bluuebunny/crossref_metadata_2025 huggingface dataset:
Dust mite-induced asthma in cynomolgus monkeys
Authors: Van Scott Michael R. , Hooker Jerry L. , Ehrmann David , Shibata Yoshimi , Kukoly Cynthia , Salleng Kenneth , Westergaard Greg , Sandrasagra Anthony , Nyce Jonathan
Published: March 2004

Animal models exhibiting high homology with humans at the genetic and pathophysiological levels will facilitate identification and validation of gene targets underlying asthma. In the present study, a nonhuman primate model of allergic asthma was developed by sensitizing cynomolgus monkeys to dust mite antigen. Sensitization elevated allergen-specific serum IgE and IgG levels, and peripheral blood mononuclear cells isolated from sensitized animals released IL-4, IL-5, and IL-10, but not IFN-γ. Aerosolized allergen decreased dynamic compliance and induced airway inflammation and hyperresponsiveness to aerosolized histamine. Albuterol and dexamethasone inhibited the airway constriction and allergen-induced inflammation, respectively. Airway wall remodeling that included goblet cell hyperplasia, basement membrane thickening, and smooth muscle hypertrophy was particularly evident in neonatally sensitized animals. In contrast to animals sensitized as adults, neonatally sensitized animals exhibited increased sensitivity to adenosine and larger allergen-induced changes in airway resistance and dynamic compliance. These results demonstrate that sensitization of cynomolgus monkeys with dust mite induces asthmalike symptoms, some of which may be dependent on age at the time of sensitization.
Lower body negative pressure as a model to study progression to acute hemorrhagic shock in humans
Authors: Cooke William H. , Ryan Kathy L. , Convertino Victor A.
Published: March 2004

Hemorrhage is a leading cause of death in both civilian and battlefield trauma. Survival rates increase when victims requiring immediate intervention are correctly identified in a mass-casualty situation, but methods of prioritizing casualties based on current triage algorithms are severely limited. Development of effective procedures to predict the magnitude of hemorrhage and the likelihood for progression to hemorrhagic shock must necessarily be based on carefully controlled human experimentation, but controlled study of severe hemorrhage in humans is not possible. It may be possible to simulate hemorrhage, as many of the physiological compensations to acute hemorrhage can be mimicked in the laboratory by applying negative pressure to the lower extremities. Lower body negative pressure (LBNP) sequesters blood from the thorax into dependent regions of the pelvis and legs, effectively decreasing central blood volume in a similar fashion as acute hemorrhage. In this review, we compare physiological responses to hemorrhage and LBNP with particular emphasis on cardiovascular compensations that both share in common. Through evaluation of animal and human data, we present evidence that supports the hypothesis that LBNP, and resulting volume sequestration, is an effective technique to study physiological responses and mechanisms associated with acute hemorrhage in humans. Such experiments could lead to clinical algorithms that identify bleeding victims who will likely progress to hemorrhagic shock and require lifesaving intervention(s).
Breath-by-breath assessment of alveolar gas stores and exchange
Authors: Aliverti A. , Kayser B. , Macklem P. T.
Published: March 2004

The volume of O2 exchanged at the mouth during a breath (Vo2,m) is equal to that taken up by pulmonary capillaries (Vo2,A) only if lung O2 stores are constant. The latter change if either end-expiratory lung volume (EELV), or alveolar O2 fraction (FaO2) change. Measuring this requires breath-by-breath (BbB) measurement of absolute EELV, for which we used optoelectronic plethysmography combined with measurement of O2 fraction at the mouth to measure Vo2,A = Vo2,m - (ΔEELV·FaO2 + EELV·ΔFaO2), and divided by respiratory cycle time to obtain BbB O2 consumption (V̇o2) in seven healthy men during incremental exercise and recovery. To synchronize O2 and volume signals, we measured gas transit time from mouthpiece to O2 meter and compared V̇o2 measured during steady-state exercise by using expired gas collection with the mean BbB measurement over the same time period. In one subject, we adjusted the instrumental response time by 20-ms increments to maximize the agreement between the two V̇o2 measurements. We then applied the same total time delay (transit time plus instrumental delay = 660 ms) to all other subjects. The comparison of pooled data from all subjects revealed r2 = 0.990, percent error = 0.039 ± 1.61 SE, and slope = 1.02 ± 0.015 (SE). During recovery, increases in EELV introduced systematic errors in V̇o2 if measured without taking ΔEELV·FaO2+EELV·ΔFaO2 into account. We conclude that optoelectronic plethysmography can be used to measure BbB V̇o2 accurately when studying BbB gas exchange in conditions when EELV changes, as during on- and off-transients.
Lipid Rafts: Feeling is Believing
Authors: Henderson Robert M. , Edwardson J. Michael , Geisse Nicholas A. , Saslowsky David E.
Published: March 2004

