挖掘机木材抓改造优化码垛起高作业工艺

木材场木材的木垛作业能够有效地提升整个场地的使用效率,同时能够为后期木材的使用提供方便。为了更好地进行码垛工作我们对挖掘机在堆放中所应用到的各类构件进行了优化,进而有效地提升挖掘机在木材场码垛工作中的效率,同时能够依据不同的木材的需求和特点,制定相应的作业标准和要求,进一步提升整个码垛作业的规范,提升码垛起高作业的操作工艺,实现提升木材场地使用率的目的。

超高功率电炉电极消耗分析

文章结合淮钢70t超高功率电炉电极消耗情况,分析了影响超高功率电炉电极消耗的因素,提出了降低电极消耗的措施和途径。

正立方超高分辨CI——一种新的用于颞下颌关节的X线影像技术

正立方超高分辨CT(Ortho-CT)是一种最新开发的高精度骨扫描图像技术。本文旨在介绍Ortho-CT及其在评价颞下颌关节骨病变中的应用。 材料和方法 Ortho-CT装置如图1所示。用一个4英时的图像增强仪代替胶片,在一个底面直径为38mm、高为32mm的圆柱体上进行360°扫描为重建图像采集数据。投照条件:85kV、10mA、17s,用1.2mm Cu滤片。

不同起垄方式及覆膜对烤烟生长发育和产质的影响

运用前期氮素调控措施(提前起高垄和覆膜)对烤烟生长发育和产质的影响进行了试验。结果表明,采用高茎壮苗提前起高垄覆膜深栽,土壤有机氮提前矿化和释放,烟株提前形成较多的根系,烤烟提前吸收养分,能提前实现早生快发,提高烟叶产量;在烤烟生长后期,植烟土壤氮素供应的减少及烤烟根系活力的减弱,避免烤烟后期生长过旺,降低了上部烟叶的烟碱含量。

Simulation of Start-Up Process of Turbofan Engine Based on Full-State Characteristics of Fan

Difficulties in obtaining component characteristics in the sub-idle state of rotor constrain the simulation capabilities of ground and windmill start-up processes for turbofan engines.This paper proposes a backbone feature method based on conventional characteristics parameters to derive the full-state characteristics of fan.The application of the fan’s full-state characteristics in component-level model of turbofan engine enables zero-speed iterative simulation for ground start-up process and windmill simulation for windmill start-up process,thereby improving the simulation capability of sub-idle state during turbofan engine start-up.

Assessing the Impacts of Initial Snow Conditions over the Tibetan Plateau on China Precipitation Prediction Using a Global Climate Model

Two ensemble experiments were conducted using a general atmospheric circulation model. These experiments were used to investigate the impacts of initial snow anomalies over the Tibetan Plateau(TP) on China precipitation prediction. In one of the experiments, the initial snow conditions over the TP were climatological values; while in the other experiment, the initial snow anomalies were snow depth estimates derived from the passive microwave remote-sensing data. In the current study, the difference between these two experiments was assessed to evaluate the impact of initial snow anomalies over the TP on simulated precipitation. The results indicated that the model simulation for precipitation over eastern China had certain improvements while applying a more realistic initial snow anomaly, especially for spring precipitation over Northeast China and North China and for summer precipitation over North China and Southeast China. The results suggest that seasonal prediction could be enhanced by using more realistic initial snow conditions over TP, and microwave remote-sensing snow data could be used to initialize climate models and improve the simulation of eastern China precipitation during spring and summer. Further analyses showed that higher snow anomalies over TP cooled the surface, resulting in lower near- surface air temperature over the TP in spring and summer. The surface cooling over TP weakened the Asian summer monsoon and brought more precipitation in South China in spring and more precipitation to Southeast China during summer.

