Duplex Configuration Research Articles

Calculations of the principal neutronic characteristics of a hypothetical VVER assembly with minor actinides incorporated into PuO2-ThO2 fuel in a duplex configuration

Calculations of the principal neutronic characteristics of a hypothetical VVER assembly with minor actinides incorporated into PuO2-ThO2 fuel in a duplex configuration

Numerical study on a Franchot double-acting heat-driven thermoacoustic-Stirling cryocooler for natural gas liquefaction

Compact heat-driven cryocoolers can harness the thermal energy produced by burning a small quantity of natural gas to accomplish liquefaction. This addresses the requirements of distributed natural gas stations in remote locations. This paper introduces a Franchot double-acting heat-driven thermoacoustic-Stirling cryocooler designed for natural gas liquefaction. It conducts a comparative analysis of the mechanical and electrical systems, focusing on the acoustic field, available energy loss, and performance. Simulation results indicate that the optimized mechanical configuration system achieves peak performance with a piston area ratio of 0.84 and a piston phase angle of 90°. It yields a cooling power of 1964 W@130 K when driven by an 873 K heat source, resulting in an overall system efficiency of 28.3%. This marks a notable enhancement compared to current thermoacoustic systems. While the electrical configuration provides superior stability, the performance is constrained by significant losses in acoustic-electric conversion of linear alternators and compressors. To further enhance efficiency, it is worthwhile to establish direct power transfer between the pistons, for example, by aligning the expansion piston and compression piston coaxially. The evolved duplex configuration eliminates the loss from electrical energy conversion, leading to a remarkable 64.7% increase in overall efficiency. Simultaneously, this evolutionary approach offers a new perspective to elucidate the inherent connections among Stirling heat engines of Franchot double-acting and duplex. It provides valuable theoretical insights for the subsequent analysis and design of Stirling heat-driven refrigerators or cryocoolers.

Programming the Assembly of Oligo-Adenine with Coralyne into a pH-Responsive DNA Hydrogel.

External stimuli-responsive DNA hydrogels present interesting platforms for drug loading and triggered release. Typically, drug molecules are encapsulated within three-dimensionally hybridized DNA networks. However, the utilization of drug molecules as cofactors to facilitate the directed assembly of DNA strands into hydrogel frameworks and their subsequent controlled release remains to be explored. Herein, we introduce the guided assembly of oligo-adenine (A-strand) into an acidic pH-responsive DNA hydrogel using an anticancer drug, coralyne (COR), as a low-molecular-weight cofactor. At pH 7, COR orchestrates the assembly of A-strand into an antiparallel duplex configuration cross-linked by A-COR-A units at a stoichiometric ratio of one COR cofactor per four adenine bases, resulting in a DNA hydrogel characterized by A-COR-A duplex bridges. At pH 4-5, the instability of A-COR-A units results in the disintegration of the duplex into its constituent components, leading to the release of COR and simultaneous dissociation of the DNA hydrogel matrix. This study introduces a method by which drug molecules, exemplified here by COR, facilitate the direct formation of a supramolecular cofactor-DNA complex, subsequently leading to the creation of a stimuli-responsive DNA hydrogel. This approach may inspire future investigations into DNA hydrogels tailored for controlled drug encapsulation and release applications.

Neutronic investigation of prospective dual-cooled micro-heterogeneous duplex fuel for small modular long-life reactors: Assembly level design and analysis

