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排序方式: 共有37条查询结果,搜索用时 15 毫秒
1.
Nader Vahdat 《应用聚合物科学杂志》1991,42(12):3165-3171
Diffusion coefficients are needed for the analysis of many mass transfer problems involving polymers. Since the diffusivity for such systems are strong functions of temperature and concentration, the analysis of these problems is greatly facilitated if predictive methods are available for the determination of the required diffusion coefficient. Because of the limitations of the theoretical approaches for estimating diffusivity, empirical correlation of solute–polymer diffusion coefficient data with physical properties of the solute were investigated. Chemical permeation measurements were made for several organic liquids through three elastomers (polychoroprene, butyl and nitrile rubber) at five different temperatures, ranging from 25 to 65°C. The collected diffusivities were correlated with liquid kinematic viscosity. Diffusivities (at different temperatures) depend mainly on the kinematic viscosity of solutes. The results also indicate a close relation between the variation of diffusivity and viscosity with temperature. 相似文献
2.
Traits, as sets of behaviors, can provide a good mechanism for reusability. However, they are limited in important ways and are not present in widely used programming and modeling languages and hence are not readily available for use by mainstream developers. In this paper, we add UML associations and other modeling concepts to traits and apply them to Java and C++ through model-driven development. We also extend traits with required interfaces so dependencies at the semantics level become part of their usage, rather than simple syntactic capture. All this is accomplished in Umple, a textual modeling language based upon UML that allows adding programming constructs to the model. We applied the work to two case studies. The results show that we can promote traits to the modeling level along with the improvement in flexibility and reusability. 相似文献
3.
Seyed Ebrahim Vahdat 《钢结构国际杂志》2014,14(3):571-578
Toughness is an important property for being used in steels in engineering applications. In this research, tensile toughness of 45WCrV7 steel was measured and calculated in 10 different processing conditions. The results of tensile test showed that two samples had maximum tensile toughness. Microstructural studies demonstrated that the required condition for high tensile toughness was simultaneous increase in two microstructural factors named content and population density of the secondary carbides because a matrix which was poor of carbon and alloying elements was softened and thus increased total tensile toughness. 相似文献
4.
Somayeh Hessam Shaghayegh Vahdat Irvan Masoudi Asl Mahnaz Kazemipoor Atefeh Aghaei Shahaboddin Shamshirband Timon Rabczuk 《计算机、材料和连续体(英文)》2019,61(1):11-26
In recent years, Parkinson's Disease (PD) as a progressive syndrome of the nervous system has become highly prevalent worldwide. In this study, a novel hybrid technique established by integrating a Multi-layer Perceptron Neural Network (MLP) with the Biogeography-based Optimization (BBO) to classify PD based on a series of biomedical voice measurements. BBO is employed to determine the optimal MLP parameters and boost prediction accuracy. The inputs comprised of 22 biomedical voice measurements. The proposed approach detects two PD statuses: 0-disease status and 1- good control status. The performance of proposed methods compared with PSO, GA, ACO and ES method. The outcomes affirm that the MLP-BBO model exhibits higher precision and suitability for PD detection. The proposed diagnosis system as a type of speech algorithm detects early Parkinson’s symptoms, and consequently, it served as a promising new robust tool with excellent PD diagnosis performance. 相似文献
5.
H. Vahdat Vasei S.M. Masoudpanah M. Adeli M.R. Aboutalebi 《Ceramics International》2018,44(7):7741-7745
Zinc oxide (ZnO) powders have been prepared by solution combustion synthesis method using cetyltrimethylammonium bromide (CTAB) as fuel. The effects of fuel to oxidant ratios (? = 0.5, 0.75, 1 and 1.5) on the combustion behavior, phase evolution, microstructure, optical properties and photocatalytic performance were investigated by thermal analysis, X-ray diffractometry, electron microscopy, and diffuse reflectance spectrometry techniques. The slow decomposition rate of CTAB guaranteed the direct formation of single phase and well-crystalline ZnO powders regardless of fuel content. The specific surface area of the as-combusted ZnO powders with platelet particles increased from 21 ± 1 to 35 ± 2?m2/g with fuel content. The band gap energy also increased from 2.99 to 3.13?eV due to the decrease of particle size. The as-combusted ZnO powders at ? = 1.5 exhibited the highest photodegradation (~69%) of methylene blue under ultraviolet light irradiation, due to their good crystallinity and smaller particle size. 相似文献
6.
