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•Ammonia can be produced in a clean manner.•Ammonia has added values of globally mature transport and storage networks.•Ammonia can be readily decomposed for clean hydrogen ...production.•Ammonia exhibits comparable cell performance with hydrogen in SOFCs.•Durability of NH3-SOFCs can be improved via highly active NH3 decomposition catalyst.
This contribution delivers the perspectives of ammonia for a clean energy future and examines the potential, achievements, and associated challenges of ammonia for power generation, with a particular focus on ammonia fuelled solid oxide fuel cells (SOFCs). Ammonia, with characteristics of zero-carbon and a high hydrogen content has been increasingly recognised as a clean fuel. The well-established facilities for ammonia production and infrastructures worldwide for storage and transport provide ammonia with indispensable advantages, underpinning its role in enabling a clean energy future. Ammonia can be decomposed into hydrogen and nitrogen free of carbon emission using an appropriate catalyst. Ni-based catalysts are more preferred candidates alternative to Ru-based catalysts with respect to cost and sources. A rational design of catalyst in terms of preparation method, support and promoter is needed to carve out a catalyst that is commercially reliable and affordable. A milestone has been recently achieved using a Ni-based catalyst with long-term stability up to 1000 h. Ammonia also shows promising potentials for clean electricity generation via SOFCs, exhibiting cell performance comparable to that of the hydrogen fuelled counterparts. However, the cell stability is compromised owing to anode degradation, which is primarily attributed to the formation of nickel nitride incurring microstructural deformations in the anode. Feeding SOFCs with pre-decomposed ammonia is then identified to effectively mitigate the nitridation reactions between ammonia and nickel. In such a manner, only a gas mixture consisted of H2 and N2 is fed into the SOFCs, eliminating the reactions of ammonia and the anode.
Data sharing becomes an exceptionally attractive service supplied by cloud computing platforms because of its convenience and economy. As a potential technique for realizing fine-grained data ...sharing, attribute-based encryption (ABE) has drawn wide attentions. However, most of the existing ABE solutions suffer from the disadvantages of high computation overhead and weak data security, which has severely impeded resource-constrained mobile devices to customize the service. The problem of simultaneously achieving fine-grainedness, high-efficiency on the data owner's side, and standard data confidentiality of cloud data sharing actually still remains unresolved. This paper addresses this challenging issue by proposing a new attribute-based data sharing scheme suitable for resource-limited mobile users in cloud computing. The proposed scheme eliminates a majority of the computation task by adding system public parameters besides moving partial encryption computation offline. In addition, a public ciphertext test phase is performed before the decryption phase, which eliminates most of computation overhead due to illegitimate ciphertexts. For the sake of data security, a Chameleon hash function is used to generate an immediate ciphertext, which will be blinded by the offline ciphertexts to obtain the final online ciphertexts. The proposed scheme is proven secure against adaptively chosen-ciphertext attacks, which is widely recognized as a standard security notion. Extensive performance analysis indicates that the proposed scheme is secure and efficient.
With the rapid development of the Internet of Things and cloud computing technologies, smart health (s-health) is expected to significantly improve the quality of health care. However, data security ...and user privacy concerns in s-health have not been adequately addressed. As a well-received solution to realize fine-grained access control, ciphertext-policy attribute-based encryption (CP-ABE) has the potential to ensure data security in s-health. Nevertheless, direct adoption of the traditional CP-ABE in s-health suffers two flaws. For one thing, access policies are in cleartext form and reveal sensitive health-related information in the encrypted s-health records (SHRs). For another, it usually supports small attribute universe, which places an undesirable limitation on practical deployments of CP-ABE because the size of its public parameters grows linearly with the size of the universe. To address these problems, we introduce PASH, a privacy-aware s-health access control system, in which the key ingredient is a large universe CP-ABE with access policies partially hidden. In PASH, attribute values of access policies are hidden in encrypted SHRs and only attribute names are revealed. In fact, attribute values carry much more sensitive information than generic attribute names. Particularly, PASH realizes an efficient SHR decryption test which needs a small number of bilinear pairings. The attribute universe can be exponentially large and the size of public parameters is small and constant. Our security analysis indicates that PASH is fully secure in the standard model. Performance comparisons and experimental results show that PASH is more efficient and expressive than previous schemes.
As a milestone in the development of outsourcing services, cloud computing enables an increasing number of individuals and enterprises to enjoy the most advanced services from outsourcing service ...providers. Because online payment and data security issues are involved in outsourcing services, the mutual distrust between users and service providers may severely impede the wide adoption of cloud computing. Nevertheless, most existing solutions only consider a specific type of services and rely on a trusted third-party to realize fair payment. In this paper, to realize secure and fair payment of outsourcing services in general without relying on any third-party, trusted or not, we introduce BPay, an outsourcing service fair payment framework based on blockchain in cloud computing. We first propose the system architecture, adversary model and design goals of BPay, then describe the design details. Our security and compatibility analysis indicates that BPay achieves soundness and robust fairness and it is compatible with the Bitcoin blockchain and the Ethereum blockchain. The key to the robust fairness and compatibility lies in an all-or-nothing checking-proof protocol and a top-down checking method. In addition, our experimental results show that BPay is computationally efficient. Finally, we present the applications of BPay in outsourcing services.
