bluuebunny/crossref_metadata_2025_split huggingface dataset:
The investigation of the influence of laser re‐melting on density, surface quality and microstructure of selective laser melting parts
Authors: Yasa Evren , Deckers Jan , Kruth Jean‐Pierre 
Published: August 2011

PurposeSelective laser melting (SLM) is a powder metallurgical (PM) additive manufacturing process whereby a three‐dimensional part is built in a layer‐wise manner. During the process, a high intensity laser beam selectively scans a powder bed according to the computer‐aided design data of the part to be produced and the powder metal particles are completely molten. The process is capable of producing near full density (∼98‐99 per cent relative density) and functional metallic parts with a high geometrical freedom. However, insufficient surface quality of produced parts is one of the important limitations of the process. The purpose of this study is to apply laser re‐melting using a continuous wave laser during SLM production of 316L stainless steel and Ti6Al4V parts to overcome this limitation.Design/methodology/approachAfter each layer is fully molten, the same slice data are used to re‐expose the layer for laser re‐melting. In this manner, laser re‐melting does not only improve the surface quality on the top surfaces, but also has the potential to change the microstructure and to improve the obtained density. The influence of laser re‐melting on the surface quality, density and microstructure is studied varying the operating parameters for re‐melting such as scan speed, laser power and scan spacing.FindingsIt is concluded that laser re‐melting is a promising method to enhance the density and surface quality of SLM parts at a cost of longer production times. Laser re‐melting improves the density to almost 100 per cent whereas 90 per cent enhancement is achieved in the surface quality of SLM parts after laser re‐melting. The microhardness is improved in the laser re‐molten zone if sufficiently high‐energy densities are provided, probably due to a fine‐cell size encountered in the microstructure.Originality/valueThere has been extensive research in the field of laser surface modification techniques, e.g. laser polishing, laser hardening and laser surface melting, applied to bulk materials produced by conventional manufacturing processes. However, those studies only relate to laser enhancement of surface or sub‐surface properties of parts produced using bulk material. They do not aim at enhancement of core material properties, nor surface enhancement of (rough) surfaces produced in a PM way by SLM. This study is carried out to cover the gap and analyze the advantages of laser re‐melting in the field of additive manufacturing.
Transient thermal response in ultrasonic additive manufacturing of aluminum 3003
Authors: Schick David , Suresh Babu Sudarsanam , Foster Daniel R. , Dapino Marcelo , Short Matt , Lippold John C. 
Published: August 2011

PurposeUltrasonic additive manufacturing (UAM) is a rapid prototyping process through which multiple thin layers of material are sequentially ultrasonically welded together to form a finished part. While previous research into the peak temperatures experienced during UAM have been documented, a thorough examination of the heating and cooling curves has not been conducted to date.Design/methodology/approachFor this study, UAM weldments made from aluminum 3003‐H18 tapes with embedded Type‐K thermocouples were examined. Finite element modeling was used to compare the theoretical thermal diffusion rates during heating to the observed heating patterns. A model was used to calculate the effective thermal diffusivity of the UAM build on cooling based on the observed cooling curves and curve fitting analysis.FindingsEmbedded thermocouple data revealed simultaneous temperature increases throughout all interfaces of the UAM build directly beneath the sonotrode. Modeling of the heating curves revealed a delay of at least 0.5 seconds should have existed if heating of lower interfaces was a result of thermal diffusion alone. As this is not the case, it was concluded that ultrasonic energy is absorbed and converted to heat at every interface beneath the sonotrode. The calculated thermal diffusivity of the build on cooling was less than 1 percent of the reported values of bulk aluminum, suggesting that voids and oxides along interfaces throughout the build may be inhibiting thermal diffusion through thermal contact resistance across the interface.Originality/valueThis work systematically analyzed the thermal profiles that develop during the UAM process. The simultaneous heating phenomenon presented here has not been documented by other research programs. The findings presented here will enable future researchers to develop more accurate models of the UAM process, potentially leading to improved UAM bond quality.
Enhancing aerospace engineering students' learning with 3D printing wind‐tunnel models
Authors: Kroll Ehud , Artzi Dror 
Published: August 2011

