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Articles de revues sur le sujet "Down-shifting method"
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Xu, Chun Hua. « Down-Shift Control for Wet Dual Clutch Transmission Based on FCMAC ». Advanced Materials Research 753-755 (août 2013) : 1800–1803. http://dx.doi.org/10.4028/www.scientific.net/amr.753-755.1800.
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In order to solve the problems existed in gearshift with wet dual clutch transmission; the down-shift control strategy is developed on the basis of analysis on gear shift process. Clutch pressure intelligent control arithmetic based on FCMAC (Fuzzy Cerebellar Model Articulation Controller) is designed to realize accuracy control of clutch pressure. The transmission control unit is designed, and the control program is written. Taking down-shift from 2 to 1 for example, down-shifting control strategy was drawn. After applied the introduced method into the experiments on both power-on and power-off downshift under different throttle positions, ideal shifting quality was achieved. The result indicated that the speed of vehicle changed gently without distinct impact. This essay verifies the validity of the proposed method of the strategy of shifting control.
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Liu, Ni, Ling Xu, Hongyu Wang, Jun Xu, Weining Su, Wei li, Zhongyuan Ma et Kunji Chen. « Improved efficiency of ZnSe QDs—Si hybrid solar cell system by down shifting process ». Canadian Journal of Physics 92, no 7/8 (juillet 2014) : 862–66. http://dx.doi.org/10.1139/cjp-2013-0550.
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Traditional Si solar cells have a narrow active absorption cross section among the short wavelength range (200–400 nm). The down-shifting process can efficiently improve the spectral response of Si solar cells by converting shorter wavelengths (i.e., ultraviolet, UV) to longer wavelengths (i.e., the visible range). Here, ZnSe quantum dots (QDs), prepared by an aqueous solution method and employed as a luminescent down-shifting layer, were spin coated onto the upper surface of manufactured Si solar cells. Measurements under standard test conditions (AM1.5, 100 mW/cm2) show that the efficiency of the ZnSe QDs–Si hybrid solar cell is increased from 11.48% to12%. The improvement of the ZnSe QDs–Si hybrid solar cell is ascribed to the efficient down-shifting process of ZnSe QDs, which enhances spectra response in the UV region for Si solar cells. The mechanism of this optical coupling and efficiency enhancement is investigated in detail. These results support the case that low-cost ZnSe QDs can be employed as efficient down-shifting material on large-area solar cells.
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Lin, Zhi Wei, Li Da, Hao Wang, Wei Han et Fan Lin. « The Comparison of the Effect of Haimming Window and Blackman Window in the Time-Scaling and Pitch-Shifting Algorithms ». Advanced Engineering Forum 1 (septembre 2011) : 221–25. http://dx.doi.org/10.4028/www.scientific.net/aef.1.221.
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The real-time pitch shifting process is widely used in various types of music production. The pitch shifting technology can be divided into two major types, the time domain type and the frequency domain type. Compared with the time domain method, the frequency domain method has the advantage of large shifting scale, low total cost of computing and the more flexibility of the algorithm. However, the use of Fourier Transform in frequency domain processing leads to the inevitable inherent frequency leakage effects which decrease the accuracy of the pitch shifting effect. In order to restrain the side effect of Fourier Transform, window functions are used to fall down the spectrum-aliasing. In practical processing, Haimming Window and Blackman Window are frequently used. In this paper, we compare both the effect of the two window functions in the restraint of frequency leakage and the performance and accuracy in subjective based on the traditional phase vocoder[1]. Experiment shows that Haimming Window is generally better than Blackman Window in pitch shifting process.
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Tao, Jing, Yaru Ni, Chunhua Lu et Zhongzi Xu. « Harvesting uniform and high bright Sm complex via microwave ultrasound method ». Functional Materials Letters 08, no 01 (février 2015) : 1550004. http://dx.doi.org/10.1142/s1793604715500046.
