Literatura académica sobre el tema "Variable load conditions"
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Artículos de revistas sobre el tema "Variable load conditions"
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Almeida, K. C. y R. Salgado. "Optimal power flow solutions under variable load conditions". IEEE Transactions on Power Systems 15, n.º 4 (2000): 1204–11. http://dx.doi.org/10.1109/59.898091.
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SHAO, Yimin. "Gearbox Deterioration Detection under Steady State, Variable Load, and Variable Speed Conditions". Chinese Journal of Mechanical Engineering 22, n.º 02 (2009): 256. http://dx.doi.org/10.3901/cjme.2009.02.256.
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Zhao, Haoyang. "Classical PID Control of A Quadcopter UAV Under Variable Load Conditions". Academic Journal of Science and Technology 9, n.º 2 (23 de febrero de 2024): 44–46. http://dx.doi.org/10.54097/13m5xg10.
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In recent years, the application of UAVs has become more and more extensive, resulting in a number of special operation UAVs. Quadrotor aerial robots have become one of the most popular vehicles at home and abroad because of their small size, light weight, simple structure, low cost, low requirements for takeoff and landing, and good maneuverability. UAVs are required to perform different tasks in the current complex environment, so variable loads are inevitable, and the stability of the UAV body is especially important when performing variable loads, and there are many ways to help and verify the attitude of the UAV during flight. In this paper, in order to more intuitively see the self-generated stability of the UAV under variable load conditions, the dynamics model of the UAV will be established first, and the simulation results show that the movement of the UAV has a very good stability. However, in the previous research, it is not possible to visualize the stability and flight state of the UAV when it is flying under variable load, this paper will make the UAV keep its own flight stability under two kinds of loads through the PID design model. At the same time, the function of the UAV's own mass change during flight is found, and the design function is used to show the stability curve of the UAV when it flies with its own changing mass. Through the final simulation and calculation, the experiment found that through the PID control, the flight state of the UAV when flying with variable load can be observed more intuitively, and the stability state of the UAV when flying can also be observed.
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Lukasik, Konstanty, Jerome Cheron, Gustavo Avolio, Arkadiusz Lewandowski, Dylan F. Williams, Wojciech Wiatr y Dominique M. M. P. Schreurs. "Uncertainty in Large-Signal Measurements Under Variable Load Conditions". IEEE Transactions on Microwave Theory and Techniques 68, n.º 8 (agosto de 2020): 3532–46. http://dx.doi.org/10.1109/tmtt.2020.2995618.
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Pollock, H. "Simple constant frequency constant current load-resonant power supply under variable load conditions". Electronics Letters 33, n.º 18 (1997): 1505. http://dx.doi.org/10.1049/el:19971063.
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Alwadie, Abdullah. "A Real Time Condition Monitoring System for Gears Operating under Variable Load Conditions". Indonesian Journal of Electrical Engineering and Computer Science 9, n.º 2 (1 de febrero de 2018): 493. http://dx.doi.org/10.11591/ijeecs.v9.i2.pp493-501.
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Gears are important component of the rotational power transmission system and are largely used in variable load and speed applications. The faults on the gear generate excessive vibration which leads to breakdown of the machine. Sensor based methods could diagnose gear faults but proved to be expensive and have limited applications due to heavy cost and need of access of gear box for sensor installation. The motor stator current analysis has been reported to overcome the drawbacks of the sensor based fault detection methods. However, motor stator current analysis has a limited capability for reliable detection of small gear fault signatures typically for low load conditions. This paper presents an alternative non-invasive approach based on instantaneous power analysis of the motor to reliably diagnose gear faults for variable load applications. The theoretical and experimental results indicates that the instantaneous power analysis offers three fault related harmonics and amplitude variations on these harmonics could give the indication of health status of the gear.<strong> </strong> The superiority of the proposed instantaneous power analysis technique has been confirmed through experiments performed on three operating points of the motor. The comparison of the amplitude sensitivity of the motor stator current and instantaneous power at three operating points has been performed to validate the superiority of the proposed technique.
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Gao, Changlun, Junliang Huo, Zhantong Li, Beihuo Yao, Zhaokai He, Fangren Zhang, Shunli Sun y Weibin Wu. "Research and Development of Gearbox Load Spectrum Database under Variable Working Conditions". International Journal of Emerging Technology and Advanced Engineering 11, n.º 10 (15 de octubre de 2021): 29–39. http://dx.doi.org/10.46338/ijetae1021_04.
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Gearbox load spectrum is the data basis for gearbox fatigue life prediction and strength verification. As the amount of load spectrum data increases exponentially and the demand for sharing increases, it is necessary to introduce database technology to store and manage load spectrum data. In this paper, the collection and processing of load data and the compilation of load spectrum are introduced in turns firstly. Then it sums the development and research status of database technology and the technical route of combining load spectrum database up secondly. Moreover, the current status of load spectrum database and the design steps of load spectrum database are summarized. Finally, the development trend of load spectrum database research is generalized and the prospect is put forward.
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Chen, Chong Liang, Li Guo Liu y Zi Feng Ni. "The Wear Mechanism of DLC Films at Variable Working Conditions". Advanced Materials Research 199-200 (febrero de 2011): 683–88. http://dx.doi.org/10.4028/www.scientific.net/amr.199-200.683.
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The Diamond-like carbon coating (DLC) was derived by the PVCD method on the 45 steel surfaces. The frictional properties and fatigue failure of 45 steel with the DLC films were investigated under three different conditions including full contact condition, horizontal reciprocating movements and vertical reciprocating movements. It was found that (a) at full contact conditions: the increase in the load leads to the initial decrease in the frictional coefficient and then increase, and a lowest frictional coefficient of 0.205 appears at 250N; (b) at horizontal reciprocating conditions: the slow decrease in the frictional coefficient was caused by the increase in load, and frictional coefficients of 0.213 and 0.178 appears at 100N and 300N, respectively; (c) at vertical reciprocating conditions: the frictional coefficient was initially enhanced and then followed by a decrease trend; the highest frictional coefficients of 0.640 appears at load of 200N. The wear rate was slightly enhanced as the load is lower than 200N, and was sharply increased with the further increase in the load. The lowest wear rate was 1.55 mg/10000r, and the highest wear rate was 15.6mg/10000r.
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Akhtulov, A. L., O. M. Kirasirov y M. O. Kirasirov. "Features of calculation of steel structures of bridge cranes at variable loads". MATEC Web of Conferences 298 (2019): 00032. http://dx.doi.org/10.1051/matecconf/201929800032.
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The article deals with the calculation of metal bridge cranes operating under the influence of variable loads. Requirements to static and dynamic characteristics of mechanisms of load-lifting cranes are caused by specifics of work, features of a design and operating conditions of the cranes working at variable loadings. Thus, it is proposed to perform calculations of parts of crane mechanisms for endurance, operating under non-stationary variable load, based on the principle of linear summation of damage, allowing the calculation from the point of view of the load equivalent to the entire range of operating loads.
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Liu, Haigang, Chu Sun, Mengyu He, Na Wang y Yuanjun Zhou. "Analysis of Synchronous Generator Self-Excitation under Capacitive Load Condition in Variable-Frequency Aviation Power System". Machines 11, n.º 1 (23 de diciembre de 2022): 15. http://dx.doi.org/10.3390/machines11010015.
