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Influence of additional strut elements in 3D Re-Entrant auxetic unit cells on the damage and energy absorption properties
Full text linkBackground Geometric parameter optimization, novel design, and mechanism modeling of auxetic materials have been widely studied. However, manipulating the topology of the 3d printed auxetic unit cells and its influence on the damage have yet to be explored. Objective This study aims to characterize the energy absorption properties and damage mechanisms of the modified auxetic unit cells. Methods In the current study, bending-dominated re-entrant auxetic unit cells (Cell0), torsion-dominated auxetic unit cells with cross elements (CellX), buckling-dominated auxetic unit cells with vertical elements (CellB), and bending-dominated auxetic unit cells with panels (CellW) have been fabricated by FDM (Fused deposition modeling). Uniaxial compression testing of the PLA (Polylactic acid) unit cells has been carried out, and a camera has observed their deformation behavior. SR- µCT (Synchrotron radiation microtomography) and an SEM (Secondary electron microscope) accomplished further damage analysis of the struts. Results Adding additional struts hinders the lateral shrinking of the re-entrant auxetics, and re-entrant auxetic unit cells with cross elements have shown higher energy absorption capacity and efficiency than others. The struts’ damage has been governed by building direction, printed material, and strut dimensions. Intra-layer and interlayer fracture of the layers and rupture in the circumferential direction of the PLA struts have been observed in the SR- µCT slices. Conclusions By additional struts, it is possible to fabricate complex auxetic structures with enhanced energy absorption properties, but their inherent characteristics dominate the damage of the struts in the auxetic unit cells
Atomically dispersed zeolite-supported rhodium complex: Selective and stable catalyst for acetylene semi-hydrogenation
Full text linkSupported rhodium catalysts are known to be unselective for semi-hydrogenation reactions. Here, by tuning the electronic structure of supported mononuclear rhodium sites determined by the metal nuclearity and the electron-donor properties of the support, we report that atomically dispersed HY zeolite-supported rhodium with reactive acetylene ligands affords a stable ethylene selectivity > 90 % for acetylene semi-hydrogenation at 373 K and atmospheric pressure, even when ethylene is present in a large excess over acetylene. Infrared and X-ray absorption spectra and measurements of rates of the catalytic reaction complemented with calculations at the level of density functional theory show how the catalyst performance depends on the electronic structure of the rhodium, influenced by the support as a ligand that is a weak electron donor
Predicting world electricity generation by sources using different machine learning algorithms
No full textElectrical energy plays a crucial role in both social and economic growth. It is thought to be an essential part of industrial manufacturing. In addition to its contribution to industry, electrical energy is essential for addressing the needs of people on a daily basis. Therefore, electricity generation prediction is crucial for accurate electricity planning and energy usage, with machine learning (ML) algorithms becoming popular for their ability to extract complex relationships and make precise predictions. With the data from the period 2000-2022, this study predicts world electricity generation for 2023 by different energy sources employing seven different ML algorithms, namely long short-term memory (LSTM), artificial neural network (ANN), linear regression (LR), support vector regression (SVR), decision tree regression (DTR), random forest regression (RFR) and eXtreme gradient boosting (XGBoost). The algorithms were also contrasted in the study, and it was discovered that LSTM produced the most accurate predictions. [Received: June 16, 2023; Accepted: August 19, 2023
Explainable ensemble learning predictive model for thermal conductivity of cement-based foam
No full textCement-based foam has emerged as a strong contender in sustainable construction owing to its superior thermal and sound insulation properties, fire resistance, and cost-effectiveness. To effectively use cement-based foam as a thermal insulation material, it is important to accurately predict its thermal conductivity. The current study aims at coining an accurate methodology for predicting the thermal conductivity of cement-based foam using state-ofthe-art machine learning techniques. A comprehensive experimental dataset of 504 data points was developed and used for training ensemble learning models including XGBoost, CatBoost, LightGBM and Random Forest. The independent variables of this dataset affecting the thermal conductivity are the cast density, percentage of pozzolan, porosity, percentage of moisture, and duration of hydration in days. Using the Isolation Forest algorithm proved effective in detecting and eliminating outliers in the dataset. All the ensemble learning techniques explored in this study achieved superior predictive accuracy with a coefficient of determination greater than 0.98 on the test dataset. The influence of the input features on the thermal conductivity was visualized using the SHapley Additive exPlanations (SHAP) approach and individual conditional expectation (ICE) plots. The cast density had the greatest effect on thermal conductivity. The explainable machine learning models demonstrated superior accuracy, efficiency, and reliability in estimating the thermal insulation of cement-based foam, opening the door for wider acceptance of this material in sustainable energy efficient construction
