S. Ranji Ranjithan's research while affiliated with North Carolina State University and other places

Publications (77)

Article
Policies and regulations such as Extended Producer Responsibility (EPR) have been implemented to potentially increase the recycling rate of electronic waste (e-waste), but the cost and environmental impacts of associated collection, transportation, material recovery, material re-processing, and disposal could outweigh the benefits of recycling if t...
Article
The authors previously analysed a real-world solid waste management (SWM) system using the solid waste optimization life-cycle framework (SWOLF) to identify optimal SWM strategies that meet modelled objectives (e.g. cost, environmental impacts, landfill diversion). While mathematically optimal strategies can support SWM decision making, they may no...
Article
Solid waste management (SWM) is a key function of local government and is critical to protecting human health and the environment. Development of effective SWM strategies should consider comprehensive SWM process choices and policy implications on system-level cost and environmental performance. This analysis evaluated cost and select environmental...
Article
The design community lacks simple, data-driven energy assessment tools to explore energy-efficient alternatives during the early stages of building design. A promising option is to utilize a whole building energy simulation engine (e.g. EnergyPlus) within a Monte Carlo simulation framework to develop a linear regression-based building energy model...
Article
Solid waste management (SWM) systems must proactively adapt to changing policy requirements, waste composition, and an evolving energy system to sustainably manage future solid waste. This study represents the first application of an optimizable dynamic life-cycle assessment framework capable of considering these future changes. The framework was u...
Conference Paper
Leak detection and management is an important problem in water distribution systems because it has been documented that up to 40% of the water may be lost to leaks in many aging systems. Small gradual leaks, which represent more than half of all leaks, are difficult to locate. Routinely measured pressure, flow, and water quality data in combination...
Conference Paper
It is estimated that 15-40% of water is unaccounted for in urban water systems. This is mostly caused by small leaks, which are difficult to locate. Routinely measured pressure, flow, and water quality data can be used to locate leaks in the water network using an inverse modeling approach. For a known sensor configuration, the leak locations can b...
Article
This paper presents a new modeling approach to quantify building energy performance in early design stages. Building simulation models can accurately quantify building energy loads, but are not amenable to the early design stages when architects need an assessment tool that can provide rapid feedback based on changes to high level design parameters...
Article
Full-text available
This paper presents a simulation–optimization-based method for identification of contamination source characteristics in a water distribution system using filtered data from threshold-based binary water quality signals. The effects of quality and quantity of the data on the accuracy of the source identification methodology are investigated. This st...
Article
Full-text available
The rapid discovery of the contaminant source in a water distribution system (WDS) is vital for generating an efficient control strategy during a contamination event. An inverse problem can be constructed, given sensor measurements in a WDS, to identify the contaminant source characteristics by integrating a WDS simulation model with an optimisatio...
Article
Accidental or intentional drinking water contamination has long been and remains a major threat to water security throughout the world. An inverse problem can be constructed, given sensor measurements in a water distribution system (WDS), to identify the contaminant source characteristics by integrating a WDS simulation model with an optimization m...
Article
This work aims to solve the water distribution network design problem presented by the Battle of the Water Networks II (BWN II) design competition. A simulation-optimization framework was developed to run on high-performance computing (HPC) platforms, and it was used to develop solutions to the network expansion design problem. The simulation-optim...
Article
Solid waste management is an issue that must be addressed by every community in the U.S. The demand for waste management strategies that are protective of the environment has increased due to heightened environmental awareness and major evolution in both environmental policy and regulation over the last 20-30 years. Unfortunately, the quantities of
Article
Accidental or intentional contamination in a water distribution system (WDS) has recently attracted attention due to the potential hazard to public health and the complexity of the contaminant characteristics. The accurate and rapid characterization of contaminant sources is necessary to successfully mitigate the threat in the event of contaminatio...
