Average modeling of Single Stage Flyback PFC ＋ Flyback DC／DC converter

With the use of this novel average model for Single Stage Flyback PFC+Flyback DC/DC converter, voltage control mode, peak current control mode and average current control mode can be simulated easily by changing the model's parameters. It can be used to do various analysis not only for small signal and static behavior but also for large signal and dynamic behavior of the converter. By using this average model the simulation speed can be improved by 2 orders of magnitude above that obtained by using the conventional switched model. It can be applied to optimize the trade\|off between high power factor, voltage stress, current stress and good output performance while designing this kind of single stage PFC converter. A 60W single stage power factor corrector was built to verify the proposed model. The modeling principle can be applied to other Single Stage PFC topologies.

Sequential Extraction of Natural Surface Coatings: Comparison with Single Stage Extraction and Its Application in Investigating Adsorption Characteristics of Surface Coating Components for Metals

Multistage sequential extraction with different sequences was applied to extracting natural surface coa tings（NSCs）, and the results were compared with those by single stage extraction technique. The optimal sequential extraction scheme with the best performance was selected and incorporated into the method of selective extraction followed by adsorption and statistic analyses to study the adsorption parameters of Fe oxides, Mn oxides and organic matters in NSCs for Pb and Cd, to validate the applicability of the sequential extraction scheme. The Langmuir ad sorption parameters of each component of surface coating estimated according to the adsorption data of single stage extraction of NSCs were all similar to those of sequential extraction of NSCs, and the maximum difference between the metal adsorption abilities of the components estimated via the two extraction techniques was only about 20%, in dicating that either extraction techniques could be used. The optimal sequential extraction scheme obtained was first extracted with NH2OH·HCl, then with Na2S2O4, and finally with oxalic acid.

Systematic review of single stage revision for prosthetic joint infection

While advanced technology,increased medical knowledge and improved surgical technique has improved patient outcomes in total joint arthroplasty,prosthetic joint infection still remains one of the leading causes of increased healthcare costs,medical resources and societal burdens in orthopaedic care.Two stage arthroplasty revision remains the gold standard for treatment of prosthetic joint infection.Proponents of single stage revision arthroplasty for infection argue that it results in lower healthcare costs while improving patient reported functional outcomes and with equivalent success rates.Here we review the history of single stage revision arthroplasty,discuss the key principles,highlight the indications and contraindications,and review the reported outcomes with a focus on future developments of single stage revision arthroplasty for hip and knee periprosthetic joint infections.

Design and Optimization of a Single Stage Centrifugal Compressor for a Solar Dish-Brayton System

According to the requirements of a solar dish-Brayton system,a centrifugal compressor stage with a minimum total pressure ratio of 5,an adiabatic efficiency above 75% and a surge margin more than 12% needs to be designed.A single stage,which consists of impeller,radial vaned diffuser,90° crossover and two rows of axial stators,was chosen to satisfy this system.To achieve the stage performance,an impeller with a 6:1 total pressure ratio and an adiabatic efficiency of 90% was designed and its preliminary geometry came from an in-house one-dimensional program.Radial vaned diffuser was applied downstream of the impeller.Two rows of axial stators after 90° crossover were added to guide the flow into axial direction.Since jet-wake flow,shockwave and boundary layer separation coexisted in the impeller-diffuser region,optimization on the radius ratio of radial diffuser vane inlet to impeller exit,diffuser vane inlet blade angle and number of diffuser vanes was carried out at design point.Finally,an optimized centrifugal compressor stage fulfilled the high expectations and presented proper performance.Numerical simulation showed that at design point the stage adiabatic efficiency was 79.93% and the total pressure ratio was 5.6.The surge margin was 15%.The performance map including 80%,90% and 100% design speed was also presented.

S4Net: Single stage salient-instance segmentation

In this paper, we consider salient instance segmentation. As well as producing bounding boxes,our network also outputs high-quality instance-level segments as initial selections to indicate the regions of interest. Taking into account the category-independent property of each target, we design a single stage salient instance segmentation framework, with a novel segmentation branch. Our new branch regards not only local context inside each detection window but also the surrounding context, enabling us to distinguish instances in the same scope even with partial occlusion.Our network is end-to-end trainable and is fast(running at 40 fps for images with resolution 320 × 320). We evaluate our approach on a publicly available benchmark and show that it outperforms alternative solutions. We also provide a thorough analysis of our design choices to help readers better understand the function of each part of our network. Source code can be found at https://github.com/Ruochen Fan/S4 Net.

