bluuebunny/crossref_metadata_2025 huggingface dataset:
CASSAVA STARCH-BASED EDIBLE COATINGS ENRICHED WITH Alpina purpurata AND Kaempferia rotunda ESSENTIAL OILS FOR PATIN FILLETS PRESERVATION
Authors: Utami Rohula , Praseptiangga Danar , Nurhartadi Edhi , Jati Manuhara Godras , Umi Khasanah Lia , Amalia Azzahra Fitri , Indrayati Febi
Published: April 2016

Cassava starch–based edible coating enriched with essential oil of Alpinia purpurata and Kaempferia rotunda was applied to preserve patin fillets during frozen storage. The quality of fillets was analyzed based on microbiological and chemical properties. Different concentration of essential oil in distilled water, 0 % (control), 0.1 % and 1 % (v/v), was added in cassava starch–based edible coating. The addition of essential oil significantly inhibited the microbial growth by reducing protein deterioration and delaying lipid oxidation in fillets during 4 mo of frozen storage. The results indicates that essential oil of Alpinia purpurata and Kaempferia rotunda can be used as an alternative preservation as it could protect frozen fish fillets from deterioration and extend the shelf life.
ENVIRONMENTAL ASSESSMENT OF POLYCULTURE FARMING PRACTICE BASED ON MACROBENTHIC ASSEMBLAGES: A STUDY CASE AT COASTAL AREA OF KALIWUNGU, KENDAL (CENTRAL JAVA, INDONESIA)
Authors: Purnomo Putro Sapto , Widowati Widowati , Jeudi Febria Ibni , Muhammad Fuad , Suhartana Suhartana , Suminto Suminto , Sudaryono Agung , Koshio Sunshuke
Published: April 2016

The purpose of this study was to determine environmental quality parameters using number of species, diversity and similarity of macrobenthic communities. This study was conducted at two locations, the Location I was a polyculture farming area, farming milkfish (Chanos Chanos) and black tiger shrimp (Penaeus monodon) and seaweed Gracilaria sp. in the coastal area of Mororejo, Kendal District, Central Java. Location II was the coastal area of PT. Plywood Indonesia, which is located adjacent to industrial activities as well as directly affected the tide. Systematic random sampling was employed, measuring physical-chemical parameters of water and sediment. Samples of macrobenthos were taken from the sediment. Data was analysed using diversity and evenness indices approach. Samples of macrobenthos were taken from the sediment using Eckman grab, then was analysed using diversity and evenness indices approach. Results showed that the Location I was dominated by Cerithidea cingulata and Terebralia sulcata (Potamididae), Minima batillaria (Batillaridae). The Location II was dominated by Cirratulus sp., Cirriformia sp. and Aphelochaeta (Cirratulidae) and Prionospio sp. (Spionidae), which are considered as indicators of disturbed area. This results implied that the use of area for both polyculture and industrial activities may lead to environmental disturbance, thus environmental coastal management need to be applied in regular basis, both temporally and spatially.
TRIVALENT CHROMIUM (CR+3) IN DIETARY CARBOHYDRATE AND ITS EFFECT ON THE GROWTH OF COMMONLY CULTIVATED FISH
Authors: Subandiyono Subandiyono , Hastuti Sri
Published: April 2016

Trivalent chromium (Cr+3) is an essential trace mineral for fish bio-physiological functions.  Researches on Cr+3  in the form of organic compound indicated that the mineral affected the bio-activity of insulin, the blood glucose influx, and subsequently the blood glucose metabolic rate. By increasing the blood glucose metabolism, dietary carbohydrate will be more efficiently used as a main energy source, thereby, dietary protein couldbe efficiently retained as for somatic growth.  Researches on various feeding habits of fish (e.g. gouramy-herbivorous fish, tilapia-omnivorous fish, and catfish-carnivorous fish) showed that dietary Cr+3 in certain amount increased diet utilization and the fish growth.
SAND DOLLARS DISTRIBUTION PATTERN AND ABUNDANCE AT THE COAST OF CEMARA KECIL ISLAND, KARIMUNJAWA, JEPARA, INDONESIA
Authors: Suryanti Suryanti , Rudolf Muskananfola Max , E. Simanjuntak Kevin
Published: April 2016

This research is aimed to know the distribution patterns and abundance of sand dollars [Clypeaster subdepressus (Gray, 1840)] at different spatial distances from the coast of Cemara Kecil Island Karimunjawa, Indonesia. The data were collected using purposive sampling and analyzed using cluster analysis PAST-3. The results indicate that the abundance of sand dollar amounts to 2 200 individuals, and the existing species are Laganum centrale, L. laganum, L. fudsiyama, L. depressum, L. retinens, L. boschi, L. depressum tonganense, L dickersoni, L. decagonale  rectum, L. joubini and  L. decagonale. The cluster analysis using PAST-3 reveals that there are clumped distributions and uniform distributions of L. centrale and Laganum laganum. At a distance of 23 m to 38 m from the coastline the animals form clumped distributions.
Influence of Starling's Hypothesis and Joule Heating on Peristaltic Flow of an Electrically Conducting Casson Fluid in a Permeable Microvessel
Authors: Sutradhar A. , Mondal J. K. , Murthy P. V. S. N. , Gorla Rama Subba Reddy
Published: April 2016

