Harmonic Effects on Electromechanical Overcurrent Relays

Elektromekanik aşırı akım koruma röleleri sinüsoidal akım altında çalışmak üzere tasarlanmıştır. Bu rölelerin harmonikli akımda çalışmaları güvenilir değildir. Literatürde harmonikler ve rölelerle ilgili pek çok teorik çalışma bulunmaktadır. Bu makalede, harmoniklerin elektromekanik ters zamanlı aşırı akım rölesinin (TZAAR) çalışmasına etkileri incelenmiş ve TZAAR’nin bozulmuş dalga şekilleri için davranışı deneysel çalışma ile analiz edilmiştir. Deneyde, elektromekanik TZAAR olarak, indüksiyon disk yapısında bir röle kullanılmıştır. Değişik harmonik spektrumlara sahip, sinüsoidal olmayan yük akımları TZAAR’a uygulanmış ve bu yük akımları data toplama kartı ve harmonik analiz programı ile bilgisayar ortamında işlenmiştir. Deney sonuçları gözönüne alındığında, TZAAR’ın çalışma akımı ve çalışma zamanının, sinüsoidal olmayan akımın toplam harmonik distorsiyonu (THD) ile orantılı olarak arttığı görülmüştür. Bu yapıda olan bir rolenin, akımın harmonik içermesi durumunda sistemi güvenli bir şekilde koruyamayacağı sonucu elde edilmiştir.The electromechanical overcurrent protection relays are designed to operate with sinusoidal current. The operation of protective relay with harmonic currents is not reliable. The literature on harmonics and relays covers mostly the theoretical studies. In this paper, the harmonic effects on operation of electromechanical inverse time overcurrent relay (ITOCR) were examined. Not common in existing studies, the behaviour of ITOCR was analysed with laboratory experiments for distorted waveforms. A type of induction disc relay was used as an electromechanical ITOCR in the experiments. The non-sinusoidal load currents that consist of different harmonic spectra were applied to ITOCR and these nonlinear-load currents were processed by a data acquisition card and a harmonic analysis programme in the computer environment. According to the experiment results, the pick up current and the operating time of the ITOCR increase proportionally to the total harmonic distortion (THD) value of the non-sinusoidal current. It is concluded that, this type of relay cannot protect the system reliably due to the harmonic components of current

Bulanık Kazanç Ayarlamalı Nonlineer Pı Kontrolörün Kalıcı Mıknatıslı Doğru Akım Motor - Dinamo Sistemine Uygulanması

This paper describes the realization of a fuzzy gain scheduling scheme of a PI controller using a RISC microcontroller. Fuzzy rules and reasoning are utilised on-line to determine the PI controller parameters based on the error signal and its first difference. The Fuzzy control algorithm is implemented in the RISC microcontroller to regulate the speed of a permanent magnet DC motor (PMDC) and works on-line. The microcontroller directly tunes the motor speed with a chopper converter which changes the motor terminal voltage. Application results demonstrate that better control performance can be achieved in comparison with traditional PI controllers.Bu makalede bulanık olarak kazancı ayarlanabilen PI kontrolör yapısı, RISC mimariye sahip bir mikrokontrolör ile gerçekleştirilmiştir. Bulanık kural yapısı ve bulanık işlemler, hata ve türevinin değişimini baz alarak, PI kontrolörün oran ve integral kazançlarını on-line olarak ayarlamaktadır. Bulanık-PI kontrol algoritması, kalıcı mıknatıslı doğru akım motorunun (KMDA) hızını kontrol etmek amacıyla RISC bir mikrokontrolör içerisinde on-line olarak çalıştırılmaktadır. Mikrokontrolör motorun hızını, endüvisine uygulanan gerilimi bir doğru akım kıyıcısı vasıtasıyla değiştirerek ayarlamaktadır. Uygulama sonuçları gözönüne alındığında, hazırlanan kontrolörün PI kontrolör ile karşılaştırılması sonucunda daha iyi bir kontrol performansı yakaladığı görülmüştür

Volumetric upper airway changes after rapid maxillary expansion: a systematic review and meta-analysis

