Bound Approach Research Articles

TNT equivalency analysis of specific impulse distribution from close-in detonations

Detonation of a high explosive close to a structural component results in a blast load that is highly localized and nonuninform in nature. Prediction of structural response and damage due to such loads requires a detailed understanding of both the magnitude and distribution of the load, which in turn are a function of the properties and dimensions of the structure, the standoff from the charge to the structure, and the composition of the explosive. It is common to express an explosive as an equivalent mass of TNT to facilitate the use of existing and well-established semi-empirical methods. This requires calculation of a TNT equivalency factor (EF), that is, the mass ratio between the equivalent mass of TNT and the explosive mass in question, such that a chosen blast parameter will be the same for the same set of input conditions aside from explosive type. In this paper, we derive EF for three common explosives: C4, COMP-B, and ANFO, using an equivalent upper bound kinetic energy approach. A series of numerical simulations are performed, and the resultant magnitudes and distributions of specific impulse are used to derive the theoretical upper bound kinetic energy that would be imparted to a flexible target. Based on the equivalent mass of TNT of each explosive, which is required to impart the same kinetic energy for a given target size and standoff distance as of TNT, the EF is calculated. It is shown that in the near-field, the EFs are non-constant and are dependent on both standoff and target size. The results in the current study are presented in a scaled form and can be used for any practical combination of charge mass, distance from the charge to the target, target size, thickness, and density.

Chlorinated paraffins in baby food from the German market

Infant formula and baby cereal are products specifically intended for a vulnerable consumer group and should therefore be strictly controlled. In this study, we analysed 21 infant formula and 10 instant baby cereal samples for the presence of chlorinated paraffins (CPs) and estimated dietary exposure to these compounds. Results covered short chain chlorinated paraffins (SCCPs, globally restricted as persistent organic pollutants in 2017) and medium chain chlorinated paraffins (MCCPs, currently used in high quantities). Of the 21 infant formula and 10 instant baby cereal samples, 45% of SCCP results and 94% of MCCP results were below the limit of quantification. Most positive detections were in the range of 25–100 ng/g lipids CPs, and only three samples contained SCCPs at >100 ng/g lipids. The SCCP homologue patterns were shifted to shorter chain lengths (C10 usually predominant) which indicated that CPs were partly removed compared to the normal pattern in food items. Calculated daily exposures for infant formula for 3-month-olds ranged from 97 to 360 ng/kg bw/day for SCCPs using the upper bound approach. The SCCP exposure was lower than data from European pooled human milk samples by a factor of two.

Numerical upper bounds to the ultimate load bearing capacity of three‐dimensional reinforced concrete structures

ABSTRACTThis contribution is addressing the ultimate limit state design of massive three‐dimensional reinforced concrete structures based on a finite‐element implementation of yield design theory. The strength properties of plain concrete are modeled either by means of a tension cutoff Mohr Coulomb or a Rankine condition, while the contribution of the reinforcing bars is taken into account by means of a homogenization method. This homogenization method can either represent regions of uniformly distributed steel rebars smeared into the concrete domain, but it can also be extended to model single rebars diluted into a larger region, thereby simplifying mesh generation and mesh size requirements in this region. The present paper is mainly focused on the implementation of the upper bound kinematic approach formulated as a convex minimization problem. The retained strength condition for the plain concrete and homogenized reinforced regions are both amenable to a formulation involving positive semidefinite constraints. The resulting semidefinite programming problems can, therefore, be solved using state‐of‐the‐art dedicated solvers. The whole computational procedure is applied to some illustrative examples, where the implementation of both static and kinematic methods produces a relatively accurate bracketing of the exact failure load for this kind of structures.