Nuclear fuel is a critical component of any nuclear reactor, influencing both its safety and economic viability. Continuous fuel quality improvements resulted in a significant reduction in failure rate, and assembly design changes contributed to a significant increase in power density and performance during irradiation. In terms of fuel development, a new fuel type called “dual-cooled annular fuel” has recently been proposed to be used in nuclear reactors. The dual-cooled annular fuel design benefits from heat transfer to the coolant at both the outer and inner channels. Another emerging trend in nuclear fuel development is the use of thorium-based fuel in the form of duplex fuel design. As a result, the current work is an attempt to incorporate potential dual-cooled annular duplex fuels into the assembly of an innovative Small Modular Reactor (SMR). This paper, therefore, compares the neutronic properties of annular duplex fuel to those of annular UO2 fuel. Considering the dual-cooled feature, this study presents both duplex configurations (i.e. ThO2– UO2 and UO2–ThO2). The neutronic properties include fissile loading determination, multiplication factors, discharge burnup, and isotopic concentration. This analysis also determined the reactivity coefficients, power peaking factors, energy-dependent neutron flux, and an analysis of possible burnable absorbers and configurations. The results of this study show that both annular duplex fuels can achieve 6% higher discharge burnup than annular UO2 fuel, despite nearly identical reactivity values at the beginning of the cycle. The production of plutonium and other minor actinides has been greatly reduced. Annular duplex fuels have lower power peaking factors, which are beneficial for reactor operation, and the UO2–ThO2 configuration performs better. The calculated reactivity feedback coefficients show negative patterns and are within the annular UO2 fuel's range. The proposed annular duplex fuel designs have additional intriguing neutronic properties that open up possibilities for future research.

Acid-Resistant and Physiological pH-Responsive DNA Hydrogel Composed of A-Motif and i-Motif toward Oral Insulin Delivery.

An acid-resistant DNA hydrogel that is stable in an extremely acidic environment with pH as low as 1.2 has not been reported before, largely due to the instability of DNA-hybridized structures. To achieve this, adenine (A)-rich and cytosine (C)-rich oligonucleotides are rationally designed and integrated to form copolymers with acrylamide monomers via free-radical polymerization. In an acidic environment (pH 1.2-6.0), the generated copolymers form a hydrogel state, which is cross-linked by parallel A-motif duplex configurations (pH 1.2-3.0) and quadruplex i-motif structures (pH 4.0-6.0) due to the protonation of A and C bases, respectively. Specifically, the protonated A-rich sequences under pH 1.2-3.0 form a stable parallel A-motif duplex cross-linking unit through reverse Hoogsteen interaction and electrostatic attraction. Hemi-protonated C bases under mildly acidic pH (4.0-6.0) form quadruplex i-motif cross-linking configuration via Hoogsteen interaction. Under physiological pH, both A and C bases deprotonated, resulting in the separation of A-motif and i-motif to A-rich and C-rich single strands, respectively, and thereby the dissociation of the DNA hydrogel into the solution state. The acid-resistant and physiological pH-responsive DNA hydrogel was further developed for oral drug delivery to the hostile acidic environment in the stomach (pH 1.2), duodenum (pH 5.0), and small intestine (pH 7.2), where the drug would be released and absorbed. As a proof of concept, insulin was encapsulated in the DNA hydrogel and orally administered to diabetic rats. In vitro and in vivo studies demonstrated the potential usage of the DNA hydrogel for oral drug delivery.

Comparison of noise generated from simplex and duplex configurations of drum brake using non-linear vibro-acoustic models

The drum brakes used on the rear wheels of automobiles have various configurations. These contribute to the differences in kinematic (geometry) and dynamic (contact, friction) aspects, eventually leading to significantly different vibration and acoustic response. This work attempts to estimate the difference in the vibro-acoustic noise generated by the drum brake's simplex and duplex variants using a combination of non-linear analytical vibration models and a numerical acoustic model. Four degrees-of-freedom lumped parameter models developed for the simplex and the duplex configurations with conformal contact predict the contact and reaction forces during braking. These forces act as the sources for the finite element based acoustic models developed for the two configurations to obtain the sound pressure to force transfer functions. The sound pressure levels are estimated by the product of the predicted forces with the respective transfer functions in the frequency domain. The sound pressure levels of the simplex and duplex drum brakes are quantitatively compared under different braking conditions, and the results are presented. It is expected that this vibro-acoustic analysis will help in designing quieter drum brakes.

