Special Casting Research Articles

The Effect of Degassing Pressure Casting Molds on the Quality of Pressure Casting

In these days in foundry branch there is a rapid development of sectors of special casting technology with the aim to increase the quality and the efficiency of pressure casting production.. Internal homogeneity of pressure casting, characterized by the extent of porosity can be affected by the setup of technological parameters of pressure casting and last but not least by vacuuming the molds, that means to exhaust air and gases from the mold cavity. Contribution is specifically aimed on the analyzing the impact of degassing pressure molds on the porosity of pressure casting.

A Global Community Psychology of Mobility

This special issue heralds the coalescence of a new field in social sciences – the psychology of global mobility. This field whilst distinctive is certainly not insular. Contributions in this special issue are interdisciplinary and cross-level, reflecting an open systems perspective. Political motivation, sociological networks, community inclusion, educational institutions, socio-cultural identity processes, and organizational processes are all represented in the collection. Organizational dynamics are perhaps a special theme that runs throughout. They are a timely reminder that the organizational level of analysis in general, and the psychology of work in particular, is a major yet often overlooked component in the study of global mobility processes, including policy development. In a wider sense, the contributions in this special issue cast new light on the interaction between psychology and social/community structures, and the role of these essentially interactive processes in human development. The special issue is about a developing global consciousness, and a role that psychology as one discipline and applied profession can play in this process. A major challenge remains, of course: Connecting psychological research and evidence with social policymaking. To achieve more credibility in the policy domain, psychology will need itself to become more political, and overtly skilled in social advocacy. As these papers remind us, we will need to build more stakeholder alliances, including between research and community groups.

The TUNEL assay suggests mandibular regression by programmed cell death during presoldier differentiation in the nasute termite Nasutitermes takasagoensis

Termite soldiers are the most specialized caste of social insects in terms of their morphology and function. Soldier development requires increased juvenile hormone (JH) titer and the two molts via a presoldier stage. These molts are accompanied by dramatic morphological changes, including the exaggeration and regression of certain organs. Soldiers of the most apical termitid subfamily Nasutitermitinae possess not only a horn-like frontal tube, called the nasus, for the projection of defensive chemicals from the frontal gland reservoir but also regressed mandibles. Although candidate genes regulating soldier mandibular growth were reported in a relatively basal termite species, the regulatory mechanisms of mandibular regression remain unknown. To clarify these mechanisms, we performed morphological and histological examinations of the mandibles during soldier differentiation in Nasutitermes takasagoensis. Mandibular size reduced dramatically during soldier differentiation, and mandibular regression occurred just prior to the presoldier molt. Spotted TUNEL signals were observed in regressing mandibles of presoldiers, suggesting that the regression involved programmed cell death. Because soldiers of N. takasagoensis possess exaggerated organs (nasus and frontal gland), the present results suggest that JH-dependent regressive mechanisms exist in the mandibles without interfering with the formation of the exaggerated organs.

Understanding consumption as political and moral practice: Introduction to the special issue

This special issue of the Journal of Consumer Culture addresses the complex intersections and interrelationships that exist among everyday consumption practices, broader ideological structures, and moralistically infused citizenship ideals. The politicized marketplace relationships (and recursive effects) that emanate from these intersections are not reducible to conventional dichotomies between the marketplace and the body politic or between consumption and civic engagement. Building upon this insight, the articles in this special issue cast new theoretical light on how political ideologies and moralistic narratives — often reproducing entrenched class, gender, and racial hierarchies — are institutionalized and contested through consumption practices.

Bioethics in a clinic for women with psychosis

Clinical ethics takes on a special cast in a rehabilitation clinic for psychosis where many patients come from severely disadvantaged backgrounds and many suffer from fluctuating decisional capacity. This paper...

Investigation of vibration characteristics of bonded structures by time-averaged electronic speckle pattern interferometry

In this paper, the vibration characteristics of bonded structures were experimentally investigated by incorporating amplitude fluctuation electronic speckle pattern interferometry (AF-ESPI) with modal testing technique. A special casting procedure was employed to manufacture the naturally bonded structures to avoid the influence resulted from the adhesive. Vibration characteristics of bonded structures with different geometrical combinations of constituent adherends and the influence of presence of an interfacial crack were investigated.

