Separation Method Research Articles

Production of high purity 47Sc from proton irradiation of natural vanadium targets

BackgroundScandium-47 is the therapeutic counterpart to the diagnostic radionuclides, 43Sc and 44Sc. Together, these form elementally matched theranostic nuclide pairs, but their incorporation into radiopharmaceuticals requires developing production techniques leading to radioscandium isotopes with high chemical and radionuclidic purity. Previous 47Sc production methods involved expensive, enriched titanium targets that require additional procedures for target recovery. This work investigates the irradiation of natural vanadium targets and the development of purification methods for high-purity 47Sc. Natural vanadium foils were used in cyclotron target configurations. Targets were irradiated with 24 MeV protons at currents of up to 80 µA. A purification method was developed by determining the Kd values of Sc, Cr, and V using MP-50 resin. The final purification method used MP-50 and CM resin columns to isolate the 47Sc from natV and co-produced 51Cr. Inductively Coupled Plasma Mass Spectrometry (ICP-MS), gamma-ray spectroscopy, and a DOTA titration were used to characterize the 47Sc product. ResultsTwo cyclotron targets were designed, a small-scale target for developing a purification procedure and a high-power target for scaled-up production. The high-power target maximum current was 80 µA of 24 MeV protons. The yield for an 8 h irradiation at 80 µA of 24 MeV protons, was 128.02 ± 11.1 MBq of 47Sc at End of Bombardment. The radionuclidic purity of 47Sc was 99.5 ± 0.2%. The purification using MP-50 and CM columns resulted in the removal of natV target and 51Cr contaminate in the final 47Sc product, with an average recovery of 72 ± 2.1% and a DOTA apparent molar activity of 7733 ± 155 MBq/µmol. ICP-MS results showed that all top-row transition metals were below the limit of detection (< 1 ppb) with the exception of Zn, which was 64.6 ± 10.3 ppb.ConclusionsA high-power cyclotron target capable of withstanding a proton current of 80 µA was developed. A novel separation method was developed for isolating the 47Sc from the vanadium target and the co-produced 51Cr contaminate. The final product characterization resulted in a chemically and radionuclidically pure 47Sc product with high recovery yields.

Transcending Resolution Limits in HPLC and Diffusion NMR.

Mixture analysis is crucial in many areas of chemistry, and a wide variety of separation methods are in use. A common method for physical separation is high-performance liquid chromatography (HPLC), but resolution is a problem: chemically similar species coelute. An alternative approach is diffusion-ordered NMR spectroscopy (DOSY), in which the signals of mixture components are separated according to the diffusion coefficient. Again, separation is limited if species diffuse similarly or have overlap in their NMR spectra. Using the two techniques in combination can resolve both NMR spectra and the elution profiles of individual components, even where both techniques fail when used in isolation. Recording diffusion NMR data as a function of HPLC retention time gives a three-dimensional (3D) data set that can be analyzed using multiway statistical methods. PARAFAC analysis of diffusion NMR data measured from HPLC eluate for commercial "monoacetin" (a mixture of glycerol and its mono-, di-, and triacetates) yielded fully resolved and quantitative NMR spectra and elution profiles for all four components, whereas neither HPLC nor diffusion NMR applied independently was able to resolve the components.

Error Separation Method for Geometric Distribution Error Modeling of Precision Machining Surfaces Based on K-Space Spectrum

The geometric error distributed on components’ contact surfaces is a critical factor affecting assembly accuracy and precision instrument stability. Effective error separation methods can improve model accuracy, thereby aiding in performance prediction and process optimization. Here, an error separation method for geometric distribution error modeling for precision machining surfaces based on the K-space spectrum is proposed. To determine the boundary of systematical error and random error, we used a cruciform boundary line method based on the K-space spectrum, achieving the optimal separation of the two with frequency difference. The effectiveness of the method was experimentally verified using two sets of machined surfaces. By comparing with current common random error filtering methods, the outstanding role of the proposed error separation method in separating random error and preserving processing features has been verified.

