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INTRODUCTION: Physical activity has been reduced in the 21st century and is a phenomenon which is now an important problem. The study focuses on the reasons for this lack of physical activity in adolescent girls diagnosed with scoliosis, and the possibility of preventing and effectively promoting a healthy lifestyle. The aim of the study is to investigate the relationship between place of residence (rural and urban) and physical activity in girls with scoliosis. MATERIAL AND METHODS: A group of 43 girls aged 16-18 years (x = 16.97 ± 0.88) with AIS (mean Cobb angle = 16.32 ± 3.55) who were rural inhabitants were examined. The control group included 39 young girls in the same age group and AIS who were living in towns (mean Cobb angle = 18.53 ± 4.3). BMI was calculated in percentiles and the IPAQ (International Physical Activity Questionnaire s) was administered. RESULTS: The results showed decreased physical activity and a reduction in total sedentary time each week, which was higher in girls living in the countryside than in those living in towns (P<.001). Electronic devices were commonly used in both groups of girls. CONCLUSIONS: The global weekly physical activity in girls living in the countryside was higher than that in girls living in the towns. A lower level of physical activity was noted in the girls exempted from PE at school. Body acceptance and fewer body image issues were noted in girls living in the countryside.
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Electrónica/estadística & datos numéricos , Escoliosis/fisiopatología , Adolescente , Índice de Masa Corporal , Ejercicio Físico , Femenino , Humanos , Estilo de Vida , Conducta SedentariaRESUMEN
BACKGROUND: The purpose of this study was to examine the association between electronic media use, including use of social media and gaming, and symptoms of depression, and whether gender or having friends moderated these associations. METHODS: This study was based on self-reported cross-sectional data from the Ungdata survey, conducted in 2018 by the Norwegian Social Research (NOVA) Institute in cooperation with seven regional drug and alcohol competence centres. The target group comprised 12,353 15-16 years old adolescents. Binominal logistic regression was used to analyse the association between electronic media use and symptoms of depression. RESULTS: The odds of having symptoms of depression were higher for those who used social media more than 3 hours per day (OR: 1.60, 95% CI: 1.43-1.80), compared to those who used social media 3 hours or less per day. Additionally, the odds of having symptoms of depression was higher for those who used more than 3 hours on gaming per day (OR: 1.57, 95% CI: 1.36-1.80), compared to those who used 3 hours and less on gaming per day after adjustment for potential confounders. There were no interaction effects between social media and gaming use with symptoms of depression. Neither were the associations between social media use and gaming with symptoms of depression moderated by gender or having friends. CONCLUSIONS: The odds of having symptoms of depression were significantly higher for adolescents with a more frequent use of electronic media.
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Depresión/etiología , Electrónica/estadística & datos numéricos , Medios de Comunicación Sociales/estadística & datos numéricos , Adolescente , Medios de Comunicación/estadística & datos numéricos , Estudios Transversales , Femenino , Amigos , Humanos , Masculino , Noruega , Autoinforme/estadística & datos numéricos , Encuestas y Cuestionarios , Juegos de Video/estadística & datos numéricosRESUMEN
This study investigates associations between after-school tutoring and availability of electronic devices with overweight/obesity among fifth-grade children in Ho Chi Minh City, Vietnam. A complex cross-sectional design was used to randomly select students and their parents in 8 public schools in Ho Chi Minh City in 2016. Students were categorized as overweight/obesity if their body mass index z score >+1 using the World Health Organization reference. Parents self-reported child's attendance in after-school tutoring and availability of electronic devices at home. Sampling weights were used to account for unequal selection probability and nonresponses in analyses. Students attending tutoring were more likely to be overweight/obesity (odds ratio = 1.59, P < .001). Overweight/obesity students spent on average about 1.5 hours/week more attending tutoring; most of these hours were during weekdays (P < .05). Students living in households with ≥2 types of devices were more likely to be overweight/obesity (odds ratio = 2.83, P < .001). Strategies to reduce study sitting time and the use of electronic devices may help with childhood overweight/obesity prevention.
