Constant High Rate Research Articles

Incorporating slow NMDA-type receptors with nonlinear voltage-dependent magnesium block in a next generation neural mass model: derivation and dynamics

We derive a next generation neural mass model of a population of quadratic-integrate-and-fire neurons, with slow adaptation, and conductance-based AMPAR, GABAR and nonlinear NMDAR synapses. We show that the Lorentzian ansatz assumption can be satisfied by introducing a piece-wise polynomial approximation of the nonlinear voltage-dependent magnesium block of NMDAR current. We study the dynamics of the resulting system for two example cases of excitatory cortical neurons and inhibitory striatal neurons. Bifurcation diagrams are presented comparing the different dynamical regimes as compared to the case of linear NMDAR currents, along with sample comparison simulation time series demonstrating different possible oscillatory solutions. The omission of the nonlinearity of NMDAR currents results in a shift in the range (and possible disappearance) of the constant high firing rate regime, along with a modulation in the amplitude and frequency power spectrum of oscillations. Moreover, nonlinear NMDAR action is seen to be state-dependent and can have opposite effects depending on the type of neurons involved and the level of input firing rate received. The presented model can serve as a computationally efficient building block in whole brain network models for investigating the differential modulation of different types of synapses under neuromodulatory influence or receptor specific malfunction.

Cause Analysis of Salinity Intrusion by Environmental Changes Considering Water Intake and Sand Mining on Seomjin River Estuary Using Model for Maintaining Corbicula Habitats

Anthropogenic development can strongly influence natural river processes, leading to environmental changes that negatively affect important habitats and biodiversity and consequently reduce economically important natural resources. This study investigated the effects of salinity intrusion on the habitat of the clam Corbicula japonica in the Seomjin River estuarine zone. We employed the Environmental Fluid Dynamics Code (EFDC) model, which incorporates topographic data and hydrological changes, to simulate salinity. Two salinity measurement facilities were installed in Seomjin River estuarine and operated to optimize the EFDC model. The results show that reduced flow rates due to intake have a negligible impact on the increased salinity. Maintaining optimal salinity (15–20 psu) during neap tides at the Seomjin River Bridge requires constant high flow rates, which poses significant challenges. Saltwater stratification is identified as the primary cause of pronounced salinity stratification, particularly during neap tides. Addressing this issue through river discharge and intake facility operation is challenging. Structural measures, including riverbed restoration and underwater barriers, are recommended to improve resistance to seawater intrusion. Future research should aim to develop scenarios to reduce salinity, quantify the reduction efficiency, and propose region-specific measures.

Investigating the high-impact deformation behavior of induced-nano precipitation hardened in718 alloy

Superalloys are the preferred materials for modern high-rotational complex components due to their exceptional ability to maintain critical properties such as strength, oxidation/corrosion resistance, even under extreme temperatures and dynamic impacts. This study investigates the dynamic impact response of nanoprecipitation-hardened 718 alloy (NPH-718 alloy) under various loading conditions. The wrought nickel-based NPH-718 alloy was transformed into a nanostructured state through a precise heat treatment process involving controlled cooling rates (28℃∙s‒1 to 30℃∙s‒1). A mechanical compression test, leading to failure, was employed to assess the alloy's ability to withstand dynamic impacts. The compressive dynamic behavior of the alloy at high strain rates (4000 s‒1 to 7500 s‒1) and temperatures ranging from ‒180℃ to 750℃ was evaluated using a custom-built direct impact Hopkinson pressure bar apparatus. The flow data obtained for NPH-718 alloy exhibited sensitivity to thermally activated processes. Consequently, as the temperature increased at a constant high loading rate, both flow stress and adiabatic effect increased. Conversely, at a constant deformation temperature, the flow characteristics exhibited an increase as the loading rate decreased. This study establishes key trends in the flow stress, adiabatic effect, temperature, and the strain rate sensitivities of NPH-718 alloy, offering valuable insights for design and performance evaluation purposes. It underscores the significant influence of temperature and strain rate on the flow behavior of NPH-718 alloy, further solidifying its reliability in demanding applications.

