Start Stop Research Articles

Gene-Indexed Mutations in Maize

The availability of the B73 inbred reference genome sets the stage for high-throughput functional characterization of maize genes on a whole-genome scale. Among the 39 324 protein-coding genes predicted, the vast majority are untapped due to the lack of suitable high-throughput reverse genetic resources. We have generated a gene-indexed maize mutant collection through ethyl methanesulfonate mutagenesis and detected the mutations by combining exome capture and next-generation sequencing. A total of 1086 mutated M1 plants were sequenced, and 195 268 CG>TA-type point mutations, including stop gain/loss, missplice, start gain/loss, and various non-synonymous protein mutations as well as 4610 InDel mutations, were identified. These mutations were distributed on 32 069 genes, representing 82% of the predicted protein-coding genes in the maize genome. We detected an average of 180 mutations per mutant line and 6.1 mutations per gene. As many as 27 214 mutations of start codons, stop codons, or missplice sites were identified in 14 101 genes, among which 6232 individual genes harbored more than two such mutations. Application of this mutant collection is exemplified by the identification of the ent-kaurene synthase gene, which encodes a key enzyme in the gibberellin biosynthesis pathway. This gene-indexed genome-wide mutation collection provides an important resource for functional analysis of maize genes and may bring desirable allelic variants for genetic breeding in maize.

Reconstruction Capabilities of Down-Looking Airborne GPRs: The Single Frequency Case

This paper addresses the problem of imaging shallow buried targets via ground penetrating radar surveys carried out by an airborne platform. The radar system is monostatic and collects scattered field data at a single frequency in down-looking mode and along parallel lines. The data are processed by means of an image formation algorithm based on a microwave tomographic approach valid under Born and start–stop approximations. The goal of the present study is to derive analytical results for the spatial resolution depending on the measurement configuration parameters. The achieved results highlight the peculiar features of the imaging configuration providing useful indications for setting a proper acquisition strategy. Numerical results based on synthetic data are shown to support the analysis of resolution limits.

Optimization of the operating conditions of gas-turbine power stations considering the effect of equipment deterioration

In recent years in most power systems all over the world, a trend towards the growing nonuniformity of energy consumption and generation schedules has been observed. The increase in the portion of renewable energy sources is one of the important challenges for many countries. The ill-predictable character of such energy sources necessitates a search for practical solutions. Presently, the most efficient method for compensating for nonuniform generation of the electric power by the renewable energy sources—predominantly by the wind and solar energy—is generation of power at conventional fossil-fuel-fired power stations. In Russia, this problem is caused by the increasing portion in the generating capacity structure of the nuclear power stations, which are most efficient when operating under basic conditions. Introduction of hydropower and pumped storage hydroelectric power plants and other energy-storage technologies does not cover the demand for load-following power capacities. Owing to a simple design, low construction costs, and a sufficiently high economic efficiency, gas turbine plants (GTPs) prove to be the most suitable for covering the nonuniform electric-demand schedules. However, when the gas turbines are operated under varying duty conditions, the lifetime of the primary thermostressed components is considerably reduced and, consequently, the repair costs increase. A method is proposed for determination of the total operating costs considering the deterioration of the gas turbine equipment under varying duty and start–stop conditions. A methodology for optimization of the loading modes for the gas turbine equipment is developed. The consideration of the lifetime component allows varying the optimal operating conditions and, in some cases, rejecting short-time stops of the gas turbine plants. The calculations performed in a wide range of varying fuel prices and capital investments per gas turbine equipment unit show that the economic effectiveness can be increased by 5–15% by varying the operating conditions and switching to the optimal operating modes. Consequently, irrespective of the fuel price, the application of the proposed method results in selection of the most beneficial operating conditions. Consideration of the lifetime expenditure included in the optimization criterion enables enhancement of the operating efficiency.

