One of the hot research topics in propagation dynamics is identifying a set of critical nodes that can influence maximization in a complex network.The importance and dispersion of critical nodes among them are both vi...One of the hot research topics in propagation dynamics is identifying a set of critical nodes that can influence maximization in a complex network.The importance and dispersion of critical nodes among them are both vital factors that can influence maximization.We therefore propose a multiple influential spreaders identification algorithm based on spectral graph theory.This algorithm first quantifies the role played by the local structure of nodes in the propagation process,then classifies the nodes based on the eigenvectors of the Laplace matrix,and finally selects a set of critical nodes by the constraint that nodes in the same class are not adjacent to each other while different classes of nodes can be adjacent to each other.Experimental results on real and synthetic networks show that our algorithm outperforms the state-of-the-art and classical algorithms in the SIR model.展开更多
With the fast development of integrated circuit devices as well as batteries with high energy densities,the thermal management of electronic components is becoming increasingly crucial to maintaining their reliable op...With the fast development of integrated circuit devices as well as batteries with high energy densities,the thermal management of electronic components is becoming increasingly crucial to maintaining their reliable operations.Boron nitride nanosheets(BNNS),which have superhigh thermal conductivity along the in-plane direction while remaining electrically insulating,were widely regarded as an ideal filler for preparing high-performance polymer composites to address the‘‘thermal failure''issue.However,due to the instinctive rigidity of BNNS,the nanosheets are unable to form a tightly interfacial contact between the adjoining fillers,resulting in some micro-and nanovoids within the heat transfer pathways and severely limiting further thermal conductivity enhancement for BNNS-based composites.Herein,soft and deformable liquid metal(eutectic gallium-indium,EGaIn)nanoparticles were employed to fill the gaps between the adjacent BNNS with a rational design of mass ratios of BNNS and EGaIn,leading to a strongly synergistic effect with BNNS on thermal conductivity improvement.As a result,the composite film(BNNS:63 wt%and EGaIn:7 wt%)employing cellulose nanofibers(CNF:30 wt%)as the polymer matrix achieves superhigh thermal conductivity along the in-plane direction of up to(90.51±6.71)W·m^(-1)·K^(-1),showing the highest value among the BNNSbased composites with a bi-filler system as far as we know.Additionally,the film can work as a heat spreader for the heat dissipation of high-power light emitting diodes,outperforming tin foil in cooling efficiency.展开更多
An efficient method for the identification of influential spreaders that could be used to control epidemics within populations would be of considerable importance. Generally, populations are characterized by its commu...An efficient method for the identification of influential spreaders that could be used to control epidemics within populations would be of considerable importance. Generally, populations are characterized by its community structures and by the heterogeneous distributions of out-leaving links among nodes bridging over communities. A new method for community networks capable of identifying influential spreaders that accelerate the spread of disease is here proposed. In this method, influential spreaders serve as target nodes. This is based on the idea that, in k-shell decomposition method,out-leaving links and inner links are processed separately. The method was used on empirical networks constructed from online social networks, and results indicated that this method is more accurate. Its effectiveness stems from the patterns of connectivity among neighbors, and it successfully identified the important nodes. In addition, the performance of the method remained robust even when there were errors in the structure of the network.展开更多
A long-term common belief in complex networks is that,the most connected nodes are the most efficient spreaders.However,recent investigations on real-world complex networks show that the most influential spreaders are...A long-term common belief in complex networks is that,the most connected nodes are the most efficient spreaders.However,recent investigations on real-world complex networks show that the most influential spreaders are those with the highest fc-shell values.It is well-known that,many real-world complex networks have scale free(SF),small world(SW) properties,therefore,identification of influential spreaders in general artificial SF,SW as well as random networks will be more appealing.This research finds that,for artificial ER and SW networks,degree is more reliable than fc-shell in predicting the outcome of spreading.However,for artificial SF networks,fc-shell is remarkably reliable than degree and betweeness,which indicate that the four recently investigated real-world networks[Kitsak M,Gallos L K,Havlin S,Liljeros F,Muchnik L,Stanley H E,Makse H A,Identification of influential spreaders in complex networks,Nat.Phys.,2010,6:888-893.]are more similar to scale free ones.Moreover,the investigations also indicate us an optimal dissemination strategy in networks with scale free property.That is,starting from moderate-degree-nodes will be ok and even more economical,since one can derive roughly similar outcome with starting from hubs.展开更多
Microblogging, a popular social media service platform, has become a new information channel for users to receive and exchange the most up-to-date information on current events. Consequently, it is a crucial platform ...Microblogging, a popular social media service platform, has become a new information channel for users to receive and exchange the most up-to-date information on current events. Consequently, it is a crucial platform for detecting newly emerging events and for identifying influential spreaders who have the potential to actively disseminate knowledge about events through microblogs. However, traditional event detection models require human intervention to detect the number of topics to be explored, which significantly reduces the efficiency and accuracy of event detection. In addition, most existing methods focus only on event detection and are unable to identify either influential spreaders or key event-related posts, thus making it challenging to track momentous events in a timely manner. To address these problems, we propose a Hypertext-Induced Topic Search(HITS) based Topic-Decision method(TD-HITS), and a Latent Dirichlet Allocation(LDA) based Three-Step model(TS-LDA). TDHITS can automatically detect the number of topics as well as identify associated key posts in a large number of posts. TS-LDA can identify influential spreaders of hot event topics based on both post and user information.The experimental results, using a Twitter dataset, demonstrate the effectiveness of our proposed methods for both detecting events and identifying influential spreaders.展开更多
