bluuebunny/crossref_metadata_2025 huggingface dataset:
Valuing local heritage: Issue and challenges of geographical indication protection for local artisans in Indonesia Kasongan village heritage
Authors: Asri Dyah P. B. , Sriyono Edy , Hapsari Murti A. , Syahrin Savira A.
Published: November 2021

Many studies and research that are emphasizing on intellectual property rights (IPR) tend to be focused on standardized products in established markets. This study comes from one fundamental inquiry; how to determine the value of IPR for creative products, in this case, the product of art such as handicraft? This study paper presents a study case focusing on analyzing the IPRs for handicraft products especially pottery crafts in Kasongan, Bantul, Yogyakarta, Indonesia. This study focused on the evaluation of geographical indication (GI) from its juridical impact to legal protection. The data were carefully collected through library studies and field studies. The analysis begins with data collection, data reduction, data presentation, and finally, the conclusion. From this study it is found that GI legal protection will be financially beneficial for Kasongan pottery craftsmen, thus increasing its urgency to be registered in GI to sustain the industry. Furthermore, this study also describes Kasongan product's characteristic that has different characteristics from earthenware and handicraft products from other regions in Indonesia. This study focused to complements the literature on managing and evaluating GI regulation particularly in Indonesia, while discussing current situation, problems, and challenges ahead.
Accuracy of different cutoffs of the waist‐to‐height ratio as a screening tool for cardiometabolic risk in children and adolescents: A systematic review and meta‐analysis of diagnostic test accuracy studies
Authors: Ezzatvar Yasmin , Izquierdo Mikel , Ramírez‐Vélez Robinson , del Pozo Cruz Borja , García‐Hermoso Antonio
Published: November 2021

The present systematic review with meta‐analysis sought to estimate the accuracy of different waist‐to‐height ratio (WHtR) cutoff ranges as risk indicators for cardiometabolic health in different populations of children and adolescents. Systematic searches were undertaken to identify studies in apparently healthy participants aged 3–18 years that conducted receiver operating characteristic curve analysis and reported area under the receiver operating characteristic curves for WHtR with any cardiometabolic biomarker. Forty‐one cross‐sectional studies were included in the meta‐analysis, including 138,561 young individuals (50% girls). Higher area under summary receiver operating characteristic (AUSROC) values were observed in cutoffs between 0.46 and 0.50 (AUSROC = 0.83, 95%CI: 0.80–0.86) and ≥0.51 (AUSROC = 0.87, 95%CI: 0.84–0.90) (p < 0.001 in comparison with cutoffs 0.41 to 0.45), with similar results in both sexes. The AUSROC value increased in the East and Southeast Asian regions using a WHtR cutoff of ≥0.46 (AUSROC = 0.90, 95%CI: 0.87 to 0.92). A cutoff of ≥0.54 was optimal for the Latin American region (AUSROC = 0.96, 95%CI: 0.94–0.97). Our meta‐analysis identified optimal cutoff values of WHtR for use in children and adolescents from different regions. Despite the widely accepted WHtR cutoff of 0.50, the present study indicated that a single cutoff value of WHtR may be inappropriate.
How many skin barriers haveth we: Percutaneous egression of ions?
Authors: Chiang Chavy , Maibach Howard I.
Published: November 2021

Introduction

Skin provides critical barrier properties that enable terrestrial life. Myriad research has focused on the “water barrier” to transepidermal water loss (TEWL) despite there being a multitude of skin barrier properties. We asked what other barrier properties may have been overlooked and compiled data demonstrating the “electrolyte barrier” to be of potential clinical relevance.

Methods

A literature search was conducted through PubMed, Embase, Google Scholar, and Web of Science databases for the following keywords: “transepidermal” or “epidermal” or “cutaneous” or “skin” or “percutaneous” and “ion” or “sodium” or “chloride” or “potassium” or “electrolyte” and “flux” or “egression.” Textbooks at the University of California, San Francisco were also hand reviewed. Experimental studies quantifying in vivo or ex vivo percutaneous egression of ions in response to human skin barrier perturbation were included.

Results

Experimental damage to skin, mostly by tape‐stripping, frequently induced increased ion flux rates through the epidermis, in addition to increases in TEWL values. Interestingly, barrier perturbation did not always result in a concomitant rise in TEWL and transepidermal ion flux rates, such as in delipidization, indicating a distinction between the two barriers.

Conclusion

Quantifying the percutaneous egression of ions in response to physical or chemical alterations may offer additional data that are not to be captured with TEWL studies exclusively. Continued efforts should be made to: (1) advance this technique as a method of assessing skin status and (2) enhance our understanding of other barriers and mechanisms.
Can the CutiScan CS 100® measure anisotropy and viscoelasticity in scar tissue after mastectomy? A reliability and validity study
Authors: Anthonissen Mieke , Van den Kerckhove Eric , Moortgat Peter , Geraerts Inge , Devoogdt Nele , De Vrieze Tessa , De Groef An
Published: November 2021

Background

Scars have different biomechanical characteristics, including anisotropy and viscoelasticity compared to healthy skin. To assess these characteristics, the CutiScan CS 100® can be used. The aim of the present study is to investigate reliability and validity of this device in breast cancer patients.

