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Journal of Engineering publishes research in several areas of engineering, including chemical engineering, civil engineering, computer engineering, electrical engineering, industrial engineering and mechanical engineering.
Chief Editor, Professor Wang, is the Vice Deputy Dean of the School of Aerospace Engineering at Tsinghua University.
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Standard of Crushing Value of Coarse Aggregates for Permeable Asphalt Mixture Based on Contact Stress between Aggregates
Crushing resistance of coarse aggregate is the key to the stability and durability of the skeleton structure of permeable asphalt (PA) mixture. To determine the technical requirements of crushing value of coarse aggregate used in PA mixture, step-loading compression tests were conducted on the mixtures of PA-13 and a control asphalt mixture AC-13, respectively. Virtual compression tests under the same loading conditions were simulated on the corresponding digital specimens with PFC2D®. By comparing the load-deformation curves obtained from the actual tests and virtual simulation, the values of the microscopic parameters of the two graded mixtures were obtained through trial calculation and adjustment. Then, the states of contact stress between aggregates in PA-13 and AC-13 mixtures under the standard crushing pressure (400 kN) were analyzed with PFC2D®. It was found that the average normal contact stress and the maximum normal contact stress between aggregates in PA-13 were 1.71 times and 1.28 times larger than those in AC-13, respectively. The crushing values of two different lithologic coarse aggregates were measured under different pressures, 400 kN or 600 kN, respectively. The crushing value criterion of coarse aggregates used in the PA mixture was suggested to be no greater than 16% after comparative analysis.
Hybrid Design of Optimal Capacitor Placement and Reconfiguration for Performance Improvement in a Radial Distribution System
Distribution System Reconfiguration (DSR) and Optimal Capacitor Placement (OCP) are the most alternative techniques for increasing the power system generation and covering the growth of power demands. These techniques reduce the Radial Distribution System (RDS) losses and enhance the voltage profile. Combining both techniques gives better performance than using the individual technique. In this paper, two operation modes were implemented. First, the individual mode of OCP is applied. Second, the dual mode of DSR after OCP process is applied. Multiobjective functions with considering the weighting factors are used for minimizing real losses, improving voltage profile, and increasing saving cost. The optimal selections of open switches, location, and size of capacitors in the individual and dual design for RDS are achieved using four different optimization algorithms. These algorithms are Modified Biogeography-Based Optimization (MBBO) algorithm, Cuckoo Search (CS) algorithm, Modified Imperialist Competitive (MIC) algorithm, and Modified Bacterial Foraging-Based Optimization (MBFBO) algorithm. These algorithms are applied for two standard networks (IEEE 33- and IEEE 69-bus). Comparisons among the proposed algorithms are done, and the results demonstrated that the MBBO algorithm is the most strong and fast algorithm to attain the optimum solution. In addition, comparisons with literature works are done to validate the effectiveness of proposed algorithms.
Eliminating Rogue Femtocells for IoT Open Meter System Based on Expert System
The Internet of things (IoT), including power meters, water meters, natural gas meters, and meter collectors in an open metering system (OMS), which is dispersed around the user side, relies on wireless virtual private networks (VPNs) to communicate with head end, and thus it is exposed to malicious cyber attacks. The General Packet Radio Service (GPRS), which is vulnerable to rogue femtocells, is widely used for communication among meter collectors and the head end. Because telecommunication fraud related to rogue femtocells is a serious offence, rogue femtocells will be turned on for some time and immediately turned off and moved from here to there to escape from being caught. The signal strength (SS) of rogue femtocells is characterized by abrupt changes. Because meter collectors and lawful femtocells are deployed at the fixed location, there is a notable difference between signal strength profile of lawful and rogue femtocells. Prior knowledge of variation of signal strength is utilized to formulate rules to detect rogue femtocells. An expert system is developed to detect rogue femtocells and prevent meter collectors from attaching to them. Numerical simulation indicates that the proposed approach can detect both stationary and moving rogue femtocells online. Since computation load of the proposed approach is not high, it can be implemented in existing IoT meter collectors with limited computation resource and the proposed approach can harden cyber security of OMS.
