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Friction surfacing is a solid-state metal deposition technology, which has potential application in additive manufacturing. In this paper, multilayer of AA6061 deposition was fabricated on 316L steel plate by friction surfacing. The morphology, temperature field, axial force, microstructure, and mechanical properties of the deposition were analyzed. It was found that with the increase of substrate surface roughness, the thickness of deposition increased, the width decreased, and the bonding strength increased. The grain size increased and the hardness decreased from the top layer to the bottom layer of the deposition as a result of reheating by subsequent layer surfacing process. The bonding strength between the substrate and deposition decreased when the number of layers increased.

The IC engine still plays an important role in global markets, although electrified vehicles are highly demanded in some markets. Emission requirements for stoichiometric operation are challenging. This requires the bolted joints for turbo, EGR (Exhaust Gas Recirculation) and exhaust manifold to work under much higher temperature than before. How to avoid fastener breakage due to bolt bending caused by cyclic changes of the thermal conditions in engines is a big challenge. The temperatures of the components in the exhaust, EGR (Exhaust Gas Recirculation) and turbo systems change from ambient temperature to about 800 ~ 1000 °C when engines run at peak power with wide-open throttle. The temperature change induces catastrophic cyclic bending and axial strain to the fasteners. This research describes a method to reduce the cyclic bending displacement in the fasteners using a low friction washer. Mathematical modeling and FEA methods have been employed to specify the design space based on the engine operating conditions. A series of tribological bench tests were conducted to evaluate different coatings on the washer under room temperature and up to 600 °C. A sensitivity study has also been done to identify the factors that affect the coefficient of friction (CoF). A multi-layer coating has been found to be able to provide a low coefficient of friction under high temperature and high pressure. It meets the design requirements and has been validated by engine dyno tests on the exhaust system.

The present research investigated the effects of welding current and welding time on the shearing strength of resistance spot-welded joints of low carbon steel and stainless steel plates. The macro characteristics, microstructure and micro-hardness of welded joints were also examined. It was found that the welded joints produced with a welding current of 10 kA and welding time of 80 ms showed the highest shearing strength. The diameter of welded joints and nuggets increased with increasing welding current and welding time. For evaluation of the microstructure, different regions including the nugget, coarse heat-affected zone, fine heat-affected zone and base materials were observed within the welded joints. Also, the nugget and coarse heat-affected zone showed higher hardness than the fine heat-affected zone and base materials due to the presence of martensite. The findings obtained in this research are applicable in the development of resistance spot welding processes for joining dissimilar steel plates.

The tribological properties of SnO2 nanofluids were investigated using ball-on-plate reciprocating sliding wear tests. It was found that the coefficient of friction was reduced by 34.9% using 3 wt% SnO2 nanoparticles. The wear width and wear depth were reduced by 42% and 50.1%, respectively, using 2 wt% SnO2 nanoparticles. In the orthogonal tests, the frequency had the greatest influence on the friction and wear loss. Additionally, the optimal working conditions were a normal load of 50 N, a motion frequency of 1 Hz, and a surface roughness of 500–600 nm. Additionally, the excellent tribological performance of SnO2 nanofluids could be attributed to the formation of a tribo-film with a low shearing resistance due to the oleic acid and a protective layer due to the embedment of SnO2 nanoparticles.

The current generative adversarial network (GAN) is limited in the application of data augmentation in object recognition. The training of the GAN is unstable, and the generated image quality is poor. Methods such as progressive growing of GANs and multi-scale gradient GAN solve these problems. The packed GAN (PacGAN) solves the problem of mode collapse during training. However, these methods can generate only one type of image at a time, and the training time is long. To solve the above problems, this paper proposes the multi-class GAN (Mc-GAN). It uses an augmented discriminator to train multiple generators at the same time. Through iterative training, the discriminator can accurately judge the output of each generator and guide it to generate the corresponding image. This paper analyzes the optimization process of the objective function of Mc-GAN. Experiments show that the method can generate high-quality images and reduce training time, and it can be used for data augmentation in object recognition. It effectively improves the practicality of GAN.

