Commercial Software Applications Research Articles

A case study on entropy generation in MHD nanofluid flow in L- shaped triangular corrugated permeable enclosure

Enclosure with irregular boundaries by providing surface corrugations is considered an efficient strategy to elevate the heat transfer mechanism in laser technology, cooling of electronic instrument, photonic systems in material processing, magnetic resonance, and the automobile industry are few to mention. In view of such mesmerizing utilization present work is articulated by considering L-shaped corrugated enclosure saturated with water and copper (Cu) nanoparticles are included. The physical impacts of a horizontally oriented magnetic field and permeable medium are accounted along with measurement of entropy. Mathematical modelling of the problem is attained in dimensionless version through a set of similar variables. Computational experiments are conducted through the application of commercial software (COMSOL) based on the finite element approach. A grid independence and comparison tests are also accounted to ensure credibility of simulations. Impact of parameters is revealed through sketches. Quantities of interest, including local and average Nusselt numbers, Bejan number, and total entropy, are also evaluated for flat and correlated surfaces. Induction of nanoparticles in the base fluids tends to reduce the entropy generation by up to 12.45 %. Growth in NuAvg (3.08 % approx.) is attained by increasing the frequency of imposed triangular waved corrugation.

Cancer Radiomic and Perfusion Imaging Automated Framework: Validation on Musculoskeletal Tumors.

Limitations from commercial software applications prevent the implementation of a robust and cost-efficient high-throughput cancer imaging radiomic feature extraction and perfusion analysis workflow. This study aimed to develop and validate a cancer research computational solution using open-source software for vendor- and sequence-neutral high-throughput image processing and feature extraction. The Cancer Radiomic and Perfusion Imaging (CARPI) automated framework is a Python-based software application that is vendor- and sequence-neutral. CARPI uses contour files generated using an application of the user's choice and performs automated radiomic feature extraction and perfusion analysis. This workflow solution was validated using two clinical data sets, one consisted of 40 pelvic chondrosarcomas and 42 sacral chordomas with a total of 82 patients, and a second data set consisted of 26 patients with undifferentiated pleomorphic sarcoma (UPS) imaged at multiple points during presurgical treatment. Three hundred sixteen volumetric contour files were processed using CARPI. The application automatically extracted 107 radiomic features from multiple magnetic resonance imaging sequences and seven semiquantitative perfusion parameters from time-intensity curves. Statistically significant differences (P < .00047) were found in 18 of 107 radiomic features in chordoma versus chondrosarcoma, including six first-order and 12 high-order features. In UPS postradiation, the apparent diffusion coefficient mean increased 41% in good responders (P = .0017), while firstorder_10Percentile (P = .0312) was statistically significant between good and partial/nonresponders. The CARPI processing of two clinical validation data sets confirmed the software application's ability to differentiate between different types of tumors and help predict patient response to treatment on the basis of radiomic features. Benchmark comparison with five similar open-source solutions demonstrated the advantages of CARPI in the automated perfusion feature extraction, relational database generation, and graphic report export features, although lacking a user-friendly graphical user interface and predictive model building.

Tridimensional characterization of open cells and hollow strut cavities from SiC and ZrO2 foams: A study accomplished with open-source software tools

The characterization of ceramic foams via X-ray microtomography imaging method is often restricted to a general overview of samples, either to perform qualitative or quantitative analyses. To assess the foam with a focus on some specific components of its structure, such as hollow struts’ cavities and open cells, the generalized characterizations must be overcome. This work presents image analysis methodologies, based on open-source software, tools, and plugins, to achieve the aforementioned characterizations. SiC and ZrO2 foams samples were analyzed and some of the results were compared with those accomplished with pieces of commercial software. The results show good agreement between open-source and commercial software applications, indicating that the presented methodologies can be freely applied by any researcher to analyze their foams.

