Simple Cost Function Research Articles

Multiple object tracking using a neural cost function

This paper presents a new approach to the tracking of multiple objects in CCTV surveillance using a combination of simple neural cost functions based on Self-Organizing Maps, and a greedy assignment algorithm. Using a reference standard data set and an exhaustive search algorithm for benchmarking, we show that the cost function plays the most significant role in realizing high levels of performance. The neural cost function’s context-sensitive treatment of appearance, change of appearance and trajectory yield better tracking than a simple, explicitly designed cost function. The algorithm matches 98.8% of objects to within 15 pixels.

Economies of scale in global iron-making

In this paper, we investigate the presence of economies of scale in the global iron-making industry for integrated steel plants, iron making being the first stage in the steel-making process. Iron making depends on basic commodities, such as iron ore, coke and various forms of energy, required in the operation of the blast furnace, which can be classified as essential inputs and used in fixed proportions to produce iron. A generalized Leontief cost function is estimated using panel data for 69 integrated plants, such a specification being appropriate for technologies with essential inputs that are used in fixed proportions in production. A significant scale effect is observed due to the existence of fixed costs and a linear dependence of the cost function on production. Under a simple linear cost function, a rough estimate of the breakeven scale of plant, where costs equal revenue, is 4.5 Mt per year. Competitiveness, as measured by the ratio of plant average cost per tonne to best practice cost per tonne, can be shown to be positively related to the scale of production as well as the cost of essential inputs. Therefore, low-cost producers are also often producers with low raw material costs and production levels below the estimated breakeven scale of operation. Labor costs, although significant, are comparatively less important as a driver towards low costs.

Two arms are better than one: parasite variation leads to combined inducible and constitutive innate immune responses

Parasites represent a major threat to all organisms which has led to the evolution of an array of complex and effective defence mechanisms. Common to both vertebrates and invertebrates are innate immune mechanisms that can be either constitutively expressed or induced on exposure to infection. In nature, we find that a combination of both induced and constitutive responses are employed by vertebrates, invertebrates and, to an extent, plants when they are exposed to a parasite. Here we use a simple within-host model motivated by the insect immune system, consisting of both constitutive and induced responses, to address the question of why both types of response are maintained so ubiquitously. Generally, induced responses are thought to be advantageous because they are only used when required but are too costly to maintain constantly, while constitutive responses are advantageous because they are always ready to act. However, using a simple cost function but with no a priori assumptions about relative costs, we show that variability in parasite growth rates selects for a strategy that combines both constitutive and induced defences. Differential costs are therefore not necessary to explain the adoption of both forms of defence. Clearly, hosts are likely to be challenged by variable parasites in nature and this is sufficient to explain why it is optimal to deploy both arms of the innate immune system.

Investigation of graph edit distance cost functions for detection of network anomalies

Computer networks are becoming ubiquitous. Accurately monitoring and managing the behaviour of these complex and dynamic networks is a challenging task. It has become crucial to develop and employ good network monitoring techniques that assist in identifying and correcting abnormalities that affect network reliability, performance, security and future planning. There has been significant research in the detection of change and anomalous events in computer networks. A recent novel approach represents the logical communications of a periodically observed network as a time series of graphs and applies the graph matching technique, graph edit distance, to monitor and detect anomalous behaviour in the network. To date, only simple cost functions for graph edit operations have been used in application to computer network monitoring. This article investigates simple normalisation and non-linear techniques in the graph edit distance cost function, to improve detection of specific traffic related network anomalies in the computer network domain.

