Search results

Smart contracts are written in high-level programming languages, compiled into Ethereum Virtual Machine (EVM) bytecode, deployed onto blockchain systems and called with the corresponding address by transactions. The deployed smart contracts are immutable, even if there are bugs or vulnerabilities. Therefore, it is critical to verify smart contracts before deployment. This paper aims to help developers effectively and efficiently locate potential defects in smart contracts.

GethReplayer, a smart contract testing method based on transaction replay, is proposed. It constructs a parallel transaction execution environment with two virtual machines to compare the execution results. It uses the real existing transaction data on Ethereum and the source code of the tested smart contacts as inputs, conditionally substitutes the bytecode of the tested smart contract input into the testing EVM, and then monitors the environmental information to check the correctness of the contract.

Experiments verified that the proposed method is effective in smart contract testing. Virtual environmental information has a significant effect on the success of transaction replay, which is the basis for the performance of the method. The efficiency of error locating was approximately 14 times faster with the proposed method than without. In addition, the proposed method supports gas consumption analysis.

This paper addresses the difficulty that developers encounter in testing smart contracts before deployment and focuses on helping develop smart contracts with as few defects as possible. GethReplayer is expected to be an alternative solution for smart contract testing and provide inspiration for further research.

This paper aims to investigate the problem of estimating the angle of attack (AoA) and relative velocity for vertical axis wind turbine (VAWT) blades from computational fluid dynamics data.

Two methods are implemented as function objects within the OpenFOAM framework for estimating the blade’s AoA and relative velocity. For the numerical analysis of the flow around and through the VAWT, 2 D unsteady Reynolds-averaged Navier–Stokes (URANS) simulations are carried out and validated against experimental data.

To gain a better understanding of the complex flow features encountered by VAWT blades, the determination of the AoA is crucial. Relying on the geometrically-derived AoA may lead to wrong conclusions about blade aerodynamics.

This study can lead to the development of more robust optimization techniques for enhancing the variable-pitch control mechanism of VAWT blades and improving low-order models based on the blade element momentum theory.

Assessment of the reliability of AoA and relative velocity estimation methods for VAWT’ blades at low-Reynolds numbers using URANS turbulence models in the context of dynamic stall and blade–vortex interactions.

The present work involves analytical and experimental investigation of sloshing in a two-dimensional rectangular tank including the effect of porous baffles to control and/or reduce the wave motion in the sloshing tank. The purpose of this study is to assess the analytical solutions of the drag coefficient effect on porous baffles performance to track free surface motion variation in the sloshing tank by comparison with experimental shake table tests under a range of sway excitation.

The linear second-order ordinary differential equations for liquid sloshing in the rectangular tank were solved using Newmark’s beta method and obtained the analytical solutions for liquid sloshing with dual vertical porous baffles of full submergence depths in a sway-oscillated rectangular tank following the methodology similar to Warnitchai and Pinkaew (1998) and Tait (2008).

The porous baffles significantly reduce wave elevation in the varying filled levels of the tank compared to the baffle-free tank under the range of excitation frequencies. It is observed that the Reynolds number-dependent drag coefficient for porous baffles in the tank can significantly reduce the sloshing elevations and is found to be effective to achieve higher damping compared to the porosity-dependent drag coefficient for porous baffles in the sloshing tank. The analytical model’s response to free surface elevation variations in the sloshing tank was compared with the experiment’s test results. The analytical results matched with shake table test results with a quantitative difference near the first resonant frequency.

The scope of the study is limited to porous baffles performance under range sway motion and three different filling levels in the tank. The porous baffle performance includes Reynolds number dependent drag coefficient to explore the damping effect in the sloshing tank.

The porous baffles with low-level porosities in the sloshing tank have many engineering applications where the first resonant mode of sloshing in the tank is more important. The porous baffle drag coefficient is an important parameter to study the baffle’s damping effect in sloshing tanks. Hence, obtained analytical solution for liquid sloshing in the rectangular tank with Reynolds number as well as porosity-dependent drag coefficient (model 1) and porosity-dependent drag coefficient porous baffles (model 2) performance is discussed. The model’s test results were validated using a series of shake table sloshing experiments for three fill levels in the tank with sway motion at various excitation frequencies covering the first four sloshing resonant modes.

Poor cash flow management and lack of profitability have plagued the construction industry for decades. In response, the UK Government published the project bank account (PBA) payment strategy in 2012 to mitigate main contractors unfairly withholding liabilities. However, PBAs suffer from adoption challenges, such as systems fragmentation and a lack of incentives for main contractors to adopt them effectively. This study aims to investigate how to reduce systems fragmentation in construction by integrating PBA procedures with existing management workflows to increase payment automation, resulting in improved cash liquidity and better incentives for using PBAs.