Novel calculation method to predict gas–water two-phase production for the fractured tight-gas horizontal well

The prediction of production capacity in tight gas wells is greatly influenced by the characteristics of gas–water two-phase flow and the fracture network permeability parameters. However, traditional analytical models simplify the nonlinear problems of two-phase flow equations to a large extent, resulting in significant errors in dynamic analysis results. To address this issue, this study considers the characteristics of gas–water two-phase flow in the reservoir and fracture network, utilizes a trilinear flow model to characterize the effects of hydraulic fracturing, and takes into account the stress sensitivity of the reservoir and fractures. A predictive model for gas–water two-phase production in tight fractured horizontal wells is established. By combining the mass balance equation with the Newton–Raphson iteration method, the nonlinear parameters of the flow model are updated step by step using the average reservoir pressure. The accuracy of the model is validated through comparisons with results from commercial numerical simulation software and field case applications. The research results demonstrate that the established semi-analytical solution method efficiently handles the nonlinear two-phase flow problems, allowing for the rapid and accurate prediction of production capacity in tight gas wells. Water production significantly affects gas well productivity, and appropriate fracture network parameters are crucial for improving gas well productivity. The findings of this work could provide more clear understanding of the gas production performance from the fractured tight-gas horizontal well.

Halogenate electroreduction from acidic solution at rotating disc electrode. Maximal steady-state convective-diffusion current for comparable concentrations of halogenate ions and protons

Process of electrochemically inactive halogenate-anion (XO3-, X = halogen) electroreduction at rotating disk electrode (RDE) under steady-state conditions via a mediator cycle: XO3- + 5 X- + 6H+→ 3 X2 + 3 H2O in solution (*), X2 + 2 e-⇄ 2 X- on electrode surface in acidic aqueous medium has been analyzed theoretically on the basis of a set of coupled convective-diffusional transport equations for predicting the dependence of its rate on numerous parameters of the system, without application of expensive commercial software for its numerical integration. Approximate solution of these equations for the concentration distributions of all reactive species (halogenate and halide anions, halogen molecules and protons), as well as for the maximal current, as functions of the RDE frequency, bulk-solution concentrations of XO3-, X2 and H+ species, diffusion coefficients of all reactive components, rate constant of comproportionation reaction (*), kinematic viscosity of solution, etc., is given as a simple analytical procedure which provides this solution in the numerical form for any set of values of these parameters.These characteristics of the process are determined primarily by the ratio of the diffusion (for species X2) and kinetic layer thicknesses: xdkC = zdC/ zk, which depends on the RDE frequency and the bulk-solution concentrations of species XO3- (Ao) and H+ (Ho), as well as on other parameters of the system. Weak-current regime takes place for its relatively small values: xdkC < 6, i.e. for sufficiently high RDE frequencies, where the maximal current is proportional to the bulk-solution concentration of X2 molecules, Co, being independent of the Ao and Ho concentrations. Within the opposite range of this parameter: xdkC>6, i.e. for sufficiently low RDE frequencies, the maximal current is comparable to the smaller of the diffusion-limited currents of XO3- and H+ species, jAlim and jHlim, being practically independent of the Co concentration. This strong-current regime which does not exist for the conventional EC-cat (or EC') mechanism is entirely due to the autocatalytic feature of the mediating redox cycle (EC-autocat mechanism) which may lead to enormous accumulation of the X2/X- redox couple components near electrode surface.

Three-dimensional temperature field inversion calculation based on an artificial intelligence algorithm

An increasing number of practical problems in heat transfer area are attributed to inverse heat transfer problems (IHTPs). One of the typical applications of the inverse problem is the prediction of the temperature field of an object from discrete temperature measurements of the surface. The study combines machine learning algorithms with numerical heat transfer methods to inversely predict the heat transfer boundary conditions of a hexahedral geometry from a finite number of discrete temperature measurements on its surface and then calculate the overall temperature field distribution. For the implementation of the numerical heat transfer forward problem, we first complete the coding of the finite element program to generate a training dataset for the inverse calculation by batch inputting the predefined boundary conditions. The inverse problem is modelled by constructing a neural network (NN) approach. The model is trained by calling data from the above dataset. The discrete temperature data are brought into the trained neural network for temperature field prediction. The results are tested for accuracy and generalisability. Finally, by comparing different hyperparameters and different training methods, a method of improving the efficiency and accuracy of the reconstruction results is proposed. The inversion calculation error is finally controlled to less than 0.1. In addition, the model implements the validation of commercial software simulation data and application to aero-engine turbine blades and vapour chambers. The approach can be extended as a generalised 3D temperature field reconstruction method.

