Axis Distance Research Articles

鉄筋コンクリート断面の破壊時コンクリート圧縮縁ひずみに関する研究

The flexural failure of reinforced concrete section is generally caused by crushing of concrete at the compression zone. For the calculation of ultimate flexural capacity or corresponding deformation of a beam, the compressive fiber strain of concrete at failure should be assumed. In practice, the empirical values, for instance, εcu=0.25∼0.35%, are being used in the calculation. However, these values are not always clearly defined from the theoretical viewpoint.In this study, based on the stress-strain curve of concrete having the strain softening region, the theoretical estimation was made on the compressive fiber strain of concrete at the ultimate flexural capacity as well as that at the failure or the crushing of concrete in compression zone of the reinforced concrete rectangular beam section. The results obtained are as follows:(1) The extreme compressive fiber strain to be used for ultimate flexural strength calculation is defined as the value at which the compressive stress brock coefficient, k2/k1k3, obtained from the stress-strain curve of concrete becomes minimum, where k1k3 and k2 denote the ratio of the average stress of stress-strain curve up to an arbitrary strain to the compressive strength and the ratio of the location of center of gravity of the corresponding area to the arbitrary strain, respectively.(2) It is reasonable to assume that the compression failure of concrete in compression zone takes place primarily when the distance of neutral axis from compressive fiber becomes minimum. The corresponding compressive fiber strain can be defined from the stress-strain curve of concrete as the strain at the maximum value of stress brock coefficient, k1k3.(3) Practically, the compressive strain at the failure of concrete described in (2) can be used for the calculation of ultimate flexural strength or deformation of beams.(4) The increase of negative slope of the strain softening region in concrete stress-strain curve reduces the value of compressive fiber strains, especially that for the failure of concrete. On the contrary, the increase of strain at the peak stress (that is, at the compressive strength) in stress-strain curve results in much increase of the ultimate compressive fiber strains.

A standard system of coordinates for radiotherapy apparatus

Suggests a system of standard coordinates to which the following names are given: gantry, rotation, head rotation, head pitch, collimator rotation, turntable rotation, couch rotation, couch height, couch lateral, couch longitudinal, source axis distance, and source height distance.

Evidence for Na sequestration in muscle from Na diffusion measurements.

Intrafiber diffusion of 22Na and 14C-sorbitol was measured along the longitudinal axis of a single muscle fiber which had been placed inside the lumen of a glass capillary at least 24 h beforehand. Compared to their diffusion in 1% agar, the self-diffusion coefficients of 22Na at 10 °C (0.438 × 10−5 cm2/s) and 14C-sorbitol (0.216 × 10−5 cm2/s) were reduced by a factor of 2 when intrafiber pH was 7.5. However, the theoretical and experimental concentration–distance profile curves only matched for 14C-sorbitol but not for 22Na. In the latter case, the experimental curves were consistently higher than the theoretical curve indicating an excess accumulation of 22Na at all x values (axis distance). This Na accumulation was found to be highly dependent on the pH inside the fiber. From pH 10.1 to 5.2, the fraction of excess Na (excess 22Na per total 22Na at a given x) decreased from 0.34 to zero. We interpret this excess Na to be a measure of the amount of myoplasmic Na which is acting as counterion for the fixed negative charge on the contractile filaments.

On the problem of causality

The possibility of formulating the causality principle in terms of observable transition probabilities is discussed. It is found that only a very weak asymptotic condition can be plausibly deduced from the causality requirement. This condition implies regularity of the forward scattering amplitudeS(p) in an infinitesimal strip of the first quadrant along the realp-axis. Singularities ofS(p) located at a finite distance of the real axis have also observable effects, but they cannot be interpreted as obvious acausalities.

Determination of upper-atmosphere air density and scale height from satellite observations

A solution is obtained for the rate of change of semi-major axis and perigee distance of a satellite orbit with time due to the resistance of the atmosphere. The logarithm of air density is assumed to vary quadratically with height, and the oblateness of the atmosphere is taken into account. The calculation of perigee air density in terms of the rate of change of satellite period is dealt with; and the method is applied to data at present available on six different satellites. The variation of air density with height is obtained as ln ρ = -28·59(±0·15) - ( h - 200 )/46(±5) + 0·028(±0·013) ( h - 200) 2 /(46) 2 for h in the range of approximately 170 to 700 km, where ρ is in grams/cm 3 , h is in kilometres and standard deviations are given in brackets.

On the transition effect of extensive air showers

From experimental results reported in a previous paper it is concluded that the ratio of the number of primary particles in an extensive shower, which are capable of producing at least one ionizing secondary beneath a given absorber, to the number of all ionizing particles (this ratio is called “transition factor”) depends on the shower density. It follows further that the transition factor is a power function of the total number of particles contained in the shower with an exponent between 0 and 0,2 for thicknesses of lead absorber between 0 and 25 mm. This power function permits the determination of the average total number of particles contained in showers registrated by the apparatus and the average distance of the shower axis from the apparatus.

