Kind Of Filter Research Articles

Blank and sample handling troubleshooting in ultratrace analysis of alkylphenols and bisphenol A by liquid chromatography tandem mass spectrometry

Blank contamination is a notorious problem in the ultratrace analysis of alkylphenols and bisphenol A. The achievement of low detection limits is complicated due to the high background signals. Furthermore, overestimations and underestimations in the analytical results can occur when blank levels are not stable. Thus, a review of sources of blank contamination in this type of analysis was carried out. Several sources of contamination were identified and useful guidelines are proposed for the determination of these compounds in water samples by liquid chromatography coupled with mass spectrometry. The system contamination was maintained below 0.09ng (reagent blank) for all compounds and below 0.003μgL−1 (procedure blank). The main improvement was obtained by using LC-MS grade solvent in the mobile phase and PTFE syringe filters for the filtration of the sample extracts. Sample handling aspects such as filtration and storage of the water samples were also considered. The filtration of the samples should be avoided because both contamination and adsorption problems were observed when different kinds of filters were assayed. The refrigerated storage of water samples should be limited to 5 days (without addition of methanol) or 8 days (with 5% methanol).

Optimisation of analytical procedures for the quantification of ionic and carbonaceous fractions in the atmospheric aerosol and applications to ambient samples

In the last decade, our research group set up and optimised analytical techniques for the characterisation of the major components of atmospheric aerosol (i.e. secondary inorganic ions and carbonaceous material) and source markers (e.g. levoglucosan, carbonates). In this study, we present a complete overview on the most problematic aspects that can be encountered during the quantification of the two main components of aerosol, i.e. the ionic and carbonaceous fractions. More in detail, different liquid chromatographic approaches were set up for main ions and anhydrosugars determination. Quality assurance procedures (i.e. tests on data reliability) were applied during the set-up phase and they are presented in this work. As regards the carbonaceous component characterisation, two evolved gas analysis techniques were set up and applied: the thermogravimetric technique coupled to the Fourier transformed infrared spectroscopy (TGA/FTIR) and the thermal-optical transmittance method (TOT). A suitable protocol for organic and elemental carbon separation was set up for the TGA/FTIR system and a comparison with the results obtained by the TOT method was carried out. Studies on the impact of filter load, field blanks, and sample composition on OC/EC quantification by the TOT method were performed. Moreover, approaches for carbonate carbon quantification on different kinds of filters were developed. It was demonstrated that this approach allows to reach the ionic balance in samples impacted by carbonate compounds. The optimised methods have been applied for the analysis of thousands of PM filters allowing the obtainment of reliable results.

Compact dual-mode filter with flexible transmission zeros using slot-line square loop resonator

A new type of dual-mode planar filter with flexible transmission zeros using slot-line square loop resonator (SSLR) is presented. This resonator is based on the slot-line loop on the ground plane. Four slot-line stepped impedance stubs are loaded in the center loop to achieve compact size and harmonic suppression. Two sizes of slot patches added at the inner corners can split the degenerate modes and adjust the coupling between even and odd modes. A pair of T-shaped feed lines on the top plane can provide flexible source–load coupling, which leads to symmetrical or asymmetrical frequency response. Both the equivalent circuit and coupling matrix analysis methods are utilized to design the dual-mode filter. Two kinds of filters operating at 3.35 and 3.80 GHz with wideband and flexible transmission zeros are designed and fabricated.

Development and preclinical evaluation of a new viewing filter system to control reflection and enhance dye staining during vitrectomy

We developed a new artificial image enhancement system and evaluated its usefulness in controlling intraoperative reflection and enhancing of Brilliant Blue G (BBG) staining. The system was composed of three kinds of filters (a polarizing filter, a blue-enhancing filter, and a sharp-cut filter Y) and attached to the inferior surface of the operating microscope. Twenty-seven post-mortem extracted porcine eyes were used for a series of examinations. We performed surgery using the 23G-vitrectomy system with a halogen light and xenon lights and compared the reduction of intraoperative reflection under air condition and visibility and BBG contrast with and without this system. The evaluation of images was calculated in CIE 1976 (L*, a*, b*) color space (CIELAB) carried out by ImageJ software. The transmission of each filter and absorbance of BBG was measured by a spectrophotometer. We measured spectral irradiance at each wavelength about each filter from each light source with a spectroradiometer. Under both light sources, intraoperative reflection was controlled using a polarizing (PL) filter or combination of filters under air condition. Evaluation of the value of L* within the cutter surface was changed by 37.8 % under the halogen light, and 61.6 % (averaged) under the xenon light with inserted filters versus no filter. The BBG intensity difference was obtained with sharp-cut Y filter under both light source and PL with blue enhancing filter under the halogen light using each L*, a*, b* parameter with statistically significant (p < 0.01, 0.05). However, there was a relative decrease in the observation illuminance when the filter inserted according to the attenuation total spectral irradiance. This system can reduce intraoperative reflections under the air condition and obtain an excellent BBG staining intensity induced by various light sources.