Optimal Task-Dependent Changes of Bimanual Feedback Control and Adaptation

SummaryThe control and adaptation of bimanual movements is often considered to be a function of a fixed set of mechanisms [1, 2]. Here, I show that both feedback control and adaptation change optimally with task goals. Participants reached with two hands to two separate spatial targets (two-cursor condition) or used the same bimanual movements to move a cursor presented at the spatial average location of the two hands to a single target (one-cursor condition). A force field was randomly applied to one of the hands. In the two-cursor condition, online corrections occurred only on the perturbed hand, whereas the other movement was controlled independently. In the one-cursor condition, online correction could be detected on both hands as early as 190 ms after the start. These changes can be shown to be optimal in respect to a simple task-dependent cost function [3]. Adaptation, the influence of a perturbation onto the next movement, also depended on task goals. In the two-cursor condition, only the perturbed hand adapted to a force perturbation [2], whereas in the one-cursor condition, both hands adapted. These findings demonstrate that the central nervous system changes bimanual feedback control and adaptation optimally according to the current task requirements.

Effective and simple EOQ-like solutions for stochastic demand periodic review systems

In this paper we examine a periodic review system under stochastic demand with variable stockout costs. The optimal values for cycle length and amount of safety stock are difficult to obtain because one of the First Order Conditions does not have a closed form solution. However, by using a Taylor series expansion to approximate part of the cost function, we produce a simple cost function structure which is similar to that of deterministic models. We argue that this simple structure is also beneficial to promote the solution in other problems where coordination of cycles is required. To illustrate, we use the joint replenishment problem for multiple items under stochastic demand and suggest simple and efficient solution procedures.

A parameter-space search algorithm tested on a Hodgkin–Huxley model

We demonstrate a parameter-space search algorithm using a computational model of a single-compartment neuron with conductance-based Hodgkin-Huxley dynamics. To classify bursting (the desired behavior), we use a simple cost function whose inputs are derived from the frequency content of the neural output. Our method involves the repeated use of a stochastic gradient descent-type algorithm to locate parameter values that allow the neural model to produce bursting within a specified tolerance. We demonstrate good results, including those showing that the utility of our algorithm improves as the pre-defined allowable parameter ranges increase and that the initial approach to our method is computationally efficient.

Efficient MPEG-2 to H.264/AVC Transcoding of Intra-Coded Video

This paper presents an efficient transform-domain architecture and corresponding mode decision algorithms for transcoding intra-coded video from MPEG-2 to H.264/AVC. Low complexity is achieved in several ways. First, our architecture employs direct conversion of the transform coefficients, which eliminates the need for the inverse discrete cosine transform (DCT) and forward H.264/AVC transform. Then, within this transform-domain architecture, we perform macroblock-based mode decisions based on H.264/AVC transform coefficients, which is possible using a novel method of calculating distortion in the transform domain. The proposed method for distortion calculation could be used to make rate-distortion optimized mode decisions with lower complexity. Compared to the pixel-domain architecture with rate-distortion optimized mode decision, simulation results show that there is a negligible loss in quality incurred by the direct conversion of transform coefficients and the proposed transform-domain mode decision algorithms, while complexity is significantly reduced. To further reduce the complexity, we also propose two fast mode decision algorithms. The first algorithm ranks modes based on a simple cost function in the transform domain, then computes the rate-distortion optimal mode from a reduced set of ranked modes. The second algorithm exploits temporal correlations in the mode decision between temporally adjacent frames. Simulation results show that these algorithms provide additional computational savings over the proposed transform-domain architecture while maintaining virtually the same coding efficiency.

Conditional length distributions induced by the coverage of two points by a Poisson Voronoï tessellation: application to a telecommunication model

The end points of a fixed segment in the Euclidian plane covered by a Poisson Voronoï tessellation belong to the same cell or to two distinct cells. This marks off one or two points of the underlying Poisson process that are the nucleus(i) of the cell(s). Our interest lies in the geometrical relationship between these nuclei and the segment end points as well as between the nuclei. We investigate their probability distribution functions conditioning on the number of nuclei, taking into account the length of the segment. The aim of the study is to establish some tools to be used for the analysis of a telecommunication problem related to the pricing of leased lines. We motivate and give accurate approximations of the probability of common coverage and of the length distributions that can be included in spreadsheet codes as an element of simple cost functions. Copyright © 2006 John Wiley & Sons, Ltd.

