Study of EVA operations associated with satellite services

Extravehicular mobility unit (EMU) factors associated with satellite servicing activities are identified and the EMU improvements necessary to enhance satellite servicing operations are outlined. Areas of EMU capabilities, equipment and structural interfaces, time lines, EMU modifications for satellite servicing, environmental hazards, and crew training are vital to manned Eva/satellite services and as such are detailed. Evaluation of EMU capabilities indicates that the EMU can be used in performing near term, basic satellite servicing tasks; however, satellite servicing is greatly enhanced by incorporating key modifications into the EMU. The servicing missions involved in contamination sensitive payload repair are illustrated. EVA procedures and equipment can be standardized, reducing both crew training time and in orbit operations time. By standardizing and coordinating procedures, mission cumulative time lines fall well within the EMU capability

Wave-number-explicit bounds in time-harmonic scattering

In this paper we consider the problem of scattering of time-harmonic acoustic waves by a bounded sound soft obstacle in two and three dimensions, studying dependence on the wave number in two classical formulations of this problem. The first is the standard variational/weak formulation in the part of the exterior domain contained in a large sphere, with an exact Dirichletto-Neumann map applied on the boundary. The second formulation is as a second kind boundary integral equation in which the solution is sought as a combined single- and double-layer potential. For the variational formulation we obtain, in the case when the obstacle is starlike, explicit upper and lower bounds which show that the inf-sup constant decreases like k −1 as the wave number k increases. We also give an example where the obstacle is not starlike and the inf-sup constant decreases at least as fast as k −2. For the boundary integral equation formulation, if the boundary is also Lipschitz and piecewise smooth, we show that the norm of the inverse boundary integral operator is bounded independently of k if the coupling parameter is chosen correctly. The methods we use also lead to explicit bounds on the solution of the scattering problem in the energy norm when the obstacle is starlike in which the dependence of the norm of the solution on the wave number and on the geometry are made explicit

A Review of the Iraqi Housing Sector Problems

Housing is one of the important necessities for people. It comes after food and drink according to Maslow’s pyramid of human needs. It also influences countries’ social cohesion, stability and development and at the same time is affected by their general conditions. Iraq has a housing sector crisis. The county experiences a large housing shortage. The Iraqi National Housing Policy identifies critical challenges in seven housing-related fields: housing production, land management, housing finance, infrastructure, construction materials, housing stock status and slums. This paper aims to present a better understanding of these housing challenges as a first step to the development of appropriate solutions. It presents a critical investigation of the housing sector’s issues through exploring a wide range of literature to build a framework that critically evaluates and identifies the problems. The paper also quantifies the current housing shortage at around 1 million dwellings. Based on the extrapolation of trends towards 2030, it is estimated that Iraq has to build around 230000 dwellings annually to satisfy future demand. Results confirm the importance of the issues identified in the National Housing Policy, which gives it more validity. The paper concludes by proposing a series of measures to address Iraq’s housing challenges

Application of strategic fuzzy games to wage increase negotiation and decision problems

We propose a flexible decision support scheme which could be used in managing the wage negotiation between employers and employees. This scheme uses fuzzy inference systems and game theory concepts in arriving at decisions on future wage increase which could be more mutually agreeable. For example, rather than specifying 5% yearly increase of wages, we propose that the uncertain factors which are mostly difficult to predict and that could affect wage decisions need to be taken into consideration by the wage formula. These include business revenues or (profit), inflation rate, number of competitors, cost of production, and other uncertain factors that may affect business operations. The accuracy of the fuzzy rule base and the game strategies will help to mitigate the adverse effects that a business may suffer from these uncertain factors. Based on our scheme, we propose that employers and employees should calculate their future wage by using a fuzzy rule base and strategies that take into consideration these uncertain variables. The proposed approach is illustrated with a case study and the procedure and methodology may be easily implemented by business organizations in their wage bargaining and decision processes. © 2012 Elsevier Ltd. All rights reserved