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The uniform ball-like luminescence down-shifting (LDS) Sm ( TTA )3 Phen materials have been synthesized by microwave ultrasonic method. Microwave ultrasonic plays a synergistic effect of microwave with ultrasonic, including thermal effect, dipole vortex and air bombard make the particles aggregation reach to the lowest energy. Through this method, we successfully synthesised 1–4 μm ball-like uniform Sm ( TTA )3 Phen clusters. The Sm ( TTA )3 Phen can transfer violet light to red-orange flourescence with a feature large Stokes shift and completely avoid self-absorption losses.
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CHENG, ZUJUN, LIKUN PAN, FENFANG SU, MEILING CAO et ZHUO SUN. « Eu3+ DOPED SILICA FILM AS LUMINESCENT DOWN-SHIFTING LAYER FOR CRYSTALLINE Si SOLAR CELLS ». Surface Review and Letters 16, no 05 (octobre 2009) : 669–73. http://dx.doi.org/10.1142/s0218625x09013141.
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Eu3+ doped silica films have been prepared by sol–gel method and employed as luminescent down-shifting layer on the front side of a crystalline Si solar cell to improve their conversion efficiency. Measurements under standard test conditions (AM1.5, 100 mW/cm2) show the conversion efficiency of Si solar cell with silica film containing Eu 3+ is improved 9.5% maximally as compared to the Si solar cell with pure silica film. However, high Eu 3+ concentration is not encouraged because concentration quenching effect will decrease the efficiency of the solar cell.
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Yadav, R. V., R. S. Yadav, A. Bahadur et S. B. Rai. « Down shifting and quantum cutting from Eu3+, Yb3+ co-doped Ca12Al14O33 phosphor : a dual mode emitting material ». RSC Advances 6, no 11 (2016) : 9049–56. http://dx.doi.org/10.1039/c5ra23117e.
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Leyre, Sven, Jan Cappelle, Guy Durinck, Aimi Abass, Johan Hofkens, Geert Deconinck et Peter Hanselaer. « The use of the adding-doubling method for the optical optimization of planar luminescent down shifting layers for solar cells ». Optics Express 22, S3 (1 avril 2014) : A765. http://dx.doi.org/10.1364/oe.22.00a765.
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Ben-David, Anat. « Counter-archiving Facebook ». European Journal of Communication 35, no 3 (1 mai 2020) : 249–64. http://dx.doi.org/10.1177/0267323120922069.
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The article proposes archival thinking as an analytical framework for studying Facebook. Following recent debates on data colonialism, it argues that Facebook dialectically assumes a role of a new archon of public records, while being unarchivable by design. It then puts forward counter-archiving – a practice developed to resist the epistemic hegemony of colonial archives – as a method that allows the critical study of the social media platform, after it had shut down researcher’s access to public data through its application programming interface. After defining and justifying counter-archiving as a method for studying datafied platforms, two counter-archives are presented as proof of concept. The article concludes by discussing the shifting boundaries between the archivist, the activist and the scholar, as the imperative of research methods after datafication.
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Dawi, Klara, Didi Haryono, Anita Yuliastini et Agustinus Astono. « Restorative Justice Paradigm of Kanayat'n Dayak Customary Law on Environmental Damage Caused By Shifting Cultivation ». Jurnal Analisis Hukum 5, no 2 (25 septembre 2022) : 245–52. http://dx.doi.org/10.38043/jah.v5i2.3918.
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The culture of farming and clearing land has existed since the transition of primitive humans to the modern age, as has the agricultural culture of the Dayak Kanayat’n indigenous people, which has been handed down from their predecessors for generations is currently evolving. The Kanayat’n Dayak are a sub-tribe of the Dayak who reside primarily in West Kalimantan on the island of Kalimantan. The Dayak Kanayat’n indigenous people are predominantly traditional farmers using traditional farming techniques. Agriculture is a part of the culture; agricultural techniques give rise to a farming culture, which absorbs local practices in cultivating the land. The pattern of land clearing can deduce the traditional nature of this agriculture. Conventional Dayak kanayat’n farmers clear the ground by identifying the area, chopping down the vegetation, and burning the remnants. This method of land clearance employed by the indigenous Dayak Kanyat‘n is also known as shifting cropping. This shifting cultivation activity has a positive aspect, namely the development and preservation of traditional Dayak kanayat’n agricultural culture customs. Still, it also has a wrong side, environmental damage, if carried out in large quantities and without measurement. This research focuses on the sociological juridical approach. Methods of data collection employing both primary and secondary legal materials. Article 80 of the Provisions for the Traditional Deliberation in Sengah Temila District, dated March 12-13, 2010, stipulates the administration of restorative justice to farmers who violate Dayak Kanayat customary law and cause forest fires. The sanction is Siam Pahar Pangalabur Temenggung.
