Construction of enhanced multi-polarization and high performance electromagnetic wave absorption by self-growing ZnFe_(2)O_(4)on Cu_(9)S_(5)

The development of 3D structural composites with electromagnetic(EM)wave absorption could attenuate EM waves.Herein,magnetized flower-like Cu_(9)S_(5)/ZnFe_(2)O_(4)composites were fabricated through a multistep hydrothermal method.The crystallographic and surface phase chemical information,morphological structure,and magnetic and EM parameters of the composites were analyzed.The prepared Cu_(9)S_(5)/ZnFe_(2)O_(4)composites have multiple loss paths for EM waves and present an overall 3D flower-like structure.The Cu_(9)S_(5)/ZnFe_(2)O_(4)composites exhibit a minimum reflection loss of-54.38 dB and a broad effective absorption bandwidth of 5.92 GHz.Through magnetization,ZnFe_(2)O_(4)particles are self-assembled and grown on the surfaces of Cu_(9)S_(5).Such a modification is conducive to the generation of additional cross-linking contact sites and the effective introduction of a large number of phase interfaces,crystalline defects,special three-dimensional flower-like structures,and magneto-electrical coupling loss effects.Moreover,the synergistic effect of multiple loss strategies effectively improves EM wave absorption by the material.This work can provide a strategy for the use of magnetizationmodified sulfide composite functional materials in EM wave absorption.

The internal COF features in Dome A of Antarctica revealed by multi-polarization-plane RES

The ice exceeding one million years old has significant meaning for verifying and interpreting the middle Pleistocene transition （MPT） and the relationship between greenhouse gas and climate change. The region near Dome A in Antarctica satisfies the conditions for obtaining million-years-old ice since it has low temperatures and low accumulation rates. We analyze the corresponding relation between radar wave features and the crystal orientation fabric （COF） types based on the results of multi-polarization plane radio echo sounding （RES）. The results show that, even in the summit of the ice sheet, the COF type is not perfect, but is an elongated single-pole COF. Principal-axis-orientation differences of the COF among the different periods exist and reveal that the ice flow orientations are not constant but deviate clockwise with the increasing depth. This may be related to the adjacent basal valley or both height and position changes of the summit during the glacial-interglacial periods.

Multi-polarization reconstruction from compact polarimetry based on modified four-component scattering decomposition

An improved algorithm for multi-polarization reconstruction from compact polarimetry （CP） is proposed. According to two fundamental assumptions in compact polarimetric reconstruction, two improvements are proposed. Firstly, the four-component model-based decomposition algorithm is modified with a new volume scattering model. The decomposed helix scattering component is then used to deal with the non-reflection symmetry condition in compact polarimetric measurements. Using the decomposed power and considering the scattering mechanism of each component, an average relationship between copolarized and crosspolarized channels is developed over the original polarization state extrapolation model. E-SAR polarimetric data acquired over the Oberpfaffenhofen area and JPL/AIRSAR polarimetric data acquired over San Francisco are used for verification, and good reconstruction results are obtained, demonstrating the effectiveness of the proposed algorithm.

Research on novel multi-layer and multi-polarized slot-coupling planar antenna array

A novel multi-layer planar antenna array to achieve multi-polarized radiation is developed. U-shaped coupling slots are embedded in the ground plane to extend the bandwidth. The phase relation between adjacent elements in the radiation field is analyzed when adjacent elements are fed in opposite phase. Return loss and radiation pattern are measured for a 16-element antenna array at 12.5 GHz. The radiation pattern shows a good agreement with the calculated one in the shape of the main beam. The return-loss of the proposed antenna array is less than -20 dB in the 12.5 GHz frequency band （12.25-12.75 GHz）. Because of two feed ports the antenna can transmit arbitrary elliptic polarized waves if the two feed ports have different amplitude and phase. The main factors such as element spacing, substrate medium and manufacturing imperfection are analyzed and the corresponding conclusions are presented.

The Multi-Polar Structure and New Balance of the China-US Relationship

The multi-polar structure is a new international relationship structure, which differs greatly from both the bi-polar and uni-polar structures in both structure and nature, mainly emerging from the evolution of two aspects： first, the meaning of ＂polar＂ has undergone a major change; and second, beyond the power structure, the relationship structure between nations is much different from the past and is inflicting an increasingly important impact on core implication of the multi-polar the structure. Decentralization is the structure. In the current reality of international politics, decentralization refers to the dissolution of US hegemony, as different nations and power centers are busy competing and cooperating with one another at different levels in accordance with their own advantages and characteristics. Globally, the multi-polar structure manifests a state in which the current power structure is loosening, while international relationships have become more diversified due to their ongoing development. This is the development of a new relationship structure that is of great significance and what calls for our closest attention.

