Splitting Strategies Research Articles

Postponing trauma: The dangers of telling

Surviving a major historical trauma has consequences that are difficult to live with. Survivors who remain silent are often condemned to a desiccated existence, a dried‐out life, a death in life. Survivors who speak out run an even greater risk. Telling their ghastly tale may trigger somatic consequences, psychotic episodes, or even suicide. As to the psychoanalytic cure, the free association it requires carries its own danger: negative therapeutic reaction in sometimes extreme forms. Avoidance of horror may turn into avoidance of life itself. Awful as it may seem, this avoidance of life may represent a victory over a menacing chaos. Should we as analysts accept the risk of endangering such a victory, no matter how unsatisfactory? The psychoanalytical injunction to speak out may trigger an upsurge of shame and terror. Is subjectivation always possible? This paper is about what happens when denial and splitting strategies are suspended, when ‘crypts’ are opened. Is there an analytic ‘poros’ allowing for a controlled return of affects? Is there a therapeutic solution to the problem of telling a wreckage without being caught in it? The dangers of ‘telling’ will be discussed in regard to new analytic strategies and new interpretive registers. When the ‘silent psychic sharing’ proves insufficient, some analysts go so far as to take part in the shame, share the grief, ‘lend their own psyche’, become a ‘double’ of the analysand, accept the existence of ‘sanctuaries’. To what effect?

Strategic Order Splitting in Automated Markets

We identify and characterize order splitting strategies in an automated limit order market. We model the market conditions and order characteristics, which lead to the use of order splitting strategies. We find a positive correlation between price aggressiveness and the propensity to split an order, which implies, in a utility maximization framework, that traders trade-off one type of aggressiveness for another. We are able to identify two types of traders that use order splitting strategies for different purposes: the reduction of execution costs through split market orders, and voluntary supply of liquidity through split limit orders. The interpretation that split limit orders are submitted by voluntary market makers is consistent with the findings in the experimental study Bloomfield, O’Hara, and Saar (2005).

Fertiliser strategies for improved nutrient use efficiency on sandy soils in high rainfall regimes

Fertiliser application strategies for maize (Zeamays L.) production on sandy soils under high rainfall regimes need to be carefully designed to minimise nutrient losses through leaching and maximise crop yield. Experiments were conducted to determine N, P, and K leaching in sandy soils with 3-6% clay in surface layers under maize production, and the effectiveness of different N, P, and K fertiliser timing and splitting strategies on leaching of N, P, and K and on maize yield. In a column experiment on an Oxic Paleustult (Korat series) with 3% clay, leaching of N, P, and K from fertiliser (114N-17P-22K in kg ha-1) was significant under simulated rainfall, but decreased to negligible levels with 3-5 split applications of fertiliser. Maize N and K uptake increased with 3-5 split applications, but not P uptake. Despite continued intense rainfall and further fertilizer additions, leaching was not recorded after day 30, and this was attributed to the effect of plant water uptake on reducing deep drainage. Split applications of fertilizer maintained NP and K in the 0-30 cm layer during 30-60 days when maize nutrient demand was likely to be at its highest, while in the recommended fertilizer regime NPK in the surface layers declined after 30 days. In a field experiment on an Oxic Paleustult (Korat series) with 6% clay, 3-4 splits of fertiliser increased N and K uptake and increased maize yields from 3.3 to 4.5 Mg ha-1. Postponing basal fertiliser application from pre-planting to 7-15 days after emergence increased uptake of N, P, and K and grain yield emphasising the greater risk of nutrient losses from fertiliser applied at planting than later. Strategies designed to reduce the amount of nutrients applied as fertiliser at planting, such as split application and postponing basal application can decrease the risk of leaching of N, P, and K from fertiliser and improve nutrient use efficiency, and grain yield of maize on sandy soils under high growing season rainfall regimes.

