Journal articles on the topic 'Path length enhancement'
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Mupparapu, Rajeshkumar, Kevin Vynck, Tomas Svensson, Matteo Burresi, and Diederik S. Wiersma. "Path length enhancement in disordered media for increased absorption." Optics Express 23, no. 24 (October 8, 2015): A1472. http://dx.doi.org/10.1364/oe.23.0a1472.
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David, Michael, Tay Ching En Marcus, Maslina Yaacob, Mohd Rashidi Salim, Nabihah Hussin, Mohd Haniff Ibrahim, Sevia Mahdaliza Idrus, Nor Hafizah Ngajikin, and Asrul Izam Azmi. "Incident Angle Approach to Sensitivity Enhancement for Ozone Sensor." Applied Mechanics and Materials 735 (February 2015): 255–59. http://dx.doi.org/10.4028/www.scientific.net/amm.735.255.
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The design and mathematical model of a reflective type optical gas sensor is presented. Light source is radiated at an incident angle for 10 cm gas cell with an internal diameter of 0.4 cm. At an incident angle of 1o, optical path length obtained is 342.7886 cm, at 27o incident angle, optical path length is 10.4926 cm and at an incident angle of 28o, optical path length is 9.9631 cm. The model is most efficient at lower incident angles, precisely between (1o and 27o). Effects of variation in diameter and length of gas cell are also demonstrated.
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Liu, Jun Xia, Shao Hua Liu, Jun Sheng Yu, Peng Xie, Ze Jian Lu, and Xiao Dong Chen. "Optimizing Navigation Satellite Enhancement Information Distribution Network Based on X10 and MPI." Applied Mechanics and Materials 58-60 (June 2011): 2177–82. http://dx.doi.org/10.4028/www.scientific.net/amm.58-60.2177.
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To meet large-scale and time-sensitive needs of navigation Satellite enhance information distribution network in Global Position System(GPS)/Beidou and other systems [1], use small-world network model of complex network to study the topology. Small-world model has a large clustering coefficient and smaller average shortest path length so it can meet performance requirements better. Use Python language to product WS model, and simulate the important parameter-the average shortest path length. Use Dijkstra parallel algorithm and sparse matrix storage method to simulate under the use of X10 parallel language. Analyze the relationship between average shortest path length and random reconnection probability. Additionally, simulate in parallel MPI library and compare the two.
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Fortes, M., E. Comesaña, J. A. Rodríguez, P. Otero, and A. J. Garcia-Loureiro. "Evaluation of the Collection Length and Optical Path Enhancement in a-Si:H Solar Cells." Journal of Physics: Conference Series 647 (October 13, 2015): 012047. http://dx.doi.org/10.1088/1742-6596/647/1/012047.
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Guo, Xiaonan, Tiago Simas, Meng‐Chuan Lai, Michael V. Lombardo, Bhismadev Chakrabarti, Amber N. V. Ruigrok, Edward T. Bullmore, Simon Baron‐Cohen, Huafu Chen, and John Suckling. "Enhancement of indirect functional connections with shortest path length in the adult autistic brain." Human Brain Mapping 40, no. 18 (August 29, 2019): 5354–69. http://dx.doi.org/10.1002/hbm.24777.
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Kamble, Kanishka N., and Suresh K. Shirgave. "Hybrid Method for Semantic Similarity Computation Using Weighted Components in Ontology." International Journal of Software Innovation 10, no. 1 (January 1, 2022): 1–12. http://dx.doi.org/10.4018/ijsi.309734.
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In this paper, the researchers propose an approach to measure the semantic similarity between two concepts in an ontology like WordNet and DBpedia. Some earlier semantic similarity approaches proposed concentrated on the ontology structure between concepts and some concentrated only on the information content of concepts. This paper proposes a semantic similarity approach with path length, information content, and semantic depth (i.e., PLICD) to combine both path length as well as information content-based approaches. This proposed approach uses weighted shortest path length and information content calculated using semantic depth and hyponyms of the concepts to measure semantic similarity between two concepts. Through experimentations performed on WordNet and DBpedia, the researchers note that the PLICD semantic similarity approach has delivered a statistically meaningful enhancement as compared to the other semantic similarity approaches concerning accuracy and F score.
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Shribak, Michael, Kieran G. Larkin, and David Biggs. "Mapping optical path length and image enhancement using quantitative orientation-independent differential interference contrast microscopy." Journal of Biomedical Optics 22, no. 1 (January 6, 2017): 016006. http://dx.doi.org/10.1117/1.jbo.22.1.016006.
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Beghou, Lotfi. "Methodology for the design of multi-source transmitters dedicated to perpendicular dynamic wireless power transfer: theoretical study." Wireless Power Transfer 5, no. 1 (January 21, 2018): 54–63. http://dx.doi.org/10.1017/wpt.2017.20.
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In this paper, a theoretical study for the design of multi-source transmitters suitable for perpendicular dynamic wireless power transfer is presented. Unlike conventional systems, the concept presented here overcomes the traditional limitation on the receiver's orientation by providing an optimal distribution of the transmitted energy obtained by using different sources. For this purpose, a theoretical study of different transmitters has been achieved by solving the inverse problem. Comparison with conventional single-source transmitters carrying the same total current as the multi-source transmitters, shows a significant enhancement of the power gain when a Genetic Algorithm is used. The obtained theoretical results show power gain levels over 7.5 dB for different path lengths at different heights. At the end, a solution for a path of an infinite length is presented.
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Dubois, S., A. Michel, J. P. Eymery, J. L. Duvail, and L. Piraux. "Fabrication and properties of arrays of superconducting nanowires." Journal of Materials Research 14, no. 3 (March 1999): 665–71. http://dx.doi.org/10.1557/jmr.1999.0091.
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We report on the fabrication and structural characterization of arrays of superconducting nanowires by electroplating lead into the nanopores of track-etched polymer membranes. The diameters of the lead nanowires range from 400 down to 70 nm, whereas their length is about 20 μm. Large enhancement of the critical field has been observed in good agreement with the Ginsburg–Landau–Silin theory. By comparing the predicted critical field enhancement for thin cylinders with experimental results, we have extracted the effective penetration depth. The dependence of the effective penetration depth and electron mean free path on the wire diameter is also discussed.
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Xiao, Ruoxiu, Cheng Chen, Hanying Zou, Ying Luo, Jiayu Wang, Muxi Zha, and Ming-An Yu. "Segmentation of Cerebrovascular Anatomy from TOF-MRA Using Length-Strained Enhancement and Random Walker." BioMed Research International 2020 (September 21, 2020): 1–16. http://dx.doi.org/10.1155/2020/9347215.
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Cerebrovascular rupture can cause a severe stroke. Three-dimensional time-of-flight (TOF) magnetic resonance angiography (MRA) is a common method of obtaining vascular information. This work proposes a fully automated segmentation method for extracting the vascular anatomy from TOF-MRA. The steps of the method are as follows. First, the brain is extracted on the basis of regional growth and path planning. Next, the brain’s highlighted connected area is explored to obtain seed point information, and the Hessian matrix is used to enhance the contrast of image. Finally, a random walker combined with seed points and enhanced images is used to complete vascular anatomy segmentation. The method is tested using 12 sets of data and compared with two traditional vascular segmentation methods. Results show that the described method obtains an average Dice coefficient of 90.68%, and better results were obtained in comparison with the traditional methods.
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Abed, Mustafa S., Omar F. Lutfy, and Qusay F. Al-Doori. "Online Optimization Application on Path Planning in Unknown Environments." Journal Européen des Systèmes Automatisés 55, no. 1 (February 28, 2022): 61–69. http://dx.doi.org/10.18280/jesa.550106.
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For autonomous mobile robots, determining the shortest path to the target is an indispensable requirement. In this work, two modifications of the Grey Wolf Optimization (GWO) method, which are called MGWO1 and MGWO2, are suggested for online path planning to make the mobile robot reach the goal using the shortest path and safely avoiding the obstacles in unknown environments. To avoid sharp curves, a cost function is derived using a path smoothing parameter and an integrated distance function. The results of the proposed approach are presented based on computer simulation in various unknown environments. A study was conducted to compare the performance of the proposed algorithm with those of other algorithms and the results indicated that the proposed GWO, MGWO1, and MGWO2 algorithms are competent in avoiding obstacles successfully including the local minima situation. Finally, the average enhancement rate in path length compared with Adaptive Particle Swarm Optimization (APSO), GWO is 5.30%, MGWO1 is 5.52%, and MGWO2 is 7.44%.