The study on how to identify influential spreaders in complex networks is becoming increasingly significant.Previous studies demonstrate that considering the shortest path length can improve the accuracy of identifica...The study on how to identify influential spreaders in complex networks is becoming increasingly significant.Previous studies demonstrate that considering the shortest path length can improve the accuracy of identification,but which ignore the influence of the number of shortest paths.In many cases,even though the shortest path length of two nodes is rather larger,their interaction influence is also significant if the number of shortest paths between them is considerable.Inspired by this fact,the authors propose an improved centrality index(ICC)based on well-known closeness centrality and a semi-local iterative algorithm(semi-IA)to study the impact of the number of shortest paths on the identification of the influential spreaders.By comparing with several traditional centrality indices,such as degree centrality,k-shell decomposition,betweenness centrality and eigenvector centrality,the experimental results on real networks indicate that the ICC index and semi-IA have a better performance,regardless of the identification capability or the resolution.展开更多
Thermal management is a critical challenge in modern electronics and recent key innovations have focused on integrating diamond directly onto semiconductors for efficient cooling.However,the connection of diamond/semi...Thermal management is a critical challenge in modern electronics and recent key innovations have focused on integrating diamond directly onto semiconductors for efficient cooling.However,the connection of diamond/semiconductor that can simultaneously achieve low thermal boundary resistance(TBR),minimal thermal budget,and sufficient mechanical robustness remains a formidable challenge.Here,we propose a collective wafer-level bonding technique to connect polycrystalline diamonds and semiconductors at 200℃by reactive metallic nanolayers.The resulting silicon/diamond connections exhibited an ultra-low TBR of 9.74 m^(2)K GW^(–1),drastically outperforming conventional die-attach technologies.These connections also demonstrate superior reliability,withstanding at least 1000 thermal cycles and 1000 h of high temperature/humidity torture.These properties were affiliated with the recrystallized microstructure of the designed metallic interlayers.This demonstration represents an advancement for low-temperature and high-throughput integration of diamonds on semiconductors,potentially enabling currently thermally limited applications in electronics.展开更多
The control method of rubber tyre gantry （RTG） spreader in Qingdao Port Container Terminal is logic board control,which has many shortcomings such as expensive spare parts and high faults.This paper designs a new co...The control method of rubber tyre gantry （RTG） spreader in Qingdao Port Container Terminal is logic board control,which has many shortcomings such as expensive spare parts and high faults.This paper designs a new control system using programmable logic controller （PLC） centralized control to replace the original logic board control.The new system mainly contains complete ELME spreader control scheme design,hardware selection and PLC control program development.Its field application shows that the system has characteristics of high efficiency,low running cost,easy maintenance.展开更多
A gravitational flat-plate heat pipe is designed and fabricated in this paper to serve as a heat spreader to diffuse the local heat source to the hot side of the thermoelectric power module.Based on this, an experimen...A gravitational flat-plate heat pipe is designed and fabricated in this paper to serve as a heat spreader to diffuse the local heat source to the hot side of the thermoelectric power module.Based on this, an experimental test for the thermoelectric power generation system is conducted to study the influences of the heat spreader on the temperature uniformity and power generation performance when exposing to a local heat source.In addition,the effects of the heating power, inclination angle, and local heat source size on the power generation performance of the thermoelectric power module using a flat-plate heat pipe as a heat spreader are examined and compared with that using a metal plate.The results indicate that the gravitational flat-plate heat pipe has considerable advantages over the metal plate in the temperature uniformity.The superiority of temperature uniformity in the improvement of power generation performance for the thermoelectric power system using a heat pipe is demonstrated.Particularly, the heat pipe shows good adaptability to placement mode and the local heat source size, which is beneficial to the application in the thermoelectric power generation.展开更多
This paper describes a general modeling and control approach for steering wheel variable rate liquid fertilizer applicator. An adaptive numerical modeling approach for describing the system input-output dynamics is pr...This paper describes a general modeling and control approach for steering wheel variable rate liquid fertilizer applicator. An adaptive numerical modeling approach for describing the system input-output dynamics is proposed, and an optimal control that accounts for the control hardware limits is developed. Field tests have demonstrated the effectiveness of the theoretical development.展开更多
The continuing increase in IC （Integrated Circuit） power levels and microelectronics packaging densities has resulted in the need for detailed considerations of the heat sink design for integrated circuits. One of t...The continuing increase in IC （Integrated Circuit） power levels and microelectronics packaging densities has resulted in the need for detailed considerations of the heat sink design for integrated circuits. One of the major components in the heat sink is the heat spreader which must be designed to effectively conduct the heat dissipated from the chip to a system of fins or extended surfaces for convective heat transfer to a flow of coolant. The heat spreader design must provide the capability to dissipate the thermal energy generated by the chip. However, the design of the heat spreader is also dependent on the convection characteristics of the fins within the heat sink, as well the material and geometry of the heat spreader. This paper focuses on the optimization of heat spreaders in a heat sink for safe and efficient performance of electronic circuits. The results of the study show that, for air-cooled electronics, the convective effects may dominate the thermal transport performance of the heat spreader in the heat sink.展开更多
