Forced Resonant Oscillations as a Response to Periodic Winds in a Stratified Reservoir

The response of the Sau reservoir to a wind field characterized by having marked periodicities of 12?h and 24?h has been studied. Measurements of temperature, with a thermistor string, and currents, with an acoustic Doppler current meter, show that the reservoir also responds with the same water periodicities. During certain times of the stratified period, some of the natural oscillation modes of the reservoir are close to these forcing wind periods. In particular, in mid-July the vertical Mode V2 is close to 12?h and in mid- to end of September the vertical Mode V3 is close to 24?h. In these situations, these modes are selected out of the spectrum of possible internal waves and the reservoir behaves as a forced oscillator in resonance with the wind. The structure and the period of these vertical modes have been elucidated by using the 3D model ELCOM. Both modes are affected by the Earth’s rotation at the widest part of the reservoir.     

Modeling Volatilization of MTBE from Standing Surface Waters

The discovery in California of methyl tertiary-butyl ether (MTBE) in surface waters used for recreational boating has raised concerns over the potential impact on drinking water quality. Concentrations of MTBE above the California secondary maximum contaminant level of 5 ppb have been reported. Here we present a model to predict the fate of MTBE in surface waters as a function of wind speed, water temperature, epilimnion depth, and lake surface area. The model was validated with MTBE concentration data from Lake Perris in southern California and Calero Reservoir in northern California. When applied to typical lake conditions in California [i.e., epilimnion depth <11 m (<35 ft) and water temperature >15°C], the maximum half-life for MTBE is <40 days for quiescent conditions, and as low as 6 days if the average wind speed is >4.5 m∕s (10 mi∕h). The model can be used for management of recreational boating based on a target MTBE concentration in the reservoir.     

The Construction of SCM in GRAPES and Its Applications in Two Field Experiment Simulations

T A Single Column Model (SCM) for Global and Regional Atmospheric Prediction Enhanced System (GRAPES) is constructed for the purpose of evaluating physical process parameterizations. Two observational datasets including Wangara and the third Global Energy and Water Cycle Experiment Atmospheric Boundary Layer Study (GABLS-3) SCM field observations have been applied to evaluate this SCM. By these two numerical experiments, the GRAPES_SCM is verified to be correctly constructed. Furthermore, the interaction between the land surface process and atmospheric boundary layer (ABL) is discussed through the second experiment. It is found that CASE3 (CoLM land surface scheme coupled with ABL scheme) simulates less sensible heat fluxes and smaller surface temperature which corresponds with its lower potential temperature at the bottom of the ABL. Moreover, CASE3 simulates turbulence that is weaker during the daytime and stronger during nighttime, corresponding with its wind speed at 200 m which is bigger during daytime and smaller during nighttime. However, they are generally opposite in CASE2 (SLAB coupled with ABL). The initial profile of the water vapor mixing ratio is artificially increased by the experiment setup which results in the simulated water vapor mixing becoming wetter than actually observed. CASE1 (observed surface temperature taken as lower thermal forcing) and CASE2 have no soil moisture prediction and simulate a similar water vapor mixing ratio, while CASE3 has a soil moisture prediction and simulates wetter. It is also shown that the time step may affect the stabilization of the ABL when the vertical levels of the SCM are fixed.     

Geomorphological and Meteorological Control of Estuarine Processes: A Three-Dimensional Modeling Analysis

The proper timing, duration, and direction of wind events interacting with the geometry of an estuarine system can control the intensity of stratification. A three-dimensional, time-dependent hydrodynamic model was used to examine this process. Intense mixing is closely tied with wind-generated internal velocity shear. A south wind generates up-estuary directed surface currents, which eventually leads to downwelling movements of water. This downwelling process in the upper bay region accelerates the bottom current in a down-estuary direction. A vertical instability occurs, especially in the upper bay region, due to the generation of shear across the pycnocline, causing mixing sufficient to destratify the entire water column. On the other hand, strong stratification occurs when a north wind advects fresher upper bay surface water into the lower bay. A downwelling movement of water is produced, which in turn drives bottom saline water in the up-estuary direction.     

Effect of sodium warfarin of plasma insulin estimations

The influence of the heating rate on the readiness of forced meat products determined from inactivation of the acid phosphatase and the temperature of the product, was studied. Changes in the enzyme activity and in organoleptic characteristics were studied by using forced meat prepared from high-quality beef (2 per cent of kitchen salt, curing in a salt solution for 24 hours at 4 degrees with addition of 25 per cent of water to the raw meat during cutting). The analyses were made when the temperature of the forced meat reached 68-80 degrees (with an interval of 1 degree) the rates of heating being as follows: 0, 1, 1, 2, 4, 6, 8, 10 degrees with the field tension ranging from 2000 up to 16000 V/m. The power applied amounted to 40-2000 W. The readiness of a product undergoing the UHF-treatment with different heating rates was found to be achieved at temperatures ranging from 72.0 to 75.2 degrees and it may be assessed objectively from inactivation of the acid phosphatase and with reference to the temperature of the product matching each heating rate individually. An equation from which the temperature of the forced meat products readiness may be determined is given.     