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Lalthankhumi, R., et Joseph Lalmalsawma. « Agricultural Practices in Lawngtlai Rural Development Block of Mizoram ». Senhri Journal of Multidisciplinary Studies 5, no 2 (12 janvier 2021) : 01–08. http://dx.doi.org/10.36110/sjms.2020.05.02.001.
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Agriculture constitutes one of the major sources of income among the people of Mizoram. The areas used for cultivation in Mizoram are usually slashed and burnt down to ashes and are abandoned for years, the land is used and the same plot is re-use after 3-5 years. More than half of the total population is either directly or indirectly involved in agriculture. However, the income from agriculture is less than 5% of the State Gross Domestic Product (State Economic Report, 2015). In the last few decades Mizoram witnessed several changes in agriculture pattern as many farmers have been shifting from cultivation to small- scale agricultural farming. This paper highlights the transformation of agricultural practices and the major factors affecting agricultural production and attempt is made to examine the prevailing socio- economic aspects associated with farmers with special reference to Lawngtlai Rural Development Block and a questionnaire method was used for collecting relevant information for the purpose. The research found that there exist major transformations of agricultural practices in the last couple of decades. The cycle of shifting agriculture period has been shortened drastically. It is also revealed that farmers are gradually adopting settled farming from shifting agriculture and that government intervention and assistance has been increasing more and more in this field. It is suggested that agricultural practice be transformed from jhuming to settled farming and from cultivating the traditional crops to cash crops with governmental and institutional support for shifting to higher income in agricultural and horticultural crops.
Thèses sur le sujet "Down-shifting method"
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JANA, SOURAV KANTI. « Light harvesting methods in photovoltaic devices with superficial treatments ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2012. http://hdl.handle.net/10281/28621.
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Photovoltaics is fast emerging as an attractive renewable energy technology due to concerns of global warming, pollution and scarcity of fossil fuels supplies. However to compete in the global energy market, solar cells need to be cheaper and more energy efficient. Silicon is the favourite semiconductor used in solar photovoltaic cells because of its abandoned in nature, well established technology and non toxicity. But due to its indirect band gap, silicon is poor absorber of light and theoretical limiting efficiency of single junction wafer based silicon solar cells is ~31% which is called Shockley Queisser limit. But up to now the maximum achievable efficiency in laboratory for single crystal single junction silicon solar cells is ~ 24.7%. So far the cost of the wafer based silicon photovoltaics is high. Also thin film cells play an important role in low cost photvoltaics, but efficiency of the cost reduced cells is lower compared to wafer based cells. So light trapping into photovoltaic cells is a great issue inorder to increase the carrier generation inside the active layer of both bulk as well as thin film cells with out disturbing their fabrication technology. There many light harvesting methods; among them Surface Plasmon method using metal nanoparticles and spectrum downshifting method using nanocrystals are discussed here.
Metal nanoparticles support surface plamson when light is incident on them, which cause the scatter light into the underlying substrate. This process is realized on standard silicon solar cells. The feasible light scattering related enhancement was examined using spectral response and I-V measurements. Relative increases of the total delivered power under simulated solar irradiation were observed for cells both with and without antireflection coating using both silver and gold nanoparticles. The relative enhancement of External Quantum Efficiency derived from the spectral response measurements was observed for both the silicon cells. The better results obtained from both spectral response and I-V measurements were ascribed in the case of cells without antireflection coating. The results from I-V measurements under Air Mass 1.5 irradiation on the cells (without antireflection coating) correspond to a clear increase of the short circuit current due to both silver (relative increase of 7.5%) and gold (relative increase of 6.1%) nanoparticles. Also there is a relative enhancement (1.5%) of short circuit current was ascribed in the cells (with antireflection coating). Further realization of this method on copper indium gallium selenide based thin film solar cells attributed the enhancement of external quantum efficiency in the red wavelength region where these cells have already a poor spectral response.
