Packet classification activity performed by a FireWall (FW) introduces high latency in network communications due to the computation time required to check whether any packet matches one of the FW ...rules. Such a classification process is done by sequentially checking the list of rules until a match is found or the end of the list is reached. Given the complexity of FW rules in some environments, this latency could become relevant. This problem is addressed by ordering the list of FW rules to minimize the classification latency, where the rules with higher activation frequencies are placed accordingly starting from the top of the list. This is not always feasible because dependency constraints between rules could exist: swapping the positions of dependent rules results in a loss of the integrity of the implemented security policy. For this reason, the FW rule ordering problem belongs to the realm of constrained combinatorial optimization.
This paper proposes a two-stage algorithm to address this problem. The first stage performs an innovative topological sorting algorithm aimed at finding an optimal ordering for the constrained rules, taking into account the fact that rule activation frequencies are influenced by inter-packet arrival time, which typically obeys Zipf's law. The second stage employs a genetic algorithm to find the optimal ordering of all rules within the list. The proposed approach is evaluated using different filtering lists of different complexity provided by ClassBench. A comparison with other state-of-the-art algorithms addressing the same problem is performed. Furthermore, the performance analysis is extended employing an exact optimization method. The results obtained show the effectiveness of the proposed algorithm in minimizing packet classification latency, while a short reordering time is required.
•This paper presents an innovative two-stage algorithm to solve the firewall rule ordering optimization problem.•The first stage employs an innovative topological sort algorithm capable of identifying the high activation frequency rules.•The second stage finds the overall optimal solution by applying a genetic algorithm.•The proposed algorithm is effective in minimizing packet classification latency, while requiring a short reordering time.
Complex oxides with pyrochlore and fluorite phases offer several advantages for the Immobilization of actinides or high-level radioactive wastes. In this report, we present the different behavior of ...structural ordering/crystallinity of Gd2Zr2O7 (GZO) ceramics upon sintering at two different temperatures (1400°C–1500 °C). XRD and Raman spectroscopy studies revealed the enhancement of structural ordering/crystallinity with the increase of sintering temperature. Further, the ion irradiation experiments using 100 MeV iodine at the fluence of 1.0 × 1014 ions/cm2 were performed to investigate the radiation effects on both GZO ceramics. The irradiation studies insinuate that the GZO ceramic sintered at 1500 °C possesses relatively better radiation resistance than GZO ceramic sintered at 1400 °C. The variation in the radiation resistance response of GZO ceramics seems associated with the different degrees of structural ordering. These results suggest the role of structural ordering in the radiation resistance response of GZO ceramics. The relatively better radiation tolerance of GZO15 ceramic with some extant pyrochlore phase ordering may be suitable for applications in harsh environments.
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Nikiforov defined the Aα-matrix of a graph G as Aα(G)=αD(G)+(1−α)A(G), where α∈0,1, D(G) and A(G) are the diagonal matrix of degrees and the adjacency matrix respectively. The largest eigenvalue of ...Aα(G) is called the Aα-spectral radius of G, denoted by ρα(G). In this paper, we first give an upper bound on ρα(G) of a connected graph G with fixed size m≥3k and maximum degree Δ≤m−k, where k is a positive integer. For two connected graphs G1 and G2 with size m≥4, employing this upper bound, we prove that ρα(G1)>ρα(G2) if Δ(G1)>Δ(G2) and Δ(G1)≥2m3+1. As an application, we determine the graph with the maximal Aα-spectral radius among all graphs with fixed size and girth. Our theorems generalize the recent results for the signless Laplacian spectral radius of a graph.
In this article we address specific inventory management decisions with transportation cost consideration in a multi-level environment consisting of a supplier–warehouse–retailers. We develop two ...models – namely, decentralized ordering model and centralized ordering model to investigate the effect of collective ordering by retailers on the total inventory cost of the system. A numerical study shows that the proposed model is robust and generates reasonable cost savings. The models have potential in several multi-level applications such as fresh or frozen food delivery to stores of different supermarkets or the supply of medicine to a number of hospitals from a wholesaler.