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Electrónica/estadística & datos numéricos , Obesidad Infantil/epidemiología , Estudiantes/estadística & datos numéricos , Enseñanza/estadística & datos numéricos , Niño , Ciudades/epidemiología , Estudios Transversales , Femenino , Humanos , Masculino , Instituciones Académicas , Vietnam/epidemiologíaRESUMEN
Continuous, battery-free operation of sensor nodes requires ultra-low-power sensing and data-logging techniques. Here we report that by directly coupling a sensor/transducer signal into globally asymptotically stable monotonic dynamical systems based on Fowler-Nordheim quantum tunneling, one can achieve self-powered sensing at an energy budget that is currently unachievable using conventional energy harvesting methods. The proposed device uses a differential architecture to compensate for environmental variations and the device can retain sensed information for durations ranging from hours to days. With a theoretical operating energy budget less than 10 attojoules, we demonstrate that when integrated with a miniature piezoelectric transducer the proposed sensor-data-logger can measure cumulative "action" due to ambient mechanical acceleration without any additional external power.
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Ingeniería Biomédica/instrumentación , Recolección de Datos/instrumentación , Suministros de Energía Eléctrica , Transductores , Aceleración , Fuentes de Energía Bioeléctrica , Ingeniería Biomédica/estadística & datos numéricos , Recolección de Datos/estadística & datos numéricos , Electrónica/instrumentación , Electrónica/estadística & datos numéricos , Diseño de Equipo , Fenómenos Mecánicos , Procesamiento de Señales Asistido por Computador/instrumentaciónRESUMEN
OBJECTIVES: Young adults (YAs) are vulnerable to insomnia and mood disturbance. YAs also engage in back-lit device use which has been implicated in the development and maintenance of insomnia. This study explored the association between device use, mood disturbance, and insomnia symptoms in YAs. PARTICIPANTS: Two thousand three hundred and ninety students at a Canadian university, aged 18-35 years. DESIGN: Cross-sectional online survey MEASUREMENTS: Participants self-reported duration and frequency of back-lit device use before sleep and during the night. The Insomnia Severity Index and the Hospital Anxiety and Depression Scale were used to measure symptoms. Univariate and multivariate logistic regressions explored associations between device use behaviors and insomnia symptoms. A hierarchical regression analysis identified the unique contribution of back-lit device use on insomnia severity adjusting for mood disturbance, age, and sex. RESULTS: Using a back-lit device for 1-2 hours after lights out (adjusted odds ratio [AOR] = 1.50, p < 0.001), being awakened by a device (AOR = 1.34, p = 0.002), and believing that device use negatively impacts sleep (AOR = 2.27, p < 0.001) were associated with insomnia symptoms. Depression contributed to the greatest unique variance to insomnia (11.8%), followed by anxiety (7.2%). Duration of device use after lights out, being awakened by a device and a negative perception of device use on sleep accounted for an additional 3%. CONCLUSIONS: Device use contributed to insomnia symptoms over and above mood disturbance, age, and biological sex in YAs. Additional research is needed to determine the direction of effect and inform prevention/intervention programs specific to device use and insomnia symptomology in this population.
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Electrónica/estadística & datos numéricos , Trastornos del Humor/epidemiología , Trastornos del Inicio y del Mantenimiento del Sueño/epidemiología , Sueño , Adolescente , Adulto , Canadá/epidemiología , Estudios Transversales , Humanos , Autoinforme , Estudiantes/psicología , Estudiantes/estadística & datos numéricos , Factores de Tiempo , Universidades , Adulto JovenRESUMEN
OBJECTIVES: The objective was to describe (1) the type, (2) the amount of use, and (3) the time of usage of electronic devices, for school days and weekends, as well as its impact on adolescents' sleep quality. DESIGN: A cross-sectional study using hierarchical regressions accounting for confounding sleep-related variables was used. SETTING: The participants were from six public schools in Porto Alegre, Brazil. PARTICIPANTS: The participants included 177 students of both sexes aged between 11 and 18 years. MEASUREMENTS: An electronic usage diary assessed the span of time during which the electronic device was used (separated by "TV and computer monitors", "tablets, e-readers and portable video games," and "cell phones") for school days and weekends. The Munich Chronotype Questionnaire was used to assess sleep duration, midpoint of sleep, and social jetlag. Sleep quality was assessed using the Pittsburgh Sleep Quality Index. RESULTS: Greater nighttime use and last time of use of cell phones at night are associated with worse sleep quality in univariate analyses. A hierarchical regression model shows that poor sleep quality associates with shorter sleep duration on school days and with a delayed midpoint of sleep on weekends. Electronic device use did not reach statistical significance in the regression model with confounding factors. CONCLUSIONS: Adequate sleep duration is imperative to maintain a good sleep quality on school days, independently of the use of cell phones. It is important to underpin the need for evaluation of sleep phase and chronotype in future research on the topic aiming to elucidate its relationship with electronic use on school-free days.
