Operation optimization of prefabricated light modular radiant heating system:Thermal resistance analysis and numerical study

The utilization of prefabricated light modular radiant heating system has demonstrated significant increases in heat transfer efficiency and energy conservation capabilities.Within prefabricated building construction,this new heating method presents an opportunity for the development of comprehensive facilities.The parameters for evaluating the effectiveness of such a system are the upper surface layer’s heat flux and temperature.In this paper,thermal resistance analysis calculation based on a simplified model for this unique radiant heating system analysis is presented with the heat transfer mechanism’s evaluation.The results obtained from thermal resistance analysis calculation and numerical simulation indicate that the thermal resistance analysis method is highly accurate with temperature discrepancies ranging from 0.44℃ to−0.44℃ and a heat flux discrepancy of less than 7.54%,which can meet the requirements of practical engineering applications,suggesting a foundation for the prefabricated radiant heating system.

1.3μm AlInGaAs Strained Single Quantum Well Laser Diodes with High Characteristic Temperature of 200K

A high characteristic temperature （T0） of 200K from a 1.3μm AlInGaAs/AlInAs single-quantum-well laser diode with the asymmetric waveguide layer structure under CW operation at 20 to 80℃ was obtained,which is the best result reported in the laser diodes （LDs） of the same active materials structure and emitting wave- length. AllnGaAs as an active layer,therefore,is very promising for the fabrication of long-wavelength LDs with excellent high-temperature performance. It is found that the asymmetric waveguide layer structure can decrease optical absorption and improve the high-temperature performance and catastrophic optical damage threshold of LDs.

A CMOS Voltage Reference Based on V_(GS) and ΔV_(GS) in the Weak Inversion Region

A CMOS voltage reference, which is based on VGs and/x ΔGS in the weak inversion region, has been designed and implemented in standard 0.6μm CMOS technology. No diodes and parasitic bipolar junction transistors （BJTs） are used. The proposed voltage reference uses a current-mode topology by summing a PTAT current and a CTAT current into a re- sistor to generate the required reference voltage. It can also provide more than one reference voltage output, which is quite suitable for systems requiring many different reference voltages simultaneously. The occupied chip area is 0. 023mm^-2 . The operation supply voltage is from 2.5 to 6V, and the maximum supply current is 8.25μA. The designed three different out- puts are respectively about 203mV, 1.0V, and 2.05V at room temperature when the supply voltage is 4V. The circuit achieves a temperature coefficient of 31ppm/℃ in the temperature range of 0 to 100℃ and an average line regulation of ± 0. 203%/V. The voltage reference has been successfully applied in a white LED backlight driver chip.

Material Growth and Device Fabrication of GaN-Based Blue-Violet Laser Diodes

Studies on first GaN-based blue-violet laser diodes(LDs) in China mainland are reported.High quality GaN materials as well as GaN-based quantum wells laser structures are grown by metal-organic chemical vapor deposition method.The X-ray double-crystal diffraction rocking curve measurements show the full-width half maximum of 180″ and 185″ for (0002) symmetric reflection and (10 12) skew reflection,respectively.A room temperature mobility of 850cm2/(V·s) is obtained for a 3μm thick GaN film.Gain guided and ridge geometry waveguide laser diodes are fabricated with cleaved facet mirrors at room temperature under pulse current injection.The lasing wavelength is 405 9nm.A threshold current density of 5kA/cm2 and an output light power over 100mW are obtained for ridge geometry waveguide laser diodes.

Research on Drainage Network Extraction in Liaohe Basin Based on SRTM DEM and ASTER GDEM

In this study,SRTM DEM data and ASTER GDEM data were used as the basic topographic data,and Arc Hydro Tools was utilized for extension module so as to study on extracting digital drainage network of watershed based on surface runoff model,as well as to compare the two extracted results.The result showed that through the introduction of drainage density parameter to determine the river drainage area threshold,the both extracted drainages showed the goodness-of-fit with the factual drainage network on 1∶250 000 scale topographic map,and the extracted digital river could be used in practical operation of the risk assessment model of mountain torrents disaster in Liaohe basin.

