Low-energy Areas Research Articles

Lanthanum ions decorated 2-dimensional g-C3N4 for ciprofloxacin photodegradation

The low band gap energy and high surface area two-dimensional materials allow it to tune its basic properties using surface decoration. Here, La3+ are decorated on two-dimensional graphitic carbon nitride using a simple and easily scalable chemisorption process with an adsorption capacity of 657.32 mg g−1. In the X-ray diffraction (XRD) study, the positive slope of the W–H plot elucidates the tensile strain generation (0.103) in La3+ ions decorated 2D-g-C3N4 (La3+-2D-g-C3N4). The high-resolution transmission electron microscope (HR-TEM) study and the higher ID/IG ratio (0.82) in the Raman spectroscopy study confirm the more defects intensification in La3+-2D-g-C3N4. The reduction in band gap energy for La3+-2D-g-C3N4 (from 2.83 eV to 2.21 eV) has shown a good correspondence with the band structures study as obtained from the DFT study. In the DFT study, the significant contributions of N atoms in charge transfer validate the N 1s findings from the X-ray photoelectron spectroscopy (XPS) study for La3+-2D-g-C3N4. La3+-2D-g-C3N4 shows the photodegradation efficiency (93%) of ciprofloxacin under UV irradiation, which is superior to pristine 2D-g-C3N4 (82%) as well as other g-C3N4 based nanocatalysts. Also, La3+ decoration results in enhancement (32.3%) in photodegradation kinetics rate. The degradation and kinetics studies in the presence of different scavengers ensure that the O2ˉ and OH− radicals are mostly responsible for the ciprofloxacin photodegradation. The Liquid chromatographic-mass spectroscopy and the high-performance liquid chromatography studies confirm the photodegradation. The reusability of La3+-2D-g-C3N4 is tested up to the fifth cycle. FTIR and UV–visible absorption spectroscopy confirm the stability of the used photocatalyst.

Stable Luminescent CsPbI3 Quantum Dots Passivated by (3-Aminopropyl)triethoxysilane.

Perovskite nanomaterials have been fascinating for commercial applications and fundamental research owing to their excellent optical properties and satisfactory processability. They are expected to be alternative downconversion materials in phosphor-converted LEDs for lighting or display technology. However, owing to their low formation energy and large specific surface area, perovskite nanomaterials are sensitive to environmental stress like humidity, heat, etc. In this paper, cubic CsPbI3 quantum dots (QDs) with improved stability are synthesized using (3-aminopropyl)triethoxysilane (APTES). These luminescent CsPbI3 QDs passivated by APTES not only show excellent stability when stored in hexane but also possess outstanding steadiness for lattice structure when prepared as a thin film in open air. They do not decompose immediately in the water. Such excellent stability is attributed to the hindrance from hydrolysis of APTES, which forms an analogous core-shell structure to protect the "core" CsPbI3 QDs. Furthermore, an additional iodine source is added to enhance their emissionm and CsPbI3QDs with a PLQY of 84% are synthesized.

Variable Growth Across Species and Life Stages in Caribbean Reef Octocorals

Growth rates often measured as linear extension rates can serve as a proxy for organismal performance across environments, yet few estimates of these growth rates exist, and fewer are reported from multi-year monitoring. We studied the effect of species, depth, exposure and life stages on the linear extension rates of common octocorals inhabiting Caribbean reefs. We monitored 16 species from the families Briareidae, Gorgoniidae, and Plexauridae, including eight genera: Antillogorgia, Briareum, Eunicea, Gorgonia, Muricea, Muriceopsis, Plexaura, and Plexaurella. We surveyed over 2,000 colonies across eight reefs in Southwest Puerto Rico from 2003 to 2006. Our surveys include reefs along a gradient of water motion from inside protected reefs to offshore unprotected reefs and from shallow (5 m) forereefs to deeper environments reaching 25 meters. We observed that linear extension rates vary across species and largely follow branch thickness variation and colony architecture, with thin plume-like shapes growing faster. We also found that in 7 out of the 16 species, colonies from shallow habitats with brighter and warmer environments have higher growth rates than colonies in deep, low energy, and darker areas. Importantly, small/juvenile corals of most species (< 10 cm) grew faster than adult colonies. Our data highlight the possibility that, as climate change continues to deteriorate Caribbean reefs by decimating scleractinian corals and opening new habitat for less vulnerable species, plume-like corals with fast growth rates such as species within the genus Antillogorgia may become the most abundant benthic cnidarians on Caribbean shallow forereefs.

