表面组装PCB焊盘图形的设计与布排

本文介绍了各种ＳＭＤ在ＰＣＢ上的焊盘设计及其布排等一系列经验性数据。表面焊装工艺不同，其焊盘的尺寸就不同。

关于确定真空预压施工中滤水管间距及布排形式的探讨

本文应用渗透排水理论建立相关的公式,来确定真空预压加固软土地基施工中的滤水管的布设间距及布排形式,使该问题由长期的定性化转为合理的定量化,以期更好地指导施工获得预期的加固效果。

锻模型槽组合布排与模锻技术简化

模锻件锻模型槽组合布排，是指对两个以上的模锻件在锻模型槽中合理地进行布排的方法。根据实践，把模锻件锻模型槽组合布排分为轴线平行错位布排法；轴线重合对称布排法；轴线倾斜对称错位布排法及多件连续布排法等……方法。简化了模锻技术并取得了明显的经济效果。

从黄山谷看书法艺术的继承与创新

进入新时期以来,与整个文化艺术界一样,我国书法艺术有了空前规模的繁荣和发展。其群众之广泛,活动之频繁,视野之开阔,创新意识之强烈,心态之自由,时代色彩之鲜明,……都是史无前例的,真正出现了“书道振兴”的大好形势。但是,当我们对这种社会的“书法热”现象.冷静地加以理性的观照和反思时,就会令人忧虑地发现,其中不无某种急功近利,华而不实的特点。有的人一听到“创新”“现代派”字眼就摇头,视若洪水猛兽;

EXPERIMENTAL STUDY OF HTC FOR FILM COOLING OF PARALLEL-INLET HOLES

The parallel-inlet holes with one-row, two-row and three-row film hole arrangements and different di- ameters are proposed to experimentally study their cooling characteristics. Detailed experimental processes and results are described and carried out. Results indicate that heat transfer coefficient （HTC） is increased with the increase of blowing ratio. When the blowing ratio is lower, the distribution of HTC along the heated wall can be divided into three regions. For larger blowing ratio or diameter, the cooling characteristics oi parallel-inlet film holes are similar to those of convective heat transfer around flat. Furthermore, when hole diameter is deter- mined, the arrangement patterns of film hole and the blowing ratio take a great influence on HTC.

铝合金模板体系设计及结构力学研究

为解决现有铝合金模板在结构设计及布排设计方面存在的诸多问题,现需研发一种结构合理、满足施工安全要求、方便施工的新型铝合金模板体系;并依托切实可靠的结构力学研究及相关实验数据,保证模板体系的先进性和安全性。通过对布排方法的研究及新型三维布排软件的不断应用和探索,克服现有铝合金模板布排应用时的诸多难题。

The Structural Transformation of Nucleolar DNA and Its Arrangement in Nucleolus of Allium cepa Cells

By using the DNA specific cytochemical staining method (NAMA_Ur) and conventional electron microscopic technique, the authors examined the configuration of intranucleolar DNA in Allium cepa L. cells and found that nucleolar DNA within the fibrillar center (FC) underwent a structural transformation process from condensed to extended state. The authors' observations also displayed a continuous arrangement process of nucleolar DNA, i.e., the extranucleolar DNA entered FC through the nucleolar organizer region (NOR) channel, then extended to the periphery of FC or to the border between FC and dense fibrillar component (DFC), and distributed along the periphery of FC. Thence, by passing through the NOR channel between FCs, the nucleolar DNA continued to transfer to other FCs and arranged in the same above_mentioned forms.

Data-Path Placement Based on Regularity Extraction and Implementation

An algorithm named DPP is addressed.In it,a new model based on the concept of irregularity degree is founded to evaluate the regularity of cells.It generates the structure regularity of cells by exploiting the signal flow of circuit.Then,it converts the bit slice structure to parallel constraints to enable Q place algorithm.The design flow and the main algorithms are introduced.Finally,the satisfied experimental result of the tool compared with the Cadence placement tool SE is discussed.

Tissue distribution,excretion and pharmacokinetics of R-hap in rats

The purpose of this study is to characterize the tissue distribution, excretion and pharmacokinetics profiles of R-hap in healthy Wistar rats. R-hap was radiolabeled by the IODO-GEN method. Tissue distribution and urinary, fecal and biliary excretion patterns of ^125I-R-hap were investigated following a single i.v. bolus injection. Pharmacokinetics properties of ^125I-R-hap were also examined after a single i.v. bolus injection. The trichloroacetic acid （TCA） precipitated radioactivity was widely distributed and rapiclly diminished in most tissues. Kidney contained the highest radioactivity among all organs and the distribution of ^125I-R-hap to fat was minimal. The cumulative excretion of ^125I-R-hap reached 71.81% ± 2.15% of the administered radioactivity at 48 h and 94.71% ± 1.50% at 120 h. Urinary excretion was the dominant route of elimination following i.v. administration, as 80.64% ± 1.47% and 14.07% ± 0.95% of administered radioactivity were recovered in urine and feces, respectively, in intact rats over 120 h. The mean areas under the plasma concentration-time curve was （8818.4 ± 576.1） Bq/h/mL. The results of tissue distribution, excretion and pharmacokinetics of R-hap in rats provided biopharmaceutical basis for the design of future clinical trials.