Materials and methods

Thirty female patients, with scar adhesions following mastectomy were assessed with the CutiScan CS 100®. Maximal distensibility (pixels) (V1), after‐suction return rate (pixels) (V2), and their ratio (%) (V3) at three points on and around the scar were assessed as measures of viscoelasticity. For intra‐ and interrater reliabilities, the intra‐class correlation coefficient (ICC) and its 95% confidence intervals were calculated. The standard error of measurement (SEM) was calculated to interpret reproducibility of these measurements. To investigate criterion validity of the measurement of anisotropy, measurements in the direction of healthy skin were compared with measurements in the direction of the scar, using a paired t‐test.

Results

V1, V2, and V3 show poor to moderate intrarater reliability (ICC 0.00–0.72) and interrater reliability (ICC 0.00–0.53). The maximum displacement (V1) on the measurement point above the scar shows the best reliability (ICC 0.33–0.72). The SEM is about the same for all parameters at all three points. The paired sample t‐test showed a significant difference (p < 0.05) between V1 in the direction towards the scar versus the measurement towards healthy tissue, on the point below the scar.

Conclusion

These first reliability and validity results of the CutiScan CS 100® for measuring anisotropy and viscoelasticity in scar tissue adhesions after mastectomy seem promising. Further research is needed addressing the limitations of the present study design.
Conceptualizing careers: Is there an element of STEM in every profession?
Authors: Navy Shannon L. , Heisler Jennifer , Papa Jeffrey , Gjurkovitsch Anna
Published: November 2021

Science, technology, engineering, and mathematics (STEM) is widely visible in education and workforce policies and discussions in the United States (US). However, there is a lack of consensus on what is considered a STEM career. In addition, little is known about how K‐12 teachers conceptualize STEM careers and how this information is portrayed to students. This mixed methods study investigated 52 K‐12 teachers’ conceptions of STEM careers and if they included this information in their classroom instruction. The data collected consisted of a questionnaire and follow‐up interviews with a subset of teachers. The data analysis revealed that there was a range of how teachers defined and conceptualized STEM careers from narrow to very broad. This led to the development of the STEM‐Peripheral, Adjacent, Central (STEM‐PAC) career classifications which categorizes careers based on the application of STEM knowledge and skills. Additionally, teachers articulated benefits and drawbacks of including STEM career information in their instruction. Benefits included increasing student interest in STEM careers and making learning relevant. Drawbacks included limits to teacher time and knowledge. This study suggests teachers should present STEM as it is connected to various careers and that administrators should support teachers who wish to include this in their curriculum.
Experimental and Numerical Assessments of the Effects of Vacuum and Solar Film on the Performance of a Low Concentration Eccentric Solar Collector
Authors: Teles Mavd P. R. , Ismail Kamal A. R.
Published: November 2021

Low concentration collectors are usually recommended for water heating and refrigeration systems. The literature reveals lack of information on numerical modeling, experimental data, and thermal performance of eccentric evacuated double tube solar collectors. This study is focused on eccentric solar collectors since this arrangement allows adequate concentration for achieving relatively high temperatures while having small size and occupying less space. The effects of the vacuum in the annular space and reflective film on the enhancement of working fluid heating and overall thermal performance were also assessed. An in-house numerical code using the finite volume method was used to discretize the conservation equations and the predictions were validated by experimental results obtained from an experimental rig that was constructed and instrumented for outdoor tests. The experiments were performed in the city of Campinas-Brazil during the autumn season. The investigated versions of the eccentric double tube solar collector include a version with a reflective film and vacuum, a second version with a reflective film but without vacuum, a third arrangement without a reflective film but with vacuum, and finally a version without both a reflective film and vacuum. The results showed that the version with reflective film and vacuum demonstrated high efficiency achieving 89%. The lowest efficiency of 42% was achieved by the version without both reflective film and vacuum. The comparative analysis of the four versions shows that the incorporation of reflective film increases the collector efficiency by 28%, while the vacuum increases the efficiency by about 1.3%.
Thermal and Hydraulic Performances of Porous Microchannel Heat Sink Using Nanofluids
Authors: Ahmed Zahir U. , Raihan Md. Roni , Ghaffari Omidreza , Ikhlaq Muhammad
Published: November 2021

Microchannel heat sink is an effective method in compact and faster heat transfer applications. This paper numerically investigates thermal and hydraulic characteristics of a porous microchannel heat sink (PMHS) using various nanofluids. The effect of porosity (γ = 0.32–0.60), inlet velocity (win = 0.5–1.5 m/s), and nanoparticle concentration (ϕ=0.0025 – 0.05) on thermal-hydraulic performance is systematically examined. The result shows a significant temperature increase (40 °C) of the coolant in the porous zone. The pressure drop reduces by 35% for γ = 0.32 compared to the non-porous counterpart, and this reduction of pressure significantly continues when γ further increases. The pressure drop with win is linear for PMHS with nanofluids, and the change in pressure drop is steeper for nanofluids compared to their base fluids. The average heat transfer coefficient increases about 2.5 times for PMHS, and a further increase of 6% in h¯ is predicted with the addition of nanoparticles. The average Nusselt number Nu¯ increases nonlinearly with Re for PMHS. The friction factor reduces by 50% when γ increases from 0.32 to 0.60, and the effect of nanofluid on friction factor is insignificant beyond the mass flowrate of 0.0004 kg/s. Whilst Cu and CuO nanoparticles help to dissipate the larger amount of heat from the microchannel, Al2O3 nanoparticle appears to have a detrimental effect on heat transfer. The thermal-hydraulic performance factor strongly depends on the nanoparticles, and it slightly decreases with the mass flowrate. The increase of nanoparticle concentration, in general, enhances both h¯ and ΔP linearly for the range considered.
The Influence of Initial Stresses and Boundary Restraints on the Nonlinear Vibrations of Cylindrical Shells
Authors: Evensen David A.
Published: November 2021

