Cylindrical Cone Research Articles

CAD models for asymmetrical, elliptical, cylindrical, and elliptical cone coplanar strip lines

By the conformal mapping method, we give analytical closed form expressions for the quasi-TEM parameters for asymmetrical coplanar strip lines (ACPSs) with finite boundary substrate. Then, based on the analysis of ACPSs, elliptical coplanar strip lines (ECPSs) and cylindrical coplanar strip lines (CCPSs), and elliptical cone coplanar strip lines (ECCPSs) are studied. Computer-aided-design oriented analytical closed-form expressions for the quasi-TEM parameters for ACPSs, ECPSs, CCPSs, and ECCPSs are obtained. All of the expressions are simple and accurate for microwave circuit designs and are useful for transmission-line theory and antenna theory. The reasonableness of the method and results are verified and various design curves are given.

Early invasive adenocarcinoma of the uterine cervix.

In an attempt to determine the natural history of early invasive adenocarcinoma of the cervix, defined as depth of invasion of 5 mm or less, an extensive review of the literature was undertaken, together with recent unpublished material of the author. Many of the cases had to be extracted from series dealing with microinvasive squamous cell carcinoma. The pons asinorum for the pathologist is the differentiation between adenocarcinoma in situ and early invasion. The criteria for microinvasion are: 1.) obvious invasion to 5 mm or less; 2.) usually complete obliteration of the normal endocervical crypts; 3.) extension beyond the normal glandular field; and 4.) a stromal response characteristic of invasive carcinoma. Not all of these criteria are present in every case. In all 436 cases were collected. Allowing for vagueness of reports, 126 patients were treated by radical hysterectomy, and none had parametrial involvement. No cases of adnexal tumors were found in the 155 patients in whom one or both ovaries were removed. Of the 219 patients with pelvic lymph node dissection, five (2%) had metastasis. There were 15 recurrences and six tumor-related deaths in the 436 patients. Only 21 patients had conization as the only treatment, and none has suffered a recurrence. It appears that early invasive adenocarcinoma behaves in the same way as its squamous counterpart. Cold knife conization is acceptable treatment only when the cone biopsy has been adequately sampled and the margins are free, especially when preservation of fertility is an issue. Loop excision procedures obscure depth of invasion and margins and are not acceptable either for diagnosis or therapy. Multicentricity does not appear to require cylindrical cones. If hysterectomy is contemplated, removal of the adnexa, per se, is unnecessary.

Crash and energy absorption behaviour of interleaved carbon-fibre-reinforced epoxy tubes

It is well known that the energy absorption capacity per unit weight of composite structural parts under axial crush load is much better than those of steel or aluminium [1±4]. For that reason they are increasingly used in crush-loaded structures of any kind of vehicle, especially in automobiles. Beside special composite crush elements, complex composite structures such as longitudinal girder, cross-members, mudguards, underbodies and even complete car bodies are subjects of research. The investigations on the crush behaviour of composites focused mainly on crush elements with simple geometry, e.g., tubes with cylindrical and quadratic cross-sections and cones [1±7]. A useful measure of energy absorption capability is the speci®c sustained crash stress. The speci®c sustained crash stress, oss, is de®ned as follows: o ss ˆ Fav Ar

Harvesting backscatter electrons for radiation therapy

Purpose : An innovative technique is used to harvest backscatter electrons for the treatment of superficial small lesions of skin, oral cavity, and rectum where a significant dose gradient and maximum surface dose is desired. Methods and materials : Backscatter electrons are harvested out of the primary electron beams from the linear accelerators. The design consists of a short cylindrical cone that fits snugly over a long cylindrical electron cone. The shore cylindrical cone has a thick circular palte of high atomic number medium (Pb) attached to the distal end, and a lateral slit of variable length and width. The width of the slit could be closed as desired by rotating the two cones and the length can be increased by lowering the short cylindrical cone. Primary electrons strike the Pb plate perpendicularly and produce backscatter electrons that pass through the laterla slit for treatment. Using film and a parallel palte ion chamber, backscattered electron dose characteristics are studied. Results : Teh depth dose characteristics of the backscatter electron is very similar to that of the 0.2 mm Al half-value layer x-ray beam that is commonly used for the intracavitary and superficial lesions. The backscatter electron energy is nearly constant and effectively ≤ 1 MeV from the clinical megavoltage beams. The backscatter electron dose rate of 0.32–0.8 Gy/min could be achieved frommodern accelerators without any modification. The beam flatness is dependent on the slit size and the depth of treatment, but is satisfactory to treat small lesions. Conclusion : The measured data for backscatter electron energy, fluence, depth dose, flatness, dose rate, and absolute dose indicates that the harvested backscaterred electrons are suitable for clinical use.

