Academic literature on the topic 'Random mode Cycle'
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Journal articles on the topic "Random mode Cycle"
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Pan, Chaofeng, Yuanxue Tao, Limei Wang, Huanhuan Li, and Jufeng Yang. "Fuzzy energy management strategy for electric vehicle combining driving cycle construction and air-conditioning load identification." Advances in Mechanical Engineering 13, no. 2 (February 2021): 168781402199438. http://dx.doi.org/10.1177/1687814021994381.
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Energy management strategy is developed by considering the random and air conditioning load fluctuation, which greatly affected the torque control of the electric motor in electric vehicle. Firstly, the vehicle power consumption model is established, based on the influencing factors of electric vehicle energy consumption: random load and air conditioning load. Therefore, driving conditions with random characteristics representing the actual random load are constructed. According to the clustered characteristic parameters, the driving conditions were classified as different driving modes. Secondly, the mode of predicted condition was taken as a variable to evaluate the logic threshold strategy and fuzzy control strategy in which the influence of air conditioning was considered. Finally, under the condition of New European Driving Cycle (NEDC), the proposed management strategy was simulated in software environment, and the hardware in-loop (HIL) test was performed to verify the strategy. The simulation and HIL test results show that the proposed energy management strategy can increase the driving range by considering the load fluctuation of air conditioning. Furthermore, the strategy combining the driving mode prediction can alleviate the decline rate of SOC. And the fuzzy control strategy has better adaptability in complex conditions and lower battery energy consumption rate.
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Zhang, Bing Zhan, Han Zhao, and An Dong Yin. "Depleting Mode Control Strategies for Plug-in Hybrid Electric Vehicles." Applied Mechanics and Materials 130-134 (October 2011): 2211–15. http://dx.doi.org/10.4028/www.scientific.net/amm.130-134.2211.
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Control strategy is the most important issue in the Plug-in Hybrid electric vehicles (PHEV) design, which has two modes: charge depleting mode (CD) and charge sustaining mode (CS). The different control strategies in depleting mode will have a great influence on PHEV dynamic performance and fuel economy. The engine optimal torque control strategy was proposed in the paper. The vehicle simulation model in Powertrain Systems Analysis Toolkit (PSAT) was adopted to evaluate the proposed control strategy. The aggressive highway drive cycle Artemis_hwy and a random drive cycle generated by Markov Process were used. The simulation results indicate the proposed control strategy has great improvement in fuel economy.
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Antar, Bilal I., and Hong Tae Kang. "Fatigue Life Prediction for Caliper Guide Pin under Random Vibrational Loading." Advanced Materials Research 891-892 (March 2014): 1755–60. http://dx.doi.org/10.4028/www.scientific.net/amr.891-892.1755.
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A fatigue life prediction tool was developed for caliper guide pins under random vibrational loading. The Pie-Slice model was designed to provide detailed information about the failure location, orientation, and damage magnitude. A component test fixture was developed to determine the strain-life curve for a given guide pin design. Statistical analysis was conducted to insure the repeatability of the failure mode and the robustness of the setup. Weibull analysis was performed to the measured guide pin strain-life in order to insure that the developed strain-life data to insure that developed strain-life curve will account for all the manufacturing process variations, from a component, assembly, and a system level to a certain level of reliability and confidence. Rainflow cycle count was used to bin the damaging and non-damaging cycles based on their stain level. Fatigue life calculation was performed using the Smith-Watson-Topper strain-life approach. The predictive tool was able to accurately estimate the cumulative fatigue damage for guide pins under random loading conditions. The Pie-Slice model was also able to predict the failure location and orientation of a crack, as well as the damage magnitude. Both tools were validated using a pre-designed random block-load sequence at constant amplitude..
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MAZZINI, G., G. SETTI, and R. ROVATTI. "MULTIMODE TIME-MARKOV SYSTEMS: RECURSIVE TENSOR-BASED ANALYSIS, CHAOTIC GENERATION, LOCALLY LOOPING PROCESSES." International Journal of Bifurcation and Chaos 16, no. 04 (April 2006): 961–88. http://dx.doi.org/10.1142/s0218127406015234.
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The paper proposes a systematic solution to the problem of mixing different stochastic processes, each implied by a certain mode of operation of the system at hand and with a random duration whose distribution depends on the previous and present modes. We do so by widening the scope of an existing framework for the statistical characterization of finite valued processes with memory-one properties. The point of view is that of stochastic dynamics and the state space of the process is partitioned into regions (that we identify with modes) such that, if sojourn in a mode can be assumed, the statistical characterization is fully understood. The process is also allowed to stochastically move from one mode to another and the number of time steps for which it remains in each mode is a random variable whose distribution is a function only of the mode visited before. A general theoretical framework is developed here for the computation of any-order joint probabilities. The framework is then exemplified for the case of locally looping systems that are random sequences of modes comprising the cyclical execution of given atomic actions. They are the model of choice for complex appliances that operate following the steps of a communication protocol, and/or the various phases of a bus cycle, and/or the load-compute-store mechanism of a microprocessor, etc. Exploiting the theory put forward by the paper, we highlight how these processes could be generated by suitably designed 2-d chaotic maps and how their second- and third-order spectra may be obtained and interpreted when exponentially or polynomially decaying distributions are assumed for mode sojourn times.
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Xu, Fei, Chuanri Li, and Tongmin Jiang. "On the Shaker Simulation of Wind-Induced Non-Gaussian Random Vibration." Shock and Vibration 2016 (2016): 1–10. http://dx.doi.org/10.1155/2016/5450865.
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Gaussian signal is produced by ordinary random vibration controllers to test the products in the laboratory, while the field data is usually non-Gaussian. Two methodologies are presented in this paper for shaker simulation of wind-induced non-Gaussian vibration. The first methodology synthesizes the non-Gaussian signal offline and replicates it on the shaker in the Time Waveform Replication (TWR) mode. A new synthesis method is used to model the non-Gaussian signal as a Gaussian signal multiplied by an amplitude modulation function (AMF). A case study is presented to show that the synthesized non-Gaussian signal has the same power spectral density (PSD), probability density function (PDF), and loading cycle distribution (LCD) as the field data. The second methodology derives a damage equivalent Gaussian signal from the non-Gaussian signal based on the fatigue damage spectrum (FDS) and the extreme response spectrum (ERS) and reproduces it on the shaker in the closed-loop frequency domain control mode. The PSD level and the duration time of the derived Gaussian signal can be manipulated for accelerated testing purpose. A case study is presented to show that the derived PSD matches the damage potential of the non-Gaussian environment for both fatigue and peak response.
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Singh, Salvinder, and Shahrum Abdullah. "Durability analysis using Markov chain modeling under random loading for automobile crankshaft." International Journal of Structural Integrity 10, no. 4 (August 12, 2019): 454–68. http://dx.doi.org/10.1108/ijsi-03-2018-0016.
