Observability Analysis of Continuous‐Time LTI Systems with Limited Derivative Data

We consider continuous‐time LTI systems with either unknown‐input or with lack of information about the input and output derivatives. We compute the unknown‐input observability subspace and the observability subspace with unknown derivatives of input and output. We first formulate the unknown‐input observability subspace via projection matrices, then show that through having the unknown‐input observability subspace, one can easily evaluate the effect of known input and output signals but unknown derivatives on the observability subspace. Our method is demonstrated on the dynamics of a longitudinal aircraft in steady‐state flight.     

Structure and properties of polyimide‐bonded magnets processed from prepolymers based on diacetyl derivatives of aromatic diamines and dianhydrides

We report a novel method of polyimide (PI) synthesis from prepolymers based on dianhydrides and diacetyl derivatives of aromatic diamines that facilitate the preparation of a melt processable mixture at 300 ± 10°C of the prepolymer and magnetic Nd‐Fe‐B alloy to provide PI‐bonded magnets with enhanced properties. It is shown that chemical structure of the prepolymers strongly influences viscosity behavior via crystallization of the oligoimide in the melt, leading to formation of PI with rigid‐rod like structure. This structural ordering of the prepolymers based on diacetyl derivative of diamine used in this study, if not controlled, leads to exponential increase of melt viscosity with time, making it practically impossible to prepare melt processable mixture of the magnetic particles and the PI prepolymers at elevated temperatures. The results obtained demonstrate that appropriate dianhydrides and diacetyl derivatives of diamines that do not lead to crystallization of oligoimides in prepolymer mixture can be used under controlled processing conditions to prepare melt‐processable PI‐bonded magnets containing rigid‐rod like PI structure that significantly increases thermal stability of the magnets. The temperature dependencies of the magnetic properties of the PI‐bonded magnets under conditions that they are likely to encounter during their service life were found to be remarkably similar to that of commercial thermoplastic magnets such as injection‐molded nylon magnets. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 478–485, 2006     

Mechanical properties and crosslink density of rare earth‐modified high‐abrasion furnace‐filled powdered natural rubber

High‐abrasion furnace‐filled powdered natural rubber [P(NR/HAF)] has more advantages than traditional HAF‐filled bale NR (NR/HAF) because of its better environmental performance and easier processing quality, but its lower mechanical properties are disadvantageous. To improve the mechanical properties, rare earth‐modified HAF‐filled powdered NR [P(NR/HAF‐Ln)] (Ln = Sm,La,Pr) was prepared by means of coacervation–coprecipitation, using rare earth‐modified HAF as separant and filler. The effect on mechanical properties of P(NR/HAF‐Ln) vulcanizate exerted by the emulsifier/HAF ratio, powdering temperature, Ln/HAF ratio and type of Ln, and HAF content were studied. The results indicated that when optimum formulation, the mechanical properties of P(NR/HAF‐Ln) vulcanizate were better than P(NR/HAF) vulcanizate. In addition, the relationship of the apparent crosslink density and HAF content of P(NR/HAF‐Ln), P(NR/HAF), NR/HAF vulcanizates was also investigated, along with their SEM microphotographs of tensile fracture surface, which indicated that the excellent mechanical properties of P(NR/HAF‐Ln) vulcanizate was attributed to correct amount of Ln that could increase crosslink density and reinforce the interface structure of NR matrix/HAF‐Ln particle. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1755–1762, 2006     

Damping of vinyl acetate–n‐butyl acrylate copolymers

A photopolymerization process at room temperature was devised to copolymerize vinyl acetate (VAc) and n‐butyl acrylate (BA) mainly to prepare rubber‐like damping sheet bearing pressure‐sensitive adhesive property in this study. The investigations using both the differential scanning calorimeter and rheometric dynamic analysis show the existence of two glass transition temperatures for each copolymer. The scanning electron microscopic pictures reveal that the degree of microphase separation increases with increasing annealing time at 70°C. It was suggested that the rubbery domain (formed by the PBA blocks) disperses in the glassy domain (constituted by the PVAc blocks), making an effective damping entity. Excellent damping was observed for the copolymer samples, with the tanδ peak values as high as 1.76–1.80 at a certain temperature range and with tanδ> 0.3 at quite wide temperature ranges. In addition, the copolymers containing more VAc tend to have the higher damping. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1396–1403, 2004     