In the late 1990s, accumulated evidence led to the proposal that biological membranes are composed of microdomains of different lipids, which form functional “rafts.” Recent work using atomic force microscopy has given us new insights into the factors influencing the formation and behavior of these physiological microenvironments
The Transfiguration: an Exercise in Markan Accommodation
Authors: Moss Candida
Published: March 2004

The transfiguration in Mark is traditionally understood as a re-working of Exodus 24 and 1Kings 19. There are a number of elements of the Markan transfiguration account, however, which resonate more strongly with the conventions of Hellenistic epiphany stories. This paper attempts to demonstrate that the author of the gospel of Mark appealed to a variety of religious traditions in order to make his narrative accessible to a diverse audience. This practice of accommodation conveyed the gospel message to a variegated audience with varying degrees of familiarity with Jewish and non-Jewish Hellenistic traditions.
Satellite Observations of Cool Ocean–Atmosphere Interaction
Authors: Xie Shang-Ping
Published: March 2004

Over most of the World Ocean, sea surface temperature (SST) is below 26°C and atmospheric deep convection rarely takes place. Cool ocean–atmosphere interaction is poorly understood and this lack of understanding is a stumbling block in the current effort to study non-ENSO climate variability. Using new satellite observations, the response of surface wind and low clouds to changes in SST is investigated over cool oceans, where the planetary boundary layer (PBL) is often capped by a temperature inversion. While one-way atmospheric forcing is a major mechanism for basinscale SST variability in the extratropics, clear wind response is detected in regions of strong ocean currents. In particular, SST modulation of vertical momentum mixing emerges as the dominant mechanism for SST-induced wind variability near oceanic fronts around the world, which is characterized by a positive SST–wind speed correlation. Several types of boundary layer cloud response are found, whose correlation with SST varies from positive to negative, depending on the role of surface moisture convergence. Noting that the surface moisture convergence is strongly scale dependent, it is proposed that horizontal scale is important for setting the sign of this SST–cloud correlation. Finally, the processes by which a shallow PBL response might lead to a deep, tropospheric-scale response and the implications for the study of extratropical basin-scale air–sea interaction are discussed.
Understanding User Decision Making and the Value of Improved Precipitation Forecasts: Lessons From a Case Study
Authors: Stewart Thomas R. , Pielke Roger , Nath Radhika
Published: March 2004

A case study of the impact of improved precipitation forecasts on the snow-fighting operations of the New York State Thruway is reported. The goal was to use currently available data and literature on forecast process, communication, and use in conjunction with observations and interviews with key decision makers to derive a model that yields estimates of value to users based on a model of their decision processes rather than an optimal decision-making model. That goal proved too ambitious due to limitations in available data. A major lesson learned from this research is the importance of improved, ongoing data collection to support studies of use and value of weather information. A more holistic approach to understanding and realizing forecast value is needed, that is, one in which information (both of forecast skill and usage) centered on the decision process is collected in a much more intensive manner than is presently the case.
Characteristics and outcome for admissions to adult, general critical care units with acute severe asthma: a secondary analysis of the ICNARC Case Mix Programme Database
Authors: Gupta Dheeraj , Keogh Brian , Chung Kian Fan , Ayres Jon G , Harrison David A , Goldfrad Caroline , Brady Anthony R , Rowan Kathy
Published: March 2004

Introduction

This report describes the case mix, outcome and activity (duration of intensive care unit [ICU] and hospital stay, inter-hospital transfer, and readmissions to the ICU) for admissions to ICUs for acute severe asthma, and investigates the effect of case mix factors on outcome.

Methods

We conducted a secondary analysis of data from a high-quality clinical database (the Intensive Care National Audit and Research Centre [ICNARC] Case Mix Programme Database) of 129,647 admissions to 128 adult, general critical care units across England, Wales and Northern Ireland over the period 1995–2001.

Results

Asthma accounted for 2152 (1.7%) admissions, and in 57% mechanical ventilation was employed during the first 24 hours in the ICU. A total of 147 (7.1%) patients died in intensive care and 199 (9.8%) died before discharge from hospital. The mean age was 43.6 years, and the ratio of women to men was 2:1. Median length of stay was 1.5 days in the ICU and 8 days in hospital. Older age, female sex, having received cardiopulmonary resuscitation (CPR) within 24 hours before admission, having suffered a neurological insult during the first 24 hours in the ICU, higher heart rate, and hypercapnia were associated with greater risk for in-hospital death after adjusting for Acute Physiology and Chronic Health Evaluation II score. CPR before admission, neurological insult, hypoxaemia and hypercapnia were associated with receipt of mechanical ventilation after adjusting for Acute Physiology and Chronic Health Evaluation II score.