To study the effects of cooking methods on the structure and digestion changes of starch encapsulated by cellular structure, intact potato parenchyma cells were successfully isolated and then subjected to different domestic cooking methods, including baking, frying, boiling, and autoclaving. The morphology, crystalline structure, thermal properties, and in vitro starch digestibility of cooked cell samples were investigated. Our results indicated that potato cell walls remained intact and performed as physical barriers preventing the diffusion/absorption of α-amylase to intracellular starch substrates after baking or frying treatment. However, boiling or autoclaving treatment destroyed cell wall structure, and the disrupted cellular structure reduced the digestion rate, likely by inhibiting diffusion of amylase through a weakened cell wall barrier, but could not lower the final digestion extent when compared to the pure starch. These findings suggested that potato products with lower glycemic index can be obtained by baking or frying treatment.

With the rapid growth in the use of electronics, more studies are focusing on the tribological performance of electrical connectors. The most common electroplating coating materials are tin and copper. One major issue is when fretting corrosion produces metal oxides, which are likely to increase the electrical resistance at the contact interface. This research aims to reduce metal oxidation of electrical connectors by studying the tribological performance of various thicknesses of tin and copper layers with a designated electrical circuit to be used with a reciprocating wear test. This research considers the effect of tin and copper layer thickness, including the lack of a tin layer, on the tribological behavior. Among coatings tested, a thin coating of copper with no tin resulted in the least wear. A thicker coating of copper significantly increased the wear due to the high roughness of the sample with a thick copper coating. Scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) results indicated that adhesive wear occurred during sliding. Adhered particles led to two-body abrasive wear and when the adhered particles break away three-body abrasive wear is produced.

In this research, the effects of laser surface hardening treatment on the phase transformation of austempered and quench-tempered grey cast irons were investigated. It was found that there were fou...

The generative adversarial network (GAN) has recently emerged as a promising generative model. Its application in the image field has been extensive, but there has been little research concerning point clouds.The combination of a GAN and a graph convolutional network has been the state-of-the-art method for generating point clouds. However, there is a significant gap between the generated point cloud and the point cloud used for training. In order to improve the quality of the generated point cloud, this study proposed multi-scale gradient point GAN (MSG-Point-GAN). The training of the GAN is a dynamic game process, and we expected the generation and discrimination capabilities to be symmetric, so that the network training would be more stable. Based on the concept of progressive growth, this method used the network structure of a multi-scale gradient GAN (MSG-GAN) to stabilize the training process. The discriminator of this method used part of the PointNet structure to resolve the problem of the disorder and rotation of the point cloud. The discriminator could effectively determine the authenticity of the generated point cloud. This study also analyzed the optimization process of the objective function of the MSG-Point-GAN. The experimental results showed that the training process of the MSG-Point-GAN was stable, and the point cloud quality was superior to other methods in subjective vision. From the perspective of performance metrics, the gap between the point cloud generated by the proposed method and the real point cloud was significantly smaller than that generated by other methods. Based on the practical analysis, the point cloud generated by the proposed method for training the point-cloud classification network was improved by about 0.2%, as compared to the original network. The proposed method provided a stable training framework for point cloud generation. It can effectively promote the development of point-cloud-generation technology.

At present, the LiDAR ground filtering technology is very mature. There are fewer applications in 3D-object detection due to the limitations of filtering accuracy and efficiency. If the ground can be removed quickly and accurately, the 3D-object detection algorithm can detect objects more accurately and quickly. In order to meet the application requirements of 3D-object detection, inspired by Universal-RANSAC, we analyze the detailed steps of RANSAC and propose a precise and efficient RANSAC-based ground filtering method. The principle of GroupSAC is analyzed, and the sampled points are grouped by attributes to make it easier to sample the correct point. Based on this principle, we devise a method for limiting sampled points that is applicable to point clouds. We describe preemptive RANSAC in detail. Its breadth-first strategy is adopted to obtain the optimal plane without complex iterations. We use the International Society for Photogrammetry and Remote Sensing (ISPRS) datasets and the KITTI dataset for testing. Experiments show that our method has higher filtering accuracy and efficiency compared with the currently widely used methods. We explore the application of ground filtering methods in 3D-object detection, and the experimental results show that our method can improve the object detection accuracy without affecting the efficiency.