Node Scheduling Scheme for Wireless Sensor Networks with Partial Coverage

Sensor nodes in a wireless sensor network are distributed across an area for data collection. These nodes have basic capabilities in terms of interfaces and components, and they often operate in dynamic, hostile environments. Sensor networks present numerous challenges: they are dispersed, generate constant high rates data streams, function in dynamic and time-changing situations; and may involve a large number of sensors. Sensor nodes have enough power to transmit their readings to a central high-performance computing unit for processing. Sensor networks generate data streams, which are sequences of real-time data records characterized by their high data rates that consume significant network computing resources. However, only a few studies address the issue of collecting highly redundant data, leading to nodes wasting energy by sending redundant information to a central high-performance computing unit. Improved scheduling tactics can help reduce energy consumption in sensor nodes. This research developed a Node Scheduling Scheme for Wireless Sensor Networks with Partial Coverage (NSPC). Partial coverage can be obtained by dividing the area of interest into smaller sub-regions and determining the monitoring intensity for each sub-region by sensor nodes. Various strategies, such as clustering and scheduling, can be employed to accomplish partial coverage. Considering partial coverage when designing a WSN is crucial, as it can enhance network stability and reliability while reducing the cost and energy consumption of each sensor nodes.

N→π* Electron Transitions and Directional Charge Migration Synergistically Promoting O2 Activation and Holes Utilization on Carbon Nitride for Efficiently Photocatalytic Degradation of Organic Contaminants.

Stimulating electron transitions and promoting exciton dissociation are crucial for improving the photocatalytic performance of polymeric carbon nitride (CN) yet still challenging. Herein, a novel CN with C dopant and asymmetric structure (CC-UCN2 ) is ingeniously synthesized. The obtained CC-UCN2 not only reinforces the intrinsic π→π* electron transitions, but also successfully awakens additional n→π* electron transitions. Besides, charge centers dislocation caused by symmetry breaking induces a spontaneous polarized electric field, effectively breaking the constraints of Coulomb electrostatic interaction between electrons and holes and driving their directional migration. Along with the spatial separation of reduction and oxidation sites, CC-UCN2 shows exceptional O2 activation and holes oxidation efficiency, thus exhibits a high degradation rate constant (0.201min-1 ) and mineralization rate (80.1%) for bisphenol A (BPA)(far outperforming pristine and other modified CNs). This work proposes a novel perspective for developing high-efficiency photocatalysts and comprehending the underlying mechanism of O2 activation and holes oxidation for pollutant degradation.

76 Resuscitation Volumes Affect Perfusion and Inflammatory Cytokine Expression in Peri-Burn Skin: Implications for Burn Conversion

