Dense Rows Research Articles

A Fossil Thrips (Thysanoptera: Terebrantia) from a Cretaceous Deposit in Orapa1

Abstract A fossil thrips is described using a single compression fossil from an Upper Cretaceous deposit, the Orapa Diamond Mine in Botswana. It is the first record of a Cretaceous thrips from Africa. It is diagnosed by the following characteristics: general habitus; narrow, straplike forewing and hindwing with fringe cilia; with forewing becoming progressively larger in distal third; and abdomen with dense transversal rows of microtrichia and terminal setae. The specimen is complete, except that the antennae are absent. At Orapa, the fossil thrips would have been possibly found feeding on leaves, stem or flower tissues of both gymnosperms and angiosperms in and around the crater lake. The fossil thrips adds to the taxonomic diversity of the Orapa fauna. Moreover, it broadens the knowledge of the diversity, geography and evolution of Mesozoic Thysanoptera.

Ecosystem engineering: Rufous-bellied woodpecker Dendrocopos hyperythrus (Vigors, 1831) modifying tree shapes of Himalayan broadleaved forests

The study, conducted from 2005 to 2018, encompassed twelve sites in Nepal, including both protected and non-protected areas. The primary focus of the observations was on tree species, their shapes, structures, and their interactions with the rufous-bellied woodpecker. The rufous-bellied woodpecker in Nepal's Himalayas predominantly utilized specific tree species, notably oak (Quercus semecarpifolia and Q. glauca), birch (Betula utilis), Himalayan holly (Ilex dyperina), and maple (Acer species). These trees displayed a remarkable diversity in girth sizes, ranging from 0.5 meters to almost 2.5 meters, with tree heights varying from 5 to 30 meters. Among these, Quercus semecarpifolia was the preferred choice. Notably, rufous-bellied woodpeckers exhibited a distinctive behavior of drilling numerous small holes around tree trunks, often forming ring-like structures. These "sap-wells" were meticulously created by drilling dense rows of small holes encircling the tree trunks and served as the primary food source for the woodpeckers. They attracted a wide array of insects and offered a valuable source of protein. This continuous interaction between the woodpeckers and the trees resulted in unique modifications to the trunks of old-growth forest trees. Over time, the trees developed swollen trunks, and some trunks even displayed bending and deformations due to the woodpecker’s sap-well chiselling activities. Furthermore, the study observed several other bird species benefiting from these sap-wells created by the rufous-bellied woodpeckers. This observation underscores the broader ecological significance of these structures, benefiting a diverse range of species within the ecosystem. In essence, this study sheds light on the rufous-bellied woodpecker's role as an "ecosystem engineer" and an indicator of forest health in the temperate Himalayas, emphasizing its critical ecological importance.

High-Temperature Superconducting Interconnects for Ultra-Low Temperature, High-Field Environments

Coplanar (with the ground) 20 cm long waveguides are manufactured from the YBCO-on-Kapton material. We inves-tigate the effect of parasitic ground plane resonances on the per-formance of these waveguides. It is concluded that dense rows stitching vias are essential for isolating the lines to a level below 60 dB at 6 GHz. We demonstrate a metalized via technology that is compatible with both the traditional Flexible Printed Circuit (FPC) process and the epitaxial YBCO material. Stitching via fence with the via period 10 mm is shown as effective in suppress-ing parasitic resonances at 77 K.

Density estimation method of mature wheat based on point cloud segmentation and clustering

The sustainable development of agriculture needs to rely on precision agricultural technology. The premise and key to realizing precision agriculture is the research on the characteristics of crops in the field. For wheat plants, the ear is the flower or fruit part at the top of the wheat stem, which is one of the important components of yield, and its density can be said to be one of the most important traits. Its number is arguably-one of the most important phenotypic traits. The traditional method of density measurement is manual, which is time-consuming and laborious. Therefore, an efficient and convenient wheat density estimation scheme is needed to provide data support for crop yield monitoring, to achieve a better production management system. Stereo vision is a 3D imaging method that allows rapid measurement of plant structures, and point cloud segmentation is the key to studying the 3D spatial characteristics of plants. In this paper, the three-dimensional point cloud of wheat reconstructed by stereo vision technology is used for segmentation and clustering, and a method for clustering dense wheat rows is proposed. Firstly, a binocular camera was used to record video to reconstruct the wheat point cloud; then, point cloud pre-processing was used to remove noise; then, the octree splitting algorithm and voxel mesh merging algorithm were used to divide the dense wheat, and then clustering algorithm was used to get the point cloud of wheat ears; finally, the relationship model between the number of wheat ears point clouds and the number of wheat plants was established by linear regression analysis with R2 of 0.97. To verify the effectiveness of the algorithm, the actual field measurements and the predicted values of the algorithm were compared, with R2 of 0.93. The density estimation method provides a new method for the study of phenotypic information of crop population information and also provides a reference for nondestructive crop measurements.