Surface and subsurface architecture of the Kasseb structures: implications for petroleum exploration beneath the Tellian allochthon, the easternmost portion of the Maghrebides

In this study, we present field investigations based on structural analyses and interpretations in the onshore part of the Tunisian Tell, at the front of the Numidian Flysch units. Field observations allow the deciphering of the main structural styles and tectonic events in the Tell domain of Northern Tunisia, especially at the type locality of the Kasseb units. New field data collected in the Kasseb area, a key area to understand the structures of the Tunisian Tell, outline a major north-dipping normal fault located between the Numidian Flysch and the underlying imbricated fan of the Kasseb basinal units. Detailed observations allow the viewing of the Numidian allochthon as a passively transported domain at the top of the underlying duplexes, which implies an overall duplex configuration within the Tellian thrust wedge in the Kasseb area. The Kasseb basinal units represent the southernmost extent of pelagic carbonate series issued from a paleo-basinal domain situated farther north. These pelagic carbonate units have been progressively tectonically accreted within a dominantly submarine environment since the Oligocene, before reaching their current position just after the Langhian. Currently, shallow marine Oligocene-Langhian siliciclastic series rest unconformably on top of these Late Cretaceous-Eocene pelagic carbonate units. The post-Langhian compression events induced a progressive inversion of the underthrust foreland platform domain, as well as the re-folding of the overlying thin-skinned structures of the Tell domain as observed today. The Kasseb units show duplications with duplex configurations with a sole thrust located in the Paleocene shales and synsedimentary thrust tectonics active presumably during the Eocene, as the Oligocene to Early Miocene Numidian Flysch rests unconformably on top of the underlying thrust structures. The tectonic style is therefore a combination of thin-skinned and thick-skinned deformations: the thin-skinned structures correspond to the nappe structures and Tellian units thrust contacts. By contrast, the thick-skinned deformational structures correspond to the rejuvenation of deeper structures accounting for the inversion of underlying foreland structures with deep-seated thrust faults, pop-up and pop-down folded structures. For the oil/gas exploration, we propose a tectono-stratigraphic and oil occurrence conceptual model for the Tell, outlining the structural control on the hydrocarbon occurrences in different potential structural traps associated with (1) ramps and duplexes anticlines within the thin-skinned allochthonous structures as well as (2) inversional thick-skinned structures such as pop-up anticlines in the subsurface of the Tellian allochthon. We discuss potential traps associated with the nappes anticlines which should be viewed as important petroleum structural prospects emphasizing their future exploration and drilling.

Performance of Network-Assisted Full-Duplex for Cell-Free Massive MIMO

Network assisted full-duplex (NAFD) is a spatial-division duplex technique for future wireless networks with cell-free massive multiple-input multiple-output (CF massive MIMO) network, where a large number of remote antenna units (RAUs), either using half-duplex or full-duplex, jointly support truly flexible duplex including time-division duplex, frequency-division duplex and full duplex on demand of uplink and downlink traffic by using network MIMO methods. With NAFD, bi-directional data rates of the wireless network could be increased and end-to-end delay could be reduced. In this paper, the spectral efficiency of NAFD communications in CF massive MIMO network with imperfect channel state information (CSI) is investigated under spatial correlated channels. Based on large dimensional random matrix theory, the deterministic equivalents for the uplink sum-rate with minimum-mean-square-error (MMSE) receiver as well as the downlink sum-rate with zero-forcing (ZF) and regularized zero-forcing (RZF) beamforming are derived. Numerical results show that under various environmental settings, the deterministic equivalents are accurate in both a large-scale system and system with a finite number of antennas. It is also shown that with the downlink-to-uplink interference cancellation, the uplink spectral efficiency of CF massive MIMO with NAFD could be improved. The spectral efficiencies of NAFD with different duplex configurations such as in-band full-duplex, and half-duplex are compared. With the same total numbers of transmit and receive antennas, NAFD with half-duplex RAUs offers a higher spectral efficiency. To alleviate the uplink-to-downlink interference, a novel genetic algorithm based user scheduling strategy (GAS) is proposed. Simulation results show that the achievable downlink sum-rate by using the GAS is greatly improved compared to that by using the random user scheduling.

