图说毕宿五毕星团昴星团(二)

金牛座是冬季星空的代表星座,大约11月的傍晚之后,它便出现于东方天空,1月到2月它横越过头顶方向,直到4月的傍晚才降到西方天空.由于金牛座出现的时间长,升空的位置又相当高,因此,很利于大家观赏.在金牛座的"牛眼"附近有一颗闪耀着橙色光的亮星,中名毕宿五,学名金牛座α星,是全天21颗最亮恒星之一,在<中国大百科全书·天文学卷·最亮星表>中排名第13位.在毕宿五附近有7颗小星,与毕宿五一起排列成Y字形,这是著名的毕星团.由毕星团向西北方向寻去,可以找到6～7小星,这是金牛座的另一个著名星团--昴星团.毕宿五、毕星团和昴星团这三个天体就是本文的主角.     

UFO研究在苏联——冰山之一角

随着苏联的解体,一些严密封锁的档案资料逐渐解密,铁幕慢慢拉开,越来越多鲜为人知的内幕在世人面前露出了真面目.对UFO研究爱好者而言,苏联作为一个先进的航天强国,在发展航天技术的过程中,获取了哪些有关UFO的绝密信息,又是怎样实施对各种异常现象的研究,在研究中投入了哪些力量,有什么研究结果,都是大家迫切想了解的.人们兴奋的心情难以言表,期待能得到出乎意料的信息.     

激战海天

星光碧影,海浪声声,一艘神秘的远望号船正快速航行在太平洋的深处,庞大的船体灯火通明,甲板上高高低低、形态各异的天线,正在高速运转,向太空发散着电波,船舱的机房内各类仪器仪表的指示灯跳跃闪动,一切繁忙有序。此刻距离天宫发射升空不到10分     

帕斯卡格拉事件

事情发生于1973年10月11日夜的美国密西西比州东南部的帕斯卡格拉镇,它是面向墨西哥湾的渔港。事发那天,在流经这个小镇的帕斯卡格拉河的荒凉岸边,有两个在造船厂工作的男人正在垂钓,其中一个是45岁的主任,名叫查尔斯·希克松,另一个是18岁的青年帕卡·朱尼耶。晚上21时左右,希克松听到金属物体发出的"嗖嗖"声。他抬头仰望夜空,看见了一个像放大的青灰色蛋那样的椭圆形物体。物体转瞬间靠近二人,悬停在附近的岸上,离地面约60厘米。整个物体高约2.4米,长约3米。按照希克松的说法,那个物体看上去好像是宇宙飞船,尽     

追踪宇宙第一道光"新一代太空望远镜"

□□研究宇宙的起源与演化是天文学的重要任务之一。20世纪中叶,一些著名的天文学家认为,宇宙起源于(137±2)亿年前的一次大爆炸,大爆炸后,整个宇宙不断地膨胀,星系整体退行。各个方向上的星系都在飞快地离地球远去。 由于多普勒效应,地球上接收到离其远去的星系发射的电磁波,频率会降低,也就是发射光谱向长波(红光)方向移动,天文学上称之为“红移”。离地球越远的星系,退行速度越大,产生的红移越大。遥远的、退行中的恒星、星系和类星体等天体发射的光本是可见光和紫外辐射,由于红移,地球上探测接收到的大多是红外辐射。所以,利用红外探测,…     

孩子们的乐园

无边无际的宇宙,神秘、神奇、神妙,令人无限神往,对儿童和青少年来说,更是充满巨大的诱惑力。这个时期,如果孩子们得到良好的引导和教育,将来很有可能成为航天领域的有用人才。为此,美国几十年来始终致力于孩子们的航天科普教育,精心为他们营造喜闻乐见的航天乐园。教育从孩子开始儿童和青少年大多活泼、好动,     

两弹一星秘史

1960年11月5日,凝聚着中国人民自力更生精神和顽强意志的争气弹"1059"竖立在酒泉发射场.发射现场,从设计师、指挥员到操作手,清一色的"中国牌".上午9时2分,我国自己仿制的第一枚近程导弹点火起飞,直上蓝天,8分钟后,导弹击中目标,试验圆满成功.聂荣臻亲赴发射试验场,指挥了这次试验,并在发射场举行的庆祝宴会上说:"在祖国的地平线上,飞起了我国自己制造的第一枚导弹,这是我国军事装备史上一个重要的转折点."从苏联专家全部撤走之日算起,到11月15日导弹发射成功,这是第83天.     

2012:如果气候灾难来了,你要留下什么?