Abstract Introduction Fluid resuscitation after thermal injury is paramount to avoiding the effects of burn shock and restoring organ perfusion. Both over and under resuscitation can lead to unintended consequences affecting patient outcomes. While many studies have focused on the systemic effects of resuscitation, there is limited information on how fluid resuscitation might affect the burn wound, specifically burn wound progression, in the acute period. Furthermore, the mechanisms underlying burn wound progression are not fully understood. For these reasons, a polytrauma swine model was used to investigate varying levels of resuscitation on burn wound dynamics. Methods Nine female Yorkshire pigs were used in this experiment. Pigs were anesthetized and subjected to 40% total body surface area burn and 15% hemorrhage. Pigs were randomized (n=3) to receive different resuscitative strategies: decision support driven (adequate, 2-4ml/kg/%TBSA), fluid withholding (under, < 2ml/kg/%TBSA) or high constant rates (over, > >4ml/kg/%TBSA). Pigs were then monitored for 24hrs in an intensive care setting prior to necropsy. Laser Doppler Imaging (LDI) was conducted over the burn wound and peri-wound skin at pre-determined timepoints to assess perfusion. Skin biopsies were also taken from the burn, peri-burn (within 2cm of burn) and normal skin areas. RNA was isolated from normal skin and peri-burn skin biopsies at hour 6 and qRT-PCR was conducted to assess levels of common inflammatory cytokines: interlukein-6 (IL-6), chemokine CXC motif ligand-8 (CXCL8), and interferon-gamma (IFN-y). Results At hour 2, LDI analysis demonstrated increased perfusion in the peri-burn skin of over-resuscitated animals when compared to adequate and under-resuscitated groups (p=0.002 and p=0.007, respectively). At hour 6, peri-burn skin of over-resuscitated animals showed increased perfusion when compared to the adequate resuscitation groups (p=0.01). At hour 6, peri-burn skin samples showed increased expression of all 3 cytokines in adequately resuscitated animals when compared to over and under resuscitated groups (IL-6: 2.94 vs. 1.47 and -0.11-fold, CXCL8: 9.04 vs. 0.82 and -0.31-fold, IFN-g: 2.09 vs. -0.48 and -0.81-fold). Conclusions This animal model shows differences in both perfusion and inflammatory cytokine expression in peri-burn skin samples based on resuscitation strategy. Varying levels of resuscitation following burn can have wide ranging consequences that may affect burn wound progression. Applicability of Research to Practice Under or over-resuscitation may lead to local changes in the burn wound that could affect the overall severity and evolution of the injury over time. Judicious fluid resuscitation may not only be useful in dampening the possible systemic complications associated with fluid creep (eg. compartment syndrome), but may have direct effects on the local wound bed. By further elucidating mechanisms for burn conversion, interventions may be developed.

Nodal and least-cost analysis on the optimization of natural gas production system constraints to extend the plateau rate of a conceptual gas field

The supply of natural gas in any country is determined by energy demand. Furthermore, supply agreements specify that gas should be supplied at a constant rate for a specified period. However, due to the decline in reservoir pressure as gas fields continue to produce, high constant rate production is usually uncertain, and the plateau may not reach the agreed-upon period. Therefore, this study was conducted to optimize gas production system constraints and extend the production plateau rate of a conceptual dry gas field. The field was made up of the sand packages CF2 upper, CF2 lower, CF1 upper, and CF1 lower. A total of 1316.9 Bscf were assumed to be the estimated gas field reserves, and 423.3 Bcf were assumed to be the remaining economically recoverable gross 2 P sales of natural gas. The field also contained natural gas at the Miocene and five production wells, numbered PW-1, PW-2, PW-3, PW-4, and PW-5. The field's estimated average constant gas production rate as of July 2021 was 85 MMscfd. The field's gas demand was forecasted in three phases, with the third beginning on November 1, 2019, at a rate of 130 MMscfd. After applying Nodal Analysis with the help of Integrated Production Modelling (IPM) and Least Cost Analysis methods, the study found that the gas production plateau of that field started to decline on March 1, 2017, after 1 year and 5 months of production when constrained to 130 MMscfd. However, after modifying the constraints to match various assumed production histories, it was discovered that the plateau would start to decline on June 1, 2023, after 8 years of production. Therefore, eight possible combinations of varying the three production constraints were developed and simulated to examine their effect on extending the field production plateau. These constraints were separator pressure, tubing size, and the number of layers perforated. The best combination was to lower the separator pressure to 725 psia, increase the tubing size to 4 inches, and perforate three more zones (zones I, C, and D). This was the only combination that appeared to extend the production plateau for 8 years until October 1, 2031, as required in the 16 years gas sales agreement (GSA). This approach was economically compared to the options of using a compressor and drilling future wells, and it was found to be 34.05% cheaper than the compressor usage option and 98.25% cheaper than drilling a well. As a result, the operators of this conceptual gas field are advised to adopt this approach to extend the field's plateau.