BACKGROUND Although Rapid Maxillary Expansion (RME) has been used for over a century, its effect on upper airways has not yet adequately been assessed in an evidence-based manner. OBJECTIVE To investigate the volumetric changes in the upper airway spaces following RME in growing subjects by means of acoustic rhinometry, three-dimensional radiography and digital photogrammetry. SEARCH METHODS Literature search of electronic databases and additional manual searches up to February 2016. SELECTION CRITERIA Randomized clinical trials, prospective or retrospective controlled clinical trials and cohort clinical studies of at least eight patients, where the RME appliance was left in place for retention, and a maximum follow-up of 8 months post-expansion. DATA COLLECTION AND ANALYSIS After duplicate data extraction and assessment of the risk of bias, the mean differences and 95 per cent confidence intervals (CIs) of upper airway volume changes were calculated with random-effects meta-analyses, followed by subgroup analyses, meta-regressions, and sensitivity analyses. RESULTS Twenty studies were eligible for qualitative synthesis, of which 17 (3 controlled clinical studies and 14 cohort studies) were used in quantitative analysis. As far as total airway volume is concerned patients treated with RME showed a significant increase post-expansion (5 studies; increase from baseline: 1218.3mm(3); 95 per cent CI: 702.0 to 1734.6mm(3)), which did not seem to considerably diminish after the retention period (11 studies; increase from baseline: 1143.9mm(3); 95 per cent CI: 696.9 to 1590.9mm(3)). LIMITATIONS However, the overall quality of evidence was judged as very low, due to methodological limitations of the included studies, absence of untreated control groups, and inconsistency among studies. CONCLUSIONS RME seems to be associated with an increase in the nasal cavity volume in the short and in the long term. However, additional well-conducted prospective controlled clinical studies are needed to confirm the present findings. REGISTRATION None. FUNDING Australian Society of Orthodontics Foundation for Research and Education Inc

The effects of a clinically feasible application of low-level laser therapy on the rate of orthodontic tooth movement: A triple-blind, split-mouth, randomized controlled trial

INTRODUCTION This split-mouth trial aimed to investigate the effect of low-level laser therapy (LLLT) on the amount of maxillary canine distalization when applied every 4 weeks over 12 weeks. METHODS Twenty-two adolescents and young adults (15 female, 7 male; aged 13-25 years; n = 22) requiring bilateral maxillary first premolar extractions were recruited. After extractions and leveling-alignment, canines were retracted using closed-coil nickel-titanium springs delivering 150 g of force. LLLT was applied to 8 intraoral points on the buccal and palatal sides around the canine root for 10 seconds per point, on day 0, 28, and 56 with the control side receiving sham application. Alginate impressions were taken every 4 weeks on day 0, 28, 56, and 84. The amount of tooth movement, anchorage loss, and canine rotation were measured digitally. Randomization was generated using www.randomisation.com and allocation concealment through sequentially numbered, opaque, sealed envelopes. Participants, operator, and statistic assessor were blinded. Linear regression modeling accounting for clustering within each patient was used to identify differences between LLLT and control sides. RESULTS Twenty-one patients completed the study. The total amount of tooth movement was similar in the LLLT (2.55 ± 0.73 mm) and control group (2.30 ± 0.86 mm), whereas 0.25 mm (95% confidence interval, -0.21, 0.71 mm) of difference was insignificant (P = 0.27). No significant differences were found for anchorage loss (P = 0.22) or canine rotation (P = 0.25). No harms were reported. CONCLUSIONS Application of LLLT every 4 weeks did not result in differences in the amount of tooth movement, anchorage loss, and canine rotation during extraction space closure

The upper airway volume effects produced by Hyrax, Hybrid-Hyrax, and Keles keyless expanders: a single-centre randomized controlled trial

OBJECTIVE To assess upper airway volume changes after rapid maxillary expansion (RME) with three different expanders. TRIAL DESIGN Three-arm parallel randomized clinical trial. METHODS Sixty-six patients, 10-16 years old, in permanent dentition, with maxillary transverse deficiency were recruited and assigned with block randomization (1:1:1 ratio) and allocation concealment to three groups of 22 patients each (Hyrax, Hybrid-Hyrax, and Keles keyless expander). The primary outcome (overall upper airway volume change) and secondary outcomes (volume changes in the nasal cavity, nasopharynx, oropharynx, and hypopharynx) were blindly assessed on the initial (T0) and final (T1, 6 months at appliance removal) cone beam computed tomography. Differences across groups were assessed with crude or adjusted for confounders (gender, age, growth stage, skeletal pattern, baseline airway volume, and amount of expansion) linear regression models. RESULTS Fifty-one patients were analysed (19, 19, and 13 in the Hyrax, Hybrid-Hyrax, and Keles groups). Maxillary expansion resulted in considerable increases in total airway volume in the Hybrid-Hyrax group (+5902.1 mm3) and less in the Hyrax group (+2537.9 mm3) or the Keles group (+3001.4 mm3). However, treatment-induced changes for the primary and all secondary outcomes were of small magnitude and no significant difference was seen among the three expanderes in the total airway volume in either crude or adjusted analyses (P > 0.05 in all instances). Finally, among pre-peak patients (CVM 1-3), the Hybrid-Hyrax expander was associated with significantly greater increases in total airway volume compared to the Hyrax expander (P = 0.02). CONCLUSIONS RME resulted in relatively small increases in total upper airway volume and its separate compartments, with mostly no statistically significant differences across the Hyrax, Hybrid-Hyrax, and Keles groups. LIMITATIONS Significantly greater attrition was found in the Keles group due to appliance failure. The current trial might possibly be under-powered to detect differences between groups, if such exist. HARMS Keles expanders blocked during activations and required substitution for completion of treatment. PROTOCOL The protocol was not published before trial commencement. REGISTRATION Australian and New Zealand Clinical Trial Registry (ACTRN12617001136392)

