Simple Twist Research Articles

Statistical Study on Compression Flange Plates

This paper summarizes the reduced ultimate strength of the compression flange of plate girders containing initial deflection. The major findings are as follows: There is no interrelation between the maximum initial deflection and plate dimension such as width, thickness or width‐thickness ratio of the flange. The slenderness parameter of plate, R, a function of the widththickness ratio, and the aspect ratio, are the two factors reducing the ultimate strength. The ultimate strength is minimum with the aspect ratio in the range of 2 to 3. However, the reducing effect does not increase when the aspect ratio is beyond 3. Among the three initial deflection modes—plate bending, cylindrical bending and simple twisting, the simple twisting has the least effect. R=0.9 is the most sensitive value to the initial deflection in reducing the ultimate strength. A procedure has been established to obtain expected and theoretical ultimate strength by a probability density function through Weibull distribution or Gamma distribution.

Topotactic lithium reactions with ReO3 related shear structures

Several examples of compounds with the ReO3 structure and shear structures derived from it have been lithiated using n-BuLi. Lithiation of ReO3 results in two new hexagonal compositions LiReO3 and Li2ReO3 which are related to cubic ReO3 by a simple twist of the structure. The extensively edge shared structured of FeV3O8 forms Li2FeV3O8 which contains a similar amount of lithium on a per cavity basis, but cannot undergo this type of twist. Results on similar compounds are also discussed.

FFT as Nested Multiplication, with a Twist

A simple, yet complete and detailed description of the fast Fourier transform for general N is given with the aim of making the underlying idea quite apparent. To help with this didactic goal, a simple twist, i.e., a shifting of information from rows to columns during the calculations, is introduced which allows us to give a simple meaning to intermediate results and assures that the final results need no further reordering.

Part 3. Present plate boundary and its evolution in the New Zealand region: New Zealand 60 m.y. ago

Rigid plate theory has been highly successful in explaining the origin of the oceans, but far less so in explaining the twisted rock belts of the continents. The New Zealand region is the smallest of the continents, and its rocks have a fairly simple twist, which is well mapped and has been termed a recurved arc. Can New Zealand be straightened out while keeping the ocean floor rigid? The following is a preliminary attempt.

69—THE MECHANICS OF SELF-PLYING STRUCTURES. PART I: MONOFILAMENT STRANDS

Analyses of the mechanics of self-plying structures developed for monofilament strands are presented, and an account is given of the experimental verification, by means of the use of rubber strands in simple twisting and plying experiments, of theoretical predictions of the extent of self-plying twist on the basis of monofilament pre-twist and filament properties.

A Criterion for Ductile Fracture in Mild Steels

A criterion of the ductile fracture of mild steels is investigated from the view point of mathematical theory of plasticity.Round bar test specimens are brought to fracture, some under simple tension, some others under simple twist and the rest prestrained under tension and then twisted. The true stress-strain curves at the very point of fracture initiation are carefully examined and correlations between fracture criteria for different stress states are investigated.As the conclusion the criterion is best expressed by the amount of slip energy on the fracture plane. To evaluate the amount of slip energy from a stress-strain curve it is neccessary to make use of the concept of slip theory of plasticity, which constructs plastic strains from integration of infinitesimal slips on every planes. The slip theory is suitable to evaluate the slip energy on any single plane from a stress-strain relation. On the other side another theories of plasticity are not appropriate to distinguish the slip energy on a particular plane from the total plastic strain energy which has no direct relation to the ductile fracture.

Topological Dissipation and the Small-Scale Fields in Turbulent Gases

It is shown that a large-scale magnetic field possesses a hydrostatic equilibrium only if the pattern of small-scale variations is uniform along the large-scale field. Thus equilibrium obtains only if the variations in the field consist of simple twisting of the lines, with the twists extending uniformly the full length of the field. Any more complicated topology, such as two or more flux tubes wrapped around each other to form a rope, or braided or knotted flux tubes, is without equilibrium, no matter what fluid pressures are applied along the individual lines of force. The result is rapid dissipation and field-line merging, which quickly reduces the topology to the simple equilibrium form. The effect explains the absence of strong small-scale fields in the solar photosphere and in interstellar space in spite of the vigorous turbulence.

Influence of Orientation on Properties of Grain Boundaries in NaCl

Simple (100) tilt, twist, and double‐tilt bicrystals of NaCl, grown by the Kyropoulos technique from melts of high‐purity NaCl, alone and with controlled impurity additions, were examined for mechanical strength and structure of the grain boundaries. Grain boundary fracture strengths, measured in three‐point bending, showed that high‐purity bicrystals with simple tilt orientations were stronger than those with simple twist at high mismatch angles (37° to 45°). The results did not show a functional dependence of strength on angle of mismatch in either tilt or twist bicrystals. Pips observed on parted grain boundaries of high‐purity NaCl (100] twist and double‐tilt bicrystals were believed to represent regions of continuity across the boundary. This feature was rare in similar‐purity NaCl (100) tilt bicrystals. Separate additions of 100 ppm SiO2, CaCl2, FeCls, and KCl to the melt had no apparent effect on the character of the grain boundary. However, an addition of 1000 ppm CaCl2 nearly doubled the strength of a (1001) 30° twist bicrystal, whereas the same addition weakened a (100) 45° tilt bicrystal. Sodium chloride (100) tilt grain boundaries, examined in situ under dark‐field illumination, showed randomly distributed spots, believed to be impurity segregations, with their maximum density at the boundary. The spot densities increased with increasing tilt angle for angles of 15° and greater. The spots were not observed in the low‐angle tilt boundaries (<15°) and were seen only in intermittent clusters in the few twist bicrystals examined.