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Hainfeld, James F., and Frederic R. Furuya. "Silver enhancement of nanogold and undecagold." Proceedings, annual meeting, Electron Microscopy Society of America 52 (1994): 130–31. http://dx.doi.org/10.1017/s0424820100168384.
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Silver enhancement of colloidal gold is commonly used to improve visibility of small gold particles in the electron microscope, or to visualize immunogold labeling in the light or confocal microscope. Silver enhancement can also produce a signal visible by eye in such applications as immunodot blotsor staining of gels or transfers with gold reagents. A recent advance in gold technology has been theuse of gold clusters, which are gold compounds, and can be covalently linked to antibodies or other molecules. Two gold clusters developed for such uses are undecagold (Au11 ), which has a 0.8 nm gold core, and a larger, 1.4 nm gold core cluster, •Nanogold•. Because of their small size, many uses requirefurther enlargement via silver deposition.Here we report quantitative studies of the silver reaction rates for Nanogold and undecagold. These were followed by measuring the UV-visible (UV-vis) spectra at 1 min intervals of solutions of gold clusters mixed with a light insensitive silver enhancer (LI Silver). Solutions were in a 1 cm path length disposable cuvette and spectra were recorded using a Hewlett Packard 8452A diode array spectrophotometer.
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Lai, Jia Jiun, Victor N. S. Bong, Basil T. Wong, and Khameel B. Mustapha. "Modeling of Light Propagation and Phonon Conduction inside Metallic Nanoparticles Enhanced Thin-Film Solar Cells." Journal of Nano Research 38 (January 2016): 26–35. http://dx.doi.org/10.4028/www.scientific.net/jnanor.38.26.
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The main aim of this work is to analyze the various heat transport mechanisms and their roles in efficiency enhancement of a thin-film solar cell due to embedded metallic nanoparticles at the rear of the cell, from both electrical and thermal aspects. The nanoparticles present deep inside the cell reflect incident radiation which then increases the optical path length for enhanced electricity generation. The increase in the optical path length also tends to induce additional but undesirable thermal heating which reduces the performance of the cells. The relationship between the improved conversion efficiency and the thermal effect is the crucial factor of maximizing the performance of thin-film solar cells and has yet to be explored. An accurate theoretical/numerical modeling is warranted in this case. Here, we present an analysis of combined light propagation and preliminary phonon transport in the cell to study solar-energy deposition and the associated thermal gradient.
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David, Michael, Patrick Enenche, Caroline O. Alenoghena, Mohd Haniff Ibrahim, Sevia M. Idrus, and Tay Ching En Marcus. "The concurrent upshot of optical path-length and pressure on O<sub>3</sub> absorption cross-section in relation to green communication." International Journal of Advances in Applied Sciences 11, no. 2 (June 1, 2022): 97. http://dx.doi.org/10.11591/ijaas.v11.i2.pp97-106.
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<span>Ozone gas is a greenhouse gas. Accurate measurement of its concentration is dependent on the right value of the ozone gas absorption cross-section. In the literature, discrepancies and inconsistencies have been however linked with ozone gas absorption cross-section. In the literature, information on the pressure effect on pressures less than 100 mbar and greater than 100 but less than 1000 mbar is not available for the visible spectrum. Thus, creating an information gap which this manuscript is intended to fill up. This is the problem that has been addressed in this present work. The method of simulation with SpectralCalc is the method adopted for the present work. HITRAN 2012 simulator, available on spectralcalc.com, was used in simulating the ozone gas absorption cross-section to determine the simultaneous effect of optical path length and pressure at two peak wavelengths in the visible spectrum. Simulation outcomes were obtained for an optical path length of 10 cm to 120 cm shows that the optimum absorption cross-section value of 5.1084×10-25 m<sup>2</sup>/molecule at 603 nm and 4.7182×10-25 m<sup>2</sup>/molecule at 575 nm for gas cells length between 10 cm and 120 cm are obtained at peak points. Pressure values at which ozone gas absorption cross-section becomes a constant value of 5.1058×10-25 m<sup>2</sup>/molecule at 603 nm and 4.7158×10-25 m<sup>2</sup>/molecule at 575 nm is optical path length dependent. The percentage difference between 5.1084×10-25 m<sup>2</sup>/molecule and 5.1058×10-25 m<sup>2</sup>/molecule is 0.05% for all lengths of gas cells considered. Similarly, the percentage difference between 4.7182×10-25 m<sup>2</sup>/molecule and 4.7158×10-25 m<sup>2</sup>/molecule is also 0.05% for all lengths of gas cells considered. These results are relevant for high accuracy and high precision ozone gas measurements. Furthermore, efficient measurement of ozone gas is a direct enhancement of green communication.</span>
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Spörri, Jörg, Josef Kröll, Hermann Schwameder, and Erich Müller. "The role of path length- and speed-related factors for the enhancement of section performance in alpine giant slalom." European Journal of Sport Science 18, no. 7 (March 27, 2018): 911–19. http://dx.doi.org/10.1080/17461391.2018.1453870.
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Zheng, Gaige, Linhua Xu, Min Lai, Yunyun Chen, Yuzhu Liu, and Xiangyin Li. "Enhancement of optical absorption in amorphous silicon thin film solar cells with periodical nanorods to increase optical path length." Optics Communications 285, no. 10-11 (May 2012): 2755–59. http://dx.doi.org/10.1016/j.optcom.2012.01.084.
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Loukas, Constantinos, Nikolaos Nikiteas, Meletios Kanakis, and Evangelos Georgiou. "The Contribution of Simulation Training in Enhancing Key Components of Laparoscopic Competence." American Surgeon 77, no. 6 (June 2011): 708–15. http://dx.doi.org/10.1177/000313481107700625.
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This study aims to investigate how basic training contributes to the performance of complex laparoscopic tasks performed in a virtual reality (VR) environment. An assessment methodology is proposed based on quantitative error analysis of key components of laparoscopic competence. Twenty-five inexperienced surgeons were trained on four basic tasks. The effect of training was assessed on three independent scenarios (two procedural: adhesiolysis and bowel suturing, and a laparoscopic cholecystectomy [LC]). Several error parameters were post hoc analyzed to yield a quantitative performance index for two fundamental skills: proficiency and safety. Time and instrument path length were also measured and compared. Correlation analysis was performed to study how these indices correlate one another. Significant learning curves were demonstrated during training. For adhesiolysis, all four indices improved significantly ( P < 0.05). Time and path length presented plateaus for all basic tasks, whereas proficiency and safety only for two and one task(s), respectively. For bowel suturing, only time and safety errors showed a decrease ( P < 0.05). Significant performance enhancement was observed for LC in which errors and path length reduced after training ( P < 0.05). Our results revealed also an increased number of correlations after training, especially for proficiency. This study finds it possible to assess key competence skills based on the quantitative analysis of various parameters generated by a VR simulator. The improvement in basic training is transferred to more complex tasks. The proposed methodology is useful for structured evaluation of laparoscopic performance demonstrating fundamental elements of surgical competence.
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Liu, Ying, Yuqi Cao, Xue Li, Yang Li, and Bowei Wang. "Cyano-Functionalized Diarylethene Derivatives with Aggregation-Induced Emission Enhancement and Piezofluorochromic Behaviours." Australian Journal of Chemistry 72, no. 5 (2019): 369. http://dx.doi.org/10.1071/ch18450.
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Four donor–acceptor (D-A) type phenothiazine derivatives were designed and synthesized and all of them exhibited an aggregation-induced emission enhancement (AIEE) effect and red-shifted piezofluorochromic (PFC) behaviour. Moreover, it was found that the compound containing a shorter alkyl chain displayed more remarkable PFC properties. This result was probably ascribed to highly twisted conformations which can lead to loose solid molecular packing with cavities and weak interactions. After they were pressed, the planarization of the molecular conformation increased and molecular conjugation degree enhanced, resulting in a red-shift in the photoluminescence spectrum. In addition, optimized geometric structures indicate that the compound with a longer alkyl chain has a more planer geometric structure, which leads to a smaller bathochromic shift upon grinding. In summary, we provide a new path to regulate the PFC behaviours of fluorescent materials by changing the length of their substituted alkyl chain.
