Model-based feedforward register control of roll-to-roll web printing systems

Roll-to-roll (R2R) printing press provides a continuous printing process to print the multi-color patterns onto a web. To correctly print patterns on webs without the register error, it is necessary to regulate the web tension and transport velocity. In this paper, a mathematical model is built for R2R web printing system, and a model-based feedforward PD (MFPD) control method is proposed to reduce the effects of interaction in adjacent print units whose print cylinders are driven by electrical line shafts and is compared with other control methods. The proposed control method is applied to an industrial 7-color gravure printing register system. The register error can be controlled in the range of ±0.1 mm at a steady high speed, which meets the requirement of modern industrial application.     

Motion effect on the dynamic contact angles in a capillary tube

A mathematical model is developed to predict the effect of motion of a liquid plug in a capillary tube on the dynamic contact angles including the effects of driving pressure, liquid plug length, tube diameter, and operating temperature. Results show that the advancing contact angle significantly affects the flow resistance of the liquid plug occurring in a capillary tube. For a given driving pressure difference, the pressure difference due to the increase of the advancing contact angle is the primary contribution to the flow resistance of capillary flow in a capillary tube. For example, when the liquid plug length is equal to 5?mm at a driving pressure difference of 10?Pa and a tube radius of 500?μm, the flow resistance caused by the dynamic contact angle can be 92% of the total flow resistance at an operating temperature of 60°C. It can be concluded that the effect of the dynamic contact angle on the fluid flow of a liquid plug in a capillary tube must be considered.     

A numerical study of capillary stability in a circular cylindrical container with a concave spheroidal bottom

We study computationally the stability under gravitational and surface forces of a liquid in a circular cylindrical container with a concave spheroidal bottom for the case in which the volume of liquid is sufficiently small so that the bottom is not covered entirely. We assume the gravitational field to be directed along the axis of symmetry of the container, and for a specific container shape we compute the critical Bond number as a function of liquid volume for contact angles γ = 0°, 1°, 2°, and 4°. For the case γ = 0° we present graphically several critical equilibrium configurations and corresponding perturbation modes.     

Structure-induced spreading of liquid in micropillar arrays

Contact angle measurements on micropillar arrays were used to determine the conditions that trigger spontaneous penetration of liquids into surface structures. Square micropillars (20 μm) were fabricated in photoresist or quartz and modified chemically to alter the inherent contact angle (i.e., for a flat surface). The lattice spacing of the pillar array and pillar height was also adjusted to investigate the influence of geometry on the wetting behavior. A critical inherent contact angle, θ ₀, was observed below 90°, at which enhanced hydrophobicity switches to enhanced hydrophilicity. This differs from Wenzel’s prediction of θ ₀ = 90°. The transition is not a Cassie-Wenzel state transition. Above the critical angle, the static advancing contact angle increased with pillar coverage due to pinning. Below the critical angle, liquid spreads ahead of the droplet between the pillars to form a stable film. An example of chemical detection and the implications for multiphase microfluidics is discussed.     

张力变频在七电机型凹印机上的应用

本文着重阐述英威腾张力变频在七电机凹印机现场的成功应用,展示张力变频在印刷领域的张力与同步控制的先进方案,引导一种新的变频控制技术。     

Surface tension driven flow for open microchannels with different turning angles

Present study examines the flow characteristics of open microchannels with sharp turns by experimental and numerical methods. For the open channel system in microscale, the flow is mainly driven by surface tension at atmospheric pressure. The open channels are of various aspect ratios of depth-to-width, ranging from 0.75 to 3, and of turning angles from 45° to 135°. It is found that the turning angle and the aspect ratio of depth-to-width play major roles in the velocity of liquid front advancing, the meniscus of liquid–gas interface shape, and head loss of flow due to turning. Besides, the radius of curvature of the liquid front is reduced as the liquid front travels downstream and over the turning elbow. The loss coefficient remains the same for turning angles less than 75°, whereas it is increased further and is even more pronounced for turning angles larger than 105°. Numerical predications based on conservation laws agree with the experimental observations, and the flow characteristics are well described for open channel in microscale, as the aspect ratio is greater than or near to 1.5.     

