Seismic performance evaluation of reinforced concrete bridge piers considering postearthquake capacity degradation

Bridges play a key role in the transportation sector while serving as lifelines for the economy and safety of communities. The need for resilient bridges is especially important following natural disasters, where they serve as evacuation, aid, and supply routes to an affected area. Much of the earthquake engineering community is interested in improving the resiliency of bridges, and many contributions to the field have been made in the past decades, where a shift towards performancebased design (PBD) practices is underway. While the Canadian Highway Bridge Design Code (CHBDC) has implemented PBD as a requirement for the seismic design of lifeline and major route bridges, the nature of PBD techniques translate to a design process that is not universally compatible for all scenarios and hazards. Therefore, there is great benefit to be realised in the development of PBD guidelines for mainshock-aftershock seismic sequences for scenarios in which the chance to assess and repair a bridge is not possible following a recent mainshock. This research analytically explored a parameterized set of 20 reinforced concrete bridge piers which share several geometrical and material properties with typical bridge bents that support many Canadian bridges. Of those piers, half are designed using current PBD guidelines provided in the 2019 edition of the CHBDC, whereas the remaining half are designed with insufficient transverse reinforcement commonly found in the bridges designed pre-2000. To support this study, a nonlinear fiber-based modelling approach with a proposed material strength degradation scheme is developed using the OpenSEES finite element analysis software. A multiple conditional mean spectra (CMS) approach is used to select a suite of 50 mainshock-aftershock ground motion records for the selected site in Vancouver, British Columbia, which consist of crustal, inslab, and interface earthquakes that commonly occur in areas near the Cascadia Subduction zone. Nonlinear time history analysis is performed for mainshock-only and mainshock-aftershock excitations, and static pushover analysis is also performed in lateral and axial directions for the intact columns, as well as in their respective post-MS and post-AS damaged states. Using the resulting data, a framework for post-earthquake seismic capacity estimation of the bridge piers is developed using machine learning regression methods, where several candidate models are tuned using an exhaustive grid search algorithm approach and k-fold crossvalidation. The tuned models are fitted and evaluated against a test set of data to determine a single best performing model using a multiple scorer performance index as the metric. The resulting performance index suggests that the decision tree model is the most suitable regressor for capacity estimation due to this model exhibiting the highest accuracy as well as lowest residual error. Moreover, this study also assessed the fragility of the bridge piers subjected to mainshock-only and mainshock-aftershock earthquakes. Probabilistic seismic demand models (PSDMs) are derived for the columns designed using current PBD guidelines (PBD-compliant) to evaluate whether the current PBD criteria is sufficient for resisting aftershock effects. Additional PSDMs are generated for the columns with inadequate transverse reinforcement (PBD-deficient) to assess aftershock vulnerability of older bridges. The developed fragility curves indicate an increased fragility of all bridge piers for all damage levels. The findings indicate that adequate aftershock performance is achieved for bridge piers designed to current (2019) CHBDC extensive damage level criteria. Furthermore, it is suggested that minimal damage performance criteria need to be developed for aftershock effects, and the repairable damage level be reintroduced for major route bridges

Characterization and design of non-adiabatic micro-compressor impeller and preliminary design of self-sustained micro engine system

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2005."February 2005."Includes bibliographical references (p. 96-99).As part of the MIT research program on micro-engines (of size [approximately] 1 cm), this thesis defines concepts and designs to improve micro-turbomachinery and overall system performance. Three-dimensional Reynolds-averaged Navier-Stokes computations (FLUENT) have been carried out to quantify the performance limiting processes in micro-impellers. These processes include (i) heat transfer to the compressor flow responsible for up to 25 points efficiency penalty, (ii) impeller casing drag (17 points penalty) and (iii) passage boundary layer loss (10 points penalty). The magnitude of the first effect is a result of the engine small length scale selection and is characterized by the total heat to impeller flow as fraction of inlet flow enthalpy. The magnitudes of the last two effects can be attributed to low Reynolds number. Scaling laws for elucidating the parametric controlling trend in these effects have been formulated. A mean-line analysis and design tool based on the above micro-impeller characterization is developed to formulate design guidelines. The guidelines show that the optimal micro-impeller geometry changes with impeller wall temperature, an effect, not present for large turbomachinery. In particular, impeller inlet angle, back-sweep angle, solidity and radial size for peak efficiency decrease with increasing impeller wall temperature. This behavior is a result of the competing effects of geometry on (i) aerodynamic loss and (ii) on heat transfer to impeller flow. In accord with these findings, CFD calculations show that configuring a micro-impeller excluding the heat addition as a design variable can incur a penalty of more than 10 efficiency points. An aero-thermal system model is developed to enable micro-engine system analysis and(cont.) selection of system design parameters. It is shown that, in contrast to large engine design, an optimal turbine inlet temperature, associated with peak system efficiency, exists for the micro-engine thermodynamic cycle. This condition is related to the competition between the benefit in cycle performance associated with increasing turbine inlet temperature, and the degradation in compressor performance associated with increasing heat transfer. Furthermore, system efficiency approximately doubles as turbomachinery size is scaled up two times. This is related to the different scaling of heat transfer, parasitic power loss, and Reynolds number in micro-engines. Minimum requirements on advanced technology levels are established for a self-sustaining micro-engine. Two designs, based on different advanced technologies, producing 10-20 Watts of net shaft power with chemical-to-shaft mechanical conversion efficiency of 1.5-2.0% are proposed for micro-engine development.by Borislav T. Sirakov.Ph.D

