Optimization of Key Techniques for Maintaining Bus Voltage Stability in Variable Speed Turbine of Ventilator / 中国医疗器械杂志

OBJECTIVE@#To explore the optimization scheme of maintaining bus voltage stability during turbo-turbine acceleration and deceleration of ventilator.@*METHODS@#The ideal diode is used to replace the diode in the busbar power supply circuit, and a comparative discharge circuit is added to the busbar. When the busbar voltage is higher than the preset threshold, the comparator can be opened and the energy could be discharged through the power resistor.@*RESULTS@#When the turbine starts and stops rapidly, the optimized scheme can effectively reduce the bus impedance, and the discharge circuit can maintain the bus voltage fluctuation less than 2 V.@*CONCLUSIONS@#The optimization scheme proposed in this study can effectively improve the efficiency and stability of the turbine in the process of acceleration and braking, and provide reference for the design of the stability maintenance circuit of the ventilator turbine bus.

Influencia del tallado en la lisura superficial del esmalte / The influence of carving on surface smoothness of enamel

Al momento de realizar una preparación dental existen diferentes alternativas. Dentro del instrumental rotatorio hay dos opciones: la turbina dental (ultra-velocidad) y el micromotor acoplado a un contra-ángulo multiplicador (alta velocidad). El propósito de este estudio fue evaluar cualitativamente la diferencia en la lisura superficial sobre esmalte, que se genera al desgastarlo, utilizando para esto, una turbina dental y un micromotor eléctrico acoplado a un contra-ángulo multiplicador 1:5 (anillo rojo). Se realizó un análisis cualitativo sobre una muestra de 24 superficies de esmalte obtenidas de 12 premolares extraídos por indicación ortodóntica, los cuales fueron preparados y observados al microscopio óptico. Luego de observar las 24 superficies al microscopio se pudo constatar una mayor lisura superficial sobre el esmalte al utilizar micromotor eléctrico acoplado a contraángulo multiplicador en comparación con turbina (AU)

Revisión de los perfiles aerodinámicos apropiados para turbinas eólicas de eje horizontal y de pequeña escala en zonas boscosas / A review of horizontal axis small wind turbine blades suitable for wooded areas / Revisão dos perfis aerodinâmicos apropriados para turbinas eólicas de eixo horizontal e pequena escala nas zonas arborizadas

Resumen Introducción: la energía eólica ha crecido de forma acelerada en los últimos 20 años y los sitios para instalar parques eólicos se empiezan a agotar. Las turbinas eólicas de pequeña escala representan una alternativa viable, en particular en zonas boscosas: de bajo potencial eólico y alta turbulencia. Objetivo: presentar una revisión de los perfiles aerodinámicos para aerogeneradores de pequeña escala, para determinar su posible aplicación en zonas boscosas. Materiales y métodos: se efectúa una revisión literaria en las bases de datos Web of Science y Scopus, sobre turbinas eólicas de pequeña escala de eje horizontal, en las revistas Energy, Journal of Wind Engineering and Industrial Aerodynamics, Renewable and Sustainable Energy Reviews y Renewable Energy, entre otras. Se define una clasificación de tres grandes grupos para los perfiles aerodinámicos: de uso muy frecuente, de uso con frecuencia media y de uso con baja frecuencia. Resultados: los perfiles de uso muy frecuente son el SG6043, S809 y NACA0012, siendo el primero de ellos el que presenta mejor desempeño aerodinámico. A pesar de esto, otros perfiles como el SH3055 son ampliamente usados en turbinas eólicas de pequeña escala. Conclusiones: un perfil adecuado para una turbina eólica de pequeña escala para zonas boscosas debe ser diseñado para regulación por pérdida (stall) y poseer una alta robustez ante cambios de rugosidad superficial. El perfil con mayor potencial, según la literatura para esta aplicación, es el SG6043, siendo 110 % y 85 % más eficiente que NACA0012 y S809, respectivamente, para un Re de 2 x 105; empero, se requiere más investigación en temas como desempeño aerodinámico de los perfiles ante altos niveles de turbulencia.

