Dynamic Inflow Research Articles

Designing evolving user profile in e-CRM with dynamic clustering of Web documents

Internet technology enables companies to capture new customers, track their performances and online behavior, and customize communications, products, services, and prices. Analyses of customers and customer interactions for electronic customer relationship management (e-CRM) can be performed by way of using data mining (DM), optimization methods, or combined approaches. One key issue in the analysis of access patterns on the Web is the clustering and classification of Web documents. Generally, the classification has its base on analytical models which assume a pre-fixed set of keywords (attributes) with predefined list of categories. This assumption is not realistic for large and evolving collections of documents such as World Wide Web. We propose a new approach to solve the problem of unknown number of evolving categories. The approach begins with the classification of test documents into a set of initial categories. A working prototype system which is based on Fuzzy Clustering CRM (FC-CRM) has been developed and presented to validate the proposed approach and illustrate how it handles the dynamic inflow of new documents.

Dynamic inflow modelling for autorotating rotors

AbstractThe dynamic inflow model is a powerful tool for predicting the induced velocity distribution over a rotor disc. On account of its closed form and simplicity, the model is especially practical for studying flight mechanics or for designing control systems for helicopters. Scant attention has, however, been paid so far in utilising the dynamic inflow model to analyse an autorotating rotor, which is different from a powered rotor in the geometric relation between the direction of the inflow and the rotor disc. Autorotation is an abnormal condition for helicopters, but for gyroplanes it is the normal mode of operation. Therefore the theoretical discussion on an autorotating rotor is of importance not only to improve the understanding of present gyroplanes, but also in the development of new gyroplanes and to analyse the windmill-brake state of helicopters. Dynamic inflow modelling is reviewed from first principles, and this identifies a modification to the mass flow parameter. A qualitative assessment of this change indicates that it is likely to have a negligible impact on the trim state of rotorcraft in autorotation, but a significant effect on the dynamic inflow modes in certain flight conditions. This is confirmed by numerical simulation, although considerable differences only become apparent for steep descents with low forward speed. It is concluded that while modification of the mass flow parameter is perhaps mathematically accurate, for practical purposes it is required only in a limited area of the flight envelope of autorotating rotorcraft.

Rotorcraft simulation modelling and validation for control law design

AbstractThis paper describes the development and validation of a high fidelity simulation model of the Bell 412 helicopter for handling qualities and flight control investigations. The base-line model features a rigid, articulated blade-element formulation of the main rotor, with flap and lag degrees of freedom. The Bell 412 HP engine/governor dynamics are represented by a second-order system. Other key features of the base-line model include a finite-state dynamic inflow model and lag damper dynamics. The base-line model gives excellent agreement with flight-test data over the speed range 15-120kt for on-axis responses. Prediction of off-axis responses is less accurate. Several model enhancement options were introduced to obtain an improved off-axis response. It is shown that the pitch/roll off-axis responses in transient manoeuvres can be improved significantly by including wake geometry distortion effects in the Peters-He finite-state dynamic inflow model.