A model of protein translation including codon bias, nonsense errors, and ribosome recycling

We present and analyse a model of protein translation at the scale of an individual messenger RNA (mRNA) transcript. The model we develop is unique in that it incorporates the phenomena of ribosome recycling and nonsense errors. The model conceptualizes translation as a probabilistic wave of ribosome occupancy traveling down a heterogeneous medium, the mRNA transcript. Our results show that the heterogeneity of the codon translation rates along the mRNA results in short-scale spikes and dips in the wave. Nonsense errors attenuate this wave on a longer scale while ribosome recycling reinforces it. We find that the combination of nonsense errors and codon usage bias can have a large effect on the probability that a ribosome will completely translate a transcript. We also elucidate how these forces interact with ribosome recycling to determine the overall translation rate of an mRNA transcript. We derive a simple cost function for nonsense errors using our model and apply this function to the yeast ( Saccharomyces cervisiae) genome. Using this function we are able to detect position dependent selection on codon bias which correlates with gene expression levels as predicted a priori. These results indirectly validate our underlying model assumptions and confirm that nonsense errors can play an important role in shaping codon usage bias.

Error quantification of a high-resolution coupled hydrodynamic–ecosystem coastal–ocean model: Part 1 model overview and assessment of the hydrodynamics

We present an assessment of the uncertainties present in a high-resolution (∼7 km horizontal resolution and 20 s-levels in the vertical) coupled hydrodynamic–ecosystem model of the northwest European continental shelf. The models in question are a three-dimensional baroclinic circulation model developed for massively parallel computers (the Proudman Oceanographic Laboratory Coastal–Ocean Modelling System) and a sophisticated ecosystem model, representing the functioning of the ecosystem with 52 state variables (The European Regional Seas Ecosystem Model). In this paper and part 2, which focuses on the ecosystem model, we simulate the period of the North Sea Project (August 1988 to October 1989) and attempt as comprehensive an examination of model uncertainties as the available data permits. We are able to make some degree of assessment for all aspects of the physics model, apart from the turbulence closure scheme, and use a simple cost function to systematically compare the accuracy of different variables. We find some aspects (notably tidal currents and elevation, and sea surface temperature) are well modelled, with RMS errors less than 0.4 standard deviations of the data, whereas some aspects (e.g. residual current speed and salinity) have RMS errors similar to the standard deviation of the data. Improving the residual currents and salinity comparison requires improving several aspects of both the model (forcing and formulation) and observational data (quantity and quality). In addition to directing improvements in the model, this exercise also suggests where data assimilation effort might prove most fruitful. We also demonstrate that this resolution is sufficient to model complex biophysical interaction in both the horizontal (e.g. enhanced production at fronts) and vertical (e.g. mid-water production modulated by the spring–neap cycle).

Rigid-Cluster Models of Conformational Transitions in Macromolecular Machines and Assemblies

We present a rigid-body-based technique (called rigid-cluster elastic network interpolation) to generate feasible transition pathways between two distinct conformations of a macromolecular assembly. Many biological molecules and assemblies consist of domains which act more or less as rigid bodies during large conformational changes. These collective motions are thought to be strongly related with the functions of a system. This fact encourages us to simply model a macromolecule or assembly as a set of rigid bodies which are interconnected with distance constraints. In previous articles, we developed coarse-grained elastic network interpolation (ENI) in which, for example, only C α atoms are selected as representatives in each residue of a protein. We interpolate distance differences of two conformations in ENI by using a simple quadratic cost function, and the feasible conformations are generated without steric conflicts. Rigid-cluster interpolation is an extension of the ENI method with rigid-clusters replacing point masses. Now the intermediate conformations in an anharmonic pathway can be determined by the translational and rotational displacements of large clusters in such a way that distance constraints are observed. We present the derivation of the rigid-cluster model and apply it to a variety of macromolecular assemblies. Rigid-cluster ENI is then modified for a hybrid model represented by a mixture of rigid clusters and point masses. Simulation results show that both rigid-cluster and hybrid ENI methods generate sterically feasible pathways of large systems in a very short time. For example, the HK97 virus capsid is an icosahedral symmetric assembly composed of 60 identical asymmetric units. Its original Hessian matrix size for a C α coarse-grained model is >(300,000) 2. However, it reduces to (84) 2 when we apply the rigid-cluster model with icosahedral symmetry constraints. The computational cost of the interpolation no longer scales heavily with the size of structures; instead, it depends strongly on the minimal number of rigid clusters into which the system can be decomposed.