B-tries for disk-based string management

A wide range of applications require that large quantities of data be maintained in sort order on disk. The B-tree, and its variants, are an efficient general-purpose disk-based data structure that is almost universally used for this task. The B-trie has the potential to be a competitive alternative for the storage of data where strings are used as keys, but has not previously been thoroughly described or tested. We propose new algorithms for the insertion, deletion, and equality search of variable-length strings in a disk-resident B-trie, as well as novel splitting strategies which are a critical element of a practical implementation. We experimentally compare the B-trie against variants of B-tree on several large sets of strings with a range of characteristics. Our results demonstrate that, although the B-trie uses more memory, it is faster, more scalable, and requires less disk space.

High-utility pattern mining: A method for discovery of high-utility item sets

We present an algorithm for frequent item set mining that identifies high-utility item combinations. In contrast to the traditional association rule and frequent item mining techniques, the goal of the algorithm is to find segments of data, defined through combinations of few items (rules), which satisfy certain conditions as a group and maximize a predefined objective function. We formulate the task as an optimization problem, present an efficient approximation to solve it through specialized partition trees, called High-Yield Partition Trees, and investigate the performance of different splitting strategies. The algorithm has been tested on “real-world” data sets, and achieved very good results.

Time Splitting Error in DSMC Schemes for the Spatially Homogeneous Inelastic Boltzmann Equation

The paper is concerned with the numerical treatment of the uniformly heated inelastic Boltzmann equation by the direct simulation Monte Carlo (DSMC) method. This technique is presently the most widely used numerical method in kinetic theory. We consider three modifications of the DSMC method and study them with respect to their efficiency and convergence properties. Convergence is investigated with respect to both the number of particles and the time step. The main issue of interest is the time step discretization error due to various splitting strategies. A scheme based on the Strang-splitting strategy is shown to be of second order with respect to time step, while there is only first order for the commonly used Euler-splitting scheme. On the other hand, a no-splitting scheme based on appropriate Markov jump processes does not produce any time step error. It is established in numerical examples that the no-splitting scheme is about two orders of magnitude more efficient than the Euler-splitting scheme. The Strang-splitting scheme reaches almost the same level of efficiency as that of the no-splitting scheme, since the deterministic time step error vanishes sufficiently fast.

Searching for feasible splitting strategies of controlled system islanding

Controlled system islanding, also called system splitting, can effectively prevent blackouts of power systems. The splitting strategy determining how to split a power network into islands should be given in real time. Previous papers proposed an ordered binary decision diagram method to search for the splitting strategies satisfying necessary steady-state constraints, e.g. generation–load balance and transmission-line capacity constraint, and also showed that, without any other corrective controls, the splitting strategies may produce unstable islands according to a further simulation study. A modified method to find feasible splitting strategies in real time for large power network is presented. Each feasible splitting strategy not only satisfies necessary steady-state constraints but also easily produces stable islands to prevent a blackout. The method also introduces new techniques into strategy searching to increase its efficiency and practicality, e.g. network partitioning and parallel processing, generator classifying, deriving splitting strategies from cut-set splitting strategies, etc. Simulations on the IEEE 118-bus system show that the real-time portion of the modified method finds feasible splitting strategies in less than one second.

Quadtree-based disparity estimation for intermediate view synthesis of stereoscopic image sequences

In stereoscopic or multiview 3-D display systems, the synthesis of intermediate sequences is essential to assure lookaround capability and continuous motion parallax so that it can enhance comfortable 3-D perception. The quadtree-based disparity estimation is one of the most popular methods for the synthesis of intermediate sequences, due to the simplicity of its algorithm and hardware implementation. We propose two solutions in order to reduce annoying flicker at object boundaries of synthesized intermediate sequences using quadtree-based disparity estimation. The first requires a new splitting scheme, providing more consistent quadtree splitting strategies during the disparity estimation. The second involves adaptive temporal smoothing, using the dissimilarity between the present frame and the previous one to reduce the error of disparity estimation. These two proposals are tested by using several stereoscopic sequences, and the results show that flicker is remarkably reduced by them.

