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In order to support low power wide area networks (LPWANs) with a scarce pilot resource, we discuss the data framing and its corresponding optimization problem. In specific, we design a general pilot-symbol-assisted-modulation (G-PSAM) frame based on the standard PSAM (S-PSAM) frame and derive joint data-aided & non-data-aided Cramer-Rao bounds (DA&NDA CRBs) for carrier frequency offset (CFO), phase offset (PO), and time delay estimation, followed by an approximate DA&NDA CRB for the CFO. With the approximate DA&NDA CRB and the well-known control-variate method (CVM), we then provide an efficient G-PSAM frame optimization scheme, which is asymptotically optimal in terms of the mean-squared-error (MSE) performance. Simulation results show the superiority of the optimized G-PSAM frame over the S-PSAM frame for both the short-packet and long-packet transmissions. Meanwhile, we also present an example verification on the joint DA&NDA aided carrier synchronization (i.e., Turbo synchronization).

This paper discusses different air management technologies for fuel cell systems. Two different types of compressors are analyzed for Proton-exchange membrane fuel cells (PEMFC). Some important criteria are analyzed thoroughly for the selection of turbo compressor among different types of compressors illustrated with the help of matrix representations. The impacts of various input parameters for Fuel Cell (FC) are also explained thoroughly. Later the numerical modeling of an automobile fuel cell system using a high speed turbo-compressor for air supply is explained. The numerical model incorporates the important input parameters related with air and hydrogen. It also performed energy and mass balances across different components such as pump, fan, heat-exchanger, air compressor and also keeps in consideration the pressure drop across the flow pipes and various mechanical parts. The model is solved to obtain the characteristics of the FC system at different operating conditions. Therefore, it can be concluded that the high speed turbo compressor with a turbo-expander can have significant effects on the overall system power and efficiency.

The characteristics of the combustion chamber of turbo jet engine with various parameters are examined in this article. The scientific works of other authors analyzing operating parameters of the jet engines were reviewed. Their recommendations were considered. Computer simulations of the combustion chamber were performed using different combustion reactions. The exhaust gas temperature and its dependence on the combustion mixture were determined. A practical study was also carried out, during which the experimental exhaust gas temperature was measured, and the trends of temperature change were determined. After analyzing both theoretical and practical results, the conclusions are presented.

The alternating direction method of multipliers (ADMM) has been adapted for decoding low-density parity-check (LDPC) codes over intersymbol interference (ISI) channels in order to reduce the complexity of the traditional Turbo equalization (TE) method. However, the error rate performance of ADMM decoding may be degraded in certain ISI channels when compared with the TE at high signal-to-noise ratio regions. In order to address the problem, we derive a novel ADMM-based decoding method, called $l_2$ -box ADMM decoding, for LDPC codes over ISI channels. By introducing suitable penalty functions to $l_2$ -box ADMM decoding, we present an enhanced method, called $l_2$ -box ADMM penalized decoding, to further improve the performance. Simulation results on several ISI channels indicate that the proposed $l_2$ -box ADMM penalized decoding can achieve better error rate performances compared with the TE and the existing ADMM penalized decoding methods, especially for ISI channels with long memory, while maintaining the low-complexity advantage of the ADMM penalized decoding.

A new horizontal turbo air classifier equipped with two inclined air inlets has been introduced. The flow field and classification performance of the classifier have been investigated using CFD method and response surface methodology (RSM). Simulation results show that the flow field is composed of the primary swirling flow and the secondary upward washing air, and the uniformly distributed swirling flow occupies the classifying chamber. The tangential gas velocity reaches the maximum value on the outer surface of the rotor cage, generating strong centrifugal force for the particle classification. The discrete phase model (DPM) can predict the cut sizes, but cannot present the fish-hook phenomenon. The desirable experimental condition by targeting the cut size of 20 μm and minimizing the classifying accuracy index is, rotor speed of 1373.6 rpm, primary air volume flow rate of 261.8 m3/h and secondary air volume flow rate of 42.4 m3/h. The corresponding fine and coarse fraction loss are less than 1.42% and 7.24%, respectively. This study provides a new strategy to design the horizontal turbo air classifier.

