Inhomogeneous Density Research Articles

New Strategy to Construct Mechanically Strong and Tough Phenolic Networks by Considering the Effect of Curing Reactions and Physical States on the Cross-Linking Density and Cross-Linking Inhomogeneity

New Strategy to Construct Mechanically Strong and Tough Phenolic Networks by Considering the Effect of Curing Reactions and Physical States on the Cross-Linking Density and Cross-Linking Inhomogeneity

Permeability of Polymer Membranes beyond Linear Response

The permeability of a membrane to solute penetrants is well defined on the linear response level simply as the ratio of penetrants’ flux and concentration gradient at the membrane boundary layers. However, nonlinearities emerge in the flux–force relation j(f) for large driving forces f, in which the definition of permeability becomes ambiguous. Here, we study nonequilibrium membrane permeation orchestrated by a generic driving force using penetrant- and monomer-resolved computer simulations of transport in a polymer network, supported by exact solutions of the Smoluchowski (drift–diffusion) equation in the stationary state. In the simulations, we consider the transport across a finite polymer membrane immersed in a reservoir of penetrants, addressing one- and two-component penetrant systems. We calculate the f-dependent inhomogeneous steady-state density profiles, boundary layer concentrations, and fluxes of the penetrants. The Smoluchowski approach, using solely coarse-grained equilibrium partitioning and diffusion profiles as input, exhibits remarkable qualitative agreement with our nonequilibrium simulations, which serves for rationalization of the observations. We discuss possible definitions of nonequilibrium, f-dependent permeability, distinguishing between “system” and “membrane” permeabilities. In particular, we introduce the concept of differential permeability as a response to f. The latter turns out to be a highly nonmonotonic function of f for low-permeable systems, demonstrating how a differential permselectivity is substantially tunable by the driving force beyond linear response.

Combined analysis of remote sensing, gravity and magnetic data across Moyar Bhavani Shear Zone, Southern Granulite Terrane (SGT), India: appraisals for crustal architecture and tectonics

We present a combined analysis of remote sensing, gravity and magnetic data across Moyar Bhavani Shear Zone (MBSZ), Southern Granulite Terrane (SGT), India to study crustal architecture and tectonics. The horizontal gradient of gravity data shows strong density inhomogeneity across the MBSZ. The magnetic data and residual gravity analysis shows corroboration of a NE–SW trending linear magnetic anomaly zone and residual gravity high strip along the MBSZ. The low magnetic anomalies dominate the northern part of the MBSZ, while the southern part is dominated by moderate to high anomalies. The integration of potential data and remote sensing data clearly reveals that ENE–WSW is the dominant structural trend that coincides with the Mettur Shear Zone (MeSZ) trend. The joint gravity and magnetic modelling suggest that the MBSZ, is characterized by the disposition of mélange of moderate to high-density rocks of diamagnetic nature.

Using machine learning to predict the density profiles of surface-densified wood based on cross-sectional images

Over the past decades, the surface densification of solid wood has received increased attention. However, the inhomogeneous density distribution in the densification direction might be a challenge with regard to process control within a large-scale production process, as the density profile governs many relevant properties of surface-densified wood. Currently, the measurement of density profiles relies on sensitive X-ray equipment and is difficult to integrate into an on-line process. Hence, in this study, three machine learning approaches were applied to predict the density profiles of surface-densified Scots pine specimens, only based on visual image acquisition—a technology that is ubiquitous in the wood industry: partial least squares (PLS) regression, artificial neural networks (ANN), and convolutional neural networks (CNN). The machine learning models were trained on images of the specimen cross-sections as input data, and X-ray density profiles as output data. There were 1850 observations, and the model performance was evaluated on external test sets. The models had mean absolute percentage errors of the predicted values between 9 and 18%; the CNN achieving the smallest error (9.24%). A deeper analysis of the data revealed that the ANN approach performed inconsistently between observations. PLS regression predicted the main density peak to a high accuracy but could not model other features. Only the CNN could reliably model the main density peak, wide growth rings, and the important region between the specimen surface and the main density peak. The ability of the models to generalise to untypical new data was improved by augmentation of the training data.

New Framework for Computing a General Local Self-Diffusion Coefficient Using Statistical Mechanics.

