Abstract: Three dimensional non-Interlaced carbon fibre
reinforced silicon carbide (3-D-Cf/SiC) composites with pyrocarbon
interphase were fabricated using isothermal chemical vapor
infiltration (ICVI) combined with polymer impregnation pyrolysis
(PIP) process. Polysilazane (PSZ) is used as a preceramic polymer to
obtain silicon carbide matrix. Thermo gravimetric analysis (TGA),
Infrared spectroscopic analysis (IR) and X-ray diffraction (XRD)
analysis were carried out on PSZ pyrolysed at different temperatures
to understand the pyrolysis and obtaining the optimum pyrolysing
condition to yield β-SiC phase. The density of the composites was
1.94 g cm-3 after the 3-D carbon preform was SiC infiltrated for 280 h
with one intermediate polysilazane pre-ceramic PIP process.
Mechanical properties of the composite materials were investigated
under tensile, flexural, shear and impact loading. The values of
tensile strength were 200 MPa at room temperature (RT) and 195
MPa at 500°C in air. The average RT flexural strength was 243 MPa.
The lower flexural strength of these composites is because of the
porosity. The fracture toughness obtained from single edge notched
beam (SENB) technique was 39 MPa.m1/2. The work of fracture
obtained from the load-displacement curve of SENB test was 22.8
kJ.m-2. The composites exhibited excellent impact resistance and the
dynamic fracture toughness of 44.8 kJ.m-2 is achieved as determined
from instrumented Charpy impact test. The shear strength of the
composite was 93 MPa, which is significantly higher compared 2-D
Cf/SiC composites. Microstructure evaluation of fracture surfaces
revealed the signatures of fracture processes and showed good
support for the higher toughness obtained.
Abstract: With the rapid progress of modern cities, the railway
construction must be developing quickly in China.As a typical
high-density country, shopping center on the subway should be one
important factor during the process of urban development. The paper
discusses the influence of the layout of shopping center on the subway,
and put it in the time and space’s axis of Shanghai urban development.
We usethe digital technology to establish the database of relevant
information. And then get the change role about shopping center on
subway in Shanghaiby the Kernel density estimate.The result shows
the development of shopping center on subway has a relationship with
local economic strength, population size, policysupport, and city
construction. And the suburbanization trend of shopping center would
be increasingly significant.By this case research, we could see the
Kernel density estimate is an efficient analysis method on the spatial
layout. It could reveal the characters of layout form of shopping center
on subway in essence. And it can also be applied to the other research
of space form.
Abstract: In this paper, an edge-strength guided multiscale
retinex (EGMSR) approach will be proposed for color image contrast
enhancement. In EGMSR, the pixel-dependent weight associated with
each pixel in the single scale retinex output image is computed
according to the edge strength around this pixel in order to prevent
from over-enhancing the noises contained in the smooth dark/bright
regions. Further, by fusing together the enhanced results of EGMSR
and adaptive multiscale retinex (AMSR), we can get a natural fused
image having high contrast and proper tonal rendition. Experimental
results on several low-contrast images have shown that our proposed
approach can produce natural and appealing enhanced images.
Abstract: It is known that residual welding deformations give
negative effect to processability and operational quality of welded
structures, complicating their assembly and reducing strength.
Therefore, selection of optimal technology, ensuring minimum
welding deformations, is one of the main goals in developing a
technology for manufacturing of welded structures.
Through years, JSC SSTC has been developing a theory for
estimation of welding deformations and practical activities for
reducing and compensating such deformations during welding
process. During long time a methodology was used, based on analytic
dependence. This methodology allowed defining volumetric changes
of metal due to welding heating and subsequent cooling. However,
dependences for definition of structures deformations, arising as a
result of volumetric changes of metal in the weld area, allowed
performing calculations only for simple structures, such as units, flat
sections and sections with small curvature. In case of complex 3D
structures, estimations on the base of analytic dependences gave
significant errors.
To eliminate this shortage, it was suggested to use finite elements
method for resolving of deformation problem. Here, one shall first
calculate volumes of longitudinal and transversal shortenings of
welding joints using method of analytic dependences and further,
with obtained shortenings, calculate forces, which action is
equivalent to the action of active welding stresses. Further, a finiteelements
model of the structure is developed and equivalent forces
are added to this model. Having results of calculations, an optimal
sequence of assembly and welding is selected and special measures to
reduce and compensate welding deformations are developed and
taken.
Abstract: High temperature deformation behavior of cast
Fe-20Cr-5Al alloy has been investigated in this study by performing
tensile and compression tests at temperatures from 1100 to 1200oC.
