运用AHP方法实现空调冷热源方案的优选

应用AHP方法建立了空调冷热源方案的评价模型,并结合工程实例对4种空调冷热源方案进行分析,选出最佳方案。从而证明该方法可辅助设计人员对备选方案进行比较、分析,并且做出决策,提高了决策的科学性。     

基于启发式动态规划的冷热源优化控制

随着经济社会的发展和进步,人们对舒适度的要求也不断提高。楼宇所消耗的能量也在不断上升,尤其是空调系统的能耗占所有能耗的主要成分。然而已安装的楼宇冷热源控制只能提供单一的控制,效率低下,耗电量还是很大。针对这种各自为占的控制方式,本文提出了一种基于启发式动态规划(HDP)的冷热源优化控制算法,包括模型网络、执行网络和评价网络三个部分。该算法对整个冷热源系统进行了全局优化,降低了楼宇冷热源的电能耗损,实现了对冷热负荷的有效控制。     

两种基于个体偏好集结的多属性群决策共识方法

针对多属性群决策中的共识问题, 提出两种使群体达成共识的方法. 假设群体决策的结果以从个体偏好通过集结得到的群体偏好为基础, 在使用算术加权集结算子和几何加权集结算子的条件下, 分别设计相应的共识达成算法, 并对算法的收敛性进行分析. 与已有方法相比, 所提出算法能够体现决策个体的差异和决策个体对群体的影响. 通过某市政图书馆空调系统安装方案的选择表明了所提出方法的合理性和可行性.

     

乙烯装置汽油分馏塔系统中循环急冷油流量对产品的影响

分析了高温裂解热回收系统及其汽油分馏塔系统,并提出可能的节能方案,由于该节能方案会引起循环急冷油流量的改变,因此需要对节能方案的影响进行分析.作者通过对汽油分馏塔进行分析和简化,选用了相应的模型和方法,以循环急冷油流量为自变量,裂解气和燃料油产品为因变量进行灵敏度分析,得出循环急冷油流量在很大范围内波动不会影响产品的质量及后续流程的改变,说明所提出的节能方案可行.     

Design of VAV Air-condition Temperature Control Based on Smith Prediction Control

通过对变风量空调控制系统空气处理过程的分析,提出了一种变风量空调房间温度的串级控制方法.针对温度控制过程中出现的大滞后现象,采用Smith预估控制消除其对控制过程的影响,提高控制效果.并对该方案进行了仿真验证,结果证明本方案在VAV空调系统中的应用效果较好,有利于改善和提高系统的性能.     

Vague集的多目标模糊决策方法

在进行了阐述Vague集的相关概念和运算后,对多目标模糊决策进行了定义,给出多目标模糊决策的基本思路,并对已有的基于Vague集的多目标模糊决策方法进行了分析,得出现有Vague集的多目标模糊决策方法存在着缺陷,从而提出了一种新的多目标模糊决策的Vague集方法,该方法利用一个新的评分函数对方案进行排序,选出最优方案.最后给出其相关性质,证明其解决了现有方法的缺陷,并通过实例阐明本文方法的有效性和优越性.     

基于单片机实现机房水冷空调的改造

提出了如何以单片机为核心改造机房水冷空调的方案,在保证机房中设备正常运行的同时能降低电能消耗,还具体阐述了硬件组成与软件编程.     

基于权重集结和相对优势关系的多属性决策方法

分析多属性决策方法中决策矩阵规范化和属性权重计算等步骤可能对决策方法合理性造成的不良影响,为克服这些不良影响,提出一种新的多属性决策方法.该方法采用群决策模式进行赋权,在对专家意见进行一致性分析的基础上,集结各位专家给出的属性权重,通过定义备选方案在属性值为实数、区间数和语言值等不同类型属性上的相对优势关系构造判断矩阵,并以此建立方案效用值计算的线性目标规划模型,从而实现备选方案的评价和排序.实例研究表明了所提出方法的可行性和有效性.     

