Another Optical—Geometrical Illusion

Perception ◽  
1978 ◽  
Vol 7 (2) ◽  
pp. 225-228 ◽  
Author(s):  
Giovanni B Vicario
Keyword(s):  
Geometrical Illusion ◽  
Middle Point ◽  
Unknown Factor

A new optical—geometrical illusion is described. The parallelism of short rows of dots is affected by some unknown factor, so that the rows appear as pivoting on their middle point. Some explanations of the illusion are considered, but with no success.

Campania, Latium, and Rome

2018 ◽  
Author(s):  
Simon Hornblower
Keyword(s):  
Middle Point ◽  
Full Treatment ◽  
The Dead ◽  
Relevant Section

Campania receives very full treatment by Kassandra. Naples is especially prominent, and the relevant section ends at the poem’s exact middle point. This is a deliberate emphasizing device: Naples was of maritime importance in the Roman war against Hannibal and earlier. Hannibal’s visit to the oracle of the dead at Campanian Aornos is hinted at by Kassandra. The important narrative about Aineias and the twins Romulus and Remus is examined for topicality in the 190s. Dido’s surprising absence from the Alexandra is noted and explained.

scholarly journals 1. On an Instrument for measuring the extensibility of Elastic Solids.

1851 ◽  
Vol 2 ◽  
pp. 173-175
Author(s):  
Forbes
Keyword(s):  
Modulus Of Elasticity ◽  
Elastic Solids ◽  
Middle Point ◽  
The Wire

This instrument is almost a faithful reproduction of S'Gravesande's apparatus described in his “Physices Elementa Mathematica,” 1742 (but not in the previous editions). It is described or alluded to by few modern writers, except Biot in his “Traité de Physique.” It consists of a strong wooden table or frame, with a vice at each end, between which a wire or lamina may be stretched with a determinate tension by means of a weight attached by a cord, passing over a pulley in the manner of the musical apparatus, called a Monochord. After the tension is adjusted, both vices are screwed fast, the space included between them being exactly 50 inches. If now, any deviation of the middle point of the wire included by the vices be made (similar to the action of sounding a harp-string), the force required to pull it a certain distance aside will depend, 1st, on the length of the wire; 2d, on its tension; 3d, on its extensibility, or the modulus of elasticity.

Status of the Hawaiian monk seal (Monachus schauinslandi) population

1995 ◽  
Vol 73 (6) ◽  
pp. 1185-1190 ◽  
Author(s):  
W. G. Gilmartin ◽  
L. L. Eberhardt
Keyword(s):  
Complex System ◽  
Sex Ratios ◽  
Current Trend ◽  
Survival Rates ◽  
Hawaiian Monk Seal ◽  
Monachus Schauinslandi ◽  
Young Females ◽  
Adult Females ◽  
Unknown Factor ◽  
Adult Sex Ratio

Restoration of the Hawaiian monk seal (Monachus schauinslandi) population to its former abundance poses a number of problems in managing a complex system. Sharp differences in history and current trend exist among the six major pupping sites. A severely unbalanced adult sex ratio has resulted in deaths from "mobbing" of estrus females at two sites. Some unknown factor apparently severely reduced the numbers of females at three of the sites and thus produced the observed excess of males. Sex ratios subsequently decreased, but losses of adult females continue at two sites. A simple model indicates that sex ratios at the two sites where mobbing is a problem would require more than 10 years to approach an equilibrium value. Data on trends from counts are compared with estimates from reproduction and survival rates and agree closely except at one site (Kure Atoll), where introductions of young females have been made.

scholarly journals A Simple Linkage for Describing Equal Areas

1912 ◽  
Vol 31 ◽  
pp. 105-110
Author(s):  
E. M. Horsburgh
Keyword(s):  
Middle Point

If H (Fig. 1) be the middle point of a straight bar QP and if a straight bar OH of length one-half of QP be pin-jointed to QP at H, a simple linkage is formed, which may be called a T -linkage.

