bluuebunny/crossref_metadata_2025 huggingface dataset:
An Update on Coronary Artery Disease and Chronic Kidney Disease
Authors: Afsar Baris , Turkmen Kultigin , Covic Adrian , Kanbay Mehmet
Published: March 2014

Despite the improvements in diagnostic tools and medical applications, cardiovascular diseases (CVD), especially coronary artery disease (CAD), remain the most common cause of morbidity and mortality in patients with chronic kidney disease (CKD). The main factors for the heightened risk in this population, beside advanced age and a high proportion of diabetes and hypertension, are malnutrition, chronic inflammation, accelerated atherosclerosis, endothelial dysfunction, coronary artery calcification, left ventricular structural and functional abnormalities, and bone mineral disorders. Chronic kidney disease is now recognized as an independent risk factor for CAD. In community-based studies, decreased glomerular filtration rate (GFR) and proteinuria were both found to be independently associated with CAD. This paper will discuss classical and recent epidemiologic, pathophysiologic, and clinical aspects of CAD in CKD patients.
Digging Up the Human Genome: Current Progress in Deciphering Adverse Drug Reactions
Authors: Su Shih-Chi , Chung Wen-Hung , Hung Shuen-Iu
Published: March 2014

Adverse drug reactions (ADRs) are a major clinical problem. In addition to their clinical impact on human health, there is an enormous cost associated with ADRs in health care and pharmaceutical industry. Increasing studies revealed that genetic variants can determine the susceptibility of individuals to ADRs. The development of modern genomic technologies has led to a tremendous advancement of improving the drug safety and efficacy and minimizing the ADRs. This review will discuss the pharmacogenomic techniques used to unveil the determinants of ADRs and summarize the current progresses concerning the identification of biomarkers for ADRs, with a focus on genetic variants for genes encoding drug-metabolizing enzymes, drug-transporter proteins, and human leukocyte antigen (HLA). The knowledge gained from these cutting-edge findings will form the basis for better prediction and management for ADRs, ultimately making the medicine personalized.
Influence of Sn Doping on Phase Transformation and Crystallite Growth of TiO2 Nanocrystals
Authors: Fu Guozhu , Yang Yanqiu , Wei Gang , Shu Xin , Qiao Ning , Deng Li
Published: March 2014

Sn doped TiO2 nanocrystals were synthesized via a single‐step hydrothermal method and the influences of Sn doping on TiO2 have been investigated. It is found that Sn doping not only facilitates the crystal transfer from anatase to rutile but also facilitates the morphology change from sphere to rod. The states of Sn were studied by XPS and the creation of oxygen vacancies by Sn doping is confirmed. Moreover, the HRTEM results suggest that Sn facilitates preferential growth of resulting nanocrystals along (110) axis, which results in the formation of rod‐like rutile nanocrystals.
Contrast-Induced Acute Kidney Injury: Definition, Epidemiology, and Outcome
Authors: Meinel Felix G. , De Cecco Carlo N. , Schoepf U. Joseph , Katzberg Richard
Published: March 2014

Contrast-induced acute kidney injury (CI-AKI) is commonly defined as a decline in kidney function occurring in a narrow time window after administration of iodinated contrast material. The incidence of AKI after contrast material administration greatly depends on the specific definition and cutoff values used. Although self-limiting in most cases, postcontrast AKI carries a risk of more permanent renal insufficiency, dialysis, and death. The risk of AKI from contrast material, in particular when administered intravenously for contrast-enhanced CT, has been exaggerated by older, noncontrolled studies due to background fluctuations in renal function. More recent evidence from controlled studies suggests that the risk is likely nonexistent in patients with normal renal function, but there may be a risk in patients with renal insufficiency. However, even in this patient population, the risk of CI-AKI is probably much smaller than traditionally assumed. Since volume expansion is the only preventive strategy with a convincing evidence base, liberal hydration should be encouraged to further minimize the risk. The benefits of the diagnostic information gained from contrast-enhanced examinations will still need to be balanced with the potential risk of CI-AKI for the individual patient and clinical scenario.
Chain Hexagonal Cacti with the Extremal Eccentric Distance Sum
Authors: Qu Hui , Yu Guihai
Published: March 2014

Eccentric distance sum (EDS), which can predict biological and physical properties, is a topological index based on the eccentricity of a graph. In this paper we characterize the chain hexagonal cactus with the minimal and the maximal eccentric distance sum among all chain hexagonal cacti of lengthn, respectively. Moreover, we present exact formulas for EDS of two types of hexagonal cacti.
Association of Sex Hormones, Aging, and Atrial Fibrillation in Men
Authors: Magnani Jared W. , Moser Carlee B. , Murabito Joanne M. , Sullivan Lisa M. , Wang Na , Ellinor Patrick T. , Vasan Ramachandran S. , Benjamin Emelia J. , Coviello Andrea D.
Published: March 2014

Background—

Endogenous sex hormones have been related to cardiovascular outcomes and mortality. We hypothesized that sex hormones are related to atrial fibrillation (AF) in a community-based cohort of middle-aged to older men.

