Academic literature on the topic 'Two and three level charge pumping'
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Journal articles on the topic "Two and three level charge pumping"
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Massaq, Zakaria, Abdelouahed Abounada, and Mohamed Ramzi. "Fuzzy and predictive control of a photovoltaic pumping system based on three-level boost converter." Bulletin of Electrical Engineering and Informatics 10, no. 3 (2021): 1183–92. http://dx.doi.org/10.11591/eei.v10i3.2605.
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In this work, an efficient control scheme for a double stage pumping system is proposed. On the DC side, a three-level boost converter is employed to maximize the photovoltaic power and to step-up the DC-link voltage. For maximum power point tracking, the classical incremental conductance method is substituted by a fuzzy logic controller. The designed controller estimates the optimal step size which speeds up the tracking process and improves the accuracy of the extracted photovoltaic power. Afterwards, the voltages across the three-level boost converter (TLBC) capacitors are balanced by phase shifting the applied duty ratios. On the motor pump side, a two-level inverter drives the motor pump with the cascaded nonlinear predictive control. The predictive controller is preferred over the conventional field-oriented control because it accelerates the torque response and resists to the change of the engine parameters. The designed controllers are evaluated using MATLAB/Simulink, and compared with the conventional controllers (incremental conductance algorithm and field-oriented control). The robust control scheme of the entire system has increased the hydraulic power by up to 23% during the system start-up and up to 10% in steady state.
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Gallagher, John, and Laurence W. Gill. "The Life Cycle Environmental Performance of On-Site or Decentralised Wastewater Treatment Systems for Domestic Homes." Water 13, no. 18 (2021): 2542. http://dx.doi.org/10.3390/w13182542.
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There is little knowledge regarding the environmental sustainability of domestic on-site or decentralised wastewater treatment systems (DWWTS). This study evaluated six unique life cycle environmental impacts for different DWTTS configurations of five conventional septic tank systems, four packaged treatment units, and a willow evapotranspiration system. Similar freshwater eutrophication (FE), dissipated water (DW), and mineral and metal (MM), burdens were noted between the packaged and conventional system configurations, with the packaged systems demonstrating significantly higher impacts of between 18% and 56% for climate change (CC), marine eutrophication (ME), and fossils (F). At a system level, higher impacts were observed in systems requiring (i) three vs. two engineered treatment stages, (ii) a larger soil percolation trench area, and (iii) pumping of effluent. The evapotranspiration system presented the smallest total environmental impacts (3.0–10.8 lower), with net benefits for FE, ME, and MM identified due to the biomass (wood) production offsetting these burdens. Further analysis highlighted the sensitivity of results to biomass yield, operational demands (desludging or pumping energy demands), and embodied materials, with less significant impacts for replacing mechanical components, i.e., pumps. The findings highlighted the variation in environmental performance of different DWTTS configurations and indicated opportunities for design improvements to reduce their life cycle impacts.
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Meaški, Hrvoje, Ranko Biondić, Jelena Loborec, and Dijana Oskoruš. "The Possibility of Managed Aquifer Recharge (MAR) for Normal Functioning of the Public Water-Supply of Zagreb, Croatia." Water 13, no. 11 (2021): 1562. http://dx.doi.org/10.3390/w13111562.
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With its quantities of groundwater, the Zagreb aquifer is an irreplaceable water-supply resource that forms the basis of the water-supply of Zagreb, the capital and largest city of the Republic of Croatia. The depth of the Zagreb aquifer system is about 100 m at the deepest part, and the two main aquifers of the aquifer system can be separated vertically by low-permeable clay deposits. In the area of the Zagreb aquifer, there are several active and reserve public water-supply sites, the largest of which are Mala Mlaka and Petruševec. The groundwater level of the Zagreb aquifer is directly related to the water levels of the Sava River, so any erosive change in the Sava riverbed decreases the groundwater levels in the aquifer. In the last 50 years, the groundwater levels in the Zagreb aquifer have decreased significantly, being most pronounced in the area of the Mala Mlaka water-supply site. This has affected the normal functioning of the public water-supply because the suction baskets of the pumps in the dug wells at the Mala Mlaka water-supply site occasionally remain partially or completely in the unsaturated aquifer zone during low groundwater levels, which reduces capacity or prevents pumping from these water-supply facilities. Immediately next to the Mala Mlaka water-supply site is the Sava-Odra Canal, which was built to protect Zagreb from flooding and into which the Sava River flows when its flow rate exceeds 2350 m3/s. This reduces the flow rate of the Sava River near Zagreb and the possibility of flooding urban areas. To prevent problems with groundwater levels at the Mala Mlaka water-supply facilities and to enable normal water-supply, even in extremely dry periods, several variants of managed aquifer recharge (MAR) are proposed here. In order to determine the optimal solution for MAR and to enable the normal functioning of one of the main sites of water-supply in the Zagreb water-supply system. Groundwater flow for the period of 2006 to 2010 was simulated for six different variants of MAR. One assumes a constant potential in the Sava-Odra Canal, three are related to recharge from the Sava-Odra Canal with different backwater levels in the infiltration facility (elevations of 114, 114.5, and 115 m a.s.l.), and two with three absorption wells upstream of the Mala Mlaka water pumping station (injection of 300 L/s each and 500 L/s each). The most favorable method to recharge artificially the Zagreb aquifer near the Mala Mlaka pumping station is achieved with an infiltration facility using an elevation of 115 m a.s.l. The use of such a facility will enable the smooth operation of the water pumping station and the possibility of increasing the pumping quantities at the Mala Mlaka water pumping station for the future development of the area.
