Case History Illustrating the Challenges of Foundation Design and Construction in Karst Terrain

This paper discusses the challenges associated with design and construction of foundation systems for a Corporate Campus located in Chester County, Pennsylvania that is underlain by Karst terrain. A comprehensive subsurface investigation was implemented to develop adequate foundation systems and related site work precautions. Because there was evidence of sinkhole activity prior to any construction work, and the subsoils revealed some variability from a consistency/density standpoint, the selected foundation system design included a combination of soil improvement using compaction grouting for shallow foundations and deep drilled-pier foundations. After construction activities began, several occurrences of solution activity were documented and repaired. During construction of drilled-pier foundations at one of the structure locations, a significant number of voids and discontinuities in the rock were encountered. The impact of these discontinuities and voids was dramatic to the effort and time necessary to complete the drilled pier foundation construction for this structure. After careful consideration of potential cost and schedule impacts, the foundation design for remaining structures was modified to eliminate the use of drilled piers and incorporated only compaction grouting for support of shallow foundation systems. Interaction of the Geotechnical Engineer, Construction Manager, Owner, and Contractor began early in the construction process and this interaction became critical to the project success as work proceeded on this project

Evaluation of Selected Sludge Disposal Methods

This research was undertaken to determine the feasibility of dewatering digested sludge using vacuum filters or centrifuges followed by land spreading as opposed to the present method of sludge hauling and disposal. The objectives of these experiments were to: 1 Determine whether the sludge from the Sioux Falls Wastewater Treatment Plant with the addition of a selected polymer could be dewatered by means of a vacuum filter. 2. Determine whether the sludge from the Sioux Falls Wastewater Treatment Plant with the addition of a selected polymer could be dewatered by means of a solid bowl centrifuge. 3. Establish capita costs for sludge dewatering and disposal by means of vacuum filtration, centrifugation and the existing method of lagoons and drying beds with land application.4. Establish operation and maintenance costs for sludge dewatering and disposal by means of vacuum filtration, centrifugation and the existing method of lagoons and drying beds with land application. 5. Compare the average annual costs of the three mentioned dewatering and disposal methods

Making internal fixation work with limited bone stock

Fractures are common in small animal practice and there are many options for managing them. Plates and screws remain a popular means to manage many fractures; however, some fractures are sufficiently close to a joint (juxta-articular), that they limit the amount of bone available to achieve a standard stable plate and screw fixation. This article discusses the options to achieve a stable internal fixation when there is limited bone stock

A comparative study of p(+)n and n(+)p InP solar cells made by a closed ampoule diffusion

The purpose was to demonstrate the possibility of fabricating thermally diffused p(+)n InP solar cells having high open-circuit voltage without sacrificing the short circuit current. The p(+)n junctions were formed by closed-ampoule diffusion of Cd through a 3 to 5 nm thick anodic or chemical phosphorus-rich oxide cap layer grown on n-InP:S Czochralski LEC grown substrates. For solar cells made by thermal diffusion the p(+)n configuration is expected to have a higher efficiency than the n(+)p configuration. It is predicted that the AM0, BOL efficiencies approaching 19 percent should be readily achieved providing that good ohmic front contacts could be realized on the p(+) emitters of thickness lower than 1 micron

Comparison Of Quasi-Phase-Matching Geometries For Second-Harmonic Generation In Poled Polymer Channel Waveguides At 1.5 Mu M

We have investigated three different quasi-phase-matching approaches to second-harmonic generation (SHG) in DANS (4-dimethylamino-4\u27-nitrostilbene) poled polymer channel waveguides at 1.5 mu m. Periodic photobleaching and periodically poled electrodes deposited directly on the film produced unacceptably high propagation losses. However, periodic electrodes on the substrate gave low losses and useful SHG

What do cyclists need to see to avoid single-bicycle crashes?

The number of single-bicycle crash victims is substantial in countries with high levels of cycling. To study the role of visual characteristics of the infrastructure, such as pavement markings, in single-bicycle crashes, a study in two steps was conducted. In Study 1, a questionnaire study was conducted among bicycle crash victims (n = 734). Logistic regression was used to study the relationship between the crashes and age, light condition, alcohol use, gaze direction and familiarity with the crash scene. In Study 2, the image degrading and edge detection method (IDED-method) was used to investigate the visual characteristics of 21 of the crash scenes. The results of the studies indicate that crashes, in which the cyclist collided with a bollard or road narrowing or rode off the road, were related to the visual characteristics of bicycle facilities. Edge markings, especially in curves of bicycle tracks, and improved conspicuity of bollards are recommended. Statement of Relevance: Elevated single-bicycle crash numbers are common in countries with high levels of cycling. No research has been conducted on what cyclists need to see to avoid this type of crash. The IDED-method to investigate crash scenes is new and proves to be a powerful tool to quantify 'visual accessibility'. © 2011 Taylor & Francis

Fluctuating Bond Aggregation: a Model for Chemical Gel Formation

The Diffusion-Limited Cluster-Cluster Aggregation (DLCA) model is modified by including cluster deformations using the {\it bond fluctuation} algorithm. From 3$d$ computer simulations, it is shown that, below a given threshold value $c_g$ of the volumic fraction $c$, the realization of all intra-aggregate bonding possibilities prevents the formation of a gelling network. For $c>c_g$, the sol-gel transition occurs at a time $t_g$ which, in contrast to DLCA, doesnot diverge with the box size. Several results are reported including small angle scattering curves and possible applications are discussed.Comment: RevTex, 9 pages + 3 postscript figures appended using "uufiles". To appear in Phys. Rev. Let

Spiral high-speed scanning tunneling microscopy: Tracking atomic diffusion on the millisecond timescale

Scanning tunneling microscopy (STM) is one of the most prominent techniques to resolve atomic structures of flat surfaces and thin films. With the scope to answer fundamental questions in physics and chemistry, it was used to elucidate numerous sample systems at the atomic scale. However, dynamic sample systems are difficult to resolve with STM due to the long acquisition times of typically more than 100 s per image. Slow electronic feedback loops, slow data acquisition, and the conventional raster scan limit the scan speed. Raster scans introduce mechanical noise to the image and acquire data discontinuously. Due to the backward and upward scan or the flyback movement of the tip, image acquisition times are doubled or even quadrupled. By applying the quasi-constant height mode and by using a combination of high-speed electronics for data acquisition and innovative spiral scan patterns, we could increase the frame rate in STM significantly. In the present study, we illustrate the implementation of spiral scan geometries and focus on the scanner input signal and the image visualization. Constant linear and constant angular velocity spirals were tested on the Ru(0001) surface to resolve chemisorbed atomic oxygen. The spatial resolution of the spiral scans is comparable to slow raster scans, while the imaging time was reduced from ~100 s to ~8 ms. Within 8 ms, oxygen diffusion processes were atomically resolved

Blind Inversion of Wiener Systems

A system in which a linear dynamic part is followed by a non linear memoryless distortion a Wiener system is blindly inverted This kind of systems can be modelised as a postnonlinear mixture and using some results about these mixtures an e cient algorithm is proposed Results in a hard situation are presented and illustrate the e ciency of this algorith