bluuebunny/crossref_metadata_2025 huggingface dataset:
Capability‐coordinated frequency control scheme of a virtual power plant with renewable energy sources
Authors: Kim Jinho , Muljadi Eduard , Gevorgian Vahan , Mohanpurkar Manish , Luo Yusheng , Hovsapian Rob , Koritarov Vladimir
Published: June 2019

Growing trends in the deployment of inverter‐based renewable energy will decrease the inertia and frequency control capability of electric power systems by replacing conventional power plants; thus, the frequency of future power systems might be dynamic. This study proposes a capability‐coordinated frequency control (CCFC) scheme of a virtual power plant (VPP) including adjustable‐speed pumped storage hydropower (AS‐PSH), a wind power plant (WPP), and an energy storage system to support the frequency nadir and reduce the steady‐state error of system frequency. The CCFC scheme is based on a hierarchical‐control structure in which a CCFC organises the output of local frequency control units. To support the frequency nadir, the CCFC dispatches weighted frequency errors that are proportional to the available headroom of the units; thus, the errors are forwarded separately with a system frequency error to the primary control loop of each unit and thereby arrest the frequency nadir at a higher value than a system without the CCFC. To reduce the steady‐state error of the system frequency, the CCFC determines a partial active power command by additionally feeding an integrator of the CCFC with a modified frequency error that depends on the unit with the largest control.
Full‐current‐based directional pilot protection for VSC‐DC distribution systems
Authors: Li Meng , Jia Ke , Bi Tianshu , Wang Congbo , Zhu Rui , Yang Qixun
Published: June 2019

Line protection is of great challenge for Voltage Source Converter‐Direct Current (VSC‐DC) distribution systems because the protection scheme must selectively identify the fault section as fast as possible. This study proposes a full‐current‐based directional pilot protection to meet the above requirements. The proposed protection utilises the full‐current (the measured current). The theoretical analyses, which have considered the influence of the VSC blocking, have proved that the full‐current has a certain direction during a pole‐to‐pole short‐circuit fault. Therefore, the protection is robust to the non‐linearity of the DC system. The theoretical analyses have also pointed out that the protection is immune to the line‐distributed capacitance. Both experimental and simulation results have demonstrated the analyses. The proposed protection can trip in <2 ms at a 1.6 kHz sampling rate in the experiments and within 1 ms at a 10 kHz sampling rate in the simulations. It can also correctly operate with 20 dB white noise and 20 Ω fault resistance. There is also no strict synchronisation requirement for the measurements of both the terminals. These features make the protection feasible for industry application.
Decentralised wide‐area back‐up protection scheme based on the concept of centre of reactive power
Authors: Nougain Vibhuti , Jena Manas Kumar , Panigrahi Bijaya Ketan
Published: June 2019

Here, a new decentralised approach‐based wide‐area back‐up protection (WABP) scheme is proposed for faulted line identification (FLI). The scheme is divided into two sub‐routines, i.e. possible faulted region (PFR) identification and FLI. Initially, the power system under study is divided into different coherent regions. The concept of centre of reactive power (CORP) is used to accomplish the task of PFR. Once the faulted region is identified, FLI is done by continuously monitoring the direction of reactive power flow (DORPF) of each line within the PFR. The proposed scheme is extensively tested on IEEE‐39 bus test system for different types of faults. The performance of the scheme under stressed system conditions is also investigated. The obtained results show that the suggested algorithm is able to maintain the balance between dependability and security aspects of the protection logic.
Unscented Rauch–Tung–Streibel smoother‐based power system forecasting‐aided state estimator using hybrid measurements
Authors: Geetha Sreenath Jayakumar , Sharma Ankush , Chakrabarti Saikat
Published: June 2019

A hybrid estimator to track the power system states considering fast‐rate PMUs and slow‐rate supervisory control and data acquisition (SCADA) system is proposed in this article. SCADA measurements arrive at the control centre with various time delays. The estimates obtained using these delayed measurements significantly differs from the actual power system states and is known as the time skew problem. The missing SCADA measurements, owing to their time skewness, are replaced by their predicted values which lead to reduced estimation accuracy. Optimal smoothing algorithms can be utilised to include dynamics in the future measurements to reduce the errors introduced by the time skew problem. Unscented Rauch–Tung–Streibel smoother is used in this study to handle the time skew problem. The performance of the proposed techniques in handling anomalous situations is also studied. The proposed estimator is validated under real‐time environment using RTDS, a real‐time simulation tool, to assess its applicability in the control centre.
Unstructured road detection via combining the model‐based and feature‐based methods
Authors: Qi Naixin , Yang Xiaogang , Li Chuanxiang , Lu Ruitao , He Chuan , Cao Lijia
Published: June 2019

