LNG接收站冷能利用方案

浙江液化天然气(Liquefied Natural Gas,LNG)接收站项目一期设计生产能力为300万t/a,可利用的冷能相当于6亿度电。冷能利用是工艺优化、节能环保和经济效益最大化的重要步骤。本文通过对冷能利用方案的原料、市场、冷能利用率、与LNG冷能工艺的匹配性、投资及回报等进行对比分析,选择合适的冷能利用方案,为其他LNG接收站项目提供参考。     

Experimental study on the effects of HP and LP EGR on thermal efficiency and emissions of a two-stage turbocharged diesel engine

An experimental study was performed to compare the effects of high- and low-pressure exhaust gas recirculation loops (HP and LP EGR loops) on thermal efficiency and emissions of a diesel engine. Tests were conducted on a 12-L six-cylinder turbocharged diesel engine under various operating conditions. We found that at a low speed of 1100 r/min, 1 MPa BMEP, the LP EGR loop could achieve higher brake thermal efficiency and lower emissions than the HP EGR. This is because the lower enthalpy available at the turbine inlet of the HP EGR loop increased the fuel/oxygen equivalence ratio. For the HP EGR, the gross indicated thermal efficiency was reduced by 1%, but pumping losses were only reduced by 0.5%, compared to the LP EGR loop. At a higher speed of 1600 r/min, 1 MPa BMEP, the HP EGR loop attained a higher brake thermal efficiency and lower emissions because of the relatively sufficient flow through the turbocharger. For the HP EGR loop, the gross indicated thermal efficiency was only reduced by 0.5% and pumping losses were reduced by 1.5%, compared to the LP EGR loop. Lower fuel consumption and a longer ignition delay made the distribution of fuel/oxygen equivalence ratio more homogeneous, leading to lower emissions. Our data also showed that at the high speed of 1600 r/min, 0.55 MPa BMEP, the brake thermal efficiency of the HP EGR loop first increased, then decreased as the EGR rate increased. Therefore, under all conditions, a reasonable match of both EGR loops could achieve a good balance between fuel consumption and emissions of NO _x and soot.     

公共建筑节能改造节能量修正计算方法

针对当前公共建筑节能改造节能量确定方法尚不完善的现状,提出了一种新的节能量修正计算方法,即以改造前建筑为基准的节能量修正模型,包括4个修正系数和3个计算式,4个修正系数分别为气象修正系数、室内热环境修正系数、内部负荷修正系数和运行时间修正系数,3个计算式为采暖节能量计算、空调节能量计算和总节能量计算。以天津市某大型办公建筑节能改造项目为例,采用节能量修正模型,得到修正节能量,此节能量保证了比较条件的一致性。通过比较修正节能量与改造前后能耗直接相减的节能量,修正节能量计算方法引起10.23%的节能量差别,从而证明了修正的必要性。通过与模拟软件计算结果的对比,差别为3.03%,在10%的可接受范围内,验证了该节能量修正计算方法的准确性。     

预氯化对输水管道净水效能影响及恢复研究

为保障原水输水过程中水质安全性,采用生物膜环状反应器(BAR, Biofilms Annular Reactor)考察预氯化对管道生物膜净水效能的影响及其性能恢复过程．结果表明,管道预氯化后,对管道生物膜损伤较大,影响NH₄+-N、NO₂--N、CODMn、TP去除效果;出水出现短暂的CODMn和TP质量浓度上升、NO₂--N积累现象,出水NO₂--N最大积累量可达7倍．冲击实验后稳定运行阶段,生物膜对NH₄+-N去除效能恢复时间较NO₂--N快2 d,NH₄+-N、NO₂--N分别在第8天和第10天完成恢复;稳定运行至第8天,管壁生物膜完成对CODMn和TP去除效能的恢复．     

粉尘粒子纤维层湿式过滤的试验研究

在传统基本假设的基础上,利用等效类比的方法引进水均匀分布于纤维丝表面并形成当量直径的假设,实现了湿式纤维层粉尘过滤过程的理论分析.同时,借助正交试验和常规实验的手段对理论式进行了无量纲修正,得到半理论半经验公式,并给予实际应用的适用范围.该公式对湿式纤维层的粉尘过滤具有实际指导意义.     

