Hydrogen production from water using solar cells powered nafion membrane electrolyzers

Thesis (Master)--Izmir Institute of Technology, Energy Engineering, Izmir, 2007Includes bibliographical references (leaves: 69-71)Text in English; Abstract: Turkish and Englishx, 84 leavesThe aims of this thesis are two folds; to construct single and multi cell proton exchange membrane electrolyzers and to evaluate the performance of these electrolyzers powered by solar panels on Iztech campus. All other parts, except the purchased membrane electrode assemblies, were designed, manufactured and assembled in our labs.In the construction of single and multiple cell proton exchange membrane electrolyzers, Nafion-117 based membrane electrode assemblies were used. Graphite bipolar plates, end plates, current collectors and gaskets were machined on institute.s computer numerical controlled lathe. In the first stage, a single cell electrolyzer with 20cm2 available electrolysis surface areas was examined with a direct current power supply by varying current density (0-500mAmp/cm2), water flow rate (0.05 to 0.5g/cm2min), and temperature (30-50oC). It was found that average cell voltage decreases from 2.18V at 30oC to 1.97V at 50oC when the current density is 500mAmp/cm2. Since cell gaskets were softened and stick to the membrane above 50oC of operating temperature, temperatures higher than 50 oC could not be tested. Five cell electrolyzer stack was constructed according to the final single cell design. It was observed that the stack could generate 388ml/min hydrogen under 500mAmp/cm2 and 10.09V of the operating condition at 41.5oC. When the stack was directly coupled with a solar array, voltage of the stack was found to vary from 7.5V to 12.5V and the current density changes from 0 to 1000mAmp/cm2 with respect to the solar radiance of the day. This results in a voltage efficiency ranging from 98.7% to 60% based on the higher heating value of hydrogen. Electrolyzer powered by solar cells can generate up to 750ml/min hydrogen and total daily production could be as high as 350L per day but weather condition greatly affects the production rate. Together with the losses inside the electrolyzer, another important energy loss is due to voltage mismatches between PV array and electrolyzer in low solar irradiance during sunrise and sunset

Economic analyses for the evaluation of is projects

Information system projects usually have numerous uncertainties and several conditions of risk that make their economic evaluation a challenging task. Each year, several information system projects are cancelled before completion as a result of budget overruns at a cost of several billions of dollars to industry. Although engineering economic analysis offers tools and techniques for evaluating risky projects, the tools are not enough to place information system projects on a safe budget/selection track. There is a need for an integrative economic analysis model that will account for the uncertainties in estimating project costs benefits and useful lives of uncertain and risky projects. The fuzzy set theory has the capability of representing vague data and allows mathematical operators and programming to be applied to the fuzzy domain. The theory is primarily concerned with quantifying the vagueness in human thoughts and perceptions. In this article, the economic evaluation of information system projects using fuzzy present value and fuzzy B/C ratio is analyzed. A numerical illustration is included to demonstrate the effectiveness of the proposed methods

Üreter taşı hastalarında postüreteroskopik lezyon skalası ile emilen irrigasyon sıvısı arasında bağlantı var mı?

