Analytical prediction of part dynamics for machining stability analysis

An analytical procedure is developed to predict workpiece dynamics in a complete machining cycle in order to obtain frequency response functions (FRF) which are needed in chatter stability analyses. For this purpose, a structural modification method which is an efficient tool for updating FRFs is used. The removed mass by machining is considered as a structural modification in order to determine the FRFs at different stages of the process. The method is implemented in a computer code and demonstrated on different geometries. The predictions are compared and verified by FEA. Predicted FRFs are used in chatter stability analyses, and the effect of part dynamics on stability is studied. Different cutting strategies are compared for increased chatter free material removal rates considering part dynamics

Biyokütleden hızlı piroliz

06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.Bu çalışmada, toz formda etüvde kurutulmuş odun talaşının yavaş ve hızlı piroliz teknikleri kullanılarak katalizör, sönmüş kireç ve atık yağ eşliğinde katalitik depolimerizasyona uğratılması sonucunda sıvı ürün eldesi araştırılmıştır. Odun talaşının lignoselülozik içerikli yapısından dolayı içeriğinde bulunan lignin selüloz ve hemiselüloz bozunma aralığını belirlemektedir. Odun talaşının nem ve uçucularından kaynaklı kütle kaybı, kalan külün elementel içeriği TGA (Termo Gravimetrik Analiz) cihazı ile ASTM (Ameriakn Malezeme ve Test Tekniği) standartlarına göre belirlenmiştir. Odun talaşının kül oranının düşük olması sıvı ürün veriminin yüksek olmasına kaynak sağlamıştır. Hızlı ve yavaş piroliz koşullarında, 300°C ve 650°C'lerde farklı oranlarda hazırlanan karışımlar ile yapılan deneylerde, atık yağ varlığında toplam sıvı ürün veriminin arttığı, katı ürün veriminin ise azaldığı görülmektedir. Atık yağ içerisinde bulunan doymuş ve doymamış hidrokarbonların, sıcaklık ile bozunarak sıvı ürün oluşumuna katkıda bulunduğu görülmüştür. Atık yağ ve talaş karışımınına katalizör ve kireç eklenmesi ile sıvı ürün miktarının artmasını dolayısıyla sıvı ürün veriminin artmasını sağlamıştır. Bu çalışmada odun talaşının katalitik bozunması işlemlerinde ısıtma hızının ve sıcaklığın yüksek olması sıvı ve gaz ürün verimlerinde artışa katı ürün veriminde ise azalmaya sebep olmuştur. Ayrıca atık yağ, kireç ve katalizörün varlığında sıvı ve gaz ürün veriminin yükseldiği gözlemlenmiştir. Anahtar kelimeler: Odun talaşı hızlı pirolizi, katalitik depolimerizasyon, yavaş ve hızlı piroliz.In this study, the liquid product was investigated as a result of the catalytic depolymerization of the calcined wood shavings in powder form using slow and fast pyrolysis techniques in catalyst, lime and waste oil mixture. Due to the lignocellulosic composition of the wood chips, the content of lignin in the content determines the range of degradation of cellulose and hemicelluloses. Moisture loss due to moisture and volatile components of the wood chips, resıdual cloudy elemental content was determined by ASTM (American Society for Testing and Material) standarts with TGA (Thermo Gravimetric Analysis) device and constant carbon value was calculated. Low ash content of wood chips provides a source of high liquid product yield. Experiments with blends prepared at different rates at 300°C and 650°C under and gradual pyrolysis conditions show that total liquid product yield and solid product yield decrease in the presence of waste oil. It has been found that saturated and unsaturated hydrocarbons in waste oil are degraded by temperature and contribute to liquid product formation. The addition of catalyst and lime to the waste oil and sawdust mixture increases the liquid product yield and thus increases the liquid product yield. In this study, the heating rate and the high temperature in the catalytic degradation of wood chips resulted in an increase in liquid and gas product yields and a decrease in solid product yields. It has also been observed that in the presence of waste oil, lime and catalyst, the yield of liquid and gaseous products increases. Keywords: Rapid pyrolysis of wood chips, catalytic depolymerization, gradual and rapid pyrolysis

Acute renal failure developing for the forgotten dj stent in patient’s functional solitary kidney: case report

