Discontinuity Surfaces Research Articles

Spherical data validation of rock discontinuities orientation from Drone-derived 3D Point Clouds

This work presents a methodology for the statistical validation of discontinuity surfaces obtained from point clouds using digital photogrammetry from drones. Our methodology allows you to review the quality of the data obtained with photogrammetry and decide whether these measurements are representative of the discontinuity surfaces that they analyze. It consists of three steps, the first one being a shape analysis that allows defining which statistical model should be used: Fisher for circularly symmetric clusters or Bingham fits better for axially symmetric clusters. This step also makes the most significant difference to other works since our methodology starts from the premise that not all discontinuity surfaces are flat. Therefore, Fisher parameters do not allow validating data that do not correspond to a plane.
 In the second step of the methodology, we calculate the consistency parameters that depend on the statistical model defined in step 1. The parameters are similar for both models; both estimate κ which indicates how much the sample is concentrated around the mean orientation and validates the existence of this and which is the value of the generating angle of a cone with a 95 % confidence limit that it contains within the mean orientation.
 Finally, step 3 is used when there are control measurements to compare the point cloud data and define if both samples characterize the same discontinuity surface in the rock mass.
 The results obtained on a rock outcrop allowed us to observe that the measurements obtained from the drone faithfully represent the discontinuity surface analyzed when these were compared with the measurements made manually with the compass. Furthermore, the dispersion parameters (

Outwardly growing premixed flames in turbulent media

The propagation of outwardly expanding premixed flames in turbulent media is examined within the context of the hydrodynamic theory wherein the flame, treated as a surface of density discontinuity separating fresh combustible mixture from burned products, is propagating at a speed dependent upon local geometric and mixture/flow characteristics. An embedded manifold approach, one adept at handling multi-valued and disjointed surfaces which are frequently observed in real flames, is used to couple the flow and flame evolution. A sensitivity analysis, based on mixtures with different Markstein numbers, is performed to investigate early flame kernel development in addition to its long-term evolution. The focus is to understand the effect of turbulent flow characteristics, distinguished by the intensity of velocity fluctuations and its integral length scale, in addition to intrinsic flame instabilities (predominantly the Darrieus-Landau instability) on flame propagation. The overarching objective is to quantify their influence on the flame morphology and burning rate and to construct scaling laws for the turbulent flame speed through appropriate modifications of Damköhler’s first hypothesis. Flame-turbulence interactions are inferred from statistical quantities based on its developing flame topology, including local flame curvature and hydrodynamic strain, and their combined effects integrated into the flame stretch rate experienced by the flame and the local flame speed deviation from the laminar flame speed.

Improved dielectric constant and leakage current characteristics of BaTiO3 thin film on SrRuO3 seed layer

The fabrication of high-k BaTiO3 (BTO) films for applications such as multilayer ceramic capacitors or dynamic random access memory has been achieved via the ex-situ crystallization of amorphous BTO into perovskite structure through post-deposition annealing (PDA). However, high-temperature PDA at temperatures exceeding 700 °C results in the severe degradation of BTO properties. In other words, ex-situ crystallization via PDA results in an increased dielectric constant but is accompanied by inferior leakage current characteristics caused by rough surface morphologies and defects such as voids and cracks. In this study, we demonstrate the in-situ crystallization of BTO films by introducing a high-quality SrRuO3 (SRO) film as a seed layer. The SRO film is deposited using rf magnetron sputtering at 270–350 °C, and stoichiometric SRO films are obtained on SiO2, Al2O3, and TiN substrates by controlling the growth temperature; subsequently, rapid thermal annealing at 700 °C is conducted to crystallize the SRO film. The polycrystalline SRO film on the TiN substrate exhibits excellent morphology with uniform grains as well as a continuous and smooth surface, whereas the SRO films on the SiO2 and Al2O3 substrates exhibit rough and discontinuous surfaces. The SRO seed layer on TiN permits the in-situ growth of crystalline BTO films at a relatively low temperature of 500 °C featuring a high dielectric constant of 160 and a low leakage current density of 9.5 × 10−7 A/cm2 at 0.8 V, which are 2.2 and 3.4 × 107 times improved compared with those of the ex-situ crystallized BTO film on bare TiN, respectively.

