Teething Research Articles

The computer as style guide

A report on the nature and teething troubles of software packages that advise on writing skills.

The private sector in the Soviet Union and China

The private sector in the fields of agriculture, wholesaling and retailing, craft trades and light industry, already well-developed in the People’s Republic of China and a number of Eastern European countries, is now to be given a more significant role in the Soviet Union. Moscow’s economic reformers believe this will contribute to an improved standard of living, as has been the case in China during the economic reform which has now been underway since 1978/79. It is therefore tempting to compare the concepts underlying the reforms and the course they have taken in the two socialist “super-powers”, the key question being whether the Russians will achieve similar successes with their reforms, once all the teething troubles are overcome, to those of the Chinese.

The Use of Quality Circles in a Health Care Environment

As part of a research project, funded by the Manpower Services Commission, which examined how quality circles have developed within different types of environments, a study has been carried out in a health authority. The main findings of this study are reported. There is little doubt that circles have proved effective as a means of improving service quality, communication and staff morale. They have also helped to promote a multi‐disciplinary approach to health care. The point is also made that the implementation of circles in two different types of hospital resulted in very different approaches to circles being taken at each location. The health authority in question has also moulded the circle philosophy to suit its own particular organisational culture. The programme has not been without its problems ‐ caused primarily by lack of training, careless implementation and the absence of a circle steering committee. Another problem encountered was nurse management scepticism of the circle concept. However, many of these early teething troubles were a result of the organisation being the first UK health authority to implement a circle programme. Consequently, it had no model from which to learn and compare operating experiences.

上顎中切歯の歯髄腔形態のＸ線学的研究

The purpose of this study is to estimate the form of pulp cavities of upper central incisors using roentgenograms. Materials were fifty extracted upper central incisors. First, roentgenograms of these materials were taken from labio-lingual and mesio-distal directions. Then ten dentists read and traced the form of pulp cavities as shown by the roentgenograms, after which the percentage of readability was determined. Furthermore, the incisors were then cut in order to trace the actual form of pulp cavities and these tracings were compared with those made by the dentists as based on the roentgenograms. It was shown by this study that the tracings of pulp chamber at the dental cervix based on the roentgenograms taken from the labio-lingual direction and the tracings at the horn of pulp chamber based on the roentgenograms taken from the mesio-distal direction closely approximated the tracings of the cut materials. It was also found that readability of these points was 100% for all ten dentists. Based on these results, the two above mentioned points were designated as the datum points to be used when estimating the form of pulp cavities. Furthermore, the form of pulp cavities of the cut teeth was considered in order to determine the angle of the mesial and distal projection of the horn of pulp chamber against the datum plane of the dental cervix. In the above manner, a possible method of estimating the form of pulp cavities of upper central incisors using two roentgenograms was investigated.

Relieving teething discomfort

Relieving teething discomfort

Micrographic and profilometric evaluation of the finish produced by diamond and tungsten carbide finishing burs on enamel and dentin

This study ranked the surfaces of bevels cut in enamel and dentin by four ultraspeed burs: DTP, MF3, 12F, and 30F. Each bur was used to cut a bevel in enamel and dentin and stereoscopic micrographs were made at X600 magnification. These micrographs were sorted into sets representing the four burs at three separate locations on the margin (entry, exit, and gingival). The micrographs were ranked for surface roughness at two locations: (1) at the margin between the cut and uncut tooth surface and (2) within the body of the cut dentin. In addition, the bevel was examined within the cut dentin with a profilometer. A CLA of roughness was identified for the finish created by each bur. Mean CLA (±SE) values revealed that the DTF bur produced the roughest finish (3.84 ± 0.13 μm) whereas the 30F bur produced the smoothest finish (0.29 ± 0.02 μm) ( p < .01). No significant difference was found between the 12F and MF3 burs ( p = .05). Micrographs of the finish within the body of the cut dentin ranked from roughest to smoothest: DTF, MF3, 12F, and 30F ( p < .01). Micrographs of the surface at the margin of the cut enamel ranked from roughest to smoothest: DTF, 12F, 30F, and MF3 ( p < .05). The 12F and 30F burs frequently produced a chipped entry margin, because the direction of rotation was away from the margin. This chipping was infrequent for the MF3 and DTF burs. Because the direction of rotation was toward the exit margin, none of the bars caused chipping of this margin.

