SD-GIS-based temporal-spatial simulation of water quality in sudden water pollution accidents

System dynamics (SD) is well suited for studying dynamic nonlinear complex systems. In this paper, SD is applied to a rapid-onset water pollution accident using a 1-D water quality model and a conceptual GIS-SD framework is constructed to simulate the temporal-spatial changes of pollutant concentration. Based on the component GIS and the SD model, a prototype system of water quality simulation in water pollution accidents is developed. The data collected on the spot in the Songhua River water pollution accident in November 2005 were used for model parameter calibration and model validation. The results showed that: (1) the constructed model could simulate the changes of nitrobenzene concentration with time in the Songhua River water pollution accident, especially during the peak concentration and at the arrival time of peak concentration, and that the simulated values and the on-the-spot monitored values corresponded with each other well; (2) the scenario simulation could be made by adjusting parameters u (longitudinal current velocity), E (longitudinal diffusion coefficient), and k (decay rate coefficient). Such a model can provide decision makers with quantitative information to optimize related emergency response measures.     

Coupled optimization-simulation water quality model for regional water quality management

The objective pursued in water quality management is to secure water qualities such that marginal cost of the cleaning water equals the accuring marginal benefits. It is the purpose of this paper to show how the methods of system analysis may be used to plan more economical new pollution control facilities or how to upgrade existing systems. The particular problem investigated is the following: Given a region with a number of industries and/or municipalities, where should one build treatment plants and will be necessary levels that total regional cost of waste water treatment is minimum. To approach these problems, a stream water quality simulation is linked with a treatment cost minimization model in order to capitalize on the unique adventage of each in managing river basin water quality.     

Hydrologic and water quality impacts and biomass production potential on marginal land

Marginal land is proposed as viable land resources for biofuel production. However, environmental impacts of perennial biomass production on marginal lands is not clear. This study defined three marginal land types and assessed their availability and potential for biofuel production in the St. Joseph River watershed. The potential impacts were evaluated using the Agricultural Policy/Environmental eXtender (APEX) model. The total area of marginal land was estimated to be 611 km² covering 21.7% of the watershed. 161 and 207 million liters of bioethanol could be produced from the marginal land utilizing switchgrass and Miscanthus, respectively. Converting marginal land currently under corn/soybean production to switchgrass and Miscanthus reduced water yield by 13.4–36.3% and improved water quality by reducing soil erosion by 27%–98%. Similarly, total nitrogen losses were reduced by 30–91% and total phosphorus losses were reduced by 65–76%, respectively, at the field scales under various energy crop production scenarios.     

Choosing,Agreeing, and Eliminating in Communication Complexity

We consider several questions inspired by the direct-sum problem in (two-party) communication complexity. In all questions, there are k fixed Boolean functions f ₁,…,f _k and each of Alice and Bob has k inputs, x ₁,…,x _k and y ₁,…,y _k , respectively. In the eliminate problem, Alice and Bob should output a vector σ₁,…,σ _k such that f _i (x _i , y _i ) ≠ σ _i for at least one i (i.e., their goal is to eliminate one of the 2 ^k output vectors); in the choose problem, Alice and Bob should return (i, f _i (x _i , y _i )), for some i (i.e., they choose one instance to solve), and in the agree problem they should return f _i (x _i , y _i ), for some i (i.e., if all the k Boolean values agree then this must be the output). The question, in each of the three cases, is whether one can do better than solving one (say, the first) instance. We study these three problems and prove various positive and negative results. In particular, we prove that the randomized communication complexity of eliminate, of k instances of the same function f, is characterized by the randomized communication complexity of solving one instance of f.     

Application of fuzzy probability in water quality management of a river system

Water quality management of a river system is addressed in a fuzzy and probabilistic framework. Two types of uncertainty, namely randomness and vagueness, are treated simultaneously in the management problem. A fuzzy-set-based definition that is a more general case of the existing crisp-set-based definition of low water quality is introduced. The event of low water quality at a check-point in the river system is considered as a fuzzy event. The risk of low water quality is then defined as the probability of the fuzzy event of low water quality. Instead of constraining the risk of violation of water quality standard by a finite value of risk through a chance constraint, a fuzzy set of low risk that considers a range of risk levels with appropriate membership values is introduced. Different goals associated with the management problem are expressed as fuzzy sets. The resulting management problem is formulated as a fuzzy multiobjective optimization problem.     

