Flexible Channel Research Articles

Capillary Imbibition in a Diverging Flexible Channel.

We study the imbibition of a wetting liquid between flexible sheets that are fixed at both ends. Assuming a narrow gap between the sheets, we solve the lubrication equation coupled with a slender body deformation. When the sheets are parallel, we find that the deformation initially speeds up the flow, as shown in previous studies, but only up to the middle of the channel. As the channel contracts, the hydrodynamic resistance increases and ultimately slows down the filling process. Below a threshold stiffness, the channel collapses and imbibition stops. We propose a scaling of the filling duration near this threshold. Next, we show that if the sheets are initially tilted with a minimal angle, the channel avoids collapse. The liquid front pulls the diverging sheets and spreads in a nearly parallel portion, which maintains the capillary propulsion and enhances the wicking. Therefore, while it is established that diverging rigid plates imbibe liquids slower than parallel ones do, we show that elasticity reverses this principle: diverging flexible sheets imbibe liquids faster than parallel ones. We find an optimal tilt angle that gives the shortest filling time.

Flexible optical fiber channel modeling based on a neural network module.

Optical fiber channel modeling, which is essential in optical transmission system simulations and designs, is usually based on the split-step Fourier method (SSFM), making the simulation quite time-consuming owing to the iteration steps. Here, we train a neural network module termed NNSpan to learn the transfer function of a single fiber (G652 or G655) span with a length of 80 km and successfully emulate long-haul optical transmission systems by cascading multiple NNSpans, which gives remarkable prediction accuracy, even over a transmission distance of 1000 km. Even when trained without erbium-doped fiber amplifier (EDFA) noise, NNSpan performs quite well when emulating the systems affected by EDFA noise. An optical bandpass filter can optionally be added after EDFA, making the simulation more flexible. Comparison with the SSFM shows that NNSpan has a distinct computational advantage, with the computation time reduced by a factor of 12. This method based on NNSpan could be a supplementary option for optical transmission system simulations, thus contributing to system designs as well.

Multi-objective study using entropy generation for Ellis fluid with slip conditions in a flexible channel

A mathematical model is developed to investigate the entropy generation on peristaltic transport of the Ellis fluid through a uniform two-dimensional symmetric channel with elastic nature of the walls. An analysis of heat and mass transfer is also made to examine the effects of viscous dissipation. To simplify the governing equations, nondimensional analysis with low Reynolds number and large wavelength is done. Solutions of the problems are presented via a NDSolve Mathematica numerical technique. The effects of various parameters on flow characteristics, thermal characteristics and species characteristics have been computed and physically interpreted. The numerically acquired solutions are studied graphically for the effective analysis of the flow. The velocity and temperature profiles are parabolic in nature. Higher values of elastic parameters and chemical reaction parameters rapidly increase concentration profile for Newtonian case as compared to non-Newtonian case. The outcomes of this model can be applicable in various fields of biomedical engineering where smart peristaltic pumps can be engineered to transport the biological fluids without any contamination, i.e., electromagnetic peristaltic micro pumps.

A Fully Bayesian Approach for Massive MIMO Unsourced Random Access

In this paper, we propose a novel fully Bayesian approach for the massive multiple-input multiple-output (MIMO) massive unsourced random access (URA). The payload of each user device is coded by the sparse regression codes (SPARCs) without redundant parity bits. A Bayesian model is established to capture the probabilistic characteristics of the overall system. Particularly, we adopt the core idea of the model-based learning approach to establish a flexible Bayesian channel model to adapt the complex environments. Different from the traditional divide-and-conquer or pilot-based massive MIMO URA strategies, we propose a three-layer message passing (TLMP) algorithm to jointly decode all the information blocks, as well as acquire the massive MIMO channel, which adopts the core idea of the variational message passing and approximate message passing. We verify that our proposed TLMP significantly enhances the spectral efficiency compared with the state-of-the-arts baselines, and is more robust to the possible codeword collisions.

