Biologic stability of plasma ion-implanted miniscrews

published_or_final_versio

Experimental investigation on the deformation characteristics of granular materials under drained rotational shear

Rotational shear is the type of loading path where samples are subjected to cyclic rotation of principal stress directions while the magnitudes of principal stresses are maintained constant. This paper presents results from an experimental investigation on the drained deformation behaviour of saturated sand in rotational shear conducted in a hollow cylinder apparatus. Two types of granular materials, Leighton Buzzard sand and glass beads are tested. A range of influential factors are investigated including the material density, the deviatoric stress level, and the intermediate principal stress. It is observed that the volumetric strain during rotational shear is mainly contractive and most of strains are generated during the first 20 cycles. The mechanical behaviour of sand under rotational shear is generally non-coaxial, i.e., there is no coincidence between the principal axes of stress and incremental strain, and the variation of the non-coaxiality shows a periodic trend during the tests. The stress ratio has a significant effect on soil response in rotational shear. The larger the stress ratio, the more contractive behaviour and the lower degree of non-coaxiality are induced. The test also demonstrates that the effect of the intermediate principal stress, material density and particle shape on the results is pronounced

Associations between IL12B polymorphisms and tuberculosis in the Hong Kong Chinese population

Background. Interleukin (IL)-12 plays a vital role in regulating cell-mediated immunity against tuberculosis (TB). Methods. To test whether IL12B genetic polymorphisms might contribute to human TB susceptibility, we examined the genotype frequencies of 5 IL12B polymorphisms (at promoter, intron 2, intron 4, exon 5, and 3′ untranslated region [UTR]) in 516 patients with TB and 514 healthy control subjects from the Hong Kong Chinese population. Results. Individuals homozygous for the IL12B intron 2-repeat marker (ATT) 8 had a 2.1-fold increased risk of developing TB (P < .001) (odds ratio, 2.14 [95% confidence interval, 1.45-3.19]). Estimation of the frequencies of multiple-locus haplotypes composed of IL12B promoter, intron 2, intron 4, and 3′ UTR alleles revealed potential risk haplotypes (designated "A" and "K") and protective haplotypes (designated "B") for TB. Furthermore, combining the genotype data of the 4 informative IL12B loci revealed a strong association between a specific genotype pattern, termed "diplotype I" (heterozygous A and K haplotypes), and TB. In contrast, diplotype II (homozygous BB haplotypes) appeared protective against TB. Conclusions. These findings support the association between IL12B intron 2 polymorphism and TB and between specific IL12B haplotypes and TB.published_or_final_versio

Reconstruction of plasma density profiles by measuring spectra of radiation emitted from oscillating plasma dipoles

We suggest a new method for characterising non-uniform density distributions of plasma by measuring the spectra of radiation emitted from a localised plasma dipole oscillator excited by colliding electromagnetic pulses. The density distribution can be determined by scanning the collision point in space. Two-dimensional particle-in-cell simulations demonstrate the reconstruction of linear and nonlinear density profiles corresponding to laser-produced plasma. The method can be applied to a wide range of plasma, including fusion and low temperature plasmas. It overcomes many of the disadvantages of existing methods that only yield average densities along the path of probe pulses, such as interferometry and spectroscopy

Numerical shakedown and non-shakedown responses of a Tresca half-space to a three-dimensional moving load

Flexible pavements may fail due to excessive rutting as a result of accumulative plastic deformation; otherwise, if the load is small enough, pavements may deform plastically in the first number of load cycles and then reach a stable state which is termed as ‘shakedown’. Recently some lower-bound and upper-bound solutions have been developed to directly determine the load limit (i.e. shakedown limit) below which an elastic-plastic half space can shake down. However, the actual responses of an elasticplastic half-space subjected to repeated moving loads were not well revealed. In the present study, repeated moving surface loads are applied to a three-dimensional finite element model established in ABAQUS to research on the development of stresses and strains in a Tresca half-space. Also, a numerical shakedown limit can be determined according to the yield condition of structure under a static load following a number of load passes. It is found the development of residual stresses induced by plastic strains plays a key role in helping the half-space to reach the shakedown state. Good agreements are also observed between numerical and theoretical solutions for both shakedown limit and residual stress fields

An easy to control all-metal in-line-series ohmic RF MEMS switch

Copyright @ 2010 Springer-VerlagThe analysis, design and simulation of a novel easy to control all-metal in-line-series ohmic RF MEMS switch is presented, for applications where the operating frequency ranges from DC to 4 GHz. The proposed switch, due to its unique shape and size, assures high isolation and great linearity fulfilling the necessary requirements as concerns loss, power handling and power consumption. Simplicity has been set as the key success factor implying robustness and high fabrication yield. On the other hand, the specially designed cantilever-shape (hammerhead) allows distributed actuation force ensuring high controllability as well as reliability making the presented RF MEMS switch one of its kind

Discrete element modelling and cavity expansion analysis of cone penetration testing

This paper uses the discrete element method (DEM) in three dimensions to simulate cone penetration testing (CPT) of granular materials in a calibration chamber. Several researchers have used different numerical techniques such as strain path methods and finite element methods to study CPT problems. The DEM is a useful alternative tool for studying cone penetration problems because of its ability to provide micro mechanical insight into the behaviour of granular materials and cone penetration resistance. A 30° chamber segment and a particle refinement method were used for the simulations. Giving constant mass to each particle in the sample was found to reduce computational time significantly, without significantly affecting tip resistance. The effects of initial sample conditions and particle friction coefficient on tip resistance are investigated and found to have an important effect on the tip resistance. Biaxial test simulations using DEM are conducted to obtain the basic granular material properties for obtaining CPT analytical solutions based on continuum mechanics. Macro properties of the samples for different input micro parameters are presented and used to obtain the analytical CPT results. Comparison between the numerical simulations and analytical solutions show good agreement

Electromagnetic emissions from the IC packaging

The EMC and EMI of the IC packaging are becoming increasingly important to modern electronics. Its EMC, SI, and PI have been broadly attested. But electromagnetic radiations from IC packaging and the corresponding EMI were seldom studied. In this paper, the fundamental principles and properties of the electromagnetic radiations caused by vias and traces in IC packagings are carefully investigated. Various radiation mechanisms are analyzed for different representative scenarios. Numerical simulations are employed to support the analyzing results. © 2012 IEEE.published_or_final_versio

A New Technique for Reachability of States in Concatenation Automata

We present a new technique for demonstrating the reachability of states in deterministic finite automata representing the concatenation of two languages. Such demonstrations are a necessary step in establishing the state complexity of the concatenation of two languages, and thus in establishing the state complexity of concatenation as an operation. Typically, ad-hoc induction arguments are used to show particular states are reachable in concatenation automata. We prove some results that seem to capture the essence of many of these induction arguments. Using these results, reachability proofs in concatenation automata can often be done more simply and without using induction directly.Comment: 23 pages, 1 table. Added missing affiliation/funding informatio

Shakedown for slab track substructures with stiffness variation

In this paper, shakedown analyses are carried out to predict the long-term response of slab track substructures under repeated moving train loads. The train loads are converted into a distributed moving load on the substructure surface by using a simplified track analysis. Based on Melan’s static shakedown theorem, a well-established shakedown analysis method is extended to determine shakedown limits of the slab track substructures. The influence of a linearly increasing stiffness modulus on the shakedown limits is considered by conducting finite- element analysis with a user-defined material. It is found that a rise in stiffness modulus or stiffness variation ratio can either increase or decrease the shakedown limit, depending on the competitive effects of the two mechanisms. Furthermore, the subgrade thickness determines the dominant mechanism