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71.
A stochastic ODE model is developed for the motion of a superparamagnetic cluster suspended in a Hagen-Poiseuille flow and
guided by an external magnet to travel to a target. The specific application is magnetic drug targeting, with clusters in
the range of 10–200 nm radii. As a first approximation, we use a magnetic dipole model for the external magnet and focus on
a venule of 10−4 m radius close to the surface of the skin as the pathway for the clusters. The time of arrival at the target is calculated
numerically. Variations in release position, background flow, magnetic field strength, number of clusters, and stochastic
effects are assessed. The capture rate is found to depend weakly on variations in the velocity profile, and strongly on the
cluster size, the magnetic moment, and the distance between the magnet and the blood vessel wall. A useful condition is derived
for the optimal capture rate. The case of simultaneous release of many clusters is investigated. Their accumulation in a neighborhood
of the target at the venule wall follows a normal distribution with the standard deviation roughly half of the distance between
the magnet and the target. Ideally, this deviation should equal the tumor radius, and the magnet should be beneath the center
of the tumor. The optimal injection site for a cluster is found to be just prior to arrival at the target. Two separate mechanisms
for capturing a cluster are the magnetic force and, for radii smaller than 20 nm, Brownian motion. For the latter case, the
capture rate is enhanced by Brownian motion when the cluster is released near the wall. 相似文献
72.
Abstract We have observed kilohertz and sub-kilohertz resonance structures in RF-optical double resonance experiments of rare-earth-doped solids, when the frequency of the RF field is scanned across the hyperfine transitions while monitoring the resonant optical absorption of a CW laser. The effect is observed only when the laser spectral width is broad compared to the hyperfine structure. The observed line widths are apparently free of the inhomogeneous widths of hyperfine levels and the line shape has peculiar double peak structure. The effect is modelled with a resonance involving three atomic levels interacting with three electromagnetic fields, two optical and one RF, in a triangular or “delta’ configuration. While the ordinary optical-RF two-field resonance is limited by spin inhomogeneous width, the simultaneous excitation of three coupled transitions leads to narrow and highly nonlinear resonance structures that are not averaged by the inhomogeneous distribution of hyperfine transition. 相似文献
73.
Advancing research on service quality requires clarifying the theoretical conceptualizations and validating an integrated service quality model. The purpose of this study is to facilitate and elucidate practical issues and decisions related to the development of a hierarchical service quality model in mobile health (mHealth) services research. Conceptually, it extends theory by reframing service quality as a reflective, hierarchical construct and modeling its impact on satisfaction, intention to continue using and quality of life. Empirically, it confirms that PLS path modeling can be used to estimate the parameters of a higher order construct and its association with subsequent consequential latent variables in a nomological network. The findings of the study show that service quality is the third-order, reflective construct model with strong positive effects on satisfaction, continuance intentions and quality of life in the context of mHealth services. Finally, the study discusses the implications of hierarchical service quality modeling in electronic markets and highlights future research directions. 相似文献
74.
Journal of Materials Science - In this paper, graphite nanoplatelets (GNPs)-based polymer nanocomposites were reviewed. This review mainly discusses various synthesis techniques for making graphite... 相似文献
75.
Kenya Kani Joel Henzie
mer Dag Kathleen Wood Muhammad Iqbal Hyunsoo Lim Bo Jiang Carlos Salomon Alan E. Rowan Md. Shahriar A. Hossain Jongbeom Na Yusuke Yamauchi 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(35)
The electrochemical synthesis of mesoporous ruthenium (Ru) films using sacrificial self‐assembled block polymer micelles templates, and its electrochemical surface oxidation to RuOx is described. Unlike standard methods such as thermal oxidation, the electrochemical oxidation method described here retains the mesoporous structure. Ru oxide materials serve as high‐performance supercapacitor electrodes due to their excellent pseudocapacitive behavior. The mesoporous architectured film shows superior specific capacitance (467 F g?1 Ru) versus a nonporous Ru/RuOx electrode (28 F g?1 Ru) that is prepared via the same method but omitting the pore‐directing polymer. Ultrahigh surface area materials will play an essential role in increasing the capacitance of this class of energy storage devices because the pseudocapacitive redox reaction occurs on the surface of electrodes. 相似文献
76.
Negahdaripour S 《IEEE transactions on pattern analysis and machine intelligence》2007,29(10):1776-1788
Optical and acoustic cameras are suitable imaging systems to inspect underwater structures, both in regular maintenance and security operations. Despite high resolution, optical systems have limited visibility range when deployed in turbid waters. In contrast, the new generation of high-frequency (MHz) acoustic cameras can provide images with enhanced target details in highly turbid waters, though their range is reduced by one to two orders of magnitude compared to traditional low-/midfrequency (10s-100s KHz) sonar systems. It is conceivable that an effective inspection strategy is the deployment of both optical and acoustic cameras on a submersible platform, to enable target imaging in a range of turbidity conditions. Under this scenario and where visibility allows, registration of the images from both cameras arranged in binocular stereo configuration provides valuable scene information that cannot be readily recovered from each sensor alone. We explore and derive the constraint equations for the epipolar geometry and stereo triangulation in utilizing these two sensing modalities with different projection models. Theoretical results supported by computer simulations show that an opti-acoustic stereo imaging system outperforms a traditional binocular vision with optical cameras, particularly for increasing target distance and (or) turbidity. 相似文献
77.