Macro-mechanical properties of magnetorheological fluids based on body-centered cubic structure

This paper addresses the problem that the microstructure model of magnetorheological fluid established by traditional single-chain or multi-chain dense rows is unable to accurately describe the rheological behavior and the sudden change of macroscopic mechanical properties under the action of an applied magnetic field, and analyzes the stable cluster-like structure formed by a specific volume fraction of magnetorheological fluids in a micro-narrow channel under the action of external magnetic field and extrusion pressure. This paper also establishes the equations of motion and dynamics of magnetic particles under the action of external magnetic field, analyzes the dynamic evolution of particle microstructure, performs numerical simulations of two-dimensional chaining using Matlab, and establishes a microscopic observation test bench for comparison and verification; and it establishes a model of complex cluster-like structure of magnetorheological fluids body-centered cubic, and analyzes the system energy, stability and force of the body-centered cubic structure based on the minimum system energy theory and Hertzian contact theory; and further establishes a shear yield stress model based on the body-centered cubic microstructure to analyze the macroscopic mechanical properties of magnetorheological fluids, thereby enriching the theoretical system of extrusion strengthening of magnetorheological fluids in the microscale.

Solving large linear least squares problems with linear equality constraints

We consider the problem of solving large-scale linear least squares problems that have one or more linear constraints that must be satisfied exactly. While some classical approaches are theoretically well founded, they can face difficulties when the matrix of constraints contains dense rows or if an algorithmic transformation used in the solution process results in a modified problem that is much denser than the original one. We propose modifications with an emphasis on requiring that the constraints be satisfied with a small residual. We examine combining the null-space method with our recently developed algorithm for computing a null-space basis matrix for a “wide” matrix. We further show that a direct elimination approach enhanced by careful pivoting can be effective in transforming the problem to an unconstrained sparse-dense least squares problem that can be solved with existing direct or iterative methods. We also present a number of solution variants that employ an augmented system formulation, which can be attractive for solving a sequence of related problems. Numerical experiments on problems coming from practical applications are used throughout to demonstrate the effectiveness of the different approaches.

A null-space approach for large-scale symmetric saddle point systems with a small and non zero (2, 2) block

Null-space methods have long been used to solve large sparse n × n symmetric saddle point systems of equations in which the (2, 2) block is zero. This paper focuses on the case where the (1, 1) block is ill conditioned or rank deficient and the k × k (2, 2) block is non zero and small (k ≪ n). Additionally, the (2, 1) block may be rank deficient. Such systems arise in a range of practical applications. A novel null-space approach is proposed that transforms the system matrix into a nicer symmetric saddle point matrix of order n that has a non zero (2, 2) block of order at most 2k and, importantly, the (1, 1) block is symmetric positive definite. Success of any null-space approach depends on constructing a suitable null-space basis. We propose methods for wide matrices having far fewer rows than columns with the aim of balancing stability of the transformed saddle point matrix with preserving sparsity in the (1, 1) block. Linear least squares problems that contain a small number of dense rows are an important motivation and are used to illustrate our ideas and to explore their potential for solving large-scale systems.

Electron‐Beam‐Induced Current and Deep‐Level Transient Spectroscopy Study of Dislocation Trails in Au‐Doped Si

The properties of extended defects introduced by plastic deformation at 600 °C in n‐Si co‐doped with gold are studied by the electron‐beam‐induced current (EBIC) and deep‐level transient spectroscopy (DLTS) methods. It is shown that intrinsic point defects generated by moving dislocations stimulate the gold redistribution. As a result, regions depleted with gold are formed near dense dislocation rows. It is shown that dislocation trails decorated with gold are charged, which is a reason for the formation of bright EBIC contrast outside the Schottky barrier.