A Rayleigh-Ritz procedure is used in conjunction with nonlinear shallow shell theory to study the influence of axisymmetric initial stresses on the nonlinear flexural vibrations of thin-walled cylindrical shells. A similar formulation is used to determine the effect of in-plane boundary conditions on the nonlinear vibrations. Both analyses make use of an assumed vibration mode which possesses a moment restraint at the edges of the shell. The results show that compressive initial stresses cause the vibrations to become increasingly nonlinear as buckling is approached. Initial tensile stresses generally cause the vibrations to become more nearly linear. In-plane restraints on the axial displacement at the ends of the shell have a hardening influence on the nonlinear behavior. This influence is most pronounced for vibration modes with high axial wave numbers. A study of the moment restraint at the boundary shows that for thin shells, the conditions of simple-support are closely approximated by the present analysis.
Non-Linear Vibrations of Fluid-Filled, Simply Supported Circular Cylindrical Shells: Theory and Experiments
Authors: Amabili M. , Pellicano F. , Païdoussis M. P.
Published: November 2021

The large-amplitude response of thin, simply supported circular cylindrical shells to a harmonic excitation in the spectral neighbourhood of one of the lowest natural frequencies is investigated. Donnell’s nonlinear shallow-shell theory is used and the solution is obtained by Galerkin projection. A mode expansion including driven and companion modes, axisymmetric modes and additional asymmetric modes is used. In particular, asymmetric modes with twice the number of circumferential waves of driven and companion modes are included in the analysis. The boundary conditions on radial displacement and the continuity of circumferential displacement are exactly satisfied. The effect of internal quiescent, incompressible and inviscid fluid is investigated. The equations of motion are studied by using a code based on the Collocation Method. Validation of the present model is obtained by comparison with other authoritative results and new experimental results. The effect of the number of axisymmetric modes used in the expansion on the response of the shell is investigated, clarifying questions open for a long time. The contribution of additional longitudinal modes is absolutely insignificant in both the driven and companion mode responses. The effect of modes with harmonics of the circumferential mode number n under consideration is limited so far as the trend of nonlinearity is concerned, but is significant in the response with companion mode participation for lightly damped shells (empty shells). Results show the occurrence of travelling wave response in the proximity of the resonance frequency, the fundamental role of the first and third axisymmetric modes in the expansion of the radial deflection with one longitudinal half-wave, and limit cycle responses. A liquid (water) contained in the shell generates a much stronger softening behaviour of the system. Experiments with a water-filled circular cylindrical shell made of steel are in very good agreement with the present theory.
Robust Design Applied to Concurrent Parameter and Tolerance Selection
Authors: Gupta Rahul , Feng Chang-Xue Jack
Published: November 2021

This research discusses the robust design method for reducing cost and improving quality using the fractional factorial design approach. Robust design is proposed by Professor Genichi Taguchi to determine the optimum configuration of design parameters for better performance, higher quality and lower cost. The philosophy Taguchi recommends is sound and should be included in the quality improvement process of any organization. However, some methods of statistical data analysis and some approaches to the design of experiments, which he advocates, are unnecessarily complicated and sometimes ineffective. His sound engineering concepts can be combined with more efficient and effective experimental design and statistical data analysis methods. This is demonstrated by simultaneously optimizing the nominal value and the tolerances for a nonlinear RL electric circuit using the fractional factorial design approach instead of the Taguchi orthogonal array approach. Another contribution of this research is the incorporation of manufacturing cost data into the design stage.
Product/Component Information Field and Its Application to Concurrent Product Development
Authors: Qiao Lihong , Yang Zhibing , Zhang Chuck , Wang Ben
Published: November 2021

This paper presents a new modeling method for representing the spatial and configuration information involved for concurrent product development in design and its supporting processes. This method is called information field representation (IF-Rep). Based on this method, product/component models can be easily created — regardless of the complexity of the product/component — and are convenient to be used in various DFX processes to support design. This paper introduces applications of the IF-Rep and a key procedure in implementing IF-Rep modeling to support concurrent product development.
Thin Film NiTi Shape Memory Alloy Microactuator With Two-Way Effect
Authors: Gill John J. , Carman Gregory P.
Published: November 2021

