Tolerance allocation for compliant beam structure assemblies

This paper presents a tolerance allocation methodology for compliant beam structures in automotive and aerospace assembly processes. The compliant beam structure model of the product does not require detailed knowledge of product geometry and thus can be applied during the early design phase to develop cost-effective product specifications. The proposed method minimizes manufacturing costs associated with tolerances of product functional requirements (key product characteristics, KPCs) under the constraint(s) of satisfying process requirements (key control characteristics, KCCs). Misalignment and fabrication error of compliant parts, two critical causes of product dimensional variation, are discussed and considered in the model. The proposed methodology is developed for stochastic and deterministic interpretations of optimally allocated manufacturing tolerances. An optimization procedure for the proposed tolerance allocation method is developed using projection theory to considerably simplify the solution. The non-linear constraints, that ellipsoid defined by τ(stochastic case) or rectangle defined by T x (deterministic case) lie within the KCC region, are transformed into a set of constraints that are linear in σ(or T x )-coordinates. Experimental results verify the proposed tolerance allocation method.     

Effects of interdiffusion-induced strain inGa0.51In0.49P-GaAs intermixed quantum wells

The effects of interdiffusion and strain introduced by interdiffusion in lattice-matched GaInP-GaAs single quantum wells are investigated using an error function distribution to model the compositional profile after interdiffusion. Group-III only and dominant group-III interdiffusion produce a large strain build up at the interface, with compressive strain in the well, and tensile strain in the barrier. In the case of group-III only interdiffusion, an abrupt carrier confinement profile is maintained even after significant interdiffusion, with a double-welled bottom, and a potential buildup in the barrier near the interface. Group-V only and group-V dominant interdiffusion again cause a large strain buildup at the interface, with tensile strain in the well and compressive strain in the barrier. Degeneracy of the heavy-hole and light-hole ground states can be achieved, and the electron-light-hole ground state transition energy can also become the effective bandgap energy of the intermixed structure. The model results are consistent with reported experimental results, and show that the effects of the interdiffusion-induced strain on the carrier confinement profiles can be of interest for various quantum-well device applications in this material system, including intersubband infrared photodetectors, polarization-insensitive electroabsorption modulators, and lasers     

Two-dimensional Laplacianfaces method for face recognition

In this paper we propose a two-dimensional (2D) Laplacianfaces method for face recognition. The new algorithm is developed based on two techniques, i.e., locality preserved embedding and image based projection. The 2D Laplacianfaces method is not only computationally more efficient but also more accurate than the one-dimensional (1D) Laplacianfaces method in extracting the facial features for human face authentication. Extensive experiments are performed to test and evaluate the new algorithm using the FERET and the AR face databases. The experimental results indicate that the 2D Laplacianfaces method significantly outperforms the existing 2D Eigenfaces, the 2D Fisherfaces and the 1D Laplacianfaces methods under various experimental conditions.     

The non-uniformity of microcrystalline cellulose bilayer tablets

The material response of the constrained microcrystalline cellulose particles during the manufacture of bilayer tablets has been investigated. This work exploits the ability of a non-contact optical profilometer to elucidate both the intricate roughness detail and the inherent form of a compacted sample surface within one measurement. Thus the effects of the imposed non-uniform stress pattern that develops during the two sequential compaction cycles have been determined. The indirect measurement procedure has been able to infer the degree of particle deformation and hence the relative local porosity can be determined. The application of two compaction cycles has shown to exasperate the inhomogeneity of the localised regions of stored elastic strain energy and this is highlighted by the non-uniform and complex ejected tablet geometry. The localised stored energy release by volume expansion in the radial direction is thought to be responsible for the fracture of tablets during the ejection phase of the manufacturing process. When the magnitude of the final layer compaction stress is greater than the initial layer compaction stress the radial volume expansion can even result in the rupture of junctions between particles in the adjacent layers at the periphery of the interfacial zone. Thus the energy dissipation by volume expansion is a possible explanation for the stress concentrating crack commonly present at interfacial boundary zone within the bilayer formulations.     