Multidata Study to Evaluate the Impact of Submarine Outfall in a Beach Sedimentary Dynamic: The Case of Samil Beach (Galicia, Spain)

The Ria de Vigo (NW Iberian Peninsula) is one of the most impacted coastal areas of Galicia, due to demographic and industrial pressure. One of the main consequences of this pressure is the need to extend the current wastewater treatment plant of the city of Vigo (295,000 inhabitants). This extension includes a new submerged pipeline construction to discharge the treated water in the central channel of the Ria. The new planned pipeline must cross Samil Beach, the most important urban beach of the city. Based on a multitool strategy, this work characterizes the interactions between the new pipeline route alternatives and the sediment dynamics of Samil Beach. This approximation improves the reliability of the results in the subtidal area of the beach, where studies are scarce due to the complexity of the data acquisition. The present study is based on high resolution bathymetry data, seabed physical characterization, a granulometric study of the superficial sediment, and a numerical simulation of the tide, wave climate, and sediment transport in low and high energy conditions using open source Delft3D software. The results showed that the area of interest is a low energy area, which is significantly shielded from wave attack, where fine sand predominates. However, the field data indicated an interaction (accretion-erosion) in the submerged obstacles between 0 and 12 m deep. The model revealed that there is significant sediment movement above a 7.4 m isobath, and that the pipeline would not alter the general transport dynamics of the beach, but would interact in the shallowest section. The main conclusion of this work states that the future structure would not alter the global sediment dynamics of the beach. In addition, in order to guarantee the safety of the new pipeline, it should emerge above an 8 m isobath. The multiapproach methodology presented can be applied to other studies of the interaction between coastal structures and the environment.

Theoretical investigation of the crystallographic structure, anisotropic elastic response, and electronic properties of the major borides in Ni-based superalloys

ABSTRACT In Ni-based superalloys, it is usually found that borides can strengthen the grain boundaries, thereby resulting in an increase in mechanical strength and high-temperature creep properties. Due to their importance and prevalence in Ni-based superalloys, this study employs first-principles methods to investigate the crystallographic structure, anisotropic elastic response, and electronic properties of the major borides, such as M2B, M5B3 and M3B2 (M: Cr, Mo, W), respectively, which is necessary for the assessment of complex mechanical responses of Ni-based superalloys. The results demonstrate that the studied borides are all thermodynamically and mechanically stable. Among the M x B y binary borides analysed, Cr x B y exhibits the largest shear modulus, Young’s modulus, and Vicker hardness values, and these properties increase with the increase of B contents. The studied borides display nearly isotropic elastic properties except for W5B3 and W3B2. The electronic structure analysis of M x B y shows that the strong hybridisation between M-d and B-p orbitals leads to these borides exhibiting higher theoretical hardness, and the overlapping peaks of M-d and B-p orbitals move to a lower energy area with the increase of B contents, which leads to the increase of shear and Young’s moduli of M x B y . Furthermore, for M3B2 borides, the Cr-B bonds and Cr–Cr bonds are much stronger than the W-B & Mo-B bonds, and W-W & Mo-Mo bonds, respectively, which leads to Cr x B y yielding the largest values of elastic moduli.

First-principles study on electronic and optical properties of S, N single-doped and S-N co-doped ZnO

The electronic and optical properties of undoped, N single-doped, S single-doped, and S-N co-doped ZnO were systematically investigated by first-principles calculations. The lattice parameters of S single-doped and S-N co-doped ZnO clearly increased. After N-doping, a strongly localized impurity energy level of N was formed near the Fermi level at the top of valence band (VB). In S-N co-doped ZnO, the localization of N weakened, and the Fermi level went deeper into the VB, indicating that the acceptor energy level of N formed in S-N co-doped system became shallower due to the effect of 3p state of S. Therefore, S-N co-doping is beneficial to obtain p-type ZnO with a higher hole concentration than N single-doping. Compared with undoped ZnO, the static dielectric constant, absorption coefficient, refractive index, energy loss function, and reflectivity of N single-doped, S single-doped, and S-N co-doped ZnO exhibited an increase in low-energy area.