To achieve robust and accurate unstructured road detection, a model‐based and feature‐based combinatory method is proposed. This method obtains the road saliency map via the graph‐based manifold ranking approach and accurately segments the road region by fitting the road model. First, a road graph is constructed with the superpixel nodes and the road distribution model. Then, the seed query nodes are robustly selected. Second, the manifold rankings with the foreground and background queries are conducted successively. To improve the robustness to false queries, the authors propose using two different ranking approaches to obtain the foreground and background saliency maps, and then they are combined into the road saliency map. In the end, they propose using a binomial model to fit the road with which the accuracy of the detected road region is improved. The performance of the proposed method is illustrated using two datasets in terms of the subjective visual quality and the objective quality measurements. The experimental results demonstrate that the proposed method achieves accurate and robust unstructured road detection even under the influence of water stains, kerbstones and hard light.
Accurate frequency‐domain analysis and hybrid control method for isolated dual active bridge series resonant DC/DC converters
Authors: Wang Shien , Zheng Zedong , Li Chi , Xu Lie , Wang Kui , Li Yongdong
Published: June 2019

This study proposes an accurate frequency model of dual active bridge series resonant DC/DC converters (DABSRC). Differing from the conventional first harmonic approximation method, the proposed steady‐state model considers all the harmonic components, which gives an accurate expression of transferred power and resonant current. Based on the proposed model, a precise soft switching criterion was derived, and the soft switching region was extended. On top of that, a hybrid control strategy combining phase shift modulation and frequency modulation was proposed, to achieve soft switching under wide voltage gain and load variations. Thanks to the extended soft switching region, DABSRC can achieve zero‐voltage‐switching turn‐on at light loads, only with a slight increase in switching frequency, hence improving the efficiency a lot. The accurate frequency model and the hybrid control were validated using a 500 W laboratory prototype. The experiment results showed accurate predictions of the proposed model and significant improvements in light load efficiency over a wide range of input voltages.
Soft switching flyback inverter for photovoltaic AC module applications
Authors: Arab Ansari Sajad , Shokrollahi Moghani Javad
Published: June 2019

The soft switching flyback inverters still cannot provide high efficiency and low output current total harmonic distortion (THD) in all load ranges. Therefore, a new flyback inverter with soft switching for photovoltaic AC module applications is presented in this study. The introduced inverter is simple and a small auxiliary circuit is added to the conventional topology of the flyback inverter. Since the primary current of the transformer is not affected by the auxiliary branch, the output current THD does not increase. In addition, all of the high‐frequency switches of the proposed topology are switched under soft switching condition, which allows high‐switching frequency. Hence, high efficiency, as well as compact design, can be achieved in the proposed inverter. Moreover, the voltage overshoot of the main switch during the turn‐off process is limited. This effect decreases the conduction losses because the lower voltage rating switch can be used. Furthermore, a new control method is presented, which provides high efficiency in all load ranges. The operations of the introduced flyback inverter and component selection have been discussed in detail. The performance of the proposed inverter with the auxiliary circuit and corresponding controllers are validated with the help of experimental results.
Oscillation induced by Hopf bifurcation in the p53–Mdm2 feedback module
Authors: Gao Chunyan , Ji Jinchen , Yan Fang , Liu Haihong
Published: June 2019

This study develops an integrated model of the p53–Mdm2 interaction composed of five basic components and time delay in the DNA damage response based on the existing research work. Some critical factors, including time delay, system parameters, and their interactions in the p53–Mdm2 system are investigated to examine their effects on the oscillatory behaviour induced by Hopf bifurcation. It is shown that the positive feedback formed between p53 and the activity of Mdm2 in the cytoplasm can cause a slight decrease in the amplitude of the p53 oscillation. The length of the time delay plays an important role in determining the amplitude and period of the oscillation and can significantly extend the parameter range for the system to demonstrate oscillatory behaviour. The numerical simulation results are found to be in good agreement with the published experimental observation. It is expected that the results of this research would be helpful to better understand the biological functions of p53 pathway and provide some clues in the treatment of cancer.
Interconnection of VSC‐HVDC and LCC‐HVDC using DC–DC autotransformer
Authors: Yang Zhihan , Li Mengbo , Lu Xiaojun , Xiang Wang , Zuo Wenping , Yao Liangzhong , Lin Weixing , Wen Jinyu
Published: June 2019

This article investigates the feasibility of interconnecting LCC‐HVDC and VSC‐HVDC through an un‐interrupted DC autotransformer (DC AUTO). The interconnected system aims at taking advantage of two HVDC technologies. To begin with, the system configuration and the potential benefits are illustrated. Then, the corresponding control strategies towards LCC‐HVDC, VSC‐HVDC, and the un‐interrupted DC AUTO are proposed. The installed controllers enable the system stable operation during both normal time and faulted conditions. Finally, a four‐terminal test system is built on PSCAD/EMTDC platform to validate the technical feasibility of the interconnected system and the effectiveness of the proposed control strategy.
Parameter estimation for sparse targets in phased‐MIMO radar
Authors: Zhu Can , Zhang Ning , Chen Zhimin , Chen Peng
Published: June 2019