Scanning electron microscopy and microspectrophotometry of the photoreceptors of ictalurid catfishes

The retinal photoreceptors from larval channel catfish (Ictalurus punctatus) were studied using single cell, in situ microspectrophotometry. Rods appear at 5 days after hatch; cones are present from day one. The rods contain a visual pigment which absorbs light maximally at 540 nm. The cones contain either a green sensitive visual pigment with peak absorbance at 535 nm or a red sensitive visual pigment with peak absorbance at 608 nm. All pigments are based on vitamin A2. Visual pigment complement does not change with age, as photoreceptors from adultI. punctatus, I. catus andI. melas contain visual pigments virtually identical to those of the larvalI. punctatus. Regardless of age, no visual pigment with peak absorbance in the short wavelength region of the spectrum was ever observed. Scanning electron microscopy of adultI. punctatus retinas showed large rods with long, cylindrical outer segments and smaller cones with short, tapered outer segments. The myoids of both rods and cones are extensable. The rods, embedded in a granular tapetal material, comprise from 50 to 60% of the photoreceptors. Only single cones are present. The data are consistent with the idea that the ictalurid catfishes spend their entire lives in an environment deficient in blue light.

Dosimetry of a kilovoltage radiotherapy x-ray machine

We present the percent depth doses, half-value thicknesses, exposure rates in air, dose uniformity, backscatter factors, isodose curves, and penumbra widths for 75-kVp, 100-kVp, 150-kVp, 200-kVp, and 250-kVp beams for rectangular cones (4 cm × 6 cm, 6 cm × 8 cm, and 8 cm × 10 cm) and exposure rates in air and backscatter factors for cylindrical cones (diameters 2 cm, 3 cm, and 3.5 cm) with flat and bevelled ends for the Philips RT-250 x-ray machine. Published dosimetry data specific to this machine are limited to percent depth doses and beam qualities. Rectangular cone percentage depth dose curves and beam quality agreed with published values. While measured backscatter factors for large rectangular fields generally agree with calculated and published values, smaller field backscatter factors were less than those reported by others. Monte Carlo calculations for small field backscatter factors appear more accurate than those measured.

PITYOSTROBUS MAKAHENSIS, A NEW SPECIES OF SILICIFIED PINACEOUS SEED CONE FROM THE MIDDLE TERTIARY OF WASHINGTON

A single structurally preserved ovulate cone forms the basis for the description of a new species of Pityostrobus from the early Oligocene of the Olympic Peninsula of Washington. The specimen consists of about two‐thirds of a cylindrical cone. In living condition the cone was 8–10 cm long and 3.5–4 cm in diameter. Critical features of the cone include decurrent bract bases, an elongate bract‐scale adnation, perpendicular disposition of the proximal part of the scale, and seeds with vesciculate seed coat. An unusual feature of the cone is a distinctive cortical region of thin‐walled parenchyma, mineral‐filled lacunae, and resin canals. This region can be traced to the adaxial side of the scale where it can be recognized by an extensive development of resin canals in the adaxial ground tissue opposite the seed cavities, and by distinctive lacunae around the vascular bundles. The fossil shares several significant characters with modern cones of Abies, Pseudotsuga, Larix, Tsuga, and Picea, thereby calling to question the abietoid/pinoid division of the family, or suggesting that abietoid and pinoid genera of the early Oligocene had not yet diverged to the extent seen in the modern flora.

TRANSIENT THERMAL STRESSES IN A FINITE CYLINDER OF NONUNIFORM CROSS SECTION

Boundary fitted coordinate variables are used to map the region of interest into a square. The governing transient heat conduction and displacement equilibrium equations are rewritten in terms of the new coordinate variables and are solved by a direct power series approach through the application of the Lanczos-Chebyshev and the discrete least squares methods. A finite cylindrical cone section is used to demonstrate how numerical solutions can be obtained

Heat transfer from continuous moving fibers in a micropolar fluid

The laminar micropolar boundary layer in axial flow along a continous moving fiber is studied using the theory of micropolar fluids formulated by Eringen. The fiber filament, is taken as a cylindrical cone that moves steadily through an otherwise quiescent environment. The governing equations for momentum angular momentum and energy have been solved numerically. It has been found that the heat transfer rate increases with increasing values of the dimensionless material parameters of the fluid as well as a reduction in the diameter of the filament.

A comparison of rectangular and cylindrical collimation for intraoral radiographs

This study was conducted to compare the type and frequency of cone-cuts that occur with rectangular and cylindrical collimation in dental radiography. Thirty-eight hundred radiographs, half made with cylindrical cones and half made with rectangular cones, were examined for major and minor cone-cuts. A total of 156 cone-cuts was found. Thirty-three of these were of the major category, 86 percent of which occurred with rectangular collimation. Although cone-cuts appeared much more frequently when a rectangular cone was used, a significant reduction in useless radiation makes this type of collimation a worthwhile consideration.