Effectiveness of temperature and preparation method on stability kinetic of Curcumin nanodispersion: Cytotoxicity and in vitro release assessment

Curcumin is a natural and non-polar pigment with unique properties such as antioxidant activity that has been widely utilized in food and pharmaceutical formulations. In this study, solvent displacement and subcritical water methods were used to prepare Curcumin nanodispersions. The influences of the method and storage temperature were evaluated on physical and chemical stability of the prepared nanodispersions. Obtained results indicated that prepared transparent nanodispersions maintained their physical and chemical stability at 4 and 25 °C for 4 months. The results also showed that the prepared nanodispersions using subcritical water (temperature of 120 °C and pressure of 1.5 atm for 2 h) had a higher stability (minimum changes in the particle size) and less Curcumin loss (0.36%). Release of Curcumin from prepared nanodispersions was also evaluated at different pH values (1.2, 5.4, and 7.4) and the results indicated that its release rate was higher in pH values ranging 5 to 7. Kinetic study showed that release of Curcumin from dialysis bag was controlled by diffusion at pH value of 7.4 with a high constant rate. The viability percentage of HT-29 cells against pure Curcumin and Curcumin nanodispersions prepared using solvent displacement and subcritical water methods for 72 h incubation were 94, 30 and 18%, respectively. Moreover, In drug delivery systems, mathematical modeling and simulation play an important role in elucidating important drug release mechanisms; therefore, the results of experimental data of diffusion rate were compared with those obtained from simulation, and a good agreement was found.

A review of freshwater benthic clams (Corbicula fluminea): Accumulation capacity, underlying physiological mechanisms and environmental applications.

Asian clams (Corbicula fluminea) have been extensively applied in biomonitoring and other environmental fields based on their high enrichment capacity and rapid response to pollutants. This review first summarizes the kinetic process of metals and organic pollutants enriched by C. fluminea and discusses the environmental behavior and application. The accumulation ability of Cu, Zn, and Mn were significantly higher than that of other metals, which were attributed to their high uptake rate constant and low elimination rate constant. The visceral mass was found to be the major burden tissue. However, large knowledge gaps existed regarding the accumulation capacity of C. fluminea for organic pollutants and nanoparticles. Moreover, physiological mechanisms underlying the accumulation of environmental pollutants were proposed. C. fluminea can improve the niche of benthic algae by ingesting pelagic algae, mitigating water eutrophication. It can also remove pathogens and parasites based on the biological assimilation of nonspecific immunity, interrupting disease transmission. The novel insight into the application of C. fluminea in wastewater treatment further broadens the range of pest management strategies and offers the feasibility of blocking the spread of invasive bivalves.

Exploiting the Complementary Potential of Rice Bran Oil as a Low-Cost Raw Material for Bioenergy Production

Rice is one of the most consumed cereals in the world. From rice processing, rice bran is obtained, and only a part of this by-product is effectively used. Rice bran oil can be obtained and used as an alternative feedstock for biodiesel production, although few studies exist to support its exploitation. In addition, pretreatment is required to reduce its acidity and allow for its integration in the conventional industrial process. This work evaluated two pretreatment processes aiming to reduce the free fatty acids (FFAs) content of rice bran oil by employing an acid-catalyzed process and a biocatalyzed process. The results allowed us to assess the efficiency and effectiveness of both pretreatments. For that purpose, acid (45, 55 and 65 °C, using H2SO4 concentrations of 2 wt.% or 4 wt.% and a methanol:oil molar ratio of 9:1) and enzymatic FFAs conversion (35 °C using a 6:1 methanol:oil molar ratio and 5 wt.% of Thermomyces lanuginosus) were evaluated using rice bran oil with an acid value around 47 mg KOH.g−1, and the reaction kinetics were assessed. Acid esterification enabled a 92% acidity reduction (65 °C, 4 wt.% of catalyst) after 8 h, with the final product presenting an acid value of 3.7 mg KOH.g−1 and a biodiesel purity of 42 wt.%. The enzymatic process allowed an acidity reduction of 82%, resulting in a product with an acid value of 7.0 mg KOH.g−1; however, after 24 h, the biodiesel purity was 87 wt.% (almost a two-fold increase compared to that obtained in the homogeneous process), revealing the conversion of both free fatty acids and glycerides. The study of the reaction kinetics of the homogeneous (acid) esterification showed that, for temperatures > 45 °C, the constant rate increased with temperature. A higher constant rate was obtained for the temperature of 55 °C using 4 wt.% of catalyst (k′ = 0.13 min−1). For the heterogeneous (enzymatic) esterification, the constant rate obtained was lower (k′ = 0.028 min−1), as expected. The study revealed the technical viability of the esterification pretreatment of rice bran oil and the important parameters concerning the performance of the pretreatment solutions. Finally, the enzymatic process should be further explored, aiming to develop more ecofriendly processes (water and energy savings) to produce biodiesel from oils with a high acidity (low-cost raw materials).