Tunable Frequency-Division Duplex RF Front End Using Electrical Balance and Active Cancellation

This paper presents a novel, tunable, frequency-division duplexing radio frequency (RF) front end that combines passive and active self-interference (SI) cancellation. An electrical-balance duplexer is used to passively cancel transmitter noise in the receive band, and an active canceller is employed to suppress SI in the transmit (Tx)-band. Subsystem specifications are developed, and a system-level analysis of noise and SI powers in this novel architecture is provided, thereby illustrating its operation. A proof-of-concept demonstrator, built from a software-defined radio and discrete RF components, has been characterized across a range of duplex configurations in the 700–950-MHz range and also at 1900 (Long-Term Evolution (LTE) band 3) and 2600 MHz (LTE band 7). The prototype achieves an impressive 6.0–7.4-dB noise figure in the presence of a +27-dBm LTE uplink Tx blocker for duplex separations of 47.5 MHz and above. The duplexer has also been tested against reference sensitivity test cases defined in the 3GPP LTE specification, demonstrating specification compliant sensitivity in LTE bands 28 (700 MHz), 3, and 7.

Assessment of the Diagnostic Ability of the DIVA Real-Time PCR in a Duplex Configuration to Differentiate Between the Turkey Meningoencephalitis Vaccine and Wild-Type Viruses

Assessment of the Diagnostic Ability of the DIVA Real-Time PCR in a Duplex Configuration to Differentiate Between the Turkey Meningoencephalitis Vaccine and Wild-Type Viruses

TDD-Based Rapid Fault Detection and Recovery for Fronthaul Bridged Network

Fronthaul bridged network has been a hot research topic in recent years. A challenge for existing path-control protocols for bridged networks is that the route computation is executed after the advertisement of the link fault based on the updated link state information. To address this issue, this letter proposes a novel fault detection and recovery scheme for fronthaul bridged networks. With the proposed scheme, bridges estimate the fault location utilizing the time-division duplex configuration of fronthaul streams and immediately switch the forwarding paths for the affected flows to backup paths. Consequently, the end-to-end communication of fronthaul streams is rapidly recovered compared with the existing protocols.

Performance Characterization of a Real-Time Massive MIMO System With LOS Mobile Channels

The first measured results for massive MIMO performance in a line-of-sight (LOS) scenario with moderate mobility are presented, with 8 users served in real-time using a 100-antenna base Station (BS) at 3.7 GHz. When such a large number of channels dynamically change, the inherent propagation and processing delay has a critical relationship with the rate of change, as the use of outdated channel information can result in severe detection and precoding inaccuracies. For the downlink (DL) in particular, a time division duplex (TDD) configuration synonymous with massive multiple-input, multiple-output (MIMO) deployments could mean only the uplink (UL) is usable in extreme cases. Therefore, it is of great interest to investigate the impact of mobility on massive MIMO performance and consider ways to combat the potential limitations. In a mobile scenario with moving cars and pedestrians, the massive MIMO channel is sampled across many points in space to build a picture of the overall user orthogonality, and the impact of both azimuth and elevation array configurations are considered. Temporal analysis is also conducted for vehicles moving up to 29km/h and real-time bit error rates (BERs) for both the UL and DL without power control are presented. For a 100-antenna system, it is found that the channel state information (CSI) update rate requirement may increase by 7 times when compared to an 8-antenna system, whilst the power control update rate could be decreased by at least 5 times relative to a single antenna system.

Integrated full duplex radios

Full duplex wireless has drawn significant interest in the recent past due to the potential for doubling network capacity in the physical layer and offering numerous other benefits at higher layers. However, the implementation of integrated full duplex radios is fraught with several fundamental challenges. Achieving the levels of self-interference cancellation required over the wide bandwidths mandated by emerging wireless standards is challenging in an integrated circuit implementation. The dynamic range limitations of integrated electronics restrict the transmitter power levels and receiver noise floor levels that can be supported in integrated full duplex radios. Advances in compact antenna interfaces for full duplex are also required. Finally, networks employing full duplex nodes will require a complete rethinking of the medium access control layer as well as cross-layer interaction and co-design. This article describes recent research results that address these challenges. Several generations of full duplex transceiver ICs are described that feature novel RF self-interference cancellation circuits, antenna cancellation techniques, and a non-magnetic CMOS circulator. Resource allocation algorithms and rate gain/improvement characterizations are also discussed for full duplex configurations involving IC-based nodes.

