The extracted heat from geothermal reservoirs can thermally alter in-situ stress conditions and may lead to triggering slip on pre-existing faults within the affected volume of rock. Noticeable seismic events may arise if the slip is unstable characterized by significant radiation of energy. Reported seismicity in geothermal reservoirs indicates that there is a direct relationship between the initial temperature of a reservoir and the magnitude of a triggered seismic event. We discuss the role of thermal stresses in triggering seismicity by modeling a two-dimensional, strike-slip, slip-weakening fault. A cooling source simulates the injection process into the reservoir so that the temperature of surrounding elastic rock decreases until the slip is initiated due to the evolution of thermal stresses. The rupture intensity is estimated by the energy radiated from the seismic event. Faults under four different initial temperatures are modeled. Results show that all ruptures radiate the same magnitude events regardless the level of the initial temperature. Next, we use available published data on the effects of temperature on the rock and fault mechanical properties. Results show that the reported scaling of event magnitudes with the model initial temperatures cannot be reproduced unless we introduce in-situ alterations of the temperature-dependent reservoir properties to the models. Our analyses suggest that, in this simple modeling, the amount of heat extracted from models can indicate whether a fault is activated while the thermally affected volume of rock can denote the intensity of the triggered rupture.

Previous studies investigated on friction reduction at the solid–liquid interface due to the presence of metal nanoparticles and fine bubbles such as microbubbles. This paper experimentally investigated how nanobubbles (ultrafine bubbles) change the tribological nature of water flow at the solid–liquid interface. We flowed air nanobubbles-containing water into a cylindrical cell filled with soda-lime glass, alumina, and high-carbon chromium-bearing steel beads. We then estimated the changes in the ratio of Darcy's friction factor of nanobubbles-containing water flow (fnb) to that of water flow before injecting nanobubbles (fref) with the time of injecting nanobubbles. We found that nanobubbles are capable of reducing the friction in water flow running through the soda glass beads, accounting for up to 6.1% reduction in terms of Darcy's friction factor ratio (fnb/fref) in our experiment. The magnitude of friction reduction by nanobubbles can be greater with a larger total surface area where surface nanobubbles are present. In contrast, nanobubbles encouraged enhancement of the friction of water flow within the high-carbon chromium-bearing steel beads, showing 3.8% enhancement in the friction factor ratio (fnb/fref). The results indicate that nanobubbles play a role in the friction reduction of water flow when the surface of the bead material is rougher than the size of nanobubbles, while nanobubbles enhance the friction of water flow when the bead surface is smooth enough. Therefore, nanobubbles can be a green nanoscopic additive for modifying the friction and lubrication performance of water flow depending on the surface roughness of the flow material.

One of the biggest challenges in developing renewable energy, such as geothermal energy, is understanding how to be accepted by the community impacted by the development. However, very few studies attempted to numerically express the time-dependent process of social acceptance in renewable energy projects. We quantify how social acceptance for a geothermal energy project is acquired from the involved communities. First, we present a compartment model for simulating how the numbers of supporters and opponents of developing geothermal energy change over several decades. We then introduce a time-varying index, an effective susceptibility number (Re), similar to the effective reproduction number used in modeling epidemiologic phenomena. Second, we share our findings about the history of the number of supporters and opponents of the geothermal power plant construction project in Japan based on the articles published in local and national newspapers between 1970 and 2020. Our simulation results show that the proposed compartment model could predict documented changes in the numbers of supporters and opponents. Also, the effective susceptibility number (Re) could represent the frequency of interactions among the community members. We suggest that an effort should be made to avoid having Re<1 in the community, to maintain a steady increase in the number of supporters to eventually acquire the social acceptance of a geothermal energy project. Our simple but novel approach using the compartment model will help better understand the dynamics and predict the community acceptance process in geothermal and other renewable energy projects.

