Pengaruh Penambahan Admixture Terhadap Karakteristik Self Compacting Concrete (Scc)

Penelitian ini adalah eksperimen laboratorium yang sifatnya pengenalan terhadap materi SCC.SCC atau Self Compacting Concrete adalah sebuah inovasi dalam teknologi konstruksi betondewasa ini yang menggunakan bahan tambah (admixture) untuk menghasilkan beton berkinerjatinggi. Pada penelitian ini ingin diketahui pengaruh penambahan admixture kimiaSuperplasticizer “Mighty 150 S” dan Retarder “Conplast Dessue Possolit” terhadap karakteristikSCC. Superplasticizer diberikan dalam 3 variasi kadar (1,5%, 2,0%, 2,5%) dengan mengurangikadar air campuran. Metode pengujian SCC dengan Slump-Cone Test pada kondisi segar dantes kuat tekan pada umur 3, 7, dan 28 hari. Hasil penelitian menunjukkan keadaan selfcompactibilitySCC tercapai pada semua kadar Superplasticizer yang diberikan. Tingkatkelecakan aliran (workabilitas) SCC meningkat sesuai penambahan kadar Superplasticizer, dansebaliknya, kekuatan tekan SCC menurun sesuai penambahan kadar Superplasticizer. Kondisioptimal SCC tercapai pada kadar 1,5% Superplasticize

Bioresorbable Materials on the Rise: From Electronic Components and Physical Sensors to In Vivo Monitoring Systems

Over the last decade, scientists have dreamed about the development of a bioresorbable technology that exploits a new class of electrical, optical, and sensing components able to operate in physiological conditions for a prescribed time and then disappear, being made of materials that fully dissolve in vivo with biologically benign byproducts upon external stimulation. The final goal is to engineer these components into transient implantable systems that directly interact with organs, tissues, and biofluids in real-time, retrieve clinical parameters, and provide therapeutic actions tailored to the disease and patient clinical evolution, and then biodegrade without the need for device-retrieving surgery that may cause tissue lesion or infection. Here, the major results achieved in bioresorbable technology are critically reviewed, with a bottom-up approach that starts from a rational analysis of dissolution chemistry and kinetics, and biocompatibility of bioresorbable materials, then moves to in vivo performance and stability of electrical and optical bioresorbable components, and eventually focuses on the integration of such components into bioresorbable systems for clinically relevant applications. Finally, the technology readiness levels (TRLs) achieved for the different bioresorbable devices and systems are assessed, hence the open challenges are analyzed and future directions for advancing the technology are envisaged

Finite-size effects on the dynamic susceptibility of CoPhOMe single-chain molecular magnets in presence of a static magnetic field

The static and dynamic properties of the single-chain molecular magnet [Co(hfac)$_2$NITPhOMe] are investigated in the framework of the Ising model with Glauber dynamics, in order to take into account both the effect of an applied magnetic field and a finite size of the chains. For static fields of moderate intensity and short chain lengths, the approximation of a mono-exponential decay of the magnetization fluctuations is found to be valid at low temperatures; for strong fields and long chains, a multi-exponential decay should rather be assumed. The effect of an oscillating magnetic field, with intensity much smaller than that of the static one, is included in the theory in order to obtain the dynamic susceptibility $\chi(\omega)$. We find that, for an open chain with $N$ spins, $\chi(\omega)$ can be written as a weighted sum of $N$ frequency contributions, with a sum rule relating the frequency weights to the static susceptibility of the chain. Very good agreement is found between the theoretical dynamic susceptibility and the ac susceptibility measured in moderate static fields ($H_{\rm dc}\le 2$ kOe), where the approximation of a single dominating frequency turns out to be valid. For static fields in this range, new data for the relaxation time, $\tau$ versus $H_{\rm dc}$, of the magnetization of CoPhOMe at low temperature are also well reproduced by theory, provided that finite-size effects are included.Comment: 16 pages, 9 figure

Macroscopic fluctuations theory of aerogel dynamics

We consider the thermodynamic potential describing the macroscopic fluctuation of the current and local energy of a general class of Hamiltonian models including aerogels. We argue that this potential is neither analytic nor strictly convex, a property that should be expected in general but missing from models studied in the literature. This opens the possibility of describing in terms of a thermodynamic potential non-equilibrium phase transitions in a concrete physical context. This special behaviour of the thermodynamic potential is caused by the fact that the energy current is carried by particles which may have arbitrary low speed with sufficiently large probability.Comment: final versio

LUT-less Sensorless Control of Synchronous Reluctance Machines using the Locus of Incremental Saliency Ratio Tracking (LIST)

This paper deals with the LUT-less sensorless control of synchronous reluctance (SyR) machines at zero and low speed, where LUT-less stands for avoiding the use of flux-map look-up tables (LUTs) or other pre-determined machine parameters. The new signal-injection based control scheme called the Locus of Incremental Saliency ratio Tracking (LIST) is presented, where a pulsating high-frequency voltage component is used for position tracking and a second rotating signal-injection is dedicated to on-line estimating the incremental saliency ratio. A trajectory of constant incremental saliency ratio is used for torque regulation, resulting in stable control at all operating conditions, including overload. This despite the effect of cross-saturation, which is known to introduce position error and harm the control stability progressively with the load. The proposed scheme is validated experimentally on a 1.1 kW SyR machine test-bench. Alternative LUT-less torque control laws are investigated, and their stability limits put in evidence using convergence analysis and experiments

A top-down, three-scale numerical analysis of wafer-to-wafer metallic bonding

To study the sensitivity to micro-scale imperfections of the strength of a metallic, wafer-to-wafer MEMS bonding, we propose a three-scale numerical (finite element) approach. At the wafer level (macro-scale), accounting for the whole metallic sealing through nonlinear springs connecting the two silicon wafers modelled as thin plates, we link the force transferred by each single MEMS die to the external pressure applied to the wafers. This force is next used as an index for the input pressure at the die level (meso-scale), where the geometry of the metallic rings is accurately described: the local stress field at the interface between the upper and lower metallic rings is so obtained. Finally, a local (micro-scale) model is used to link the aforementioned local stress field in each die to the bonding strength: representative volumes of the rings getting into contact, accounting in a statistically way for the relevant surface roughness (which is on the order or tens of nanometers at most), are adopted to obtain the relationship between the external pressure and the percentage of sealed area. This information is exploited to assess the properties of the rings, in terms of expected bonding strength

Frontal Polymerization and Geopolymerization, the First Example: Organic-Inorganic Hybrid Materials

This work shows the first example of frontal geopolymerization, obtained in the same reactor in which the frontal polymerization of 1,6 hexanediolodiaacrylate occurs at the same time; the simultaneous frontal polymerization allows to obtain an organic-inorganic hybrid material in a single step and in a short time (a few minutes), thanks to the exothermicity of the two reactions which are mutually self-supporting. This technique represents the only way to obtain hybrid organic polymer-geopolymer mate-rials: using the classical polymerization (prolonged heating) the reaction is explosive due to the formation of gaseous products, while the polymerization at room temperature, due to the very long times, leads to a phase separation