Maximum Number Of Contacts Research Articles

Numerical Simulations of Particle Motions at Continuous Rotational Speed Changes in Horizontal Rotating Drums

The motion of binary particles in three horizontal rotating drums with continuous rotational speed changes was studied based on the Discrete Element Method (DEM). Different simulation conditions were compared between two circular drums and an elliptical drum using the same number of physical properties for binary particles and drums, rotating at a speed series from 0.01 to 21.9 rad/s. By varying the rotational speed, four flow regimes were produced in the simulation. Flow regimes, velocity vectors, normal forces, and the number of contacts between 1 mm particles and 3 mm particles were comparatively analyzed, especially the particle velocity at transient changing rotational speeds. The results showed that four flow regimes were found at the same rotational speed for three different rotating drums, and normal forces were weakest for the cataracting regime; moreover, the three layers of particles were damaged when the rotational speed was suddenly decreased and the velocity direction of the particle motion was changed at the top of the particles’ bed. The maximum number of contacts was found with the rolling regime, based on the simulation results. The number of contacts of the major axis circular drum was smaller than for the minor axis at the same rotational speed, and the number of contacts of the elliptical drum was the largest among the three rotating drums.

Numerical Simulation of Integrated Mechanics of Drilling and Mechanical Cavitation in Coal Seam.

For coal and gas outburst and difficult extraction in soft, low-permeability, and high-gas seam, the integration technology of drilling and mechanical cavitation is put forward to relieve pressure and improve permeability of coal seam. Through the test of mechanical parameters of the coal body, the physical model of drilling and cave-making in coal seam is established, and the mechanical characteristics of drilling and mechanical cavitation are simulated numerically. The results show that the peak strength of coal increases linearly with confining pressure. When the drill bit just touches the coal, the maximum stress occurs at the center of the coal sample. With the increase in the drilling depth of the drill bit, the maximum stress point shifts to the depth. When the coal at the center of the sample is broken, the position of the maximum stress shifts to the surrounding. With the increase of drilling depth, the maximum contact number between the drill bit and coal body increases sharply. When the bit body basically enters the coal body, the maximum contact number between the drill bit and coal body remains unchanged. When the drill pipe rotates, the reaming tool collides with the hole wall at the reaming position on the axis. In general, the contact area increases with the opening of the reaming tool, but the contact between the reaming tool and the hole wall is random. As time increases, the contact force begins to increase and then basically stabilizes; at this time the reaming tool has been fully opened.

ON CONTACT NUMBERS OF LOCALLY SEPARABLE UNIT SPHERE PACKINGS

The contact number of a packing of finitely many balls in Euclidean $d$-space is the number of touching pairs of balls in the packing. A prominent subfamily of sphere packings is formed by the so-called totally separable sphere packings: here, a packing of balls in Euclidean $d$-space is called totally separable if any two balls can be separated by a hyperplane such that it is disjoint from the interior of each ball in the packing. Bezdek, Szalkai and Szalkai (Discrete Math. 339(2): 668-676, 2016) upper bounded the contact numbers of totally separable packings of $n$ unit balls in Euclidean $d$-space in terms of $n$ and $d$. In this paper we improve their upper bound and extend that new upper bound to the so-called locally separable packings of unit balls. We call a packing of unit balls a locally separable packing if each unit ball of the packing together with the unit balls that are tangent to it form a totally separable packing. In the plane, we prove a crystallization result by characterizing all locally separable packings of $n$ unit disks having maximum contact number.

Modeling of the high-strength clinker-free binder structure

Modern approaches in materials science should provide a solution to the problems of energy and resource conservation. They are also called upon to develop a line of directed synthesis of composites that possess the required parameters over the entire spectrum of properties. In order to obtain a high-strength structure of a clinker-free binder, the possibility of obtaining it on the basis of natural gypsum stone is considered. As is known, the strength of crystallization structures by adhesion in contact and the number of contacts is determined. To optimize the internal structure of a high-strength clinker-free binder, to obtain the maximum number of contacts and increase their strength, the possibilities of geometric topological approaches were used. When solving such problems, the geometric parameters and organization levels of the structures of disperse systems allow topology to be described. The fundamental possibility of obtaining a high-strength composite structure through the prism of the formation of a dispersed system with a maximum number of phase contacts between crystals of calcium sulfate dihydrate is considered. The granulometric composition of gypsum stone must meet the requirements (principles) of hardening, physical-chemical model and type of structure. Therefore, in the work, the possibility of obtaining high binder strength by optimizing it in accordance with the model was studied. mixtures of two powders with different average particle sizes were used. This increases efficiency and improves the properties of the binder.

