著者

Liu Xizheng Li Huiqiao Li De Ishida Masayoshi Zhou Haoshen

出版者

Elsevier B.V.

雑誌

Journal of power sources (ISSN:03787753)

巻号頁・発行日

vol.243, pp.374-380, 2013-12

被引用文献数

84

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Layered LiNi1/3Co1/3Mn1/3O2 was modified by poly(3,4-dioxyethylenethiophene) PEDOT via a facile method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and infrared spectroscopy (IR). PEDOT modified samples exhibited both improved rate and cycle performance compared with the pristine LiNi1/3Co1/3Mn1/3O2. At a charge/discharge current of 1500 mA g−1, the discharge capacity was improved from 44.3 to 73.9 mAh g−1. The sample with 2 wt% and heat treated at 300 °C showed the optimized electrochemical performance. Galvanostatic intermittent titration technique (GITT) and cyclic voltammetry (CV) results indicated that the battery polarization of coated samples have been suppressed obviously because the PEDOT layer facilitated the electron transfer at the interface of electrode and electrolyte.

著者

Fuchibe Kohei Koseki Yuta Aono Tatsuya Sasagawa Hisashi Ichikawa Junji

出版者

Elsevier B.V.

雑誌

Journal of fluorine chemistry (ISSN:00221139)

巻号頁・発行日

vol.133, pp.52-60, 2012-01

被引用文献数

34 11

---

Controlled generation of difluorocarbene was effected by an NHC catalyst under mild conditions starting from trimethylsilyl 2,2-difluoro-2-fluorosulfonylacetate (TFDA). Cyclohexenones and tetralones were treated with TFDA in the presence of catalytic amounts of N,N′-dimesitylimidazolium chloride and sodium carbonate. The ketones were difluoromethylated with the generated difluorocarbene to afford enol difluoromethyl ethers without difluorocyclopropanation. The ethers thus obtained were dehydrogenated with DDQ to furnish aryl difluoromethyl ethers in high yield. Under similar conditions, secondary amides underwent difluoromethylation selectively on the oxygen atom to give difluoromethyl imidates, which allows the formation of 2-difluoromethoxypyridines.

著者

Sanai Tatsunori Ito Keita Toko Kaoru Suemasu Takashi

出版者

Elsevier B.V.

雑誌

Journal of crystal growth (ISSN:00220248)

巻号頁・発行日

vol.378, pp.342-346, 2013-09

被引用文献数

5 1

---

We formed CoxFe4−xN (0≤x≤2.9) epitaxial thin films on SrTiO3 (001) substrates by molecular beam epitaxy supplying solid Co and Fe and a radio frequency N2 plasma, simultaneously. The composition ratio of Co/Fe in CoxFe4−xN was controlled by changing the weight ratio of Co to Fe flakes in the crucible of the Knudsen cell used. Epitaxial growth of CoxFe4−xN thin films were confirmed by reflection high-energy electron diffraction and θ–2θ X-ray diffraction patterns. Magnetization versus magnetic field curves measured at room temperature using a vibrating sample magnetometer showed that the axis of easy magnetization was changed from [100] to [110] with increasing x in CoxFe4−xN.

著者

Baba M. Toh K. Toko K. Hara K.O. Usami N. Saito N. Yoshizawa N. Suemasu T.

出版者

Elsevier B.V.

雑誌

Journal of crystal growth (ISSN:00220248)

巻号頁・発行日

vol.378, pp.193-197, 2013-09

被引用文献数

5 1

---

BaSi2 epitaxial films were grown on Si(111) substrates by a two-step growth method including reactive deposition epitaxy (RDE) and molecular beam epitaxy (MBE). To enlarge the grain size of BaSi2, the Ba deposition rate and duration were varied from 0.25 to 1.0 nm/min and from 5 to 120 min during RDE, respectively. The effect of post-annealing was also investigated at 760 °C for 10 min. Plan-view transmission electron micrographs indicated that the grain size in the MBE-grown BaSi2 was significantly increased up to approximately 4.0 μm, which is much larger than 0.2 μm, reported previously.

著者

Khan M. Ajmal Hara Kosuke O. Nakamura Kotaro Du Weijie Baba Masakazu Toh Katsuaki Suzuno Mitsushi Toko Kaoru Usami Noritaka Suemasu Takashi

出版者

Elsevier B.V.