Particle segregation is a common phenomenon observed in rotating drums. This study found that the mixing of dissimilar particles in a rotating drum depended on the orientation of the rotation axis. When the rotation axis of the drum was selected to be perpendicular to the drum's own axis, two species of particles of different sizes mixed together. Numerical simulation study revealed that four counter convection flows formed in the drum. The movements of the small and large particles were similar in the cores of the convection zones but different in the vicinity of the free surface. The convection flows carried particles from the inner cores to the free surface. The difference in velocities between small and large particles in the vicinity of the free surface caused the particles to mix together. The finding of this study provides an alternative approach for the design of devices for mixing dissimilar particles.

Nanobubbles are ubiquitous but invisible. Neither a single nanobubble nor billions of nanobubbles are easy to study. However, reports on positive benefits of nanobubbles in everyday life are numerous and seem to increase by the day. There seems to be a significant gap between everyday usage and firm scientific understanding of nanobubble behavior. The authors were interested in conducting simple fluid dynamic experiments that are often used in textbooks to challenge how the inclusion of nanobubbles may alter commonly accepted findings. This approach led us to discover that nanobubbles can be an entirely new, inexpensive, and environmentally friendly modifier of flow behavior. This paper is a start of our efforts and reports our preliminary results on nanobubbles as a friction modifier.

Demands for "green" additives that control the crystal growth and inhibit the scale formation in industrial processes are growing as never before. Nanobubbles can be the green additive for inhibiting and/or promoting the crystal growth of calcium carbonate, given their well-known unique physicochemical properties. This paper reports for the first time the changes in the crystal growth rate of calcite in liquid in the presence of air nanobubbles. We injected the air nanobubbles into the solution and studied the calcite crystal growth for the first 4 h in a static condition at 20 degrees C and 88 degrees C. We found that air nanobubbles retarded the growth rate of calcite crystal by up to 53 % and 33 % at 20 degrees C and 88 degrees C, respectively. The retardation of calcite crystal growth could differ with different number densities of air nanobubbles added to the solution. A higher number density of nanobubbles generally showed slightly greater retardation throughout the tested 4 h. Air nanobubbles may influence the crystal growth either by changing solid-liquid interfacial tension on the crystal surface, reducing the free growth sites, adsorbing Ca2+ ions, playing roles in bubble mattress and thermal buffering on the crystal surface, or combinations of them. Our findings suggest that air nanobubbles can be utilized as a green inhibitor of calcite crystal growth and calcium carbonate scale in broad industrial areas.

Geothermal resources with lower temperatures highlight many successful industrial applications; however, many share a common problem of scaling and/or corrosion. The cost to mitigate the problems with scaling and corrosion should not be underestimated so that the operators can better plan for the maintenance. It is also increasingly becoming difficult to justify using chemical agents to prevent these problems because of the elevated level of environmental concerns. The authors have started to investigate environmentally friendly and cost-effective ways to solve these problems. In this paper, we will share our preliminary experimental results on nanobubble usage as a corrosion and scale inhibitor.

Metallic corrosion is a major issue that leads to an efficiency loss and eventual failure of the system in geothermal power plants. Despite the growing understanding of mechanisms of corrosion, inhibiting steel corrosion in the acidic geothermal fluids, remains to present formidable challenges due to its intrinsic physicochemical complexity. Here, we study the use of nanobubbles as a possible corrosion inhibitor by testing alteration of the low-carbon steel plates immersed in acidic geothermal water with continuously injected air-nanobubbles. Nanobubbles have been used in a broad range of areas as they are eco-friendly, low-cost, easy-to-use and high-functional materials. We, for the first time to our knowledge, found that air-nanobubbles could inhibit steel corrosion, with inhibition efficiency of up to 50 % in the studied acidic geothermal fluid. Air-nanobubbles could act as a nanoscopic coating material in the acidic geothermal fluid, through generating a bubble mattress and/or promoting nucleation and aggregation of a very small quantity of silica precipitation on the surface of steel plates. Our finding suggests that nanobubbles can inhibit steel corrosion in various chemically different geothermal fluids, highlighting the physicochemical significance of nanobubbles as the coating material for inhibiting metal degradation in the geothermal infrastructures.

