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1
Content available remote Influence of Fabric Parameters on Thermal Comfort Performance of Double Layer Knitted Interlock Fabrics
Afzal A., Ahmad S., Rasheed A., Ahmad F., Iftikhar F., Nawab Y.
Autex Research Journal
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2017
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Vol. 17, no. 1
20--26
EN
The aim of this study was to analyse the effects of various fabric parameters on the thermal resistance, thermal conductivity, thermal transmittance, thermal absorptivity and thermal insulation of polyester/cotton double layer knitted interlock fabrics. It was found that by increasing fibre content with higher specific heat increases the thermal insulation while decreases the thermal transmittance and absorptivity of the fabric. It was concluded that double layer knitted fabrics developed with higher specific heat fibres, coarser yarn linear densities, higher knitting loop length and fabric thickness could be adequately used for winter clothing purposes.
2
Content available remote Effect of Weave Structure on Thermo-Physiological Properties of Cotton Fabrics
Ahmad S., Ahmad F., Afzal A., Rasheed R., Mohsin M., Ahmad N.
Autex Research Journal
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2015
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Vol. 15, no. 1
30--34
EN
This paper aims to investigate the relationship between fabric weave structure and its comfort properties. The two basic weave structures and four derivatives for each selected weave structure were studied. Comfort properties, porosity, air permeability and thermal resistance of all the fabric samples were determined. In our research the 1/1 plain weave structure showed the highest thermal resistance making it suitable for cold climatic conditions. The 2/2 matt weave depicted the lowest thermal resistance which makes it appropriate for hot climatic conditions.
3
Content available Prediction cost maintenance model of office building based on condition-based maintenance
Au-Yong C. P., Ali A. S., Ahmad F.
Eksploatacja i Niezawodność
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2014
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Vol. 16, no. 2
319--324
PL
Koszty konserwacji budynków nieustannie rosną ze względu na nieodpowiednią konserwację. Z tej racji, niezbędne jest wypracowanie rozwiązań obniżających koszty konserwacji. Różne badania wykazały, iż charakterystyki utrzymania urządzeń zależnie od ich bieżącego stanu technicznego (condition-based maintenance, CBM) są bezpośrednio powiązane z wydajnością kosztu. Niniejszy artykuł stara się więc ustalić związek pomiędzy charakterystykami utrzymania budynków zależnie od ich bieżącego stanu technicznego a wydajnością kosztu. Następnie opracowano model regresji dla planowania konserwacji jak i predykcji. W badaniach użyto metody mieszanej łączącej badania kwestionariuszowe, wywiad oraz studium przypadku. Rezultaty podkreśliły, iż wiarygodność danych z konserwacji i informacji to najbardziej istotne charakterystyki CBM. W konsekwencji, wnioski z badań sugerują, iż planowanie i wdrożenie strategii utrzymania w zależności od bieżącego stanu technicznego powinno brać pod uwagę jej istotne charakterystyki i odwoływać się do wynikającego z niej modelu predykcji. Ponadto, praca zawiera zalecenia jakimi środkami można w praktyce poprawić istotne charakterystyki i wydajność kosztu.
EN
Building maintenance costs are continuously increasing as a result of poor maintenance. Consequently, there is an urgent need to develop solutions to reduce the maintenance costs. Various studies demonstrated that the characteristics of condition-based maintenance are directly related to the cost performance. Thus, this paper seeks to establish the relationships between the characteristics of condition-based maintenance and the cost performance. The researcher then developed a regression model for maintenance planning and prediction. The study adopted a mix method approach that includes questionnaire survey, interview, and case study. The findings highlighted the reliability of maintenance data and information as the most significant characteristic of conditionbased maintenance. Consequently, the study concluded that the planning and the application of the condition-based maintenance strategy should consider its significant characteristics and make reference to the resulting prediction model. Furthermore, the study recommended measures to improve the significant characteristics and the cost performance in practice.
4
Content available remote Effect of knitting parameters on moisture management and air permeability of interlock fabrics
Nazir A., Hussain T., Ahmad F., Faheem S.
Autex Research Journal
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2014
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Vol. 14, no. 1
39--46
EN
The aim of this study was to investigate the effect of knitting parameters on the moisture management and air permeability of the interlock fabrics. Samples were produced at two different knitting gauges, each with three different stitch lengths. It was found that the fabric mass per square metre increases by increasing machine gauge and decreasing the stitch length, whereas the fabric thickness and porosity increase at these settings. It was further concluded that the loosely knitted fabric samples with higher amount of entrapped air exhibit good air permeability but poor moisture management properties.
