Search

Molecular dynamics (MD) simulation with the embedded-atom method (EAM)/alloy potential is used to investigate the property of the nanoscale hollow spherical Nickel (Ni) powder during the laser additive manufacturing (AM) process. The thermomechanical properties of the Ni nanopowder is also explored (1) at room temperature and (2) from room temperature to the melting temperature during laser AM of powder bed fusion. As a result, the optimum parameters for the laser AM process are proposed. The optimal coalescence temperature of the nanoscale hollow spherical Ni powder is in the range between 980 and 1421K, while the melting temperature is in the range between 1320 and 1470 K. The coalescence and melting temperatures are lower than the melting point of Ni (1728 K).

The material point method (MPM) has not been evaluated in a systematic manner for the fully coupled thermodynamic fluid–structure interaction (FSI) cases. Since the constitutive models and heat transfer in solid and fluid materials are quite different, a fully coupled computational scheme is designed in this paper for simulating the FSI with the MPM, in which the governing equations for both solid and fluid material points are related to each other. A simply supported beam with a temperature difference between the top and bottom, and a cantilever beam immersed in an isothermal fluid environment are firstly considered for demonstrating the reasonable agreement with available analytical solutions. The aforementioned beam samples are then, respectively, immersed in a fluid environment involving heat transfer to study the thermal effect on the dynamic structural responses. It is illustrated that the thermal effect would induce a thermal pressure wave propagating from the high- to low-temperature ends. Furthermore, this pressure wave would affect the vibration responses of both the cantilever and simply supported beams in different ways due to its wavefront direction that is, respectively, perpendicular and parallel to the longitudinal axis of the cantilever and simply supported beams. The thermal pressure waves with the two propagating directions would also affect the buckling and flexural behaviors, respectively. The obtained results demonstrate the potential of the proposed numerical scheme in evaluating fully coupled thermodynamic FSI responses such as composites subject to extreme loadings.

e15061 Background: Pancreatic ductal adenocarcinoma (PDAC) remains an extremely aggressive disease for which no effective therapeutic modality has been found. Our group and others have previously found that miR-198 acts as a tumor suppressor in PDAC and several other cancers, through the regulation of a tumorigenic network of factors through a central vantage point. In this study, we investigate the efficacy and safety profile of NM198, (NoPass Mimic-miR-198) a novel therapeutic based on a specially engineered miR-198 mimic condensed with LGA-PEI-based nanoparticles-for systemic delivery. Methods: NM198 formulation consists of two technologies: (i) a novel lactic-co-glycolic acid-modified polyethyleneimine (LGA-PEI) polymer that spontaneously forms nanoparticles when it condenses with nucleic acids through electrostatic interaction and (ii) a non-canonical miRNA processing engineered flexible single-stranded RNA scaffolding system that enables administration of RNA interference (RNAi) molecules while minimizing off-target effects. MIA-PaCa2 cell lines were modified to overexpress mesothelin, an important factor involved in PDAC pathogenesis, and a target of miR-198. Nude (Crl: NU-Foxn1nu) CDX and PDX mouse models were used for NM198 efficacy studies, while Wistar Han rats, CD-1 mice, and ex vivo human blood were used for NM198 safety studies. Results: Orthotopic CDX mice were treated with 2.4 mg/kg of NM198 in a q.o.d dosing regimen for 4 weeks, resulting in a significant > 40% reduction of tumor growth when compared to controls in several different CDX animal models. To address the potential of the observed effect in the context of the heterogenic nature of PDAC, we confirmed our findings in a PDX mouse model, where a marked reduction of 44% in tumor growth was observed when treating with 2.4 mg/kg of NM198 in a q.o.d. dosing regimen for 8 weeks. Finally, to complete NM198 profiling, safety studies were carried out in two rodent models (mice and rats) where no MTD was reached in a dosing range of up to 10 times the effective dose in a q.o.d dosing regimen for 12 weeks, as observed per clinical signs, hematology, blood chemistry, and histopathology analysis. In addition, no hematotoxicity or significant immune responses were observed when exposing human blood from healthy volunteers to NM198. Conclusions: Our results indicate that therapeutic administration of a miR-198 mimic formulated for processing through a non-canonical RNAi administration pathway delivered through the use of a non-toxic polymeric nanoparticle formulation prevents off-target effects and unwanted immune responses while successfully delivering therapeutic doses to tumors through intravenous injection. These findings establish the novel therapeutic LGA-PEI polymer as an effective delivery mechanism for RNAi and nucleic acids in vivo and NM198 as a potential clinical cancer treatment.

