多型面衔接回转体零件数控加工技巧分析

根据多型面衔接回转体零件结构特点,在大量实验的基础上,对产品进行对比分析,得出了利用数控机床加工时,制定加工工艺应该特别注意的问题,并提出解决和改进意见;特别是坐标延伸法,对于多型面衔接回转体零件的数控加工具有普遍的推广价值.

多型面组合模具的研制及其在复杂结构玻璃钢产品中的应用

本文从模具结构设计以及实际应用情况的角度,验证了多型面组合模具在复杂结构的玻璃钢产品制造上的可行性。

多型面复合材料支架成型技术

阐述了一种多型面复合材料支架整体成型技术,重点对工艺方案、模具设计、铺层工艺优化设计、固化方式进行了探究。结果表明:采用一体化成型方案,能够实现一种多型面复合材料支架的成型。通过工艺研究,突破了组合式模具设计,对称、阶梯过渡的铺层,真空辅助硅橡胶加压关键技术。产品具有较优的成型质量、尺寸精度及力学性能。复合材料制件内部无分层、疏松、孔隙等缺陷,纤维体积分数可控制在(60±3)%,孔隙率测试值均低于1.0%。产品安装面平面度优于0.3 mm,角度公差在±0.1°范围内。随炉试件力学性能高于设计指标,满足用户使用要求。

Dynamic response of multi-scale structure in flexible pavement to moving load

In order to study the dynamic responses in the microstructures of the pavement structure, the multi-scale modeling subjected to moving load is analyzed using the discrete element method （DEM）. The macro-scale discrete element model of the flexible pavement structure is established. The stress and strain at the bottom of the asphalt concrete layer under moving load are calculated. The DEM model is validated through comparison between DEM predictions and the results from the classical program. Based on the validated macro-scale DEM model, the distribution and the volumetric fraction of coarse aggregate, mastics and air voids at the bottom of the asphalt layer are modeled, and then the multi-scale model is constructed. The dynamic response in the microstructures of the multi-scale model are calculated and compared with the results from the macro model. The influence of mastic stiffness on the distribution of dynamic response in the microstructures is also analyzed. Results show that the average values and the variation coefficient of the tensile stress at the aggregate-mastic interface are far more than those within the mastics. The dynamic response including stress and strain distributes non-uniformly in both mastics and the interface. An increase in mastic stiffness tends to a uniform distribution of tensile stress in asphalt concrete.

A new electromagnetic functional material composed of metallic hollow micro-spheres

This paper presents a new electromagnetic functional material developed byelectron-less nickel deposition technique, with a single hollow micro-sphere as the core templateand a thin nickel layer as the shell. The micrograph taken by a scanning electron microscope showsthe microstructures of the materials in detail. Scattering parameters of the waveguide sample holderfilled with the materials have been obtained over X band. The electromagnetic parameters computedfrom the measured S parameters show that the material with metallic hollow spheres has as highrelative permeability μ'_r as 19.0 with about 0.6 magnetic loss tangent over the whole bandwidth.Compared to the material with non-metallic spheres, the permeability μ'_r and the magnetic losstangent μ'_r increase greatly, while the permittivity remains lower than 1.8.

Gas–liquid two-phase flow in serpentine microchannel with different wall wettability

Gas–liquid flow in serpentine microchannel with different surface properties exhibits drastically different flow behavior. With water and air as working fluids, the method of numerical simulation was adopted in this paper based on CLSVOF(coupled level set and volume of fluid method) multiphase model. After verifying the reasonability of the model through experiment, by changing wall properties and Re number(Re<1500), the influences of contact angle and surface roughness on flow regime and Po number were discussed. Moreover, the difference of pressure drop between curve and straight microchannel was also calculated. Beyond that, the combined effect of curve channel and wall properties on flow resistance was analyzed. This paper finds that wall properties have great influence on gas–liquid flow in microchannels not only on flow regime but also flow characteristics. Meanwhile, the pressure drop in curve microchannels is larger than straight. It is more beneficial for fluid flowing when the straight part of microchannel is hydrophilic smooth wall and curve part is hydrophobic with large roughness.