Accurate clinical means of measuring intervisual axis distance.

INCREASING emphasis is being placed on the proper positioning of the optical centers of ophthalmic lenses (trial case, refractor, or spectacle) with relation to the visual axes. Recognition is not generally given to the inaccuracies inherent in Viktorin's method, commonly used to measure the so-called interpupillary distance (P. D.). Furthermore, this method of P. D. measurement, even when performed accurately, does not determine the location of the visual axis upon which the optical center of the lens should be placed. Ideally, the distance between optical centers of lenses (termed O. C. D.) should correspond to the intervisual axis distance, or interocular distance, 1 abbreviated I. O. D., a term recently suggested to supplant the less accurate term interpupillary distance. Viktorin's method of measuring P. D.'s is illustrated in Figure 1. A few of the inaccuracies of this method of measurement may be noted: The observer's P.D. should be the same

Device for the control of radiation distribution in moving beam therapy.

When a physician implants radium or other radioactive material in tissues in the pelvis following a cycle of roentgen therapy, he is attempting to improve the distribution pattern of radiation or energy absorbed in certain specific areas. If we ask, what, from a physical standpoint, constitutes an approach to an ideal radiation technic, one of the answers may be stated as follows. It is the production within the body of three-dimensional isodose curves at some specific optimum level of dosage whose shape will closely approximate the shape of the particular tissue mass under treatment; the dosage within the mass outlined by such isodose curves shall be relatively uniform and of a high order of magnitude relative to dosage external to the mass. Although we cannot, strictly speaking, add up in r units and equivalents the tissue or integral dose from varying sources such as x-radiation and gamma emitters, none the less it is quite generally agreed that the type of radiation is of little particular importance, provided the distribution of energy absorption is satisfactory. Howard Nielsen (1) and others (2) have plotted numerous isodose curves for rotational roentgen therapy in the medium-voltage range and have pointed out that, particularly in the pelvis, the shape of the curves and therefore the distribution from simple rotational or pendulum therapy alone is not satisfactory. Nielsen states: “Both the rotatory axis and the target axis distance are fixed.” After careful consideration of all the factors affecting the shape of isodose curves within various portions of the body, including use of wedge filters and multiple positioning of the centers of rotational cycles, it becomes apparent that, if rotational therapy in the medium-voltage range is employed, variation of both the target-skin and target-tumor distance, together with variation of milli-amperage or speed during the rotational cycle, must be accomplished in order to modify satisfactorily the distribution of the radiation. Thus, we may rotate a patient in a vertical or horizontal axis, concomitantly varying the target-skin distance, or we may keep the patient motionless while moving the radiation source through an irregular orbit about the tumor, and preferably in more than one plane. If we rotate the patient around a vertical axis, then the patient must sit up or stand erect lashed to some supporting framework. Not only is this an unpleasant and oftentimes a frightening procedure, but in many instances it may be prohibited by the physical condition of the patient. Organs, particularly in the abdomen and pelvis, assume different positions and relationships with the patient vertical than when he is prone or supine. Also, because of fatigue and relaxation, the relationship of organs may and probably will change even during the period of rotation.

Accurate clinical means of measuring intervisual axis distance.

INCREASING emphasis is being placed on the proper positioning of the optical centers of ophthalmic lenses (trial case, refractor, or spectacle) with relation to the visual axes. Recognition is not generally given to the inaccuracies inherent in Viktorin's method, commonly used to measure the so-called interpupillary distance (P. D.). Furthermore, this method of P. D. measurement, even when performed accurately, does not determine the location of the visual axis upon which the optical center of the lens should be placed. Ideally, the distance between optical centers of lenses (termed O. C. D.) should correspond to the intervisual axis distance, or interocular distance, 1 abbreviated I. O. D., a term recently suggested to supplant the less accurate term interpupillary distance. Viktorin's method of measuring P. D.'s is illustrated in Figure 1. A few of the inaccuracies of this method of measurement may be noted: The observer's P.D. should be the same

Rupture of Cast Iron Beams under Bending

The stress distribution being taken into account, the rupture strength of cast iron beams of rectangular section under bending becomes, [numerical formula] where, MB=bending moment at rupture, b=breadth of the beam, h=height of the beam, nh=distance of the neutral axis from the surface of tension side, and σB=tensile strength under uniform stress. From stress-strain curves of compression and tension, the tension curve being somewhat extended, the moment-deflection curve and the rupture moment were calculated. These calculated values conform very closely with experiment.