Siting Process Research Articles

Electrochemical Cell Design and Operation for Copper Recovery from Chemical Mechanical Polishing Slurries

Copper (Cu) removal from chemical mechanical polishing (CMP) waste is critical to maintaining discharge compliance with local municipalities and the Environmental Protection Agency (EPA). Typical treatment of this waste stream has followed two conventions: either coagulant-based precipitation or ion exchange (IX).1 Many industries use iron-based coagulants for metal removal from wastewater to meet discharge compliance. However, the process is often cumbersome, requires long settling times and significant chemical utilization, and results in a sludge stream that must be shipped and disposed of properly, eliminating the possibility for metal recovery. Since the concentrations for Cu removal from CMP waste streams is normally low (<100 ppm), IX has generally been the preferred treatment method. Nevertheless, IX also has some negatives associated with the process. Hydrogen peroxide can and will damage the IX media, resulting in premature replacement. The industry has dealt with this impact by employing one-time use media, but this adjustment means that media is only used once before being shipped offsite for regeneration. This results in operational impacts due to the need for oversight of media replacement and also eliminates the ability for Cu to be recovered at the originating process site.In this talk, electrochemical methods to recover Cu from CMP wastewaters will be described. Electrochemical cell design and operation will be shown to provide Cu removal across wide ranges of concentration, and the depth of Cu separation (<2 ppm) and efficiency of the process will be discussed. The presence of hydrogen peroxide and its influence on the process will be evaluated. The removal and recovery of Cu will be shown in a complete cycle, demonstrating the ability to recover and reuse Cu directly at a process site. The impact of (1) pH, (2) chelator type, and (3) abrasive (SiO2) will also all be reviewed. Changes to the slurry, as analyzed pre- and post-electrochemical separation, will be characterized to determine possibilities for the reuse of the CMP slurry itself. Ultimately, the ability to design process systems using electrical input and minimal chemical additives to treat wastewater to municipal and EPA specifications while maximizing recycling efforts will be evaluated and presented.

Barriers and proposed solutions to at-home colorectal cancer screening tests in medically underserved health centers across three US regions to inform a randomized trial.

At-home colorectal cancer (CRC) screening is an effective way to reduce CRC mortality, but screening rates in medically underserved groups are low. To plan the implementation of a pragmatic randomized trial comparing two population-based outreach approaches, we conducted qualitative research on current processes and barriers to at-home CRC screening in 10 community health centers (CHCs) that serve medically underserved groups, four each in Massachusetts and California, and two tribal facilities in South Dakota. We conducted 53 semi-structured interviews with clinical and administrative staff at the participating CHCs. Participants were asked about CRC screening processes, categorized into eight domains: patient identification, outreach, risk assessment, fecal immunochemical test (FIT) workflows, FIT-DNA (i.e., Cologuard) workflows, referral for a follow-up colonoscopy, patient navigation, and educational materials. Transcripts were analyzed using a Rapid Qualitative Analysis approach. A matrix was used to organize and summarize the data into four sub-themes: current process, barriers, facilitators, and solutions to adapt materials for the intervention. Each site's process for stool-based CRC screening varied slightly. Interviewees identified the importance of offering educational materials in English and Spanish, using text messages to remind patients to return kits, adapting materials to address health literacy needs so patients can access instructions in writing, pictures, or video, creating mailed workflows integrated with a tracking system, and offering patient navigation to colonoscopy for patients with an abnormal result. Proposed solutions across the three regions will inform a multilevel intervention in a pragmatic trial to increase CRC screening uptake in CHCs.

Simultaneous Optimization and Integration of Multiple Process Heat Cascade and Site Utility Selection for the Design of a New Generation of Sugarcane Biorefinery.

Biorefinery plays a crucial role in the decarbonization of the current economic model, but its high investments and costs make its products less competitive. Identifying the best technological route to maximize operational synergies is crucial for its viability. This study presents a new superstructure model based on mixed integer linear programming to identify an ideal biorefinery configuration. The proposed formulation considers the selection and process scale adjustment, utility selection, and heat integration by heat cascade integration from different processes. The formulation is tested by a study where the impact of new technologies on energy efficiency and the total annualized cost of a sugarcane biorefinery is evaluated. As a result, the energy efficiency of biorefinery increased from 50.25% to 74.5% with methanol production through bagasse gasification, mainly due to its high heat availability that can be transferred to the distillery, which made it possible to shift the bagasse flow from the cogeneration to gasification process. Additionally, the production of DME yields outcomes comparable to methanol production. However, CO2 hydrogenation negatively impacts profitability and energy efficiency due to the significant consumption and electricity cost. Nonetheless, it is advantageous for surface power density as it increases biofuel production without expanding the biomass area.

