Geometric Surface Research Articles

Silica-Encapsulated Intermetallic Nanoparticles for Highly Active and Selective Heterogeneous Catalysis

ConspectusIntermetallic nanoparticles (iNPs) have been the subject of many recent reports for their demonstrated applications as highly active and selective heterogeneous catalysts. As a subclass of alloys, intermetallic compounds possess ordered crystal structures and, therefore, well-defined atomic environments, unlike the solid solution of alloys whose atomic arrangements are random and locally unpredictable. Catalytically active iNPs typically contain a group 8–10 transition metals as the “active” metals. They usually also include an “inactive” metal that does not directly participate in the catalytic reaction but can significantly modify the active metal’s behavior. The choice of the inactive metal component can range across the periodic table.A few general challenges remain to design iNPs as heterogeneous catalysts with outstanding performance. Synthetically, the high surface energy of small nanoparticles is prone to their aggregation, while maximizing the surface-to-volume ratios is highly desired for efficient noble metal utilization. Additionally, even though the formation of bulk intermetallic compounds has been extensively studied, the formation of intermetallic phases at the nanoscale can behave differently. For example, the formation temperatures of iNPs are often drastically different from those predicted from the bulk phase diagrams. This behavior often leads to further challenges in the synthesis of iNPs.In addition to synthetic challenges, it is also critical to demonstrate the performance of iNPs in catalysis and establish the structure–property relationships. Instrumental and computational techniques often assist the understanding of catalytic properties. Due to the long-range order of intermetallic structure, various electron and X-ray techniques are often used to precisely determine the structure of iNPs. Structural modeling in density functional theory (DFT) calculation can also benefit from such ordered structures. These techniques have siginificantly improved the understanding of enhanced catalytic properties of iNPs in thermo-, electro-, and photocatalysis. Hydrogenation of furfural to furfuryl alcohol, for example, is a model reaction where PtSn iNPs show enhanced activity and chemoselectivity in hydrogenating C═O rather than C═C bonds. This superior catalytic performance can be correlated to the change in the geometric and electronic surface structure of the PtSn iNPs based on careful instrumental and computational characterizations. Additionally, intermetallic surfaces can be further modified by ligands or defects. While adding complexity to iNP systems, these modifiers provide additional control over their catalytic properties.In this Account, taking encapsulated iNPs in mesoporous silica as an example, we review the current strategies to develop iNPs as high-performance heterogeneous catalysts, with insights on the distinct formation behavior of iNPs compared to bulk intermetallic materials. We then highlight thermo- and electro-catalysis reactions to which these iNP catalysts are applied. We also discuss the unique pairwise hydrogenation reaction with parahydrogen catalyzed by iNPs. In this reaction, iNPs show unparalleled potential. We anticipate that this Account could foster additional interests in studying intermetallic catalysts and lay the foundation for their applications.

Combination of regional and global geoid models at continental scale: application to Iranian geoid

High precision geoid determination is a challenging task at the national scale. Many efforts have been conducted to determine precise geoid, locally or globally. Geoid models have different precision depending on the type of information and the strategy employed when calculating the models. This contribution addresses the challenging problem of combining different regional and global geoid models, possibly combined with the geometric geoid derived from GNSS/leveling observations. The ultimate goal of this combination is to improve the precision of the combined model. We employ fitting an appropriate geometric surface to the geoid heights and estimating its (co)variance components. The proposed functional model uses the least squares 2D bi-cubic spline approximation (LS-BICSA) theory, which approximates the geoid model using a 2D spline surface fitted to an arbitrary set of data points in the region. The spline surface consists of third- order polynomial pieces that are smoothly connected together, imposing some continuity conditions at their boundaries. In addition, the least-squares variance component estimation (LS- VCE) is used to estimate precise weights and correlation among different models. We apply this strategy to the combined adjustment of the high-degree global gravitational model EIGEN-6C4, the regional geoid model IRG2016, and the Iranian geometric geoid derived from GNSS/leveling data. The accuracy of the constructed surface is investigated with five randomly selected subsamples of check points. The optimal combination of the two geoid models along with the GNSS/leveling data shows a reduction of 21 mm (~20%) in the RMSE values of discrepancies at the check points.