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As power electronic converters become more widely used in aviation power systems, the associated capacitive loads in the harmonic filter circuits increase accordingly. The risk of self-excitation of aeronautical synchronous generators due to capacitive loads is thus increased. Compared with the self-excitation of a generator in a conventional fixed-frequency power system, this process is more complicated in a variable-frequency aviation power supply (360–800 Hz), as both the varied frequency and the loading conditions contribute to the self-excitation. To quantify this effect, in our study, a series-parallel model of simplified RLC loads under a variable-frequency power supply was built. The criterion of generator self-excitation, given in terms of the generator impedance and the load impedance, was then derived. To facilitate the load configuration design in the case of an aviation power system, a comprehensive analysis of the influences of the varied load power and system frequency on the load impedance was conducted. A graphical approach was proposed to determine self-excitation by comparing the series load reactance and resistor with three critical impedances corresponding to three self-excitation criteria, which is more intuitive and enables one to visualize the tendency of self-excitation with varied frequencies and loading conditions more effectively. Finally, the influence of variable frequency on the self-excitation of the aeronautical synchronous generator was verified by the simulation results.
Tesis sobre el tema "Variable load conditions"
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Alger, Lawrence Charles. "The advantages and control of variable valve timing under part-load operating conditions". Thesis, University of Nottingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417421.
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Rashel, Masud Rana. "Modeling photovoltaic panels under variable internal and environmental conditions with non-constant load". Doctoral thesis, Universidade de Évora, 2018. http://hdl.handle.net/10174/23565.
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This thesis focuses on the modeling and simulation of photovoltaic electric energy
conversion systems, that considering different internal and environmental parameters,
important for the forecast of the electric energy production. For the cell or panel
modeling, the single diode five-parameter model is used. The internal parameters
considered are the photocurrent, the cell temperature, the ideality factor, the series
resistance, the shunt resistance and the saturation current; and on the other hand the
external parameters considered are solar irradiance, ambient temperature and wind
speed. New contributions are presented in the context of the modeling and simulation of
the error function that identifies the more and less sensitive internal parameters of the
cell model and the sensitivity of the external parameters. In the context of obtaining the
experimental results, a monocrystalline silicon photovoltaic panel is used. And a signal
generator, data acquisition device, an anemometer, a pyranometer and a sensor for
measuring the ambient temperature are used. In the context of internal relation between
external parameters, correlation studies are performed in order to show the relationships
between them; and the obstacle concept is presented as a generalization of shadow types,
namely dust and elements that reduce solar irradiance on the surface of the cell or panel; Modelação de painéis fotovoltaicos sob condições
internas e ambientais variáveis com carga não
constante
Resumo:
Esta tese incide sobre o tema da modelação e simulação de sistemas de conversão de
energia elétrica fotovoltaica considerando diferentes parâmetros internos e ambientais,
importantes para a previsão da produção de energia elétrica. Para a modelação da
célula ou do painel é utilizado o modelo de cinco parâmetros de um díodo. Os parâmetros
internos considerados são a corrente que atravessa o díodo, a temperatura interna da
célula, o fator de idealidade, a resistência série da célula, a resistência paralela da célula
e a corrente de saturação; os parâmetros externos considerados são a irradiância solar,
a temperatura ambiente e a velocidade do vento. São apresentadas novas contribuições
no contexto da modelação e simulação da função de erro que identifica os parâmetros
internos mais e menos sensíveis do modelo da célula e a sensibilidade dos parâmetros
externos. No contexto para a obtenção dos resultados experimentais foram utilizadas
células e um painel fotovoltaico de silício monocristalino respetivamente, um gerador de
sinais, dispositivos aquisição de dados, um anemómetro, um piranómetro e um sensor
para medir a temperatura ambiente. Em ambos contextos, são realizados estudos de
correlação entre os parâmetros externos no sentido de mostrar as relações entre eles; e
é apresentado o conceito de obstáculo como uma generalização dos tipos de sombras,
nomeadamente a poeira e elementos que reduzem a irradiância solar na superfície da
célula ou do painel.
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Al, Tubi Issa. "Effects of variable load and rotational speed conditions on gear micropitting in wind turbine gearboxes". Thesis, University of Sheffield, 2014. http://etheses.whiterose.ac.uk/7173/.
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Micropitting damage is one of the failure modes commonly observed on gears and bearings in wind turbine (WT) gearboxes. It can lead to destructive failures which, in turn, lead to unplanned WT shutdown and expensive replacement. This research provides an insight into effects of variable load and rotational speed condition on micropitting in WT gearboxes. It also investigates in detail the occurrence of micropitting in WT gearboxes under various operational conditions using an experimental study and an analytical study, employing two methods: an analytical method based on selected SCADA (Supervisory Control and Data Acquisition) data and a probabilistic modelling of SCADA data method. This study focuses predominantly on the micropitting of the high speed shaft (HSS) gear of a WT gearbox operating under nominal and varying load and speed conditions. The SCADA datasets recorded from WT gearboxes in operation are used. Based on the SCADA data, the recorded WT generator power output and generator rotational speed are used to obtain the shaft torque of the HSS driven gear. Based on ISO Technical Report ISO/TR 15144-1 (2010) and various ISO gear standards, an analytical study is carried out to assess the risk of gear micropitting by determining the contact stress, sliding parameter, local contact temperature, lubricant film thickness and specific lubricant film thickness along the line of action of the gear tooth contact by considering the WT operating load and speed conditions. The experimental study investigates the initiation and progression of gear micropitting when gear tooth flanks are subjected to varying torque levels at a constant rotational speed. The study is conducted by carrying out gear micropitting testing and surface inspection, as well as validating implementing analytical evaluations by comparing the obtained results with that obtained by using various commercial software packages based on ISO Technical Report ISO/TR 15144-1 and AGMA 925-A03 standard. The surface inspection of tested gears is carried out using procedures of surface roughness measurement, replica of surface micropits and profile deviation measurement. The analytical results are compared to the experimental results to predict the occurrence of gear micropitting through evaluating tooth contact stress, sliding parameter, local contact temperature and specific lubricant film thickness at different points along the gear tooth flank. The surface roughness measurements, obtained from the tested gears after each cycle run under specific torque levels, are considered in the analytical investigation. The gear testing results show that micropitting initiates at the pinion dedendum, but escalates at the addendum because of the greater severity of progressive micropitting at the mating wheel dedendum. The micropitting initiates at the beginning of the tip relief area of the pinion and at the root of the pinion with which the wheel tip relief area first starts to mesh. The analytical results confirm that maximum contact stresses and minimum lubricant film thickness occur at these areas. The lubricant film thickness varies considerably because of changes in surface roughness after the gears undergo various running cycles under varying torque levels. The validation process reveals that the ISO/TR 15144-1 results provide a better correlation with experimental results, as compared to AGMA 925-A03 results. The analysis of WT operational condition using selected one month SCADA data identifies three regions of relationships between the generator power and wind speed, the generator speed and wind speed variations. Non-uniform distributions of contact stress, contact temperature and lubricant film thickness over the tooth flank are observed. This is due to the conditions of torque and rotational speed variations and sliding contact along the gear tooth flanks. The lubricant film thickness varies along the tooth flank and is at its lowest when the tip of the HSS wheel gear engages with the root of the HSS driven gear. The lubricant film thickness increases with the increase of the rotational speed and decreases as the torque and sliding increase. It can be concluded that micropitting is most likely to initiate at the dedendum of pinion gear. The lowest film thickness occurs when the torque is high and the rotational speed is at its lowest, which may cause direct tooth surface contact. In low torque condition, the varying rotational speed condition may cause a considerable variation in lubricant film thickness, thus interrupting the lubrication, which may result in micropitting. Finally, a probabilistic analysis is carried out to investigate the probabilistic risk of tooth flank micropitting failure using the entire SCADA datasets. A random number of datasets of smaller sizes of gear shaft torque and rotational speed are generated to substitute for the large amounts of data in the original SCADA datasets. Based on the selected random number datasets, the effect of variations in gear shaft torque and rotational speed on the probabilistic characteristics of gear tooth flank micropitting is investigated. The study shows that the HSS driven pinion gear is subject to overloading conditions, resulting in maximum contact stresses higher than the allowable contact stress of the material. Thus, the high torque value, which occurs at low rotational speed according to the data analysis, is the main cause of micropitting in WTs as it leads to high contact stress. In addition, the results of the analysis of specific lubricant film thickness show that there is a considerable risk of micropitting at the dedendum region of gear teeth under variable operational condition.
