Initial Expansion Stage Research Articles

Experimental study of vegetable oil droplets vaporization under low temperature conditions such as those found in diesel engine cold parts

This paper presents an analysis of three vegetable oil droplets vaporization process in the range temperature from 473 to 723 K corresponding to low temperature conditions found in diesel engine cold parts. This process is analyzed for a droplet evaporating in a hot environment at atmospheric pressure using the fiber-suspended droplet technique well used in the literature, and analyzing the droplet normalized square diameter and temperature evolution surrounding the droplet when vaporizing. The main difference between those already studied in literature is the range temperature which varies between 473 and 723 K in which vegetable oils vaporizing problems leading to deposits formation in the cold regions of diesel engines especially in direct injection. This presents a scientific challenge for resolving deposit formation. The findings reveal that vegetable oil droplets experience expansion and heating for temperatures below 623 K: no other changes are observed. Between temperatures of 623 and 683 K, an increase in temperature, expansion, and an inconsistent vaporization is observed. This is followed by a phase of low and constant vaporization. From 683 K, vegetable oils experience an initial stage of heating and expansion, which is accompanied by a phenomenon of puffing and bursting. Finally, in the last phase, residue formation occurs. Puffing and bursting phenomena manifest once the temperature reaches 683 K, indicating the emergence of substantial quantities of light compounds including carboxylic acids, aromatics, acrolein, ketene, and fatty acids. These compounds are formed through the thermal degradation and polymerization of vegetable oils. This process causes deposits to form in the colder areas of diesel engines.

Effect of oxidizer on the energy release during the initial detonation stage of aluminized explosives

ABSTRACT The addition of an oxidizer to aluminized explosives can promote the reaction of the aluminum particles to release more energy, significantly increasing the energy of the explosion. In this study, metal plate acceleration tests of CL-20-based explosives under strong constraints were performed, and the metal plate velocity was measured by laser interferometry, then the metal plate acceleration processes were simulated. By combining experiment and numerical simulation, the metal acceleration characteristics of the initial detonation stage were obtained, and the energy release and aluminum reaction law of oxidizer-containing cast cured aluminized explosives were investigated. The results showed that, in the initial stage of the detonation product expansion, the energy released from the aluminum reaction in the explosives with an oxidizer was slower than that in the explosives without an oxidizer. As the oxidizer content increased, the acceleration ability decreased, and the energy utilization rate of the explosive decreased. This may be because of the relatively low CL-20 content and high oxidizer content, where the oxidizer does not participate in the initial reaction and absorbs a large amount of the heat released by the CL-20 reaction, resulting in weak acceleration ability in the initial detonation stage of aluminized explosives.

Hotspots and Trends in International of international forest ecological compensation research: A knowledge mapping analysis using CiteSpace

Forest ecological compensation has received widespread attention from the academic community and has become an important knowledge field that is constantly developing and evolving. Analyzing its academic situation and knowledge structure relationship can provide reference for subsequent theoretical research and practical exploration. Using the Web of Science Core Collection as the data source and the CiteSpace tool, this study mapped the current knowledge domain of international forest ecological compensation research from 1990 to 2020. The following results are derived: The paper issuing countrieswith “the United States, China, the United Kingdom and Germany” as the core, form a close contact network; Research hotspot evolution trend overview for the initial stage (1990-2001), mature stage (2002-2011) and expansion stage (2012-2020).

Kinetic Theory of Expansion of Two-Component Plasma in a Plane Vacuum Diode

The results of study of the initial stage of expansion of a collisionless plasma with the electric current into a plane vacuum gap on the basis of kinetic equations for electrons and ions and the Poisson equation for the electric field are given. Self-consistent dynamics of a two-component plasma and electric field are theoretically modeled and the fundamental mechanism for establishing superthermal velocities of charged particles is described in detail. The parameters of anode-directed flows of positive ions in the cathode plume plasma are calculated. The expansion velocities of the cathode plume plasma observed in vacuum arcs at the level of (1−5) × 106 cm/s can be explained within the framework of the proposed collisionless mechanism.