Methods and Results—

We examined testosterone, estradiol, and dehydroepiandrosterone sulfate in relation to incident AF in men participating in the Framingham Heart Study. We assessed the 10-year risk of AF in multivariable-adjusted hazard models. The cohort consisted of 1251 men (age, 68.0±8.2 years), of whom 275 developed incident AF. We identified a significant interaction between age and testosterone and, therefore, stratified men into age 55 to 69 years (n=786), 70 to 79 years (n=351), and ≥80 years (n=114). In men aged 55 to 69 years, each 1 SD decrease in testosterone was associated with hazard ratio (HR) 1.30 (95% confidence interval [CI], 1.07–1.59) for incident AF. The association between testosterone and 10-year incident AF in men 70 to 79 years did not reach statistical significance. In men ≥80 years, a 1 SD decrease in testosterone was associated with HR 3.53 (95% CI, 1.96–6.37) for AF risk. Estradiol was associated with incident AF (HR, 1.12; 95% CI, 1.01–1.26). Dehydroepiandrosterone sulfate had a borderline association with risk of AF that was not statistically significant (HR, 1.12; 95% CI, 0.99–1.28).

Conclusions—

Testosterone and estradiol are associated with incident AF in a cohort of older men. Testosterone deficiency in men ≥80 years is strongly associated with AF risk. The clinical and electrophysiological mechanisms underlying the associations between sex hormones and AF in older men merit continued investigation.
Un-War: An Aesthetic Sketch
Authors: Deutsche Rosalyn
Published: March 2014

Attempts to abolish war—not a particular war but war as a social institution—are often dismissed as utopian idealism, wild fantasies far removed from the realm of real politics. War, we are told, is inevitable. Humans are territorial and predatory beings. Besides, there has always been war. Who can forget the opening pages of Kurt Vonnegut's Slaughterhouse-Five, wherein the narrator says that he is writing an antiwar novel and his interlocutor replies, “You know what I say to people when I hear they're writing antiwar books? … I say, ‘Why don't you write an anti-glacier book instead?’” “What he meant, of course,” the narrator explains, “was that there would always be wars, that they were as easy to stop as glaciers. I believe that, too.” (Of course, that was before global warming.)
Staging Soviet Art: 15 Years of Artists of the Russian Soviet Republic, 1932–33
Authors: Chlenova Masha
Published: March 2014

A documentary photograph from the exhibition 15 Years of Artists of the RSFSR (Khudozhniki RSFSR za 15 let) that opened in Moscow in June 1933 shows the extent to which contemporaries perceived this show as a watershed, a moment when the last remnants of the bourgeois culture of prerevolutionary Russia definitively gave way to the proletarian culture of the rapidly modernizing Soviet Union. A clean-cut and athletic Soviet youth looks straight into the eyes of the refined symbolist poet, playwright, critic, and translator Mikhail Kuz'min as painted in 1926 by a fellow member of the artistic group World of Art (Mir Iskusstva), Nikolai Radlov. In this confrontation, Kuz'min seems to embody everything the Soviet Union had done away with. The height of his fame as a Symbolist poet was the 1900s and 1910s; in the early 1930s, he was still writing poetry, but was unable to publish and increasingly marginalized. In the painting's background, a mythic landscape set within an arched window typical of Renaissance portraits ties him to the Western humanist tradition. Kuz'min's bodily posture invites contact: Seated close to the picture plane with open arms, he appears to look out. Yet the poet also seems reserved and distant, perhaps because of his formal dress, and introspective: The lit cigarette at the level of his mouth and his semi-open book signal that he is preoccupied with a subject other than his interlocutor. The youth, on the other hand, has the confident, even somewhat condescending look of a master of the universe (khoziain zhizni), with folded arms and a slightly skeptical glance. Wearing a fashionable sports shirt on his fit body, he represents the ideal of the times: a healthy, physically strong, and ideologically prepared builder of a socialist society who, both literally and figuratively, embodies the Soviet future. Such an ideal is exemplified by Aleksandr Samokhvalov's contemporaneous painting Girl in a Soccer Jersey (Devushka v futbolke), which was displayed in the same exhibition and quickly became an iconic symbol of Soviet athletic youth. This seemingly antagonistic encounter between representatives of the Soviet past and future simultaneously reflects the change in the official rhetoric. By 1933 it was conciliatory in tone, having firmly replaced the open class conflict of the preceding years, and bourgeois specialists were not only welcomed back into the fold of Soviet society, they were offered privileges if they worked for the new state.
Entropic Balance Theory and Variational Field Lagrangian Formalism: Tornadogenesis
Authors: Sasaki Yoshi K.
Published: March 2014

