Flat Modules Research Articles

Resource recovery from landfill leachate by two-stage of direct contact membrane distillation

Landfill leachate (LL) is a high organic matter and ammonia strength wastewater. The recovery of ammonia and water as by-products can be a path to a more sustainable management of LL. This study aims to evaluating the performance of a two-stage of Direct Contact Membrane Distillation for resource recovery from LL. In the first stage, the hot LL flows through the shell side of the polypropylene hollow fiber membrane module while the sulfuric acid solution passes through the lumen side. Ammonia is recovered as ammonium sulfate. In the second stage, the hot effluent from the first stage flows through the hot channel of the poly(tetrafluoroethylene) flat sheet membrane module, while cooled distillate water flows through the other side in countercurrent. The water evaporates and cross the membrane from the hot to the cold channel where it condenses. The results revealed the ammonia recovery rate was 87.38 % in the first stage, then, for each 1 m3 of LL, 2.20 kg of ammonia could be recovered. The water recovered (flux of 11.7 kg m−2 h−1) showed high quality, due to the great membrane rejection rate of colour (99.99 %), turbidity (99.88 %), TOC (99.98 %), NH3 (99.85 %) and phosphorus (99.88 %).

Modules of finite Gorenstein flat dimension and approximations

AbstractWe study approximations of modules of finite Gorenstein flat dimension by (projectively coresolved) Gorenstein flat modules and modules of finite flat dimension. These approximations determine the Gorenstein flat dimension and lead to descriptions of the corresponding relative homological dimensions, for such modules, in more classical terms. We also describe two hereditary Hovey triples on the category of modules of finite Gorenstein flat dimension, whose associated exact structures have homotopy categories equivalent to the stable category of projectively coresolved Gorenstein flat modules and the stable category of cotorsion Gorenstein flat modules, respectively.

A note on Matlis localizations

Let R be a commutative ring and S a multiplicative subset of R. A ring R is called an S-Matlis ring if pd R R S ≤ 1 . In this note, we give some new characterizations of S-Matlis rings in terms of S-strongly flat modules, S-weakly cotorsion modules and S-h-divisible modules.

Performance characteristics on up-scaling vacuum membrane distillation modules

Large-scale CFD studies are currently lacking in membrane distillation due to high computational overhead. This study utilizes a validated CFD model for vacuum membrane distillation and reduces the order of the model to enable prototype scale simulations. Different module designs were considered: a baseline flat sheet membrane module, a spacer-filled channel, a wavy channel, and a wavy channel with embedded stiffeners. Different lengths (330 mm, 660 mm, and 990 mm) were studied to simulate lab to prototype upscaling. Large Eddy Simulations were run in the laminar (Re 900) and turbulent (Re 3600) flow regimes. For Re 900, cases with geometric alterations (wavy membrane, spacer-filled channel) locally outperformed the baseline case within the first 330 mm before axial temperature polarization equilibrated the performance between the baseline and altered channels. The improvement in local performance was seen over the whole 990 mm length at Re 3600, culminating in a 35–40 % flux improvement versus the baseline at Re 3600 versus a 0–35 % difference at Re 900. Axial temperature polarization was mitigated using heat injection, showing a 5 % flux drop as length tripled compared to a 20–27 % decline. Higher operational Reynolds numbers should be considered cautiously for increasing pressure drop and violating the liquid entry pressure limit for wetting.

Lithium solvent extraction by a novel multiframe flat membrane contactor module

Comparing to conventional liquid–liquid extraction, membrane extraction is an efficient and environmentally friendly separation technique to recover lithium from the salt-lake brine. Development of suitable hydrophilic solvent resistant nanoporous membranes for membrane extraction has been based on bench-scale small module. Because module design has significant impact on the performance, this work reported a novel multiframe flat membrane contactor module (MFMC) for lithium extraction from synthetic brine. The hydrophilic poly (ethylene-co-vinyl alcohol)/sulfonated poly(etheretherketone) membrane supported with polypropylene nonwoven (EVAL/SPEEK-NW) was prepared for module evaluation. The membrane mass transfer coefficients km of 1.1 × 10-6 m/s was obtained by Wilson plot. The global mass transfer coefficient Ke increased from 4.5 × 10-7 m/s to 9.9 × 10-7 m/s following the flow velocity from 0.4 to 1.8 cm/s in membrane extraction. We further evaluated the characteristics of MFMC via height of transfer units (HTU) and module efficiency (ME). High module efficiency of 90% was obtained, demonstrating MFMC’s efficient flow distribution. HTU of 28 m was estimated and was expected to decrease to 3 m by optimizing thickness of gasket and spacer as well as membrane performance. The MFMC module effectively reduced the loss of tributyl phosphate (TBP) by 91% comparing to liquid–liquid extraction. The research presented herein provides a flat membrane module design for potential future application of membrane extraction in wide applications.

