A stability condition for turbulence model: From EMMS model to EMMS-based turbulence model

The closure problem of turbulence is still a challenging issue in turbulence modeling. In this work, a stability condition is used to close turbulence. Specifically, we regard single-phase flow as a mixture of turbulent and non-turbulent fluids, separating the structure of turbulence. Subsequently, according to the picture of the turbulent eddy cascade, the energy contained in turbulent flow is decomposed into different parts and then quantified. A turbulence stability condition, similar to the principle of the energy-minimization multi-scale (EMMS) model for gas-solid systems, is formulated to close the dynamic constraint equations of turbulence, allowing the heterogeneous structural parameters of turbulence to be optimized. We call this model the `EMMS-based turbulence model', and use it to construct the corresponding turbulent viscosity coefficient. To validate the EMMS-based turbulence model, it is used to simulate two classical benchmark problems, lid-driven cavity flow and turbulent flow with forced convection in an empty room. The numerical results show that the EMMS-based turbulence model improves the accuracy of turbulence modeling due to it considers the principle of compromise in competition between viscosity and inertia.Comment: 26 pages, 13 figures, 2 table

The method of coal and gas outburst risk zones division based on quantitative coupling of gas and stress

In order to realize the accurate division of coal and gas outburst risk zones, taking Juji Coal Mine as the case study, the method of coal and gas outburst risk zones division based on quantitative coupling of gas and stress is proposed. The results show that the high gas pressure zones are concentrated in the eastern of No.23 mining area, and most of No.26 and No.27 mining area. The vertical stress in the mine ranges from 6 MPa to 36 MPa. The comprehensive weights of gas pressure and stress are determined by AHP-entropy weight method, and the outburst risk comprehensive index Q is calculated accordingly. According to the range of Q, the mine is divided into low risk zone (Q \u3c 0.5), medium risk zone (0.5 ≤ Q ≤ 0.75) and high risk zone (Q \u3e 0.75). It has been verified that the drilling cuttings S value in No.26 mining area (high risk zone), No.27 mining area (medium risk zone) and No.211 mining area (low risk zone) is 3.6~4.8 kg/m, 3.2~4.6 kg/m and 3.0~4.4 kg/m, and the initial gas emission velocity q value ranged from 0 to 3.7 L/min, 0 to 0.46 L/min and 0 L/min, respectively

A Three-Stage Stirling Pulse Tube Cryocooler Approaching 4 K

Presented at the 16th International Cryocooler Conference, held May 17-20, 2008 in Atlanta, Georgia.It is a great challenge for a Stirling Pulse tube cryocooler (PTC) to reach liquid-helium temperature, where there are promising applications such as superconducting digital electronics, midinfrared instrument, heterodyne detectors. Lockheed Martin first achieved a temperature below 4 K with a four-stage configuration with He-3 as working fluid. A single-stage Stirling PTC precooled by a self-made two-stage GM-type PTC has been constructed and tested to explore the loss mechanism of 4 K PTC working at high frequency at Zhejiang University. Temperature as low as 4.2 K has been successfully obtained with He-4 as working fluid by the end of 2008. In this paper, we report a newly-designed three-stage PTC, which aims to reach 4 K. The 4 K cooler is a thermalcoupled type, whose mass flows are easier t ocontrol and whose energy flows are more readily monitored. It will be working with He-4 instead of He-3. The first and second stages have been finished. A bottom temperature of 35 K and 9 W at 77 K with 300 We input has been achieved in the first stage. The bottom temperature of second stage is as low as 20.6 K, and the cooling power is measured as 1.0 W at 28.6 K. The test results are in good agreement with the model for both stages. The first and second stage is designed to couple with the a stage, which is expected to reach below 5.0 K at 30 Hz

Impact of water uptake and mixing state on submicron particle deposition in the human respiratory tract (HRT) based on explicit hygroscopicity measurements at HRT-like conditions

Particle hygroscopicity plays a key role in determining the particle deposition in the human respiratory tract (HRT). In this study, the effects of hygroscopicity and mixing state on regional and total deposition doses on the basis of the particle number concentration for children, adults, and the elderly were quantified using the Multiple-Path Particle Dosimetry model, based on the size-resolved particle hygroscopicity measurements at HRT-like conditions (relative humidity = 98 %) performed in the North China Plain. The measured particle population with an external mixing state was dominated by hygroscopic particles (number fraction = (91.5 ± 5.7) %, mean ± standard deviation (SD); the same below). Particle hygroscopic growth in the HRT led to a reduction by around 24 % in the total doses of submicron particles for all age groups. Such a reduction was mainly caused by the growth of hygroscopic particles and was more pronounced in the pulmonary and tracheobronchial regions. Regardless of hygroscopicity, the elderly group of people had the highest total dose among three age groups, while children received the maximum total deposition rate. With 270 nm in diameter as the boundary, the total deposition doses of particles smaller than this diameter were overestimated, and those of larger particles were underestimated, assuming no particle hygroscopic growth in the HRT. From the perspective of the daily variation, the deposition rates of hygroscopic particles with an average of (2.88 ± 0.81) × 109 particles h-1 during the daytime were larger than those at night ((2.32 ± 0.24) × 109 particles h-1). On the contrary, hydrophobic particles interpreted as freshly emitted soot and primary organic aerosols exhibited higher deposition rates at nighttime ((3.39 ± 1.34) × 108 particles h-1) than those in the day ((2.58 ± 0.76) × 108 particles h-1). The traffic emissions during the rush hours enhanced the deposition rate of hydrophobic particles. This work provides a more explicit assessment of the impact of hygroscopicity and mixing state on the deposition pattern of submicron particles in the HRT. Copyright

