Single-Phase Inverter Synchronized to the Grid by Linear Kalman Filter in Microgrids

This paper presents the analysis and implementation of a synchronizer to the grid using a linear Kalman filter. The synchronizer is used in a single-phase inverter, which is applied in an environment of microgrids. The inverter converts the energy that comes from renewable energy sources （photovoltaic, wind, fuel cell, etc.）. The main objective of obtaining the phase of the grid is to achieve a power factor close to unity in the inverter. For this reason it is vital that the phase difference between the synchronizer and the grid zero. To obtain synchronizer algorithm using LKF （linear Kalman filter） is necessary to know the EKF （extended Kalman filter）. This allows to analyze the operation of the filter, which allows to reach reduce linear Kalman filter or also known as simplified Kalman filter. It is necessary to generate an orthogonal signal in order to obtain a stationary reference frame from a single-phase grid because the linear Kalman filter works with a stationary reference frame. Orthogonal signal is created with an all-pass filter.     

Modification of stool's water content in constipated infants: management with an adapted infant formula

Background

There is increasing global acceptance that viscous soluble fibers lower serum LDL cholesterol (LDL-C), but most evidence for this comes from studies in Caucasians. To see if oat β-glucan lowers LDL-C in Caucasians and non-Caucasians we conducted a post-hoc analysis of the results of a randomized, controlled, double-blind, multi-center clinical trial whose primary aim was to determine if molecular-weight (MW) influenced the LDL-C-lowering effect of oat β-glucan.

Results

Caucasian and non-Caucasian subjects with LDL-C-C ≥ 3.0 and ≤ 5.0 mmol/L (n = 786 screened, n = 400 ineligible, n = 19 refused, n = 367 randomized, n = 345 completed, n = 1 excluded for missing ethnicity) were randomly assigned to consume cereal containing wheat-fiber (Control, n = 74:13 Caucasian:non-Caucasian) or 3 g high-MW (3H, 2,250,000 g/mol, n = 67:19), 4 g medium-MW (4 M, 850,000 g/mol, n = 50:17), 3 g medium-MW (3M, 530,000 g/mol, n = 54:9) or 4 g low-MW (4 L, 210,000 g/mol, n = 51:12) oat β-glucan daily for 4 weeks. LDL-C after 4 weeks was influenced by baseline LDL-C (p < 0.001) and treatment (p = 0.003), but not ethnicity (p = 0.74). In all subjects, compared to control, 3 H, 4 M and 3 M reduced LDL-C significantly by 4.8 to 6.5%, but 4 L had no effect. Compared to control, the bioactive oat β-glucan treatments (3H, 4M and 3M) reduced LDL-C by a combined mean (95% CI) of 0.18 (0.06, 0.31) mmol/L (4.8%, n = 171, p = 0.004) in Caucasians, a value not significantly different from the 0.37 (0.09, 0.65) mmol/L (10.3%, n = 45, p = 0.008) reduction in non-Caucasians.

Conclusion

We conclude that oat β-glucan reduces LDL-C in both Caucasians and non-Caucasians; there was insufficient power to determine if the magnitude of LDL-C-lowering differed by ethnicity.

Trial Registration

ClinicalTrials.gov: NCT00981981     

Identification of Lactobacillus spp. in colostrum from Chilean mothers

The biodiversity of Lactobacillus spp. in colostrum samples from 116 Chilean mothers was analyzed by PCR and 16S rDNA sequencing. Lactobacilli were isolated in 55.3% of the samples, with concentrations of 3.33 +/- 0.55 (log CFU/ml). The predominant species were L. plantarum (64%), L. fermentum (16%) and L. pentosus (9%). 28% of the isolated strains were resistant to gastric pH and bile salts, suggesting that they could be used as probiotics.     

