Flat Surface Profile Research Articles

Numerical analysis of liquid desiccant dehumidification system with novel trapezoidal baffled surface

Environmental concerns as well as a rapid decrease in fossil fuel reserves, raise the need for a substitute to the conventional vapor compression system (VCS). Low-grade energy run liquid desiccant absorption system is emerging to be a viable substitute to the VCS. One of the major barriers to the development of a liquid desiccant absorber (LDA) is its low effectiveness. Current study proposes a modification of the flat surface profile of a falling film type liquid desiccant absorber with a trapezoidal baffled profile. The numerical model involves a 2-D transient, multiphase-multicomponent system with conjugate heat-mass interaction. The complex governing equations are solved using ANSYS FLUENT 19.2. The computational model under consideration is validated using the experimental results. The maximum deviation is observed to be 10.31% and 0.38 K in terms of humidity and temperature, respectively. It is observed that the performance is maximized with an trapezoidal baffled configuration of p:e = 10:1.5. The incorporation of trapezoidal baffled surface (p:e = 10:1.5) augmented the dehumidification and enthalpy effectiveness of the system by 26.1% and 24.2%, respectively. The desiccant solution concentration of 35% and temperature of 293 K are optimum inlet conditions for better designing of the absorber. Also, it is observed that minimum the air velocity, maximum is the effectiveness. The proposed modification is found to have 12.1% improved dehumidification effectiveness compared to the earlier configuration of the triangular corrugated solution wall. The same is observed to yield lesser dehumidification effectiveness of 4.85% compared to sinusoidal geometry, proposed earlier.

To inhibit coffee ring effect in inkjet printing of light-emitting polymer films by decreasing capillary force

Polymer thin film with uniform thickness and flat surface profile is the key point for polymer light emitting diodes (PLEDs) by inkjet printing. However, the coffee ring effect is usually observed due to the mismatch between the evaporation of the solvent and the decrease of solution volume, which promotes the formation of radial flow from the interior of the drop to the edge. In this paper, coffee ring effects of inkjet printed poly(spirobifluorene) films were proposed to be restrained by decreasing capillary force by adding co-solvent with high boiling point and high viscosity to the main solvent. The low evaporation rate of the co-solvent can reduce the driving force of the radial flow; meanwhile the high viscosity of the co-solvent can increase the resistance of the radial flow. Thus, polymer films with improve uniformity can be obtained due to the suppression of the radial flow. The device performance was greatly improved under the condition of proper film thickness and film uniformity and the maximum luminous efficiency of devices with inkjet printed poly(spirobifluorene) can reach 80% of the spin-coated devices.

Coffee-Ring-Free Quantum Dot Thin Film Using Inkjet Printing from a Mixed-Solvent System on Modified ZnO Transport Layer for Light-Emitting Devices.

Inkjet printing has been considered an available way to achieve large size full-color RGB quantum dots LED display, and the key point is to obtain printed film with uniform and flat surface profile. In this work, mixed solvent of 20 vol % 1,2-dichlorobenzene (oDCB) with cyclohexylbenzene (CHB) was used to dissolve green quantum dots (QDs) with CdSe@ZnS/ZnS core/shell structure. Then, by inkjet printing, a flat dotlike QDs film without the coffee ring was successfully obtained on polyetherimide (PEI)-modified ZnO layer, and the printed dots array exhibited great stability and repeatability. Here, adding oDCB into CHB solutions was used to reduce surface tension, and employing ZnO nanoparticle layer with PEI-modified was used to increase the surface free energy. As a result, a small contact angle is formed, which leads to the enhancement of evaporation rate, and then the coffee ring effect was suppressed. The printed dots with flat surface profile were eventually realized. Moreover, inverted green QD-LEDs with PEI-modified ZnO film as electron transport layer (ETL) and printed green QDs film as emission layer were successfully fabricated. The QD-LEDs exhibited the maximum luminance of 12 000 cd/m2 and the peak current efficiency of 4.5 cd/A at luminance of 1500 cd/m2.

Inkjet printed fine silver electrodes for all-solution-processed low-voltage organic thin film transistors

Inkjet printed silver (IJP Ag) source/drain (S/D) and gate electrodes were incorporated into a bottom-gate bottom-contact organic thin film transistor (OTFT) architecture to develop all-solution-processed low voltage OTFTs. With well controlled ink wetting on a cross-linked polyvinyl-alcohol surface, IJP Ag S/D electrode pairs were fabricated with controllable short channels down to 20 μm using a Dimatix 2831 inkjet printer with a 10 pL cartridge, and formed good contacts with the organic semiconductor layer. IJP gate electrodes with a low flat surface profile were also achieved to obtain OTFTs of high quality gate dielectric layer for low leakage current. The fabricated low voltage all-solution-processed OTFTs present good device performance with a low operation voltage below 2 V, a mobility of 0.3 cm2 V−1 s−1, and an ON/OFF current ratio larger than 104.