中厚板中间坯冷却过程中晶粒长大及控制方法

为控制中厚板中间坯长时间待温导致的晶粒长大,研究了中间强制水冷却对奥氏体组织的影响.通过对Q345B钢和含Nb-Ti钢采用1050℃变形后快冷至1050~950℃预定温度保温的热模拟方法,确定了中间坯冷却过程中的晶粒尺寸变化规律,提出了中厚板冷却过程中晶粒长大的控制方法,建立了Q345B钢和含Nb-Ti钢在中间冷却过程中的晶粒长大模型.在中间冷却过程中,Q345B钢晶粒稳定性较差,而含Nb-Ti钢晶粒稳定性良好,归因于以铌为主的析出相对奥氏体晶界的钉扎作用.中间坯的强制冷却可控制奥氏体晶粒长大,63mm厚中间坯强制冷却可有效减小平均晶粒尺寸约20μm.在实际生产中,经中间强制冷却后16 mm厚度Q345B钢板的冲击韧性提高25%~70%.      

X80管线钢238 mm x 1 650 mm连铸坯温度场及凝固末端位置的数学模拟

用二维切片跟踪铸坯凝固传热的方法建立了X80管线钢（/%:0.04C,1.85Mn,0.25Si,0.006P,0.003S,0.30Ni,0.21Mo,0.06Nb,0.02V）238 mm×1650 mm板坯连铸过程中垂直拉坯方向传热的数学模型,通过ANSYS对X80管线钢连铸过程中温度场及坯壳厚度的渐变进行计算,得出拉速1.2mm/min时,出结晶器坯壳厚为18.14 mm,铸坯液芯长22.58 m。凝固壳厚度计算值射钉测试结果的相对误差≤2.5%,凝固末端位置的相对误差为0.68%。分析了过热度（25~55℃）,拉速（1.2~1.3m/min）和二冷水量（79.2~96.8 m³/h）对切片各点温度和凝固末端位置的影响。结果表明,增大拉速、减小二冷配水量,连铸坯表面温降变慢,凝固末端位置距离结晶器液面越远,凝固时间变长;该X80管线钢板坯连铸最佳工艺参数为钢水过热度35℃,拉速1.2 m/min和二冷配水量88m³/h。     

Three-Dimensional Hydrothermal Model of Onondaga Lake, New York

A three-dimensional time-dependent hydrodynamic model of Onondaga Lake, an inland lake in central New York, emphasizing the simulation of dynamics and thermal structure has been developed. The model is based on the ECOM family of models; this version, called ECOMsiz, employs a semi-implicit time splitting algorithm and a z-level vertical coordinate system. Proper assignment of boundary conditions, especially surface heat fluxes, has been found crucial in simulating the lake's hydrothermal dynamics. Formulas for atmospheric radiation and sensible and latent heat fluxes are introduced, which have been found most appropriate for evaluating the heat budget for this midlatitudinal urban lake. The ECOMsiz model has been calibrated and validated against data for two years, 1985 and 1989, representing a wide spectrum of atmospheric and hydrographic conditions in the lake. These two years, marked by significantly different freshwater inputs from tributary inflows, ionic waste loadings, wind forcing, and atmospheric heating and cooling, form a firm basis for evaluating the robustness of the hydrodynamic model. The simulation period chosen for both years, April through October, spans the entire range of lake physical processes as it covers the well-mixed spring condition, the summer period marked by strong vertical stratification, and the well-mixed fall period. Significant differences in thermal structure have been observed in 1985 and 1989 as a result of different meteorological conditions. The mixed layer depth in 1985 is about 3 m deeper (about 9 m) than that in 1989 (about 6 m), consistent with a stronger prevailing wind in 1985. The model has successfully predicted the mixed layer depth for both the years. The model computed total heat storage for both years is in good agreement with the observed conditions.     