Propagation of Non-stationary Skew-Symmetric Waves from a Spherical Cavity in a Porous-elastic Half-space

Problems of propagation and diffraction of non-stationary waves in porous-elastic mediums are of great theoretical and practical importance in such fields of science and technology as geophysics, seismic exploration of minerals, seismic resistance of structures, and many others. The work considers the problem of propagation of non-stationary skew-symmetric waves from a spherical cavity in a porous-elastic half-space saturated with liquid. To solve the problem, the integral Laplace transform in dimensionless time and the method of incomplete separation of variables were used. In the space of Laplace images in time, known and unknown functions are expanded into Gegenbauer polynomials. The problem is reduced to solving an infinite system of linear algebraic equations, the solution of which is sought in the form of an infinite exponential series. Recurrence relations for the coefficients of the series and initial conditions for them are obtained, which makes it possible to obtain a solution to the infinite system without using the reduction method. Recurrence relations make it possible to determine the coefficients of a series in the form of rational functions, which makes it possible to calculate their originals using the theory of residues. In image space, formulas are obtained for the coefficients of the series of components of the displacement vector and stress tensor. Numerical experiments were carried out, the results of which are presented in the form of graphs. The results obtained can be used in geophysics, seismology, and design organizations during the construction of structures, as well as in the design of underground reservoirs.

Detecting flying objects in synthetic aperture radar images using Moving Target Indicator methods

AbstractThe growing proliferation of synthetic aperture radar (SAR) sensors brings the tantalising prospect of extending their utility into ‘novel’ applications. One potential extension is the detection of fast moving and accelerating flying objects in SAR imagery. However, since SAR image formation typically assumes the scene to be static over the coherent processing interval, moving objects give rise to blurred point spread functions, significant range migration and even potential aliasing of target signatures. The result is reduced target to clutter ratio (TCR) and poor detection performance. Successful detection of airborne targets thus requires compensation for potentially large target acceleration and velocity values observed over the comparatively long dwell times typical of practical SAR collection paradigms. This paper considers this problem and presents two main ideas to achieve this goal: a carefully constructed Moving Target Indicator (MTI) detection method implemented using real‐world Ingara SAR data, and a theoretical ground clutter suppression method. The MTI detection method combines several well‐known techniques for the flying target detection problem: interferometric processing, clutter suppression, and autofocus, and provides an extended acceleration phase compensation technique for highly accelerating targets such as planes. This proposed processing pipeline has been applied to experimental data of a plane during take off (a challenging Doppler unambiguous moving target), with the goal of continued detecting and tracking of this target. A generalised SAR signal model is presented that parameterises a flying moving target signature in terms of range and azimuthal target velocities and accelerations. Data driven approaches for estimating these motion parameters are examined and applied to experimental data acquired with the Ingara SAR sensor. The detection method was found to improve TCR by around 6 dB, along with superior detection and tracking performance. Following this, a theoretical study into suppressing ground clutter via multi‐channel cross‐track interferometry is investigated. Three separate ground clutter suppression methods, coherent subtraction, conventional beamforming, and minimum variance distortionless response (MVDR) beamformer, are presented then analysed using stochastic simulations. The MVDR adaptive beamformer method was found to provide the best performance for the scenario simulated.

Optimized separation of astaxanthin stereoisomers from microbial sources using chiral HPLC.

Astaxanthin (AST) is a high-value antioxidant, and its efficient isolation and utilization are challenging owing to the presence of different stereoisomers from various sources. In the present study, a semi-preparative HPLC method for the efficient separation of AST stereoisomers using a Chiralpak IC chiral column with good loading capacity and chiral recognition ability was successfully developed. The mobile phase was methanol-methyl tert-butyl ether (90 : 10, v/v), with a flow rate of 3.06 mL min-1 and a maximum injection volume of 0.32 mg. The results indicated that the purity of all-trans AST was 97.9% for Haematococcus pluvialis and 97.5% for Phaffia rhodozyma. Additionally, molecular weights and fragmentation patterns analyzed using mass spectrometry were consistent with those of all-trans AST. Linearity validation and reproducibility experiments revealed that all calibration curves had coefficients of determination (R2) greater than 0.999 and a relative standard deviation (RSD) of <3.8%. This is because all-trans AST stereoisomers could undergo specific rotations or spins due to π-π interactions, hydrogen bonding, and inclusion interactions. This process allowed the successful separation of the three all-trans AST optical isomers and provides a theoretical basis for large-scale preparation of all-trans AST stereoisomers from different sources.