Comprehensive theoretical prediction of the dynamics and stability properties of Tegafur pharmaceutical agent on the Graphene based nanostructures in aqueous environment

In this study, the molecular dynamics (MD) simulations are applied to elucidate the mechanisms governing the dynamics and binding strength of Tegafur (TG) anticancer drug interacting with two-dimensional carbon-based nanomaterials including hydroxyl (G-OH) and carbonyl (G-CO) functionalized Graphene nanosheets as well as Graphene oxide (GO). It is found that Tegafur drug exhibits the strongest affinity for the adsorption on Graphene oxide in terms of van der walls (vdW) amount energy. Furthermore, the total number of hydrogen bonding (HB) for the interaction of TG drug with GO is more than those with G-OH and G-CO models which be associated with maximum number of contacts between Tegafur molecules and Graphene oxide and higher stability. Based on these results, selection of Graphene oxide nanosheet as the suitable nano-carrier plays an important role in the greater effectiveness of TG drug with further experimental and theoretical investigations of nanoscale drug delivery systems.

The effect of antagonist tooth contact on the biomechanical response of custom‐fitted mouthguards

Custom-fitted mouthguards are devices used to prevent dental injuries. The aim of this study was to verify the influence of the antagonist contact on the stresses and strains of the anterior teeth, shock absorption and displacement of EVA custom-fitted mouthguards during a horizontal impact. Finite element models of human maxillary central incisors with and without a mouthguard for different occlusion conditions (with and without antagonist contact) were created based on tomography. A nonlinear dynamic impact analysis using the single-step Houbolt method was performed in which a rigid object hit the model at 1 m s-1 . Strain and stress were evaluated by means of Von Mises and Critical modified Von Mises criterion and shock absorption during impact were calculated as well as the mouthguard displacement. The model without mouthguard and without antagonist contact showed the highest stress and strain values at the enamel and dentin in the tooth crown on impact compared to the model without mouthguard and with antagonist contact. Mouthguard presence reduced the stress and strain values regardless of the occlusion condition. The mouthguard displacement decreased with the mandibular antagonist contact. Mouthguards are efficient at decreasing the stress and strain values on the tooth in front of an impact reaching more than 90% of shock absorption. A mouthguard with balanced occlusion and maximum number of contacts with mandibular anterior teeth should be considered because it reduces mouthguard displacement.

Packing concave molecules in crystals and amorphous solids: on the connection between shape and local structure

The structure of the densest crystal packings is determined for a variety of concave shapes in 2D constructed by the overlap of two or three discs. The maximum contact number per particle pair is defined and proposed as a useful means of categorizing particle shape. We demonstrate that the densest packed crystal exhibits a maximum in the number of contacts per particle but does not necessarily include particle pairs with the maximum contact number. In contrast, amorphous structures, generated by energy minimisation of high temperature liquids, typically do include maximum contact pairs. The amorphous structures exhibit a large number of contacts per particle corresponding to over-constrained structures. Possible consequences of this over-constraint are discussed.

Study on the Manufacturing Technology of Wood-Based Artificial Stone Composite Countertop for Integrated Cabinet

Countertop of integrated cabinet is the maximum number of contacts and the highest cost component, its material quality directly determines the final using functions. Artificial stone is an ideal material for the cabinet countertop, in order to solve its high cost, easy to crack and deformation problem, we try to develop a new technology to manufacture wood-based artificial stone composite board, which take particle board as core material and artificial stone as a surface material. Article studied the mechanism of composite materials, analyzed the selection principle of raw material for wood-based artificial stone composite countertop, designed two form structure of wood-based artificial stone composite countertop for integrated cabinet. Studied the process techniques and determined the production technology lines and optimum process parameters. Wood-based artificial stone composite countertop not only saved the usage amount of artificial stone, but also retain its lots of advantages, and improved strength, reduced costs, opening up the application scope of artificial stone materials.

Confocal mapping of cortical inputs onto identified pyramidal neurons

Using a confocal microscopy protocol, we carried out a microcircuitry investigation of cortical connections in monkey temporal cortex. Inputs were labeled by BDA injections in posterior area TE, and potential postsynaptic pyramidal neuron targets were labeled with EGFP, by injection of retrogradely transported adenovirus. We scored the number and distribution of putative contacts onto dendritic compartments of neurons in different layers. Initial results show that about 50 percent of apical dendrites of layer (L.) 6 neurons receive contacts, as they ascend through L.4 (n=1 brain), but only 30-35 percent of those from L.5 neurons (n=2). Basal dendrites of L.3 neurons also receive few contacts in L.4. This supports the role of layer 4 as an interlaminar relay in association cortex. In addition, our results indicate spatial heterogeneity in the occurrence and number of contacts, possibly due to subtype specificity in target preference. The maximum number of contacts, for a L.2 neuron projecting from anterior to posterior TE, was 29. This approach seems a useful alternative or complement to electron microscopic analyses of long distance connectivity.

