FDserver: A web service for protein folding research

*Summary:* To facilitate the study of protein folding, we have developed a web service for protein folding rate and folding type prediction as well as for the calculation of a variety of topological parameters of protein structure, which is freely available to the community.
*Availability:* http://sdbi.sdut.edu.cn/FDserve

Numerical investigation on impacts of leakage sizes and pressures of fluid conveying pipes on aerodynamic behaviors

Small hole leakage of pipes caused by erosion and perforation is the major form leading to the leakage. The leakage rate is an important premise and foundation for consequence computation and risk evaluation. Those published papers fail to systematically study impacts of initial pressures and leakage sizes of a pipe on the leakage rate. More numerical simulation results are not verified by experimental test. This paper applies numerical simulation technology to establish the model of small hole leakage in pipes, designs and processes different leakage modules to simulate different leakage scenes, and then experimentally validates the model correctness. On this basis, this paper studies impacts of initial pressures and leakage sizes on leakage rates and obtains fluid dynamic characteristics around the leakage hole, including velocity distribution and pressure distribution. However, in actual engineering, the position of leakage hole could not be predicted and changed in general. Therefore, this paper further studies impacts of leakage hole positions on the pipe leakage rate. In this way, this research is refined and could provide a theoretical basis for emergency rescue and accident survey of pipe leakage accidents

Study on the Relationship between Yogurt Packages, Drinking Methods and Residues and the Countermeasures

The aim of the study was to evaluate the relationship between different yogurt packages, drinking methods, and residues and the countermeasures. We chose 7 of the most common yogurt packages in the Chinese market, calculated the amount of residue left after yogurt consumption, compared the amount of yogurt residue left after using different methods of consumption from different types of packages, and conducted surveys in supermarkets, schools and other public places. After yogurt consumption, there are always residues left, and different packages and different drinking methods lead to different amounts of residues. The selection of yogurt package and the adoption of a good drinking method can clearly reduce the amount of residue. The solution that we suggest is to provide proper and clearly visible drinking instructions on the package to significantly reduce the amount of residue and wasted materials

Spin-quadrupole ordering of spin-3/2 ultracold fermionic atoms in optical lattices in the one-band Hubbard model

Based on a generalized one-band Hubbard model, we study magnetic properties of Mott insulating states for ultracold spin-3/2 fermionic atoms in optical lattices. When the \textit{s}-wave scattering lengths for the total spin $S=2,0$ satisfy conditions $a_{2}>a_{0}>0$, we apply a functional integral approach to the half filled case, where the spin-quadrupole fluctuations dominate. On a 2D square lattice, the saddle point solution yields a staggered spin-quadrupole ordering at zero temperature with symmetry breaking from SO(5) to SO(4). Both spin and spin-quadrupole static structure factors are calculated, displaying highly anisotropic spin antiferromagnetic fluctuations and antiferroquadrupole long-range correlations, respectively. When Gaussian fluctuations around the saddle point are taken into account, spin-quadrupole density waves with a linear dispersion are derived. Compared with the spin density waves in the half filled spin-1/2 Hubbard model, the quadrupole density wave velocity is saturated in the strong-coupling limit, and there are no transverse spin-quadrupole mode couplings, as required by the SO(4) invariance of the effective action. Finally, in the strong-coupling limit of the model Hamiltonian, we derive the effective hyperfine spin-exchange interactions for the Mott insulating phases in the quarter filled and half filled cases, respectively.Comment: 12 pages, 5 figure

Mott insulating phases and quantum phase transitions of interacting spin-3/2 fermionic cold atoms in optical lattices at half filling

We study various Mott insulating phases of interacting spin-3/2 fermionic ultracold atoms in two-dimensional square optical lattices at half filling. Using a generalized one-band Hubbard model with hidden SO(5) symmetry, we identify two distinct symmetry breaking phases: the degenerate antiferromagnetic spin-dipole/spin-octupole ordering and spin-quadrupole ordering, depending on the sign of the spin-dependent interaction. These two competing orders exhibit very different symmetry properties, low energy excitations and topological characterizations. Near the SU(4) symmetric point, a quantum critical state with a $\pi$-flux phase may emerge due to strong quantum fluctuations, leading to spin algebraic correlations and gapless excitations.Comment: 11 pages, 4 figure

Fuzzy PID control of a two-link flexible manipulator

For a flexible manipulator system, the unwanted vibrations deteriorate usually the performance of the system due to the coupling of large overall motion and elastic vibration. This paper focuses on the active vibration control of a two-link flexible manipulator with piezoelectric materials. The multi flexible body dynamics (MFBD) model of the two-link flexible manipulator attached with piezoelectric sensors and actuators is established firstly. Based on the absolute nodal coordinate formulation (ANCF), the motion equations of the manipulator system are derived and motion process and dynamic responses of the system are simulated. According to the time varying feature of system, a fuzzy PID controller is developed to depress the vibration. This controller can tune control gains online accommodating to the variation of the system. Control results obtained by the fuzzy PID control and the conventional PID control indicate that the fuzzy PID controller can effectively suppress the elastic vibration of the manipulator system and performs better than the conventional PID controller