Austempered ductile iron has been considered as a substitution to replace conventional steel castings, steel forgings and even aluminum in many applications. Its excellent mechanical properties are mainly attributed to its unique ausferritic structure containing acicular ferrite and carbon saturated austenite. Some ADI components such as camshaft and engine valve commonly experience surface contact and relative motion under external load and pressure. Outstanding wear resistance of ADI is required to ensure the satisfactory working performance and service life of these key components. In order to meet the advanced requirements of mechanical properties and wear behavior of ADI, a dual-step austempering process and additional surface hardening treatments are suggested to be utilized. In this review, conventional single-step austempering process and corresponding ausferritic structure are introduced. Second, the positive effects of a novel dual-step austempering process on microstructure and mechanical properties of ADI are provided. Next, wear behavior of single-step and dual-step ADIs and wear mechanisms are discussed. Then, studies regarding the applications of surface hardening treatments on wear resistance of ADI are reviewed. Finally, a summary and expectations are discussed. The information presented in this paper would be beneficial to future studies and applications for any grade of ADI.

The current research focused on the tribological properties of flake-like WS2 particles dispersed into PAO4 base oil with oleic acid as surfactant. Various concentrations of 0.2 mass%, 1 mass% and 3 mass% were applied in the preparation of WS2-OA lubricant. The wear tests were carried out using a ball-on-plate reciprocating sliding test configuration. It was found that the highest COF of 0.578 was obtained using PAO4 base oil with significant fluctuations. The COF could be reduced to approximately 0.34 and stabilized after adding the OA. When introducing the WS2 articles, the COF was around 0.158 under 0.2 mass%, 0.143 under 1 mass% and 0.145 under 3 mass%, and became almost constant after 4 min. In addition, the highest wear rate in width of 61.5 µm/m and in depth of 2.2 µm/m was found using PAO4 base oil. The wear rate can be reduced to 51.6 µm/m in width (16.1%) and 0.9 µm/m (59.1%) in depth under 3 mass% OA. While using the WS2 particles, the wear rate in width could be further reduced to 45.2 µm/m using 1 mass% but with slightly higher wear rate in depth than that of OA. Based on the analysis in SEM and EDX, the abrasive grooves became less after introducing the OA, some dark spots composed of carbon acted as tribo-films on the worn area. While using WS2 particles, it could be found that WS2 flakes were adhered on the surfaces to reduce the friction and wear.

The present research studied the combined effects of quench-tempering and laser surface hardening treatments on wear behavior of gray cast iron, and compared results with conventional austempered gray cast iron. Four tempering temperatures of 316 °C (600 °F), 399 °C (750 °F), 482 °C (900 °F) or 552 °C (1025 °F) with a constant holding time of 60 min and four austempering temperatures of 232 °C (450 °F), 288 °C (550 °F), 343 °C (650 °F) or 399 °C (750 °F) with a constant holding time of 120 min were utilized in the heat treatment design. The wear tests were carried out on a universal mechanical tribometer with a reciprocating ball-on-plate sliding configuration. Also, the microstructure, micro-hardness profiles and worn tracks were examined. Through this work, it was found that three zones existed under the laser hardened surface. Zone 1 was the laser hardened zone containing ledeburite with hardness of approximately 68HRC. Zone 2 was the heat affected zone containing the martensite with hardness of approximately 66HRC. Zone 3 was the substrate with hardness ranging from 42.1 to 24.8HRC. In the sliding wear tests, the quench-tempering treatment only resulted in higher wear resistance of gray cast iron when compared with untreated specimens, but lower wear resistance than that of austempered gray cast iron under similar macro-hardness. The wear performance of the quench-tempered gray cast iron was enhanced after receiving the laser surface hardening treatment. Finally, the laser hardened and quench-tempered gray cast iron with tempering temperature of 552 °C showed similar mass loss due to wear as austempered gray cast iron with an austempering temperature of 232 °C. By observing the worn surfaces, the laser hardened regions could effectively inhibit the formation and propagation of cracks developed within the substrate regions. In addition, the substrate with low hardness in laser hardened and quench-tempered gray cast iron may provide enhanced ductility and toughness for gray cast iron engineering components. The results obtained in this research have significant value in selecting the optimum heat treatment process for laser hardened gray cast iron components.

