This paper investigates the feasibility of application of a unified power flow controller (UPFC) to damp subsynchronous Resonance in a power system. The basic dynamic characteristics of the UPFC and its parameters impact on SSR modes are investigated and based on the introduced control strategy, its ability of damping SSR for sample study systems is demonstrated.

This paper presents the mitigation of subsynchronous Resonance (SSR) based on wide-area wide-area fuzzy controller in power systems including a double-fed induction generator (DFIG)-based wind farms linked to series capacitive compensated transmission networks. SSR damping is achieved by adding the fuzzy controller as a supplementary signal at the stator voltage loop of the grid-side converter (GSC) of doubly-fed induction generator (DFIG)-based wind farms. In addition, delays due to communication signals are important in using WAMS. If these delays are ignored, it causes system instability. In this paper, the delays are modeled with a separate fuzzy input to the controller. The effectiveness and efficiency of the WAMS-based fuzzy controller has been demonstrated by comparison with the particle swarm optimization (PSO), and imperialist competitive algorithm (ICA) optimization methods. The effectiveness and validity of the proposed Auxiliary damping control are verified on a modified version of the IEEE second benchmark model including DFIG-based wind farms via time simulation analysis by using MATLAB/Simulink.

Background and Aims: Disc displacement is the most common temporomandibular joint disorder and magnetic Resonance imaging (MRI) is the gold standard in its diagnosis. This disorder can lead to changes in signal intensity of magnetic Resonance (MR). The purpose of this study was evaluation of correlation between relative signal intensity of MR images of retrodiscal tissue, superior and inferior head of lateral ptrygoid muscle with type of anterior disk displacement and condylar head flattening in patients with temporomandibular disorder (TMD).Materials and Methods: In this retrospective study, 31 MR images of patients who had anterior disc displacement were evaluated. After relative signal intensity measurement for retrodiscal tissue, superior and inferior head of lateral ptrygoid muscle, the correlation between relative signal intensity and type of anterior disc displacement was evaluated with repeated measure ANOVA test. In each of these 3 areas, t-test was used to compare the groups with and without condylar head flattening.Results: The correlation between relative signal intensity of MR images and type of anterior disc displacement in retrodiscal tissue, superior and inferior head of lateral ptrygoid muscle was not significant. There was also no statistically significant correlation between relative signal intensity of MR images and flattening of condylar head in retrodiscal tissue, superior and inferior head of lateral ptrygoid muscle (P>0.05).Conclusion: According to findings of this study, relative signal intensity of MR images in retrodiscal tissue, superior and inferior head of ptrygoid muscle is not a good predictor for type of anterior disc displacement and flattening of condylar head. It seems that this cannot be used as a diagnostic marker for TMD progression.

Introduction: Usually osseointegration takes between three to six months after implant placement but patients are interested to have early loading. There are no definitive criteria for measuring bone mineral density (BMD), insertion torque (IT) (final torque force) and Resonance frequency analysis (RFA) (primary implant stability) to determine exact loading time based on the relationship between the above-mentioned parameters. The aim of this study was to determine the relationship between IT, RFA and BMD in screw-type implants.Materials and Methods: This clinical trial was conducted on 18 patients who were candidates for ITI implant placement. Written consent was taken and jaw bone density was determined via a digital radiography technique before surgery. After implant placement, RFA and IT were measured. Fifty-five ITI implants of the total 62 implants placed were evaluated; the implants were 12 mm long with a diameter of 4.1 mm. Data was analyzed with Pearson’s test using SPSS.15 software (a=0.05).Results: There was a significant relationship between IT, RFA and BMD. Pearson’s test showed a correlation coefficient of 0.872 to 0.789 between the three parameters, indicating a strong relationship between them. The mean bone density was 1.468±0.042 g/cm2; the mean RFA was 66.01±2.2 ISQ and the mean IT was 34.62±3.33 N/cm2.Conclusion: Based on the results of the present study there is a significant relationship between, IT, RFA and BMD (p value=0.001).