MHD peristaltic flow of chemically reactive casson nanofluid in a nonuniform porous inclined flexible channel with cross-diffusion effects

This model is designed to provide clarity on how blood travels through tiny veins in physiological systems with heat and mass transfer characteristics. Further, the purpose of this paper is to examine the Ohmic heating and heat source/sink effects on peristaltic transport of radiative Casson nanofluid in a nonuniform porous inclined channel in the presence of a normal/inclined magnetic field. We also considered the sway of chemical reaction, Soret and Dufour effects. The momentum, temperature and mass equations for Casson fluid model are obtained with the utilization of the lubrication approach. The exact solutions have been acquired for stream function and axial velocity. Further, the temperature and concentration equations are solved numerically by using the R–K based shooting method. We also tabulated the Nusselt and Sherwood numbers for various relevant parameters. Finally, the impacts of all major factors on the physical properties of the flow for both normal and inclined magnetic fields are explored and discussed in depth using graphs. The Casson fluid velocity is more for an inclined magnetic field than a normal magnetic field. The nonuniform parameter of the channel boosts the trapped fluid bolus size. The heat source/sink parameter improves the temperature field but the opposite trend is observed in the field of concentration. Moreover, the findings are validated with the existing works for some special circumstances.

Potential of Transition Metal Dichalcogenide Transistors for Flexible Electronics Applications

AbstractSemiconducting transition metal dichalcogenides (TMDC) are 2D materials, combining good charge carrier mobility, ultimate dimension down‐scalability, and low‐temperature integration. These properties make TMDCs interesting for flexible electronics, where the thermal fabrication budget is strongly substrate limited. In this perspective, an overview of the state of TMDC research is provided by evaluating two scenarios, both with their own merit depending on the target application. First, high‐quality chemically grown 2D TMDCs are promising for nanoscale high‐performance and high‐frequency devices with excellent gate control and high current on/off ratios. Second, TMDC thin films can also be solution deposited from chemically exfoliated flakes allowing for moderate performance, but providing a path toward low‐cost production. A strong advantage of TMDCs is the possibility to realize p‐type and n‐type channels for complementary transistors having similar performance figures‐of‐merit. This aspect, as well as common transistor performance metrics are also compared with other flexible channel materials providing an overview of the state of the art of thin‐film transistors in the field of flexible electronics.

On-chip non-uniformly spaced multi-channel microwave photonic signal processor based on an ultrahigh-Q multimode micro-disk resonator.

Multi-channel microwave photonic (MWP) signal processing can simultaneously perform different task operations on multiple signals carried by multiple wavelengths, which holds great potential for ultrafast signal processing and characterization in a wavelength-division-multiplexed (WDM) network. As emerging telecommunication services create more data, an elastic optical network, which has a flexible and non-uniform spectrum channel spacing, is an alternative architecture to meet the ever-increasing data transfer need. Here, for the multi-channel ultra-fast signal processing in the elastic optical network, we propose and demonstrate an on-chip non-uniformly spaced multi-channel microwave photonic signal processor based on an ultrahigh-Q multimode micro-disk resonator (MDR). In the proposed signal processor, an MDR supporting multiple different order whispering-gallery modes (WGMs) with an ultrahigh Q-factor is specifically designed. Benefiting from the large and different free spectral ranges (FSRs) provided by the different order WGMs, a non-uniformly spaced multi-channel microwave photonic signal processor is realized, and various processing functions are experimentally demonstrated including bandpass filtering with a narrow passband of 103 MHz, a rejection ratio of 22.3 dB and a frequency tuning range from 1 to 30 GHz, multiple frequency measurement with a frequency measurement range from 1 to 30 GHz, a frequency resolution better than 200 MHz and a measurement accuracy of 91.3 MHz, and phase shifting with a phase tuning range from -170°∼160°, an operational bandwidth of 26 GHz from 6 GHz to 32 GHz and a small power variation of 0.43 dB. Thanks to the coexistence of different order WGMs supported by the MDR, non-uniformly spaced multi-channel signal processing is enabled with the key advantages including a broad operation bandwidth, an ultra-narrow frequency selectivity, and a large phase tuning range with a small power variation. The proposed signal processor is promising to be widely used in future elastic optical networks with flexible spectrum grids.

