“三定法”精准提取公因式

无论在哪个版本的初中数学教材中,也无论身处我国哪个地区的初中生,只要接触因式分解就几乎会被提公因式法中的如何正确提取公因式所困扰.从多年的一线教学情况来看,正确提取公因式确实是因式分解的难点.基于此,本文中总结出“三定法”帮助学生解决这一问题.

二重积分转化为二次积分的“三定法”

计算二重积分最关键的是在定积分计算的基础上,掌握好将二重积分转化为二次积分的方法步骤。笔者结合自身的教学经验,将二重积分转化为二次积分的方法总结为"三定法",即"定系、定序和定限"。

三定法等长机械式钢筋调直切断机

在预应力水泥制品中配置的冷拔低碳钢丝一般都须经过调直,并按规定长度进行等长切断。钢筋的长度偏差直接影响施加应力的平衡,导致产品开裂、变形。我厂是生产邮电通信用环形预应力混凝土电杆的专业厂家,根据国际要求,在预应力水泥电杆生产工艺中,钢筋下料相对长度偏差不应大于钢筋长度的1.5/10000。过去,我厂对钢筋都要进行两次切断才能满足精度要求。钢筋经过两次切断既浪费材料又浪费工时,为此。

“三定法”在3min跳绳训练中的应用

三定法是指定技术动作、定运动主题、定运动条件，笔者以“三定法”为指导，以学生跳绳练习为主线，总结出提高速度、减少失误次数、提高专项协调性、增强供氧的四个方法，经过实证，能够快速有效地提高跳绳成绩。

农田害鼠“三定”监测法

农田害鼠“三定”监测法,是固定监测点4—6.7公顷以上;每月每点布夹3天,月间相距25天以上;布夹定位,夹距5m;每月布夹同一地点、同一时间、同一夹位。

“三定”熔样法制备松香软化点(环球法)试样

提出了制备松香软化点试样的“三定”熔样法。“三定”是定试样重量、定熔样温度和熔样时间。本方法又分为圆环法和柄皿法。本方法易控制熔样温度、经济、熔样效果好、精密度高。实验证明：熔样温度对试样软化点有显著影响。

“被害人研究”在侦查实务界的实践与应用——对“三定侦查法”之“被害人研究”课题的探讨

刑事司法中,对被害人研究的关注早在我国宋代便有记载。"被害人研究"是"三定侦查法"理论体系的有机组成部分,从属于"定性质"范畴,并贯穿于整个"三定侦查"体系。被害人的研究意义体现在:一是可以推断案件的起因和背景,发现犯罪行为人与被害人之间的相互联系,解读犯罪行为人;二是可以推断犯罪行为人的犯罪动机和惯技行为,为案件串并提供帮助;三是可以更好地预测犯罪行为人下一个最可能的侵害目标,对侦查破案及安全防范均有益处。被害人研究应该重视被害调查研究,重视被害预防研究,重视人才培养。

新疆兵团九十团“三定两剪”种葡萄

在红提葡萄修剪埋土的安全越冬期间，新疆生产建设兵团农五师九十团全面推广了“三定两剪”法，为2005年生产优质绿色商品果奠定了坚实基础。

Chromosome Location of the Male-sterility and Yellow Seedling Gene in Line 1066A of Foxtail Millet

Using foxtail millet (Setaria italica (L.) Beauv.) male-sterile line 1066A as female parent and Yugu 1 primary trisomic series (1 - 7) and tetrasomics 8, 9 as male parents, chromosome location of gene for male-sterility and yellow seedling in line 1066A was studied by primary trisomic analysis. The plants of F-1 generation of trisomics 2 - 9 were obtained by crossing with a great many plants of 1066A. F-1 generation of trisomics was similar to their male parent in morphologic characters, the color of their seedling was green, and pollen was partially fertile. The segregation ratio of fertility to sterility is 3:1 in F-2 generation of trisomics 2, 3, 4, 5, 7, 8 and 9; and 14:1 only in F-2 generation of trisomic 6 (chi(0.05)(2) = 0.012). The segregation ratio of green seedling to yellow seedling is 12:1 only in F-2 generation of trisomic 7 (chi(0.05)(2) = 0.31), but in other cases, this ratio is 3:1. The results indicated that the male-sterility gene was located on chromosome 6, and the gene for yellow seedling was monogenic recessive and located on chromosome 7. The rate of trisomics transmission by pollen was tested, trisomics 8 and 9 were the highest in rates of trisomics transmission and followed by trisomics 6 and 4.