A number of companies have announced the vaccines for COVID-19 pandemic that has caused extreme poverty, famine, and more than a billion people have lost livelihood all across the globe. Mass production of vaccine Spu...A number of companies have announced the vaccines for COVID-19 pandemic that has caused extreme poverty, famine, and more than a billion people have lost livelihood all across the globe. Mass production of vaccine Sputnik V is underway at different locations to inoculate population in Russia, Philippines, Vietnam, Brazil, Saudi Arab, and United Arab Emirates (UAE), and India. mRNA based vaccine of Pfizer-BioNTech after passing phase 2 trial is ready for testing on thousands of volunteers. Oxford University-AstraZeneca vaccine is also under phase 3 trial in US, Brazil, and India. In September, Novavax Inc.’s vaccine will be ready for phase 3 trial. By early next year, two billions of doses will be ready of Novavax. Moderna Therapeutics conducting vaccine trial on 30 thousands volunteers, results will be known soon. Hundreds of thousand volunteers have registered already for vaccination in US and other parts of the world. SinoVac Biotech Ltd. has prepared a vaccine “CoronaVac” and inoculating volunteers in Indonesia and Brazil. CanSino Biologics Inc. in phase 2 trial on 508 volunteers found a satisfactory immune response to COVID-19 virus. Apart from vaccine preparation and availability, we provided data for therapy and treatment for COVID-19 and transmission and stability aspect of COVID-19 SARS-Cov-2 virus. The data and results presented in this article are very important and useful in containing, treating, and eliminating the pandemic COVID-19.展开更多
We present a new method of treatment for nasal valve dysfunction caused by insufficiency or stenosis in a patient who refused open septum revision despite a significant degree of septum deviation. The Anterior Spreade...We present a new method of treatment for nasal valve dysfunction caused by insufficiency or stenosis in a patient who refused open septum revision despite a significant degree of septum deviation. The Anterior Spreader Flap (ASF) technique was suggested as an alternative to open nasal septum revision and was performed under local anesthesia. Computational fluid dynamics (CFD) tests were performed pre- and post-operatively and our patient was asked to complete a self-assessment using a Visual Analog Scale (VAS) for nasal breathing (0 = free nasal breathing, 10 = complete nasal blockage) before and 12 months after surgery. The ASF is a minimally invasive endonasal procedure in which the caudal edge of the upper lateral cartilage is dissected from the septum, and folded inwards and fixed. The ASF allows for less airflow resistance and more free space. CFD techniques revealed a reduction in local pressure based on extended space. In addition, VAS scores improved from 9 to 2 points (right side) and from 8 to 2 points (left side). On the basis of these findings, the ASF technique can be considered a safe, minimally invasive spreader flap technique. It can easily be combined with other nasal surgical techniques, as it is necessary in most cases. In selected cases, the ASF may be performed as a single procedure in patients with nasal valve dysfunction caused by septum deviation as an alternative to open septum revision.展开更多
This paper describes the field tests carried out to evaluate the new Vicon RS-EDW centrifugal fertilizer spreader, to be used in Precision Agriculture. The results of initial dynamic calibration tests showed a signifi...This paper describes the field tests carried out to evaluate the new Vicon RS-EDW centrifugal fertilizer spreader, to be used in Precision Agriculture. The results of initial dynamic calibration tests showed a significant and systematic difference between the application rates of the two discs （about 20%）. This difference had to be corrected by the manufacturer that carried out the necessary changes to the electric actuators. The fertilizer spreader had good distribution homogeneity, considering different working velocities and different positions in the parcel. The pattern distribution curve for 18% super phosphate fertilizer led to an effective working width of 28 meters, with a coefficient of variation of 15%. The longitudinal test, under experimental working conditions led to a machine delay time of 6-7 seconds. The results show an actual fertilization application density between 74%-90% of that determined for each location. These results confirm that the spreader can be used to spread fertilizer differentially in the field.展开更多
Flat plate pulsating heat pipe is useful for hot spot heat spreader. Two kinds of flat plate spreader of pulsating heat pipe are designed, fabricated and experimented. For the embedded circular capillary type, the tra...Flat plate pulsating heat pipe is useful for hot spot heat spreader. Two kinds of flat plate spreader of pulsating heat pipe are designed, fabricated and experimented. For the embedded circular capillary type, the transferred heat flux could reach 32 W/cm2, the smallest thermal resistance for acetone, methanol and FC-72 were respectively 0.50, 0.57 and 0.40℃/W. While for the square capillary type, the transferred heat flux could reach 26 W/cm2, the equivalent thermal conductivity could reach 3211 W/（m. ℃）. There are ranges of optimal transferred power and filling ratio for different working liquid. If the transferred power is constant, changing the heating area and the place has little effects on the performance.展开更多
High-power vertical-cavity surface-emitting lasers（VCSELs） are processed using a wet thermal-selective oxidation technique.The VCSEL chips are packaged by employing three different bonding methods of silver solder,I...High-power vertical-cavity surface-emitting lasers（VCSELs） are processed using a wet thermal-selective oxidation technique.The VCSEL chips are packaged by employing three different bonding methods of silver solder,In-Sn solder,and metalized diamond heat spreader.After packaging,optical output power, wavelength shift,and thermal resistance of the devices are measured and compared in an experiment.The device packaged with a metalized diamond heat spreader shows the best operation characteristics among the three methods.The 200-μm-diameter device bonded with a metalized diamond heat spreader produces a continuous wave optical output power of 0.51 W and a corresponding power density of 1.6 kW/cm^2 at room temperature.The thermal resistance is as low as 10 K/W.The accelerated aging test is also carried out at high temperature under constant current mode.The device operates for more than 1000 h at 70℃,and the total degradation is only about 10%.展开更多
With the sustainable development of precision agriculture and the steady progress of variable-rate fertilization technology,the centrifugal variable-rate fertilizer spreader has attracted research attention due to its...With the sustainable development of precision agriculture and the steady progress of variable-rate fertilization technology,the centrifugal variable-rate fertilizer spreader has attracted research attention due to its lower incidence of crush damage,high efficiency,and low cost.To improve fertilization accuracy and uniformity,spreading performance tests were conducted using this spreader in accordance with the test methods specified in ISO 5690 and ASAE S341.2,in which particle mass was weighed in a two-dimensional matrix of collection boxes.The effects of fertilization strategies that control the feed gate flow rate and the disc rotation speed on particle distribution,and application rate per unit area and effective swath width,were investigated.A variable-rate fertilization model was developed by analyzing the variation characteristics resulting from an increasing and decreasing application rate,and field experiments were conducted to verify its accuracy.The results indicated that when the feed gate flow rate was 300 g/s,the mean application rate was 26.47 g,the standard deviation is 2.81,and the coefficient of variation of particle distribution is at its minimum value of 14.25%.When the disc rotation speed was 600 r/min,the fertilizer was most evenly distributed with a coefficient of variation of 13.86%,and an average effective spreader swath width of 24.51 m.The proposed variable-rate fertilization model showed a high fitting degree with an S-shaped function curve for both increasing and decreasing distribution rates and the yielding coefficients of determination were more than 0.82 and 0.71,respectively.The average error between the model predictions and the test results was 9.47%,and the coefficients of determination for the increasing and decreasing distribution rates were 0.91 and 0.82,respectively,which confirmed the accuracy of the proposed variable-rate fertilization model.This investigation provided a theoretical basis for traditional empirical fertilization using centrifugal variable-rate fertilizer spreaders,and guides the selection of a multiple trajectory,variable-rate fertilization strategy.展开更多
