Design and Optimization of Dynamic System for a One-kW Free Piston Linear Engine Alternator-GENSETS Program

In power/energy systems, free-piston linear machines are referred to as a mechanism where the constrained crank motion is eliminated and replaced with free reciprocating piston motion. Depending on the application, the piston motion can be converted into other types of energy and includes compressed air/fluid, electricity, and high temperature/pressure gas. A research group at West Virginia University developed a free-piston linear engine alternator (LEA) in 1998 and have achieved significant accomplishment in the performance enhancement of the LEAs to date. The present LEA design incorporates flexure springs as energy restoration components and as bearing supports. The advantages of using flexure springs are threefold and include: (1) it increases the LEA’s stiffness and resonant frequency, and hence the power density; (2) it eliminates the need for rotary or linear bearings and lubrication system; and (3) it reduces the overall frictional contact area in the translator assembly which improves the durability. The current research focuses on the design and optimization of the flexure springs as the system’s resonant dominating component for a 1 kW free-piston LEA. First, the flexure springs were characterized according to the LEA’s target outputs and dimensional limitations. The finite element method (FEM) was used to analyze the stress/strain, different modes of deformation, and fatigue life of a range of flexure spring designs under dynamic loadings. Primary geometric design variables included the number of arms, inside and outside diameter, thickness, and arm’s length. To find the near-optimum designs, a machine learning algorithm incorporating the FEM results was used in order to find the sensitivity of the target outputs to the geometrical parameters. From the results, design charts were extracted as a guideline to flexure spring selection for a range of operations. Then, methods were introduced, investigated, and analyzed to improve the overall energy conversion performance and service life of the flexure springs and the overall LEA system. These included: a transient FE tool used for fatigue analysis to quantify the life and factors of safety of the flexure springs as well as the spring’s hysteresis; a fluid/structure interaction model used to quantify the energy loss due to drag force applied on the flexures’ side surfaces; packaging of multiple flexures to increase the overall stiffness and to reduce the vibration-induced stresses on flexure arms due to higher harmonics; a model to investigate the two-way interactions of the flexures’ dynamics with the alternator and engine components to find an optimum selection of the LEA’s assembly; a non-linear friction analysis to identify/quantify the energy losses due to the friction of the sliding surfaces of the flexures and spacers; and a series of static and transient experiment to determine the non-linearity of flexures’ stiffness and comparison to FEM results and for validation of the energy audit results from numerical and analytical calculations. With over 6000 flexure designs evaluated using artificial intelligent methods, the maximum achievable resonant frequency of a single flexure spring for a 1 kW LEA was found to be around 150 Hz. From the FEM results, it was found that under dynamic conditions the stress levels to be as high as twice the maximum stress under static (or very low speed) conditions. Modifications of the arm’s end shape and implementation of a shape factor were found as effective methods to reduce the maximum stress by 20%. The modal analysis showed that the most damaging modes of deformations of a flexure spring were the second to fourth modes, depending on the number of arms and symmetry of the design. Experiment and FEM results showed that using bolted packaging of the springs can damp a portion of the vibration and improve the performance. The drag force loss was found to account for 10-15% of the mechanical losses in a 100 Wnet LEA prototype. From the manufacturing perspective, use of water jet was found the most economical method for manufacturing the flexures which could make the commercial production of the LEAs feasible; however, for high-efficiency, high-durability machines, additional material treatments, and alternative manufacturing methods are essential

Fabrication and Model Based Position Estimation of Novel Laser Processed Shape Memory Alloy Actuator with an Embedded Strain Gauge Sensor

Shape Memory Alloys have sparked great amount of interest in the eld of actuation over the past decades. Until now, sensorless position estimation of SMA actuators under dynamic unknown applied stresses has not been feasible due to the complexity of the system and the number of unknown parameters which the proposed extra information obtained from the embedded sensor solves. In this thesis, a novel laser processed NiTi Shape Memory Alloy (SMA) actuator is proposed containing two di erent material compositions in one monolithic piece of actuator wire. Each of these compositions behaves di erently at room temperature, one exhibits a shape memory e ect (SME) for actuation, and the other is pseudo-elastic (PE) which is used to enable an embedded sensor. Fabrication of the wire included laser processing, heat-treatment, and cold-working procedures. The actuator wire was subsequently trained to stabilize its properties using iso-stress thermal cycling. Additionally, a novel model-based sensorless position estimation algorithm is presented. Proposed model can estimate the position of the actuator under varying applied stresses with an approximate accuracy of 95% only using dual resistance measurements across the two di erent material compositions. The proposed actuator has signi cant application in robotics, wearables, haptics, automotive, and any other application which the mechanical load is not known in advance. Two simple position and force controller schemes using the proposed dual-resistance measurement position (and force) estimation are discussed and the control results presented. The proposed position estimation algorithm is used for the feedback-signal of a simple PID position and force controller scheme. Moreover, another novel sensorless position estimation of SMA actuator wires are presented using the power measurement of the standing wave cause by the re ection of a high-frequency signal at an un-terminated end