Ecohydraulic modelling of anabranching rivers

AbstractIn this paper we provide the first quantitative evidence of the spatial complexity of habitat diversity across the flow regime for locally anabranching channels and their potential increased biodiversity value in comparison to managed single‐thread rivers. Ecohydraulic modelling is used to provide evidence for the potential ecological value of anabranching channels. Hydraulic habitat (biotopes) of an anabranched reach of the River Wear at Wolsingham, UK, is compared with an adjacent artificially straightened single‐thread reach downstream. Two‐dimensional hydraulic modelling was undertaken across the flow regime. Simulated depth and velocity data were used to calculate Froude number index, known to be closely associated with biotope type, allowing biotope maps to be produced for each flow simulation using published Froude number limits. The gross morphology of the anabranched reach appears to be controlling flow hydraulics, creating a complex and diverse biotope distribution at low and intermediate flows. This contrasts markedly with the near uniform biotope pattern modelled for the heavily modified single‐thread reach. As discharge increases the pattern of biotopes altered to reflect a generally higher energy system, interestingly however, a number of low energy biotopes were activated through the anabranched reach as new subchannels became inundated and this process creates valuable refugia for macroinvertebrates and fish, during times of flood. In contrast, these low energy areas were not seen in the straightened single‐thread reach. Model results suggest that anabranched channels have a vital role to play in regulating flood energy on river systems and in creating and maintaining hydraulic habitat diversity.

Electronic and optical properties of defective MoSe2 repaired by halogen atoms from first-principles study

Using first-principles calculations, we have investigated the electronic and optical properties of MoSe2 with Se vacancies (SVSe, α-DVSe, and β-DVSe) and further repaired by halogen atoms (F, Cl, Br and I). For the MoSe2 with Se vacancies, Cl, Br and I atoms can occupy the Se vacancies and form three bonds with the neighboring Mo atoms, but F atom only can form two F-Mo bonds with the lowest adsorption energies due to its smaller atomic radius. Halogen atoms possess one more electron than Se atom, which results in a local magnetic moment of 1µB for single vacancy and 2µB for double vacancies. The MoSe2 with Se vacancies exhibits n-type doping semiconductor, which agrees well with the experimental observations. After halogen atoms doping in the defective site, the defective levels shift from electron donor levels to the electron acceptor levels, and finally reduces the n-type doping from the defective structure through a p-doping process. Compared to the defective MoSe2, absorption enhancement around low energy area of 0∼3 eV is observed in the halogen-repaired MoSe2 structures. Our results provide new insights in structural repairing of the transition metal dichalcogenides and promote their remarkable properties for applications in optoelectronics.

Study on hydrodynamic performance of the sealed-buoy wave energy converter

For investigating the wave energy converter working in low-energy flow density sea area, a novel sealed-buoy wave energy converter (SBWEC) was analysed by using the fluid simulation software ANSYS and AQWA according to Shandong Peninsula marine environment in this paper. For the SBWEC in the range of 5-20 m buoy diameter, the effect of mass on the response amplitude operator (RAO) and the motion response were analysed based on the frequency domain method and the time domain method. The wavelength range with higher wave energy was also investigated. Within the mass range of 8-12 t, the study found that the mass did not has a significant impact on the roll, yaw and pitch RAO and the pitch motion response except for the SBWEC with 5 m buoy diameter. The wavelength range with higher wave energy in Shandong Peninsula is 10-40 m, which is more suitable for operation of the SBWEC. These results can provide a reference for the design of related wave energy converters.

On the Impact of Mobility on Battery-Less RF Energy Harvesting System Performance.

The future of Internet of Things (IoT) envisions billions of sensors integrated with the physical environment. At the same time, recharging and replacing batteries on this infrastructure could result not only in high maintenance costs, but also large amounts of toxic waste due to the need to dispose of old batteries. Recently, battery-free sensor platforms have been developed that use supercapacitors as energy storage, promising maintenance-free and perpetual sensor operation. While prior work focused on supercapacitor characterization, modelling and supercapacitor-aware scheduling, the impact of mobility on capacitor charging and overall sensor application performance has been largely ignored. We show that supercapacitor size is critical for mobile system performance and that selecting an optimal value is not trivial: small capacitors charge quickly and enable the node to operate in low energy environments, but cannot support intensive tasks such as communication or reprogramming; increasing the capacitor size, on the other hand, enables the support for energy-intensive tasks, but may prevent the node from booting at all if the node navigates in a low energy area. The paper investigates this problem and proposes a hybrid storage solution that uses an adaptive learning algorithm to predict the amount of available ambient energy and dynamically switch between two capacitors depending on the environment. The evaluation based on extensive simulations and prototype measurements showed up to 40% and 80% improvement compared to a fixed-capacitor approach in terms of the amount of harvested energy and sensor coverage.