A Career in Catalysis: Bernhard Hauer

On the occasion of Professor Bernhard Hauer′s (partial) retirement, we reflect on and highlight his distinguished career in biocatalysis. Bernhard, a biologist by training, has greatly influenced biocatalysis with his vision and ideas throughout his four-decade career. The development of his career went hand in hand with the evolution of biocatalysis and the application and development of enzymes for chemical processes. In this Account, we present selected examples of his early work on the development of enzymes and their application in an industrial setting, with a focus on his specific contributions to harnessing the catalytic power of enzymes for novel reactions and the understanding and engineering of flexible loops and channels on catalysis.

Chemically reactive MHD peristaltic flow of Jeffrey nanofluid via a vertical porous conduit with complaint walls under the effects of bioconvection and double diffusion

Inspired by significant physiological applications of peristaltic transport, a mathematical model for the peristaltic pumping of a Jeffrey nanofluid containing gyrotactic microorganisms through a flexible and vertical symmetric channel is investigated, along with the effects of thermal radiation, heat source/sink, chemical reaction, porous medium and Hall current. Swimming microorganisms in a model of non-Newtonian fluid has several biological and ecological benefits, including in the pharmaceutical industry, biofertilizers, biofuel technology, biosensors, etc. With these presumptions in mind, a conducting Jeffery fluid flow containing microorganisms via a porous vertical conduit is proposed. The expressions for the flow quantities are established by solving the governing equations of this study analytically using the homotopy perturbation method (HPM). A detailed examination is performed using the tables and graphical representations to comprehend the impact of significant components on this analysis. In addition, the results for Newtonian nanofluid are obtained as a special case and discovered that its velocity is lower than the Jeffrey nanofluid. It is observed that the best velocity distribution can be seen at larger thermal Grashof number and Darcy number. The size of the trapped bolus enhances with the increase of the Hall parameter. Furthermore, the density of the motile microorganism distribution declines for higher bioconvection Peclet number and bioconvection constant.

Analysis of nonlinear radiative peristaltic transport of hyperbolic tangent nanomaterial with chemical reaction

In this research, we examine the mixed convection effects for peristaltic motion of tangent hyperbolic nanoliquid. On flexible channel walls, partial slip characteristics are applied. Influences of Ohmic heating and viscous dissipation are analyzed in the modeling. We evaluated the transportation of heat under nonlinear thermal radiation. The governing problem is first reduced into dimensionless form by using suitable transformations and then numerical technique is employed for the solution after utilizing small Reynolds number and large wavelength assumption. The problem is simulated employing the so-called Buongiorno’s formulation which includes the features of thermophoresis and random motion. In addition, a mass transport scheme is developed with first-order chemical reactions. The roles of sundry variables on velocity, coefficient of heat transfer, temperature and concentration are examined graphically. Velocity and temperature show similar behavior against thermal Grashof parameter. Concentration decreases for larger thermophoresis parameter. Heat transfer coefficient and temperature have decreasing effects against radiation parameter.