Temperature and Concentration Fields in a Generator Integrated to Single Stage Heat Transformer Using Water/Carrol Mixture

The generator is the starter device of single stage heat transformer(SSHT) and its characteristics have main effects on the overall efficiency of this kind of absorption machines.This article reports a study of the generation of steam and changes in the concentration of the working solution(Water/Carrol mixture) into a plate heat exchanger as a function of its horizontal and vertical position by gravity effect.It is considered the analysis of six experimental tests;two were evaluated in a plate heat exchanger in a horizontal position and four in a vertical position(90 degree inclination).The generation of steam and increased concentration of the working solution are more sensitive to the vertical position of exchanger than in horizontal position.The results of numerical-experimental analysis indicates that a heat exchanger in horizontal position,the steam generation and the change in the concentration of the working solution occurring in the middle of the plate(or at greater distance depending to the thermodynamic conditions) and instantly in vertical position(at the input of the plate).

Isolated single stage high power factor AC/DC converter

The problem of harmonic pollution has brought wide attention with the increase of power customers. The adoption of the technology of active power factor correction (APFC) with advanced high frequency power converter is a more efficient solution to the problem of harmonic pollution. A single stage isolated high power factor AC/DC converter, which features wide range DC output, high power factor, lower harmonic pollution in input current, and phase shift PWM full bridge circuit can achieve soft switching. The principle of the circuit topology and the reasons of voltage surges across the power switch are analyzed. Experiment results illustrate that this circuit has the advantages of high power factor and lower harmonic distortion.

Single-stage active clamp power factor correction AC/DC converter

A simple single-stage AC/DC converter circuit with active clamp is presented. The operation theory and state are analyzed. The experimental results show that the voltage across main switch can be clamped to a certain value,and zero voltage switching (ZVS) can be achieved. The voltage stress and switching loss are both decreased. In range of the whole load,power factors can be always more than 97%,and the highest efficiency can reach 88%.

Single-Stage Repair of a Critical Aortic Coarctation, a Bicuspid Aortic Stenosis and an Ascending Aortic Aneurysm

We report a 26-year-old man with critical aortic coarctation, severe bicuspid aortic valve stenosis, infective endocarditis and ascending aortic aneurysm. He underwent simultaneously in singlestage a Bentall’s procedure and an extra-anatomic ascending-descending aortic bypass grafting by 14-mm Dacron tube, through median sternotomy. The immediate postoperative outcome was favourable. The CT scan control for 7 years after surgery showed a good patency of the extra-anatomic bypass.

COMMINUTION CIRCUIT FOR LARGE CONCENTRATOR

This paper provides a summary of the current comminution circuit and its development trend,focusing the discussion on the comminution circuit selection for the No.3 concentrator with 60000 t/d througput in the Dexing Copper Mine.Based on the large amount of information and data on autogenous grinding tests and conventional grinding practices in the Dexing Copper Mine,the comparison results for various comminution circuits as well as the authors suggestions for the comminution system are presented.

Approximation-Exact Penalty Function Method for Solving a Class of Stochastic Programming

We present an approximation-exact penalty function method for solving the single stage stochastic programming problem with continuous random variable. The original problem is transformed into a determinate nonlinear programming problem with a discrete random variable sequence, which is obtained by some discrete method. We construct an exact penalty function and obtain an unconstrained optimization. It avoids the difficulty in solution by the rapid growing of the number of constraints for discrete precision. Under lenient conditions, we prove the equivalence of the minimum solution of penalty function and the solution of the determinate programming, and prove that the solution sequences of the discrete problem converge to a solution to the original problem.