Physiological responses of fire-fighter instructors during training exercises

Thirteen male instructors were monitored during a total of 44 live fire training exercises (ambient temperature 74?±?42°C). Exposure time during the ‘Hot Fire’ (HF), ‘Fire Behaviour’ and ‘Fire Attack’ exercises was 33.0?±?7.9?min (n?=?30); 26.3?±?5.5?min (n?=?6); and 7.3?±?2.6?min (n?=?8) respectively. At the end of the exercises, mean core temperature (t_core) was 38.5?±?0.9°C (n?=?32), however eight instructors had a t_core above 39°C. The mean maximum temperature under the fire hood was 41.2?±?4.6°C (n?=?40). Mean maximum heart rate (HR) was 138?±?26 bpm (n?=?34) however, in five exercises, HR exceeded 90% of the instructors' HR reserve. Mean fluid deficit was 0.62?±?0.6?l (n?=?30) at the end of the HF exercises, the maximum being 2.54?l. Four instructors doubted their ability to perform a rescue at the end of the exercise. The energy cost of performing simulated rescues of a 50?kg dummy in the cool was investigated in a pilot study. Mean HR during the rescues was 79?±?7% of the instructors' HR reserve and it was estimated that this could increase t_core by 0.4 to 0.6°C. The physiological responses to the fire-fighting exercises varied considerably and reflected the differences in work performed and external heat load. The results obtained from some individuals give cause for concern, and signs of heat strain were seen in at least two individuals.     

凹印机张力与速度解耦控制

印刷包装行业中,由于凹印机张力控制系统中动力学模型变化大,张力-速度的强耦合,很容易造成控制系统的不稳定。如何降低张力-速度的强耦合,提高产品质量,成为凹印机张力控制的重要课题之一。通过建立凹印机张力控制系统的数学模型,在此基础上实现了对张力-速度的解耦控制,并对解耦效果进行了仿真,仿真结果表明该方法能降低张力-速度之间的耦合程度,改善系统的控制效果。     

MHD natural convection in a nanofluid filled inclined enclosure with sinusoidal wall using CVFEM

Magnetohydrodynamic flow in a nanofluid filled inclined enclosure is investigated numerically using the Control Volume based Finite Element Method. The cold wall of cavity is assumed to mimic a sinusoidal profile with different dimensionless amplitude, and the fluid in the enclosure is a water-based nanofluid containing Cu nanoparticles. The effective thermal conductivity and viscosity of nanofluid are calculated using the Maxwell–Garnetts and Brinkman models, respectively. Numerical simulations were performed for different governing parameters namely the Hartmann number, Rayleigh number, nanoparticle volume fraction and inclination angle of enclosure. The results show that in presence of magnetic field, velocity field retarded, and hence, convection and Nusselt number decreases. At Ra = 10³, maximum value of enhancement for low Hartmann number is obtained at γ = 0°, but for higher values of Hartmann number, maximum values of E occurs at γ = 90°. Also, it can be found that for all values of Hartmann number, at Ra = 10⁴ and 10⁵, maximum value of E is obtained at γ = 60° and γ = 0°, respectively.     

Binary collision of drops in simple shear flow at finite Reynolds numbers: Geometry and viscosity ratio effects

The collision of two equal-size drops in an immiscible phase undergoing a shear flow is simulated over a range of viscosity ratios (??) and different geometries. The full Navier-Stokes equations are solved by a finite difference/front tracking method. Based on experimental data, different cases were simulated by changing the offset, size of drops, and viscosity ratio. The distance between drop centres along the velocity gradient direction (z) was measured as a function of time. It was found that ??z increases after collision and reaches a new steady-state value after separation. The values of ??z, during the interaction, increases with increasing initial offset. Our results show that the time of approaching of drops at low initial offset is greater than the other cases, but the maximum deformation is the same for equal drop sizes. The deformation decreases with decreasing the size of drops. As the initial offset increases, the drops rotate more quickly and the available contact time for film drainage decreases. We found that the trajectories of drops in the approaching stage are different owing to the different initial offsets. However, after the drops come into contact, it observed that they follow the same trajectories. As ?? increases, the drops rotate more slowly, and the point at which the drops separate is delayed. The trajectories of drops become more symmetric with the increased ??.     