Male rats emit aversive 44-kHz ultrasonic vocalizations during prolonged Pavlovian fear conditioning.

Rats are believed to communicate their emotional state by emitting two distinct types of ultrasonic vocalizations. The first is long '22-kHz' vocalizations (>300 ms, <32-kHz) with constant frequency, signaling aversive states, and the second is short '50-kHz' calls (<150 ms, >32 kHz), often frequency-modulated, in appetitive situations. Here, we describe aversive vocalizations emitted at a higher pitch by male Wistar and spontaneously hypertensive rats (SHR) in an intensified aversive state - prolonged fear conditioning. These calls, which we named '44-kHz' vocalizations, are long (>150 ms), generally at a constant frequency (usually within 35-50-kHz range) and have an overall spectrographic image similar to 22-kHz calls. Some 44-kHz vocalizations are comprised of both 22-kHz-like and 44-kHz-like elements. Furthermore, two separate clustering methods confirmed that these 44-kHz calls can be separated from other vocalizations. We observed 44-kHz calls to be associated with freezing behavior during fear conditioning training, during which they constituted up to 19.4% of all calls and most of them appeared next to each other forming uniform groups of vocalizations (bouts). We also show that some of rats' responses to the playback of 44-kHz calls were more akin to that of aversive calls, for example, heart rate changes, whereas other responses were at an intermediate level between aversive and appetitive calls. Our results suggest that rats have a wider vocal repertoire than previously believed, and current definitions of major call types may require reevaluation. We hope that future investigations of 44-kHz calls in rat models of human diseases will contribute to expanding our understanding and therapeutic strategies related to human psychiatric conditions.

First report of leaf brown spot caused by Diaporthe phoenicicola on Lithocarpus polystachyus in China.

The leaves of Lithocarpus polystachyus (Wall. ex A. DC.), an economically significant tree species in China, are commonly referred to as 'sweat tea' due to their high dihydrochalcone content, which holds biomedical importance, particularly in the treatment of diabetes (Hou et al. 2011). In January 2024, brown spots on L. polystachyus leaves were widely observed in Ningxiang (28°23'N, 112°59'E), Hunan Province, China. According to the investigation, the incidence rate of this disease was about 74% (222/300 plants surveyed). On each infected plant, nearly 60% leaves had symptoms. The disease initially presented as small yellow lesions that eventually developed into large brown patches with dark brown edges. More than 80% of the area was covered by leaf lesions, which eventually turned into leaf necrosis. To ascertain the pathogenic species responsible for this disease, pathogen isolation was conducted using a tissue separation method (Xu et al. 2023). The infected leaf tissues were surface-disinfected by immersing in 75% ethanol followed by 0.1% HgCl2. Small pieces (0.5 × 0.5 cm) were then excised and placed onto PDA medium, and incubated at 28°C for 6-9 days. Sterilized dissecting needles were used to pick mycelia from the edge of the colonies and placed onto PDA for strains purification. On the PDA, the colony color of upper side initially appeared white (Rayner 1A1), and then turned grey (Rayner 11C1), while the reverse side turnd faint yellow (Rayner 4A3). Black pycnidia were induced on PDA at 28°C under a 12 h/12 h light/dark cycle for 12 days. Alpha conidia were 5.37 _8.84 × 1.53 _3.19 μm (average: 6.77 × 2.37 μm, n = 50), hyaline, fusiform or ellipsoidal. Beta conidia were 13.61 _23.45 μm × 0.94 _1.47 μm (average: 18.78×1.18 μm, n = 50), hyaline, aseptate, filiform, straight or hamate. Morphologically, the fungi were identified as Diaporthe sp. (Guarnaccia and Crous 2017). To further affirm the identification of the pathogen, the genomic DNA was extracted from representative isolate, referred to as Dip, for molecular identification. The internal transcribed spacer region (ITS), translation elongation factor 1α (EF1-α), β-tubulin (TUB2) and histone H3 (HIS) genes were amplified from genomic DNA using primers ITS1/ITS4, EF1-728F/EF1-986R, Bt2a/Bt2b, and CYLH3F/H3-1b, respectively, to sequence for BLAST (Huang et al. 2015). The results showed that the ITS (GenBank: PP502145), EF1-α (GenBank: PP505773), TUB2 (GenBank: PP505774) and HIS (GenBank: PP505772) sequences of Dip isolate, respectively, showed 100% (469/469 bp), 98.47% (257/261 bp), 97.63% (617/632 bp), and 100% (379/379 bp) identity to their counterparts (GenBank: MW504747, ON049530, MW514138 and ON113058) in Diaporthe phoenicicola. The Maximum Likelihood tree was built based on the ITS, EF1-α, HIS and TUB2 sequences using MEGA11.0. Isolate Dip clustered with D. phoenicicola. The fungus was finally identified as D. phoenicicola by combining morphological and molecular characteristics. To confirm the pathogenicity of the isolated D. phoenicicola to induce brown spot, the pathogenicity assay was assessed following Koch's postulates (Gradmann, 2014). Conidial suspension (1×105 conidia per mL) was inoculated on 12 unwounded leaves collected from six 3-years-old plants, and sterile water was as control. The inoculated leaves were then incubated in chambers at 28℃ and 90% humidity with a 12 h photoperiod. The experiment was repeated three times. The results showed that inoculated leaves other than control developed brown spot symptoms within six days after inoculation. The test proved D. phoeicicola as the causal agent of this brown spot disease on L. polystachyus. The pathogen was exclusively re-isolated from the infected leaves and showed identical morphological characteristics to those of the original pathogens. To our knowledge, this is the first report of leaf brown spot of L. polystachyus caused by D. phoenicicola in China. This disease severely delays the plant development of L. polystachyus and significantly reduces the yield and quality of sweat tea. Our findings will contribute to the control of brown spot of L. polystachyus.