e16290 Background: The mechanism of human pancreatic ductal adenocarcinoma (PDAC) resistance to nucleoside analog and first-line chemotherapy drug gemcitabine is not clearly understood, but some studies have associated it with increased autophagy. In cancer biology, autophagy plays dual roles as it can promote tumor suppression during early stages, but in established tumors, it plays a crucial role in tumor growth by enhancing survival under metabolic and therapeutic stress. We have previously found that miR-198 acts as a tumor suppressor in PDAC through the targeting of a network of tumorigenic factors, including the Valosin-containing protein (VCP), which has been reported to play an important role in autophagy. In this study, we investigate whether the repression of VCP through miR-198 replacement disrupts the autophagy process and sensitizes PDAC cells to gemcitabine treatment. Methods: MIAPaCa2 cells with forced overexpression of mesothelin (MSLN) and AsPC-1 cell lines and, CDX and PDX mouse models were used for gemcitabine sensitization studies. For miR-198 replacement, a miR-198 expression vector-loaded lactic co-glycolic-acid-modified polyethylenimine polyplex (LPNP-p198) was used. Autophagy disruption experiments were run over miR-198 and/or VCP overexpressing cell lines. Nude mice were used for subcutaneous and orthotopic CDX models and SCID/Beige were used for the subcutaneous PDX model. Results: Cell lines were treated with LPNP-p198 in combination with gemcitabine and cell growth was significantly inhibited when compared to gemcitabine alone. Additionally, it was determined that miR-198 disrupts the autophagy maturation process and, that it is then restored by overexpression of VCP. LPNP-p198 can effectively enter tumor cells and induce tumor sensitization in vivo, resulting in an 80-90% reduction of tumor burden and metastatic spread in the LPNP-p198 plus gemcitabine group when compared to controls, with the concomitant downregulation of VCP expression in the tumor tissue. In addition, this group had the fewest mice with jaundice, ascites, and metastases to the abdominal cavity, spleen, liver, and kidney. Finally, to address the potential of the observed effect in the context of the heterogenic nature of PDAC, we confirmed our findings in a PDX mouse model, where a marked reduction in tumor burden was observed in the LPNP-p198 plus gemcitabine group compared to controls. Conclusions: Our findings indicate that miR-198 replacement disrupts the autophagy maturation process and sensitizes PDAC cells to gemcitabine through VCP repression, indicating a potential therapeutic strategy for targeting gemcitabine-resistant PDAC and, establishing the use of LPNPs as a prototype for effective nucleic acid delivery in vitro and in vivo, with potential to be used from bench to clinic.

Nitrogen (N) plays an important role in sugarcane (Saccharum spp. hybrids) growth and development, however, long-term effects of N application levels on cane and sugar production in different sugarcane cultivars under field conditions remain unclear. In this study, we investigate the agronomic, yield, and quality traits in three sugarcane cultivars (GT11, B9, and ROC22) under different N levels (0, 150, and 300 kg/ha urea) from 2015 to 2019. Continuous four-year field experiments of plant and ratoon crops were carried out by using two-factor split-plot design. The results showed that N fertilizer application improved the tillering rate, stalk diameter, plant height, stalk weight, millable stalks/ha, cane yield, sugar yield and juice rate of cane, and the difference between N application and non-N application was significant. The cane yield, millable stalks/ha, juice rate, and juice gravity purity increased with the increase of N application, but the milled juice brix and sucrose % cane decreased with the increase of N application. The sugar yield was the highest at 150 kg/ha urea application, while the cane yield was the highest at 300 kg/ha urea application. Different N fertilizer application levels significantly regulated the activities of glutamic pyruvic transaminase (GPT) and glutamic oxaloacetic transaminase (GOT) and the contents of chlorophyll and nitrate N in plant leaves, which reflected the regulation in nitrogen metabolism and alteration in dry matter production and distribution, cane yield and sugar accumulation in different sugarcane cultivars. During the four-year experiment duration, the cane yield and sugar yield generally showed ROC22 &gt, B9 &gt, GT11. These data suggested that 300 kg/ha urea application was suitable for the plant and first ratoon crops, and 150 kg/ha urea application was suitable for the second and third ratoon crops. Both cane and sugar yields could be the highest in a four-year production cycle under this circumstance.

