Casting Position Research Articles

3D morphological assessment of occlusal treatment by measuring dental casts with a micro‐focus X‐ray CT

The analysis of occlusal relationship is important for the success of dental treatment. Three-dimensional (3D) computer models of upper and lower dental casts can play a significant role. In this study, we proposed and applied a new method in actual clinical assessment to measure dental casts with occlusal relationship by using a micro-focus X-ray CT system. We examined the modelling accuracy by comparing multiple 3D images taken by shifting the dental cast position. Modelling accuracy was confirmed as 0.03 mm. One occlusal treatment in clinical practice was selected as a case example. The dental casts and bite impression, taken before treatment, were scanned and the occlusal contacts and distance distribution between the upper and lower casts were visualized by a coloured map and overlaid on the computer models. Distances between the upper and lower casts of selected points were compared before and after the treatment. Initially, the subject had early contact on the anterior teeth, where distance was measured as 0.04 mm, and only one area measured less than 0.15 mm. After treatment, five areas measured less than 0.15 mm. Also, by comparing the dental cast models taken before and after occlusal adjustment of the tooth, the position and amount of adjustment were visualized. We successfully demonstrated the quantitative clinical assessment of occlusal treatment.

Entrepreneurship among Diasporic Communities

A comparative examination of two communities of India, namely, the Patidars of Gujarat and the Jats of Punjab, who constitute a majority in the Indian diaspora, reveals that both these communities share certain features such as landownership, middle caste status and a dominant caste position besides some socio-cultural similarities. Despite their common background, each has performed differently in foreign countries. The nature and streams of their immigration patterns differ. In the case of Patidars, it is a step migration while amongst the Jats the pioneers were ex-soldiers. The innovativeness and entrepreneurship of the Patidars significantly contributed to the economic development of the host countries. The Jats—the most progressive community—are found in almost all parts of the globe. They have largely taken up agricultural and industrial labour activities. They invariably invest their surplus money in buying some agricultural land. The differential performance of two communities points towards their different attributes, orientations towards work, work ideologies and primordial ties such as sense of family and kinship networks.

Effects of Bar-Placement Conditions on Steel-Concrete Bond

Vertical sections exhibit a variety of factors that affect the bond between the embedded steel bars and the concrete, like casting position, concrete characteristics, and compaction procedure. The results obtained in this project indicate that bond strength decreases if the concrete depth below the horizontal bar increases, primarily because of the water-stop effect underneath the bar, and of the settlement of fresh concrete. This effect increases for larger values of water content and water-cement ratio (w/c), which normally cause an increase in slump, and a decrease in stability of concrete (resistance to bleeding, settlement, and segregation). However, very good bond properties were achieved by using self-compacting concrete (SCC) tested versus standard concrete mixes, is a demonstration that in the case of SCC higher slump values do not mean lower bond properties.

Mental Hygiene and Socio‐Environmental Factors

Mental Hygiene and Socio‐Environmental Factors

A new method for recording and reproducing cast orientation on a survey table

Cast position on a survey table is determined with an inclinometer, allowing tilt to be measured in 1-degree increments in the frontal and sagittal planes. With this device, cast reorientation is simplified and tilt modifications can be accomplished accurately because of direct visualization of tilt measurements in the 2 planes. (J Prosthet Dent 2003;89:76-8.)

Local pressurization during solidification of Al-Si-Cu alloys

Local pressurization is a squeeze method for eliminating the shrinkage porosity. In this study, local pressurization was carried out with a specially designed permanent mold to examine the effect of pressurization on the shrinkage porosity through the investigation of macrostructure, partial density variation under the pin tip for two types of aluminium alloys of hypoeutectic (AC4B) and eutectic (ADC12). Then copper concentration at the different positions in AC4B casting was analysed in order to investigate segregation. And in order to estimate the flow of liquid or solid-liquid zone by local pressurization, the ratio of flowing volume of two alloys was measured with varied pressurization timing and different pressures. The solid fraction of flowing zone was calculated by the use of both the solidification simulation and the characteristic macrostructure change of flowing zone. The solid fraction indicates the fraction within which the present pressurization can induce interdendritic liquid flow.The results showed that the partial density of two alloys cannot be affected within the certain limits of pressurization timing for a given pressure and pressurizing speed, and does not increase obviously even if pressure increases, such as 64 to 128MPa for ADC12 casting. It was also found that the negative segregation of copper in AC4B casting occurred under the pin tip. The concentration of copper varied with distance from the pin tip. The degree of segregation was severe in the position 15mm distant from the pin tip. Opposite to the negative segregation, the positive segregation occurred in the upper zone around the pin. From the simulation, the maximum solid fraction of flowing zone, where interdendritic liquid moves, is shown to be about 0.46 and 0.53 for AC4B casting with pressure of 32 and 64Mpa, respectively.