On the Cooling of Fibers

The effects of the stretching of filaments on the cooling of fibers during the melt-spinning process are studied numerically. The filament is modeled as a continuous, cylindrical cone that moves steadily through an otherwise quiescent environment, with its diameter attenuating exponentially. Radiative cooling from the fiber surface is also accounted for in the analysis. The buoyancy-affected laminar and turbulent boundary layer equations are solved by a finite difference scheme, to determine the axial temperature variation of the filament. It is found that the reduction of the fiber diameter and the subsequent increase in the local speed of the filament enhances greatly the cooling from the filament surface, whereas the increase of the cooling due to radiative losses is not significant for all the flow cases considered.

A high-energy, laser accelerator for electrons using the inverse Cherenkov effect

A laser method for accelerating electrons is described, based on the inverse Cherenkov effect in a gas. The laser fields are in the form of a cylindrical cone of plane waves on whose axis travel the electrons, with the cone angle and the gas refraction index such that each electron sees constant fields in time. Expressions are obtained relating the overall energy transfer to total laser power and wavelength, and to gas index and interaction length. With laser powers now available, energy increments of tens of GeV are possible. For comparative purposes, a related alternative scheme involving electrons in vacuum and evanescent laser fields is also analyzed. It is found that the method applies particularly well to adding energy to the electron bunches produced by large microwave accelerators, as collision effects are less troublesome at high injection energies.

Radiant emission characteristics of isothermal diffuse cylindrical-inner-cone cavities

A new calculation of the local hemispherical effective emissivities along an isothermal diffuse cylindrical-inner-cone cavity has been made. Results are presented for cylindrical inner cones with dimensions such that the effective emissivities along the inner cones and the surface nearby are very close to unity. Comparison is made between Bedford–Ma techniques and the present method for a cone half-angle of 90°. The results show that high accuracy can be obtained with our method, especially for cavities with high surface emissivity, long cylinder length, and small aperture radius.

Calculation of the directional emissivities of cavities by the Monte Carlo method

An iterative formula for the directional hemispherical apparent reflectivity of an opaque isothermal cavity with an arbitrary surface is derived on the basis of an integral equation representing the apparent reflectivity. Nested integrals in the formula are computed by the hit-or-miss Monte Carlo method. The formula is applied to right circular cylinders whose surfaces are diffuse and to cylindrical cones whose surfaces are characterized by a uniform specular-diffuse model. For the cylinders, a table is given from which one can easily calculate the apparent emissivities of the center of the bottoms for arbitrary surface reflectivities. An analytical recalculation of I2 of Quinn gives corrected values that agree with those produced by the Monte Carlo method. For the cylindrical cones the directional apparent emissivities of the bottoms are obtained by varying the apex angle and the fraction of specular component. We point out that angles of 120° and 70° have advantages even for cavities with moderate specular components. Results are analyzed by studying numerically the individual terms of the iterative formula. The validity of an approximation for the directional apparent emissivity is discussed in terms of the constant asymptotic distribution of impact points of rays in cavities.

Coning and breast compression. An aid in mammographic diagnosis.

Although passing reference to the employment of coned views with compression in mammography has been made (1), the technic has been largely ignored in the literature. Gershon-Cohen (3) recommended spot-films for more accurate delineation of suspicious areas, but Wolfe (4) reported that these added little information to that of routine views. Neither author stressed compression of the breast during the spot-film exposures. Our experience has indicated that coned views combined with the additional aid of breast compression often result in a more accurate and confident diagnosis in borderline or indeterminate cases (Figs. 2 and 3). Technic The routine mammographic technic utilized at the University of California Medical Center is patterned after that recommended by Egan (2). Kodak Industrial M film is used exclusively, as is a 12-inch telescoping cylindrical cone of 4-inch diameter. The target-film distance is constant at 30 inches. Other constant factors are a milliamperage of 300 and an exposure time of six seconds. The only variable in the craniocaudad and mediolateral views is that of kilovoltage, which varies between 26 and 34 kV, according to the thickness and density of the breast. The routine craniocaudad, mediolateral, and axillary views are examined immediately after processing. If the results are either unequivocally negative or clearly indicate the presence of benign or malignant disease, the examination is terminated. If the findings are equivocal, however, or an indeterminate lesion is noted, coned-down compression spot-films are obtained. Coned views with compression may be obtained either in the craniocaudad or mediolateral projections. The patient is positioned in the routine manner, and an exposure of one-fifth second is made. This “flash” exposure provides an outline of the entire breast for purposes of localizing the coned area when the films are interpreted (Fig. 2). Without the position of the patient or the film being altered, the cylindrical cone is then extended to a total length of 18 inches, and a simple Styrofoam compression device is inserted. The tube is centered directly over the area of concern and is lowered until the desired amount of compression has been achieved (Fig. 1). To compensate for the reduced target-film distance, which is now at 22 to 25 inches, kilovoltage is reduced from 2 to 6 kV. The full exposure of 1,800 milliamperage seconds is then made. Discussion Although enhancement of detail by cone and compression is in part the result of reduction in scatter, the reduced object-film distance and more complete immobilization of breast tissue appear to be the principal advantages of this technic. These factors are especially critical when a fine-grain film, such as Kodak Industrial M, is used.