Waterborne polyurethane/acrylate: Comparison of hybrid and blend systems

Polyurethane/acrylate hybrid composites in a broad range of composition (10, 30, 50, 70 and 90 wt.% of acrylic content), were obtained by emulsion polymerization of acrylic monomers (methyl methacrylate/n-butyl acrylate/acrylic acid mixture) in the presence of preformed polyurethane chains with polymerizable terminal vinyl groups. Blends with the same acrylic content were also prepared by mixing polyurethane and acrylic dispersions. Samples were characterized by SEC, DLS, FTIR, UV, TEM, AFM, SAXS/WAXS and gel fraction content. Mechanical properties, Buccholz and pencil hardness, surface roughness and water contact angle of films were also determined. The effect of the acrylic content on morphology and film properties was also evaluated. Hybrids are crosslinked systems showing changes in the particle and film morphologies with increasing acrylic content. The properties of hybrid films show a non-linear behavior with the increase of the acrylic component, while physical blends exhibit a gradual behavior from PU to AC. FTIR results indicate better acrylic-polyurethane compatibility in hybrid systems than in physical blends. Hybrid composites with up to 70 wt.% of acrylic component are homogeneous by SAXS. On the other hand, AFM results show that blends are phase segregated systems at all composition levels.     

Increase of plasma fatty acids without changes in n-6/n-3-PUFA ratio in asymptomatic obese subjects

Obesity is associated with a low grade inflammation which contributes to the development of insulin resistance and diabetes. The aim of this study was to assess the total saturated (SFAs), monounsaturated (MUFAs) and polyunsaturated fatty acids (PUFAs) in plasma from asymptomatic obese subjects and to determine the arachidonic/eicosapentanoic acid ratio [ARA/EPA] as a marker of inflammation, and its eventual association with ultrasensitive CRP. Fourteen obese (34.4 +/- 11.1y.; BMI: 36.0 +/- 4,5 kg/m2) and 12 normal-weight (30.6 +/- 7.8y.; BMI: 23,6 +/- 2,4 kg/m2) subjects were recruited and their plasma fatty acids were determined by gas chromatography. usCRP was higher in the obese subjects (p = 0.01) and correlates with their body fat content. The percentages of SFAs, MUFAs, PUFAs were not affected in the obese subjects but their concentrations were increased, compared with the control group. However, no differences in the long chain PUFAs (DHA and EPA) concentrations or in the plasmatic ARA/EPA ratio were observed in these subjects. These observations do not support a relation between the ARA/EPA ratio and the presence of low grade inflammation evaluated by plasma usCRP in this group of asymptomatic obese subjects.     

Optimisation of microwave-assisted acid digestion for the purification of supported carbon nanotubes

Experimental optimisation of microwave-assisted acid digestion for supported carbon nanotube (CNT) purification is reported. Process variables including ramp rate, temperature, duration, scalability, acid type, volume and concentration were investigated using thermogravimetric, Fourier transform infra-red and Raman spectroscopy performance metrics. Key factors in purification were temperature, duration and acid. HNO₃ damaged CNTs and introduced carboxyl and C–O functional groups. HCl and H₂SO₄ achieved similar impurity removal but, despite the incorporation of sulphur-based functional groups, H₂SO₄ was preferred due to a more homogeneous product. Concentration and volume variables could be condensed into a single factor – the stoichiometric excess of acid to impurities – for process simplification and to permit direct literature comparison. The scalable optimised process increased CNT purity from ∼22 wt% to > 95 wt% with negligible damage in a single 15 min isothermal treatment at 230 °C with a H₂SO₄ excess of 4.5 times the required stoichiometry (1 M).     

Damage detection in elevated spherical containers partially filled with liquid

Damage detection through changes in the dynamic properties has received considerable attention in recent years. However, approaches in structures supporting tanks partially filled with liquid are scarce in the technical literature.In this paper, a numerical-experimental study of damage detection in coupled fluid-structure elevated spherical tank systems is presented. The main objective is to investigate the feasibility to detect structural damage in the support structure by monitoring changes in natural frequencies. The major difficulty arises due to the changes in natural frequencies when the liquid level varies. Thus, in order to gain insight into the dynamical behaviour of the spherical containers and distinguish between the frequency shift caused by container filling conditions or by structural damage, experimental free vibration tests with small vibration amplitudes on a scaled spherical tank model are performed. The dependency of the identified frequencies on the structural damage severity is studied assuming three increasing levels of damage in the support structure. The results indicate that it is possible to detect structural damage, with acceptable confidence, up to liquid filling level of 30%. Moreover, only the “associated structural frequency” reflects the structural damage with a perceptible drop. Next, a numerical model of a real spherical container that takes into account the coupling between fluid and structure is presented to demonstrate the usefulness and validity of the results.     