Abstract Introduction: Wind energy has grown rapidly in the last 20 years and sites to install full-scale wind farms are starting to run out. Small-scale wind turbines represent a feasible alternative, particularly in forested areas of low wind potential and high turbulence. Objective: to present a review of the aerodynamic profiles for small-scale wind turbines, to determine their possible application in wooded areas. Materials and methods: a review of small-scale horizontal axis wind turbines is carried out using the Web of Science and Scopus databases mainly on the journals: Energy, Wind Engineering and Industrial Aerodynamics, Renewable and Sustainable Energy Reviews, and Renewable Energy. A classification of three large groups is defined for the aerodynamic profiles: very frequent use, medium frequency use and low frequency use. Results: the profiles of very frequent use are the SG6043, S809 and NACA0012, the first of them is the one having the best aerodynamic performance. Despite this, other profiles such as the SH3055 are widely used in the small-scale wind turbine field. Conclusions: a suitable profile for a small-scale wind turbine for forested areas should be designed for stall regulation and have low sensitivity against changes in surface roughness. The profile with the greatest potential, according to the literature for this application, is the SG6043, being 110 % y 85 % more efficient than NACA0012 and S809, respectively, for a Re of 2 x 105; however, more research is required on issues such as aerodynamic performance of the profiles at high levels of turbulence.

Resumo Introdução: a energia eólica há crescido de forma acelerada nos últimos 20 anos e os sítios para instalar parques eólicos empeçam a diminuir. As turbinas eólicas de pequena escala representam uma alternativa viável, em particular nas zonas arborizadas: de baixo potencial eólico e alta turbulência. Objetivo: apresentar uma revisão dos perfis aerodinâmicos para aerogeradores de pequena escala, para determinar uma possível aplicação nas zonas arborizadas. Materiais e métodos: efetuou-se uma revisão literária nas bases de dados Web of Science e Scopus, sobre turbinas eólicas de pequena escala de eixo horizontal, nos jornais Energy, Journal of Wind Engineering and Industrial Aerodynamics, Renewable and Sustainable Energy Reviews e Renewable Energy, entre outras. Define-se uma classificação dos três grandes grupos para os perfis aerodinâmicos: de uso muito frequente, de uso com frequência meia e de uso com baixa frequência. Resultados: os perfis de uso muito frequente são o SG6043, S809 y NACA0012, sendo o primeiro deles o que apresenta melhor desempenho aerodinâmico. Apesar disso, os perfis como o SH3055 são amplamente usados nos negócios das turbinas eólicas. Conclusões: um perfil adequado para uma turbina eólica de pequena escala para zonas arborizadas deve ser projetado para regulação por stall e possuir uma alta robustez ante mudanças na rugosidade superficial. O perfil com maior potencial, segundo a literatura e para essa aplicação é o SG6043, sendo 110 % e 85 % mais eficiente que NACA0012 e S809, respectivamente, para um Re de 2x 105, no entanto, requere mais investigação em temas como o desempenho aerodinâmico dos perfis

Application of T-shaped splitting method in the extraction of lower-level horizontal-impacted mandibular third molars / 口腔疾病防治