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Purpose The purpose of this paper is to present the durability analysis in predicting the reliability life cycle for an automobile crankshaft under random stress load using the stochastic process. Due to the limitations associated with the actual loading history obtained from the experimental analysis or due to the sensitivity of the strain gauge, the fatigue reliability life cycle assessment has lower accuracy and efficiency for fatigue life prediction. Design/methodology/approach The proposed Markov process embeds the actual maximum and minimum stresses by a continuous updating process for stress load history data. This is to reduce the large credible intervals and missing loading points used for fatigue life prediction. With the reduction and missing loading intervals, the accuracy of fatigue life prediction for the crankshaft was validated using the statistical correlation properties. Findings It was observed that fatigue reliability corresponded well by reporting the accuracy of 95–98 per cent with a mean squared error of 1.5–3 per cent for durability and mean cycle to failure. Hence, the proposed fatigue reliability assessment provides an accurate, efficient, fast and cost-effective durability analysis in contrast to costly and lengthy experimental techniques. Research limitations/implications An important implication of this study is durability-based life cycle assessment by developing the reliability and hazard rate index under random stress loading using the stochastic technique in modeling for improving the sensitivity of the strain gauge. Practical implications The durability analysis is one of the fundamental attributes for the safe operation of any component, especially in the automotive industry. Focusing on safety, structural health monitoring aims at the quantification of the probability of failure under mixed mode loading. In practice, diverse types of protective barriers are placed as safeguards from the hazard posed by the system operation. Social implications Durability analysis has the ability to deal with the longevity and dependability of parts, products and systems in any industry. More poignantly, it is about controlling risk whereby engineering incorporates a wide variety of analytical techniques designed to help engineers understand the failure modes and patterns of these parts, products and systems. This would enable the automotive industry to improve design and increase the life cycle with the durability assessment field focussing on product reliability and sustainability assurance. Originality/value The accuracy of the simulated fatigue life was statistically correlated with a 95 per cent boundary condition towards the actual fatigue through the validation process using finite element analysis. Furthermore, the embedded Markov process has high accuracy in generating synthetic load history for the fatigue life cycle assessment. More importantly, the fatigue reliability life cycle assessment can be performed with high accuracy and efficiency in assessing the integrity of the component regarding structural integrity.
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Jiang, Shanhe, Chaolong Zhang, and Shijun Chen. "Sequential Hybrid Particle Swarm Optimization and Gravitational Search Algorithm with Dependent Random Coefficients." Mathematical Problems in Engineering 2020 (April 21, 2020): 1–17. http://dx.doi.org/10.1155/2020/1957812.
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Particle swarm optimization (PSO) has been proven to show good performance for solving various optimization problems. However, it tends to suffer from premature stagnation and loses exploration ability in the later evolution period when solving complex problems. This paper presents a sequential hybrid particle swarm optimization and gravitational search algorithm with dependent random coefficients called HPSO-GSA, which first incorporates the gravitational search algorithm (GSA) with the PSO by means of a sequential operating mode and then adopts three learning strategies in the hybridization process to overcome the aforementioned problem. Specifically, the particles in the HPSO-GSA enter into the PSO stage and update their velocities by adopting the dependent random coefficients strategy to enhance the exploration ability. Then, the GSA is incorporated into the PSO by using fixed iteration interval cycle or adaptive evolution stagnation cycle strategies when the swarm drops into local optimum and fails to improve their fitness. To evaluate the effectiveness and feasibility of the proposed HPSO-GSA, the simulations were conducted on benchmark test functions. The results reveal that the HPSO-GSA exhibits superior performance in terms of accuracy, reliability, and efficiency compared to PSO, GSA, and other recently developed hybrid variants.
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Popov, Pavel P., Athanasios Sideris, and William A. Sirignano. "Stochastic modelling of transverse wave instability in a liquid-propellant rocket engine." Journal of Fluid Mechanics 745 (March 17, 2014): 62–91. http://dx.doi.org/10.1017/jfm.2014.96.
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AbstractThe combustion stability of a liquid-propellant rocket engine experiencing a random, finite perturbation from steady-state conditions is examined. The probability is estimated for a nonlinear resonant limit-cycle oscillation to be triggered by a random disturbance. Transverse pressure waves are considered by using a previously published two-dimensional nonlinear pressure wave equation coupled with Euler equations governing the velocity components. The cylindrical combustion chamber is a complex system containing multiple co-axial methane–oxygen injectors; each co-axial jet is analysed for mixing and burning on its own local grid scheme, with the energy release rate coupled to the wave oscillation on the more global grid. Two types of stochastic forcing for the random disturbance are explored: a travelling Gaussian pressure pulse and an oscillating pressure dipole source. The random variables describing the pulse are magnitude, location, duration and orientation of the disturbances. The polynomial chaos expansion (PCE) method is used to determine the long-time behaviour and infer the asymptote of the solution to the governing partial differential equations. Depending on the random disturbance, the asymptote could be the steady-state solution or a limit-cycle oscillation, e.g. a first tangential travelling wave mode. The asymptotic outcome is cast as a stochastic variable which is determined as a function of input random variables. The accuracy of the PCE application is compared with a Monte Carlo calculation and is shown to be significantly less costly for similar accuracy.
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Hoffmann, Ralf, Bernhard Hirt, Viviane Bechtold, Peter Beard, and Kenneth Raj. "Different Modes of Human Papillomavirus DNA Replication during Maintenance." Journal of Virology 80, no. 9 (May 1, 2006): 4431–39. http://dx.doi.org/10.1128/jvi.80.9.4431-4439.2006.
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ABSTRACT Human papillomavirus (HPV) begins its life cycle by infecting the basal cells of the epithelium. Within these proliferating cells, the viral genomes are replicated, maintained, and passed on to the daughter cells. Using HPV episome-containing cell lines that were derived from naturally infected cervical tissues, we investigated the mode by which the viral DNAs replicate in these cells. We observed that, whereas HPV16 DNA replicated in an ordered once-per-S-phase manner in W12 cells, HPV31 DNA replicated via a random-choice mechanism in CIN612 cells. However, when HPV16 and HPV31 DNAs were separately introduced into an alternate keratinocyte cell line NIKS, they both replicated randomly. This indicates that HPV DNA is inherently capable of replicating by either random-choice or once-per-S-phase mechanisms and that the mode of HPV DNA replication is dependent on the cells that harbor the viral episome. High expression of the viral replication protein E1 in W12 cells converted HPV16 DNA replication to random-choice replication and, as such, it appears that the mode of HPV DNA replication in proliferating cells is dependent on the presence or the increased level of this protein in the host cell. The implications of these observations on maintenance, latency, and persistence are discussed.
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Nurgaliyev, M. K., A. K. Saymbetov, B. N. Zholamanov, A. Т. Yeralkhanova, and G. B. Zhuman. "PREDICTING THE LIFETIME OF LORA BASED WIRELESS SENSOR NETWORKS USING A PROBABILISTIC MODEL OF MARKOV CHAINS." PHYSICO-MATHEMATICAL SERIES 2, no. 336 (April 15, 2021): 157–64. http://dx.doi.org/10.32014/2021.2518-1726.36.
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Real-time monitoring systems and sensors are not complete without wireless data transmission modules. Improving energy efficiency requires examining various system parameters that affect the power consumption of transmitting and receiving devices. The most important parameter of any autonomous wireless network is its uptime. In this work, we used LoRa wireless modules on the SX1278 chip manufactured by Semtech to determine their power consumption in various operating modes. The obtained data were used to build a consumption model of the device when connected to a receiver. Three operating modes are considered: transmit mode, receive mode and sleep mode. In an ideal communication channel, all transmitted data reaches the receiver with 100% probability. In a real situation, data reaches the receiver with a certain probability, depending on the communication channel, transmission power, distance to the addressee, and network parameters. In this work, the occurrence of an error is random. In this case, the occurrence of an error during reception entails a lack of confirmation of receipt or a request for re-sending data. Sending data again increases the power consumption of the device and, consequently, decreases the operating time of the wireless device. This paper shows the dependences of the operating time on various initial monitored parameters of the device, such as: confirmation timeout, packet length, time of one transmission cycle and the maximum number of retransmissions in one cycle. The developed model for predicting the consumption of the device can be used in the design of autonomous wireless sensor monitoring networks.
Dissertations / Theses on the topic "Random mode Cycle"
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Міхненко, Ярослав Олександрович. "Модифікований метод передачі даних в мережі Інтернету Речей." Master's thesis, КПІ ім. Ігоря Сікорського, 2021. https://ela.kpi.ua/handle/123456789/42139.