Article
Market based policies to reduce greenhouse gas emissions have become increasingly popular in the last decade. These policies provide economic incentives for reducing greenhouse gas emissions. A life-cycle inventory model was developed to evaluate three alternatives for the management of waste hot mix asphalt (HMA) including, (1) recycling as new ag...
Article
The design of sensor networks for monitoring contaminants in water distribution systems is currently an active area of research. Much of the effort has been directed at the contamination detection problem and the expression of public health protection objectives. Monitoring networks once they are in place, however, are likely to be used to gather m...
Article
This paper describes experiences developing a grid-enabled framework for solving environmental inverse problems. The solution approach taken here couples environmental simulation models with global search methods and requires readily available computational resources of the grid for computational tractability. The solution framework developed by th...
Article
The use of evolutionary algorithms (EAs) is beneficial for addressing optimization problems in dynamic environments. The objective function for such problems changes continually; thus, the optimal solutions likewise change. Such dynamic changes pose challenges to EAs due to the poor adaptability of EAs once they have converged. However, appropriate...
Article
Contamination source identification involves the characterization of the contaminant source based on observations that stream from a set of sensors in a water distribution system (WDS). The streaming data can be processed adaptively to provide an estimate of the source characteristics at any time once the contamination event is detected. In this pa...
Article
This paper presents outcomes from a research effort to develop models for estimating the dynamic modulus (|E*|) of hot-mix asphalt (HMA) layers on long-term pavement performance test sections. The goal of the work is the development of a new, rational, and effective set of dynamic modulus |E *| predictive models for HMA mixtures. These predictive m...
Conference Paper
The rapid discovery of the contaminant source and its mass loading characteristics in a water distribution system (WDS) is vital for generating an efficient control strategy during a contamination event. Previous work on the Adaptive Dynamic Optimization Technique (ADOPT), which was developed as an Evolution Strategy (ES) based procedure, presents...
Article
Mathematical models of integrated solid waste management (SWM) are useful planning tools given the complexity of the solid waste system and the interactions among the numerous components that constitute the system. An optimization model was used in this study to identify and evaluate alternative plans for integrated SWM for the State of Delaware in...
Article
The NCHRP Project 1-37A "Guide for Mechanistic–Empirical Design of New and Rehabilitated Pavement Structures" introduces the dynamic modulus (|E*|) as the material property for the characterization of hot-mix asphalt mixtures. This is a significant change from the resilient modulus used in the previous AASHTO "Guide for the Design of Pavement Struc...
Conference Paper
Given a set of contaminant concentration observations at sensors in a water distribution network, an inverse problem can be constructed to identify the contaminant source characteristics (including location, strength and release history) by coupling a water distribution simulation model with an optimization method. This approach, however, requires...
Article
Full-text available
The problem of contaminant source identification in a water distribution system can be solved as an inverse problem using a simulation-optimization approach. The optimization method searches for contaminant source characteristics which lead to matching observations at the sensors. Accuracy of identification depends on the quantity and quality of da...
Conference Paper
Accidental drinking water contamination has long been and remains a major threat to water security throughout the world. Consequently, contamination source identification is an important and difficult problem in the managing safety in water distribution systems. This problem involves the characterization of the contaminant source based on observati...
Article
The source of contamination in a water distribution system may be identified through a simulation-optimization approach. The optimization method searches for the contaminant source characteristics by iteratively estimating the contaminant plume concentrations until they match observations at sensors. The amount of information available for characte...
Article
The development of integrated solid-waste management (SWM) strategies that are efficient with respect to both cost and environmental performance is a complex task. It must incorporate the numerous interrelations among different unit operations in the solid waste system (e.g., collection, recycling, and combustion), and the large number of design pa...
Article
Performance models of high performance computing (HPC) applications are important for several reasons. First, they provide insight to designers of HPC systems on the role of subsystems such as the processor or the network in determining application performance. Second, they allow HPC centers more accurately to target procurements to resource requir...
Conference Paper
Full-text available
This paper describes a preliminary cyberinfrastructure for contaminant characterization in water distribution systems and its deployment on the grid. The cyberinfrastructure consists of the application, middleware and hardware resources. The application core consists of various optimization modules and a simulation module. This paper focuses on the...
