Call centers record and store customer-agent conversations for quality assurance. To ensure data security, it is important to locate and mask sensitive information pertaining to personal details in the transcripts of the audio recordings. In this article, we describe our development of a model for identifying person names in transcripts from call centers in Hong Kong. We describe the types of names that can potentially appear in the transcript and discuss a careful sampling of negative examples. Our experiment results show that a well fine-tuned transformer-based encoder model can significantly outperform generative large language models.

Autonomous vehicles (AVs) are vehicles that traverse on the road without active human intervention. With a coordinator, AVs can be connected to provide high-efficiency transport services, such as AV-based public transport networks. The controller can manage the network by coordinating the transport request assignment, traveling, and charging/discharging schedule. On the other hand, AVs are likely to be electric and benefit the smart grid via vehicle-to-grid technology. A well-designed mobility network connecting electric AVs (EAVs) and smart grid can substantially reduce unnecessary travel and energy costs. In this article, we aim to maximize utilities in the AV-based public transport network and the power distribution network for the vehicle network containing EAVs, charging stations, and distributed power generations. We formulate the assignment and scheduling problem as a multiobjective mixed-integer program (MIP). To solve the optimization problem, we develop a hybrid heuristic approach based on nondominated sorting genetic algorithm II (NSGA-II) and branch-and-bound (BnB) algorithms. Experiments are conducted on a modified 15-bus distribution system and a simulated traffic network. The results show that the proposed strategy effectively minimizes the total travel and energy purchase cost by 21%. This study provides valuable insights on vehicle coordination for multiple tasks, offering visionary guidance for stakeholders engaged in multifaceted transportation endeavors.

Autonomous vehicles (AVs) traverse on the road without active human intervention. In an AV-based public transport system, AVs can be supported by an intelligent controller to provide high-efficiency transport services. The intelligent controller manages a fleet of AVs by determining their assignments to transport requests, sending instructions concerning the optimized plans, and managing the charging/discharging schedule and locations for the governed AVs. On the other hand, vehicle-to-grid is a promising technology to benefit the power system operation by using the battery storage of electric vehicles (EVs). A well-designed request assignment and travel schedule controller can substantially reduce the unnecessary travel and energy purchase cost for the transport system and power system, respectively. In this paper, we aim at coordinating the transport request assignment, traveling and charging/discharging schedule for a fleet of electric AVs (EAVs), and the reactive power support from distributed generations (DGs) to maximize utility in both the AV-based public transportation system and power distribution system. We formulate the assignment and scheduling problem as a mixed-integer program. Experiments on a modified 15-bus distribution system and a simulated traffic network are conducted. The results show that the formulated problem effectively minimizes the total travel and energy purchase cost by controlling the EAV behaviors and DG outputs. This study may promote the integration of transport and power technologies in smart grids as well as incentivize the utilization of EAVs.

Crowdsourcing has become an important tool to collect data for various artificial intelligence applications, and auction can be an effective way to allocate work and determine reward in a crowdsourcing platform. In this article, we focus on the crowdsourcing of small tasks such as image labeling and voice recording, where we face a number of challenges. First, workers have different limits on the amount of work they would be willing to do, and they may also misreport these limits in their bid for the work. Second, if the auction is repeated over time, unsuccessful workers may dropout of the system, reducing competition and diversity. To tackle these issues, we first extend the results of the celebrated Myerson’s optimal auction mechanism for a single-parameter bid to the case where the bid consists of the unit cost of work, the maximum amount of work one is willing to do, and the actual work completed. We show that a simple payment mechanism is sufficient to ensure a dominant strategy from the workers, and that this dominant strategy is robust to the true utility function of the workers. Second, we propose a novel, flexible work allocation mechanism, which allows the requester to balance between cost efficiency and equality. While cost minimization is obviously important, encouraging equality in the allocation of work increases the diversity of the workforce as well as promotes a long-term participation on the crowdsourcing platform. Our main results are proved analytically and validated through simulations.

