流与留:山东省乡村人口“空心化”的生成机制与治理路径

随着山东省新型城镇化的推进,乡村常住人口持续减少,老龄化程度加深,乡村人才总量不足,人力资源结构上缺乏系统的聚合,使得乡村振兴战略的实施面临着乡村振兴主体缺失、村民增收困难、乡村文化没落、乡村自治弱化等现实困境。为破除制约乡村振兴的因素,文章结合“推拉理论”分析山东省乡村人口“空心化”的生成机制,并提出乡村振兴中人口“空心化”的治理路径。

灌溉型黄土滑坡变形破坏特征的离心机模型研究

在黑方台地区,自1968年开始人工大规模农田灌溉之后,随着灌溉量的不断增加,台塬面上陆续出现了大面积沉降湿陷,相继发生数十次大规模的黄土滑坡,在台塬周边形成了黄土滑坡群。本文以黑方台焦家13#滑坡为地质原型,利用原状黄土制成1∶200室内灌溉模型,采用成都理工大学500 g·t大型土工离心机进行离心试验,模拟和实时监测灌溉诱发黄土滑坡变形破坏过程。对区域边坡预测预报、现场防治施工等具有一定的指导意义。

Characterization of Ultra Fine Solids(BS) in Athabasca Bitumen

The ultra fine (<200 nm) inorganic solids (BS) were separated from bitumen which was washed by toluene and centrifugated at 2000 rpm. The result of PAS FTIR and image of TEM showed that the structure of BS particles was smiliar to that of kaolinite clay. On the surface of BS, both toluene insoluble organic matter and structural OH group are detected at the same time. The surface characteristics imparted a bi-wettable nature to the BS. As a result, the BS is able to stabilize fine water emulsion in the bitumen phase. The organic matter associated with BS is a possible factor of the fouling on catalyst and equipment.

Ion mechanism of isoproterenol on delayed afterdepolarization and triggered activity in the infarcted ventricle

Objectives This study aimed at investigating the cellular mechanism of isoproterenol （ISO） on delayed afterdepolarizations （DADs） and triggered activity （TA） of the noninfarcted myocardium in the myocardial infarcted rabbit model.Methods Rabbits with the left anterior descending coronary artery occlusion were prepared and recovered for 8 wk （healed myocardial infarction, HMI）. Myocytes were isolated from regions of the noninfarcted left ventricular free wall. ISO was added to cellular surface by perfusion way. Action potentials and ion currents were recorded with whole-cell patch clamp. Results The results showed that treatment with ISO induced more DADs and TA events in HMI myocytes. Iti and IC,_L of myocytes treated with ISO were increased significantly compared with HMI cells, which contributed to DADs-related triggered arrhythmia. Conclusions The results suggested that more arrhythmia events of DADs and TA developed in myocytes with ISO treatment. The underlying mechanism was associated with the augment of I6 and calcium influxing

热轧生产中重负荷齿轮油净化、除水新型净油机

针对重负荷的齿轮传动装置中齿轮油杂质含量大、含水量高且难以分离等问题,介绍了一种具备自动排水功能的新型离心式净油机。主要介绍了其工作原理、自动排水功能的设计及其附加特殊功能。应用表明,该离心式净油机能够高效地将油液中水、杂质快速分离并自动连续排出;此外,还具有强大的破乳化能力,去除油液中的溶解水,使油液中含水量低于0.05%,排出的水中含油量低至6.99mg/L,远远低于30mg/L的国家环保直排水指标要求;还有,对大颗粒杂质和15μm以下的微小杂质均具有非常好的去除效果。采用新型离心式净油机,可有效提高油品利用率,降低成本消耗,提高设备使用寿命。

Surge Control of a Centrifugal Compression System by Using a Bouncing Ball

The purpose of this study is to suppress the fluctuations of surge by a simple passive control method. A bouncing ball system with different weight of the balls was tested. As a result, the bouncing ball system suppressed mild surge without the deterioration of the performance characteristics, and moved the initiation point of surge toward the lower flow rate when the steel ball of 15mm outer diameter was used. The present system was effective to suppress the surge and to widen the stable operating range of a centrifugal compressor when the ball was chosen appropriately.

Arrhythmogenic mechanisms in ryanodine receptor channelopathies

Ryanodine receptors(Ry Rs) are the calcium release channels of sarcoplasmic reticulum(SR) that provide the majority of calcium ions(Ca2+) necessary to induce contraction of cardiac and skeletal muscle cells.In their intracellular environment,Ry R channels are regulated by a variety of cytosolic and luminal factors so that their output signal(Ca2+) induces finely-graded cell contraction without igniting cellular processes that may lead to aberrant electrical activity(ventricular arrhythmias) or cellular remodeling.The importance of Ry R dysfunction has been recently highlighted with the demonstration that point mutations in RYR2,the gene encoding for the cardiac isoform of the Ry R(Ry R2),are associated with catecholaminergic polymorphic ventricular tachycardia(CPVT),an arrhythmogenic syndrome characterized by the development of adrenergically-mediated ventricular tachycardia in individuals with an apparently normal heart.Here we summarize the state of the field in regards to the main arrhythmogenic mechanisms triggered by Ry R2 channels harboring mutations linked to CPVT.Most CPVT mutations characterized to date endow Ry R2 channels with a gain of function,resulting in hyperactive channels that release Ca2+ spontaneously,especially during diastole.The spontaneous Ca2+ release is extruded by the electrogenic Na+/Ca2+ exchanger,which depolarizes the external membrane(delayed afterdepolarization or DAD) and may trigger untimely action potentials.However,a rare set of CPVT mutations yield Ry R2 channels that are intrinsically hypo-active and hypo-responsive to stimuli,and it is unclear whether these channels release Ca2+ spontaneously during diastole.We discuss novel cellular mechanisms that appear more suitable to explain ventricular arrhythmias due to Ry R2 loss-of-function mutations.

Unsteady Behavior and Control of Vortices in Centrifugal Compressor

Two examples of the use of vortex control to reduce noise and enhance the stable operating range of a centrifugal compressor are presented in this paper.In the case of high-flow operation of a centrifugal compressor with a vaned diffuser,a discrete frequency noise induced by interaction between the impeller-discharge flow and the diffuser vane,which appears most notably in the power spectra of the radiated noise,can be reduced using a tapered diffuser vane(TDV) without affecting the performance of the compressor.Twin longitudinal vortices produced by leakage flow passing through the tapered portion of the diffuser vane induce secondary flow in the direction of the blade surface and prevent flow separation from the leading edge of the diffuser.The use of a TDV can effectively reduce both the discrete frequency noise generated by the interaction between the impeller-discharge flow and the diffuser surface and the broadband turbulent noise component.In the case of low-flow operation,a leading-edge vortex(LEV) that forms on the shroud side of the suction surface near the leading edge of the diffuser increases significantly in size and blocks flow in the diffuser passage.The formation of an LEV may adversely affect the performance of the compressor and may cause the diffuser to stall.Using a one-side tapered diffuser vane to suppress the evolution of an LEV,the stable operating range of the compressor can be increased by more than 12 percent,and the pressure-rise characteristics of the compressor can be improved.The results of a supplementary examination of the structure and unsteady behavior of LEVs,conducted by means of detailed numerical simulations,are also presented.