Nonlinear dynamics and control of electrodynamic tether for deorbiting space debris

The ever increasing population of space debris poses a great threat to the sustainable development of space industry. Electrodynamic tether has been recognized as a promising technology for the active removal of space debris from overpopulated orbital regions. A typical electrodynamic tether system consists of two end-bodies connected by a conductive tether in space. The electric current flowing in the tether will interact with the magnetic field of the Earth to generate the Lorentz force, by which the system can be deorbited almost without expending propellant. The dynamics and control of any electrodynamic tether system is highly nonlinear by nature and have two critical aspects for practical application: the deployment of electrodynamic tether and the attitude stability during the deorbiting process. This paper summarizes some recent efforts made to address these two issues by the authors’ research team in Nanjing University of Aeronautics and Astronautics. Moreover, some open problems deserving future investigation are discussed

Multiparameter Stochastic Dynamics of Ecological Tourism System with Continuous Visitor Education Interventions

Management of ecological tourism in protected areas faces many challenges, with visitation-related resource degradations and cultural impacts being two of them. To address those issues, several strategies including regulations, site managements, and visitor education programs have been commonly used in China and other countries. This paper presents a multiparameter stochastic differential equation model of an Ecological Tourism System to study how the populations of stakeholders vary in a finite time. The solution of Ordinary Differential Equation of Ecological Tourism System reveals that the system collapses when there is a lack of visitor educational intervention. Hence, the Stochastic Dynamic of Ecological Tourism System is introduced to suppress the explosion of the system. But the simulation results of the Stochastic Dynamic of Ecological Tourism System show that the system is still unstable and chaos in some small time interval. The Multiparameters Stochastic Dynamics of Ecological Tourism System is proposed to improve the performance in this paper. The Multiparameters Stochastic Dynamics of Ecological Tourism System not only suppresses the explosion of the system in a finite time, but also keeps the populations of stakeholders in an acceptable level. In conclusion, the Ecological Tourism System develops steadily and sustainably when land managers employ effective visitor education intervention programs to deal with recreation impacts

Numerical Simulation of Aerodynamic Noise of Soundproof Enclosure of Air Compressor Unit

During the operation of the air compressor unit, the suction and exhaust process of the air compressor and the operation of other equipment will cause air flow pulsation, which is often accompanied by the generation of air compressor noise. Numerical simulation method, as an important means to study the flow field characteristics and noise characteristics of air compressors, has been widely used in recent years. This article takes the noise enclosure of a certain air compressor unit as the research object, and use numerical simulation method to study the air intake part of the enclosure. The influence of inlet louver and suction deflector on the aerodynamic performance of air compressor noise enclosure was analyzed, and the influence of different inlet louver structures and different suction deflector structures on noise was compared. This paper uses the broadband noise model to predict the distribution of air flow pulsation noise. In order to quantitatively study the noise, the FW-H model based on Lighthill\u27s acoustic analogy method was used for the aerodynamic noise simulation, and the frequency response of the aerodynamic noise of air compressor was obtained

Asiakastyytyväisyystutkimus : Case: Recycling Oy R. Okkonen

Opinnäytetyössä tutkittiin Recycling Oy R. Okkosen asiakkaiden tyytyväisyyttä yrityksen palveluihin sekä pyrittiin saamaan tietoa asiakkaiden tarvitsemista palveluista. Tutkimukseen ryhdyttiin, koska tutkimuksella oli sekä tutkijaa että yritystä hyödyntävä näkökulma. Tutkijalla oli kokemusta yrityksen toiminnasta, jolloin opinnäytetyön toteuttaminen tuntui mielenkiintoiselta, ja lisäksi yrityksellä oli tarvetta tutkimukselle, koska sellaista ei oltu aikaisemmin tehty. Tutkimus käynnistyi aiheen valinnalla, jonka jälkeen laadittiin haastattelulomake ja se jaettiin tutkimussuunnitelman asettaman rajauksen mukaisesti taloyhtiöihin, joissa yrityksellä oli kuukausikohtainen huoltosopimus. Saadut vastaukset muokattiin sähköiseen muotoon ja tämän jälkeen alkoi tutkimuksen kirjallisen raportin toteuttaminen. Tutkimusta tarkasteltiin yrityksen näkökulmasta. Raportissa käytettiin kvantitatiivista tutkimustapaa, eli asiakastyytyväisyyttä mitattiin survey-tyyppisellä haastattelulomakkeella. Lisäksi tutkimuksessa oli havaittavissa kvalitatiivisen tutkimuksen piirteitä, kun saatuja vastauksia tulkittiin. Tutkimuksen tutkimusote oli kuvaileva. Teoreettisen lähdemateriaalin osuus jätettiin työssä pienemmälle painoarvolle, koska case-metodologialla toteutetussa työssä suurempi paino haluttiin antaa tutkijan omalle pohdinnalle ja syvemmälle analyysille yrityksestä. Tutkimus osoitti, että yrityksen palveluita ei tunnettu tarpeeksi hyvin. Näin ollen tunnettuutta olisi lisättävä. Yrityksen kotisivujen sisältöön saatiin myös paljon kehitysideoita. Vaikkei yritys kerännyt varsinaisesti palautetta, oli vastaajien mielestä palautteen antaminen helppoa. Jatkossa palautetta toivottiin kerättävän palautelaatikon muodossa. Yrityksen yhteystiedot koettiin olevan helposti saatavilla. Erityistä kiitosta annettiin puheluihin vastaamisesta sekä töiden toteuttamisesta nopeasti myös virka-ajan ulkopuolella.Tutkimus osoitti, että vastaajat olivat kokonaisuudessaan tyytyväisiä yrityksen palveluihin. Tutkimuksen avulla saatiin esiin uusia kehitettävissä olevia palveluja. Näin ollen tutkimus onnistui saamaan asiakkaiden mielipiteitä ilmi heidän tarvitsemistaan palveluista. Tutkimuksesta selvisi, että yksilöllisille palveluille löytyi kysyntää. Asiakkaat olivat myös valmiita maksamaan kiinteistönhuoltopalveluista. Myös isännöitsijä oli tyytyväinen kiinteistönhoitajan toimiin sekä kiinteistönhoitajan ja isännöitsijän väliseen toimeksiantosuhteeseen.The purpose of this thesis was to study a customer satisfaction and service about Recycling Oy R. Okkonen. The subject of thesis was chosen because it had mutual benefit for the company and researcher. The research was needed because company wanted to know their customers' needs and if there were something to improve in their operations. The research started from letter survey in January 2008. Letters were delivered to housing organizations which had monthly maintenance contract with the company. Received answers were later transferred in electrical form so that they were easier to process and analyze. The thesis was examined from the company's point of view. The research that was used was quantitative one. The thesis also used forms of qualitative research. Because of the case methodology, the amount of source material was minor. It gave opportunity for researcher to anylyze deeper the results of the study. The research pointed out that services of the company were not known well enough. Therefore research ended up in conclusion that the company has to improve its conspicuousness. The thesis managed to receive information that was needed to develop company's home pages. Opinions of respondents proved that feedback was easy to give to the company. The study revealed that company's contact information was easy to reach. Especially positive opinion was given to the company's work performance out of office hours. The results revealed that the customers of Recycling Oy R. Okkonen were highly satisfied with company's operations. The study managed to find out which were the customers needs for the services. The study also pointed out that there was demand for customer services. Customers were ready to pay for services of repair and maintenance of properties. Estate manager was satisfied for the assignment relationship between him and property manager. The study reached reliable research results from the author of the thesis point of view