Spectral downshifting method by the nanocrystals was investigated on the silicon based solar cells. Down shifting of photons on the silicon solar cells is realized by the absorption and emission property of the manganese doped zinc sulfide nanocrystals. The variation of band gap and photoluminescence intensity of different nanocrystals due to different doping concentration was observed. Relative enhancement of External Quantum Efficiency has been attributed in UV region (where silicon solar cells have poor spectral response) due to lower concentration of nanocrystals. A strong concentration quenching effect which causes decrease of external quantum efficiency in both UV and visible region has been observed.
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Toson, Valentina. « Preparation of functional nanostructured materials by facile and green methods ». Doctoral thesis, Università del Piemonte Orientale, 2018. http://hdl.handle.net/11579/97205.
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A challenging goal of Chemistry is its sustainability towards a circular no-waste approach. This statement has been the mainstream of this PhD work, applied to innovative functional materials based on inorganic hosting substrates.
The experimental work has used synthetic strategies, optimization tools and characterization methods to identify and pursue materials with facile, rapid and green preparations for functional photoactive materials, improving durability and performances.
A part of the work dealt with the study and optimization of the preparation of tailored inorganic hosts, as synthetic layered clay-like materials (saponite), with a study of the synthetic conditions and the thermal treatment features to achieve high yield, morphological and compositional quality with a reduced energetic payload. Aside, in a waste-reduction strategy, a highly innovative approach was carried on using biomasses (i.e. rice husk and straw) as sources of inorganics for materials with controlled composition. The preparation of functional materials via host-guest architectures was targeted on photoactive
systems using anionic (i.e. DyeA) and neutral (GAM2-35) photoactive dyes, to be incorporated in hydrotalcite and synthetic saponite clay respectively.
A mechanochemical methodology of intercalation of DyeA into hydrotalcite based on the Liquid Assisted Grinding (LAG) was fully optimized using statistical tools as factorial design and Simplex. Intercalating neutral optically active dyes in saponite was then pursued using a quasi-solid state co-intercalation of GAM2-35 and a proper cationic surfactant (CTAB), avoiding the use of harsh conditions of temperature and pH. To fulfill an approach to sustainable hotoactive host-guest materials, a full asset of high throughput characterization techniques, as in situ XRPD and Uv-Vis methods and chemometric methodologies, was applied to an established fully thermal process coming from the past, the Maya Blue formation from palygorskite and indigo.
Chapitres de livres sur le sujet "Down-shifting method"
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Buccafurri, Francesco, Gianluca Caminiti et Gianluca Lax. « Approximate Range Querying over Sliding Windows ». Dans Database Technologies, 2037–50. IGI Global, 2009. http://dx.doi.org/10.4018/978-1-60566-058-5.ch121.
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In the context of Knowledge Discovery in Databases, data reduction is a pre-processing step delivering succinct yet meaningful data to sequent stages. If the target of mining are data streams, then it is crucial to suitably reduce them, since often analyses on such data require multiple scans. In this chapter, we propose a histogram-based approach to reducing sliding windows supporting approximate arbitrary (i.e., non biased) range-sum queries. The histogram is based on a hierarchical structure (as opposed to the flat structure of traditional ones) and it results suitable to directly support hierarchical queries, such as drill-down and roll-up operations. In particular, both sliding window shifting and quick query answering operations are logarithmic in the sliding window size. Experimental analysis shows the superiority of our method in terms of accuracy w.r.t. the state-of-the-art approaches in the context of histogram-based sliding window reduction techniques.