Conclusion

ICU admission for asthma is relatively uncommon but remains associated with appreciable in-hospital mortality. The greatest determinant of poor hospital survival in asthma patients was receipt of CPR within 24 hours before admission to ICU. Clinical management of these patients should be directed at preventing cardiac arrest before admission.
Glucose-stimulated acrolein production from unsaturated fatty acids
Authors: Medina-Navarro R , Duran-Reyes G , Diaz-Flores M , Hicks J J , R J Kumate
Published: March 2004

Glucose auto-oxidation may be a significant source of reactive oxygen species (ROS), and also be important in the lipid peroxidation process, accompanied by the release of toxic reactive products. We wanted to demonstrate that acrolein can be formed directly and actively from free fatty acids in a hyperglycemic environment. A suspension of linoleic and arachidonic acids (2.5 mM) was exposed to different glucose concentrations (5, 10 and 15 mmol/L) in vitro. The samples were extracted with organic solvents, partitioned, followed at 255 / 267 nm, and analysed using capillary electrophoresis and mass spectroscopy. The total release of aldehydes significantly (P ≤ 0.01) increased from 1.0 to 5.1, 8.3 and 13.1 μmol/L after 6 hours of incubation, proportional to glucose concentrations. It was possible to verify a correlate hydroperoxide formation as well. Among the lipid peroxidation products, acrolein (5% of total) and its condensing product, 4-hydroxy-hexenal, were identified. From the results presented here, it was possible to demonstrate the production of acrolein, probably as a fatty acid product, due to free radicals generated from the glucose auto-oxidation process. The results led us to propose that acrolein, which is one of the most toxic aldehydes, is produced during hyperglycemic states, and may lead to tissue injury, as one of the initial problems to be linked to high levels of glucose in vivo.
The radiation-induced bystander effect: evidence and significance
Authors: Azzam Edouard I , Little John B
Published: March 2004

A multitude of biological effects observed over the past two decades in various in vivo and in vitro cell culture experiments have indicated that low dose/low fluence ionizing radiation has significantly different biological responses than high dose radiation. Exposure of cell populations to very low fluences of particles or incorporated radionuclides results in significant biological effects occurring in both the irradiated and nonirradiated cells in the population. Cells recipient of growth medium from irradiated cultures can also respond to the radiation exposure. This phenomenon, termed the ‘bystander response’, has been postulated to impact both the estimation of risks of exposure to ionizing radiation and radiotherapy. Amplification of radiation-induced cyto-toxic and genotoxic effects by the bystander effect is in contrast to the observations of adaptive responses, which are generally induced following exposure to low dose, low linear energy transfer radiation and which tend to attenuate radiation-induced damage. In this article, the evidence for existence of radiation-induced bystander effects and our current knowledge of the biochemical and molecular events involved in mediating these effects are described. Potential similarities between factors that mediate the radiation-induced bystander and adaptive responses are highlighted.
Evidence for ‘bystander effects’ in vivo
Authors: Brooks Antone L
Published: March 2004

The observation of bystander effects in vitro have raised some serious questions as to the appropriate target size for calculation radiation dose. This has implications on the risk from ionizing radiation since dose is often directly related to radiation risk. This paper demonstrates that bystander effects do occur in vivo. It demonstrates that at low dose rates the bystander effects and risk are limited to the organ where the radiation dose is delivered. On the other hand, exposure to high radiation dose rates produces clastogenic factors that are released into the blood. These factors have been demonstrated both in vitro and in vivo and may influence risk in organs not directly exposed to the radiation. Bystander effects suggest that organs respond as a unit and are not just a bag of individual cells acting independently. Dose and risk must consider this unit.
In vivo validation of the bystander effect
Authors: Kassis Amin I
Published: March 2004

The bystander effect post radionuclide decay describes the biologic response(s) of cells not directly targeted by the radiation insult. Recently, we demonstrated that the specific irradiation of human tumor cells in vivo leads to a bystander effect in subcutaneously growing tumors. These in vivo findings 1) call for the re-evaluation of approaches currently used for estimating the risks to individuals/populations inadvertently exposed internally to radioactivity (e.g., alpha particles) as well as to patients undergoing routine diagnostic nuclear medical procedures, and 2) impact significantly the current dogma for assessing the therapeutic potential of internally administered radionuclides.
A theoretical approach to the role and critical issues associated with bystander effect in risk estimation
Authors: Nikjoo Hooshang , Khvostunov Igor K
Published: March 2004