New intent discovery aims to uncover novel intent categories from user utterances to expand the set of supported intent classes.It is a critical task for the development and service expansion of a practical dialogue system.Despite its importance, this problem remains under-explored in the literature.Existing approaches typically rely on a large amount of labeled utterances and employ pseudo-labeling methods for representation learning and clustering, which are label-intensive, inefficient, and inaccurate.In this paper, we provide new solutions to two important research questions for new intent discovery: (1) how to learn semantic utterance representations and (2) how to better cluster utterances.Particularly, we first propose a multi-task pre-training strategy to leverage rich unlabeled data along with external labeled data for representation learning.Then, we design a new contrastive loss to exploit self-supervisory signals in unlabeled data for clustering.Extensive experiments on three intent recognition benchmarks demonstrate the high effectiveness of our proposed method, which outperforms state-of-the-art methods by a large margin in both unsupervised and semi-supervised scenarios.The source code will be available at https://github. com/

We consider few-shot out-of-distribution (OOD) intent detection, a practical and important problem for the development of task-oriented dialogue systems. Despite its importance, this problem is seldom studied in the literature, let alone examined in a systematic way. In this work, we take a closer look at this problem and identify key issues for research. In our pilot study, we reveal the reason why existing OOD intent detection methods are not adequate in dealing with this problem. Based on the observation, we propose a promising approach to tackle this problem based on latent representation generation and self-supervision. Comprehensive experiments on three real-world intent detection benchmark datasets demonstrate the high effectiveness of our proposed approach and its great potential in improving state-of-the-art methods for few-shot OOD intent detection.

Haode Zhang, Haowen Liang, Yuwei Zhang, Li-Ming Zhan, Xiao-Ming Wu, Xiaolei Lu, Albert Lam. Proceedings of the 2022 Conference of the North American Chapter of the Association for Computational Linguistics: Human Language Technologies. 2022.

A vehicular energy network (VEN) uses electric vehicles (EVs) to transport energy across a wide geographical area. EVs can charge and discharge wirelessly at road junctions while moving and, thus, transfer energy between junctions. In this article, we propose a method to optimally route energy from multiple energy-supplying junctions to multiple energy-demanding junctions while minimizing energy loss in four different VEN scenarios: 1) a time-invariant VEN; 2) a VEN with time-varying vehicular flows and energy demands; 3) a VEN with time-varying vehicular flows and time-averaged demands; and 4) a VEN with significant storage capacities at junctions. The method employed to solve these scenarios is to model the VEN as a graph specific to each scenario, and then solve the generalized flow problem on the graph. Simulations are performed on all four scenarios and show that transmission efficiency improves when a small number of long vehicular routes are introduced, and when storage capacities at junctions increase. The error in approximating a time-varying VEN as a static VEN is also investigated.

An Autonomous Vehicle (AV) is believed to be the next generation transport that can enhance safety and efficiency for smart mobility. In an AV-based public transportation system, the full autonomy of AVs enables high-efficiency transport services and the potential ride-sharing feature of AV system enhances the utilization. The system manages a fleet of AVs, determines their assignments to transport requests, sends instructions concerning the optimized plans, and recommends the parking locations for the unoccupied AVs. The parking location of an empty AV is crucial in the sense that rebalancing AVs to areas with high potential service demand can curtail the unnecessary waiting time for passengers. As AVs are generally electric, proper parking locations can also facilitate vehicle-to-grid (V2G) support. In this paper, we propose a joint rebalancing and V2G coordination strategy for AV-based public transportation system. We formulate the problem as an integer linear program and propose a heuristic based on Genetic Algorithm and Model Predictive Control to solve the problem in low time complexity. Extensive experiments are performed with the real taxi service data from New York City. The formulated integer linear program is solved dynamically where each problem instance contains 3 to 5 AVs and 3 to 8 requests in 30s time interval. Compared with the transport system without rebalancing, the results show that the coordination strategy is efficient and effective in reducing unnecessary waiting time for passengers while satisfying V2G support. Compared to computational time with the standard solver, the proposed heuristic dramatically reduces the computational time.

An efficient transportation system can substantially benefit our society, but road intersections have always been among the major traffic bottlenecks leading to traffic congestion. Appropriate traffic signal timing adapted to real-time traffic may help mitigate such traffic congestion. However, most existing traffic signal control methods require a huge amount of road information, such as vehicle positions. In this paper, we focus on a particular road intersection and aim to minimize the average waiting time. We propose a traffic signal control (TSC) system based on an end-to-end off-policy deep reinforcement learning (deep RL) agent with background removal residual networks. The agent takes real-time images at the road intersection as input. Upon sufficient training, the agent can perform (near-) optimal traffic signaling based on real-time traffic conditions. We conduct experiments on different intersection scenarios and compare various TSC methods. The experimental results show that our end-to-end deep RL approach can adapt to the dynamic traffic based on the traffic images and outperforms other TSC methods.

Li-Ming Zhan, Haowen Liang, Bo Liu, Lu Fan, Xiao-Ming Wu, Albert Y.S. Lam. Proceedings of the 59th Annual Meeting of the Association for Computational Linguistics and the 11th International Joint Conference on Natural Language Processing (Volume 1: Long Papers). 2021.