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Blanco, Villaverde Norbert. "Variable mixed-mode delamination in composite laminates under fatigue conditions: testing & analysis". Doctoral thesis, Universitat de Girona, 2005. http://hdl.handle.net/10803/7760.
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La majoria de les fallades en elements estructurals són degudes a càrrega per fatiga. En conseqüència, la fatiga mecànica és un factor clau per al disseny d'elements mecànics. En el cas de materials compòsits laminats, el procés de fallada per fatiga inclou diferents mecanismes de dany que resulten en la degradació del material. Un dels mecanismes de dany més importants és la delaminació entre capes del laminat. En el cas de components aeronàutics, les plaques de composit estan exposades a impactes i les delaminacions apareixen facilment en un laminat després d'un impacte. Molts components fets de compòsit tenen formes corbes, superposició de capes i capes amb diferents orientacions que fan que la delaminació es propagui en un mode mixt que depen de la grandària de la delaminació. És a dir, les delaminacions generalment es propaguen en mode mixt variable. És per això que és important desenvolupar nous mètodes per caracteritzar el creixement subcrític en mode mixt per fatiga de les delaminacions. El principal objectiu d'aquest treball és la caracterització del creixement en mode mixt variable de les delaminacions en compòsits laminats per efecte de càrregues a fatiga. Amb aquest fi, es proposa un nou model per al creixement per fatiga de la delaminació en mode mixt. Contràriament als models ja existents, el model que es proposa es formula d'acord a la variació no-monotònica dels paràmetres de propagació amb el mode mixt observada en diferents resultats experimentals. A més, es du a terme un anàlisi de l'assaig mixed-mode end load split (MMELS), la característica més important del qual és la variació del mode mixt a mesura que la delaminació creix. Per a aquest anàlisi, es tenen em compte dos mètodes teòrics presents en la literatura. No obstant, les expressions resultants per l'assaig MMELS no són equivalents i les diferències entre els dos mètodes poden ser importants, fins a 50 vegades. Per aquest motiu, en aquest treball es porta a terme un anàlisi alternatiu més acurat del MMELS per tal d'establir una comparació. Aquest anàlisi alternatiu es basa en el mètode dels elements finits i virtual crack closure technique (VCCT). D'aquest anàlisi en resulten importants aspectes a considerar per a la bona caracterització de materials utilitzant l'assaig MMELS. Durant l'estudi s'ha dissenyat i construït un utillatge per l'assaig MMELS. Per a la caracterització experimental de la propagació per fatiga de delaminacions en mode mixt variable s'utilitzen diferents provetes de laminats carboni/epoxy essencialment unidireccionals. També es du a terme un anàlisi fractogràfic d'algunes de les superfícies de fractura per delaminació. Els resultats experimentals són comparats amb les prediccions del model proposat per la propagació per fatiga d'esquerdes interlaminars.Most of the failures in structural elements in use are a consequence of mechanical fatigue. Therefore, fatigue is a decisive factor in designing durable mechanical elements. In laminated composite materials, the fatigue process involves different damage mechanisms that result in the degradation of the material. One of the most important damage mechanisms is the delamination between plies of the laminate. In aeronautical applications, composite plates are sensitive to impact and delamination occurs readily in composite laminates on impact. Many composite components have curved shapes, tapered thickness and plies with different orientations, which make the delamination grow with a mode mix that depends on the extent of the crack. Thus, delaminations generally grow under varying mode mix. It is therefore important to develop methods that can characterise subcritical, mixed-mode growth in fatigue delamination. The main objective of the present investigation is the characterisation of the variable mixed-mode delamination in composite laminates under fatigue conditions. To this end, a mixed-mode fatigue delamination model is proposed. Oppositely to the mixed-mode fatigue delamination models present in the literature, the proposed model takes into account the non-monotonic variation of the propagation parameters with the mode mix observed in different experimental data. Moreover, the mixed-mode end load split (MMELS) test, which main characteristic is that the propagation mode of the interlaminar crack varies with the crack extent, is analysed. Two theoretical approaches present in the literature are considered. However, the resulting expressions for the MMELS test are not equivalent and the differences between approaches can be up to 50 times. A more accurate alternative analysis of the MMELS test is carried out in the present study for comparison. The alternative analysis is based on the finite element method and the virtual crack closure technique. Significant findings are found for precise materials characterisation using the MMELS test. A MMELS test rig is also designed and built. Different specimens of essentially unidirectional carbon/epoxy laminates are tested for the experimental characterisation of fatigue delamination under varying mode mix. A fractographic analysis is also conducted in some of the delaminated fracture surfaces. The experimental results are compared to the predictions of a proposed model for the fatigue propagation of interlaminar cracks.
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Pinot, Julien. "Etude de la puissance mécanique comme variable d'amélioration de la performance en cyclisme à travers l'interface homme-machine". Thesis, Besançon, 2014. http://www.theses.fr/2014BESA1007/document.
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Ce travail de thèse s’est déroulé dans le cadre d’une convention CIFRE entre mon laboratoire de rattachement C3S (EA4660) et le département Recherche et Développement (R&D) de l’équipe cycliste professionnelle FDJ. Les différentes études que nous avons conduites se sont articulées autour de l’amélioration de la performance sportive chez le cycliste à travers une variable centrale qui est la puissance mécanique qu’il développe lors de la locomotion (Pméca) selon deux axes principaux : 1) l’évaluation et le suivi du potentiel physique avec pour but l’amélioration du processus d’entraînement et 2) l’optimisation de l’interface homme – machine à partir de l’analyse du matériel et des équipements utilisés par les cyclistes dans l’équipe FDJThis thesis has been completed as part of a CIFRE agreement between the laboratory C3S(EA4660) and the Research and Development (R&D) department of the FDJ professionalcycling team. The various studies that we conducted centred on analysing sport performanceoptimisation in cyclists through a central variable: the mechanical power output (PO)developed during locomotion. There were two main areas of focus: 1) evaluation andmonitoring of physical potential, with the aim of improving the training process, and 2)optimisation of the human–machine interface via analysis of the materials and equipmentused by the FDJ team cyclists
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Shong, Chie-Yuan y 熊芝源. "The Characteristic of the Lead-Acid Batteries Under Variable Load Conditions". Thesis, 2003. http://ndltd.ncl.edu.tw/handle/v323uz.
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碩士中原大學
電機工程研究所
91
Due to the fact that load is changed from time to time, this thesis proposes a system which can be used to measure the characteristics of Lead-acid battery under varying load conditions. The reason of developing such a system is that the capacity of the Lead-acid battery may change under different load conditions. In this thesis, lamps are used to simulate the load. By changing the number of the lamps, the load condition is changed. In order to achieve the objective, LabVIEW is used to control the load. By varying the change rate of the lamps, the capacity of the battery can be measured and recorded. The result of the thesis indicates that the capacity of the batteries maintains at relative constant value no matter how the loads are changed. This indicates that the constant discharge rate can be used to measure the capacity of batteries precisely.
