卷积完全匹配层在二维声波吸收流体介质中的有限元计算

将基于复坐标变换和复频移扩展坐标变量的卷积完全匹配层Convolution Perfectly Matched Layer(CPML)引入到二维吸收流体介质声波方程的有限元(FEM)计算中,其作为一种吸收边界条件应用在了数值计算的边界截断上。与传统的PML相比,CPML的优势在于它不需要把场方程分裂开,使待求解方程的数目减少,并使其具有更好的稳定性和更高的吸收性能。文中给出了二维吸收声波的频域和时域CPML方程,并在有限元计算软件COMSOL中完成数值计算。结果表明,CPML边界层能有效吸收损耗流体介质中的声波,能有效衰减了进入其中的声场能量。

可吸收止血流体明胶预防术后脑脊液漏

目的 ：探索可吸收止血流体明胶预防术后脑脊液漏的有效性。方法 ：对2013年3月至9月有硬脊膜撕裂脑脊液漏的脊柱损伤17例患者进行回顾性分析,男16例,女1例;年龄16~67岁,平均（39.6±15.4）岁;颈椎1例,胸椎9例,胸腰段4例,腰椎3例;爆裂骨折4例,骨折脱位13例。神经损伤ASIA分级：A级12例,B级2例,D级2例,E级1例。车祸伤2例,高处坠落伤10例,重物砸伤4例,地震时从楼梯滚落1例。术中应用可吸收止血流体明胶封堵以预防术后脑脊液漏。记录术后每日的引流量。结果：17例患者有15例术后无脑脊液漏出现。2例术后出现脑脊液漏者引流管保留至术后第6~7天。术后未出现头痛、头晕、发热、颈项抵抗、皮疹、切口不愈合、切口感染、血肿、神经症状加重等并发症。随访9个月均未见到切口周围有异常现象。结论：术中应用可吸收止血流体明胶封堵硬脊膜撕裂预防术后脑脊液漏是有效的方法。

可吸收止血流体明胶和可吸收明胶海绵在ACDF术中的止血作用对比

目的比较可吸收止血流体明胶和可吸收明胶海绵在两个节段颈椎前路间盘切除融合(ACDF)术中的止血效果。方法筛选2014年2月~2015年10月在我科行两个节段ACDF(Zero-P)手术的颈椎病患者62例,随机分为2组:流体明胶组31例,使用可吸收止血流体明胶止血;明胶海绵组31例,使用可吸收明胶海绵止血。比较两组手术时间、椎管减压时间、术中出血量、术后引流量,术后不良事件及术后并发症。结果两组患者手术时间分别为(156.1±20.6)min、(164.5±30.8)min,二者无显著统计学差异;两组椎管减压所用时间分别为(91.2±17.2)min、(108.4±27.5)min,=0.005,HFG组椎管减压时间少于GS组,差异具有统计学意义。流体明胶组患者术中出血量及术后引流量均少于明胶海绵组,术中出血量分别为(45.2±16.3)mL VS(106.1±107.8)mL,<0.05;术后引流量分别为(38.1±34.5)mL VS(76.3±56.2)mL,<0.05,差异具有统计学意义。两组患者均未出现术后颈部急性血肿及其他严重术后并发症。结论在ACDF术中,可吸收流体明胶操作简单,可以减少椎管减压时间、术中出血量和术后引流量,是一种安全、有效并且效果优于传统止血方式的止血材料。

可吸收止血流体明胶在腰椎后路手术中的临床应用研究

目的探讨可吸收止血流体明胶在腰椎后路椎间融合术中控制出血的有效性和安全性。方法选取我科2016年10月至2017年10月期间因腰椎管狭窄症,行单节段腰椎后路减压椎间融合植骨内固定术的患者共96例,分为试验组和对照组,每组分别为48例。对照组采用常规外科手术方法止血,试验组术中除常规外科止血外,同时使用可吸收止血流体明胶。通过对比两组患者的手术时间、术中出血量、术后引流量,术后感染的发生情况等综合评价两组患者的治疗效果。结果试验组应用可吸收止血流体明胶后,其术中出血量(180.7±15.6)mL、手术时间(95.6±13.8)min,均少于对照组术中出血量(216.8±19.2)mL、手术时间(103.7±18.9)min,差异有统计学意义(P<0.05);试验组术后第1、2、3天的引流量分别为(186.8±29.2)mL、(286.7±27.1)mL、(320.7±30.2)mL,与对照组(210.8±36.1)mL、(315.5±20.5)mL、(372.8±22.2)mL相比,差异有统计学意义(P<0.05)。术后伤口发生感染的情况,试验组发生率为2/48,对照组发生率为3/48,无统计学差异(P>0.05)。结论流体明胶可减少手术时间、术中出血量以及术后引流量,并不增加伤口感染的风险。它是一种安全、有效的止血剂,在腰椎后路手术中有其应用价值。