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Робота містить 70 сторінок, 15 рисунків, та 10 таблиць. Було використано 35 джерел.
Мета роботи: підвищити енергоефективність сенсорної мережі IoT за рахунок модифікації методу передачі інформації, що дозволить збільшити час роботи вузлів збору та передачі інформації сенсорної мережі IoT.
Проведено детальний аналіз проблем Інтернету речей, особливу увагу було звернено на питання модернізації архітектури мережі задля підвищення енергоефективності та збільшення терміну служби мережі. Детально розібрано метод випадкового циклу Sleep/Wake. Поставлено та виконано завдання модифікації архітектури бездротової сенсорної мережі Інтернету речей. Запропоновано координований метод циклу Sleep/Wake для передачі пакетів інформації в межах сенсорної мережі Інтернету речей. Після проведення оцінки нового методу та його імітаційного моделювання, було зроблено висновок, що такий модифікований метод може бути корисним для впровадження, оскільки:
1. Життєвий цикл мережі за допомогою запропонованого координованого методу обчислення робочого циклу та визначення черг збільшився від 3,8% до 11,25%.
2. Збільшився термін служби сенсорної мережі в порівнянні з асинхронним циклом черг в сенсорних мережах Інтернету речей від 8,4% до 14,8%.The thesis contains 70 pages, 15 figures, and 10 tables. 35 sources have been used. The purpose of the work is to increase the energy efficiency of the IoT sensor network by modifying the method of information transmission, which will increase the operating time of the nodes of collection and transmission of information of the IoT sensor network. The detailed analysis of the problems of the Internet of Things has been made. Special attention has been paid to modernizing the architecture of the network for improving its energy efficiency and extending its lifetime. The method of random Sleep/Wake cycle has been analyzed in detail. The task to modify the architecture of the wireless sensorу network of the Internet of Things has been fulfilled. The co-ordinated Sleep/Wake cycle method is proposed for transmitting information packets within the sensory network of the Internet of Things. After evaluating the new method and its simulation model, it was concluded that this modified method might be useful for implementation, since: 1. The life cycle of the network with the proposed coordinated method for calculating the duty cycle and queue determination increased from 3.8% to 11.25%. 2. The lifetime of the sensory network increased from 8.4% to 14.8%, compared to the asynchronous cycle of queues in the sensory networks of the Internet of Things.
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Sun, Wangru. "Modèle de forêts enracinées sur des cycles et modèle de perles via les dimères." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS007/document.
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Le modèle de dimères, également connu sous le nom de modèle de couplage parfait, est un modèle probabiliste introduit à l'origine dans la mécanique statistique. Une configuration de dimères d'un graphe est un sous-ensemble des arêtes tel que chaque sommet est incident à exactement une arête. Un poids est attribué à chaque arête et la probabilité d'une configuration est proportionnelle au produit des poids des arêtes présentes. Dans cette thèse, nous étudions principalement deux modèles qui sont liés au modèle de dimères, et plus particulièrement leur comportements limites. Le premier est le modèle des forêts couvrantes enracinées sur des cycles (CRSF) sur le tore, qui sont en bijection avec les configurations de dimères via la bijection de Temperley. Dans la limite quand la taille du tore tend vers l'infini, la mesure sur les CRSF converge vers une mesure de Gibbs ergodique sur le plan tout entier. Nous étudions la connectivité de l'objet limite, prouvons qu'elle est déterminée par le changement de hauteur moyen de la mesure de Gibbs ergodique et donnons un diagramme de phase. Le second est le modèle de perles, un processus ponctuel sur $\mathbb{Z}\times\mathbb{R}$ qui peut être considéré comme une limite à l'échelle du modèle de dimères sur un réseau hexagonal. Nous formulons et prouvons un principe variationnel similaire à celui du modèle dimère \cite{CKP01}, qui indique qu'à la limite de l'échelle, la fonction de hauteur normalisée d'une configuration de perles converge en probabilité vers une surface $h_0$ qui maximise une certaine fonctionnelle qui s'appelle "entropie". Nous prouvons également que la forme limite $h_0$ est une limite de l'échelle des formes limites de modèles de dimères. Il existe une correspondance entre configurations de perles et (skew) tableaux de Young standard, qui préserve la mesure uniforme sur les deux ensembles. Le principe variationnel du modèle de perles implique une forme limite d'un tableau de Young standard aléatoire. Ce résultat généralise celui de \cite{PR}. Nous dérivons également l'existence d'une courbe arctique d'un processus ponctuel discret qui encode les tableaux standard, defini dans \cite{Rom}The dimer model, also known as the perfect matching model, is a probabilistic model originally introduced in statistical mechanics. A dimer configuration of a graph is a subset of the edges such that every vertex is incident to exactly one edge of the subset. A weight is assigned to every edge, and the probability of a configuration is proportional to the product of the weights of the edges present. In this thesis we mainly study two related models and in particular their limiting behavior. The first one is the model of cycle-rooted-spanning-forests (CRSF) on tori, which is in bijection with toroidal dimer configurations via Temperley's bijection. This gives rise to a measure on CRSF. In the limit that the size of torus tends to infinity, the CRSF measure tends to an ergodic Gibbs measure on the whole plane. We study the connectivity property of the limiting object, prove that it is determined by the average height change of the limiting ergodic Gibbs measure and give a phase diagram. The second one is the bead model, a random point field on $\mathbb{Z}\times\mathbb{R}$ which can be viewed as a scaling limit of dimer model on a hexagon lattice. We formulate and prove a variational principle similar to that of the dimer model \cite{CKP01}, which states that in the scaling limit, the normalized height function of a uniformly chosen random bead configuration lies in an arbitrarily small neighborhood of a surface $h_0$ that maximizes some functional which we call as entropy. We also prove that the limit shape $h_0$ is a scaling limit of the limit shapes of a properly chosen sequence of dimer models. There is a map form bead configurations to standard tableaux of a (skew) Young diagram, and the map is measure preserving if both sides take uniform measures. The variational principle of the bead model yields the existence of the limit shape of a random standard Young tableau, which generalizes the result of \cite{PR}. We derive also the existence of an arctic curve of a discrete point process that encodes the standard tableaux, raised in \cite{Rom}
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KC, Rabi. "Study of Some Biologically Relevant Dynamical System Models: (In)stability Regions of Cyclic Solutions in Cell Cycle Population Structure Model Under Negative Feedback and Random Connectivities in Multitype Neuronal Network Models." Ohio University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou16049254273607.
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Sun, Yu-Ting, and 孫毓廷. "Deteriating Inventory Model considering a Random Product Life Cycle and Warranty Policy." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/91104280587780249898.
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碩士中原大學
工業工程研究所
94
In recent years, the problem of deteriorating inventory has received considerable attention. And exponential distribution is usually used to represent the distribution of deterioration. Due to the shortened product life cycle and the diversified product demand, new product development is vital to sustain customer demand and competitiveness. However, there are few current researches which take EPQ models incorporating a random product life cycle and the time-value of money into consideration. Moreover, it is necessary to consider rework and defective item as well as warranty policy which is a mechanism to compensate failures during the warranty period. The purpose of this study is to develop a deteriorating EPQ model with a random product life cycle, free-repair warranty policy and it also considers the time-value of money effect or inflation. The product life cycle is considered to be exponentially distributed. The research developed an integrated model to minimize the present worth total cost. The Golden Section Search, a kind of One-Dimensional Search approach and a computer code are used to derive the optimal policies. Numerical examples including sensitivity analysis are presented to validate the results of the models.
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Chang, Wei-Che, and 張維哲. "An inventory model with a random product life cycle and taking account of time-value of money." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/yfk398.
