An improvement of current driving and electrical conductivity properties in covetics

Compared to pure Cu, Cu lattice retaining carbon atoms, called a covetic material, can have better electrical conductivity. Furthermore, the incorporation of carbon nanostructures into Cu-alloys could improve the mechanical properties of Cu-alloys. In the simulation study, we investigated Joule heating due to applied DC current on molten Cu metal concerning how to improve current density of covetic materials. In addition, we will discuss interfacial effects on covetic-metal electrodes to meet better current driving performance. The covetic composite excited at one electrode (width = 10 nm) has a higher current drive capability as a value of 3.54 107 A/m2 , for 1000 A current at a temperature of 1073.2 K, this value is a constant while temperature is changing up to 1573.2 K. We measured the conductivity of the proposed covetic materials at various carbon nanotube densities at room temperature. Experimental results show the lowest resistivity value accomplished after mixing and temperature annealing as a value of 1.78 10−8 Ω.m, where the covetic sample has 1.27% carbon nanotube density, and that the electrical conductivity is superior to that of Cu-carbon nanotube composites previously report

Morfološka i kemijska varijabilnost plodova medvjeđe lijeske (Corylus colurna L.) na području Turske

AbstractTurkish hazel (Corylus colurna L.) is naturally distributed in southeast Europe, Anatolia, the Caucasus and Western Himalayas. In Turkey, there are many isolated populations in the Black Sea, Marmara, Aegean, and Central Anatolian Regions. Many of the small populations in Turkey are endangered. In this study, the morphological and chemical characteristics of Turkish hazelnut fruits collected from seven populations were researched. In this regard, considering the morphological characteristics of fruits and kernels, significant differences were observed between the populations. Length, width, thickness, and weight averages were 15.98 mm, 15.38 mm, 12.00 mm and 1.4651 g in the fruits, and 13.03 mm, 11.22 mm, 7.64 mm and 0.5047 g in the kernels, respectively. The average shell thickness was 1.92 mm, shell weight was 0.9604 g, and kernel ratio was 35.16%. Statistically significant differences were found out between the populations whose chemical contents were analyzed. As a result of the analysis, the average fat content, protein, starch, and ash were 64.1%, 15.9%, 10.2 g, and 2.5%, respectively. According to the averages in the obtained fatty acids, the main fatty acids were oleic acid (79.53%), linoleic acid (11.34%), palmitic acid (5.68%), and stearic acid (2.03%), while the rest of other oils were found in trace amounts. Overall, our results suggest that the information relating to morphological and chemical characteristics of Turkish hazelnut can be useful for discriminating among populations.SažetakMedvjeđa lijeska (Corylus colurna L.) prirodno je rasprostranjena u jugoistočnoj Europi, Anatoliji, Kavkazu i zapadnoj Himalaji. U Turskoj postoje mnoge izolirane populacije ove vrste u regijama Crnog mora, Mramornog mora, Egeja i središnje Anatolije. Mnoge male populacije medvjeđe lijeske u Turskoj su ugrožene. U ovoj studiji istraživana su morfološka i kemijska svojstva lješnjaka prikupljenih iz sedam populacija na području Turske. Provedenim istraživanjem utvrđene su statistički značajne razlike između populacija s obzirom na morfološke karakteristike plodova i sjemenki. Prosječne vrijednosti za dužinu, širinu, debljinu i masu plodova bile su 16,04 mm, 15,38 mm, 12,00 mm i 1,4650 g te za dužinu, širinu, debljinu i masu sjemenke 13,03 mm, 11,21 mm, 7,64 mm i 0,5047 g. Prosječna debljina ljuske bila je 1,91 mm, težina ljuske 0,9603 g, a omjer jezgre 34,64%. Utvrđene su statistički značajne razlike između populacija čiji je kemijski sastav analiziran. Kao rezultat analize, prosječni sadržaj masti, proteina, škroba i pepela iznosio je 64,1%, 15,9%, 10,2 g, odnosno 2,5%. Prema prosjeku u dobivenim masnim kiselinama, glavne masne kiseline bile su oleinska (79,53%), linolna (11,34%), palmitinska (5,68%) i stearinska kiselina (2,03%), dok su ostale masti bile pronađena u tragovima. Naši rezultati upućuju na to da se morfološke i kemijske karakteristike plodova medvjeđe lijeske mogu uspješno koristiti za razlikovanje populacija

