Resonance Raman spectra of aggregated meso-tetra（4-pyridinium）porphyrin diacid （H8TPyP^6＋） were studied with excitation near the exciton absorption bands of 470 nm. The UV-Vis absorption and resonance light scatt...Resonance Raman spectra of aggregated meso-tetra（4-pyridinium）porphyrin diacid （H8TPyP^6＋） were studied with excitation near the exciton absorption bands of 470 nm. The UV-Vis absorption and resonance light scattering spectra of HsTPyP^6＋ monomers and aggregates were also measured. The observed Raman bands of monomeric and aggregated HsTPyP^6＋ were assigned on the basis of the observed deuteration shifts and by comparing with the Raman spectra of analogous porphyrin diacids. Aggregation causes moderate downshifts （2-6 cm^-1） for high-frequency modes involving the in-plane CC/CN stretches of the porphyrin core and a dramatic upshift （12 cm^-1） for the out-of-plane saddling mode of the porphyrin ring. The structural changes induced by aggregation and the possible hydrogen bonding interaction between the HsTPyP^6＋ molecules in the aggregate are discussed based on the spectral observations.展开更多
Mathematical modeling of pulsating heat pipes through ‘first’ principles is a contemporary problem which remains quite elusive. Simplifications and assumptions made in all the modeling approaches developed so far re...Mathematical modeling of pulsating heat pipes through ‘first’ principles is a contemporary problem which remains quite elusive. Simplifications and assumptions made in all the modeling approaches developed so far render them unsuitable for engineering design. In this paper, a more realistic modeling scheme is presented which provides considerable try for thought toward the next progressive step. At high enough heat flux level, closed loop pulsating heat pipes experience a bulk internal unidirectional fluid circulation. Under such a condition, conventional two-phase flow modeling in capillary tubes may be applied. This has been attempted for single-loop PHPs. A homogeneous model and a separated two-fluid flow model based on simultaneous conservation of mass, momentum and energy, have been developed for an equivalent ‘open flow’ system. The model allows prediction of two-phase flow parameters in each sub-section of the device thereby providing important insights into its operation. The concept of ‘void fraction constraint’ in pulsating heat pipe operation is introduced and its relevance to future modeling attempts is outlined.展开更多
By means of the reduced-density linear entropy, we investigate the properties of dynamical entanglement of vibrations in integrable dimer and realistic small molecules which are initially in the two-mode squeezed vacu...By means of the reduced-density linear entropy, we investigate the properties of dynamical entanglement of vibrations in integrable dimer and realistic small molecules which are initially in the two-mode squeezed vacuum state. It is found that the entropy of the integrable dimer is periodic for weak coupling strength cl and small squeezing parameter r, and there exists a beat phenomenon for strong el and large r. Moreover, the entropy of the small molecules is quasi-periodic for small r, ＆nd the begt phenomenon occurs in the entropy evolution of the two molecules C2D2 and S02 for large r. Our results might be used for molecular quantum computing based on vibrational states.展开更多
Iron oxide particles with various shapes,sizes and phase concentrations(including--Fe2O3 and Fe3O4) have been synthesized through a simple hydrothermal method in the ethylene glycol(EG)-water system.In the preparation...Iron oxide particles with various shapes,sizes and phase concentrations(including--Fe2O3 and Fe3O4) have been synthesized through a simple hydrothermal method in the ethylene glycol(EG)-water system.In the preparation conditions,ferric chloride(FeCl3.6H2O) was used as the iron source in the presence of sodium hydroxide(NaOH) without any surfactants.By adjusting the experimental parameters(EG/H2O ratio,base content,iron ions concentration,etc.),the shape,the size,the phase and the magnetic property of the products could be easily controlled.The products were characterized by using X-ray diffraction(XRD),scanning electron microscopy(SEM),and a vibrating sample magnetometer(VSM).A further investigation revealed that high EG content and high alkaline condition favored the formation of Fe3O4 phase.A possible growth mechanism was proposed based on the experimental results.The magnetic properties were deeply affected by the morphology and phase of the as-synthesized products.The controlled shape,size and phase structure of the iron oxides through simple synthetic procedures provides potential opportunities to realize the promising size and shape-dependent applications.展开更多
基金ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.20473078） and the Specialized Research Fund for the Doctoral Program of Higher Education （No.200803580022）.
