Gap Distribution Research Articles

Experimental Analysis of the Annular Velocity of a Capsule When Starting at Different Positions of a Horizontal Bend Pipe

The study of the annular slit flow field is important for energy consumption, transport efficiency, and the force on the capsule for hydraulic capsule transportation. A combination of physical experiments and theoretical analysis was used to study the annular flow field around a capsule that was set in motion at different positions of a horizontal bend pipe. We study the flow velocity distribution of the gap flow field at different bend positions of the capsule by changing the position of the capsule at the bend. We found that the distribution of the flow field remained similar for different starting positions of the capsule, but the flow velocity increased suddenly and dramatically at the inflow section of the ring gap. We recorded different velocity distributions of the annular gap on the concave and convex sides of the pipe; on the convex side, the streamline of the gap was smooth, and the change in velocity was relatively small. The flow velocity of the slit flow varied more notably on the concave side of the pipe, and there was a greater fluctuation in the flow velocity distribution. Because the effects of the capsule and the pipe on water flow were not the same, we found large fluctuations in gap flow velocity at different measuring points on the concave side. Gap flow velocity was most influenced by axial flow velocity. We found that the axial flow velocity was about one order of magnitude greater than the radial flow velocity or circumferential flow velocity. In this paper, we analyze the changes in the ring gap flow field of the capsule at different bending positions and analyze the reasons for the flow field changes and the flow velocity distribution law. This is of great significance to the study of the transport efficiency and energy consumption of the capsule. The results of this paper complement the study of capsule initiation at different positions in the bend and provide a reference point in terms of transport efficiency, energy consumption, and capsule stress. The results of this study promote the development of hydraulic capsule transportation.

Forty years later: The status of the “Big Five” mass extinctions

Abstract Over 40 years ago, Raup and Sepkoski identified five episodes of elevated extinction in the marine fossil record that were thought to be statistically distinct, thus warranting the term the “Big Five” mass extinctions. Since then, the term has become part of standard vocabulary, especially with the naming of the current biodiversity crisis as the “sixth mass extinction.” However, there is no general agreement on which time intervals should be viewed as mass extinctions, in part because the Big Five turn out not to be statistically distinct from background rates of extinction, and in part, because other intervals of time have even higher extinction rates, in the Cambrian and early Ordovician. Nonetheless, the Big Five represent the five largest events since the early Ordovician, including in analyses that attempt to compensate for the incompleteness of the fossil and rock records. In the last 40 years, we have learned a great deal about the causes of many of the major and minor extinction events and are beginning to unravel the mechanisms that translated the initial environmental disturbances into extinction. However, for many of the events, further understanding will require going back to the outcrop, where the patchy distribution of environments and pervasive temporal gaps in the rock record challenge our ability to establish true extinction patterns. As for the current biodiversity crisis, there is no doubt that the rate of extinction is among the highest ever experienced by the biosphere, perhaps the second highest after the end-Cretaceous bolide impact. However (and fortunately), the absolute number of extinctions is still relatively small – there is still time to prevent this becoming a genuine mass extinction. Given the arbitrariness of calling out the Big Five, perhaps the current crisis should be called the “incipient Anthropocene mass extinction” rather than the “sixth mass extinction.”

Method for the design of additively manufactured inner channels intended for adhesive application

Joining of metal parts manufactured by laser beam powder bed fusion (PBF-LB/M) eliminates the inherent size restriction of this additive manufacturing process and reduces the manufacturing effort. Adhesive bonding presents great potential for joining of PBF-LB/M parts, as there are no constraints on the shape of the connecting surfaces, as long as the adhesive can be applied. The freedom of design underlying the PBF-LB/M process enables the construction of inner channels in the parts, which can facilitate the adhesive application. The adhesive can be injected into a single inlet on the exterior of a part and directed through inner channels before leaking from multiple outlets into the adhesive fill gap between the pre-aligned adherents. To avoid insufficient adhesive distribution and air inclusions in the adhesive fill gap, both of which reduce the bond strength, a methodical approach for the design of inner channels intended for adhesive application by injection is required. This work provides a corresponding design method based on the theory of fluid mechanics. Moreover, an example case of a PBF-LB/M sleeve to be joined to a circular tube is presented. Results from a CFD analysis show that the inner channels designed using the presented method lead to excellent coverage of the adhesive fill gap with adhesive and minimal air inclusions.