The Fluid Behavior of a Non-Orifice TLCD under Harmonic Excitation: From Experiments to Analytical Solution
No full textTuned liquid column damper (TLCD) is a well-known liquid damper designed to absorb the vibration of structures used in many applications, such as high-story buildings, wind turbines, and offshore platforms, requiring an accurate mathematical determination of the liquid level to model the TLCD structure system motion. The mathematical model of a TLCD is a nonlinear ordinary differential equation, unlike the structure, due to the term containing a viscous damping coefficient, and cannot be solved analytically. In this study, the fluid behavior of a TLCD without an orifice, directly connected to a shaking table under harmonic excitation, was investigated experimentally and a new linearization coefficient was proposed to be used in the mathematical model. First, the nonlinear mathematical model was transformed to a nondimensional form to better analyze the parameter relations, focusing on the steady-state amplitude of the liquid level during the harmonic excitation. The experimental data were then processed using the fourth-order Runge-Kutta method, and a correlation to calculate the viscous damping coefficient was proposed in the dimensionless form. Accordingly, a novel empirical model was proposed for the dimensionless steady-state amplitude of the liquid level using this correlation. Finally, with the help of the proposed correlation and the empirical model, an original linearization coefficient was introduced which does not need experimental data. The nonlinear mathematical model was linearized by using the developed linearization coefficient and solved analytically using the Laplace transform method. The study presents a generalized method for the analytical determination of the liquid level in a non-orifice TLCD under harmonic excitation, using a correlation and an empirical model proposed for the first time in this study, providing a novel and simple solution to be used in the examination of various TLCD structure systems.Scientific and Technological Research Council of Turkiye (TUBITAK) [221M148]; Sakarya UniversityThis research was funded by the Scientific and Technological Research Council of Turkiye (TUBITAK), grant number 221M148, and the APC was funded by Sakarya University
Temporary legal protection measures in the cases regarding the liability and dismissal of the director of limited company and the dissolution
Full text linkLimited şirket müdürlerinin kanundan ve esas sözleşmeden do- ğan yükümlülüklerini kusurlarıyla ihlal etmeleri durumunda şirkete, ortaklara ve şirket alacaklılarına verdikleri zararların tazmini Türk Ticaret Kanunu’nun 553. maddesi uyarınca açılacak sorumluluk dava- sı ile talep edilebilmektedir. Kanunda işaret edilen haklı sebeplerin bulunması hâlinde de şirket ve ortakları ilgilendiren benzeri haksız eylemlere dayanılarak TTK’nın 630. maddesinin ikinci fıkrası uyarın- ca müdürlerin görevden alınmaları, yönetim haklarının ve temsil yet- kilerinin sınırlanması ile aynı Kanun’un 636. maddesinin üçüncü fık- rası gereğince limited şirketin feshi davalarının açılması mümkündür. Söz konusu eylemler nedeniyle doğacak telafisi mümkün olmayan zararlardan kaçınılması için hukuk muhakemesine özgü geçici hukuki koruma tedbirleri hiç kuşkusuz anılan davalar bakımından da uygula- ma alanı bulmaktadır. Her ne kadar limited şirketler özelinde açık bir yasal güvenceye kavuşturulmamış olsa da söz konusu tedbirler; ihtiya ti tedbir, müdürlerin yönetim ve temsil yetkilerinin geçici olarak kaldı- rılması veya sınırlandırılması, şirkete kayyım atanması, delil tespiti ve ihtiyati haciz şeklinde sayılabilir. Çalışmamızda, bir kısmı farklı ka- nunlarda düzenlenen ve niteliği itibarıyla çoğu hukuki duruma uygu- lanabilen genel nitelikteki bu tedbirler limited şirket müdürlerinin so- rumlulukları nedeniyle açılan davalar bağlamında incelenmiştir.In case the directors of limited companies violate their obligations arising from the law and the contract provisions with their faults, com- pensation for the damages they have caused to the company, partners, and company creditors can be demanded through a liability case to be filed according to Article 553 of the Turkish Commercial Code. It is possible to open cases because of the dismissal of the directors, the limi- tation of their management rights and representation powers under the second paragraph of Article 630 of the TCC, and the dissolution of the limited liability company pursuant to the third paragraph of the article 636 of the same Law, based on similar unfair acts concerning the com- pany and its partners where there are justified reasons indicated in the law. Temporary legal protection measures specific to civil procedure to avoid irreparable damages that may arise due to the aforementioned ac- tions undoubtedly find application in the cases concerned as well. Alt- hough there is no clear legal regulation specific to limited liability com- panies, the measures in question can be counted as the interim injunction, temporary removal or limitation of the management and rep- resentation powers of the directors, the appointment of a judicial factor to the company, determination of evidence, and the lien. In our study, these general measures, some of which are regulated by different laws and can be applied to most legal situations, are examined in the context of the cases due to the responsibilities of limited company directors