This paper presents a quantitative biophysical model of the radiation-induced bystander effect. The principle aim of the bystander model is to establish whether bystander signal can be associated with low molecular weight factors that are transmitted by diffusion type processes in the medium surrounding the recipient cells. Cell inactivation and induced oncogenic transformation by microbeam and broadbeam irradiation systems were considered. The biophysical model postulates that the oncogenic bystander response observed in non-hit cells originates from specific signals received from inactivated cells. The bystander signals are assumed to be protein like molecules spreading in the culture media by Brownian motion. The bystander signals are assumed to switch cells into a state of cell death (apoptotic/mitotic/necrosis) or induced oncogenic transformation modes. The bystander cell survival observed after treatment with the irradiated conditioned medium using broadbeam and the microbeam irradiation modalities were analysed and interpreted in the framework of the Bystander Diffusion Model (BSDM). The model predictions for cell inactivation and induced oncogenic transformation frequencies agree well with observed data from microbeam and broadbeam experiments. In the case of irradiation with constant fraction of cells, transformation frequency for the bystander effect increases with increasing radiation dose. The BSDM predicts that the bystander effect cannot be interpreted solely as a low-dose effect phenomenon. It is shown that the bystander component of radiation response can increase with dose and can be observed at high doses as well as low doses. The validity of this conclusion is supported by analysis of experimental results from high-LET microbeam experiments.
Commentary on radiation-induced bystander effects
Authors: Wright Eric G
Published: March 2004

The paradigm of genetic alterations being restricted to direct DNA damage after exposure to ionizing radiation has been challenged by observations in which effects of ionizing radiation arise in cells that in themselves receive no radiation exposure. These effects are demonstrated in cells that are the descendants of irradiated cells (radiation-induced genomic instability) or in cells that are in contact with irradiated cells or receive certain signals from irradiated cells (radiation-induced bystander effects). Bystander signals may be transmitted either by direct intercellular communication through gap junctions, or by diffusible factors, such as cytokines released from irradiated cells. In both phenomena, the untargeted effects of ionizing radiation appear to be associated with free radical-mediated processes. There is evidence that radiation-induced genomic instability may be a consequence of, and in some cell systems may also produce, bystander interactions involving intercellular signalling, production of cytokines and free radical generation. These processes are also features of inflammatory responses that are known to have the potential for both bystander-mediated and persisting damage as well as for conferring a predisposition to malignancy. Thus, radiation-induced genomic instability and untargeted bystander effects may reflect interrelated aspects of inflammatory type responses to radiation-induced stress and injury and contribute to the variety of the pathological consequences of radiation exposures.
An integrated modelling environment for the computer-based embodiment of engineering systems with standard components
Authors: Hicks B J , Culley S J
Published: March 2004

In today's competitive global manufacturing industries, standard components play an important role in the commercial success of any product or machine system. The consideration of standard components during the early stages of the new product introduction process is therefore particularly important. However, the ability of the designer to explore different configurations and combinations of standard components is severely frustrated by the analytically intensive and time-consuming aspects of not only embodying a concept but also dealing with standard components and their associated mechanisms for design and selection. This paper presents the application of an integrated modelling environment for the computer-based embodiment of a machine system. The role of such an approach in the design process is discussed and the elements of the modelling environment are summarized. The processes of constructing and embodying a machine system are described and an industrial case study is presented. This case study is used to demonstrate the capabilities and potential of the new approach for supporting the embodiment and evaluation of alternative system configurations.
Process fusion: Tube hydroforming and crushing in a square die
Authors: Hwang Y M , Allan T
Published: March 2004

The objectives of this study are to evaluate the quality of the tubes formed by process fusion: hydroforming and crushing. The plastic flow pattern of the tubes during the process fusion in a square cross-sectional die is explored. Finite element simulations using the commercial software DEFORM for the tube expansion test and process fusion of circular tubes formed into a square cross-section have been conducted. The tubes in the process fusion have larger diameter and smaller thickness than the tubes used in the expansion test. The relationship between the forming pressurization and loading pass is discussed. Comparisons of the simulation results such as thickness distribution of the formed product, clamping force and forming pressure for the expansion test and process fusion are made. It is known that the internal pressures and the clamping forces of the die needed in process fusion are much less than those in the expansion test. The thickness distribution obtained by process fusion is much more uniform than that obtained in the expansion test.
A comparison of shrink-fit holding torque using probabilistic, micromechanical and experimental approaches
Authors: Booker J D , Truman C E , Wittig S , Mohammed Z
Published: March 2004

