The blocking effect of the sand fences quantified using wind tunnel simulations

Fences are one of the most effective measures to prevent and control wind-blown sand disasters,and the blocking effect of fences is largely determined by their porosity and height(H).This study employed wind tunnel experiments to measure wind velocities on both sides of wire mesh sand fences with porosities of 75%,63%,56%,36%and heights of 10,5 and 2 cm.The effects of porosity and height on the blocking effect of the fences were evaluated on the basis of velocity variability,flow field,and the wind velocity reduction coefficient.Results show that the smaller the porosity,the stronger the blocking effect.The fence with a porosity of 36%had the strongest windproof efficiency of 0.70 and longest protection range of 9 H,and thus showed the best applicability in preventing and controlling wind-blown sand disasters.The fence with a porosity of 56%showed a windproof efficiency of 0.31 and a protection range of 7 H,which could be considered for adoption.However,fences with porosities of 75%and 63%were not recommended to be adopted,because their windproof efficiency and protection range were very small.Overall,the higher the fence,the stronger the blocking effect.The highest fence(10 cm)had the longest protection range of 90 cm,which was the best in application.Nevertheless,the 5 and 2 cm fences were almost consistent with 10 cm fence in windproof efficiency,which was still suitable for wind and sand fixation.

Water blocking effect caused by the use of hydraulic methods for permeability enhancement in coal seams and methods for its removal

To research techniques for removing the water blocking effect caused by hydraulic applications in coal seams,the use of surfactants is proposed,based on the mechanics of the water blocking effect.Centrifugal experiments were used to validate the effects of using surfactants;the results show that after dealing with vacuum saturation with water,the volume of micropores decreases,which results in a larger average pore size,and the volume of transitional pores,mesopores,macropores and total pores increases.Based on the distribution of pore size,the operation mode of ‘‘water infusion after gas extraction,then continuing gas extraction" is recommended to improve the volume of coal mine gas drainage.When the reflectance of vitrinite in coal samples is less than 1,using the surfactants Fast T,1631,APG,BS can mitigate the damage caused by the water blocking effect.But when the reflectance of vitrinite is larger than 1.4,the damage caused by the water blocking effect can be increased.When the surfactant CMC is used in hydraulic applications,the capillary forces of coal samples are almost negative,which means the capillary force is in the same direction as the gas extraction.The direction of capillary forces benefits the gas flow.So,using CMC can play an active role in removing the water blocking effect.Centrifugal experiments confirm that using CMC can effectively remove the water blocking effect,which has a beneficial effect on improving the gas drainage volume.

Blocking Effects of Spleen Vaccine on Vertical Transmission of Classical Swine Fever Virus in Sows

[ Objective] To investigate the blocking effects of spleen vaccine on vertical transmission of classical swine fever virus （CSFV） in sows. [ Method] Sows infected by CSFV were selected from three large-scale pig farms and they were randomly divided into group Ⅰ, group Ⅱ and control group. The sows in the group Ⅰ were vaccinated with CSF spleen vaccine at a 1.5 times normal dose per pig; those in the group Ⅱ were vaccinated with CSF spleen vaccine at a 2.0 times normal dose per pig; and those in the control group were vaccinated with cell vaccine at a 4.0 times normal- dose per pig. The CSF antigens of piglets were detected by enzyme-linked immunosorbent assay （ELISA）. [ Result] The antigen positive rate of piglets in the experimental group （18.5%） was significantly lower than that in the control group （48.1% ）. No significant difference was found be- tween the group Ⅰ and the group Ⅱ. [ Condmion] CSF spleen vaccine has good blocking effects on vertical transmission of CSFV in sows.

The Blocking Effect of Phenolic Acid on N-Nitrosomorpholine Formation in vitro

Phenolic acids (PAs) are widely found in many daily consumed vegetables and fruits.The inhibitory effects of PAs on Nnitrosomorpholine (NMOR) formation in vitro undersimulated gastric juice condition were studied. The results showed that the inhibjtoryIX)tency of thirteen varieties of PAs differed greatly, which may be related to theirchemical structures; the blocking rate (BR) of different killds of PAs were as follows:caf feic acid, 92.5%; tannic acid, 90.0%; gallic acid, 86.8%; sinaPinic acid, 86.2%; ferulicacid, 8l.l%; chlorogenic acid, 69.4%; gentisic acid, 69.2%; syringic acid, 62.1%; protocatechuic acid, 56.0%; p-coumaric acid, 52.5%; vannilic acid, 35.4%; moreover,p-hydroxybenzoic acid and m-coumaric acid had the least blocking effect or even slightcatalyzing effect. The results also demonstrated that amounts of NMOR formed werenegatively correlated with molar ratio of PAs to nitrite and that the optimum pH forinhibition was between 2 and 3.