PurposeThe purpose of this paper is to present the benefits offered by rapid prototyping (RP) models for wind‐tunnel testing as part of fourth‐year aerospace engineering student projects. Ways of overcoming some of the difficulties associated with the 3D printing technology are also discussed.Design/methodology/approachPolymer‐based RP was used to fabricate two‐aircraft models, which included stiffening metallic inserts. Testing in a subsonic‐wind tunnel was carried out and the results compared to analytic performance predictions.FindingsLow‐cost rapid prototypes of wind‐tunnel models yielded satisfactory aerodynamic performance. The savings in acquisition cost and time allowed incorporating actual testing in the aircraft design process within the framework of a tight academic budget and schedule.Practical implicationsConducting real‐wind‐tunnel testing contributes significantly to the educational experience of students; however, it had rarely been carried out when metal model fabrication was the only option. In contrast, RP facilitates an enhanced and more realistic learning experience by offering a quick and affordable means of model manufacturing.Originality/valueSimple methods of reinforcing polymer‐based models were incorporated, thus presenting an inexpensive way to test and evaluate preliminary aircraft designs, in both academia and industry.
Catalyst‐free growth and characterization of ZnO nanoscrewdrivers prepared by thermal evaporation
Authors: Chuah L.S. , Hassan Z. , Tneh S.S. , Ahmad M.A. , Mohd Bakhori S.K. , Yusof Y. 
Published: August 2011

PurposeThe purpose of this paper is to propose a simple physical evaporation route in which catalyst‐free zinc oxide (ZnO) nanoscrewdrivers were deposited on silicon (Si) (111) substrates.Design/methodology/approachPrior to the deposition, the Si (111) wafer was cut into pieces of 2×2 cm2. Then, the wafers were dipped for 1 min into mixture buffered oxide etchant to remove native oxide. Then, the samples were rinsed in an ultrasonic bath cleaned with boiling acetone, ethanol, and de‐ionized (DI) water for 10 min. Lastly, the wafers were rinsed in 25 ml DI water in stirred and then were blown dry with nitrogen. In this technique, the starting material is high‐purity metallic zinc (Zn) powder (99.99 per cent pure). Following, the Zn films were then annealed under air environment in the furnace at 500°C for 1 h deprived of any catalysts.FindingsThese ZnO samples were studied by scanning electron microscopy, high‐resolution X‐ray diffraction (HR‐XRD), and photoluminescence (PL) spectroscopy. Atomic force microscope (AFM) images were applied to ascertain surface morphology of produced ZnO nanoscrewdrivers. XRD pattern confirmed that the ZnO nanoscrewdrivers were of polycrystalline structure in universe with a hexagonal close packed type and c‐axis is perpendicular to the substrate. The peak at 34° correspond to the reflection planes of ZnO(002) crystallographic plane is perceived. The AFM surface images disclosed that the surfaces of produced ZnO thin films are not smooth. The PL spectrum of as‐synthesized nanoscrewdrivers shows a UV emission peak at 380 nm and a broad green emission peak at 500 nm.Originality/valueThe paper reports on a simple physical evaporation route, ZnO nanoscrewdrivers were synthesized via the thermal evaporation of the high‐purity Zn powders and annealed at 500°C under air atmosphere without introducing any hetero‐metal catalysts or other carrier gases approach.
Effect of sputtering time on physical and electrical properties of ZrOx thin film on Si
Authors: Tedi K. , Cheong K.Y. , Lockman Z. 
Published: August 2011

PurposeThe purpose of this paper is to report the effect of sputtering time on the electrical and physical properties of ZrOx. ZrOx (measured thickness is ranging from 20.5 to 51.3 nm) thin films as gate oxide materials are formed by metal deposition at different sputtering time and thermal oxidation techniques.Design/methodology/approachZirconium is deposited on silicon substrate at three different sputtering time; 30‐, 60‐ and 120‐s continued with an oxidation process conducted at 500°C for 15 min to form ZrOx thin films. High‐resolution X‐ray diffraction (HR‐XRD), Fourier transform infrared (FTIR) spectroscopy and electrical characterizations were used to examine the properties of the thin film.FindingsA broad ZrOx peak lies in between 26° and 31° from HR‐XRD is presumed as the effect of small thickness of ZrOx and or the ZrOx is still partially crystalline. FTIR spectroscopy results suggested that besides ZrOx, SiOx interfacial layer (IL) has also formed in all of the investigated samples. As the sputtering time increases, hysteresis between the forward and reverse bias of capacitance‐voltage curve has reduced. The lowest leakage current density and the highest oxide breakdown voltage have been demonstrated by 60‐s sputtered sample. These may be attributed to a lower effective oxide charge and interface trap density. The extracted dielectric constant (κ) of these oxides is ranging from 9.4 to 18, in which the κ value increases with the increase in sputtering time.Originality/valueZrOx thin film which was fabricated by sputtering method at different sputtering time and thermal oxidation techniques showed distinctive electrical results. SiOx IL formed in the samples.
Parametric study of efficient thermal dissipation in an LED back light unit
Authors: Taek Kim Jin , Ro Lee Cheul , Kim Daesuk , Joon Baek Byung 
Published: August 2011