The Detection of Tool Breakage in Milling Operations

The paper describes a rather simple and efficient algorithm for processing the milling force signal to detect cutter breakage. Using sampling synchronized with cutter teeth the basic variation per tooth is removed by calculating average forces per tooth. The first difference of these forces detects both breakage and some sudden changes in cutting conditions (cornering, milling over a slot). The second difference distinguishes between the two. The algorithm is illustrated by computational simulations as well as by measurements in milling tests.

Development of solid propellant technology in India

Space research in India started in 1961 when a two-stage rocket was launched from Thumba on 21 November 1963. On the sudden passing away of Dr. Vikram Sarabhai, the originator of the Indian space programme, Prof. Satish Dhawan became the second chairman of ISRO. His stewardship saw it through its teething troubles on to launching of several R & D tasks and growth of several ISRO Centres. Major breakthrough in many hightech areas took place during this period. High energy composite solid propellants were developed, characterized and produced at the Vikram Sarabhai Space Centre and at the Sriharikota Centre. Exotic fuel binders such as CHEF-20, Polyol and HTPB for these propellants were also developed in ISRO as part of the indigenisation programme. The Satellite Launch Vehicle-3 (SLV-3) conceived in the early seventies, was fitted with four stage motors filled with solid propellants made in ISRO’s own plants. These facilities, including critical process equipment, have come up as a result of ISRO’s indigenization efforts. The SHAR Plant known as PROB has been further augmented to produce large propellant grains to meet the needs of the Polar Satellite Launch Vehicle (PSLV).

Effect of calcium hydroxide treated dentine on pulpal responses.

Summary. The purpose of the present study was to test the hypotheses that calcium hydroxide enhances pulpal protection against irritating substances in and around dental restorations when topically applied to cut dentine, and to acquire further information regarding the possible mechanisms involved. Cavities in dentine were treated for 30 days with either a water slurry of calcium hydroxide or a hard‐setting calcium hydroxide containing base. Control cavities were treated with saline. The additional effect of dry cutting prior to the restoration was also included as a control. Pulpal responses after placement of a silicate cement restoration were evaluated after an additional period of 30 or 150 days. From histological sections the volumes of inflamed pulp and the volumes of irregular secondary dentine were calculated with a morphometric method of evaluation. Changes in dentine to the calcium hydroxide treatment were observed with scanning electron microscopy. Most pulps in teeth with cavities treated with saline and restored for 30 days with silicate cement exhibited inflammatory alterations. Calcium hydroxide treated teeth had a significantly lower volume of inflamed pulp compared with the saline controls. Dry preparation was also associated with reduced inflammatory reaction. Pulps in teeth with dentine treated by the calcium hydroxide containing hard‐ setting base displayed the same magnitude of pulpal inflammation as the saline treated controls. After restoration for 150 days the volumes of inflamed pulp tissue were reduced in all treatment groups, however the least pulpal responses were found in teeth treated with calcium hydroxide slurry. Data also showed that the calcium hydroxide treatment was associated with only small volumes of irregular secondary dentine, while in contrast dry cut teeth showed large volumes of irregular secondary dentine. Scanning electron microscopic evaluation of dentine treated with calcium hydroxide revealed reticular structures inside the dentinal tubules

Periapical abscesses of cut canine teeth in cynomolgus macaques.

Periapical abscesses of canine teeth in a group of 47 male cynomolgus macaques are found to be associated with a procedure, involving cutting the canine teeth, used to make non-human primates less hazardous. Examination of 150 canine teeth in dry specimens revealed 30 cut teeth with no exposure of the pulpal chamber and 107 cut teeth where the dental pulp had been exposed. Of those teeth which had the pulpal chamber exposed by the cutting procedure, 85 (79.4%) showed clear evidence of osseous changes consistent with abscess formation in the apical regions.