Parameter estimation using phased‐multiple‐input multiple‐output (MIMO) radar is investigated in this study, where transmitting antennas are partitioned into subarrays to provide both waveform diversity and high coherent processing gain. By exploiting the target sparsity in the spatial domain, a compressed sensing‐based estimation method is proposed to jointly estimate the direction of arrivals and scattering coefficients of multiple targets in phased‐MIMO radar. Cramér‐Rao lower bound is derived from setting a performance limit on the presented algorithm, and simulation results are provided to validate its efficiency. Numerical examples reveal that efficient estimation can be obtained when the received signal‐to‐noise ratio exceeds a threshold at the level of about 5 dB. Also, the authors also show that the number of subarrays and the size of each subarray constitute a fundamental trade‐off in improving the estimation performance.
Investigation of Bragg gratings in planar hybrid metal–insulator–metal plasmonic waveguide using graded profile
Authors: Srivastava Kritarth , Chitimireddy Sindhura , Sharma Prateeksha , Vishwakarma Dinesh Kumar
Published: June 2019

The design of integrated components using hybrid plasmonics is attracting a widespread interest in the recent years. This work proposes a consistent approach to design Bragg gratings employing the concept of graded profile in a planar hybrid metal–insulator–metal plasmonic waveguide. A comparative study of various width modulations such as triangular, parabolic and rectangular profiles is presented. The most striking observation is that Bragg gratings with parabolic profile offer best performance in terms of compact track length (3.48 μm), wide stopband (168 nm) and good transmission characteristics with fewer side lobes. Additionally, a nanocavity analysis is performed by introducing a defect length of 140 nm in the Bragg grating structure with parabolic profile. A peak transmission of 89% is observed at the resonance wavelength of 1550 nm.
Effects of22Ne sedimentation and metallicity on the local 40 pc white dwarf luminosity function
Authors: Tononi Jordi , Torres Santiago , García-Berro Enrique , Camisassa María E. , Althaus Leandro G. , Rebassa-Mansergas Alberto
Published: June 2019

Aims. We analyzed the effect of the sedimentation of22Ne on the local white dwarf luminosity function by studying scenarios under different Galactic metallicity models.

Methods. We use an advanced population synthesis code based on Monte Carlo techniques to derive the synthetic luminosity function. The code incorporates the most recent and reliable cooling sequences and an accurate modeling of the observational biases under different scenarios. We first analyzed the case for a model with constant solar metallicity and compared the models with and without22Ne sedimentation with the observed luminosity function for a pure thin-disk population. Then we analyzed the possible effects of a thick-disk contribution. We also studied model scenarios with different metallicities, including22Ne sedimentation. The analysis was quantified from a statisticalχ2-test value for the complete and also for the most significant regions of the white dwarf luminosity function. Finally, a best-fit model along with a disk age estimate was derived.

Results. Models with constant solar metallicity cannot simultaneously reproduce the peak and cutoff of the white dwarf luminosity function. The additional release of energy due to22Ne sedimentation piles up more objects in brighter bins of the faint end of the luminosity function. The contribution of a single-burst thick-disk population increases the number of stars in the magnitude interval centered aroundMbol = 15.75. The metallicity model that follows a Twarog profile is disposable. Our best-fit model was obtained when a dispersion in metallicities of about solar metallicity was considered along with a22Ne sedimentation model, a thick-disk contribution, and an age of the thin disk of 8.8 ± 0.2 Gyr.

Conclusions. Our population synthesis model is able to reproduce the local white dwarf luminosity function with a high degree of precision when a dispersion in metallicities around a model with solar values is adopted. Although the effects of22Ne sedimentation are only marginal and the contribution of a thick-disk population is minor, both of them help in better fitting the peak and the cutoff regions of the white dwarf luminosity function.
Comparison and Mathematical Modelling of Leakage Tests
Authors: Fojtášek Kamil , Dvořák Lukáš , Krabica Lukáš
Published: June 2019

Leak tests are used in many industrial applications, a typical example are the headlights of cars. In these tests are use different principles and different working media. The monitored parameters are usually the amount of leakage media depending on the pressure drop and the time at which the leakage occurs. The article describes the possibility of performing leak tests using compressed air, their comparison and the subsequent creation of mathematical models.
Determining 2D temperature field in flow boiling with the use of Trefftz functions
Authors: Ho ejowska Sylwia
Published: June 2019

The paper proposes the use of Trefftz method to solve the triple coupled heat conduction problem in flow boiling of refrigerant in an asymmetrically heated minichannel. A mathematical model of heat transfer in a rectangular minichannel is suggested. Two sets of Trefftz functions were used to determine 2D temperature fields at a fluid flow in the minichannel tilted at a known angle. The procedure for the calculation of the liquid temperature was coupled with the process of determining temperature fields in two adjacent elements of the experimental stand with the minichannel, i.e. in the glass pane and the heating foil. Heat transfer in the glass, foil and liquid is described using various 2D differential equations with an adequate set of boundary conditions. Solving those equations led to the solving of the triple coupled heat conduction problem made up of one direct and two subsequent inverse problems. The results are presented as: (1) 2D temperature of the glass pane, the heating foil, the flowing liquid, (2) mean square errors between temperature approximations and selected boundary conditions, (3) the heat transfer coefficient versus the distance from the minichannel inlet.
Test Facility for High-Speed Probe Calibration
Authors: Jelínek Tomáš , Flídr Erik , Němec Martin , Šimák Jan
Published: June 2019

