诺·格公司推出“天卫”激光空中防御系统

诺斯罗普·格鲁门公司近日推出了新一代激光空中防御系统——“天卫”系统。该系统能够为部队、军事设施、民用机场、港口和工业部门等提供光速防御能力。恐怖分子已经将袭击转向了空中。火箭或迫击炮在伊拉克对美军和盟军造成了很大威胁。据诺·格公司官员介绍．一套“天卫”系统能够产生直径约10km的安全区域。它能够以光速探测、跟踪和摧毁短距离弹道导弹、短程和远程火箭、火炮、迫击炮、巡航导弹、无人机、反坦克导弹和便携式导弹的威胁。对诺·格公司的激光武器研究可追溯到20世纪60年代。“天卫”系统源于诺·格公司为美国陆军和以色列国防部开发的战术高能激光（THEL）先进概念技术验证测试平台。“天卫”系统采用新型激光，比THEL小4倍。诺·格公司已经向美国国土安全部推荐了“天卫”系统。国土安全部将发布一份价值700万美元的合同，以研发机载防便携式导弹威胁的替代对抗方案。诺·格公司正在试验用于保护商用飞机的直接红外干扰（DIRCM）技术。

诺·格公司交付F一-22新一代改进型有源相控阵雷达

诺斯罗普·格鲁门公司已经向美国空军交付了配装在F-22空中优势战斗机上的新一代改进型有源相控阵(AESA)雷达。新雷达将于今年夏天在美国加州爱德华兹空军基地经受空中综合试验。

诺·格公司的天网反射器成功安置在Inmarsat4卫星上

据美国太空参考网站3月28日报道，诺·格公司的“天网”可展开反射器(AstroMesh deployable reflector)系统已经成功地部署在3月11日由卡纳维拉尔角发射的国际海事卫星组织的1-4卫星上。3月25日在地面控制人员的指挥下，直径9米(30英尺)的“天网”反射器和优良的支持系统已成功地被安置。进一步的无线电频率试验将确认反射器的形态和位置是否与预期的一致。

洛·马公司和诺·格公司竞标无人战斗武装旋翼机

美国《航空周刊》2003年8月25日刊号报道．美国国防预研局(DARPA)不仅希望对洛克西德·马丁公司和诺斯罗普·格鲁门公司的无人战斗武装旋翼机(UCAR)进行详细设计评审，而且还希望在选定开发商之前看到每个系统与有人直升机如何配合行动。UCAR打算最终装备陆军，但海军方面对于它所具有的垂直起降能力也表现十分关注。

FLOW FIELD ANALYSES OF PLANE JET AT LOW REYNOLDS NUMBERS USING LATTICE BOLTZMANN METHOD

A two-dimensional（2-D） incompressible plane jet is investigated using the lattice Boltzmann method（LBM） for low Reynolds numbers of 42 and 65 based on the jet-exit-width and the maximum jet-exit-velocity. The results show that the mean centerline velocity decays as x-1/3 and the jet spreads as x2/3 in the self-similar region, which are consistent with the theoretical predictions and the experimental data. The time histories and PSD analyses of the instantaneous centerline velocities indicate the periodic behavior and the interaction between periodic components of velocities should not be neglected in the far field region, although it is invisible in the near field region.

The Formation of Precipitation Anomaly Patterns during the Developing and Decaying Phases of ENSO

This study proposes a new explanation for the formation of precipitation anomaly patterns in the boreal summer during the E1 Nifio-Southem Oscillation （ENSO） developing and decaying phases. During the boreal sum- mer June-July-August （JJA） （0） of the E1 Nino （La Nina） developing phase, the upper level （300-100 hPa） positive potential temperature anomalies resemble a Ma- tsuno-Gill-type response to central Pacific heating （cool- ing）, and the lower level （1000-850 hPa） potential tem- perature anomalies are consistent with local SST anoma- lies. During the boreal summer JJA（1） of the E1 Nifio （La Nifia） decaying phase, the upper level potential tempera- ture warms over the entire tropical zone and resembles a Matsuno-Gill-type response to Indian Ocean heating （cooling）, and the lower level potential temperature anomalies follow local SST anomalies. The vertical heterogeneity of potential temperature anomalies influences the atmospheric stability, which in turn influences the precipitation anomaly pattern. The results of numerical experiments confirm our observations.