Adaptive Dictionary Identification Framework and its Application to Sparsity-Optimized Harmonic Noise Separation

Coherent noise separation stands as a critical step in seismic data processing. The Morphological Component Analysis (MCA)-based separation method, treating coherent noise and signal as distinct components and representing them sparsely with dictionaries, has found widespread application in the effective suppression of coherent noise. In practice, when constructing effective fixed dictionaries for MCA-based separation methods, a common approach involves conducting numerous experiments to meticulously select appropriate transform basis functions from an extensive dictionary library and tune their parameters. To mitigate time consumption and ensure optimal dictionary construction, we introduce a framework for adaptive identification of the optimal dictionaries used in MCA-based coherent noise separation. Specifically, we initially characterize the notion of a fixed dictionary library, which encompasses dictionaries constructed using various transform basis functions and their corresponding parameters. Then, we present a Relative Sparsity Minimization Problem (RSMP), formulated to identify the optimal fixed dictionaries that lead to minimum relative sparsity within the predefined library. Finally, we design a genetic algorithm to solve RSMP. The optimal dictionaries obtained for representing signal and coherent noise, respectively, are applied to MCA-based coherent noise separation. Synthetic and field data examples demonstrate the effectiveness of the proposed method.

Quasi-projective synchronization of nonidentical fractional-order neural networks with inconsistent orders in quaternion field

Abstract The present study explores the quasi-projective synchronization (QPS) for nonidentical fractional-order quaternion-valued neural networks (FOQVNNs) with inconsistent orders. We construct two controls: quaternion-valued feedback control and quaternion-valued adaptive control to examine QPS of the FOQVNNs. Rather than employing the conventional separation method, the quaternion-valued state is treated as an integrated whole, and the synchronization results for FOQVNNs are established using the Lyapunov direct method and the fractional derivative properties. Lastly, we give two numerical examples to validate the effectiveness of the acquired results.

Ultra-Antifouling Liquid-Like Surfaces for Sustainable Viscous Water-in-Oil Emulsions Separation and Oil Recovery.