Рассмотрены вопросы использования турбокомпрессоров (ТРК), производителей ТРК, принцип работы, пути совершенствования, причины отказов. Работу ТРК совершенствуют инженеры во всём мире, при этом основная задача заключается в том, чтобы продлить срок эксплуатации и увеличить эффективность ТРК. Принцип работы ТРК заключается в том, что энергию на вращение вала ТРК получает от отработанных газов, воздействующих на горячую улитку, расположенную на одном валу с холодной улиткой, которая нагнетает воздух во впускной коллектор. ТРК совершенствуют следующими путями: уменьшают размеры и увеличивают скорость вращения вала ТРК; добавляют управление (электронное, механическое) перепускным клапаном давления; используют турбину с регулируемым сечением и ротором, который содержит дополнительные подвижные лопатки, регулирующие поток отработанных газов на низких и на высоких оборотах двигателя; используют параллельную установку ТРК, применяют сдвоенные ТРК, турбокомпаунд; используют современные материалы – керамику. При работе двигателя внутреннего сгорания ТРК выходят из строя. Рассмотрены неисправные узлы, проведён анализ причин выхода из строя турбин и разработан ряд мероприятий, придерживаясь которых можно продлить срок службы ТРК или выработать тот срок службы, который был заложен заводом-изготовителем. К основным причинам выхода из строя ТРК можно отнести следующие: недостаток масла, попадание посторонних предметов в ТРК, загрязнённое масло, попадание абразива через воздушный фильтр. Для устранения указанных причин рекомендуется выполнять своевременную замену масла с масляным фильтром; выполнять своевременную замену воздушного фильтра; использовать только качественное масло, соответствующее виду топлива и рекомендованное для турбин; использовать турботаймер или после поездки выключать двигатель транспортного средства не сразу, а дав поработать ему на холостых оборотах, чтобы охладилась турбина и снизилось число оборотов вращения вала ТРК. The issues of use of turbo-compressors (TC), manufacturers of TC, operation principle, ways of improvement, causes of failures are considered. The work of the TC is being improved by engineers around the world, the main task being to extend the service life of the TC and increase the efficiency of the TC. The principle of the TC operation is that the energy for rotation of the TC shaft is received from the exhaust gases acting on the hot volute located on the same shaft as the cold volute, which pumps air into the inlet manifold. TC is improved in the following ways: reduce the size and increase the rotation speed of the TC shaft; add control (electronic, mechanical) of the pressure relief valve; use a turbine with a variable area and a rotor, which includes additional movable vanes that control the flow of exhaust gases at low and high engine speeds; use a parallel TC installation, use dual TC, a turbocompound; use modern materials – ceramics. During operation of the internal combustion engine the TC fails. The faulty units were considered, the causes of turbine failure were analyzed and a number of measures were developed, adhering to which it is possible to extend the service life of the TC or develop the service life that was laid down by the manufacturer. The main reasons for the failure of the TC include the following: lack of oil, ingress of foreign objects into the TC, contaminated oil, ingress of abrasive material through the air filter. To eliminate these reasons, it is recommended to perform timely replacement of oil with oil filter; perform timely replacement of air filter; use only the quality oil corresponding to the type of fuel and recommended for turbines; use a turbo timer or after the trip turn off the vehicle engine not immediately, but by letting it work at idle speed so that the turbine cools and the rate speed of the TC shaft rotation decreases.

Turbo pump is one of the elements with the most complex flow of liquid rocket engine, and as an important component of turbo pump, an impeller is the weak point affecting its reliability. In this study, a noncontact modal characteristic identification technique was proposed for the liquid oxygen pump impeller. Modal characteristics of the impeller under three different submerged media, air, pure water, and brine with same density as liquid oxygen, were tested based on the noncontact modal identification technology. Submersion state directly affects the modal frequencies and damping ratio. The transient vibration response characteristics of the impeller excited by the unsteady flow field was achieved combining with unsteady flow field analysis and transient dynamic analysis in the whole flow passage of the liquid oxygen pump. Vibration responses at different positions of the impeller show 10X and 20X frequencies, and the amplitude at the root of short blade is significant, which needs to be paid more attention in structural design and fatigue evaluation.

This article presents a concatenated Bahl–Cocke–Jelinek–Raviv (BCJR) detector, low-density parity-check (LDPC) decoder, and deep neural network (DNN) architecture for a turbo-detection system for 1-D and 2-D magnetic recording (1DMR and TDMR). The input readings first are fed to a partial response (PR) equalizer. Two types of the equalizer are investigated: a linear filter equalizer with a 1-D/2-D PR target and a convolutional neural network (CNN) PR equalizer that is proposed in this work. The equalized inputs are passed to the BCJR to generate the log-likelihood-ratio (LLR) outputs. We input the BCJR LLRs to a CNN noise predictor to predict the signal-dependent media noise. Two different CNN interfaces with the channel decoder are evaluated for TDMR. Then, the second pass of the BCJR is provided with the estimated media noise, and it feeds its output to the LDPC decoder. The system exchanges LLRs between BCJR, LDPC, and CNN iteratively to achieve higher areal density. The simulation results are performed on a grain flipping probabilistic (GFP) model with 11.4 Teragrains per square inch (Tg/in2). For the GFP data with 18 nm track pitch (TP) and 11 nm bit length (BL), the proposed method for TDMR achieves 27.78% areal density gain over the 1-D pattern-dependent noise prediction (PDNP). The presented BCJR-LDPC-CNN turbo-detection system obtains 3.877 Terabits per square inch (T/bin2) areal density for 11.4 Tg/in2 GFP model data, which is among the highest areal densities reported to date.