A Quantitative Method for the Study of Orientation Relationship between Subgrains by Dark-Field Transmission Electron Microscopy

An experiment has been carried out to demonstrate that the orientation relationship between subgrains can be deduced from dark-field microscopy. When a specimen is tilted in dark field with a g vector perpendicular to the tilting axis, contrast reversal occurs between neighboring subgrains if they are joined by a simple twist boundary parallel to g, or by a simple tilt boundary perpendicular to g. It is also shown that the tilt and twist components of a mixed boundary can be determined quantitatively by repeating the tilting experiment with different g vectors. The precision of this method and its advantages and disadvantages for quantitative studies of low-angle boundaries are evaluated from various considerations.

In the classroom: The twist

I heartily recommend it, whether you're facing your first math class, sweetly suggesting, ”Now keep your columns straight,” or if you're a veteran of 40 or 50 years, still insisting, “KEEP YOUR COLUMNS STRAIGHT.” Now if someone told you that with a simple twist you could banish three-fourths of all your difficulties in long division, in hard multiplication, in addition of uneven decimals, and probably in comprehension of borrowing and carrying, wouldn't you at least give it a try? Unorthodox? Yes, but EFFECTIVE.

Crystal Interfaces. Part I. Semi-Infinite Crystals

This paper presents a calculation of the stresses and energies for interfaces between different crystals. Only simple cases corresponding to interfacial dislocations of pure screw or edge type are treated. The difference between the two crystals is expressed in terms of different elastic constants and variable interfacial bondings. Two kinds of interfacial forces appear: tangential forces with a periodic character and normal forces. The latter are induced by different normal displacements of the two contact surfaces of the crystals due to the equal and opposite tangential interfacial forces and are accounted for by assuming a linear relation between force and relative displacement. By using a periodic parabolic model to represent the periodic potential associated with the tangential forces, it is shown that the contribution of the normal force to the interfacial energies is negligible for the approximation used. When these normal forces are neglected, the Peierls-Nabarro representation of the interfacial forces yields simple results in terms of an interfacial rigidity modulus μ and an effective elastic constant λ+ defined by 1/λ+=1/λa+1/λb=(1−σa)μa+(1−σb)/μb, where σ is Poisson's ratio and the two crystals are designated by a and b. It is seen that ½λa≤λ+≤λa, where λa is the smaller of λa and λb. Apart from being proportional to μc, the interfacial energy E depends only on a parameter β=2π(c/p)(λ+/μ), where p is the dislocation spacing and the lattice constant c of the reference lattice is given by 2/c=1/a+1/b. The dependence on β is such that below a poorly defined value of the order of unity the variation of E is very rapid while beyond this it remains practically constant. It is further shown that the elastic energies stored in the two crystals are in the ratio λa/λb and that less than 2% of these energies is stored at distances from the interface greater than half the distance between dislocations. Similar results are shown to hold for simple twist and tilt boundaries.

The geometry of twisted multi-filament structures

A self-consistent geometry of cords made from multi-filament yarns is derived from the assumption that all filaments in a cord follow an epihelical path. This path is defined mathematically using a definition of ply twist not considered before, which leads to simpler formulae than those developed by previous workers. Formulae for changes in ply length, ply twist and cord length on cording are derived which enable the retraction of cords and yarns on twisting to be predicted accurately. An experimental method of cord twisting (simple twisting) is described which enables a simple experimental verification of this theory of twist to be carried out.

DRILL PERFORATION, A SIMPLIFIED METHOD FOR VENTRICULAR PUNCTURE

DRILL perforation of the cranium to our knowledge has not been employed in recent years except by a few neurologic surgeons. 1 The simplicity of the method and the rapidity with which it can be carried out make it especially suitable for the emergency treatment of the patient with increased intracranial pressure. At first glance it may be considered hazardous because of possible hemorrhage from ruptured cortical vessels. Our experience, however, indicates that it is safe when performed on patients with increased intracranial pressure and with due regard to anatomic and physiologic factors. METHOD Perforation of the skull is performed by the use of a simple twist drill point 2 mm. in diameter (fig. 1). The dura mater can be perforated in a like fashion or by the use of an 18 gage lumbar puncture needle. Since the ventricular needle has little or no leeway in this small opening, it