Special Purpose Pulsar Telescope for the Detection of Cosmic Gravitational Waves

Pulsars can be used to search for stochastic backgrounds of gravitational waves of cosmological origin within the very low frequency band (VLF), $10^{-7}$ to $10^{-9}$ Hz. We propose to construct a special 50 m radio telescope. Regular timing measurements of about 10 strong millisecond pulsars will perhaps allow the detection of gravitational waves within VLF or at least will give a more stringent upper limits.Comment: 5 pages, no figure, Latex fil

Robust Stability of Switched Delay Systems with Average Dwell Time under Asynchronous Switching

The problem of robust stability of switched delay systems with average dwell time under asynchronous switching is investigated. By taking advantage of the average dwell-time method and an integral inequality, two sufficient conditions are developed to guarantee the global exponential stability of the considered switched system. Finally, a numerical example is provided to demonstrate the effectiveness and feasibility of the proposed techniques

Numerical Analysis of Friction power and Wear of Vane in Rotary Compressor

In this article, a numerical method was established to analyze the friction power and wear of vane in the rotary compressor. In this method, the time domain was divided into many steps, the physical process was simplified as an explicit model. At each delta time step, three sub models were calculated iteratively, the geometric model, the contact model and the friction model. Firstly, in the geometric model, geometric kinematics of vane and piston were obtained by calculating multi body dynamical equation. Secondly, in the contact model, Reynolds equation and elastic contact equation were solved as a coupled problem to get the thickness distribution of oil film in the sliding surface. From the oil film thickness distribution, the asperity contact stress and oil film pressure could be obtained, and all other mechanical information could be calculated. Thirdly, in the friction model, the friction power and wear depth distribution were obtained. The friction power was calculated by the time integration of PV value. The PV value was calculated by substituting asperity contact stress and vane sliding velocity. The friction power was input into the Archard wear theory to get the wear depth distribution. Base on this numerical method, the friction power and wear depth distribution of vane friction pairs were got for different rotary compressors in different conditions. Some of the experiments can be replaced by this numerical method, especially the durability experiment. The parametric sensitivity analysis could be done, so, furthermore, it can offer design reference for rotary compressor

Supramolecular assembly of cucurbit[6]uril and N-butyl-4-pyrrolidinopyridine

The nature of the supramolecular host-guest complex involving 4-pyrrolidinopyridine (BuPC4) and cucurbit[6]uril (Q[6]) has been investigated by NMR and UV spectroscopy, MALDI-TOF mass spectrometry, X-ray crystallography and isothermal titration calorimetry (ITC). The results revealed that the alkyl chain of the guest BuPC4 is located inside the cavity of the Q[6] host, whereas the other section of the BuPC4 guest remains outside of the portal

Interaction of a symmetrical α,α',δ,δ'-Tetramethyl-cucurbit[6]uril with Ln³⁺ : potential applications for isolation of lanthanides

The interaction of a symmetrical α,α′,δ,δ′-tetramethyl-cucurbit[6]uril (TMeQ[6]) with a series of lanthanide cations (Ln³⁺) was investigated in neutral water and in acidic solution. Analysis by single crystal X-ray diffraction revealed that different isomorphous families formed under different synthetic conditions. Such differences in the interaction between TMeQ[6] and Ln³⁺ could potentially be used for isolating heavier Ln³⁺ from their lighter counterparts in neutral solution, and lighter lanthanide cations from their heavier counterparts in acidic solution

Di-μ-benzoato-κ3 O,O′:O;κ3 O:O,O′-bis­[(benzoato-κ2 O,O′)(1,10-phenanthroline-κ2 N,N′)lead(II)]

In the centrosymmetric dinuclear title compound, [Pb2(C7H5O2)4(C12H8N2)2], two Pb2+ ions are connected by two tridentate bridging benzoate anions. The Pb2+ ion is seven-coordinated by five O atoms from three benzoate anions and two N atoms from the 1,10-phenanthroline ligands. The benzoate anions adopt two different coordination modes, one bidentate–chelating and one tridentate bridging–chelating. The three-dimensional supra­molecular framework is achieved by inter­molecular π–π stacking inter­actions, with a shortest centroid–centroid distance of 3.617 (4) Å

Poly[[triaqua­(μ3-4-oxidopyridine-2,6-dicarboxyl­ato)thulium(III)] monohydrate]

In the title coordination polymer, {[Tm(C7H2NO5)(H2O)3]·H2O}n, the TmIII atom is eight-coordinated by a tridentate 4-oxidopyridine-2,6-dicarboxyl­ate trianion, two monodentate anions and three water mol­ecules, forming a distorted bicapped trigonal–prismatic TmNO7 coordination geometry. The anions bridge adjacent TmIII ions into double chains. Adjacent chains are further connected into sheets. O—H⋯O hydrogen bonds involving both coordinated and uncoordinated water mol­ecules generate a three-dimensional supra­molecular framework

Molecular states from BˉN\bar{B}N interactions

In 2019, two new structures $\Lambda_b(6146)^0$ and $\Lambda_b(6152)^0$ at the invariant mass spectrum of $\Lambda_b^0\pi^{+}\pi^{-}$ observed by the LHCb Collaboration triggers a hot discussion about their inner structure. Although many works study seem to indicate that these two states are conventional three-quark states, $\Lambda_b(6146)^0$ and $\Lambda_b(6152)^0$ might still be $\bar{B}N$ hadronic molecule state, because the mass of $\Lambda_b(6146)^0$ and $\Lambda_b(6152)^0$ are close to the $\bar{B}N$ threshold. In this work, we perform a systematical investigation of the possible heavy molecular states from the interaction of $\bar{B}N$ in a one-boson-exchange approach. The interaction of the system considered is described by the $t$-channel $\sigma$, $\omega$, and $\rho$ mesons exchange. With the one-boson-exchange potentials obtained, the $\bar{B}N$ bound states with different quantum number configurations are got by solving the non-relativistic Schr\"{o}dinger equation. Our calculation suggests that recently observed $\Lambda_b(6146)^0$ can be assigned as a $P$-wave molecular state of $\bar{B}N$ with $I(J^P)=0(3/2^{+})$. However, the $\Lambda_b(6152)^0$ state cannot be accommodated in the current $F$-wave $\bar{B}N$ molecular picture. The calculation also favors the existence of a $S$-wave $\bar{B}N$ state that can not be associated with the $\Lambda_b(5912)^0$. The results in this work are helpful for understanding the high wave molecular states, and future experimental search for the new molecular states