Influence of pH on the performance of anaerobic piggery wastewater treatment coupled with membrane-based NH3 extraction

The influence of the pH of piggery wastewater (PWW) on both ammonia recovery and anaerobic digestion performance during PWW treatment was evaluated in a continuous stirred tank reactor coupled with a membrane-based extraction module. The anaerobic digester was operated at a hydraulic retention time of 20 days at 37 °C, while the flat sheet PTFE membrane module operated continuously at liquid recirculation rates of 250 mL min−1. The membrane module was able to gradually decrease the total ammoniacal concentration from 1.27 ± 0.01 to 0.62 ± 0.01 g L−1 after 360 days of operation. Membrane-based NH3 extraction induced a CH4 yield increase of 1.3-fold. Moreover, COD and VS removal efficiencies increased up to 1.2-fold and 1.5-fold, respectively, along with the increase in PWW pH from 7.5 to 12. Total VFAs removal efficiencies were higher at a PWW pH of 9.

All-top-contact 0.59 eV InGaAs thermophotovoltaic cells and modules

InGaAs cells are ideal converters for low temperature thermophotovoltaic power generation systems. Commonly, the positive and negative electrodes of InGaAs cells are deposited on the top and bottom of the cells, respectively. In the engineering of level modules, solder strips are used to connect the top and bottom of adjacent cells, the distance between the cells is considerable in order to prevent short circuits from the side wall of the cells, and the area ratio of cells to modules is relatively low. In this paper, we design and fabricate a novel all-top-contact InGaAs cell, with the positive electrode deposited on top of the p-InGaAs epitaxial layer, and the negative electrode deposited on top of the n-InPAs-grade epitaxial layer by precise etching of the p–n junction layers. The novel all-top-contact cells show good efficiencies compared to traditional cells with top-and-bottom electrodes under the same testing conditions. Novel flat and compact cell modules were fabricated using all-top-contact InGaAs cells, the distance between the adjacent cells was controlled within tens of microns, and the area ratio of cells to modules was improved efficiently.

The finitely presented torsion-free SG-projective modules are not necessarily projective

It is proved in [Strongly Gorenstein projective, injective and flat modules, J. Algebra 320 (2008) 2659–2674, Theorem 2.8] that a finitely presented torsion-free module is SG-projective if and only if it is projective. Let L⊆F be an extension of fields with [F:L]=2. Set R=L+XF[X], m=XF[X] and D=R[Y]. Via the study of w-invertibility over infra-Krull domains, we prove that the w-conductor m[Y] of D is SG-projective but not projective, and all maximal w-ideals other than m[Y] are w-invertible. It follows that a finitely presented torsion-free SG-projective module do not need to be projective.

Design of a multi‐function global navigation satellite system and 5G cellular antenna structure for automotive applications using characteristic mode analysis

AbstractThis paper illustrates a single antenna structure that simultaneously satisfies the antenna requirement for 5G cellular and global navigation satellite systems (GNSS). The antenna has a linearly polarised omnidirectional radiation for the newly defined 5G sub‐6 GHz cellular bands in the 617–5000 MHz frequency range. In contrast, a right‐hand circular polarisation (RHCP) with a hemispherical radiation pattern at the GNSS L1 has a frequency range of 1559–1606 MHz. This multi‐function antenna would provide a simplified product design and better space utilisation, particularly suitable for flat antenna modules and automotive. The primary concept involves employing a planar inverted F antenna structure to generate radiation modes for cellular bands and incorporate U‐slot on the top plate to generate the GNSS radiation modes. The design methodology utilises the characteristic mode analysis tool to tune the desired radiation characteristic mode at the intended frequency range for each function. The antenna was fabricated, and the performance was evaluated on a 1‐m ground plane. The GNSS RHCP gain measures 5 dBc at boresight, with an axial ratio below 2 dB across the L1 bands, while the cellular gain maintains an excellent return loss and omnidirectional radiation pattern performance across the cellular bands.