Multiphase Numerical Study of Ice Accretion on Circular Cylinders in Duplex Configuration

Numerical study of atmospheric ice accretion on circular cylinders in duplex configuration has been carried out at different operating and geometric conditions. Analyses showed a difference in ice accretion on both cylinders, as streamline accumulated ice shapes were observed along front cylinder and irregular ice shapes were found along rear cylinder. Results also showed a change in accreted ice load and ice shape along rear cylinder with the change in distance between both cylinders. Parametric study at different droplet sizes and temperatures showed a variation in ice accretion. This prelimenary research work provides a useful base for better understanding and further investigation of atmospheric ice accretion on circular overhead conductors in duplex configuration, installed in cold climate of high north regions.

Downlink Packet Scheduling in LTE Cellular Networks: Key Design Issues and a Survey

Future generation cellular networks are expected to provide ubiquitous broadband access to a continuously growing number of mobile users. In this context, LTE systems represent an important milestone towards the so called 4G cellular networks. A key feature of LTE is the adoption of advanced Radio Resource Management procedures in order to increase the system performance up to the Shannon limit. Packet scheduling mechanisms, in particular, play a fundamental role, because they are responsible for choosing, with fine time and frequency resolutions, how to distribute radio resources among different stations, taking into account channel condition and QoS requirements. This goal should be accomplished by providing, at the same time, an optimal trade-off between spectral efficiency and fairness. In this context, this paper provides an overview on the key issues that arise in the design of a resource allocation algorithm for LTE networks. It is intended for a wide range of readers as it covers the topic from basics to advanced aspects. The downlink channel under frequency division duplex configuration is considered as object of our study, but most of the considerations are valid for other configurations as well. Moreover, a survey on the most recent techniques is reported, including a classification of the different approaches presented in literature. Performance comparisons of the most well-known schemes, with particular focus on QoS provisioning capabilities, are also provided for complementing the described concepts. Thus, this survey would be useful for readers interested in learning the basic concepts before going into the details of a particular scheduling strategy, as well as for researchers aiming at deepening more specific aspects.

Reliability Evaluation for Distributed PONs With Ring and Tree Topologies

This study describes resilient access network structures in time-division multiplexing passive optical networks (TDM-PONs) and wave-division multiplexing (WDM)/ TDM-PONs, and compares their network unavailability versus outage scale. In addition, this study discusses the unavailability for media networks with simple ladder and more realistic ring-to-tree topologies for cases with simplex and full/partial duplex configurations between drop points and central offices. In large-scale networks, the unavailability in duplex networks is drastically improved by 4-5 orders of magnitude compared with that in simplex networks for large outage scales. Cable failure significantly affects the unavailability, especially in feeder sections, whereas failures due to optical fiber or optical add-drop multiplexers are mostly masked by cable failure in WDM/TDM-PONs. Consequently, there is little difference in the unavailability of the two PON schemes, except for the difference due to PON splitters. A comparison of the unavailability for fully and partially duplicated networks shows that the latter with a ring-to-tree topology has the advantage of lower unavailability in large-scale regions. These results imply that a realistic duplication scheme successfully enhances the network reliability regardless of imperfect duplex structure.

A Human 3′ miR-499 Mutation Alters Cardiac mRNA Targeting and Function

MyomiRs miR-499, miR-208a and miR-208b direct cardiac myosin gene expression. Sequence complementarity between miRs and their mRNA targets determines miR effects, but the functional consequences of human myomiR sequence variants are unknown. To identify and investigate mutations in human myomiRs in order to better understand how and to what extent naturally-occurring sequence variation can impact miR-mRNA targeting and end-organ function. Screening of ≈2,600 individual DNAs for myomiR sequence variants identified a rare mutation of miR-499, u17c in the 3' end, well outside the seed region thought to determine target recognition. In vitro luciferase reporter analysis showed that the 3' miR-499 mutation altered suppression of a subset of artificial and natural mRNA targets. Cardiac-specific transgenic expression was used to compare consequences of wild-type and mutant miR-499. Both wild-type and mutant miR-499 induced heart failure in mice, but miR-499 c17 misdirected recruitment of a subset of miR-499 target mRNAs to cardiomyocyte RNA-induced silencing complexes, altering steady-state cardiac mRNA and protein make-up and favorably impacting cardiac function. In vitro analysis of miR-499 target site mutations and modeling of binding energies revealed abnormal miR-mRNA duplex configurations induced by the c17 mutation. A naturally occurring miR-499 mutation outside the critical seed sequence modifies mRNA targeting and end-organ function. This first description of in vivo effects from a natural human miR mutation outside the seed sequence supports comprehensive studies of individual phenotypes or disease-modification conferred by miR mutations.

