A Soft Switched DC-DC Boost Converter for Use in Grid Connected Inverters

This paper presents a soft-switching DC-DC boost converter, which can be utilized in renewable energy systems such as photovoltaic array, and wind turbine connections to infinite bus of a big power network, using grid connected inverters. In the proposed topology for the DC-DC boost converter, the main and the auxiliary power switches are turned on and turned off with zero voltage switching (ZVS) and zero current switching (ZCS), respectively. Furthermore, by applying soft-switching techniques to driving power switches, the power losses and stresses associated with commutation of power devices decrease significantly. The efficiency of the proposed soft-switched DC-DC converter at various output powers is compared with that of the traditional DC-DC converter and a few topologies proposed in recent literature. This comparison indicates that the proposed DC-DC boost converter is much more efficient around the rated power (1 kW). The power topology and the control strategy applied to the proposed soft-switched DC-DC boost converter, which is connected to a grid-tied inverter, are analyzed theoretically by simulation studies. Moreover, an experimental prototype is implemented to verify the theoretical analysis and the simulation studies

Post parturient hemoglobinuria in a sheep flock

ΔΕΝ ΥΠΑΡΧΕΙ ΠΕΡΙΛΗΨΗ ΣΤΑ ΕΛΛΗΝΙΚΑThe syndrome of intravascular hemolysis, hemoglobinuria, and anemia has been recognized in post parturient dairy cattle and buffaloes. In this report, the occurrence of post parturient hemoglobinuria in a sheep flock was described. Six ewes were affected and 3 of them were died. The affected animals had lambed 1-2 weeks before. The clinical signs included hemoglobinuria, tachycardia, tachypnea, weakness and recumbency. Serum phosphorus concentrations and PCV values were lower than reference parameters for sheep. Phosphorus supplementation and supportive treatment were recommended. In conclusion, grazing on frozen pasture following phosphorus deficiency could be responsible for the development of post parturient hemoglobinuria in the sheep flock

Iteration Complexity of Randomized Primal-Dual Methods for Convex-Concave Saddle Point Problems

In this paper we propose a class of randomized primal-dual methods to contend with large-scale saddle point problems defined by a convex-concave function $\mathcal{L}(\mathbf{x},y)\triangleq\sum_{i=1}^m f_i(x_i)+\Phi(\mathbf{x},y)-h(y)$. We analyze the convergence rate of the proposed method under the settings of mere convexity and strong convexity in $\mathbf{x}$-variable. In particular, assuming $\nabla_y\Phi(\cdot,\cdot)$ is Lipschitz and $\nabla_\mathbf{x}\Phi(\cdot,y)$ is coordinate-wise Lipschitz for any fixed $y$, the ergodic sequence generated by the algorithm achieves the convergence rate of $\mathcal{O}(m/k)$ in a suitable error metric where $m$ denotes the number of coordinates for the primal variable. Furthermore, assuming that $\mathcal{L}(\cdot,y)$ is uniformly strongly convex for any $y$, and that $\Phi(\cdot,y)$ is linear in $y$, the scheme displays convergence rate of $\mathcal{O}(m/k^2)$. We implemented the proposed algorithmic framework to solve kernel matrix learning problem, and tested it against other state-of-the-art solvers

