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81.
The Universal Mobile Telecommunications System (UMTS) offers IP-based multimedia applications and services with end-to-end Quality of Service (QoS) guarantee. The key component providing these services is the IP Multimedia Subsystem (IMS) that uses Service-Based Local Policy (SBLP) management for QoS control. To support end-to-end QoS, the UMTS IMS network should be scalable, reliable and flexible in policy deployment and enforcement, characteristics that are not found in single-domain policy architecture. A hybrid policy architecture is proposed, in which a hierarchical architecture is applied to the multi-domain environment in a single operator UMTS IMS network, while a peering architecture is employed in a multi-operator UMTS IMS network. The proposed multi-domain policy architecture potentially minimizes the session setup delay and policy exchange traffic while maximizing network scalability. 相似文献
82.
OBJECTIVE: To examine the relationship between allergy-related symptoms, food intolerance and psychological distress in primary care. METHODS: Two thousand three hundred and thirty two adults in five General Practices in the South of England completed questionnaires regarding allergy-related symptoms and psychological symptoms, but no association was demonstrated between a history of diagnosed or treated asthma, eczema or hay fever and psychological morbidity. Cases of food intolerance had lower levels of psychological distress than expected compared to hospital samples. Current, but not past wheezing and eczema, was associated with an excess of life stresses in the previous six months. CONCLUSIONS: The association between psychological distress and the label of food allergy/intolerance found in specialist care does not extend to primary care. 相似文献
83.
It has been demonstrated previously that endothelin-1 stimulates the Ca2+-activated K+ (BK(Ca)) channel activity in porcine coronary artery smooth muscle cells. The purpose of the present study was to delineate the endothelin receptor subtype involved in this action. In receptor binding studies, [125I]endothelin-1 was shown to bind to the homogenate of porcine primary coronary artery smooth muscle cells in a single class of binding sites with K(D) and Bmax values of 73 pM and 99 fmol/mg protein, respectively. Furthermore, endothelin-1 and endothelin-3 displaced the binding of [125I]endothelin-1 to these cells with respective IC50 values of 70 and 17000 pM, a 240-fold difference in potency. The effects of endothelin-3 on the activity of the BK(Ca) channel in porcine coronary artery smooth muscle cells were examined using the cell-attached patch-clamp technique. Similar to endothelin-1, endothelin-3 also exhibited a bell-shaped concentration-response curve. A maximal increase of 95% in channel open-state probability (Po) was induced by 100 nM endothelin-3 as compared with the 320% increase in Po by 1 nM endothelin-1. Thus, endothelin-1 was about 100-fold more potent and 3.4-fold more efficacious than endothelin-3 in this action. Both the receptor binding and the electrophysiological results suggest that the effects of endothelins on the BK(Ca) channel are mediated through the endothelin ET(A) receptor subtype. 相似文献
84.
The local implicit scheme of Reddyet al. is extended to the minmod and third-order upwind TVD schemes. Numerical tests show that the proposed scheme is stable. In addition, it is found that if the flow field has a dominant direction, setting the iteration sweep to align with this direction can significantly improve the converging speed. 相似文献
85.
Yih-Jyi Jeng Chien-Chung Yeh 《Signal Processing, IEEE Transactions on》1997,45(5):1161-1172
A cluster-based maximum-likelihood sequence estimator (MLSE) for nonlinear channels was described, which consists of a clustering network and an MLSE implemented by the Viterbi algorithm. The cluster-based MLSE can be used for digital communication through nonlinear finite-length channels because channel mapping estimation is used instead of channel estimation in the conventional MLSE. The clustering network of the cluster-based MLSE, which estimates the channel mapping between the signal input vectors and the noiseless channel outputs, is a supervised network and requires a training sequence. We propose a blind channel mapping estimator to estimate the channel mapping without using the training sequence. The blind channel mapping estimator has a clustering block and a mapping block. The clustering block estimates the channel outputs, which represent the channel mapping, subject to an unknown permutation operation because no training sequence is utilized. That permutation operation is resolved by the mapping block, and therefore, the channel mapping is obtained. Introducing the blind channel mapping estimator into the cluster-based MLSE, a blind cluster-based MLSE for nonlinear channels can be done. Computer simulations of the blind channel mapping estimator and the blind MLSE for nonlinear channels are presented 相似文献
86.
