Good Engineering Research Articles

Research on Pilot Protection for Tie Line of Renewable Energy Sources

With the continuous increase in the proportion, renewable energy sources have brought great challenges to the traditional protection based on fundamental frequency, due to their complex short-circuit current characteristics which are different from synchronous generators. As the main protection of the tie line (outgoing line) of the renewable energy station, the differential protection will also be seriously affected in terms of its operation performance, and even the operation failure or maloperation may occur in some cases. This paper proposes a new principle of pilot protection based on cosine similarity comparison by analyzing the fault characteristics of renewable energy sources. With the full current as the main criterion and the current fault component as the auxiliary criterion, this principle comprehensively utilizes the time domain information of the current on both sides of the line to improve the protection sensitivity. At the same time, a method of capacitive current compensation for the sampling value is proposed according to the algorithm characteristics of similarity comparison, to prevent the protection maloperation in the case of external faults. The simulation results show that, compared with the existing pilot protection based on similarity comparison, the new protection principle proposed in this paper has good engineering application value by identifying internal and external faults in a more reliable and sensitive manner.

BIM-Integrated Construction Safety Risk Assessment at the Design Stage of Building Projects

The construction industry has a higher rate of work accidents than other industries. As a proactive approach to safety management, Construction Hazard Prevention through Design (CHPtD) can significantly eliminate or reduce construction safety risks. This method consists of three indices namely Likelihood, Consequence and Exposure. Likelihood and consequence index of 19 construction jobs using 2018 injury and death data. Only 4 types of work are shown in this case. The findings conclude that the index of relative mortality frequency (RFI) of roofers (47-2180) and the index of relative frequency of day-going injuries (RDAIFI) of construction workers (47-2060) are relatively high. In addition, construction equipment operators relative day-to-day injury severity (RDAIS) rates (47–2070) are 3.3 times that of roof operators (47–2180). These results validate that using plug-ins in Revit can quickly calculate the construction safety risks of various design plans in a very short time and show that the plug-ins developed have very good engineering application value.

Planning and analysis of safety-optimal lunar sun-synchronous spatiotemporal routes

Lunar sun-synchronous roving is an affordable and promising manner of acquiring continuous power supply and warmth in robotic polar exploration. Sun-synchronous route planning is challenging to meet the spatiotemporal constraints of lunar topography and time-varying illumination. Moreover, in pursuit of spaceflight feasibility and safety, the safety-optimal planning method adapting to spatiotemporal maps remains to be addressed. This paper takes the first step to investigate this issue, in which the distribution of roving speed is considered a critical factor. Three-dimensional lunar spatiotemporal maps are constructed based on topography and illumination analysis. A spatiotemporal planning algorithm named MSST-A* is proposed, which takes a multi-speed node expansion mechanism, thus supporting speed distribution optimization. Afterward, route evaluation functions involving motion, energy, and integrated risk, together with the optimal heuristic function, are designed for safety-optimal planning. Two comparative tests are conducted, and results indicate that the proposed approach is practical and superior in terms of motion safety and energy reliability. Besides, an integrated-risk-minimal route circumnavigating the Shackleton Crater at the south pole in three lunar days is solved, demonstrating the existence of long-term lunar sun-synchronous routes with good engineering significance.

Design and Development of a High-Speed Precision Internal Grinding Machine and the Associated Grinding Processes

In order to meet the P2-grade bearing grinding requirements, we designed a high-speed internal grinding machine to be used for grinding bearing raceways and inner circles. The machine has a T-type layout and a four-axis numerical control linkage. It is supported by hydrostatic pressure and driven directly by a torque motor. In addition, it is equipped with a high-speed hydrostatic grinding wheel spindle. Our design includes a hydrostatic workpiece shaft and hydrostatic turntable, and the process has a good engineering application value. Finally, the designed precision grinding machine was used to grind a P2-grade bearing raceway.

On business adoption and use of reproducible builds for open and closed source software

Reproducible builds (R-Bs) are software engineering practices that reliably create bit-for-bit identical binary executable files from specified source code. R-Bs are applied in some open source software (OSS) projects and distributions to allow verification that the distributed binary has been built from the released source code. The use of R-Bs has been advocated in software maintenance and R-Bs are applied in the development of some OSS security applications. Nonetheless, industry application of R-Bs appears limited, and we seek to understand whether awareness is low or if significant technical and business reasons prevent wider adoption. Through interviews with software practitioners and business managers, this study explores the utility of applying R-Bs in businesses in the primary and secondary software sectors and the business and technical reasons supporting their adoption. We find businesses use R-Bs in the safety-critical and security domains, and R-Bs are valuable for traceability and support collaborative software development. We also found that R-Bs are valued as engineering processes and are seen as a badge of software quality, but without a tangible value proposition. There are good engineering reasons to use R-Bs in industrial software development, and the principle of establishing correspondence between source code and binary offers opportunities for the development of further applications.