外加剂对陶瓷釉面表面性质的影响研究

研究了不同外加剂对陶瓷釉面表面性质的影响。研究表明 ,外加剂的加入可改变陶瓷釉面的表面张力 ,即影响液体对陶瓷釉面的润湿性能。在所选择的外加剂中 ,降低陶瓷釉面表面张力最强的为PbO ,其合适的加入量为 1.5 %。     

用接触角法测量聚合物共混体系的表面性能

利用接触角的方法研究了聚合物HDPF、PET及其共混物HDPE／PET的表面自由能、极化度以及与不同液体一水和甘油间界面张力的大小。     

Characterization and application of polypropylene films modified with stimuli‐sensitive copolymers with an Ar‐plasma postpolymerization technique

Surface‐modified polypropylene (PP) films with thermally and photochemically sensitive copolymers consisting of N‐(2‐hydroxypropyl)methacrylamide (HPMA) and 4‐(4‐methoxyphenylazo)phenyl methacrylate (MPAP), poly(HPMA‐co‐MPAP)‐g‐PP (abbreviated g‐PP) film, were prepared by graft copolymerization with an Ar‐plasma postpolymerization technique. The surfaces of the g‐PP films were characterized by means of X‐ray photoelectron spectroscopy; the percentage grafting of poly(HPMA‐co‐MPAP) with a number‐average molecular weight of 3.28 × 10⁴ was 7.12%, and the molar ratio of HPMA–MPAH in the copolymer was 0.75:0.25. The stimuli‐sensitive adsorption of albumin and polystyrene microspheres on the g‐PP film was also measured. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 143–148, 2003     

Physical agglomeration behavior in preparation of cellulose‐N‐methyl morpholine N‐oxide hydrate solutions by simple mixing

The different melting temperatures of N‐methyl morpholine N‐oxide (NMMO) hydrates in the cellulose–NMMO hydrate solution may be explained by the rather different crystal structures of NMMO hydrates, which are determined by the amount of the hydrates. The preparative process of cellulose–NMMO hydrate solution may result in cellulose structural change from cellulose I to cellulose II, depending on the amount of the hydrate. Mixtures of cellulose and NMMO hydrate in a blender was changed from the granules to slurry with increasing mixing time at 60–70°C, which is below the melting point of the NMMO hydrate. In the case of 15 wt % cellulose–NMMO hydrate granules, which were made by mixing for 20 min, the melting points of various NMMO hydrates were obtained as 77.8°C (n = 0.83), 70.2°C (n = 0.97), and 69.7°C (n = 1.23), respectively, depending on the hydrate number. However, the melting points of cellulose–NMMO hydrate slurry and solution were shifted lower than those of cellulose granules, while the mixing time of slurry and solution are 25 and 35 min, respectively. These melting behaviors indicate instantaneous liquefaction of the NMMO hydrate and the diffusion of the NMMO hydrate into cellulose during mixing in a blender. When cellulose was completely dissolved in NMMO hydrate, the crystal structure of cellulose showed only cellulose II structure. In the cellulose–NMMO products of granules or slurry obtained by high‐speed mixing, which is a new preparation method, they still retained the original cellulose I structure. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1687–1697, 2004     

Pricing strategies with reference effects in competitive industries

This paper examines the effect of reference prices on companies operating within competitive industries. We confirm that even with competition, firms optimally price high in the short term to generate a high reference price and then decrease this price over time. Competitors' prices converge toward each other over time, emphasizing the short‐term nature of reference prices. We then show that pricing optimally to take advantage of reference prices generates a positive externality for other firms in an industry, such that competitors may generate higher profit. The longer the focus of a given firm, the more profit the firm generates, but less relative to its competitors. This arises because the externalities created through pricing high to increase reference prices outweigh the benefits of the higher reference prices themselves. If pricing managers are compensated relative to their competition, this suggests that short‐termism may be implicitly encouraged to the detriment of profit.     

A bi‐objective approach to reschedule new jobs in a one machine model

We consider a one machine scheduling model, minimizing a classical objective function—either the total completion time or the maximum tardiness—and with two sets of jobs: one with initial jobs already scheduled and one with new jobs that must be inserted in the schedule. As such rescheduling can create a modification of the schedule of the initial jobs, a disruption objective is considered in addition to the original objective. This additional objective can be formulated in four different ways. Such model has been introduced by Hall and Potts, minimizing either a linear aggregation of the two objectives or the initial objective under a constraint giving an upper limit of the disruption objective. In this paper, the aim is to obtain the set of efficient schedules in regard to the two objectives. Algorithms are provided for the eight possible bi‐objective problems and illustrated by some didactic examples.