scholarly journals Electrostatic Fragmentation of Irregularly Shaped Particles

1991 ◽  
Vol 126 ◽  
pp. 371-374
Author(s):  
Tadashi Mukai
Keyword(s):  
Spherical Particle ◽  
Small Radius ◽  
Radius Of Curvature ◽  
The Earth ◽  
Shaped Particle ◽  
Charge Concentration ◽  
Electrostatic Stress

AbstractAn enhancement of the electrostatic stress forces due to the charge concentration on a position with small radius of curvature on the surface of irregularly shaped particle causes the fragmentation of fluffy particle more than expected for a spherical particle. This mechanism may act to produce “dust clusters” as detected in comet P/Halley by Simpsonet al.(1987) and also “dust swarms” near the Earth as reported in Fechtig(1982).

scholarly journals The relation between wind velocity at 1000 metres altitude and the surface pressure distribution

1908 ◽  
Vol 80 (540) ◽  
pp. 436-443 ◽  
Keyword(s):  
Angular Velocity ◽  
Pressure Distribution ◽  
Wind Velocity ◽  
Centrifugal Force ◽  
Surface Pressure ◽  
Atmospheric Pressure ◽  
Horizontal Motion ◽  
Radius Of Curvature ◽  
Surface Pressure Distribution ◽  
The Earth

For the steady horizontal motion of air along a path whose radius of curvature is r , we may write directly the equation (ω r sin λ ± v ) 2 / r = 1/ρ ∂ p / ∂ r +(ω r sin λ ) 2 / r , expressing the fact that the part of the centrifugal force arising from the motion of the wind is balanced by the effective gradient of pressure. In the equation p is atmospheric pressure, ρ density, v velocity of moving air, λ is latitude, and ω is the angular velocity of the earth about its axis.

Lasing from the domain of collision of ionisation waves produced due to electric field concentration at electrodes with a small radius of curvature

2011 ◽  
Vol 41 (12) ◽  
pp. 1098-1103 ◽  
Author(s):  
Viktor F Tarasenko ◽  
A E Tel'minov ◽  
A G Burachenko ◽  
D V Rybka ◽  
E Kh Baksht ◽  
...  
Keyword(s):  
Electric Field ◽  
Small Radius ◽  
Radius Of Curvature

Preparation and Field Emission Properties of Ag-CNTs by Electroless Plating

2010 ◽  
Vol 148-149 ◽  
pp. 983-986 ◽  
Author(s):  
Yu Xiang You ◽  
Yun Ye ◽  
Yi Jing Su ◽  
Qiao Zhi Tang ◽  
Tai Liang Guo
Keyword(s):  
Carbon Nanotubes ◽  
Field Emission ◽  
Electroless Plating ◽  
Emission Current Density ◽  
Small Radius ◽  
Radius Of Curvature ◽  
Emission Properties ◽  
Field Emission Properties ◽  
Pristine Cnts ◽  
Electrophoresis Deposition

Carbon nanotubes (CNTs) demonstrate attractive characteristics as cold cathode emitters for high aspect ratio, small radius of curvature, high mechanical strength and chemical stability. In this article, Ag-CNTs were prepared by a series of processes including acid-treating, sensitizing, activating and electroless plating. Then Ag-CNTs cathode were sucessfully fabricated by electrophoresis deposition (EPD) method. The morphologies of Ag-CNTs cathode and pristine CNTs cathode were observed by scanning electron microscopy (SEM). The results showed that the field emission properties of Ag-CNTs cathode were better than pristine CNTs cathode, for presenting lower turn-on field, larger emission current density, more stabilization and longer lifetime. Thus it can be seen that the Ag-CNTs cathode can improve the characteristics of carbon nanotubes field emission display (CNT-FED).

scholarly journals COMPARATIVE ANALYSIS OF MAMMALIAN SPERM MOTILITY

1972 ◽  
Vol 53 (2) ◽  
pp. 561-573 ◽  
Author(s):  
David M. Phillips
Keyword(s):  
High Speed ◽  
Mammalian Species ◽  
Chinese Hamster ◽  
Small Radius ◽  
Radius Of Curvature ◽  
Large Radius ◽  
Cross Sectional ◽  
Mammalian Sperm ◽  
High Speed Cinematography ◽  
Pass Through

Spermatozoa of several mammalian species were studied by means of high-speed cinematography and electron microscopy. Three types of motile patterns were observed in mouse spermatozoa. The first type involved an asymmetrical beat which seemed to propel the sperm in circular paths. The second type involved rotation of the sperm and appeared to allow them to maintain straight paths. In the third type of pattern, the sperm appeared to move by crawling on surfaces in a snakelike manner. Spermatozoa of rabbit and Chinese hamster also had an asymmetrical beat which sometimes caused them to swim in circles. In spite of the asymmetry of the beat, these spermatozoa were also able to swim in straight paths by rotating around a central axis as they swam. Spermatozoa of some species appeared very flexible; their flagella formed arcs with a very small radius of curvature as they beat. Spermatozoa of other species appeared very stiff, and their flagella formed arcs with a very large radius of curvature. The stiffness of the spermatozoan appeared to correlate positively with the cross-sectional area of the dense fibers. This suggests that the dense fibers may be stiff elastic elements. Opossum sperm become paired as they pass through the epididymis. Pairs of opossum spermatozoa beat in a coordinated, alternating manner.