Peristaltic transport of electrically conducting blood through a permeable microvessel is investigated by considering the Casson model in the presence of an external magnetic field. The reabsorption process across the permeable microvessel wall is regarded to govern by Starling's hypothesis. Under the long wavelength approximation and low-Reynolds number assumption, the nonlinear governing equations along with the boundary conditions are solved using a perturbation technique. Starling's hypothesis at the microvessel wall provides a second-order ordinary differential equation to be solved numerically for pressure distribution which in turn gives the stream function and temperature field. Also, the location of the interface between the plug and core regions is obtained from the axial velocity. Due to an increasing reabsorption process, the axial velocity is found to increase initially but decreases near the outlet. The temperature is appreciably intensified by virtue of the Joule heating produced due to the electrical conductivity of blood.
Modeling and Simulation of an Electronic Oxygen Regulator Based on All-Coefficient Adaptive Control
Authors: Jiang Yuxin , Sun Qinglin , Tan Panlong , Chen Zengqiang
Published: April 2016

Safe and reliable automatic pressure regulation of the oxygen mask is a primary consideration for the oxygen supply system. One kind of electronic oxygen regulator (EOR) structure is proposed, and its operation principle is explained in this paper. To avoid long controller design cycle, herein, some simulations are carried out on matlab for analysis by establishing a mathematical model according to the EOR flow dynamic characteristics. In the simulations, the all-coefficient adaptive control method based on a characteristic model (CM) and the proportional–integral–derivative (PID) algorithm are applied, and the results are thoroughly investigated by considering some disturbance, such as the user's changing pulmonary ventilation parameters, the air leakage of the mask, and the sensor noise. Results suggest that the all-coefficient control method is more effective to guarantee superior lower inspiratory resistance than the PID method with the environmental disturbance, which may be a plausible reference for the EOR controller design.
Experimentally Verified Transient Models of Data Center Crossflow Heat Exchangers
Authors: Gao Tianyi , Sammakia Bahgat , Geer James , David Milnes , Schmidt Roger
Published: April 2016

Heat exchangers are key components that are commonly used in data center cooling systems. Rear door heat exchangers, in-row coolers, overhead coolers and fully contained cabinets are some examples of liquid and hybrid cooling systems used in data centers. A liquid to liquid heat exchanger is one of the main components of the Coolant Distribution Unit (CDU), which supplies chilled water to the heat exchangers mentioned above. Computer Room Air Conditioner (CRAC) units also consist of liquid to air cross flow heat exchangers. Optimizing the energy use and the reliability of IT equipment in data centers requires Computational Fluid Dynamics (CFD) tools that can accurately model data centers for both the steady state and dynamic operations. Typically, data centers operate in dynamic conditions due to workload allocations that change both spatially and temporally. Additional dynamic situations may also arise due to failures in the thermal management and electrical distribution systems. In the computational simulation, individual component models, such as transient heat exchanger models, are therefore needed. It is also important to develop simple, yet accurate, compact models for components, such as heat exchangers, to reduce the computational time without decreasing simulation accuracy.

In this study, a method for modeling compact transient heat exchangers using CFD code is presented. The method describes an approach for installing thermal dynamic heat exchanger models in CFD codes. The transient effectiveness concept and model are used in the development of the methodology. Heat exchanger CFD compact models are developed and tested by comparing them with full thermal dynamic models, and also with experimental measurements. The transient responses of the CFD model are presented for step and ramp change in flow rates of the hot and cold fluids, as well as step, ramp, and exponential variation in the inlet temperature. Finally, some practical dynamic scenarios involving IBM buffer liquid to liquid heat exchanger, rear door heat exchanger, and CRAC unit, are parametrically modeled to test the developed methodology. It is shown that the compact heat exchanger model can be used to successfully predict dynamic scenarios in typical data centers.
Development of 45° Incident Angle Sound Absorption Coefficient Test Device for Design of Vehicle Interior Trim Sound Package
Authors: Zhao Yuli , Egab Laith Neima , Chen Weishan , Wei Haiqiao , Wang Xu
Published: April 2016

This paper presents a new type of test device, which is the 45-degree incident angle sound absorption coefficient (SAC) test device. A V-shaped acoustic wave-guide with the two branches forming a 45 degree angle from the horizontal direction was designed to measure the sound absorption coefficient of installed trim materials. The device was also designed for the subjective evaluation and objective psychoacoustic metric target setting of a sound source. The 45-degree incident angle sound absorption coefficient test device can also be applied to the design of the vehicle interior trim materials or sound package to minimize the negative effect of interior noise. The measurement principle of the 45-degree incident angle SAC device will be introduced first, and the experiment procedure will be then illustrated. Different kinds of trim materials were tested. The measured sound pressure data was processed with the help of the MATLAB program codes, and then the sound absorption coefficient curves were calculated and plotted. The results show the 45-degree incident angle sound absorption coefficient measurement device is a useful tool for the measurement of the trim materials for their sound absorption coefficient and for analysis of their effect on the psychoacoustic performance of a sound source. Meanwhile, a psychoacoustic analysis of sound pressure data of a sound source using ArtemiS software allows for the design of a preferred sound in the device using trim materials. These have been tested by the 45-degree incident angle SAC device.
Nanoparticle-Enhanced Plasmonic Light Absorption in Thin-Film Silicon Solar Cells
Authors: Jia Zhenhui , Liu Changhong , Li Ben Q.
Published: April 2016