The entropic balance theory has been applied with outstanding results to explain many important aspects of tornadic phenomena. The theory was originally developed in variational (probabilistic) field Lagrangian formalism, or in short, variational formalism, with Lagrangian density and action appropriate for supercell-storm and tornadic phenomena. The variational formalism is broadly used in in modern physics, not only in classical mechanics, with Lagrangian density and action designed for each physical problem properly. The Clebsch transformation (equation) was derived in the classical variational formalism but has not been used because of the unobservable and nonmeteorological Lagrange multiplier. The entropic balance condition is thus developed from the Clebsch transformation, changing the unobservable nonmeteorological Lagrange multiplier to observable meteorological rotational flow velocity with entropy and making it applicable to tornadic phenomena. Theoretical details of the entropic balance are presented such as the entropic right-hand rule, entropic dipole, source and sink, overshooting mechanism of hydrometeors against westerlies and the existence of single and multiple vortices and their relation to tornadogenesis. These results are in reasonable agreement with the many observations and data analysis publications. The Clebsch transformation and entropic balance are the new balance conditions, different from the known other balance conditions such as hydrostatic, (quasi-)geostrophic, cyclostrophic, Boussinesq, and anelastic balance.

The variations in calculus of variations and in the classical variational formalism are hypothetical. However, this article suggests that the hypothetical variations could be physical, relating to quantum variations and their interaction with the classical systems.
Perfumed the axe that laid it low: The endangerment of sandalwood in southern India
Authors: Rashkow Ezra D.
Published: March 2014

Between 1950 and 1970, on average over 480,000 Indian sandalwood (Santalum album) trees were harvested annually in the state of Karnataka in southern India. Then, in 1974, it was suddenly discovered that there were only approximately 350,000 standing trees left in the entire state. Overnight, India’s sandalwood industry ground to a halt. The species was on the brink of extinction. Harvesting and trade in Indian sandalwood, long considered the most precious wood in the world, was ineffectively banned. Smugglers could now make more money by felling sandal trees than by poaching elephants for ivory. This article uses the history of sandalwood to assess claims about the nature and impact of colonial and postcolonial forestry, arguing that at least when it came to Indian sandalwood, though European foresters did overexploit the species and also failed to conserve it, the real watershed moment for the species came not during the colonial period but rather in the independence period when industrialisation led to a major endangerment crisis for the tree.
Book Review: The Trading World of the Indian Ocean, 1500–1800
Authors: Roy Tirthankar
Published: March 2014

OM PRAKASH, ed., The Trading World of the Indian Ocean, 1500–1800, Delhi: Pearson Education and Centre for Studies in Civilizations, 2012, pp. 684.
The origin of the controlling power of managing agents over modern business enterprises in colonial India
Authors: Nomura Chikayoshi
Published: March 2014

Under the joint stock company system, ultimate control over management is derived from the effective rate of shareholding. In colonial India, the joint stock company system was widely used from the mid-nineteenth century; however, control was considered to come not from the effective rate of shareholding but from the managing agency contract that guaranteed practical control to a managing agent, typically a business group that had far-reaching influence over business enterprises. Based on archival evidence, this paper clarifies that fundamental control was derived from dominant shareholding. This finding has two implications. First, the significant role of the rate of shareholding implies that managing agents had a keen interest in the value of share capital of the joint stock companies. Second, this significant role also implies that managing agents attempted to hold the dominant portion of shareholdings to keep control over their companies.
A new direction in political sociology?
Authors: Rowland Nicholas J
Published: March 2014

This essay reviews works in (political) sociology that offer alternatives to sociology-as-usual. Sociologists with even fleeting awareness of the recent history of political sociology are surely familiar with the cultural turn, the global turn, and the turn toward complexity; however, another turn seems to be afoot, one toward existential concerns that direct us to recover how people experience ‘the complex contradictions of the social and political world’ (Taylor, The New Political Sociology, p. 197). Complex experiences often leave behind residues or ‘traces,’ and contributors in a recently edited volume challenge sociologists to unlock the social significance of these traces and find new ways to capture what our methods capture so poorly, namely, popular forgettings, geographies of exclusion, and the slow erasure of deeds, memories, and other subjugated knowledges belonging to individuals who find themselves dismissed, dispelled, or disenfranchised by nation-states. Traces left behind by individuals navigating the complexities of contemporary experiments in human ‘being’ are just the sort of analysis that must, in principle, place the actor at the center of analysis, and, after careful study, we now appreciate that despite the analytical ease of assuming that actors are singular, sociologists should examine actors as plural and unearth their essential multiplicity.
A process engineering approach to the ALSTOM gasifier problem
Authors: Asmar B N , Jones W E , Wilson J A
Published: March 2014

The approach made here to designing a coal gasifier control system has its roots in process engineering. The favoured solution is largely based around conventional single-input single-output loops which control gas calorific value with air flow, gas pressure with steam flow, gas temperature with char flow, and bed mass with coal flow. Evolution towards this solution is discussed in relation to three intermediate schemes (in some cases involving non-linear control elements) that were found viable but less effective in terms of the defined performance criteria.