The demand for efficient separation techniques in industries dealing with high viscosity emulsions has surged due to their widespread applications in various scenarios, including emulsion-based drug delivery systems, the removal of emulsified impurities in formulations and oil spill remediation. However, membrane fouling is a major challenge for conventional separation methods, leading to decreased efficiency and increased maintenance costs. Herein, a novel approach is reported by constructing liquid-like surfaces with double anti-fouling structure, incorporating soft nanomicelles within a rigid, chemically cross-linked network for both anti-membrane-fouling and effective viscous water-in-oil emulsion separation. The coating significantly outperforms perfluorinated and commercial polytetrafluoroethylene (PVDF) membranes, effectively preventing the adhesion of viscous oils like crude oil and pump oil, and alleviating severe membrane fouling. For high-viscosity emulsions (97.3 cP and 52.8 cP), it maintains over 99% separation efficiency after 3h continuous use. Even after 15h immersion in strong acids, alkalis, salts, or organic solvents, its separation efficiency remains above 95%. In addition, thanks to the anti-membrane-fouling ability, this work achieved 6h continuous emulsion separation performance for the first time, demonstrating unparalleled long-term stability. Overall, this study offers valuable insights into the development of innovative coatings for efficient and eco-friendly separation of high-viscosity emulsions.

Effect of stretching ratio on the structure and enactment of porous PVDF-HFP hollow fiber membranes for CO2 absorption

Carbon dioxide (CO2) is responsible for increment of the Earth surface temperature and the subsequent environmental issues. In this regard, membrane contactor is one of the emerging technologies that can be applied for controlling CO2 emission. More specifically, the intrinsic structure of membrane plays an important role to govern the performance of CO2 absorption. In this study, considering stretching ratio (SR) as a key factor to affect membrane structural properties, highly porous poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) hollow fiber membranes were fabricated by a non-solvent induced phase separation method. The results showed that the membrane dimension and thickness were significantly reduced by optimizing the SR. The optimum membrane structure was found at SR of 1.5 where the mean pore size, CO2 permeance, collapsing pressure and liquid entry pressure of 0.032 μm, 3440 GPU, 550 kPa and 500 kPa were achieved, respectively. The prepared membranes showed open structure with overall porosity of more than 80%. The upgraded membrane at SR of 1.5 presented the maximum CO2 absorption flux of 9.8 × 10− 4 mol/m2 s and the minimum mass transfer resistance of 49,544 (m/s)−1. Furthermore, a stable CO2 absorption performance was achieved during 80 h continuous operation with a flux decline of only about 9%. The findings of this work demonstrated that by applying a cost-effective fabrication method, we can potentially enhance the PVDF-HFP membrane properties for CO2 adsorption without requiring an additional post-modification step.

A Review of Principles, Applications, and Recent Developments in HPTLC and HPLC

High-Performance Thin Layer Chromatography (HPTLC) and High-Performance Liquid Chromatography (HPLC) represent fundamental analytical techniques in modern chemical analysis. These sophisticated separation methods have revolutionized the field of analytical chemistry through their precision, reliability, and versatility. HPTLC, an enhancement of traditional thin-layer chromatography, offers advantages such as minimal sample preparation, simultaneous analysis of multiple samples, and cost-effectiveness. It has found extensive applications in pharmaceutical analysis, natural product research, and food quality assessment. HPLC, characterized by its high resolution, sensitivity, and automation capabilities, has become an indispensable tool in various industries, including pharmaceutical, environmental, and biochemical analyses. The technique employs different modes such as reverse phase, normal phase, and ion exchange, enabling the separation of complex mixtures with remarkable accuracy. Recent technological advancements have led to the development of ultra-high-performance liquid chromatography (UHPLC), offering enhanced speed and resolution. Both HPTLC and HPLC complement each other in analytical laboratories, with HPTLC providing rapid screening and HPLC offering detailed quantitative analysis. The continuous evolution of these techniques through technological innovations ensures their pivotal role in modern analytical chemistry.

Facile and versatile PDMS-glass capillary double emulsion formation device coupled with rapid purification toward microfluidic giant liposome generation