In this paper, numerical simulations are performed for different configurations of plasmonic and dielectric scatters for the purpose of enhancing light absorption in Si solar cells. The numerical model is developed on the basis of FDTD solution of the transient Maxwell equations. Results show that for Ag nanoparticles, the optimal light absorption is achieved with a particle radius of 75 nm and particle spacing of 3r to 5r. For dielectric SiO2 nanoparticles, a closely packed configuration with particle size of 50 nm in radius yields the optimal light absorption. The enhancement for both optimal cases is similar, measured by the short currents. Simulations with SiO2 nanoparticles embedded into Si at various different positions were conducted and results suggest that when the SiO2 particle buried half-way into the Si substrate, the light absorption enhancement is better than that with the particles placed at the top or embedded completely inside the Si layer. Analysis of a new design, with Ag atop the surface of and SiO2 inside the Si layer, was also performed. The results suggest that such a combined configuration produces the best light absorption enhancement among all those studied, achieving an 80% improvement compared with bare thin film.
A Biomimetic Microfluidic Device for the Study of the Response of Endothelial Cells Under Mechanical Forces
Authors: Li Lei , Shi Xuetao , Lv Xiaoqing , Liu Jing
Published: April 2016

Vascular science is an active area of medicine and biological research. In recent years, intensive research has been focused on the reaction of endothelial cells (ECs) to relevant biological, chemical, or physical cues in vitro. The primary thing of these studies is to make a biomimic environment of ECs which is closer to the in vivo conditions. Here we developed a microfluidic system and fabricated a grooved micropattern thin film to simulate inner blood vessel wall. The micropattern structure was generated by using the elastic biocompatible material poly(dimethylsiloxane) (PDMS). Human umbilical vein endothelial cells (HUVECs) were cultured on the grooved micropattern film. After the cells reached confluence, the thin PDMS film with cells was inserted into the biological grade plastic tube. Then cell culture medium was perfused into the tube and the cellular responses under shear stress and pressure were investigated. The F-actin cytoskeleton and the nuclei of the cells were stained for examination. This microfluidic system provides a convenient and cost-effective platform for the studies of cellular response to mechanical forces. Moreover, this system could also be used for studying cellular responses to drugs under mechanical forces.
Vibration Analysis of Defective Double Walled Carbon Nanotube Based Nano Resonators
Authors: Patel Ajay M. , Joshi Anand Y.
Published: April 2016

The dynamic analysis of zigzag and armchair double walled carbon nanotubes (DWCNTs) with different boundary condition has been performed using atomistic finite element method. The double walled carbon nanotube is modeled considering it as a space frame structure similar to a three dimensional beam. The elastic properties of beam element are calculated by considering mechanical characteristics of covalent bonds between the carbon atoms in the hexagonal lattice. Spring elements are used to describe the interlayer interactions between the inner and outer tubes caused due to the van der Waals forces. The mass of each beam element is assumed as point mass at nodes coinciding with carbon atoms at inner and outer wall of DWCNT. It has been reported that multiple atomic vacancies are formed during the manufacturing process in DWCNT which tend to migrate leading to a change in the mechanical characteristics. Simulations have been carried out to visualize the behaviour of such defective DWCNTs subjected to different boundary conditions. The results clearly state that the dynamic characteristics are greatly influence by defects like vacancies in it. Comparison with the other experimental and theoretical studies exhibits good association which suggests that defective DWCNTs can further be explored for mass sensing. This investigation is helpful in applications involving ultra-high frequency nano resonators which contain one or other type of manufacturing defects in it.
Unsteady Force Measurement for a Beam Using Small Piezoelectric End Sensors
Authors: Goldschmidt Margalit Z. , Jonson Michael L. , Lesieutre George A.
Published: April 2016

A new method to measure the total unsteady lift force across a propeller blade is presented in this paper. Unsteady forces across propeller blades are generated from the interaction of the blade boundary with a rotating pressure field associated with the propeller. The oscillating nature of the unsteady forces, particularly at higher harmonics, suggests that the unsteady lift fluctuations nearly cancel out over the blade span, and that it is possible to find the total unsteady force across the propeller from parameters at the root and tip. These parameters were determined from an approximation provided by the Method of the Stationary Phase. A newly designed apparatus for the measurement of total unsteady force across a propeller blade based on this theory is described in detail. For future experimental validation of the newly designed sensors, a propeller blade is modeled as a uniform beam, and a known unsteady force is generated across the beam surface.
Applicability of Dynamic Homogenization for Acoustic Metamaterials
Authors: Srivastava Ankit , Nemat-Nasser Sia
Published: April 2016

