Dynamic model metallo-supramolecular dual-network hydrogels with independently tunable network crosslinks

Hybrid polymer networks emerge between chemical and physical crosslinking, where two different modes of chain connectivity control the material behavior. However, rational relations between their microstructural characteristics, supramolecular kinetics, and the resulting network mechanics and dynamics are not well developed. To address this shortcoming, this study introduces a material platform based on a model dual-network hydrogel, comprising independently tunable chemical and physical crosslinks. The idea is realized by a click reaction between a tetra-PEG and a linear-PEG precursor, whereby the linear block also carries a terpyridine ligand at each end that can form additional physical crosslinks by metal ion–bis(terpyridine) complexation. We change the number of chemical crosslinks by varying the molar mass of the tetra-PEG, and we independently tune the metallo-supramolecular bonds by using different metal ions, Mn2+, Zn2+, Co2+, and Ni2+. Based on that modular approach, we study the rheological behavior and the diffusivity of fluorescent polymeric tracers. The dissociation of the metallo-supramolecular bonds provides a relaxation step, whose timescale and intensity are quantified by a sticky Rouse model. These two characteristics differ not only depending on the metal ion but also according to the chemical network mesh size, which highlights an interplay between the chemical and physical crosslinks

Crime mapping and spatial analysis

Crime maps are becoming significant tools in crime and justice. Advances in the areas of information technology and Geographic Information Systems (GIS) have opened new opportunities for the use of digital mapping in crime control and prevention programs. Crime maps are also valuable for the study of the ecology and the locational aspects of crime. Maps enable areas of unusually high or low concentration of crime to be visually identified. Maps are however only pictorial representations of the results of more or less complex spatial data analyses. A hierarchical model dealing with crime analysis is proposed and applied to the regional analysis of crime in Tehran, the model helps to identify spatial concentration of crimes in specific area (area based method). In area-based methods, crime data are aggregated into geographical areas such as blocks, precincts, and for each area, the analyst computes a measure of crime value. Multicriteria evaluation concept has been used to assess the crime rate in various blocks a discrete (part) of Tehran city. In this part we used two methods for crime density assessment: • Crime assessment based on crime per block, • Crime assessment based on density of crime per population. After determination of hot spots based on two methods mentioned above spatial function is used to find suitable location to establish new police station or direct patrol to the hot spots to reduce of crime

Supply chain single vendor – Single buyer inventory model with price-dependent demand

Purpose: The aim of this article is developing an integrated production-inventory-marketing model for a two-stage supply chain. The demand rate is considered as the Iso-elastic decreasing function of the selling price. The main research goal of the article is to obtain the optimal values of the selling price, order quantity and number of shipments for the proposed model under independent and also joint optimization. In addition, the effects of the model’s parameters on the optimal solution are investigated. Design/methodology/approach: Mathematical modeling is used to obtain the joint total profit function of the supply chain. Then, the iterative solution algorithm is presented to solve the model and determine the optimal solution. Findings and Originality/value: It is observed that under joint optimization, the demand rate and the supply chain’s profit are higher than their values under independent optimization, especially for the more price sensitive demand. Therefore, coordination between the buyer and the vendor is advantageous for the supply chain. On the other hand, joint optimization will be less beneficial when there isn’t a significant difference between the buyer’s and the vendor’s holding costs. Originality/value: The contribution of the article is determining the ordering and pricing policy jointly in the supply chain, which contains one vendor and one buyer while the demand rate is the Iso-elastic function of the selling pricePeer Reviewe

Multiphysic Design and Modeling of Rotating Electrical Machines

This paper presents a general overview on design process of electrical machines considering a multiphysic point of view, and a road map for a comprehensive design approach is drawn. The objective multi-physical criterion including electromagnetism and mechanics physics, thermodynamics, fluid dynamics, structural dynamics, noise and vibration are discussed. Also, various modelling methodologies are presented and compared in terms of computational-time resources and accuracy. Current state of art in this approach will be presented highlighting the advantages and disadvantages of such methodologies

Union of Low-Rank Subspaces Detector

The problem of signal detection using a flexible and general model is considered. Due to applicability and flexibility of sparse signal representation and approximation, it has attracted a lot of attention in many signal processing areas. In this paper, we propose a new detection method based on sparse decomposition in a union of subspaces (UoS) model. Our proposed detector uses a dictionary that can be interpreted as a bank of matched subspaces. This improves the performance of signal detection, as it is a generalization for detectors. Low-rank assumption for the desired signals implies that the representations of these signals in terms of some proper bases would be sparse. Our proposed detector exploits sparsity in its decision rule. We demonstrate the high efficiency of our method in the cases of voice activity detection in speech processing

Effect of junction aggregation on the dynamics of supramolecular polymers and networks

Transient structures based on associative polymers can deliver complex functions; as such, they hold promise for advanced applications as in drug delivery, tissue engineering, and electronics. The network structure and timescale of its rearrangement are key factors that define their range of utility. However, the inevitable phase separation of polar pairwise associations from nonpolar polymer chains frequently causes junction aggregation, whose stability and functionality significantly affect the network structure and dynamics, and as such, redefine its utility. Engineering the extent of association is a necessity for controlling properties of supramolecular materials, yet the current knowledge of the effect of design parameters on specificities of aggregates and their consequent effects on material properties is limited. To address this gap, the importance of aggregation is highlighted, the available theories and models of the dynamics of associative polymers in the presence of aggregates are reviewed, and the existing experimental records to draw a general guideline for interpreting the effect of aggregates on polymer dynamics are classified. Moreover, pitfalls and considerations like the applicability of time–temperature superposition, and the interplay of kinetics and thermodynamics of aggregation that may undermine the authenticity of the reported data are reviewed

Reversible hydrogels with switchable diffusive permeability

Hydrogels are polymer networks swollen in water that are characterized by soft mechanics and high permeability. This makes them good candidates for separation and membrane technologies. The diffusion is controlled by the mesh size of the network, and this can be made tunable through the introduction of thermoresponsive polymers. However, this is still a developing field. To contribute to this development, a dual dynamic network is formed composed of four-arm polyethylene glycol precursors in which each arm is functionalized with both a terpyridine moiety capable of forming reversible metal–ligand complexes along with branches of poly(N-isopropylacrylamide) (pNIPAAm), which can be switched between expanded and collapsed states and therewith offers a path for switching the microscopic gel-network mesh size, along with the macroscopic gel elasticity. The dually sensitive hydrogel has the capability of doubling its elastic modulus when going above the lower critical solution temperature (LCST) of pNIPAAm. In addition, the diffusive permeability of the hydrogel is switched upon change of temperature, whereby diffusants are trapped above the LCST of pNIPAAm. Moreover, it is possible to disassemble and reform the gel upon change of pH. With that, the hydrogel has potential application as a switchable and reversible membrane

Effects of dynamic eccentricity in Flux Switching Permanent Magnet machines

This paper investigates the effect of rotating eccentricity fault on a 10/12 Flux Switching Permanent Magnet (FSPM) machine. Main characteristics of the studied machine such as air-gap flux density, magnetic force between rotor and stator and torque profile are calculated by using finite element analysis (FEA) which is the most accurate numerical method. Furthermore, Fourier analysis is performed in order to study the impacts of rotating eccentricity faults on magnetic force and torque profiles. In addition, the results of Fourier analysis of the machine in healthy condition are compared with the machine with 40% rotating eccentricity. This studies shows that the eccentricity has significant effects on FSPM characteristics which shows the importance of investigating the fault. To the best awareness of the authors, the effects of the rotating eccentricity on FSPM machines have not been studied before