Thin film SMA (Shape memory alloy) is a useful material for MEMS (Microelectromechanical Systems) actuator. This is because the thin film has an improved frequency response compared to bulk SMA, high work density, and produces large strain. A novel two-way thin film NiTi (Nickel Titanium) shape memory alloy actuator is presented in this paper. Thin film shape memory alloy is sputter-deposited onto a silicon wafer in an ultra high vacuum system. Transformation temperatures of the NiTi film are determined by measuring the residual stress as a function of temperature. Test results show that the Martensite-Temperature-Finish (Mf) is approximately 60° C, and the Austenite-Temperature-Finish (Af) is 110° C. A free standing NiTi membrane (12 mm × 12 mm and 2.5 μm thick) is fabricated using MEMS technology. We found that a mixture of HF (Hydro Fluoric Acid), HNO3 (Nitric Acid) and DI (Deionized) water with thick photo resist mask works best for the fabrication process. The membrane is hot-shaped into a dome shape. Results indicate that when the temperature of the NiTi film exceeds Af, the NiTi membrane transforms into the trained hot-shape. When the temperature cools down to room temperature, the membrane returns to the initial flat shape. The performance of the SMA micro actuator is characterized with a laser measurement system for deflection vs. input power and frequency response. The maximum deflection of SMA microactuator is 230 μm. The corresponding frequency responses at the maximum deflection are 30 Hz with Copper (Cu) block placed underneath the microactuator and less than 1 Hz when Plexi-glass is placed.
Cooling Effect of a MEMS Based Micro Capillary Pumped Loop for Chip-Level Temperature Control
Authors: Kirshberg Jeffrey , Yerkes Kirk , Trebotich Dave , Liepmann Dorian
Published: November 2021

Utilizing current Micro Electro Mechanical Systems (MEMS) technologies, a three-port micro-capillary pumped loop (micro-CPL) was designed, fabricated and tested to provide integral cooling to electronics or MEMS type devices. The two wafer design consists of one silicon and one borofloat glass wafer. An analytical study was used in determining the geometry of the device, including the evaporator dimensions (1000 μm × 2000 μm) and the length of the liquid and vapor lines (35 mm). Using laser spot heating, the finished device was run near steady-state. It was determined that the micro-CPL resulted in a backside cooling effect of at least 7 C when a laser delivering 7.5 W (+/− 0.2 W) with a spot-size diameter of 1.0 mm was focused on the front side of the evaporator region.
An Integrated SOI Optical Microswitch Using Electrostatic Micromirror Actuators With Insulated Touch-Down Beams and Curved Electrodes
Authors: Jin Young-Hyun , Seo Kyoung-Sun , Cho Young-Ho , Lee Sang-Shin , Song Ki-Chang , Bu Jong-Uk
Published: November 2021

We present an integrated SOI optical microswitch, composed of silicon waveguides and electrostatically actuated gold-coated silicon micromirrors. The optical microswitch serves as an optical signal transceiver containing an LD receiver and a PD transmitter. For lower micromirror switching voltage, we modify the conventional curved electrode microactuator into the new microactuator with touchdown beams. In addition, we simplify the structure and the process of the microswitch by using the ICP etching of SOI wafers. From the fabricated microswitch, we measure the switching voltage of 31.7±4V at the resonant frequency of 6.89kHz. Compared to the conventional microactuator, the touch-down beam microactuator achieves 87.4% reduction of the switching voltage. We observe the single mode wave propagation through the silicon waveguide with the measured micromirror loss of 4.18±0.25dB. We analyze major source of the micromirror loss, thereby presenting design guidelines for low-loss micromirror switches. We discuss a feasible method to reduce the switching voltage to 10V by reducing the residual stress of electrode insulation layer to 30MPa.
Scaling Relations for Piezoresistive Microphones
Authors: Saini Rahul , Bhardwaj Sunil , Nishida Toshikazu , Sheplak Mark
Published: November 2021

This paper presents a comprehensive model of a circular-diaphragm piezoresistive microphone. The structural characteristics of the diaphragm are developed as a function of both in-plane stress and transverse loading. The mechanical scaling for piezoresistor location and maximum sensitivity is given. The dynamics of the microphone are explored by combining the fundamental structural model with a lumped-element energy model. A description of the elements is given along with the frequency limitations of the lumped approximation for each element. This model is then used to provide insight into the key aspects of the dynamic response.
Design of a Micro Heat Engine
Authors: Xu C. , Hall J. , Richards C. , Bahr D. , Richards R.
Published: November 2021

The design for a totally new class of heat engine, a micro heat engine, which takes advantage of thermophysical phenomena unique to small scales, is introduced. The proposed engine is an external combustion engine, in which thermal power is converted to mechanical power through the use of a novel thermodynamic cycle which approaches the ideal vapor Carnot cycle. Mechanical power is converted into electrical power through the use of a piezoelectric generator. The generator, which takes the form of a flexible membrane, can be readily manufactured using MEMS fabrication techniques but still delivers high conversion efficiency. This approach eliminates the requirement to manufacture complex micromachines such as rotary compressors and turbines, resulting in a very simple but highly efficient device.
Design and Characterization of Small-Scale Sandwich Beams Fabricated by Photolithography and Electrodeposition
Authors: Sugimura Yuki
Published: November 2021