Corrosion and scaling have presented serious technical challenges to make geothermal power reliable and affordable. Due to the large quantities of geothermal water that must be processed to obtain heat, many conventional chemical inhibitors are not economically viable. Moreover, most chemical inhibitors are costly and can readily change the fluid chemistry that results in generating undesired products. Nanobubbles are environment-friendly, inexpensive, and easy-to-use, and thus have been used in a broad area of applications by taking advantage of their unique physicochemical properties. Here we propose that nanobubbles can be used as inhibitors of corrosion and scaling in the geothermal system. First, this paper reviews the mitigation methods for corrosion and scale currently used in a geothermal power system, and second, provides an overview on the novel use of nanobubbles as inhibitors of corrosion and scale from theoretical and experimental perspectives. We suggest that nanobubbles can be powerful, chemically benign, environment-friendly, and inexpensive inhibitors of corrosion and scaling, compared with the chemical products commonly used. The mechanisms on how nanobubbles act as inhibitors and their inhibition effectiveness vary with different chemical conditions of geothermal fluid.

This paper aims at mechanistically studying some aspects of earthquake energy partitioning with a focus on the radiated energy (E-s) and seismic moment (M-o) relationships for investigating differences between estimates of average dynamic stress drop and static stress drop. We evaluate to what extent a relatively simple but analytically verified faulting simulation can explain such differences. We adopt a numerical methodology developed in the 2-D Universal Distinct Element Code to simulate fault slip with slip-weakening responses. A method is introduced for recording the ground reaction to slip and from which we discuss the energy partitioning in ideal cases of rupture. We examine a shallow strike-slip fault model where a locally peaked stress is gradually developed on the fault by applying tectonic stresses away from the fault surface until a rupture is initiated locally and propagated outward. The rupture is terminated when the available energy is exhausted by the fracture energy and friction work especially as the rupture is followed by a creep. With investigating roles of the available energy for rupture and the fracture energy, we display limited cases where Mo does not, at least proportionately, scale with Es. Results show this is because Mo, compared to Es, does not fully represent the energy available for initiating a rupture and the fracture energy consumed during its propagation. That is why estimates, with the radiation ratio eta(R) and rigidity mu, may significantly differ from (Delta sigma) over bar (d) and (Delta sigma) over bar (s). Plain Language Summary Numerical techniques are a practical way of understanding earthquake energy budget components that cannot be directly measured. The potential energy stored in rocks partially transforms into kinetic energy that generates earthquakes. This simple concept is translated into a modeling methodology that calculates energy terms contributing to the occurrence and intensity of an earthquake. In order to verify the modeling approach, the results are compared to existing analytical solutions and globally recorded seismic data. Given the consistency between numerical results, analytical solutions, and field measurements, we study a controversy in this field regarding the scaling of the radiated energy with the seismic moment, two commonly used measures of earthquake size. We also evaluate to what extent a simple model can explain the dependence of the stress changes on the earthquake size. This can help us understand what parameters really determine the occurrence and size of earthquakes.

The title crystalline compound, [Cu 2 (NCS) 2 (C 9 H 16 N 2 ) 2 ], was obtained from the reaction of copper(I) thiocyanate (CuSCN) with ( N -prop-2-en-1-yl)piperidine-1-carbothioamide as a chelating and bridging thiourea ligand in chlorobenzene. The Cu 2 S 2 core of the dimeric molecule is situated on a crystallographic inversion centre. The copper atom is coordinated by a thiocyanate nitrogen atom, each sulfur atom of the two thiourea ligands, and the C=C double bond of the ligand in a distorted tetrahedral geometry. The dimers are linked by N—H...S hydrogen bonds, forming a network extending in two dimensions parallel to (100).