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Xin, Gongfeng, Lei Shi, Guanxu Long, Weigang Pan, Yiming Li, and Jicun Xu. "Mobile robot path planning with reformative bat algorithm." PLOS ONE 17, no. 11 (November 4, 2022): e0276577. http://dx.doi.org/10.1371/journal.pone.0276577.
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Mobile robot path planning has attracted much attention as a key technology in robotics research. In this paper, a reformative bat algorithm (RBA) for mobile robot path planning is proposed, which is employed as the control mechanism of robots. The Doppler effect is applied to frequency update to ameliorate RBA. When the robot is in motion, the Doppler effect can be adaptively compensated to prevent the robot from prematurely converging. In the velocity update and position update, chaotic map and dynamic disturbance coefficient are introduced respectively to enrich the population diversity and weaken the limitation of local optimum. Furthermore, Q-learning is incorporated into RBA to reasonably choose the loudness attenuation coefficient and the pulse emission enhancement coefficient to reconcile the trade-off between exploration and exploitation, while improving the local search capability of RBA. The simulation experiments are carried out in two different environments, where the success rate of RBA is 93.33% and 90%, respectively. Moreover, in terms of the results of success rate, path length and number of iterations, RBA has better robustness and can plan the optimal path in a relatively short time compared with other algorithms in this field, thus illustrating its validity and reliability. Eventually, by the aid of the Robot Operating System (ROS), the experimental results of real-world robot navigation indicate that RBA has satisfactory real-time performance and path planning effect, which can be considered as a crucial choice for dealing with path planning problems.
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Matson, Michael T., Tore Ramstad, and Michael J. Dunn. "Purity Determination of Alprostadil by Micellar Electrokinetic Chromatography with Signal Enhancement Involving Field‐Amplified Sample Stacking and Extended Path Length Detection." Journal of Liquid Chromatography & Related Technologies 28, no. 20 (December 2005): 3181–203. http://dx.doi.org/10.1080/10826070500330794.
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Michel, Anna P. M., David J. Miller, Kang Sun, Lei Tao, Levi Stanton, and Mark A. Zondlo. "Long-Path Quantum Cascade Laser–Based Sensor for Methane Measurements." Journal of Atmospheric and Oceanic Technology 33, no. 11 (November 2016): 2373–84. http://dx.doi.org/10.1175/jtech-d-16-0024.1.
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AbstractA long-path methane (CH4) sensor was developed and field deployed using an 8-μm quantum cascade laser. The high optical power (40 mW) of the laser allowed for path-integrated measurements of ambient CH4 at total pathlengths from 100 to 1200 m with the use of a retroreflector. Wavelength modulation spectroscopy was used to make high-precision measurements of atmospheric pressure–broadened CH4 absorption over these long distances. An in-line reference cell with higher harmonic detection provided metrics of system stability in rapidly changing and harsh environments. The system consumed less than 100 W of power and required no consumables. The measurements intercompared favorably (typically less than 5% difference) with a commercial in situ methane sensor when accounting for the different spatiotemporal scales of the measurements. The sensor was field deployed for 2 weeks at an arctic lake to examine the robustness of the approach in harsh field environments. Short-term precision over a 458-m pathlength was 10 ppbv at 1 Hz, equivalent to a signal from a methane enhancement above background of 5 ppmv in a 1-m length. The sensor performed well in a range of harsh environmental conditions, including snow, rain, wind, and changing temperatures. These field measurements demonstrate the capabilities of the approach for use in detecting large but highly variable emissions in arctic environments.
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Rong, Lin, Xiaoqing Mu, Jinchao Zhao, Leping Huang, Mingqiao Ye, and Na Wang. "Rapid Coating of Aqueous Pearls with Carbon Nanotubes via In Situ Polymerization of Dopamine." Advances in Materials Science and Engineering 2021 (August 20, 2021): 1–7. http://dx.doi.org/10.1155/2021/6757935.
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Millimeter-scale calcium alginate aqueous core capsules (mm-CaSA-Caps) are suitable for embedding of temperature and chemical sensitive substances because of its excellent biocompatibility and biodegradability. In this study, mm-CaSA-Caps were coated with multiwalled carbon nanotubes (MWNTs) via in situ self-polymerization of dopamine (DA) under mild conditions. During the modification process, mm-CaSA-Caps transferred quickly from colorless and transparent capsules to dark and opaque “pearls” in 15 min. The obtained MWNTs-polydopamine- (PDA-) modified mm-CaSA-Caps (mm-MWNTs-PDA@CaSA-Caps) retained the spherical appearance of mm-CaSA-Caps with uniform coating of MWNTs-PDA. Obviously, the MWNTs were easily coated on the mm-PDA@CaSA-Caps due to the strong adhesive property of PDA. As the MWNTs content increased, the stacking density of MWNTs on surface of the mm-MWNTs-PDA@CaSA-Caps raised. The water loss ratio of mm-MWNTs-PDA@CaSA-Caps was enhanced ascribed to increasing the path length of water by raising stacking density of MWNTs. This study provided a new path for enhancement of the barrier property of hydrogel capsules.
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Sharma, Aanchal, and Sudhir Pathak. "Enhancement of k-anonymity algorithm for privacy preservation in social media." International Journal of Engineering & Technology 7, no. 2.18 (June 5, 2018): 40. http://dx.doi.org/10.14419/ijet.v7i2.27.11747.
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In recent times, more and more social data is transmitted in different ways. Protecting the privacy of social network data has turn out to be an essential issue. Hypothetically, it is assumed that the attacker utilizes the similar information used by the genuine user. With the knowledge obtained from the users of social networks, attackers can easily attack the privacy of several victims. Thus, assuming the attacks or noise node with the similar environment information does not resemble the personalized privacy necessities, meanwhile, it loses the possibility to attain better utility by taking benefit of differences of users’ privacy necessities. The traditional research on privacy-protected data publishing can only deal with relational data and even cannot applied to the data of social networking. In this research work, K-anonymity is used for providing the security of the sensitive information from the attacker in the social network. K-anonymity provides security from attacker by making the graph and developing nodes degree. The clusters are made by grouping the similar degree into one group and the process is repeated until the noisy node is identified. For measuring the efficiency the parameters named as Average Path Length (APL) and information loss are measured. A reduction of 0.43% of the information loss is obtained.
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Elahi, Fazle, and Zubaer M. Hossain. "Crack-path bifurcation, arrest, and renucleation in porous 3C-SiC." Journal of Applied Physics 131, no. 11 (March 21, 2022): 115105. http://dx.doi.org/10.1063/5.0079588.
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This paper presents the physics of crack-path formation in single-crystalline [Formula: see text]-SiC containing an isolated pore as a combination of three physical processes: bifurcation, arrest, and renucleation. Results show that, depending on the symmetry of the crystal structure, three distinctive crack paths form: (i) crack bifurcates and propagates in the domain without being affected by the pore, (ii) crack bifurcates and interacts strongly with the pore leading to a termination of the propagating crack, and (iii) crack does not bifurcate, retains its propagation path on the symmetry plane, and gets arrested at the pore. The continued growth of the terminated crack requires crack renucleation at the pore edge, and the renucleation event enhances the effective toughness of the domain. The degree of toughness enhancement depends on the pore diameter, the crack length, and the crack–pore distance. While the crystallographic anisotropy forms the basis for bifurcation, the conditions for bifurcation and arrest are governed by the strength of elastic interactions emanating from the crack tip and the pore edge. As such, there exists a critical crack–pore distance of 40 nm below which the crack–porosity interaction is strong enough to enforce the bifurcated crack to divert toward the pore, leading to instant termination of its growth.
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Xia, Zhetao, Chenxi Zhang, Zhiying Feng, Zhixing Wu, Zengbo Wang, Xiaohong Chen, and Sumei Huang. "Synergetic Effect of Plasmonic Gold Nanorods and MgO for Perovskite Solar Cells." Nanomaterials 10, no. 9 (September 14, 2020): 1830. http://dx.doi.org/10.3390/nano10091830.
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We report new structured perovskite solar cells (PSCs) using solution-processed TiO2/Au nanorods/MgO composite electron transport layers (ETLs). The proposed method is facile, convenient, and effective. Briefly, Au nanorods (NRs) were prepared and introduced into mesoporous TiO2 ETLs. Then, thin MgO overlayers were grown on the Au NRs modified ETLs by wet spinning and pyrolysis of the magnesium salt. By simultaneous use of Au NRs and MgO, the power conversion efficiency of the PSC device increases from 14.7% to 17.4%, displaying over 18.3% enhancement, compared with the reference device without modification. Due to longitudinal plasmon resonances (LPRs) of gold nanorods, the embedded Au NRs exhibit the ability to significantly enhance the near-field and far-field (plasmonic scattering), increase the optical path length of incident photons in the device, and as a consequence, notably improve external quantum efficiency (EQE) at wavelengths above 600 nm and power conversion efficiency (PCE) of PSC solar cells. Meanwhile, the thin MgO overlayer also contributes to enhanced performance by reducing charge recombination in the solar cell. Theoretical calculations were carried out to elucidate the PV performance enhancement mechanisms.