3D Measurement of Discontinuous Objects with Optimized Dual-frequency Grating Profilometry

Abstract Three-dimensional profilometry tends to be less effective at measuring discontinuous surfaces. To overcome this problem, an optimized profilometry based on fringe projection is proposed in this paper. Due to the limitation of the shooting angle, there are projection blind spots on the surface of discontinuous objects. Since the noises and unwrapping errors are always localized at the projection blind spots, an algorithm is designed to determine the blind spots automatically with the light intensity difference information. Besides, in order to improve the measurement accuracy, a processing scheme is introduced to deal with the local height distortion introduced by the dual-frequency grating profilometry. Lots of measurement tests on various surfaces are carried out to assess the optimized profilometry, and experimental results indicate that the modified profilometry system works more robust with high reliability and accuracy in measuring different kinds of surfaces, especially discontinuous ones.

Wildfires Effect on Debris Flow Occurrence in Italian Western Alps: Preliminary Considerations to Refine Debris Flow Early Warnings System Criteria

Rarely, a close correlation between wildfires and the occurrence of channelized debris flows has been observed in the Western Italian Alps. Only two cases in history have been reported, after brief and localized rainfall events of moderate intensity in Italy’s Piemonte region (NW Italy) caused debris flows, on 18 July 2005, in Verbania province (Pallanzeno municipality), and on June 2018 in Turin province (Bussoleno municipality). These phenomena occurred after a large portion of the catchments were affected by wide wildfires in the preceding months. Debris flow deposits showed an unusually large number of fine-grained particles, forming dark-brown mud-rich deposits associated with burnt wood deposits. Rainfall analysis related to the period between the wildfires’ occurrence and the debris flow events, using both raingauge and weather radar data, pointed out that the debris flows triggered in July 2005 and June 2018 were characterized by greater magnitude but associated with less precipitation intensity rates as compared with previous mud flows occurring just after wildfires. These behaviors can be explained by the presence of burned organic material and fine-grained sediment, generated from the soil’s thermal reworking, which formed a thick layer, centimeters deep, covering a large percentage of catchments and slopes. Most of this layer, generated by wildfires’ action were winnowed by rainfall events that had occurred in the months before the debris flow events, of significant magnitude, exhuming a discontinuous hydrophobic soil surface that changed the slopes’ permeability characteristics. In such conditions, runoff increased, corrivation time shortened, and, consequently, discharge along the two catchments’ channels-network increased as well. Consequently, the rainfall effects associated with rainfall events in July 2005 and June 2019 were more effective in mobilizing coarse sediments in channel beds than was typical for those catchments.

Foraminiferal micro-buildups (“reefs”) in the Wuchiapingian basin facies of the basal Zechstein carbonates in western Poland

Encrusting foraminifers locally can play an essential reef-forming role such as in the Carnian fossiliferous Hallstatt Limestones of Austria where a dense succession of hardgrounds occurs with numerous small buildups (up to 2 cm high) composed of sessile foraminifers. Similar foraminiferal micro-buildups occur in a 10-cm-thick bed in the basinal facies in the basal Zechstein (Upper Permian) strata in the Radlin 60 borehole, in western Poland. Foraminiferal micro-buildups of presumably columnar habit account for up to a half of the volume. The growth of columns was interrupted by hiatal surfaces, although usually the growth of columns was restored afterwards. In the upper part of the bed with foraminiferal micro-buildups, the foraminiferal encrustations become visibly less abundant, and in most cases, they have a shape of less regular masses. The bed with foraminiferal micro-buildups abounds in closely spaced discontinuity (hiatal) surfaces, occasionally encrusted by foraminifers. Tubular foraminifers in the bed with foraminiferal micro-buildups are accompanied by various encrusting organisms, possibly microbes; they are grouped under the name Palaeonubecularia. In the intercolumnar spaces, common Midiella sp. occur. During deposition, the conditions were mostly suboxic, and various types of ferruginous morphs, common in the lower part of the bed, suggest that dysoxic–anoxic interfaces produced various microaerophilic environments for iron-bacteria. The environmental conditions during the deposition of the upper part of the bed were very similar to those characterizing the starved basin environment in which the bioclastic-peloidal and oncoidal sediments in the Zechstein Limestone have been formed. In turn, the lower part of the bed registers the transition from normal (= not starved) marine conditions, with a clear chemocline, to the starved basin conditions. The deposition of the bed was coeval with the Kupferschiefer deposition based on the correlation of δ13C curves, which implies that the previous stratigraphical concept of basal Zechstein strata has to be re-evaluated.

