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Active magnetic bearing systems provide contact-free rotor levitation, which allows near frictionless rotation and high rotational speeds when they operate normally. Under certain operational conditions, a transient fault, overload condition, or disturbance may occur. Touchdown bearings or bushings are therefore implemented in such systems to prevent contact between rotor and stator laminations. If the rotor makes contact with a touchdown bearing, the rotor dynamics may become transient or persistent in contact. Appropriate control strategies through the magnetic bearings to restore contact-free rotor operation may extend the life of touchdown bearings, and minimise operational downtime. To achieve this, an understanding of the contact dynamics is required, together with the relationship between contact and magnetic bearing forces. In this paper, rotor/touchdown bearing contact conditions are investigated experimentally using an active magnetic bearing system with a flexible rotor. Design methodology is presented for a measurement system capable of providing rotor/touchdown bearing contact related data, based on strain measurement. Strain induced contact signals are calibrated against applied magnetic bearing forces. The frequency dependent behaviour of the active magnetic bearing system is considered using evaluated force and phase measurements. The measurement data represent system identification for the potential of active magnetic bearing force-based contact control.

Background. The coronavirus disease-19 (COVID-19) pandemic caused a major impact on blood donation process and supply globally. A lockdown management procedure was launched nationally in Saudi Arabia to manage this global health crisis. The main aim of this study was to determine the effect of COVID-19 lockdown on blood donation services and supply in different regions of Saudi Arabia. Study Design and Methods. A retrospective cross-sectional study was conducted in the blood bank centers of 5 major cities including Riyadh, Jeddah, Dammam, Hail, and Jizan in Saudi Arabia. Demographic and blood characteristics were retrieved from the first 6 months of 2019 (January–June) and compared to the same period of 2020. Results. Our findings showed variation in the characteristics of blood donation and supply among the centers surveyed, as some of these centers were adversely affected, while others showed an increase in the availability of blood products during the pandemic. For example, Jeddah’s center was significantly affected by COVID-19 lockdown whereas Hail’s center showed a significant increase in the analyzed characteristics of blood donation services in 2020 compared to 2019. Overall, there was no major difference among the surveyed centers between 2020 and 2019, and this might be due to the effective management of blood supply and transfusion. Discussion. Although blood supply and transfusion practice was slightly affected at various degree among the surveyed centers, the whole process did not show a significant effect on the overall outcome. This is in fact due to the proper preparedness, management of blood requirements and supplies, and efficient response of the surveyed centers in Saudi Arabia.

In the fifth generation of wireless communication systems (5G), the millimeter wave (mmWave) signal can be affected by many challenges in irregular environments such as dust and sand storms. In this paper, we investigate the attenuation that faces a mmWave link signal in a dusty environment for different sizes of dust particles. Further, we derive a model to calculate the total attenuation in mobile communication systems and/or internet of things (IoT) in different base stations highnesses. The obtained results show that in a dusty environment it is better to have high base station transmitters as the signal may escape the dense dust area. The paper also studies the case of the city of Mosul to find that not only the dry weather is increasing the attenuation, but wet weather also may impact more on the attenuation in the mmWave systems.

A smart, low-cost and efficient farming system is proposed in this work. Good farm resources management via recent technologies is pursued here in this proposed work such as effective water usage, decreasing human labor, and reducing efforts and errors due to human carelessness. This leads to improve the overall efficiency and work accuracy of the green farm. Smart farming could be realized using modern management technologies to increase the quantity and quality of the farm goods. New available technologies such as sensors for water and temperature could be used in this sort of works. In addition to the advanced microcontrollers that could give precise data management about the farm. Also, solar cells technologies for clean and saving used power in the green farm. This proposed smart, cheap, and accurate farming system could be a good solution for current agriculture challenges.