Nowadays rumors spread by virtual identities of people in online social networks. In order to study the influence of forcing silence on spreaders, we propose a rumor propagation model with a silence-forcing function in online social networks. The theoretical analysis of the rumor propagation model reveals the existence of the equilibrium points, the backward bifurcation and the local stability. Meanwhile, by choosing the key parameter and time delay as the bifurcation parameters, we have given some conditions of Hopf bifurcation that are easy to judge. Furthermore, the optimal control is discussed to reduce the frequency of rumor propagation. Finally, numerical simulations are presented to prove the correctness of the theoretical results.

The present study mainly investigated the phase transformation and wear performance of laser hardened austempered gray cast iron specimens. Ball-on-Plate reciprocating sliding wear tests with PAO4 base oil were carried out on untreated, quench-tempered, austempered, laser hardened austempered gray cast iron specimens. Micro hardness profiles and worn surfaces were analyzed for specific wear mechanisms. It was found that four different zones were formed beneath the laser hardened surface including laser hardened zone (Ledeburite, ≈67HRC), upper heat affected zone (Martensite, ≈69HRC), lower heat affected zone (Tempered Ausferrite, ≈36HRC) and substrate (Ausferrite, ≈39HRC). In the sliding wear tests, the laser hardened austempered gray cast iron specimens showed higher wear resistance than others, which could be associated with the benefits of ausferritic structure with high fracture toughness and laser hardened regions with high hardness. By observing the worn surface, grooves and micro-sized material removal occurred within the substrate. The surface of the substrate ploughed by the asperities of the ball and hard wear debris stopped on the edge of the laser hardened regions since ledeburite and martensite had high hardness and abrasive wear resistance. However, some micro-cracks and spalls were developed within the laser hardened zone. The results obtained from this study could be used as reference in future research and applications of laser hardened austempered gray cast iron. Keywords: Gray cast iron, Austempering, Laser hardening, Sliding wear resistance

The tensile test is an important test to determine several mechanical properties in which a sample is subjected to a constant strain rate until failure. Properties that are directly measured in a tensile test are ultimate tensile strength, breaking strength, maximum elongation, and reduction in area. The present research compared the tensile properties between austempered SAE52100 steel and quench-tempered SAE52100 steel under equivalent hardness. The experimental results showed that the ultimate tensile strength and yield strength of quench-tempered specimens was higher than austempered specimens. However, the total elongation and area reduction of quench-tempered specimens was lower than austempered specimens. Transgranular quasi-cleavage fracture was found on the austempered SAE52100 steel specimens. While using the austempering temperature of 288 °C, slight plastic deformation with existence of cleavage facets and ductile risers around the edges was obtained. However, while using the austempering temperature of 427 °C, the presence of tear marks on the cleavage facets surrounded by dimples indicated significant plastic deformation or ductile rupture. The fracture analysis could be correlated with the elongation obtained in tensile tests.

Austempered ductile iron (ADI) is a type of graphite cast iron produced by an isothermal heat treatment process. It is an alternative to traditional steel castings and forgings and even aluminum due to the exceptional mechanical properties such as high strength, good toughness and excellent machinability. In the matrix, the unique ausferritic structure consists of graphite nodules uniformly surrounded by acicular ferrite and carbon saturated austenite. In the automotive industry, ADI has been commonly applied in the manufacturing of camshafts, crankshafts, gears and engine valves. These components are frequently subjected to surface contact with relative motion and external load. Therefore, it is necessary to understand the wear behavior of ADI in order to solve the tribological issues in existing ADI applications and utilize ADI into future designs appropriately. This paper was aimed at reviewing the fabrication processes of single-step and dual-step ADIs. The corresponding microstructure and mechanical properties were also briefly discussed. The studies on wear performance of ADI and potential mechanisms have been systemically reviewed. Keywords: Austempered ductile iron, Single-step austempering, Dual-step austempering, Stress-induced transformation, Wear resistance