Closed loop IBC results from CH-53G flight tests

ZF Luftfahrttechnik GmbH (ZFL) has conducted open and closed loop IBC (Individual Blade Control) flight tests with the CH-53G IBC testbed of the German Federal Armed Forces Engineering Center for Aircraft. Over 25 flight hours had been spent in an “open loop” campaign to investigate the positive IBC effects. Early during the flight tests, it became clear that the response of the aircraft to the IBC inputs exceeded the initial expectations. ZFL has expanded the open loop IBC system to enable a closed loop operation for automatic online optimization of the required IBC inputs. The controller design was performed under Matlab/Simulink and automatically implemented on a dSPACE real-time system. The closed loop control system added to the open loop core system extends the existing cascade control structure by an outer control loop. This outer control loop was used to implement different control tasks which were then investigated during the closed loop campaign. The main focus was put on vibration reduction in the fuselage. Further tests have addressed the load reduction potential of IBC. The capabilities of IBC were demonstrated for different single- and multiple-harmonic inputs in different steady and maneuvering flight conditions at different forward speeds. The predicted improvements through the application of more than one frequency could clearly be shown. Different cost functions have been investigated with the controller using single or multiple sensor signals. It turned out that even simple cost functions based on only a few sensor signals were practical since often the not included sensor locations clearly benefited from that particular input. The amplitudes applied by the controller were on the order of 0.1 to 0.5 deg which has underlined the effectiveness of even small blade pitch inputs. The paper gives a brief overview of the architecture of the closed loop system and the implemented control strategies. The main focus is put on the test results gathered during the different closed loop flights. Beside the beneficial vibration reduction also some other IBC effects are discussed.

Potential and limitations of 1D modelling of urban flooding

Urban flooding is an inevitable problem for many cities around the world. In the present paper, modelling approaches and principles for analyses of urban flooding are outlined. The paper shows how urban flooding can be simulated by one-dimensional hydrodynamic modelling incorporating the interaction between (i) the buried pipe system, (ii) the streets (with open channel flow) and (iii) the areas flooded with stagnant water. The modelling approach is generic in the sense that it handles both urban flooding with and without flood water entry into houses. In order to visualize flood extent and impact, the modelling results are presented in the form of flood inundation maps produced in GIS. In this paper, only flooding from local rainfall is considered together with the impact in terms of flood extent, flood depth and flood duration. Finally, the paper discusses the data requirement for verification of urban flood models together with an outline of a simple cost function for estimation of the cost of the flood damages.

Enumeration of periodic tetrahedral frameworks. II. Polynodal graphs

In a previous study, we developed a database of periodic 4-connected graphs [Zeit. Kristallogr. 212 (1997) 768]. The database was built using a symmetry constrained intersite bonding search (SCIBS) method. This method enumerates all possible 4-connected nets within each space group type given the number of unique tetrahedral vertices, n T. Approximately 10 7 graphs were obtained, mostly for n T = 1, 2. n T = 4 was achieved for some space groups that were rich in mirror symmetry. There was a combinatorial explosion of graphs with increasing n T in some space groups, which ultimately limited the method. The uninodal graphs, n T = 1, were refined by simulated annealing. A simple cost function was used that favoured a regular tetrahedral arrangement of neighbouring silicon atoms to emulate zeolite frameworks. Many plausible hypothetical uninodal zeolitic frameworks were reported. Since that report, we have improved the efficiency of the combinatorial search, and extended the range of our graph database to n T = 7 for some high mirror symmetry space groups. We have also implemented a more sophisticated Monte Carlo strategy for imbedding graphs in real space as an SiO 2 composition. Plausible refinements are then further optimized using the GULP program. Presently, there are almost 10 10 graphs in our database, and the number of plausible regular tetrahedral SiO 2 frameworks identified now exceeds 100,000.

