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Based on the Froude similarity law, a small-scale tunnel model (1/14) was built based in this study to investigate critical velocities of tunnels. Critical velocity is the minimum air velocity required to resist the spread of smoke from a fire upstream in a tunnel. A set of experiments was conducted to investigate the critical velocities under different experimental conditions by varying the heat release rate of the fire, ambient temperature, operating pressure and arrangement of the nozzles. The results of the tests with no spray indicated that the ambient temperature has little impact on the critical velocity. Moreover, based on the dimensionless analysis method, a new correlation was established to predict the critical velocities in the tunnel without Water spray-based Fixed Fire Fighting Systems (WFFFS). The accuracy of the correlation was illustrated by the results of the present tests and a number of tests on different scales published by other scholars. Furthermore, 60 tests with WFFFS activation were carried out. The results show that the critical velocity is significantly reduced after the water spray discharged from the nozzles. The maximum reduction of the critical velocity is approximately 31%. The reduction of the critical velocity strongly depends on the number, positions and operating pressures of the nozzles. The mechanisms of the reduction of the critical velocity caused by spraying were discussed. The cooling effect of the water droplets on hot gas is not the only mechanism for decreasing the critical velocity caused by spraying. Spraying increases the inertial force of the longitudinal airflow and is the other mechanism for the reduction.

AIM To analyse the outcomes of oesophageal stenting for malignant strictures and to study the correlation between the follow-up time and major complications. MATERIALS AND METHODS Patients with oesophageal malignancy who underwent stent placement between 2011 and 2016 for dysphagia were included. The data included age, sex, dysphagia, length and location of stenosis, date of stent placement, complications, follow-up time, and survival. RESULTS Two hundred and ninety-eight patients were included in the study. Minor complications occurred in 113 patients (37.9%) including chest pain (17.1%), foreign body sensation (25.5%), hiccups (1.68%), and reflux symptoms (27.5%). Major adverse events occurred in 93 (31.1%) patients including pneumonia (25.5%), migration (3%), perforation (0.67%), bleeding (1.68%), and restenosis (22.5%). oesophago-airway fistula occurred in 45 (15.1%) patients. The incidence of recurrent dysphagia, pneumonia, and oesophago-airway fistula increased over 3 months and decreased after another 3 months. The incidence of major complications as a percentage of survivors remained high after 3 months (>40%). Spearman analysis revealed a significant positive correlation between the incidence and the follow-up time over this period (rs=0.907, p CONCLUSION The major complications of oesophageal stenting increased with time over 3 months and remained high for another 3 months. Therefore, stenting should be considered for palliation in patients with short expected survival (usually

To study the fatigue damage of a cutter used for cutting cashew nut, the integratedsimulation platform is established with Hypermesh, LS-Dyna, LS-PrePost, and nCode GlyphWorks.The simulation model is established by Hypermesh. LS-Dyna is used to calculate the k file.LS-PrePost is used as the post-processing software. The rain-flow counting, load superposition andextrapolation are executed using Rainflow module in nCode GlyphWorks. The analysis of thefatigue damage of the cutter is executed using Stress Life module in nCode GlyphWorks. Theequivalent stress time history of different elements in the upper and lower cutters, rain-flowcounting histogram after load spectrum superposition, rain-flow counting histograms after loadspectrum extrapolation, and damage histogram of the cutter are obtained. The results show that thecutter has excellent mechanical properties, and the minimum fatigue life of the cutter is about 495days, which is a conservative solution.

The curvelet transform is a known tool used in the attenuation of coherent and incoherent noise in seismic data. It utilises the fact that signal and noise are usually better separated in the curvelet domain than in the time-space (TX) domain. Coefficients of the transform are not independent and neighbouring coefficients are strongly correlated, which existing curvelet-based noise attenuation algorithms do not fully utilise. In this work we propose to use a data structure called a ‘dip map’ to describe dip information in seismic data. This information links local curvelet coefficients together in adaptive thresholding or subtraction of curvelet coefficients in seismic denoising algorithms. We used the dip map to improve curvelet multiple subtraction algorithm and the results show significant improvement over traditional methods with real data.