Üreteral stentlerin endikasyonlarının artması ve kullanımının giderek yaygınlaşmasının doğal sonucu olarak stentlere bağlı komplikasyonların görülme sıklığı da artmıştır. Literatürde soliter böbrekli hastalarda unutulmuş stentlere bağlı gelişen böbrek yetmezliği, sepsis ve ölüm vakaları rapor edilmiştir. Soliter böbrekli hastalar klinik önemlerine rağmen stentlerine yeterli ilgiyi göstermemektedir. Bu olgu sunumunda sağ nonfonksiyone böbrekli hastada dört yıl süre ile unutulan double J stente bağlı gelişen akut böbrek yetmezliği tablosu sunulmuştur. Fonksiyonel tek böbreği olan hastalarda unutulmuş stentin oluşturabileceği katastrofik sonuçlar nedeniyle daha dikkatli olunmalıdır. Üreteral stent takılması planlanan hastalara stent endikasyonları, süresi ve komplikasyonlarının ayrıntılı anlatılması hastanın daha ilgili olmasını sağlayabilir.The frequency of complications subject to stents has increased as a natural result that ureteral stent indications increase and its usage becomes widespread gradually. There has been renal insufficiency, sepsis and death cases reported developing due to stents forgotten in patients with solitary kidneys in literature. Patients with solitary kidneys cannot give sufficient care to their stents instead of clinic precautions. In this case report, we present acute renal failure findings developed subject to double J stent forgotten for four years in a patient right non-functional kidney. We should be more careful due to catastrophic results created by stent forgotten in patients with single functional kidney. Telling stent indications, period and complications in details to patients to whom ureteral stent will be placed might provide them become more interested

Clinical Value of Core Lenght in Saturation Prostate Biopsy

Objective: To investigate the effect of core length on cancer detection in saturation prostate biopsy. We hypothesized that increasing mean and total core length in saturation prostate biopsy may allow more tissue sampling, thus, may increase the prostate cancer detection rate. Materials and Methods: We retrospectively analyzed medical records of 145 patients who underwent 24-core transrectal ultrasound-guided saturation biopsy at our institution. We evaluated the clinopathological factors, including age, prostate specific antigen (PSA), prostate volume, mean core length and the total biopsy core length. The patients were divided into 3 groups according to their total biopsy core length; group 1: 30 cm. These groups were compared according to age, PSA value, prostate volume and cancer detection rate. Results: The mean age, core length and total core length were 62.4±7.0 years, 10.91±1.8 mm, and 26.2±4.7 cm, respectively. The overall cancer detection rate was 33.8%. There was no statistically significant difference in mean core length and total core length between patients diagnosed with prostate cancer and those without it. The cancer detection rates in group 1, 2 and 3 were 25%, 37.4% and 23.1%, respectively. When these 3 groups were compared with each other, group 2 had a statistically significantly higher cancer detection rate relative to group 1 (p=0.001). Multivariate analysis showed no statistically difference in cancer detection rate between the groups (p=0.302). Conclusion: Mean and total core length may not have any significant effect on prostate cancer detection in patients undergoing saturation prostate biopsy

Association between large prostate calculi and prostate cancer

Objective: We investigated the relationship between large prostate calculi and prostate cancer (PCa) risk. Materials and methods: The medical records of 340 patients who received a prostate biopsy at our institution between January 2015 and August 2016 were reviewed retrospectively. Of the patients, 82 had large prostatic calculi visualised by transrectal ultrasonography and 88 did not or had scarce prostatic calculi. We divided these patients into two groups: patients with large prostatic calculi (group 1) and patients without prostatic calculi (group 2). These groups were compared according to age, total prostate specific antigen (PSA) level, prostate volume, and final pathological diagnosis. Results: The mean age of all patients was 61.4 ± 6.2 years, the mean total PSA was 12.3 ± 17.4 ng/mL, the mean prostate volume was 41.7 ± 17.6 mL, and the overall cancer detection rate was 31.5%. The cancer detection rates were 41.3% and 22.6% in groups 1 and 2, respectively (p = 0.018). No significant differences in mean age, mean total PSA, or mean prostate volume were observed between the groups. Conclusions: In the present study, large prostatic calculi were associated with PCa. However, more study is needed to examine the relationship between large prostatic calculi and PCa in more detail. The effects of particularly large prostate calculi in the development of PCa will be a necessary focus of future research

A Novel Technique for Anterior Vaginal Wall Prolapse Repair: Anterior Vaginal Wall Darn

Aim. The aim of this study is to introduce a new technique, anterior vaginal wall darn (AVWD), which has not been used before to repair the anterior vaginal wall prolapse, a common problem among women. Materials and Methods. Forty-five women suffering from anterior vaginal wall prolapse were operated on with a new technique. The anterior vaginal wall was detached by sharp and blunt dissection via an incision beginning from the 1 cm proximal aspect of the external meatus extending to the vaginal apex, and the space between the tissues that attach the lateral walls of the vagina to the arcus tendineus fascia pelvis (ATFP) was then darned. Preoperation and early postoperation evaluations of the patients were conducted and summarized. Results. Data were collected six months after operation. Cough stress test (CST), Pelvic Organ Prolapse Quantification (POP-Q) evaluation, Incontinence Impact Questionnaire (IIQ-7), and Urogenital Distress Inventory (UDI-6) scores indicated recovery. According to the early postoperation results, all patients were satisfied with the operation. No vaginal mucosal erosion or any other complications were detected. Conclusion. In this initial series, our short-term results suggested that patients with grade II-III anterior vaginal wall prolapsus might be treated successfully with the AVWD method