Failure mechanism of continuous large deformation and a novel pressure relief control technology on the two sides of deep coal roadway

Traditional intensive drilling (or grooving) technology in a roadway destroys the rock mass and supporting structure in the shallow anchoring area while implementing pressure relief. In Dongpang coal mine, it is difficult to avoid the failure of the supporting system and continuous large deformations of the deep roadways influenced by disturbance, despite the application of strong bolt (cable) supporting systems and grouting reinforcements. Therefore, this study proposes a novel “anchoring and pressure relief” synergistic supporting technique to eliminate the dilemma among the anchoring supporting and pressure relief. With strong anchoring supporting in the shallow surrounding rock, this novel technology realizes pressure relief by excavating large-diameter holes in the deep peak stress area, to enable active regulation of the move of the peak stress area to the deep surrounding rock without impairing the shallow anchoring area. The path of coal body rheology and stress move is cut off by large-diameter holes using this novel technology, achieving the purpose of absorbing energy and deformation, decreasing the stress applied on the supporting structure in the anchoring area. The novel technology effectively solves the control problems of continuous large deformation in deep roadway and has a good engineering application prospect. This study findings will add scientific value for the improvement of surrounding rock control of deep roadway.

Bandgap and Vibration Suppression Mechanisms of Novel Star‐Shaped Hybrid Metamaterials

Herein, a novel star‐shaped hybrid acoustic metamaterial structure is proposed. Based on Bloch's theorem and the finite element method, the bandgap characteristics and the bandgap formation mechanism of different combinations of structures are first analyzed. Then, the propagation characteristics of elastic waves in Model C2 are studied with focus on equal frequency contours, phase velocity, and group velocity. And the attenuation of elastic waves in the finite size structure of Model C2 illustrates that the elastic waves are effectively suppressed in the bandgap frequency range, which further confirms the perfect correspondence between the bandgap and the vibration attenuation region. Finally, the influence of structural parameters on the bandgap is analyzed, as well as the change of the bandgap when the structure undergoes large deformation, which can realize the tunability and flexibility of the bandgap. This study provides important clues for the design of vibration isolators and metamaterials, and shows the good engineering application potential of the structure for vibration isolation.

Overall structural seismic damage rapid assessment method based on period and displacement response characteristics

The seismic damage state of building structure can be rapidly evaluated by coupling effect of structural displacement response and periodic characteristics. Firstly, the fundamental period calculation formula that adapts to the deformation pattern and distribution mode of horizontal seismic action for reinforced concrete frame structure is derived. Secondly, the seismic damage assessment standard of building structure considering period variation is established. Then, the seismic damage assessment method of building structure is constructed. Finally, the seismic damage example is used to verify the established evaluation method. The results show that the established research method has high accuracy and good engineering practicability.

Experimental study and simulation for unfrozen water and compressive strength of frozen soil based on artificial freezing technology

Artificial ground freezing is widely used in various projects, such as mine, bridge, and subway tunnel construction and emergency repair, and has achieved good engineering results. The freezing strength and freezing effect based on artificial freezing technology have become a hot research topic. However, the relationship between the freezing strength and unfrozen water content under extremely low-temperature conditions has not been sufficiently studied. In view of this, a series of laboratory experiments were carried out. The unfrozen water characteristics and compressive strength of soil at ultralow temperatures from 0 °C to −80 °C were studied by nuclear magnetic resonance (NMR). The applicability of a genetic algorithm-back propagation (GA-BP) prediction model to unfrozen water content was discussed. The results show that there is a very small amount of unfrozen water present at −80 °C, with a content of approximately 0.1%. The GA-BP network prediction model can be used to predict the unfrozen water content of soil at very low temperatures. The compressive strength of frozen soils is significantly affected by temperature and unfrozen water content. The compressive strength of frozen soil is directly proportional to the absolute value of the soil temperature. The unfrozen water content and compressive strength follow a power function. As the temperature decreases, the stress–strain relationship of frozen soil is of the elasto-plastic type. Interestingly, soil at temperatures down to −80 °C show significant brittle failure. This paper supplements the basic theory of extremely-low-temperature frozen soil and quantitatively determines that the unfrozen water content affects the frozen soil strength. These conclusions are highly significant and can provide a theoretical reference for practical engineering applications, especially artificial freezing engineering.

