Desired Point Research Articles

Automatic carrier landing system based on active disturbance rejection control with a novel parameters optimizer

This paper proposes an active disturbance rejection control (ADRC) scheme for automatic carrier landing system (ACLS) in final approach. To track desired touchdown point (DTP) altitude in the presence of carrier air wake turbulence and deck motion, based on the estimation and compensation of internal dynamics and external disturbances by extended state observer (ESO), outer-loop altitude controller and inner-loop attitude controllers are designed via ADRC. Moreover, tracking differentiator-based deck motion compensation (TD-DMC) is designed to eliminate the inherent phase lag in ACLS. In addition, controller parameters are optimized via a novel Levy flight based whale optimization algorithm (LWOA). Finally, comparative simulations demonstrate that the proposed ADRC-based ACLS has better tracking performance and robustness compared to conventional ACLS.

Dynamic Modeling and Feedback Linearization Control of Wheeled Mobile Cable-Driven Parallel Robot Considering Cable Sag

Cable robots are one of the subcategories of parallel robots used particularly for the applications where the large workspace is required. This type of robots can cover larger workspace compared with serial robots or parallel robots with rigid links. The main issues of cable robots are the cable flexibility due to the need to long cable length as well as inappropriate cable tension distribution in the proximity of the workspace boundaries. By combining a cable robot with a wheeled mobile robot, an unlimited area of workspace can be reached with shorter cable length. Moreover, as the end-effector does not need to come close to its boundary in the mobile platform frame to reach any desired point in the workspace, the tensions are distributed appropriately. The cable sagging in the cable robots is another issue that increases the system error and deviation of the end-effector from the desired trajectory. Therefore, this paper presents the dynamic modeling and control of a cable-suspended parallel robot with a wheeled mobile platform considering the weight of the cable. To this end, the dynamic equations of the wheeled mobile cable robot are obtained using Gibbs–Appel method. Then, the equations related to the weight and sagging of the cable are added to the equations of motion. Control of the system using feedback linearization method is presented. Furthermore, investigating the effect of cable sag on the tension and the end-effector pose of the closed-loop system is demonstrated. Finally, verification is carried out by comparing the simulation and experimental results.

Experimental and numerical investigation on the transient vascular thermal response to multi-pulse Nd:YAG laser.

Port wine stains (PWS) are congenital vascular malformations that progressively darken and thicken with age. Laser therapy is currently the most effective way in clinical practice for PWS. A 1,064 nm Nd:YAG laser in the near-infrared band can achieve a deeper treatment depth compared to the current widely adopted pulsed dye laser. However, because of its relatively weak absorption by blood, single-pulse Nd:YAG laser requires high energy density to cause effective vessel damage, but may inflict undesirable burning to surrounding collagen. Multi-pulse laser has great potential in clinical treatment because it needs less energy density for each pulse. This paper presented an experimental and theoretical study of the transient thermal effects of low-energy multi-pulse Nd:YAG laser on blood vessels. In vivo experiments were performed on dorsal skin chamber. By using a high speed camera (up to 2,000 fps), the complete and dynamic thermal response of blood vessels during laser irradiation and between pulse intervals was obtained. In vitro experiment in capillary tubes and Numerical simulations by two-scale heat transfer model were also conducted to further explore the in vivo experimental findings. The complete and dynamic response of blood vessels were obtained, including vessel dilation, thrombus formation, partial vessel constriction, thread-like constriction, cavitation and bubbles, and hemorrhage. Thread-like constriction is the desirable treatment end point, which will only occur after thrombus completely occludes the vessel lumen. Cavitation can cause hemorrhage when thrombus fails to occlude the vessel lumen. In vitro experiment found that vessel constriction was due to the constriction of thrombus induced by laser irradiation. Theoretical investigation revealed that the mechanism for the effective reduction of energy density by multi-pulse Nd:YAG laser was due to enhanced light absorption of the blood with thrombus formation. For multi-pulse treatment, laser parameters are recommended as repetition rate of 10 Hz and pulse number of 10. The incident energy in each pulse should be strong enough to induce blood coagulation through seven or eight pulses and should be lower than the threshold of blood cavitation. Lasers Surg. Med. 49:852-865, 2017. © 2017 Wiley Periodicals, Inc.