Techno-economic analysis of grid-connected PV and second-life battery systems for net-zero energy houses
No full textNet-zero energy houses (ZEHs) rely on energy-efficient building design and the incorporation of distributed generation and battery energy storage units. Nevertheless, two primary concerns arise: high investment cost of these units and harmful environmental impact of batteries. Using second-life batteries can overcome these concerns by reducing the cost of photovoltaic (PV)- battery systems and mitigating the adverse environmental effects of battery supply chain. Therefore, this study examines the techno-economic feasibility of utilizing second-life batteries for PV storage in grid-connected ZEHs in two provinces (Antalya and Istanbul) of Türkiye. First, two ZEHs with air-to-water heat pumps are designed using BEopt software. Next, the optimal PVbattery capacity in the ZEHs is determined using HOMER Grid software. Finally, the economic feasibility of using three types of batteries (new lead acid, new Li-ion, second-life Li-ion) in ZEHs is compared. The optimal design for a typical ZEH comprises a 5.92 kW PV and an 8.96 kWh second-life Li-ion battery in Istanbul (northern Türkiye), yielding an NPV of 16,402. The results indicate that using second-life Li-ion increases the NPV of PV-battery systems by 15 % in Istanbul and by 21 % in Antalya. The feasible system configuration categories for Türkiye’s economic and climatic conditions are ranked as: PV-second-life Li-ion > PV-no battery ? PV-new Li-ion > PV-new lead acid. Incentivizing the use of second-life batteries due to their environmental contribution could result in an even higher NPV increase
Determination of amino acids and other clinically significant molecules at surfactant-based electrochemical sensors and biosensors
No full textSurfactants (surface-active agents) are substances that, when used in very small amounts, significantly reduce the surface tension of water. Surfactants are usually organic compounds with hydrophobic groups (water repellent) that play the tail and hydrophilic groups (water absorbent) that play the role of head, so they dissolve in organic solvents and water according to their molecular structure. They can be classified as anionic, cationic, amphoteric, and nonionic. Amino acids are the primary building blocks of proteins, and extensive research has been dedicated to amino acids and biologically important compounds. Many methods have been developed for detecting amino acids and biologically important compounds based on high-performance liquid chromatography, colorimetry, fluorimetry, molecular imprinted polymer methods, capillary electrophoresis, etc. Hence, this chapter will deal with the electrochemical sensors and biosensors for detecting amino acids and biologically important compounds. © 2024 Elsevier Inc. All rights reserved
Almanya’da yüksek nitelikli göçmenlerin gündelik hayat deneyimleri ve baş etme süreçleri
Full text linkAlmanya’da Türkiye kökenli göçmenlere yönelik olumsuz tutumlar, toplumda kurulan ilişkileri zedelemekte ve yükselen gündelik hayat ayrımcılığının temelini teşkil etmektedir. Türkiye-Almanya arası göç dalgalarından birini de akademik kaygılarla göç eden doktora öğrencileri oluşturmaktadır. Çalışma kapsamında, Berlin’e doktora eğitimleri için gitmiş ve sahip oldukları sosyal-kültürel sermaye ile yüksek nitelikli göçmen statüsünde kabul edilebilecek 10 katılımcı ile yarı yapılandırılmış mülakat yapılarak, öğrencilerin gündelik hayat deneyimleri ve bu doğrultuda geçirdikleri baş etme süreçleri nitel araştırma yöntemlerinden içerik analizi ile değerlendirilmiştir. Bu doktora öğrencileri, kendilerine özgü göç amaç ve koşulları ile Almanya’nın en büyük azınlığını oluşturan diğer göçmen kuşaklardan farklılaşmaktadırlar. Bütün bu farklılaşmaya rağmen gündelik hayat deneyimlerinin, algıladıkları kalıp yargıların azınlık toplumunun üyeleri ile benzerlikler gösterdiği gözlemlenmektedir. Öte yandan baş etme süreçleri göz önüne alınırsa onlardan ayrışmaktadırlar. Bu aktörlerin deneyimleri, algıladıkları kalıp yargılarla geliştirdikleri taktikleri ve bu bağlamda kendisini gösteren aidiyet süreçleri makalenin ana sorunsalını oluşturmaktadır
Parteipolitische neutralität von amtsträgern und freie meinungsäußerung
No full textEin eigenständiges Rechtsgebiet erblickt das Licht der Welt: das öffentlich rechtliche Äußerungsrecht bzw. das Äußerungsrecht von Hoheitsträgern.1 Die Vielzahl der prozessualen Entscheidungen der letzten Jahre auf diesem Gebiet gaben dafür den Startschuss, denn sie haben ein großes Echo hervorgerufen.2 Daher ist die Aktualität und Prüfungsrelevanz3.dieses Themas unbestreitbar und beschäftigt auch die vorliegende Arbeit. Aber was genau ist die parteipolitische Neutralität? Das BVerfG aber auch die Landesgerichte haben in den letzten Jahren mehrfach die Frage zu beantworten gehabt, inwiefern sich staatliche Organe politisch äußern dürfen.4 Wann und wie dürfen Amtsträger am öffentlichen Diskurs teilnehmen? In der Rechtssprechung des BVerfG ist zum Schutze des demokratischen Wettbewerbs die sog. Neutralitätspflicht für Amtsträger bzw