5
Content available remote Existence of zero-group velocity modes in an incompressible plate
Hussain T., Ahmad F.
Archives of Mechanics
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2014
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Vol. 66, nr 1
55--65
EN
Zero-group velocity (ZGV) Lamb modes are studied in an incompressible orthotropic plate. The existence of such modes critically depends on the anisotropy parameter a = (c11 + c22 − 2c12 − 4c66)/c66. With materials having a > −1, none of the modes possesses any ZGV points and every mode has such a point if a < −1. Several modes have multiple ZGV points.
6
Content available remote Water column conditions in a coastal lagoon near Jeddah, Red Sea
Albarakati A. M. A., Ahmad F.
Oceanologia
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2012
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No. 54 (4)
675-685
EN
Water column conditions in a lagoon near Jeddah are investigated on the basis of changes in potential energy. Three major factors including balance of surface heat at the air-sea interface, wind and tidal mixing are considered. A negative potential energy change dv/dt will develop stratification, whereas positive dv/dt will tend to mix the water column. The tidal effect is greater in summer with wind mixing showing no great variations. The buoyancy effect of the heat balance at the surface is negative from April to October. This negative buoyancy effect will tend to develop stratification but the positive contributions of wind and tide counteract this and the water column remains mixed except in September and October, when a weak stratification may develop. Generally, the water column remains practically mixed throughout the year. The change in heat content of the water column from mid-April to mid-September is about 3.3 × 10^8 J. During this period the net heat input at the air interface is about 2.0 × 10^8 J, which is about 40% less than the heat content of the water column, showing that the heat is advected towards the central area from the shallower periphery of the lagoon.
7
Content available remote Detection and quantification of Naringenin and kaempferol in Melastoma decemfidum extracts by GC-FID and GC-MS
Sarju N, Abd Samad A., Abd Ghani M, Ahmad F.
Acta Chromatographica
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2012
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Vol. 24, no. 2
221--228
EN
Melastoma decemfidum is a plant species from the Melastomataceae family. The plant was reported to have bioactive flavonoids, which showed antioxidant and cytotoxic activities. Extracts from the leaves of 26 plants were made at room temperature with methanol. Detection and quantification of two of the flavonoids, namely naringenin and kaempferol, in the extracts were carried out by using gas chromatography-flame ion detection (GC-FID) and gas chromatography-mass spectrometry (GC-MS). By optimizing the key experimental parameters, a linear response for the individual target compounds was obtained in the concentration range LOQ from 3.44 to 8.26 g mL -1 (r2 = 0.9731–0.9772), with LODs from 1.13 up to 2.72 μg mL-1 per 1.0 g of crushed leaves, and with repeatability within the relative standard deviation (RSD) of 1.65–1.81%.
8
Content available remote Invariants of a Cartesian tensor of rank 3
Ahmad F.
Archives of Mechanics
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2011
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Vol. 63, nr 4
383-392
EN
General methods are applied to find complete sets of invariants of a tensor of rank 3.When the results are specialized to the piezoelectric tensor, it is found that the tensor has no linear invariant. Also under SO(2), as well as SO(3), the piezoelectric tensor has five quadratic invariants. The sets of invariants are complete.
9
Content available remote Cowin-Mehrabadi Theorem in six dimensions
Ahmad F.
Archives of Mechanics
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2010
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Vol. 62, nr 3
215-222
EN
The Cowin-Mehrabadi Theorem concerning normals to the planes of symmetry of an anisotropic material is generalized to six dimensions. Commutation of the reflection matrix with the 6×6 matrix representing the elasticity tensor in the six-dimensional formulation of the elasticity tensor, provides the condition for the existence of a plane of symmetry. This condition implies the existence of at least two isochoric states for every class except the triclinic one. A simple proof is presented of the fact that an axis of symmetry An, with n > 4 must be an axis of isotropy.
10
Content available remote Shape of dispersion curves in the Rayleigh--Lamb spectrum
Ahmad F.
Archives of Mechanics
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2004
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Vol. 56, nr 2
157-165
EN
The following features of the symmetric Lamb modes in an elastic waveguide are well known: 1. There exists no mode with phase speed less than cR. 2. There is only one mode whose speed asymptotically approaches cR. 3. A horizontal line above c = cT (including the line c = cL) cannot be an asymptote to any of the modes. 4. Phase speed of all modes, except the lowest mode, approaches cT as the frequency becomes very large. The above features characterize the spectrum which is obtained numerically or experimentally but are not fully understood analytically. We analyze the Rayleigh-Lamb equation and provide analytical explanation for the above features.
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