Recoverable underwater superhydrophobicity from a fully wetted state via dynamic air spreading

SummaryMaintaining the superhydrophobicity underwater offers drag resistance reduction, antifouling, anti-corrosion, noise reduction, and gas collection for boat hulls and submarine vehicles. However, superhydrophobicity typically does not last long underwater since the Cassie state is metastable. Here, we report a reversible and localized recovery of superhydrophobicity from the fully wetted state via air bubble spreading. Composed of sparse fluorinated chained nanoparticles, the submerged surface shows super-low energy barrier for bubble attachment. Especially the recovered plastron exhibits excellent longevity. Based on a simplified, truncated nanocone model, the dynamic spreading of bubbles is analyzed considering two basic parameters, i.e., surface geometric structure and surface energy (which appeared as intrinsic water contact angle). Numerical simulation results via COMSOL confirms the effect of geometric structure on bubble spreading. This investigation will not only offer new insights for the design of robust recoverable superhydrophobic surfaces but also broaden the applications of superhydrophobic coatings.

Post-processing of additively manufactured metal parts by ultrashort laser pulses for high-quality net shape geometries and advanced functionality

Additive manufacturing by means of laser-based powder bed fusion (LPBF) offers high flexibility with respect to the generation of individualized and light-weight metal parts. However, the produced parts are typically attached to support structures and deviate a few tens of micrometers from the targeted final component in geometrical net shape and surface roughness due to the melt-based fusion process. Therefore, different post-processing techniques were examined in the past to resolve the mentioned quality drawbacks. In our work, we investigated the potential of post-processing of LPBF-generated Ti6Al4V parts with ultrashort pulse laser ablation. As a result, the support structures were effectively removed, the surface roughness was reduced by 81% and complex geometries with high shape accuracy were fabricated. Furthermore, the LBPF-generated parts were laser surface structured to investigate the potential of post-processing with ultrashort laser pulses for advanced functionality, such as water-repellent surfaces. The generation of surface structures on the LPBF-generated Ti6Al4V part changed the wetting behaviour from hydrophilic to hydrophobic with an increased contact angle from 73° up to 130°.

A comprehensive model to predict friction factors of fluid channels fabricated using laser powder bed fusion additive manufacturing

Laser powder bed fusion (L-PBF), or selective laser melting, can be used to significantly reduce the size and weight of hydraulic components. However, the current design approach still greatly depends on the technician’s experience. The friction loss of the L-PBF fabricated fluid channels is greatly affected by the fabrication quality but remains unknown, which is essential for the design approach. In this study, circular 316L SS fluid channels with various diameters (4–10 mm) and build angles (0–90°) were fabricated using L-PBF. Fabrication quality was characterized, and the friction factors were measured and analyzed. The results indicate that the geometric tolerance and surface roughness are closely related to the build angle. The friction factor of the L-PBF fabricated channels, which is higher than the classical theory in the turbulent flow, is influenced by both channel diameters and build angles. A comprehensive model is developed to predict friction factors of the L-PBF fabricated fluid channels. Design guidelines of fluid channels are proposed, for the first time, by considering both fabrication quality and friction factors. • The influence of build angle on channel forming quality is studied. • The relationship between forming quality and friction factor is developed. • A comprehensive friction factor prediction model for 316L SS L-PBF channel is developed. • Design guidelines of L-PBF fabricated fluid channels are proposed.

Mechanical behavior of Al–Si10–Mg gyroid surface with variable topological parameters fabricated via laser powder bed fusion

Metallic cellular materials with triply periodic minimal surface (TPMS) topologies have great potential for lightweight and multi-functional applications. However, the effect of level-set values, which can control the topology of TPMS, on the performance of TPMS have not been fully understood because previous studies have mainly focused on the shell thickness, cell size and periodicity of TPMS. In this paper, Al–Si10–Mg gyroid surfaces with three different level-set values are fabricated by using selective laser melting (SLM). Micro computed tomography (Micro-CT) is used to reconstruct the 3D models of as-built samples, then the geometric deviations and surface quality are investigated. Mechanical behavior and energy absorption characteristics of these gyroid surfaces are investigated both experimentally and numerically, which provide a solid basis for predicting and controlling the deformation behavior in gyroid surfaces. Afterwards, the Gibson–Ashby model is used for understanding the effect of the level-set value on Young's modulus and plateau stress of gyroid surfaces. Finally, the relationship between level-set values and densification strain and energy absorbed per unit volume is also presented to gain insight into the role of level-set values on the energy absorption capability of the gyroid surfaces. Such understanding provides a new method to develop desired properties of implants or energy absorption applications by selecting an optimal combination of level-set value, thickness, periodicity etc.

