scholarly journals NMR shim coil design utilising a rapid spherical harmonic calculation method

2002 ◽  
Vol 43 (3) ◽  
pp. 375-386 ◽  
Author(s):  
C. J. Snape-Jenkinson ◽  
S. Crozier ◽  
L. K. Forbes
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Cross Section ◽  
Calculation Method ◽  
Spherical Harmonic ◽  
Design Method ◽  
Rectangular Cross Section ◽  
Coil Design ◽  
Circular Arc ◽  
Tesseral Harmonics ◽  
Shim Coils

AbstractA rapid spherical harmonic calculation method is used for the design of Nuclear Magnetic Resonance shim coils. The aim is to design each shim such that it generates a field described purely by a single spherical harmonic. By applying simulated annealing techniques, coil arrangements are produced through the optimal positioning of current-carrying circular arc conductors of rectangular cross-section. This involves minimizing the undesirable harmonics in relation to a target harmonic. The design method is flexible enough to be applied for the production of coil arrangements that generate fields consisting significantly of either zonal or tesseral harmonics. Results are presented for several coil designs which generate tesseral harmonics of degree one.

Measurement and analysis of three-dimensional flow in a centrifugal fan volute with large volute width and rectangular cross-section

2006 ◽  
Vol 220 (2) ◽  
pp. 133-153 ◽  
Author(s):  
D Qi ◽  
Y Zhang ◽  
S Wen ◽  
Q Liu
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Design Method ◽  
Rectangular Cross Section ◽  
Three Dimensional ◽  
Centrifugal Fan ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Flow Parameters ◽  
Flow Phenomena

Among all the elements of a centrifugal fan, the volute is the one that has the lowest flow efficiency. Therefore, improving the performance of the volute is an efficient way to improve the total performance of a centrifugal fan. To contribute a better understanding of the flow structure in the fan volute, the three-dimensional flow in a centrifugal fan volute with a large volute width and rectangular cross-section has been measured in detail by means of five-hole probe at three different flowrates. The time-average swirling and throughflow velocity, static and total pressure distributions on eight cross-sections in the throughflow direction of the volute are presented. The results show the formation and development of the flow in the fan volute of this type, indicate the variation of flow parameters, and discover some peculiar flow phenomena different from the traditional understanding. On the basis of the experimental results, the main hydraulic losses in this kind of fan volute have been preliminarily classified and analysed. The results show that the traditional one-dimensional design method of the volute should be further improved as it is only based on the law of momentum moment conservation and the ideal assumption that the distribution of flow parameters are uniform at the volute inlet.

scholarly journals Strength of cast-in-place slabs for rectangular cross-section columns punching

2021 ◽  
Vol 263 ◽  
pp. 02035
Author(s):  
Andrey Istomin ◽  
Maksim Kudryavtsev
Keyword(s):  
Cross Section ◽  
Experimental Research ◽  
Design Method ◽  
Rectangular Cross Section ◽  
Concrete Slabs ◽  
Slab Thickness ◽  
Test Results ◽  
Short Side ◽  
Flat Slabs ◽  
Reinforced Concrete Slabs

Flat slabs in contemporary buildings are most commonly supported by rectangular cross-section columns. Research of slabs supported by rectangular cross-section columns for punching is rather narrow. The purpose of this work was the experimental research of slabs punching by rectangular cross-section columns and adjustment of their design method. Reinforced concrete slabs 6 cm in thickness without transverse reinforcement were used as testing specimens. During tests load on the slab was transferred using stamps. Side ratios for stamps varied from 1 to 5 in experiments. Strength and strain properties of concrete were determined before slabs testing for punching. Ultimate loads, that resulted in slab punching, were acquired from test results. Formulae for punching load are suggested for rectangular cross-section columns punching based on obtained results. Generalized analysis of experimental research results shows that slab strength for punching is also influenced by short side of rectangular cross-section to slab thickness ratio.

scholarly journals Designing for People’s Safety on Flooded Streets: Uncertainties and the Influence of the Cross-Section Shape, Roughness and Slopes on Hazard Criteria

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2119
Author(s):  
Luís Mesquita David ◽  
Rita Fernandes de Carvalho
Keyword(s):  
Cross Section ◽  
Overland Flow ◽  
Rectangular Cross Section ◽  
Safety Hazard ◽  
Cross Section Shape ◽  
Section Shape ◽  
Flood Flows ◽  
The Cross ◽  
Flooding Risk

Designing for exceedance events consists in designing a continuous route for overland flow to deal with flows exceeding the sewer system’s capacity and to mitigate flooding risk. A review is carried out here on flood safety/hazard criteria, which generally establish thresholds for the water depth and flood velocity, or a relationship between them. The effects of the cross-section shape, roughness and slope of streets in meeting the criteria are evaluated based on equations, graphical results and one case study. An expedited method for the verification of safety criteria based solely on flow is presented, saving efforts in detailing models and increasing confidence in the results from simplified models. The method is valid for 0.1 m2/s 0.5 m2/s. The results showed that a street with a 1.8% slope, 75 m1/3s−1 and a rectangular cross-section complies with the threshold 0.3 m2/s for twice the flow of a street with the same width but with a conventional cross-section shape. The flow will be four times greater for a 15% street slope. The results also highlighted that the flood flows can vary significantly along the streets depending on the sewers’ roughness and the flow transfers between the major and minor systems, such that the effort detailing a street’s cross-section must be balanced with all of the other sources of uncertainty.

scholarly journals Analysis of Seepage Characteristics of a Foundation Pit with Horizontal Waterproof Curtain in Highly Permeable Strata

Water ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1303
Author(s):  
Chenghua Shi ◽  
Xiaohe Sun ◽  
Shengli Liu ◽  
Chengyong Cao ◽  
Linghui Liu ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Theoretical Calculation ◽  
Calculation Method ◽  
Design Method ◽  
Water Pressure ◽  
Water Inflow ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit ◽  
Seepage Characteristics

At present, jet-grouted horizontal waterproof curtain reinforcement has become an essential method for deep foundation pit groundwater control. However, there is still a lack of an effective theoretical calculation method for horizontal waterproof curtain reinforcement, and there is little research on the seepage laws of foundation pits under different horizontal waterproof curtain conditions. Based on Darcy’s seepage theory, theoretical analysis models of deep foundation pit seepage were established considering the effect of a horizontal curtain in a highly permeable formation. Through the established models, the calculation method of the water inflow and the water pressure under the condition of a horizontal curtain was derived. Then through indoor tests, the reliability of the theoretical calculation method was verified. Furthermore, the established theoretical calculation method is used to analyze the influence of various factors on the water inflow and the water pressure, such as the ratio of hydraulic conductivity of the horizontal curtain to surrounding soil, thickness, and reinforcement position of the horizontal curtain. It is found that the hydraulic conductivity ratio has the most significant influence on the seepage characteristics of the foundation pit. Finally, the design method was applied to an example of the horizontal waterproof curtain of the foundation pit, which is located at Juyuanzhou Station in Fuzhou (China). The water inflow per unit area is 0.36 m3/d in the foundation pit, and this implies that the design method of the horizontal waterproof curtain applied for the excavation case is good and meets the requirements of design and safety.

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