Rights against the Adverse Effects of Climate Change! Who &amp; How to Ensure? -Not Only National Governments!

In 2022, the United Nations General Assembly declared that access to a clean, healthy and sustainable environment is a universal human right. The Supreme Court of India has recently in a judgment, a significant step towards acknowledging the impact of climate change on human life, has said that the "right against the adverse effects of climate change" falls under the scope of Articles 14 and 21, which guarantee rights to equality and life and country must take action to mitigate it. Focusing on the mean surface air temperature offers a reliable way to compare the relentless heat affecting both deserts and rainforests. In order of highest mean temperature Mali, Burkina Faso, Senegal, Mauritania, Tuvalu, Djibouti the Gambia, Maldives, Benin, and Palau. Eight states of Rajasthan, Uttar Pradesh, Gujarat, Madhya Pradesh, Telangana, Delhi, Andhra Pradesh in India are sizzling hot right now. Heat stress is a common problem encountered in farming in hot weather, emergency response activities or recovery operations, when workers are required to work in hot environments, and sometimes for extended periods. Any process or job site that is likely to raise the workers deep core temperature {&gt; 100.4 degrees F/ (38°C)} raises the risk of heat stress. Materials &amp; Methods: This article is based on recent reports of heat stroke across &amp; India managing one case each of heat stress, Prickly heat, Heat exhaustion in first week of May 2024 and literature search of management practices across the world. Results: All the cases managed had recovered fully. Among the media reports of heat stroke fatalities, there is a need to authenticate all such deaths by medical teams. Synthesis of the Conclusion: The world must be concerned, not just climate change but other environmental crises such as air and water pollution, noise and light pollution in cities, micro plastics, freshwater availability, biodiversity loss, ocean acidification etc. We need an integrated approach for addressing all the global environmental issues. Ultimately, we should strive for a safe and resilient Earth for that, States must reduce a) carbon emissions levels, b) concrete jungles and increase c) number of trees, and d) number of lakes!.

Enhanced degradation of Congo-red dye by Cr3+ doped α-Fe2O3 nano-particles under sunlight and industrial wastewater treatment

Considering the increasing amount of water pollution, nanocomposite advances for the effective elimination of hazardous pollutants are still needed. α-Fe2O3, Cr0·5Fe1·5O3 and CrFeO3 nanoparticles were synthesized via an eco-friendly material synthesis i. e hydrothermal route without using any precipitating agent and were studied to remove congo-red dye using photocatalytic properties. X-ray diffraction (XRD), Transmission electron microscopy (TEM), Field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FESEM), Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS) characterizations have been performed to know about the material structure and properties of synthesized samples. High efficiency (95.2%) of degradation was achieved under sunlight using a very low amount of CrFeO3 catalyst (0.2 g/L) at a 6-pH level of dye and was confirmed using UV spectroscopy, TOC (84%), LC-HRMS. Also, the potential to degrade the CR dye was concluded from the high rate of BOD5/COD. The results showed a significant enhancement in the degradation of α-Fe2O3 from 52.3% to 95.2% in a short duration of 15 min by introducing chromium as a dopant. The doping of chromium influenced the major factors responsible for the photocatalytic activity such as the increase in range of absorbance, increased e−-h+ pair separation, improvement in the charge transfer process and active site formation which significantly enhanced the process of degradation. We found that the Cr-doped α-Fe2O3 nanomaterial could effectively remove dyes, such as congo-red, from industrial water-waste.