In this paper, we consider iterative detection and decoding (i.e., turbo equalization) for nonbinary low-density parity-check (LDPC) coded partial-response channels, where a quantizer is present to discretize the continuous received signal. We propose a turbo equalizer that uses the pre-computed quantized channel transition probabilities in the symbol-level BCJR channel detection algorithm, which significantly reduces the computational complexity by avoiding real-time floating-point multiplications. The proposed approach is further extended to nonbinary LDPC coded bit-patterned media recording (BPMR) channels. Simulation results show that with a small number of quantization bits, the proposed receiver approaches closely the performance of the conventional turbo equalizer operating on unquantized signals.

This work concerns the receiver design for light emitting diode (LED) communications, where the LED nonlinearity can severely degrade the system performance. The LED nonlinearity makes high speed LED communications more challenging when it is time-varying (e.g., due to temperature drifting) and/or combined with time-varying channels (due to the relative movement between the transmitter and the receiver). In this work, we use adaptive neural network techniques to address this issue. We first propose a new adaptive extreme learning machine (AELM) with a variable forgetting factor for adaptive learning in dynamic scenarios. Then, an AELM based (turbo) receiver is designed to handle the time-varying LED nonlinearity and memory effects jointly. It is demonstrated that the proposed AELM based receiver can efficiently mitigate the dynamic nonlinearity and memory effects, and outperform the state-of-the-art adaptive techniques significantly.

Since their introduction in the late 1990s, basic turbo roundabouts have made a great success in several European countries. Researchers, however, have been unable to reach a general consensus on the operational performance advantages and benefits derived from such a novel design of multi-lane roundabouts, as compared with conventional double-lane roundabouts. Those contradictory results could be mostly attributed to wide variations in driver behavior among different traffic environments. This study aims to analyze and evaluate the operational performance of an existing, congested double-lane roundabout in the State of Florida and a proposed, simulated basic turbo roundabout. Local field data was used to accurately calibrate and validate the microsimulation models and to precisely capture local driving behavior. Three scenarios were created for evaluation. Results indicated that basic turbo roundabouts with regulatory entry speed as per Dutch standards, that is, 25 mph, were the most suitable alternative to reduce average delay and provide comparable capacity to double-lane conventional roundabouts for traffic flow ranging between 4,350 and 6,050 vehicles per hour. However, double-lane conventional roundabouts, including their major and minor approaches, always managed to process significantly more vehicles.

Bit-Patterned Magnetic Recording (BPMR) is one of the emerging data storage technologies, which promises an Areal Density (AD) of about 4 Tb/in2. However, a major problem practically encountered in a BPMR system is Inter-Track Interference (ITI) that can deteriorate the overall system performance, especially at high ADs. This paper proposes an iterative ITI cancellation method for an m-head m-track BPMR system, which uses m heads to read m adjacent tracks and decodes them simultaneously. To cancel the ITI, we subtract the weighted readback signals of adjacent tracks, acting as the ITI signals, from the readback signal of the target track, before passing the refined readback signal to a turbo decoder. Then, the decoded data will be employed to reconstruct the ITI signal for the next turbo iteration. Experimental results indicate that the proposed system performs better than the conventional system that uses one head to read one data track. Furthermore, we also find out that the proposed system is more robust to media noise and track misregistration than the conventional system.

In journal bearings the misalignment of the journal and sleeve axis causes a load concentration on their edges, mixed lubrication conditions, an increase in the bearing temperature, rotor instability, and intensive wear of mating parts. The rotating machines are controlled by means of the temperature and vibration transducers, which are placed in the middle plain of the bearing housing. This arrangement of transducers gives no information about the real distance between the journal surface and bearing edges, and, in case of misaligned shaft, it has crucial meaning for the correct operation of turbo unit. This paper presents the theoretical and some experimental results of turbo unit journal bearing operating in misaligned conditions. The results point out the necessity of the precise control of the lubricating gap and the temperature generated on the bearing edges. It was also found that the increase in misalignment also generates an increase in power loss.

The article investigates the significance of the ‘turbo’ imagery that Dante adds at the end of Ulysses’s tale (Inferno xxvi) as a possible key to decoding the nature of this character’s sin. It arg...

The blades of axial turbomachines (steam and gas turbines, axial compressors) are highly stressed by centrifugal force, temperature, and alternating fluid forces, which leads to vibrations and fatigue cracking. This requires the studious engagement of designers and technologists. In this paper, a procedure for accelerated fatigue testing of a gas turbine compressor blade based on the modified Locati method is presented. The tests were performed on a vibration shaker with the frequency that equal the blade’s first natural frequency. S-N curves were estimated according to two approximate representation namely one-slope and two-slope models. Then, the blades were tested at different stress levels starting at a level below foreseen fatigue strength at the specified fatigue life. In each loading block, a blade was subjected to 2ˑ107 cycles. After the first block was completed, the stress level in the second loading block was increased by 20 MPa and a new 2ˑ107 cycles were applied. A procedure was repeated until the blade failure occurred. It was considered that a blade has failed when its natural frequency drops by more than 2%. After the failure, the fatigue strength was calculated using Palmgren -Miner rule.