Sildenafil does not influence hepatic venous pressure gradient in patients with cirrhosis

AIM： To investigate if sildenafil increases splanchnic blood flow and changes the hepatic venous pressure gradient （HVPG） in patients with cirrhosis. Phosphodiesterase type-5 inhibitors are valuable in the treatment of erectile dysfunction and pulmonary hypertension in patients with end-stage liver disease. However, the effect of phosphodiesterase type-5 inhibitors on splanchnic blood flow and portal hypertension remains essentially unknown. METHODS： Ten patients with biopsy proven cirrhosis （five females/five males, mean age 54：1：8 years） and an HVPG above 12 mmHg were studied after informed consent. Measurement of splanchnic blood flow and the HVPG during liver vein catheterization were done before and 80 min after oral administration of 50 mg sildenafil. Blood flow was estimated by use of indocyanine green clearance technique and Fick＇s principle, with correction for non-steady state. RESULTS： The plasma concentration of sildenafil was 222 ± 136 ng/mL 80 min after administration. Mean arterial blood pressure decreased from 77 ±7 mmHg to 66 ± 12 mmHg, P = 0.003, while the splanchnicblood flow and oxygen consumption remained unchanged at 1.14 ± 0.71 L/min and 2.3 ± 0.6 mmol/ min, respectively. Also the HVPG remained unchanged （18 ± 2 mmHg vs 16 ± 2 mmHg） with individual changes ranging from -8 mmHg to ±2 mmHg. In seven patients, HVPG decreased and in three it increased. CONCLUSION： In spite of arterial blood pressure decreases 80 min after administration of the phosphodiesterase type-5 inhibitor sildenafil, the present study could not demonstrate any clinical relevant influence on splanichnic blood flow, oxygen consumption or the HVPG.

Numerical model for homogeneous cohesive dam breaching due to overtopping failure

Based on the large-scale model tests, a simplified dam breach model for homogeneous cohesive dam due to overtopping failure is put forward. The model considers headcut erosion as one of the key homogeneous cohesive dam breaching mechanisms and we calculate the time-averaged headcut migration rate using an energy-based empirical formula. A numerical method is adopted to determine the initial scour position at the downstream slope in terms of the water head and dam height, and the broad-crested weir equation is utilized to simulate the breach flow. The limit equilibrium method is used to analyze the stability of breach slope during the breach process. An iterative method is developed to simulate the coupling process of soil and water at each time step. The calculated results of three dam breach cases testify the reasonability of the model, and the sensitivity studies of soil erodibility show that sensitivity is dependent on each test case's soil conditions. In addition, three typical dam breach models, NWS BREACH, WinDAM B, and HR BREACH, are also chosen to compare with the proposed model. It is found that NWS BREACH may have large errors for cohesive dams, since it uses a noncohesive sediment transport model and does notconsider headcut erosion, WinDAM B and HR BREACH consider headcut erosion as the breaching mechanism and handle well homogeneous cohesive dam overtopping failure, but overall, the proposed model has the best performance.

Experimental study on biaxial mechanical behavior of concrete suffered high temperature and constitutive model

Biaxial compression tests on plain concrete suffered high temperature ranging from 200 ℃ to 600 ℃ were carried out using the large-scale dynamic-static tri-axial concrete test system at the State Key Laboratory of Coastal and Offshore Engineering with designated stress ratios of 0, 0.25, 0.5, 0.75 and 1, respectively. The measured strength and strain were reported and the changes in both biaxial compressive failure envelopes and strains at peak stresses were analyzed. The regressive equation of initial elastic modulus in the biggest principal compressive stress direction was derived from test results. With the published results from previous biaxial tension-compression experiments, a three-parameter failure criterion has been proposed. A biaxial nonlinear elastic incremental constitutive model was developed for the compressive stress directions by using the equivalent uniaxial strain values deduced from test results. Analytical results obtained from the proposed biaxial constitutive model achieve good agreement with the experimental results.