Application of Parallel Indexing Cam Design Software Platform in Intermittent Mechanism Designing of Die-Cutting Machine

2010 ◽  
Vol 174 ◽  
pp. 303-306 ◽  
Author(s):  
Xiang Dong Shi ◽  
Shao Hua Shen ◽  
Cheng Wen Chai
Keyword(s):  
Small Radius ◽  
Radius Of Curvature ◽  
Software Platform ◽  
Design Quality ◽  
Excessive Pressure ◽  
Improve Design ◽  
Cam Mechanism ◽  
Cam Design ◽  
Cutting Machine ◽  
Cam Profile

The formation of parallel indexing cam profile was described in detail with the calculation of the cam profile data. With VB as the software platform, the parallel indexing cam contour was calculated, the contour mapping was also displayed, and the data was saved as required format. Then a three-dimensional entity of the parallel indexing cam mechanism is drawn up directly in SolidWorks in order to perform the 3D parameterization design and motion emulation of the parallel indexing cam mechanism. This can help designers to find the problems, such as the rotation difficulties caused by excessive pressure angle, the motion distortion caused by small radius of curvature. So the designer can make modification in time to improve design quality and shorten the product development cycles. The software platform can select type of the interval splitter by calculating and selecting the power motor according to the input drive shaft angle and the output shaft such shares. The system could perform the transmission of information and share the information between subsystems, enhancing the degree of integration and automation of parallel indexing cam design and manufacture. A good software platform was developed for parallel indexing cam mechanism’s design, manufacturing and performance studying. Finally, the example of interval paper-feed mechanism in an automatic die-cutting machine was verified the usability and effectiveness of the software platform.

scholarly journals Experimental and Numerical Investigation on the Bearing Behavior of Curved Continuous Twin I-Girder Composite Bridge with Precast Concrete Slab

2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Chuandong Shen ◽  
Yifan Song ◽  
Lei Yan ◽  
Yuan Li ◽  
Xiaowei Ma ◽  
...  
Keyword(s):  
Yield Strength ◽  
Bearing Capacity ◽  
Ultimate Load ◽  
Ultimate Bearing Capacity ◽  
Experimental Result ◽  
Small Radius ◽  
Radius Of Curvature ◽  
Construction Scheme ◽  
Composite Bridge ◽  
Bearing Behavior

Curved twin I-girder composite bridge (TGCB) is becoming popular in Chinese highway bridge building. To study its ultimate bearing behavior, in this paper, one 1 : 5 scale intact model of a two-span curved continuous TGCB was tested to failure to evaluate its safety reserve and ductility. Afterwards, based on the experimental result, 3D FE models were developed and validated. At last, using the validated 3D FE models, the effect of construction scheme, radius of curvature, yield strength of steel, concrete compressive strength, crossbeams, and bottom lateral bracings on the ultimate bearing capacity were examined. The experimental results showed that the ultimate load (Pu) is approximate 13.6 times the service equivalent load. The cracking load and yielding load are approximately 0.12 and 0.47 Pu, respectively. The ductility coefficients are 4.06∼4.40. These above may indicate that the TGCB designed according to Chinese codes has good safety reserve and ductility. From parameter analysis results, it was concluded that the TGCB with full-support construction scheme has larger yield load and ultimate load compared with the one with erecting machine construction scheme. On the other hand, the ultimate bearing capacity reduces nonlinearly with the increase of curvature. Besides, the yield strength of steel, crossbeams, and bottom lateral bracings has a significant effect on the ultimate bearing capacity of curved TGCB. And the smaller the radius of curvature, the more obvious the effect of the latter two factors is. Unfortunately, it is unwise to continuous to improve the ultimate load by increasing the grade of steel for the TGCB when steel grade exceeds Q390. Moreover, in consideration of the big difference in bearing capacity between the inner girder and outer girder of the TGCB with small radius of curvature as well as the economy, it is suggested that the inner and outer steel girders of that TGCB should be designed differently.

scholarly journals Ground Deformation Characteristics Induced by Mechanized Shield Twin Tunnelling along Curved Alignments

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Dangzhong Wu ◽  
Kaiping Xu ◽  
Panpan Guo ◽  
Gang Lei ◽  
Kang Cheng ◽  
...  
Keyword(s):  
Ground Deformation ◽  
Three Dimensional ◽  
Ground Surface ◽  
Small Radius ◽  
Radius Of Curvature ◽  
Deformation Characteristics ◽  
Ground Deformations ◽  
Ground Surface Settlement ◽  
Tunnel Alignment ◽  
3D Finite Element Method