Design and Development of a Delta 3D Printer Using Salvaged E-Waste Materials
The next phase of industrialization in the world is the use of 3D printing technology. Various 3D printing technologies are employed all over the world and for different purposes, from 3D printed houses to 3D printed food nutrients. Printer movement is achieved by carriages moving in a clearly defined X, Y, and Z orientation. The 3D printer has a lower work rate; subsequently, many printouts consume a lot of time due to their complexity. This paper elaborates on the design and development of a faster and fixed build platform 3D printer (Delta 3D printer) using locally available materials and e-waste. The Delta 3D printer movement is faster with a stable bed. Printer movement is achieved using three vertical axes placed 120° apart. Accuracy and speed are achieved with the use of NEMA 17 stepper motors to drive the various carriages on the vertical axes. Design calculations show that the least force delivered by the stepper motor is 1.73 N which exceeds 0.8334 N, the weight of the load to be carried. Furthermore, a stepper motor must turn 80 steps (rotational motion) in order to achieve 1 mm advance (linear motion). This ensures a higher printout resolution. In place of traditional linear rails, locally sourced square pipes were adopted coupled with bearings and a 3D printed carriage support, and a relatively cheaper but stable linear rail was developed. The goal of this research was to develop an alternative easy-to-build Delta 3D printer using locally sourced materials. This goal of this research was achieved, and the developed prototype was test-run under load conditions. It is recommended that salvaged e-waste should be properly managed for easy acquisition.
Design and Implementation of Runtime Verification Framework for Cyber-Physical Production Systems
Traditional factories are turning into smart factories with the advent of various ICT technologies, and various control decisions are derived by AI technologies. In this circumstance, runtime verification of a control command is important for zero-defect manufacturing processes but challengeable because factories of the future are highly complex and heterogeneous systems. In this paper, we propose DigTwinOps, a Digital Twin framework for Runtime Verification of Cyber-Physical Production Systems (CPPSs). DigTwinOps features a Digital Twin Execution Engine (DTEE) that manages a Digital Twin Model to synchronize states of a real CPPS object in a production environment. With a monitoring and simulation combination process, a human worker can observe the states of the CPPS object and verify the effectiveness of control commands before applying it to a real production environment. The proposed framework is applied to a CPPS prototype production system, and the results show that the framework can work effectively in the controllability verification of control commands.
Performance of Ground Clay Brick Mortars in Simulated Chloride and Sulphate Media
The durability of cement-based structures majorly depends on their resistivity to the aggressive media in the construction environment. The most aggressive ions commonly encountered in construction environment are chloride (Cl−) and sulphate (). The interactions of these ions with hydrated cement influence their durability and ultimate service life. This paper reports the experimental findings on an investigation on the diffusivity of Cl− and ions into mortars made from two mixtures: one made from ground calcined clay bricks (GB) and commercial ordinary Portland cement (OPC) and the other consisting of GB and Portland pozzolana cement (PPC). The test media were 3.5% Cl− and 1.75% solutions. For comparison, commercial OPC and PPC were also investigated. GB was blended with OPC at replacement levels of 25, 35, 45, and 50% to make OPCGB. Similar blends were also made with PPC replacement levels of 15, 20, and 25% to make PPCGB. Mortar prisms measuring 160 mm × 40 mm × 40 mm were cast at the water-to-cement ratios (w/c) of 0.40, 0.50, and 0.60 using each category of cement and cured in water for 3, 7, and 28 days. Compressive strength measurements were taken at each of the curing ages. The 28-day cured mortar prisms were subjected to compressive strength analysis and accelerated Cl− and ingress for 36 hours at 12 V. Ion profiling was done on the mortars, and diffusion coefficients of the Cl− and ions were approximated. The results showed that there was an increase in compressive strength after exposure to Cl− and ions. In addition, the ingress of Cl− and ions decreased with an increase in depth of cover. Blended cement exhibited lower Cl− and ingress than OPC. The ingress of Cl− was observed to be higher than that of ions. The ingress of Cl− and ions increased with an increase in w/c ratio. The results further showed that there was a drop in the ingress of Cl− and ions with an increase in replacement up to 35 percent for OPC. A 15 percent replacement showed a better compressive strength development compared with 20 and 25 percent replacement for PPC. Blended cement showed lower apparent diffusion coefficients (Dapp) compared with OPC. PPC, OPCGB-35, and PPCGB-15 exhibited similar performance in terms of strength development, aggressive ions ingress, and Dapp. In conclusion, it was found that the test cements, PPCGB-15 and OPCGB-35, can be used in similar tested environments as commercial PPC.