Expanding the rejection band of planar bandpass filters

Combined stripline and microstrip filters combining a bandpass filter with stepped-impedance resonators and one or two low-pass filters are considered. Special features of the frequency characteristics of these two kinds of filters, which form the basis of this combination, are revealed. It is confirmed experimentally that, in combined planar filters, wide rejection bands exceeding a decade are provided.

Comparative Study on the Mn&lt;sup&gt;2+&lt;/sup&gt; Removing Performance of Several Filters

The Mn2+ removing effect from groundwater by four kinds of filters——Zeolites ,Activated Carbon ,Manganese Sand and a new filter ANJ.SiC, were comparatively studied and analyzed respectively .The results show that, the Mn2+ removing effect of ANJ.SiC is significantly better than the other three .It is an ideal filter in Mn2+ removing ,which can be reused for a long time .These filters’ surface characteristics before and after saturation were compared through their SEM figures ,and the Mn2+ removing mechanism were further studied.

Molecular comparison of the sampling efficiency of four types of airborne bacterial samplers

In the present study, indoor and outdoor air samples were collected using four types of air samplers often used for airborne bacterial sampling. These air samplers included two solid impactors (BioStage and RCS), one liquid impinger (BioSampler), and one filter sampler with two kinds of filters (a gelatin and a cellulose acetate filter). The collected air samples were further processed to analyze the diversity and abundance of culturable bacteria and total bacteria through standard culture techniques, denaturing gradient gel electrophoresis (DGGE) fingerprinting and quantitative polymerase chain reaction (qPCR) analysis.The DGGE analysis indicated that the air samples collected using the BioStage and RCS samplers have higher culturable bacterial diversity, whereas the samples collected using the BioSampler and the cellulose acetate filter sampler have higher total bacterial diversity. To obtain more information on the sampled bacteria, some gel bands were excised and sequenced. In terms of sampling efficiency, results from the qPCR tests indicated that the collected total bacterial concentration was higher in samples collected using the BioSampler and the cellulose acetate filter sampler.In conclusion, the sampling bias and efficiency of four kinds of air sampling systems were compared in the present study and the two solid impactors were concluded to be comparatively efficient for culturable bacterial sampling, whereas the liquid impactor and the cellulose acetate filter sampler were efficient for total bacterial sampling.

Comparison between explicit filterings with smooth and cutoff filters in the large eddy simulation of turbulent channel flows

The Large Eddy Simulation (LES) equations are obtained by applying a low-pass filter to the Navier–Stokes equations. The turbulence modeling in the LES method is affected by the shape of the applied filter. In this paper, two explicit filtering methods are compared during the simulation of fully developed turbulent channel flows. First, a fully developed turbulent channel flow is simulated by explicit filtering, using a smooth Laplace filter. In this case, the subfilter stress term is added to the subgrid model. Good agreement is observed between the calculated results and the available direct numerical simulation results. Second, to evaluate the effects of the explicit filter shape as it relates to the cutoff filter, three kinds of filters are used for the flow simulation. Finally, the ability of each approach to predict turbulence statistics is investigated. Moreover, the boundary layer regions that have the highest effect on each approach are specified.

Treatment and remediation methods for arsenic removal from the ground water

Globally, ground water is contaminating by arsenic continously, which needs economic treatment and remediation technologies. Physical, chemical and biological treatment methods have been developed, that include different kinds of filters, bucket type units, fill and draw, kalshi etc. The remediation methods discussed are air oxidation, reactive barriers, utilisation of deeper aquifers and sanitary protected dug wells. To the best of our knowledge no technology is available capable to remove arsenic from water at efficient, economic and commercial levels. Therefore, fast, efficient and economic arsenic removal technologies are required. Attempts have been made to suggest the future technologies of arsenic removal.