The objective of this research was to investigate the bainitic formation in austempered SAE 52100 steel. The original microstructure of SAE 52100 steel consisted of spheroidized pearlite. In the formation of bainite, SAE 52100 steel samples were austenitized at a temperature of 849 °C for 20 min, and then quickly quenched to the isothermal temperatures between 232 °C and 427 °C for various holding times from 20 s to 120 min. The hardness and microstructure of austempered SAE 52100 samples were analyzed using a Rockwell C hardness tester and metallurgical optical microscope. In addition, the bainitic formation in SAE 52100 steel was characterized using the theory of kinetic phase transformation. The activation energies of lower bainite and upper bainite microstructure were found to be 4.72 × 104 J/mol and 6.07 × 104 J/mol with frequency factors of 23.03 (1/s) and 273.65 (1/s), respectively. Keywords: SAE 52100 steel, Austempering, Bainite, Rockwell hardness, Transformation kinetics

Organophosphorus pesticides (OPs) play a certain role in promoting the development of agriculture and forestry, but they may cause potential harm to aquatic life when entering rivers and polluting water sources. Previous researches have shown that OPs participate in the regulation mechanism of aquatic organisms. Here, our aim is to determine the underlying mechanisms of one OP (dimethoate) at the transcriptional level using the clam Meretrix meretrix. 4119 DEGs were obtained from high-throughput RNA sequencing data. Then, expression profiles of some genes were verified by qPCR, which showed a positive correlation with the RNA sequencing results. 14,481 simple sequence repeats were also identified and could be further used as molecular markers. In addition, some oxidative, immune, and stress-related genes were further discussed and could also be used as biomarkers to indicate the biological response of dimethoate. This study will help to better understand the clam's response mechanism to dimethoate stress.

The Press-in-Place (PIP) gasket is a static face seal with self-retaining feature, which is used for the mating surfaces of engine components to maintain the reliability of the closed system under various operating conditions. Its design allows it to provide enough contact pressure to seal the internal fluid as well as prevent mechanical failures. Insufficient sealing pressure will lead to fluid leakage, consequently resulting in engine failures. A test fixture was designed to simulate the clamp load and internal pressure condition on a gasket bolted joint. A sensor pad in combination with TEKSCAN equipment was used to capture the overall and local pressure distribution of the PIP gasket under various engine loading conditions. Then, the test results were compared with simulated results from computer models. Through the comparisons, it was found that gasket sealing pressure of test data and CAE data shows good correlations in all internal pressure cases when the bolt load was 500 N. Compared to 0.138 MPa and 0.276 MPa, better correlation to CAE results was observed at the 0 MPa internal pressure condition. Moreover, the gasket cross-sectional pressure distribution obtained by experimental tests and CAE models correlated very well with R2 (Coefficient of Determination) ranging from 90% to 99% for all load cases. Both CAE and sensor pad test results shows an increase in sealing pressure when internal side pressure is applied to the gasket seal.

The present research evaluated the tribological performance of oil-based WS2 nanofluids applied on steel-brass friction pairs. It was found that the coefficient of friction could be reduced by up to 39%, and the wear width and depth could be reduced by up to 28.7% and 66.4% using 1 wt% WS2 nanofluid. While using the WS2 nanofluids, almost no adhesive wear was detected on the worn surfaces. By analyzing the chemical compositions, carbon percentage increased after engaging the oleic acid which suggested tribo-films with low shear resistance were formed. In addition, elements of sulfur and tungsten were found within the wear track lubricated by WS2 nanofluids. It was believed that the WS2 nanoparticles were involved in the formation of the tribo-layers and mixed with the oleic acid tribo-films to improve the tribological behavior. Moreover, the tribo-layers produced by the WS2 nanoparticles could provide solid lubricating and mending effects on the mating surfaces.