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Ye, S., Y. Luo, J. Wu, P. Teatini, H. Wang, and X. Jiao. "Three dimensional numerical modeling of land subsidence in Shanghai." Proceedings of the International Association of Hydrological Sciences 372 (November 12, 2015): 443–48. http://dx.doi.org/10.5194/piahs-372-443-2015.
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Abstract. Shanghai city has been suffering land subsidence caused by overly exploitation of ground water since 1921, which is a serious problem for this coastal city with altitude of 2.2–4.8 m above mean sea level. The largest cumulative land subsidence amounted to 2.6 m in the downtown area. Measures to decrease the ground water exploitation, change the pumping aquifers, and increase aquifer artificial recharge have been used to mitigate land subsidence since 1961. It is necessary to develop a proper numerical model to simulate and predict land subsidence. In this study, a decoupled three-dimensional (3-D) finite element land subsidence model including a 3-D ground water flow model and a 3-D geo-mechanical model was developed to simulate the 3-D deformation of the aquifer systems in the center area of Shanghai. The area of downtown Shanghai is 660 km2, with 10 million inhabitants, dense high buildings, and 11 metro lines. The simulation spans the period from 1979 to 1995. Two different assumptions have been tested on the side boundary, i.e., precluding the three components of the displacement, or assuming a free-displacement condition. The distribution of calculated land subsidence and horizontal displacements in different aquifers was analyzed. The computed vertical displacement fitted well with the available observations. It has been verified that the two different assumptions on the lateral boundaries in the geo-mechanical model caused different results just limited on nodes close to boundary. The developed 3-D land subsidence model is reasonable and can be used to simulate and predict 3-D movement of aquifer systems in the center area of Shanghai, which could provide scientific support to local government in controlling land subsidence and differential movements of the land surface.
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Autran, J. L., F. Djahli, B. Balland, C. Plossu, and L. M. Gaborieau. "Three-level charge pumping on submicronic MOS transistors." Solid State Communications 84, no. 6 (1992): 607–11. http://dx.doi.org/10.1016/0038-1098(92)90200-s.
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Davidson, J. H., W. T. Carlson, and W. S. Duff. "Impact of Component Selection and Operation on Thermal Ratings of Drain-Back Solar Water Heaters." Journal of Solar Energy Engineering 114, no. 4 (1992): 219–26. http://dx.doi.org/10.1115/1.2930009.
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A half-factorial, two-level experimental design is used to determine the effects of changes in collector area, storage tank volume, collector flow rate, recirculation flow rate, and storage tank design on thermal rating of a solar drain-back water heating system. Experimental ratings are determined in accordance with the Solar Rating and Certification Corporation guidelines. Storage tank design is varied by using a stratification manifold in place of the standard drop tube. Variations in other component sizes and operating factors are based on current industry standards. Statistical analyses indicate that a change in collector area accounts for nearly 90 percent of the variation in heat output. Doubling collector area from 2.78 m2 to 5.56 m2 increases delivered solar energy by 31 percent. Use of a stratification manifold increases the delivery of solar energy by six percent. Doubling collector flow rate from 0.057 to 0.114 1/s increases solar output by approximately three percent; however, the increase in pumping energy outweighs the benefits of increasing collector flow rate. The effects of recirculation flow rate and tank volume are obscured by experimental error.
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Militaru, L., P. Masson, and G. Guegan. "Three level charge pumping on a single interface trap." IEEE Electron Device Letters 23, no. 2 (2002): 94–96. http://dx.doi.org/10.1109/55.981317.
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Kivi, M. J., and S. Taylor. "SHE injection as studied by three level charge pumping." Microelectronics Journal 27, no. 7 (1996): 687–91. http://dx.doi.org/10.1016/0026-2692(96)00060-2.