Unmanned aerial vehicles(UAVs)are widely being used to spread granular fertilizer in China.Granular fertilizer spreaders equipped with UAVs are mainly centrifugal disc-type and pneumatic.The multichannel pneumatic gra...Unmanned aerial vehicles(UAVs)are widely being used to spread granular fertilizer in China.Granular fertilizer spreaders equipped with UAVs are mainly centrifugal disc-type and pneumatic.The multichannel pneumatic granular fertilizer spreaders(MPGFSs)have a banded fertilizer deposition distribution pattern,which are more suitable for variable rate fertilization with high precision requirement than the circular deposition distribution pattern of disc-type granular fertilizer spreaders(DGFSs).However,the existing MPGFS has the disadvantage of inconsistent discharge rate of each channel,which affects the uniformity of fertilization.In order to explore the causes of inconsistent discharge rate of each channel,the discrete element method(DEM)and bench test were performed to analysis the discharge process of the fluted roller fertilizing apparatus and distribution of fertilizer in axial direction of fluted roller.The computational fluid dynamics(CFD)was used to simulate the airflow field of pneumatic system to analyze the influence of airflow on the movement of fertilizer particles.The simulation results of the discharge process of the fluted roller fertilizing apparatus showed that the filling velocity at the axial ends of the fluted roller fertilizing apparatus was lower than that of the middle.The reason was that the filling capacity was weak near the wall.The simulated results of the airflow field without partitions showed that the airflow provided by the axial flow fan was rotational,and this caused the particles to move irregularly in the throat,resulting in inconsistency discharge rate of each channel.Based on the analysis of reasons of inconsistent discharge rate of each channel,a MPGFS with partitions in the throat was developed.The discharge rate bench tests were carried out to optimize the partition spacing parameters,and fertilization test was performed to test the performance of the improved MPGFS.The discharge rate test results showed better consistency with partition.The coefficient of variation(CV)of the discharge rate of each channel was 20.16%without the partition and 7.70%with the optimal partition.The fertilizer spreading uniformity bench test results shown that the CV of spreading uniformity of MPGFS without partitions was 15.32%,and that MPGFS with partitions was 8.69%.The partitions design was beneficial to improve the consistency of each channel discharge rate and the uniformity of fertilization.The finding can provide a strong reference to design the MPGFS.展开更多
Two different flow channel configurations on thermal resistances associated with the behavior of cooling of power device were studied in this paper. ANSYS Icepak 14.0 has been adopted as a numerical simulation tool. T...Two different flow channel configurations on thermal resistances associated with the behavior of cooling of power device were studied in this paper. ANSYS Icepak 14.0 has been adopted as a numerical simulation tool. The simulation results from this study showed that the shapes of channels in cooling radiator play an important role in the thermal management of water cooling radiation system. The optimal channel design could improve the heat- dissipating efficiency by 80% in water cooling radiation system. The result also indicated that the thermal resistance of heat sinks decreased with the volumetric flow rate and the number of cylindrical columns in the flow channel. Experimental results were obtained under certain channel configurations and volume rates. Moreover, the results of numerical simulation can be explained well by the experimental results.展开更多
Waste heat management holds great promise to create a sustainable and energy-efficient society as well as contributes to the alleviation of global warming.Harvesting and converting this waste heat in order to improve ...Waste heat management holds great promise to create a sustainable and energy-efficient society as well as contributes to the alleviation of global warming.Harvesting and converting this waste heat in order to improve the efficiency is a major challenge.Here we report biomimetic nacre-like hydroxyl-functionalized boron nitride(BN)-polyimide(PI)nanocomposite membranes as efficient 2D in-plane heat conductor to dissipate and convert waste heat at high temperature.The hierarchically layered nanostructured membrane with oriented BN nanosheets gives rise to a very large anisotropy in heat transport properties,with a high in-plane thermal conductivity(TC)of 51 Wm^(-1) K^(-1) at a temperature of~300 C,7314%higher than that of the pure polymer.The membrane also exhibits superior thermal stability and fire resistance,enabling its workability in a hot environment.In addition to cooling conventional exothermic electronics,the large TC enables the membrane as a thin and 2D anisotropic heat sink to generate a large temperature gradient in a thermoelectric module(△T=23 ℃)through effective heat diffusion on the cold side under 220 C heating.The waste heat under high temperature is therefore efficiently harvested and converted to power electronics,thus saving more thermal energy by largely decreasing consumption.展开更多
基金the National Natural Science Foundation of China(Grant No.62176217)the Program from the Sichuan Provincial Science and Technology,China(Grant No.2018RZ0081)the Fundamental Research Funds of China West Normal University(Grant No.17E063)。
文摘One of the hot research topics in propagation dynamics is identifying a set of critical nodes that can influence maximization in a complex network.The importance and dispersion of critical nodes among them are both vital factors that can influence maximization.We therefore propose a multiple influential spreaders identification algorithm based on spectral graph theory.This algorithm first quantifies the role played by the local structure of nodes in the propagation process,then classifies the nodes based on the eigenvectors of the Laplace matrix,and finally selects a set of critical nodes by the constraint that nodes in the same class are not adjacent to each other while different classes of nodes can be adjacent to each other.Experimental results on real and synthetic networks show that our algorithm outperforms the state-of-the-art and classical algorithms in the SIR model.