Effect of Drying Conditions on the Catalytic Performance, Structure, and Reaction Rates over the Fe-Co-Mn/MgO Catalyst for Production of Light Olefins

The MgO-supported Fe-Co-Mn catalysts, prepared using co-precipitation procedure, were tested for production of light olefins via CO hydrogenation reaction. The effect of a range of drying conditions including drying temperature and drying time on the structure and catalytic performance of Fe-Co-Mn/MgO catalyst for Fischer-Tropsch synthesis was investigated in a fixed bed micro-reactor under the same operational conditions of T = 350 °C, P = 1 bar, H2/CO = 2/1, and GHSV = 4500 h-1. It was found that the catalyst dried at 120 °C for 16 h has shown the best catalytic performance for CO hydrogenation. Furthermore, the effect of drying conditions on different surface reaction rates was also investigated and it was found that the precursors drying conditions influenced the rates of different surface reactions. Characterization of catalyst precursors and calcined samples (fresh and used) was carried out using powder X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Brunauer-Emmett-Teller (BET) measurements, Temperature Programmed Reduction (TPR), Thermal Gravimetric Analysis (TGA), and Differential Scanning Calorimetry (DSC). Characterization results showed that different investigated variables (drying conditions) influenced the structure, morphology and catalytic performance of the ternary catalysts.

Assessing Attitudes of Medical Students towards First Contact with Patient in Tehran (2016-17)

Background: Early experience of clinical arena as first situations can be effective in selection or refusing medicine as profession is so important that programmers and administrators should consider these settings as one of the most elements in educational programs.Materials and Methods: This study was a cross-sectional study and including presently studying students in medicine field of medical sciences universities. Sample size was estimated for 275 students. Participants were selected from schools of medicine: Iran University (IUMS), Shahid Beheshti University, and Islamic Azad University using stratified random sampling method. Data was collected in March of 2016 by a researcher made questionnaire determined its validity and reliability. Data was analyzed using chi-squared test, t-test, Mann-Whitney and Kruskal-Wallis test.Results: Mean score of medical students’ attitude from 15 five-degree scale questions was 51.22 ± 6.32. The mean scores of attitude in men and women were 51.37±6.16 and 51.06±6.53, respectively (p=0.687). Overall, 13.8 % of students had positive attitude towards first contact with patient, 10.5 % of students had negative attitude and 75.6 % had no opinion. The mean scores of attitude towards first contact with patient in Iran university, Shahid Beheshti university and Islamic Azad university were 50.40±5.00, 52.71±5.91 and 46.12±5.97, respectively (p<0.001). The mean scores of attitude towards first contact with patient in reformed educational system and old educational system were 52.35±5.83 and 46.12±5.97 respectively, with a significant difference between two types of educational system (p<0.001).Conclusion: As respects more positive attitude of students in reformed educational system in comparison with old educational system, special attention to courses of early contact with patient may contribute to decreasing educational insufficiency and distance between theory and practice and lead to the satisfaction all of beneficiaries

Favorable association between Mediterranean diet (MeD) and DASH with NAFLD among Iranian adults of the Amol Cohort Study (AmolCS)

Nonalcoholic fatty liver disease (NAFLD) is an emerging cause of chronic liver diseases and a major health problem worldwide. Dietary patterns may play a critical role in controlling and preventing this disease, but the available evidence is scarce. The current study aims to ascertain the association of adherence to the Dietary Approach to Stop Hypertension (DASH) diet and Mediterranean diet (MeD) with nonalcoholic fatty liver disease (NAFLD) among Iranian adults of the Amol Cohort Study (AmolCS). In a cross-sectional analysis among 3220 adults (55.3% men), age ≥ 18 years (46.96 ± 14.67), we measured usual dietary intake with a validated food frequency questionnaire (FFQ) and then calculated dietary pattern scores for DASH and MeD. Sociodemographic and lifestyle factors were collected by a structured questionnaire. The presence and degree of NAFLD were also determined by abdominal sonography. Multiple regression models were used to estimate NAFLD odds across tertiles of DASH and Mediterranean dietary scores. Dietary DASH and Mediterranean components were adjusted for total energy intake, based on the residual methods. After adjusting for multiple potential confounders, we found an inverse association of DASH and MeD with NAFLD (Ptrend = 0.02, and Ptrend = 0.002, respectively). Those in the highest tertiles of adherence to the DASH and MeD had the lowest risk for NAFLD (OR = 0.80, 95%CI = 0.66–0.96, OR = 0.64, 95%CI = 0.52–0.78, respectively). The results of logistic analysis of MeD, stratified by gender and abdominal obesity, revealed the favorable association was more pronounced in women (OR = 0.42, 95%CI = 0.29–0.61, Ptrend = 0.004), and in participants with or without abdominal obesity (OR = 0.62, 95% CI = 0.47–0.81, Ptrend = 0.03, OR = 0.64, 95%CI = 0.475–0.91, Ptrend = 0.04, respectively). Similar results were obtained for the adherence to DASH diet score with the prevalence of NAFLD patients with abdominal obesity (OR = 0.75, 95% CI = 0.57–0.97, Ptrend = 0.04). The findings suggested the favorable association between DASH and MeD with NAFLD in Iranian adults, especially women and subjects with or without abdominal obesity. Further prospective investigations are needed to confirm the integrity of our findings