Leadership of Latin American women in the professional scientific and research context: an exploration based on the gender gap

Gender equality is clearly framed by and defined in the knowledge society in particular. Struggles towards all goals in this regard unfold in the context of a large gender gap and unequal distribution of power. These are circumstances in which women are clearly disadvantaged, facing obstacles in every aspect of their lives: family, relationships, education, and, therefore, work. Occupying senior leadership roles in institutions related to science and research remains an arduous task. The study takes a descriptive and analytical approach, drawing on official documents by international agencies such as UN, UNESCO, UN WOMEN, ECLAC, WB, IDB, and CODS as well as specialist websites. Title searches were carried out and variables identified through key words and phrases in recently published scientific articles found in open-access databases and scientific journals such as Scopus, WOS, SciELO, Redalyc. It found that intensive assertion of claims has resulted in the enshrinement of many women’s rights, the unconditional support of an array of international organizations, advances in narrowing the gender gap, and the positioning and leadership of women in professional scientific contexts, as part of the broader pursuit of parity between men and women.

Slope gap distribution of saddle connections on the <inline-formula><tex-math id="M1">$ 2n $</tex-math></inline-formula>-gon

<p style='text-indent:20px;'>We explicitly compute the limiting slope gap distribution for saddle connections on any <inline-formula><tex-math id="M2">\begin{document}$ 2n $\end{document}</tex-math></inline-formula>-gon for <inline-formula><tex-math id="M3">\begin{document}$ n\geq 3 $\end{document}</tex-math></inline-formula>. Our calculations show that the slope gap distribution for a translation surface is not always unimodal, answering a question of Athreya. We also give linear lower and upper bounds for number of non-differentiability points as <inline-formula><tex-math id="M4">\begin{document}$ n $\end{document}</tex-math></inline-formula> grows. The latter result exhibits the first example of a non-trivial bound on an infinite family of translation surfaces and answers a question by Kumanduri-Sanchez-Wang.</p>

CONTACT INTERACTION OF SIMILAR SHAPE BODIES AT SMALL DISTURBANCE OF INITIAL GAP DISTRIBUTION

In this work, on the development of previous research, a model of contact interaction of similar shape bodies is built. Contact in the system "punch - stamped material - matrix" is considered. A gap is set between the material to be stamped and the matrix, which varies in circular coordinate. The regularities of the change of contact pressure and contact areas with variation of the law of distribution of the initial gap are determined. The influence of the load level on these parameters is also determined. In particular, the analysis of the influence of the number of waves in the distribution of the initial gap in the circular direction on the nature of the distribution of contact areas and contact pressure. It is established that at low level of loads significant non-uniformity of the contact pressure distribution along the circular coordinate is realized. In the future, with increasing load levels, this unevenness decreases. The distribution of contact pressure tends to the case of contact with nominally coincident surfaces of the matrix and the material to be stamped, i.e. at zero gap. Thus, an analytical-numerical method for studying the contact interaction of closely shaped bodies with low perturbation of the initial gap distribution has been developed. Regularities of influence of constructive and technological parameters on contact interaction of these bodies on an example of elements of stamp equipment are also established. Keywords: contact interaction; stress-strain state; elements of stamps; contact area; contact pressure

