Global adaptive neural backstepping control of a flexible hypersonic vehicle with disturbance estimation

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
He-Wei Zhao ◽  
Li-bin Yang
Keyword(s):  
Rbf Neural Network ◽  
Tracking Error ◽  
Hypersonic Vehicle ◽  
Nonlinear Dynamic Model ◽  
Content Type ◽  
Lateral Dynamics ◽  
Disturbance Estimation ◽  
System A ◽  
Complexity Problem ◽  
Velocity Tracking

Purpose This paper aims to discuss the precise altitude and velocity tracking control of a hypersonic vehicle, a global adaptive neural backstepping controller was studied based on a disturbance observer (DOB). Design/methodology/approach The DOB combined with a radial basis function (RBF) neural network (NN) was used to estimate the disturbance terms that are generated by the flexible modes of the hypersonic vehicle system. A global adaptive neural method was introduced to approximate the unknown system dynamics, with robust control terms pulling the system transient states back into the neural approximation domain externally. Findings The globally uniformly ultimately bounded for all signals of a closed-loop system can be guaranteed by the proposed control algorithm. Additionally, the command filtered backstepping methods can avoid the explosion of the complexity problem caused by the backstepping design process. In addition, the effectiveness of the proposed controller can be verified by the simulation used in this study. Research limitations/implications Normally lateral dynamics issue should be discussed in the process of control system designed, the lateral dynamics are not included in the nonlinear dynamic model of hypersonic vehicle used in this paper, merely the longitudinal flight dynamics are discussed in this paper. Originality/value The flexible states in rigid modes are considered as the disturbance of the system, which is estimated by structuring DOB with NN approximations. The compensating tracking error and prediction error are used in the update law of RBF NN weight. The differential explosions complexity derived from the backstepping procedure is dealt with by using command filters.

Professionals freaking out: the case of accreditation in Dutch higher education

2009 ◽  
Vol 21 (5) ◽  
pp. 473-485 ◽  
Author(s):  
Everard van Kemenade ◽  
Teun W. Hardjono
Keyword(s):  
The Netherlands ◽  
Design Methodology ◽  
Iso 9000 ◽  
Preliminary Survey ◽  
External Evaluation ◽  
Content Type ◽  
Evaluation Systems ◽  
System A ◽  
Engineering And Technology ◽  
Insight Into

PurposeThe purpose of this paper is to define what factors cause willingness and/or resistance among lecturers in universities towards external evaluation systems, especially accreditation.Design/methodology/approachA model has been designed to describe possible factors of willingness and/or resistance towards accreditation based on Ajzen and Metselaar. A literature review has been undertaken on the effects of external evaluation like ISO 9000 as well as accreditation systems such as Accreditation Board for Engineering and Technology and European Quality Improvement System. A questionnaire has been administered to a group of 63 lecturers from three departments at Fontys University in The Netherlands. The results of this preliminary survey have been presented to 1,500 academics in The Netherlands and Flanders to collect empirical data.FindingsResistance to accreditation can be found in the consequences of accreditation for the work of the lecturer (workload), negative emotions (stress and insecurity); the lack of knowledge and experience (help from specialists is needed); and lack of acceptance (other paradigm).Originality/valueThe paper provides more insight into the difficulties that organizations, especially universities, have to commit their employees to external evaluation. It might be possible to generalize the findings to other professionals in other organizations. Little research in this field has been undertaken so far.

Portfolio revision and optimal diversification strategy choices

2014 ◽  
Vol 10 (4) ◽  
pp. 537-564
Author(s):  
Mourad Mroua ◽  
Fathi Abid
Keyword(s):  
Transaction Costs ◽  
Tracking Error ◽  
Investment Strategy ◽  
Selection Strategy ◽  
Revision Procedure ◽  
Content Type ◽  
Efficient Frontiers ◽  
Statistical Inferences ◽  
Diversification Strategies ◽  
International Portfolios