A PBA blockchain decentralised application is developed, presented and critically evaluated. Blockchain is the technology used because of its permissionless, license-free, open-source and immutability properties. It is a suitable general-purpose technology layer for building and testing applications without the limitations associated with centralised technologies, such as high proprietary fees, vendor lock and intellectual property restrictions.

The research demonstrates how a blockchain application can integrate siloed construction workflows such as cash flow scheduling, supply chain management and payment executions, reducing the management workload for implementing PBAs in construction projects. Furthermore, the proposed application is open-source and replicable, and its user interface is available for external testing here: https://console.atra.io/app/bf26f846-7f16-4f80-90a0-c5488ab6edd3.

PBA is a suitable test case because it enforces an auditable, transparent and neutral account, which are inbuilt properties of blockchains; thus, both systems are harmonious to integrate. PBA is mandated in UK public sector construction projects; therefore, the research has a solid practical foundation.

Technical advantages embraced by blockchain, such as distributed ledger, P2P networks, consensus mechanisms and smart contracts, are highly compatible with addressing the security issues of transferring and storing judicial documents and obtaining the feedback and evaluation of judicial translation services in cases with foreign elements. Therefore, based on this, a consortium blockchain-based model for supervising the overall process of judicial translation services in cases with foreign elements is proposed.

Some judicial documents are required to be translated when there are language barriers in cases with foreign elements. The purpose of this paper is expected to address security issues, which is ignored, in the process of translating judicial documents.

The experimental results show that the model constructed in this paper can effectively guarantee the security and privacy of transferring and storing translated judicial documents in cases with foreign elements, and realize the credibility and traceability of feedbacks and evaluations of judicial translation services. In addition, the underlying network communications is stable and the speed for processing data can meet the requirements of practical application.

The research in this paper provides an innovative scheme for judicial translation services in cases with foreign elements. The model constructed is conducive to protecting the security of the transfer and storage of judicial documents and improving the efficiency and modernization ability of hearing cases with foreign elements.

This study aims to find the characteristics of supercritical airfoil in helicopter rotor blades for hovering phase using numerical analysis and the validation using experimental results.

Using numerical analysis in the forward phase of the helicopter, supercritical airfoil is compared with the conventional airfoil for the aerodynamic performance. The multiple reference frame method is used to produce the results for rotational analysis. A grid independence test was carried out, and validation was obtained using benchmark values from NASA data.

From the analysis results, a supercritical airfoil in hovering flight analysis proved that the NASA SC rotor produces 25% at 5°, 26% at 12° and 32% better thrust at 8° of collective pitch than the HH02 rotor. Helicopter performance parameters are also calculated based on momentum theory. Theoretical calculations prove that the NASA SC rotor is better than the HH02 rotor. The results of helicopter performance prove that the NASA SC rotor provides better aerodynamic efficiency than the HH02 rotor.

The novelty of the paper is it proved the aerodynamic performance of supercritical airfoil is performing better than the HH02 airfoil. The results are validated with the experimental values and theoretical calculations from the momentum theory.

The purpose of this paper is to examine the impact of supervision on banking risk to determine whether prudential measures taken especially after financial crises are effective in limiting banking risks.

The empirical study focused on 210 annual reports of almost all Tunisian banks during the 2010–2019 period. Banking supervision effectiveness is measured by enforcement outputs (i.e. on-site audits and sanctions). The generalized least squares method of multivariate analysis was used to analyze this study.

The results show that supervision set up and on-site audits reduce bank risk, while the relationship between sanctions and risk appears to be non-significant. The results still hold after robustness tests by changing the bank's risk-taking indicators.

This study has important implications for managers and investors in the Tunisian context. In particular, the findings provide microevidence for the impact of supervision in Tunisian banks to reduce their risk-taking. The empirical results have important implications for the decision-making of bank managers and regulators in Tunisia as well as for relevant actors in similar emerging economies.

This study extends the previous literature on supervision by examining the relationship between supervision and banking risk in an emerging country, which has been little explored, Tunisia in particular. Furthermore, this study examines whether supervision reduces risk borne by Tunisian banks, and to the best of the researchers' knowledge, it is one of the pioneering studies of supervision in the Tunisian market. This latter market has different economic, political and social attributes compared to developed countries. So, this paper helps to clarify the impact of supervision enforcement and macroprudential policies. In addition, this paper strongly contributes to the various stakeholders “understanding of the importance and implication of supervision practices. However, since banks tend not to reduce their participation in risky activities to seek higher profits, supervisory policymakers and practitioners should also take a closer look at the composition of banks” investment portfolios to reduce moral hazard and regulatory arbitrage behavior. Empirically, the authors measure supervision by on-site audits and sanctions and examine how they affect bank risk level, which was never approached in Tunisia.