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Olivier, Allan Andre. "Mechanical shock values applied in condition monitoring of bearings operating under variable speed and load conditions". Thesis, 2014. http://hdl.handle.net/10352/299.
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M. Tech. (Mechanical Engineering) Vaal University of TechnologyMonitoring the condition of equipment in industry is very important to prevent unplanned breakdowns and to prolong their life. This is necessary, since it is not always economically viable to stop equipment at regular intervals to do maintenance. Failure on machines can lead to high repair costs and production losses. It is thus of paramount importance that early failure symptoms be identified by means of condition monitoring. This study in the field of condition monitoring is performed to determine if the mechanical shock values induced in defect bearings could be used to measure the condition of a bearing while operating under variable speed and variable load. Variable speed and variable load is becoming more popular in industry because variable speed drives applications ensure effective process control. Variable speed application, cause fault frequencies to fluctuate and therefore vibration applications for constant speed applications, which are speed-dependent, can no longer apply. Vibration-monitoring techniques that have applied for many years have now become obsolete in these variable speed applications. Methods such as Short Time Fourier Transformation (STFT), time scale like wavelet transform, and Order tracking has been applied in variable speed applications with some success. These methods analyses the vibration phases on the signal buy compensating for the speed changes. In this thesis, the Shock pulse method is selected as the analyses tool to measure the mechanical shock. Shock pulse monitoring does not focus on the vibration phases but measures in a small-time window when mechanical shocks are induced in the bearing material before the vibration phase. There is very little documented research in the field of mechanical shock pulse monitoring for conditions of variable speed and variable loads, and therefore this research focuses on recording these mechanical shock values by empirical tests. The tests were performed on a bearing with an induced defect on the outer race. The rolling element of the bearing strikes the defect and the mechanical shock value (dBsv) is measured. The mechanical shock is measured with the Shock pulse method in a small-time window before vibration occurs. In this time window, the dBsv is recorded over time to provide diagnostic information of the bearing during acceleration, deceleration and various loading conditions. These mechanical shocks are elastic waves that mirror the impact-contact-force's time function and the Shock pulse monitoring accelerometer, which is tuned to 32 kHz, will respond to the elastic wave fronts with transient amplitudes proportional to the square of the impact velocities. The mechanical shock values were analysed and reoccurring fault levels were identified on each empirical test. These recurring events from the empirical tests were used as primary data for analysis in this research. These tests were performed on a bearing with an induced failure and it was found that the dBsv measured over time could not be used to monitor the condition of the bearing under variable speed applications. This was because the dBsv changed as the speed increased. To overcome this problem Sohoel’s theory was applied and the initial mechanical shock value (dBi) was calculated for the bearing. The dbi value was subtracted from the dBsv and a value called the maximum mechanical shock value (dBm) was obtained. The dBm values stayed constant for the duration of the test and this allowed the condition of the bearing to be measured under variable speed and variable load conditions with some exception. The exception to the findings was that the dBm values stayed constant during acceleration phases, but during the deceleration phases the values were erratic and scattered. At speed below 200rpm the dBm values did not stay constant and therefore it was concluded that the dBm value recorded the best results only when thrust on the bearing was maximum. The other exception was under no-load conditions. The values were erratic and scattered, and therefore the results were not a true reflection of the bearing condition. The third exception was that the results on bearings with various loads remained constant during increased load changes unless the loading was erratic. During erratic load changes, the results were affected. The results also indicated that the larger the defect on the bearing raceway, the higher the dBm values were. Multipil defects on the bearing race ways were not part of this thesis and this gives an opertunity for futher research. The Shock pulse monitoring technique was 100% successful in monitoring the bearing condition only while the speed of the bearing was increasing. The results obtained in this work demonstrated that the condition of bearings can be monitored in applications of variable speed and variable load if the exception are eliminated and to obtain conclusive results the mechanical shock pulses should be measured over time and not be used as once-off value.
Libros sobre el tema "Variable load conditions"
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Creagh-Brown, Benedict, Joerg Steier y Nicholas Hart. Prolonged Weaning. Oxford University Press, 2014. http://dx.doi.org/10.1093/med/9780199653461.003.0049.
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In 25% of critically ill patients, weaning from mechanical ventilation takes longer than 10 days; indeed, 5–10% of patients still require ventilation at 30 days. Those with prolonged weaning, after adjustment for other variables, have a higher mortality within the intensive care unit than those without weaning delay or failure. The pathophysiological processes that result in weaning failure are complex and result of an imbalance between the neural respiratory drive, respiratory muscle load, and capacity. The clinical conditions resulting in these pathophysiological conditions should be methodically considered in patients requiring prolonged weaning. These patients often need a personalized weaning and rehabilitation approach, based on their underlying pathological condition as well as their psychological and physiological status.
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Wyatt, Laura A. y Michael Doherty. Morphological aspects of pathology. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780199668847.003.0003.
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Osteoarthritis (OA) is the commonest condition to affect synovial joints, but although any synovial joint can be affected, most studies of pathology relate to large joints (knees and hips). OA involves the whole joint and pathological alterations typically occur in all joint tissues. Established OA is characterized by a mixture of tissue loss and new tissue production resulting in focal loss of articular hyaline cartilage together with bone remodelling and osteophyte formation. Articular cartilage may show increased thickness in the earliest stages of OA with increased numbers of hypertrophic chondrocytes, followed by progressive decline in matrix components, thickness, and chondrocyte number. Surface fibrillation and vertical clefts become evident in mid- to end-stage OA and eventual complete loss of cartilage can occur, predominantly in maximum load-bearing regions, with subsequent eburnation and furrowing of bone. Bone remodelling may lead to alteration of bone shape and variable trabecular thickness in subchondral bone, whilst subchondral microfractures may result in localized osteonecrosis, fibrosis, and ‘cysts’. Endochondral ossification of new fibrocartilage produced predominantly at the joint margin produces characteristic bony osteophytes. The synovium shows areas of hyperplasia with varying amounts of lymphocyte aggregates and inclusion of osteochondral ‘loose’ bodies, and the outer fibrous capsule thickens to help stabilize the compromised joint. Synovial fluid increases in volume but decreases in viscosity. Periarticular changes include type II muscle atrophy and enthesophytes.
Capítulos de libros sobre el tema "Variable load conditions"
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Calì, Michele, Salvatore Massimo Oliveri y Marco Evangelos Biancolini. "Thread Couplings Stress Analysis by Radial Basis Functions Mesh Morphing". En Lecture Notes in Mechanical Engineering, 114–20. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-70566-4_19.
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AbstractTraditional analytical methods are approximate and need to be validated when it comes to predict the tensional behavior of thread coupling. Numerical finite element simulations help engineers come up with the optimum design, although the latter depends on the constraints and load conditions of the thread couplings which are often variable during the system functioning. The present work illustrates a new method based on Radial Basis Functions Mesh Morphing formulation to optimize the stress concentration in thread couplings which is subject to variable loads and constraints. In particular, thread root and fillet under-head drawings for metric ISO thread, which are the most commonly used thread connection, are optimized with Radial Basis Functions Mesh Morphing. In metric ISO threaded connection, the root shape and the fillet under the head are circular, and from shape optimization for minimum stress concentration it is well known that the circular shape becomes seldom optimal. The study is carried out to enhance the stress concentration factor with a simple geometric parameterization using two design variables. Radial Basis Functions Mesh Morphing formulation, performed with a simple geometric parameterization, has allowed to obtain a stress reduction of up to 12%; some similarities are found in the optimized designs leading to the proposal of a new standard. The reductions in the stress are achieved by rather simple changes made to the cutting tool.