A Semi-Analytical Model for Gas–Water Two-Phase Productivity Prediction of Carbonate Gas Reservoirs

The productivity prediction of gas wells in carbonate gas reservoirs is greatly affected by the characteristics of gas–water two-phase flow and fracture seepage parameters. Compared with numerical simulation, the productivity prediction based on the analytical model is fast and widely used, but the traditional analytical model is fairly simplified while dealing with the nonlinear problem of the two-phase seepage equation, leading to a large discrepancy in the results of dynamic analysis. To solve this problem, this paper considers the characteristics of gas–water two-phase flow in the reservoir and fracture, uses the dual-medium model to characterize the stress sensitivity of the fracture and reservoir, and establishes a gas–water two-phase productivity prediction model for carbonate gas reservoirs. Combining the flowing material balance equation with the Newton iteration method, the nonlinear parameters of the percolation model are updated step by step with the use of average formation pressure, and the gas–water two-phase model is linearized through successive iterations to obtain the semi-analytical solution of the model. The accuracy of the model was verified using a comparison with the results of commercial numerical simulation software and field application, the gas–water two-phase productivity prediction curve was obtained, and the influence of sensitive parameters on productivity was analyzed. The results show that: (1) the semi-analytical solution method can efficiently deal with the gas–water two-phase nonlinear seepage problem and obtain the productivity prediction curve of carbonate gas wells rapidly and (2) the water production of the carbonate gas reservoir seriously affects the productivity of gas wells. During the development process, the production pressure difference should be reasonably controlled to reduce the negative impact of stress sensitivity on productivity performance.

Overview of Numerical Analysis and Optimization Methods for Eddy Current Retarders

Aiming at the analysis and optimization of eddy current retarder, this paper reviews the development of numerical analysis based on finite element method. The characteristics of finite element method and the application of numerical method in the analysis of eddy current retarder are briefly introduced. In terms of algorithm, the different applications of multi-objective genetic algorithm, robustness principle, Taguchi algorithm and Rogowski method in the analysis of important parameters of eddy current retarder are introduced and summarized; In terms of software, the application of commercial software in magnetic field and temperature field is briefly introduced; In industrial practice, the development of numerical simulation methods in the research of braking torque is introduced. On the basis of reviewing the numerical analysis and optimization methods of eddy current retarder, the future of its digital design is prospected.

Structural, electronic, and thermal properties of hydrogenated silicon carbide with thermal heat transfer application in nanoscale metal oxide semiconductor field-effect transistor

In this paper, studies of thestructural electronic and thermal properties of hydrogenated silicon carbide (6H-SiC) have been carried out applying first-principles calculations based on the linearized augmented plane wave method. A two-dimensional numerical model is proposed for 6H-SiC Metal oxide semiconductor field-effect transistor (MOSFET) to investigate the heat transfer on the transistor characteristics using a commercial software application. Structural and electronic results show 6H-SiC lattice parameters (a) and (c) of 3.0817Å and 15.1179Å respectively and an indirect band gap about 2.015 eV. The thermodynamic calculations show that the heat capacity of 6H-SiC is stable at higher temperature. Moreover, the single-phase-lag heat conduction model is used to calculate the temporal temperature distribution in centerline of 6H-SiC MOSFET. The temperature values obtained are 300K-360K at time 7 ps and 12 ps respectively.

