A comprehensive review on microchannel heat sinks for electronics cooling

The heat generation of electronic devices is increasing dramatically,which causes a serious bottleneck in the thermal management of electronics,and overheating will result in performance deterioration and even device damage.With the development of micro-machining technologies,the microchannel heat sink(MCHS)has become one of the best ways to remove the considerable amount of heat generated by high-power electronics.It has the advantages of large specific surface area,small size,coolant saving and high heat transfer coefficient.This paper comprehensively takes an overview of the research progress in MCHSs and generalizes the hotspots and bottlenecks of this area.The heat transfer mechanisms and performances of different channel structures,coolants,channel materials and some other influencing factors are reviewed.Additionally,this paper classifies the heat transfer enhancement technology and reviews the related studies on both the single-phase and phase-change flow and heat transfer.The comprehensive review is expected to provide a theoretical reference and technical guidance for further research and application of MCHSs in the future.

基于随机移动模型的移动sinks无线移动传感器网络性能分析与改进

引入移动sinks节点是解决网络连通性、能耗平衡、提高网络生命周期和网络容量的有效方法。针对移动sinks节点的移动机制直接与网络性能相关,结合mWSNs体系结构,分析了基于随机移动模型的网络性能,提出了零数据包分片率的随机移动模型。理论分析与仿真结果表明,该模型能够保证数据零分片,提高了网络的时延性能和数据包传输成功率。

移动sinks无线移动传感器网络时延性能分析

结合mWSNs体系结构,分析了移动sinks无线传感器网络的时延组成和时延特性,并通过仿真实验分析了移动性对时延的影响。该分析结果既能用于mWSNs时延系统性能评价,又可为mWSNs系统参数(如移动sinks数量、速度、传输半径及数据包长度等)优化提供理论依据。同时,时延性能要与能量消耗综合考虑。

Effects of viscoelasticity on the stability and bifurcations of nonlinear energy sinks

Due to the increasing use of passive absorbers to control unwanted vibrations,many studies have been done on energy absorbers ideally,but the lack of studies of real environmental conditions on these absorbers is felt.The present work investigates the effect of viscoelasticity on the stability and bifurcations of a system attached to a nonlinear energy sink(NES).In this paper,the Burgers model is assumed for the viscoelasticity in an NES,and a linear oscillator system is considered for investigating the instabilities and bifurcations.The equations of motion of the coupled system are solved by using the harmonic balance and pseudo-arc-length continuation methods.The results show that the viscoelasticity affects the frequency intervals of the Hopf and saddle-node branches,and by increasing the stiffness parameters of the viscoelasticity,the conditions of these branches occur in larger ranges of the external force amplitudes,and also reduce the frequency range of the branches.In addition,increasing the viscoelastic damping parameter has the potential to completely eliminate the instability of the system and gradually reduce the amplitude of the jump phenomenon.

Fractional nonlinear energy sinks

The cubic or third-power(TP)nonlinear energy sink(NES)has been proven to be an effective method for vibration suppression,owing to the occurrence of targeted energy transfer(TET).However,TET is unable to be triggered by the low initial energy input,and thus the TP NES would get failed under low-amplitude vibration.To resolve this issue,a new type of NES with fractional nonlinearity,e.g.,one-third-power(OTP)nonlinearity,is proposed.The dynamic behaviors of a linear oscillator(LO)with an OTP NES are investigated numerically,and then both the TET feature and the vibration attenuation performance are evaluated.Moreover,an analogy circuit is established,and the circuit simulations are carried out to verify the design concept of the OTP NES.It is found that the threshold for TET of the OTP NES is two orders of magnitude smaller than that of the TP NES.The parametric analysis shows that a heavier mass or a lower stiffness coefficient of the NES is beneficial to the occurrence of TET in the OTP NES system.Additionally,significant energy transfer is usually accompanied with efficient energy dissipation.Consequently,the OTP NES can realize TET under low initial input energy,which should be a promising approach for micro-vibration suppression.