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Plant, R. S., and S. E. Belcher. "Numerical Simulation of Baroclinic Waves with a Parameterized Boundary Layer." Journal of the Atmospheric Sciences 64, no. 12 (2007): 4383–99. http://dx.doi.org/10.1175/2007jas2269.1.
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Abstract A dry three-dimensional baroclinic life cycle model is used to investigate the role of turbulent fluxes of heat and momentum within the boundary layer on midlatitude cyclones. Simulations are performed of life cycles for two basic states: with and without turbulent fluxes. The different basic states produce cyclones with contrasting frontal and mesoscale flow structures. The analysis focuses on the generation of potential vorticity (PV) in the boundary layer and its subsequent transport into the free troposphere. The dynamic mechanism through which friction mitigates a barotropic vortex is that of Ekman pumping. This has often been assumed to also be the dominant mechanism for baroclinic developments. The PV framework highlights an additional, baroclinic mechanism. Positive PV is generated baroclinically due to friction to the northeast of a surface low and is transported out of the boundary layer by a cyclonic conveyor belt flow. The result is an anomaly of increased static stability in the lower troposphere, which restricts the growth of the baroclinic wave. The reduced coupling between lower and upper levels can be sufficient to change the character of the upper-level evolution of the mature wave. The basic features of the baroclinic damping mechanism are robust for different frontal structures, with and without turbulent heat fluxes, and for the range of surface roughness found over the oceans.
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Zhu, Wu, Xue-qi Zhang, Zhan-ke Liu, and Qian Zhu. "Spatiotemporal Characterization of Land Subsidence in Guandu (China) Revealed by Multisensor InSAR Observations." Journal of Sensors 2020 (October 15, 2020): 1–13. http://dx.doi.org/10.1155/2020/8855364.
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Excessive groundwater exploitation has brought about severe ground subsidence in Guandu (China), threatening the stability of urban infrastructure. Mapping of the spatiotemporal variations of ground deformation is urgently needed for disaster prevention and mitigation. In this study, multisensor interferometric synthetic aperture radar (InSAR) observations were applied to Guandu to derive the time series deformation from 2007 to 2019. The annual deformation velocity revealed three severe subsiding regions in Guandu. Based on the ascending and descending Sentinel-1 images with overlapping temporal and spatial coverage, two-dimensional vertical and horizontal east–west deformation was calculated and indicated that the deformation in Guandu was dominated by vertical direction. After connecting the multisensor results, long-term ground deformation spanning from January 9, 2007, to September 1, 2019, was produced and showed that the north subsiding region experienced fast followed by slow subsidence, whereas the south subsiding region experienced slow followed by fast subsidence. This difference was due to the changes of groundwater pumping centers and rates. The cumulative maximum subsidence reached 400 mm during the period of 2007–2019. The similar variations in temporal domain between the change of groundwater level and ground deformation suggested that groundwater exploitation accounted for the severe subsidence in Guandu. Our results may provide scientific evidence regarding the sound management of groundwater exploitation to mitigate potential damage to infrastructure and the environment.
Dissertations / Theses on the topic "Two and three level charge pumping"
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Zbierska, Inga Jolanta. "Study of electrical characteristics of tri-gate NMOS transistor in bulk technology." Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10282/document.