ANALYSIS ON A TYPE OF SERVICING MACHINES MODEL WITH REPAIRABLE SERVICE STATION

This paper deals with a type of servicing machines model, which service station has a life time of the kth Er-langian distribution and can be repaired just like a new one. The cyclic time and the inefficiency quantities of this system in equilibrium are obtained.

Drainage performance and capillary rise restraint effect of wicking geotextile

Wicking geotextile(WG)is considered as a possible countermeasure to reduce water content in unsaturated soil.In this research,rainfall tests were carried out to verify the drainage performance of WG.And capillary rise tests were conducted to study the effect of WG on the prevention of capillary rise.Test results indicated that WG with good drainage performance could drain gravitational and capillary water out of kaolinite soil.For kaolinite soil column with water content of 12%and compaction degree of 90%,the whole process of capillary rise in soil column with a layer of WG was a typical two-stage mode,and the maximum capillary height was about 380 mm,which provided that the WG could work as a barrier to prevent capillary rise effectively.In addition,the total vertical influential regions of WG in kaolinite soil above and below the WG layer were 400 and 100 mm,respectively.

Electric field distribution in 75 kA drained aluminum reduction cell

Current distribution in a drained aluminum reduction cell is critical due to its influence on the current efficiency, electrolysis stability, anodes and cathodes integrity. A finite element model was developed to simulate the electric field in a 75 kA drained aluminum reduction cell. The current distribution and influences of the cathode inclination angle and anode-cathode distance (ACD) were studied. The results show that relatively large horizontal current density appears in the aluminum film, and the maximum value reaches 600 kA/m2. As the cathode inclination angle increases from 2° to 15°, the maximum current density of the metal pad increases by 15%, while the maximum current density of the aluminum-wettable coating layer decreases by 27%. The influence of the ACD on the current distribution is not obvious.

Combustion and emission characteristics of diesel/n-butanol blends with split-injection and exhaust gas recirculation stratification

Oxygen fuels have broad application prospects and great potential for realizing efficient and clean combustion,and hence this study applies diesel/n-butanol blends to explore the influence of split-injection strategy on combustion and emission characteristics.Simultaneously,changing the way of exhaust gas recirculation(EGR)gas introduction forms uneven in-cylinder components distribution,and utilizing EGR stratification optimizes the combustion process and allows better emission results.The results show that the split-injection strategy can reduce the NO_(x)emissions and keep smoke opacity low compared with the single injection,but the rise in accumulation mode particles is noticeable.NO_(x)emissions show an upward trend as the injection interval expands,while soot emissions are significantly reduced.The increase in pre-injection proportion causes the apparent low-temperature heat release,and the two-stage heat release can be observed during the process of main combustion heat release.More pre-injection mass makes NO_(x)gradually increase,but smoke opacity reaches the lowest point at 15%pre-injection proportion.EGR stratification can optimize the emission results under the split injection strategy,especially the considerable suppression of accumulation mode particulate emissions.Above all,fuel stratification coupled with EGR stratification is beneficial for further realizing the in-cylinder purification of pollutants.

Exploring the phytoconstituents targeting TNF-αas potential lead compounds to treat inflammatory diseases:an in-silico approach

Objective To explore the anti-inflammatory phytoconstituents from various plant sources as tumour necrosis factor-α(TNF-α)-inhibitor,a mediator involved in the inflammatory disorder,by in silico molecular docking.Methods Based on previous findings,we performed the in silico assessment of anti-inflammatory phytoconstituents from different medicinal plants to understand their binding patterns against TNF-α(PDB ID:6OP0)using AutoDock Vina.Molecular docking was performed by setting a grid box(25×25×25)Åcentered at[-12.817×(-1.618)×19.009]A with 0.375A of grid spacing.Furthermore,Discovery Studio Client 2020 program was utilized to assess two-and three-dimensional(2D and 3D)hydrogen-bond interactions concerning an amino acid of target and ligand.Physicochemical properties were reported using the Lipinski’s rule and SwissADME database to support the in silico findings.Results From the selected medicinal plants,more than 200 phytocompounds were screened against TNF-α protein with binding scores in the range of -12.3 to -2.5 kcal/mol.Amongst them,emodin,aloe-emodin,pongamol,purpuritenin,semiglabrin,ellagic acid,imperatorin,α-tocopherol,and octanorcucurbitacin A showed good binding affinity as -10.6,-10.0,-10.5,-10.1,-11.2,-10.3,-10.1,-10.1,and -10.0 kcal/mol,respectively.Also,the absorption,distribution,metabolism,excretion,and toxicology(ADMET)profiles were well within acceptable limits.Conclusion Based on our preliminary findings,we conclude that the selected phytoconstituents have the potential to be good anti-inflammatory candidates by inhibiting the TNF-α target.These compounds can be further optimized and validated as new therapeutic components to develop more effective and safe anti-inflammatory drugs.