A shrink-fit is a semi-permanent assembly system that can resist the relative movement or transmit torque between two components through the creation of high radial pressures at the interface of its constituent parts. The traditional approach to determine the holding torque of a shrink-fit is based on Lame's equation to predict radial pressures at the interface of the components and knowledge of the coefficient of friction and length of contact. This paper examines the validity of this approach and a variant, which takes into account surface roughness conditions of the interfacing components, by comparing statistical distributions of the holding torque with those found experimentally for a sample of a particular shrink-fit configuration. The probabilistic results of a micromechanical approach are presented which show good comparison with experimental results, indicating that current design formulae are inadequately predicting holding torque. In addition, the phenomenon of increased holding torque with loading cycle number is observed experimentally, and areas where further work needs to be conducted in order to model the situation using frictional and plastic shakedown are outlined.
Design optimization of the blow moulding process using a fuzzy optimization algorithm
Authors: Hsu Y-L , Liu T-C , Thibault F , Lanctot B
Published: March 2004

Blow moulding is the forming of a hollow part by ‘blowing’ a mould cavity shaped parison made by a thermoplastic molten tube. Blow-moulded parts often require strict control of the thickness distribution in order to achieve the required mechanical performance and final weight. A fuzzy optimization algorithm for determining the optimal die gap openings and die geometry for the required thickness distribution in the blow moulding process is presented. The idea of the fuzzy optimization algorithm is that, instead of using purely numerical information to obtain the new design point in the next iteration, engineering knowledge and the human supervision process can be modelled in the optimization algorithm using fuzzy rules. The structure of an optimization algorithm is still maintained to guide the engineering decision process and to ensure that an optimal solution rather than a trial and error solution can be obtained. It is shown how a single fuzzy engine can be used in various cases and types of optimization of the blow moulding process.
Developing cost models by advanced modelling technology
Authors: Stockton D , Wang Q
Published: March 2004

The aim of this paper is to examine the use of artificial neural network (ANNs) in the development of cost models. Although such advanced modelling techniques have been highly successful in many engineering areas, this success has been strongly dependent on the ability to choose the correct ANN structure. In this respect, choosing the most suitable structure for the individual processing elements that make up the ANN is essential. The research reported in this paper, therefore, makes use of the Taguchi methodology to identify best and worst structural elements for ANN processing elements. In order clearly to determine the accuracy of the models developed, cost information has been generated using a published cost model of a turning process. The cost information generated from this model has been used to train ANNs and test the resulting model for estimating accuracy. In order to measure accuracy, the ‘percentage average absolute error’ value has been adopted. Using this measure, the accuracy of models developed using the best and worst ANN structural elements have been compared with the use of regression analysis. The results indicate that the use of ANN to develop cost models is superior to regression analysis, although both methods fail to develop models that provide useful accuracies when large numbers of variables are involved.
Laser hole drilling quality and efficiency assessment
Authors: Yilbas B S , Aleem A
Published: March 2004

In laser hole drilling, the end-product quality, the efficiency of the process and the cost of operation are important. In the present study, the laser drilling process is examined by means of statistical analysis. The significance levels of the parameters affecting the hole feature are tested using an F-test. The thermal efficiency of the drilling process is presented. Tantalum is selected as the workpiece material, while four levels of ambient gas pressure (subatmospheric), laser output energy, focus setting of the focusing lens and workpiece thickness are selected as affecting parameters. The drilling experiment is conducted according to the levels of the parameters selected. It is found that all the parameters influence the hole feature and the hole geometry improves for certain combinations of the affecting parameters, provided that overall hole quality is sensitive to the levels of ambient gas pressure and workpiece thickness.
Automatic generation of numerical control part programs using object-oriented software
Authors: Srinivas J
Published: March 2004

This paper presents an automatic approach to the generation of numerical control (NC) part programs for a specified manufacturing process plan. Generation of NC part programs for a specified process plan is a tedious task, especially when there are repetitive sequences of operations. The interactive graphics software developed in the present work simultaneously generates manual part programs. Three modules of the present software separately create an interactive process plan and NC code for point-to-point operations, straight-cut operations and contouring operations. Outputs of the present software are shown with examples.
On the numerical modelling of laser shearing of glass sheets used to optimize production methods
Authors: Paterson N , Tawn A , Williams K , Nurse A D
Published: March 2004

The problem of the control of the propagating crack tip during laser shearing (or zero width laser cutting of glass) is essentially one of controlling the stress field within the substrate. The glass substrate is stressed thermally using surface absorption of 10.6 μm laser radiation followed by cooling, in this case from a fine atomized waterjet. The stresses created in a large sheet, combined with the residual stresses within the glass substrate, are sufficient to propagate a subsurface flaw to form a controlled crack that gives excellent cut quality. This process has previously been studied experimentally and is successful for large plates and shapes with large radii of curvature. In order for future work to extend the process to minimize damage at the end of a cut, at the close of a profiled cut or close to the edge of the plate, it is necessary to understand the stresses that control the crack propagation and control these as the stress field changes. This work outlines an initial theoretical study of the heating and cooling cycle coupled with finite element analysis of the induced stresses to increase the understanding of laser shearing of glass. It provides a thorough description of how to perform the complex numerical studies, including how to determine the quasi-static crack tip position. The results provide levels of stresses in the immediate vicinity of the crack tip and show that thermal heating/cooling loading conditions are favourable for straight line cutting.
Predicting winding stresses for wound coils of non-linear orthotropic material
Authors: de Hoog F R , Yuen W Y D , Cozijnsen M , Huynh H-N
Published: March 2004