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Johnson, Andi, Richard Lessey, Rebeca Ramos O'Reilly et Jessica Shi. « Moving In-Frame ». Dans Creativity as Progressive Pedagogy, 217–34. IGI Global, 2022. http://dx.doi.org/10.4018/978-1-7998-8287-9.ch011.
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The researchers explored the dual experience of individuals who are both taking dance and movement classes digitally at the same time as they are also teaching dance and movement classes digitally. By focusing on this duality through a series of interviews with practitioners, the researchers explore how the learner/educators do or do not adapt one set of skills into the other area of work and the lessons learned from this reflective practice. The results are analyzed and broken down into five sections: glitches of the practice, reflective practice, active learning, engagement, and reframing communication. Through further analysis, the researchers explore possibilities for shifting the mindset around digital education methods. The researchers then offer suggestions for further development in the field and where further research can expand on the subject area.
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Bonner, Thomas Neville. « A Closing Word ». Dans Becoming a Physician. Oxford University Press, 1996. http://dx.doi.org/10.1093/oso/9780195062984.003.0018.
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Despite all the changes in undergraduate medical education after World War II, especially in its core of scientific training, it actually had shifted only slightly in essential ways by the end of the twentieth century. If a student from an earlier era sat down in the classrooms and clinics of the 1990s—although doubtless overwhelmed by the new knowledge and technology—he or she would still find much that was familiar in the teaching methods, curriculum, conduct of clinics, bedside training, laboratory instruction, and educational preparation of fellow students. “The medicine of 1900,” writes William Bynum, “[is] closer to us almost a century later than it was to the medicine of 1790.” The historic differences among nations in teaching methods, too, though less striking than in earlier times, were still visible in the characteristic responses of medical educators and students to the social and scientific changes. Alone among the professions, education for medicine had come to combine a long period of theoretical study with an intensely practical experience in the observation, handling, and treatment of patients. The resulting tension and shifting balance between academic study and clinical training, between theory and practice, between medicine as art and medicine as science, has been the perpetual condition of medical pedagogy since the Enlightenment. That a different balance was struck at different times in different nations because of differing social and political circum- stances is the underlying theme of this book. In the first half of this century, if a boundless faith in science and the ultimate rationality of medicine came to dominate nearly everywhere, that faith has been overwhelmed in our own time by postmodern doubts about human progress and the explanatory powers of science. But the pendulum will doubtless swing again. In any case, for most educators and students, the ideal remains what it has been for most of the period covered in this book—a unity of systematic academic study, especially in the sciences, with hands-on experience to create a physician who thinks critically, can solve problems, possesses a wide knowledge of underlying disease processes, and is skilled at applying what has been learned to real-life situations.
Actes de conférences sur le sujet "Down-shifting method"
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Leyre, Sven, Guy Durinck, Johan Hofkens, Geert Deconinck et Peter Hanselaer. « Quick evaluation method for solar modules with a luminescent down-shifting layer ». Dans Optics for Solar Energy. Washington, D.C. : OSA, 2014. http://dx.doi.org/10.1364/ose.2014.rtu2b.5.
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Zhao, Gangming, Jingdong Wang et Zhaoxiang Zhang. « Random Shifting for CNN : a Solution to Reduce Information Loss in Down-Sampling Layers ». Dans Twenty-Sixth International Joint Conference on Artificial Intelligence. California : International Joint Conferences on Artificial Intelligence Organization, 2017. http://dx.doi.org/10.24963/ijcai.2017/486.
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Down-sampling is widely adopted in deep convolutional neural networks (DCNN) for reducing the number of network parameters while preserving the transformation invariance. However, it cannot utilize information effectively because it only adopts a fixed stride strategy, which may result in poor generalization ability and information loss. In this paper, we propose a novel random strategy to alleviate these problems by embedding random shifting in the down-sampling layers during the training process. Random shifting can be universally applied to diverse DCNN models to dynamically adjust receptive fields by shifting kernel centers on feature maps in different directions. Thus, it can generate more robust features in networks and further enhance the transformation invariance of down-sampling operators. In addition, random shifting cannot only be integrated in all down-sampling layers including strided convolutional layers and pooling layers, but also improve performance of DCNN with negligible additional computational cost. We evaluate our method in different tasks (e.g., image classification and segmentation) with various network architectures (i.e., AlexNet, FCN and DFN-MR). Experimental results demonstrate the effectiveness of our proposed method.
