none that has quantified spinal stability during pushing exertions. Data recorded from 11 healthy participants performing isometric pushing exertions demonstrated that trunk posture, vector force direction of the applied load, and trunk moment were influenced (p < .01) by exertion level, elevation of the handle for the pushing task, and foot position. A biomechanical model was used to analyze the posture and hand force data gathered from the pushing exertions. Model results indicate that pushing exertions provide significantly (p < .01) less stability than lifting when antagonistic cocontraction is ignored. However, stability can be augmented by recruitment of muscle cocontraction. Results suggest that cocontraction may be recruited to compensate for the fact that equilibrium mechanics provide little intrinsic trunk stiffness and stability during pushing exertions. If one maintains stability by means of cocontraction, additional spinal load is thereby created, increasing the risk of overload injury. Thus it is important to consider muscle cocontraction when evaluating the biomechanics of pushing exertions. Potential applications of this research include improved assessment of biomechanical risk factors for the design of industrial pushing tasks.
Target Acquisition With UAVs: Vigilance Displays and Advanced Cuing Interfaces
Authors: Gunn Daniel V. , Warm Joel S. , Nelson W. Todd , Bolia Robert S. , Schumsky Donald A. , Corcoran Kevin J.
Published: November 2005

Vigilance and threat detection are critical human factors considerations in the control of unmanned aerial vehicles (UAVs). Utilizing a vigilance task in which threat detections (critical signals) led observers to perform a subsequent manual target acquisition task, this study provides information that might have important implications for both of these considerations in the design of future UAV systems. A sensory display format resulted in more threat detections, fewer false alarms, and faster target acquisition times and imposed a lighter workload than did a cognitive display format. Additionally, advanced visual, spatial-audio, and haptic cuing interfaces enhanced acquisition performance over no cuing in the target acquisition phase of the task, and they did so to a similar degree. Thus, in terms of potential applications, this research suggests that a sensory format may be the best display format for threat detection by future UAV operators, that advanced cuing interfaces may prove useful in future UAV systems, and that these interfaces are functionally interchangeable.
Limitations in Drivers' Ability to Recognize Pedestrians at Night
Authors: Wood Joanne M. , Tyrrell Richard A. , Carberry Trent P.
Published: November 2005

This study quantified drivers' ability to recognize pedestrians at night. Ten young and 10 older participants drove around a closed road circuit and responded when they first recognized a pedestrian. Four pedestrian clothing and two beam conditions were tested. Results demonstrate that driver age, clothing configuration, headlamp beam, and glare all significantly affect performance. Drivers recognized only 5% of pedestrians in the most challenging condition (low beams, black clothing, glare), whereas drivers recognized 100% of the pedestrians who wore retroreflective clothing configured to depict biological motion (no glare). In the absence of glare, mean recognition distances varied from 0.0 m (older drivers, low beam, black clothing) to 220 m (722 feet; younger drivers, high beam, retroreflective biomotion). These data provide new motivation to minimize interactions between vehicular and pedestrian traffic at night and suggest garment designs to maximize pedestrian conspicuity when these interactions are unavoidable.
Audibility of Train Horns in Passenger Vehicles
Authors: Dolan Thomas G. , Rainey Jess E.
Published: November 2005

Studies of accident rates associated with train horn bans indicate that motorists rely on horns to warn them of approaching trains. However, researchers have not yet established the levels of horn sounds necessary for detection at railroad crossings. The purpose of this study was to obtain baseline measures of the auditory component of the motorist's detection task. Horn sounds recorded in three test vehicles were presented to 20 normal-hearing listeners in quiet and in four types of vehicle interior noise: engine idling, ventilation fan off; engine idling, fan on; vehicle moving at 30 miles/hr (mph), fan off; and vehicle moving at 30 mph, fan on. Thresholds of the horn sounds were determined by an adaptive procedure. Mean thresholds were lowest in quiet (1.8--4.4 dBA) and highest for the 30-mph, fan-on condition (49.7--58.4 dBA). Mean horn thresholds for all 12 noise conditions were more than 10 dB below the overall level of the vehicle interior noise. Our data are compared with those of previous studies and their implications are discussed. Actual or potential applications of this research include the establishment of a lower limit of signal-to-noise ratios required for the detection of horn sounds at highway-rail crossings.
Heuristic Automation for Decluttering Tactical Displays
Authors: St. John Mark , Smallman Harvey S. , Manes Daniel I. , Feher Bela A. , Morrison Jeffrey G.
Published: November 2005

Tactical displays can quickly become cluttered with large numbers of symbols that can compromise effective monitoring. Here, we studied how heuristic automation can aid users by intelligently "decluttering" the display. In a realistic simulated naval air defense task, 27 experienced U.S. Navy users monitored a cluttered airspace and executed defensive responses against significant threats. An algorithm continuously evaluated aircraft for their levels of threat and decluttered the less threatening ones by dimming their symbols. Users appropriately distrusted and spot--checked the automation's assessments, and decluttering had very little effect on which aircraft were judged as significantly threatening. Nonetheless, decluttering improved the timeliness of responses to threatening aircraft by 25% as compared with a baseline display with no decluttering; it was especially beneficial for threats in more peripheral locations, and 25 of 27 participants preferred decluttering. Heuristic automation, when properly designed to guide users' attention by decluttering less important objects, may prove valuable in many cluttered monitoring situations, including air traffic management, crisis team management, and tactical situation awareness in general.
Audio and Visual Cues in a Two-Talker Divided Attention Speech-Monitoring Task
Authors: Brungart Douglas S. , Kordik Alexander J. , Simpson Brian D.
Published: November 2005

Although audiovisual (AV) cues are known to improve speech intelligibility in difficult listening environments, little is known about their role in divided attention tasks that require listeners to monitor multiple talkers at the same time. In this experiment, a call-sign-based multitalker listening test was used to evaluate performance in two-talker AV configurations that combined zero, one, or two channels of visual information (neither, one, or both talkers visible) with zero, one, or two channels of audio information (no audio, both talkers played from the same loudspeaker, and both talkers played through different, spatially separated loudspeakers). The results were analyzed to determine the relative performance levels that would occur with each AV configuration with target information that was equally likely to originate from either of the two talkers in the stimulus. The results indicate that spatial separation of the audio signals has the greatest impact on performance in multi-channel AV speech displays and that caution should be used when presenting a visual representation of only a single talker unless that talker is known to be the highest priority talker in the combined AV stimulus. Potential applications of this research include the design of improved audiovisual speech displays for multi-channel communications systems.
Relationships Among Display Features, Eye Movement Characteristics, and Reaction Time in Visual Search
Authors: Murata Atsuo , Furukawa Nobuyasu
Published: November 2005

The relative contribution of number of fixations and fixation duration to reaction time in visual search was investigated. Ten participants (age 20--24 years) took part in each of two experiments. In Experiment 1, the experimental factors were display type (icon and file name), organization (arrangements with and without grouping), and number of stimuli presented (4, 8, and 16). In Experiment 2, a search task for a target stimulus (three prespecified random letters) was conducted, and the experimental factor was the display's layout complexity. Multiple regression analysis was used to examine whether reaction time was explained by a mediational model in which reaction time is mediated by eye movements and display features are not directly related to reaction time. The mediational model was not supported, and the effects of display features on reaction time were not attributable solely to eye movements. The interaction between number of fixations and fixation duration was also explored as a function of display features. As the display feature changed and the task became more difficult, the contribution of the number of fixations to explain the variation in reaction time became dominant for both experiments. Potential applications include measurements of cognitive ability, eye muscle balance disorders, and binocular fusion ability.