Successive Closure Research Articles

Sliding connectors for cyclic construction of steel-UHPC composite truss arch bridges: design method and feasibility study

To break through the three major technical bottlenecks of traditional long-span arch bridges, which are excessive self-weight, high cost and difficult construction, a new steel-ultra high performance concrete (UHPC) composite truss arch bridge scheme and a matching cyclic construction method were proposed. The main arch can be divided into several times for closure from the inside out. Special transverse connection devices need to be installed between the arch ribs constructed with successive closures by step. The devices can not only ensure the stability of the arch ribs constructed subsequently, but also do not cause serious stress superposition on the already closed arch ribs. Therefore, sliding connectors for the cyclic construction of new arch bridges and the corresponding simplified modeling method were proposed in this paper. Subsequently, the working mechanism was analyzed, and the design method was proposed. Finally, the feasibility of sliding connectors and the correctness of the corresponding design method were verified by the experiment. The results indicate that it is necessary to install a transverse sleeve structure in the sliding connector, which plays a key role in transverse adjustment. The design of key dimensions in sliding connectors is controlled by the maximum vertical and longitudinal displacements of the inner arch. The outer arch could slide freely under the premise of ensuring stability, and the mechanical superposition response of the inner arch was relatively small. For the inner arch, the vertical displacement at the crown only increased by 10.94 %, and the maximum compressive stress in the UHPC arch ribs only increased by 16.3 %. The sliding connector also has the potential for further optimization to achieve smaller stress superposition.

Dual Closure: a New Tool for Recognizing Thresholds Between Levels of Organization in Big History

Big Historians study the development of the universe and how it passed through different phases. A fascinating trend is the historical increase in the complexity of a part of all systems. To analyse this trend, rankings have been proposed with different scientific and pedagogical aims. For example, they rank epochs, regimes, levels of organisation or dynamic domains. As a result of this variation, the number of levels differs between approaches, while the systems ranked at these levels are the result of unequal processes and belong to different overall types. Such diversity invites a re-examination of the fundamentals involved in these ranking processes. Moreover, if rankings are to be predictive, they must be consistent in their logic. To this end, it would be useful to have a sequence of levels that share a common logic. As such a common logic, and building on existing systems science and hierarchy theory, a new theory called O-theory proposes the use of a process called ‘dual closure’. Each successive dual closure represents a threshold between the old and new types of objects and their respective levels of organisation. In this way a causal logic is obtained, ranking systems from fundamental particles to organisms with brains, all of which are addressed by the generic name of operator. The hierarchy of the operators provides a basic framework that can be used to re-examine existing transdisciplinary classifications and learn more about why they differ in the number of levels they have. It is discussed how big historians might more easily achieve their broad goals if they added the operator hierarchy to their theoretical toolbox.

Glacier, permafrost and thermokarst interactions in Alpine terrain: Insights from seven decades of reconstructed dynamics of the Chauvet glacial and periglacial system (Southern French Alps)

AbstractThis study analyses the long‐term dynamics in the Chauvet glacial and periglacial system (southern French Alps) over seven decades (1948–2020), where several lake outburst floods have been documented since 1930. To accurately describe and explain the complex dynamics of this site, our multidisciplinary approach combines (1) photogrammetry of historical aerial photographs and modern high‐resolution satellite and UAV images, (2) geophysical surveys and (3) geomorphological mapping. We provide evidence for spatial and functional interactions between glacial and periglacial features, especially in the lower sector where different landforms with variable ice‐ and debris‐content and specific dynamics are interplayed. We found the highest thinning rates on ice‐rich terrain located in the central part of the valley bottom, which, together with bedrock morphology, most probably determine the location of the thermokarst. We also documented an overall acceleration of the creeping of the landforms after the 2000s, with a flow direction largely oriented towards the thermokarst depression. The outburst water flowed through a conduit whose successive opening and closure seem to mainly depend on the rate of lateral convergence of left‐ and right‐hand landforms and on the rate of ice melting (and roof collapse) along the conduit walls. Today, the site of Chauvet still represents a potential hazard for the region due to the large water storage capacity (up to 180 000 ± 450 m3) and the development of a predominantly bucket shape in the thermokarst sector.

