Accurate Prediction Of Vibronic Levels And Branching Ratios For Laser-coolable Linear Polyatomic Molecules: The Construction Of The Quasidiabatic Hamiltonian

The vibronic structures of the low-lying electronic states in linear polyatomic molecules, which are utilized to construct closed optical cycling, play crucial roles in the laser-cooling processes. The construction of a multi-state K\"oeppel-Domcke-Cederbaum (KDC) quasidiabatic Hamiltonian with spin-orbit coupling, linear vibronic coupling, and Renner-Teller effects taken into account is reported aiming to obtain accurate vibronic levels and wave functions for laser-coolable triatomic molecules. The parameters for this KDC Hamiltonian were obtained from relativistic equation-of-motion coupled-cluster singles and doubles (EOM-CCSD) calculations. Discrete variable representation (DVR) calculations were then carried out to obtain the vibronic levels and wave functions. The accuracy of the present parametrization for the KDC Hamiltonian is demonstrated with calculations for vibronic levels of the $X^2\Sigma$ and $A^2\Pi$ states of the SrOH molecule

Polyurethane films, foams and nanocomposites prepared from vegetable oil-based polyols

ABSTRACT Polyurethanes (PUs) have been widely used in coatings, adhesives, sealants, and foams. Historically, the raw materials of a PU, polyol and isocyanate, were derived from petroleum. Nowadays, the increasing concerns regarding the depletion of petroleum resources and environmental problems caused by fossil fuels, has triggered great interest in the development of monomers based on renewable resources for PU production. In this project, a novel solvent-free/catalyst-free method was developed to prepare polyols from epoxidized soybean oil and castor oil for PU production. The effects of reaction temperature, reaction time, and reaction ratios of carboxyl acid and epoxy groups on the properties of the resulting polyols were investigated. Moreover, the properties of final PUs were compared with that from castor oil and methoxylated soybean oil polyol. To validate the versatility of this approach, this method was extended to other vegetable oils systems. Polyols with a broad functionality were prepared by castor oil fatty acid initiating ring opening reaction of various epoxidized vegetable oils, which were prepared with formic acid and hydrogen peroxide. The effect of the polyols\u27 structure on the thermal, mechanical, and shape memory properties of the resulting PU was studied. Possible catalysts (DBU, Pyridine) were found that could promote the ring opening reaction in this method by decreasing the reaction temperature and reaction time. The ring opening reaction kinetic for the vegetable oil systems was investigated by dynamic differential scanning calorimetry. The effect of DBU on the structure of polyols was studied as well as the properties of PU. The polyols prepared by this novel method were used to prepare PU foam for potential application in automobile seat cushions. The compatibility between this vegetable oil-based polyol and a petroleum-based polyol was investigated by solution tests and theoretical prediction. The effect of bio-component on the physical, mechanical, thermal stability, and thermal conductivity of resulting PU was investigated. Also, two approaches were proposed to modify lignin to compatibilize them with PU matrix for preparation of PU nanocomposites. The effects of this cheap and abundant renewable filler on the thermo-mechanical and dielectric properties of the final PU composites were studied. In order to increase the hydroxyl numbers of vegetable oil-based polyols, another method was developed for high performance PUs. A strong reductant, LiAlH4, was used to reduce the ether and epoxy groups in epoxidized vegetable oils to prepare high functionality bio-polyols. The properties of the final PU based on those novel polyols were characterized and compared with that from a petroleum-based polyol. Finally, carbon nanotubes were incorporated into the PU matrix to improve the thermo-mechanical properties of nanocomposites. The surface of carbon nanotube was functionalized with an amine group, which formed a covalent bond with the PUs. The loading effect of carbon nanotube on the properties of the resulting PU was investigated

MES-Attacks: Software-Controlled Covert Channels based on Mutual Exclusion and Synchronization