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Sellamna, Hemza, Nassir Rouibah, Adel Mellit, Giuseppe Marco Tina y Hajji Bekkay. "Power Flow Control in Autonomous Micro-grid Operation Using Ants Colony Optimization Under Variable Load Conditions". En Lecture Notes in Electrical Engineering, 392–98. Singapore: Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-13-1405-6_47.
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Pandey, Shruti, Bharti Dwivedi y Anurag Tripathi. "Performance Analysis of Supercapacitor-Integrated PV-Fed Multistage Converter with SMC Controlled VSI for Variable Load Conditions". En Advances in Intelligent Systems and Computing, 455–65. Singapore: Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-13-1822-1_42.
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Shailaja, M. y A. V. Sita Rama Raju. "Neural Network—Based Diesel Engine Emissions Prediction for Variable Injection Timing, Injection Pressure, Compression Ratio and Load Conditions". En Lecture Notes in Electrical Engineering, 109–22. Singapore: Springer Singapore, 2016. http://dx.doi.org/10.1007/978-981-10-1540-3_12.
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Ponter, A. R. S. y M. Engelhardt. "Shakedown Limits for a General Yield Condition: Implementation and Application for a Von Mises Yield Condition". En Inelastic Analysis of Structures under Variable Loads, 11–29. Dordrecht: Springer Netherlands, 2000. http://dx.doi.org/10.1007/978-94-010-9421-4_2.
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Telega, Józef Joachim. "On Shakedown Theorems in the Presence of Signorini Conditions and Friction". En Inelastic Behaviour of Structures under Variable Loads, 183–201. Dordrecht: Springer Netherlands, 1995. http://dx.doi.org/10.1007/978-94-011-0271-1_10.
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Mahgoun, Hafida, Fakher Chaari, Ahmed Felkaoui y Mohamed Haddar. "L-Kurtosis and Improved Complete Ensemble EMD in Early Fault Detection Under Variable Load and Speed". En Applied Condition Monitoring, 3–15. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-94616-0_1.
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Mahgoun, H., Fakher Chaari, A. Felkaoui y Mohamed Haddar. "Early Detection of Gear Faults in Variable Load and Local Defect Size Using Ensemble Empirical Mode Decomposition (EEMD)". En Applied Condition Monitoring, 13–22. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-41459-1_2.
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Mahgoun, Hafida, Fakher Chaari, Ahmed Felkaoui y Mohamed Haddar. "The Time-Frequency Filtering (TFF) Method Used in Early Detection of Gear Faults in Variable Load and Dimensions Defect". En Applied Condition Monitoring, 56–67. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-96181-1_5.
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Boškoski, Pavle y Đani Juričić. "Rényi Entropy Based Statistical Complexity Analysis for Gear Fault Prognostics under Variable Load". En Condition Monitoring of Machinery in Non-Stationary Operations, 25–32. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-28768-8_3.
Texto completoActas de conferencias sobre el tema "Variable load conditions"
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Merkel, Philip Amos, Yannick Duensing y Katharina Schmitz. "Slipper Wear in Variable Operating Conditions". En ASME/BATH 2023 Symposium on Fluid Power and Motion Control. American Society of Mechanical Engineers, 2023. http://dx.doi.org/10.1115/fpmc2023-111597.
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Abstract Electro-hydrostatic actuators (EHA) offer highperformance hydraulic control while featuring a range of advantages compared to classic valve-controlled actuation. They are highly efficient, modular, power-by-wire actuators thus enabling the design of efficient hydroelectric drives urgently needed for the electrification of hydraulic machinery. EHAs are therefore steadily replacing valve-controlled actuators in many applications. However, in some cases, the robustness of the existing EHA systems has proven to be insufficient for their respective applications. Especially pumps are known to limit the service life of EHAs. [1] A very commonly used pump type here is the axial piston pump. The robustness of its hydrostatically partially balanced contacts has proven to be particularly challenging under the variable load conditions typically arising in EHA applications. [1], [12], [13] This contribution aims at the description of the relevant wear effects on the slipper-swashplate contact under variable load conditions as well as the impact of the wear on the load-carrying capabilities of the slipper contact. For this, occurring wear is experimentally identified on component-level tests. A simulative elastohydrodynamic lubrication study of the slipper-swashplate contact allows the identification of the wear progress as well as a study of the influence of existing wear profiles on the slipper behavior.
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Teng, Chin-Pun y Jorge Angeles. "Structural Optimization Under Variable Loading Conditions". En ASME 2000 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/detc2000/dac-14299.
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Abstract The problem of structural optimization under variable loading conditions is discussed here. We assume a linearly-elastic structure subject to one single load of constant magnitude but of arbitrary orientation. Moreover, we assume that the structure is discretized by finite elements. The result of this study is an optimality criterion: the eigenvalues of the stiffness matrix of the optimum structure observe a minimum variance. In other words, the optimum structure under variable load must have a stiffness matrix that is as close as possible to isotropy. Furthermore, in order to implement the foregoing criterion, we introduce a novel method of automatic mesh generation, that is based on the concept of penalty functions of nonlinear programming. Finally, we illustrate these concepts by means of the optimization of a triangular lamina of given side lengths, with an elliptical hole centered at its centroid, of a prescribed area, the design parameters being the semiaxes of the ellipse and the orientation of these axes with respect to the edges of the lamina.
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Vinayak, Sulluru, Shrey Baluapuri, Lakkidi Raju y Swapnajit Pattnaik. "Interleaved high step-up converter for variable load conditions using microcontroller". En 2014 IEEE 9th Conference on Industrial Electronics and Applications (ICIEA). IEEE, 2014. http://dx.doi.org/10.1109/iciea.2014.6931290.
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Di Fatta, Alessio, Pietro Romano, Giuseppe Rizzo, Antonino Imburgia, Fabio Viola y Guido Ala. "Behaviour of HVDC Cables Under Variable Load Conditions: PD Detection and Recognition". En 2023 AEIT HVDC International Conference (AEIT HVDC). IEEE, 2023. http://dx.doi.org/10.1109/aeithvdc58550.2023.10179082.
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Antonino-Daviu, Jose A., V. Climente-Alarcon, J. Pons-Llinares y E. Wiedenbrug. "Advanced rotor assessment of motors operating under variable load conditions in mining facilities". En 2014 IEEE Energy Conversion Congress and Exposition (ECCE). IEEE, 2014. http://dx.doi.org/10.1109/ecce.2014.6953452.
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Yao, Kun, Junfeng Fu, Shuyang Li, Jie Wan, Guiping Zhou, E. Peng y Yiling Ma. "Comprehensive Optimization of Variable Load Capacity of Heating Unit under Complicated Working Conditions". En 2019 International Conference on Sensing, Diagnostics, Prognostics, and Control (SDPC). IEEE, 2019. http://dx.doi.org/10.1109/sdpc.2019.00125.
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Chishti, Abdul Rehman, Affifa Adeeb, Muhammad Nawaz Abbasi y Muhammad Jawad Masud. "Robust Controller Design for Speed Control of Induction Motor Under Variable Load Conditions". En 2020 IEEE 23rd International Multitopic Conference (INMIC). IEEE, 2020. http://dx.doi.org/10.1109/inmic50486.2020.9318152.
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Venkatesan, Suresh G., Sumant G. Kadwane, Monali P. Samarth y Snehal P. Gawande. "Harmonic analysis of grid connected Z-source inverter under variable load/input conditions". En 2016 IEEE 6th International Conference on Power Systems (ICPS). IEEE, 2016. http://dx.doi.org/10.1109/icpes.2016.7584096.