International Atomic Energy Agency (IAEA) support for the management of site investigations for radioactive waste disposal facilities

Abstract. Providing safe, secure and environmentally acceptable radioactive waste disposal is a national responsibility that requires a long-term commitment, adequate resources and the involvement of multiple stakeholders. The choice of a particular disposal concept and its detailed design will depend on several factors, such as the properties of the waste inventory to be disposed of, national circumstances and strategic preferences. A concept is likely to evolve iteratively as one or more sites are investigated and the repository design is refined to reflect local conditions. In this context, the International Atomic Energy Agency (IAEA) recently published technical guidance on the management of site investigations for radioactive waste repositories. A key objective of the publication Management of Site Investigations for Radioactive Waste Disposal Facilities (IAEA, 2023) is to ensure that site investigation efforts in Member states have firm foundations based on a clear understanding of data and information requirements. The publication was developed to reflect the experiences and knowledge from a range of disposal programmes, and it is intended to support initiation of well-planned and focused site investigations in Member states with a need to develop and site radioactive waste disposal facilities. A siting process is intended to result in the identification of a suitable location for any nuclear installation, including a deep geological repository, and ultimately to receive authorisation to construct and operate the facility. To achieve this objective, it will be necessary to ensure that the combination of site properties and engineered barrier properties provides requisite levels of safety for the inventory under consideration (IAEA, 2015). The siting process and associated site investigations for a radioactive waste disposal facility follow a stepwise process, irrespective of whether the early stages of siting start with investigating and screening the national territory or whether the iterative investigation process starts with a more focused approach, e.g. volunteer sites, sites with already well-known characteristics, sites with existing nuclear facilities or similar ones (IAEA, 2023). Site investigations should follow a graded approach in an iterative manner, reflecting a phased approach to decision-making and the development of disposal facilities (IAEA, 2011). At each stage in the siting process the disposal system is to be evaluated based on the data and information available at that time. Following an assessment, a gap analysis comparing requirements to knowledge about the site would identify process model and data uncertainties affecting confidence in the implementation of the disposal concept at the site. Furthermore, the IAEA also recently launched a project to develop guidance reflecting good practices in Member states' programmes for establishing site selection criteria and applying a decision-making framework as part of a siting process.

A physics‐based spectral matching (PBSM) method for generating fully site‐related ground motions

AbstractThe response spectrum is generally adopted in the seismic design to represent the seismic fortification level, but the structural dynamic analysis requires the ground motions as an input. However, ground motions generated by the traditional spectral matching methods do not have site‐related physical backgrounds for the target site. In this study, a physics‐based spectral matching (PBSM) method is developed to generate fully site‐related broadband ground motions (i.e., the generated ground motions have real physical backgrounds for the target site, including the source process, propagation path, and local site conditions) that are compatible to the target spectrum. In this method, the three‐dimensional (3D) numerical model around the target site is constructed to calculate the strain Green's tensors of all potential source locations using adjoint simulations. The variable space dimension of the seismic source is significantly reduced by applying the self‐similar feature of the multidimension source model, so that the optimization algorithm can be used to search for the rupture process that generates the physics‐based and spectrum‐matched ground motions (abbreviated to PBSM ground motions). The proposed method is applied to the Xiluodu dam in China. Compared with the traditional techniques, the generated ground motions have fully site‐related physical backgrounds and are compatible to the target spectrum. Additionally, as this method generates broadband ground motions based on the deterministic rupture process, any features of ground motions, such as large velocity pulses, can be taken into account throughout the optimization process. This study introduces the deterministic physical backgrounds of earthquakes to performance‐based seismic design and analysis. The proposed method may have a significant application potential in earthquake engineering.

A Laborer’s Mask-Wearing Behavior Detection Approach in the Manufacturing Field

Industry 4.0 has considerably advanced multiple manufacturing fields through digitalization and intelligentization. Many technologies, such as supervisory control, data acquisition, and data analytics, have been used widely in manufacturing sites to enhance production efficiency. Therefore, this created a cloud-based anomaly detection module for epidemic prevention at the manufacturing site. Image process technologies, deep learning algorithms, and cloud computing were employed in the proposed module to automatically identify labor anomaly behavior in the manufacturing site and prevent the epidemic. This study used image processing technologies and deep learning to recognize and train the manufacturing site image. Accordingly, the analyzed result could be incorporated into the cloud system using the Message Queuing Telemetry Transport (MQTT) protocol. Therefore, the administrators and laborers can be notified regarding the anomaly behavior. The author used the image data obtained from the cylinder head process site as a data source for DA. As per the experimental results, the proposed method has an accuracy of 90%. Therefore, deep learning algorithms provide a practical approach to anomaly detection for epidemic prevention. Furthermore, this study’s primary contributions are designing an improved approach and connecting the manufacturing site to the cloud side using the proposed module.

