Acoustic phased arrays are capable of steering and focusing a beam of sound via selective coordination of the spatial distribution of phase angles between multiple sound emitters. Here, we propose a controllable acoustic phased array with space-time modulation that breaks time-reversal symmetry, and enables phononic transition in both momentum and energy spaces. By leveraging the dynamic phase modulation, the proposed linear phased array is no longer bound by the reciprocity principle, and supports asymmetric transmission and reception patterns that can be tuned independently. Through theoretical and numerical investigations, we develop and verify a mathematical framework to characterize the nonreciprocal phenomena, and analyze the frequency conversion between the wave fields. The space-time acoustic phased array facilitates unprecedented control over sound waves in a variety of applications including underwater telecommunication.

This research, a part of more extensive research, presents pre-feasibility and unit sizing analysis of a hybrid system equipped with renewable energy resources in Tabriz, Iran (46°26/E, 38°06/N). This case study examines a GSM telecommunication station as a stand-alone load system. Renewable energy resources include photovoltaic (PV), a wind turbine as primary resources and fuel cell, and a battery stack as backup and energy storage systems, while an electrolyzer is used to provide the required hydrogen in the fuel cell system. Feasibility analysis and unit sizing are conducted based on climatic data such as solar irradiance and wind speed to derive an optimal model during the study. HOMER software is used to simulate the feasibility analysis, measure the size, and optimize the system. The results showed that the hybrid system performs cost-effectively. According to wind energy data and fuel-cell costs, sensitivity analysis is conducted. The load is a stand-alone GSM station that consumes 60kW per day with a maximum of 3.8kW per hour. This analysis showed that wind, PV, electrolyzer, battery, and fuel cells are not currently the best solutions. Shortly, according to improved prediction in fuel-cell technology, it is expected that this source as a backup will be the best option because it has decreased fuel-cell costs up to 65 percent. Some criteria such as size, application, and cost, have been mainly examined. These results provide excellent opportunities for this hybrid system. The result shows using fuel cells in a hybrid system is not affordable by considering current fuel cell price, and the main suggestion hybrid system configuration is PV, wind turbine, and battery, while for the nearby location of Tabriz by decreasing wind speed, using wind turbines is not feasible and more PV array should be added to the system.

Surface acoustic wave (SAW) devices have been applied as telecommunication filter for decades. Due to its simple interdigitated transducer (IDT) layout and geometry-dependent frequency, the SAW filter operates at the designed frequency and its working bandwidth could be designed to fulfill specific applications. Researchers also use SAW devices for sensing the mass or pressure in air. Furthermore, SAW device can be employed in liquid environments. The main focus of this paper is to present a Love mode device for liquid sensing. The Love mode device included a shear-horizontal surface acoustic wave (SH-SAW) delay-line configuration with a photoresist waveguide, which was deposited on split-electrode IDT and reflectors. The substrate was ST-cut quartz, and the SH-SAW propagated between the waveguide and the piezoelectric substrate. Using the Love mode device, we monitored the frequency shift corresponding to a water drop. We demonstrate that the insertion loss level is not critical for S-parameter transmission signal readout. The signal quality within the resonant narrowband is very important for water sensing. In this study, two types of SH-SAW devices were fabricated and tested; SH-SAW resonator and SH-SAW delay-line. We also demonstrate single and split electrodes electrode configurations to generate acoustic waves. Four different waveguide thickness values were tested to prove the benefit of thick polymer waveguide. This research also offers a standard method to fabricate SAW on ST-quartz for liquid application. In the future, we plan to integrate the Love mode device with a cell-culturing chamber to obtain a biosensor.