Investigation on Degradation of HT-PEM Membrane-Electrode-Assemblies for Fuel Cells Under Start-Stop-Cycling

The emphasis of this study is the investigation of high-temperature polymer electrolyte membrane fuel cells (HT-PEMFC) of various manufacturers with simulated start-stop cycles. This study is part of the national project QUALIFIX, which is funded by the German Ministry of Economy and Energy. Its purpose is to develop a framework to log, revise and improve the quality of fuel cells, its system components, as well as its manufacturing chain. Coherent test procedures enable the comparability of single fuel cells of various manufacturers. Furthermore, these framework conditions should enhance the lifetime of fuel cells, as well as minimize the production costs in an early stage. In this study all tested membrane electrode assemblies (MEAs) have been investigated under identical test conditions using simulated Start-Stop (S/S) cycles. Consequently, the MEAs have been started up under defined conditions and operated for twelve hours at a constant current density of 0.3 A/cm². Following this, the MEAs have been shut down for another twelve hours and have been allowed to cool down to room temperature. Furthermore, all MEAs have been held under a nitrogen atmosphere at 30 °C during the stop phases before the next startup procedure has been performed. Figure one presents the fuel cell voltage at 0.3 A/cm² as function of time for one examinee after 500 h, correlating to 21 S/S cycles. As a result, a continuous cell degradation rate of -33 µV/h could be observed. Next, degradation for HT-PEMFC MEAs have been evaluated by an extensive in situ electrochemical characterization, which has been executed before and after 21 S/S cycles. This characterization includes among the voltage curve, electrochemical impedance spectra, cyclic as well as linear sweep voltammetry. Additionally, all MEAs have been analyzed through ex situ characterizations, including, among others, micro computed tomography (µ-CT), analysis of product water via ion chromatography (IC), as well as the determination of the phosphoric acid content, once S/S cycling has been stopped. Simultaneously, fresh MEAs of the same batch have been tested with the same ex situ methods. This allows to determine the ‘begin of life’ (BoL) condition in a pristine state. As mentioned above, an unprecedented benchmarking of MEAs of various manufacturers has been performed with respect to HT-PEMFC degradation. Moreover, the results will be compared to the ex situ findings of the BoL-Analysis. Figure 1: Voltage as function of time of one MEA under start stop cycles for 500 hours Figure 1

Electric motor-based crankshaft stop position control to suppress range extender start vibration in electric vehicle

Range-extended electric vehicles have the most complex noise and vibration problems since certain control strategies often make range extenders (REs) shut down or restart for the sake of better fuel consumption. This paper deals with this uncomfortable riding experience, especially during the range extender start phase. A control-oriented nonlinear model for the start–stop vibration analysis, including range extender mount system, engine–clutch–motor shaft system, engine inertia torque and force, engine friction torque, engine gas torque, engine manifold pressure, electric motor torque, and range extender controller, is thus built. In the developed model, a new estimation method for gas torque is proposed, where the initial crank angle is considered and the relevant equations are simplified. The method has proven to predict gas torque accurately without using a complex calculation process. According to the developed model, the active control method, crankshaft stop position control (CSPC) has been proposed. The crankshaft stop position is analyzed as well as the crankshaft movement with different speeds at top dead center is discussed, which lead to the design of the target curves for crankshaft movement during the stop phase. Based on the set-up model, CSPC is finally applied through the cascade control of the motor to evaluate the control effectiveness. The simulation outcomes demonstrate that CSPC can help the crankshaft to finally stop at the optimal initial crank angle, which effectively lessens the vibration in the next start phase.

