Abstract: A new approach has been developed to estimate the
load share and distribution of worm gear drives, and to calculate the
instantaneous tooth meshing stiffness. In the approach, the worm gear
drive was modelled as a series of spur gear slices, and each slice was
analyzed separately using the well-established formulae of spur gear
loading and stresses. By combining the results obtained for all slices,
the entire envolute worm gear set loading and stressing was obtained. The geometric modelling method presented allows tooth elastic
deformation and tooth root stresses of worm gear drives under
different load conditions to be investigated. Based on the slicing
method introduced in this study, the instantaneous meshing stiffness
and load share are obtained. In comparison with existing methods,
this approach has both good analysis accuracy and less computing
time.
Abstract: The properties of hollow sandcrete blocks produced in
Minna, Nigeria are presented. Sandcrete block is made of cement,
water and sand binded together in certain mix proportions. For the
purpose of this work, fifty (50) commercial sandcrete block industries
were visited in Minna, Nigeria to obtain block samples and
aggregates used for the manufacture, and to take inventory of the mix
composition and the production process. Sieve analysis tests were
conduction on the soil sample from various block industries to
ascertain their quality to be used for block making. The mix ratios
were also investigated. Five (5) nine inches (9’’ or 225mm) blocks
were obtained from each block industry and tested for dimensional
compliance and compressive strength. The results of the soil test
shows that the grading fall within the limit for natural aggregate and
can easily are used to obtain workable mix. Physical examinations of
the block sizes show slight deviation from the standard requirement
in NIS 87:2000. Compressive strength of hollow sandcrete blocks in
range of 0.12 N/mm2 to 0.54 N/mm2 was obtained which is below the
recommendable value of 3.45 N/mm2 for load bearing hollow
sandcrete blocks. This indicates that these blocks are below the
standard for load-bearing sandcrete blocks and cannot be used as load
bearing walling units. The mix composition also indicated low
cement content resulting in low compressive strength. Most of the
commercial block industries visited does not take curing very serious.
Water were only sprinkled ones or twice before the blocks were
stacked and made readily available for sale. It is recommended that a
mix ratio of 1:4 to 1:6 should be used for the production of sandcrete
blocks and proper curing practice should be adhered. Blocks should
also be cured for 14 days before making them available for
consumers.
Abstract: A new design of aerostatic thrust bearing is proposed
for high static stiffness. The bearing body, which is mead of polymer
covered with metallic membrane, is held by a circular ring. Such a
support helps form a concave air gap to grasp the air pressure. The
polymer body, which can be made rapidly by either injection or
molding is able to provide extra damping under dynamic loading. The
smooth membrane not only serves as the bearing surface but also
protects the polymer body. The restrictor is a capillary inside a silicone
tube. It can passively compensate the variation of load by expanding
the capillary diameter for more air flux. In the present example, the
stiffness soars from 15.85 N/μm of typical bearing to 349.85 N/μm at
bearing elevation 9.5 μm; meanwhile the load capacity also enhances
from 346.86 N to 704.18 N.
Abstract: Twin steel plates-concrete composite shear walls are
composed of a pair of steel plate layers and a concrete layer
sandwiched between them, which have the characteristics of both
reinforced concrete shear walls and steel plate shear walls. Twin steel
plates-composite shear walls contain very high ultimsate bearing
capacity and ductility, which have great potential to be applied in the
super high-rise buildings and special structures. In this paper, we
analyzed the basic characteristics and stress mechanism of the twin
steel plates-composite shear walls. Specifically, we analyzed the
effects of the steel plate thickness, wall thickness and concrete
strength on the bearing capacity of the twin steel plates-composite
shear walls. The analysis results indicate that: (1) the initial shear
stiffness and ultimate shear-carrying capacity is not significantly
affected by the thickness of concrete wall but by the class of concrete,
(2) both factors significantly impact the shear distribution of the
shear walls in ultimate shear-carrying capacity. The technique of twin
steel plates-composite shear walls has been successfully applied in
the construction of an 88-meter Huge Statue of Buddha located in
Hunan Province, China. The analysis results and engineering
experiences showed that the twin steel plates-composite shear walls
have great potential for future research and applications.