PurposeThermal management under high heat flux is crucial to developing high‐power light‐emitting diode (LED) applications. The purpose of this paper is to propose an efficient thermal dissipation technique for an LED back light unit (BLU) system.Design/methodology/approachA typical BLU system includes an LED package (GaN on sapphire, cathode/anode, silicone encapsulant, resin plus phosphor) on a printed circuit board (PCB), a light guide panel, and an aluminum cover frame. The temperature distribution of this system has been simulated and the thermal behavior within a 3D model has been investigated using a commercial computational fluid dynamic code (FLUENT 6.3).FindingsThe authors examined the heat‐spreading effect of cover lengths ranging from 6 to 300 mm and also observed the effect of back cover thickness on the junction temperature and cover frame temperature and investigated the influence of the air gap between the package and the cover frame. Removing the air gap lowers the maximum temperature by about 6 percent. It was found that the addition of a copper layer covering the external surfaces of the LED chip enhanced the cooling efficiency. Finally, the maximum junction temperature can be decreased by more than 21 percent in the range of parameters considered by removing the air gap, adding a heat spreader, and using a thick cover frame.Originality/valueIn this paper, thermal management for efficient heat spreading through a typical BLU system without using any additional devices is investigated. Several parameters that increase the system's temperature are examined, and a combination of design features that attenuate the junction temperature is proposed.
Deformations in stretched surface mounted ceramic strips for sensor applications
Authors: Gschohsmann Walter , Nicolics Johann , Suhir Ephraim 
Published: August 2011

PurposeThe purpose of this paper is to present a most accurate analytical model suit for the prediction of the elastic displacements in a ceramic strip for sensing longitudinal deformations. Accordingly, the objective of the analysis given is to develop a physically meaningful and simple‐as‐possible stress‐strain model for an elongated strip attached to a thick‐and‐stiff substrate.Design/methodology/approachToday's advanced strain gage designs intended for measuring deformations and related physical characteristics use sensitive elements manufactured as ceramic strips. The output signal depends to a great extent on the ability to measure and to adequately interpret the induced elastic displacements in the strip, as the global electric resistor is coupled strongly to the strain field in the sensitive layer. The dependence of the strain on the thickness of a strip is calculated using an analytical 2D stress‐strain model using a shear tension applied at its interface with the substrate and zero‐stress at the opposite face as boundary conditions. All necessary considerations and calculations to develop the model are discussed.FindingsA significant result is the gradual reduction in the deformation depending on the layer thickness. Applying the model combines easy numerical effort with an expressive approximation.Originality/valueThe developed model can be used in the analysis and physical design of the structural elements of the type in question, not necessarily in the field of strain gage and sensor engineering.
Polysilicon nanogap structure development using size expansion technique
Authors: Hashim Uda , Taib Nazwa , Dhahi Thikra S. , Saifullah Azizullah 
Published: August 2011

PurposeNanobiosensors based on nanogap capacitor are widely used for measuring dielectric properties of DNA, protein and biomolecule. The purpose of this paper is to report on the fabrication and characterization polysilicon nanogap patterning using novelties technique.Design/methodology/approachOverall, the polysilicon nanogap pattern was fabricated based on conventional lithographic techniques. For size expansion technique, by employing simple dry thermal oxidation, the couple of nanogap pattern has been expanded to lowest nanogap value. The progress of nanogap pattern expansion was verified by using scanning electron microscopy (SEM). Conductivity, resistivity, and capacitance test were performed to characterize and to measure electrical behavior of full device fabrication.FindingsSEM characterization emphasis on the expansion of polysilicon nanogap pattern increasing with respect to oxidation time. Electrical characterization shows that nanogap enhanced the sensitivity of the device at the value of nano ampere of current.Originality/valueThese simple least‐cost method does not require complicated nanolithography method of fabrication but still possible to serve as biomolecular junction. This approach can be applied extensively to different design of nanogap structure down to several nanometer levels of dimensions. A method of preparing a nanogap electrode according to the present innovation has an advantage of providing active surface that can be easily modified for immobilizations of biomolecules.
Thick‐film photoimageable and laser‐shaped arms for thermoelectric microgenerators
Authors: Markowski Piotr 
Published: August 2011