Analysis of Cost and Schedule Variances in Construction Works with Artificial Intelligence Approaches: The Case of Turkey

Realistic estimation of construction cost is a vital issue for both successful planningand completion of every construction project. However, fluctuations in input prices due to the unexpected changes in factors like inflation and supply/demand balance make realistic costestimation very difficult to achieve. Thus, various estimation methods have been developedand these can be grouped as methods based on; statistics-probability analysis, comparison with similar projects and artificial intelligence techniques.Statistics-probability analysis is the most widely used method for construction costestimation in Turkey. Based on the so called method, Ministry of the Environment and Urbanism publishes and updates "Unit Costs of Construction" every year and the data is widely used for preliminary cost estimation by both the contractors and the developers.Meanwhile, methods based on artificial intelligence techniques are rarely used within the industry. Thus, the aim of this study has been to compare the estimation results obtained by using statistics-probability analysis and artificial intelligent techniques. In order to achieve this, construction cost data from 198 projects; completed between 2004-2010 in Izmir (the third largest city in Turkey) were used. Multi layer perceptron (MLP) and grid partitioning algorithm (GPA) were used to obtain estimation results and root mean square error (RMSE)and coefficient of determination (R2) were calculated for comparisons

The effect of DC voltage pre-stress on breakdown voltage of air under composite DC & LI voltage and test circuit: design and application

The use of HVDC systems is increasing in number due to technological innovations, increasing power capacity and increasing customer demand. The characteristics of insulation systems under composite DC and LI voltage must be examined and clarified. In this study, firstly, experimental circuits were designed to generate and measure composite DC and LI high voltage using a simulation program. The coupling elements used were chosen according to simulation results. Afterward, experimental circuits were established in the laboratory according to the simulation results of the designed experimental circuit. Then, breakdown voltages under composite DC and LI voltage for less uniform and non-uniform electric fields were measured with four different electrode systems for positive and negative DC voltage pre-stresses with different amplitudes. The 50% breakdown voltage was calculated using the least-squares method. Finally, 3D models were created for the electrode systems used in the experiments using the finite element method. The efficiency factors of electrode systems calculated with the FEM results were correlated with the experimental breakdown voltage results. Thus, the breakdown behavior of air under bipolar and unipolar composite voltages (CV) was investigated. In conclusion, the experimental results showed that very fast polarity change in bipolar CV causes higher electrical stress compared to unipolar CV

Investigation of impact of DC component on breakdown characteristics for different electric fields under composite AC & DC voltage

The valve side of the converter in the high-voltage direct current is subjected to mixed voltages such as composite AC & DC voltage. In this study, the effects of the homogeneity of electric field on breakdown voltage were investigated for different ±DC component amplitudes of the composite voltage. The field efficiency factor was calculated using mean and maximum field strengths for all of them. Variation of breakdown voltage of air was examined under the composite AC & DC voltage for different ratios ±DC. As one result of the study, the breakdown occurs at the positive half-wave of the AC voltage despite −DC voltage being applied due to positive corona discharge pulses. This breakdown point is named as the polarity change point. The breakdown voltage increases with the decrease of DC voltage component up to polarity change point in non-uniform electric field. In less uniform electric field, the AC breakdown voltage was measured slightly higher than the DC breakdown voltage. In less uniform electric field, as the ratio of the applied AC voltage to DC voltage increases, the breakdown voltage gradually approaches the AC breakdown voltage. This result is similar to the result obtained for the +DC component in non-uniform electric field experiments

Iatrogenic Mandibular Fracture Associated with Third Molar Removal

Third molar extraction is one of the most common procedures performed in oral and maxillofacial surgery units. It is sometimes accompanied by complications such as alveolar osteitis, secondary infection, hemorrhage, dysesthesia and, most severely, iatrogenic fracture. This article describes two mandibular angle fractures that occurred in two patients during the surgical extraction of one erupted and one unerupted third molar, including a brief review of the literature