Search

The transport of nanoparticles in porous media has received growing attention in the last decades due to environmental concerns in, for example, the printing industry, filtration, and transport of pollutants. Experimental studies on the imbibition of particle dispersions in porous media with sufficiently high spatial and temporal resolution are still challenging. This study shows how Ultra-Fast Imaging (UFI) NMR is an ideal tool for studying Fe3O4-latex particles penetration with a temporal resolution of 15 ms and spatial resolution of 18 µm. In the first part, it is shown that a calibration curve between the UFI‐NMR signal intensity and the particle concentration exists. In the second part, UFI‐NMR is used to study the penetration of a particles inside a thin nylon membrane during capillary uptake, which revealed liquid-particle front splitting and an inhomogeneous buildup of the particle concentration. Both the liquid-particle front splitting and inhomogeneous build up could be verified by Scanning Electron Microscopy. Our method allows to determine particle concentration profiles during capillary uptake within thin, porous media. Therefore, the technique can be easily extended to study particle penetrations in a wide variety of systems such thin interfaces, biomaterials, films, and filter media.

Inkjet printing inks frequently contain polar liquids of low volatility such as glycerol or poly(ethylene glycols) in addition to the main solvent water. The deposition of these liquids on paper sheets induces swelling of the cellulose fibers, which leads to an overall, anisotropic deformation of the sheet. We characterized the corresponding strain components by means of a grid projection method and white light interferometry. For pure water, most of the hydroexpansion strain vanishes again after drying is complete. However, for aqueous solutions of non-volatile co-solvents, a large fraction of the deformation persists after the water has evaporated. Because swelling occurs only after liquid enters the cellulose fibers, monitoring the dynamics of expansion provides insight into the pore-fiber distribution of co-solvents. The corresponding timescales of pore-fiber transport strongly depend on the co-solvent concentration, as a sufficient quantity of water is needed to plasticize the fiber walls.

The way a material is synthesized and processed has an immense effect on its microstructure, which in turn has a big impact on its transport properties. Here, we compare the thermoelectric (TE) properties of n- and p-type Bi2−xSbxTe3 (x: 0 and 1.5) materials synthesized through two different routes, specifically mechanochemical alloying (MA)—as a solid-state synthesis route—and microwave(MW)-assisted polyol synthesis—as a solution synthesis route. Reaction time is significantly reduced in the MW synthesis, leading to significantly lower energy consumption (i.e., higher energy efficiency) per batch than using the MA route. The resultant materials are compared for their crystallinity, phase purity, morphology, and microstructure. Spark plasma sintering was used to prepare pellets, and the resultant consolidates were evaluated for their transport properties. TE properties and microstructure of the specimens were investigated in relation to processing conditions and composition. MA samples formed fused structures (from 200 nm to several micrometers in size) composed of smaller particles. MW-synthesized materials exhibited hexagonal platelet morphology, high crystallinity, and phase purity. They also showed lower thermal conductivity, leading to a higher resultant TE figure-of-merit ZT. TE properties of Bi2−xSbxTe3 samples were studied on sintered cylindrical pellet samples, where the highest ZT values achieved were 1.04 (at 440 K) for MW-Bi2Te3 and 0.76 (at 523 K) for MW-Bi0.5Sb1.5Te3 samples, while MA-Bi2Te3 and MA-Bi0.5Sb1.5Te3 samples showed maximum ZT values of 0.74 (at 460 K) and 0.27 (at 300 K), respectively, as n- and p-type TE materials. The observed trend is much higher ZT values for MW samples, ascribed to their higher degree of texturing and nanostructured grains reducing the thermal conductivity, thus achieving a better overall performance, verifying the prospect to enhance ZT using MW-assisted solution synthesis approach., QC 20201214