The mesoscale coarse-grained molecular dynamics (CG-MD) models for copper nanowires with different crystallographic orientations are developed via increasing the integration time step and grouping a certain number of atoms into one mesoscale particle. The tensile and torsional responses of copper nanowires at various temperatures and loading rates are then studied using the CG-MD and molecular dynamics (MD) simulations. In the tensile cases, the CG-MD simulations yield the tendency of Young’s modulus with a good agreement with that by the MD. For the torsional loading, the relation between loading rate and critical angle by the CG-MD is also in line with that by the MD, while the CG-MD predictions for low temperatures are not in close agreement with those by the MD. Although the CG-MD model could not perfectly fit the results from the MD and requires further improvement, it could be used as a starting point to evaluate the mechanical response of nanowire with less computational expenses than the MD model.

In recent years, toxic Microcystis blooms have occurred annually in Lake Taihu, China. In order to elucidate the relationships between photosynthetic activity of Microcystis , Microcystis genotypic composition, microcystin (MC) production and environmental factors, water samples and associated environmental data were collected from January to December 2014 in Lake Taihu. Seasonal variations in photosynthetic activity were measured using a Phyto-PAM Analyzer, abundances of total and toxic Microcystis genotypes were determined by quantitative real-time PCR (qPCR), and MC concentrations were quantified by HPLC. The maximum quantum yield of photosystem II ( F v / F m ) of Microcystis cells changed on a seasonal basis. F v / F m was not detectable in the winter, but increased from spring to early summer, after which, it gradually decreased until the winter. The level of non-photochemical quenching ( NPQ ) increased from March to August and then decreased until December. qPCR data showed that the abundances of total Microcystis genotypes ranged from 1.91 × 10 5 to 8.64 × 10 7 copies/mL and toxic Microcystis genotypes ranged from 2.38 × 10 4 to 5.67 × 10 7 copies/mL. The toxic proportion varied from 12.5 to 65.6%, with an average value of 27.9%. Correlation analysis revealed that there was a positive correlation between photosynthetic activity, genotypic composition and MC production. Water temperature was the only environmental factor that was positively correlated with F v / F m , NPQ , total and toxic Microcystis and intracellular MC. Additionally, total phosphorus was also significantly correlated with intracellular MC. These results indicate that future global warming, in addition to eutrophication, could promote Microcystis blooms in Lake Taihu and that blooms may increase in intensity and toxicity.

The molecular dynamics simulation method is utilized to investigate the physical characteristics of nanoscale vanadium powder during 3D printing powder bed fusion laser sintering process. The radius of gyration, neck width, and root mean square of different powder size of nanoscale vanadium powder during 3D printing laser sintering process under different heating rate is analyzed and discussed. The neck width and internal lattice changes are also observed.It is observed that the temperature of solid state diffusion decrease with heating rate increasing, but the temperature of that increase with powder size decreasing. It is found that the coalescence temperature of nanoscale vanadium powder is range of between 1600K and 1950K, and the melting temperature of that is range of between 1850K and 1990K.

With the rapid development of industrial automation technology, electric motor control has also become an important technology. However, motor failure has many possible causes, and it is not easy to detect in advance. Therefore the fault diagnosis is an important issue for motors. The augmented reality (AR) technology is also developing towards various industrial and educational application in recent years. This research is focused on developing the intelligent diagnosis system and AR application for electric motors. The intelligent diagnosis system applies cloud data management and machine learning methods to predict the health status of electric motors. And the time-recurrent Long Short-Term Memory (LSTM) neural network algorithm is applied to establish a motor health diagnostic model. The experimental results show that the motor diagnosis method can predict the health status of motor effectively. The proposed system will also provide more industrial application services in the future.