两种止血材料在腰椎退变手术中止血疗效的临床研究

目的观察评价可吸收流体明胶与明胶海绵在腰椎退变后路手术中的止血效果。方法前瞻性随机对照研究自2016年8月至2017年5月在本科收治的腰椎管减压固定融合的后路手术患者,随机分为两组:流体明胶组28例中,男12例,女16例;明胶海绵组27例中,男12例,女15例;术中分别应用流体明胶和(或)明胶海绵止血,如果出血速度逐渐减慢至不再有明显的出血即认为止血成功,否则视为止血失败。记录止血3 min、5min的止血成功率,记录手术时间、术中出血量、自体血回输量、止血过程中的出血量、输血量,记录术前、术后2～3 d和术后5～7 d的BP、RBC、HCT、HB的变化,记录术后每天的引流量,记录全部的不良事件。结果全部病例至少随访1个月。明胶海绵组有18例3 min成功止血、3例5 min成功止血,流体明胶组有21例3min内快速止血,3例5 min成功止血。两组止血过程中的出血量差异明显(P=0.000);术前流体明胶组RBC和HCT小于明胶海绵组(P=0.038,P=0.030),术后两组之间差异无统计学意义(P>0.05);术前两组收缩压差异无统计学意义(P>0.05),术后2～3 d流体明胶组收缩压比明胶海绵组高(P=0.005);流体明胶组的术后1 d和术后2～4 d的引流量均少于明胶海绵组(P=0.014;P=0.011)。结论与明胶海绵相比,可吸收流体明胶可以减少止血过程中的出血量,可以减少术后引流量,是一种安全、有效的脊柱外科术中止血剂。

两种止血材料在颈椎单开门椎管扩大成形术中的止血效果观察

目的:比较可吸收止血流体明胶(HFG)和可吸收明胶海绵(GS)在颈椎后路单开门椎管扩大成形术中的止血效果。方法:回顾性分析2014年2月至2016年5月接受颈椎后路单开门椎管扩大成形术治疗的患者83例,根据患者术中使用不同止血材料分两组:HFG组41例,男30例,女11例;年龄29~81岁,平均(55.6±11.6)岁;其中14例为单纯颈椎管狭窄症,9例合并后纵韧带骨化,18例合并多节段颈椎间盘突出。GS组42例,男32例,女10例;年龄36~78岁,平均(55.4±11.1)岁;其中12例为单纯颈椎管狭窄症,10例合并后纵韧带骨化,20例合并多节段颈椎间盘突出。两组患者性别、年龄及病变类型等一般资料比较,差异均无统计学意义(P>0.05)。比较两组手术时间、术中出血量、术后引流量、术后不良事件及术后并发症。结果:HFG组和GS组患者手术时间分别为(137.2±30.0)、(154.8±33.5)min(P<0.05);术中出血量分别为(156.1±74.6)、(242.9±120.7)ml(P<0.001);术后引流量分别为(212.1±67.6)、(303.3±115.5)ml(P<0.001)。HFG组手术时间、术中出血量及术后引流量均少于GS组。两组患者均未发生术后切口急性血肿及其他止血相关并发症。结论:颈椎后路单开门椎管扩大成形术中,HFG操作简单,可以减少手术时间、术中出血量和术后引流量,是一种安全并且效果优于传统止血方式的止血材料。

可吸收止血流体明胶在神经内镜下经鼻蝶入路垂体腺瘤切除术中的应用价值分析

目的观察可吸收止血流体明胶（商品名Surgiflo，简称流体明胶）在神经内镜下经鼻蝶入路垂体腺瘤切除术中的止血效果。方法中山大学附属第一医院神经外科自2016年1月至2016年6月应用流体明胶治疗神经内镜下垂体腺瘤切除术中出血患者40例．其中16例瘤腔出血，24例海绵窦／海绵间窦出血；出血程度：2级出血10例，3级出血21例，4级出血9例。回顾性分析患者的临床资料和疗效。结果2级及3级出血患者使用流体明胶止血成功，4级出血患者中5例单纯使用流体明胶止血成功，另外4例应用流体明胶结合电凝、骨蜡、止血纱止血成功；2级、3级、4级出血患者流体明胶平均喷涂次数分别为1、1．5、2．5次；全部患者术后复查CT均未见瘤腔及海绵窦／海绵间窦部位积血，随访1个月均未见相关不良反应。结论流体明胶在神经内镜下经鼻蝶垂体腺瘤切除术中具有良好的止血效果，适用于瘤腔出血及海绵窦、海绵间窦出血。