Early Hominin Dispersal across the Qinling Mountains, China, during the Mid-Pleistocene Transition

The Qinling Mountain Range (QMR), where more than 500 hominin fossils and Paleolithic sites have been preserved, was a major center of hominin evolution and settlement and an important link for the hominin migration and dispersal between the north and the south during the Pleistocene in China. The rich culture remains and the related data make it possible and meaningful to study the characteristics and mechanisms of hominin occupation and dispersal in the region. This paper has summarized and analyzed the geographical distributions and chronologies of 55 dated hominin fossils and Paleolithic sites in the QMR to date. By combining them with the evidence from the loess–paleosol sequence, a relatively continuous and chronological sequence of hominin occupation and dispersal has been established, in which we have identified five stages, viz. ~before 1.2 Ma, the sporadic occurrence stage of early hominin occupation; ~1.2–0.7 Ma, the initial expansion stage; ~0.7–0.3 Ma, the stability and maintenance stage; ~0.3–0.05 Ma, the large-scale expansion stage; ~0.05–0.01 Ma, the sharp decline stage of the record of hominin occupation. We conclude that the environmental and ecosystem changes associated with the MPT drove early hominins to disperse southwards across the QMR. In addition, the evidence suggests that the hominin occupation and dispersal here was broadly continuous during both glacial and interglacial scales from early to late Pleistocene, and that the southern QMR provided a glacial refuge.

Initial kinetics of electrons, ions and electric field in planar vacuum diode with plasma cathode

The paper presents the results of a 1D1V theoretical study of the initial stage of plasma expansion into a planar vacuum gap 1 cm long with an applied voltage of 500–5000 V. Based on the collisionless kinetic and Maxwell equations, the motion of a two-component electron–ion plasma in a self-consistent electric field is described. The fundamental mechanism of ‘superthermal’ velocities of the emission edge of the plasma and anode-directed velocities of positive ions is demonstrated in detail. The general regularities of this process are established for variations in the number density of the initial plasma and the applied voltage.

Extracellular vesicles derived from M1 macrophages enhance rat midpalatal suture expansion by promoting initial bone turnover and inflammation

BackgroundMidpalatal suture (MPS) expansion can be affected by many factors, and researchers have attempted to regulate the initial inflammatory stage of expansion to optimize clinical outcomes and their underlying mechanisms. This study aimed to investigate the potential effects and mechanisms of M1 macrophage small extracellular vesicles during rat MPS expansion.Materials and methodsRAW264.7 cells were induced to M1 or M2 polarization and, small extracellular vesicles were isolated from the polarized macrophages. Male Sprague–Dawley rats (6–7 weeks) were administered 70 ± 5 g expansion force devices for 7 days. Rats with expanders without force served as controls. M1/M2 small extracellular vesicles were injected into the MPS region (50 µg/day) in the M1 and M2 small extracellular vesicle-assisted groups, while 0.9% saline was injected into the expansion-only group. Suture width, bone mass, and morphological changes in the region of interest (ROI) were examined.ResultsThe M1 small extracellular vesicle-assisted group showed a significantly increased MPS suture width in vivo (P < 0.001), and less bone mass was observed in the ROI (P < 0.05). Histological examination showed that the M1 small extracellular vesicle-assisted group exhibited a wider palatal area and obvious fibrous tissue rearrangement. The expression of RANKL and the number of osteoclasts were increased (P < 0.01) in the bony edges, and the p65 protein expression was significantly higher (P < 0.001).ConclusionsM1 macrophage-derived small extracellular vesicles have a positive effect in MPS expansion and increase p65 protein content and RANKL expression, thus promoting bone turnover. This study may contribute to the clinical application of small extracellular vesicles in the expansion of the palatal suture.

Genus Corydalis s. l. (Papaveraceae) in the flora of Ukraine: wild and cultivated taxa and the success of naturalization of alien species

