Tomas Vaitkunas, Paulius Griskevicius, Gintautas Dundulis
et al.
Abstract Numerical fatigue process modelling is complex and still an open task. Discontinuity caused by fatigue cracks requires special finite element techniques based on additional parameters, the selection of which has a strong effect on the simulation results. Moreover, the calculation of fatigue life according to empirical material coefficients (e.g., Paris law) does not explain the process, and coefficients should be set from experimental testing, which is not always possible. A new nonlocal continuum mechanics formulation without spatial derivative of coordinates, namely, peridynamics (PD), which was created 20 y ago, provides new opportunities for modelling discontinuities, such as fatigue cracks. The fatigue process can be better described by using the atomistic approach-based kinetic theory of fracture (KTF), which includes the process temperature, maximum and minimum stresses, and loading frequency in its differential fatigue damage equation. Standard 316L stainless steel specimens are tested, and then the KTF-PD fatigue simulation is run in this study. In-house MATLAB code, calibrated from the material S‒N curve, is used for the KTF-PD simulation. A novel KTF equation based on the cycle stress‒strain hysteresis loop is proposed and applied to predict fatigue life. The simulation results are compared with the experimental results, and good agreement is observed for both symmetric and asymmetric cyclic loading.
Mechanics of engineering. Applied mechanics, Systems engineering
Supaporn Sankul, Naratip Supattananon, Raknoi Akararungruangkul
et al.
This research paper introduces an adaptive differential evolution algorithm (ADE algorithm) designed to address the multi-compartment vehicle routing problem (MCVRP) for cold chain transportation of a case study of twentyeight customers in northeastern Thailand. The ADE algorithm aims to minimize the total cost, which includes both the expenses for traveling and using the vehicles. In general, this algorithm consists of four steps: (1) The first step is to generate the initial solution. (2) The second step is the mutation process. (3) The third step is the recombination process, and the final step is the selection process. To improve the original DE algorithm, the proposed algorithm increases the number of mutation equations from one to four. Comparing the outcomes of the proposed ADE algorithm with those of LINGO software and the original DE based on the numerical examples In the case of small-sized problems, both the proposed ADE algorithm and other methods produce identical results that align with the global optimal solution. Conversely, for larger-sized problems, it is demonstrated that the proposed ADE algorithm effectively solves the MCVRP in this case. The proposed ADE algorithm is more efficient than Lingo software and the original DE, respectively, in terms of total cost. The proposed ADE algorithm, adapted from the original, proves advantageous for solving MCVRPs with large datasets due to its simplicity and effectiveness. This research contributes to advancing cold chain logistics with a practical solution for optimizing routing in multi-compartment vehicles.
Industrial engineering. Management engineering, Management information systems
Yuan Alfinsyah Sihombing, Uperianti, Rizky Indah Sari
et al.
In the development of biosensors, it is essential to have sensors that provide rapid responses, exhibit high sensitivity and selectivity, and are non-invasive, such as screen-printed carbon electrode-based biosensors. In this study, SPCE-based and fabric-based biosensors were fabricated by modifying the working electrode (WE) surface using functionalized Multi-walled Carbon Nanotube/AgNi nanocomposites (f-MWCNT/AgNi) to enhance the biosensor's performance in detecting uric acid (UA). The successful synthesis of the f-MWCNT/AgNi nanomaterial was confirmed through UV–Vis, Raman, SEM–EDX, and XRD analyses. The f-MWCNT/AgNi nanomaterials were deposited on the WE surface using drop-casting. Subsequently, electrochemical characteristic tests and UA detection performance were conducted using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods. The DPV curves revealed sensitivities of 27.699 μA/mM and 4.638 μA/mM for SPCE-based and fabric-based electrodes, respectively. The limit of detection (LOD) values for UA detection were 0.024 and 0.017 mM, with linearity (R2) 0.997 and 0.999 observed within the linear ranges of 0.05–1.00 and 1.0–5.0 mM, respectively. Both biosensors exhibited strong selectivity for UA against other components, including ascorbic acid, glucose, lactic acid, and ethanol. Based on these parameter values, f-MWCNT/AgNi-modified SPCE and fabric-based electrodes can be promoted as biosensors for uric acid detection.
