practical design
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2021 ◽  
Vol 33 (6) ◽  
pp. 321-332
Jong-In Lee ◽  
Geum Yong Lee ◽  
Young-Taek Kim

The crown wall with parapet on top of the rubble mound breakwater represents a relatively economic and efficient solution to reduce the wave overtopping discharge. However, the inclusion of parapet leads to increased wave pressure on the crown wall. The wave pressure on the crown wall is investigated by physical model test. To design the crown wall the wave loads should be available, and the horizontal wave pressure is still unclear. Regarding to the horizontal wave pressure on the crown wall, a series of experiments were conducted by changing the rubble mound type structure and the wave conditions. Based on these results, pressure modification factors of Goda’s (1974, 2010) formula have been suggested, which can be applicable for the practical design of the crown wall of the rubble-mound breakwater covered by tetrapods.

2021 ◽  
Shixun Bai ◽  
Jan Kubelka ◽  
Mohammad Piri

Abstract Wettability is a key factor influencing oil production, particularly from the oil-wet carbonate reservoirs where the recoveries are often low. This is a serious problem for the oil industry as significant portion of the world's hydrocarbon reserves resides in carbonate formations. Since the wettability has its roots in the inter-molecular interactions between the oil and the mineral, our objectives are, first, to provide the molecular-level understanding of the carbonate wettability and, second, to apply this understanding to devise effective approaches for wettability alteration. Specifically, we focused on chemical additives such as surfactants and ions, which have demonstrated potential as wettability reversal agents. Molecular dynamics (MD) simulations were used as the primary method to study the wettability properties on newly-developed model calcite and dolomite surfaces that mimic experimentally-known mineral properties. Wettability reversal by cationic, anionic, and non-ionic surfactants, as well as by divalent ions (Ca2+, Mg2+, and SO42-) were investigated. A systematic approach for maximizing the surfactant efficiency by tuning the cationic surfactant head-group chemistry was proposed. To validate the MD simulation results, experimental contact angle measurements on dolomite chips were conducted. The MD simulation results demonstrated that, in the absence of asphaltenes, the oil-wetness of the carbonate minerals arises from the electrostatic attraction between the (negatively charged) oil carboxylates and the (positive) surfaces. Due to this electrostatic nature, the wettability could be reversed only by the cationic (positive) surfactants, which screen the oil-surface attraction. Other surfactant types had negligible effect, in agreement with the experimental contact angle measurements. Moreover, the wettability alteration efficiency of the cationic surfactants was directly related to their molecular charge distributions, offering guidelines for the practical design of the most potent wettability-reversing molecules. The simulations of the wettability alteration by Mg2+, Ca2+, and SO42- ions were likewise consistent with the contact angle measurements. The roles of individual ions in the multiple ion exchange (MIE) mechanism were deduced, and the known strong temperature dependence of their wettability alteration effect explained by the stability of the ion hydration shells. Finally, the simulations also exposed differences between the wettability reversal mechanisms on calcite and dolomite minerals, which may have important practical impact. Our results offer a novel perspective on the carbonate wettability and its reversal from the standpoint of atomic-level interactions and molecular mechanisms. New models for the carbonate surfaces were developed for reliable simulations of the wetting properties, which led to new insights into the origins of carbonate oil-wetness and the mechanisms of its reversal in two types of minerals. Lastly, the MD simulations demonstrated their utility as a powerful tool for the practical design and evaluation of potential chemical agents for EOR from carbonate reservoirs.

2021 ◽  
Mustafa Aziz ◽  
Reyah Abdula ◽  
Mohamad Al-Dujaili

Abstract A high-sensitivity, low-power and portable coiled-tubing (CT) inspection tool is developed based on magnetic flux leakage (MFL) technology. The tool provides enhanced real-time integrity monitoring of CT operations to minimize the risks of unexpected failures and enable efficient management of CT operations. This paper discusses practical design and engineering considerations to enhance the sensitivity of the magnetic inspection head, including magnetic characterization of the CT material, pole-piece separation, parametric calculations of the gap field, eddy currents, and MFL signal bandwidth. Experimental measurements illustrate the capability of detecting defects down to 1 mm in diameter and depth in a 1.5" CT pipe.