Non-alcoholic fatty liver disease is not independent risk factor for cardiovascular disease event : a cohort study

There are no consistent results between previous studies for an independent association between non-alcoholic fatty liver disease (NAFLD) and cardiovascular disease (CVD) events. To determine if there is an independent association between NAFLD and CVD events. In the present study, valid outcome data of 4808 subjects were available for phase 2 of our cohort study. These subjects had been followed up for seven years from phase 1, beginning in 2009-2010 to phase 2 during 2016-2017. Simple and multiple Cox proportional models were used to determine the association between NAFLD in the primary phase of the cohort and subsequent fatal and non-fatal CVD events during follow-up. The incidence of non-fatal CVD events in males with NAFLD was significantly higher ( = 0.004) than in males without NAFLD. A positive association was demonstrated between NAFLD and non-fatal CVD events in males (Hazard ratio = 1.606; 95%CI: 1.166-2.212; = 0.004) by the simple Cox proportional hazard model, but no independent association was detected between these in the multiple Cox models. No independent association was detected between NAFLD and CVD. It is likely that diabetes mellitus and age may be the principle mediators in this regard. [Abstract copyright: ©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.

A population based study on hepatitis B virus in Northern Iran, Amol.

BACKGROUND: Viral hepatitis is a major health problem worldwide. Change in transmission patterns of hepatitis B makes it necessary to re-evaluate its prevalence and risk factors. OBJECTIVES: We aimed to determine the prevalence of HBV infection and its related risk factors in Amol city, Northern Iran. PATIENTS AND METHODS: As a population based study, a cluster sampling approach was used and 6146 individuals from the general population of urban and rural areas of Amol, Iran, from both genders and different ages were enrolled. Inclusion criteria were willingness to participate in the study, being a lifelong resident in Amol city or its surrounding areas with Iranian nationality. Ten milliliters (10 mL) of blood was taken from each study subject and checked regarding hepatitis B markers including HbsAg, HBsAb and HBcAb using a third generation ELISA. The prevalence of HBV infections and its potential risk factors were recorded. RESULTS: The prevalence of HBsAg, HBsAb and HBcAb were estimated as 0.9%, 30.7% and 10.5%, respectively. The mean age of all participants was 43.9 (95% CI: 43.4, 44.3) in females and 55.6 in (n = 3472) males. In our study, there was a significant association between family history of hepatitis, rural residency and presence of HBsAg. There was also a positive correlation between HBcAb and family history of hepatitis, history of other types of hepatic diseases, history of tattooing, traditional phlebotomy, male gender and age. In backward logistic regression, a significant association was found between history of hepatitis in first-degree family members (OR = 13.35; 95% CI: 6.26, 28.47) and place of residence (OR = 2.32; 95% CI: 1.27, 4.22) with presence of HBsAg. There was also a positive correlation between history of hepatitis among first-degree family members (OR = 2.49; 95% CI: 1.52, 4.08), history of tattooing (OR = 2.13; 95% CI: 1.33, 3.42), history of previous hepatitis (OR = 1.87; 95% CI: 1.06, 3.28), male sex (OR = 1.36; 95% CI: 1.12, 1.66) and age (OR = 1.03; 95% CI: 1.03, 1.04) with presence of HBcAb. CONCLUSIONS: The prevalence of hepatitis B in Amol City and its surrounding areas was about one percent, a lower rate than other reports from Iran

Signal transduction pathway mutations in gastrointestinal (GI) cancers : a systematic review and meta-analysis

The present study was conducted to evaluate the prevalence of the signaling pathways mutation rate in the Gastrointestinal (GI) tract cancers in a systematic review and meta-analysis study. The study was performed based on the PRISMA criteria. Random models by confidence interval (CI: 95%) were used to calculate the pooled estimate of prevalence via Metaprop command. The pooled prevalence indices of signal transduction pathway mutations in gastric cancer, liver cancer, colorectal cancer, and pancreatic cancer were 5% (95% CI: 3–8%), 12% (95% CI: 8–18%), 17% (95% CI: 14–20%), and 20% (95% CI: 5–41%), respectively. Also, the mutation rates for Wnt pathway and MAPK pathway were calculated to be 23% (95% CI, 14–33%) and 20% (95% CI, 17–24%), respectively. Moreover, the most popular genes were APC (in Wnt pathway), KRAS (in MAPK pathway) and PIK3CA (in PI3K pathway) in the colorectal cancer, pancreatic cancer, and gastric cancer while they were beta-catenin and CTNNB1 in liver cancer. The most altered pathway was Wnt pathway followed by the MAPK pathway. In addition, pancreatic cancer was found to be higher under the pressure of mutation compared with others based on pooled prevalence analysis. Finally, APC mutations in colorectal cancer, KRAS in gastric cancer, and pancreatic cancer were mostly associated gene alterations