Effect of coupling crater structure and Ag nanoparticles on SERS enhancement

Journal of Materials Science - This study was aimed at enhancing surface plasmon resonance through a combination of Ag nanoparticles (NPs) and an asymmetric crater structure capable of...     

Immunosuppressive activities of water-soluble barley β-glucan on alloantigen reactive cell proliferation and cytotoxicity

In this study, we investigated the immunosuppressive effects of water-soluble barley β-glucan (BP) in mouse immune cells. The BP was prepared from barley (Hordeum vulgare), and it suppressed the proliferation of splenocytes stimulated with concanavalin A (Con A), interleukin-2 (IL-2), and alloantigenic splenocytes in a dose-dependent manner (0.25, 0.5, and 1mg/mL). Furthermore, the death-inducing activities of cytotoxic T lymphocytes (CTLs) and lymphokine-activated killer cells (LAKs) in alloantigen-reactive splenocytes were significantly suppressed by more than 50%. Also, the production of IL-2 in the splenocytes decreased. These results suggest that these barley-originated polysaccharides can be used as potential immunosuppressive agents.     

Thermo-electrochemical activation of Cu3Sn negative electrode for lithium-ion batteries

A Cu₃Sn film electrode (thickness = ca. 3 μm) is prepared by DC magnetron sputtering deposition of Sn on Cu substrate and subsequent annealing at 300 °C for 30 h. At 25 °C, this Cu-Sn binary intermetallic compound is inactive for lithiation, but becomes active at elevated temperatures due to facilitation of Cu-Sn bond cleavage for the conversion-type lithiation. The lithiated product at 120 °C is the most Li-rich Li-Sn alloy (Li₁₇Sn₄). Upon de-lithiation, the Cu-Sn intermetallics of different compositions are generated by the reaction between the metallic Sn that is restored from Li₁₇Sn₄ and the idling metallic Cu. The nature of the resulting intermetallics is dependent on the de-lithiation temperature: Cu₁₀Sn₃ at 120 °C and Cu₆Sn₅ at 25 °C. Only the latter is active for lithiation in the subsequent room-temperature cycling. That is, Cu₃Sn is thermo-electrochemically activated to be Cu₆Sn₅ by lithiation at 120 °C and subsequent de-lithiation at 25 °C. The higher lithiation activity observed with the more Sn-rich phase (Cu₆Sn₅) compared to the initial one (Cu₃Sn) has been accounted for by the higher equilibrium lithiation potential (thermodynamic consideration) and smaller number of Cu-Sn bonds to be broken (kinetic consideration).     

Development of an on-line tool-life monitoring system using acoustic emission signals in gear shaping

Sensing techniques for monitoring machining processes have been one of the focuses of research on process automation. This paper presents the development of on-line tool-life monitoring system for gear shaping that uses acoustic emission (AE). Characteristics of the AE signals are related to the cutting condition, tool material and tool geometry in the cutting of metals. The relationship between AE signal and tool wear was investigated experimentally. Experiments were carried out on the gear shaping of SCM 420 material with a pinion cutter having 44 teeth. Root-mean-square (RMS) AE voltages increase regularly according to tool wear. It is suggested that the maximum value of RMS AE voltage is an effective parameter to monitor tool life. In this study, not only the acquisition method of AE signals for rotating objects but also the signal-processing technique were developed in order to realize the in-process monitoring system for gear shaping. The on-line tool-life monitoring system developed has been successfully applied to gear machining processes.     

Effect of fabrication method on the aging behavior of 6061 Al matrix composites reinforced with SiC whiskers

Age hardening behaviors of SiC whisker reinforced composites with 6061 Al matrix fabricated by P.M. (powder metallurgy) and squeeze casting were investigated to examine the effect of the fabrication method on the aging kinetics. In the squeeze cast composite, numorous triangular particles which is believed to be MgAlp₂O₄ were observed at Al/SiC interfaces whereas no visible interface particles were observed in the P. M. composite. P.M. composite showed faster age hardening and reached the maximum hardness earler than the squeeze cast composites. The decrease of the aging kinetics in squeeze cast 6061 Al matrix composites compared to that in P.M. composites is thought to result from more severe depletion of Mg atoms due to interfacial reactions in squeeze cast composites. The uniformity of whisker distribution is suggested to influence the general aging behavior through its effect on the local dislocation density. Data on the aging kinetics and the interfacial reactions in other Al alloys were also examined to study various factors which can influence the aging kinetics.     

静力疲劳荷载作用下的带预制板的连续组合双肋桥的裂缝控制

为研究裂缝控制,选取了一个带有预制板的两跨连续组合双肋梁的足尺模型,并对其进行试验及观察。在试验中,第一次荷载加到360kN,然后进行疲劳荷载试验。最后静力加载至900kN。试验结果证实了带预制板的双肋连续组合梁显示出了在静力疲劳荷载作用下的组合截面的强度和刚度特性。然而,在负弯矩作用区域,裂缝集中在内部支撑之上的桥面之间的接缝部位,初始的裂缝间距由接缝处间的距离决定,在使用荷载作用下,带有预制板的组合桥梁的桥面和横向接缝的裂缝宽度可以被控制在一个容许裂缝宽度之内。弯矩曲率曲线或者由欧洲规范4-2中规定的抗弯刚度仍可被用于评估考虑到在这种桥梁上拉伸硬化作用的有效刚度。     

Aging Baby Boomers and the Generational Housing Bubble: Foresight and Mitigation of an Epic Transition

Problem, research strategy, and findings: Transit-oriented developments (TODs) often consist of new housing near rail stations. Channeling urban growth into such developments is intended in part to reduce the climate change, pollution, and congestion caused by driving. But new housing might be expected to attract more affluent households that drive more, and rail access might have smaller effects on auto ownership and use than housing tenure and size, parking availability, and the neighborhood and subregional built environments.