Electronic Transport and Magnetic Properties in Ferroelectric- Ferromagnetic Composites La5/8Ca3/8MnO3：ErMnO3

The crystal structures and electronic transport properties of composites, xLa5/8Ca3/8MnO3 （1-x）ErMnO3 （x=0, 0.2, 0.4, 0.5, 0.6, 0.8, 1）, where ErMnO3 is the insulating ferroelectric and La5/8Ca3/8MnO3 is the metallic ferromagnetic component, were studied. The magnetization of samples （x=0, 0.5, 1） were also measured as a function of temperature from 4 K to 300 K. The X-ray diffraction data show La5/8Ca3/8MnO3 and ErMnO3 are almost complete immiscible, originating from the significant difference in their crystal structures. All the composites show a metal-insulator transition when the molar fraction of xLa5/8Ca3/8MnO3 component x≥0.4 and the electronic transport behaviors follow the classical percolation theory model very well. Magnetization of the mixture with x=0.5 is unique and enhanced greatly compared with that of pure ErMnO3. Comprehensive analysis of the electronic transport and magnetic results suggests that this material system is a new kind of multiferroic with stronger magnetism in a wider temperature range compared with the single phase multiferroic ErMnO3.

Strong/weak limits and strong/weak differentials of multi-variable indeterminate forms. III: Transformations

Various transforms of the indeterminate forms are presented in this part, which include simplification in spherical coordinates, origin translation, axis alteration, transformation of limit conservation and application of Xh?K0. Fundamental factors for numerical simplification are provided respectively for bi-variable indeterminate forms, tri-variable indeterminate forms and the universal extending multiplier.

Influence of Weather and Climate on Malaria Occurrence Based on Human-Biometeorological Methods in Ondo State, Nigeria

This study focuses on the influence of weather and climate on malaria occurrence based on human-biometeorological methods was carried out in Ondo State, Nigeria using meteorological and malaria dataset in the state for the period from 1998 to 2008. In addition, sea surface temperatures （SSTs） over equatorial Pacific Ocean were integrated in the analysis. The association between each of the meteorological-biometeorological parameters and clinical-reported malaria cases was examined by using Poisson distribution and log as link function between the two categories of dataset. The next step was the building of a model by using Poisson multiple regression models （GLMs） in order to know the weather variables that lead to statistically changes in clinical-reported malaria cases. The study revealed that an increase of I m.s1 of wind speed can lead to an increase of about 164% and 171% in the monthly occurrence of malaria at 95% confidence interval in derived savanna and humid forest zone respectively. Also, an increase of I ℃ in air temperature and sea surface temperature is associated with 53.4% and 29% increase in monthly malaria occurrence （CI： 95%） in derived savanna while an increase of 1 ℃ in air temperature and sea surface temperature is associated with 56.4% and 15.4% increase in monthly malaria occurrence at 95% confidence interval in humid forest zone of Ondo State

Fertility Mediating Factors in Sub-Saharan Africa （SSA）： Macro-Level Cross Sectional Perspectives

The aim of this paper is to investigate the mediating factors of fertility levels and trends in Sub-Saharan African CSSA） countries. The major sources of data of the study are the 2001 and 2002 UNDP （United Nations Development Program）, covering 42 SSA countries. The selected antecedent variables of fertility levels and trends include： GDP per capita; female adult literacy rate; infant mortality rate; contraceptive prevalence rate; breastfeeding; access to health services; undernutrition; and level of urbanization. The main analytical techniques of the study include simple central tendency descriptive statistics and advanced multiple regression models. The outputs of the correlation matrix and regression models are shown to influence the levels and trends of fertility positively or negatively, increasing or decreasing fertility levels among the countries. But, contraceptive prevalence level appears to be relatively powerful at 5% significance level, relatively more decline with the level of urbanization and positively related with poverty level, which cumulatively gives rise to 5.9 total fertility rate per woman. Accordingly, with declining mortality and high fertility level, the era of rapid population growth in SSA countries has not yet been over with all its implications on sustainable development.

Model predictive control synthesis algorithm based on polytopic terminal region for Hammerstein-Wiener nonlinear systems

An improved model predictive control algorithm is proposed for Hammerstein-Wiener nonlinear systems.The proposed synthesis algorithm contains two parts:offline design the polytopic invariant sets,and online solve the min-max optimization problem.The polytopic invariant set is adopted to replace the traditional ellipsoid invariant set.And the parameter-correlation nonlinear control law is designed to replace the traditional linear control law.Consequently,the terminal region is enlarged and the control effect is improved.Simulation and experiment are used to verify the validity of the wind tunnel flow field control algorithm.