Sequential dynamic event recommendation in event-based social networks: An upper confidence bound approach

In recent years, there have been some platforms that have focused on recommending commodities or events to users using event-based social networks (EBSNs). Some studies have attempted to find the optimal recommendation sequence of these items, assuming that the sequence stops once the user accepts one recommendation or the item list runs out. However, in reality, social media platforms will not stop recommending different commodities or social events to users until the user becomes bored and abandons the platform. Since it is 5 to 25 times more difficult to attract a new user than to retain an old one,11https://hbr.org/2014/10/the-value-of-keeping-the right-customers. it would be helpful if the platform could determine when to stop making recommendations. In this work, we investigate the problem of sequential dynamic event recommendation with feedback (SDERF), where the platform continues recommending events even when the user has accepted one that is satisfactory. We first model the SDERF problem and provide two variants, namely, an online learning model with/without contextual information. Then, we apply an upper confidence bound (UCB) approach with an expected regret polynomial in the number of events and rounds. Finally, we evaluate the performance of our proposed algorithms using both real and synthetic datasets.

Visual programming for structural assessment of out-of-plane mechanisms in historic masonry structures

This work aims at proposing a novel procedure for the seismic assessment of historic masonry structures which is computationally efficient and does not rely on destructive material tests. Digital datasets describing the geometric configuration of historic masonry structures are employed to automatically generate a non-linear Finite Element (FE) model and investigate on possible collapse modes. A configuration of failure surfaces is therefore detected through the Control Surface Method (CSM), which is here proposed for the first time. In a following step of the analysis, structural macroblocks are identified, whereas an upper bound limit analysis approach is employed to estimate the structural capacity of the structure. Genetic Algorithms are also employed to detect the actual failure mode for the structure. The procedure is implemented into a visual coding environment, which allows one to parametrically explore all possible failure surfaces and immediately visualize the effects of the user assumptions. This is particularly suited to support a decisions-making process which strongly relay on engineering judgement. The procedure is validated by the analysis of two benchmark cases, whose results are presented and discussed.

The Dynamic Effects of Terrorism on Tourism: A Bound Testing Co-integration Approach

Tourism industry is considered a key driver promoting socioeconomic development in under development economy, but there are several factors which hindering this development. The terror incidence in swat valley have severely affected tourism industry of the area. Terrorism is a growing hazard across the globe with severs socio-economic consequences. Pakistan is also playing it’s was against terrorism that it has affected its various economic activities including tourism. During the first decade of the ongoing century, northern mountainous area of Khyber Pakhtunkhwa, which was famous for tourism, was badly affected by incidences of terror2. The objective of this research work is to estimate the impact of terror incidents on domestic tourism in Pakistan, Khyber Pakhtunkhwa, Swat Valley (TA –domestic visitors’ arrivals).The current research is an effort to evaluate the short-term and long-term association between events of terror and domestic visitation. Primary data was collected using stratified random sampling techniques and interview method and secondary data was taken from various sources to evaluate the model. Auto Regressive Distributive Lag (ARDL) model is used to evaluate the data. The ARDL bound test confirms the co-integration between terror incidents and tourism. Additionally, the examined findings undoubtedly ensure the negative short-term and long-term impact of events of terror on domestic tourism in the study area.

Preparation of rivet shape head from sintered aluminum specimen at varying strain rates by cold forging

Nowadays industries are taking strength enhancement and weight reduction its main criteria’s for selecting any material. This paper analyses the process of slow speed, shape heading forging where the initially circular porous aluminum powder specimen fixed by one of its ends, is headed into a circular shaped head rivet by appropriate yield criterion, friction law and using an upper bound approach. For the relative average forging pressure of the specimen for different strain intensity, a mathematical model was formulated. The specimens were prepared and subjected to upset rivet head forging process for strain rates of 1.5, 50, 100 and 150 mm/min under lubricated end conditions. Parametric analysis showing deviation of the average forging pressure with percentage reduction in height during rivet head forging process was done graphically. Theoretically and experimentally obtained values of forging load versus percentage reduction in height of the specimen during the process were plotted and a satisfactory equivalence was perceived. Effects of strain rate on load forging during the process of forming the circular rivet head versus percentage height reduction were analyzed and critically addressed.