In another work, the authors presented an analysis of stresses in wound coils under the assumption that the coil could be modelled as an orthotropic linear material. In this paper the authors extend the theory to the case where the constitutive relations of the coil material are non-linear. The approach adopted for both the linear and non-linear theory differs radically from that usually reported in this field of research. Instead of the traditional ‘forward solution’ of calculating stresses for a given winding policy, an ‘inverse solution’ is obtained in which the winding stresses required to achieve specified stress distributions in a coil are calculated. Stress distributions required to avoid coiling problems can often be specified. This method can therefore offer considerable advantages in industrial applications, since winding stresses required to achieve a specified stress distribution in a coil can be calculated directly. The non-linear solutions are compared to those for the linear case for different winding stresses and coil properties. An example of the effect of modifying the stress distribution in a coil on the winding stress is given to illustrate the advantage of this method.
Use of a liquid shock tube as a device for the study of material deformation under impulsive loading conditions
Authors: Skews B W , Kosing O E , Hattingh R J
Published: March 2004

The deformation of metal plates and tubes achievable through the use of liquid shock waves generated in a shock tube is studied, with reference to both free-forming and forming the metal into dies, as well as to imprinting detailed features. The process is highly controllable, in terms of the magnitude and duration of the applied pressure pulse. A projectile is fired into a liquid column producing a high-pressure liquid shock wave which impinges on the testpiece. Different projectile materials, driving pressures and impact velocities are used to alter the energy and impulse transmitted. A particular attraction of its use in a laboratory is the application of high-speed photography to the deformation process. Illustration of the application of the facility to slamming studies and to fracture of brittle materials is included. It is concluded that the techniques employed offer a useful and versatile tool for many studies of material deformation.
Two-stage electrohydraulic servovalve using stack-type piezoelectric elements
Authors: Bang Y-B , Lee K-I , Joo C-S , Hur J-W
Published: March 2004

This paper presents a two-stage electrohydraulic servovalve with a nozzle-flapper pilot stage, which is controlled by stack-type piezoelectric elements. The flapper moving mechanism proposed in this research compensates for the thermal expansion of the piezoelectric elements and applies preload to the piezoelectric elements. The experimental result shows that this flapper moving mechanism has a frequency response of over 500 Hz without oil pressure, and a simplified servovalve system using this flapper moving mechanism has a frequency response of about 150 Hz at the supply pressure of 210 bar.
Pressure control of a pneumatic valve system using a piezoceramic flapper
Authors: Choi S B , Yoo J K
Published: March 2004

This paper presents a robust pressure control of a pneumatic valve system driven by piezoceramic actuators. The piezoceramic actuator bonded to both sides of a flexible beam makes a movement required to control the pressure at the flapper nozzle of a pneumatic system. After deriving the governing equation of motion, an appropriate size of the valve system is constructed. A sliding mode controller that is known to be robust to system uncertainties is then formulated in order to achieve accurate tracking control of a set of desired pressure trajectories. The closed-loop control bandwidth of the proposed valve system is empirically evaluated with respect to the supplying pressure and desired pressure. Tracking control performances for various pressure trajectories are presented in the time domain. In addition, the pressure control response achieved from the proposed feedback control method is compared with the response obtained from the open-loop control method.
An experimental study of underexpanded sonic, coaxial, swirl jets
Authors: Lee K-H , Setoguchi T , Matsuo S , Kim H-D
Published: March 2004

The present study addresses experimental investigations of the near-field flow structures of an underexpanded sonic, dual, coaxial, swirl jet. The swirl stream is discharged from the secondary annular nozzle and the primary inner nozzle provides the underexpanded free jets. The interactions between the secondary swirl and primary underexpanded jets are quantified by a fine pitot impact and static pressure measurements and are visualized using a shadowgraph optical method. The pressure ratios of the secondary swirl and primary underexpanded jets are varied below 7.0. Experiments are conducted to investigate the effects of the secondary swirl stream on the primary underexpanded jets, compared with the secondary stream of no swirl. The results show that the presence of an annular swirl stream causes the Mach disc to move further downstream, with an increased diameter, and remarkably reduces the fluctuations of the impact pressures in the underexpanded sonic dual coaxial jet, compared with the case of the secondary annular stream with no swirl.
An energy-based approach for modelling the behaviour of packaging material during processing
Authors: Hicks B J , Berry C , Mullineux G , McPherson C J , Medl A J
Published: March 2004