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Electrónica/estadística & datos numéricos , Sueño , Estudiantes/psicología , Adolescente , Brasil , Teléfono Celular/estadística & datos numéricos , Niño , Computadores/estadística & datos numéricos , Estudios Transversales , Femenino , Humanos , Masculino , Instituciones Académicas , Estudiantes/estadística & datos numéricos , Encuestas y Cuestionarios , Televisión/estadística & datos numéricos , Factores de Tiempo , Juegos de Video/estadística & datos numéricosRESUMEN
BACKGROUND: Despite recent declines in consumption of sugary beverages, energy drinks (ED) and sodas continue to contribute a substantial amount of sugar and caffeine to the diet of youth. Consumption of these beverages has been linked with electronic device use, however in-depth associations between sugar and caffeine intake from energy drinks and sodas with various electronic devices are not clear. OBJECTIVE: Describe the relationship of soda and energy drink consumption and associated added sugar and caffeine intake with electronic device use among adolescents. METHODS: Secondary data from the 2013-2016 cycles of Monitoring the Future Survey, a national, repeated, cross-sectional study, were analyzed. Information on energy drink and soda consumption by students in grades 8 and 10 (n = 32,418) from 252-263 schools randomly sampled from all US states was used. RESULTS: Soda and energy drink consumption decreased each year from 2013-2016 while daily use of electronic devices remained stable. An additional hour/day of TV was linked to a 6.92g (6.31,7.48; p<0.001) increase in sugar intake and a 32% (OR = 1.32; 1.29,1.35; p < .001) higher risk of exceeding World Health Organization (WHO) recommended sugar intakes. Further, each hour/day of TV was linked to a 28% increased risk of exceeding caffeine recommendations (OR = 1.25-1.31; p<0.001). Each hour per day talking on a cellphone was associated with an increased risk of exceeding WHO sugar and caffeine intakes by 14% (OR = 1.11-1.16; p<0.001) and 18% (OR = 1.15-1.21; p<0.001) respectively. Video game use was only weakly linked to caffeine intake. Computer use for school was associated with lower likelihood of exceeding sugar intake cut-offs. CONCLUSION: While a trend towards reduced energy drink and soda intake from 2013-2016 was evident, greater electronic device use, especially TV time, was linked to higher intake of beverage-derived added sugar and caffeine amongst adolescents. Addressing these behaviours through counselling or health promotion could potentially help to reduce excess sugar and caffeine intake from sodas and energy drinks among this population.
