Fully Decou pled Controller Models for Voltage Source Converter based High Voltage DC Transmission

VSC-HVDC has two distinct advantages over its earlier generation thyristor based High Voltage DC transmission. Synchronous voltage source is not required to commutate against, for its operation and it does not suffer from commutation failures under adverse conditions in interfacing ac system. These two properties make it amenable to wider application areas. To make it adapt to operational conditions imposed on it in various applications, its controller parameters need to be assessed and tuned through extensive simulation studies. To facilitate this, two alternative controllers viz. a fully decoupled controller model and also an instantaneous theory based fully decoupled hybrid controller model are developed in the thesis. The decoupling is achieved by exploiting similarity transformation in both the controllers. In the first controller model, the Park's currents and voltages are directly obtained from the measured network variables and the reference park's currents for the inner current loop are obtained from the instantaneous measured power. In the second one, both the feedback as well as reference Park's currents for the inner current loop are obtained from the Clarke's variables. An AC system interfacing electronics based power transmission or distribution network experiences non-sinusoidal voltage and current waveforms. Instantaneous power theory being suitable for steady as well as transient states, is used for handling measured inputs. The performance of the models is assessed through SIMULINK Power system Blockset aided simulations on a VSC-HVDC link interfacing an ac system, having normal fault level, low fault level and also witnessing a single line to ground fault on its rectifier transformer primary side

Fully Decou pled Controller Models for Voltage Source Converter based High Voltage DC Transmission

VSC-HVDC has two distinct advantages over its earlier generation thyristor based High Voltage DC transmission. Synchronous voltage source is not required to commutate against, for its operation and it does not suffer from commutation failures under adverse conditions in interfacing ac system. These two properties make it amenable to wider application areas. To make it adapt to operational conditions imposed on it in various applications, its controller parameters need to be assessed and tuned through extensive simulation studies. To facilitate this, two alternative controllers viz. a fully decoupled controller model and also an instantaneous theory based fully decoupled hybrid controller model are developed in the thesis. The decoupling is achieved by exploiting similarity transformation in both the controllers. In the first controller model, the Park's currents and voltages are directly obtained from the measured network variables and the reference park's currents for the inner current loop are obtained from the instantaneous measured power. In the second one, both the feedback as well as reference Park's currents for the inner current loop are obtained from the Clarke's variables. An AC system interfacing electronics based power transmission or distribution network experiences non-sinusoidal voltage and current waveforms. Instantaneous power theory being suitable for steady as well as transient states, is used for handling measured inputs. The performance of the models is assessed through SIMULINK Power system Blockset aided simulations on a VSC-HVDC link interfacing an ac system, having normal fault level, low fault level and also witnessing a single line to ground fault on its rectifier transformer primary side

Hubble Ultraviolet Spectroscopy of Jupiter Trojans

We present the first ultraviolet spectra of Jupiter Trojans. These observations were carried out using the Space Telescope Imaging Spectrograph on the Hubble Space Telescope and cover the wavelength range 200-550 nm at low resolution. The targets include objects from both of the Trojan color subpopulations (less-red and red). We do not observe any discernible absorption features in these spectra. Comparisons of the averaged UV spectra of less-red and red targets show that the subpopulations are spectrally distinct in the UV. Less-red objects display a steep UV slope and a rollover at around 450 nm to a shallower visible slope, whereas red objects show the opposite trend. Laboratory spectra of irradiated ices with and without H$_{2}$S exhibit distinct UV absorption features; consequently, the featureless spectra observed here suggest H$_{2}$S alone is not responsible for the observed color bimodality of Trojans, as has been previously hypothesized. We propose some possible explanations for the observed UV-visible spectra, including complex organics, space weathering of iron-bearing silicates, and masked features due to previous cometary activity.Comment: 7 pages, 4 figures, accepted by A

A damage model for transversely isotropic materials

International audienceIn a nuclear disposal project, the damage of the hosting rock is a capital issue that should be studied and understood. This problem is even more complex when the studied rock is anisotropic. In the present paper, a damage model that takes into account both initial and induced anisotropy is introduced using equivalence relations between the real material and a fictitious isotropic one on which we can take all the advantages of the well established isotropic theory. Numerical simulations using a Finite Element Method (FEM) code shows an agreement between the theoretical predictions and the experimental data of Brazilian tests with different orientation angles