Propulsion control strategies for ship emergency manoeuvres

This work deals with the propulsion control aspects relating to some of the most critical emergency manoeuvres of a ship: slam start and crash stop. In these particular situations a very important role is played by the automation system that has to manage the whole propulsive chain (i.e. main engine, mechanical transmission and propeller) in a safe and efficient way. With regard to this, a simulation based design methodology is adopted to develop and test new control schemes for ship propulsion. The proposed control layout is applicable to any type of propulsion systems equipped with controllable pitch propellers, since it is mainly based on the automatic adjustment of the propeller pitch. Thus the desired performance requirements are met through adaptive control strategies able to address the complex issues of slam start, crash stop and similar stressful manoeuvres. The adaptivity of the automation process to several critical propulsive conditions reduces significantly the number of the control parameters to be estimated, as recently demonstrated by the automation design of a new twin-screw ship. For this application, the comparison between simulation results and sea trials data is finally shown for validation design purposes.

A Relation of Dominance for the Bicriterion Bus Routing Problem

Abstract A bicriterion bus routing (BBR) problem is described and analysed. The objective is to find a route from the start stop to the final stop minimizing the time and the cost of travel simultaneously. Additionally, the time of starting travel at the start stop is given. The BBR problem can be resolved using methods of graph theory. It comes down to resolving a bicriterion shortest path (BSP) problem in a multigraph with variable weights. In the paper, differences between the problem with constant weights and that with variable weights are described and analysed, with particular emphasis on properties satisfied only for the problem with variable weights and the description of the influence of dominated partial solutions on non-dominated final solutions. This paper proposes methods of estimation a dominated partial solution for the possibility of obtaining a non-dominated final solution from it. An algorithm for solving the BBR problem implementing these estimation methods is proposed and the results of experimental tests are presented.

Steam-to-carbon ratio control strategy for start-up and operation of a fuel processor

The purpose of this work is to suggest a steam-to-carbon ratio (SCR) control strategy for the start-up and operation of a fuel processor and to experimentally verify this strategy. To overcome ambient temperature variability and manufacturing deviations, a controlled SCR method (CSM) is suggested. The CSM controls the water flow rate independently through heat exchangers (HEXs) to maintain a constant inlet temperature of the reactors. To consistently satisfy the target SCR value, the remaining water after control is fed to the last HEX used as a buffer. To verify the CSM, seven gasoline fuel processors (GFPs) were constructed. The GFPs consisted of an autothermal reformer (ATR), hydrodesulphurization (HDS), a high-temperature shift reactor (HTS), a medium-temperature shift reactor (MTS), a preferential oxidation reactor (PROX), a HEX, and an exhaust gas burner. Water was individually supplied to HEX #1 ∼ HEX #4 as a cool-side fluid. One of the GFPs was operated at a low (−32 °C) and a high (50 °C) temperature. The CSM maintained a constant inlet temperature of the reactors; only the inlet temperature of the PROX was affected by the ambient temperature thanks to the CSM. Temperature results for the other six GFPs showed that manufacturing deviations appeared only in the inlet temperature of the PROX by the CSM. To confirm the effect of the CSM on durability, 38 start–stop cycles were performed over 314 h of operation. The results showed that the repeated use of the CSM led to a slow degradation of efficiency, while the temperatures of the reformer and reactor remained steady during cycling testing.

Design of the Brushless DC Motor Driving System Based on STM32

As a mechanical and electrical integration product, brushless DC motor has better controllability and wide speed range. According to its characteristics, a brushless DC motor control system based on STM32F103ZET6 MCU is designed and realized, and then the control system was analyzed and discussed. Adopted GPIO module, PWM module, timer module, etc., coupled with efficient PID algorithm, three main functions of this system have been implemented, such as start stop control, position detection and closed-loop speed regulation. The experimental results show that this control system works well with low cost and high price-performance ratio.

Wear of metals in lubricated joints operating in start–stop mode

Friction and wear regularities of the bronze-steel joint have been studied during continuous sliding and friction with recurrent start and stop periods. The test results for friction without cooling and constant temperature of the lubricating material have been compared. Under the conditions of the forced cooling of the oil, transfer from continuous to periodic sliding is accompanied by a growing coefficient of friction and the wear rate of the bronze counterbody. Under conditions without cooling and in certain loading modes, the reverse scenario is probable.