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Cafeína/administración & dosificación , Bebidas Gaseosas/estadística & datos numéricos , Electrónica/estadística & datos numéricos , Bebidas Energéticas/estadística & datos numéricos , Estudiantes/psicología , Azúcares/administración & dosificación , Adolescente , Estimulantes del Sistema Nervioso Central/administración & dosificación , Estudios Transversales , Femenino , Humanos , Masculino , Encuestas Nutricionales , Encuestas y Cuestionarios , Edulcorantes/administración & dosificación , Estados UnidosRESUMEN
OBJECTIVES: We examined (Study #1) the association of attitudes, subjective norms (SN), and perceived behavioral control (PBC) with intentions to reduce late evening electronic device (e-device) use and (Study #2) the impact of a brief theory-driven message on reducing the use. METHODS: Young adults aged 18-30â¯years participated in Internet surveys to assess sleep quality, attitudes, SN, PBC, and intentions to reduce and patterns of late evening e-device use. In Study #1, participants (nâ¯=â¯160) were randomized to receive a Theory of Planned Behavior (TPB)-driven message based on information from the National Sleep Foundation and were assessed for intentions to decrease late evening e-device use immediately afterward. In Study #2, participants (nâ¯=â¯148) were given the same message but were assessed for behaviors 24â¯hours-1 week afterward. RESULTS: In Study #1, regressions indicated that less supportive attitudes and higher PBC were associated with higher intention to reduce e-device use at baseline (Pâ¯<â¯.01); intentions and PBC were associated with current use (Pâ¯<â¯.01). Participants receiving the message were more likely to reduce late evening e-device use intentions (adjusted odds ratio: 2.30, 95% confidence interval: 1.06-4.99). In Study #2, those receiving the intervention with attitudes consistent with limiting use were more likely to reduce use 24â¯hours-1â¯week after the intervention (adjusted odds ratio: 3.13, 95% confidence interval: 1.10-8.91). CONCLUSION: Attitudes and PBC were associated with intention to reduce late evening e-device use, and our brief TPB-driven message benefited young adults with attitudes inconsistent with use. TPB-based interventions can decrease late evening e-device use and promote better quantity and quality of sleep.
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Electrónica/estadística & datos numéricos , Intención , Adolescente , Adulto , Actitud , Femenino , Humanos , Masculino , Teoría Psicológica , Sueño , Encuestas y Cuestionarios , Factores de Tiempo , Adulto JovenRESUMEN
Styrene is one of the essential components in making thousands of everyday products. Occupational exposure to styrene causes pulmonary, neurological, genetic and ocular complications, and leukemia and affects reproduction. The aim of this study was to assess the health risks of exposure to styrene in the electronics industry of Neyshabur, Iran. This descriptive and analytical cross-sectional study was carried out in three electronics industries, in Neyshabur city, in 2017-2018. Occupational exposure to styrene was measured according to the NIOSH1501 method, using a low-flow rate sampling pump (0.2 L/min) and an active charcoal absorber tube. Health risk assessment was done according to the Singapore semi-quantitative method and the United States Environmental Protection Agency (OEHHA) method. The average occupational exposure to styrene in men employed in the compact plastic parts production halls was 79.61 mg m-3 (range 28-208.33). 45.8% of exposed subjects (27 people) encountered exposure above the permitted limit. The average lifetime carcinogenic risk of styrene was 1.4 × 10-3; therefore, 100% (59 people) had a definite risk of getting cancer. The highest lifetime risk of getting cancer was observed in plastic injection device users (1.9 × 10-3) and then in shift managers (1.6 × 10-3). The results of this study indicate a definite risk of getting cancer for all workers. Strategies to reduce workers exposure to styrene through engineering controls and routine measurements are necessary.
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Contaminantes Ocupacionales del Aire/análisis , Electrónica/estadística & datos numéricos , Exposición Profesional/estadística & datos numéricos , Estireno/análisis , Adulto , Estudios Transversales , Humanos , Industrias , Irán/epidemiología , Masculino , Neoplasias/epidemiología , Exposición Profesional/análisis , Plásticos/análisis , Medición de Riesgo , Estados UnidosRESUMEN
The use of electronic media has increased substantially and is already observable in young children. The present study explored associations of preschoolers’ use of electronic media with age, gender, and socio-economic status, investigated time trends, and examined reciprocal longitudinal relations between children’s use of electronic media and their behavioral difficulties. The study participants included 527 German two- to six-year-old children whose parents had provided information on their use of electronic media and their behavioral difficulties at two time points, with approximately 12 months between baseline and follow-up. The analyses revealed that older vs. younger children, as well as children from families with a lower vs. higher socio-economic status, were more often reported to use electronic media. Furthermore, the usage of mobile phones increased significantly between 2011 and 2016. Most interestingly, baseline usage of computer/Internet predicted more emotional and conduct problems at follow-up, and baseline usage of mobile phones was associated with more conduct problems and hyperactivity or inattention at follow-up. Peer relationship problems at baseline, on the other hand, increased the likelihood of using computer/Internet and mobile phones at follow-up. The findings indicate that preschoolers’ use of electronic media, especially newer media such as computer/Internet and mobile phones, and their behavioral difficulties are mutually related over time.