Abstract: By enhancing the applicatıon of grounds for
establishment and due to the lack of appropriate sites, engineers
attempt to seek out a new method to reduce the weakness of soils. İn
aspect of economic situation, various ways have been used to
decrease the weak grounds. Because of the rapid development of
infrastructural facilities, spreading the construction operation is an
obligation. Furthermore, in various sites with the really bad soil
situation, engineers have considered obvious problems. One of the
most essential ways for developing the weak soils is stone column.
Obviously, the method was introduced in France in 1830 to improve
a native soil initially. Stone columns have an expanding range of
usage in different rough foundation sites all over the world to
increase the bearing capacity, to reduce the whole and differential
settlements, to enhance the rate of consolidation, to stabilize slopes
stability of embankments and to increase the liquefaction resistance
as well. A recent procedure called installing vertical nails along the
round stone columns in order to make better the performance of
considered columns is offered. Moreover, thanks to the enhancing the
nail diameter, number and embedment nail depth, the positive points
of vertical circumferential nails increases. Based on the result of this
study, load caring capacity will be develop with enhancing the length
and the power of reinforcements in vertical encasement stone column
(CESC). In this study, the main purpose is comparing two methods of
stone columns (installed a nail surrounding the stone columns and
using geogrid on clay) for enhancing the bearing capacity, decreasing
the whole and various settlements.
Abstract: Work presented is interested in the characterization of
the quasistatic mechanical properties and in fatigue of a composite
laminated in jute/epoxy. The natural fibers offer promising prospects
thanks to their interesting specific properties, because of their low
density, but also with their bio-deterioration. Several scientific
studies highlighted the good mechanical resistance of the vegetable
fiber composites reinforced, even after several recycling. Because of
the environmental standards that become increasingly severe, one
attends the emergence of eco-materials at the base of natural fibers
such as flax, bamboo, hemp, sisal, jute. The fatigue tests on
elementary vegetable fibers show an increase of about 60% of the
rigidity of elementary fibers of hemp subjected to cyclic loadings. In
this study, the test-tubes manufactured by the method infusion have
sequences of stacking of 0/90° and ± 45° for the shearing and tensile
tests. The quasistatic tests reveal a variability of the mechanical
properties of about 8%. The tensile fatigue tests were carried out for
levels of constraints equivalent to half of the ultimate values of the
composite. Once the fatigue tests carried out for well-defined values
of cycles, a series of static tests of traction type highlights the
influence of the number of cycles on the quasi-static mechanical
behavior of the laminate jute/epoxy.
Abstract: This paper presents a methodology for probabilistic
assessment of bearing capacity and prediction of failure mechanism
of masonry vaults at the ultimate state with consideration of the
natural variability of Young’s modulus of stones. First, the
computation model is explained. The failure mode corresponds to the
four-hinge mechanism. Based on this consideration, the study of a
vault composed of 16 segments is presented. The Young’s modulus of
the segments is considered as random variable defined by a mean
value and a coefficient of variation. A relationship linking the vault
bearing capacity to the voussoirs modulus variation is proposed. The
most probable failure mechanisms, in addition to that observed in the
deterministic case, are identified for each variability level as well as
their probability of occurrence. The results show that the mechanism
observed in the deterministic case has decreasing probability of
occurrence in terms of variability, while the number of other
mechanisms and their probability of occurrence increases with the
coefficient of variation of Young’s modulus. This means that if a
significant change in the Young’s modulus of the segments is proven,
taking it into account in computations becomes mandatory, both for
determining the vault bearing capacity and for predicting its failure
mechanism.