Taxonomic composition of native and alien plants of the genus Corydalis s. l. in the flora of Ukraine has been analyzed. Based on literature, herbarium, inventory and other information, it was established for the first time that 3 native taxa (outside natural ranges) and 16 alien taxa of the genus Corydalis were recorded among ergasiophytes in botanical gardens and dendrological parks of Ukraine. The majority of these ergasiophytes (73.7 %) have not been preserved in the collections of living plants, indicating a low level of naturalization. The leading scientific center for the plant cultivation, where 82.4 % of alien taxa of the genus Corydalis have been cultivated, is the M. M. Gryshko National Botanical Garden of the National Academy of Sciences of Ukraine (Kyiv). Additionally, 4 alien taxa at different stages of naturalization were noted in the spontaneous flora of Ukraine. These include the ephemerophyte C. bracteata, colonophyte C. lutea, epecophyte C. cava subsp. marschalliana (outside the natural range) and hemiagryophyte C. caucasica. In the conditions of M. M. Gryshko National Botanical Garden and Syretsky Dendrological Park (Kyiv) ontogenetic structure of native coenopopulations of C. solida and introduced coenopopulations of naturalized alien taxa C. cava subsp. marschalliana and C. caucasica have been found. It was found that the coenopopulations of C. solida belong to the mature or aging types; C. cava subsp. marshalliana – to the young type; C. caucasica – young with a bias towards an invasive type. The highest density and a high seed germination in various coenotic conditions, which emphasizes the invasive nature of this species, distinguish coenopopulations of C. caucasica. Its expansion in the conditions of the M. M. Gryshko National Botanical Garden corresponds to the existing trend of the invasive spread of alien species from the southern regions, which is intensified by Global Climate Change. Due to the invasive activity of C. caucasica, this alien taxon, according to existing recommendations, should be considered as an invasive plant at the initial stage of expansion, so it should not be recommended for introduction to other countries and should be prevented from spreading in Ukraine.

The Roles of Hormone Signals Involved in Rhizosphere Pressure Response Induce Corm Expansion in Sagittaria trifolia.

Soil is the base for conventional plant growth. The rhizosphere pressure generated from soil compaction shows a dual effect on plant growth in agricultural production. Compacted soil leads to root growth stagnation and causes bending or thickening, thus affecting the growth of aboveground parts of plants. In arrowhead (Sagittaria trifolia L.), the corms derived from the expanded tips of underground stolons are its storage organ. We found that the formation of corms was significantly delayed under hydroponic conditions without rhizosphere pressure originating from soil/sand. In the initial stage of corm expansion, the anatomic structure of arrowhead corm-forming parts harvested from hydroponics and sand culture was observed, and we found that the corm expansion was derived from cell enlargement and starch accumulation. Comparative transcriptome analysis indicated that the corm expansion was closely related to the change in endogenous hormone levels. Endogenous abscisic acid and salicylic acid concentrations were significantly increased in sand-cultured corms. Higher ethylene and jasmonic acid contents were also detected in all arrowhead samples, demonstrating that these hormones may play potential roles in the rhizosphere pressure response and corm expansion. The expression of genes participating in hormone signaling could explain the rising accumulation of certain hormones. Our current results draw an extensive model to reveal the potential regulation mechanism of arrowhead corm expansion promoted by rhizosphere pressure, which will provide important references for further studying the molecular mechanism of rhizosphere pressure modulating the development of underground storage organs in other plants.

Metabolic regulation of stress erythropoiesis, outstanding questions, and possible paradigms.

Steady state erythropoiesis produces new erythrocytes at a constant rate to replace the senescent cells that are removed by macrophages in the liver and spleen. However, infection and tissue damage disrupt the production of erythrocytes by steady state erythropoiesis. During these times, stress erythropoiesis is induced to compensate for the loss of erythroid output. The strategy of stress erythropoiesis is different than steady state erythropoiesis. Stress erythropoiesis generates a wave of new erythrocytes to maintain homeostasis until steady state conditions are resumed. Stress erythropoiesis relies on the rapid proliferation of immature progenitor cells that do not differentiate until the increase in serum Erythropoietin (Epo) promotes the transition to committed progenitors that enables their synchronous differentiation. Emerging evidence has revealed a central role for cell metabolism in regulating the proliferation and differentiation of stress erythroid progenitors. During the initial expansion stage, the immature progenitors are supported by extensive metabolic changes which are designed to direct the use of glucose and glutamine to increase the biosynthesis of macromolecules necessary for cell growth and division. At the same time, these metabolic changes act to suppress the expression of genes involved in erythroid differentiation. In the subsequent transition stage, changes in niche signals alter progenitor metabolism which in turn removes the inhibition of erythroid differentiation generating a bolus of new erythrocytes to alleviate anemia. This review summarizes what is known about the metabolic regulation of stress erythropoiesis and discusses potential mechanisms for metabolic regulation of proliferation and differentiation.