Late Paleozoic–Cenozoic Tectonothermal Evolution of Transbaikalia: Thermochronology of the Angara–Vitim Granitoid Batholith

Abstract —The tectonothermal evolution of Transbaikalia is reconstructed using U/Pb, 40Ar/39Ar, and apatite fission track thermo-chronology of samples from the Late Paleozoic Angara–Vitim granitoid batholith (AVB). Successive closure of the zircon and amphibole isotope systems provides evidence that the AVB rocks cooled down rapidly soon after crystallization and 7–4 km of rocks were denuded subsequently during an extensive late Paleozoic orogeny in southern Siberia. The isotopic system of feldspar closed in the Middle Jurassic–Early Cretaceous (170–140 Ma) after a period of tectonic stability and slow closure of the biotite isotopic system in the early Permian–Middle Jurassic (295–170 Ma). The 170–140 Ma span was the time when the Mongol–Okhotsk orogen began its evolution, and the orogeny caused denudation of ~3 km of rocks. Denudation was slow in the Paleogene–Miocene (60–5 Ma) but accelerated over the past 5 million years (a ~3–2 km thick layer) during rapid cooling of rocks and activity under a far-field effect of the India–Eurasia collision.

Robust and Optimal Control Designed for Autonomous Surface Vessel Prototypes

It is well known that activities in running water or wind and waves expose the Autonomous Surface Vessels (ASVs) to considerable challenges. Under these conditions, it is essential to develop a robust control system that can meet the requirements and ensure the safe and accurate execution of missions. In this context, this paper presents a new topology for controller design based on a combination of the Successive Loop Closure (SLC) method and optimal control. This topology enables the design of robust autopilots based on the Proportional-Integral-Derivative (PID) controller. The controllers are tuned from the solution of the optimal control problem, which aims to minimize the effects of model uncertainties. To verify the effectiveness of the proposed controller, a numerical case study of a natural ASV with 3 Degree of Freedom (DoF) is investigated. The results show that the methodology enabled the tuning of a PID controller capable of dealing with different parametric uncertainties, demonstrating robustness and applicability for different prototype scenarios.

Epidermal growth factor-loaded microspheres/hydrogel composite for instant hemostasis and liver regeneration

Rapid hemostasis and effective healing for the non-compressible liver wounds which are not able to be sewn, especially for those large-area wounds, remain great clinical challenges. In this study, we fabricated epidermal growth factor (EGF)-loaded chitosan microspheres (CM) and then incorporated them into a photo-crosslinking gelatin methacryloyl (GelMA) hydrogel. The results showed that the EGF-loaded CM/GelMA precursor solution could transform into a hydrogel and cease bleeding at laceration sites without external stress. Subsequently, the sustained release of EGF accelerated wound closure and promoted liver regeneration. The in vitro experiments demonstrated that the microsphere/hydrogel composite could promote the proliferation and migration of L02 ​cells. Moreover, the histological and immunohistological analyses indicated that EGF-CM/GelMA composite could alleviate inflammation in the mouse liver and promote liver remodeling. Overall, this multi-functional microsphere/hydrogel composite will inspire the development of clinical applications for noncompressible hemostasis and successive wound closure.

Recognizing the Role of Tropical Seaways in Modulating the Pacific Circulation

AbstractVarious modeling studies have examined the climatic effects of either the Central American Seaway or the Indonesian seaway. The co‐existence of these two tropical seaways may have a greater influence than the existence of a single seaway. Although the dual seaway situation is closer to that reconstructed during Miocene/Pliocene, relevant studies remain scarce. Here, we investigate the co‐effects of dual tropical seaway changes on the Pacific circulation through a set of sensitivity experiments. Our results show that the combined shallow opening of tropical seaways can generate an active Pacific meridional overturning circulation and maintain strong upwelling conditions along the equatorial Pacific, which may have helped favor a “biogenic bloom” during the late Miocene and early Pliocene. Moreover, the logically successive closure of the tropical seaways can provide patterns of zonal sea surface temperature gradients that are similar to those recorded in the equatorial Pacific from the late Miocene to the Pliocene.