A smart and precise mixing strategy for efficient and cost-effective microalgae production in open ponds

Microalgae biotechnology is a great candidate for carbon neutralization, wastewater treatment and the sustainable production of biofuels and food. Efficient and cost-effective microalgae production depends on highly coordinating the resources used for algal growth. However, dynamic natural disturbances such as culture temperature and sunlight can lead to the poor coordination and waste of resources. Open ponds are the most commonly used commercial microalgal production systems, and enhanced mixing can significantly increase their productivity, but mixing energy can be seriously wasted due to dynamic disturbances, presenting a hindrance to further reducing production costs. Herein, a smart and precise mixing strategy was developed for open ponds in which a paddle wheel's stirring speed for an open pond was smartly and precisely controlled in real time based on dynamic variations in light intensity and culture temperature. The proposed technology achieved the same biomass productivity of Spirulina platensis (8.37 g m−2 day−1) as a control with a constant high mixing rate under dynamic disturbances while reducing mixing energy inputs by approximately 30 % compared to the control. This study provides a promising method to address serious resource waste and poor coordination due to dynamic natural disturbances, holding great potential for efficient and cost-effective microalgae production.

Invasive squamous cell carcinoma arising from long‐lasting enterocutaneous fistula due to Crohn's disease

Chronic inflammation led to squamous cell carcinoma. We experienced squamous cell carcinoma from Crohn’s disease. A 53-year-old woman with Crohn's disease (CD) diagnosed more than 30 years earlier was referred to us because of a 4 month history of abdominal tumors. She underwent a total colectomy, small intestinal resection, and an eternal enterostomy 24 years earlier and had two enterocutaneous fistulous tracts with repeated inflammation on the lower-right side of her abdomen for 13 years. She had been treated with 5-aminosalicylic acid for more than 15 years, but did not receive immunosuppressants or tumor necrosis factor alpha inhibitors. Physical examination revealed a 6 × 3.5 cm reddish ulcerative tumor on the lower-right side of her abdomen surrounded by brownish pigmentation with indurations (Figure 1A). Histopathological examination of the tumor revealed atypical squamous cell proliferation with marked keratinization (Figure 1B,C). Histological continuity between the epidermis and atypical cells was not observed, and immunostaining of the cells was negative for human papillomavirus. Computed tomography and positron emission tomography/computed tomography demonstrated a large mass involving the abdominal walls and enlargement of the inguinal and right external iliac lymph nodes (Figure 1D). Her serum squamous cell carcinoma (SCC) antigen level was also elevated (5.4 ng/ml; normal range, <2.5 ng/ml). The patients were then diagnosed with SCC arising from an enterocutaneous fistula (ECF) related to CD. She was treated with radiation therapy (30 Gy) for a skin tumor and bilateral inguinal lymph nodes, followed by chemotherapy with pepleomycin. Unfortunately, her disease slowly progressed and she died 5 months after her initial visit. Crohn's disease is a chronic inflammatory bowel disorder characterized by transmural inflammation and fistula formation.1 Perianal fistulas are common complications of the disease, and patients with anal and/or perianal CD have a high risk of perianal fistula-related cancer.2 Fistula-related carcinoma develops in approximately 1% of patients with fistulizing perianal CD. More than half of these carcinomas are adenocarcinoma; most of the rest are SCC. Compared with perianal fistulas, ECF is rare, but it is associated with significant morbidity and mortality due to various complications.3 Late complications, such as late onset of malignancy, have been given little attention in the literature, with a limited number of patients with cancers arising from ECF and only one fistula-associated SCC patient, who was treated with long-lasting azathioprine followed by infliximab, being reported.4 The causes of malignancies arising from chronic fistulas are unclear, but chronic inflammation and immunosuppression are considered mechanisms of carcinogenesis in CD patients. Chronic inflammation, a feature of CD, induces constant epithelial regeneration, ulceration, and high cell turnover rates, leading to dysplasia and subsequently carcinoma. Our patient was not treated with immunosuppressants or biologics; however, so it is likely that her chronic inflammation led to carcinogenesis. The onset of malignancies arising from ECF in CD patients may increase in future because of the expanding use of immunosuppressants and/or biologics and improvements in the treatment of acute complications of ECF. Therefore, diagnosticians should be alert to early signs of fistula-associated malignancies. The authors declare no conflict of interest. Approval of the research protocol: N/A. Informed Consent: The written informed consent was obtained from the patient. Registry and the Registration No. of the study/trial: N/A. Animal Studies: N/A.

