رساله دکتری با عنوان: Fracturing of layered reservoir rocks
اختصاصی از یارا فایل رساله دکتری با عنوان: Fracturing of layered reservoir rocks دانلود با لینک مستقیم و پرسرعت .
رساله دکتری با عنوان: Fracturing of layered reservoir rocksدانشگاه : The University of Oklahoma
استاد راهنما: Dr. Ze’ev Reches
پژوهشگر: Seth Busetti
سال 2009
فرمت فایل: PDF و شامل 272 صفحه
چکیده:
The development of fractures in rock layers reflects a history of complex, non-linear, time-dependent mechanical processes. The processes strongly depend on the rock rheology, particularly the behavior during progressive deformation, layering effects such as the mechanical stratigraphy, and the local stress conditions. In the past, the complex mechanics associated with fracture initiation and propagation contributed to the application of simplified models based on linear rheology and using quasi-static solutions. While this approach is effective in solving infinitesimal strain problems, it provides no explanation for strain localization, damage accumulation and rock failure, and it oversimplifies fracture propagation. The objective of the present work is to contribute to the understanding of these processes.
The approach of this study is as follows. (Chapter 1) Theoretical advancements on fracturing and the concept of continuum damage mechanics are compared with rock mechanics experiments to understand progressive deformation, failure, and fracture propagation for rock. It is demonstrated that non-local (away from the crack-tip) yielding behavior must be considered to understand complex fracturing. (Chapter 2) A numerical rheology based on the elastic-plastic-damage properties of Berea sandstone is developed and calibrated to experimental rock mechanics data. A method for translating the stress-strain curve and acoustic emissions data into a material model included in the commercial finite element code Abaqus is presented. Two rock mechanics experiments are simulated in 3-D to test the rheology model. (Chapter 3) The rheology is implemented into finite element models based on classical hydraulic fracturing configurations. The explicit dynamic finite element method is used to simulate damage and transient propagation of a hydrofracture segment. It is shown that the complexity of fracturing depends on the local stress-strain response, which is controlled by the evolving damage pattern. The dynamical characteristics of arrest, rupture, branching, and segmentation of the fracture are described in terms of damage evolution. (Chapter 4) An analytical model for natural fracture reactivation is paired with the finite element simulations to understand the development of complex hydraulic fracture networks in the subsurface. The models' predictions are compared with data from hydraulically stimulated wells in the Barnett Shale. Recommendations are made for optimizing hydrofracture operations in wells for different states of stress (Chapter 5). The occurrence of zones of anomalously high fracture density is characterized in a carbonate sequence near Cedar Mountain Utah, and in Jackfork Group sandstone layers in Oklahoma and Arkansas. The results indicate that fracture density should be examined as a function of the evolving rock properties of the host layer in addition to the layer thickness.
The investigation contributes to understanding the process of damage and fracturing during the deformation of rock layers. The results describe the development of mechanical inhomogeneity in fractured rock layers and can be applied to explain the formation of complex hydraulic fractures in unconventional reservoirs.
مشاهده آنلاین و دریافت فایل نمونه:
https://drive.google.com/file/d/0B3BBM5yT_t4ZcmpQUjBiZmR3WW8
** توجه: خواهشمندیم در صورت هرگونه مشکل در روند خرید و دریافت فایل از طریق بخش پشتیبانی در سایت مشکل خود را گزارش دهید. **
رساله دکتری با عنوان: The lack of a clearly defined retention strategy and the impact of the retention of civil engineers
اختصاصی از یارا فایل رساله دکتری با عنوان: The lack of a clearly defined retention strategy and the impact of the retention of civil engineers دانلود با لینک مستقیم و پرسرعت .