Vector Network Analysis Using a One-Path, Frequency-Multiplied Photonic Link

A simplified, practical vector network analyzer (VNA) that uses mature radio-over-fiber technology has been designed and demonstrated. The measurement concept allows the full S-parameters of a microwave device (or antenna) to be obtained while minimizing the detrimental effects of electrical cables, which are replaced with a photonic link. A variety of high-frequency light modulation schemes with frequency sweeping capabilities are presented to realize a one-path (single, forward), frequency-multiplied optical link for VNA applications. Using the photonic one-path link, full two-port S-parameters have been extracted based on five-term error modeling, which has half the error terms compared with the standard duplex configuration. The S-parameters of a microwave filter and antenna measured using frequency-multiplied optical links are found to be in good agreement with those obtained using a conventional VNA.

Vertical Ionization Potentials of Nucleobases in a Fully Solvated DNA Environment

Vertical ionization potentials (IPs) of nucleobases embedded in a fully solvated DNA fragment (12-mer B-DNA fragment + 22 sodium counterions + 5760 water molecules equilibrated to 298 K) have been calculated using a combined quantum mechanical molecular mechanics (QM/MM) approach. Calculations of the vertical IP of the anion Cl(-) are reported that support the accuracy of the application of a QM/MM method to this problem. It is shown that the pi nucleotide HOMO origin for the emitted electron is localized on the base by the hydration structure surrounding the DNA in a way similar to that recently observed for pyrimidine nucleotides in aqueous solutions (Slavicek, P.; et al. J. Am. Chem. Soc. 2009, 131, 6460). In a first step, a high level of theory, CCSD(T)/aug-cc-pVDZ, was used to calculate the vertical IP of each of the four single bases isolated in the QM region while the remaining DNA fragment, counterions, and water solvent molecules were included in the MM region. The calculated vertical IPs show a large positive shift of 3.2-3.3 eV compared to the corresponding gas-phase values. This shift is similar for all four DNA bases. The origin of the large increase in vertical IPs of nucleobases is found to be the long-range electrostatic interactions with the solvation structure outside the DNA helix. Thermal fluctuations in the fluid can result in IP changes of roughly 1 eV on a picosecond time scale. IPs of pi-stacked and H-bonded clusters of DNA bases were also calculated using the same QM/MM model but with a lower level of theory, B3LYP/6-31G(d=0.2). An IP shift of 4.02 eV relative to the gas phase is found for a four-base-pair B-DNA duplex configuration. The primary goal of this work was to estimate the influence of long-range solvation interactions on the ionization properties of DNA bases rather than provide highly precise IP evaluations. The QM/MM model presented in this work provides an attractive method to treat the difficult problem of incorporating a detailed long-range structural model of physiological conditions into investigations of the electronic processes in DNA.

Hydrolysis of DNA and its molecular components in the dry state

The biochemistry of dry state DNA is of interest to the field of forensic biology. The precise chemical nature of the hydrolytic degradation products of the DNA molecule in the dry state has not been previously investigated in detail. In this study we found that the mechanistic chemistry of DNA hydrolysis appears to be the same for the hydrated and dry states. The thermodynamic parameters are also similar in both states and the activation energies for base hydrolysis are indistinguishable. The principal difference between the two states is the rate at which hydrolytic degradation occurs. The duplex configuration of dry state DNA offers much more protection for the molecule than is offered in single strand and nucleotide species. Single strand breaks of dry state duplex DNA occur with a half life of 24 ± 2 days at 65 °C and appear to occur in a mechanistic manner.