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Chu, Wei Ping, Fuh Shyang Juang, Jian Shian Lin, Tien Chai Lin, and Chen Wei Kuo. "Nanoimprint Photonic Crystal Film Enhanced Light-Trapping in a-Si Thin Film Solar Cells." Applied Mechanics and Materials 110-116 (October 2011): 497–502. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.497.
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We utilize photonic crystals to enhanced lighttrapping in a-Si:H thin film solar cells. The photonic crystals effectively increase Haze ratio of glass and decrease reflectance of a-Si:H solar cells. Therefore, increase the photon path length to obtain maximum absorption of the absorber layer. The photonic crystals can effective in harvesting weakly absorbing photons with energies just above the band edge. We were spin coated UV glue on the glass, and then nanoimprint of photonic crystals pattern. Finally, used UV lamp was curing of UV glue on the glass. When the 45∘composite photonic crystals structures, the haze was increase to 87.9 %, resulting the short circuit current density and efficiency increasing to 13.96 mA/cm2 and 7.39 %, respectively. Because 45∘composite photonic crystals easy to focus on the point of light lead to the effect of scattering can’t achieve. So, we designs 90∘V-shaped photonic crystals structures to increase scattering. When the 90∘V-shaped photonic crystals structures, the Haze was increase to 93.9 %. Therefore, the short circuit current density and Efficiency increasing to 15.62 mA/cm2 and 8.09 %, respectively. We observed ~35 % enhancement of the short-circuit current density and ~31 % enhancement of the conversion efficiency.
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Borse, Kunal, Ramakant Sharma, Dipti Gupta, and Aswani Yella. "Simultaneous enhancement of light absorption and improved charge collection in PTB7-Th: PC70BM organic solar cells." MRS Advances 2, no. 15 (2017): 835–40. http://dx.doi.org/10.1557/adv.2017.248.
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ABSTRACTEnhancing the light absorption and improving the charge collection are considered as two major prerequisite for achieving highly efficient bulk heterojunction organic solar cells (BHJ OSCs). In the present study, we have explored Ga doped ZnO as an electron transport layer for improving the charge collection in one of the promising donor: acceptor system comprised of Poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b’]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)] (PTB7-Th):phenyl-C71-butyric acid methyl ester (PC70BM). With the inverted geometry having a configuration of ITO/GZO (40nm)/PTB7-Th: PC70BM (100nm)/MoO3 (10nm)/Ag (100nm), maximum power conversion efficiency (PCE) of 7.24% has been achieved, while it is limited at 6.89% for devices with undoped ZnO.It was found that PCE can be further improved to 8.35 % after V-grooved textured PDMS films were attached to the backside of OSC substrates. We attribute this performance enhancement in OSCs is due to increased total optical path length of the incident light within the device.
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Wei, Xiangyu, Kai Xu, Peng Jiao, Quanjun Yin, and Yabing Zha. "A Decomposition Approach for Stochastic Shortest-Path Network Interdiction with Goal Threshold." Symmetry 11, no. 2 (February 15, 2019): 237. http://dx.doi.org/10.3390/sym11020237.
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Shortest-path network interdiction, where a defender strategically allocates interdiction resource on the arcs or nodes in a network and an attacker traverses the capacitated network along a shortest s-t path from a source to a terminus, is an important research problem with potential real-world impact. In this paper, based on game-theoretic methodologies, we consider a novel stochastic extension of the shortest-path network interdiction problem with goal threshold, abbreviated as SSPIT. The attacker attempts to minimize the length of the shortest path, while the defender attempts to force it to exceed a specific threshold with the least resource consumption. In our model, threshold constraint is introduced as a trade-off between utility maximization and resource consumption, and stochastic cases with some known probability p of successful interdiction are considered. Existing algorithms do not perform well when dealing with threshold and stochastic constraints. To address the NP-hard problem, SSPIT-D, a decomposition approach based on Benders decomposition, was adopted. To optimize the master problem and subproblem iteration, an efficient dual subgraph interdiction algorithm SSPIT-S and a local research based better-response algorithm SSPIT-DL were designed, adding to the SSPIT-D. Numerical experiments on networks of different sizes and attributes were used to illustrate and validate the decomposition approach. The results showed that the dual subgraph and better-response procedure can significantly improve the efficiency and scalability of the decomposition algorithm. In addition, the improved enhancement algorithms are less sensitive and robust to parameters. Furthermore, the application in a real-world road network demonstrates the scalability of our decomposition approach.
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Schäfer, Sören, Patrick McKearney, Simon Paulus, and Stefan Kontermann. "Analytical model for extracting optical properties from absorptance of femtosecond-laser structured hyperdoped silicon." Journal of Applied Physics 131, no. 24 (June 28, 2022): 243102. http://dx.doi.org/10.1063/5.0094177.
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We set up an analytical optical model to emulate the absorptance spectra of light scattering, sulfur-hyperdoped silicon that we fabricate by using femtosecond laser pulses. The model allows us to distinguish between contributions to the absolute sub-bandgap absorptance from the path length enhancement of photons due to laser-induced surface roughness, on the one hand, and from the actual hyperdoped layer, on the other hand. Both effects are quantified via the two free parameters of the model. By varying the laser fluence and the areal pulse density, we create a range from almost planar to heavily structured hyperdoped Si samples that we show to behave almost like a Lambertian scatterer. The optical depth a1, i.e., the product of the absorption coefficient close to the Si bandgap energy and the effective thickness of the hyperdoped layer, scales with the surface area enhancement, which we identify as the main driving force for large sub-bandgap absorptances of this material type. It reaches maximum values of nearly a1 = 0.4, which refers to an absolute absorptance of 82% at a wavelength of 1450 nm. We furthermore discuss, quantify, and reduce possible error sources when determining the absorptance of such optically rough, hyperdoped samples with a spectrophotometer.
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Fita Dwi Untari, Dwi Sadono, and Lukman Effendy. "Partisipasi Anggota Kelompok Tani dalam Pengembangan Usahatani Hortikultura di Kecamatan Pacet Kabupaten Cianjur." Jurnal Penyuluhan 18, no. 01 (February 8, 2022): 87–104. http://dx.doi.org/10.25015/18202236031.
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The horticultural sub-sector has the prospect of boosting the economic value and income of farmers. This study aims: (1) to analyze perception of farmer group members about the role of the group in the development of horticultural farming and the factors that influence; (2) to analyze participation of group members in the development of horticultural farming and the factors that influence; and (3) developing strategies to increase group member participation. This study used a survey method and was conducted from February to April 2021 in Pacet District, Cianjur Regency, West Java Province. The samples this study were 100 people. The analysis method used was descriptive and inferential statistics (Path Analysis) equipped with qualitative data. The results showed: (1) perception of farmer group members was in the medium category, influenced by extension activities; (2) participation of group members was in the medium category, directly influenced by members' perceptions of the role of farmer groups, access to information, the length of formal education, and negatively affacted by involvement on group; (3) Strategies to increase participation are through efforts: enhancement the role of farmer groups, utilization of access to information, optimizing the role of change agents, and enhancement quality of extension services.
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Al-Sharman, Alham, and Catherine F. Siengsukon. "Sleep Enhances Learning of a Functional Motor Task in Young Adults." Physical Therapy 93, no. 12 (December 1, 2013): 1625–35. http://dx.doi.org/10.2522/ptj.20120502.