Porosity of cement paste cured at 45 °C as a function of location relative to casting position

The influence of location relative to the casting position, on porosity and pore size distribution of cement pastes, was investigated. Three different pastes were prepared at a constant water/binder ratio of 0.45. The pastes were the control paste (CP) in which Portland cement was used and no cement replacement materials were added, pastes with 22% and 9% replacement (by mass) of cement with fly ash (FA) and silica fume (SF), respectively. Paste specimens were cast in cube moulds and were either cured in air at a temperature of 45 °C and relative humidity of 25% for 28 days or moist cured for 14 days after casting at 45 °C, followed by air curing at 45 °C and 25% relative humidity for further 14 days. Samples were taken from various locations of the cube specimens. Porosity and pore size distribution were conducted on the paste samples using the mercury intrusion porosimetry technique. The results show that large differences in porosity and pore size distribution exist between samples taken from different locations relative to casting positions. These differences are larger in pastes subjected to dry curing as compared to pastes subjected to some initial moist curing. The influence of sample location relative to casting position on porosity and pore size distribution of paste is compared with absorption of concrete performed in a previous investigation. The correlation between pore volume of paste and water absorption of concrete is also conducted.

Role of casting position on bond strength of reinforcement in eccentric pullout silica fume concrete specimens

This paper reports on a study designed to investigate the effect of silica fume, bar size, and concrete confinement on the bond-slip characteristics of bottom cast reinforcing bars anchored in eccentric pullout silica fume specimens. The main objective was to assess the effect of casting position by comparing the test results with those of top cast specimens tested earlier and identical except for the casting position.

Factors controlling cracking of concrete affected by reinforcement corrosion

The present paper tries to contribute to quantifying the relationship between the amount of corrosion and cover cracking. The variables studied were: cover/diameter (c/o), proportions of cement, w/c, cast position of the bar, transverse reinforcement and corrosion rate. The corrosion is accelerated by applying constant currents causing the rebar to act as an anode. The results indicate that the cracking process develops in two steps: generation and propagation. Radius losses of about 15–50 μm are necessary to generate the first visible crack (<0.1 mm width). The propagation follows a behaviour of the type: w (crack width in mm)=a+bx (radius loss in μm).

Behavior of Tension Splices for Reinforcing Bars Embedded in High-Strength Concrete

Safety concerns and a lack of test data on bond capacity of deformed reinforcing bars embedded in high-strength concrete (HSC) have been reasons that the American Concrete Institute (ACI) 318 building code has imposed an arbitrary limitation of 69 MPa (10,000 psi) in the calculation of tension development and splice lengths. This limitation was first introduced in the 1989 revision of the ACI 318 building code. In an attempt to evaluate the impact of this limitation and develop provisions for its removal, a two-phase investigation was carried out at the University of Nebraska-Lincoln. During both phases of the investigation, 70 beam splices were tested. The parameters studied included diameter, length, and deformation type of the reinforcing bars; amount of transverse reinforcement over the splice length; casting position; and concrete compressive strength. Results of the investigation are used to discuss the differences that exist between normal concrete and HSC, develop hypotheses to explain these observed differences, and suggest alternatives for removal of the current concrete compressive strength limitations existing in the ACI 318 building code for calculating tension development and splice lengths.

