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In order to understand the impact of layer-wise scanning direction in the Selective Laser Sintering process, test coupons were manufactured for mechanical testing from DuraForm(TM) Polyamide powder. The effects of laser energy density, varying between 0.003 and 0.024 J/mm2 were examined in test specimens rotated 90º through the Z axis. SLS machines do not always facilitate 'cross-hatching' of layers and therefore orientation has a major influence on part quality. When employed, the cross-hatching technique scans successive layers perpendicularly to the previous. Studying how parts perform with scan lines in a common direction, will assist in the understanding of how SLS parts behave in practice. Results showed that physical density, tensile strength and elongation rose with energy density up to 0.012 J/mm². This initial rise was due to a continued improvement in particle fusion with increasing energy density. Above 0.012 J/mm², these properties started to decline at different rates depending on their orientation (scan direction) on the part bed. Specimen's oriented perpendicularly to the X axis exhibited a greater elongation at the expense of tensile strength, when compared to parallel specimens.

Next month the United Nations is sponsoring a World Conference on Agrarian Reform and Rural Development (WCARRD). The purpose of this Rome-based conference is, according to the Food and Agriculture Organization, \"the transformation of the rural areas of the world from backwardness and poverty into healthy environments capable of contributing fully to national progress.\"

Nelson reviews \"History of the Mass Media in the United States: An Encyclopedia\" edited by Margaret A. Blanchard.

Nelson reviews \"Red Blood & Black Ink: Journalism in the Old West\" by David Dary.