KP Papadopoulos JH Garvin M Fetell LT Vahdat TJ Garrett DG Savage C Balmaceda J Bruce M Sisti S Isaacson R De LaPaz R Hawks E Bagiella KH Antman CS Hesdorffer 《Canadian Metallurgical Quarterly》1998,22(7):661-667
The prognosis in patients with primary brain tumors treated with surgery, radiotherapy and conventional chemotherapy remains poor. To improve outcome, combination high-dose chemotherapy (HDC) has been explored in children, but rarely in adults. This study was performed to determine the tolerability of three-drug combination high-dose thiotepa (T) and etoposide (E)-based regimens in pediatric and adult patients with high-risk or recurrent primary brain tumors. Thirty-one patients (13 children and 18 adults) with brain tumors were treated with high-dose chemotherapy: 19 with BCNU (B) and TE (BTE regimen), and 12 with carboplatin (C) and TE (CTE regimen). Patients received growth factors and hematopoietic support with marrow (n = 15), peripheral blood progenitor cells (PBPC) (n = 11) or both (n = 5). The 100 day toxic mortality rate was 3% (1/31). Grade III/IV toxicities included mucositis (58%), hepatitis (39%) and diarrhea (42%). Five patients had seizures and two had transient encephalopathy (23%). All patients had neutropenic fever and all pediatric patients required hyperalimentation. Median time to engraftment with absolute neutrophil count (ANC) >0.5 x 10(9)/l was 11 days (range 8-37 days). Time to ANC engraftment was significantly longer (P = 0.0001) in patients receiving marrow (median 14 days, range 10-37) than for PBPC (median 9.5 days, range 8-10). Platelet engraftment >50 x 10(9)/l was 24 days (range 14-53 days) in children. In adults, platelet engraftment >20 x 10(9)/l was 12 days (range 9-65 days). In 11 patients supported with PBPC, there was a significant inverse correlation between CD34+ dose and days to ANC (rho = -0.87, P = 0.009) and platelet engraftment (rho = -0.85, P = 0.005), with CD34+ dose predicting time to engraftment following HDC. Overall, 30% of evaluable patients (7/24) had a complete response (CR) (n = 3) or partial response (PR) (n = 4). Median time to tumor progression (TTP) was 7 months, with an overall median survival of 12 months. These TE-based BCNU or carboplatin three-drug combination HDC regimens are safe and tolerable with promising response rates in both children and older adults. 相似文献
7.
This article reviews the different components, conductors, semiconductive shields, insulation, sheaths, and jackets, that make up extruded, high-voltage cables. The different types of conductors are described as are the different insulation systems that are available for medium and HV cables. There is a comparison of the two main insulators used in extruded HV cables, EPR, and XLPE. Each material has some properties that are better than those of the other material. 相似文献
8.
AA Ross TJ Layton AB Ostrander JL Passos-Coelho JM Davis AM Huelskamp SJ Noga NE Davidson MJ Kennedy BW Cooper SL Gerson HM Lazarus K Holland S Gluck TJ Moss A Kaubish L Vahdat K Antman 《Canadian Metallurgical Quarterly》1996,5(5):549-552
We report a case of an 18-month-old female who presented with three supernumerary upper limbs of varying lengths on the right side. Each limb had a proximal, middle, and distal segment, and an intercalated elbow and wrist joint. A single digit was present in the superior limb, three digits in the middle limb, and two digits in the caudal-most limb. Right plagiocephaly, congenital torticollis, scoliosis involving the upper and mid thoracic region, and a hypoplastic right pectoralis major were the other abnormal features noted. Radiography showed two scapulae, humerus, a single forearm bone in each limb, and rudimentary metacarpals and phalanges. Limb duplication may rarely be encountered in parasitic conjoined twins. The role of mutagens, drugs, cellular contributions, and morphogens in the growth and differentiation of limbs has been studied in animals. It is rather difficult to deduce the time of action of the factors responsible for such a malformation. 相似文献
9.
