Porous organic cages for sulfur hexafluoride separation

A series of porous organic cages is examined for the selective adsorption of sulphur hexafluoride (SF6) over nitrogen. Despite lacking any metal sites, a porous cage, CC3, shows the highest SF6/N2 selectivity reported for any material at ambient temperature and pressure, which translates to real separations in a gas breakthrough column. The SF6 uptake of these materials is considerably higher than would be expected from the static pore structures. The location of SF6 within these materials is elucidated by x-ray crystallography, and it is shown that cooperative diffusion and structural rearrangements in these molecular crystals can rationalize their superior SF6/N2 selectivity.

Search filters: mapping the literature using a novel form of content analysis.

Background: Search filters are combinations of words and phrases designed to retrieve an optimal set of records on a particular topic (subject filters) or study design (methodological filters). Information specialists are increasingly turning to reusable filters to focus their searches. However, the extent of the academic literature on search filters is unknown. We provide a broad overview to the academic literature on search filters.
Objectives: To map the academic literature on search filters from 2004 to 2015 using a novel form of content analysis.
Methods: We conducted a comprehensive search for literature between 2004 and 2015 across eight databases using a subjectively derived search strategy. We identified key words from titles, grouped them into categories, and examined their frequency and co-occurrences.
Results: The majority of records were housed in Embase (n = 178) and MEDLINE (n = 154). Over the last decade, both databases appeared to exhibit a bimodal distribution with the number of publications on search filters rising until 2006, before dipping in 2007, and steadily increasing until 2012. Few articles appeared in social science databases over the same time frame (e.g. Social Services Abstracts, n = 3).
Unsurprisingly, the term ‘search’ appeared in most titles, and quite often, was used as a noun adjunct for the word 'filter' and ‘strategy’. Across the papers, the purpose of searches as a means of 'identifying' information and gathering ‘evidence’ from 'databases' emerged quite strongly. Other terms relating to the methodological assessment of search filters, such as precision and validation, also appeared albeit less frequently.
Conclusions: Our findings show surprising commonality across the papers with regard to the literature on search filters. Much of the literature seems to be focused on developing search filters to identify and retrieve information, as opposed to testing or validating such filters. Furthermore, the literature is mostly housed in health-related databases, namely MEDLINE, CINAHL, and Embase, implying that it is medically driven. Relatively few papers focus on the use of search filters in the social sciences.

Effects of Poly (ε-caprolactone) Coating on the Properties of Three-Dimensional Printed Porous Structures

Powder-based inkjet three-dimensional printing (3DP) to fabricate pre-designed 3D structures has drawn increasing attention. However there are intrinsic limitations associated with 3DP technology due to the weak bonding within the printed structure, which significantly compromises its mechanical integrity. In this study, calcium sulphate ceramic structures demonstrating a porous architecture were manufactured using 3DP technology and subsequently post-processed with a poly (ε-caprolactone) (PCL) coating. PCL concentration, immersion time, and number of coating layers were the principal parameters investigated and improvement in compressive properties was the measure of success. Interparticle spacing within the 3DP structures were successfully filled with PCL material. Consequently the compressive properties, wettability, morphology, and in vitro resorption behaviour of 3DP components were significantly augmented. The average compressive strength, Young’s modulus, and toughness increased 217%, 250%, and 315%, following PCL coating. Addition of a PCL surface coating provided long-term structural support to the host ceramic material, extending the resorption period from less than 7 days to a minimum of 56 days. This study has demonstrated that application of a PCL coating onto a ceramic 3DP structure was a highly effective approach to addressing some of the limitations of 3DP manufacturing and allows this advanced technology to be potentially used in a wider range of applications.

Simple brightness models with low-pass and Gabor filters

A syntactical brightness model based on a multiscale line and edge representation obtained by a set of anisotropic Gabor filters is quite complex (du Buf and Fischer, 1995 Optical Engineering 34 1900-1911). Although only tested in 1-D, it was shown to yield correct brightness effects for many patterns.

Application of fractional delay filters to tune the centre frequency location of single-band sigma-delta modulators

This paper presents a novel technique for the design of narrow-band sigma-delta modulators with an embedded tunable centre frequency mechanism. This method demonstrates that the use of sum filters combined with a fractional delayer provide the flexibility of tuning the noise shaping band for any desired variable centre frequency input signal.