PurposeThe purpose of this paper is to investigate the possible application of thick‐film, metal‐based thermocouples to microsystems power supply. The subject of matter was development of the procedure of thick‐film thermopile miniaturisation.Design/methodology/approachThe aptitude of four photoimageable inks (based on silver or silver‐palladium) to fabrication of miniaturised thermocouples' arms was investigated. The object of interest was their compatibility with different kinds of low temperature cofired ceramic (LTCC) substrates, maximum resolution, shrinkage and electrical resistivity. Usage of the laser shaping technique to fabrication of narrow thermocouples' arms was also subject of matter. After tests and processes optimization both techniques were combined to fabricate the thick‐film Ag/Ni microthermopile.FindingsMost of investigated inks were compatible with all tested LTCC tapes – fired as well as unfired (green tapes). Photoimageable inks technique can be successfully used for thermocouples' arms miniaturization. 40 μm/40 μm line/spaces resolution can be easily achieved. Combining this technique with laser shaping enabled microthermopile fabrication. It consisted of 42 Ag (photoimageable)/Ni (laser shaped) thermocouples. Arms width was 40 μm and 225 μm (Ag‐ and Ni‐arm, respectively), spaces between them – 65 μm. Overall, width of single thermocouple was smaller than 0.4 mm.Practical implicationsFabrication of microthermopile consisting of several hundreds of thick‐film thermocouples will be possible if described procedure is applied. Such microgenerator will generate output power sufficient to supply some microsystems or microelectronic circuits.Originality/valueThe properties of four photoimageable inks were investigated as well as their compatibility with five different LTCC substrates (fired and unfired). Procedure of thick‐film microthermopile fabrication using photoimageable inks technique combined with laser shaping was proposed for the first time.
An analysis of value management in practice: the case of Northern Ireland's construction industry
Authors: Perera Srinath , Hayles Carolyn S. , Kerlin Stephen 
Published: August 2011

PurposeThe purpose of this paper is to report the findings of research into the principles and procedures associated with value management (VM) and assess its use and effectiveness within the construction industry in Northern Ireland. It provides a brief review of the principles, various procedures and methods associated with VM, investigates the positive and negative factors relating to its use whilst analysing the extent of its usage and determining its effectiveness.Design/methodology/approachUsing a mixed method approach, the authors present the results of a survey of construction professionals operating in Northern Ireland and provide an examination of three case studies exploring the use of VM within the Northern Ireland construction industry.FindingsIn an industry where the client's needs and demands are of paramount importance, VM has emerged as a tool which can help satisfy these needs. This study shows that VM is frequently used within the Northern Ireland construction industry and on the whole is quite effective. However, the research exposed a general consensus that the VM process is frequently not implemented at the most appropriate stage of a project, which suggests that if it was, it could perhaps be more effective than it is at present. There is an apparent lack of formal methods used to carry out the VM process. Instead, rather loose and informal methods are used.Originality/valueIn the absence of a similar study that analyses the factors that influence the VM process highlighting and documenting the views and opinions expressed by the professionals within today's industry and reviewing the effectiveness of its usage, this paper documents a snapshot of practice of VM within the Northern Ireland construction industry.
Evaluating development and community benefits of shopping malls
Authors: Musil Thomas A. 
Published: August 2011

PurposeThe purpose of this paper is to focus on the real estate development and community interaction aspects of US shopping malls. The existing research on shopping mall development and redevelopment can more comprehensively address the importance of malls to the communities in which they are located. Existing shopping mall research focuses on lease valuation, tenant location, retail agglomeration economies, retail demand externalities and intangible asset value. Largely, neglected areas of research are the community and economic contributions of shopping malls. These are critical issues given the age of shopping malls worldwide, the need for adjacent area redevelopment and requirement of large public subsidies for infrastructure construction.Design/methodology/approachThis paper investigates the critical role of shopping malls as town centres and catalysts for area development and redevelopment. A review of the existing research on shopping malls and retail economic contributions to communities is addressed along with how mall redevelopment can be a catalyst for the revitalization of urban core and suburban areas. Methodology on the measurement of shopping centre economic and employment impacts using input/output (IO) modelling is reviewed and analysed.FindingsIO modelling is an effective tool to evaluate publically supported infrastructure to accompany shopping mall and retail redevelopment. As an example of an IO analysis of construction and mall operations economic impacts, the paper presents a case study of the proposed $2 billion Mall of America (Bloomington, Minnesota) expansion employing IO modelling.Originality/valueThe paper demonstrates the community benefits and economic justification for public support for mall revitalization and provides a reliable analytical tool for quantifying the benefits of mall redevelopment to the community.
A contingent valuation model for assessing electricity demand
Authors: Otegbulu Austin C. 
Published: August 2011

PurposeThe purpose of this paper is to focus on households' willingness to pay for electricity consumption and mitigation expenditure due to poor electricity infrastructure as a measure of demand and tariff setting.Design/methodology/approachIn this paper, the demand side management (DSM) approach was adopted in establishing user demand for electricity in the study area.FindingsBased on the high cost (averting expenditure) of providing alternative power supply, households are willing to pay extra for more reliable and regular power supply.Practical implicationsThe study is a deviation from the usual command or supply side management approach to infrastructure provision and management.Originality/valueThere is limited research on DSM approach to electricity infrastructure provision in Nigeria. The study will enhance the chances of cost recovery under private‐public partnership arrangement. The paper identifies that a reliable and reasonable priced electricity supply is essential for a developing country.