Determination of Wide Burnishing Energy-Force Parameters based on Constructing the Kinematically Admissible Velocity Field

Processing technology using productive surface plastic deformation (SPD) was developed and is known as “wide burnishing” (WB). The mechanics of new WB technology differs from classic SPD technologies (rolling or burnishing). For example, force, applied during burnishing, is equal to 150–300 N, but for WB it is equal to 2500–5000 N due to implementing this process in mass production, characterized with limited processing time (3–4 turns of the work piece). WB also has a high degree of deformation due to a multiple deformation passes. An analytical study of burnishing with the upper bound approach method energy-force parameters was carried out. Its results were compared with the results of finite elements analysis in Deform 2D and with experimental data. Field of reasonable burnishing parameters, assuring minimum surface roughness, was determined experimentally.

Design method for quantifying embankment safety against lateral spreading and determining contribution of basal reinforcements

This study proposes an analytical method for the calculation of the safety factor against lateral spreading in embankments, both for cases with and without basal reinforcement. Hence, a new limit equilibrium approach is presented based on the lower bound plasticity theorem, which allows the computation of the required distribution of stresses along presumed slip surfaces at the limit state. Comparing the required distribution of stresses with the available resistances, the safety factor in the absence of basal reinforcement is calculated. If the safety factor is unsatisfactory, basal reinforcement can be introduced and its contribution to stability quantified. The lower bound approach allows the computation of mobilized resistance along the reinforcement. Accordingly, the proposed method allows the calculation of the safety factor against lateral spreading for problems involving basal reinforcements. Finally, the proposed method is compared with well-established methods in literature. Results suggest that the proposed method is reliable, practical, and applicable to safe and economical designs.

Optimally solving a versatile Traveling Salesman Problem on tree networks with soft due dates and multiple congestion scenarios

This paper considers a versatile Traveling Salesman Problem (TSP) on tree networks with soft due date restrictions. Data unreliability is handled by introducing multiple congestion scenarios. The objective function sums up customizable monotonous cost assessments of the scenario-dependent total tardiness. Due to its generality, this covers a versatile application of different concepts including several robustness issues. Various complexity results are derived for the minimization of total tardiness: While the problem is proven to be at least binary NP-hard in all cases, strongly NP-hardness is shown if either the number of congestion scenarios or the number of roads are allowed to increase linearly with the number of requests. The same applies if non-zero unloading times occur. In order to efficiently solve the problem, a best-first Branch&Bound approach is proposed that attains a pseudo-polynomial running time if none of the three aforementioned cases applies. The Branch&Bound approach is evaluated by a computational study.

Micromechanics Characterization on the Lower Bound Young’s Moduli of Composite Materials Measured from Nanoindentation

The measurements of the through-thickness Young’s moduli of composite materials are important, but they were not systematically reported because of the complexity. In this paper, a lower bound characterization approach for the Young’s moduli using nanoindentation is proposed based on contact mechanics and micromechanics analysis. This approach was applied to grid nanoindentation of a glass-fiber composite material system, and the estimated lower bound was around 40% lower than the directly measured Young’s modulus of the same composite system using Hertz’s contact law. Therefore, the proposed approach provides a conservative measurement if the actual through-thickness Young’s modulus is not available. This approach is helpful for nanoindentation users without comprehensive knowledge of micromechanics and contact mechanics to conduct complicated nanoindentation experiments for composite materials.

Modeling and Analysis of Wireless Cyberphysical Systems Using Stochastic Methods

Wireless mesh network control systems (WMNCSs) are typical Cyberphysical Systems (CPSs) widely used in industries that need to meet stringent performance requirements. These WMNCSs are characteristic of stochasticity at different levels as system behavior, network performance, and wireless signal propagation, which grievously increases the difficulties of system modeling and analysis. In this paper, we propose a three-layered modeling framework to capture the stochastic properties of WMNCSs at different levels with stochastic hybrid system (SHS), stochastic network calculus (SNC), and physical layer models. We also bridge the gaps between these methods with an upper bound approach. All the efforts give us a methodology of modeling and analysis WMNCSs with stochastic methods, so we can know how the factors as channel conditions, network topology, etc. affect the stability and performance of the system. To the best of our knowledge, it is the first work that provides such a unified and flexible framework to model and analyze WMNCSs with stochastic methods.