Dexamethasone conjugated polyallylamine: Synthesis, characterization, and in vitro transfection and cytotoxicity

Nuclear transportation of genetic materials is a critical step in gene therapy. Human gene therapy is not routine enough in clinic because an effective and safe gene carrier does not exist yet. It is reported that glucocorticoids such as dexamethasone (Dexa) facilitate nuclear transportation of plasmid DNA or other polynucleotide molecules to the nucleus. This study is aimed to investigate the influences of Dexa on physicochemical properties, cell transfection and toxicity of polyallylamine (PAA). After activation, Dexa mesylate was conjugated to both unmodified PAA and hexyl acrylate-conjugated PAAs (PAA-6c Acr) through a one-step reaction. PAA-Dexa was purified with dialysis against distilled water and then freeze-dried. The physicochemical properties of the synthesized vectors such as buffering capacity, DNA condensing ability, size, and zeta potential were determined. The PAA 15 kDa-based polyplexes showed better cell transfection than those based on PAA65 kDa in Neuro2A cell line. To sum up, transfection activity was improved in two types of the modified vectors including PAA15-6c Acr30%-Dexa5% at lower carrier to pDNA (C/P) ratios and PAA15-6c Acr50%-Dexa10% at higher C/P ratios. Altogether, the modification of PAA and PAA-6c Acr with Dexa significantly reduced their cytotoxicity, but had not guided their cell transfection to a desired point.

Introducing Teacher Mentoring in Kosovo Schools – Potential and Challenges for Sustainability

This study examined the lessons learned from the introduction of a teacher mentoring culture within a teacher professional development program in selected pilot schools in Kosovo. Four mentor teachers and four mentee focus groups were involved in the open interviews, and their portfolios were examined. The important themes in terms of developing a schoolmentoring culture in a system that had lacked mentoring practices and is embarking on an ambitious curricular reform were identified. The study revealed that individual, collegial and institutional dimensions are critical in attempting to introduce the mentoring culture. The study concluded that mentoring is a mixed concept and is viewed as hierarchical but is,nevertheless, an important professional development tool for teachers who are facing the pressure of the reform. This formalized way, known as “Balkanization” culture, marks a critical step towards developing a collaborative school culture as the desired end point.

Dynamic focusing of acoustic wave utilizing a randomly scattering lens and a single fixed transducer

In this study, we report a randomly scattering lens (RSL) coupled with a single fixed transducer to realize dynamic acoustic focusing. This acoustic lens is composed of randomly distributed acoustic scatterers, and a single ultrasound transducer is fixed on one side of the lens. Benefitting from the high-order multiple scattering in the RSL, the ultrasound emitted by the single fixed transducer can be dynamically focused onto any desired point by manipulating the transmitting waveform. Then, we successfully apply such a single channel system to decode a photoacoustic image from the received ultrasound signal. Further studies demonstrate that the focusing ability of the proposed system can be approximated by a classic acoustic lens. Its axial resolution is related to the speed of sound and the bandwidth of the signal; its lateral resolution depends not only on the ultrasound frequency but also on the numerical aperture of the RSL; furthermore, the image quality improves as the numerical aperture increases. In comparison with other acoustic focusing methods, dynamic focusing achieved by the proposed system needs neither special materials or delicate structures nor a large number of channels. Therefore, the proposed system could find broad applications ranging from medical ultrasound imaging to nondestructive detection.

Emergency preparedness training preferences and perceived barriers to training among various healthcare providers and public health practitioners in Massachusetts.