Rectangular ingots of which the dimensions were 300×300×100 in
millimeter were cast using vacuum induction melting. Phase
equilibrium was calculated using the FactSage®, thermodynamic
software and database. Tensile strength of cast Fe-20Cr-5Al alloy was
4 MPa at 1200oC. With temperature decreased, tensile strength
increased rapidly and reached up to 13 MPa at 1100oC. Elongation
also increased from 18 to 80% with temperature decreased from
1200oC to 1100oC. Microstructure observation revealed that M23C6
carbide was precipitated along the grain boundary and within the
matrix.
Abstract: In this paper, GSM signal strength was measured in
order to detect the type of the signal fading phenomenon using onedimensional
multilevel wavelet residual method and neural network
clustering to determine the average GSM signal strength received in
the study area. The wavelet residual method predicted that the GSM
signal experienced slow fading and attenuated with MSE of 3.875dB.
The neural network clustering revealed that mostly -75dB, -85dB and
-95dB were received. This means that the signal strength received in
the study is a weak signal.
Abstract: This study investigates the effect of moisture
conditioning on the Indirect Tensile Strength (ITS) of asphalt
concrete. As a first step, cylindrical samples of 100 mm diameter and
50 mm thick were prepared using a Superpave gyratory compactor.
Next, the samples were conditioned using Moisture Induced
Susceptibility Test (MIST) device at different numbers of moisture
conditioning cycles. In the MIST device, samples are subjected water
pressure through the sample pores cyclically. The MIST conditioned
samples were tested for ITS. Results show that the ITS does not
change significantly with MIST conditioning at the specific pressure
and cycles adopted in this study.
Abstract: Bureaucracy reform program drives Indonesian
government to change their management to enhance their
organizational performance. Information technology became one of
strategic plan that organization tried to improve. Knowledge
management system is one of information system that supporting
knowledge management implementation in government which
categorized as people perspective, because this system has high
dependency in human interaction and participation. Strategic plan for
developing knowledge management system can be determine using
some of information system strategic methods. This research
conducted to define type of strategic method of information system,
stage of activity each method, strength and weakness. Literature
review methods used to identify and classify strategic methods of
information system, differentiate method type, categorize common
activities, strength and weakness. Result of this research are
determine and compare six strategic information system methods,
Balanced Scorecard and Risk Analysis believe as common strategic
method that usually used and have the highest excellence strength.
Abstract: Because of high thermal efficiency and low CO2
emission, diesel engines are being used widely in many industrial
fields although it makes many PM and NOx which give both human
health and environment a negative effect. NOx regulations for diesel
engines, however, are being strengthened and it is impossible to meet
the emission standard without NOx reduction devices such as SCR
(Selective Catalytic Reduction), LNC (Lean NOx Catalyst), and LNT
(Lean NOx Trap). Among the NOx reduction devices, urea-SCR
system is known as the most stable and efficient method to solve the
problem of NOx emission. But this device has some issues associated
with the ammonia slip phenomenon which is occurred by shortage of
evaporation and thermolysis time, and that makes it difficult to achieve
uniform distribution of the injected urea in front of monolith.
Therefore, this study has focused on the mixing enhancement between
urea and exhaust gases to enhance the efficiency of the SCR catalyst
equipped in catalytic muffler by changing inlet gas temperature and
spray conditions to improve the spray uniformity of the urea water
solution. Finally, it can be found that various parameters such as inlet
gas temperature and injector and injection angles significantly affect
the evaporation and mixing of the urea water solution with exhaust
gases, and therefore, optimization of these parameters are required.
Abstract: The use of low quality concrete has been identified as one of the main causes of the incessant collapse of buildings in Nigeria. Emphasis has been on the use of poor quality aggregates, poor workmanship and the use of lean concrete mix with low cement quantity as the reasons for the low quality of concrete used for building construction in Nigeria. Surveys conducted revealed that in the construction of most privately owned buildings where concrete trial mixes and concrete compressive strength quality assurance tests are not conducted, concretes used for building constructions are produced using the 1:2:4 mix ratio irrespective of the cement grade/strength class. In this paper, the possible role of the use of inappropriate cement grade/strength class as a cause of the incessant collapse of building in Nigeria is investigated. Investigation revealed that the compressive strengths of concrete cubes produced with Portland-limestone cement grade 32.5 using 1:2:4 and 1:1.5:3 mix ratios are less than the 25MPa and 30MPa cube strengths generally recommended for building superstructures and foundations respectively. Conversely, the compressive strengths of concrete cubes produced with Portland-limestone cement grade 42.5 using 1:2:4 and 1:1.5:3 mix ratios exceed the 25MPa and 30MPa generally recommended for building superstructures and foundations respectively. Thus, it can be concluded that the use of inappropriate cement grade (Portland-limestone cement grade 32.5), particularly for the construction of building foundations is a potential cause of the incessant collapse of buildings in Nigeria. It is recommended that the Standards Organisation of Nigeria should embark on creating awareness for Nigerians, particularly, the home owners and the roadside craftsmen that Portland-limestone cement grade 32.5 should not be used for the construction of building load-carrying members, particularly, building foundations in order to reduce the incessant incidence of collapsed building.