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Al-Baik, Deema y Vinod Khadkikar. "Effect of variable PV power on the grid power factor under different load conditions". En 2011 2nd International Conference on Electric Power and Energy Conversion Systems (EPECS). IEEE, 2011. http://dx.doi.org/10.1109/epecs.2011.6126844.
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Tang, Chuanyu, Tianru Wang, Tao Jiang, Yong Tang y Jinlei Sun. "Remaining Discharge Capacity Online Estimation for Lithium-Ion Batteries Under Variable Load Current Conditions". En IECON 2020 - 46th Annual Conference of the IEEE Industrial Electronics Society. IEEE, 2020. http://dx.doi.org/10.1109/iecon43393.2020.9254332.
Texto completoInformes sobre el tema "Variable load conditions"
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Brust, F. W., P. Krishnaswamy y B. S. Majumdar. An investigation of the effects of history dependent damage in time dependent fracture mechanics, variable load conditions. Office of Scientific and Technical Information (OSTI), noviembre de 1992. http://dx.doi.org/10.2172/7019350.
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Brust, F. W., P. Krishnaswamy y B. S. Majumdar. An investigation of the effects of history dependent damage in time dependent fracture mechanics, variable load conditions. Progress report, Phase 2. Office of Scientific and Technical Information (OSTI), noviembre de 1992. http://dx.doi.org/10.2172/10191403.
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Brust, F. W., P. Krishnaswamy y B. S. Majumdar. An investigation of the effects of history dependent damage in time dependent fracture mechanics; Phases I, II, and one half of Phase III - variable load conditions. Progress report. Office of Scientific and Technical Information (OSTI), octubre de 1993. http://dx.doi.org/10.2172/10182458.
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Currier, Brad, Jonathan Mcleod y Stuart Phillips. The Influence of Resistance Exercise Training Prescription Variables on Muscle Mass, Muscle Strength, and Physical Function in Healthy Adults: An Umbrella Review. INPLASY - International Platform of Registered Systematic Review and Meta-analysis Protocols, febrero de 2022. http://dx.doi.org/10.37766/inplasy2022.2.0028.
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Review question / Objective: To determine how resistance training prescription variables (load, sets, frequency, time under tension, etc) affect muscle mass, muscle strength, and physical function in healthy adults. Condition being studied: To determine how resistance training prescription variables (load, sets, frequency, time under tension, etc) affect muscle mass (hypertrophy), muscle strength, and physical function in healthy adults. Information sources: OVID MEDLINE, SPORTDiscus, Web of Science.
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Schiller, Brandon, Tara Hutchinson y Kelly Cobeen. Cripple Wall Small-Component Test Program: Wet Specimens II (PEER-CEA Project). Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, noviembre de 2020. http://dx.doi.org/10.55461/ldbn4070.
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This report is one of a series of reports documenting the methods and findings of a multi-year, multi-disciplinary project coordinated by the Pacific Earthquake Engineering Research Center (PEER and funded by the California Earthquake Authority (CEA). The overall project is titled “Quantifying the Performance of Retrofit of Cripple Walls and Sill Anchorage in Single-Family Wood-Frame Buildings,” henceforth referred to as the “PEER–CEA Project.” The overall objective of the PEER–CEA Project is to provide scientifically based information (e.g., testing, analysis, and resulting loss models) that measure and assess the effectiveness of seismic retrofit to reduce the risk of damage and associated losses (repair costs) of wood-frame houses with cripple wall and sill anchorage deficiencies as well as retrofitted conditions that address those deficiencies. Tasks that support and inform the loss-modeling effort are: (1) collecting and summarizing existing information and results of previous research on the performance of wood-frame houses; (2) identifying construction features to characterize alternative variants of wood-frame houses; (3) characterizing earthquake hazard and ground motions at representative sites in California; (4) developing cyclic loading protocols and conducting laboratory tests of cripple wall panels, wood-frame wall subassemblies, and sill anchorages to measure and document their response (strength and stiffness) under cyclic loading; and (5) the computer modeling, simulations, and the development of loss models as informed by a workshop with claims adjustors. This report is a product of Working Group 4 (WG4): Testing, whose central focus was to experimentally investigate the seismic performance of retrofitted and existing cripple walls. This report focuses stucco or “wet” exterior finishes. Paralleled by a large-component test program conducted at the University of California, Berkeley (UC Berkeley) [Cobeen et al. 2020], the present study involves two of multiple phases of small-component tests conducted at the University of California San Diego (UC San Diego). Details representative of era-specific construction, specifically the most vulnerable pre-1960s construction, are of predominant focus in the present effort. Parameters examined are cripple wall height, finish style, gravity load, boundary conditions, anchorage, and deterioration. This report addresses the third phase of testing, which consisted of eight specimens, as well as half of the fourth phase of testing, which consisted of six specimens where three will be discussed. Although conducted in different phases, their results are combined here to co-locate observations regarding the behavior of the second phase the wet (stucco) finished specimens. The results of first phase of wet specimen tests were presented in Schiller et al. [2020(a)]. Experiments involved imposition of combined vertical loading and quasi-static reversed cyclic lateral load onto ten cripple walls of 12 ft long and 2 or 6 ft high. One cripple wall was tested with a monotonic loading protocol. All specimens in this report were constructed with the same boundary conditions on the top and corners of the walls as well as being tested with the same vertical load. Parameters addressed in this report include: wet exterior finishes (stucco over framing, stucco over horizontal lumber sheathing, and stucco over diagonal lumber sheathing), cripple wall height, loading protocol, anchorage condition, boundary condition at the bottom of the walls, and the retrofitted condition. Details of the test specimens, testing protocol, including instrumentation; and measured as well as physical observations are summarized in this report. Companion reports present phases of the tests considering, amongst other variables, impacts of various boundary conditions, stucco (wet) and non-stucco (dry) finishes, vertical load, cripple wall height, and anchorage condition. Results from these experiments are intended to support advancement of numerical modeling tools, which ultimately will inform seismic loss models capable of quantifying the reduction of loss achieved by applying state-of-practice retrofit methods as identified in FEMA P-1100,Vulnerability-Base Seismic Assessment and Retrofit of One- and Two-Family Dwellings.
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Fuchs, Marcel, Ishaiah Segal, Ehude Dayan y K. Jordan. Improving Greenhouse Microclimate Control with the Help of Plant Temperature Measurements. United States Department of Agriculture, mayo de 1995. http://dx.doi.org/10.32747/1995.7604930.bard.
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A model of the energy balance of a transpiring crop in a greenhouse was developed in a format suitable for use in climate control algorithms aimed at dissipating excess heat during the warm periods. The model's parameters use external climatic variables as input. It incorporates radiation and convective transfer functions related to the operation of control devices like shading screens, vents, fans and enhanced evaporative cooling devices. The model identified the leaf boundary-layer resistance and the leaf stomatal and cuticular resistance as critical parameters regulating the temperature of the foliage. Special experiments evaluated these variables and established their relation to environmental factors. The research established that for heat load conditions in Mediterranean and arid climates transpiring crops maintained their foliage temperature within the range allowing high productivity. Results specify that a water supply ensuring minimum leaf resistance to remain below 100 s m-1, and a ventilation rate of 30 air exchanges per hour, are the conditions needed to achieve self cooling. Two vegetable crops, tomato and sweet pepper fulfilled maintained their leaf resistance within the prescribed range at maturity, i.e., during the critical warm season. The research evaluates the effects of additional cooling obtained from wet pad systems and spray wetting of foliage.
