Compaction Problem Research Articles

COMPACT INTERPOLATION ON Ax = y IN A TRIDIAGONAL ALGEBRA ALG<TEX>$\mathcal{L}$</TEX>

Given vectors x and y in a separable complex Hilbert space , an interpolating operator is a bounded operator A such that Ax = y. In this article, we investigate compact interpolation problems for vectors in a tridiagonal algebra. We show the following : Let Alg be a tridiagonal algebra on a separable complex Hilbert space and let x = and y = be vectors in H. Then the following are equivalent: (1) There exists a compact operator A = in Alg such that Ax = y. (2) There is a sequence in such that converges to zero and for all k , .

RF Specification Test Compaction Using Learning Machines

We present a machine learning approach to the problem of RF specification test compaction. The proposed compaction flow relies on a multi-objective genetic algorithm, which searches in the power-set of specification tests to select appropriate subsets, and a classifier, which makes pass/fail decisions based solely on these subsets. The method is demonstrated on production test data from an RF device fabricated by IBM. The results indicate that machine learning can identify intricate correlations between specification tests, which allows us to infer the outcome of all tests from a subset of tests. Thereby, the number of tests that need to be explicitly carried out and the corresponding cost are reduced significantly without adversely impacting test accuracy.

Influence of the fluid-dynamic and rheological properties of sediments on the process of viscoelastic compaction at different rates of sedimentation

The problem of compaction of depositing sediments is studied for different geophysical characteristics of the process of sedimentation. A model is proposed for describing the compaction of sediments with growing thickness. The model is based on the modern concepts of the viscoelastic rheology of accumulating sediments; and, in terms of mathematics, it is a system of nonlinear differential equations in partial derivatives, which describe the processes of compaction and filtration with an increasing thickness of sediments. I have studied numerically the dependence of the regimes of compaction on the formulated characteristic criteria of similarity in the system of equations. Fluid-dynamic criterion, which characterizes the ratio of the rate of sedimentation to the rate of the filtration of a fluid (the rate of fluidization), and the rheological criterion of compaction, which characterizes the proportion between the viscous and elastic strains on the time scale of the process of compaction, i.e., the ratio of the two time scales—the time scale of the elastic strains’ relaxation and the time scale of the viscous compaction. The complex modeling of the mechanics and hydrodynamics of the interrelated processes of compaction and movement to the surface of the saturating fluids with an increase in the thickness of sediments reproduces the mechanism of the formation of different regimes of compaction, including those, which lead to an anomalously high pore pressure and to significant, in some circumstances step-like rise in the pressure of the saturating fluid, frequently observed at depths of 2–3 km.

Soil Compaction in the Urban Landscape

SL317, a 4-page illustrated fact sheet by Amy L. Shober and Geoffrey C. Denny, discusses the problem of soil compaction, and methods for dealing with it. Published by the UF Department of Soil and Water Science, March 2010. SL 317/SS529: Soil Compaction in the Urban Landscape (ufl.edu)

Alternative characterizations of the proportional solution for nonconvex bargaining problems with claims

Three alternative characterizations of the proportional solution defined on compact and comprehensive bargaining problems with claims are provided. Two new contraction-type and expansion-type axioms are used. Moreover, the single-valuedness axiom is dispensable if the classical symmetry axiom is imposed.

On the compactness problem of extremal functions to sharp Riemannian [formula omitted]-Sobolev inequalities