A Simulation Study of OBDD-Based Proper Splitting Strategies for Power Systems Under Consideration of Transient Stability

System splitting, also called controlled system islanding, can effectively prevent blackouts. Following the OBDD-based three-phase method given in for proper splitting strategies, which satisfy necessary steady-state constraints, This work studies the feasibility of the proper splitting strategies by means of power system transient simulations on the IEEE 118-bus system. Simulation results show that a considerable proportion of proper splitting strategies can successfully split the power system into stable islands. Furthermore, considering a general knowledge that a controlled power system can easily maintain its stability after a small disturbance, This work presents value to restrict the degrees of the disturbances caused by proper splitting strategies. An approach is proposed to select threshold values for the constraint. Further simulation results show that by checking the constraint for proper splitting strategies, feasible splitting strategies can be found, which can successfully split the system into islands satisfying transient stability constraints.

Mitigating the impact of mobility on H.264 real-time video streams using multiple paths

One of the main problems associated with MANETs is that mobility and the associated route discovery and maintenance procedures of reactive routing protocols cause severe interruptions on real-time video streams. Some of these interruptions are too large to be concealed using any sort of video technology, resulting in communications breaks unpleasant for the final end user. We present a solution for enhanced video transmission that increases route stability by using an improved route discovery process based on the DSR routing protocol, along with traffic splitting algorithms and a preventive route discovery mechanism. We also present some video adaptative mechanisms that improve the overall performance of multipath routing in terms of video data replication and video packet splitting strategies. Combining our proposals, we achieve up to 97% less interruptions on communication with high mobility and over 1.2 dB of improvements in terms of video distortion.

TRIOPT: a triangulation-based partitioning algorithm for global optimization

We propose a triangulation-based partitioning algorithm, TRIOPT, for solving low-dimensional bound-constrained black box global optimization problems. The method starts by forming a Delaunay triangulation of a given set of samples in the feasible domain, and then, it assesses the simplices (partitions) obtained for re-partitioning. Function values at the vertices of each partition are mapped into the zero one interval by a nonlinear transformation function and their aggregate entropy is calculated. Based on this entropy, partitions that hold a promise of containing the global optimum are re-partitioned according to different triangular splitting strategies, forming new partitions. These strategies are efficient in terms of the number of new function evaluations required per new partition. A novelty in the search scheme proposed here is that once a partition narrows down to a small size, its vertices are eliminated from the available sample set. This changes global information on the best solution and triggers a re-calculation of transformed values. Hence, revised entropies change the direction of the search to new areas. The latter scheme leads to a dynamic parallel search policy which is based on an entropy cut. The tree adopts flexible breadth depending on the status of the search. In the experimental results it is demonstrated that TRIOPTs performance is compatible and often better than that of a well-known response surface methodology and two other efficient black box partitioning approaches proposed for global optimization.

Spectral beam splitting technology for increased conversion efficiency in solar concentrating systems: a review

Solar concentrating systems that employ one or more quantum receivers may realize improved energy utilization and higher electric conversion efficiency by incorporating spectral beam splitting technology. Such techniques were investigated in thermophotovoltaic conversion, introduced in the early 1960s, and in concentrating PV devices using cells of different band-gap materials, proposed as early as 1955. One major application was found in systems combining quantum and thermal receivers. This article presents a review of the various solar hybrid beam splitting systems proposed in the literature and the different spectrum splitting strategies employed.

A study of system splitting strategies for island operation of power system: a two-phase method based on OBDDs

System splitting problem, also known as controlled system separation problem, is to determine the splitting points for splitting the entire power network into islands when island operation of system is unavoidable. By proper we mean that the splitting strategies should guarantee both the power balance and satisfaction to capacity constraints of transmission lines and other facilities in each island. The system splitting problem is very hard because the strategy space is huge for even middle-scale power networks. This paper proposes a two-phase method to search for splitting strategies in real-time. The method narrows down the strategy space using highly efficient OBDD-based algorithm in the first phase, then finds splitting strategies using power-flow analysis in the reduced strategy space in the second phase. Simulation with symbolic model checking tool SMV indicates that this method is very promising.