Purpose – Since equity markets have a dynamic nature, the purpose of this paper is to investigate the performance of a revision procedure for domestic and international portfolios, and provides an empirical selection strategy for optimal diversification from an American investor's point of view. This paper considers the impact of estimation errors on the optimization processes in financial portfolios. Design/methodology/approach – This paper introduces the concept of portfolio resampling using Monte Carlo method. Statistical inferences methodology is applied to construct the sample acceptance regions and confidence regions for the resampled portfolios needing revision. Tracking error variance minimization (TEVM) problem is used to define the tracking error efficient frontiers (TEEF) referring to Roll (1992). This paper employs a computation method of the periodical after revision return performance level of the dynamic diversification strategies considering the transaction cost. Findings – The main finding is that the global portfolio diversification benefits exist for the domestic investors, in both the mean-variance and tracking error analysis. Through TEEF, the dynamic analysis indicates that domestic dynamic diversification outperforms international major and emerging diversification strategies. Portfolio revision appears to be of no systematic benefit. Depending on the revision of the weights of the assets in the portfolio and the transaction costs, the revision policy can negatively affect the performance of an investment strategy. Considering the transaction costs of portfolios revision, the results of the return performance computation suggest the dominance of the global and the international emerging markets diversification over all other strategies. Finally, an assessment between the return and the cost of the portfolios revision strategy is necessary. Originality/value – The innovation of this paper is to introduce a new concept of the dynamic portfolio management by considering the transaction costs. This paper investigates the performance of a revision procedure for domestic and international portfolios and provides an empirical selection strategy for optimal diversification. The originality of the idea consists on the application of a new statistical inferences methodology to define portfolios needing revision and the use of the TEVM algorithm to define the tracking error dynamic efficient frontiers.

scholarly journals Restoration of Bioactive Lantibiotic Suicin from a RemnantlanLocus of Pathogenic Streptococcus suis Serotype 2

2013 ◽  
Vol 80 (3) ◽  
pp. 1062-1071 ◽  
Author(s):  
Jian Wang ◽  
Yong Gao ◽  
Kunling Teng ◽  
Jie Zhang ◽  
Shutao Sun ◽  
...  
Keyword(s):  
Gene Promoter ◽  
Streptococcus Suis ◽  
Gene Clusters ◽  
Disulfide Bridge ◽  
Gram Positive ◽  
Content Type ◽  
Gram Positive Bacteria ◽  
System A ◽  
Bactericidal Activities

ABSTRACTLantibiotics are ribosomally synthesized, posttranslationally modified antimicrobial peptides. Their biosynthesis genes are usually organized in gene clusters, which are mainly found in Gram-positive bacteria, including pathogenic streptococci. Three highly virulentStreptococcus suisserotype 2 strains (98HAH33, 05ZYH33, and SC84) have been shown to contain an 89K pathogenicity island. Here, on these islands, we unveiled and reannotated a putative lantibiotic locus designatedsuiwhich contains a virulence-associated two-component regulator,suiK-suiR. In silicoanalysis revealed that the putative lantibiotic modification genesuiMwas interrupted by a 7.9-kb integron and that other biosynthesis-related genes contained various frameshift mutations. By reconstituting the intactsuiMinEscherichia colitogether with a semi-in vitrobiosynthesis system, a putative lantibiotic named suicin was produced with bactericidal activities against a variety of Gram-positive strains, including pathogenic streptococci and vancomycin-resistant enterococci. Ring topology dissection indicated that the 34-amino-acid lantibiotic contained two methyllanthionine residues and one disulfide bridge, which render suicin in an N-terminal linear and C-terminal globular shape. To confirm the function ofsuiK-suiR, SuiR was overexpressed and purified.In vitroanalysis showed that SuiR could specifically bind to thesuiAgene promoter. Its coexpression withsuiKcould activatesuiAgene promoter inLactococcus lactisNZ9000. Conclusively, we obtained a novel lantibiotic suicin by restoring its production from the remnantsuilocus and demonstrated that virulence-associated SuiK-SuiR regulates its production.

Robotic system design and development for automated dismantling of PCB waste

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ioan Doroftei ◽  
Daniel Chirita ◽  
Ciprian Stamate ◽  
Stelian Cazan ◽  
Carlos Pascal ◽  
...  
Keyword(s):  
Design Methodology ◽  
Printed Circuit Board ◽  
Vision System ◽  
Electronic Waste ◽  
Robotic System ◽  
Circuit Board ◽  
Short Introduction ◽  
Content Type ◽  
Printed Circuit ◽  
System A

Purpose The mass electronics sector is one of the most critical sources of waste, in terms of volume and content with dangerous effects on the environment. The purpose of this study is to provide an automated and accurate dismantling system that can improve the outcome of recycling. Design/methodology/approach Following a short introduction, the paper details the implementation layout and highlights the advantages of using a custom architecture for the automated dismantling of printed circuit board waste. Findings Currently, the amount of electronic waste is impressive while manual dismantling is a very common and non-efficient approach. Designing an automatic procedure that can be replicated, is one of the tasks for efficient electronic waste recovery. This paper proposes an automated dismantling system for the advanced recovery of particular waste materials from computer and telecommunications equipment. The automated dismantling architecture is built using a robotic system, a custom device and an eye-to-hand configuration for a stereo vision system. Originality/value The proposed approach is innovative because of its custom device design. The custom device is built using a programmable screwdriver combined with an innovative rotary dismantling tool. The dismantling torque can be tuned empirically.