Small-scale sandwich beams with core structures having cell diameters and wall widths on the order of 500 μm and 100 μm, respectively, have been produced through fabrication methods that combine photolithography and electrodeposition. Two core configurations have been examined: 1) regular hexagonal honeycomb and 2) high-aspect ratio hexagonal shells having an open architecture. The bending response of the sandwich beams has been examined and compared with the beam theory predictions. Shear stiffness of the honeycomb core was considerably high and therefore the bending behavior was dominated by the face sheets. The bending of the sandwich specimens with the hexagonal shells, on the other hand, was largely dependent on the core. The sandwich beam dimensions investigated in this study have not been optimized for weight minimization and structural efficiency. Further advances in fabrication methods to produce micrometer-size features and high-aspect ratio cores will enable realization of structurally efficient, lightweight sandwich beams and panels that can be used as multifunctional components in small-scale devices.
Time-Periodic Forced Convection in Micro Heat Spreaders
Authors: Sert Cuneyt , Beskok Ali
Published: November 2021

A new micro heat spreader (MHS) concept for efficient dissipation of large, concentrated heat loads is introduced. The MHS is a single-phase, closed micro-fluidic system, which utilize time-periodic forced convection cooling. We verified the MHS concept by numerically simulating its operation under various conditions. Our parametric studies have shown that, unlike the steady laminar forced convection, the Nusselt number for time-periodic forced convection laminar flows have strong dependence on the Reynolds and Prandtl numbers. The increase in the Nusselt number indicates enhanced cooling capability of the MHS device. Based on our parametric studies, we calculated the optimum operation conditions, device dimensions and the maximum heat-dissipation rates.
A Hybrid Microfluidic Mini System Towards a “Lab-on-a-Chip” for Biochemical Immunoassay
Authors: Dharmatilleke Saman , Wijayawardhana C. A. , Okulan N. , Medis P. , Thomas J. H. , Henderson H. Thurman , Heineman William R. , Halsall H. Brian
Published: November 2021

Hand-held, fully automated microfluidic systems have been developed and characterized to perform a magnetic bead-based biochemical immunoassay. The magnetic beads were coated with a polymer on which a dendritic antibody had been prepared to form the basis of a “sandwich” immunoassay for sensing biomolecules. With the press of a button, a complete immunoassay is performed to detect biohazards, and the result of the assay is displayed on a LCD. One system was made by using biocompatible silicone tubing for interconnections between the devices while another system was fabricated on a micromachined “glass-on-silicon” motherboard (Dharmatilleke et al.,. 2000). The first system consists of four collapsible reservoirs for reagent storage, made of very thin biocompatible Teflon™; an array of zero dead volume pinch valves; two magnetic curtain magnetic particle separators; a micro wire electrode or IDA for detection; a flow sensor, a valveless rotary pump to pull the reagents through the microfluidic system and associated electronics. On the second system, the mini pinch valves have been replaced by “collapsible” membrane type zero dead volume valves and pumping is by peristaltic operation of the valves. This work preceeds the next step, which is an all-MEMS system “on-a-chip”.
A Surface-Micromachined Nitride-Diaphragm High-Pressure Sensor for Oil Well Application
Authors: Xu Yong , Jiang Fukang , Tai Yu-Chong , Donzier Eric , Loomis William A. , Liberman Arthur D.
Published: November 2021

A surface-micromachined, high-pressure sensor with polysilicon piezoresistors for oil well applications has been successfully developed. This work represents the first report of a nitride-diaphragm (3μm thick) oil-well pressure sensor with a diaphragm diameter of 44μm. The sensors have been calibrated up to 4000 psi. A sensitivity of 7.7 μV/V/psi is obtained. With 5 V excitation voltage, the full scale output (FSO, 4000 psi) is 154 mV. The nonlinearity is less than ± 0.2% of FSO. The hysteresis is less than 0.04% of FSO. A temperature coefficient of 25 μV/V/°C (equivalent to 0.08% of FSO/°C) is observed under 1000 psi pressure bias.
The Correct Treatment of Harmonic Pressure-Flow Behavior in Microchannels
Authors: Morris Christopher J. , Forster Fred K.
Published: November 2021

Advances in microfluidic technology give great potential for integrated systems with many components. Because continuum modeling is difficult even for simple systems, low-order modeling is essential to their design. Unsteady flow in microfluidic components such as channels and valves may require special treatment to achieve accurate low-order models of entire systems. One example is the fixed-valve micropump, in which the interaction between mechanical, electrical, and fluidic components produces maximum pump output at a resonant frequency near the corner frequency of the valves. In this frequency range the commonly-used value for fluid impedance was found to be in error by 30%, causing errors in predictions of pump membrane motion by as much as 300%. Proper treatment of the pressure-flow relations based on the exact solution of the Navier-Stokes equations for oscillatory flow corrected these deficiencies.
Microdegasser for HPLC Devices
Authors: Rummler Zeno , Berndt Manfred , Härtl Hans-Georg , Hempel Mario , Peters Ralf-Peter , Schomburg Werner K.
Published: November 2021

The market of chemical analysis calls for more sensitive devices which are able to analyze very small sample volumes of only a few nanoliters in a very short time. Therefore, devices are required, which contain components with microscopic dimensions. Such micro devices can be fabricated with the AMANDA process.