Abstract: Main objective of this paper is to establish a link
between inertial forces of the bearings used in construction of wind
power plant and its behavior. Using bearings with lower inertial
forces has the immediate effect of decreasing inertia rotor system,
with significant results in increased energy efficiency, due to
decreased friction forces between rollers and raceways. The F.E.M.
analysis shows the appearance of uniform contact stress at the ends of
the rollers, demonstrated the necessity of production of low mass
bearings. Favorable results are expected in the economic field, by
reducing material consumption and by increasing the durability of
bearings. Using low mass bearings with hollow rollers instead of
solid rollers has an impact on working temperature, on vibrations and
noise which decrease. Implementation of types of hollow rollers of
cylindrical tubular type, instead of expensive rollers with logarithmic
profile, will bring significant inertial forces decrease with large
benefits in behavior of wind power plant.
Abstract: Indonesia has experienced annual forest fires that have
rapidly destroyed and degraded its forests. Fires in the peat swamp
forests of Riau Province, have set the stage for problems to worsen,
this being the ecosystem most prone to fires (which are also the most
difficult, to extinguish). Despite various efforts to curb deforestation,
and forest degradation processes, severe forest fires are still
occurring. To find an effective solution, the basic causes of the
problems must be identified. It is therefore critical to have an indepth
understanding of the underlying causal factors that have
contributed to deforestation and forest degradation as a whole, in
order to attain reductions in their rates. An assessment of the drivers of deforestation and forest
degradation was carried out, in order to design and implement
measures that could slow these destructive processes. Research was
conducted in Giam Siak Kecil–Bukit Batu Biosphere Reserve
(GSKBB BR), in the Riau Province of Sumatera, Indonesia. A
biosphere reserve was selected as the study site because such reserves
aim to reconcile conservation with sustainable development. A
biosphere reserve should promote a range of local human activities,
together with development values that are in line spatially and
economically with the area conservation values, through use of a
zoning system. Moreover, GSKBB BR is an area with vast peatlands,
and is experiencing forest fires annually. Various factors were
analysed to assess the drivers of deforestation and forest degradation
in GSKBB BR; data were collected from focus group discussions
with stakeholders, key informant interviews with key stakeholders,
field observation and a literature review. Landsat satellite imagery was used to map forest-cover changes
for various periods. Analysis of landsat images, taken during the
period 2010-2014, revealed that within the non-protected area of core
zone, there was a trend towards decreasing peat swamp forest areas,
increasing land clearance, and increasing areas of community oilpalm
and rubber plantations. Fire was used for land clearing and most
of the forest fires occurred in the most populous area (the transition
area). The study found a relationship between the deforested/
degraded areas, and certain distance variables, i.e. distance from
roads, villages and the borders between the core area and the buffer
zone. The further the distance from the core area of the reserve, the
higher was the degree of deforestation and forest degradation. Research findings suggested that agricultural expansion may be
the direct cause of deforestation and forest degradation in the reserve,
whereas socio-economic factors were the underlying driver of forest
cover changes; such factors consisting of a combination of sociocultural,
infrastructural, technological, institutional (policy and governance), demographic (population pressure) and economic
(market demand) considerations. These findings indicated that local
factors/problems were the critical causes of deforestation and
degradation in GSKBB BR. This research therefore concluded that
reductions in deforestation and forest degradation in GSKBB BR
could be achieved through ‘local actor’-tailored approaches such as
community empowerment.
Abstract: Structure-borne noise is an important aspect of
offshore platform sound field. It can be generated either directly by
vibrating machineries induced mechanical force, indirectly by the
excitation of structure or excitation by incident airborne noise.