Global Power Structure Shifted and Transitional Multi-polarity Emerged

The world is facing the third important global power shift.The United States,EU, Japan,Russia,China,and the newly emerging power group are becoming the six big forces in the international center stage,while the former three forces and the latter three belong to two groups,waning and waxing respectively.The major shift in the global balance of power is bound to give rise to the transitional multi-polar configuration,which implies a shifting of leadership over the configuration,China and U.S.outweighing other forces,global issues looming large,homogeneity blending with heterogeneity,and a shifting center of world powers.The transitional multi-polar configuration is all about change,upon which China is one of the decisive forces.

Study on New Generation Spaceborne Rain and Cloud Measuring Radar System Techniques

Dual-frequency and multi-polarization spaceborne rain and cloud measuring radar is the inevitable trend of remote sensing techniques.Techniques of new generation dual-frequency and multi-polarization spaceborne rain and cloud measuring radar are studied systematically.Radar block diagram and main parameters are presented.Antenna subsystem scheme is analyzed and antenna parameters are proposed.Central electronic device subsystem scheme is given and data rate of spaceborne radar is calculated.This paper is a meaningful try for carrying out spaceborne rain and cloud measuring radar design,acting as a reference to Chinese spaceborne rain and cloud measuring radar design and production in future.

Contributing Asian Wisdom to World Development

WITH the trend of multi-polarization, economic globalization, cultural diversity, and wide IT application, the uncertainties in the international landscape have been increasing and the global challenges we face have never been more serious. In this scenario, there is still hope for the world to continue its development which depends on a prosperous, stable, and sustainable Asia.

SCATTERING OF CIRCULAR CAVITY IN RIGHT-ANGLE PLANAR SPACE TO STEADY SH-WAVE

Complex function method and multi-polar coordinate transformation technology are used here to study scattering of circular cavity in right-angle planar space to SH-wave with out-of-plane loading on the horizontal straight boundary. At first, Green function of right-angle planar space which has no circular cavity is constructed; then the scattering solution which satisfies the free stress conditions of the two right-angle boundaries with the circular cavity existing in the space is formulated. Therefore, the total displacement field can be constructed using overlapping principle. An infinite algebraic equations of unknown coefficients existing in the scattering solution field can be gained using multi-polar coordinate and the free stress condition at the boundary of the circular cavity. It can be solved by using limit items in the infinite series which can give a high computation precision. An example is given to illustrate the variations of the tangential stress at the boundary of the circular cavity due to different dimensionless wave numbers, the location of the circular cavity, the loading center and the distributing range of the out-of-plane loading. The results show the efficiency and effectiveness of the mothod introduced here.

Impact of Depolarization Phenomena on Polarized MIMO Channel Performances

The performance and capacity of multiple-input multiple-output (MIMO) wireless channels are limited by the spatial fading correlation between antenna elements. This limitation is due to the use of mono polarized antennas at receiver and transmitter sides. In this paper, in order to reduce the antenna correlation, the polarization diversity technique is employed. Although the spatial antenna correlation is attenuated for multi-polarization configurations, the cross-polar components appear. This paper highlights the impact of depolarization effect on the MIMO channel capacity for a 4×4 uniform linear antenna array. We assume that the channel is unknown at the transmitter and perfectly known at the receiver so that equal power is distributed to each of the transmit antennas. The numerical results illustrate that for low depolarization and spatial correlation, the capacity of single-polarization configuration behaves better than that of multi-polarization configuration.

Dynamic Stress and Pore Pressure Around Circular Cavity in Saturated Porous Elastic Half-space Under Harmonic Plane Dilatational Waves

Dynamic stress concentration and pore pressure concentration around an infinitely long cylindrical cavity of circular cross-section subjected to harmonic plane dilatational waves in fluid-saturated porous elastic half-space were obtained by a complex function method based on potential function and multi-polar coordinate. The steady state Biot’s dynamic field equations of porous elastic solid with a viscous liquid were uncoupled into Helmholtz equations via given potential functions. A circular cavity with large radius is used to replace the straight boundary of the saturated porous elastic half-space. The stresses and pore pressures were obtained by using complex functions in multi-polar coordinates with certain boundary conditions of the solid matrix and the fluid matrix. The approximate solutions were compared to existing numerical solutions. Then the variations of the coefficients of dynamic stress concentration and the pore pressures concentration on boundaries of the cavity were discussed with different parameter conditions. The results of the given numerical example indicate that the method used is useful and efficient to the scattering and dynamic stress concentration of plane dilatational waves in saturated porous elastic half-space.

Scattering of SH-waves on triangular hill joined bysemi-cylindrical canyon

Scattering of SH-waves on the triangular hill joined by semi-cylindrical canyon in half-space is studied using the method of complex function and moving coordinates. The model being studied is divided into two domains. The wave functions satisfying the required condition at each wedge are constructed in each equation. The equations are solved with Fourier expansion. Numerical results are provided to discuss the influence of scattering of SH-waves.

