3-D Dynamic Analysis of High-Speed Railroad Track

High-Speed Rail (HSR) as a fast, reliable and environmentally friendly mode of transportation has received a lot of attention in recent decades. The International Union of Railways reported that there are more than 18600 miles of HSR in operation and about 1.6 billion passengers per year are carried by them. Although there are plans for HSR in many states including Florida, the United States, however, is still hesitant to develop its own HSR network. One of the main barriers to developing high-speed rail is excessive vibration propagation to the media which may cause annoyance to people who live in the track neighborhood. Train induced vibration also contributes to track settlement, developing track flaws, and increasing life cycle cost of track and supporting structures. The aim of this research is to address this problem by conducting a comprehensive investigation into track dynamics. For this purpose, three-dimensional mass-spring-damper models of vehicle, track and supporting structures were developed and matrices of mass, stiffness, and damping of each subsystem were formed. The response of the whole system was, then, determined by coupling the subsystems using Hertz contact theory. The differential equations of the coupled system were solved by the Newmark integration method and the results including vertical and lateral displacements and forces were presented in the time domain. Since the purpose of this dissertation is to quantify the effect of track and vehicle condition on vibration level, rail defects were also taken into account and rail random irregularities for the vertical profile, Gauge, alignment and cross level (super elevation) were incorporated into a numerical solution. The results of the study show the effect of track and vehicle parameters on the response of the vehicle, track, and substructures. Since Florida and some other states in the United States are very prone to hurricanes, an investigation was conducted into the effect of wind speed on vehicle stability. For this purpose, a curved beam was modeled to consider the influence of track curvature, cant deficiency, wind speed and train speed simultaneously. The results from the study show the maximum allowable values of train speed and axle load for different wind speeds. The findings can be used to decide under what circumstances there is a risk of vehicle overturning and how to avoid it

The Effect of Rail Defects on Track Impact Factors

This paper investigates the effect of rail surface flaws on track impact factors for different track and vehicle conditions. For this purpose, a three dimensional vehicle and track as an integrated system modelled. The vehicle, consists car body, bogie frames and wheelsets, is able to model displacements in vertical and lateral directions. Hertz nonlinear springs utilized to connect vehicle to track structure and simulate the interaction between vehicle and track subsystems. Track comprises rail, rail pads, sleepers and ballast materials. For each subsystem, matrices of mass, stiffness and damping were formed and then matrices of total vehicle-track system considering their interaction were solved. Using FRA spectral density functions for rail irregularities, response of track with different qualities to train dynamic forces obtained. Rail random irregularities, rail corrugation and rail joint defects as three common rail defects have been considered in this paper. For each defects the influence of different track and train parameters on impact factor has been studied. The results of study indicate substantial effect of the depth and frequency of the rail flaws on impact factors. This paper has also considered the impact of vehicle speed on dynamic forces and found the critical speed for each case

Prolonged fever in a case of end stage renal disease with remained guidewire

Central venous catheters,introduced for short-term dialysis,but occationally used as permanent vascular access in patient without alternative option. Hemodialysis(HD) patients presenting with fever have high rates of bacteremia,specially in patients with dialysis catheters and those with a history of bacteremia. [1]Herein,we report a case of  end stage renal disease with catheter infection complicated with endocarditi

Nappe flow regime energy loss in stepped chutes equipped with reverse inclined steps: experimental development

With advances in technology and the invention of the Roller-Compacted Concrete (R.C.C) technique, stepped spillway construction has become much faster than in the past. Due to this, designers have become more interested in using this kind of chute as one of the best energy dissipaters. Along with the increasing use of stepped spillways, researchers have focused on increasing the efficiency of this hydraulic structure. They have proposed different methods to achieve this. Step geometry optimization, regarding flow regime type, is one of these efforts. In this experimental research, reverse inclined steps have been applied for three degrees (7o, 10 o, and 12o) to investigate their effect on the energy dissipation rate in the Nappe Flow Regime of stepped spillways. Energy loss rates obtained from the reverse inclined steps have been compared with the energy loss rate in a horizontal step. Results indicate a slight increase in the energy loss rate when the reverse inclined steps have been applied in the Nappe Flow Regime of stepped spillways

Nappe flow regime energy loss in stepped chutes equipped with reverse inclined steps: experimental development

With advances in technology and the invention of the Roller-Compacted Concrete (R.C.C) technique, stepped spillway construction has become much faster than in the past. Due to this, designers have become more interested in using this kind of chute as one of the best energy dissipaters. Along with the increasing use of stepped spillways, researchers have focused on increasing the efficiency of this hydraulic structure. They have proposed different methods to achieve this. Step geometry optimization, regarding flow regime type, is one of these efforts. In this experimental research, reverse inclined steps have been applied for three degrees (7o, 10 o, and 12o) to investigate their effect on the energy dissipation rate in the Nappe Flow Regime of stepped spillways. Energy loss rates obtained from the reverse inclined steps have been compared with the energy loss rate in a horizontal step. Results indicate a slight increase in the energy loss rate when the reverse inclined steps have been applied in the Nappe Flow Regime of stepped spillways

Nappe flow regime energy loss in stepped chutes equipped with reverse inclined steps: experimental development

With advances in technology and the invention of the Roller-Compacted Concrete (R.C.C) technique, stepped spillway construction has become much faster than in the past. Due to this, designers have become more interested in using this kind of chute as one of the best energy dissipaters. Along with the increasing use of stepped spillways, researchers have focused on increasing the efficiency of this hydraulic structure. They have proposed different methods to achieve this. Step geometry optimization, regarding flow regime type, is one of these efforts. In this experimental research, reverse inclined steps have been applied for three degrees (7o, 10 o, and 12o) to investigate their effect on the energy dissipation rate in the Nappe Flow Regime of stepped spillways. Energy loss rates obtained from the reverse inclined steps have been compared with the energy loss rate in a horizontal step. Results indicate a slight increase in the energy loss rate when the reverse inclined steps have been applied in the Nappe Flow Regime of stepped spillways