To improve the accuracy of impact failure prediction of ductile material under complex stress states, a novel multi-parameters dynamic ductile fracture model with constitutive relation and fracture criterion is proposed by involving the effects of hydrostatic pressure, Lode angle and strain rate. This novel dynamic fracture model is based on our proposed ductile fracture model under quasi-static loading. Furthermore, the corresponding material calibration strategy with some simple quasi-static and dynamic tests is also presented. In order to verify the present dynamic fracture model under complex stress states, both hydrostatic pressure and Lode angle, a plate specimen with notch made from Al 7075 was designed and the split Hopkinson bar (SHPB) tension tests with elevated loading forces were conducted. Meanwhile, parallel numerical simulations were performed with two fracture models, i.e., the Johnson–Cook model and the present novel model, implemented into the commercial finite element platform ABAQUS/explicit through user material subroutine VUMAT. By comparing with the numerical results and the SHPB experimental data, it is demonstrated that the novel dynamic ductile fracture model can predict favorably well with the SHPB experimental data. Furthermore, local strain rates and stress states of the specimen in the notch region during deformation were also studied.

Based on continuum damage mechanics and stress invariants, a novel multi-parameters ductile fracture model is proposed by coupling the synergistic effects of hydrostatic pressure and Lode angle in the developed fracture envelope. To improve accuracy for complex stress states, the material parameters associated with the coupling effects are considered and integrated into the proposed damage criterion. Furthermore, the corresponding calibration strategy is also presented to obtain the necessary material parameters. In order to predict the fracture behavior of ductile materials, parallel analyses are performed with the fracture model incorporated into the commercial finite element platform ABAQUS/Explicit through a user material subroutine VUMAT. The validity of this model is examined by comparing the numerical results with the experimental data of notched round bar and compact tension tests. Comparing with other previous stress-invariant based models, it is demonstrated that the new ductile fracture model can predict favorably well with the experimental data, especially for those tests which correspond to wide ranges of pressure and Lode angle. The model can be adopted to predict fracture patterns and to investigate wide range of elastic–plastic ductile fracture behaviors.

With the help of MgO mask layer, LiNbO 3 (LN) ferroelectric films were etched effectively using wet etching method and LN/AlGaN/GaN ferroelectric field-effect transistors (FFETs) were fabricated. The electrical properties of the FFETs were studied. Due to the ferroelectric polarization nature of LN films, normally-off characteristics with a turn-on voltage of about + 1.0 V were exhibited in the device. The operation mechanisms of the LN/AlGaN/GaN FFET devices were proposed by the numerical calculations of the electronic band structure and charge distribution.

In this paper, a series of study were conducted on the effect of hole quality on the fatigue life of open holes in 2A12-T4 aircraft quality aluminum alloy. Four metrics that can define holes quality are analyzed. They are roughness, verticality, cylindricity and roundness. Firstly, open holes with different roughness were fatigue tested under constant amplitude remote tensile load and post-failure investigations were performed by scanning electron microscope. Further, the effects of another three metrics on the stress distributions around the holes have been studied by the finite element method (FEM). The fatigue lives are determined based on the stress distributions by the method of nominal stress approach. The results show that the fatigue lives of open holes are dependent on the holes quality. For these four metrics, the fatigue lives decrease with the increasing of the values of the tolerance of these metrics. At last, empirical equations that relate these four metrics to fatigue lives were established by linear regression method.