رساله دکتری با عنوان: The lack of a clearly defined retention strategy and the impact of the retention of civil engineersدانشگاه : Capella University
استاد راهنما: Tony Pizur
پژوهشگر: Aaron E. Forsythe
سال 2008
فرمت فایل: PDF و شامل 115 صفحه
چکیده:
Developing retention strategies for retaining professional employees has the potential of providing large cost savings to an organization associated with employee turnover. However, determining the needs of select groups of professional employees can be difficult to determine in today's markets. Through a quantitative fixed research design, this research used a survey to investigate the impact of a non-articulated retention strategy and the retention of civil engineering professionals. The responses from 361 participants indicated that there is statistical support that there is a root cause as to the low retention rate experienced by the organization. However, there does not appear to be a correlation between the root cause and the satisfaction of the civil engineers.
مشاهده آنلاین و دریافت فایل نمونه:
https://drive.google.com/file/d/0B3BBM5yT_t4ZUU1xS2UzMTNGSHc
** توجه: خواهشمندیم در صورت هرگونه مشکل در روند خرید و دریافت فایل از طریق بخش پشتیبانی در سایت مشکل خود را گزارش دهید. **
رساله دکتری با عنوان: Multi-Scale Adhesion and Fracture: From Eco-friendly Structures to Biomedical Devices
اختصاصی از یارا فایل رساله دکتری با عنوان: Multi-Scale Adhesion and Fracture: From Eco-friendly Structures to Biomedical Devices دانلود با لینک مستقیم و پرسرعت .
رساله دکتری با عنوان: Multi-Scale Adhesion and Fracture: From Eco-friendly Structures to Biomedical Devicesدانشگاه : Princeton University
استاد راهنما: Winston Soboyejo
پژوهشگر: Ting Tan
سال 2011
فرمت فایل: PDF و شامل 166 صفحه
چکیده:
This thesis presents the results of a combined experimental, analytical and numerical study of fracture and adhesion in: sustainable building materials (bamboo and natural fiber-reinforced composites), restoration of a historical statue (Adam by Tullio Lombardo), and drug eluting stents. In each of these cases, multi-scale mechanism-based models were used to predict robustness.
In an effort to study the functionally graded bamboo structure, bamboo cross sections were examined using optical microscopy. This revealed the details of the functionally graded distribution of fiber bundles. Atomic Force Microscopy (AFM) was also used to characterize the microstructures of the molecular fiber bundles. Then, nano-indentation was used to measure the graded elastic moduli along with the radial direction. The measured elastic moduli were incorporated in finite element simulation of deformation and crack growth in resistance-curve experiments. The predictions from the models were in agreement with measured resistancecurves obtained for moso culm bamboo in the outside, inside and side orientations.
OPC-based cementitious fiber reinforced composites were fabricated using slurry vacuum method with carbonate filler, phyllite or metakaolin matrices and polypropylene or sisal fibers. Optical microscopy was used to study the in-situ fiber-bridging images obtained during three-point bend fracture/resistance-curve experiments. Single-fiber tensile tests were also used to measure the fiber tensile strengths. The measured fiber strengths were included in crack bridging models that were used to predict composite resistance-curve behavior. The predictions were in good agreement with the measured resistance curves.
Drug Eluting Stents (DES) are small drug coated scaffolds used to open the blocked arteries for patients with cardiovascular diseases. The CYPHER ® stent is a multilayered structure with drug, parylene C and bare 316L steel layers. Based on prior AFM adhesion work, Brazil Nut experiments were performed to measure the interfacial fracture energy release rate for the interface of silane-parylene and bare 316L steel at various mode mixities. Interfacial fracture mechanics models were used to then link nano-scale AFM measurements of adhesives to microscale fracture mechanics measurement of interfacial fracture energies at different mode mixities.
Brazil Nut is used to study the subcritical crack growth rate in marble/adhesive interfaces. Four types of adhesives, Paraloid B72, Paraloid B48, a hybrid of B72/B48 and Epoxy, were selected to bond the Carrara marble Brazil Nut disks with fractured and smooth surfaces. Creep crack growth experiments were used to measure the dependence of energy release rates on crack growth rates between the Carrara marble and thermoplastic and thermosetting adhesives. The measured crack growth rates were incorporated into fracture mechanics predictions of service lives that were shown to be consistent with the lives of historical objects.