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Teléfono Celular/estadística & datos numéricos , Computadores/estadística & datos numéricos , Electrónica/estadística & datos numéricos , Internet/estadística & datos numéricos , Problema de Conducta , Juegos de Video/psicología , Juegos de Video/estadística & datos numéricos , Factores de Edad , Niño , Preescolar , Femenino , Alemania , Humanos , Masculino , Factores Sexuales , Factores Socioeconómicos , Factores de TiempoRESUMEN
In this paper, a scheme for chaotic modulation secure communication is proposed based on chaotic synchronization of an improved Lorenz system. For the first time, the intensity limit and stability of the transmitted signal, the characteristics of broadband and the requirements for accuracy of electronic components are presented by Multisim simulation. In addition, some improvements are made on the measurement method and the proposed experimental circuit in order to facilitate the experiments of chaotic synchronization, chaotic non-synchronization, experiment without signal and experiment with signal. To illustrate the effectiveness of the proposed scheme, some numerical simulations are presented. Then, the proposed chaotic secure communication circuit is implemented through analog electronic circuit, which is characterized by its high accuracy and good robustness.
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Algoritmos , Electrónica/estadística & datos numéricos , Redes Neurales de la Computación , Comunicación , Simulación por Computador , Humanos , Dinámicas no LinealesRESUMEN
Based on recent studies, this paper examines whether an increased use of electronic stability control can replace studded tyres. A re-analysis of a study that evaluated the effects on accidents of changes in the use of studded tyres in major cities in Norway is presented. It is found that if all cars have electronic stability control, the use of studded tyres can be reduced to about 15 percent before any increase in the number of accidents occurs. Even if studded tyres were eliminated entirely, any increase in the number of accidents is likely to be considerably smaller than it would have been if electronic stability control had never been invented.
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Prevención de Accidentes/instrumentación , Prevención de Accidentes/estadística & datos numéricos , Accidentes de Tránsito/estadística & datos numéricos , Automóviles/normas , Electrónica/estadística & datos numéricos , Electrónica/normas , Humanos , Hielo , Noruega , Lluvia , NieveRESUMEN
BACKGROUND AND OBJECTIVE: Assessing the behavior of active implanted medical devices (AIMDs) in response to electromagnetic field (EMF) transmitters is a current issue of great importance. Given the numerous telecommunication systems and our lack of knowledge as to the impact of electromagnetic effects, this study investigated the reality of possible AIMD disturbance by EMFs by interviewing health professionals. METHOD: A self-administered postal questionnaire was sent to almost 5,000 physicians in five specialties: cardiology; endocrinology; ears, nose, and throat; urology; and neurology. It collected data on the existence and annual number of incidents observed and the conditions under which they occurred, the EMF sources involved, and the means of managing the malfunctions. RESULTS: A total of 1,188 physicians agreed to participate. Sixteen percent of participants reported cases of implant failure, three-quarters of whom, mainly in cardiology, reported rates of at least one incident per year-amounting to more than 100 incidents per year in all. Severity appeared to be moderate (discomfort or transient symptoms), but frequently required resetting or, more rarely, replacing the device. Some serious incidents were, however, reported. The sources implicated were basically of two types: electronic security systems (antitheft and airport gates) and medical electromagnetic radiation devices. These incidents were poorly reported within the public health system, preventing follow-up and effective performance of alert and surveillance functions. CONCLUSION: Although minor, the risk of interference between EMF sources and AIMDs is real and calls for vigilance. It particularly concerns antitheft and airport security gates, though other sources may also cause incidents.