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碩士中原大學
工業工程研究所
93
For decades, the Economic Production Quantity (EPQ) model and its variations have received much attention from researchers. However, EPQ models incorporating a random product life cycle and the time-value of money have not been researched much. The main purpose of this paper is to develop an EPQ model with a random product life cycle, and considers the time-value of money effect and inflation. We consider the normal distribution as a product life cycle besides the exponential distribution. Furthermore, we also consider deteriorating item inventory and time varying unit production cost. Golden Section Search, a kind of One-Dimensional Search approach, is used to solve the optimal solution of the inventory model. A sensitivity analysis has been conducted to show how certain parameters affect the enterprise’s performance.
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Ραπτόπουλος, Χριστόφορος. "Σχεδιασμός και ανάλυση αλγορίθμων για τυχαία εξελικτικά δίκτυα." Thesis, 2008. http://nemertes.lis.upatras.gr/jspui/handle/10889/2107.
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Έστω $V$ ένα σύνολο $n$ κορυφών και έστω ${\cal M}$ ένα πεπερασμένα αριθμήσιμο σύνολο $m$ ετικετών. Ένα γράφημα ετικετών προκύπτει αν αντιστοιχήσουμε σε κάθε κορυφή $v \in V$ ένα υποσύνολο $S_v$ του ${\cal M}$ και στη συνέχεια ενώσουμε όποιες κορυφές έχουν κοινά στοιχεία στα αντίστοιχα σύνολα ετικετών τους. Η παρούσα διδακτορική διατριβή ασχολείται με την εξέταση συνδυαστικών ιδιοτήτων και το σχεδιασμό και ανάλυση αλγορίθμων που σχετίζονται με δυο μοντέλα τυχαίων γραφημάτων που προκύπτουν από την επιλογή των συνόλων $S_v$ με βάση συγκεκριμένες κατανομές. Το πρώτο από αυτά τα μοντέλα ονομάζεται \emph{Μοντέλο Τυχαίων Γραφηματων Τομής Ετικετών} ${\cal G}_{n, m, p}$ (\textlatin{random intersection graphs model}) και κάθε σύνολο ετικετών $S_v$ διαμορφώνεται επιλέγοντας ανεξάρτητα κάθε ετικέτα με πιθανότητα $p$. Το δεύτερο μοντέλο ονομάζεται \emph{Ομοιόμορφο Μοντέλο Τυχαίων Γραφηματων Τομής Ετικετών} ${\cal G}_{n, m, \lambda}$ (\textlatin{uniform random intersection graphs model})
και κάθε σύνολο ετικετών $S_v$ επιλέγεται (ανεξάρτητα για κάθε κορυφή) ισοπίθανα ανάμεσα σε όλα τα υποσύνολα του ${\cal M}$ μεγέθους $\lambda$.
Τα μοντέλα αυτά μπορούν να χρησιμοποιηθούν για να μοντελοποιήσουν καταστάσεις που αφορούν θέματα ασφάλειας σε δίκτυα αισθητήρων, αλλά και για την αναπαράσταση των συγκρούσεων (\textlatin{conflicts}) που δημιουργούνται σε περιπτώσεις διαμοιρασμού πόρων. Ακόμα, μπορούν να χρησιμοποιηθούν για τη μοντελοποίηση κοινωνικών γραφημάτων (\textlatin{social graphs}) στα οποία δυο οντότητες συνδέονται όταν έχουν κάποιο κοινό χαρακτηριστικό.
Στο Μοντέλο Τυχαίων Γραφηματων Τομής Ετικετών ${\cal G}_{n, m, p}$ μελετάμε καταρχήν το πρόβλημα της ύπαρξης κύκλων \textlatin{Hamilton}. Συγκεκριμένα, αποδεικνύουμε ένα άνω φράγμα για την πιθανότητα επιλογής ετικετών $p$ έτσι ώστε κάθε στιγμιότυπο του ${\cal G}_{n, m, p}$ να περιέχει ένα κύκλο \textlatin{Hamilton} με πιθανότητα που τείνει στο 1 καθώς το $n$ τείνει στο άπειρο. Ακόμα, αναλύουμε δυο πιθανοτικούς αλγορίθμους που, για ορισμένες τιμές των παραμέτρων $m, p$ του μοντέλου, καταφέρνουν να κατασκευάσουν ένα κύκλο \textlatin{Hamilton} με πιθανότητα που τείνει στο 1, δηλαδή σχεδόν πάντα. Επίσης, δείχνουμε ότι σχεδόν κάθε στιγμιότυπο του ${\cal G}_{n, m, p}$ έχει καλή επεκτασιμότητα (\textlatin{expansion}), ακόμα και για $p$ πολύ κοντά στο κατώφλι συνεκτικότητας του μοντέλου. Στη συνέχεια, δίνουμε βέλτιστα άνω φράγματα (που ισχύουν με πιθανότητα που τείνει στο 1 σε ένα ευρύ πεδίο τιμών των παραμέτρων του μοντέλου) για σημαντικές ποσότητες που αφορούν τυχαίους περιπάτους σ
ε στιγμιότυπα του ${\cal G}_{n, m, p}$ όπως ο χρόνος μίξης (\textlatin{mixing time}) και ο χρόνος κάλυψης (\textlatin{cover time}). Στο Ομοιόμορφο Μοντέλο Τυχαίων Γραφηματων Τομής Ετικετών ${\cal G}_{n, m, \lambda}$ μελετάμε την ύπαρξη κύκλων \textlatin{Hamilton} σε ένα ορισμένο πεδίο τιμών των παραμέτρων $m, \lambda$ του μοντέλου. Τέλος, υπολογίζουμε με τη βοήθεια της Πιθανοτικής Μεθόδου το κατώφλι ύπαρξης ανεξάρτητων συνόλων κορυφών.Let $V$ be a set of $i$ vertices and let ${\cal M}$ be a finite set of $m$ labels. An intersection graph is then constructed by assigning to each vertex $v \in V$ a subset $S_v$ of ${\cal M}$ and then connecting every pair of vertices that have common labels in their corresponding label sets. This thesis concerns the study of combinatorial properties, as well as the design and analysis of algorithms on two kinds of random intersection graphs models that arise from different choices of the distribution that we use to construct the sets $S_v$. In the first of these models, called \emph{Random Intersection Graphs Model} ${\cal G}_{n, m, p}$, each set of labels $S_v$ is constructed by choosing independently each label with probability $p$. In the second model, called \emph{Uniform Random Intersection Graphs Model} ${\cal G}_{n, m, \lambda}$, each label set $S_v$ is selected equiprobably (and independently for each vertex $v$) among all subsets of ${\cal M}$ of size $\lambda$. These models can be used to abstract situations that concern the efficient and secure communication in sensor networks, but can also be used to model the conflicts that occur in oblivious resource sharing in distributed settings. Moreover, random intersection graph models can be used to model social graphs, in which two entities are connected when they have a common feature. In the Random Intersection Graphs Model ${\cal G}_{n, m, p}$, we first study the existence and efficient construction of Hamilton cycles. More specifically, we give an upper bound for the probability $p$ that is needed for almost every random instance $G_{n, m, p}$ of the model to have a Hamilton cycle. We also present two polynomial time, randomized algorithms for constructing Hamilton cycles in a wide range of the parameters $m, p$. Moreover, we show that almost every random instance of the ${\cal G}_{n, m, p}$ model is an expander, even for $p$ very close to the connectivity threshold. Finally, we give close to optimal bounds (that hold with probability that goes to 1 for a wide range of the parameters of the model) for important quantities (like the mixing time and the cover time) concerning random walks on random instances of ${\cal G}_{n, m, p}$. In the Uniform Random Intersection Graphs Model ${\cal G}_{n, m, \lambda}$ we study the existence of Hamilton cycles for a ce rtain range of the parameters $m, \lambda$. Finally, by using the probabilistic method we compute the independence number of ${\cal G}_{n, m, \lambda}$.