Research on Activity-Based Costing and its applications has mainly been focused on organisations in developed countries. Little has been learnt as to whether ABC techniques can be implemented successfully in organisations in developing countries. With the adoption of an innovation action research approach, we have successfully developed an ABC system jointly with a large Chinese manufacturing company, Xu Ji Electric Co. Ltd. (Xu Ji), for the period 2001–2005. The research provides a unique opportunity to examine some key success factors pertinent to ABC implementation within a Chinese organisational and cultural setting. The findings indicate that top management support, which has been identified as an important success factor in ABC literature, is evidently the predominant success factor in this organisation. In addition, Xu Ji's corporate culture of “top–down” instigation of the adoption of a series of management innovations (e.g., Economic-Value Added ® , Balanced Scorecards and Six Sigma) and its hierarchical command and communication structure, coupled with active involvement of a high proportion of dedicated professionals, can be seen as another success factor in achieving a relatively high level of diffusion of this accounting concept within the organisation. This study also reveals a different insight of internal resistance to change, which is contrary to the evidence presented in the existing ABC literature.

This paper analysis the PCC voltage fluctuation from the perspective of active and reactive load, and points out that voltage flicker mitigation needs both active and reactive power compensation. Battery energy storage system designed by this paper adopts the current feed forward decoupling control, energy storage system after receive compensation instruction, fast response, send out a certain amount of reactive power and active power to compensate for voltage flicker. After building the simulation models and designing the control strategy of the BESS system, this paper carries on the simulation under the environment of SIMULINK and RT-LAB. The simulation results show that the proposed method can accurately detect voltage flicker frequency and amplitude and it can effectively weaken the negative influence of imbalance of the three-phase voltage. With the active and reactive power compensation of the battery energy storage system, it can get better compensation effect of voltage flicker. Keywords-IRPT; BESS; Voltage Flicker; Hardware-in-the-loop

This study examined the prevalence of retinopathy in 2131 patients with type 2 diabetes attending a Beijing hospital for the first time. The median age of patients was 58 years (IQR 50-65). The overall prevalence of retinopathy was 27.3% (95% CI: 25.4-29.2) and for proliferative retinopathy 7.8% (95% CI: 6.7-8.9). When all patients were considered together, duration of diabetes (OR=1.8; P=0.001) and albumin excretion rate (OR=1.5; P=0.019) were independent risk factors for retinopathy. Blue-collar occupation (OR=1.5; P=0.047) and blood pressure (OR=1.2; P=0.021) were additional risk factors for non-proliferative and proliferative retinopathy respectively. Amongst the 773 newly diagnosed patients, 21% (95% CI: 17.8-23.6) already had retinopathy. The median age of those patients with retinopathy at diagnosis of diabetes was 3 years higher that those without retinopathy, and blue-collar workers (OR=2.2; P=0.012) as well as female gender were particularly at risk (OR=2.0; P=0.033). There was a strong correlation between duration of diabetes with the presence of retinopathy (r=0.95; P=0.01). By extrapolation, it could be estimated that some degree of hyperglycaemia might have been present for more than 20 years before diabetes was diagnosed. These findings emphasise the importance of earlier diagnosis of diabetes and its complications, especially in socially disadvantaged groups.

Three-dimensional fundamental solutions corresponding to a unit point force and point electric charge are obtained for a semi-infinite transversely isotropic piezoelectric solid. The free boundary is parallel to the plane of isotropy. They can be used as the Green’s function for solving the problem of a flat circular crack near the free surface which will be dealt with in Part II of this work.

This is part II of the work concerned with finding the stress intensity factors for a circular crack in a solid with piezoelectric behavior. The method of solution involves reducing the problem to a system of hypersingular integral equations by application of the unit concentrated displacement discontinuity and the unit concentrated electric potential discontinuity derived in part I [1]. The near crack border elastic displacement, electric potential, stress and electric displacement are obtained. Stress and electric displacement intensity factors can be expressed in terms of the displacement and the potential discontinuity on the crack surface. Analogy is established between the boundary integral equations for arbitrary shaped cracks in a piezoelectric and elastic medium such that once the stress intensity factors in the piezoelectric medium can be determined directly from that of the elastic medium. Results for the penny-shaped crack are obtained as an example.