建筑垃圾粉土对水泥砂浆性能影响的研究

本研究采用正交试验法,开展建筑废弃物的再利用和绿色环保新材料的研发。试验中,将建筑垃圾破碎过筛筛选出细度小于75μm的粉土掺入水泥砂浆,探讨掺量对其抗压强度和流度值的影响。结果表明,水灰比和粉土掺量都会影响水泥砂浆流度值和抗压强度。建筑垃圾粉土掺量相同时,水泥砂浆的流度值随水灰比的增加而增大;水灰比相同时,水泥砂浆的抗压强度随建筑垃圾粉土掺量增加而降低;当建筑垃圾粉土掺量相同时,水泥砂浆的最佳水灰比在0.5~0.6取值。

不同水尾土取代比例对水泥砂浆强度的影响

本研究以垃圾焚化炉融渣细粒料作为主要试验材料,筛选出融渣细粒料中粒径<75μm的粉料(俗称水尾土),然后添加不同比例的水尾土取代水泥含量制作砂浆,并且使用不同水灰比研究水泥浆体流度值及抗压强度的变化。实验结果表明,使用相同水灰比时添加水尾土于水泥中取代其含量后其水泥浆体流动性变高,并且随着水尾土取代水泥含量比例增加,其水泥浆体流度值上升。但使用水尾土取代水泥含量后不能有效地使水泥浆体包裹粒料进而提升抗压强度。

Numerical prediction of vortex flow and thermal separation in a subsonic vortex tube

This work was aimed at gaining understanding of the physical behaviours of the flow and temperature separation process in a vortex tube. To investigate the cold mass fraction’s effect on the temperature separation, the numerical calculation was carried out using an algebraic Reynolds stress model (ASM) and the standard k-ε model. The modelling of turbulence of com-pressible, complex flows used in the simulation is discussed. Emphasis is given to the derivation of the ASM for 2D axisymmet-rical flows, particularly to the model constants in the algebraic Reynolds stress equations. The TEFESS code, based on a staggered Finite Volume approach with the standard k-ε model and first-order numerical schemes, was used to carry out all the computations. The predicted results for strongly swirling turbulent compressible flow in a vortex tube suggested that the use of the ASM leads to better agreement between the numerical results and experimental data, while the k-ε model cannot capture the stabilizing effect of the swirl.

Effects of temperatures and pH values on rheological properties of cemented paste backfill

In this study,different influence mechanisms associated with temperatures and pH values were investigated through cemented paste backfill(CPB)systems.CPB samples were prepared with temperatures ranging from 10 to 50℃ in 10℃ increments and pH values of 3,7,and 13.Then,the CPB mixture were subjected to rheological tests,thermogravimetric analysis(TG),derivative thermogravimetry analysis(DTG),Fourier-transform infrared spectroscopy(FT-IR),and scanning electron microscopy(SEM).Results demonstrated that the temperatures had significant effects on the rheological properties of CPB,whereas the effects of pH values were relatively unapparent.Higher temperatures(over 20℃)were prone to bring higher shear stress,yield stress,and apparent viscosity with the same pH value condition.However,an overly high temperature(50℃)cannot raise the apparent viscosity.Non-neutral conditions,for pH values of 3 and 13,could strengthen the shear stress and apparent viscosity at the same temperature.Two different yield stress curves could be discovered by uprising pH values,which also led to apparent viscosity of two various curves under the same temperatures(under 50℃).Microscopically,rheological properties of CPB were affected by temperatures and pH values which enhanced or reduced the cement hydration procedures,rates,products and space structures.