Multi-process concurrency is effective in improving program efficiency and maximizing CPU utilization. The correct execution of concurrency is ensured by the mutual exclusion and synchronization mechanism (MESM) that manages the shared hardware and software resources. We propose MES-Attacks, a new set of software-controlled covert channel attacks based on MESM to transmit confidential information. MES-Attacks offer several advantages: 1) the covert channels are constructed at software level and can be deployed on any hardware; 2) closed share of resource ensures the quality of the channels with low interference and makes them hard to be detected; and 3) it utilizes the system's software resources which are abound and hence difficult to isolate. We built covert channels using different MESMs on Windows and Linux, including Event, Timer, FileLockEX, Mutex, Semaphore and flock. Experimental results demonstrate that these covert channels can achieve transmission rate of 13.105 kb/s, 12.383 kb/s, and 6.552 kb/s, respectively in the scenarios of local, cross-sandbox and cross-VM, where the bit error rates are all under 1\%

Intensity-borrowing mechanisms pertinent to laser cooling of linear polyatomic molecules

A study of the intensity-borrowing mechanisms important to optical cycling transitions in laser-coolable polyatomic molecules arising from non-adiabatic coupling, contributions beyond the Franck-Condon approximation, and Fermi resonances is reported. It has been shown to be necessary to include non-adiabatic coupling to obtain computational accuracy that is sufficient to be useful for laser cooling of molecules. The predicted vibronic branching ratios using perturbation theory based on the non-adiabatic mechanisms have been demonstrated to agree well with those obtained from variational discrete variable representation calculations for representative molecules including CaOH, SrOH, and YbOH. The electron-correlation and basis-set effects on the calculated transition properties, including the vibronic coupling constants, the spin-orbit coupling matrix elements, and the transition dipole moments, and on the calculated branching ratios have been thoroughly studied. The vibronic branching ratios predicted using the present methodologies demonstrate that RaOH is a promising radioactive molecule candidate for laser cooling

Government regulation of emergency supplies under the epidemic crisis

This paper constructs a multi-oligopoly model of emergency supplies and analyses the market equilibrium results under normal conditions and epidemic conditions. The impacts of the degree of change in market demand, externalities, the material cost of emergency supplies and government regulation on the equilibrium results, especially on the prices of emergency supplies, are discussed. The results show that an increase in material cost will lead to low output and social welfare and a high price, under either normal conditions or epidemic conditions. Moreover, under epidemic conditions, the degree of change in market demand, externalities, material cost and the presence and mode of government regulation all have multiple and complex influences on the equilibrium results. Under epidemic conditions, both government output and price regulation can increase the supply of emergency supplies. In addition, when market demand changes drastically, consumer surplus and social welfare can be enhanced by the implementation of regulations. Particularly, price regulation is more effective when there is a high material cost

Preindustrial nitrous oxide emissions from the land biosphere estimated by using a global biogeochemistry model

To accurately assess how increased global nitrous oxide (N2O) emission has affected the climate system requires a robust estimation of the preindustrial N2O emissions since only the difference between current and preindustrial emissions represents net drivers of anthropogenic climate change. However, large uncertainty exists in previous estimates of preindustrial N2O emissions from the land biosphere, while preindustrial N2O emissions on the finer scales, such as regional, biome, or sector scales, have not been well quantified yet. In this study, we applied a process-based Dynamic Land Ecosystem Model (DLEM) to estimate the magnitude and spatial patterns of preindustrial N2O fluxes at the biome, continental, and global level as driven by multiple environmental factors. Uncertainties associated with key parameters were also evaluated. Our study indicates that the mean of the preindustrial N2O emission was approximately 6.20TgNyr−1, with an uncertainty range of 4.76 to 8.13TgNyr−1. The estimated N2O emission varied significantly at spatial and biome levels. South America, Africa, and Southern Asia accounted for 34.12, 23.85, and 18.93%, respectively, together contributing 76.90% of global total emission. The tropics were identified as the major source of N2O released into the atmosphere, accounting for 64.66% of the total emission. Our multi-scale estimates provide a robust reference for assessing the climate forcing of anthropogenic N2O emission from the land biospher