Recessed ground microstrip line at 60 GHz and its application of band‐pass filter

The effect of finite‐size recessed ground on characteristic features of a microstrip transmission line is investigated and verified experimentally on alumina substrate of height 0.127 mm with ε_r = 9.8 at 60 GHz. A measured characteristic impedance of 238 Ω, effective dielectric constant of 3.09, and attenuation constant of 3.4 Np/m is achieved by using a recessed ground of dimensions (width × depth) 4.5 mm × 0.95 mm, below a 50‐Ω (on conventional ground plane) microstrip line. The effect of recessed ground on lumped equivalent circuit elements of microstrip line discontinuities including series‐gap, open‐end, and step discontinuities is also studied. To show the usefulness of recessed ground microstrip line, a prototype of fifth‐order Chebyshev‐type recessed ground end‐coupled band‐pass filter is designed and fabricated at 60 GHz. The filter exhibits measured insertion loss lower than 2.2 dB and return loss better than 13 dB over 3‐dB passband of 6% centered at 60 GHz. The measured results show good consistency with simulated results and confirm the usefulness of recessed ground plane microstrip line.     

Optimum design of 6‐18 GHz ultra‐wideband microstrip filters with arbitrary source and load impedances by the least mean squares Method

In this article, the method of least mean squares (LMS) is employed to design ultra‐wideband (UWB) filters with various input and output port impedances in 6‐18 GHz frequency range. Optimization process on the circuit dimensions is done by MATLAB and AWR microwave office softwares utilizing exact closed‐form relations for microstrip transmission lines and microstrip T‐junction discontinuities. The advantages of this method are its simplicity, fast design time, including impedance matching. Two design examples are depicted in the article. To validate the designed structures, the circuit model results are compared with full‐wave analysis and measurements. The first design example corresponds to equal source and load impedances. For this design, maximum measured transmission coefficient in the frequency range 5.9‐16.6 GHz is obtained as ?12 dB, upper out‐of‐band rejection around image frequency is better than ?17 dB and lower out‐of‐band rejection at 5 GHz is obtained better than ?30 dB. The second design example describes the case of unequal source and load impedances.     

Effect of discontinuity size on the energy absorption of structural steel beam profiles

The effect of size discontinuities on the energy absorption performance of squared steel profiles is reported. Finite element simulations of the compression strength of profiles with discontinuities, placed at mid span of the steel profiles in two opposite walls, were carried out. Circular and elliptical forms of the discontinuities were evaluated. Energy absorption capabilities were increased up to 12.54% and the peak load value was decreased to 10.52% with respect to the same structure without discontinuities. A buckling effect is observed in structures with discontinuities, which contributes to reducing the peak value while the energy absorbing characteristics decrease.     

Expert system to automate the finite element analysis for non-destructive testing

This work describes an expert system that provides an intelligent interface between the non-destructive testing engineer and the finite element analysis (SDRC/I-DEAS) software. The system helps in efficiently evaluating the stress concentration resulting from the presence of volumetric discontinuities inside the body of the material.This expert system has a wide knowledge base and decision-making skills that are taken from the published documentation and the experience of human experts. In addition, it contains a large number of rules that determine the appropriate type of elements, meshing and solving techniques that should be used for different welded joints.The expert system asks the user questions about the shape and dimensions of the basic part that contains the discontinuities and the shape and dimensions of the embedded discontinuities. Then, it operates I-DEAS, creates the geometry of the basic part and the discontinuities, prepares surfaces for meshing, meshes according the appropriate set of rules, applies loads and boundary conditions and solves the model using the appropriate solving techniques. Finally, it produces a report describing the stress concentration around each discontinuity and checks whether it is harmful to the structure or not.The expert system has a modular structure that can be easily updated and applied for more sophisticated jobs.     

Mechanism of wall caving in Muruntau open pit mine

Interrelation between movements in walls of an open pit mine and formation of fracture pattern in host rocks is considered. __________ Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 5, pp. 62–71, September–October, 2008.     

Constructing continuities in virtual work environments: A multiple case study of two firms with differing degrees of virtuality

In this paper, we study how continuities are constructed in virtual work environments by comparing two firms with differing degrees of virtuality. Using Organizational Discontinuity Theory and drawing on a qualitative study of two accounting firms operating in Finland, we observe virtual work discontinuities in the two firms and identify constructed continuities. We find that in constructing continuities, virtual organizations need to balance rigid and flexible approaches regarding governance structure, the role of technology, communication management, and workflow management. Our main contributions are an empirical application of Organizational Discontinuity Theory to the comparison of virtual work environments and a set of propositions regarding how firms approach continuity construction in different virtuality contexts.     

Studying radiative shocks using laser driven blast waves in clustered gases

We report on the creation of radiative blast waves by irradiating gases of atomic clusters with intense short pulse laser light. The efficient absorption of the cluster medium leads to high energy deposition and development into a cylindrical shock. These non-equilibrium, optically thin shocks have great potential for hydrodynamic scaling with astrophysical relevance, particularly for supernova remnants. We discuss how cluster blast waves may become susceptible to spatial and temporal instabilities and the application of the RAPCAL atomic physics code to determine our plasma conditions.     

大连泰山热电厂新建工程岩质边坡稳定性工程地质评价

大连泰山热电厂新建工程岩质边坡主要受两组优势结构面控制,其结构破坏方式主要为单滑面破坏与楔状破坏,根据现场结构面调查的结果采用概率优势组划分与结构面组合分析即赤平投影法评价了边坡的稳定性。