Relationship between the transition frequency of local fluid flow and the peak frequency of attenuation

Local fluid flow（LFF） at the mesoscopic scale is the main dissipation mechanism of seismic waves in heterogeneous porous media within the seismic frequency band.LFF is easily influenced by the structure and boundary conditions of the porous media,which leads to different behaviors of the peak frequency of attenuation.The associated transition frequency can provide detailed information about the trend of LFF;therefore,research on the transition frequency of LFF and its relationship with the peak frequency of the corresponding attenuation（i.e.,inverse of quality factor） facilitates the detailed understanding of the effect of inner structures and boundary conditions in porous media.In this study,we firstly obtain the transition frequency of fluid flux based on Biot＇s theory of poroelasticity and the fast Fourier transform algorithm in a sample containing one repeating unit cell（RUC）.We then analyze changes of these two frequencies in porous media with different porous properties.Finally,we extend our analysis to the influence of the undrained boundary condition on the transition frequency and peak frequency in porous media with multiple RUCs.This setup can facilitate the understanding of the effect from the undrained boundary condition.Results demonstrate that these two frequencies have the same trend at low water saturation,but amplitude variations differ between the frequencies as the amount of saturation increases.However,for cases of high water saturation,both the trend and the amplitude variation of these two frequencies fit well with each other.

Brezis-Nirenberg Theorem on Non_compact Sets

In present paper we prove that on non_compact sets the conclusion in the Brezis_Nirenberg Theorem is also true.

Numerical simulation on melt flow with bubble stirring and temperature field in aluminum holding furnace

The numerical model for predicting the flow and temperature fields of the melt in holding furnace with porous brick purging system were set up using Euler-Lagrange approach.In this model,bubbles coalescence and disintegration were ignored based on the dimensionless analysis,and the bubble size was assumed to be obedient to Rosin-Rammler distribution with a mean size of 0.6 mm.The results show that on reference operating condition,during the heating and agitation process,melt mixes well in the furnace,and the melt velocity increases with the increase of gas flux.Holding the melt for 30 min causes the max temperature in the bulk melt to increase to 60 K.After holding the heat,the agitation processing restarts,and it takes 10 min for the stratified melt to retrieve the homogeneous temperature field when the gas flux is 10 L/min,which shows deficient alloying and degassing in the melt.With the increase of gas flux from 10 to 20,30 and 40 L/min,the necessary recovery time decreases from 10 to 6,5 and 4 min gradually,which shows the improvement of the stirring efficiency.Depending on the processing purposes,for both good degassing performance and gas saving,proper operating strategy and parameters (gas flux,primarily) could be adjusted.

Characteristics of Clustering Debris Flows in Wenchuan Earthquake Zone

Clustering debris-flow events, namely many debris flows simultaneously triggered by a regional rainstorm in a large-scale mountainous area,occurred in four regions of Wenchuan earthquake stricken areas in 2008 and 2010. The characteristics of the clustering debris flows are examined with regard to triggering rainfall, formation process, and relationship with the earthquake by field survey and remote sensing interpretation. It is found that the clustering events occurred nearly at the same time with the local peak rainstorms, and the rainfall intensity-duration bottom limit line for clustering debris flows is higher than the worldwide line. It means that more rainfall is needed for the occurrence of the clustering debris flows. Four kinds of major formation processes for these debris flows are summarized: tributary-dominated, mainstreamdominated, transformation from slope failures, and mobilization or liquefaction of landslide. The four regions has a spatial correlation with the strongquake-influenced zone with the peak ground acceleration = 0.2 g and the seismic intensity > X.

Numerical Simulation of Torrential Rainfall and Vortical Hot Towers in a Midlatitude Mesoscale Convective System

A cloud-resolving model simulation of a mesoscale convective system （MCS） producing torrential rainfall is performed with the finest horizontal resolution of 444 m. It is shown that the model reproduces the observed MCS, including its rainfall distribution and amounts, as well as the timing and location of leading rainbands and trailing stratiform clouds. Results show that discrete convective hot towers, shown in Vis5D at a scale of 2-5 kin, are triggered by evaporatively driven cold outflows converging with the high-θe air ahead. Then, they move rearward, with respect to the leading rainbands, to form stratiform clouds. These convective towers generate vortical tubes of opposite signs, with more intense cyclonic vorticity occurring in the leading convergence zone. The results appear to have important implications for the improvement of summertime quantitative precipitation forecasts and the understanding of vortical hot towers, as well midlevel mesoscale convective vortices.

