Dynamic fracture and spall in aluminum with helium bubbles

Investigation of the dynamic properties of aluminum targets with helium bubbles is presented. The targets were obtained by melting pure aluminum with 0.15% wt.¹⁰B powder. The solid targets were neutron irradiated to get homogeneous helium atoms inside the aluminum boron 10 matrix according to the reaction ¹⁰B + n → ⁷Li+⁴He. Helium atoms further accumulated into bubbles by diffusion in the bulk aluminum. Shock wave experiments were performed by accelerating the aluminum impactor into different targets: (1) pure aluminum, (2) Al-¹⁰B, and (3)Al-¹⁰B with different radii and concentrations of helium bubbles. The spall strength was calculated and analyzed from the free surface velocity measurements. It was found that the addition of ¹⁰B in pure aluminum reduces the spall strength of the material by 25–32%. However, irradiated sample with helium bubbles was found to have higher spall strength compared to samples without bubbles. This finding was reconstructed by numerical simulations. The impacted targets were collected after the impact experiments and examined by TEM. These targets were compared to TEM pictures before the impact. The number of helium atoms in the bubbles was calculated from the electron energy loss spectrum (EELS). TEM comparison between the pre-impacted and the impacted targets shows bubbles coalescence and EELS measurements demonstrate a reduction of the helium atoms concentration in the bubbles from ~10²⁸ m^?3 before the impact to ~10²⁷ m^?3 after the impact.     

10 Gbit/s EPON引领光纤接入技术进入新时代(下)

3 从1 Gbit/s EPON升级至10 Gbit/s EPON 10 Gbit/s EPON从一开始就明确作为现有EPON的兼容升级方案,所选择的波长不会影响当前的EPON,因此可以在现有光纤链路上同时部署两种技术.     

ModelTalk: When Everything Is a Domain-Specific Language

Many see a great future for domain-specific software development. Yet, the path to fulfilling the potential of domain-specific languages on a large scale remains largely uncharted. This article presents ModelTalk, a model-driven framework for DSL-based development. ModelTalk can be used to produce a product line of commercial business support systems for the telecommunications industry.     

How to Achieve Perfect Simulation and a Complete Problem for Non-interactive Perfect Zero-Knowledge

This paper studies perfect zero-knowledge proofs. Such proofs do not allow any simulation errors, and therefore techniques from the study of statistical zero-knowledge (where a small error is allowed) do not apply to them. We introduce a new error shifting technique for building perfect simulators. Using this technique we give the first complete problem for the class of problems admitting non-interactive perfect zero-knowledge (NIPZK) proofs, a hard problem for the class of problems admitting public-coin PZK proofs, and other applications.     

Study of transition metal complexes as curing accelerators for anaerobic adhesives

Reported are the results of studying the influence of the composition of the complexes of transition metal salts with crown ethers on the kinetics of the curing of anaerobic adhesives developed in Kargin Research Institute of Polymer Chemistry and Technology. It is established that the use of copper salts makes it possible to substantially decrease the setting time on zinc-coated surfaces; however, in this case, the working life of adhesive decreases abruptly. It is shown that the activity of salts can be decreased by their complexation with various chelating agents. It is revealed that transition metal salts in the form of complexes with some crown ethers not only increase the rate of curing of anaerobic adhesives, but also considerably enhance the thermal stability of cured products that is explained by the ability of organic salts of metals to the inhibition of thermal-oxidative degradation of polymers.     

Flow distribution in manifolded solar collectors with negligible buoyancy effects

To understand the influence of collector design parameters on the flow distribution among the solar collector absorber tubes, and as a first step to any detailed analysis of the influence of flow on heat transfer in the collector and on its consequent thermal performance, this study investigates the distribution of flow through a typical system consisting of two manifolds connected by a number of parallel riser tubes. No thermal effects, such as buoyancy, are taken into account. A discrete hydrodynamic model was developed for this system, and the resulting set of simultaneous nonlinear algebraic equations was solved numerically for 54 different combinations of the major independent variables. Quantitative flow distribution results are presented. In the investigated range, it was determined that the three parameters which have the major influence on flow distribution are, in the order of significance, the ratio of riser diameter to manifold diameter, the number of risers, and the length of the risers, with maldistribution increasing with the increase of the first two and with the decrease of the third one. To demonstrate the most dramatic influence, changing the value of d_r/d_i from 0.25 to 0.75 causes the peak riser flow excess above the average flow to increase 100-fold: from 5% for the first diameter ratio, to 500% for the second. Consistent with his finding, pressure changes in the system arising from inertia in the manifolds become larger than the frictional pressure changes in the risers when the riser tube length-to-diameter is decreased below about 75, causing large flow maldistribution. Predictions from the model are successfully compared with limited experimental data and with the closed-form solutions of two existing models.