Signature verification is essential to prevent the forgery of documents in financial, commercial, and legal settings. There are many researchers have focused on this topic, however, utilizing the 3-D information presented by a signature using a 3D optical profilometer is a relatively new idea, and the convolutional neural network is a powerful tool for image recognition. The present research focused on using the 3 dimensions of offline signatures in combination with a convolutional neural network to verify signatures. It was found that the accuracy of the data for offline signature verification was over 90%, which shows promise for this method as a novel method in signature verification.

Nanoparticles acting as additives to improve the tribological performance of base fluids have attracted much attention in the last several decades to lower wear loss, reduce the frictional force, enhance the service performance and extend the service life of sliding components. Different nanoparticles with various concentrations, mixing methodologies, surfactants and surface modifications have been frequently studied for in-depth understanding. The present research reviews the applications of nanoparticles as lubricant additives and their tribological properties. The common nano-sized materials, production processes, classifications of surfactants, surface modifications, friction reduction and anti-wear behavior of various nanolubricants are summarized. The potential mechanisms which can result in excellent tribological properties of nanolubricants are discussed. The limitations and challenges in applications and commercialization of nanolubricants are introduced. Finally, the recommendations for the development and the directions of future studies related to nanolubricants are provided. The information reported in the present work can be utilized as references in the development of high-performance nanolubricants and specific applications of nanolubricants in mechanical systems.

Reinforced vermicular graphite cast irons were prepared by using aluminum precursor master alloy containing TiC-TiB2 nanoparticles. It was found that the vermicularity and amount of graphite increased by 15.0% and 16.6%, and grain size decreased by 32.9%. The yield strength, tensile strength and elongation were improved by 10.0%, 6.0% and 26.3% at a temperature of 20 °C, and 11.6%, 6.8% and 22.1% at a temperature of 150 °C. In addition, the wear volume loss was reduced by 18.0% by addition of the nanoparticles.

The current research studied the effects of laser surface hardening treatment on the phase transformation and wear properties of gray cast irons heat treated by austempering or quench-tempering, respectively. Three austempering temperatures of 232 &deg, C, 288 &deg, C, and 343 &deg, C with a constant holding duration of 120 min and three tempering temperatures of 316 &deg, C, 399 &deg, C, and 482 &deg, C with a constant holding duration of 60 min were utilized to prepare austempered and quench-tempered gray cast iron specimens with equivalent macro-hardness values. A ball-on-flat reciprocating wear test configuration was used to investigate the wear resistance of austempered and quench-tempered gray cast iron specimens before and after applying laser surface-hardening treatment. The phase transformation, hardness, mass loss, and worn surfaces were evaluated. There were four zones in the matrix of the laser-hardened austempered gray cast iron. Zone 1 contained ledeburite without the presence of graphite flakes. Zone 2 contained martensite and had a high hardness, which was greater than 67 HRC. Zone 4 was the substrate containing the acicular ferrite and carbon-saturated austenite with a hardness of 41&ndash, 27 HRC. In Zone 3, the substrate was tempered by the low thermal radiation. For the laser-hardened quench-tempered gray cast iron specimens, three zones were observed beneath the laser-hardened surface. Zone 1 also contained ledeburite, and Zone 2 was full martensite. Zone 3 was the substrate containing the tempered martensite. The tempered martensite became coarse with increasing tempering temperature due to the decomposition of the as-quenched martensite and precipitation of cementite particles. In the wear tests, the gray cast iron specimens without heat treatment had the highest wear loss. The wear performance was improved by applying quench-tempering heat treatment and further enhanced by applying austempering heat treatment. Austempered gray cast iron specimens had lower mass loss than the quench-tempered gray cast iron specimens, which was attributed to the high fracture toughness of acicular ferrite and stable austenite. After utilizing the laser surface hardening treatment, both austempered and quench-tempered gray cast iron specimens had decreased wear loss due to the high surface protection provided by the ledeburitic and martensitic structures with high hardness. In the worn surfaces, it was found that cracks were the dominant wear mechanism. The results of this work have significant value in the future applications of gray cast iron engineering components and provide valuable references for future studies on laser-hardened gray cast iron.