Let ( M , g ) be a smooth compact Riemannian manifold without boundary of dimension n ⩾ 2 . For 1 < p < q 0 = min { 2 , n } , Djadli and Druet (2001) [13] proved the existence of extremal functions to the following sharp Riemannian L p -Sobolev inequality: ‖ u ‖ L p ∗ ( M ) p ⩽ K ( n , p ) p ‖ ∇ u ‖ L p ( M ) p + B 0 ( p , g ) ‖ u ‖ L p ( M ) p , where p ∗ = n p n − p and K ( n , p ) p and B 0 ( p , g ) stands for, respectively, the first and second Sobolev best constants for this inequality. Let then E g ( p ) be the corresponding extremal set normalized by the unity L p ∗ -norm. In contrast what happens in the whole space R n for 1 < p < n and in the Euclidean sphere S n for p = 2 , we establish the C 0 -compactness of E g ( p ) for any 1 < p < q 0 . Moreover, we address the question from a uniform viewpoint on p. Precisely, we prove that the set ⋃ 1 + ε ⩽ p ⩽ q 0 − ε E g ( p ) is C 0 -compact for any ε > 0 . The continuity of the map p ∈ [ 1 , q 0 ) ↦ B 0 ( p , g ) is discussed in detail since it plays a key role in the proof of the main theorem.

Effect of the metal structure on the loss of stability of a thin plate separating a powder compressed by a shock wave

Results of an experimental and theoretical study of the problem of shock-wave compaction of a metallic powder enclosed into a metallic container with a transverse partition are presented. It is demonstrated that internal stresses in the partition generate disturbances, which evolve under explosive loading and compression of the partition together with the powder. In addition to the loss of stability in the powder, which occurs owing to filling of voids, wave formation on the partition is observed.

Soil compaction and soil management – a review

AbstractSoil compaction is an important component of the land degradation syndrome which is an issue for soil management throughout the world. It is a long standing phenomenon not only associated with agriculture but also with forest harvesting, amenity land use, pipeline installation, land restoration and wildlife trampling. This review concentrates on the impact of soil compaction on practical soil management issues, an area not previously reviewed. It discusses in the context of the current situation, the causes, identification, effects and alleviation of compaction. The principal causes are when compressive forces derived from wheels, tillage machinery and from the trampling of animals, act on compressible soil. Compact soils can also be found under natural conditions without human or animal involvement. Compaction alters many soil properties and adverse effects are mostly linked to a reduction in permeability to air, water and roots. Many methods can be used to measure the changes. In practical situations, the use of visual and tactile methods directly in the field is recommended. The worst problems tend to occur when root crops and vegetables are harvested from soils at or wetter than field capacity. As discussed by a farmer, the effects on crop uniformity and quality (as well as a reduction in yield) can be marked. By contrast, rendzinas and other calcareous soils growing mainly cereals are comparatively free of compaction problems. The effect of a given level of compaction is related to both weather and climate; where soil moisture deficits are large, a restriction in root depth may have severe effects but the same level of compaction may have a negligible effect where moisture deficits are small. Topsoil compaction in sloping landscapes enhances runoff and may induce erosion particularly along wheeltracks, with consequent off‐farm environmental impacts. Indirect effects of compaction include denitrification which is likely to lead to nitrogen deficiency in crops. The effects of heavy tractors and harvesters can to some extent be compensated for by a reduction in tyre pressures although there is concern that deep‐seated compaction may occur. Techniques for loosening compaction up to depths of 45 cm are well established but to correct deeper problems presents difficulties. Several authors recommend that monitoring of soil physical conditions, including compaction, should be part of routine soil management.

Quadratic compact knapsack public-key cryptosystem

Knapsack-type cryptosystems were among the first public-key cryptographic schemes to be invented. Their NP-completeness nature and the high speed in encryption/decryption made them very attractive. However, these cryptosystems were shown to be vulnerable to the low-density subset-sum attacks or some key-recovery attacks. In this paper, additive knapsack-type public-key cryptography is reconsidered. We propose a knapsack-type public-key cryptosystem by introducing an easy quadratic compact knapsack problem. The system uses the Chinese remainder theorem to disguise the easy knapsack sequence. The encryption function of the system is nonlinear about the message vector. Under the relinearization attack model, the system enjoys a high density. We show that the knapsack cryptosystem is secure against the low-density subset-sum attacks by observing that the underlying compact knapsack problem has exponentially many solutions. It is shown that the proposed cryptosystem is also secure against some brute-force attacks and some known key-recovery attacks including the simultaneous Diophantine approximation attack and the orthogonal lattice attack.