基金financially supported by the National Natural Science Foundation of China (Nos.52075527,5227020331 and 52102055)the National Key R&D Program of China (Nos.2017YFB0406000 and 2017YFE0128600)+12 种基金the Project of the Chinese Academy of Sciences (Nos.XDC07030100,XDA22020602,ZDKYYQ20200001 and ZDRW-CN-2019-3)CAS Youth Innovation Promotion Association (No.2020301)the Science and Technology Major Project of Ningbo (Nos.2021Z115,2021Z120,2018B10046 and 2016S1002)the Key Research and Development Program of Ningbo City (No.2022Z084)the Natural Science Foundation of Ningbo (No.2017A610010)the Foundation of State Key Laboratory of Solid lubrication (No.LSL-1912)China Postdoctoral Science Foundation (Nos.2020M681965 and2022M713243)the National Key Laboratory of Science and Technology on Advanced Composites in Special Environments (No.6142905192806)K.C.Wong Education Foundation (No.GJTD-2019-13)the Youth Fund of Chinese Academy of Sciences (No.JCPYJJ-22030)the Science and Technology Project of Zhejiang Province (No.2022C01182)Zhejiang Provincial Natural Science Foundation of China (No.LY19B010003)the 3315 Program of Ningbo。
文摘With the fast development of integrated circuit devices as well as batteries with high energy densities,the thermal management of electronic components is becoming increasingly crucial to maintaining their reliable operations.Boron nitride nanosheets(BNNS),which have superhigh thermal conductivity along the in-plane direction while remaining electrically insulating,were widely regarded as an ideal filler for preparing high-performance polymer composites to address the‘‘thermal failure''issue.However,due to the instinctive rigidity of BNNS,the nanosheets are unable to form a tightly interfacial contact between the adjoining fillers,resulting in some micro-and nanovoids within the heat transfer pathways and severely limiting further thermal conductivity enhancement for BNNS-based composites.Herein,soft and deformable liquid metal(eutectic gallium-indium,EGaIn)nanoparticles were employed to fill the gaps between the adjacent BNNS with a rational design of mass ratios of BNNS and EGaIn,leading to a strongly synergistic effect with BNNS on thermal conductivity improvement.As a result,the composite film(BNNS:63 wt%and EGaIn:7 wt%)employing cellulose nanofibers(CNF:30 wt%)as the polymer matrix achieves superhigh thermal conductivity along the in-plane direction of up to(90.51±6.71)W·m^(-1)·K^(-1),showing the highest value among the BNNSbased composites with a bi-filler system as far as we know.Additionally,the film can work as a heat spreader for the heat dissipation of high-power light emitting diodes,outperforming tin foil in cooling efficiency.
基金Supported by Fundamental Research Funds for the Central Universities(JBK170133)Natural Science Foundation of Sichuan Province of China(17ZB0434)Ministry of Education of Humanities and Social Science Foundation of China(11XJCZH002)
文摘An efficient method for the identification of influential spreaders that could be used to control epidemics within populations would be of considerable importance. Generally, populations are characterized by its community structures and by the heterogeneous distributions of out-leaving links among nodes bridging over communities. A new method for community networks capable of identifying influential spreaders that accelerate the spread of disease is here proposed. In this method, influential spreaders serve as target nodes. This is based on the idea that, in k-shell decomposition method,out-leaving links and inner links are processed separately. The method was used on empirical networks constructed from online social networks, and results indicated that this method is more accurate. Its effectiveness stems from the patterns of connectivity among neighbors, and it successfully identified the important nodes. In addition, the performance of the method remained robust even when there were errors in the structure of the network.
基金supported by the National Natural Science Foundation of China under Grant Nos.11172215,61304151,61174028China-Australia Health and HIV/AIDS Facility(FA36 EID101)the Science Foundation of Henan University under Grant No.2012YBZR007
文摘A long-term common belief in complex networks is that,the most connected nodes are the most efficient spreaders.However,recent investigations on real-world complex networks show that the most influential spreaders are those with the highest fc-shell values.It is well-known that,many real-world complex networks have scale free(SF),small world(SW) properties,therefore,identification of influential spreaders in general artificial SF,SW as well as random networks will be more appealing.This research finds that,for artificial ER and SW networks,degree is more reliable than fc-shell in predicting the outcome of spreading.However,for artificial SF networks,fc-shell is remarkably reliable than degree and betweeness,which indicate that the four recently investigated real-world networks[Kitsak M,Gallos L K,Havlin S,Liljeros F,Muchnik L,Stanley H E,Makse H A,Identification of influential spreaders in complex networks,Nat.Phys.,2010,6:888-893.]are more similar to scale free ones.Moreover,the investigations also indicate us an optimal dissemination strategy in networks with scale free property.That is,starting from moderate-degree-nodes will be ok and even more economical,since one can derive roughly similar outcome with starting from hubs.