Tessellation in Architecture from Past to Present

Tessellation, which has examples of use in art and architecture, is the covering of a surface using one or more geometric shapes without overlapping or gaps. Based on Roman mosaics, the tessellation has an important place in architecture since the ancient times. Through the history, different patterns have been used by many cultures for various applications ranging from decorative covering elements to multi-functional latticework screens. The tessellation has still been used in contemporary architecture since it not only allows creating the geometrical surface in an order but also provides multi-functionality to the surface when applied as shading elements. The tessellation can be reviewed under three categories such as regular, semi-regular and demi-regular tessellations. Two- and three-dimensional examples of the tessellations can be seen in contemporary architecture either as façade elements or patterns used for structural elements. Because the tessellation plays a significant role in architecture in terms of geometrical or structural design, the interest on this topic has been increased in recent years. Due to their great potentials, more studies should be conducted on the tessellations. For this reason, within the scope of this paper, the applied examples of the tessellations in buildings from past to present are examined which include both static and kinetic ones. In this paper, the geometric design principles, combination methods and iteration processes of the examples are also presented. As well as providing a deeper understanding of such tessellation methods, this study will serve as a basis of reference for future studies in this field.

In Vitro Electrochemical Properties of Titanium Nitride Neural Stimulating and Recording Electrodes as a Function of Film Thickness and Voltage Biasing.

Thin film titanium nitride (TiN), with a geometric surface area of 2,000 μm2, was deposited on planar test structures with thicknesses of 95, 185, 315, and 645 nm. Electrochemical measurements of electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and voltage transient (VT) were performed. We found that impedance values decreased and charge storage and charge injection capacities increased with increasing film thicknesses. Additionally, applying a anodic bias to TiN can increase the charge injection of the film to nearly double that of a non-biased film.

Impact of Compression Force on Mechanical, Textural, Release and Chewing Perception Properties of Compressible Medicated Chewing Gums.

Medicated chewing gums (MCGs) represent a beneficial platform for realizing drugs intended for dental prophylaxis and treatment. The present study aimed to investigate the impact of compression force on the mechanical, textural, release, and chewing perception characteristics of compressible MCGs with the combination of lysozyme hydrochloride (LH) and ascorbic acid (AsA). Four batches of MCGs were obtained on a laboratory single-punch tablet machine applying different forces, i.e., 5, 7, 10, and 15 kN, and evaluated by their geometrical parameters, mechanical resistance, surface and internal structure characteristics, texture profile, release behavior, and perception attributes during mastication. It was found that increasing compression force slightly affected resistance to crushing and friability of MCGs, but resulted in surface smoothing and formation of a thicker layer with highly compacted particle arrangement. According to the texture analysis, increasing compression force led to harder and more adhesive gums, indicating possible difficulties in chewing and, therefore, impairment of their consumer properties. Lower compression forces were also found to be preferable in terms of better drug release from the obtained chewing gums. The volunteers’ assessment showed that an increase of compression force led to significantly raising the initial hardness and crumbliness as well as to decreasing the rate of the integral gum mass formation during mastication, which may negatively affect perceptive sensations when using MCGs. Based on the results obtained, the optimal compressing force was selected to be 7 kN, which allows obtaining MCGs with good organoleptic, mechanical, textural, and release properties.

The Impact of Mn addition on Ta Oxide-Based Electrocatalysts for Oxygen Evolution Reaction in Acid

