催化氧化法合成脂肪醇醚羧酸盐的研究进展

详细介绍了氮氧自由基催化氧化法和贵金属催化氧化法合成脂肪醇醚羧酸盐。氮氧自由基催化时,反应温度20～60℃,反应时间3～6 h,得到酸型产品。贵金属催化剂中,钯的催化活性比铂高。贵金属催化时,加入铅、铋等助催化剂,并以活性炭为载体,碱性条件下于50～90℃反应2～6 h,得到盐型产品。在适当的条件下,这两种方法均可使醇醚转化率达95％,选择性达90％以上。     

Rapid Prototyping and Tooling of Custom-Made Tracheobronchial Stents

Rapid prototyping (RP) and rapid tooling (RT) techniques can be applied to the field of medicine primarily because of their ability to produce customised profiles and geometries in relatively short lead times. In this paper, the process by which these techniques can be applied for the production of customised tracheobronchial stents for the purpose of maintaining patency in an occluded respiratory tract is described. A comparison of RP systems was carried out to establish the preferred RP method to produce the master model. The vacuum casting RT process was then used to produce the stent.     

A new method of preform design in hot forging by using electric field theory

The preform design in metal forging plays a key role in improving product quality, such as ensuring defect-free property and proper metal flow. In industry, preforms are generally designed by the iterative trial-and-error approach. This approach, however, leads not only to the increase of significant tool cost but also to the extended down-time of the production equipment. It is thus necessary to reduce time and man power through an effective method of preform design. In this paper, the equi-potential lines designed in the electric field are introduced to find an appropriate preform shape. The equi-potential lines generated between two conductors of different voltages show similar trends for the minimum work paths between the undeformed shape and the deformed shape. Based on this similarity, the equi-potential lines obtained by the arrangement of the initial and final shapes are utilized for the design of the preform, and then the artificial neural network is used to find the range of initial volume and potential value of the electric field.     

克拉玛依原油中各组分的乳化性质

用沉淀法和色谱分离法将克拉玛依原油分离成沥青质，极性物和抽余油三组分，红外光谱分析表明，沥青质和极性物中存在一些含氧官能团的羧酸类或酚类以及含氮化合物，而抽余油则主要为烃类物质，因而沥青质和极性物的界面活性大于抽余油，沥青质具有较强的油包水（W／O）乳化能力，是造成克拉玛依原油W／O乳化的主要组分，极性物具有较强的水包油（O／W）乳化能力，是造成克拉玛依原油O／W乳化的主要组分，抽余油的乳化能力很弱。     

曙—区超稠油间歇蒸汽吞吐技术探讨

针对曙-区超稠油井进入高周期后产量递减，成本上升的矛盾，提出用间歇吞吐技术改善高周期蒸汽吞吐效果，通过对吞吐机理和现场实际资料统计的分析。对这项技术实施的条件及效果进行了探讨。结果表明，该项技术在高周期井实施效果较好。具有较好的推广前景。     

Electromagnetic interference mitigation by using a spread-spectrumapproach

We investigate a new technique, referred to as spread-spectrum clock generation (SSCG), for reducing the level of radiated emission from devices with digital clock signals. To calculate the radiated emissions from such devices, we model the radiating geometry and compute the radiated field at a multitude of frequencies by using NEC-4, which is an electromagnetic field solver based on the method of moments (MoM). We consider a variety of modulating profiles for the spread spectrum clock and demonstrate that by using a frequency deviation of only 1%, we can achieve from 10 to 30 dB reduction in the radiated emission levels     

Dynamic sectorization of microcells for balanced traffic in CDMA:genetic algorithms approach

With the increase of cellular users, traffic hot spots and unbalanced call distributions are common in wireless networks. As a solution to this problem, code-division multiple-access techniques enable a base transceiver station to connect microcells with optical fibers and to control the channels by sectorizing the microcells. To solve the load balancing among microcells, we dynamically sectorize the microcells depending on the time-varying traffic. The microcell sectorization problem is formulated as an integer linear programming that minimizes the blocked and handoff calls in the network. In the proposed sectorization, proper, connected, and compact sectors are considered to keep the handoffs as small as possible while satisfying the channel capacity at each sector. Three genetic algorithms (GAs) are proposed to solve the problem: standard GA, grouping GA, and parallel GA. Computational results show that the proposed GAs are highly effective. All three GAs illustrate outstanding performance for small size problems. The parallel GA, which is based on the operators used in grouping GA, demonstrates excellent solution quality in a reasonable time     

50 nm MOSFETs with side-gates for induced source/drain extension

50 nm long MOSFETs with side-gates were optimised in terms of the side-gate length and successfully fabricated with conventional MOS technology. The simulated and fabricated 50 nm long MOSFET shows a reasonable subthreshold swing of 81 mV/dec and a low drain induced barrier lowering of 77 mV     

Rate-driven key frame selection using temporal variation of visualcontent

A simple and fast method to select the assigned number of key frames in a video shot is presented. The algorithm selects the key frames so that the temporal variation of visual content within a video shot is equally distributed to each key frame. Simulation results on a real video sequence are shown to be in agreement with the human visual perception     

An elementary proof of Sylvester’s double sums for subresultants

In 1853 Sylvester stated and proved an elegant formula that expresses the polynomial subresultants in terms of the roots of the input polynomials. Sylvester’s formula was also recently proved by Lascoux and Pragacz using multi-Schur functions and divided differences. In this paper, we provide an elementary proof that uses only basic properties of matrix multiplication and Vandermonde determinants.