<正>在2012年12月21日,美国黄石公园的火山洞熔岩爆炸,加州发生10.5级强烈大地震,一瞬间地层下陷,陆地应声崩裂,洛杉矶的大楼被震得拦腰断裂倒向地面,高架公路折断,行驶中的汽车、建筑物跟着掉进地底……不只美国,欧洲的梵蒂冈教堂因为地震而整个坍塌;西斯汀教堂屋顶的创世纪壁画龟裂了;里约热内卢的耶稣像也倒下,震得粉碎;大海啸紧随而来,全世界的沿海城市因为板块推挤,全都掉     

华尔兹的舞步

一夜微凉,窗栏轻湿,在风舞之下旋出华尔兹典雅的步调,映着皓明的月光,蹁跹于桂花飘香的气息之中,任思绪随舞步飞扬,划出一道道唯美的弧线,构成一个圆,恰似那轮明月华丽的身姿。     

一种恒温箱快速自适应控制方法

随着测量技术的不断发展,恒温箱的应用越来越广泛,传统的温度控制方法多采用全模拟电路进行控制,在控制精度及实时控制方面不能满足需求,且无法进行功能设定,本文设计了一种恒温箱快速自适应控制方法,基于该方法设计的便携式控温箱,根据恒温箱内外温度差采用不同的控制策略,采用加热与制冷双态工作模式,实现对控温箱内部温度的高精度控制,满足更高的应用需求。     

引力场中运动物体加速度的各向异性

在引力或任何其它力的作用下 ,运动物体的加速度是各向异性的。即在同样大小力的作用下 ,力与速度方向垂直时的加速度要大于力与速度方向一致时的加速度。将这种横向额外加速度理论应用在天体力学方面 ,正确地计算了行星近日点的“多余”进动角和光线在经过太阳表面时由引力引起的偏转角。并且定性地解释了最近发现的所谓航天器的“奇异”加速度。因此 ,行星、航天器和光子等等完全不同的物体在引力场中的运动轨道可以用完全相同的物理机制——“加速度各向异性”理论扩展了的牛顿理论加以描述。     

疲劳统计学智能化中的高镇同法

在疲劳统计学中威布尔分布起着非常重要的作用，但3个参数的威布尔分布在数学形式上比较复杂。通过样本数据估计这3个参数，可通过威布尔概率坐标纸，但其使用不便，且误差较大；也可通过解析法，求解3个联立的超越方程组，但存在不自冾的问题。为此，提出了智能化解决方案——高镇同法，高镇同法充分利用了Python的特点，能够方便地同时给出威布尔分布的3个参数，为威布尔分布的理论研究、实际应用和疲劳统计学的智能化奠定了坚实的基础。      

基于小波域的图像椒盐噪声密度估计

提出一种基于小波域的椒盐噪声密度估计方法.利用图像信号在小波域的系数具有稳定近似的分布,以及噪声对小波系数影响的特点,定量地分析了含噪图像的系数幅值直方图与原始图像的系数幅值直方图之间的偏离程度随噪声密度的变化规律,揭示这种变化关系对图像具有强的鲁棒性,从而利用这种关系对噪声进行估计.仿真结果表明,相对于目前方法,提出算法性能更佳,能够获得更准确的估计值和更小的估计偏差.     

The application of micro-CT in monitoring bone alterations in tail-suspended rats in vivo

Osteopenia is a pathological process that affects human skeletal health not only on earth but also in long-time spaceflight. Micro-computed tomography (micro-CT) is a nondestructive method for assessing both bone quantity and bone quality. To investigate the characteristics of micro-CT on evaluating the microgravity-induced osteopenia (e.g. early detection time and the sensitive parameters), the bone loss process of tail-suspended rats was monitored by micro-CT in this study. 8-Week-old female Sprague Dawley rats were divided into two groups: tail suspension (TS) and control (CON). Volumetric bone mineral density (vBMD) and microstructure of the femur and tibia were evaluated in vivo by micro-CT at 0, 7, 14, 22 days. Biomechanical properties of the femur and tibia were determined by three-point bending test. The ash weight of bone was also investigated. The results showed that (1) bone loss in the proximal tibia appeared earlier than in the distal femur. (2) On day 7, the percent bone volume (BV/TV) of the tibia 15.44% decreased significantly, and the trabecular separation (Tb.Sp) 30.29% increased significantly in TS group, both of which were detected earlier than other parameters. (3) Biomechanical properties (e.g. femur, −22.4% maximum load and −23.75% Young’s modulus vs. CON) and ash weight of the femur and tibia decreased significantly in the TS group in comparison to CON group. (4) vBMD of the femur and tibia were clearly related to bone ash and dry weight (r = 0.75–0.87, p < 0.05). (5) BV/TV of both femur and tibia were clearly related to maximum load and Young’s modulus (r = 0.66–0.87, p < 0.05). Similarly, trabecular vBMD and BV/TV of the femur and tibia were clearly related to Young’s modulus (r = 0.73–0.89, p < 0.05). These indicated that BV/TV and Tb.Sp were more sensitive than other parameters for evaluating bone loss induced by tail suspension, moreover, trabecular vBMD and other parameters might be used to evaluate bone strength. Therefore, micro-CT is a reliable and sensitive method for predicting unloading-induced bone loss in small animals.     

Use of an otolith-deficient mutant in studies of fish behavior in microgravity.