Reproducibility of fascicle length and pennation angle of gastrocnemius medialis in human gait in vivo

The purpose of the current study was to examine the reproducibility of fascicle length and pennation angle of gastrocnemius medialis while human walking. To the best of our knowledge, this is the first study of the reproducibility of fascicle length and pennation angle of gastrocnemius medialis in vivo during human gait. Twelve males performed 10 gait trials on a treadmill, in 2 separate days. B-mode ultrasonography, with the ultrasound probe firmly adjusted in the transverse and frontal planes using a special cast, was used to measure the fascicle length and the pennation angle of the gastrocnemius medialis (GM). A Vicon 624 system with three cameras operating at 120 Hz was also used to record the ankle and knee joint angles. The results showed that measurements of fascicle length and pennation angle showed high reproducibility during the gait cycle, both within the same day and between different days. Moreover, the root mean square differences between the repeated waveforms of both variables were very small, compared with their ranges (fascicle length: RMS = ∼3 mm, range: 38–63 mm; pennation angle: RMS = ∼1.5°, range: 22–32°). However, their reproducibility was lower compared to the joint angles. It was found that representative data have to be derived by a wide number of gait trials (fascicle length ∼six trials, pennation angle more than 10 trials), to assure the reliability of the fascicle length and pennation angle in human gait.

Schumpeterian Competition and Antitrust

Joseph Schumpeter's vision of competition saw it as a destructive process in which effort, assets and fortunes were continuously destroyed by innovation. One possible implication is that antitrust's attention on short-run price and output issues is myopic: what seems at first glance to be a monopolistic exclusionary practice might really be an innovative enterprise with enormous payoffs in the long run. While this may be the case, three qualifications are critical. First, one must not confuse the prospect of innovation with the scope of the intellectual property laws; their excesses and special interest capture cast serious doubt on the proposition that they are any better at fostering innovation than antitrust is. Second, for many antitrust practices positive innovation effects are difficult to foresee even on Schumpeter's own expansive and nonmathematical terms. Third, many antitrust violations serve to restrain rather than promote innovation.

When Was the First AWWA Standard Created?

This article discusses the first AWWA standard, Standard Specifications for Cast Iron Pipe and Special Castings, published on May 12, 1908. The article provides a brief history of cast iron pipe used in water service, including how it was made, and discusses the need at that time for a uniformly dependable product. The article tells how the standard was developed, starting with AWWA's Annual Conference in 1886 in Denver, Colorado, and concerns about water hammer, to AWWA's 1889 Annual Conference where three men were appointed to draft a “standard series of pipes”. After years of consensus‐building, Standard C100 was published in 1908 and remained unchanged until the 1950s.

Effect of Process Parameters, Casting Thickness, and Alloys on the Interfacial Heat-Transfer Coefficient in the High-Pressure Die-Casting Process

The heat transfer at the metal-die interface is believed to have great influence on the solidification process and cast structure of the high-pressure die-casting (HPDC) process. The present article focused on the effects of process parameters, casting thickness, and alloys on the metal-die interfacial heat-transfer coefficient (IHTC) in the HPDC process. Experiment was carried out on a cold-chamber die-casting machine with two casting alloys AM50 and ADC12. A special casting, namely, “step-shape” casting, was used and cast against a H13 steel die. The IHTC was determined using an inverse approach based on the temperature measurements inside the die. Results show that the IHTC is different at different steps and changes as the solidification of the casting proceeds. Process parameters only influence the IHTC in its peak value, and for both AM50 and ADC12 alloys, a greater fast shot velocity leads to a greater IHTC peak value at steps 1 and 2. The initial die surface temperature has a more prominent influence on the IHTC peak values at the thicker steps, especially step 5. Results also show that a closer contact between the casting and die could be achieved when the casting alloy is ADC12 instead of AM50, which consequently leads to a higher IHTC.