•Four metamorphic stages are identified in garnet–mica schist from the Wutai Group.•New metamorphic ages of ∼1.95Ga were obtained by zircon dating.•There may be a long-lived orogeny with the new ages ...representing the main collision.
The amalgamation of the North China Craton (NCC) is popularly viewed as a result of assembling between the Western and Eastern Blocks at ∼1.85Ga, forming the Trans-North China Orogen. Disputations still exist on the age and detailed tectonic processes involved in the assembling. Garnet–mica schist samples were collected from the lower part of Wutai Group in the central Trans-North China Orogen for determination of the metamorphic P–T path and age and for better understanding the tectonic evolution of the NCC. The garnet–mica schist generally contains mega-garnet porphyroblasts together with biotite, muscovite, quartz and ilmenite with or without plagioclase, epidote, ortho-amphibole, staurolite and kyanite. Garnet is mostly weakly zoned with core–rim increasing pyrope and decreasing grossular, but occasionally exhibits pronounced zoning involving different patterns in the core and mantle, suggesting two-stage growth. Pseudosections were calculated using THERMOCALC for three representative samples. The modeling results, together with the petrographic observations suggest that the garnet–mica schist may have experienced four metamorphic stages. The first-stage (S-I), which is revealed only from the infrequent garnet core zoning, is characterized by a flat P–T vector dominated by heating, closing to the low-pressure facies series. The second-stage (S-II) exhibits a steep P–T vector with increasing pressure and temperature to the pressure peak at >9.0kbar/615–645°C, being the medium-pressure facies series (kyanite type). The third stage (S-III) is the decompression with heating to the temperature peak at ∼7.5kbar/660°C. The fourth stage (S-IV) is the further decompression after the temperature peak, accompanied with considerable cooling. Metamorphic overgrowth rims of zircon and fully metamorphic crystals from two samples dated using SHRIMP and LA-ICP-MS methods yield new metamorphic ages of ∼1.95Ga, which were interpreted to represent the pre- or peak stages (i.e. S-II and S-III) of the kyanite type metamorphism for the dated zircon grains contain inclusions similar to the minerals in the host rocks and the REE patterns in zircon show metamorphic characteristics. This suggests that there would be a collision or crust thickening event coupled with the kyanite type metamorphism occurring at ∼1.95Ga, which is about 100Ma older than the popularly viewed collision age (∼1.85Ga). A probable interpretation is that there may be a long-lived orogenic process where the older metamorphic ages of ∼1.95Ga represent the main collision stage, and the younger ages of ∼1.85Ga indicate uplifting and cooling of high-grade terranes. The first stage (S-I) metamorphism of low-pressure facies series could be an indicator of crust extension before the collision event.
Two‐dimensional (2D) covalent organic frameworks (COFs) feature open and ordered one‐dimensional column nanochannels which offer immense possibilities for incorporation of various guests for specific ...functions. However, the relatively low chemical stability of most COFs originating from the dynamic covalent linkages hinders their practical application. In this work, a highly crystalline and heteroporous dibenzog,pchrysene‐based COF (DBC‐2P) was synthesized and served as a host material for ionic conduction. DBC‐2P exhibits excellent stability both in strong acid and base due to the large conjugated DBC‐based knot that reinforces the interlayer interactions. Subsequent encapsulation of linear polyethylene glycol (PEG) and PEG‐LiBF4 salt into the nanochannels of DBC‐2P affords a hybrid material with a high ionic conductivity of 2.31×10−3 S cm−1. This work demonstrates an efficient post‐synthetic strategy for the development of new COF–polymer composites with intriguing properties.
Planarization‐enhanced stability: Dibenzog,pchrysene (DBC), a “closed” version of tetraphenylethene (4PE), was integrated into a 2D heteroporous imine covalent organic framework (COF). The resulting DBC‐COF exhibited much better crystallinity and stability than its counterpart 4PE‐COF, and is a promising host material for ionic conduction.
Although many users outsource their various data to clouds, data security and privacy concerns are still the biggest obstacles that hamper the widespread adoption of cloud computing. Anonymous ...attribute-based encryption (anonymous ABE) enables fine-grained access control over cloud storage and preserves receivers’ attribute privacy by hiding attribute information in ciphertexts. However, in existing anonymous ABE work, a user knows whether attributes and a hidden policy match or not only after repeating decryption attempts. And, each decryption usually requires many pairings and the computation overhead grows with the complexity of the access formula. Hence, existing schemes suffer a severe efficiency drawback and are not suitable for mobile cloud computing where users may be resource-constrained.
In this paper, we propose a novel technique called match-then-decrypt, in which a matching phase is additionally introduced before the decryption phase. This technique works by computing special components in ciphertexts, which are used to perform the test that if the attribute private key matches the hidden access policy in ciphertexts without decryption. For the sake of fast decryption, special attribute secret key components are generated which allow aggregation of pairings during decryption. We propose a basic anonymous ABE construction, and then obtain a security-enhanced extension based on strongly existentially unforgeable one-time signatures. In the proposed constructions, the computation cost of an attribute matching test is less than one decryption operation, which only needs small and constant number of pairings. Formal security analysis and performance comparisons indicate that the proposed solutions simultaneously ensure attribute privacy and improve decryption efficiency for outsourced data storage in mobile cloud computing.