Abstract: Flow forming is widely used in many industries, especially in defence technology industries. Pressure vessels requirements are high precision, light weight, seamless and optimum strength. For large pressure vessels, flow forming by 3 rollers machine were used. In case of long range rocket motor case flow forming and welding of pressure vessels have been used for manufacturing. Due to complication of welding process, researchers had developed 4 meters length pressure vessels without weldment by 4 rollers flow forming machine. Design and preparation of preform work pieces are performed. The optimization of flow forming parameter such as feed rate, spindle speed and depth of cut will be discussed. The experimental result shown relation of flow forming parameters to quality of flow formed tube and prototype pressure vessels have been made.
Abstract: Poly(lactic acid) (PLA) is a biodegradable polymer
which has good mechanical properties, however, its brittleness limits
its usage especially in packaging materials. Therefore, in this work,
PLA based polyurethane films were prepared by synthesizing with
different types of isocyanates; methylene diisocyanate (MDI) and
hexamethylene diisocyanates (HDI). For this purpose, PLA based
polyurethane must have good strength and flexibility. Therefore,
polycaprolactone which has better flexibility were prepared with
PLA. An effective way to endow polylactic acid with toughness is
through chain-extension reaction of the polylactic acid pre-polymer
with polycaprolactone used as chain extender. Polyurethane prepared
from MDI showed brittle behaviour, while, polyurethane prepared
from HDI showed flexibility at same concentrations.
Abstract: Biometallic materials are the most important materials for use in biomedical applications especially in manufacturing a variety of biological artificial replacements in a modern worlds, e.g. hip, knee or shoulder joints, due to their advanced characteristics. Titanium (Ti) and its alloys are used extensively in biomedical applications based on their high specific strength and excellent corrosion resistance. Beta-Ti alloys containing completely biocompatible elements are exceptionally prospective materials for manufacturing of bioimplants. They have superior mechanical, chemical and electrochemical properties for use as biomaterials. These biomaterials have the ability to introduce the most important property of biochemical compatibility which is low elastic modulus. This review examines current information on the recent developments in alloying elements leading to improvements of beta Ti alloys for use as biomaterials. Moreover, this paper focuses mainly on the evolution, evaluation and development of the modulus of elasticity as an effective factor on the performance of beta alloys.
Abstract: In this study, a liquid phase microextraction by hollow fiber (HF-LPME) combined with high performance liquid chromatography-UV detector was applied to preconcentrate and determine trace levels of Cyproheptadine in human urine and plasma samples. Cyproheptadine was extracted from 10 mL alkaline aqueous solution (pH: 9.81) into an organic solvent (n-octnol) which was immobilized in the wall pores of a hollow fiber. Then was back-extracted into an acidified aqueous solution (pH: 2.59) located inside the lumen of the hollow fiber. This method is simple, efficient and cost-effective. It is based on pH gradient and differences between two aqueous phases. In order to optimize the HF-LPME some affecting parameters including the pH of donor and acceptor phases, the type of organic solvent, ionic strength, stirring rate, extraction time and temperature were studied and optimized. Under optimal conditions enrichment factor, limit of detection (LOD) and relative standard deviation (RSD(%), n=3) were up to 112, 15 μg.L−1 and 2.7, respectively.
Abstract: Polymer composite nano-fibers including (1, 3 wt %)
silver nano-particles have been produced by electrospinning method.
Polyacrylonitrile/N,N-dimethylformamide (PAN/DMF) solution have
been prepared and the amount of silver nitrate have been adjusted to
PAN weight. Silver nano-particles were obtained from reduction of
silver ions into silver nano-particles by chemical reduction by
hydrazine hydroxide (N2H5OH). The different amount of silver salt
was loaded into polymer matrix to obtain polyacrylonitrile composite
nano-fiber containing silver nano-particles. The effect of the amount
of silver nano-particles on the properties of composite nano-fiber web
was investigated. Electrical conductivity, mechanical properties,
thermal properties were examined by Microtest LCR Meter 6370
(0.01 mΩ-100 MΩ), Tensile tester, Differential scanning calorimeter
DSC (Q10) and SEM respectively. Also antimicrobial efficiency test
(ASTM E2149-10) was done against to Staphylococcus aureus
bacteria. It has been seen that breaking strength, conductivity,
antimicrobial effect, enthalpy during cyclization increase by use of
silver nano-particles while the diameter of nano-fiber decreases.
