Mono Components Research Articles

Constructing an oxide-fluoride heterojunction supported on carbon cloth as a highly active and stable catalyst for enhancing overall water-splitting

To realize large-scale production of hydrogen by water electrolysis, the development of inexpensive and high-performance catalysts is urgently needed. Herein, we developed an oxide-fluoride (Co3O4–CoF2) heterojunction catalyst with mooncake shape morphology supported on carbon cloth (CC) used as a bifunctional water electrolysis catalyst in 1 M KOH. The obtained Co3O4–CoF2 heterojunction exhibits a preferable kinetic process and more active sites than its mono components Co3O4 and CoF2, which only needs 46 mV for HER and 169 mV for OER at 10 mA cm−2 comparable to benchmark Pt/C and even super to benchmark IrO2. Meanwhile, it also demonstrates long-term stability, maintaining activity for 100 h for both HER and OER. Importantly, when assembled as a water electrolysis device, only a low cell voltage of 1.45 V is required to achieve the current density of 10 mA cm−2. Meanwhile, it can output continuous and stable current densities of 10, 100, and 10 mA cm−2 approaching 24 h under constant cell voltages of 1.47, 1.69, and 1.47 V, respectively. Therefore, the oxide-fluoride heterojunction catalyst unambiguously is a type of ideal bifunctional water electrolysis catalyst in alkaline media.

Synchrosqueezing transform-based identification of time-varying structural systems using multi-sensor data

In this paper, a hybrid time-frequency method combining Synchrosqueezing Transform (SST) and Multivariate Empirical Mode Decomposition (MEMD) is proposed for the identification of time-varying structural systems. MEMD is first used to decompose the closely spaced modal responses of structures into mono components, and SST is then used to track time-varying modal frequencies with a better time-frequency resolution, thereby improving the capability of both methods. A single degree-of-freedom model is first used to study the sensitivity for damage duration and frequency resolution of the SST under measurement noise. The proposed method is then validated using a multi-degree-of-freedom simulation model, an experimental model, and a full-scale study using MIT Green Building data. The results show that the proposed method has successfully identified time-varying frequencies of various types of structures under different extent of measurement noise.

An adaptive sensitive frequency band selection method for empirical wavelet transform and its application in bearing fault diagnosis

Empirical wavelet transform (EWT) is an adaptive wavelet based analysis which can be used to extract useful amplitude modulated-frequency modulated (AM-FM) mono components from a bearing vibration signal. However, the pre-requisite segmentation method on the Fourier support of a signal without a rigorous theoretical principle has limited the application of EWT in bearing fault diagnosis. To overcome this difficulty, an adaptive frequency band selection technique utilizing the Harmonic Significance Index (HSI) and Particle Swarm Optimization (PSO) is proposed in this paper. In this approach, HSI is employed as the fitness value of PSO to quantify the fault information contained in various frequency bands, and the optimal parameters (i.e., the lower cutoff frequency and the bandwidth) of the most sensitive frequency band (i.e., the band having the largest HSI value) identified by the PSO are then used in EWT to bandpass filter the original signal to extract the fault related AM-FM mono component. Results from the case studies presented in this work confirm the effectiveness of the proposed technique for bearing fault diagnosis. The proposed technique is particularly useful for situations where a bearing defect signal is contaminated by strong non-Gaussian noise such as random impacts from other mechanical components.

Simultaneous biosorption and bioaccumulation of phenol and cyanide using coconut shell activated carbon immobilized Pseudomonas putida (MTCC 1194)

In this study, Pseudomonas putida (MTCC 1194) was used as biosorbent for simultaneous biosorption and bioaccumulation of phenol and cyanide from liquid phase. Biosorption potential of free and immobilized cells of P. putida (MTCC 1194) was studied in batch process. Effect of pH, biosorbent dose, contact time, temperature and initial concentration was studied on simultaneous removal of phenol and cyanide. Phenol and cyanide binary solution were used for all batch studies with initial concentration of 500mg/L and 50mg/L, respectively. The biosorption removal efficiency of immobilized cells were found higher than the biosorption removal efficiency of free cells and attained removal efficiency of 71.36% for phenol and 88.40% for cyanide. Five mono components and six binary component equilibrium isotherm models were considered. Model parameters were estimated using non-linear regression technique. Among tested binary component isotherm models extended Langmuir model found to fit well for phenol and extended Freundlich found to fit well for cyanide in immobilized cell system.

Simultaneous treatment of phenol and cyanide containing aqueous solution by adsorption, biotreatment and simultaneous adsorption and biotreatment (SAB) process

This study presents a comparative study of adsorption and biotreatment process alone with simultaneous adsorption and biotreatment (SAB) process. Adsorption studies were conducted with coconut husk activated carbon (CHAC), as adsorbent. SAB and biodegradation studies were carried out with immobilized and suspended cultures of Serratia odorifera MTCC 5700, respectively. Phenol and cyanide solution were used for all studies with initial concentration of 300mg/L and 30mg/L, respectively, initial pH of 8 and temperature of 30°C. The optimum adsorbent dose was found 30g/L for adsorption process and SAB process. In SAB process, the removal efficiency was found more than adsorption and biodegradation process and achieved removal efficiency of 89.88% for phenol and 93.06% for cyanide. Three mono components and six multicomponent equilibrium isotherm models were considered. Non-linear regression technique was used for estimation of model parameters. Among tested multicomponent isotherm models Extended Freundlich model found to fit well with the experimental data. The kinetics of microbial growth and biotreatment of phenol and cyanide were also investigated. Haldane’s and Monod model have been used to interpret experimental data on phenol and cyanide biotreatment. It was established that simultaneous adsorption and biotreatment process is more effective than biotreatment and adsorption process alone.