Effects of fluid flow on the rate limiting for CO2 capture by an AEEA containing membrane

The efficiency of CO2 capture using a hollow fiber membrane containing 2-(2-Aminoethylamino) ethanol (AEEA) from the emission gas in the Integrated Gasification Combined Cycle (IGCC) was investigated by density functional theory and fluid dynamics. A reaction path for CO2 sorption to AEEA involving two H2O molecules with three – proton transfer was found to give the low barrier of the reaction due to 6 intermolecular hydrogen bonds which make the transition state structure more stable. The activation energy in the reaction path for CO2 sorption to AEEA was 7.11 kcalmol−1 which is approximately 10 kcalmol−1 lower than that involving one H2O molecule with two – proton transfer discussed in our previous study (Higashino et al., 2023). Since the activation energy is much lower than those in the other reaction paths we have investigated, it can occur much more frequently than others when sufficient moisture is maintained in the membrane. The estimated reaction rate k = 3.407 × 108 s−1 indicates that CO2 becomes carbamate by reaction with AEEA as soon as reaching the surface of the membrane, and thus, CO2 attachment to AEEA cannot be the rate limiting. Since flow in the hollow fiber membrane can be laminar, simulated CO2 permeance for the temperature of 358 K and the pressure of 2.4 MPa has a range from 10−10 to 10−9 m3 (STP) m−2s−1Pa−1, which is a few orders smaller than that for the flat sheet membrane, flow over which is turbulent, i.e.10−8 to 10−7 m3(STP) m−2s−1Pa−1 (Higashino et al., 2023). Overall, the reaction rate of CO2 attachment to AEEA is sufficiently large, and hence, any one of mass transfer of CO2 induced by turbulence (turbulent flow), molecular diffusion of CO2 from feed gas to the membrane surface (laminar flow), and molecular diffusion of bicarbonate (HCO3-) from the feed side to the permeate side in the membrane can be the rate limiting depending on which type of membrane, e.g. a flat sheet membrane module, a spiral membrane module, a hollow fiber membrane contactor, etc., is used for CO2 capture.

Finiteness criteria for Gorenstein flat dimension and stability

Projectively coresolved Gorenstein flat modules were introduced recently by Saroch and Stovicek and were shown to be Gorenstein projective. While the relation between Gorenstein projective and Gorenstein flat modules is not well understood, the class of projectively coresolved Gorenstein flat modules is contained in the class of Gorenstein flat modules. This paper proves necessary and sufficient conditions for a module of finite Gorenstein flat dimension to be projectively coresolved Gorenstein flat, or of finite flat dimension. Stability results for the class of projectively coresolved Gorenstein flat modules are also established.

Absolutely pure covers of sheaves

Let [Formula: see text] be a scheme and [Formula: see text] be the category of all sheaves of [Formula: see text]-modules. Enochs’ conjecture states that any covering class in [Formula: see text] is closed under directed colimits. In this work, if Abs[Formula: see text] is the class of all absolutely pure objects in [Formula: see text], then we prove the validity of the conjecture for Abs[Formula: see text]. This gives a characterization of locally coherent schemes. In addition, we study some homological properties of absolutely pure sheaves of [Formula: see text]-modules and answer a question raised in [P. Rothmaler, When are pure injective envelopes of flat modules flat? Comm. Algebra 30(6) (2002) 3077–3085].