Ichnofabric analysis of bathyal chalks: the Miocene Inglis Formation of the Andaman and Nicobar Islands, India

In the Bay of Bengal, the Andaman and Nicobar Islands represent part of the Burma–Sunda–Java subduction complex. The Islands are composed of sediments ranging in age from Jurassic to Recent, represented by ophiolites, flysch sediments, along with deep marine sediments scraped off from the subducting plate. The stratigraphic succession that overlies meta-sedimentary and ophiolite suites consists of turbidite and non-turbidite sequences, along with thick-bedded nannofossil chalks. The present study describes ichnofabrics of chalks from the Inglis Formation (Early to Middle Miocene). These chalks are highly to moderately bioturbated and comprise several levels of ferruginised layers as weak discontinuity surfaces. The studied section shows the recurring occurrence of ichnotaxa belonging to Asterosoma, Chondrites, Cladichnus, Ophiomorpha, Palaeophycus, Planolites, Taenidium, Thalassinoides, and Zoophycus. Sediments are represented by Bioturbation indices varying between BI-2 to BI-5, represented by (a) light coloured trace fossils in dark sediment (LID ichnofabric) and (b) dark coloured trace fossils in light sediment (DIL ichnofabric). Ichnofabric analysis suggests multiple colonization, complex tiering, and multilayer tiering. The LID ichnofabric exposed at Kalapathar reveals three tiers, a diverse shallow tier and a moderately low diverse middle and deep tiers. At the Lacam Point Section, in contrast, the LID ichnofabric is represented by condensation of the tiers and the absence of shallow tiers. The DIL ichnofabric at the Kalapathar Section seems to be more expanded and is represented by four tiers with extensive bioturbation. Ichnofabric analysis supports deposition of the chalk sediments in a lower bathyal paleoenvironment and suggests that organic matter, pore water, and bottom-water oxygenation were the main controlling factors. Thus, the ichnofabric analysis of the Early-Middle Miocene Inglis Formation gives first-hand information regarding the poorly known chalk facies of the Andaman and Nicobar Islands pre-Bengal fan stage of the Indian plate.

Effects of photobiomodulation therapy in chondrocyte response by in vitro experiments and experimental model of osteoarthritis in the knee of rats.

The purpose of this study is to evaluate the effects of photobiomodulation (PBM) therapy in chondrocyte response by in vitro experiments and cartilage repair using an experimental model of osteoarthritis (OA) in the knee of rats. The in vitro experiment was performed with chondrocyte cells, and they were divided into two groups: non-irradiated and irradiated with PBM (808nm; 0.8J or 1.4J). Then, cell proliferation was evaluated after 1, 3, and 5days. The experimental model of osteoarthritis (OA) was performed in the knee of 64 Wistar rats, and they were assorted into control group (CG), PBM (808nm; 1.4J). The results of in vitro showed that PBM 1.4J increased cell proliferation, on days 1 and 5. However, after 3days was demonstrated a significant increase in cell proliferation in PBM 0.8J. The in vivo experiment results demonstrated, on histological analysis, that PBM presented less intense signs of tissue degradation with an initial surface discontinuity at the superficial zone and disorganization of the chondrocytes in the cartilage region when compared to CG, after 4 and 8weeks. These findings were confirmed by immunohistochemistry and qRT-PCR analysis which showed that PBM increased IL-4, IL-10, COL-2, Aggrecan, and TGF-β which are anabolic factors and acts on extracellular matrix. Also, PBM reduces the IL1-β, an inflammatory marker that operates as a catabolic factor on articular cartilage. In conclusion, these results suggest that PBM may have led to a return to tissue homeostasis, promoting chondroprotective effects and stimulating the components of the articular tissue.

Ducted wind turbines in yawed flow: a numerical study

Abstract. Ducted wind turbines (DWTs) can be used for energy harvesting in urban areas where non-uniform flows are caused by the presence of buildings or other surface discontinuities. For this reason, the aerodynamic performance of DWTs in yawed-flow conditions must be characterized depending upon their geometric parameters and operating conditions. A numerical study to investigate the characteristics of flow around two DWT configurations using a simplified duct-actuator disc (AD) model is carried out. The analysis shows that the aerodynamic performance of a DWT in yawed flow is dependent on the mutual interactions between the duct and the AD, an interaction that changes with duct geometry. For the two configurations studied, the highly cambered variant of duct configuration returns a gain in performance by approximately 11 % up to a specific yaw angle (α= 17.5∘) when compared to the non-yawed case; thereafter any further increase in yaw angle results in a performance drop. In contrast, performance of less cambered variant duct configuration drops for α>0∘. The gain in the aerodynamic performance is attributed to the additional camber of the duct that acts as a flow-conditioning device and delays duct wall flow separation inside of the duct for a broad range of yaw angles.