Migration law of respirable dust on a super-long fully mechanized double-shearer working face

In order to understand the migration law of respirable dust and gain reasonable design parameters for dust control on a super-long double-shearer fully mechanized working face, this paper describes research carried out using a numerical simulation package(Fluent) based on gas-solid coupling dispersed multiphase flow model and field measurement to research different technology modes, dust distribution law at different intervals where shearers work in opposite directions on the lower 9303 face, No. 2 Jining Mine,Yankuang Coal Mining Co. Results show that the concentration of dust 3–6 m away from the shearers working in the same directions was large, while the impact area of respirable dust near the shearer increased significantly to 5–6 m with the distance between two shearers working in opposite directions.The concentration of dust on a double-shearer face was considerably higher than that of a face with one shear under the combined effect of wind speed on the face and disturbed wind around the shearer, while the dust concentration near the shearer on the return side was considerably higher than that on the inlet side. The concentration of dust on a double-shearer face along the airflow declined slowly so that dust was hard to control. Simulation results confirmed the results of field measurement, which could provide reference for dust prevention design.

A method of dealing polygon’s self-intersection contour in SLA

The contour of the slices of SLA parts is composed of a great deal of small lines. When offsetting the contour to compensate for the radius of laser spot, many self-intersection contours come into being, which decrease the precision of formed parts. A new lemma to judge the local self-intersection contour and the global self-intersection contour separately is put forward, according to which self-intersection contour can be removed reliably. Meanwhile, a new beam offsetting algorithm for SLA parts is described, which brings about good resuits in the practical manufacturing process.

STUDY OF SOURCES OF SCORE VARIABILITY IN PERFORMANCE ASSESSMENT USING MFRM:A CASE OF SPEAKING TEST IN PETS BAND3

As direct measure of learners' communicative language ability, performance assessment (typically writing and speaking assessment) claims construct validity and a strong power for predictive utility of test scores. However, it is also of common concern that the subjectivity of rating process and the potential unfairness for test takers who encounter different writing prompts and speaking tasks would constitute threats to reliability and validity of test scores, especially in those large-scale and high-stakes tests. Therefore, appropriate means for quality control of subjective scoring should be held essential in test administration and validation. Based upon raw scores from one administration of speaking test in PETS Band3 held in Hangzhou, the present study investigates and models possible sources of score variability within the framework of Many-Facet Rasch Model (MFRM). MFRM conceptualizes the possibility of a examinee being awarded a certain score as a function of several facets — examinee ability, rater severity, domain difficulty and step difficulty between the adjacent score categories and provides estimates of the extent to which the examinee's test score is influenced by those facets. Model construction and data analysis was carried out in FACETS Version 3.58, computer program for conducting MFRM analysis. The results demonstrate statistically significant differences within each facet. Despite the generally acceptable rater consistency across examinees and rating domains, fit statistics indicate some unexpected rating patterns in certain raters such as inconsistency and central tendency, to be avoided through future rater training. Fair scores for each examinee are also provided, minimizing the variability due to facets other than examinees' ability. MFRM manifests itself as effective in detecting whether each test method facet functions as intended in performance assessment and providing useful feedback for quality control of subjective scoring.

Effect of polypeptide 2B1 on condition of dampness pattern in rats in terms of Traditional Chinese Medicine

OBJECTIVE： This study investigated how polypeptide 2B1 is involved in regulating and governing dampness in rat models with dampness pattern defined in terms of Traditional Chinese Medicine. METHODS： We randomly divided 48 SPF 10-week-old male Sprague-Dawley （SD） rats into a normal group, normal ＋ Aristolochic acid I （AA-I） for 5 min group, normal ＋ AA-I for 60 min group, dampness pattern group （DS-Group）, dampness pattern ＋ AA-I for 5 rain tern ＋ AA-I for 60 min group, and dampness pat- group. Groups were then treated accordingly. We took out the lung, stom- ach, liver, spleen, kidney, large intestine, and small intestine tissues to detect gene and protein expres- sion of organic anion transporter polypeptide 2B1 （OATP2B1）. RESULTS= Gene expression of OATP2B1 in spleen, kidney, and small intestine of rats with dampness pattern was lower than that in normal rats （P〈0.05）. The gene expressions of OATP2B1 in liver, stomach, large intestine, and small intestine were lower than that in control rats at different time points after being stimulated by AA-I （P〈0.05）. CONCLUSION There is coordination among multiple viscera in handling the condition of dampness, and the mechanism underlying the action may rely on regulating the expression of OATP2B1.

