Using the Sum of Roots and Its Application to a Control Design Problem

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Studies on the Power Requirement of Mixing Impellers (IV) : Empirical Equations Applicable for a Wide Range

The present authors have already reported on the empirical equations for the power requirement of paddle agitators. In this report, equations for the three ranges of high, medium, and low viscosity were made and equations for the maximum power required under fully baffled conditions were also formed separately. Although the results are accurate, these equations are not always convenient because of the complexity in deciding which form to be used. On the basis of a reasonable assumption derived from the essential concept of power consumption, the authors derived an empirical equation which covers wide ranges of power data as follows : Nₚ=A/Rₑ + B(10³+1.2Rₑ⁰.⁶⁶/10³+3.2Rₑ⁰.⁶⁶)ᵖ(H/D)⁽⁰.³⁵⁺ᵇ/ᴰ⁾ (sinθ)¹.² (27) where A=14+(b/D){670(d/D-0.6)²+185} (19) B=10{1.3-4(b/D-0.5)²-1.14(d/D)} (22) p=1.1+4(b/D)-2.5(d/D-0.5)²-7(b/D)⁴ (23) The maximum power consumption of paddle agitators can also be calculated by Eq. (27) by substituting Re with the values of Rc and Rθ which can be obtained by the following equations : For the paddle having a blade angle of 90°, Rc=25/(b/D)(d/D-0.4)²+{b/D0.11(b/D)-0.0048} (28) For the paddle having an arbitrary angle of θ, Rθ=10⁴(1-sinθ)Rc (30) Fairly good agreements were obtained between those values calculated by the equations and those obtained by the experiments

Factor Analysis of Damage to Small Earth Dams Due to the 1995 Hyogoken-Nambu Earthquake

Damage to small earth dams due to the Hyogoken-Namby Earthquake of January 17, 1995 is discussed. Investigations of 266 dams were conducted in the area where the JMA seismic intensity was 5 or higher, and which were located within about 50 kilometers from the earthquake source fault. Small earth dams suffered various forms of damage such as longitudinal cracking, transverse cracking, settlement and deformation of the dam body. The damage to small earth dams was classified into five grades from no damage to severe damage such as a complete failure. The damage grade was analyzed by several factors such as distance from the fault, topography and geology, intensity of quake motion, direction of dam axis against the fault, year of completion, and height of dam. The characteristics of factors affecting damage to small earth dams were evaluated