Quantitative investigation on the heterogeneity of deformation fields in sandstone pre-existing cracks during damage evolution

The inherently heterogeneous microstructures of rocks lead to heterogeneity of the deformation distribution within the rock volume. In this study, experiments were conducted on red sandstone specimens with four different pre-existing crack inclinations stressed under uniaxial loading to investigate these features. Acoustic emission and digital image correlation techniques were used to confirm the damage process and obtaining deformation fields, respectively. The results showed that the heterogeneity of the deformation fields in the rock specimens amplifies with increasing stress magnitude, i.e., the displacement field heterogeneity shows two dense bands around the pre-existing crack, and the strain field heterogeneity shows localized regions with a numerical difference (quantified by the normalized standard deviation) and spatial concentration (quantified by the spatial correlation coefficient). The variations in the normalized standard deviation and spatial correlation coefficient were closely related to the damage process. The normalized standard deviation presented four evolution stages: relatively constant low value, steady growth, significant growth, and high rate growth. The spatial correlation coefficient changed from increasing at a relatively constant rate to increasing at a gentle rate and finally increasing rapidly. The evolution rate along with the strain showed two sharp fluctuations. The first could be used as precursor information of the damage. Finally, we confirmed the feasibility of the damage variable obtained from the heterogeneous deformation indicators used to calibrate or form damage evolution laws.

Kinetic and molecular insight into immunoglobulin G binding to immobilized recombinant protein A of different orientations

Mechanistic understanding of immunoglobulin G (IgG) binding to protein A is crucial for the design and development of high-performance protein A chromatography. In this work, the IgG binding domain (Z) of protein A from Staphylococcus aureus was genetically modified by introducing a cysteine residue at the N-terminus (Cys-Z) or a cysteine-lysine dipeptide at the C-terminus (Z-Cys), and the two ligands were used to unravel the IgG binding mechanism by means of binding kinetics and different single molecule measurements. Surface plasma resonance (SPR) measurement of the binding kinetics of mouse myeloma IgG2a (mIgG2a) to the two ligands indicated that oriented ligand immobilization significantly increased the association rate constant of mIgG2a, and Z-Cys had the highest binding affinity to mIgG2a among the three ligands (Cys-Z, Z-Cys and Z). This was attributed to the synergistic contribution of the high association rate constant and low dissociation rate constant to mIgG2a. Furthermore, quartz crystal microbalance with energy dissipation monitoring (QCM-D) measurement provided the maximum adsorption densities of IgGs on the Z-Cys-immobilized chip as zeta potentials of IgGs were nearly zero. The QCM-D investigation revealed that the adsorbed layer was dependent on ligand type and density, and IgG. Moreover, Z-Cys and Cys-Z induced IgG binding in flipped orientations, as evidenced by the antigen-antibody reaction. Finally, rectangular DNA origami tiles were introduced to analyze the molecular orientation of adsorbed IgG. Single-molecule imaging showed that mIgG2a was associated with flexible Z-Cys on the tiles predominantly in side-on and end-on orientations. The research has provided molecular insight into the binding mechanism of IgG molecules at liquid–solid interfaces and would help design new protein A-based ligands and high-capacity adsorbents.