Conference Paper
Characterizing the sources of contamination in water distribution networks continues to be a challenging problem. Several methods have been reported to address this problem. The authors previously presented and continue to investigate an adaptive search procedure that attempts to solve this problem under dynamic conditions. Since demand variability...
Conference Paper
Due to the present state of sensor technology, during a water distribution contamination event, sensors may be able to detect only the presence of a contaminant and not necessarily the complete concentration profile. Some sensors trigger a detection based on a specified threshold concentration of observation, yielding a binary detection/no-detectio...
Conference Paper
Full-text available
An interactive method is developed to aid decision makers in public sector planning and management. The method integrates machine learning algorithms along with multiobjective optimization and modeling-to-generate-alternatives procedures into decision analysis. The implicit preferences of the decision maker are elicited through screening of several...
Article
Calibration is typically used for improving the predictability of mechanistic simulation models by adjusting a set of model parameters and fitting model predictions to observations. Calibration does not, however, account for or correct potential misspecifications in the model structure, limiting the accuracy of modeled predictions. This paper prese...
Article
A genetic algorithm (GA)-based method for the least-cost design of looped pipe networks for various levels of redundancy is presented in this paper. Redundancy constraints are introduced in the optimization model by considering the number of pipes assumed to be out of service at any one time. Using this approach, trade-off relationships between cos...
Article
Full-text available
The management of tropospheric ozone (O3) is particularly difficult. The formulation of emission control strategies requires considerable information including: (1) emission inventories, (2) available control technologies, (3) meteorological data for critical design episodes, and (4) computer models that simulate atmospheric transport and chemistry...
Conference Paper
Full-text available
Threat management in drinking water distribution systems involves real-time characterization of any contaminant source and plume, design of con- trol strategies, and design of incremental data sampling schedules. This requires dynamic integration of time-varying measurements along with analytical mod- ules that include simulation models, adaptive s...
Conference Paper
This paper investigates a groundwater source identification problem in which concentrations at observation wells are used to reconstruct the pollution loading scenario. This inverse problem is solved using a simulation-optimization approach using evolutionary algorithms to conduct the search. Varying levels of complexity may be modeled, leading to...
Article
When solving real engineering design problems, exploring the decision space for alternative and near-optimal solutions, and identifying non-unique solutions are useful. An e卤cient way to conduct this search is to identify alternative solutions that are as far apart as possible in the decision space. This will help not only provide meaningful design...
Conference Paper
This paper investigates a groundwater source identification problem in which chemical signals at observation wells are used to reconstruct the pollution loading scenario. This inverse problem is solved using a simulation-optimization approach that uses a genetic algorithm to conduct the search. As the numerical pollution-transport model is solved i...
Conference Paper
Traditional model calibration attempts to correct a model so that the model output will match a set of system observations by tweaking a set of model parameters. Potential model structural error limits, however, the effectiveness and accuracy of calibration, undermining the predictive capabilities of the calibrated model. An evolutionary computatio...
Conference Paper
This paper describes the development of an evolutionary algorithm called Multipopulation Cooperative Coevolutionary Programming (MCCP) that extends Genetic Programming (GP) to search for a set of maximally different solutions for program induction problems. The GP search is structured to generate a set of alternatives that are similar in design per...
Conference Paper
Parameter determination of advanced cyclic plasticity models which are developed for simulation of cyclic stress-strain and ratcheting responses is complex. This is mainly because of the large number of model parameters which are interdependent and three or more experimental responses are used in parameter determination. Hence the manual trial and...
Conference Paper
In this paper, we report our experiences developing a grid-enabled framework for solving environmental inverse problems. The solution approach taken here couples environmental simulation models with global search methods and requires the readily available computational resources of the grid for computational tractability. We present a set of result...
