Terminal Problem Research Articles

A Modified IEEE 802.15.6 Mac Scheme to Enhance Performance of Wireless Body Area Networks in E-Health Applications

The recently released IEEE 802.15.6 standard specifies several physical (PHY) layers and medium access control (MAC) layer protocols for variety of medical and non-medical applications of Wireless Body Area Networks (WBAN). The medical applications of WBAN has several obligatory requirements and constrains viz. high reliability, strict delay deadlines and low power consumption. The standard IEEE 802.15.6 MAC scheme is not able to fulfil the all requirements of medical applications of WBAN. To address this issue we propose an IEEE 802.15.6-based MAC scheme that is the modification of superframe structure, user priorities and access mechanism of standard IEEE 802.15.6 MAC scheme. The proposed superframe has three access phases: random access phases (RAP), manage access phases (MAP) and contention access phase (CAP). The proposed four user priorities nodes access the channel during RAP using CAMA/CA mechanism with a large value of contention window. The proposed MAC scheme uses RTS/CTS access mechanism instead of basic access mechanism to mitigate the effect of hidden and expose terminal problem. Moreover, we develop an analytical model to evaluate the performance of proposed MAC scheme and solve the analytical model using Maple. The results show that the modified IEEE 802.15.6 MAC scheme achieve the better performance in terms of reliability, throughput, average access delay, energy consumption, channel utilization and fairness compared to standard IEEE 802.15.6 MAC scheme in E-health applications.

Existence and Uniqueness of Solution to a Terminal Value Problem of First-Order Differential Equation

The terminal value problem of differential equations has an important application background. In this paper, we are concerned with the terminal value problem of a first-order differential equation. Some sufficient conditions are given to obtain the existence and uniqueness results of solutions to the problem. Firstly, some comparison lemmas are established; secondly, an iterative technique and fixed point method are used to set up the main results; Finally, an example is provided to illustrate the application of the main results.

On a terminal value problem for stochastic space‐time fractional wave equations

This work is to investigate terminal value problem for a stochastic time fractional wave equation, driven by a cylindrical Wiener process on a Hilbert space. A representation of the solution is obtained by basing on the terminal value data and the spectrum of the fractional Laplacian operator (in a bounded domain , ). First, we show the existence and uniqueness of a mild solution in , for a suitable sub‐space of . A limitation of this result is the lack of time continuity at . Second, we study the inverse problem (IP) of recovering when the terminal value data and the source are given. We give an explanation why the time continuity of the solution at could not derived. The main reason comes from unboundedness of a solution operator, so the problem (IP) is then ill‐posed, that is, recovery cannot be obtained in general. Hence, we propose a truncation regularization method with a suitable choice of the regularization parameter. Finally, we present a numerical example to demonstrate our proposed method.

Household investment-consumption-insurance policies under the age-dependent risk preferences

In this paper, we examine the optimal investment-consumption-insurance policies for a wage earner with time-varying risk preferences. The wage earner's objective is to find the optimal investment-consumption-insurance strategies that maximise the expected discounted utilities from intertemporal consumption, legacy and terminal wealth over the uncertain lifetime horizon. Similar to Lichtenstern et al. [Optimal life-cycle consumption and investment decisions under age-dependent risk preferences. Mathematics and Financial Economics, 15, 275–313], by using a separation approach, the problem is divided into two sub-problems, including the consumption-legacy problem and the terminal wealth-only problem. For each sub-problem, the analytical expressions for the optimal strategies and value functions are derived by using the martingale method. In such a way, we obtain the optimal strategies for the original problem by merging the solutions of the two individual problems. Finally, we conduct some numerical experiments to illustrate the effects of some parameters on the optimal strategies and obtain some economic insights.