R07. Identification of Antifungal Bisphosphocholines from Medicinal Gentiana Species

Corresponding author (NCNPR): Xing-Cong Li, [email protected]://egrove.olemiss.edu/pharm_annual_posters/1006/thumbnail.jp

Secondary Production of Gaseous Nitrated Phenols in Polluted Urban Environments

Nitrated phenols (NPs) are important atmospheric pollutants that affect air quality, radiation, and health. The recent development of the time-of-flight chemical ionization mass spectrometer (ToF-CIMS) allows quantitative online measurements of NPs for a better understanding of their sources and environmental impacts. Herein, we deployed nitrate ions as reagent ions in the ToF-CIMS and quantified six classes of gaseous NPs in Beijing. The concentrations of NPs are in the range of 1 to 520 ng m(-3). Nitrophenol (NPh) has the greatest mean concentration. Dinitrophenol (DNP) shows the greatest haze-to-clean concentration ratio, which may be associated with aqueous production. The high concentrations and distinct diurnal profiles of NPs indicate a strong secondary formation to overweigh losses, driven by high emissions of precursors, strong oxidative capacity, and high NOx levels. The budget analysis on the basis of our measurements and box-model calculations suggest a minor role of the photolysis of NPs (Peer reviewe

Effect of 17α-methyltestosterone (MT) on osmoregulatory responses and apoptosis in genetically improved farmed tilapia (GIFT), Oreochromis niloticus (L.)

361-368Androgenic compounds can affect osmoregulatory response and apoptosis in fish. In the present study, we exposed genetically improved farmed tilapia (GIFT) Oreochromis niloticus (L.) to 17α-methyltestosterone (MT, 0.5 and 5 mg/L) for 7, 14 and 21 days for understanding the phenomenon. The activities of Na+/K+ ATPase (NKA) and Ca2+/Mg2+ ATPase (CMA) were measured in the gill, kidney and intestine to evaluate the change in osmoregulation of GIFT, and genotoxicity was also detected. Results showed that organic NKA were significantly decreased in 5 mg/L MT exposure groups. The intestine NKA was significantly increased (0.5 mg/L MT). MT exposures increased the CMA of kidney and intestine (0.5 mg/L), together with gill CMA (5 mg/L MT). The results of genotoxicity assay showed gill atp1a1a and nkcc2 transcripts significantly increased, while intestine atp1a1a and fxyd7 transcripts revealed significant increases for MT exposure groups. Caspases proteins demonstrated significant increases at 7th and 21st day, and their transcripts were enhanced in 0.5 mg/L MT exposure groups. The results have evidently demonstrated that chronic exposure of MT could result in organic osmoregulatory response and hepatic apoptosis in GIFT O. niloticus

Effect of 17α-methyltestosterone (MT) on osmoregulatory responses and apoptosis in genetically improved farmed tilapia (GIFT), Oreochromis niloticus (L.)

Androgenic compounds can affect osmoregulatory response and apoptosis in fish. In the present study, we exposed genetically improved farmed tilapia (GIFT) Oreochromis niloticus (L.) to 17α-methyltestosterone (MT, 0.5 and 5 mg/L) for 7, 14 and 21 days for understanding the phenomenon. The activities of Na+/K+ ATPase (NKA) and Ca2+/Mg2+ ATPase (CMA) were measured in the gill, kidney and intestine to evaluate the change in osmoregulation of GIFT, and genotoxicity was also detected. Results showed that organic NKA were significantly decreased in 5 mg/L MT exposure groups. The intestine NKA was significantly increased (0.5 mg/L MT). MT exposures increased the CMA of kidney and intestine (0.5 mg/L), together with gill CMA (5 mg/L MT). The results of genotoxicity assay showed gill atp1a1a and nkcc2 transcripts significantly increased, while intestine atp1a1a and fxyd7 transcripts revealed significant increases for MT exposure groups. Caspases proteins demonstrated significant increases at 7th and 21st day, and their transcripts were enhanced in 0.5 mg/L MT exposure groups. The results have evidently demonstrated that chronic exposure of MT could result in organic osmoregulatory response and hepatic apoptosis in GIFT O. niloticus

A CsI hodoscope on CSHINE for Bremsstrahlung {\gamma}-rays in Heavy Ion Reactions

Bremsstrahlung $\gamma$ production in heavy ion reactions at Fermi energies carries important physical information including the nuclear symmetry energy at supra-saturation densities. In order to detect the high energy Bremsstrahlung $\gamma$ rays, a hodoscope consisting of 15 CsI(Tl) crystal read out by photo multiplier tubes has been built, tested and operated in experiment. The resolution, efficiency and linear response of the units to $\gamma$ rays have been studied using radioactive source and $({\rm p},\gamma)$ reactions. The inherent energy resolution of $1.6\%+2\%/E_{\gamma}^{1/2}$ is obtained. Reconstruction method has been established through Geant 4 simulations, reproducing the experimental results where comparison can be made. Using the reconstruction method developed, the whole efficiency of the hodoscope is about $2.6\times 10^{-4}$ against the $4\pi$ emissions at the target position, exhibiting insignificant dependence on the energy of incident $\gamma$ rays above 20 MeV. The hodoscope is operated in the experiment of $^{86}$Kr + $^{124}$Sn at 25 MeV/u, and a full $\gamma$ energy spectrum up to 80 MeV has been obtained.Comment: 9 pages, 19 figure