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Асламов, Г. С., and G. S. Aslamov. "Исследование стохастической модели нейронной динамики : магистерская диссертация." Master's thesis, 2015. http://hdl.handle.net/10995/36215.
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В работе рассматривается дискретная нейронная модель, введенная впервые Рульковым Н.Ф., которая хорошо отражает быстро-медленную динамику нейрона. В работе проводится исследование устойчивости точек покоя и предельных циклов модели Рулькова к случайным возмущениям. В первой части изучаются точки покоя и циклы детерминированной одномерной модели, исследуется их устойчивость и проведен бифуркационный анализ. Во второй части анализируется поведение аттракторов этой модели под влиянием случайных возмущений. В третьей части проведен анализ расширенной двумерной модели, построены бифуркационные диаграммы и фазовые портреты, проведен анализ устойчивости.This paper considers a discrete neural model pioneered by Rulkov N.F. This model clearly reflects the fast-slow dynamics of the neuron. In this paper, we study the stability of equilibrium points and limit cycles of Rulkov model to random perturbations. In the first part, we study equilibria and cycles of deterministic one-dimensional model, investigate stability and carry out the bifurcation analysis. In the second part, we analyze the behavior of the attractors under the influence of random perturbations. In the third part, the bifurcations and phase portraits of extended two-dimensional model are studied, and stability analysis is carried out.
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Екатеринчук, Е. Д., and E. D. Ekaterinchuk. "Анализ стохастических аттракторов модели Ферхюльста с запаздыванием : магистерская диссертация." Master's thesis, 2015. http://hdl.handle.net/10995/36212.
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We investigate attractors of the Verhulst model with delay under the influence of random perturbations.
In this work, we study dynamic regimes and bifurcations for the deterministic discrete model in zones of stable equilibria, closed invariant curves and discrete cycles. Here, a stability level of attractors is studied by Lyapunov exponents. Transformations of the closed invariant curve that appears as a result of Neimark-Sacker bifurcation, were analyzed via the rotation number and angular density.
A parametric analysis of stochastically forced regular attractors of this model is performed using the stochastic sensitivity functions technique. A spatial arrangement of random states in stochastic attractors is described by confidence domains. The phenomenon of noise-induced transitions in a zone of discrete cycles is discussed.Мы исследуем аттракторы модели Ферхюльста с запаздыванием под влиянием случайных возмущений. В работе мы изучаем динамические режимы и бифуркации для детерминированной дискретной модели в зонах устойчивых равновесий, замкнутых инвариантных кривых и дискретных циклов. Исследована устойчивость регулярных аттракторов. Замкнутая инвариантная кривая, которая появляется в результате бифуркации Неймарка–Сакера, анализируется с помощью числа вращения и секторной плотности. Параметрический анализ стохастически возмущенных регулярных аттракторов этой модели выполняется с помощью техники функции стохастической чувствительности. Пространственное распределение случайных состояний стохастических аттракторов описывается с помощью доверительных областей. Наблюдается явление индуцированных шумом переходов в зоне дискретных циклов.
Books on the topic "Random mode Cycle"
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M. C. M. de Gunst. A random model for plant cell population growth. [Amsterdam, the Netherlands]: Centrum voor Wiskunde en Informatica, 1989.
Find full textBook chapters on the topic "Random mode Cycle"
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Ferenc, Jaroslav, and Charisios D. Tsiairis. "Studying Mechanical Oscillations During Whole-Body Regeneration in Hydra." In Methods in Molecular Biology, 619–33. New York, NY: Springer US, 2022. http://dx.doi.org/10.1007/978-1-0716-2172-1_33.
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AbstractCells of the freshwater cnidarian Hydra possess an exceptional regeneration ability. In small groups of these cells, organizer centers emerge spontaneously and instruct the patterning of the surrounding population into a new animal. This property makes them an excellent model system to study the general rules of self-organization. A small tissue fragment or a clump of randomly aggregated cells can form a hollow spheroid that is able to establish a body axis de novo. Interestingly, mechanical oscillations (inflation/deflation cycles of the spheroid) driven by osmosis accompany the successful establishment of axial polarity. Here we describe different approaches for generating Hydra tissue spheroids, along with imaging and image analysis techniques to investigate their mechanical behavior.
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Hoyt, Douglas V., and Kenneth H. Shatten. "Cyclomania." In The Role of the Sun in Climate Change. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195094138.003.0013.
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In his 1874 book Contributions to Solar Physics, Sir Norman Lockyer writes the following: . . . Surely in meteorology, as in astronomy, the thing to hunt down is a cycle, and if that is not to be found in the temperate zone, then go to frigid zones, or the torrid zones and look for it, and if found, then above all things, and in whatever manner, lay hold of, study it, record it, and see what it means. If there is no cycle, then despair for a time if you will, but yet plant firmly your science on a physical basis, as Dr. Balfour Stewart long ago suggested, before, to the infinite detriment of English science, he left the Meteorological Observatory at Kew; and having got such a basis as this, wait for results. In the absence of these methods, statements of what is happening to a blackened bulb in vacuo, or its companion exposed to the sky, is, for research purposes, work of the tenth order of importance. . . . As Lockyer notes, looking for cycles is certainly an attractive prospect. If found, a cycle will help with predictions, and successful predictions are a central goal of scientific studies. Cycle hunting is also a relatively straightforward procedure, with several well-developed techniques. Cycle hunting has become even easier with the advent of computers. By feeding a stream of data into an algorithm to detect cycles, one is likely to find cycles even in a series of random numbers. Hence the danger that a cycle, if detected, may prove to be only a random fluctuation. Will the cycle persist with more data, or will it simply disappear? For ardent cycle hunters, and the sun/climate field has attracted its fair share, these questions are hardly a deterrent. The lure seems to be finding something of seeming importance with minimal effort. From a practical point of view, a cycle may be considered important only if it can be plotted. If sophisticated analyses are required to detect the cycle, the cycle probably has only secondary importance. While these criteria are not the usual mathematical criteria for significance, they are a practical, down-to-earth guide to what is important.
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"Shocks vs. Impulse-Propagation Model of Economic Dynamics." In Theory of Shocks, COVID-19, and Normative Fundamentals for Policy Responses, 1–28. IGI Global, 2021. http://dx.doi.org/10.4018/978-1-7998-4309-2.ch001.
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Ragnar Frisch, the Nobel prizer in economics, drew attention to two phenomena: propagation problems and impulse problems in dynamic economics. His deep scientific contribution relates to the interpretation of business cycle transformed under the influence of impulses (shocks). But some terminological misunderstandings arose. One of them forced the authors to focus on the phenomenon of systems' self-movement: their self-organization in statics and their self-development in dynamics. Another one relates to exogenous nature of impulses (shocks) that forced the authors to prove the endogenous embeddedness of shocks into the mechanisms of dialectical laws implementation. Eugen Slutsky demonstrated the stochastic approach as to random fluctuations as a source of cyclical processes in the economy. The confusion in the concepts of cycles and waves predetermines the need to create a wave theory of systemic self-organization (Chapter 2). Modern shocks theory develops a new approach which makes it possible to eliminate misconceptions of past theories.
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Zalasiewicz, Jan. "5. Earth surface geology." In Geology: A Very Short Introduction, 55–73. Oxford University Press, 2018. http://dx.doi.org/10.1093/actrade/9780198804451.003.0005.
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‘Earth surface geology’ considers the particular conditions created by the water cycle governing the distinctive surface geology of Earth. It looks at the efficiency of the rock cycle: the breakdown of ‘primary’ igneous rocks into sediments, which are buried and lithified to produce sedimentary rock, which in turn becomes metamorphosed as heat and pressure increase, finally ending in melting and magma production. It also looks at the ways that geological time has been subdivided using biostratigraphy (the tracking of species’ evolution through fossils) and tracing chemical changes in the rocks. Earth’s evolution has included regular and gradual influences, with episodes of sudden massive change from more or less random events.