A model study is conducted to investigate the possible wind energy harnessing potential of a recently designed personal use wind turbine, PWT, having efficient and economical blades. The study is conducted for the conditions usually found in United Arab Emirates, UAE. The PWT has a total length of 4.5 m while the disk diameter is 3 m. The PWT dimensions make it big enough to be used to power household appliances or to charge batteries yet small enough to be installed on rooftops or buildings. The wind turbine setup uses a tail vane to keep the wind turbine aligned with the airflow. The wind turbine blades are installed at an angle of 22°, with respect to the disk plane, as it gives the highest power. For electrical power generation, a permanent magnet generator is used which is rated for 250 RPM to 100 RPM. Gears are used to increase the generator RPM to six times than that of the wind turbine. The UAE wind data is used to find the total possible power from each wind turbine. Possible number of housing units, buildings and telecommunication towers are found, in UAE, where a PWT can be installed. An analysis is conducted for the energy and exergy potential of the wind turbine rotor. The clean energy potential of the PWT is also investigated when operated by their possible users. Calculations are made at variable wind speeds to represent the average wind speed during each month. It is concluded that a country like UAE can produce on average 500 MW using PWTs. The efficiencies come out to be low for summer months while high for winter months. It is also concluded that a system like PWT would help reduce the monthly billing cost by the end user.

Wind turbines have seen increasing use over the past decades as an alternative mode of energy production. One specific use of vertical axis wind turbines is for the powering of rural telecommunication towers. In this research a cradle-to-gate life cycle analysis is used to compare three different designs for a stackable, capped, Savonius-style vertical axis wind turbine blade capable of producing from one to three kilowatts. The analysis compares the energy consumed and carbon dioxide emissions from material production and manufacturing of two different aluminum blade designs and a polypropylene design each having the same energy generation capacity. Primary and secondary aluminum materials were included in the analysis. Life cycle inventories from two software programs were used and compared with values gleaned from published literature. The results of the analysis revealed that the least energy and carbon dioxide impact came from using a recycled aluminum design while the most was from manufacturing using primary aluminum.

The actual applicative research concerning airships and their use as HAP (High Altitude Platforms for telecommunications and military use) presents new applicative hypothesis of these systems, also concerning energetic high quote production. Authors present the energetic balance of a high quote photovoltaic platform with capability of static hovering realized by electric powered propellers. This is the first step trough the design of the P. S. I. C. H. E. (Photovoltaic Space Island for Conversion of Hydrogen as Energy vector) airship concept: a stratospheric airship which could be considered a platform for hydrogen and oxygen production by photovoltaic. It investigates the behaviour of a similar platform operating at altitudes between 10 and 20 km, positioned at 45° latitude north [1, 2]. This paper analyses the design process for a High Altitude Platform based on photovoltaic energy caption, but the process could be generalized in order to be applied to any airship project. It is considers airship shapes equipped with large PV array that covers energy request during the day. Surplus in power supplies electrolyser equipments for hydrogen and oxygen production from water, which could be captured by atmospheric humidity or brought by an auxiliary airship. Hydrogen and Oxygen are compressed and stored in gas cylinders. With insufficient solar irradiance, with severe wind conditions and during the night, a fuel cell system fed by hydrogen and oxygen tanks supplies power requirements. The Standard Atmosphere Model is used to evaluate PV performance at various operative altitudes. A propulsion system with electric motors grants airship manoeuvrability and hovering. Energy balance of PV-hydrogen energy supply system has been analyzed for three airship shapes with equal volume with concern of overabundant hydrogen and oxygen production. Total weight and payload are calculated in relation to altitude. Storage tanks dimensions and products ground transportation frequency has been estimated. Hydrogen annual production for PV square meter has been evaluated in relation to ground production at the same latitude.

Telecommunication shelters are generally used for housing the electronic equipments and are an integral component at various levels of wireless access networks. The electronics which dissipate heat needs to be cooled for proper functioning of the equipment. Telecom shelters are generally stand-alone, modular structures with their own electrical HVAC systems. The effect of cabinet’s location in the shelter on temperature is studied. The outline of the paper is to validate the shelter model with the test data available by using CFD tool and perform thermal analysis for different location of 2G cabinets and then, to study the effect of isolation in the shelter. It is observed that the isolation in the shelter attributes to lowering the temperature of the cabinets.