Abstract: Effect of 2wt% Cu addition on tensile properties and
fracture behavior of Al-6Si-0.5Mg-2Ni alloy at various strain rates
were studied. The solution treated Al-6Si-0.5Mg-2Ni (-2Cu) alloys,
were aged isochronally for 1 hour at temperatures up to 300oC. The
uniaxial tension test was carried out at strain rate ranging from 10-4s-1
to 10-2s-1 in order to investigate the strain rate dependence of tensile
properties. Tensile strengths were found to increase with ageing
temperature and the maximum being attained ageing for 1 hr at
225oC (peak aged condition). Addition of 2wt% Cu resulted in an
increase in tensile properties at all strain rates. Evaluation of tensile
properties at three different strain rates (10-4, 10-3 and 10-2 s-1)
showed that strain rates affected the tensile properties significantly.
At higher strain rates the strength was better but ductility was poor.
Microstructures of broken specimens showed that both the void
coalescence and the interface debonding affect the fracture behavior
of the alloys
Abstract: High temperature is one of the most detrimental
effects that cause important changes in concrete’s mechanical,
physical, and thermo-physical properties. As a result of these
changes, especially high strength concrete (HSC), may exhibit
damages such as cracks and spallings. To overcome this problem,
incorporating polymer fibers such as polypropylene (PP) in concrete
is a very well-known method. In this study, using RRH, as a
sustainable material, instead of PP fiber in HSC to prevent spallings
and improve physical and thermo-physical properties were
investigated. Therefore, seven HSC mixtures with 0.25 water to
binder ratio were prepared incorporating silica fume and blast furnace
slag. PP and RRH were used at 0.2-0.5% and 0.5-3% by weight of
cement, respectively. All specimens were subjected to high
temperatures (20 (control), 300, 600 and 900˚C) with a heating rate
of 2.5˚C/min and after cooling, residual physical and thermo-physical
properties were determined.
Abstract: This study compared the mechanical and microstructural properties produced during friction stir welding (FSW) of S275 structural steel in air and underwater. Post weld tests assessed the tensile strength, micro-hardness, distortion, Charpy impact toughness and fatigue performance in each case. The study showed that there was no significant difference in the strength, hardness or fatigue life of the air and underwater specimens. However, Charpy impact toughness was shown to decrease for the underwater specimens and was attributed to a lower degree of recrystallization caused by the higher rate of heat loss experienced when welding underwater. Reduced angular and longitudinal distortion was observed in the underwater welded plate compared to the plate welded in air.
Abstract: Outrigger-braced wall systems are commonly used to provide high rise buildings with the required lateral stiffness for wind and earthquake resistance. The existence of outriggers adds to the stiffness and strength of walls as reported by several studies. The effects of different parameters on the elasto-plastic dynamic behavior of outrigger-braced wall systems to earthquakes are investigated in this study. Parameters investigated include outrigger stiffness, concrete strength, and reinforcement arrangement as the main design parameters in wall design. In addition to being significantly affect the wall behavior, such parameters may lead to the change of failure mode and the delay of crack propagation and consequently failure as the wall is excited by earthquakes. Bi-linear stress-strain relation for concrete with limited tensile strength and truss members with bi-linear stress-strain relation for reinforcement were used in the finite element analysis of the problem. The famous earthquake record, El-Centro, 1940 is used in the study. Emphasize was given to the lateral drift, normal stresses and crack pattern as behavior controlling determinants. Results indicated significant effect of the studied parameters such that stiffer outrigger, higher grade concrete and concentrating the reinforcement at wall edges enhance the behavior of the system. Concrete stresses and cracking behavior are too much enhanced while less drift improvements are observed.
Abstract: There are several types of metal-based devices conceived as dampers for the seismic energy absorber whereby damages to the major structural components could be minimized for both new and existing structures. This paper aimed to develop and evaluate structural performance of slit circular shear panel damper for passive seismic energy protection by inelastic deformation. Structural evaluation was done using commercially available nonlinear FE simulation program. The main parameters considered are: diameter-to-thickness (D/t) ratio and slit length-to-width ratio (l/w). Depending on these parameters three different buckling mode and hysteretic behavior was found: yielding prior to buckling without strength degradation, yielding prior to buckling with strength degradation and yielding with buckling and strength degradation which forms pinching at initial displacement. The susceptible location at which the possible crack is initiated is also identified for selected specimens using rupture index.