Hemobilia as a result of right hepatic artery pseudoaneurysm rupture: An unusual complication of laparoscopic cholecystectomy

INTRODUCTION Laparoscopic cholecystectomy has many complications which may be seen due to anatomical variations, lack of experience of the surgeon or three dimensional visualization, or insufficient exposure of the surgical field; including vascular injuries. Here we present a case of pseudoaneurysm of the right hepatic artery leading to hemobilia after rupturing into the biliary system. PRESENTATION OF CASE A 43-year-old male patient presented to our clinic 3 weeks post laparoscopic cholecystectomy with right upper quadrant pain, melena and hematemesis. After stabilizing the patient, Doppler ultrasonography, abdominal computer tomography and selective right hepatic artery angiography were performed and a pseudoaneurysm was established on the anterior posterior bifurcation of right hepatic artery. Right hepatic artery ligation and a T-tube placement after choledocotomy were performed. The patient recovered completely. DISCUSSION Pseudoaneurysms of the hepatic artery may arise as a complication of laparoscopic cholecystectomy. Clip encroachments, mechanical or thermal injury during the procedure are likely to be precipitating factors. Today, transarterial embolization (TAE) is the gold standard for the management of hemobilia, and if it fails, the next step in management is surgical. Surgery is limited to extra-hepatic or gallbladder bleeding, and for TAE failure. CONCLUSION In cases of GI bleeding the awareness of the surgeon should be drawn to a clinical suspicion of hemobilia and an underlying hepatic artery pseudoaneurysm that can arise as a complication. CT angiography should be performed for early diagnosis and management in such patients. © 2014 The Authors

Trauma-related giant Spigelian hernia: A case report

Spigelian hernia is a rare entity and includes 0.1-2% of all abdominal wall hernias. Trauma is a rare cause of SH. To our knowledge, there are only five cases of trauma-related Spigelian hernia that have been reported in the literature. The current study reports a case of the largest spigelian hernia with trauma-related and adds the sixth case to the literature. The physical examination and imaging findings is supported spigelian hernia. A hernia sac of approximately 27 x 18 cm was identified. The hernia sac was opened, and it was observed that the hernia sac contained the omentum, small intestines and the sigmoid colon. The defect extended from the left lumbal region to the left inguinal area up to the pubic bone. The maximum size of the abdominal defect was 13 x 17 cm. For abdominal defect repair, a 30 x 30 cm monofilamented polypropylene mesh (sublay) was placed submuscularly beneath the fascia. Post-operative period was uneventful. Trauma constitutes an etiological factor in the formation of spigelian hernia. We believe that standardization criteria is necessary for the term giant spigelian hernia, so this will provide the more accurate results

Antiviral Combination Therapy with Low-Dose Hepatitis B Immunoglobulin for the Prevention of Hepatitis B Virus Recurrence in Liver Transplant Recipients: A Single-Center Experience

PubMedID: 26093739Objectives This study presents the overall long-term hepatitis B virus (HBV) recurrence rate with possible associated factors after hepatitis B immunoglobulin (HBIG) was given in combination with 4 different antiviral (lamivudine, adefovir, entecavir, and tenofovir) drugs. Patients and Methods Between September 2000 and October 2013, the medical records of 42 adult patients who underwent liver transplantation at the Cukurova University Medical Hospital for chronic liver failure or hepatocellular carcinoma (HCC) secondary to chronic HBV were reviewed retrospectively. The analyses of risk factors for recurrence were performed based on the efficacy of hepatitis B envelope antigen (HBeAg), hepatitis B core antibody (anti-HBc), HBV DNA, preoperative prophylaxis, and the presence of HCC. Posttransplantation HBV recurrence was defined as persistence of hepatitis B surface antigen (HBsAg) positivity after orthotopic liver transplantation, or the reappearance of HBsAg and HBV DNA after initial HBsAg undetectability despite prophylaxis. Results The mean follow-up of 28 patients having HBIG and lamivudine prophylaxis was 73.25 ± 37.5 months with a recurrence rate of 3.5%. The mean follow-up of 2 patients having HBIG and adefovir prophylaxis was 90 ± 46.6 months with a 50% recurrence rate. The mean follow-up of each 6 patients who received prophylaxis with entecavir and tenofovir groups were 27.5 ± 16.1 and 16.17 ± 5.3 respectively, with no posttransplantation recurrence for both groups. On univariate analysis, preoperative factors such as anti-HBc, HBV DNA, preoperative prophylaxis, and the presence of HCC did not show any correlation with recurrence. However, HBeAg showed statistical significance for recurrence. Conclusions Low-dose HBIG in combination with antiviral agents (lamivudine, entecavir, and tenofovir) is efficacious in preventing recurrence of HBV in posttransplantation patients. © 2015 Elsevier Inc. All rights reserved