Distortion and regulation characterization of a Mapham inverter

Output voltage Total Harmonic Distortion (THD) of a 20kHz, 6kVA Mapham resonant inverter is characterized as a function of its switching-to-resonant frequency ratio, f sub s/f sub r, using the EASY5 engineering analysis system. EASY5 circuit simulation results are compared with hardware test results to verify the accuracy of the simulations. The effects of load on the THD versus f sub s/f sub r ratio is investigated for resistive, leading, and lagging power factor load impedances. The effect of the series output capacitor on the Mapham inverter output voltage distortion and inherent load regulation is characterized under loads of various power factors and magnitudes. An optimum series capacitor value which improves the inherent load regulation to better than 3 percent is identified. The optimum series capacitor value is different than the value predicted from a modeled frequency domain analysis. An explanation is proposed which takes into account the conduction overlap in the inductor pairs during steady-state inverter operation, which decreases the effective inductance of a Mapham inverter. A fault protection and current limit method is discussed which allows the Mapham inverter to operate into a short circuit, even when the inverter resonant circuit becomes overdamped

Failure of a Pipeline in an 800-year Old Debris Fill

In June of 1994 a 20-m section of 1.4-m diameter, restrained-joint, ductile iron pipe failed during construction of a new section of water pipeline for the city of Cairo in the Arab Republic of Egypt. The failure occurred in an area where the pipe was supported on piles, and compacted silica sand was used as side support for the pipe. Soil above the crown of the failed section of pipe was 6 m or more in thickness. Results of a detailed review of the failure revealed that a number of unique and related factors apparently caused the failure. The most significant of these causes was the native soil surrounding the pipeline, which was formed from an accumulation of 800 years of building and construction debris. At the location of the failure the debris was in excess of 15-m thick. When subjected to water at this location, this debris underwent significant settlement, which eventually led to loss in side support for the pipeline. To repair the pipeline and to avoid future similar failures, a utilidor was used to protect the pipeline in areas where overburden thickness was greater than 4.5 m, and a pipe encasement was used where the overburden thickness was less

A national cross-sectional survey of the attitudes, skills and use of evidence-based practice amongst Spanish osteopaths

Background Although evidence-based practice (EBP) is largely supported across healthcare professions, its implementation in manual therapy professions such as osteopathy remains limited and debated. There is currently little knowledge of how Spanish osteopaths relate to EBP. Objectives The main aim of this study was to investigate the attitudes, skills and use of EBP among Spanish osteopaths. A secondary aim was to identify barriers and facilitators for the adoption of EBP in the Spanish osteopathic context. Methods National cross-sectional survey of Spanish osteopaths registered and non-registered to an osteopathic association in Spain. Eligible participants were invited by a range of recruitment strategies including email and social media campaigns to complete the Spanish-translated Evidence-Based practice Attitude and utilization Survey (EBASE) anonymously online. Results A total of 567 osteopaths completed the survey which represents an approximate response rate of 9%. Participant’s attitudes toward EBP were largely positive. Most respondents agreed or strongly agreed that EBP was necessary in the practice of osteopathy (89.6%) and that professional literature and research findings were useful to their day-to-day practice (88.9%). Levels of perceived skill in EBP were reported as low to moderate with lowest levels for items related to ‘research conduct’. Except reading/reviewing professional literature and using online search engines to find practice-related literature, participant engagement in all other EBP-related activities was generally infrequent. The perceived proportion of clinical practice that was based on clinical research evidence was reported to be very small. Main barriers to EBP uptake included a lack of clinical evidence in osteopathy and insufficient skills for applying research findings. Main facilitators of EBP uptake included access to full-text articles, internet at the workplace and online databases. Conclusions Spanish osteopaths were largely supportive of evidence-based practice, had low to moderate skills in EBP and engaged in EBP activities infrequently. Formal regulation of the profession in Spain and the inclusion of osteopathic programs into the university sector would potentially improve EBP skills and use

Casimir Energy For a Massive Dirac Field in One Spatial Dimension: A Direct Approach

In this paper we calculate the Casimir energy for a massive fermionic field confined between two points in one spatial dimension, with the MIT Bag Model boundary condition. We compute the Casimir energy directly by summing over the allowed modes. The method that we use is based on the Boyer's method, and there will be no need to resort to any analytic continuation techniques. We explicitly show the graph of the Casimir energy as a function of the distance between the points and the mass of the fermionic field. We also present a rigorous derivation of the MIT Bag Model boundary condition.Comment: 8 Pages, 4 Figure