Megaoesophagus in the upper cervical oesophagus in a steer: a case report

ABSTRACT: Acquired megaoesophagus was diagnosed in a seven-month-old Holstein steer. Clinical signs included salivation, mild recurrent bloat, dysphagia or regurgitation of ingesta after swallowing and coughing lasting three days. Endoscopic examination revealed mild rhinitis and pharyngitis. Positive contrast radiography of the oesophagus outlined dilatation in the cervical oesophagus without evidence of obstruction. Treatment consisted of feeding management, oral electrolytes, intravenous fluids, and systemic antimicrobial therapy. Clinical signs of megaoesophagus resolved gradually after prolonged antimicrobial therapy and supportive care. However, the steer persisted with episodes of regurgitation and coughing. In conclusion, oesophagitis may have been the principle cause of megaoesophagus in this case but this could not be confirmed because a postmortem examination was not performed. Keywords: megaoesophagus; oesophagitis; cattle; bloat; regurgitation Megaoesophagus is a pathological dilatation and atony of the body of the oesophagus usually associated with asynchronous function of the oesophagus and the caudal oesophageal sphincter. There are a limited number of reports in the literature regarding this ailment in ruminants. Megaoesophagus is usually a congenital condition although the acquired condition has also been reported (Smith 2009). Functional or morphologic defects due to systemic diseases are the underlying cause of acquired megaoesophagus. The dilated oesophagus is dysfunctional and filled with saliva, feed and water. This results in regurgitation and may lead to aspiration pneumonia (Smith 2009). The condition occurs sporadically and is uncommon in adult cattle ), calves ) sheep (Braun et al. 1990), goats , dogs , llamas This case report describes the clinical and radiographical features of megaoesophagus in the cranial cervical region of a steer. Case description History and clinical findings. A seven-monthold Holstein steer was referred to the Clinic of the Faculty of Veterinary Medicine of Urmia University with a history of salivation, mild recurrent bloat, diarrhoea, dysphagia and coughing lasting three days. The regurgitation occurred within several minutes of feeding. The ration had been a mixture of pasture forage and concentrate. The steer had a rectal temperature of 39.6 °C (reference range: 38-39 °C), a heart rate of 100/ min (reference range: 60-80/min), a respiratory rate of 36/min (reference range: 10-30/min) and was in good condition, but slightly dehydrated. The level of dehydration was estimated to be 5%. 49 Veterinarni Medicina, 60, 2015 (1): 48-51 Case Report doi: 10.17221/7925-VETMED Abnormal swelling was not present or palpable along the left jugular groove. There was no visual evidence of inflation of the oesophagus associated with each cycle of eructation. Resistance was not encountered to passage of a stomach tube into the rumen although accumulated gas was removed from the rumen to relieve clinical signs of bloat. Both nostrils were covered with dark, dried discharge due to frequent regurgitation. Examination of rumen fluid indicated moderate inactivation of forestomach flora and fauna. The parasitological examination of faeces revealed a few oocytes of coccidia and Haemonchus contortus, Ostertagia ostertagi, Nematodiurs and Cooperia sp. nematode eggs. No abnormalities were heard during auscultation of the trachea, heart or lungs. Pulmonary abnormalities compatible with clinical signs of bronchopneumonia were not observed. The steer's drinking and eating behaviour was normal, however, after swallowing there were episodes of head and neck extension, and rapid chewing motions of the jaw with passive regurgitation of ingesta and water as well as coughing from the mouth. A neurologic examination was performed but no abnormalities were detected involving the cranial nerves, peripheral nerves, or CNS. Diagnostic results and treatment. Haematology and plasma biochemistry performed upon admission disclosed PCV (38%; reference range, 24-46%) and total protein concentration (9.1 g/dl; reference range, 6.6-7.8 g/dl). Leukocytosis (WBC: 15 000 µl) with a marked neutrophilia (9000/µl), increased blood fibrinogen concentration (850 mg/dl) and hyperproteinaemia (91 g/l) was recorded on the haemogram. Serum chemistry showed elevated plasma sorbital dehydrogenase (22.4 IU/l) and alkaline phosphatase (794 IU/l) concentrations. Ketonuria was not detected. Endoscopic examination of the upper airway and oral cavity revealed a mild rhinitis and pharyngitis. There was a frothy mixture of mucus and feed material within the nasopharynx and an abnormal upper oesophagus. Approximately 40 cm of the mucosal surface of the upper cervical oesophagus was dilated with no mucosal folds visualised. No stricture, stenosis, or foreign body could be found associated with the oesophagus. The only lesions detected were discoloration and the presence of fibrinous deposits of the oesophageal mucosa. Positive contrast radiography of the cervical oesophagus was taken in standing lateral position by a portable X-ray unit (Mobile Drive AR 30, Model TM8105, Smam X-Ray Equipment, Muggio Lombardy, Milan 20053, Italy) and oral administration of 500 ml barium sulphate in 30% suspension (Barex, Darou Pakhsh Pharmaceutical Mfg. Co. Tehran, Iran). Barium study outlined regional dilatation of the cervical oesophagus Treatment of the megaoesophagus consisted of frequent small daily feedings of corn silage and a commercial dairy ration, limited ingestion of long stem hay, and systemic antimicrobials. Oral electrolytes and twelve litres of Ringer's solution were administered intravenously to overcome dehydration. After ten days a slight improvement was observed but the steer continued to have episodes of regurgitation and coughing. Eventually, the medical treatment was not effective and the animal died after one month with protrusion of bones of the shoulders, ribs, back-bone and hips, sunken eyes 50 Case Repor