Quantifying Antimicrobial Exposure: Hazards in Populations With End-Stage Renal Disease.

Using a rigorously collected data set of antimicrobial use among patients receiving chronic hemodialysis, antimicrobial use was calculated using 3 different methodologies: daily defined dose, days of therapy, and start-stop days. Estimates of antimicrobial use varied by as much as 10-fold, depending on the type of antimicrobial. Infect Control Hosp Epidemiol 2017;38:360-363.

Sequence Analysis of Mitochondrial Genome of Toxascaris leonina from a South China Tiger.

Toxascaris leonina is a common parasitic nematode of wild mammals and has significant impacts on the protection of rare wild animals. To analyze population genetic characteristics of T. leonina from South China tiger, its mitochondrial (mt) genome was sequenced. Its complete circular mt genome was 14,277 bp in length, including 12 protein-coding genes, 22 tRNA genes, 2 rRNA genes, and 2 non-coding regions. The nucleotide composition was biased toward A and T. The most common start codon and stop codon were TTG and TAG, and 4 genes ended with an incomplete stop codon. There were 13 intergenic regions ranging 1 to 10 bp in size. Phylogenetically, T. leonina from a South China tiger was close to canine T. leonina. This study reports for the first time a complete mt genome sequence of T. leonina from the South China tiger, and provides a scientific basis for studying the genetic diversity of nematodes between different hosts.

Oxygen‐Tolerant Electrodes with Platinum‐Loaded Covalent Triazine Frameworks for the Hydrogen Oxidation Reaction

AbstractReducing the use of platinum (Pt) on polymer electrolyte fuel cell anodes is critical for the widespread dissemination of these energy conversion systems. Although Pt usage can be minimized by the even dispersion of isolated Pt atoms, no atomically dispersed Pt catalysts that promote hydrogen oxidation at a rate required for practical fuel cells have been reported to date. Covalent triazine frameworks with atomically dispersed Pt atoms (0.29 wt %) are described and it is demonstrated that the material has a high electrocatalytic hydrogen oxidation activity without an overpotential. Importantly, when the loading amount was increased to 2.8 wt %, the electrocatalytic hydrogen oxidation activity of the resulting electrode was comparable to that of commercial carbon supported 20 wt % Pt catalysts, and the catalytic activity for oxygen reduction was markedly reduced. Thus, Pt‐modified covalent triazine frameworks selectively catalyze hydrogen oxidation, even in the presence of dissolved oxygen, which is critical for limiting cathode degradation during the start–stop cycles of fuel cells.

Integration of Start–Stop Mechanism to Improve Maximum Power Point Tracking Performance in Steady State

Maximum power point tracking (MPPT) is important in photovoltaic systems for effective solar energy harvesting. One of the most popular MPPT techniques is the widely adapted perturb and observe (P&O) method owing to its simple and low-cost implementation. The downside is that the steady-state performance is compromised by the inherent perturbation. The magnitude of the steady-state oscillation can be lessened by reducing the perturbation size. However, the approach slows down the tracking speed during rapidly changing atmospheric conditions. Thus, the selection of perturbation value becomes difficult since it always involves the tradeoff between the tracking speed and steady-state ripple. This paper proposes a novel start–stop mechanism to eliminate the compromise of the traditional P&O MPPT method. Thanks to the advantages of simplicity and ease of implementation, the mechanism targets the MPPT solution for submodule integrated converters, which demand for a low-cost solution. The experimental evaluation of the proposed algorithm is compared with the benchmark P&O algorithm showing the claimed advantages.

