Population size versus runtime of a simple evolutionary algorithm

Evolutionary algorithms (EAs) find numerous applications, and practical knowledge on EAs is immense. In practice, sophisticated population-based EAs employing selection, mutation and crossover are applied. In contrast, theoretical analysis of EAs often concentrates on very simple algorithms such as the (1+1) EA, where the population size equals 1. In this paper, the question is addressed whether the use of a population by itself can be advantageous. A population-based EA that neither makes use of crossover nor any diversity-maintaining operator is investigated on an example function. It is shown that an increase of the population size by a constant factor decreases the expected runtime from exponential to polynomial. Thereby, the best gap known so far is improved from superpolynomial vs. polynomial to exponential vs. polynomial. Moreover, it is proved that the exponential and polynomial runtime bounds occur with a probability exponentially close to one if the population size is a constant (resp., a small polynomial). Finally, a second example function, where only a small population leads to a polynomial runtime, and a hierarchy result on the appropriate population size are presented. The analyses show formally how the population size can lead to different attractors in the search space.     

Real-time compliance control of an assistive joint using QNX operating system

An assistive robot is a novel service robot, playing an important role in the society. For instance, it can amplify human power not only for the elderly and disabled to recover/rehabilitate their lost/impaired musculoskeletal functions but also for healthy people to perform tasks requiring large forces. Consequently, it is required to consider both accurate position control and human safety, which is the compliance. This paper deals with the robot control compliance problem based on the QNX real-time operating system. Firstly, the mechanical structure of a compliant joint on the assistive robot is designed using Solidworks. Then the parameters of the assistive robot system are identified. The software of robot control includes data acquisition and processing, and control to meet the compliance requirement of the joint control. Finally, a Hogan impedance control experiment is carried out. The experimental results prove the effectiveness of the method proposed.     

Generalisation log for managing and utilising a multi-representation spatial database in map production

This paper describes a data model for logging map generalisation process information to facilitate data authentication and update propagation in a multi-representation spatial database environment. Generalisation is modelled as a directed acyclic diagram of prioritised generalisation process instances, which is further divided into independent operations as the atomic functional unit for generalisation. Generalisation parameter values and the roles of features in operations are stored. The full generalisation history of each feature may be traced for data authentication and quality analysis, or for update propagation. This model also includes the design of a feature versioning mechanism. In addition, OSGenLog, a set of platform-independent APIs to create generalisation logs, has been implemented in Gothic object-oriented database management system.     

Line Integration for Rendering Heterogeneous Emissive Volumes

Emissive media are often challenging to render: in thin regions where only few scattering events occur the emission is poorly sampled, while sampling events for emission can be disadvantageous due to absorption in dense regions. We extend the standard path space measurement contribution to also collect emission along path segments, not only at vertices. We apply this extension to two estimators: extending paths via scattering and distance sampling, and next event estimation. In order to do so, we unify the two approaches and derive the corresponding Monte Carlo estimators to interpret next event estimation as a solid angle sampling technique. We avoid connecting paths to vertices hidden behind dense absorbing layers of smoke by also including transmittance sampling into next event estimation. We demonstrate the advantages of our line integration approach which generates estimators with lower variance since entire segments are accounted for. Also, our novel forward next event estimation technique yields faster run times compared to previous next event estimation as it penetrates less deeply into dense volumes.     

Automatically Proving Termination and Memory Safety for Programs with Pointer Arithmetic

While automated verification of imperative programs has been studied intensively, proving termination of programs with explicit pointer arithmetic fully automatically was still an open problem. To close this gap, we introduce a novel abstract domain that can track allocated memory in detail. We use it to automatically construct a symbolic execution graph that over-approximates all possible runs of a program and that can be used to prove memory safety. This graph is then transformed into an integer transition system, whose termination can be proved by standard techniques. We implemented this approach in the automated termination prover AProVE and demonstrate its capability of analyzing C programs with pointer arithmetic that existing tools cannot handle.     

