Control and operation of a spinning disc reactor

PhD ThesisThe aim of the present research is to assess the control and operation of a Spinning Disc Reactor (SDR), carried out via four separate investigations. Firstly, the effect of equipment size reduction on control is studied by comparing the performance of a PID controller applied to simulated intensified and conventional processes. It was found that superior control performance in terms of Integral of Absolute Error (IAE) is achieved for the simulated intensified system. However, the results showed that intensified systems are more susceptible to disturbances and the controlled variable exhibits larger overshoots. Furthermore, the frequency response analysis of the two systems showed that the simulated intensified system has reduced stability margins. The second part of the research investigates the task of pH control in a SDR using a PID controller by means of simulation and experimental studies. The effectiveness of a disturbance observer (DO) and a pH characteriser to compensate for the severe pH system nonlinearity is also explored in detail. The experimental studies showed that a PID controller provides adequate setpoint tracking and disturbance rejection performances. However, sluggish transient responses prevailed and the effluent pH limit cycled around the setpoint. There were indications of unstable behaviour at lower flowrates, which implied more advanced control schemas may be required to adapt to various operating regions dictated by the complex thin film hydrodynamics. The addition of the DO scheme improved the control performance by reducing the limit cycles. In the third segment of the investigations, the potential of exploiting the disc rotational speed as a manipulated variable is assessed for the process of barium sulphate precipitation. A PI controller is successfully used to regulate the conductivity of the effluent stream by adjusting the disc rotational speed. The results are immensely encouraging and show that the disc speed may be used as an extra degree of freedom in control system design. Finally, the flow regimes and wave characteristics of thin liquid films produced in a SDR are investigated by means of a thermal imaging camera. The film hydrodynamics strongly affect the heat and mass transfer processes within the processing films, and thus the intensification aspects of SDRs. Therefore, effective control and operation of such units is significantly dependent on the knowledge of film hydrodynamics and the underlying impact of the operating parameters and the manipulated variables on a given process. The results provided an interesting insight and unveiled promising potentials for characterisation of thin liquid film flow and temperature profiles across the disc by means of thermographic techniques. The present study reveals both challenges and opportunities regarding the control aspects of SDRs. It is recommended that equipment design and process control need to be considered simultaneously during the early stages of the future developments. Furthermore, intensified sensors and advanced controllers may be required to achieve an optimum control capability. Currently, the control performance is inhibited by the lack of sufficient considerations during the SDR design and manufacturing stages, and also by the characteristics of the commercially available instrumentation.EPSRC Doctoral Training Awar

Evaluation of 200 Mm, 365 Mm and 500 Mm Fibers of Laser Ho YAG in Transurethral Lithotripsy of Ureteral Stone

Introduction: At present, different Holmium: YAG laser caliber for endoscopic stone treatment are used, which includes 200, 365, 500 and 1000 Mm fiber. Currently there are not enough studies to compare the performance of these fibers. In this retrospective investigation the outcome of 200, 365 and 500 Mm fibers of Laser Ho YAG in Transurethral lithotripsy of ureteral stone evaluated.Methods: Seventy-four subjects with mean age of 35.3 ± 5.4 years old treated by endoscopic laser management from January 2016 to June 2017. The main purpose of investigation was to evaluation Mean Operation Time(MOT), Stone Free Rate (SFR) and complications of 200 Mm, 365 Mm and 500 Mm fibers of Laser Ho YAG in Transurethral lithotripsy.Results: MOT and SFR were significantly different in 500 Mm laser caliber (P = 0.046, P = 0.029, respectively). There was no remarkable difference between the three groups in this regard.Conclusion: Based upon our data, the clinical potency of the Ho: YAG laser was great in all three fiber calibers. The most important results of this comparison were the significantly higher SFR with increased laser caliber

Laser Application in Iran Urology: A Narrative Review

The usage of laser in medicine is not recent, and its history in urology goes back to 40 years ago. For the last 2 decades, common uses of laser have been treatments of subjects with urolithiasis, bladder tumors, benign prostatic enlargement, lesions of the genitalia and urinary tract strictures. To evaluate laser application in urology in Iran, we reviewed all of the Iranian literature on the topic. This study was designed to retrieve all studies on laser application in urology in Iran, regardless of publication status or language, covering years 1990–2017. Twenty-six articles were identified: 12 about urolithiasis, 8 about benign prostatic hyperplasia (BPH), 2 case reports, 1 paper about prostate cancer, 1 on female urethral stricture, 1 review and 1 basic sciences study. We conclude that the use of this technology has not yet found its position in Iran, especially in the field of urology. The main causes for it are the difficult accessibility and disturb of laser devices and its accessories, as well as the lack of adequate knowledge of the medical community about this modality

