高频

The opened magnetic circuit is composed as tow NdFeB permanent magnets and a top plate without U-yoke. After take analyzed deeply for the opened magnet circuit with FEMM (Finite Element Method Magnetics) we find out the field distributing that is separated into three sections . One is the main area what we called as positive field section. Beside the main field there are tow areas that are called the inverted field sections. Loudspeaker arise a very serious distortion when the voice coil moving into inverted field areas. The direction of induced current in the coil part of entered inverted field area is same with the current driving into loudspeaker so that total currents increas largely and heat increase rapidly. With more coils moving into inverted area the voice coil will take on negative inductance properties. It is the main reason that voice coil is burned by heating with increasing current due to arise negative inductance. So opened magnetic circuit is not suitable for the woofers in which the voice coil have wider displacement range. When using this kind magnetic circuit design, the voice coil moving range should be less than the range of positive field to avoid loudspeaker arise serious distortion and heating. Even though voice coil moving range is in the positive area, loudspeaker will still arise more distortion because the field distribution is very cliffy at tow sides of the positive area and full range of magnetic field distribution is not parallel that will arise distortion. Base on above reasons, opened magnetic circuit is not an ideal magnetic circuit for low-frequency loudspeakers. But it can be used in mid-range or high-frequency productions.

开式磁路是由2片钕铁硼磁铁和主导磁板和导磁垫片组成，我们在实践过程中发现这种磁路结构不适合于低频扬声器的使用，我们通过使用FEMM（Finite Element Method Magnetics）软件包对该磁路进行了分析，该磁路的磁场范围被分成3个区域，其中在主导磁板附近形成一个正向磁场，在正向磁场的两边存在反向的磁场，音圈在工作时有很大一部分进入了反向磁场中，在反向磁场内线圈的感应电流方向与驱动电流方向相同，使得音圈呈现出负感抗特性，由于音圈的负感抗特性引起电流的增加导致音圈发热甚至烧毁，因此在扬声器中使用开式磁路时，音圈的运动范围应控制在正向磁场范围之内，否则音圈运动到反向磁场区域时将会产生很大的失真和发热，即使在设计时已经将音圈的运动范围控制在正向磁场范围之内，由于正向磁场的2个边缘磁场强度衰减太快，同时开式磁路中磁场的分布不是平行的，而是自由发散的分布，这样肯定会导致扬声器的非线性失真，因此我们得到的结论是：开式磁路并不是一个理想的磁路，它不适合于低频扬声器的使用，但它还可以应用于中高频扬声器。

The continuous nature of peat accumulation means that terrestrial coaly rocks may provide a higher resolution and more complete record of base-level change than the time-equivalent shallow-marine strata, thus enabling the identification of highfrequency cycles that are not recorded in themarine strata.

泥炭积累的持续性质的手段，陆地coaly岩石可提供较高的分辨率和更完整的记录基准面变化的影响时，相当于浅海阶层，从而使确定的高频周期，不记录在themarine 阶层。

Using the intracellular recording technique for monitoring the excitatory postsynaptic potentials of CA1 pyramidal neuron and delivering an activator of protein kinase C and/or inhibitors of PKC and 〓/calmodulin-dependent protein kinase Ⅱ into postsynaptic cell in hippocampal slices, we studied the role of postsynaptic PKC and CaMKⅡ in long-term potentiation induced by high frequency stimulation at the CA1 synapses made by Schaffer collateral/commissural and perforant pathway afferents.

用电生理学方法在大鼠海马脑片CA1区锥体细胞记录Schaffer侧枝和穿通通路到CA1神经元突触的兴奋性突触后电位，通过送蛋白激酶抑制剂和激活剂进入突触后细胞，我们研究了突触后蛋白激酶C和依赖钙/钙调蛋白的Ⅱ型蛋白激酶在高频刺激诱导的长时程增强产生和维持中的作用。

The lower PBG exists in one third of the first Brilloin zone while the upper one can appear, simultaneously and complimentarily, in the rest two thirds of the first Brillouin zone.

低频光子带隙在1/3布里渊区内存在，而高频的光子能带在另外的2/3布里渊区内存在。

The results in this paper are used in the developing of the first gyroklystron, its output power is about 38kW. All the research is continuate.

学位论文的专题研究己应用于工艺样管研制，得到了38kW的高频输出，各项专题工作正在不断深化。

Methods High frequency ultrasonography of normal cubital and carpal tunnel were performed in 30 healthy volunteers.

应用高频超声观察30例正常人的肘管及腕管的超声解剖并对20例肘管综合征、10例腕管综合征患者术前行超声检查。

Objective:To study the effects of mag netic material which has low curie temperatue induced by high frequency electromagnet for tumors.Methods:The needle-like magnetic material made of nickel-copper alloy which has low cuir e temperature,was implanted in S180 tumors of mice.

将镍铜合金制作的居里点温度为60 ℃的柱状磁性材料植入小鼠S180 内，从体外用高频电磁场诱导植入瘤体内的磁性材料感应产热，观察瘤体的温度变化和加热后的病理改变、瘤体大小及动物生存时间等。

Methods: The needle-like magnetic material made of nickel-copper alloy which has low cuir e temperature,was implanted in S180 tumors of mice.Then high frequency el ectrom agnetic field was applied outside body to make the magnetic material produce the hyperthermia.

将镍铜合金制作的居里点温度为60 ℃的柱状磁性材料植入小鼠S180 内，从体外用高频电磁场诱导植入瘤体内的磁性材料感应产热，观察瘤体的温度变化和加热后的病理改变、瘤体大小及动物生存时间等。

Concerned with the extent of transient expression of explatns, the results show that the effectiveness of transient expression is rather high(60%) after the cotyledons of Jatropha curcas L.

为了构建麻疯树的遗传转化体系，首先应建立其高频再生和高效转化系统，而瞬时表达测试是优化转化系统条件的快速有效的方法。

Objective To determine the content of blood strontium for diagnosis of deathful causes of drowning and postmortem submergence. Methods The content of Sr content in the water sample of Nan Du River on Hainan Province, and in the left heart's blood sample of rabbits died of drowning, postmortem submergence were determined with ICP-XSP. The results were compared with that the controls.

目的 研究动物溺水死后不同时间血锶的变化方法以高频电感偶合等离子体光谱分析仪检测外样水体中锶离子含量，并分别测定家兔溺死与死后入水的左心血的锶含量。

She gently rebuff ed him, but agreed that they could be friends

她婉言拒绝了，但同意作为朋友相处。

If in the penal farm, you were sure to be criticized.

要是在劳改农场，你等着挨绳子吧！