Nominal Point Research Articles

Repair volume extraction method for damaged parts in remanufacturing repair

The remanufacturing repair of damaged parts provides great potential for restoring them to a like-new condition. Existing methods cannot build an effective connection between 3D point cloud reconstruction and laser metal deposition (LMD) repair, which results in a low degree of integration and automation through the entire remanufacturing repair process. In this paper, we propose a repair volume extraction method that integrates surface reconstruction and repair volume extraction. For the surface reconstruction, a few reference points reconstructed by a close-range photogrammetry system (XJTUDP) were used to perform the initial registration and coordinate system transformation. Then, the internal and external parameters of two cameras embedded into a 3D optical scanning system (XJTUOM) were estimated using an eight-step calibration method. After completing the reconstruction of local point clouds through XJTUOM, we utilized another initial registration strategy depending on reference points and fine registration via the ICP algorithm to determine a refined complete point cloud for the damaged part. For the repair volume extraction, the refined complete point cloud was converted from the XJTUDP coordinate system to the LMD coordinate system, and two types of initial registration approaches and the ICP algorithm were used to achieve a best-fit position between the refined complete point cloud and the nominal point cloud. Finally, a point cloud representation of the repair volume was extracted by a distance-based filtering operation. The proposed method is validated by two experiments designed to extract the repair volume of a damaged gear with both planar and non-planar broken surfaces and is proven to be effective, robust, and highly automated.

Islanding detection scheme for distributed generation systems using modified reactive power control strategy

The reactive power control (RPC)-based technique is a promising solution for islanding detection. The existing RPC-based islanding detection techniques have limitations of injecting unwanted reactive power during normal operation, almost same detection time for various percentage of unbalance in load and false detection of islanding for small disturbances when steady-state frequency is close to its threshold limit. To overcome the first limitation, the phase angle (θ) between the actual and nominal point of common coupling (PCC) voltage is added to the reference reactive power signal of the controller. The angle (θ) has zero value during normal system operation and increases prominently after islanding. To obtain proportionately faster detection for various percentage of unbalanced load conditions, the positive sequence PCC voltage is used in the detection scheme. Owing to major power imbalance between generation and load at steady state, the frequency may come close to its threshold. Under this situation, even a small disturbance will drag the frequency beyond threshold and false islanding detection will occur. To overcome this problem, discrete wavelet transform analysis of θ is considered in the decision-making criteria. The proposed scheme is tested for islanding conditions as well as under various non-islanding events.

Quadratic buck–boost converter with positive output voltage and minimum ripple point design

This study presents a novel topology of a buck-boost converter that features: (i) quadratic voltage gain; (ii) positive output voltage with respect to the input; (iii) continuous input current. Moreover, as the main contribution, (iv) it features a minimum ripple design, for which input current and output voltage ripples are simultaneously cancelled at the desired operating point. It is also shown that even though the duty cycle deviates from a nominal minimum ripple point, the converter exhibits a significantly low switching ripple percentage within a full operation range. The operation mechanism, steady-state equations and overall analysis are presented. Furthermore, simulations and experiments were performed to validate the theory.

Effect of Flowing Preformed Spherulites on Shear-Induced Melt Crystallization Behaviors of Isotactic Polypropylene

The effects of flowing preformed spherulites on shear-induced melt crystallization behaviors of isotactic polypropylene (iPP) had been investigated by using a Linkam shearing cell coupled with an optical microscope, atomic force microscope, and rheometer. By quenching iPP melt to 130 °C for a short time, preformed spherulites were intentionally obtained. While iPP films were heated up to temperatures below the nominal melting point of iPP (164 °C), various shear conditions were applied, and then the crystalline morphologies during crystallization at the isothermal crystallization temperature of 135 °C were traced by alternately using phase contrast optical microscopy and polarized optical microscopy modes. Two distinct highly orientated thread- and cylinder-like crystalline morphologies were induced by shearing with preformed spherulites present, which were dependent on the applied shear rate and temperature. The distinct crystalline morphologies were attributed to relative movements between shear flowing...