A regional scale coseismic landslide analysis framework: Integrating physics-based simulation with flexible sliding analysis

This paper describes a framework for regional scale coseismic landslide evaluation that combines physics-based wave propagation simulation at a regional scale, with flexible sliding analysis at a site scale. The physics-based simulation incorporates fault rupture process, complex topography and dynamic site response. The sliding displacements of flexible masses are calculated by integrating seismic parameter k obtained from the physics-based simulation over seismic resistance.The framework is applied to the case study of coseismic landslides during the 2016 Mw 7.0 Kumamoto earthquake in Japan, which has well documented fault mechanism, geologic information and landslide inventory. The performance of the model prediction is evaluated by receiver operating characteristic (ROC) analysis. This study highlights the near-fault effect and soil nonlinear effect on landslide distribution, and it is demonstrated that the landslide prediction can be notably improved with the consideration of topographic amplification of ground motions. Empirical correlations between topographic amplification of key intensity measures and parameterized topographic features are developed. Overall, the simulation captures 58% of observed landslides in the inventory (using a displacement threshold of 15 cm), showing the proposed framework is a promising tool for regional coseismic landslide analysis.

Combination of Snow Process Model Priors and Site Representativeness Evaluation to Improve the Global Snow Depth Retrieval Based on Passive Microwaves

The spatiotemporal distribution of snow depth (SD) has a significant impact on the energy and water balances of the Earth’s system. However, passive microwave remote sensing widely used for SD estimation has large uncertainties due to the variations in snow physical properties. In this study, we demonstrate a new method to minimize these uncertainties and to increase the accuracy of SD estimation. Our method is based on the synergy between the passive microwave AMSR-2 brightness temperature (TB) and a physical snow process model (SNTHERM) to estimate snow grain size, snow density and first-guess SD as priors. On one hand, we used TB from three frequencies and removed non-representative ground measurements at the stations to improve deep snow estimation. Then, we applied a machine learning (ML) algorithm based on both the AMSR-2 TB and the SNTHERM simulations to retrieve the global SD. The results showed that the root-mean-squared error (RMSE) of the retrieved SD was 12.4 cm at the meteorological stations. Independent validations showed that our method significantly reduced the SD and snow water equivalent (SWE) underestimation in the mountains compared to the current satellite products.

A Mass Transfer-Enhanced Pyrolysis-Free Bifunctional Catalyst to Boost Ultralong Lifespan Zinc-Air Batteries

The development of efficient and low-cost bifunctional oxygen catalysts is essential yet a challenge for zinc-air batteries (ZABs). Here, we prepared a pyrolysis-free 3-dimensional hybrid catalyst (COP-Fe@3D-LDH) with bifunctional oxygen-catalytic activity by integrating layered double hydroxides (3D-LDH) and a fully conjugated iron phthalocyanine-based covalent organic polymer (COP-Fe). More hierarchically porous and larger specific surface area (170.4 m 2 g −1 ) can effectively enhance the mass transfer process and active site exposure of cathode, allowing COP-Fe@3D-LDH to exhibit an outstanding peak power density (148.5 mW cm −2 ) and an ultralong lifespan (over 400 h at 10 mA cm −2 ) in ZABs. Accordingly, this work provides a new perspective to enhance the performance of pyrolysis-free catalysts in ZABs.

Microwave Plasma Assisted Aerosol Deposition (μ-PAD) for Ceramic Coating Applications

To improve plasma and chemical resistance on various vacuum components used for semiconductor manufacturing equipment, various ceramic coating techniques have been applied. Among these methods for ceramic coating, the well-known atmospheric plasma spray (APS) is advantageous for providing thick film (100 µm or more) deposition. However, there are problems associated with the phase transition of the coating film and poor film quality due to formation of voids. To solve these problems, the aerosol deposition (AD) method has been developed. This method provides nice ceramic film quality. However, the coating rate is quite slow and has difficulty producing thick films (&gt;30 µm). To overcome these limitations, microwave plasma-assisted aerosol deposition (μ-PAD) is applied at low vacuum conditions without the AD nozzle. This method uses a microwave plasma source during the AD process. After enduring a long-term durability test, as a trial run, μ-PAD has been applied on the actual process site. With the Al2O3 powder, μ-PAD shows a coating rate that is 12 times higher than the AD method. In addition, the formation of a thicker film (96 µm) deposition has been demonstrated. On the other hand, the coating film hardness, porosity, adhesion, and withstand voltage characteristics were confirmed to be less than the AD method.

