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نتیجه جستجو - شبیه سازی عددی

تعداد مقالات یافته شده: 15
ردیف عنوان نوع
1 Response laws of rock electrical property and saturation evaluation method of tight sandstone
قوانین پاسخ به ویژگی الکتریکی سنگ و روش ارزیابی اشباع ماسه سنگ محکم-2020
To solve the problem that the law of rock electrical response under low and medium water saturation in tight sandstone reservoirs is not clear, an experimental method of high-speed centrifugal displacement rock electricity and nuclear magnetic resonance T2 spectrometry under different water saturation was proposed, which can drive the tight sandstone cores with the permeability less than 0.1×103 μm2, and provide a reliable experimental means for the study of tight sandstone electrical property. By carrying out supporting experiments such as high-resolution CT scan, MAPS and Qemscan, a multi-mineral component fine three-dimensional digital core based on multi-source information fusion was constructed. The finite element numerical simulation method was used to obtain the electrical response of tight sandstone core with low water saturation which cannot be obtained in laboratory conditions. By combining experiment and numerical simulation, the electrical response laws have been clear of tight sandstone with complex pore structure, and the saturation evaluation method of variable rock electrical parameters based on pore structure has been developed. The processing of logging data of multiple wells in tight sandstone reservoir of Chang 7 Member in the Ordos Basin shows that this method can obtain more accurate oil saturation, and provides a new idea and method for fine logging evaluation of tight sandstone reservoir.
Key words: tight sandstone | rock electrical response | nuclear magnetic resonance logging | saturation | petrophysics | numerical simulation
مقاله انگلیسی
2 Distribution laws of freeze-thaw cycles and unsaturated concrete experiments in cold-region tunnels
قوانین توزیع چرخه انجماد و ذوب و آزمایش های بتن اشباع نشده در تونل های منطقه سرد-2020
Studying tunnel temperature fields could prevent frost damage. However, few studies have revealed the distribution laws of freeze-thaw cycles in cold-region tunnels. In this study, the distribution laws of freeze-thaw cycles in a tunnel were carried out, and the concrete deterioration induced by freeze-thaw cycling was explored. First, in situ monitoring equipment was used to collect the temperature in the longitudinal direction of the tunnels. A one-dimensional heat transfer model was used to analyze the temperature distribution in the circumferential direction of the tunnels, where a function was proposed to describe both the annual and diurnal temperature fluctuations. After that, the distribution laws of freeze-thaw cycles inside a tunnel were investigated. Specifically, in the tunnel longitudinal direction, the number of freeze-thaw cycles decreased from the entrance to the middle and then increased while approaching the exit, thereby exhibiting a V-shaped distribution. In the circumferential direction, the intrados lining nearly always exhibited freeze-thaw cycles. The number of freeze-thaw cycles and the temperature amplitude decreased rapidly with increasing depth. Furthermore, a series of unsaturated concrete experiments were performed to explore the concrete deterioration under different numbers of freeze-thaw cycles. The results showed that after being subjected to 100 freeze-thaw cycles, the concrete specimens displayed visible damage, whereas the concrete compressive strength was not affected. These findings can enrich the research of freeze-thaw cycles for cold-region tunnels and are significant for guiding tunnel maintenance.
Keywords: Cold-region tunnels | Temperature field | Freeze-thaw cycles | Unsaturated concrete | Numerical simulation
مقاله انگلیسی
3 Emergence and interpretation of oscillatory behaviour similar to brain waves and rhythms
ظهور و تفسیر رفتار نوسانی شبیه به امواج مغزی و ریتم-2020
Electroencephalography (EEG) monitors —by either intrusive or noninvasive electrodes—time and frequency variations and spectral content of voltage fluctuations or waves, known as brain rhythms , which in some way uncover activity during both rest periods and specific events in which the subject is under stimulus. This is a useful tool to explore brain behav- ior, as it complements imaging techniques that have a poorer temporal resolution. We here approach the understanding of EEG data from first principles by numerical simulating and studying a networked model of excitatory and inhibitory neurons which generates a vari- ety of comparable waves. In fact, we thus numerically reproduce oscillatory behavior sim- ilar to α, β, γand other rhythms as observed by EEG recordings, and identify the details of the respectively involved complex phenomena, including a precise relationship between an input and the collective response to it. It ensues the potentiality of our model to better understand actual brain oscillatory activity in normal and pathological situations, and we also describe kind of stochastic resonance phenomena which could be useful to locate main qualitative changes of brain activity in (e.g.) humans.
