1,979 research outputs found

    Vibration control of single floor seismically excited structure using active mass damper

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    The purpose of this paper is to dampen the vibrations using active mass damper (AMD) flexible structure has been tested using Shake Table by linear cart. The active and passive mass properties has been discussed. An observer based state-feedback card controller was used for one floor AMD using MATLAB/SIMULINK modelling. Several laboratory experimental setup using AMD, general system description, model, parameters, and comparison of data obtained by Pakistan earthquake occurred on Oct 8, 2005 has been discussed

    Seismic vulnerability assessment and evaluation of high rise buildings in Islamabad

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    Primarily the aim of this research is to carry out seismic evaluation study of buildings structures in Islamabad in order to propose basic guidelines and suggestions for Pakistan Code. Knowing the important nature of the subject, the earthquake based organizations are serious to compile a document for seismic threatened countries and areas. It is aimed that the document will work as a guideline source for the seismic evaluation, calculation and assessment of strength, behavior and expected performance and also the safety of already existing buildings. This study is based on review of already available documents on seismic vulnerability and evaluation of present buildings at different sites is carried out in order to know the key components of this very procedure so that it can be used in Pakistan and also in other developing countries as well. This would not only be robust, safe and reliable, but also can be convenient to use within the domain of available resources. ASCE 31-03 guidelines among the available documents are considered to be a suitable and the most reliable for to be in Pakistan

    Comparison between the visco-elastic dampers and magnetorheological dampers and study the effect of temperature on the damping properties

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    A number of studies have been carried out to investigate the performance of visco-elastic dampers (VEDs) and Magnetorheological dampers (MRDs) in controlling the seismic response of buildings but very few studies regarding the effect of temperature on the behavior of those dampers. As the energy absorption properties of the VEDs are dependent on the ambient temperature, excitation frequency and strain amplitude. Several mathematical models have been investigated for reproducing the experimental behavior of single degree of freedom VEDs and MEDs. Of these, only the fractional derivative model can reflect the influence of temperature which is, however, so complex that it is difficult to apply in structural analysis. In order to verify the effect of temperature we took two case studies of structural element been damped once using VED and once using MRD. Kelvin-Voigt mathematical model applied and after analyzing the results, the force vs. displacement showed that MRD achieved a high force capacity and better performance than VED. Furthermore, the effect of temperature in case of VED observed via plotting the dissipated energy hysteresis at different temperature. Those results validate the effect of temperature as the lower the temperature the more viscous the dashpot element becomes and hence improved damping, but this is up to a specific low temperature

    COVID-19 Case Complicated with Organizing Pneumonia and Pneumothorax: Correspondence

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    Frequency of Predisposing Factor of Nausea and Vomiting After Chest Surgery Under General Anaesthesia

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    Background: Postoperative nausea and vomiting are common and distressing postsurgical symptoms. These symptoms are of particular concern in outpatient surgery because they may require additional direct resources, such as supplies and antiemetic drugs, and may delay discharge. The objective of this study was to measure the frequency of factors which can cause nausea and vomiting under general anaesthesia after chest surgery. Methodology: This descriptive case series evaluated frequency of predisposing factor of nausea and vomiting in patients of anaesthesia department of Gulab Devi Hospital Lahore. Questionnaire is made and patients were asked about their age, fever, previous surgery, NPO status, smoking history and hospital stay. This study included 140 patients with post-operative nausea and vomiting. Results: In this study, 140 patients were taken in which  65 (46.43%) were female and 75 (53.57%) were male. In 140 patient 134 (95.7%) were NPO and 6 (4.3%) were not  NPO, 25 (17.9%) were obese and 115 (82.1%) were not obese, 88 (62.9%) patients were suffering fever and 52 (37.1%) were not suffering fever, 80 (57.1%) were infected and 59 (42.1%) were not infected, 53 (37.9%) patients had previous surgery and 87 (62.1%) had no previous surgery, 94 (67.1%) patients had received nitrous oxide and 46 (32.9%) didn\u27t, 97 (69.3%) received volatile gases and 43 (30.7%) not received, 29 (20.7%) received ketamine and 111 (79.3%) not received, 87 (62.1%) received suxamethonium and 53 (37.9%) not received, 119 (85.0%) received propofol and 21 (15.0%) not received, 110 (78.6%) received naluphine and 28 (20.0%) not received. Out of 140 patients, there were 122 (87.1%) who were suffering from pain and 18 (12.9%) were not. 91 (65.0%) patients had gastric distention and 49 (35.0%) patients didn\u27t. Opioids were given to 34 (24.3%) patients and not given to 106 (75.7%) patient. Conclusion: It is concluded that the nausea and vomiting after surgey under genral anesthesia is due to patient related factors in which most frequent is NPO. Drug related factors include propofol and nalbupin administration. Post operative factors include pain. In whole study of 140 patients, the  most frequent is patient related factor (NPO) other than drug related factors and post-operative factors

    COVID-19 Case Complicated with Organizing Pneumonia and Pneumothorax: A Case Report

