Sharp Growth Research Articles

A parametric study of a hybrid battery thermal management system that couples PCM/copper foam composite with helical liquid channel cooling

A battery thermal management system that effectively maintains its temperature is highly desired. However, the promising cooling method utilizing phase change materials (PCM) has challenges of low thermal conductivity and sharp temperature growth after complete melting. To address the problems, a hybrid system that couples PCM/copper foam with helical liquid channels is proposed and the effects of the influencing factors are investigated numerically. Results showed that the hybrid system achieved more than 30 K temperature drop than the natural convection case. The maximum temperatures with the helical pitch of 10 mm and 40 mm were 332.28 K and 332.88 K, respectively, compared to 334.17 K for the straight-channel system. The increments of helical diameter and tube number improved the battery temperature but raised the power consumption. The flow velocity growth could significantly reduce the battery temperature, but beyond 0.05 m/s the temperature became relatively stable. In the studied ranges, the temperature reached the optimum at the foam porosity of 0.92 and was reduced with the increasing pore density. The maximum temperature with the melting point of 28 °C was around 4 K and 8 K lower than that of PCM35HC and PCM44HC cases. The conclusions in this study could provide insights into the design of hybrid battery thermal management systems.

КОНЦЕПЦІЯ ПЕРЕТВОРЕННЯ ТЕКСТУ В БІТОВУ КАРТУ З ВИКОРИСТАННЯМ БУДЬ-ЯКОГО ШРИФТУ

The modern world is impossible to imagine without the exchange of information. Newspapers, magazines, books, printed advertising products play an important role and are constantly being improved and require more and more resources and opportunities. At the moment, due to the sharp growth of digital technology, there is a problem between the capabilities of hardware and software. That is, when transferring data from the electronic world to paper, the difference between the computing capabilities of hardware and software is displayed. This applies to print media that cannot convey the full volume and depth of what is displayed on the screen. Raster fonts are used for printing faster, the main drawback of which is their non-scalability. When studying fonts in embedded systems, there were problems with the fact that there are quite a few ready-made options for converting text to a bitmap without certain restrictions. The font displayed on the screen and printed directly by the printer or other device may differ significantly because the number of pixels that can be printed is too large. Therefore, there is a need to optimize the conversion of the font into a bitmap, ie reducing the number of points without losing the base of the glyph. The paper presents the conversion of a font into a bitmap using a program based on a ruler, ie the division of the image into lines, which is used in printing. In order to create the required bitmap image in the program, you need to specify a specific glyph and its size, as well as the device for which it will be used. The scan converter takes a path and applies a set of rules to determine which pixels will be part of the glyph image when printed or displayed on the screen. The obtained results allow us to print the fonts we like, instead of the standard ones.

Investigation on the effect of convective outflow boundary condition on the bubbles growth, rising and breakup dynamics of nucleate boiling

In this work, a phase-change lattice Boltzmann model was employed to simulate the effects of two computational domains with confined space and free outlet boundary considering the conjugate heat transfer on entire nucleate boiling. This model was validated by Laplace's law and droplet wetting process, especially in the improved convective outlet boundary for multiphase flow in detail. The film boiling was employed to verify the phase change model quantitatively, and the results exhibited a good agreement with a theoretical model so that the accuracy and robustness of the current model were ensured. The dynamic behaviors of the entire nucleate boiling including nucleation embryo, embryo growth, twin and triple vapors coalescence, departure, rise and subsequent rupture were investigated comprehensively. The temperature and velocity fields, as well as pressure propagations associated with nucleate boiling were investigated. The automatically sharp growth of nucleation vapor pushes away the vicinity of vapor outwardly, while the bottom fluid still flows into the root of the vapor contact line, which coincides with experimental observation. The flow dynamic behaviors of double and triple bubbles coalescence are almost the same, whereas more isolated bubbles merge is beneficial to the growth and departure dramatically. The sliding growth on the heating substrate was found clearly, which is mainly due to the non-uniform temperature gradient below the two side of the vapor bubble. The curvilinear rising trajectory and large deformation of rising vapor bubbles were observed, leading to a temperature wake in the rear of the rising bubble. The increasing volume of the rising bubbles occurred in the free outlet domain was found, which is mainly caused by the combined pressure influence between the inside and vicinity of the bubble. Moreover, the comparisons of nucleate boiling in both two computational domains were also studied.