Shuen-Yih Wang Shyh-Kang Jeng 《Electromagnetic Compatibility, IEEE Transactions on》1997,39(4):315-323
This paper presents a deterministic method to establish the scattering-center model for complex radar targets. By this method, high frequency techniques including physical optics, physical theory and diffraction and shooting and bouncing rays are used to establish scattering centers. Numerical results show that, by using this method with only single-frequency scattering centers at large aspect increments, the RCS pattern at finer aspect increments is well reconstructed; besides, it can be extended to predict the RCS pattern at any frequency of interest in a required narrow bandwidth. Good agreement between direct RCS calculation, scattering-center model and measured results is obtained 相似文献
87.
Polymers filled with conducting fibers to prevent electromagnetic interference (EMI) performance have recently received great attention due to the requirements of 3C (computer, communication, and consumer electronics) products. In the present article, the effect of fiber content and processing parameters, including melt temperature, mold temperature, and injection velocity, on the electromagnetic interference shielding effectiveness (SE) in injection molded ABS polymer composites filled with conductive stainless steel fiber (SSF) was investigated. The influence of fiber orientation and distribution resulting from fiber content and molding conditions on EMI performance was also examined. It was found from measured results that fiber content plays a significant role in influencing part EMI SE performance. SE value can reach the highest values of approximately 40 dB and 60 dB at 1000 MHz frequency for fiber content 7 wt % and 14 wt %, respectively, under the best choice of molding conditions. Higher melt and mold temperature would increase shielding effectiveness due to a more uniform and random fiber orientation. However, higher injection velocity leading to highly‐orientated and less uniform distribution of fiber reduces shielding effectiveness. Among all molding parameters, melt temperature affects SE performance most significantly. Its influence slightly decreases as fiber content increases. Injection speed plays a secondary importance in affecting SE values, and its influence increases as fiber content increases. Upon examination of fiber distribution via optical microscope and subsequent image analysis, it was found that the fiber becomes more densely and random distributed toward the last melt‐filled region, whereas fiber exhibits less concentration around the middle way of the flow path. This can be attributed to the combined effects of fountain flow, frozen layer thickness, and gapwise melt front velocity. The results indicate that molding conditions, instead of fiber content alone, are very important on the SE performance for injection molded SSF filled ABS composites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1072–1080, 2005 相似文献
88.
Lihua Zhu Yingying Jiang Jinbao Zheng Nuowei Zhang Changlin Yu Yunhua Li Chih‐Wen Pao Jeng‐Lung Chen Chuanhong Jin Jyh‐Fu Lee Chuan‐Jian Zhong Bing H. Chen 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(34):4385-4393
The design of an ideal heterogeneous catalyst for hydrogenation reaction is to impart the catalyst with synergetic surface sites active cooperatively toward different reaction species. Herein a new strategy is presented for the creation of such a catalyst with dual active sites by decorating metal and metal oxide nanoparticles with ultrafine nanoclusters at atomic level. This strategy is exemplified by the design and synthesis of Ru nanoclusters supported on Ni/NiO nanoparticles. This Ru‐nanocluster/Ni/NiO‐nanoparticle catalyst is shown to exhibit ultrahigh catalytic activity for benzene hydrogenation reaction, which is 55 times higher than Ru–Ni alloy or Ru on Ni catalysts. The nanoclusters‐on‐nanoparticles are characterized by high‐resolution transmission electron microscope, Cs‐corrected high angle annular dark field‐scanning transmission electron microscopy, elemental mapping, high‐sensitivity low‐energy ion scattering, and X‐ray absorption spectra. The atomic‐scale nanocluster–nanoparticle structural characteristics constitute the basis for creating the catalytic synergy of the surface sites, where Ru provides hydrogen adsorption and dissociation site, Ni acts as a “bridge” for transferring H species to benzene adsorbed and activated at NiO site, which has significant implications to multifunctional nanocatalysts design for wide ranges of catalytic reactions. 相似文献
89.
