Cavitation effects on the pressure distribution of a squeeze film damper bearing

High speed motion pictures have revealed several operating regimes in a squeeze film damper. Pressure measurements corresponding to these distinct regimes were made to examine their effect on the performance of such dampers. Visual observation also revealed the means by which the pressure in the feed groove showed higher amplitudes than the theory predicts. Comparison between vapor and gaseous cavitation are made based on their characteristic pressure wave, and the effect this has on the total force and its phase

A performance based design approach for tall buildings under wind loading

The wind design of buildings is typically based on strength provisions under ultimate loads. This is unlike the ductility-based approach used in seismic design, which allows inelastic actions to take place in the structure under extreme seismic events. This research investigates the application of a similar concept in wind engineering. In seismic design, the elastic forces resulting from an extreme event of high return period are reduced by a load reduction factor. A load reduction factor is chosen by the designer and accordingly a certain ductility capacity needs to be achieved in the structure. Two reasons have triggered the investigation of this ductility-based concept under wind loads. First, there is a trend in the design codes to increase the return period used in wind design approaching the large return period used in seismic design. Second, the structure always possesses a certain level of ductility that the wind design does not benefit from. The load reduction factor that could be applied in wind design might not be as high as its counterpart in seismic design, and it should be applied only on the resonant component of the wind loading. Many technical issues arise when applying a ductility-based approach under wind loads. The use of reduced design loads will lead to the design of a more flexible structure with larger natural periods. While this might be beneficial for seismic response, it is not necessarily the case for the wind response, where increasing the flexibility is expected to increase the fluctuating response. This particular issue is examined by considering a case study of a sixty five-story high-rise building previously tested at the Wind Tunnel Laboratory at the University of Western Ontario using a pressure model. A three-dimensional finite element model is developed for the building. The wind pressure from the tested rigid model are applied to the finite element model and a time history dynamic analysis is conducted. The time history variation of the straining actions on various structure elements of the building are evaluated and decomposed into mean, background and fluctuating components. A reduction factor is applied to the fluctuating components and a modified time history response of the straining actions is calculated. The building components are redesigned under this set of reduced straining actions and its fundamental period is then evaluated. A new set of loads is calculated based on the modified period and is compared to the set of loads associated with the original structure. This is followed by non-linear static pushover analysis conducted individually on each shear wall module after redesigned these walls. Displacement-controlled pushover analysis is carried out to assess the ductility demand of shear walls with reduced cross sections to justify the application of the load reduction factor “R”. Furthermore, a parametric study is conduced to evaluate the effect of ductility level on target performance level reached in each shear wall

Fluid Film Bearing Fundamentals And Failure Analysis.

Tutorialpg. 161-186Fluid film bearing technology is presented in this tutorial as it applies to turbomachinery equipment. The focus here is on the practical aspects of fluid film journal bearings, as opposed to theoretical analysis. Failure modes and the mechanisms leading to these failures will be discussed, along with techniques used to identify and cure them. The influence of different bearing configurations on the dynamics of rotor bearing systems will also be discussed

Resilience as a communal concept: Understanding adolescent resilience in the context of the Syrian refugee crisis in Bar Elias, Lebanon

Background: The conflict in Syria has led to the displacement of 1.5 million refugees into the neighboring country of Lebanon, with a majority that have yet to return to their homeland. Syrian adolescents in the town of Bar Elias in the Bekaa Valley, Lebanon have lived and grown in the face of resource-limited environments, restricted movement, and a longing for return. Resilience is manifested in the adaptation to such circumstances through close supportive relationships, social engagement, employment, and religion. There is a communal aspect to resilience that is important to the adolescent refugee experience and to the efforts supporting these communities. / Methods: Fifteen one-to-one interviews and two focus groups, with a total of eighteen Syrian adolescents, were analyzed using an inductive thematic analysis informed by grounded theory principles. Participants were recruited through partnering non-governmental organizations (NGOs) in the area, and ethical approval was granted through UCL and the American University in Beirut (AUB). / Results: Syrian adolescents highlighted supportive relationships, communal activities and spaces, memories of home, employment, and shared environments as integral elements to their personal adaptation. Methods of resilience involved social cohesion and establishing stability for one's family and close community. Adaptation to the present is intertwined with facing the consequences of displacement in this new context and maintaining aspirations for a bright future. Engaging with the environments they share and help create is an important facet of resilience and occurs through group gatherings , hobbies, and online communication. Additionally, inner strength can be derived from religious activities and empowers individual processing. / Conclusion: This study illuminates the elements and mechanisms embodied in these adolescents’ communities and relationships that allow for adaptation to life in Bar Elias. These factors strengthen their approach to overcome social barriers and practice resilience. These communal aspects of the adolescents’ lives also connect to their memories of home, current environment, and future aspirations