Magnitude and Forming Factors of Mass Elevation Effect on Qinghai-Tibet Plateau

Mass elevation effect （MEE） refers to the thermal effect of huge mountains or plateaus, which causes the tendency for tem- perature-related montane landscape limits to occur at higher elevations in the inner massifs than on their outer margins. MEE has been widely identified in all large mountains, but how it could be measured and what its main forming-factors are still remain open. This paper, supposing that the local mountain base elevation （MBE） is the main factor of MEE, takes the Qinghai-Tibet Plateau （QTP） as the study area, defines MEE as the temperature difference （AT） between the inner and outer parts of mountain massifs, identifies the main forming factors, and analyzes their contributions to MEE. A total of 73 mountain bases were identified, ranging from 708 m to 5081 m and increasing from the edges to the central parts of the plateau. Climate data （1981-2010） from 134 meteorological stations were used to acquire ATby comparing near-surface air temperature on the main plateau with the free-air temperature at the same altitude and simi- lar latitude outside of the plateau. The AT for the warmest month is averagely 6.15 ~C, over 12~C at Lhatse and Baxoi. A multivariate linear regression model was developed to simulate MEE based on three variables （latitude, annual mean precipitation and MBE）, which are all significantly correlated to AT. The model could explain 67.3% of MEE variation, and the contribution rates of three independent variables to MEE are 35.29%, 22.69% and 42.02%, respectively. This confirms that MBE is the main factor of MEE. The intensive MEE of the QTP pushes the 10~C isotherm of the warmest month mean temperature 1300-2000 m higher in the main plateau than in the outer regions, leading the occurrence of the highest timberline （4900 m） and the highest snowline （6200 m） of the Northern Hemisphere in the southeast and southwest of the plateau, respectively.

Ultrathin 3D radial tandem‐junction photocathode with a high onset potential of 1.15 V for solar hydrogen production

Combining a progressive tandem junction design with a unique Si nanowire(SiNW)framework paves the way for the development of high‐onset‐potential photocathodes and enhancement of solar hydrogen production.Herein,a radial tandem junction(RTJ)thin film water‐splitting photo‐cathode has been demonstrated experimentally for the first time.The photocathode is directly fab‐ricated on vapor‐liquid‐solid‐grown SiNWs and consists of two radially stacked p‐i‐n junctions,featuring hydrogenated amorphous silicon(a‐Si:H)as the outer absorber layer,which absorbs short wavelengths,and hydrogenated amorphous silicon germanium(a‐SiGe:H)as the inner layer,which absorbs long wavelengths.The randomly distributed SiNW framework enables highly efficient light‐trapping,which facilitates the use of very thin absorber layers of a‐Si:H(~50 nm)and a‐SiGe:H(~40 nm).In a neutral electrolyte(pH=7),the three‐dimensional(3D)RTJ photocathode delivers a high photocurrent onset of 1.15 V vs.the reversible hydrogen electrode(RHE),accompanied by a photocurrent of 2.98 mA/cm^(2) at 0 V vs.RHE,and an overall applied‐bias photon‐to‐current effi‐ciency of 1.72%.These results emphasize the promising role of 3D radial tandem technology in developing a new generation of durable,low‐cost,high‐onset‐potential photocathodes capable of large‐scale implementation。

Uplift behavior and load transfer mechanism of prestressed high-strength concrete piles

Prestressed high-strength-concrete (PHC) tube-shaped pile is one of the recently used foundations for soft soil. The research on uplift resistance of PHC pile is helpful to the design of pile foundations. A field-scale test program was conducted to study the uplift behavior and load transfer mechanism of PHC piles in soft soil. The pullout load tests were divided into two groups with different diameters, and there were three piles in each group. A detailed discussion of the axial load transfer and pile skin resistance distribution was also included. It is found from the tests that the uplift capacity increases with increasing the diameter of pile. When the diameter of piles increases from 500 to 600 mm, the uplift load is increased by 51.2%. According to the load-displacement (Q-S) curves, all the piles do not reach the ultimate state at the maximum load. The experimental results show that the piles still have uplift bearing capacity.

Preparation and Performance of Overbased Complex Sulphonates

Overbased complex sulphonates containing two metals -- sodium and magnesium -- were prepared by using overbased magnesium sulphonate as the starting material. Borated overbased complex sulphonate containing two metals was synthesized by reaction of boric acid with the corresponding sulphonate. The total base number （TBN） of overbased complex sulphonates decreased compared with that of magnesium sulphonate, while TBN of borated overbased complex sulphonate further decreased. The detergency, anti-oxidation and extreme pressure performances of overbased complex sulphonates were improved compared with those of overbased magnesium sulphonate; the anti-oxidation and extreme pressure performances of borated overbased complex sulphonates were further improved whereas its detergency was reduced.