Widely applicable, modified Green-Kubo expressions for the local diffusion coefficient (Dl) are obtained using linear response theory. In contrast to past definitions in use, these expressions are statistical mechanical results. Molecular simulations of systems with anisotropic diffusion and an inhomogeneous density profile confirm the validity of the results. Diffusion coefficients determined from different expressions in terms of currents and velocity correlations agree in the limit of large systems. Furthermore, they apply to arbitrarily small local regions, making them readily applicable to nanoscale and inhomogeneous systems where knowledge of Dl is important.

Thermal Mitigation and Optimization Via Multitier Bond Wire Layout for IGBT Modules Considering Multicellular Electro-Thermal Effect

The stitch wire configuration is widely adopted for large-area IGBT chips. However, an inhomogeneous wire current density introduces uneven self-heating and nonuniform chip heating, which exacerbates the chip thermal stress. In this article, a multicellular electro-thermal model considering the stitch-bonding wires is derived to optimize the wire layout parameters. Furthermore, the current density alleviation of wire bonds is investigated to be the most sensitive and effective method to comprehensively mitigate the thermal nonequilibrium and local overheating. Consequently, an improved multitier layout is proposed to further achieve thermal stress suppression without any additional components and advanced materials. Finally, a triple-tier-bonded IGBT module with optimal design parameters is fabricated to validate the thermal mitigation performance. The prototype experimental results demonstrate that the modeling error is less than 3.0%. The multitier layout decreases the current density by 57.6%, hence, the maximum and average chip temperature are reduced by 21.8% and 12.4%, respectively.

Cloudlet Capture Model for Asymmetric Molecular Emission Lines Observed in TMC-1A with ALMA

TMC-1A is a protostellar source harboring a young protostar, IRAS 04365+2353, and shows highly asymmetric features of a few 100 au scale in its molecular emission lines. Blueshifted emission is much stronger in the CS (J = 5–4) line than redshifted emission. This asymmetry can be explained if the gas accretion is episodic and takes the form of cloudlet capture, given that the cloudlet is approaching toward us. The gravity of the protostar transforms the cloudlet into a stream and changes its velocity along the flow. The emission from the cloudlet should be blueshifted before the periastron, while it should be redshifted after the periastron. If a major part of cloudlet has not reached the periastron, the former should be dominant. We perform hydrodynamical simulations to examine the validity of the scenario. Our numerical simulations can reproduce the observed asymmetry if the orbit of the cloudlet is inclined to the disk plane. The inclination can explain the slow infall velocity observed in the C18O (J = 2–1) line emission. Such episodic accretion may occur in various protostellar cores since actual clouds could have inhomogeneous density distributions. We also discuss the implication of the cloudlet capture on observations of related objects.

Imaging Findings and Clinical Features of Primary Spinal Epithelioid Hemangioendothelioma.

Rationale and ObjectivesPrimary spinal epithelioid hemangioendothelioma (SEHE) is an extremely rare angiocentric vascular neoplasm with inherent metastatic potential, which pursues a clinical course intermediate between hemangioma and angiosarcoma. The present study sought to present computed tomography (CT) and magnetic resonance imaging (MRI) findings and clinical features of primary SEHE and review the literature.Materials and MethodsClinical data of four patients with primary SEHE confirmed by pathology from January 2011 to May 2020 were analyzed retrospectively. Two cases underwent CT scan, while 3 cases underwent MRI scan. Image observation included the tumor location, bone changes, morphology, density/signal characteristics, and enhanced features.ResultsThe four patients were all women who ranged in age from 25 to 74 years. Four cases of the lesions were in the vertebral body; among them, two cases involved the accessory of the vertebra. Soap bubble appearance was detected in 2 cases, honeycomb osteolytic appearance in 2 cases, a sclerotic margin in 3 cases, and accompanying vertebral compression fracture in 1 case. CT showed a slightly inhomogeneous low density with punctate high-density foci. MRI showed an inhomogeneous low signal on T1-weighted image (T1WI) and a high signal on T2WI. Contrast-enhanced CT/MRI demonstrated moderate to intensive inhomogeneous enhancement of the lesions. The discs were normal. In one case, lesions presented a dural tail sign.ConclusionsPrimary SEHE is so rare in the clinic as an aggressive vascular tumor. The relatively typical clinical features and radiographic findings can help in preoperative diagnosis.