Dynamic homogenization seeks to define frequency dependent effective properties for heterogeneous composites for the purpose of studying wave propagation in them. These properties can be used to predict and design for metamaterial behavior. However, there is an approximation involved in replacing a heterogeneous composite with its homogenized equivalent. In this paper we propose a quantification to this approximation. By way of explicit examples we show that a comprehensive homogenization scheme proposed in earlier papers is applicable in a finite composite setting and in the low frequency regime. We also show that there exist good arguments for considering the second branch of a locally resonant composite a true negative branch. Furthermore, we note that infinite-domain homogenization is more applicable to finite cases of locally resonant metamaterial composites than it is to 2-phase composites. We also study the effect of the interface location on the applicability of homogenization. The results open intriguing questions regarding the effects of replacing a semi-infinite periodic composite with its Bloch-wave (infinite domain) dynamic properties on such phenomenon as negative refraction.
Hot Spot Cooling and Harvesting CPU Waste Heat Using Thermoelectric Modules
Authors: Lee Soochan , Phelan Patrick E. , Wu Carole-Jean
Published: April 2016

The increasing integration of high performance processors and dense circuits in current computing devices has produced high heat flux in localized areas (hot spots) that limits their performance and reliability. To control the hot spots on a CPU, many researchers have focused on active cooling methods such as thermoelectric coolers (TECs) to avoid thermal emergencies. This paper presents the optimized thermoelectric modules on top of the CPU combined with a conventional air-cooling device to reduce the hot spot temperature and at the same time harvest waste heat energy generated by the CPU. To control the temperature of the hot spots, we attach small-sized TECs to the CPU and use thermoelectric generators (TEGs) placed on the rest of the CPU to convert waste heat energy into electricity. This study investigates design alternatives with an analytical model considering the non-uniform temperature distribution based on two-node thermal networks. The results indicate that we are able to attain more energy from the TEGs than energy consumption for running the TECs. In other words, we can allow the harvested heat energy to be reused to power other components and reduce hot spots simultaneously. Overall, the idea of simultaneous hot spot cooling and waste heat harvesting using thermoelectric modules on a CPU is a promising method to control the problem of heat generation and to reduce energy consumption in a computing device.
Advanced Real Time and Long Term Monitoring of Transportation Pipelines
Authors: Bernasconi Giancarlo , Del Giudice Silvio , Giunta Giuseppe
Published: April 2016

A key factor for the sustainable development of oil&gas industry is the remote monitoring of integrity and reliability of transportation pipelines. In order to mitigate the risk associated to third party interference (TPI) risks and to minimize the environment exposure, it is possible to deploy a Multipoint Acoustic Sensing (MAS) technology which makes use of multi sensors placed at discrete distances along the pipeline. Any interaction with the pipe generates acoustic waves that are guided within the fluid (gas, oil, products or water) for long distances, providing information on the source event and on the “transmission” channel. Acoustic propagation is mainly governed by both absorption coefficient and sound speed, which in turn are functions of the pipe, fluid and surrounding medium system. These features have been analyzed by processing real-time data collected with a proprietary MAS system (e-vpms™) on fluid transportation pipelines, in different operational and flow service conditions, producing exhaustive sets of TPI actions, leak trials and tracking pig inspections. The paper presents original procedures for real-time monitoring, as well as for long term supervision and advance intervention planning.
Design for a Hybrid Absorbing Element in the Time Domain Using PML and Infinite Element Concepts
Authors: Cipolla Jeffrey L.
Published: April 2016

We introduce an approach blending the Perfectly Matched Layer (PML) and infinite element paradigms, to achieve better performance and wider applicability than either approach alone. In this paper, we address the specific challenges of unbounded problems when using time-domain explicit finite elements:

1. The algorithm must be spatially local, to minimize storage and communication cost,

2. It must contain second-order time derivatives for compatibility with the explicit central-difference time integration scheme,

3. Its coefficient for the second-order derivatives must be diagonal (“lumped mass”),

4. It must be time-stable when used with central-differences,

5. It must converge to the correct low-frequency (Laplacian) limit,

6. It should exhibit high accuracy across typically encountered dynamic frequencies, i.e. at short to long wavelengths,

7. Its user interface should be as simple as possible.

Here, we will describe the derivation of a time-domain implementation of the hybrid PML/infinite element, and discuss its advantages for implementation.
Synchronized Heterogeneous Viscous Behavior of Soft Materials Upon Macroscopic Loading
Authors: Gu Wenting , Shen Jiayue , Palmer Xavier-lewis , Hao Zhili
Published: April 2016

This paper presents a preliminary study on characterizing the synchronized heterogeneous viscous behavior of soft materials upon macroscopic sinusoidal loading. Built upon a polymer-based microfluidic device capable of detecting distributed normal loads at a spatial resolution of 1.5mm, a rigid cylinder probe is employed to exert a macroscopic sinusoidal load on a sample placed on the device. Consequently, the synchronized heterogeneous viscous behavior of a sample translates to sinusoidal distributed loads, which are captured by the device. In a measurement, the input and output signals of a sample are the macroscopic sinusoidal load and the DC voltage outputs of the device, respectively, with the latter being representative of the sinusoidal deflections of a sample along its length. A preliminary data analysis is conducted on the recorded input and output signals to obtain their phase shifts at different frequencies, which are representative of the heterogeneous viscosity of a sample along its length. Several agar and polydimethylsiloxane (PDMS) samples and two animal cartilage tissue samples are prepared and measured. Variations among the measured phase shifts in a sample manifest its structural heterogeneity and demonstrate the feasibility of using the device to characterize the synchronized heterogeneous viscous behavior of soft materials upon macroscopic loading.
Finite Element Analysis of Prosthetic Running Blades Using Different Composite Materials to Optimize Performance
Authors: Rahman Mosfequr , Bennett Tyler , Glisson David , Beckley Darrell , Khan Jobaidur
Published: April 2016