Design of high efficiency photonic crystal terahertz filter

A new type of terahertz photonic crystal filter is presented, which includes the waveguide parts realized by line defects, and the frequency selection parts realized by micro cavities. The band gap property was investigated by using plane wave method (PWM), and then the transmission characteristic of terahertz in this kind of filter was studied by means of the finite difference time domain method (FDTD) simulation. The results show that, the filter can achieve high coupling efficiency filtering of single-channel and single-frequency, by changing the point defects structure and increasing the radius of certain dielectric cylinder. High efficiency THz-band photonic crystal filter was designed in this thesis.

一维电磁介质互联的光子晶体偏振带通滤波器

One-dimensional traditional pure dielectric photonic crystals have disadvantages that the design of TE-polarization band-pass filters is difficult,and the bandgaps of TE-and TM-polarization band-pass filters are narrow.Based on the fact that a greater permittivity(permeability) than permeability(permittivity) makes wider TE(TM) bands than TM(TE) bands,three kinds of filters,(TE-polarization band-pass filter,TM-polarization band-pass filter and double-polarization band-pass filter),were designed by stop-band superposition of one-dimensional photonic crystals.Each of them was a heterostructure constructed by two sub-photonic-crystals,hence the structure provided a narrow-frequency pass-band and the bandgap was enlarged.Due to the combination of dielectric and magnetic materials,the proposed design has simple structures with wide bandgaps and narrow-frequency pass-bands.Besides,the effect of magnetic material dispersion on the performance of polarization filters was discussed using a kind of magnetic material which has been reported.

Synthesis and Design of Generalized Chebyshev Wideband Hybrid Ring Based Bandpass Filters With a Controllable Transmission Zero Pair

A systematic and analytical method for the exact synthesis of generalized Chebyshev wideband hybrid ring based bandpass filters with a controllable transmission zero pair is developed in this paper. The basic configuration of the proposed filters consists of a hybrid ring, a multi-section short-circuited stub and a multi-section open-circuit stub. In this configuration, the position of the controllable transmission zero pair can be easily designed by setting the impedances of the multi-section short-circuited stub and the multi-section open-circuit stub. According to the position of the controllable transmission zero pair, two kinds of filters are proposed. The filter has a controllable transmission zero pair on the real axis (imaginary frequency) that they can be arranged to improve the group delay flatness. On the other hand, the filter has a controllable transmission zero pair on the imaginary axis (real frequency) and the desired stopband suppression can be obtained by adjusting the optimal position of them. This synthesis method is developed to obtain the impedance value of each line section and ripple factors of the filters with respect to given specifications (center frequency, passband bandwidth and transmission zeros). Two design examples, the fifth-order filter with a controllable imaginary frequency transmission zero pair and the fifth-order filter with a controllable real frequency transmission zero pair, are synthesized and fabricated. The measured results validate and confirm the theoretical predictions.

Log-Domain Filter Design Based on Impedance Scaling of LC Ladder Structures

In this paper, a log-domain filter design based on an impedance scaling technique of passive LC ladder structures is considered. To this end a general circuit for the simulation of any kind of two-terminal component, both grounded and floating, is presented. Depending on the kind of filter, the proposed technique can produce implementation advantages by reducing the number of required components. The validity of the approach is demonstrated through the simulation of a fifth-order LC ladder elliptic low-pass filter.

Ecosystem services and hydroelectricity in Central America: modelling service flows with fuzzy logic and expert knowledge

Because ecosystem services are generally not produced and used in the same place, their assessment should consider the flows of services from ecosystems to users. These flows depend on the characteristics and spatial distribution of ecosystems and users, the spatial relationships between them, and the presence of filters or barriers between ecosystems and users. The objective of this paper is to map the ecosystem services provided to the Costa Rican and Nicaraguan hydroelectric sectors, which are crucial sectors for national sustainable development and depend directly on hydrological ecosystem services. The paper presents an approach for modelling the flows of multiple services from diverse ecosystems to diverse users through different kinds of filters in a landscape. The approach uses expert knowledge and fuzzy numbers to handle uncertainties. The analyses for Costa Rica and Nicaragua show how the approach helps identify priority areas for the conservation and restoration of forests for the services they provide to the hydroelectric sector. As such, it is a useful tool for defining spatially targeted policies for the conservation of ecosystem services and for involving the users of ecosystem services in ecosystem management.

