A New Inductive Debris Sensor Based on Dual-Excitation Coils and Dual-Sensing Coils for Online Debris Monitoring

Lubricants are of key importance for mechanical processing, and exist in nearly every mechanical system. When the equipment is in operation, debris particles will be generated in mechanical lubricants. The detection of debris particles can indicate the wear degree of machinery components, and provide prognosis warning for the system before the fault occurs. In this work, a novel type of inductive debris sensor consisting of two excitation coils and two sensing coils is proposed for online debris monitoring. The developed sensor was proven to be of high sensitivity through experimental verification. The testing results show that, using the designed sensor, ferrous metal debris with a size of 115 μm and nonferrous metal debris with a size of 313 μm in a pipe with an inner diameter of 12.7 mm can be effectively detected. Moreover, the proposed inductive debris sensor structure has better sensitivity at higher throughput and its design provides a useful insight into the development of high-quality sensors with superior performances.

Numerical models of hydrodynamics and marine debris in the Malacca Strait

The Malacca Strait is a very strategic world trade route and the potential for environmental pollution is also very large, especially pollution from ship and people activities. This study aims to perform numerical simulations to determine the movement of marine debris particles around the waters of Rupat Island, Malacca Strait. The modelling was carried out from June to December 2020 using a modelling application with the basic principles of mesh discretization and the Lagrangian method. The results showed maximum current velocity during the simulation around the distribution area of debris is a maximum of 0.92 m/s. Marine debris around the waters of Rupat Island, the Malacca Strait has the potential to be stranded on the mainland of Rupat Island, mainland Riau, Bengkalis Island and also mainland Malaysia.

Influence of Carbon: Metal Ratio on Tribological Behavior of Mo-W-C Coating

Mo-W-C coatings with three different C/(Mo+W) ratios (5:1, 2.8:1 and 2.2:1) were deposited by using combined unbalanced magnetron sputtering (UBMS) and high-power impulse magnetron sputtering (HIPIMS) technology. The influence of the C/(Mo+W) ratio on coating microstructure and related tribological properties at ambient temperature and at 200 °C were studied in lubricated condition (up to 7500 m and 1800 m of sliding distances, respectively). Results showed that a decrease in the C/(Mo+W) ratio could be correlated with an increase in coating thickness, adhesion strength, hardness and elastic modulus values, and a decrease in the degree of graphitization. At ambient temperature, outstanding tribological properties (very low friction and negligible wear) were observed irrespective of the C/(Mo+W) ratio. At 200 °C, low C/(Mo+W) ratios (2.8:1 and 2.2:1) were found particularly beneficial to achieve excellent tribological properties. The keys to significant friction reduction at 200 °C were (i) in situ formation of MoS2 and WS2 due to tribo-chemical reactions and (ii) presence of amorphous carbon debris particles in the protective tribolayer. With an increase in sliding distance, the tribolayer gradually lowered the friction coefficient by protecting both the coating and counterpart from severe wear. On the other hand, a high C/(Mo+W) ratio (5:1) led to low friction but noticeable abrasive wear at 200 °C.

Dynamic Simulation of Space Debris Cloud Capture Using the Tethered Net

Space debris, especially the space debris cloud, has threatened severely the safety of future space missions. In the framework of multibody system dynamics, a computational approach is proposed in this study to investigate the dynamics of net deployment and capture of space debris cloud using this net subject to large overall motions and large deformations. To obtain high simulation fidelity of capturing space debris cloud, the gradient deficient beam element of the absolute nodal coordinate formulation (ANCF) is employed to discretize threads which are woven into the net. The normal contact force between the net and the debris cloud and among debris particles is computed by using the penalty method. Some deployment examples are presented to investigate the influences of shooting velocity of bullets and microgravity as well as the angle between the traveling direction of the net and the microgravity direction on the deployment characteristics of the tethered net. Other capturing examples are given to clarify the effect of the deployment area of the net at the moment it starts to contact with the debris cloud on the capture rate and to demonstrate the effectiveness of the proposed approach for capturing space debris cloud using the net in microgravity conditions.

Effect of Titanium and Zirconium Oxide Microparticles on Pro-Inflammatory Response in Human Macrophages under Induced Sterile Inflammation: An In Vitro Study