From the southern Gangdese Yeba arc to the Bangong-Nujiang Ocean: Provenance of the Upper Jurassic-Lower Cretaceous Lagongtang Formation (northern Lhasa, Tibet)

The stratigraphic records of sedimentary basins situated on the Lhasa block provide crucial evidence to reconstruct the early history of the Tibetan Plateau associated with the successive closure of oceanic branches and related magmatic activities. The Upper Jurassic to Lower Cretaceous Lagongtang Formation of the Nagqu Basin located in the northern part of the Lhasa block chiefly consists of fine-grained quartzose to litho-quartzose sandstones, siltstones and shales deposited in continental shelf to bathyal environments. Provenance data, including sandstone petrography, U-Pb ages and in situ Hf isotopes of detrital zircon, together with paleocurrent indicators, suggest that the Lagongtang Formation was mainly fed by recycling of quartz-rich siliciclastic strata of the central-southern Lhasa block. Fresh felsitic volcanic rock fragments, plagioclase prevailing among detrital feldspars, and zircon grains yielding the same age as that indicated by biostratigraphic analysis testify to penecontemporaneous magmatic activity. Volcanic detritus may have been derived from the Middle Triassic-Lower Cretaceous Yeba and/or Sangri volcanics exposed in the southern Lhasa block to the south as well as from Middle Triassic-Lower Cretaceous magmatic rocks of the central Lhasa block. Although the Nagqu Basin is adjacent to the Bangong–Nujiang suture, no debris from Bangong–Nujiang suture and Qiangtang was found in the Lagongtang Formation here. Our provenance data rule out the hypothesis that the Lagongtang Formation could have been deposited in a forearc basin associated with the southward subduction of the Bangong-Nujiang Ocean or in a basin related to the supposed Shiquanhe-Namco Ocean.

Direct observation of cyclic poly(N-substituted maleimide)s with broad size distributions synthesized by anionic polymerization using an N-heterocyclic carbene and successive ring closure without high dilutions

The N-heterocyclic carbene 1,3-di-tert-butylimidazol-2-ylidene (NHCtBu) and its 1:1 adduct with methyl sorbate (MS) were found to initiate anionic polymerization of N-substituted maleimides (RMIs) in organic solvents at −20 °C to afford linear and cyclic poly(RMI)s, respectively. Quantitative monomer consumption was observed when a bulky aluminum Lewis acid, such as methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide) (MAD), was used as an additive. In the presence of the NHCtBu:MS adduct as an initiator, monomer consumption was followed by ring closure without the need for highly diluted conditions to give cyclic poly(RMI)s containing α-terminal MS units, which exhibited an Mn of 3.4 × 103–6.2 × 103 and a broad polydispersity index (Mw/Mn = 2.43–2.65). Dilution was not required due to the presence of an α-terminal NHCtBu group, which acted as a counter cation for the propagating center during polymerization. The broad molecular weight distributions of the obtained polymers were ascribed to a chain transfer upon abstraction of the α-carbonyl proton of the RMIs, particularly to the neighboring NHCtBu cation unit. 1H NMR and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass analyses indicated that the proton transfer of the acidic proton was induced by the propagating anion. The topologies of the linear and cyclic poly(RMI)s were directly observed by transmission electron microscopy (TEM). Direct Observation of Cyclic Poly(N-substituted maleimide)s with Broad Size Distributions Synthesized by Anionic Polymerization using an N-Heterocyclic Carbene and Successive Ring Closure Without High Dilutions.

