Efficient algorithms for flow models coupled with geomechanics for porous media applications

The coupling between subsurface flow and reservoir geomechanics plays a critical role in obtaining accurate results for models involving reservoir deformation, surface subsidence, well stability, sand production, waste deposition, hydraulic fracturing, CO₂ sequestration, and hydrocarbon recovery. From a pure computational point of view, such a coupling can be quite a challenging and complicated task. This stems from the fact that the constitutive equations governing geomechanical deformations are different in nature from those governing porous media flow. The geomechanical effects account for the influence of deformations in the porous media caused due to the pore pressure and can be very important especially in the case of stress-sensitive and fractured reservoirs. Considering that fractures are very much prevalent in the porous media and they have strong influence on the flow profiles, it is important to study coupled geomechanics and flow problems in fractured reservoirs. In this work, we pursue three main objectives: first, to rigorously design and analyze iterative and explicit coupling algorithms for coupling flow and geomechanics in both poro-elasitc and fractured poro-elastic reservoirs. The analysis of iterative coupling schemes relies on studying the equations satisfied by the difference of iterates and using a Banach contraction argument to derive geometric convergence (Banach fixed-point contraction) results. The analysis of explicit coupling schemes result in analogous stability estimates. In this work, conformal Galerkin is used for mechanics, and a mixed formulation, including the Multipoint Flux Mixed Finite Element method as a special case, is used for the flow model. For fractured poro-elastic media, our iteratively coupled schemes are adaptations, due to the presence of fractures, of the classical fixed stress-splitting scheme, in which fractures are treated as possibly non-planar interfaces. The second main objective in this work is to exploit the different time scales of the mechanics and flow problems. Due to its physical nature, the geomechanics problem can cope with a coarser time step compared to the flow problem. This makes the multirate coupling scheme, the one in which the flow problem takes several (finer) time steps within the same coarse mechanics time step, a natural candidate in this setting. Inspired by that, we rigorously formulate and analyze convergence properties of both multirate iterative and explicit coupling schemes in both poro-elastic and fractured poro-elastic reservoirs. In addition, our theoretically derived Banach contraction estimates are validated against numerical simulations. The third objective in this work is to optimize the solution strategy of the nonlinear flow model in coupled flow and mechanics schemes. The global inexact Newton method, combined with the line search backtracking algorithm along with heuristic forcing functions, can be efficiently employed to reduce the number of flow linear iterations, and hence, the overall CPU run time. We first validate these computational savings for challenging two-phase benchmark problems including the full SPE10 model. Motivated by the obtained results, we incorporate this strategy as a nonlinear solver framework to solve the nonlinear flow problem in multirate iteratively coupled schemes. This leads to a scheme that reduces both the number of flow and mechanics linear iterations efficiently. All our numerical implementations in this work are built on top of our in-house reservoir simulator (IPARS).Computational Science, Engineering, and Mathematic

Modern studies of training modalities in the professional sport field

This paper highlights on the different modern trainings at the professional sport activities. All the modern methods of Karate trainings were discussed in details, even the training obstacles that confront coaches. All the modern training methods have seen in details taken from scientific and practical studies belong to the trainee and coaches of that sport. This paper contains more than twenty training method with schedules supported with statistics and comparisons between the basic training methods that are taken from some exercise of different sports such as pushing the iron ball and the hammer's sight, and the influence of these sports to develop the coach and the trainee of karate

Multi-Mixed Fractional Brownian Motions and Orstein--Uhlenbeck Processes

We consider the so-called multi-mixed fractional Brownian motions (mmfBm) and multi-mixed fractional Ornstein--Ulhenbeck processes (mmfOU). These processes are constructed by mixing or by superimposing infinitely many independent fractional Brownian motions and fractional Ornstein--Uhlenbeck processes, respectively. We prove their existence as $L^2$ processes and study their path properties, viz. H\"older continuity and conditional full support property. In the finite mixture case we study their statistical parameter estimation by using generalized method of moments (GMM) estimators

Makian Pada Kolom Komentar Berita di Instagram

Penelitian ini bertujuan untuk mendeskripsikan bentuk dari makian yang terdapat dalam kolom komentar berita di Instagram dan menjelaskan fungsi serta makna dari kata makian yang terdapat dalam kolom komentar berita di Instagram. Penelitian ini dilatarbelakangi oleh komentar-komentar yang memakai kata makian pada kolom komentar berita di Instagram. Penelitian ini menggunakan metode deskriptif dan pendekatan kualitatif. Data yang digunakan dalam penelitian ini adalah komentar yang dituliskan pengguna Instagram kepada pengunggah berita di Instagram. Hasil dari penelitian ini yang pertama menemukan tiga bentuk makian. Yaitu, berbentuk kata, frasa dan klausa. Yang kedua fungsi dan makna dari kata makian yang dilihat dari konteks. Kedua hasil penelitian ini didapat dari 20 data komentar yang diambil secara acak di Instagram