The favoured solution fully meets the required performance in both the 100 and the 50 per cent load cases but at 0 per cent load, while responses are all stable, there are constraint violations which are transient following the pressure step disturbance but sustained for the sinusoidal disturbance. An important operational issue to be addressed in relation to the proposed scheme is the management of automatic-manual transfers for some loops to avoid possible system instability.

During the study a number of issues, including equipment design and measurement precision, were identified as important. Their influence on controllability of the gasifier, and on the robustness of the proposed control scheme, is discussed.
Traffic assignment: Equilibrium models
Authors: Florian M , Hearn D W
Published: March 2014

The formulation of static traffic assignment models, with variable and fixed demand, based on Wardrop's first principle, are presented for deterministic and stochastic models. The main algorithms used to obtain solutions for these network equilibrium models are given for each class of assignment problems. Calibration and validation issues are considered.
Route guidance and information systems
Authors: Ben-Akiva M , Bottom J , Ramming M S
Published: March 2014

This paper reviews key aspects of route guidance and information systems (RGISs), which disseminate to drivers messages with information and recommendations intended to assist their route choice decisions. It first summarizes the major features that characterize and distinguish different RGIS designs. An important distinction exists between non-predictive and predictive systems. In the former, guidance messages are based on measurements or estimates of prevailing network conditions, while, in the latter, messages are derived from forecasts of future conditions. For predictive systems, the key issue is consistency: ensuring that drivers’ reactions to guidance derived from forecasts do not invalidate those forecasts. It is shown that the determination of consistent guidance must be model based and can be formulated as a fixed-point problem. The modelling of driver response to guidance is a relatively new subject; the paper surveys the main issues, and relates these to the user-and system-level evaluation of RGISs. A final section identifies some areas of current research.
Stopping rules formation and faults detection in parametric identification problems
Authors: Hajiyev Ch
Published: March 2014

An approach to the generation of stopping rules in parametric identification problems is proposed on the basis of the computation of a statistic of the difference between two successive estimates. This statistic is also used for fault detection in the Kalman filter. The developed decision rules are applied to a linear system identification problem. Experimental results are presented to demonstrate the performance of the proposed algorithms.
Robust rank preservation of matrices with both structured and unstructured uncertainties and its applications
Authors: Chen S-H , Chou J-H , Fong I-K
Published: March 2014

In this paper, the rank preservation problem is converted to the non-singularity analysis problem of the minors of the matrix under discussion. Under the assumption that a nominal matrix has a specified rank, a sufficient condition is proposed to preserve the assumed property when both structured and unstructured parameter uncertainties are added to the nominal matrix. The proposed sufficient condition can provide the explicit relationship of the bounds on both structured and unstructured parameter uncertainties for preserving the assumed property. The robust controllability problem for linear state-space models with both structured and unstructured parameter uncertainties is given to illustrate the application of the proposed sufficient condition and, for the case when only structured parameter uncertainties are considered, the presented sufficient condition is shown to be less conservative than the existing condition reported in the literature.
Fast sampling control of a class of differential linear repetitive processes
Authors: Benton S E , Rogers E , Owens D H
Published: March 2014

Repetitive processes are a distinct class of two-dimensional linear systems of practical and theoretical interest. Most of the available control theory for them is for the case of linear dynamics and focuses on systems theoretic properties such as stability and controllability/observability. This paper uses an extension of standard, or one-dimensional, feedback control schemes to control a physically relevant subclass of these processes.
Fuzzy model-based condition monitoring and fault diagnosis of a diesel engine cooling system
Authors: Twiddle J A , Jones N B
Published: March 2014

This paper describes a fuzzy model-based diagnostic system and its application to the cooling system of a diesel engine. The aim is to develop generic cost-effective knowledge-based techniques for condition monitoring and fault diagnosis of engine systems.

A number of fuzzy systems have been developed to model the cooling system components. Residuals are generated on line by comparison of measured data with model outputs. The residuals are then analysed on line and classified into a number of fuzzy classes symptomatic of potential system conditions. A fuzzy rule-based system is designed to infer a number of typical fault conditions from the estimated state of the valve and patterns in the residual classes. The ability to diagnose certain faults in the system depends on the state of the thermostatic valve.