Disturbance, which is generally unknown to the controller, is unavoidable in real-world systems and it may affect the expected system state and output. Existing control methods, like robust model predictive control, can produce robust solutions to maintain the system stability. However, these robust methods trade the solution optimality for stability. In this article, a method called generative adversarial control networks (GACNs) is proposed to train a controller via demonstrations of the optimal controller. By formulating the optimal control problem in the presence of disturbance, the controller trained by GACNs obtains neuro-optimal solutions without knowing the future disturbance and determines the objective function explicitly. A joint loss, composed of the adversarial loss and the least square loss, is designed to be used in the training of the generator. Experimental results on simulated systems with disturbance show that GACNs outperform other compared control methods.

User intent classification plays a vital role in dialogue systems.Since user intent may frequently change over time in many realistic scenarios, unknown (new) intent detection has become an essential problem, where the study has just begun.This paper proposes Understanding user intent is crucial for developing conversational and dialogue systems.It is essential to accurately identify the intent behind a user utterance to better guide downstream decisions and policies.With the advent of conversational AI, dialogue systems are becoming central tools in many applications such as mobile apps, companion bots, virtual assistants and so on.Since user interests may change frequently over time, the AI agents may continuously see unknown (new) user intents.Manual annotation can hardly catch up with such rapid development, which motivates the problem * Equal contribution.

An effective intelligent transportation system is a core part of modern smart city. The Internet of Things and vehicular communication technologies facilitate rapid development of connected and autonomous vehicles (CAVs). While most studies focus on standalone CAV technologies, collective CAV control has much potential. With the connectivity and automation of CAVs, we can employ dynamic lane reversal (DLR) to optimize the travel schedules of CAVs for performance enhancement. In this paper, we propose the dynamic lane reversal-traffic scheduling management (DLR-TSM) scheme for CAVs. The system collects the travel requests from CAVs and determines their optimal schedules and routes over dynamically reversible lanes. We formulate the routing and scheduling problem on DLR as an integer linear program. To address the scaling effect, an algorithm based on alternating direction method of multipliers is designed to solve the problem in a distributed manner. We extensively evaluate the DLR-TSM and the distributed algorithm with real-world transportation data. The simulation results show that the DLR-TSM can significantly improve the travel times of CAVs and the distributed algorithm can dramatically reduce the required computational time.

Advancements in sensing and the Internet of Things (IoT) technologies generate a huge amount of data. Mobility on demand (MoD) service benefits from the availability of big data in the intelligent transportation system. Given the future travel demand or origin-destination (OD) flows prediction, service providers can pre-allocate unoccupied vehicles to the customers' origins of service to reduce waiting time. Traditional approaches on future travel demand and the OD flows predictions rely on statistical or machine learning methods. Inspired by deep learning techniques for image and video processing, through regarding localized travel demands as image pixels, a novel deep learning model called multi-scale convolutional long short-term memory network (MultiConvLSTM) is developed in this paper. Rather than using the traditional OD matrix which may lead to loss of geographical information, we propose a new data structure, called OD tensor to represent OD flows, and a manipulation method, called OD tensor permutation and matricization, is introduced to handle the high dimensionality features of OD tensor. MultiConvLSTM considers both temporal and spatial correlations to predict the future travel demand and OD flows. Experiments on real-world New York taxi data of around 400 million records are performed. Our results show that the MultiConvLSTM achieves the highest accuracy in both one-step and multiple-step predictions and it outperforms the existing methods for travel demand and OD flow predictions.

Speaker Diarization and Linking discovers “who spoke when” across recordings without any speaker enrollment. Diarization is performed on each recording separately, and the linking combines clusters of the same speaker across recordings. It is a two-step approach, however it suffers from propagating the error from diarization step to the linking step. In a situation where a unique speaker appears in a given set of recordings, this paper aims at locating the common speaker using the prior knowledge of his or her existence. That means there is no enrollment data for this common speaker. We propose Pairwise Common Speaker Identification (PCSI) method that takes the existence of a common speaker into account in contrast to the two-step approach. We further show that PCSI can be used to reduce the errors that are introduced in the diarization step of the two-step approach. Our experiments are performed on a corpus synthesised from the AMI corpus and also on a in-house conversational telephony Sichuanese corpus that is mixed with Mandarin. We show up to 7.68% relative improvements of time-weighted equal error rate over a state-of-art x-vector diarization and linking system.

