Generalized construction of binary bent sequences with optimal correlation property

We generalize the construction method of the family of binary bent sequences introduced by Olsen, Scholtz, and Welch (1982) to obtain a family of generalized binary bent sequences with optimal correlation and balance property by using the modified trace transform. Then, the conventional binary bent sequence becomes a special case of our construction method. Several families of the generalized binary bent sequences are constructed by using the bent functions on the intermediate field. Using some of the generalized binary bent sequences, new families of binary sequences with optimal correlation and balance property can be constructed by the lifting idea similar to No (1988) sequences, which are referred to as binary bent-lifted sequences.     

Development of a radiative transfer model for the determination of toxic gases by Fourier transform–infrared spectroscopy with a support vector machine algorithm

Abstract

This report describes a radiative transfer model for Fourier transform-infrared (FT-IR) spectroscopy to create close-to-reality toxic gas spectra by reflecting the unique spectral responses of detectors and using the atmospheric radiative transfer code, MODTRAN. This system can be highly useful in overcoming the limitations for measuring toxic gases in open environments. The emulated gas spectra can be used to train support vector machine (SVM) for chemical gas detection. Its detection performance is evaluated with nerve agents (tabun, sarin, soman, and cyclosarin) and a simulant gas (sulfur hexafluoride) for indoor and outdoor experiments by using two off-the-shelf FT-IR gas detectors. The experimental results show that the proposed SVM algorithm successfully detected and classified targeted gases while reducing false negative and false positive detection rates.     

Linear complexity over F/sub p/ and trace representation of Lempel-Cohn-Eastman sequences

In this article, the linear complexity over F/sub p/ of Lempel-Cohn-Eastman (1977) sequences of period p/sup m/-1 for an odd prime p is determined. For p=3,5, and 7, the exact closed-form expressions for the linear complexity over F/sub p/ of LCE sequences of period p/sup m/-1 are derived. Further, the trace representations for LCE sequences of period p/sup m/-1 for p=3 and 5 are found by computing the values of all Fourier coefficients in F/sub p/ for the sequences.     

New construction for families of binary sequences with optimalcorrelation properties

We present a construction, in a closed form, for an optimal family of 2^m binary sequences of period 2^2m-1 with respect to Welch's (1974) bound, whenever there exists a balanced binary sequence of period 2^m-1 with ideal autocorrelation property using the trace function. This construction enables us to reinterpret a small set of Kasami and No (1988) sequences as a family constructed from m-sequences. New optimal families of binary sequences are constructed from the Legendre sequences of Mersenne prime period, Hall's sextic residue sequences, and miscellaneous sequences of unknown type. In addition, we enumerate the number of distinct families of binary sequences, which are constructed from a given binary sequence by this method     

Electrochemical Intercalation of Sodium into Silicon Thin Film

In order to investigate the possibility of Si thin film as an anode for Na battery, we studied the electrochemical intercalation of sodium into the Si film. Amorphous Si thin film electrode was prepared using DC magnetron sputtering. Sodium ion could intercalate into Si thin film upto Na0.52Si, i.e. 530mAh · g-1-Si. The first discharge capacity was 80mAh.·g-1-Si, which meant reversible amount of sodium intercalation. The discharge capacity slightly decreased to 70mAh · g-1-Si after 10 cycles.     

New Design of Low-Correlation Zone Sequence Sets

In this paper, we present several construction methods for low-correlation zone (LCZ) sequence sets. First, we propose a design scheme for binary LCZ sequence sets with parameters (2ⁿ⁺¹-2,M,L,2). In this scheme, we can freely set the LCZ length L and the resulting LCZ sequence sets have the size M, which is almost optimal with respect to Tang, Fan, and Matsufuji bound. Second, given a q-ary LCZ sequence set with parameters (N,M,L,epsi) and even q, we construct another q-ary LCZ sequence set with parameters (2N,2M,L,2epsi) or (2N,2M,L-1,2epsi). Especially, the new set with parameters (2N,2M,L,2) can be optimal in terms of the set size if a q-ary optimal LCZ sequence set with parameters (N,M,L,1) is used     

The electrochemical properties of lithium/sulfur cell using sulfur-carbon nanotubes composite

Sulfur electrode was prepared using sulfur-CNT composite powder. The sulfur electrode showed homogenous mixture of sulfur and the CNTs with a network structure. We investigated on the discharge behavior and cycling property of lithium/sulfur cell using sulfur electrodes with CNTs as unique conducting agents. The discharge capacity of the Li/TEGDME/S cell was about 1227 mAh/g-sulfur for the first cycle and decreased to 155 mAh/g-sulfur after 14 cycles.     

Reconstruction of Complex Sparse Signals in Compressed Sensing with Real Sensing Matrices

The existing greedy algorithms for the reconstruction in compressed sensing were designed no matter which type the original sparse signals and sensing matrices have, real or complex. The reconstruction algorithms definitely apply to real sensing matrices and complex sparse signals, but they are not customized to this situation so that we could improve those algorithms further. In this paper, we elaborate on the compressed sensing with real sensing matrices when the original sparse signals are complex. We propose two reconstruction algorithms by modifying the orthogonal matching pursuit to include some procedures specialized to this setting. It is shown via analysis and simulation that the proposed algorithms have better reconstruction success probability than conventional reconstruction algorithms.

     

The discharge properties of Na/Ni3S2 cell at ambient temperature

The discharge properties of a Na/Ni₃S₂ cell using 1 M NaCF₃SO₃ in tetra(ethylene glycol)dimethyl ether liquid electrolyte were investigated at room temperature. The products were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. Electrochemical properties of Na/Ni₃S₂ cells were also presented by cyclic voltammetry and the galvanostatic current method. Na/Ni₃S₂ cells have an initial discharge capacity of 420 mAh g⁻¹ with a plateau potential at 0.94 V versus Na/Na⁺. After the first discharge, Ni₃S₂ and Na react at room temperature and then form sodium sulfide (Na₂S) and nickel. Sodium ion can be partially deintercalated from Na₂S charge reaction. The discharge process can be explained as follows: Ni₃S₂ + 4Na ↔ 3Ni + 2Na₂S.     

Synthesization and characterization of FeS2 by mechanical alloying for Na/FeS2 cell

In this study, the FeS2 fine compound powders were synthesized by mechanical alloying (MA) for 15 hrs and stearic acid was added as PCA (Process Control Agent) to prevent the excessive cold welding and agglomeration. For the purpose of ulteriorly reducing the particle size to improve the contact areas between the active materials and conducting agents, the wet ball milling process was applied by employing normal hexane (C6H14) as the milling solvent. The mean particle size of FeS2 powders about 1.14 microm were obtained after 24 hrs wet ball milling. The powders were characterized by FE-SEM, XRD, TEM and EDS. To compare the influence of particle size on the properties of charge/discharge, the same electrolyte was employed for both tests by dissolving 1M NaCF3SO3 (sodium trifluoromethanesulfonate) in a liquid of TEGDME (tetraethylene glycol dimethylether). The first discharge capacity of Na/FeS2 cell made by dry ball milled powders was 440 mAh/g with a plateau potential at approximately 1.25 V versus Na/Na+ and 260 mAh/g at the 25th cycle at room temperature. Meanwhile, the initial discharge capacity of Na/FeS2 cell made by wet ball milled powders was 614 mAh/g with the same discharge plateau potential and retained 385 mAh/g at the 25th cycle. And the discharge capacity for wet milled system decreased continuously by repeated charge/discharge cycling in the first 20 cycles and has little change after 60 cycles, which means the good cycling properties, remaining half of its initial discharge capacity of 320 mAh/g even after 100 cycles.