Mesostructured Arrays of Nanometer‐spaced Gold Nanoparticles for Ultrahigh Number Density of SERS Hot Spots
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Ying‐Huang Lai Shiaw‐Woei Chen Michitoshi Hayashi Ying‐Jen Shiu Chiao‐Cheng Huang Wei‐Tsung Chuang Chun‐Jen Su Hu‐Cin Jeng Jhe‐Wei Chang Yao‐Chang Lee An‐Chung Su Chung‐Yuan Mou U‐Ser Jeng 《Advanced functional materials》2014,24(17):2544-2552
A novel one‐trough synthesis via an air‐water interface is demonstrated to provide hexagonally packed arrays of densely spaced metallic nanoparticles (NPs). In the synthesis, a mesostructured polyoxometalate (POM)‐silicatropic template (PSS) is first self‐assembled at the air‐water interface; upon UV irradiation, anion exchange cycles enable the free‐floating PSS film to continuously uptake gold precursors from the solution subphase for diffusion‐controlled and POM‐site‐directed photoreduction inside the silica channels. NPs ≈ 2 nm can hence be homogeneously formed inside the silica‐surfactant channels until saturation. As revealed via X‐ray diffraction, small‐angle X‐ray scattering (SAXS), grazing incidence SAXS, and transmission electron microscopy, the Au NPs directed by the PSS template are arrayed into a 2D hexagonal lattice with inter‐channel spacing of 3.2 nm and a mean along‐channel NP spacing of 2.8 nm. This corresponds to an ultra‐high number density (≈1019 NPs cm?3) of narrowly spaced Au NPs in the Au‐NP@PSS composite, leading to 3D densely deployed hot‐spots along and across the mesostructured POM‐silica channels for surface‐enhanced Raman scattering (SERS). Consequently, the Au‐NP@PSS composite exhibits prominent SERS with 4‐mercaptobenzoic acid (4‐MBA) adsorbed onto Au NPs. The best 4‐MBA detection limit is 5 nm , with corresponding SERS enhancement factors above 108. 相似文献
90.
TC Chao LB Jeng YY Jan TL Hwang CS Wang MF Chen 《Canadian Metallurgical Quarterly》1998,45(22):921-926
BACKGROUND/AIMS: Primary carcinoma of the gallbladder is rare and associated with a late diagnosis and poor prognosis. Concurrent acute cholecystitis frequently obscures the presence of carcinoma. The information regarding gallbladder carcinoma with acute cholecystitis is limited. In order to better understand the presentation of gallbladder carcinoma with acute cholecystitis, we retrospectively reviewed the data of patients with primary carcinoma of the gallbladder. METHODOLOGY: The data of 86 patients with primary carcinoma of the gallbladder treated between 1979 and 1994 were compiled and reviewed. The patients were divided into 2 groups: Group 1 (with acute cholecystitis, 21 patients) and Group 2 (without cholecystitis, 65 patients). Clinicopathological comparisons were made and evaluated between these two groups RESULTS: The average age of Group 1 patients was older than that of Group 2 patients (75+/-2 years vs. 63+/-2 years; p<0.05). Three Group 1 patients presented with sepsis. The interval between the onset of symptoms and hospital admission in Group 2 patients was significantly (p<0.05) longer than that in Group 1 patients (243+/-95 days vs. 20+/-11 days). Leukocytosis (>11,000/mm3) was more common in Group 1 patients than in Group 2 patients (47.6% vs. 15.4%). Jaundice was more common in Group 2, and fever was common in Group 1. The majority of Group 2 gallbladder cancers were stage V (75.4%). In contrast, 52.4% of Group 1 gallbladder cancers were stage III and 38.1% were stage V. The 30-day postoperative mortality rate in Group 1 and Group 2 patients was 9.5% and 7.7%, respectively. The cumulative survival of Group 1 patients was not different from that of Group 2 patients (log-rank test, p>0.05). CONCLUSIONS: Age, the interval of symptoms prior to admission, the location of abdominal pain, fever, leukocytosis, and the absence of jaundice suggested the presence of acute cholecystitis in gallbladder carcinoma. A high index of suspicion of the disease, intraoperative examination of gallbladder specimens, and more aggressive surgical treatment may improve patient survival. 相似文献