Design Recommendations for Bond of GFRP Rebars to Concrete

To develop design guidelines for bond of glass-fiber-reinforced plastic (GFRP) rebars to concrete, a total of 102 specimens were constructed and tested subjected to monotonic static loading. The research program was inclusive of the experimental testing of 48 beam specimens, 18 pull-out specimens, and 36 hooked rebar specimens. The tensile load was applied to the rebars in a gradual increment of load level until splitting of concrete, rebar pull-out failure, or rebar fracture occurred. The slip between the rebars and concrete was measured at the loaded and free ends at each load level. Variables included in the study were concrete compressive strength, embedment length, clear concrete cover, rebar diameter, concrete cast depth, radius of bend, and tail length. New criteria for acceptable bond performance of GFRP rebars to concrete were developed and were used to evaluate the experimental results. Design guidelines for calculating the development lengths for straight and hooked GFRP rebars to concrete were derived. In addition, confinement factors were calculated to reflect the influence of concrete cover and casting position.

Robotic Deburring of Small Series of Castings

Robotic cleaning of castings is currently limited to large series of parts with small burrs. The costs for fixtures and clamping and for online programming of the robot largely exceed the potential savings of using robots for small series. Less expensive fixtures only add to the positioning uncertainties by which the use of online programmed robots becomes prohibitive. The paper presents a robotic deburring system for small series of heavy-duty castings with large burrs and risers. Strategies are presented to cope with large burrs and with the allowed large position uncertainty of the casting. CAD data of the nominal castings is used to program the robot offline, resulting in reduced programming time. Active force control is used for burr detection and for coping with uncertainties in the casting position. The test set-up consists of an offline-programmed, hydraulic, force-controlled robot and an example of the cleaning of a gray iron casting of a heavy-duty crank case for a truck is presented.

Digital Imaging of Occlusal Contacts in the Intercuspal Position

The purpose of this study was to develop an approach to the measurement of occlusal contact area and location using digitized video images of occlusal records. Five occlusal records in the intercuspal position were made using a polyvinylsiloxane material on five subjects with intact, natural dentition. In regions of occlusal contact, the material showed a minimal film thickness without perforation. A dental cast of the mandibular arch was video digitized and followed by digitization of each of the five occlusal records in place on the cast. An impression of a calibration stepwedge was video digitized to provide the relationship between impression material thickness and pixel density. Contact surface areas ranged from 0.02 to 3.16 mm2 between subjects. The contact positions on a single tooth determined in five records from a single individual showed coefficients of variation between 7.4% to 36.1%. Large variations in contact size were found in this group of five records from a single individual (coefficient of variation ranged from 10.8% to 156.7%). The large difference in contact size between records may be due to variations in biting force at the time the records were made. When the cast position was changed and records redigitized, the mean area of the contact was not significantly different (P > .20) from measurements at the original position. For the small sample evaluated, a large variation in occlusal contact size was found in the five records. The occlusal contact location was consistent in the five records. The measurement method developed seems to provide reliable measures of occlusal contact surface area and location.

Equality and hierarchy in untouchable intergenerational relations and conflict resolution

Untouchable intergenerational relations in three Indian hamlets are shaped by the Hindu age hierarchy, the untouchable egalitarian ethos, the degraded caste position of untouchables, and their intercaste relations. However, historical, social compositional, and geographical differences among the hamlets have led to different adaptations to the needs of the old for authority and the young for equality. These intergenerational differences have led to great differences in intercaste relations. In Anbur, the most isolated, intergenerational conflicts are resolved peaceably, and their relative solidarity has staved off serious intercaste conflict. In Pudur, which has some caste Hindus, deteriorating intergenerational relations have contributed to community disorder, to the collapse of the informal justice forum, and to intercaste conflict. In Ennakulam the youth disregarded their elders' attempts to resolve intercaste conflict, and they escalated the violence until the untouchable community, located in the center, was routed from the village.

Evaluation of the accuracy of cast reorientation to a surveyor by prosthodontic residents

This study investigated the accuracy of a group of evaluators in reestablishing the orientation of a tripoded master cast to a surveyor instrument. Three prosthodontic residents served as evaluators to reestablish the tilt of a previously tripoded cast with three known reference coordinates. The distance from the known to the reference point was recorded for the three points in four trials by a judge with a machinist height gauge. Analysis of variance revealed a significant difference between the evaluator cast position and the known reference position. The investigation demonstrated ±0.2 mm errors at each of the three locations; 0.3-degree angulation errors occurred in reestablishing the tilt of the master cast in relation to the surveyor.