Increasing the variability of centre frequency locations in multiple-band sigma-delta modulators via the use of fractional delay filters

This paper presents the design analysis of novel tunable narrow-band bandpass sigma-delta modulators, that can achieve concurrent multiple noise-shaping for multi-tone input signals. This approach utilises conventional comb filters in conjunction with FIR, or allpass IIR fractional delay filters, to deliver the desired nulls for the quantisation noise transfer function. Detailed simulation results show that FIR fractional delay comb filter based sigma-delta modulators tune accurately to most centre frequencies, but suffer from degraded resolution at frequencies close to Nyquist. However, superior accuracies are obtained from their allpass IIR fractional delay counterpart at the expense of a slight shift in noise-shaping bands at very high frequencies.

Optically reconfigurable CPW filters for UWB applications

A miniature optically reconfigurable ultra-wideband CPW bandpass filter is proposed. With the optical switch in the ON state (200W), the circuit behaves as a bandpass filter while in the OFF state (0W), the circuit behaves as a bandstop filter within the same frequency band. The simulation results of the proposed bandpass/bandstop filter are presented.

Compact dielectric-filled waveguide filters and diplexers

This paper presents electromagnetic simulations of dielectric-filled rectangular waveguide bandpass filter structures with microstrip to waveguide transitions as well as a diplexer based on such filters for modern wireless systems. The two bandpass filters have been designed and simulated at centre frequencies of 11.85 and 14.25 GHz, respectively. A significant size reduction is achieved through dielectric filling.

Compact high linearity switchable dual-mode microstrip bandpass filters

A compact highly linear microstrip dual-mode electronically switchable filter is presented. The key characteristics of the dual-mode switchable filter are investigated and described. A second order filter design procedure is outlined to facilitate the realisation of Butterworth and Chebyshev functions. The proposed filter was built and tested with NXP pin diode model BAP65-03. The measured and simulated results are in good agreement. The measured insertion loss in the ON state was 3.0 dB the isolation in the OFF state was 45 dB at the centre frequency. An evaluation of filter distortion is presented for digitally modulated 16 QAM and QPSK signals.

Compact filters using metal-dielectric inserts

A novel filter based on e-plane metal-dielectric insert in rectangular waveguide is proposed. Properties of the structure containing metallic septa, C- and I-shaped resonators placed in waveguide are investigated. Pseudo-elliptic cross-coupled filter with direct source-load coupling is designed, simulated and fabricated. Experimental results are presented to prove feasibility of the filter. Significant size reduction is achieved.

Ultra compact pseudo-elliptic inline waveguide bandpass filters using bypass coupling

This paper presents an ultra compact waveguide bandpass filter that exhibits a pseudo-elliptic response. The transmission zero created in the upper stopband to form a rapid roll off is produced through a bypass coupling with higher order modes. A 3rd order filter is designed at the centre frequency of 9.4 GHz with a 5.3% fractional bandwidth. The proposed structure's size is 38% smaller than one of a 3rd order E-plane extracted pole filter with comparable response. Additionally, this configuration allows larger span of different bandwidths. The filter has been fabricated and tested using E-plane waveguide technology, which has benefits of being inexpensive and having mass producible capabilities. Measurements of such a fabricated filter validate the simulated results.

Ultra compact inline E-plane waveguide extracted pole bandpass filters

This letter presents an ultra compact extracted pole E-plane filter. The proposed structure can achieve up to 65% size reduction in comparison with a standard extracted pole filter designed at 9.5 GHz centre frequency with a 3% fractional bandwidth. The filter has been fabricated and tested using E-plane waveguide technology. Measurements on a fabricated filter confirm the accuracy of the design method.

Optically reconfigurable E-plane waveguide resonators and filters

This paper presents an optically reconfigurable E-plane waveguide resonator and filter. N-type silicon dice doped with phosphorus is used as the switching element and is connected to the edge of a metallic fin. Illumination of the silicon dice allows realization of a different length of the fin, thus creating a shift in resonant frequency of the structure. Frequency tuning range up to about 5.2% is achieved for the resonator as well as the filter. Measurements on a fabricated optically reconfigurable resonator confirm the accuracy of the design procedure. Measured responses show good agreement with simulation.

Compact tunable bandstop filters using defected microstrip structure for multi-standard wireless systems

A novel compact tunable bandstop filter using Defected Microstrip Structure (DMS) is presented in this paper. The structure utilizes a modified T shaped DMS which helps in miniaturization of the filter. To verify the concept, one such filter was simulated, designed, fabricated and tested. Measurements on a fabricated tunable filter confirm the accuracy of the design procedure. The tuning range of 20% is achieved, ranging from 2.26 GHz to 2.747 GHz. Tuning is achieved by using NXP BB179 varactor diode. A nonlinear distortion evaluation in a tunable filter was experimentally verified. Experimental verification shows the filter is highly linear.