Diagnostic Study of Apparent Heat Sources and Moisture Sinks in the South China Sea and its Adjacent Areas during the Onset of 1998 SCS Monsoon

The apparent heat sources (?Q1 ?) and moisture sinks (?Q2 ?) are calculated based on the reanalyzed data of the South China Sea Monsoon Experiment (SCSMEX) from May 1 to August 31, 1998. It is found that the formation and distribution of the atmospheric heat sources are important for the monsoon onset. The earlier onset of the SCS monsoon is the result of enduring atmospheric heating in the Indo–China Peninsula and South China areas. The atmospheric heating firstly appears in the Indo–China Peninsula area and the sensible heat is the major one. The 30–50 day periodic oscillation of atmospheric heat sources between the SCS area and the western Pacific warm pool has a reverse phase distribution before the middle of July and the low frequency oscillation of heat sources in SCS area has an obvious longitudinal propagation. The 30–50 day low frequency oscillation has vital modificatory effects on the summer monsoon evolution during 1998. Key words Apparent heat sources - Apparent moisture sinks - The South China Sea monsoon - Diagnostic Study Sponsored by the National Key Project of Fundamental Research “ SCSMEX” and the Research Fund for the Doctoral Program of Higher Education: “ Study of the Air-sea Interaction in the SCS Monsoon Region”.

The Variability of Air-sea O_(2)Flux in CMIP6:Implications for Estimating Terrestrial and Oceanic Carbon Sinks

The measurement of atmospheric O_(2)concentrations and related oxygen budget have been used to estimate terrestrial and oceanic carbon uptake.However,a discrepancy remains in assessments of O_(2)exchange between ocean and atmosphere(i.e.air-sea O_(2)flux),which is one of the major contributors to uncertainties in the O_(2)-based estimations of the carbon uptake.Here,we explore the variability of air-sea O_(2)flux with the use of outputs from Coupled Model Intercomparison Project phase 6(CMIP6).The simulated air-sea O_(2)flux exhibits an obvious warming-induced upward trend(~1.49 Tmol yr−2)since the mid-1980s,accompanied by a strong decadal variability dominated by oceanic climate modes.We subsequently revise the O_(2)-based carbon uptakes in response to this changing air-sea O_(2)flux.Our results show that,for the 1990−2000 period,the averaged net ocean and land sinks are 2.10±0.43 and 1.14±0.52 GtC yr−1 respectively,overall consistent with estimates derived by the Global Carbon Project(GCP).An enhanced carbon uptake is found in both land and ocean after year 2000,reflecting the modification of carbon cycle under human activities.Results derived from CMIP5 simulations also investigated in the study allow for comparisons from which we can see the vital importance of oxygen dataset on carbon uptake estimations.

Second Law Analysis and Optimization of Elliptical Pin Fin Heat Sinks Using Firefly Algorithm

One of the most significant considerations in the design of a heat sink is thermal management due to increasing thermal flux and miniature in size.These heat sinks utilize plate or pin fins depending upon the required heat dissipation rate.They are designed to optimize overall performance.Elliptical pin fin heat sinks enhance heat transfer rates and reduce the pumping power.In this study,the Firefly Algorithm is implemented to optimize heat sinks with elliptical pin-fins.The pin-fins are arranged in an inline fashion.The nature-inspired metaheuristic algorithm performs powerfully and efficiently in solving numerical global optimization problems.Based on mass,energy,and entropy balance,three models are developed for thermal resistance,hydraulic resistance,and entropy generation rate in the heat sink.The major axis is used as the characteristic length,and the maximum velocity is used as the reference velocity.The entropy generation rate comprises the combined effect of thermal resistance and pressure drop.The total EGR is minimized by utilizing the firefly algorithm.The optimization model utilizes analytical/empirical correlations for the heat transfer coefficients and friction factors.It is shown that both thermal resistance and pressure drop can be simultaneously optimized using this algorithm.It is demonstrated that the performance of FFA is much better than PPA.

The Carbon Sinks and Mitigation Potential of Deodar (<i>Cedrus deodara</i>) Forest Ecosystem at Different Altitude in Kumrat Valley, Pakistan