The Performance of PS400 Subjected to Sliding Contact at Temperatures from 260 to 927°C

ABSTRACTAdequate high-temperature lubrication between loaded surfaces in sliding contact can be one of the most challenging tribological problems confronting today's designers. In an attempt to provide a possible solution a test program was initiated to evaluate PS400, a recently patented, high-temperature solid lubricant coating. Made from nickel–molybdenum–aluminum, chrome oxide, silver, and barium fluoride–calcium fluoride, PS400 is a variant of the earlier coating, PS304, but is formulated for higher density, smoother surface texture, and greater dimensional stability. It was initially developed to minimize the start–stop wear in foil air bearings but is expected to perform well in other high-temperature applications where sliding friction and wear are a concern, such as variable inlet guide vanes and process control valve stems. To better define its operational capabilities, a series of tests was conducted to study the behavior of PS400 under reciprocating sliding contact at temperatures from 260 to 927°C. The tests were performed on stationary, uncoated cobalt-based superalloy bushings loaded against reciprocating PS400-coated shaft specimens in a flat-on-cylinder configuration at Hertz contact pressures from 14.1 to 20.1 MPa. For tests conducted below 927°C, friction coefficients ranged from 0.37 to 0.84 with wear factors on the order of 10−5 and 10−6 at the high temperatures but substantially increased at the lowest temperature. Data collected at 927°C were limited because the coating was found to be dimensionally unstable at this temperature.

Life cycle evaluation of an intercooled gas turbine plant used in conjunction with renewable energy

The life cycle estimation of power plants is important for gas turbine operators. With the introduction of wind energy into the grid, gas turbine operators now operate their plants in Load–Following modes as back-ups to the renewable energy sources which include wind, solar, etc. The motive behind this study is to look at how much life is consumed when an intercooled power plant with 100MW power output is used in conjunction with wind energy. This operation causes fluctuations because the wind energy is unpredictable and overtime causes adverse effects on the life of the plant – The High Pressure Turbine Blades. Such fluctuations give rise to low cycle fatigue and creep failure of the blades depending on the operating regime used. A performance based model that is capable of estimating the life consumed of an intercooled power plant has been developed. The model has the capability of estimating the life consumed based on seasonal power demands and operations. An in-depth comparison was undertaken on the life consumed during the seasons of operation and arrives at the conclusion that during summer, the creep and low cycle life is consumed higher than the rest periods. A comparison was also made to determine the life consumed between Load–Following and stop/start operating scenarios. It was also observed that daily creep life consumption in summer was higher than the winter period in-spite of having lower average daily operating hours in a Start–Stop operating scenario.

Influences of the fuel injection parameters on the first-cycle firing and the combustion characteristics during the direct-start process for a gasoline direct-injection engine

The direct-start method without requiring a starter is a viable and cost-effective solution for generating a frequent and efficient restarting process when start–stop technology is used on a gasoline direct-injection engine. During the direct-start process, the first-cycle combustion characteristics play a key role in determining whether the start mode is successful or not, because the start energy is wholly derived from the in-cylinder combustion without the support of a starter motor on the gasoline direct-injection engine. However, the first-cycle fuel–air mixing and combustion characteristics during the direct-start process of a gasoline direct-injection engine are not fully understood. In this work, the influences of the injection parameters, including the delay between the injection and ignition, the excess air ratio for the single-injection strategy, the delay between the first injection and the second injection for the dual-injection strategy and the ratio of the fuel mass in the first injection to the fuel mass in the second injection for the dual-injection strategy, on the combustion pressure, the heat release rate, the accumulated heat release and the indicated work were investigated experimentally by cycle-by-cycle analysis. The results show that the optimal delay between the injection and ignition of the single-injection strategy was 200 ms as a longer delay or a shorter delay can result in a reduction in the heat released rate, the indicated work and the firing boundary. A shorter delay with the optimal injected fuel mass tended to be more beneficial to the accumulated heat released, the indicated work and the crankshaft speed. Furthermore, with increasing delay and increasing fuel ratio of the fuel mass in the first injection to the fuel mass in the second injection for the dual-injection strategy, the heat release rate, the accumulated heat release and the indicated work first increased and then decreased. The optimum delay was 10 ms and the ratios of the fuel mass in the first injection to the fuel mass in the second injection were 4/1 and 5/1 respectively under the test conditions. Additionally, the dual-injection strategy with an optimized control parameter produced a higher heat release and higher indicated work than the single-injection strategy did.