This paper describes a microdegasser for high performance liquid chromatography (HPLC), which was developed in a cooperation of Agilent Technologies, Forschungszentrum Karlsruhe (Karlsruhe Research Center), and STEAG microParts and is manufactured now by STEAG microParts. The microdegasser is one of the components, which help the new generation of HPLC devices of Agilent Technologies to achieve their excellent market position.
On a Constitutive Model for Twisted Hybrid Yarns
Authors: Godfrey Thomas A. , Rossettos John N.
Published: November 2021

A simple micromechanical model is developed for the interactions in a parallel square-stacked mixed array of elastic fibers representing the microstructure of a hybrid yarn undergoing axial extension. The mixed array consists of a small fraction of relatively high-modulus, low-elongation-to-break (LE) fibers dispersed among high-elongation-to-break (HE) fibers. The LE fibers are assumed to break into fragments, and the LE fiber fragments are assumed to slip relative to neighboring fibers in regions near the fragment tips. The fiber array experiences lateral compression arising from the remote tension on the twisted yarn, and frictional forces acting at slipping fiber-to-fiber contact surfaces are assumed to obey Amontons’ Law. Solutions of a dimensionless boundary value problem for deformations in a unit cell of the fiber array are presented. Dimensionless parameters involving the constituent LE and HE fiber properties are identified and their influence on hybrid yarn tensile behavior is illustrated.
New Frontiers in Enhanced Heat Transfer
Authors: Bergles Arthur E.
Published: November 2021

This review paper considers the many techniques that have been developed to enhance convective heat transfer. A summary is given of the techniques that are effective for the various modes of heat transfer. Of particular interest currently is compound enhancement that involves the simultaneous application of several techniques, so as to produce an enhancement that is larger than the individual techniques operating separately. There are many experimental and analytical challenges that relate to obtaining and applying data. The current advanced enhancement represents 3rd generation heat transfer technology. This technology will find increasing application in all industries.
Heat Transfer Enhancement for Finned-Tube Heat Exchangers With Winglets
Authors: O’Brien James E. , Sohal Manohar S.
Published: November 2021

This paper presents the results of an experimental study of forced convection heat transfer in a narrow rectangular duct fitted with a circular tube and/or a delta-winglet pair. The duct was designed to simulate a single passage in a fin-tube heat exchanger. Heat transfer measurements were obtained using a transient technique in which a heated airflow is suddenly introduced to the test section. High-resolution local fin-surface temperature distributions were obtained at several times after initiation of the transient using an imaging infrared camera. Corresponding local fin-surface heat transfer coefficient distributions were then calculated from a locally applied one-dimensional semi-infinite inverse heat conduction model. Heat transfer results were obtained over an airflow rate ranging from 1.51 × 10−3 to 14.0 × 10−3 kg/s. These flow rates correspond to a duct-height Reynolds number range of 670–6300 with a duct height of 1.106 cm and a duct width-to-height ratio, W/H, of 11.25. The test cylinder was sized such that the diameter-to-duct height ratio, D/H is 5. Results presented in this paper reveal visual and quantitative details of local fin-surface heat transfer distributions in the vicinity of a circular tube, a delta-winglet pair, and a combination of a circular tube and a delta-winglet pair. Comparisons of local and average heat transfer distributions for the circular tube with and without winglets are provided. Overall mean fin-surface Nusselt-number results indicate a significant level of heat transfer enhancement associated with the deployment of the winglets with the circular cylinder. At the lowest Reynolds numbers (which correspond to the laminar operating conditions of existing geothermal aircooled condensers), the enhancement level is nearly a factor of two. At higher Reynolds numbers, the enhancement level is close to 50%.
Measurements of Property Data for LiNO3,KNO3,NaNO3-H2O Mixture
Authors: Andersen Jens Møller , Costa Andrea , Ziegler Felix
Published: November 2021

Construction and simulation of high temperature absorption systems need good property data. At the moment a mixture of LiNO3,KNO3,NaNO3-H2O is among few non-corrosive working-pairs for absorption systems working above 160°C. The properties of this mixture have been published by Erickson in 1986 but these data only represent some concentrations and a part of the temperature pressure field. If this nitrate mixture should be used for an absorption machine generating steam at 150 °C or as a topping cycle to a 2-effect libr cycle, the data are insufficient. The measurements presented in this article validate and extend the Erickson property data. And a more precise and detailed detection of the crystallisation behaviour is presented. Furthermore, it is seen that the solution has a tendency to deviate from the expected Temperature Pressure relation. Finally methods for estimation of the concentration are discussed.
Inverse Solution of Radiative Heat Transfer in Two-Dimensional Irregularly Shaped Enclosures
Authors: Ertürk Hakan , Ezekoye Ofodike A. , Howell John R.
Published: November 2021