Emergency preparedness training is vital to a wide range of healthcare and public health disciplines. Although agencies may try to tailor their training efforts based on perceived need, the topics and methods of instruction may be misguided, resulting in wasted effort and poor participation in training events. The objective of this study was to understand in a rigorous way, the training preferences and barriers to training among practitioners in Massachusetts. In August 2013, the Massachusetts Department of Public Health distributed an online survey to health professionals in Massachusetts regarding their emergency preparedness training topic preferences and any perceived barriers and challenges associated with obtaining this training. A total of 796 healthcare and public health professionals responded to the survey and answered some or all of the questions asked. The results of the survey identified important differences in preference for some topics based on a provider's practice location and discipline. However, Community Recovery and Community Preparedness were seen as desirable by all disciplines with more than 80 percent of respondents rating each of these issues as being highly important. Barriers to training were also assessed. Time spent away from work was the most commonly identified barrier (77.41 percent). Travel distance and financial constraints were also rated highly with scores of 65.48 and 63.71 percent, respectively. This study demonstrates important areas of agreement with respect to desired training topics and points out areas where providers in different disciplines and from different geographic areas may have differing educational preferences. Even within the limitation of this investigation, we expect that this study will be a valuable tool for those attempting to effectively target emergency preparedness training and structure course offerings in ways that minimize the impact of barriers to training.

Challenges and Pitfalls of Entrainment Mapping of Ventricular Tachycardia: Ten Illustrative Concepts.

The use and interpretation of entrainment mapping, or continuous resetting, of a reentrant tachycardia has been regarded as the gold standard for delineation of the components of a reentrant circuit.1,2 The response during and after overdrive pacing, whereby 2 wavefronts enter the circuit antidromically (with fusion) and orthodromically, is used to confirm reentry as the arrhythmia mechanism and determine the relationship of the pacing site to the circuit. The fulfillment of classical criteria outlined by Waldo and colleagues3,4 were synthesized into an anatomic concept for scar-related ventricular tachycardia (VT) by Stevenson et al5 to portray the structural and architectural basis of circuit conduction meandering between regions of fibrosis. In this construct, a central corridor, or protected isthmus, is bordered between 2 regions of dense scar with a single entrance that is distinct from a single exit, which yields the QRS morphology.6 This reentrant model has been central to our current mechanistic understanding of scar-mediated VT and is critically important for differentiating critical sites from bystander sites and regions that are unlikely to interrupt or eliminate reentry.7 However, the nature of reentrant VT in man is more complex than our idealized working construct for many reasons. In clinical practice, the majority of VT is hemodynamically unstable, which precludes the ability to perform entrainment mapping and activation mapping of the entire circuit.8 Differences in the circuit between patients with untolerated and tolerated VT are not well understood. VT circuits are 3 dimensionally complex with transmural conduction and circuit conduction is unlikely to be planar, as depicted by electroanatomic mapping of the myocardial surface. Exits may be multiple9,10 and patterns other than loop reentry around scar are likely. Channels of preserved myocardium are frequently not “normal” in voltage (>1.5 mV) …

Renal Support Therapy

Knowledge regarding the practical aspects of managing continuous renal replacement therapy (CRRT) in the surgical intensive care unit is a prerequisite for achieving desired physiologic end points. Familiarity with the initiation, dosing, adjustment, and termination of CRRT is a core skill for surgical intensivists. Modalities, terminology, and components of CRRT are discussed in this review, with an emphasis on the practical aspects of dosing, adjustments, and termination. Filter selection and management of electrolyte and acid-base derangements are emphasized. Key words: continuous renal replacement therapy, continuous venovenous hemofiltration, continuous venovenous hemofiltration dialysis, dialysis, intensive care unit

A least squares approach for efficient and reliable short-term versus long-term optimization

The uncertainties related to long-term forecasts of oil prices impose significant financial risk on ventures of oil production. To minimize risk, oil companies are inclined to maximize profit over short-term horizons ranging from months to a few years. In contrast, conventional production optimization maximizes long-term profits over horizons that span more than a decade. To address this challenge, the oil literature has introduced short-term versus long-term optimization. Ideally, this problem is solved by a posteriori multi-objective optimization methods that generate an approximation to the Pareto front of optimal short-term and long-term trade-offs. However, such methods rely on a large number of reservoir simulations and scale poorly with the number of objectives subject to optimization. Consequently, the large-scale nature of production optimization severely limits applications to real-life scenarios. More practical alternatives include ad hoc hierarchical switching schemes. As a drawback, such methods lack robustness due to unclear convergence properties and do not naturally generalize to cases of more than two objectives. Also, as this paper shows, the hierarchical formulation may skew the balance between the objectives, leaving an unfulfilled potential to increase profits. To promote efficient and reliable short-term versus long-term optimization, this paper introduces a natural way to characterize desirable Pareto points and proposes a novel least squares (LS) method. Unlike hierarchical approaches, the method is guaranteed to converge to a Pareto optimal point. Also, the LS method is designed to properly balance multiple objectives, independently of Pareto front’s shape. As such, the method poses a practical alternative to a posteriori methods in situations where the frontier is intractable to generate.