The relationship between steeplechase hurdle economy, mechanics, and performance

Background： Research surrounding the steeplechase is scarce, with most research focusing primarily on how biomechanical factors relate to maintaining running speed while crossing barriers. One area that has not been well explored is the relationship between biomechanical factors and hurdling economy. The purpose of this study was to investigate how pel：formance times and biomechanical variables relate to hurdling economy during the steeplechase. Methods： This was accomplished by measuring running economy of collegiate and professional steeplechasers while rmming with and without hurdles. Biomechanical measures of approach velocity, takeoff distance, clearance height, and lead knee extension while hurdling, as well as steeplechase performance times were correlated to a ratio of running economy with and without hurdles. Results： While oxygen uptake was 2.6% greater for the laps requiring five barriers, there was no correlation between steeplechase performance time and the ratio of running economy during the hurdle and non-hurdle laps. Results also indicated no correlation between the aforementioned biomechanical variables and ratio of running economy during the hurdle and non-hurdle laps. Conclusion： Increasing approach velocity did not negatively affect running economy. Increased approach velocity is a benefit for maintenance of race pace, but does not hurt economy of movement.

Numerical Investigation of an Active Jet Control Method for Hypersonic Inlet Restart

A flow control method based on an active jet is developed to restart hypersonic inlets. The dynamic restarting process is numerically reproduced by unsteady Reynolds averaged Navier-Stokes(RANS) modeling to verify the effectiveness and reveal the influence of jet conditions. The active jet improves the inlet unstart status by drawing the high-pressure separation bubble from the internal compression duct and performing a full expansion to alleviate the adverse pressure gradient. Moreover, the favorable pressure gradient in the inlet caused by jet expansion allows for a successful restart after turning off the jet. The influence of the jet momentum ratio is then analyzed to guide the design of the active jet control method and choose the proper momentum ratios. A low jet momentum does not eliminate the high-pressure separation bubble, whereas an excessive jet momentum causes severe momentum loss due to the induced shock. The general rule in restarting the inlet using an active jet is to allow a full jet expansion downstream of the jet slot while avoiding excessive momentum loss upstream and preventing the thick low-speed layer.

Reliability investigation of demolition initiation network for urban viaduct

This paper presented the delay characteristics of relay point detonator used in multiple parallel initiation networks and proposed the simple formula to calculate expectations of relay point initiation time.Corresponding reliability standards were established based on the different scale of non-electric initiation network.A multiple parallel initiation network were created,which could not only avoid the occurrence of the viaduct rollover during dumping process,but also improve the reliability standard and realize the unlimited segmentation.Results could provide a good reference for the design of viaduct blasting initiation network.

多模态影像融合在颅底肿瘤的诊断、治疗中的应用价值

目的探讨多模态影像融合在颅底肿瘤的诊断、治疗中的应用价值。方法 9例颅底肿瘤术前均行DynaCTA检查及MRI薄层(2 mm)增强扫描检查,将多组影像数据输入工作站,采用"双容积重建"技术进行脑血管及MRI的影像融合,通过静态及动态融合影像观察肿瘤与脑结构、血管及颅骨的毗邻关系,并对肿瘤的诊断、手术治疗及预防血管并发症进行分析。结果 9例均获得满意的影像融合、具有很好的空间一致性,在一张影像上可以清晰显示病变及其周围脑结构、血管及颅骨解剖关系,提高精准性诊断,并应用于指导治疗策略、设计手术划及预防并发症。9例均恢复满意出院。结论多模态影像融合对提高颅底肿瘤的诊断精准性、提高肿瘤全切除率、降低病死率和残疾率效果肯定,对血管损伤并发症治疗疗效肯定。

冷积银膜的二次谐波研究

冷积金属膜在退火过程中对外场的二次谐波响应,理论预计可同时观察到局域的和非局域的表面等离子体激光(SPP)对二次谐波的增强.在超高真空环境下和120～400K退火范围内观察到了冷积银膜表面这两种SPP激发,讨论了它们与入射场的角度关联特性.