Metal-organic frameworks (MOFs) derived carbon-based composites exhibit great potential in the fields of electromagnetic wave (EMW) absorption. However, which kind of MOFs derivative structure has ...better electromagnetic wave absorption is an urgent problem to be addressed. Herein, caterpillar-like hierarchically structured Co/MnO/CNTs was successfully prepared by pyrolysis of core-shell manganese dioxide and zeolitic imidazolate framework template. The material shows excellent EMW absorption performance in different frequencies range based on the hierarchical structure. Owing to the unique distribution of carbon nanotubes on the caterpillar-like hierarchical structure, the generated multi heterogeneous interfaces and local conductive network are beneficial to interfacial polarization, conduction loss, matched impedance as well as multiple scattering. The composite composites present outstanding EMW absorption achieved with effective absorption bandwidth covering from 13.52 GHz to 18 GHz with thickness of only 1.32 mm. Moreover, the composite also demonstrates a microwave absorption with the qualified frequency bandwidth of 5.36 GHz, and a strong reflection loss of −58.0 dB with a low filling amount of 35%. The result provides a new approach for developing EMW absorbing materials with hierarchical structure.
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•The caterpillar-like hierarchical structure composed of carbon nanotubes was prepared.•The composites have wide microwave absorption bandwidth and strong reflection loss.•The hierarchical material has the advantage in broadband impedance matching design.
The pine caterpillar (Dendrolimus spectabilis Bulter, Lepidoptera: Lasiocampidae), as an ectotherm, temperature plays a crucial role in its development. With climate change, earlier development of ...insect pests is expected to pose a more frequent threat to forest communities. Yet the quantitative research about the extent to which global warming affects pine caterpillar populations is rarely understood, particularly across various elevations and latitudes. Spring phenology of pine caterpillars showed an advancing trend with 0.8 d/10a, 2.2 d/10a, 2.2 d/10a, and 3.3 d/10a under the SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5 scenario, respectively. There was a maximum advance of 20 d in spring phenology of pine caterpillars during the 2090s, from mid-March to early March, and even late February. This study highlighted the significant advance in spring phenology at elevations >1000 m and lower latitudes. Consequently, the differences in elevational and latitudinal gradients were relatively small as the increasing temperatures at the end of the 21st century. And the average temperature in February–March was effective in explaining theses variability. These findings are crucial for adapting and mitigating to climate change.
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•Global warming has led to a notable advancement in pine caterpillar spring phenology.•Pine caterpillars are earlier by 0 to 48 %, shifting from mid-March to late February.•Significant shifts in pine caterpillar development at >1000 m elevations, 38–38.5°N.
On caterpillar factors in graphs Bujtás, Csilla; Jendroľ, Stanislav; Tuza, Zsolt
Theoretical computer science,
12/2020, Volume:
846
Journal Article
Peer reviewed
Open access
A caterpillar is either a K2 or a tree on at least 3 vertices such that deleting its leaves we obtain a path of order at least 1. Given a simple undirected graph G=(V,E), a caterpillar factor of G is ...a set of caterpillar subgraphs of G such that each vertex v∈V belongs to exactly one of them. A caterpillar factor F is internally even if every vertex of degree degF(v)≥2 has an even degree; F is odd if degF(v) is odd for every v∈V(G). We present a linear-time algorithm that decides whether a tree admits an internally even caterpillar factor and, on the other hand, we prove that the decision problem is NP-complete on the class of planar bipartite graphs. For the odd caterpillar factor problem, we obtain similar results. It can be decided in linear time over the class of trees, but the problem is NP-complete on the class of bipartite graphs.
Let m≥1 be an integer and G be a graph with m edges. We say that G has an antimagic orientation if G has an orientation D and a bijection τ:A(D)→{1,…,m} such that no two vertices in D have the same ...vertex-sum under τ, where the vertex-sum of a vertex v in D under τ is the sum of labels of all arcs entering v minus the sum of labels of all arcs leaving v. Hefetz et al. (2010) conjectured that every connected graph admits an antimagic orientation. The conjecture was confirmed for certain classes of graphs such as regular graphs, graphs with minimum degree at least 33, bipartite graphs with no vertex of degree zero or two, and trees including caterpillars and complete k-ary trees. We prove that every subdivided caterpillar admits an antimagic orientation, where a subdivided caterpillar is a subdivision of a caterpillar T such that the edges of T that are not on the central path of T are subdivided the same number of times.
Urbanization can have marked effects on plant and animal populations’ phenology, population size, predator–prey, interactions and reproductive success. These aspects are rarely studied simultaneously ...in a single system, and some are rarely investigated, e.g., how insect phenology responds to urban development. Here, we study a tri-trophic system of trees, phytophagous insects (caterpillars), and insectivorous birds (Great Tits) to assess how urbanization influences (1) the phenology of each component of this system, (2) insect abundance, and (3) avian reproductive success. We use data from two urban and two forest sites in Hungary, central Europe, collected over four consecutive years. Despite a trend of earlier leaf emergence in urban sites, there is no evidence for an earlier peak in caterpillar abundance. Thus, contrary to the frequently stated prediction in the literature, the earlier breeding of urban bird populations is not associated with an earlier peak in caterpillar availability. Despite this the seasonal dynamics of caterpillar biomass exhibited striking differences between habitat types with a single clear peak in forests, and several much smaller peaks in urban sites. Caterpillar biomass was higher in forests than urban areas across the entire sampling period, and between 8.5 and 24 times higher during the first brood’s chick-rearing period. This higher biomass was not associated with taller trees in forest sites, or with tree species identity, and occurred despite most of our focal trees being native to the study area. Urban Great Tits laid smaller clutches, experienced more frequent nestling mortality from starvation, reared fewer offspring to fledging age, and their fledglings had lower body mass. Our study strongly indicates that food limitation is responsible for lower avian reproductive success in cities, which is driven by reduced availability of the preferred nestling diet, i.e., caterpillars, rather than phenological shifts in the timing of peak food availability.
