Synthesis of a New Zn2+/Fe3+ Octa(aminopropyl)silsesquioxane Complex and Its Voltammetric Behavior Towards N-acetylcysteine

Silicon - A zinc-modified octa(aminopropyl)silsesquioxane and the cyan compound Na2[Fe(CN)5NO] were prepared to create a hybrid electroactive material (ACZnN) characterized employing the...     

Isolation and characterization of Mexican jackfruit (Artocarpus heterophyllus L) seeds starch in two mature stages

Starch was isolated from jackfruit (Artocarpus heterophyllus L) seeds grown in México at different stages of fruit maturity and ripeness. Seeds represent about 8–15% from the fruit that can weigh around 2–36 kg. Proximate composition of seeds showed a high protein content (ca. 22%). Starch yield was 14% with a purity of 81% in both ripeness stages and AM content was lower (12.27%) than other non‐common starch sources. The starch granules in physiological mature (PM) and consumption ripeness (CR) jackfruit showed birefringence with diverse shapes such as semi‐oval or bell shapes. The size of starch granules for PM ranged between 3 and 9.5 µm and for CR between 3 and 12 µm. A‐type XRD pattern was similar to cereal starches. PM starch had higher peak viscosity than CR, but CR did not show breakdown; both starches presented setback during cooling. Thermal properties of gelatinization and retrogradation in PM and CR starches were similar. Characterization performed on this non‐common starch showed that it could be an alternative to use in food systems.     

A Metal-Organic Framework Incorporating Eight Different Size Rare-Earth Metal Elements: Toward Multifunctionality À La Carte

Multi-metallic multivariate (MTV) rare earth (RE) metal−organic frameworks (MOFs) are of interest for the development of multifunctional materials, however examples with more than three RE cations are rare and obstructed by compositional segregation during synthesis. Herein, this work demonstrates the synthesis of a multi-metallic MTV RE MOF incorporating two, four, six, or eight different RE ions with different sizes and in nearly equimolar amounts and no compositional segregation. The MOFs are formed by a combination of RE cations (La, Ce, Eu, Gd, Tb, Dy, Y, and Yb) and a 1,7-di(4-carboxyphenyl)-1,7-dicarba-closo-dodecaborane (mCB-L) linker. The steric bulkiness and acidity of mCB-L is crucial for the incorporation of different size RE ions into the MOF structure. Demonstration of the incorporation of all RE cations is performed via compositional and structural characterization. The more complex MTV MOF, including all eight RE ions (mCB-8RE), are also characterized using optical, thermal, and magnetic techniques. Element-selective X-ray absorption spectroscopy and X-ray Magnetic Circular Dichroism measurements allow us to characterize spectroscopically each of the eight RE ions and determine their magnetic moments. This work paves the way for the investigation of MTV MOFs with the possibility to combine RE ions à la carte for diverse applications.     

Autonomous detection and loading of ore piles with load–haul–dump machines in Room & Pillar mines

Automation of machines in underground mines is a topic with increasing interest, both for research and industrial applications. Autonomous load–haul–dump (LHD) machines need to load material successfully before dumping it into a crusher or an ore pass. The autonomous loading method must be robust to enable reliable operation of the LHD during long periods of time. In this work, a method to perform autonomous loading in Room & Pillar mines is presented. It is based on detecting all ore piles in real-time, and then computing attack poses in each pile. Then, a positioning process is performed to get the machine in front of the selected ore pile, and an excavation algorithm is executed for loading until the bucket is filled. The proposed method is able to detect multiple ore piles, with different slopes and sizes, and to consider different possible trajectories for attacking and loading the most feasible pile. The method was tested in the Werra Potash Mine, under real operational conditions. The results show that the method can load about 80% of the material that an experienced operator can load. Also, the success rate of the autonomous loading process is very high, being able to load enough material in all trials, and performing successfully the full procedure in 88% of the cases. Thus, the proposed autonomous loading method is a suitable alternative to be used in Room & Pillar mines.     

Vertical channel stabilization of barometer-aided inertial navigation systems by optimal control

This study investigates the problem of inertial navigation system's (INS's) vertical channel instability, which primarily results from the positive gravity feedback that takes place in the numerical integration step of the accelerometer measurements. Traditional solutions to the problem include using information from auxiliary sensors, typically barometers and global navigation satellite systems (GNSSs), integrated into INSs through feedback control loops (referred to as mechanizations) and/or Kalman filters (KFs). Most studies on this subject lack clarity regarding the methodology used for the mechanization tuning (by showing excessive empiricism) and/or disregard the benefits of using optimal control techniques for the purpose of the latter. This study, therefore, reviews the main mechanization used for vertical channel stabilization of baro-inertial integrations and presents, as its main contribution, the performance analysis of new tuning techniques based on optimal control theory, namely, by linear quadratic regulator (LQR) and by minimization of performance indices such as the integral absolute error (IAE), integral squared error (ISE), integral of time multiplied absolute error (ITAE), and integral of time multiplied squared error (ITSE). To validate the proposed tunings, the integrated altitude and vertical velocity mean errors (MEs) and standard deviations (SDs) are used as metrics, which are compared with the corresponding MEs/SDs of the empirical tuning with highest performance/acceptance in the literature. We also evaluate the ability of the mechanizations to fulfill their ultimate goal, namely, to track the reference barometer input, by also attenuating its noise. Based on simulated and experimental results, the present study demonstrates and validates the effectiveness/robustness of the proposed optimal tunings, particularly those based on LQR and ITAE minimization.     

Application of factorial model for an optimization of partial replacement of feldspar by talc on the sintering process

This research used a factorial model containing two levels and three variables to evaluate the partial substitution of sodium feldspar (albite) by a talc ore found in abundance in the region of Itaiacoca—Brazil. The model can also be used to verify the influence of initial talc particle size, proportion, and sintering threshold temperature on the following physical properties, such as linear shrinkage, water absorption, bulk density, total porosity, and firing color. In this study, the mechanical strength of the compositions was evaluated by the flexural strength test. The factorial model indicated the sintering temperature as the variable that most affects the samples’ densification and the proportion of talc as the variable that changes the firing color. The experiment that used a higher sintering temperature combined with a coarser talc granulometry presented the highest mechanical strength. When more refined granulometry was used, there was the beginning of an overfire process. Water absorption values in the range of .04% and modulus of rupture of 49 MPa were obtained, confirming the talc's effectiveness as a secondary flux agent suitable for the formulation of ceramic bodies.     

The Zwitterion Isomer of Orthosilicic Acid and its Role in Neutral pH Dimerization from Density Functional Theory

Silicon - The speciation and characteristics of silica in water at standard conditions are still poorly understood. Using density functional theory, the plausible existence of the zwitterion isomer...