The conventional multicarrier faster-than-Nyquist (MFTN) achieves the spectral efficiency (SE) gain by deep compression. However, deep compression leads to severe intersymbol interference (ISI) or intercarrier interference (ICI). We propose the MFTN based on efficient implementation and probabilistic amplitude shaping (PAS) to achieve the SE gain with low complexity. We use mild compression instead of conventional deep compression to achieve the compression gain. The MFTN transceiver with the mild compression can be efficiently implemented by fast Fourier transform (FFT)/inverse FFT (IFFT) and filtering operation. The linear pre-equalization (LPE) method eliminates the ISI for mild compression. The MFTN with efficient implementation employs PAS to achieve extra shaping gain. The theoretical results and simulation results show that our method can achieve better performance than the conventional FTN/MFTN with deep compression. The proposed method does not require a complex equalization algorithm and global turbo iteration so that the total complexity is reduced.

Reliable acoustic communication between submersibles and surface vessels plays a critical role in deep-sea exploration. Adaptive turbo equalization can effectively combat the selective fading of underwater acoustic channels, thereby becoming one of the enabling technologies for single-carrier deep-sea vertical acoustic communications. Existing adaptive turbo equalizer designs are usually based on a minimum-mean-squared-error criterion or a minimum-mean-absolute-error criterion. These criteria are inherently suboptimal with respect to the achievable symbol error rate (SER). In this article, an improved proportionate normalized minimum-SER (IPNMSER) algorithm is proposed for adaptive turbo equalization in deep-sea vertical acoustic communications. The proposed algorithm utilizes the minimum-SER (MSER) criterion to derive the equalizer update equations, aiming to minimize the system's SER directly. In addition, because the deep-sea vertical channel has a sparse structure, which leads to a sparse equalizer, a sparsity-aware proportionate-type approach is therefore incorporated into the framework of the MSER criterion to achieve faster convergence. To investigate the effectiveness of the proposed algorithm, we conducted a deep-sea vertical acoustic-communication experiment in the Challenger Deep of the Mariana Trench. The results demonstrated that the proposed IPNMSER algorithm can outperform a conventional normalized MSER algorithm and other well-known proportionate-type algorithms, achieving error-free detection for all data blocks over a vertical communication range of approximately 10500 m.

Underwater Acoustic Channels (UAC) have inherent sparse characteristics. The traditional adaptive equalization techniques do not utilize this feature to improve the performance. In this paper we consider the Variable Adaptive Subgradient Projection (V-ASPM) method to derive a new sparse equalization algorithm based on the Minimum Symbol Error Rate (MSER) criterion. Compared with the original MSER algorithm, our proposed scheme adds sparse matrix to the iterative formula, which can assign independent step-sizes to the equalizer taps. How to obtain such proper sparse matrix is also analyzed. On this basis, the selection scheme of the sparse matrix is obtained by combining the variable step-sizes and equalizer sparsity measure. We call the new algorithm Sparse-Control Proportional-MSER (SC-PMSER) equalizer. Finally, the proposed SC-PMSER equalizer is embedded into a turbo receiver, which perform turbo decoding, Digital Phase-Locked Loop (DPLL), time-reversal receiving and multi-reception diversity. Simulation and real-field experimental results show that the proposed algorithm has better performance in convergence speed and Bit Error Rate (BER).

We present a probabilistically shaped (PS) time-frequency-packing (TFP) wavelength-division multiplexing superchannel system employing higher order modulation (HoM) formats, with an objective to improve the spectral efficiency (SE). However, TFP systems suffer from inter-symbol interference (ISI) and/or inter-carrier interference (ICI). Additionally, the bandwidth limitations of the wavelength selective switches in the fiber link may cause severe ISI for the edge sub-channels (SCs) in a superchannel. Mitigation of such interferences is particularly challenging for HoM systems, since the implementation of the well-known turbo equalization schemes, such as the Bahl-Cocke-Jelinek-Raviv equalizer, is computationally challenging for larger constellations. In this paper, we investigate an expectation propagation based, computationally efficient, turbo decision feedback equalizer for ISI cancellation, in tandem with a parallel interference cancellation based ICI mitigation. By optimizing the parameters in the shaping and the packing dimensions, we show through our numerical results that the proposed PS-TFP superchannels enabling 1.8 Tbps data rates offer up to 1.05 dB packing gain over an unpacked system using the same modulation format, and a 1.15 dB shaping gain over an unshaped system that uses a lower modulation order to achieve the same SE.