Variabilidade espacial da densidade e da porosidade de um Latossolo Vermelho Eutroférrico sob semeadura direta por vinte anos

Todas as práticas de manejo causam impacto sobre os atributos do solo que se traduzem em influência sobre o desenvolvimento das culturas. Sabe-se que no sistema de semeadura direta ocorre compactação do solo na camada superficial, com tendência a progredir com o tempo de cultivo. Este trabalho teve como objetivo avaliar a variabilidade espacial da densidade e da porosidade de um Latossolo Vermelho eutroférrico sob semeadura direta por vinte anos. O trabalho foi desenvolvido em Campinas (SP) considerando o período entre 1985 e 2005. Os atributos analisados neste estudo foram: argila (g kg-1), silte (g kg-1), areia (g kg-1), densidade (kg dm-3), porosidade total (%), macroporosidade (%) e microporosidade (%). Ferramentas de geoestatística foram utilizadas para análise dos dados e construção de mapas de variabilidade espacial da densidade e da porosidade do solo. A amostragem realizada em 1985 não foi capaz de detectar a variabilidade espacial da densidade e porosidade do solo. Nos atributos físicos amostrados em 2005, observou-se alta razão de dependência espacial. Nos mapas de variabilidade espacial não se constatou relação clara entre a textura, a densidade e a porosidade do solo. Na área após vinte anos de manejo com semeadura direta não havia problemas com compactação. O manejo do solo com semeadura direta influenciou favoravelmente a variabilidade espacial dos atributos amostrados em 2005.

Essential norms of weighted composition operators on Müntz spaces

In this paper, we discuss the problem of compactness for weighted composition operators, defined on a Müntz space M Λ ∞ . We compute the essential norm of such operators on the Müntz spaces. As a corollary, we obtain the exact values of essential norms of composition and multiplication operators.

Finding compact structural motifs

Protein structural motif detection has important applications in structural genomics. Compared with sequence motifs, structural motifs are more sensitive in revealing the evolutionary relationships among proteins. A variety of algorithms have been proposed to attack this problem. However, they are either heuristic without theoretical performance guarantee, or inefficient due to employing exhaustive search strategies. This paper studies a reasonably restricted version of this problem: the compact structural motif problem. We prove that this restricted version is still NP-hard, and we present a polynomial-time approximation scheme to solve it. This is the first approximation algorithm with a guaranteed ratio for the protein structural motif problem. 1 1 A preliminary version of this paper appeared in CPM’2007.

Weighted inequalities for a class of matrix operators: the case p ≤ q

We prove a new discrete Hardy-type inequality ||A/||q,u ≤ C||f||p,v, where the matrix operator A is defined by (Af) i:= Σj=1i ai,jfj, ai,j ≥ 0. Moreover, we study die problem of compactness of the ...

Is Deep Zone Tillage Agronomically Viable in Minnesota?

Deep zone tillage is a strategy used to alleviate compaction problems, including plow pans, and to improve internal drainage. Midwestern soils do not typically form a defined plow pan under normal production practices. Despite lack of scientific evidence for yield benefits associated with deep tillage, it is still used in Minnesota as a low cost alternative to tile drainage. To evaluate the soil and economic impact of deep zone tillage on crop yield when a restrictive layer is lacking, a 20-acre field was deep zone tilled to a 20-inch depth, every other 12 rows at 30-inch spacing. After zone tilling, the entire field was ridge tilled. Ridge tillage confines wheel traffic to the same rows, reducing the percent of the field trafficked. All crop and soil measurements were collected in the depressional and upland areas of the field to distinguish if zone till is of benefit in different landscape areas. Crop yields were measured for two seasons following zone tilling a ridge-tilled field. Zone till failed to increase corn and soybean yields. A restrictive layer was not observed in this field and as a result, potential economic losses occurred due to deep zone tillage.