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Schiller, Brandon, Tara Hutchinson y Kelly Cobeen. Cripple Wall Small-Component Test Program: Wet Specimens I (PEER-CEA Project). Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, noviembre de 2020. http://dx.doi.org/10.55461/dqhf2112.
Texto completoResumen
This report is one of a series of reports documenting the methods and findings of a multi-year, multi-disciplinary project coordinated by the Pacific Earthquake Engineering Research Center (PEER and funded by the California Earthquake Authority (CEA). The overall project is titled “Quantifying the Performance of Retrofit of Cripple Walls and Sill Anchorage in Single-Family Wood-Frame Buildings,” henceforth referred to as the “PEER–CEA Project.” The overall objective of the PEER–CEA Project is to provide scientifically based information (e.g., testing, analysis, and resulting loss models) that measure and assess the effectiveness of seismic retrofit to reduce the risk of damage and associated losses (repair costs) of wood-frame houses with cripple wall and sill anchorage deficiencies as well as retrofitted conditions that address those deficiencies. Tasks that support and inform the loss-modeling effort are: (1) collecting and summarizing existing information and results of previous research on the performance of wood-frame houses; (2) identifying construction features to characterize alternative variants of wood-frame houses; (3) characterizing earthquake hazard and ground motions at representative sites in California; (4) developing cyclic loading protocols and conducting laboratory tests of cripple wall panels, wood-frame wall subassemblies, and sill anchorages to measure and document their response (strength and stiffness) under cyclic loading; and (5) the computer modeling, simulations, and the development of loss models as informed by a workshop with claims adjustors. This report is a product of Working Group 4: Testing and focuses on the first phase of an experimental investigation to study the seismic performance of retrofitted and existing cripple walls with sill anchorage. Paralleled by a large-component test program conducted at the University of California [Cobeen et al. 2020], the present study involves the first of multiple phases of small-component tests conducted at the UC San Diego. Details representative of era-specific construction, specifically the most vulnerable pre-1960s construction, are of predominant focus in the present effort. Parameters examined are cripple wall height, finish materials, gravity load, boundary conditions, anchorage, and deterioration. This report addresses the first phase of testing, which consisted of six specimens. Phase 1 including quasi-static reversed cyclic lateral load testing of six 12-ft-long, 2-ft high cripple walls. All specimens in this phase were finished on their exterior with stucco over horizontal sheathing (referred to as a “wet” finish), a finish noted to be common of dwellings built in California before 1945. Parameters addressed in this first phase include: boundary conditions on the top, bottom, and corners of the walls, attachment of the sill to the foundation, and the retrofitted condition. Details of the test specimens, testing protocol, instrumentation; and measured as well as physical observations are summarized in this report. In addition, this report discusses the rationale and scope of subsequent small-component test phases. Companion reports present these test phases considering, amongst other variables, the impacts of dry finishes and cripple wall height (Phases 2–4). Results from these experiments are intended to provide an experimental basis to support numerical modeling used to develop loss models, which are intended to quantify the reduction of loss achieved by applying state-of-practice retrofit methods as identified in FEMA P-1100, Vulnerability-Base Seismic Assessment and Retrofit of One- and Two-Family Dwellings.
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Brossia. L52119 Comparative Consumption Rates of Impressed Current Cathodic Protection Anodes. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), enero de 2004. http://dx.doi.org/10.55274/r0010953.
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There is a variety of impressed current anode materials available for onshore applications, including High Silicon Cast Iron (HSCI), Mixed Metal Oxides (MMO), graphite, platinum (or platinum coated titanium), and conductive polymers. Many end users simply select the anode material that they have experience with. What is lacking is a clear, direct comparison of relative anode consumption rates conducted under identical conditions. The present study examined the behavior of the various anode types under different current loads and soil conditions in an effort to establish baseline consumption rates under controlled conditions. Variables that were examined included soil resistivity, the presence of coke backfill, current load, and soil type (sand or 50/50 clay/sand mix). The consumption rates of the anodes evaluated decreased in the order of: AnodeFlex, HSCI, Graphite, Pt, and MMO. A survey of field experiences yielded a slightly different order in terms of anode life with Graphite and HSCI lasting the longest. However, given the wide range of anode sizes used in the various field sites, it is difficult to directly link the field results to the consumption rates measured in the laboratory. Soil composition and resistivity were not observed to have a significant influence on anode consumption rates. The presence of coke, however, led to a decrease in consumption for all anodes in some cases by as much as a factor of nearly 70. Utilizing anode cost estimates and neglecting installation costs, the life-cycle material costs for MMO and Pt anodes are much lower than the other anode materials. Furthermore, AnodeFlex was noted to be the highest cost system from a materials perspective. This may be slightly misleading since installation and replacement costs are not factored in. Given that the installation of AnodeFlex is often much easier and less expensive than the other anode types, this may prove to be a viable financial decision when the other factors are considered. ����������� The primary implications of the present study are: Despite higher material costs, MMO and Pt anodes may offer significant long-term cost savings as compared to other anode types for many applications Use of coke backfill is critical to ensure lower anode consumption rates for AnodeFlex, Graphite, and to a lesser extent HSCI; coke does not appear necessary for MMO or Pt Soil composition (sand vs. clay/sand mix) and resistivity do not appear to significantly influence anode consumption rates, thus consideration of the soil environment (except groundwater chemistry) is not needed in selection of an appropriate anode Because the influence of groundwater chemistry (as part of the soil environment) was not examined, the effects of sulfate, chloride, and pH will need to be evaluated in detail to better aid in anode material selection Field use survey responses showed a wide range in observed anode lifespan, with graphite and HSCI experiencing the longest life and cable anodes the shortest The field survey also revealed that a significant cause of anode failures was connector and cable problems
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Brosh, Arieh, David Robertshaw, Yoav Aharoni, Zvi Holzer, Mario Gutman y Amichai Arieli. Estimation of Energy Expenditure of Free Living and Growing Domesticated Ruminants by Heart Rate Measurement. United States Department of Agriculture, abril de 2002. http://dx.doi.org/10.32747/2002.7580685.bard.