Nathan Dunkelberger, Jeffrey Berning, Eric M. Schearer
et al.
IntroductionIndividuals who have suffered a cervical spinal cord injury prioritize the recovery of upper limb function for completing activities of daily living. Hybrid FES-exoskeleton systems have the potential to assist this population by providing a portable, powered, and wearable device; however, realization of this combination of technologies has been challenging. In particular, it has been difficult to show generalizability across motions, and to define optimal distribution of actuation, given the complex nature of the combined dynamic system.MethodsIn this paper, we present a hybrid controller using a model predictive control (MPC) formulation that combines the actuation of both an exoskeleton and an FES system. The MPC cost function is designed to distribute actuation on a single degree of freedom to favor FES control effort, reducing exoskeleton power consumption, while ensuring smooth movements along different trajectories. Our controller was tested with nine able-bodied participants using FES surface stimulation paired with an upper limb powered exoskeleton. The hybrid controller was compared to an exoskeleton alone controller, and we measured trajectory error and torque while moving the participant through two elbow flexion/extension trajectories, and separately through two wrist flexion/extension trajectories.ResultsThe MPC-based hybrid controller showed a reduction in sum of squared torques by an average of 48.7 and 57.9% on the elbow flexion/extension and wrist flexion/extension joints respectively, with only small differences in tracking accuracy compared to the exoskeleton alone.DiscussionTo realize practical implementation of hybrid FES-exoskeleton systems, the control strategy requires translation to multi-DOF movements, achieving more consistent improvement across participants, and balancing control to more fully leverage the muscles' capabilities.
Mohsen Esamaeilpour, Majid Ghahraman Afshar, Morteza Faghihi
et al.
Lack of water is considered the most important threat to the survival of human beings and natural ecosystems. Food and energy security, health and industrial progress, which are the main components of the sustainable development of societies, depend on water more than anything else. Water consumption in Loshan power plant is 2600 L/MWh raw water, which is very high compared to the production capacity and is due to having a tower in its cooling system. Considering the high volume of water consumed in this power plant compared to the production efficiency and on the other hand, reducing the amount of rainfall and droughts that have occurred, it is necessary to provide a solution to modify the consumption pattern for this power plant. Considering the special position of this power plant, solutions to modify the water consumption pattern by recycling clean drains (blow down of boilers, back wash of sand filters and water sampling), purification and recycling the blow down of cooling towers into the water cycle and optimization of cooling towers (replacing drippers, replacing nozzles and optimizing water distribution to increase efficiency, using a rotating nozzle to increase the time and speed of the water droplets hitting the air in order to transfer more heat) are suggested. According to the experimental data, the conductivity of boiler blowdown is about 10 μs/cm and the expenses of recycling the blowdown of boiler by using heat exchanger is estimated about 324.425.000 Rials.
Technology, Water supply for domestic and industrial purposes
For survival and quality of human life, the search for better ways to ensure food safety is constant. However, food contaminants still threaten human health throughout the food chain. In particular, food systems are often polluted with multiple contaminants simultaneously, which can cause synergistic effects and greatly increase food toxicity. Therefore, the establishment of multiple food contaminant detection methods is significant in food safety control. The surface-enhanced Raman scattering (SERS) technique has emerged as a potent candidate for the detection of multicomponents simultaneously. The current review focuses on the SERS-based strategies in multicomponent detection, including the combination of chromatography methods, chemometrics, and microfluidic engineering with the SERS technique. Furthermore, recent applications of SERS in the detection of multiple foodborne bacteria, pesticides, veterinary drugs, food adulterants, mycotoxins and polycyclic aromatic hydrocarbons are summarized. Finally, challenges and future prospects for the SERS-based detection of multiple food contaminants are discussed to provide research orientation for further.
Pilar Bernal-Ortega, Elfi Gaillard, Frances van Elburg
et al.