Peristaltic transport of MHD Ree–Eyring fluid through a flexible channel under the influence of activation energy

Peristalsis of Ree–Eyring non-Newtonian fluid is significant to investigate the rheological features of biological fluids such as blood, saliva, intravascular fluids, intracellular fluids, and interstitial fluids. As a consequence of this development, the present article explores the cross-diffusive magnetohydrodynamic peristaltic transport of a Ree–Eyring fluid conveying tiny particles through a flexible porous channel under the influence of activation energy. A lubrication approach is adopted to reduce the complexity of the system. The analytical solution is achieved for the velocity field. In addition, the Runge–Kutta-based shooting technique is employed to solve the temperature and fluid concentration equations. Dual solutions are executed for the Newtonian and Ree–Eyring fluid cases and discussed through tabular and graphical findings for several sets of pertinent parameters. In this investigation, it is perceived that an enhancement in the Darcy number optimizes the velocity field. The fluid temperature rises with elevated values of the Brinkman and Dufour numbers whereas the reverse trend is noticed in the fluid concentration field for Soret and activation energy parameters. Moreover, the obtained outcomes are applicable to a variety of fields in the medical sciences and engineering, such as the radiosurgery, the spectroscopy, the optoelectronics, the power conversion devices, and the nuclear reactor cooling.

Flexible channel selection method based on optical combs for broadband signals receiving.

A flexible channel selection method based on optical combs is proposed for reconfigurable optical channels in this paper. Optical-frequency combs with a large frequency interval are used to modulate broadband radio frequency (RF) signals, and an on-chip reconfigurable optical filter [Proc. of SPIE, 11763, 1176370 (2021).10.1117/12.2587403] is used to perform periodic carrier separation of wideband and narrowband signals and channel selection. In addition, flexible channel selection is achieved by presetting the parameters of a fast-response programmable wavelength-selective optical switch and filter device. Channel selection only relies on the combs through the Vernier effect of the combs and the passbands for different periods and does not require the use an additional switch matrix. Finally, flexible switching between and selection of specific channels for 13 GHz and 19 GHz broadband RF signals are experimentally verified.

Clinical Evaluation of Miniature Flexible Scope for Diagnosis of Ureteroscope Working Channel Defects.

Introduction: To evaluate flexible ureteroscope working channels with a 1.06 mm digital borescope (Clarus Medical, Minneapolis, MN) and identify factors contributing to ureteroscope damage over time. Materials and Methods: We performed a single institutional prospective study of patients undergoing stone surgery using a nondisposable flexible ureteroscope. A 1.06 mm borescope was used to evaluate ureteroscopes before and after surgery. Borescope videos were reviewed by two independent researchers to quantify average pre- and postprocedural damage. Results: Twenty-five procedures were performed with pre- and postprocedural borescope assessment between August 2021 and February 2022. All patients received preoperative CT imaging depicting a mean axial stone size of 14.1 ± 8.4 mm and density of 923.4 ± 458.1 HU. Mean operative time was 63.8 ± 34.0 minutes. The average number an instrument passes through the working channel was 2.1 ± 1.6. Laser was used in 11 cases with mean laser time of 18.8 ± 19.7 minutes and mean total energy of 5.8 ± 4.2 KJ. On preoperative assessment, all ureteroscopes had some form of defect (24% shave, 32% pinhole, 96% dents and scratches, and 28% discolorations). During postoperative assessment, 23/25 (92%) ureteroscopes showed additional damage with an average of 3.7 ± 2.8 imperfections acquired after one use. Significant differences were seen in acquired shavings (p = 0.028) and scratches or dents (p = 0.018). Of the 355 imperfections seen on postoperative evaluation, 0.4% were shave, 3% were pinhole, 85.8% were dents and scratches, and 10.8% were discolorations. Conclusion: The Clarus borescope observed defects after the majority of flexible ureteroscopy procedures for nephrolithiasis. Although such disruptions may not immediately render ureteroscopes nonfunctional, they are more common than previously described and could increase maintenance costs. Further studies are needed to investigate the burden of unit damage per procedure to raise operator awareness and reduce preventable ureteroscope imperfections.