Having tools and techniques of project management are a necessary but not a sufficient condition for project success. If a manager cannot handle people, she or he will have difficulty with managing projects. Many successful projects have teams of people that are involved and committed; however, friction between the team members still occurs due to misunderstandings, conflicts, and personality differences. Project managers must be prepared to deal with these behavioral problems of team members. One way to minimize the impact of behavioral problems is to provide training for all team members (including managers themselves) in interpersonal skills. This area has often been neglected in many organizations; other times, just managers are required to be trained but not team members. This paper presents a unique opportunity for both managers and team members to gain insight into understanding the complex nature of collective behavior. The only way to understand how individual behavioral problems translate into those of a team is to model problems using a bottom-up simulation method like the one presented here. This introductory paper presents basic concepts and a simple application of Agent-based modeling.

There has been a divide between scientists making recommendations for sustainable natural resource development and the community living around those resources. Masami Nakagawa argues that the community should be considered first, as the successful development of sustainable natural resources requires their cooperation and trust.

One of the challenges to overcome in Moon mining operations, such as soil handling, drilling, excavation, and wheeled movement, is understanding the mechanical behaviors of lunar soil, which is composed of grains characterized by highly irregular shapes. The impracticality of performing mechanical experiments on lunar soil samples has made computational techniques useful for exploring the mechanical behaviors of lunar soil. This paper uses particle flow code and describes a procedure for simulating lunar soil grains with specific size, shape, and strength distributions. We adopt data from soil samples 64501 and 60501 retrieved in Apollo 16. Lunar soil samples are simulated as assemblies of different shapes of grains consisting of rigid spheres connected through parallel bonds. We classify grains into four categories based on their shape: agglutinate, breccia A, breccia B, and plagioclase. We simulate each grain based on available imaging studies on their shape characteristics. We reveal the significance of grain shape irregularity through angle-of-repose tests on samples with and without irregularly shaped agglutinates. Results show that the shape irregularity increases the angle of repose by 6 degrees. We repeat the test under different gravitational acceleration ranging from 0.1 to 25 m/s(2) and show that for values below about 10 m/s(2), the angle of repose is inversely related to the gravity but above10 m/s(2), remains independent of the gravity.We perform triaxial compression tests to investigate behaviors of simulated samples under confined loadings. The confinement varies from zero to 15kPa, corresponding to the lateral in situ stress at depths up to 250cm. The cohesion and friction angle derived from the triaxial tests are shown to agree with the lab and in situ measurements. This numerical practice and presented methodology pave the way for full-scale simulation of mining operations on the Moon surface. Plain Language Summary Utilizing space resources such as water, atmospheric constituents, volatiles, and minerals is critical for making the Moon habitable. To explore and mine these resources, we need to advance technologies whose main requirement is to understand mechanical behaviors of lunar soil. There are limited lunar soil samples retrieved in the Apollo missions, but due to their scarcity, performing destructible mechanical tests on them is impractical. Numerical modeling techniques are useful for simulating the lunar soil with a behavior similar to real samples. However, devising modeling approaches capable of simulating irregularly shaped grains of lunar soil has been a challenge in this field. We present a modeling approach here that can simulate lunar soil grains with irregular shapes. Following this approach and using available data on the soil samples 64501 and 60501 from Apollo 16, we also simulate the lunar soil sample and analyze some aspects of its mechanical behaviors under different gravity. These analyses provide helpful information for designing mining operations on the Moon surface, while the analyses on the effects of gravity make the approach applicable to Mars and other celestial bodies.

Indium tin oxide (ITO) as an electrode is generally sputtered to fabricate semitransparent perovskite solar cells (PSCs). In this work, ITO as the electrode of the PSC was deposited at a high rate (5 nm sec−1) by activated reactive evaporation (ARE) using a pressure-gradient-type plasma gun instead of sputtering. The power-conversion efficiency of the PSC with ITO (14.2%) deposited by ARE was comparable to that of a PSC with Ag (14.4%) deposited by thermal evaporation. This result shows that ARE is an effective method for depositing ITO to fabricate the semitransparent PSC.

The social license to operate is an emergent convergence of opinion, the production and durability of which is highly interdependent with the structure of the stakeholder network. This structure evolves over time as new links are formed and old links decay. In this paper, we propose a social license model in which agent interactions lead to the evolution of network structures, which are then classified according to observed stakeholder networks.