MCHOKeM algorithm with assured bandwidth allocation in DiffServ networks

An active queue management（AQM） algorithm called MCHOKeM is presented,which is borrowed from CHOKeW that draws multi-packets at random from the buffer,the multi-packets are compared with an arriving packet and abandoned if they are from the same flow.But MCHOKeM uses multiple virtual queues for different priority packets and enhances the drawing function by adjusting the maximum number of draws based on the current status of virtual queue length.The number of parameters that MCHOKeM needs to maintain is determined by the number of priority levels being supported by the router,which usually has a small limited value.In order to explain the features of MCHOKeM,an analytical model is used.A series of simulation tests to evaluate the performance are given.

Concurrency Control of Single-Level Transaction in WHYMX Object-Oriented Database System

The data model of WHYMX complicates transaction management. Traditional locking method is not powerful enough to solve the new problem of concurrency control of WHYMX's transaction. This paper presents a number of concurrency control algorithms based on the extended locking method.

Transactive control:a framework for operating power systems characterized by high penetration of distributed energy resources

The increasing number of distributed energy resources connected to power systems raises operational challenges for the network operator, such as introducing grid congestion and voltage deviations in the distribution network level, as well as increasing balancing needs at the whole system level. Control and coordination of a large number of distributed energy assets requires innovative approaches. Transactive control has received much attention due to its decentralized decision-making and transparent characteristics. This paper introduces the concept and main features of transactive control, followed by a literature review and demonstration projects that apply to transactive control. Cases are then presented to illustrate the transactive control framework. At the end, discussions and research directions are presented, for applying transactive control to operating power systems, characterized by a high penetration of distributed energy resources.

Ensemble-based uncertainty quantification for coordination and control of thermostatically controlled loads

This work investigates an uncertainty quantification(UQ)framework that analyses the uncertainty involved in modelling control systems to improve control strategy performance.The framework involves solving four problems:identifying uncertain parameters,propagating uncertainty to the quantity of interest,data assimilation and making decisions under quantified uncertainties.A specific group of UQ approaches,known as the ensemble-based methods,are adopted to solve these problems.This UQ framework is applied to coordinating a group of thermostatically controlled loads,which relies on simulating a second-order equivalent thermal parameter model with some uncertain parameters.How this uncertainty affects the prediction and the control of total power is examined.The study shows that uncertainty can be effectively reduced using the measurement of air temperatures.Also,the control objective is achieved fairly accurately with a quantification of the uncertainty.

Design and Implementation of a Concurrency Control Mechanism in an Object-Oriented Database System

This paper presents a practical concurrency control mechanism - ObjectLockingin OODBMS. Object-Locking can schedule transactions, each of themcan be considered as a sequence of high level operations defined on classes. Bythe properties of parallelity and coatativity between high level operations,proper lock modes for each operation are desigued and the compatibility matrixis constructed. With these lock modes, phatoms are kept away from databasesand a high degree of concurrency is achieved.

Distributed Dispatch of Multiple Energy Systems Considering Carbon Trading

As an integrated carrier of energy production,transmission,distribution,conversion,storage,and utilization,multiple energy systems(MESs)have significant low-carbon potential.This paper proposes a hierarchical distributed dispatch model of MESs considering carbon trading,which is composed of the lower autonomous operation level of each MES and the upper coordinated control level.Different carbon emission sources are considered,including combined heat and power(CHP)units,gas boilers,and power to gas(P2G)devices.The transactive control(TC)mechanism is used to solve the model by introducing a virtual price signal.In the case study based on a 3-MES system,the effectiveness of the proposed distributed method is proved by comparison with a centralized algorithm.Meanwhile,the impacts of different carbon prices on MESs with different resource endowments are analyzed from the aspects of scheduling results,carbon emissions,clean energy consumption rate,and comprehensive operating costs.