A prosthetic limb is an artificial device that replaces missing body part, or parts. Prosthetic limbs are used for many different applications however the application of prosthetic limbs focused in this paper categorized as prosthetic enhancements. Prosthetic enhancements are special prosthetic that allow the patients to participate in more rigorous recreational activities, such as running. These prosthetic limbs now have started to arise in major sporting events like the Olympics. Some researchers say that the legs use only 25% of the energy that an able bodied leg would use.

High performance prosthetic running legs made of carbon fiber, show great advantages over their metal counterparts. Including being lighter and being able to retain more strain energy, current carbon fiber running blades offered by Ossur provide the best performance in the market. In this study, prosthetic racing legs known as blades were analyzed using finite element analysis technique. Performance improvements of these blades were sought by creating mechanical models of the current Ossur products using the finite element analysis software ANSYS and incorporating better performing composite materials into the mechanical simulations. Two different composite materials have taken in consideration by which the legs are created from, these are thermoplastic values for polyethylene epoxy and Vinylester. The use of a new composite material reduces the strain in each of the existing blade geometries, and it permits fewer layers of carbon fiber to be required in the construction of these running blades, which reduces the weight of each leg. Three different blade designs such as Cheetah blade, Flex-Run blade and Flex-Sprint blade have been considered in this study. Also two different loading conditions on the blade such as standing and running conditions have been considered.
Semi-Dirac Points in Phononic Crystals
Authors: Zhang Xiujuan , Wu Ying
Published: April 2016

A semi-Dirac cone refers to a peculiar type of dispersion relation that is linear along the symmetry line but quadratic in the perpendicular direction. It was originally discovered in electron systems, in which the associated quasi-particles are massless along one direction, like those in graphene, but effective-mass-like along the other. It was reported that a semi-Dirac point is associated with the topological phase transition between a semi-metallic phase and a band insulator. Very recently, the classical analogy of a semi-Dirac cone has been reported in an electromagnetic system.

Here, we demonstrate that, by accidental degeneracy, two-dimensional phononic crystals consisting of square arrays of elliptical cylinders embedded in water are also able to produce the particular dispersion relation of a semi-Dirac cone in the center of the Brillouin zone. A perturbation method is used to evaluate the linear slope and to affirm that the dispersion relation is a semi-Dirac type.

If the scatterers are made of rubber, in which the acoustic wave velocity is lower than that in water, the semi-Dirac dispersion can be characterized by an effective medium theory. The effective medium parameters link the semi-Dirac point to a topological transition in the iso-frequency surface of the phononic crystal, in which an open hyperbola is changed into a closed ellipse. This topological transition results in drastic change in wave manipulation. On the other hand, the theory also reveals that the phononic crystal is a double-zero-index material along the x-direction and photonic-band-edge material along the perpendicular direction (y-direction).

If the scatterers are made of steel, in which the acoustic wave velocity is higher than that in water, the effective medium description fails, even though the semi-Dirac dispersion relation looks similar to that in the previous case. Therefore different wave transport behavior is expected.

The semi-Dirac points in phononic crystals described in this work would offer new ways to manipulate acoustic waves with simple periodic structures.
Understanding the Impact of Flow Bypass on the Thermal Performance of Air Cooled Heat Sinks
Authors: Kota Krishna , Awad Mohamed M.
Published: April 2016

In this effort, theoretical modeling was employed to understand the impact of flow bypass on the thermal performance of air cooled heat sinks. Fundamental mass and flow energy conservation equations across a longitudinal fin heat sink configuration and the bypass region were applied and a generic parameter, referred as the Flow Bypass Factor (α), was identified from the theoretical solution that mathematically captures the effect of flow bypass as a quantifiable parameter on the junction-to-ambient thermal resistance of the heat sink. From the results obtained, it was found that, at least in the laminar regime, the impact of flow bypass on performance can be neglected for cases when the bypass gap is typically less than 5% of the fin height, and is almost linear at high relative bypass gaps (i.e., usually for bypass gaps that are more than 10–15% of the fin height). It was also found that the heat sink thermal resistance is more sensitive to small bypass gaps and the effect of flow bypass decreases with increasing bypass gap.
Silicon Pillars as Resonators in an Acoustical Metamaterial
Authors: Bonello Bernard , Marchal Rémi , Moiseyenko Rayisa , Pennec Yan , Djafari-Rouhani Bahram , Zhao Jinfeng , Boyko Olga
Published: April 2016