Characterization of aromaticity in analogues of titan's atmospheric aerosols with two-step laser desorption ionization mass spectrometry

The role of polycyclic aromatic hydrocarbons (PAH) and Nitrogen containing PAH (PANH) as intermediates of aerosol production in the atmosphere of Titan has been a subject of controversy for a long time. An analysis of the atmospheric emission band observed by the Visible and Infrared Mapping Spectrometer (VIMS) at 3.28 micrometer suggests the presence of neutral polycyclic aromatic species in the upper atmosphere of Titan. These molecules are seen as the counter part of negative and positive aromatics ions suspected by the Plasma Spectrometer onboard the Cassini spacecraft, but the low resolution of the instrument hinders any molecular speciation. In this work we investigate the specific aromatic content of Titan's atmospheric aerosols through laboratory simulations. We report here the selective detection of aromatic compounds in tholins, Titan's aerosol analogues, produced with a capacitively coupled plasma in a N2:CH4 95:5 gas mixture. For this purpose, Two-Step Laser Desorption Ionization Time-of-Flight Mass Spectrometry (L2DI-TOF-MS) technique is used to analyze the so produced analogues. This analytical technique is based on the ionization of molecules by Resonance Enhanced Multi-Photon Ionization (REMPI) using a {\lambda}=248 nm wavelength laser which is selective for aromatic species. This allows for the selective identification of compounds having at least one aromatic ring. Our experiments show that tholins contain a trace amount of small PAHs with one to three aromatic rings. Nitrogen containing PAHs (PANHs) are also detected as constituents of tholins. Molecules relevant to astrobiology are detected as is the case of the substituted DNA base adenine

Graduates Perception towards Instructional Methods of Emergency Medicine: Affecting Their Self-confidence in Emergency Departments

Background: Teaching emergencies has the ability to provide medical students with animportant knowledge and skills. In this study, we assessed the perception of Faculty of medicine, University of Gezira graduates regarding instructional methods of emergencies and their performance in emergency departments. Materials and Methods: This is a cross-sectional survey, which was conducted among newly graduated doctors, during their internship rotation. We assessed the graduateperception about instructional methods of teaching EM during medical school and how they deal with emergencies. Likert’s scale of five points was used for assessment of the graduate response. This data was used for a correlation analysis. Result: Ninety three graduates were enrolled. Male doctors’ numbers was 41(44%). Most of the graduated doctors agreed that clinical round and practical session in teaching emergency are useful among 80(86%) and 74(79.6%) of them respectively. Less number of graduated students 45 (48.4%) and 43 (36.6%) agreed that Problem-based learning and Seminar are useful in teaching emergency. Numbers of graduates who feel competence to assess and diagnose patients, request a relevant investigation, and can put a treatment plan and start the managements are 60(68.8%), 76(81.8%) and 61 (65.6%) respectively. Conclusion: There are some strength and weakness in emergency teaching during medical school which affects their self-confidence when dealing with emergencies

The Initial Experience of Trans-Rectal Ultrasound and Biopsy in Diagnosis of Carcinoma Prostate In Gezira Hospital For Renal Disease And Surgery (GHRDS)