Article
Typically for a real optimization problem, the optimal solution to a mathematical model of that real problem may not always be the ‘best’ solution when considering unmodeled or unquantified objectives during decision-making. Formal approaches to explore efficiently for good but maximally different alternative solutions have been established in the...
Article
A study was performed on evaluating environmental impacts of solid waste management alternatives. A computer model using the Life Cycle Assessment (LCA) techniques provides a basis for comparing landfilling and organics recovery options for municipal MSW. The Integrated Solid Waste Management Decision Support Tool (ISWM DST) is designed to address...
Article
Full-text available
A review on comparison between recycling, composting and landfills is presented. In the life cycle assessment model, three scenarios with six alternative systems are studied. Each scenario included a landfill, both traditional and a bioreactor. Key defaults associated with the landfill process model include the waste density and the landfill gas co...
Conference Paper
Evolutionary algorithms (EAs) continue to offer an effective, powerful, and sometimes exclusive way to search for solutions to real optimization problems. While these algorithms can help solve a complex optimization problem, whether the results represent the “best” choices for making decisions about a solution to a real problem is questionable. In...
Article
This paper presents a systematic comparative study of CMEA (constraint method-based evolutionary algorithm) with several other commonly reported mulitobjective evolutionary algorithms (MOEAs) in solving a three-objective optimization problem. The best estimate of the noninferior space was also obtained by solving this multiobjective (MO) problem us...
Conference Paper
The watershed water quality management problem considered in this study involves the identification of pollution control choices that help meet water quality targets while sustaining necessary growth. The primary challenge is to identify nondominated management choices that represent the noninferior tradeoff between the two competing management obj...
Article
Nonpoint source management using wet detention ponds to reduce pollutant loading into receiving water bodies is a common practice. Design of these ponds is typically carried out individually to meet a target total suspended solids (TSS) removal level. An improvement to this approach is to generate cost-effective pond configurations that meet system...
Article
The Asphalt Pavement Layer Condition Assessment Program (APLCAP) is developed in this research to help highway agencies assess layer conditions of asphalt pavements. APLCAP implements a new integrated procedure for condition assessment from falling-weight deflectometer (FWD) deflections. The main components of this procedure include screening of FW...
Article
Regional wastewater-treatment strategies offer cost-effective options to meet pollution limits in fast-growing urban areas. Formal optimisation procedures have been applied effectively to solve relatively simpler versions of this problem. Contemporary heuristic search procedures (e.g., evolutionary algorithms (EAs)) offer enhanced capabilities to s...
Article
New relationships have been identified between the layer condition indicators of flexible pavements and failing weight deflectometer (FWD) deflections. Synthetic databases were generated using dynamic finite element analysis with nonlinear material models. The sensitivity of various deflection basin parameters (DBPs) to layer conditions was compreh...
Article
Nondestructive condition assessment criteria were developed for application in conjunction with the condition evaluation indicators that are estimated based on falling weight deflectometer (FWD) deflections. Data obtained from state departments of transportation and DATAPAVE 2.0 were used in developing these criteria. To account for the effects of...
Conference Paper
. Evolutionary algorithms are becoming increasingly valuable in solving large-scale, realistic engineering multiobjective optimization (MO) problems, which typically require consideration of conflicting and competing design issues. The new procedure, Constraint Method-Based Evolutionary Algorithm (CMEA), presented in this paper is based upon underl...
Article
Public sector decision-making typically involves complex problems that are often not completely understood. In these problems, there are invariably unmodeled issues that can greatly impact the acceptability of solutions. Modeling to Generate Alternatives (MGA) is an approach for addressing unmodeled issues in an optimization context. MGA techniques...
Conference Paper
A genetic algorithm- (GA-) based method is being investigated for determining the least cost design of looped networks while considering the residence time of the water in the network as a quality surrogate and various levels of redundancy. The conflict among the three design objectives, i.e., cost, redundancy, and water quality, is examined via mu...