加拿大某精矿高配比烧结特性

 采用烧结杯试验、冶金性能检测及基础物化性能检测等多种方法研究了产自加拿大的某精矿的配矿烧结性能、烧结矿冶金性能及物化性质,对其烧结特点从物化性质方面进行了分析。结果表明:随精矿配比(质量分数)由24%增加到42%,烧结料层透气性阻力由857 Pa提高到1 150 Pa,垂直烧结速度由21.87 mm/min下降到18.38 mm/min,利用系数从1.14 t/(m2·h)降低到0.93 t/(m2·h),转鼓强度由67.47%下降到64.13%,无烟煤固体燃耗由62.46 kg/t提高到70.42 kg/t,烧结成品矿还原性指数(RI)由82.31%下降到78.76%,低温还原粉化率(RDI＞3.15 mm)由70.71%下降到64.41%,烧结各项指标及烧结矿的冶金性能均出现较大幅度恶化。物化性质分析表明,加拿大精矿的主要矿物组成是镜铁矿和假象赤铁矿,矿物表面亲水性差,且粒度组成不合理,恶化混合料制粒;同时,该精矿的颗粒表面光滑致密,高温反应性能差,软化温度在1 450 ℃以上,烧结过程中难以形成足够液相。加拿大精矿制粒性能差导致烧结料层透气性阻力大造成烧结利用系数低,而较高的软化温度导致随着该矿配比的提高烧结矿转鼓强度降低。     

Preparation and Characterization of Porous Yttrium Oxide Powders with High Specific Surface Area

Y2O3isoftenusedinthemanufactureofphos phorsandceramics[1～3].However,itisalsousedas selectivecatalysts[1,4,5],suchasforthedehydrationof2alkanols,thedimerizationofmethane,1butene isomerization,hydrogenationof1,3butadieneandac etonealdoladdition,andsupport[6,7]formetalsthat catalyzetheformationofmethanolfromCO2andH2.It iswidelyacceptedthatthecatalysispropertiesofox idesdependstronglyontheirphysicalcharacteristics,especiallyontheirspecificsurfaceareaandporous structure.Agreatdealofattentionhasb…     

Depth-Averaged Model of Open-Channel Flows over an Arbitrary 3D Surface and Its Applications to Analysis of Water Surface Profile

A new set of depth-averaged equations is introduced to study the flow over an arbitrary three-dimensional (3D) surface. These equations are derived based on a generalized curvilinear coordinate system attached to the 3D bed surface, therefore it allows us to include the effect of centrifugal force due to the bottom curvature. These general equations make it possible to analyze flows over complex terrain without the limitation of mild slope assumption used in conventional depth-averaged models. This new model is then applied to calculate the water surface profiles of (1) flow over a cylindrical surface; (2) flow over a circular surface; and (3) flow with an air-core vortex at a vertical intake. A simple hydraulic experiment is conducted in the laboratory to observe the water surface profile of flow over a circular surface. The results obtained from the model are in good agreement with experimental measurements and calculation by an empirical formula. Consequently, it demonstrates the applicability of the model in cases of flow over a highly curved bottom.     

Effects of heat production attributable to forced walking on thermoregulatory physiological responses of chickens in a warm environment

1. To determine the effects of heat production on thermoregulatory physiological responses, 5 chickens were forced to walk to increase heat production. The study consisted of two experiments. One involved 3 walking speeds (8, 16 and 24 m/min) at 25 degrees C ambient temperature. The other involved a single walking speed of 16 m/min at 3 ambient temperatures (20, 25 and 30 degrees C). Heat production, heart rate, abdominal temperature, shank skin temperature and respiration rate were measured before, during and after walking. 2. Heat production, heart rate and respiration rate increased abruptly after the start of walking and with increase in walking speed. At the start of walking, an abrupt increase in abdominal temperature occurred independently of walking speed and environmental temperature; then, as walking continued, abdominal temperature increased further with increasing walking speed and increasing environmental temperature. Shank skin temperature declined at the initiation of walking, then increased. 3. Heat production and heart rate recovered rapidly after walking, while shank skin temperature and respiration rate increased and then recovered, except at 30 degrees C. 4. A proportion, 17% to 35%, of the increased heat production was stored, increasing body temperature during walking. After walking, the stored heat was lost by means of panting until abdominal temperature recovered to 41 degrees C or shank skin temperature recovered to 37 degrees C. 5. These results suggest that the greatly-increased heat production attributable to forced walking leads to abrupt thermoregulatory physiological responses, and the heat stored in the body is actively dissipated by panting until abdominal temperature recovers to the pre-walking level. The chief mode of heat loss of birds changes with deep body temperature.     