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Research objectives were: 1) To study the effect of diet energy density, level of exercise, thermal conditions and reproductive state on cardiovascular function as it relates to oxygen (O2) mobilization. 2) To validate the use of heart rate (HR) to predict energy expenditure (EE) of ruminants, by measuring and calculating the energy balance components at different productive and reproductive states. 3) To validate the use of HR to identify changes in the metabolizable energy (ME) and ME intake (MEI) of grazing ruminants. Background: The development of an effective method for the measurement of EE is essential for understanding the management of both grazing and confined feedlot animals. The use of HR as a method of estimating EE in free-ranging large ruminants has been limited by the availability of suitable field monitoring equipment and by the absence of empirical understanding of the relationship between cardiac function and metabolic rate. Recent developments in microelectronics provide a good opportunity to use small HR devices to monitor free-range animals. The estimation of O2 uptake (VO2) of animals from their HR has to be based upon a consistent relationship between HR and VO2. The question as to whether, or to what extent, feeding level, environmental conditions and reproductive state affect such a relationship is still unanswered. Studies on the basic physiology of O2 mobilization (in USA) and field and feedlot-based investigations (in Israel) covered a , variety of conditions in order to investigate the possibilities of using HR to estimate EE. In USA the physiological studies conducted using animals with implanted flow probes, show that: I) although stroke volume decreases during intense exercise, VO2 per one heart beat per kgBW0.75 (O2 Pulse, O2P) actually increases and measurement of EE by HR and constant O2P may underestimate VO2unless the slope of the regression relating to heart rate and VO2 is also determined, 2) alterations in VO2 associated with the level of feeding and the effects of feeding itself have no effect on O2P, 3) both pregnancy and lactation may increase blood volume, especially lactation; but they have no effect on O2P, 4) ambient temperature in the range of 15 to 25°C in the resting animal has no effect on O2P, and 5) severe heat stress, induced by exercise, elevates body temperature to a sufficient extent that 14% of cardiac output may be required to dissipate the heat generated by exercise rather than for O2 transport. However, this is an unusual situation and its affect on EE estimation in a freely grazing animal, especially when heart rate is monitored over several days, is minor. In Israel three experiments were carried out in the hot summer to define changes in O2P attributable to changes in the time of day or In the heat load. The animals used were lambs and young calves in the growing phase and highly yielding dairy cows. In the growing animals the time of day, or the heat load, affected HR and VO2, but had no effect on O2P. On the other hand, the O2P measured in lactating cows was affected by the heat load; this is similar to the finding in the USA study of sheep. Energy balance trials were conducted to compare MEI recovery by the retained energy (RE) and by EE as measured by HR and O2P. The trial hypothesis was that if HR reliably estimated EE, the MEI proportion to (EE+RE) would not be significantly different from 1.0. Beef cows along a year of their reproductive cycle and growing lambs were used. The MEI recoveries of both trials were not significantly different from 1.0, 1.062+0.026 and 0.957+0.024 respectively. The cows' reproductive state did not affect the O2P, which is similar to the finding in the USA study. Pasture ME content and animal variables such as HR, VO2, O2P and EE of cows on grazing and in confinement were measured throughout three years under twenty-nine combinations of herbage quality and cows' reproductive state. In twelve grazing states, individual faecal output (FO) was measured and MEI was calculated. Regression analyses of the EE and RE dependent on MEI were highly significant (P<0.001). The predicted values of EE at zero intake (78 kcal/kgBW0.75), were similar to those estimated by NRC (1984). The EE at maintenance condition of the grazing cows (EE=MEI, 125 kcal/kgBW0.75) which are in the range of 96.1 to 125.5 as presented by NRC (1996 pp 6-7) for beef cows. Average daily HR and EE were significantly increased by lactation, P<0.001 and P<0.02 respectively. Grazing ME significantly increased HR and EE, P<0.001 and P<0.00l respectively. In contradiction to the finding in confined ewes and cows, the O2P of the grazing cows was significantly affected by the combined treatments (P<0.00l ); this effect was significantly related to the diet ME (P<0.00l ) and consequently to the MEI (P<0.03). Grazing significantly increased O2P compared to confinement. So, when EE of grazing animals during a certain season of the year is estimated using the HR method, the O2P must be re measured whenever grazing ME changes. A high correlation (R2>0.96) of group average EE and of HR dependency on MEI was also found in confined cows, which were fed six different diets and in growing lambs on three diets. In conclusion, the studies conducted in USA and in Israel investigated in depth the physiological mechanisms of cardiovascular and O2 mobilization, and went on to investigate a wide variety of ruminant species, ages, reproductive states, diets ME, time of intake and time of day, and compared these variables under grazing and confinement conditions. From these combined studies we can conclude that EE can be determined from HR measurements during several days, multiplied by O2P measured over a short period of time (10-15 min). The study showed that RE could be determined during the growing phase without slaughtering. In the near future the development microelectronic devices will enable wide use of the HR method to determine EE and energy balance. It will open new scopes of physiological and agricultural research with minimizes strain on animals. The method also has a high potential as a tool for herd management.
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Financial Stability Report - Second Semester of 2020. Banco de la República de Colombia, marzo de 2021. http://dx.doi.org/10.32468/rept-estab-fin.sem2.eng-2020.
Texto completoResumen
The Colombian financial system has not suffered major structural disruptions during these months of deep economic contraction and has continued to carry out its basic functions as usual, thus facilitating the economy's response to extreme conditions. This is the result of the soundness of financial institutions at the beginning of the crisis, which was reflected in high liquidity and capital adequacy indicators as well as in the timely response of various authorities. Banco de la República lowered its policy interest rates 250 points to 1.75%, the lowest level since the creation of the new independent bank in 1991, and provided ample temporary and permanent liquidity in both pesos and foreign currency. The Office of the Financial Superintendent of Colombia, in turn, adopted prudential measures to facilitate changes in the conditions for loans in effect and temporary rules for rating and loan-loss provisions. Finally, the national government expanded the transfers as well as the guaranteed credit programs for the economy. The supply of real credit (i.e. discounting inflation) in the economy is 4% higher today than it was 12 months ago with especially marked growth in the housing (5.6%) and commercial (4.7%) loan portfolios (2.3% in consumer and -0.1% in microloans), but there have been significant changes over time. During the first few months of the quarantine, firms increased their demands for liquidity sharply while consumers reduced theirs. Since then, the growth of credit to firms has tended to slow down, while consumer and housing credit has grown. The financial system has responded satisfactorily to the changes in the respective demands of each group or sector and loans may grow at high rates in 2021 if GDP grows at rates close to 4.6% as the technical staff at the Bank expects; but the forecasts are highly uncertain. After the strict quarantine implemented by authorities in Colombia, the turmoil seen in March and early April, which was evident in the sudden reddening of macroeconomic variables on the risk heatmap in Graph A,[1] and the drop in crude oil and coal prices (note the high volatility registered in market risk for the region on Graph A) the local financial markets stabilized relatively quickly. Banco de la República’s credible and sustained policy response played a decisive role in this stabilization in terms of liquidity provision through a sharp expansion of repo operations (and changes in amounts, terms, counterparties, and eligible instruments), the purchases of public and private debt, and the reduction in bank reserve requirements. In this respect, there is now abundant aggregate liquidity and significant improvements in the liquidity position of investment funds. In this context, the main vulnerability factor for financial stability in the short term is still the high degree of uncertainty surrounding loan quality. First, the future trajectory of the number of people infected and deceased by the virus and the possible need for additional health measures is uncertain. For that reason, there is also uncertainty about the path for economic recovery in the short and medium term. Second, the degree to which the current shock will be reflected in loan quality once the risk materializes in banks’ financial statements is uncertain. For the time being, the credit risk heatmap (Graph B) indicates that non-performing and risky loans have not shown major deterioration, but past experience indicates that periods of sharp economic slowdown eventually tend to coincide with rises in non-performing loans: the calculations included in this report suggest that the impact of the recession on credit quality could be significant in the short term. This is particularly worrying since the profitability of credit establishments has been declining in recent months, and this could affect their ability to provide credit to the real sector of the economy. In order to adopt a forward-looking approach to this vulnerability, this Report presents several stress tests that evaluate the resilience of the liquidity and capital adequacy of credit institutions and investment funds in the event of a hypothetical scenario that seeks to simulate an extreme version of current macroeconomic conditions. The results suggest that even though there could be strong impacts on the credit institutions’ volume of credit and profitability under such scenarios, aggregate indicators of total and core capital adequacy will probably remain at levels that are above the regulatory limits over the horizon of a year. At the same time, the exercises highlight the high capacity of the system's liquidity to face adverse scenarios. In compliance with its constitutional objectives and in coordination with the financial system's security network, Banco de la República will continue to closely monitor the outlook for financial stability at this juncture and will make the decisions that are necessary to ensure the proper functioning of the economy, facilitate the flow of sufficient credit and liquidity resources, and further the smooth operation of the payment systems. Juan José Echavarría Governor