Preparation and evaluation of a fluorinated nano-silica superhydrophobic coating for cement pavement

To reduce the traffic risk of pavement icing, a fluorinated nano-silica superhydrophobic coating for cement pavement was prepared with fluorinated nano-silica, carbon black, and waterborne epoxy resin. The component and spraying dosage were analyzed for optimal performance by combining the fluorination verification, component contents determination, and spraying dosage optimization. The engineering performance was evaluated for applicability, basing anti-icing performance and pavement durability. The test results showed that the fluorine group has successfully drafted on the nano-silica. The determined content of nano-silica is 75 wt% and of carbon black is 17.5 wt% of waterborne epoxy resin. The optimal application amount is 0.5 L/m2 to balance the requirement of superhydrophobic property and skid resistance. Meanwhile, the prepared coating has a good engineering performance. It can boost 70 % ability to repulse incoming water droplets, delay 40 % time of ice formation, and increase 40 % ratio of ice-layer removal compared with the uncoated. It can also maintain the basic appearance and superhydrophobic property after about 150,000 times wheel abrasion or three high-low temperature cycles. This demonstrates that the prepared coating has a good potential for practical use.

CFD analysis of a wire-wrapped infinite sub-channel using temperature-dependent LBE properties

Once a significant number of LMFRs (liquid-metal cooled fast nuclear reactors) employ wire-wrapped fuel assemblies, considerable attention should be directed to this engineering feature. Given the many contact points and tight gaps, wire-wrapped fuel assemblies are difficult to analyze without numerical tools, out of which CFD (computational fluid dynamic) is the leading tool in the field. This work presents a CFD analysis of a wire-wrapped infinite sub-channel, based on MYRRHA’s fuel assembly geometry and with LBE (lead bismuth eutectic) coolant properties implemented as temperature-dependent polynomial curves. Periodic boundary conditions were applied, and the turbulence model chosen was k-w SST. All calculations were run on ANSYS Fluent R19.3. Following good engineering practices for CFD simulations, a GCI (grid convergence index) analysis was carried out, in order to ensure grid/mesh independence on the results. Ultimately, the main goal of this work was to evaluate if the implementation of temperature-dependent thermal-physical properties for LBE coolant would lead to any different results, when compared to the static properties. However, no significant result change was observed in this case, only an increase in computational time, which leads to the conclusion that for small domains with periodic boundaries, the implementation of temperature-dependent coolant properties is not justifiable.

TBM penetration rate prediction ensemble model based on full-scale linear cutting test

Accurate and effective prediction of TBM penetration rate (PR) is significant for ensuring TBM tunneling safety, improving tunneling efficiency and optimizing construction cost. Establishing a prediction model is usually an effective method to solve this critical problem. The type of TBM penetration rate prediction models can be divided into two categories: theoretical models and empirical models. Each model has its advantages, but there are also shortcomings. To make the advantages of the two models complement each other and further improve the accuracy and application scope of the prediction model, this paper proposes a prediction ensemble model of PR based on a full-scale linear cutting test and machine learning algorithm. A semi-theoretical TBM penetration rate prediction model is established through the full-scale linear cutting test and the rock-breaking analysis of granite and sandstone with different strengths. Based on the XGBoost intelligent algorithm, an empirical model of the penetration rate prediction is also established. On this basis, the Bagging algorithm combines these two models to form an ensemble prediction model of TBM penetration rate. We collected rock mass and operational parameters in the Hangzhou Second Water Source Water Transfer Channel Project to verify the semi-theoretical, empirical, and ensemble models, respectively. The results show that the three models' prediction errors are all less than 15%, and the ensemble model has a smaller error of 10.2%. This result confirms that the ensemble model can effectively improve prediction accuracy and has good engineering applicability.

Engineering Properties of PVA Fibre-Reinforced Geopolymer Mortar Containing Waste Oyster Shells.

