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Data are the basis in Digital Twin (DT) to set up bidirectional mapping between physical and virtual spaces, and realize critical environmental sensing, decision making and execution. Thus, trustworthiness is a necessity in data content as well as data operations. A dual blockchain framework is proposed to realize comprehensive data security in various DT scenarios. It is highly adaptable, scalable, evolvable, and easy to be integrated into Digital Twin Network (DTN) as enhancement.

Subscription permanent identifier has been concealed in the 5G systems by using the asymmetric encryption scheme as specified in standard 3GPP TS 33.501 to protect the subscriber privacy. The standardized scheme is however subject to the SUPI guess attack as the public key of the home network is publicly available. Moreover, it lacks the inherent mechanism to prevent SUCI replay attacks. In this paper, we propose three methods to enhance the security of the 3GPP scheme to thwart the SUPI guess attack and replay attack. One of these methods is suggested to be used to strengthen the security of the current subscriber protection scheme.

Some issues such as CRL/OCSP (Certificate Revocation List / Online Certificate Status Protocol) unavailable, previsioned trust anchor unavailable, high communication load arise when PKI (Public Key Infrastructure) is leveraged into mobile networks. A blockchain based PKI framework in mobile network is proposed to solve these issues. The system is constituted by submission nodes, validator nodes, inquiry nodes. Scenarios and application cases are provided, and it shows the system can be widely used in mobile networks. The blockchain based PKI system is analyzed and compared to traditional solutions. It shows the trustworthy of SSL (Security Socket Layer) certificates and device certificates are the same as those in traditional PKI system. The storage requirement and certificate capacity of blockchain based PKI system is analyzed. Since certificates have expiry dates, the optimization method based on the invalid certificates is proposed. The optimization improves the storage efficiency of the blockchain based PKI certificate management system.

In this study, a 1-D piezoelectric touchscreen that can provide the capability of touch position and sliding movement detection is proposed. To overcome the output voltage decay issue due to the capacitive behaviors of piezoelectric materials, a proposed sliding analysis approach was developed to implement the touch position detection. A structure of two piezoelectric cantilevers embedded on two ends of a beam was employed, in which one of the cantilevers serves as an actuator and the other a sensor. With the vibration provided by one of the piezoelectric cantilevers on the beam, the other would generate a corresponding voltage. According to the comparison of phase delays between the input and the generated voltage of the two piezoelectric cantilevers, the applied position of external static loading is estimated. Thus, the voltage decay issue of the general piezoelectric sensor can be efficiently solved, and the sliding movement can also be detected. From the experimental results, the proposed 1-D piezoelectric touchscreen can be demonstrated to detect sliding movement in real-time within 2∼5mm position detection error at sliding velocity of 9mm/s.

In order to simulate the dynamic behaviors of mid-water trawl in fishing simulator, a hydrodynamic model of mid-water trawl is established according to lumped mass model and researches on the numerical method for solving the model have also been done. In the modeling process, the mid-water trawl has been simplified by using an equivalent method, then the trawl is divided into finite mass points connected with springs without mass and fluid force of each mass point is calculated by simplifying the point to a spherical object or a rod-shaped object. To take a relative bigger step size for calculation, calculated positions of mass points instituting variables of position are used to calculate connected mass points' elastic force and every mass point's equations can be solely solved. Simulation researches of a mid-water trawl have been done, and simulated results are compared with that of flume experiments, which verifies model's rationality.

Generation capacity investment holds the origin of the electric power supply chain, and creates significant impacts on the reliability of power supply service. Based on the system dynamics theory, this paper builds up a model that describes the development of electric power generation investment, and uses the model to perform the dynamic simulation of generation capacity investment in different market scenarios, such as the energy-only market and the capacity payment mechanism. Particularly, imperfections of the real world are taken into consideration, which is reflected by the accuracy of load forecast. The simulation shows that generation investment would fluctuate due to the volatility of price and imperfection of information, even if the average revenue recovers the investment cost of the optimal installation, and thus result in shortage of supply in the market. Furthermore, suitable capacity mechanisms help reduce the possibility of shortage, but may trigger overinvestment in generation capacity and remain the fluctuation that threatens the reliability of power supply service.