冲击式环锤破碎机试制成功

由山东煤矿莱芜机械厂引进技术开发的冲击式破碎机PCH-1010型环锤破碎机，日前一次性空载、负载试车成功。该环锤破碎机是一种带有环锤的冲击式破碎机，主要用于煤、煤矸石、焦炭等脆性物料的破碎。该机工作时环锤不仅转子公转，而且还能绕锤自转，当物料进入破碎腔后，首先受到随转子高速旋转的环锤的冲击而破碎，被冲击的物料同时从环锤处获得功能，高速地冲向破碎板，受到二次破碎，     

反击式破碎机冲击时间的仿真研究(续)

运用瞬态动力学软件MSC．Dytran对反击式破碎机中板锤冲击碰撞岩石的过程进行有限元仿真，研究板锤磨损前后不同形状和粒度岩石的冲击时间，对反击式破碎机的设计优化具有一定的理论指导意义。     

反击式破碎机冲击时间的仿真研究

运用瞬态动力学软件MSC．Bytan对反击式破碎机中板锤冲击碰撞岩石的过程进行有限元仿真，研究板锤磨损前后不同形状和粒度岩石的冲击时间，对反击式破碎机的设计优化具有一定的理论指导意义。     

提高破碎机锤头（板锤）寿命的研究

鞍钢东鞍山烧结厂的反击式破碎机锤头和腭式破碎机板锤,材质为65Mn,热处理工艺为普通淬火加中温回火,使用寿命为76h,满足不了生产要求。在不改变原材质的情况下,采用重新加热或锻后余热薄壳淬火-自回火新工艺后,获得了如下结果:①进一步发挥了材料潜力,使锤头寿命提高40%以上,使板锤寿命提高100%;②表面层获得马氏体组织,心部获得具有一定韧性的混合组织,从而获得了良好的强度与韧性的配合;③采用锻后余热进行薄壳淬火,可降低生产费用。     

立轴锤式破碎机在二道沟矿业公司的应用

破碎是金属矿山选矿工艺中的重要工序,破碎机是选矿作业的重要设备,直接影响选矿厂的处理能力和能耗。以二道沟矿业公司为工程背景,介绍了红旗选矿厂扩能及技改过程,详述了立轴锤式破碎机结构、特点及生产实践。立轴锤式破碎机的应用,增大了红旗选矿厂给矿粒度（-350mm）,降低了产品粒度（-10mm）,提高了破碎比,取得了很好的应用效果。     

单段锤式破碎机选型研究

单段锤式破碎机80年代才开始在我国使用,本文对各种单段锤式破碎机进行了较详细的分析比较,并对选型设计中的若干问题进行了分析研究。     

φ1000×700毫米反击式破碎机的改进

为了提高反击式破碎机处理粉矿的生产能力,我们对原破碎机进行了一些改造。改造后的破碎机结构牢固、衬板寿命延长,锤头使用时间增加并且更换拆卸方便,生产能力也有一定程度提高。现将改进前后主要方面分述如下: (一) 锤头的改进 改进前锤头(三个)和锤     

双动简摆颚式破碎机高效和减振机理的探讨

从力学角度探讨了一种新型双动颚板破碎机高效和减振的原理，以此寻求提高颚式破碎机的效率和生产能力的有效途径。     

高压辊压机在耐火材料行业的应用

结合国外磨粉设备的生产技术和使用情况，山东镁矿开发了新型高压辊压机，它克服了国外同类设备存在的结构复杂、造价高、机械磨损严重、维修更换复杂等缺点。使用证明，与对辊破碎机和锤式破碎机闭路工艺相比，高压辊压机可以方便地调节物料，提高生产效率，节能降耗，可用做耐材行业的粉碎、研磨机械。     

单辊破碎机复合箅板的研制与应用

介绍了烧结机单辊破碎机异板，由普通铸钢改为复合铸造，提高了箅板的使用寿命。     

PFJ—0707型反击式破碎机板锤的改进

PFJ—0707型反击式破碎机板锤头的材质由ZGMn13改为45号钢，并将板锤头上的单槽改为两槽，使机体振动减轻，锤头利用率提高一倍。     

打壳机工作机构的设计

论述了气动打壳机工作机构的设计。对机头、机械臂等作了周密的设计计算。采用这种工作机构的打壳机 ,实现了全机械化打壳 ,并且可靠性大大提高 ,满足了电解铝厂安全生产的需要     