The diagnostic systems have been tested with data obtained by experimental simulation of a number of target fault conditions on a diesel generator set test bed. In five test cases for separate cooling system operating conditions, the diagnostic system's successful diagnosis rate ranged between 73 and 97.7 per cent of the test data.
Robust adaptive fuzzy control application to uncertain non-linear systems in robotics
Authors: Hamzaoui A , Elkari A , Zaytoon J
Published: March 2014

In this paper the problem of tracking of a non-linear system in the presence of external disturbances is analysed. An adaptive fuzzy controller is proposed to improve performance of an H∞ tracking problem. The proposed approach benefits from the high performance of H∞ on the one hand, and the intuitive ‘smart’ approach of fuzzy control on the other. An example of a two-link manipulator is used for illustration.
Iterative learning algorithm with a quadratic criterion for linear time-varying systems
Authors: Huang S N , Tan K K , Lee T H
Published: March 2014

A novel iterative learning controller for linear time-varying systems is developed. The learning law is derived on the basis of a quadratic criterion. This control scheme does not include package information. The advantage of the proposed learning law is that the convergence is guaranteed without the need for empirical choice of parameters. Furthermore, the tracking error on the final iteration will be a class K function of the bounds on the uncertainties. Finally, simulation results reveal that the proposed control has a good setpoint tracking performance.
Control of gas turbine power plants by means of the weighted one-step-ahead adaptive technique
Authors: Dambrosio L , Camporeale S M , Fortunato B
Published: March 2014

The one-step-ahead controllers represent a branch of minimum prediction error adaptive controllers. They combine the parameter estimation of the controlled system model with the control scheme; therefore, they are especially suitable for non-linear and time-varying systems. Since the estimated parameters are updated at each time step (by using the sampled data), these methods can be adopted for non-linear applications. Consequently, the one-step-ahead controllers do not require knowledge of the dynamic characteristics of the controlled system (e.g. state-space systems or transfer functions).

Sometimes, in the gas turbine field, the control system could produce an excessive control effort, due to sudden variations of the electric load. In order to reduce this control action, the weighted one-step-ahead adaptive (WOSAA) control algorithm considers a penalty associated with the control effort using an appropriate cost function. In this way, the control variable does not assume values that are too large, even when the gas turbine undergoes sudden changes in the external load. As a consequence, the robustness and stability features of the WOSAA control system are increased.

The results show that the WOSAA control technique, applied to both the double-shaft aero-derivative gas turbine and the single-shaft heavy-duty gas turbine, effectively counteracts the load reduction with limited overshoot in the controlled variables with reduced control effort.
Quasi-optimal trajectory planning and control of a CRS A251 industrial robot
Authors: Miro J V , White A S
Published: March 2014

A near-optimal solution to the path-unconstrained time-optimal trajectory planning problem is described in this paper. While traditional trajectory planning strategies are entirely based on kinematic considerations, manipulator dynamics are usually neglected altogether. The strategy presented in this work has two distinguishing features. Firstly, the trajectory planning problem is reformulated as an optimal control problem, which is in turn solved using Pontryagin's maximum/minimum principle. This approach merges the traditional division of trajectory planning followed by trajectory tracking into one process. Secondly, the feedback form compensates for the dynamic approximation errors derived from linearization and the fundamental parameter uncertainty of the dynamic equations of motion. This approach can cope with flexible robots as well as rigid links. The terminal phase of the motion is controlled by a feedforward controller to reduce chatter vibrations. Results from simulations and an on-line implementation to a general-purpose open-chain industrial manipulator, the CRS A251, confirm the validity of the approach and show that maximizing the capabilities of the device can lead to an overall improvement in the manipulator time response of up to 24 per cent, while retaining an acceptable overshoot and steady state error regime.
Self-tuning mechanism for sliding surface slope adjustment in fuzzy sliding mode controllers
Authors: Eksin I , Güzelkaya M , Tokat S
Published: March 2014

There is an important relationship between fuzzy logic control and sliding mode control and integrating them to exploit the superior sides of these two techniques is an active area in control theory. The dynamic behaviour of the hybrid fuzzy sliding mode depends quite heavily on the sliding surface on which the control structure is switched. The main objective of this paper is to improve the system performance by continuously updating the slope of the sliding surface by a new time-varying coefficient. General and system independent meta-rules are generated in order to update this coefficient. Then, an algorithm that satisfies these meta-rules is first obtained using a fuzzy inference mechanism. Later, the fuzzy inference mechanism is replaced by an empirical formula that also satisfies the related meta-rules. The effectiveness of the proposed methods over the conventional fuzzy sliding mode controller is illustrated through the simulations performed on a second-order system with uncertain parameters.
A new design method for sliding mode controllers using a linear time-varying sliding surface
Authors: Tokat S , Eksin I , Güzelkaya M
Published: March 2014