Conference Paper
We explore the use of chance-constrained genetic algorithms (CCGAs) for stochastic optimization in air quality management. CCGAs allow uncertainties in optimization model parameters to be considered explicitly in the design of least cost strategies. To incorporate uncertainties into the CCGA, the original fitness function is replaced with a Monte C...
Conference Paper
Vitri is an object-oriented framework implemented in Java for high-performance distributed computing. Using Vitri, applications can engage in cooperative problem solving by dividing their tasks among heterogeneous clusters of workstations and PCs. Vitri's features include basic support for distributed computing and communication, as well as visual...
Conference Paper
A genetic algorithm-based search procedure in conjunction with an array of other tools is packaged into BASINS-STAR to form a decision support framework for watershed management. Some of the capabilities of this framework are demonstrated through several illustrative scenarios for the Suwanee Creek watershed in Georgia. Through these case study sce...
Conference Paper
Watershed management requires consideration of multitude of factors affecting water quality at the watershed-scale while integrating point and non-point sources of pollution and control. EPA's TMDL development tool, Better Assessment Science Integrating Point and Nonpoint Sources (BASINS) provides a GIS-based framework to assist in this process. Th...
Article
Existing solid waste management (SWM) planning software provides only limited assistance to decision makers struggling to find strategies that address their multifarious concerns. The combinatorial nature (many waste items and many management options) and multiple objectives of the SWM problem severely constrain the effectiveness of a manual search...
Conference Paper
A new method is proposed for the least cost design of looped piped networks under various levels of redundancy using a genetic algorithm. Various levels of redundancy can be obtained by considering the number of pipes to be taken out of service at any one time. As a result, a tradeoff curve of redundancy and cost can be developed. The approach is b...
Article
Designing air quality management strategies is complicated by the difficulty in simultaneously considering large amounts of relevant data, sophisticated air quality models, competing design objectives, and unquantifiable issues. For many problems, mathematical optimization can be used to simplify the design process by identifying cost-effective sol...
Article
This paper presents a methodology based on deflection basin parameters and artificial neural networks (ANNs) for processing dynamic falling weight deflectometer (FWD) measurements to estimate layer moduli and condition. Two-dimensional, dynamic, finite element analysis using the ABAQUS program was employed to develop the deflection information for...
Conference Paper
Genetic algorithms (GAs) provide a convenient framework to search for good solutions for a wide range of problems that are typically difficult to solve by means of traditional optimization techniques. Their application in solving real-world engineering problems is becoming increasingly popular. A common drawback of this procedure is its poor abilit...
Article
In using non-linear optimization techniques for estimation of parameters in a distributed ground water model, the initial values of the parameters and prior information about them play important roles. In this paper, the genetic algorithm (GA) is combined with the truncated-Newton search technique to estimate groundwater parameters for a confined s...
Article
Most of the deflection analysis programs used today to analyze falling weight deflectometer (FWD) data are based on static analysis, which often underestimates the subgrade strength. Unfortunately, dynamic analysis usually involves complex calculations and requires significant computation time, thus making it impractical for routine applications. A...
Article
A methodology is presented that emulates the transportation improvement planning process using mathematical optimization techniques. The scheduling problem is formulated as a mixed integer linear program (MILP) and can be considered as a multiperiod network design problem. The three primary model components are discussed: (a) the input modale in wh...
Article
Automating the process of cold-bending steel reinforcing bars for concrete structures can save time, prevent serious injuries, and increase productivity. Neural network models can play a key role in the adaptive control of this process

Citations

... The remaining articles (approximately 39%) employed other methods, such as the Vehicle Routing Problem (VRP) optimization [35,36], complex waste management processes [37], MSW management system [38], MSW-to-biofuel supply chain [39], and different MSW strategies alternatives [40]. Morero et al. [41] used the municipal waste treatment alternatives selection, while the benefit limited resources maximization by Peng et al. [42]. ...
... A life cycle GHG study followed the international standards of ISO 14040. E-waste management involves collecting, disassembling, transporting, recycling, and disposing of residue [22]. The system boundaries of the life cycle GHG study of each e-waste type are displayed in Fig. 2. ...