Simulation analysis on three-dimensional slope failure under different conditions

The failure mechanism of two-dimensional（2D） and three-dimensional（3D） slopes were investigated by using the strength reduction method.An extensive study of 3D effect was conducted with respect to boundary conditions,shear strength and concentrated surcharge load.The results obtained by 2D and 3D analyses were compared and the applicable scope of 2D and 3D method was analyzed.The results of the numerical simulation show that 3D effect is sensitive to the width of slip surface.As for slopes with specific geometry,3D effect is influenced by dimensionless parameter c/（γHtanφ）.For those infinite slopes with local loading,external load has the major impact on failure mode.For those slopes with local loading and geometric constraints,the failure mode is influenced by both factors.With the increase of loading length,boundary condition exerts a more significant impact on the failure mode,and then 2D and 3D stability charts are developed,which provides a rapid and reliable way to calculate 2D and 3D factor of safety without iteration.Finally,a simple and practical calculation procedure based on the study of 3D effect and stability charts is proposed to recognize the right time to apply 2D or 3D method.

STUDY OF NON-CONTACT MEASUREMENT OF FREE-FORM SURFACES

A non contact three dimensional measurement method is presented in this paper.This system consists of a laser triangulation probe,a probe head and a coordinate measuring machine (CMM).The measurement principle of the system is discussed,and a system calibration method employing a reference ball is proposed.The geometric model involving four frames is established to calculate the data points based on the reading of the laser probe and position information from the CMM.A measuring experiment for gesso free form surface using this system is carried out.

食管(贲门)癌手术连续326例无吻合口瘘的治疗经验

我院自1987年1月～1991年12月,用外科手术治疗食管癌202例,贲门癌156例,切除326例,总切除率91%.食管癌切除率94.5%,贲门癌切除率86.6%.本文着重介绍三定点吻合法加大网膜包绕吻合口技术,应用此法未发生吻合口瘘.此法的优点:(1)三定点吻合法显露清楚,吻合准确可靠.(2)利用定点吻合牵引线使食管胃的全层创缘自然合拢一条线上保证粘膜平整.(3)使吻合口建立在有良好血供的健康组织上才有利于愈合.通过术后部分病例的纤维食管镜检查发现食管胃吻合的粘膜平整,生长好,对合满意,术后发生各种并发症24例,发生率7.5%(24/326),其中吻合口狭窄8例,肺炎6例,单纯性包裹性脓胸4例,切口感染3例,左侧乳糜胸2例,急性心梗1例,死亡.其余23例经治疗后痊愈出院.

Influences of nonassociated flow rules on three-dimensional seismic stability of loaded slopes

The influences of soil dilatancy angle on three-dimensional （3D） seismic stability of locally-loaded slopes in nonassociated flow rule materials were investigated using a new rotational collapse mechanism and quasi-static coefficient concept. Extended Bishop method and Boussinesq theorem were employed to establish the stress distribution along the rupture surfaces that are required to obtain the rate of internal energy dissipation for the nonassociated flow rule materials in rotational collapse mechanisms. Good agreement was observed by comparing the current results with those obtained using the translational or rotational mechanisms and numerical finite difference method. The results indicate that the seismic stability of slopes reduces by decreasing the dilatancy angle for nonassociated flow rule materials. The amount of the mentioned decrease is more significant in the case of mild slopes in frictional soils. A nearly infinite slope under local loading, whether its critical failure surface is 2D or 3D, not only depends on the magnitude of the external load, but also depends on the dilataney angle of soil and the coefficient of seismic load.