Strengths and Limitations of Stretching for Least-squares Problems with Some Dense Rows

We recently introduced a sparse stretching strategy for handling dense rows that can arise in large-scale linear least-squares problems and make such problems challenging to solve. Sparse stretching is designed to limit the amount of fill within the stretched normal matrix and hence within the subsequent Cholesky factorization. While preliminary results demonstrated that sparse stretching performs significantly better than standard stretching, it has a number of limitations. In this article, we discuss and illustrate these limitations and propose new strategies that are designed to overcome them. Numerical experiments on problems arising from practical applications are used to demonstrate the effectiveness of these new ideas. We consider both direct and preconditioned iterative solvers.

The Most Caribbean of Stories

The Most Caribbean of Stories Maya Doig-Acuña (bio) Click for larger view View full resolution Two men harvest bananas at a United Fruit Company plantation, Tiquisate, Guatemala, 1945. Photograph from Frank Scherschel/The LIFE Picture Collection, Getty Images. [End Page 12] i was in college when I first learned that my great-grandmother, Lydia Andrews, who my father and his siblings and cousins called Ganny, was born on the United Fruit Plantation in Puerto Limón, Costa Rica. Before Papi shared this fact with me, I knew Ganny only in small glimpses of family memory that seemed to contract the world in which she existed, such that she existed only in ours—that is, she belonged specifically to my family, and not to history. We had briefly shared this world—between 1994, when I was born, and 1998, when she died—though we never met, because she lived in Panama and I in Brooklyn. But I had seen photos of her: mostly sepia-toned images of a dark-skinned, white-haired woman with glasses, a nose like my father's, and a graceful neck that made her the center of each picture. There was one photo in vivid color taken just a few years before her passing, in Coronado, Panama. She sat on a chair surrounded by our family, wearing a red dress patterned with white flowers, her hands folded on her lap. When Ganny died, my grandmother went to Panama for the funeral, and on her return to New York, brought me back a purple stuffed beaver named Benny that she said Ganny had gotten for me. And though it wasn't possible—though Ganny and I no longer occupied the same world—I believed her, and treasured the beaver like an intimate conversation between me and my great-grandmother. As I've gotten older, however, the new details I learn of Ganny's life seem to place her, and our family, into larger orbits of history. Ganny was born in 1900 on a wide swath of US territory, a banana plantation, on the Caribbean coast of Costa Rica. Its proprietor, the United Fruit Company, had been officially founded just a year earlier in 1899, through a company merger [End Page 13] Click for larger view View full resolution A mule-drawn cart hauls bananas on the United Fruit Company plantation near La Lima, Honduras, August 31, 1954. Though tractors were common on the plantation, mules were still used in some areas. Photograph from Associated Press. in Boston. United Fruit owned massive expanses of land stretching across several countries in Central America and the Caribbean, and Ganny's parents had migrated to one of them from St. Lucia as part of a wave of West Indians gone to work for, as Gabriel García Márquez called it, the Banana Company. Ganny's father was a carpenter whose labor was likely tied to the Church, and particularly to a white St. Lucian priest who ministered to the West Indian migrants. Ganny's father, we believe, followed the priest from island to isthmus to island—St. Lucia to Puerto Limón to Bocas del Toro, Panama. Our family doesn't know for sure; what record we have of these migrations lived in Ganny's memory, not on paper.1 But plantation gets stuck on my tongue. What did a Central American plantation owned and operated by white men from the United States look, sound, and feel like? Because Ganny was born but not raised on United Fruit, I wonder about the conditions of birth there; about [End Page 14] Click for larger view View full resolution ID photo of Ganny, aged eighteen, from her time as a laundry worker in the Panama Canal Zone, 1918. midwives, or about the possibility of friends come to help with the baby. The photos I've seen of the plantations from company archives do not tell me much about these conditions. They mostly document labor, though with little attention to laborers: dense rows of banana trees abundant with fruit, wholly cleared dirt pathways dividing those rows, thatched-roof buildings that mark "engineers' quarters" or "overseer's quarters." Even when workers are present...

Sparse Stretching for Solving Sparse-Dense Linear Least-Squares Problems

Large-scale linear least-squares problems arise in a wide range of practical applications. In some cases, the system matrix contains a small number of dense rows. These make the problem significant...