The sufficiency of 6 core sextant prostate biopsy in patients with prostate specific antigen (PSA) values over 20 ng/mL

Objective: In this study, we aimed to investigate sufficiency of 6 core prostate biopsy in patients with PSA levels elevated above 20 ng/mL. Materials and methods: The medical record of the patients who received prostate biopsy at our institution between August 2011 to August 2016 who had serum total PSA values above 20 ng/mL, were reviewed retrospectively. In this study, we included 40 patients who received 6 core prostate biopsy and 40 patients who received 12 core prostate biopsy. A total number of 80 patients were enrolled in this study. Patients were divided into two groups, a 6 core biopsy group and a 12 core biopsy group. These groups are compared according to age, total PSA, prostate volume and final pathological diagnosis. Results: Based on final pathological diagnosis, 2 patients (5%) had benign pathology and 38 patients (95%) had PCa in both group 1 and 2. The cancer detection rate in both groups was 95%. Although there were higher values of mean age, mean total PSA, and mean prostate volume in group 1, there was no statistically significantly difference at this variables in both groups. Conclusion: Although taking 6 core biopsies is not recently recommended, we proved that 6 core biopsy is adequate for patients with PSA values above 20 ng/mL

Can proliferative hypertrophic scars of the median sternotomy incision predict the occurrence and characteristics of urethral stricture?

Conclusion: A poorly healed median stemotomy incision scar can predict a poor wound healing in the urethra tissue. Further large scale, multi-center and prospective studies are needed to clarify this relationship

Predictive factors of successful salvage microdissection testicular sperm extraction (mTESE) after failed mTESE in patients with non-obstructive azoospermia: Long-term experience at a single institute

Objective: To observe the clinical practice of salvage microdissection testicular sperm extraction (mTESE) in patients with non-obstructive azoospermia (NOA) and to determine the factors that may predict the presence of spermatozoa in preoperative salvage mTESE. Methods: We retrospectively reviewed the medical records of 445 patients with the diagnosis of NOA, who had undergone the mTESE operation consecutively in our institution between the dates of March 2008 and June 2017. The study included a total of 49 patients with failure to detect spermatozoa in the first mTESE and who had then undergone salvage mTESE. In order to investigate the factors that predict the result of salvage mTESE, the patients were classified into two groups according to the outcome of salvage mTESE, as those with and without spermatozoa retrieval. Patients in these two groups were compared with regard to age, body mass index, history of varicocele, history of cryptorchidism, duration of infertility, outcomes of genetic analysis, results of hormone profiles and the testicular histopathology results of the first mTESE. Results: The sperm retrieval rate following salvage mTESE was observed to be 42.8%. Statistically a significant difference was determined between the mean follicle stimulating hormone (FSH) values of the groups (p = 0.013). No significant difference was observed between the groups with regard to the remaining parameters. Conclusion: It was observed that among the factors that predict the success of sperm retrieval in salvage mTESE in patients with NOA and previous unsuccessful sperm retrieval in mTESE operation, only the pre-operative FSH level was observed to significantly correlate with the success in salvage mTESE

The effect of the American Society of Anesthesiology classification scores on complications associated with percutaneous nephrolithotomy

Objectives: We aimed to evaluate the effect of American Society of Anesthesiology (ASA) classification scoring and age on complications and surgical outcomes during and after percutaneous nephrolithotomy (PCNL) operation. Material and methods: The records of 263 patients, above the age of 18 years, that underwent PCNL surgery between October 2014 and May 2017 were evaluated retrospectively. The patients were divided into three groups based on their ASA risk scores (ASA 1, 2, 3) and into two groups based on their age (younger and older than 65 years). Postoperative complications were assessed according to the ASA groups and age and according to the Clavien classification system. Results: The number of patients in the ASA 1, 2, and 3 groups were 97 (36.8%), 131 (49.8%) and 35 (13.3%), respectively. Four patients in ASA4 were not included in the study. There was no significant difference in ASA 1, 2, 3 groups in terms of changes in Hgb values, mean duration of operation, and mean hospital stay. When ASA1 was compared to ASA3 and ASA2 was compared to ASA3, there was no significant difference in the incidence of all complication rates. There were 159 (60.4%) patients in the young group and 104 (39.5%) patients in the elderly group. Postoperative PCNL complications of these 2 groups were compared according to Clavien classification system and no significant difference was found in incidence of complications. Conclusions: We believe that PCNL operation can be performed effectively and safely in both ASA3 patients and patients above the age of 65 years