Therefore, limiting of the transmission of vibration energy
throughout the offshore platform is the key to control the structureborne
noise. This is usually done by introducing damping treatment
to the steel structures. Two types of damping treatment using onboard
are presented. By conducting a Statistical Energy Analysis
(SEA) simulation on a jack-up rig, the noise level in the source room,
the neighboring rooms, and remote living quarter cabins are
compared before and after the damping treatments been applied. The
results demonstrated that, in the source neighboring room and living
quarter area, there is a significant noise reduction with the damping
treatment applied, whereas in the source room where air-borne sound
predominates that of structure-borne sound, the impact is not
obvious. The conclusion on effective damping treatment in the
offshore platform is made which enable acoustic professionals to
implement noise control during the design stage for offshore crews’
hearing protection and habitant comfortability.
Abstract: The use of titanium fluoride and iron fluoride
(TiF3/FeF3) catalysts in combination with polutetrafluoroethylene
(PTFE) in plain zinc- dialkyldithiophosphate (ZDDP) oil is important
for the study of engine tribocomponents and is increasingly a strategy
to improve the formation of tribofilm and provide low friction and
excellent wear protection in reduced phosphorus plain ZDDP oil. The
influence of surface roughness and the concentration of
TiF3/FeF3/PTFE were investigated using bearing steel samples
dipped in lubricant solution at 100°C for two different heating time
durations. This paper addresses the effects of water drop contact
angle using different surface; finishes after treating them with
different lubricant combination. The calculated water drop contact
angles were analyzed using Design of Experiment software (DOE)
and it was determined that a 0.05 μm Ra surface roughness would
provide an excellent TiF3/FeF3/PTFE coating for antiwear resistance
as reflected in the Scanning electron microscopy (SEM) images and
the tribological testing under extreme pressure conditions. Both
friction and wear performance depend greatly on the PTFE/and
catalysts in plain ZDDP oil with 0.05 % phosphorous and on the
surface finish of bearing steel. The friction and wear reducing effects,
which was observed in the tribological tests, indicated a better micro
lubrication effect of the 0.05 μm Ra surface roughness treated at
100°C for 24 hours when compared to the 0.1 μm Ra surface
roughness with the same treatment.
Abstract: Currently, green rating systems are mainly utilized for
correctly sizing mechanical and electrical systems, which have short
lifetime expectancies. In these systems, passive solar and bio-climatic
architecture, which have long lifetime expectancies, are neglected.
Urban rating systems consider buildings and services in addition to
neighborhoods and public transportation as integral parts of the built
environment. The main goal of this study was to develop a more
consistent point allocation system for urban building standards by
using six different lifetime shearing layers: Site, Structure, Skin,
Services, Space, and Stuff, each reflecting distinct environmental
damages. This shearing-layer concept was applied to internationally
well-known rating systems: Leadership in Energy and Environmental
Design (LEED) for Neighborhood Development, BRE
Environmental Assessment Method (BREEAM) for Communities
and Comprehensive Assessment System for Building Environmental
Efficiency (CASBEE) for Urban Development. The results showed
that LEED for Neighborhood Development and BREEAM for
Communities focused on long-lifetime-expectancy building designs,
whereas CASBEE for Urban Development gave equal importance to
the Building and Service Layers. Moreover, although this rating
system was applied using a building-scale assessment, “Urban Area +
Buildings” focuses on a short-lifetime-expectancy system design,
neglecting to improve the architectural design by considering bioclimatic
and passive solar aspects.
Abstract: Typical load-bearing biological materials like bone,
mineralized tendon and shell, are biocomposites made from both
organic (collagen) and inorganic (biomineral) materials. This
amazing class of materials with intrinsic internally designed
hierarchical structures show superior mechanical properties with
regard to their weak components from which they are formed.
Extensive investigations concentrating on static loading conditions
have been done to study the biological materials failure. However,
most of the damage and failure mechanisms in load-bearing
biological materials will occur whenever their structures are exposed
to dynamic loading conditions. The main question needed to be
answered here is: What is the relation between the layout and
architecture of the load-bearing biological materials and their
dynamic behavior? In this work, a staggered model has been
developed based on the structure of natural materials at nanoscale and
Finite Element Analysis (FEA) has been used to study the dynamic
behavior of the structure of load-bearing biological materials to
answer why the staggered arrangement has been selected by nature to
make the nanocomposite structure of most of the biological materials.