An inverse solution technique is used to predict the necessary temperature and heat flux distributions of the heater section of a two-dimensional enclosure so the heater satisfies the specified heat flux and temperature distributions of design surfaces, while satisfying one thermal boundary condition for the other walls. Radiation is the dominant mode of heat transfer in systems where high temperatures are present; therefore, it is considered as the only mode of heat transfer in this study. The two-dimensional enclosures considered in this study are made up of straight segments, positioned so that they form irregularly shaped enclosures approximating situations for many of the real cases in industrial applications. The enclosure walls are gray, emitting diffusely and reflecting either diffusely or specularly. The medium inside the enclosure may be transparent, absorbing-emitting or absorbing-emitting and isotropically scattering. For the participating medium cases, the gray medium is considered as isothermal, homogeneous and isotropically scattering. The Monte Carlo method is used for formulation of radiative heat transfer. The method is preferred for its accuracy and ease of handling complex geometries and various surface and medium properties. The main contribution of this study is to solve inverse design problems for complex geometries that contain blockage and shading effects, as could be the case in many real industrial applications. The resulting system of equations, which includes Fredholm equations of the first kind, is known to be highly ill-conditioned in nature. The solution for this ill-conditioned system is handled by the conjugate gradient method, an iterative solution method, which obtains smooth and very accurate solutions in a few steps for linear systems.
A Monte Carlo Study of the Transient Radiative Transfer Within the One-Dimensional Multi-Layered Slab
Authors: Sawetprawichkul A. , Hsu P.-F. , Mitra K. , Sakami M.
Published: November 2021

Short pulse lasers are considered a useful tool for material processing and diagnostics. Only recently, fundamental understanding of the pulse laser interactions with materials gained much attention. The analysis of the underlying process involves solving the transient radiative transfer equation, which is very challenging, and most prior work relied on the approximate models. In this paper, a time-dependent Monte Carlo method is used to study the transient radiative transfer within the nonhomogeneous absorbing and scattering media. The Monte Carlo results compared very well with the accurate deterministic models and such comparisons have been lacking in many prior Monte Carlo studies.

The problem of interest has one-dimensional multi-layered slab geometry. Two different media are examined; a two-layer slab with different absorption and scattering coefficients in each layer; and a three-layer medium with different scattering albedo in the mid-layer. The temporal spreads of the transmittance and reflectance of a pulsed, collimated incident beam are obtained. The photon propagation across the interface and the resultant output radiative signatures due to the layered properties are discussed in detail.
Measurement and Prediction of the Contact Conductance Across Epoxied Copper Contacts at Cryogenic Temperatures
Authors: De Bellis Lisa , Phelan Patrick E.
Published: November 2021

Literature has demonstrated that the investigation of the contact conductance (hc) across epoxied joints at cryogenic temperatures is important to the microelectronic, satellite and other space industries. The accurate theoretical prediction of the hc arising across a metal-epoxy interface is still being researched. Several researchers have shown that the acoustic mismatch and other theories do not agree well with experimental data. This paper presents the results of an experimental and theoretical investigation of the hc across copper/epoxy/copper contacts. From the hc data, it was possible to extract the thermal conductivity (k) of the epoxy and the thermal boundary resistance (Rb) between the epoxy and copper. The Rb extracted from the experimental data was compared to model predictions made by the Acoustic Mismatch Model (AMM) and the Scattering Mediated Acoustic Mismatch Model (SMAMM). In the case of the AMM, the predictions underestimated the experimental values significantly. This finding is consistent with many investigations to date. The SMAMM was able to predict the experimental data very well when using an extremely small scattering time of 5×10−18 s.
Flow Characteristics in Convective Melting of a Solid Particle in a Fluid
Authors: Hao Y. L. , Tao Y.-X.
Published: November 2021

Flow visualization based on the particle image velocimetry (PIV) technique is conducted to quantitatively investigate the flow around a melting ice sphere in horizontally flowing water. The distributions of velocity, streamtrace, and vorticity around the ice sphere are obtained for different upstream velocities and temperatures. General flow characteristics around the melting ice sphere and effects of velocity and temperature are analyzed. The visualization of melting of a dyed ice sphere is also conducted to qualitatively investigate the motion of the melt and the mixing with mainstream. The original experimental results are published to serve as benchmark data for numerical model development.
Critical Heat Flux in Heated Horizontal Thin Annuli
Authors: Stoddard R. M. , Dowling M. F. , Abdel-Khalik S. I. , Ghiaasiaan S. M. , Jeter S. M.
Published: November 2021

The objectives of the work reported here were to experimentally study the critical heat flux in a heated thin, horizontal, annular flow passage cooled by subcooled water and to examine the applicability and relevance of the current predictive methods for critical heat flux to such passages. Experiments were performed in the Georgia Tech Microchannel Test Facility (GTMTF). The test section was an annulus with 6.45 and 7.77 mm inner and outer diameters, respectively (0.66 mm gap width), and an 18.5-cm long heated section. The experimental parameters investigated covered the following ranges: test section exit pressure: 0.344–1.034 MPa; coolant (water) mass flux: 100–380 kg/m2s; wall heat flux: 0.231–1.068 MW/m2; water inlet temperature: 30–65°C.

