Computational modeling of degradation process of biodegradable magnesium biomaterials

Despite the advantages of using biodegradable metals in implant design, their uncontrolled degradation and release remain a challenge in practical applications. A validated computational model of the degradation process can facilitate the tuning of implant biodegradation by changing design properties. In this study, a physicochemical model was developed by deriving a mathematical description of the chemistry of magnesium biodegradation and implementing it in a 3D computational model. The model parameters were calibrated using the experimental data of hydrogen evolution by performing a Bayesian optimization routine. The model was validated by comparing the predicted change of pH in saline and buffered solutions with the experimentally obtained values from corrosion tests, showing maximum 5% of difference, demonstrating the model's validity to be used for practical cases

Pengaruh Media Pembelajaran Berbantuan Website Google Sites Terhadap Hasil Belajar Siswa Materi Segiempat dan Segitiga

Penelitian Ini bertujuan untuk mengetahui perbedaan hasil belajar siswa yang dibelajarkan dengan menggunakan media pembelajaran berbantuan website google sites dengan hasil belajar siswa yang dibelajarkan dengan menggunakan media pembelajaran powerpoint. Metode penelitian ini adalah penelitian eksperimen. Desain penelitian yang digunakan adalah posttest only control group design. Teknik pengambilan sampel dilakukan dengan teknik simple sampling random, sampel yang digunakan berjumlah 2 kelas. Berdasarkan hasil pengambilan, kelas VII-4 terpilih sebagai kelas eksperimen yang dibelajarkan menggunakan media berbantuan website google sites sedangkan kelas VII-1 sebagai kelas yang dibelajarkan menggunakan media powerpoint. Instrumen pada penelitian ini menggunakan tes hasil belajar yang berbentuk uraian/essay. Pengujian hipotesis dengan menggunakan uji-t  yang menghasilkan thitung = 4,637, setelah dibandingkan dengan ttabel = t0,95:48 = 2,0106. Diperoleh thitung> ttabel yaitu 4,637 > 2,0106, maka H0 ditolak. Hasil penelitian ini dapat disimpulkan bahwa terdapat perbedaan hasil belajar siswa yang dibelajarkan dengan menggunakan media pembelajaran berbantuan website google sites dan hasil belajar siswa yang dibelajarkan dengan menggunakan media pembelajaran powerpoin

Corrosion protection mechanisms of carbon steel by an epoxy resin containing indole-3 butyric acid modified clay

This work is an extension of studies into the mechanisms of corrosion protection of mild steel by an epoxy resin containing organically modified clay (Hang et al. [1]; Truc et al. [2]). In a previous study (Truc et al. [2]), it was shown that indole-3 butyric acid (IBA)-modified clay improved the corrosion performance of epoxy. In the present study, it was shown that the IBA is an anodic inhibitor and its efficiency was about 93%. Exfoliation and dispersion of the IBA-modified clay in the epoxy coating were checked by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The improvement of the corrosion performance of the epoxy coating containing IBA-modified clay by comparison with pure epoxy coating was confirmed for a low film thickness (10 μm). Local electrochemical impedance measurements performed on scratched samples revealed the inhibitive action of IBA at the carbon steel/coating interface. It was shown that the inhibitor release from the IBA-modified clay was favoured for high pH values. Thus, in neutral media, the corrosion process which induces a local increase of pH will increase the self-healing performance

Evaporation of Electrolyte During SVET Measurements: The Scale of the Problem and the Solutions

The objective of this work is to investigate the scale of the effect of spontaneous solution evaporation during SVET (Scanning Vibrating Electrode Technique) measurements and demonstrate how it biases the final results. When SVET maps are continuously acquired for more than several hours, the measured currents are smaller than expected. This is attributed to solvent (typically water) evaporation which leads to an increase in solution conductivity over time. If this is not considered when converting the measured potential differences into the local current densities, the SVET results display currents smaller than the true ones. Here, this effect is studied with a platinum disk electrode as source of a constant current and a model corroding system consisting of the AA2024/CFRP galvanic couple. Corrective actions are proposed to mitigate the problem, either in the experimental set‐up or as numerical correction

Uses of scanning electrochemical microscopy in corrosion research

This paper provides a brief review of a relatively new technique, namely scanning electrochemical microscopy (SECM), and its applications in measuring, characterising and evaluating corroding systems. Localized corrosion processes and electrochemical activity distributions in surfaces can thus be investigated in real time with high spatial resolution. The SECM is a unique near-field scanning technique that is electrochemically integrated as to detect chemical and electrochemical activities in electrochemical heterogeneous systems such as those operating in corrosion research. The SECM can be used in a variety of ways, which can be broadly classified into amperometric and potentiometric modes, depending on the type of the sensing probe, namely an ultramicroelectrode (UME) and an ion-selective microelectrode, respectively. The operation modes of the instrument are described together with typical experiments selected to illustrate their application in sensing localised corrosion

In situ surface film evolution during Mg aqueous corrosion in presence of selected carboxylates