The quantum Hall effect (QHE) in a 3D Dirac semimetal thin film is attributed to either the quantum confinement induced bulk subbands or the Weyl orbits that connect the opposite surfaces via bulk Weyl nodes. However, it is still unknown whether the QHE based on the Weyl orbit can survive as the bulk Weyl nodes are gapped. Moreover, there are closed Fermi loops rather than open Fermi arcs on the Dirac semimetal surface, which can also host the QHE. Here we report the QHE in the 3D Dirac semimetal ${\mathrm{Cd}}_{3}{\mathrm{As}}_{2}$ nanoplate by tuning the gate voltage under a fixed 30 T magnetic field. The quantized Hall plateaus at odd filling factors are observed as a magnetic field along the [001] crystal direction, indicating a Berry's phase $\ensuremath{\pi}$ from the topological surface states. Furthermore, even filling factors are observed when the magnetic field is along the [112] direction, indicating the ${C}_{4}$ rotational symmetry breaking and a topological phase transition. The results shed light on the understanding of QHE in 3D ${\mathrm{Cd}}_{3}{\mathrm{As}}_{2}$.

The quantum Hall effect (QHE) in a 3D Dirac semimetal thin film is attributed to either the quantum confinement induced bulk subbands or the Weyl orbits that connect the opposite surfaces via bulk Weyl nodes. However, it is still unknown whether the QHE based on the Weyl orbit can survive as the bulk Weyl nodes are gapped. Moreover, there are closed Fermi loops rather than open Fermi arcs on the Dirac semimetal surface, which can also host the QHE. Here we report the QHE in the 3D Dirac semimetal Cd_{3}As_{2} nanoplate by tuning the gate voltage under a fixed 30 T magnetic field. The quantized Hall plateaus at odd filling factors are observed as a magnetic field along the [001] crystal direction, indicating a Berry's phase π from the topological surface states. Furthermore, even filling factors are observed when the magnetic field is along the [112] direction, indicating the C_{4} rotational symmetry breaking and a topological phase transition. The results shed light on the understanding of QHE in 3D Cd_{3}As_{2}.

The farming of lake fisheries is an important part of the freshwater fishery industry in China. However, farming patterns of traditional fisheries maintain serious negative effects on the ecosystem of Eastern Lake Taihu. In recent years, the enclosure culture model of this lake has been optimized. In order to investigate the effects of aquaculture on the sediment properties, samples were collected from different areas of the lake (i.e. within the culture areas, outside the culture areas; from the crab-plant co-culture areas, mixed culture areas, ecological restoration areas, and control areas), in different months (January, March, April, August, and November), and at different depths (0-1 cm and 9-10 cm). The results of this sampling indicates that ① the concentrations of total nitrogen (TN) and total phosphorus (TP) in the sediments samples collected within the culture areas are slightly higher than samples collected outside the culture areas; ② compared to the crab-plant co-culture areas, lower concentrations of TN and TP are found in the samples collected from the mixed culture areas; ③ in the ecological restoration areas, aquatic plants exhibit certain positive effects with decreasing concentrations of TN and TP in the sediment. The lowest concentrations of TN and TP are detected in the sediment during the growing season of aquatic plants.

We develop the tight-binding model to study electronic and optical properties of graphane. The strong sp3 chemical bondings among the carbon and hydrogen atoms induce a special band structure and thus lead to the rich optical excitations. The absorption spectrum hardly depends on the direction of electric polarization. It ex- hibits a lot of shoulder structures and absorption peaks, which arise from the extreme points and the saddle points of the parabolic bands, respectively. The threshold op- tical excitations, only associated with the 2px and 2py orbitals of the carbon atoms, are revealed in a shoulder structure at ?3.5 eV. The first symmetric absorption peak, appearing at ~11 eV, corresponds to energy bands due to the considerable hybridiza- tion of carbon 2pz orbitals and H 1s orbitals. Also, some absorption peaks at higher frequencies indicate the bonding of 2s and 1s orbitals. These results are in sharp contrast to those of the sp2 graphene systems., 16 pages, 5 figures

Set-net surveys were performed monthly between January 2010 and December 2012 at six sampling sites in Lake Taihu in order to determine the spatial and temporal variation in fish assemblages in Lake Taihu and to assess the influence on fish assemblages of eutrophication and disconnection of migration routes. A total of 134,604 specimens (1456.7 kg total biomass) were caught, representing 61 species, 18 families, and 10 orders. Cyprinidae fish (36 species) contributed most of the total species richness and the most dominant species was Coilia nasus. Sampling months and sampling sites each significantly affected the Margalef richness index, Shannon–Wiener diversity index (H′), and Pielou's evenness index (J′) of fish assemblages and there were interactive effects between them. The ANOSIM analysis indicated that the fish assemblage structure had significant differences among the sample sites. Total nitrogen (TN) and total phosphorus (TP) both differed significantly among sites. The results of correlation ana...