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He, Dongwei, Guangqiang Wu, Yimin Shi et Wenbin Yang. « Dynamic Performance Optimization of the Dual Clutch Transmission Based on Genetic Algorithm ». Dans ASME 2018 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/detc2018-85525.
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Gear shift law is determined, and shifting control logic, clutch pressure control strategy are developed, Simulation models of the continuous up-shift and down-shift process of DCT are established. Comparison of simulation results by the indicators of friction work, friction power and jerk, Influence on shifting performance about clutch pressure rate and circulates pressure are analyzed qualitatively. According to the fitness function of overall performance of shifting quality, the pressure optimal control objectives of DCT are proposed, and based on genetic algorithm for present control method in engagement process of DCT, the parameter optimization is studied.
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Romero, Jose´ A., Subhash Rakheja et Alejandro Lozano. « Simulation of Solid Cargo-Vehicle Interaction During Braking of a Heavy Vehicle With ABS ». Dans ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-79996.
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The effect of cargo shifting on the braking efficiency of a freight truck is investigated thorough development and analysis of an analytical model of the cargo-vehicle system together with the tie-down system. Braking efficiency is characterized in terms of the stopping distance, as a function of the cargo securement method (direct and indirect) and deck vibration caused by varying levels of road roughness. The relative movement of the cargo with respect to the deck causes decoupling of the cargo and the vehicle masses. The effective braking forces are thus applied to a reduced total mass. An important phenomenon that influences the cargo-vehicle interaction derives from the decoupling of the cargo and vehicle masses during the shifting of the cargo, leading to a situation in which the braking forces are applied to a reduced mass. The vehicle performance with a rigidly fixed cargo is also evaluated for comparison purposes. Results show that the indirectly restrained cargo produces the minimum stopping distances, irrespective of the road roughness, while the maximum stopping distances are attained for the directly restrained cargo.
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Pelz, Peter F., et Stefan S. Stonjek. « Introduction of an Universal Scale-Up Method for the Efficiency of Axial and Centrifugal Fans ». Dans ASME Turbo Expo 2014 : Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-25403.
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Acceptance tests on large fans to prove the performance (efficiency and total pressure rise) to the customer are expensive and sometimes even impossible to perform. Hence there is a need for the manufacturer to reliably predict the performance of fans from measurements on down-scaled test fans. The commonly used scale-up formulas give satisfactorily results only near the design point, where inertia losses are small in comparison to frictional losses. At part- and overload the inertia losses are dominant and the scale-up formulas used so far fail. In 2013 Pelz and Stonjek introduced a new scaling method which fullfills the demands ( [1], [2]). This method considers the influence of surface roughness and geometric variations on the performance. It consists basically of two steps: Initially, the efficiency is scaled. Efficiency scaling is derived analytically from the definition of the total efficiency. With the total derivative it can be shown that the change of friction coefficient is inversely proportional to the change of efficiency of a fan. The second step is shifting the performance characteristic to a higher value of flow coefficient. It is the task of this work to improve the scaling method which was previously introduced by Pelz and Stonjek by treating the rotor/impeller and volute/stator separately. The validation of the improved scale-up method is performed with test data from two axial fans with a diameter of 1000 mm/250mm and three centrifugal fans with 2240mm/896mm/224mm diameter. The predicted performance characteristics show a good agreement to test data.
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Ahmed, Usman, Zhiheng Zhang et Ruben Ortega Alfonzo. « Case Study- Real Time Downhole Telemetry CCL and Tension Compression, a Differentiator for Successful Manipulation of ICD's in Horizontal Wells ». Dans SPE Middle East Oil & Gas Show and Conference. SPE, 2021. http://dx.doi.org/10.2118/204873-ms.