The increase in the data center server heat density waves a scope for developing improved cooling technologies without raising the power consumption. It is commonly observed that 40% of the total data center energy is consumed by its cooling equipments. For higher server density cabinets, typical air cooling techniques leads to a substantial increase in the power consumption. Rear door heat exchanger, an open looped cooling technique is one of the solutions for such scenarios. In this paper, emphasis is laid on the analytical determination of the optimum heat load after calculating the effectiveness of heat exchanger at given operating conditions of the data center and heat exchanger. Later, thermal analysis is performed and the working of heat exchanger is compared for different data center heat loads. Based on the results, a ‘rule of thumb’ is verified that rear door heat exchanger could be 100% efficient in cooling the cabinets of heat loads up to 27kW. Thus, for rack heat loads less than 27KW, CRAC units can be non-operational resulting in energy savings. Furthermore, effect of RDHx in different configuration is studied and compared.

The present trends in the cooling technologies have marked a significant improvement in the outdoor telecommunications systems and the need of cooling has marked an important requirement for the proper functioning of these cabinets. This aim of this paper is to review all of the articles and to gather the information regarding the different cooling technologies used and their reliability in the outdoor telecommunication systems especially the telecommunication cabinets.

Telecommunication cabinets are standalone outdoor enclosures, which houses electronic components and switching devices. These electronics are powered by DC power and have backup batteries to support them in the event of power supply failure. The heat loads on these cabinets are dependent not only on the heat dissipated by the internal components but also by solar heating. Therefore the ambient temperatures around the cabinet, based on the location and time of day can vary anywhere from −40°C to +50°C. The life of a battery is dependent on the nature of the load applied, recharging conditions and most importantly ambient temperatures. Batteries supporting the cabinet electronics are either housed within the cabinet or in compartments attached to the cabinet. For long standing battery life, the temperature inside these battery compartments should be kept below 25°C [1]. Active cooling using air-conditioners are often used to achieve this, but air-conditioners are difficult to backup and are high in maintenance. A more convenient way to cool the battery compartments are to use Thermo-electric Coolers (TEC) as they are less bulky and quite. This paper discusses the validation of results of numerical modeling of a telecommunication cabinet, which uses TEC to cool its battery compartment, with experimental data for the corresponding real world model.

In recent years there has been an ever increasing need to launch small payloads (∼1–100 kg) into low earth orbit (LEO); examples include the defense, telecommunications and other civilian industries. NASA’s stated mission of launching a manned mission to Mars requires many tons of raw materials to be economically launched into LEO and assembled there. Conventional rocket launch from earth is prohibitively expensive for small mass payloads. Estimates range from $7000–$20,000 to launch 1 kg of mass into low earth orbit. Several concepts have been proposed to economically launch small payloads from earth, including light gas guns, electromagnetic launchers and the so called “slingatron” concept. The goal of these concepts is to reduce the cost per kg (to under $1000) to achieve LEO. Each of these concepts involves launching small payloads that traverse the atmosphere and then placed into a circular low earth orbit. As the launch vehicle traverses the dense lower portion of the atmosphere it experiences thermal heating loads that must be absorbed by a thermal protection system (TPS) if the payload is to survive the transit. High launch angles are desirable from the standpoint of minimizing TPS mass. However, for ballistic trajectories, high launch angles require a large propellant mass to achieve a stable circular orbit. This effort performs aerothermal and trajectory analyses on a nominal 10 kg payload launched from 16 km altitude airborne platform into a 200 km circular orbit. The study focuses on two efforts: 1) computing ballistic trajectories of sphere cones with ablation assuming laminar and turbulent flow in order to quantify the total ablation and required propellant mass to circularize the orbit for given launch conditions and 2) study lifting trajectories without ablation by flying axisymmetric sphere-cone projectiles at small angles of attack and asymmetric projectiles (ellipsleds) that turn the velocity vector during atmospheric transit in an effort to reduce the Δ V needed to circularize the orbit. The TPS is assumed to be made of graphite. Total parasitic mass is reported for several launch angles. Even though ablation is not considered for the lifting trajectories, the study allows comparison of relative effectiveness of various lifting trajectories in reducing the Δ V required to circularize the orbit.