Study on the Regional Distribution of Energy Efficiency from the Point of Pollutant Emissions

In this paper, the author uses super-efficiency DEA model to measure the national and regional energy efficiency in China; using spatial econometric model and from the perspective of geo-spatial spillover, the author interprets the spatial characteristies of energy efficiency and extracts the main factors that influ- ence the regional energy efficiency. The analysis results show that： （1） the national and regional energy efficiency is consistent with inverted U-shaped curve, and the nationwide energy efficiency gap is increasing; （2） energy efficiency has the obvious effect of the spatial external effect, and when the government makes energy saving strategies, inter-regional energy cooperation and the prolif- eration of advanced production technology should be given more priority; （3） energy efficiency has significant negative correlation with government intervention, industrial structure, ownership structure, the energy consumption structure, and resource endowments, and has positive correlation with the degree of opening-up and energy price.

Simulation of CO_2 Brayton Cycle for Engine Exhaust Heat Recovery under Various Operating Loads

A bottoming cycle system based on CO2 Brayton cycle is proposed to recover the engine exhaust heat. Its performance is compared with the conventional air Brayton cycle under five typical engine conditions. The results show that CO2 Brayton cycle proves to be superior to the air Brayton cycle in terms of the system net output power, thermal efficiency and recovery efficiency. In most cases, the recovery efficiency of CO2 Brayton cycle can be higher than 9% and the system has a better performance at the engine＇s high operating load, The thermal efficiency can be as large as 24.83% under 100% olaerating load, accordingly, the net outnut nower of 14.86 kW in nhtnined

Estimation of Ordered Means of Two Normal Distributions with Ordered Variances

The authors consider the problem of estimating the ordered means of two normal distributions with unknown ordered variances. The authors discuss the estimation of two ordered means, individually, in terms of stochastic domination and MSE （mean squared error）. The authors show that in estimating the mean with larger variance, the usual estimator under order restriction on means can be improved upon. However, in estimating the mean with smaller variance, the usual estimator can＇t be improved upon even under MSE. The authors also discuss simultaneous estimation problem of two ordered means when unknown variances are ordered.

In-Situ Observation of Co Rearrangement of Near-Surface Skin Layer in Al70Ni15Co15 Quasicrystal

Using anomalous X-ray scattering, kinetics of X-ray diffuse scattering in an Al70Ni15Co15 decagonal quasicrystal was investigated at fixed temperature （807℃）. Short-range order diffuse scattering from the single quasicrystal disappeared gradually on time scale. At the same time, some extra weak Debye rings appeared near the Bragg reflection. The volume of the polycrystallization is quite small due from the intensity ratio of weak powder patterns to the Bragg reflection. The extremely weak Debye rings were observed only near the Co K-edge. By the Co enhancement using anomalous X-ray scattering, we might probe the local movement of Co atoms in the skin layer as well as Al enrichment and Co depletion on the surface of decagonal Al65Co20Cu15.

Effect of single dead end entry inclination on DPM plume dispersion

Diesel particulate matter(DPM) is a by-product from operating diesel engines. Since diesel powers are one of the major sources of energy for mobile underground mining equipment, the adverse health effects of DPM are of a great concern. This paper used computational fluid dynamics(CFD) method to study the effect of entry inclination on DPM plume distribution in a dead end entry. An upward mining face and a downward mining face were built with a truck and a loader in loading operation close to the face area. A species transport model with incorporated buoyancy effect was used to examine the DPM dispersion pattern for the above steady-state scenarios. High DPM and temperature regions were identified for the two different faces. The model was used to assess the role of auxiliary ventilation in reducing DPM exposures of underground miners working in those entries. In this study, it is suggested to provide local ventilation at least three times of the diesel exhaust rate to be able to lower the average DPM level for the mining upward face. The requirement for local ventilation is much less for the mining downward face. This can provide guidelines for good working practices and selection of diesel emission reduction technologies underground.

Security in gas discharge while unsealing a closed stope

Given the problem of harmful gas discharge in unsealing coal mining faces, we numerically simulated the process of change of gas flows and movements, We have pointed out that, at the moment of unsealing a closed stope, the gas discharge is naturally divided into two parts, i.e., the discharge of gas in the working face and that in the goaf, because of the difference in the spatial medium. The absolute volume of gas discharged has a tendency to decrease from its initial peak value to a final stable value. The rate of decrease and the time needed to reach a stable discharge are related to the scale of the mining stope. The discharge of gas from the working face is closely related to the amount of air distributed in the air return way. The most important thing in unsealing a stope is to have the initial peak volume of gas discharged well under control. A commonly used method in solving this problem is at first to use a small amount of air and then increasing it gradually. Our study shows that, by extracting gas from the upper corner, we can use a large volume of air at first in order to shorten considerably the discharge time and improve efficiency, thereby making mining, activitv safer.