CFD simulation of ammonia-based CO_2 absorption in a spray column

A comprehensive computational fluid dynamics（CFD） model is developed based on the gas-liquid two-phase hydrodynamics,gas-liquid mass-transfer theory and chemical reaction kinetics,and the ammonia-based CO2 absorption in a spray column is numerically studied.The Euler-Lagrange model is applied to describe the behavior of gas-liquid twophase flowand heat transfer.The dual-film theory and related correlations are adopted to model the gas-liquid mass transfer and chemical absorption process.The volatilization model of multi-component droplet is utilized to account for ammonia slippage.The effect of operation parameters on CO2 removal efficiency is numerically studied.The results showa good agreement with the previous experimental data,proving the validity of the proposed model.The profile studies of gasphase velocity and CO2 concentration suggest that the flowfield has a significant impact on the CO2 concentration field.Also,the local CO2 absorption rate is influenced by both local turbulence and the local liquid-gas ratio.Furthermore,the velocity field of gas phase is optimized by the method of adjusting the orifice plate,and the results showthat the CO2 removal efficiency is improved by approximately 4%.

Radiative squeezing flow of unsteady magneto-hydrodynamic Casson fluid between two parallel plates

Present numerical study examines the heat and mass transfer characteristics of magneto-hydrodynamic Casson fluid flow between two parallel plates under the influence of thermal radiation,internal heat generation or absorption and Joule dissipation effects with homogeneous first order chemical reaction.The non-Newtonian behaviour of Casson fluid is distinguished from those of Newtonian fluids by considering the well-established rheological Casson fluid flow model.The governing partial differential equations for the unsteady two-dimensional squeezing flow with heat and mass transfer of a Casson fluid are highly nonlinear and coupled in nature.The nonlinear ordinary differential equations governing the squeezing flow are obtained by imposing the similarity transformations on the conservation laws.The resulting equations have been solved by using two numerical techniques,namely Runge-Kutta fourth order integration scheme with shooting technique and bvp4c Matlab solver.The comparison between both the techniques is provided.Further,for the different set physical parameters,the numerical results are obtained and presented in the form of graphs and tables.However,in view of industrial use,the power required to generate the movement of the parallel plates is considerably reduced for the negative values of squeezing number.From the present investigation it is noticed that,due to the presence of stronger Lorentz forces,the temperature and velocity fields eventually suppressed for the enhancing values of Hartmann number.Also,higher values of squeezing number diminish the squeezing force on the fluid flow which in turn reduces the thermal field.Further,the destructive nature of the chemical reaction magnifies the concentration field;whereas constructive chemical reaction decreases the concentration field.The present numerical solutions are compared with previously published results and show the good agreement.

Heat transfer and nanofluid flow over a porous plate with radiation and slip boundary conditions

Presence of different terms with various values can alter the thermal behavior of the nanofluids flow over porous surfaces.The aim of this research is to study the influence of nanoparticles volume fraction,nanoparticles type,suction or injection,the heat generation or absorption,the Eckert number,thermal and velocity slip parameters,and radiation on the velocity and temperature fields on the flow and heat transfer over a porous flat plate.Four different types of nanoparticles including metal nanoparticles (Cu),metal oxide nanoparticles (Al2O3) and carbon-based nanomaterials (MWCNTs and SWCNTs) which were dispersed in the water (as based fluid) are studied.The governing equations are converted into the ordinary differential equations using similarity solution and solved numerically by the RKF45 algorithm.The results of the simulations showed a contradiction with the results of other researchers who expressed that using nanoparticles with higher thermal conductivity and volume fraction led to increasing heat transfer rate in nanofluids;this study proves that,in some cases,boosting the volume fraction of nanoparticles has a potential to decrease the heat transfer rate due to significant changes in values of some parameters including radiation,heat generation,and viscous dissipation.

