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Comparative Study of the Microstructure and Mechanical Properties of WC/High-Speed Steel Composite Materials Prepared with Co, Ni, and Fe Binders
No full textThree-mm-diameter WC/HSS composites with different binders (Co and Co-Ni-Fe) were prepared. The effect of two different binders on the microstructure and properties of WC powder and HSS composites was compared to investigate the feasibility of substituting Fe and Ni for Co in WC and steel composites. The results show that the WC/HSS sample without binder has significant macropores at the interface, with a porosity of up to 43.76%. The porosity of the composite material containing Co binder is 6.07%. The partial substitution of Ni and Fe for Co significantly reduces the shrinkage temperature of WC powder, and the porosity was reduced to 0.77%. The addition of Ni and Fe in WC facilitates the mutual diffusion among Cr, Mo, and Co elements and the interface bonding between WC and HSS. After adding Ni and Fe elements, the microhardness of the WC/HSS composite materials is slightly lower than that of the Co-added composites, with a microhardness of 1204 HV in the WC region. The HSS microhardness remains almost constant during the binder substitution, maintaining around 600 HV. The wear resistance of the composite outer layer can be effectively enhanced by the use of Co, Ni, and Fe additives
Effect of strengthening mechanisms on mechanical properties of alumina-forming austenitic steel after pre-strain
No full textAlumina-forming austenitic (AFA) steel, a promising candidate for use in high-temperature components of ultra-supercritical power plants, has high creep strengths and outstanding high-temperature corrosion resistance. The effects of microstructural evolution on the mechanical properties of Fe-20Ni-14Cr-3Al alumina-forming austenitic (3Al-AFA) steel with micro-cold deformation were investigated by multiple characterization methods, and the micro-cold deformation process was analyzed by conducting compression experiments. Tensile properties and hardness were also examined. The results show that the reduction of deformation has significant influences on the increase in the density of dislocation, the reduction of grain size, and the distribution of precipitates, which play an essential role in the enhancement of mechanical properties. As the reduction of deformation increases, the density of dislocations rises, the fragmentation of grains results in a reduction of grain size, and the distribution of precipitates at the grain boundaries gradually increases, which causes a rise in strength and a decrease in elongation. Since the elastic deformation range expands with an increase in deformation before the strain reaches 5 % of the CR0 sample in the compression test, the variation in the average grain aspect ratio between a reduction of 2 % and 6 % is relatively small. It contributes more to hardness and strength when the grain aspect ratio is high
Emerging Cu-Based Tandem Catalytic Systems for CO2 Electroreduction to Multi-Carbon Products
No full textConversion of carbon dioxide (CO2) to valuable chemicals and feedstocks through electrochemical reduction holds promise for achieving carbon neutrality and mitigating global warming. C2+ products are of interest due to their higher economic value. Since the CO2 to C2+ conversion process involves multiple steps, tandem catalytic strategies are commonly employed in the design of electrochemical CO2 reduction reaction (CO2RR) catalysts and systems/reactors. Among the diverse catalysts that are capable of reducing CO2 to CO, Cu stands out for more efficiently further converting CO to C2+ products. In this review, the emerging Cu-based tandem catalysts and their impact on CO2RR performance, focusing on three positional relationships are summarized. It delves into the integration of tandem catalytic strategies into membrane electrolyzers, utilizing catalyst-coated substrate (CCS) and catalyst-coated membrane (CCM) technologies. Several typical examples are presented to illustrate this integration. Finally, the challenges and prospects of applying tandem strategies in the development of CO2RR catalysts/systems, as well as their device-level implementation are indicated
The Role of Battery Energy Storage Systems and Market Integration in Indonesia’s Zero Emission Vision
No full textIndonesia has committed to achieving net zero emissions by 2060, with emphasis on the electricity sector eliminating harmful gas emissions by that year. Using the Balmorel energy model, this study simulated the impact of the target on optimal capacity expansion, electricity production mix, emissions, and electricity supply costs across 230 grid systems. The results indicate the substantial benefits of integrating solar photovoltaics (PV) and Battery Energy Storage Systems (BESS). Solar energy sees a remarkable capacity increase, reaching 288.7 GWp by 2060. Other renewable sources, including hydro and wind energies, also exhibited significant growth, increasing from 6.2 GW and 130 MW in 2030 to 29.4 GW and 22.5 GW, respectively, by 2060. Intermittent renewables’ growth necessitates a rise in BESS capacity from 1 MW in 2022 to 73.4 GW by 2060. The study also underscores to replace phased-out coal-fired power plants with nuclear power by 2060. The study concludes with policy implications arising from these findings
