Resonance in flow past oscillating cylinder under subcritical conditions

Flow around an oscillating cylinder in a subcritical region are numerically studied with a lattice Boltzmann method(LBM). The effects of the Reynolds number,oscillation amplitude and frequency on the vortex wake modes and hydrodynamics forces on the cylinder surface are systematically investigated. Special attention is paid to the phenomenon of resonance induced by the cylinder oscillation. The results demonstrate that vortex shedding can be excited extensively under subcritical conditions, and the response region of vibration frequency broadens with increasing Reynolds number and oscillation amplitude. Two distinct types of vortex shedding regimes are observed. The first type of vortex shedding regime(VSR I) is excited at low frequencies close to the intrinsic frequency of flow, and the second type of vortex shedding regime(VSR II)occurs at high frequencies with the Reynolds number close to the critical value. In the VSR I, a pair of alternately rotating vortices are shed in the wake per oscillation cycle,and lock-in/synchronization occurs, while in the VSR II, two alternately rotating vortices are shed for several oscillation cycles, and the vortex shedding frequency is close to that of a stationary cylinder under the critical condition. The excitation mechanisms of the two types of vortex shedding modes are analyzed separately.

Possible Spread of adenovirus type 3 from poultry to humans:indirect evidence from an outbreak in China

Objective：To explore the epidemiology and etiology for an outbreak of acute respiratory tract infection that occurred in one county of Jiangsu Province, China 2004. Methods： Only cases meeting the case definition were included in the study. We reviewed the medical records of the cases who were admitted to the local hospitals, interviewed cases by a standard questionnaire, and then described the epidemiologic features and analyzed risk factors by means of a case-control study. We collected pharyngeal swab specimens and sent them to different laboratories for isolation and culture. The laboratory used different detection methods such as DIF, PCR, electron microscope exahaination and microneutralization assay, to identify and then type the positive specimens. Results：A total of 871 cases were reported during the period from April 18 to July 4, 2004. The distribution of onset times presented two peaks, one in late May and another in middle June. The epidemic occurred mainly in the elementary and junior high schools in ten townships of one county, and the mean age of the cases was 12 years （range 7 months to 18 years）. The course of the disease was acute, and was characterized by fever accompanied with sore throat and tonsillitis. The WBC count of cases was normal or elevated. The mean duration of illness was 5 days （range 2 to 12 days）. No fatalities from illness were reported. A case-control study indicated that the possible risk factors were close contact with a case and/or poultry before onset and sharing of towels among members of the family. The typical CPE was observed through inoculating pharyngeal swab specimens into the HEP-2 cell cultures in different laboratories. An infection of adenovirus type 3 was verified by detecting positive specimens in different methods. Conclusion：This investigation demonstrated that the acute respiratory infection in cases was caused by adenovirus type 3. Cases occurred in over 70 schools in ten townships in 2004, and the route of transmission was possibly close contact with cases or droplet transmission.

Gd_(3)Al_(3)Ga_(2)O_(12):Ce^(3+), Yb^(3+) fluorescent ceramic with highly increased trap density for optical information storage

Electron-trapping materials,due to their exceptional ability of energy storage and controllable photon release under external stimulation,have attracted considerable attention in the field of optical information storage(OIS).In this work,Gd_(3)Al_(3)Ga_(2)O_(12):Ce^(3+), Yb^(3+)fluorescent ceramics,were developed using air and vacuum sintering technology.By co-doping Ce^(3+)and Yb^(3+),the trap density was significantly increased by 7.5 times compared to samples containing only Ce^(3+).Vacuum annealing further enhanced trap density by 1.6 times compared to samples sintered solely in air,while generating deep traps(1.44 eV),making Gd_(3)Al_(3)Ga_(2)O_(12):Ce^(3+), Yb^(3+) an excellent OIS medium.This work is expected to facilitate the development of OIS materials.