Effect of cerebral lymphatic block on cerebral morphology and cortical evoked potential in rats

BACKGROUND: It has been shown that although brain does not contain lining endothelial lymphatic vessel, it has lymphatic drain. Anterior lymphatic system of lymphatic vessel in brain tissue plays a key role in introducing brain interstitial fluid to lymphatic system; however, the significance of lymphatic drain and the effect on cerebral edema remains unclear. OBJECTIVE: To investigate the effect of cerebral lymphatic block on cerebral morphology and cortical evoked potential in rats. DESIGN: Randomized controlled animal study. SETTING: Institute of Cerebral Microcirculation of Taishan Medical College and Department of Neurology of Affiliated Hospital. MATERIALS: A total of 63 healthy adult male Wistar rats weighing 300-350 g were selected in this study. Forty-seven rats were used for the morphological observation induced by lymphatic drain and randomly divided into three groups: general observation group (n =12), light microscopic observation group (n =21) and electronic microscopic observation group (n =14). The rats in each group were divided into cerebral lymphatic block subgroup and sham-operation control subgroup. Sixteen rats were used for observing the effect of cerebral lymphatic block on cortical evoked potential, in which the animals were randomly divided into sham-operation group (n =6) and cerebral lymphatic block group (n =10). METHODS: The experiment was carried out in the Institute of Cerebral Microcirculation of Taishan Medical College from January to August 2003. Rats in cerebral lymphatic block group were anesthetized and separated bilateral superficial and deep cervical lymph nodes under sterile condition. Superior and inferior boarders of lymph nodes were ligated the inputting and outputting channels, respectively, and then lymph node was removed so as to establish cerebral lymphatic drain disorder models. Rats in sham-operation control group were not ligated the lymphatic vessel and removed lymph nodes, and other operations were as the same as those in cerebral lymphatic block group. Morphological changes of the brain and alterations of latency of cortical evoked potential were detected on the 1st, 2nd, 3rd, 5th, 7th, 10th and 15th days after operation under general, light microscope and electronic microscope observations. MAIN OUTCOME MEASURES: ① Cerebral morphological changes; ② latent changes of cortical evoked potential. RESULTS: A total of 63 rats were involved in the final analysis. ① Cerebral morphological changes: General observation showed that, for cerebral lymphatic block rats, the surface of brain was pale and full, and cerebral gyrus was wide and flattened sulci after cerebral lymphatic block; and cerebral tissue space prolongation, increased interstitial fluid, neuronal degeneration and necrosis, diffused phagocytes and satellitosis were observed under light microscope. Neuronal swell and necrosis, glial cell swell, apparent subcellular changes such as mitochondron were observed under electronic microscope. ② Latent changes of cortical evoked potential: As compared with sham-operation control group, latency of cortical evoked potential in cerebral lymphatic blockage group prolonged on the 5th day and 7th day after cerebral lymphatic block [(6.28±0.23), (6.97±0.35) ms; (6.23±0.22), (7.12±0.20) ms; P < 0.01]. CONCLUSION: ① Cerebral lymphatic block plays an important role in cerebral morphology, and may result in abnormality of sensitive impulse conduction and prolong latency of cortical evoked potential. ② Examination of cortical evoked potential is easy and convenient, so it is regarded as a key index for lymphatic disturbed cerebral injury.

Blocking Response Surface Designs Incorporating Neigh-bour Effects

In this paper, blocking in response surface for fitting first order model incorporating neighbour effects has been investigated. The conditions for orthogonal estimation of the parameters of the model have been obtained. A method of constructing designs which ensures the constancy of variance of the parameter estimates of the model has also been given.

