A new method based on two freedom-degree PD-P flow rate controller for congestion control in computer networks

The rate-based feedback PD-P controller of two freedom-degrees is proposed for the congestion control in computer networks to improve the abilities against disturbance. Moreover, the Dahlin algorithm is used for setting the controller to overcome the adverse effect caused by the propagation delay effectively. The research results show that the proposed scheme not only can make sources respond to the changes of network state more quickly, but also has a good robustness against estimated error of the delay. Then the packet queue level in buffer will be stabilized on the set-point quickly, and the delay and its jitter of the packet queuing will also become smaller. Besides, the flexible bandwidth allotment can be obtained by setting the weight coefficients.

Improvement of uniformity in cultivation environment and crop growth rate by hybrid control of air flow devices

A complete control type plant factory has high efficiency in terms of cultivation area by constructing vertical multiple layered cultivation beds.However,it has a problem of irregular crop growth due to temperature deviation at upper and lower beds and increases in energy consumption by a prolonged cultivation period.In this work,air flow rate inside a facility was improved by a hybrid control of air flow devices like air conditioning and air circulation fan with an established wireless sensor network to minimize temperature deviations between upper and lower beds and to promote crop growth.The performance of proposed system was verified with an experimental environment or Case A wherein air conditioning device was operated without a control algorithm and Case B wherein air conditioning and circulation fans were alternatively operated based on the hybrid control algorithm.After planting leafy vegetables under each experimental condition,crops were cultivated for 21 days.As a result,Case B wherein AC(air conditioning) and ACF(air-circulation fan) were alternatively operated based on the hybrid control algorithm showed that fresh mass,number of leaves,and leaf length for the crops grown were increased by 40.6%,41.1%,and 11.1%,respectively,compared to Case A.

Intelligent Flow Control Technique of ABR Service in ATM Networks Based on Fuzzy Neural Networks

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BUFFER DIMENSIONING FOR RATE-BASED CONTROL IN ATM NETWORK

Available Bit Rate (ABR) service has been developed to support data applications to asynchronous transfer mode (ATM) networks.Since a ratebased feedback flow control mechanism has been selected as a standard by ATM Forum,buffering becomes an issue that needs intensive study.In this paper,the queuing performance in a switch is studied in detail.It is theoretically proven that the goals of no cell loss and full utilization of link capacity can be achieved by choosing an appropriate buffersize and threshold of the switch buffer which is supported by our simulation results of a complex network.

DOUBLE LOOP ACTIVE VIBRATION CONTROL OF PNEUMATIC ISOLATOR WITH TWO SEPARATE CHAMBERS

A newly designed pneumatic spring with two separate chambers is promoted and double-loop active control is introduced to overcome the following drawbacks of passive pneumatic isolation： ① The low frequency resonances introduced into the system; ② Conflict between lower isolation frequency and stiffness high enough to limit quasi-static stroke;③ Inconsistent isolation level with different force load. The design of two separate chambers is for the purpose of tuning support frequency and force independently and each chamber is controlled by a different valve. The inner one of double-loop structure is pressure control, and in order to obtain good performance, nonlinearities compensation and motion flow rate compensation （MFRC） are added besides the basic cascade compensation, and the influence of tube length is studied. The outer loop has two functions： one is to eliminate the resonance caused by isolation support and to broaden the isolation frequency band by payload velocity feedback and base velocity feed forward, and the other is to tune support force and support stiffness simultaneously and independently, which means the support force will have no effect on support stiffness. Theoretical analysis and experiment results show that the three drawbacks are overcome simultaneously.

同轴反应流反应速率的唯象表征与影响规律研究

目的 为了提高同轴反应流工艺的控制精度,探索反应速率的宏观唯象表征方法和影响规律,方法 通过紫脲酸铵对Ca2+进行示踪,在线观测海藻酸钙水凝胶中空纤维的交联成形过程,利用洗脱法对交联层边界的灰度阈值进行标定,从宏观唯象的角度定义同轴反应流的平均反应速率,通过在线监测提取的交联层厚数据,计算得到反应速率值,并通过试验研究海藻酸钠和氯化钙溶液的流量(定流率比)、质量分数、共流距离对交联层厚和平均反应速率的影响规律。结果 结果表明:对比在线图像识别和洗脱法实测所得中空纤维尺寸,两者误差仅1.09%,满足工程应用需求;增加反应物质量分数能提高平均反应速率,增加交联层厚,且氯化钙质量分数具有更好的调控性能;定流率比条件下,随着两溶液流速增加,中空纤维交联层厚减小而平均反应速率增大;随着反应流共流距离增加,交联层厚增加而平均反应速率逐渐减小。上述唯象平均反应速率受流体速度场和化学反应物质量分数的影响规律与经典反应速率是一致的,说明该唯象定义是有效的。结论 研究采用的同轴反应流在线监测方法、反应速率的唯象表征方法、材料工艺参数影响规律等有助于实现中空纤维结构尺寸、交联层厚和保留溶胶层厚的精确控制,有助于同轴反应流工艺的推广与应用。

Modeling and Control of Time-pressure Dispensing for Semiconductor Manufacturing

To improve the consistency of the adhesive amount dispensed by the time-pressure dispenser for semiconductor manufacturing, a non-Newtonian fluid flow rate model is developed to represent and estimate the adhesive amount dispensed in each cycle. Taking account of gas compressibility, an intelligent model-based control strategy is proposed to compensate the deviation of adhesive amount dispensed from the desired one. Both simulations and experiments show that the dispensing consistency is greatly improved by using the model-based control strategy developed in this paper.