The Simulation of High Reynolds Number Cavity Flow Based on Fractional Volumetric Lattice Boltzmann Method

The fractional volumetric lattice Boltzmann method with much better stability was used to simulate two-chmensional cavity flows. Because the effective viscosity was reduced by the fraction factor, it is very effective for simulating high Reynolds number flows. Simulations were carried out on a uniform grids system. The stream lines and the velocity profiles obtained from the simulations agree well with the standard lattice Boltzmann method simulations. Comparisons of detailed flow patterns with other studies via location of vortex centers are also satisfactory.

Effective-Field Theory for Kinetic Ising Model on Honeycomb Lattice

As an analytical method, the effective-field theory （EFT） is used to study the dynamical response of the kinetic Ising model in the presence of a sinusoidal oscillating field. The effective-field equations of motion of the average magnetization are given for the honeycomb lattice （Z = 3）. The Liapunov exponent A is calculated for discussing the stability of the magnetization and it is used to determine the phase boundary. In the field amplitude ho / ZJ-temperature T/ZJ plane, the phase boundary separating the dynamic ordered and the disordered phase has been drawn. In contrast to previous analytical results that predicted a tricritical point separating a dynamic phase boundary line of continuous and discontinuous transitions, we find that the transition is always continuous. There is inconsistency between our results and previous analytical results, because they do not introduce sufficiently strong fluctuations.

Neumann Boundary Conditions Inhibiting SSB in Coleman-Weinberg Mechanism

In this work we show that homogeneous Neumann boundary conditions inhibit the Coleman-Weinberg mechanism for spontaneous symmetry breaking in the scalar electrodynamics if the length of the finite region is small enough （a = e2Mφ-1, where M, is the mass of the scalar field generated by the Coleman-Weinberg mechanism）.

Numerical Investigation of Tip Clearance Effects in an Axial Transonic Compressor

Numerical investigations of the Darmstadt transonic single stage compressor (DTC), in the Rotor1-Stator1 configuration, aimed at advancing the understanding of the effect of different rotor tip gaps and transition modelling on the blade surfaces are presented. Steady three dimensional Reynolds Averaged Navier Stokes (RANS) simulations were performed to obtain the flow fields for the different configurations at different operating conditions using the RANS-Solver TRACE. The stage geometry and the multi-block structured grid were generated by G3DMESH and a grid sensitivity analysis was conducted. For the clearance gap region, a fully gridded special H-grid was chosen. Comparisons were made between the flow characteristic at design speed, representative for a transonic flow regime, and at 65% speed, representative for a subsonic flow regime. The computations were used to analyse the flow phenomena through the tip clearance region for the different configurations and their impact on the performance of the compressor stage.

THE GOLDBACH-VINOGRDOV THEOREM WITH THREE PRIMES IN A THIN SUBSET

It is proved constructively that there exists a thin subset S of primes, satisfying for some absolute constant c＞0, such that every sufficiently large odd integer N can beLet r be prime, and hi positive integers with (bj, r) = 1,j = 1, 2, 3. It is also proved that, for almost all prime moduli r＜ log- N, every sufficiently large odd integer N = b1 + b2 +ba(modr) can be represented as where c ＞ 0 is an absolute constant.

Noether symmetries of the nonconservative and nonholonomic systems on time scales

In this paper we give a new method to investigate Noether symmetries and conservation laws of nonconservative and nonholonomic mechanical systems on time scales , which unifies the Noether's theories of the two cases for the continuous and the discrete nonconservative and nonholonomic systems. Firstly, the exchanging relationships between the isochronous variation and the delta derivatives as well as the relationships between the isochronous variation and the total variation on time scales are obtained. Secondly, using the exchanging relationships, the Hamilton's principle is presented for nonconservative systems with delta derivatives and then the Lagrange equations of the systems are obtained. Thirdly, based on the quasi-invariance of Hamiltonian action of the systems under the infinitesimal transformations with respect to the time and generalized coordinates, the Noether's theorem and the conservation laws for nonconservative systems on time scales are given. Fourthly, the d'Alembert-Lagrange principle with delta derivatives is presented, and the Lagrange equations of nonholonomic systems with delta derivatives are obtained. In addition, the Noether's theorems and the conservation laws for nonholonomic systems on time scales are also obtained. Lastly, we present a new version of Noether's theorems for discrete systems. Several examples are given to illustrate the application of our results.