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    Organizing pneumonia can be idiopathic or caused by multiple etiologies, including viral or bacterial pneumonia, drugs, and autoimmune disorders. It can rarely lead to cyst formation and pneumothorax with the exact mechanism remaining unclear. This case presents a previously healthy 50-year-old male who contracted COVID-19 with subsequent development of organizing pneumonia and pneumothorax. Patients presenting with hypoxic respiratory failure due to COVID-19 should be screened for organizing pneumonia upon discharge. This case also illustrates the importance of following such patients radiologically to monitor interstitial lung disease and consider pneumothorax for patients re-presenting with acute symptoms

    Output Tracking via Adaptive Backstepping Higher Order Integral Sliding Mode for Uncertain Nonlinear Systems

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    The authors propose a new tracking control design strategy for uncertain non-linear systems which are convertible to Semi-Strict Feedback Form (SSFF). The system in SSFF is first converted into new variables via existing adaptive backstepping control techniques. The control law is obtained by combining adaptive backstepping procedure and higher order integral sliding mode. The component of control law designed via backstepping is continuous which shows robustness against parametric uncertainties where as the discontinuous control component provides robustness against unmodeled dynamics and external disturbances. Since, this strategy relies on an integral manifold of the adaptively developed variables, therefore, the reaching phase is eliminated in this approach, which is an advantage in term of robustness. Furthermore, the parameters update law correctly provides the estimation of parameters which is again results in enhanced robustness of the strategy. The stability of proposed method is analysed theoretically and validated through a numerical example

    Achieving maternal and child health gains in Afghanistan: a Countdown to 2015 country case study

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    Background After the fall of the Taliban in 2001, Afghanistan experienced a tumultuous period of democracy overshadowed by confl ict, widespread insurgency, and an infl ow of development assistance. Although there have been several cross-sectional assessments of health gains over the last decade, there has been no systematic analysis of progress and factors infl uencing maternal and child health in Afghanistan. Methods We undertook a comprehensive, systematic assessment of reproductive, maternal, newborn, and child health in Afghanistan over the last decade. Given the paucity of high-quality data before 2001, we relied mainly on 11 nationally representative surveys conducted between 2003 and 2013. We estimated national and subnational time trends for key reproductive, maternal, and child health indicators, and used linear regression methods to determine predictors of change in health-care service use. All analyses were weighted for sampling and design eff ects. Additional information was collated and analysed about health system performance from third party surveys and about human resources from the Afghan Ministry of Public Health. Findings Between 2003 and 2015, Afghanistan experienced a 29% decline in mortality of children younger than 5 years. Although defi nite reductions in maternal mortality remain uncertain, concurrent improvements in essential maternal health interventions suggest parallel survival gains in mothers. In a little over a decade (2003–13 inclusive), coverage of several maternal care interventions increased—eg, for antenatal care (16% to 53%), skilled birth attendance (14% to 46%), and births in a health facility (13% to 39%). Childhood vaccination coverage rates for the basic vaccines from the Expanded Programme of Immunisation (eg, BCG, measles, diphtheria-tetanus-pertussis, and three doses of polio) doubled over this period (about 40% to about 80%). Between 2005 and 2013, the number of deployed facility and community-based health-care professionals also increased, including for nurses (738 to 5766), midwives (211 to 3333), general physicians (403 to 5990), and community health workers (2682 to 28 837). Multivariable analysis of factors contributing to overall changes in skilled birth attendance and facility births suggests independent contributions of maternal literacy, deployment of community midwives, and proximity to a facility. Interpretation Despite confl ict and poverty, Afghanistan has made reasonable progress in its reproductive, maternal, newborn, and child health indicators over the last decade based on contributions of factors within and outside the health sector. However, equitable access to health care remains a challenge and present delivery models have high transactional costs, aff ecting sustainability. To maintain and further accelerate health and development gains, future strategies in Afghanistan will need to focus on investments in improving social determinants of health and targeted cost-eff ective interventions to address major causes of maternal and newborn mortality

    Evidence for t\bar{t}\gamma Production and Measurement of \sigma_t\bar{t}\gamma / \sigma_t\bar{t}

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    Using data corresponding to 6.0/fb of ppbar collisions at sqrt(s) = 1.96 TeV collected by the CDF II detector, we present a cross section measurement of top-quark pair production with an additional radiated photon. The events are selected by looking for a lepton, a photon, significant transverse momentum imbalance, large total transverse energy, and three or more jets, with at least one identified as containing a b quark. The ttbar+photon sample requires the photon to have 10 GeV or more of transverse energy, and to be in the central region. Using an event selection optimized for the ttbar+photon candidate sample we measure the production cross section of, and the ratio of cross sections of the two samples. Control samples in the dilepton+photon and lepton+photon+\met, channels are constructed to aid in decay product identification and background measurements. We observe 30 ttbar+photon candidate events compared to the standard model expectation of 26.9 +/- 3.4 events. We measure the ttbar+photon cross section to be 0.18+0.08 pb, and the ratio of the cross section of ttbar+photon to ttbar to be 0.024 +/- 0.009. Assuming no ttbar+photon production, we observe a probability of 0.0015 of the background events alone producing 30 events or more, corresponding to 3.0 standard deviations.Comment: 9 pages, 3 figure
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