Mechanisms of inhibition of Mg aqueous corrosion in presence of chloride by sodium salicylate (Sal), 2,5-pyridinedicarboxylate (PDC) and fumarate (Fum) were studied by in situ Raman spectroscopy, ATR-FTIR, GD-OES and hydrogen collection. In situ detected surface films were composed by Mg(OH)2 nano-crystals and included inhibitors. All carboxylates significantly modified Mg(OH)2 growth kinetics as well as pevented chloride incorporation in the film. Vibrational spectra of the surface films demonstrated specific interactions between the carboxylates and the surface: adsorption of Sal and Fum on the oxide/hydroxide, precipitation of coordination polymer by PDC, dissolution of iron inclusions via formation of iron-Sal soluble complexes.publishe

Получение фотоспектральных данных с использованием беспилотного комплекса авиационного спектрометрирования

Study of the Earth’s surface objects reflectance characteristics with unmanned aerial vehicles is one of the most actual remote sensing trends. Aim of this work was to develop a method for obtaining of photospectral data using unmanned aerial spectrometry vehicle.An adaptation of the cameras spatial resolution evaluating technique based on a specialized target photographic fixation was proposed. A method for synchronizing of the camera and spectrometer of the videospectral device was also proposed. It was based on an experiment with spectra and screen images recording. Different colors were sequentially displayed on the screen. The percentage contribution of each of colors to the “mixed” spectra was calculated. So the out-of-sync time estimation became possible. In addition the work proposed the method for combining images and spectra with their merging into photospectral images. The method allows to consider the aircraft displacement when linking the spectrometer field of view to the RGB image. The way for photospectral images combining based on the images key points detectors was also proposed.Spatial resolutions for 3 aerial vehicle cameras were obtained. The study showed that the spatial resolution decrease of Zenmuse H20T caused by the device carrier movement with a speed of up to 5 m/s can be ignored. The videospectral device camera and spectrometer out-of-sync time was evaluated. An automatic merging of a set of images using key points detection was made. The spectrometry areas were linked to the panoramic image. The reflectance coefficients were obtained for each of the areas in the range of 350–900 nm. The areas to image linking accuracy was 84.9 ± 11.6 %.A discrepancy between the angular spatial resolution values got experimentally and theoretically was revealed as a result of the cameras spatial resolution evaluating. This indicates the importance of the imaging equipment spatial resolution experimental evaluation. The videospectral device spectrometer and observation camera out-of-sync time evaluation made it possible to correct the data recording time. This led to the timing error standard deviation reduction from 142 ms to 15 ms. The way for the unmanned aerial spectrometry vehicle data obtaining in a photospectral representation was developed. The proposed methods and techniques can be used in similar unmanned systems.Исследование отражательных характеристик объектов на поверхности Земли с использованием беспилотных летательных аппаратов является одним из развивающихся направлений в дистанционном зондировании Земли. Целью работы являлась разработка способа получения фотоспектральных данных с использованием беспилотного комплекса авиационного спектрометрирования.Предложена адаптация методики определения пространственной разрешающей способности камер на основе фотофиксации специализированной миры. Также предложен способ синхронизации камеры и спектрометра видеоспектрального комплекса, основанный на проведении эксперимента по регистрации спектров и изображений экрана, где последовательно отображаются различные цвета. Предложен способ комбинирования изображений и спектров с объединением их в единое фотоспектральное изображение. Способ позволяет учитывать смещение летательного аппарата при привязке поля зрения спектрометра к изображению. Предложен способ объединения фотоспектральных изображений, основывающийся на сшивке изображений по особым точкам.Получены угловые разрешающие способности для 3 камер из состава беспилотного комплекса. Показано, что при движении беспилотного комплекса со скоростью до 5 м/с ухудшение разрешающей способности камеры Zenmuse H20T, вызванное движением носителя аппаратуры, можно не учитывать. Определено время рассинхронизации работы камеры и спектрометра из состава видеоспектрального комплекса. Проведена автоматическая сшивка ряда изображений по особым точкам с привязкой к сшитому изображению областей спектрометрирования (относительная точность привязки к изображению – 84,9 ± 11,6 %). Для каждой из областей спектрометрирования получены коэффициенты спектральной яркости в диапазоне 350–900 нм.В исследовании выявлено расхождение экспериментальных и теоретических значений углового пространственного разрешения, что свидетельствует о важности проведения экспериментальной оценки пространственного разрешения съёмочной аппаратуры. Определение времени рассинхронизации спектрометра и обзорной камеры видеоспектрального комплекса позволило осуществить коррекцию времени регистрации данных, что привело к уменьшению среднеквадратичной величины ошибки синхронизации со 142 мс до 15 мс. Разработан способ получения данных БЕКАС в фотоспектральном представлении

Plasmodium Falciparum Gene Polymorphisms Pfmdr1 N86Y and Drug Self Medication in the Endemic Areas of West Papua Region, Indonesia

West Papua Province of Indonesia has the highest malaria incidence (5.1%) and prevalence (12.5%) and the population is used to Self medication (2.8%)