Objective@#The present study evaluated postoperative reactions in adjacent teeth after the extraction of lower-level horizontal-impacted mandibular third molars using a T-shaped splitting method. @*Methods@#A total of 101 patients with lower-level horizontal impaction of mandibular third molars were selected and randomly divided into two groups. The impacted mandibular third molar was extracted using a T-shaped splitting method in group A （56 cases）, and the traditional two-section method was used in group B （45 cases）。 Postoperative reactions, including temperature sensitivity, percussion pain and mobility in the adjacent teeth, were compared between the 2 groups at 1-week, 2-week, and 1-month follow-up visits. The SPSS 13.0 software package was used for the statistical analysis.@*Results @#The postoperative reactions of temperature sensitivity （χ21w= 11.81, χ22w = 17.43, P < 0.05）, percussion pain （χ21w = 8.70, χ22w = 4.75, P < 0.05） and mobility （χ21w = 4.50, χ22w = 7.10, P < 0.05） in adjacent teeth in group A were significantly less than those in group B at the 1-week and 2-week follow-up visits. The temperature sensitivity in adjacent teeth in group A was significantly less than that in group B at the 1-month follow-up visit （χ2 = 7.10, P < 0.05）, but percussion pain and mobility in adjacent teeth disappeared in both groups. @*Conclusion@#The T-shaped splitting method for the extraction of mandibular lower-level horizontal impacted third molars can reduce the postoperative reactions in adjacent teeth.

Extraction of low horizontally and buccally impacted mandibular third molars by three-section methud / 口腔疾病防治

Objective@# This study aims to investigate the clinical effect of the improved extraction of low horizontally impacted mandibular third molars via a “three-section” method.@*Method@#Sixty patients with low horizontally impacted mandibular third molars on both sides were selected for this study. A high-frequency electrotome, a 45 degree high-speed turbine and a special long drill needle were used in the test group. The improvement was called “three section”, which meant that the tooth was cut into three parts; first, the middle part was taken, then the root, and then the crown. One month later, the other side (control) was extracted using the regular method (the tooth was cut in two parts, and the crown was removed first). Operation time, swelling, pain, and limitations to mouth opening were carefully recorded and statistically analyzed.@*Results@#The time for the modified “three-section” method, which was used to remove the third molar embedded in the lower part of the lower jaw, was (10.05 ± 0.51) min, while the mean time for conventional extraction was (20.15 ± 0.88) min, and the difference was statistically significant (P< 0.01). There were significant differences (P< 0.01) in swelling, pain and limitations to mouth opening between the test group and the control group.@*Conclusion@#he use of the “three-section” method to extract third molars horizontally embedded in the lower jaw is associated with a shorter operation time, reduced trauma and reduced postoperative reactions, and it has valuable clinical applications.

Contaminación bacteriana generada por aerosoles en ambiente odontológico / Analysis of bacterial contamination produced by aerosols in dental clinic environments

En odontología estamos expuestos a muchos microorganismos por la producción de aerosoles. Por ello es esencial conocer la naturaleza de éstos y su potencial patogénico. El objetivo de esta investigación es determinar contaminación bacteriana, generada por aerosoles durante procedimientos odontológicos, con uso de pieza de mano de alta velocidad, realizados por alumnos de la carrera, en Clínica Odontológica Docente Asistencial (CODA), Universidad de La Frontera, Temuco, Chile. Estudio con muestra aleatoria, de 16 de un total de 32 unidades dentales, estratificado por box, con 40 muestras, ocho placas control y 32 placas prueba. El medio de cultivo, se mantuvo por diez minutos, donde se realizaron acciones de operatoria con turbina, bajo aislamiento absoluto, ubicadas en frente del operador y pechera del paciente. Las muestras fueron analizadas microscópicamente, incubadas a 37°C en atmósfera de oxígeno por 24 horas y dióxido de carbono a las 48 horas. Treinta y dos placas prueba fueron positivas, registrándose diversidad de crecimiento bacteriano, promedio 58,874 Unidad Formadora de Colonias (UFC) por unidad dental. El mayor porcentaje de microorganismos fueron: Bacillus spp. (28,56%) y Bacilos Gram positivos (24,31%). Siete placas control resultaron negativas y una con 3 UFC de Micrococcus spp. La mayoría de los microorganismos encontrados son comensales potencialmente patógenos. Al comprobar que los aerosoles constituyen una fuente importante de emisión de microorganismos, se hace imprescindible cumplir con todas las normas de bioseguridad que protegen tanto al operador como al paciente

