A neural-network approach to radiometric sensing of land-surfaceparameters

A biophysically-based land-surface process/radiobrightness (LSP/R) model is integrated with a dynamic learning neural network (DLNN) to retrieve the land-surface parameters from its radiometric signatures. Predictions from the LSP/R model are used to train the DLNN and serve as the reference for evaluation of the DLNN retrievals. Both horizontally polarized and vertically polarized brightnesses at 1.4 GHz, 19 GHz, and 37 GHz for an incidence angle of 53° make up the input nodes of the DLNN. The corresponding output nodes are composed of land-surface parameters, canopy temperature and water content, and soil temperature and moisture (uppermost 5 mm). Under no-noise conditions, the maximum of the root mean-square (RMS) errors between the retrieved parameters of interest and their corresponding reference from the LSP/R model is smaller than 28 for a four-channel case with 19 GHz and 37 GHz brightnesses as the inputs of the DLNN. The maximum RMS error is reduced to within 0.5% if additional 1.4 GHz brightnesses are used (a six-channel case). This indicates that the DLNN produces negligible errors onto its retrievals. For the realization of the problem, two different levels of noises are added to the input nodes. The noises are assumed to be Gaussian distributed with standard deviations of 1 K and 2 K. The maximum RMS errors are increased to 9.3% and 10.3% for the 1 K-noise and 2 K-noise cases, respectively, for the four-channel ease. They are reduced to 6.0% and 9.1% for the 1 K-noise and 2 K-noise cases, respectively, for the six-channel case. This is an implication that 1.4 GHz is a better frequency in probing soil parameters than 19 GHz and 37 GHz     

A Multimedia World Wide Web Based Conference Minute System for Group Collaboration

In this paper, we propose a World Wide Web based conference minute system which preserves important information in the conference as web documents and maintains hyperlinks to related minutes to accelerate the progress of the project. This system, based on our Java application sharing framework, provides capabilities to record and replay the audio/video data of the video conference and operations of the shared applications used in the meeting in a synchronous manner. Through the hyperlinks, people can quickly understand the logic flow of every meeting held in the project duration and select any part in a meeting for replay to know what has actually happened. Furthermore, when a new meeting is held, a minute template is generated by the system to inherit the hyperlinks from its predecessors. Other related minutes and the execution status of the resolutions in the project can be easily accessed through the hyperlinks between them. Through the help of the system, execution of the project and management of its organizational memory could be easily achieved to increase the productivity of the collaborative groups with geographically dispersed members.     

Preparation and characterization of a star‐shaped polystyrene‐b‐poly(ethylene‐co‐propylene) block copolymer as a viscosity index improver of lubricant

A saturated star‐shaped polystyrene‐b‐poly(ethylene‐co‐propylene) block copolymer, (SEP)_star, was synthesized for use as a viscosity index improver in lubricants. Polystyrene‐b‐polyisoprene arms were first made anionically, followed by a linking reaction at the optimum temperature of 60°C with divinylbenzene. The resulting star‐shaped (SI)_star was hydrogenated to eliminate the double bonds on the polyisoprene segment, thus forming the star‐shaped (SEP)_star. The number of arms on each molecule increased with an increase in the mol ratio of divinylbenzene to n‐butyllithium. Increasing the arm length adversely affected the linking efficiency but caused a slight increase in the degree of branching. The T_g of the poly(ethylene‐co‐propylene) block was 13°C higher than that of the original polyisoprene block. Compared with (SI)_star, (SEP)_star has a thermal decomposition temperature 50°C higher but independent of the arm length or the degree of branching. Viscosity measurements for (SEP)_star revealed that intrinsic viscosity depends only on the arm length, but not on the degree of branching. Adding 1 wt % of (SEP)_star markedly increased the viscosity index of a HN base oil. With a fixed arm length, a (SEP)_star having a higher degree of branching increased the viscosity index more than that having a lower degree of branching. On the other hand, the viscosity index increased with an increase in the arm length when the degree of branching was fixed. The addition of 1wt % of (SEP)_star increased the vioscosity index up to a number between 111 and 166, with the exact number depending upon its arm length and degree of branching. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1838–1846, 2001     

Synthesis and properties of new poly(amide‐imide)s based on 2,5‐bis(trimellitimido)chlorobenzene

A series of new aromatic poly(amide‐imide)s were synthesized by the triphenyl phosphite‐activated polycondensation of the diimide‐diacid, 2,5‐bis(trimellitimido)chlorobenzene (I) with various aromatic diamines in a medium consisting of N‐methyl‐2‐pyrrolidone (NMP), pyridine, and calcium chloride. The poly(amide‐imide)s had inherent viscosities of 0.76–1.42 dL g⁻¹. The diimide‐diacid monomer (I) was prepared from 2‐chloro‐p‐phenylenediamine with trimellitic anhydride. Most of the resulting polymers showed an amorphous nature and were readily soluble in a variety of organic solvents, including NMP and N,N‐dimethylacetamide. Transparent, flexible, and tough films of these polymers could be cast from N,N‐dimethylacetamide or NMP solutions. Their cast films had tensile strengths ranging from 74 to 95 MPa, elongations at break from 7 to 11%, and initial moduli from 1.38 to 3.25 GPa. The glass transition temperatures of these polymers were in the range of 233°–260°C, and the 10% weight loss temperatures were above 450°C in nitrogen. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1691–1701, 1999     

Synthesis and characterization of new poly(amide‐imide)s based on 1,4‐bis(trimellitimido)‐2,5‐dichlorobenzene

A series of new aromatic poly(amide‐imide)s were synthesized by the triphenyl phosphite‐activated polycondensation of the diimide‐diacid, 1,4‐bis(trimellitimido)‐2,5‐dichlorobenzene (I), with various aromatic diamines in a medium consisting of N‐methyl‐2‐pyrrolidone (NMP), pyridine, and calcium chloride. The poly(amide‐imide)s had inherent viscosities of 0.88–1.27 dL g⁻¹. The diimide‐diacid monomer (I) was prepared from 2,5‐dichloro‐p‐phenylenediamine with trimellitic anhydride. All the resulting polymers were amorphous and were readily soluble in a variety of organic solvents, including NMP and N,N‐dimethylacetamide. Transparent, flexible, and tough films of these polymers could be cast from N,N‐dimethylacetamide or NMP solutions. Cast films had tensile strengths ranging from 92 to 127 MPa, elongations at break from 4 to 24%, and initial moduli from 2.59 to 3.65 GPa. The glass transition temperatures of these polymers were in the range of 256°–317°C, and the 10% weight loss temperatures were above 430°C in nitrogen. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 271–278, 1999     

包装设计的时间和空间特征

时间和空间是包装的表层效果，论述时间和空间特征，以使在包装设计过程中加强认识，更好地发挥其功能作用。