The increasing demand on passenger car tires requires a continuous effort of tire manufacturers to improve their performance and safety. Achieving a balance between the three properties that form the “Magic Triangle of Tires” is one of the biggest challenges in this field. This work aims to improve this balance between wet grip, rolling and wear resistance by the use of performance hydrocarbon resins as an alternative to treated distillate aromatic extracted (TDAE) oil in tire tread compounds. In this framework, the effect on the in-rubber properties of five different hydrocarbon resins with different chemical nature, was studied in a styrene butadiene rubber (SBR)/polybutadiene rubber (BR) blend. The effect of the resins was analyzed by the use of different experimental techniques. All the compounds containing resin in their formulation, independently of their amount and chemical nature, showed an increase in the wet grip indicator and abrasion resistance indicator. However, it also was observed a deterioration in the rolling resistance indicator.
Chun-Ho Wu, Stephen Chi-Hung Ng, Keith Chun-Man Kwok
et al.
The proliferation of Industry 4.0 (I4.0) technologies has created a new manufacturing landscape for manufacturing, requiring that companies follow I4.0 trends to stay competitive. However, in this novel digital automated environment, these companies must also ensure that lean manufacturing principles are upheld. This study proposes a data-driven framework for analysing raw data across machines in manufacturing systems that can provide a comprehensive understanding of idle time and facilitate adjustments to reduce defect rates. This framework offers an alternative approach to improving manufacturing processes that involves utilising the power of I4.0 technologies in conjunction with lean manufacturing principles. This study’s examination of unprocessed data also provides guidance on improving legislation. The findings of this study provide direction for future research in the field of manufacturing and offer useful advice to businesses wishing to integrate I4.0 technologies into their operations.
Time-dependent and space-dependent source identification problems for partial differential and difference equations take an important place in applied sciences and engineering, and have been studied by several authors. Moreover, the delay appears in complicated systems with logical and computing devices, where certain time for information processing is needed. In the present paper, the time-dependent identification problem for delay hyperbolic equation is investigated. The theorems on the stability estimates for the solution of the time-dependent identification problem for the one dimensional delay hyperbolic differential equation are established. The proofs of these theorems are based on the Dalambert’s formula for the hyperbolic differential equation and integral inequality.
Nerve guidance conduits (NGCs) are tubular scaffolds that act as a bridge between the proximal and distal ends of the native nerve to facilitate the nerve regeneration. The application of NGCs is mostly limited to nerve defects less than 3 mm due to the lack of sufficient cells in the lumen. The development of drug-release-system-embedded NGCs has the potential to improve the nerve regeneration performance by providing long-term release of growth factors. However, most of the past works only focused on one type of drug release system, limiting the variation in drug release system types and features. Therefore, in this study, computer-aided design (CAD) models were constructed and Computational Fluid Dynamics (CFD) simulations were carried out to investigate the effect of growth factor transporting efficiency on different drug release systems. To overcome the challenges posed by the current NGCs in treating long nerve gap injuries (>4 cm), a novel ‘relay’ NGC design is first proposed in this paper and has the potential to improve the nerve regeneration performance to next level. The intermediate cavities introduced along the length of the multi-channel NGCs act as a relay to further enhance the cell concentrations or growth factor delivery as well as the regeneration performance. Four different drug release systems, namely, a single-layer microsphere system, a double-layer microsphere system, bulk hydrogel, and hydrogel film, were chosen for the simulation. The results show that the double-layer microsphere system achieves the highest growth factor volume fraction among all the drug release systems. For the single-layer microsphere system, growth factor concentration can be significantly improved by increasing the microsphere quantities and decreasing the diameter and adjacent distance of microspheres. Bulk hydrogel systems hold the lowest growth factor release performance, and the growth factor concentration monotonically increased with the increase of film thickness in the hydrogel film system. Owing to the easy fabrication of hydrogel film and the even distribution of growth factors, the hydrogel film system can be regarded as a strong candidate in drug-eluting NGCs. The use of computational simulations can be regarded as a guideline for the design and application of drug release systems, as well as a promising tool for further nerve tissue engineering study.