Hydrogen energy ministerial meeting (H2 EM 2020) was held on Oct. 14, 2020 by the ministry of economy, trade and industry (METI) of Japanese government as online special event with cabinet members and officials from 23 countries, regions, and organizations. In the open session, presenter from industrial company of water electrolysis introduced to improve its technologies for producing hydrogen from renewable energies [1]. In our previous study, the hydrogen producing from renewable energies is called as “Green Hydrogen” [2].Polymer electrolyte water electrolysis (PEWE) has partly commercialized and recently applied its system for the Power-to-Gas (PtG). However, conventional anode is precious metal oxide such as IrO2 and the cost of raw material is expensive. Moreover, it is reported that the IrO₂ is afraid to cause the degradation operating by variable renewable energy (VRE) because the catalytic activity of oxygen evolution reaction became lower by potential cycling of VRE simulation [3]. From this point of view, the non-precious metal oxide anode with high durability against VRE should be required for green hydrogen production. We focused on tatanium oxide-based electrocatalyst (TaOx) and have studied its catalytic activity for oxygen evolution reaction (OER) [4]. In this study, we have investigated the catalytic activity of TaOx with and Mn addition for the OER in acidic solution.Ti rod was used as substarate. TaOx was prepared by RF magnetron sputtering method. In the case of fabrication for Mn-TaOx, Ta metal piece for 60% surface area was set on the Mn disc as additional material. Each partial pressure of Ar and O2 gas was adjusted to 0.23 Pa in fabrication of Mn-TaOx. The substrate heating temperature was constant at 673 K during sputtering. We used conventional three electrode cell with each sample as working electrode while the reversible hydrogen electrode (RHE) and carbon plate were used as reference and counter electrode to demonstrate the electrochemical measurement. In order to evaluate the OER activity of samples, the slow scan voltammetry was performed from 1.2 to 2.5 V vs. RHE in 1 M H2SO4 solution with saturated nitrogen atmosphere at 303 K. We also carried out electrochemical impedance spectroscopy (EIS) to obtain resistance components and semiconducting properties.Figure 1 shows the polarization curve of OER on Ta oxide-based electrocatalysts with Mn addition. The results of Ti oxide-based electrocatalysts with Mo addition (Mo-TiOx) that is our past study [4] is also shown in this figure. The current density was based on geometric surface area. According to figure, the Mn-TaOx has obviously higher OER current than that on Mo-TiOx, and the Tafel slope of OER on Mn-TaOx was 105 mV dec-1 the while the that on the Mo-TiOx was 91 mV dec-1. The peak over 1.5 V was detected from polarization curve of Mn-TaOx in Fig. 1. This peak corresponded to Mn ion, and it suggests that Mn species affected on the OER activity while the amounts of Mn on the sample after electrochemical measurement showed below detection limit from XPS analysis. According to these results, the surface of Mn-TaOx was consisted of Ta oxide mainly with very few amount of Mn after electrochemical measurements. From the results of EIS, resistances of film and charge transfer on Mn-TaOx were lower than that of Mo-TiOx. In addition, the slope of Mott-Schottky plots on the Mn-TaOx was much gentle than that on the Mo-TiOx, and it means that the carrier concentration in Mn-TaOx was higher than that in Mo-TiOx. Therefore, the reason why the Mn-TaOx showed higher OER current than the Mo-TiOx is that both factors of electrical conductivity and catalytic activity were improved.Acknowledgement: This work is partially supported by Toyota Mobility Foundation and ENEOS Tonen General Research / Development Encouragement & Scholarship Foundation.Reference https://www.meti.go.jp/english/press/2020/1015_001.htmlK. Ota, A. Ishihara, K. Matsuzawa, and S. Mitsushima, Electrochemistry, 78, 970 (2010).S. M. Alia, and G. C. Anderson, J. Electrochem. Soc., 166, F282 (2019).K. Matsuzawa, S. Hirayama, K. Sumi, A. Ishihara, Abst. PRiME2020, I01F-2492, Online (2020). Figure 1

Relationship between Evaluation of Oer Performance and Oxygen Bubble Generation Behavior in Alkaline Water Electrolysis

Introduction Alkaline Water Electrolysis (AWE) is anticipated as a mean of producing hydrogen as an energy carrier for sustainable development goals. One of the problems in alkaline water electrolysis is the rise in anode overvoltage at the high current density range. To further improve the efficiency of hydrogen production, grasping the bubble generation behavior and development of electrode materials based on it are important. In this study, using nickel electrodes with different diameters, the formation behavior of oxygen bubbles on the electrodes was observed with a high-speed video camera, and the relationship between the current density / electrode potential and the bubble formation behavior was investigated. Experimental Working electrode were Ni wire (NiW) (two types with diameters of 100 and 200 μm). A reference and a counter electrode were a reversible hydrogen electrode (RHE) and Ni rods (diameter 3 mm), respectively. All measurements were performed with a three-electrode electrochemical cell [1] at 303±1K with KOH aqueous solution. To reduce the solution resistance as much as possible, the working electrode and the reference electrode were placed as close as possible (about 1 mm). To equalize the current density distribution, Ni rods counter electrode were inserted from both sides of the cell. Observation windows were fitted on the sides of the cell. The working electrode was exposed only the horizontal part about 3 mm where we want to observe the electrolytic reaction, and the other parts were covered by PTFE heat-shrink tube and epoxy resin. After appropriate pretreatments, cyclic voltammetry (CV) measurement was performed at a scan rate of 5 mV s-1 to obtain polarization curves. Electrochemical impedance spectroscopy (EIS) measurement was performed at 1.5-1.8 V vs. RHE with a potential amplitude 10 mV, a frequency range of 1-106 Hz and 20 repeated measurements for each frequency. The solution resistance was obtained from the Nyquist plots, and the potential loss was corrected. The current density i geo / A cm-2 was normalized by the geometric surface area of the cylindrical shaped working electrode. Constant current electrolysis was performed under five conditions of i geo = 0.05-1.0 A cm-2. Under each condition, the formation behavior of oxygen bubbles was photographed with a high-speed video camera. From the obtained photographed images, the diameters of hundreds of oxygen bubbles detached from the electrodes were analyzed to calculate the Sauter mean diameter d 32. Results and discussion Figure 1 shows the polarization curves of the Ni wire electrodes with different diameters. In the range of i geo < 0.3 A cm-2 where the logarithmic value of the current density i geo changed linearly with respect to the potential, there was no significant difference in an OER performance among the two types of electrodes. In the range of i geo > 0.3 A cm-2, the overvoltage increased with i geo regardless of the electrode diameter, and it was confirmed that the smaller the diameter of the electrode was, the smaller the overvoltage at the same current density was, especially in the high current density range.Figure 2 shows the relationship between current density and overvoltage. It was confirmed that the overvoltage increased as the current density increased, and the smaller the surface curvature of the electrode was, the larger the overvoltage was.Figure 3 shows the relationship between the current density and oxygen bubble diameter. The larger the current density was, the larger the oxygen bubble diameter was, and the oxygen bubble diameter was in proportion to the 1/3 power of i geo. From the in-situ observation of the oxygen bubble generation behavior on the electrode with a high-speed video camera [2], the oxygen bubbles generated on the electrode coalesced and detached from the upper end of the Ni wire electrode placed horizontally. From the above, it was considered that the larger the surface curvature of the electrode was, i.e. the smaller the electrode diameter was, the smoother the detachment of oxygen bubbles from the electrode was. It is implied that large curvature of electrode surface contributed to the smaller overvoltage. Acknowledgements A part of this study was based on results obtained from the Development of Fundamental Technology for Advancement of Water Electrolysis Hydrogen Production in Advancement of Hydrogen Technologies and Utilization Project (JPNP14021) commissioned by the New Energy and Industrial Technology Development Organization (NEDO). Reference [1] Y. Kojima, R. Misumi, M. Kaminoyama, S. Mitsushima, 43rd Electrolysis Technology Debate, 14 (2019)[2] H. Ikeda, Y. Kojima, R. Misumi, M. Kaminoyama, S. Mitsushima, 22nd Society of Chemical Engineers Student Presentation, D08 (2020) Figure 1