Keywords: EEG numerical simulation | Brain phase transitions | Brain activity stochastic resonance
مقاله انگلیسی
4 High-performance fiber reinforced concrete as a repairing material to normal concrete structures: Experiments, numerical simulations and a machine learning-based prediction model
بتن مسلح با فیبر با کارایی بالا به عنوان یک ماده ترمیم کننده سازه های بتونی عادی: آزمایش ها ، شبیه سازی عددی و یک مدل پیش بینی مبتنی بر یادگیری ماشین-2019
High-performance fiber reinforced concrete (HPFRC) has been reported as a repairing material to normal concrete (NC) structures due to its predominant mechanical performance. Here, we investigate the debonding behavior between HPFRC and NC subjected to direct shear loading. HPFRC specimens are fabricated and experimentally calibrated to determine the compressive and bending (i.e., flexural) strengths. HPFRC-NC samples are fabricated using two bonding strategies, i.e., mechanical surface treatments with and without chemical agent. Direct shear loading is applied to test the HPFRC-NC debonding behavior. A finite element (FE) model is developed to predict the direct shear debonding response. The FE model is validated by the experimental observations and then used to characterize the debonding behavior with various geometric and material parameters, as well as bonding interface treatments. Subsequently, a robust machine learning model is developed to formulate the shear debonding strength of HPFRC-NC with those influencing parameters. Design examples are presented to illustrate the efficiency of the proposed machine learning model in describing the debonding response of HPFRC-NC. A sensitivity analysis is further conducted to investigate the contribution of the chosen predictors to the debonding behavior of HPFRC-NC. The reported HPFRC and machine learning-based prediction model provide powerful tools to address repairing issues in various existing normal concrete structures.
Keywords: High-performance fiber reinforced concrete | (HPFRC) | Normal concrete (NC) | Debonding behavior | Machine learning | Prediction model | Direct shear test
مقاله انگلیسی
5 Analyzing a mixed supply chain with a WeChat channel
تحلیل یک زنجیره تامین ترکیبی با یک کانال وی چت-2018
By combining traditional marketing methods with WeChat, this study introduces the WeChat channel into multi-channel supply chain systems. We analyze and compare the profit levels of different supply chain channels. Our results show that retailers tend to open the WeChat channel for increased profits. Whether manufacturers can benefit from the WeChat channel is determined by other factors though. In the multi-channel supply chain setting, when most consumers accept the Internet channel and the WeChat channel, or consumers are insensitive to service and adopt the new WeChat channel, then manufacturers will be able to obtain considerable profits. The results complement traditional supply chain research and offer significant guidance for supply chain channel design.
keywords: Analytical modeling |Demand functions |Economics and e-commerce |Firm strategy |Multi-channel supply chain |Numerical simulation |Policy analytics |Stackelberg game |WeChat channel
مقاله انگلیسی
6 ادغام پاسخ های پیشگیرانه و اضطراری برای تقویت انعطاف پذیری شبکه برق
سال انتشار: 2017 - تعداد صفحات فایل pdf انگلیسی: 13 - تعداد صفحات فایل doc فارسی: 44
تقویت انعطاف پذیری سیستم های قدرت یکی از الزامات اصلی شبکه هوشمند است .در این مقاله، یک چارچوب پاسخ انعطاف پذیری یکپارچه ارائه شده است که نه تنها آگاهی موقعیتی را با ارتقای انعطاف-پذیری مرتبط می کند، بلکه پاسخ های مؤثر و کارآمد را در هر دو وضعیت پیشگیرانه و اضطراری فراهم می کند. هسته چارچوب پیشنهاد شده یک مدل بهینه سازی عددصحیح مختلط قوی دو مرحله ای است که فرمول ریاضی آن در این مقاله ارائه شده است .برای حل مدل فوق، یک الگوریتم مبتنی بر تجزیه تولید ستون و محدودیت تو در تو ارائه شده است، و تکنیک های بهبود کارآیی محاسبات پیشنهاد شده است. پاسخ پیشگیرانه در این مقاله توزیع مجدد ژنراتور و سوئچینگ توپولوژی را در نظر می گیرد، در حالی که پاسخ اضطراری شامل توزیع مجدد ژنراتور، سوئیچینگ توپولوژی و قطع بار است. چندین شبیه سازی عددی اثربخشی چارچوب پیشنهاد شده و کارآیی روش راه حل را اثبات می کنند. یافته های کلیدی عبارتند از: 1) از نظر افزایش انعطاف پذیری شبکه برق، پاسخ انعطاف پذیر یکپارچه به هر دوی پاسخ پیشگیرانه مستقل و پاسخ اضطراری مستقل ترجیح داده می شود. 2) انعطاف پذیری شبکه برق می تواند با استفاده از سوئیچینگ توپولوژی در پاسخ انعطاف پذیر یکپارچه افزایش یابد.
