一种Ka频段超低交叉极化宽频带波纹喇叭天线

波纹喇叭天线是一种结构紧凑、具有良好辐射性能的馈源天线,特别是轴向槽波纹喇叭天线可以在宽频段内实现极低的交叉极化,对扩展工作频段、实现极化复用有重要的价值。文章对轴向槽波纹喇叭天线的设计方法进行了研究,利用模式匹配法和全波算法软件设计了一种Ka频段超低交叉极化宽频带轴向槽波纹喇叭天线。实测数据表明,该喇叭天线工作频段可覆盖整个Ka频段（26.5~40 GHz）,在频段内回波损耗小于-20 dB、交叉极化小于-45 dB,同时天线具备良好的方向图对称性和相位中心稳定性,在卫星通信领域具有广阔的应用前景。     

On the thermopower and thermomagnetic properties of Er<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Sn<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript>Se solid solutions

The Er _x Sn_1–x Se system is characterized by a significant deviation of the temperature dependence of the differential thermopower from linearity at temperatures below room temperature and a change in the sign of the thermomagnetic coefficient. The deviation of the thermopower of Er _x Sn_1–x Se samples in the nonequilibrium state from linearity is found to be caused mainly by the entrainment of charge carriers by phonons α_ph. The statistical forces of electronic entrainment, A _ph(ε), are estimated.     

Specific features of the capacitance–voltage characteristics of a Cu–SiO<Subscript>2</Subscript>–<Emphasis Type="Italic">p</Emphasis>-InSb MIS structure

The capacitance–voltage and conductance–voltage characteristics of InSb-based MIS structures are measured at different probe signal frequencies with the aim of studying the influence exerted by the technological-synthesis conditions on the capacitive properties of these structures. The influence of positive charge built into the insulator on the sample characteristics is discussed. This influence manifests itself as a sharp capacitance “switch” upon changing the polarity of a low-field (E < 10⁶ V/cm) external signal.     

Varistor effect in highly heterogeneous polymer–ZnO systems

Semiconductors - Composite varistors based on polar and nonpolar polymers (the matrix) and inorganic phase (dispersant) ZnO are studied. It is shown that composite varistors with a high breakdown...     

On Balanced Clustering (Indices,Models, Examples)

Journal of Communications Technology and Electronics - The paper describes and approach to balanced clustering problems. The list of balanced structures includes balanced partitioning of a set,...     

Effect of anions from calcium sources on the synthesis of nano-sized xonotlite fibers

The xonotlite fibers were synthesized via the hydrothermal synthesis method with CaO and SiO2 as the raw materials and the molar ratio of Si/Ca of 1.0. Effect of anions from various calcium sources on the microstructure of the xonotlite fibers is studied in this paper. These obtained products were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM) techniques to investigate their crystalline phase, crystal structure and morphology. The results indicate that anion from various calcium sources has little influence on the crystalline phases of xonotlite fibers but poses a great impact on their morphologies. Xonotlite fibers with single crystal characteristics and large aspect ratio of 50—100 were successfully fabricated from CaCl2 as calcium material at 225 °C for 15 h. The existence of Cl? anion in the CaO-SiO2-H2O system significantly contributes to the formation of xonotlite crystal.     

Simulation of the molecular dynamics of the evolution of argon structural characteristics in the area of glass transition

The results of the simulation of the glass transition process of argon at cooling rates of 10¹², 10¹³, 10¹⁴, and 10¹⁵ K/s are reported. At temperatures far below the melting point, T _f = 83.8 K, the second maximum of the radial distribution function is split into two peaks, which is connected with the glass transition. In addition, the form of this split changes depending on the cooling rates, which points to different structural states of the system. The calculation of the sound velocity in argon by means of correlation functions gives rise to quite reasonable results in the gaseous, liquid, glass, and crystalline states, including the areas of phase transitions.     

Synthesis,molecular dynamic simulation,and density functional theory insight into the cocrystal explosive of 2,4,6-trinitrotoluene/1,3,5-trinitrobenzene

This paper reports the experimental and theoretical studies of the synthesis and behavior of a cocrystal energetic material 2,4,6-trinitrotoluene/1,3,5-trinitrobenzene (TNT/TNB). The performance tests show that this material is more powerful and less sensitive than TNT and TNB. A molecular dynamic simulation is conducted for the cocrystal TNT/TNB by using a COMPASS force field with an NPT ensemble. The density function theory is applied to investigate the band structure and the density of states for various pressures and temperatures. The results show that the TNT/TNB crystal is sensitive to pressures in the interval of 35–50 GPa, and the melting temperature of the crystal is around ≈320 K, which agrees well with experimental results. The Hirshfeld analysis is carried out to ascertain weak interactions and associated two-dimensional fingerprint plots. The crystal packing is demonstrated to be ensured by H· · · O, C· · · O, and O· · ·O contacts.     

Assessment of material use in relation to climate in historical buildings

Climate is among the most significant factors on the environmental performance, life span and/or durability of construction materials in buildings. Although some historical buildings have been abandoned and neglected for a very long period, their existence through centuries can be explained because of their durability to climatic conditions of the area where they are situated. In this study, construction techniques and characteristics of building materials used in some madrasas (historical education buildings) in Western Anatolia (Turkey) were examined in order to evaluate the conditions of the buildings by taking into account climatic conditions of the region. The studied Western Anatolian madrasas, which are in the moderate climatic conditions, were constructed out of rubble stone, brick and mortar in random bond with local workmanship by local builders who continued the older traditions and have survived for more than 300 years without maintenance and repair. On the other hand, most of the madrasa buildings in Central and Eastern Anatolia, which are in the steppe climatic conditions, were differently constructed with cut stone on their exterior surfaces to prevent the main structures of the walls composed of rubble stone and mortar from harsh climatic conditions of these regions. This study indicated that construction techniques and building materials appropriate to the climate might have been intentionally chosen for the survival of historical buildings over the centuries.     

精细化尺度下的城市绿地建设公众 参与途径——以柏林、伦敦“植树计划” 为例

绿地空间具有减缓城市热岛效应、调节微气候、减轻噪声、改善城市居民身心健康、增加生物多样性等诸多优点。城市绿地建设是城市可持续发展的基础,不能仅依靠“自上而下”的上层规划来进行,同时应关注社会公平性、经济效益、市民意愿等因素,从精细化尺度贯彻公众参与制度,真正实现市民共建的“人民城市”。对公众参与政策的起源与发展情况进行简要介绍,并探讨在城市绿地建设中不同阶段的公众参与方式。以柏林、伦敦的“植树计划”政策为例,从资金来源、公众参与方式、参与形式、参与层次、计划成效几方面,比较分析2个城市植树计划的公众参与模式与深度及优点与不足,以对中国绿地建设提供借鉴。最后,针对我国公众参与绿地建设存在的问题,提出精细化构建制度法规保障体系、精细化资金来源途径,以及搭建精细化参与渠道三方面的启示与建议。