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排序方式: 共有1363条查询结果,搜索用时 15 毫秒
161.
As vacuum‐assisted resin transfer molding (VARTM) is being increasingly used in aerospace applications, the thickness gradient and variation issues are gaining more attention. Typically, thickness gradient and variations result from the infusion pressure gradient during the process and material variations. Pressure gradient is the driving force for resin flow and the main source of thickness variation. After infusion, an amount of pressure gradient is frozen into the preform, which primarily contributes to the thickness variation. This study investigates the mechanism of the thickness variation dynamic change during the infusion and relaxing/curing processes. A numerical model was developed to track the thickness change of the bagging film free surface. A time‐dependent permeability model as a function of compaction pressure was incorporated into an existing resin transfer molding (RTM) code for obtaining the initial conditions for relaxing/curing process. Control volume (CV) and volume of fluid (VOF) methods were combined to solve the free surface problem. Experiments were conducted to verify the simulation results. The proposed model was illustrated with a relatively complex part. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers 相似文献
162.
Pietro Russo Giorgio Simeoli Domenico Acierno Valentina Lopresto 《Polymer Composites》2015,36(11):2022-2029
Polyolefin‐based composite laminates reinforced with jute fabric were prepared by compression molding and investigated in terms of flexural properties and impact behavior. The use of a virgin polypropylene as the matrix was compared with two polyolefin matrices coming from discarded car bumpers and selected packaging wastes, respectively, and mainly constituted by mixtures of polyethylene and polypropylene resins. The influence of a coupling agent (maleated polypropylene) was always considered in order to improve the interfacial adhesion and, consequently, the composite strength. The effect of this coupling agent, clearly dependent on the amount of polypropylene phase in the overall mixture, was found to be satisfactory only in the case of virgin polypropylene‐based systems. These latter, in presence of maleated polypropylene, have shown higher flexural parameters, lower propagation energy and higher breaking impact load with respect to uncompatibilized ones. Results were supported by morphological observations of impact surfaces, always highlighting a poor adhesion at the reinforcement–matrix interface except in compatibilized virgin polypropylene‐based laminates. POLYM. COMPOS., 36:2022–2029, 2015. © 2014 Society of Plastics Engineer 相似文献
163.
Diethyltoluenediamines (DETDA) was grafted to single‐walled carbon nanotubes (SWNTs) through diazonium‐based addition for improving dispersion and interfacial bonding in SWNT/epoxy nanocomposites. Characterization results of Fourier Transformed Infrared spectroscopy and Raman spectroscopy validated covalent bonding between DETDA and carbon nanotubes. The degree of functionalization was about 4% based on thermo‐gravimetric analysis. Interfacial bonding strength was computed in the presence of chemical bonding and the computation results indicated that the interfacial shear strength in the presence of functionalized carbon nanotubes was significantly enhanced. The experimental test revealed that the tensile strength of nanocomposites was enhanced about 23% and Young's modulus about 25%, with 0.5 wt% loading of functionalized‐nanotubes. These considerable improvements further verified the load‐transfer enhancement in the functionalized‐SWNTs/epoxy nanocomposites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers 相似文献
164.
V Bonfante S Viviani A Santoro L Devizzi A Di Russo M Zanini F Soncini H Soto Parra P Valagussa G Bonadonna 《Canadian Metallurgical Quarterly》1998,103(2):533-535
Twenty-six patients with relapsed or refractory Hodgkin's disease (HD) were treated with an intensive salvage regimen combining ifosfamide (3000 mg/m2/d, days 1-4 through continuous intravenous infusion) and vinorelbine (25 mg/m2, i.v. days 1 and 5) with mesna uroprotection and G-CSF support. Courses were given at 3-week intervals. Ten patients achieved a complete and 10 patients a partial response, yielding an overall response rate of 77%. The main toxic effect was neutropenia and the combination was well tolerated. 相似文献
165.