Single-shot circular fringe projection for the profiling of objects having surface discontinuities.

Fringe projection profilometry (FPP) is a widely used non-contact optical method for 3D profiling of objects. The commonly used linear fringe pattern in FPP has periodic intensity variations along the lateral direction. As a result, the linear fringe pattern used in FPP cannot uniquely represent the lateral shift induced by the objects having surface discontinuities. Thus, unambiguous surface profiling of objects, especially with surface discontinuities, using a single linear fringe image having a single fringe frequency, is unfeasible. This paper proposes using a radially symmetric circular fringe pattern as the structured light pattern for accurate unambiguous surface profiling of sudden height-discontinuous objects. To the best of our knowledge, this is the only method that can reconstruct discontinuous height profiles with the help of a single fringe image having a single frequency. The performance of the proposed algorithm is evaluated on several synthetic and real objects having smooth variations and discontinuities. Compared to the well-known fringe projection methods, the results depict that for a tolerable range of error, the proposed method can be applied for the reconstruction of objects with 4 times higher dynamic range and even at much lower fringe frequencies.

Three-dimensional thermal fracture analysis of piezoelectric material by extended finite element methods

The effect of poling direction and thermal fracture analysis of penny-shaped crack (PSC) in piezoelectric material (PM) exposed to a uniform temperature and steady-state heat flow is presented using the XFEM approach. The intrinsic coupling, thermo-electro-mechanical under thermal shocks are studied and thermal stress intensity factors (TSIFs), and electrical displacement intensity factors (EDIF) are evaluated using the strain energy-based, thermal interaction integral. The discontinuous crack surfaces are treated as adiabatic and electrically impermeable. The discontinuity in both the temperature gradient and electrical field displacement over the crack surface is enriched using the Heaviside enrichment function. The fracture parameters, TSIFs, and EDIF of penny-shaped crack are a function of applied temperature fields and the thermo-electro-mechanical properties of piezoelectric material are studied. Further, the effect of poling direction, and in-plane and out-plane offset of crack position, and the inclined crack on the TSIFs and EDIF are presented. The comparison of both analytical and numerical results of the intended formulation showed excellent accuracy which has been verified on benchmark problems. The results are quite useful for the design of the sensors, transducers, and actuators in heat transfer applications.

Three dimensional cells with embedded strong discontinuity for material failure analysis by the boundary element method

The Boundary Element Method (BEM) associated with the Continuum Strong Discontinuity Approach (CSDA) can be used as a non-geometric alternative for the modelling of crack growth in physically non-linear three-dimensional problems of solid mechanics. This work makes use of the refereed approach through the implementation of volumetric hexahedral cells with embedded discontinuity that enables the evaluation of discontinuous jumps in the displacement field along a crack discontinuity surface. This is made with an internal equilibrium verification, using a regularized isotropic damage constitutive model. Although this formulation has been extensively studied for two-dimensional problems over the past few years, this is the first time that a three-dimensional extension is presented. The strong discontinuity regime in the cells were imposed directly after the end of the elastic regime, as a typical behaviour of the fracture process of brittle materials. These cells are needed only at the specific region of the solid domain where the cracks propagation is supposed to occur, while the remaining non-discretized regions of domains are considered to work in elastic regime. Some simple numerical examples shows the feasibility of such methodology.

Study of Effect of the Chrome Additive on the Structural, Morphology and Optical Properties of Nanostructured Titanium dioxide Thin Film

Undoped Titanium dioxide (TiO2) and Cr-doped TiO2 films were prepared by Spray Pyrolysis Technique (SPT). XRD styles showed that TiO2 films were grown along dominant orientation of (111). Crystallite size increases from 8.95 nm to 9.70 nm as vanadium concentration increase, whereas the strain(%) parameter increased from 3.87 to 3.57. the AFM imaging shows that the Undoped TiO2 and TiO2: Cr thin films was discontinuous surface with spherically grains decreased from (65.95-44.23 nm) with increase doping from 0% to 3%, and root-mean square (rms) roughness of surface is about (9.70-2.41) nm. Spectrometric analysis of deposited films showed high transmittance in spectral range from 300 to 900 nm, whereas the corresponding value of bandgaps was ranged from 3.48 to- 3.38 eV by Cr doping. Results show that doping of TiO2 with Cr enhances the optical properties. the absorption coefficient (α), extinction coefficient (k) and refractive index (n) are increased when Cr additive is increasing.