Predictors of sperm retrieval with micro TESE, A narrative review article

Introduction: Regarding the financial and psychological effects of micro-TESE on patients with NOA, it is important to determine the parameters by which the sperm retrieval with micro-TESE can be predicted. Methods: The key words used for conducting a search in the PubMed database included nonobstructive azoospermia and TESE. The abstracts of the articles were reviewed, and the articles which reported the parameters’ influence on sperm retrieval with micro TESE were included. All non-English papers, case reports, and case series, were excluded from the review. Eventually, 25 articles were selected to be included. Results:  It is recommended that diagnostic test is biopsy should be performed at the time of micro-TESE. The histopathology of testis, testicular volume, hormone profile, aging, and genetic factors, are parameters that might influence the results of sperm retrieval with micro-TESE. Heterogeneous histopathological pattern and report of hypospermatogenesis on pathology, lower serum FSH level, normal testis volume, and varicocelectomy, increase the chance of sperm retrieval with micro-TESE. In terms of sperm retrieval, some genetic factors such as AZFa, AZFb, and chromosome Y micro deletion provide poor prognosis. Conclusion: Testis histopathology is the most important factor which predicts sperm retrieval with micro-TESE. Other factors that influence the sperm retrieval rate are testis volume, genetic factor, serum FSH level, and history of varicocelectomy

The Impact of the First Covid 19 Pandemic on Urology Residency Training in Iran

Background: During the pandemic, Iranian healthcare system had faced many challenges including the continuation of medical education. In this time, almost all elective surgeries have been suspended, outpatient visits have been limited to seriously ill patients, and academic meeting have been cancelled. This process has caused a significant decrease in clinical and surgical practice in the field of urology. In this article, we assess as to what extent and how this pandemic has impacted the urology residency training in Iran. Material and Methods: a 15-item-long questionnaire was designed and sent to all Iranian urology residents via social network and/or email from the 10th of MAY to the 10th of Jun 2020. This questionnaire assessed different training activities, including on-call duty, outpatient visits, diagnostic procedures such as cystoscopy, endoscopic procedures, and open major surgeries, prior and during the pandemic. The results were evaluated using t-test and ANOVA. Results: the percentage of urology resident’s involvement in each training activity, including on-call duty, outpatient visits, diagnostic procedures such as cystoscopy, endoscopic procedures, and open major surgeries, demonstrated a significant decline (p<0.001) during this time compared to the pre-COVID-19 period. Conclusion: urology residency training significantly decreased during the COVID-19 period. In order to address the second and third waves of COVID-19 outbreak, long-term action plans, such as telemedicine and stimulation, can help prepare training programs and residents during these unprecedented times

Experience of 138 Transurethral Urethrotomy With Holmium:YAG Laser

Introduction: Many valid option modalities are available for the management of urethral stricture disease (USD), such as internal urethrotomy which has the success rates of 33%–60%. The aim of this study was to assess the outcome of holmium: YAG (Ho: YAG) laser urethrotomy (HLU).Methods: One hundred thirty-eight patients with urethral stricture with the mean age of 48±3.03 years old treated by HLU from March 2011 to August 2017. The main purpose of this investigation was to evaluate mean operation time, stricture recurrence rate and post-operation Qmax and complications of transurethral HLU.Results: The most common cause of USD was trauma in 82 (59.4%) patients. Mean laser operation time, mean hospital stay and mean postoperative duration of catheterization were 23.08 ± 9.1 minutes, 19.02 ± 10.7 hours and 10.3 ± 1.05 days respectively. The mean Qmax was 8.3 ± 2.07 mL/s before surgery and 16 ±3.1 mL/s afterward. At the end of 12 months follow-up, a total of 37 (26.8%) patients developed recurrence of the stricture. Patients with posterior, longer urethral strictures and previous history of interventions have more recurrence rate of the stricture.Conclusion: HLU is minimally invasive and seems to be an effective and safe management option for primary, short, urethral strictures. The hospital stay is remarkably short and complications are negligible

Thermographic analysis of thin liquid films on a rotating disc: approach and challenges

Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.This paper examines the temperature profiles and flow characteristics of thin liquid films on a rotating surface by means of an Infrared (IR) thermal imaging camera. The challenges of obtaining accurate temperature measurements using thermographic techniques, in particular for thin liquid films of varying thicknesses, are outlined in this study. The captured images of the liquid film provide a visual insight into the heat transfer mechanism as the cold liquid moves from centre of a rotating disc towards its edges. The effect of liquid film viscosity, rotational speed, feed flowrate and disc temperature on heat transfer efficiency from the heated disc to the cold film is investigated. The temperature profiles obtained by the Infrared camera are compared to those estimated by a theoretical model of disc/film heat transfer. The results provide an excellent platform for qualitative analysis of heating thin liquid films in highly accelerated centrifugal fields. The quantitative analysis is, however, associated with some degrees of uncertainty due to the limitations described in this paper.mp201

Surgical Management of Vesical Stones in Children: A Comparison Between Open cystolithotomy, Percutaneous Cystolithotomy and Transurethral Cystolithotripsy with Holmium-YAG Laser