The main objective of this study is to present a time-varying sliding surface using a new design method to improve the performance of a classical sliding mode controller that has a constant linear sliding surface. In the proposed method, the sliding surface is defined on new coordinate axes: one of the coordinates is the original sliding surface and the other one is naturally chosen as perpendicular to this axis. An important property of the proposed method is that it has a simple geometric interpretation and provides continuous movement of the sliding surface. A comparison of the proposed method against both the classical sliding mode controller and sliding mode controller with a discretely rotating sliding surface is made through simulations. Simulations are first performed on a typical second-order linear system without any disturbances and parameter variations. Next, bounded external disturbance and parameter variations are inserted into the system simulations. Results have shown that the proposed method improved the system performance, providing decreases in the reaching and settling times, and the proposed method has demonstrated more robustness to disturbances and parameter variations compared to its counterparts.
Hybrid control schemes for input tracking and vibration suppression of a flexible manipulator
Authors: Mohamed Z , Tokhi M O
Published: March 2014

This paper presents investigations into the development of hybrid control schemes for input tracking and end-point vibration suppression of a flexible manipulator system. The dynamic model of the flexible manipulator is derived using the finite element method. Initially, a collocated proportional-derivative (PD) controller utilizing hub angle and hub velocity feedback is developed for control of rigid-body motion of the system. This is then extended to incorporate a non-collocated proportional-integral-derivative (PID) controller and a feedforward controller based on input shaping techniques for control of vibration (flexible motion) of the system. Simulation results of the response of the manipulator with the controllers are presented in time and frequency domains. The performances of the hybrid control schemes are assessed in terms of input tracking and level of vibration reduction in comparison to the PD control. The effectiveness of the control schemes in handling various payloads is also studied. Finally, a comparative assessment of the hybrid control schemes is presented.
Comparison of thermal-hydraulic network control strategies
Authors: Franco W , Sen M , Yang K T , McClain R L
Published: March 2014

A dynamic thermal-hydraulic analysis of strategies used for the control of hydronic piping and heat exchanger networks is carried out. Three common temperature control methods are analysed and compared using a mathematical model. For this purpose a general thermal network with a primary loop, a secondary loop and a bypass that has the three control systems as special cases is proposed. The primary loop includes a chiller, while the secondary has a water-air cooling coil which serves as a thermal load. Integral controllers are used to vary the valve settings to control the air temperature leaving the cooling coil. The system responses for each of the three control schemes as a function of the thermal load are then compared to assess their relative merits using the temperature drop in the chiller as a criterion.
Design and control of a two-dimensional telerobotic system with a haptic interface
Authors: Her M-G , Karkoub M , Hsu K-S
Published: March 2014

A model for a ‘master-slave’ two-dimensional telerobotic dynamic system with a haptic interface device is derived. The telerobotic system consists of a ‘master’ robot, which is a direct-drive robot operated by a human arm, and a ‘slave’ robot, which is an x-y type pallet located at a remote site. When the active handle of the master is moved along an arbitrary trajectory, the remote slave duplicates the motion in a constrained or unconstrained environment. The behaviour of the environment is felt by the operator through the active handle of the master. This is achieved by feeding back the disturbance and reaction forces from the environment and the loads to the active handle. Consequently, the operator gets a feel of the task being performed without being physically at the location of the task. A control scheme is devised for the telerobotic system to establish smooth communication between the master and slave robots. This control scheme integrates the dynamics of the human arm, actuators and the environment in the closed-loop system. It was shown that the experimental and the theoretical results are in good agreement and that the design controller is robust to constrained/unconstrained environments.
Higher-order sliding mode control of a diesel generator set
Authors: Goh K B , Spurgeon S K , Jones N Barrie
Published: March 2014

Diesel engines are used as prime movers and independent power sources in many applications because of their advantages in terms of fuel efficiency, robustness and reliability. This paper presents the results of isochronous speed controller design and experimental analysis of robustness and efficiency of a turbocharged diesel generator set (genset). The steady state performance and transient response of the genset speed utilizing second-order sliding mode techniques with a super twisting sliding mode control algorithm are assessed. The algorithm does not require the time derivative of the sliding variable. It only uses the measured genset speed and does not require the use of an observer. A modification made to the algorithm shows improvement of the genset performance over a wide operating envelope. The influence of this methodology and modification of the algorithm on overall generator performance, in particular in the presence of large load changes and in terms of fuel efficiency, exhaust emissions, starting speed transient response and steady speed variation, are assessed. An algorithm for tuning the higher-order sliding mode (HOSM) controller for the genset is established and presented. The robustness of the controller is investigated and the performance is compared with that obtained by a commercial genset controller and a classical proportional-integral controller.
A method for behavioural organization for autonomous robots based on evolutionary optimization of utility functions
Authors: Wahde M
Published: March 2014

A method for behavioural organization for autonomous robots, based on evolutionary optimization of utility functions, is introduced and illustrated through several simulation examples. The method is shown to be efficient in generating behavioural organization systems that are both flexible and robust to noise. With this method, the amount of hand-tuning of parameters is minimized and, in principle, the user is only required to define fitness functions for the behaviours directly related to the task of the robot. The utility functions representing the beliefs and intentions of the robot are, in general, obtained through evolutionary optimization. However, if desired, the user also has the freedom to specify utility functions by hand.
Modelling and control of an unmanned excavator vehicle
Authors: Zweiri Y H , Seneviratne L D , Althoefer K
Published: March 2014

