Undercooling,Freezing Point Depression,and Ice Nucleation of Soil Water

Certain aspects of the phenomena of undercooling and ice nucleation in soils are discussed with respect to recently established properties of phase boundary water in soils. Nucleation temperature as a function of water content is given for representative clays. In view of the fact that silicate surfaces seem always to be separated from ice by an interfacial layer of unfrozen, liquid like water a new concept of heterogeneous nucleation is outlined. It is proposed that ice nucleation occurs in the undercooled interfacial water layer at some distance removed from the particle surfaces. This concept, in effect, suggests that heterogeneous nucleation (nucleation of ice due to the influence of a substrate) in all its essential aspects may be only a special case of homogeneous nucleation (no substrate present) of water.     

Oxidation and reforming reactions of CH4 on a stepped Pt(5 5 7) single crystal

The oxidation and reforming kinetics of methane by O₂, CO₂ and H₂O were studied on a stepped Pt(5 5 7) single crystal from 623 to 1050 K under methane rich conditions. The rate of carbon deposition was followed by ex-situ Auger electron spectroscopy under non-oxidative conditions. The apparent activation energy for methane decomposition was significantly lower than the apparent barriers measured for both total oxidation, CO₂ and H₂O reforming. Total oxidation of methane to CO₂ and H₂O followed by combined dry and steam reforming (combined combustion-reforming) led to CO production rates which were higher than direct CO₂ or H₂O reforming rates. The enhanced rates are most likely due to the ability of adsorbed oxygen to prevent carbon nucleation and/or scavenge carbon enabling the reforming reaction to turnover on a larger fraction of sites. Comparable amounts of carbon were found by Auger electron spectroscopy measurements after both direct dry or steam reforming, while combined oxidation-reforming had considerable less carbon. During direct dry or steam reforming, CO₂ and H₂O serve only to scavenge adsorbed atomic carbon, while in the presence of oxygen, carbon is removed by both combustion and reforming routes.     

Removal of fatty soil from glass by surfactants and surfactant-builder compositions

Previous papers have reported radiotagged fatty soil removal from glass either by solvents or by aqueous solutions of sodium tripolyphosphate and other builders. This paper provies soil-removal data for aqueous systems of both pure and built surfactant compositions of the nonionic and alkylbenzene sulfonate types. In general, nonionics are the most effective detergents for the system fatty soil/glass; the 10-mole ethylene oxide adduct products show peak soil-removal. Nonionic surfactants appear most effective for soil removal when used in baths closely approaching their cloud-points. Though modification of hydrophobe by EO addition can affect cloud point, peak soil-removal effectiveness seems to be controlled by hydrophobe selection. Highest soil removal for the alkylbenzene series occurred with the longer alkyl chain (pentadecyl). Admixture of surfactant and sodium tripolyphosphate provided synergistic compositions with certain 10-EO surfactants. Building of anionics markedly improved soil removal over the pure material but seldom exceeded the removal by STP alone. Presented at 34th fall meeting, American Oil Chemists' Society, New York, October 17–19, 1960.     

Influence of a high‐head dam as a dispersal barrier to fish community structure of the Upper Mississippi River

In river systems, high‐head dams may increase the distance‐decay of fish community similarity by creating nearly impermeable dispersal barriers to certain species from upstream reaches. Substantial evidence suggests that migratory species are impacted by dams, and most previous studies in stream/river networks have focused on small streams and headwaters. Here, we assess whether a high‐head dam (Lock and Dam 19; LD 19) on a large river, the Upper Mississippi River (UMR), substantially alters fish community structure relative to variability expected to occur independent of the dam's effect as a fish dispersal barrier. Using fish catch per unit effort data, we modelled the distance‐decay function for the UMR fish community and then estimated the similarity that would be expected to occur across LD19 and compared it with measured similarity. Measured similarity in the fish community above and below LD19 was close to the expected value based on the distance‐decay function, suggesting LD19 does not create an abrupt transition in the fish community. Although some migratory fish species no longer occur above LD19 (e.g., skipjack herring, Alosa chrysochloris), these species do not occur in high abundance below the dam and so do not drive variation in fish community structure. Instead, much of the variation in species structure is driven by the loss/gain of species across the latitudinal gradient. Lock and Dam 19 does not appear to be a clear transition point in the river's fish community, although it may function as a meaningful barrier for particular species (e.g., invasive species) and warrant future attention from a management perspective.     

