Uncoupled actuation of pan-tilt wrists

Using algebraic properties of displacement (or rigid-body motion) subsets, the paper introduces new two-degree-of-freedom (2-DOF) nonoverconstrained orientation mechanisms. The angles of pan and tilt are also referred to as the angles of precession /spl psi/ and nutation /spl theta/, respectively, employing the standard terminology of Euler angles. A serial array of two revolute pairs provides the kinematic constraint of an end-effector. For instance, the first axis of rotation is fixed vertically, and the second axis rotates around the first axis, remaining parallel to the horizontal plane. Such a 2-DOF wrist is fit for orienting various devices like telescopes, cameras, antennas, etc. The first axis is fixed, and can be actuated by any powerful heavy servomotor. The paper discloses new mechanisms that allow the actuation of the second movable axis by a fixed servomotor. Moreover, the actuation of the movable axis is not a function of the pan /spl psi/. In other words, the pan and the tilt are controlled independently or in a fully uncoupled manner.     

Oil removal from water by selective sorption on hydrophobic cotton fibers. 1. Study of sorption properties and comparison with other cotton fiber-based sorbents

Hydrophobic cotton fibers, obtained by acylation of cellulose with fatty acid using microwaves radiations, have a high selective affinity for vegetable or mineral oil, fuel, and petroleum, in aqueous medium. Their sorption capacity (SC) (weight of liquid picked up by a given weight of sorbent) is about 20 g/g, after draining. They are reusable after simple squeezing, and their SC reaches a constant value, ca. 12 g/g. Moreover, this product is stable in water, whereas raw cotton can develop molds, after oil sorption. Besides, it is also biodegradable.     

对北京葡萄酒市场和大学生葡萄酒消费群体的调查

通过问卷,对在校大学生进行了葡萄酒市场和营销的调查.结果表明,在购买目的不同时,受访者对葡萄酒的心理期望价格存在明显的差异,自我期望价格在30～80元/瓶,而用于宴请和送礼等活动时,对葡萄酒的期望价格明显提高.产地是影响葡萄酒选购的另一个重要因素,国产酒具有显著的优势,用于自己消费时选购国产酒的占66.4%,对进口酒只有法国葡萄酒具有较高的消费认同度,且集中在以送礼等为目的的高端消费.与价格、产地因素相比,年份对受访群体的葡萄酒选购影响相对较小,同时受访者对葡萄酒的星级与获奖的信任程度也很低.