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Lambin, Xavier, and Charles J. Krebs. "Population Cycles Inferences from Experimental, Modeling, and Time Series Approaches." In Population Cycles. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780195140989.003.0013.
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Some of the most interesting debates in population ecology have taken place within the context of population cycles. Their study has been a fertile ground for the development of ideas on how population models should be formulated and confronted with data. It is the setting in which the use of field experiments became established in ecology (e.g., Krebs and DeLong 1965), and also the context of many methodological and conceptual developments in the fields of population demography (Leslie and Ranson 1940), pest management (Berryman 1982), and community dynamics (Sinclair et al. 2000). Yet, as with many other issues in population dynamics, identifying without ambiguity the causes of population cycles in general, and for any organism in particular, continues to prove an extraordinarily difficult task. The major purpose of this book is to review recent research developments on the role of food web architecture, and more specifically on the effects of food, predators, and pathogens in population cycles. Its stated aim is to present evidence that population cycles could be caused by food web architecture in some natural systems. Whereas in chapter 1 Alan Berryman promotes a research program centered on the analysis of time series data for formulating, selecting, and even testing hypotheses on population cycles, the case studies encompass a much broader diversity of research approaches. The authors and coworkers of the seven case studies have combined time series analysis, model building, natural history observation, and experiments in different proportions to reach the conclusion that trophic interactions play an important role in generating cyclic dynamics. This diversity of approaches reflects, in part, a taxonomic divide between vertebrates and invertebrates, experiments being more common with the former, but also profound differences in research traditions. Indeed, the investment required to estimate population size and quantify the causes of mortality of moths and beetles is substantially less than that required for estimating the abundance of voles, hares, and grouse and their predators. From these practical constraints, divergent research traditions have evolved.
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Lechuga, Gilberto Pérez, Francisco Venegas Martínez, and Elvia Pérez Ramírez. "Stochastic Optimization of Manufacture Systems by Using Markov Decision Processes." In Handbook of Research on Modern Optimization Algorithms and Applications in Engineering and Economics, 185–208. IGI Global, 2016. http://dx.doi.org/10.4018/978-1-4666-9644-0.ch007.
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In real-world most of manufacturing systems are large, complex, and subject to uncertainty. This is mainly due to events as random demands, breakdowns, repairs of production machines, setup and cycle times, inventory fluctuations and more. If items move too quickly, workers may work too hard. If items move too slowly, workers may have great leisure times. However, must make decisions here and now regarding the operation of the system optimally and quickly. In practice, these decisions are based on recent statistics of the system behavior, in the experience of the analyst and the urgency of the solution. In this chapter, we present a real problem associated with the production of individual parts in metalworking industry for the refrigerators production. We develop a model based on the Markov Decision Process to study the dynamics of the trajectory of end products in a manufacturing line that works by process. Then, we propose a measure of the average production rate of the line by using the Monte Carlo method. We illustrate our proposal using a numerical example with real data obtained in situ.
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Previtali, Pietro. "Evolutional Patterns of Intranet Applications." In Measuring Organizational Information Systems Success, 367–84. IGI Global, 2012. http://dx.doi.org/10.4018/978-1-4666-0170-3.ch018.
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The objective of this chapter is to propose a theoretical examination, strengthened by an empiric survey of intranet evolutional patterns and the neologism that designates a communication system, for access to and searching of business information based on Internet technologies. This chapter analyses intranet applications and functionalities in order to classify them according to a taxonomy that allows us to distinguish between an institutional intranet, a knowledge management intranet, and an operating intranet. The main research hypothesis is the existence of an intranet life cycle, as an evolutional model starting from an institutional intranet that moves to a knowledge management intranet and then to an operating one. This last one is considered as a proxy for successful IS implementation. To substantiate the above-mentioned hypothesis an empirical study was conducted among 110 large Italian corporations, with a response rate of 66% (73 corporations). The method used was a survey conducted during the months of March, April, and May 2010, applying a mix of random sampling (randomly selected interviewees from the directory) and “snowball” sampling (contacting interviewees through leads). The results show how, basically, companies approach intranet implementation processes in an incremental way, which begins with the integration of the basic functionalities as “communication channel,” “service platform,” or “document management.”
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Tsoukis, Christopher. "Sectoral Analyses." In Theory of Macroeconomic Policy, 605–86. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198825371.003.0011.
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This wide-ranging chapter reviews a number of models that underpin aggregate analyses (‘sectoral’ models). It begins with the profusion of work on consumption (Permanent Income Hypothesis, the Life-Cycle Model, and the modern analyses that sprang from the ‘random walk’ model). Saving, durable consumption, demographics, and behavioural elements are among the many topics reviewed. The chapter continues with investment, including issues such as: the accelerator, neoclassical model, user cost of capital, Tobin’s q, effects of financial imperfections, uncertainty, state-contingent (‘S-s’) models, vintages, technical progress, and inventories. Housing is reviewed next, another innovation of the book. Finally, the models of consumption are a stepping-stone towards the macroeconomics of finance. The topics reviewed here include the CCAPM and CAPM models, the equity premium puzzle, and the term structure of interest rates, as well as developments in stock markets and the growth of finance (‘financialization’).
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Ross, David. "Condensation Reactions Synthesize Random Polymers." In Assembling Life. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780190646387.003.0011.
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Over the past half century of serious research on the origin of life, several schools of thought have emerged that focus on “worlds” and what came first in the pathway to the origin of life. One example is the RNA World, a term coined by Walter Gilbert after the discovery of ribozymes. Other examples include the Iron-Sulfur World of Günther Wächtershäuser and the Lipid World proposed by Doron Lancet and coworkers. Then we have a competition between “metabolism first” and “replication first” schools. The worlds and schools have the positive effect of sharpening arguments and forcing us to think carefully, but they also can lock researchers into defending their individual approaches rather than looking for patterns in a larger perspective. One of the main themes of this book is the notion that the first living cells were systems of functional polymers working together within membranous compartments. Therefore, it is best not to think of “worlds” and “firsts” as fundamentals but instead as components evolving together toward the assembly of an encapsulated system of functional polymers. At first the polymers will be composed of random sequences of their monomers, and the compartments will contain random assortments of polymers. Here, we refer to these structures as protocells which are being produced in vast numbers as they form and decompose in continuous cycles driven by a variety of impinging, free-energy sources. This chapter describes how thermodynamic principles can be used to test the feasibility of a proposed mechanism by which random polymers can be synthesized. There is a current consensus that early life may have passed through a phase in which RNA served as a ribozyme catalyst, as a replicating system, and as a means for storing and expressing genetic information. For this reason, we will use RNA as a model polymer, but condensation reactions also produce peptide bonds and oligopeptides. At some point in the evolutionary steps leading to life, peptides and RNA formed complexes with novel functional properties beyond those of the individual molecular species.
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Stone, Reynold J. "Modelling the Frequency of Tropical Cyclones in the Lower Caribbean Region." In Advances in Environmental Engineering and Green Technologies, 341–49. IGI Global, 2017. http://dx.doi.org/10.4018/978-1-5225-1607-1.ch013.
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Modelling the frequency of occurrence of tropical cyclones is an important step in assessing risk with a view toward mitigating their adverse impacts The Poisson model was evaluated for modelling the frequency of tropical cyclones over and around Trinidad and Tobago's area of influence by statistically analysing a data series extracted from the Atlantic HURDAT2 count time series data for the period 1851 to 2014. This was tested for serial correlation and the residuals of a Poisson regression analysis. Both tests failed to detect the presence of trends or cycles thereby indicating that the data series is random. The Poisson model was subsequently fitted to the data. It was concluded that there has been no increasing trend in the frequency of tropical cyclones. Therefore, widespread claims of an increasing trend in the frequency of tropical cyclones in Trinidad and Tobago's area of influence have no valid empirical basis. The Poisson model is recommended for estimating the probabilities of occurrence of tropical cyclones.