Detonation development in PRF/air mixtures under engine-relevant conditions

The development of advanced boosted internal combustion engines (ICEs) is constrained by super-knock which is closely associated with end gas autoignition and detonation development. The present study numerically investigates the transient autoignition and detonation development processes under engine-relevant conditions for primary reference fuel (PRF) consisting of n-heptane and isooctane. The effects of PRF composition are systematically examined. By considering the transient local sound speed rather than its initial value, a new non-dimensional parameter is proposed to assess the transient chemical-acoustic interaction and to quantify the autoignition modes. Two detonation sub-modes, normal and over-driven detonation, are identified and the corresponding mechanisms are interpreted. For the over-driven detonation, there exist two developing regimes with weak/strong chemical-acoustic coupling and slow/rapid pressure enhancement. It is found that the maximum pressure caused by autoignition decreases with the blending ratio of isooctane, mainly due to the increase in excitation time. Besides, the strongest detonation induced by hot spot usually occurs within the over-driven detonation sub-regime. Its condition can be well quantified by the new non-dimensional parameter proposed in work and its strength is determined by the ratio of hot spot acoustic time to excitation time. The deviation of transient autoignition front propagation from prediction based on homogenous ignition is mainly attributed to the non-uniform compression effect caused by gradually enhanced pressure wave, while the influence of heat conduction and mass diffusion is negligible. The initial expansion stage dominating the induction period of local autoignition is greatly influenced by the compression of pressure wave. Therefore, the continuously enhanced pressure wave non-uniformly changes the local ignition delay (i.e. reduces its spatial gradient) within the hot spot and thereby accelerates the autoignition front propagation. The relationship among the parameters quantifying the detonation propensity is assessed and interpreted. The present study provides helpful understanding of detonation development under engine conditions.

DNA metabarcoding reveals the threat of rapidly expanding barred owl populations to native wildlife in western North America

Invasive predators can have detrimental impacts on native species and biological communities through direct consumptive effects and indirect effects on trophic interactions, yet these relations are often poorly understood through the initial stages of predator expansion. Leveraging early, lethal collection efforts to study invasive barred owls (Strix varia) at the leading edge of their range expansion in northeastern California, we conducted DNA metabarcoding of intestinal samples to assess the diet of this invasive predator. Through the development of customized primers and this novel approach to observing owl diet, we screened the intestinal contents of 124 barred owls and detected a broad diet of 78 unique prey types (48 vertebrates and 30 invertebrates), including prey types undetected in previous methodologies. Mammals were the most consumed vertebrate class (frequency of occurrence = 65 %), followed by amphibians (32 %), birds (22 %), and reptiles (19 %). Diets differed regionally but were similar among ages and sexes and exhibited limited variation in response to local environmental conditions. Our work highlights the generalist predatory strategy of invasive barred owls, identifies numerous native species potentially threatened by their range expansion, and indicates that they will not serve as ecological replacements for congeneric spotted owls (Strix occidentalis) they displace. These findings suggest that expanding currently limited barred owl removals could benefit native species and communities in western North America. More broadly, we demonstrate DNA metabarcoding, combined with early intervention, provides a powerful tool for conducting detailed assessments of species consumed by invasive predators, potentially incentivizing conservation actions and improving outcomes.

Financing model of New urban construction in China

With the continuous development of China's urban construction, China's urbanization rate has increased from 17.92% in the early stage of reform and opening-up to 63.89% now. At present, urban construction in mainland China has reached the present stock stage from the initial expansion stage, and more and more infrastructure has been completed. China is going to strive to create an enabling environment for people to work, live, enjoy and travel, so that government will create a greater sense of gain and create a happier and better life for the people. But a new era for the construction of the urban construction will lead to higher costs, as the stock of the real estate market has reached the age, at the same time, each region of government began to implement measures, for the most of the local government gradually out of the land within the revenue, in this case study the new era of urban construction investment and financing mode is particularly important. Local governments need to attract more social capital to participate in urban construction in the new era by updating their own investment and financing modes. This paper first expounds the background of urban construction in the new era, then analyzes the investment and financing problems existing in Local governments in China, and finally gives suggestions at the national, provincial and project levels according to the current specific policies.