We have investigated the propagation of Lamb waves in structures made of either an isolated resonant pillar or a set of pillars arranged in a line on a thin plate. The resonators as well as the plate are made of silicon. FEM computations show that two bending modes and one compressional mode are unambiguously identified in the frequency range of interest (0–10 MHz). We used a laser ultrasonic technique to map both the amplitude and the phase of the normal displacements on top of the pillars and at the surface of the sample. When the frequency is tuned to a resonant mode, either compressional or bending, the pillars vibrate 180° out-of-phase with respect to the Lamb waves, resulting in a negative modulus or negative mass density respectively.
Microparticle Trapping in Streaming Flows in Open Rectangular Chambers Undergoing Low Frequency Vertical Vibrations
Authors: Agrawal Prashant , Gandhi Prasanna S. , Neild Adrian
Published: April 2016

Microparticle collection in microfluidic systems via mechanical vibrations has been demonstrated in both low frequency systems (in the range of 100Hz) and in the high frequency regime (in the range of 1MHz). However, in most systems, collection of particles with lower inertia is hindered by second order time-averaged streaming flows. In our approach, we experimentally demonstrate collection of small particles (about 3 μm in diameter) by trapping them in streaming flows in a liquid filled open rectangular chamber undergoing vertical vibrations at low frequencies. The proposed method is then utilized to separate two different types of particles in distinct patterns through mode-switching.
Characterization of the Damping Behavior of Thin Films With Dynamic Mechanic Analysis in Bending Mode
Authors: Knapp Gilbert , Leyrer Martin , Oreski Gernot , Pinter Gerald
Published: April 2016

Usually damped structures, consisting of a constrained layer damping (CLD) and free layer damping (FLD) design, are characterized via dynamic mechanic analysis (DMA) in bending mode. Since laminates with thicknesses from 10 to 100 μm exhibit a very low bending stiffness it isn’t possible to determine their damping properties in bending mode with standard DMA setups. Therefore in the present work the main objective was to introduce a new method to overcome this drawback.

Two main geometries were used, such as a variation of the bending mode where the laminates were clamped at the outer supports and on the other hand a set-up where the geometry of a support of loudspeakers was replicated, which was called “speaker” mode. The damping behavior of the laminates then was characterized via the mechanical loss factor tan δ and subsequently compared to results in DMA shear mode. The second objective was to characterize the influence of the design, with a 2-layer laminate consisting of a free layer damping design and a 3-layer laminate with a constrained layer damping design.

A method in DMA “speaker” mode was successfully set up. The test parameters were chosen in order to resemble the support of loudspeakers. Therefore with the laminates two beads with a height of approximately 1 mm were formed symmetrically in gaps of 3 mm between the outer fixtures and the drive shaft. Furthermore in the test the laminates were loaded with a dynamic displacement of 600 μm. Due to the low bending stiffness of the laminates the highest test frequency was limited to 10 Hz. In accordance with literature for the 2-layer laminates significant lower damping levels were found than for the 3-layer laminates. Whereas the constrained layer damping laminate (3-layer) showed a good correlation between measurements in “speaker” and in shear mode, the 2-layer laminate showed a significant loss factor increase at high temperatures in shear mode, which was related to entropy elastic effects.
On the Formation of Photopolymerized Voxel With Varying Focal Length During Bulk Lithography
Authors: Bhole Kiran , Gandhi Prasanna , Kundu T.
Published: April 2016

Unconstraint depth photopolymerization has been used in recently developed 3D microfabrication process termed as Bulk lithography for the development of varying depth 3D microstructures. Prediction of the curing behaviour is the key for successful implementation of the process towards the development of the varying depth 3D microstructure. This paper presents the evolution of the cured voxel resulting from unconstraint depth photopolymerization under off-focus condition (on either side of the focal point). Variation in cured geometry is presented in the non-dimensional way under off-focus condition. The simulation carried out has predicted the significant variation of cured width under off-focus condition. This works points towards an alternative way of varying the geometry of the cured voxel for bulk lithography by positioning of the focal point relative to the resin surface.
Impedance Effects During High-Frequency Dielectrophoresis
Authors: Hadady Hanieh , Michael Kelsey A. , Geiger Emil J.
Published: April 2016

Dielectrophoresis refers to the motion of electrically neutral particles in a spatially non-uniform electric field as a function of frequency. Analytical models predict a second or upper crossover frequency, but there is little experimental evidence to supporting this prediction. One reason for this is that standard bench top function generators are typically limited to maximum frequency of 20 MHz, and those with higher bandwidths are often unable to generate higher frequency electric fields with sufficient amplitude to induce DEP motion. Our experimental set-up seeks to sort cells on the basis of the upper crossover frequency in the range of 10–160 MHz. At these frequencies, the DEP response is expected to depend primarily on the dielectric properties of the cytoplasm.

A needle pattern was used due to the ease of making spatially non-uniform electric fields. Sine waves were generated with a signal generator capable of generating sine waves with frequencies up to 160 MHz which was amplified with an RF amplifier. In order to help match the load to the amplifier and reduce the amount of reflected power an attenuator was placed between the amplifier and the electrodes. Two different amplifiers and attenuators were tested. Conductive copper tape and alligator clips were used to connect the glass slide to the electronic equipment. These systems were capable of 30 Volts peak-to-peak (Vpp) amplitudes in the given frequency range as monitored by an oscilloscope probing the electrodes.