A new test facility was built up as a part of a closed-loop transonic wind tunnel in VZLU´s High-speed Aerodynamics Department. The wind tunnel is driven by a twelve stage radial compressor and Mach and Reynolds numbers can be changed by the compressor speed and by the total pressure in the wind tunnel loop by a set of vacuum pumps, respectively. The facility consists of an axisymmetric subsonic nozzle with an exit diameter de = 100 mm. The subsonic nozzle is designed for regimes up to M = 1 at the nozzle outlet. At the nozzle inlet there is a set of a honeycomb and screens to ensure the flow stream laminar at the outlet of the nozzle. The subsonic nozzle can be supplemented with a transonic slotted nozzle or a supersonic rigid nozzle for transonic and supersonic outlet Mach numbers. The probe is fixed in a probe manipulator situated downstream of the nozzle and it ensures a set of two perpendicular angles in a wide range (±90°). The outlet flow field was measured through in several axial distances downstream the subsonic nozzle outlet. The total pressure and static pressure was measured in the centreline and the total pressure distribution in the vertical and horizontal plane was measured as well. Total pressure fluctuations in the nozzle centreline were detected by a FRAP probe. From the initial flow measurement in a wide range of Mach numbers the best location for probe calibration was chosen. The flow field was found to be suitable for probe calibration.
Pulse flow of liquid in flexible tube
Authors: Klas Roman , Fialová Simona
Published: June 2019

The simulation of liquid flow in significantly deformed elastic material is one of the more challenging tasks. Tube wall motion prediction implemented directly into CFD software can noticeably reduce the computational and time demands of such problems. The FSI simulation of a liquid-flowed flexible plastic tube was analyzed on the FEA and CFD solvers coupling basis. The flexible tube is the basic symmetric test body that could be appropriately tested on the experimental stand. A comparison of experimental data and FSI problem using commercial code and one-dimensional tube models was made by evaluating the tube wall deformation magnitudes at defined flow ratios. The type of tube material, which can be understood as a nonlinear from the stress and deformation point of view, was considered. The paper shows several possibilities of tube modeling using the main constitutive relations of linear and nonlinear mechanics. The hyperelastic material models such as neo-Hookean and Mooney-Rivlin were tested. The results represent differences in impacts on the tube liquid flow and differences in the magnitudes of the wall tube deformations. Based on these findings it should be possible to simulate the problems of liquid flow in more complicated shape flow zones, such as arteries affected by various defects, in our future research.
Experimental methods for visualization of hydrodynamic instability caused by the neutralization reaction in a miscible two-layer system
Authors: Mosheva Elena
Published: June 2019

This paper focuses on experimental investigations of the spatio-temporal distributions of fluid velocity and temperature and the concentration of reagents and reaction products. We study concentration-dependent diffusion (CDD) convection driven by the neutralization reaction in a two-layer miscible system in a vertical Hele-Shaw cell using the original experimental complex. A comprehensive understanding of the physical mechanisms of convective motion and instabilities requires employing various experimental methods simultaneously. The proposed experimental complex provides simultaneous visualization and facilitates identification of the location of the reaction front, which is of importance to the study of its characteristics.
The second frequencies in the wake behind two circular cylinders
Authors: Vitkovicova Rut , Yokoi Yoshifumi
Published: June 2019

The wake behind the cylinders is often characterized by a dominant frequency and dimensionless Strouhal number. However, the experiments performed using the CTA and visualization method and their analysis revealed that other significant frequencies were present in the wake. With the Proper Orthogonal Decomposition analysis, connections between these frequencies and their own eigenmodes were found.
Introductory Numerical Study on Supersonic Ejector Working with R32
Authors: Vojta Lukas , Kracik Jan , Dvorak Vaclav
Published: June 2019

Nowadays, there is an increasing demand for devices which work efficiently with the smallest possible consumption of energy. In this regard, incorporating ejectors seems to be an interesting choice. This paper describes the numerical analysis of the flow in a supersonic ejector working with R32 (difluoromethane) as the working fluid. The ejector geometry under investigation in this paper has already been experimentally analysed, however, air was used as the working fluid. Therefore, this paper deals with a numerical analysis of the same geometry but with a different working fluid. Furthermore, the design of the ejector enabled the adjustment of a particular distance of the motive nozzle from the beginning of the mixing chamber, i.e. the nozzle exit position (NXP). This work examines the ejector numerically for eleven values of back-pressure with the NXP of two millimetres; consequently, the performance line of the ejector with fixed boundary conditions at both inlets was obtained. Finally, the obtained results are discussed and some recommendations for future research have been made.
Experimental analysis on air-to-water sound transmission loss in shallow water
Authors: Peng Zhaohui , Zhang Lingshan , Wang Guangxu
Published: June 2019

Research on the propagation characteristics of air-to-water sound transmission is of great importance to the detection of aerial target from underwater. In order to study the propagation characteristics of air-to-water sound transmission in shallow water, an experiment was conducted in the South China Sea in March, 2013. During the experiment, signals transmitted by a hooter hung on a research ship were received by an underwater hydrophone. The source signals were also recorded by a microphone under the hooter. The distance between the hooter and the hydrophone was from 2.4 km to 9.8 km approximately. Data measured during the experiment is analysed in this paper. The transmitted signals and received signals were carefully filtered and calibrated one-by-one. It is shown that the SNRs at 9.8km are up to 12 dB and 18 dB at the frequencies 128 Hz and 256 Hz, respectively. The experimental air-to-water sound transmission loss is estimated up to 9.8 km in range, which has clear oscillation structure. A wave-number integration approach is used to predict the air-to-water transmission losses, which are in good agreement with experimental data.
Acoustic Signature Analysis for Localization Estimation of Unmanned Aerial Vehicles Using Few Number of Microphones
Authors: Blanchard Torea , Thomas Jean-Hugh , Raoof Kosai
Published: June 2019