Fp-Projective periodicity

The phenomenon of periodicity, discovered by Benson and Goodearl, is linked to the behavior of the objects of cocycles in acyclic complexes. It is known that any flat Proj-periodic module is projective, any fp-injective Inj-periodic module is injective, and any Cot-periodic module is cotorsion. It is also known that any pure PProj-periodic module is pure-projective and any pure PInj-periodic module is pure-injective. Generalizing a result of Šaroch and Št'ovíček, we show that every FpProj-periodic module is weakly fp-projective. The proof is quite elementary, using only a strong form of the pure-projective periodicity and the Hill lemma. More generally, we prove that, in a locally finitely presentable Grothendieck category, every FpProj-periodic object is weakly fp-projective. In a locally coherent category, all weakly fp-projective objects are fp-projective. We also present counterexamples showing that a non-pure PProj-periodic module over a regular finitely generated commutative algebra (or a hereditary finite-dimensional associative algebra) over a field need not be pure-projective.

Collimated solar simulator for curved PV modules characterization

The vehicle integrated photovoltaic (VIPV) technology, which consists in integrating PV solar panels in the surfaces of electric vehicles, is a promising technology to increase car autonomy. Free-form curved PV surfaces are demanded to meet the specific design constraints of the automotive. The proper characterization of three dimensional PV surfaces requires specific methods and equipment that must be developed. This paper describes the design principles and requirements of a solar simulator for characterization of curved PV modules. Its effectiveness is demonstrated by means of ray-tracing simulations, the results show the advantages provided by the use of a collimated light source in comparison to the conventional solar simulators used for flat modules. The light beam divergence of a non-collimated light source produces a non-uniformity boost between 2% and 20% depending on the module size and curvature. The module performance will be affected by this non-uniform irradiance, but the performance loss will also depend on specific characteristics of the module such as curvature, number and size of cells, series/parallel electrical connection and number of by-pass diodes. On the contrary, the proposed collimated solar simulator reproduces the solar illumination profile over the curved surface. The Helios 3198, a solar simulator with collimated light developed for concentrator modules, has been adapted accordingly to the design proposed. A module of 1 m of curvature has been tested, the short-circuit current of the cells follows the ideal cosine response of the curvature, differences are lower than 0.5% which proves the quality of the collimated beam.

A dumbbell-shaped 3D flat plate pulsating heat pipe module augmented by capillarity gradient for high-power server CPU onsite cooling

With the development of the data center industry and the increasing power density of servers, it is crucial to remove waste heat from small-area heat sources to ensure the safe and efficient operation of data processing chips. To complement existing studies, in this paper, a novel three-dimensional flat plate aluminum pulsating heat pipe (3D-FPPHP) with four different channel structures for radial heat dissipation of high-power server chips was proposed. The results showed that under the favorable influence of the additional capillarity force provided by the variable diameter channels, the FPPHP filled with acetone can start up easily and has good robustness during variable power operation. When the input power was 150 W, the junction temperature of the heating source could be reduced by 42.49 °C (48.67%) compared to an identical aluminum plate. In addition, a heat sink module based on the proposed 3D-FPPHP with optimal charging ratio was tested in a 1U server chassis. The results showed that it can manage an input power of 300 W (corresponding to a heat flux of 41.15 W/cm2) and achieve a total thermal resistance of 0.2053 °C/W under the premise of ensuring a safe junction temperature of chips below 85 °C.

Flat relative Mittag-Leffler modules and approximations

The classes [Formula: see text] of flat relative Mittag-Leffler modules are sandwiched between the class [Formula: see text] of all flat (absolute) Mittag-Leffler modules, and the class [Formula: see text] of all flat modules. Building on the works of Angeleri Hügel, Herbera, and Šaroch, we give a characterization of flat relative Mittag-Leffler modules in terms of their local structure, and show that Enochs’ Conjecture holds for all the classes [Formula: see text]. In the final section, we apply these results to the particular setting of [Formula: see text]-projective modules.

Multimodal laparoscopic coincidence gamma imaging system for near-infrared fluorescence guided surgery: a preclinical study.

