Comparative Study of Sensorless Control Methods of PMSM Drives

Recently, permanent magnet synchronous motors (PMSMs) are increasingly used in high performance variable speed drives of many industrial applications. This is because the PMSM has many features, like high efficiency, compactness, high torque to inertia ratio, rapid dynamic response, simple modeling and control, and maintenance-free operation. In most applications, the presence of such a position sensor presents several disadvantages, such as reduced reliability, susceptibility to noise, additional cost and weight and increased complexity of the drive system. For these reasons, the development of alternative indirect methods for speed and position control becomes an important research topic. Many advantages of sensorless control such as reduced hardware complexity, low cost, reduced size, cable elimination, increased noise immunity, increased reliability and decreased maintenance. The key problem in sensorless vector control of ac drives is the accurate dynamic estimation of the stator flux vector over a wide speed range using only terminal variables (currents and voltages). The difficulty comprises state estimation at very low speeds where the fundamental excitation is low and the observer performance tends to be poor. The reasons are the observer sensitivity to model parameter variations, unmodeled nonlinearities and disturbances, limited accuracy of acquisition signals, drifts, and dc offsets. Poor speed estimation at low speed is attributed to data acquisition errors, voltage distortion due the PWM inverter and stator resistance drop which degrading the performance of sensorless drive. Moreover, the noises of system and measurements are considered other main problems. This paper presents a comprehensive study of the different methods of speed and position estimations for sensorless PMSM drives. A deep insight of the advantages and disadvantages of each method is investigated. Furthermore, the difficulties faced sensorless PMSM drives at low speeds as well as the reasons are highly demonstrated. Keywords: permanent magnet, synchronous motor, sensorless control, speed estimation, position estimation, parameter adaptation

IMPACT OF DIFFERENT SOURCES OF NITROGEN FERTILIZERS ON PERFORMANCE GROWTH OF DATE PALM (Phoenix dactylifera L. cv. Bartomouda)

A green house experiment was carried out in two successive seasons on date Palm plantlets (Phoenix dactylifera L. cv. Bartomouda) from 2012 to 2013, to evaluated the effectiveness of different sources of nitrogen fertilizer at four treatments as (T2) 5 g/l ammonium sulfate 20 % (1 g nitrogen), (T3) 3 g/l potassium nitrate 33% (1 g nitrogen) and (T4) 2 g/l urea (46%) with the irrigation water one time/ week.The design of the experiment was randomized complete with three replicates. The results revealed that, plant height cm, leaves numbers, root length cm and numbers, and fresh and dry weights of leaves and roots were increasing highly significantly with 3 g/l of potassium nitrate graduated by 2 g/l urea and 5 g/l ammonium sulfate respectively at both seasons. Chlorophyll a, b and carotenoids contents showed significant rising with 3 g/l potassium nitrate. Greatest significant contents of indole and proline were obtained under T3 for two seasons. Leaves nitrogen content N was increased by 2 g/l urea in the two seasons; on the other hand, root nitrogen content was increased with treatment 3 g/l potassium nitrate, sequenced by T2 and T4 treatments. Leaves and roots phosphorus P content significantly raising under 3g/l potassium nitrate and 5 g/l ammonium sulfate for two seasons. In the presence of 5 g/l ammonium sulfate and 3 g/l potassium nitrate leaves and root potassium content K were largest at two seasons respectively. This research shows that the nitrogen formula as potassium nitrate > ammonium sulfate > urea were recommended to highly increasing growth of date palm plantlets in the green house

Causes of Gross Hematuria in Patient at a Tertiary Care Hospital

Objective: To determine the causes of hematuria in patients coming to a tertiary care hospital. Patients and Methods: This cross-sectional study was carried out at Pakistan Institute of Medical Sciences (PIMS), Islamabad, Pakistan. Data was collected over a period of six months (June 2016 to December 2016). Data of all the adult male and female patients presenting with complaint of gross hematuria during the period were gathered and analyzed for etiological profile.Results: In the study the most common cause was urological malignancy, which was present in 29 (58%) of patients. This includes all the urological cancers. Among other causes, 11 (22%) patients had urolithiasis while 5 (10%) patients had gross hematuria due to trauma to renal tract. 3 (6%) males had hematuria due to enlarged vascular prostate and only 2 (4%) females had gross hematuria due to urinary tract infection. Conclusion: Urological malignancy was the most common cause of gross hematuria, which is associated with male gender, older age and history of smoking. Other causes were urolithiasis, trauma, BPH and UTI. We recommend screening for malignant disease of all the patients presenting to the departments of urology with the complaint of gross hematuria

