Limitations on the use of the power-law form of S/sub y/(f) to compute Allan variance

An exact solution to the well-known integral transform that relates the spectral density of the instantaneous fractional frequency deviation, S/sub y/(f), to the Allan variance, /spl sigma//sub y//sup 2/ (/spl tau/), is presented for the case of a power-law representation of S/sub y/(f). The approximate solution to this integral transform, which is found throughout the literature, is also derived. A graphical convergence analysis is presented, showing the range of applicability of the approximate solution. The results reinforce the use of the approximate solution, which converges quickly to the exact solution under virtually all reasonable measurement conditions.     

Limitations on the use of the power-law form of Sy(f) to compute Allan variance.

An exact solution to the well-known integral transform that relates the spectral density of the instantaneous fractional frequency deviation, Sy(f), to the Allan variance, sigma2y(tau), is presented for the case of a power-law representation of Sy(f). The approximate solution to this integral transform, which is found throughout the literature, also is derived. A graphical convergence analysis is presented, showing the range of applicability of the approximate solution. The results reinforce the use of the approximate solution, which converges quickly to the exact solution under virtually all reasonable measurement conditions.     

Microstructure and second-phase particles in low- and high-pressure die-cast magnesium alloy AM50

The microstructure and phase composition of low-pressure die-cast (LPDC) and high-pressure diecast (HPDC) magnesium alloy AM50 were examined by transmission electron microscopy (TEM) techniques in combination with optical microscopy, scanning electron microscopy (SEM), and electron-probe microanalysis (EPMA). It has been established that the dimensions and morphology of the constituent phases (α-Mg solid solution, Mg₁₇Al₁₂, and Al₈Mn₅) depend on the processing parameters. The results obtained suggest that there is a ternary eutectic with the aforementioned three phases in the Mg-Al-Mn system. Phase transformations leading to the observed microstructures are discussed.     

矿山设备遥控技术的发展

鉴于自动化是一个长远目标，本文按逻辑发展顺序介绍了无线遥控技术的进展。遥控使操作人员实时直接控制设备，文中介绍了三个层次的遥控系统，即视距遥控、扩展的视距遥控和全程铲运机遥控。车辆控制区域网络中的控制和传感子系统提高了三种遥控系统的能力，为将来技术成熟时采用更高程度的自动化控制奠定了基础，该方法加快了当前采矿自动化技术发展的步伐。     

Mud,Dust, and Marougé: Precarious Construction in a Congolese Refugee Camp

This photo essay combines text and images to convey how the Congolese who reside in Nyarugusu, a United Nations refugee camp in Tanzania, interact with and interpret camp architecture. To establish the camps as temporary spaces, the Tanzanian government requires that refugees construct their houses with sundried mud brick and thatched roofs so that they can eventually be destroyed without a trace. The red dirt of their homes and the camp environment colours almost every facet of Nyarugusu residents' lives, adding a sense of dirtiness to the camp. The violence built into the camp architecture is not only contained in its eventual destruction, but also in the ways in which it visibly marks the residents' alienation and subordination in Tanzania.     

Modeling the interdependence of processing and alloy composition on the evolution of microstructure in Sn-based lead-free solders in fine pitch flip chip

Market demands and legislation are driving the electronics-manufacturing sector to move rapidly toward a lead-free future, with Pb-containing electronics products to be banned in Europe after 2006. Although the related scientific research has been undertaken for a decade, a number of technical complications still exist, which are further exacerbated due to the concurrent developments in miniaturization and multifunctionality of microelectronic products. As the packaging joint geometry shrinks toward a microscopic scale, the joint fabrication and reliability become extremely sensitive to the composition and resulting microstructure generated from the chosen joining process and materials. The current level of understanding of such issues is still in its infancy and therefore requires further fundamental study. Thermodynamic modeling is employed in this work as a computational tool to study the sensitivity of processing ranges (e.g., reflow temperature) and the resultant reliability of the microjoints by changing the alloying elements and their content in Sn-based lead-free systems. The work is implemented using the MTDATA program developed by the National Physical Laboratory. With a newly developed database containing critically assessed thermodynamic data appropriate for lead-free solder systems, MTDATA allows the prediction of the liquid-solid transformation and phase formation, for example, as a function of chemical composition and temperature. The paper emphasizes the formation and mass fraction of intermetallic precipitates of different phases in the bulk solder joints and the modeling is also validated through experimental work and recent literature. The results are expected to assist the optimization of processing parameters and cost-effective production using lead-free solders.     