Cost overruns in infrastructure projects: Evidence and implications

In recent years, there has been a sharp growth in both the magnitude and frequency of major infrastructure investments worldwide. Despite this boom in infrastructure spending, major projects continue to systematically underperform, as demonstrated in numerous empirical studies. In this paper, the author will discuss the factors underlying this growth in public spending, evaluate the empirical evidence on project cost overruns, and discuss the broader macroeconomic implications of this phenomenon. Keywords. Macroeconomic implications, Major infrastructure investments, Growth. JEL. H73, J42, J61, J62, J68, F22, F42.

VACUUM BASED WIPING SYSTEM FOR POLLEN AND DUST FREE SURFACES - IN A CASE STUDY WITH BLACKBOARD

Due to the sharp growth in technologies, humans demand high-performance machines to perform their tasks to make their life a bit effortless. This wiping system is made to ease the monotonous job of erasing blackboards by teachers. In this paper, a roller wiper is used that is rested upon the blackboard and it moves in line with the split-up made in blackboard using a DC motor and collects the dust spontaneously using a vacuum cleaner. To push and pull the roller wiper a servomotor is accustomed, and the position of the wiper is automated by an Arduino. Thus, it eludes the dust flow to the atmosphere thereby averting health issues triggered by dust and keeping the environment clean.

Has the Crisis Introduced a New Paradigm in Banks' Credit Allocation? The Non‐financial Corporations' Perspective

AbstractIn the years prior to the onset of the global financial crisis, the sharp credit growth, in a context of optimistic income expectations, boosted by an increase in competition in the banking system, less restrictive lending criteria and favorable financing conditions in international wholesale debt market, led to a marked rise in the debt levels of non‐financial corporations. In this paper, we use a panel data regression, with fixed effect estimators, to study how the relationship between bank credit granted to each firm and a set of firm‐specific indicators, that measure overall balance sheet performance and riskiness, changed over the 2006–2017 period. The results suggest that, during and after the Portuguese sovereign debt crisis, the sensitivity of the bank credit granted to firms to overall balance sheet strength and riskiness of firms increased, except in the case of leverage, where the sensitivity decreased slightly. Nonetheless, banks on average lent more to lower leveraged firms than to higher leveraged firms throughout the period considered. The results also show that statistical significance slightly reduces with the size of the firm and, when compared with the pre‐crisis sub‐period, banks did not increase lending to higher leveraged large firms in the crisis and post‐crisis sub‐periods. Finally, we find that the most capitalized banks were the ones more willing and/or able to support firms, during the crisis, even firms that experienced a deterioration in their indicators.

Freestanding polyimide fiber network as thermally safer separator for high-performance Li metal batteries

A stable and high-performance polyimide (PI) fiber mat was prepared via a facile two-step procedure, electrospinning deposition followed by an imidization process. The PI fiber separator presents higher thermal stability (>300 °C) than the commercial polypropylene (PP) separator (<160 °C). In Li/Cu half-cell configuration, PI fiber separator shows long cycle life performance with a coulombic efficiency of 82% at 0.5 mA cm–2 after 100 cycles and an impedance of 29 Ω. It also showed suppression of sharp Li dendrite growth. While the commercial PP separator delivers a poor coulombic efficiency of 24% after 100 cycles and an impedance of 99 Ω because of the formation of dendritic Li. Moreover, the Li/LiFePO4 full cell with a PI fiber separator exhibits a lower polarization and charge transfer impedance than the commercial PP separator. The PI fibers enhanced the electrochemical cycle performance and stability of the full cells that deliver a charge capacity of 118 mAh g−1 at a C-rate of 0.5 C with a capacity retention of 86% and a coulombic efficiency of > 99% after 200 cycles. Additionally, the multimode calorimetry (MMC) studies under in-situ mode revealed that the freestanding PI fiber separator presents high thermal stability in Li/LiFePO4 full cells.

