Single phase Unified Power Flow Controller (UPFC) : simulation and construction.

Unified Power Flow Controller (UPFC) is used to control the power flow in the transmission systems by controlling the impedance, voltage magnitude and phase angle. This controller offers advantages in terms of static and dynamic operation of the power system. It also brings in new challenges in power electronics and power system design. The basic structure of the UPFC consists of two voltage source inverter (VSI); where one converter is connected in parallel to the transmission line while the other is in series with the transmission line. The main scope of this paper involves the designing of a single phase UPFC using Matlab and Simulink software, and constructing a lab scale model of the UPFC. A microcontroller program has been developed to provide the required phase shift. The experimental result which has been obtained from a lab scale system showed a good agreement with the simulation result

Functional Biomimetic Dental Restoration

Bioinspired functionally graded approach is an innovative material technology, which has rapidly progressed both in terms of materials processing and computational modeling in recent years. Bioinspired functionally graded structure allows the integration of dissimilar materials without formation of severe internal stress and combines diverse properties into a single material system. It is a remarkable example of nature’s ability to engineer functionally graded dental prostheses. Therefore, this novel technology is designed to improve the performance of the materials in medical and dental fields. Thus, this chapter book reviews the current status of the functionally graded dental prostheses and biomimetic process inspired by the human bone, enamel and dentin-enamel junction (DEJ) structures and the linear gradation in Young’s modulus of the human bone, enamel and dentin-enamel junction, as a new material design approach, to improve the performance compared to traditional dental prostheses. Notable research is highlighted regarding application of biomimetic prostheses into various fields in dentistry. The current chapter book will open a new avenue for recent researches aimed at the further development of new dental prostheses for improving their clinical durability

Niveles de percepción y confianza entre estudiantes de odontología y pasantes en la realización de diversos procedimientos de endodoncia.

Aim: The present study aimed to collect information from senior students and new interns enrolled at the College of Dentistry, University of Science and Technology (UST), regarding their confidence levels in performing endodontic treatments. Materials and Methods: Anonymous surveys were distributed to 40 senior students and 37 new interns at UST, in Sana'a, Yemen. They were asked to indicate their self-confidence level using a Likert scoring system ranging from 1 and 5. Mann-Whitney U test and chi-squared test were used to determine statistical significance between the studied groups. Results: 37.5% of students and 35.1% of interns rated endodontic practice as difficult. Only 55% of students found that the number of treated cases were satisfactory, similar to that reported by interns (56.8%). There were no statistically significant differences between both groups regarding self-confidence levels for most endodontic procedures (p<0.05). Placing of a rubber dam, followed by managing inter-appointment flare-ups were procedures in which both groups reported the lowest confidence. On the other hand, both groups felt the lowest confidence in the treatment of maxillary followed by mandibular molars. Statistically significant differences were reported between the two groups for performing root canal treatments (RCT) (p< 0.05). Self-confidence levels on the management of most different indications showed no statistically significant differences between both groups (p>0.05) with exception to the management of irreversible pulpitis, necrotic pulp, asymptomatic apical periodontitis, chronic abscess, and traumatic cases, in which significant differences were noticed (p<0.05). Immature apices, root resorption, endodontic-periodontal (EP) lesions, trauma, symptomatic apical periodontitis and acute abscess were ranked as the cases in which both groups reported the lowest confidence. Canal blockage and ledge formation were the main mishaps encountered during practice among students and interns. Conclusion: Students and interns displayed neutral confidence in performing endodontic treatments.Objetivo: El presente estudio tuvo como objetivo recopilar información de estudiantes de último año y nuevos pasantes inscritos en la Facultad de Odontología, Universidad de Ciencia y Tecnología (UST), con respecto a sus niveles de confianza en la realización de tratamientos de endodoncia. Materiales y métodos: se distribuyeron encuestas anónimas a 40 estudiantes de último año y 37 nuevos pasantes en UST, en Sana'a, Yemen. Se les pidió que indicaran su nivel de confianza en sí mismos utilizando un sistema de puntuación Likert que oscilaba entre 1 y 5. Se utilizaron la prueba U de Mann-Whitney y la prueba de ji al cuadrado para determinar la significación estadística entre los grupos estudiados. Resultados: el 37.5% de los estudiantes y el 35.1% de los pasantes calificaron la práctica de endodoncia como difícil. Solo el 55% de los estudiantes encontró que el número de casos tratados fue satisfactorio, similar al reportado por los pasantes (56.8%). No hubo diferencias estadísticamente significativas entre ambos grupos con respecto a los niveles de autoconfianza para la mayoría de los procedimientos de endodoncia (p<0.05). La colocación de una presa de goma, seguida de la gestión de brotes entre citas, fueron procedimientos en los que ambos grupos informaron la menor confianza. Por otro lado, ambos grupos sintieron la menor confianza en el tratamiento del maxilar seguido de los molares mandibulares. Se informaron diferencias estadísticamente significativas entre los dos grupos para realizar tratamientos de conducto radicular (ECA) (p<0.05). Los niveles de autoconfianza en el manejo de la mayoría de las indicaciones diferentes no mostraron diferencias estadísticamente significativas entre ambos grupos (p>0.05) con excepción del manejo de pulpitis irreversible, pulpa necrótica, periodontitis apical asintomática, absceso crónico y casos traumáticos, en los cuales se notaron diferencias (p<0.05). Los ápices inmaduros, la reabsorción radicular, las lesiones endodóncicas-periodontales (EP), los traumatismos, la periodontitis apical sintomática y el absceso agudo se clasificaron como los casos en que ambos grupos informaron la menor confianza. El bloqueo del canal y la formación de repisas fueron los principales percances encontrados durante la práctica entre estudiantes y pasantes. Conclusión: los estudiantes y los pasantes mostraron una confianza neutral en la realización de tratamientos de endodoncia