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Background Sleep has been demonstrated to enhance simple motor skill learning “offline” in young adults. “Offline learning” refers to either the stabilization or the enhancement of a memory through the passage of time without additional practice. It remains unclear whether a functional motor task will benefit from sleep to produce offline motor skill enhancement. Physical therapists often teach clients functional motor skills; therefore, it is important to understand how sleep affects learning of these skills. Objective The purpose of this study was to determine whether sleep enhances the learning of a functional motor task. Design A prospective, cross-sectional, repeated-measures design was used. Methods Young participants who were healthy (N=24) were randomly assigned to either a sleep group or a no-sleep group. The sleep group practiced a novel walking task in the evening and underwent retention testing the following morning, and the no-sleep group practiced the task in the morning and underwent retention testing in the evening. Outcome measures included time around the walking path and spatiotemporal gait parameters. Results Only participants who slept after practicing the novel walking task demonstrated a significant offline improvement in performance. Compared with the no-sleep group, participants in the sleep group demonstrated a significant decrease in the time around the walking path, an increase in tandem velocity, an increase in tandem step length, and a decline in tandem step time. Limitations Time-of-day effect and inability to ensure a certain amount of sleep quantity and quality of participants were limitations of the study. Conclusions This study is the first to provide evidence that sleep facilitates learning clinically relevant functional motor tasks. Sleep is an important factor that physical therapists should consider when teaching clients motor skills.
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Abed, Mustafa S., Omar F. Lutfy, and Qusay F. Al-Doori. "Online Path Planning of Mobile Robots Based on African Vultures Optimization Algorithm in Unknown Environments." Journal Européen des Systèmes Automatisés 55, no. 3 (June 30, 2022): 405–12. http://dx.doi.org/10.18280/jesa.550313.
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Autonomous mobile robots developed using metaheuristic algorithms are increasingly becoming a hot topic in control and computer sciences. Specifically, finding the shortest root to the goal and avoiding hurdles are current subjects of autonomous mobile robots. The main drawbacks of classic methods are the incapacity to move the robot in a dynamic and unknown environment, deadlock in a local minimum and complicated environments, and incapacity to foretell the speed vector of obstacles and non-optimality of the route. This article exhibits a recent path planning approach that utilizes the African Vultures Optimization (AVOA) for navigation of the mobile robot in static and dynamic unknown environments with a dynamic target. The proposed online optimization approach is used in three different environments including an environment with unknown static obstacles, an environment with unknown dynamic obstacles, and an environment with a dynamic target. The proposed approach can solve a local minima problem in the environment with static obstacles. The online optimization method is performed using two phases which are the sensors’ reading phase and the path calculation phase and the results are given based on computer simulation in different unknown environments. A comparative study was conducted between the suggested algorithm and two other algorithms and the results showed that the AVOA algorithm was better in avoiding obstacles successfully including the local minima situation. Finally, the average enhancement rates in the path length compared with the Adaptive Particle Swarm Optimization (APSO) and the Hybrid Fuzzy-Wind Driven Optimization (WDO) are 2.21% and 1.02207%, respectively.
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Deng, Yuxuan, Hequn Tan, Minghang Tong, Dianzhuo Zhou, Yuxiang Li, and Ming Zhu. "An Automatic Recognition Method for Fish Species and Length Using an Underwater Stereo Vision System." Fishes 7, no. 6 (November 10, 2022): 326. http://dx.doi.org/10.3390/fishes7060326.
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Developing new methods to detect biomass information on freshwater fish in farm conditions enables the creation of decision bases for precision feeding. In this study, an approach based on Keypoints R-CNN is presented to identify species and measure length automatically using an underwater stereo vision system. To enhance the model’s robustness, stochastic enhancement is performed on image datasets. For further promotion of the features extraction capability of the backbone network, an attention module is integrated into the ResNeXt50 network. Concurrently, the feature pyramid network (FPN) is replaced by an improved path aggregation network (I-PANet) to achieve a greater fusion of effective feature maps. Compared to the original model, the mAP of the improved one in object and key point detection tasks increases by 4.55% and 2.38%, respectively, with a small increase in the number of model parameters. In addition, a new algorithm is introduced for matching the detection results of neural networks. On the foundation of the above contents, coordinates of head and tail points in stereo images as well as fish species can be obtained rapidly and accurately. A 3D reconstruction of the fish head and tail points is performed utilizing the calibration parameters and projection matrix of the stereo camera. The estimated length of the fish is acquired by calculating the Euclidean distance between two points. Finally, the precision of the proposed approach proved to be acceptable for five kinds of common freshwater fish. The accuracy of species identification exceeds 94%, and the relative errors of length measurement are less than 10%. In summary, this method can be utilized to help aquaculture farmers efficiently collect real-time information about fish length.
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Li, Huimin, Qianqian Shen, Han Zhang, Jiaqi Gao, Husheng Jia, Xuguang Liu, Qi Li, and Jinbo Xue. "Oxygen vacancy-mediated WO3 phase junction to steering photogenerated charge separation for enhanced water splitting." Journal of Advanced Ceramics 11, no. 12 (November 29, 2022): 1873–88. http://dx.doi.org/10.1007/s40145-022-0653-8.
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AbstractEffective charge separation and transfer is deemed to be the contributing factor to achieve high photoelectrochemical (PEC) water splitting performance on photoelectrodes. Building a phase junction structure with controllable phase transition of WO3 can further improve the photocatalytic performance. In this work, we realized the transition from orthorhombic to monoclinic by regulating the annealing temperatures, and constructed an orthorhombic-monoclinic WO3 (o-WO3/m-WO3) phase junction. The formation of oxygen vacancies causes an imbalance of the charge distribution in the crystal structure, which changes the W-O bond length and bond angle, accelerating the phase transition. As expected, an optimum PEC activity was achieved over the o-WO3/m-WO3 phase junction in WO3-450 photoelectrode, yielding the maximum O2 evolution rate roughly 32 times higher than that of pure WO3-250 without any sacrificial agents under visible light irradiation. The enhancement of catalytic activity is attributed to the atomically smooth interface with a highly matched lattice and robust built-in electric field around the phase junction, which leads to a less-defective and abrupt interface and provides a smooth interfacial charge separation and transfer path, leading to improved charge separation and transfer efficiency and a great enhancement in photocatalytic activity. This work strikes out on new paths in the formation of an oxygen vacancy-induced phase transition and provides new ideas for the design of catalysts.
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Ma, Teng-Fei, Min-Jie Wang, Sheng-Zhi Wang, Hao-Le Jiao, Yan Xie, Shu-Jing Li, Zhong-Xiao Xu, and Hai Wang. "Experimental study of retrieval efficiency of Duan-Lukin-Cirac-Zoller quantum memory by optical cavity-enhanced." Acta Physica Sinica 71, no. 2 (2022): 020301. http://dx.doi.org/10.7498/aps.71.20210881.
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<sec>Long-distance entanglement distribution is an important task for quantum communication, but difficult to achieve due to the loss of photons in optical fiber transmission. Quantum repeater is a scheme to solve this problem. In this scheme, the long distance of entanglement distribution is divided into several small parts, the entanglement is established first at both ends of each part, then, the entanglement distance is extended through the entanglement exchange of adjacent interval parts, in order to achieve the long distance entanglement distribution. Of them, the Duan-Lukin-Cirac-Zoller (DLCZ) protocol based on the cold atom ensemble and the linear optics which can generate and store entanglement, is regarded as one of the most potential schemes. In the process of DLCZ, retrieval efficiency is an important index of the quantum repeater, because it will influence each entanglement exchange operation between adjacent quantum repeater nodes. Generally, the retrieval efficiency is improved by optimizing the reading pulse, increasing the optical depth (OD) of the atomic ensemble and the cavity enhancement. The ring cavity constrains the light field to increase the intensity of the interaction between light and atoms, and effectively improve the retrieval efficiency of the quantum memory.</sec><sec>In this work, atomic ensembles are placed in a ring cavity. The cavity length is 3.3 m and the fineness is 13.5. The optical loss of all ring cavity is 21%, mainly including 15% loss of other optical elements and 6% loss of the cell. In order to increase the retrieval efficiency, we need to ensure the mode resonance of read-out photon, write-out photon and locking. The cavity needs two input beams of light: one comes from the path of read-out photon and the other from the path of write-out photon in the reverse direction. The two beams are locked at the same frequency as the write-out photon and the read-out photon respectively. The cavity length is adjusted by moving the cavity mirrors’ positions through translating the frame, to make two light modes resonate. The acousto-optic modulator (AOM) is inserted into the path of the locking to control the frequency of the locking. By adjusting the AOM to change the frequency of the locking, the locking can be coincident with the write-out and read-out cavity modes. Then, the three-mode resonance can be achieved</sec><sec>When the cavity mode resonates with the atomic line, it will lead the atomic formants to split. thereby affecting the enhancement effect of retrieval efficiency. In the experiment, the detuning of the read light will affect the frequency of the read-out photon, and further affect the detuning of the cavity mode with the resonance line of the atom. Thus, by increasing the detuning between the reading light and the atomic transition line, the frequency splitting between the two modes can be reduced, then enhance the retrieval efficiency. We study the relation between the enhancement factor of the retrieval efficiency and the detuning amount of the reading light relative to the atomic resonance line. The results show that when the detuning amount of reading light is 80 MHz, the intrinsic readout efficiency is 45%, and the readout efficiency is enhanced by 1.68 times.</sec>
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Nguyen, Xuan-Huy, Chao-Ming Chen, Hien-Thanh Le, and Hsiao-Yi Lee. "Enhancement of a Single-Axis Femtosecond Laser Scanning System by Using Two Galvanometers to Improve the Telecentricity and the Effective Scanning Length on Laser Process." Applied Sciences 12, no. 23 (December 5, 2022): 12434. http://dx.doi.org/10.3390/app122312434.