We have developed the generalized tight-binding model to understand how the electronic structures of ABC-stacked trilayer graphene can be modulated by external fields. A band-like Hamiltonian matrix is used to obtain the electronic properties efficiently. A uniform perpendicular magnetic field gives rise to three groups of Landau levels that can be distinguished from one another by the subenvelope functions of the distinct sublattices. Intergroup Landau-level anticrossings occurring between any two groups and intragroup anticrossings coming from the second group are revealed in the magnetic field-dependent energy spectrum. Such anticrossings are induced by specific interlayer atomic interactions. In the presence of an electric field, each Landau-level group will split into two subgroups, which are characterized by the two different localization centers. The anticrossings in the second group can be suppressed or produced by varying the electric field strength, the reason being the significant modification of the band structures. Furthermore, the intragroup anticrossings arise in two split subgroups of the first group.

The generalized tight-binding model is developed to largely reduce the numerical computation time in calculating optical properties. Modulated electric potentials can control the low-frequency magneto-optical absorption spectra of monolayer graphene. They induce the oscillatory energy dispersions of Landau subbands and the spatial symmetry breaking of the wave function; therefore, the original peaks and extra peaks of different selection rules come into existence simultaneously. Such peaks mainly arise from the band-edge states and/or the middle states. Their number, intensities, frequencies and structures are dominated by the modulation strength and period. More absorption peaks appear with an increase in potential. The extra peaks can relatively easily be observed for higher frequencies and stronger potentials. However, the absorption spectra remain unchanged for a fixed ratio of strength over period.

The microstructure and electrical properties of ZnTe films were investigated by using thermal evaporation with emphasis on the effects of a deposition temperature. Microstructure, crystallinity, carrier concentration, resistivity, and mobility are shown to be dependent on the deposition temperature. The highest carrier concentration of 9.1×1014 cm-3, the lowest resistivity of 9.9 Ω-cm and the largest mobility of 667 cm2V-1S-1 are presented at a deposition temperature of 580oC, respectively. The ZnTe thin films using thermal evaporation can find applications in solar cell or light emitting diodes.

The adsorption and dissociation properties of carbon monoxide (CO) molecule on tungsten W(n) (n = 10-15) nanoparticles have been investigated by density-functional theory (DFT) calculations. The lowest-energy structures for W(n) (n = 10-15) nanoparticles are found by the basin-hopping method and big-bang method with the modified tight-binding many-body potential. We calculated the corresponding adsorption energies, C-O bond lengths and dissociation barriers for adsorption of CO on nanoparticles. The electronic properties of CO on nanoparticles are studied by the analysis of density of state and charge density. The characteristic of CO on W(n) nanoparticles are also compared with that of W bulk.

In our previous study, we have proven two ultrathin Pd nanowires can prevent from Pd embrittlement. In this study, we further demonstrate the material properties of a larger Pd nanowire. Both classical potential function and density functional theory calculation were used. The results show once the larger Pd nanowire has interior Pd atoms, hydrogen atoms can stably stay within the nanowire. Consequently, the hydrogen embrittlement could happen with a higher probability than two ultrathin Pd nanowires reported in our previous study.

Separation and concentration of blood cells are vital steps in biological sample preparation for the design and operation of microfluidic biochips. There have been significant efforts toward developing approaches for effective separation and capture of blood cells in microfluidic devices recently. The present paper is aimed to evaluate separation and capture of micro-particles in passive microfluidic channels using numerical simulations. Two passive layouts of microfluidic channels are employed in this study: imbalance-bifurcation and filter-trench. Results reveal that (i) infusion of different micro-particle sizes results in reduction of separation efficiency; (ii) it requires high splitting ratio of bifurcation branch to main channel to achieve high separation rate; (iii) the layout of two consecutive filter-trench microfluidic channel increases the capture rate of micro-particles and achieves better concentration efficiency.

The real and measurable model is helpful for structure simulation. Photogrammetry technology provides a new method to model a structure by photos. This article explored the feasibility of photo-based 3D modeling for the arc bridge structures by ordinary digital camera. Firstly, the preparation processes before modeling were introduced, that included camera calibration, designation of shooting program, how to take photos and plan measurement. Secondly, photo orientation and modeling process were introduced, too. A measurement test was put forward to get some good points to enhance the accuracy. By comparing the measurement accuracy of modeling results from the four photos and eight photographs, some proposals were presented to improve the accuracy. The 3D model can be integrated with the loading conditions and material properties, to provide the detailed data for analyzing the structure.