This paper investigates the ground deformation characteristics induced by mechanized shield twin tunnelling along curved alignments by adopting the nonlinear three-dimensional (3D) finite element method (FEM). The performance of the adopted FEM is demonstrated to be satisfactory by comparing the numerical analysis results with the field monitoring data in a typical case history and with the predicted results generated by a modified version of the Peck’s empirical Gaussian formula. It has been found that the tunnelling-induced transverse ground surface settlement troughs and the distributions of the subsurface horizontal and vertical ground displacements are mostly similar in both form and magnitude for the considered various radii of curvature of tunnel alignment including 50 m, 100 m, 150 m, 200 m, 250 m, 300 m, 400 m, and infinity (i.e., straight-line tunnel). Considering the variational characteristics of the ground deformations with the magnitude of the radius of curvature, the radius of curvature of 100 m can be regarded as a critical tunnel alignment radius of curvature controlling the transformation of the curved tunnelling-induced ground deformational behaviors. For the benefit of geotechnical engineers interested in curved tunnelling with a small radius of curvature, a discussion of the technologies for reducing the overexcavation and improving the accuracy of tunnel lining segment installation is also presented.

Fracture-Directed Steerable Needles

2019 ◽  
Vol 04 (01) ◽  
pp. 1842002 ◽  
Author(s):  
Fan Yang ◽  
Mahdieh Babaiasl ◽  
John P. Swensen
Keyword(s):  
Lower Bound ◽  
Soft Tissues ◽  
Target Location ◽  
Needle Insertion ◽  
Small Radius ◽  
Radius Of Curvature ◽  
Step Size ◽  
Tissue Phantoms ◽  
Kinematic Models ◽  
Steerable Needles

Steerable needles hold the promise of improving the accuracy of both therapies and biopsies as they are able to steer to a target location around obstructions, correct for disturbances, and account for movement of internal organs. However, their ability to make late-insertion corrections has always been limited by the lower bound on the attainable radius of curvature. This paper presents a new class of steerable needle insertion where the objective is to first control the direction of tissue fracture with an inner stylet and later follow with the hollow needle. This method is shown to be able to achieve radius of curvature as low as 6.9[Formula: see text]mm across a range of tissue stiffnesses and the radius of curvature is controllable from the lower bound up to a near infinite radius of curvature based on the stylet/needle step size. The approach of “fracture-directed” steerable needles indicates the promise of the technique for providing a tissue-agnostic method of achieving high steerability that can account for variability in tissues during a typical procedure and achieve radii of curvature unattainable through current bevel-tipped techniques. A variety of inner stylet geometries are investigated using tissue phantoms with multiple stiffnesses and discrete-step kinematic models of motion are derived heuristically from the experiments. The key finding presented is that it is the geometry of the stylet and the tuning of the bending stiffnesses of both the stylet and the tube, relative to the stiffness of the tissue, that allow for such small radius of curvature even in very soft tissues.

scholarly journals Identification of Apical and Cervical Curvature Radius of Human Molars

2015 ◽  
Vol 26 (4) ◽  
pp. 351-356 ◽  
Author(s):  
Carlos Estrela ◽  
Mike R. Bueno ◽  
Fernando B. Barletta ◽  
Orlando A. Guedes ◽  
Olavo C. Porto ◽  
...  
Keyword(s):  
Sagittal Plane ◽  
Small Radius ◽  
Radius Of Curvature ◽  
Curvature Radius ◽  
Large Radius ◽  
Chi Square ◽  
Root Canals ◽  
Plane Analysis ◽  
Chi Square Test ◽  
Curved Root Canals

<p>To determine the frequency of apical and cervical curvatures in human molars using the radius method and cone-beam computed tomography (CBCT) images. Four hundred images of mandibular and maxillary first and second molars were selected from a database of CBCT exams. The radius of curvature of curved root canals was measured using a circumcenter based on three mathematical points. Radii were classified according to the following scores: 0 - straight line; 1 - large radius (r>8 mm, mild curvature); 2 - intermediate radius (r>4 and r<8 mm, moderate curvature); and 3 - small radius (r≤4 mm, severe curvature). The frequency of curved root canals was analyzed according to root canal, root thirds, and coronal and sagittal planes, and assessed using the chi-square test (significance at α=0.05). Of the 1,200 evaluated root canals, 92.75% presented curved root canals in the apical third and 73.25% in the cervical third on coronal plane images; sagittal plane analysis yielded 89.75% of curved canals in the apical third and 77% in the cervical third. Root canals with a large radius were significantly more frequent when compared with the other categories, regardless of root third or plane. Most root canals of maxillary and mandibular first and second molars showed some degree of curvature in the apical and cervical thirds, regardless of the analyzed plane (coronal or sagittal).</p>

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