Decentralised control method for DC microgrids with improved current sharing accuracy

© The Institution of Engineering and Technology 2016. A decentralised control method that deals with current sharing issues in dc microgrids (MGs) is proposed in thisstudy. The proposed method is formulated in terms of 'modified global indicator' concept, which was originally proposedto improve reactive power sharing in ac MGs. In this work, the 'modified global indicator' concept is extended tocoordinate dc MGs, which aims to preserve the main features offered by decentralised control methods such as no need ofcommunication links, central controller or knowledge of the microgrid topology and parameters. This global indicator isinserted between current and voltage variables by adopting a virtual capacitor, which directly produces an output currentsharing performance that is less relied on mismatches of the multi-bus network. Meanwhile, a voltage stabiliser iscomplementary developed to maintain output voltage magnitude at steady state through a shunt virtual resistance. Theoperation under multiple dc-buses is also included in order to enhance the applicability of the proposed controller. Adetailed mathematical model including the effect of network mismatches is derived for analysis of the stability of theproposed controller. The feasibility and effectiveness of the proposed control strategy are validated by simulation andexperimental results

Sequential Phase-Shifted Model Predictive Control for multicell power converters

© 2017 IEEE. This paper proposes a sequential Phase-Shifted Model Predictive Control (PS-MPC) strategy for multicell power converters. The key novelty of this proposal lies in the way the predictive control strategy is formulated to fully exploit a phase-shifted pulse width modulation (PS-PWM) stage. Normally, when using a linear controller along with a standard PS-PWM stage, the modulator receives the same duty cycle for all the internal carriers. In contrast, by means of an appropriate choice of synchronized models for each carrier, the proposed predictive controller obtains independent optimal duty cycles for each carrier in a sequential manner. This allows one to formulate the optimal control problem to govern not only the output current but also the internal floating capacitor voltages, similarly to the finite-control-set MPC (FCS-MPC) case. As a result, the proposed sequential PS-MPC can attain a faster floating voltage balancing dynamic when compared to a standard PS-PWM implementation. Moreover, it generates a fixed-spectrum in the steady state with a constant commutation rate, which outperforms a standard FCS-MPC strategy. Simulation results of the proposed sequential PS-MPC strategy governing a single-phase four-level flying capacitor converter are presented to verify its dynamic and steady-state performance

The Basic Reproduction Number ℛ0 and Effectiveness of Reactive Interventions during Dengue Epidemics: The 2002 Dengue Outbreak in Easter Island, Chile

We use a stochastic simulation model to explore the effect of reactive intervention strategies during the 2002 dengue outbreak in the small population of Easter Island, Chile. We quantified the effect of interventions on the transmission dynamics and epidemic size as a function of the simulated control intensity levels and the timing of initiation of control interventions. Because no dengue outbreaks had been reported prior to 2002 in Easter Island, the 2002 epidemic provided a unique opportunity to estimate the basic reproduction number ℛ0 during the initial epidemic phase, prior to the start of control interventions. We estimated ℛ0 at 27.2 (95%CI: 14.8, 49.3). We found that the final epidemic size is highly sensitive to the timing of start of interventions. However, even when the control interventions start several weeks after the epidemic onset, reactive intervention efforts can have a significant impact on the final epidemic size. Our results indicate that the rapid implementation of control interventions can have a significant effect in reducing the epidemic size of dengue epidemics

First end-to-end PQC protected DPU-to-DPU communications

The appearance of quantum computing in the short foreseeable future and its capability to break conventional cryptographic algorithms forces to change the paradigm of secure real-time communications. Thus, government organizations, data centers, and enterprises among others are migrating their public key infrastructure towards using post-quantum cryptography (PQC) algorithms in order to mitigate the security threats posed by quantum computers. This letter presents the first quantum resilient secure end-to-end communication link based on PQC algorithms operating between two data-processing units DPU. Both data-processing units employ on-board ARM processors to perform the computationally expensive cryptographic building blocks—in that case CRYSTALS-Kyber as a key encapsulation mechanism and CRYSTALS-Dilithium for digital signature scheme in combination with advanced encryption standard with 256-bit key

First end-to-end PQC protected DPU-to-DPU communications

The appearance of quantum computing in the short foreseeable future and its capability to break conventional cryptographic algorithms forces to change the paradigm of secure real-time communications. Thus, government organizations, data centers, and enterprises among others are migrating their public key infrastructure towards using post-quantum cryptography (PQC) algorithms in order to mitigate the security threats posed by quantum computers. This letter presents the first quantum resilient secure end-to-end communication link based on PQC algorithms operating between two data-processing units DPU. Both data-processing units employ on-board ARM processors to perform the computationally expensive cryptographic building blocks—in that case CRYSTALS-Kyber as a key encapsulation mechanism and CRYSTALS-Dilithium for digital signature scheme in combination with advanced encryption standard with 256-bit key