Temperature dependent dynamic compressive response of PA66-GF30 composite under constant strain rate multiaxial loading

This paper studies the uniaxial and multiaxial dynamic compressive behaviour and failure of PA66-GF30 (30 wt % glass fibre reinforced polyamide 66), a typical light weight and high strength composite increasingly used in automobiles including the electric cars in applications from ambient temperature to elevated temperatures up to 90 °C. Likewise, the constitutive relation of PA66-GF30 is characterized from quasi-static to high strain rates. Constant high strain rate loading is achieved by pulse shaping technique on a bespoke split Hopkinson bar. The stress-strain relations are pressure, strain rate and temperature dependent. Effects of strain rate and temperature are found to be decoupled on the pressure sensitivity of PA66-GF30. Beyond maximum stress, micro crack has already formed in dynamically deformed PA66-GF30, which corresponds to macro strain localization monitored by high speed photography and digital image correlation techniques. The PA66-GF30 with confinement shows adiabatic shear failure, with fibres coated by severe shear matrix facets and evenly distributed filaments. This is different from the unconfined PA66-GF30 which shows fibres pull out in the fractured matrix. A modified Drucker-Prager model is proposed to describe the pressure dependent compressive strength of PA66-GF30 over various strain rates and temperatures.

Theoretical instructions for experimenting controllable Hopkinson pressure bar

Hopkinson bar loading technique needs theoretical instruction for desired stress waves, to achieve controllable deformation under constant high strain rate loading, for it is the indispensable access while investigating material's rate-dependence and deformation mechanism under transient loading. In this work, theoretical and experimental studies are focused on the involved issues. Firstly, the theoretical deduction based on stress wave theory is performed for constant true strain rate loading, and the equation is formulated of an ideal incident strain wave for different materials. The formulated waves are further clarified by case studies of specimens with various mechanical behaviors, and they are found to present concave characteristics under large deformation. Secondly, an efficient methodology is proposed for single stress wave loading, and the target requirement is deduced theoretically. It is easily achieved experimentally by performing specific strain-controlled experiments: prior to and beyond peak stress of epoxy. Finally, some methods are proposed for achieving the formulated stress waves, and experimental verifications are also conducted on various materials.

Повышение эффективности передачи данных в беспроводных системах связи с ортогональным частотным мультиплексированием

The active introduction of Orthogonal Frequency Division Multiplexing (OFDM) technology is now beginning to be widely used in wireless transmission systems, television, radio communication, and radio broadcasting. The efficiency of using a dedicated frequency band at a constant high transmission rate allows you to combat interference arising from the transmission of a useful information on the radio channel. A method of improving quality of information transmission in communication systems with orthogonal frequency multiplexing is described. It is shown that with an increase in the number of receiving and transmitting antennas, the noise immunity increases significantly. An experiment was carried out to change the number of receiving-transmitting antennas and the signal-to-noise ratio, and the dependence of the appearance of an error on the number of transmitting antennas was obtained. The work investigated the software model of MIMO OFDM (modulators and demodulators). As a result of the analysis, the dependence of the appearance of the error frequency on the probability of the error was obtained. This showed that the use of OFDM and MIMO places increased demands on channel estimation.