On the ability of New Zealand actively managed funds to generate outperformance in their domestic equity allocations

2018 ◽  
Vol 30 (4) ◽  
pp. 463-481 ◽  
Author(s):  
Bart Frijns ◽  
Ivan Indriawan
Keyword(s):  
New Zealand ◽  
Stock Returns ◽  
Tracking Error ◽  
Tracking Errors ◽  
Content Type ◽  
Portfolio Holdings ◽  
Market Index ◽  
Stock Picking ◽  
Fund Size ◽  
Managed Funds

Purpose This paper aims to assess the ability of New Zealand (NZ) actively managed funds to generate risk-adjusted outperformance using portfolio holdings data. Focusing on domestic equity allocations addresses the benchmark selection issue, particularly for funds with national and international exposures. Design/methodology/approach The authors assess performance using several asset pricing models including the CAPM, three-factor and four-factor models. The authors also assess performance across funds with different characteristics such as fund size, size of local holdings, type of fund provider, past returns and fees. The authors further examine whether funds engage in any stock-picking or market timing by considering the active share and tracking error. Findings The returns on NZ equity holdings of NZ actively managed funds from 2010 to 2017 provide little evidence of risk-adjusted outperformance and stock-picking skill. These exposures yield pre-cost returns that have a nearly perfect correlation with the market index and an insignificant alpha. Funds show little tendency to bet on any of the main characteristics known to predict stock returns, such as size, book-to-market and momentum. In addition, the authors show that the average active shares and tracking errors are low, suggesting that the majority of funds hold NZ equity portfolios that closely mimic the market index. Originality/value Existing studies rely on returns data which aggregate performance across all asset classes with varying exposures. This may lead to benchmark selection issues (particularly for funds with international exposures) which may obscure the fund manager’s true stock-picking skills. Assessment using holdings data would enable suitable performance measurement by researchers and industry analysts.

Credit risk in dual banking systems: does competition matter? Empirical evidence

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mohsin Ali ◽  
Mudeer Ahmed Khattak ◽  
Nafis Alam
Keyword(s):  
Credit Risk ◽  
Banking System ◽  
Islamic Banks ◽  
Content Type ◽  
Panel Data Estimation ◽  
System A ◽  
Size Groups ◽  
Conventional Banks ◽  
Fierce Competition ◽  
Data Estimation

PurposeThe study of credit risk has been of the utmost importance when it comes to measuring the soundness and stability of the banking system. Due to the growing importance of Islamic banking system, a fierce competition between Islamic and conventional banks have started to emerge which in turn is impacting credit riskiness of both banking system.Design/methodology/approachUsing the system GMM technique on 283 conventional banks and 60 Islamic banks for the period of 2006–2017, this paper explores the important impact of size and competition on the credit risk in 15 dual banking economies.FindingsThe authors found that as bank competition increases credit risk seems to be reduced. On the size effect, the authors found that big Islamic banks are less risky than big conventional banks whereas small Islamic banks are riskier than small conventional banks. The results are robust for different panel data estimation models and sub-samples of different size groups. The findings of this paper provide important insights into the competition-credit risk nexus in the dual banking system.Originality/valueThe paper is specifically focused on credit risk in dual banking environment and tries to fill the gap in the literature by studying (1) do the Islamic and conventional banks exhibit a different level of credit risk; (2) does competition in the banking system impact the credit risk of Islamic and conventional banks and finally (3) do the big and small banks exhibit similar levels of credit risk.

Modeling for tracking error of theodolite based on RBF neural network

2012 ◽  
Vol 20 (4) ◽  
pp. 818-825
Author(s):  
李淼 LI Miao ◽  
高慧斌 GAO Hui-bin
Keyword(s):  
Neural Network ◽  
Rbf Neural Network ◽  
Tracking Error

scholarly journals Adaptive Dynamic Surface Control for a Class of Nonlinear Pure-Feedback Systems with Parameter Drift

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Cheng He ◽  
Jian Wu ◽  
Jin Ying ◽  
Jiyang Dai ◽  
Zhe Zhang ◽  
...  
Keyword(s):  
Tracking Error ◽  
Feedback System ◽  
Dynamic Surface Control ◽  
Projection Algorithm ◽  
Feedback Systems ◽  
Simulation Experiments ◽  
Dynamic Surface ◽  
Parameter Drift ◽  
System A ◽  
Surface Control

In order to solve the problem of unknown parameter drift in the nonlinear pure-feedback system, a novel nonlinear pure-feedback system is proposed in which an unconventional coordinate transformation is introduced and a novel unconventional dynamic surface algorithm is designed to eliminate the problem of “calculation expansion” caused by the use of backstepping in the pure-feedback system. Meanwhile, a sufficiently smooth projection algorithm is introduced to suppress the parameter drift in the nonlinear pure-feedback system. Simulation experiments demonstrate that the designed controller ensures the global and ultimate boundedness of all signals in the closed-loop system and the appropriate designed parameters can make the tracking error arbitrarily small.