To address the problem of the harsh time-varying multi-path interference (TMI) incurred by moving underwater acoustic communications, a joint multiple turbo equalization (JMTE) algorithm is proposed. The superimposed training scheme and the single turbo equalization have been proposed to address the issue of the TMI. To tackle the more challenging fast TMI, the symbol block has been successfully divided into the segments, and the channel correlation between (among) the segments has been established, improving the tracking performance for fast time-varying channels. When the channels sharply change, the channel correlation between (among) the segments is broken, leading to decoding failure. Therefore, we develop the JMTE algorithm with the calculational complexity of the logarithmic order per symbol, where the channel of each segment is separately estimated, so that the establishment of the channel correlation is avoided, and the corresponding separate equalization results of the segments are combined to construct a joint equalization result. Unlike the Gaussian approximate process of the input symbols of the traditional linear minimum mean square error equalization, the discrete independent random variable form of the input symbols of the JMTE algorithm is retained to avoid input information loss. The ‘separate’ channel estimates, the JMTE and decoding are iteratively operated, where based on the low-complexity diagonal-matrix message passing, the information exchange between the JMTE equalizer and the decoder is carried out to dramatically enhance the equalization performance by utilizing the encoding redundant information. Moving underwater communication experiments were done in 2021 (the communication distance was about 5.5 km, and the relative speed was about 0.5 m/s), and the experimental results verify the effectiveness of the proposed algorithm.

There is an increasing trend to liquid-propellant rocket engines which run on eco-friendly storable propellant. This trend is mostly dictated by the refusal to use traditional toxic storable propellant in many countries. The most widespread eco-friendly storable propellant is hydrogen peroxide with kerosene. Though, this propellant has a lower specific impulse in comparison with traditional liquid oxygen with kerosene. To compensate the loss of specific impulse, there is a reason to design a staged combustion engine. Evidently, the turbopump is the most complicated system in the staged combustion propulsion system. This fact makes research devoted to turbo-pumps a top priority. The paper aims to determine the influence of propellant leakage from the pump area into the turbine area and create recommendations which would allow organizing the stable operation of turbopump. As a result of turbopump staged combustion cycle testing, a conclusion had been made that leakage, which opens during the test, significantly influences the stability of turbopump operation. Depending on the amount of leakage, the turbine generated power drop was between 20 and 45%, which led to a decrease in rotation speed and outlet pressure of the pump. During the R&D process, a way of leakage influence elimination had been offered. Formulated recommendations may be used during the design process of the turbopump for staged combustion liquid propulsion systems.

In this paper is presented a method for anomalies identification that may occur in equipments operation because of the large variations, above the limits, of the process parameters. The method is developed by using statistical approach and visualization tools of the processed data. The scientific visual method is generally used to control, monitor and improve processes by removing special cause variation. The statistical process control (SPC) has an advantage over other methods, because it can be applied to any process with its emphasis on early detection and prevention of problems. The objective for this paper is to present the technique used to control and monitor the Turbo Blower equipment, from steel industry. The purpose of statistical analysis is to ensure that all processes function as accurately as possible within the tolerance limits.

Turbo codes are widely used in satellite communications. When a turbo decoder is implemented on a field-programmable gate array (FPGA) in a space platform, it will suffer single-event upsets (SEUs) that can cause failures and disrupt communications. Therefore, the protection of turbo decoders implemented on FPGAs is important. In this article, first the reliability of an SRAM-FPGA-implemented turbo decoder to SEUs on user memory and configuration memory is evaluated based on fault injection experiments. Then, based on the features of the turbo decoder and the characteristics of the failures revealed by the reliability study, a duplication with comparison (DWC) scheme is proposed for the protection of the turbo decoder. Experimental results show that the reliability of the protected turbo decoder to SEUs on user memory and configuration memory is improved by 99.4% and 95.6%, respectively. The resource usage is about $2.2\times $ that of an unprotected turbo decoder, which is significantly lower than the more than $3\times $ required by the traditional triple modular redundancy (TMR) protection. Finally, the proposed scheme is compared with another two protection schemes.

In this correspondence paper, an adaptive turbo equalizer for differential OFDM systems in underwater acoustic communications is proposed. This scheme first reconstructs the demodulation symbols using the soft information fed back from the channel decoder, and then eliminates the residual intercarrier interference (ICI) induced by estimated symbols using an adaptive turbo equalizer. Moreover, a pilot-based differential encoding method is presented to mitigate the impact of the feedback error, thereby improving the convergence of turbo equalization. Theoretical analysis and simulation results demonstrate that, the proposed equalizer outperforms the linear minimum mean-squared error (MMSE) estimation-based turbo equalizer for coherent systems in medium-to-high signal-to-noise ratio (SNR) region, while enjoys significantly reduced computational complexity, and its performance is more robust against the change of Doppler frequency.

