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Prediction of Effective Thermal Conductivity of Fluid Saturated Porous Media: in Situ Thermo Physical Measurements

Thesis Info

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Author

Zeb, Aurang

Program

PhD

Institute

Quaid-I-Azam University

City

Islamabad

Province

Islamabad.

Country

Pakistan

Thesis Completing Year

2009

Thesis Completion Status

Completed

Subject

Physics

Language

English

Link

http://prr.hec.gov.pk/jspui/handle/123456789/1031

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676726987300

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The density related properties of igneous (dunite and gabbro) and sedimentary (limestone) rocks are measured at room temperature and normal pressure, using ASTM Standards. Dunite samples are taken from Chillas near Gilgit and gabbro samples from Warsik near Peshawar, both of these places are located in north of Pakistan. The limestones are taken from Nammal Gorge sections, Western Salt Range, Pakistan. The thermal properties are determined using the well known transient plane source (TPS) technique. The thermal parameters of dunite are measured in temperature range from 83K to 483K, using air as saturant in pore spaces. The thermal properties of gabbro samples are reported using air as well as water as saturants in pore spaces at room temperature where as the thermal properties of limestones are measured in temperature range from 293K to 443K. All of the measurements on thermal parameters are carried out at normal pressure. Precise measurements on thermal conductivity are difficult to conduct and are very time consuming. Consequently, a lot of work is done on the prediction of effective thermal conductivity of porous media. To become a part of these efforts, an empirical model is proposed, as given below: 1 λ e = 1 λ s + mΦ λ f Where λ e is the effective thermal conductivity, λ f is the thermal conductivity of fluid in pore spaces, λ s is the thermal conductivity of solid phase, Φ is the fractional porosity and m is the empirical coefficient whose value can be determined by the method of least squares. The results of this proposal are compared with the existing models and the corresponding improvements are reported.⎛ 1 ⎞ Using the concept that thermal resistivity ⎜ ⎟ is a linear function of temperature, the ⎝ λ ⎠ above model is then extended to involve the effect of temperature, given as: 1 λ e = 1 λ s + mΦ ⎛ T ⎜ λ f ⎜ ⎝ T o ⎞ ⎟ ⎟ , ⎠ where T o is certain reference temperature. An exponential decay trial is also given for the prediction of effective thermal conductivity of porous media under ambient conditions, as: λ e = λ s e − zΦ λ s λ f , where z is the empirical coefficient. This formula is tested on gabbro samples with air and water as fluids in pore spaces. The results of this relation are again compared with the results obtained from the existing models and the corresponding variations are discussed.
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نعت کہنے کے لیے لفظ نیا ڈھونڈیں گے


نعت کہنے کے لئے لفظ نیا ڈھونڈیں گے
ہم بھی جامیؔ کی طرح رنگ جُدا ڈھونڈیں گے

اِن ستاروں سے بھری راہوں میں کیا رکھا ہے
نقشِ پائے شہِ انوارِ ہُدیٰ ڈھونڈیں گے

وہ تو صدیقؓ کی آنکھوں میں سمایا ہوا ہے
کس طرح اہلِ جفا نورِ خدا ڈھونڈیں گے

تاجِ شاہی بھی یہاں کاسہ بنا دیکھا ہے
تیری دہلیز کو سب شاہ و گدا ڈھونڈیں گے

نورِ بُرہانِ ہُدیٰ ، منزلِ ایقانِ خدا
ڈھونڈنے والے ترے قدموں میں جا ڈھونڈیں گے

جن کی خواہش ہے کھلے دل کی امیدوں کا چمن
گلشنِ طیبہ کی وہ لوگ فضا ڈھونڈیں گے

ہوں گے میزان پہ اعمال مگر کوثر پر
ہم ثنا گوئی کا عرفانؔ! صلہ ڈھونڈیں گے

الربافی بلاد غیرالمسلمة: دراسة فقهیة مقارنة

Islam is not a mere set of worships but it leaves no stone unturned to guide its followers regarding the social conduct be it politico-legal, sociocultural or economic etc to name a few. The interest-based transactions have been categorically rendered impermissible and unlawful by virtue of Quranic injunctions and authentic ahadith. In this article the issue of interest based transactions – Muslim to Muslim, Muslim to non-Muslim and vice versa, a Muslim resident of a non-Muslim state and a Muslim non-resident of a nonMuslim state – has been discussed in detail in the light of Quran, hadith and juristic rulings of the eminent Islamic scholars including the great four imams.

Genetics of Drought Tolerance in Wheat Triticum Aestivum L. .

Seventy five diversified accessions of Triticum aestivum L. were screened to assess the variability for drought tolerance at seedling stage in the green-house of Department of Plant Breeding and Genetics, University of Agriculture, Faisalabad. On the basis of relative performance of the genotypes, five tolerant and two sensitive genotypes were selected and crossed in 7 × 7 diallel mating design. The breeding material was evaluated under green-house and field conditions with three replications following completely randomized design and randomized complete block design, respectively under normal and drought conditions. The data regarding various seedling traits viz; root length, shoot length, root weight shoot weight and other plant traits like days to heading, days to maturity, plant height, flag leaf area, tillers per plant, spike length, number of spikelets per spike, spike weight, grains per spike, spike grain weight/spike straw weight ratio, thousand-kernel weight, biomass per plant, harvest index, rate of photosynthesis, rate of transpiration and grain yield per plant. All the traits showed decreasing trends due to drought stress except root length. Existence of sufficient amount of genetic variability was evident among genotypes for all the parameters. On performing adequacy test, it was suggested that data was fully adequate for spike length, plant height, spike weight, spikelets per spike and rate of photosynthesis under normal condition while for traits like shoot weight, days to maturity, plant height, spike length, tillers per plant, thousand-kernel weight, harvest index and grain yield per plant under drought condition indicating the presence of dominance and absence of epistasis.All the remaining traits exhibited the partial adequacy under both the conditions. The results of the genetic studies showed that almost all the traits exhibited additive genetic effects with partial dominance and with moderate to high heritability. High heritability estimates were observed for root weight, shoot weight, plant height, grain weight per spike, flag leaf area, days to heading, thousand-kernel weight, biomass per plant, rate of transpiration and grain yield per plant under both the conditions. Correlation studies among seedling traits revealed significant and positive genotypic and phenotypic association of root length with root weight, shoot length with shoot weight and root weight with shoot weight under both environments. Grain yield per plant had positive and significant genotypic and phenotypic association with almost all the traits under both conditions. Negatively significant genotypic and phenotypic association of grain yield was found with days to heading under both conditions. Although grain yield can be enhanced through selection on yield components as they have strong association with yield under both conditions but special emphasis should be given to plant height, thousand-kernel weight and plant biomass because of their strong association with yield. The genotypes with adequate grain-fill period can have better yielding ability under normal and stress as well because of negative association of days to heading with yield while it was positive with days to maturity. The partial dominance with additive gene action in most of the traits suggests that selection could be carried out in early generations using pedigree or single seed descent methods to have genetic gains under water limited environment. The G7´G2, G5´G6 and G4´G7 were found the potential cross combinations in terms of yield and yield related traits for future breeding programs. The information may also be used to evolve high yielding varieties for sustainable wheat production in those areas where drought stress is a major threat.