The k-in-a-Path Problem for Claw-free Graphs

The k-in-a-Path problem is to test whether a graph contains an induced path spanning k given vertices. This problem is NP-complete in general graphs, already when k=3. We show how to solve it in polynomial time on claw-free graphs, when k is an arbitrary fixed integer not part of the input. As a consequence, also the k-Induced Disjoint Paths and the k-in-a-Cycle problem are solvable in polynomial time on claw-free graphs for any fixed k. The first problem has as input a graph G and k pairs of specified vertices (s _i ,t _i ) for i=1,…,k and is to test whether G contain k mutually induced paths P _i such that P _i connects s _i and t _i for i=1,…,k. The second problem is to test whether a graph contains an induced cycle spanning k given vertices. When k is part of the input, we show that all three problems are NP-complete, even for the class of line graphs, which form a subclass of the class of claw-free graphs.     

Efficient algorithm for transversal of disjoint convex polygons

Given a set S of n disjoint convex polygons {P_i∣1?i?n} in a plane, each with k_i vertices, the transversal problem is to determine whether there exists a straight line that goes through every polygon in S. We show that the transversal problem can be solved in O(N+nlogn) time, where N=∑_i=1ⁿk_i is the total number of vertices of the polygons.     

Transversal of disjoint convex polygons

Given a set S of n disjoint convex polygons {P_i∣1?i?n} in a plane, each with k_i vertices, the transversal problem is to find, if there exists one, a straight line that goes through every polygon in S. We show that the transversal problem can be solved in O(N+nlogn) time, where N=∑_i=1ⁿk_i is the total number of vertices of the polygons.     

A New Approach to Primary Decomposition

The first purpose of this paper is to describe a new mathematical approach for the computation of an irredundant primary decomposition of a given polynomial ideal I. This presentation will be formed of three parts: a decomposition of the associated radical ideal I to an intersection of prime ideals P_i, then the determination of ideals I_iwhose radical is prime (equal to P_i), and finally, the extraction of the possible embedded components included in I_i. The second is to give an implementation of this algorithm via a new software component, called The Central Control², in which we implemented distributed algorithms performing the basic operations of algebraic geometry.     

An analytical technique for uni,bi, and trimodal paleocurrent data

Accurate paleogeographic reconstructions of sedimentary rock associations require a method of paleocurrent analysis in which each individual current system present can be analyzed separately. Such a method has been developed whereby mixtures of up to three populations in any one paleocurrent distribution can be analyzed individually. For each population the mean direction (u_i), concentration about the mean (k_i), and proportion of that population in the entire distribution (p_i) are determined from the data, along with a chi-square, goodness-of-fit test of the model selected.     

Thek-track assignment problem

Thek-track assignment problem is a scheduling problem withn jobs andk machines. Each machinej has a certain operational period (track) which starts at timea _j and ends at timeb _j . Each jobi has a specific start times _i and a specific finish timet _i . A schedule is an assignment of certain jobs to machines such that the intervals [s _i ,t _i [assigned to the same machinej do not overlap and fit into track [a _j ,b _j [. We are interested in a schedule which maximizes the number of assigned jobs. AO(n ^k?1 k!k ^k+1 )-algorithm which solves this problem is presented. Furthermore it is shown that the more general problem, in which for each track only a given set of jobs can be scheduled on that track, can be solved inO(n ^k k!k ^k )-time.     

The Space Complexity of Approximating the Frequency Moments

The frequency moments of a sequence containingm_ielements of typei, 1⩽i⩽n, are the numbersF_k=∑ⁿ_i=1 m^k_i. We consider the space complexity of randomized algorithms that approximate the numbersF_k, when the elements of the sequence are given one by one and cannot be stored. Surprisingly, it turns out that the numbersF₀,F₁, andF₂can be approximated in logarithmic space, whereas the approximation ofF_kfork⩾6 requiresn^Ω(1)space. Applications to data bases are mentioned as well.     