The mutant strain (ha) of medaka (Oryzias latipes) lack utricular otoliths as fry, and some never form otoliths for life. The cross (F1 generation) between the strain having good eyesight and another strain having ordinary eyesight augmented visual acuity of the F1 generation. Crossing the good eyesight strain and ha mutant produced fish having good eyesight and less sensitivity to gravity in the F2 population. Their tolerance to microgravity was tested by parabolic flight using an airplane. The fish exhibited less looping and no differences in degree of looping between light and dark conditions, suggesting that loss of eyesight (in darkness) is not a direct cause for looping behavior in microgravity. The ha embryos could not form utricular otoliths. They did form saccular otoliths, but with a delay. Fry of the mutant fish lacking the utricular otoliths are highly dependent on light upon hatching and exhibit a perfect dorsal-light response (DLR). As they grow, they eventually shift from being light-dependent to being gravity-dependent. Continuous treatment of the fry with altered light direction suppressed this shift to gravity dependence. Being less dependent on gravity, these fish can serve as models in studying the differences expected for the vestibular system of fish reared in microgravity. When these fish were exposed to microgravity (parabolic flights) of an airplane, they spent far less time looping than fish reared in an ordinary light regimen.     

共轴式双旋翼尾迹流场的水洞PIV测量

采用粒子图像测速(PIV)技术,对共轴式双旋翼在悬停和以不同前进比前飞时的流场进行水洞实验.将激光片光定位于旋翼的纵向截面,桨叶的方位角和图像的获取是同步的.测量得到了旋翼流场的瞬时涡量和速度分布、桨尖涡的结构和脱落轨迹、悬停时的尾迹边界收缩和前飞时的尾迹边界倾斜角等.研究了不同状态下共轴式双旋翼流场的气动干扰特性.为了比较,对单旋翼也进行了同样的测量.实验得到了有价值的结果,对共轴式直升机的气动计算和合理设计具有重要意义.      

多元分析在大学研究生院规模研究中的应用

运用因子分析和聚类分析等多元统计分析方法,对中国设立研究生院的18所理工科大学研究生院1994年的部分数据进行分析、处理,将表征规模的各统计变量综合为博士规模因子和硕士规模因子两个综合变量,并根据每一样本点的因子得分对18所理工科大学研究生院办学规模进行排序和分类,为评估理工科大学研究生院办学规模提供参考依据.     

可体内降解的骨固定材料的制备研究

为制备强度和韧性都适中且可体内降解的骨固定材料,首先借助聚D,L丙交酯与聚己内酯的扩链反应获得一系列扩链反应聚合物;然后通过测定聚合物拉伸强度和降解性能随扩链剂和扩链反应条件的变化规律,来选择扩链剂和制定最佳制备工艺.利用按上述方法选定的扩链剂和制备工艺,最终制备出了拉伸强度为24.47MPa,延伸率为1091%,降解时间为6个月,且对人体无害的骨固定材料.      

Changes in the numbers of osteoclasts in newts under conditions of microgravity.

Intensity of osteoclastic resorption and calcium content were investigated in intact limb bones of the newts flown on board of a biosatellite Cosmos-2229 after amputation of their forelimbs and tail. Using X-ray microanalysis it was shown an increase in calcium content in the bones on 20th day after operation. Histological study revealed an activation of osteoclastic resorption on endosteal surface of long bones. The newts exposed after surgery on a biosatellite had the same level of bone mineralisation as operated ground control ones, but the increase in number of polynuclear osteoclasts was lower.     

Changes in vacuolation in the root apex cells of soybean seedlings in microgravity.

Changes in the vacuolation in root apex cells of soybean (Glycine max L. [Merr.]) seedlings grown in microgravity were investigated. Spaceflight and ground control seedlings were grown in the absence or presence of KMnO4 (to remove ethylene) for 6 days. After landing, in order to study of cell ultrastructure and subcellular free calcium ion distribution, seedling root apices were fixed in 2.5% (w/v) glutaraldehyde in 0.1 M cacodylate buffer and 2% (w/v) glutaraldehyde, 2.5% (w/v) formaldehyde, 2% (w/v) potassium antimonate K[Sb(OH)6] in 0.1 M K2HPO4 buffer with an osmolarity (calculated theoretically) of 0.45 and 1.26 osmol. The concentrations of ethylene in all spaceflight canisters were significantly higher than in the ground control canisters. Seedling growth was reduced in the spaceflight-exposed plants. Additionally, the spaceflight-exposed plants exhibited progressive vacuolation in the root apex cells, particularly in the columella cells, to a greater degree than the ground controls. Plasmolysis was observed in columella cells of spaceflight roots fixed in solutions with relatively high osmolarity (1.26 osmol). The appearance of plasmolysis permitted the evaluation of the water status of cells. The water potential of the spaceflight cells was higher than the surrounding fixative solution. A decrease in osmotic potential and/or an increase in turgor potential may have induced increases in cell water potential. However, the plasmolysed (i.e. non-turgid) cells implied that increases in water potential were accompanied with a decrease in osmotic potential. In such cells changes in vacuolation may have been involved to maintain turgor pressure or may have been a result of intensification of other vacuolar functions like digestion and storage.