Subharmonic resonance in a limit cycling voltage regulator

In practice, thyristor rectifiers are used as high current-low voltage power supplies. Under certain conditions such rectifiers introduce subharmonic resonances. In this paper, a limit cycling voltage regulator system is simulated in the digital computer. The reference voltage and load are varied and the system gain is changed for better understanding of their effects on the subharmonics. A Fourier analysis of the output wave shape then determined the existence and amplitude of subharmonic components.http://archive.org/details/subharmonicreson00guleLieutenant, Junior Grade, Turkish NavyApproved for public release; distribution is unlimited

A Comparison of the Effects of Extraction and Nonextraction Orthodontic Treatments on Cephalometric Parameters and Arch Widths

Objectives: To compare the effects of two different treatment approaches on cephalometric measurements and arch widths. Materials and Methods: The retrospective study evaluated pre- and post-treatment cephalometric radiograms and dental models of 45 patients with Class I malocclusions and moderate-severe dental tooth size arch length discrepancies that underwent extraction or nonextraction treatment between 2015 and 2020. Group I (n=22 [9 female, 13 male]; mean age, 18.0 ± 1.68 years) was treated with the Damon Q bracket system and Group II (n=23 [11 female, 12 male]; mean age, 17.9 ± 1.34 years) was treated with the conventional MBT bracket system. Pre- and post-treatment lateral cephalometric radiograms were obtained and arch widths were measured for each subject. Paired samples t-test was used to evaluate the treatment changes within each group. To compare the changes between groups, independent samples t-test was performed. Results: No significant change was detected in the sagittal and vertical skeletal parameters in both groups (p>0.05). The upper and lower incisors proclined significantly in Group I (p<0.01) and the mandibular incisors retroclined significantly in Group II (p<0.05). The lips protruded significantly and the upper lip thickness decreased significantly in Group I (p<0.01), whereas no significant difference was observed in Group II (p>0.05). All the transversal dimensions increased significantly in Group I (p<0.01), while only the intermolar distance decreased significantly in Group II (p<0.01). Conclusions: Both treatment methods provided significantly different outcomes with regard to soft tissue parameters and arch widths

Graft position in arthroscopic anterior cruciate ligament reconstruction: Anteromedial versus transtibial technique

Introduction: When treating anterior cruciate ligament (ACL) injuries, the position of the ACL graft plays a key role in regaining postoperative knee function and physiologic kinematics. In this study, we aimed to compare graft angle, graft position in tibial tunnel, and tibial and femoral tunnel positions in patients operated with anteromedial (AM) and transtibial (TT) methods to those of contralateral healthy knees. Materials and methods: Forty-eight patients who underwent arthroscopic ACL reconstruction with ipsilateral hamstring tendon autograft were included. Of these, 23 and 25 were treated by AM and TT techniques, respectively. MRI was performed at 18.4 and 19.7 months postoperatively in AM and TT groups. Graft angles, graft positions in the tibial tunnel and alignment of tibial and femoral tunnels were noted and compared in these two groups. The sagittal graft insertion tibia midpoint distance (SGON) has been used for evaluation of graft position in tunnel. Results: Sagittal ACL graft angles in operated and healthy knees of AM patients were 57.78° and 46.80° (p  0.05). Conclusions: Precise reconstruction on sagittal plane cannot be obtained with either AM or TT technique. However, AM technique is superior to TT technique in terms of anatomical graft positioning. Posterior-placed grafts in tibial tunnel prevent ACL reconstruction, although tibial tunnel is drilled on sagittal plane

Factor XIII Val34Leu polymorphism in patients with cardiac syndrome X

Background: The aim of the study was to examine the frequency of factor XIII polymorphism among patients with cardiac syndrome X (CSX).Methods: This study was designed as a cross-sectional and observational study. Forty-eight female patients with CSX and 36 controls matched by age, gender, diabetes, and hypertension were studied. CSX was defined as typical chest pain during rest or effort, abnormal test result for exercise ECG, and presence of angiographically normal epicardial coronary arteries after ruling out inducible spasm. Factor XIII gene polymorphism was investigated by using CVD Strip Assay (ViennaLab Diagnostic GmbH) commercial kit.Results: The frequency of factor XIII (Val/Leu + Leu/Leu) mutation was significantly higher in patients with CSX (43%) than in controls (19%) (p = 0.02). Frequency of the Leu allele was significantly higher in the patient group (23.5% vs. 11.1%, p = 0.04). Factor XIII (Val/Leu + Leu/Leu) mutation (p = 0.01, OR = 3.42; 95% CI 1.22–9.58) and smoking (p = 0.04, OR = 3.33, 95% CI 1.05–10.58) were identified as independent predictors of the disease in multivariate regression analysis.Conclusions: This study indicates that there is an evidence for association between factor XIII Val34Leu polymorphism and CSX