Han Liu, Xiaotong Zhang, Lu Fan, Xuandi Fu, Qimai Li, Xiao-Ming Wu, Albert Y.S. Lam. Proceedings of the 2019 Conference on Empirical Methods in Natural Language Processing and the 9th International Joint Conference on Natural Language Processing (EMNLP-IJCNLP). 2019.

End-to-end automatic speech recognition (ASR) has simplified the traditional ASR system building pipeline by eliminating the need to have multiple components and also the requirement for expert linguistic knowledge for creating pronunciation dictionaries. Therefore, end-to-end ASR fits well when building systems for new domains. However, one major drawback of end-to-end ASR is that, it is necessary to have a larger amount of labeled speech in comparison to traditional methods. Therefore, in this paper, we explore domain adaptation approaches for end-to-end ASR in low-resource settings. We show that joint domain identification and speech recognition by inserting a symbol for domain at the beginning of the label sequence, factorized hidden layer adaptation and a domain-specific gating mechanism improve the performance for a low-resource target domain. Furthermore, we also show the robustness of proposed adaptation methods to an unseen domain, when only 3 hours of untranscribed data is available with improvements reporting upto 8.7% relative.

The Internet of Things forms the backbone of connectivity for the smart city, which revolutionizes the transportation and energy sectors and drives the development of vehicular energy network (VEN). VEN is a vehicular network which can transport energy over a large geographical area by means of electric vehicles (EVs). In the near future, an abundance of EVs, plentiful generation of renewables, and mature wireless energy transfer and vehicular communication technologies will expedite the realization of VEN. To transmit energy from a source to a destination, we need to establish energy paths, which are composed of segments of vehicular routes, while satisfying various design objectives. In this paper, we develop a method to construct all energy paths for a particular energy source-destination pair, followed by some analytical results of the method. We describe how to utilize the energy paths to develop optimization models for different design goals and propose two solutions. We also develop a heuristic for the power loss minimization problem. We compare the performance of the three solution methods with artificial and real-world traffic networks and provide a comprehensive comparison in terms of solution quality, computation time, solvable problem size, and applicability. This paper lays the foundations of VEN routing.

The smart city embraces gradual adoption of autonomous vehicles (AVs) into the intelligent transportation system. Contributed by their full-fledged controllability, AVs can respond to instantaneous situations with high efficiency and flexibility. In this paper, we propose a novel AV logistic system (AVLS) to accommodate logistic demands for smart cities. We focus on determining the optimal routes for the governed AVs in consideration of various requirements imposed by the vehicles, logistic requests, renewable generations, and the underlying transportation system. By coordinating their routes and charging schedules, the system can effectively utilize the renewable energy generated by distributed generations. We formulate the joint routing and charging problem in the form of quadratic-constrained mixed integer linear program. To improve its scalability, we develop a distributed solution method via dual decomposition. We conduct extensive simulations to evaluate the performance of proposed system and solution methods. The results show that AVLS can effectively utilize excessive renewable energy while accomplishing all logistic requests. The distributed solution can develop near-optimal solutions with compelling improvement in computational speed.

In recent years, the vehicle-to-grid (V2G) system, which utilizes electric vehicles (EVs) to provide ancillary services for power grid, draws a lot of interests in smart grid research community. When considering a large number of EVs distributed in different geographical locations, how to coordinate these EVs to provide ancillary services becomes a critical issue. In this paper, a generic hierarchical framework for V2G system to provide frequency regulation services is proposed to address this issue. A practical multi-level online V2G algorithm is proposed for the hierarchical V2G scheduling and it requires no forecasting information for regulation signals.We test our proposed algorithm in the simulation of a four- level hierarchical V2G system. The results show that the proposed algorithm has advantages over the existing methods on smoothing out the real- time power fluctuations.

The renewables will constitute an important part of the future smart grid. As a result, the growing portion of renewable generation in the power grid will bring challenges to the operations of the power grid because of the fluctuation and intermittency properties of renewables. In order to make the operations of power grid stable and reliable, the power outputs from renewable energy sources must be smoothed. In this paper, we propose a scheme inspired from the idea of the leaky bucket mechanism for smoothing the power output from a renewable energy system. In our proposed method, the settings of energy storage size and power output level have significant effects on the system performance and thus needs to be determined. An optimization framework is thus proposed for storage and power output planning of the renewable energy system. To operate our proposed scheme practically, a load-adaptive power smoothing algorithm is devised aiming to match the power output level with the actual load in the grid. Our simulation studies show that the proposed algorithm can reduce the operation cost comparing to other algorithms and maintain high renewable energy utilization.