An integrated study based on the development of road infrastructure related to transport modes is one of the main methods to reduce both social and safety and pollution impacts. In this sense, optimal planning aims to reduce the use of private vehicles and reduce pollutant emissions and accidents. In general, the most successful cities have been those where different types of interventions have been applied in an integrated way to reinforce each other. This paper aims to show the impact of the existence of innovative public transport systems, such as the bus rapid transit. In particular, an unconventional urban intersection geometry – namely, the turbo roundabout – was chosen for investigation. The assessment of pollutant emissions was analysed by traffic microsimulation with the Vissim 9 software program, comparing different geometry scenarios with or without the presence of dedicated lanes and taking into account the ascent and descent areas that are reasonably far away from the typical manoeuvres of an urban at-grade intersection.

Most Kenyans are so much concerned in the way forests are destroyed by the get rich quickly Kenyans. The wanton destruction of forests and indigenous trees has left many people wondering as to what is happening with the people especially their leaders. This wanton destruction has had big effects on the country’s environment such as drastic climatic change, which has affected farming greatly. Farming is the main occupation in Kenya that earns the country foreign currency. While this cruel destruction is going no drastic measures have been taken to instil a sense of value and education to the growing and developing children as part of discipline to preserve forests. Therefore, this paper discusses ways and means of preparing children as early as possible. This preparation is meant to help children grow with a high sense of respect towards the environment especially the preservation of forests for the benefit of mankind.

The NUMECA FINE/Turbo package was used to simulate gas-dynamic flow in a model Advanced Noise Control Fan; the calculation results were compared with experimental data. Fan tonal noise was simulated for two geometry options (14 and 13 outlet guide vanes) in FINE/Acoustics, and the calculated and experimental parameters were compared.

In the Slovak republic, there is an increase of building roundabouts in both urban and non-build-up areas. The construction of roundabouts in urban areas brings mainly calming of traffic intensity. A roundabout in non-build-up areas could be built only within certain conditions. In this paper, we have been studying a small roundabout location and its traffic characteristics in the city of Hlohovec. In some cases, a small roundabout could be very good solution for exceeded traffic flow capacity of signal controlled intersections as well as for intersections with a high number of traffic incidents. But in our case, a small roundabout is not suitable for such intensity of vehicles as we measured in transport survey. So we focused on other possibilities how to improve this current situation. We have decided to make a proposal of signal controlled intersection as well as a turbo roundabout and compare the results of traffic characteristics of each proposal. We have made several simulations of each variant of traffic situation, using transport-planning software Aimsun, and calculate average values of all recorded traffic characteristics. As inputs, we have used intensities and other basic data obtained from transport survey. Using simulations outputs of transport planning software, we have been able to compare a current state with signal controlled intersection and turbo roundabout. Traffic characteristics of turbo roundabout show significant improvements compare to signal controlled intersection, f.e. in delay time (more than 68 %), travel time (more than 22 %), number of stops (more than 73 %). Turbo roundabout seems to be the best solution for traffic organising at this chosen intersection in the city of Hlohovec, regarding travel time, delays, number of stops and safety at all.

Big data analytics are practiced in many fields to extract insights from massive amounts of data. With exponential growth in both the volume and variety of data, analytic queries have expanded from those executed in a single datacenter to those requiring inputs from multiple datacenters that are geographically separate or even globally distributed. Unfortunately, the software stack that supports data analytics is designed originally for a cluster environment and is not tailored to execute global analytic queries, where resources such as inter-datacenter networks may vary on the fly. Existing optimization strategies that determine the query execution plan before its execution are not able to adapt to resource variations at query runtime. In this article, we present Turbo, a lightweight and non-intrusive global analytics system that can dynamically adjust query execution plans for geo-distributed analytics in the presence of time-varying resources and network bandwidth across datacenters. Turbo uses machine learning to accurately predict the time cost of a query execution plan so that dynamic adjustments can be made to it when necessary. Turbo is non-intrusive in the sense that it does not require modifications to the existing software stack for data analytics. We have implemented a real-world prototype of Turbo, and evaluated it on a cluster of 33 instances across eight regions in the Google Cloud Platform. Our experimental results have shown that Turbo can achieve an accuracy of 95 percent for estimating time costs, and can reduce the query completion time by 41 percent.