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Afin de dépasser la limite d'échelle, il existe une solution innovante qui permet de fabriquer des structures multi-grilles. Ainsi, un NMOSFET composé de trois grilles indépendantes fabriquées dans la technologie CMOS. En dehors de leur forme, géométrique, le transistor multi-grille est similaire à une structure classique. Une multi-grille NMOSFET peut être fabriquée par l'intégration de tranchées de polysilicium. Ces tranchées sont utilisées dans diverses applications telles que les mémoires DRAM, électronique de puissance ou de capteurs d'image. Les capteurs d'image présentent le problème des charges parasites entre les pixels, appelées diaphonie. Les tranchées sont l'une des solutions qui réduisent ce phénomène. Ces tranchées assurent l'isolation électrique sur toute la matrice des pixels. Nous avons étudié ses caractéristiques en utilisant des mesures I-V, méthode du split C-V et de pompage de charge à deux et à trois niveaux. Son multi-seuil caractéristique a été vérifié. Nous n'avons observé aucune dégradation significative de ces caractéristiques grâce à l'intégration des tranchées. La structure a été simulée par la méthode des éléments finis en 3D via le logiciel TCAD. Ses caractéristiques électriques ont été simulées et confrontées avec les résultats obtenus à partir de mesures électriques. La tension de seuil et la longueur de canal effective ont été extraites. Sa mobilité effective et les pièges de l'interface Si/SiO2 ont également été simulés ou calculés. En raison des performances électriques satisfaisantes et d'un bon rendement, nous avons remarqué que ce dispositif est une solution adéquate pour les applications analogiques grâce aux niveaux de tension multi-seuil<br>One of the recent solutions to overcome the scaling limit issue are multi-gate structures. One cost-effective approach is a three-independent-gate NMOSFET fabricated in a standard bulk CMOS process. Apart from their shape, which takes advantage of the three-dimensional space, multi gate transistors are similar to the conventional one. A multi-gate NMOSFET in bulk CMOS process can be fabricated by integration of polysilicon-filled trenches. This trenches are variety of the applications for instance in DRAM memories, power electronics and in image sensors. The image sensors suffer from the parasitic charges between the pixels, called crosstalk. The polysilicon - filled trenches are one of the solution to reduce this phenomenon. These trenches ensure the electrical insulation on the whole matrix pixels. We have investigated its characteristics using l-V measurements, C-V split method and both two- and three-level charge pumping techniques. Tts tunable-threshold and multi-threshold features were verified. Tts surface- channel low-field electron mobility and the Si/SiO2 interface traps were also evaluated. We observed no significant degradation of these characteristics due to integration of polysilicon-filled trenches in the CMOS process. The structure has been simulated by using 3D TCAD tool. Tts electrical characteristics has been evaluated and compared with results obtained from electrical measurements. The threshold voltage and the effective channel length were extracted. Tts surface-channel low-field electron mobility and the Si/SiO2 interface traps were also evaluated. Owing to the good electrical performances and cost-effective production, we noticed that this device is a good aspirant for analog applications thanks to the multi-threshold voltages
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Kivi, Michael John. "A study of semiconductor-insulator interfaces using the three level charge pumping technique." Thesis, University of Liverpool, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243245.
Full textBook chapters on the topic "Two and three level charge pumping"
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de Rond, Mark. "A Record-Breaking Month." In Doctors at War. Cornell University Press, 2017. http://dx.doi.org/10.7591/cornell/9781501705489.003.0009.
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The author says the last month was a record-breaking one for the field hospital in terms of blood use. Because the numbers of casualties were not significantly different from previous months, this meant that people were getting increasingly badly injured, fueled by more powerful and often badly contaminated improvised explosive devices. The author also discusses the controversy sparked by one of the doctors' comments that the field hospital should stop giving one of the Afghans more opiates as he wouldn't get the same pain medications in any local hospital. After mentioning the day's casualties, he describes the three helicopter crews that were in charge of the evacuation of casualties: MERT, Dustoff, and Pedro. MERT is a British-staffed medical crew, comprising a physician, one or two advanced paramedics, and an emergency nurse. Dustoff and Pedro are American-staffed helicopter crews with a limited level of medical care.
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Emmett, Stevan R., Nicola Hill, and Federico Dajas-Bailador. "Cardiovascular medicine." In Clinical Pharmacology for Prescribing. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780199694938.003.0010.
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Hypertension (HTN) is the most common condition man¬aged in primary care and a major risk factor for cardio-vascular disease. Numerous randomized controlled trials have demonstrated that the use of antihypertensives to manage blood pressure (BP) helps reduce cardiovascular disease risk. Prevalence of HTN increases with age so that around 33% of men and 25% of women aged 45– 54 years have a clinical diagnosis. It is generally defined as a raised blood pressure exceeding 140/ 90 mmHg, divided into two types: ● Essential (or primary) hypertension: accounts for 95% of cases and is where no secondary cause is identified. ● Secondary hypertension: the result of an underlying disease (e.g. renal, pulmonary, endocrine, or drug/ toxin). Pre- HTN is defined as systolic BP (SBP) 120– 139 mmHg and diastolic BP (DBP) 80– 89 mmHg. BP is the product of cardiac output (heart stroke volume and heart rate) and the total peripheral resistance of vessels supplied by the heart. Thus, three main systems are responsible for generating BP: the heart (pumping pressure), vessel tone (being the systemic resistance), and the kidney (regulating intravascular volume). Three main physiological systems regulate heart, vessels, and kidney with respect to blood pressure: 1. The sympathetic nervous system: changes in BP are sensed by a feedback mechanism mediated by baroreceptors in the walls of the aortic arch and carotid sinuses. Increasing BP causes firing of glossopharyngeal and vagus nerves, inhibiting sympathetic outflow via the medulla (tractus solitarius). This, in turn, leads to parasympathetic dominance and a reduction in peripheral resistance (vasodilation through β1- adrenoceptors) and cardiac output (by reduced heart rate and reduced contractility through α1- adrenoceptors). Centrally acting antihypertensive drugs act at the nucleus tractus solitarius (e.g. clonidine/ methyldopa) or ventrolateral medulla (e.g. moxonidine). 2. The renin- angiotensin- aldosterone system: this system regulates blood volume and systemic vascular resistance, thus influencing cardiac output and arterial pressure. This feedback mechanism starts in the kidney with the release of renin into the peripheral circulation. Renin release, from juxtaglomerular cells (JC), is stimulated by sympathetic mechanisms (involving α1- receptors on JC themselves), decreased afferent arteriole pressure (from systemic hypotension or renal artery stenosis) or declining Na<sup>+</sup> levels in the distal tubules of the kidney. Prostaglandins, such as PGE2 and PGI2 (prostacyclin), also cause release of renin secondary to reduced NaCl transport in the macular densa (see Topic 5.2 ‘Acute kidney injury’).