Juancheng Yellow River Highway Bridge is the largest externally pre-stressed concrete continuous box-girder bridge with corrugated steel webs in the world with the total length of 1460m and span arrangement of 70m+11×120m+70m. Based on the monitoring practice for this bridge construction, the paper illustrates the application of the two modeling methods for box-girder with corrugated steel webs in the calculation of alignment control using bridge analysis system GQJS, i.e. the one-node method and two-node method. Additionally, the comparison between the measured and predicted deformation under different construction stages including cantilever construction, closure construction, system transformation and external prestress tension is presented and discussed. The results turn out both the two proposed modeling methods can perfectly meet the requirements of alignment control of this kind of bridge.

The scratch deformation behaviors of two bicrystal coppers (Cu(100)/Cu(110) and Cu(110)/Cu(100)) during the nanoscratching process were explored and compared with their single crystal ingredients by the molecular statics simulations. The effects of lattice configuration and scratch depth were investigated in this study. The results showed that the motion of dislocations was blocked in the bicrystal interface until the dislocations accumulated enough energy to move. From the study, it was found that the bicrystal interfaces can provide resistance to the motion of dislocations, and can strengthen the mechanical properties of copper materials.

Dissipative particle dynamics (DPD), a mesoscopic simulation approach, has been used to investigate the effect of volume fraction, the different degree of functionalization, and the effect of PE length on the structural property of the immiscible polyethylene (PE)/carbon nanotube (CNT) in a system. In this work, the interaction parameter in DPD simulation, related to the Flory−Huggins interaction parameter, χ, is estimated by the calculation of mixing energy for each pair of components in molecular dynamics (MD) simulation. The immiscibility property of CNT and PE polymer induces the phase separation and exhibits different architectures at different volume fractions. In order to observe the effects of different degrees of functionalization, we change the repulsive interaction parameter to simulate the different degrees of functionalization. In order to observe the effect of volume fraction and different degrees of functionalization, the radius of gyration and order parameter are used to observe the arrang...

Electronic structures of nanotube–graphene hybrid carbon systems are calculated by the tight-binding model. The Lennard-Jones potential is used to determine the optimal geometry between nanotubes and a monolayer graphene. The periodic alignment of nanotubes on graphene results in quasi-one-dimensional physical phenomena. The low-frequency energy dispersions are significantly influenced by the interlayer interactions, such as the removal of subband degeneracy, creation of extra band-edge states, and modulation of energy gaps. The composite systems could be either metals or semiconductors according to the alignment and geometry of nanotubes.

The mechanical behavior of multi-walled carbon nanotubes (MWNTs), being fixed at both ends under uniaxial tensile loading, is investigated via the molecular dynamics (MD) simulation with the Tersoff interatomic potential. It is found that Young's modulus of the MWNTs is in the range between 0.85 and 1.16 TPa via the curvature method based on strain energy density calculations. Anharmonicity in the energy curves is observed, and it may be responsible for the time-dependent properties of the nanotubes. Moreover, the number of atomic layers that is fixed at the boundaries of the MWNTs will affect the critical strain for jumps in strain energy density vs. strain curves. In addition, the boundary conditions may affect “yielding” strength in tension. The van der Waals interaction of the double-walled carbon nanotube (DWNT) is studied to quantify its effects in terms of the chosen potential.

Molecular dynamics simulation was carried out to investigate the behavior of (5,5) and (10,10) armchair carbon nanotubes in water under tensile loading. The water molecules inside a nanoscale tube, unlike inside a bulk tube, have a confined effect. The local density distributions of oxygen and hydrogen atoms inside the carbon nanotubes were calculated to find the confinement effect. Moreover, the mechanical behavior of carbon nanotubes in water was studied under tensile loading. The results show that the Young's modulus of nano-tubes in water remains the same as that in vacuum. However, the tensile stress of nanotube in water is less than that in vacuum.

Buckling strengths, in terms of compressive strain, of single-, double- and triple-walled carbon nanotubes (CNTs) are investigated to study the effects of slenderness ratio (S R ) via the molecular dynamics (MD) simulations with the Tersoff potential. Under constant ratio of slenderness, the CNTs with small S R behave like a continuum shell object. For large S R 'S, multi-walled CNTs exhibit the characteristics of the Euler columns. In addition, smaller nanotubes possess higher buckling-resistance. The buckling strength of multi-walled nanotubes is controlled by the size of their outermost shell.