فهرست عبارات: خاموشی | پاسخ اضطراری | توزیع مجدد ژنراتور | پاسخ انعطاف پذیر یکپارچه | قطع بار | بلایای طبیعی | بهینه سازی | پاسخ پیشگیرانه | تعریف انعطاف پذیری | افزایش انعطاف پذیری | وضعیت انعطاف پذیری | بهینه سازی قوی | آگاهی موقعیتی | سوئیچینگ توپولوژی.
مقاله ترجمه شده
7 Combined experimental observation and numerical simulation of the cloud cavitation with U-type flow structures on hydrofoils
مشاهدات تجربی ترکیب شده و شبیه سازی عددی کاویتاسیون ابر با ساختارهای جریان U-نوع بر روی hydrofoils-2016
Article history:Received 29 January 2015Revised 3 October 2015Accepted 5 October 2015Available online 11 November 2015Keyword:Sheet/cloud cavitation Vortex structures Homogeneous model RANS simulations Twisted hydrofoilSheet/cloud cavitation is an important topic that is a very common type of cavitation in turbo-machinery and marine propeller. Up to now we still have limited understanding of the cavitation shedding dynamics and cloud cavity formation and development. The present study used experimental and numerical studies to gain a better understanding of the complex physics involved in this problem. A series of experimental observa- tions around hydrofoils are carried out in the cavitation tunnel of the China Ship Scientific Research Center (CSSRC) to illustrate the spatial–temporal evolution of the cloud cavity in detail. The results demonstrate that U-type flow structures are common in cloud cavities and can be divided into three stages and the closure line in a sheet cavity often has a convex–concave profile. Reentrant flows occur in the convex region with the jet direction normal to the contour edge so the shedding is mainly caused by the converging reentrant flows. Further analysis demonstrated that there was a striking difference with the cavity growth suppressed substantially in the twisted hydrofoil case if compared with straight hydrofoil and the effect of side entrant jets might make the cavity more uniform across the span. Numerical simulations were used to simulate the formation and development of the cloud cavity. The results show that the strong adverse pressure gradient in the stagnation region at the downstream end of the attached cavity forces the re-entrant flows into the vapor structure with a radially-diverging re-entrant jet and a pair of side-entrant jets, which causes the cavity shed- ding. Further analyzes of the local flow fields show that the interactions between the circulating flow and the shedding vapor cloud may be the main reason for the formation of the U-type cloud cavity structures.© 2015 Elsevier Ltd. All rights reserved.