The current research investigated the microstructure and tensile properties of as-cast low carbon steels manipulated by TiC-TiB2 nanoparticles. It was found that the microstructure mainly contained blocky ferrite and pearlite. Widmanstatten structure consisting of acicular ferrite was also obtained in the matrix of unmodified low carbon steels. After introducing 0.01 wt% and 0.02 wt% TiC-TiB2 nanoparticles, the formation of widmanstatten structure was inhibited. The pearlite content increased from 26.3% to 36% and 36.7% respectively. The grain size reduced from 58.3 μm to 43.3 μm and 42.8 μm. For tensile properties, the yield strength, tensile strength and elongation of low carbon steels increased by 9.8%, 7.6%, 20.4% and 14.0%, 11.0% and 8.2%. The as-cast microstructure was refined since the nanoparticles act as heterogenous cores to promote the nucleation rate and hinder the growth of grains. The improved strength could be associated with the fine-grain, thermal-mismatch and dispersion strengthening mechanisms, and the improved ductility could be associated with the fine microstructure and scattering effects of nanoparticles.

In this research, an austempering heat treatment was applied on gray cast iron using various austempering temperatures ranging from 232 &deg, C to 371 &deg, C and holding times ranging from 1 min to 120 min. The microstructure and hardness were examined using optical microscopy and a Rockwell hardness tester. Rotational ball-on-disk sliding wear tests were carried out to investigate the wear behavior of austempered gray cast iron samples and to compare with conventional quenched and tempered gray cast iron samples under equivalent hardness. For the austempered samples, it was found that acicular ferrite and carbon saturated austenite were formed in the matrix. The ferritic platelets became coarse when increasing the austempering temperature or extending the holding time. Hardness decreased due to a decreasing amount of martensite in the matrix. In wear tests, austempered gray cast iron samples showed slightly higher wear resistance than quenched and tempered samples under similar hardness while using the austempering temperatures of 232 &deg, C, 260 &deg, C, 288 &deg, C, and 316 &deg, C and distinctly better wear resistance while using the austempering temperatures of 343 &deg, C and 371 &deg, C. After analyzing the worn surface, abrasive wear and fatigue wear with the presence of pits, spalls, voids, long cracks, and wear debris were the main mechanisms for austempered gray cast iron with a low austempering temperature. However, only small pits and short cracks were observed on the wear track of austempered gray cast iron with high austempering temperature. Furthermore, the graphite flakes were exposed and ground by the counterpart surface during wear tests. Then, the graphite particles would form a tribo-layer to protect the contact surface.

Tor is the most widely used system for anonymous low-latency communication. However, the anonymity of TOr is not invulnerable according to a large amount of researches, even with the traffic obfuscation provided by pluggable transports. Concerned about security issues such as identity leakage, users deploy fronting servers as proxies that forward traffic to the entry node of Tor, and encrypted tunneling services such as secure shell (SSH) protocol are commonly used to connect users with proxies. To quantitatively analyze the plugin-based Tor traffic over encrypted tunnels, experiments involving the traffic identification and correlation are performed. Identification aims at recognizing tunneled Tor flows among background traffic at the client side, while correlation associates outward flows of Tor at the server side with corresponding inward flows at the client side. We access to the self-built server through the SSH proxy and Tor successively, capturing data flows generated by different pluggable transports and upper applications. Then identification and correlation techniques based on various machine learning algorithms are used to break anonymity. The accuracy and F1 scores reach above 95% while false positive rates approach 0% under certain conditions. The result demonstrates that Tor traffic encrypted by tunneling protocols is also at risk of anonymity revealing when confronted with traffic analysis.

Austempered ductile iron (ADI) is produced by an isothermal heat treatment. Tempering is an effective method to increase the toughness and decrease the hardness of ADI. In the present research, the transformation of ADI was investigated after applying various tempering temperatures. The hardness of ADI samples with and without tempering was measured and the microstructure of ADI samples was analyzed by using metallographic optical microscopy. It was found that the ausferrite decomposed into dispersive cementite particles above a tempering temperature of 538 °C. Thus, the tempering process for ADI must be carefully selected so that the excellent properties of ADI are not degraded. Keywords: ADI, Tempering process, Hardness measurement, Phase transformation, Microstructure