Conference papers on the topic "Random mode Cycle"
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Jiang, Dongqi, Shanquan Liu, Tao Chen, and Gang Bi. "Machine learning-based failure mode identification of RCSPSW." In IABSE Congress, Christchurch 2021: Resilient technologies for sustainable infrastructure. Zurich, Switzerland: International Association for Bridge and Structural Engineering (IABSE), 2021. http://dx.doi.org/10.2749/christchurch.2021.1150.
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<p>Reinforced concrete – steel plate composite shear walls (RCSPSW) have attracted great interests in the construction of tall buildings. From the perspective of life-cycle maintenance, the failure mode recognition is critical in determining the post-earthquake recovery strategies. This paper presents a comprehensive study on a wide range of existing experimental tests and develops a unique library of 17 parameters that affects RCSPSW’s failure modes. A total of 127 specimens are compiled and three types of failure modes are considered: flexure, shear and flexure-shear failure modes. Various machine learning (ML) techniques such as decision trees, random forests (RF), <i>K</i>-nearest neighbours and artificial neural network (ANN) are adopted to identify the failure mode of RCSPSW. RF and ANN algorithm show superior performance as compared to other ML approaches. In Particular, ANN model with one hidden layer and 10 neurons is sufficient for failure mode recognition of RCSPSW.</p>
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Hanschke, Benjamin, Thomas Klauke, and Arnold Kühhorn. "The Effect of Foreign Object Damage on Compressor Blade High Cycle Fatigue Strength." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-63599.
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For a considerable amount of time blade integrated disks (blisks) are established as a standard component of high pressure compressors (HPCs) in aero engines. Due to the steady requirement to increase the efficiency of modern HPCs, blade profiles get thinned out and aerodynamic stage loading increases. Ever since, aerofoil design has to balance structural and aerodynamic requirements. One particularity of aero engines is the possibility to ingest different kinds of debris during operation and some of those particles are hard enough to seriously damage the aerofoil. Lately, a growing number of blisk-equipped aero engines entered service and the question of foreign object damage (FOD) sensitivity relating to compressor blade high cycle fatigue (HCF) has emerged. Correct prediction of fatigue strength drop due to a FOD provides a huge chance for cost cutting in the service sector as on-wing repairs (e.g. borescope blending) are much more convenient than the replacement of whole blisks and corresponding engine strips. The aim of this paper is to identify critical FOD-areas of a modern HPC stage and to analyze the effects of stress concentrations — caused by FOD — on the fatigue strength. A process chain has been developed, that automatically creates damaged geometries, meshes the parts and analyses the fatigue strength. Amplitude frequency strength (af-strength) has been chosen as fatigue strength indicator owing to the fact, that amplitudes and frequencies of blade vibrations are commonly measured either by blade tip timing or strain gauges. Furthermore, static and dynamic stress concentrations in damaged geometries compared to the reference design were computed. A random variation of input parameters was performed, such as the radial damage position at blade leading edge and damage diameter. Based on results of the different samples, correlations of input parameters and the fatigue strength drop have been investigated. Evaluation shows a significant mode dependence of critical blade areas with a large scatter between drops in fatigue strength visible for mode to mode comparison. Keeping in mind the necessity of fast response times in the in-service sector, FOD sensitivity computations could be performed for all blade rows of the HPC — including the analysis of possible borescope blending geometries — in the design stage. Finally, the actual amplitude frequency levels (af-levels) of the modes excited during operation have to be appropriately taken into consideration. For example, a pronounced af-strength drop due to a FOD may not be critical for safe engine operations because the observed mode is excited by small af-levels during operation. Hence, the endurance ratio — a quotient of af-level and af-strength — is used as assessment criterion.
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Prakash, Niket, Jason B. Martz, and Anna G. Stefanopoulou. "A Phenomenological Model for Predicting the Combustion Phasing and Variability of Spark Assisted Compression Ignition (SACI) Engines." In ASME 2015 Dynamic Systems and Control Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/dscc2015-9883.
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An advanced combustion mode, Spark Assisted Compression Ignition (SACI) has shown the ability to extend loads relative to Homogenous Charge Compression Ignition (HCCI) combustion but at reduced fuel conversion efficiency. SACI combustion is initiated by a spark, with flame propagation followed by a rapid autoignition of the remaining end-gas fuel fraction. Extending upon previous work [1,2], the Wiebe function coefficients used to fit the two combustion phases are regressed here as functions of the air path variables and actuator settings. The parameterized regression model enables mean-value modeling and model-based combustion phasing control. SACI combustion however, exhibits high cyclic variability with random characteristics. Thus, combustion phasing feedback control needs to account for the cyclic variability to correctly filter the phasing data. This paper documents the success in regressing the cyclic variability (defined as the standard deviation in combustion phasing) at various operating conditions, again as a function of air path variables and actuator settings. The combination of the regressed mean and standard deviation models is a breakthrough in predicting the mean-value engine behavior and the random statistics of the cycle-to-cycle variability.
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Hu, Dianyin, Ying Shi, Xi Liu, and Rongqiao Wang. "Reliability Analysis on a Turbine Disk Considering the Coupling of Multiple Failure Modes." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-76477.
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Current probabilistic design methods mainly focus on single mode of failure, under the consideration on random variables including geometry, loading, and material properties. However, due to the complex structural characters and unevenly distributed temperature, turbine disks are always undergoing multiple potential failure modes, which should be effectively evaluated under a coupling scheme in reliability analysis. To this end, a collaborative response surface method involving multiple potential modes was established, aligning individual failure modes that were precisely evaluated via linear heteroscedastic regression analysis. To validate our model, reliability assessment was conducted on a turbine disk in turbo-shaft engine, where the coupling failure including low cycle fatigue and creep-fatigue was considered. This method can be an effective tool in the evaluation of reliability analysis involving multiple failure modes.
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Bifano, Michael F. P., Lyle Breaux, Anthony J. Feller, and Richard Brodzinski. "New Fatigue Screening Criteria for the Fitness-for-Service Assessment of In-Service Process Piping Vibrations." In ASME 2018 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/pvp2018-84847.
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Commonly used piping vibration screening limits are typically justified by experience and lack a well-documented technical basis. This paper presents technical background for future Level 1 Fitness-for-Service (FFS) vibration screening criteria. The criteria assess the risk of fatigue in process piping due to bending mode type vibrations. Finite element analysis (FEA) of 20,000 randomly generated candidate-piping models and high-cycle welded joint fatigue curves for both constant amplitude and variable amplitude loading form the stress limits and basis for the proposed criteria. Most importantly, the proposed criteria aligns with historically used allowable vibration limits rooted in substantial experience. The allowable stress basis implemented in this paper considers periodic and random vibrations making it applicable to situations of mechanically induced, two-phase flow induced, turbulent-induced vibration of single-phase process fluid, or wind-induced, which may be manifested as either periodic or random. To reduce conservatism, limits are set for butt-welded and non-butt welded mainline piping to prevent use of a single blanket limit that may lead to unnecessary piping support alterations/additions, or costly piping configuration changes and unit downtime. Furthermore, the proposed Level 1-type criteria are consistent with previously proposed FFS Level 2 and 3 piping vibration fatigue evaluations [1] intended for inclusion in the ASME FFS-1/API 579 (API 579) Fitness for Service Standard [2].
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Tang, Weihan, Seunghun Baek, and Bogdan I. Epureanu. "Reduced Order Models for Blisks With Small and Large Mistuning and Friction Dampers." In ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-57850.