氟化改性硅树脂制备的超疏水涂层防覆冰性能

研究具有超疏水表面特性的疏水涂层实际防覆冰效果.首先理论分析了水滴在固体表面浸润性影响因素,利用不同硅烷水解缩合反应制备出低表面能的含氟硅树脂,之后引入分形理论在含氟硅树脂中添加二氧化硅微粒制备疏水涂层.观察掺杂微粒的涂层表面微观结构,并测试水滴在不同涂层表面的接触角;为直观分析涂层防覆冰效果,将不同涂层涂覆试验件后在结冰风洞中进行覆冰测试.结果显示掺混不同量级微粒的疏水涂层表面形成复合粗糙结构,有着更好的粗糙度;含氟硅树脂表面水滴接触角较普通硅树脂提升10°,含有不同量级粒径微粒的涂层表面水滴接触角较单一粒径微粒掺混的涂层提升近20°,达到超疏水表面效果;具有复合微观结构的疏水涂层涂覆的试验件在5 m·s-1和15 m·s-1的风速下较无涂层表面覆冰减少率分别达到35.6%和25.9%,较只有一级粗糙结构的表面有效防覆冰时间长,具有较好的防覆冰能力.结果表明本文设计的超疏水涂层达到超疏水表面效果,且具有较好的防覆冰性能.      

Periodic Diffusional Mass Transfer near Sediment/Water Interface: Theory

Time-variable (periodic) flow over a lake bed, and the associated boundary layer development, have the potential to control or at least influence rates of mass transfer across the sediment/water interface. An analysis for instantaneous and time averaged flux of a material across the sediment/water interface for infinite supply in the water and infinite sink in the sediment is presented. The water flow above the interface is characterized by the shear velocity (U?) which is a periodic function of time with a maximum amplitude of (U?0) as may be typical of an internal seiche (internal standing wave) motion in a density stratified lake. The relationship between the shear velocity on the lake bed and the wind shear on the lake surface is illustrated for an extremely simplified two-layered lake of constant depth. For a less restrictive analysis, shear velocities on a lake bed have to be obtained either from field measurements or from a three-dimensional lake circulation model driven by atmospheric forcing including wind. Smaller and wind-sheltered lakes will have lower (U?0) and periodicities (T). The response of the diffusive boundary layer was related to the period of the periodic motion (T), Schmidt number (Sc), and shear velocity (U?). The vertical diffusive flux at the sediment/water interface was expressed by a Sherwood number (Sh), either instantaneous or time averaged. The mean Sherwood number (Shave) varies with shear velocity of the wave motion over the sediment bed, Schmidt number (Sc) and the period (T) due to the response of the diffusive boundary layer to the time variable water velocity. Effective diffusive boundary layers develop only at low shear velocities. Where they do, maximum and minimum boundary layer thickness depends on all three independent variables (T, Sc, and U?0). The diffusive boundary layer strongly affects sediment/water mass transfer, i.e., Sherwood numbers. Mass transfer averaged over a period can be substantially less than that produced by steady-state flow at the same U?0 and Sc. At Sc = 500, typical for dissolved oxygen, the mass transfer ratio can be reduced to 60% of steady state, depending on the internal wave period (T).     

低温钢筋穿水冷却工艺

 根据低温钢筋穿水冷却工艺特点,利用现场实测数据并结合理论分析得到不同规格低温钢筋穿水冷却过程中的对流换热系数。采用MSC Marc有限元软件与现场试制结果对低温钢筋穿水冷却过程进行了研究。研究了冷却水流量、终轧温度、穿水时间等工艺参数对低温钢筋温度场和组织演变的影响。模拟结果表明：当冷却水流量为120 m3/h时,钢筋芯部开始有珠光体转变;当冷却水流量为400 m3/h时,钢筋芯部无铁素体转变;冷却水流量为160～200 m3/h时,所获得的组织为针状铁素体与贝氏体。终轧温度增加50 ℃,出水冷装置后钢筋表面温度约增加10 ℃,返红温度约增加30 ℃;在200 m3/h水流量下冷却1.2 s,终轧温度为1 050 ℃时,其芯部组织为针状铁素体与细小的贝氏体。在相同水压与水流量条件下,随着穿水速度的增加,淬透层深度减小,返红温度增加。     

渗透剪切作用下黄土的力学特征

黄土高原地区黄土在灌溉作用下,逐渐达到饱和状态,饱和中,陡坡类黄土坡体自重增加引起下滑力增加. 该过程持续进行后,坡体内部同时发生渗流和剪切过程,导致坡体的变形不断增大,直至破坏后形成滑坡. 本文选取黑方台4.29滑坡为研究对象,在现场调查的基础上,利用滑坡后壁原状黄土试样,基于三轴试验设置10组共60个原状样对饱和黄土的渗透剪切行为进行模拟. 试验中设置了0.5、0.1和0.05 mm·min-1三个不同的加载速率对黄土试样进行剪切,为比较分析,对0.1 mm·min-1剪切速率试样设置了0、1、2和5 m几个不同水头进行了试验. 试验结果表明:饱和黄土在渗流与剪切耦合作用下,表现出应变硬化特征,渗透作用明显降低了黄土的强度,尤其是黄土黏聚力降低,其降幅达5.24%~63.35%. 对已有强度指标拟合后获得黄土在渗透剪切工况下的强度修正公式.      