Double-Sided Bidding Mechanism for Resource Sharing in Mobile Cloud

Recently, a new architecture regarding a crowd of mobile devices as mobile cloud has been proposed, where the neighboring mobile devices are pooled together for resource sharing. Most existing works focus on mobile cloud framework design and assume that the nearby users are willing to share their resources. Since each user is rational and self-interested, a proper market mechanism is needed to incentivize users to participate and allocate resources among multiple users. In this paper, we consider a broker-based mobile cloud, where multiple supplying users have idle resources to share, and multiple demanding users suffer from resource limitations. We propose and analyze a double-sided bidding mechanism where each demanding user submits a bid to choose a demand resource-price function, and each supplying user submits a bid to choose a supply resource-price function. We consider the cases with price-taking users and price-anticipating users who would anticipate the influence of their own bids on the price, respectively. For the case with price-taking users, we first show that the proposed mechanism admits a unique competitive equilibrium that maximizes the social welfare of the mobile cloud and then develop an optimal distributed algorithm to achieve the desired equilibrium point. For the case with price-anticipating users, we first formulate the interaction among multiple users as a strategic game and prove the existence and uniqueness of the Nash equilibrium and then develop a distributed algorithm to compute the Nash equilibrium. Numerical results validate the efficacy of our proposed algorithms and illustrate that the social welfare achieved at the Nash equilibrium is very close to the optimal social welfare.

Acoustic emission sensor system using a chirped fiber-Bragg-grating Fabry–Perot interferometer and smart feedback control

We demonstrate a fiber-optic acoustic emission (AE) sensor system that is capable of performing AE detection, even when the sensor is experiencing large quasi-static strains. The sensor is a Fabry-Perot interferometer formed by cascaded chirped fiber-Bragg gratings (CFBGs). The reflection spectrum of the sensor features a number of narrow spectral notches equally spaced within the reflection bandwidth of the CFBG. A semiconductor laser whose wavelength can be fast tuned through current injection is used to lock the laser line to the center of a slope of a spectral notch. When the notch is knocked out of the tuning range of the laser, a neighboring notch moves into the range. Through a smart feedback control scheme, the laser is unlocked from the current spectral lock and relocked to the desired point of the new notch. The fast speed of the unlocking/relocking process (<1 ms) ensures that the AE signal is monitored without significant disruption.

Bounded Integral Control of Input-to-State Practically Stable Nonlinear Systems to Guarantee Closed-Loop Stability

A fundamental problem in control systems theory is that stability is not always guaranteed for a closed-loop system even if the plant is open-loop stable. With the only knowledge of the input-to-state (practical) stability (ISpS) of the plant, in this note, a bounded integral controller (BIC) is proposed which generates a bounded control output independently from the plant parameters and states and guarantees closed-loop system stability in the sense of boundedness. When a given bound is required for the control output, an analytic selection of the BIC parameters is proposed and its performance is investigated using Lyapunov methods, extending the result for locally ISpS plant systems. Additionally, it is shown that the BIC can replace the traditional integral controller (IC) and guarantee asymptotic stability of the desired equilibrium point under certain conditions, with a guaranteed bound for the solution of the closed-loop system. Simulation results of a dc/dc buck-boost power converter system are provided to compare the BIC with the IC operation.