A passive through hole microvalve for capillary flow control in microfluidic systems

A passive through hole microvalve is proposed to stop the capillary-driven flow in microchannels with small static contact angle (θ_s < 45°). Its gating condition on regulating flow is derived based on contact line theory. Using numerical simulations in certain limits and some experiments, we investigated the valve performance of a few different valve designs. A kind of converging through hole microvalve is found which can stop the relative faster capillary flow and is easier to fabricate and integrate. It is shown that allowable flow velocity for DI water could reach 0.5 m/s, and the height of microvalve could be as short as to 20 μm.     

Determination of color changes of inks on the uncoated paper with the offset printing during drying using artificial neural networks

This study attempts to determinate color changes based on time in inks applied on the surface of wood-free uncoated paper with offset printing during drying. This study consists of two main cases: (1) Experimental analysis: By preparing a test page according to the 12647-2 principle with an offset printing system, test prints were applied to 120 g/m² wood-free uncoated paper using an ECI 2002 CMYK test chart. Each press was measured being subject to process every 15 min in the first 2 h, then hour by hour between 2 and 12 h, then 4–4 h between 12 and 24 h, and then 6–6 h between 24 and 48 h. CIELAB and reflectance values between 380 and 720 nm of the target, 1,485 colors of the test chart were obtained. To see the drying and color changes of the ink on paper, changes were determined by printing on the paper and applying artificial neural network (ANN) to spectrophotometer data at the stated time intervals. (2) Empirical analysis: The use of the ANN has been proposed as numerical approach to get of empirical equations of color changes in inks applied on the surface of wood-free uncoated paper with offset printing during drying. Based on the outputs of the study, ANN model can be used to estimate the effects of digital proofing systems used in color management on print quality with high confidence with the use of the acquired equations without experimental study. In the study, as colors are defined in terms of wave length, in case, all wave lengths are taken into consideration, certain wave length changes have been taken into consideration.     

Effects of low back disability status on lower back discomfort during sustained and cyclical trunk flexion

A laboratory study was conducted to determine the effects of back disability status on endurance time and perceived discomfort during trunk flexion. Eighty participants (40 with chronic or recurrent low back pain (CRLBP), 40 pain-free) were tested. The trunk was flexed to 15°, 30°, 45° and 60° under three conditions: 1) continuous static flexion; 2) cyclical flexion with 20% rest; and 3) cyclical flexion with 40% rest. Each condition was performed for up to 600?s or until the participant reached his/her pain tolerance limit. Dependent variables included time to distracting discomfort (TDD), total endurance time (TET) and perceived discomfort. For continuous exertions, CRLBP participants had lower TDD (p?<?0.001), lower TET (p?<?0.001) and greater discomfort (p?<?0.001) compared to pain-free controls. In both groups, TDD and TET decreased and perceived discomfort increased as the flexion angle increased. For intermittent exertions, CRLBP participants reported greater discomfort than pain-free participants (p?<?0.001). Increasing rest from 20 to 40% reduced discomfort in CRLBP participants, but produced no consistent benefit in pain-free participants. To accommodate persons with CRLBP, consideration should be given to reducing both the magnitude (angle) and duration of trunk flexion required by their jobs.     

Control of downrange and crossrange motion of a descent module in a certain range of reentry angles with load factor constraints

Results concerning the terminal guidance algorithm at the reentry of the descent module into the Earth atmosphere are presented. This algorithm simultaneously eliminates predicted deviations in the downrange and crossrange directions. The restriction on the tolerable load factor n ?? 3 is taken into account. Three reentry angles are analyzed: the medium angle ?1.5°, the steep angle ?1.9°, and the flat angle ?1.2°. The motion of the descent module is considered in the disturbed Earth atmosphere represented by the TsNIIMash model. This model includes variations of the atmosphere density and the wind field. It is demonstrated that, depending on the reentry angle, the proposed algorithm guarantees the downrange maneuver zone in the range 1240?C1890 km and the crossrange maneuver zone of 210?C220 km on one side. The maximum guidance error at the altitude of 1 km does not exceed 0.8 km, and the average error is 0.1 km. The algorithm uses up to three bank angle reversals and uses the numerical prediction of the remaining part of the trajectory when choosing the guidance parameters. The concept of the automatic adjustment of the bank angle reference function depending on the entry angle and the prescribed distance to the target point in the maneuver zone is formulated.     