In dental practice we are exposed to many microorganisms due to aerosol production. It is essential to be aware of the nature of these elements and their pathogenic potential. The purpose of this research is to determine the presence of bacterial contamination in aerosols produced during dental procedures that require the use of a high speed dental handpiece. These dental procedures were carried out by dentistry students at the dental clinic of the Universidad de La Frontera. In order to determine the presence of bacteria in aerosols, cultivation plates were used. A total of 40 samples were taken from 16 dentistry students while performing dental procedures that required the use of a high speed dental handpiece in conditions of complete isolation. Eight control plates and 32 test plates were used. Two selected areas were examined: operator´s front andpatient´s chest protector, during 10 minutes. The samples were then taken to the laboratory and incubated in an oxygen atmosphere for 24 hours and subsequently in carbon dioxide for another 24 hours at a temperature of 37 degrees Celsius. Finally the samples were microscopically analyzed. Seven control plates showed no bacterial contaminants and one showed 3UFC of Micrococcus spp. The 32 test plates were found to be positive showing diverse bacterial growth (58.874 UFC average per subject). The highest percentage of microorganisms was constituted by Bacillus spp. (28.56 %) and Bacillus Grampositivos (24.31 %), representing more than 50% of the total. The majority of the microorganisms found belong to the commensal family, although they can change into opportunistic pathogen microorganisms. Verifying that aerosols are an important source of emission of microorganisms, it is essential to comply with all biosecurity standards in order to protect the operator as well as the patient

Downstream effects of hydropower production on aquatic macroinvertebrate assemblages in two rivers in Costa Rica

Despite the fact that little is known about the consequences of hydropower production in tropical areas, many large dams (>15m high) are currently under construction or consideration in the tropics. We researched the effects of large hydroelectric dams on aquatic macroinvertebrate assemblages in two Costa Rican rivers. We measured physicochemical characteristics and sampled aquatic macroinvertebrates from March 2003 to March 2004 in two dammed rivers, Peñas Blancas and San Lorenzo, as well as in the undammed Chachagua River. Sites above and below the dam had differences in their physicochemical variables, with wide variation and extreme values in variables measured below the dam in the San Lorenzo River. Sites below the dams had reduced water discharges, velocities, and depths when compared with sites above the dams, as well as higher temperatures and conductivity. Sites above dams were dominated by collector-gatherer-scrapers and habitat groups dominated by swimmer-clingers, while sites below dams had a more even representation of groups. In contrast, a comparison between two sites at different elevation in the undammed river maintained a similar assemblage composition. Tributaries might facilitate macroinvertebrate recovery above the turbine house, but the assemblage below the turbine house resembled the one below the dam. A massive sediment release event from the dam decreased the abundance per sample and macroinvertebrate taxa below the dam in the Peñas Blancas River. Our study illustrates the effects of hydropower production on neotropical rivers, highlighting the importance of using multiple measures of macroinvertebrate assemblage structure for assessing this type of environmental impact. Rev. Biol. Trop. 62 (Suppl. 2): 179-201. Epub 2014 April 01.

Existe poca información publicada sobre el efecto de grandes represas hidroeléctricas (>15m alto) en ríos tropicales. Investigamos los efectos de estas represas en las comunidades de macroinvertebrados acuáticos en dos ríos de Costa Rica. Medimos características físico-químicas y recolectamos macroinvertebrados a lo largo del año en dos ríos represados, Peñas Blancas y San Lorenzo, así como en el río Chachagua, el cual no era utilizado para la producción hidroeléctrica. Los sitios arriba y debajo de las represas presentaron diferencias físico-químicas, con amplia variación y valores extremos en las variables medidas debajo de la represa en el Río San Lorenzo. Los sitios arriba de las represas estaban dominados por colectores-recolectores-raspadores y nadadores-colgadores, mientras que debajo de las represas hubo una representación más equitativa de grupos funcionales. En contraste, las comunidades fueron semejantes en dos sitios a diferente elevación en el río sin represa. La presencia de afluentes podría haber facilitado la recuperación de macroinvertebrados arriba de la casa de máquinas, pero las comunidades fueron similares bajo la casa y abajo de la represa. Una liberación masiva de sedimentos disminuyó la abundancia y el número de táxones bajo la represa en el Río Peñas Blancas.