Effects of upstream unsteady flow conditions on rotor tip leakage flow

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2001.Includes bibliographical references (leaves 60-61).by Borislav Todorov Sirakov.S.M

Treatment options in late Parkinson's disease: decimeter wave therapy

Late stage Parkinson's disease (PD) is characterized by significant worsening of symptoms, motor fluctuations and decrease of effectiveness of drug therapy. Decimeter wave therapy (DWT) is one option to enlarge treatment strategy in late PD. We studied the effect of DWT in 12 patients (7 males), aged 65,83± 4,02 years, with 6,42± 1,51 years disease duration. Seven were at Hoehn-Yahr stage III and remaining 5 at stage IV. Mean UPDRS total score sum was 39,25± 1,91, and mean UPDRS part III sum was 24,67± 2,1. DMW was performed according to a standard protocol with apparatus Volna - 2, 10 consecutive procedures, once daily. Evaluation of UPDRS total and part III was performed on baseline, on days 11, 31 and 61. On day 11 all patients showed decrease in their both UPDRS total and part III. We lowered the levodopa doses of 6 patients in Hoehn-Yahr stage III with greatest decrease of UPDRS. On days 31 and 61 UPDRS total and part III were still lower. Our results demonstrate substantial effect of DWT on motor symptoms in late PD patients. All patients showed improvement, assessed by UPDRS, as the effect still lasted for 2 months after the physical therapy, even slightly diminished on day 61, compared to day 11. According to our results and patients subjective satisfaction reported, we could propose DWT become a part of the treatment strategy in late PD patients

Free thyroxine in needle washout after fine needle aspiration biopsy of toxic thyroid nodules

The main diagnostic tool for toxic adenomas (TA) is radionuclide imaging indicated in patients with evidence of thyroid nodules in combination with thyrotoxic syndrome. Thyroid ultrasound and fine-needle aspiration biopsy (FNAB) are widely used for the valuation of thyroid masses. There is no literature data concerning the utility of FNAB and related tests for the diagnosis of hyperfunctioning thyroid nodules. The purpose of this study is to determine the levels of free thyroxine (FT4) in the needle washout after FNAB of hot thyroid nodules. The results of our study show that the FT4 levels in needle washout from TA were significantly higher than the surrounding parenchyma and correlated with the hormonal changes in patients with thyroid hyperfunctioning nodules. Further studies on a large number of patients are needed to refine the diagnostic value of this method and evaluate its importance in quantitative risk assessment of thyroid autonomy.The main diagnostic tool for toxic adenomas (TA) is radionuclide imaging indicated in patients with evidence of thyroid nodules in combination with thyrotoxic syndrome. Thyroid ultrasound and fine-needle aspiration biopsy (FNAB) are widely used for the valuation of thyroid masses. There is no literature data concerning the utility of FNAB and related tests for the diagnosis of hyperfunctioning thyroid nodules. The purpose of this study is to determine the levels of free thyroxine (FT4) in the needle washout after FNAB of hot thyroid nodules. The results of our study show that the FT4 levels in needle washout from TA were significantly higher than the surrounding parenchyma and correlated with the hormonal changes in patients with thyroid hyperfunctioning nodules. Further studies on a large number of patients are needed to refine the diagnostic value of this method and evaluate its importance in quantitative risk assessment of thyroid autonomy

Theoretical and Experimental Study of a Thermo-Mechanical Model of a Shape Memory Alloy Actuator Considering Minor Hystereses