A Method for Determining the AGMA Tooth Form Factor from Equations for the Generated Tooth Root Fillet

The determination of the AGMA tooth form factor requires that the dimensions of the critical tooth section, at which the maximum bending stress is deemed to occur, be found. Critical section dimensions have traditionally been measured from a scaled generated layout of the tooth profile. The layout procedure, however, requires very careful drafting, and even then it is difficult to achieve really satisfactory accuracy because of the complex operations required to produce the fillet curve, with the added difficulty of estimating the point of tangency with the Lewis iso-bending stress parabola. Although a number of analytical methods are available for computing the critical section dimensions, their solution has generally been cumbersome, or convergence on the correct solution remained a problem. This paper presents equations for the gear tooth root fillet curve which have been derived from an analysis of the relative motion between a rack cutter and gear tooth during the generating cycle. An improved iterative procedure is used to find the critical tooth section dimensions from these equations. A further application of the root fillet equations, which is also covered, is in the computer generation of tooth profiles for assessment of the final tooth shape.

Dynamics of High-Speed Milling

This paper is based on previous work of the author and his associates which was published in a series of papers, mainly on those given here as references [2–6], dealing with time domain simulation of chatter in milling, with cutting process damping and with stability lobes. These matters are reevaluated here from the particular point of view of high-speed milling. First, the derivation of limit of stability of chatter in the frequency domain is recapitulated, and lobes of stability explained. These lobes should lead to substantial increases of stability at high speeds of milling. Further, corrections to the results of the simple theory using time domain are presented as they are obtained by time domain simulation which takes into account, in a very realistic way, all the main aspects of milling. It is shown that still, in many instances, high gains of stability are achievable by determining and using a particular spindle speed such that the cutter tooth frequency approaches the frequency of the decisive mode of vibrations as measured on the cutter. The usual modes of vibration of a spindle with a long end mill are discussed, and it is shown how a long end mill stabilizes cutting at medium speeds but becomes a flexible element strongly involved in chatter at higher speeds. In the following section, cutting process damping is discussed which has a very strong stabilizing effect at low speeds but is also partly effective at speeds presently in use. This damping is lost in high-speed milling. Typical cases of high-speed face milling of steel and long end milling of aluminum are discussed and a need of about seven times more stiffness for spindle modes and 14 times more stiffness for the end mill mode derived. The former should be achieved by spindles with larger diameter roller bearings while simultaneously the technology for the design of these spindles running at high speeds must be developed. Present research work shows good promise for this development. For the latter, methods of maximum use of the lobing effect should be developed as well as methods of increasing the damping of the end mill mode.

Properties of steels used in petroleum engineering

This paper investigates the mechanical properties, local plastic deformation, and character of failure of D5KhN2MFASh and 16KhN3MASh steels after different heat treatments. The chemical analyses of these steels are shown in a table. An analysis of the geometry of type T drill bit roller cutter teeth of different diameters showed that the relative area of the tough core of the roller cutters in the most dangerous (from the point of view of failure) cross section for 93-151 mm diam. bits is 0.38-0.45. Taking into consideration the higher strength properties of D5KhN2MFASh steel, higher wear resistance and life of drill bits (type T) with roller cutters of this steel may be expected in comparison with the wear resistance of drill bits with standard roller cutters produced of 16KhN3MASh steel.

Computer modeling of rack-generated spur gears

A general method is presented for describing external involute spur gears produced from the basic rack form. The resulting description is a computer graphic drawing of the cut tooth as an individual tooth, several teeth in a segment or a complete gear. It is established that the surface normal vector at the cutting point must pass through the instant center. Equations describing the tooth root, fillet, involute and top land are derived based on this fact. The points of demarcation between these tooth sections are also found. The tooth description is based on the tooth addendum and dedendum, the number of teeth on the gear, the rack pressure angle, the diametral pitch and the rack tip radius. The effect of tool shift on the cut tooth is included. The importance of the rack from addendum on involute interference is also presented.