Preparation and oil–water separation evaluations of polypropylene/low‐melt‐point polyester composites reinforced by thermal bonding and one‐step solution immersion

Nonwoven fabrics have been fabricated for oil–water separation, but simplifying the manufacturing processes is still a challenge. In this work, a facile and easily scaled up approach based on thermal bonding and one‐step solution immersion has been successfully developed to prepare nonwoven fabrics with high separation efficiency and flux of oil. Here, polypropylene (PP) and low‐melt‐point polyester (LPET) fibers with a unique sheath–core structure are employed to form PP/LPET nonwoven fabrics. Thermal bonding by hot press and hydrophobic treatment with 1H,1H,2H,2H‐perfluorodecyl‐1‐thiol (PFDT) are used to manufacture oil–water separation nonwoven fabrics. Effects of the ratio of LPET fibers and the concentration of PFDT are discussed in terms of mechanical properties, morphology, surface chemical composition, water contact angle and performance of oil–water separation and flux of the nonwoven fabrics. The results show that the strength of the nonwoven fabrics gradually increases with increasing ratio of LPET fibers. After immersion in PFDT, the nonwoven fabrics show high hydrophobicity with a water contact angle of 143°. They can be used to separate oil–water mixtures. The separation efficiency is 97–99% and the oil flux is 62 364.92 L m^?2 h^?1. This study provides a new prospect for simple introduction of a hydrophobic agent on a nonwoven fabric to achieve various functional oil–water separation materials. © 2020 Society of Chemical Industry     

Assessing future rainfall uncertainties of climate change in Taiwan with a bootstrapped neural network‐based downscaling model

To investigate the impacts of climate change on Taiwan, a downscaling model (DSM) was used due to the large grid size of general circulation models (GCMs). DSM is a data‐driven model based on the Radial Basis Function Neural Network (RBFNN). A Genetic Algorithm (GA) was adapted for parameter optimization, and the bootstrap method was employed to assess uncertainty. Two weather stations at similar latitudes but separated by mountains with altitudes of above 3000 m were selected as examples. Three GCMs were chosen for the model building and the assessment of near future (2050–2060) and far future (2080–2090) climate change impacts of three future scenarios A1B, A2 and B1. The results suggest that in the future, rainfall will tend to increase in winter but decrease in summer, with a similar average rainfall. In addition, our results suggest that in the future, typhoons might arrive later in the season.     

A cluster-based scheduling model using SPT and SA for dynamic hybrid flow shop problems

The hybrid flow shop (HFS) scheduling, typically found in a variety of real-world industries, is an NP-hard combinatorial optimisation problem. Consideration of uncertainties hugely aggravates its complexity. This paper considers makespan minimisation of dynamic HFS scheduling problems under machine breakdown and stochastic processing times. It presents a novel cluster-based scheduling model (CBSM) that combines the good features of the shortest processing time (SPT) algorithm and the simulated annealing (SA) heuristic to synergise HFS scheduling under uncertainties. In this model, a neighbouring agglomerative hierarchical clustering algorithm is firstly developed. This algorithm decomposes an HFS into an appropriate number of machine clusters with different stochastic natures. The CBSM then performs a decision-tree-based assignment procedure using the classification and regression trees to determine an appropriate approach, either SPT or SA, for each machine cluster. Finally, the machine clusters are scheduled by their assigned approaches. To validate the effectiveness of the CBSM, a discrete-event simulator is conducted to evaluate its performance. The simulation results show that the CBSM outperforms all the compared algorithms in solving the dynamic HFS scheduling problems.     

AUTOMATIC TUNING OF SYSTEMS WITH ONE OR TWO UNSTABLE POLES

Stabilizability and identification of systems with one or two unstable poles is addressed. Two limit points of conditional stability are characterized using closed-loop dynamics with a relay and a novel nonlinear element. An algorithm is developed to analyze information from the resultant stable limit cycles in the process input and output. An easily tuned cascade PID control structure is then proposed to stabilize the system and achieve desirable performance. The proposed autotuning technique is tested with good results on a wide variety of unstable systems.     

M235T polymorphism of the angiotensinogen gene and hypertension in Chinese

OBJECTIVES: To compare the distributions of the genotypes and alleles of the M235T polymorphism of the angiotensinogen gene for hypertensive patients and normotensive controls. DESIGN: A study of association of genetic polymorphisms. SETTING: An outpatient clinic run by a university department handling referrals from primary care. PATIENTS: Two hundred and four subjects, 103 normal controls and 101 patients with newly diagnosed or documented hypertension. METHOD: Genomic DNA was extracted from peripheral blood leucocytes, amplified by polymerase chain reaction and digested with the restriction enzyme Tth 111 I. Methionine (M) and threonine (T) alleles were identified after electrophoresis. MAIN OUTCOME MEASURES: Prevalences of angiotensinogen genotypes and alleles for hypertensive patients and controls. Results: MM, TM and TT genotypes occurred in 3, 24 and 73% of controls and 1, 22 and 77% of hypertensive patients, respectively. The prevalences of the M and T alleles were 0.15 and 0.85 among controls and 0.12 and 0.88 among hypertensive patients. The prevalences of the angiotensinogen genotypes and alleles for controls and hypertensive patients did not differ significantly. CONCLUSIONS: Our findings differed from previous reports and suggested that this polymorphism is not associated with hypertension in this population.