A novel Li(2)FeSiO(4)/C composite: Synthesis, characterization and high storage capacity

A Li(2)FeSiO(4)/C composite material has been prepared via a solution-polymerization approach. The composite is characterized by X-ray diffraction (XRD), X-ray absorption near edge structure (XANES), scanning electron microscope (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and superconducting quantum interference device (SQUID). The electrochemical performance of the Li(2)FeSiO(4) is greatly enhanced and the initial discharge capacity is similar to 220 mA h g(-1), when it is cycled between 1.5-4.8 V. This indicates that more than one lithium ion can be extracted out of the Li(2)FeSiO(4) lattice. At high current densities, the Li(2)FeSiO(4)/C also exhibits excellent rate capability and cycling stability. This indicates that it is a very promising cathode material for next generation lithium-ion batteries.National Natural Science Foundation of China[20873115, 20473068, 29925310]; National Basic Research Program[2007CB209702, 2011CB905903

Facilitated Li+ ion transfer across the water/1,2-dichloroethane interface by the solvation effect

National Basic Research Program of China [2012CB932902, 2009CB220100, 2011CB933700]; Open Foundation of State Key Laboratory for Physical Chemistry of Solid Surfaces, Xiamen University [2010-18]; Beijing Higher Institution Engineering Research Center of Power Battery and Chemical Energy Materials; National Science Foundation of China [20973142, 21061120456, 21021002]; Ministry of Science and Technology (MOST) of China [2010DFA72760]; US-China Collaboration on Cutting-edge Technology Development of Electric VehiclesWe demonstrate that the solvation effect can be the driving force for ion transfer across the water/1,2-dichloroethane interface. Voltammetric behaviours of facilitated Li+ ion transfer by the solvents of lithium-based batteries are investigated, which is valuable for the dual-electrolyte Li-air batteries, but also for the ion detection, separation and extraction

Y-Chromosome Evidence for Common Ancestry of Three Chinese Populations with a High Risk of Esophageal Cancer

High rates of esophageal cancer (EC) are found in people of the Henan Taihang Mountain, Fujian Minnan, and Chaoshan regions of China. Historical records describe great waves of populations migrating from north-central China (the Henan and Shanxi Hans) through coastal Fujian Province to the Chaoshan plain. Although these regions are geographically distant, we hypothesized that EC high-risk populations in these three areas could share a common ancestry. Accordingly, we used 16 East Asian-specific Y-chromosome biallelic markers (single nucleotide polymorphisms; Y-SNPs) and six Y-chromosome short tandem repeat (Y-STR) loci to infer the origin of the EC high-risk Chaoshan population (CSP) and the genetic relationship between the CSP and the EC high-risk Henan Taihang Mountain population (HTMP) and Fujian population (FJP). The predominant haplogroups in these three populations are O3*, O3e*, and O3e1, with no significant difference between the populations in the frequency of these genotypes. Frequency distribution and principal component analysis revealed that the CSP is closely related to the HTMP and FJP, even though the former is geographically nearer to other populations (Guangfu and Hakka clans). The FJP is between the CSP and HTMP in the principal component plot. The CSP, FJP and HTMP are more closely related to Chinese Hans than to minorities, except Manchu Chinese, and are descendants of Sino-Tibetans, not Baiyues. Correlation analysis, hierarchical clustering analysis, and phylogenetic analysis (neighbor-joining tree) all support close genetic relatedness among the CSP, FJP and HTMP. The network for haplogroup O3 (including O3*, O3e* and O3e1) showed that the HTMP have highest STR haplotype diversity, suggesting that the HTMP may be a progenitor population for the CSP and FJP. These findings support the potentially important role of shared ancestry in understanding more about the genetic susceptibility in EC etiology in high-risk populations and have implications for determining the molecular basis of this disease