Rock Bit Cutter Tooth Design and Analysis

The finite element method was used to analyze the stresses in a rock bit cutter tooth under applied loads. Detailed finite element models were constructed to allow accurate descriptions of the structural material properties of a tooth design which includes carburization and hardmetal application. Numerical solutions were obtained for investigating stress concentrations and plastic region growths in a cutter tooth when loaded beyond its yield point. It was found that the finite element method can be a powerful tool for improving the performance of a cutter tooth. Design objectives can be achieved through parameteric studies of stress level variations against geometry and material property changes on a computer system.

Stability Lobes in Milling

The time domain simulation approach to the analysis of chatter is applied here to improve the knowledge of the effect of cutting speed “lobing” and of special cutters (nonuniform pitch) on stability of milling. In this method the stability lobes are obtained under more realistic conditions where all the simplifying assumptions made in the previous analyses of these effects, especially the restriction that all cutter teeth have the same directional orientation, are abolished, The new approach shows that, in general, the gains in stability are much smaller than previously maintained. Experimental results presented here verify that the digital simulation of chatter in milling compares with reality very closely.

Punch shear testing of extracted vital and endodontically treated teeth

Plano-parallel specimens of human dentin cut from vital and endodontically treated teeth were tested by the punch shear test. Shear strength values were found to positively correlate with approximate toughness values. Statistically significant differences were found between shear strength and toughness values for vital and endodontically treated teeth, the latter showing lower values. The clinical impression that endodontically treated teeth are weaker and more brittle than vital teeth has therefore been quantitated. Anatomically different teeth or the methods used to store and cut teeth could not be consistently correlated with punch shear and toughness values. When dentin slices were constrained during punching so that bending was prevented, the precision of the results was improved and higher values were recorded.

工具すくい面上に作用する応力の食いつき角による変化 断続切削時における食いつきの研究 ＩＩＩ

A primary factor of the wide fluctuation of tool life owing to an engagement angle Ea in face milling may expect that the transient stresses in the cutter tooth are varied with the angle Ea, and then, their transient stresses distribution upon the rake surface for the various angle Ea at milling are analyzed by photoelastic experimental method, in which the lead alloy plates are cut with a tool of epoxy resin. Moreover, it makes a model of stresses distribution from these results and this model is applied here for the computational stress analysis in the tool on the same cutting process by the finite element method and these computed values are verified with the photoelastic experimental results, after that, it makes another attempt to calculate about the varied tool wedge forms and boundary conditions. The main results have proved as follows. When a rake surface of tool contacts at the outward face of workpiece with a positive engagement angle and it bigins biting from apart point of the tool edge, the parallel stress σy for the rake surface acts only at a neiborhood of tool edge as tensile stress, at last, their stresses turn to compression one in entirely biting to the tool edge. Thereupon, these tensile stresses are induced by the friction force of chip flowed on the rake surface. Such the alternating stresses acted at the neiborhood of tool edge become a cause of chipping or breakage and it is supposed that stresses exert a great influence upon the tool life.

A method of high production milling of drill bit cutter teeth

A method of high production milling of drill bit cutter teeth

A Grassland Renovator with a Unique Tillage Device

ABSTRACT A cooperative program of development, design, and research involving farmers, county extension per-sonnel, John Deere Des Moines Works, and the Agricultural Engineering and Agronomy Departments of the University of Kentucky has resulted in a unique machine specifically designed to interseed forage crops into existing grass fields. The machine, which is now in production, is a three point hitch machine consisting of an integral frame on which are mounted powered tillage blades, drive train, seed tubes, press wheels, spray noz-zles, and seed boxes. The machine is 2.44 m wide and has 12 tillage blades which cut through the grass sod and provide tilled furrows 1.9 cm wide and 1.9 to 5.7 cm deep for placement of legume and other forage seed. Each tillage blade is 30.5 cm in diameter, has hard-faced cut-ting teeth, and is powered to rotate in the direction of travel at an angular velocity of 730 rpm. In comprehen-sive field tests, over 1200 ha were seeded in 30 different counties in Kentucky to fully evaluate the machine-design principles and functional and mechanical reliabil-ities. These field tests demonstrated that the design principles were sound and that they could be incorporat-ed into a production machine to provide a reliable method of grassland renovation.