Mechanical Characteristics of the Combination System of Medium-Diameter Anti-Slide Piles and Tunnel-Under-Landslide Loading

Landslides have significant impacts on the stress and deformation of existing tunnel that can damage the existing tunnel lining structures and thus affect normal traffic operation. It is of importance to study the mechanical mechanism of tunnel–landslide support systems. However, there are few studies on the mechanical mechanism of existing tunnels in landslide areas. The combination of medium-diameter anti-slide piles (300 mm ≤ D ≤ 800 mm) overcomes the disadvantages of the complex construction process and higher site requirements for large-diameter anti-slide piles (D &gt; 800 mm) and the disadvantage of lower support with micro anti-slide piles (D &lt; 300 mm). In this study, considering the influence of landslides on existing tunnel deformation, a new type of medium-diameter anti-slide pile reinforcement system for existing tunnels is proposed based on the Nanping Tunnel project. In order to study the influence of pile spacing on tunnel support, first, the maximum pile spacing of 12.5 d (25 cm) was calculated by the mathematical geometric method, and then, three physical models were established for experimental comparison and analysis, including three different spacing cases of 7.5 d (15 cm), 10 d (20 cm), and 12.5 d (25 cm). In addition, numerical simulation was used to analyze the landslide and tunnel deformation under three pile spacing working conditions. The following conclusions are reached: As the distance between the combined pile increased, the deformation of the pile body and the tunnel lining structure also increased gradually, and the earth pressure and bending moments acting on the tunnel and the pile body increased progressively. However, when the pile spacing was increased from 7.5 d to 10 d, the increase in tunnel bending moment (52.9% increase in tunnel lining moment) was much more significant than when the pile spacing was increased from 10 d to 12.5 d (28.1% increase in tunnel lining moment). The results showed that if the landslide thrust is small, the pile spacing can be increased to 12.5 d or more in the design of combined medium-diameter anti-slide piles; if the landslide thrust is large, the pile spacing should be reduced to 7.5 d or less. Whether the landslide’s thrust is large or small, the combined medium-diameter anti-slide piles with a 10 d pile spacing are less cost-effective for landslide control. The new combined medium-diameter anti-slide piles have high loading capacity and stability, which can further improve the strength of existing tunnels.

Data-driven strategies for optimization of integrated chemical plants

Operation optimization over large-scale integrated chemical plants is an inherently complex problem. We propose a surrogate-based optimization approach to optimize the operation of an industrial site that addresses both short-term market change and long-term maintenance plans. We develop a platform for automating the simulation and construction of surrogate models with a propagation error mitigation strategy. We are the first to investigate the impact of different levels of abstraction for surrogate models in site-level optimization. We also develop a deterministic, discrete-time optimization model that uses data-driven surrogate models. By optimizing a rolling horizon model with the above optimization model as the underlying model for each planning interval, we show that the plant level of abstraction is the superior approach. We demonstrate how data-driven surrogates can help address site-level process optimization by abstracting the process site network to a level that balances relevant details with tractability.

A Cost-Driven Method for Determining the Optimum Selling Price in Tofu Production on the Household-Scale Tofu Agroindustry: A Case Study in Mataram, Indonesia

The determination of the cost of production is a necessity for every entrepreneur to establish the cost of the goods sold. The methods commonly used are the Cost Structure method, the Activity-Based Costing method, and the Volume Cost Profit method. The solution proposed in this article is a cost-driven method which is considered simpler in determining the optimal selling price for the tofu agroindustry on a household scale. This study aims to analyze the correlational relationship between raw material costs, firewood costs and labor wages with production, and to find a cost-driven formulation by modifying the Volume Cost Profit method. The research was conducted in the tofu agro-industry center in Kekalik Jaya Village, Sekarbela District and in Abianbadan Baru Village, Sandubaya District with the number of respondents 40 units of tofu agro-industry selected by the accidental proportional sampling method consisting of 27 agro-industry units in Kekalik Jaya sub-district and 13 agro-industry units in Abianbadan Baru village. Collecting data using triangulation methods, namely the method of sending questionnaires to respondents, survey methods with direct interviews with tofu agro-industry business actors, and observation methods at the production process site. The results showed that there was a positive correlation between the cost of raw material for soybean seeds and production and was the largest component of production costs so that it could be used as a cost determinant in the processing of soybeans into tofu, the cost driven method could be used as strategic planning in determining the selling price.