Anomalous time of flight behavior of fast ions in laser produced aluminum plasma

In this work, dynamics of multi-charged ions emitted from an aluminum plasma produced by Q switched Nd: Yag laser is studied using time of flight (TOF) measurements from Langmuir probe and spectroscopy under Ar ambient of 0.02 mbar. The temporal evolution of multi-charged ions, background neutrals, and ions is systematically studied for varying laser intensities. The temporal evolution shows all species have double-peak structure for all laser intensities considered in the study. The fast peak is sharp whereas the slow peak is broadly similar to that observed in previous studies. Moreover, higher charged ions have higher velocity, indicating acceleration from the transient electric field produced at the very initial temporal stages of expansion. Interestingly, the fast peak gets delayed, whereas the slow peak advances in time with increased laser intensity, which has not been reported in earlier studies. The observations point toward the possible role of ambipolar electric fields in the unexpected observed behavior of the TOF profiles.

Insights into the dynamics of non-Newtonian droplet formation in a T-junction microchannel

The non-Newtonian shear-thinning droplet formation mechanism in a T-junction microchannel is experimentally investigated using the aqueous solutions of xanthan gum as the dispersed phase and mineral oil as the continuous phase. Influences of both phase flow rates and polymer concentration on flow regime transition are explored. It is observed that the initial vertical expansion stage is present only for the Newtonian and lower shear-thinning systems. The droplet evolution rate shows the influence of continuous phase flow rate and shear-thinning properties on the dynamics of necking stages, viz., squeezing, transition, pinch-off, and filament thinning. Analysis of Ohnesorge number (Oh) reveals that inertial force dominates in the squeezing stage, whereas viscous and interfacial force control in the filament thinning stage. Longer and stable filament generation is detected as a discerning feature for non-Newtonian systems that appears more prominent with increasing dispersed phase shear-thinning properties. The results also indicate an inverse relation of droplet length with the continuous phase flow rate and xanthan gum concentration, while the droplet formation frequency and its polydispersity vary directly with those parameters.

Research on the Impact of Factor Flow on Urban Land Use Efficiency from the Perspective of Urbanization

Researching the impact of factor flow on urban land use efficiency (ULUE) is significant in alleviating the contradiction between the accelerated promotion of urbanization and the inefficient use of urban land. This paper theoretically analyzes the impact mechanism of the flow of the three major factors of production—land, capital, and labor—on ULUE. On this basis, taking 54 cities in the urban agglomeration in the middle and lower reaches of the Yangtze River in China as the research object, the stochastic frontier model, fixed effect model, and K-means clustering method are used to empirically analyze the impact of the flow of labor, capital, and land on ULUE. The heterogeneous effect of factor flow on ULUE in different urbanization stages is also discussed. The results are as follows: (1) Labor flow and capital flow play a significant role in promoting ULUE; land flow plays the opposite role. (2) With the continuous improvement of the level of urbanization, the promotion effect of labor flow first decreases and then increases, while the promotion effect of capital flow continues to decrease, and the inhibitory effect of land flow is significant in the initial stage and expansion stage of urbanization, and the effect increases gradually, but it is not significant in the mature stage. (3) The level of urbanization has an obvious threshold effect on factor flow. There are single thresholds for labor and land flow, and there is a double threshold for capital flow. Research conclusions: we should continue to promote the market-oriented reform of factors, break the institutional shackles which restrict the free flow of factors, implement policies according to the city and the stage, and give full play to the positive impact of factor flow on ULUE.

Experimental investigation on the velocity of cathode spots in a vacuum arc with high di/dt

With the development of DC transmission and aerospace technology, the demands on the breaking capacity of vacuum circuit breakers (VCBs) under high condition are getting higher and higher. The breaking capacity of VCBs is determined by cathode spots, which provide electrons and metal vapor to maintain the arc. In this paper, the experiments of cathode spot observation were carried out based on the detachable vacuum interrupter and the cup-shaped axial magnetic field contacts. The images of cathode spot distribution were obtained by an ultra high-speed camera. In the initial expansion stage of arcing, it was discovered that the distribution of cathode spots is ring-shaped and symmetrical. The initial expansion velocity of cathode spot ring is approximately proportional to the value of and is independent of frequency. During the whole arcing process, the expansion velocity of cathode spot ring rises first and then drops with arcing time. The effects of the magnetic field and metal vapor density on the expansion process of cathode spot were analyzed. Based on the experimental conditions and results, the values of magnetic field and metal vapor density were calculated which can reasonably explain the variation of expansion velocity of cathode spot.