Effects of Gas Flow Field on Clogging Phenomenon in Close-Coupled Vortical Loop Slit Gas Atomization

In order to study the basic characteristics of gas flow field in the atomizing chamber near the nozzle outlet of the vortical loop slit atomizer and its influence mechanism on clogging phenomenon,the computational fluid dynamics(CFD)software Fluent is used to conduct a numerical simulation of the gas flow field in the atomizing chamber near the nozzle outlet of this atomizer under different annular slit widths,different atomization gas pressures and different protrusion lengths of the melt delivery tube. The results show that under atomization gas pressure p=4.5 MPa,the greater the annular slit width D,the lower the static temperature near the central hole outlet at the front end of the melt delivery tube,and the smaller the aspirating pressure at the front end of the melt delivery tube. These features can effectively prevent the occurrence of the clogging phenomenon of metallic melt. Under an annular slit width of D=1.2 mm,when the atomization gas pressure satisfies 1 MPa ≤ p ≤ 2 MPa and increases gradually,the aspirating pressure at the front end of the melt delivery tube will decline rapidly. This can prevent the clogging phenomenon of metallic melt. However,when the atomization gas pressure p >2 MPa,the greater the atomization gas pressure,the lower the static temperature near the central hole outlet at the front end of the melt delivery tube,and the greater the aspirating pressure at the front end of the melt delivery tube. Hence,the effect of preventing the solidification-induced clogging phenomenon of metallic melt is restricted. When atomization gas pressure is p =4.5 MPa and annular slit width is D=1.2 mm,the greater the protrusion length H of the melt delivery tube,and the smaller the aspirating pressure at its front end. The static temperature near the central hole that can be observed in its front end is approximate to effectively prevent the occurrence of clogging phenomenon of metallic melt. However,because of the small aspirating pressure,the metallic melt flows into the atomizing chamber from the central hole at the front end of the melt delivery tube at an increasing speed and the gas-melt ratio in the mass flow rate is reduced,which is not conducive to the improvement of atomization performance.

Investigation of Barree-Conway non-Darcy flow effects on coalbed methane production

Coalbed gas non-Darcy flow has been observed in high permeable fracture systems,and some mathematical and numerical models have been proposed to study the effects of non-Darcy flow using Forchheimer non-Darcy model.However,experimental results show that the assumption of a constant Forchheimer factor may cause some limitations in using Forchheimer model to describe non-Darcy flow in porous media.In order to investigate the effects of non-Darcy flow on coalbed methane production,this work presents a more general coalbed gas non-Darcy flow model according to Barree-Conway equation,which could describe the entire range of relationships between flow velocity and pressure gradient from low to high flow velocity.An expanded mixed finite element method is introduced to solve the coalbed gas non-Darcy flow model,in which the gas pressure and velocity can be approximated simultaneously.Error estimate results indicate that pressure and velocity could achieve first-order convergence rate.Non-Darcy simulation results indicate that the non-Darcy effect is significant in the zone near the wellbore,and with the distance from the wellbore increasing,the non-Darcy effect becomes weak gradually.From simulation results,we have also found that the non-Darcy effect is more significant at a lower bottom-hole pressure,and the gas production from non-Darcy flow is lower than the production from Darcy flow under the same permeable condition.