The article discusses the results of diagnostics-in-place of the reduction gear of the main turbo-gear unit (MTGU) of the Sevmorput LASH carrier. The main characteristics and a brief description of the MTGU design are given. The constructive arrangement of the MTGU project684 OM5 has been illustrated. There are substantiated the methods that can be used for diagnostics-in-place of the turbo-gear units: monitoring vibration levels on bearing housings and comparing them with the results of the previous measurement, comparing the third-octave vibration velocity spectra in the frequency band up to 500 Hz between the power flows of the sides and with the norms of the Russian Maritime Register of Shipping, monitoring the temperature of the bearing assemblies of the gearbox, etc. Choosing the in-situ diagnosis method for the MTGU is determined by the specific features of its design. The diagnostics results are provided. Vibration control was carried out twice: in 1995, on sea trials, and in 2006, during a ship’s voyage to the port of Dudinka under normal running conditions. It was noted that the difference in vibration levels is insignificant; the scatter of values in 2006 appears smaller than in 1995. Changes in the values of temperatures and vibration levels of bearing assemblies during measurement in 2006 were caused by different power modes, compared to measurement made in 1995. The MTGU project 684 OM5 has been approved for further operation after agreeing on the measurement results with the manufacturer of Kirovsky Zavod Production Association. It has been inferred that determining the technical condition of such complex objects by methods of diagnostics-in-place is possible.

This study aimed to investigate the effect of geometric characteristics and traffic scenarios on the performance measures, including delay, volume to capacity (v/c) ratio, capacity, and the level o...

The flow in a four-stage axial compressor is investigated by numerical modeling using the Numeca FINE/Turbo software. A few approaches to modeling the rotor-stator interaction are considered: the steady statement with the use of the Mixing Plane boundary condition, the fully unsteady statement (URANS), and the non-linear harmonic (NLH) method. These approaches are compared by considering the time-averaged and instantaneous integral parameters of the compressor and the pulsations of local parameters.

In many applications in wireless communications, we need to recover a structured sparse signal from a linear measurement model with uncertain sensing matrix. There are two challenges of designing an algorithm framework for this problem. How to choose a flexible yet tractable sparse prior to capture different structured sparsities in specific applications? How to handle a sensing matrix with uncertain parameters and possibly correlated entries? As will be explained in the introduction, existing common methods in compressive sensing (CS), such as approximate message passing (AMP) and variational Bayesian inference (VBI), may not work well. To better address this problem, we propose a novel Turbo-VBI algorithm framework, in which a three-layer hierarchical structured (3LHS) sparse prior model is proposed to capture various structured sparsities that may occur in practice. By combining the message passing and VBI approaches via the turbo framework, the proposed Turbo-VBI algorithm is able to fully exploit the structured sparsity (as captured by the 3LHS sparse prior) for robust recovery of structured sparse signals under an uncertain sensing matrix. Finally, we apply the Turbo-VBI framework to solve two application problems in wireless communications and demonstrate its significant gain over the state-of-art CS algorithms.

Hybrid turbo equalization is a novel and effective approach for communication systems as it can benefit from two turbo equalizers at different stages of iterative process. Despite its notable potential for performance improvement, hybrid turbo equalization has rarely been validated experimentally and its feasibility in underwater acoustic communications is presently not well understood. In this paper, a hybrid frequency–time domain turbo equalizer (FTD-TEQ) is proposed for underwater acoustic communications with comprehensive experimental investigations. In contrast to the traditional direct-adaptation-based turbo equalizers (DA-TEQs), which use one type of turbo equalizer for all iterations and may suffer from slow-convergence problem, the FTD-TEQ employs the frequency-domain channel-estimation-based turbo equalizer in the first iteration to provide a good initialization and utilizes the time-domain DA-TEQ in the subsequent iterations to maintain low-complexity implementation, aiming at benefiting from both turbo equalizers without incurring high computational burden. In the meantime, the high-quality soft-decision symbols and the relatively optimal initialization of the filter coefficients derived from the first iteration can be delivered to the next iteration, so as to improve symbol detection performance in the bottleneck region and achieve faster convergence rate. The effectiveness of this hybrid equalization mechanism has been well interpreted by numerical simulations, and also has been verified through an undersea communication experiment with high-order 8-phase shift keying modulation and 16-quadrature amplitude modulation. The results demonstrate that the FTD-TEQ not only shows more excellent performance, but also has lower computational complexity than the traditional DA-TEQ for the experimental data configuration.

With significant interest in the use of high-temperature superconducting (HTS) components in electric aircraft, there is a need for novel modelling techniques that allow architecture-level studies of the electrical systems including HTS components. In this study, a simple electric network architecture, as proposed in the literature has been considered, which includes generators, dynamic propulsion load and cables. This electric network has been modelled considering conventional technology and using HTS cables by replacing the conventional copper cables, to evaluate the variations in the network performance. The network performance has been studied for the dynamically varying propulsion load, which is nearly equivalent to the aircraft load over the entire flight duration. Following this, electric faults have been applied at various locations, and the impact of HTS cables on the network fault levels has been evaluated. The fault current levels are compared using both conventional and HTS cables, due to the fault current limiting properties of the HTS cables, they are observed to offer lowered fault current values.