Urban shared energy systems and behaviour change − simulating a common pooled resource problem

2019 ◽  
Vol 9 (1) ◽  
pp. 17-26 ◽  
Author(s):  
Craig Alexander Burton ◽  
Christopher Ryan ◽  
Behzad Rismanchi ◽  
Seona Candy
Keyword(s):  
Energy Demand ◽  
Direct Action ◽  
Energy Systems ◽  
Social Benefits ◽  
Control Group ◽  
Dynamic Interactions ◽  
Content Type ◽  
System A ◽  
Electricity Use ◽  
Future Supply

Purpose The purpose of this paper is to test a new methodology for simulating shared electricity generation among small groups of neighbours with Ostrom’s (1994) principles of common pool resource (CPR) (human behaviour-based) efficiencies. The approach does not anticipate exclusive off-grid communities but instead, diverse energy users taking advantage of the averaging effects of aggregation, the social benefits of a CPR and direct action on emissions. Design/methodology/approach The study tested three groups of five adjacent − or same-building − neighbours for three months to measure how electricity demand (import) is affected by an in-home display issuing nudges and sanctions by the group around a simulated (limited capacity) shared solar and battery system. A control group of six homes’ energy data was obtained for the same period. Findings Two groups reduced their energy demand with weak but significant correlation between stimulus and reduced energy demand and one group increased demand. There were no significant effects in time-of-use behaviours. Research limitations/implications The study shows that the interaction between consumers and energy systems can in this instance be simulated with inexpensive equipment. Studying dynamic interactions between people and systems provides new data where supply simulations have been one-sided. There is support in this work that the energy supply can be presented as a rivalrous commons system. Practical implications Urban adjacent neighbours (and apartment occupants in the same building or campus) exhibit emergent group behaviours around electricity use conservation and time-of-use. Managing energy demand is very difficult but very important for making consumer behaviour “fit” the future supply of energy which may be unreliable and limited. Social implications There are likely social benefits and other overflow benefits when neighbours can share a critical resource. There are other critical services that may be managed according to the Ostrom commons principles. The sharing group will be more resilient in terms of electricity but also in terms of social capital. Originality/value The work builds on the work of Rachel Coxcoon and others who have identified that groups perform better at certain challenges than individuals do. This aligns with scale and operational efficiencies in shared renewable energy infrastructure. Shaping behaviour and the generation systems together for optimal outcomes is new work.

Smooth second-order nonsingular terminal sliding mode control for reusable launch vehicles

2014 ◽  
Vol 7 (1) ◽  
pp. 95-110 ◽  
Author(s):  
Shaobo Ni ◽  
Jiayuan Shan
Keyword(s):  
Finite Time ◽  
Sliding Mode ◽  
Tracking Error ◽  
Second Order ◽  
Convergence Time ◽  
Control Input ◽  
Terminal Sliding Mode ◽  
Content Type ◽  
Nonsingular Terminal Sliding Mode ◽  
Attitude Tracking

Purpose – The purpose of this paper is to present a sliding mode attitude controller for reusable launch vehicle (RLV) which is nonlinear, coupling, and includes uncertain parameters and external disturbances. Design/methodology/approach – A smooth second-order nonsingular terminal sliding mode (NTSM) controller is proposed for RLV in reentry phase. First, a NTSM manifold is proposed for finite-time convergence. Then a smooth second sliding mode controller is designed to establish the sliding mode. An observer is utilized to estimate the lumped disturbance and the estimation result is used for feedforward compensation in the controller. Findings – It is mathematically proved that the proposed sliding mode technique makes the attitude tracking errors converge to zero in finite time and the convergence time is estimated. Simulations are made for RLV through the assumption that aerodynamic parameters and atmospheric density are perturbed. Simulation results demonstrate that the proposed control strategy is effective, leading to promising performance and robustness. Originality/value – By the proposed controller, the second-order sliding mode is established. The attitude tracking error converges to zero in a finite time. Meanwhile, the chattering is alleviated and a smooth control input is obtained.

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