Biological Removal of Nitrogen Compounds at a Coke-Oven Effluent Stream

The steel company SSAB in Oxel?sund, Sweden operates a coke-oven plant and has since a long time operated an activated sludge plant for treatment of effluent water. Along with more stringent requirements on discharge quality, especially focusing on nitrogen compounds and a new consent value for total nitrogen discharge (< 30 ppm of total N) the company decided to operate a pilot plant facility to investigate two major issues: 1) To define the conditions and restrictions for nitrification of ammonia nitrogen in the water;2) To find out how efficiently a denitrification would perform. In order to find answers to these questions SSAB hired a pilot plant for testing. The test facility is based on a single sludge activated sludge reactor system for biological nutrient removal, with a reactor volume of 3.8 m3. After a test period of 5 months it was possible to draw reliable conclusions regarding the performance. The untreated wastewater has a high content of total nitrogen, around 240 ppm. The major nitrogen part is ammonia nitrogen, but an important fraction is found as thiocyanate nitrogen. The following main conclusions were drawn from the test operation: · It was found to be crucial that the solids retention time (SRT) was kept at a sufficiently high level. During the successful operation the SRT was in the range of 40 - 50 days;· It is desirable to have an equalization basin upstream the main biological reactor to meet short time peak loads, defined as both flow and pollution;· The major toxic risks for the biological process were high thiocyanate and ammonia concentrations in the raw wastewater;· The system showed however a good microbiological capacity to acclimatize to the prevailing conditions after the needed time;· The tests did not include an optimization of the oxygen supply with respect to nitrification;however it was evident that the oxygen level was sufficient to maintain a complete nitrification at normal operating conditions;· Once the nitrification was established it was also possible to reach a high degree of denitrification—as long as an external carbon source was applied;· It was found that both the cyanide nitrogen and especially the thiocyanate nitrogen were reduced by the process. The cyanide reduction is probably related both to precipitation by ferrous ions and biological transformation.

A novel approach to achieve breast symmetry in a single-stage procedure

Preservation of the skin envelope and the inframammary fold is the main factor in achieving breast symmetry in unilateral reconstruction.Skin sparing mastectomy(SSM)type-IV followed by immediate autologous reconstruction and contralateral symmetrization permits realizing this goal in large,ptotic breasted patients,and tumor superficially located in the inferior quadrants.If the tumor is superficially located in the superior or inferior quadrants with a previous lumpectomy or quadrantectomy scar in the superior quadrants,modified radical mastectomy and a staged procedure are recommended to avoid poor cosmetic results.Two patients who underwent immediate autologous reconstruction following SSM type-V with contralateral symmetrization in a one-stage procedure are presented.

新凉水塔风机振动问题的治理

针对凉水塔风机振动较大，提出了从电机开始逐级单试，解决国产凉水塔风机振动的一种行之有效的方法。

Optimization of acid fracturing for a tight carbonate reservoir

In this study,acid fracturing treatments were simulated for a tight limestone reservoir within a shale formation using FRACPRO software.The purpose was to investigate the optimum acid fracturing design that leads to a higher fracture etched length and width,and higher fracture conductivity.Moreover,the impact of the rock-acid contact time and whether to consider a post-flush or fluids flowback,on the acid fracturing outcomes were also investigated.A simple geological model was constructed which consists of different lithological layers.Different acid fracturing design scenarios were considered starting from a single stage of acid injection to multi-stage treatment.In multi-stage acid treatment,alternate acid-slickwater injection was considered.Plain HCl acids with different concentrations and other acids that are already included in FRACPRO database were used.The results showed that the acid loss during post-flush is among the main problems of the acid fracturing in tight carbonate shale reservoir.For the single stage of acid injection,it is recommended to flow back the acid after well shut-in instead of considering a post-flush stage.The multi-stage alternate acid slickwater injection reduces or even eliminated the acid loss.However,it is recommended to inject a slickwater before well shut-in to reduce the rock-acid contact time,thus reducing the formation damage.The results also showed that the created fracture etched width decreases and the fracture etched length increases as the fracturing stages increase.In this study,because of the low carbonate layer permeability and compressive strength,a two-stage alternate 28%HCl and slickwater injection with a post-flush stage is recommended.

Experimental Analysis of the Aerodynamic Performance of an Innovative Low Pressure Turbine Rotor

In the present work the aerodynamic performances of an innovative rotor blade row have been experimentally investigated. Measurements have been carried out in a large scale low speed single stage cold flow facility at a Reynolds number typical of aeroengine cruise, under nominal and off-design conditions. The time-mean blade aerodynamic loadings have been measured at three radial positions along the blade height through a pressure transducer installed inside the hollow shaft, by delivering the signal to the stationary frame with a slip ring. The time mean aerodynamic flow fields upstream and downstream of the rotor have been measured by means of a five-hole probe to investigate the losses associated with the rotor. The investigations in the single stage research turbine allow the reproduction of both wake-boundary layer interaction as well as vortex-vortex interaction. The detail of the present results clearly highlights the strong dissipative effects induced by the blade tip vortex and by the momentum defect as well as the turbulence production, which is generated during the migration of the stator wake in the rotor passage. Phase-locked hot-wire investigations have been also performed to analyze the time-varying flow during the wake passing period. In particular the interaction between stator and rotor structures has been investigated also under off-design conditions to further explain the mechanisms contributing to the loss generation for the different conditions.