Tribological Properties of Solid Lubricant WS2 in Dimples on the Cylinder of Diesel Engine at High Temperature.

Solid lubricant WS2 was encapsulated in the dimples on the cylinder surface by the hot-pressing method. The tribological and releasing performance of the as-prepared sample were investigated under high temperature conditions. The results indicate that, compared with the original cylinder, WS2 in the dimples exhibited better tribological properties at high temperature than at room temperature. The average friction coefficients of the as-prepared samples were about 0.13 and 0.15 at high temperature and room temperature, respectively, which were 27.8% and 16.7% lower than that of the original cylinder, respectively. Moreover, compared with the original cylinder, the anti-adhesion time of the as-prepared sample increased 2.3-fold. Additionally, the reduced viscosity of the lubricating oil caused by high temperature accelerated the erosion effect and release rate of the solid lubricant in the dimples. Thus, the polar additives in the lubricating oil and the chemical reactions between the cylinder substrates and solid lubricants that WS2 released from the dimples are the main factors in friction reduction. This study provides some guidance for anti-friction design of cylinders under high temperature conditions.

Effect of nickel-coated carbon nanotubes on the preparation and wear resistance of microarc oxidation ceramic coating on ZL109 aluminum alloy.

In order to adapt to the development of lightweight equipment, and further improve the wear resistance of ZL109 aluminum alloy, the influence of nickel-coated carbon nanotubes as an electrolyte additive on the preparation and wear resistance of microarc oxidation ceramic coatings on ZL109 aluminum alloy surface was investigated. In this work, 0.4 g/L, 0.8 g/L, 1.2 g/L, 1.6 g/L, and 2 g/L nickel-coated carbon nanotubes were added to the electrolyte respectively. The microarc oxidation ceramic coatings were prepared under bipolar pulse constant pressure mode, which were analyzed from the aspects of morphology, chemical composition, and wear resistance property. The results show that the nickel-coated carbon nanotubes possess a great influence on ceramic coatings. The morphology of ceramic coatings was significantly changed. In this work, the coating prepared by 1.2 g/L nickel-coated carbon nanotubes exhibits excellent wear resistance property.

Effect of nano h-BN particles on growth regularity and tribological behavior of PEO composite ceramic coating of ZL109 alloy.

A composite ceramic coating containing h-BN particles was prepared on the ZL109 alloy via plasma electrolytic oxidation. The h-BN particles were modified by Polyethylene glycol to improve the dispersibility. The results revealed that the h-BN particles in the electrolyte were inertly incorporated into the coating. Meanwhile, the incorporation of h-BN particles can reduce the porosity and slightly increase the roughness of the composite ceramic coating. Furthermore, the growth rate of the coating and the conversion of γ-Al2O3 and α-Al2O3 were promoted by the incorporation of h-BN particles via the change of the current. In addition, due to the presence of h-BN particles, the composite ceramic coating had a lower friction coefficient and a lower wear rate under dry sliding condition.

Evidence of the Berezinskii-Kosterlitz-Thouless phase in a frustrated magnet.

The Berezinskii-Kosterlitz-Thouless (BKT) mechanism, building upon proliferation of topological defects in 2D systems, is the first example of phase transition beyond the Landau-Ginzburg paradigm of symmetry breaking. Such a topological phase transition has long been sought yet undiscovered directly in magnetic materials. Here, we pin down two transitions that bound a BKT phase in an ideal 2D frustrated magnet TmMgGaO4, via nuclear magnetic resonance under in-plane magnetic fields, which do not disturb the low-energy electronic states and allow BKT fluctuations to be detected sensitively. Moreover, by applying out-of-plane fields, we find a critical scaling behavior of the magnetic susceptibility expected for the BKT transition. The experimental findings can be explained by quantum Monte Carlo simulations applied on an accurate triangular-lattice Ising model of the compound which hosts a BKT phase. These results provide a concrete example for the BKT phase and offer an ideal platform for future investigations on the BKT physics in magnetic materials.

Printable, Highly Sensitive Flexible Temperature Sensors for Human Body Temperature Monitoring: A Review.