Recycling crushed waste oyster shells (WOS) as a fine aggregate is an attractive method of disposal. However, its use in geopolymer mortar has not been reported. The influence of PVA fibres on the engineering properties of the new geopolymer mortar is still unclear. To bridge the gap, this study investigated the influence of various PVA fibre contents (0–1.05 vol%) on the flowability, compressive, flexural strengths, drying shrinkage, sorptivity, chloride resistance, porosity, fibre dispersion, embodied CO2 emissions (ECO2e), and embodied energy (EE) of the geopolymer mortar. The results indicated that the inclusion of 0.15–1.05 vol% of PVA fibres improved the flexural strength by 10.10–42.31% and reduced the drying shrinkage by 13.37–65.79%. The flowability and compressive strength decreased by 10.78–34.28% and 7.50–27.65%, respectively, but they were sufficient for construction. The sorptivity increased by 1.45–15.16%, and the chloride resistance decreased by 15.09–56.35%, but the geopolymer mortar was still classified as low chloride penetrability. In summary, the optimal content of PVA fibres is 0.45 vol%, and the geopolymer mortar has good engineering properties and eco-efficiency. The cost analysis and high-temperature resistance of the geopolymer mortar are neglected in this study, which should be evaluated in future work.

Robust Flow Estimation Algorithm of Multichannel Ultrasonic Flowmeter Based on Random Sampling Least Squares.

The multi-path ultrasonic flowmeter is widely used in engineering practice, and the flow algorithm is important for its accuracy. The least-squares estimation method is simple and efficient and has good engineering application value. In practical applications, noises are inevitably introduced to the measurement process because of the flowmeter itself or flow-field interference. The results of classical least squares will deviate from reality because it lacks robustness. In this regard, two flow algorithms of multi-path ultrasonic flowmeter are proposed based on least-squares and random-sampling consensus algorithms, which are widely used in the image field. The two algorithms can resist gross errors effectively by avoiding the interference of external points in the sampling points. To verify the effectiveness of the proposed algorithms, we take the double-bend flow field, which is a typical damaged flow field in engineering, as the research object, and then we compare the four algorithms. It can be seen that the two flow algorithms have higher accuracy and better robustness in the presence of interference noise.

Improved reduce-order modeling of bidirectional interleaved boost with coupled inductors converter

In this paper, an improved reduced-order average modeling method for the bidirectional interleaved boost with coupled inductors (BIBCI) converter is proposed, based on the PWM and phase-shift dual-degree-of-freedom modulation and traditional reduced-order average model. Considering the power loss of the coupled inductor, the core loss, and the parasitic parameters of the inductors, capacitors, and switches in the circuit topology, the new model reflects the dynamic performance of the converter in a wide frequency domain more accurately than the traditional model. The small-signal model and transfer function are further deduced to provide a basis for the design of closed-loop controllers and have good engineering practicability. According to voltage source load or resistive load, the double-loop or triple-loop controller is designed correspondingly. The two models are theoretically analyzed and compared, and the proposed controller is verified by a 1.5 kW prototype.

The axial compression mechanical properties and factors influencing spiral-ribbed thin-walled square concrete-filled steel tube composite members

Thin-walled concrete-filled steel tubular members have significant economic advantages, but are prone to local buckling, which has a great impact on structural safety. Therefore, this paper proposes a new spiral stiffened thin-walled CFST composite column to solve the above problems. The axial compression test found that spiral stiffeners can significantly improve the buckling resistance of thin-walled steel tubes, with the ultimate bearing capacity increased by 18 % and the ductility coefficient reaching about 2.0. Through the study of the mechanical mechanism, it is found that the spiral rib has little contribution to the vertical stiffness of the component, mainly by restricting the transverse deformation of the steel pipe to improve the mechanical performance of the component. At the same time, it is also found that the spiral rib can also play a strong constraint on the external concrete, and with a small amount of reinforcement, it can ensure the synergistic force of each part of the component. Based on the test, a parametric analysis was conducted on the pitch, the width-thickness ratio of the spiral rib and the influence law were quantified, and the design suggestions were provided. Finally, based on the fitting method, a formula for calculating the bearing capacity of this superimposed member was proposed. The new composite member has the advantages of less steel consumption, good mechanical properties, strong fire resistance, corrosion resistance, and good engineering application prospects.

Influence of obstacle morphology on safety of nuclear hydrogen production system

The safety of the nuclear hydrogen production system is a key issue that cannot be ignored in the future commercialization. The reasonable arrangement of obstacles can effectively improve the safety of the system under accident conditions. In this paper, based on the high-pressure hydrogen storage tank model of a nuclear hydrogenation plant, two mechanisms by which obstacles can effectively improve safety are analyzed. In order to determine the obstacle design scheme with outstanding effect, the response surface methodology is used to study the influence of the structural parameters and spatial position parameters of obstacles of different shapes, and the comprehensive performance of different obstacles is compared by the TNO multi-energy method. The results show that the semi-cylindrical surface can control the separation distance within 141 m at a lower processing cost, which has good engineering utilization value. This study can provide a valuable reference for the design of nuclear hydrogen production systems.

