Effect of specimen size and grain size on deformation in microextrusion

Miniaturization of systems and devices continues unabated, which in turn requires the production of microscale components. Similar to the macroscale process, microextrusion provides a means to fabricate metallic micropins having characteristic dimensions on the order of 1 mm or less with a lower-cost, high-throughput process. In this paper, the effect of the specimen size and grain size on deformation during microextrusion is investigated. Microhardness, microstructure, and X-ray texture analyses show that when the grain size becomes comparable to the specimen feature size, together with miniaturization, penetration of the shear deformation occurs. As a result, the coarse-grained structure has higher hardness than the fine-grained structure, especially in the central regions of the cross-section for the two smallest size extrusion cases investigated, which have Ø0.76/0.57 mm and Ø1.5/1.0 mm dimensions before and after extrusion, respectively. For the largest size extrusion case investigated, Ø2.0/1.33 mm pins, the coarse-grained structure has a lower hardness than the fine-grained one, which is typical for macroscale processes and consistent with the Hall–Petch relationship.     

Effects of Starch Sources and Supplementary Materials on Starch Based Foam Trays

Firstly, foam trays were produced from glyoxal cross-linked wheat, potato and corn starches and their mixtures. The most suitable starch type for starch-based foam tray production was selected according to the level of water absorption, density, surface and cross-section micrographs of the foam trays. It was decided that a wheat and potato starch blend was the most suitable starch source for producing the foam trays because they have the lowest water absorption percentage (25.5 ± 0.7%), low density (0.17 ± 0.01 g/cm³) and a smooth surface. Potato–wheat starch foam trays with fibres were produced by adding wheat and wood fibres. Unlike wood fibres addition, wheat fibres significantly decreased the percentage of water absorption (16.63 ± 1.2%) and density (0.115 ± 0.013 g/cm³) of the tray. Also, the trays including wheat fibre had a lighter colour than the wheat–potato starch tray. To further reduce water absorption of the tray, the trays were made by adding two different types of lipids (beeswax or shortening and three different types of filler materials—kaolin, montmorillonite or zinc oxide nanoparticles). According to the level of water absorption of the trays, it was decided that shortening and zinc oxide nanoparticles, in addition to kaolin, were respectively the most suitable lipid and filler materials. The foam trays were produced by adding these supplementary materials. The addition of shortening slightly, zinc oxide nanoparticles moderately and kaolin greatly increased the density of the wheat potato starch tray including fibre. However, the percent of water absorption of the trays containing wheat fibre + shortening or wheat fibre + shortening + zinc oxide nanoparticles decreased 6.4 ± 0.01 and 5.9 ± 0.3%, respectively.     

Geoenvironmental behavior of foundry sand amended mixtures for highway subbases

The high cost of landfilling and the potential uses of waste foundry sands have prompted research into their beneficial reuse. Roadways have a high potential for large volume usage of the foundry sands. A laboratory testing program was conducted on soil-foundry sand mixtures amended with cement and lime to assess their applicability as highway subbase materials. The mixtures were compacted in the laboratory at a variety of moisture contents and compactive efforts and subjected to unconfined compression, California bearing ratio, and hydraulic conductivity tests. The environmental suitability of the prepared mixtures was evaluated by analyzing the effluent collected during hydraulic conductivity tests. Finally, required subbase thicknesses were calculated using the laboratory-based strength parameters. The results of the study show that the strength of a mixture is highly dependent on the curing period, compactive energy, lime or cement presence, and water content at compaction. The resistance of foundry sand-based specimens to winter conditions is generally better than that of a typical subbase reference material. Laboratory leaching tests indicated that if these mixtures later come in contact with water that has been discharged directly to the environment (e.g., drainage through asphalt pavement), the quality of water will not be affected.     

Analysis of Atmospheric Conditions during Air Pollution Episodes in Ankara,Turkey

ABSTRACT

This paper presents a detailed analysis of the meteorological conditions that are associated with strong air pollution episodes in Ankara, Turkey. Based on climatological and air quality data [SO₂ and TSP (total suspended par-ticulates)] obtained for the winter months during 19891994, the analysis showed that the presence of weak atmospheric pressure gradients and warm air advection were the most important factors leading to high SO₂ and TSP concentrations. In addition, the onset of the high air pollution episodes was generally associated with a trend toward negative vorticity at the 850-hPa level.     