Minimally invasive surgery has advantages in terms of quality of life and patient outcomes. Recently, near-infrared (NIR) fluorescence guided surgery has widely used for preclinical and clinical trials. However, NIR fluorescence has a maximum penetration capability of 10mm. Radiographic imaging can be a solution to overcome the depth issue of NIR fluorescence. For this reason, the performance of the multimodal imaging system, which integrates annihilation gamma (511keV) rays, NIR fluorescence, and color images, was evaluated. The multimodal imaging system consisted of a laparoscopic module, containing an internal detector for annihilation gamma events and cameras for optical imaging, and a flat module for coincidence detection with the internal detector. The acquired images were integrated by an algorithm with post image processing and registration. To evaluate the performance of the proposed multimodal imaging system, the images of a resolution target, a square bar target filled with a fluorescence dye, and a sodium-22 point source were analyzed. A preclinical test for axillary sentinel lymph node (SLN) biopsy with a rat model was conducted. The spatial resolution of color images was equivalent to 4 lp/mm. The modulation transfer function of NIR fluorescence at 1 lp/mm was 0.83. The 511keV gamma sensitivity and spatial resolution of the point source were 0.54cps/kBq and 2.1mm, respectively. The image of 511keV gamma rays showed almost the same intensity regardless of the thickness of the tissue phantom. In the preclinical test, an integrated image of the SLN sample of the rat model was obtained with the proposed multimodal imaging system. With the proposed laparoscopic system, a merged image of the sample was obtained with the rat model. The annihilation gamma rays showed penetration capability with the tissue-mimicking phantom superior to that of NIR fluorescence.

Gorenstein (ℒ,𝒜)-flat dimension of complexes and relative singularity categories

Assume that the class of all Gorenstein [Formula: see text]-flat modules is closed under extensions. We define a notion of Gorenstein [Formula: see text]-flat dimension for complexes and consider equivalent characterizations of the finiteness of Gorenstein [Formula: see text]-flat dimension of complexes. Furthermore, in addition, assume that [Formula: see text] is a right coherent ring. We construct the relative singularity category with respect to Gorenstein [Formula: see text]-flat modules, as the triangulated quotient of the triangulated subcategory of [Formula: see text] consisting of all complexes with both finite Gorenstein [Formula: see text]-flat dimension and cotorsion dimension by the bounded homotopy category of flat-cotorsion modules, and show that the relative singularity category is triangulated equivalent to the stable category of the Frobenius category consisting of all Gorenstein [Formula: see text]-flat and cotorsion modules.

Development of an electric furnace for heat treatment of vermiculite with curved surfaces of firing modules

A new modification of electric modular firing furnaces for heat treatment of vermiculite with curved surfaces of firing modules is considered. The basic designs of such furnaces consist of three or two flat modules installed at an angle to each other for pouring material from one module to another and firing in a thermal field created by electric heaters. With the same length of the refractory base of curved modules, the heat treatment time increases by 23 %, and the exit velocity of the swelling vermiculite grains decreases to 0,6‒0,65 m/s, which is enough so that all particles, regardless of size, do not settle at the exit of the modules and do not form congestion. Increasing the duration of firing does not reduce the productivity of the furnace, but reduces the specific energy intensity of this process. The energy consumption and energy intensity of vermiculite firing have been reduced by 13 %, but the module design is not optimal. Optimization of the size and shape of modules to increase the energy efficiency of the furnace unit is the task of subsequent research.

Incipient Biofouling Detection via Fiber Optical Sensing and Image Analysis in Reverse Osmosis Processes.

Reverse osmosis (RO) is a widely used membrane technology for producing process water or tap water that is receiving increased attention due to water scarcity caused by climate change. A significant challenge in any membrane filtration is the presence of deposits on the membrane surfaces, which negatively affect filtration performance. Biofouling, the formation of biological deposits, poses a significant challenge in RO processes. Early detection and removal of biofouling are essential for effective sanitation and prevention of biological growth in RO-spiral wound modules. This study introduces two methods for the early detection of biofouling, capable of identifying initial stages of biological growth and biofouling in the spacer-filled feed channel. One method utilizes polymer optical fibre sensors that can be easily integrated into standard spiral wound modules. Additionally, image analysis was used to monitor and analyze biofouling in laboratory experiments, providing a complementary approach. To validate the effectiveness of the developed sensing approaches, accelerated biofouling experiments were conducted using a membrane flat module, and the results were compared with common online and offline detection methods. The reported approaches enable the detection of biofouling before known online parameters become indicative, effectively providing an online detection with sensitivities otherwise only achieved through offline characterization methods.