In recent years, the current technological improvements of Unmanned Aerial Vehicles (UAV) have allowed more and more efficient use for applications ranging from simple amateur shooting to more professional tasks. Being handy, drones can easily fly near sensitive sites, such as power plants, airports or ministries. It is therefore necessary to develop systems able to keep watch such sites. However, the size and the composition of these devices make optical or electromagnetic systems inefficient for their detection. This study proposes an alternative exploiting the sound wave emitted by their motorization and / or their aerodynamic whistling. For this, an acoustic antenna with few microphones was sized to be sensitive to frequencies emitted by a drone. Firstly, an experimental analysis on the noise made by a drone was carried out. The results allowed us to settle the geometry of the antenna in order to process localization. Two methods of location are used. The first is based on an energy approach providing the acoustic field reconstruction in all directions of space. The second estimates the position of the source by inverting a system exploiting the arrival time differences of the acoustic wave between different pairs of microphones. Numerical simulations, supported by a measurement campaign, make it possible to highlight the performance of the methods used.
A method of jellyfish detection based on high resolution multibeam acoustic image
Authors: Zhang Yang , Li Guijuan , Zhang Mingwei , Jiang Yi
Published: June 2019

A method based on high resolution multi-beam acoustic image was brought forward for jellyfish detection, and a moon jellyfish detection experiment was conducted on sea. In this experiment, clear acoustic images of individual moon jellyfish were obtained, acoustic method was verified available in moon jellyfish detection. Echo characteristics of individual moon jellyfish were analysed. In the echo image of individual moon jellyfish, four evident echo highlights were found, which were due to the four stomach pouches. Three acoustic characteristic parameters were proposed and estimated to describe jellyfish acoustic characteristics, which were acoustic diameter, acoustic height, and relative target strength. In addition, dynamic characteristic of moon jellyfish was also studied during its pulse motion.
Effect of incorrect sound velocity on synthetic aperture sonar resolution
Authors: Ji Xia , Zhou Lisheng , Cong Weihua
Published: June 2019

Synthetic aperture sonar (SAS) is an imaging technique to produce centimeter resolution over hundreds-of-meter range on the sea floor, by constructing a virtual aperture whose length automatically adjusts itself for a given focusing range. SAS is near-field acoustic imaging, and this implies that the sound velocity should be accurately estimated for well focused imaging. Otherwise there will be image quality loss. However, sound velocity in the ocean varies with space and time, and there might also be measuring error of CTD (Conductivity, Temperature, and Depth) sensor, so sound velocity error has become one of the limiting factors to improve SAS resolution further. To characterize the effect of sound velocity error quantificationally, the practice SAS resolution is mode as the convolution of ideal seafloor reflectivity function and a phase error function in frequency domain, where the phase error is caused by incorrect sound velocity. Then the SAS resolution parameterized is calculated as a function of the sound velocity measuring error, or sound velocity gradient. It is shown that SAS azimuthally (along track) resolution loss, caused by sound velocity measurement error, increases linearly with detection range. Meanwhile the loss caused by sound velocity gradient increases squarely. It is simulated by considering the synthetic aperture data collection for a particular pixel, and results show that the point scatter response will defocus when the sound velocity measuring error is up to 1% at 200m range, or the sound velocity changes up to 2% over a typical gradient at 200m range, and be worse at a longer range. Furthermore, we demonstrate the influence of sound velocity errors on SAS imagery using a sea trial data and real CTD measurements at South China Sea. We evaluate the degradation in image quality with respect to sound velocity errors by using two plastic balls and a variable seafloor scene, and results also support the accuracy of theoretical conclusions above.
Calibration of echosounder using standard target method
Authors: Yang Liuqing , Chen Yi , Zhang Jun
Published: June 2019

In this work, we develop an underwater echosounder and use the standard target method to calibrate the performance of the device. In the calibration experiments, a solid tungsten carbide sphere of 38mm diameter is used as a standard target for calibrating a HPCTB-200-35 echosounder (manufactured by Hangzhou Applied Acoustics Research Institute) with a working frequency of 220 kHz. Further, the measurement data and uncertainty are presented and analyzed; these results demonstrate that the standard target method can calibrate the combined transmitting-receiving response of echosounders effectively. In our calibration experiment, the combined transmitting-receiving response of HPCTB-200-35 is about 33.8 dB, and the measurement uncertainty is about 1.0 dB (k = 2).
Method of MAI cancellation in asynchronous underwater acoustic CDMA system
Authors: Xiong Shengjun , Zhou Lisheng , Wang Zhengduo , Wang Chao , Zhang Yuyan
Published: June 2019