Background Studies have shown that poor shelter or dwelling conditions may lead to deteriorations in health. Those with asthma may be more susceptible to compromised living conditions and stress leading to a higher risk of asthma exacerbations. To describe the asthma control and quality of life of individuals with diagnosed asthma living in a shelter in Damascus, Syria and estimate the prevalence of respiratory symptoms in shelter dwellers without diagnosed asthma. Methods In this cross-sectional study, all individuals 5 years and older living in Al-Herjalleh shelter with diagnosed asthma were recruited to complete a questionnaire, which included items related to their respiratory symptoms, asthma exacerbations, exposure to asthma triggers, medication use, and health-related quality of life before and since entering the shelter. A representative sample of shelter dwellers without diagnosed asthma also completed a questionnaire to establish their demographics, respiratory symptoms, environment and chronic disease co-morbidities, in order to identify factors associated with under-diagnosed asthma. All participants underwent spirometry to measure their lung function. Descriptive statistics were calculated, and chi-square tests and Student's t-tests were used to compare individuals with asthma before and since entering the shelter, as well as to compare those with under-diagnosed asthma and individuals without asthma. Results The prevalence of asthma at the Al-Herjalleh shelter in those aged 5 years and older was approximately 8.5%. Nearly 70% of the asthma group felt their asthma had worsened since entering the shelter, and there was a significant drop in the proportion of individuals using inhaled corticosteroids (ICS), with only 4.3% using daily ICS in the shelter (P

Fawaz Y Azizieh,1 Diaa Shehab,2 Khaled Al Jarallah,2 Olusegun Mojiminiyi,3 Renu Gupta,4 Raj Raghupathy51Department of Mathematics and Natural Sciences, International Centre for Applied Mathematics and Computational Bioengineering, Gulf University for Science and Technology, Kuwait City, Kuwait; 2Department of Medicine, Faculty of Medicine, Kuwait University, Kuwait City, Kuwait; 3Department of Pathology, Faculty of Medicine, Kuwait University, Kuwait City, Kuwait; 4Department of Radiology, Faculty of Medicine, Kuwait University, Kuwait City, Kuwait; 5Department of Microbiology, Faculty of Medicine, Kuwait University, Kuwait City, KuwaitObjective: Inaddition to some well-characterized bone turnover markers (BTMs), cytokines and adipokines have also been suggested to be linked to osteoporosis seen in menopause. However, there is much controversy on the possible association between these markers and bone mineral density (BMD). This study was aimed at measuring circulatory levels of selected cytokines, adipokines and BTMs in postmenopausal women with normal and low BMD.Methods: The study population included 71 post-menopausal women, of whom 25 had normal BMD, 31 had osteopenia and 13 had osteoporosis. Circulatory levels of selected pro-resorptive (TNF-α, IL-1β, IL-6, IL-8, IL-12, IL-17), anti-resorptive (IFN-γ, IL-4, IL-10, IL-13, TGF-β) and five adipokine markers (adiponectin, adipsin, lipocalin-2/NGAL, PAI-1 and resistin) were measured using the Multiplex system and read on the Magpix ELISA platform. Further, two bone turnover markers (PINP, CTX) as well as estradiol levels were assayed from the same samples.Results: While circulatory levels of cytokines were comparable between groups, women with low BMD had statistically significantly higher median circulatory levels of adipokines as compared to those with normal BMD. Further, while levels of CTX were not different between the two groups; PINP, PINP/CTX ratio and estradiol levels were significantly lower in women with low BMD. Levels of adiponectin, PINP, PINP/CTX ratio and estradiol correlated significantly with BMD of the hip and spine.Conclusion: The associations between various markers and BMD are complex and multivariate. Our data provide insights into the possible use of circulatory levels of cytokines, adipokines and bone turnover markers on the pathogenesis of postmenopausal osteoporosis because of the well-documented effects of these molecules on bone tissue and their relevance to osteoporosis.Keywords: cytokines, adipokines, BTM, osteoporosis, menopause

paper, the parameters of the Random Access Channel (RACH) of LTE/ LTE-A based M2M communication under congestion situation are investigated. These parameters include the effect of the Backoff Indicator (BI), Hybrid Automatic Repeat-reQuest (HARQ) and contention resolution timer (CRT) on the Performance of LTE-based M2M Communication. The results indicate that the parameters of the RACH procedure have an impact on the network's performance, such as delay and packets dropped.