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The galvanometer scanning system plays a crucial role in modern laser material processing. With the development of this industry, the requirements for galvanometer scanners are getting higher and higher, especially to overcome the inherent disadvantages that still exist, such as image distortion, marking speed and accuracy in state-of-the-art scanning systems. In this paper, a single-axis optical scanner using two galvanometers in combination with one f-theta telecentric lens and a 343 nm femtosecond pulse laser source is proposed as a new approach for enhancing the precision of laser micromachining technology. The additional second galvanometer is used to manipulate the output laser beam of the first galvanometer to the path with less lens aberration to enhance the telecentricity correction and the effective scanning area. This is based on the international standard regulation ISO (the International Organization for Standardization) 11145:2018 requirements in optics and photonics, in which an important criterion is for the roundness of the focused beam spot to be greater than 87% to determine the effective working length of the proposed scanning system compared to the conventional scanning system. It is demonstrated by optical simulations and real optical experiments that the effective working length can be increased by 3.6 mm, corresponding to 8.1% of the effective scanning field, to achieve a laser material processing system with ISO standard. The damped least squares (DLS) algorithm in optical design software ZEMAX is used to optimize the deflected angle of the two galvanometers to obtain the optimal incident position of the f-theta lens.
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Gao, Feng, Yuhao Hu, Guannan Liu, and Yugui Yang. "Experiment Study on Topological Characteristics of Sandstone Coating by Micro CT." Coatings 10, no. 12 (November 24, 2020): 1143. http://dx.doi.org/10.3390/coatings10121143.
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The pore structure is an important factor of tunnel coating failure, cracking and water leakage. Some investigations on the statistical law of pores and pore networks have been conducted, but little quantitative analysis is observed on topology structure of the pore network, and even the pore structure of sandstone is complex and cross-scale distributed. Therefore, it is of theoretical and engineering significance to quantitatively characterize the connectivity of the pore network in sandstone. This study proposes a new complex network theory to analyze the three-dimensional nature of pore network structure in sandstone. The topological network structure, such as clustering degree, average path length and the module, which cannot be analyzed by traditional coordination number and fractal dimension methods, is analyzed. Numerical simulation results show that a scale-free network model is more suitable for describing the sandstone pore network than random models. The pore network of sandstone has good uniformity. The connectivity of sandstone pore networks has great potential for permeability enhancement. Therefore, this new method provides a way to deeply understand the pore connectivity characteristics of sandstone and to explore the distribution of crack grids in the arch of tunnel coatings.
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Bakke, Paul D., Michael Hrachovec, and Katherine D. Lynch. "Hyporheic Process Restoration: Design and Performance of an Engineered Streambed." Water 12, no. 2 (February 5, 2020): 425. http://dx.doi.org/10.3390/w12020425.
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Stream restoration designed specifically to enhance hyporheic processes has seldom been contemplated. To gain experience with hyporheic restoration, an engineered streambed was built using a gravel mixture formulated to mimic natural streambed composition, filling an over-excavated channel to a minimum depth of 90 cm. Specially designed plunge-pool structures, built with subsurface gravel extending down to 2.4 m, promoted greatly enhanced hyporheic circulation, path length, and residence time. Hyporheic process enhancement was verified using intra-gravel temperature mapping to document the distribution and strength of upwelling and downwelling zones, computation of vertical water flux using diurnal streambed temperature patterns, estimation of hyporheic zone cross section using sodium chloride tracer studies, and repeat measurements of streambed sand content to document evolution of the engineered streambed over time. Results showed that vertical water flux in the vicinity of plunge-pool structures was quite large, averaging 89 times the pre-construction rate, and 17 times larger than maximum rates measured in a pristine stream in Idaho. Upwelling and downwelling strengths in the constructed channel were larger and more spatially diverse than in the control. Streambed sand content showed a variety of response over time, indicating that rapid return to an embedded, impermeable state is not occurring.
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Sharmin, Afsah, F. Anwar, and S. M. A. Motakabber. "A novel bio-inspired routing algorithm based on ACO for WSNs." Bulletin of Electrical Engineering and Informatics 8, no. 2 (June 1, 2019): 718–26. http://dx.doi.org/10.11591/eei.v8i2.1492.
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The methods to achieve efficient routing in energy constrained wireless sensor networks (WSNs) is a fundamental issue in networking research. A novel approach of ant colony optimization (ACO) algorithm for discovering the optimum route for information transmission in the WSNs is proposed here for optimization and enhancement. The issue of path selection to reach the nodes and vital correspondence parameters, for example, the versatility of nodes, their constrained vitality, the node residual energy and route length are considered since the communications parameters and imperatives must be taken into account by the imperative systems that mediate in the correspondence procedure, and the focal points of the subterranean insect framework have been utilized furthermore. Utilizing the novel technique and considering both the node mobility and the existing energy of the nodes, an optimal route and best cost from the originating node to the target node can be detected. The proposed algorithm has been simulated and verified using MATLAB and the simulation results demonstrate that new ACO based algorithm achieved improved performance, about 30% improvement compared with the traditional ACO algorithm, and faster convergence to determine the best cost route, and recorded an improvement in the energy consumption of the nodes per transmission.
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Graf, Manuel, Philipp Scheidegger, André Kupferschmid, Herbert Looser, Thomas Peter, Ruud Dirksen, Lukas Emmenegger, and Béla Tuzson. "Compact and lightweight mid-infrared laser spectrometer for balloon-borne water vapor measurements in the UTLS." Atmospheric Measurement Techniques 14, no. 2 (February 22, 2021): 1365–78. http://dx.doi.org/10.5194/amt-14-1365-2021.
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Abstract. We describe the development, characterization, and first field deployments of a quantum cascade laser direct absorption spectrometer (QCLAS) for water vapor measurements in the upper troposphere and lower stratosphere (UTLS). The instrument is sufficiently small (30×23×11 cm3) and lightweight (3.9 kg) to be carried by meteorological balloons and used for frequent soundings in the UTLS. The spectrometer is a fully independent system, operating autonomously for the duration of a balloon flight. To achieve the required robustness, while satisfying stringent mass limitations, the concepts for optics and electronics have been fundamentally reconsidered compared to laboratory-based spectrometers. A significant enhancement of the mechanical and optical stability is achieved by integrating a newly designed segmented circular multipass cell which allows for 6 m optical path length in a very compact fashion. The H2O volume mixing ratio is retrieved by calibration-free evaluation of the spectral data, i.e., only relying on SI-traceable measurements and absorption line parameters. The open-path design reduces the risk of contamination and allows for fast response and thus high vertical resolution. Laboratory-based characterization experiments show an agreement within 2 % of reference measurements and a precision of 0.1 % under conditions comparable to the UTLS. The instrument successfully performed two balloon-borne test flights up to 28 km altitude. In the troposphere, the retrieved spectroscopic data show an excellent agreement with the accompanying measurements by a frost point hygrometer (CFH). At higher altitude, the quality of the spectral data remained unchanged, but outgassed water vapor within the instrument enclosure was hindering an accurate measurement of the atmospheric water vapor. Despite this limitation, these test flights demonstrated the operation of a compact laser spectrometer in the UTLS aboard a low-volume meteorological balloon, opening the perspective for future highly resolved, accurate, and cost-efficient soundings.
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Smedley, Andrew R. D., Geoffrey W. Evatt, Amy Mallinson, and Eleanor Harvey. "Solar radiative transfer in Antarctic blue ice: spectral considerations, subsurface enhancement, inclusions, and meteorites." Cryosphere 14, no. 3 (March 5, 2020): 789–809. http://dx.doi.org/10.5194/tc-14-789-2020.