CIRCULAR TARGET OBSERVATION OF POINT CLOUD USING LASER REFLECTION INTENSITY BY AN UNMANNED AERIAL VEHICLE EQUIPPED WITH A LASER SCANNER

Abstract. Unmanned aerial vehicles (UAVs) equipped with laser scanners have been widely used for various purposes, such as in construction sites, forestry, and disaster management, as they can obtain high density point clouds with millimeter to centimeter scale accuracy. However, systematic errors in the height of a UAV relative to the earth's surface may occur owing to the method of direct georeferencing using the global navigation system satellite (GNSS) and inertial measurement unit (IMU). Therefore, to enable highly accurate surveying, adjustments must be made using ground control points. However, interpreting the ground control points of a discrete, inhomogeneous density point cloud requires a high degree of skill and effort. In this study, a high-end UAV laser scanner was used to obtain the point clouds of a site using a white circular target enclosed within a black frame in a measurement setup of 500 points/m2. The center coordinates of the circle, calculated using the conventional and proposed methods, were evaluated qualitatively and quantitatively. As a result, the average of 10 error distances was found to be 0.028 m for the weighted center of gravity method, 0.014 m for the fitting circle equation method, and 0.008 m for the proposed method. These results corresponded to one-fifth to one-half of the 0.045-m point intervals of the measurement plan. Thus, using the reflection intensity of point clouds, the circular target observation could be performed.

Production of Closed-Cell Foams Out of Aluminum Chip Waste: Mathematical Modeling and Optimization

The main aim of this research is to mathematically describe the influence of the processing parameters of metal foam production from machining chip waste. Using this method, metal foams were produced without a remelting step, which should be both economically and environmentally effective. Firstly, expensive metal powders were replaced with waste in the form of machining chips. Secondly, machining chip waste was recycled without any significant material losses, which usually occurs during conventional recycling (using the melting process). To describe the innovative process and to relate metal foam properties to foaming temperature, the blowing agent weight percentage, and foam density (controlled by foaming height), response surface methodology, and the design of experiments were used. The quality of the produced metal foams was evaluated by determination of density, yield strength, compression strength, plateau stress, energy absorption, pore perimeter, and pore inhomogeneity for specimens obtained following the experimental plan. It was proven that pore inhomogeneity increased in the range from 1.41 to 4.81 mm with a higher temperature and the addition of a foaming agent. However, higher energy absorption and yield strength were obtained with a higher temperature but a lower percentage of TiH2. Despite the production from machining chips, pores were homogenous without significant cracks. These kinds of metal foams are comparable to commercial foams made of metal powders.

Ultra-dense dislocations stabilized in high entropy oxide ceramics

Dislocations are commonly present and important in metals but their effects have not been fully recognized in oxide ceramics. The large strain energy raised by the rigid ionic/covalent bonding in oxide ceramics leads to dislocations with low density (∼106 mm−2), thermodynamic instability and spatial inhomogeneity. In this paper, we report ultrahigh density (∼109 mm−2) of edge dislocations that are uniformly distributed in oxide ceramics with large compositional complexity. We demonstrate the dislocations are progressively and thermodynamically stabilized with increasing complexity of the composition, in which the entropy gain can compensate the strain energy of dislocations. We also find cracks are deflected and bridged with ∼70% enhancement of fracture toughness in the pyrochlore ceramics with multiple valence cations, due to the interaction with enlarged strain field around the immobile dislocations. This research provides a controllable approach to establish ultra-dense dislocations in oxide ceramics, which may open up another dimension to tune their properties.

P203 CHALLENGES IN THE MANAGEMENT OF RECTUS MUSCLE HEMATOMA DURING TRIPLE ANTITHROMBOTIC THERAPY IN RECENT ANTERIOR STEMI COMPLICATED BY LEFT ENDOVENTRICULAR THROMBOSIS

