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排序方式: 共有248条查询结果,搜索用时 15 毫秒
1.
Sanaz Nazari Hadi Basirzadeh 《International Journal of Control, Automation and Systems》2014,12(1):84-92
Therapeutic vaccines are being developed as a promising new approach to treatment for cancer patients. There are still many unanswered questions about which kind of therapeutic vaccines are the best for the cancer treatments? In this paper we consider a mathematical model, in the form of a system of ordinary differential equations (ODE), this system is an example from a class of mathematical models for immunotherapy of the tumor that were derived from a biologically validated model by Lisette G. de Pillis. The problem how to schedule a variable amount of which vaccines to achieve a maximum reduction in the primary cancer volume is consider as an optimal control problem and it is shown that optimal control is quadratic with 0 denoting a trajectory corresponding to no treatment and 1 a trajectory with treatment at maximum dose along that all therapeutics are being exhausted. The ODE system dynamics characterized by locating equilibrium points and stability properties are determined by using appropriate Lyapunov functions. Especially we attend a parametric sensitivity analysis, which indicates the dependency of the optimal solution with respect to disturbances in model parameters. 相似文献
2.
Sanaz Motamedi 《International journal of human-computer interaction》2013,29(6):427-439
By their nature, smartphones must have small screens, and that is one of their limitations. Many users have trouble reading information on the Internet on such small screens because Internet browsers are usually designed for computers that have larger screens than smartphones. This study evaluates the usability of alternative user interfaces when reading news articles on smartphones. An experiment was conducted involving 120 smartphone users who were asked to evaluate six types of user interfaces based on three methods (pop-up, full-screen, and auto-zooming) and two display orientations (horizontal, vertical) in one of two languages (English and Persian). The participants were assigned four typical tasks that users must perform to obtain information from the Internet, that is, finding, refinding, reading, and browsing; they were asked to conduct the tasks in random order. In addition, a questionnaire was used to measure the efficiency and effectiveness of the participants’ completion of the tasks, as well as their satisfaction, compatibility, and enjoyment of the undertakings. The results indicated that method, orientation, and language affected the actual usage and the time used. Based on the human factor experiment, the full-screen method was preferred in refinding and reading, whereas the pop-up method was preferred in browsing and finding. In terms of orientation, the vertical mode was preferred, and each user’s performance in the vertical mode was better in all tasks except browsing. Of interest, using the English language turned out to be more satisfying, enjoyable, and efficient to the Persian users who did the experiment in English as their second language. 相似文献
3.
In this paper, we present an analysis and synthesis approach for guaranteeing that the phase of a single-input, single-output closed-loop transfer function is contained in the interval [−α,α] for a given α>0 at all frequencies. Specifically, we first derive a sufficient condition involving a frequency domain inequality for guaranteeing a given phase constraint. Next, we use the Kalman–Yakubovich–Popov theorem to derive an equivalent time domain condition. In the case where , we show that frequency and time domain sufficient conditions specialize to the positivity theorem. Furthermore, using linear matrix inequalities, we develop a controller synthesis approach for guaranteeing a phase constraint on the closed-loop transfer function. Finally, we extend this synthesis approach to address mixed gain and phase constraints on the closed-loop transfer function. 相似文献
4.
Jafar Biazar Behzad Ghanbari Mehdi Gholami Porshokouhi Mohammad Gholami Porshokouhi 《Computers & Mathematics with Applications》2011,61(4):1016-1023
In this paper, He’s homotopy perturbation method is applied to solve non-linear systems of mixed Volterra–Fredholm integral equations. Two examples are presented to illustrate the ability of the method. Also comparisons are made between the Adomian decomposition method and the homotopy perturbation method. The results reveal that He’s homotopy perturbation method is very effective and simple and in these examples leads to the exact solutions. 相似文献
5.
Maziar Gholami Korzani Sergio A. Galindo-Torres Alexander Scheuermann David J. Williams 《水科学与水工程》2017,10(2):143-153
Simulations of two-dimensional (2D) flow past a circular cylinder with the smoothed particle hydrodynamics (SPH) method were conducted in order to accurately determine the drag coefficient. The fluid was modeled as a viscous liquid with weak compressibility. Boundary conditions, such as a no-slip solid wall, inflow and outflow, and periodic boundaries, were employed to resemble the physical problem. A sensitivity analysis, which has been rarely addressed in previous studies, was conducted on several SPH parameters. Hence, the effects of distinct parameters, such as the kernel choices and the domain dimensions, were investigated with the goal of obtaining highly accurate results. A range of Reynolds numbers (1–500) was simulated, and the results were compared with existing experimental data. It was observed that the domain dimensions and the resolution of SPH particles, in comparison to the obstacle size, affected the obtained drag coefficient significantly. Other parameters, such as the background pressure, influenced the transient condition, but did not influence the steady state at which the drag coefficient was determined. 相似文献
6.