This paper investigates the modelling and control of a full-scale excavator vehicle. A detailed analytical model for an unmanned excavator vehicle is developed. The model takes into account the kinematics and dynamics of the mobile platform (vehicle) and the excavation arm (links and hydraulic system). The model describes the dynamic relationship between the operator input commands (fuelling and joystick commands to excavation arm and steering lever) and the trajectories and forces of the excavator vehicle. The dynamic model of the excavation arm system is validated against measured data. The validation of the model is conducted in collaboration with QinetiQ Limited (the new science and technology company formed from the major part of DERA, the British Government's defence research and development organization). A unified model is important for design of control strategies, since in order to move the bucket of a mobile excavator, movements of the entire vehicle are required. A key requirement for automating the excavation task is automated trajectory tracking, and a proportional-integral-derivative (PID) controller for trajectory tracking is developed and tested. It is noted that even though the results presented in this paper are focused on a particular excavator, the research is generic and can be adapted to any tracked ground vehicle with an on-board closed-chain manipulator.
Intelligent system modelling of a three-dimensional ultrasonic positioning system using neural networks and genetic algorithms
Authors: Unnikrishnan N , Mahajan A , Chu T
Published: March 2014

This paper presents a neural network model for a three-dimensional ultrasonic position estimation system that uses the difference in the time of arrivals of waves from a transmitter to various receivers. Even though a linearized analytical model for the three-dimensional system exists and is currently being used to estimate the position of the transmitter, its accuracy is highly dependent on complex and time consuming signal conditioning. A neural network approach is developed to train the system based on unconditioned training sets obtained directly from the receivers. It is proposed to use the final trained system to estimate the three-dimensional position in real time using these raw signals, thereby simplifying the hardware and the computational software as well as increasing the update rate. The weights of the neural network are obtained from a traditional back-progation method and by using genetic algorithms. Results for one-, two- and three-dimensional systems are presented as proof of concept. The performance of the neural network model using the raw signals is shown to be comparable to the analytical model using conditioned signals. Further, it is shown that the neural network model is extremely robust in terms of providing accurate position estimates, even after loss of information from multiple receivers. This work has significant applications in robotics, autonomous systems, virtual reality and image-guided surgery.
Optimization of a fed-batch fermentation process control competition problem using the NEOS server
Authors: Liang J , Chen Y-Q
Published: March 2014

An optimal control solution to a fed-batch fermentation process, responding to a competition call, was developed using the NEOS (network enabled optimization solution) server ( http://www-neos.mcs.anl.gov/neos/ ). Substantial improvement to the nominal performance achieved in the paper demonstrates the ability of the NEOS server and the asynchronous parallel pattern search algorithm.
Model reduction in the physical domain
Authors: Orbak A Y , Turkay O S , Eskinat E , Youcef-Toumi K
Published: March 2014

This paper is concerned with obtaining physical-based low-order approximations of linear physical systems. Low-order models possess some advantages, including the reduction of computational difficulty and understanding of the physics of the original system in a simpler manner. Previously, a number of methods have been suggested to develop suitable low-order approximations. However, most of these approaches do not reflect the relation between the mathematical model and the physical subsystems. Specifically, these techniques do not indicate which of the physical subsystems should be retained or eliminated in the reduced-order model. The proposed model reduction method is based on identifying subsystem types of a physical system using the bond graph method. These subsystems are then removed or retained based on the information from the physical system decomposition procedures and partial fraction expansion residues to obtain a reduced-order model. The physical model reduction procedure is verified on physical linear systems.
Modelling and experimental study of the transient response of an active magnetic bearing rotor during rotor drop on back-up bearings
Authors: Zeng S
Published: March 2014

The back-up bearing is a key safety component of active magnetic bearing (AMB) machinery. For many unexpected reasons, the rotor operating at full speed may drop onto the back-up bearings. Sometimes, full-clearance whirling motion is induced, which is particularly harmful to the machine. Thus, it is of great importance to understand the transient behaviour of the back-up bearing as well as the AMB rotor. In this paper the transient response of the AMB rotor during rotor drop is studied numerically and experimentally. Firstly, a modelling method is introduced. Then, an experimental set-up is built, and varied AMB rotor drop tests with different back-up support conditions are performed. Factors leading to full-clearance backward whirling motion are studied. The experimental results are compared with simulation results. Finally, conclusions based on both simulation and experiment are given.
Inverse dynamic analysis of multiphysics systems
Authors: Sahinkaya M N
Published: March 2014