雑誌

Journal of crystal growth (ISSN:00220248)

巻号頁・発行日

vol.378, pp.201-204, 2013-09

被引用文献数

18 1

---

We have successfully grown a-axis-oriented p-type BaSi2 films on Si(111) by in situ boron (B) doping using molecular beam epitaxy (MBE). The hole concentration in B-doped BaSi2 was controlled in the range between 1017 and 1019 cm−3 at room temperature by changing the temperature of the B Knudsen cell crucible. The acceptor level was estimated to be approximately 23 meV.

著者

Nakamura K. Toh K. Baba M. Khan M. Ajmal Du W. Toko K. Suemasu T.

出版者

Elsevier B.V.

雑誌

Journal of crystal growth (ISSN:00220248)

巻号頁・発行日

vol.378, pp.189-192, 2013-09

被引用文献数

9 4

---

Al or B layers of a few hundreds of nm in thickness deposited on BaSi2 epitaxial films on Si(1 1 1) substrates were annealed at different temperatures, and the diffusion coefficients of Al and B were evaluated using secondary ion mass spectrometry with O2+. We also investigated the effect of post annealing (850 °C, 10 min) of BaSi2 films on the diffusion coefficients. It was found that both the lattice diffusion and the grain boundary diffusion were decreased by the post-annealing. The plan-view transmission electron microscopy images revealed that the grain size was increased from approximately 0.2 to 0.6 μm by the annealing, and the X-ray diffraction intensities also increased. The activation energies of lattice and grain boundary diffusions in the post-annealed BaSi2 are 0.63 eV and 0.58 eV for Al, and 4.6 eV and 4.4 eV for B, respectively.

著者

Hino Hideitsu Wakayama Keigo Murata Noboru

出版者

Elsevier B.V.

雑誌

Computational statistics & data analysis (ISSN:01679473)

巻号頁・発行日

vol.67, pp.105-114, 2013-11

被引用文献数

5 2

---

The importance of dimension reduction has been increasing according to the growth of the size of available data in many fields. An appropriate dimension reduction method of raw data helps to reduce computational time and to expose the intrinsic structure of complex data. Sliced inverse regression is a well-known dimension reduction method for regression, which assumes an elliptical distribution for the explanatory variable, and ingeniously reduces the problem of dimension reduction to a simple eigenvalue problem. Sliced inverse regression is based on the strong assumptions on the data distribution and the form of regression function, and there are a number of methods to relax or remove these assumptions to extend the applicability of the inverse regression method. However, each method is known to have its drawbacks either theoretically or empirically. To alleviate drawbacks in the existing methods, a dimension reduction method for regression based on the notion of conditional entropy minimization is proposed. Using entropy as a measure of dispersion of data, a low dimensional subspace is estimated without assuming any specific distribution nor any regression function. The proposed method is shown to perform comparable or superior to the conventional methods through experiments using artificial and real-world datasets.

著者

Toko Kaoru Fukata Naoki Nakazawa Koki Kurosawa Masashi Usami Noritaka Miyao Masanobu Suemasu Takashi

出版者

Elsevier B.V.

雑誌

Journal of crystal growth (ISSN:00220248)

巻号頁・発行日

vol.372, pp.189-192, 2013-06

被引用文献数

15 4

---

High-quality crystalline Ge thin films on low-cost glass substrates are desired to reduce the fabrication cost of high-efficiency tandem solar cells. We applied an Al-induced crystallization technique to amorphous-Ge films (50-nm thickness) on SiO2 glass substrates. The annealing temperature of the sample strongly influenced the grain size and the crystal orientation in the grown polycrystalline Ge layers: low annealing temperatures resulted in large grains and high (111)-orientation fractions. As a result, annealing at 325 °C provided 98% (111)-oriented grains with average diameters of 30 μm. Moreover, the grown Ge layers could be used as an epitaxial template for chemical vapor deposition. This large-grained Ge film on a SiO2 substrate appears promising for use as a Ge light-absorbing layer, as well as an epitaxial buffer layer for group III–V compound semiconductors.

著者

Shivaram Niranjan Timmers Henry Tong Xiao-Min Sandhu Arvinder

出版者

Elsevier B.V.