Evaluation of CPoint obturation system for voids & gaps using digital microscope

ABSTRACT
 Aim: This study was aimed to evaluate the quality of CPoint obturation system by calculating the percentage of surface area of voids and gaps in different levels in comparison with Guttapercha point/GuttaFlow 2 and Guttacore/Endofill.
 Method: Sixty palatal roots of extracted upper first molars were prepared and divided into three groups of 20 samples each, the first group was obturated with CPoint/BC sealer, the second one was obturated with Guttapercha point/ GuttaFlow2 and the third was obturated with GuttaCore/Endofil. Each root sectioned into four sections at 8 mm, 6 mm, 4 mm, and 2 mm levels from the W.L and transferred to be photographed under digital microscope, the canal cross sectional area, and the area of voids and gaps were measured then surface area percentages of unfilled areas were calculated. Data then analyzed statistically using ANOVA and LSD tests.
 Results: Higher percentages of unfilled areas were observed in Group1 (p < 0.01) in comparison to Group2 and Group3 except with S2 of Group3 (p > 0.05). And there was no significant difference between Group2 and Group3 except at S2. The results of comparison among different
 
 sections within each group showed that there is a highly significant difference (p < 0.01) between S2and (S8, S6, S4) within Group 1, in Group 2 the results showed that there is a highly significant difference between S8 and the other sections, and also showed a significant difference (p < 0.05) between S2 and (S4, S6).
 Within Group 3 the results revealed significant difference between the (S4, S6) and the (S8, S2) sections.
 Conclusion: All systems showed voids and gaps and CPoint obturation system showed the highest percentage of unfilled areas and level of root section had an effect on voids and gaps distribution.

Universal properties of mesoscopic fluctuations of the secondary gap in superconducting proximity systems

The energy levels of a quasicontinuous spectrum in mesoscopic systems fluctuate in positions and the distribution of the fluctuations reveals information about the microscopic nature of the structure under consideration. Here, we investigate mesoscopic fluctuations of a secondary gap that appears in the quasiclassical spectrum of a chaotic cavity coupled to one or more superconductors. Utilizing a random matrix model, we compute numerically the energies of Andreev levels and access the distribution of the gap widths. We mostly concentrate on the universal regime ${E}_{\mathrm{Th}}\ensuremath{\gg}\mathrm{\ensuremath{\Delta}}$, with ${E}_{\mathrm{Th}}$ being the Thouless energy of the cavity and $\mathrm{\ensuremath{\Delta}}$ being the superconducting gap. We find that the distribution is determined by an intermediate energy scale ${\mathrm{\ensuremath{\Delta}}}_{g}$ with the value between the level spacing in the cavity ${\ensuremath{\delta}}_{s}$ and the quasiclassical value of the gap ${E}_{g}$. From our numerics we extrapolate the first two cumulants of the gap distribution in the limit of large level and channel number. We find that the scaled distribution in this regime is the Tracy-Widom distribution: the same as found by Vavilov et al. [Phys. Rev. Lett. 86, 874 (2001)] for the distribution of the minigap edge in the opposite limit ${E}_{\mathrm{Th}}\ensuremath{\ll}\mathrm{\ensuremath{\Delta}}$. This leads us to the conclusion that the distribution found is a universal property of chaotic proximity systems at the edge of a continuous spectrum in agreement with the known random matrix models featuring a square root singularity in the density of states.

Logging leaves a fingerprint on the number, size, spatial configuration and geometry of tropical forest canopy gaps

AbstractRecent advances in remote sensing such as airborne laser scanning have revolutionized our ability to accurately map forest canopy gaps, with huge implications for tracking forest dynamics at scale. However, few studies have explored how canopy gaps vary among forests at different successional stages following disturbances, such as those caused by logging. Moreover, most studies have focused exclusively on the size distribution of gaps, ignoring other key features such as their spatial distribution and shape. Here, we test a series of hypotheses about how the number, size, spatial configuration, and geometry of gaps vary across a logging disturbance gradient in Malaysian Borneo. As predicted, we found that recently logged forests had much higher gap fraction compared to old‐growth forests, a result of having both a greater total number of gaps and a higher proportion of large gaps. Regrowing forests, on the other hand, fell at the opposite end of the spectrum, being characterized by both fewer and smaller gaps compared to nearby old‐growth forests. Across all successional stages gaps were found to be spatially clustered. However, logging significantly diluted the degree of spatial aggregation and led to the formation of gaps with much more complex geometries. Our results showcase how logging and subsequent regrowth substantially alter not just the number and size of gaps in a forest, but also their spatial arrangement and shape. Linking these emergent patterns to their underlying processes is key to better understanding the impacts of human disturbance on the structure and function of tropical forests.Abstract in Malay is available with online material.