Initialization will affect the performance of Evolutionary Algorithm (EA), especially under computationally expensive environments. To investigate the optimal resource allocation between the initialization and optimization stages, we studied the Computational Resource Optimization Problem (CROP) in our previous work. In this paper, we extend our resource allocation model by separating “initial solutions” into two sets, namely, Generated Initial Solutions (GIS) and Used Initial Solutions (UIS). Such separation in the model allows us to conduct a more comprehensive analysis and reveal more insights into how initial solutions can affect the performance of EAs under computationally expensive environments. Simulations are conducted on the BBOB'09 benchmark functions with the standard settings to mimic the expensive environment. We have shown that proper computational resource allocation can improve the solution quality. Our analysis allows us to find the best allocation scheme for a particular EA on a specific problem and also demonstrates the importance of initialization.

A smart city provides its people with high standard of living through advanced technologies, and transport is one of the major foci. With the advent of autonomous vehicles (AVs), an AV-based public transportation system has been proposed recently, which is capable of providing new forms of transportation services with high efficiency, high flexibility, and low cost. For the benefit of passengers, multi-tenancy can increase market competition leading to lower service charge and higher quality of service. In this paper, we study the pricing issue of the multi-tenant AV public transportation system and three types of services are defined. The pricing process for each service type is modeled as a combinatorial auction, in which the service providers, as bidders, compete for offering transportation services. The winners of the auction are determined through an integer linear program. To prevent the bidders from raising their bids for higher returns, we propose a strategy-proof Vickrey-Clarke-Groves-based charging mechanism, which can maximize the social welfare, to settle the final charges for the customers. We perform extensive simulations to verify the analytical results and evaluate the performance of the charging mechanism.

Technology of autonomous vehicles (AVs) is becoming mature, and many AVs will appear on roads in the near future. AVs become connected with the support of various vehicular communication technologies, and they possess a high degree of control to respond to instantaneous situations cooperatively with high efficiency and flexibility. In this paper, we propose a new public transportation system based on AVs. It manages a fleet of AVs to accommodate transportation requests, offering point-to-point services with ride sharing. We focus on the two major problems of the system: scheduling and admission control. The former is to configure the most economical schedules and routes for the AVs to satisfy the admissible requests, whereas the latter is to determine the set of admissible requests among all requests to produce maximum profit. The scheduling problem is formulated as a mixed-integer linear program, and the admission control problem is cast as a bilevel optimization, which embeds the scheduling problem as the major constraint. By utilizing the analytical properties of the problem, we develop an effective genetic-algorithm-based method to tackle the admission control problem. We validate the performance of the algorithm with real-world transportation service data.

A newly proposed chemical-reaction-inspired metaheurisic, Chemical Reaction Optimization (CRO), has been applied to many optimization problems in both discrete and continuous domains. To alleviate the effort in tuning parameters, this paper reduces the number of optimization parameters in canonical CRO and develops an adaptive scheme to evolve them. Our proposed Adaptive CRO (ACRO) adapts better to different optimization problems. We perform simulations with ACRO on a widely-used benchmark of continuous problems. The simulation results show that ACRO has superior performance over canonical CRO.

The set covering problem (SCP) is one of the representative combinatorial optimization problems, having many practical applications. This paper investigates the development of an algorithm to solve SCP by employing chemical reaction optimization (CRO), a general-purpose metaheuristic. It is tested on a wide range of benchmark instances of SCP. The simulation results indicate that this algorithm gives outstanding performance compared with other heuristics and metaheuristics in solving SCP.

Optimization techniques are frequently applied in science and engineering research and development. Evolutionary algorithms, as a kind of general-purpose metaheuristic, have been shown to be very effective in solving a wide range of optimization problems. A recently proposed chemical-reaction-inspired metaheuristic, Chemical Reaction Optimization (CRO), has been applied to solve many global optimization problems. However, the functionality of the inter-molecular ineffective collision operator in the canonical CRO design overlaps that of the on-wall ineffective collision operator, which can potential impair the overall performance. In this paper we propose a new inter-molecular ineffective collision operator for CRO for global optimization. To fully utilize our newly proposed operator, we also design a scheme to adapt the algorithm to optimization problems with different search space characteristics. We analyze the performance of our proposed algorithm with a number of widely used benchmark functions. The simulation results indicate that the new algorithm has superior performance over the canonical CRO.