In recent years, the development and research of flexible sensors have gradually deepened, and the performance of wearable, flexible devices for monitoring body temperature has also improved. For the human body, body temperature changes reflect much information about human health, and abnormal body temperature changes usually indicate poor health. Although body temperature is independent of the environment, the body surface temperature is easily affected by the surrounding environment, bringing challenges to body temperature monitoring equipment. To achieve real-time and sensitive detection of various parts temperature of the human body, researchers have developed many different types of high-sensitivity flexible temperature sensors, perfecting the function of electronic skin, and also proposed many practical applications. This article reviews the current research status of highly sensitive patterned flexible temperature sensors used to monitor body temperature changes. First, commonly used substrates and active materials for flexible temperature sensors have been summarized. Second, patterned fabricating methods and processes of flexible temperature sensors are introduced. Then, flexible temperature sensing performance are comprehensively discussed, including temperature measurement range, sensitivity, response time, temperature resolution. Finally, the application of flexible temperature sensors based on highly delicate patterning are demonstrated, and the future challenges of flexible temperature sensors have prospected.

Anticorrosive non-crystalline coating prepared by plasma electrolytic oxidation for ship low carbon steel pipes.

A corrosion-resistant non-crystalline coating was fabricated by plasma electrolytic oxidation (PEO) on Q235 low carbon steel for ship pipes. The distribution and composition of chemical elements and phases of PEO coatings were analyzed by an orthogonal experiment, and the formation mechanism of PEO coatings was discussed. The corrosion current densities and corrosion potentials were measured. The results indicated that the formation of a transition layer mainly containing Fe3O4 was crucial for achieving an excellent coating quality. Furthermore, the corrosion current density of coated steel was reduced by 78% compared with the bare steel.

A semi-automatic method of generating subject-specific pediatric head finite element models for impact dynamic responses to head injury.

To account for the effects of head realistic morphological feature variation on the impact dynamic responses to head injury, it is necessary to develop multiple subject-specific pediatric head finite element (FE) models based on computed tomography (CT) or magnetic resonance imaging (MRI) scans. However, traditional manual model development is very time-consuming. In this study, a new automatic method was developed to extract anatomical points from pediatric head CT scans to represent pediatric head morphological features (head size/shape, skull thickness, and suture/fontanel width). Subsequently, a geometry-adaptive mesh morphing method based on radial basis function was developed that can automatically morph a baseline pediatric head FE model into target FE models with geometries corresponding to the extracted head morphological features. In the end, five subject-specific head FE models of approximately 6-month-old (6MO) were automatically generated using the developed method. These validated models were employed to investigate differences in the head dynamic responses among subjects with different head morphologies. The results show that variations in head morphological features have a relatively large effect on pediatric head dynamic response. The results of this study indicate that pediatric head morphological variation had better be taken into account when reconstructing pediatric head injury due to traffic/fall accidents or child abuses using computational models as well as predicting head injury risk for children with obvious difference in head size and morphologies.

Brain Injury Differences in Frontal Impact Crash Using Different Simulation Strategies.

In the real world crashes, brain injury is one of the leading causes of deaths. Using isolated human head finite element (FE) model to study the brain injury patterns and metrics has been a simplified methodology widely adopted, since it costs significantly lower computation resources than a whole human body model does. However, the degree of precision of this simplification remains questionable. This study compared these two kinds of methods: (1) using a whole human body model carried on the sled model and (2) using an isolated head model with prescribed head motions, to study the brain injury. The distribution of the von Mises stress (VMS), maximum principal strain (MPS), and cumulative strain damage measure (CSDM) was used to compare the two methods. The results showed that the VMS of brain mainly concentrated at the lower cerebrum and occipitotemporal region close to the cerebellum. The isolated head modelling strategy predicted higher levels of MPS and CSDM 5%, while the difference is small in CSDM 10% comparison. It suggests that isolated head model may not equivalently reflect the strain levels below the 10% compared to the whole human body model.

An ordered mesoporous Ag superstructure synthesized via a template strategy for surface-enhanced Raman spectroscopy.