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Abstract Horizontal well completions are often equipped with Inflow Control Devices (ICDs) to optimize flow rates across the completion for the whole length of the interval and to increase the oil recovery. The ICD technology has become useful method of optimizing production from horizontal wells in a wide range of applications. It has proved to be beneficial in horizontal water injectors and steam assisted gravity drainage wells. Traditionally the challenges related to early gas or water breakthrough were dealt with complex and costly workover/intervention operations. ICD manipulation used to be done with down-hole tractor conveyed using an electric line (e-line) cable or by utilization of a conventional coiled tubing (CT) string. Wellbore profile, high doglegs, tubular ID, drag and buoyancy forces added limitations to the e-line interventions even with the use of tractor. Utilization of conventional CT string supplement the uncertainties during shifting operations by not having the assurance of accurate depth and forces applied downhole. A field in Saudi Arabia is completed with open-hole packer with ICD completion system. The excessive production from the wells resulted in increase of water cut, hence ICD's shifting was required. As operations become more complex due to fact that there was no mean to assure that ICD is shifted as needed, it was imperative to find ways to maximize both assurance and quality performance. In this particular case, several ICD manipulating jobs were conducted in the horizontal wells. A 2-7/8-in intelligent coiled tubing (ICT) system was used to optimize the well intervention performance by providing downhole real-time feedback. The indication for the correct ICD shifting was confirmed by Casing Collar Locator (CCL) and Tension & Compression signatures. This paper will present the ICT system consists of a customized bottom-hole assembly (BHA) that transmits Tension, compression, differential pressure, temperature and casing collar locator data instantaneously to the surface via a nonintrusive tube wire installed inside the coiled tubing. The main advantages of the ICT system in this operation were: monitoring the downhole force on the shifting tool while performing ICD manipulation, differential pressure, and accurately determining depth from the casing collar locator. Based on the known estimated optimum working ranges for ICD shifting and having access to real-time downhole data, the operator could decide that required force was transmitted to BHA. This bring about saving job time while finding sleeves, efficient open and close of ICD via applying required Weight on Bit (WOB) and even providing a mean to identify ICD that had debris accumulation. The experience acquired using this method in the successful operation in Saudi Arabia yielded recommendations for future similar operations.
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Mondal, Pranab, et Joseph Mathew. « Large Eddy Simulation of a Compressor Stage ». Dans ASME 2017 Gas Turbine India Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gtindia2017-4849.
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A methodology for large eddy simulation (LES) of a turbomachine stage is presented. Computations of mean fields (RANS) of stages may be performed separately of rotor and stator rows by providing an averaged solution as input to the down-stream row. In unsteady simulations, unsteady field information must be exchanged in both directions after every time step. Here a procedure for linear cascade simulations of a stage has been implemented in a high-resolution compressible flow solver for LES. The LES uses an explicit filtering method for sub-grid-scale modelling. Grids overlap at the interface between blade rows. Field data is transferred in both directions. Rotor velocity is added or subtracted as needed to tangential velocity component during this transfer. The relative movement of the rotor and stator grids is accounted for by suitable periodic tangential shifting of the paired grid points in the overlap for the transfer. The method has been tested against a published DNS of a statorrotor stage. The Reynolds number based on blade chord and mean axial velocity at inflow was 40000. Solution fields show the wake vortex street of the upstream blade row impinging on downstream blades and being convected through the downstream blade passage. The LES captured transition on rotor blade surface boundary layers. Blade surface pressure distributions agree closely on pressure surfaces. Separation and transition on downstream blade suction surface is delayed slightly at the present resolution, but this will improve with grid refinement, monotonically, for this LES method.
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Ruiz Domingo, Javier, et Amanda Pieyre. « Flow Separation Modelling Dowstream of Military Low Pressure Compressors ». Dans ASME Turbo Expo 2022 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/gt2022-79112.
