The present paper proposes a novel model for estimating the free-volume size of porous materials based on the analysis of various experimental ortho-positronium (o-Ps) lifetime data. The model is ...derived by combining the semi-classical (SE) physics model, which works in the region of large pores (pore size R> 1 nm), with the conventional Tao-Eldrup (TE) model, which is applicable only for the small-pore region (R< 1 nm). Thus, the proposed model, called the hybrid (HYB) model, is able to smoothly connect the o-Ps lifetimes in the two regions of the pore. Moreover, by introducing the o-Ps diffusion probability parameter (D), the HYB model has reproduced quite well the experimental o-Ps lifetimes in the whole region of pore sizes. It is even in a better agreement with the experimental data than the most up-to-date rectangular TE (RTE) and Tokyo models. In particular, by adjusting the value of D, the HYB model can also describe very well the two defined sets of experimental o-Ps lifetimes in the pores with spherical and channel geometries. The merit of the present model, in comparison with the previously proposed ones, is that it is applicable for the pore size in the universal range of 0.2−400 nm for most of porous materials with different geometries.
•A novel model for estimating free-volume size of porous materials.•Smooth connection of pore size from quantum to classical regime.•Ortho-positronium diffusion probability affected by pore size and geometry.
The present study reports a design of a unique holder for modifying the structure of ZSM-5 zeolite using electron beam generated from an industrial UERL-10-15S2 linear accelerator with a fixed energy ...of 10 MeV. The design was made based on a unique holder, named EDSCholder, which can be simultaneously used as the beam energy degrader and the sample container. Metal materials with different thicknesses and geometries were utilized for simulating and designing (using the Monte-Carlo N particle code) such a EDSCholder. In particular, a mathematical formula was proposed for correcting the energy distribution of the electron beam generated from the accelerator, which is not precisely mono-energetic. By comparing the simulated results with the experimental data, we found that the 1050 aluminum alloys with thicknesses of 2.5, 4.7, and 6.8 mm and having a cylindrical geometry are optimal for generating the electron energies of 9.00, 8.04, and 7.12 MeV, respectively. It was also found that, by using a rotated-cylinder EDSCholder in combination with the scanning process of the linear accelerator, one can produce a homogeneous dose rate distribution in the samples, which is similar to that obtained by using a parallel electron beam. For the structural modification of ZSM-5 zeolite using the above rotated-cylinder EDSCholder, the simulated results indicated that the sample thickness in the range of 2.5−3 cm can ensure the uniformity of absorbed dose in the irradiated samples. In addition, the influence of sample density (in a range of 0.65−0.85 g/cm3) and contribution of the X-ray scatterings to the absorbed dose was found to be insignificant and negligible. Moreover, our present design is able to significantly shorten the irradiation time as compared to the conventional design for irradiation using a traditional conveyor system. Hence, this paper proposes an effective solution to reduce the operation cost and enhance the applicability of industrial electron beam accelerators to the structural modification of materials.
The present paper proposes a novel model for estimating the free-volume size of porous materials based on the analysis of various experimental ortho-positronium (\(o\)-Ps) lifetime data. The model is ...derived by combining the semi-classical (SE) physics model, which works in the region of large pores (pore size \(R >\) 1 nm), with the conventional Tao-Eldrup (TE) model, which is applicable only for the small-pore region (\(R <\) 1 nm). Thus, the proposed model, called the hybrid (HYB) model, is able to smoothly connect the \(o\)-Ps lifetimes in the two regions of the pore. Moreover, by introducing the \(o\)-Ps diffusion probability parameter (\(D\)), the HYB model has reproduced quite well the experimental \(o\)-Ps lifetimes in the whole region of pore sizes. It is even in a better agreement with the experimental data than the most up-to-date rectangular TE (RTE) and Tokyo models. In particular, by adjusting the value of \(D\), the HYB model can also describe very well the two defined sets of experimental \(o\)-Ps lifetimes in the pores with spherical and channel geometries. The merit of the present model, in comparison with the previously proposed ones, is that it is applicable for the pore size in the universal range of \(0.2 - 400\) nm for most of porous materials with different geometries.
A technique using two measurements from opposing directions for the assay of the activity of radioactive waste drums, mainly consisting of organic materials, has been studied. A model for the ...calculation of systematic errors is given by simulating the measurement system. The calculated values are in good agreement with the experimental values. This confirms the validity of the model and proofs the good performance of this technique in practice. These results may provide guidelines for setting up a measuring system for the assay the radwaste drums.