Using low-cost UAVs in post-mining exploration - a case study

The use of low-cost, unmanned aerial vehicles (UAVs) has been growing in many sectors. Due to the sufficient accuracy of the products acquired from UAVs, this technology has also been applied in geodesy and remote sensing. It results from many factors: the low prices of UAVs and the availability of different sensors and software applications, which allows for simple data processing. Due to the required high accuracy, the inventory of a mine is usually performed with the use of conventional surveying techniques, such as tacheometry. This paper discusses the possibilities of applying low-cost UAVs to inventory open-cut mining. Using Phantom 3 Professional equipped with a factory-made camera, RGB photographs were acquired, which were then processed using three commercial software applications: Pix4D, 3D Survey and Agisoft Metashape. Different algorithms for image orientation (Structure-from-Motion, SfM) and dense point generation (Multi-View Stereo, MVS) were implemented for each of those applications, which influenced the accuracy of the final products. The results of the experiments proved that the highest accuracy in terms of photograph processing was achieved using the Pix4D software. The mean difference between the DTM (Digital Terrain Model) generated from surveys, and the DTM generated from photographs using Pix4D was equal to 0.106 m. This paper compared the DTMs and the DSMs (Digital Surface Models) generated by the selected software applications. The models generated with the use of Pix4D were assumed as a reference. According to the analysis of the DTMs and the DSMs, the smallest differences were obtained for the models generated by Pix4D and Agisoft Metashape. They equalled 0.080 m for the DTM and 0.246 m for the DSM. The differences between the DSMs generated by Pix4D and 3D Survey were two times bigger; the differences between the DTMs generated by those software applications were six times bigger. The differences between the models may result from the presence of vegetation and escarpments at the edges of the test site and different algorithms for generating dense point clouds applied in particular applications.

Technical Note: Open‐Source Software for Water‐Level Measurement in Images With a Calibration Target

AbstractImage‐based water level measurements offer data quality assurance through visual verification that no other method can provide. GaugeCam Remote Image Manager‐Educational 2 (GRIME2) is a mature, open‐source commercial friendly software application that automatically detects and measures water level in laboratory and field settings. The software relies on a dedicated target background for water line detection and image calibration. The system detects the change in pixel gray scale values associated with the intersection of the water level at the target surface. Fiducials on the target background are used to precisely create a pixel to real world coordinate transfer matrix and to correct for camera movement. The presented software package implements the algorithms and automates the water level measurement process, annotation of images with result overlays, creation of animations, and output of results to files that can be further analyzed in a spreadsheet or with R or Python. These GRIME2 features are illustrated using imagery from a coastal marsh field site. Tradeoffs between workflow and algorithm complexity and ease of use are discussed and future improvements are identified with the intention that this Findable, Accessible, Interoperable, and Reusable‐inspired software can be adopted, modified and improved by the user community. While image resolution, quality and other factors associated with field deployment (e.g., water surface roughness, sun glare, shadows, and bio‐fouling) will have an impact on measurement quality, previous controlled laboratory testing that did not manifest these issues showed potential for accuracy of ±3 mm (Gilmore et al., 2013, https://doi.org/10.1016/j.jhydrol.2013.05.011).

CT-Based Commercial Software Applications: Improving Patient Care Through Accurate COPD Subtyping.

Chronic obstructive pulmonary disease (COPD) is heterogenous in its clinical manifestations and disease progression. Patients often have disease courses that are difficult to predict with readily available data, such as lung function testing. The ability to better classify COPD into well-defined groups will allow researchers and clinicians to tailor novel therapies, monitor their effects, and improve patient-centered outcomes. Different modalities of assessing these COPD phenotypes are actively being studied, and an area of great promise includes the use of quantitative computed tomography (QCT) techniques focused on key features such as airway anatomy, lung density, and vascular morphology. Over the last few decades, companies around the world have commercialized automated CT software packages that have proven immensely useful in these endeavors. This article reviews the key features of several commercial platforms, including the technologies they are based on, the metrics they can generate, and their clinical correlations and applications. While such tools are increasingly being used in research and clinical settings, they have yet to be consistently adopted for diagnostic work-up and treatment planning, and their full potential remains to be explored.

A generalized numerical framework for solving cocurrent and counter-current membrane models for gas separation

Membrane separation has become a panacea for various scientific and engineering problems, including water treatment, gas separation, purification, hemodialysis, and drug delivery. Modeling and simulation of such systems are necessary for the design, analysis, and optimization of membrane separation processes. Despite numerous studies, an efficient numerical solution of such systems is an open problem, especially when speed and reliability matter. In this study, a generalized numerical framework for solving cocurrent and counter-current membrane models is proposed, which hinges on a straightforward and reliable Gauss-Seidel method with successive over-relaxation. The results confirm the speed and reliability of the proposed algorithm, while it is validated by the experimental data for the separation of a mixture of CH4 and CO2, as well as a mixture of He, CO2, N2, and CH4. The permeate outlet pressure estimation error can be reduced to any value as low as ∼10−14%, while the computational time on a personal laptop is not more than 4.5 s. This algorithm can be readily implemented in various programming languages and commercial software applications.

