Laboratory and field investigation of the effect of geogrid-reinforced ballast on railway track lateral resistance

Continuous welded rail (CWR) tracks have particular advantages over common tracks with jointed rails such as increased ride comfort, reduced noise and vibration and decreased maintenance costs due to the removal of joints in rail connections. Alternatively, some complications associated with CWR tracks, for instance increased lateral forces, are the main reason of track buckling and its subsequent lateral deformation. These problems are usually more severe in curved tracks. In order to overcome the large lateral forces caused by temperature deviations of CWR tracks which results in railway vehicle instability, the ballasted track lateral resistance should be improved. Among the various methods proposed in this area, no specific study has been carried out on the effect of geogrid reinforcement on ballasted track lateral resistance. Thus, the present research was allocated to investigating the effect of geogrid on the lateral resistances of both single tie and track panel via laboratory and field tests. In this regard, at the first stage, the ballast layer was reinforced with various number of geogrid layers, the effect of which was investigated by conducting the single tie push test (STPT) in the lab environment to assess the optimum number of geogrid layers and their installation levels along the ballast layer thickness. Afterwards, a test track was executed in the field including various sections which were reinforced in the same way as the lab tests. Consequently, many STPTs and track panel displacement tests (TPDTs) were accomplished. As a result, the STPTs in the lab and field confirmed more than 31% and 42% increase in single tie lateral resistance for ballast layers reinforced respectively with one and two geogrid layers, while these values were reached to 29% and 40% in the case of TPDT.     

The application of time domain ground penetrating radar to evaluate railway track ballast

This paper will evaluate Ground Penetrating Radar (GPR) as a Non Destructive Test (NDT) technique for the assessment of railway track bed ballast. Ballast and tracked deterioration is responsible for the majority of differential settlement of tracks, resulting in poor track geometry. Traditionally ballast is only replaced when it has visually deteriorated, resulting in the planning and programming of maintenance and renewals currently being condition driven. There is a significant potential cost saving if ballast deterioration can be detected earlier. GPR can survey large lengths of track ballast in a relatively short space of time. This paper will show how GPR can be used to quickly identify the degree of track bed ballast deterioration and detect the ballast/formation interface.     

Assessing ballast water treatments: Evaluation of viability methods for ambient freshwater microplankton assemblages

For decades the Great Lakes have been subject to invasive species introductions through the discharge of ships' ballast water. Several treatment technologies involving physical, chemical, and biological processes have been developed to remove or inactivate organisms in this discharge. Assessing the efficacy of these technologies involves estimating the number of viable propagules in treated discharge relative to untreated controls. For organisms in the 10–50 µm size range, for example, the International Maritime Organization (IMO) mandates that fewer than 10 viable organisms per milliliter may be discharged. To date, however, there is no standard method to assess viability of natural assemblages of organisms in this size group (largely phytoplankton and protozoans) in freshwater environments. We report here on a process of assemblage concentration, staining with fluorescein diacetate (FDA), and microscopic observation as a reliable and efficient method to assess densities of viable freshwater organisms in this size category in ballast discharge. A number of other methods, including digestion with enzymes, flow cytometry, and a variety of vital and mortal stains, were tested and discarded during this vetting process due to inconsistent or ambiguous results.     

Scattering analysis of ground-penetrating radar data to quantify railroad ballast contamination

This paper will evaluate ground-penetrating radar (GPR) as a non-destructive method to rapidly, effectively, and continually assess the conditions of railroad ballast. Compared to uniformly graded, clean ballast, fouled ballast has a finer, well-graded particle size with fewer air voids. Ballast under different conditions generates various GPR electromagnetic scattering patterns. A field GPR survey with multiple sets of 1 and 2 GHz air-horn antennae was conducted in summer 2005 at the Transportation Technology Center, Inc. (TTCI) in Pueblo, Colorado. The 2 GHz antenna was found to be more sensitive to the change in scattering pattern. Appropriate data processing was used to remove the effects of the rails to obtain clear GPR images of the subsurface layers. From the image analysis, ballast thickness, ballast fouling condition, and trapped water can be assessed.     