Effective network intrusion detection using stacking-based ensemble approach

The increasing demand for communication between networked devices connected either through an intranet or the internet increases the need for a reliable and accurate network defense mechanism. Network intrusion detection systems (NIDSs), which are used to detect malicious or anomalous network traffic, are an integral part of network defense. This research aims to address some of the issues faced by anomaly-based network intrusion detection systems. In this research, we first identify some limitations of the legacy NIDS datasets, including a recent CICIDS2017 dataset, which lead us to develop our novel dataset, CIPMAIDS2023-1. Then, we propose a stacking-based ensemble approach that outperforms the overall state of the art for NIDS. Various attack scenarios were implemented along with benign user traffic on the network topology created using graphical network simulator-3 (GNS-3). Key flow features are extracted using cicflowmeter for each attack and are evaluated to analyze their behavior. Several different machine learning approaches are applied to the features extracted from the traffic data, and their performance is compared. The results show that the stacking-based ensemble approach is the most promising and achieves the highest weighted F1-score of 98.24%.

     

Superconducting and normal state properties of dilute alloys of LaSn3 containing Nd impurities

The results of an investigation of the superconducting and normal state physical properties of (LaNd)Sn₃ alloys are reported. Superconducting state data are presented describing the depression of the superconducting transition temperature T _cwith Nd impurity concentration, the reduction of the reduced jump in heat capacity C/C ₀ with decreasing reduced superconducting transition temperature T _c/T_c0, and the pressure dependence of T _c. Normal state data for the temperature dependences of the magnetic susceptibility and heat capacity demonstrate the importance of crystalline electric field effects in the physical behavior of (LaNd)Sn₃ alloys and indicate that Nd interimpurity magnetic interactions and possibly a small amount of Nd-Sn antisite disorder are manifested in the experimental results. Theories based on an isotropic exchange depairing model are unable to give a satisfactory account of all of the experimental data, suggesting that the physical properties of(LaNd)Sn₃ alloys may be modified by processes involving the orbital exchange scattering of host conduction electrons by the Nd impurities.Supported by the U.S. Department of Energy under Contract No. Ey-76-S-03-0034-PA227-3.Fellow of the Consejo Nacional de Investigaciones, Cientificas y Tecnicas, de la Republica Argentina; leave from Centro Atomico Bariloche, Bariloche, Argentina.     

Measurements of volatile organic compounds in the earth's atmosphere using proton-transfer-reaction mass spectrometry

Proton-transfer-reaction mass spectrometry (PTR-MS) allows real-time measurements of volatile organic compounds (VOCs) in air with a high sensitivity and a fast time response. The use of PTR-MS in atmospheric research has expanded rapidly in recent years, and much has been learned about the instrument response and specificity of the technique in the analysis of air from different regions of the atmosphere. This paper aims to review the progress that has been made. The theory of operation is described and allows the response of the instrument to be described for different operating conditions. More accurate determinations of the instrument response involve calibrations using standard mixtures, and some results are shown. Much has been learned about the specificity of PTR-MS from inter-comparison studies as well the coupling of PTR-MS with a gas chromatographic interface. The literature on this issue is reviewed and summarized for many VOCs of atmospheric interest. Some highlights of airborne measurements by PTR-MS are presented, including the results obtained in fresh and aged forest-fire and urban plumes. Finally, the recent work that is focused on improving the technique is discussed.     

Structure and catalytic activity characterization of bismuth molybdate catalysts

We present a study of Bi-Mo catalysts prepared from pure oxides (MoO₃ and Bi₂O₃) by solid state reaction methods. The structure characterization by X-ray diffraction shows only the low temperature (koechlinite) and high temperature ((H)) phases in varying proportions depending on the calcination temperature. The carbon monoxide oxidation shows a synergetic effect for mixed oxides as compared to pure oxides. Significant differences in catalytic activity, surface morphology and surface concentration were observed when the molybdenum precursor was changed from molybdenum trioxide to ammonium heptamolybdate in the catalyst preparation.     

A Representation of Fω in LF

We study how the type theory F_ω can be adequately represented in the meta-logical framework Twelf [16]. This development puts special emphasis on the way how terms, types, and kinds are represented in that it uses higher-order abstract syntax to model variable binding and dependent types to model typing constraints. Furthermore our design ensures that only well-typed terms and well-kinded types can be constructed. A possible application of this work lies in the development of safe intermediate languages for compilation.