Pitch-synchronous single frequency filtering spectrogram for speech emotion recognition

Convolutional neural networks (CNN) are widely used for speech emotion recognition (SER). In such cases, the short time fourier transform (STFT) spectrogram is the most popular choice for representing speech, which is fed as input to the CNN. However, the uncertainty principles of the short-time Fourier transform prevent it from capturing time and frequency resolutions simultaneously. On the other hand, the recently proposed single frequency filtering (SFF) spectrogram promises to be a better alternative because it captures both time and frequency resolutions simultaneously. In this work, we explore the SFF spectrogram as an alternative representation of speech for SER. We have modified the SFF spectrogram by taking the average of the amplitudes of all the samples between two successive glottal closure instants (GCI) locations. The duration between two successive GCI locations gives the pitch, motivating us to name the modified SFF spectrogram as pitch-synchronous SFF spectrogram. The GCI locations were detected using zero frequency filtering approach. The proposed pitch-synchronous SFF spectrogram produced accuracy values of 63.95% (unweighted) and 70.4% (weighted) on the IEMOCAP dataset. These correspond to an improvement of + 7.35% (unweighted) and + 4.3% (weighted) over state-of-the-art result on the STFT sepctrogram using CNN. Specially, the proposed method recognized 22.7% of the happy emotion samples correctly, whereas this number was 0% for state-of-the-art results. These results also promise a much wider use of the proposed pitch-synchronous SFF spectrogram for other speech-based applications.

Metropolitan rail network robustness

In large-scale urban agglomerations, heavy rail in the form of metro and commuter train serves as the backbone of the metropolitan public transport network. The objective of this paper is to investigate whether networks with strikingly different structure and development pattern exhibit different robustness properties in the event of random and targeted attacks. We adopt a complex network theory approach, investigating network performances under alternative sequential disruption scenarios corresponding to the successive closure of either stations or track segments. We also investigate the case where the removal of a network node or link implies the closure of all traversing lines Network performance is measured both in terms of the capacity of the network to function in terms of connectivity as well as the additional impedance induced for those that remain connected. An aggregate robustness indicator based on the integral of the deterioration of network performance is adopted. Three exemplary networks are selected, the urban rail networks of London, Shanghai and Randstad. These three networks offer showcases of short and long development patterns, mono- and polycentric agglomeration structures, including the largest and the oldest metropolitan heavy rail networks. The polycentric network of the Randstad was found the least robust in this analysis when compared to the more monocentric networks of London and Shanghai. The London network is in general more robust than the Shanghai network thanks to the presence of cycles beyond the core. Our findings provide more nuanced evidence on the relation between network structure and development pattern, and its robustness.

TRBR: Flight body posture compensation for transverse ricochetal brachiation robot

Transverse ricochetal brachiation is a sophisticated locomotion style that mimics athletes swinging their bodies with their hands on a ledge in order to propel themselves for a leap to a target ledge. This paper describes the development of a transverse ricochetal brachiation robot (TRBR) and outlines motion control strategies for active flight body posture compensation. The crucial design parameters were obtained by formulating an optimization problem with the goal of maximizing flight distance. Shoulder joints with switchable stiffness were used to enable resonance excitation via the swinging of a robot tail during the swing phase, while enabling tight arm-and-body engagement during the flight phase. Novel electric grippers were designed to provide the required holding forces as well as quick-release functionality to ensure that the kinetic energy accumulated during the swing phase could be transferred smoothly to the flight phase. The reference trajectory of the robot tail was obtained using an optimization procedure based on a dynamic model of the swing phase. We also adopted a dynamic model for the flight phase to elucidate the effects of midair body rotation with the aim of developing body posture compensation methods. Simulation and experimental results demonstrate the efficacy of the proposed body posture compensation method based on a successive loop closure design in improving flight body posture during transverse ricochetal brachiation. The integration of arm swing motion with tail compensation also proved highly effective in enhancing hang time and travel distance.