Contact line characteristics of liquid–gas interfaces over grooved surfaces

Surface wetting is an important phenomenon in many industrial processes including micro- and nanofluidics. The wetting characteristics depend on the surface tension forces at the three-phase contact line and can be altered by introducing patterned groove structures. This study investigates the effect of the grooves on the transition in the wetting behavior between the Cassie to Wenzel regimes. The experiments demonstrate that the wettability on a patterned surface depends on the spacing factor (S = channel depth/channel width). The spacing factor influences the contact angle, contact angle hysteresis, and the transition characteristics between the Cassie and Wenzel states. It was noted that under certain conditions (S > 1) the droplet behaved as a Cassie droplet, while exhibiting Wenzel wetting the rest of the time on the silicon microchannels tested. This criterion was used to design the groove structures on the sidewall of the proton exchange membrane fuel cell gas channel to remove the water effectively. The water coming from the land region into the gas channel is pulled by the grooves to the top wall where the airflow aided in its removal. Also, the contact angles measured on the surfaces were compared with the classical models that use wetted area, and the contact line model that uses the three-phase contact line length. It was found in our experiments that the contact line model predicts the contact angle on the patterned groove surfaces more accurately than the classical models.     

Buckling analysis of laminated composite plates with an elliptical/circular cutout using FEM

In this study, a buckling analysis was carried out of a woven–glass–polyester laminated composite plate with an circular/elliptical hole, numerically. In the analysis, finite element method (FEM) was applied to perform parametric studies on various plates based on the shape and position of the elliptical hole. This study addressed the effects of an elliptical/circular cutout on the buckling load of square composite plates. The laminated composite plates were arranged as symmetric cross-ply [(0°/90°)₂]_s and angle-ply [(15°/−75°)₂]_s, [(30°/−60°)₂]_s, [(45°/−45°)₂]_s. The results show that buckling loads are decreased by increasing both c/a and b/a ratios. The increasing of hole positioned angle cause to decrease of buckling loads. Additionally, the cross-ply composite plate is stronger than all other analyzed angle-ply laminated plates.     

Spin coating of hydrophilic polymeric films for enhanced centrifugal flow control by serial siphoning

In this paper, we implement rotational flow control on a polymeric microfluidic “lab-on-a-disc” platform by combining serial siphoning and capillary valving for sequential release of a set of on-board stored liquid reagents into a common (assay) channel. The functionality of this integrated, multi-step, multi-reagent centrifugal assay platform critically depends on the capability to establish very reproducible, capillary-driven priming of the innately only weakly hydrophilic siphon microchannels made from common poly(methyl methacrylate) (PMMA) substrates. Due to the relatively high contact angle of the native PMMA substrate, it was practically impossible to ensure sequential release of on-board stored reagents using the capillary-driven serial siphon valves. In this work, we demonstrate that spin-coated hydrophilic films of poly(vinyl alcohol) (PVA) and (hydroxypropyl)methyl cellulose (HPMC) provide stable contact angles on PMMA substrates for more than 60 days. The deposited films were characterized using contact angle measurements, surface energy calculations and X-ray photoelectron spectroscopy spectra. The PVA and HPMC films reduced the water contact angle of the PMMA substrate from 68° to 22° and 27° while increasing their surface energies from 47 to 62 and 57 mN m^?1, respectively. On the centrifugal microfluidic platform, the films were validated to enable the effective and reproducible priming of the serial siphon microchannels at low rotational frequencies while ensuring that the in-line capillary valves are not opened until their respective burst frequencies are passed. Furthermore, the biocompatibility of the proposed surface modification method was examined, and the platform was used to run a sandwich immunoassay for the detection of human immunoglobulin G, and its performance was proven to be comparable to dynamic coating using surfactants.     