Classification of dimension stone wastes

Purpose

For countries in which the stone industry is well developed, opposition to quarry and plant waste is gradually increasing. The primary step for waste control and environmental management is to define the problem of concern. In this study, natural building stone wastes were classified for the first time in the literature.

Methods

Following on-site physical observations and research at more than 50 quarries and 20 plants, stone wastes were classified as (1) solid, (2) dust and (3) semi-slurry, slurry and cake.

Conclusions

As a result of this study, the characteristics of wastes, their main environmental threats and the industries in which wastes could be used were defined for each group.     

Resident perceptions of livelihood impacts arising from the Kızıldağ National Park,Turkey

In this study, perceptions, needs, expectations and participation levels in the park management of residents of the K?z?lda? National Park were investigated. It was focused on especially how residents’ livelihood was affected by establishment and management of K?z?lda? National Park. It was examined why residents do not support protection efforts. Research data were obtained with the help of a survey form prepared to determine the perceptions of residents living in the national park. For the analyses of obtained data, statistics package program (SPSS 20) was used and also independent-samples t test and one-way analyses of variance were applied. As a result, the most important negative effects were loss of income and changes in traditional lifestyle. The most affected group from these negative effects was the ones dealing with animal husbandry. For the sustainable management and protection of national park, sense of belonging should be brought to residents so as to increase participation, traditional lifestyle of residents should be conserved and new sources of income should be generated for residents. To improve the participation of residents in national park management, community engagement mechanisms can be used as a tool.     

Assessment of groundwater quality of the Tatlicay aquifer and relation to the adjacent evaporitic formations (Cankiri,Turkey)

One of the most important hydrogeologic problems in and adjacent areas of evaporitic formations is severe quality degradation of groundwaters. These kinds of groundwaters contain high content of dissolved solids and generally have some limitations for use. Tatlicay basin (north-central Turkey) is an example to effects of the evaporites on groundwater quality in the adjacent alluvium aquifer. Gypsum and anhydrites in the two evaporite formations (Bayindir and Bozkir) effect of the groundwater quality in the alluvium adversely, by dissolution of the evaporites by surface drainage and infiltration into the alluvium aquifer (widespread effect) and by infiltration of low quality gypsum springs (local effect) into the aquifer. Evaporitic formations significantly increased EC, TDS, Ca and SO₄ parameters in the alluvium aquifer in the central and downstream regions. EC has increased roughly from 500–800 to 1,700–2,000 μS/cm, Ca has roughly increased from 3–4 to 10 meq/l, SO₄ has increased 0.5–1 to 11–12 meq/l. Consequently, three clusters were distinguished in the basin; (1) nonevaporitic waters in low TDS, Na, Ca, Mg, Cl and SO₄, (2) diluted waters in high TDS and relatively high Cl, moderate-relatively high Na, Ca, Mg, SO₄, (3) gypsum springs in highest TDS, Ca, SO₄, but moderate Mg and low Na, Cl.     

Alkali-silica reactions of mortars produced by using waste glass as fine aggregate and admixtures such as fly ash and Li2CO3

Use of waste glass or glass cullet (GC) as concrete aggregate is becoming more widespread each day because of the increase in resource efficiency. Recycling of wastes is very important for sustainable development. When glass is used as aggregate in concrete or mortar, expansions and internal stresses occur due to an alkali-silica reaction (ASR). Furthermore, rapid loss in durability is generally observed due to extreme crack formation and an increase in permeability. It is necessary to use some kind of chemical or mineral admixture to reduce crack formation. In this study, mortar bars are produced by using three different colors of glass in four different quantities as fine aggregate by weight, and the effects of these glass aggregates on ASR are investigated, corresponding to ASTM C 1260. Additionally, in order to reduce the expansions of mortars, 10% and 20% fly ash (FA) as mineral admixture and 1% and 2% Li(2)CO(3) as chemical admixture are incorporated by weight in the cement and their effects on expansion are examined. It is observed that among white (WG), green (GG) and brown glass (BG) aggregates, WG aggregate causes the greatest expansion. In addition, expansion increases with an increase in amount of glass. According to the test results, it is seen that over 20% FA and 2% Li(2)CO(3) replacements are required to produce mortars which have expansion values below the 0.2% critical value when exposed to ASR. However, usages of these admixtures reduce expansions occurring because of ASR.