Objective: Post-Ureteroscopic Lesion Scale (PULS) is used to classify ureteral wall injury that occurs during ureteroscopy. In this study we presented the preliminary results of absorbed irrigation fluid volumes according to PULS grades. Material and Methods: Forty-four patients to whom 7F semirigid ureteoscopy was performed due to ureteral stone were included in the study. All patients received general anesthesia. Izotonic containing 1% ethanol was used as irrigation fluid. Ethanol concentration in venous blood was commenced to be measured at the start of irrigation use and was carried on at 15-minute intervals including the post-operative period in the recovery room. Absorbed fluid volume was calculated by using blood ethanol concentrations. Irrigation time, stone size and PULS grade were recorded. Results: Mean operation time was found to be 44.2 ± 19.9 minutes. Mean stone size was measured to be 12.7± 6 mm and mean irrigation fluid amount used was 1371±1262 ml. PULS grade of 0 was seen in 26 patients and that of 1 or more was seen in 18 patients. No patient had a PULS grade of 3 or 4. Mean absorbed fluid volume was measured to be 58 ± 50,6 ml. No significant correlation was found between PULS grade and mean absorbed fluid volume. Conclusion: Fluid absorption during URS is not correlated with the PULS grade. Semirigid URS is a safe treatment option for ureteral stone disease in terms of the level of irrigation fluid being absorbed.Amaç: Üreteroskopi esnasında üreter duvarında oluşan hasarı sınıflandırmak için Post-Üreteroskopik Lezyon Skalası (PULS) kullanılmaktadır. Bu çalışmada PULS derecelerine göre absorbe edilen irrigasyon sıvı hacimlerinin ön sonuçlarını sunduk. Gereç ve Yöntemler: Bu çalışmaya üreter taşı nedeniyle 7 F semirijid üreteroskopi uygulanan 44 hasta dahil edildi. Tüm hastalara genel anestezi uygulandı. %1 etanol içeren izotonik irrigasyon sıvısı olarak kullanıldı. Venöz kan etanol konsantrasyonları irrigasyon kullanılmaya başlaması ile ölçülmeye başlandı, operasyon sonrası derlenme odasını kapsayacak şekilde 15 dakika arayla periyodik ölçüldü. Absorbe edilen sıvı hacmi kan etanol konsantrasyonları kullanılarak hesaplandı. İrrigasyon süresi, taş boyutu, PULS derecesi kaydedildi.Bulgular: Ortalama operasyon süresi 44.2 ± 19.9 dakika olarak saptandı. Ortalama taş hacmi 12.7± 6 mm ve ortalama kullanılan irrigasyon sıvı miktarı 1371±1262 mL olarak ölçüldü. Hastaların 26’sınde PULS derecesi 0 iken 18’inde 1 veya üzerindeydi üzerindeydi. Hiçbir hastada PULS derecesi 3 veya 4 olmadı. Ortalama absorbe edilen sıvı hacmi 58 ± 50,6 mL olarak hesaplandı. PULS derecesi ile ortalama absorbe edilen sıvı miktarı arasında istatistiksel anlamlı fark saptanmadı.Sonuç: URS esnasında oluşan PULS derecesi 1-2 olan veya düşük dereceli submukozal üreter lezyonlarıyla sıvı emilimi korele bulunmamıştır. Semirijid URS, üreter taşı hastalığı tedavisinde irrigasyon sıvısının emilimi açısından güvenli bir yöntemdir

Impact of opioid-free analgesia on pain severity and patient satisfaction after discharge from surgery: multispecialty, prospective cohort study in 25 countries

Background: Balancing opioid stewardship and the need for adequate analgesia following discharge after surgery is challenging. This study aimed to compare the outcomes for patients discharged with opioid versus opioid-free analgesia after common surgical procedures.Methods: This international, multicentre, prospective cohort study collected data from patients undergoing common acute and elective general surgical, urological, gynaecological, and orthopaedic procedures. The primary outcomes were patient-reported time in severe pain measured on a numerical analogue scale from 0 to 100% and patient-reported satisfaction with pain relief during the first week following discharge. Data were collected by in-hospital chart review and patient telephone interview 1 week after discharge.Results: The study recruited 4273 patients from 144 centres in 25 countries; 1311 patients (30.7%) were prescribed opioid analgesia at discharge. Patients reported being in severe pain for 10 (i.q.r. 1-30)% of the first week after discharge and rated satisfaction with analgesia as 90 (i.q.r. 80-100) of 100. After adjustment for confounders, opioid analgesia on discharge was independently associated with increased pain severity (risk ratio 1.52, 95% c.i. 1.31 to 1.76; P < 0.001) and re-presentation to healthcare providers owing to side-effects of medication (OR 2.38, 95% c.i. 1.36 to 4.17; P = 0.004), but not with satisfaction with analgesia (beta coefficient 0.92, 95% c.i. -1.52 to 3.36; P = 0.468) compared with opioid-free analgesia. Although opioid prescribing varied greatly between high-income and low- and middle-income countries, patient-reported outcomes did not.Conclusion: Opioid analgesia prescription on surgical discharge is associated with a higher risk of re-presentation owing to side-effects of medication and increased patient-reported pain, but not with changes in patient-reported satisfaction. Opioid-free discharge analgesia should be adopted routinely

Hydrogen production from water using solar cells powered nafion membrane electrolyzers