Effect of Mg-Preflow for p-AlGaN Electron Blocking Layer on the Electroluminescence of Green LEDs with V-Shaped Pits

In GaN-based green light-emitting diodes（LEDs） with and without Mg-preflow before the growth of p-Al GaN electron blocking layer（EBL） are investigated experimentally.A higher Mg doping concentration is achieved in the EBL after Mg-preflow treatment,effectively alleviating the commonly observed efficiency collapse and electrons overflowing at cryogenic temperatures.However,unexpected decline in quantum efficiency is observed after Mg-preflow treatment at room temperature.Our conclusions are drawn such that the efficiency decline is probably the result of different emission positions.Higher Mg doping concentration in the EBL after Mg-preflow treatment will make it easier for a hole to be injected into multiple quantum wells with emission closer to pGaN side through the（8-plane rather than the V-shape pits,which is not favorable to luminous efficiency due to the preferred occurrence of accumulated strain relaxation and structural defects in upper QWs closer to p-GaN.Within this framework,apparently disparate experimental observations regarding electroluminescence properties,in this work,are well reconciled.

Left- and Right-Handers May Unintentionally Apply Different Cognitive Strategies in Response to Situational Demands: Study Using the Block-Wise Proportion Congruency Effect

We investigated the effects of handedness on developing latent cognitive response strategies according to situation variables. We used the findings of the block-wise Proportion Congruency (PC) effect in which the proportion of congruent trials in a given block modulates the compatibility effect in its block. The block-wise PC effect cannot be intentionally controlled. A Simon task with three different types of Proportion Congruency (PC) in a given block was used to measure the block-wise PC effects. This task was administered to 24 left-handed and 24 right-handed participants. The reaction time and error rates, consistent with previous studies, demonstrated that the block-wise PC effect was observed in left- and right-handers. Crucially, the block-wise PC effect was more pronounced in left- than right-handers, suggesting that left- and right-handers unintentionally apply different cognitive strategies in response to conflict resolution experiences.

Mechanisms of shale hydration and water block removal

Shale samples of Silurian Longmaxi Formation in the Changning area of the Sichuan Basin, SW China, were selected to carry out scanning electron microscopy, CT imaging, high-pressure mercury injection, low-temperature nitrogen adsorption and imbibition experiments to compare the hydration characteristics of montmorillonite and illite, analyze the main factors affecting the water block removal of shale, and reveal the mechanisms of pore structure evolution during shale hydration. The hydration characteristics of shale are closely related to the composition of clay minerals, the shale with high illite content is not susceptible to hydration and thus has limited room for pore structure improvement;the shale with high montmorillonite is susceptible to hydration expansion and thus has higher potential of pore structure improvement by stimulation;the shale with high illite content has stronger imbibition in the initial stage, but insufficient diffusion ability, and thus is likely to have water block;the shale with high montmorillonite content has weaker imbibition in the initial stage but better water diffusion, so water blocking in this kind of shale can be removed to some degree;the shale reservoir has an optimal hydration time, when it is best in physical properties, but hydration time too long would cause damage to the reservoir, and the shale with high illite content has a shorter optimal hydration time;inorganic cations can inhibit the hydration of clay minerals and have stronger inhibition to illite expansion, especially K^(+);for the reservoir with high content of montmorillonite, the cation content of fracturing fluid can be lowered to promote the shale hydration;fracturing fluid with high K^(+) content can be injected into reservoirs with high illite content to suppress hydration.

Effect of specifically-adsorbed polysulfides on the electron transfer kinetics of sodium metal anodes

Room-temperature sodium-sulfur(RT Na-S)batteries hold great promise for large-scale energy storage applications owing to the high energy density and earth-abundance of Na and S.However,the dissolution and migration of sodium polysulfides,uncontrollable Na dendrite growth,and the lack of studies on Na electrodeposition kinetics have hindered the development of these batteries.Herein,we reveal the mechanism of sodium polysulfides on the Na plating/stripping kinetics using a three-electrode system.First,the kinetic behavior deviates from the commonly supposed Butler-Volmer model,which is well described by the Marcus model.In addition,the specific adsorption of polysulfides on the sodium electrode surface is a key factor influencing the kinetics.Higher-order polysulfides(S_(8)^(2-)and S_(6)^(2-))exhibit distinct specific adsorption behaviors because of their high adsorption energies compared to lower-order polysulfides(S_(4)^(2-)and S_(2)^(2-)).The electrostatic effect caused by specific adsorption can accelerate the kinetics,whereas the blocking effect can slow the kinetics.Thus,this competitive relationship enables low concentrations of high-order polysulfides to stimulate kinetics.This implies that a weak shuttle effect is beneficial for obtaining a stable Na deposition in RT Na-S batteries.An in-depth understanding of the Na electrodeposition kinetics provides beneficial clues for future metal sodium/electrolyte interface designs.