Direct numerical simulation of turbulent flow over backward-facing at high Reynolds numbers

Direct numerical simulation(DNS) was performed for the first time to study the flow over a backward-facing step at a high Reynolds number on a coarse grid.The flow over backward-facing step is the typical turbulent flow controlled by large eddy,in which the effect of small eddy could be negligible as an approximation.The grid dimension could easily satisfy the resolution requirement to describe the characteristics of a large eddy flow.Therefore,direct numerical simulation of N-S equations to obtain the turbulent flow field on the coarse grid could be realized.Numerical simulation of a two-dimensional flow over a backward-facing step at a Reynolds number Re=44000 was conducted using Euler-Lagrange finite element scheme based on the efficient operator-splitting method(OSFEM).The flow field was descretized by triangle meshes with 16669 nodes.The overall computational time only took 150 min on a PC.Both the characteristics of time-averaged and instantaneous turbulent flow were simultaneously obtained.The analysis showed that the calculated results were in good agreement with the test data.Hence,the DNS approach could become the reality to solve the complex turbulent flow with high Reynolds numbers in practical engineering.

Three-dimensional Numerical Simulation of the Movement of the Flexible Body under Different Constraints

For the large deformation of the flexible body may cause the fluid grid distortion,which will make the numerical calculation tedious,even to end,the numerical simulation of the flexible body coupling with the fluid is always a tough problem.In this paper,the flexible body is under two kinds of constrained conditions and the ratio of length-diameter is 1:30.The Reynolds number of the airflow is 513,belonging to the area of low Reynolds number.The control equations of the coupling of flexible body with airflow are built and the adaptive grid control method is adopted to conduct the three-dimensional numerical simulation of the movement of the flexible body.The numerical results show that it is possible to simulate the characteristics of the flexible body's movement in the low Reynolds number airflow when the appropriate control equations are modeled and suitable equation-solving method is adopted.Unconstrained flexible body would turn over forward along the airflow's diffusion direction,while constrained flexible body in the flow field will make periodic rotation motion along the axis of the flexible body,and the bending deformation is more obvious than that of unconstrained flexible body.The preliminary three-dimensional numerical simulation can provide references for further research on the characteristics of the yam movement in high Reynolds number airflow.

Unsteady analysis of six-DOF motion of a 6:1 prolate spheroid in viscous fluid

Free-moving simulations of airplanes, submarines and other automobiles under extreme and emergency conditions are becoming increasingly important from operational and tactical perspectives. Such simulations are fairly challenging due to the extreme unsteady motions and high Re(Reynolds) numbers. The aim of this study is to perform a six-DOF motion simulation of a 6:1prolate spheroid that is falling in a fluid field. Prior to conducting the six-DOF simulation, some verification simulations were performed. First, a laminar flow past an inclined prolate spheroid at a Re number of 1000 and incidence angle of 45. with a tetrahedral mesh was simulated to verify the relevant targeted discrete method for an unstructured mesh. Second, to verify the LES(large eddy simulation) models and dependent parameters for the DDES(delayed detached eddy simulation), a turbulent flow past a sphere was performed at a subcritical Re number of 10000. Third, a steady maneuvering problem about a prolate spheroid pitching up from 0. to 30. incidence at a uniform angular velocity was established based on a dynamic tetrahedral mesh with changing topology and the ALE(arbitrary Lagrangian-Eulerian) method of fluid-structure coupling at a Re number of 4.2 × 10~6.Finally, two six-DOF motions of an inclined 6:1 prolate spheroid at an initial incidence of 45. were simulated at different Re numbers of 10000 and 4.2 × 10~6.