New Procedure for Optimal Integration of Steam Power Plant With Process Site Utility to Produce Power, Steam, and Freshwater

Abstract Steam power plants are usually used for producing electricity and can simultaneously work as a multigeneration plant to produce steam, freshwater, and power. This study performed the optimal combination of a steam power station as the source and a site utility system as the sink of power and steam. Approximating the potential of the cogeneration before designing a central utility system for site utility systems is vital to set goals for onsite fuel demand along with power, freshwater, and steam production. For this purpose, a precise and efficient cogeneration targeting strategy was utilized to couple a site utility of a process and a steam power plant. This study proposed a novel strategy for optimal designing integrated steam power plants and site utility consisting of process station industries. Accordingly, exergy, exergoenvironmental, and exergoeconomic analyses were conducted. The environmental impacts of life cycle assessment (LCA) in exergoenvironmental analysis were apportioned to the exergy streams, pointing out the key factors of the system with the most significant impact on the environment and possible improvements related to them. Besides, the water cycle algorithm (WCA) was employed to optimize the integrated plant. The capabilities of the proposed procedure were implemented to the petrochemical complex site utility and steam power plant. The results showed that an optimum solution was achieved using the new procedure with significantly reduced computation time.

Modified Analytic Hierarchy Process Site Selection Model for Dental Clinics in High-Rent Commercial Buildings.

ABSTRACTIntroduction:Location is a factor that highly influences a business’s ability to carry out various activities. Site selection, therefore, must take into account all the potential benefits. A dental clinic is an enterprise that should prioritize the site selection. In Thailand, many dental clinics operate in rented commercial buildings on a long-term lease basis.Objective:The objective of this research was to create a model for selecting suitable sites for dental clinic businesses in commercial buildings in Bangkok with rental fees exceeding $750 per month.Materials and Methods:The research was conducted by collecting data from a sample group consisting of 30 participants who were owners, partners, or dentists of dental clinics located in commercial buildings in Bangkok with rental fees more than $750 per month. Data were then analyzed with descriptive statistics: namely, frequency, percentage, mean, and modified analytic hierarchy process.Results:The results revealed the ranking of the main criteria, as well as their weights, for the site selection of commercial buildings in Bangkok with rents greater than $750 per unit per month to be used as a dental clinic: transportation (39.40%), neighborhood (23.61%), facilities (19.45%), parking (12.82%), and competition (4.72%), respectively, with three most important subcriteria: namely, being on a major road (19.00%), being near an electric express train station (9.10%), and being on the secondary road (8.92%), respectively.

Total Site Material Recycling Network Design and Headers Targeting Framework with Minimal Cross-Plant Source Transfer

Proper resources recycle or reuse planning helps the industrial sites to reduce reliance on raw resources. There are a lot of previous researches that had applied the Pinch Analysis on the resources recycling problem. However, there is not much work completed on targeting the materials headers or mains from the sources of the plants. This work extends the Material Recovery Pinch Diagram to provide an insightful yet straightforward approach to targeting the material headers/mains with minimum fresh resource consumption (e.g. water, hydrogen or CO2) with single quality. The flowrates and the concentration of the exchanged streams in the material headers, as well as the minimum number of headers, can be targeted using a Pinch-based strategy, which can be applied at either process or Total Site scale. This study also proposes a novel algorithm to minimise the cross-plant material source transfer for the Total Site material network with header/mains design while ensuring the overall minimum fresh resource target is satisfied. A Source Transfer Diagram is proposed to identify optimal reuse opportunities of the purged sources from individual plants. A case study is used to demonstrate the proposed framework, comparing results obtained using direct integration and centralised headers. The benefits of this framework are two-fold. It provides the minimum resource consumption rates for the overall network, and it also enables the network and mains/header design through graphical visualisation, which is a non-linear problem. The graphical interface allows users to explore different source mixing options from individual plants while ensuring the number of headers, resource consumptions, and cross-plant source transfer are minimal.