基金supported by the National Natural Science Foundation of China(Nos.61502209 and 61502207)the Natural Science Foundation of Jiangsu Province of China(No.BK20130528)Visiting Research Fellow Program of Tongji University(No.8105142504)
文摘Microblogging, a popular social media service platform, has become a new information channel for users to receive and exchange the most up-to-date information on current events. Consequently, it is a crucial platform for detecting newly emerging events and for identifying influential spreaders who have the potential to actively disseminate knowledge about events through microblogs. However, traditional event detection models require human intervention to detect the number of topics to be explored, which significantly reduces the efficiency and accuracy of event detection. In addition, most existing methods focus only on event detection and are unable to identify either influential spreaders or key event-related posts, thus making it challenging to track momentous events in a timely manner. To address these problems, we propose a Hypertext-Induced Topic Search(HITS) based Topic-Decision method(TD-HITS), and a Latent Dirichlet Allocation(LDA) based Three-Step model(TS-LDA). TDHITS can automatically detect the number of topics as well as identify associated key posts in a large number of posts. TS-LDA can identify influential spreaders of hot event topics based on both post and user information.The experimental results, using a Twitter dataset, demonstrate the effectiveness of our proposed methods for both detecting events and identifying influential spreaders.
基金supported by the National Natural Science Foundation of China under Grant Nos.61973001,61806001the Natural Science Foundation of Anhui Province under Grant No.1808085MF201+1 种基金the State Key Laboratory for Ocean Big Data Mining and Application of Zhejiang Province under Grant No.OBDMA201502Anhui University Foundation under Grant No.01005102。
文摘The study on how to identify influential spreaders in complex networks is becoming increasingly significant.Previous studies demonstrate that considering the shortest path length can improve the accuracy of identification,but which ignore the influence of the number of shortest paths.In many cases,even though the shortest path length of two nodes is rather larger,their interaction influence is also significant if the number of shortest paths between them is considerable.Inspired by this fact,the authors propose an improved centrality index(ICC)based on well-known closeness centrality and a semi-local iterative algorithm(semi-IA)to study the impact of the number of shortest paths on the identification of the influential spreaders.By comparing with several traditional centrality indices,such as degree centrality,k-shell decomposition,betweenness centrality and eigenvector centrality,the experimental results on real networks indicate that the ICC index and semi-IA have a better performance,regardless of the identification capability or the resolution.
基金supported by the National Natural Science Foundation of China(Grant No.62104206)the Fundamental Research Funds for the Central Universities(Grant No.20720220072).
文摘Thermal management is a critical challenge in modern electronics and recent key innovations have focused on integrating diamond directly onto semiconductors for efficient cooling.However,the connection of diamond/semiconductor that can simultaneously achieve low thermal boundary resistance(TBR),minimal thermal budget,and sufficient mechanical robustness remains a formidable challenge.Here,we propose a collective wafer-level bonding technique to connect polycrystalline diamonds and semiconductors at 200℃by reactive metallic nanolayers.The resulting silicon/diamond connections exhibited an ultra-low TBR of 9.74 m^(2)K GW^(–1),drastically outperforming conventional die-attach technologies.These connections also demonstrate superior reliability,withstanding at least 1000 thermal cycles and 1000 h of high temperature/humidity torture.These properties were affiliated with the recrystallized microstructure of the designed metallic interlayers.This demonstration represents an advancement for low-temperature and high-throughput integration of diamonds on semiconductors,potentially enabling currently thermally limited applications in electronics.
基金Shandong University of Science and Technology Spring Buds Program(No.2010AZZ170)
文摘The control method of rubber tyre gantry （RTG） spreader in Qingdao Port Container Terminal is logic board control,which has many shortcomings such as expensive spare parts and high faults.This paper designs a new control system using programmable logic controller （PLC） centralized control to replace the original logic board control.The new system mainly contains complete ELME spreader control scheme design,hardware selection and PLC control program development.Its field application shows that the system has characteristics of high efficiency,low running cost,easy maintenance.
基金Supported by the National Natural Science Foundation of China(U1737104)the Natural Science Foundation of Jiangsu Province(BK20170082)+1 种基金the Special Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund(the second phase)(U1501501)the Postgraduate Research&Practice Innovation Program of Jiangsu Province
文摘A gravitational flat-plate heat pipe is designed and fabricated in this paper to serve as a heat spreader to diffuse the local heat source to the hot side of the thermoelectric power module.Based on this, an experimental test for the thermoelectric power generation system is conducted to study the influences of the heat spreader on the temperature uniformity and power generation performance when exposing to a local heat source.In addition,the effects of the heating power, inclination angle, and local heat source size on the power generation performance of the thermoelectric power module using a flat-plate heat pipe as a heat spreader are examined and compared with that using a metal plate.The results indicate that the gravitational flat-plate heat pipe has considerable advantages over the metal plate in the temperature uniformity.The superiority of temperature uniformity in the improvement of power generation performance for the thermoelectric power system using a heat pipe is demonstrated.Particularly, the heat pipe shows good adaptability to placement mode and the local heat source size, which is beneficial to the application in the thermoelectric power generation.
文摘This paper describes a general modeling and control approach for steering wheel variable rate liquid fertilizer applicator. An adaptive numerical modeling approach for describing the system input-output dynamics is proposed, and an optimal control that accounts for the control hardware limits is developed. Field tests have demonstrated the effectiveness of the theoretical development.
文摘The continuing increase in IC （Integrated Circuit） power levels and microelectronics packaging densities has resulted in the need for detailed considerations of the heat sink design for integrated circuits. One of the major components in the heat sink is the heat spreader which must be designed to effectively conduct the heat dissipated from the chip to a system of fins or extended surfaces for convective heat transfer to a flow of coolant. The heat spreader design must provide the capability to dissipate the thermal energy generated by the chip. However, the design of the heat spreader is also dependent on the convection characteristics of the fins within the heat sink, as well the material and geometry of the heat spreader. This paper focuses on the optimization of heat spreaders in a heat sink for safe and efficient performance of electronic circuits. The results of the study show that, for air-cooled electronics, the convective effects may dominate the thermal transport performance of the heat spreader in the heat sink.