In this study, details of Berkovich nanoindentation-induced mechanical deformation mechanisms of metal-organic chemical-vapor deposition-derived GaN thin films have been systematic investigated with the aid of the cathodoluminescence (CL) and the cross-sectional transmission electron microscopy (XTEM) techniques. The multiple “pop-in” events were observed in the load-displacement (P–h) curve and appeared to occur randomly by increasing the indentation load. These instabilities are attributed to the dislocation nucleation and propagation. The CL images of nanoindentation show very well-defined rosette structures with the hexagonal system and, clearly display the distribution of deformation-induced extended defects/dislocations which affect CL emission. By using focused ion beam milling to accurately position the cross-section of an indented area, XTEM results demonstrate that the major plastic deformation is taking place through the propagation of dislocations. The present observations are in support to the massive dislocations activities occurring underneath the indenter during the loading cycle. No evidence of either phase transformation or formation of micro-cracking was observed by means of scanning electron microscopy and XTEM observations. We also discuss how these features correlate with Berkovich nanoindentation produced defects/dislocations structures.

This study reports the surface roughness and nanomechanical characteristics of ZnO thin films deposited on the various substrates, obtained by means of atomic force microscopy (AFM), nanoindentation and nanoscratch techniques. ZnO thin films are deposited on (a- and c-axis) sapphires and (0001) 6H-SiC substrates by using the pulsed-laser depositions (PLD) system. Continuous stiffness measurements (CSM) technique is used in the nanoindentation tests to determine the hardness and Young’s modulus of ZnO thin films. The importance of the ratio (H/E film) of elastic to plastic deformation during nanoindentation of ZnO thin films on their behaviors in contact-induced damage during fabrication of ZnO-based devices is considered. In addition, the friction coefficient of ZnO thin films is also presented here.

A proposed method based on a so-called meshless method is designed to simulate the structural behaviors of 3D medical parts. To do the simulation, the STL (Stereo-Lithography) geometry, which is the main geometry format used in 3D printing and medical models, is adopted to be the analysis model. Moreover, the geometry model of the objects in STL format becomes the only model needed for the simulation. To achieve this, some geometry-related treatments are required, so some checking processes are designed to handle the analysis model during the analysis. Hence, with the proposed meshless method based on STL geometry, the simulation can be carried out in a simple and straightforward way with less preparation effort for analysis models. A 3D simulation has been conducted to demonstrate the effectiveness and efficiency of this proposed method. Besides, the parts with highly complicated shapes can also be simulated without difficulty.

This paper employs molecular dynamics (MD) simulations to investigate the influence of the Ar ion incident energy and incident angle on the surface roughness of Cu films fabricated using the ion assisted deposition (IAD) process. The MD simulations use the tight-binding potential and the Moliere potential to simulate the Cu–Cu and Cu–Ar+ interactions, respectively. The numerical results indicate that the dependency of the surface roughness on the incident angle of the ions is a function of the ion incident energy. At lower incident energies, a weaker dependency exists, and the surface roughness is improved irrespective of the ion incident angle. However, at intermediate and higher ion incident energies, the dependency of the surface roughness on the incident angle becomes more apparent. Under these conditions, a higher incident angle yields an improved surface roughness. Increasing the ion assisted ratio has a similar effect on the surface roughness as increasing the ion incident energy. The results indicate that an excessive ion assisted ratio leads to the formation of a rougher surface; particularly at higher ion incident energies.

This study uses molecular dynamics simulations to investigate the intrinsic thermal vibrations of a single-walled carbon nanotube (SWNT) modelled as a clamped cantilever. Using an elastic model defined in terms of the tube length, the tube radius and the tube temperature, the standard deviation of the vibrational amplitude of the tube's free end is calculated and the Young's modulus of the SWNT evaluated. The numerical results reveal that the value of the Young's modulus is independent of the tube length, but decreases with increasing tube radius. At large tube radii, the Young's modulus value approaches the in-plane modulus of graphene, which can be regarded as an SWNT of infinitely large radius. The results also indicate that the Young's modulus is insensitive to changes in the tube temperature at temperatures of less than approximately 1100 K, but decreases significantly at higher temperatures.