The determinants of hotels' marketing managers' green marketing behaviour

Little is known about the factors underlying the pro-environmental behaviour of marketing managers. This paper explores the determinants of green marketing practices in the Red Sea hotel sector in Egypt. The research model assesses green marketing practices against the personal and organisational values of the marketing managers, together with a range of organisational and demographic variables expected to influence hotels' environmental behaviour. From a valid sample of 89 marketing managers responsible for 194 hotels, it was found that organisational contextual variables, and in particular targeting Western tourists, being affiliated to an international hotel chain and the marketers' own demographics, including age, academic subject studied and gender, were the best predictors of more proactive green marketing. Personal environmental values did not explain the pro-environmental behaviour of marketers, and the organisational environmental values that had explained part of their ethical behaviour had resulted from voluntarism rather than utilitarian or conformance-based values. Government policies also appeared to be ineffective determinants. The implications for green marketing practices are also discussed. © 2010 Taylor & Francis

Dehydration of Glucose to 5-Hydroxymethylfurfural Using LaOCl/Nb2O5 Catalysts in Hot Compressed Water Conditions

The dehydration of fructose and glucose to 5-hydroxymethylfurfural was studied using LaOCl/Nb2O5 in hot compressed water conditions. The catalysts were prepared by impregnation of LaCl3 on Nb2O5 with different loadings. The solids were characterized by EDX, XRD, TGA and N2 physisorption at 77 K and pyridine and CO2 adsorption followed by FTIR; the strength of acidity and basicity was determined by NH3- TPD and CO2- TPD, respectively. The use of acid–base systems for HMF production mainly from glucose requires weak basic sites and moderate acidity condition that is reached with LaOCl/ Nb2O5 as was confirmed by acidity and basicity analyses. The presence of Nb2O5 increase HMF yield (>50%) and prevented the formation of undesirable products in hot compressed water conditions, similar results could be obtained with DMSO.Centro de Investigación y Desarrollo en Ciencias Aplicada

Evaluation of grip strength in hook of hamate fractures treated with osteosynthesis. Is this surgical treatment necessary?

Objective: The aim of this study was to evaluate the outcomes of open reduction and internal fixation (ORIF) in hamate hook fractures and review the literature on this surgical procedure. Methods: We report the outcomes of ORIF of hamate hook fractures in 13 consecutive patients (12 men and 1 woman; mean age: 32 years (range, 22-48 years)). In eight patients (61%) the fracture was associated with ulnar nerve neuritis in Guyon's canal. We assessed the following clinical data: age, sex, mechanism of injury, side of the injured hand and associated lesions, fracture classification, average time from injury to correct diagnosis, surgical technique, complications, and length of follow-up. All patients underwent radiological imaging, including standard radiographs in two planes (anteroposterior and lateral projections), and a CT study. Functional outcomes evaluated were pain, range of motion, grip strength, Disabilities of the arm, shoulder and hand (DASH) and Mayo wrist score. Results: The mean follow-up was 36 months (range, 12-144 months). All 13 cases were treated with ORIF of the hook of the hamate. Mean VAS pain score was 5 preoperatively (4-9) and 1 (0-2) postoperatively. All patients returned to pre-injury level and only one patient felt pain on activity. Preoperative modified Mayo wrist score was 51 and the postoperative value was 94. All outcomes scores improved significantly from preoperative values. The patients who participated in sports postoperatively were able to do so at or near pre-injury levels. Postoperative average range of wrist motion was 76° in extension, 71° in flexion, 14° in ulnar deviation, and 21° in radial deviation. Mean grip strength in the hand with the hook fracture was 58 kg compared with 53 Kg in the unaffected hand. All patients returned to their pre-injury level of functioning after 10-12 weeks and there were no complications. Analysis of grip strength revealed values comparable with the unaffected hand. Conclusion: ORIF of hamate hook fractures is a safe and effective technique to restore normal grip strength and return to pre-injury level. In cases of ulnar nerve neuritis, neurolysis of the deep palmar branch is mandatory. Level of evidence: Level IV, Therapeutic study

On some products of finite groups

Please read abstract in the article.https://www.cambridge.org/core/journals/proceedings-of-the-edinburgh-mathematical-societyhj2023Mathematics and Applied Mathematic

Solving atomic multicast when groups crash

In this paper, we study the atomic multicast problem, a fundamental abstraction for building faulttolerant systems. In the atomic multicast problem, the system is divided into non-empty and disjoint groups of processes. Multicast messages may be addressed to any subset of groups, each message possibly being multicast to a different subset. Several papers previously studied this problem either in local area networks [3, 9, 20] or wide area networks [13, 21]. However, none of them considered atomic multicast when groups may crash. We present two atomic multicast algorithms that tolerate the crash of groups. The first algorithm tolerates an arbitrary number of failures, is genuine (i.e., to deliver a message m, only addressees of m are involved in the protocol), and uses the perfect failures detector P. We show that among realistic failure detectors, i.e., those that do not predict the future, P is necessary to solve genuine atomic multicast if we do not bound the number of processes that may fail. Thus, P is the weakest realistic failure detector for solving genuine atomic multicast when an arbitrary number of processes may crash. Our second algorithm is non-genuine and less resilient to process failures than the first algorithm but has several advantages: (i) it requires perfect failure detection within groups only, and not across the system, (ii) as we show in the paper it can be modified to rely on unreliable failure detection at the cost of a weaker liveness guarantee, and (iii) it is fast, messages addressed to multiple groups may be delivered within two inter-group message delays only