The use of pre-split controlled blasting and blast pattern optimisation is described for the horseshoe-shaped main opening for the Faryab mine in Iran. The controlled blasting parameters used were a hole diameter of 45 mm, hole length 3 m, burden 0.7 m, spacing 0.6 m, stemming 0.45 m, explosive concentration 0.17 kg/m, explosive per hole 0.4 kg, number of dynamite charges per hole 3, number of contour holes 24, total charge 10 kg and 93 m of detonating cord. Compared with results obtained with the previous patterns the amount of overbreak was reduced by up to 40%, the advance rate increased by to up to 96% and the half-cast factor by up to 40%., The use of pre-split controlled blasting and blast pattern optimisation is described for the horseshoe-shaped main opening for the Faryab mine in Iran. The controlled blasting parameters used were a hole diameter of 45 mm, hole length 3 m, burden 0.7 m, spacing 0.6 m, stemming 0.45 m, explosive concentration 0.17 kg/m, explosive per hole 0.4 kg, number of dynamite charges per hole 3, number of contour holes 24, total charge 10 kg and 93 m of detonating cord. Compared with results obtained with the previous patterns the amount of overbreak was reduced by up to 40%, the advance rate increased by to up to 96% and the half-cast factor by up to 40%.

Conventional design techniques such as the Swedish method cannot be used to design the blast pattern when employing short holes of less than 2 m. Tests were carried out at the Hamkar and Pabedana coal mines, Kerman, Iran, in order to determine the relationship between burden and relief hole diameter. Trials were first conducted to determine the optimum pattern of the cut section in tunnel blasting and the results validated using full face tests. The results showed that in cuts with hole lengths of less than 1.5 m, the first quadrangle burden may increase to 4 times the relief hole diameter, in contrast to the Swedish blasting method in which the burden of the first quadrangle is 1.5 times the relief hole diameter, indicating that a reduction in drilling and blasting costs can be achieved. The advance rate was used to evaluate the results of full-face tests. The results showed that with a burden of 4 times the relief hole diameter advance rates of more than 90% can be achieved in full face blasting., Conventional design techniques such as the Swedish method cannot be used to design the blast pattern when employing short holes of less than 2 m. Tests were carried out at the Hamkar and Pabedana coal mines, Kerman, Iran, in order to determine the relationship between burden and relief hole diameter. Trials were first conducted to determine the optimum pattern of the cut section in tunnel blasting and the results validated using full face tests. The results showed that in cuts with hole lengths of less than 1.5 m, the first quadrangle burden may increase to 4 times the relief hole diameter, in contrast to the Swedish blasting method in which the burden of the first quadrangle is 1.5 times the relief hole diameter, indicating that a reduction in drilling and blasting costs can be achieved. The advance rate was used to evaluate the results of full-face tests. The results showed that with a burden of 4 times the relief hole diameter advance rates of more than 90% can be achieved in full face blasting.

The economic benefits are discussed of employing controlled blasting instead of diamond wire cutting. Tests were carried out on blocks of granite 5 m wide, 11.3 m long and 2.5 m-5.8 m high from the Shahkooh quarry in Iran using split controlled blasting. A total of 102 holes with a diameter of 32 mm were drilled, of which 37 were horizontal with a spacing of 30 cm and 65 were vertical with a spacing of 25 cm. Blasting was carried out using 60 g/m of PETN detonating cord, with a detonation velocity of 6 000 m/s, density of 943 kg/m3 and diameter of 10 mm. The amount of damage to the intact rock and the half-cast factor (HCF), defined as the ratio of the total length of half-cast holes to the total length of the holes drilled, were used to evaluate the results. Good breakage was obtained, leaving very flat excavation surfaces and an HCF of 85%., The economic benefits are discussed of employing controlled blasting instead of diamond wire cutting. Tests were carried out on blocks of granite 5 m wide, 11.3 m long and 2.5 m-5.8 m high from the Shahkooh quarry in Iran using split controlled blasting. A total of 102 holes with a diameter of 32 mm were drilled, of which 37 were horizontal with a spacing of 30 cm and 65 were vertical with a spacing of 25 cm. Blasting was carried out using 60 g/m of PETN detonating cord, with a detonation velocity of 6 000 m/s, density of 943 kg/m3 and diameter of 10 mm. The amount of damage to the intact rock and the half-cast factor (HCF), defined as the ratio of the total length of half-cast holes to the total length of the holes drilled, were used to evaluate the results. Good breakage was obtained, leaving very flat excavation surfaces and an HCF of 85%.