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Abstract. We describe and validate a Monte Carlo model to track photons over the full range of solar wavelengths as they travel into optically thick Antarctic blue ice. The model considers both reflection and transmission of radiation at the surface of blue ice, scattering by air bubbles within it, and spectral absorption due to the ice. The ice surface is treated as planar whilst bubbles are considered to be spherical scattering centres using the Henyey–Greenstein approximation. Using bubble radii and number concentrations that are representative of Antarctic blue ice, we calculate spectral albedos and spectrally integrated downwelling and upwelling radiative fluxes as functions of depth and find that, relative to the incident irradiance, there is a marked subsurface enhancement in the downwelling flux and accordingly also in the mean irradiance. This is due to the interaction between the refractive air–ice interface and the scattering interior and is particularly notable at blue and UV wavelengths which correspond to the minimum of the absorption spectrum of ice. In contrast the absorption path length at IR wavelengths is short and consequently the attenuation is more complex than can be described by a simple Lambert–Beer style exponential decay law – instead we present a triple-exponential fit to the net irradiance against depth. We find that there is a moderate dependence on the solar zenith angle and surface conditions such as altitude and cloud optical depth. Representative broadband albedos for blue ice are calculated in the range from 0.585 to 0.621. For macroscopic absorbing inclusions we observe both geometry- and size-dependent self-shadowing that reduces the fractional irradiance incident on an inclusion's surface. Despite this, the inclusions act as local photon sinks and are subject to fluxes that are several times the magnitude of the single-scattering contribution. Such enhancement may have consequences for the energy budget in regions of the cryosphere where particulates are present near the surface. These results also have particular relevance to measurements of the internal radiation field: account must be taken of both self-shadowing and the optical effect of introducing the detector. Turning to the particular example of englacial meteorites, our modelling predicts iron meteorites to reside at much reduced depths than previously suggested in the literature (< 10 cm vs. ∼ 40 cm) and further shows a size dependency that may explain the observed bias in their Antarctic size distribution.
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Vattathurvalappil, Suhail Hyder, Mahmoodul Haq, and Saratchandra Kundurthi. "Hybrid nanocomposites—An efficient representative volume element formulation with interface properties." Polymers and Polymer Composites 30 (January 2022): 096739112210846. http://dx.doi.org/10.1177/09673911221084651.
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Reinforcement of polymers with multiple inclusions of varying length scales and morphologies enable enhancement and tailorability of thermo-mechanical properties in resulting polymers. Computational material models can eliminate the trial-and-error approach of developing these hybrid reinforced polymers, enable prediction of interphase properties, and allow virtual exploration of design space. In this work, computational models, specifically representative volume elements were developed for acrylonitrile butadiene styrene polymer reinforced with nanoscale iron oxide particles and micro-scale short carbon fibers. These representative volume elements were used to predict the tensile modulus of resulting polymer nanocomposite with varying particle concentrations, orientations, interphases, and clustering to realistically replicate the actual material as observed in optical and electron microscopy. The interphase elastic modulus was obtained through established analytical formulations and incorporated into the representative volume elements by defining an interphase region around the reinforcements. The tensile modulus estimated using representative volume elements agreed well with the experiments, evidently showing that the effective tensile modulus of the polymer nanocomposite increased with increase in interphase thickness, aspect ratio, and particle content. Clustering was only observed in Fe3O4 nanoparticles but its size did not have any effect on the effective tensile modulus. The developed computational modeling framework and the resultant prediction of tensile modulus offers a design path which can be extended to other polymer nanocomposites containing multiple inclusions.
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Phuong, Pham Hoai, Kang Jea Lee, Huynh Tran My Hoa, Hoang Hung Nguyen, Quang Trung Tran, Nguyen Thi Hai Yen, and Tran Viet Cuong. "Au Nanoparticles Effect on Inverted ZnO Nanorods/Organic Hybrid Solar Cell Performance." International Journal of Renewable Energy Development 11, no. 1 (October 26, 2021): 165–71. http://dx.doi.org/10.14710/ijred.2022.40492.
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The sun provides a plentiful and inexpensive source of carbon-neutral energy that has yet to be fully utilized. This is a major driving force behind the development of organic photovoltaic (OPV) materials and devices, which are expected to offer benefits such as low cost, flexibility, and widespread availability. For the photovoltaic performance enhancement of the inverted ZnO-nanorods (NR)/organic hybrid solar cells with poly(3-exylthiophene):(6,6)-phenyl-C61-butyric-acid-methylester (P3HT:PCBM) and poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) active layers, gold nanoparticles (Au-NPs) were introduced into the interface between indium-thin-oxide cathode layer and ZnO cathode buffer layer, and the efficiency improvement was observed. It's worth noting that adding Au NPs had both a positive and negative impact on device performance. Au NPs were shown to be advantageous to localized surface plasmon resonance (LSPs) in the coupling of dispersed light from ZnO NRs in order to extend the light's path length in the absorbing medium. Although the light absorption in the active layer could be enhanced, Au NPs might also act as recombination centers within the active layer. To avoid this adverse effect, Au NPs are covered by the ZnO seeded layer to prevent Au NPs from direct contact with the active layer. The dominant surface plasmonic effect of Au NPs increased the photoelectric conversion efficiency from 2.4% to 3.8%.
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Dawe, Jordan T., and Lu Anne Thompson. "Viscosity-Dependent Internal Variability in a Model of the North Pacific." Journal of Physical Oceanography 35, no. 5 (May 1, 2005): 747–56. http://dx.doi.org/10.1175/jpo2707.1.
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Abstract A 2°-resolution isopycnal model of the North Pacific Ocean is shown to produce anomalies that propagate around the subtropical gyre on the decadal time scale that do not appear in a 1°-resolution version of the same model. A principal oscillation pattern (POP) analysis of the isopycnal interface anomaly is performed to examine the dynamics responsible for the anomaly generation. The POPs show a coherent oscillation around the entire subtropical gyre with two centers of action, one in the Central Mode Water (CMW) region, the other in the Subtropical Countercurrent (STCC). Lead–lag covariances between the subduction rate in the CMW and the layer thickness along the oscillation path indicate that anomalous subduction events are not the driving mechanism for the oscillation. A linearized quasigeostrophic mode analysis shows that the anomalies are generated by flow instability in the region of the STCC. The instability disappears in the 1° model because of changes in the horizontal viscosity, which is set in each model to the minimum value necessary to resolve the western boundary current and preserve numerical stability. A criterion for model resolution of an instability of a given length and time scale damped by biharmonic viscosity is derived. The enhancement of the large-scale instabilities in the low-resolution model emphasizes the importance of achieving mesoscale resolution in ocean models used for climate studies.
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Gao, Shike, Ze Chen, Yanan Lu, Zhen Li, Shuo Zhang, and Wenwen Yu. "Comparison of Marine Ecosystems of Haizhou Bay and Lvsi Fishing Ground in China Based on the Ecopath Model." Water 14, no. 9 (April 27, 2022): 1397. http://dx.doi.org/10.3390/w14091397.
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Recently, under the impacts of environmental shifts and human activities, marine ecosystem conservation and recovery have become increasingly important for the management and sustainable development of fishery resources. We construct two Ecopath models to describe and compare the similarities and differences in the structure and function of the ecosystems in Haizhou Bay (HZB) for 2020–2021 and Lvsi Fishing Ground (LSFG) for 2018–2019 in this study. Our results highlight the similarities of the two ecosystems in which plankton (e.g., zooplankton and phytoplankton) are important functional groups with bottom-up effect control and congers control the top-down effect. The differences between the two ecosystems indicate that the HZB ecosystem is relatively mature due to higher Finn’s cycling index (FCI), Finn’s mean path length (FMPL), Connectance Index (CI), System Omnivory Index (SOI), and Ascendency/capacity (A/C). However the food web structure in the LSFG is more diverse and stable with higher Overhead/capacity (O/C) and Overhead/capacity (H). The differences are possibly due to the low trophic level (TL) species composition in the two ecosystems. Therefore, we suggest that stock enhancement and release methods should be deployed to release high TL species into designated water areas to increase food web complexity and ecosystem maturity in HZB and LSFG. This study will help inform ecosystem and fishery regulations in different ways and facilitate discussion towards the establishment of strategic conservation planning and adaptive management.
