Florida DOT Project-Level Bridge Management Models

The Florida Department of Transportation (FDOT) is in the process of implementing Pontis, a Bridge Management System, to provide decision support to engineers in the headquarters and district offices as they make routine policy, programming, and budgeting decisions regarding the preservation and improvement of the state’s bridges. As part of this effort, an ongoing research program is underway to adapt the system to FDOT needs as well as to advance the state of the art in several areas important to the Department. Most of the research results are organized around a new project-level decision support framework that complements and builds on Pontis’ existing network-level analysis. Specific new models include accident risk and user cost due to roadway width and alignment deficiencies; user cost of load capacity and vertical clearance restrictions, and moveable bridge openings; project-level prediction models for bridge element condition and costs; and prediction of economics of scale and scoping possibilities. The new models are built into a highly graphical spreadsheet model for decision support use.     

Probabilistic analysis of a static frame model

This paper describes our efforts during our participation in the Sandia Validation Workshop. The focus of the paper is the calibration of material models and simulation of random fields to characterize the variations of material properties across spatial field. Both parametric and non-parametric methods were used to represent uncertainty. Part of the challenge of this problem is the small amount of data that is available for the necessary probabilistic analyses in support of calibration, validation, accreditation and prediction activities. The analysis methods and corresponding results are described.     

Microstructure and fatigue properties of hydroformed aluminum alloys 6063 and 5754

This study investigated the microstructure and fatigue properties of hydroformed sections of the 5754 and 6063 aluminum alloys. The second-phase particles in 6063-T7 are identified as a mixture of Al₁₂Fe₃Si and Al₉Fe₂Si₂, with a slightly higher fraction of the former. The constituent particles in the 5754 alloy are Al₄Mn-type hexagonal compounds, where Mn is partially substituted by various other elements, resulting in Al₄(Fe,Mn,Si,Cr). The results show that despite its lower yield strength, the hydroformed 5754 alloy has higher ultimate tensile strength, ductility, and, more importantly, higher fatigue resistance than the 6063 material. Both crystallographic stage I and noncrystallographic stage II cracking are found in the 6063-T7 samples, but only stage II cracking is observed in the 5754 alloy. This implies that the low fatigue strength of 6063-T7 is related to its relatively large grain size, resulting in rapid stage I crack propagation. The higher fatigue lives of the 5754 alloy compared to the 6063 alloy in both the low- and high-cycle life regimes are due to the increased fatigue-crack-initiation and propagation resistance of the 5754 alloy and its probable cyclic strain-hardening behavior.     

Fluoride catalysis at 175°C. of the reaction: Glycerol plus fatty acid

1. In uncatalyzed reactions the esterification of stearic, oleic, and linolenic acid proceeded at the same general rate though the speed was somewhat enhanced as the degree of unsaturation of the fatty acid increased. None of the reactions went to completion, after 15 hours being 72%, 83%, and 84%, respectively, completed. Only a small fraction of the distearate was converted to the triglyceride; a greater amount of the dioleate was esterified to the trioleate and about half the dilinolenate was changed to the trilinolenate.
2. Of 15 metallic fluorides studied, all afforded some catalysis, but only antimony trifluoride and zinc and cobalt fluorides were outstanding. Antimony trifluoride was the most active although in large amount it caused severe decomposition and charring of the products. Zinc fluoride had the best general properties, approaching antimony trifluoride yet causing practically no decomposition even in high concentration. Its activity was enhanced with an increase in amount, the best concentration apparently being 0.1 mole per 100 grams fatty acid. Antimony trifluoride was also better in larger amount within limits, but cobalt fluoride did not exhibit this property.
3. With zinc fluoride as catalyst the reactions of stearic, oleic and linolenic acids after 15 hours were 95%, 94%, and 92%, respectively, completed. At least three-fourths of the diglycerides were converted to triglycerides. From a study of reaction velocities, zinc fluoride caused the monoglyceride to form at a rate approximately four times that of the uncatalyzed reaction and the diglyceride at a six-fold rate. The triglyceride was formed at an almost undiminished rate whereas in the uncatalyzed reaction the formation of triglyceride was diminished rapidly.
4. Unsaturation and viscosity were not affected seriously in the presence of the fluorides except antimony trifluoride. Certain other fluorides caused severe darkening but without accompanying serious decomposition.

     

Maltreated children's memory: Accuracy, suggestibility, and psychopathology.

Memory, suggestibility, stress arousal, and trauma-related psychopathology were examined in 328 3- to 16-year-olds involved in forensic investigations of abuse and neglect. Children's memory and suggestibility were assessed for a medical examination and venipuncture. Being older and scoring higher in cognitive functioning were related to fewer inaccuracies. In addition, cortisol level and trauma symptoms in children who reported more dissociative tendencies were associated with increased memory error, whereas cortisol level and trauma symptoms were not associated with increased error for children who reported fewer dissociative tendencies. Sexual and/or physical abuse predicted greater accuracy. The study contributes important new information to scientific understanding of maltreatment, psychopathology, and eyewitness memory in children. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

What does the object decision task measure? Reflections on the basis of evidence from semantic dementia.

The authors investigated the impact of semantic knowledge on visual object analysis by assessing the performance of patients with semantic dementia on a different-views object matching test and on 2 object decision tests differing, for example, in whether the nonreal items were nonsense objects or chimeras of 2 real objects. On average, the patients scored normally on both the object matching and the object decision test including nonsense objects but were impaired on the object decision test including chimeras; this latter was also the only visual object test that correlated significantly with degree of semantic impairment. These findings demonstrate that object decision is not a single task or ability and that it is not necessarily independent of conceptual knowledge. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of Thickness of the p-AlGaN Electron Blocking Layer on the Improvement of ESD Characteristics in GaN-Based LEDs

The following letter presents a study regarding GaN-based light-emitting diodes (LEDs) with p-type AlGaN electron blocking layers (EBLs) of different thicknesses. The study revealed that the LEDs could endure higher electrostatic discharge (ESD) levels as the thickness of the AlGaN EBL increased. The observed improvement in the ESD endurance ability could be attributed to the fact that the thickened p-AlGaN EBL may partly fill the dislocation-related pits that occur on the surface of the InGaN-GaN multiple-quantum well (MQW) and that are due to the strain and the low-temperature-growth process. If these dislocation-related pits are not partly suppressed, they will eventually result in numerous surface pits associated with threading dislocations that intersect the InGaN-GaN (MQW), thereby reducing the ESD endurance ability. The results of the experiment show that the ESD endurance voltages could increase from 1500 to 6000 V when the thickness of the p-AlGaN EBL in the GaN LEDs is increased from 32.5 to 130 nm, while the forward voltages and light output powers remained almost the same.     

程控电流源无需电源支持

工程实验室通常都配有各种电源设备、伏特计、函数信号发生器和示波器。然而．许多这样的工程实验室却缺少电流源。这令人感到非常遗憾，因为电流源有助于生成I-V（电流对电压）曲线，它能对电池进行充放电操作，对电源设备预加负荷，并可实现许多其他的应用。