Objective To evaluate cardiovascular outcomes in patients with aortic arch repair and their possible correlation with arch geometry. Methods Ten patients who underwent end-to-side repair for aortic arch interruption (IAA), older than 10 years were compared to a cohort of 10 post coarctation (CoA) repair patients matched for age, sex and age at repair. Mean age at operation was 9.7 ± 6.5 days. Patients underwent a resting and 24 h blood pressure measurements, exercise study, MRI, transthoracic echocardiography and vascular studies. Results Seven patients developed hypertension, two from IAA group and five from CoA group. Nine patients (45%) had gothic arch geometry, three from IAA group and six from CoA group. Despite differences in arch geometry, both groups had normal LV mass, LV function and vascular function. Conclusion No differences in functional or morphologic outcomes could be demonstrated between the end-to-side repair of the arch by sternotomy and the conventional coarctation repair by thoracotomy. A favourable arch geometry can be achieved after the end-to-side repair of the aortic arch. In the present study, we could not correlate adverse arch geometry with any adverse cardio-vascular outcomes. After neonatal arch repair, the contributive role of aortic arch geometry to late hypertension remains uncertain.

Spare parts management is an important part of the maintenance activities and the spare parts are the basic guarantee of maintenance. Classified Management of spare parts is an important issue in the management of spare parts. Only classifying the spare parts scientifically that the maintenance tasks can be completed economically and on time. In the paper, AHP and the importance principle were used to establish the model for classified storage of spare parts. Then a comprehensive index that the importance of the spare parts was used to classify the maintenance spares so that reserving a reasonable amount of the spare parts. Finally, a specific example was used to show the practicability of the method.

A sphere in air will roll down a plane that is tilted away from the vertical. The only couple acting about the point of contact between the sphere and the plane is due to the component of the weight of the sphere along the plane, provided that air friction is negligible. If on the other hand the sphere is immersed in a liquid, hydrodynamic forces will enter into the couples that turn the sphere, and the rotation of the sphere can be anomalous, i.e., as if rolling up the plane while it falls. In this paper we shall show that anomalous rolling is a characteristic phenomenon that can be observed in every viscoelastic liquid tested so far. Anomalous rolling is normal for hydrodynamically levitated spheres, both in Newtonian and viscoelastic liquids. Normal and anomalous rolling are different names for dry and hydrodynamic rolling. Spheres dropped at a vertical wall in Newtonian liquids are forced into anomalous rotation and are pushed away from the wall while in viscoelastic liquids, they are forced into anomalous rotation, but are pushed toward the wall. If the wall is inclined and the fluid is Newtonian, the spheres will rotate normally for dry rolling, but the same spheres rotate anomalously in viscoelastic liquids when the angle of inclination from the vertical is less than some critical value. The hydrodynamic mechanisms underway in the settling of circular particles in a Newtonian fluid at a vertical wall are revealed by an exact numerical simulation based on a finite-element solution of the Navier-Stokes equations and Newton's equations of motion for a rigid body.

UNLABELLED: To determine whether conventional coarctation repair results in sustained growth of hypoplastic transverse arches, we examined the follow-up of 20 patients operated through a thoracotomy between 1990 and 1995 who had available serial echocardiographic examinations. Mean age at operation was 8.6+/-5.7 days. In the distal transverse arch, maximum change was observed in the early postoperative period and sustained growth was observed thereafter. At last follow-up, no patients had Z-scores of less than -2. In contrast, only minimal growth occurred in the proximal transverse arch (mean Z-score diameter before and after repair: -1.87+/-0.12 vs. -1.66+/-0.09; P=0.05) in the postoperative period. At last follow-up, seven patients (35%) kept a diameter Z-score of less than -2, and 5 of them had a gradient of 15 mmHg (P=0.01). No correlation was found between the size of the proximal arch at last follow-up and its size before repair or technique used. CONCLUSION: Patients with moderately hypoplastic arch treated by conventional coarctation repair have adequate growth of the distal arch demonstrated at long-term follow-up, but one-third of them keep a small proximal arch. This subset of patients is at risk of developing hypertension and may warrant further investigation.