Evaluating the governance and preparedness of the Lebanese health system for the COVID-19 pandemic: a qualitative study

From BMJ via Jisc Publications RouterHistory: received 2021-10-29, accepted 2022-05-16, ppub 2022-06, epub 2022-06-01Publication status: PublishedFunder: World Health Organization; FundRef: http://dx.doi.org/10.13039/100004423; Grant(s): 2002577199Objectives: This study aimed to assess the capacities and governance of Lebanon’s health system throughout the response to the COVID-19 pandemic until August 2020. Design: A qualitative study based on semi-structured interviews. Setting: Lebanon, February–August 2020. Participants: Selected participants were directly or indirectly involved in the national or organisational response to the COVID-19 pandemic in Lebanon. Results: A total of 41 participants were included in the study. ‘Hardware’ capacities of the system were found to be responsive yet deeply influenced by the challenging national context. The health workforce showed high levels of resilience, despite the shortage of medical staff and gaps in training at the early stages of the pandemic. The system infrastructure, medical supplies and testing capacities were sufficient, but the reluctance of the private sector in care provision and gaps in reimbursement of COVID-19 care by many health funding schemes were the main concerns. Moreover, the public health surveillance system was overwhelmed a few months after the start of the pandemic. As for the system ‘software’, there were attempts for a participatory governance mechanism, but the actual decision-making process was challenging with limited cooperation and strategic vision, resulting in decreased trust and increased confusion among communities. Moreover, the power imbalance between health actors and other stakeholders affected decision-making dynamics and the uptake of scientific evidence in policy-making. Conclusions: Interventions adopting a centralised and reactive approach were prominent in Lebanon’s response to the COVID-19 pandemic. Better public governance and different reforms are needed to strengthen the health system preparedness and capacities to face future health security threats

Quels espaces pour enseigner l'architecture? Une école d'architecture à New York (Chelsea, New York, USA)

Les écoles d'architecture conçues par des architectes ont moins de succès que celles occupant des lieux réhabilités. On peut dès lors remettre en question l'obstination de l'architecte pour concevoir une forme qui corresponde à un programme, son désir de prévoir les activités et sa volonté de créer un système autoritaire qui oblige l'utilisateur à vivre comme il l'a pensé. Une fois sa liberté réduite, l'être humain se retrouve prisonnier d'une architecture qu'il doit subir. Le plan type du gratte-ciel est l'architecture du degré zéro. Il permet l'événement, le changement, la mutation, la déformation et devient "background" de la vie. En ne faisant pas de choix, le plan type ne prévoit pas le futur et le laisse ouvert. L'île de Manhattan est un ensemble de blocs limités par des rues et des avenues orthogonales. Les différences entre les blocs révèlent la présence en négatif de la structure unifiante : la grille. Le projet est une grille tridimensionnelle, régie par un plan type, où les activités et les gens sont les acteurs principaux. La grille est non isotrope et se compose de différents types d'espaces. Les qualités du bâtiment varient selon les niveaux et suggèrent des utilisations particulières. Elles stimulent la créativité et l'appropriation par des initiatives personnelles. Poussés par leurs envies et leurs pulsions, les étudiants prennent possession de la structure et agissent pour améliorer leur environnement. Premiers actes d'architecture au sein de l'école. La grille est une ossature de poutres et de poteaux préfabriqués en béton brut, représentée à l'extérieur du bâtiment par du métal. L'ossature blanche, abstraite, minimale et primitive est un exemple d'économie de moyens dans une société qui ne peut plus se permettre le luxe. L'école d'architecture est un modèle