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TEMPORAL AND SPATIAL VARIATION OF WATER TEMPERATURE IN PROCESS OF DESTRATIFICATION IN LAKES
No full textTemporal and spatial variation of water temperature was measured in a lake by using three different probes. A P-probe has seven sensors for depth, temperature, light attenuation due to sediment concentration, solar radiation and so on. Temperature fluctuations were compared between the moving and fixed P-probes.Period of these fluctuations ranges from several seconds to some tens of seconds and seems to be higher components of internal wave of the maximum buoyancy frequency. T-probe as a vertical array of thermistors, also showed a patchy structure consisting of eddies of a few centimeter likely due to the cellular motion, which was verified in the other shallow lake during the previous measurements. Discussing the stability parameters, the current field in the vertical during the measurements was proved to be on the critical stability condition.Temporal and spatial variation of water temperature was measured in a lake by using three different probes. A P-probe has seven sensors for depth, temperature, light attenuation due to sediment concentration, solar radiation and so on. Temperature fluctuations were compared between the moving and fixed P-probes.Period of these fluctuations ranges from several seconds to some tens of seconds and seems to be higher components of internal wave of the maximum buoyancy frequency. T-probe as a vertical array of thermistors, also showed a patchy structure consisting of eddies of a few centimeter likely due to the cellular motion, which was verified in the other shallow lake during the previous measurements. Discussing the stability parameters, the current field in the vertical during the measurements was proved to be on the critical stability condition
MEASUREMENTS OF DESTRATIFICATION IN A SHALLOW LAKE USING THE THERMISTOR GRIDS
No full textTemperature fluctuations due to interfacial waves were measured in a shllow lake using the thermistor grids. The waves as roughness on the deformable density interface were observed between the basic internal wave of the maximum buoyant frequency and the surface wind ripples.On the transition from smooth to rough interface, where frequency spectrum shows an inertial subrange, beyond which the viscous-convective subrange is seen as mixing goes on.The waves are generated from amplified internal wave, and wind waves copy themselves on the interface through the resonance with much slower interfacial ones.Diffusivity takes the peak at the bottom of thermocline, and for such a diffusivity profile, the log+linear law for temperature was deduced.Assuming the system is non-rotating, a profile model considering the wave steepness is shown, which estimates the flux as well as the diffusivity, and the former was compared well with the measured flux.Superimposing the first few modes of the cellular motion, the fluctuation of buoyancy in vertical was found similar with the measured one.Temperature fluctuations due to interfacial waves were measured in a shllow lake using the thermistor grids. The waves as roughness on the deformable density interface were observed between the basic internal wave of the maximum buoyant frequency and the surface wind ripples.On the transition from smooth to rough interface, where frequency spectrum shows an inertial subrange, beyond which the viscous-convective subrange is seen as mixing goes on.The waves are generated from amplified internal wave, and wind waves copy themselves on the interface through the resonance with much slower interfacial ones.Diffusivity takes the peak at the bottom of thermocline, and for such a diffusivity profile, the log+linear law for temperature was deduced.Assuming the system is non-rotating, a profile model considering the wave steepness is shown, which estimates the flux as well as the diffusivity, and the former was compared well with the measured flux.Superimposing the first few modes of the cellular motion, the fluctuation of buoyancy in vertical was found similar with the measured one
CURRENT IN THE SOUTHERN BASIN OF LAKE BIWA-TIME VARIATIONS OF THE WIND-DRIVEN CURRENTS-
No full textAt the fixed station in Lake Biwa, 123 profiles of the current, wind, air and watertemperatures were measured in every 10-20 minutes within the two periods. Magnitude ofthe wind-driven current is largely affected by stability condition; steeper gradients andlarger deflections of surface current were observed in stable stratification due to radiation.The former is found to be well described by the shear function used in meteorology. Theroughness decreases as wind increases, and smooth conditions are to be proved. Thecurrent consists of the viscous sublayer, log-linear and bottom regions. Extending theeffective viscosity to the hydraulically rough conditions with use of the analogy betweenthe shear function and the effective viscosity, a resistance law is derived from that for pipeflows.At the fixed station in Lake Biwa, 123 profiles of the current, wind, air and watertemperatures were measured in every 10-20 minutes within the two periods. Magnitude ofthe wind-driven current is largely affected by stability condition; steeper gradients andlarger deflections of surface current were observed in stable stratification due to radiation.The former is found to be well described by the shear function used in meteorology. Theroughness decreases as wind increases, and smooth conditions are to be proved. Thecurrent consists of the viscous sublayer, log-linear and bottom regions. Extending theeffective viscosity to the hydraulically rough conditions with use of the analogy betweenthe shear function and the effective viscosity, a resistance law is derived from that for pipeflows
CURRENTS IN THE SOUTHERN BASIN OF LAKE BIWA-VERTICAL DISTRIBUTIONS OF CURRENT VELOCITY AND TURBIDITY-