Simultaneous Allocation and Scheduling of Quay Cranes, Yard Cranes, and Trucks in Dynamical Integrated Container Terminal Operations

We present a dynamical modeling of integrated (end-to-end) container terminal operations using finite state machine (FSM) framework where each state machine is represented by a discrete-event system (DES) formulation. The hybrid model incorporates the operations of quay cranes (QC), internal trucks (IT), and yard cranes (YC) and also the selection of storage positions in container yard (CY) and vessel bays. The QC and YC are connected by the IT in our models. As opposed to the commonly adapted modeling in container terminal operations, in which the entire information/inputs to the systems are known for a defined planning horizon, in this research we use real-time trucks, crane, and container storage operations information, which are always updated as the time evolves. The dynamical model shows that the predicted state variables closely follow the actual field data from a container terminal in Tanjung Priuk, Jakarta, Indonesia. Subsequently, using the integrated container terminal hybrid model, we proposed a model predictive algorithm (MPA) to obtain the near-optimal solution of the integrated terminal operations problem, namely the simultaneous allocation and scheduling of QC, IT, and YC, as well as selecting the storage location for the inbound and outbound containers in the CY and vessel. The numerical experiment based on the extensive Monte Carlo simulation and real dataset show that the MPA outperforms by 3-6% both of the policies currently implemented by the terminal operator and the state-of-the-art method from the current literature.

Inverting the discrete curl operator: A novel graph algorithm to find a vector potential of a given vector field

We provide a novel framework to compute a discrete vector potential of a given discrete vector field on arbitrary polyhedral meshes. The framework exploits the concept of acyclic matching, a combinatorial tool at the core of discrete Morse theory. We introduce the new concept of complete acyclic matchings and we show that they give the same end result of Gaussian elimination. Basically, instead of doing costly row and column operations on a sparse matrix, we compute equivalent cheap combinatorial operations that preserve the underlying sparsity structure. Currently, the most efficient algorithms proposed in literature to find discrete vector potentials make use of tree-cotree techniques. We show that they compute a special type of complete acyclic matchings. Moreover, we show that the problem of computing them is equivalent to the problem of deciding whether a given mesh has a topological property called collapsibility. This fact gives a topological characterization of well-known termination problems of tree-cotree techniques. We propose a new recursive algorithm to compute discrete vector potentials. It works directly on basis elements of 1- and 2-chains by performing elementary Gaussian operations on them associated with acyclic matchings. However, the main novelty is that it can be applied recursively. Indeed, the recursion process allows us to sidetrack termination problems of the standard tree-cotree techniques. We tested the algorithm on pathological triangulations with known topological obstructions. In all tested problems we observe linear computational complexity as a function of mesh size. Moreover, the algorithm is purely graph-based so it is straightforward to implement and does not require specialized external procedures. We believe that our framework could offer new perspectives to sparse matrix computations.

A Reliable Merging Link Scheme Using Weighted Markov Chain Model in Vehicular Ad Hoc Networks.

The vehicular ad hoc network (VANET) is a potential technology for intelligent transportation systems (ITS) that aims to improve safety by allowing vehicles to communicate quickly and reliably. The rates of merging collision and hidden terminal problems, as well as the problems of picking the best match cluster head (CH) in a merged cluster, may emerge when two or more clusters are merged in the design of a clustering and cluster management scheme. In this paper, we propose an enhanced cluster-based multi-access channel protocol (ECMA) for high-throughput and effective access channel transmissions while minimizing access delay and preventing collisions during cluster merging. We devised an aperiodic and acceptable merge cluster head selection (MCHS) algorithm for selecting the optimal merge cluster head (MCH) in centralized clusters where all nodes are one-hop nodes during the merging window. We also applied a weighted Markov chain mathematical model to improve accuracy while lowering ECMA channel data access transmission delay during the cluster merger window. We presented extensive simulation data to demonstrate the superiority of the suggested approach over existing state-of-the-arts. The implementation of a MCHS algorithm and a weight chain Markov model reveal that ECMA is distinct and more efficient by 64.20–69.49% in terms of average network throughput, end-to-end delay, and access transmission probability.