3D stability analysis method of concave slope based on the Bishop method

In order to study the stability control mechanism of a concave slope with circular landslide, and remove the influence of differences in shape on slope stability, the limit analysis method of a simplified Bishop method was employed. The sliding body was divided into strips in a three-dimensional model, and the lateral earth pressure was put into mechanical analysis and the three-dimensional stability analysis methods applicable for circular sliding in concave slope were deduced. Based on geometric structure and the geological parameters of a concave slope, the influence rule of curvature radius and the top and bottom arch height on the concave slope stability were analyzed. The results show that the stability coefficient decreases after growth, first in the transition stage of slope shape from flat to concave, and it has been confirmed that there is a best size to make the slope stability factor reach a maximum. By contrast with average slope, the stability of a concave slope features a smaller range of ascension with slope height increase, which indicates that the enhancing effect of a concave slope is apparent only with lower slope heights.

An iterative calibration method for nonlinear coefficients of marine triaxial accelerometers

Single-axis rotation technique is often used in the marine laser inertial navigation system so as to modulate the constant biases of non-axial gyroscopes and accelerometers to attain better navigation performance.However,two significant accelerometer nonlinear errors need to be attacked to improve the modulation effect.Firstly,the asymmetry scale factor inaccuracy enlarges the errors of frequent zero-cross oscillating specific force measured by non-axial accelerometers.Secondly,the traditional linear model of accelerometers can hardly measure the continued or intermittent acceleration accurately.These two nonlinear errors degrade the high-precision specific force measurement and the calibration of nonlinear coefficients because triaxial accelerometers is urgent for the marine navigation.Based on the digital signal sampling property,the square coefficients and cross-coupling coefficients of accelerometers are considered.Meanwhile,the asymmetry scale factors are considered in the I-F conversion unit.Thus,a nonlinear model of specific force measurement is established compared to the linear model.Based on the three-axis turntable,the triaxial gyroscopes are utilized to measure the specific force observation for triaxial accelerometers.Considering the nonlinear combination,the standard calibration parameters and asymmetry factors are separately estimated by a two-step iterative identification procedure.Besides,an efficient specific force calculation model is approximately derived to reduce the real-time computation cost.Simulation results illustrate the sufficient estimation accuracy of nonlinear coefficients.The experiments demonstrate that the nonlinear model shows much higher accuracy than the linear model in both the gravimetry and sway navigation validations.

An RSSl Gradient-based AP Localization Algorithm

Recent rapid rise of indoor location based services for smartphones has further increased the importance of precise localization of Wi-Fi Access Point(AP).However,most existing AP localization algorithms either exhibit high errors or need specialized hardware in practical scenarios.In this paper,we propose a novel RSSI gradient-based AP localization algorithm.It consists of the following three major steps:firstly,it uses the local received signal strength variations to estimate the direction(minus gradient) of AP,then employs a direction clustering method to identify and filter measurement outliers,and finally adopts triangulation method to localize AP with the selected gradient directions.Experimental results demonstrate that the average localization error of our proposed algorithm is less than 2meters,far outperforming that of the weighted centroid approach.

A three-dimensional positioning method based on three satellites

A three-dimensional positioning method for global positioning system(GPS)receivers based on three satellites was proposed.In the method,the measurement equation used for positioning calculation was expanded by means of two measures.In this case,the measurement equation could be solved,and the function of positioning calculation could be performed.The detailed steps of the method and how to evaluate the positioning precision of the method were given,respectively.The positioning performance of the method was demonstrated through some experiments.It is shown that the method can provide the three-dimensional positioning information under the condition that there are only three useful satellites.

A three-dimensional matching localization algorithm based on helix triangular pyramid array

On the eve of the occurrence of geological hazards,part of the rock and soil body begins to burst,rub,and fracture,generating infrasound signals propagating outward.3D advanced positioning of the landslide has remained unsolved,which is important for disaster prevention.Through the Fourier transform and Hankel transform of the wave equation in cylindrical coordinates,this work established a three-dimensional axisymmetric sound field model based on normal waves,and designed a 4-element helix triangular pyramid array with vertical and horizontal sampling capabilities.Based on this,the three-dimensional matching localization algorithm of infrasound for geological hazards is proposed.Applying the algorithm to the infrasound signal localization of rock and soil layers,it was found that the helix triangular pyramid array can achieve accurate estimation of depth and distance with a smaller number of array elements than the traditional array,and may overcome the azimuth symmetry ambiguity.This study shows the application prospects of this method for predicting geohazards position several hours in advance.