Many ultra-bright light-emitting diodes (LEDs), especially the white LEDs, are being actively developed for solid-state lighting and many other commercial applications. Hence, it is important to evaluate and understand the failure mechanisms that affect the performance characteristics and lifetimes of these new LEDs. This study concerns the humidity effect on the degradation of GaN-based packaged white LEDs. Under the accelerated humidity test, the LEDs showed a degradation of optical output. With the mixture statistical distribution analysis method, it is noted that the luminous flux degradation of the packaged white LEDs is dependent on more than two failure mechanisms. Two of the failure mechanisms are observed to follow the lognormal distribution. With detailed spectrum analysis and by employing the parameters extraction method, one of the two failure mechanisms that follow the lognormal distribution is observed to be caused by chip related failure due to the accumulated moisture in the encapsulation. For the other failure mechanism, phosphor degradation is noted to be the primary cause. Published version

A pilot-scale fluidised pellet bed (FPB) bioreactor, which combines chemical coagulation, biological degradation, particle pelletisation and separation in one unit, was applied for onsite wastewater treatment and reuse. As a result of rational use of inorganic coagulant and organic polymer and moderate mechanical agitation, spherical particles were generated in the upflow column and a well-fluidised bed was formed. With a continuous supply of dissolved oxygen through a recycling loop, an aerobic condition was kept in the bottom section of the FPB column. Under such conditions the pellets in the FPB column showed the following characteristics: (1) compact structure and high density; (2) rich in microorganisms; and (3) high MLSS and MLVSS concentrations. Therefore, the FPB bioreactor achieved more than 90% removal of SS, COD, BOD and TP from raw domestic wastewater within a total hydraulic retention time (HRT) of only about 30 minutes. It also showed nitrification and denitrification ability and the TN removal could be about 50% as the recycling ratio was increased to 1:1. The treated water quality is generally competitive with the secondary effluent from a conventional activated sludge process. With these advantages the FPB bioreactor is recommendable as a compact system for onsite wastewater treatment and reuse.

The analytical method is developed to calculate the equilibrium and forward-bias conditions of p-Si/beta-FeSi2/n-Si DH LED. The Poisson's equation is solved to investigate the equilibrium electric field and free carriers distributions. Diffusion and thermionic emission mechanisms are used to calculate I-V characteristics and ideal internal quantum efficiency.

Power quality is a growing concern to both electric utilities and their customers. Among the commonly seen nonlinear loads, electric arc furnaces (EAFs) in the steel plant play important roles that cause power quality disturbances. The nonlinear characteristics of the EAF generate significant harmonic currents and flickers flowing through the plant and the utility power system. This paper presents a harmonic analysis for a steel plant with an ac EAF load. Simulation results obtained by using Matlab/Simulink are then validated by the actual measuring data. It is shown that the simulation model including the power network and the EAF load is relatively accurate in comparing with the actual field measurements.

This paper concerns performance optimization using the Taguchi parameter optimization methodology[M.S. Phaadke, May 12 1989] in a network based on SUO-SAS (situational awareness system for small unit operations)-a new state-of-the-art communication system developed by ITT Industries. For the subject experiment, the network consisted of 20 nodes. The nodes are mobile and move in accordance with an operationally relevant scenario based upon a topology provided by DARPA. The scenario specifies the input traffic variations and other noise factors such as message size, message types and mobility. The throughput is the most important performance metric and is selected as the output characteristic. The criterion for throughput optimization amounts to generating as large a throughput as possible. Four crucial parameters associated with the intranet layer and link layer, and an L/sub 9/ orthogonal array are selected for optimization through OPNET modeling and simulation. Parameter optimization yields a 34% improvement in message completion rate and a 35% improvement in system throughput.