基于动态负荷需求分析的冷冻站测控系统设计

依据某病房办公楼空调系统的历史运行数据,进行了动态负荷需求分析,研究了空调运行冷负荷次数、时间频数和空调系统循环水温差随空调负荷变化趋势,提出了将模块化冷水机组4∶2∶4分组控制和空调水系统恒温差变频控制相结合的按需供冷方案。搭建了以PLC为核心的节能控制系统,经过运行实验,节能率26.1%,达到了很好的节能效果和经济性。     

云计算大数据对制冷设备空调的控制

通过云计算大数据的分析,采取相应的自动控制制冷设备空调的运行措施,能让制冷设备空调运行效率提高,同时还能节省用电量.它通过传感器、控制器控制空调的各个部件,并且它能够进行海量数据运算.利用BP神经网络分析预测出蓄冷装置空调第二天需要的冷量,并在晚上进行预测存储的冷量,供第二天白天使用,这样,企业能够节省资金,避开白天用电高峰.     

LNG冷能利用方案的本质安全性评价

为了获得本质安全性较高的LNG冷能利用方案,利用本质安全指标法评价了3个可选方案,根据评价结果对方案进行了优选。首先介绍了本质安全及典型的指标型本质安全评价方法,阐述了本质安全指标法的结构及其评分体系;应用本质安全指标法分别评价了LNG与空气换热,LNG与污氮换热,LNG与氮气、空气换热3个LNG冷能回收利用方案,得到它们的本质安全指标值分别为21,20,18;结果表明LNG与氮气、空气换热方案的本质安全指标值最低,即其本质安全性最高,主要原因是用氮气作中间介质能够消除潜在的LNG与空气、或污氮混合而引发爆炸的可能性;最后,确定该方案的本质安全性最佳,并给出了该方案的流程图。本研究改良了LNG冷能利用方案的本质安全性并对方案的优选提供了数据支持。     

Identification and PID Control for a Class of Delay Fractional-order Systems

In this paper, a new model identification method is developed for a class of delay fractional-order system based on the process step response. Four characteristic functions are defined to characterize the features of the normalized fractionalorder model. Based on the time scaling technology, two identification schemes are proposed for parameters' estimation. The scheme one utilizes three exact points on the step response of the process to calculate model parameters directly. The other scheme employs optimal searching method to adjust the fractional order for the best model identification. The proposed two identification schemes are both applicable to any stable complex process, such as higher-order, under-damped/over-damped, and minimum-phase/nonminimum-phase processes. Furthermore, an optimal PID tuning method is proposed for the delay fractionalorder systems. The requirements on the stability margins and the negative feedback are cast as real part constraints (RPC) and imaginary part constraints (IPC). The constraints are implemented by trigonometric inequalities on the phase variable, and the optimal PID controller is obtained by the minimization of the integral of time absolute error (ITAE) index. Identification and control of a Titanium billet heating process is given for the illustration.      

基于多层次灰色综合评价法的工业设计方案优选决策模型及其应用

为辅助企业在产品设计方案评估阶段进行合理地决策,减少设计的盲目性和主观性,基于多层 次灰色综合评价法构建了工业产品设计方案优选决策模型。在评价流程中,首先依据层次分析法(AHP)与熵权 法通过定性、定量分析,合理地进行评价指标权重系数的确定。其次,采用灰色关联度分析法对各设计方案进 行灰色加权关联度的计算,确定其排序,并依据结果完成对设计方案的综合评价与优选工作。基于该模型完成 了对某款多旋翼无人机的 5 个设计方案的优先级排序,并将结果依据熵权 TOPSIS 法进行验证,以证明其可行 性。最后,基于指标权重与方案得分完成了对优选方案的优化,并对方案进行三维建模视觉化展示,有效地表 明了基于多层次灰色综合评价法的无人机产品评价优选决策模型的设计辅助作用。     

Difference schemes for time-dependent heat conduction models with delay

Different non-Fourier models of heat conduction, that incorporate time lags in the heat flux and/or the temperature gradient, have been increasingly considered in the last years to model microscale heat transfer problems in engineering. Numerical schemes to obtain approximate solutions of constant coefficients lagging models of heat conduction have already been proposed. In this work, an explicit finite difference scheme for a model with coefficients variable in time is developed, and their properties of convergence and stability are studied. Numerical computations showing examples of applications of the scheme are presented.     

基于时间矩阵序列的多指标方案综合排序分配法

针对多指标方案排序选优决策问题,提出了一种基于时间矩阵序列的方案综合排序分配法.假设存在一个"隐评价函数",它能对方案的各种优先排序进行综合评价,由此得到方案的最优排序和最优决策方案.利用方案的时序信息,构造了"隐评价函数"关于方案排序的"综合效率"评价矩阵,提出了方案综合排序选优分配模型,5个供应商6个指标的综合排序案例表明该方法合理、可行.     