LT Vahdat K Papadopoulos C Balmaceda T McGovern J Dunleavy E Kaufman B Fung T Garrett D Savage A Tiersten J Ayello E Bagiella D Heitjan K Antman C Hesdorffer 《Canadian Metallurgical Quarterly》1998,4(7):1689-1695
A single high-dose cycle of chemotherapy with stem cell support can produce disease-free survival of 15-20% for at least 3 years in women with responding stage IV breast cancer. North American Autologous Bone Marrow Transplant Registry data suggest that a complete response (CR) is the single most important prognostic factor associated with prolonged disease-free survival. Therefore, if sequential high-dose chemotherapy can increase the CR rate, then perhaps an increased proportion of patients will remain disease free. Women with at least a partial response (PR) to induction chemotherapy received three separate high-dose cycles of chemotherapy with peripheral blood progenitor support and granulocyte colony-stimulating factor. The first intensification was a dose escalation of paclitaxel (400-825 mg/ m2), the second intensification was melphalan (180 mg/m2), and the third intensification consisted of 6000 mg/m2 cyclophosphamide (1500 mg/m2/day), 500 mg/m2 thiotepa (125 mg/m2/day), and 800 mg/m2 carboplatin (200 mg/m2/day; CTCb). Thirty-six women were enrolled and 31 completed all three cycles. After the paclitaxel infusion most patients developed reversible predominantly sensory neuropathy. Of the 19 patients with measurable disease, 6 converted to CR, 7 converted to a PR* (the complete resolution of all soft tissue or visceral disease with sclerosis of prior lytic bone lesions), and 2 had a further PR for an overall response rate of 79%. Two patients had no further response and disease in two patients progressed, and thus they were taken off the study before CTCb. Seventy-eight percent are progression-free at a median follow-up of 14 months (range, 3-24+). Three sequential cycles of high-dose chemotherapy are feasible and were administered in this study with no mortality. Single agent paclitaxel at doses up to 825 mg/m2 were well tolerated with moderate reversible toxicity. 相似文献
10.
Chandra S. Ellis C.S. Vahdat A. 《Selected Areas in Communications, IEEE Journal on》2000,18(12):2544-2565
The ability of a Web service to provide low-latency access to its content is constrained by available network bandwidth. While providing differentiated quality of service (QoS) is typically enforced through network mechanisms, in this paper we introduce a robust mechanism for managing network resources using application-specific characteristics of Web services. We use transcoding to allow Web servers to customize the size of objects constituting a Web page, and hence the bandwidth consumed by that page, by dynamically varying the size of multimedia objects on a per-client basis. We leverage our earlier work on characterizing quality versus size tradeoffs in transcoding JPEG images to supply more information for determining the quality and size of the object to transmit. We evaluate the performance benefits of incorporating this information in a series of bandwidth management policies using realistic workloads and access scenarios to drive our system. The principal contribution of this paper is the demonstration that it is possible to use informed transcoding techniques to provide differentiated service and to dynamically allocate available bandwidth among different client classes, while delivering good quality of information content for all clients. We also show that it is possible to customize multimedia objects to the highly variable network conditions experienced by mobile clients in order to provide acceptable quality and latency depending on the networks used in accessing the service. We show that policies that aggressively transcode the larger images can produce images with quality factor values that closely follow the untranscoded base case while still saving as much as 150 kB. A transcoding policy that has knowledge of the characteristics of the link to the client can avoid as many as 40% of (unnecessary) transcodings 相似文献