Current signature analysis to detect induction motor faults

Three-phase induction motors are the “workhorses” of industry and are the most widely used electrical machines. In an industrialized nation, they can typically consume between 40 to 50% of all the generated capacity of that country. This article focuses on the industrial application of motor current signature analysis (MCSA) to diagnose faults in three-phase induction motor drives. MCSA is a noninvasive, online monitoring technique for the diagnosis of problems in induction motors. Reliability-based maintenance (RBM) and condition-based maintenance (CBM) strategies are now widely used by industry, and health monitoring of electrical drives is a major feature in such programs     

Chronic tolerance and sensitization to alcohol in sons of alcoholics: II. Replication and reanalysis.

Data from D. B. Newlin and J. B. Thomson (1991) were reanalyzed, and data from an independent replication study were analyzed, relative to tonic (baseline) and phasic (response to alcohol challenge) aspects of drinking alcohol administered at the same dose on several occasions. Among the high-risk men (sons of alcoholic fathers), linear trends across days for resting (predrinking) baselines were opposite to alcohol-evoked changes for finger pulse amplitude, finger temperature, and skin conductance in Study 1 and for pulse transit time and body sway (static ataxia) in Study 2. In contrast, the structure of the low-risk men's (sons of nonalcoholic parents) data was precisely the opposite. Results are discussed in terms of sensitization as a potential mechanism that relates vulnerability to final manifestation of addictive behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Use of an isogenic mutant constructed in Moraxella catarrhalis To identify a protective epitope of outer membrane protein B1 defined by monoclonal antibody 11C6

Moraxella catarrhalis-induced otitis media continues to be a significant cause of infection in young children, prompting increased efforts at identifying effective vaccine antigens. We have previously demonstrated that M. catarrhalis expresses specific outer membrane proteins (OMPs) in response to iron limitation and that this organism can utilize transferrin and lactoferrin for in vitro growth. One of these proteins, which binds human transferrin, is OMP B1. As the human host presents a naturally iron-limited environment, proteins, like OMP B1, which are expressed in response to this nutritional stress are potential vaccine antigens. In this study, we have developed monoclonal antibody (MAb) 11C6, which reacts to a surface-exposed epitope of OMP B1 expressed by M. catarrhalis 7169. This antibody was used to clone ompB1, and sequence analysis suggested that OMP B1 is the M. catarrhalis homologue to the transferrin binding protein B described for pathogenic Neisseriaceae, Haemophilus influenzae, Actinobacillus pleuropneumoniae, and M. catarrhalis. Expression of recombinant OMP B1 on the surface of Escherichia coli confers transferrin binding activity, confirming that this protein is likely involved in iron acquisition. In addition, ompB1 was used to construct an isogenic mutant in M. catarrhalis 7169. This mutant, termed 7169b12, was used as the control in bactericidal assays designed to determine if OMP B1 elicits protective antibodies. In the presence of MAb 11C6 and human complement, wild-type 7169 demonstrated a 99% decline in viability, whereas the ompB1 isogenic mutant was resistant to this bactericidal activity. Further analysis with MAb 11C6 revealed the presence of this OMP B1 epitope on 31% of the clinical isolates tested. These data suggest that OMP B1 is a potential vaccine antigen against M. catarrhalis infections.