An Efficient Algorithm for the k-Pairwise Disjoint Paths Problem in Hypercubes

A graph G(V, E) (|V|⩾2k) satisfies property A_k if, given k pairs of distinct nodes (s₁, t₁), …, (s_k, t_k) of V(G), there are k mutually node-disjoint paths, one connecting s_i and t_i for each i, 1⩽i⩽k. A necessary condition for any graph to satisfy A_k is that it is (2k−1)-connected. Hypercubes are important interconnection topologies for parallel computation and communication networks. It has been known that hypercubes of dimension n (which are n-connected) satisfy A_⌈n/2⌉. In this paper we give an algorithm which, given k=⌈n/2⌉ pairs of distinct nodes (s₁, t₁), …, (s_k, t_k) in the n-dimensional hypercube, finds the k disjoint paths of length at most n+⌈log n⌉+1 in O(n² log* n) time.     

Fine structure of a one-dimensional discrete point system

We consider a system of N points x ₁ < ... < x _N on a segment of the real line. An ideal system (crystal) is a system where all distances between neighbors are the same. Deviation from idealness is characterized by a system of finite differences ? _i ¹ = x _x+1 ? x _i , ? _i ^k+1 = ? _i+1 ^k ? ? _i ^k , for all possible i and k. We find asymptotic estimates as N ?? ??, k????, for a system of points minimizing the potential energy of a Coulomb system in an external field.     

Bandwidth packing

We model a server that allocates varying amounts of bandwidth to “customers” during service. Customers could be computer jobs with demands for storage bandwidth or they could be calls with demands for transmission bandwidth on a network link. Service times are constants, each normalized to 1 time unit, and the system operates in discrete time, with packing (scheduling) decisions made only at integer times. Demands for bandwidths are for fractions of the total available and are limited to the discrete set {1/k, 2/k, …, 1} wherek is a given parameter. More than one customer can be served at a time, but the total bandwidth allocated to the customers in service must be at most the total available. Customers arrive ink flows and join a queue. Thejth flow has rate λ _j and contains just those customers with bandwidth demandsj/k. We study the performance of the two packing algorithms First Fit and Best Fit, both allocating bandwidth by a greedy rule, the first scanning the queue in arrival order and the second scanning the queue in decreasing order of bandwidth demand. We determine necessary and sufficient conditions for stability of the system under the two packing rules. The average total bandwidth demand of the arrivals in a time slot must be less than 1 for stability under any packing rule, i.e., the condition $$\rho {\text{ : = }}\sum\limits_i {\lambda i\left( {i/k} \right)} {\text{< 1}}$$ must hold. We prove that if the arrival rates λ₁, …, λ _k?1 are symmetric, i.e., λ _i =λ _k?i for alli, 1 ≤i ≤k ? 1, theρ<1 is also sufficient for stability under both rules. Our Best Fit result strengthens an earlier result confined to Poisson flows and equal rates λ₁=…=λ _{k ? 1}, and does so using a far simper proof. Our First Fit result is completely new. The work here extends earlier results on bandwidth packing in multimedia communication systems, on storage allocation in computer systems, and on message transmission along slotted communication channels. It is not surprising thatρ<1 is sufficient under Best Fit, since in a congested system, Best Fit tends to serve two complementary (matched) customers in each time slot, with bandwidth demands beingi/k and (k ? i)/k for somei, 1 ≤i ≤k ? 1. It is not so obvious, however, thatρ<1 is also sufficient under First Fit. Interestingly, when the system becomes congested, First Fit exhibits a “self-organizing” property whereby an ordering of the queue by time of arrival becomes approximately the same as an ordering by decreasing bandwidth demand.     