Background: Prostate cancer prevalent cancer in males above sixty-five worldwide, this lead to the introduction of screening of the PSA and using of the transrectal ultrasound scanning, and sextant biopsy of the prostate.Objectives: To compare the accuracy of the Transrectal Ultrasound guided biopsy (TRUS/BX) in the diagnosis of prostate cancer in Gezira Hospital for Renal Diseases and Surgery (GHRDS), with specific considerations to the digital rectal examination (DRE) findings and prostate specific antigen (PSA) level.                      .Materials and Methods:  This is a prospective, descriptive small-scale hospital based study.  A total of 297 patients with clinically symptomatic enlarged prostate underwent transrectal ultrasound guided true cut needle biopsy of the prostate were studied in (GHRDS) in the period from June2006 to June2009.                    Results: The majority 188 (63.3%) of patients were between 50-70 years of age. Abnormal digital rectal examination (DRE) like obliteration of the median sulcus, and fixed mucosa revealed higher incidence of carcinoma prostate (CaP) with a significant value (p= 0.0000). PSA level showed significant relation (p= 0.0001) with the diagnosis of carcinoma prostate. Transrectal U/S findings well correlated to the histopathological results, where abnormal findings (like hypo-echoic lesions or calcifications and cysts) showed higher incidence of malignancy in 46 patients constitute 52.8% of the abnormal U/S findings.Conclusions and recommendations: PSA level is highly sensitive but less specific in detection of prostate cancer. Normal DRE doesn’t exclude prostate cancer, fixed mucosa and obliterated median sulcus has the highest predictors of cancer prostate in DRE. Presence of calcifications and cyst on trans-rectal ultrasound has the highest liability for cancer prostate in compare to the other ultrasonic findings.                 Key words: Prostate cancer, DRE, PSA level, TRUS/ BX (Transrectal ultra sound biopsy), sextant biopsy

Association of SNP3 polymorphism in the apolipoprotein A-V gene with plasma triglyceride level in Tunisian type 2 diabetes

BACKGROUND: Apolipoprotein A-V (Apo A-V) gene has recently been identified as a new apolipoprotein involved in triglyceride metabolism. A single nucleotide polymorphism (SNP3) located in the gene promoter (-1131) was associated with triglyceride variation in healthy subjects. In type 2 diabetes the triglyceride level increased compared to healthy subjects. Hypertriglyceridemia is a risk factor for coronary artery disease. We aimed to examine the interaction between SNP3 and lipid profile and coronary artery disease (CAD) in Tunisian type 2 diabetic patients. RESULTS: The genotype frequencies of T/T, T/C and C/C were 0.74, 0.23 and 0.03 respectively in non diabetic subjects, 0.71, 0.25 and 0.04 respectively in type 2 diabetic patients. Triglyceride level was higher in heterozygous genotype (-1131 T/C) of apo A-V (p = 0.024). Heterozygous genotype is more frequent in high triglyceride group (40.9%) than in low triglyceride group (18.8%) ; p = 0.011. Despite the relation between CAD and hypertriglyceridemia the SNP 3 was not associated with CAD. CONCLUSION: In type 2 diabetic patients SNP3 is associated with triglyceride level, however there was no association between SNP3 and coronary artery disease

Application of R.E.N.A.L Nephrometry Score in Planning Type of Surgery and Predicting Complications in RCC Patients in Gezira Hospital

Background: Adult renal cell carcinomas account for 80–85% of all renal tumors, making them the most common primary renal tumors. As a method for categorizing renal masses by anatomical characteristics, R.E.N.A.L score is suggested to study the effect on surgical approach in addition to perioperative outcomes and complications. Methods: A cross-sectional prospective hospital-based study enrolled 48 RCC patients in GHRDS in the period between September 2020 and September 2021. Data regarding demographics, histological subtypes, surgical approach, intraoperative and postoperative complications were collected. Based on R.E.N.A.L score, the complexity of renal tumors is grouped into low, moderate, and high. Results: The study sample size was 48. Twenty-five participants (52.1%) were men with a mean age of 51 years. Most cases had clear cell RCC 22 (45.8%) and papillary RCC 19 (39.6%). Thirty-nine (81.5%) patients underwent radical nephrectomy (flank incision [extraperitoneal] in 32 [82.1%] and midline incision [transperitoneal] in 7 [17.3%]), and 9 (18.5%) patients underwent partial nephrectomy. One-third of the patients 15 (31.2%) had intraoperative complications and 7 (14.6%) had postoperative complications. All intraoperative and most postoperative complications were associated with radical nephrectomy (P = 0.001). According to complexity, 21 (43.8%) patients had moderate complexity, 15 (31.2%) high complexity, and 12 (25%) low complexity. Conclusion: Most RCC patients had moderate complexity and were subjected to radical nephrectomy. High complexities were linked to the decision of radical nephrectomy, and intraoperative and postoperative complications. More prospective research with large sample size and multi-centered studies is essential to ensure the generalizability of study findings