Abstract A 69–year–old woman suffering from hypercholesterolemia, GERD, was admitted to our department for anterior ST elevation myocardial infarction and was treated with primary PCI and DES on the mid–distal LAD. Dual antiplatelet therapy (DAPT) with ticagrelor and cardioaspirin was started. The pre–discharge echocardiogram (echo) showed the presence of left ventricular thrombus (LVT) and anticoagulant therapy (enoxaparin and warfarin) was started. On the 9th day the patient complained abdominal pain with onset of chills and hyperthermia and was suspected an uro–septic fever. The day after a mass appeared on the right abdominal wall at the site of the enoxaparin injection and abdominal contrast CT showed a mass of inhomogeneous density, actively supplied by the inferior epigastric artery and its terminal branches, indicative of hematoma of the abdominal rectus muscle. Anticoagulant therapy was suspended. Interventional radiologists in consideration of clinical stability and stable Hb value and the absence of the signs of active arterial bleeding on CT have not indicated an urgent endovascular treatment and DAPT with clopidogrel and cardioaspirin was continued. After V days, echo showed persistent pedunculated and mobile LVT and aspirin was therefore suspended and anticoagulant therapy was reintroduced with fondaparinux 2.5 mg daily. After two days, considering the stability of hematoma dimensions and the Hb values but the persistence of the extremely floating LVT, fondaparinux was increased at dose of 5 mg daily. In the following days, echo showed LVT reworking until its complete disappearance. On the 32th day blood test showed significant reduction in Hb values and a contrast CT showed an increase in size of the hematoma and resumption of micro bleeding. Fondaparinux was stopped and the patient was transferred to the interventional radiology center. Angiography highlights point–like spreads of extravascular contrast from branches of the inferior epigastric artery and branches of the external circumflex iliac artery. Embolization was performed. After a close monitoring of the hemoglobin values and of the echo which showed no LVT and recovery of LV function, in consideration of her thrombotic and hemorragic risks, she was discharged with DAPT with clopidogrel and low dose of aspirin. Abdominal wall hematoma may be a rare complication of subcutaneous enoxaparin therapy especially in STEMI patients undergoing also a DAPT therapy.

Complexity of a dynamical dissipative cylindrical system in non-minimally coupled theory

This paper aims to formulate certain scalar factors associated with the matter variables for a self-gravitating non-static cylindrical geometry by considering a standard model R+ζQ of f(R,T,Q) gravity, where Q=RφϑTφϑ and ζ is the arbitrary coupling parameter. We split the Riemann tensor orthogonally to calculate four scalars and deduce YTF as a complexity factor for the fluid configuration. This scalar incorporates the influence of the inhomogeneous energy density, heat flux and pressure anisotropy along with correction terms for the modified gravity. We discuss the dynamics of the cylinder by considering the two simplest modes of structural evolution. We then take YTF=0 with a homologous condition to determine the solution for the dissipative as well as non-dissipative scenarios. Finally, we discuss the criterion under which the complexity-free condition shows stable behavior throughout the evolution. It is concluded that the complex functional of this theory results in a more complex structure.

Spatial Structure of Gas Dynamic Characteristics In A Glow Discharge With A Supersonic Axisymmetric Gas Flow

The paper presents the results of theoretical calculations of the gas-dynamic parameters of a supersonic flow in an axisymmetric Laval nozzle for the case when the central body removed from the nozzle serves as one of the glow discharge electrodes. It is shown that the presence of a supersonic flow makes it possible to establish a stationary inhomogeneous density of gas particles between the cathode and the anode of a glow discharge. The density of gas particles near the cathode and anode may differ by tens of times. The results of the study of the glow pattern of a discharge with a supersonic gas flow are presented. The dependence of the characteristics of the glow discharge on the distribution of inhomogeneous gas density in the interelectrode region is revealed. This effect opens up new possibilities for the use of discharges with supersonic gas flow for nanocoating and synthesis of nanostructures.

Ray tracing and finite element modeling of sound propagation in a compartment fire

A compartment fire (a fire in a room or building) creates temperature gradients and inhomogeneous time-varying temperature, density, and flow fields. This work compared experimental measurements of the room acoustic impulse/frequency response in a room with a fire to numerically modeled responses. The fire is modeled using a Fire Dynamics Simulator (FDS). Acoustic modeling was performed using the temperature field computed by FDS. Room acoustics were modeled using two-dimensional ray and finite element modeling. A three-dimensional model was used to simulate an open flame. COMSOLTM Multiphysics was used for finite element acoustic modeling and BELLHOPTM for ray trace acoustics modeling. The results show that the fire causes wave-fronts to arrive earlier (due to the higher sound speed) and with more variation in the delay times (due to the sound speed perturbations). The resonance frequencies of low-frequency modes were shifted upwards. Model results are compared with data and show good agreement in observed trends.