The results showed that the staggered structures will efficiently
attenuate the stress wave rather than the layered structure.
Furthermore, such staggered architecture is effectively in charge of
utilizing the capacity of the biostructure to resist both normal and
shear loads. In this work, the geometrical parameters of the model
like the thickness and aspect ratio of the mineral inclusions selected
from the typical range of the experimentally observed feature sizes
and layout dimensions of the biological materials such as bone and
mineralized tendon. Furthermore, the numerical results validated with
existing theoretical solutions. Findings of the present work emphasize
on the significant effects of dynamic behavior on the natural
evolution of load-bearing biological materials and can help scientists
to design bioinspired materials in the laboratories.
Abstract: This study was conducted to determine sex
differentiation of laboratory reared Elm nymphalid (Nymphalis
polychloros Linnaeus, 1758) by examining the morphological
structure of pupal stage. Laboratory colony of elm nymphalid, reared
on pear leaves, was used to set up experiments. It was performed
with 5 replications having 8 pupae for each replication. Dorsal,
ventral and lateral parts of external morphological structures of pupae
were examined by Olympus SZX9 stereozoom microscope and
photographed. When fully grown, mature larvae wander the highest
part of the rearing cage and pupae were formed hanging by
cremaster. After completing prepupa stage about 1.5±0.3 days, they
all pupated. Pupal stage was completed at 24±1°C about 4.38±1.20
days. Pupal weights were 0.483±0.05 g in females and 0.392±0.08 g
(n=40) in males respectively. Pupal emergence rate was 95%, with
22 females and 16 males. Examinations of ventral parts of 8th, 9th,
and 10th abdominal segments revealed that anal opening were found
at 10th abdominal segment in both sexes, 3 lumps were determined at
9th abdominal segments then the specific opening structure at 8th
segment was only found on female pupae.
Abstract: Dynamics of a rotor supported by air bearings is
strongly depends on the pressure distribution between the rotor and
the bearing. In this study, internal pressure in air bearings is
numerical and experimental analyzed for different radial clearances.
Firstly the pressure distribution between rotor and bearing is modeled
using Reynold's equation and this model is solved numerically. The
rotor-bearing system is also modeled in four degree of freedom and it
is simulated for different radial clearances. Then, in order to validate
numerical results, a test rig is designed and the rotor bearing system
is run under the same operational conditions. Pressure signals of left
and right bearings are recorded. Internal pressure variations are
compared for numerical and experimental results for different radial
clearances.
Abstract: This study was aimed to investigate the machining
stability of a spindle tool with different preloaded amount. To this end,
the vibration tests were conducted on the spindle unit with different
preload to assess the dynamic characteristics and machining stability
of the milling machine. Current results demonstrate that the tool tip
frequency response characteristics and the machining stabilities in X
and Y direction are affected to change due to the different preload of
spindle bearings. As found from the results, a high preloaded spindle
tool shows higher limited cutting depth at mid position, while a spindle
with low preload shows a higher limited depth. This indicates that the
machining stability of a milling machine is affected to vary by the
spindle unit when it was assembled with different bearing preload.
Abstract: This study focuses on a novel method for dispersion
and distribution of reinforcement under high intensive shear stress to
produce metal composites. The polyacrylonitrile (PAN)-based short
carbon fiber (Csf) and Nextel 610 alumina fiber were dispersed under
high intensive shearing at mushy zone in semi-solid of A356 by a
novel method. The bundles and clusters were embedded by
infiltration of slurry into the clusters, thus leading to a uniform
microstructure. The fibers were embedded homogenously into the
aluminum around 576-580°C with around 46% of solid fraction.