Voltage regulation of uninterrupted power supplies

Uninterrupted Power Supply (UPS) systems are used as one solution of power quality problems and to provide ultimate protection for power disturbances such as power blackouts and brownouts. Many UPS systems suffer from poor output voltage regulation especially with heavy loads. This work is aimed to design and implement the UPS hardware system capable of producing continuous and constant 230Vac, 50 Hz output supply. A feedback loop has been implemented using microcontroller to adjust the dc level supplying the UPS inverter. At the end of the hardware implementation, tests have been carried out to determine the reliability and effectiveness of the designed system, and a good results have been obtained in improving the voltage regulation

Application of inverter based shunt device for voltage sag mitigation due to starting of an induction motor load

This paper shows a study of the static synchronous compensator (STATCOM) behaviors for voltage sag mitigation to an induction motor. The proposed of STATCOM stability model is justified based on the basic operation characteristics of phase control strategies. The simulation of 6 pulses STATCOM based on voltage source inverter (VSI) using Matlab Simulink is presented to show its good performance under balanced voltage sag condition due to the motor starting. Experimental testing has been made by using thyristor firing board control (FS36M). The STATCOM response of compensated reactive power to the system during voltage sag has been shown. Finally simulation results and experimental results have been described and compared once and good performance has been obtained

Tensile stress distribution in maxillary central incisors restored with cast-made and prefabricated dental posts.

Abstract: Aim: To analyze and compare the tensile stress distribution in endodontically treated teeth restored with cast-made (Ni-Cr and gold) and prefabricated (titanium and glass fibre) dental posts. Methodology: Four three-dimensional finite element (FE) models of a maxillary central incisor restored with Ni-Cr cast-made (Model Ni-Cr), gold cast-made (Model GO), prefabricated titanium (Model TI) and prefabricated glass fibre (Model FP) posts were constructed. An oblique loading of 100N was applied to each three-dimensional model. Tensile stress distribution within the root dentine and at the post and surrounding structure interfaces were analysed. Results: In all the FE models studied, a higher magnitude of tensile stresses was observed on the palatal aspect of the cervical dentin as compared to the labial aspect and progressively decreases from the outer to the inner part of the root. The gold cast-made and glass fibre post models showed significantly less tensile stress concentration in the post-core component than the other experimental models. The maximum tensile stress was seen on the palatal aspect of the Ni-Cr compared to other posts. The higher magnitude interfacial tensile stress concentration was observed in a pulpless tooth restored with a Ni-Cr cast-made post, followed by titanium and gold cast-made posts, respectively. However, the minimum interfacial tensile stress was noticed in a pulpless tooth restored with a glass fibre post. Conclusion: Glass fibre posts tend to transfer tensile stress more homogenously within the tooth and at interfaces than the other types of investigated posts

The relationship of the parotid duct to the buccal and zygomatic branches of the facial nerve; an anatomical study with parameters of clinical interest

There have been studies concerning the protection of the facial nerve during plastic surgery intended for the parotid gland. The close relationship between the parotid duct and the buccal and zygomatic branches of the facial nerve is studied here. The dissections were performed on 10 fixed cadavers at the Anatomy Dissection Laboratory of Ankara University in 2004. The reference points used for surgery of this region were taken into consideration as the landmarks for morphometric measurements. In 7 of the cases the zygomatic branch was double and in 3 it was single. In 4 of the 7 cases with a double zygomatic branch both superior and inferior branches crossed the parotid duct. In the remaining 3 cases the superior branches of the zygomatic nerve coursed through the zygomatic major and minor muscles. In 9 of all the cases the zygomatic branch of the facial nerve crossed the duct anteriorly and in one it did so posteriorly (case 10). The buccal branch was single in 4 of the cases and double in 6. Among these one of the most precise measurements was the distance between the lateral canthus and the intersection point of the zygomatic branch and the duct with a coefficient of variation of 9.9%. With the use of this reliable measurement the intersection point of the zygomatic branch and the duct may be estimated to be within 5.16 ± 1.01 centimetres of the lateral canthus. Facial nerve paralysis is the most important complication of superficial face surgery and the anatomy of this region must thus be taken into detailed consideration by surgeons

Antimicrobial Activity Of Neem (Azadirachta Indica A. Juss) Leaf Extracts Against Snakehead Fish (Channa Striata) Common Pathogens Aeromonas Hydrophila, Streptococcus Agalactiae, And Staphylococcus Xylosus

The present study describes the potential of neem leaf (Azadirachta indica) extracts to control common bacterial fish pathogens under in-vitro and in-vivo conditions. The first experiment was conducted to assess the antimicrobial activity and minimum inhibitory concentrations of three crude extracts of neem (acetone, methyl alcohol and water), against three common fish pathogens Aeromonas hydrophila, Streptococcus agalactiae and Staphylococcus xylosus. Using well-diffusion methods invitro, the acetone extracts showed activity against all the tested bacteria with zones of inhibition at 13.25, 18.75 and 13.75 mg/ml respectively, while the methyl alcohol and water extracts showed activity only against A. hydrophila. Under in-vitro conditions, minimum inhibitory concentration determinations were conducted using a microdilution method. The acetone and methyl alcohol extracts showed the lowest MIC values, 0.078 and 0.156 mg/ml against S. agalactiae, respectively. A second experiment was conducted to evaluate the biological activities of the three crude extracts, using a brine shrimp (Artemia nauplii) toxicity bioassay. Among the three tested crude extracts, the water extracts showed the lowest toxicity, with LC50 values of 6.41 mg/ml within 24 hours. In the third experiment, the results of qualitative preliminary phytochemical screening of the non-toxic extract showed the presence of Flavonoids and Tannins