With this set-up, the amplitude of the signal was observed by oscilloscope to vary as much as 40 Vpp across the range of frequencies which is supplied by signal generator. We suspect that the impedance of the experimental set-up was highly frequency dependent at the high frequencies used in this study. Furthermore, the oscilloscope may also be enough of a load on the system to affect the impedance. To maintain the 30 Vpp output, the input amplitude to the RF amplifier was adjusted at each individual frequency across all frequencies of the DEP experiment.
Computational Study on a Novel Micropump Driven by a Built-In Thermal Bimorph Microvalve
Authors: Han Yen-Lin
Published: April 2016

Using the rarefied gas dynamic phenomenon of thermal edge flow, a micropump with a built-in thermal bimorph microvalve is proposed to provide pumping needs for systems such as micro fuel cells. A thermal bimorph cantilever used as a microvalve is located within one gas molecular mean free path away from a narrow flow channel, which connects two larger size connectors on either side. The sharp edge of the heated microvalve, whose length is several times of the gas molecular mean free path, can induce flows along its surface and into the narrow channel. Using the DSMC (Direct Simulation Monte Carlo) simulation technique, the thermal edge flow characteristics are studied computationally to determine the feasibility of the proposed design. The result for a closed simulation domains at steady state determined that a pressure ratio of 1.22 can be achieved by the proposed design. The average flow velocities in open simulation domains were found to be closely related to the heater location. This preliminary computational study has proven that with particular parameters, such as the microvalve’s size and location, matching the gas mean free path, the proposed micropump with a built-in microvalve design appears to be viable to drive the thermal edge gas flows and create noticeable pressure difference to serve as a micropump.
Characterization of the Electromechanical Response of a Dielectric Elastomer Membrane
Authors: Rubio Jose E. , Sarker Pratik , Chakravarty Uttam K.
Published: April 2016

Dielectric elastomers hold much promise as smart materials that could rapidly adapt to changes in environmental conditions due to their mechanical response to an electrical input. They belong to the group of electroactive polymers which have unique mechanical properties such as flexibility, light-weight, and electrical field-induced deformation. These characteristics make dielectric elastomers suitable candidates as actuators, sensors, or energy converter media. The objective of this study is to characterize the structural dynamic response of a dielectric elastomer membrane exposed to stagnant air environment and steady airflow at different angles of attack. A simulation of the fluid-structure interaction of the membrane is performed by coupling an electromechanical finite element model of the membrane with a computational fluid dynamics model representing the external flow. From the fluid-structure interaction simulation, the vibration frequencies and mode shapes, the time-varying out-of-plane deformation, and the coefficients of lift and drag are determined. Furthermore, a convergence study and mesh refinement are performed to guarantee mesh independence of the calculations from the fluid-structure interaction simulation. Results indicate that the stiffness of the electroactive membrane decreases nonlinearly with an increase of the applied voltage. The electrostatic force from the applied voltage adds compressive stress to the membrane, effectively softening the membrane, increasing the out-of-plane deformation, and reducing the resonance frequency.
Excimer Laser-Machined SU-8 Microstructures for Polydimethylsiloxane (PDMS) Replica Molding
Authors: Liu Kewei , Kim Yoontae , Noh Hongseok (Moses)
Published: April 2016

Excimer laser ablation is considered a versatile technique to machine three-dimensional (3-D) structures which is difficult to create only by conventional microfabrication technique. We introduce the use of 193 nm excimer laser micromachining for fabrication of negative photoresist (SU-8) master molds for polydimethylsiloxane (PDMS) replica molding. Experimental characterization study on the effect of laser parameters (fluence, repetition rate, and number of shots) on the etch performances (etch rate, and aspect ratio) is presented here. Etch rate per shot of SU-8 was proportional to the fluence, but inversely proportional to the number of shots. The repetition rate of laser firing did not show a noteworthy influence to the etch rates. Aspect ratio was also proportional to the fluence and number of laser firing, but was not affected by the repetition rate of laser. For demonstration of replica molding, we made holes with different depth in SU-8 layer and used it to create PDMS micropillar array.
Liquid Metal Flows in Manifold Microchannel Heat Sinks
Authors: Hu Haibao , Kuravi Sarada , Ren Feng , Hsu Pei-feng
Published: April 2016

Heat transfer and flow performance of water and galinstan in manifold microchannel heat sinks is analyzed. The three dimensional flow and conjugate heat transfer is numerically simulated for microchannels of two different hydraulic diameters. The heat transfer coefficient, wall temperature variation at the base, and performance factor were analyzed for the same inlet velocity, Reynolds number and pressure drop conditions for water and liquid metal for different heat flux boundary conditions. Due to the short length of microchannels, it was found that performance factor of liquid metal is larger compared to water for all the cases.
Design and Analysis of Actuated Microneedles for Robotic Manipulation
Authors: Banerjee Steven , Wang Wenhui , Gutschmidt Stefanie
Published: April 2016