A modeling methodology to study the tributary-junction alluvial fan connectivity during a debris flow event

Abstract. Traditionally, interactions between tributary alluvial fans and the main river have been studied in the field and in the laboratory, giving rise to different conceptual models that explain their role in the sediment cascade. On the other hand, numerical modeling of these complex interactions is still limited because the broad debris flow transport regimes are associated with different sediment transport models. Even though sophisticated models capable of simulating many transport mechanisms simultaneously exist, they are restricted to research purposes due to their high computational cost. In this article, we propose a workflow to model the response of the Crucecita Alta alluvial fan in the Huasco Valley, located in the Atacama Desert, Chile, during an extreme storm event. Five different deposits were identified and associated with four debris flow surges for this alluvial fan. Using a commercial software application, our workflow concatenates these surges into one model. This study depicts the significance of the mechanical classification of debris flows to reproduce how an alluvial fan controls the tributary–river junction connectivity. Once our model is calibrated, we use our workflow to test if a channel is large enough to mitigate the impacts of these flows and the effects on the tributary–river junction connectivity.

A Comparative Study of the Application of Different Commercial Software for Topology Optimization

Topology optimization (TO) has been a popular design method among CAD designers in the last decades. This method optimizes the given design domain by minimizing/maximizing one or more objective functions, such as the structure’s stiffness, and at the same time, respecting the given constraints like the volume or the weight reduction. For this reason, the companies providing the commercial CAD/FEM platforms have taken this design trend into account and, thus, have included TO in their products over the last years. However, it is not clear which features, algorithms, or, in other words, possibilities the CAD designers do have using these software platforms. A comparative study among the most applied topology optimization software was conducted for this research paper. First, the authors developed an online database of the identified TO software in the form of a table. Interested CAD designers can access and edit its content, contributing in this way to the creation of an updated library of the available TO software. In addition, a deeper comparison among three commercial software platforms—SolidWorks, ANSYS Mechanical, and ABAQUS—was implemented using three common case studies—(1) a bell crank lever, (2) a pillow bracket, and (3) a small bridge. These models were designed, optimized, and validated numerically, as well as compared for their strength. Finally, the above software was evaluated with respect to optimization time, optimized designs, and TO possibilities and features.

Implementation of a Graphic Interface Development Tool for Prolog

&#x0D; &#x0D; &#x0D; The work examines the current problems of the spread of use of logical programming in the development of commercial multi-platform software applications, tools for convenient development of a modern graphical interface to the logical programs. Libraries with similar concepts of use have been analyzed and described. The purpose of the proposed concept, which is implemented as an open source library, is described, and the advantages of the proposed tools over similar existing tools are indicated. The main feature and advantage of the proposed concept is the implementation of Prolog business logic and interface by means of JavaScript usage of child processes. The proposed concept of interface to Prolog takes full advantage of the possibilities provided by async await. A framework library has been created for the use of Logic Programming in graphical interface development without losses in the application performance. The paper describes the proposed concept and the developed framework (library). The ways to further improve the possibilities for expanding the purpose of the implemented library were identified. The directions of further simplification for programmers of integration of the graphic interface to logical programs have been defined. A significant advantage of the proposed tool is the easy-to-use functions to wrap and control the correctness of requests to the Prolog. The main goal of the library is to create an environment for the Prolog developers where they can create any type of software, which is meant to be user friendly, fast, and cross platform using modern and flexible. This concept also tries to solve disadvantages and architectural problems that were found in other libraries. The safety of library functionality has been analyzed. The concept of potential horizontal application scalability is described. Conclusions and future of libraries were introduced, in which the usage of TypeScript for type-safety and avoidance of run-time errors is mentioned. Overall, the library extends the use of Prolog beyond logical programming and takes a leap forward in its progress.&#x0D; &#x0D; &#x0D;