The exceptional ability of liposomes to mimic a cellular lipid membrane makes them invaluable tools in biomembrane studies and bottom-up synthetic biology. Microfluidics provides a promising toolkit for creating giant liposomes in a controlled manner. Nevertheless, challenges associated with the microfluidic formation of double emulsions, as precursors to giant liposomes, limit the full exploration of this potential. In this study, we propose a PDMS-glass capillary hybrid device as a facile and versatile tool for the formation of double emulsions which not only eliminates the need for selective surface treatment, a well-known problem with PDMS formation chips, but also provides fabrication simplicity and reusability compared to the glass-capillary formation chips. These advantages make the presented device a versatile tool for forming double emulsions with varying sizes (spanning two orders of magnitude in diameter), shell thickness, number of compartments, and choice of solvents. We achieved robust thin shell double emulsion formation by operating the hybrid chip in double dripping mode without performing hydrophilic/phobic treatment a priori. In addition, as an alternative to the conventional, time-consuming density-based separation method, a tandem separation chip is developed to deliver double emulsions free of any oil droplet contamination in a continuous and rapid manner without any need for operator handling. The applicability of the device was demonstrated by forming giant liposomes using the solvent extraction method. This easy-to-replicate, flexible, and reliable microfluidic platform for the formation and separation of double emulsion templates paves the way for the high-throughput microfluidic generation of giant liposomes and synthetic cells, opening exciting avenues for biomimetic research.The presented giant liposome assembly line features a novel treatment-free hybrid chip for double emulsion formation coupled with a high throughput separation chip for sample purification.

Highly selective and effective copper removal from wastewater by magnetic precipitation separation

The presence of heavy metals in wastewater poses a substantial threat to both public health and the environment. However, the selective removal and separation of heavy metal ions at ultra-low concentrations from wastewater remains a considerable challenge. In this paper, we innovatively proposed a magnetic precipitation separation method to remove Cu (II) from wastewater using Fe3O4 nanoparticles and Na2S. In this process, the Cu (II) was reduced to CuS by Na2S, which then rapidly aggregated with Fe3O4 nanoparticles to form Fe3O4-CuS nanoclusters. SEM, DLS, XRD, VSM and XPS studies demonstrated that the removal of Cu (II) was related to the formation of Fe3O4-CuS nanoclusters. The results indicated that the removal efficiency of Cu (II) from wastewater could reach 99.75 % within 30 s. In contrast, the removal efficiencies of Co (II), Ni (II), and Zn (II) were 7.64 %, 6.14 %, and 8.41 %, respectively. In addition, the Fe3O4 nanoparticles were easily regenerated from Fe3O4-CuS nanoclusters using ultrasound, maintaining 98 % removal efficiency of Cu (II) after six consecutive cycles. These results suggested that this method held great potential for the removal of heavy metals from wastewater.

Філологічний підхід як методологічна стратегія: розвідки І. Денисюка про Лесю Українку

The purpose of the article is to trace the use of the philological approach to literary research on the materials of I. Denysiuk's scientific papers about Lesya Ukrainka. The methodological and generalizing works by R. Gromyak, M. Naienko, M. Hnatiuk, and P. Ivanyshyn, as well as topical investigations that illustrate its functioning (articles by T. Pastukh and S. Pylypchuk), outlined the theoretical framework of this study. Results. Proponents of the philological approach defined its main goal as an in-depth study of the text, which later gave reasons for researchers of this phenomenon to focus attention on the concept of form, thus bringing it closer to the formalism blocked in the Soviet period. Scientific research in this direction was conducted mainly in emigration and Western Ukraine. In post-Soviet Ukraine, in the conditions of the socialist realist dictates dominating in the artistic domain and vulgar sociological dictates in science, supporters of the structural-formalist approach sought a compromise, for example, in the use of holistic-systemic analysis. The range of I. Denysiuk's scientific interests involve numerous studies on the history and theory of literature, folkloristics and methodology, local history, and literary criticism. His research searches are characterized by scrupulousness, profound analysis, and well-balanced generalizations, which are determined primarily by a philological approach. Scientific works about Lesya Ukrainka are represented by the study of the sources and poetics of the drama "Forest Song" (co-authored with L. Mishchenko), the study of creative biography in the context of the "noble nest of Kosachy" (together with T. Skrypka), and other thematic publications. I. Denysiuk utilized the analysis of Lesya Ukrainka's texts and her critical thoughts in the development of his own genre-logical concepts. Conclusions. The notion of the philological approach is very broad and at the same time too generalizing to become a separate method of literary studies. It rather serves as the core of the methodology or defines the strategy of scientific research. The philological approach in the conditions of totalitarian systems made it possible to carry out professional research in taboo areas, such as formalism and structuralism. I. Denysiuk's scientific research is mostly determined by the text-centric principles of the philological approach in investigations of poetics, in general, and genre analysis, in particular.