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ABU, K. S. "Library Resources and Services in Tamilnadu State Central Library (Connemara Public Library)." In Library Science and Administration. IGI Global, 2018. http://dx.doi.org/10.4018/978-1-5225-3914-8.ch037.
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It is a known fact that Chennai city has a well-defined place when talking about landmark buildings, which have gone down the annals of history- Connemara library, certainly a pride of Madras is not only heaven for book lovers and research Scholars, the building by its sheer architectural beauty and marvel acquires a special significance as part of the history of Madras City. Public library is largely regarded as the People's University. It has tremendous developments in India from the early period to till date at various stages. Most of the Indian states now have free public library services to develop the people of India at different levels, which can be stated as below briefly. Majority of the users prefer to search documents directly from the stack room. The main purpose of visiting the library by the users is to prepare for completive examinations and some other purposes are to study in the library and to update their subject knowledge. The general book services provided by the library are highly useful. The Reference services provided by the library are highly useful. The users are satisfied with the information provided in the library. All the services available on the library except latest collections are found to be at satisfactory level. Nearly 7.5 lakhs of collection of books are available in the library. Selection of books is done by book selection committee. Nearly four hundred books are issued daily to the public. The uses can retain the book for a maximum of 14 days. The users can renew the books for another three times either through phone or in person. A minimum amount of Rupees two per week is charged as overdue charge.
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ABU, K. S. "Library Resources and Services in Tamilnadu State Central Library (Connemara Public Library)." In Advances in Library and Information Science. IGI Global, 2015. http://dx.doi.org/10.4018/978-1-4666-8178-1.ch017.
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It is a known fact that Chennai city has a well-defined place when talking about landmark buildings, which have gone down the annals of history- Connemara library, certainly a pride of Madras is not only heaven for book lovers and research Scholars, the building by its sheer architectural beauty and marvel acquires a special significance as part of the history of Madras City. Public library is largely regarded as the People's University. It has tremendous developments in India from the early period to till date at various stages. Most of the Indian states now have free public library services to develop the people of India at different levels, which can be stated as below briefly. Majority of the users prefer to search documents directly from the stack room. The main purpose of visiting the library by the users is to prepare for completive examinations and some other purposes are to study in the library and to update their subject knowledge. The general book services provided by the library are highly useful. The Reference services provided by the library are highly useful. The users are satisfied with the information provided in the library. All the services available on the library except latest collections are found to be at satisfactory level. Nearly 7.5 lakhs of collection of books are available in the library. Selection of books is done by book selection committee. Nearly four hundred books are issued daily to the public The uses can retain the book for a maximum of 14 days. The users can renew the books for another three times either through phone or in person. A minimum amount of Rupees two per week is charged as overdue charge.
Conference papers on the topic "Two and three level charge pumping"
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Kivi, M. J. "Characterisation of silicon carbide MOSFETs using three level charge pumping." In IEE Colloquium on New Developments in Power Semiconductor Devices. IEE, 1996. http://dx.doi.org/10.1049/ic:19960864.
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Williams, D. Ryan, Henry Knutzen, Domenico Chiera, and Gregory J. Hampson. "EGR and Backpressure Effects on Knock Behavior in Stoichiometric Natural Gas Engines." In ASME 2017 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/icef2017-3669.