New changes in the labor legislation of Ukraine during the armed aggression of the Russian Federation on the territory of Ukraine

The article examines the current changes in labor legislation, which were adopted by the Verkhovna Rada of Ukraine in March 2022 in connection with the martial law due to the armed aggression of the Russian Federation in Ukraine. The Law of Ukraine “On the organization of labor relations in martial law” is reviewed, the main provisions that are important for the development of labor relations in martial law for both employees and employers are determined.
 Changes in the conclusion of an employment contract for this period are studied in detail. Possibilities of termination of the employment contract on the initiative of both the worker and the employee are studied. The problem of registration and termination of labor relations in those regions of Ukraine where active hostilities are conducted is traced.
 The article focuses on the forms of employment contract for the period of martial law, in particular, the conclusion of an employment contract may be in writing or orally.
 There are changes in wages. From now on, the employer is released from liability for late payment of wages to the employee, if he proves that the reasons for late payment were force majeure, such as hostilities and martial law.
 An innovation such as the suspension of an employment contract, which is possible in connection with military aggression against Ukraine, is being studied in detail. Due to the suspension, it excludes the possibility of employment by the employer and its performance by the employee. It is emphasized that the termination of the employment contract is not the termination of employment with the employee. Attention is drawn to the fact that the employer, under such conditions, is not obliged to pay wages to its employees, and further reimbursement of any payments to employees who were unable to make the employer in connection with the suspension of the employment contract, in full will rely on the aggressor state, namely the Russian Federation. The article also draws attention to the new bill submitted to the Verkhovna Rada of Ukraine in April 2022 on amendments to some laws of Ukraine on the optimization of labor relations in martial law. Emphasis is placed on the new points by which this bill fills in the gaps in the Law №2136.

Modular Termination for Second-Order Computation Rules and Application to Algebraic Effect Handlers

We present a new modular proof method of termination for second-order computation, and report its implementation SOL. The proof method is useful for proving termination of higher-order foundational calculi. To establish the method, we use a variation of semantic labelling translation and Blanqui's General Schema: a syntactic criterion of strong normalisation. As an application, we apply this method to show termination of a variant of call-by-push-value calculus with algebraic effects and effect handlers. We also show that our tool SOL is effective to solve higher-order termination problems.

The impacts of longitudinal separation, efficiency loss, and cruise speed adjustment in robust terminal traffic flow problem under uncertainty

ABSTRACT Minimization of approaching time and maximization of the utilization of air route and airport resources are the two ultimate goals of air traffic control. This research considers arrival sequence and the uncertain arrival times at entry waypoints of flights and investigates the impact of air traffic controller specific parameters in the model. The two-stage optimization framework will first determine a deterministic schedule and optimize the approaching time while considering additional longitudinal separation, efficiency loss from deterministic schedule, and cruise speed adjustment in the second-stage optimization model via sample average approximation. The numerical experiments suggested an efficiency loss of 20%, which can absorb the empirical probabilistic lateness at entry waypoints with the real-world data. The proposed method could determine the estimated average delay time at runways with different settings of additional buffer for longitudinal separation and trade-off parameters between the estimated average delay time and estimated penalty cost of cruise speed adjustment.

Countermeasure to hidden terminal problem considering data rate shift algorithm in wireless LAN

Countermeasure to hidden terminal problem considering data rate shift algorithm in wireless LAN

Xe using the category of “social practice” to study the phenomenon of artiScial termination of pregnancy

The problem of artificial termination of pregnancy remains one of the unsolved problems of our time. The article presents the concept and structural feature of the phenomenon of artificial termination of pregnancy. The traditional approach to the study of the phenomenon, which is based on the category “society”, is considered. The insufficiency of this approach is explained: the limitation of the social aspect of the study of the phenomenon, an incomplete idea of the reasons for its spread. The article analyzes the approach to the study of social reality based on the category “social practice”, which appeared in sociology at the turn of the 1980. The analysis showed that this approach is aimed at studying not the phenomena themselves, but the repeated actions of individuals, the totality of which is a social practice. The article presents the stages of the formation of social practice, its signs, based on which the author came to the conclusion that the set of actions for termination of pregnancy, reproduced by individual individuals, is a social practice, which means that the proposed approach is possible to study the phenomenon of artificial termination of pregnancy. It will make it possible to trace the process of formation of the social practice of artificial termination of pregnancy, to determine its impact on the behavior of an individual and on social subjects; to identify a set of reasons that influence an individual’s decision to terminate pregnancy; which together will lead to the definition and development of more effective methods of regulating the practice of artificial termination of pregnancy.

