Estimating the unconfined compressive strength of intact rocks from Equotip hardness

In order to utilize the Equotip hardness tester, originally developed in the field of metallic engineering, as an indirect method to predict the unconfined compressive strength (UCS) of rock, laboratory tests were undertaken to establish the UCS, Equotip hardness (L-value) and porosity of nine rock types. Using existing data from Verwaal and Mulder (Int J Rock Mech Min Sci Geomech Abstr 30:659–662, 1993) and the results of laboratory tests, an equation relating UCS (MPa) and L-value obtained from single impacts (L _s) and porosity (n %) was derived, which provides a close approximation of the UCS value. An equation to relate UCS and Equotip hardness is also presented, although this is less accurate. It is considered Equotip testing has advantages over the commonly used Schmidt hammer test.      

In situ bioremediation of a cis-dichloroethylene-contaminated aquifer utilizing methane-rich groundwater from an uncontaminated aquifer

At a trichloroethylene (TCE)-contaminated site in Chikura, Chiba, Japan, TCE had spread over to the first and second aquifers over years. After 8 years of pumping and treatment, finally derivative of TCE, cis-dichloroethylene (c-DCE) remained only in the second aquifer. In this study, feasibility of a low cost in situ bioremediation utilizing groundwater of the third aquifer, which contained natural dissolved methane possibly derived from natural gas field nearby, to stimulate methane-oxidizing bacteria was examined. In vitro experiment showed that a mixture of the groundwater from the second and third aquifers stimulated a growth of methane oxidizing bacteria and enhanced c-DCE degradation. The groundwater of the third aquifer was introduced into the second aquifer in situ. The population of methanotrophs with high V(max) and K(m) for methane uptake increased, resulting in successful degradation of c-DCE at a monitoring well 2m downgradient of the injection well.     

Numerical study of a single blade row in turbomolecular pump

Research on turbomolecular pumps (TMPs) based on the analysis of single blade row has been carried out by a number of investigators Kruger CH, Ph.D. Thesis, Massachusetts Institute of Technology; 1960; Katsimichas S, Goddard AJH, Lewington R, Oliveira de CRE. J Vac Sci Technol A 1995;13:2954; Schneider TN, Katsimichas S, de Oliveira CRE, Goddard AJH. J Vac Sci Technol A 1998;16:175; De Simon M. Vacuum 1990;41:2021; Chu JG, Hua ZY. J Vac Sci Technol 1982;20:1101; Amoli A, Ebrahimi R, Hosseinalipour SM. Vacuum 2004;72:427; Sawada T. Bull Jpn Soc Mech Eng 1973;16:993; Joong-Sik Heo, Hwang Young-Kyu. Vacuum 2001;56:133; Sawada T. Bull Jpn Soc Mech Eng 1979;22:362; Amoli A, Hosseinalipour SM. Vacuum 2004;75:361; Sheng Wang, Hisashi Ninokata. Prog Nucl Energy 2005;47:664, but those calculations were either limited to free-molecule flow, or failed to obtain good results in the transition regime. Furthermore, they were usually focused on pumping performance and did not report detailed flow field characteristics. In this study, a three-dimensional direct simulation Monte Carlo (DSMC) code adopting an accurate intermolecular collision model, i.e., a generalized soft sphere (GSS) model, has been developed to simulate the single blade row of a one-stage TMP from free-molecule flow to transition flow without any geometrical simplification. Molecular velocities and position equations are deduced under a rotating frame with consideration for the Coriolis and centrifugal acceleration, and the number of sample molecules is tested for sensitivity. The validity of this study and its accuracy are verified through comparison with previous DSMC results and experimental data, and the deterioration of the maximum pressure ratio in the transition flow regime and the influence of the intermolecular collision model on the maximum pressure ratio calculation are analyzed with the aid of transmission probability. Pumping performance under differing geometrical parameters (clearance between the blade tip wall and the housing wall, and the spacing-chord ratio) is investigated, and detailed flow field characteristics, including the number of molecule-surface collisions, temperature and density distributions, particle traces of single gas components and gas mixtures are all obtained under zero pumping speed.     

Microstructure and mechanical properties of hot extruded Mg–Al–Mn–Ca alloy produced by rapid solidification powder metallurgy

The microstructure and mechanical properties of hot extruded Mg–Al–Mn–Ca alloy was investigated. Both rapid solidified powders and cast billets were extruded at 573, 623 and 673 K to optimize the processing conditions for obtaining better mechanical response. Powder was consolidated to prepare the extrusion billets using both cold compaction and Spark Plasma Sintering at 473 K. The tensile properties of the extruded alloy were then evaluated and correlated to the observed microstructure. The results show that the use of rapid solidified powder could lead to effective grain refinement, which in turn resulted in the improved mechanical response, especially compared to the extruded conventional cast material.     

