ANN-Based Failure Modeling of T-56 Engine Turbines

The T-56 turboprop engine is one of the most widely used in military transportation aircraft. It operates virtually everywhere, from the arctic circle to the Sahara. Operation in desert conditions, however, presents a challenge for maintenance engineers regarding preventive maintenance scheduling. Erosion caused by sand particles drastically decreases turbine blades life. Recent studies showed that Artificial Neural Network ANN algorithms have much better capability at modeling reliability and predicting failure than conventional algorithms. In this study, more than thirty years of local operational field data were used for failure rate prediction and validation using several algorithms. These include Weibull regression modeling to establish a reference, feed-forward back-propagation ANN, and radial basis neural network algorithm. Comparison between the three methods is carried out. Results show that the failure rate predicted by both the feed-forward back-propagation artificial neural network model and radial basis neural network model are closer to actual failure data than the failure rate predicted by the Weibull model. The results also give an insight into the reliability of the engine turbine under actual operating conditions, which can be used by aircraft operators for assessing system and component failures and customizing the maintenance programs recommended by the manufacturer

Simulation of Transonic Compressor Performance Deterioration Due to Sand Erosion

Air sand erosion is a widely effecting phenomenon in GCC region, where a solid particle impacting on a wall surface causing catastrophic mechanical damage, the engine compressor operating in a particulate environment are subjected to deterioration of performance and life due to sand ingestion. In current paper we simulate and studied the sand erosion in such transonic compressors were flow rate, particle size and concentration were investigated to study particles distribution and erosion rate along the compressor blade. Result shows that particles concentration has the most significant effect on blade erosion rate where particles size has less effect among all other measured parameters. Surface deformation and roughness is in scope for further investigation

Clinical Characteristics of TMJD in a Kuwaiti Population

Poremećaji temporomandibularnih zglobova manifestiraju se znacima i simptomima koji ne zahvaćaju samo čeljusne zglobove nego i žvačnu muskulaturu i okolna tkiva. Najčešći znaci i simptomi jesu: bol u zglobovima i mišićima, poremećaji mandibularnih kretnji, zvučne senzacije, hipertrofija žvačnih mišića, glavobolja i vrtoglavica. Ranija su istraživanja pokazala da 70% stanovniπtva ima bar jedan znak ili simptom poremećaja temporomandibularnih zglobova. No to je klinički potvrđeno kod samo 38% slučajeva (Mc Neill 1993, Nouralach H et al 1998). U naše istraživanje uključili smo 144 pacijenta s poremećajima u području temporomandibularnih zglobova (102 žene i 42 muškarca). Pacijenti su bili podijeljeni u dvije skupine: lokalno stanovništvo (60,4%) i stranci (39,6%). Od ukupnoga broja pacijenata šezdeset četiri postotka žalilo se na smetnje pri otvaranju usta. No klinički je potvrđeno da takve smetnje ima samo 37,5% naših slučajeva. Zvučne senzacije bile su čest nalaz, koji je klinički potvrđen kao škljocanje u 88% slučajeva i kao krepoitacije u 11,2% pacijenata. Razmjerno mali broj pacijenata imao je bruksizam (12,5%), a artritis 11,1%. Mi smo također utvrdili da je glavobolja u oboljelih ispitanika bila čest klinički simptom (50,2%). Glavni znaci i simptomi poremećaja temporomandibularnih zglobova utvrđeni su u objema skupinama ispitanika. Žene su se češće žalile na bol u zglobu, zvučne senzacije i glavobolju nego muškarci. Lokalno stanovništvo je češće bolovalo od poremećaja temporomandibularnih zglobova nego stranci.Different signs and symptoms both in TMJ itself and masticator muscles and surrounding tissues clinically manifest temporomandibular joint disorders (TMJD). The most common signs and symptoms are muscles and joint pain, mandibular movement disturbance, sound sensations, masticator muscle hypertrophy, headache and dizziness. Previous investigations revealed that 70% of the population complain of having at least one of these signs and symptoms, of which 38% have been clinically proved (Mc Neill 1993, Nouralach H et al 1998). Patients and Methods: TMJD was investigated in 144 patients (female = 102, male = 42). Patients were devided into two groups: local inhabitants (60.4%) and expatriates (39.6%). Sixty-four and half percent (64.5%) of our patients complained of having mouth opening disturbance, which was clinically confirmed in only 37.5% of cases. Sound sensation was a very common sign, clinically confirned as a click in 88% and as crepitation in 11.2%. A relatively small number of patients had bruxism (12.5%), and arthritis (11.1%). We also found headache as a common clinical symptom (50.2%). The main common signs and symptoms of TMJD were positive in both local and expatriate inhabitants. Females suffered more frequently than males, complaining of pain, sound sensation and headache. Local inhabitants had more frequent TMJD