Geophysical investigation of dambo groundwater reserves as sustainable irrigation water sources: case of Linthipe sub-basin

The geophysical investigation of dambo groundwater reserves using electrical resistivity methods was conducted in Linthipe 4B sub basin in Central region of Malawi. With the increasing over-utilization of shallow wells in dambos for smallholder irrigation, this study was carried out to investigate whether dambo groundwater reserves could serve as sustainable irrigation water sources and to examine the aquifer characteristics in Linthipe sub basin. Vertical Electrical Sounding (VES) points were established in the basin using the Schlumberger configuration array. Data was analysed using IPI2win and Surfer software applications. Contrary to other commercial software applications which are costly for government departments when analysing geophysical data, partial curve matching and one dimensional (1-D) computer iteration techniques were used to interpret the VES curves and the pseudo-cross section resistivity profiles due to their simplicity and cost-effectiveness. The study has revealed that the aquifer properties in the basin are exceptionally variable in terms of state of weathering, depth, thickness, lithology, aquifer recharge configuration, geologic material and hydraulic gradients. These variations showed that the shallow wells in the basin have significant fractures suggesting high water potential for climate smart irrigation usage in the study area. The potential groundwater zones for climate smart irrigated farming were detected at VES 1, 2, 3, 4, 5 and 6 noted by low aquifer resistivity with high values of aquifer thickness. However, VES points, 7, 8 and 9 were likely to be zones of low water bearing potential because they had high values of aquifer resistivity with low aquifer thickness. The findings also validated the effectiveness, timeliness, and efficiency of using vertical electrical resistivity technique in exploring groundwater for irrigation. The results from this study have highlighted that feasible shallow well depth for a sustainable irrigation system is a function of geologic resistance and aquifer thickness when the geologic material has low resistance and broader thickness. This study noted that knowledge of aquifer recharge rates in dambos is required in order to effectively control abstraction rates for sustainable irrigation in basins. There is a need to promote the usage of geophysical studies, reforestation, river basin management trainings and aquifer recharge technologies in exploring sites for shallow well development for irrigation. The study further recommends the usage of geographical information systems (GIS) and Artificial Intelligence (AI) in improving the results of groundwater monitoring studies in Malawi.

Radiomics in Oncology: A Practical Guide

Radiomics refers to the extraction of mineable data from medical imaging and has been applied within oncology to improve diagnosis, prognostication, and clinical decision support, with the goal of delivering precision medicine. The authors provide a practical approach for successfully implementing a radiomic workflow from planning and conceptualization through manuscript writing. Applications in oncology typically are either classification tasks that involve computing the probability of a sample belonging to a category, such as benign versus malignant, or prediction of clinical events with a time-to-event analysis, such as overall survival. The radiomic workflow is multidisciplinary, involving radiologists and data and imaging scientists, and follows a stepwise process involving tumor segmentation, image preprocessing, feature extraction, model development, and validation. Images are curated and processed before segmentation, which can be performed on tumors, tumor subregions, or peritumoral zones. Extracted features typically describe the distribution of signal intensities and spatial relationship of pixels within a region of interest. To improve model performance and reduce overfitting, redundant and nonreproducible features are removed. Validation is essential to estimate model performance in new data and can be performed iteratively on samples of the dataset (cross-validation) or on a separate hold-out dataset by using internal or external data. A variety of noncommercial and commercial radiomic software applications can be used. Guidelines and artificial intelligence checklists are useful when planning and writing up radiomic studies. Although interest in the field continues to grow, radiologists should be familiar with potential pitfalls to ensure that meaningful conclusions can be drawn. Online supplemental material is available for this article. Published under a CC BY 4.0 license.