Large-Area Saline-Alkali-Tolerant Rice Growth Environment Monitoring System Based on LoRa+UAV

A wireless sensor network (WSN) monitoring system for saline-alkali-tolerant rice based on long-range + unmanned aerial vehicle (LoRa + UAV) has been proposed in this paper to meet the requirements of difficult deployment, low scalability, and poor network reliability of traditional farmland environmental monitoring systems. The system automatically forms a double-layer star topology network through the terminal node and central node (intranet), central node, and UAV mobile node (extranet). Data transmission is carried out through LoRa technology, routing planning is carried out for UAV mobile receiving nodes at different flight altitudes, and an early warning mechanism for UAV energy is added. It effectively prevents the UAV from destroying the communication capability of the external network due to energy exhaustion during operation. The system transmits information remotely to the server of the management center through a 5G network, which analyzes and processes the data and publishes it on the Web. The system has been tested in the field, and the reliable communication range of the node is 1∼4 km under the saline-alkali-tolerant rice environment, and the service life of the terminal node can reach more than 3 months. During continuous operation, the maximum packet loss rate of the internal and external integrated networks is 1.45%. The system can stably and real-time monitor saline-alkali-tolerant rice environmental information, and the error rate is less than 10%, which can meet the performance requirements of the saline-alkali-tolerant rice environmental monitoring systems, such as low power consumption, wide coverage, stability, and reliability, and has a good engineering significance.

Preparation and Performances of Polyether Polytriazole Elastomers Based on Click Chemistry

Since the polyurethane elastomer synthesis process is susceptible to moisture, polytriazole polyethylene oxide-tetrahydrofuran (PTPET) elastomer was used as a replacement owing to its mild production environment. In contrast to the conventional flask-synthesis method, the twin-screw reactor instrument could provide more meaningful data in the synthesis. In this study, PTPET elastomer was prepared by the MiniLab twin-screw reactor method for the first time, and the activation energy of the PTPET elastomer was calculated using the torque variation obtained from the MiniLab twin-screw reactor during the synthesis process at two different temperatures. The addition of flame retardants could endow the composites with more useful properties. The PTPET composites poly (phenylsilsesquioxane) (PTPET-PPSQ), octaphenyl polyhedral oligomeric silsesquioxane (PTPET-OPS) and PTPET-PhVPOSS (phenyl/vinyl polysilsesquioxane) were synthesized by using the MiniLab twin-screw reactor. The prepared PTPET elastomer and composites were fully characterized by FT-IR, TG, DSC, swelling test, mechanical test, SEM and combustion test. The characterization results show that the addition of the flame retardants has little influence on the original structure and properties of PTPET elastomer. The flame retardancy was characterized by the combustion test showing that all PTPET composites form a certain thickness of char layer during the burning process. These results indicate that the addition of flame retardants maintains the outstanding properties of PTPET elastomer and also endows the materials with a certain extent of flame retardancy; thus, it is believed to be a good engineering material that could be applied in many realms.

CAR γδ T cells for cancer immunotherapy. Is the field more yellow than green?

Engineered immune cell therapy to treat malignancies refractory to conventional therapies is modernizing oncology. Although αβ T cells are time-tested chassis for CAR, potential graft versus host disease (GvHD) apart from cytokine toxicity and antigen escape pose limitations to this approach. αβ T cell malignancy challenges isolation and expansion of therapeutic T cells. Moreover, αβ T cells may pose toxicity risk to inflammation sensitive vital tissues bearing the tumor. The HLA independent, multivalent, versatile and systemic anti-tumor immunity increases the desirability of γδ T cells as an alternate chassis for CAR. Indeed, CD19 γδ CAR T cell therapy to treat advanced lymphoma reached a milestone with the fast track status by FDA. However, reduced tumor-toxicity, homing, in vivo persistence and heterogeneity limits the translation of this therapy. The field is gaining momentum in recent years with optimization of gene delivery approaches and mechanistic insights into co-signaling requirements in γδ T cells. There is a renewed interest in customizing design of CAR guided by the biology of the host immune cells. Progress has been made in the current good manufacturing practice compatible expansion and engineering protocols for the δ1 and δ2 T cells. γδ CAR T cells may find its niche in the clinical situations wherein conventional CAR therapy is less suitable due to propensity for cytokine toxicity or off-tumor effect. As the therapy is moving towards clinical trials, this review chronicles the hitherto progress in the therapeutic engineering of γδ T cells for cancer immunotherapy.