**1. Introduction**

22 Will-be-set-by-IN-TECH

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IEEE 802.16 provides last mile broadband wireless access. Also called as WiMAX, IEEE 802.16 is rapidly being adopted as the technology for Wireless Metropolitan area networking (MAN). WiMAX operates at the microwave frequency and each WiMAX cell can have coverage area anywhere between 5 to 15 kilometers and provide data rates upto 70Mbps.

IEEE 802.16m has been submitted to ITU as a candidate for 4G. With data rates of 100Mbps for mobile users and 1Gbps for fixed users, IEEE 802.16m holds a lot of promise as a true 4G broadband wireless technology.

This chapter introduces a user based framework in WiMAX. In section 2, user based bandwidth allocation algorithms are introduced. In section 3, user based packet classification mechanism is explored. In section 4 user based call admission control algorithm is explored.


**2. Methods**

A case study method has been used to achieve the research aim and objectives. The study focused on exploring the urban sustainability in a selected residential community in Dubai through analysis and evaluation using two separate software packages; (i) IES-VE [41], and (ii) CityCAD [42]. The study will adopt the following steps:

In addition to the CityCAD and IES-VE software packages, the community sustainability has been evaluated with the use of the United States Green Building Council (USGBC)'s Leadership in Energy and Environmental Design (LEED) rating system.

In this study, LEED for Neighborhood and Developments (ND), version 4 (2014), has been used [43]. The strategy for the modifications adopted passive urban design solutions to the community master plan, which was also applicable to the existing community. Five of the urban design parameters have been modified according to three scenarios in order to enhance the community livability and thermal performance. The modifications/scenarios covered; land use, accessibility, and walkability, building design, open and green areas. Moreover, the effect of the modifications has been analyzed to find out the improvements on environmental and thermal performance, as well as through enhancing solar gain performance.

#### *The Existing Community as a Case Study*

The case study of this research is represented by Al Waha community, which was developed by Dubai Properties Group (DPG). The existing residential community located in "Dubai land" adjacent to the Emirates Road with easy access to Sheikh Mohammed bin Zayed Road through Al Qudra Road. The community is close to the Arabian Ranches, Sport and Motor City communities as key developments (Figure 1). The case study "Al Waha" community consists of 206 semidetached villas where the villas are designed in three types according to bedroom numbers; two, three and four bedrooms (Figure 2). The facilities are very limited in the community, covering swimming pool, playground area, landscape and hardscape.

**Figure 1.** The case study location. Al Waha, Dubai [44].

The total area of the community is approximately 130,000 sqm, while the landscape covers 15,200 sqm from the community total area. The neighbor community is the Layan community, from the same developer (DPG), and contains seven G+2 residential buildings and 588 villas, with small facilities such as small shops and a supermarket.

(**a**) (**b**)

> **Figure 2.** Al Waha community villa view (**a**) and layout (**b**).

#### **3. Background for the Analysis**

#### *3.1. Assessing Livability in the Existing Community*

The observation and the assessment during the community site visit, and the use of the CityCAD software for livability analysis showed that there are weaknesses in many livability aspects. The major weakness is in land use diversity, as the existing land use variety is very limited. The community consists of three types of semidetached villas, playground area and a communal swimming pool, with hard and soft landscape. There is a clear absence of many services required, such as supermarket, laundry, pharmacy, school, healthcare center and amenity facilities. The livability analysis of the existing case study using CityCAD shows the average distance from community dwellings to some services and facilities (Table 1).

**Table 1.** Assessing this existing case study services and the adopted scenarios with additional services, namely new services.

The community, as a gated community, provides a good level of safety as one of the livability requirements [39]. On the other hand, the only one access through the Emirates Road indicated some weakness in accessibility, which could be enhanced and optimized by providing more than one access to improve transition and movement.