A Pizziol V Tikhonoff CD Paleari E Russo A Mazza G Ginocchio C Onesto L Pavan E Casiglia AC Pessina 《Canadian Metallurgical Quarterly》1998,52(11):846-849
BACKGROUND: Leishmaniasis recidiva cutis (LRC) is rare in New World leishmaniasis. Only seven cases have been reported so far. MATERIALS AND METHODS: Four cases are reported here. Parasite diagnosis was performed by classical methods of touch preparations, histopathologic sections, and cultures. In addition, the detection of parasite DNA by the polymerase chain reaction (PCR) was performed in all cases. RESULTS: Parasites were detected by at least one of the classical methods in all primary lesions; however, only the PCR was positive in the recidivant lesions. DISCUSSION: LRC cases most likely represent a reactivation of an initial infection, probably due to the persistence of parasites in scarred tissue. Although lupoid leishmaniasis (LL) has been used as a synonym of LRC, a clear difference between LRC and LL can be defined as LL is the initial clinical presentation while LRC is a recurrent lesion. CONCLUSIONS: The results indicate that it is not appropriate to use these two denominations as synonyms. The designation of LRC should be maintained in order to define recidives occurring at the border of an old scar of cutaneous leishmaniasis, avoiding the confusion with the lupoid form of the disease. 相似文献
166.
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168.
The implementation of the Computer-Aided Despatch system at the London Ambulance Service has been one of the most notorious cases of failure within the information systems (IS) literature. What is less well known is that there followed, some time later, a much more successful implementation, described as a turnaround. This paper, based on a case study approach, describes the context and detail of that implementation. A framework from the literature, used in an analysis of the initial failure, is used to analyse and compare the similarities and differences in the development of the two systems. The framework provides four interacting elements and relationships for analysis. These elements are Supporters, Project Organisation, Information System, and the Environment in which they operate. The turnaround system was found to address directly almost all the issues identified as problematic in the failure. These included the approach taken by management to understand the needs of users, including issues unrelated to the system itself, their involvement in the development process, an improvement in the availability of resources (brought about in some part because of the previous failure), the ability to follow a relaxed timeline driven by users' acceptance levels, the preparation of infrastructure projects to develop confidence, participation and prototyping, thorough testing, phased and simple implementation, and trust building. Certain environmental factors could not be so directly addressed but nevertheless were overcome by attention to detail and internal needs. Conclusions indicate that the factors addressed are not new and are to be found in the success literature. What is unusual is that they were implemented in this case in such unlikely circumstances. 相似文献
169.
O Olivieri D Girelli M Azzini AM Stanzial C Russo M Ferroni R Corrocher 《Canadian Metallurgical Quarterly》1995,89(6):637-642
The synthetic retinoid, N-(4-hydroxyphenyl)retinamide (4-HPR; Fenretinide), is a cancer chemopreventive and antiproliferative agent whose mechanism of action is unknown. 4-HPR alone is a poor inducer of differentiation of HL-60 cells compared to all-trans-retinoic acid (RA). Here, we found that combinations of 4-HPR and RA synergistically induced differentiation of HL-60 cells. In addition, 4-HPR increased the level of retinoylation, the covalent binding of RA to proteins. Retinoylation occurs in many eukaryotic cell lines and may be involved in RA-induced differentiation. These results suggest that 4-HPR may be a member of a class of retinoids that are active because they displace RA from extracellular and intracellular sites or because they inhibit RA catabolism. On the basis of these proposed mechanisms, retinoids that do not cause differentiation as sole agents may have utility in the clinic in combination with RA. 相似文献
170.
BACKGROUND: BB injuries continue to be one of the most common causes of severe ocular injury among adolescent males. Extraocular and nonperforating anterior globe injuries most commonly result in favorable visual outcomes. The appropriate medical management of both perforating and nonperforating anterior globe injuries resulting from BB trauma and their potential ocular sequelae are reviewed. CASE REPORTS: Three cases illustrating typical as well as atypical anterior globe injuries caused by BBs are presented. Two cases involve nonperforating anterior globe injuries--one with intracranial and one with intraorbital involvement. The third involves a retained intraocular foreign body. The biomicroscopic and ophthalmoscopic features of these injuries are discussed, as are potential complications and management strategies associated with these types of trauma. CONCLUSIONS: Injuries associated with intraocular BBs often result in enucleation if functional vision is not salvageable. Sequelae to such injuries include endophthalmitis, traumatic hyphema, ocular siderosis, and sympathetic ophthalmia. Plain-film radiography and axial computed tomography are critical first steps in determination of the position of any intracranial or intraorbital metallic foreign body. Routine observation for the development of ocular sequelae resulting from retained intraocular, intracranial, and intraorbital BB injuries is recommended. 相似文献