Project development of a precision installer for measuring inhomogeneous density of the solution in the process of automation of the technological software and hardware complex

A project of a precision installer for measuring the inhomogeneous density of the solution has been developed. This module is one of the key components of an automated program-controlled complex created for the encapsulation of cell transport systems. An analysis of existing methods for determining the values of viscosity and density shifts shows that optical measurement methods are the most appropriate for designing the precision installer due to their simplicity and reliability. Implementation of optical measurement is also due to the need to ensure sterility of analyzed material, as well as non-destructive testing of liquid. Using the ultrasound method requires immersion in liquid of transmitting element and receiver, which violates the principle of sterility. According to the results of measurements, it was found that the method of recording optical radiation can determine density distribution in the cuvette volume after centrifugation with a high degree of accuracy. The exact positioning of the needle for the selection of liquid has been achieved. A measuring optical module has been developed to determine the inhomogeneous density of the liquid. Accurate positioning of the carousel at given points by mounting permanent neodymium magnets in the base of cuvette compartments has been achieved. The simplification of measuring configuration by the exclusion of dispersive elements, filters and the monochromator significantly reduces the cost of measuring equipment and makes it easy to implement for solving such problems. The introduction of modern digital technologies into the project makes it possible to process signal packets from positioning sensors and through individual channels, which is especially important for automating measurement and positioning processes, taking into account sterility

Hydrodynamic electron transport in graphene Hall-bar devices

We consider hydrodynamic electron transport in the Hall-bar geometry. The theory is developed for systems with non-Galilean-invariant electron liquids. We show that inhomogeneity of the electron density induced by long-range disorder and gating leads to mixing between the hydrodynamic transport mode and transport relative to the electron liquid. For graphene systems near charge neutrality, these effects lead to strong coupling of the hydrodynamic flow to charge transport. As a result, the effective electrical conductivity of the system may significantly exceed the intrinsic conductivity of the electron liquid. We obtain analytic expressions for the thermoelectric transport coefficients of the system as a function of density in the full crossover region between clean and disorder-dominated regimes.

Global existence of strong solutions to the multi-dimensional inhomogeneous incompressible MHD equations

This paper is concerned with the Cauchy problem of the multi-dimensional incompressible magnetohydrodynamic equations with inhomogeneous density and fractional dissipation. It is shown that when α+β=1+n2 satisfying 1≤β≤α≤min{3β2,n2,1+n4} and max{n4,n+16}<α for n≥3, the inhomogeneous incompressible MHD equations have a unique global strong solution for the initial data in some Sobolev spaces without requiring small conditions.

Superfluidity of a laser-stirred Bose-Einstein condensate

We study superfluidity of a cigar-shaped Bose-Einstein condensate (BEC) by stirring it with a Gaussian potential oscillating back and forth along the axial dimension of the condensate, motivated by experiments of C. Raman et al. Phys. Rev. Lett. 83, 2502 (1999). Using classical-field simulations and perturbation theory we examine the induced heating rate, based on the total energy of the system, as a function of the stirring velocity $v$. We identify the onset of dissipation by a sharply increasing heating rate above a velocity $v_c$, which we define as the critical velocity. We show that $v_c$ is influenced by the oscillating motion, the strength of the stirrer, the temperature and the inhomogeneous density of the cloud. This results in a vanishing $v_c$ for the parameters similar to the experiments, which is inconsistent with the measurement of nonzero $v_c$. However, if the heating rate is based on the thermal fraction after a 100 ms equilibration time, our simulation recovers the experimental observations. We demonstrate that this discrepancy is due to the slow relaxation of the stirred cloud and dipole mode excitation of the cloud.

Determining the atom number from detection noise in a one-dimensional optical lattice clock

In this paper, we demonstrate in situ synchronous frequency comparison between distinct regions in a one-dimensional optical lattice. The synchronous comparison instability is well below the Dick limit and agrees with the limit induced by atomic detection noise. The absolute atom number is extracted from the synchronous comparison instability with an uncertainty below 3%. Surpassing the performance of absorption imaging, this method provides a way to directly and precisely determine the absolute atom number from detection noise. Taking advantage of the inhomogeneous density distribution over the whole lattice, the density shift can also be conveniently measured by this synchronous frequency comparison method. Inconsistent with the expectation of the linear relationship between density shift and atom number difference, nonlinearity is observed, indicating that the assumption of an identical density shift coefficient over the whole lattice is not always safe.