雑誌

Chemical physics (ISSN:03010104)

巻号頁・発行日

vol.414, pp.139-148, 2013-03

被引用文献数

7

---

We present experimental results and a theoretical framework for understanding the ionization dynamics in atoms exposed to XUV attosecond pulse trains and strong multi-cycle infrared (IR) fields. We invoke the Floquet formalism to model dressed atomic states as a manifold of Fourier components spaced by the laser frequency. In XUV-IR pump–probe measurements, we observe that the ionization yield oscillates due to quantum interference between photo-excitation paths to a Floquet state. We show that the intensity-dependent shifts of atomic structure modify the ionization channels and the associated interference phase. We extract this phase variation and compare it with simulations. These results provide a comprehensive description of the two-color ionization process and enable new schemes for control of attosecond ionization and fragmentation dynamics.

著者

Kubota Tadahiko Ihara Masayuki Katayama Shinichi Nakai Hideki Ichikawa Junji

出版者

Elsevier B.V.

雑誌

Journal of power sources (ISSN:03787753)

巻号頁・発行日

vol.207, pp.141-149, 2012-06

被引用文献数

20

---

Five 1,1-difluoro-1-alkenes bearing aryl groups are investigated as electrolyteadditives for high-charge-voltage lithiumionbatteries with an aim to induce favorable solid electrolyte interphase (SEI) formation. Among them, 1,1-difluoro-4-phenylbut-1-ene (DF-1) forms appropriate SEIs on the cathode and anode by its reactions under oxidative and reductive conditions, respectively, which was suggested by linear sweep and cyclic voltammetry. The SEIs formed with the DF-1 containing electrolyte on the cathode and anode were analyzed by X-ray photoelectron spectroscopy and time of flight-secondary ion mass spectrometry, indicating the following: (i) the cathode surface has a LiF-rich layer with unsaturated hydrocarbons, and (ii) the anode surface also has a LiF-rich layer, which probably includes fluoromethylene (CHF) compounds. The formation of the SEIs on both electrodes with DF-1 results in low impedance being maintained, and thus, particularly good cycle performance even at high-charge-voltage.

著者

Liu Xizheng He Ping Li Huiqiao Ishida Masayoshi Zhou Haoshen

出版者

Elsevier B.V.

雑誌

Journal of alloys and compounds (ISSN:09258388)

巻号頁・発行日

vol.552, pp.76-82, 2012-03

被引用文献数

73 17

---

The capacity fading and lower rate of layered cathode materials prohibited widely applications in lithium ion batteries. In this paper, V2O5 was coated on the surface of LiNi1/3Co1/3Mn1/3O2 to enhance its electrochemical performance at a voltage range of 2.8–4.5 V. The prepared materials were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscope (TEM). The capacity retention at the 100th cycle have been increased from 62% to over 80% for the 3 wt.% V2O5 coated sample. The rate performance has been improved by V2O5 coating which mainly because of the coating layer enhance the surface electronic/ionic transport. Cyclic voltammetry (CV) showed that the redox properties of the pristine sample have a more obvirous changes after charge–discharge cycles compared with the coated samples. Electrochemical impedance spectroscopy (EIS) results suggest that the V2O5 coating layer play an important role in suppressing the increase of cell impedance with cycling especially for the increase of charge-transfer resistance (Rct).

著者

Lin Lin Lei Zhongfang Wang Li Liu Xiang Zhang Yi Wan Chunli Lee Duu-Jong Tay Joo Hwa

出版者

Elsevier B.V.

雑誌

Separation and purification technology (ISSN:13835866)

巻号頁・発行日

vol.103, pp.15-20, 2013-01

被引用文献数

236 19

---

Zeolites, microporous aluminosilicate minerals, have high affinity to ammonium in water. This study explored the mechanisms of ammonium adsorption onto natural zeolite and NaCl-modified counterpart under different ammonium levels (10–4000 mg-N/L) and initial pH 3.4–11.1. Ion exchange dominated the ammonium adsorption process near neutral pH, with the order of exchange selectivity following Na+ > Ca2+ > K+ > Mg2+. At high ammonium levels, Ca2+ exceeded Na+ as the dominant ions for ammonium adsorption. Conversely, in strong alkaline solutions, molecular adsorption suppressed ion exchange in ammonium adsorption. NaCl modification effectively increased ammonium adsorption capacity by increasing the Na contents in zeolite and by modifying the surface morphology to enhance film mass transfer rate. The modified zeolite presents a potential adsorbent to reduce ammonium concentration in landfill leachates, livestock wastewaters or effluents from anaerobic digestion tanks of livestock manure.