Phase Shifts Induced by the Piezoelectric Transducers Attached to a Linearly Chirped Fiber Bragg Grating

A simple method enabling to generate a stable and controllable phase shift in a linearly chirped fiber Bragg grating (FBG) is theoretically and experimentally demonstrated, which is based on the utilization of the mini-size piezoelectric transducers (PZTs). The magnitude of the induced phase shift can easily be controlled by adjusting the voltage applied on the individual PZT. With this method, a narrow bandpass filter with 3-dB band width of 0.085 nm is obtained. Based on this kind of filter, an Erbium-doped fiber ring laser is also demonstrated, and both switchable and stable single-longitudinal-mode (SLM) laser emission is successfully realized.

공기주입 이중피복 플라스틱온실의 공기주입장치 설계를 위한 기초실험

This study was conducted to provide fundamental data for design of air inflating apparatus of air-inflated double-layer plastic greenhouse. The variation of static pressure in air tube for different fans and filters, filtering performance for various kinds of filters and destruction phase of experimental greenhouse collapsed by excessive static pressure in air space were analyzed. The general type of forward centrifugal fan was recommended for inflating air space in air-inflated double-layer plastic greenhouse. The experimental greenhouse was collapsed down by excessive static pressure just like fallen by heavy snow load acting on it. The static pressure in air tube without filter decreased linearly as the number of outlet openings increased. But the pressure in air tube with filter declined quadratically, the decremental ratio diminished by the increase of outlet openings. The higher filtering efficiency and the greater decrements of static pressure in air tube, the larger capacity fan was required for maintaining proper static pressure in air space. Because the porosities of filter were blocked by dust as time goes by, the static pressure in air tube with filter decreased. The higher filtering efficiency, the less decremental ratio of static pressure in air tube as time passes by. Considering the filtering efficiency, decrement of static pressure and thickness of filter, the 5mm thickness filter of 75% efficiency was recommended for air inflating filter of air-inflated double-layer plastic greenhouse.

Polarization bandpass filter based on one-dimensional photonic crystal heterostructures

A new kind of polarization bandpass filters (P-BPFs), which fulfill the functions of high reflectivity for one polarization and high transmittance in the passband for the other, are proposed. The P-BPFs consist of a stack of two one-dimensional (1D) photonic crystals (PCs) that are referred to as 1D PC heterostructures. The essential function of P-BPFs is realized by making the first transmitted peak near the photonic bandgap edges of one PC coincide with that of the other PC. Based on this method, three kinds of filters have been designed and discussed in detail: an isotropic 1D PC single-polarization bandpass filter (SP-BPF) at oblique incidence with a narrow passband for TM polarization and a broadened stop band for TE polarization, an anisotropic 1D PC SP-BPF at normal incidence with a narrow passband for TE polarization and a broadened stop band for TM polarization, and an anisotropic 1D PC double-polarization bandpass filter (DP-BPF) at oblique incidence with a spectral separated narrow passband for both polarizations, respectively. The filters can be fabricated by a lot of coating methods and integrated easily with other photonic components.

Low-cost 3D human reconstruction from multi-image

A method for low-cost 3D specific human model reconstruction from multi-image was proposed.First,the feature points on each image were matched with their generic model.Then a deformation from radial basic function was performed to obtain specific model.After that,three kinds of filters were used to refine the specific model.Finally the surface of model was texture mapped by viewpoint-independent algorithm,and skin-skeleton system by vertex blending algorithm as well.The experimental results show that this method is accurate,easy to implement and of low-cost.

A Dual-Band Filter Realized by Alternately Connecting the Main Transmission-Line With Shunt Stubs and Shunt Serial Resonators

In this letter, we present a novel network for dual-band filter, the circuit of which is a mixture of shunt stub bandpass filter and shunt serial resonator bandstop filter. The stopband of the bandstop filter will split the passband of the bandpass filter and result in a dual-band response. The simulated and measured results are given. This kind of filter has the advantage of bigger and controllable bandwidths and lower insertion loss compared with traditional SIR dual-band filters.

수중 인공구조물에 대한 사이드스캔소나 탐사자료의 영상처리

Side scan sonar using acoustic wave plays a very important role in the underwater, sea floor, and shallow marine geologic survey. In this study, we have acquired side scan sonar data for the underwater man-made structures, artificial reefs and fishing grounds, installed and distributed in the survey area. We applied digital image processing techniques to side scan sonar data in order to improve and enhance an image quality. We carried out digital image processing with various kinds of filtering in spatial domain and frequency domain. We tested filtering parameters such as kernel size, differential operator, and statistical value. We could easily estimate the conditions, distribution and environment of artificial structures through the interpretation of side scan sonar.