Evaluation of techniques used to protect tailrace fishes during turbine maneuvers at Três Marias Dam, Brazil

Turbine dewatering and stop/startup may lead to the death of tons of fish at Brazilian power dams. The Três Marias Dam (TMD) on the São Francisco River has adopted two techniques to reduce the quantity of fish, mostly mandi (Pimelodus maculatus, Pimelodidae), affected by these maneuvers. They are: (i) spill before turbine dewatering to attract fish out of the tailrace, and (ii) fish screens in the stop log slots during turbine stop/startup to prevent fish from entering the draft tube. Here, we investigated whether spill and fish screens reduced the quantity of fish affected by turbine dewatering and stop/startup at TMD. We also determined whether the biomass of mandi trapped during turbine dewatering may be predicted by turbine discharge (Q) and/or catch per unit effort (CPUE) of mandis in the tailrace. Due to insufficient statistical power, our data were inconclusive as to whether spill attracted mandi out of the tailrace. We verified that the presence of fish screens significantly reduced the biomass of dead/moribund fish during turbine stop/startup. The biomass of mandis trapped in the draft tube during turbine dewatering was mainly influenced by Q (r² = 0.67), followed by CPUE (r² = 0.49). Since the trapped fish biomass correlated negatively with Q, we recommend that Q be maximized before turbine dewatering to reduce quantity of mandi trapped in the draft tube. The information presented here may be useful for reducing the quantity of fish affected by turbine maneuvers at TMD, as well as other dams.

Drenagem e parada/partida de turbina podem provocar a morte de toneladas de peixes em usinas hidrelétricas brasileiras. A usina de Três Marias (UTM), rio São Francisco, adotou duas técnicas para reduzir a quantidade de peixes, principalmente do mandi (Pimelodus maculatus, Pimelodidae), afetada durante essas manobras. Essas são: (i) vertimento antes da drenagem de turbina para atrair peixes para fora do canal de fuga, e (ii) grades nas guias das comportas ensecadeiras durante paradas/partidas para prevenir a entrada de peixes no tubo de sucção. Neste estudo, investigamos se o vertimento e as grades reduziram a quantidade de peixes afetados durante drenagem e parada/partida de turbina na UTM. Nós também determinamos se a biomassa de mandis aprisionados em drenagem de turbina pode ser predita pela vazão da turbina (Q) e/ou pela captura por unidade de esforço (CPUE) de mandis no canal de fuga. Devido ao poder estatístico insuficiente, nossos dados foram inconclusivos se o vertimento atraiu mandis para fora do canal de fuga. Verificamos que a presença das grades reduziu significativamente a biomassa de peixes mortos/moribundos em paradas/partidas de turbinas. A biomassa de mandis aprisionada no tubo de sucção nas drenagens foi influenciada principalmente pelo Q (r² = 0.67), seguida da CPUE (r² = 0.49). Como essa biomassa foi negativamente correlacionada com Q, recomendamos que Q seja máxima antes da drenagem para reduzir a biomassa de mandis aprisionada no tubo de sucção. Acreditamos que as informações apresentadas aqui poderão ser úteis para reduzir a quantidade de peixes afetada em manobras de turbinas na UTM e outras usinas hidrelétricas.

A comparison of two methods of extracting impacted mandibular third molars / 实用口腔医学杂志

Objective:To study the feasibility of extraction of impacted mandibular wisdom teeth using turbine drill and new instruments. Methods: 600 patients with impacted mandibular third molars were divides into 2 groups. A group used turbine drill and new instruments to extract the impacted mandibular third molar. B group used the dental chisel to extract the impacted mandibular third molar. The operation time, intraoperative and postoperative complications were recorded to assess the effects of the methods. Results: The operation time of group A and group B was (22.285±12.025 01) min and (16.115±12.078 62) min respectively. The operation time of group A was shorter(P<0.05). The intraoperative and postoperative complication incidence rate was lower(P<0.05). Conclusion: Turbine drill and new instruments method is superior to dental chisel method in the extraction of impacted mandibular wisdom teeth.