We present several improvements of the full-Newton step infeasible interior-point method for linear optimization introduced by Roos (SIAM J. Optim. 16(4):1110–1136, 2006). Each main step of the method consists of a feasibility step and several centering steps. We use a more natural feasibility step, which targets the ?+-center of the next pair of perturbed problems. As for the centering steps, we apply a sharper quadratic convergence result, which leads to a slightly wider neighborhood for the feasibility steps. Moreover, the analysis is much simplified and the iteration bound is slightly better., Software Technology, Electrical Engineering, Mathematics and Computer Science

Interior-point methods for semidefinite optimization have been studied intensively, due to their polynomial complexity and practical efficiency. Recently, the second author designed a primal-dual infeasible interior-point algorithm with the currently best iteration bound for linear optimization problems. Since the algorithm uses only full Newton steps, it has the advantage that no line-searches are needed. In this paper we extend the algorithm to semidefinite optimization. The algorithm constructs strictly feasible iterates for a sequence of perturbations of the given problem and its dual problem, close to their central paths. Two types of full-Newton steps are used, feasibility steps and (ordinary) centering steps, respectively. The algorithm starts from strictly feasible iterates of a perturbed pair, on its central path, and feasibility steps find strictly feasible iterates for the next perturbed pair. By using centering steps for the new perturbed pair, we obtain strictly feasible iterates close enough to the central path of the new perturbed pair. The starting point depends on a positive number ?. The algorithm terminates either by finding an ?-solution or by detecting that the primal-dual problem pair has no optimal solution (X *,y *,S *) with vanishing duality gap such that the eigenvalues of X * and S * do not exceed ?. The iteration bound coincides with the currently best iteration bound for semidefinite optimization problems., Software Technology, Electrical Engineering, Mathematics and Computer Science

We present several improvements of the full-Newton step infeasible interior-point method for linear optimization introduced by Roos (SIAM J. Optim. 16(4):1110–1136, 2006). Each main step of the method consists of a feasibility step and several centering steps. We use a more natural feasibility step, which targets the ?+-center of the next pair of perturbed problems. As for the centering steps, we apply a sharper quadratic convergence result, which leads to a slightly wider neighborhood for the feasibility steps. Moreover, the analysis is much simplified and the iteration bound is slightly better., Software Technology, Electrical Engineering, Mathematics and Computer Science

Interior-point methods for semidefinite optimization have been studied intensively, due to their polynomial complexity and practical efficiency. Recently, the second author designed a primal-dual infeasible interior-point algorithm with the currently best iteration bound for linear optimization problems. Since the algorithm uses only full Newton steps, it has the advantage that no line-searches are needed. In this paper we extend the algorithm to semidefinite optimization. The algorithm constructs strictly feasible iterates for a sequence of perturbations of the given problem and its dual problem, close to their central paths. Two types of full-Newton steps are used, feasibility steps and (ordinary) centering steps, respectively. The algorithm starts from strictly feasible iterates of a perturbed pair, on its central path, and feasibility steps find strictly feasible iterates for the next perturbed pair. By using centering steps for the new perturbed pair, we obtain strictly feasible iterates close enough to the central path of the new perturbed pair. The starting point depends on a positive number ?. The algorithm terminates either by finding an ?-solution or by detecting that the primal-dual problem pair has no optimal solution (X *,y *,S *) with vanishing duality gap such that the eigenvalues of X * and S * do not exceed ?. The iteration bound coincides with the currently best iteration bound for semidefinite optimization problems., Software Technology, Electrical Engineering, Mathematics and Computer Science