Recent years has witnessed a large increase in the use of vibrating Micro-Electro-Mechanical-Systems (MEMS) especially in the expanding wireless telecommunication industry. In particular, the use of microresonators to generate or filter signals has facilitated a reduction in the size of many popular cell phones. Advances in microfabrication have increased the ability to create complex MEMS devices. Finite Element Analysis (FEA) has widely been used in the design of these devices. To obtain accurate simulations of complex MEMS devices, a dense FEA mesh is required resulting in computationally demanding simulation models. Arnoldi Model Order Reduction has been investigated and implemented to improve the computational efficiency of MEMS simulations. Using ANSYS, a popular FEA program, a micro resonator model was created. With Arnoldi, a Krylov subspace was extracted from the model and the model was projected onto the subspace reducing the model size. A harmonic simulation over normal operating frequencies was performed on the reduced model and compared with a simulation of the original model. It was found that the computational time was drastically reduced through the use of Arnoldi while achieving similar accuracy as compared to the original model.

Computational Fluid Dynamics (CFD) is widely used in the telecommunication industry to validate experimental data and obtain both qualitative and quantitative results during product development. A typical outdoor telecommunications cabinet requires the modeling of a large number of components in order to perform the required air flow and thermal design. Among these components, the heat exchanger is the most critical to thermal performance. The cabinet heat exchanger and other thermal components make up a complex thermal system. This thermal system must be characterized and optimized in a short time frame to support time-to-market requirements. CFD techniques allow for completing system thermal optimization long before product test data can be available. However, the computational model of the complex thermal system leads to a large mesh count and corresponding lengthy computational times. The objective of this paper is to present an overview of techniques to minimize the computational time for complex designs such as a heat exchanger used in telecommunication cabinets. The discussion herein presents the concepts which lead to developing a compact model of the heat exchanger, reducing the mesh count and thereby the computation time, without compromising the acceptability of the results. The model can be further simplified by identifying the components significantly affecting the physics of the problem and eliminating components that will not adversely affect either the fluid mechanics or heat transfer. This will further reduce the mesh density. Compact modeling, selective meshing, and replacing sub-components with simplified equivalent models all help reduce the overall model size. The model thus developed is compared to a benchmark case without the compact model. Given that the validity of compact models is not generalized, it is expected that this methodology can address this particular class of problems in telecommunications systems. The CFD code FLOTHERM™ by Flomerics is used to carry out the analysis.

Though the establishment of clinics for students to participate in engineering activities with partners around the world has achieved a high profile recently, there are major difficulties to surmount in developing workable structures for such enterprises. As with many engineering education endeavors, the focus of initiating global engineering programs is often on the hard technology to enable students to work collaboratively across distances. Too often, the soft technology aspect, such as coordinated work practice, is overlooked during the process of set-up and initial operation. It is relatively straightforward (though not particularly easy) to acquire the necessary technology and apply it to a lab development scenario. But it is not ‘global engineering’ unless there are collaborative partners across the world, on the other end of the Internet cable. In this paper, we will discuss a case study involving the setup of hard technology, such as computers, telecommunications, and integration of video into the curriculum. Equally important, we will discuss the generation of partners with similar work practice, project management, and pedagogical styles, and ways to facilitate interaction between students in different programs in different international locations, while satisfying sponsoring institutions and corporations.

MEMS industry has seen mixed success over the last decade or so. Today, there are only a limited number of MEMS products available on the market, notably airbag accelerometers, desktop inkjet print heads and pressure sensors for automotive and biomedical applications. Despite major infusion of funds in other applications, such as optical telecommunications, RF, and biomedical/microfluidics, these efforts have failed to produce working MEMS in high volumes. The net result is that MEMS have not yet lived up to their anticipated promise.