Surface-enhanced Raman scattering (SERS) substrates with high density and uniformity of nanogaps are proven to enhance the reproducibility and sensitivity of the Raman signal. Up to now, the syntheses of a highly ordered gold or silver superstructure with a controllable nanoparticle size and a well-defined particle gap have been quite limited. Here, we reported an ordered mesoporous silver superstructure replicated by using ordered mesoporous KIT-6 and SAB-15 as templates. By means of a nanocasting process, the ordered mesoporous Ag superstructure was successfully synthesized, which shows uniform distribution of the nanowire diameter (10 nm) and nanogap size (∼2 nm), thus exhibiting a high Raman enhancement of ∼10(9). The finite difference time-domain (FDTD) results indicate that the ordered mesoporous Ag superstructure has a uniform distribution of hot spots. Therefore, the mesoporous silica template strategy presented here could lead to a new class of high quality SERS substrates providing extraordinary potential for diverse applications.

TGF-ß1 induces epigenetic silence of TIP30 to promote tumor metastasis in esophageal carcinoma.

TGF-ß1, a potent EMT (epithelial-mesenchymal transition) inducer present in the tumor microenvironment, is involved in the metastasis and progression of various carcinomas, including esophageal squamous cell carcinoma (ESCC). TIP30 (30kDa HIV-1 Tat interacting protein) is a putative tumor metastasis suppressor. Here, we found TIP30 was decreased in cells undergoing EMT induced by TGF-ß1, an occurrence that was related to promoter hypermethylation. TGF-ß1 induced TIP30 hypermethylation via increasing DNMT1 and DNMT3A expression, which could be restored by TGF-ß antibodies. In our in vitro and in vivo studies, we showed that silence of TIP30 led to EMT, enhanced migrative and invasive abilities of ESCC cells, promoted tumor metastasis in xenografted mice; alternatively, overexpression of TIP30 inhibited TGF-ß1-induced EMT, and metastatic abilities of ESCC cells. Mechanically, TIP30 silencing induced the nuclear translocation and transcriptional activation of ß-catenin in an AKT-dependent manner, which further resulted in the initiation of EMT. Consistently, TIP30 was frequently methylated and downregulated in ESCC patients. Loss of TIP30 correlated with nuclear ß-catenin and aberrant E-cadherin expression. TIP30 was a powerful marker in predicting the prognosis of ESCC. Taken together, our results suggest a novel and critical role of TIP30 involved in TGF-ß1-induced activation of AKT/ß-catenin signaling and ESCC metastasis.

Impact direction effect on serious-to-fatal injuries among drivers in near-side collisions according to impact location: focus on thoracic injuries.

Occupant injury in real world vehicle accidents can be significantly affected by a set of crash characteristics, of which impact direction and impact location (or damage location) in general scale interval (e.g., frontal impact is frequently defined as general damage to vehicle frontal end with impact angle range of 11-1 o'clock) have been identified to associate with injury outcome. The effects of crash configuration in more specific scale of interval on the injury characteristics have not been adequately investigated. This paper presents a statistical analysis to investigate the combined effects of specific impact directions and impact locations on the serious-to-fatal injuries of driver occupants involved in near-side collisions using crash data from National Automotive Sampling System-Crashworthiness Data System (NASS-CDS) for the calendar years of 1995-2005. The screened injury dataset is categorized by three impact locations (side front, side center and side distributed) and two impact directions (oblique impact at 10 o'clock and pure lateral impact at 9 o'clock), resulting in six crash configurations in total. The weighted counts and the risks of different types of injuries in each subgroup are calculated, with which the relative risks along with 95% confidence intervals under oblique impacts versus lateral impacts in each impact location category are computed. Accordingly, the most frequent injury patterns, the risks and the coded-sources of serious thoracic injuries in different crash configurations are identified. The approach adopted in the present study provides new perspectives into occupant injury outcomes and associated mechanism. Results of the analyses reveal the importance of consideration of the crash configurations beyond the scope of existing side-impact regulatory tests and stress the necessity of vehicle crashworthiness and restraint system design in omni-direction to better protect occupants in real-world crash scenarios.

[The finite element study on zygomatic injury by impact in child].

