High Frequency Resonance Damping Method for Voltage Source Converter Based on Voltage Feedforward Control

High frequency resonance (HFR) is a subsistent problem which affects the operation of the voltage source converter (VSC) connected to the parallel compensated grid. The appearance of HFR introduces a significant high frequency component in the grid voltage, thereby the operation of VSC system will be seriously affected. For enhancing the operation capability of VSC system, an HFR damping method based on the voltage feedforward control is proposed in this paper, which can reshape the VSC system impedance effectively in a wideband range. Besides, different with the existing HFR damping methods, the proposed method introduces a correction factor instead of the series virtual impedance with fixed value, so that the effect of impedance reshaping is irrelevant to the parameters of controlled object. In addition, this paper analyzes the fundamental control performance of VSC system after equipping the proposed method, for verifying that the proposed method will not worsen the fundamental control. Experimental results are given to validate the effectiveness of the proposed damping method.

Does gestational diabetes result in cochlear damage?

Background:Glucose metabolism has a significant impact on inner-ear physiology. Therefore, hearing may be affected in gestational diabetes.Method:A matched case–control study was performed to evaluate 27 patients with gestational diabetes and 31 non-diabetic pregnant women with similar demographic characteristics. A medical history was taken for each participant, and otological inspections and high-frequency audiometry tests were performed.Results:There were no significant differences in average pure tone air–bone hearing thresholds between the groups (p > 0.05). However, evaluation of high-frequency hearing thresholds indicated significantly increased auditory thresholds at 10 kHz and 12 kHz for right ears and at 8, 10, 12 and 14 kHz for left ears in the gestational diabetes group (p < 0.001).Conclusion:An investigation into cochlear damage in gestational diabetic patients showed significant high-frequency hearing loss. Further studies are needed to validate these findings in different ethnic groups and geographical populations.

Análisis del uso de la metáfora en el contexto de la ingeniería / Analysis of the Use of Metaphor in the Context of Engineering

ABSTRACT:Previous studies on metaphor use (Cameron and Low 1999; Cortazzi and Jin 1999; Littlemore and Low 2006; Low 1999) claim that the pedagogic practice of metaphor in the classroom could serve to develop the comprehension and communicative skills of EFL learners. Nevertheless, the use of metaphor by technical second language learners has received little attention so far (Littlemore 2009). In this paper, the metaphorical content of the responses that a group of 4th year Spanish engineering undergraduates gave out when asked to briefly describe visual images of engineering structures have been analysed. Currently, the academic syllabuses for engineering students in most Spanish universities lack any reference to metaphor use either in Spanish or English. The responses obtained from the students were in turn crosschecked against those given by engineers in order to compare output both in the academic and the professional fields. The results reveal a significant high frequency in metaphor use in the examples produced both by engineers and by engineering students. We thus argue about the effectiveness to include pedagogical notions about metaphor theory and metaphor use as part of the linguistic training of engineering learners. These should include differences between the first and the second language, since metaphor use varies from one language to another. The theoretical framework adopted for this work follows conceptual and metaphor theory and conceptual integration/blending findings (Deignan 2005, Steen 2007, Fauconnier and Turner 2002, Fauconnier and Turner 2008).RESUMEN:Diversos estudios realizados con anterioridad sobre el uso de la metáfora (Cameron and Low 1999; Cortazzi and Jin 1999; Littlemore and Low 2006; Low 1999) aseguran que la práctica pedagógica de la metáfora en el aula puede mejorar las destrezas comunicativas de los estudiantes de lenguas extranjeras. No obstante, poca atención se ha prestado hasta el momento al uso y aprendizaje de la metáfora por parte de los estudiantes de enseñanzas técnicas que a su vez aprenden inglés como lengua extranjera (Littlemore 2009). En este trabajo, se ha analizado el contenido metafórico de las respuestas proporcionadas por un grupo de estudiantes españoles de cuarto curso de ingeniería a los que se les pidió que describieran sucintamente diversas imágenes visuales de estructuras de in-geniería. Las respuestas de los estudiantes fueron a su vez cotejadas con las suministradas por diversos profesionales de la ingeniería con el fin de examinar diferencias y similitudes entre el campo académico y el profesional. Diversos estudios realizados sobre el uso de la metáfora (Cameron and Low 1999; Cortazzi and Jin 1999; Littlemore and Low 2006; Low 1999) aseguran que la práctica pedagógica de la metáfora en el aula puede servir para mejorar las destrezas comunicativas de los estudiantes de lenguas extranjeras. No obstante, poca atención se ha prestado hasta el momento al uso y apren-dizaje de la metáfora por parte de los estudiantes de enseñanzas técnicas que a su vez están aprendiendo una segunda lengua, como el inglés (Littlemore 2009). En este trabajo, se ha analizado el contenido metafórico de las respuestas proporcionadas por un grupo de estudiantes españoles de cuarto curso de ingeniería a los que se les pidió que describieran sucintamente diversas imágenes visuales de es-tructuras de ingeniería. El marco teórico aplicado al estudio sigue la teoría de la metáfora conceptual y lingüística y de la integración conceptual (Deignan 2005, Steen 2007, Fauconnier and Turner 2002, Fauconnier and Turner 2008). Actualmente, la enseñanza curricular de estos alumnos no incluye nociones sobre el uso de la metáfora en español ni en inglés. Las respuestas de los estudiantes fueron a su vez cotejadas con las suministradas por diversos profesionales de la ingeniería con el fin de ex-minar diferencias y similitudes entre el campo académico y el profesional. Los resultados obtenidos revelan un uso considerable de la metáfora en los ejemplos en español recopilados de ambos grupos. De ahí que en las conclusiones, se señale la conveniencia de incluir en la formación pedagógica de los estudiantes de ingeniería el uso de la metáfora tanto en lengua original como en la lengua fuente, puesto que cada lengua hace un uso distinto que es preciso conocer de este importante recurso comunicativo. Contacto principal: [email protected]