Colony Dehydration and Water Collection by Specialized Caste in the Leaf-Cutting Ant Atta Sexdens Rubropilosa

Social organization enables leaf-cutting ants to keep appropriate micro-ecological nest conditions for the fungus garden (their main food), eggs, larvae and adults. To maintain stability while facing changing conditions, individual ants must perceive destabilising factors and produce a proper behavioral response. We investigated behavioral responses to experimental dehydration in leaf-cutting ants to verify if task specialization exists, and to quantify the ability of ant sub-colonies for water management. Our setup consisted of fourteen sub-colonies, ten of which were randomly assigned to different levels of experimental dehydration with silica gel, whereas the remaining four were controls. The ten experimental sub-colonies were split into two groups, so that five of them had access to water. Diverse ant morphs searched for water in dehydrated colonies, but mainly a caste of small ants collected water after sources had been discovered. Size specialization for water collection was replicable in shorter experiments with three additional colonies. Ants of dehydrated colonies accumulated leaf-fragments on the nest entrance, and covering the fungus garden. Behaviors that may enhance humidity within the nests were common to all dehydration treatments. Water availability increased the life span of dehydrated colonies.

Improving FBG Sensor Sensitivity at Cryogenic Temperature by Metal Coating

Commercially available fiber Bragg grating (FBG) sensors cannot be used for measuring cryogenic temperatures because they are made of silica the thermal expansion coefficient of which tends to zero when approaching 4 K. Because of the many advantages of fiber optic sensors with respect to conventional ones, in this paper it is shown how to circumvent such a limitation by applying a proper metal coating. This approach drastically increases temperature measuring capability of FBGs at cryogenic environments typically encountered in application involving liquid gases or in space. Various metals have been deposited by electro winning on the external fiber surface previously treated with an aluminum precoating. Also, a special casting process has been developed. The explored temperature region was 4.2-40 K. The paper reports the characterization of FBG sensors coated with different metals and shows the validity of this new temperature sensor with respect to conventional ones.

Fabrication of extruded wire of MgB2/Al composite material and its superconducting property and microstructure

Superconductive MgB2/Al composite material with low and high volume fractions of particles were fabricated by our special pre-packing technique and 3-dimensional penetration casting (3DPC) method. The composite material showed homogeneous distribution of MgB2 particles in the Al-matrix with neither any aggregation of particles nor defects such as cracks or cavities. The critical temperature of superconducting transition (TC) was determined by electrical resistivity and magnetization to be about 37 ~ 39K. A billet of the superconducting composite material was successfully hot-extruded, forming a rod of 10 mm and wires of 3 and 1 mm in diameter. These intermediate products showed the onset TC of electrical resistivity also at 37-39 K. Microstructures of these samples have been observed by TEM and SEM method to establish morphology and crystallography of particles. The magneto-optic (MO) imaging method has been also applied to measure magnetic flux through this composite material when in external field.

Microstructure and Superconductive Property of the Extruded MgB<sub>2</sub>/Al Composite Materials

The superconductive MgB2/Al composite material with low and high volume fractions of particles were fabricated by our special 3-dimensional penetration casting (3DPC) method. The composite material showed homogeneous distribution of MgB2 particles in the Al-matrix with neither any aggregation of particles nor defects such as cracks or cavities. The critical temperature of superconducting transition (TC) was obtained via electrical resistivity and magnetization to be about 37 ~ 39K. The Meissner effect was also verified in the liquid He, in which a piece of the composite floated above a permanent magnet. Extruded rod and wire were successfully fabricated and they also showed onset TC of 39 K on their electrical resistivities as the same as the billet sample.