7.
Plasticized poly(vinyl chloride) composites: Influence of different nanofillers as antimigration agents 下载免费PDF全文
In this study, plasticized poly(vinyl chloride) (PVC) composites with different nanofillers, including single‐walled carbon nanotubes (SWCNTs), organoclay, TiO2, and ZnO nanoparticles, were prepared, and their effects on plasticizer migration were investigated. Scanning electron micrographs revealed the dispersion quality of the nanofillers in the polymer matrix. It had a significant influence on the performance of the nanofillers in the process of plasticizer migration. Migration and exudation tests showed that the nanofillers could efficiently hinder plasticizer migration. On the basis of these results, we concluded that carbon nanotubes were the best antimigration agent in the plasticized system. This was ascribed to the high aspect ratio of the SWCNTs and the good interactions between them and the plasticizer. Also, TiO2 nanoparticles showed a better performance compared to the ZnO nanoparticles. This was due to the more homogeneous dispersion of the TiO2 in the polymer matrix and the higher surface area of the particles. The differential scanning calorimetry thermograms were in good agreement with the migration tests. The lowest change in the glass‐transition temperature was observed for the composite filled with SWCNTs. This indicated that a lower amount of the plasticizer migrated from PVC. The thermogravimetric analysis curves showed that the incorporation of the nanofillers improved the thermal stability of the PVC. The results could be useful for determining the efficiency of plasticized PVC in applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42559. 相似文献
8.
Mohsen Gholami Mohammad Reza Talaie Seyed Foad Aghamiri 《Korean Journal of Chemical Engineering》2014,31(2):322-326
A bi-modal porous structure MCM-41 (BPS-MCM-41) was synthesized and functionalized by 3-[2-(2-Aminoethylamino)ethylamino]propyltrimethoxysilane (TRI); also, its performance in amine grafting and CO2 capturing was compared with that of pore-expanded MCM-41 [1]. To create larger pores beside the mesoporous structure of MCM-41, carbon black nanoparticles were used as the solid template. Characterizing the BPS-MCM-41 using the BET and BJH techniques resulted in the surface reduction of 29.3 percent and volume increase of 68.46 percent. The pore size distribution showed two peaks: a narrow peak at 2.24 nm diameter, which belonged to micelles, and a wide one at about 50 nm due to the presence of used nanoparticles. The functionalization confirmed that BPS-MCM-41 is capable of accommodating a large quantity of amine groups. The CO2 adsorption measurement indicated that internal volume of the adsorbent was a critical factor affecting the adsorption capacity of the amine grafted adsorbents. 相似文献
9.
Sanaz Naghibi Hamid Reza Madaah Hosseini Mohammad Ali Faghihi Sani Mohammad Ali Shokrgozar Morteza Mehrjoo 《Ceramics International》2014
TiO2 nanoparticles (NPs) were synthesized by hydrothermal assisted sol–gel technique. In the next step, as-synthesized NPs were modified by poly ethylene glycol (PEG). Then, folic acid (FA) was conjugated to TiO2–PEG. Finally, Doxorubicin (Dox) as an anticancer drug was loaded on as-prepared TiO2–PEG–FA nanocarrier. The optimization of TiO2 and FA concentration and the influence of ultraviolet (UV) irradiation on photocatalytic activity of nanocarrier and Dox loaded carrier were assessed by utilizing the 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide (MTT)-assay method. 相似文献
10.
In recent years, droughts with increasing severity and frequency have been experienced around the world due to climate change
effects. Water planning and management during droughts needs to deal with water demand variability, uncertainties in streamflow
prediction, conflicts over water resources allocation, and the absence of necessary emergency schemes in drought situations.
Reservoirs could play an important role in drought mitigation; therefore, development of an algorithm for operation of reservoirs
in drought periods could help to mitigate the drought impacts by reducing the expected water shortages. For this purpose,
the probable drought’s characteristics and their variations in response to factors such as climate change should be incorporated.
This study aims at developing a contingency planning scheme for operation of reservoirs in drought periods using hedging rules
with the objective of decreasing the maximum water deficit. The case study for evaluation of the performance of the proposed
algorithm is the Sattarkhan reservoir in the Aharchay watershed, located in the northwestern part of Iran. The trend evaluations
of the hydro-climatic variables show that the climate change has already affected streamflow in the region and has increased
water scarcity and drought severity. To incorporate the climate change study in reservoir planning; streamflow should be simulated
under climate change impacts. For this purpose, the climatic variables including temperature and precipitation in the future
under climate change impacts are simulated using downscaled GCM (General Circulation Model) outputs to derive scenarios for
possible future drought events. Then a hydrological model is developed to simulate the river streamflow, based on the downscaled
data. The results show that the proposed methodology leads to less water deficit and decreases the drought damages in the
study area. 相似文献