A new approach for measuring the air gap between diaper and baby skin

The air gap between baby skin and top sheet of disposable diapers is the main place where baby’s metabolic heat, perspiration, and moisture produced by evaporation of urine stay and transfer. Heat and moisture transfer underneath a diaper are greatly affected by the shape and size of the air gap, therefore, it is of significant importance to explore the air gap between diaper and baby skin for comfort and skin health of babies. Currently, it is still a big problem to accurately measure and characterize the air gap of diaper for scholars. In this article, a new approach to measure the air gap, combining three-dimensional scanning, liquid silicone rubber filling, and image processing methods, was proposed to obtain the shape and size of the air gap between diaper and baby skin by region, for quantitative research on heat and moisture transfer mechanism of diapers. In addition, several indicators, including air volume, air gap thickness, and contact area, as well as clothing area factor of the diaper, were chosen to quantify the air gap size and distributions. After verification of accuracy and repeatability, this new approach can effectively measure the size of the air gap underneath the diaper, and provide a feasible way for exploration on quantitative relationship between thermal and moisture comfort of diapers and their structural design, fit, and diapering habits. Furthermore, diaper designers and baby caregivers can obtain guidelines of diaper structural design, wearing and change to improve the microclimate in the diaper for baby comfort and skin health.

Auxetics and Other Systems with Unusual Characteristics

Auxetics and Other Systems with Unusual Characteristics

Deposition, diffusion, and nucleation on an interval

Motivated by nanoscale growth of ultra-thin films, we study a model of deposition, on an interval substrate, of particles that perform Brownian motions until any two meet, when they nucleate to form a static island, which acts as an absorbing barrier to subsequent particles. This is a continuum version of a lattice model studied in the applied literature. We show that the associated interval-splitting process converges in the sparse deposition limit to a Markovian process (in the vein of Brennan and Durrett) governed by a splitting density with a compact Fourier series expansion but, apparently, no simple closed form. We show that the same splitting density governs the fixed deposition rate, large time asymptotics of the normalized gap distribution, so these asymptotics are independent of deposition rate. The splitting density is derived by solving an exit problem for planar Brownian motion from a right-angled triangle, extending work of Smith and Watson.

The impact of electron beam irradiation on some novel borate glasses doped V2O5; Optical, physical and spectral investigation

New borate glass systems with composition of 56B2O3 + 25Li2O + 10Na2O + 5CaO + 2SrO + 2Al2O3 + 0.5 TeO2 + x V2O5, where × = 0.2 or 0.3 (wt. %), were fabricated via the traditional melting-annealing method at low temperature (650–750 °C). Some of the glasses optical, physical, chemical and spectral measurements were investigated within the impact of electron beam (EB) irradiation up to 8 kGy. UV–visible spectra revealed peaks at ∼ 290 and ∼ 300 nm for 0.2 and 0.3 V2O5 glasses, respectively. In addition to broad visible band at ∼ 580 nm owing to the participation of vanadium ions as V5+ with possible conversion to V3+/V4+ under the effect of EB irradiation. FTIR spectra revealed the main trigonal BO3 and tetrahedral BO4 units with an increase in N4 values by the progressive EB irradiation. ESR spectra revealed a gradual increase in intensity with irradiation doses. While, testing chemical durability in distilled H2O at 100 °C reveals a good manner before and after irradiation process. Some physical parameters e.g. optical energy gap (Eoptdirect and Eoptindirect), Urbach energy (EUrbach), refractive index (n) and spectral distribution (k) showed also a gradual decrease with continual irradiation owing to the gradual generating of non-bridging oxygens NBOs and progressive transformation of BO3 to BO4 units. The overall data displayed some dosimetric properties of the two studied glasses with a useful dose range 3–8 kGy of EB radiation. The study recommends usage of glasses as glass dosimeters in medical sterilization, industry and food irradiation processing.