In recent years, sand filled geotextile bags (geobags) have been used as a means of long-term riverbank revetment stabilization. However, despite their deployment in a significant number of locations, the failure modes of such structures are not well understood. Three interactions influence the geobag performance, i.e. geobag-geobag, geobag-water flow and geobag-water flow-river bank. The aim of the research reported here is to develop a detailed understanding of the failure mechanisms in a geobag revetment using a discrete element model (DEM) validated by laboratory data. The laboratory measured velocity data were used for preparing a mapped velocity field for a coupled DEM simulation of geobag revetment failure. The validated DEM model could identify well the critical bag location in varying water depths. Toe scour, one of the major instability factors in revetments, and its influence on the bottom-most layer of the bags were also reasonably represented in this DEM model. It is envisaged that the use of a DEM model will provide more details on geobag revetment performance in riverbanks. 相似文献
78.
Shahriar Afandizadeh Zargari Salar Zabihi Siabil Amir Hossein Alavi Amir Hossein Gandomi 《Expert Systems》2012,29(2):124-142
This paper proposes alternative approaches for the prediction of short‐term traffic flow using three branches of computational intelligence techniques, namely linear genetic programming (LGP), multilayer perceptron (MLP) and fuzzy logic (FL). Different LGP, MLP and FL models are developed for estimating the 5‐ and 30‐min traffic flow rates. New LGP‐ and MLP‐based prediction equations are derived for the traffic flow rates in the 5‐ and 30‐min time intervals. The models are established upon extensive databases of the traffic flow records obtained from Iran's Rasht‐Qazvin highway. The results indicate that the proposed models are effectively capable of predicting the target values. The LGP‐based models are found to be simple, straightforward and more practical for predictive purposes compared with the other derived models. 相似文献
79.
Hyunseock Jie PhD Vladimir Luzin Mukter Zaman Anvar Valiyaparambil Abdulsalam Keun Hwa Chae PhD Hyung-il Choi Vladimir Levchenko Arend Nijhuis Jung H. Kim Mislav Mustapić Shi Xue Dou Yusuke Yamauchi Aslam Khan Md. Shahriar A. Hossain 《Journal of the American Ceramic Society》2020,103(10):5488-5495
In this study, we analyze the properties of boron isotope (11B)-rich powders from three different sources, that is, American, Cambridge, and Pavezyum, to fabricate the bulk Mg11B2 superconductors and evaluate their superconducting properties. While 11B-rich powder is an essential precursor to fabricate Mg11B2 superconductors for fusion magnet applications, the properties of the 11B powder turned out to be critical to determine the quality of the final superconducting product. Therefore, appropriate control of processing conditions is needed to comply with the requirements of the nuclear fusion application. Analysis of the B isotope ratio by accelerator mass spectroscopy and neutron transmission revealed that all three types of powder are enriched with 11B to better than 99 at % quality. In addition, Pavezyum's 11B shows the lowest crystallinity and smallest crystalline domain size as evidenced by the high-resolution X-ray diffractometer and scanning electron microscopy. The chemical states of the boron isotope investigated with near edge X-ray absorption fine structure spectroscopy and X-ray photoemission spectroscopy also reveals that Pavezyum boron has amorphous structure. Mg11B2 bulks and multi-filamentary (12-filament) wires have been manufactured, sintered at different temperatures and characterized via the transport critical current density. The wire with Pavezyum 11B shows three times higher current carrying capacity at a particular magnetic field compared to the wire using Cambridge 11B and hence, Pavezyum 11B boron has the potential for manufacturing fusion grade Mg11B2 based magnets. The results of this study demonstrated that Boron powders with higher purity, smaller grain size and lower crystallinity are critical for improving the superconducting and electronic properties of Mg11B2 samples fabricated from the powder. Thus, the low-neutron-activation Mg11B2 is possibly an affordable and technically viable candidate to replace NbTi superconductors in the low field poloidal field and correction coils for the next-generation fusion reactors. 相似文献
80.
Maruf Ahmed Mst Sorifa Akter Jong‐Bang Eun 《Journal of the science of food and agriculture》2010,90(3):494-502
BACKGROUND: Purple sweet potato flour could be used to enhance food products through colour, flavour and nutrients. Purple sweet potato flour has not yet been prepared with maltodextrin and amylase treatment using spray drying. Thus, the investigation was to evaluate the effect of various levels of maltodextrin (30 and 50 g kg?1 w/v), amylase (3 and 7 g kg?1 puree) and combined with maltodextrin and amylase on the physicochemical, functional and antioxidant capacity of spray dried purple sweet potato flours. RESULTS: Amylase and amylase with maltodextrin‐treated flours had a higher anthocyanin and total phenolic content than the control and maltodextrin‐treated flours. However, the antioxidant capacity was higher in the control and maltodextrin‐treated flours compared to the amylase and amylase with maltodextrin‐treated flours. The control had a higher water absorption index and lower water solubility index compared to the maltodextrin and combined with amylase and maltodextrin‐treated flours. On the other hand, maltodextrin increased whereas α‐amylase decreased the glass transition temperature. With respect to morphology, the particles of amylase‐treated flours were smaller than the control and maltodextrin‐treated flours. CONCLUSION: The results showed that good quality flour could be prepared by combining 30 g kg?1 maltodextrin and 7 g kg?1 amylase treatment. Copyright © 2009 Society of Chemical Industry 相似文献