基于应力与疲劳的锻锤结构分析

锻锤是径向精锻机的一个关键部件,它的强度和使用寿命对整机的安全可靠运行具有十分重要的影响。针对弧面锻锤与平面锻锤锻造圆柱形工件的受力与寿命问题,构建锻锤锻造的有限元计算模型,进行有限元锻造模拟,对其进行应力和寿命分析及结果对比,确定锻锤易损点。结果表明:在锻造圆柱工件时,两种锻锤的等效应力主要出现在过渡圆角处;弧面锻锤受等效应力比平面锻锤小7.75%,其寿命可以增加3.9%。     

焦化煤粉碎系统的改造

分析了反击式粉碎机存在的主要问题,提出了改进方案。通过增加预破碎系统、液力耦合器及改造反击式粉碎机,解决了对湿度较大煤炭的粉碎,并达到对煤炭细度及粒度的要求,提高焦炭的质量、产量,满足生产需求。     

业庄矿区选矿系统的优化改造

针对业庄矿区选矿系统存在的磨选生产能力过小、备件消耗大、能耗高等问题,提出了优化改造方案,一是更换可逆式锤式破碎机,使用新型耐磨合金锤头;二是采用新型圆振动筛,增加筛分面积,减小筛孔尺寸。改造后破碎粒度由-18mm降到-10mm,选矿年处理量由15万t提高到30万t,年多产出9.28万t铁精粉。     

Structural variation induced by different nucleotides at the cleavage site of the hammerhead ribozyme

The hammerhead ribozyme is capable of cleaving RNA substrates at 5' UX 3' sequences (where the cleavage site, X, can be A, C, or U). Hammerhead complexes containing dC, dA, dI, or rG nucleotides at the cleavage site have been studied by NMR. The rG at the cleavage site forms a Watson-Crick base pair with C3 in the conserved core of the hammerhead, indicating that rG substrates inhibit the cleavage reaction by stabilizing an inactive conformation of the molecule. Isotope-edited NMR experiments on the hammerhead complexes show that there are different short proton-proton distances between neighboring residues depending upon whether there is a dC or dA at the cleavage site. These NMR data demonstrate that there are significant differences in the structure and/or dynamics of the active-site residues in these hammerhead complexes. Molecular dynamics calculations were used to model the conformations of the cleavage-site variants consistent with the NMR data. The solution conformations of the hammerhead ribozyme-substrate complexes are compared with the X-ray structure of the hammerhead ribozyme and are used to help understand the thermodynamic and kinetic differences among the cleavage-site variants.     

Activities of tRNA-embedded dimeric minizymes

Ribozymes have been shown to be potent inhibitors of gene expression and viral function. Effects of ribozyme-mediated repression to target gene in living cells are correlated with the amounts of expression and stabilities of ribozyme molecules. In our previous study, it was demonstrated that a minimized hammerhead ribozyme, minizyme, with high activity forms a dimeric structure with a common stem II. We constructed dimeric minizymes that could cleave the BCR-ABL chimeric (b2a2) mRNA which had been difficult target for conventional hammerhead ribozymes without damaging the normal ABL mRNA. In order to achieve high expression of these dimeric minizymes in vivo for the treatment of CML, we embedded the dimeric minizyme portion downstream of a tRNA(Val) promoter sequence which could be recognized by RNA polymerase III. We determined cleavage activities of tRNA-embedded dimeric minizymes and compared the activities between tRNA-embedded hammerhead ribozyme and tRNA-embedded dimeric minizymes. All tRNA-embedded dimeric minizymes tested were capable of cleavage the target substrate. The activity of the tRNA-embedded dimeric minizyme targeted at BCR-ABL mRNA was almost the same as that of the naked dimeric minizymes. Interestingly, the cleavage activity of tRNA-embedded dimeric minizymes was higher than that of tRNA-embedded conventional hammerhead ribozyme.     

Hammerhead ribozymes with a faster cleavage rate

A hammerhead ribozyme that was previously reported to have a rate of chemical cleavage 10-fold faster than that of conventional hammerheads was analyzed in greater detail. Although originally found as a bimolecular hammerhead assembled through helices I and II, fast cleavage was observed in hammerheads in the more conventional helix I-helix III form, provided the sequence of helix I of teh fast hammerhead was preserved. Mutations indicted that the fast rate of cleavage was due to the presence of both the U1.1-A2.1 and A1.2-U2.2 base pairs. The faster rate of cleavage was due to a small increase in the activation entropy of the reaction. In addition, we confirmed previous reports that increasing the length of helix I by greater than five base pairs inhibits cleavage slightly and have uncovered a similar effect in helix II.