Performance enhancement strategies for multi-block overset grid CFD applications

The overset grid methodology has significantly reduced time-to-solution of high-fidelity computational fluid dynamics (CFD) simulations about complex aerospace configurations. The solution process resolves the geometrical complexity of the problem domain by using separately generated but overlapping structured discretization grids that periodically exchange information through interpolation. However, high performance computations of such large-scale realistic applications must be handled efficiently on state-of-the-art parallel supercomputers. This paper analyzes the effects of various performance enhancement strategies on the parallel efficiency of an overset grid Navier–Stokes CFD application running on an SGI Origin2000 machine. Specifically, the role of asynchronous communication, grid splitting, and grid grouping strategies are presented and discussed. Details of a sophisticated graph partitioning technique for grid grouping are also provided. Results indicate that performance depends critically on the level of latency hiding and the quality of load balancing across the processors.

Splitting strategies for islanding operation of large-scale power systems using OBDD-based methods

System splitting problem (SS problem) is to determine proper splitting points (or called splitting strategies) to split the entire interconnected transmission network into islands ensuring generation/load balance and satisfaction of transmission capacity constraints when islanding operation of a system is unavoidable. For a large-scale power system, its SS problem is very complicated in general because a combinatorial explosion of strategy space happens. This paper mainly studies how to find proper splitting strategies of large-scale power systems using an ordered binary decision diagrams (OBDD)-based three-phase method. Then, a time-based layered structure of the problem solving process is introduced to make this method more practical. Simulation results on IEEE 30- and 118-bus networks show that by this method, proper splitting strategies can be given quickly. Further analyses indicate that this method is effective for larger-scale power systems.

Hierarchical Clustering Using Non-Greedy Principal Direction Divisive Partitioning

We present a non-greedy version of the recently published Principal Direction Divisive Partitioning (PDDP) algorithm. The PDDP algorithm creates a hierarchical taxonomy of a data set by successively splitting the data into sub-clusters. At each level the cluster with largest variance is split by a hyper-plane orthogonal to its leading principal component. The PDDP algorithm is known to produce high quality clusters, especially when applied to high dimensional data, such as document-word feature matrices. It also scales well with both the size and the dimensionality of the data set. However, at each level only the locally optimal choice of spitting is considered. At a later stage this often leads to a non-optimal global partitioning of the data. The non-greedy version of the PDDP algorithm (NGPDDP) presented in this paper address this problem. At each level multiple alternative splitting strategies are considered. Results from applying the algorithm to generated and real data (feature vectors from sets of text documents) are presented. The results show substantial improvements in the cluster quality.

Factorization of analytic functions by means of Koenig's theorem and Toeplitz computations

By providing a matrix version of Koenig's theorem we reduce the problem of evaluating the coefficients of a monic factor r(z) of degree h of a power series f(z) to that of approximating the first h entries in the first column of the inverse of an \(n\times n\) Toeplitz matrix in block Hessenberg form for sufficiently large values of n. This matrix is reduced to a band matrix if f(z) is a polynomial. We prove that the factorization problem can be also reduced to solving a matrix equation \(\phi(X)=0\) for an \(h\times h\) matrix X, where \(\phi\) is a matrix power series whose coefficients are Toeplitz matrices. The function \(\phi\) is reduced to a matrix polynomial of degree 2 if f(z) is a polynomial of degreeN and \(h\geq N/2\). These reductions allow us to devise a suitable algorithm, based on cyclic reduction and on the concept of displacement rank, for generating a sequence of vectors \(\vec{v}^{(2^j)}\) that quadratically converges to the vector \(\vec{v}\) having as components the coefficients of the factor r(z). In the case of a polynomial f(z) of degree N, the cost of computing the entries of \(\vec{v}^{(2^j)}\) given \(\vec{v}^{(2^{j-1})}\) is \(O(N\log N+\theta(N))\) arithmetic operations, where \(\theta(N)=O(N\log^2 N)\) is the cost of solving an \( N\times N\) Toeplitz-like system. In the case of analytic functions the cost depends on the numerical degree of the power series involved in the computation. From the numerical experiments performed with several test polynomials and power series, the algorithm has shown good numerical properties and promises to be a good candidate for implementing polynomial root-finders based on recursive splitting strategies. Applications to solving spectral factorization problems and Markov chains are also shown.

