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Crop emergence is a major factor limiting crop yield, especially in hot climates where soil dries quickly after rainfall or irrigation. Problems with the emergence of cotton in Pakistan are of particular importance because of the high value of the crop and its contribution to national economy. A complex interaction of factors involving climate, seed properties, soil physical properties and soil management determine crop emergence and hence establishment. This means modelling of emergence is an important way of determining the combination of conditions at which emergence becomes limited. The studies reported here show the effect of temperature, matric potential and mechanical impedance on pre-emergent root and shoot growth of cotton variety MNH-147. The effect of osmotic potential and temperature on time to germination and cumulative germination of cotton is also described with some preliminary work on wheat. Finally a small field experiment was performed in Pakistan to identify major factors limiting emergence and provide data for future validation of a computer model of emergence. Time to germination was found to be a function of temperature and metric potential. It reduced with increase in temperature and osmotic potential. A linear relationship between temperature and germination rate (1/time to germination) indicated a base temperature of 9.8 °C. Germination rate also decreased linearly with decreasing osmotic potential between zero and -500 kPa. Thus the concept of hydrothermal time can be used to model germination and parameters to fit this model were determined. Root and shoot lengths of pre-emergent cotton seedling increased with increase in temperature from 22 to 32 °C but were reduced with a further increase to 38 °C. At any temperature, lengths increased linearly with time at a rate controlled by temperature. During the first 192 h after germination, growth was divided into two distinct phases: a linear increase with time followed by no further growth.

This investigation deals with the influence of initial curing periods and different curing environments, similar to those found in Middle Eastern countries, on the pore size distribution, permeability, water absorption and compressive strength of cement mortars and concretes made with and without pulverized fuel ash (pfa) and ground granulated blast-furnace slag (ggbs). Three 00 environments were chosen as follows: 1) 20C+70%RH, 2) 35C+70%RH, and 3) 45C+30%RH. To simulate in-place casting, the initial mix temperatures were controlled to be as close as possible to that of the environment in which the mixes were to be kept and moisture loss was allowed to occur from only the top-as-cast face of the specimen. Durability of the mortar specimens was assessed using pore size distribution, oxygen permeability, air permeability and water absorption. In addition to strength, the following tests were carried out on the concrete specimens to assess durability: initial surface absorption (ISAT), water absorption,relative air permeability and porosity. An the tests carried out on all specimens were undertaken at an age of 28 days. 7be test results showed that the durability properties of all specimens were significantly improved as curing periods increased. While curing durations had some significant effect on the strength of OPC/ggbs samples, the effects on OPC and OPC/pfa were in general only minimal. Furthermore, as to the effects on the pore size distribution and permeability, a critical curing duration (beyond which no further significant changes in these properties were observed) was seen to exist which depended on both curing environment and cement type. Enviromnents hotter than 20C+70%RH adversely affected the durability properties of uncured samples of all mixes. Furthermore, the durability properties of plain OPC samples were adversely affected by the two hot environments when compared to 20C+70%RH for all curing durations. On the other hand, while OPC/pfa and OPC/ggbs samples cured for one day or more at 35C+70%RH showed similar or worse durability results compared with those cured at 20C+ 70%RH, better results were obtained at 45C+30%RH than in either of the other two environments. As to the effects on strength, for any given curing period, environments hotter than 20C +70%RH adversely affected the OPC and OPC/ggbs samples but not those containing pfa. AT 20C+70%RH,the pfa specimens showed generally similar or worse durability results and weaker samples than plain OPC for all curing periods. This trend was reversed in the two hot environments. On the other hand, while OPC/ggbs samples showed similar or worse durability results at 20C+70%RH and 35OC+70%RH compared to plain OPC, at 450C+30%RH the slag specimens showed better durability results for curing periods of one day or more. Tbe 28-day strength of OPC and OPC/ggbs concretes were similar to each other in all envimnments for all curing periods except for those which were uncured. The uncured OPC specimens were stronger than the slag specimens in all envimnments.

The main objectives of this research are (a) to investigate the thermal effect of double skin facades in office buildings in hot climates and (b) to propose guidelines for their efficient design based on this evaluation. The study involves the energy performance analysis of two buildings in India. A base case with the existing building skin was simulated for both the cities. The main source for the high cooling loads was found to be heat gain through windows and walls. This led to the evolution of a series of facade strategies with the goals of reducing heat gain, providing ventilation and day-lighting. The buildings were then simulated for their energy performance with the proposed double-skin strategies. Each of these strategies was varied according to the layers constituting the facade, the transparency of the facade and the orientation of the facade to which it is applied. Final comparisons of energy consumption were made between the proposed options and the base case to find the most efficient strategy and also the factors that affected this efficiency. The simulations were done using the building simulation software, Ener-Win. The double skin was simulated as per an approximate and simplistic calculation of the u-value, solar heat gain coefficient and transmissivity properties of the layers constituting the facade. The model relied on logically arrived at assumptions about the facade properties that were approximately within 10% range of measured values. Based on inferences drawn from these simulations, a set of design guidelines comprised of goals and parameters was generated for design of double-skin facades in hot climates typical to most of the Indian subcontinent. It was realized that the double-skin defined typically as a 'pair of glass skins separated by an air corridor' may not be an entirely energy efficient design strategy for hot climates. However, when used appropriately in combination with other materials, in the right orientation and with the right transparency, a double-layered facade turns out to be an energy efficient solution.

The main objectives of this research are (a) to investigate the thermal effect of double skin facades in office buildings in hot climates and (b) to propose guidelines for their efficient design based on this evaluation. The study involves the energy performance analysis of two buildings in India. A base case with the existing building skin was simulated for both the cities. The main source for the high cooling loads was found to be heat gain through windows and walls. This led to the evolution of a series of facade strategies with the goals of reducing heat gain, providing ventilation and day-lighting. The buildings were then simulated for their energy performance with the proposed double-skin strategies. Each of these strategies was varied according to the layers constituting the facade, the transparency of the facade and the orientation of the facade to which it is applied. Final comparisons of energy consumption were made between the proposed options and the base case to find the most efficient strategy and also the factors that affected this efficiency. The simulations were done using the building simulation software, Ener-Win. The double skin was simulated as per an approximate and simplistic calculation of the u-value, solar heat gain coefficient and transmissivity properties of the layers constituting the facade. The model relied on logically arrived at assumptions about the facade properties that were approximately within 10% range of measured values. Based on inferences drawn from these simulations, a set of design guidelines comprised of goals and parameters was generated for design of double-skin facades in hot climates typical to most of the Indian subcontinent. It was realized that the double-skin defined typically as a 'pair of glass skins separated by an air corridor' may not be an entirely energy efficient design strategy for hot climates. However, when used appropriately in combination with other materials, in the right orientation and with the right transparency, a double-layered facade turns out to be an energy efficient solution.