In recent decades, numerous studies have focused on technical efficiency in rice farming, finding considerable variation in mean technical efficiency (MTE) estimates. We conducted a meta‐regression ...analysis (MRA), using a random‐effects meta‐regression model, to understand the variation in MTE estimates due to study heterogeneity, heteroscedasticity and publication bias. We used 443 observations extracted from 175 primary studies published in English in the last three decades. The results show that MTE estimates are affected by study heterogeneity. Variable returns to scale specification yielded higher MTE scores than constant returns to scale ones. Panel data, secondary data and value data had lower MTE estimates than cross‐sectional data, primary data and physical (quantity) data, respectively. Compared to Southeast Asia, countries in East and South Asia had higher MTE estimates, whereas African countries had lower MTE estimates. We suggest that practitioners and policy‐makers should consider carefully estimation specifications, data types and geographical regions of empirical studies when comparing and interpreting empirical results. The average genuine (predicted) MTE score was 0.76 (range 0.54–0.89), indicating the potential to improve technical efficiency in global rice farming and the need for further research to bridge managerial ability gaps among farmers.
The management and disposal of various types of waste (including industrial, domestic, and medical waste) are worldwide issues, which are particularly critical in developing nations such as Vietnam. ...Given the extensive population and inadequate waste treatment facilities, addressing this challenge is of utmost importance. Predominantly, the majority of such waste is not processed for composting but is instead subjected to elimination, thereby posing severe threats to public health and environmental safety. Furthermore, insufficient standards in existing waste treatment plants contribute to the rising volume of environmental waste. Emphasizing the process of waste recycling instead of total elimination is an alternate strategy that needs to be considered seriously. However, the implementation of waste segregation in Vietnam is still not sufficiently prioritized by individuals or organizations. This study presents a unique model for waste segregation and treatment, leveraging the capacities of blockchain technology and smart contracts. We also scrutinize the adherence or non-compliance to waste segregation mandates as a mechanism to incentivize or penalize individuals and organizations, respectively. To address this, we employ Non-Fungible Token (NFT) technology for the storage of compliance proofs and associated metadata. The paper’s primary contributions can be delineated into four components: i) presentation of a waste segregation and treatment model in Vietnam, utilizing Blockchain technology and Smart Contracts; ii) application of NFTs for storage of compliance-related content and its metadata; iii) offering a proof-of-concept implementation rooted in the Ethereum platform; and iv) executing the proposed model on four EVM and ERC721 compliant platforms, namely BNB Smart Chain, Fantom, Polygon, and Celo, to identify the most suitable platform for our proposition.
The global transportation of goods has evolved in response to varied economic demands. The rapid progression of modern scientific and technological innovations offers a shift from traditional ...shipping paradigms. Current systems, whether domestic like Cash-on-Delivery (CoD) or international such as Letter-of-Credit, necessitate trust-building through an intermediary—be it a carrier or a financial institution. While these conventional systems provide certain benefits, they inherently present several challenges and potential vulnerabilities, affecting both sellers and buyers. The introduction of blockchain technology and smart contracts has been explored as a viable alternative to bypass these intermediaries. However, simply removing the shipping intermediary presents its own set of issues, particularly when disputes arise. Notably, the shipper remains unaffected in situations of contention. Consequently, some models are now incorporating the shipper’s role, either as a singular entity or in collaboration with others. Yet, a considerable number of these models still depend on an external trusted party for conflict resolution. Our study introduces a unique framework, blending the robustness of blockchain, the enforceability of smart contracts, and the authenticity assurance of NFTs. This system creates a streamlined CoD operation encompassing the seller, shipper, and buyer, using NFTs to produce digital receipts, guaranteeing both proof-of-purchase and a security deposit. Furthermore, our system provides an inherent mechanism for dispute resolution. Key contributions of our work including i) The design of a novel CoD system anchored on blockchain and smart contract capabilities; ii) The incorporation of Ethereum-based NFT (specifically, ERC721) for securely logging package information; iii) The development of smart contracts that facilitate NFT generation and transfer between transactional entities; and iv) Performance evaluation and deployment of these contracts across multiple EVM-compatible platforms such as BNB Smartchain, Fantom, Celo, and Polygon, establishing the optimal environment for our innovative system.