An optimization design study of producing transuranic nuclides in high flux reactor

Transuranic nuclides (such as 238Pu, 252Cf, 249Bk, etc.) have a wide range of application in industry, medicine, agriculture, and other fields. However, due to the complex conversion chain and remarkable fission losses in the process of transuranic nuclides production, the generation amounts are extremely low. High flux reactor with high neutron flux and flexible irradiation channels, is regarded as the promising candidate for producing transuranic nuclides. It is of great significance to increase the conversion ratio of transuranic nuclides, resulting in higher efficiency and better economy. In this paper, we perform an optimization design evaluation of producing transuranic nuclides in high flux reactor, which includes optimization design of irradiation target and influence study of reactor core loading. It is demonstrated that the production rate increases with appropriately determined target material and target structure. The target loading scheme in the irradiation channel also has a significant influence on the production of transuranic nuclides.

Physical confinement and cell proximity increase cell migration rates and invasiveness: A mathematical model of cancer cell invasion through flexible channels

Cancer cell migration between different body parts is the driving force behind cancer metastasis, which is the main cause of mortality of patients. Migration of cancer cells often proceeds by penetration through narrow cavities in locally stiff, yet flexible tissues. In our previous work, we developed a model for cell geometry evolution during invasion, which we extend here to investigate whether leader and follower (cancer) cells that only interact mechanically can benefit from sequential transmigration through narrow micro-channels and cavities. We consider two cases of cells sequentially migrating through a flexible channel: leader and follower cells being closely adjacent or distant. Using Wilcoxon’s signed-rank test on the data collected from Monte Carlo simulations, we conclude that the modelled transmigration speed for the follower cell is significantly larger than for the leader cell when cells are distant, i.e. follower cells transmigrate after the leader has completed the crossing. Furthermore, it appears that there exists an optimum with respect to the width of the channel such that cell moves fastest. On the other hand, in the case of closely adjacent cells, effectively performing collective migration, the leader cell moves 12% faster since the follower cell pushes it. This work shows that mechanical interactions between cells can increase the net transmigration speed of cancer cells, resulting in increased invasiveness. In other words, interaction between cancer cells can accelerate metastatic invasion.

MHD peristaltic activity of Powell-Eyring nanomaterial through porous space with slip effects

Peristaltic activity of Powell-Eyring nanomaterial through flexible channel is reported in this paper. Magnetic field is considered to control the drug delivery process. Dissipation and Joule heating effects are taken in energy equation. Modified Darcy law addresses porous medium. Further zero mass flux and slip constraints at the walls are taken into account. Brownian motion and thermophoresis effects explain the nanomaterial characteristics. Non-dimensional expressions are further simplified in view of large wavelength assumptions. Numerical approach are used to solve simplified form of equations. Temperature, pressure gradient, concentration and velocity are analyzed. Temperature increases for larger Hartman number however opposite situation is observed for Hall parameter.

Initial Experience of Simultaneous Combined use of Percutaneous Nephrolithotomy and Flexible Ureteroscopy in Complex Renal Calculi: A Novel Surgical Technique of 'Through-Through' Approach.

For complex branched renal calculi, the endoscopic combined intrarenal surgery (ECIRS) is worldwide prevalent. This study aimed to present a novel surgical technique of percutaneous nephrolithotomy combined with antegrade flexible ureteroscopy which is named 'Through-through' approach. We retrospectively analyzed the data of 68 patients with complex renal calculi who underwent combined PNL and flexible ureteroscopy surgery using 'Through-through' approach at our center between August 2019 and December 2021. The 'Through-through' approach to surgery was indicated in residual calyceal calculi that neither rigid nephroscope nor retrograde flexible ureteroscope could reach. The brief procedure of this technique involved determining the direction of targeted calyces with the nephroscope first, followed by putting flexible ureteroscope into the targeted calyx through the nephroscope instrument channel and basketing or dusting residual calculi through the flexible ureteroscope instrument channel. The mean maximum stone diameter was 4.0 ± 0.4cm. The mean operative duration was 100.1 ± 18.0minutes, and mean hemoglobin loss was 21.4 ± 5.1g/L. In all 68 patients, calculi were cleared in 62 patients, and the stone free rate was 91.2%. Five patients underwent further surgery after 2weeks because of significant residual calculi. One patient that had a 6mm residual stone chose observational follow-up. Ten patients emerged with postoperative fever but did not progress to uroseptic shock. There were no Clavien grade ≥ III complications, and none of the patients required blood transfusion. The 'Through-through' approach is safe, feasible and effective for complex renal calculi patients. It is a complementary solution to the failed endoscopic combined intrarenal surgery.