Evaluation of Antibiotic Alternatives Used in Orthopedic Departments of 2 Hospitals According to Rational Use of Antibiotics

Amaç: Birbirine yakın ve aynı bölgede yer alan iki farklı hastanenin ortopedi ve travmatoloji servislerinde yatan hastalarda, etkeni saptanan enfeksiyon olgularında antibiyotik kullanımının, akılcı ilaç tedavi rehberleri ve kültür antibiyogram sonuçlarına göre uygunluğunun araştırılması amaçlandı.Gereç ve Yöntem: Bu araştırma projesi T.C. Sağlık Bakanlığı Genel Sekreterlik İzni doğrultusunda 01 Ocak 2014 ile 31 Aralık 2014 tarihleri arasında, iki hastanenin ortopedi ve travmatoloji servislerinde enfeksiyon tanısına sahip olguların verileri üzerinden gerçekleştirildi. Malignitesi olan veya başka bir servise taburcu edilen olgular çalışmadan dışlandı. Standart bir form oluşturuldu. Bu form içerisine, olguların demografik verilerine ek olarak, kültür antibiyogram sonuçları, enfeksiyon patojen etkeni, kültür materyalinin nereden alındığı, kullanılan antibiyotiklerin pozolojisi, süresi ve uygunluğu ile olguların yatış süreleri raporlandı. Maliyetlerin hesaplanmasında, Sağlık Bakanlığı ve Maliye Bakanlığı 2014 yılı fiyat listeleri temel alındı. Birim fiyat üzerinden hasta başına kullanılan antibiyotik maliyetleri hesaplandı.Bulgular: Saptanan enfeksiyon etkeni için her zaman uygun antibiyotiğin seçilmediği belirlendi. Antibiyogram sonuçlarına göre etkili, daha düşük maliyetli antibiyotikler kullanılabilinmesine rağmen sıklıkla daha pahalı ve toplam maliyeti yükselten antibiyotikler seçilmiştir.Sonuç: Kanıta dayalı tıp ve akılcı antibiyotik kullanımı kapsamında enfeksiyon tedavisinde kültür antibiyogram sonuçlarına göre uygun antibiyotik seçilmesi gerekliliği tartışılmaz bir bilimsel gerçektir. Ortopedi ve travmatoloji servislerinde enfeksiyon tedavisinde enfeksiyon hastalıkları ve farmakoloji uzmanlarını da sürece katarak multi-disipliner yaklaşılarak kanıta dayalı rehberlerin kullanımının artışı sağlanmalıdırBackground: The present study is an analysis of appropriateness of antibiotics use for patients in whom infectious agent was detected. Data from patients in orthopedics and traumatology department of 2 hospitals in the same district were evaluated according to rational antibiotic drug use guidelines and culture antibiogram results.Methods: Data of patients diagnosed with infection between January 1, 2014 and December 31, 2015 in orthopedics and traumatology department of 2 different hospitals were analyzed. Patients diagnosed with malignancy or who were discharged from other departments were excluded. A standard form was used to collect demographic data, culture antibiogram results, details of infectious agent, source of culture material, posology of antibiotic used, duration and appropriateness of use, and length of hospital stay. Costs were estimated based on number of units used and price per unit according to 2014 Ministry of Health price list. Mean price of antibiotics used per patient was calculated and descriptive analyses were also completed.Results: It was determined that appropriate antibiotics for detected infectious agent were not always selected. Though there were effective, less expensive antibiotics that could have been used according to antibiogram results, more expensive antibiotics were often chosen, resulting in greater total cost.Conclusion: Multidisciplinary approach in patient care and use of evidence-based guidelines should be increased. Teams should be formed and led by infectious disease and pharmacology specialists. New strategies should be developed immediately in health economics and new pharmacoeconomic models should be initiated in orthopedics and traumatology department

Sternal abscess overlying giant aortic pseudoaneurysm developed after Bentall procedure Bentall prosedürü sonrası gelişmiş dev aortik pseudoanevrizma üzerine oturmuş sternal apse Olgu Sunumu

Abstract Aortic pseudoaneurysms are one of the most important complications to be encountered in cardiac surgery. Recently, the aortic pseudoaneurysms have been diagnosed by contrast enhanced computerized tomography. It has high specificity and sensitivity rates. Late postoperative sternal abscesses are rarely seen after open heart surgery. Thorax computerized tomography scan revealed abscess extending from subcutaneous tissue to the medullar component of sternum, overlying retrosternal giant aortic pseudoaneurysms. This article presents the case of a patient, who had undergone Bentall procedure three years ago due to type I aortic dissection and later presented in our cardiovascular surgery department with a sternal mass. Pam Med J 2013;6(1):33-36 Key words: Abscess; sternal wound infection; aortic pseudoaneurysm Özet Aortic pseudoanevrizmalar kalp cerrahisinde karşılaşılabilecek en önemli komplikasyonlardan biridir. Son zamanlarda aortic pseudoanevrizmalara kontrastlı bilgisayarlı tomografi ile tanı konmaktadır. Bu test oldukça yüksek özgüllük ve hassasiyet değerlerine sahiptir. Geç dönem sternal apseler açık kalp cerrahisinden sonra nadiren gözlenmektedirler. Bilgisayarlı toraks tomografisinde subkutanöz dokudan başlayıp sternum medullasına kadar uzanan absenin aortik retrosternal dev bir pseudoanevrizma üzerine oturduğu saptandı. Bu makalede; üç yıl önce tip I aortic diseksiyon nedeni ile Bentall ameliyatı olan ve daha sonra sternal kitle yakınmasıyla kalp damar cerrahisi kliniğimize müracaat eden hasta sunulmaktadır. Tıp Derg 2013;6(1):33-36 Pa

