The Application of Continuous Wavelet Transform Based Foreground Subtraction Method in 21 cm Sky Surveys

We propose a continuous wavelet transform based non-parametric foreground subtraction method for the detection of redshifted 21 cm signal from the epoch of reionization. This method works based on the assumption that the foreground spectra are smooth in frequency domain, while the 21 cm signal spectrum is full of saw-tooth-like structures, thus their characteristic scales are significantly different. We can distinguish them in the wavelet coefficient space easily and perform the foreground subtraction. Compared with the traditional spectral fitting based method, our method is more tolerant to complex foregrounds. Furthermore, we also find that when the instrument has uncorrected response error, our method can also work significantly better than the spectral fitting based method. Our method can obtain similar results with the Wp smoothing method, which is also a non-parametric method, but our method consumes much less computing time.Comment: Accepted by Ap

Deep Captioning with Multimodal Recurrent Neural Networks (m-RNN)

In this paper, we present a multimodal Recurrent Neural Network (m-RNN) model for generating novel image captions. It directly models the probability distribution of generating a word given previous words and an image. Image captions are generated by sampling from this distribution. The model consists of two sub-networks: a deep recurrent neural network for sentences and a deep convolutional network for images. These two sub-networks interact with each other in a multimodal layer to form the whole m-RNN model. The effectiveness of our model is validated on four benchmark datasets (IAPR TC-12, Flickr 8K, Flickr 30K and MS COCO). Our model outperforms the state-of-the-art methods. In addition, we apply the m-RNN model to retrieval tasks for retrieving images or sentences, and achieves significant performance improvement over the state-of-the-art methods which directly optimize the ranking objective function for retrieval. The project page of this work is: www.stat.ucla.edu/~junhua.mao/m-RNN.html .Comment: Add a simple strategy to boost the performance of image captioning task significantly. More details are shown in Section 8 of the paper. The code and related data are available at https://github.com/mjhucla/mRNN-CR ;. arXiv admin note: substantial text overlap with arXiv:1410.109

Chandra Observation of a Weak Shock in the Galaxy Cluster A2556

Based on a 21.5 ks \chandra\ observation of A2556, we identify an edge on the surface brightness profile (SBP) at about 160$h_{71}^{-1}$ kpc northeast of the cluster center, and it corresponds to a shock front whose Mach number $\mathcal{M}$ is calculated to be $1.25_{-0.03}^{+0.02}$. No prominent substructure, such as sub-cluster, is found in either optical or X-ray band that can be associated with the edge, suggesting that the conventional super-sonic motion mechanism may not work in this case. As an alternative solution, we propose that the nonlinear steepening of acoustic wave, which is induced by the turbulence of the ICM at the core of the cluster, can be used to explain the origin of the shock front. Although nonlinear steepening weak shock is expected to occur frequently in clusters, why it is rarely observed still remains a question that requires further investigation, including both deeper X-ray observation and extensive theoretical studies.Comment: 15 pages, 4 figures, accepted by Ap

Recovery of rare-earth elements from NdFeB magnets by zirconium phosphate ion exchangers