Preparation of Polyacrylate-based Conductive Coatings and Its PTC Effect

Polyacrylate-based conductive coatings were prepared from polyacrylate emulsion as matrix and carbon black (CB) whose surface was treated with titanate coupling agent as conducting particles.One kind of organic crystal was added to study its effects on the electrical conductivity and PTC(positive temperature coefficient)effect of the conductive coatings.Experimental results show that the coatings containing only polyacrylate emulsion and CB exhibit an excellent electrical conductivity but bad PTC effect,and when organic crystal is added,PTC effect is characterized and can increase by 2 orders of magtitude.The critical transformation temperature of polyacrylate emulsion/CB PTC composites is decided by melting point of organic crystals.

CONSTRUCTION OF OPTIMAL BLOCKING SCHEMES FOR ROBUST PARAMETER DESIGNS

Robust parameter design （RPD） is an important issue in experimental designs. If all experimental runs cannot be performed under homogeneous conditions, blocking the units is effective. In this paper, we obtain the correspondence relation between fractional factorial RPDs and the blocking schemes for full factorial RPDs. In addition, we provide a construction of optimal blocking schemes that make all main effects and control-by-noise two-factor interactions estimable.

Twin-block矫治安氏Ⅱ类错合畸形临床疗效观察

目的分析采用Twin-block矫治安氏Ⅱ类错合畸形的临床疗效。方法回顾性分析2007年5月～2010年6月在我院确诊的安氏Ⅱ类错颌畸形患者38例,对治疗前后的上下切牙位置、前牙覆盖情况、磨牙关系以及上下颌骨的变化进行对比分析。结果 Twin-block矫治可以明显促进下颌骨发育,改善外观,治疗后上切牙平均后移2.8 mm,下切牙平均前移2.6 mm,前牙覆盖平均减少4.9 mm。结论Twin-block矫治安氏Ⅱ类错合畸形效果确切,不但可以有效地利用下颌骨向前生长的潜力,而且可以使下颌前移,以致下颌磨牙前移,改善Ⅱ类磨牙关系,同时可以使唇向上切牙舌向移动,进一步改善深覆盖状况,是一种安全有效的方法,值得临床大力推广。

Numerical simulation of the blocking process of gelled particles in porous media with remaining polymers

Gelled particles can be transferred deeply inside oil reservoirs to block water channels due to their physicochemical characteristics, including swelling, deformation, and synergetic effect （reacting with polymers）, and then the injection profiles are significantly modified. At present, research on gelled particles is mainly focused on laboratory studies of drive mechanisms, and rarely on mathematical models describing the blocking process of gelled particles. In this paper, the blocking process of gelled particles is divided into two sub-processes： deposition and desorption due to particle deformation. A mathematical model based on filtration theory is proposed considering the effect of characteristics of gelled particles on the blocking process. Blocking laws were simulated and researched using the mathematical model. Results of the simulation of the blocking of gelled particles are quite consistent with the experimental results, which confirms the reliability of the mathematical model developed.

罗库溴铵用于帕金森病患者的神经肌肉阻滞效应

目的观察帕金森病(Parkinson's disease,PD)与非PD患者罗库溴铵的神经肌肉阻滞效应。方法纳入年龄18~65岁,美国麻醉医师协会(American Society of Anesthesiologists,ASA)Ⅰ~Ⅲ,接受丘脑底核-脑深部电刺激手术的PD患者(PD组)31例和行面神经减压的非PD患者(non-PD组)24例为研究对象。麻醉诱导单次给予罗库溴铵(0.6 mg/kg),采用四个成串刺激(train-of-four,TOF)监测肌松,记录罗库溴铵体内作用时间(the duration of 90%recovery of TOF,DURTOF 90%)、起效时间、临床作用时间、恢复指数和术毕2 h内严重呼吸系统并发症发生情况。结果与non-PD组比较,PD组DURTOF 90%和临床作用时间均显著延长,差异有统计学意义(P<0.05);2组患者的起效时间差异无统计学意义(P>0.05)。PD患者的罗库溴铵DURTOF 90%与病程相关,病程越长,DURTOF 90%越长。2组患者术后均无严重呼吸系统并发症发生。结论PD患者应用罗库溴铵的DURTOF 90%和临床作用时间明显延长,且DURTOF 90%与病程呈正相关。