Computer Aided Analysis of Split and Mix Combinatorial Libraries.

Combinatorial chemistry using split and pool synthesis involves making and testing mixtures of compounds in pools which are subsets of the larger compound collection. These subsets are created during the synthesis of the collection through a resin splitting and mixing method. Tests are conducted on each of the final pools of mixtures and the individual compounds within a mixture of interest are then identified through some deconvolution scheme, originally involving selective re-synthesis. It is possible that different schemes for splitting and mixing will have different consequences on the overall effort necessary to deconvolute interesting mixtures. The evaluation of different protocols of splitting and mixing involves consideration of more possibilities than can be exhaustively or optimally determined manually in a realistic time frame for most compound collections. We present herein a computational scheme to aid in this analysis. The approach exhaustively examines possible splitting and mixing strategies for the interrelated values of total library size, number of combinatorial steps, number of reaction vessels, and number of compounds per final pool. Weighting factors may be introduced into the various steps. The resulting complete list of splitting and mixing options is scored based on a variable weighting strategy for the total effort of synthesis and deconvolution. The results indicate the splitting/mixing strategy used has an impact on overall efficiency and should be considered in the design of compound libraries.

Triangulation as splitting in the service of ambivalence

Ambivalence mastery is postulated as a primary dynamic in triangulation, by appealing to splitting and other defense mechanism strategies in synthesizing incompatible affect. The rationale of admissible triangles in balance theory is critically evaluated, and is elaborated in terms of directional vectors and the interpretation of the triangle as a transformed variant of the double bind. Using an illustrative case presentation where an adolescent was instrumental in forming a coalition with his father against an uncle, a theoretical model is developed reconceptualizing various family systems tenets and addressing inconsistencies in hypothesized mechanisms. Ambivalence is analyzed in terms of transference and as a prerequisite of triangulation, the role of the triangulated in relational stability is examined, and the dyad/triad evolution is elaborated. The model is then related to the basic theoretical positions in family systems literature.

Box-Splitting strategies for the interval Gauss-Seidel step in a global optimization method

We consider an algorithm for computing verified enclosures for all global minimizersx * and for the global minimum valuef *=f(x *) of a twice continuously differentiable functionf:ℝ n →→ within a box [x]∈I→. Our algorithm incorporates the interval Gauss-Seidel step applied to the problem of finding the zeros of the gradient off. Here, we have to deal with the gaps produced by the extended interval division. It is possible to use different box-splitting strategies for handling these gaps, producing different numbers of subboxes. We present results concerning the impact of these strategies on the interval Gauss-Seidel step and therefore on our global optimization method. First, we give an overview of some of the techniques used in our algorithm, and we describe the modifications improving the efficiency of the interval Gauss-Seidel step by applying a special box-splitting strategy. Then, we have a look on special preconditioners for the Gauss-Seidel step, and we investigate the corresponding results for different splitting strategies. Test results for standard global optimization problems are discussed for different variants of our method in its portable PASCAL-XSC implementation. These results demonstrate that there are many cases in which the splitting strategy is more important for the efficiency of the algorithm than the use of preconditioners.