文摘A number of companies have announced the vaccines for COVID-19 pandemic that has caused extreme poverty, famine, and more than a billion people have lost livelihood all across the globe. Mass production of vaccine Sputnik V is underway at different locations to inoculate population in Russia, Philippines, Vietnam, Brazil, Saudi Arab, and United Arab Emirates (UAE), and India. mRNA based vaccine of Pfizer-BioNTech after passing phase 2 trial is ready for testing on thousands of volunteers. Oxford University-AstraZeneca vaccine is also under phase 3 trial in US, Brazil, and India. In September, Novavax Inc.’s vaccine will be ready for phase 3 trial. By early next year, two billions of doses will be ready of Novavax. Moderna Therapeutics conducting vaccine trial on 30 thousands volunteers, results will be known soon. Hundreds of thousand volunteers have registered already for vaccination in US and other parts of the world. SinoVac Biotech Ltd. has prepared a vaccine “CoronaVac” and inoculating volunteers in Indonesia and Brazil. CanSino Biologics Inc. in phase 2 trial on 508 volunteers found a satisfactory immune response to COVID-19 virus. Apart from vaccine preparation and availability, we provided data for therapy and treatment for COVID-19 and transmission and stability aspect of COVID-19 SARS-Cov-2 virus. The data and results presented in this article are very important and useful in containing, treating, and eliminating the pandemic COVID-19.
文摘We present a new method of treatment for nasal valve dysfunction caused by insufficiency or stenosis in a patient who refused open septum revision despite a significant degree of septum deviation. The Anterior Spreader Flap (ASF) technique was suggested as an alternative to open nasal septum revision and was performed under local anesthesia. Computational fluid dynamics (CFD) tests were performed pre- and post-operatively and our patient was asked to complete a self-assessment using a Visual Analog Scale (VAS) for nasal breathing (0 = free nasal breathing, 10 = complete nasal blockage) before and 12 months after surgery. The ASF is a minimally invasive endonasal procedure in which the caudal edge of the upper lateral cartilage is dissected from the septum, and folded inwards and fixed. The ASF allows for less airflow resistance and more free space. CFD techniques revealed a reduction in local pressure based on extended space. In addition, VAS scores improved from 9 to 2 points (right side) and from 8 to 2 points (left side). On the basis of these findings, the ASF technique can be considered a safe, minimally invasive spreader flap technique. It can easily be combined with other nasal surgical techniques, as it is necessary in most cases. In selected cases, the ASF may be performed as a single procedure in patients with nasal valve dysfunction caused by septum deviation as an alternative to open septum revision.
文摘This paper describes the field tests carried out to evaluate the new Vicon RS-EDW centrifugal fertilizer spreader, to be used in Precision Agriculture. The results of initial dynamic calibration tests showed a significant and systematic difference between the application rates of the two discs （about 20%）. This difference had to be corrected by the manufacturer that carried out the necessary changes to the electric actuators. The fertilizer spreader had good distribution homogeneity, considering different working velocities and different positions in the parcel. The pattern distribution curve for 18% super phosphate fertilizer led to an effective working width of 28 meters, with a coefficient of variation of 15%. The longitudinal test, under experimental working conditions led to a machine delay time of 6-7 seconds. The results show an actual fertilization application density between 74%-90% of that determined for each location. These results confirm that the spreader can be used to spread fertilizer differentially in the field.
文摘Flat plate pulsating heat pipe is useful for hot spot heat spreader. Two kinds of flat plate spreader of pulsating heat pipe are designed, fabricated and experimented. For the embedded circular capillary type, the transferred heat flux could reach 32 W/cm2, the smallest thermal resistance for acetone, methanol and FC-72 were respectively 0.50, 0.57 and 0.40℃/W. While for the square capillary type, the transferred heat flux could reach 26 W/cm2, the equivalent thermal conductivity could reach 3211 W/（m. ℃）. There are ranges of optimal transferred power and filling ratio for different working liquid. If the transferred power is constant, changing the heating area and the place has little effects on the performance.
基金supported by the National Natural Science Foundation of China under Grant Nos.60676025 and 60306004.
文摘High-power vertical-cavity surface-emitting lasers（VCSELs） are processed using a wet thermal-selective oxidation technique.The VCSEL chips are packaged by employing three different bonding methods of silver solder,In-Sn solder,and metalized diamond heat spreader.After packaging,optical output power, wavelength shift,and thermal resistance of the devices are measured and compared in an experiment.The device packaged with a metalized diamond heat spreader shows the best operation characteristics among the three methods.The 200-μm-diameter device bonded with a metalized diamond heat spreader produces a continuous wave optical output power of 0.51 W and a corresponding power density of 1.6 kW/cm^2 at room temperature.The thermal resistance is as low as 10 K/W.The accelerated aging test is also carried out at high temperature under constant current mode.The device operates for more than 1000 h at 70℃,and the total degradation is only about 10%.
基金The authors acknowledge the financial support provided by National Key Project of Research and Development Program(Grant No.2016YFD0200600-2016YFD0200602-4)Projects funded from special funds of the National Modern Agricultural Industry and Technology System(Grant No.CARS-14-Mechanized equipment).