Dynamic Left Ventricular Inflow Obstruction Associated with a Left Atrial Myxoma

A 49-year-old female presented with lower extremity weakness, worsening dyspnea, stigmata of systemic embolism, and an acute episode of dysarthria. Brain computed tomography and magnetic resonance imaging demonstrated small embolic strokes while transthoracic echocardiographic examination showed a large left atrial (LA) mass. The patient was scheduled for surgical excision of the mass. Intraoperative two-dimensional and three-dimensional transesophageal echocardiography (TEE) (Siemens Sequoia, Mountain View, CA and Tom Tek Corporation, Boulder, CO) demonstrated a 4 × 6 cm2 pedunculated LA mass attached by a pedicle to the superior fossa of the interatrial septum [Fig. 1 and Video Loop 1 (Please see video loops available at www.anesthesia-analgesia.org)]. During diastole, the mass prolapsed through the mitral valve resulting in a turbulent color flow Doppler pattern (Video Loop 2). Continuous wave doppler revealed mild to moderate left ventricular (LV) inflow obstruction, with calculated mean and peak pressure gradients of 6 mm Hg and 9 mm Hg, respectively (Fig. 2). In general, mild mitral obstruction is suggested by a mean pressure gradient <6 mm Hg, moderate obstruction by a mean pressure gradient of 6–10 mm Hg, and severe obstruction by a gradient >10 mm Hg. Proximal isovelocity surface area can provide information about the degree of obstruction, but the asymmetry of the proximal isovelocity surface area hemisphere in this case may have resulted in an inaccurate estimate of the diminished LV inflow area. The use of pressure half-time is also commonly used to estimate the severity of mitral obstruction, however, this technique has not been validated in patients with dynamic LV inflow obstruction.Figure 1.: Intraoperative two-dimensional transesophageal mid-esophageal four-chamber view demonstrating the left atrial myxoma (arrow) prolapsing through the mitral valve during diastole. LA: left atrium; LV: left ventricle; RV: right ventricle.Figure 2.: Intraoperative continuous wave Doppler image from the transesophageal mid-esophageal four-chamber view demonstrating the left ventricular inflow velocity profile along the prolapsing left atrial myxoma. Pressure gradients (ΔP) calculated from the modified Bernoulli Equation (ΔP = 4V 2; V = peak velocity), were obtained from values averaged over three cardiac cycles. The calculated mean (6 mm Hg) and peak (9 mm Hg) pressure gradients are consistent with mild-to-moderate obstruction.A complete excision of the LA mass and its atrial septal attachment was performed and the resultant atrial septal defect was closed with pericardial patches. After cardiopulmonary bypass, TEE confirmed an intact interatrial septum. Pathologic examination confirmed the mass to be a myxoma. The patient recovered uneventfully and was discharged home on postoperative Day 5. Seventy-five percent of myxomas are found in the LA, but 10–20% originate in the right atrium, and 5% in either ventricle. In contrast to this report, LA myxomas typically attach via a narrow base to the interatrial septum at the border of the fossa ovalis, and are rarely invasive. Patients with myxomas who become symptomatic usually present with congestive heart failure (67%) because of LV inflow obstruction, signs of tumor embolization (29%), or constitutional symptoms (41%) (1,2). Intraoperative TEE is used for identifying satellite tumors and confirming the structural integrity of the interatrial septum after surgical excision of a myxoma (3). Three-dimensional TEE may be helpful for delineating the extent of the myxoma's attachment, thereby permitting more accurate surgical planning.

Enhanced Ventricular Untwisting During Exercise

The cascade of events by which early diastolic left ventricular (LV) filling increases with exercise is not fully elucidated. Doppler tissue imaging (DTI) can detect myocardial motion, including torsion, whereas color M-mode Doppler (CMM) can quantify LV intraventricular pressure gradients (IVPGs). Twenty healthy volunteers underwent echocardiographic examination with DTI at rest and during submaximal supine bicycle exercise. We assessed LV long-/short-axis function, torsion, volume, inflow dynamics, and early diastolic IVPG derived from CMM data. LV torsion and untwisting velocity increased with exercise (torsion, 11+/-4 degrees to 24+/-8 degrees ; untwisting velocity, -2.0+/-0.7 to -5.6+/-2.3 rad/s) that was associated with an increase in IVPG (1.4+/-0.5 to 3.7+/-1.2 mm Hg). Untwisting in normal subjects occurred during isovolumic relaxation and early filling, significantly before long-axis lengthening or radial expansion. The clinical feasibility of this method was tested in 7 patients with hypertrophic cardiomyopathy (HCM); torsion was higher at rest but did not increase with exercise (16+/-4 degrees to 14+/-6 degrees), whereas untwisting was delayed and unenhanced (-1.6+/-0.8 to -2.3+/-1.2 rad/s). In concert, IVPG was similar at rest (1.2+/-0.3 mm Hg), but the exercise response was blunted (1.6+/-0.8 mm Hg). In normal subjects and HCM patients, there was a similar linear relation between IVPG and untwisting rate, with an overall correlation coefficient of r=0.75 (P<0.0001). LV untwisting appears to be linked temporally with early diastolic base-to-apex pressure gradients, enhanced by exercise, which may assist efficient LV filling, an effect that appears blunted in HCM. Thus, LV torsion and subsequent rapid untwisting appear to be manifestations of elastic recoil, critically linking systolic contraction to diastolic filling.