Extrapolation of a predictive model for growth of a low inoculum size of Salmonella Typhimurium DT104 on chicken skin to higher inoculum sizes

Validation of model predictions for independent variables not included during model development can save time and money by identifying conditions for which new models are not needed. A single strain of Salmonella Typhimurium DT104 was used to develop a general regression neural network (GRNN) model for growth of a low inoculum size (0.9 log) on chicken skin with native microflora as a function of time (0 to 8 h) and temperature (20 to 45°C). The ability of the GRNN model to predict growth of higher inoculum sizes (2, 3, or 4.1 log) was evaluated. When the proportion of residuals in an acceptable prediction zone (pAPZ) from -1 log (fail-safe) to 0.5 log (fail-dangerous) was ≥0.7, the GRNN model was classified as providing acceptable predictions of the test data. The pAPZ for dependent data was 0.93 and for independent data for interpolation was 0.88. The pAPZs for extrapolation to higher inoculum sizes of 2, 3, or 4.1 log were 0.92, 0.73, and 0.77, respectively. However, residual plots indicated local prediction problems with pAPZs of < 0.7 for an inoculum size of 3 log at 30, 35, and 40°C and for an inoculum size of 4.1 log at 35 and 40°C where predictions were fail-dangerous, indicating faster growth at higher inoculum sizes. The model provided valid predictions of Salmonella Typhimurium DT104 growth on chicken skin from inoculum sizes of 0.9 and 2 log at all temperatures investigated and from inoculum sizes of 3 and 4.1 log at some but not all temperatures investigated. Thus, the model can be improved by including inoculum size as an independent variable.     

Super-twisting sliding mode differentiation for improving PD controllers performance of second order systems

Designing a proportional derivative (PD) controller has as main problem, to obtain the derivative of the output error signal when it is contaminated with high frequency noises. To overcome this disadvantage, the supertwisting algorithm (STA) is applied in closed-loop with a PD structure for multi-input multi-output (MIMO) second order nonlinear systems. The stability conditions were analyzed in terms of a strict non-smooth Lyapunov function and the solution of Riccati equations. A set of numerical test was designed to show the advantages of implementing PD controllers that used STA as a robust exact differentiator. The first numerical example showed the stabilization of an inverted pendulum. The second example was designed to solve the tracking problem of a two-link robot manipulator.     

Molecular and Electrophysiological Role of Diabetes-Associated Circulating Inflammatory Factors in Cardiac Arrhythmia Remodeling in a Metabolic-Induced Model of Type 2 Diabetic Rat

Background: Diabetic patients have prolonged cardiac repolarization and higher risk of arrhythmia. Besides, diabetes activates the innate immune system, resulting in higher levels of plasmatic cytokines, which are described to prolong ventricular repolarization. Methods: We characterize a metabolic model of type 2 diabetes (T2D) with prolonged cardiac repolarization. Sprague-Dawley rats were fed on a high-fat diet (45% Kcal from fat) for 6 weeks, and a low dose of streptozotozin intraperitoneally injected at week 2. Body weight and fasting blood glucose were measured and electrocardiograms of conscious animals were recorded weekly. Plasmatic lipid profile, insulin, cytokines, and arrhythmia susceptibility were determined at the end of the experimental period. Outward K⁺ currents and action potentials were recorded in isolated ventricular myocytes by patch-clamp. Results: T2D animals showed insulin resistance, hyperglycemia, and elevated levels of plasma cholesterol, triglycerides, TNFα, and IL-1b. They also developed bradycardia and prolonged QTc-interval duration that resulted in increased susceptibility to severe ventricular tachycardia under cardiac challenge. Action potential duration (APD) was prolonged in control cardiomyocytes incubated 24 h with plasma isolated from diabetic rats. However, adding TNFα and IL-1b receptor blockers to the serum of diabetic animals prevented the increased APD. Conclusions: The elevation of the circulating levels of TNFα and IL-1b are responsible for impaired ventricular repolarization and higher susceptibility to cardiac arrhythmia in our metabolic model of T2D.