The subsynchronous Resonance (SSR) phenomenon is a condition that the wind farm exchanges energy with the electrical network at one or more of the subsynchronous frequencies. If it is not prevented, this phenomenon causes damages to the system. The SSR phenomenon occurs in two following conditions: Induction generator effect and Torsional interaction effect. The SSR occurs in the DFIG based wind farms due to the induction generator effect. In this research, by controlling the stator voltage, the SSR is mitigated or prevented with considering the maintenance of MPPT condition. So that, with direct control of the stator voltage, line current of the system is controlled indirectly and prevented from the induction generator effect. For this purpose, an additional controller called SSR damping controller is used. This controller is applied to GSC converter of the DFIG. Because the SSR depends on the speed and frequency of the generator rotor, the rotor speed is selected as the input signal of this controller. In order to simulate, the MATLAB/SIMULINK software has been used. To verify the proposed method, a DFIG based wind farm connected to an infinite bus by a series capacitor compensated transmission line, is considered.

This paper focuses on the turbine-generator shaft models of double-cage Induction Generator (IG) based wind farm and its impact on the Sub-synchronous Resonance phenomenon. For this purpose, six different shaft models as 6-mass, 4-mass, 3-mass I, 3-mass II, 2-mass and 1-mass models are considered for double-cage IG wind-turbine. By using the linear modal analysis method, the effects of the different multi mass model of double-cage IG wind-turbine on the SSR phenomenon are studied. The results obtained by eigenvalue analysis show that the model of double-cage IG wind-turbine has an important effect on the detecting of Subsynchronous Resonance (SSR) phenomenon. The analytical results are validated by detailed electromagnetic transient simulation using PSCAD/EMTDC software.

Background: The study of the molecular dynamics of proteins based on internal motions is crucial for understanding the mechanism of protein function. Internal movements of proteins play an important role in both protein folding processes and the mechanism of action of enzyme. Knowledge about these movements will help us in understanding these processes correctly. Osmolites are small organic molecules which are utilized by the cells of all organisms, except hallobacteria. Osmolites are produced under extreme stressful conditions in order to help in stabilizing macro-molecules and retaining their biological function. They interact directly with macromolecules, but they exert their effect only when the characteristics or conditions of the solvent present around the cell change. Therefore, their presence affects the stability of the protein indirectly.Materials and Methods: In this work we studied the effect (s) of the osmolite Sorbitol on the dynamics of Hen Egg White Lysozyme, and through our study we used NMR Hydrogen-Deuterium Exchange to characterize the effect (s). We performed spectrometery in two different conditions, in the absence and presence of sorbitol. The extent of peptide hydrogen exchange was assigned as a function time and in a decreasing manner in the intensity of the peak corresponding to amino acids. The resulting TOCSY spectra were assigned using SPARKY software, as well as we integrated the peaks using this software.Results: The speed of hydrogen exchange, hydrogen atoms of the peptide bond, will give us information about the local structural oscillations where the exchange is taking place. The rate of hydrogen exchange varies from one amino acid to another, and the intensity of the peak of these hydrogen decreases as time passes by.Conclusion: We found that the presence of sorbitol causes a decrease in proton exchange rate, and since there is no noticeable chemical shifts in the peaks of the spectra, in the presence or absence of sorbitol, we can conclude that sorbitol did not cause any change in the three dimensional structure. It seems that the decrease in the rate of exchange is a representative of a decrease in the accessible surface area or to strengthening of hydrogen bonds, and sorbitol caused one of these two possibilities.

Resonance and ferroResonance in power systems are categorized as two destructive phenomena especially in HV networks which their occurrence are being initiated in consequence of a power system event. Also, FerroResonance phenomenon may be initiated by non-power system event such as lightning strike. Hence, the study of Resonance and ferroResonance requires an exhaustive evaluation of possible network events in different network configurations. In each event, the analysis of network voltages is conducted based on identified allowable limits by IEEE 519 standard as an evaluation critera. In this paper, a novel comprehensive study approach is proposed for study of ferroResonance phenomena in power networks. The proposed approach comprises different steps including substation equipment modeling, EMT simulation of the probable switching events, evaluation of correspondence results, and finally detecting the probable ferroResonance occurrence. Furthermore, a novel approach for Resonance study is also presented. Voltage and current limits are implemented to define an impedance criteria for performing Resonance evaluation of network buses. Findings – The proposed method is implemented for study of Resonance and ferroResonance in all HV substations of the Khuzestan regional electricity network. By performing the proposed evaluations, the probable condition which may lead to Resonance and ferroResonance occurrence are identified. The results are highly valuable for network operators in prevention of unintended overvoltages occurrence.