Isomers of polycyclic conjugated hydrocarbons with arbitrary ring sizes—Part II

The numbers of C_nH_s isomers (#I) for completely condensed polycyclic conjugated hydrocarbons with arbitrary ring sizes are studied. Solutions for #I in the cases r=4, n_i=2 and r=4, n_i=0 were achieved. Here r and n_i are used to denote the number of rings and number of internal carbons, respectively. Combinatorial methods were applied, in combination with computer programming. The present work, in supplement to the preceding part of this article series, completes the analysis of #I for all cases where r ⪕ 4.     

An integrated catchment-coastal modelling system for real-time water quality forecasts

This paper presents a new marine water quality forecasting system for real-time and short-term predictions. The forecasting system comprises an integrated catchment-coastal model and a database management system. The integrated model is validated in an Irish catchment-coastal system using hydrodynamic and water quality data. The forecasting system was then used to provide short-term and real-time forecasts of Escherichia coli (E. coli) and Intestinal Enterococci concentrations (IE) in the near-shore coastal waters of Bray, Ireland. Two hind-cast scenarios were simulated: 5F in which predictions were based on rainfall forecasts only; and I-5F where forecasts of 5F were improved by incorporating real-time data. Results indicate that predictions of E. coli of scenario I-5F are improved. Also predicted IE concentrations by Scenario 5F were comparably higher than the I-5F predications, but due to the wide scatter of observed IE concentrations, the superiority of one scenario over the second could not be definitively determined.     

Use of environmental sensors and sensor networks to develop water and salinity budgets for seasonal wetland real-time water quality management

Management of river salt loads in a complex and highly regulated river basin such as the San Joaquin River Basin of California presents significant challenges for current Information Technology. Computer-based numerical models are used as a means of simulating hydrologic processes and water quality within the basin and can be useful tools for organizing Basin data in a structured and readily accessible manner. These models can also be used to extend information derived from environmental sensors within existing monitoring networks to areas outside these systems based on similarity factors – since it would be cost prohibitive to collect data for every channel or pollutant source within the Basin. A common feature of all hydrologic and water quality models is the ability to perform mass balances. This paper describes the use of a number of state-of-the-art sensor technologies that have been deployed to obtain water and salinity mass balances for a 60,000 ha tract of seasonally managed wetlands in the San Joaquin River Basin of California. These sensor technologies are being combined with more traditional environmental monitoring techniques to support real-time salinity management (RTSM) in the River Basin. Two of these new technology applications: YSI-Econet (which supports continuous flow and salinity monitoring of surface water deliveries and seasonal wetland drainage); and electromagnetic salinity mapping (a remote sensing technology for mapping soil salinity in the surface soils) – have not previously been reported in the literature. Continuous sensor deployments that experience more widespread use include: weather station sensor arrays – used to estimate wetland pond evaporation and moist soil plant evapotranspiration; high resolution multi-spectral imagery – used to discriminate between and estimate the area of wetland moist soil plant vegetation; and groundwater level sensors – used primarily to estimate seepage losses beneath a wetland pond during flood-up. Important issues associated with quality assurance of continuous data are discussed and the application of a state-of-the-art software product AQUARIUS, which streamlines the process of data error correction and dissemination, is described as an essential element of ensuring successful RTSM implementation in the San Joaquin River Basin.     

Computing functions on asynchronous anonymous networks

In an “anonymous” network the processors have no identity numbers. We investigate the problem of computing a given functionf on an asynchronous anonymous network in the sense that each processor computesf(I) for any inputI = (I(v ₁),...,I(v _n )), whereI(v _i) is the input to processorv _i ,i = 1, 2,...,n. We address the following three questions: (1) What functions are computable on a given network? (2) Is there a “universal” algorithm which, given any networkG and any functionf computable onG as inputs, computesf onG? (3) How can one find lower bounds on the message complexity of computing various functions on anonymous networks? We give a necessary and sufficient condition for a function to be computable on an asynchronous anonymous network, and present a universal algorithm for computingf(I) on any networkG, which acceptsG andf computable onG, as well as {I(v _i )}, as inputs. The universal algorithm requiresO(mn) messages in the worst case, wheren andm are the numbers of processors and links in the network, respectively. We also propose a method for deriving a lower bound on the number of messages necessary to solve the above problem on asynchronous anonymous networks.