Power System Stability Improvement via TCSC Controller Employing a Multi-objective Strength Pareto Evolutionary Algorithm Approach

This paper focuses on multi-objective designing of multi-machine Thyristor Controlled Series Compensator (TCSC) using Strength Pareto Evolutionary Algorithm (SPEA). The TCSC parameters designing problem is converted to an optimization problem with the multi-objective function including the desired damping factor and the desired damping ratio of the power system modes, which is solved by a SPEA algorithm. The effectiveness of the proposed controller validates on a multi-machine power system over a wide range of loading conditions. The results of the proposed controller (SPEATCSC) are compared with the Genetic Algorithm (GA) based tuned TCSC through some operating conditions to demonstrate its superior efficiency

Design of output feedback UPFC controller for damping electromechanical oscillations using

a b s t r a c t In this paper, a novel method for the design of output feedback controller for unified power flow controller (UPFC) is developed. The selection of the output feedback gains for the UPFC controllers is converted to an optimization problem with the time domain-based objective function which is solved by a particle swarm optimization technique (PSO) that has a strong ability to find the most optimistic results. Only local and available state variables are adopted as the input signals of each controller for the decentralized design. Thus, structure of the designed UPFC controller is simple and easy to implement. To ensure the robustness of the proposed stabilizers, the design process takes into account a wide range of operating conditions and system configurations. The effectiveness of the proposed controller for damping low frequency oscillations is tested and demonstrated through nonlinear time-domain simulation and some performance indices studies. The results analysis reveals that the designed PSO-based output feedback UPFC damping controller has an excellent capability in damping power system low frequency oscillations and enhance greatly the dynamic stability of the power systems. Moreover, the system performance analysis under different operating conditions show that the d E based controller is superior to both the m B based controller and conventional power system stablizer

Probabilistic Multi Objective Optimal Reactive Power Dispatch Considering Load Uncertainties Using Monte Carlo Simulations

Optimal Reactive Power Dispatch (ORPD) is a multi-variable problem with nonlinear constraints and continuous/discrete decision variables. Due to the stochastic behavior of loads, the ORPD requires a probabilistic mathematical model. In this paper, Monte Carlo Simulation (MCS) is used for modeling of load uncertainties in the ORPD problem. The problem is formulated as a nonlinear constrained multi objective (MO) optimization problem considering two objectives, i.e., minimization of active power losses and voltage deviations from the corresponding desired values, subject to full AC load flow constraints and operational limits. The control variables utilized in the proposed MO-ORPD problem are generator bus voltages, transformers’ tap ratios and shunt reactive power compensation at the weak buses. The proposed probabilistic MO-ORPD problem is implemented on the IEEE 30-bus and IEEE 118-bus tests systems. The obtained numerical results substantiate the effectiveness and applicability of the proposed probabilistic MO-ORPD problem

A comprehensive 1000 Genomes-based genome-wide association meta-analysis of coronary artery disease

Existing knowledge of genetic variants affecting risk of coronary artery disease (CAD) is largely based on genome-wide association studies (GWAS) analysis of common SNPs. Leveraging phased haplotypes from the 1000 Genomes Project, we report a GWAS meta-analysis of 185 thousand CAD cases and controls, interrogating 6.7 million common (MAF>0.05) as well as 2.7 million low frequency (0.005<MAF<0.05) variants. In addition to confirmation of most known CAD loci, we identified 10 novel loci, eight additive and two recessive, that contain candidate genes that newly implicate biological processes in vessel walls. We observed intra-locus allelic heterogeneity but little evidence of low frequency variants with larger effects and no evidence of synthetic association. Our analysis provides a comprehensive survey of the fine genetic architecture of CAD showing that genetic susceptibility to this common disease is largely determined by common SNPs of small effect siz