‘Something happened, something bad’: Blackouts, uncertainties and event construal inThe Girl on the Train

This article examines the representation of mind style in Paula Hawkins’ (2015) best-selling novel The Girl on the Train. It examines how Hawkins presents the fictional mind of Rachel, a character who is affected by anterograde amnesia as a result of alcoholic blackouts. Rachel’s narrative voice drives the novel, and its retelling of events is characterised by her inability to recall important information related to the night that a young woman disappeared and was murdered.This article specifically draws on the Cognitive Grammar notion of construal to explore the presentation of Rachel’s mind style and its affordances and limitations. In doing so, it builds on developing scholarship that has identified the potential for Cognitive Grammar to provide a richly nuanced account of the representation of a fictional mind. The analysis specifically examines two ways in which event construal is presented: nominal grounding strategies and reference point relationships. For the latter, the article also develops emerging work that has sought to make a connection between Cognitive Grammar and Text World Theory in terms of how mental representations are projected by the text.

Discussion of \u201cThe power of monitoring: how to make the most of a contaminated multivariate sample\u201d

We contribute to the discussion of an article where Andrea Cerioli, Marco Riani, Anthony Atkinson and Aldo Corbellini review the advantages of analyzing multivariate data by monitoring how the estimated model parameters change as the estimation parameters vary. The focus is on robust methods and their sensitivity to the nominal efficiency and breakdown point. In congratulating with the authors for the clear and stimulating exposition, we contribute to its discussion with an overview of what we experienced in applying the monitoring in our application domain.

A two-phase approach based on sequential approximation for reliability-based design optimization

The original problem of reliability-based design optimization (RBDO) is mathematically a nested two-level structure that is computationally time consuming for real engineering problems. In order to overcome the computational difficulties, many formulations have been proposed in the literature. These include SORA (sequential optimization and reliability assessment) that decouples the nested problems. SLA (single loop approach) further improves efficiency in that reliability analysis becomes an integrated part of the optimization problem. However, even SLA method can become computationally challenging for real engineering problems involving many reliability constraints. This paper presents an enhanced version of SLA where the first phase is based on approximation at nominal design point. After convergence of first iterative phase is reached the process transitions to a second phase where approximations of reliability constraints are carried out at their respective minimum performance target point (MPTP). The solution is implemented in Altair OptiStruct, where adaptive approximation and constraint screening strategies are utilized in the RBDO process. Examples show that the proposed two-phase approach leads to reduction in finite element analyses while preserving equal solution quality.

Comparative studies of liquid metals for an alternative divertor target in a fusion reactor

Two liquid metals (LM), Li and LiSn (20:80 at), presently considered as alternative materials for the divertor target of a fusion reactor, have been exposed to the plasma in a capillary porous system (CPS) arrangement in TJ-II. A negligible perturbation of the plasma has been recorded in both cases, even when stellarator plasmas are particularly sensitive to high Z elements due to the tendency to central impurity accumulation. The surface temperature of the LM CPS samples (made of a tungsten mesh impregnated in SnLi or Li) has been measured during the plasma pulse with ms resolution by pyrometry and the thermal balance during heating and cooling has been used to obtain the thermal parameters of the SnLi and Li CPS arrangements. Temperatures as high as 1150 K during TJ-II plasma exposure were observed for the LiSn solid case. Strong changes in the thermal conductivity of the alloy were recorded in the cooling phase at temperatures close to the nominal melting point. The deduced values for the thermal conductivity of the LiSn alloy/CPS sample were significantly lower than those predicted from their individual components.

A General Representation of δ-normal Sets to Sublevels of Convex Functions

The (δ-) normal cone to an arbitrary intersection of sublevel sets of proper, lower semicontinuous, and convex functions is characterized, using either e-subdifferentials at the nominal point or exact subdifferentials at nearby points. Our tools include (e-) calculus rules for sup/max functions. The framework of this work is that of a locally convex space, however, formulas using exact subdifferentials require some restriction either on the space (e.g. Banach), or on the function (e.g. epi-pointed).