In the underwater passive positioning systems (UPPS), it involves a key technology of multi-user communication that the beacons synchronously send positioning messages to the targets. Interferences from other users, referred to multi-access interferences (MAIs), can induce significant bit errors for the desired user. In this paper, we designed an underwater acoustic Code Division Multiple Access (CDMA) system using the coded cyclic shift key (CCSK) modulation, and proposed a hybrid MAI cancellation scheme based on cyclic shift inverse matrix transform (CSIMT) and recursive least square (RLS) in the CDMA system. The hybrid scheme can suppress MAI better than RLS or CSIMT, and meets the requirements of strong stability to support reliable transmission for UPPS. The CSIMT interference cancellation performs well under the far-near effects, which doesn’t depend on the accuracy of the estimation of transmitted data, and the strong MAI can be reduced by transformation of the zero-forcing correlation values using m sequence cyclic shift inverse matrix. The RLS interference cancellation is used to mitigate MAI form the detected users with comparable power, by using the estimated the channel impulse response between the receiver and the detected users, and the regenerated signal of detected users form decoder output, which allows of strong error-correcting codes, and it’s robust in an asynchronous environment. The theoretical analysis and experimental result show that the hybrid MAI cancellation scheme can effectively suppress MAI better. The shallow water sea trial was carried out near Dalian Tiger Beach Ocean Park in China, at a distance of about 5 km, the data rates of 100bps, where three users could communicate asynchronously with low failure ratio and can match the UPPS application.
The acoustic insulation performance of infinite and finite locally resonant metamaterial and phononic crystal plates
Authors: Van Belle Lucas , Claeys Claus , Deckers Elke , Desmet Wim
Published: June 2019

The bending wave stop band behavior of locally resonant metamaterial and phononic crystal plates can strongly improve the vibration performance of flexible plates in targeted frequency ranges. Their acoustic insulation performance, however, is found to strongly depend on the stop band mechanism, also influencing the frequency range of improvement. While sound transmission loss improvements are predicted for both infinite periodic plates, the finite phononic crystal plate performance can differ significantly.
Research on sound absorption characteristics of Alberich anechoic coatings in debonding states
Authors: Zhao Xianwen , Shang Dejiang , Zhang Chao , Yin Lu
Published: June 2019

Viscoelastic structures with periodic cavity arrangement occupy an important position in acoustic stealth. Most studies focus on the absorption at low frequency, under large pressure and in a wide frequency band, however, the sound absorption properties of the anechoic coating in debonding states are seldom studied. The acoustic response of the composite structure is calculated by the FEM, and the incident wave and the reflected wave are separated based on the plane wave propagation principle. The sound absorption coefficient of the model can be solved with the pressure data of transmission wave, incident wave and reflected wave. Based on the finite element method, the absorption characteristics of anechoic coating in debonding states have been studied. Firstly, the FEM model is verified by comparing the solution of uniform non-cavity coatings with the corresponding analytical solution. The results indicate that the problem of acoustic pressure field can be simulated well by the symmetry condition and the absorbing boundary. Then, the Alberich anechoic coating models in different debonding ratio states and in different cavity water filling states are established by FEM, and then the corresponding absorption characteristics are calculated and analyzed. The results show that the effects of debonding on absorption characteristics are small when the cavities of coatings are filled with water, however the effects are much more when the cavities of coatings are filled with air. For the case of cavities filled with air, the main frequency band of sound absorption moves to low frequency with the debonding ratio increasing. When the frequency is very high, there are few impacts on the sound absorption coefficient no matter whether the packing medium is water or air, no matter whether the coating is debonding or not.
Cooling efficiency and cooling intensity of cooling staves in blast furnace hearth
Authors: Jiao Ke-Xin , Zhang Jian-Liang , Liu Zheng-Jian , Jiang Hai-Bin
Published: June 2019

The main function of the cooling system is to help preserve the refractory lining for as long as possible, but the evaluation indicators of blast furnace cooling system have not been studied in detail. In the study, the blast furnace cooling system was analyzed in-depth from the perspective of cooling essence and heat transfer principle based on the investigation of many blast furnaces. The concept of cooling efficiency and cooling intensity of the blast furnace hearth cooling system were proposed with quantitative characterization. The results show that the cooling efficiency is 88–99% and the cooling intensity is 70–95% generally. The effect of the cooling water velocity and specific surface area on cooling efficiency and cooling intensity are analyzed from a view of optimizing the design. Improving the specific surface area of cooling system and increasing the cooling water velocity can increase the cooling efficiency and cooling intensity. The specific surface area can be designed to be more than 1.1 and the water velocity should be greater than 1.5 m/s. Finally, the blast furnace operation strategy taken in the actual production process and the methods for improving the cooling intensity and cooling efficiency are assessed.
Effect of rare earth Ce on the isothermal oxidation behavior in air of arsenic bearing steels
Authors: Xin Wenbin , Zhang Jing , Jiang Yinju , Deng Yongchun , Meng Qingyong , Song Bo
Published: June 2019