In vitro fracture strength and thermal shock resistance of metal-ceramic crowns with cast and machined AuTi frameworks

AuTi alloys with 1.6% to 1.7% (wt%) Ti provide sufficient bond strength to veneering ceramics, but the strength of entire metal-ceramic restorations fabricated from these alloys is not known. However, this information is important to assess the clinical performance of such materials. This in vitro study evaluated the fracture strength and thermal shock resistance of metal-ceramic crowns with AuTi frameworks produced by milling or casting. Frameworks of the alloy Au-1.7Ti-0.1Ir (wt%) (Esteticor Vision) were produced by milling or casting (test groups). A high-gold alloy (Esteticor Special) was used as the control. The frameworks were veneered with ceramic (VMK 95). Specimens (n=7) were loaded until fracture. Loads at failure (N) were recorded and the mean values statistically evaluated using 1-way analysis of variance and a post hoc Dunnett test (alpha=.05). To assess the crazing resistance of the veneering ceramic, 6 additional crowns of each group were subjected to a thermal shock test. Fractured surfaces were documented by scanning electron microscopy. Coefficients of thermal expansion of the materials used were measured (n=2) to assess the thermal compatibility between alloys and ceramic. The mean fracture strength of the crowns with machined AuTi frameworks (1294 +/- 236 N) was significantly lower (P=.012) than that of the cast AuTi frameworks (1680 +/- 150 N), but statistically not different than the high-gold alloy (1449 +/- 159 N). Bonding failure to the AuTi alloy predominantly occurred at the alloy-oxide interface. For the high-gold alloy, more ceramic residues were observed. In the thermal shock test, crowns with milled AuTi frameworks showed significantly higher thermal shock resistance compared to the other groups. The coefficients of thermal expansion (Esteticor Vision cast: 14.5 microm/m.K; Esteticor Vision milled: 14.3 microm/m.K; Esteticor Special cast: 13.7 microm/m.K) did not correlate with the results of the thermal shock test. The in vitro fracture strength of crowns with milled AuTi frameworks is lower than that obtained with cast AuTi frameworks, but comparable to those crowns produced with a high-gold alloy.

Evaluation of the artificial tooth and polymer-base bond in removable dentures

Introduction: The most commonly used materials for prosthetic denture base are acrylic resins - polymethyl methacrylate, which has all the important physical and chemical properties. The bond between a denture base and an acrylic tooth has a significant functional value. Aim: To evaluate the influence of various procedures on bonding quality between the denture base and the artificial tooth, the measurement of gaps when connecting the tooth and the denture base using an optical or electron microscope, and evaluating the mechanical properties by compressive testing. Materials and methods: Forty eight acrylic models with bonds between acrylic teeth and prosthetic denturebases, and 12 models for compressive testing were created as the materials in this in vitro study. The acrylic models were allocated to four groups (with 12 samples) for microscopy, and three groups for compressive testing. The samples for microscopy contained denture bases with fixed, unprocessed acrylic teeth, mechanically processed acrylic teeth, chemically processed acrylic teeth, and mechanically and chemically processed acrylic teeth, respectively. The acrylic models had the same dimensions, and the surface of each model was prepared using a slow speed saw, abrasive diamond paste, and special paper grinders. A special metal cast was created for compressive testing with internal dimensions of 20 x 9 mm. The size of a gap was measured on the light inverse microscope (Nikon Epiphot 300) and pressure testing was performed on a Zwick/Roell Z010 pressure machine. Results: The average value of the gap on mechanically and chemically treated samples was 68.250 ?m, which was significantly lower than the gap on the untreated samples with the average value of 103.75 ?m. The compressive strength was 3200 N/mm2 on untreated samples and above 6000 N/mm2 on the mechanically and chemically treated ones. Conclusions: It can be concluded that surfaces which come into contact must be mechanically and chemically processed. Although in practice prostheses are made using mechanical tooth-base retention, larger gaps occur when compared to mechanically and chemically processed surfaces.