文摘With the sustainable development of precision agriculture and the steady progress of variable-rate fertilization technology,the centrifugal variable-rate fertilizer spreader has attracted research attention due to its lower incidence of crush damage,high efficiency,and low cost.To improve fertilization accuracy and uniformity,spreading performance tests were conducted using this spreader in accordance with the test methods specified in ISO 5690 and ASAE S341.2,in which particle mass was weighed in a two-dimensional matrix of collection boxes.The effects of fertilization strategies that control the feed gate flow rate and the disc rotation speed on particle distribution,and application rate per unit area and effective swath width,were investigated.A variable-rate fertilization model was developed by analyzing the variation characteristics resulting from an increasing and decreasing application rate,and field experiments were conducted to verify its accuracy.The results indicated that when the feed gate flow rate was 300 g/s,the mean application rate was 26.47 g,the standard deviation is 2.81,and the coefficient of variation of particle distribution is at its minimum value of 14.25%.When the disc rotation speed was 600 r/min,the fertilizer was most evenly distributed with a coefficient of variation of 13.86%,and an average effective spreader swath width of 24.51 m.The proposed variable-rate fertilization model showed a high fitting degree with an S-shaped function curve for both increasing and decreasing distribution rates and the yielding coefficients of determination were more than 0.82 and 0.71,respectively.The average error between the model predictions and the test results was 9.47%,and the coefficients of determination for the increasing and decreasing distribution rates were 0.91 and 0.82,respectively,which confirmed the accuracy of the proposed variable-rate fertilization model.This investigation provided a theoretical basis for traditional empirical fertilization using centrifugal variable-rate fertilizer spreaders,and guides the selection of a multiple trajectory,variable-rate fertilization strategy.
基金supported by the Laboratory of Lingnan Modern Agriculture Project(Grant No.NT2021009)the Project of key R&D program of Guangzhou of China(Grant No.202206010149)+2 种基金in part by Science and Technology Plan of Jian City of China(Grant No.20211-055316 and[2020]83)Science and Technology Plan of Guangdong Province of China(2023B10564002 and 2021B 1212040009)Innovative Research Team of Agricultural and Rural Big Data in Guangdong Province of China(2019KJ138)。
文摘Unmanned aerial vehicles(UAVs)are widely being used to spread granular fertilizer in China.Granular fertilizer spreaders equipped with UAVs are mainly centrifugal disc-type and pneumatic.The multichannel pneumatic granular fertilizer spreaders(MPGFSs)have a banded fertilizer deposition distribution pattern,which are more suitable for variable rate fertilization with high precision requirement than the circular deposition distribution pattern of disc-type granular fertilizer spreaders(DGFSs).However,the existing MPGFS has the disadvantage of inconsistent discharge rate of each channel,which affects the uniformity of fertilization.In order to explore the causes of inconsistent discharge rate of each channel,the discrete element method(DEM)and bench test were performed to analysis the discharge process of the fluted roller fertilizing apparatus and distribution of fertilizer in axial direction of fluted roller.The computational fluid dynamics(CFD)was used to simulate the airflow field of pneumatic system to analyze the influence of airflow on the movement of fertilizer particles.The simulation results of the discharge process of the fluted roller fertilizing apparatus showed that the filling velocity at the axial ends of the fluted roller fertilizing apparatus was lower than that of the middle.The reason was that the filling capacity was weak near the wall.The simulated results of the airflow field without partitions showed that the airflow provided by the axial flow fan was rotational,and this caused the particles to move irregularly in the throat,resulting in inconsistency discharge rate of each channel.Based on the analysis of reasons of inconsistent discharge rate of each channel,a MPGFS with partitions in the throat was developed.The discharge rate bench tests were carried out to optimize the partition spacing parameters,and fertilization test was performed to test the performance of the improved MPGFS.The discharge rate test results showed better consistency with partition.The coefficient of variation(CV)of the discharge rate of each channel was 20.16%without the partition and 7.70%with the optimal partition.The fertilizer spreading uniformity bench test results shown that the CV of spreading uniformity of MPGFS without partitions was 15.32%,and that MPGFS with partitions was 8.69%.The partitions design was beneficial to improve the consistency of each channel discharge rate and the uniformity of fertilization.The finding can provide a strong reference to design the MPGFS.
文摘Two different flow channel configurations on thermal resistances associated with the behavior of cooling of power device were studied in this paper. ANSYS Icepak 14.0 has been adopted as a numerical simulation tool. The simulation results from this study showed that the shapes of channels in cooling radiator play an important role in the thermal management of water cooling radiation system. The optimal channel design could improve the heat- dissipating efficiency by 80% in water cooling radiation system. The result also indicated that the thermal resistance of heat sinks decreased with the volumetric flow rate and the number of cylindrical columns in the flow channel. Experimental results were obtained under certain channel configurations and volume rates. Moreover, the results of numerical simulation can be explained well by the experimental results.
基金This work was financially supported by the Australian Research Council Discovery Program(DP190103290)Australian Research Council Discovery Early Career Researcher Award scheme(DE150101617 and DE140100716)+1 种基金We also thank the Australian Synchrotron for the SAXS/WAXS beamline(Beam time ID:M13292)D.G.is grateful to the Australian Research Council Laureate Fellowship FL160100089 and QUT Project No.323000-0355/51.
文摘Waste heat management holds great promise to create a sustainable and energy-efficient society as well as contributes to the alleviation of global warming.Harvesting and converting this waste heat in order to improve the efficiency is a major challenge.Here we report biomimetic nacre-like hydroxyl-functionalized boron nitride(BN)-polyimide(PI)nanocomposite membranes as efficient 2D in-plane heat conductor to dissipate and convert waste heat at high temperature.The hierarchically layered nanostructured membrane with oriented BN nanosheets gives rise to a very large anisotropy in heat transport properties,with a high in-plane thermal conductivity(TC)of 51 Wm^(-1) K^(-1) at a temperature of~300 C,7314%higher than that of the pure polymer.The membrane also exhibits superior thermal stability and fire resistance,enabling its workability in a hot environment.In addition to cooling conventional exothermic electronics,the large TC enables the membrane as a thin and 2D anisotropic heat sink to generate a large temperature gradient in a thermoelectric module(△T=23 ℃)through effective heat diffusion on the cold side under 220 C heating.The waste heat under high temperature is therefore efficiently harvested and converted to power electronics,thus saving more thermal energy by largely decreasing consumption.