Paleoenvironmental Implications of Authigenic Magnesian Clay Formation Sequences in the Barra Velha Formation (Santos Basin, Brazil)

The characterization of Mg-clays in rock samples (well P1) from the Barra Velha Formation (Early Cretaceous) allowed the establishment of mineral assemblages on the basis of their kerolite and Mg-smectite (stevensite and saponite) content. Kerolite-rich assemblages (A and B) rarely contain saponite. Assemblage B is composed of kerolite-stevensite mixed layers, while assemblage A consists of more than 95% kerolite. Mg-smectite-rich assemblages (C and CB) are made up of both Mg-smectites. The predominance of stevensite in the lower interval of the stratigraphic succession suggests evaporative conditions, higher salinity and pH, which would favor its authigenesis by neoformation. In the upper portion, the occurrence of thick kerolite-rich intervals suggests regular water inputs, contributing with a decreasing in salinity and pH, favoring the neoformation of kerolite and later kerolite-stevensite mixed layering. The saponite would be the result of the transformation from Al-smectite into Mg-smectite in a Mg2+ rich medium. The results indicate that lake hydrochemical processes would have allowed the establishment of a basic depositional sequence, from base to top, as follows: (i) initial lake expansion stage marked by the occurrence of saponite, (ii) later kerolite neoformation, (iii) formation of kerolite-stevensite mixed layer with increasing salinity, and (iv) neoformation of stevensite, marking a final stage of maximum salinity (evaporation) and alkalinity of the lake.

The method of instrumental dilatation of the anastomosis of the sphenoid sinus in the surgical treatment of chronic sphenoiditis

To study the clinical efficacy and safety of the proposed original method of dilatation of the sphenoid sinus fistula in the surgical treatment of various forms of chronic sphenoiditis. The study included 68 patients of both sexes older than 18 years with chronic sphenoiditis, who are indicated for surgery on the sphenoid sinus. Patients of the 1st group (n=36) underwent expansion of the fistula of the sphenoid sinus using the traditional method. Patients of the 2nd group (n=32) underwent dilatation of the anastomosis of the sphenoid sinus using the tool developed by us. Intraoperatively, the quality of visualization of the surgical field, the time of the operation, and the presence of complications were assessed. In the postoperative period, the number of complications, relapses of the disease and the condition of the sinus were recorded according to the results of computed tomography 3-4 months after the operation. The use of the method of dilated expansion of the anastomosis of the sphenoid sinus using special forceps developed by us helps to reduce the duration of the operation, improve intraoperative visualization of the sphenoid sinus and improve the results of treatment according to endoscopy and control computed tomography. When using the developed tool, the number of episodes of intraoperative bleeding that hindered visualization and necessitated coagulation was lower than when using an alternative technique. The technique of endoscopic dilatation of the anastomosis of the sphenoid sinus using the developed tool can be used both independently and as a preliminary step for expanding the anastomosis of the sphenoid sinus, followed by the use of a shaver or Kerrison forceps.

Groove structure on the drainage characteristics of the gas curtain

The high resistance caused by water in the barrel during the underwater launch poses a daunting challenge to launch safety. To solve this problem, a new method is proposed to form a gas curtain based on the principle of the gas-curtain launcher. The key to the method is setting up several rectangular grooves on the barrel inner wall to guide the gas flow and form a gas curtain. A three-dimensional unsteady model is established to simulate the formation of the gas curtain under different aspect ratios of the grooves. The simulation results show that as the aspect ratio increases, the convergence effect is weakened, the drainage effect is gradually improved in the near-wall region and decreased in the center of the tube. With the increase of the aspect ratio, the pressure around the projectile head increases, the high-pressure region expands in the initial stage of jet expansion and the region of pressure fluctuation is reduced in the latter stage. When the aspect ratio increases from 0.625 to 1.6, the average drainage mass per unit time is increased by 3%, and the gas efficiency-cost ratio is increased by 6%.