An object-oriented approach to dynamic simulation and analysis of multidomain, multiphysics systems is developed. Lagrangian dynamics and a novel numerical differentiation technique are used by the simulation engine to develop automatically the equations of motion from energy expressions, which can incorporate multidomain, multiphysics components. The same modelling methodology is used for both forward and inverse dynamic analysis. Different methods are presented for the solution of inverse dynamic problems, depending on how the desired motion and the control inputs are defined. A graphical approach is developed to test for the structural invertibility of a system for a particular choice of control inputs. A multistage inversion technique is introduced for systems where structural non-invertibility is due to a mismatch of the equation orders. The techniques developed for system inversion are demonstrated by simulated examples.
Hybrid modelling and simulation of a computer numerical control machine tool feed drive
Authors: Pislaru C , Ford D G , Holroyd G
Published: March 2014

The paper presents a new approach to the modelling and simulation of a computer numerical control (CNC) machine tool feed drive. The hybrid model of the drive incorporates a distributed load, explicit damping factors and measured non-linear effects in order to achieve a realistic dynamic performance. In this way, the shortcomings of traditional modelling methods applied to CNC machine tool axis drives are overcome. A MATLAB/SIMULINK package was used to simulate this new model for a CNC machine tool feed drive. A novel hybrid model with a distributed load, explicit damping factors, backlash and friction was developed and shown to have a similar dynamic response to the machine tool feed drive system under the same conditions. The simulated results display resonance frequencies, while the lumped-parameter models generate only the response of a second-order element.
Adaptive friction compensation with a time-delay friction model
Authors: Tan K K , Huang S , Lee T H
Published: March 2014

This paper presents a new compensation technique for a time-delay friction model that captures the effect of frictional memory. The proposed control utilizes a proportional-derivative (PD) control structure and an adaptive estimate of the friction force. Specifically, a radial basis function (RBF) is used to compensate the effects of the non-linearly occurring parameters in the friction model. Simulation results verify the theory and show that the method can significantly improve the tracking performance of a control system in which it is used.
A direct solution for flowrate and force along a cone-seated poppet valve for laminar flow conditions
Authors: Bergada J M , Watton J
Published: March 2014

A new set of equations is developed, giving insight into the flow and pressure distribution across poppet valves with large cone-shaped seats. The equations apply for laminar flow, which appears when the length of the seat is much greater than the valve opening gap, and are a useful design tool for applications where a linear pressure/flow characteristic could be a distinct control advantage. The momentum equation is also applied to determine the static forces on the conical spool and it is confirmed that, for small chamfered-type seats, momentum forces can still play a decisive role on the total force. However, as the length of the seat increases to a cone type the dominant role is then played by the pressure forces acting on the seat, producing a much more predictable valve characteristic. The new equations allow accurate design of the seat length to minimize this static force variation. In order to validate the equations developed, a three-dimensional computational fluid dynamics (CFD) analysis of the flow along the valve seat has been performed and a test rig was designed to check experimentally the pressure distribution and flow along such a valve. Very good agreement has been obtained between experimental, CFD and theoretical pressure/flow results.
New observer-based guaranteed cost control for neutral delay systems
Authors: Chen B , Lam J , Xu S
Published: March 2014

This paper considers the problem of guaranteed cost control for a class of neutral delay systems. Unlike the commonly used quadratic cost function involving the state, a cost function involving the delayed state is considered. This naturally leads to a memory state feedback such that the resulting closed-loop system is not only asymptotically stable but also guarantees an adequate level of performance. An observer-based output feedback guaranteed cost control problem is addressed. A sufficient condition for the existence of a guaranteed cost controller is given in terms of the feasibility condition of a linear matrix inequality. Finally, two numerical examples are used to demonstrate the effectiveness of the approach proposed.
A mixed optimal/robust control for robot manipulators
Authors: Mnif F
Published: March 2014

A mixed optimal/robust control is proposed in this paper for the tracking of rigid robotic systems under parametric uncertainties and external perturbations. The design objective is that under a prescribed disturbance norm level, an optimal control system is to be designed as well as a robust control to overcome the effect of uncertainties. The optimal control is based on the solution of a non-linear Ricatti equation, which, by virtue of the skew symmetry property of manipulators and an adequate choice of state variables, becomes an algebraic equation that is easy to solve. The design of the robust control of the uncertain system is then investigated using a continuous state feedback function. It will be shown that this approach asymptotically stabilizes the uncertain dynamical system globally. Results of simulations performed on a two-degree-of-freedom manipulator are provided to illustrate the validity of the proposed approach.
Identification of immune models for fault detection
Authors: Luh G-C , Cheng W-C
Published: March 2014

In this paper, a novel approach to model-based fault detection for non-linear systems is presented. An immune model of the system is used for the generation of residual. The orthogonal least-squares method is implemented to select the significant receptor vectors of the immune model. After the model identification, the filtered residual scheme and the fault alarm concentration are applied for the fault detection. To verify and demonstrate the performance of the proposed methodology, a simulation example on a two-link robot was studied. The results show the effectiveness and robustness in both system identification and fault detection.