An immediate response to the Indian-Eurasian collision along the northeastern Tibetan Plateau: Evidence from apatite fission track analysis in the Kuantan Shan-Hei Shan

The Tibetan Plateau offers an ideal region for understanding the processes of continental collision and related intracontinental deformation. However, when the Cenozoic deformation was initiated in the present northeastern margin of the plateau, >2000 km north to the Indian-Eurasian collision front, remains an issue in debate. Two competing end-member models have been proposed, involving immediate deformation response and progressive deformation propagation. Solving this problem partly relies on determining whether there was contemporaneous deformation with initial Indian-Eurasian collision along the northeastern margin of the Tibetan Plateau. In this study, we employ apatite fission track (AFT) analysis to shed new light on the exhumation history of the Kuantan Shan-Hei Shan along the northeastern margin of the Tibetan Plateau, with a motivation to determine whether deformation-related exhumation during initial collision stage occurred in the region. The 22 granite samples produce AFT ages ranging from 22.3 ± 2.6 Ma to 175 ± 18 Ma and mean track lengths from 11.17 ± 2.26 μm to 13.63 ± 1.93 μm. Thermal history modeling indicates five episodes of rapid exhumation-related cooling, which took place in the early Jurassic, early Cretaceous and late Cretaceous, during/since the Eocene and since the middle Miocene. The exhumation events prior to the Cenozoic are attributed to far-field responses of successive closure of fossil oceans and assembly of blocks along the southern margin of the Eurasian continent. The Eocene exhumation along the Kuantan Shan-Hei Shan is speculated to represent an immediate response to the initial Indian-Eurasian collision. These results lend support to the immediate deformation response model along the northeastern plateau. The episodic exhumation observed in this study, combined with previous geophysical findings, implies that the Kuantan Shan-Hei Shan represents the southern margin of the Alashan Block, serving as a significant and long-lived lithospheric weak zone susceptible to intracontinental deformation during episodes of far-field tectonic event.

Deformed continental arc sequences in the South Tianshan: New constraints on the Early Paleozoic accretionary tectonics of the Central Asian Orogenic Belt

The tectonic affinity and structural evolution of the South Tianshan are key issues to understand the Paleozoic accretionary or collisional orogenesis in the southwestern Central Asian Orogenic Belt, but remain controversial. Geological and structural investigations on the Early Paleozoic low-grade metamorphic volcanic-sedimentary sequences around the Bayinbuluk basin demonstrate that they were prevalently reworked by north-vergent ductile deformation and overlain unconformably by Devonian to Carboniferous carbonates. Zircon U–Pb dating indicates that the volcanic rocks erupted during the Middle Ordovician to Early Devonian time (460–410 Ma), and contain Neoarchean to Neoproterozoic zircon xenocrysts (~2.75 Ga, ~2.46 Ga, ~1.60 Ga, 997–963 Ma and 827 Ma). Their whole-rock elemental, Sr–Nd isotopic (εNd(t) = −5.0 to +3.6) and zircon Lu–Hf isotopic (εHf(t) = −13.5 to +11.6) features resemble those of Andean-type continental arc volcanic rocks. The coexisting tuffaceous sedimentary rocks indicate a depositional environment amidst a continental volcanic arc at 421 to 404 Ma. The newly obtained and available geochronological, geochemical and structural data suggest that: (1) a wide active continental margin covering the South and Central Tianshan and northern Tarim was formed due to Early-Mid Paleozoic southward subduction of the Paleo-Tianshan Ocean beneath the Tarim Craton; and (2) a Mid-Paleozoic transition from advancing to retreating accretionary orogeny was followed by opening of the South Tianshan back-arc basins and break-up of the northern Tarim continental margin. The South Tianshan was subsequently subjected to regional deformation during the successive diachronous closure of the major and back-arc oceanic basins, and locally reworked by the ductile strike-slip faulting (307–255 Ma).

