Modeling and Validating the Effective Hydraulic Detention Time for a 10 mgd Ozone Contactor at the Lake Washington Surface Water Treatment Plant,Melbourne, Florida

Ozonation has been added to the treatment process at the 20 mgd Lake Washington Surface Water Treatment Plant (SWTP), Melbourne, Florida to improve finished water quality, control taste and odor, and provide greater than 0.5-log credit for inactivation of Cryptosporidium. The new ozone contactors (2 parallel 10 mgd trains) are located between the existing Actiflo^TM clarifiers and the filters on a relatively congested site. Prior to construction, a Computational Fluid Dynamics (CFD) study indicated that the proposed contactor design was not optimized to provide the targeted Cryptosporidium log inactivation. Based on the CFD modeling, the design was modified to reduce the baffle heights (increasing end gaps at turns) and the baffle ends were chamfered to improve flow patterns within the contactor. Internal access platforms were rotated from parallel to the flow (along outside walls) to perpendicular to the flow (along baffle walls). These small design changes increased the modeled effective detention time (t₁₀) for disinfection and the corresponding hydraulic efficiency (baffling factor) by 22 %. In addition, the dosing location for the ozone quenching chemical (hydrogen peroxide) was modified to provide extra ozone detention. The ozone contactors were then constructed to incorporate the design changes optimized from the modeling. During the start up of the ozone system, fluoride tracer tests were completed to validate the effective detention time (and baffling factor) calculated by CFD. Furthermore, a series of modifications are planned for the ozonated water sampling regime to take greater advantage of Ct₁₀ credits and reduce the required ozone dose, thereby saving energy and operating costs. This paper discusses several calculation methods for Cryptosporidium inactivation Ct₁₀ reporting in compliance with the Long-Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) and the LT2ESWTR Pre-proposal Draft Regulatory Language for Stakeholder Review (USEPA, 2002). The selection of the method will depend upon ease of implementation, modifications required to the ozone-in-water residual sampling system, long-term results of bromate sampling and actual Cryptosporidium bin classification under the LT2ESWTR. The article describes the CFD studies, improvements made to the contactor design, the tracer validation of the design, Ct₁₀ reporting methods and modifications to the ozone residual sampling system that the City is considering.     

炭黑N234在全钢轻型载重子午线轮胎胎面胶中的应用

对全钢轻型载重子午线轮胎胎面胶配方进行优化。结果表明,采用炭黑N234替代炭黑N115,并对胎面胶配方进行适当调整,胶料挤出温度降低,挤出速度提高,挤出性能明显改善,硫化胶生热降低,成品轮胎耐久性能和高速性能提高。     

LT1778应用电路设计

随着电子技术的迅猛发展,单板电路正常工作所要求的电源种类越来越多,功耗越来越大,这就向产品电源系统的设计师提出了新的挑战。目前,开关电源已越来越多的用于单板电路供电。文中介绍了Linear公司的开关管控制器LT1778的工作原理、设计方法及PCB布线要点,并给出实例供有关的设计人员参考。     

LT码新型度分布及其在电力线通信中的应用

Luby变换(Luby Transform,LT)码作为信道编码应用于电力线通信(Power Line Communication,PLC),可实现电信号的可靠传输。度分布对LT码编译码性能的影响至关重要。为了得到更优的度分布,首先调整二进制指数分布(Binary Exponential Distribution,BED)中的度数比例,获得一种译码性能更优的改进的二进制指数分布(Improved BED,IBED)。然后,根据IBED在冗余度较小时译码成功率高,而冗余度增大后鲁棒孤子分布(Robust Soliton Distribution,RSD)的译码性能表现更佳的特点,通过求和归一化的方式将IBED与RSD两种度分布的优势进行有机结合,提出一种新型二进制鲁棒孤子分布(Binary RSD,BRSD)。仿真结果表明,与其他方法及传统的RSD相比,采用新度分布进行LT编码,可明显降低译码开销,并节约编译码耗时。将新型度分布应用于基于LT码的PLC系统中,能有效地抑制PLC信道中各种噪声对电信号的干扰,并提高通信效率。     

多媒体手持通信终端降压稳压器设计

文中设计采用LT1940单片双降压型稳压器,提供双路1.4A输出和双相开关,其开关频率达到1.1MHz,足够满足大功率、体积小、连续供电的要求,而且可以检测输出电压状态并单独控制其通断,满足其系统高效节能工作。     

Effect of heat treatment on tensile behaviour of Ti-6Al-5Zr-0.5Mo-0.25Si alloy

Tensile behaviour of the near a titanium alloy, Ti-6Al-5Zr-0.5Mo-0.25Si (LT26A), was investigated in (α + β) as well as β treated condition, over a wide range of temperature from RT to 823 K. It was observed that there were distinct serrations on the load-elongation curves of the a + β treated material at intermediate temperatures from 623 to 723 K. Tensile tests at 673 K over a wide range of strain rate from 0052 to 5.60 (× 10^-2) s^-1 showed negative strain rate sensitivity. Thus, occurrence of DSA was confirmed. It was established from the measured activation energy for DSA that it was essentially controlled by diffusion of the solid solution strengthener silicon in the matrix.     

AVO交汇图分析技术的应用

AVO交汇图分析技术是AVO碳氢检测技术的一种重要分析手段。本文介绍了AVO交汇图分析技术在DF1 1构造、LT33 1构造和PL19 3构造中的首次应用。利用AVO交汇图分析技术 ,可以把LT33 1构造因岩性变化引起的AVO异常与DF1 1构造的含气AVO异常明显区分开 ;在PL19 3构造的浅层油气勘探中 ,利用该技术识别含气亮点和非含气亮点也取得了较好的效果     

解组合优化的一种新方法的收敛性

对一种新型的求解组合优化的方法－混合ＬＴ法讨论了其收敛性，给出了其收敛的充分条件和必要条件，通过对这些收敛条件的分析，指出该法对非常广泛的组合优化问题都有效和收敛，因此可适用于很多类组合优化问题。     

LT6.5M和XT6.5M高传输衰耗测试夹具的制作

简述了ＬＴ６．５Ｍ和ＸＴ６．５Ｍ高传输衰耗测试夹具的基本要求，介绍了一种制作满足性能的测试夹具的方法。     

基于CPCI的嵌入式系统的电源设计

介绍一种基于CPCI的嵌入式系统的电源设计方案。分析系统的功耗需求后,介绍系统使用的3种新型电源器件。随后,重点讨论LDO型电源器件LT3501。详细阐述配置该电源电路多项重要参数的方法。该电源系统已在某嵌入式系统中得到成功运用,并且具有一定的通用性．可应用于类似的嵌入式系统中。