Financial Development and Bioenergy Consumption in the EU28 Region: Evidence from Panel Auto-Regressive Distributed Lag Bound Approach

This paper investigates the relationship between financial development and bio-energy consumption in the European Union (EU28) countries for the period from 1990 to 2013 through the panel autoregressive distributed lag (ARDL) approach and causality analysis. The empirical results show that financial development shows a significant positive impact, at a 1% statistical level, on bio-energy consumption for the EU28 during the studied period. In developing countries, the financial market indicator affects bio-energy consumption outgrowth positively and significantly at a 1% statistical level. For developed countries, there is a positive influence of financial institutions and financial market indicators on bio-energy consumption growth at the 1% and 10% levels, respectively. The study concludes that there is a significant relationship between the consumption of bio-energy and financial development factors. The study provides recommendations that are useful when formulating policy related to energy consumption and the promotion of bio-energy consumption. Financial development and economic outgrowth show a significant influence on the outgrowth of bio-energy consumption at a 1% statistical level.

Media‐based single‐symbol generalized spatial modulation

SummarySingle‐symbol generalized spatial modulation (GSM) improves upon the limitation of spatial modulation (SM) by reducing the number of required transmit antennas to achieve high data rates. In this paper, we investigate the application of media‐based modulation (MBM) based on radio frequency mirrors to single‐symbol GSM, with the aim of improving error performance. The theoretical average bit error probability of the proposed scheme is derived, employing a lower bound approach and used to validate the Monte Carlo simulation results. Finally, the effect of optimal and suboptimal mirror activation pattern selection employing Euclidean distance and channel amplitude coupled with antenna correlation is investigated for the proposed media‐based single‐symbol GSM system. The Monte Carlo simulation results obtained demonstrate a significant improvement over the conventional SM, GSM, and media‐based SM (MB‐SM) schemes in terms of error performance and spectral efficiency.

Pseudo-static analysis of cantilever retaining walls using upper bound limit analysis approach

Given the extensive utilization of cantilever retaining walls in construction and development projects, their optimal design and analysis with proper attention to seismic loads is a typical engineering problem. This research presents a new algorithm for pseudo-static analysis of retaining walls employing upper bound method. The algorithm can be utilized to design and check the external and internal stability of the wall based on the proposed mechanism. One of the main features of this algorithm is its ability to determine the critical condition of failure wedges, the minimum safety factor and maximum force acting on the wall, as well as the minimum weight of the wall, simultaneously, by effectively using the multi-objective optimization. The results obtained by the proposed failure mechanisms show that, while using the upper bound limit analysis approach, the active force should be maximized concurrent with optimizing the direction of the plane passing through the back of the heel. The present study also applies the proposed algorithm to determine the critical direction of the earthquake acceleration coefficient. The critical direction of earthquake acceleration coefficient is defined as the direction that maximizes the active force exerted on the wall and minimizes the safety factor for wall stability. The results obtained in this study are in good agreement with those of similar studies carried out based on the limit equilibrium method and finite element analysis. The critical failure mechanisms were determined via optimization with genetic algorithm.

Evaluation of mycotoxins and their estimated daily intake in popcorn and cornflakes using LC-MS techniques

The occurrence of 11 mycotoxins in samples of popcorn and cornflakes was evaluated by liquid chromatography electrospray ionization tandem mass spectrometry (LC-MS/MS), using dynamic multiple reaction monitoring. This quick, easy, cheap, effective, rugged and safe (QuEChERS) method was modified and provided good analytical results (recoveries ranged from 79 to 119%, RSDs <21% and LOQs below the established maximum level). Popcorn samples were contaminated with fumonisins, aflatoxin B1, neosolaniol and T-2 toxin, with mean concentrations of 592, 10.2 and 10.2 μg kg−1, respectively, while cornflake samples were contaminated with only T-2 (mean 11.2 μg kg−1). The co-occurrence of fumonisin B1+ aflatoxin B1 was observed in 52% of popcorn samples and was not observed in cornflake samples. The estimated intake for the Brazilian population of total fumonisins and T-2 toxin for popcorn as the upper bound approach were 0.0051 and 0.00004 μg kg −1 bw day −1, respectively, and for the 99th percentile were 0.1943 and 0.0014 μg kg −1 bw day −1, respectively, suggesting a low risk of ingestion. However heavy consumers may be exposed to a potential risk due to fumonisins (upper bound of 4.6 μg kg−1 bw day−1).