Development and Study on Nitrogen Removal Controller in A/O Process

In this paper three controllers for A/O process are developed, including a DO cascade controller, an external carbon flow rate controller and an internal recycling flow rate controller. The objective of the different controllers is to control the nitrate and ammonia concentration. Simulation study demonstrated that these controllers could efficiently control nitrogen removal and meet stricter effluent quality standards at a minimum cost.

Design of a Three-Dimensional Centrifugal Fan with Controlled Blade Loading Approach

The high flow-rate centrifugal fan needs a three-dimensional impeller to achieve a high efficiency. In this paper, the design procedure of a high-efficiency three-dimensional centrifugal fan is presented. First, the main dimensions of the fan were calculated by using the conventional one-dimensional method. Then, the blade loading or the angular momentum distribution along the meridional streamline on the blade surfaces is prescribed. After that, the three-dimensional blade is determined by using the streamline curvature method. With the aid of numerical simulations, the performance of the three-dimensional fan was improved and some of the key influence factors were investigated. The analyses indicate that, as to the high flow-rate centrifugal fan, the Stanitz modified formula is recommended to calculate the separation radius, rb. A proper increase in the separation radius is beneficial for the fan’s performance. It is also indicated that a decrease in the angular momentum on the hub leads to an increase in total pressure efficiency, under the condition of a given constant mean angular momentum at the outlet of the blade. In addition, the installation of a fairing on the hub plate can improve the fan’s efficiency evidently when the streamline curvature method is adopted to design the three-dimensional impeller.

Pressure control of PEMFC distributed power generator

Control design is important for PEMFC （proton exchange membrane fuel cell） distributed power generator to satisfy user requirement for safe and stable operation. For a complex multi-variable dynamic system, a dynamic simulation model is first established. In view of close coupling and non-linear relationships between variables, the intelligent auto-adapted PI decoupling control method is used. From the simulation results it is found that, by bringing quadratic performance index in the single neuron, constructing adaptive PI controller, and adjusting gas flow rates through the second pressure relief valve and air compressor coordinately, both anode and cathode pressures can be maintained at ideal levels.

A dynamic network Qo S control mechanism based on traffic prediction

A dynamic network Qo S control mechanism was proposed based on traffic prediction. It first predicts network traffic flow and then dynamically distributes network resources, which makes full use of network flow self-similarity and chaos. So it can meet changing network needs very well. The simulation results show that the dynamic Qo S control mechanism based on prediction has better network performance than that based on measurement.

基于流速权重系数的阻水比计算方法

阻水比是跨河桥梁防洪评价中的一个重要参数,而现有规程中阻水比的定义仅考虑阻水面积,没有考虑流速分布对阻水程度的影响,造成当河道主槽和边滩发育时计算的断面流速分布差异性较大。根据桥梁阻水引起的局部水头损失近似与水体流速平方成正比的关系,将建桥前桥墩处水体流速与桥址处全断面水体平均流速之比的平方作为流速权重系数,用以修正桥墩阻水面积,从而改进阻水比计算公式,并应用于实例验算。计算结果表明:①位于主槽的桥墩单位阻水面积对阻水比影响较大,而位于边滩的桥墩单位阻水面积对阻水比影响较小,且流速差异越大,阻水影响程度相差越大;②当主槽流速与全断面平均流速之比达到1.17以上时,应考虑流速权重影响系数对阻水比的影响。基于流速权重系数的阻水比能够较为真实地反映流速差异带来的阻水影响,更接近工程实际阻水情况,为有效减少桥墩对防洪的不利影响,桥梁设计时应尽量采用大跨度结构一跨跨越河道主槽。

电力信息物理系统中信息系统物理化的建模及分析方法

该文基于信息系统物理化的设想提出电力信息物理系统(cyber-physical power system,CPPS)中的信息流建模和计算分析方法。采用连续时间函数来刻画信息流的特征,并定义信息网络运行参数为流量累积函数、信息流速和时延。首先,基于遍历法搜索出信息流路径,建立信息流速矩阵的范式;然后利用改进的网络演算(network calculus,NC)特性赋值流速矩阵的元素;进一步采用流量累积函数表征信源数据发送规律,从而显式求解时延上界。最后将提出的信息流建模方法应用于智能变电站自动化系统的时延计算,通过与OPNET的仿真结果相比较,验证所提出模型的有效性,而且该方法可以提供定量分析指标以优化变电站组网方案设计中的信息流分布。

