Adaptive Maximum Power Transfer for Movable device in Wireless Power Transfer system

More and more applications are adopting the charging topology of wireless power transmission. However, most wireless charging systems can not charge mobile devices which are moving in position while charging. Currently, many commercialized wireless charging systems adopt an inductive coupling method, which has very short charging distances. In addition, the frequency of the two coupled coils that produce maximum power transfer keeps varying, depending on the coupling coefficient that relies on the separation between coils, and this tendency becomes more severe when the coupling is strengthened at a close charging distance by the phenomenon called frequency splitting. Therefore, the existing wireless power transmission system using a fixed operating frequency can not optimize power transmission for a fluctuating charging environment as the coupling between coils changes, and charging efficiency is greatly reduced by frequency splitting when charging at a very short distance. To solve this problem, we proposed the method of estimating the RX side power and mutual inductance using the information from the TX side such as input impedance rather than using a direct communication link which adds more cost and complexity. Also, we derived a mathematical model for the above estimation method. To prove this mathematical model, the proposed wireless power transmission system was implemented in a SIMULINK environment, and the system model was validated through simulation. Also comparison between the adaptive frequency tracking method and static impedance matching circuit is made by analyzing simulation results.Comment: 10pages, 10 figures, 3 table

Prevention and Management of Variceal Hemorrhage

Variceal hemorrhage is a common and devastating complication of portal hypertension and is a leading cause of death in patients with cirrhosis. The management of gastroesophageal varices has evolved over the last decade resulting in improved mortality and morbidity rates. Regarding the primary prevention of variceal hemorrhaging, nonselective β-blockers should be the first-line therapy in all patients with medium to large varices and in patients with small varices associated with high-risk features such as red wale marks and/or advanced cirrhosis. EVL should be offered in cases of intolerance or side effects to β-blockers, or for patients at high-risk for variceal bleeding who have medium or large varices with red wale marks or advanced liver cirrhosis. In acute bleeding, vasoactive agents should be initiated along with antibiotics followed by EVL or endoscopic sclerotherapy (if EVL is technically difficult) within the first 12 hours of presentation. Where available, terlipressin is the preferred agent because of its safety profile and it represents the only drug with a proven efficacy in improving survival. All patients surviving an episode of bleeding should undergo further prophylaxis to prevent rebleeding with EVL and nonselective β-blockers

The dark side of corporate social responsibility

The interests of employees take a back seat when firms mobilise resources for CSR, write Heung-Jun Jung and Dong-One Ki

Towards Secure Blockchain-enabled Internet of Vehicles: Optimizing Consensus Management Using Reputation and Contract Theory

In Internet of Vehicles (IoV), data sharing among vehicles is essential to improve driving safety and enhance vehicular services. To ensure data sharing security and traceability, highefficiency Delegated Proof-of-Stake consensus scheme as a hard security solution is utilized to establish blockchain-enabled IoV (BIoV). However, as miners are selected from miner candidates by stake-based voting, it is difficult to defend against voting collusion between the candidates and compromised high-stake vehicles, which introduces serious security challenges to the BIoV. To address such challenges, we propose a soft security enhancement solution including two stages: (i) miner selection and (ii) block verification. In the first stage, a reputation-based voting scheme for the blockchain is proposed to ensure secure miner selection. This scheme evaluates candidates' reputation by using both historical interactions and recommended opinions from other vehicles. The candidates with high reputation are selected to be active miners and standby miners. In the second stage, to prevent internal collusion among the active miners, a newly generated block is further verified and audited by the standby miners. To incentivize the standby miners to participate in block verification, we formulate interactions between the active miners and the standby miners by using contract theory, which takes block verification security and delay into consideration. Numerical results based on a real-world dataset indicate that our schemes are secure and efficient for data sharing in BIoV.Comment: 12 pages, submitted for possible journal publicatio