Homology Model of Dihydropyridine Receptor: Implications for L-type Ca2+ Channel Modulation by Agonists and Antagonists

L-type calcium channels (LCCs) are transmembrane (TM) proteins that respond to membrane depolarization by selectively permeating Ca2+ ions. Dihydropyridine (DHP) agonists and antagonist modulate Ca2+ permeation by stabilizing, respectively, the open and closed states of the channel. The mechanism of action of these drugs remains unclear. Using, as a template, the crystal structure of the KcsA K+ channel (Doyle et al. (1998) Science 280, 69–77), we have built several homology models of LCC with alternative alignments of TM segments between the proteins. In each model, nifedipine was docked in the pore region and in the interface between repeats III and IV. Several starting structures were generated by constraining the ligand to residues whose mutations reportedly affect DHP binding (DHP-sensing residues). These structures were Monte Carlo-minimized with and without constraints. In the complex with the maximum number of contacts between the ligand and DHP-sensing residues and the lowest ligand–receptor energy, the drug fits snugly in the “water-lake” cavity between segments S6s, which were aligned with M2 segment of KcsA as proposed for Na+ channel (Lipkind and Fozzard (2000) Biochemistry 39, 8161–8170). In the flattened-boat conformation of DHP ring, the NH group at the stern approaches the DHP-sensing tyrosines in segments IIIS6 and IVS6. Stacking interactions of IVS6 Tyr with the bowsprit aromatic ring stabilize the ligand's orientation in which the starboard COOMe group coordinates Ca2+ ion chelated by two conserved glutamates in the selectivity filter. In the inverted teepee structure of LCC, the portside COOMe group approaches a bracelet of conserved hydrophobic residues at the helical-bundle crossing, which may function as the activation gate. The dimensions of the gate may readily change upon small rotation of the pore-forming TM segments. The end of the portside group is hydrophobic in nifedipine, (R)-Bay K 8644, and other antagonists. Favorable interactions of this group with the hydrophobic bracelet would stabilize its closed conformation. In contrast, (S)-Bay K 8644 and several other agonists have hydrophilic groups at the portside. Unfavorable interactions of the hydrophilic group with the hydrophobic bracelet would destabilize its closed conformation thereby stabilizing the open conformation. In the agonist-bound channel, Ca2+ ions would permeate between the hydrophilic face of the ligand and conserved hydrophilic residues in segments IS6 and IIS6. Our model suggests mutational experiments that could further our understanding of the pharmacological modulation of voltage-gated ion channels.

Geometry selects highly designable structures

By enumerating all sequences of length 20, we study the designability of structures in a two-dimensional hydrophobic-polar (HP) lattice model in a wide range of intermonomer interaction parameters. We find that although the histogram of designability depends on interaction parameters, the set of highly designable structures is invariant. So in the HP lattice model the high designability should be a purely geometrical feature. Our results suggest two geometrical properties for highly designable structures; they have the maximum number of contacts and a unique neighborhood vector representation. Also we show that the contribution of perfectly stable sequences in the designability of structures plays a major role in making them highly designable.

Preferential Adsorption of Compounds with Long Methylene Chains on Cast Iron, Graphite, Boron Nitride, and Molybdenum Disulfide

Several layered solids, which are effective solid lubricants, have a strong affinity for methylene groups. This leads to preferential adsorption on the solids of those paraffinic molecules that can form the maximum number of contacts with the surface and with each other. Thus the strength of adsorption of mineral oils increases with their average molecular weight. The strong affinity of the surfaces of the solid lubricants and cast iron for paraffinic hydrocarbon is expected to influence their load-carrying capacity, in that it should be higher for the oleophilic sliding surfaces than for surfaces such as those of plain steel, which are devoid of this property. So far, however, this has not been confirmed experimentally. For MoS2 dispersed in mineral oils, indications have been obtained that the strong attachment of oil molecules to the surfaces of the dispersed solid reduces its EP effectiveness. Presented as an American Society of Lubrication Engineers paper at the Lubrication Conference held in San Fra...