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Artefactos , Electrodos/estadística & datos numéricos , Campos Electromagnéticos , Electrónica/estadística & datos numéricos , Falla de Equipo/estadística & datos numéricos , Seguridad de Equipos/estadística & datos numéricos , Prótesis e Implantes/estadística & datos numéricos , Francia/epidemiología , Incidencia , Médicos/estadística & datos numéricos , Medición de Riesgo , Encuestas y CuestionariosRESUMEN
PURPOSE: To assess and compare actual computed tomography (CT) x-ray tube life with manufacturer warranty coverage limits because prolonging the tube life helps to lower operating costs. METHODS: Ten GE LightSpeed CT scanners with 40 Performix Ultra tube changes and 3 GE VCT scanners with 10 Performix Pro tube changes were followed for 6 years. CT x-ray tube life measurements were performed by analyzing log files of the units after a tube change. RESULTS: The Ultra tubes warranty coverage limit is 70 kAs or 12 months, whichever comes first. For Pro tubes, it is 6000 examinations or 12 months, whichever comes first. Measurements for the Performix Ultra CT x-ray tubes showed a range of 7 to 48 months and 16.7 to 239.9 kAs. Mean values for the Ultra CT x-ray tubes were 19.2 ± 12.5 months and 81.0 ± 45.4 kAs. Seven Ultra CT x-ray tubes did not meet the warranty coverage limits, with an average life of 8 months and 48.1 kAs. For the Pro CT x-ray tubes, the measured logs indicated 22.4 ± 9.6 months of CT x-ray tube life. All 10 Pro CT x-ray tubes exceeded company warranty coverage limits. DISCUSSION: Although Pro tubes lasted longer, they acquired fewer scans than did Ultra tubes. A similar result was shown for current output. CONCLUSION: Because the clinical demand for a CT scanner varies, it is difficult to determine the reason for the failed tubes. Mechanical, environmental, and usage factors can reduce the life expectancy of an x-ray tube.
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Electrónica/instrumentación , Electrónica/estadística & datos numéricos , Falla de Equipo/estadística & datos numéricos , Tomografía Computarizada por Rayos X/instrumentación , Tomografía Computarizada por Rayos X/estadística & datos numéricos , Diseño de Equipo , Análisis de Falla de EquipoRESUMEN
Remanufactured products that can substitute for new products are generally claimed to save energy. These claims are made from studies that look mainly at the differences in materials production and manufacturing. However, when the use phase is included, the situation can change radically. In this Article, 25 case studies for eight different product categories were studied, including: (1) furniture, (2) clothing, (3) computers, (4) electric motors, (5) tires, (6) appliances, (7) engines, and (8) toner cartridges. For most of these products, the use phase energy dominates that for materials production and manufacturing combined. As a result, small changes in use phase efficiency can overwhelm the claimed savings from materials production and manufacturing. These use phase energy changes are primarily due to efficiency improvements in new products, and efficiency degradation in remanufactured products. For those products with no, or an unchanging, use phase energy requirement, remanufacturing can save energy. For the 25 cases, we found that 8 cases clearly saved energy, 6 did not, and 11 were too close to call. In some cases, we could examine how the energy savings potential of remanufacturing has changed over time. Specifically, during times of significant improvements in energy efficiency, remanufacturing would often not save energy. A general design trend seems to be to add power to a previously unpowered product, and then to improve on the energy efficiency of the product over time. These trends tend to undermine the energy savings potential of remanufacturing.
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Conservación de los Recursos Energéticos/métodos , Electrónica/estadística & datos numéricos , Artículos Domésticos/estadística & datos numéricos , Materiales Manufacturados/estadística & datos numéricos , Residuos Electrónicos/análisis , Residuos Electrónicos/estadística & datos numéricos , Electrónica/economía , Artículos Domésticos/economía , Industrias/economía , Industrias/métodos , Materiales Manufacturados/análisis , Materiales Manufacturados/economíaRESUMEN
The release of ultra-fine particles from equipment of daily use is currently a topic of high public concern. The present study reports on the measurement of 12 household appliances such as toasters, grills, and hair dryers in an emission test chamber regarding the release of particles between 5.6 and 560 nm. The devices were new at the time experiments started and had never been used for their original purpose. For instance, toasters and sandwich-makers were tested without the presence of food or residues from prior usage. During the experiments the devices released aerosols with count mean diameters mainly below 100 nm. Within the operating phase high quantities of 10 nm particles are released which form larger particles by agglomeration. The origin of the particles can be attributed to the heated surfaces but cleaning these surfaces only had a minor influence on the emission strength. The released particles are evaporated in a thermodenuder between 150 °C and 200 °C. These findings indicate the particles to be formed from semi-volatile organic compounds. However, the compounds are not located on the heated surfaces and are not released as supersaturated vapor because emission is continuous over the operating phase of the device. Furthermore, the contribution of oxygen to the formation process can be neglected because the emission can also be detected in a nitrogen atmosphere. However, the presence of additional organic compounds in the surrounding air was found to be influencing the growth of the particles within the operating phase. All in all the tested household appliances were strong particle emission sources even when there was no contact with food or clothing.
