Effect of optimal torque control on rotor loss of fault-tolerant permanent-magnet brushless machines

A faulted phase in a fault-tolerant permanent-magnet brushless machine can result in significant torque ripple. However, this can be minimized by using an appropriate optimal torque control strategy. Inevitably, however, this results in significant time harmonics in the phase current waveforms, which when combined with inherently large space harmonics, can result in a significant eddy-current loss in the permanent magnets on the rotor. This paper describes the optimal torque control strategy which has been adopted, and discusses its effect on the eddy-current loss in the permanent magnets of four-, five-, and six-phase fault-tolerant machines

The Importance of Evaluating Primary Midwifery Care for Improving the Health of Women and Infants

In most countries, maternal and newborn care is fragmented and focused on identification and treatment of pathology that affects only the minority of women and babies. Recently, a Framework for Quality Maternal and Newborn Care (QMNC) was developed, which encourages a system-level shift to provide skilled care for all. This care includes preventive and supportive care that works to strengthen women’s capabilities and focuses on promotion of normal reproductive processes while ensuring access to emergency treatment when needed. Midwifery care is pivotal in this framework which contains several elements that resonate with the main dimensions of primary care. Primary health care is the first level of contact with the health system where most of the population’s curative and preventive health needs can be fulfilled as close as possible to where people live and work. In this paper, we argue that midwifery as described in the framework requires the application of a primary care philosophy for all childbearing women and infants. Evaluation of the implementation of the framework should therefore include tools to monitor the performance of primary midwifery care

Srs2 promotes synthesis-dependent strand annealing by disrupting DNA polymerase δ-extending D-loops.

Synthesis-dependent strand annealing (SDSA) is the preferred mode of homologous recombination in somatic cells leading to an obligatory non-crossover outcome, thus avoiding the potential for chromosomal rearrangements and loss of heterozygosity. Genetic analysis identified the Srs2 helicase as a prime candidate to promote SDSA. Here, we demonstrate that Srs2 disrupts D-loops in an ATP-dependent fashion and with a distinct polarity. Specifically, we partly reconstitute the SDSA pathway using Rad51, Rad54, RPA, RFC, DNA Polymerase δ with different forms of PCNA. Consistent with genetic data showing the requirement for SUMO and PCNA binding for the SDSA role of Srs2, Srs2 displays a slight but significant preference to disrupt extending D-loops over unextended D-loops when SUMOylated PCNA is present, compared to unmodified PCNA or monoubiquitinated PCNA. Our data establish a biochemical mechanism for the role of Srs2 in crossover suppression by promoting SDSA through disruption of extended D-loops

ASSESSMENT OF THE UTILIZATION OF DIFFERENT STRENGTH CLASSES OF CEMENT IN BUILDING CONSTRUCTIONS IN LAGOS, NIGERIA

Building collapse in Nigeria is so rampant now to the extent that it’s gradually not becoming a news when one occurs. Several factors being attributed as the cause of building collapses are based on opinions and in some cases based on investigative reports of selected buildings collapse. These factors are speculative since some intrinsic properties of debris materials tested during the investigation of selected collapse might be lost due to the impact of the collapse as a result of falling from great height and other debris falling on the tested material that these properties were intact before the collapse. Also, since the major causes of collapse in Nigeria is mostly attributed to poor construction process and the use of substandard material, this study assesses the quality of cements used in some selected sites and freshly produced cement from factory to compare with relevant standards, it also assesses the level of knowledge of the Nigerian construction professional using these cements to measure its applications. It was found out that the cements used in these selected sites were not all to standard even though all the freshly purchased cements met the required standard, this indicates that other factors might be responsible for the drop in standard properties. It was also observed that many of the professionals still need more training on the application of the different cement classes in structural concrete work

Unexpected non-Wigner behavior in level-spacing distributions of next-nearest-neighbor coupled XXZ spin chains

The level-spacing distributions of XXZ spin chains with next-nearest-neighbor couplings are studied under periodic boundary conditions. We confirm that integrable XXZ spin chains mostly have the Poisson distribution as expected. On the contrary, the level-spacing distributions of next-nearest-neighbor coupled XXZ chains are given by non-Wigner distributions. It is against the expectations, since the models are nonintegrable.Comment: 4 pages, 4 figures, to be published in Physical Review

Investigating for Pozzolanic Activity in Palm Kernel Nut Waste Ash (PKNWA) with Cement towards a Sustainable Construction