不同粗糙度煤岩界面超低摩擦效应与声发射特征试验研究

为了揭示动载扰动作用下煤岩界面粗糙度对超低摩擦型冲击地压影响机制,采用自行研制的煤岩界面超低摩擦试验装置,以沈阳红阳三矿1082 m采深煤岩体为研究对象,通过改变煤块与砂岩块体表面粗糙度来模拟煤岩界面不同粗糙特性,以粗糙度系数表征煤岩界面粗糙程度,工作块体水平位移表征冲击过程中超低摩擦效应强度,声发射能量为工作块体摩擦滑动过程中的信号参数,进行应力波扰动下不同粗糙度煤岩界面超低摩擦试验.研究结果表明:(1)超低摩擦滑动过程中,工作块体水平位移、声发射能量计数以及累计能量曲线呈现出孕育阶段、激发阶段、稳定阶段变化特征;(2)煤岩界面粗糙度越小,工作块体水平位移和声发射能量峰值越大,煤岩界面越易发生超低摩擦效应;(3)不同煤岩界面粗糙度下,相比于其他扰动频率, 2 Hz时更易发生超低摩擦效应;(4)给出了声发射能量峰值与煤岩界面粗糙度系数对应关系.声发射能量峰值可以有效表征超低摩擦效应强度,可以用声发射能量峰值预测超低摩擦效应强度.

Twin-block功能矫治器联合自锁托槽治疗安氏Ⅱ类1分类错[牙合]畸形的疗效分析

目的:探讨安氏Ⅱ类1分类错[牙合]畸形患者应用Twin-block功能矫治器(TB)联合自锁托槽后的临床效果。方法:前瞻性选取2015年10月-2018年10月笔者医院收治的102例安氏Ⅱ类1分类错[牙合]畸形患者。按治疗方式的不同分为对照组和观察组,每组51例。对照组采用传统MBT直丝弓矫治器进行治疗,观察组采用TB联合自锁托槽进行治疗。比较两组临床疗效、头影测量指标、软组织变化情况及同行评估等级(PAR)指数。结果:观察组总有效率(94.12%)高于对照组(80.39%),差异有统计学意义(P<0.05)。两组上齿槽座角、下齿槽座角、上下齿槽座角、下颌平面角、下中切牙长轴与下颌平面间夹角、上切牙的倾斜度比较,差异均无统计学意义(P>0.05);观察组下切牙的倾斜度高于对照组(P<0.05);两组上唇基角、下唇基角比较,差异均无统计学意义(P>0.05)。观察组全面凸角、软组织面角均高于对照组,差异有统计学意义(P<0.05)。治疗前,两组PAR指数总分比较,差异无统计学意义(P>0.05);治疗后,观察组PAR指数总分低于对照组,且治疗前后差值高于对照组,差异有统计学意义(P<0.05)。结论:安氏Ⅱ类1分类错[牙合]畸形患者应用TB联合自锁托槽具有良好的矫正效果,可调整上下颌关系,纠正软组织畸形。