Determination of Au and Pt Current Collector Activity to Avoid Interference in the Screening of Metal Oxide Catalyst Activity in SOECs

Since solid oxides electrolysis cells (SOECs) represent a promising technology for efficient CO2 conversion to useful chemical products, there is a demand for durable, highly active, and inexpensive electrode materials for use in these systems. Many metal oxide catalysts suitable for CO2 reduction have been studied, including La0.3Me0.7Fe0.7Cr0.3O3-δ (Me = Ca, Sr; LMFCr), developed by our research group. These catalysts have comparable activity and are much more stable than conventional metal-ionic conductor cermets, known for coke formation and sulfur poisoning. However, while observed catalyst stability can be easily compared for different materials, their activity is harder to differentiate. This is because the overwhelming majority of materials tested are porous in nature, thus making their true active area unknown. To avoid this issue, we are working on determining LMFCr activity and the CO2 reduction mechanism using thin, smooth catalyst layers, obtained by pulsed laser deposition on a YSZ-(001) electrolyte, then using noble metals as the current collector.Preliminary studies of current collector-LMFCr thin film-CO2/CO combinations suggest that the current collector/LMFCr interfaces may have an electrochemical activity that would contribute measurably to that of the LMFCr-gas dual phase boundary interface. Assuming that the metal/LMFCr interface activity would be similar to that at the metal/ionic conductor triple phase boundary, the goal of the present work is to determine the catalytic activity of both Pt and Au, which are the most common current collector materials used in fuel environments, towards the CO2 reduction reaction, with the activity of these metal/YSZ interfaces toward oxygen reduction used as a reference.Two different full cell configurations were used in this work. In one direction, porous Au or Pt layers were produced by metal paste deposition onto both sides of the YSZ electrolyte and then sintered at 600°C. A polymeric YSZ precursor was then infiltrated into the porous metal backbone and sintered at 750°C to form the YSZ phase. To ensure that the counter was as non-polarizable as possible, Pt in air was chosen due to its high activity in oxygen-containing environments, while also depositing it over 5X the area and ensuring 2X the thickness of the catalyst layer at the working electrode. In the porous electrode configuration, the working electrode was exposed to the testing gas, while the counter electrode was exposed in air to achieve as high an activity as possible. In the second configuration, 0.3 mm thick Pt or Au wires were attached to a 250 µm thick YSZ electrolyte to form a point-contact working electrode. A porous LSM-YSZ composite with a geometric surface area of 0.5 cm2 was painted on the opposite side of the electrolyte to serve as the counter electrode, exposing it to the same gas as the working electrode. Electrochemical performance testing for both cell types was conducted in air and CO2 environments at 750°C with a flow rate of 50 SCCM. Morphological and compositional investigation as well as microelectrode triple phase length determination was done using SEM and EDS elemental mapping.Analysis of the EIS and CV data for the porous electrodes showed that the Pt/YSZ and Au/YSZ electrodes are both active towards the oxygen and CO2 reduction reactions. Au is less so, showing up to 40 times lower activity towards oxygen reduction and 3 times lower activity than for CO2 reduction. This would imply that Au is the preferred current collector material for future electrochemical evaluation of metal oxide catalysts. However, SEM studies indicated that Pt and Au cells had different metal particle sizes, so the triple phase boundary length may be not comparable. In addition, the double layer capacitance, often used to estimate the triple phase boundary length, could not be used here due to the high surface inhomogeneity and distribution of time constants across these catalyst layers.To eliminate these issues, microelectrode studies are currently being conducted. Preliminary results show that Au/YSZ is at least 8 times less active in air and 60 times less active in the CO2 environment than Pt/YSZ, with the activity of both of these electrodes controlled by precisely controlled triple phase boundary length determination via SEM. The cyclic voltammetry data also indicate that CO2 reduction does not occur at Au/YSZ through the full potential range (0-1.6 V vs. the counter electrode), which also implies a very low catalytic activity of Au/YSZ. Further studies, including comparison with the porous composite electrode data, are underway. In addition, determination of the reaction steps is being carried out from EIS data equivalent circuit fitting as well as verification through the use of distribution relaxation times technique.