This paper presents a heuristic approach to generate initial feasible solutions for the Unit Commitment (UC) problem in electric power generation. The Chemical Reaction Optimization (CRO) algorithm is implemented to solve this problem. Multiple generator constraints and system constraints are considered. We also program the binary PSO and the Elite PSO (EPSO) for comparison. The proposed heuristic approach is combined with the three optimization algorithms to form H-CRO, H-PSO and H-EPSO. We test the performance of all algorithms on the standard 10-unit system. Simulation results show that the heuristic can improve the performance and CRO provides better convergence than the two PSO algorithms. H-CRO is also tested on a 20-unit and 100-unit system to show its capability. The results provided in this paper suggest that the proposed heuristic approach is a better alternative for solving the UC problem. CRO also has its advantage in optimizing UC problems.

An electric vehicle (EV) may be used as energy storage which allows the bi-directional electricity flow between the vehicle's battery and the electric power grid. In order to flatten the load profile of the electricity system, EV scheduling has become a hot research topic in recent years. In this paper, we propose a new formulation of the joint scheduling of EV and Unit Commitment (UC), called EVUC. Our formulation considers the characteristics of EVs while optimizing the system total running cost. We employ Chemical Reaction Optimization (CRO), a general-purpose optimization algorithm to solve this problem and the simulation results on a widely used set of instances indicate that CRO can effectively optimize this problem.

A novel general-purpose optimization method, chemical reaction optimization (CRO), is a population-based metaheuristic inspired by the phenomenon of interactions between molecules in a chemical reaction process. CRO has demonstrated its competitive edge over existing methods in solving many real-world problems. However, all studies concerning CRO have been empirical in nature and no theoretical analysis has been conducted to study its convergence properties. In this paper, we present some convergence results for several generic versions of CRO, each of which adopts different combinations of elementary reactions. We investigate the limiting behavior of CRO. By modeling CRO as a finite absorbing Markov chain, we show that CRO converges to a global optimum solution with a probability arbitrarily close to one when time tends to infinity. Our results also show that the convergence of CRO is determined by both the elementary reactions and the total energy of the system. Moreover, we also study and discuss the finite time behavior of CRO.

Cognitive radio is a promising technology for increasing the system capacity by using the radio spectrum more effectively. It has been widely studied recently and one important problem in this new paradigm is the allocation of radio spectrum to secondary users effectively in the presence of primary users. We call it the cognitive radio spectrum allocation problem (CRSAP) in this paper. In the conventional problem formulation, a secondary user can be either on or off and its interference range becomes maximum or zero, respectively. We first develop a solution to CRSAP based on the newly proposed chemical reaction-inspired metaheuristic called Chemical Reaction Optimization (CRO). We study different utility functions, accounting for utilization and fairness, with the consideration of the hardware constraint, and compare the performance of our proposed CRO-based algorithm with existing ones. Simulation results show that the CRO-based algorithm always outperforms the others dramatically. Next, by allowing adjustable transmission power, we propose power-controlled CRSAP (PC-CRSAP), a new formulation to the problem with the consideration of spatial diversity. We design a two-phase algorithm to solve PC-CRSAP, and again simulation results show excellent performance.

In this paper, we utilize Chemical Reaction Optimization (CRO), a newly proposed metaheuristic for global optimization, to design Fuzzy Rule-Based Systems (FRBSs). CRO imitates the interactions of molecules in a chemical reaction. The molecular structure corresponds to a solution, and the potential energy is analogous to the objective function value. Molecules are driven toward the lowest energy stable state, which corresponds to the global optimum of the problem. In the realm of modeling with fuzzy rule-based systems, automatic derivation of fuzzy rules from numerical data plays a critical role. We propose to use CRO with Cooperative Rules (COR) to solve the fuzzy rule learning problem in FRBS. We formulate the learning process of FRBS in the form of a combinatorial optimization problem. Our proposed method COR-CRO is evaluated by two fuzzy modeling benchmarks and compared with other learning algorithms. Simulation results demonstrate that COR-CRO is highly competitive and outperforms many other existing optimization methods.

This paper presents an implementation of the Chemical Reaction Optimization (CRO) algorithm to solve the optimal power flow (OPF) problem in power systems with the objective of minimizing generation costs. Multiple constraints, such as the balance of the power, bus voltage magnitude limits, transmission line flow limits, transformer tap settings, etc., are considered. We adapt the CRO framework to the OPF problem by redesigning the elementary reaction operators. We perform simulations on the standard IEEE-14, -30, and -57 bus benchmark systems. We compare the perform of CRO with other reported evolutionary algorithms in the IEEE-30 test case. Simulation results show that CRO can obtain a solution with the lowest cost, when compared with other algorithms. To be more complete, we also give the average result for the IEEE-30 case, and the best and average results for the IEEE-14 and -57 test cases. The results given in this paper suggest that CRO is a better alternative for solving the OPF problem, as well as its variants for the future smart grid.