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Increasingly restrictive limits on NOx levels are driving the change from lean-burn to stoichiometric combustion strategies on heavy-duty on-highway natural gas engines in order to take advantage of inexpensive and effective three-way catalyst technology. The change to stoichiometric combustion has led to increased tendency for engine knock due to higher in-cylinder temperatures. Exhaust Gas Recirculation (EGR) has been proposed as a method to suppress knock via charge dilution while maintaining a stoichiometric air-fuel ratio. Two of the more common EGR driving architectures and the challenges associated with each architecture are described. A series of engine tests were devised and performed on a 7-liter heavy-duty natural gas engine to explore the relationships between EGR knock suppression and engine backpressure. A unique concept for an external EGR pumping cart which allowed for the exploration of higher EGR rates independent of backpressure is also described. Results showed that for the conditions tested, increasing EGR rates beyond a certain point did not result in decreased knock tendency. 1D Simulation showed that the effectiveness of the EGR is limited by trapped hot residual gasses which resulted in higher in-cylinder temperatures and nullified the cooling effects of the EGR. These results suggest that attention must be paid to reducing backpressure via efficient EGR system architecture design in order to achieve the highest possible efficiency.
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Kim, Kee-Jong, and Ohyun Kim. "Three-Level Charge-Pumping Technique for Grain-Boundary Trap Evaluation in Polysilicon Thin Film Transistors." In 1996 International Conference on Solid State Devices and Materials. The Japan Society of Applied Physics, 1996. http://dx.doi.org/10.7567/ssdm.1996.d-3-2.
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Husain, Afzal, and Kwang-Yong Kim. "Enhanced Multi-Objective Optimization of a Microchannel Heat Sink Using Multiple Surrogates Modeling." In ASME 2009 7th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2009. http://dx.doi.org/10.1115/icnmm2009-82120.
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A liquid flow microchannel heat sink has been studied and optimized with the help of three-dimensional numerical analysis and multiple surrogate methods. Two objective functions, thermal resistance and pumping power have been selected to assess the performance of the microchannel heat sink. The design variables related to the microchannel top and bottom widths, depth and fin width, which contribute to objective functions, have been identified and design space has been explored through some preliminary calculations. Design of experiments was performed and a three-level full factorial design was selected to exploit the design space. The numerical solutions obtained at these design points were utilized to construct surrogate models namely Response Surface Approximations and Kriging. A hybrid multi-objective evolutionary algorithm coupled with surrogate models and a gradient-based search algorithm is applied to find global Pareto-optimal solutions. Since, the surrogate models are highly problem-dependent, the accuracy of the two surrogate models has been discussed in view of their predictions at on- and off-Pareto-optimal front. The trade-off analysis was performed in view of the two competing objectives. The Pareto-optimal sensitivity (change in value along the Pareto-optimal front) of the design variables has been found out to economically compromise with the design variables contributing relatively less to the objective functions. The application of the multiple surrogate methods not only improves quality of multi-objective optimization but also gives the feedback of the fidelity of the model near the optimum region.
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Zhang, Yu, Praveen Kumar, Meng Tang, et al. "Impact of Geometric Compression Ratio and Variable Valve Actuation on Gasoline Compression Ignition in a Heavy-Duty Diesel Engine." In ASME 2020 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/icef2020-3035.
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Abstract Gasoline compression ignition (GCI) is a promising powertrain solution to simultaneously address the increasingly stringent regulation of oxides of nitrogen (NOx) and a new focus on greenhouse gases. GCI combustion benefits from extended mixing times due to the low reactivity of gasoline, but only when held beneath the threshold of the high temperature combustion regime. The geometric compression ratio (GCR) of an engine is often chosen to balance the desire for low NOx emissions while maintaining high efficiency. This work explores the relationship between GCR, variable valve actuation (VVA) and emissions when using GCI combustion strategies. The test article was a Cummins ISX15 heavy-duty diesel engine with an unmodified production air and fuel system. The test fuel was an ethanol-free gasoline with a market-representative research octane number (RON) of 91.4–93.2. In the experimental investigation at 1375 rpm/10 bar BMEP, three engine GCRs were studied, including 15.7, 17.3, and 18.9. Across the three GCRs, GCI exhibited a two-stage combustion process enabled through a split injection strategy. When keeping both NOx and CA50 constant, varying GCR from 15.7 to 18.9 showed only a moderate impact on engine brake thermal efficiency (BTE), while its influence on smoke was pronounced. At a lower GCR, a larger fraction of fuel could be introduced during the first injection event due to lower charge reactivity, thereby promoting partially-premixed combustion and reducing smoke. Although increasing GCR increased gross indicated thermal efficiency (ITEg), it was also found to cause higher energy losses in friction and pumping. In contrast, GCI performance showed stronger sensitivity towards EGR rate variation, suggesting that air-handling system development is critical for enabling efficient and clean low NOx GCI combustion. To better utilize gasoline’s lower reactivity, an analysis-led variable valve actuation investigation was performed at 15.7 GCR and 1375 rpm/10 bar BMEP. The analysis was focused on using an early intake valve closing (EIVC) approach by carrying out closed-cycle, 3-D CFD combustion simulations coupled with 1-D engine cycle analysis. EIVC was shown to be an effective means to lengthen ignition delay and promote partially-premixed combustion by lowering the engine effective compression ratio (ECR). By combining EIVC with a tailored fuel injection strategy and properly developed thermal boundary conditions, simulation predicted a 2.3% improvement in ISFC and 47% soot reduction over the baseline IVC case while keeping NOx below the baseline level.