Closed-form solution of the two-dimensional sliding frictional contact problem for an orthotropic medium

The two-dimensional frictional contact problem of a rigid stamp sliding over an orthotropic medium is considered. The coordinate system is chosen such that it is aligned with the principal axes of orthotropy. It is parallel and perpendicular to the contact surface which is located along the x(1) axis. It is assumed that the condition of Coulomb friction prevails on the contact area. The two-dimensional half-plane problem is formulated using the Fourier integral transform method and the analytical formulation of the contact problem is reduced to a Cauchy-type singular integral equation of the second kind for the unknown contact pressure. The singular integral equation is solved analytically utilizing the Jacobi polynomials. With the application of the results to the crack initiation in an orthotropic medium in mind, the main emphasis in the study has been on the investigation of the singular nature of the stress state at either end of the flat stamp and on the determination of the contact stresses based on orthotropic material parameters. The present study provides the analytical solution of the contact stresses in terms of orthotropic material parameters, the coefficient of friction and the spatial coordinates. The strength of the singularities and the stress intensity factors at both ends of the stamp are also found in terms of the orthotropic material parameters and the coefficient of friction. This study reveals that orthotropic material parameters and the coefficient of friction have a great effect on the strength of stress singularities and distribution of the contact stresses. Adjusting these parameters will reduce these stresses that may have a bearing on the failure of the orthotropic medium. The results of this study will provide benchmark results for finite element analysts and stress engineers. (C) 2014 Elsevier Ltd. All rights reserved.Author is grateful for the support provided by the Fulbright Visiting Scholar Program Award during his visit to the Department of Aerospace and Mechanical Engineering of the University of Arizona

Design and Analysis of a Novel Power-Split Infinitely Variable Power Transmission System

In the last few decades, power-split infinitely variable transmission (IVT) systems have attracted considerable attention as they ensure high driving comfort with high total efficiencies, especially in off-highway vehicles and agricultural machines. In this study, a novel power-split-input-coupled IVT system is developed. The effects of various dynamic parameters such as power flow and Willis transmission ratio on the mechanical efficiency of the systems are investigated. Kinematic analysis of the new system has been carried out. In addition power flow equations are derived as functions of the power that flows through the infinitely variable unit (IVU). The results indicate that the main parameters, which are strictly related to mechanical efficiency are the power and torque flows through the IVU. © 2019 by ASME.This study is supported by TUBITAK (Scientific and Research Council of Turkey) under Grant no. 1150702 and by TurkTraktor R&D Department

On the advantages of the new power-split infinitely variable transmission over conventional mechanical transmissions based on fuel consumption analysis

The use of power-split infinitely variable transmissions (PS-IVT) in off-road vehicles and, in particular, in agricultural machinery has recently increased considerably thanks to the high driving comfort they provide and the variable transmission ratios facilitating agricultural operations. Conventional mechanical transmissions are also still in use due to their high mechanical efficiency and cost-effective structure. Although the efficiency of the PS-IVT is known to be lower than that of the conventional transmission, it can reduce fuel consumption by allowing the control of internal combustion engine in an optimum way by allowing the continuous transmission ratio. This study is intended to obtain lower fuel consumption values by employing PS-IVT as compared to the conventional transmission. In order to determine the fuel consumption values to be obtained by two different types of transmission, GPS data of a real tractor at real time from the real user in real world conditions were collected, and the driving resistances for the considered vehicle were determined with the longitudinal vehicle dynamics model. Dynamometer test and theoretical calculations based on the kinematic model developed in our earlier study were carried out to determine the mechanical efficiencies of the conventional transmission and the PS-IVT respectively. Fuel consumption values obtained using different types of transmissions were compared in terms of mass by using a BSFC map of a four-cylinder common-rail turbo diesel engine. Fuel consumption simulations were performed in MATLAB environment, and two different power management strategies with eight different scenarios were evaluated. It is found that a reduction of 8.2% in fuel consumption compared with the conventional transmission can be achieved by the proper power management strategy for the PS-IVT. (C) 2019 Elsevier Ltd. All rights reserved