This paper deals with the investigation of improved methods for considering machine-material interaction during the design and production of packaging machinery. Minimum energy principles are used to create a theoretical model of the response of the packaging material during processing. The complex non-linear properties of the packaging material are encapsulated in parametric models generated through analysis of the physical measurement of the changing properties during processing. These two techniques are incorporated into a software model that represents the behaviour of a skillet during the erection process. This software model considers the material, the pack design and the machine system. The overall modelling approach is validated by comparison with a physical system, which shows a good correlation with the theoretical model.
Gearbox condition monitoring using self-organizing feature maps
Authors: Liao G , Liu S , Shi T , Zhang G
Published: March 2004

This paper proposes a novel technique for the condition monitoring of gearboxes based on a self-organizing feature maps (SOFM) network. In order to visualize the learned SOFM results more clearly, an improved method based on the unified distance matrix (U-matrix) method is presented, in which the overall topological information condensed into the map units is considered so as to project the high-dimensional input vectors into a two-dimensional space and give a better picture of their intrinsic structure than the original U-matrix method. The feature data extracted from industrial gearbox vibration signals measured under different operating conditions are analysed using the proposed technique. The results show that trained with the SOFM network and visualized with the improved method, the feature data are mapped into a two-dimensional space and formed clustering regions, each indicative of a specific gearbox condition. Therefore, the gearbox operating condition with a fatigue crack or broken tooth compared with the normal condition is identified clearly. Furthermore, with the trajectory of the image points for the feature data in two-dimensional space, the variation of gearbox conditions is observed visually, and the development of gearbox early-stage failures is monitored in time.
The torsional stiffness of involute spur gears
Authors: Wang J , Howard I
Published: March 2004

This paper presents the results of a detailed analysis of torsional stiffness of a pair of involute spur gears in mesh using finite element methods. Adaptive meshing has been employed within a commercial finite element program to reveal the detailed behaviour in the change over region from single- to double-tooth contact zones and vice versa. Analysis of past gear tooth stiffness models is presented including single- and multitooth models of the individual and combined torsional mesh stiffness. The gear body stiffness has been shown to be a major component of the total mesh stiffness, and a revised method for predicting the combined torsional mesh stiffness is presented. It is further shown tha the mesh stiffness and load sharing ratios will be a function of applied load.
Perspective on Decision Analysis Applications, 1990–2001
Authors: Keefer Donald L. , Kirkwood Craig W. , Corner James L.
Published: March 2004

This article identifies, and provides perspective on, trends and developments in decision analysis applications, based primarily on an exhaustive survey of decision analysis applications published in the period 1990–2001 in major English-language operations research and closely related journals. It serves as a guide to those interested in recent applications in specific areas or in applications that illustrate the use of particular methods. We compare the characteristics of the applications articles surveyed here with those of applications articles appearing in a similar set of journals between 1970 and 1989 and conclude that the overall rate of publication of decision analysis applications has increased. In addition, we find that both the mix of application areas and the specific aspects of decision analysis that are emphasized in applications publications have shifted somewhat. We also identify and discuss noteworthy trends in, and developments affecting, published applications, including those in computer software and software-related tools, decision conferencing, stochastic trees, value-focused thinking, normative systems, organizational processes, and real options. We highlight several award-winning decision analysis applications and discuss formation of a new practitioner-oriented professional group. Finally, we present some concerns and thoughts on future needs for advancing decision analysis practice.
Approximating Risk Aversion in Decision Analysis Applications
Authors: Kirkwood Craig W.
Published: March 2004

This paper investigates the impact of risk aversion in decision analyses under uncertainty with a single evaluation measure and presents a simple procedure for approximately addressing risk aversion in a way that is defensible for many decisions. Specifically, a simulation study is presented that leads to guidelines for determining when an expected utility analysis should be conducted for a decision, rather than simply an expected value analysis, and what form of utility function should be used for this expected utility analysis. The simulation study shows that a sensitivity analysis using an exponential utility function should be conducted for most decision analyses, but that this sensitivity analysis can often establish, without requiring utility information from the decision maker, that no further utility analysis is required. In addition, when further utility analysis is required, the simulation study shows that this can be done in a simple way using an exponential utility function that will be accurate for many decision analyses. However, in situations where there is equal or greater downside risk than upside potential, a more detailed study of the decision maker's utility function may be necessary.
Response to Comments on Keefer et al. (2004)
Authors: Keefer Donald L. , Kirkwood Craig W. , Corner James L.
Published: March 2004