Web tabanlı CSRS-PPP uygulamasının farklı uydu sistemleri üzerindeki performansı

Küresel Navigasyon Uydu Sistemleri’nden (Global Navigation Satellite Systems, GNSS) elde edilen veriler değerlendirilirken bilimsel/akademik, ticari yazılımlar ve kullanımı gittikçe artan web tabanlı uygulamalar kullanılmaktadır. GNSS veri değerlendirme stratejisi mutlak ve bağıl olarak temelde ikiye ayrılmaktadır. Kullanımı artan web tabanlı servisler temelde mutlak yöntemi kullanan ya da bağıl yöntemi kullananlar olarak ayrılmaktadır. Hassas mutlak nokta konumlama (Precise Point Positioning, PPP) yöntemi tek bir alıcı ile cm mertebesinde konum belirlemeyi mümkün kılmakta ve kullanıcılar açısından oldukça pratik olarak konum belirleme imkânı sunmaktadır. PPP yönteminin gerçek zamanlı uygulamaları da gittikçe yaygınlaşmakta, bu durum kullanıcılar açısından hem zaman hem de maliyet tasarrufu imkânları sunmaktadır. Konum belirleme tarafında bu gelişmeler yaşanırken, ilk ortaya çıktığı günden bu yana askeri amacının yanında insanoğlunun hayatına her alanda giren Küresel Konumlama Sistemi (GPS), diğer sistemlerin de (GLONASS, BeiDou, QZSS, IRNSS vb.) devreye alınması ile oldukça yaygınlaşmıştır. Bugün artık GNSS olarak hayatımızın içinde daha fazla var olmaya devam etmektedir. Çeşitli ülkeler tarafından geliştirilen ve kullanılan uydu sistemlerinin dünya üzerine yayılmış bulunan Uluslararası GNSS Servisi (International GNSS Service, IGS) istasyonlarında veri toplanarak, konum belirleme sürecine dahil edilmesi ile The Multi-GNSS Experiment (MGEX) projesi geliştirilmiş ve belirlenen istasyonlarda, tüm uydu sistemlerinden veri toplanmasına başlanılmıştır. Bu çalışmada, web tabanlı CSRS-PPP uygulaması ile dünya üzerinde dağılmış 5 MGEX istasyonunda toplanan 10 günlük GNSS gözlem verileri değerlendirilmiştir. MGEX projesi kapsamında istasyonlardan gözlem verileri 1 saniyeden 30 saniyeye kadar gözlem aralığında ve çoklu uydu sistemlerinden (GPS, GLONASS, Galileo, QZSS, NAVIC, BeiDou, SBAS) veri toplama imkânı bulunmaktadır. CSRS-PPP uygulamasının değerlendirme stratejisinde kullandığı GPS ve GLONASS (GPS, GLONASS ve GPS+GLONASS) uydu sistemleri ile 1 ile 30 saniye aralıklı toplanmış gözlem verilerinin en az 15 dakikadan 24 saate kadar gözlem aralığında ve farklı iyonosferik koşullardaki performansı değerlendirilmiş ve yorumlanmıştır.

Evaluation of the efficiency of a heat recovery steam generator via computational simulations of off-design operation

This work investigates the flow and heat transfer on the gas side of a heat recovery steam generator. During the operation of a power plant, off-design conditions that significantly impact the steam generator efficiency, caused by variations in the gas flow, corrosion and fouling of tube walls, may be encountered. In addition, passages around the heat exchanger modules develop along the equipment lifetime, allowing the bypass of flowing gas into zones of the boiler of low heat transfer effectiveness. These issues are here addressed via computational simulations, using a commercial software application for solving the mass, momentum, and energy conservation equations. The boiler geometry and the boundary conditions for the simulations are taken from a real, typical industrial heat recovery steam generator fed by gas turbines exhaust gases. Flow turbulence is modeled using the k- $${\epsilon}$$ model, and heat exchanger modules are considered as porous media, through which the exhaust gases flow while supplying heat to the water. The water flow properties are specified from process data. Numerical results for thirteen realistic off-design conditions are compared to those for the boiler normal operation point. It is found that the cases considering deviation of gas to the trapdoors and lateral passages have the greatest impact on the boiler efficiency. Results indicate an efficiency drop from 86% for the base case to 48% for the case with gas deviations. In addition, a reduction in the gas flow or the plugging of the low-pressure economizer tubes may decrease the boiler efficiency by more than 10% points.