Antennal olfactory sensitivity in response to task‐related odours of three castes of the ant Atta mexicana (hymenoptera: formicidae)

Abstract The relationship between scent composition and antennal sensitivity in different castes of Atta mexicana is investigated under laboratory conditions. Extracts of dead ants are analysed by gas chromatography‐mass spectrometry to identify the compounds presumably responsible for the specific undertaking behaviour. Oleic acid is identified as one compound that triggers undertaking behaviour. To determine differences in odour reception between workers of different castes (i.e. foragers, undertakers and soldiers), further antennal sensitivity to task‐related odours is tested using electroantennographic techniques. Soldiers are the most specialized caste because of their low response to all odours, except odourants related to alarm pheromones. The behavioural specialization of soldiers and their reduced behavioural repertoire are discussed.

Cuticular Hydrocarbons Provide Reliable Cues of Fertility in the Ant Gnamptogenys striatula

In ca. 150 species of queenless ants, a specialized queen caste is rare or absent, and mated workers take over the role of the queen in some or all of the colonies. Previously, it has been shown that reproduction in queenless ants is regulated by a combination of dominance behavior and chemical fertility signaling. It is unknown, however, whether chemical signals alone can sufficiently regulate reproduction. To investigate this possibility, we studied reproductive regulation in the facultatively queenless ant Gnamptogenys striatula, a species where dominance behavior is rare or absent. Active egg layers and infertile workers showed qualitative and quantitative differences in their cuticular hydrocarbon profile. Five long-chain methyl alkanes, 3,13- and 3,15-dimethyl pentriacontane, 3,13- and 3,15-dimethyl heptentriacontane, and 3,11,15-trimethyl heptentriacontane occurred only on the cuticles of virgin and mated egg layers. Pronounced quantitative differences were found in a further 27 alkenes; alkanes; and mono-, di-, and trimethyl alkanes. Workers that had recently stopped laying eggs had profiles similar to infertile workers, and mating status did not affect this chemical pattern. We conclude that the cuticular hydrocarbon profiles of G. striatula workers provide reliable information about their current fertility. In the interest of colony productivity, this allows reproduction to be regulated without the use of aggression.

Fabrication of fiber reinforced metal matrix composites by squeeze casting technology

Squeeze forming process is a special casting technique that combines the advantages of traditional high pressure die casting, gravity permanent mold die casting and common forging technology. It is a relatively new casting process. It is otherwise called squeeze forming, liquid forging, liquid pressing, extrusion casting, liquid metal stamping, pressure crystallization and corthias casting. The above said process was first discovered by the Russians and later it was developed in countries like USA, Europe and Japan. This advanced casting method is applied for processing of both ferrous and non-ferrous materials besides composites. The major advantages of this technology are elimination of porosity and shrinkage, 100% casting yield, attainment of greater part details, good surface finish, good dimensional accuracy, high strength to weight ratio, improved wear resistance, higher corrosion resistance, higher hardness, resistance to high temperature, improved fatigue and better creep strength. The components manufactured by this casting method requires lesser post machining operation and they have improved mechanical properties like higher strength and ductility. In squeeze casting process the liquid metal is pressurized while they solidify and hence near net shapes can be produced with sound and dense quality. The microstructural refinement of squeeze cast products is desirable for many critical applications. This process is simple, economical and it can be automated easily. The process generates the highest mechanical properties attainable in a cast product. So this process has been adopted to make composite castings at an affordable cost. This paper reviews about the principles of squeeze casting technology, which can be applied to process discontinuous fiber reinforced metal matrix composite castings. Besides this article highlights the type of engineering components produced by this advanced casting method.

Seven Big Rocks

In his column, AWWA Executive Director Jack Hoffbuhr discusses the development of product standards in the water industry, from AWWA's adoption in 1908 of the first official standard for Cast‐Iron Water Pipe and Special Castings, to the more than 140 current AWWA standards covering the essential components and chemicals used by water systems as well as pipe installation and disinfection techniques. In the year 2000 AWWA volunteers and staff reached consensus on standards in three new areas: distribution systems; water treatment; and, source water protection. In 2004 and 2005 AWWA's Board of Directors adopted standards for Distribution Systems and Water Treatment Plant Operation and Management. Hoffbuhr issues a challenge to utilities to use this new breed of standard to see how they measure up, and to use the knowledge gained as part of a continuous improvement program.