开腹子宫切除术中QLB-LSAL与双侧TAPB阻滞麻醉镇痛效果比较

目的:分析超声引导下外侧弓状韧带上腰方肌前路阻滞(QLB-LSAL)与双侧腹横肌平面阻滞(TAPB)在开腹子宫切除术(TAH)中的麻醉效果。方法:选取2022年1月-2023年1月本院择期行TAH患者95例,根据入院顺序按单双号分为48例QLB-LSAL组(超声引导下行双侧QLB-LSAL)和47例TAPB组(超声引导下行双侧TAPB),比较两组入室(T0)、切皮时(T1)、手术结束时(T2)、拔管时(T3)及离开麻醉恢复室时(T4)的心率(HR)及平均动脉压(MAP),比较术后48h舒芬太尼消耗量、补救镇痛例数及术后48h内镇痛泵按压次数,比较术后4h、8h、12h、24h静息及咳嗽时视觉疼痛模拟评分(VAS),统计两组术后不良反应和神经阻滞并发症发生情况。结果:两组MAP及HR均呈先上升后降低趋势,且QLB-LSAL组在T1和T2时低于TAPB组(P<0.05);QLB-LSAL组术后48h舒芬太尼消耗量(69.45±4.20μg)、补救镇痛(6.3%)及术后48h内镇痛泵按压(10.5±2.3次)均低于TAPB组(73.15±4.35μg、21.3%、12.2±4.4次)(均P<0.05);两组术后静息及咳嗽时VAS评分均呈降低趋势(P<0.05),两组术后4h、8h评分无差异(P>0.05),术后12h、24h静息及咳嗽时评分QLB-LSAL组低于TAPB组(均P<0.05);两组不良反应(6.3%、4.3%)无差异(P>0.05),两组均无神经阻滞情况发生。结论:相比于双侧TAPB阻滞,超声引导下QLB-LSAL阻滞在TAH中镇痛效果更佳,能有效降低镇痛药物使用剂量,减轻受术患者的疼痛应激反应。

槽式太阳能阵列挡风增速效果数值模拟

采用开源计算流体力学软件OpenFOAM中的Simple求解器对流场进行数值模拟,研究5.00 m/s风速下槽式太阳能阵列挡风墙挡风效果。对由槽式太阳能阵列组成的6个不同高度的挡风墙对整体流场速度的影响以及不同高度挡风墙背风侧30,60,90 m处的速度进行了分析。研究发现,当气流通过挡风墙时,低于墙高的位置速度大幅衰减,而高于墙高的位置开始加速,存在明显的分区作用。当气流流过挡风墙后,会在其后形成明显的速度衰减区,其面积和延伸与挡风墙的高度正相关。在挡风墙背风侧较远处,高于墙高的气流开始减速,低于墙高的气流开始加速,并随着距离的增加风速逐渐趋于平稳。

0.25%罗哌卡因用于超声引导颈中间丛阻滞的有效容量探讨

目的探索0.25%罗哌卡因用于超声引导颈中间丛阻滞的半数有效容量和95%有效容量。方法选择29例行择期颈部手术的患者,均在超声引导下进行0.25%罗哌卡因颈中间丛阻滞,若颈丛分支所属皮区痛觉均消失,则视为完全阻滞(完全阻滞组,14例),否则视为不完全阻滞(不完全阻滞组,15例)。记录阻滞效果,分析0.25%罗哌卡因用于超声引导颈中间丛阻滞的有效容量;比较完全阻滞组和不完全阻滞组患者的一般特征、罗哌卡因阻滞容量、并发症发生情况及阻滞前后深吸气膈肌移动度。结果0.25%罗哌卡因用于超声引导颈中间丛阻滞的半数有效容量为10.3 ml[95%可信区间(CI)=(7.7,13.5)ml],95%有效容量为15.6 ml[95%CI=(12.8,44.0)ml]。完全阻滞组和不完全阻滞组年龄、性别、美国麻醉医师协会(ASA)分级、身高、体重及体质量指数(BMI)比较差异无统计学意义(P>0.05)。完全阻滞组用罗哌卡因容量(11.1±2.0)ml显著高于不完全阻滞组的(9.2±2.0)ml,差异有统计学意义(P<0.05)。不完全阻滞组与完全阻滞组阻滞前深吸气膈肌移动度分别为(4.17±0.87)、(4.09±0.85)cm,比较差异无统计学意义(P>0.05);不完全阻滞组与完全阻滞组阻滞后深吸气膈肌移动度分别为(4.09±0.85)、(3.99±0.70)cm,比较差异无统计学意义(P>0.05)。完全阻滞组1例患者发生声音嘶哑,其给药容量为14 ml;其余所有患者均未发生膈神经阻滞、迷走神经阻滞、局部麻醉药物中毒、Horner征或低氧血症等情况。结论0.25%罗哌卡因用于超声引导颈中间丛阻滞的半数有效容量为10.3 ml[95%CI=(7.7,13.5)ml],95%有效容量为15.6 ml[95%CI=(12.8,44.0)ml]。