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Hon, Kai Kwong, and Pak Wai Chan. "Improving Lidar Windshear Detection Efficiency by Removal of “Gentle Ramps”." Atmosphere 12, no. 11 (November 22, 2021): 1539. http://dx.doi.org/10.3390/atmos12111539.
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The Doppler Lidar windshear alerting system at the Hong Kong International Airport (HKIA), the first of its kind in the world, has been in operation since 2006. This paper reports on an enhancement to the automatic windshear detection algorithm at HKIA, which aims at filtering out alerts associated with smoother headwind changes spread over longer distances along the aircraft glide path (called “gentle ramps”) which may nonetheless exceed the well-established alerting threshold. Real-time statistics are examined over a 46-month study period between March 2016 and December 2019, covering a total of 2,017,440 min and over 1500 quality-controlled pilot reports of windshear (PIREP). The “gentle ramp removal” (GRR) function is able to effectively cut down the alert duration over the 5 major runway corridors, inclusive of both landing and take-off, which together account for over 98% of the PIREP received at HKIA during the study period. In all 5 runway corridors this is achieved with a proportionately smaller decrease—even with no changes in 2 cases—in the hit rate, highlighting the efficiency of the GRR function. The difference in statistical behaviour across the runway corridors also echo literature findings about the differences in length scale of wind disturbances at different locations within HKIA. This study serves as a unique documentation of the state-of-the-art in operational Lidar windshear detection and can provide useful reference to airports and aviation meteorologists around the world.
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Zannou, Abderrahim, Abdelhak Boulaalam, and El Habib Nfaoui. "SIoT: A New Strategy to Improve the Network Lifetime with an Efficient Search Process." Future Internet 13, no. 1 (December 29, 2020): 4. http://dx.doi.org/10.3390/fi13010004.
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The Social Internet of Things (SIoT) means that every node can use a set of nodes that are considered as friends to search for a specific service. However, this is a slow process because each node is required to manage a high number of friends. Thus, the SIoT issue consists of how to select the right friends that improve the network navigability. The enhancement of the network navigability boosts the search for a service to be rapid but not guaranteed. Furthermore, sending requests from the shortest paths involves the rapid search, but the network lifetime can be reduced due to the number of requests that can be transmitted and processed by the nodes that have low power energy. This paper proposes a new approach that improves the network navigability, speeds up the search process, and increases the network lifetime. This approach aims at creating groups dynamically by nodes where each group has a master node, second, using a consensus algorithm between master nodes to agree with a specific capability, finally adopting a friendship selection method to create a social network. Thus, the friends will be sorted periodically for the objective of creating simultaneously a balance between the energy consumption and the rapid search process. Simulation results on the Brightkite location-based online social network dataset demonstrate that our proposal outperforms baseline methods in terms of some parameters of network navigability, path length to reach the providers, and network lifetime.
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Ottensmeyer, F. P. "Electron Spectroscopic Imaging and Analysis in the TEM: Have the Limits Been Reached." Proceedings, annual meeting, Electron Microscopy Society of America 54 (August 11, 1996): 302–3. http://dx.doi.org/10.1017/s0424820100163976.
Full textAbstract:
Electron energy filtering in the transmission electron microscope has had two major applications: 1) contrast enhancement in the image by elimination of chromatic aberrations, and 2) microanalysis by utilization of the information carried in the electron energy loss spectrum.The first application is unique to the fixed beam electron microscope, in which the image suffers from the interaction of the imaging lens with a broad spectrum of electron energies. Since the modal energy loss in the spectrum of 100 kV electrons traversing a carbonaceous light-atom material is about 25 eV per mean-free-path length in the specimen, a lens even with a chromatic aberration constant as good as 1 mm will blur the corresponding image to about 25 Å. In the STEM in which no imaging lenses are used after the electron beam has interacted with the specimen, chromatic aberrations do not occur; at most an effect due to the non-localization of the electron-specimen interaction may be detected as a blurring due to low-loss electrons. Even in the TEM, the effect of energy filtering to use only elastic electrons is small for bright field images of thin specimens stained with heavy atoms, since contrast and visibility is achieved primarily from the predominant elastic scatter from the heavy atoms. However, for dark field microscopy of unstained specimens the effect of filtering is dramatic, since for carbon atoms inelastic scattering dominates elastic scattering by a ratio of 3 to I.
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Torres Filho, Ivo P., James Terner, Roland N. Pittman, Leonardo G. Somera, and Kevin R. Ward. "Hemoglobin oxygen saturation measurements using resonance Raman intravital microscopy." American Journal of Physiology-Heart and Circulatory Physiology 289, no. 1 (July 2005): H488—H495. http://dx.doi.org/10.1152/ajpheart.01171.2004.
Full textAbstract:
A system is described for in vivo noninvasive measurements of hemoglobin oxygen saturation (HbO2Sat) at the microscopic level. The spectroscopic basis for the application is resonant Raman enhancement of Hb in the violet/ultraviolet region, allowing simultaneous identification of oxy- and deoxyhemoglobin with the same excitation wavelength. The heme vibrational bands are well known, but the technique has never been used to determine microvascular HbO2Sat in vivo. A diode laser light (power: 0.3 mW) was focused onto sample areas 15–30 μm in diameter. Raman spectra were obtained in backscattering geometry by using a microscope coupled to a spectrometer and a cooled detector. Calibration was performed in vitro by using glass capillaries containing blood at several Hb concentrations, equilibrated at various oxygen tensions. HbO2Sat was estimated using the Raman band intensities at 1,360 and 1,375 cm−1. Glass capillary path length and Hb concentration had no effect on HbO2Sat estimated from Raman spectra. In vivo observations were made in blood flowing in microvessels of the rat mesentery. The Hb Raman peaks observed in oxygenated and deoxygenated blood were consistent with earlier Raman studies that used Hb solutions and isolated cells. The method allowed HbO2Sat determinations in the whole range of arterioles, venules, and capillaries. Tissue transillumination allowed diameter and erythrocyte velocity measurements in the same vessels. Raman microspectroscopy offers distinct advantages over other currently used techniques by providing noninvasive and reliable in vivo determinations of HbO2Sat in thin tissues as well as in solid organs and tissues, which are unsuitable for techniques requiring transillumination.
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Dabiran, A. M., S. M. Seutter, and P. I. Cohen. "Direct Observations of the Strain-Limited Island Growth of Sn-Doped GaAs(100)." Surface Review and Letters 05, no. 03n04 (June 1998): 783–95. http://dx.doi.org/10.1142/s0218625x9800116x.
Full textAbstract:
We have used scanning tunneling microscopy (STM) in ultrahigh vacuum and atomic force microscopy (AFM) in air to investigate the microscopic mechanisms of Sn surface segregation during the molecular beam epitaxial growth of GaAs and AlAs(100). Submonolayer amounts of Sn segregate to the surface during growth and strongly modify the growth kinetics. This is indicated by both extra-ordinary reflection high energy electron diffraction (RHEED) measurements, and the STM and AFM images of rapidly quenched growth fronts. At the high surface coverages of 0.1–0.6 monolayers of Sn, studied in this work, neither step bunching nor three-dimensional (3D) growth of GaAs(100), was observed. Instead, STM and RHEED measurements indicated a significantly enhanced layer-by-layer growth of GaAs with increasing surface coverage of Sn. STM snapshots of the initial stages of GaAs growth revealed 2D islands which contained a higher-than-equilibrium bulk concentration of Sn, in Ga-substitutional sites, of up to 50%. Other directly observed Sn effects which are presented in this work include the removal of GaAs(100) island growth anisotropy and the formation of 2D islands with a relatively narrow distribution of size and separation. The completion of the top layers is shown to proceed by the coalescence of these islands before any significant nucleation of the next layer islands. This effect is used to explain the Sn enhancement of the layer-by-layer growth which was indicated in our RHEED and scanning probe observations. A model is presented for Sn segregation which explains these results based on an island-size-dependent, strain-driven, oscillatory Sn occupation of Ga-substitutional sites and surface interstitial sites on top GaAs(100) layers during growth. This model, which introduces a strain-limiting mechanism for the size and shape of the 2D islands, can also explain the observed enhancement of postgrowth surface recovery, as well as a delayed onset in increasing adatom surface diffusion length with increasing Sn coverage. The main conclusion is that, if impurity incorporation results in significant strain, then in addition to step climbing by surface impurities, the exchange of incorporated impurities with native species in top layers can be an important path for impurity segregation during expitaxial growth.