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Fresco, Anthony N. "Solute Ion Linear Alignment as the Energy Source to Address Aquifer Depletion Fresh Water Scarcity and Sea Level Rise." In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-65930.
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There are reports in the literature that the lives of 4 billion people are at risk either now or in the foreseeable future, and including even 130 million US citizens, mostly in the western states of California and surroundings and in Texas and Florida as being subject to water scarcity primarily due to depletion of aquifers and ground water and losses due to evaporation. 1, 2, 3 At the same time, according to the National Oceanic and Atmospheric Administration (NOAA), there is strong evidence that global sea level is now rising at an increased rate and will continue to rise during this century.4 Climate scientists at the Potsdam Institute of Climate Impact Research published a study in the journal Natural Hazards and Earth System Sciences5 that found that the economic costs of sea level rise increase more quickly than sea levels themselves. Although fresh water is scarce, obviously the oceans are virtually an infinite source of water. Rather than trying to implement difficult fresh water usage restrictions, the best solution to the sea level rise and fresh water scarcity would be to cheaply and efficiently convert sea water to fresh water and to pump the rising sea water level inland to compensate for the underground aquifer depletion. The main problem with desalination has always been, and continues to be, the high energy consumption and operating cost. Similarly, efforts in the past to transport fresh water from northern latitudes have faced the difficulty of high energy costs for pumping water over long distances. Solute ion linear alignment propulsion was presented in ASME ES2010-903966. Solute ion linear alignment is a process in which potential energy of the electrostatic fields of like charged solute ions is converted to kinetic energy. The current paper presents factors showing that solute ion linear alignment as a power generation method by flash distillation7, and which normally releases no carbon emissions, could in fact be the only way feasible to cheaply and efficiently convert sea water to fresh water and pump the rising sea water level inland to compensate for the underground aquifer depletion. Since solute ion linear alignment is based on the principle of capacitive deionization (CDI), anomalies concerning CDI are discussed. For example, for opposite electrodes separated by 1 mm and subject to a differential voltage of 1.5 volts, the resulting charge densities on opposite electrodes of over 10 Farads/gram and material densities, e.g., carbon nanofoam, of 0.5 grams/cm2, the resulting force between the positively charged ions on one electrode and the negatively charged ions on the other electrode is calculated to be in the range of 1015 Newtons based on Coulomb’s Law. The stability of charge densities in the range of 10 Coulombs/cm3 is also discussed in view of the potential energy and resulting forces of such charge densities with consideration of possible differences in dielectric properties in solids versus liquids for like-charged conditions. An analysis of the power requirements for the CDI charge absorption and regeneration cycle is compared to the potential energy available from linear alignment to show that the linear alignment process is expected to be a net energy gain process in the same category as combustion, which involves electron transfer, nuclear fission, which is the electrostatic repulsion of the protons in the nucleus, and nuclear fusion, which is caused by attraction of the nuclear force.
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Prasad, Boggavarapu V. V. S. U., and R. V. Ravikrishna. "Effect of Combustion Chamber Geometry on Emissions From a Single-Cylinder Diesel Engine." In ASME 2005 Internal Combustion Engine Division Fall Technical Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/icef2005-1275.
Full textAbstract:
Many of the stationary power generation and agricultural pumping applications in India utilize diesel engines. Recently, as per Government regulations, these engines are required to satisfy stringent emissions norms. This forms the motivation for the present study on a stationary, direct-injection, single cylinder, 10 HP diesel engine. The selected engine was not satisfying the norms. The engine has a hemi- spherical piston bowl and an injector with a finite sac volume. The combustion chamber was made re-entrant and the injector was replaced with a sac-less injector. After these modifications, there is a significant change in emission levels. To understand clearly the effect of the combustion chamber geometry on the emission levels, three-dimensional computational fluid dynamics (CFD) simulations have been performed for the complete suction and closed-valve part of the cycle. Comparisons of turbulent kinetic energy and swirl levels of old and new geometries were systematically conducted. In contrary to the expected, that the swirl and turbulence levels are consistently less in the modified geometry than that of original geometry. A third combustion chamber was proposed and tested computationally. It was found that the in the proposed combustion chamber swirl and turbulence levels are much higher than the baseline engine. Thus, the proposed combustion chamber geometry shows significant potential for the engine to meet the prescribed norms.