Influences of moisture content and compressive loading speed on the mechanical properties of maize grain orientations

Determination of the mechanical properties (rupture force, deformation, hardness, and toughness) of maize grain could be a significant concern for designing the harvester, thresher, and handling, processing, and storage equipment. Thus, the present research was conducted to assess the vertical and lateral rupture force, deformation, hardness, and toughness of maize grain (Beijing Denong, Lianchuang, Suyu 20, Liyu 88 and Suyu 29) influenced by different moisture contents (11.2%, 17.5%, and 21.3%) and compressive loading speeds (5, 10, 15, 20, and 25 mm/min, respectively). Besides, the mean length, width, thickness, geometric mean diameter, equivalent diameter, arithmetic diameter, sphericity, grain volume, surface area, and aspect ratio of the selected varieties were measured. The results showed that the highest length, width, thickness and sphericity, grain volume, surface area, and aspect ratio were obtained at moisture of 21.3%, whereas the lowest was at 11.2%. Moreover, it was observed that as increasing the loading speed from 5 to 25 mm/min, the vertical and lateral rupture forces decreased. However, as increasing moisture contents from 11.2% to 21.3%, the vertical and lateral rupture forces, hardness, and toughness decreased noticeably. Furthermore, the maximum correlation (R2=0.9957) between rupture force and loading speed was found for Liyu 88 at moisture of 17.5% and minimum correlation (R2=0.7002) was found for Suyu 29 at moisture of 11.2%. Moreover, the highest lateral and vertical rupture force was noticed (p<0.05) at a loading speed of 5 mm/min. Based on the experimentally obtained results, it was concluded that the properties of maize grain evaluated were relevant to the design of planter, harvesters, thrashers, and processing machine. Keywords: maize grain, moisture content, compressive loading speeds, mechanical properties, orientation DOI: 10.25165/j.ijabe.20211404.6072 Citation: Chandio F A, Li Y M, Ma Z, Ahmad F, Syed T N, Shaikh S A, et al. Influences of moisture content and compressive loading speed on the mechanical properties of maize grain orientations. Int J Agric & Biol Eng, 2021; 14(4): 41–49.