In order to study the segregation of arsenic impurities at the metal/oxide interface during high temperature exposure, isothermal oxidation behavior of arsenic bearing steels with various Ce content was systematically investigated. The result showed that oxidation mass gain of arsenic bearing steel in the temperature range of 950–1150 °C was decreased as a whole with increasing Ce content from 0 to 0.035 wt.%. At 1100 and 1150 °C, the best results are obtained for 0.027 and 0.035 wt.% Ce. Moreover, Ce addition could prevent grain boundaries oxidation, which reduced or even eliminated the formation of visible oxide particles along grain boundaries at 1000 and 1050 °C. In case of oxidation at 1050 and 1100 °C, the arsenic enrichment amount at the scale/metal interface was firstly decreased with increasing Ce content from 0 to 0.027 wt.% and then slightly increased as Ce content increased from 0.027 to 0.035 wt.%. This variation was attributed to the separation behavior of oxide scale, the formation of a continuous solid Fe2SiO4 layer and the arsenious rare earth particles promoted by Ce addition.
Blutung als Leitsymptom in der Notaufnahme
Authors: Schmid Bonaventura , Hodel Karin , Busch Hans-Jörg
Published: June 2019

Acute bleeding is a common and challenging condition in the emergency room. The need for staff and medical resources in these patients depends on the clinical status and extent of the bleeding. The causes of acute bleeding are heterogeneous. Patients may appear in an emergency department with gastrointestinal, traumatic, intracerebral, gynecological or urological bleeding. Bleeding may be triggered or aggravated by underlying diseases or the use of anticoagulants or antiplatelet therapy. The treatment can range from general measures to complex intensive care with antidotes, blood coagulation and transfusion management. Nevertheless, the initial management in such cases is often the same.

The purpose of this article is to give an overview of the different types of acute bleeding in an emergency room and how to overcome these specific challenges. Important is the initial management with appropriate general measures to stabilize the patient to avoid serious complications. It is helpful to set up structured processes for these cases.
Reactive Oxygen Species-Mediated Apoptosis and Cytotoxicity of Newly Synthesized Pyridazin-3-Ones In P815 (Murin Mastocytoma) Cell Line
Authors: Bouchmaa Najat , Mrid Reda Ben , Boukharsa Youness , Bouargalne Youssef , Nhiri Mohamed , Idir Abderrazak , Taoufik Jamal , Ansar Mʼhammed , Zyad Abdelmajid
Published: June 2019

Background In cancer cells, the intracellular antioxidant capacity and the redox homeostasis are mainly maintained by the glutathione- and thioredoxin-dependent systems which are considered as promising targets for anticancer drugs. Pyridazinones constitute an interesting source of heterocyclic compounds for drug discovery. The present investigation focused on studying the in-vitro antitumor activity of newly synthesized Pyridazin-3(2h)-ones derivatives against P815 (Murin mastocytoma) cell line.

Methods The in-vitro cytotoxic activities were investigated toward the P815 cell line using tetrazolium-based MTT assay. Lipid peroxidation and the specific activities of antioxidant enzymes were also determined.

Results The newly compounds had a selective dose-dependent cytotoxic effect without affecting normal cells (PBMCs). Apoptosis was further confirmed through the characteristic apoptotic morphological changes and DNA fragmentation. Two compounds (6f and 7h) were highly cytotoxic and were submitted to extend biological testing to determine the likely mechanisms of their cytotoxicity. Results showed that these molecules may induce cytotoxicity via disturbing the redox homeostasis. Importantly, the anticancer activity of 6f and 7h could be due to the intracellular reactive oxygen species hypergeneration through significant loss of glutathione reductase and thioredoxin reductase activities. This eventually leads to oxidative stress-mediated P815 cell apoptosis. Furthermore, the co-administration of 6f or 7h with Methotrexate exhibited a synergistic cytotoxic effect.

Conclusions considering their significant anticancer activity and chemosensitivity, 6f and 7h may improve the therapeutic efficacy of the current treatment for cancer.
Outcome Measures to Evaluate Upper and Lower Extremity: Which Scores are Valid?
Authors: Darwich Ali , Schüttler Viola , Obertacke Udo , Jawhar Ahmed
Published: June 2019

Objective In orthopaedics and trauma surgery scores are frequently used to assess treatment outcomes. The purpose of the review is to create an overview analysing the content of validity studies of frequently utilized scores for upper and lower extremity.

Methods Commonly used outcome measures to assess clinical outcome of upper (n = 19) and lower (n = 22) extremity were included. For each of the scores a comprehensive search in several databases (Medline, PubMed, google scholar) were performed to identify validation studies. The COSMIN-Checklist (COSMIN: Consensus-based Standards for the selection of health Measurement Instruments) introduced by Mokkink et al. were used to analyse systematically the methodological quality of the validation studies.

Results Validity, objectivity and reliability were not routinely considered and addressed in validation studies. The score related validation studies did not include all defined criteria of the COSMIN-Checklist. Six scores of the upper extremity and four scores of the lower extremity are not adequately validated. The best validated scores of the upper extremity is Oxford Shoulder Score (OSS) and for the lower extremity Hip Disabilities and Osteoarthritis Outcome Score (HOOS) as well as Western Ontario and McMaster Universities Score (WOMAC).