Prediction of Gaussian Volterra processes with compound Poisson jumps

We consider a Gaussian Volterra process with compound Poisson jumps and derive its prediction law.© 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).fi=vertaisarvioitu|en=peerReviewed

FAKTOR YANG BERHUBUNGAN DENGAN PERSEPSI KARYAWAN UNIT PRODUKSI TONASA IV TERHADAP PENERAPAN SISTEM MANAJEMEN KESELAMATAN DAN KESEHATAN KERJADI PT. SEMEN TONASA TAHUN 2013

Sejak tahun 2000 PT. Semen Tonasa telah menerapkan Sistem Manajemen Keselamatan dan Kesehatan Kerja (SMK3). Setelah melakukan observasi, masih ada tenaga kerja yang tidak mengikuti SMK3 yang ditetapkan oleh pihak manajemen perusahaan, khususnya pada Unit Produksi Tonasa IV, seperti tidak menggunakan APD yang memadai pada saat bekerja dan tidak mematuhi rambu-rambu keselamatan yang ada. Hal tersebut mungkin dikarenakan persepsi yang kurang baik terhadap penerapan SMK3 dan mempengaruhi dukungan terhadap penerapan SMK3. Penelitian ini bertujuan untuk mengetahui faktor yang berhubungan dengan persepsi karyawan unit produksi Tonasa IV terhadap penerapan SMK3 di PT. Semen Tonasa tahun 2013. Jenis Penelitian ini adalah survey analitik dengan pendekatan cross sectional study terhadap 60 karyawan Unit Produksi Tonasa IV sebagai sampel. Analisis data dengan menggunakan univariat untuk mendeskripsikan karakteristik responden dan bivariat dengan cross tabulasi dan diuji dengan uji Chi Square. Hasil penelitian diperoleh variabel yang berhubungan dengan persepsi karyawan terhadap penerapan SMK3 di PT. Semen Tonasa adalah umur (?? = 0,002), pengetahuan (?? = 0,002), masa kerja (?? = 0,008), dan pelatihan K3 (?? = 0,008) dan variabel yang tidak berhubungan persepsi karyawan Unit Produksi Tonasa IV terhadap penerapan SMK3 adalah tingkat pendidikan (?? = 1,00). Dari penelitian ini diharapkan agar perlu adanya sosialisasi kepada seluruh karyawan tentang SMK3 dan perlu adanya pelatihan K3 yang sesuai dengan peran dan tanggung jawab karywan serta pelatihan penyegaran kepada karyawan lama sehingga diharapkan mampu memiliki skill yang baik dibidangnya.\ud Kata Kunci : Persepsi, SMK3, Karyawa

Experimental and numerical study of the hydrodynamics of an isolated bubble in non-Newtonian liquid phase in a thin gap bubble column