The paper presents a theoretical and experimental investigation of a thermo-mechanical model of an actuator composed of a shape memory alloy wire arranged in series with a bias spring. The developed mathematical model considers the dynamics of the actuator in the thermal and mechanical domains. The modelling accuracy is increased through the developed algorithm for modelling the minor and sub minor hystereses, thus removing the disadvantages of the classical model. The algorithm improves the accuracy, especially when using pulse-width modulation control, for which minor and sub minor hystereses are likely to occur. Experimental studies show that the system is very sensitive, and there are physical factors whose presence cannot be considered in the mathematical model. The experimental research has shown that setting constant values of the duty cycle is impossible to obtain a stable value of displacement and force. The comparison between the developed mathematical model results and the experimental results shows that the differences are acceptable. The improved modelling serves as a basis for designing such actuators and creating an improved automatic feedback control system to maintain a given displacement (force) or trajectory tracking

A CASE REPORT OF METASTATIC BREAST CANCER MANAGED WITH HORMONE THERAPY

Introduction: Breast cancer is the most frequently diagnosed life-threatening cancer in women worldwide and the leading cause of cancer death among women. The different forms of breast cancer require specific treatment plans. In the presented case endocrine therapy has a salutary effect on the patient with expressed hormone receptors.Materials and Methods: A 55-year-old postmenstrual woman  was diagnosed with highly differentiated multifocal invasive ductal carcinoma including perineural invasion and metastases in the lymph nodes, pT2N2aM0, G1 in 2010.The premenopausal patient then had undergone a radical surgical intervention-quadrantectomy and simple mastectomy of the left mammary gland. Adjuvant chemotherapy and hormone therapy with goserelin and tamoxifen consequently were necessary to block the actions of estrogen. In 2012, during a control checkup, liver metastases were discovered and therefore the patient was given first-line therapy with bevacizumab and capecitabine. Due to further growth of the liver metastases, a second-line therapy with docetaxel and carboplatin was appointed. As the development of the metastases could not be managed yet, an ultimate third-line antiestrogene and targeted therapy with everolimus and exemestane was required. The efficiency of the treatment, proceeding 4 years already, establishes a steady state disease on PET/CT.Result: Since the patient`s type of cancer was evaluated as estrogen receptor-positive, progesterone-positive and HER2-negative, with an immunohistochemical staining score of 1+, the most appropriate and up-to-date administration is the combination of the mTOR inhibitor-everolimus with aromatase inhibitor-exemestane. Blocking both pathways not only ameliorated the antitumor activity but also reversed endocrine therapy resistance to mTOR signaling.Conclusions: According to recent researches this composite therapy results in an improved clinical outcome as both life expectancy and quality of life are enhanced

RIPK3 expression as a potential predictive and prognostic marker in metastatic colon cancer

Background: Colorectal cancer is one of the primary causes of cancer-related deaths and 5-fluorouracil (5-FU) therapy remains the cornerstone of treatment in these patients. Resistance to 5-FU represents a major obstacle; therefore, finding new predictive and prognostic markers is crucial for improvement of patient outcomes. Recently a new type of programmed cell death was discovered—necroptosis, which depends on receptor interacting protein 3 (RIPK3). Preclinical data showed that necroptotic cell death is an important effector mechanism of 5-FU-mediated anticancer activity. Purpose: To investigate the predictive and prognostic performance of RIPK3 expression in primary tumors. Methods: Colon cancer patients (n=74) with metastatic stage were included in this retrospective study and all were treated with first-line 5-FU based chemotherapy. Immunohistochemical staining was performed. Results: The progression free survival for the low expression group of RIPK3 was 5.6 months (95% CI, 4.4-6.8) vs 8.4 months (95% CI, 6.4-10.3) of the group with high expression (p=0.02). Moreover, patients with high expression of RIPK3 were associated with lower risk of disease progression HR 0.61 (95% CI, 0.38-0.97; p=0.044). Patients with high expression levels of RIPK3 also had significantly longer mean overall survival (OS) of 29.3 months (95% CI, 20.8-37.8) as compared with those with low expression: 18.5 months (95% CI, 15.06-21.9) (p= 0.036). In addition, univariate analysis showed that high level of RIPK3 expression was associated with a longer OS HR 0.59 (95% CI, 0.35-0.98; p=0.044). Conclusions: This study suggests that expression of RIPK3 in primary tumors of metastatic colon cancer patients should be further investigated for its potential as a promising predictive and prognostic marker