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Dhillon, Navdeep S., Chris Hogue, Matthew W. Chan, Jim C. Cheng, and Albert P. Pisano. "Integrating Coherent Porous Silicon as a Wicking Structure in the MEMS Based Fabrication of a Vertically Wicking Micro-Columnated Loop Heat Pipe." In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-64676.
Full textAbstract:
System design, component-wise fabrication and experimental thin-film evaporation results are presented for a vertically wicking micro-columnated loop heat pipe. Designed for fabrication using a three-layer wafer stack, this MEMS phase change device has components etched on both sides of the middle silicon wafer that are sealed by thinner top and bottom capping wafers. A coherent porous silicon (CPS) based dual-scale micro-columnated wick design uses a primary wick for capillary pumping and a secondary surface-micro-textured wick for thin-film liquid evaporation. For etching CPS, a Teflon based wafer-level electrochemical etching setup is implemented and results from a preliminary die-level etching study are reported. The main device components, which include the fluid transport channels, the condenser section and the columnated vapor chamber in a non-CPS base, are fabricated on silicon wafers using standard MEMS fabrication techniques. Thermal experiments are performed to study the phenomena of thin-film evaporation in a columnated open-loop micro evaporator.
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Al-Ani, Dhafar, and Saeid Habibi. "A New Energy Optimization Strategy for Pumping Operation in Water Distribution Systems." In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-86463.
Full textAbstract:
As time goes on, more and more operating-modes based on changing demand profiles will be compiled to enrich the range of feasible solutions for a water distribution system. This implies the conservation of energy consumed by a water pumping station and improves the ability for energy optimization. Another important goal was improving safety, reliability, and maintenance cost. In this paper, three important goals were addressed: cost-effectives, safety, and self-sustainability operations of water distribution systems. In this work, the objective functions to optimize were total electrical energy cost, maintenance costs, and reservoir water level variation while preserving the service provided to water clients. To accomplish these goals, an effective Energy Optimization Strategy (EOS) that manages trade-off among operational cost, system safety, and reliability was proposed. Moreover, the EOS aims at improving the operating conditions (i.e., pumping schedule) of an existing network system (i.e., with given capacities of tanks) and without physical changes in the infrastructure of the distribution systems. The new strategy consisted of a new Parallel Multi-objective Particle Swarm optimization with Adaptive Search-space Boundaries (P-MOPSO-ASB) and a modified EPANET. This has several advantages: obtaining a Pareto-front with solutions that are quantitatively equally good and providing the decision maker with the opportunity to qualitatively compare the solutions before their implementation into practice. The multi-objective optimization approach developed in this paper follows modern applications that combine an optimization algorithm with a network simulation model by using full hydraulic simulations and distributed demand models. The proposed EOS was successfully applied to a rural water distribution system, namely Saskatoon West. The results showed that a potential for considerable cost reductions in total energy cost was achieved (approximately % 7.5). Furthermore, the safety and the reliability of the system are preserved by using the new optimal pump schedules.
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Vargas, J. V. C., J. C. Ordonez, A. Bejan, and S. C. Amico. "The Optimal Shape for a Unit PEM Fuel Cell." In ASME 2005 3rd International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2005. http://dx.doi.org/10.1115/fuelcell2005-74162.
Full textAbstract:
This paper develops a mathematical model and a structured procedure to optimize the internal structure (relative sizes, spacings) and external shape (aspect ratios) of a unit PEM fuel cell so that net power is maximized. The optimization of flow geometry is conducted for the smallest (elemental) level of a fuel cell stack, i.e., the unit PEM fuel cell, which is modeled as a unidirectional flow system. The polarization curve, total and net power, and efficiency are obtained as functions of temperature, pressure, geometry and operating parameters. The optimization is subjected to fixed total volume. There are two levels of optimization: (i) the internal structure, which basically accounts for the relative thicknesses of two reaction and diffusion layers and the membrane space, and (ii) the external shape, which accounts for the external aspect ratios of a square section plate that contains all unit PEM fuel cell components. The available volume is distributed optimally through the system so that the net power is maximized. Temperature and pressure gradients play important roles, especially as the fuel and oxidant flow paths increase. Numerical results show that the optimized internal structure is “robust” with respect to changes in external shape. The optimized internal structure and external shape are results of the optimal balance between electrical power output and pumping power required to supply fuel and oxidant to the fuel cell through the gas channels. Directions for future improvements at the PEM fuel cell stack level in constructal geometric optimization are discussed.