The increased capital requirements and the implementation of new liquidity standards under Basel III sparked various concerns among researchers, academics and other stakeholders. The question is whether Basel III regulation is ideal, that is, adequate to deal with a crisis, such as the 2007–2009 global financial crisis? The purpose of this paper is threefold: First, perform a stress testing exercise on the US banking sector, while examining liquidity and solvency risk indicators jointly under the Basel III regulatory framework. Second, allow the study to cover the post-crisis period, while referring to key Basel III regulatory requirements. And third, focus on the resilience of domestic systemically important banks (D-SIBs), which are supposed to support the US financial system in times of stress and therefore whose failure causes the entire financial system to fail.

The authors used a sample of the 24 largest US banks observed over the period Q1-2015 to Q1-2021 and a scenario-based vector autoregressive conditional forecasting approach.

The authors found that the model successfully produces accurate forecasts and simulates the responses of the solvency and liquidity indicators to different real and historical macroeconomic shocks. The authors also found that the US banking sector is resilient and can withstand both historical and hypothetical macroeconomic shocks because of its compliance with the Basel III capital and liquidity regulations, which consist of encouraging banks to hold high-quality liquid assets and stable funding resources and to strengthen their capital, which absorbs the losses incurred in a crisis.

The authors developed a framework for testing the resilience of the US banking sector under macroeconomic shocks, while examining liquidity and solvency risk indicators jointly under Basel III regulatory framework, a point not yet well studied elsewhere, and most studies on this subject are based on precrisis data. The authors also focused on the resilience of D-SIBs, whose failure causes the failure of the entire financial system, which previous studies have failed to examine.

Presently, existing electric car sharing platforms are based on a centralized architecture which are faced with inadequate trust and pricing issues as these platforms requires an intermediary to maintain users’ data and handle transactions between participants. Therefore, this article aims to develop a decentralized peer-to-peer electric car sharing prototype framework that offers trustable and cost transparency.

This study employs a systematic review and data were collected from the literature and existing technical report documents after which content analysis is carried out to identify current problems and state-of-the-art electric car sharing. A use case scenario was then presented to preliminarily validate and show how the developed prototype framework addresses the trust-lessness in electric car sharing via distributed ledger technologies (DLTs).

Findings from this study present a use case scenario that depicts how businesses can design and implement a distributed peer-to-peer electric car sharing platforms based on IOTA technology, smart contracts and IOTA eWallet. Main findings from this study unlock the tremendous potential of DLT to foster sustainable road transportation. By employing a token-based approach this study enables electric car sharing that promotes sustainable road transportation.

Practically the developed decentralized prototype framework provides improved cost transparency and fairness guarantees as it is not based on a centralized price management system. The DLT based decentralized prototype framework aids to orchestrate the incentivize monetization and rewarding mechanisms among participants that share their electric cars enabling them to collaborate towards lessening CO₂ emissions.

The findings advocate that electric vehicle sharing has become an essential component of sustainable road transportation by increasing electric car utilization and decreasing the number of vehicles on the road.

The key novelty of the article is introducing a decentralized prototype framework to be employed to develop an electric car sharing solution without a central control or governance, which improves cost transparency. As compared to prior centralized platforms, the prototype framework employs IOTA technology smart contracts and IOTA eWallet to improve mobility related services.

Remuneration policies may differ from country to country, and their effect on bank stability could be due to the legal framework. Therefore, this study aims to investigate how the legal system impacts the relationship between CEO compensation and bank stability across countries.

To test the study hypotheses, the authors use panel data of 74 banks operating in ten OECD countries during the period 2009–2016 and apply the generalized moments method regression model to better remediate the endogeneity problem.

The findings confirm that a country’s banking regulations significantly affect its bank stability. Common law countries have less bank stability than civil law countries. This result can be interpreted by the fact that, in common-law countries, banks’ CEO are strongly protected by the law, so they allocate a large part of bank assets to risky loans to improve their variable remuneration.

The research can help policymakers understand bank stability in one country. Any legal reform would require prior knowledge of how risk-taking may arise in executive compensation.

The contribution is to explain the controversial effect of executive compensation on bank stability in the framework of legal theory. The authors argue that regulators should monitor compensation structures and that the country’s legal origin of law shapes the CEO compensation structure and is a determinant of bank stability. To the best of the authors’ knowledge, there are no studies exploring this field. So, this study tries to shed more light on the dark side of CEOs’ behavior when undertaking risky projects to maximize their remuneration.