Subcutaneous Emphysema and Pneumomediastinum After Mandibular Third Molar Extraction: a Case Report

Study of steady and unsteady wet steam condensing flows in a turbine stage / 西安交通大学学报·英文版

Objective: To develop the numerical method for the steady and unsteady wet steam condensing flow in turbine stage. Methods: An Eulerian/Eulerian numerical model is used to describe the spontaneous condensation flow in the steam turbine. For the steady condensing flow computations, the mixing plane model was used. For the unsteady condensing flow computations, the sliding mesh method was used to simulate the rotor-stator interactions. Results: The numerical results showed the obvious differences between non-condensing and condensing flows. The results also showed the unsteadiness effect due to rotor-stator interactions had a deep influence on the formation and growth process of water droplets. Conclusion: The numerical methods presented in this paper are valid for the condensing flow in the turbine stage.

An experimental study on flowrate and stability for 600MW supercritical steam-turbine control valve / 西安交通大学学报·英文版

An experimental study on flowrate and stability of a type of control valve of 600MW supercritical steam-turbine was presented by measuring instruments of static, dynamic pressure and vibration in self-designed test rig. The investigation shows that flow coefficient is 30% up more than that of the control valve of GX-1 type used widely in domestic power plants now, as small-medium lifts. If the relative lift (h/D) is less than 20%, the valve can always work steadily in all the pressure ratios. When the h/D is between 20% to 24%, big vibration of valve stem occurs if the pressure ratio is between 0.7 to 0.8. When h/D is more than 25%, relatively great vibration happens in a wide range of pressure ratios of 0.4 to 0.85.

An experimental study on flowrate and stability for 600MW supercritical steam-turbine control valve / 药物分析学报

An experimental study on flowrate and stability of a type of control valve of 600MW supercritical steam-turbine was presented by measuring instruments of static, dynamic pressure and vibration in self-designed test rig. The investigation shows that flow coefficient is 30% up more than that of the control valve of GX-1 type used widely in domestic power plants now, as small-medium lifts. If the relative lift (h/D) is less than 20%, the valve can always work steadily in all the pressure ratios. When the h/D is between 20% to 24%, big vibration of valve stem occurs if the pressure ratio is between 0.7 to 0.8. When h/D is more than 25%, relatively great vibration happens in a wide range of pressure ratios of 0.4 to 0.85.

Study of steady and unsteady wet steam condensing flows in a turbine stage / 药物分析学报

Objective To develop the numerical method for the steady and unsteady wet steam condensing flow in turbine stage. Methods An Eulerian/Eulerian numerical model is used to describe the spontaneous condensation flow in the steam turbine. For the steady condensing flow computations, the mixing plane model was used. For the unsteady condensing flow computations, the sliding mesh method was used to simulate the rotor-stator interactions. Results The numerical results showed the obvious differences between non-condensing and condensing flows. The results also showed the unsteadiness effect due to rotor-stator interactions had a deep influence on the formation and growth process of water droplets. Conclusion The numerical methods presented in this paper are valid for the condensing flow in the turbine stage.

Extraction of impacted lower mandibular wisdom teeth by turbine drill / 实用口腔医学杂志

Objective:To study the feasibility of extraction of impacted mandibular wisdom teeth using turbine drill.Methods:Fifty-one patients with impacted mandibular wisdom teeth on both sides were included.In each patient the two wisdom teeth were randomly divided into test and control groups,the tooth on one side was extracted by means of turbine drill and that on another side by dental chisel method.The operation time,postoperative swell and pain were recorded to assess the effects of the methods.Results:In the extraction of deeply impacted teeth the operation time by turbine drill was shorter(P