Growth and novel structural features of tubular biofilms produced under different hydrodynamic conditions

Biofilm growth and internal structures were investigated by Confocal Scanning Laser Microscopy and fluorescently labeled oligonucleotide probe hybridization. Biofilms on smooth flat surfaces such as glass slides grew as isolated cell clusters. Under a hydraulic linear flow velocity of 1.7 cm/s mature biofilms exhibited a network like structure consisting of large interconnected cell clusters leading to possible three-dimensional mass transport. Smooth curved tube surfaces were also colonized by isolated cell clusters. However a clustered structure was not observed in mature tubular biofilms which grew as a continuum. Under laminar flow conditions, the tubular biofilms had a uniform cell distribution along the depth with a flat surface profile. The dense tubular biofilms produced under turbulent flow had a stratified structure with thickness. Morphologically these had an irregular surface profile with protrusions extending from a thick base layer. The production of extracellular polymeric substances were both cell physiology and growth related. While hydrodynamic condition was shown to be an effective tool for manipulation of biofilm structures, the relationship of the structure to biological activity and process control needs further investigation.

A numerical study of ocean polarimetric thermal emission

A numerical model for polarimetric thermal emission from penetrable ocean surfaces rough in two directions is presented. The numerical model is based on Monte Carlo simulation with an iterative version of the method of moments (MOM) known as the sparse matrix flat surface iterative approach (SMFSIA), extended to the penetrable surface case through a numerical impedance boundary condition (NIBC) method. Since the small U/sub B/ brightnesses obtained from ocean surfaces (usually less than 1.5 K, or 0.5% of a 300-K physical temperature) require extremely accurate simulations to avoid large errors, a parallel version of the algorithm is developed to allow matrix elements to be integrated accurately and stored. The high accuracy required also limits simulations to near flat surface profiles, so that only high-frequency components of the ocean spectrum are modeled. Variations in nadir polarimetric brightness temperatures with spectrum low- and high-frequency cutoffs show the Bragg (or shortwave) portion of the spectrum to contribute significantly to emission azimuthal signatures, as predicted by the small perturbation or composite surface approximate theories. Quantitative comparisons with approximate methods show perturbation theory to slightly overestimate linear brightness temperatures, but accurately predict their azimuthal variations, while physical optics (PO) significantly underestimates both linear brightness temperatures and their azimuthal variations. Further simulations with the numerical model allow sensitivities to ocean spectrum models to be investigated and demonstrate the importance of an accurate azimuthal description for the ocean spectrum.

Exact measurement of flat surface profiles by object shifts in a phase-conjugate Fizeau interferometer

We propose a method of exact measurement of flat surface profiles in a phase-conjugate Fizeau interferometer. Aberration of lenses causes an undesirable phase distribution in the interference signal of the phase-conjugate Fizeau interferometer. To eliminate this phase distribution, we shift the object in two directions orthogonal to each other and we get difference values of the surface profile of the object. Additional displacements of the object surface involved in the shifts lead to some small errors in the difference values. We estimate an exact surface profile by solving the difference equations. Characteristics of the method are made clear through computer simulations and measurements of a 40-mm-diam flat mirror.

Theoretical growth morphology of whewellite CaC2O4�H2O

The morphological theory of Hartman and Perdok (1955, 1956) allows to deduce the character of a growth form {hkl} on the basis of structural data alone. Its application to the structure of whewellite leads to the identification of forms {100}, {010}, {021}, {011}, {12\(\bar 1\)} and {121} which show during the growth a flat surface profile (flat forms F). These forms occur very frequently in the crystals we grew from pure aqueous solutions at supersaturation β≦1,90. Other forms, {001} and {10\(\bar 1\)}, possibly show a double character (F or S, where S stays for related faces showing a stepped profile during the growth) according to the bonds assumed within some periodic bond chains (PBCs). Alternative ways of bonding water molecules lead to different structures of the same PBC. The different energy corresponding to these structures may explain the complex morphology of both natural and synthetic crystals grown at high β values.

Laser surface melting of some alloy steels

AbstractAn investigation is reported of the structures of laser surface-melted zones in a 1C- 1·4Cr steel; also some results are presented for a carburized alloy steel and a medium-carbon alloy steel. Treatment was carried out with a CW CO2 laser at a power of 1·7kW, beams of ∼O·4-4·3mm dia., and traverse speeds of ∼8-250 mm s−1 (corresponding to interaction times of 2-500 ms). Zones of smooth, flat surface profiles were produced with essentially martensitic structures and corresponding high hardness. In the high-carbon steels coated with graphite before laser melting, the hardness of the zones decreased with increasing traverse speed as a result of carbon solution, leading to a lowering of Ms and increased austenite retention. In the 1C-1·4Cr steel. zones were produced that consisted almost entirely of austenite with fine columnar cellular/dendritic structures. Refrigeration to ∼-100C was needed to form substantial amounts of martensite; stabilization effects in relation to martensite formation resulted ...