Hidden terminal aware grouping scheme for IEEE 802.11ah based dense IoT networks

IEEE 802.11ah, a prevalent standard for the Internet of Things, introduces major enhancements to PHY and MAC layer of the legacy standard. One of the significant improvements in IEEE 802.11ah is the restricted access window (RAW) mechanism. The RAW mechanism is a group-based contention technique that limits the contention among the devices by partitioning them into several groups, dividing the channel time into various time slots and assigning each group with a RAW slot. Although the grouping schemes reduce contention among the devices, it eventually leads to hidden terminals in the dense networks. In this article, we propose a hidden terminal aware grouping (HTAG) mechanism to alleviate the hidden terminal problem. The proposed scheme groups the devices based on the SINR and implements a hidden terminal avoidance algorithm to ensure each group with a minimum number of hidden terminals. We present a simple yet accurate analytical model to evaluate the performance of the RAW mechanism with the proposed HTAG scheme in terms of throughput, delay and energy consumption. Results show significant improvement in the performance of the RAW mechanism using the HTAG scheme compared to the state-of-the-art schemes. Finally, all the analytical findings are validated using extensive simulations in ns-3.

Intelligent Scheduling Method for Bulk Cargo Terminal Loading Process Based on Deep Reinforcement Learning

Sea freight is one of the most important ways for the transportation and distribution of coal and other bulk cargo. This paper proposes a method for optimizing the scheduling efficiency of the bulk cargo loading process based on deep reinforcement learning. The process includes a large number of states and possible choices that need to be taken into account, which are currently performed by skillful scheduling engineers on site. In terms of modeling, we extracted important information based on actual working data of the terminal to form the state space of the model. The yard information and the demand information of the ship are also considered. The scheduling output of each convey path from the yard to the cabin is the action of the agent. To avoid conflicts of occupying one machine at same time, certain restrictions are placed on whether the action can be executed. Based on Double DQN, an improved deep reinforcement learning method is proposed with a fully connected network structure and selected action sets according to the value of the network and the occupancy status of environment. To make the network converge more quickly, an improved new epsilon-greedy exploration strategy is also proposed, which uses different exploration rates for completely random selection and feasible random selection of actions. After training, an improved scheduling result is obtained when the tasks arrive randomly and the yard state is random. An important contribution of this paper is to integrate the useful features of the working time of the bulk cargo terminal into a state set, divide the scheduling process into discrete actions, and then reduce the scheduling problem into simple inputs and outputs. Another major contribution of this article is the design of a reinforcement learning algorithm for the bulk cargo terminal scheduling problem, and the training efficiency of the proposed algorithm is improved, which provides a practical example for solving bulk cargo terminal scheduling problems using reinforcement learning.

Cloud‐edge collaboration based peer to peer services redirection strategy for passive optical network

With the increasing number of fibre access users, P2P file sharing download traffic has gradually become one of the enormous bandwidth consumptions for the access network. Localizing traffic could save bandwidth and reduce latency, but it caused optical line terminal (OLT) overload problems. A cloud-edge collaboration technology (IRS-CECT) based P2P redirection strategy is proposed for this problem. OLT assumes the role of the cloud computing centre in the strategy. Optical network unit (ONU) serves as an edge computing node to share traffic load for the cloud computing centre. ONU intercepts the upstream query packets for OLT. This strategy can reduce the problem of OLT overload caused by increasing users. Simulation results indicate that the IRS-CECT strategy can reduce the delay by nearly half and reduce the traffic load on the cloud computing centre OLT.