基于可调文氏管的液氧流量闭环控制特性研究

针对液氧供应系统流量精准控制困难的问题,开发了一套流量闭环控制系统并应用于液氧供应系统中。为实现系统按预设目标流量进行输出,进行了四类试验:无控制试验、流量闭环控制试验、PID参数影响试验与流量阶跃调节试验,研究了贮箱压力、液氧温度、针锥位置、调节范围与PID参数等因素对液氧流量闭环控制特性的影响。结果表明,通过反馈实时测得的液氧质量流量,流量闭环控制系统控制可调文氏管节流面积变化,实现了液氧流量±1%的精准控制,解决了由于系统压力波动及液氧温度变化等原因导致的液氧流量供应不稳定的问题,并实现了液氧在5∶1流量变比内的精准阶跃调节。

藻细胞显微成像中微流控自动进样分段控制方法

藻细胞显微图像快速自动获取具有重要的应用价值。针对微流控-显微成像技术中样品进样效率与细胞成像质量问题,研究了基于藻细胞通过荧光检测窗口持续时间的样品平均流速检测方法,并提出基于体积流量调节的微流控自动进样分段控制方法。结果表明,进样速度在10~30μL/min范围内,样品平均流速检测误差小于5%;分段控制实现了藻细胞显微图像的高质量自动获取,与显微镜检成像质量基本一致,且样品进样速度提升68%以上。研究结果为藻细胞显微图像高效自动获取提供了有效实用方法。

输液介质影响输液泵流速的实证研究

目的 探究输液介质对输液泵流速的影响。方法 随机抽取10台输液泵,采用去离子水、氯化钠溶液、葡萄糖溶液和肠道外营养液分别进行流速检测,输液泵流速设为30 mL/h,检测方法依照《医用输液泵校准规范》。结果 对于输液器A,流速不受输液介质的影响,均符合质控要求标准;对于输液器B,输液介质为去离子水、氯化钠溶液和葡萄糖溶液时,流速误差在质控要求标准内,而输液介质为营养液时,流速误差超出质控要求标准。结论 输液器和输液介质对输液泵流速均有影响,根据使用的输液介质进行流速校准对于降低输液泵在使用过程中的医疗风险具有重要意义。

遂昌金矿高浓度似膏体充填系统升级改造

为解决遂昌金矿现有充填系统存在的尾砂斗仓易堵塞、大倾角带式输送机无法变频调节供料量、卧式双轴搅拌机转速过低、充填料浆工作流速过小、充填系统无自动控制系统等问题,进行了高浓度似膏体充填系统升级改造。结果表明:通过尾砂斗仓改造,使用变频板带式给料机、高转速搅拌桶、小管径充填管道,进行自动化控制系统升级,可显著提高充填质量和效果;充填系统改造总投资约90万元,综合充填成本约为40.0元/t。

局部土地利用类型变化对城市水文过程的影响研究

为探究城市下垫面局部土地利用类型变化对城市水文过程的影响,采用高效高精度城市雨洪模型(GAST)耦合管网模型(SWMM),模拟不同降雨重现期下动态改变土地利用类型(单块无下渗土地C_(1)、多块组合无下渗土地C_(2)、单块裸土地C_(3)、单块草地C_(4)和单块林地C_(5))对城市地表积水、管网排水的影响。结果表明:改变局部原始土地利用类型(B1)在小降雨重现期下降低了城市积水量,而在大降雨重现期下改变土地下渗面积和区域位置无法进一步减少积水,此时则需考虑非工程措施的极端暴雨应对模式。不同动态规划区域下渗强度导致管网排口流量增幅不同(C_(2)>C_(1)>C_(3)>C_(4)>C_(5)),隔渗能力越强对管网排口流量增幅影响越大,而管网径流控制率则呈相反趋势。结合对积水量的影响可知,增加下垫面下渗能力并结合排水系统可进一步降低城市内涝风险和管网排水负荷,且管网径流控制率同样可以作为评估动态规划可行性的一个重要指标。

Thermodynamic Characteristic Study of a High-temperature Flow-rate Control Valve for Fuel Supply of Scramjet Engines

Thermodynamic characteristics are of great importance for the performance of a high-temperature flow-rate control valve,as high-temperature environment may bring problems,such as blocking of spool and increasing of leakage,to the valve.In this paper,a high-temperature flow-rate control valve,pilot-controlled by a pneumatic servo system is developed to control the fuel supply for scramjet engines.After introducing the construction and working principle,the thermodynamic mathematical models of the valve are built based on the heat transfer methods inside the valve.By using different boundary conditions,different methods of simulations are carried out and compared.The steady-state and transient temperature field distribution inside the valve body are predicted and temperatures at five interested points are measured.By comparing the simulation and experimental results,a reasonable 3D finite element analysis method is suggested to predict the thermodynamic characteristics of the high-temperature flow-rate control valve.

煤气萘含量化验结果影响因素及优化措施分析

为提升我厂焦炉煤气中萘含量测定的准确率,分别在取样温度控制、取样流速控制、运输及储存环节温度控制等影响因素条件下,用苦味酸法测定煤气中萘的含量。通过不同实验因素影响下的对比分析,说明取样过程中各影响因素对萘的测定准确度有很大干扰,并对测定方法进行改进,改进后测定萘含量准确度得到了大幅度提升。