Thesis (Master)--Izmir Institute of Technology, Energy Engineering, Izmir, 2007Includes bibliographical references (leaves: 69-71)Text in English; Abstract: Turkish and Englishx, 84 leavesThe aims of this thesis are two folds; to construct single and multi cell proton exchange membrane electrolyzers and to evaluate the performance of these electrolyzers powered by solar panels on Iztech campus. All other parts, except the purchased membrane electrode assemblies, were designed, manufactured and assembled in our labs.In the construction of single and multiple cell proton exchange membrane electrolyzers, Nafion-117 based membrane electrode assemblies were used. Graphite bipolar plates, end plates, current collectors and gaskets were machined on institute.s computer numerical controlled lathe. In the first stage, a single cell electrolyzer with 20cm2 available electrolysis surface areas was examined with a direct current power supply by varying current density (0-500mAmp/cm2), water flow rate (0.05 to 0.5g/cm2min), and temperature (30-50oC). It was found that average cell voltage decreases from 2.18V at 30oC to 1.97V at 50oC when the current density is 500mAmp/cm2. Since cell gaskets were softened and stick to the membrane above 50oC of operating temperature, temperatures higher than 50 oC could not be tested. Five cell electrolyzer stack was constructed according to the final single cell design. It was observed that the stack could generate 388ml/min hydrogen under 500mAmp/cm2 and 10.09V of the operating condition at 41.5oC. When the stack was directly coupled with a solar array, voltage of the stack was found to vary from 7.5V to 12.5V and the current density changes from 0 to 1000mAmp/cm2 with respect to the solar radiance of the day. This results in a voltage efficiency ranging from 98.7% to 60% based on the higher heating value of hydrogen. Electrolyzer powered by solar cells can generate up to 750ml/min hydrogen and total daily production could be as high as 350L per day but weather condition greatly affects the production rate. Together with the losses inside the electrolyzer, another important energy loss is due to voltage mismatches between PV array and electrolyzer in low solar irradiance during sunrise and sunset

Clinical aspects of renal cell carcinoma

Renal cell carcinoma (RCC) represents a heterogeneous group of tumors, the most common of which is clear cell adenocarcinoma. RCC accounts for 3% of adult tumors. The incidence has increased more than 30% over the past two decades. It is generally postulated that the increased incidence rates reflect earlier diagnosis at an earlier stage, largely due to more liberal use of radiological imaging techniques. However, advanced disease has also been diagnosed more frequently and the mortality rate has increased as well. Prevention of RCC should focus on smoking cessation and maintaining ideal body mass index. Familial forms of kidney cancer have been described on four distinct histological patterns: clear cell, papillary, chromophobe, and oncocytoma. Genetic forms afflict individuals at an earlier age with a multifocal and recurrent pattern; therefore, nephron-sparing procedures should be the treatment of choice for these patients. The yield of screening the general population for RCC is still relatively low and hence not cost-effective. Screening should be reserved for individuals who carry high risk for RCC. The classic triad of flank pain, macroscopic hematuria, and palpable abdominal mass is now detected in fewer than 10% of patients, and is a late sign. Today, most tumors are diagnosed incidentally. Paraneoplastic syndromes have been reported in 10-40% of patients and can be seen at any stage of disease. The indications and application of percutaneous biopsy for renal masses are limited and mainly used to make differential diagnosis with an infectious process, lymphoma and metastases to the kidney. © 2003 Elsevier B.V. All rights reserved

Economic analyses for the evaluation of is projects

Information system projects usually have numerous uncertainties and several conditions of risk that make their economic evaluation a challenging task. Each year, several information system projects are cancelled before completion as a result of budget overruns at a cost of several billions of dollars to industry. Although engineering economic analysis offers tools and techniques for evaluating risky projects, the tools are not enough to place information system projects on a safe budget/selection track. There is a need for an integrative economic analysis model that will account for the uncertainties in estimating project costs benefits and useful lives of uncertain and risky projects. The fuzzy set theory has the capability of representing vague data and allows mathematical operators and programming to be applied to the fuzzy domain. The theory is primarily concerned with quantifying the vagueness in human thoughts and perceptions. In this article, the economic evaluation of information system projects using fuzzy present value and fuzzy B/C ratio is analyzed. A numerical illustration is included to demonstrate the effectiveness of the proposed methods

Experimental Investigation on Wire Electric Discharge Machining of Biodegradable AZ91 Mg Alloy

The AZ91 magnesium alloy, used commonly as a biodegradable material in biomedical applications, is generally formed by conventional casting method (CCM) and high-pressure die casting method (HPDCM). The AZ91 alloys exhibit poor machinability with conventional chip removal methods since they degrade at elevated temperatures. In this study, the wire electric discharge machining (WEDM) was presented as a candidate process to machine the AZ91 alloy since no cutting stresses and plastic deformations were applied by the cutting tool to the part causing elevated temperatures. In this context, the WEDM machinability of the AZ91 alloy samples produced by cold chamber HPDCM and CCM at different process parameters, was experimentally investigated. The machining performance outputs (the machining current (I), the machining rate (MR), the average surface roughness (R-a), and surface topography) were found for the varying process parameters [pulse time (t(s)), pulse-off time (t(off)), dielectric flushing pressure (P-d), and wire speed (V-w)]. The present study revealed that the I and the MR were significantly dependent on the density, the porosity, and the micro structure of the samples, and the HPDCM samples gave the higher MR and the smoother surface than that of the CCM