Experimental Implementation and Performance Evaluation of an IoT Access Gateway for the Modbus Extension

This paper presents the relevant aspects regarding the experimental implementation and performance evaluation of an Internet of things (IoT) gateway for the Modbus extension. The proposed Modbus extension specifications are extended by defining the new optimized message format, and the structure of the acquisition cycle for obtaining a deterministic temporal behavior and solutions are presented for the description of devices at the MODBUS protocol level. Three different implementations are presented, and the Modbus extension’s performance is validated regarding the efficiency in the use of the acquisition cycle time. The software and hardware processing time and the importance and effect of the various components are analyzed and evaluated. They all support the implementation of an Internet of things gateway for Modbus extension. This paper introduces solutions for the structure of the acquisition cycle to include other valuable extensions, discusses the performance of a real implementation in the form of a gateway, adds new features to the Modbus extension specification, and strengthens some of the existing ones. In accordance with the novelty and contribution of this paper to the field of local industrial networks, the results obtained in the analysis, testing, and validation of the Modbus extension protocol refer to the extending of the Modbus functions for industrial process monitoring and control management.

A two-channel slotted sense multiple access protocol for timely and reliable data transmission in industrial wireless sensor networks

In designing a real-time MAC protocol for wireless sensor networks, it is desirable to shorten the data acquisition cycle time to satisfy more applications with a tighter time constraint in data collection. To achieve this, one often tries to improve throughput by employing a slot reuse technique. Meanwhile, the slotted sense multiple access protocol that uses a sharable slot was proven to be advantageous for timely and reliable data delivery. However, since the nodes at lower tree levels process more packets or bigger packets with data aggregation, they need a bigger sharable slot. Thus, it is not easy to employ a slot reuse technique due to the size variation of sharable slots. To tackle this problem, we try to reduce the size of an aggregated packet by limiting the number of packets for aggregation using two channels. If every node is allowed to send a single packet during data acquisition cycle time, an equal-sized sharable slot can be allocated to every tree level. It is shown that the proposed approach can reduce data acquisition cycle time significantly while maintaining good reliability in data transmission compared with slotted sense multiple access and also reduce energy consumption greatly compared with another multi-channel MAC protocol.

A rapid four-dimensional resistivity data inversion method using temporal segmentation

SUMMARY 4-D electrical resistivity tomography (ERT), an important geophysical method, is widely used to observe dynamic processes within static subsurface structures. However, because data acquisition and inversion consume large amounts of time, rapid changes that occur in the medium during a single acquisition cycle are difficult to detect in a timely manner via 4-D inversion. To address this issue, a scheme is proposed in this paper for restructuring continuously measured data sets and performing GPU-parallelized inversion. In this scheme, multiple reference time points are selected in an acquisition cycle, which allows all of the acquired data to be sequentially utilized in a 4-D inversion. In addition, the response of the 4-D inversion to changes in the medium has been enhanced by increasing the weight of new data being added dynamically to the inversion process. To improve the reliability of the inversion, our scheme uses actively varied time-regularization coefficients, which are adjusted according to the range of the changes in model resistivity; this range is predicted by taking the ratio between the independent inversion of the current data set and historical 4-D inversion model. Numerical simulations and experiments show that this new 4-D inversion method is able to locate and depict rapid changes in medium resistivity with a high level of accuracy.

Systems Engineering Modelling and Simulation to Support Defence Acquisition System

Modelling and Simulations have been applied in various engineering disciplines since the 1990s, especially in the area of defence, being an essential tool in all phases of the cycle of acquisition and in all applications whose main objective are to reduce the time, resources, and risks associated with acquisition, to enable the integrated product and process development, and to improve the quality of the fielded product. One of the main purposes of this research is to demonstrate the importance of Systems Engineering (INCOSE) as part of the defence acquisition system and how this engineering discipline has incorporated the use of Modelling and Simulations into their acquisition-cycle phases and processes.

A New on-Demand Recharging Strategy Based on Cycle-Limitation in a WRSN

Recently, Wireless Rechargeable Sensor Networks (WRSNs) have been attracting increasing attention and seen rapid development. However, in previous studies, pioneering work on charging issues and data gathering strategies are always discussed separately. In this paper, we aimed to develop a strategy which can guarantee a short data acquisition cycle and high charging efficiency. We used a new Combined Recharging and Collecting Data Model (CRCM) to set-up a WRSN. In this network, mobile chargers were used to separately collected data and charge sensor nodes. A K-means algorithm was used to group sensor nodes into different clusters, from which mobile chargers collected data from sensor nodes in the center of these clusters. The Nearest-Job-Next with Preemption (NJNP) algorithm was used to determine the charging route. The data acquisition cycle was first discussed in this model in order to ensure all data from the sensor nodes could be gathered within a certain time period. Additionally, the Periodically Restricted Dynamic Mobile Chargers (PRDMCs) algorithm was proposed to determine the number of mobile chargers. Lastly, we used the normal CRCM for comparison with our new CRCM, and the results showed that the new CRCM can effectively safeguard the data acquisition cycle without requiring the addition of more mobile chargers.

Structural basis of a Ni acquisition cycle for [NiFe] hydrogenase by Ni-metallochaperone HypA and its enhancer

The Ni atom at the catalytic center of [NiFe] hydrogenases is incorporated by a Ni-metallochaperone, HypA, and a GTPase/ATPase, HypB. We report the crystal structures of the transient complex formed between HypA and ATPase-type HypB (HypBAT) with Ni ions. Transient association between HypA and HypBAT is controlled by the ATP hydrolysis cycle of HypBAT, which is accelerated by HypA. Only the ATP-bound form of HypBAT can interact with HypA and induces drastic conformational changes of HypA. Consequently, upon complex formation, a conserved His residue of HypA comes close to the N-terminal conserved motif of HypA and forms a Ni-binding site, to which a Ni ion is bound with a nearly square-planar geometry. The Ni binding site in the HypABAT complex has a nanomolar affinity (Kd = 7 nM), which is in contrast to the micromolar affinity (Kd = 4 µM) observed with the isolated HypA. The ATP hydrolysis and Ni binding cause conformational changes of HypBAT, affecting its association with HypA. These findings indicate that HypA and HypBAT constitute an ATP-dependent Ni acquisition cycle for [NiFe]-hydrogenase maturation, wherein HypBAT functions as a metallochaperone enhancer and considerably increases the Ni-binding affinity of HypA.