OLBS: Oblivious Location-Based Services
No full textWith the growing use of mobile devices, location-based services (LBS) are becoming increasingly popular. BLS deliver accurate services to individuals according to their geographical locations, but privacy issues have been the primary concerns of users. Privacy-preserving LBS (PPLBS) were proposed to protect location privacy, but there are still some problems: 1) a semi-trusted third party (STTP) is required to blur users' locations; 2) both the computation and communication costs of generating a query are linear with the size of queried areas; 3) the schemes were not formally treated, in terms of definition, security model, security proof, etc. In this paper, to protect location privacy and improve query efficiency, an oblivious location-based services (OLBS) scheme is proposed. Our scheme captures the following features: 1) an STTP is not required; 2) users can query services without revealing their exact location information; 3) the service provider only knows the size of queried areas and nothing else; and 4) both the computation and communication costs of generating a query is constant, instead of linear with the size of queried areas. We formalise both the definition and security model of our OLBS scheme, and propose a concrete construction. Furthermore, the implementation is conducted to show its efficiency. The security of our scheme is reduced to well-known complexity assumptions. The novelty is to reduce the computation and communication costs of generating a query and enable the service provider to obliviously generate decrypt keys for queried services. This contributes to the growing work of formalising PPLBS schemes and improving query efficiency
Compact Accountable Ring Signatures in the Plain Model
No full textAccountable ring signatures close the gap between ring signatures and group signatures. They support a designated opener who can identify signers when necessary while allowing for the most excellent possible flexibility in selecting the ring. Accountable ring signatures were first informally defined by Xu and Yung at CARDIS 2004. They present a compiler that transforms a traditional ring signature scheme into an accountable one by using a trusted model on the smart cards. At ESORICS 2015, Bootle et al. introduced a formal security model for accountable ring signatures. In addition, they also present a generic construction for accountable ring signatures in the random oracle model. In terms of the security proof model, the plain model is preferable since it requires neither any assumptions that sometimes do not exist in practice nor any trusted setup assumptions. Until now, there has been no construction of accountable ring signatures in the plain model, even with a linear signature size. In this paper, we present the first generic construction of accountable ring signature schemes that have the logarithmic signature size and are secure in the plain model using standard assumptions
Public Trace-and-Revoke Proxy Re-Encryption for Secure Data Sharing in Clouds
No full textProxy re-encryption (PRE), as a promising cryptographic primitive for secure data sharing in clouds, has been widely studied for decades. PRE allows the proxies to use the re-encryption keys to convert ciphertexts computed under the delegator’s public key into ones that can be decrypted using the delegatees’ secret keys, without knowing anything about the underlying plaintext. This delegable property of decryption rights enables flexible cloud data sharing, but it raises an important issue: if some proxies reveal their re-encryption keys, or collude with some delegatees to create a pirate decoder, then anyone who gains access to the pirate decoder can decrypt all ciphertexts computed under the delegator’s public key without the delegator’s permission. This paper opens up a potentially new avenue of research to address the above (re-encryption) key abuse problem by proposing the first public trace-and-revoke PRE system, where the malicious delegatees and proxies involved in the generation of a pirate decoder can be identified by anyone who gains access to the pirate decoder, and their decryption capabilities can subsequently be revoked by the content distributor. Our construction is multi-hop, supports user revocation and public (black-box) traceability, and achieves significant efficiency advantages over previous constructions. Technically, our construction is a generic transformation from inner-product functional PRE (IPFPRE) that we introduce to trace-and-revoke PRE. In addition, we instantiate our generic construction of trace-and-revoke PRE from the Learning with Errors (LWE) assumption, which was widely believed to be quantum-resistant. This is achieved by proposing the first LWE-based IPFPRE scheme, which may be of independent interest. Finally, we conduct a comprehensive performance evaluation of our LWE-based trace-and-revoke PRE scheme, and the experimental results show that the proposed LWE-based trace-and-revoke PRE scheme is practical and outperforms current state-of-the-art traceable PRE schemes
Cell Adhesion, Elasticity, and Rupture Forces Guide Microbial Cell Death on Nanostructured Antimicrobial Titanium Surfaces