Implications on Livelihoods and the Environment of Uptake of Gasifier Cook Stoves among Kenya’s Rural Households

A majority of people in developing countries use biomass energy for cooking and heating due to its affordability, accessibility and convenience. However, unsustainable biomass use leads to forest degradation and climate change. Therefore, this study was carried out in Kwale County, Kenya, on the use of a biochar-producing gasifier cook stove and implications of its uptake on livelihoods and the environment. Fifty households were trained and issued with a gasifier for free. After 2–3 months of gasifier use, a survey was conducted to investigate the implications of its uptake. The direct impacts included reduced fuel consumption by 38%, reduced time spent in firewood collection, reduced expenditure on cooking fuel, diversification of cooking fuels, improved kitchen conditions and reduced time spent on cooking. The potential benefits included income generation, increased food production, reduced impacts on environment and climate change and reduced health problems. Improved biomass cook stoves can alleviate problems with current cooking methods, which include inefficient fuel use, health issues caused by smoke, and environmental problems. These benefits could contribute to development through alleviating poverty and hunger, promoting gender equality, enhancing good health and sustainable ecosystems and mitigating climate change. The study recommends the promotion of cleaner cooking stoves, particularly gasifiers, among households in rural areas while paying attention to user needs and preferences

Reconstruction of Propagating Kelvin-Helmholtz Vortices at Mercury's Magnetopause

A series of quasi-periodic magnetopause crossings were recorded by the MESSENGER spacecraft during its third flyby of Mercury on 29 September 2009, likely caused by a train of propagating Kelvin-Helmholtz (KH) vortices. We here revisit the observations to study the internal structure of the waves. Exploiting MESSENGER s rapid traversal of the magnetopause, we show that the observations permit a reconstruction of the structure of a rolled-up KH vortex directly from the spacecraft s magnetic field measurements. The derived geometry is consistent with all large-scale fluctuations in the magnetic field data, establishes the non-linear nature of the waves, and shows their vortex-like structure. In several of the wave passages, a reduction in magnetic field strength is observed in the middle of the wave, which is characteristic of rolled-up vortices and is related to the increase in magnetic pressure required to balance the centrifugal force on the plasma in the outer regions of a vortex, previously reported in computer simulations. As the KH wave starts to roll up, the reconstructed geometry suggests that the vortices develop two gradual transition regions in the magnetic field, possibly related to the mixing of magnetosheath and magnetospheric plasma, situated at the leading edges from the perspectives of both the magnetosphere and the magnetosheath

Dehydrogenase-dependent ethanol metabolism in deer mice (Peromyscus maniculatus) lacking cytosolic alcohol dehydrogenase. Reversibility and isotope effects in vivo and in subcellular fractions

Elimination of [2H]ethanol in vivo as studied by gas chromatography/mass spectrometry occurred at about half the rate in deer mice reported to lack alcohol dehydrogenase (ADH-) compared with ADH+ deer mice and exhibited kinetic isotope effects on Vmax and Km (D(V/K] of 2.2 +/- 0.1 and 3.2 +/- 0.8 in the two strains, respectively. To an equal extent in both strains, ethanol elimination was accompanied by an ethanol-acetaldehyde exchange with an intermolecular transfer of hydrogen atoms, indicating the occurrence of dehydrogenase activity. This exchange was also observed in perfused deer mouse livers. Based on calculations it was estimated that at least 50% of ethanol elimination in ADH- deer mice was caused by the action of dehydrogenase systems. NADPH-supported cytochrome P-450-dependent ethanol oxidation in liver microsomes from ADH+ and ADH- deer mice was not stereoselective and occurred with a D(V/K) of 3.6. The D(V/K) value of catalase-dependent oxidation was 1.8, whereas a kinetic isotope effect of cytosolic ADH in the ADH+ strain was 3.2. Mitochondria from both ADH+ and ADH- deer mice catalyzed NAD+-dependent ethanol oxidation and NADH-dependent acetaldehyde reduction. The kinetic isotope effects of NAD+-dependent ethanol oxidation in the mitochondrial fraction from ADH+ and ADH- deer mice were 2.0 +/- 0.1 and 2.3 +/- 0.3, respectively. The results indicate only a minor contribution by cytochrome P-450 to ethanol elimination, whereas the isotope effects are consistent with ethanol oxidation by the catalase-H2O2 system in ADH- deer mice in addition to the dehydrogenase systems