For high performance packages in mainframe systems such as networking switch, telecommunication equipments, higher reliability is always required. Using high-lead solder ball is an effective way to enhance the solder joint performance in board level. The elongation property of high-lead alloy Sn10/Pb90 is 10 times greater than eutectic Sn/Pb alloy. The high-lead ball has higher melting temperature, it can maintain the stand off (gap) between the package and PCB when eutectic solder paste melted at 220°C. In this study, the performances of high-lead solder Sn10/Pb90 and eutectic Sn63/Pb37 are compared. A series of experiments are performed to characterize the high-lead solder ball solder joint performance. The ball shear test parameters also affect high-lead solder ball strength, such as ram height and shear speed. Lower ram height and higher speed increases the ball shear strength value. Effect of different ball pad openings, solder paste volume and reflow profile for ball placement, is also discussed in this paper. the ratio of ball pad opening diameter to solder ball diameter is related to ball shear force. When the ratio is 0.83, the ball shear is better than other value. The most important factor to ball shear strength is the solder paste amount. However, the reflow condition (the time period over 183°C) isn’t the significant factor to affect the ball shear strength.

In many applications such as computers and telecommunications, the IC chip sizes are very big, the on-chip frequency and power dissipation are very high, and the number of chip I/Os is very large. The CCGA (ceramic column grid array) package developed by IBM is one of the best candidates for housing these kinds of chips [1–7]. There are two parts in this study. One is to show that the 2-parameter Weibull life distribution is adequate for modeling the thermal-fatigue life of lead-free solder joints. This is demonstrated by comparing the 2-parameter and 3-parameter Weibull distributions with life test data of an 1657-pin CCGA package with the 95.5wt%Sn3.9wt%Ag0.6wt%Cu lead-free solder paste on lead-free PCBs (printed circuit boards) under thermal cycling conditions. The other part of this study is to determine the time-history creep strain energy density of the 1657-pin CCGA solder column with two different solder paste materials, namely, 95.5wt%Sn3.9wt%Ag0.6wt%Cu and 63wt%Sn37wt%Pb and under three different thermal cycling profiles, namely, 25 ↔ 75°C, 0 ↔ 100°C, and −25 ↔ 125°C. The effects of these solder pastes and temperature conditions on the thermal-fatigue life of the high-lead (10wt%Sn90wt%Pb) solder columns of the CCGA package are provided and discussed.

DWDM optical transport systems are an important link in communications networks. These systems are the backbone of telecommunications infrastructures and carry large volumes of telecom traffic. As a result, their reliability is critical. Thermal performance is key to meeting this reliability requirement and is therefore a major component of DWDM system development. The resulting thermal design process must balance opposing requirements such as high product density, thermal sensitivity of optical components, cooling fan noise limits, and high ambient temperature and altitude requirements. This paper describes both a thermal design approach for DWDM system development, and a thermal design solution that demonstrates high product density and field-proven reliability.

Because outsourcing and offshoring operations entail multi-site operations and inter-organizational alliances, they require effective boundary-spanning partnerships: inter-divisional, inter-organizational, and often, multi-country partnerships. This paper reports a multi-discipline research study—involving engineering, anthropology and telecommunications elements—on dispersed global engineering design teams. A framework involving power, culture, and collaborative activity is introduced. The focus here is on power and communications issues. Co-oriented, collaborative project activity is achieved when power issues are neutralized. When sub-team members perceive inequity, they frequently respond adversely. They may purposely create miscommunications among sub-teams, covertly subvert project goals, or otherwise act in ways that reduce project performance. Outsourcing of engineering design operations is a major challenge for the engineering profession. Outsourcing activity to India and China has increased; educational systems in these countries both improve in quality and augment the quantity of engineers produced. Traditional engineering skills are swiftly becoming a commodity in the global market.