Forest carbon monitoring and reporting are critical for informing global climate change assessment. The regional estimates of forest carbon attached greater attention, to assess the role of forest in carbon mitigation. Here using field inventory, we examined the carbon sink and mitigation potential of monospecific Deodar forest in the Kumrat valley, of Hindu Kush Himalaya, Region of Pakistan, at a different elevation. The elevation of monospecific Deodar forest ranges from 2300 to 2700 m (a.s.l). We divided the forest into three elevation classes (that is 2300 - 2400 m (EI) 2400 - 2500 m (EII) and 2500 - 2700 m (EIII) a.s.l respectively). In each elevation class, we laid out 09 sample plots (33*33 m2) for measuring carbon values in living tree biomass (LT), soil (SC), litter, dead wood, cone (LDWC) and understory vegetation (USV). Our results showed that the carbon density at EI was 432.37 ± 277.96 Mg·C-1, while the carbon density at EII and EIII was 668.35 ± 323.94 and 1016.79 ± 542.99 Mg·C-1 respectively. Our finding revealed that the carbon mitigation potential of the forest increases with increasing elevation. Among the different elevation classes, EIII stored significantly higher carbon due to the dominance of mature, old age, larger trees, and the minimum anthropogenic disturbance, whereas EI stored statistically lower carbon because of maximum anthropogenic disturbance, which resulted in the removal of mature and over-mature trees. Furthermore, our correlation analysis between tree height and carbon stock and basal area and LT carbon, underlines that the basal area is the stronger predictor of LT carbon estimation than height. Overall our results highlight that deodar forest stored 716.94 ± 462.06 Mg?C·ha-1. However, the rehabilitation, preservation and sustainable management of disturb forest located at a lower elevation could considerably improve carbon mitigation potential.

Characteristics of Sources and Sinks of Yugu 18

[Objectives] The study aimed to discuss the high-yield mechanism of Yugu 18.[Methods] The characteristics of sources and sinks of Yugu 18 with high quality, high yield, wide adaptability and multi-resistance to diseases were studied by using Jigu 18 as the control variety.[Results] Yugu 18 was superior in sink capability and the ability to fill sinks. In the filling period, its photosynthetic capacity was strong, and grain-leaf ratio was high. Photosynthetic products had a great contribution to grain filling after flowering, and the coordination between sources and sinks was good.[Conclusions] The research provides theoretical basis for the breeding and cultivation of high-yield foxtail millet.

A CMOS Compatible MEMS Pirani Vacuum Gauge with Monocrystal Silicon Heaters and Heat Sinks

We present a micro-Pirani vacuum gauge using the low-resistivity monocrystal silicon as the heaters and heat sinks fabricated by the post complementary metal oxide semiconductor （CMOS） microelectromechanical system （MEMS） process. The metal interconnection of the device is fabricated by a 0.5 μm standard CMOS process on 8-inch silicon wafer. Then, a SiO2-Si low-temperature fusion bonding is developed to bond the CMOS wafer and the MEMS wafer, with the electrical connection realized by the tungsten through silicon via process. Wafer- level A1Ge euteetic bonding is adopted to package the Pirani gauge in a non-hermetic cavity to protect the gauge from being damaged or contaminated in the dicing and assembling process, and to make it suitable for actual applications. To increase the accuracy of the test and restrain negative influence of temperature drift, the Wheatstone bridge structure is introduced. The test results show that before capping, the gauge has an average sensitivity of 1.04 × 104 K.W-1Torr-1 in dynamic range of 0.01 20 Torr. After capping, the sensitivity of the gauge does not decrease but increases to 1.12 × 104 K.W-1 Torr-1.

SCSBE: Secured Cluster and Sleep Based Energy-Efficient Sensory Data Collection with Mobile Sinks

Wireless sensor networks applications involve a position of inaccessible metropolitan vicinity en-closed by wireless sensor nodes (WSNs)-monitors environmental parameters like battle field surveillance, home applications like fire alarm, health monitoring, etc. Energy plays a vital role in Wireless sensor networks. So, we have to concentrate more on balanced energy consumption for maximizing the network lifetime. Minimizing the whole network overhead and vigor disbursement coupled with the multi-hop data reclamation process that ensuring balanced energy consumption among SNs which results in prolonged network lifetime. This can be achieved by forwarding the sensed data to their cluster heads and then filtering the data before sending it to their tryst nodes, which is located in proximity to MS’s trajectory. Sleep and awakening of nodes periodically helps to retain their energy for some more time. The events occurring in any part of the network should be identified by the nodes, while arrangements sleep and active among the nodes. (i.e.) the nodes should be scheduled to sleep, so that the outstanding nodes can take care of the whole network. The eXtensible Randomized Matrix Arithmetic Coding (XRMAC) Technique has been used to enhance the security among all the nodes in the network. Simulation results show that our Proposed Scheme can have better Lifetime, improved throughput, reduced delay compared to other existing methods.