Decoding sea surface and paleoclimate conditions in the eastern Mediterranean over the Tortonian-Messinian Transition

New sedimentological, micropaleontological and geochemical data from the Upper Miocene pre-evaporitic sedimentary sequence of the Faneromeni section (Crete Island, eastern Mediterranean) revealed a stepwise restriction of the Mediterranean Sea preceding the Messinian Salinity Crisis (MSC), which was modulated by a sedimentary cyclicity responding to orbital parameters. This cyclicity is manifested by lithological alternations from laminated to indurated homogeneous marls and clayey limestones, and covers the Tortonian-Messinian Transition (TMT; 7.6–6.7 Ma). This time window covers the successive closure of the marine Mediterranean-Atlantic gateways, which culminated in the onset of the MSC. In the present study, we present the first evidence for changes in the upper water column reflected by sea surface temperature (SST) and salinity (SSS) variations that correlate with pronounced paleoclimatic fluctuations. Planktonic foraminiferal isotopes, in combination with paired mixed layer Sr/Ca-derived SST data, reveal that the very warm late Tortonian interval has been followed by a strong long-term cooling (~10 °C) and desalination (~10‰) trend during the earliest Messinian, attributed to the paroxysmal phase of the so-called “siphon” event. In particular, the climate shift that occurred at the end of a global carbon isotope (δ13C) decrease suggests that changes in the carbon cycle were instrumental in driving late Miocene climate dynamics (cooling and aridity) in the progressively isolated eastern Mediterranean Sea. The observed salinity variability during this time interval also provides further insights about seasonal freshwater inputs and gives new support to the much-debated hydrologic regime (linear salinity increase vs step-function evolution with strong salinity fluctuations) preceding the deposition of evaporites. The novel methodology of foraminiferal Sr/Ca paleothermometry and results of this study could have numerous potential applications to other regions and relevant extreme geological events. Therefore, in the near future we expect this approach to add important new information to our understanding of Neogene climates.

Repeated Intrinsic Self-Healing of Wider Cracks in Polymer via Dynamic Reversible Covalent Bonding Molecularly Combined with a Two-Way Shape Memory Effect

To enable repeated intrinsic self-healing of wider cracks in polymers, a proof-of-concept approach is verified in the present work. It operates through two-way shape memory effect (SME)-aided intrinsic self-healing. Accordingly, a reversible C-ON bond is introduced into the main chain of crosslinked polyurethane (PU) containing an elastomeric dispersed phase (styrene-butadiene-styrene block copolymer, SBS). The PU/SBS blend was developed by the authors recently, and proved to possess an external stress-free two-way SME after programming. As a result, the thermal retractility offered by the SME coupled with the reversible C-ON bonds can be used for successive crack closure and remending based on synchronous fission/radical recombination of C-ON bonds. Moreover, multiwalled carbon nanotubes are incorporated to impart electrical conductivity to the insulating polymer. Repeated autonomic healing of wider cracks is thus achieved through narrowing of cracks followed by chemical rebonding under self-regulating Joule heating. No additional programming is needed after each healing event, which is superior to one-way SME-assisted self-healing. The outcomes set an example of integrating different stimuli-responsivities into single materials.

Derived topologies on ordinals and stationary reflection

We study the transfinite sequence of topologies on the ordinal numbers that is obtained through successive closure under Cantor’s derivative operator on sets of ordinals, starting from the usual interval topology. We characterize the non-isolated points in the $\xi$th topology as those ordinals that satisfy a strong iterated form of stationary reflection, which we call $\xi$-simultaneous-reflection. We prove some properties of the ideals of non-$\xi$-simultaneous-stationary sets and identify their tight connection with indescribable cardinals. We then introduce a new natural notion of $\Pi ^1_\xi$-indescribability, for any ordinal $\xi$, which extends to the transfinite the usual notion of $\Pi ^1_n$-indescribability, and prove that in the constructible universe $L$, a regular cardinal is $(\xi +1)$-simultaneously-reflecting if and only if it is $\Pi ^1_\xi$-indescribable, a result that generalizes to all ordinals $\xi$ previous results of Jensen [Ann. Math. Logic 4 (1972), pp. 229–308] in the case $\xi =2$, and Bagaria–Magidor–Sakai [Israel J. Math. 208 (2015), pp. 1–11] in the case $\xi =n$. This yields a complete characterization in $L$ of the non-discreteness of the $\xi$-topologies, both in terms of iterated stationary reflection and in terms of indescribability.