The Increase of Brazilian Students in a Portuguese Engineering School

In the last fifteen years, the number of Brazilian students in Portugal has shown an increase of more than 600%. This trend was firstly driven by Portuguese economic recovery, which included investments in university education and incentives for receiving foreign students, through the international student statute, established in 2014. In the same year, Portugal started to accept the Brazilian national exams (ENEM) for the university admission, increasing the educational migratory flux once a directly access was stablished. Moreover, other secondary reasons led to this increase, such as the opportunity to study and live in a safer country and the possibility of obtaining a prestigious foreign degree. Currently, Brazilian students represent more than 33% of the foreign students in Portugal. However, the Brazilian students are highly concentrated in the top 3 Portuguese universities, Coimbra, Lisbon and Porto. In the specific case of the University of Porto, 73% of the foreign students are of Brazilian origin, with the Faculty of Engineering (FEUP) representing the largest contingent. This sharp growth in a specific group of foreign students on the engineering courses has created several important educational challenges, as the Brazilian students often exhibit higher failure rates in exams and curricular units as well as increased dropout rates when compared with Portuguese students. This is due to several factors, such as differences on the educational methodology, the quality of the high-school education, cultural differences, difficulty of adaptation and other socioeconomics aspects. The present work evaluates the causes behind the limited academic success of Brazilian students and introduces the measures and methodologies applied to the Brazilian students on the Faculty of Engineering of University of Porto, and on the Integrated Master’s in Mechanical Engineering (MIEM) in particular, in the pursuit of maintaining educational equality and ensuring success for all enrolled students, independently of their origin.

Warmer springs have increased the frequency and extension of late-frost defoliations in southern European beech forests

Climate change is increasing the frequency of extreme climate events, causing profound impacts on forest function and composition. Late frost defoliation (LFD) events, the loss of photosynthetic tissues due to low temperatures at the start of the growing season, might become more recurrent under future climate scenarios. Therefore, the detection of changes in late-frost risk in response to global change emerges as a high-priority research topic. Here, we used a tree-ring network from southern European beech (Fagus sylvatica L.) forests comprising Spain, Italy and the Austrian Alps, to assess the incidence of LFD events in the last seven decades. We fitted linear-mixed models of basal area increment using different LFD indicators considering warm spring temperatures and late-spring frosts as fixed factors. We reconstructed major LFD events since 1950, matching extreme values of LFD climatic indicators with sharp tree-ring growth reductions. The last LFD events were validated using remote sensing. Lastly, reconstructed LFD events were climatically and spatially characterized. Warm temperatures before the late-spring frost, defined by high values of growing-degree days, influenced beech growth negatively, particularly in the southernmost populations. The number of LFD events increased towards beech southern distribution edge. Spanish and the southernmost Italian beech forests experienced higher frequency of LFD events since the 1990s. Until then, LFD events were circumscribed to local scales, but since that decade, LFD events became widespread, largely affecting the whole beech southwestern distribution area. Our study, based on in-situ evidence, sheds light on the climatic factors driving LFD occurrence and illustrates how increased occurrence and spatial extension of late-spring frosts might constrain future southern European beech forests' growth and functionality. Observed alterations in the climate-phenology interactions in response to climate change represent a potential threat for temperate deciduous forests persistence in their drier/southern distribution edge.

On the growth of maximum modulus of rational functions with prescribed poles

In this paper we prove a sharp growth estimate for rational functions with prescribed poles and restricted zeros in the Chebyshev norm on the unit disk in the complex domain. In particular we extend a polynomial inequality due to Dubinin (2007) to rational functions which also improves a result of Govil and Mohapatra (1998).

Analysis of the Global Banking Network by Random Matrix Theory

Since the financial crisis of 2008, the network analysis of financial systems has attracted a lot of attention. In this paper, we analyze the global banking network via the method of Random Matrix Theory. By applying that method on a cross border lending network, it is shown that while the connectivity between different parts of the network has risen and the profile of transactions has diversified, the role of hubs remains important in the weighted perspective. The largest eigenvalue of the transaction matrix as the leading mode of the system shows sharp growth since 2002. As well, it is observed that its growth has diminished since 2008. This indicates that the crisis of 2008 has left a long-lasting footprint on the financial system. Analyzing the mean value of the participation ratio reveals the fact that the role of countries in forming small modes, has increased since 2002. In our final analysis, we provide snapshots of the hubs in the network over time. We observe that the share of countries in total transactions is not equal to their share in shaping the eigenvector of the largest eigenvalue. In 2018 for example, while the United Kingdom leads the share of transactions, it is the United States that has the largest value in the leading eigenvector. The proposed technique in the paper can be useful for analyzing different types of interaction networks between countries.