喷淋水量分布对C38N2钢大方坯冷却效果的影响

合理的连铸二冷工艺制度是提高非调质钢连铸坯质量的关键。以某钢厂320 mm×480 mm C38N2非调质钢为研究对象,建立了基于大方坯横向水量分布的凝固传热模型,分析二冷区各段喷淋水量分布对铸坯表面温度分布的影响。研究表明,在现行工艺喷淋条件下,二冷一段和二段铸坯边角部喷淋水量较大,铸坯在二冷一段出口内弧和侧弧的表面横向温差分别达到了340 ℃和327 ℃,三段和四段铸坯表面中心喷淋水量较大,铸坯在空冷区内弧和侧弧的表面回温分别为109 ℃/m和125 ℃/m,容易引发角部裂纹和内部裂纹。在此基础上,提出“在二冷一段和二段降低喷淋高度+三段和四段升高喷淋高度”的喷嘴布置方式。水量分布优化后,二冷各段出口表面横向温差基本控制在200 ℃以内,铸坯在空冷区内弧和侧弧表面回温分别降低至95 ℃/m和107 ℃/m,角部回温由94 ℃/m降低至40 ℃/m,降低了裂纹缺陷发生率。研究结果可为该类非调质钢连铸生产提供借鉴。     

水流量对热轧钢板层流冷却过程对流换热系数的影响

提高带钢层流冷却控制模型的精度,关键是建立精确的对流换热系数与冷却工艺之间的关系.采用有限差分法和反向热传导法,获得了实验条件下钢板表面的对流换热系数及表面温度.研究了不同水流量(0.9~2.1 m3·h-1)对换热系数与表面温度变化规律的影响.在层流冷却过程中,对流换热系数与表面温度呈非线性关系;在距离驻点70 mm内,水流量对换热系数随表面温度变化规律没影响;远离驻点70 mm外,对流换热系数比随远离冲击区驻点距离的增加而减小.采用所确定的换热系数计算得到的温降曲线与实测曲线吻合较好.      

Freezing temperature of finger skin

In 45 subjects, 154 frostnips of the finger were induced by cooling in air at -15 degrees C with various wind speeds. The mean supercooled skin temperature at which frostnip appeared was -9.4 degrees C. The mean skin temperature rise due to heat of fusion at ice crystallization was 5.3 degrees C. The skin temperature rose to what was termed the apparent freezing point. The relation of this point to the supercooled skin temperature was analyzed for the three wind speeds used. An apparent freezing point for a condition of no supercooling was calculated, estimating the highest temperature at which skin freezes at a given wind speed. The validity of the obtained differences in apparent freezing point was tested by an analysis of covariance. Although not statistically significant, the data suggest that the apparent freezing point with no supercooling decreases with increasing wind velocity. The highest calculated apparent freezing point at -15 degrees C and 6.8 m/s was 1.2 degrees C lower than the true freezing point for skin previously determined in brine, which is a statistically significant difference.     

Percolation Induced Heat Transfer in Deep Unsaturated Zones

Subsurface temperature data from a borehole located in a desert wash were measured and used to delineate the conductive and advective heat transfer regimes, and to estimate the percolation quantity associated with the 1997–1998 El Ni?o precipitation. In an arid environment, conductive heat transfer dominates the variation of shallow subsurface temperature most of the time, except during sporadic precipitation periods. The subsurface time-varying temperature due to conductive heat transfer is highly correlated with the surface atmospheric temperature variation, whereas temperature variation due to advective heat transfer is strongly correlated with precipitation events. The advective heat transfer associated with precipitation and infiltration is the focus of this paper. Disruptions of the subsurface conductive temperature regime, associated with the 1997–1998 El Ni?o precipitation, were detected and used to quantify the percolation quantity. Modeling synthesis using a one-dimensional coupled heat and unsaturated flow model indicated that a percolation per unit area of 0.7 to 1.3 m height of water in two weeks during February 1998 was responsible for the observed temperature deviations down to a depth of 35.2 m. The reported study demonstrated quantitatively, for the first time, that the near surface temperature variation due to advective heat transfer can be significant at a depth greater than 10 m in unsaturated soils and can be used to infer the percolation amount in thick unsaturated soils.