Pronounced Clashes in a Changing World

Clashes between globalization and anti-globalization forces, between US hegemony and emerging powers, and between unilateralism and multilateralism have since early 2018 become pronounced. The unprecedented changes being seen now intensify the mismatch between security challenges and global security mechanisms that contributes to our uncertain times. The current US judgment over the international situation is hasty, one-sided and negative. By deliberately reducing the dependence between China and the US over shared interests, the US pushes Sino-US relations towards a new cold war. China, in analyzing causal relationships and developments at a macroscopic level, seeks convergence of its national interests and humanity’ s common interests. In pooling the wisdom to design an operable international strategy and in using international cooperation in this globalized era, China is committed to new approaches to international relations and great power relations.

BRICS and Geopolitics： A Match Made in Heaven？

We are living in a multi-polar world under the greater influence of one power. After the shutdown of the government in the US, it can be said that the sole power is about to be challenged. This paper hopes to establish the fact that the future of the international system will continue to be multi-polar. Economic groupings like the Brazil, Russia, India, China, and South Africa （BRICS）, Mexico, Indonesia, Singapore and Turkey （MIST） and others denote to this. These groupings may present an alternative to geographically locked but indispensible European Union. Despite the system being multi-polar, the United States dominates the international system. This paper deals with the BRICS countries that propose a bid for power in international relations. Will they have equidistant power form one another or will there be a hierarchy in between them？ Can they take/make economic or political decisions？ Is a geographically spread power structure more effective in controlling the balances between war and peace？ Can they remain objective on trouble spots that may arise in Europe, the Middle East, the Balkans, Asia and the Americas？ This paper hopes to achieve the goal of providing a framework for understanding a multi-polar approach to international relations based on the collaboration of BRICS countries. The first part will be the theoretical framework of the paper. The second part will be concerned with American supremacy in foreign relations and the need to question it. The third part will deal with emerging powers but since the most influential ＂power politics＂ are steered by China and Russia the main emphasis will be on them. The last part will come to the conclusion.

Cl-terminated decoration to modulate the permittivity of MXene for enhanced electromagnetic-absorbing performance

The explosive growth of communication technology has given rise to a large number of high-quality electromagnetic wave(EMW)absorbing materials,and single-component materials are often difficult to satisfy the demand.In this study,we propose an etching method of molten chlorine salts under vac-uum to prepare Cl-terminated MXene(MX-Cl)which can meet the requirements of"thin,light,wide and strong"and realize the application of single-component absorbing materials.In the X and Ku bands,MX-Cl achieves a strong reflection loss of-42.99 dB and an effective absorption bandwidth of 3.44 GHz with the 1.2 mm matching thickness.The presence of Cl groups restricts the free electron movement of surface-Ti,which controls the conductivity of the MX-Cl and optimizes its permittivity.Dipole polarization induced by Ti-Cl,interfacial polarization between MXene layers and multiple scattering effects inside the layers all significantly increase the dielectric loss of the MX-Cl considerably.This study provides a new approach to investigating the effect of single atoms on the dielectric properties of materials.This work also offers a simple and low-cost process for the preparation of single-component MXene EMW-absorbing materials.

China’s Emerging Role in the New Arab World

The Arab Spring has changed the political landscape in the Arab world.The spring which began as genuine grass-root movement designed to create more equitable social projects,was steered by Western powers and local Islamists in different directions with these powers heavily intervening to control and/or weaken Arab states.China has pursued a policy of non-intervention in the domestic affairs of Arab states,and letting the peoples decide their own future.China may have miscalculated when it allowed NATO to interfere in Libya.That intervention had catastrophic consequences for China and Libya.Consequently,China,in collaboration with Russia decided not to repeat the same experience in Syria especially since foreign intervention in this case will be even more catastrophic.China vetoed Security Council draft resolutions calling for regime change in Syria and insisted on letting the Syrians decide peacefully their future course of action.Further,China under the new leadership has suggested for the first time a four-point program to settle the Arab-Israeli conflict.The article argues that the Chinese-Russian approach to the Syrian crisis is bound to have long-term implications for the future of the Arab world.As the signs of the positive contributions of that approach are emerging,China should proceed to reinforce these contributions through a concerted approach to engage with the new regimes in the Arab world,strengthen the China-Arab States Cooperation Forum,correct the imbalances of Sino-Arab trade,especially with the countries of the Arab Spring,focus on investing in these countries in labor-intensive industries,putting the four-point proposal on the agenda of ArabIsraeli negotiations,and,most importantly,deal with the question of the Israeli nuclear capabilities and the potential of Israel going to war against Iran,a scenario which will represent a major setback to the Chinese achievements in the region.