On Cloud Analytical Database Management Systems Suitable for Data Intensive Biomedical Related Research

Per to Worldometer [1], as of mid-December 2020, there are more than 77 million Covid-19 cases worldwide with more than 1.7 million deaths worldwide. Unfortunately, with the second wave hitting many countries, positive cases are increasing rapidly at astonishing rates. Along with that, a large amount of data, both directly and indirectly related to Covid-19, is generated ready to be minded supporting decision makers, scientists, corporations, drug makers, etc. [2]. Two immediate questions naturally would be (2) where we should store the data and (2) what Database Management Systems (DBMS) we should use to analyze the data? To benefit from easy access and to accommodate sharp growth in data volume, it is hard to dispute that the data should be stored in the cloud. In this position paper, we will present our recommendations based on our more than five years of using different Analytical DBMS (ADBMS, also called data warehouses in many articles), which we will discuss briefly next.

Slums in India: making sense of place in urban planning

Cities are the growth engine of national wealth and income production; however large number of city dwellers circumvents from the mainstream, are snubbed dwellers called slum population. Existence of slums in the urban units is a challenging issue in urban planning. India experiences a very sharp growth rate of slum population over the decades. Present work focuses on a conundrum of uninterrupted slum growth in spite of the implementation of many slum removal policies in India. The state-level household amenity status reflects a quite debatable agenda as to whether or not slum up-gradation policies are succeeded and works as a significant planning tool. The up-gradation of individual slum unit through the bottom-up approach of plan may act as effective action. This work finally directs a comprehensive planning tool for slum up-gradation as well as overall urban development, by placing the slum issues in urban planning practice.

Sharp gradient estimates on weighted manifolds with compact boundary

&lt;p style='text-indent:20px;'&gt;In this paper, we prove sharp gradient estimates for positive solutions to the weighted heat equation on smooth metric measure spaces with compact boundary. As an application, we prove Liouville theorems for ancient solutions satisfying the Dirichlet boundary condition and some sharp growth restriction near infinity. Our results can be regarded as a refinement of recent results due to Kunikawa and Sakurai.&lt;/p&gt;

Физико-химический анализ структуры и свойств нанокомпозитов полимер/углеродные нанотрубки, полученных из раствора

The structural (fractal) model, applied earlier for polymer solutions, was used for description of viscosity of aqueous suspensions of carbon nanotubes. The indicated model treates adequately the dependence of suspension viscosity on concentration of carbon nanotubes. At reaching of percolation theshold of this nanofiller a sharp growth of viscosity of aqueous suspensions is observed. The model reflects adequately also the dependence of viscosity on geometry of carbon nanotubes. A knowledge of nanofiller structure, characterizing by its fractal dimension, allows to predict reinforcement degree of solid-state polymer nanocomposites.

ОСОБЕННОСТИ РЕАЛИЗАЦИИ ЧЕРЕЗ МАРКЕТПЛЕЙСЫ В УСЛОВИЯХ КРИЗИСА

The mode of self-isolation changed traditional approach to sales and promotion of goods and services. Its introduction led to the sharp growth of Internet shopping and pushed the market to development of new services. Marketplace where seek to place the goods and services even large players became the most fast-growing segment. In 2020 a large number of small and medium-sized enterprises for the first time left in online, and the existing Internet sel- lers expanded sales channels due to placement on marketplace. Marketplace became «bridge» between suppliers and buyers, they allowed to facilitate and secure transactions between them. At first sight, the benefit is obvious to all participants. For buyers – it is saving of time and monetary means, the wide range of goods and sel- lers, comfort. For the seller – a constant, mass flow of buyers, reduction (absence) of expenses on logistics, warehousing, advance and so forth. However, lately even more often to sound dissa- tisfied statements from representatives of small and medium business to marketplace. Statistics shows that marketplace develop, work on increase in traffic and popularity, but at the same time toughen conditions for suppliers and cooperation for them becomes less favorable. In article main types of marketplace, the main advantages to all subjects of activity and difficulty which sellers meet with work with marketplace are considered. In article the state and the prospects of development of marketplace in the world and Russia which demonstrate rapid development of Internet trade and high efficiency of this form of business are considered.

Maximal directional operators along algebraic varieties

We establish the sharp growth order, up to epsilon losses, of the $L^2$-norm of the maximal directional averaging operator along a finite subset $V$ of a polynomial variety of arbitrary dimension $m$, in terms of cardinality. This is an extension of the works by C\'ordoba, for one-dimensional manifolds, Katz for the circle in two dimensions, and Demeter for the 2-sphere. For the case of directions on the two-dimensional sphere we improve by a factor of $\sqrt{\log N}$ on the best known bound, due to Demeter, and we obtain a sharp estimate for our model operator. Our results imply new $L^2$-estimates for Kakeya type maximal functions with tubes pointing along polynomial directions. Our proof technique is novel and in particular incorporates an iterated scheme of polynomial partitioning on varieties adapted to directional operators, in the vein of Guth, Guth-Katz, and Zahl.