文摘Resonance Raman spectra of aggregated meso-tetra（4-pyridinium）porphyrin diacid （H8TPyP^6＋） were studied with excitation near the exciton absorption bands of 470 nm. The UV-Vis absorption and resonance light scattering spectra of HsTPyP^6＋ monomers and aggregates were also measured. The observed Raman bands of monomeric and aggregated HsTPyP^6＋ were assigned on the basis of the observed deuteration shifts and by comparing with the Raman spectra of analogous porphyrin diacids. Aggregation causes moderate downshifts （2-6 cm^-1） for high-frequency modes involving the in-plane CC/CN stretches of the porphyrin core and a dramatic upshift （12 cm^-1） for the out-of-plane saddling mode of the porphyrin ring. The structural changes induced by aggregation and the possible hydrogen bonding interaction between the HsTPyP^6＋ molecules in the aggregate are discussed based on the spectral observations.
基金German National Science Foundation (DFG)(No. GR-412/22)
文摘Mathematical modeling of pulsating heat pipes through ‘first’ principles is a contemporary problem which remains quite elusive. Simplifications and assumptions made in all the modeling approaches developed so far render them unsuitable for engineering design. In this paper, a more realistic modeling scheme is presented which provides considerable try for thought toward the next progressive step. At high enough heat flux level, closed loop pulsating heat pipes experience a bulk internal unidirectional fluid circulation. Under such a condition, conventional two-phase flow modeling in capillary tubes may be applied. This has been attempted for single-loop PHPs. A homogeneous model and a separated two-fluid flow model based on simultaneous conservation of mass, momentum and energy, have been developed for an equivalent ‘open flow’ system. The model allows prediction of two-phase flow parameters in each sub-section of the device thereby providing important insights into its operation. The concept of ‘void fraction constraint’ in pulsating heat pipe operation is introduced and its relevance to future modeling attempts is outlined.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11174081,11034002,11104075,60708003,and 11134003the National Basic Research Program of China under Grant Nos.2011CB921602 and 2012CB821302
文摘By means of the reduced-density linear entropy, we investigate the properties of dynamical entanglement of vibrations in integrable dimer and realistic small molecules which are initially in the two-mode squeezed vacuum state. It is found that the entropy of the integrable dimer is periodic for weak coupling strength cl and small squeezing parameter r, and there exists a beat phenomenon for strong el and large r. Moreover, the entropy of the small molecules is quasi-periodic for small r, ＆nd the begt phenomenon occurs in the entropy evolution of the two molecules C2D2 and S02 for large r. Our results might be used for molecular quantum computing based on vibrational states.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50832003 and 50972073)
文摘Iron oxide particles with various shapes,sizes and phase concentrations(including--Fe2O3 and Fe3O4) have been synthesized through a simple hydrothermal method in the ethylene glycol(EG)-water system.In the preparation conditions,ferric chloride(FeCl3.6H2O) was used as the iron source in the presence of sodium hydroxide(NaOH) without any surfactants.By adjusting the experimental parameters(EG/H2O ratio,base content,iron ions concentration,etc.),the shape,the size,the phase and the magnetic property of the products could be easily controlled.The products were characterized by using X-ray diffraction(XRD),scanning electron microscopy(SEM),and a vibrating sample magnetometer(VSM).A further investigation revealed that high EG content and high alkaline condition favored the formation of Fe3O4 phase.A possible growth mechanism was proposed based on the experimental results.The magnetic properties were deeply affected by the morphology and phase of the as-synthesized products.The controlled shape,size and phase structure of the iron oxides through simple synthetic procedures provides potential opportunities to realize the promising size and shape-dependent applications.