An exact algorithm for the unrestricted container relocation problem with new lower bounds and dominance rules

The container relocation problem, also known as the block(s) relocation problem, is one of the most studied optimization problems in container terminals. The problem aims at minimizing the total number of relocations for retrieving containers from a storage yard according to a specific order. The purpose of this study is to develop an efficient iterative deepening branch-and-bound algorithm for exactly solving one of the most practical variants of the problem, namely the unrestricted container relocation problem with duplicate priorities, which has received less attention in the literature. To improve the search efficiency of the proposed algorithm, we design two new lower bounds that can be computed quickly to incorporate them into the branch-and-bound algorithm. We also present a set of mutually consistent dominance rules to reduce the search space while avoiding over-pruning. The performance of the proposed algorithm is evaluated by extensive computational experiments on three commonly used benchmark datasets. The results show that the proposed algorithm outperforms the state-of-the-art exact algorithm for the unrestricted container relocation problem with distinct priorities, although our algorithm is applicable to a more general variant of the problem. Moreover, it can still provide competitive results for small- and medium-sized instances under a strict time limit of one second in comparison to existing metaheuristic approaches.

Exact and heuristic methods for the berth allocation problem with multiple continuous quays in tidal bulk terminals

The Berth Allocation Problem (BAP) is a primary seaside operations planning problem in bulk terminals. It consists of allocating quayside space to incoming vessels. In this article, the BAP for multiple continuous quays and dynamic arrivals is considered. The formulation considers the tidal constraints typical to exporting bulk terminals and restrictions regarding each vessel's possible quays. To solve the problem, a mixed-integer linear model is first presented. As the complexity of the problem grows exponentially with the size of the instances, an Iterated Local Search (ILS) approach is proposed to solve industrial-sized instances. The ILS approach works on sequences of vessels that are decoded using a bottom-left constructive heuristic. The initial sequences are obtained using a greedy scheduling heuristic that provides suitable starting solutions, especially for congested terminals. Extensive numerical experiments are carried on randomly generated instances for tidal bulk terminals and reported benchmark sets in literature. The results prove that the proposed ILS can provide good-quality solutions.

Enabling a MAC Protocol with Self-Localization Function to Solve Hidden and Exposed Terminal Problems in Wireless Ad Hoc Networks

Enabling a MAC Protocol with Self-Localization Function to Solve Hidden and Exposed Terminal Problems in Wireless Ad Hoc Networks

Cyclability in graph classes

A subset T⊆V(G) of vertices of a graph G is said to be cyclable if G has a cycle C containing every vertex of T, and for a positive integer k, a graph G is k-cyclable if every set of vertices of size at most k is cyclable. The Terminal Cyclability problem asks, given a graph G and a set T of vertices, whether T is cyclable, and the k-Cyclability problem asks, given a graph G and a positive integer k, whether G is k-cyclable. These problems are generalizations of the classical Hamiltonian Cycle problem. We initiate the study of these problems for graph classes that admit polynomial algorithms for Hamiltonian Cycle. We show that Terminal Cyclability can be solved in linear time for interval graphs, bipartite permutation graphs and cographs. Moreover, we construct certifying algorithms that either produce a solution, that is a cycle, or output a graph separator that certifies a no-answer. We use these results to show that k-Cyclability can be solved in polynomial time when restricted to the aforementioned graph classes.

Colored scheduling scheme for fast and reliable beacon safety messages broadcast in vehicular ad‐hoc networks

SummaryThe beacon transmission method in vehicular networks has to consider the mobility feature of vehicles and use the wireless channel more efficiently in order to broadcast safety‐related beacons with high reliability while respecting strict deadlines. The time division multiple access (TDMA) scheme has been proposed to improve the effectiveness of the IEEE 802.11p CSMA MAC protocol, but it is challenged with access and merging collisions caused by inefficient strategies in allocating time slots and mobile hidden terminal problems. In this paper, we propose colored velocity‐based TDMA (CVTDMA), an original colored scheduling scheme for the broadcast of safety beacons on the control channel. Based on vehicles speed and colors that it assigns to time slots according to their occupation statuses, it mitigates the mobility effect and maximizes the reuse of slots while avoiding collisions. The simulation results show that our protocol uses the wireless channel much more effectively than the default one defined in IEEE 802.11p.