Oil palm cultivation stands as a crucial industry in Indonesia, significantly contributing to the nation’s economy by generating employment opportunities and fostering social welfare for communities ...residing near plantations. Despite its economic importance, oil palm plantations face various challenges, with one prominent issue being the infestation of nettle caterpillar pests. These pests cause leaf skeletonization, resulting in a staggering 36% reduction in oil palm productivity over a two-year period. This paper explores diverse strategies for pest management in oil palm plantations, encompassing biological control through the stimulation of natural predators, mechanical control involving the collection and incineration of cocoons, and chemical control through pesticide application. The research introduces a predator–prey mathematical model for oil palm plantation pests, where the leaf area serves as the primary food source for caterpillars, acting as prey. Through dynamic model analysis, four equilibrium points are identified, with interconnected conditions dictating their existence and stability. These conditions are visually represented in a bifurcation plane, providing concise information. The study further includes bifurcation diagrams of equilibrium points to elucidate the influence of each parameter on pests, predators, and the leaf area of oil palm plants. Additionally, sensitivity analysis of the stable interior equilibrium point is conducted to understand the impact of individual parameters. The paper extends its investigation to optimal control strategies, evaluating six scenarios categorized into two population conditions: with predators and without predators. Within each population condition, three control strategies are considered—chemical control only, mechanical control only, and a combination of chemical and mechanical control. Simulation results from the optimal control study reveal that the presence of natural predators emerges as a pivotal strategy in effectively managing nettle caterpillars. Notably, the control of resistant pests through pupa incineration has a substantial impact on reducing the caterpillar population in subsequent life cycles.
•In current study, the MELP-S-B predator-prey model is proposed for managing nettle caterpillar pests in oil palm plantations involving the control measures.•The inclusion of prey populations, specifically oil palm leaves, in this predator-prey model constitutes the most fundamental novelty of this study.•The main objective of this research is to determine the dynamics of pests in plantations and avoid economic losses due to pests in oil palm plantations.•In-depth analysis of system dynamics around four equilibrium points conducted. Sensitivity analysis is carried out to measure the influence of parameters at the interior point.•Optimal control study conducted to manage pest abundance in oil palm plantations under varying predator presence. Numerical simulations of six strategies, blending mechanical and chemical measures, offer insights into effective pest control combinations.
Maximizing the mean subtree order Mol, Lucas; Oellermann, Ortrud R.
Journal of graph theory,
August 2019, 2019-08-00, 20190801, Volume:
91, Issue:
4
Journal Article
Peer reviewed
Open access
This article focuses on properties and structures of trees with maximum mean subtree order in a given family; such trees are called optimal in the family. Our main goal is to describe the structure ...of optimal trees in Tn and Cn, the families of all trees and caterpillars, respectively, of order n. We begin by establishing a powerful tool called the Gluing Lemma, which is used to prove several of our main results. In particular, we show that if T is an optimal tree in Tn or Cn for n≥4, then every leaf of T is adjacent to a vertex of degree at least 3. We also use the Gluing Lemma to answer an open question of Jamison and to provide a conceptually simple proof of Jamison's result that the path Pn has minimum mean subtree order among all trees of order n. We prove that if T is optimal in Tn, then the number of leaves in T is O(log2n) and that if T is optimal in Cn, then the number of leaves in T is Θ(log2n). Along the way, we describe the asymptotic structure of optimal trees in several narrower families of trees.
In this paper, we investigate whether the symbolic and ordinary powers of a binomial edge ideal
J
G
are equal. We show that the equality
J
G
t
=
J
G
(
t
)
holds for every
t
≥
1
when
|
Ass
(
J
G
)
|
=
...2
. Moreover, if
G
is a caterpillar tree, then one has the same equality. Finally, we characterize the generalized caterpillar graphs which the equality of symbolic and ordinary powers of
J
G
occurs.
Optimizing the layout of sparse planar arrays constrained by minimum element spacing to reduce the peak side lobe level (PSLL) is a difficult and challenging task in engineering applications. Here, a ...new sparse array design method is proposed under the constraints of aperture size, the number of array elements, and minimum spacing between elements. The approach is based on a new element mutation method which is proposed for mutating the position of any element within the aperture without changing the position of other elements. Because a mutating element can be thought of as being placed inside the board like a black/white stone in Go or crawling somewhere nearby like a caterpillar, we call it Go-Caterpillar-mutation (GCM). Based on GCM, a stochastic optimization algorithm (GCM-OA) is proposed to optimize the layout of sparse planar arrays. Several examples demonstrate the robustness and rapidity of GCM-OA in reducing PSLL by adjusting the array element positions under various constraints.
This paper studies two inverse eigenvalue problems for two kinds of acyclic matrices whose graphs are caterpillars. The spectral data of the first problem considers the minimal and maximal ...eigenvalues of all leading principal submatrices of the matrix. The second consists of an extremal eigenvalue of each leading principal submatrix and one eigenpair of the matrix. In the main results, we give sufficient conditions for the existence of such matrices, and their proofs provide algorithmic procedures for their construction. Finally, we present some numerical examples that illustrate the applicability of the solutions obtained.
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