著者

Tomimoto Shinichi Kawana Keisuke Murakami Akira Masumoto Yasuaki

出版者

Elsevier B.V.

雑誌

Journal of Luminescence (ISSN:00222313)

巻号頁・発行日

vol.133, pp.162-168, 2013-01

被引用文献数

1

---

We have experimentally observed the spin polarization process of single electrons in InP/InGaP quantum dots by time-resolved Kerr rotation measurements. It is found that the inversion of the spin polarization direction occurs with the variation of the intensity of the optical pulse. The spin coherence lifetime abruptly changes on the occurrence of the inversion. We have reproduced the inversion in numerical simulations using the density operator of the electron–trion four-level system, assuming a small deviation of the optical pulse from circular polarization. The change of the spin lifetime is attributed to the qualitative change of the four-level system in the electric polarization state.

著者

Tao Yaling Zhang Yongbing Ji Yusheng

出版者

Elsevier B.V.

雑誌

Ad hoc networks (ISSN:15708705)

巻号頁・発行日

vol.11, no.1, pp.541-554, 2013-01

被引用文献数

40 4

---

Power efficiency and coverage preservation are two important performance metrics for a wireless sensor network. However, there is scarcely any protocol to consider them at the same time. In this paper, we propose a flow-balanced routing (FBR) protocol for multi-hop clustered wireless sensor networks that attempts to achieve both power efficiency and coverage preservation. The proposed protocol consists of four algorithms, one each for network clustering, multi-hop backbone construction, flow-balanced transmission, and rerouting. The proposed clustering algorithm groups several sensors into one cluster on the basis of overlapping degrees of sensors. The backbone construction algorithm constructs a novel multi-level backbone, which is not necessarily a tree, using the cluster heads and the sink. Furthermore, the flow-balanced routing algorithm assigns the transferred data over multiple paths from the sensors to the sink in order to equalize the power consumption of sensors. Lastly, the rerouting algorithm reconstructs the network topology only in a place where a head drops out from the backbone due to the head running out of its energy. Two metrics called the network lifetime and the coverage lifetime are used to evaluate the performance of FBR protocol in comparison with previous ones. The simulation results show that FBR yields both much longer lifetime and better coverage preservation than previous protocols. For example, FBR yields more than twice network lifetime and better coverage preservation than a previous efficient protocol, called the coverage-preserving clustering protocol (CPCP) [18], when the first sensor dies and the network coverage is kept at 100%, respectively.

著者

Takahashi Y. Hara K. Kim S. Ikegami Y. Takubo Y. Terada S. Unno Y. Mitsui S. Kamada S. Yamamura K.

出版者

Elsevier B.V.

雑誌

Nuclear instruments & methods in physics research. Section A (ISSN:01689002)

巻号頁・発行日

vol.699, pp.107-111, 2013-01

被引用文献数

1 1

---

We are developing p-bulk microstrip sensors for the high luminosity upgrade of the LHC accelerator, HL-LHC. The stability of FZ (float zone) wafers available to Hamamatsu Photonics was examined by irradiating them at rates expected at the HL-LHC. They show degradation in the operational voltage at low dose but recover after the dose is accumulated. The instability is dependent on the bias voltage and dose rate, and also on the irradiation history. We have characterized the instability and attributed the cause to the charge concentration at the electrode edge. The strip isolation, which is degraded while in irradiation, is shown not to induce any practical problem for the operation.

著者

Hara K. Baccehtta N. Spalding W.J. Worm S.D.

出版者

Elsevier B.V.

雑誌

Nuclear instruments & methods in physics research. Section A (ISSN:01689002)

巻号頁・発行日

vol.699, pp.84-88, 2013-01

---

On September 30, 2011, the Collider Detector at Fermilab (CDF) finished physics data-taking at the Tevatron proton–antiproton collider. The original CDF silicon tracking detector, proposed in 1981 (SVX) and later replaced and updated (SVX′), was again replaced for Run-2 in 2002–2011 (SVX-II, ISL, L00). These systems operated successfully for many years, performing essential roles in exploring physics at the energy frontier, most notably the discovery of the top quark.