I surveyed households in northern New Jersey living within two miles of 10 rail stations about their housing age and type, access to off-street parking, work and non-work travel patterns, demographics, and reasons for choosing their neighborhoods. The survey data were geocoded and joined to on-street parking data from a field survey, along with neighborhood and subregional built environment measures. I analyzed how these factors were correlated with automobile ownership and use as reported in the survey.

Auto ownership, commuting, and grocery trip frequency were substantially lower among households living in new housing near rail stations compared to those in new households farther away. But rail access does little to explain this fact. Housing type and tenure, local and subregional density, bus service, and particularly off- and on-street parking availability, play a much more important role.

Takeaway for practice: Transportation and land use planners should broaden their efforts to develop dense, mixed-use, low-parking housing beyond rail station areas. This could be both more influential and less expensive than a development policy oriented around rail.

Research support: Data collection and initial research were funded under contract with the New Jersey Department of Transportation.     

The effect of W and N addition on the mechanical properties of 10Cr steels

The effect of W and N on the creep properties and microstructural degradation in 10Cr steels was studied. Creep testing was performed to determine the creep rupture strength and minimum creep rate. Transmission electron microscopy was used to observe the microstructural degradation during the creep deformation. W and N which were added to the 10Cr steel increased the creep rupture strength and decreased the minimum creep rate. As W and N were added, the thermal stability of the subgrain and carbide was improved, thus the growth of the subgrain and carbide during creep deformation was restricted. In W added steel, the Laves phase played an important role in increasing creep rupture strength. But the impact toughness was rapidly degraded by the addition of W after aging at 600°C for 5000 hours. So one must evaluate more accurately the effect of the Laves phase on long term creep and impact properties. In N added steel, V(C, N) was precipitated in the lath boundary and within the lath. The size of the precipitates was 20–50 nm. The increase of creep rupture strength in N added steel may be due to the precipitate of the V(C, N). Future tests are required to clarify the effect of N on creep and impact properties.     

Effects of sintering conditions on mechanical properties of mechanically alloyed tungsten heavy alloys

The effects of sintering conditions on the microstructural evolution and mechanical properties of mechanically alloyed tungsten heavy alloys were investigated. W, Ni and Fe powders were mechanically alloyed in a tumbler ball mill at a milling speed of 75 rpm, ball-to-powder ratio of 20∶1 and ball filling ratio of 15%. The mechanically alloyed powders were compacted and solid-state sintered at a temperature of 1300°C for 1 hour in a hydrogen atmosphere. The solid-state sintered tungsten heavy alloy was subsequently liquid-phase sintered at 1470°C with varying sintering times from 4 min to 90 min. The solid-state sintered tungsten heavy alloy showed fine tungsten particles of 3 μm in diameter and high relative density above 99%. The volume fraction of the W-Ni-Fe matrix phase was measured, as 11% and tungsten/tungsten contiguity was 0.74 in solid-state sintered tungsten heavy alloys. Mechanically alloyed and two-step sintered tungsten heavy alloys showed tungsten particles of 6–15 μm and a volume fraction of the W-Ni-Fe matrix phase of 16% and tungsten/tungsten contiguity of 0.40. The solid-state sintered tungsten heavy alloy exhibited a yield strength of about 1100 MPa due to its finer tungsten particles, while it showed low elongation and impact energy due to its large tungsten/tungsten contiguity. The yield strength of two-step sintered tungsten heavy alloys increased with the decreasing of tungsten particle size and volume fraction of the W-Ni-Fe matrix. This article is based on a presentation made in “The 4th International Conference on Fracture and Strength of Solid”, held at POSTECH, Pohang, Korea, August 16–18, 2000 under the auspices of Far East and Ocean Fracture Society (FEOFS)et al.     

Optimum design of 6-DOF parallel manipulator with translational/rotational workspaces for haptic device application

This paper proposes an optimum design method that satisfies the desired orientation workspace at the boundary of the translation workspace while maximizing the mechanism isotropy for parallel manipulators. A simple genetic algorithm is used to obtain the optimal linkage parameters of a six-degree-of-freedom parallel manipulator that can be used as a haptic device. The objective function is composed of a desired spherical shape translation workspace and a desired orientation workspace located on the boundaries of the desired translation workspace, along with a global conditioning index based on a homogeneous Jacobian matrix. The objective function was optimized to satisfy the desired orientation workspace at the boundary positions as translated from a neutral position of the increased-entropy mechanism. An optimization result with desired translation and orientation workspaces for a haptic device was obtained to show the effectiveness of the suggested scheme, and the kinematic performances of the proposed model were compared with those of a preexisting base model.