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

Evaluation of Chlamydomonas reinhardtii Microalgae as a Sustainable Feed Supplement and Fishmeal Substitute in Aquaculture with a Positive Impact on Human Nutrition

Currently, there is an urgent need for the growing aquaculture sector to rely on sustainable ingredients which can achieve optimal growth while maintaining fish’s nutritional value (especially omega-3 fatty acid content) for human consumption. Here, C. reinhardtii biomass was substituted for fishmeal in zebrafish (Danio rerio) diets in wild-type and mutant (Casper) strains. Four isonitrogenous (46% cp), isocaloric (19–21 MJ/kg DW) diets were prepared with C. reinhardtii replacing 10% (C10), 20% (C20), and 50% (C50) of the fishmeal component of the diet formulation. Over 8 weeks of feeding trials, the zebrafish showed a significant growth improvement when fed C10, C20, and C50 compared with the control (no C. reinhardtii), with C20 giving the best performance in terms of growth, feed conversion ratio (FCR), and specific growth rate (SGR). Interestingly, C. reinhardtii in the diet increased the levels of linolenic acid (C18:3 n-3) and hexadecatrienoic acid (C16: 4-n-3) (p ≤ 0.05) in the zebrafish. Yellow pigmentation, which was shown to be lutein, was observed in eggs and zebrafish flesh for fish fed a diet containing C. reinhardtii. Moreover, the zebrafish assimilated β-carotene from C. reinhardtii and converted it to vitamin A. Overall, while replacing 20% of fishmen in the zebrafish’s diet with C. reinhardtii biomass offers the best results, replacement with only 10% showed a significant benefit for the zebrafish. Furthermore, replacing fishmeal with 50% C. reinhardtii is still possible and beneficial, and C. reinhardtii whole cells are digestible by zebrafish, thus demonstrating that C. reinhardtii not only has the potential to serve as a feed supplement but that it can also act as a feed substitute once the production cost of microalgae becomes competitive

Nurses' perceptions of aids and obstacles to the provision of optimal end of life care in ICU

Contains fulltext : 172380.pdf (publisher's version ) (Open Access

Factors affecting the development of deformation bands in the Nubian Sandstone, Central Eastern Desert, Egypt

Reservoir quality prediction is a key element in petroleum exploration and investigation of reservoir potential. The Nubian Sandstone reservoir in Egypt has excellent potential for hydrocarbon production. However, many deformation bands of different scales were rerecorded regionally and have a substantial influence on the porosity and permeability of the Nubian Sandstone Unit. Therefore, the effects of these deformation bands need to be quantified. Samples from the Cretaceous succession along the Qift-El-Qusier road were petrographically and petrophysically studied. Three sets of deformation bands trending in a NE-SW direction were identified during mapping. The host sandstone unit is quartz arenite where is composed mainly of quartz. A significant petrographic difference in grain size was noticed, where deformation bands have smaller grain sizes. Two lithological facies were recognized based on the mineralogy, grain size, sorting, and porosity. Facies 1 is coarse-grained, well sorted and with high porosity characteristics, where deformation bands dominated. On the other hand, Facies 2 with fine grains, well sorting and low porosity possesses deformation bands with a lower degree of cataclasis. The deformation bands have negatively impacted the porosity and permeability of the sandstone. The porosity in the Nubian Sandstone ranges from 24.3 to 29.7%, which is reduced from 9.6 to 17.1% in plugs containing the deformation bands. A similar trend for permeability was also found, where permeability is tremendously reduced from 1200 to 8400 mD in the host sandstone to 0.08-0.3 mD in deformation bands.Web of Science192art. no. 10457

Evaluation of various techniques for separation of non-polar modifier concentrates from petroleum waxy by-products

Two petroleum waxy by-products (light and middle slack wax crudes) were evaluated for separation of non-polar modifiers by using different techniques. The results showed that, the light slack wax is selected as a suitable wax for separation of n-alkanes with even number of carbon atoms ranging from C20 to C26 for their high n-paraffin contents and can be used as non-polar structural modifiers. Different separation techniques; multistage fractional crystallization and liquid–solid chromatography; followed by the urea adduction technique have been used to separate non-polar modifier concentrates from the light slack wax crude. The light slack wax, its saturate components, the hard wax fractions isolated from light slack wax by the multistage fractional crystallization technique and their adducts were analyzed by GC to characterize and compare the produced components. The resulting data reveal that, the adducts of light slack wax and its saturate components; can be used as non-polar modifier concentrates of low carbon atoms (C20 + C22). From an economic point of view, the light slack wax adduct is selected as a non-polar modifier concentrate whereas, the separation step can be neglected to save energy. Meanwhile, the adduct of the hard wax isolated at 30 °C can be used as the preferable non-polar modifier concentrate of the high carbon number atoms (C24 + C26)

Evaluation of sleep quality and pruritus severity in psoriatic patients and their impact on quality of life: a cross section correlational study

Abstract Psoriasis is a chronic inflammatory condition associated with genetic and immunological susceptibility. The objective of the study was to evaluate pruritus and sleep quality in correlation (r) to psoriasis severity and to detect their impact on quality of life. Two hundred (200) patients with psoriasis were included. Psoriasis severity was determined using the psoriasis area severity index (PASI), the quality of life (QoL) was assessed by the psoriasis disability index (PDI) questionnaire, and the sleep quality was evaluated by the Pittsburgh sleep quality index (PSQI). Finally, the severity of itching was evaluated using a 12-item pruritus severity scale (PSS). Poor sleep quality was found in 16.0% of patients in this study. Poor sleep was detected among 50.0% of cases with severe psoriasis. PASI scores correlated significantly with sleep quality, duration and sleep disturbances (p < 0.001). The global PSQI and PASI were also significantly correlated (p = 0.004). In conclusion patients complaining of psoriasis exacerbated by pruritus and sleep problems demonstrated lower quality of life in all domains. Sleep disturbances and depressive symptoms impairing quality of life should be taken into consideration when screening patients suffering from psoriasis

Electroplating of brass from citrate-based alloy baths

147-152<span style="font-size:11.0pt;line-height: 115%;font-family:Calibri;mso-fareast-font-family:" times="" new="" roman";mso-bidi-font-family:="" "times="" roman";mso-ansi-language:en-us;mso-fareast-language:en-us;="" mso-bidi-language:ar-sa"="" lang="EN-US">The electrodeposition of copper, zinc and brass onto steel substrates from citrate-based alloy baths has been studied for a variety of bath compositions, temperatures and current densities. The influences of these variables on cathodic polarization, cathodic current efficiencies, quality of the deposits and composition of the alloys have been determined. The surface morphology of the deposits has been examined by scanning electron microscopy and crystal structure by X-ray. Fine-grained and adherent deposits of brass have been plated in most cases.</span