No full textNaturally occurring and synthetic nanostructured surfaces have been widely reported to resist microbial colonization. The majority of these studies have shown that both bacterial and fungal cells are killed upon contact and subsequent surface adhesion to such surfaces. This occurs because the presence of high-aspect-ratio structures can initiate a self-driven mechanical rupture of microbial cells during the surface adsorption process. While this technology has received a large amount of scientific and medical interest, one important question still remains: what factors drive microbial death on the surface? In this work, the interplay between microbial-surface adhesion, cell elasticity, cell membrane rupture forces, and cell lysis at the microbial-nanostructure biointerface during adsorptive processes was assessed using a combination of live confocal laser scanning microscopy, scanning electron microscopy, in situ amplitude atomic force microscopy, and single-cell force spectroscopy. Specifically, the adsorptive behavior and nanomechanical properties of live Gram-negative (Pseudomonas aeruginosa) and Gram-positive (methicillin-resistant Staphylococcus aureus) bacterial cells, as well as the fungal species Candida albicans and Cryptococcus neoformans, were assessed on unmodified and nanostructured titanium surfaces. Unmodified titanium and titanium surfaces with nanostructures were used as model substrates for investigation. For all microbial species, cell elasticity, rupture force, maximum cell-surface adhesion force, the work of adhesion, and the cell-surface tether behavior were compared to the relative cell death observed for each surface examined. For cells with a lower elastic modulus, lower force to rupture through the cell, and higher work of adhesion, the surfaces had a higher antimicrobial activity, supporting the proposed biocidal mode of action for nanostructured surfaces. This study provides direct quantification of the differences observed in the efficacy of nanostructured antimicrobial surface as a function of microbial species indicating that a universal, antimicrobial surface architecture may be hard to achieve
Wood heater smoke and mortality in the Australian Capital Territory: a rapid health impact assessment
No full textObjectives: To estimate the number of deaths and the cost of deaths attributable to wood heater smoke in the Australian Capital Territory. Study design: Rapid health impact assessment, based on fine particulate matter (PM2.5) data from three outdoor air pollution monitors and published exposure–response functions for natural cause mortality attributed to PM2.5 exposure. Setting: Australian Capital Territory (population, 2021: 454 000), 2016–2018, 2021, and 2022 (2019 and 2020 excluded because of the impact of extreme bushfires on air quality). Main outcome measures: Proportion of PM2.5 exposure attributable to wood heaters; numbers of deaths and associated cost of deaths (based on the value of statistical life: 57–136 million (most conservative exposure–response function) and $140–333 million (least conservative exposure–response function). Conclusions: The estimated annual number of deaths in the ACT attributable to wood heater PM2.5 pollution is similar to that attributed to the extreme smoke of the 2019–20 Black Summer bushfires. The number of wood heaters should be reduced by banning new installations and phasing out existing units in urban and suburban areas
Accountability enablers? The role of transnational activism in the use of the multilateral development bank grievance mechanisms
No full textThe proliferation of concerns over the transparency, accountability, and democracy of international organizations has contributed to an increase in accountability mechanisms to hold global governors to account, by both state and non-state actors. Much of the scholarly focus on this subject has been on how levers of accountability can improve global governance for Member States and actors seeking to improve decision-making, and thus outputs. This article instead examines how individuals and com-munities, or neglected publics, are using accountability mechanisms designed to provide them with recourse for environmental and social harm. It probes the use of the grievance mechanisms for the multilateral development banks to examine what kinds of actors use them (e.g., international non-governmental organizations, nongovernmental organizations, or project-affected people [PAP]) and to what effect. To explore these questions, we analyze 500 complaints submitted to the grievance mechanisms of the World Bank Group; the Asian, African, and Inter-American Development Banks; and the European Bank for Reconstruction and Development. The results demonstrate that claims for recourse come from a range of primarily local actors, but that PAP in developing countries will more often achieve positive outcomes from the grievance mechanism process if they receive assistance from international and national nongovernmental organizations. These findings therefore demonstrate that transnational activists can fulfill a facilitating role as "accountability enablers"and that domestic rep-resentatives are especially effective in problem-solving processes, while international representatives are especially effective in compliance processes