COTTON ROOT VOLUME AND ROOT DRY MATTER AS A FUNCTION OF HIGH SOIL BULK DENSITY AND SOIL WATER STRESS

COTTON ROOT VOLUME AND ROOT DRY MATTER AS A FUNCTION OF HIGH SOIL BULK DENSITY AND SOIL WATER STRESS Charles Duruoha1; Cassio Roberto Piffer2; Paulo Roberto Arbex Silva21United States Department of Agriculture (USDA-ARS), National Soil Dynamics Laboratory, Auburn, AL, U.S.A,. duruohan@juno.com 2Rural Engineering Departament, School of Agronomic Sciences, São Paulo State University, Botucatu, SP 1 ABSTRACT Soil compaction reduces root growth, affecting the yield, especially in the Southern Coastal Plain of the USA. Simulations of the root restricting layers in greenhouses are necessary to develop mechanisms which alleviate soil compaction problems. The selection of three distinct bulk densities based on the Standard Proctor Test is also an important factor to determine which bulk density restricts root penetration. This experiment was conducted to evaluate cotton (Gossypium hirsutum L.) root volume and root dry matter as a function of soil bulk density and water stress. Three levels of soil density (1.2, 1.4, and 1.6 g cm-3), and two levels of water content (70 and 90% of field capacity) were used. A completely randomized design with four replicates in a 3x2 factorial pattern was used. The results showed that mechanical impedance affected root volume positively with soil bulk density of 1.2 and 1.6 g cm-3, enhancing root growth (P&gt;0.0064). Soil water content reduced root growth as root and shoot growth was higher at 70% field capacity than that at 90% field capacity. Shoot growth was not affected by the increase in soil bulk density and this result suggests that soil bulk density is not a good indicator for measuring mechanical impedance in some soils. KEY WORDS: soil density, water stress, root growth. DURUOHA, C.; PIFFER, C. R.; SILVA, P. R. A. VOLUME E MATÉRIA SECA RADICULAR DE ALGODÃO EM FUNÇÃO DA DENSIDADE DO SOLO ELEVADA E DO ESTRESSE HÍDRICO 2 RESUMO A compactação do solo reduz o crescimento radicular e, conseqüentemente, afeta a produção, especialmente no sudoeste do EUA. Simulações de camadas de restrição de raízes em casa de vegetação são necessárias para desenvolver mecanismos que reduzam problemas de compactação dos solos. A seleção de três diferentes densidades de solo baseadas no ensaio de Proctor é também um fator importante para determinar qual densidade restringe a penetração da raiz. O presente trabalho foi realizado para avaliar o volume e matéria seca radicular em função da densidade do solo e da disponibilidade hídrica em algodão (Gossypium hirsutum L.). Foram utilizados três níveis de densidade do solo (1,2; 1,4 e 1,6 g.cm-3) e dois níveis de teor de água no solo (70 e 90% da capacidade de campo). Os tratamentos foram inteiramente casualizados com quatro repetições em arranjo fatorial (3 x 2). Os resultados mostraram que o impedimento mecânico afetou o volume radicular com densidade do solo de 1,2 a 1,6 g.cm-3, proporcionando aumento do crescimento radicular (P&gt;0,0064). A compactação subsuperficial restringiu a matéria seca radicular com densidade do solo de 1,2 cm.cm-3, aumentando a quantidade de matéria seca radicular na camada compactada (P&lt;0,0291). O teor de água reduziu o crescimento radicular onde, na capacidade de campo de 70 %, houve aumento de raízes e da parte aérea, em relação à capacidade de campo de 90%. O crescimento da parte aérea não foi afetado pela densidade do solo, este resultado sugere que a densidade do solo não é um bom indicador de impedimento mecânico em alguns solos. UNITERMOS: densidade do solo, estresse hídrico, crescimento radicular.