Pseudo-Anosov Mapping Classes and Their Representations by Products of Two Dehn Twists

Let S be a Riemann surface of analytically finite type （p, n） with 3p-3＋n 〉 0. Let a ∈ S and S = S - {a}. In this article, the author studies those pseudo-Anosov maps on S that are isotopic to the identity on S and can be represented by products of Dehn twists. It is also proved that for any pseudo-Anosov map f of S isotopic to the identity on S, there are infinitely many pseudo-Anosov maps F on S - {b} = S - {a, b}, where b is a point on S, such that F is isotopic to f on S as b is filled in.

Polymorph selection in the crystallization of hard-core Yukawa system

Colloid-colloid interactions in charge-stabilized dispersions can to The crystallization process and polymorph selection of hard-core some extent be represented by the hard-core Yukawa model. Yukawa model are studied by means of smart Monte Carlo simulations in the region of face-centered-cubic （fcc） phase. The contact value of bard-core Yukawa potential and the volume fraction of the colloids are fixed, while the Debye screening length can be varied. In the early stage of the crystallization, the precursors with relatively ordered liquid structure have been observed. Although the crystal structure of thermodynamically stable phase is fcc, the system crystallizes into a mixture of fcc and hexagonal close-packed （hcp） structures under small Debye screening length since the colloidal particles act as effective hard spheres. In the intermediate range of Debye screening length, the system crystallizes into a mixture of fcc, hcp, and body-centered-cubic （bcc）. The existence of metastable hcp and bcc structures can be interpreted as a manifestation of the Ostwald＇s step rule. Until the Debye screening length is large enough, the crystal structure obtained is almost a complete fcc suggesting the system eventually reaches to a thermodynamically stable state.

The growth mechanism of hydrotalcite crystal

From the point of growth units, the growth mechanism of hydrotalcite (HT) crystal is investigated in this paper. Results show that the growth morphology of HT is consistent with the model of anion coordination polyhedron growth units. The Raman shift of growth solutions of HT, Cu-HTlc, and Cu-Zn-HTlc are monitored using Raman spectroscopy. In the experiment, the growth units of Mg-Al-hydrotalcite are [Mg-(OH)6]4- and [Al-(OH)6]3-, and the growth units of Cu-Htlc and Cu-Zn-HTlc are [Mg-(OH)6]4- and [Al-(OH)6]3-, respectively. The growth process of hydrotalcite is as follows: growth units first incorpo- rate into metal layers, then metal layers adsorb An- and H2O, and the growth units incorporate into layer compounds according to this rule. Growth units will have different incorporations and growth morphologies caused by different growth surroundings. Furthermore, the reason why Cu-HTlc is difficult to synthesize is also interpreted in this paper.

Monitoring rapid urban expansion using a multi-temporal RGB-impervious surface model

In this paper, we developed a novel method of combining remote sensing tools at the sub-pixel level for accurate identification of impervious surface time series changes. We examined the use of the red-green-blue impervious surface model (RGB-IS) in detecting time series internal modification of urban regions by integrating Landsat data collected over four different periods between 1987 and 2009 (i.e., 1987, 2000, 2002, and 2009). The performance of this approach was compared with two conventional methods, namely standard RGB-normalized difference vegetation index (NDVI) and post-classification technique. In contrast to conventional techniques, RGB-IS could monitor between-class changes, within-class changes, and location of these modifications. The proposed method was independent of seasonal changes and was also able to serve as a useful alternative for quick mapping growth hotspots and updating transportation corridor map. The results also showed that Cixi County, Zhejiang Province, China experienced tremendous impervious surface changes, especially along the corridors of newly constructed highways and around urban areas over the past 22 years.

F-theory and N=1 Quivers from Polyvalent Geometry

We study four-dimensional quiver gauge models from F-theory compactified on fourfolds with hyper-K¨ahler structure.Using intersecting complex toric surfaces,we derive a class of N =1 quivers with charged fundamental matter placed on external nodes.The emphasis is on how local Calabi–Yau equations solve the corresponding physical constraints including the anomaly cancelation condition.Concretely,a linear chain of SU(N) groups with flavor symmetries has been constructed using polyvalent toric geometry.