Model-based evaluation of struvite recovery from an in-line stripper in a BNR process (BCFS)

Phosphate removal and recovery can be combined in BNR processes. This may be realised by struvite precipitation from the supernatant of the sludge in anaerobic compartments. This can be beneficial for either improving bio-P removal effluent quality or lowering the influent COD/P ratio required for bio-P removal. For this reason, a patented BNR process, BCFS, was developed and applied in The Netherlands. Several questions relating to P-recovery and behaviour of the system remain unclear and need to be ascertained. For this purpose, a modelling technique was employed in this study. With the help of a previous developed model describing carbon oxidation and nutrient removal, three cases were fully simulated. The simulations demonstrated that there was an optimal stripping flow rate and P-recovery would increase in costs and bio-P activity might be negatively affected due to decreased bio-P efficiency if this value was exceeded. The simulations indicated that the minimal COD(biod)/P ratio required for the effluent standard (1 g P/m3) could be lowered from 20 to 10 with 36% of P-recovery. A simulation with dynamic inflow revealed that the dynamic influent loads affected slightly the anaerobic supernatant phosphate concentration but the effluent phosphate concentration would not be affected with regular P-recovery.

Integrated operation of sewer system and WWTP by simulation-based control of the WWTP inflow

In recent years numerical modelling became a standard procedure to optimise urban wastewater systems design and operation by integration. For dynamic control of the wastewater teatment plant (WWTP) inflow, a model-based predictive concept is introduced aiming at improving the receiving water quality. An on-line simulator running parallel to the real WWTP operation reflects the actual state of operation and provides this model information to a prognosis tool which determines the best option for the WWTP inflow. The investigations showed that it is possible to reduce the NH4-N peak concentrations in the receiving water by dynamic WWTP inflow control based on predictive scenario analysis.

A Method of Hub Vibratory Load Prediction under High Speed State

The research of hub vibratory loads is a very complicated problem of blade aeroelastic response. Based on the airflow environment of blade, the method of hub vibratory loads prediction will be produced when the helicopter flights forward with high speed. It involves the Leishman-Beddoes unsteady model and dynamic stall model, the dynamic inflow theory, the Piters He generalized dynamic wake theory, elastic flap movement of blade and so on. The State-Space method is used to solve the equation, which is fit for numerical calculation. Comparing calculational results of several models, it is revealed that the distributions of rotor wake and blade dynamic response have great influence upon the hub vibratory loads prediction.

Simulation of Pilot Workload for a Helicopter Operating in a Turbulent Ship Airwake

This article describes a recent study in helicopter/ship dynamic interface simulation to examine pilot workload in the presence of a ship's airwake. The flight dynamics model represents a UH-60 helicopter and is based on the GENHEL software. This flight model has been updated to include a high-order dynamic inflow model and gust penetration effects of the time-varying ship airwake. The airwake model is derived from time-accurate computational fluid dynamics (CFD) solutions and provides an appropriately detailed level of fidelity to capture its effect on pilot workload. To simulate pilot control inputs for shipboard approach operations, an optimal control model of the human pilot is developed. The pilot model can be easily tuned to achieve different tracking performances, based on a desired crossover frequency, in each control axis and is designed to operate over a range of airspeeds using a simple gain scheduling algorithm. The pilot model is used to predict pilot workload for shipboard approaches in two different wind-over-deck conditions. Validation studies are conducted using both time and frequency domain analyses. The pilot control input autospectra predicted from the simulation model are compared to those of flight test data from the Joint Shipboard Helicopter Integration Process program. The paper also discusses the application of a stochastic airwake model for more efficient simulation. This new airwake model is derived from the simulation with the full CFD airwake by extracting an equivalent six-dimensional gust vector. The spectral properties of the gust components are then analysed, and shaping filters are designed to simulate the gusts when driven by white noise. It is proposed that the stochastic gust model can be used to optimize the automatic flight control system in order to improve disturbance rejection properties of the aircraft.