The earth is not inherited from our ancestors but borrowed from our children and should be returned the way we met it and even better. This is the essence of sustainability, preserving the earth. One of the main consequence of a non-sustainable world is global warming caused by the release of greenhouse gasses into the atmosphere that deplete the earth’s protective layer from extreme sun radiation. This results in global temperature rise leading to tsunamis and other “natural disasters” making us more vulnerable to extreme weather elements. Urbanization and industrialization bring about high construction rate to accommodate them resulting to global demand for concrete production. Concrete production contributes about 5% of the world’s carbon dioxide (CO2) emission and bulk of these emissions are in cement production. Cement is not an eco-friendly material and the sharp decrease in its use is highly needed to improve sustainable construction. Another issue discouraging its use is the rising cost, making housing unaffordable even to the middle class. This have resulted in finding series of housing financing systems to cope with rising cost of housing. One of the ways of achieving this is by the use of pozzolanic and blended cements to reduce the quantity of cements needed to meet the global concrete demand. This study examines the Pozzolanic Potentials of Palm Kernel Nut Waste Ash (PKNWA) as a blend with cement in Nigeria. Nigeria is currently the third world leading producer of palm which bears the nut and also accounts for over half of the palm produced in Africa. Palm kernel nut becomes an agro-waste when the oil is extracted. This study shows that PKNWA can comfortably replace cement by 10% and even produce a more durable binder than when cement is wholly used. The utilization of PKNWA in blended cement production will reduce the need for cement and prevent the ecological hazard resulting from the disposal of the waste palm nuts

Modified mix design development specification batched by volume from specified mix design by weight towards improved concrete production

Concrete production process is usually designed to meet certain fresh properties, target strength and durability requirement. This process is referred to as the mix design, which guides the quantity and proportions of the various constituent materials to produce the concrete. Concrete mix designs are usually done in accordance to specified standard procedures in codes developed by recognized institutions like the Building Research Establishments (BRE) [ 1 ]. Other acceptable mix design methods includes the three (3) equation and double coating methods in [ 2,3 ]. Standardized prescribed mix designs are generally accepted designs that meet strength requirements in normal strength concrete class as specified in [ 4,5 ]. Standardized Prescribed Concrete mixes have been designed and the characteristic strengths specified in the British standards [ 4,5 ] and the specified concrete mix design is recommended to be batched by weight. •Predominantly, mix designs are batched by volume within the study area and most developing countries which results to the production of less durable concrete than when batched by weight. This practice is due to the higher cost of acquiring the batching plants [ 6 ] employed in concrete production by medium to small scale construction firms. •This study developed a method of deriving a mix design to be batched by volume from the specified mix designed by weight using a design chat developed from [ 4,5 ]. Concrete can then be produced with the derived mixed design and batched by volume as though it was batched by weight from the specified mix design. This method eliminates the strength disparity by both batching methods and production of more durable concrete in most developing countries

Level statistics of XXZ spin chains with a random magnetic field

The level-spacing distribution of a spin 1/2 XXZ chain is numerically studied under random magnetic field. We show explicitly how the level statistics depends on the lattice size L, the anisotropy parameter $\Delta$, and the mean amplitude of the random magnetic field h. In the energy spectrum, quantum integrability competes with nonintegrability derived from the randomness, where the XXZ interaction is modified by the parameter $\Delta$. When $\Delta \ne 0$, the level-spacing distribution mostly shows Wigner-like behavior, while when $\Delta$=0, Poisson-like behavior appears although the system is nonintegrable due to randomness. Poisson-like behavior also appears for $\Delta \ne 0$ in the large h limit. Furthermore, the level-spacing distribution depends on the lattice size L, particularly when the random field is weak.Comment: 4 pages, 3 figures, to be published in Phys. Rev.

Level Statistics of XXZ Spin Chains with Discrete Symmetries: Analysis through Finite-size Effects

Level statistics is discussed for XXZ spin chains with discrete symmetries for some values of the next-nearest-neighbor (NNN) coupling parameter. We show how the level statistics of the finite-size systems depends on the NNN coupling and the XXZ anisotropy, which should reflect competition among quantum chaos, integrability and finite-size effects. Here discrete symmetries play a central role in our analysis. Evaluating the level-spacing distribution, the spectral rigidity and the number variance, we confirm the correspondence between non-integrability and Wigner behavior in the spectrum. We also show that non-Wigner behavior appears due to mixed symmetries and finite-size effects in some nonintegrable cases.Comment: 19 pages, 6 figure