In the theory of polynomial-time interior-point methods (IPMs) two important classes of methods are distinguished: small-update and large-update methods, respectively. Small-update IPMs have the best theoretical iteration bound and IPMs with full-Newton steps belong to this class of methods. Within each of these classes one has feasible and infeasible interior-point methods (IIPMs). In this thesis we first deal with full-Newton step IIPMs, and we consider feasible full-Newton step IPMs., Electrical Engineering, Mathematics and Computer Science

In the theory of polynomial-time interior-point methods (IPMs) two important classes of methods are distinguished: small-update and large-update methods, respectively. Small-update IPMs have the best theoretical iteration bound and IPMs with full-Newton steps belong to this class of methods. Within each of these classes one has feasible and infeasible interior-point methods (IIPMs). In this thesis we first deal with full-Newton step IIPMs, and we consider feasible full-Newton step IPMs., Electrical Engineering, Mathematics and Computer Science

Pre-splitting controlled blasting tests were carried out at the Sarcheshmeh, Iran, Cu mine using a long hole diameter of 251 mm. The optimum values for parameters such as spacing, charge length (decoupled or decoupled-deck), coupling ratio and stemming were determined for different types of rock. Good results were obtained with decoupling and continuous charging using 3 m spacing between holes in the pre-split row and 2.5-3.5 m of stemming. Continuous rather than deck charging is preferred when using bulk explosives in wet conditions. Cartridged rather than bulk explosives are recommended when using the pre-splitting decoupled method in wet conditions., Pre-splitting controlled blasting tests were carried out at the Sarcheshmeh, Iran, Cu mine using a long hole diameter of 251 mm. The optimum values for parameters such as spacing, charge length (decoupled or decoupled-deck), coupling ratio and stemming were determined for different types of rock. Good results were obtained with decoupling and continuous charging using 3 m spacing between holes in the pre-split row and 2.5-3.5 m of stemming. Continuous rather than deck charging is preferred when using bulk explosives in wet conditions. Cartridged rather than bulk explosives are recommended when using the pre-splitting decoupled method in wet conditions.

Vibrations resulting from 39 blasts were monitored at different distances from the blasts in the Sar Cheshmeh, Iran, Cu mine. The results were analysed to determine peak particle velocities, acceleration, displacement, frequency, signal length and duration. The dynamic effects of the vibrations on slope stability were studied and the maximum block size on the western wall that could be coherently displaced by vibration was determined. Blasts which could potentially cause overbreak in the final pit wall were analysed and the minimum distance to the final wall within which production blasting should not be permitted was determined. The results indicated that production blasts could be carried out 50 m away from the final wall without any risk of overbreak on the final wall., Vibrations resulting from 39 blasts were monitored at different distances from the blasts in the Sar Cheshmeh, Iran, Cu mine. The results were analysed to determine peak particle velocities, acceleration, displacement, frequency, signal length and duration. The dynamic effects of the vibrations on slope stability were studied and the maximum block size on the western wall that could be coherently displaced by vibration was determined. Blasts which could potentially cause overbreak in the final pit wall were analysed and the minimum distance to the final wall within which production blasting should not be permitted was determined. The results indicated that production blasts could be carried out 50 m away from the final wall without any risk of overbreak on the final wall.

The use is discussed of controlled blasting close to the final wall of open-pit mines, and the results are presented of investigations into the optimisation of pre-splitting patterns at the Sarcheshmeh, Iran, Cu mine for different rock conditions. The results showed that continuous charging for the pre-splitting row was easy to achieve compared with deck charging. For small diameter holes, decoupling was not feasible. A salt- ANFO mixture was preferred for continuous charging as it was easy to use and the operation was less time consuming., The use is discussed of controlled blasting close to the final wall of open-pit mines, and the results are presented of investigations into the optimisation of pre-splitting patterns at the Sarcheshmeh, Iran, Cu mine for different rock conditions. The results showed that continuous charging for the pre-splitting row was easy to achieve compared with deck charging. For small diameter holes, decoupling was not feasible. A salt- ANFO mixture was preferred for continuous charging as it was easy to use and the operation was less time consuming.