Feasibility analysis of SO_2 absorption using a hydrophilic ceramic membrane contactor

Hydrophilic ceramic membranes would be potential candidates for membrane gas absorption if they could be applied to appropriate separation processes.This study highlights a novel concept for the practical implementation of SO_2 absorption in hydrophilic ceramic membrane that exhibits outstanding thermal and mechanical stabilities.With this aim,we investigated experimentally the performance of SO_2 absorption into aqueous sodium hydroxide (NaOH) solution in a hydrophilic alumina (Al_2O_3) membrane contactor in terms of SO_2 removal efficiency and SO_2 mass transfer flux,and compared the performance with that in a hydrophobic one.A series of experiments were performed at various conditions over a NaOH concentration range of 0–1.0 mol·L^(-1),a liquid flow rate range of 30–180 ml·min^(-1),a gas flow rate range of 120–1000 ml·min^(-1),an inlet SO_2 concentration range of 400–2000μl·L^(-1),and a temperature range of 10–35°C.It was found that the hydrophilic membrane was more competitive when using a NaOH concentration higher than 0.2 mol·L^(-1).Furthermore,it can be inferred that the hydrophilicα-Al_2O_3 membrane exhibited exceptional long-term stability under 480 h continuous operation.

The effect of membrane pores wettability on CO_2 removal from CO_2/CH_4 gaseous mixture using NaOH, MEA and TEA liquid absorbents in hollow fiber membrane contactor

The present paper renders a modeling and a 2D numerical simulation for the removal of CO_2from CO_2/CH_4gaseous stream utilizing sodium hydroxide(NaOH),monoethanolamine(MEA)and triethanolamine(TEA)liquid absorbents inside the hollow fiber membrane contactor.Counter-current arrangement of absorbing agents and CO_2/CH_4gaseous mixture flows are implemented in the modeling and numerical simulation.Non-wetting and partial wetting modes of operation are considered where in the partial wetting mode,CO_2/CH_4gaseous mixture and liquid absorbents fill the membrane pores.The deteriorated removal of CO_2in the partial wetting mode of operation is mainly due to the mass transfer resistance imposed by the liquid in the pores of membrane.The validation of numerical simulation is done based on the comparison of simulation results of CO_2removal using Na OH and experimental data under non-wetting mode of operation.The comparison illustrates a desirable agreement with an average deviation of less than 5%.According to the results,MEA provides higher efficiency for CO_2removal in comparison with the other liquid absorbents.The order for CO_2removal performance is MEAN Na OHN TEA.The influence of non-wetting and partial wetting modes of operation on CO_2removal are evaluated in this article as one of the novelties.Besides,the percentage of CO_2sequestration as a function of gas velocity for various percentages of membrane pores wetting ranging from 0(non-wetting mode of operation)to 100%(complete wetting mode of operation)is studied in this research paper,which can be proposed as the other novelty.The results indicate that increase in some operational parameters such as module length,membrane porosity and absorbents concentration encourage the removal percentage of CO_2from CO_2/CH_4gaseous mixture while increasing in membrane tortuosity,gas velocity and initial CO_2concentration has unfavorable influence on the separation efficiency of CO_2.

Effect of Chinese Medicines on the Subretinal Fluid Absorption after Operation for Retinal Detachment

Purpose:To determine the effects of traditional Chinese medicines on subretinal fluld absorption after Operation for retinal detachment.Mehods:Among100eyes with operations fo retinal detachment without drainage of fluid,there were 50eyes in traditional Chinese medicine treatment group and 50eyes in the control group.and there were no significant difference between the two groups in age,myopia and retinal detachment area.We observed the time for the absorption of subretinal fluid and visual acuity improvement aftr the opera-tions for retinal detachment.Results;he result showed that the average time for the absorption of subretinal fluid was14.5days in the traditional Chinese medicine treatment group,21.7days in the control group and the visual acuity was better in the former than in the latter.Conclusions:The taditional Chinese medicine treatment could increase the ab-sorption of subretional fluid,the mechanisms of which may be that Chinese medicines regulated and impved the general blood circulation and local eye blood criculation and the function of blood-retinal barrier so that they increase the out-ward osmotic suction forces of the pigment epithelium.

Bubble Pump Models Verification Based on the Experimental Results

DAR （diffusion absorption refrigeration） cycle is driven by heat and has no moving parts. It is based on refrigerant and absorbent as the working fluid together with hydrogen as an auxiliary inert gas. To circulate the working fluid without a mechanical pump, the diffusion absorption cycle relies on a bubble pump. Experimental system was designed and operated. Its aim was to investigate the performance of a bubble pump operating with three lifting tubes. The experimental results of the system were compared to existing models. The comparison showed that there was a bad agreement between the experimental and the theoretical results.