Introduction: Bladder stone in children is rare but is more common in developing countries. In recent years, the urologists have trend to minimal invasive approaches. The aim of this study, was to compare the outcomes of surgical bladder stone management in our single tertiary center.Methods and materials: The 159 children younger than 18 years with vesical stones treated during January 2000 to January 2015 in Shohada e Tajrish hospital, Tehran, Iran that 146 subjects entered to the study. According to type of intervention, patients stratified to three groups. First group was included 80 patient’s that open cystolithotomy(OCL) was done for them, second group, 39 patients who underwent percutaneous cystolithotomy(PCCL)and third group,27 patients who treated by transurethral cystolithotripsy with holmium-YAG laser(TULL). Demographic data, operation time, hospital stay, and post operation complications were extracted and compared between groups.Results: Mean age was 8.3±5.1 years (8.6±5.1, 6±4.2 years for boys and girls, respectively). Mean stone size was 2.76±1.07 cm that was not significant between three groups but it was larger in OCL group. Mean operative time was 29.15(±7.12) min that in separate, mean operative time in TULL was significantly higher than PCCL and OCL respectively (36.3±5.97, 30.54±5.27 and 26.06±6.32 min/P:0.000). Mean hospital stay in OCL group was 3.55±1 day that was higher than PCCL and TULL groups significantly (P=0.000).Conclusion: based on our study, Ho:YAG lithotripsy is a safe with high success rate minimally invasive management method for children bladder calculi if proper equipment was available and done in expert hands

Is Holmium Laser an Appropriate Modality to Treat Genital Warts?

Introduction: Genital warts in young adults aged 18-28 years are very common. Several approaches are routinely used in the treatment of warts, viz., medical treatment (podophyllin and trichloroacetic acid), conventional surgery (excision or electrocautery), cryotherapy, and laser treatment. Because of high recurrence rates after treatment, complications and long duration of treatment, newer modalities have been developed. One of these newer methods is laser, which has been used in several urologic diseases. However, there are only a few studies about use of Holmium laser for treatment of genital warts. This retrospective study compared the success rate of Holmium laser with other available treatments for genital warts.Methods: Between October 2011 and May 2016, 142 patients with genital warts attended the urology clinics at Shohada-e-Tajrish hospital in Tehran, Iran. Out of these, a total of 101 patients were included in this study consisting of 42, 39, 11 and 9 patients treated with cryotherapy, laser, conventional surgery and podophyllin respectively.Results: The most successfully cleared lesions were seen in the holmium laser treatment group (P = 0.001). The lowest recurrence rate was observed in the holmium laser treatment group (P = 0.001). 17 patients had one of these following problems: dysuria, initial hematuria or a change in the force and caliber of their urinary stream that after physical examination showed them to have a meatal wart. These patients then underwent cystoscopy up to urinary sphincter. All of them in addition to the meatus wart had a penile shaft lesion(s). Thirteen patients had meatal lesions, 9 of whom received holmium laser therapy and 4 patients were treated with electrocautery. Based on routine follow up after treatment, none of the patients treated with holmium laser had urinary stricture, but one case treated with electrocautery returned with a penile urethral stricture.Conclusion: This study showed that treatment with Holmium laser has the highest clearance rate (92.2%) and lowest recurrence rate (14.3%) compared to other available treatments in this study. It may be concluded that holmium laser is a safe and effective treatment for genital warts with a low rate of recurrence

Re-admission Rate of Patients with Ureteral Stone: A Descriptive Study

Introduction: Patients with acute renal colic need to choose between undergoing medical treatments and receiving interventions. The Aim of this study is to evaluate the outcomes of patients who are discharged from emergency departments with ureteral stones lesser than 6 millimeters. In doing so, the effect of diagnostic treatment approaches on clinical outcomes and referral rate is to be assessed.Patients and Methods: This study was performed on patients with ureteral stones referred to emergency department of Shohadaye Tajrish Hospital between May2015 to June 2018. A checklist was filled out for each patient and it included their complete medical history, physical examination results and paraclinical data. Patients were then studied for 4 weeks to determine referral times to hospital and clinical outcomes.Results: 105 patients include 81 men (77.14%) with average age of 37.1±12.4 years were studied. The mean stone diameter was 4.2±2.1 mm.  Most of ureteral stones were seen in the right-hand side (60 percent). 71 patients (67.6%) did not have any history of nephrolithiasis and 73 (69.5%) did not have positive family history for nephrolithiasis. Ureteral stones were still observed in 42 patients (40%) after two weeks of studies and only one patient (1.1%) had stone in Ultrasound Imaging after 4 weeks of observations.Conclusion: Most Patients (95%) with stones smaller than 6 mm responded to Medical Expulsive Therapy (MET) after 4 weeks and passed spontaneously ureteral calculi