OBJECTIVE: The purpose of this study was to establish the constructive of craniofacial suture in the three-dimensional finite element model of craniofacial complex in child, to analyse the response procedure of the zygomatic impact, to explore the biomechanics characteristic of the children craniofacial trauma. METHODS: A 7-year-old female was adopted for study The complex cranial geometry was measured from a series of two-dimensional CT images. The multi-lay spiral CT scans were transformed with a self-developed preprocessor into a finite element mesh. The craniofacial sutures were constructed through the MSC Patran program. Identical impact and boundary conditions were used for the zygomatic impact simulations. RESULTS: It has been shown that the finite element model (FEM) exhibited fine morphological and mechanical comparability. The higher stress was showed in the zygomatic regions and atlas occipital articular in 3d FEM. The maximum von Mises stress was found at the zygomatic regions and atlas occipital articular. CONCLUSION: The concentrations of shear stress and tension stress in the suture and articular would increase the risk of injury in this area. But the conduction of the stress might be weakening in the suture of child skull.

Biomechanical response of the bovine pia-arachnoid complex to normal traction loading at varying strain rates.

The pia-arachnoid complex (PAC) covering the brain plays an important role in the mechanical response of the brain due to impact or inertial loading. The mechanical properties of the bovine PAC under tensile loading have been characterized previously. However, the transverse properties of this structure, such as shear and normal traction which are equally important to understanding the skull/brain interaction under traumatic loading, have not been investigated. These material properties are essential information needed to adequately define the material model of the PAC in a finite element (FE) model of human brain. The purpose of this study was to determine, experimentally, the material properties of the PAC under normal traction loading. PAC Specimens were obtained from freshly slaughtered bovine subjects from various locations. Quasi-static and dynamic tests along the radial direction were performed at four different strain rates (0.36, 2.0, 20.5, and 116.3 s(-1)) to investigate the rate and regional effects. Results suggest that the PAC under traction loading is stiffer than brain tissue, rate dependent, and can be characterized as linearly elastic until failure. However, no regional difference was observed.

Matched-pairs tests of homogeneity with applications to homologous nucleotide sequences.

MOTIVATION: Most phylogenetic methods assume that the sequences of nucleotides or amino acids have evolved under stationary, reversible and homogeneous conditions. When these assumptions are violated by the data, there is an increased probability of errors in the phylogenetic estimates. Methods to examine aligned sequences for these violations are available, but they are rarely used, possibly because they are not widely known or because they are poorly understood. RESULTS: We describe and compare the available tests for symmetry of k-dimensional contingency tables from homologous sequences, and develop two new tests to evaluate different aspects of the evolutionary processes. For any pair of sequences, we consider a partition of the test for symmetry into a test for marginal symmetry and a test for internal symmetry. The proposed tests can be used to identify appropriate models for estimation of evolutionary relationships under a Markovian model. Simulations under more or less complex evolutionary conditions were done to display the performance of the tests. Finally, the tests were applied to an alignment of small-subunit ribosomal RNA sequences of five species of bacteria to outline the evolutionary processes under which they evolved. AVAILABILITY: Programs written in R to do the tests on nucleotides are available from http://www.maths.usyd.edu.au/u/johnr/testsym/

[Developing a finite element model of human head with true anatomic structure mandible].

A finite element model of human mandible is developed from CT scan images by the technologies of three-dimensional reconstruction, image processing and meshing. The mandible model is connected to one modified head model of Hybrid III dummy with joint according to the anatomic structure and mechanical characteristics of the temporomandibular joint. Then a finite element model of the human head with the true anatomic structure mandible is developed. This model has been validated with the cadaver test results. It can be used in researches on the mechanism of craniofacial blunt-impact injury and on the assessment of injury severity.

[Department of a finite element model of the Head Model of HYBRID III Dummy with the Human Mandible].

OBJECTIVE: To analyze the biomechanics of impact injury in the condition of the simulate impact on mandible. METHODS: A finite element model of human mandible was developed from the CT scan images by the technologies of three-dimensional reconstruction, image processing and meshing. The mandible model was connected to a modified head model of HYBRID III dummy with joint according to the anatomic structure and mechanical characteristics of the temporomandibular joint. RESULTS: A finite element model of human head with true anatomic structure mandible has been developed. This model has been validated with the cadaver test results. The higher stress was showed in the condyle rejoins and coracoid in the model when mandible was in impact simulation. CONCLUSIONS: This model can be used to research the mechanism of craniofacial blunt-impact injury and assess the injury severity. The model of HYBRID III dummy with the human mandible was helpful for the boundary design of mandibular model in the impact simulations.