#### *3.2. Assessing Thermal and Environmental Performance in the Existing Community*

Analysis he community layout using integrated environmental solution—virtual environment (IES-VE) software, and adopting a sun path application and unit orientation showed that only 40% of the units are extended along the East-West axis. The benefit of the orientation along the East-West axis is to obtain a minimum amount of solar exposure, as the long facade is facing the North–South axis [43]. The IES-VE software was used to analyze the community shading performance and solar gains through the SunCast application. Figure 3 shows the community layout orientation and the sun path on a summer day, 1 June.

**Figure 3.** The Sun Path analysis during morning and evening along the East-West axis. (**a**) 1 June, 6:00 a.m.; (**b**) 1 June, 6:00 p.m.

The community plot is a triangle shape and one edge of the community plot is extended along the East-West axis, but only 40% of the units extend along the same direction. Thus, the community urban plan would be more sustainable if the units were arranged parallel to the side along the East-West axis in an early planning stage. Yet, it was observed that the compacted form provides more shading and less exposure to solar radiation for the inner units compared to the outer units (Figure 4).

**Figure 4.** Solar attitude in the compact form community during 1 June. (**a**) Solar Gain in Hours; (**b**) Solar Gain in Percentage.

Furthermore, the thermal and environmental performance of the community could be improved through increasing green areas and planting empty/uncultivated areas, which are about 35% of the community landscape area (Figure 5).

**Figure 5.** Uncultivated areas in the community.

As part of the analysis, exploring the potential of enhancing the community performance towards sustainability, three scenarios were adopted to improve the Al Waha community sustainability. The thinking or the criteria behind these scenarios was to suggest an applicable practice to enhance the community sustainability. Community urban sustainability is improved from two aspects; livability and environmental or thermal performance. Enhancing livability covers a number of parameters; (1) land use, (2) accessibility, (3) walkability, and (4) open and green areas. While the thermal performance parameters represented by improving solar shading and reducing total solar gains through adopting (5) height diversity. The modifications consist of three adopted scenarios to enhance the community sustainability, which are simulated and analyzed by using CityCAD and IES-VE. In addition, using LEED (ND) v4 checklist as an overall and integrated urban sustainability evaluation and assessment tool was to find the sustainability level of the existing and modified case study.


**1. Introduction**

Composite structures have been increasingly used in various aircraft structures due to their superior stiffness and weight characteristics. However, composite structures are susceptible to low velocity impacts, which can cause internal damage that will lead to a significant reduction of the local structural strength [1]. Therefore, impact monitoring has become an important task of structural health monitoring (SHM) to ensure the safety of these applications.

Recently, sensor array signal processing-based methods have emerged as a set of new promising SHM methods. Yin et al. constructed two Z-shaped clusters at different positions for acoustic source localization in anisotropic plates [2]. Xiao et al. proposed an acoustic emission source localization approach based on beamforming with two uniform linear arrays [3]. He developed a method for localizing two acoustic emission sources simultaneously based on beamforming and singular value decomposition. Agarwal and Machán proposed a statistical super-resolution technique ˇ called the multiple signal classification (MUSIC) algorithm published in Nature Communications,

and demonstrated that the MUSIC algorithm had a comparable or better performance in comparison with other localization techniques [4]. Because it has such advantages, the MUSIC algorithm was developed for the impact monitoring of plate-like structures. By processing the whole sensor array outputs using the MUSIC algorithm, the transfer function and material properties of the structure are not needed [5]. Since the MUSIC algorithm belongs to an eigen-structure and sub-space approach, it can effectively extract the key features of signals received and successfully detect the source signal under a low signal-to-noise ratio [6]. Some developments have been published by applying this method to process the sensor array signals in the structural health monitoring area. Stepinski and Engholm [7] presented a far-field MUSIC algorithm-based method to estimate the direction of arrival (DOA) of single elastic waves on an aluminum plate using a uniform circular array. Yang et al. [8] employed the far-field MUSIC algorithm to estimate the DOA of one impact on an aluminum plate. Yuan et al. presented a single frequency component-based re-estimated MUSIC algorithm to reduce the localization error caused by the anisotropy of the complex composite structure [9]. To deal with the near-field monitoring problem, the authors in previous work proposed the near-field 2D-MUSIC algorithm-based impact localization method for a composite plate using Gabor wavelet transform [10,11]. However, in previous MUSIC-based impact location methods, the narrowband signals at a particular central frequency had to be extracted from the wideband Lamb waves induced by each impact, and the specific center frequency had to be obtained after carefully analyzing the impact signal, which is time consuming.