Dual geometric perception for cross-domain road segmentation

Road segmentation plays an important role in navigation systems and autonomous driving. However, many methods in road segmentation are based on supervised learning and suffer from performance degradation in the real world. There is a certain domain gap (distribution shift problem) between the source domain (training data) and the target domain (testing data). In this paper, we propose a Dual-Geometric Perception (DGP) approach for cross-domain road segmentation, which jointly uses semantic and dual-geometric information to learn the domain-invariant feature for road segmentation. First, we propose an RGB-N dual stream network structure, which effectively fuses normal vector information and RGB information to reduce domain gap. Moreover, a dual geometric adversarial learning strategy is proposed to utilize depth-aware and normal vector features to perform better domain alignment. Furthermore, a self-training learning strategy is used to further improve the model’s generalizability in the target domain. Extensive experiments demonstrate that our proposed DGP achieves superior performance on lane-to-lane and lane-to-sidewalk road domain adaptation tasks.

Clothing air gaps in various postures in firefighters’ work

Both the physical properties of the fabric materials used in clothing and the effective design of the clothing, primarily in terms of the air gap thickness, restrict the transmission of the thermal energy from the heat source to the firefighter’s body. The air gap distribution over the body in real deployment conditions of firefighters will vary, and is likely to be different from the air gap distribution in standardised manikin tests in standing upright posture. In this study, we investigated differences in the distribution of air layers in firefighters' clothing in three postures reflecting realistic on-duty exposure conditions (crawling, hose-holding, and standing upright used in laboratory tests) using 3D body scanning technology. The body posture induced substantial changes in the air gap thickness on the upper body (chest and back) and lower body. These changes were reflected in both the thermal and evaporative resistance of the ensemble, and consequently, in their potential thermal performance in the field. Therefore, it is recommended to consider body postures during the evaluation of clothing protective performance. Secondly, the knowledge of local clothing properties in real-life exposure provides a true protection mapping and gives design inputs to improve the local protective properties of firefighters' clothing.

Structural Optimization of Single Crystal Turbine Blade Based on Recrystallization Critical Stress

In view of the problem that the surface structural recrystallization (SRR) is very easy to occur in the splitting gap area of the single crystal blade. A method to control the residual stress is proposed that based on the critical stress of single crystal recrystallization, and the structural details are optimized by combined with the numerical calculation and experimental verification. To reduce the residual stress level and change the residual stress distribution in the single crystal blade splitting gap. So as to control the level of residual stress, which is no more than the recrystallization critical stress. Finally, the experimental verification is completed by the optimized blade. The verification results show that the maximum residual stress is reduced by about 10% in the tail splitting region, and the recrystallization structure is completely eliminated in the original structure. It is proved that this method is a great effectiveness to control the structural integrity and surface structure connectivity of the single crystal blade.

Efficient Probabilistic Computing with Stochastic Perovskite Nickelates.

Probabilistic computing has emerged as a viable approach to solve hard optimization problems. Devices with inherent stochasticity can greatly simplify their implementation in electronic hardware. Here, we demonstrate intrinsic stochastic resistance switching controlled via electric fields in perovskite nickelates doped with hydrogen. The ability of hydrogen ions to reside in various metastable configurations in the lattice leads to a distribution of transport gaps. With experimentally characterized p-bits, a shared-synapse p-bit architecture demonstrates highly parallelized and energy-efficient solutions to optimization problems such as integer factorization and Boolean satisfiability. The results introduce perovskite nickelates as scalable potential candidates for probabilistic computing and showcase the potential of light-element dopants in next-generation correlated semiconductors.

Research on nonlinear characteristics for frequency domain dielectric response of transformer oil-paper insulation