The Inflection Point of the Speed-Density Relation and the Social Force Model

It has been argued that the speed-density diagram of pedestrian movement has an inflection point. This inflection point was found empirically in investigations of closed-loop single-file pedestrian movement.The reduced complexity of single-file movement does not only allow a higher precision for the evaluation of empirical data, but it also significantly simplifies analytical considerations. This is especially true if one assumes homogeneous conditions, i.e. neglects temporal variations (consider time averages, neglect stop-and-go waves), individual differences of pedestrians (all simulated pedestrians have identical parameters) and investigates only steady-state (not the initial phase). As will be shown in this contribution one then can make a transition from the microscopic to a continuous and macroscopic perspective.Building on that it will be shown that certain (common) variants of the Social Force Model (SFM) do not produce an inflection point in the speed-density diagram if – assuming periodic boundary conditions – infinitely many pedestrians contribute to the force computed for one pedestrian. It will furthermore be shown that if – in said 1d movement situation – one only considers nearest neighbors for the computation of the inter-pedestrian forces the Social Force Model in the continuous description results in the so called Kladek formula for the speed-density relation. Since the Kladek formula exhibits the desired inflection point this observation is used as a motivation for an extension of the Social Force Model which allows to transform the continuous description of the SFM continuously to the Kladek formula and which also exhibits the inflection point in the speed density relation. It will be shown then, that this extended SFM yields astonishingly similar speed density relations as the original SFM when only a fixed limited number of (nearest) pedestrians are considered in the computation of the inter-pedestrian force.Finally it will be discussed, if also the description of the speed-density diagram for (motorized, four-wheel) vehicular and/or bicycle traffic could benefit from these measures.

Automatic and Robust Delineation of the Fiducial Points of the Seismocardiogram Signal for Non-invasive Estimation of Cardiac Time Intervals.

The purpose of this research was to design a delineation algorithm that could detect specific fiducial points of the seismocardiogram (SCG) signal with or without using the electrocardiogram (ECG) R-wave as the reference point. The detected fiducial points were used to estimate cardiac time intervals. Due to complexity and sensitivity of the SCG signal, the algorithm was designed to robustly discard the low-quality cardiac cycles, which are the ones that contain unrecognizable fiducial points. The algorithm was trained on a dataset containing 48,318 manually annotated cardiac cycles. It was then applied to three test datasets: 65 young healthy individuals (dataset 1), 15 individuals above 44 years old (dataset 2), and 25 patients with previous heart conditions (dataset 3). The algorithm accomplished high prediction accuracy with the rootmean- square-error of less than 5 ms for all the test datasets. The algorithm overall mean detection rate per individual recordings (DRI) were 74, 68, and 42 percent for the three test datasets when concurrent ECG and SCG were used. For the standalone SCG case, the mean DRI was 32, 14 and 21 percent. When the proposed algorithm applied to concurrent ECG and SCG signals, the desired fiducial points of the SCG signal were successfully estimated with a high detection rate. For the standalone case, however, the algorithm achieved high prediction accuracy and detection rate for only the young individual dataset. The presented algorithm could be used for accurate and non-invasive estimation of cardiac time intervals.

A Novel Unified and Self-Stabilizing Algorithm for Generalized Eigenpairs Extraction.

Generalized eigendecomposition problem has been widely employed in many signal processing applications. In this paper, we propose a unified and self-stabilizing algorithm, which is able to extract the first principal and minor generalized eigenvectors of a matrix pencil of two vector sequences adaptively. Furthermore, we extend the proposed algorithm to extract multiple generalized eigenvectors. The performance analysis shows that only the desired equilibrium point of the proposed algorithm is stable and all others are (unstable) repellers or saddle points. Convergence analysis based on the deterministic discrete-time approach shows that, for a step size within a certain range, the norm of the principal/minor state vector converges to a fixed value that relates to the corresponding principal/minor generalized eigenvalue. Thus, the proposed algorithm is a generalized eigenpairs (eigenvectors and eigenvalues) extraction algorithm. Finally, the simulation experiments are carried to further demonstrate the efficiency of the proposed algorithm.

Subsidy-Based Control of Heterogeneous Multiagent Systems Modeled by Replicator Dynamics

We propose a subsidy-based control law of a multiagent system that consists of many selfish and heterogeneous agents under incomplete information on the criterion of each agent. The system's behavior is modeled by multipopulation replicator dynamics where the payoff functions of the populations are different from one another and correspond to the criteria of the agents who belong to the populations. In general, several equilibrium points exist in the replicator dynamics. A controller called a “government” attempts to stabilize the desirable equilibrium points of multiagent systems by offering a subsidy to the agents. A previous study assumed that the government determined the subsidy on the basis of the population that each agent belonged to. In general, however, the government cannot identify the members of each population. In this technical note, we assume that the government observes the action of each agent and determines the subsidy on the basis of the observed action profile. Then, we model the controlled behavior of the system using replicator dynamics with feedback. We derive the stabilization condition of the target equilibrium point for two special cases.