International audienceDevelopment of photobioreactors (PBR) for microalgae cultivation is a primary concern, keeping in mind the applicative potential of these photosynthetic microorganisms. For this purpose, optimization of culture parameters and PBRs design are the two possible solutions in order to obtain high volumetric productivities. The thin-gap intensified PBR allows to obtain these performances via an increase of culture concentration for a given illuminated surface. When compared with usual PBRs, the confinement results in a high change of the hydrodynamics and mass transfer[1]. To optimize these production systems, our study focuses on the characterization of local hydrodynamics in a 2D bubble column of 4 mm thickness (FIG. 1). Furthermore, it has been shown that the increase in cell concentration is accompanied by rheological properties modifications of the microalgae suspension. To mimic such high concentration of Chlorella vulgaris cultures which have non-Newtonian shear thinning behaviour at concentrations ranging from 30-40 g/L[2], solutions of Xanthan Gum (XG) and Carboxymethyl cellulose (CMC) are used respectively at the concentrations of 1 g/L and 2 g/L. In order to put forward the effect of the rheological behaviour, demineralized water is also used as a Newtonian fluid. In this preliminary work, the main purpose is to estimate the terminal velocity (V t) of an isolated bubble in this confined column. In fact, if the terminal velocity for an isolated bubble is modified due to wall effects, there will have consequences for hydrodynamics and mass transfer of the whole bubble column: for instance, bubble residence time or gas hold up will be modified[1]. B.Figueroa Espinoza et al. [3] reported the confinement effect for a single clean bubble, pointing out that the drag coefficient widely increases for oscillating bubbles rising in a Hele-shaw cell. The experimental part consists in studying the local hydrodynamics behaviour of isolated bubbles of different diameters for three liquid media: water, CMC and XG solutions. Capillaries tubes, having diameters (d c) of 0.127, 0.264, 0.508, 0.762 or 1.016 mm are used to generate isolated bubbles at different diameter sizes with the help of a low-pressure syringe pump (NEMESYS, GERMANY). Bubble injection is performed 7 cm away from the lateral wall which can be considered sufficient to avoid wall influence on the hydrodynamics of isolated bubble. Bubble size and instantaneous bubble velocity are estimated by a shadowgraphy method using the DANTEC DYNAMICS Shadow Strobe. These measurements are performed at mid height of the column, where bubble terminal velocities have been reached. The experimental terminal velocities for different bubble diameters (d b) in water, CMC and XG liquid media are reported in Table 1 and plotted in FIG. 2(a). Water measurements are also compared to the correlation established by M.Jamialahmadi et al.[4] and the data of R.Clift et al. [5] which concern isolated bubble in pure water in infinite liquid medium (FIG. 2(b)). It is found that for an isolated bubble rising in quiescent liquid, with a diameter lower than 4 mm, the terminal velocity is divided by V t ratio between 1.2 and 1.6 for water. Besides this in non-Newtonian solutions, for lower bubble diameters the terminal velocity is less than water medium and as the bubble diameter increases it becomes constant this phenomena was also experienced by Shahram Amirnia et al.[6]. In parallel to experiments, a numerical study is performed to characterize the behaviour of one single bubble in the confined space between two walls in Newtonian and Non-Newtonian media. Simulations are performed with academic Ansys Fluent 17.2 solver using volume of fluid (VOF) method for interface tracking along with continuum surface Force (CSF) model to treat surface tension. Firstly, mesh independency verification has been performed by 2D and 3D simulations of a 3 mm diameter bubble in infinite medium. These results have been validated with the results of F.Bertola et al.[7](FIG.2(b)). Thereafter the same confined geometry as experimental setup has been adopted to simulate the bubble diameters determined experimentally. Numerical results are reported in FIG. 2(b) and seem to be in good agreement with the experiments results (FIG 2(b))

Design and implementation of image based object recognition

The aim of this paper is to design and implement image based object recognition. This represents more of a challenge when speaking of advance object recognition systems. A practical example of this issue is the recognition of objects in images. This is a task that humans can perform very well, but convolutional neural network systems don’t struggle to perform. AlexNet pre-trained model was used for the training the dataset because of it trouble-free architecture on very large scale dataset “Cifar-10” using R2019a Matlab. The dataset was split with the ratio of 70% for training and 30% for the testing part. This has prompted convolutional neural network to start experimenting with networks architectures as well as new algorithms to train them. This research paper presents an approach to train networks such as to improve their robustness to the recognition of object images on R2019a Matlab. This training strategy is then evaluated for designed AlexNet network architecture. The result of the study was that the training algorithm could improve robustness to different image recognition at the expense of an increase in performance for the performance of images of objects (i.e. Dog, Frog, Deer, Automobile, Airplane etc.) with high accuracy of recognition. When the advantages of different types of architectures were evaluated, it was found that accuracy of all object recognition were around 98% based on the image. It followed the findings from classical object recognition that feed-forward neural networks could perform as well their high accuracy of recognition

Employees Perceptions Towards the Implementation of Occupational Health and Safety Management System at PT. Sementonasa

Since the year 2000, PT. Semen Tonasa has implemented the Occupational Health and Safety Management System (OHSMS). After the observation was conducted, there were still some workers who did not follow the OHSMS set by the company management, especially workers in Tonasa Production Unit IV, such as not using adequate protective equipmentat work and not obeying the safety signs. This is probably due to a poor perception of the implementation of OHSMS and affects support for the implementation of OHSMS. This study aims to determine the factors related to Tonasa production unit IV employees' perceptions of the application of the OHSMS at PT.Semen Tonasa in 2013. This study was conducted using an analytical survey method with cross sectional study approach. 60 employees in the Tonasa production unit IV acted as samples for this study. Data analysis was conducted using chi square test. Results of this study found that the variables associated with employee perceptions of the implementation of the occupational health and safety management system at PT.Semen Tonasa were age (p=0,002), knowledge (p=0,002), work period (p=0,008) and K3 training (p=0,008), while the variable that was not related to Tonasa production unit IV employee perceptionsof the implementation of OHSMS was the level of education (p=1,00). In conclusion, there were relationships between age, knowledge, work period, and K3 training with the implementation of OHSMS in PT.Semen Tonasa