Classifying Cognitive Profiles Using Machine Learning with Privileged Information in Mild Cognitive Impairment

Early diagnosis of dementia is critical for assessing disease progression and potential treatment. State-or-the-art machine learning techniques have been increasingly employed to take on this diagnostic task. In this study, we employed Generalized Matrix Learning Vector Quantization (GMLVQ) classifiers to discriminate patients with Mild Cognitive Impairment (MCI) from healthy controls based on their cognitive skills. Further, we adopted a "Learning with privileged information" approach to combine cognitive and fMRI data for the classification task. The resulting classifier operates solely on the cognitive data while it incorporates the fMRI data as privileged information (PI) during training. This novel classifier is of practical use as the collection of brain imaging data is not always possible with patients and older participants. MCI patients and healthy age-matched controls were trained to extract structure from temporal sequences. We ask whether machine learning classifiers can be used to discriminate patients from controls and whether differences between these groups relate to individual cognitive profiles. To this end, we tested participants in four cognitive tasks: working memory, cognitive inhibition, divided attention, and selective attention. We also collected fMRI data before and after training on a probabilistic sequence learning task and extracted fMRI responses and connectivity as features for machine learning classifiers. Our results show that the PI guided GMLVQ classifiers outperform the baseline classifier that only used the cognitive data. In addition, we found that for the baseline classifier, divided attention is the only relevant cognitive feature. When PI was incorporated, divided attention remained the most relevant feature while cognitive inhibition became also relevant for the task. Interestingly, this analysis for the fMRI GMLVQ classifier suggests that (1) when overall fMRI signal is used as inputs to the classifier, the post-training session is most relevant; and (2) when the graph feature reflecting underlying spatiotemporal fMRI pattern is used, the pre-training session is most relevant. Taken together these results suggest that brain connectivity before training and overall fMRI signal after training are both diagnostic of cognitive skills in MCI.PT and YS were supported by EPSRC grant no EP/L000296/1 “Personalized Medicine through Learning in the Model Space.” This work was supported by grants to ZK from the Biotechnology and Biological Sciences Research Council (H012508), the Leverhulme Trust (RF-2011-378), and the (European Community's) Seventh Framework Programme (FP7/2007-2013) under agreement PITN-GA-2011-290011

Vibration And Eccentricity Measurements Combined With Rotordynamic Analyses On A Six Bearing Turbine Generator.

LecturePg. 85-92This lecture discusses how the vibration characteristics and eccentricity measurements were combined with rotordynamic analyses to help improve the reliability of a turbine generator unit. It also explains certain vibration characteristics at partial load conditions that resulted in changes of the bearing load magnitude and direction. The measurements of a stable backward whirl orbit at certain load conditions will be shown and discussed. The rotordynamic analyses also simulated field balancing measurements that compared well with the synchronous response calculations. These analyses were also used to examine the benefits of retrofitting a steady bearing at the unsupported shaft pump extension

Application Of High Speed And High Performance Fluid Film Bearings In Rotating Machinery.