基于L6574控制器的可调光电子镇流器

该文介绍了可调光荧光灯电子镇流器控制器L6574的功能和特点,重点阐述了基于L6574和三端双向可控硅（Triac）调光器的节能灯可调光镇流器的解决方案和工作原理。     

Numerical simulation of mixing process of gas–liquid impinging jet in ballast water discharge pipe

When a gas–liquid turbulent jet with hydroxyl free radicals is jetted into a ballast water discharge pipe to kill the invasive microbes, there is a challenge for hydroxyl free radicals to contact a large number of microbes in ballast water. In this paper, the Eulerian–Eulerian two-equation model is employed to simulate the mixing process of gas–liquid being jetted into the ballast water crossflow. The results show that the upstream wall-surface vortices lead to counter-rotating scarf vortex pairs (CVSPs) at downstream in confined crossflow, which enhance the mixing process. However, it is hard for the gas in the downstream wall-surface jet to diffuse due to the fact that the CVSPs have no influence on the downstream wall-surface jet. Therefore, the higher the momentum ratio is, the lower the value of weighted coefficient of variation of gas volume fraction at outlet is, however, when the momentum ratio is constant, the weighted coefficient of variation first drops and then goes up with increasing diameter ratio.     

Ballast water management system certification testing requirements for protists are a poor fit for the Great Lakes

Challenge condition requirements for testing of ballast water management systems (BWMS) are a poor fit with regard to protection of the Laurentian Great Lakes from aquatic invasive species, particularly with respect to protists. Though protists are abundant in the Great Lakes, required densities of cells (1000 cells/mL) meeting the 10–50 µm (“protist”) regulatory size class of the ballast water discharge standard (BWDS) are rarely achievable under ambient conditions. This deficiency drives certification testing to aquatic systems dissimilar to the Great Lakes or necessitates manipulation of intake water during testing. This requirement is unnecessary because: (1) protist cells both within and smaller than the regulatory size class are largely equivalent in their challenge to BWMS performance and their threat to ecosystems; and (2) lower densities of cells in challenge water can meet regulatory requirements; i.e. at least 100 live cells/mL in untreated discharge (control) water are required for test validity. We describe how current requirements for high densities of protists within the regulatory size class as a challenge condition in certification testing unnecessarily undermine vetting of BWMS performance and operation. We posit a range of alternatives and identify approaches to modifying challenge requirements to alleviate problems while protecting test rigor and relevancy to the BWDS. Without a change to these requirements there will be no certification testing in freshwater resources like the Great Lakes without substantial intake stream manipulation during testing, and therefore, little way to confirm whether a BWMS will perform in the Great Lakes and other freshwater systems.     

基于PSoC CY8C26233的电子调光镇流器设计

CY8C26233是赛普拉斯微系统公司生产的可调光电子镇流器PSoC器件。这种芯片带有数字可寻址照明接口，可实现1％～100％的调光幅度。文中介绍了CY8C26233的内部结构、引脚功能和主要特点，给出了基于CY8C26233的调光镇流器电路及参考设计。     

Evaluation of railway trackbed and formation: a case study

To determine the causes of poor track geometry, a trackbed investigation should comprise a full assessment of ballast, sub-ballast and formation condition. If information about any of these layers is omitted, the true cause of poor formation sites cannot be ascertained satisfactorily and consequently appropriate ground improvement schemes may not be implemented. This has been observed in the UK rail network with examples of a lack of detailed site investigation and subsequent expensive remedial work being carried out without eliminating the initial cause of the problem. This paper summarises the trackbed investigation performed at a site requiring high maintenance, suspected as being caused by poor formation. The paper concludes with an analysis of ground conditions and possible choice of remedial schemes.     

A simple finite element to consider the non-linear influence of the ballast on vibrations of railway bridges

This article proposes a new and simple finite element which can be used to analyze vertical vibrations in railway bridges. The main feature of the element is that the effect of the ballast is introduced through a non-linear longitudinal stiffness associated to the slip at the interface between the bridge and the ballast. Two numerical applications show that this element can be used to model the variation of the natural frequencies of the bridge as a function of the amplitude of vibration.