The analysis of short tandem repeats (STRs) in DNA sequences has become an attractive method for determining the genetic profile of an individual. Here we focus on a more general and practical issue named short adjacent repeats identification problem (SARIP), which is extended from STR by allowing short gaps between neighboring units. Presently, the best available solution to SARIP is BASARD, which uses Markov chain Monte Carlo algorithms to determine the posterior estimate. However, the computational complexity and the tendency to get stuck in a local mode lower the efficiency of BASARD and impede its wide application. In this paper, we prove that SARIP is NP-hard, and we also solve it with Chemical Reaction Optimization (CRO), a recently developed metaheuristic approach. CRO mimics the interactions of molecules in a chemical reaction and it can explore the solution space efficiently to find the optimal or near optimal solution(s). We test the CRO algorithm with both synthetic and real data, and compare its performance in mode searching with BASARD. Simulation results show that CRO enjoys dozens of times, or even a hundred times shorter computational time compared with BASARD. It is also demonstrated that CRO can obtain the global optima most of the time. Moreover, CRO is more stable in different runs, which is of great importance in practical use. Thus, CRO is by far the best method on SARIP.

Chemical Reaction Optimization (CRO) is a powerful metaheuristic which mimics the interactions of molecules in chemical reactions to search for the global optimum. The perturbation function greatly influences the performance of CRO on solving different continuous problems. In this paper, we study four different probability distributions, namely, the Gaussian distribution, the Cauchy distribution, the exponential distribution, and a modified Rayleigh distribution, for the perturbation function of CRO. Different distributions have different impacts on the solutions. The distributions are tested by a set of wellknown benchmark functions and simulation results show that problems with different characteristics have different preference on the distribution function. Our study gives guidelines to design CRO for different types of optimization problems.

Air pollution monitoring is a very popular research topic and many monitoring systems have been developed. In this paper, we formulate the Bus Sensor Deployment Problem (BSDP) to select the bus routes on which sensors are deployed, and we use Chemical Reaction Optimization (CRO) to solve BSDP. CRO is a recently proposed metaheuristic designed to solve a wide range of optimization problems. Using the real world data, namely Hong Kong Island bus route data, we perform a series of simulations and the results show that CRO is capable of solving this optimization problem efficiently.

Optimization problems can generally be classified as continuous and discrete, based on the nature of the solution space. A recently developed chemical-reaction-inspired metaheuristic, called chemical reaction optimization (CRO), has been shown to perform well in many optimization problems in the discrete domain. This paper is dedicated to proposing a real-coded version of CRO, namely, RCCRO, to solve continuous optimization problems. We compare the performance of RCCRO with a large number of optimization techniques on a large set of standard continuous benchmark functions. We find that RCCRO outperforms all the others on the average. We also propose an adaptive scheme for RCCRO which can improve the performance effectively. This shows that CRO is suitable for solving problems in the continuous domain.

Evolutionary algorithms (EAs) are very popular tools to design and evolve artificial neural networks (ANNs), especially to train them. These methods have advantages over the conventional backpropagation (BP) method because of their low computational requirement when searching in a large solution space. In this paper, we employ Chemical Reaction Optimization (CRO), a newly developed global optimization method, to replace BP in training neural networks. CRO is a population-based metaheuristics mimicking the transition of molecules and their interactions in a chemical reaction. Simulation results show that CRO outperforms many EA strategies commonly used to train neural networks.

Network coding may improve network efficiency. However, it is not necessary to code every link to meet a given transmission rate. In this paper, we consider the NP-hard problem of minimizing the number of coding links of a network for a given target transmission rate. Chemical Reaction Optimization (CRO) is a general purpose metaheuristic, which have been demonstrated to be effective in many optimization problems. We adopt the CRO framework to develop an algorithm to solve this NP-hard problem. Simulation results show that CRO outperforms existing algorithms with two sets of test network topologies.

For the low-cost hardware-based intrusion detection systems, this paper proposes a memory-efficient parallel string matching scheme. In order to reduce the number of state transitions, the finite state machine tiles in a string matcher adopt bit-level input symbols. Long target patterns are divided into subpatterns with a fixed length; deterministic finite automata are built with the subpatterns. Using the pattern dividing, the variety of target pattern lengths can be mitigated, so that memory usage in homogeneous string matchers can be efficient. In order to identify each original long pattern being divided, a two-stage sequential matching scheme is proposed for the successive matches with subpatterns. Experimental results show that total memory requirements decrease on average by 47.8 percent and 62.8 percent for Snort and ClamAV rule sets, in comparison with several existing bit-split string matching methods.