Compressed sensing (CS) is becoming a hot topic in recent years for its advantages such as low-power consumption, low memory requirement, and low sampling frequency. However, high-dimensional nonlinear signals will inevitably introduce notable complexity and low efficiency in signal recovery. Generalized turbo signal recovery (G-Turbo-SR) is a cutting-edge method, which efficiently reduces complexity with a partial discrete Fourier transform (DFT) sensing matrix. However, in practical applications, G-Turbo-SR still suffers from high complexity for probability computations and matrix multiplications. This article optimizes the algorithm of G-Turbo-SR in scheduling to reduce the matrix multiplications by half. High-precision numerical approximation method is proposed to replace the complex integral calculation, which efficiently reduces the hardware cost with acceptable performance degradation. Based on the data-flow graph (DFG) analysis, detailed hardware architecture is proposed with module designs. Proper quantization scheme is selected according to the mean square error (MSE) performance. Pipelining, folding, and variable precision quantization (VPQ) scheme are employed for higher hardware efficiency. FPGA implementation on Xilinx 7k325tffg900-2 shows a higher throughput and hardware efficiency compared to existing recovery methods for CS.

Two-stage turbocharging technology is a solution to reduce turbo lag and improve the performance of engine and matching characteristics at high altitudes. In the present study, an engine testing system was established to study combustion performance and matching characteristics of a regulated two-stage turbocharging system (R2S) at different simulated altitudes. An equivalent turbocharger concept was put forward aiming to simplify the R2S with three bypass valves, and the total equivalent turbine flow area and equivalent efficiency of the R2S were obtained based on a theoretical study. Intake characteristics, combustion process, torque, power and fuel economy of the diesel engine matched with R2S were analyzed at different altitudes. The results showed that compared with 0 m, intake pressure, maximum combustion pressure, cumulative heat release, heat release rate decreased by 36.5%, 33.6%, 33.5%, 21.6%, −8.9% at 4000 r/min, and decreased by 12.3%, 2.9%, 16.4%, 8.8%, −5.4% at the speed of 2000 r/min at the altitude of 5000 m. The torque, fuel consumption and fuel consumption rate decreased by 10.1%, 5.1% and 5.4% at engine speed of 2000 r/min and by 35.7%, 27.6% and 8.9% at engine speed of 4000 r/min at 5000 m.

Failure of a bearing in reduction gear box of a turbo shaft engine is investigated to determine its root cause. Teardown inspections followed by metallurgical investigations are carried out on the parts of the failed bearing. Severe flaking is observed on both inner and outer race as well as on balls. It indicates progressive fatigue due to overload. Insufficient clearance due to differential expansion of inner race and contraction of outer race due to heating and cooling, respectively, can also result in this type of phenomena. Maintaining oil discipline and using correct grade of oil at proper frequency can address these issues. A comprehensive engine-bearing prognostic approach may be followed utilizing available sensor information on-board the aircraft to predict bearing life and incipient bearing failure.

In this work, the problem of calculating the efficiency of turbo-units of various types that are part of the equipment of electric and thermal energy sources was solved. In simplified approaches to the representation of turbine units, often used in algorithms of power system optimization programs, in order to reduce the estimated time, the dependence of the plant efficiency on the current power is ignored, the influence of the pressure in the steam extraction of cogeneration turbines to cover the heat load and the idle speed of the turbines are not taken into account. These approaches are easy to use and implement, however, they can introduce noticeable errors in the optimization results due to the lack of consideration of parameters and dependencies that occur in real equipment operation modes and significantly affect the amount of fuel used by the optimized system. In contrast to the simplified approach, energy characteristics were used in the work to determine the efficiency factors characterizing the efficiency of turbine units. This allows providing a more accurate assessment of the effectiveness in various operating modes without significantly complicating the algorithm with a slight increase in the estimated time. Using the proposed approach showed the presence of a noticeable refinement of efficiency compared to simple models and, therefore, the feasibility of representing turbine units using energy characteristics in program algorithms designed to optimize energy systems.

Both turbo Hadamard codes and concatenated zigzag Hadamard codes are ultimate-Shannonlimit-approaching channel codes. The former one requires the use of Bahl-Cocke-Jelinek-Raviv (BCJR) in the iterative decoding process, making the decoder structure more complex and limiting its throughput. The latter one, however, does not involve BCJR decoding. Hence its decoder structure can be much simpler and can potentially operate at a much higher throughput. In this paper, we investigate the hardware design of a concatenated zigzag Hadamard encoder/decoder system and implement it onto an FPGA board. We design a decoder capable of decoding multiple codewords at the same time, and the proposed system can operate with a throughput of 1.44 Gbps - an increase of 50% compared with the turbo Hadamard encoder/decoder system. As for the error performance, the encoder/decoder system with a 6-bit quantization achieves a bit error rate of 2 × 10-5 at Eb/N0 = -0.2 dB.