Sn-Ag-Cu solders and solder joints: Alloy development, microstructure, and properties

Slow cooling of Sn-Ag-Cu and Sn-Ag-Cu-X (X = Fe, Co) solder-joint specimens made by hand soldering simulated reflow in surface-mount assembly to achieve similar as-solidified joint microstructures for realistic shearstrength testing, using Sn-3.5Ag (wt.%) as a baseline. Minor substitutions of either cobalt or iron for copper in Sn-3.7Ag-0.9Cu refined the joint matrix microstructure, modified the Cu₆Sn₅ intermetallic phase at the copper substrate/solder interface, and increased the shear strength. At elevated (150°C) temperature, no significant difference in shear strength was found in all of the alloys studied. Ambient temperature shear strength was reduced by largescale tin dendrites in the joint microstructure, especially by the coarse dendrites in solute poor Sn-Ag-Cu.     

Distributed formation control with relaxed motion requirements

Heterogeneous formation shape control with interagent bearing and distance constraints involves the design of a distributed control law that ensures the formation moves such that these interagent constraints are achieved and maintained. This paper looks at the design of a distributed control scheme to solve different formation shape control problems in an ambient two‐dimensional space with bearing, distance and mixed bearing and distance constraints. The proposed control law allows the agents in the formation to move in any direction on a half‐plane and guarantees that despite this freedom, the proposed shape control algorithm ensures convergence to a formation shape meeting the prescribed constraints. This work provides an interesting and novel contrast to much of the existing work in formation control where distance‐only constraints are typically maintained and where each agent's motion is typically restricted to follow a very particular path. A stability analysis is sketched, and a number of illustrative examples are also given. Copyright © 2014 John Wiley & Sons, Ltd.     

Subroutine based detection of APT malware

Statistical detection of mass malware has been shown to be highly successful. However, this type of malware is less interesting to cyber security officers of larger organizations, who are more concerned with detecting malware indicative of a targeted attack. Here we investigate the potential of statistically based approaches to detect such malware using a malware family associated with a large number of targeted network intrusions. Our approach is complementary to the bulk of statistical based malware classifiers, which are typically based on measures of overall similarity between executable files. One problem with this approach is that a malicious executable that shares some, but limited, functionality with known malware is likely to be misclassified as benign. Here a new approach to malware classification is introduced that classifies programs based on their similarity with known malware subroutines. It is illustrated that malware and benign programs can share a substantial amount of code, implying that classification should be based on malicious subroutines that occur infrequently, or not at all in benign programs. Various approaches to accomplishing this task are investigated, and a particularly simple approach appears the most effective. This approach simply computes the fraction of subroutines of a program that are similar to malware subroutines whose likes have not been found in a larger benign set. If this fraction exceeds around 1.5 %, the corresponding program can be classified as malicious at a 1 in 1000 false alarm rate. It is further shown that combining a local and overall similarity based approach can lead to considerably better prediction due to the relatively low correlation of their predictions.     

A logarithmic complexity divide-and-conquer algorithm for multi-flexible-body dynamics including large deformations

A new algorithm is presented for the modeling and simulation of multi-flexible-body systems. This algorithm is built upon a divide-and-conquer-based multibody dynamics framework, and it is capable of handling arbitrary large rotations and deformations in articulated flexible bodies. As such, this work extends the current capabilities of the flexible divide-and-conquer algorithm (Mukherjee and Anderson in Comput. Nonlinear Dyn. 2(1):10–21, 2007), which is limited to the use of assumed modes in a floating frame of reference configuration. The present algorithm utilizes the existing finite element modeling techniques to construct the equations of motion at the element level, as well as at the body level. It is demonstrated that these equations can be assembled and solved using a divide-and-conquer type methodology. In this respect, the new algorithm is applied using the absolute nodal coordinate formulation (ANCF) (Shabana, 1996). The ANCF is selected because of its straightforward implementation and effectiveness in modeling large deformations. It is demonstrated that the present algorithm provides an efficient and robust method for modeling multi-flexible-body systems that employ highly deformable bodies. The new algorithm is tested using three example systems employing deformable bodies in two and three spatial dimensions. The current examples are limited to the ANCF line or cable elements, but the approach may be extended to higher order elements. In its basic form, the divide-and-conquer algorithm is time and processor optimal, yielding logarithmic complexity O(log(N _b )) when implemented using O(N _b ) processors, where N _b is the number of bodies in the system.