The wear-debris particles released by shearing forces during dental implant insertion may contribute to inflammatory reactions or osteolysis associated with peri-implantitis by stimulating inflammasome-activation. The study aim was to examine cytotoxic and pro-inflammatory effects of titanium (TiO2) and zirconia (ZrO2) particles in macrophages regarding their nature/particle concentration over time under sterile lipopolysaccharide (LPS) inflammation. Macrophages were exposed to TiO2 and ZrO2 particles (≤5 µm) in cell culture. Dental glass was used as inert control and LPS (1 μg/mL) was used to promote sterile inflammation. Cytotoxicity was determined using MTT assays and cytokine expression of TNF-α, IL-1β and IL-6 was evaluated by qRT-PCR. Data were analyzed using Student’s t-test and ANOVA (p ≤ 0.05). Cytotoxicity was significantly increased when exposed to higher concentrations of glass, TiO2 and ZrO2 (≥107 particles/mL) compared to controls (p ≤ 0.05). Macrophages challenged with TiO2 particles expressed up to ≈3.5-fold higher upregulation than ZrO2 from 12 to 48 h. However, when exposed to LPS, TiO2 and ZrO2 particle-induced pro-inflammatory gene expression was further enhanced (p ≤ 0.05). Our data suggest that ZrO2 particles produce less toxicity/inflammatory cytokine production than TiO2. The present study shows that the biological reactivity of TiO2 and ZrO2 depends on the type and concentration of particles in a time-dependent manner.

Cold Welding Based Space Debris Removal System

Space Debris is a major problem posing a great threat to all the future space travels as well as to all the satellites which are orbiting around the earth. According to a definition by the Inter-Agency Debris Coordination Committee (IADC) “space debris are all man-made objects including fragments and elements thereof, in Earth orbit or re-entering the atmosphere, that are non-functional” [1]. According to J. C. Liou, even if we stop all the space launches the amount of space debris will remain constant up to 50 years but will increase later due to collisions among them [3], [4]. Till December 16, 2019 a total of 20047 objects are on orbit out of which 5370 objects are payloads and 14677 are debris, this means about 73% of the objects in orbit constitutes debris. [2] The rate at which the debris is generated is much greater than the rate at which this debris deaccelerates, leaves the earth orbit and re-enters the earth atmosphere. We can protect the future space missions from huge debris particles that are traceable but the small debris elements pose a major threat. In this paper we propose a technique to remove the small debris particles from Lower earth orbits based on cold welding. Cold welding is the process in which two similar metals stick to each other when there is a metal to metal contact in space. This happens because on the ground these metals have layers of oxides thus, two pure metals never come in contact but in space, due to wear and tear, this layer of oxides get removed irreversibly and as a result, pure metals come in contact and the adhesive forces cause the metals to join. The debris is orbiting around the earth at a speed of 17500 mph [10]. For our system we use a composite material made up of a combination of elements that usually orbit the earth. Since, in relative frames they are stationary by increasing the velocity with controlled amount we can control the impact during contact. We will propel this composite material with the same speed around the earth as the debris, so that in their relative frames it appears stationary. By bringing the debris particles into contact with the composite material, cold welding will take place between them and then, we will send the system to international space station where the captured debris particles are removed from the composite material. By repeating this process, we can remove most of the small debris particles of size less than 10cm which are orbiting around the earth in lower earth orbit.

Post-Covid-19 Pandemic Awareness on The Use of Micro- and Nano Plastic and Efforts into Their Degradation - A Mini Review

Micro- and nanoplastic pollution possess a global threat and cause a future problem and needs greater attention. Its pollution is also exacerbated recently by the use of abundance of plastic polymers in efforts to prevent and handle COVID-19 pandemic at the global scale. This review covered the major concerns about the characteristic, effect and bioremediation of micro- and nanoplastics of post COVID-19. Based on size, microplastic is described as debris particles smaller than 5 mm whereas, nanoplastic is referred to any particles smaller than 100 nm. Micro- and nanoplastic are easily ingested by many aquatic organisms at different trophic levels. This ingestion caused negative health impacts to all living organisms. Microplastic direct effect on living organism for example mechanical injury, false satiation, declined growth, promoted immune response, energy loss, disrupted enzyme activity and production, decreased fecundity, production of oxidative stress, and mortality. Nanoplastic could enter the circulatory system and caused negative effects on the cellular and molecular levels. Bioremediation of microplastic by magnoliophyta, bacteria, fungus and algae on several polymer forms was previously reported, however, not many on nanoplastic biodegradation. Therefore, current review will focus on the characteristics, effect and bioremediation effort of micro- and nanoplastic.

Wear Resistance of Medium Carbon Steel with Different Microstructures

In this research, the tribological properties of different microstructures of medium carbon steel produced by either an austempered process or quenched-tempered process are investigated. The as-received samples with annealed microstructure (spherodized) are austempered to obtain a bainite microstructure or quenched-tempered to obtain a tempered martensite microstructure. The tribological performance of these microstructures was studied using a ball-on-disk UMT3 tribometer. The results indicated that both bainite microstructures and tempered-martensite microstructures produced better wear resistance than pearlite microstructures. At the same hardness level, the austempered disk specimens have less cracking due to higher fracture toughness compared to quenched and tempered steel. For the disks, tempered martensite microstructures produced more plastic deformation compared with bainite microstructures. Mild abrasive wear was observed on the harder disks, however, smearing wear was observed on the softer disks. Adhered debris particles were observed on the balls.