A Study of Co-occurrences of Foraminifera and Mussels in a Polluted Nova Scotian Wetland, Atlantic Canada

Abstract Studies of foraminiferal assemblages in intertidal marshes and subtidal creeks usually rely upon sediment samples collected along transects, such that associations with other organisms often go unnoticed. We show that ecologically useful data can be obtained by sampling that is stratified by substrate and microenvironment. The tidal wetland at Lower LaHave, Nova Scotia, Atlantic Canada (44º16′37.39″N, 64º19′46.45″W, area ∼1 km2) comprises mostly sandy sediment occupied largely by the low marsh grass Spartina alterniflora. The wetland is situated next to LaHave Estuary, which is polluted with domestic waste. Microenvironments within the marsh were sampled for total (living + dead) foraminiferal assemblages. The mass of dried sediment examined at each site was used to calculate the foraminiferal number (FN, number of foraminiferal tests per gram of sediment). Sediment samples from the intertidal grass beds reflect a typical low- to high-marsh zonal distribution of benthic foraminifera [FN = 24.7 ± 16.6 g−1 (mean ± standard deviation); n = 716 tests]. Samples from a tidal channel yielded few tests (FN = ∼0.3 ± 0.7 g−1; n = 22). Clutches of the mussel Mytilus edulis occurred in areas of strong current action within the channel and on lower energy slip-off slopes. Mussel clutches from the channel base yielded few tests (FN = ∼0.7 ± 0.7 g−1; n = 25), mostly Miliammina fusca. Clutches from slip-off slopes yielded a significantly richer assemblage (FN = 8.7 ± 4.6 g−1; n = 229) dominated by Elphidium umbilicatulum. We concluded that mussel clutches in low energy areas can be suitable habitat for E. umbilicatulum, either associated with structural complexity of the clutches or with waste products excreted by mussels that may stimulate growth of bacteria or microalgae upon which the foraminifera feed. The results from this study provide a baseline for examining the biotic impact of remediation of the LaHave River on the Lower LaHave wetland.

Comparisons of microplastic pollution between mudflats and sandy beaches in Hong Kong.

Most of the previous studies of microplastic pollution on coastal habitats focused on high energy beaches although low energy areas such as mudflats are supposed to retain more microplastics, not to mention that mudflats are biologically more diverse. We quantified and characterized microplastics from 10 mudflats and 10 sandy beaches in Hong Kong spanning from the eastern to western waters. Sediment samples were collected at 1.0 m and 1.5 m above chart datum (CD) and at the strandline. Abundance of microplastics ranged between 0.58 and 2116 items kg-1 sediment with that on mudflats being ten times more than on beaches. Polyethylene (46.9%) was the most abundant and followed by polypropylene (13.8%) and polyethylene terephthalate (13.5%). Expanded polystyrene was the most abundant in the strandline samples but not at 1.0 m and 1.5 m above CD. Although previous studies have concluded that the input from Pearl River is a major source of microplastics on Hong Kong shores, this study has demonstrated that the contribution of local pollution sources such as discharge from sewage treatment plants to microplastic pollution should not be neglected.

A first principles study of the phonon anharmonicity, electronic structure and optical characteristics of LaAlO3