VIII. On the automatic registration of magnetometers, and other meteorological instruments, by photography

1847 ◽  
Vol 137 ◽  
pp. 69-77 ◽  
Keyword(s):  
Thin Sheet ◽  
Outer Cylinder ◽  
Cylindrical Tube ◽  
Vertical Movement ◽  
Base Line ◽  
Plate Viii ◽  
Middle Point ◽  
Vertical Slit ◽  
Focal Line ◽  
Pass Through

During the period of the summer recess, the system of automatic meteorological registration by photography has been rendered complete by the adaptation of the barometer and thermometer to the apparatus previously described. It having been found a matter of much difficulty to obtain a photographic base-line from the lamp already described as being placed near the magnet, the idea naturally arose that the base-line might be simultaneously described by a second lamp placed on the opposite side of the cylinder, as represented in fig.1, Plate V. A pencil of light proceeding from this lamp through a horizontal slit in the chimney is received by a cylindrical lens placed, as before, horizontally, and the focal line of light thus formed is allowed to pass through a corresponding slit in the covering of the cylinder. A small section only of this focal line is transmitted through a vertical slit in a piece of thin sheet brass attached to the stand on which the cylinders rest, and placed very near the surface of the outer cylinder. A line thus described maybe seen in Plate VIII. fig. 4,and Plate IX. figs. 6, 7, 8, and the same light has been by the following means rendered available for the registration of the barometer. A siphon barometer has been con­structed with a column of mercury a little more than one inch in diameter, Plate VI. figs. 1 and 2. As the weight of an entire column of this size would be inconvenient, and as it would be difficult to obtain a tube more than three feet long of so large a bore, both ends of which were of the same internal area, two adjacent short pieces of a very nearly cylindrical tube have been united to the extremities of a tube of small bore, and form the ends of the instrument which contain the surfaces of the mercury.A wooden cap about two inches high is fitted to the open end of the tube, at each end of which are fixed three small friction rollers, placed radially, vertical, and equidistant from each other. The stem of a glass float, having a bulb about half an inch in diameter, resting on the surface of the mercury, passes up vertically between these fric­tion rollers, by which the free vertical movement of the float is much facilitated. At the upper end of the stem is a cap containing a small grooved roller. The barometer tube is attached to a board by two clamps, so as to be capable of being raised or lowered at pleasure, and the bend at the lowest part rests on a piece of wood, which is likewise capable of a vertical adjustment. Another piece of wood, about half an inch thick, two inches wide, and five or six long, is made to slide horizontally between two slips fixed to the surface of the board at such a height that the top of the float may be opposite the middle point between them. To this sliding piece a pulley about three inches in diameter, having a fixed axis about 3 inches long, is attached by a suitable support; to this pulley two slender wooden arms are attached, one thirty inches, the other five inches long, and fixed at right angles to each other. A piece of wire with an adjustible balancing weight is fixed in the pulley in such a position that the axis of the pulley may be the centre of gravity of its appendages. The long arm passes through a slit in the stand of the apparatus, and carries a black paper screen with a vertical slit in front of the horizontal aperture in the cover above described (see Plate V. fig. 2); and is so placed that the point at which the slits cross each other is exactly thirty inches from the axis of the pulley. The short arm rests on the roller at the end of the float, and is marked at the distances of 3, 3.75, and 5 inches from the axis of the pulley. The mark which rests on the float may be changed at pleasure by sliding horizontally the piece to which the pulley is attached; and accordingly as the marks are respectively placed in the above position, it is evi­dent that the movement of the point of light transmitted through the slit in the moveable screen will be five, four, or three times the variation in the height of the column of mercury; and thus by the same lamp the base-line and the barometric curve are traced out. Of this, fig. 4, Plate VIII. and fig. 7, Plate IX. are given as examples. In these it may be remarked that both the lines are so sharply defined, that by ap­plying a scale divided into Troths of an inch, the position of both may be read to half a division, which is equivalent to 0.001 inch of mercury, if the first scale be adopted, which has been the case in these instances. A small weight suspended by a string passing round a groove in the pulley keeps the short arm in contact with the float, by a constant pressure. There being an annulus of mercury rather more than one-fourth of an inch wide between the tube and the float, the effect of capillarity is so much reduced as to exert scarcely any influence on the variations of the column, the weight of which is sufficient to over­ come the small amount of friction that exists in the various parts, without sensibly influencing its variation, and consequently the barometric curve is frequently continuous, and not interrupted by jerks. In one of the registers, not introduced for want of space, the passage of an aerial wave is recorded, equivalent to less than 1/300th of an inch of mercury, the duration of which was about 4 1/2 minutes.