The results, in agreement with the existing CHF data for large horizontal channels, indicated that CHF values were considerably lower than the expected CHF values for vertical test section configuration. In all the tests CHF occurred at relatively high equilibrium qualities, and was preceded by flow stratification which caused dryout of the upper surface of the flow channel. The data were correlated by introducing empirical correction multipliers into three widely-used correlations for vertical channels, and based on the compensated distortions method.
Heat Transfer and Pressure Drop of CO2 Flow Boiling in Microchannels
Authors: Zhao Yuan , Molki Majid , Ohadi Michael M.
Published: November 2021

An experimental investigation was performed to study the flow boiling heat transfer of CO2 in microchannels. Tests were conducted in a horizontal triangular microchannel with the hydraulic diameter of 0.86 mm. Heat to the test section was provided by direct electrical heating. Experiments were conducted with CO2 at saturation temperatures of 273 to 293 K, mass fluxes of 100 to 820 kg/m2s, heat fluxes of 3 to 23 kW/m2, and qualities of 20% to 85%. It was demonstrated that heat flux had an enhancing effect on the heat transfer coefficient, while mass flux had a negligible effect. Nucleate boiling mechanism is found to be the dominant factor for CO2 flow boiling in microchannels. Heat transfer coefficient degraded quickly at high vapor quality region (0.6–0.7), which is possibly due to flow mal-distribution. Pressure drop increases slightly with vapor quality and/or heat flux. Mass flux has a strong increasing effect on pressure drop.
Design of a High Performance Cryocooler for Propellant Liquefaction and Storage on Mars
Authors: Zhou Lei , Kapat J. S. , Chow L. C. , Lei S. Y.
Published: November 2021

Human exploration of space is extending beyond low earth orbit and Moon as NASA is planning a human mission to Mars in 2014. Past studies indicate that In Situ Propellant Production (ISPP) on Mars is a key enabling technology in Mission to Mars. In ISPP, oxygen and methane, which are to be used as cryogenic propellants for any return vehicle from Mars to Earth, are produced on the Martian surface. Once the propellants are produced in gaseous state, they must be liquefied for storage and use in the ascent vehicle. Cryogenic cooling is needed for both liquefaction and storage since the storage temperature, around 90K for oxygen and 112K for methane, are considerably lower than the average temperature on the Martian surface, which is around 220K.

This paper presents the preliminary design of a single-stage, lightweight and compact, cryocooler based on reverse Brayton cycle with performance comparable to, but more reliable than, a corresponding Stirling cycle. With the application of micro-scale highly-effective recuperative heat exchanger, the estimated COP of the miniature cryocooler can reach 0.2. Thermal cycle parameters that can influence the cycle performance are studied. The two key enabling components, an integrated and micro-fabricated compressor and motor and a micro-fabricated recuperative heat exchanger, are discussed and shown to be possible with modern technology.
Analysis of Fin-Tube Evaporator Performance With Limited Experimental Data Using Artificial Neural Networks
Authors: Pacheco-Vega Arturo , Sen Mihir , McClain Rodney L.
Published: November 2021

In the current study we consider the problem of accuracy in heat rate estimations from artificial neural network models of heat exchangers used for refrigeration applications. The network configuration is of the feedforward type with a sigmoid activation function and a backpropagation algorithm. Limited experimental measurements from a manufacturer are used to show the capability of the neural network technique in modeling the heat transfer in these systems. Results from this exercise show that a well-trained network correlates the data with errors of the same order as the uncertainty of the measurements. It is also shown that the number and distribution of the training data are linked to the performance of the network when estimating the heat rates under different operating conditions, and that networks trained from few tests may give large errors. A methodology based on the cross-validation technique is presented to find regions where not enough data are available to construct a reliable neural network. The results from three tests show that the proposed methodology gives an upper bound of the estimated error in the heat rates.
The Development of a Neural Network Based System for the Optimal Control of Chain-Grate Stoker-Fired Boilers
Authors: Chong A. Z. S. , Wilcox S. J. , Ward J.
Published: November 2021

A novel Neural Network Based Controller (NNBC) was developed following a comprehensive set of experiments carried out on a pilot-scale stoker test facility at CRE Group Ltd., U.K. The NNBC mimicked the actions of an expert boiler operator, by providing ‘near optimum’ settings of coal feed and air flow, as well as ‘staging’ these parameters during load following conditions, before fine tuning the combustion air under quasi-steady-state conditions. Test results from the online implementation of the NNBC have demonstrated that improved transient and steady-state combustion conditions were attained. The prototype NNBC thus provides both stoker manufacturers and users with a means of reducing pollutant emissions, as well as improving the combustion efficiency of this type of coal firing equipment.
Experimental and Numerical Study of Transport Phenomena in a Simulated Hydrothermal Crystal Growth System of Fluid-Saturated Porous Layer
Authors: Mishra D. , Pal A. , Nemick N. , Saha A. K. , Prasad V. , Zhang H.
Published: November 2021

A simulated, non-pressurized hydrothermal system consisting of a fluid-superposed porous layer is fabricated and used for visualization and measurement of the temperature field using liquid crystal thermography. The system is used for various boundary conditions with pure glycerine as the working fluid and the porous layer is made of 3mm diameter glass beads. Experimental data is recorded using a color CCD camera and flow visualization is obtained through a long exposure video photography. A calibration is performed to relate the temperature with scattered colors at an orthogonal angle to the incoming white light sheet. Quantitative temperature data is obtained through this calibration and compared with the numerical predictions. For numerical studies the system is modeled as a composite layer of fluid and porous charge using the Darcy-Brinkman-Forchheimer flow model. A two-dimensional curvilinear algorithm using finite volume technique with a non-staggered grid is used to simulate the temperature field and transport phenomena for various Rayleigh–Darcy number combinations of varying aspect ratio. The results, for the first time, make an attempt towards understanding the transport process in hydrothermal system through both numerical simulation and experimental validation.