Field assessment of railway ballast degradation and mitigation using geotextile

Rail tracks continue to deform due to degradation of ballast under the application of heavy train traffic. The resulting track deformations often lead to drainage impairment as well as loss of resiliency. For track replenishment, deep screening of ballast is usually adopted by Indian Railway (IR) either after 10 years or passage of 500 MGT traffic, whichever is earlier. To study the effectiveness of geotextile on track stability and assess possible reductions in maintenance costs, a layer of woven geotextile was installed at the ballast-subgrade interface in Bhusawal-Akola central railway section of IR which is the present study area. The results show that the amount of degradation and fouling are different in UP and DN tracks due to inherent variation in traffic characteristics. This study also shows that the placement of geotextile in the track has led to prolonged maintenance cycle with favorable implications on cost and track shutdown periods. The findings of the present case study results will be useful for IR to reduce the ballast procurement and reuse of discarded material during deep screening in future.     

Ozonation of the marine dinoflagellate alga Amphidinium sp.--implications for ballast water disinfection

Ozone has been investigated for its potential to remove marine dinoflagellate algae from ships' ballast water. Dinoflagellate algae, Amphidinium sp. isolated from the Great Barrier Reef, Townsville, Australia were used as indicators since these produce a type of cyst that is difficult to inactivate, but are relatively easy to culture. The ozonation experiments have demonstrated a high ozone demand for inactivation of the algal cultures, which increases as the culture ages. The main ozone demand in seawater is due to its reaction with bromide to form bromine compounds. The non-bromide ozone demand has been estimated by measuring the residuals produced after various doses of ozone. The Amphidinium sp. show an unexpected response to both ozonation and bromination, with an instantaneous inactivation of the organisms for all doses that produced an oxidant residual in the seawater, followed by an effect of the disinfection residual. The standard design procedure of comparing Ct will not be effective for predicting the response of the organism to varying dose, C, and contact time, t, and a plot of ozone produced oxidant residual against organism inactivation for various contact times is proposed for design purposes. High doses of ozone (5-11 mg/L) and up to 6h of residual contact were required for a 4-log inactivation of the Amphidinium sp. Ozonation is likely to be a difficult technology to implement for organisms with this ozone requirement in combination with characteristics of ballast tanks, which contain areas of sediments high in detritus and areas of corrosion.     

Flexible resonant tank for a combined converter to achieve an HPS and LED compatible driver

High pressure sodium (HPS) lamp has been widely used in street lighting applications because of its maturity, relia-bility, high lighting efficiency, long life-time, and low cost. Light emitting diode ...     

Behavior of Railroad Ballast under Monotonic and Cyclic Loading

A relatively new method for mechanized maintenance of railroad ballast (stoneblowing) puts a layer of single size stone between the ballast and each tie creating a two-layer gravel support. To get a better understanding of the behavior of this arrangement series of large diameter, triaxial tests have been carried out on single size and layered specimens. A new method of quantifying particle breakage during testing has been developed, and a conceptual model used to explain the combined effects of shearing and breakage on observed specimen behavior.     

The initiation of rotational motion of a lying object caused by wind gusts

In this paper, the initiation of motion of an object lying on a horizontal floor due to the aerodynamic force produced by a time-dependent wind is considered. It is assumed in this paper that when the aerodynamic force is large enough, the body starts to rotate around the most rearward supporting contact point, or pivoting point. This motion is analyzed by studying the dynamics of the rotation of the body around a pivoting point fixed to the floor, and placed in a gravity field under time-dependent aerodynamic loads produced by a non-steady incoming flow. This rotation initiation phase, which is relevant in the case of a time-varying gusty flow, is an intermediate phase between the two stages generally considered, namely, the initial static equilibrium without motion, and the final flight. In this intermediate phase, which is studied here, the rotational dynamics of the body should be taken into account and the gust characteristics as well, in order to determine whether once initiated the motion it leads to either a frustrated motion or to a successful one. A non-linear mathematical model has been developed, and a linear approximation is deduced, which allows us to obtain the condition for a successful flight. This condition shows two limits, valid for either long or short duration gusts, respectively. Some experiments have been performed in a gust wind tunnel, and results show a satisfactory agreement. To take into account the intrinsic random character of the phenomena in practical situations, expressions for the probability of exceeding the condition for successful flight under short duration gusts are obtained, assuming common probability density functions for the random parameters involved.     

Disinfection by-products in ballast water treatment: An evaluation of regulatory data

To reduce the global spread of invasive aquatic species, international regulations will soon require reductions of the number of organisms in ballast water discharged by ships. For this purpose, ballast water treatment systems were developed and approved by an international procedure. These systems rely on established water treatment principles which, to different degrees, have been proven to generate disinfection by-products with hazardous properties but have only scarcely been investigated in marine environments. Our study evaluates the publicly available documentation about approved ballast water treatment systems with regard to by-product formation. The most commonly employed methods are chlorination, ozonation, and ultraviolet (UV) irradiation. Chlorination systems generate trihalomethanes, halogenated acetic acids, and bromate in substantially larger quantities than reported for other areas of application. Levels are highest in brackish water, and brominated species predominate, in particular bromoform and dibromoacetic acid. Ozonation, which is less frequently utilized, produces bromoform in lower concentrations but forms higher levels of bromate, both of which were effectively reduced by active carbon treatment. In systems based on UV radiation, medium pressure lamps are employed as well as UV-induced advanced oxidation. For all UV systems, by-product formation is reported only occasionally. The most notable observations were small increases in nitrite, hydrogen peroxide, halogenated methanes and acetic acids. The assessment of by-product formation during ballast water treatment is limited by the lacking completeness and quality of available information. This concerns the extent and statistical characterisation of chemical analysis as well as the documentation of the test water parameters.     

一种金卤灯电子镇流器的分析与设计

该文在简单叙述金卤灯存在的声谐振问题的基础上,给出了一种两级全桥模式,低频方波驱动的电子镇流器的设计与实现,详细论述了电子镇流器的工作过程。     

管道配重新材料的探讨

在水下长输管道的敷设施工过程中,由于浮力和水动力作用,仅依靠管道自身重力,不能保持管道沉降深度和稳定,需采取有效经济的稳管措施,才能将管道稳定的固定在管沟内。文章简要介绍了常用的几种稳管方式,并对比介绍了一种新型用于水下管道施工过程中稳管的袋式压重方法,论述了软袋式压重的结构形式、工程应用范围及应用实例,通过与其他管道稳管形式比较,得出结论:新型填充式压重软袋与传统的混凝土压重相比,优点在于由织物制作的袋体将减少刮伤管道涂层的几率,有利于延长管道使用寿命。     

高频HID灯电子镇流器谐振参数设计

LCC谐振逆变器的设计是LCC谐振型HID灯电子镇流器系统的设计重点。本文在介绍了HID灯电子镇流器中LCC谐振逆变器的应用背景后,推导出一种LCC参数计算方法,这种方法通过分析谐振逆变器各关键参数间的关系,简化了设计变量并得到了该变量与镇流器各指标间的关系曲线,从而使参数的选择更加明确,减少了确定设计参数过程中由某些参考文献给出的经验尝试以及对经验数据的依赖。考虑到实际设计中元件参数选择的局限,本文并给出了相应的修正办法。最后给出的仿真及实验结果验证了这种方法的正确性     

ST电子镇流器计算机辅助设计软件V.1.1.2.0简介(续)

本文主要介绍2007年由意法半导体公司（ST）开发推出的电子镇流器计算机辅助设计软件ST Lighting Designer V．1．1．2．0的主要特点、功能与使用。