Peer-to-peer (P2P) live streaming applications are very popular in recent years and a Markov open queueing network model was developed to study the population dynamics in P2P live streaming. Based on the model, we deduce an optimization problem, called population transition problem, with the objective of maximizing the probability of universal streaming by manipulating population transition probability matrix. We employ a chemical reaction-inspired metaheuristic, Chemical Reaction Optimization (CRO), to solve the problem. Simulation results show that CRO outperforms many commonly used strategies for controlling population transition in many practical P2P live streaming systems. This work also shows that CRO also demonstrates the usability of CRO to solve optimization problems.

In this paper, we study the performance of opportunistic scheduling in wireless networks from the perspective of information and entropy. In opportunistic scheduling, we allocate a limited number of channels to a certain number of nodes so as to maximize the network performance. Due to the inherent uncertainty of the system input represented by random variables with certain probability distributions, even under the optimal scheduling strategy, we may not achieve the best network performance. In our proposed model, we mathematically formulate the relationship between system uncertainty characterized by entropy and network performance, i.e., we give the lower and upper bounds of network performance with given entropy of the uncertain input. Based on this result, we can determine quantitatively the impact of system uncertainty on the performance of of opportunistic scheduling in wireless networks.

Cognitive radio can help increase the capacity of wireless networks by allowing unlicensed users to use the licensed bands, provided that the occupancy do not affect the prioritized licensed users. One of the fundamental problems in cognitive radio is how to allocate the available channels to the unlicensed users in order to maximize the utility. In this work, we develop an allocation algorithm based on the newly proposed chemical reaction-inspired metaheuristic called Chemical Reaction Optimization (CRO). We study three utility functions for utilization and fairness, with the consideration of the hardware constraint. No matter which utility function is used, simulation results show that the CRO-based algorithm always outperforms the others dramatically.

Grid computing collects geographically dispersed resources ranging from laptops to supercomputers to compute tasks requested by clients. Grid scheduling, i.e., assigning tasks to resources, is an NP-hard problem, and thus, metaheuristic methods are employed to find the optimal solutions. In this paper, we propose a Chemical Reaction Optimization (CRO) algorithm for the grid scheduling problem. CRO is a population-based metaheuristics mimicking the interactions between molecules in a chemical reaction. We compare the CRO approach with four generally acknowledged metaheuristics, and show that CRO performs the best.

In this paper, we study the performance of resource-constrained systems from the perspective of information theory. Such a system consists of many components which may contribute to the performance, but resource can only be allocated to some of them. We desire to allocate the limited resources effectively so as to maximize the system performance. Usually, we have incomplete information about the system or the system has inherent randomness. Even with the optimal allocation strategy according to the available (uncertain) information, we may not achieve the best system performance. We propose a model for the generic resource-constrained system and mathematically formulate the relationship between system uncertainty, characterized by entropy, and performance. Based on this result, we can determine how the system uncertainty quantitatively influences the performance. Examples of applications of the model to data storage and peer-to-peer file sharing are also given.

We encounter optimization problems in our daily lives and in various research domains. Some of them are so hard that we can, at best, approximate the best solutions with (meta-) heuristic methods. However, the huge number of optimization problems and the small number of generally acknowledged methods mean that more metaheuristics are needed to fill the gap. We propose a new metaheuristic, called chemical reaction optimization (CRO), to solve optimization problems. It mimics the interactions of molecules in a chemical reaction to reach a low energy stable state. We tested the performance of CRO with three nondeterministic polynomial-time hard combinatorial optimization problems. Two of them were traditional benchmark problems and the other was a real-world problem. Simulation results showed that CRO is very competitive with the few existing successful metaheuristics, having outperformed them in some cases, and CRO achieved the best performance in the real-world problem. Moreover, with the No-Free-Lunch theorem, CRO must have equal performance as the others on average, but it can outperform all other metaheuristics when matched to the right problem type. Therefore, it provides a new approach for solving optimization problems. CRO may potentially solve those problems which may not be solvable with the few generally acknowledged approaches.

The No-Free-Lunch (NFL) Theorem provides a fundamental limit governing all optimization/search algorithms and has successfully drawn attention to theoretical foundation of optimization and search. However, we find several limitations in the original NFL paper. In this work, using results from the nature of search algorithms, we enhance several aspects of the original NFL Theorem. We have identified the properties of deterministic and probabilistic algorithms. We also provide an enumeration proof of the theorem. In addition, we show that the NFL Theorem is still valid for more general performance measures. This work serves as an application of the nature of search algorithms.