Structural, Morphology and Optical properties of Ag-doped Nanostructured CdS thin films

Chemical Spray Pyrolysis (CSP) method is employed to deposit CdS and Silver (Ag)-doped CdS films. The effect of Ag doping at 1, and 3 wt-% levels is considered. The principal X-ray diffraction peak was along (020) plane. Maximum grain size was observed at the (CdS:3% Ag) films. The dislocation density parameter increased from 53.04 to 37.08, whereas the strain(%) parameter decreases from 25.23 to 21.10. Atomic force Microscope (AFM) images indicate a polycrystalline structure, and reveal that the undoped CdS and doped CdS:Ag films have discontinuous surfaces with spherically grains decreased from (58.05 to 45.77 nm) with the increase of doping from 0% to 3%. Root-mean square (Rrms) roughness of surface is about (9.81-5.42) nm. Also, there was a clear decrement in transmittance as Ag increment. The optical energy bandgap Eg has been decreased from 2.47 to 2.37 eV due to increase in Ag content. The absorption coefficients with photon energy increase with increasing concentration doping in Ag.

A NEW CLOSED FORM SOLUTION FOR DYNAMIC STABILITY ANALYSIS OF ROLLING AIRFRAMES HAVING ONE PAIR ON-OFF ACTUATOR

In this paper, the dynamic stability analysis of a rolling airframe actuated by one pair ON-OFF actuator using linear theory is presented via developing a new closed form solution. The effect of discontinuous forcing term on rolling airframe stability is studied. In contrast to tricyclic motion with constant forcing term (constant non-homogeneous term) in which only the amplitude of nutation and precession is affected, it is found that ON-OFF control affects both amplitude and phase of nutation and precession motions. In the case of discontinuous control surface, there are two sources for resonance instability. Finally, through simulation results of closed form solutions, a comparison between airframe’ response to ideal and real ON-OFF command is achieved. The effect of ON-OFF control on angular motion is also evaluated.

Review of Wide-Baseline Stereo Image Matching Based on Deep Learning

Strong geometric and radiometric distortions often exist in optical wide-baseline stereo images, and some local regions can include surface discontinuities and occlusions. Digital photogrammetry and computer vision researchers have focused on automatic matching for such images. Deep convolutional neural networks, which can express high-level features and their correlation, have received increasing attention for the task of wide-baseline image matching, and learning-based methods have the potential to surpass methods based on handcrafted features. Therefore, we focus on the dynamic study of wide-baseline image matching and review the main approaches of learning-based feature detection, description, and end-to-end image matching. Moreover, we summarize the current representative research using stepwise inspection and dissection. We present the results of comprehensive experiments on actual wide-baseline stereo images, which we use to contrast and discuss the advantages and disadvantages of several state-of-the-art deep-learning algorithms. Finally, we conclude with a description of the state-of-the-art methods and forecast developing trends with unresolved challenges, providing a guide for future work.

The effect of a novel pillar surface morphology and material composition demonstrates uniform osseointegration

Long-term survival of orthopedic implants requires a strong and compliant interface between the implant and surrounding bone. This paper further explores the in-vivo response to a novel, macro-scale osseointegration surface morphology. In this study, we examine the effects of material composition on osseointegration in relation to the controlled surface geometry. The pillared surface is constructed of discontinuous surface geometry which creates an open space for unencumbered bone migration. In creating an open, macro-scale morphology we have demonstrated a bone migration and integration that is less dependent on the underlying implant material and is substantially driven thru surface geometry.In this in-vivo study an established ovine model was used to examine the effects of implant material composition on bone ingrowth and mechanical performance. Cortical and cancellous sites in the tibia and distal femur were examined at 6 and 12 weeks with μCT, histology, histomorphometry, and mechanical performance. Implant materials tested included PEEK (Evonik, VISTAKEEP®), PEEK HA (Invibio, PEEK-OPTIMA HA Enhanced), Titanium coated PEEK, Titanium (Ti–6Al–4V, Grade 5), and Ultra-High Molecular Weight Polyethylene (UHMWPE). Extensive bone ingrowth was noted in all implant materials at 12 weeks with maturation of the bone within the pillar structure from 6 weeks to 12 weeks. Histology demonstrated little fibrous deposition at the implant interface with no adverse cellular reactions. Histomorphometric review of cortical sites revealed greater than 60% bone ingrowth at 6 weeks increasing to nearly 80% by the 12 week timepoint. Cancellous sites yielded a mean of 30% ingrowth at 6 weeks increasing to 35% by 12 weeks. Pushout testing of cortical site samples demonstrated increase in pushout force between the 6 and 12 week timepoints. Increases were significant in all but the UHMWPE samples. Stiffness likewise increased in all samples between the two times.These results demonstrated the effectiveness of the pillar morphology with full integrating from the surrounding bony tissue regardless of the material.