EDITORIAL

The editorial of Thermal Engineering of this issue continues the discussion on scientific research needs in vital areas in which thermal engineering has important participation. The main goal is to motivate the readers, within their specialties, to identify possible subjects for their future research. Natural Convection is present in the most diverse applications of Thermal Engineering, such as controlling and reducing temperatures in electronic systems, reducing the thermal efficiency of cooling in machining processes by the Leidenfrost effect and even in biological systems. With the increasing technological evolution and the development of industrial automation, microelectronics, quantum computing, signal processing, mobile telephony, etc., transmission systems operate increasingly with smaller spacing and higher integration rates between components, with greater power density and heat generation. As a result, there is a growing demand for cooling systems with greater safety, reliability, and efficiency. Therefore, natural convection cooling systems are viable alternatives due to their characteristics of: (A) protection and safety of the transmission system, especially in cases of mechanical and/or electrical failures of the forced cooling system; (B) high reliability and safety of operation; (C) low maintenance costs and (D) no noise. However, due to their low thermal efficiency, such cooling systems are still limited to applications with the low power density and/or combined with forced convection cooling systems. In this sense, the natural convection area is increasingly being researched to create and enable even smaller and more robust high power density transmission systems, with greater economic feasibility (lower costs of acquisition, manufacturing, and maintenance) and exclusively refrigerated (or with minimal use of forced cooling components) by natural convection; all without reducing the efficiency or reliability of these systems. One of the main technologies for thermal optimization of cooling systems researched is the inclusion of geometric surface modifications, through fins (extended surfaces) or corrugated surfaces. The use of corrugated surfaces has been gaining more space in the academic community and industry, standing out for: (A) increasing the area of exposure to the heated surface and the transfer of energy to the circulating fluid; (B) induce changes in the flow in the vicinity of the heated surface, such as the formation of vortices, recirculations, and zones of rarefaction and stagnation; and (C) anticipate and facilitate the flow transition process for the turbulent regime. The study of natural convection – in its most diverse applications and areas of theoretical, applied, and experimental investigation – has been widely explored by Thermal Engineering, arousing more and more the academic community's interest and motivating further research in this area. The mission of Thermal Engineering is to document the scientific progress in areas related to thermal engineering (e.g., energy, oil and renewable fuels). We are confident that we will continue to receive articles’ submissions that contribute to the progress of science. Sílvio Aparecido Verdério JúniorProfessor of Mechanical Engineering

Exact solution for nonlinear static behaviors of functionally graded beams with porosities resting on elastic foundation using neutral surface concept

In this paper, an exact solution for nonlinear static behaviors of functionally graded (FG) beams with porosities resting on the elastic foundation is presented. The FG material properties with porosities are assumed to vary along the thickness of the beam, and two types of porosity distributions are considered. Actually, the geometrical middle surface of the FG beam selected in computations is very popular in the literature. By contrast, in this study, the physical neutral surface of the beam is utilized. Based on the Timoshenko beam theory, von Kármán nonlinear assumption, together with neutral surface concept, the nonlinear governing equations of the FG beam resting on the elastic foundation are derived. By using the physical neutral surface, the nonlinear governing equations have simple forms and can be solved directly. The exact solution for the problem with all immovable and moveable boundary conditions is conducted in detail. Some numerical investigations to show the effects of boundary conditions, material properties, length-to-thickness ratio, elastic foundation coefficients and several types of applied load on nonlinear static bending behaviors of the beam are given.

The temporal evolution of the carbon isotope composition of calcite in the presence of cyanobacteria

Quantifying the link between cyanobacterial activity and the carbon isotope signature of precipitated carbonate minerals is crucial for reconstructing the environmental conditions present at the time of carbonate mineral formation. In this study, calcite was precipitated in the presence and absence of Synechococcus sp. cyanobacteria in batch reactors. The temporal evolution of the carbon isotope composition of calcite (δ13CCalcite) and dissolved inorganic carbon (δ13CDIC) was monitored to evaluate the rate and degree to which the carbon isotope compositions in calcite are modified during and after its precipitation. The presence of cyanobacteria promoted calcium carbonate formation by increasing fluid pH and the CaCO3 saturation state. It also changed significantly the carbon isotope composition of dissolved inorganic carbon due to the preferential incorporation of 12C into the biomass. This generated an isotope disequilibrium between the calcite and the aqueous fluid phase over time after the calcite precipitated. The carbon isotope composition of the calcite evolved continuously towards mineral-fluid isotope equilibrium after its precipitation, at geometric surface area normalized rates ranging from 1.75 × 10−14 to 1.71 × 10−13 mol 13C/m2/s. These rates are sufficiently fast such that the δ13CDIC value of aqueous fluids in calcite-rich rocks would be buffered by the δ13CCalcite value of the co-existing calcite. Mass balance calculations suggest that the carbon isotope composition of calcite could change noticeably when the calcite is in isotope disequilibrium with its co-existing fluid, for example through the presence of a local 12C sink such as photosynthetic microorganisms or 12C source such as decomposition of organic material.

Assessment of the Functional Properties of 316L Steel Alloy Subjected to Ion Implantation Used in Biotribological Systems.