In order to extend the lifetime of wireless sensor network (WSN), a clustering routing algorithm for WSN based on Cuckoo Search (CS) algorithm optimized K-means was presented.In the clustering stage, the initial cluster centers were selected by CS algorithm, which make the clustering results of the K-means algorithm more uniform to balance node energy consumption.The remaining energy of the node, the distance from the center of the cluster were comprehensively considered in the cluster election, and the weight according to the remaining energy of the node was dynamically adjusted.In the data communication stage, in order to further balance the load of the cluster head, the remaining energy of the relay node and its load, and the cluster head routing energy consumption were comprehensively considered, CS algorithm was combined to plan routing for the cluster head.The simulation results show that the proposed algorithm is better than LEACH-K, LEACH-improve and DTK-means in terms of energy consumption balance.With the death of the first node as the life cycle of the network, the network lifespan was increased by 173%, 21%, and 6% respectively.The proposed algorithm effectively extending the network life cycle.
Information technology, Management information systems
Background: Many scholars lament of poor infrastructure for the management and preservation of digital records in the public sector in South Africa. For example, in South Africa, the national archives repository and its subsidiary provincial archives do not have infrastructure to ingest digital records into archival custody. As a result, digital records are left to the creating agencies to manage and preserve. The problem is compounded by the fact that very few public sector organisations in South Africa have procured systems to manage digital records.
Objective: This study investigated whether government departments in South Africa entrust their records to cloud storage. The study asked the questions: How are digital records managed and stored in these organisations? Do government departments entrust their records to the cloud as an alternative storage?
Method: Qualitative data were collected through interviews with purposively chosen chief information officers, records managers and IT managers from public entities that implemented e-government services, as well as officials from the National Archives and Services of South Africa, which is charged with the statutory regulatory role of records management in governmental bodies and the State Information Technology Agency, a public sector Information Communication Technology (ICT) company established in 1999 to consolidate and coordinate the state’s information technology resources.
Results: The key findings suggest that although public servants informally and unconsciously save some records in the cloud, government departments in South Africa are sceptical to entrust their records in the cloud because of a number of reasons such as lack of trust in the cloud storage, jurisdiction, legal implications, privacy and security risks related to Minimum Information Security Standards, as well as lack of policy and legislative framework, specifically regarding cloud storage.
Conclusion: Because of lack of infrastructure for management and preservation of digital records, for the purpose of increased storage and access, this study recommends that government departments should cautiously consider exploring the possibility of storing their records in a trusted digital repository cloud as an interim solution whilst observing legal obligations. As cloud storage is not very prevalent amongst government departments in South Africa, given the present challenges in managing digital records, it would be advantageous to have cloud storage tested rigorously before embarking on the exercise.
Management information systems, Information theory
P. Buschinelli, J. D. Salazar, J. D. Salazar
et al.
The oil and gas offshore industry demands regular inspections of components and structures that are subjected to extreme operational and environmental conditions. In this context, risers are pipelines that transport mainly oil, gas, water, and cables between submarine structures and the surface offshore platform, in the portion not touching the ocean floor. The emerged part of these risers is typically inspected by industrial climbing, which is a very time-consuming activity, has high operational costs, is dangerous and has a strong dependence on inspector skills. Remotely Piloted Aircraft Systems (RPAS) have been recently used for visual inspection of risers, however, no quantitative or geometrical evaluation has been conducted using this kind of image acquisition yet. An image-based measurement technique, such as close-range photogrammetry, can provide a 3D reconstruction using images, but a series of requisites is mandatory to achieve good results as image acquisition sequence, overlap, camera positioning network, spatial resolution and object texture in non-prepared and targetless scenes. The analysis of different image acquisition strategies using a real RPAS is too difficult because it demands a lot of time, good weather, daylight, and a scene similar to where risers are installed. An alternative is to use simulation. In this paper a ROS/Gazebo simulation is described and used to create a realistic textured 3D virtual environment of the platform, risers and RPA, providing a fast and low-cost solution to simulate different RPA trajectories for photogrammetry image acquisition in targetless scenes. These trajectories are evaluated by comparing the measured risers through photogrammetry to its CAD/simulated model. Since the scene is not prepared, the RPA position/orientation or a stereo vision setup can be used to set scale to the measurement result. The best trajectory found during simulations was also evaluated in a real experiment.