Keyword:Sheet / cloud cavitation | Vortex structures | Homogeneous model | RANS simulations | Twisted hydrofoil
مقاله انگلیسی
8 رمزگذاری چند تصویر با استفاده از کشت های طیفی و تسهیم فضایی
سال انتشار: 2016 - تعداد صفحات فایل pdf انگلیسی: 6 - تعداد صفحات فایل doc فارسی: 17
طرح رمزگذاری چند تصویر با استفاده از کشت طیفی و تسهیم فضایی بر اساس چند پارامتر گسسته تبدیل فوریه کسری (DSP FFT) ارائه شده است. اسپکتروم هر تصویر اصلی ابتدا توسط یک فیلتر پایین گذر نابود و لگدمال شده، و سپس تصویر با همان اندازه از فیلتر بازیافت شده است. تصاویر ترمیم شده بطور فضایی منتقل شده و تسهیم شده به یک سیگنال پیچیده با همان اندازه از تصویر اصلی هستند. سیگنال مرکب توسط یک عملیات درهم سازی پیکسل و ماسک فاز تصادفی ضرب شده است، و سپس به یک تصویر توسط DMPFRFT رمزگذاری شده است. اسکن تصویر چندگانه با کلیدهای صحیح بازیابی می شود و اسکن تصویر اصلی سپس با بزرگ کردن تصاویر دی مالتی پلکس شده بدست آمده است. شبیه سازی عددی برای نشان دادن اعتبار و امنیت روش پیشنهادی انجام شده است.
کلمات کلیدی: رمزگذاری چند تصویر | فراکشنال چند پارامتری گسسته | تبدیل فوریه | برداشت طیفی | تسهیم فضایی
مقاله ترجمه شده
9 Behaviour of cylindrical steel drums under blast loading conditions
رفتاربا طبل های فلزی استوانه ای تحت شرایط بار انفجار-2016
The Buncefield incident in the UK in 2005 involved an explosion of 240,000 m3 of vapour cloud which resulted in considerable damage to properties in the surrounding area. A number of objects that can be used as overpressure indicators such as standard steel drums were located at various points around the site. These were found deformed to different levels after the explosion. These overpressure sensitive objects were used to assess the overpressure level at the locations of the objects during the incident. This study describes full scale validation tests and numerical simulations of far-field air blast loading acting on de formable steel drums in order to investigate possible forensic methods to aid the incident investigation. Subsequently, a number of numerical models are developed in order to simulate the tests. Two models with varying complexity are used in the simulations: uncoupled Eulerian–Lagrangian model and coupled Eulerian–Lagrangian approaches. These models are validated against the test data from gas detonation explosion. Comparison between the numerical and experimental results suggests that both approaches tend to over-predict the deformation of drums due to identified inaccuracies from test measurements and numerical methods. However, both methods can comparatively capture the different levels of damage arising from blast loads with various intensities. These comparative levels are in general agreement with observations from test data. Parametric studies using the validated techniques are also carried out to further examine the response of steel drums. The results are summarised in the form of pressure–impulse dia grams, and typical residual shapes of drum models are selected to complement the pressure–impulse diagrams. The methods and results presented in this paper offer a very useful tool which could be em ployed to aid forensic investigations of future explosion incidents involving steel drums or similar field objects.
Blast tests | Numerical simulation | Buncefield incident | Dynamic response | Vapour cloud explosions
مقاله انگلیسی
10 آنالیز حرارتی HVAC و پنل های خورشیدی با استفاده از الگوریتم بهینه سازی ژنتیک
سال انتشار: 2016 - تعداد صفحات فایل pdf انگلیسی: 8 - تعداد صفحات فایل doc فارسی: 21
پژوهش حاضر، به بررسی کاربرد HVAC و سیستم های گرمایش خورشیدی در داخل مناطق مسکونی؛ با استفاده از ترکیب مدل سازی عددی مستقیم و روش بهینه سازی ژنتیکی در آب و هوای مختلف ایران می¬پردازد. مدل سازی عددی مستقیم قادر به محاسبه¬ی دمای محیط داخل ساختمان است. سپس الگوریتم مدل سازی مستقیم نیز برای تعیین میزان مصرف انرژی ساختمان در اقلیم های مختلف ایران توسط استفاده شد. نتایج حاصل از مدل سازی عددی مستقیم در برابر نرم افزار کریر(carrier) و انرژی اضافی بررسی شد. نتایج با شبیه سازی های عددی ارائه شده در بیشتر منابع مطابقت مناسبی دارد.
کلمات کلیدی: انتقال حرارت | شبیه سازی عددی | مصرف انرژی | گرمایش خورشیدی | HVAC | آب و هوا | ایران
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