Aged forests could still act as carbon sinks

Old-growth forests are traditionally negligible as carbon sinks, but CAS scientists recently reported that

Carbon Fluxes and Sinks:the Consumption of Atmospheric and Soil CO_2 by Carbonate Rock Dissolution

Carbonate rock outcrops cover 9%-16% of the continental area and are the principal source of the dissolved inorganic carbon （DIC） transferred by rivers to the oceans, a consequence their dissolution. Current estimations suggest that the flux falls between 0.1-0.6 PgC/a. Taking the intermediate value （0.3 PgC/a）, it is equal to 18% of current estimates of the terrestrial vegetation net carbon sink and 38% of the soil carbon sink. In China, the carbon flux from carbonate rock dissolution is estimated to be 0.016 PgC/a, which accounts for 21%, 87.5%-150% and 2.3 times of the forest, shrub and grassland net carbon sinks respectively, as well as 23%-40% of the soil carbon sink flux. Carbonate dissolution is sensitive to environmental and climatic changes, the rate being closely correlated with precipitation, temperature, also with soil and vegetation cover. HCO3 in the water is affected by hydrophyte photosynthesis, resulting in part of the HCO~ being converted into DOC and POC, which may enhance the potential of carbon sequestration by carbonate rock dissolution. The possible turnover time of this carbon is roughly equal to that of the sea water cycle （2000a）. The uptake of atmospheric/soil CO2 by carbonate rock dissolution thus plays an important role in the global carbon cycle, being one of the most important sinks. A major research need is to better evaluate the net effect of this sink in comparison to an oceanic source from carbonate mineral precipitation.

Optimal Coverage Multi-Path Scheduling Scheme with Multiple Mobile Sinks for WSNs

Wireless Sensor Networks(WSNs)are usually formed with many tiny sensors which are randomly deployed within sensing field for target monitoring.These sensors can transmit their monitored data to the sink in a multi-hop communication manner.However,the‘hot spots’problem will be caused since nodes near sink will consume more energy during forwarding.Recently,mobile sink based technology provides an alternative solution for the long-distance communication and sensor nodes only need to use single hop communication to the mobile sink during data transmission.Even though it is difficult to consider many network metrics such as sensor position,residual energy and coverage rate etc.,it is still very important to schedule a reasonable moving trajectory for the mobile sink.In this paper,a novel trajectory scheduling method based on coverage rate for multiple mobile sinks(TSCR-M)is presented especially for large-scale WSNs.An improved particle swarm optimization(PSO)combined with mutation operator is introduced to search the parking positions with optimal coverage rate.Then the genetic algorithm(GA)is adopted to schedule the moving trajectory for multiple mobile sinks.Extensive simulations are performed to validate the performance of our proposed method.

Spatial Analysis Approach in Revealing the Global Sinks of Atmosphere Carbon Dioxide through “Leave One Out” Method

Global warming and climate change are the most important ecological issues of our time. The most well-known factor in this phenomenon is the redundancy of carbon dioxide in the atmosphere. Over the past 50 years the amount of residual CO2 in the atmosphere has risen from 40% to 45%. Reducing CO2 redundancy requires precise knowledge of the gas sources and sinks throughout the atmosphere. Despite having a leading role in residual gas levels of atmosphere, the diagnosis and types of changes of absorbing carbon dioxide are very much in doubt. Atmospheric measurements of CO2 concentrations are highly precise and provide a reliable measure of increase of CO2 in the atmosphere every year but they do not lead to the location of sources and sinks. Studies about understanding CO2 cycles began mainly around 1990 and most of these studies have been focused on non-spatial analysis. By ignoring the spatial effects, an important property such as closeness (adjacent) has been disregarded. The emission sources of gas are stronger than their sink sources i.e., whenever a sink is adjacent to a strong emission source, the measurements will show a massive existence of CO2 gas in that region although there exists a fine CO2?gas sink at below. Using the global measurements of CO2 and applying spatial analysis approach to “Leave One Out” method, our studies reveal the most probable spots of CO2 sources and sinks and that Negev Desert in Middle East is a distinguished CO2 sink region.