To improve the properties of α-amylase from Bacillus stearothermophilus (AmyS), a deletion mutant AmyS∆R179-G180 was constructed by deleting arginine (Arg179) and glycine (Gly180) using site-directed mutagenesis. AmyS and AmyS∆R179-G180 were expressed in Bacillus subtilis and purified by ammonium sulfate precipitation, after which the enzymatic properties were characterized and compared. By deleting amino acids Arg179 and Gly180, the thermostability of α-amylase AmyS∆R179-G180 was enhanced and the half-life at 100 °C significantly increased from 24 to 33 min. In addition, AmyS∆R179-G180 exhibited greater acid resistance and lower calcium requirements to maintain α-amylase activity. The secretory capacity of the recombinant strain was evaluated by fed-batch fermentation in a 7.5-litre fermentor in which high α-amylase activity was obtained. The highest activity reached 3300 U/mL with a high productivity of 45.8 U/(mL•h).
Single-phase power electronic traction transformer (PETT) is the power device to realize higher efficiency and reduction of weight in railway traction system, and parallel operated full-bridge isolated DC-DC converters are an important part of single-phase PETT to realize a stable DC-voltage output. In order to ensure the reliability of DC-DC level, in this paper, an open-circuit fault diagnosis method based on state estimator was proposed for open-circuit fault of a single IGBT. Through establishment of mixed logic dynamic (MLD) model and state estimator model, estimator residuals of the DC-DC level were analyzed under normal and faulty conditions. According to the residuals including information of the fault, fault diagnosis was achieved. Finally, the proposed fault diagnosis method was verified in a hardware-in-loop (HIL) experimental platform with RT-LAB simulator. Experimental results show that the diagnosis method can effectively locate the fault switch in four switching cycles after open-circuit fault of IGBT.
Control engineering systems. Automatic machinery (General), Technology
Both the slope and elevation of scaling relationships between log metabolic rate and log body size vary taxonomically and in relation to physiological or developmental state, ecological lifestyle and environmental conditions. Here I discuss how the recently proposed metabolic-level boundaries hypothesis (MLBH) provides a useful conceptual framework for explaining and predicting much, but not all of this variation. This hypothesis is based on three major assumptions: (1) various processes related to body volume and surface area exert state-dependent effects on the scaling slope for metabolic rate in relation to body mass; (2) the elevation and slope of metabolic scaling relationships are linked; and (3) both intrinsic (anatomical, biochemical and physiological) and extrinsic (ecological) factors can affect metabolic scaling. According to the MLBH, the diversity of metabolic scaling relationships occurs within physical boundary limits related to body volume and surface area. Within these limits, specific metabolic scaling slopes can be predicted from the metabolic level (or scaling elevation) of a species or group of species. In essence, metabolic scaling itself scales with metabolic level, which is in turn contingent on various intrinsic and extrinsic conditions operating in physiological or evolutionary time. The MLBH represents a “meta-mechanism” or collection of multiple, specific mechanisms that have contingent, state-dependent effects. As such, the MLBH is Darwinian in approach (the theory of natural selection is also meta-mechanistic), in contrast to currently influential metabolic scaling theory that is Newtonian in approach (i.e., based on unitary deterministic laws). Furthermore, the MLBH can be viewed as part of a more general theory that includes other mechanisms that may also affect metabolic scaling.
It is analyzed detailedly the mechanism of common mode current for the transformerless photovoltaic inverter system. Different control methods are used to analyze the common mode current of single-phase transformerless full-bridge topology, and a new topology is also analyzed and simulated. It introduces several different three-phase transformerless topologies, and makes a simple analysis and simulation. Finally, the differences of single-phase and three-phase transformerless photovoltaic inverter topologies are compared.
Control engineering systems. Automatic machinery (General), Technology
This paper describes a system which generates variations on theme music fitting to story scenes represented by texts and/or pictures. Inputs to the present system are original theme music and numerical information on given story scenes. The present system varies melodies, tempos, tones, tonalities, and accompaniments of given theme music based on impressions of story scenes. Genetic algorithms (GAs) using modular neural network (MNN) models as fitness functions are applied to music generation in order to reflect user's feeling of music and stories. The present system adjusts MNN models for each user on line. This paper also describes the evaluation experiments to confirm whether the generated variations on theme music reflect impressions of story scenes appropriately or not.