Multichannel Blind Deconvolution of Nonminimum-Phase Systems Using Filter Decomposition

In this paper, we present a new filter decomposition method for multichannel blind deconvolution of nonminimum-phase systems. With this approach, we decompose a doubly finite impulse response filter into a cascade form of two filters: a causal finite impulse response (FIR) filter and an anticausal FIR filter. After introducing a Lie group to the manifold of FIR filters, we discuss geometric properties of the FIR filter manifold. Using the nonholonomic transform, we derive the natural gradient on the FIR manifold. By simplifying the mutual information rate, we present a very simple cost function for blind deconvolution of nonminimum-phase systems. Subsequently, the natural gradient algorithms are developed both for the causal FIR filter and for the anticausal FIR filter. Simulations are presented to illustrate the validity and favorable learning performance of the proposed algorithms.

一自由度近似を用いた免震構造物の最適設計

This paper presents a practical optimum design method for base isolated buildings. In this study, first, we propose a simple cost function for a base-isolation story. Then, we present a two-stage optimization problem by dividing a base isolated building into two substructures, the base-isolation story and its upper and lower structures. This allows us to get a closed-form solution to the sub-optimization problem of base-isolation story. The use of the closed form solution makes the proposed method efficient. Design examples demonstrate the validity of the present method.

Estimates of scale economies in the garment industry in Nepal

Using plant level data from 1992 census and from 1997 census of manufacturing establishments in Nepal, a simple cubic cost function and a more general translog cost function are examined for the garment industry of Nepal. Homothetic, homogeneous and Cobb-Douglas cost functions are also estimated by imposing some appropriate restrictions on translog cost function. The study suggests that the industry has an increasing returns to scale over the current production range. Most of the firms have not been able to exploit the economies of scale in this industry.

A technique for the determination of post-yield material properties from the small punch test

The aim of the present work was to determine post-yield material properties from small punch test results, i.e. from the force-displacement curve obtained in such a test. This determination was made by comparing the experimental curve with a large set of previously determined finite element (FE) curves for differing post-yield properties expressed in terms of Ramberg and Osgood parameters. A simple cost function was then used to find the closest FE curve and thus provide an estimate of the post-yield properties. This estimate was then updated using an optimization technique based on the Matlab ‘fminsearch’ function and an interface with the ABAQUS FE code, giving a reliable estimate of the post-yield material properties. The FE analysis and model were validated by comparison with other small punch tests and the FE curves were additionally used to determine von Mises stresses, equivalent plastic strains and displacements. The method used to determine post-yield properties from small specimens has been demonstrated by determining the material properties of stainless steel. The technique is particularly relevant to those steels used in pressure vessels.

Optimization of Electric Thrusters for Primary Propulsion Based on the Rocket Equation

IEPC-01-181 During the last decade, electric propulsion systems have been established for orbit maintenance of satellites. More than 150 spacecrafts are now equipped with almost 400 thrusters for this purpose. The current decade will see the use of electric propulsion for primary propulsion. The purpose of this paper is to determine optimal mission parame ters for these tasks. Depending on the mission profile, ion thrusters, Hall thrusters, thermal arcjets or MPD thrusters are preferable. All electric propulsion systems have in common that they can be operated in a wide range of the specific impulse and that the thrust efficiency and therefore also the specific power of the propulsion system depend strongly on the specific impulse. The optimal specific impulse for a particular mission depends, therefore, on the kind of thruster and the chosen propellant. This paper shows that for MPD, ion, Hall ion and thermal arcjet thrusters the optimal specific impulse for a particular mission can be determined by an optimization which is based on the rocket equation. Using, in addition, a simple cost function, the influence of the cost factors is explained. Finally, the results for a few missions for which electric propulsion systems for primary propulsion have been selected are discussed.