基于RFID的自动化立体仓库优化管理系统的设计与实现

介绍了RFID技术,构建了基于RFID技术的自动化立体仓库管理系统的基本结构,对其结构和功能进行了分析.并通过对典型RFID阅读器的研究,对基于中间件技术的数据采集子系统进行设计,实现RFID硬件与调度系统软件的正常通信,对基于RDID技术的仓储管理系统的设计有指导意义.通过RFID技术的应用,提高了自动化立体仓库的运作效率和准确性,减少了人为的差错.     

Novel anti-noise-uncertainty spectrum sensing algorithm based on power spectral density segment cancellation

Since noise uncertainty seriously degrades the spectrum sensing performance of energy detection algorithms, a novel spectrum sensing algorithm based on the power spectral density segment cancellation (PSDSC) is proposed. This spectrum sensing algorithm, which can yield real-time and robust performance, makes use of the un-correlation of different power spectrum lines and takes the ratio of some PSD (power spectral density) lines to the residual PSD lines as the detection statistics. Theoretical analysis and simulation results show that the PSDSC algorithm can overcome the noise uncertainty problem effectively and that the decision threshold does not vary with the ambient noise level of secondary users. The PSDSC algorithm could offer a high probability of detection (P_d) at a low probability of the false alarm (P_fa) for a wide range of signal to noise ratios (SNR) and could be applied to spectrum monitoring and cognitive radio systems in the complex electromagnetic environment.     

Study of high efficiency of evaluation of a PDP in authorization service

In authorization service, the efficiency of evaluation of a PDP(policy decision point) is a key issue that affects the efficiency of authorization service. However, the efficiencies of evaluation of many PDPs available are frequently influenced by the factors of conditions in rules. Said Marouf et al put forward a method in which the evaluation speed can be increased by adjusting the rules in policies according to user history access records. This paper analyzes the shortcomings of this method in real-time applications, and proposes that the rules order in policies can be instantaneously adjusted by user history access records and indexes as well as self-adaptation are added to a PDP so that the evaluation speed can be increased substantially. Experimental results indicate that when there are 9795 rules in a PDP, the evaluation time and the time consumption taken for a PDP applied with indexes and self-adaptation to complete an authorized operation call are shortened by 93.33％ and 76.32％ respectively, compared with those for a PDP which is not applied with indexes and self-adaptation. When the number of repeat visits from the same user is 7, the time consumption taken for a PDP applied with indexes and adaptation to complete an authorized operation call is shortened by 24.29％ compared with that for a PDP which is applied with indexes only.     

基于PSpice的功率放大电路输出功率和效率的分析

为了分析OCL功率放大电路的输出功率和效率,借助电子电路辅助设计,分析软件PSpice,采用直流扫描分析和瞬态分析两种方法,对功率放大电路的最大输出电压、最大输出功率和电源提供的功率进行仿真实验及数据分析。由仿真输出波形可以看到仿真结果与理论分析基本一致,并以此为依据计算效率,从而加深对功率放大电路理论的理解。     

线谱频率参数的快速、低存储矢量量化

为降低码书的存储空间和搜索复杂度,更充分地利用线谱频率参数帧内和帧间的相关性,提出了一种快速、低存储的矢量量化器。将线谱频率参数去除平均值后进行一阶滑动平均预测,将残差进行三级矢量量化。在第二级量化时,将高维线谱频率参数矢量分裂成两个低维的部分,分别用不同的码书进行量化,降低了码书的存储空间和搜索复杂度。C语言仿真结果显示,在满足低速率编码的前提下,平均谱失真达到0.91dB,2～4dB的谱泄露为0.13%,无4dB以上谱泄露,同时码书的存储空间和搜索复杂度均降低了31%以上。