THE APPROACH TO THE ANALYSIS OF ELECTRICAL FIELD DISTRIBUTION IN THE SETUP OF PAPER INSULATED ELECTRODES IN OIL

Article presents the problem of the approach to the analysis of electrical field distribution in the model insulating system, which, in the author's experimental research, was used to the assessment of the influence of paper insulation on the mechanism of electrical discharge initiation in mineral oil. The main assumptions of the planned numerical works based on the finite element method were described and scientific aim of the numerical analysis were characterized in this paper. Both the assumptions and the scientific aim were related to the conclusions from the experimental works, especially to the measured times to initiation of the discharges developing in mineral transformer oil, indicating on the important role of the oil quality in the process of discharge initiation in the system of the insulated by paper electrodes immersed in oil

Measurement and ab initio Investigation of Structural, Electronic, Optical, and Mechanical Properties of Sputtered Aluminum Nitride Thin Films

We report our results on highly textured aluminum nitride (AlN) thin films deposited on glass substrates, oriented along the c-axis, using DC-magnetron sputtering technique for different values of back pressure. The structural, electronic, optical, piezoelectric, dielectric, and elastic properties of sputtered AlN thin films are measured and characterized. In particular, X-ray powder diffraction (XRD) technique shows that AlN thin films exhibit a hexagonal structure. Moreover, we employed ab initio simulations of AlN using the Vienna Ab Initio Simulation Package (VASP) to investigate the structural and the electronic properties of hexagonal AlN structures. The experimental lattice parameters of the as-prepared thin films agree well with those calculated using the total energy minimization approach. The optical parameters of AlN thin films, such as transmittance and refractive index, were measured using UV–vis measurements. Our measurements of refractive index, n, of AlN thin films yield a value of 2.2. Furthermore, the elastic, piezoelectric, and dielectric tensors of AlN crystal are calculated using VASP. The dynamical Born effective charge tensor is reported for all atoms in the unit cell of AlN. Interestingly, ab initio simulations indicate that AlN has a static dielectric constant approximately equal to 4.68, which is in good agreement with the reported experimental value. In addition, the clamped-ion piezoelectric tensor is calculated. The diagonal components of the piezoelectric tensor are found to be e33=1.79 C/m2 and e31=−0.80 C/m2. The large values of the piezoelectric coefficients show that a polar AlN crystal exhibits a strong microwave piezoelectric effect. Additionally, the components of the elastic moduli tensor are calculated. The extraordinary electronic, optical, piezoelectric, and elastic properties make AlN thin films potential candidates for several optoelectronic, elastic, dielectric, and piezoelectric applications

Solitary neurofibroma in the male breast

BACKGROUND: Neurofibroma of the male breast outside of neurofibromatosis is extremely rare with only one previous case having been reported. CASE PRESENTATION: A 48 year old male patient with a neurofibroma in the breast presenting with gynaecomastia is reported. Clinical and mammogram findings with fine needle aspiration cytology and full histology are presented. CONCLUSION: To our knowledge this is only the second case of a neurofibroma in a male breast in the English literature and the first report to include the mammographic findings

Angiomatoid giant cellular blue nevus of vaginal wall associated with pregnancy

<p>Abstract</p> <p>Background</p> <p>Blue nevi that arise from the Müllerian tract are rare melanocytic lesions. Several histopathologic variants of cellular blue nevi have been described. The angiomatoid variant is characterized by a vascular component, and is considered to be a rare variant. Few studies have explored the influence of pregnancy on melanocytic lesions.</p> <p>Case</p> <p>A 29-year-old woman was presented with a pigmented vaginal lesion that increased gradually during pregnancy. A full term gynecologic examination showed a tumor mass protruding into the vaginal canal. The mass was resected during cesarean-section under the clinical impression of vaginal hemangioma.</p> <p>Result</p> <p>Gross examination revealed a cystic mass measuring 6.0 × 4.3 × 3.5 cm, which was filled with dark friable material. Histologically, the mass showed a subepithelial cellular proliferation of heavily pigmented dendritic melanocytes with prominent vascular stroma. Cytologic pleomorphism, junctional activity, atypical mitosis, and necrosis were not found. The proliferation was immunoreactive for HMB-45, S-100 and melan-A, and non-immunoreactive for CD34, smooth muscle actin, and AE1/AE3. The MIB-1 proliferative index was less than 1%. The patient had a postoperative course without complication.</p> <p>Conclusions</p> <p>Angiomatoid giant cellular blue nevus arising from the vagina during pregnancy is extremely rare. The low proliferative index and absence of cytologic pleomorphism, or necrosis, supports a benign biological behavior. Clinical follow-up showed no evidence of recurrence at one year after the resection of the mass.</p