A near wake model for trailing vorticity compared with the blade element momentum theory

AbstractA near wake model for trailing vorticity originally proposed by Beddoes for high‐resolution helicopter blade vortex interaction computations has been implemented and compared with the usual blade element momentum models used for wind turbine calculations. The model is in principle a lifting line model for the rotating blade, where only a quarter revolution of the wake system behind the blade is taken into account. This simplification of the wake enables a fast computation of the downwash from the trailed vortex system along the blade using the indicial function method and thus makes it realistic to use the model in aeroelastic time simulations. The downwash from the shed vorticity is also computed with a fast indicial function algorithm. In particular the model is investigated for use in calculations of aerodynamic damping for the different mode shapes of an operating wind turbine. Numerical results for the downwash of a wing in straight flow with elliptical circulation are compared with analytical results. Further, the downwash distribution of a 40 m long rotating blade is computed. Aerodynamic damping of the blade in axial harmonic translation and in the first flapwise mode is computed with the near wake model and compared with the results of a standard momentum model including a model for dynamic inflow. Copyright © 2004 John Wiley &amp; Sons, Ltd.

Prospective randomized comparison of early and late results of 4 different stent designs

Background Late results of interventional procedures using coronary stents are largely determined by the rate of restenosis. So far, few data are available addressing the effect of stent design on this crucial variable and on early and late adverse events after stent implantation. Methods From 1996 through1998, a total of 965 lesions in 925 patients with coronary artery disease were randomized to treatment with 1 of 4 different stent designs (Micro stent II [M] AVE, Düsseldorf, Germany; Sito [S] Sitomed, Rangendingen, Germany; Pura Vario [PV], Devon, Hamburg, Germany; Inflow [ID] Inflow Dynamics, München, Germany). The primary end point of the study was the degree of diameter stenosis measured by quantitative coronary angiography 6 months after stent implantation. Results Diameter stenosis at 6 months follow-up was not different in the 4 study arms (M 40.3 ± 24.1, S 42.8 ± 27.0, PV 42.6 ± 26.9 and ID 42.3 ± 26.8, P = .7). No significant differences could be detected in net lumen gain and late lumen loss, resulting in comparable restenosis rates (≥50% diameter stenosis) at follow-up (M 26.0%, S 30.5%, PV 31.3%, and ID 28.7%, P = .7). Early adverse events like stent loss, stent thrombosis, periinterventional acute myocardial infarctions and emergency coronary artery bypass graft also showed no significant differences. Multivariate regression analyses revealed reference vessel diameter <3.0 mm, overall stented length, a history of bypass grafting, localization of the target lesion in the left anterior descending coronary artery, type C lesions, dissection before stent implantation, and diabetes mellitus to be independent predictors for restenosis. Conclusion Stent design does not have significant influence on development of restenosis. Adverse event rates were similar with all stent types used in this trial.

Characteristic mechanical properties of balloon-expandable peripheral stent systems

To measure in vitro geometric-mechanical characteristics of balloon-expandable peripheral stent systems for determining suitability for specific vascular regions. Balloon-expandable stents including their delivery systems manufactured by Guidant (OTW Megalink trade mark ), Inflow Dynamics (Antares), Medtronic (AVE Bridge trade mark ), Biotronik (Peiron trade mark ) and Cordis (Corinthian IQ trade mark ) were selected for this study. When expanded, all stents had a nominal diameter of 8 mm. The length was 38 - 40 mm. Stent profile, trackability, length change on expansion, stiffness, elastic recoil, and radio-opacity in the crimped and expanded state of these stent systems were determined with specially developed test methods. The Corinthian IQ trade mark, Megalink trade mark and Peiron trade mark required the smallest force to pass through the vascular model. While the Bridge trade mark system had the largest profile with a diameter of 2.430 mm, all other stent systems had a significantly smaller diameter ranging from 1.970 mm for the Peiron trade mark to 2.078 mm for the Corinthian IQ trade mark. In the distal region of the stent delivery system, the Megalink trade mark was the most flexible and the Bridge trade mark system the stiffest. Elastic recoil for all stents was in the range of 2.5 % to 3.5 %, with the exception of the Bridge trade mark stent, which had an elastic recoil of 4.79 %. The Corinthian IQ trade mark stent had noticeably the highest radial stiffness. In the expanded condition, the Peiron trade mark was the most flexible while the Corinthian IQ trade mark and the Antares trade mark were found to be the stiffest. Length change (shrinkage on expansion) ranged from 0.54 to 6.57%, with the exception of the Corinthian IQ, which shrunk > 7mm (18.5%) on expansion. All stent systems in the crimped and expanded state were readily visible radiographically. Specific data of significant parameters are available to aid in the selection of balloon expandable stents systems to be deployed in complex vascular regions. All examined stent systems showed adequate mechanical properties, but clinically relevant differences were found in stent trackability, bending stiffness and shrinkage on expansion.