Optimal Task Recommendation for Mobile Crowdsourcing With Privacy Control

Mobile crowdsourcing (MC) is a transformative paradigm that engages a crowd of mobile users (i.e., workers) in the act of collecting, analyzing, and disseminating information or sharing their resources. To ensure quality of service, MC platforms tend to recommend MC tasks to workers based on their context information extracted from their interactions and smartphone sensors. This raises privacy concerns hard to address due to the constrained resources on mobile devices. In this paper, we identify fundamental tradeoffs among three metrics-utility, privacy, and efficiency-in an MC system and propose a flexible optimization framework that can be adjusted to any desired tradeoff point with joint efforts of MC platform and workers. Since the underlying optimization problems are NP-hard, we present efficient approximation algorithms to solve them. Since worker statistics are needed when tuning the optimization models, we use an efficient aggregation approach to collecting worker feedbacks while providing differential privacy guarantees. Both numerical evaluations and performance analysis are conducted to demonstrate the effectiveness and efficiency of the proposed framework.

On the Joint Probability of Wave-Heights and Periods in Intermediate and Shallow Waters

In the present paper, a package model is derived, based on a joint probability density function and on a Boussinesq-class numerical wave model. The key task was to produce joint probability density estimates of wave-height and wave period in intermediate and shallow waters given the respective information offshore. This is of paramount importance in the context of design of resilient coastal structures. The approach followed includes an extension of given joint probability density estimate images in deep waters and their decomposition into a manageable data of time series of free surface elevation. These data serve as input to a recently developed wave propagation model of the Boussinesq-class, able to cover the whole range from deep to shallow waters and give the corresponding surface elevation there. The time history of the latter is finally recomposed to produce the associated probability density estimates at any desired point of the nearshore. Additional information concerning the directional energy spreading in shallow waters is obtained. The package model was verified with experimental results proving its validity and ability to produce satisfying results. Finally, characteristic representations of joint probability densities between wave-height and wave period are given, for typical sea bottom slopes and wave incidence.

Bayesian updating of land-cover estimates in a data-rich environment

Abstract Since the opening of the Landsat archive, the availability of remote sensing data has increased dramatically, and algorithms that can interpret large time series of satellite imagery are in rapid development as additions to the decades of interpretation of remotely-sensed images. To date, processing of these massive data repositories has focused mostly on tracing forest growth and loss across very large areas within pre-defined study periods. Despite these very considerable advances, there is a need for methodology that could allow analysts to use their own specific land-cover categories of interest, and update existing land-cover classifications either forward or backward to a desired point in time. Here we demonstrate an algorithm (Bayesian Updating of Land-Cover, or BULC ) developed for the continuous updating of land-cover classifications through time in large data sets. The BULC algorithm is designed to permit users to build new classifications or update existing classifications based on long streams of imagery, but with minimal storage and memory requirements. The algorithm ingests a sequence of classified land-cover data for a user-specified set of detectable classes, and maintains a continually updated estimate of land-cover probabilities and the most probable class at all time points along the sequence. We tested this algorithm in central Quebec with Landsat 8 imagery for summer 2013, when a series of large fires erupted and burned through forests. In this very dynamic setting, many of the summer's images were contaminated by ordinary standards, yet parts of the region could be seen through the clouds, smoke, and haze of each image. Across 11 dates of widely varying quality, BULC tracked the fires, ignored contaminated image information, and mapped fire borders consistently throughout the summer, autumn, and subsequent winter and spring. Building on images having a median accuracy of 78% and 8% NoData, the BULC algorithm created 11 sequenced land-cover maps each having more than 90% overall accuracy and covering the entire study area. BULC's classifications mapped each of the land-cover categories with user's and producer's accuracies that compared well to the best individual images used as input, while accurately tracking land-cover change that occurred between those infrequent clear images. As we leave remote sensing's data-poor era and enter a period with many images of Earth's surface supplied by multiple sensors over a short period of time, the BULC algorithm may help to sift through images of varying quality to extract the most useful information for mapping time series of land-cover classifications.