RESUMO
Flow-electrode capacitive deionization (FCDI) is novel capacitive deionization (CDI) technology that exhibits continuous deionization and a high desalting efficiency. A flow-electrode with high capacitance and low resistance is required for achieving an efficient FCDI system with low energy consumption. For developing high-performance flow-electrode, studies should be conducted considering porous materials, conductive additives, and electrolytes constituting the flow-electrode. Here, we evaluated the desalting performances of flow-electrodes with spherical activated carbon and aqueous electrolytes containing various concentrations of NaCl in the FCDI unit cell for confirming the effect of salt concentration on the electrolyte of a flow-electrode on desalting efficiency. We verified the necessity of a moderate amount of salt in the flow-electrode for compensating for the reduction in the performance of the flow-electrode, attributed to the resistance of water used as the electrolyte. Simultaneously, we confirmed the potential use of salt water with a high salt concentration, such as seawater, as an aqueous electrolyte for the flow-electrode.
Assuntos
Salinidade , Purificação da Água , Capacitância Elétrica , Eletrodos , Cloreto de SódioRESUMO
This paper proposes a voice activity detection (VAD) method in a kernel subspace domain to improve the performance of the kernel-based VAD. A linear transform matrix that can simultaneously diagonalize the two covariance matrices using kernel principal component analysis is presented to generate the kernel subspace. The likelihood ratio test based on Gaussian distributions is applied for the VAD in the kernel subspace. Experimental results show that the proposed VAD algorithm outperforms the conventional approaches under various noise conditions.
Assuntos
Algoritmos , Processamento de Sinais Assistido por Computador , Espectrografia do Som , Acústica da Fala , Percepção da Fala , Voz , Análise de Fourier , Humanos , Modelos Lineares , Distribuição NormalRESUMO
This paper proposes a statistical voice activity detection method in a high-dimensional kernel feature space by a nonlinear mapping. A Gaussian density model is presented using kernel principal component analysis to represent the nonlinear characteristics of the speech signal. The proposed approach offers a decision rule based on a multiple observation likelihood ratio test in the kernel space.
Assuntos
Modelos Estatísticos , Processamento de Sinais Assistido por Computador , Medida da Produção da Fala/métodos , Fala , Voz , Algoritmos , Humanos , Funções Verossimilhança , Ruído , Dinâmica não Linear , Análise de Componente Principal , Espectrografia do Som , Fatores de TempoRESUMO
This paper presents a subspace approach for voice activity detection (VAD). The proposed approach is based on an embedded prewhitening scheme for the simultaneous diagonalization of the clean speech and noise covariance matrices to provide a decision rule based on likelihood ratio test in signal subspace domain. Experimental results show that the proposed subspace-based VAD algorithm outperforms the method using a Gaussian model in a conventional discrete Fourier transform domain at the low signal-to-noise conditions.
Assuntos
Algoritmos , Modelos Estatísticos , Processamento de Sinais Assistido por Computador , Interface para o Reconhecimento da Fala , Fala , Voz , Técnicas de Apoio para a Decisão , Análise de Fourier , Humanos , Funções Verossimilhança , RuídoRESUMO
Flow-electrode-based capacitive deionization (FCDI) has attracted much attention owing to its continuous and scalable desalination process without the need for a discharging step, which is required in conventional fixed-electrode capacitive deionization. However, flow electrode slurry is poorly conductive, which restricts desalination performance, but higher carbon mass loading in the slurry could improve salt removal capacity due to enhanced connectivity. However, increased viscosity restricts higher loading of active materials. Herein, we report a significant increase in salt removal performance by introducing functionalized carbon nanotubes (FCNTs) into activated carbon (AC)-based flow electrodes, which led to the generation of conducting bridges between AC particles. The salt removal rate in the presence of 0.25â¯wt% FCNT with 5â¯wt% AC improved four-fold from that obtained with only 5â¯wt% AC, which is the highest value reported in the literature so far (from 1.45 to 5.72 mmol/m2s, at a saline water concentration of 35.0â¯g/L and applied potential of 1.2â¯V). Further, FCNTs with a high aspect ratio (â¼50,000) can more effectively enhance salt removal than low-aspect ratio FCNTs (â¼1300). Electrochemical analysis further confirms that the addition of FCNTs can efficiently form a connecting percolation network, thus enhancing the conductivity of the flow electrode slurry for the practical application of highly efficient desalination systems.
Assuntos
Nanotubos de Carbono , Purificação da Água , Carvão Vegetal , Eletrodos , Cloreto de SódioRESUMO
A series of polyester-based ionomers containing dimethyl 5-sulfoisophthalate sodium salt (DMSI) with up to 5 mol-% diacid units was synthesized by two-step polycondensation. Furthermore a polylactic acid (PLA) was modified by introducing poly(ethylene-co-methacrylic acid) ionomers with different ion groups, such as Na, Li, and Zn, using the melt blending method. This review examines the effect of the ionic group on the dynamic mechanical properties, melt rheology, crystallization behavior, degradation behavior, and biocompatibility with human dermal cells, as well as the nucleating effect of poly(ethylene-co-methacrylic acid) ionomer in PLA.
Assuntos
Poliésteres/química , Poliésteres/metabolismo , Biodegradação Ambiental , Cristalização , Humanos , Íons/síntese química , Íons/química , Íons/metabolismo , Microscopia Eletrônica de Transmissão , Poliésteres/síntese química , TemperaturaRESUMO
Two new metal-organic frameworks based on trinuclear pinwheel motifs are prepared using dicarboxylate and diamine ligands. The structure of [Co3(bdc)3(dabco)] (1) (bdc = 1,4-benzenedicarboxylate; dabco = 1,4-diazabicyclo[2.2.2]octane) is described as pillared layers, whereas [Co3(ndc)3(dabco)] (2) (ndc = 2,6-naphthalenedicarboxylate) forms a variation of primitive cubic net with 3D connected pores. The two 8-connected MOFs are thermally stable at 160 and 250 degrees C for 1 and 2 respectively in the air and possess corrugated channels owing to the high connectivities of the secondary building unit. As a result, they show highly efficient hydrogen sorption capabilities. Especially, a high hydrogen uptake (2.45 wt % at 77 K and 1 bar) is observed for 2 that has the unique combination of high surface area and small portals.