Other experiments at 615°C and 568°C which are contained 0% and
90% solid respectively were not successful for dispersion and
infiltration of aluminum into bundles of Csf. The alumina fiber has
been cracked by high shearing load. The morphologies and
crystalline phase were evaluated by SEM and XRD. The adopted
thixo-process effectively improved the adherence and distribution of
Csf into Al that can be developed to produce various composites by
thixomixing.
Abstract: In this study, one of the tools of Islamic financing
known as “Sukuk” a non-interest bearing investment which has
started to be implemented in Turkey and the world as a whole is
discussed. In order to increase the vitality and efficiency of the
economy, by taking lessons from the recent economic crisis new
developments in the banking and investment sector are being
expanded. The purpose of all investors is to obtain more revenue
through the use of capital. The inability of traditional investment
tools to meet the expectations of investors and the interest based
financial system where one investor benefits at the expense of
another there has been the need for a different, reliable and noninterest
bearing financial market that is consistent with the Islamic
rule. As a result an alternative and more reliable interest free
financing tool “Sukuk” rental certificates covering people who are
sensitive to Islamic rules, appeal to all segments, hidden remaining
capital that contributes to the economy, reduce disparities in income
distribution, common risk sharing system of profit and loss sharing
has emerged. Today, for the structural countries by examining the
state of the world market economy the applicability, enactment and
future issues associated with this attractive kind of Islamic finance
namely the “Sukuk” market has been explained.
Abstract: Auditory hallucinations among the most invalidating
and distressing experiences reported by patients diagnosed with
schizophrenia, leading to feelings of powerlessness and helplessness
towards their illness. In more severe cases, these auditory
hallucinations can take the form of commanding voices, which are
often related to high suicidality rates in these patients. Several
authors propose that the meanings attributed to the hallucinatory
experience, rather than characteristics like form and content, can be
determinant in patients’ reactions to hallucinatory activity,
particularly in the case of voice-hearing experiences. In this study, 48
patients diagnosed with paranoid schizophrenia presenting auditory
hallucinations were studied. Multiple regression analyses were
computed to study the influence of several developmental aspects,
such as family and social dynamics, bullying, depression, and sociocognitive
variables on the auditory hallucinations, on patients’
attributions and relationships with their voices, and on the resulting
invalidation of hallucinatory experience. Overall, results showed how
relationships with voices can mirror several aspects of interpersonal
relationship with others, and how self-schemas, depression and actual
social relationships help shaping the voice-hearing experience. Early
experiences of victimization and submission help predict the
attributions of omnipotence of the voices, and increased hostility
from parents seems to increase the malevolence of the voices,
suggesting that socio-cognitive factors can significantly contribute to
the etiology and maintenance of auditory hallucinations. The
understanding of the characteristics of auditory hallucinations and the
relationships patients established with their voices can allow the
development of more promising therapeutic interventions that can be
more effective in decreasing invalidation caused by this devastating
mental illness.
Abstract: Froth flotation remains to date as one of the most used
metallurgical processes for concentrating metal-bearing minerals in
ores. Oxide ores are relatively less amenable to froth flotation and
require a judicious choice of reagents for the recovery of metals to be
optimised. Laboratory batch flotation tests were conducted to
determine the effect of two types of gasoil-rinkalore mixtures on the
flotation response of a copper cobalt oxide ore sample. The head
assay conducted on the initial ore sample showed that it contained
about 2.90% of Cu, 0.12% of Co.
Upon the flotation test work, the results obtained indicated that the
concentrate obtained with use of the mixture gazoil-rinkalore RX
yielded 8.24% Cu and 0.22% Co concentrate grades with recoveries
of 76.0% Cu and 78.0% Co respectively. But, the concentrate
obtained by use of the mixture gazoil-rinkalore RX3 yielded
relatively bad results with 5.92% Cu and 0.18% Cu concentrate
grades with recoveries of 70.3% Cu and 65.3% Co respectively.