The Peristaltic Flow of Williamson Fluid through a Flexible Channel

The purpose of this study is to investigate the effect of an elastic wall on the peristaltic flow of Williamson fluid between two concentric cylinders, where the inner tube is cylindrical with an inelastic wall and the outer wall is a regular elastic sine wave. For this problem, cylindrical coordinates are used with a short wavelength relative to channel width for its length, as well as the governing equations of Williamson fluid in the Navier-Stokes equations. The results evaluated using the Mathematica software program. The Mathematica program used by entering the various data for the parameters, where the program shows the graphs, then the effect of these parameters became clear and the results mentioned in the conclusion. Williamson fluid peristaltic flow through an elastic conduit is the subject of this investigation. For a number of significant elements, such as velocity distribution, stress and wave frame streamlines, graphic findings are supplied at the end of the article.

Impacts of Liquid Level on Microwave Resonance Sensing with a Flexible Microfluidic Channel

AbstractPermittivity sensing based on resonance tracking lays the fundamental principle for a variety of biochemical sensors, which has found vast applications in cancer biomarker detection, antigen‐antibody analysis, and so on. Driven by continuous promotion of the detection limit, precise environmental control highlights its critical importance. Here, the impacts of liquid level on microwave resonance sensing are investigated, in which a flexible polydimethylsiloxane microfluidic channel and soft tubing are employed to control the liquid under test. The hydraulic pressure affects the effective permittivity of the liquid and the channel material, hence causing extra resonance shift signals. Both contactless and contacting sensing scenarios are studied in numerical simulations and experiments. It is demonstrated that the resonance frequency varies sensitively with the liquid level, and a sensitivity of 343 kHz mm−1 is measured. Meanwhile, a spoof localized surface plasmon resonator and its optimized excitation structure are employed and analyzed for a good figure of merit, addressing the detectability difficulties for high‐permittivity and high‐loss aqueous solutions. These results provide general guidelines for understanding and controlling the resonance sensors in aqueous environments and help to realize further lower detection limits.

The constructions of the fully flexible s-triazine-based covalent organic frameworks for adsorping iodine and fluorescence sensing p-nitrophenol and iodine

The effective capture of radioactive vapor waste during fission is of great significance to the safe utilization of nuclear energy. Covalent organic frameworks (COFs) are a kind of novel porous crystal polymers, with highly flexible channel structure and molecular designability. COFs containing nitrogen-rich structures and flexible units can provide effective binding sites for adsorption of iodine, and are potential adsorption materials. In this study, the fully flexible s-triazine-based COFs were prepared by one-pot condensation using fully flexible building blocks of 2,4,6-tris(4-formylphenoxy)- 1,3,5-triazine (TPT–3–CHO) as a knot and ether-based diamines as flexible linkers. The three fully flexible s-triazine-based COFs have large surface areas (1490, 1596, and 1657 m2 g−1), good crystallinity and outstanding adsorption capacitiy of volatile iodine (4.10, 4.13 and 3.40 g g−1) with excellent recyclability. As the linker lengths increase, the specific surface areas increase, but the adsorption amounts of iodine decrease. Moreover, the fully flexible s-triazine-based COFs also have high sensitivities for fluorescence detection against p-nitrophenol and iodine. Their quenching constants (KSV) for p-nitrophenol are 5.59 × 104, 4.05 × 104 and 2.35 × 104 L mol−1, respectively. The fully flexible s-triazine-based COFs have larger specific surface area, high iodine adsorption, and more sensitive fluorescence sensing performance than the COFs formed by the corresponding rigid linkers.