Physical-Layer Network Coding Based Throughput-Optimal Transmission for Bidirectional Traffic

In this study, we develop a physical-layer network coding based throughput-optimal transmission scheduling policy, which we call network coding aware maximum differential backlog (NCMDB), and demonstrate its throughput optimality. As the proposed policy requires an NP-hard network-wide centralized algorithm to determine the optimal transmission schedule, we propose a distributed NCMDB based on link prioritization (D-NCMDB) as a lower bound approach. We further propose a bidirectionality-aware route establishment scheme for the best application of the NCMDB and D-NCMDB policies. Simulations confirm that compared to the signal-to-interference-based interference avoidance transmission approach and random maximal physical-layer network coding approach, the proposed D-NCMDB scheme offers $48\%$ and $27\%$ increased throughput, $78\%$ and $63\%$ reduced access delay, and $80\%$ and $20\%$ enlarged stability, respectively. The proposed distributed transmission scheduling scheme can be employed in future communication networks in which both the number of nodes and the amount of interference increase exponentially.

Reliable frequency determination: Incorporating information on service uncertainty when setting dispatching headways

Frequency setting requires the determination of the dispatching headways of all bus lines in a city network and constitutes the main activity in the tactical planning of public transport operations. Determining the dispatching headways of bus services in a city network is a multi-criteria problem that typically involves balancing between passenger demand coverage and operational costs. In this study, the problem of setting the optimal dispatching headways is formulated with the explicit consideration of operational variability issues for mitigating the adverse effects of passenger demand and travel time variations inherent to bus operations. The proposed model for setting the dispatching headways of bus lines considers the demand, headway and travel time variations along every section of each bus route for different times of the day, as well as operational costs, vehicle capacity and fleet size constraints.We first formulate the problem while accounting for the consequences of variability in service operations. The resulting optimization problem is then solved by employing a Branch and Bound approach together with Sequential Quadratic Programming in order to find the optimal dispatching headway for each bus line. Experimental results demonstrate (a) the improvement potential of the base case dispatching headways when considering the service reliability; (b) the sensitivity of the determined dispatching headways to changes in different criteria, such as passenger demand and/or bus running costs, and (c) the convergence accuracy of the proposed solution method when compared to heuristic approaches.

Assessment of the Malaysian tidal stream energy resource using an upper bound approach

In this paper, an upper bound approach is used to determine the maximum power available to tidal stream turbines placed at five sites along the west coast of Peninsular Malaysia. A depth-averaged hydrodynamic model of the Malacca Strait is built and validated against field measurements. Actuator disc theory is then used to introduce rows of tidal stream turbines as line sinks of momentum and to determine the maximum time-averaged power available to rows of both moderately sized and very large turbines, placed strategically at the locations of highest naturally occurring kinetic energy flux. Results suggest that although the Malaysian tidal stream energy resource is not large enough to make a significant contribution to the country’s energy mix, there may yet be opportunities to use low-speed tidal turbines in small-scale and off-grid electricity generation schemes. Methods are described in detail and links to source codes and results are provided to encourage the application of this simple, yet effective resource assessment methodology to other promising tidal energy sites.

A Branch and Bound Approach to System Identification based on Fixed-rank Hankel Matrix Optimization

We consider identification of linear systems with a certain order from a set of noisy input-output observations. We utilize the fact that the system order corresponds to the rank of the Hankel matrix associated with the system impulse response. Then, the system identification problem is formulated as the minimization of the output error subject to a rank constraint on a Hankel matrix. As this problem is non-convex, we propose a branch and bound (BB) solver, which is a powerful tool for solving non-convex problems to optimality. The main ingredients of the proposed BB method are a convex relaxation problem and a local minimizer of the original non-convex problem. We illustrate the promising performance of the proposed scheme in a system identification problem. The results demonstrate the higher accuracy and stability of our method in estimating the true system compared to the standard output error (OE) algorithm.