A Novel Method to Identify the Global Sources and Sinks of Carbon Dioxide Based on Spatial Analysis

Today global warming has become one of the most important concerns of environmental science. The redundancy of greenhouse gases in the atmosphere is known as a major factor in this phenomenon. These gases contain water vapor, carbon dioxide, methane, nitrous oxide, and ozone. The CO2?gas is one of their most effective among these gases. According to scientific warnings, the amount of CO2?gases in the atmosphere has increased by 40% to 45% over the last 50 years. Reducing the abundant gas in the atmosphere requires a good knowledge of related factors involved, including sources that emit gases into the atmosphere and sinks that absorb the gas from the atmosphere. The amount of CO2?gas in the atmosphere has been accurately measured in previous years with great certainty. But the predicted values of emissions from sources and removals by sinks have large ambiguities. As studies show, even the computed residuals trends (which is obtained by subtracting the amounts of sinks from sources) strongly disagree with the trends of the existence of CO2?in the atmosphere. This study as a preliminary review, proposes a method to identify the locations of sources and sinks of carbon dioxide using global statistical information and adding spatial analysis approaches. By applying this method to the data observed from 2000 to 2011 and the extraction of likely sources and sinks, the region of the Black Sea, near Romania recognized as one of the strong points issued and Bukit Kototabang near Indonesia acknowledged as an Impressive CO2?absorption zone.

Optimal Stop Points for Data Gathering in Sensor Networks with Mobile Sinks

Given a wireless sensor network (WSN) in which a mobile sink is used to collect data from the sensor nodes, this paper addresses the problem of selecting a set of stop points that results in low energy usage by the sensor nodes. This paper assumes an approach in which a mobile sink travels along a fixed path and uses a stop-and-collect protocol since this has previously been shown to be an efficient WSN data collection method. The problem of selecting an optimal set of stop points is shown to be an NP-hard problem. Then, an Integer Linear Programming (ILP) formulation is used to derive an optimal algorithm that can be used for small problem instances. Next, a polynomial-time Tabu-search-based heuristic algorithm is proposed. Simulations are used to compare the energy consumption values, computation times and expected network lifetimes when using the optimal ILP algorithm, the proposed heuristic algorithm and several other possible heuristic algorithms. The results show that the proposed heuristic algorithm results in near-optimal energy usage values with low computation times, thereby making it suitable for large-sized WSNs.

An investigation on topologies of hybrid manifold,impinging-jet nozzle and micro-pin-fin heat sinks

The hybrid manifold micro-pin-fin(MMPF)heat sink combined nozzle jets is an option for large-scale integrated circuits(LSI).The demond for uniform and ultra-high heat flux removal by MMPF heat sink has not been adequately investigated.This work aims to solve the problem of fluid organization.The proposed basic tiling topologies,including square,regular hexagon,30°rhombus,and 60°rhombus topologies,provide different organized fluid flows and heat transfer patterns.The present study focuses on comparing these topologies according to independent porous medium parameters,such as nozzle pore size D_(Z),flow pore size D_(X,Y),and porosityε.The results show that the square topology achieves the smallest total thermal resistance R_(tot)value of0.0975×10^(-4)K m^2/W,while the hexagon topology achieved the highest value of COP/?T,which was 2033.9 K^(-1).According to the sensitivity analysis results,the optimal total thermal resistance can be obtained by balancing the influences of nozzle pore size,flow pore size,and porosity.The optimal pressure drop can be obtained by maximizing the porosity.

Achieving accurate regional carbon-sink accounting and its significance for “missing” carbon sinks

In the 2019 revision of the IPCC’s 2006 national inventory guidelines,the atmospheric inversion of greenhouse gas(GHG)emissions based on atmospheric concentrations was proposed for the first time to better support inventory verifi-cation initiatives.Thus,a globally unified verification reference standard was formulated,commonly known as the“top-down inversion”method.1 The characteristics of this method are its thorough coverage,strong timeliness,and low bias.The 2019 IPCC guideline’s“refinement”can effectively improve the accuracy and credibility of the bottom-up method that is currently being used to account for the carbon(C)source/sink status of various ecosystem types.It will be necessary to couple and synchronize atmospheric and ecological C processes to accurately calculate the status of ecosystem C sinks while also reducing errors introduced by anthropogenic-based emission uncertainties.