Experimental investigation on solar-flue gas chimney

Flue gases exhausted from thermal power plants contain more than 50% of the fuel thermal energy. In the present work, experimental investigation was carried out to study the utilization of thermal energy in flue gases to enhance the performance of modified solar chimney consisting of Savonius wind rotor. A modified solar chimney model was designed and fabricated to carry out experimental measurement. The model consists of thermal energy conversion unit; Savonius wind rotor and a chimney. The thermal energy in the flue gas transfers to the air particles in the air channel across the absorber plate and results in upward air stream due to the buoyancy effect. With an 9 absorber area of 2.36 re＇and flue gas mass flow rate of0.18 kg/s, air velocity＇ of 4.1 m/s was achieved at the top of the thermal unit. Increasing the mass flow rate of the flue gas to 0.24 kg/s enhances the air velocity to be 4.6 m/s. The results have demonstrated the possibility＇ of utilizing the thermal energy in the waste flue gas to enhance the performance of a solar chimney and facilitate the continuous operation during the absence of the sun.

Diurnal Variations of Greenhouse Gas Fluxes from Mixed Broad-leaved and Coniferous Forest Soil in Dinghushan

The subtropical mixed broad-leaved and coniferous forest, a typical successional monsoon forest, is one of the major forests in the subtropics of China. Therefore, it is very important to estimate the fluxes of the greenhouse gases from the forest soil in order to evaluate the impact of subtropical forests on the greenhouse gas emissions or absorptions. This study investigated the diurnal variations of fluxes of three greenhouse gases （CO 2 , CH 4 , and N 2 O） from a mixed broad-leaved and coniferous forest soil. A static chamber-gas chromatograph technique was used to measure the fluxes of three greenhouse gases. By using the improved gas chromatography sampling system, the fluxes were analyzed with a single injection. In order to find out the effects of litter and seedling on the emissions or absorptions of these greenhouse gases, three treatments were set in the field:（1）bare soil surface （litter was removed previously）; （3） litter + soil; （3） seedling + litter + soil. The experimental results demonstrated that the forest soil was a source of CO 2 , N 2 O and a weak sink of CH 4 .The daily fluxes of CO 2 , CH 4 , and N 2 O from the soil surface were in the range of 488.99700.57, 0.0490.108 and –0.025 –0.053 mg/（m 2 ·h ）, respectively. CO 2 from the litter decomposition accounted for about 1/3 of the total CO 2 emission from the soil surface, while the litter and seedling had no significant effect on the fluxes of CH 4 and N 2 O. The fluxes of CO 2 and N 2 O measured at 9:00 11:00 a.m. were significantly different from their daily averages. Therefore, caution must be taken if the CO 2 and N 2 O fluxes measured within 9:0011:00 a.m. are used for extrapolation.

Convergence of global attractors of a 2D non-Newtonian system to the global attractor of the 2D Navier-Stokes system

This paper discusses the relation between the long-time dynamics of solutions of the two-dimensional （2D） incompressible non-Newtonian fluid system and the 2D Navier-Stokes system. We first show that the solutions of the non-Newtonian fluid system converge to the solutions of the Navier-Stokes system in the energy norm. Then we establish that the global attractors {.Aε^H}0〈≤1 of the non-Newtonian fluid system converge to the global attractor .A0H of the Navier-Stokes system as ε → 0. We also construct the minimal limit A^H min of the H global attractors {Aε^H}0〈ε≤ as ≤→ 0 and prove that A^Hmin iS a strictly invariant and connected set.

A fast SOI-based variable optical attenuator with a p-i-n structure with low polarization dependent loss

According to the plasma dispersion effect of silicon(Si),a silicon-on-insulator(SOI) based variable optical attenuator(VOA) with p-i-n lateral diode structure is demonstrated in this paper.A wire rib waveguide with sub-micrometer cross section is adopted.The device is only about 2 mm long.The power consumption of the VOA is 76.3 mW(0.67 V,113.9 mA),and due to the carrier absorption,the polarization dependent loss(PDL) is 0.1dB at 20dB attenuation.The raise time of the VOA is 34.5 ns,the fall time is 37 ns,and the response time is 71.5 ns.