No full textVelocity profiles of two-dimensional wind-driven current were measured in Lake Biwa. Thebottom stress was estimated from a vertical momentum analysis. Comparing the measuredprofiles of turbidity with the equilibrium concentration distributions of fine suspended sediment, it is found that the sediment particles of 10-15 Mm settle down under the ordinary wind condition.The equilibrium distribution is formed when the wind speed exceeds 5 m/s.Velocity profiles of two-dimensional wind-driven current were measured in Lake Biwa. Thebottom stress was estimated from a vertical momentum analysis. Comparing the measuredprofiles of turbidity with the equilibrium concentration distributions of fine suspended sediment,it is found that the sediment particles of 10-15 Mm settle down under the ordinary wind condition.The equilibrium distribution is formed when the wind speed exceeds 5 m/s
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
DEFLECTION AND RESISTANCE IN LAKE CURRENTS
No full textFrom the mesurement of wind-driven current in shallower part of Lake Biwa, itwas verified stable stratification makes the current profile significant. Another effectof stratification is the deflection in the surface current. Considering that these factsare explained as the reduction of the eddy viscosity, the basic effect of the Ekmannumber was detected in pipe flow experiments. Eddy diffusivities were evaluatedfrom the field data and the profile of the coeficient in neutral case and the variationdue to the temperature stratification. Estimating the surface Rossby number R*=u*/fL, significant deflection occurs arround R*=10, where L is the Monin-Obukhovlength, f Coriolis parameter. The destratification is regarded as a typical en-trainment process to the neutral state, on which the deflection occurs. The resultssuggest diurnal patterns of diffusion exist in lakes.From the mesurement of wind-driven current in shallower part of Lake Biwa, itwas verified stable stratification makes the current profile significant. Another effectof stratification is the deflection in the surface current. Considering that these factsare explained as the reduction of the eddy viscosity, the basic effect of the Ekmannumber was detected in pipe flow experiments. Eddy diffusivities were evaluatedfrom the field data and the profile of the coeficient in neutral case and the variationdue to the temperature stratification. Estimating the surface Rossby number R*=u*/fL, significant deflection occurs arround R*=10, where L is the Monin-Obukhovlength, f Coriolis parameter. The destratification is regarded as a typical en-trainment process to the neutral state, on which the deflection occurs. The resultssuggest diurnal patterns of diffusion exist in lakes
EXPERIMENTS ON THE THREE-DIMENSIONAL PHENOMENA IN DENSITY CURRENTS
No full textA series of experiments on the interfacial waves which emerge within the transitionalrange between laminar and turbulent flow was conducted. These waves have well describedtwo-dimensional chracteristics such as the steep configuration and cusped breaking.In this study, the interfacial visualization of lock exchange flow was achieved by thechemical reaction. The size of the interfacial waves tends to become smaller with the decreasein the inner scale of boundary layer. Common features between interfacial structure of thestratified flow and wall boundary layers are discussed.Besides the above features, another phenomenon is found in the curved channels, wheresecondary currents in the upper layer maintain the outer side mixing layer very thin.A series of experiments on the interfacial waves which emerge within the transitionalrange between laminar and turbulent flow was conducted. These waves have well describedtwo-dimensional chracteristics such as the steep configuration and cusped breaking.In this study, the interfacial visualization of lock exchange flow was achieved by thechemical reaction. The size of the interfacial waves tends to become smaller with the decreasein the inner scale of boundary layer. Common features between interfacial structure of thestratified flow and wall boundary layers are discussed.Besides the above features, another phenomenon is found in the curved channels, wheresecondary currents in the upper layer maintain the outer side mixing layer very thin
CORIOLIS' EFFECTS ON DENSITY CURRENTS (2)-Experiment on the Rotating Exchange Flow-
No full textIn order to clarify the effects of Coriolis' force on density currents in estuaries and lakes, experiments of rotating lock exchange flow were carried out under the condition of Reynoldsnumber Ro=140～1400, Rossby number Ro=O.14～11.8 and Ekman number Ev=2.4x10 -4～2.Ox10 -2.Discharge reduction in the underflow, transverse deviation of the underflow (salt water)fronts and increase of the front velocity were observed under rotating condition, and criterionof rotating regime is estimated from the discharge reduction as Ro-4.0. For the strongrotaing regime Ro<1, it was found that inviscid rotating hydraulics could be applied tothe flow in Ev<O(10-3). The effects of Ro and Ev on the exchange flow are evaluated fromthree kinds of time 1/f, b/V⊿ and H2/ν, where f; Coriolis' parameter, b; breadth of thebasin, V⊿=√g'H ; densimetric velocity, g'; reduced gravity accelaration, H ; the depth, ν;kinematic (eddy) viscosity.The characteristics of mixing layer of lock exchange flow and effects of abrupt channelexpansion on density currents are briefly discussed on the basis of experimental results bymeans of a new flow visualization technique.In order to clarify the effects of Coriolis' force on density currents in estuaries and lakes,experiments of rotating lock exchange flow were carried out under the condition of Reynoldsnumber Ro=140～1400, Rossby number Ro=O.14～11.8 and Ekman number Ev=2.4x10 -4～2.Ox10 -2.Discharge reduction in the underflow, transverse deviation of the underflow (salt water)fronts and increase of the front velocity were observed under rotating condition, and criterionof rotating regime is estimated from the discharge reduction as Ro-4.0. For the strongrotaing regime Ro<1, it was found that inviscid rotating hydraulics could be applied tothe flow in Ev<O(10-3). The effects of Ro and Ev on the exchange flow are evaluated fromthree kinds of time 1/f, b/V⊿ and H2/ν, where f; Coriolis' parameter, b; breadth of thebasin, V⊿=√g'H ; densimetric velocity, g'; reduced gravity accelaration, H ; the depth, ν;kinematic (eddy) viscosity.The characteristics of mixing layer of lock exchange flow and effects of abrupt channelexpansion on density currents are briefly discussed on the basis of experimental results bymeans of a new flow visualization technique
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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