Clinical, epidemiological, and mycological features of patients with candidemia: Experience in two tertiary referral centers in Iran

Background and purpose: Candidemia is a major cause of morbidity and mortality among patients receiving immunosuppressive therapy and those hospitalized with serious underlying diseases. Here, we investigated the epidemiological, clinical, and mycological features of candidemia in Tehran, Iran. Materials and methods: A prospective observational study of all patients diagnosed with candidemia was performed at two referral teaching hospitals in Tehran, Iran, from February to December 2018. Demographic characteristics, underlying diseases, risk factors, clinical symptoms, and laboratory analyses of candidemic patients with positive culture were mined. Candida isolates were molecularly identified by sequencing of the internal transcribed spacer region (ITS1-5.8S-ITS2). The antifungal susceptibility testing for fluconazole, itraconazole, voriconazole, posaconazole, amphotericin B, caspofungin, micafungin, and anidulafungin against the isolates was performed using CLSI broth microdilution reference method (M27-A3). Results: A total of 89 episodes were identified, with an incidence of 2.1 episodes/1000 admissions. The common underling disease were malignancy (46%), renal failure/dialysis (44%), and hypertension (40%). The overall crude mortality was 47%. C. albicans (44%) was the most frequent causative agent, followed by C. glabrata (21%), C. parapsilosis complex (15%), C. tropicalis (11%), and C. lusitaniae (3.5%). All the isolates were susceptible to amphotericin B. The activity of all four azoles was low against non-albicans Candida species, especially C. tropicalis. Conclusion: The increase in non-albicans Candida species with reduced susceptibility to antifungal drugs might be alarming in high-risk patients. Therefore, accurate knowledge of predisposing factors and epidemiological patterns in candidemia are effective steps for managing and decreasing the mortality rate in candidemia.This study has been funded and supported by Tehran University of Medical Sciences, Tehran, Iran (Grant no. 99-2-99-48944).S

Urbach-Wiethe Syndrome and the Ophthalmologist: Review of the Literature and Introduction of the First Instance of Bilateral Uveitis

Patients suffering from Urbach-Wiethe syndrome (UWS), also known as lipoid proteinosis or hyalinosis cutis et mucosae, may have an ophthalmologist involved in the diagnosis and management of their disease. Along with moniliform blepharosis as a pathognomonic feature of the disease, an ophthalmologist may encounter other manifestations of UWS in any part of the eye such as cornea; conjunctiva; sclera; trabecular meshwork; iris/pupil; lens and zonular fibers; retina; nasolacrimal duct. This paper provides a review on the pathogenesis and the diverse ocular manifestations seen in UWS patients. Uncommon complications are discussed in this paper (glaucoma; dry eye and epiphora; complications of lens, retina, cornea; iris/pupil and conjunctiva). Moreover, a 27-year-old male UWS patient is described with bilateral diffuse anterior stromal iris atrophy, diffuse keratic precipitates; posterior subcapsular cataract; 1 + vitreous cell in anterior vitreous examination. This case was thought to be the first instance of bilateral uveitis associated with UWS. Overall, ophthalmologists may encounter diverse ocular complications accompanying this syndrome. They should be familiar with well-established ophthalmologic manifestations leading them to cooperate with other specialists in diagnosis and management of the disease

Evaluation of the Effect of Combination Therapy on Treatment of COVID-19: A Cohort Study

Background: COVID-19 is a new disease for which a definitive treatment has not yet been proposed. Objectives: The present study aimed to investigate the effect of combination therapy on the treatment of COVID-19 due to the importance of finding an appropriate treatment for this epidemic disease. Methods: This two-center cohort study included 175 confirmed COVID-19 inpatients at two medical centers designated for the treatment of COVID-19 patients in Qom and Qazvin, Iran. In this study, four different groups of drug regimens were studied which included G1 (azithromycin, prednisolone, and naproxen), G2 (lopinavir/ritonavir, azithromycin, naproxen, and prednisolone), G3 (hydroxychloroquine, azithromycin, naproxen, and prednisolone), and G4 (levofloxacin, vancomycin, hydroxychloroquine, and oseltamivir). It should be noted that G1, G2, G3, and G4 treatment regimens were used on 48, 39,30, and 77 patients, respectively. Results: The study participants included 175 confirmed COVID-19 patients with mean±SD age of 58.9 ±15.1 years, out of whom 80 (46%) patients were male and the rest were females. The results indicated that the hospital stay period was significantly shorter in the G1 compared to other groups (G1:5.9±2.4, G2:8.1±4.2, G3: 6.3±1.7, and G4: 6.4±2.9; [P-value=0.008]). It should be noted that pulse rate, oxygen saturation, hemoglobin, and platelet count (PLT) changed significantly during the study in four treatment groups; however, a significant change in temperature, creatinine, and white blood cell (WBC) was observed only in G3, G4, and G1 groups, respectively. The number of ICU admissions and deaths were not statistically significant among the patients who received the four treatment regimens (P=0.785). Based on the results, the history of ischemic heart disease, baseline oxygen saturation, WBC, neutrophil, lymphocyte count, and C-reactive protein (CRP) are the risk factors for the prolonged hospital stay in COVID-19 patients. Conclusion: The obtained results in this study indicated that the combination of azithromycin, prednisolone, and naproxen is the most effective regimen for the treatment of COVID-19, compared to three other combination treatment regimens. Keywords: Anti-inflammatory drugs, Antiviral drugs, Combination therapy, Corticosteroid, COVID-19, Immunomodulators drug