| 1. | If its density is equal to the critical density
最后若密度和临界值一样，便会得出一个 |
| 2. | If the mass density is larger than the critical density , then the universe will eventually stop its expansion and start to collapse
的数值，引力便足以使宇宙停止膨胀，并令它重新收缩，这称为 |
| 3. | If the density of matter and energy in the universe is less than the critical density , the space curvature will be negative
事实上，宇宙中暗物质和暗能量的多寡决定了宇宙的几何结构。假若宇宙中的物质和能量的总密度低于临界密度，它是一个空间曲率 |
| 4. | As an extension of the big bang theory , inflation theory predicts the universe density is rather close to the critical density . thus , the universe is flat
根据为改进大爆炸理论而发展出来的暴胀理论，宇宙密度必定接近于临界密度，所以宇宙应是平坦的。 |
| 5. | The reflected light spectrum from interaction of uv laser with solid plasma was measured to investigate the frequency shift due to doppler effect of expanding critical density
测量了紫外超短脉冲激光等离子体中的光谱频移，分析表明是有质动力和等离子体热压力共同作用的结果。 |
| 6. | It is found that there exists the metastability and hysteresis effect of traffic flow in the neighborhood of critical density under different initial conditions . a computer simulation system named cats was fulfilled with all celluar automata models in java language
利用面向对象的java语言，设计实现了cats仿真系统，模拟了各种一维周期性边界条件下高速公路上车流运动，显示了交通流的各种现象。 |
| 7. | The space geometry is open and negatively curved as a saddle . if the density equals to the critical density exactly , the space is flat as a sheet of paper . if the density is greater than the critical density , the space geometry is closed and positively curved as a ball
为负马鞍形的开放宇宙假若密度和临界密度相等，空间曲率为零，宇宙如一张白纸般平坦假若密度高于临界密度，它则是一个空间曲率为正球形的封闭宇宙。 |
| 8. | Secondllv in the 1 d random traffic flow model . the relation function between the correlation and the creation . disappearance . brake probabilities of the vehicles is presented . according to the statistical mechanical approach to the spatial correlation functions . the theoretical results agree with that of the computer simulation . thirdh . based on the bml model . a main - road traffic flow model with two speeds on two dimensions is designed . this model simulate the traffic situation of one main road and several branches in the cit traffic lights placed on the crossing . vehicles breaking ~ vhile running and turning to other direction while jamming . we investigate the ~ ' e1ocitv and flo ~ ~ of the model when the initial densitvthe brake and turning probabilities . the green to signal rati3 . thc number of the branches and the period of the signal are changed . then the reasons causing all the kinds of phenomena are analvzed . finallv . we simulate the bml model using the method of lattice boltzmann which ~ vas brought out by liu mu - renand obtain the velocity - density graph similar to the previous result . the upper critical densiw above which there are oniv jamming configurations . and the lo ~ ver critical density below which there are only moving configurations are the same as before . the boltzmann function which is on the lattices shows the moving and jaxmning transition obviouslv . thus it proves the possibilit of this method on the traffic research
接着，建立了和研究了二维二速的主干道模型，该模型模拟了城市交通中一条主干道，多条支道的交通情况，在干道与支道的交叉路口设置红绿灯，车辆在运行中可以有对突发事件发生反应的刹车，在发生堵塞时，路口的车辆可考虑通过转向来缓解交通等各种实际情况的发生，给出了车辆演化的演化方程，并通过计算机模拟，研究模型在改变车辆的初始密度、刹车概率、转向概率、支道数、红绿灯信号的绿信比、红绿灯信号周期等各种情况下支、主干道车辆的速度、流量的变化，并分析在各种情况下交通状况的成因，提出改善交通的有效措施。最后，在刘慕仁提出的用格子boltzmann方法研究一维决定论交通流的思路下，将此法推广到对二维bml模型的模拟上，得到了与用以往方法的研究结果相类似的速度-密度图线，且车辆从运动相到堵塞相转变的上下临界密度是一致的，同时分别给出车辆在处于畅通相和堵塞相时， boltzmann函数在格子上的分布情况，进一步验证了此法的可行性。 |