Trajectory tracking in quadrotor platform by using PD controller and LQR control approach

The purpose of the paper is to discuss a comparative evaluation of performance of two different controllers i.e. Proportional-Derivative Controller (PD) and Linear Quadratic Regulation (LQR) in Quadrotor dynamic system that is under-actuated with high nonlinearity. As only four states can be controlled at the same time in the Quadrotor, the trajectories are designed on the basis of the four states whereas three dimensional position and rotation along an axis, known as yaw movement are considered. In this work, both the PD controller and LQR control approach are used for Quadrotor nonlinear model to track the trajectories. LQR control approach for nonlinear model is designed on the basis of a linear model of the Quadrotor because the performance of linear model and nonlinear model around certain nominal point is almost similar. Simulink and MATLAB software is used to design the controllers and to evaluate the performance of both the controllers.

The accuracy of calculating form deviations of selected free-form surfaces

The possible reason for the incorrect form deviations calculated using an algorithm available in the selected software of coordinate measuring machine was identified. This method is available in the Calypso software and it is based on local deviations calculated at nominal points. The analysis was made for the selected examples of free-form surfaces. There are presented the results of numerical investigations based on simulations of coordinate measurements of selected object. The measured points were generated with assumed values of scatter in relation to the nominal profiles of the analyzed product. The simulations were made using 3 selected methods for computing the form deviations and various distances between the measured points. In order to verify the results of simulation studies there were made experimental investigations. The experimental investigations were done using selected coordinate measuring system and chosen measurement parameters. The results of performed measurements confirm the simulation results.

Improved results on BIBO stability and stabilization of networked control systems with short time-varying delays

Based on the multiple nominal points method (MNPM), the problems of BIBO stability and BIBO stabilization for networked control systems (NCSs) with short time-varying delays (STVDs) are researched, and some improved results are obtained in this article. Using the single nominal point method, a NCS with STVDs is modeled as a time-varying uncertain discrete system, in which the uncertain parameters are norm bounded and with single nominal point. Applying the small gain theorem to this model, an improved BIBO stability criterion of the NCS is obtained. To further reduce the conservativeness arising from STVDs, the uncertain parameters are modeled as N norm bounded uncertainties based on the MNPM. The presented stability criteria depend on the bounds of STVDs. Furthermore, the controller design methods are also provided. A numerical example is given to show that the proposed methods are better than existing ones.

A Fourier-based single phase PLL algorithm: Design, analysis, and implementation in FPGA controller

Summary Control of grid tied inverter attached to the distribution level single phase grid needs to be robust in order to be resilient to grid disturbances and dynamics, without dissension of output power quality. This calls for an improvement of existing synchronization techniques whose bedrock is the phase locked loop algorithm. The paper proposes a phase and frequency estimation technique which shows excellent performance to dynamic changes and has high distortion rejection capability. The technique used interpolated FFT which estimates the frequency followed by sample value adjustment which gives highly accurate phase estimate by transforming off-nominal frequency samples into nominal data points. The technique being a discrete algorithm, system identification is performed to estimate the transfer function model upon which stability and dynamic analysis are performed. A comparative analysis with SOGI PLL, PARK PLL, TPFA PLL, and Fourier PLL shows the superiority of the proposed technique in terms of accurate steady and dynamic state estimation capacity during grid disturbance and faults. The study of the computational complexity and applicability in FPGA controller reveals the feasibility of implementation of the technique in low level FPGA controllers. The proposed algorithm has been implemented in NI cRIO FPGA controller to tap real-time signals and control the inverter. Thus, this PLL is suitable for fault-ride-through operation of the inverter in feeding power to the distribution grid.

Mechanical properties of the high-entropy alloy Al0.5CoCrCuFeNi in various structural states at temperatures of 0.5–300 K

The mechanical properties and fracture characteristics of the high-entropy alloy Al0.5CoCrCuFeNi are studied in different structural states (cast and after two heat treatments) at temperatures of 0.5–300 K with quasistatic deformation by uniaxial compression and distension. Mechanical resonance spectroscopy is used to measure the temperature variations of the Young modulus in the different structural states. It is found that heat treatment of the samples leads to an increase (by roughly 25%) in the Young modulus, the nominal yield point τ0.2, and the deforming stress. The form of the deformation curves is analyzed. The temperature interval for the transition from smooth to discontinuous plastic flow is determined. For the cast state the differences in τ0.2 under tension and compression are determined, an anomalous temperature dependence of τ0.2 (for temperatures in the 0.5–4.2 K range) is discovered, and thermal activation analysis of the experimental data yields empirical estimates for the parameters of the interactions of dislocations with local barriers. After heat treatment the samples break up into two parts under compression, as opposed to the cast state, where the samples acquire a “barrel” shape during compression. It is found that fracture of the heat treated samples at temperatures of 300–4.2 K has a viscous character.