Our article “Perspective on Decision Analysis Applications, 1990–2001” provides a comprehensive listing of decision analysis applications published between 1990 and 2001 in the 16 journals that we surveyed and uses this together with results from a previous survey to identify, and provide perspective on, trends and developments in decision analysis applications. Cantor (2004) and Hämäläinen (2004) provide useful comments and additional references that supplement the material in our article, and we agree with many of their comments. However, we do not agree with their view that our definition of “decision analysis” is too restrictive. We believe that, after 35 years, the core of decision analysis is now well established and that we have used the generally understood definition in selecting the applications included in our article.
Scheduling Banner Advertisements on the Web
Authors: Menon Syam , Amiri Ali
Published: March 2004

Despite the slowdown in the economy, advertisement revenue remains a significant source of income for many Internet-based organizations. Banner advertisements form a critical component of this income, accounting for 40 to 50% of the total revenue. There are considerable gains to be realized through the efficient scheduling of banner advertisements. This problem has received only limited attention in the literature. This paper introduces formulations for an important version of the banner advertisement scheduling problem. Two solution approaches, one based on Lagrangean decomposition and the other based on column generation, are presented, along with extensive results based on 1,500 randomly generated data sets. These results suggest that, while both approaches do very well in general, column generation consistently performs better than Lagrangean decomposition, giving gaps of 0.0004% or better in 4.4 seconds or less, even on relatively large problem instances.
On Bridging the Gap Between Stochastic Integer Programming and MIP Solver Technologies
Authors: Parija Gyana R. , Ahmed Shabbir , King Alan J.
Published: March 2004

Stochastic integer programs (SIPs) represent a very difficult class of optimization problems arising from the presence of both uncertainty and discreteness in planning and decision problems. Although applications of SIPs are abundant, nothing is available by way of computational software. On the other hand, commercial software packages for solving deterministic integer programs have been around for quite a few years, and more recently, a package for solving stochastic linear programs has been released. In this paper, we describe how these software tools can be integrated and exploited for the effective solution of general-purpose SIPs. We demonstrate these ideas on four problem classes from the literature and show significant computational advantages.
A Branch-and-Cut Approach for a Generic Multiple-Product, Assembly-System Design Problem
Authors: Wilhelm Wilbert E. , Gadidov Radu
Published: March 2004

This paper presents two new models to deal with different tooling requirements in the generic multiple-product assembly-system design (MPASD) problem and proposes a new branch-and-cut solution approach, which adds cuts at each node in the search tree. It employs the facet generation procedure (FGP) to generate facets of underlying knapsack polytopes. In addition, it uses the FGP in a new way to generate additional cuts and incorporates two new methods that exploit special structures of the MPASD problem to generate cuts. One new method is based on a principle that can be applied to solve generic 0-1 problems by exploiting embedded integral polytopes. The approach includes new heuristic and pre-processing methods, which are applied at the root node to manage the size of each instance. This paper establishes benchmarks for MPASD through an experiment in which the approach outperformed IBM's Optimization Subroutine Library (OSL), a commercially available solver.
A New Pricing Scheme for Airline Crew Scheduling
Authors: Makri Alexandra , Klabjan Diego
Published: March 2004

Solving LP relaxations of airline crew scheduling models is computationally challenging due to the presence of a large number of variables, complex feasibility rules to generate columns, and nonlinear cost. We perform computational experiments with a nonlinear pricing strategy. We develop a column generation scheme that uses several pruning rules to fathom column enumeration. The pruning rules are categorized into approximate and exact, where the approximate rules might prune columns that would yield an improved objective value. The pruning rules use the fact that columns are paths in a network, and we use shortest path algorithms and their extensions to obtain bounds.
A New Formulation and Resolution Method for the p-Center Problem
Authors: Elloumi Sourour , Labbé Martine , Pochet Yves
Published: March 2004

The p-center problem consists of choosing p facilities among a set of M possible locations and assigning N clients to them in order to minimize the maximum distance between a client and the facility to which it is allocated. We present a new integer linear programming formulation for this min-max problem with a polynomial number of variables and constraints, and show that its LP relaxation provides a lower bound tighter than the classical one. Moreover, we show that an even better lower bound LB*, obtained by keeping the integrality restrictions on a subset of the variables, can be computed in polynomial time by solving at most O(log2(NM)) linear programs, each having N rows and M columns. We also show that, when the distances satisfy triangle inequalities, LB* is at least one third of the optimal value. Finally, we use LB* in an exact solution method and report extensive computational results on test problems from the literature. For instances where the triangle inequalities are satisfied, our method outperforms the running time of other recent exact methods by an order of magnitude. Moreover, it is the first one to solve large instances of size up to N = M = 1,817.