Evaluation of Full-Depth Asphalt Pavement Construction Using X-Ray Computed Tomography and Ground Penetrating Radar

In the past few years, a number of full-depth or perpetual pavements have been designed and constructed in the State of Texas. A study was conducted to examine the quality of the compaction of the thick asphalt layers within these pavements using advanced forensic tools such as X-ray computed tomography (X-ray CT) and ground penetrating radar (GPR). The GPR is a nondestructive tool for evaluating the uniformity of density in pavements at highway speed. X-ray CT is a laboratory tool that is used to conduct detailed analysis of air void distribution and uniformity in asphalt pavement cores. This paper presents the results of analyzing one of the perpetual pavements constructed in State Highway 114 (SH-114). In this project, two different structural asphalt pavement sections were placed, one included a 1in. (25.4 mm) stone filled (SF) Superpave mix and the other included a traditional dense graded Type B material. The dense graded Type B material was found to be uniformly compacted. However, major compaction problems were identified with the coarse SF Superpave mix. The poor compaction and associated high percent air vsoids were found to permit moisture infiltration, which could potentially lead to rapid pavement deterioration. The analysis showed very good agreement between the GPR and X-ray CT results and demonstrated the efficiency of using GPR and X-ray CT in the evaluation of asphalt pavement compaction.

Efeitos da rochagem e de resíduos orgânicos sobre aspectos químicos e microbiológicos de um subsolo exposto e sobre o crescimento de Astronium fraxinifolium Schott

Áreas degredadas, como as oriundas da construção da Usina Hidrelétrica de Ilha Solteira, de onde as camadas superficiais do solo foram removidas, apresentam baixa regeneração natural e subsolo desnudo, com problemas de compactação, alta densidade global, alta resistência à penetração de raízes e falta de matéria orgânica. Para revegetar essas áreas, torna-se necessário melhorar as condições gerais do subsolo. Este trabalho objetivou verificar os efeitos da rochagem (basalto) e da aplicação de diferentes resíduos orgânicos sobre aspectos químicos e microbiológicos de um subsolo exposto e sobre o crescimento de Gonçalo Alves (Astronium fraxinifolium Schott), uma espécie arbórea nativa de Cerrado. O experimento foi conduzido em casa de vegetação e constou de 17 tratamentos, como se segue: subsolo de "área de empréstimo" com quatro doses de basalto (0, 2, 4 e 8 t ha-1), combinadas ou não com 8 t ha-1 de três resíduos orgânicos (aguapé, esterco de curral e lodo doméstico), gerando 16 tratamentos, além de um adicional, com solo de Cerrado preservado, utilizado como referência, com quatro repetições por tratamento. Foram realizadas análises químicas e microbiológicas do subsolo, além de medidas de altura, massa seca e fresca da parte aérea e do sistema radicular das plantas. Os resultados indicam que os procedimentos com esterco e aguapé, adicionados ou não de basalto, foram os que mais contribuíram para melhorar as condições químicas do subsolo e proporcionar os maiores resultados para as variáveis microbiológicas, enquanto as plantas apresentaram o maior crescimento nos tratamentos em que foram adicionados lodo de esgoto e basalto. A rochagem, realizada com basalto, proporcionou resultados positivos.

Dynamic compaction model for a granular medium

A model for dynamic compaction of granular medium is proposed for the case in which the external action far exceeds the yield strength of the material. A radial axisymmetric compaction problem is solved for a granular medium with nanosize structure in the presence of a rigid rod at the symmetry axis. Simulated data are compared with experimental data on magnetic pulsed compaction of oxide nanopowders.

The second bifurcation branch for radial solutions of the Brezis-Nirenberg problem in dimension four

Existence results available for the semilinear Brezis-Nirenberg eigenvalue problem suggest that the compactness problems for the corresponding action functionals are more serious in small dimensions. In space dimension n = 3, one can even prove nonexistence of positive solutions in a certain range of the eigenvalue parameter. In the present paper we study a nonexistence phenomenon manifesting such compactness problems also in dimension n = 4.

Boundedness and compactness of a class of matrix operators in weighted sequence spaces

We study the problem of boundedness and compactness of operators of multiple sum- mation with weights in weighted sequence spaces.