We present the design of a MEMS based single-unit actuator consisting of a single microneedle with 3D mobility. The four-sided single-unit actuator (4SA) microrobot design can achieve an in-plane actuation (x, y) of 76 μm (±38 μm) at 160 V and an out-of-plane actuation (z) of more than 6.5 μm at 35 V. The mechanical stress developed within the operational range is between 0.08 to 0.5 percent of the yield strength of silicon i.e. 7000 MPa. We discuss both the analytical modeling and finite element analysis (FEA) simulation of the design based on the range of dimensions analyzed for the individual actuator components. Our primary goal is to integrate multiple actuators into a parallel architecture for independent actuation of multiple microneedles for targeted micro- and nano-robotic manipulation tasks, such as single-cell analyses. We have also successfully fabricated sample 4SA microrobot without the microneedle as a pre-cursor to experimenting with our future advanced design of microrobots. We demonstrate successfully the 3D actuation of the 4SA microrobot of up to 10 μm at 120 V (in-plane) and more than 0.5 μm at 600 V (out-of-plane) with minimum decoupling.
Facile and Effective Phononic Structures for Ultrasound Focusing Application
Authors: Guo Qiuquan , Cai Xiaobing , Yang Jun
Published: April 2016

Ultrasound therapy is a highly popular non-invasive method to treat diseases. It is desired to increase the resolution of ultrasound therapy, providing more efficient therapeutic effect. In this study, a simple but effective phononic structure was designed to achieve higher resolution close to wavelength resolution of ultrasound focusing.

The objective of this study is to design a unique phononic structure to focus acoustic wave into human body more deeply and precisely. It is known that overheating by high frequency ultrasound will cause a series of side effects including bone burns, soft tissue burns, swelling and bleeding problems. In addition, due to the limited propagation of recovered evanescent wave, the penetration depth of acoustic energy being focused by the acoustic metamaterials is often hindered. In this study, we will design a multilayer acoustic metamaterial which shows sub-wavelength focusing ability at relatively low frequencies. More importantly, our design will also extend the ability of penetration depth by manipulating the focusing length through optimization of the phononic structure.
Change in Spatial Distribution of State Densities of Carbon Nanotubes Under Anisotropic Strain Field
Authors: Ohnishi Masato , Meng Yang , Suzuki Ken , Miura Hideo
Published: April 2016

In any electronic devices and sensors, unexpected changes in their function occur due to internal strain caused by contact of different materials which leads to thermal deformation or lattice mismatch. Thus, understanding of the effect of strain on electronic properties of carbon nanotubes (CNTs) is indispensable for assuring the reliability of CNTs-based electronic devices and for developing new electronic devices and sensors. In this study, the change in spatial distribution of state densities of zigzag CNTs under radial strain is analyzed by using first-principles calculation. The analysis shows that when a radial strain is applied to a CNT, its state densities are localized at high curvature regions. Such localization of state densities decrease their energies, and then decrease the band gap. In addition, since the behavior of the state energy under the radial strain is dominated by its spatial distribution, the strain sensitivity of CNTs depends on their chirality. The founding gives a guideline on how to fabricate high-performance novel CNTs devices, sensors, for example, biaxial strain sensor.
Fault-Mode Classification of Solid State Luminaires Using Bayesian Probabilistic Models
Authors: Lall Pradeep , Wei Junchao , Sakalaukus Peter
Published: April 2016

A new method has been developed for assessment of the onset of degradation in solid state luminaires to classify failure mechanisms by using metrics beyond lumen degradation that are currently used for identification of failure. Luminous Flux output, Correlated Color Temperature Data on Philips LED Lamps has been gathered under 85°C/85%RH till lamp failure. The acquired data has been used in conjunction with Bayesian Probabilistic Models to identify luminaires with onset of degradation much prior to failure through identification of decision boundaries between lamps with accrued damage and lamps beyond the failure threshold in the feature space. In addition luminaires with different failure modes have been classified separately from healthy pristine luminaires. It is expected that, the new test technique will allow the development of failure distributions without testing till L70 life for the manifestation of failure.
Investigation of Two-Phase, Vapor Chamber Based Thermal Management of Multiple Microserver Chips
Authors: Parhizi Mohammad , Merrikh Ali Akbar , Jain Ankur
Published: April 2016

Thermal management of microserver chips is of much interest to the semiconductor industry due to the significant performance benefits associated with heat spreading, resulting in very effective hot spot cooling in active cooling environments. This paper investigates thermal management of a multi-chip microserver module using two-phase heat transfer in a vapor chamber. A simulation model capturing two-phase flow of H2O in a vapor chamber was developed for understanding the effect of various parameters on thermal performance of the vapor chamber. The performance of a single high power chip is compared with a system of multiple lower power chips. Emphasis is on the impact of using multiple lower power chips instead of a single high power chip on the heat spreading capability of a flat, thin, vapor chamber. Also, it is shown that using a system of multiple low power chips, provides designers with the opportunity for designing vapor chamber with same functionality as single chip but reduced mass. Results highlight the challenges and opportunities involved in such an approach. The results shown in this paper will be useful for the design of two-phase cooling for microserver chips.