Numerical investigation of flow pattern and components of three-dimensional velocity around a submerged T-shaped spur dike in a 90° bend

Spur dike is one of the river training structures. This work presented a numerical simulation of flow field and three-dimensional velocity around a T-shaped spur dike located in bend using SSIIM model. The main objective of this work is to investigate the three-dimensional velocities and streamlines at transverse and longitudinal sections and plan views around the T-shaped spur dike in different submergence ratios(0, 5%, 15%, 25% and 50%). It is concluded that by increasing the submergence ratio from 5% to 50%, the maximum of scour is reduced; the maximum of longitudinal velocity increases by 7.7% and occurs at the water surface in spur dike axis. Near the bed, the maximum of vertical velocity occurs at the end of spur wing. By analyzing the streamlines at transverse sections, the followings were deduced for different submergence ratios: different dimensions and different positions of vortices around the spur dike.

Study on the Rainfall and Aftershock Threshold for Debris Flow of Post-earthquake

Due to the special condition of provenance and disaster environment after "5·12" Earthquake, the probability and conditions of the occurrence of gully debris flow change greatly after the event, which make it difficult to prevent disaster effectively. In this study the hydrological model of ground water table in loose sediment is established. According to infinite slope theory, the safety factor of deposits is defined as the ratio of resistance force to driving force. The starting condition of post-earthquake gully debris flow is clearly studied by analyzing the effects of rainfall intensity, seismic strength, slope gradient and mechanical properties on the balance of accumulation body. Then the formulas of rainfall and aftershock threshold for starting of gully debris flow are proposed, and an example is given to illustrate the effect of rainfall, aftershocks and their coupling action on a debris flow. The result shows the critical rainfall intensity decreases as the lateral seismic acceleration and channel gradient increases, while the critical intensity linearly increases as the friction angle increases.

Preoperative predictors of portal vein thrombosis after splenectomy with periesophagogastric devascularization

AIM:To evaluate the predictive value of preoperative predictors for portal vein thrombosis(PVT)after splenectomy with periesophagogastric devascularization.METHODS:In this prospective study,69 continuous patients with portal hypertension caused by hepatitis B cirrhosis underwent splenectomy with periesophagogastric devascularization in West China Hospital of Sichuan University from January 2007 to August 2010.The portal vein flow velocity and the diameter of portal vein were measured by Doppler sonography.The hepatic congestion index and the ratio of velocity and diameter were calculated before operation.The prothrombin time(PT)and platelet(PLT)levels were measured before and after operation.The patients'spleens were weighed postoperatively.RESULTS:The diameter of portal vein was negatively correlated with the portal vein flow velocity(P<0.05).Thirty-three cases(47.83%)suffered from postoperative PVT.There was no statistically significant difference in the Child-Pugh score,the spleen weights,the PT,or PLT levels between patients with PVT and without PVT.Receiver operating characteristic curves showed four variables(portal vein flow velocity,the ratio of velocity and diameter,hepatic congestion index and diameter of portal vein)could be used as preoperative predictors of postoperative portal vein thrombosis.The respective values of the area under the curve were 0.865,0.893,0.884 and 0.742,and the respective cut-off values(24.45 cm/s,19.4333/s,0.1138 cm/s-1 and 13.5 mm) were of diagnostically efficient,generating sensitivity values of 87.9%,93.9%,87.9%and 81.8%,respectively,specificities of 75%,77.8%,86.1%and 63.9%,respectively.CONCLUSION:The ratio of velocity and diameter was the most accurate preoperative predictor of portal vein thrombosis after splenectomy with periesophagogastric devascularization in hepatitis B cirrhosis-related portal hypertension.

Macro modeling and analysis of traffic flow with road width

The macro modeling and the solution of traffic flow with road width were investigated.Firstly,a new macro model with the consideration of road width was proposed.Secondly,the effects of road width on uniform flow and small perturbation were studied.The analytical and numerical results show that widening (shrinking) road can enhance (reduce) the equilibrium speed and flow,and the increments (decrements) will increase with the absolute value of road width gradient.In addition,the numerical results illustrate that the new model can describe the effects of road width on the evolutions of uniform flow and small perturbation.