A rotor spinning within an active magnetic bearing (AMB) system will normally be levitated and hence operate without rotor-stator contact. External disturbances and inherent unbalance may be compensated with appropriate control to keep rotor deviations within the clearance gap. However, AMBs have limited dynamic load capacity due to magnetic material field saturation. Hence overload conditions may result in rotor-stator contact. A touchdown bearing (TDB) and rotor landing sleeve are usually included to protect the expensive rotor, magnetic bearing and sensor components from damage. Once rotor-TDB contact has been made, rotor dynamic conditions may ensue resulting in persistent rotor bouncing or rubbing limit cycle responses. Prolonged exposure to these severe dynamics will cause TDB degradation and require regular replacement. If possible, a clear aim should be to restore contact-free levitation through available control capability in an efficient manner. This paper is used to guide the control options that are available to restore contact-free levitation. The use of AMB control is appropriate if the required control forces are within saturation limits. It is also possible to actuate TDBs and destabilize persistent rotor dynamic contact conditions. For example, piezo-based actuation offers larger control forces than those from magnetic bearing systems. Hybrid control action involving both types of actuation system has the greatest potential for completely robust restoration of contact-free levitation.

Many applications of wireless sensor network such as smart metering, environment monitoring and health care [1] use a large number of sensor nodes, which generate a huge amount of traffic with the specification of the different QoS requirements. Broadband transmission can be achieved through the mobile systems. Long Term Evolution (LTE) is the main efficient broadband technology in current mobile communications. Introducing Wireless sensor networks into the Long Term Evolution (LTE) networks, can be achieved successfully but with some challenges, such as the traffic overload due to a large number of sensor nodes. Traffic scheduling plays an important role in LTE technology; this can be achieved by assigning the shared resources among users in an efficient and optimized manner. This paper discusses the effect of many types of scheduling algorithms on the downlink performance, this can be done in terms of throughput, block error rate (BLER) and fairness measurements using a MATLAB-based system level Simulator is provide which from Vienna University under License Agreement for ”Academic Usage” [8]. An effective radio scheduler to optimize the distribution of radio resources among the sensor nodes is also studied. The guaranteed QoS user demands can be considered as a great challenge in the current field of research. General Terms Computer Network, Wireless Networks, Modeling, Scheduling, Algorithms.

Fault tolerance is achieved through hardware redundancy in repeated hardware elements to provide protection against localised damage in safety-critical systems. Examples of such systems include aircraft, space vehicles, nuclear power plants and plants handling dangerous chemicals. One method in achieving fault detection and fault isolation is through hardware cross monitoring, where the performance of the repeated components is continuously assessed and compared. This technique is simple to apply and is widely used. The drawbacks include the extra hardware cost and the additional space required to accommodate the duplicated equipment. In this chapter, this technique will be presented to calculate the threshold values on a multi-lane actuator in torque and velocity summed architectures. The brushless dc motors in both architectures will be represented by their lumped models. The FDI system (discussed in Chapter 5) will be implemented to monitor the actuator for failures in feedback transducers as well as the currents in each lane.

One of the main advantages of new wireless systems is the freedom to make and receive calls anywhere and at any time; handoffs are considered a key element for providing this mobility. This paper presents the handoff queuing problem in cellular networks. The queuing priority is employed to enhance the performance of the system in terms of reduced blocking probability of handoff calls and original calls. It proposes a model to study handoff queuing schemes, and provides a performance evaluation of these schemes. The paper begins by a presentation of the different handoff strategies and prioritization queuing scheme to evaluate, then gives an evaluation model with the different assumption considered in the simulations. The evaluation concerns the blocking probability for handoff and original calls with queue size for each other. These simulations are conducted for each scheme, according to different offered loads, size of call (original and handoff) queue, and number of voice channels. A model is proposed and introduced in this paper for the study of channel assignment schemes; the non-prioritized schemes, the original call queuing schemes, and the handoff call queuing schemes. Finally a comparison among these schemes is presented and observed that the blocking probability of handoff calls is affected visibly by original calls queue size.

The term fading, in the context of mobile communications, refers to the interference caused by the reception of numerous scattered copies of a given signal at an antenna. Fading can produce significant random variations of signal power — in the scale of 10s of dBs over fractions of a wavelength- and hence, can be extremely destructive to the signal. Therefore, in order to achieve reliable mobile communications, provisions must be considered to counter the effects of fading. Indeed, a first step towards this end is to understand these effects through producing models of and simulating this phenomenon. An approximation method is applied to simulate a mobile radio fading channel using Matlab and LabVIEW environment, based on a somewhat simplified mathematical model. Clearly the simplified model might not present a very realistic view of the highly complex and random nature of fading; nevertheless, this simulation serves as an extremely useful research tool for comparing and measuring the effectiveness of different communication techniques.