An Adaptive Thermal Comfort Model for Residential Buildings ‎in Iraq

In Iraq, the temperature reaches around 0 °C in winter and 50 °C in summer. Aiming at providing thermal comfort for people, studies have been advocating developing innovative thermally responsive designs or adopting traditional architecture’s passive design strategies. However, to develop appropriate solutions for the country, it is critical to determine the thermal comfort limits to define the targeted thermal performance of buildings. This research worked on defining Iraqis’ thermal comfort limits in residential buildings for two reasons. First, they are the dominant building type in the country. Second, to inform the design of large housing developments Iraq is planning to have to satisfy large housing needs. Exploring previous literature in Iraq or regional countries shows that residential thermal comfort limits for people have not been defined properly. To achieve this aim, the research conducted thermal comfort survey in four Iraqi cities for a year. Nearly 4800 thermal comfort votes were recorded by 90 participants. The results show that the lower thermal comfort Globe temperature in winter is 17 °C and the highest acceptable Globe temperature in summer is 33 °C

The Thermal Performance Prospects of Courtyards in Cold Conditions

Aiming at developing more thermally comfortable and energy efficient buildings, some studies have been advocating using traditional architecture’s passive design strategies. Among the rarely investigated architectural elements to achieve this objective in cold climates is the courtyard space. This environmental element, in most cases, has been examined and suggested for hot conditions. However, some studies have shown indications of its potential environmental efficiency in cold conditions as well. In principle, courtyards enable having sheltered outdoor spaces to regulate indoor spaces’ interaction with the outdoor climate instead of having them outward oriented to directly face outdoor conditions. This research aims to determine whether this thermal performance of courtyards can be positive in cold conditions as it is in hot conditions, for instance, through protecting buildings from cold winds. To achieve this objective, the research conducted simulation experiments to determine the thermal conditions of 360 different courtyards and compared them with a typical modern urban outdoor space’s conditions. If the courtyard space offers a warmer environment than modern urban outdoor spaces, then it might lead to a wider positive impact on buildings’ thermal conditions and energy consumption. The used simulation tool to conduct the simulation experiments is Envi-met 4.2, which has been widely used and validated by previous simulation studies. The tested courtyard forms are of different geometric configurations to show a wide range of possible conditions in courtyards. The simulation was done for Baghdad, in which courtyards have been widely used for centuries. This city has a hot summer, but its winter temperature is between 0°C and 12°C. The Globe Temperature was used to determine peoples’ thermal sensation. Its value includes the impact of air velocity, radiation and air temperature, which makes it representing people’s actual thermal sensation properly. The results showed that courtyards offer higher Globe Temperature than modern urban spaces in cold conditions, mainly, through protecting buildings and occupants from winds. The air velocity inside courtyards can be one-tenth of air velocity in a modern urban outdoor space. The geometric properties of courtyards significantly affect courtyards’ thermal conditions. These results indicate that the courtyard space can be more thermally efficient than modern urban spaces even in cold climate conditions. However, its geometric properties need to be properly considered to have its highest possible thermal efficiency. Otherwise, the courtyard might lose its efficient thermal performance

Courtyards thermal efficiency during hot regions’ typical ‎winter

Many researchers have experimentally proven the thermal efficiency of courtyard buildings in hot regions during summer. However, a limited number of studies have tackled courtyards’ winter performance. In these studies, it has been stated that courtyards are possibly not efficient for winter conditions. This study aims to address this point. It investigated the impact of changing courtyards geometrical properties on occupants’ thermal perception during typical winter conditions of a hot region. The study conducted a simulation experiment using Envi-met 4.2 simulation tool. Baghdad was used as a case study. Thermal comfort limits for hot regions were used as a reference. IBM SPSS statistics 23 was used to analyse variables’ correlations. The results show that all courtyard forms are thermally comfortable during typical winter conditions of a hot region. Courtyards’ geometry has a significant impact on their thermal conditions. The most effective property is the ratio of courtyard width to height