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Contaminantes Atmosféricos/análisis , Contaminación del Aire Interior/estadística & datos numéricos , Electrónica/estadística & datos numéricos , Artículos Domésticos/estadística & datos numéricos , Material Particulado/análisis , Aerosoles/análisis , Monitoreo del Ambiente , Vivienda , Tamaño de la PartículaRESUMEN
Cogging effect which can be treated as a type of position-dependent periodic disturbance, is a serious disadvantage of the permanent magnetic synchronous motor (PMSM). In this paper, based on a simulation system model of PMSM position servo control, the cogging force, viscous friction, and applied load in the real PMSM control system are considered and presented. A dual high-order periodic adaptive learning compensation (DHO-PALC) method is proposed to minimize the cogging effect on the PMSM position and velocity servo system. In this DHO-PALC scheme, more than one previous periods stored information of both the composite tracking error and the estimate of the cogging force is used for the control law updating. Asymptotical stability proof with the proposed DHO-PALC scheme is presented. Simulation is implemented on the PMSM servo system model to illustrate the proposed method. When the constant speed reference is applied, the DHO-PALC can achieve a faster learning convergence speed than the first-order periodic adaptive learning compensation (FO-PALC). Moreover, when the designed reference signal changes periodically, the proposed DHO-PALC can obtain not only faster convergence speed, but also much smaller final error bound than the FO-PALC.
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Inteligencia Artificial , Electrónica/estadística & datos numéricos , Diseño de Equipo/estadística & datos numéricos , Magnetismo , Algoritmos , Simulación por Computador , Redes Neurales de la Computación , Dinámicas no Lineales , Estándares de ReferenciaRESUMEN
This paper focuses on the use of the techniques based on linear matrix inequalities for robust H(infinity) position control synthesis of an electro-hydraulic servo system. A nonlinear dynamic model of the hydraulic cylindrical actuator with a proportional valve has been developed. For the purpose of the feedback control an uncertain linearized mathematical model of the system has been derived. The structured (parametric) perturbations in the electro-hydraulic coefficients are taken into account. H(infinity) controller extended with an integral action is proposed. To estimate internal states of the electro-hydraulic servo system an observer is designed. Developed control algorithms have been tested experimentally in the laboratory model of an electro-hydraulic servo system.
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Electrónica/estadística & datos numéricos , Industrias/estadística & datos numéricos , Algoritmos , Simulación por Computador , Diseño de Equipo/estadística & datos numéricos , Modelos Lineales , Dinámicas no LinealesRESUMEN
INTRODUCTION: The purpose of this study was to investigate the ability of three electronic apex locators (EALs) to detect the minor foramen and morphological influencing factors relative to working length determination. METHODS: Three hundred fifty-six extracted teeth were decoronated, and the coronal portion of the canal was flared. The distance between the major foramen and the file tips (DMFF) was determined by different EALs. The relationship between the DMFFs determined by the EAL and the morphological features of the root apex was analyzed by linear regression analysis. RESULTS: The average DMFFs were 0.261 mm, 0.376 mm, and 0.383 mm for the Root ZX (J. Morita, Kyoto, Japan), Raypex 5 (VDW, Munich, Germany), and Elements Apex Locator (SybronEndo, Anaheim, CA), respectively. The file tips determined by EALs were much closer to the major foramen in teeth with a "lateral major foramen" (p < 0.001). The area and diameters of the minor foramen were significantly related to the variation of the DMFFs determined by EALs. CONCLUSION: When the "minor foramen" reading was given, the file tip connected to the Root ZX was much closer to the major foramen than the other two EALs. The minor foramen's morphology and the major foramen's location were both important influencing factors on the performance of EALs.