Study on the gas composition of hydrate phase and unreacted liquid phase for hydrate-based gas separation

Hydrate-based gas separation (HBGS) method is an environment-friendly gas separation technique. At the end of the hydrate formation stage, the system usually consists of gas phase, hydrate phase and residual unreacted liquid phase. The separation efficiency of HBGS is usually determined by measuring the gas composition of gas phase before and after hydrate formation. It is currently unclear the gas composition of hydrate phase and residual unreacted liquid phase, and how they will affect the gas separation efficiency of HBGS separately. This work developed a novel method for efficiently separating the hydrate phase and the unreacted liquid phase, making it possible to directly measure the gas composition in the hydrate phase and residual unreacted liquid phase for the gas mixture hydrate system. The influence factors, such as operation conditions, gas composition of feed gas and types of guest gas on the gas composition of liquid and hydrate phases were studied. The experimental results show the mole fraction of CO2 in both hydrate phase and liquid phase are higher than that in the feed gas. The increase of system pressure and the mole fraction of CO2 in feed gas will obviously lead to the increase of the mole fraction of CO2 in hydrate phase, while slightly affect the mole fraction of CO2 in the liquid phase. When the mole fraction of CO2 in feed gas exceeds 80 %, the mole fraction of CO2 in the water phase will reach over 96 %, resulting in other influence factors being negligible. The mole fraction of N2 in hydrate phase is higher than that of H2, while the mole fraction of N2 in water phase is close to H2.

Investigation on coupling vibration characteristics of asymmetric rails with variable cross-sections based on modal separation

In railway turnouts, asymmetric switch rails with variable cross-sections are designed for wheel load transitions. However, the dynamic characteristics of these specially shaped switch rails are not yet fully understood. This paper investigates the vibration characteristics of switch rails through theoretical simulations, on-site admittance tests, and operational deflection shape (ODS) measurements. The study reveals that the modes of the switch rail involve multi-directional coupling vibrations, making the mode types indiscernible through direct observation. To address this, a modal separation method is proposed, based on the calculation of modal mass. The vertical vibration of the switch rail can be categorized into three types: torsional mode, vertical bending mode, and reverse torsion mode of the rail head and base above 600 Hz. As the position approaches the switch rail point, the degree of cross-sectional asymmetry increases, which consequently intensifies torsional vibration. Cross-sectional asymmetry is identified as the primary factor causing the coupling of bending-torsional vibrations, while variable cross-sections contribute to mode shape asymmetry and the gradual alteration of natural frequency along the rail.

Optical wave packet compression using counterpropagating Scorer beams

Abstract We investigate the diffractive paraxial wave equation with an external potential, utilizing self-similarity and variable separation methods. The exact solution to this evolution equation, expressed through Scorer functions, gives rise to the new Scorer beams. We explore the dynamics of counterpropagating Scorer beams, as promising optical wave packets, focusing on their compression behavior. The Scorer beams are characterized by two key parameters: the attenuation factor and the initial pulse width. By appropriately adjusting these parameters, significant beam compression can be achieved. Specifically, increasing the attenuation factor enhances compression and raises pulse amplitude, while reducing the initial pulse width further amplifies these effects. Along the way, we observe interesting interference patterns of the counterpropagating Scorer beams, never seen before. This study introduces a novel approach to beam compression and opens up new possibilities for their practical applications.

Dissociation extraction: Theoretical foundations and applications

Dissociation extraction (DE) is a separation method that has been known for many decades but is not yet widely used in industry. However, there are a number of applications for which DE may be applied, for example, for new biorefinery separations. To facilitate future applications, we derived a new shortcut method for DE processes and demonstrated its application in the conceptual design of a separation process for acidic and basic organic mixtures. The new method allows for the calculation of the minimum energy requirement and a fast comparison of dissociation extraction with other separation methods. The shortcut method was validated using experimental data from the literature and is easy to implement because it is based only on the physical distribution coefficients and dissociation constants of the acids or bases to be separated.In the second part of this paper, we identify several areas that require effective separation techniques, where dissociation extraction can have an impact. These include biorefinery separation, polymer recycling, and fatty acid fractionation.In conclusion, we hope to promote DE as a known but less-used separation method for difficult separation problems in both fossil-based and bio-based sustainable chemical products.