Effect of work station design on sitting posture in young children

The purpose of the study was to compare muscular activity levels and sitting posture displayed by 10 children (mean age =4·7 years) when performing tracing tasks while seated at a traditional work station (level desk top, 5^° backward sloping seat) and at an ergonomically designed work station (15^° sloping desk top, 15^° forward sloping seat). EMG profiles of latissimus dorsi (LD), erector spine (ES), and superior trapezius (ST) were sampled using Medi-trace disposable surface electrodes for 10min on the non-dominant side. Muscle activity was sampled (1000 Hz) every 2min for 5000 ms while the subjects performed the tracing tasks at each station. Raw EMG signals of the five trials for each muscle were processed by removing signal offset, full-wave rectification, and integration. The subjects' posture was monitored from a lateral view using a Panasonic VHS video camera while the children were seated at each work station. Neck flexion angle and the angle between the torso and thigh (hip angle) were manually sampled from the video images each 1 min as an indication of the posture adopted by the subjects during the tracing tasks. Use of f-tests for dependent means indicated that there was no significant difference in either mean ES or ST muscle activity as a function of work station design. However, subjects demonstrated significantly less LD activity when seated at the ergonomic work station (mean = 20·9 V ms) compared with the traditional work station (mean = 24·4 V ms, t = ? 2·88, p = 0·018). When seated at the ergonomically designed work station, subjects demonstrated less neck flexion (mean = 34·4^°) and a significantly larger hip angle (mean = 107·8^°, t= ? 3·46, p = 0·003) than when seated at the traditional work station (neck flexion = 38·7^°, hip angle = 95·5^°). It was concluded that use of the ergonomic work station could assist in maintaining a more efficient anatomical alignment of young children when sitting and writing.     

A novel biorthogonal wavelet network system for off-angle iris recognition

One important category of non-ideal conditions for iris recognition is off-angle iris images. Practically it is very difficult for images to be captured with no offset. It then becomes necessary to account for off angle information in order to maintain robust performance. A biorthogonal wavelet based iris recognition system, previously designed at our lab, is modified and demonstrated to perform off-angle iris recognition. Biorthogonal wavelet network (BWN) are developed and trained for each class. The non-ideal factors are adjusted by repositioning the BWN. To test, along with the real data, synthetic iris images are generated by using affine and geometric transforms of 0°, 10° and 20^° experimentally collected images. The tests were carried out on the experimentally collected off-angle data and synthetically generated data for angles from 0° to 60^° with a resolution of 5^°. This approach is shown to have less constraints than a transformation based iris recognition approach. Iris images off-angle by up to 42^° for synthetic data and up to 45^° for experimental data are successfully recognized.     

Hexagon-based all-quadrilateral mesh generation with guaranteed angle bounds

In this paper, we present a novel hexagon-based mesh generation method which creates all-quadrilateral (all-quad) meshes with guaranteed angle bounds and feature preservation for arbitrary planar domains. Given any planar curves, an adaptive hexagon-tree structure is constructed by using the curvature of the boundaries and narrow regions. Then a buffer zone and a hexagonal core mesh are created by removing elements outside or around the boundary. To guarantee the mesh quality, boundary edges of the core mesh are adjusted to improve their formed angles facing the boundary, and two layers of quad elements are inserted in the buffer zone. For any curve with sharp features, a corresponding smooth curve is firstly constructed and meshed, and then another layer of elements is inserted to match the smooth curve with the original one. It is proved that for any planar smooth curve all the element angles are within [60° ? ε, 120° + ε] (ε ? 5°). We also prove that the scaled Jacobians defined by two edge vectors are in the range of [sin (60° ? ε),  sin 90°], or [0.82, 1.0]. The same angle range can be guaranteed for curves with sharp features, with the exception of small angles in the input curve. Furthermore, an approach is introduced to match the generated interior and exterior meshes with a relaxed angle range, [30°, 150°]. We have applied our algorithm to a set of complicated geometries, including the China map, the Lake Superior map, and a three-component air foil with sharp features. In addition, all the elements in the final mesh are grouped into five types, and most elements only need a few flops to construct the stiffness matrix for finite element analysis. This will significantly reduce the computational time and the required memory during the stiffness matrix construction.