Key-dependent 3D model hashing for authentication using heat kernel signature

Multimedia-based hashing is considered an important technique for achieving authentication and copy detection in digital contents. However, 3D model hashing has not been as widely used as image or video hashing. In this study, we develop a robust 3D mesh-model hashing scheme based on a heat kernel signature (HKS) that can describe a multi-scale shape curve and is robust against isometric modifications. We further discuss the robustness, uniqueness, security, and spaciousness of the method for 3D model hashing. In the proposed hashing scheme, we calculate the local and global HKS coefficients of vertices through time scales and 2D cell coefficients by clustering HKS coefficients with variable bin sizes based on an estimated L² risk function, and generate the binary hash through binarization of the intermediate hash values by combining the cell values and the random values. In addition, we use two parameters, bin center points and cell amplitudes, which are obtained through an iterative refinement process, to improve the robustness, uniqueness, security, and spaciousness further, and combine them in a hash with a key. By evaluating the robustness, uniqueness, and spaciousness experimentally, and through a security analysis based on the differential entropy, we verify that our hashing scheme outperforms conventional hashing schemes.     

Thermal effects of steel toe caps in footgear

This study investigated cold weather safety footwear and the possible thermal effects of steel toe caps in footwear. Two models of boots were used. Both models were manufactured in two variants – with and without steel toe cap. The boot insulation was measured with an artificial, heated foot (AHF). One model was used in experiment with subjects (n=6). Cold exposure consisted of sitting for 60 min at −10°C. There were no differences between insulation levels of boots with and without steel cap for one boot model, but the differences were statistically significant for the second model showing slightly higher insulation values for the boot without steel cap. No significant differences due to insulation dissimilarities could be found from the measurements on subjects. Statistically significant differences were found for both models regarding the rate of change of heat loss from AHF when its location was changed from warm to cold and back to warm. The rise and decrease of heat loss from AHF depended on the rate of temperature change of the boots. The results showed that a faster change in heat loss from AHF occurred for boots without steel toe caps. Data from subjects seemed to confirm this by a somewhat faster, though not significant, rise in toe skin temperatures after cold exposure in boots without steel toe caps. The effect may be attributed to the higher mass and heat contents of the boots with steel toe cap.

Relevance to industry

Many jobs need additional protection of the toes or shins. The steel toe cap and its alleged cooling effect have been a frequent subject of complaints. This study discusses reasons that could explain the complaints, and presents a standard method for evaluating thermal properties of footwear.     

The control of robot manipulators with bounded input

The problem of tracking a desired trajectory in the state space of ann-link robotic manipulator with bounds on the allowable input torque is considered. Using a so-called optimal decision strategy (ODS), a pointwise optimal control law is derived which, at each timet, minimizes the deviation between the vector of joint accelerations and a desired joint acceleration vector, subject to the input constraints. The design of the optimal control law is reduced to the solution of a quadratic programming problem which is solved using the primal-dual method. The solution gives an on-line feedback control scheme for trajectory following in the presence of input constraints. In addition, we extend the above optimal decision strategy to the case where the controller design is based on a simplified model or where the plant itself is imprecisely known. The resulting torque optimization scheme may be incorporated into any existing control scheme to account for input bounds. This has important implications for the problem of deriving robust control schemes that take into account parameter uncertainty and model simplification. Simulations are presented for the case of a three-link manipulator with bounded torque, and our results are compared to the computed torque method. Our simulations show that by optimally adjusting the input torque to each joint when one or more of them saturates, significant improvement in tracking performance can result.     

Cost minimization in utility computing systems

Utility computing is a form of computer service whereby the company providing the service charges the users for using the system resources. In this paper, we present system‐optimal and user‐optimal price‐based job allocation schemes for utility computing systems whose objective is to minimize the cost for the users. The system‐optimal scheme provides an allocation of jobs to the computing resources that minimizes the overall cost for executing all the jobs in the system. The user‐optimal scheme provides an allocation that minimizes the cost for individual users in the system for providing fairness. The system‐optimal scheme is formulated as a constraint minimization problem, and the user‐optimal scheme is formulated as a non‐cooperative game. The prices charged by the computing resource owners for executing the users jobs are obtained using a pricing model based on a non‐cooperative bargaining game theory framework. The performance of the studied job allocation schemes is evaluated using simulations with various system loads and configurations. Copyright © 2012 John Wiley & Sons, Ltd.