Parametric Evaluation of Swirl Injector Dynamics in the High-Frequency Range

This work augments the classical linear swirl injector dynamics theory to evaluate the hydrodynamic frequency response characteristics of a single element as an analysis aid for experimental results from cold flow testing. Specific focus is placed on how surface waves within the swirl injector are modeled. A modified formulation of wave interactions within the vortex chamber includes disturbance origins displaced from the posterior wall of the injector. Differing phase delays in both downstream and upstream directions are accounted for by dispersive calculations valid at all frequencies rather than by the traditional long wave approximation. The model is semiempirically tailored to hydraulic conditions for a study element, and a response function analysis is presented for an example case. Distinct features in the range of 2000–4000 Hz are found to be predominately related to surface wave patterns within the injector’s vortex chamber. Comparisons are made to experimental data, showing qualitative agreement with injector response and detection of computed high-frequency surface wave responses. Calculations are then mapped over steady mass flow conditions that range from 39 to 89% of the injector’s nominal design point. The results show that response features associated with surface wave dynamics consistently manifest across the entire parameter space investigated for the study injector element.

Flexible robot-based cast iron deburring cell for small batch production using single-point laser sensor

The presented work here is devoted to the definition of innovative methodologies to speed up the programming time of a robotized deburring task. The proposed solutions are defined in a standard cast iron foundry scenario, where the deburring workstations are equipped with flexible but inaccurate fixturing system, the working environment is dirty, and the production is characterized by small batches. The developed system exploits a 3D vision sensor, namely a single-point laser displacement sensor (SP-LS), in combination to a handshaking communication process for the robot-sensor information synchronization. Such approach enables the robot to be used as a measuring instrument allowing a fast reconstruction of 3D images extremely robust in hard working conditions. Adopting a two-stage methodology, the comparison of the reconstructed 3D point cloud with the nominal 3D point cloud allows the automatic adjustment of the robot deburring trajectories. An experimental campaign demonstrates the feasibility and the effectiveness of the proposed solutions.

Construction of the initial deorbit region for landing at the given place

The algorithm of the two-point boundary problem is developed for choice the nominal deorbit point, from which a descent vehicle is enabled to land at a given place without a cross-range maneuver. The method is suggested and the example is given of constructing the initial deorbit region for landing at the Vostochny cosmodrome.

Cognitive–behavioural therapy and short-term psychoanalytic psychotherapy versus brief psychosocial intervention in adolescents with unipolar major depression (IMPACT): a multicentre, pragmatic, observer-blind, randomised controlled trial