High Definition Metrology-Based Quality Improvement of Surface Texture in Face Milling of Workpieces With Discontinuous Surfaces

AbstractIn face milling process, the quality of surface texture is vital for mechanical performance of workpieces. The quality of surface texture, especially for waviness, is directly affected by tool marks, a commonly observed phenomenon in face milling. However, appropriate approaches for evaluation and modeling of tool marks are absent to date. Limited to the resolution as well as the efficiency of conventional measurement instruments, the height data of tool marks is hard to be entirely obtained, leading to valuable information omission. Besides, most existing models of tool marks are established for general workpieces with regular geometry and continuous surfaces. Since the cutter-workpiece engagement mode has a significant impact on the generation of tool marks, current models could be inaccurate or invalid when dealing with workpieces with discontinuous surfaces. To overcome this shortage, a novel approach is proposed in this research, aimed at quality improvement of surface texture in face milling of workpieces with discontinuous surfaces. First, the evaluation indexes for tool marks are defined based on the recently developed high definition metrology (HDM). Second, the physical modeling of tool marks is presented, taking the face milling mechanism into account. Third, the physical-informed optimization model is developed to search for the optimal processing parameters for surface quality improvement. At last, the effectiveness of the proposed approach is verified by a face milling experiment on the engine blocks.

Effect of sampling interval on the output statistics of large 3D discontinuity surfaces generated by a multiscale random field model

The scale effect is known to hinder reliable shear strength estimation of large-scale discontinuities. Recently, a stochastic approach was proposed to predict shear strength of large discontinuities directly at problem scale, thereby bypassing the scale effect. One aspect of the stochastic approach seeks to use the available roughness information from the 1D profile of a discontinuity to create a series of statistically representative 3D synthetic rock surfaces, via a rigorous random field model. The application procedure for producing such synthetic surfaces was validated at small scale; however, preliminary large-scale applications were not quite satisfactory. It was found that the absence of consideration for the multiscale nature of discontinuity roughness contributed to the issues encountered. This paper presents the details of the revised multiscale-based 2D LAS approach for producing representative large-scale synthetic surfaces with an emphasis on the effect of sampling interval, called segment length, on the statistics of the synthetic surfaces.

Theory and simulation of shock waves: Entropy production and energy conversion.

We have considered a shock wave as a surface of discontinuity and computed the entropy production using nonequilibrium thermodynamics for surfaces. The results from this method, which we call the "Gibbs excess method" (GEM), were compared with results from three alternative methods, all based on the entropy balance in the shock-front region, but with different assumptions about local equilibrium. Nonequilibrium molecular dynamics (NEMD) simulations were used to simulate a thermal blast in a one-component gas consisting of particles interacting with the Lennard-Jones/spline potential. This provided data for the theoretical analysis. Two cases were studied, a weak shock with Mach number M≈2 and a strong shock with M≈6 and with a Prandtl number of the gas Pr≈1.4 in both cases. The four theoretical methods gave consistent results for the time-dependent surface excess entropy production for both Mach numbers. The internal energy was found to deviate only slightly from equilibrium values in the shock front. The pressure profile was found to be consistent with the Navier-Stokes equations. The entropy production in the weak and strong shocks were approximately proportional to the square of the Mach number and decayed with time at approximately the same relative rate. In both cases, some 97% of the total entropy production in the gas occurred in the shock wave. The GEM showed that most of the shock's kinetic energy was converted reversibly into enthalpy and entropy, and a small amount was dissipated as produced entropy. The shock waves traveled at almost constant speed, and we found that the overpressure determined from NEMD simulations agreed well with the Rankine-Hugoniot conditions for steady-state shocks.