Hearing threshold in patients with diabetes mellitus

Hearing threshold of 30 diabetic patients and 30 healthy controls attending the medical outpatient department were determined using pure tone audiometry (Arphi Digital 900). All subjects were less than 50 years old. Subjects with otological and other metabolic diseases were excluded from the study. The patients were categorized into groups according to age, duration of disease, complications and control of diabetes. These observations were compared with those from the control subjects using appropriate statistical methods.It was found that diabetics had a poorer hearing threshold than the non-diabetics; all age groups with diabetes showed a significant high frequency hearing loss, as compared to the control population; poorly controlled and complicated diabetics have significant, high frequency hearing loss as compared to those who were well controlled and uncomplicated; there was no relationship between duration of the diabetes and the level of hearing loss.

Hearing Function and Chronic Renal Failure

In order to evaluate the degree and type of hearing loss in patients with chronic renal failure, 61 patients undergoing chronic hemodialysis were examined. Hearing threshold levels, adjusted for age and sex, demonstrated a significant high frequency deficit, which in some patients was noted early in the course of hemodialysis. Fluctuations in hearing were noted over single dialysis events but were transient and apparently independent of corresponding changes in Na, K, Ca, BUN, creatinine, glucose, mean blood pressure, and weight. Preliminary attempts to evaluate hyperlipidemia as a possible cause of hearing loss did not reveal any hearing deficit or gain as related to triglyceride or cholesterol levels. The data suggested other possible causes of observed auditory loss.

High frequency teleseismic energy from Aleutian sources

abstract The Long Shot event, detonated at Amchitka in the Aleutian Islands, was recorded at three sites in Michigan at distances of 57 to 63 degrees. Analysis of the data recorded on magnetic tape shows significant high frequency (4-5 Hz) energy in the first compressional wave arrivals at all three stations, although the most prominent spectral peaks are in the range 1.0 to 1.6 Hz. Initial P phases of aftershocks of the Good Friday earthquake of 1964 recorded at the Ann Arbor station do not contain appreciable energy above about 2 Hz. However, the P-wave spectrum of an earthquake of comparable magnitude whose epicenter is near Long Shot is very similar to that of Long Shot, and indicates a favorable signal-to-noise ratio to 5 Hz. The Long Shot spectra and apparent angle of incidence at the Michigan stations appear to be influenced by the presence of pP and by crustal layering. The effective response of an intermediate-depth well system is shown to be strongly affected by surface reflections.