Model predictive direct power control of three-level T-type inverter-fed doubly-fed induction generator for wind energy system

The paper proposes a simplified direct power control strategy of a doubly-fed induction generator fed by a three-level T-type inverter based on finite control set model predictive control. A mathematical model based on grid voltage orientation was employed to determine the predictive values of the stator flux, rotor current, and capacitor voltages for all feasible rotor-side inverter output voltages. The active and reactive powers were calculated by using the grid voltage and the rotor current. A cost function was applied to track the active and reactive powers, maintain the balance of capacitor voltages, and reduce the common-mode voltage. The best switching control input was chosen by minimizing the cost function and implemented to the inverter. Different operating conditions of wind turbine systems were studied with Matlab/Simulink environment. The simulation results validate the improved performance of the proposed method compared with the classical control in terms of transient response and steady-state conditions

Influence of alloying elements on the corrosion of fine art bronze in the strong corrosive environment

The influence of Sn, Zn, and Pb on the corrosion of fine art bronze in strong corrosive environment were investigated. The value of loss mass and the potential of the specimens were determined in the artificial sea-water environment. Corrosion of specimens was compared each to other to find the effect of the elements. The corrosion products were determined with the XRD/SEM/EDS analyses. The results shown that, Sn decreases the corrosion rate of the bronze alloy in marine environment while Zn increases it. The corrosion rates and potential curves showed that the corrosion rate of the bronzes reduced with immersion time. Alloy containing 0.7% Pb; 1.6% Zn; 9.7 % Sn; 88% Cu (in %wt.) has the corrosion rate as lowest. Keywords. Corrosion, strong corrosive environments, fine art bronze, Sn, Pb, Zn

Safety and efficacy of fluoxetine on functional outcome after acute stroke (AFFINITY): a randomised, double-blind, placebo-controlled trial

Background Trials of fluoxetine for recovery after stroke report conflicting results. The Assessment oF FluoxetINe In sTroke recoverY (AFFINITY) trial aimed to show if daily oral fluoxetine for 6 months after stroke improves functional outcome in an ethnically diverse population. Methods AFFINITY was a randomised, parallel-group, double-blind, placebo-controlled trial done in 43 hospital stroke units in Australia (n=29), New Zealand (four), and Vietnam (ten). Eligible patients were adults (aged ≥18 years) with a clinical diagnosis of acute stroke in the previous 2–15 days, brain imaging consistent with ischaemic or haemorrhagic stroke, and a persisting neurological deficit that produced a modified Rankin Scale (mRS) score of 1 or more. Patients were randomly assigned 1:1 via a web-based system using a minimisation algorithm to once daily, oral fluoxetine 20 mg capsules or matching placebo for 6 months. Patients, carers, investigators, and outcome assessors were masked to the treatment allocation. The primary outcome was functional status, measured by the mRS, at 6 months. The primary analysis was an ordinal logistic regression of the mRS at 6 months, adjusted for minimisation variables. Primary and safety analyses were done according to the patient's treatment allocation. The trial is registered with the Australian New Zealand Clinical Trials Registry, ACTRN12611000774921. Findings Between Jan 11, 2013, and June 30, 2019, 1280 patients were recruited in Australia (n=532), New Zealand (n=42), and Vietnam (n=706), of whom 642 were randomly assigned to fluoxetine and 638 were randomly assigned to placebo. Mean duration of trial treatment was 167 days (SD 48·1). At 6 months, mRS data were available in 624 (97%) patients in the fluoxetine group and 632 (99%) in the placebo group. The distribution of mRS categories was similar in the fluoxetine and placebo groups (adjusted common odds ratio 0·94, 95% CI 0·76–1·15; p=0·53). Compared with patients in the placebo group, patients in the fluoxetine group had more falls (20 [3%] vs seven [1%]; p=0·018), bone fractures (19 [3%] vs six [1%]; p=0·014), and epileptic seizures (ten [2%] vs two [<1%]; p=0·038) at 6 months. Interpretation Oral fluoxetine 20 mg daily for 6 months after acute stroke did not improve functional outcome and increased the risk of falls, bone fractures, and epileptic seizures. These results do not support the use of fluoxetine to improve functional outcome after stroke

Actuation design and assistive control for a soft wearable exosuit

The development of a portable assistive device to aid patients affected by neuromuscular disorders has been the ultimate goal of assistive robots since the late 1960s. Traditional robotic devices have been engineered to assist the users' limbs in both activities of daily living (ADLs) and physical therapy, mostly consisting of load-bearing exoskeletons made of rigid links that operate in parallel to the human skeleton. These devices can be extremely accurate and are able to deliver high forces/torques to their users, making them optimal solutions for improving physical therapy in clinical environments. However, their structural complexity cause them to be poor candidates for daily at-home use, where portability, lightweight, compliance, and low profile are preferable. A new frontier of assistive devices aims at designing exoskeletons based on fabric and flexible materials for applications where kinematic transparency is the primary requirement. Bowden-cable transmission is the widely employed solution in most of the aforementioned applications due to advantages in durability, lightweight, safety, and flexibility. The major advantages of soft assistive exoskeletons driven by Bowden-cable transmission can be identified in the superior ergonomics and wearability, allowing users to freely move and allocating the actuation stages far away from the end effector. Despite of having many advantages in assistive technology, this actuation strategy presents several intrinsic limitations caused by the presence of nonlinearities, such as friction and backlash of the cables, which make it difficult to predict and control the kinematics and dynamics between the device and the user. In this thesis, I present the design and control implementation of a soft, textile-based exosuit driven by Bowden-cable transmission for assisting human upper limb movements, especially elbowflexion/extension. I describe a model-based design, characterisation and testing of an actuation stage, driving a set of artificial tendons to apply torques to the human elbow joint. I also propose a novel hierarchical control paradigm for the actuation unit, considering all the aspects ranging from human motion intention detection for assistance, to adaptive compensation for the detrimental effects arising from the presence of nonlinear behaviours in the exosuit, i.e. friction and backlash. The resulting system is a low profile, lightweight, wearable exosuit with high accuracy, designed to intuitively assist the wearer in activities of daily living.Doctor of Philosophy (MAE