مشاهده آنلاین و دریافت فایل نمونه:
https://drive.google.com/file/d/0B3BBM5yT_t4ZcDJDdURBYVNjdUE
** توجه: خواهشمندیم در صورت هرگونه مشکل در روند خرید و دریافت فایل از طریق بخش پشتیبانی در سایت مشکل خود را گزارش دهید. **
رساله دکتری با عنوان: Dynamic Finite Element Modeling and Analysis of Blast-resistant Sandwich Structures
اختصاصی از یارا فایل رساله دکتری با عنوان: Dynamic Finite Element Modeling and Analysis of Blast-resistant Sandwich Structures دانلود با لینک مستقیم و پرسرعت .
رساله دکتری با عنوان: Dynamic Finite Element Modeling and Analysis of Blast-resistant Sandwich Structuresدانشگاه : University of Connecticut
استاد راهنما: Jeong-Ho Kim
پژوهشگر: Linhui Zhang
سال 2012
فرمت فایل: PDF و شامل 165 صفحه
چکیده:
Blast-resistant composites and structures are gaining more and more academic and industrial interests currently. The metal sandwich structure is proven to perform better than the monolithic plate with the same mass under blast loading. Besides, the foam or foam-like cores with stacking of graded layers can further mitigate the blast effects. In this work, the dynamic responses of corrugated sandwich plates with various homogeneous and graded core arrangements under shock tube loading are investigated by finite element method. By comparing the maximum back face deflection, maximum back face velocity, plastic energy absorption, stress history and contact force, the corrugated sandwich plate with the gradually graded core has a better overall performance.
The parametric study on unit-cell corrugated and trapezoid sandwich structures with given mass and various core arrangements subjected to idealized air-blast loading is also carried out. The sandwich structures with graded cores can prevent the structure to get fully crushed. It is also shown that the trapezoid sandwich structures have larger impact tolerance, but the trapezoid sandwich structures are more sensitive to the initial geometric imperfections than corrugated sandwich structures.
Due to the benefits of the graded cores, a modified rule of mixture and linear strain-rate dependence are used to derive the rate-dependent elastic-plastic constitutive relation for functionally graded (FG) material. The derived constitutive relations are implemented in ABAQUS/Explicit through a VUMAT subroutine to simulate the dynamic response of a FG plate subjected to shock tube loading.
مشاهده آنلاین و دریافت فایل نمونه:
https://drive.google.com/file/d/0B3BBM5yT_t4ZWkUxUGdNRzNLS0k
** توجه: خواهشمندیم در صورت هرگونه مشکل در روند خرید و دریافت فایل از طریق بخش پشتیبانی در سایت مشکل خود را گزارش دهید. **
دانلود مقالهISI دکتری دانشگاه والادولید در روانشناسی صنعتی و سازمانی
اختصاصی از یارا فایل دانلود مقالهISI دکتری دانشگاه والادولید در روانشناسی صنعتی و سازمانی دانلود با لینک مستقیم و پرسرعت .
موضوع فارسی : دکتری دانشگاه والادولید در روانشناسی صنعتی و سازمانی
موضوع انگلیسی : El Colegio Doctoral Tordesillas en Psicología del Trabajo y de las Organizaciones
تعداد صفحه : 2
فرمت فایل :pdf
سال انتشار : 2014
زبان مقاله : انگلیسی
چکیده
محیط زیست تغییرات sociolaboral که در آن ES بخش این است
مطالعه و پژوهش در زمینه روانشناسی سازمانی
روش و کار نیاز به یک تلاش جمعی از محققان
RES این منطقه را در بهبود فرایند و نوآوری برای انطباق خود
خواسته های محیط های جدید. کشف فرصت های ممکن
روابط از این محیط و پاسخگویی به چالش های است که الزامات
rido بهینه سازی منابع مادی و انسانی موجود در
دانشگاهها و مراکز تحقیقاتی ملی و بین المللی مختلف
اتباع. بنابراین، هماهنگی و همکاری بین دی
دانشگاه Versas و بخش های تحقیقاتی و یا واحد خود
روش به عنوان یک نیاز پاسخ رقابتی ظهور
به جهان در حال تغییر از کار و سازمان
روابط در سال های اخیر.