... About 1/3 of the approximately 2 billion tons of municipal waste produced annually is inadequately managed [7]. According to a forecast by the World Bank, in the next three years, the global production of solid waste in cities will increase to as much as 6,100,000 tons per day [8,9]. Groundwater risk assessment is an effective way to protect groundwater resources and should be performed on the basis of the results of groundwater monitoring. ...
... Study [10] explores sensitivity of the magnitude of a leak to the leak site and the distance to the sensor. The leaks themselves are measured by minimizing the difference between actual and simulated measurements. ...
... Aerobic microorganisms convert organic waste into carbon monoxide and water and thus lead to reduction of CH 4 concentration up to 80-90% (Cossu, 2003;Read et al. 2001). Aerobic treatment is done to stabilize the waste rapidly and to recirculation of leachate with in landfill and thereby increasing the LFG collection efficiency by 10% (Barlez et al. 2003) and showed higher energy recovery as compared to anaerobic landfills which is 9.6MJ/kg of waste (Cabaraban et al. 2008) and 4.108MJ/kg of waste as recovered by Lou (2008). Under aerox treatment, although there are inputs of energy in term of aeration and leachate circulation as well as some associated N 2 O production that have GWP higher than CO 2 . ...
... Output: Solución para una fuga tubería 30 m Fuente: elaboración propia La validación de estos resultados se realizó a través del software Epanet ® desarrollado por la Agencia de Protección Ambiental de Estados Unidos, este software es utilizado para modelar y diseñar sistemas a presión, de igual forma, es posible realizar el seguimiento de sustancias en la red, también es viable para la detección de fugas a partir de emisores (Mashford et al., 2009). Epanet ® resuelve diferentes ecuaciones no lineales simultáneamente utilizando métodos iterativos con el objetivo de alcanzar el equilibrio de red (Jasper et al., 2013). Si la red no presenta fuga el valor del coeficiente del emisor será igual a cero. ...
... Several authors have adapted this library in order to incorporate functions that originally were not thought about being included. This is the case of Kandiah et al. [10], who partially modified the EPANET Programmer's Toolkit in order to include functions for control adaptation in EPANET. Another example is the CWSNet Library [11]. ...
... Usually, once a small sample size is implemented, the solution of the approximation model of P-model will greatly deviate from the optimal solution; conversely, it is inevitable to cause high computational complexity. With regard to noise handling, several representative sampling approaches can be found in the literature, e.g., static sampling (Charles et al. 2011;Li et al. 2012;Robert and Casella 2013;Lughofer et al. 2016), sample bound estimation (Luedtke and Ahmed 2008;Shapiro et al. 2009), dynamic sampling (Yang and Zhang 2015), adaptive sampling (Cantú-Paz 2004;Higle and Zhao 2012;Chen 2003;Zhang et al. 2013), important sampling (Hesterberg 1995), Latin hypercube sampling (Loughlin and Ranjithan 1999), etc. Among these approaches, the first is an alternative way to handle various kinds of complex noises, but requires that each individual attach the same sufficiently large sample size in order to obtain an approximate solution; this causes computationally expensive resource consumption. ...
... In light of these reasons the accepted FWD interpretation approach for pavement management is based on some index derived directly from the deflection peaks. The index is chosen such that it exhibits good statistical correlation with some definition of "structural capacity" or "remaining life" (7). The Surface Curvature Index SCI 300 is one such a parameter; it has units of length and denotes the difference between the central FWD peak deflection and the peak deflection at an offset of 300 mm (8,9). ...
... Wastes are unwanted or discarded materials after primary uses such as plastics and glasses. However, we can produce different products, such as composite, from those waste materials by combining or separately using different recycling methods [2,3]. Short life packaging materials (bags, bottles, etc.), used goods (computers, cell phones, furniture, cars, etc.), demolition materials from buildings (insulation, flooring, pipes, etc.), and disposables are some of the waste materials [4,5]. ...