Ring Contraction Reactions of a Non-Benzenoid Aromatic Cation and a Neutral Homoaromatic System into Benzene Derivatives

Aromaticity is one of the most intriguing concepts in organic chemistry. Simple and extended benzenoid aromatic systems have been very well established in undergraduate textbooks, and there are also mentions of non-benzenoid aromatic structures such as cyclopropenium, cyclopentadienide and cycloheptatrienylium (tropylium) ions. However, the structural relationship and the comparison of stabilization energy of such aromatic ions to benzene ring have been rarely studied and remained an underexplored area of advanced organic chemistry research. To contribute some insights into this topic, we focused on the chemical transformation, namely a ring contraction reaction, of the tropylium ion to benzene ring in this work. With an approach combining computational studies with experimental reactions, we also aim to turn this transformation into a synthetically useful tool. Indeed, this work led to the development of a new synthetic protocol, which involved an oxidative ring-contraction of tropylium ion, to formally introduce the phenyl ring onto a range of organic structures. Furthermore, the homoaromatic cycloheptatrienyl precursors of tropylium salts used in these reactions can also be rearranged to valuable benzhydryl or benzyl halides, enriching the synthetic utility of this ring-contraction protocol

Tropolonate Salts as Acyl Transfer Catalysts for Esterification Reactions under Thermal and Photochemical Conditions

Acyl transfer catalysis is a frequently used tool to promote the formation of carboxylic acid derivatives, which are important synthetic precursors and target compounds in organic synthesis. However, there have been only a few structural motifs known to efficiently catalyze the acyl transfer reaction. Herein we introduce a new acyl transfer catalytic paradigm based on the tropolone framework. We show that tropolonate salts, due to their strong nucleophilicity and photochemical activity, can promote the coupling reaction between alcohols and carboxylic acid anhydrides or chlorides to give the products with excellent efficiency under thermal or blue light-photochemical conditions. Kinetic studies and density functional theory (DFT) calculations suggest interesting mechanistic insights for reactions promoted by this new acyl transfer catalytic system

First Molecular Detection of Zoonotic <i>Chlamydia</i> Species in Vietnamese Goats

The genus Chlamydia comprises obligate intracellular bacteria that infect a wide variety of hosts, with infection leading to a range of diseases in humans and animals; they thus constitute a major public health threat. Among the members of the Chlamydiaceae family, Chlamydia suis, C. abortus, C. pecorum, and C. psittaci represent the most important pathogenic species infecting a large range of hosts and are a well-established threat to livestock. Information regarding the circulation of Chlamydia species in ruminants from Vietnam is lacking. In this study, DNA extracted from 60 blood samples collected from goats in Hue province was used for Chlamydia spp. identification by classic PCR and Sanger sequencing. Chlamydia spp. were detected in eleven samples (18.3%) and C. abortus and C. psittaci were molecularly identified by sequencing. Despite the limited sample size in this study, findings point out the relevance of ruminants as hosts of chlamydial species in Central Vietnam and the importance of monitoring chlamydial strains through the activation of surveillance programs in this country. The need for a deeper evaluation of human and animal health risk analysis in terms of chlamydiosis should be also considered

Risk factors related to diabetic retinopathy in Vietnamese patients with type 2 diabetes mellitus

Along with the rising incidence of diabetes, the prevalence of diabetic retinopathy (DR) is quickly growing across the world. The incidence of DR complications is high, and many people are not detected until they have complications and visual impairment, causing many difficulties for the treatment process. Aims: The goal of this cross-sectional was to investigate the clinical and subclinical features of Vietnamese diabetic retinopathy patients. Methods: DR was diagnosed using International Clinical Diabetic Retinopathy scale. Complete clinical information (Age, sex, weight, height, history of hypertension and diabetes mellitus, smoking, alcohol), subclinical information (Glucose, urea, creatinine, HbA1c, uric acid, cholesterol, triglyceride, HDL-cholesterol, LDL-cholesterol blood levels, Complete blood count) were collected. Results: The research enrolled 140 type 2 diabetic patients (70 in each group: DR and no DR). DR patients had significantly higher age, RBC, Hb, eGFR, uric acid, and creatinine blood levels than patients without DR. A duration of diabetes mellitus of over 15 years was associated with an 8.319-fold increased risk of DR. In conclusion, age, RBC, Hb, eGFR, uric acid, creatinine blood levels and duration of diabetes mellitus over 15 years are risk factors for DR