Method Proposed for Construction of Multispan Cable‐Stayed Bridges

A new method of construction for multispan cable‐stayed bridges is described. This method is one of several options developed for construction of the 13‐km‐long fixed link across the Northumberland Strait connecting Prince Edward Island with New Brunswick in eastern Canada. A 250‐m‐long cable‐stayed span is constructed by launching a 525‐m‐long steel truss underneath the bridge deck. The special feature of the method is the casting of the concrete deck slab of the 250‐m span in one operation in an elevated position (approximately 0.5 m above the final position). While the reinforcing and prestressing steel for the deck is placed, the stay cables are installed and temporarily anchored to the top chords of the steel truss. Because of the elevated deck position, the cables near the pylon are slack, and those further away are stressed much lower than the final level. By lowering the truss supporting the hardened deck by about 1 m, all the stay cables are stressed fully and the deck is suspended at the desired level. The truss is then launched to the next casting position. To support the truss during launching, flotation tanks are submerged from the ends of the truss into the water, exerting a constant uplift force of approximately 3 MN.

Caste and labour relations in north west Nepal*

Anthropological work in South Asia has been dominated by cultural approaches which emphasise pan‐Indian cultural categories. Such cultural categories, particularly those pertaining to caste and kinship, it has been claimed, explain adequately the working and reproduction of caste society. Few anthropologists have considered agrarian and tenurial relationships and their representation or the economic processes which ensue from such relationships. An analysis of agricultural relations of production in a Himalayan community is presented here. It is suggested that although people present an idealised picture in which caste and economic position coincide, in reality ownership of means of production depends on control of the labour of others. Labour relations and processes of economic differentiation are shown to be crucial for the maintenance of caste hierarchy.

Nondestructive hardness testing of malleable cast iron castings

At the same time, taking into consideration the fact that the castings of housings for piping fittings have a quite complex and developed surface, the character of the relationship of their residual magnetization to hardness is dependent to a significant degree upon the mutual location of the casting and the sensor. Therefore, during the investigations a casting position was selected so that with the greatest sensitivity of the sensor the relationship of the residual magnetization to hardness was the closest to linear. However, during the investigations cases were observed of quite large deviations of the values of such a relationship: Castings with the same hardness had different residual magnetizations. The reason for this was that the chemical analysis of the castings had significant deviations. Therefore, with the use of this method it is necessary to take into consideration deviations in the chemical analysis of the iron. In metrological parameters the instruments developed by the institute are indicators and make it possible to inspect castings based onboundary values of hardness established from control specimens of castings with sufficient accuracy for production. All of the instruments are made on a modern element base, which provides high service reliability of them. The U226, U252, U382, and U416 instruments are designed for manual inspection of castings. They consist of two basic assemblies, the magnetizing and measuring devices, and differ only in the dimensions and design of the magnetizing device. The U415 instrument (Fig. i) is designed for semiautomatic inspection and sorting of castings by hardness. In addition to the magnetizing and measuring devices it includes additional equipment for delivery of the castings and a sorting mechanism. The magnetizing device consists of a magnetizing coil, a guide for placement of the casting being inspected, and a controllable rectifier. The measuring device consists of a ferromagnetic probe magnetometer with a stabilized power block, an output signal amplifier with a dial indicator, and one or two threshold devices with controllers and signal lights. In contrast to the majority of known ferromagnetic probe instruments, in those developed

Accuracy of laminated wax interocclusal wafers

Different types of wax interocclusal records were tested to determine if the type of recording material affects cast position when dental plaster is used to mount casts. The results indicate that a difference in the type of wax record is not a significant factor in cast fixation.

Caste, class, and gender: Production and reproduction in North India

Major changes in the technology and economic organisation of Indian agriculture have had far‐reaching effects on other aspects of social life. A critical area of neglected research has been the effect that the changing technology and accompanying social relations of production have had on women's role in agricultural production and on gender relations. Research carried out in a village in North India concretises general statistical trends affecting the lives of Indian women under capitalist development. Female participation in production activities mirrors their caste and class positions. Differential participation directly affects, and is intimately related to, other aspects of women's lives. The article also discusses some of the major contradictions for women's status stemming from the transformation of agrarian relations.