A DIRECT EVALUATION OF MONO-COMPONENTS BY INSTANTANEOUS FREQUENCY

We present a new criterion based on instantaneous frequency (IF) to distinguish mono-components (MCs). We first notice that the "offset of local extremum" caused by low-frequency envelope is often significant on envelope extraction, which determines the calculation of IF for MCs. We estimate the upper and lower bounds of the offset for a general family of signals. Conducted by the offset estimation, we propose a direct and effective algorithm to calculate IF. Our algorithm, which is based on an empirical pursuit of knots and natural splines, provides an accurate estimation of the envelope and derives a well-behaved IF. A theoretical explanation for the good approximation of proposed envelope is also stated. Experiment results show the fast convergence of our algorithm, which leads to a reliable IF and local mean to provide a flexible criterion for MC classification. We emphasize that it is important to pursue a certain balance among different requirements to define MC depending on specific applications.

Intrinsic mono‐component decomposition of functions: An advance of Fourier theory

AbstractWe propose a function decomposition model, called intrinsic mono‐component decomposition (IMD). It is a continuation of the recent study on adaptive decomposition of functions into mono‐components (MCs). It is a further improvement of two recent results of which one is adaptive decomposition of functions into modified inner functions, and the other is decomposition by using adaptive Takenaka‐Malmquist systems. The proposed new decomposition model is of less restriction and thus gains more adaptivity. The theory is valid to both the unit circle and the real line contexts. Copyright © 2009 John Wiley & Sons, Ltd.

Hybrid multi-channel/cue coding/decoding of audio signals

Part of the spectrum of two or more input signals is encoded using conventional coding techniques, while encoding the rest of the spectrum using binaural cue coding (BCC). In BCC coding, spectral components of the input signals are downmixed and BCC parameters (e.g., inter-channel level and/or time differences) are generated. In a stereo implementation, after converting the left and right channels to the frequency domain, pairs of left- and right-channel spectral components are downmixed to mono. The mono components are then converted back to the time domain, along with those left- and right-channel spectral components that were not downmixed, to form hybrid stereo signals, which can then be encoded using conventional coding techniques. For playback, the encoded bitstream is decoded using conventional decoding techniques. BCC synthesis techniques may then apply the BCC parameters to synthesize an auditory scene based on the mono components as well as the unmixed stereo components.

Apparatus and method for multichannel sound reproduction system

The sound reproduction of a multichannel sound reproduction system with a plurality of speakers which is connected to the output of an FM stereo receiver is controlled by a control signal derived from the reception quality. Preferably, the control signal from the FM stereo receiver for controlling the stereo and mono components is also employed to control the multichannel sound reproduction system. For example, stereo, pseudo-stereo or mono reproduction are provided in the multichannel sound reproduction system in response to the stereo component within the output signal.

Kinetics of hydrolysis of PCl5 in situ as evaluated from the partial hydrolysis products formed in [18O]water

The in situ hydrolysis products of PCl 5 1, namely POCl 3 , HPO 2 Cl 2 , H 2 PO 3 Cl and H 3 PO 4 5, were identified and their mol proportions measured at different extents of overall hydrolysis (from 7.0 to 93%). Partial hydrolysis in 95 atom % [ 18 O]H 2 O, step 1, was followed by complete hydrolysis in non-enriched water, step 2. The phosphoric acid isotopomers obtained at step 2 were derived from mixtures that contained from 0 to 4 18 O atoms per phosphate incorporated at step 1, depending upon the composition of the mixtures formed at step 1. The relative mol proportions of mixtures were deduced by regression analysis of the normalized peak intensities of the trimethyl phosphate isotopomer cluster at m/z = 140, 142 . . . 148 (obtained by electron-impact GC analysis). The mixture compositions were used to evaluate kinetically a sequential, irreversible model for hydrolysis of PCl 5 . The relative values obtained for apparent hydrolysis constants and the species to which they were attributed were: PCl 5 , 1.0; POCl 3 , 0.24; PO 2 Cl 2 - , 0.02; with that for HPO 3 Cl - being too great to measure. These values accurately predicted the composition of mixtures in all but a narrow range of overall hydrolysis between 60 and 70% where the hitherto undetected monochloro acid accumulated in yields up to 30%. As the water content becomes small with respect to the acid components in this region, the equilibrium between the monoanion and undissociated forms of the acids is shifted in favour of the undissociated acids (the final end products as the mixture becomes anhydrous). The relative rate constants in this region were estimated to be 0.02 and 0.08 for HPO 2 Cl 2 and H 2 PO 3 Cl, respectively, thereby accounting for accumulation of the monochloro acid in this range. It is proposed that under these conditions the rates of hydrolysis of the mono and dichloro components are comparable because both components are present largely in their free acid forms which undergo hydrolysis by an associative mechanism.