U.S. National Laboratory Research Supporting Low Wind Speed Technology

Harvesting wind energy from sites with lower annual average wind speeds at costs comparable to what can now be achieved in higher wind sites is an international challenge. It requires pushing the technology to optimize the use of materials and machinery and tuning the structure to withstand the loads unique to the lower wind speed sites. The U.S. Department of Energy’s laboratories— The National Renewable Energy Laboratory NREL and Sandia National Laboratories—are engaged in both basic science and applied research to overcome current technology limitations and enhance the individual components necessary to achieve costeffective low wind speed turbines. Technology improvements are necessary in three principal areas to minimize the cost of electricity production at lower wind speed sites.

Velocity Field Above a Rotor Disk by a New Dynamic Inflow Model

The potential e ow equations are converted to ordinary differential equations through a Galerkin approach in which velocity and pressure potential functions are expanded in terms of closed-form solutions to Laplace’ s equation. Because the method gives differential equations for the e ow in terms of a relatively few generalized coordinates that represent modes of the e owe eld, the resultant equations can be used effectively in preliminary design, real-time simulations, and dynamic eigenvalue analysis for aeroelasticity. This new theory is more general than the Peters ‐He dynamic wake model because it has a more rigorous derivation and includes ine ow modes previously neglected in the Peters ‐He model. Results are presented in the frequency domain for simple harmonic motion. Thecompletevelocity e eld above the disk is obtained by this new methodology, foraxial and skewed e ows, for various skew angles, and for different pressure distributions and are compared with the Peters ‐He model and with an exact solution obtained by a convolution integral.

Aeromechanical Stability Analysis and Control of Smart Composite Rotor Blades

The use of segmented constrained layer damping treatment and closed loop control is investigated for improved rotor aeromechanical stability. The rotor blade load-carrying member is modeled using a composite box beam with arbitrary wall thickness. The ACLs are bonded to the upper and lower surfaces of the box beam to provide active and passive damping in the aeromechanical stability analysis. A finite element model based on a hybrid displacement theory is used to accurately capture the transverse shear effects in the composite primary structure, the viscoelastic and the piezoelectric layers within the ACL. The Pitt-Peters dynamic inflow model is used in the air resonance analysis under hover conditions. Rigid body pitch and roll degrees of freedom and fundamental flap and lead-lag modes are considered in this analysis. A transformation matrix is introduced to transform the time-variant system to a time-invariant system. A LQG controller is designed for the transformed system based on the available measurement output. The control performance is compared with the results of the open loop and the passive control systems. Numerical results indicate that the proposed control system with surface bonded ACL damping treatment significantly increases rotor lead-lag regressive modal damping in the coupled rotor-body system.

Inverse method in tilt-rotor optimization

Tilt-rotor aircraft performance in hover and forward flight modes is optimized using the stiffnesses of the rotor blade as design variables. The performance in both flight modes is maximized simultaneously using a combined objective function. Aeroelastic analysis is based on mixed variational formulation for dynamics of moving beams along with finite-state dynamic inflow theory. Stiffnesses of an extension-torsion coupled and a fully coupled box beam are chosen as design parameters. Constraints are imposed on non-rotating natural frequencies of the beam, angle of attack and material failure. Based on the optimized stiffnesses, different composite materials for the rotor are studied to obtain a maximum performance in both flight regimes. Results show that significant improvements in the tilt-rotor performance are possible using optimally stiffened beam. The key stiffnesses affecting the performance of the rotor are identified.