EMD is a new time–frequency analysis technique which can decompose the complicated signal into a set of complete and almost orthogonal components named intrinsic mode functions (IMFs) [12]. The IMFs represent the natural oscillatory mode embedded in the signal and work as the basis functions, which are determined by the signal itself [13]. Thus, it is a self-adaptive signal processing method that can be applied to a nonlinear and non-stationary process to decompose it into stationary signals. Generally, EMD cannot accurately extract fault features because of the mode mixing phenomena. Wu and Huang proposed a new ensemble EMD (EEMD) method to reduce mode mixing [14]. However, the EMD and its improved version EEMD are computation intensive methods, which are not suitable for on-line detection. A noise-assisted approach in conjunction with a multivariate empirical mode decomposition (MEMD) algorithm has been proposed for the computation of EMD, in order to produce localized frequency estimates at the accuracy level of instantaneous frequency [15–17]. Leo developed Bivariate EMD to detect defective areas in composite materials [18]. Wang et al. [19] proposed a fast HHT with an optimized EEMD algorithm to speed up the computational efficiency by 1000 times. They also proved that the computational complexity of the EMD is equivalent to fast Fourier transform (FFT). Hence, the optimized EEMD method might be a good choice to be applied to the real-time impact localization of composite structures.

This paper presents an improved approach that combines the optimized EEMD and 2D-MUSIC algorithm for the on-line impact localization on composite structures without selecting the center frequency. The layout of the paper is structured as follows: In Section 2, an optimized EEMD-based 2D-MUSIC method for impact monitoring is presented. An impact monitoring experiment on a cross-ply glass fiber reinforced composite plate is performed in Section 3 to verify the proposed method. Finally, the conclusion and future works are given in Section 4.


**7. Conclusions**

During their service life, bridges, like other structures, undergo functional and material degradation. In many cases, tests show that despite non-strict conformity with actual design standards, they are able to carry actual service loadings. According to [1], calculations of existing steel bridges resistance should be carried out more precisely and in a more readable manner following a three-phase assessment: a preliminary evaluation, a detailed investigation, and an expert investigation. Some other studies have recommended using five assessment levels: a bridge rating, a preliminary evaluation, a detailed investigation, an expert investigation, and advance testing [16, 35–37]. Application of the assessment procedure led to improvements in knowledge and a calibration of confidence factors.

At the same time, the project "Sustainable bridges – assessment for future traffic demands and longer lives" with nine packages, deals with the increasing capacity and service life of existing railway bridges [35]. New methods for the resistance assessment of existing bridges were developed in standards and guidelines using calibrated partial safety coefficients.

The Steel Structure Chair at the Technical University in Szczecin (now WPUT) contributed to these issues by carrying out a multiyear program for the quality-level assessment of welded butt splices in existing railway bridges in service in Poland. Radiological tests on butt splices in the steel girders of around 200 railway bridges were carried out. Nearly, 200 bridges were tested using X-ray examination over a 37 year period. The number of joints tested was over 15,000; cracks were discovered in 400 welded joints in 34 bridges tested. Repeated tests on welded joints with cracks were undertaken as well as laboratory investigations for their complex assessment. Partial results of the laboratory fatigue testing are given in the paper.

Numerical analysis of tensile stresses in welded splices was undertaken to support and confirm the results of laboratory fatigue tests. The results of the FEM analysis of tensile stresses in welded joints with rhomboid cover plates are given. The FEM method allowed us to determine tensile stresses at each service stage. The analysis allowed for: