The empirical heat capacities of some hot-rotating A ∼ 200 nuclei (184Re, 200Tl, 211Po, and 212At) have been investigated by combining the angular-momentum dependent back-shifted Fermi gas (BSFG) model of nuclear level density (NLD) with the experimental NLD data extracted from the neutron-evaporation spectra at the total angular momentum J = 12 hbar. The parameters of the BSFG are obtained by fitting its NLD to the corresponding measured data by using an advanced package of Program Modeling (CPM) provided by Python feature of IBM Decision Optimization CPLEX. The results obtained show that the shell correction plays an important role in the formation of empirical S-shaped heat capacity, which serves as a fingerprint for the pairing phase transition in finite nuclear systems. The 184Re nucleus, which is deformed and has small shell correction, exhibits a weaker S-shaped heat capacity than the remaining three spherical 200Tl, 211Po, and 212At nuclei that have large shell effect. This result contrasts with that recently predicted by the microscopic exact pairing plus independent-particle model at finite temperature (EP+IPM), in which the S-shaped heat capacity was predicted in 184Re only. This discrepancy between the heat capacities obtained within the BSFG and EP+IPM models suggests that an NLD model capable of well describing the experimental data while also having intrinsic and as complete as possible physical interpretations is still required in order to provide the exact description of nuclear thermodynamic quantities. In addition, more experimental NLD data in other mass and higher energy regions are also demanded.
AbstractGamma spectrum measured by an NaI(Tl) detector is known to be unstable with the in situ temperature. In the present work, an advanced method has been applied to stabilize the gamma spectrum measured by the NaI(Tl) detector at environmental radiation monitoring (ERM) stations. The method is based on experimental data obtained under controlled conditions in laboratory. In the temperature range from 4 to 45°C, the relative deviation of the peak positions within the stabilized gamma spectrum is less than 2%. To test this method in a real scenario, it has been integrated into the ERM station at the Military Institute of Chemical and Environmental Engineering in Hanoi, Vietnam. The results show that the proposed method is ready for a real application.
This paper investigates the problem of output feedback attitude control for rigid spacecraft subject to inertia matrix uncertainty, space disturbance, and input saturation. Firstly, a model transformation is adopted to convert an attitude system with immeasurable angular velocity into a new system. All states of the new converted system are measurable and available for feedback; however, the system contains mismatched uncertainty resulting from the coordinate transformation. Then, an adaptive nonsingular back-stepping control with practical predefined-time convergence is designed. To resolve the problem of input saturation, an anti-windup compensator is developed. It is analytically proved that the spacecraft attitude and angular velocity are practical predefined-time stable, such that the convergence time is a given tunable constant. The simulation results reveal that the proposed control framework provides rapid attitude maneuver and actuator saturation elimination.
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