The way elementary excitations work together with their couplings and interact as condensed matter systems is very important when designing optimum energy-conversion devices. We investigated the electronic structure of LaAlO3, and we show that the bandgap insulator of LaAlO3 obtained theoretically by the hybrid functional HSE06 is an indirect 5.649eV that show a very good agreement with experimental data. The lattice constant is obtained exactly as experiment. In thermos-electric materials, the concept of conversion-efficiency (heat to electricity) is improved instantly by suppressing the phonon quasi-particles propagations that are responsible for draft macroscopic thermal transport. The material presented here for thermo-electric conversion-efficiency of cubic perovskite LaAlO3, show that it has an ultralow thermal-conductivity, while the formalism to its strong phonon scattering interactions resides mostly unclear. From the bases of Ab-initio simulations, the 4-dimensional phonon-dispersion surfaces of the cubic perovskite LaAlO3, have been mapped and we found that the origins of the ionic potential an-harmonicity being responsible for the unique behaviour and properties of LaAlO3. It is investigated that these phonon scattering arise solely from the LaAlO3 unstable electronic-structure, with its orbital interactions resulting to lattice instability similar to the ferroelectric instabilities. Our results show a microscopic insight bonding electronic-structure and phonon an-harmonicity in LaAlO3, and provides some new picture the way interactions happen between phonon–electron and phonon–phonon this lead to understand the concept of ultralow thermal-conductivity. Ab-initio calculations was performed on cubic perovskite LaAlO3 to obtain the phonon density of states (DOS) from 50 K to 5000 K, we find that the anharmonic behaviour starts around temperature limits of 500 K. The computed optical spectra were obtained using both the Beth Slapter Equation BSE and compared with the perturbed method using HSE06, optical spectra show that the inter-band transition occur precisely from the O-valence bands to the La-conduction bands throughout the low energy area. The energy-loss spectrum, optical conductivity and reflectivity and the refractive index are computed from first principles by using HSE06 hybrid functional. The optical band gap of material shows about 6.21 eV, which agrees with some cited experimental measurements.

Electronic structure and optical properties of Cu-O co-doped AlN

The geometry parameters, band structure, electronic density of states, and optical properties of AlN before and after being co-doped by Cu and O are investigated by the ultra-soft pseudo-potential plane wave based the density functional theory. The results show that the lattice volume increases and the total energy of the system decreases after doping. The Cu doping system makes Cu 3d electrons hybridize with its nearest neighbor N 2p electrons strongly. In the Cu-O co-doped system, Cu and O attract each other to overcome the repelling of acceptor Cu atoms, thereby increasing the doping concentration of Cu atoms and the stability of the system. Dielectric function calculation results show that Cu-O co-doping can improve the optical transition characteristics in low energy area of AlN electrons, and thus enhancing the optical transition of electrons in visible area. The complex refractive index calculation results indicate that Cu-O co-doped system increases the absorption of low frequency electromagnetic wave.

Response of intertidal benthic macrofauna to migrating megaripples and hydrodynamics

Migrating flow-transverse mesoscale intertidal bedforms (megaripples or dunes) may pose disturbance but may also provide heterogeneity in microhabitats to the inhabiting fauna. We investigated how the macrofauna community responds to these migrating intertidal bedforms, based on surveys in the Westerschelde estuary. Considering the entire estuary, low- and high-energy intertidal areas differed in macrofauna, and high-energy flat areas had a macrofauna community intermediate to those in low-energy flat areas and high-energy areas with megaripples. In megaripple areas on a polyhaline and a mesohaline tidal flat, the macrofauna community depended on hydrodynamics, morphodynamics, grain size, elevation and steepness of the megaripples. The relative importance of the environmental variables for structuring the macrofauna community differed for each site. Within the megaripples, conditions on crests, at flanks and in troughs were distinctly different: crests had more chl a and coarser sediment than troughs, while flanks had intermediate levels; troughs were higher in carbon and mud content than flanks and crests. The microhabitats supported a different macrofauna community but with a very large overlap in species. Troughs typically had higher species richness, while crests had higher densities of, in particular, (mobile) surface deposit feeders. Part of the macrofauna could benefit from the habitat heterogeneity within the megaripples, but the effect was relatively small. The distribution of macrofauna in the intertidal zone was particularly regulated by overall current velocities and bedform morphodynamics

Application potential of small-scale solar desalination for brackish water in the Jordan Valley, Palestine

This paper investigates the feasibility of using solar energy coupled to reverse osmosis (RO) units for the desalination of brackish water in the Jordan Valley, the food basket for the West Bank, Palestine. Pilot-scale RO units are appropriate because of the low energy requirement, market availability, size and area and convenience of installation in the Jordan Valley’s harsh conditions. The study concerned the Marj Naajeh desalination unit. The economic feasibility was compared to other alternative energy sources (diesel generators and network electricity). The environmental costs were considered as well as the economic costs. The results obtained suggest upgrading 162 agricultural wells of different water capacities and quality. Further studies on design capacity and efficiency of future desalination facilities would be beneficial.