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Abstract In military turbofan architectures, a flow separation is operated downstream the Low Pressure Compressor (LPC), mainly to increase the propulsive efficiency and to cool down and provide oxygen to the reheat channel. The flow is separated into a primary flow that goes through the high-pressure components and combustion chamber and a secondary flow which remains cold and is mixed with the primary flow before the reheat. The Bypass Ratio (BPR) represents the mass flow rate ratio between secondary and primary flow. During engine operation from high to low power, the BPR varies drastically. Moreover, current and future military engines present many variable geometries to improve their maneuverability, and the BPR can strongly depend on the settings of these geometries. BPR variations lead to a shift in the LPC exit separation streamline and therefore to modifications on the thermodynamic conditions in both primary and secondary flows. Existing methods usually perform the separation on the overall LPC map using corrective coefficients. The aim of this work is to provide an alternative method to model the effects of the shifting of the separation line on the thermodynamic parameters. Instead of using an overall compressor map, this method uses two compressor maps, one for the inner and one for the outer stream, at a reference BPR. When the BPR is different from this reference value, corrections are applied to the reference maps. The main hypothesis of this method is that the aerodynamics of the LPC is uncoupled from the splitter, meaning that the total temperature and total pressure profiles do not depend on the BPR. Analytical profiles are used from hub to tip for work and losses coefficients parameters. The analytical profiles are chosen to better fit the actual profiles in the working BPR range of interest. This method is designed to be included in a performance model. The method presented is validated on LPC Rig test and CFD data.
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Dickens, Tony, et Ivor Day. « The Design of Highly Loaded Axial Compressors ». Dans ASME Turbo Expo 2009 : Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-59291.
Texte intégralRésumé :
Increasing compressor pressure ratios (thereby gaining a benefit in cycle efficiency), or reducing the number of stages (to reduce weight, cost, etc.), will require an increase in pressure rise per stage. One method of increasing the pressure rise per stage is by increasing the stage-loading coefficient and it is this topic which forms the focus of the present paper. In the past, a great deal of effort has been expended in trying to design highly loaded blade rows. Most of this work has focused on optimizing a particular design rather than looking at the fundamental problems associated with high loading. This paper looks at the flow physics behind the problem, makes proposals for a new design strategy and explains sources of additional loss specific to highly loaded designs. Detailed experimental measurements of three highly loaded stages (Δh0/U2 ≈ 0.65) have been used to validate a CFD code. The calibrated CFD has then been used to show that as the stage loading is increased the flow in the stator passages breaks down first. This happens via a large corner separation which significantly impairs the stage efficiency. The stator can be relieved by increasing stage reaction, thus shifting the burden to the rotor. Fortunately, the CFD calculations show that the rotor is generally more tolerant of high loading than the stator. Thus, when stage loading is increased, it is necessary to increase the reaction to achieve the optimum efficiency. However, the design exercise using the calibrated CFD also shows that the stage efficiency is inevitably reduced as the stage loading is increased (in agreement with the experimental results). In the second part of the paper, the role profile loss plays in the reduction in efficiency at high stage loading is considered. A simple generic velocity distribution is developed from first principles to demonstrate the hitherto neglected importance of the pressure surface losses in highly loaded compressors.
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Shao, Weidong, et Jun Li. « Subsonic Flow Over Open Cavities : Part 2 — Passive Control Methods ». Dans ASME Turbo Expo 2016 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-56415.
Texte intégralRésumé :
A global description of the intrinsic instabilities of shear layer for further understanding of the aeroacoustical oscillation of subsonic flow over open cavities has been given in the companion paper. The needs to suppress dynamic pressure loads in open cavities play an important role in many aeronautical applications. Large eddy simulation (LES) of passive control methods including recessed leading edge step and sloping trailing edge wall arrangements is performed. The unsteady flow characteristics and aeroacoustical oscillation mechanism of baseline cavity are given in advance. Effects of both passive control methods on resonant frequency and sound pressure levels are demonstrated and analyzed. Recessed leading edge step tends to decrease the resonant Strouhal numbers and the maximal reduction of overall sound pressure levels (OASPL) reaches 8.5dB. Sloping trailing edge wall reduces OASPL by shifting down the impinging location on cavity back wall. The optimal reduction of OASPL arrives at 11dB when the angle of inclination is maximal. The drag induced by cavity flows is found to be highly correlated with dynamic loads on cavity walls.