scholarly journals Experimental Study of the Debris Flow Slurry Impact and Distribution

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Haixin Zhao ◽  
Lingkan Yao ◽  
Yong You ◽  
Baoliang Wang ◽  
Cong Zhang
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Impact Force ◽  
Influence Factors ◽  
Flume Experiment ◽  
Middle Point ◽  
Laboratory Flume ◽  
Critical Issues ◽  
Maximum Impact Force ◽  
The Impact

In this study, we present a new method to calculate debris flow slurry impact and its distribution, which are critical issues for designing countermeasures against debris flows. There is no unified formula at present, and we usually design preventive engineering according to the uniform distribution of the maximum impact force. For conducting a laboratory flume experiment, we arrange sensors at different positions on a dam and analyze the differences on debris flow slurry impact against various densities, channel slopes, and dam front angles. Results show that the force of debris flow on the dam distributes unevenly, and that the impact force is large in the middle and decreases gradually to the both sides. We systematically analyze the influence factors for the calculation of the maximum impact force in the middle point and give the quantitative law of decay from the middle to the sides. We propose a method to calculate the distribution of the debris flow impact force on the whole section and provide a case to illustrate this method.

Level I to III craniofacial approaches based on Barrow classification for treatment of skull base meningiomas: surgical technique, microsurgical anatomy, and case illustrations

2011 ◽  
Vol 30 (5) ◽  
pp. E5 ◽  
Author(s):  
Emel Avcı ◽  
Erinç Aktüre ◽  
Hakan Seçkin ◽  
Kutluay Uluç ◽  
Andrew M. Bauer ◽  
...  
Keyword(s):  
Surgical Technique ◽  
Skull Base ◽  
Surgical Anatomy ◽  
Microsurgical Anatomy ◽  
Middle Point ◽  
The Mean ◽  
The Right ◽  
Skull Base Meningiomas ◽  
Supraorbital Foramen ◽  
Ethmoidal Foramen

Object Although craniofacial approaches to the midline skull base have been defined and surgical results have been published, clear descriptions of these complex approaches in a step-wise manner are lacking. The objective of this study is to demonstrate the surgical technique of craniofacial approaches based on Barrow classification (Levels I–III) and to study the microsurgical anatomy pertinent to these complex craniofacial approaches. Methods Ten adult cadaveric heads perfused with colored silicone and 24 dry human skulls were used to study the microsurgical anatomy and to demonstrate craniofacial approaches in a step-wise manner. In addition to cadaveric studies, case illustrations of anterior skull base meningiomas were presented to demonstrate the clinical application of the first 3 (Levels I–III) approaches. Results Cadaveric head dissection was performed in 10 heads using craniofacial approaches. Ethmoid and sphenoid sinuses, cribriform plate, orbit, planum sphenoidale, clivus, sellar, and parasellar regions were shown at Levels I, II, and III. In 24 human dry skulls (48 sides), a supraorbital notch (85.4%) was observed more frequently than the supraorbital foramen (14.6%). The mean distance between the supraorbital foramen notch to the midline was 21.9 mm on the right side and 21.8 mm on the left. By accepting the middle point of the nasofrontal suture as a landmark, the mean distances to the anterior ethmoidal foramen from the middle point of this suture were 32 mm on the right side and 34 mm on the left. The mean distance between the anterior and posterior ethmoidal foramina was 12.3 mm on both sides; the mean distance between the posterior ethmoidal foramen and distal opening of the optic canal was 7.1 mm on the right side and 7.3 mm on the left. Conclusions Barrow classification is a simple and stepwise system to better understand the surgical anatomy and refine the techniques in performing these complex craniofacial approaches. On the other hand, thorough anatomical knowledge of the midline skull base and variations of the neurovascular structures is crucial to perform successful craniofacial approaches.

