Earth-observation satellite attitude control using passive and active hybrid magnetically suspended flywheels

The control strategy is presented using passive and active hybrid magnetically suspended flywheels（P＆A MSFWs）,which can help meet the requirements of high precision and high stability for earth-observation satellites.Compared with the conventional flywheel,P＆A MSFW has more rotation degrees of freedom（DOFs）since the rotor is suspended by magnetic bearings,and thus requires more efficient controllers.A modified sliding mode control law（SMC）to our novel nonlinear and coupled system is presented,which is interrupted by inertia matrix uncertainties and external disturbances.SMC law via Lyapunov method is improved,and a fuzzy control scheme is used to attenuate the chatting and control attitude accuracy and maintain the robustness of SMC.Simulation results are provided to illustrate the efficiency of our model by using our control law.

An Overview of Passive and Active Dust Detection Methods Using Satellite Measurements

In this paper,the methods to detect dust based on passive and active measurements from satellites have been summarized.These include the visible and infrared（VIR） method,thermal infrared（TIR） method,microwave polarized index（MPI） method,active lidar-based method,and combined lidar and infrared measurement（CLIM） method.The VIR method can identify dust during daytime.Using measurements at wavelengths of 8.5,11.0,and 12.0 fan,the TIR method can distinguish dust from other types of aerosols and cloud,and identify the occurrence of dust over bright surfaces and during night.Since neither the VIR nor the TIR method can penetrate ice clouds,they cannot detect dust beneath ice clouds.The MPI method,however,can identify about 85%of the dust beneath ice clouds.Meanwhile,the active lidar-based method,which uses the Cloud-Aerosol Lidar with Orthogonal Polarization（CALIOP） data and five-dimensional probability distribution functions,can provide very high-resolution vertical profiles of dust aerosols.Nonetheless,as the signals from dense dust and thin clouds are similar in the CALIOP measurements,the lidar-based method may fail to distinguish between them,especially over dust source regions.To address this issue,the CLIM method was developed,which takes the advantages of both TIR measurements（to discriminate between ice cloud and dense dust layers） and lidar measurements（to detect thin dust and water cloud layers）.The results obtained by using the new CLIM method show that the ratio of dust misclassification has been significantly reduced.Finally,a concept module for an integrated multi-satellites dust detection system was proposed to overcome some of the weaknesses inherent in the single-sensor dust detection.

Two Concepts in Optics of Anisotropic Dispersive Media and Polariton Case in Coordinate-Invariant Way

Two concepts of phenomenological optics of homogeneous, anisotropic and dispersive media are compared, the younger and more general concept of media with spatial dispersion and the older concept of (bi)-anisotropic media with material tensors for electric and magnetic induction which only depend on the frequency. The general algebraic form of the polarization vectors for the electric field and their one-dimensional projection operators is discussed without the degenerate cases of optic axis for which they become two-dimensional projection operators. Group velocity and diffraction coefficients in an approximate equation for the slowly varying amplitudes of beam solutions are calculated. As special case a polariton permittivity for isotropic media with frequency dispersion but without losses is discussed for the usual passive case and for the active case (occupation inversion of two energy levels that goes in direction of laser theory) and the group velocity is calculated. For this active case, regions of frequency and wave vector with group velocities greater than that of light in vacuum were found. This is not fully understood and due to large diffraction is likely only to realize in guided resonator form. The notion of “negative refraction” is shortly discussed but we did not find agreement with its assessment in the original paper.

The Skills of A Practical Writing for Tour Guide(I)——Language Differentials

This thesis is about the skills of practical writing for Tour Guide.In this article,the differences between English and Chinese are discussed.As a Tour Guide,one needs to grasp these characteristics of the two languages,and has ability of describing sceneries beautifully and accurately by writing.

A Survey of Experience Gained from the Treatment of Coal Mine Wastewater

During coal mining, water resources may be polluted by acid mine drainage (AMD) if appropriate measures are not taken. AMD releases metals to the environment, which can be harmful to aquatic species and reduce biodiversity. There is a great deal of information available in the literature on the generation and treatment of AMD and this paper tries to summarize some of them in order to facilitate the choice of the most appropriate method for AMD treatment at a specific mining site. The objective of this study was to identify and describe different methods of treating polluted water from coal mining, and to discuss the choice of suitable methods at specific mining sites. Both active and passive methods of AMD treatment are discussed in order to provide a general picture of the measures that have been taken around the world by coal mining companies. From this study, we were able to conclude that in order to choose the appropriate method for a specific mining site it is necessary to analyze the chemistry of the acid water and the flow rate from that site. The cost, implementability and effectiveness of the method should also be considered. Minimizing the amount of drainage water generated is naturally the first choice of management strategy and the containment of the AMD is the second choice. The third alternative is the treatment of the wastewater.

Emerging nanomedicine and prodrug delivery strategies for the treatment of inflammatory bowel disease

Inflammatory bowel disease(IBD)is a chronic and recurrent disease of the gastrointestinal tract,mainly including Crohn's disease(CD)and ulcerative colitis(UC).However,current approaches against IBD do not precisely deliver drugs to the inflammatory site,which leads to life-long medication and serious side effects that can adversely impact patients’adherence.It is necessary to construct optimal drug delivery systems(DDSs)that can target drugs to the region of inflammation,thereby improve therapeutic efficacy and reduce side effects.With the burgeoning development of nanotechnology-based nanomedicines(NMs)and prodrug strategy,remarkable progresses in the treatment of IBD have been made in recent years.Herein,the latest advances are outlined at the intersection of IBD treatment and nanotherapeutics as well as prodrug therapy.First,the pathophysiological microenvironment of inflammatory sites of IBD is introduced in order to rationally design potential NMs and prodrugs.Second,the necessity of NMs for the IBD therapy is elaborated,and the representative nanotherapeutics via passive targeted and active targeted NMs developed to treat the IBD are overviewed.Furthermore,the emerging prodrug-based therapeutics are summarized,including 5-aminosalicylic acid-,amino acid-,and carbohydrate-conjugated prodrugs.Finally,the design considerations and perspectives of these NMs and prodrugs-driven IBD therapeutics in the clinical translation are spotlighted.