2021 ◽  
Vol 11 (23) ◽  
pp. 11504
Zijing Wang ◽  
Xiangdong Xie ◽  
Jinfeng Zhang ◽  
Guofeng Du

In view of the low output power density of the existing footstep harvesters, two pairs of distinctive L-shaped beams and the corresponding piezoelectric brick models are developed to improve the utilization efficiency of the piezoelectric patches bonded on the beams. A theory model of the aforesaid L-shaped beam is established to analyze its dynamic performance. Two pairs of L-shaped beams and corresponding piezoelectric brick specimens are customized. The influences of some factors on the output voltage and average power from piezoelectric patches of aforesaid piezoelectric bricks are tested and analyzed. Numerical computation based on the theory model of L-shaped beam is conducted to extend the study on the electric output performances of the proposed piezoelectric bricks. Experiment and simulation results indicate that the peak-to-peak voltage and average power can reach up to 376 V (0.15 V/mm3) and 94.72 mW (37.89 μW/mm3) for a piezoelectric patch with a dimension of 50 mm × 50 mm × 1 mm of brick specimens. This research provides novel piezoelectric bricks to harvest footstep energy and obtains some instructive conclusions for the practical design of the piezoelectric brick with ideal energy harvesting efficiency and cost-effectiveness.

2021 ◽  
Vol 11 (4) ◽  
pp. 1-7
Y.U. Sharif ◽  
M.J. Brown ◽  
M.O. Ciantia ◽  
A.J. Lutenegger ◽  
P.V. Pavan Kumar ◽  

Screw piles have been used to support a variety of structures due to their ease of installation and high axial capacity. Recently, screw piles have been proposed as an alternative foundation solution for offshore renewable structures due to their quiet or silent installation. Due to their variable geometry, design and prediction of installation requirements and its effect on in-service capacity may be challenging. In this research study, the discrete-element method (DEM) is used to numerically recreate a series of onshore field tests. The aim of the study is to investigate the ability of DEM to be used as a practical design tool for the design and deployment of screw piles. In this case study, the effect of the geometric helix pitch on the installation torque and tensile capacity of screw piles installed into sand is investigated. DEM results show that the geometric pitch of a screw pile appears to have little effect on the installation torque. The results show that DEM has the potential to be used as a practical design procedure for complex foundation installation where the simulation needs to capture installation effects.

2021 ◽  
Ya Li ◽  
Lijun Xie ◽  
Ciyan Zheng ◽  
Dongsheng Yu ◽  
Jason K. Eshraghian

Abstract Fractional-order systems generalize classical differential systems and have empirically shown to achieve fine-grain modeling of the temporal dynamics and frequency responses of certain real-world phenomena. Although the study of integer-order memory element (mem-element) emulators has persisted for several years, the study of fractional-order memory elements (FOMEs) has received little attention. To promote the study of the characteristics and applications of mem-element systems in fractional calculus (FC) and memory systems, in this paper, we propose a novel universal interface for constructing floating FOMEs. When the topological structure of the interface remains unchanged, the floating fractional-order memristor (FOMR), fractional-order memcapacitor (FOMC) and fractional-order meminductor (FOMI) emulators can be realized by using the impedance combinations of different passive elements, without any mem-element emulators and mutators. When compared with previously proposed FOMEs, the proposed fractional-order mem-element emulators based on a universal interface not only feature the characteristics of floating terminals and simpler circuit structures, but can also realize all three different types of FOMEs. To explore the dynamical relationships between the mem-elements and the fractional order, we mathematically derive and analyze the maximum and minimum possible values of memductance, memcapacitance and inverse meminductance which accounts for practical design considerations when building FO systems. The memory characteristics of FOMEs are analyzed by varying their orders and stimuli frequencies. The consistency of theoretical analysis, numerical calculation and simulation results validates the correctness of our proposed emulators.

2021 ◽  
Timothy Jones

<p>Objects have been categorised into classes that declare and implement their behaviour ever since the paradigm of object-orientation in programming languages was first conceived. Classes have an integral role in the design and theory of object-oriented languages, and often appear alongside objects as a foundational concept of the paradigm in many theoretical models.  A number of object-oriented languages have attempted to remove classes as a core component of the language design and rebuild their functionality purely in terms of objects, to varying success. Much of the formal theory of objects that eschews classes as a fundamental construct has difficulty encoding the variety of behaviours possible in programs from class-based languages.  This dissertation investigates the foundational nature of the class in the object-oriented paradigm from the perspective of an ‘objects-first’, classless language. Using the design of theoretical models and practical implementations of these designs as extensions of the Grace programming language, we demonstrate how objects can be used to emulate the functionality of classes, and the necessary trade-offs of this approach.  We present Graceless, our theory of objects without classes, and use this language to explore what class functionality is difficult to encode using only objects. We consider the role of classes in the types and static analysis of object-oriented languages, and present both a practical design of brand objects and a corresponding extension of our theory that simulates the discipline of nominal typing. We also modify our theory to investigate the semantics of many different kinds of implementation reuse in the form of inheritance between both objects and classes, and compare the consequences of these different approaches.</p>

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