Wave hazards on microtidal shore platforms: testing the relationship between morphology and exposure

Open-ocean rocky coasts are dangerous environments when there is a coincidence of recreational activities occurring in areas of high wave energy. Management of drowning fatalities and near-drowning incidents on these landforms is difficult as traditional approaches to beach safety cannot be easily transferred to rocky shores. In this study, we take a morphological approach to quantifying the relative danger of shore platforms in microtidal regions. Platform elevation and nearshore water depth are key variables in determining the likelihood of wave overtopping of the platform edge. The relationship between these variables is tested along a 70-km-long section of the Otway Ranges coast in Victoria, Australia. It is found that exposure is highly variable along short (100 m scale) sections of shore platforms. This variability is driven by the complexity of the nearshore morphology which can have metre-scale relief. As exposed platforms may occur in areas of low wave energy, the morphological exposure index is combined with nearshore wave energy to produce a risk rating. Risk, like exposure, was found to be highly spatially variable. The relationship between elevation and water depth has the potential to provide managers with a tool for assessing safety on rocky shores.

Constant SNR, Rate Control, and Entropy Coding for Predictive Lossy Hyperspectral Image Compression

Predictive lossy compression has been shown to represent a very flexible framework for lossless and lossy onboard compression of multispectral and hyperspectral images with quality and rate control. In this paper, we improve predictive lossy compression in several ways, using a standard issued by the Consultative Committee on Space Data Systems, namely CCSDS-123, as an example of application. First, exploiting the flexibility in the error control process, we propose a constant-signal-to-noise-ratio algorithm that bounds the maximum relative error between each pixel of the reconstructed image and the corresponding pixel of the original image. This is very useful to avoid low-energy areas of the image being affected by large errors. Second, we propose a new rate control algorithm that has very low complexity and provides performance equal to or better than existing work. Third, we investigate several entropy coding schemes that can speed up the hardware implementation of the algorithm and, at the same time, improve coding efficiency. These advances make predictive lossy compression an extremely appealing framework for onboard systems due to its simplicity, flexibility, and coding efficiency.

Challenges of eWALL Wireless Interoperability

Due to development of different technologies there has been significant improvement in quality of life. As a result of that, average person's lifetime duration has been increased. That triggers the problem of independent living of senior citizens. One of the main concerns of the world today is how to enable senior citizens to live independently. As a response to that, systems like eWALL are being developed. eWALL for Active Long Living is a FP7 funded project and it aims to develop system which will enable elderly people to live independently. These systems consist of a large number of sensors which make wireless sensor network. In this paper, different wireless technologies that can be used for communication in systems that are designed to support independent living of elderly people, have been described. The most important focus is at wireless personal area network technologies, like ZigBee, Bluetooth, Bluetooth Low Energy and wireless local area network technologies (e.g., Wi-Fi). There are many obstacles in designing wireless sensor network and most of them concern energy efficiency and interoperability of different technologies that are being used for communication. The main challenge in the current technology world is tremendous increase of use of various wireless devices and technologies, which can cause relatively high interference, so that the wireless devices can stop working. Using cognitive radio in solving the interoperability problem of different wireless technologies in wireless sensor networks has become interesting research topic. In this paper, research on interoperability of different wireless technologies is presented. Using Spectrum Engineering Advanced Monte Carlo Analysis Tool wireless sensors network in home environment was modelled. Interference based on devices layout and activity was investigated. Also, possible improvements that can be made with cognitive radio are investigated and obtained results are given in this paper.

The five-parameter grain boundary curvature distribution in an austenitic and ferritic steel

The distribution of grain boundary curvatures as a function of five independent crystallographic parameters is measured in an austenitic and a ferritic steel. Both local curvatures and integral mean curvatures are measured from three dimensional electron backscattered diffraction data. The method is first validated on ideal shapes. When applied to real microstructures, it is found that the grain boundary mean curvature varies with the boundary crystallography and is more sensitive to the grain boundary plane orientation than to the disorientation. The grain boundaries with the smallest curvatures also have low grain boundary energy and large relative areas. The results also show that the curvature is influenced by the grain size and by the number of nearest neighbors. For austenite, when the number of faces on a grain is equal to the average number of faces of its neighbors, it has zero integral mean curvature.