Tutorialpg. 209-234Some of the critical parameters in the design and application of high performance fluid film bearings are emphasized. The limitations and problems associated with high speed and highly loaded bearings will be discussed. Examples of bearing failures, the symptoms associated with these failures, and their impact on the machine performance will be shown. Some of the common failure mechanisms will also be described with suggestions on how to eliminate the failures or reduce their consequences by changes to some of the bearing design features. New developments in bearing technology and testing specifically designed to address some of these limitations will be demonstrated. Case studies and analysis will be used in many common and newly developed turbomachinery equipment to help illustrate some of the key attributes in the design and application of high performance fluid film bearings and squeeze film dampers

Nanoparticles for intestinal sepsis prevention synthesized via inverse miniemulsion polymerization

Previous research has shown that phosphate becomes depleted in the intestinal mucosa following local surgical injury or disease, triggering bacterial virulence and sepsis. Consequently, replenishment of depleted phosphate levels has been shown to prevent bacterial virulence in vitro[3] and sepsis in vivo[1]. Inverse phase miniemulsion polymerization (IPMP) has been extensively used in recent years in the production of nanocapsules for drug delivery of water-soluble therapeutic compounds that can be rendered degradable with time while allowing for sustained release of the encapsulated agent. In previous work we have successfully encapsulated inorganic phosphate salts, such as potassium monophosphate[2], into nanoparticles formed using IPMP. Our in vitro studies, however, have shown that polyphosphate salts, specifically sodium hexametaphosphate (PPi), are more effective at suppressing bacterial virulence[3]. This study focuses on the production and encapsulation of sodium hexametaphosphate into nanoparticles for controlled and extended release. Previous studies demonstrated[3] that encapsulation of sodium hexametaphosphate presents a series of challenges affecting the reproducibility of the IPMP process. Sodium hexametaphosphate is a strong lipophobe whose presence induces a high degree of order for water molecules. This modification in water structure weakens the surfactant interaction with water molecules, actively affecting the stability of the emulsion. This process, known as “salting-out”, has been shown to shift the hydrophilic-lipophilic balance (HLB) of nonionic surfactants towards a more lipophilic value[4]. While this issue has been addressed in a variety of previous studies, no mathematical correlation currently exists describing the effect of salt concentration on the HLB of a specific surfactant. Since miniemulsions require combinations of different phase-soluble surfactants, this adds to the complexity in predicting the extent and strength of the electrolyte effect on the stability of the emulsion system. In this study, we adjusted the IPMP process to counter the unstabilizing force created by the presence of sodium hexametaphosphate in the aqueous phase of the system. A precursor solution containing PEG diacrylate (PEGDA) macromer and NVP comonomer were chosen to create the hydrogel matrix, due to its biocompatibility and the ability to control the crosslinking density. The emulsion was formed of water in cyclohexane with the help of two nonionic surfactants, Tween 20 and SPAN 80. The effect of variations in HLB ranging from 4.0 to 9.5 on emulsion droplet size was investigated, for which the optimum overall HLB occurred at 6.5, an increase of two HLB points over the theoretical required value without salt interference[2, 3]. The effects of total surfactant amounts, reaction time, temperature and initiator concentration on nanoparticle yield were also explored. A final emulsion with 3.2% w/v of surfactants, 2 hours of reaction time, 64ºC and an initiator concentration equal to 1% of the initial double concentration resulted in a maximum nanoparticle mass yield of ~39%. Finally, the particles were characterized in terms of crosslink density, showing an efficient encapsulation of the studied salt and a promising path for in-vivo testing. This study helped us develop a reproduceable formulation of an IPMP process that yields stable nanoparticles with suitable therapeutic levels of phosphates. [1] Hyoju, S.K. et al, “Oral Polyphosphate Suppresses Bacterial Collagenase Production and Prevents Anastomotic Leak Due to Serratia marcescens and Pseudomonas aeruginosa”, Annals of Surgery, Feb, 2017. [2]Vadlamudi, S. et al., “Inverse miniemulsion polymerization of phosphate-loaded hydrogel nanoparticles for sepsis prevention”, Unpublished master dissertation, Illinois Institute of Technology, Chicago, Illinois (2014) [3] Yin Y et al, “De Novo Synthesis and Functional Analysis of Polyphosphate-Loaded Poly(Ethylene) Glycol Hydrogel Nanoparticles Targeting Pyocyanin and Pyoverdin Production in Pseudomonas aeruginosa as a Model Intestinal Pathogen”. Annals of Biomedical Engineering. 45(4):1058-1068, 2017. [4] Shinoda, K., & Takeda, H. “The effect of added salts in water on the hydrophile-lipophile balance of nonionic surfactants: The effect of added salts on the phase inversion temperature of emulsions”. Journal of Colloid And Interface Science, 32(4), 642–646, 1970