The detection of water pipeline leakage is important to ensure that water supply networks can operate safely and conserve water resources. To address the lack of intelligent and the low efficiency of ...conventional leakage detection methods, this paper designs a leakage detection method based on machine learning and wireless sensor networks (WSNs). The system employs wireless sensors installed on pipelines to collect data and utilizes the 4G network to perform remote data transmission. A leakage triggered networking method is proposed to reduce the wireless sensor network's energy consumption and prolong the system life cycle effectively. To enhance the precision and intelligence of leakage detection, we propose a leakage identification method that employs the intrinsic mode function, approximate entropy, and principal component analysis to construct a signal feature set and that uses a support vector machine (SVM) as a classifier to perform leakage detection. Simulation analysis and experimental results indicate that the proposed leakage identification method can effectively identify the water pipeline leakage and has lower energy consumption than the networking methods used in conventional wireless sensor networks.
Unsupervised heterogeneous face translation requires obtaining heterogeneous images with the same identities at training time, limiting the use in unconstrained real‐world scenarios. Taking a step ...further towards unconstrained heterogeneous face translation, the authors explore unsupervised zero‐shot heterogeneous face translation for the first time, which is expected to synthesize images that resemble the style of target images and whose identities in the source domain have been preserved but never seen in the target domain during training. Essentially, asymmetry between heterogeneous faces under the zero‐shot setting further exacerbates the distortion and blurring of the translated images. The authors therefore propose a novel frequency‐structure‐guided regularization, which can jointly encourage to capture detailed textures and maintain identity consistency. Through extensive experimental validation and comparisons to several baseline methods on benchmark datasets, the authors verify the effectiveness of the proposed framework.
Unsupervised heterogeneous face translation requires obtaining heterogeneous images with the same identities at training time, limiting the use in unconstrained real‐world scenarios. Taking a step further towards unconstrained heterogeneous face translation, the authors explore unsupervised zero‐shot heterogeneous face translation for the first time, which is expected to synthesize images that resemble the style of target images and whose identities in the source domain have been preserved but never seen in the target domain during training. The authors therefore propose a novel frequency‐structure‐guided regularization, which can jointly encourage to capture detailed textures and maintain identity consistency.
•HP granulites record prograde path before inferred peak stage 760–820 °C/∼15 kbar.•Decompression to Tmax stage 840–860 °C/6–8 kbar, followed by isobaric cooling.•Metamorphic ages 1.90–1.83 Ga of the ...granulites represent the post-orogenic cooling.
The Hengshan complex has drawn attention for the occurrence of typical high-pressure mafic granulites, representing the Paleoproterozoic collisional orogeny in the North China Craton. Mafic granulites occur as boudins of various scales in tonalite–trondhjemite–granodiorite (TTG) gneisses. They are composed of garnet, clinopyroxene, plagioclase, orthopyroxene, hornblende, biotite, quartz, rutile and ilmenite. Garnet porphyroblasts are usually surrounded by plagioclase coronas, and early jadeite-rich clinopyroxene is totally decomposed to the symplectite of clinopyroxene and plagioclase. Two high-pressure granulites and one two-pyroxene granulite were studied by the pseudosection approach, and clockwise P–T paths with four metamorphic stages were recognized. The pre-peak prograde stage was identified from garnet core to mantle compositions, with increasing P–T from 630 to 710 °C at 11–13 kbar. The peak pressure stage hasn’t been well preserved but its mineral assemblages inferred from petrography to be garnet + jadeite-rich clinopyroxene + quartz + rutile ± plagioclase, with P–T condition of 760–820 °C at ∼15 kbar. The post-peak decompression with slight heating is characterized by symplectite, plagioclase coronas, and the formation of orthopyroxene. Locally, two-pyroxene granulite assemblages develop, defining P–T condition of 6–8 kbar and 840–860 °C for the temperature peak (Tmax). The post-Tmax cooling is represented by the occurrence of amphibolite facies assemblages especially in boudin margins with P–T condition of 6–8 kbar and 720–760 °C, suggesting an isobaric cooling process with fluid infiltration. U–Pb dating of metamorphic zircons record ages mainly ranging from 1897 to 1830 Ma with weighted mean ages of 1862 ± 11 Ma for the high-pressure granulite and 1837 ± 7 Ma for the two-pyroxene granulite. These metamorphic ages were interpreted to record the post-peak cooling stage especially the time close to solidus, which is also supported by the result of Ti-in-zircon thermometer. A summary of P–T–t evolution for metamorphic terrains corresponding to different crust levels in Hengshan–Wutai area indicates that the main episode of crust thickening-dominated collisional orogeny is ∼1.95 Ga or earlier and finished at ∼1.92 Ga. This was followed by post-orogenic cooling-uplifting or the overprinting of another thermal-tectonic event during the period of 1.92–1.80 Ga.
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