Characterization of Posterior Glenoid Bone Loss

Objectives:The purpose of this study was to characterize the morphology and location of posterior glenoid bone loss in pat ients with posterior instability instability utilizing computed tomography (CT).Methods:Clinical data was selected for patients with posterior shoulder instability that had undergone posterior stabilization (open or arthroscopic) or posterior osseous augmentation (distal tibia or iliac crest). Three fellowship-trained surgeons from two institutions contributed patients. Pre-operative CT data was collected for all patients. The axial cuts were segmented and reformatted in three-dimensions for glenoid analysis using Osirix. From this three-dimensional model, the following was calculated: percent bone loss (Nobuhara), total arc of the defect (degrees), and a clock-face description (start point, stop point, and average or direction). Pearson correlation coefficients were performed using significance of p<0.05.Results:Fifty shoulders from 50 patients were reviewed. Fourteen patients (average age 30 years; 93% male) had evidence of posterior glenoid bone loss and were included for evaluation. Defects on average involved 13.7±8.6% of the glenoid (range, 2-35%). The average start time (assuming all right shoulders) on the clock face was 10 o’clock ± 40 minutes and stopped at 6:30 ± 25 minutes. The average direction of the defect pointed toward 8:15 ± 25 minutes. The percent bone loss correlated with the total arc of the defect (Pearson: 0.93, p<0.05, R2: 0.86) and the direction of the bone loss (Pearson: 0.64, p<0.05, R2: 0.40). The direction of bone loss significantly moved more posterosuperior the larger the defect became (Pearson: 0.63, p<0.05, R2: 0.40).Conclusion:Posterior bone loss associated with posterior glenohumeral instability is typically directed posteriorly at 8:15 on the clock. As defect get bigger, this direction moves more posterosuperior. This information will help guide clinicians in understanding the typical location of posterior bone loss aiding in diagnosis, cadaveric models, and treatment.

Non-lane-discipline-based car-following model considering the effect of visual angle

This study proposes a new car-following (CF) model considering the effect of visual angle under the non-lane-discipline environment. In particular, a car-following model is proposed to capture the impacts from the visual angle of the driver between the following vehicle and the preceding vehicle as well as its change rate on a road without lane discipline. Stability analysis of the proposed CF model is performed using the perturbation method to obtain the stability condition. Numerical experiments analyze three scenarios: start process, stop process, and evolution process for lane-discipline-based FVD model, non-lane-discipline-based CF model with lateral gap, and the proposed model, respectively. Results from numerical experiments illustrate that the proposed CF model that considers the effects of both lateral gap and visual angle has larger stable region compared with FVD model and the NLBCF model. Also, the responsiveness and smoothness of the proposed CF model is improved with respect to the velocity, and acceleration or deceleration profiles.

Wear characteristics of commercial gas turbine components

Wear is one of the common degradations in a commercial gas turbine. A stainless steel grade 304 (SS 304) fuel nozzle and its collar made of nickel-based superalloy (Hastelloy X) are two vital components that normally suffer from rapid wear. During an installation, the fuel nozzle is slotted into the collar of the combustion liner. In operation, these two surfaces are subjected to high pressure from the fuel combustion, hence continuously rubbing against each other causes vibrations. During the start–stop operation, these surfaces had undergone a large relative motion. The vibration is the main cause of the wear occurrence on the surfaces. Physical properties of the worn surfaces were obtained through visual observations: wear measurement, hardness and microstructure examination. Through visual observations, fretting wear was mainly suspected as the dominant wear mode, particularly after 8,000 of running hours at high temperature and vibration. In short, this paper discusses the preliminary findings of wear on the fuel nozzle and its collar. It also discusses the changes in the mechanical properties before and after the operation. Solutions for mitigating the problem were discussed.