Ratchet analysis of structures under a generalised cyclic load history

This paper introduces a new approach based upon the Linear Matching Method in order to obtain the ratchet limit of structures subjected to an arbitrary thermo-mechanical load history. This method varies from the traditional Linear Matching Method ratchet analysis, where the cyclic load history is decomposed into cyclic and constant components, instead calculating the ratchet limit with respect to a proportional cyclic load variation, as opposed to an additional constant load. The shakedown and limit load boundaries are initially obtained for the given structure, followed by the utilisation of a bisection procedure in order to calculate an approximate ratchet boundary based upon a predefined magnitude of ratchet strain per cycle. The method also yields the total and plastic strain ranges based upon perfect plasticity, for low-cycle fatigue post-processing considerations. The effects of analysing the ratcheting mechanism of structures undergoing a cyclic primary load that varies proportionally with a cyclic secondary load can be seen to lead to modified and less conservative ratchet boundaries compared to the traditional Bree solution in which the thermal ratcheting requirement (NB-3222.5) of ASME III is based upon. This paper introduces the theory, numerical implementation and verification of the proposed method via a series of example problems

Parametrically excited helicopter ground resonance dynamics with high blade asymmetries

The present work is aimed at verifying the influence of high asymmetries in the variation of in-plane lead-lag stiffness of one blade on the ground resonance phenomenon in helicopters. The periodical equations of motions are analyzed by using Floquet's Theory (FM) and the boundaries of instabilities predicted. The stability chart obtained as a function of asymmetry parameters and rotor speed reveals a complex evolution of critical zones and the existence of bifurcation points at low rotor speed values. Additionally, it is known that when treated as parametric excitations; periodic terms may cause parametric resonances in dynamic systems, some of which can become unstable. Therefore, the helicopter is later considered as a parametrically excited system and the equations are treated analytically by applying the Method of Multiple Scales (MMS). A stability analysis is used to verify the existence of unstable parametric resonances with first and second-order sets of equations. The results are compared and validated with those obtained by Floquet's Theory. Moreover, an explanation is given for the presence of unstable motion at low rotor speeds due to parametric instabilities of the second order

The Personality of Policy Preferences: Analyzing the Relationship between Myers-Briggs Personality Types and Political Views

For political scientists and politicians alike, much research has been devoted to understanding the American citizen. Comprehension is the key to capturing votes, pushing forward new ideas, and retaining support in the years to come. This project centers on the theory that people structure their political opinions around problem-solving tendencies that they apply to everyday situations and are particular to their personalities. To evaluate this idea, this study uses the Myers-Briggs Type Indicator (1962) in addition to several questions regarding personal policy preferences to determine whether there is a significant correlation between certain elements of one\u27s personality type and political ideas. Controlling for Intolerance of Ambiguity (Budner 1962), sociodemographic variables, and religiosity, it was found that an individual exhibits clear political preferences based on certain parts of personal characteristics. The results of this study imply a further fusion of psychology and politics for policymakers and voters

"The Love of America is on Move:" Victimization, Cold War Consensus, and the Hungarian Revolution, 1956-1957

On November 4, 1956, Soviet forces brutally suppressed the Hungarian Revolution in Budapest. Although Nikita Khrushchev had attempted to "repair" the Soviet Union's image by denouncing Stalin's crimes, the Soviet invasion of Hungary damaged the Soviet Union's legitimacy in the international community. This thesis examines the popular and religious press' coverage of the 1956 Hungarian Revolution. By publishing anticommunist editorials and letters to the editor, the popular press furthered the phenomenon known as Cold War Consensus. Historians have looked at Cold War Consensus as a conscious political project created by a number of individuals and institutions. This thesis emphasizes the role of the popular and religious press as agents in the solidification of the Cold War Consensus. Most notable was the popular and religious press' use of the victimization narrative. By portraying the Hungarian freedom fighters as victims of the Soviet system, the popular and religious press condemned the Soviet Union's actions while extolling "American values" such as democracy, freedom, and charity. The popular and religious press' treatment of Soviet brutality also built a sensationalized image of Hungarian refugees. The emphasis on Soviet savagery and narrative centered on incoming Hungarian refugees as heroes strengthened anticommunist rhetoric that was typical during the 1950s.Histor

Triage of women with equivocal or low-grade cervical cytology results: a meta-analysis of the HPV test positivity rate