Clinical trials conducted in many centres worldwide indicate that, despite advances made in the use of biomaterials for medical applications, tribocorrosive wear remains a significant issue. The release of wear residue into body fluids can cause inflammation and, as a result, implant failure. Surface modification is one of the methods used to improve the mechanical, tribological, and fatigue properties of biomaterials. In this article, the authors investigated the impact of ion implantation on improving the functional properties of implant surfaces. This paper presents morphology, geometric surface structure, hardness, and tribological test results for layers obtained by ion implantation with nitrogen and oxygen ions on alloy 316L. The surface morphology and thickness of the implanted layer were examined using scanning microscopy. Atomic force microscopy was used to evaluate the geometric structure of the surface. Instrumented indentation was used to measure nanohardness. Model tribo tests were carried out for reciprocating motion under conditions of dry friction and lubricated friction with Ringer’s solution. The tribological tests showed that the implanted samples had a lower wear than the reference samples. Nitrogen ion implantation increased the hardness of 316L steel by about 45% and increased it by about 15% when oxygen ions were used.

BIM-based Facility Management Models for Existing Buildings

Building Information Modeling (BIM) is mainly used for the design and construction of new buildings. However, one of the main challenges facing BIM adoption for existing or old buildings constructed without consideration for their modeling is obtaining raw and accurate building data and converting it to the BIM model. Based on this challenge, this study develops a framework that uses different data capture techniques for existing buildings, then transforms this captured data into 3D BIM models through which it can improve its management processes as facilities during their service life. Specifically, 3D laser scanning techniques were used to capture indoor building data, while drones equipped with high-definition cameras (UAV) were used to capture outdoor building data such as geometric dimensions, material shapes, surfaces and various shapes. Then the captured data was converted into a high-resolution 3D model. This has been verified the accuracy of this engineering model by converting the two-dimensional engineering plans to three-dimensional through the well-known engineering design tools. Moreover, the 3D model has been integrated with the Web Based Building Management System (BMS) platform. This research framework helps in developing engineering facility management processes and modern digital transformation processes that aim at speeding up facility management during their service period using modern technologies. This study aims to develop current knowledge in the construction industry and facility management by reviewing a comprehensive understanding of how to use modern technologies to obtain various information to develop BIM models for existing and non-modeled buildings in order to exploit and integrate them with advanced facility management systems and platforms, which constitutes a major progress in this field allowing to save a lot of effort and money in the future.

Synthesis, Characterization and Theoretical Studies of New Organotellurium Compounds Based on (4-(((1S,E)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-ylidene)amino)phenyl)mercury(II) Chloride

The current study aimed to prepare new organomercury and organotellurium compounds based on the condensation reaction of 1,7,7-trimethylbicyclo[2.2.1]heptan-2-one (camphor) and p-aminophenyl mercuric(II) chloride. All the prepared compounds were characterized using different methods such as infrared spectrum, nuclear magnetic resonance, and CHN analysis. The analysis results concurred with the suggested chemical structures of the prepared compounds. Density functional theory has been applied with the basis set 3-21G to investigate the molecular structure of the prepared organotellurium compounds. Geometrical structure, HOMO surfaces, LUMO surfaces, and energy gap have been produced throughout the geometry optimization. The molecular geometry and contours for organotellurium compounds have been investigated throughout the geometrical optimization. Also, the donor and acceptor have been studied by comparing the HOMO energies of the prepared organotellurium compounds. Finally, the electronegativity, electrophilicity, ionization potential, electron affinity, and lower case of organotellurium compounds have been calculated and discussed.

Classification of space-like translation surfaces in the 3-dimensional Lorentz Heisenberg group H3

PurposeIn the Lorentz Heisenberg space H3 endowed with flat metric g3, a translation surface is parametrized by r(x, y) = γ1(x)*γ2(y), where γ1 and γ2 are two planar curves lying in planes, which are not orthogonal. In this article, we classify translation surfaces in H3, which satisfy some algebraic equations in terms of the coordinate functions and the Laplacian operator with respect to the first fundamental form of the surface.Design/methodology/approachIn this paper, we classify some type of space-like translation surfaces of H3 endowed with flat metric g3 under the conditionΔri = λiri. We will develop the system which describes surfaces of type finite in H3. For solve the system thus obtained, we will use the calculation variational. Finally, we will try to give performances geometric surfaces that meet the condition imposed.FindingsClassification of six types of translation surfaces of finite type in the three-dimensional Lorentz Heisenberg group H3.Originality/valueThe subject of this paper lies at the border of geometry differential and spectral analysis on manifolds. Historically, the first research on the study of sub-finite type varieties began around the 1970 by B.Y.Chen. The idea was to find a better estimate of the mean total curvature of a compact subvariety of a Euclidean space. In fact, the notion of finite type subvariety is a natural extension of the notion of a minimal subvariety or surface, a notion directly linked to the calculation of variations. The goal of this work is the classification of surfaces in H3, in other words the surfaces which satisfy the condition/Delta (ri) = /Lambda (ri), such that the Laplacian is associated with the first, fundamental form.