Conclusion There is no gold standard for the content-comprehension of validation studies due to the structure of the original study. The more criteria were tested the more informative and significant the outcome measure is. However some scores, such as Neer and Castaing Score, that lack validation are still being successfully used in research and clinical practice. The present review provides an overview of frequently used score in orthopaedics and trauma surgery and their grade of validity.
Medikamentöse Behandlung psychischer Störungen in Schwangerschaft und Stillzeit
Authors: Jordan Wolfgang
Published: June 2019

Psychische Störungen gehören zu den häufigsten Erkrankungen in der Peripartalzeit. Für eine Behandlung mit Psychopharmaka in Schwangerschaft und Stillzeit sind Nutzen und Risiken sorgfältig abzuwägen. Der Artikel vermittelt Hintergrundwissen zur medikamentösen Behandlung psychischer Erkrankungen rund um die Geburt.
Continuous Beta-Blocker Therapy Delays Structural Deterioration after Bioprosthetic Mitral Valve Replacement
Authors: Ma Wenrui , Tan Yan , Shi Qiuxia , Xu Zhiwei
Published: June 2019

The impact of continuous beta-blocker (BB) therapy on structural valve deterioration (SVD) after bioprosthetic mitral replacement was investigated. From 2000 to 2005, 138 such patients were propensity score matched in a 1:1 fashion (continuous BB therapy after surgery, n = 69; without BB therapy, n = 69). Median follow-up was 12.3 years. Cardiac mortality was comparable between patients with and without BB therapy (p = 0.13), while the 10-year freedom from SVD was significantly higher in patients with BB therapy (92.4 vs. 76.3%, p = 0.001). In conclusion, continuous BB therapy may be considered in patients after bioprosthetic mitral valve replacement to delay SVD and improve prosthetic durability.
Kinetics and mechanism of the abiotic decomposition of dimethyl polysulfides with three, four and five sulfur atoms under dark, oxic conditions
Authors: Buchshtav Tamir , Amrani Alon , Said-Ahmad Ward , Kamyshny Jr Alexey
Published: June 2019

Environmental contextDimethyl polysulfides are malodorous compounds formed from decomposing algal matter. The decomposition of dimethylpolysulfides with 3–5 sulfur atoms was studied in aqueous solution under dark, oxygenated conditions and compared with observations of natural systems. The half-lives of dimethyl tri- and tetrasulfides are very long (176–100000 years), while the half-life of dimethyl pentasulfide (<2 years) is similar to the observed time of its removal from natural aquatic systems.
AbstractThe presence of malodorous dimethyl polysulfides (DMPSs) has been documented in various aquatic systems. In this work, we studied the kinetics and mechanisms of the chemical decomposition of DMPSs with 3–5 sulfur atoms in aqueous solutions in the presence of oxygen and absence of light. DMPSs are shown to undergo reaction with hydroxyl ions, which results in their decomposition. The orders of the decomposition reactions with respect to dimethyl trisulfide (DMTS), dimethyl tetrasulfide (DM4S) and dimethyl pentasulfide (DM5S) are 2.0±0.3, 1.7±0.3 and 2.0±0.2, respectively. The reaction orders with respect to OH− are 0.59±0.06, 0.56±0.08 and 0.58±0.11, respectively. The activation energies of these reactions are 170kJmol−1K−1, 114kJmol−1K−1 and 75kJmol−1K−1, respectively. The initial products of the decomposition are Me2Sn−1 and Me2Sn+1 and the apparent final products are elemental sulfur and dimethyl disulfide (DMDS). DMDS, which is formed during the decomposition of DMTS, is depleted in 34S (ϵ=−13.2 ‰), while the DM4S is enriched 34S (ϵ=4.7 ‰). A mechanism for the decomposition of DMPSs is proposed based on the results. Under these conditions, half-lives for the decomposition of DMPSs in Lake Kinneret vary from 2 months for DM5S to 100000 years for DMTS. The relatively short time scale of the reported odour episodes indicates that other chemical, photochemical or biological processes are responsible for the decomposition of DMTS and DM4S.
Variations in the adenohypophysis of the expression of proliferating cellular nuclear antigen, oestrogen and androgen receptors in relation to gonadal steroids during pregnancy of viscachas (Lagostomus maximus maximus)
Authors: Rosales Gabriela J. , Perez Edith , Rodriguez Graciela B. , Filippa Verónica P. , Mohamed Fabian H.
Published: June 2019

Viscachas are native rodents of South America that present a long pregnancy of ~154 days. In this work, we analysed variations in the expression of proliferating cellular nuclear antigen, oestrogen and androgen receptors (ERα and AR) in pituitary pars distalis (PD) and pars tuberalis (PT) in relation to oestradiol and testosterone serum levels in non-pregnant and pregnant viscachas. In PD, cell proliferation increased with pregnancy and lactotrophs proliferated during mid-pregnancy (MP). ERα nuclear-immunoreactive cells (ERαn-ir) were maximal in late pregnancy and AR expression did not vary during pregnancy. In PT, cell proliferation and AR expression increased during pregnancy, but ERα expression was very scarce. The immunostaining pattern of receptors was different in PD and PT. The peak of serum oestradiol and testosterone occurred during MP. Our results suggest that cell proliferation and gonadal receptors might be differentially regulated in the pituitary by oestradiol and testosterone during viscacha pregnancy.