Frequency domain dielectric response technology is widely used to detect the major insulation status of transformers. The influence of the test excitation amplitude on the nonlinear change of the dielectric characteristics of oil-paper insulation will interfere with the accuracy of the assessment results. In this paper, the electric field intensity distribution law of the oil gap in the oil-paper insulation model is obtained through test and simulation analysis. The influence of insulation aging, test temperature, and excitation frequency on the electric field distribution in the oil gap is clarified, it provides a reference for field strength for nonlinear loss calculation of oil-paper insulation. Meanwhile, based on the Garton’s ion motion nonlinear response model, considering the influence of the external electric field on the ion recombination in the oil gap, the nonlinear loss calculation model of transformer oil-paper insulation is corrected. Furthermore, the mechanism of positive and negative nonlinear loss variation for the oil-paper insulation model in a wide frequency range is revealed, and the calculation method of critical frequency and critical field strength of nonlinear loss variation in the oil-paper insulation model is proposed. Finally, according to the test results of the frequency domain dielectric response of oil-paper insulation with different aging and the apparent ion mobility in transformer oil, combined with the corrected calculation method proposed in this paper, the influence of the test excitation amplitude on the nonlinear change of the loss factor of oil-paper insulation is eliminated at different temperatures. The mean square error (MSE) of the corrected loss factor is reduced by 88.03% on average compared with that before.

Forest disturbance and growth processes are reflected in the geographical distribution of large canopy gaps across the Brazilian Amazon

Abstract Canopy gaps are openings in the forest canopy resulting from branch fall and tree mortality events. The geographical distribution of large canopy gaps may reflect underlying variation in mortality and growth processes. However, a lack of data at the appropriate scale has limited our ability to study this relationship until now. We detected canopy gaps using a unique LiDAR dataset consisting of 650 transects randomly distributed across 2500 km2 of the Brazilian Amazon. We characterized the size distribution of canopy gaps using a power law and we explore the variation in the exponent, α. We evaluated how the α varies across the Amazon, in response to disturbance by humans and natural environmental processes that influence tree mortality rates. We observed that South‐eastern forests contained a higher proportion of large gaps than North‐western, which is consistent with recent work showing greater tree mortality rates in the Southeast than the Northwest. Regions characterized by strong wind gust speeds, frequent lightning and greater water shortage also had a high proportion of large gaps, indicating that geographical variation in α is a reflection of underlying disturbance processes. Forests on fertile soils were also found to contain a high proportion of large gaps, in part because trees grow tall on these sites and create large gaps when they fall; thus, canopy gap analysis picked up differences in growth as well as mortality processes. Finally, we found that human‐modified forests had a higher proportion of large gaps than intact forests, as we would expect given that these forests have been disturbed. Synthesis. The proportion of large gaps in the forest canopy varied substantially over the Brazilian Amazon. We have shown that the trends can be explained by geographical variation in disturbance and growth. The frequency of extreme weather events is predicted to increase under climate change, and changes could lead to greater forest disturbance, which should be detectable as an increased proportion of large gaps in intact forests.

Performance Analysis and Optimization of a Novel Outer Rotor Field-Excited Flux-Switching Machine with Combined Semi-Closed and Open Slots Stator

Slotting effect in electric machines reduces flux per pole that effect magnetic flux density distribution in the air gap which induces harmonics in magnetic flux density causing flux pulsation, that in turn generates dominant torque pulsation in the form of cogging torque and torque ripples. To overcome the abovesaid demerits, a novel outer rotor field-excited flux-switching machine (OR-FSFSM) with a combined semi-closed and open slots stator is proposed in this study. The developed OR-FEFSM offers a high-power factor, due to the utilization of the semi-closed slot for armature coils. The open slot stator structure was chosen for the field excitation coil, which effectively suppresses leakage reluctance that causes flux pulsation. Thus, the influence of torque ripples is reduced, and the average torque is improved. In order to investigate the effectiveness of the proposed OR-FEFSM, a detailed study of stator slot and rotor pole combinations are performed. Based on simplified mathematical formulation, 12S/7P (stator slot/rotor poles), 12S/11P, 12S/13P, and 12S/17P are the most feasible combinations. Finite Element Analysis (FEA) based on comprehensive electromagnetic performance is performed on each combination, and found that 12S/13P offers the highest average torque of 4.62 Nm, whereas 3.72 Nm, 2.72Nm, and 1.68 Nm average torque is offered by 12S/17P, 12S/7P, and 12S/11P, respectively. Based on the initial analysis, 12S/13P was considered for further analysis and optimized using JMAG built-in Genetic Algorithm (GA). Moreover, thermal analysis was performed, and the proposed design was compared with the conventional design.