Introduction Methods Results Discussion Conclusion Abstract Consistent evidence underlines the utility of human papillomavirus (HPV) DNA testing in the management of women with equivocal cervical cytological abnormalities, but not in case of low-grade lesions. We performed a meta-analysis including studies where the high-risk probe of the Hybrid Capture-II is used to triage these two cytological categories. The triage test-positivity rate reflects the colposcopy referral workload.Data were pooled on the HPV test positivity rate in women with atypical squamous cells of undetermined significance (ASCUS/ASC-US) or low-grade squamous intraepithelial lesions (LSIL), derived from different cytological classification systems. The meta-analysis was restricted to studies, published between 1991 and 2007. A random-effect model was applied for meta-analytical pooling and the influence of covariates on the HPV positivity rate was analyzed by meta-regression. The variation by age was assessed within individual studies since age strata were not defined uniformly. On an average, 43% (95% CI: 40-46%) of women with ASCUS/ASC-US were high-risk HPV positive (range 23-74%). In women with LSIL, the pooled positivity rate was 76% (95% CI: 71-81%; range 55-89%). In spite of considerable inter-study heterogeneity, the difference in HPV positivity between the two triage groups was large and highly significant: 32% (95% CI: 27-38%). HPV rates dropped tremendously as age and cutoffs of test positivity increased. Other factors (cytological classification system, country, continent, collection method and year of publication) had no statistically significant impact, except in LSIL triage where HPV positivity was significantly lower in European compared to American studies. Women with LSIL, especially younger women, have high HPV positivity rates suggesting limited utility of reflex HPV triaging these cases. Research is needed to identify more specific methods to triage women with low-grade squamous cervical lesions

Energy-Optimal Control of Underactuated Bipedal Locomotion Systems

The paper deals with modeling and design of energy-optimal motion of mechatronic system having less number of actuators than degrees of freedom. Such mechatronic system is termed underactuated. We consider an underactuated mechatronic system modeled a bipedal locomotion robot with 11 degrees of freedom. The system comprises nine links and is used to represent the bipeds planar dynamics in sagittal plane. The bodies are connected by friction-free hinge joints. Its assumed that the control inputs are torque actuators acting only at hip and knee joints. The ankle and the metatarsal joints of the feet are spanned with springs al-lowing discrete switching of their stiffness parameters in accordance to varying constraints imposed on the systems motion. The algorithm has been developed for synthesizing the energy-optimal anthropomorphic motion of the bipedal locomotion system with passively controlled feet and discrete switching of their joint stiffness parameters. Algorithm uses the smoothing cubic splines for approximation of variable functions, inverse dynamics approach, extern penalty functions method, and minimization of the nonsmooth objective function in orthogonal directions. The efficiency of the developed algorithm has been confirmed by simulation of human gait like motions for considered underactuated system. Applications of the results obtained can be found in robotics, bioengineering (prosthetics, orthotics), others

Calculation of dynamical characteristics of human gait with below-knee prosthesis

The mathematical modeling problem of human gait with below-knee prosthesis is investigated. The kinematic, dynamic and energetic characteristics of the gait are determined based on mathematical model of human locomotor apparatus and experimental data. The experimental data of joint angles in hip, knee and ankle and reaction forces are obtained by biomechanical investigation in a sequence consisting of nearly 20 steps. The sequence of N steps reduced to double stride period and mean square domains (\u1d700 -tubes) of variations of joint angles and reaction forces have been built. The stiffness characteristicsof ankle and metatarsal joints of the prosthesis device are also given from experimental investigation.The human gait with below-knee prosthesis modeling problem is formulated as a nonlinear optimal control problem with restrictions imposed both on the phase coordinates and controlling stimuli and non-differentiable energetic functional. The optimization approach based on energetic optimal principle of human locomotion is used forgait characteristics calculating

Energy-Optimal Control of Underactuated Bipedal Locomotion Systems

The paper deals with modeling and design of energy-optimal motion of mechatronic system having less number of actuators than degrees of freedom. Such mechatronic system is termed underactuated. We consider an underactuated mechatronic system modeled a bipedal locomotion robot with 11 degrees of freedom. The system comprises nine links and is used to represent the bipeds planar dynamics in sagittal plane. The bodies are connected by friction-free hinge joints. Its assumed that the control inputs are torque actuators acting only at hip and knee joints. The ankle and the metatarsal joints of the feet are spanned with springs al-lowing discrete switching of their stiffness parameters in accordance to varying constraints imposed on the systems motion. The algorithm has been developed for synthesizing the energy-optimal anthropomorphic motion of the bipedal locomotion system with passively controlled feet and discrete switching of their joint stiffness parameters. Algorithm uses the smoothing cubic splines for approximation of variable functions, inverse dynamics approach, extern penalty functions method, and minimization of the nonsmooth objective function in orthogonal directions. The efficiency of the developed algorithm has been confirmed by simulation of human gait like motions for considered underactuated system. Applications of the results obtained can be found in robotics, bioengineering (prosthetics, orthotics), others

Full Fluid Film Face Seals

SealsPg. 141-144The basic types of seal face lubrication are described and the basic design concepts and deflection analysis are discussed. Present field installations are presented, along with operating conditions and common problems experienced by power plant operators. A full fluid film seal is described along with the potential advantages these seals have for high energy pumps