著者

Liu Yaping Yamanaka Tsutomu

出版者

Elsevier B.V.

雑誌

Journal of hydrology (ISSN:00221694)

巻号頁・発行日

vol.464–465, pp.116-126, 2012-09

被引用文献数

99 4

---

Mountain–plain transitional landscapes are especially important as groundwater recharge zones. In this study, the oxygen and hydrogen stable isotopic composition (δ18O and δD) of water and hydrochemical information were employed to quantify contribution ratios of different sources of groundwater recharge in the Ashikaga area of central Japan. The study area is situated between the Ashio Mountains and the Kanto Plain, and the Watarase River flows into the region parallel to the mountain–plain boundary. There was an obvious isotopic altitude effect in and around the study area (−0.25‰ per 100 m for δ18O and −1.7‰ per 100 m for δD), and the isotopic signatures of water from the Watarase River and local precipitation could be clearly distinguished. In addition, it was possible to identify the occurrence of mountain block recharge using hydrochemistry, specifically the chloride ion. End-member mixing analysis using δ values and Cl− concentration revealed spatial variation in the contribution ratios of the river water, mountain block groundwater and local precipitation. Seepage from the Watarase River contributed a significant amount of water to aquifers along its channel. The river-recharged water reached 5 km from the channel in the south (i.e., plain) side and 1.6 km or less in the north (i.e., mountain) side. Remarkable mountain block recharge was observed in the foothills near the axis of the syncline, which has layers of chert and sandstone that likely hinder river channel seepage into the mountain-side aquifers. Major factors controlling the river-water contribution ratio include the distance from the river channel, topography, and hydrogeological settings. The results presented here should facilitate integrated management of groundwater and surface water resources.

著者

Sanai Tatsunori Ito Keita Toko Kaoru Suemasu Takashi

出版者

Elsevier B.V.

雑誌

Journal of crystal growth (ISSN:00220248)

巻号頁・発行日

vol.357, pp.53-57, 2012-10

被引用文献数

13

---

We attempted to grow CoxFe4−xN epitaxial thin films on SrTiO3(001) substrates by molecular beam epitaxy supplying solid Co and Fe and a radio frequency N2 plasma, simultaneously. The composition ratio of Co/Fe in CoxFe4−xN was controlled by changing the weight ratio of Co to Fe flakes in the crucible of the Knudsen cell used. We confirmed epitaxial growth of CoxFe4−xN (0.4<x<2.9) thin films by reflection high-energy electron diffraction and θ−2θ X-ray diffraction patterns. The in-plane lattice parameter of the CoxFe4−xN films was almost the same as the out-of-plane lattice parameter, and they decreased with increasing Co composition, following Vegard's law.

著者

Okada Atsushi Toko Kaoru O. Hara Kosuke Usami Noritaka Suemasu Takashi

出版者

Elsevier B.V.

雑誌

Journal of crystal growth (ISSN:00220248)

巻号頁・発行日

vol.356, pp.65-69, 2012-10

被引用文献数

20

---

We have fabricated poly-Si thin films on fused silica substrates by the Al-induced crystallization (AIC) method with SiO2 insertion layers of various thicknesses (0–20 nm). The growth morphologies of poly-Si layers were dramatically changed by the SiO2 thickness, i.e., thin layers (2 nm) provided high growth rates and (100) orientations, and thick layers (10 nm) provided low growth rates and (111) orientations. These results showed that the crystal orientation of AIC-Si significantly depends on the diffusion rate of Si atoms into the Al layer.

著者

Yoshida Hiroyuki

出版者

Elsevier B.V.

雑誌

Chemical Physics Letters (ISSN:00092614)

巻号頁・発行日

2012-05

被引用文献数

120

---

In previous inverse photoemission spectroscopy (IPES) experiments, either X-ray (hv > 1 keV) or vacuum ultraviolet (hv ≈ 10 eV) photons were detected following the injection of electrons with energies of 10 - 1000 eV into solid materials. Here, we demonstrate IPES in the near-ultraviolet range (hv < 5 eV) using electrons with kinetic energies less than 4 eV. The energy resolution of the instrument is attained to be 0.27 eV. From the spectra of copper phthalocyanine films, it is found that damage to the organic sample is significantly reduced, demonstrating that this method is especially suitable for organic semiconducting materials.