Effects of porosity and inertia on the apparent permeability tensor in fibrous media

The flow in three-dimensional fibrous porous media is studied in the inertial regime by first simulating for the motion in unit, periodic cells, and then solving successive closure problems leading – after applying an intrinsic averaging procedure – to the components of the apparent permeability tensor. The parameters varied include the orientation of the driving pressure gradient, its magnitude (which permits to define a microscopic Reynolds number), and the porosity of the medium. All cases tested refer to situations for which the microscopic flow is steady. When the driving force is oriented in a direction which lies on the plane perpendicular to the fibers’ axis, the results found agree with those available the literature. The fact that the medium is composed by bundles of parallel fibers favours a deviation of the mean flow towards the fibers’ axis when the driving pressure gradient has even a small component along it, and this is enhanced by a decreasing porosity; this phenomenon is well quantified by the knowledge of the components of the permeability. Contrary to our initial expectations, for the over one hundred cases which we have simulated, the apparent permeability tensor remains, to a very good approximation, diagonal, a fact mainly related to the transversely isotropic nature of the medium. To obtain a complete, albeit approximate, database of the diagonal components of the apparent permeability tensor we have developed a metamodel, based on kriging interpolation, and carefully calibrated it. The resulting response surfaces can be invaluable in determining the force caused by the presence of inclusions in macroscopic simulations of the flow through bundles of fibers whose orientations and dimensions can vary in space and/or time.

Strong population structure deduced from genetics, otolith chemistry and parasite abundances explains vulnerability to localized fishery collapse in a large Sciaenid fish, Protonibeadiacanthus.

As pressure on coastal marine resources is increasing globally, the need to quantitatively assess vulnerable fish stocks is crucial in order to avoid the ecological consequences of stock depletions. Species of Sciaenidae (croakers, drums) are important components of tropical and temperate fisheries and are especially vulnerable to exploitation. The black‐spotted croaker, Protonibea diacanthus, is the only large sciaenid in coastal waters of northern Australia where it is targeted by commercial, recreational and indigenous fishers due to its food value and predictable aggregating behaviour. Localized declines in the abundance of this species have been observed, highlighting the urgent requirement by managers for information on fine‐ and broad‐scale population connectivity. This study examined the population structure of P. diacanthus across north‐western Australia using three complementary methods: genetic variation in microsatellite markers, otolith elemental composition and parasite assemblage composition. The genetic analyses demonstrated that there were at least five genetically distinct populations across the study region, with gene flow most likely restricted by inshore biogeographic barriers such as the Dampier Peninsula. The otolith chemistry and parasite analyses also revealed strong spatial variation among locations within broad‐scale regions, suggesting fine‐scale location fidelity within the lifetimes of individual fish. The complementarity of the three techniques elucidated patterns of connectivity over a range of spatial and temporal scales. We conclude that fisheries stock assessments and management are required at fine scales (100 s of km) to account for the restricted exchange among populations (stocks) and to prevent localized extirpations of this species. Realistic management arrangements may involve the successive closure and opening of fishing areas to reduce fishing pressure.

Optimal tuning of cascaded control architectures for nonlinear HVAC systems

Cascaded controllers have been shown in recent literature to significantly reduce hunting behavior and improve the performance of a variety of HVAC systems. The cascaded architecture uses multiple proportional-integral-derivative loops, standard in industry and building automation controls, to minimize the effects of load dependent nonlinearities. This article builds on previous work by defining and demonstrating the properties of two nonlinear gap metrics that quantify the closed-loop linearization of the cascaded control structure and enable proper tuning of the inner-loop proportional gain. This is followed by the development of a linear quadratic framework that enables simultaneous tuning of inner- and outer-loop control gains. The proposed gap metrics and tuning procedures are demonstrated with two case studies. A simple single input, two output example plant is used to demonstrate the benefits of the proposed tuning method compared to standard proportional-integral-derivative control and successive loop closure tuning techniques. The tuning approach is also applied to the control of a two-ton, residential heat pump system. The proposed metrics and tuning techniques showed significant improvement in control over standard proportional-integral-derivative control tuning methods in both simulation and experiment.