Obliquity Integration: Variations on a Theme of Delbœuf

Perception ◽  
1993 ◽  
Vol 22 (6) ◽  
pp. 705-712
Author(s):  
Giovanni B Vicario ◽  
Giulio Vidotto ◽  
Elena Zambianchi
Keyword(s):  
Frame Of Reference ◽  
The Other ◽  
Geometrical Illusion ◽  
Tilt Illusion ◽  
Variations On A Theme ◽  
Rod And Frame

An optical—geometrical illusion, described by Delbœuf and not familiar to specialists, is investigated. The results of two experiments show that the divergence between a bar filled with parallel slanting lines and a line drawn above it is clearly related to this angle of the lines which fill the bar. The illusion is already present when this angle is 10°, reaches its maximum at 20°, decreases at 30°, and almost disappears at 40°. These results are similar to those found for the tilt illusion, are slightly different from those found for the rod-and-frame illusion, and differ greatly from those found for the Zöllner illusion. The other variables considered—the distance between the slanting lines filling up the bar, the distance between the upper line and the bar, and the width of the bar—do not influence the illusion as much. Since either the line appears as diverging from the bar, or the bar seems inclined in relation to the line, the illusion should be considered a complex one. The small oblique lines inside the bar induce obliquity in the opposite sense in the display, but which of the elements is seen as diverging from the other depends on which of the two is established as the frame of reference.

scholarly journals Tensile and Flexural Strength of Commercially Pure Titanium Submitted to Laser and Tungsten Inert Gas Welds

2013 ◽  
Vol 24 (6) ◽  
pp. 630-634 ◽  
Author(s):  
Juliana Abdallah Atoui ◽  
Daniela Nair Borges Felipucci ◽  
Valeria Oliveira Pagnano ◽  
Iara Augusta Orsi ◽  
Mauro Antonio de Arruda Nobilo ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Flexural Strength ◽  
Laser Welding ◽  
Pure Titanium ◽  
Strength Test ◽  
Inert Gas ◽  
Commercially Pure Titanium ◽  
Middle Point ◽  
Strength Data ◽  
Commercially Pure

This study evaluated the tensile and flexural strength of tungsten inert gas (TIG) welds in specimens made of commercially pure titanium (CP Ti) compared with laser welds. Sixty cylindrical specimens (2 mm diameter x 55 mm thick) were randomly assigned to 3 groups for each test (n=10): no welding (control), TIG welding (10 V, 36 A, 8 s) and Nd:YAG laser welding (380 V, 8 ms). The specimens were radiographed and subjected to tensile and flexural strength tests at a crosshead speed of 1.0 mm/min using a load cell of 500 kgf applied on the welded interface or at the middle point of the non-welded specimens. Tensile strength data were analyzed by ANOVA and Tukey's test, and flexural strength data by the Kruskal-Wallis test (α=0.05). Non-welded specimens presented significantly higher tensile strength (control=605.84±19.83) (p=0.015) and flexural strength (control=1908.75) (p=0.000) than TIG- and laser-welded ones. There were no significant differences (p>0.05) between the welding types for neither the tensile strength test (TIG=514.90±37.76; laser=515.85±62.07) nor the flexural strength test (TIG=1559.66; laser=1621.64). As far as tensile and flexural strengths are concerned, TIG was similar to laser and could be suitable to replace laser welding in implant-supported rehabilitations.

Sign in / Sign up

Export Citation Format

Share Document