Simulation of Convection–Diffusion Transport in a Laminar Flow Past a Row of Parallel Absorbing Fibers

A numerical simulation of the laminar flow field and convection–diffusion mass transfer in a regular system of parallel fully absorbing fibers for the range of Reynolds numbers up to Re = 300 is performed. An isolated row of equidistant circular fibers arranged normally to the external flow is considered as the simplest model for a hollow-fiber membrane contactor. The drag forces acting on the fibers with dependence on Re and on the ratio of the fiber diameter to the distance between the fiber axes, as well as the fiber Sherwood number versus Re and the Schmidt number, Sc, are calculated. A nonlinear regression formula is proposed for calculating the fiber drag force versus Re in a wide range of the interfiber distances. It is shown that the Natanson formula for the fiber Sherwood number as a function of the fiber drag force, Re, and Sc, which was originally derived in the limit of high Peclet numbers, is applicable for small and intermediate Reynolds numbers; intermediate and large Peclet numbers, where Pe = Re × Sc; and for sparse and moderately dense rows of fibers.

A Schur complement approach to preconditioning sparse linear least-squares problems with some dense rows

The effectiveness of sparse matrix techniques for directly solving large-scale linear least-squares problems is severely limited if the system matrix A has one or more nearly dense rows. In this paper, we partition the rows of A into sparse rows and dense rows (As and Ad) and apply the Schur complement approach. A potential difficulty is that the reduced normal matrix AsTAs is often rank-deficient, even if A is of full rank. To overcome this, we propose explicitly removing null columns of As and then employing a regularization parameter and using the resulting Cholesky factors as a preconditioner for an iterative solver applied to the symmetric indefinite reduced augmented system. We consider complete factorizations as well as incomplete Cholesky factorizations of the shifted reduced normal matrix. Numerical experiments are performed on a range of large least-squares problems arising from practical applications. These demonstrate the effectiveness of the proposed approach when combined with either a sparse parallel direct solver or a robust incomplete Cholesky factorization algorithm.

Passive fire protection in high density village (case study, Bustaman Semarang)

Fire hazard is the disaster that always has an unpredictable process of coming. When it comes, its level scope and the magnitude of the effects cannot be predicted. Dense settlements especially in big cities, among others Bustaman Kampong Semarang never escape from physical problems such as flooding and wildfire. If both are compared in dense settlements scope, so that, wild fire is the most potentially catastrophic. It is necessary to do a research on passive fire protection in a village of high density city such as Bustaman. Qualitative research was conducted using descriptive method to conduct observations and interviews in the Bustaman.Bustaman as a high density village, with narrow roads and dense rows of houses. The terraced buildings are also encountered, and found many buildings use combustible material. That environmental conditions can facilitate the propagation of flames in case of fire.To improve the established Bustaman's environment, in terms of the application of passive fire protection systems, it is recommended to utilize the road as the dividing buildings. Need to build the separation wall fireproof in every each series in several units of too long buildings and attempted open space procurement that separates rows of buildings that are too long, and also the replacement of combustible material with a material that is more incombustible.

Prestructuring sparse matrices with dense rows and columns via null space methods

SummarySeveral applied problems may produce large sparse matrices with a small number of dense rows and/or columns, which can adversely affect the performance of commonly used direct solvers. By posing the problem as a saddle point system, an unconventional application of a null space method can be employed to eliminate dense rows and columns. The choice of null space basis is critical in retaining the overall sparse structure of the matrix. A new one‐sided application of the null space method is also presented to eliminate either dense rows or columns. These methods can be considered techniques that modify the nonzero structure of the matrix before employing a direct solver and may result in improved direct solver performance.

Pivotal Variable Detection of the Covariance Matrix and Its Application to High-Dimensional Factor Models

To estimate the high-dimensional covariance matrix, row sparsity is often assumed such that each row has a small number of nonzero elements. However, in some applications, such as factor modeling, there may be many non-zero loadings of the common factors. The corresponding variables are also correlated to one another and the rows are non-sparse or dense. This paper has three main aims. First,a detection method is proposed to identify the rows that may be non-sparse, or at least dense with many non-zero elements. These rows are called dense rows and the corresponding variables are called pivotal variables. Second, to determine the number of rows, a ridge ratio method is suggested, which can be regarded as a sure screening procedure. Third, to handle the estimation of high-dimensional factor models, a two-step procedure is suggested with the above screening as the first step. Simulations are conducted to examine the performance.

Pivotal variable detection of the covariance matrix and its application to high-dimensional factor models

To estimate the high-dimensional covariance matrix, row sparsity is often assumed such that each row has a small number of nonzero elements. However, in some applications, such as factor modeling, there may be many nonzero loadings of the common factors. The corresponding variables are also correlated to one another and the rows are non-sparse or dense. This paper has three main aims. First, a detection method is proposed to identify the rows that may be non-sparse, or at least dense with many nonzero elements. These rows are called dense rows and the corresponding variables are called pivotal variables. Second, to determine the number of rows, a ridge ratio method is suggested, which can be regarded as a sure screening procedure. Third, to handle the estimation of high-dimensional factor models, a two-step procedure is suggested with the above screening as the first step. Simulations are conducted to examine the performance of the new method and a real dataset is analyzed for illustration.