Preparation and properties of TiN and AlN films from alkoxide solution by thermal plasma CVD method

Single phase TiN and AlN films were prepared on a Si wafer from titanium tetra-etoxide and aluminum tri-butoxide solutions dissolved in ethanol and toluene, respectively, using an Ar/N₂/H₂ radio-frequency (r.f.) inductive thermal plasma chemical vapor deposition (CVD) method. The films were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, measurement of electrical resistivity and Vickers microhardness. Factors affecting the formation of the films (lattice parameter, chemical composition, oxygen/carbon content, and deposition rate of the films) were examined in terms of the N₂ flow rate (2.5–4.5 slm), substrate temperature (300–700°C), feed rate of the solution (0.025–0.3 ml/min), and the mole ratio of the alkoxide solution (1:1–1:3). The optimum conditions for preparation of TiN films produced a film 0.2–3 μm thick with an oxygen content of 8 at.% and a free carbon content of 4 at.%, showing an electrical resistivity of 370 μΩ cm. The optimum conditions for AlN films produced a film 0.3 μm thick containing 14 at.% oxygen and 8 wt.% carbon. The deposition rate of the TiN film was determined to be 30–35 nm/min. The Vickers microhardness of the TiN and AlN films was found to be 10±1 and 13±3 GPa, respectively.     

Gigacycle fatigue data sheets for advanced engineering materials

Gigacycle fatigue data sheets have been published since 1997 by the National Institute for Materials Science. They cover several areas such as high-cycle-number fatigue for high-strength steels and titanium alloys, the fatigue of welded joints, and high-temperature fatigue for advanced ferritic heat-resistant steels. Some unique testing machines are used to run the tests up to an extremely high number of cycles such as 10¹⁰ cycles. A characteristic of gigacycle fatigue failure is that it is initiated inside smooth specimens; the fatigue strength decreases with increasing cycle number and the fatigue limit disappears, although ordinary fatigue failure initiates from the surface of a smooth specimen and a fatigue limit appears. For welded joints, fatigue failure initiates from the notch root of the weld, because a large amount of stress is concentrated at the weld toe. The fatigue strength of welded joints has been obtained for up to 10⁸ cycles, which is an extremely high number of cycles for large welded joints. The project of producing gigacycle fatigue data sheets is still continuing and will take a few more years to complete. r 2007 Published by Elsevier Ltd.     

液氦自动补加实验

一种简易的液氦自动补加装置业已制成并通过了试验。该装置由一个１００Ｌ液氦贮存容器、一个蒸发率约５Ｌ／ｄ的低温恒温器、一条１ｍ长的柔性输送管、两个电磁阀、一个５Ｗ电加热器、一个容器压力传感器和控制器以及两个液面传感器和控制器组成。它没有旁通管和输送冷却的阀门。由于用加热器通过液氦蒸发使容器的压力升高，所以安全装置具有防止超压和无液加热的作用。这一简易可靠的装置，它的工作性能已通过模型试验和正常使用所     

Multi-objective genetic algorithm for solving N-version program design problem

N-version programming (NVP) is a programming approach for constructing fault tolerant software systems. Generally, an optimization model utilized in NVP selects the optimal set of versions for each module to maximize the system reliability and to constrain the total cost to remain within a given budget. In such a model, while the number of versions included in the obtained solution is generally reduced, the budget restriction may be so rigid that it may fail to find the optimal solution. In order to ameliorate this problem, this paper proposes a novel bi-objective optimization model that maximizes the system reliability and minimizes the system total cost for designing N-version software systems. When solving multi-objective optimization problem, it is crucial to find Pareto solutions. It is, however, not easy to obtain them. In this paper, we propose a novel bi-objective optimization model that obtains many Pareto solutions efficiently.We formulate the optimal design problem of NVP as a bi-objective 0–1 nonlinear integer programming problem. In order to overcome this problem, we propose a Multi-objective genetic algorithm (MOGA), which is a powerful, though time-consuming, method to solve multi-objective optimization problems. When implementing genetic algorithm (GA), the use of an appropriate genetic representation scheme is one of the most important issues to obtain good performance. We employ random-key representation in our MOGA to find many Pareto solutions spaced as evenly as possible along the Pareto frontier. To pursue improve further performance, we introduce elitism, the Pareto-insertion and the Pareto-deletion operations based on distance between Pareto solutions in the selection process.The proposed MOGA obtains many Pareto solutions along the Pareto frontier evenly. The user of the MOGA can select the best compromise solution among the candidates by controlling the balance between the system reliability and the total cost.     

Microstructures and mechanical responses of powder metallurgy non-combustive magnesium extruded alloy by rapid solidification process in mass production

Spinning Water Atomization Process (SWAP), which was one of the rapid solidification processes, promised to produce coarse non-combustible magnesium alloy powder with 1–4 mm length, having fine α-Mg grains and Al₂Ca intermetallic compounds. It had economical and safe benefits in producing coarse Mg alloy powders with very fine microstructures in the mass production process due to its extreme high solidification rate compared to the conventional atomization process. AMX602 (Mg–6%Al–0.5%Mn–2%Ca) powders were compacted at room temperature. Their green compacts with a relative density of about 85% were heated at 573–673 K for 300 s in Ar gas atmosphere, and immediately consolidated by hot extrusion. Microstructure observation and evaluation of mechanical properties of the extruded AMX602 alloys were carried out. The uniform and fine microstructures with grains less than 0.45–0.8 μm via dynamic recrystallization during hot extrusion were observed, and were much small compared to the extruded AMX602 alloy fabricated by using cast ingot. The extremely fine intermetallic compounds 200–500 nm diameter were uniformly distributed in the matrix of powder metallurgy (P/M) extruded alloys. These microstructures caused excellent mechanical properties of the wrought alloys. For example, in the case of AMX602 alloys extruded at 573 K, the tensile strength (TS) of 447 MPa, yield stress (YS) of 425 MPa and 9.6% elongation were obtained.