The escalating demand for blood and its derivatives in the medical field underpins its indispensable nature for disease diagnosis and therapy. Such essential life-giving components are irreplaceable, ...necessitating a continuous reliance on voluntary blood donors. Existing methodologies primarily address the challenges of blood storage and its logistical distribution among healthcare centers. These conventional strategies lean towards centralized systems, often compromising data transparency and accessibility. Notably, there remains a significant gap in incentivizing and raising awareness among potential and existing donors regarding the life-saving act of blood donation. Recognizing these challenges, we introduce a robust and innovative framework that harnesses the potential of Blockchain technology, coupled with the power of smart contracts. Furthermore, to foster a sustainable blood donation ecosystem, we advocate the shift from traditional paper-based recognition to digitized donor acknowledgment using Non-Fungible Tokens (NFTs). Our novel approach encapsulates four key areas: (a) Introduction of a supply chain oversight mechanism for blood and its derivatives through Blockchain and smart contracts; (b) Development of a digital certification system for blood donors utilizing NFTs; (c) Execution of our suggested framework via smart contracts, offering a tangible proof-of-concept; and (d) Assessment and implementation of the proof-of-concept across four prominent platforms: ERC721 (ETH’s NFT), and the Ethereum Virtual Machine (EVM) employing the Solidity language – this encompasses the BNB Smart Chain, Fantom, Polygon, and Celo, aiming to discern the optimal platform compatible with our innovative framework.
Medical waste is deemed hazardous due to its potential health implications and the predominant practice of discarding it post six months of utilization. Furthermore, the reusable proportion of such ...waste is minimal. The implications of this scenario were brought to the fore during the COVID- 19 pandemic when sub-optimal medical waste management was identified as a factor exacerbating the spread of the virus worldwide. The predicament is particularly grave in developing nations, such as Vietnam, where the underdeveloped state of medical infrastructure renders efficient waste management a daunting task. The waste management challenge also stems from the significant roles played by different stakeholders (healthcare workers and patients confined to isolation wards), whose actions directly influence waste classification, impact the waste treatment process, and indirectly contribute to environmental pollution. Given that waste management involves a chain of activities requiring the coordinated efforts of medical, transportation, and waste treatment personnel, inaccuracies in the initial stages, such as waste sorting, can negatively impact subsequent processes. In light of these issues, our study puts forth a unique model aimed at enhancing waste classification and management practices in Vietnam. This model innovatively integrates Blockchain technology, smart contracts, and non-fungible tokens (NFTs) with the intent to foster an increased individual and collective consciousness towards effective waste classification within healthcare settings. Our research is notable for its four-fold contribution: (a) suggesting a unique mechanism based on blockchain technology and smart contracts, designed specifically to improve medical waste classification and treatment in Vietnam; (b) introducing a model for instituting rewards or penalties based on NFT technology to influence behaviors of individuals and organizations; (c) demon-strating the feasibility of the proposed model through a proof-of-concept; (d) executing the proof-of-concept on four prominent platforms that support ERC721 - NFT of Ethereum and EVM for executing smart contracts programmed in the Solidity language, namely BNB Smart Chain, Fantom, Polygon, and Celo.
In today’s medical landscape, the effective management and availability of diagnostic data, including current and historical medical tests, play a critical role in inform-ing physicians’ therapeutic ...decisions. However, the conventional centralized storage system presents a significant impediment, particularly when patients switch healthcare providers. Given the sensitive nature of medical data, retrieving this information from a different healthcare facility can be fraught with challenges. While decentralized storage models using blockchain and smart contracts have been suggested as potential solutions, these methodologies often expose sensitive personal information due to the inherently open nature of data on the blockchain. Addressing these challenges, we present an innovative approach integrating Non-Fungible Tokens (NFTs) to facilitate the creation and sharing of medical document sets based on test results within a medical environment. This novel approach effectively balances data accessibility and security, introducing four key contributions: (a) We introduce a mechanism for sharing medical test results while preserving data privacy. (b) We offer a model for generating certified, NFT-based document sets that encapsulate these results.(c) We provide a proof-of-concept reflecting the proposed model’s functionality and (d) We deploy this proof-of-concept across four EVM-supported platforms—BNB Smart Chain, Fantom, Polygon, and Celo—to identify the most compatible platform for our proposed model. Our work underscores the potential of blockchain, smart contracts, and NFTs to revolutionize medical data management, demonstrating a practical solution to the challenges posed by centralized storage systems.
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