Solving Mixed Sparse-Dense Linear Least-Squares Problems by Preconditioned Iterative Methods

The efficient solution of large linear least-squares problems in which the system matrix $A$ contains rows with very different densities is challenging. Previous work has focused on direct methods for problems in which $A$ has a few relatively dense rows. These rows are initially ignored, a factorization of the sparse part is computed using a sparse direct solver, and then the solution is updated to take account of the omitted dense rows. In some practical applications the number of dense rows can be significant, and for very large problems, using a direct solver may not be feasible. We propose processing rows that are identified as dense separately within a conjugate gradient method using an incomplete factorization preconditioner combined with the factorization of a dense matrix of size equal to the number of dense rows. Numerical experiments on large-scale problems from real applications are used to illustrate the effectiveness of our approach. The results demonstrate that we can efficiently solve prob...

X-ray topographic study of defects in Si-based multilayer epitaxial power devices

Silicon based multilayered epitaxial structures are currently the main material for large-scale commercial fabrication of generally used power semiconductor devices such as fast recovery epitaxial diodes (FRED), isolate gate bipolar transistor (IGBT), power MOSFETs etc.Defects in silicon based multilayer epitaxial structures used as the initial material for power epitaxial-diffusion devices have been studied by X-ray topography techniques. We show that the dislocation nets with nonuniform distribution of dislocations both over thickness and layer square in the form of dense rows (dislocation walls) or slip bands were principal defects in the initial epitaxial layers and have influenced the electrical characteristics of power devices.The X-ray methods used in the work allow revealing and identifying growth and process defects in device structures, studying their distributions, analyzing their mutual interactions and obtaining valuable information on the nature and evolution of the defects during device structure fabrication processes. This information allowed us to optimize the choice of initial materials and processes aiming to reduce the content of critical electrically active structural defects in the crystals that can influence the parameters of fabricated semiconductor devices; we also increased process yield and tangibly improved semiconductor device operation reliability in severe conditions and emergency modes.

Tomato yield, nitrogen uptake and water use efficiency as affected by planting geometry and level of nitrogen in an arid region

Water has always been the main factor limiting crop production in arid and semi-arid regions where rainfall is insufficient to meet crop demand. The invite to improve water use efficiency and crop productivity, to ensure future food security, has never been more urgent. Tomato yield performance was studied under different planting methods combined with different nitrogen (N) levels to evaluate the potentials and constraints of plant arrangement under drip irrigation for sustaining crop yield, N uptake, N use efficiency (NUE) and water use efficiency (WUE). Three planting methods were tested included arrangement of tomato plants in single rows, 100cm apart (SR), normal twin rows at 40/160cm alternately (NT) and dense twin rows at 40/100cm alternately (DT), which resulted in rising total plant population by 150% as high as SR and NT. This was done along with four N levels (120, 180, 240 and 300kgNha−1), applied continuously by drip irrigation system. Drip laterals were laid out along each single row or in the center of the twin rows; consequently the relative number of laterals and water applied were reduced by 50% and 75% for NT and DT, respectively compared with SR. Dense twin planting produced 24% higher tomato fruit yield over SR although 75% of irrigation water was applied. Otherwise, NT with 50% saving in irrigation water and cost of drip laterals can be realized by loss only 15% fruit yield as compared with SR. Nitrogen supply tended to increase tomato fruit yield significantly up to the highest level of N with all planting methods. The interaction effect of planting method×level of N was significant for almost yield components. Nitrogen supply increased tomato N uptake linearly with maximum N removal from the field 193kgha−1 under DT and N300 treatment combination, which contributed to higher fruit yield and total dry biomass. The lowest N treatment (N120) gave the higher N recovery with all planting methods, despite the sand texture of the soil. NUE was higher under DT as compared with SR but the NUE consistently decreased with increase level of N supply with all planting methods. WUE of both twin planting were higher (69% for NT and 64% for DT) compared with SR indicating to efficient use of water applied under this method of planting. The results of this study suggest that dense twin planting can be viable and rational practice to increase crop yield and saving substantial amount of irrigation water as well as cost of drip laterals.