The societal transformation from fossil fuel-based energy sources to ecologically friendly energy sources has sparked the development and utilization of electric (and hybrid) vehicles and electric generators for wind turbines, among others. Permanent magnets are essential components of these technologies. Over the years, the production of NdFeB permanent magnets has surpassed all other kinds because of their low cost and improved magnetic properties. The rare-earth elements (REEs) Nd and Dy are critical for the production of these magnets, and they come with a significant supply risk. Also since REEs exist simultaneously in minerals, the balance problem has become increasingly evident; Nd and Dy are produced at the cost of overproduction and stockpiling of other REEs. Due to their limited life span, more and more end-of-life (EOL) NdFeB magnets have accumulated as scrap. Recycling Nd and Dy from EOL NdFeB magnets could be a more ecological means to reduce supply chain pressure and to partially solve the balance problem. The purpose of this thesis is to develop new ion exchangers based on zirconium phosphate (ZrP) for selective recovery of Co, Nd, and Dy from EOL magnets. In general, inorganic ion exchangers, such as ZrPs, are more selective than organic resins because of the ion-sieve functionality originated from rigid structures. Two inorganic ion exchangers, crystalline alpha zirconium phosphate (α-ZrP) and amorphous ZrP (am-ZrP) and one inorganic (am-ZrP)-organic (PAN) ion exchange composite material were synthesized and characterized for their ion exchange properties in this study. The α-ZrP was synthesized with a lower energy and acid consumption. The ion-exchange capacity from the titration result was 6.65 meq/g. Co was taken up minimally from the Co-Nd-Dy ternary solution in acidic solution (pH 1-3) when compared with the total uptake amount. The am-ZrP was synthesized by using an easy scalability synthesis method at the room temperature. The molecular formula Zr(H2PO4)0.17 (HPO4)1.78 (PO4)0.09 • 0.96H2O was calculated from the results of digestion experiment, 31P NMR, and TG analysis. The molecular formula suggested that the theoretical ion-exchange capacity of am-ZrP was 6.97 meq/g. The column elution study of am-ZrP utilized a stepwise gradient elution; Almost complete metal separation was achieved from a mixed 1.0 mM equimolar solution. These promising results encouraged us to apply am-ZrP to a larger lab-scale study. To solve the possible operation problems in scale-up column separation, an am-ZrP/polyacrylonitrile composite was synthesized as bead form. X-ray tomography demonstrated a good spatial distribution of ion-exchange active component am-ZrP in the polymer matrix. Column-optimized experiments for the synthesized composite were performed by altering running temperature, speed, and concentration of the elution agent (HNO3) as well as feed concentration and loading degree. When the column was run at lower speed and at higher temperature, the purity of metal fractions in the effluent was highly enhanced relative to the feed. Gradient elution at 50°C was adopted for metals recovery from the simulated leachate with the concentration 7.6 g/L which in total consisted of 1.4% Co, 9.3% Dy, and 89.3% Nd. Obtaining complete separation was not possible by a single column due to the high Nd concentration in the feed. It is possible to obtain pure Co at the beginning of elution but the separation of Nd and Dy was not possible due to the materials uptake preference for Dy/Nd and their concentration in the feed.Yhteiskunnan siirtyminen fossiilisten energialähteiden käytöstä ympäristöystävällisiin vaihtoehtoihin on vauhdittanut mm. sähkö- ja hybridikulkuneuvojen sekä tuuliturbiinien sähkögeneraattorien kehitystä. Kestomagneetit ovat olennaisia komponentteja näille teknologioille. Viime aikoina neodyymikestomagneetit (NdFeB) ovat syrjäyttäneet muut alhaisen hintansa ja parempien magneettisten ominaisuuksiensa vuoksi. Harvinaiset maametallit neodyymi ja dysprosium, joiden saatavuudessa on huomattavia riskejä, ovat avainasemassa näiden magneettien valmistuksessa. Lisäksi, koska harvinaiset maametallit esiintyvät samoissa mineraaleissa, neodyymia ja dysprosiumia tuotetaan muiden harvinaisten maametallien ylituottamisenkin hinnalla. Koska NdFeB-magneettien käyttöikä on rajallinen, yhä enemmän magneetteja kertyy jätteeksi. Neodyymin ja dysprosiumin kierrättäminen olisi ekologinen keino saatavuusongelman ratkaisemiseksi samalla vähentäen muiden harvinaisten maametallien kertymistä varastoon. Tämän väitöstyön tarkoitus on kehittää uusia zirkoniumfosfaattiin (ZrP) pohjautuvia ioninvaihtimia, joiden avulla voidaan selektiivisesti eli kohdennetusti talteenottaa kobolttia, neodyymia ja dysprosiumia käytetyistä kestomagneeteista. Yleisesti ottaen epäorgaaniset ioninvaihtimet, kuten ZrP:t, ovat selektiivisempiä kuin orgaaniset hartsit, koska niiden tukevat rakenteet toimivat kiinteinä ioniseuloina. Väitöskirjassa on esitetty kahden täysin epäorgaanisen ioninvaihtimen (kiteinen alfa-zirkoniumfosfaatti (α-ZrP) ja amorfinen zirkoniumfosfaatti (am-ZrP)) ja yhden komposiitti-ioninvaihtimen (epäorgaaninen am-ZrP ja orgaaninen polyakryylinitriili) synteesit ja ioninvaihto-ominaisuuksien selvitys. α-ZrP syntetisoitiin menetelmällä, jossa energiantarve ja haponkulutus ovat tavallista pienemmät. Sen ioninvaihtokapasiteetiksi määritettiin 6,65 meq/g, ja kobolttia päätyi vaihtimeen happamasta (pH 1-3) Co-Nd-Dy liuoksesta vain hyvin vähän verrattuna metallien kokonaismäärään. am-ZrP syntetisoitiin helposti skaalattavalla menetelmällä huoneenlämmössä. Sille määritettiin rakennekaava Zr(H2PO4)0,17 (HPO4)1,78 (PO4)0,09 • 0.96H2O yhdistämällä tulokset alkuainemäärityksestä, 31P NMR-analyysista ja termogravimetrisesta analyysista. Rakennekaavan perusteella teoreettinen ioninvaihtokapasiteetti on 6,97 meq/g. am-ZrP:lla tehdyillä kolonnierotuskokeilla saavutettiin lähes täydellinen tutkittujen metallien erotus 1,0 mM metalliliuoksesta (Co, Nd ja Dy). Lupaavat tulokset ajoivat kokeilemaan am-ZrP:a suuremman mittakaavan kolonnierotuksessa. Käyttöongelmia suuremman mittakaavan kolonnikokeissa aiheuttaa hienojakoisten synteesituotteiden aiheuttama paine ja tukkeutuminen. Tätä ehkäistiin syntetisoimalla am-ZrP-polyakryylinitriilikomposiittia pieninä helminä. Röntgentomografialla varmistettiin, että ioninvaihdin oli hyvin jakautunut komposiitissa. Kolonnikokeissa optimoitiin seuraavat tekijät: syöttönopeus, lämpötila, typpihapon vahvuus, syötettävien metallien pitoisuus ja kokonaiskapasiteetin käyttöaste. Kun kolonnia käytettiin hitaammalla syöttönopeudella ja korkeammassa lämpötilassa, metallit erottuivat paremmin. Gradienttimenetelmä 50 °C lämpötilassa valikoitui parhaaksi, kun kokeissa käytettiin simuloitua magneettilietettä, missä metallipitoisuus oli 7,6 g/L (1,4 % Co, 9,3 % Dy, 89,3 % Nd). Koboltin erottaminen muista metalleista onnistui erotuksen alussa, mutta täydellinen neodyymin ja dysprosiumin erottaminen ei ollut mahdollista ainoastaan yhdellä kolonnilla verrattain suuren neodyymikonsentraation johdosta