Demand for interconnectivity from local area networks (LANs) to wide area networks (WANs) has been increasing rapidly. Several strategies exist to provide LAN/WAN internetworking capabilities, with each method exhibiting distinct performance issues. Performance issues are presented for bridge, router, and Brouter technologies specifically as they relate to WAN networking. The case of an ISO-to-X.25 router is discussed including a set of recommendations to improve the performance of such a router. >

A fuzzy attributed finite-state grammar and corresponding automation are introduced for recognizing line segments and an ordering arrangement is provided according to intrinsic structural properties of Chinese characters. Arrangement is provided. As a result, an online Chinese character recognition system has been implemented. The system consists of a small input tablet interfaced with a IBM-PC/XT/AT which can recognize about seven thousand online handwritten Chinese characters, with some constraints. >

The selected directed broadcast is specified in MIL-STD-2045-14502-1A in order for the source to send a message to multi-destinations. The performance of this multi-destination protocol is compared to single-destination protocol using 16 kbps SINCGARS radios running in packet mode. The OPNET simulation study shows that the multi-destination protocol outperforms single-destination protocol with and without the acknowledgement service from segmentation/reassembly (SAR). It also demonstrates that it is better to send this acknowledgement using a higher precedence without the link layer acknowledgement.

Three issues concerning TCP in a tactical internet are addressed. They are TCP connection procedure, TCP parameter optimization and its performance comparison with UDP. Extensive OPNET simulations with various net models and scenarios were performed. The results showed that initial retransmission timeout is a critical parameter and UDP with SAR (segmentation and reassembly) outperforms TCP. A TCP connection procedure that is suitable to set up any number of connections based upon the need is also discussed.

This research project aims at establishing a computer platform especially for the analysis of process of laser welding. After the laser induced plasma photographs, metallographic photographs of the weld are scanned into computer and the welding parameters are input, the results of the analysis can be obtained by means of selecting different function-keys. The main results of analysis include: the solid angle of spatter distribution, the velocity of the unit volume spatter, the area of the weld, the penetration-to-width ratio of the weld, the included angle of side boundary line of the weld, the RGB chart and the grey isothermal chart of plasma and the area of laser welding plasma in the different temperature district and so on.

By using the fault tree logic, an evaluation of the design basis accident frequencies at the Canister Storage Building has been performed. The evaluation demonstrates that due to low frequency of occurrences, the following design basis accidents are considered not credible (annual frequency of less than 10{sup -6}): Rearrangement of multi-canister overpack (MCO) internals; Gaseous release from the MCO; MCO internal hydrogen explosion; MCO external hydrogen explosion; Thermal runaway reactions inside the MCO; and Violation of design temperature criteria.

A theoretical model for creep crack based on energy balance criterion in the fracture process region is proposed in the present paper. A concept based on the dissipation of thermoelastic-plastic-creep flux into the fracture process region is introduced from which a generalized power integral Cg* was derived. This integral when is used in conjunction with the tearing modulus and other material parameters can characterize the crack growth behaviour in solids subject to general thermomechanical loadings. The analytical results computed by the proposed model have shown excellent agreement with some experimental results published by other prominent researchers.

Summary The pattern recognition technique was applied to recognize the cutting states for the difficult-to-cut materials. This is the first step for realization of the adaptive control in the cutting process. According to the processed results of the cutting force random signals from tests, the relationship between the autocorrelation and the auto power spectrum diagrams and the cutting states have been found. Furthermore, the discriminant functions used to identify the formation of BUE and types of chip have been established respectively. By using these discriminant functions in recognizing the cutting states, the results are encouraging. Moreover, in pattern recognition technique, the feature extraction, the training pattern selection and the classifier design, all of them play important roles for increasing the correct probability of recognition. Some different features, training patterns and classifiers are introduced. After calculation, comparison and analysis, the satisfactory results were obtained.

InGaAsN films grown by MOCVD were examined by X-ray photoelectron spectroscopy (XPS). The success of N atoms incorporation was demonstrated. The existence of two N configurations is observed. In addition, the addition of N atoms increases the atomic ratio of both Ga:As and In:Ga. All these results imply the formation of InN+GaAs configuration in InGaAsN quaternary alloy.