Skewed Wake Induction Effects on Thrust Distribution on Small Wind Turbine Rotors

Accurate prediction of both the center of thrust location and the magnitude of the thrust on a rotor disk are critical to satisfactory modeling of the yawing of small wind turbines to large angles to passively control overshoots in power and loads at higher wind speeds. Of the two, the prediction of the center of thrust location upwind of the center of a yawed rotor disk appears to be the most uncertain and potentially in serious error. This error is due to uncertainties in skewed wake effects on the thrust distribution on the disk. Three skewed wake models are examined to better understand the potential sources of error. First is the dynamic inflow model originally developed for helicopters, and second is a modification of this model developed for wind turbines. Third is an earlier cylindrical vortex wake model which pioneered the study of skewed wake effects for helicopters, and which can be generalized for wind turbine applications. It is concluded that this generalized model and the original dynamic inflow model are the most promising for small wind turbine applications, and their predictions of center of thrust and blade root moments are compared for an idealized rotor. The focus is on static equilibrium loads, and note is taken of the potential importance of accounting for expanding wake effects. The basic results of the study are applicable to large as well as small wind turbine rotors.

A grey‐box model describing the hydraulics in a creek

AbstractThe Saint‐Venant equation of mass balance is used here to derive a stochastic lumped model describing the dynamics of the flow in a river. The flow dynamics are described by the evolution of the cross‐sectional area of the flow at two locations in the river. The unknown parameters of the model are estimated by combining the physical equations with a set of data. This method is known as grey‐box modelling. The data consist of water level measurements, taken every minute at two locations in a river, over a period of nine days. The data are sub‐sampled to a sampling period of 15 minutes before further processing, and a maximum likelihood method is used to estimate the parameters of the model.Three different models were applied to the data set. All three are linear reservoir models with an estimate of the dynamic lateral inflow as a function of precipitation. The first model is a single reservoir model, which proved to be too simple to adequately describe the effect of precipitation. The second model is also a single reservoir model, but the data from the downstream station were translated forward in time, corresponding to a time delay in the system (a retention time). This model responds in a physically reasonable manner to precipitation, capturing very well the flow peaks caused by rain events. The third model is based on two reservoirs, and like the second model, it responds reasonably to precipitation. Its description of the dynamics seems quite good, though it does not capture the flow peaks quite as well as the second model. However, it is shown, that this model statistically provides the best description of the system. Copyright © 2001 John Wiley &amp; Sons, Ltd.

Helicopter Rotor Dynamic Inflow Modeling for Maneuvering Flight

Helicopter Rotor Dynamic Inflow Modeling for Maneuvering Flight

Performance Enhancement of a Composite Tilt-Rotor Using Aeroelastic Tailoring

An optimization technique is applied in an attempt to improve the performance of a tilt-rotor aircraft with composite blades that are enhanced by aeroelastic tailoring. The aeroelastic analysis is based on a published mixed variational formulation of the exact intrinsic equations of motion of beams, along with a finite-state dynamic inflow theory for the rotor. The composite rotor blade is modeled structurally as a composite box beam with nonstructural mass included. For optimization the design variables are blade twist, box dimensions and wall thicknesses, ply angles of the laminated walls, and nonstructural mass. The rotor is optimized using an objective function that is weighted equally between the figure of merit in hover and the axial efficiency in for ward flight. Constraints are considered on blade weight, autorotational inertia, geometry, and aeroelastic stability. The effects of all structural couplings on rotor performance are studied. Of all possible couplings, extension-twist coupling is found to be the most effective parameter to enhance performance. The effects of accounting for pretwist and thin- vs thick-walled theories in the blade cross-sectional analysis are discussed. Significant improvements in the objective function are shown to be possible even when optimizing only the extension-twist coupling of the rotor blade.