Internal and Total Site Water Network Design with Water Mains Using Pinch-Based and Optimization Approaches

This work addresses the internal and Total Site Water Network design with water mains. A Material Recovery Pinch Diagram is used for freshwater targeting and a Water Integration Network design with a water main framework, and a mathematical model is formulated for total cost optimization. The Pinch-based method can target an optimum number of water mains, flow rates, and concentrations in the water mains, which can achieve the identified freshwater target. The proposed method can be used for both single and multiple contaminants and applied on both process and total site scales. Two case studies are used to illustrate the application procedure of the proposed method for single- and multiple-contaminant cases. The case study results showed that the optimum number of water mains is three in both single-contaminant and multiple-contaminant Total Site Water Network designs (excluding freshwater and wastewater mains). In the single-contaminant case, the water network of internal integration with three water mains can achieve a total annual cost reduction of 82% compared to direct Water Integration and a total annual cost of 42% in the multiple-contaminant case. The proposed method is beneficial as it provides a graphical interface for the water main targeting and design, and the mathematical optimization enables the selection of optimum options with a minimum cost. To pursue a more accurate design, water piping cost based on real plant locations should be incorporated in future studies.

Low-mass low-metallicity AGB stars as an efficient i-process site explaining CEMP-rs stars

Context. Among carbon-enhanced metal-poor (CEMP) stars, some are found to be enriched in slow-neutron capture (s-process) elements (and are then tagged CEMP-s), some have overabundances in rapid-neutron capture (r-process) elements (tagged CEMP-r), and some are characterized by both s- and r-process enrichments (tagged CEMP-rs). The current distinction between CEMP-s and CEMP-rs is based on their [Ba/Fe] and [Eu/Fe] ratios, since barium and europium are predominantly produced by the s- and the r-process, respectively. The origin of the abundance differences between CEMP-s and CEMP-rs stars is presently unknown. It has been claimed that the i-process, whose site still remains to be identified, could better reproduce CEMP-rs abundances than the s-process. Aims. We propose a more robust classification method for CEMP-s and CEMP-rs stars using additional heavy elements other than Ba and Eu. Once a secure classification is available, it should then be possible to assess whether the i-process or a variant of the s-process better fits the peculiar abundance patterns of CEMP-rs stars. Methods. We analyse high-resolution spectra of 24 CEMP stars and one r-process enriched star without carbon-enrichment, observed mainly with the high-resolution HERMES spectrograph mounted on the Mercator telescope (La Palma) and also with the UVES spectrograph on VLT (ESO Chile) and HIRES spectrograph on KECK (Hawaii). Stellar parameters and abundances are derived using MARCS model atmospheres. Elemental abundances are computed through spectral synthesis using the TURBOSPECTRUM radiative transfer code. Stars are re-classified as CEMP-s or -rs according to a new classification scheme using eight heavy element abundances. Results. Within our sample of 25 objects, the literature classification is globally confirmed, except for HE 1429−0551 and HE 2144−1832, previously classified as CEMP-rs and now as CEMP-s stars. The abundance profiles of CEMP-s and CEMP-rs stars are compared in detail, and no clear separation is found between the two groups; it seems instead that there is an abundance continuum between the two stellar classes. There is an even larger binarity rate among CEMP-rs stars than among CEMP-s stars, indicating that CEMP-rs stars are extrinsic stars as well. The second peak s-process elements (Ba, La, Ce) are slightly enhanced in CEMP-rs stars with respect to first-peak s-process elements (Sr, Y, Zr), when compared to CEMP-s stars. Models of radiative s-process nucleosynthesis during the interpulse phases reproduce well the abundance profiles of CEMP-s stars, whereas those of CEMP-rs stars are explained well by low-metallicity 1 M⊙ models experiencing proton ingestion. The global fitting of our i-process models to CEMP-rs stars is as good as the one of our s-process models to CEMP-s stars. Stellar evolutionary tracks of an enhanced carbon composition (consistent with our abundance determinations) are necessary to explain the position of CEMP-s and CEMP-rs stars in the Hertzsprung–Russell diagram using Gaia DR2 parallaxes; they are found to lie mostly on the red giant branch (RGB). Conclusions. CEMP-rs stars present most of the characteristics of extrinsic stars such as CEMP-s, CH, barium, and extrinsic S stars; they can be explained as being polluted by a low-mass, low-metallicity thermally-pulsing asymptotic giant branch (TP-AGB) companion experiencing i-process nucleosynthesis after proton ingestion during its first convective thermal pulses. As such, they could be renamed CEMP-sr stars, since they represent a particular manifestation of the s-process at low-metallicities. For these objects a call for an exotic i-process site may not necessarily be required anymore.