Research on parallel control of CMAC and PD based on U model

In this paper, the nonlinear U model with time-varying coefficients is investigated and the transformation of the nonlinear model is accomplished by the Newton iterative algorithm. Based on the nonlinear U model, a control algorithm with cerebellar model articulation controller and proportional derivative (PD) in parallel is proposed. The algorithm learns online through a neural network while optimizing the output of the PD, which ultimately enables the actual output of the system to track up to the desired output. Considering that the nonlinear object has the characteristic of rapid change with time, the article improves the PD algorithm to nonlinear PD control algorithm to complete the design of the system. The algorithm automatically adjusts the weights according to the error magnitude to complete the controller parameter adjustment, thus reducing the error of the system. The simulation results show that the nonlinear PD algorithm is better than the PD algorithm, meanwhile, the tracking speed and control precision of the system are improved

Column Separation of Am(III) and Eu(III) by α-Zirconium Phosphate Ion Exchanger in Nitric Acid

The trivalent lanthanide-actinide separations are a major challenge in reprocessing of nuclear fuels. To achieve this, commonly organic extractants and solvents are utilized in elaborate processes. Here we report a simple new method that can perform a supportive or alternative role. A nanocrystalline α-zirconium phosphate ion exchanger was utilized for Eu(III)/Am(III) column separation. Comprehensive preliminary studies were done using batch experiments to optimize the final separation conditions. The distribution coefficients for Eu were determined as a function of pH (from 0 to 3) and salinity (Na, Sr). The distribution coefficients for Am were determined as a function of pH, and Eu concentration, from 1:40 to 10,000:1 Eu:Am molar ratio. The exchanger always preferred Eu over Am in our experimental conditions. Separation factors (Eu:Am) of up to 400 were achieved in binary Eu-Am solution in pH 1. The breakthrough capacity was determined in dynamic column conditions using Eu: 0.3 meq∙g−1, which is approximately 4% of the theoretical maximum capacity. Two types of hot column separation tests were conducted: (i) binary load (selective Am elution), and (ii) continuous equimolar binary feed. In both cases separation was achieved. In (i), the majority (82% of the recovered 93%) of Am could be purified from Eu with extremely high 99.999% molar purity, while alternatively even more (95% of the recovered 93%) at a lower purity of 99.7 mol %. In (ii), up to 330 L∙kg−1 of the equimolar solution per mass of the exchanger could be treated with Am purity above 99.5 mol % in the total eluate. Alternatively, up to 630 L∙kg−1 above 95 mol %, or up to 800 L∙kg−1 above 90 mol % purities