After a zero temperature quench, we study the kinetics of the one-dimensional Ising model with long-range interactions between spins at distance r decaying as r−α, with α≤1. As shown in our recent ...study (Corberi et al., 2021) that only a fraction of the non-equilibrium trajectories is characterised by the presence of coarsening domains while in the remaining ones the system is quickly driven towards a magnetised state. Restricting to realisations displaying coarsening we compute numerically the probability distribution of the size of the domains and find that it exhibits a scaling behaviour with an unusual α-dependent power-law decay. This peculiar behaviour is also related to the divergence of the average size of domains with system size at finite times. Such a scenario differs from the one observed when α>1, where the distribution decays exponentially. Finally, based on numerical results and on analytical calculations we argue that the average domain size grows asymptotically linearly in time.
Due to the prevalence of supply disruptions disturbing supply chain and logistics operations, a firm should tackle such disruptions using appropriate approaches. In this research work, a ...dual-sourcing approach is applied by a firm. The main decision regarding the firm sourcing from two unreliable suppliers is to derive an optimal ordering policy that maximizes the firm's expected profit. Considering the stochastic ordering yield bridges a gap in the literature. The firm's expected profit function is analytically formulated, and the viability of the developed mathematical expression is illustrated using numerical experiments and sensitivity analyses. Through the sensitivity analyses, the importance of considering the stochastic ordering yield is confirmed, as the optimal ordering policy varies on the variance of the ordering yield. Furthermore, failing to consider the stochastic ordering yield leads to incorrect conclusions regarding the optimal ordering policy; in addition, the increase in the variance of the ordering yield prevents the firm from benefiting from incremental profit.
This paper investigates the queue-dependent service rates(QDSR) in the stochastic queueing-inventory system(SQIS). This SQIS consists a single server service channel, S number of inventories, and a ...finite queue. An arriving customer gets the service immediately if the server is free and there exists a positive stock in the SQIS. When the server is busy, they have to wait in the finite queue. Suppose they find that the waiting hall is full, either they leave the system or enter into an infinite orbit under the Bernoulli trial. The service rate of any arrival is dependent on the number of customers in the queue at present. The orbital customer can compete for the service only through joining into the waiting hall based on the classical retrial policy. Whenever the number of inventories in SQIS is reached a certain limit s, the replenishment of Q(=S−s) items is placed. Due to the structure of rate matrix, the stability analysis, minimal non-negative solutions of the quadratic systems are derived through the Neuts matrix-geometric approximation(MGA). Further, the waiting time distribution(WTD) of arrival and necessary system characteristics are derived. Finally, adequate numerical examples are presented to highlight the proposed SQIS.
We have investigated magnetic ordering in the heavy lanthanide terbium (Tb) for pressures up to 70 GPa and temperatures down to 20 K by synchrotron x-ray diffraction at the Advanced Photon Source, ...Argonne National Laboratory. The x-ray diffraction studies were complemented by neutron diffraction studies at the Spallation Neutron Source, Oak Ridge National Laboratory. We focused on the higher-pressure phases of Tb, such as the double hexagonal close-packed (dhcp, above 16 GPa), distorted face-centered cubic (hR24, above 30 GPa), and orthorhombic (oF16, above 51 GPa) phases. We observed the phenomenon of spontaneous magnetostriction in the dhcp and hR24 phases, where magnetic ordering at low temperatures gives rise to subtle splitting in x-ray diffraction peaks. The neutron diffraction study of the dhcp phase at 20 GPa revealed magnetic peaks that can be assigned a propagation vector k=(12,0,12), and a magnetic ordering temperature that is consistent with the magnetostriction effect observed with x-ray diffraction. The high-pressure and low-temperature x-ray diffraction study at 70 GPa in the collapsed oF16 phase did not show any evidence of magnetostriction, indicating a significant decrease in the magnetic moment of the 4f-shell due to band broadening at ultra-high compression.
Now, 20 years after our article “Bordering, Ordering and Othering”, the editorial team of TESG has asked me to look back on its formation, and to comment on the appraisals of its continued relevance ...and influence offered by Anssi Paasi, Bastian Vollmer, James Scott and Chiara Brambilla in this Forum. To this end, I will first explain what the inspiration was for our essay and will shortly revisit the geopolitical triadic frame that we proposed; then, I will discuss the reflections of the commentators while briefly analyzing how the field of border studies has developed; and lastly, I will look ahead and offer, also using their reflections, a brief research agenda to address present and upcoming b/ordering and othering challenges.
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