Heat-tolerant pepper cultivar exhibits high rates of chlorophyll, photosynthesis, stomatal conductance and transpiration in heat stress regime at fruit developing stage

Relevance. Abiotic stress, as heat, significantly affect plant and floral organs growth and development, fruit set, productivity, the quality, and survival of crops. Heat injury occurs when plants are exposed to these temperatures for a long period of time. Depending on the intensity and duration of exposure to the high temperatures, photosynthesis, respiration, membrane integrity, water relations and the hormone balance of the plants may affected.Material and methods. In this study used the commercial pepper cultivar “NW Bigarim” (HT37) released in South Korea and accessions “Kobra” (HT1) and “Samchukjaere” (HT7) selected as heat tolerant and susceptible, respectively. Total chlorophyll index and photosynthetic activities measured using a SPAD meter (Konica, Japan) and portable photosynthesis measurement system (LI-6400, LI-COR Bioscience, Lincoln, NE, USA), respectively.Results. To evaluate the positive effects of high temperature regime (40/28°C day/night, 14/10-h light/dark cycle) on the response of photosynthetic parameters in pepper plants with different heat susceptibility, we measured the total chlorophyll content (CHL) and photosynthetic activities such as photosynthesis (Pn), stomatal conductance to H2O (Gs) and transpiration rate (Tr) in a heat-tolerant (HT1) and -susceptible cultivars (HT7) in comparison with released cultivar (HT37) at fruit development stage. Heat-tolerant cultivars showed higher and more stable index of the CHL, Pn, Gs and Tr than those in heat-sensitive cultivars for 14 days of heat treatment (HT) period. However, the initial index of Pn, Gs and Tr showed significant alteration among pepper plants regardless of thermotolerance rate before HT on day 0 and day 7 after recovery at normal treatment condition (NT) except for CHL, meaning that plants response to high temperature regime is different from that in normal condition. These results suggest that constant high rates of Pn, Gs and Tr as well as of CHL in heat stress condition periods confer to avoid from heat injury during reproductive growth stages.

Consolidation testing of tailings in a slurry consolidometer using constant rate and accelerated loading

A high rate of rise of fine-grained mine tailings slurry on disposal in a tailings storage facility (TSF) may maintain their condition as underconsolidated. The proper simulation of such field deposition of tailings in conventional laboratory consolidation testing is challenging. A slurry consolidation test using a high constant rate of loading (CRL) simulates a faster rate of tailings disposal in a TSF. A better simulation is achieved, however, by applying accelerated loading in a slurry consolidometer to allow for the increased drainage path length as tailings are built up in the TSF. CRL and accelerated loading were used in a purpose-built, large, instrumented, stress-controlled slurry consolidometer to examine and compare the consolidation behaviour of coal tailings, red mud and gold tailings. At the end of the CRL and accelerated loading tests, the excess pore water pressures had not fully dissipated and the maximum applied stress was maintained to achieve full primary consolidation. The findings of this study showed that the consolidation behaviour of the tailings studied varied with the nature of the tailings and with the loading applied.

Mechanism of the improvement of the energy of host\u2013guest explosives by incorporation of small guest molecules: HNO3 and H2O2 promoted C\u2013N bond cleavage of the ring of ICM-102

Host–guest materials exhibit great potential applications as an insensitive high-energy–density explosive and low characteristic signal solid propellant. To investigate the mechanism of the improvement of the energy of host–guest explosives by guest molecules, ReaxFF-lg reactive molecular dynamics simulations were performed to calculate the thermal decomposition reactions of the host–guest explosives systems ICM-102/HNO3, ICM-102/H2O2, and pure ICM-102 under different constant high temperatures and different heating rates. Incorporation of guest molecules significantly increased the energy level of the host–guest system. However, the initial reaction path of the ICM-102 molecule was not changed by the guest molecules. The guest molecules did not initially participate in the host molecule reaction. After a period of time, the H2O2 and HNO3 guest molecules promoted cleavage of the C–N bond of the ICM-102 ring. Stronger oxidation and higher oxygen content resulted in the guest molecules more obviously accelerating destruction of the ICM-102 ring structure. The guest molecules accelerated the initial endothermic reaction of ICM-102, but they played a more important role in the intermediate exothermic reaction stage: incorporation of guest molecules (HNO3 and H2O2) greatly improved the heat release and exothermic reaction rate. Although the energies of the host–guest systems were clearly improved by incorporation of guest molecules, the guest molecules had little effect on the thermal stabilities of the systems.