Full textAbstract:
In operation, rotating bladed disks (blisks) are often subject to high levels of dynamic loading, resulting in large amplitudes of forced vibrations especially at resonance. Moreover, variations in structural properties of individual sectors, referred to as mistuning, can lead to strain energy localization and can amplify forced responses. To prevent damages caused by high cycle fatigue, various frictional damping sources are introduced to dissipate vibration energy. Due to the nonlinear behavior of frictional contacts, conventional methods to study the dynamics of the blisk-damper systems are based often on numerical time integration, which is time-consuming and can be computationally prohibitive due to the large sizes of commercial blisk models. Existing techniques for model reduction either rely heavily on cyclic symmetry of the blisk-damper system, or are based on component mode synthesis (CMS). However, in the presence of mistuning, cyclic symmetry no longer exists. Also, mistuning is random and best studied statistically. Repetitive CMS condensation for a large amount of random mistuning patterns can lead to a computationally formidable task. This paper presents a reduced-order modeling technique to efficiently capture the nonlinear dynamic responses of blisk-damper systems with both small perturbations in blade material properties (small mistuning), and significant changes in the blisk geometries (large mistuning). The reduced-order models (ROMs) are formed by projecting the blisk-damper systems onto a novel mode basis that mimics the contact behavior. This mode basis contains normal mode shapes of the mistuned blisk-damper systems with either sliding or sticking conditions enforced on the contact surfaces. These mode shapes are computed through the N-PRIME method, a technique recently developed by the authors to efficiently obtain mode shapes for blisks with simultaneous large and small mistuning. The resulting modal nonlinear equations of motion are solved by a hybrid frequency/time (HFT) domain method with continuation. In the HFT method, the contact status and friction forces are determined in the time domain by a quasi-two-dimensional contact model at each contact point, whereas the modal equations of motion are solved in the frequency domain according to a harmonic balance formulation. The forced responses computed by the proposed ROMs are validated for two systems with distinct mistuning patterns. A statistical analysis is performed to study the effectiveness of the frictional dampers under random mistuning patterns.
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Todd, Michael, William Gregory, Christopher Key, Michael Yeager, and Jordan Ye. "Composite Laminate Fatigue Damage Detection and Prognosis Using Embedded Fiber Bragg Gratings." In ASME 2018 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/smasis2018-8182.
Full textAbstract:
In many structural applications the use of composite material systems in both retrofit and new design modes has expanded greatly. The performance benefits from composites such as weight reduction with increased strength, corrosion resistance, and improved thermal and acoustic properties, are balanced by a host of failure modes whose genesis and progression are not yet well understood. As such, structural health monitoring (SHM) plays a key role for in-situ assessment for the purposes of performance/operations optimization, maintenance planning, and overall life cycle cost reduction. In this work, arrays of fiber Bragg grating optical strain sensors are attached to glass-epoxy solid laminate composite specimens that were subsequently subjected to specific levels of fully reversed cyclic loading. The fatigue loading was designed to impose strain levels in the panel that would induce damage to the laminate at varying numbers of cycles. The objectives of this test series were to assess the ability of the fiber Bragg grating sensors to detect fatigue damage (using previously developed SHM algorithms) and to establish a dataset for the development of a prognostic model to be applied to a random magnitude of fully reversed strain loading. The prognostic approach is rooted in the Failure Forecast Method, whereby the periodic feature rate-of-change was regressed against time to arrive at a failure estimate. An uncertainty model for the predictor was built so that a probability density function could be computed around the time-of-failure estimate, from which mean, median, and mode predictors were compared for robustness.
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Cheng, Hang Shawn, Jian Cao, and Hui-Ping Wang. "Experimental and Numerical Analysis of the Buckling and Post-Buckling Phenomenon in the Yoshida Test." In ASME 2006 International Manufacturing Science and Engineering Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/msec2006-21029.
Full textAbstract:
Simulation-based Design and Manufacturing has shown its great effectiveness in shortening the design cycle. The objective of this work was to further increase the robustness of numerical prediction in capturing subtle wrinkling in sheet metal forming process. A stress-based wrinkling predictor is further developed to predict the initiation and wave mode of potential wrinkling in forming of flat sheet. The predictor is linked to the LS-DYNA commercial FEM package. Stress prediction from LS-DYNA was compared to the implicit code ABAQUS and satisfactory results were obtained. Hence, stress, nodal coordinates and connectivity information of the LS-DYNA simulation are fed into the predictor via an automatic interface program. A set of Yoshida buckling tests was used as a verification tool for the wrinkling predictor. 0.78mm thick 180B steel and 1.012mm thick 6111-T4P aluminum are tested. Through the comparison of the experiments and simulations, it shows that the wrinkling predictor is able to predict the initiation point and wave mode for the wrinkling accurately. In addition, post-buckling behavior in numerical simulations was captured through including initial imperfections following the wrinkling mode predicted. It was found that such a method provides more reliable results in terms of the post-buckling behavior than random imperfection.
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Potluri, P., V. S. Thammandra, and R. B. Ramgulam. "Modelling Tow Compression in Textile Preforms During Composites Processing." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-61470.
Full textAbstract:
Fiber assemblies, in the form of woven, braided, nonwoven or knitted structures, are used as reinforcements in composites. These textile structures are subjected to in-plane membrane stresses such as tensile and shear, and out-of-plane stresses such as bending and transverse compression. Amongst various modes of deformation, transverse compaction behaviour is the least understood mode; however this mode is very important for composites processing using vacuum forming, resin transfer moulding, thermoforming and hot compaction methods. The present paper reports a computational approach to predicting the load-deformation behaviour of textile structures under compressive loading. During the compression of a random fiber assembly, fibers are subjected to kinematic displacements, bending and finally transverse compression of individual fibres. In the case of interlaced architectures, such as woven and braided structures, it is convenient to deal with deformations at meso-scale involving yarns or tows, and deal with inter-fiber friction and fibre compression at yarn/tow level. It can be seen from the load deformation graphs that the initial part is dominated by bending energy and the final part by compression energy. A combined yarn bending and compression model was in good agreement with the experimental curve during the entire load-deformation cycle. On the other hand, an elastica-based bending model predicts well during the initial part while tow compression model predicts well during the final part. Inter-fiber friction was initially ignored — this is being introduced in the refined model for both the dry and wet states.
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Zhai, Yaoguang, Ronnie Bladh, and Go¨ran Dyverfeldt. "Aeroelastic Stability Assessment of an Industrial Compressor Blade Including Mistuning Effects." In ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-45800.
Full textAbstract:
This paper presents a comprehensive investigation into the aeroelastic stability behavior of a transonic front blade in an industrial compressor when operating outside its normal range of service parameters. The evolution of the airfoil’s aeroelastic stability in the first flexural mode is studied as the front blade operation progresses towards choked flow conditions. First, linearized 3D flutter computations representing today’s industry standard are performed. The linearized calculations indicate a significant, shock-driven flutter risk at these off-design flow conditions. To further explore the aeroelastic behavior of the rotor and to find a viable solution toward flutter risk elimination, two parallel investigations are undertaken: (i) flow perturbation nonlinearity effects and potential presence of limit-cycle oscillation; and (ii) effects of blade mistuning and flutter mitigation potential of intentional mistuning, including its impact on forced response behavior. The nonlinear harmonic analyses show that the minimum aerodynamic damping increases rapidly and essentially linearly with blade oscillation amplitude beyond the linear regime. Thus, a state of safe limit-cycle oscillation is predicted for the fully tuned blade. Additionally, it is found that intentional, realizable blade frequency offsets in an alternating pattern efficiently stabilize the blade. Finally, it is verified that alternating mistuning has a beneficial effect versus the inevitable random mistuning also in the forced response.