Although there are effective psychological treatments for unipolar major depression in adolescents, whether or not one or more of the available therapies maintain reduced depressive symptoms 1 year after the end of treatment is not known. This is a non-trivial issue because maintaining lowered depressive symptoms below a clinical threshold level reduces the risk for diagnostic relapse into the adult years. To determine whether or not either of two specialist psychological treatments, cognitive-behavioural therapy (CBT) or short-term psychoanalytic psychotherapy (STPP), is more effective than a reference brief psychosocial intervention (BPI) in maintaining reduction of depression symptoms in the year after treatment. Observer-blind, parallel-group, pragmatic superiority randomised controlled trial. A total of 15 outpatient NHS clinics in the UK from East Anglia, north-west England and North London. Adolescents aged 11-17 years with Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition major depression including those with suicidality, depressive psychosis and conduct disorder. Patients were randomised using stochastic minimisation controlling for age, sex and self-reported depression sum score; 470 patients were randomised and 465 were included in the analyses. In total, 154 adolescents received CBT, 156 received STPP and 155 received BPI. The trial lasted 86 weeks and study treatments were delivered in the first 36 weeks, with 52 weeks of follow-up. Mean sum score on self-reported depressive symptoms (primary outcome) at final study assessment (nominally 86 weeks, at least 52 weeks after end of treatment). Secondary measures were change in mean sum scores on self-reported anxiety symptoms and researcher-rated Health of the Nation scales for children and adolescents measuring psychosocial function. Following baseline assessment, there were a further five planned follow-up reassessments at nominal time points of 6, 12, 52 and 86 weeks post randomisation. There were non-inferiority effects of CBT compared with STPP [treatment effect by final follow-up = -0.578, 95% confidence interval (CI) -2.948 to 4.104; p = 0.748]. There were no superiority effects for the two specialist treatments (CBT + STPP) compared with BPI (treatment effect by final follow-up = -1.898, 95% CI -4.922 to 1.126; p = 0.219). At final assessment there was no significant difference in the mean depressive symptom score between treatment groups. There was an average 49-52% reduction in depression symptoms by the end of the study. There were no differences in total costs or quality-of-life scores between treatment groups and prescribing a selective serotonin reuptake inhibitor (SSRI) during treatment or follow-up did not differ between the therapy arms and, therefore, did not mediate the outcome. The three psychological treatments differed markedly in theoretical and clinical approach and are associated with a similar degree of clinical improvement, cost-effectiveness and subsequent maintenance of lowered depressive symptoms. Both STPP and BPI offer an additional patient treatment choice, alongside CBT, for depressed adolescents attending specialist Child and Adolescent Mental Health Services. Further research should focus on psychological mechanisms that are associated with treatment response, the maintenance of positive effects, determinants of non-response and whether or not brief psychotherapies are of use in primary care and community settings. Neither reason for SSRI prescribing or monitoring of medication compliance was controlled for over the course of the study, and the economic results were limited by missing data. Current Controlled Trials ISRCTN83033550. This project was funded by the National Institute for Heath Research Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 21, No. 12. See the National Institute for Heath Research Journals Library website for further project information. Funding was also provided by the Department of Health. The funders had no role in the study design, patient recruitment, data collection, analysis or writing of the study, any aspect pertinent to the study or the decision to submit to The Lancet.

Effect of splitter leading edge location on performance of an automotive turbocharger compressor

Design of centrifugal compressors can be accomplished using methods provided in text books and open literature. In this general approach, after determination of dimensions in meridional plane, blade profiles are designed using aerodynamic methods. Then, some blades are trimmed at the beginning to avoid inlet blockage. But there is no clear guidance on how this trimming must be performed. With this widely implemented method, splitter blades have the same profile as main ones.In this research, blade profiles and dimensions of the compressor impeller are not changed while the effect of changes in the position and angle of splitters leading edge are investigated. An optimization scheme is performed to find the best configuration over the complete operating curve of the compressor using genetic algorithm and considering structural aspect of the problem. CFD codes with experimental support are used to predict the compressor performance and flow field specifications with the original impeller as well as the modified one. After taking into account some geometrical details, a new impeller is manufactured based on the modified design and tested in a wide range of operating conditions. Results show 2.7 points improvement in efficiency at the nominal point and 5% decrease in impeller moment inertia. No change in choke behavior, but notable improvement in surge margin of the modified compressor is observed. This is an important achievement in all applications of centrifugal compressors, especially in turbochargers.

A Scheduling Scheme of Linear Model Predictive Controllers for Turbofan Engines

An adaptive model predictive controller with a new scheduling scheme for turbofan engines is proposed, which can transfer engine from one working state to the others within the flight envelope. First, the flight envelope is divided into several sections according to the engine inlet parameters, and the nominal points in each section are determined, respectively. Then, considering the requirements of the turbofan engines, a constrained linear model predictive control algorithm is improved, and a series of constrained predictive controllers are designed based on the linear models at different nominal points. Furthermore, a novel scheduling scheme with two layers is constructed, where the first layer is the flight envelope scheduling layer that introduces fuzzy membership degree logic to distribute the weights of all nominal predictive controllers, and the second layer is the power scheduling layer by adopting a linear interpolation method. Simulation results show that the proposed scheduling scheme can coordinate these two layers to realize the steady-state and transition-state control of the turbofan engines at off-nominal points within the envelope, which provides an effective approach for the design of the adaptive controllers.