SLES/CMEA mixed surfactant system: Effect of electrolyte on interfacial behavior and microstructures in aqueous media

In aqueous anionic sodium lauryl ether sulfate (SLES) solution, presence of nonionic cocamide monoethanolamine (CMEA) depicts intriguing interfacial and bulk properties. CMEA has poor water solubility but can be readily solubilized in SLES solution to form mixed micellar aggregates as revealed by surface tension measurements. Sphere-to-rod micellar transition in aqueous SLES-CMEA binary mixtures occurs at higher surfactant concentration (total surfactant concentration beyond 15 wt%), inducing a sharp growth in the viscosity (>1000 cP). Nevertheless, adding NaCl in SLES-CMEA mixtures, substantial growth in viscosity is perceived at much lower surfactant concentration (~5–10 wt%) attributed to the formation of intertwined worm-like micelles. Micellar sizes were obtained by dynamic light scattering (DLS) measurements and small-angle neutron scattering (SANS) investigations is used to determine micellar shapes and aggregation number for SLES-CMEA mixtures. Furthermore, it is observed that foaming behavior of SLES can be modulated by CMEA ascribed to the change in foam film rigidity. Corresponding experiments were also performed with nonethoxylated counterpart sodium lauryl sulfate (SLS) under analogous condition for comparison. The study reported here may prove to be an appropriate tactic to alter not only the rheology or foaming behavior of SLES-CMEA mixed surfactant system but also provide pre-solubilized composition of CMEA which could be highly beneficial for personal care products enabling CMEA blending at room temperature, which otherwise needs high temperature mixing.

Quantitative phase-field modeling of solute trapping in rapid solidification

A quantitative phase-field model is developed for prediction of solute trapping for solidification velocities relevant to the additive manufacturing. An anti-trapping flux is proposed to generate a chemical potential jump independent of the interface width and consistent with the sharp interface continuous growth (CG) model. The thin-interface analysis up to the second order is implemented to quantitatively parametrize the phase-field model based on the material properties for both full and zero solute drag limits of the CG model. As a benchmark example, the experimental data on Si-9at.%As (Kittl et al., Acta Materialia, 2000) is used to compare the partition coefficient and kinetic undercooling predicted by this phase-field model with those of the CG model. Our results, especially with the full-drag limit, present a very good agreement with the experimental data and theoretical models for solidification velocities up to the diffusive velocity. Unlike other phase-field models, this proposed model predicts accurate partition coefficient and kinetic undercooling for a wide range of solidification velocities, and the results are less sensitive to the diffusive interface width, enabling quantitative simulations in larger length scales. The model performance in prediction of the cellular growth is highlighted by showing that the primary dendritic arm spacing is also weakly dependent on the diffusive interface width.

Monitoring of Sugarcane Harvest in Brazil Based on Optical and SAR Data

The algorithms for determining sugarcane harvest dates are proposed; the algorithms allow the ability to monitor large areas and are based on the publicly available Synthetic Aperture Radar (SAR) and optical satellite data. Algorithm 1 uses the NDVI (Normalized Difference Vegetation Index) time series derived from Sentinel-2 data. Sharp and continuous decrease in the NDVI values is the main sign of sugarcane harvest. The NDVI time series allows the ability to determine most harvest dates. The best estimates of the sugarcane areas harvested per month have been obtained from March to August 2018 when cloudy pixel percentage is less than 45% of the image area. Algorithm 2 of the harvest monitoring uses the coherence time series derived from Sentinel-1 Single Look Complex (SLC) images and optical satellite data. Low coherence, demonstrating sharp growth upon the harvest completion, corresponds to the harvest period. The NDVI time series trends were used to refine the algorithm. It is supposed that the descending NDVI trend corresponds to harvest. The algorithms were used to identify the harvest dates and calculate the harvested areas of the reference sample of 574 sugarcane parcels with a total area of 3745 ha in the state of São Paulo, Brazil. The harvested areas identified by visual interpretation coincide with the optical-data algorithm (algorithm 1) by 97%; the coincidence with the algorithm based on SAR and optical data (algorithm 2) is 90%. The main practical applications of the algorithms are harvest monitoring and identification of the harvested fields to estimate the harvested area.