Studying And Analyzing the modulators and demodulators of PCM

Modulating signals of transmission stations to reception stations is a key factor to guarantee the best possible transmission and reception of these signals .Digital modulation represents a huge evolution in communication field and modulation, which used to depend on analog signal modulation of one parameter-Amplitude . frequency or phase. Digital modulation depends on transforming the transmitted data signal (Bits) and then sending it as samples, and changed back into an analog signals in reception station . In digital systems, digital data are transformed into analog data in the transmitter and does the reverse in the receiver. In digital transmission, on the other hand, as in wired local area networks (WLAN), Digital data are transmitted in their digital state.

Use of PCM materials for the reduction of thermal energy requirements in buildings

Latent heat storage is an economical way to achieve energy efficiency and improve thermal comfort in buildings. In this research, the effects of using PCM Wallboards in a residential apartment envelop located in Homs was studied by PCM Express software. PCM wallboard with 23°C melting temperature was used and installed on the inner face of the walls and ceiling of the apartment. This investigation shows that the importance of using PCMs in buildings envelope, compared with conventional thermal insulation materials, due to the effectiveness of PCMs materials and storing and releasing of thermal energy, which contributed to reducing of thermal loads and improved the internal thermal comfort.

Optimization of a wall containing a Phase Change Material included in a metal matrix

The walls containing phase change materials (PCM) play a significant role in the air conditioning of buildings. However, one of the characteristics which limits the use of PCMs is their low conductivity. It is possible to solve this problem by coupling a metal matrix with the PCM. The aim of this study is to determine the optimal size of a wall which allows a complete change of state, and a homogenization of the temperature without a too fast change-of-state rate. To study the thermal behavior of the wall, we have carried out a numerical simulation using the COMSOL® software in considering a unit cell. To describe the change of state, the method of the equivalent heat capacity has been used. Paraffin has been chosen as PCM (melting temperature 24.5 °C). The influence of the nature and the volume fraction of the metal were determined. The case of honeycombs made of aluminum has been specifically treated.

A Study of The Effectiveness and Sound Quality in Audio Compression Algorithms

The sound is an essential component of multimedia, and due to the needto be used in many life applications such as television broadcasting andcommunication programs, so it was necessary for the existence of audio signal processing techniquessuch as compressing, improving, and noisereduction. Data compression process aims to reduce the bit rate used, by doing encoding information using fewer bits than the original representation for transmitting and storing. By this process,the unnecessary information is determined and removed, that means it gives the compressed information for useable compression, which we need as a fundamental, not the minutest details. This research aims to study how to process sound and musical signal. It's a process that consists of a wide range of applications like coding and digital compression for the effective transport and storage on mobile phones and portable music players, modeling and reproduction of the sound of musical instruments and music halls and the harmonics of digital music, editing digital music, and classification of music content, and other things.

Selection of Phase Change Materials (PCMs) for residential air conditioning in summer

The Phase Change Materials (PCM) are materials which absorb a great quantity of energy during the change of phase solid /liquid and relies it during solidification An application of these materials is thermal energy storage. The PCM integrated into materials of the building can reinforce their inertia and reduce the power necessary for the heating and air conditioning. This is particularly true for the buildings of the tertiary sector whose envelope is light. Nevertheless, one of the characteristics which limits the use of the PCM is their low conductivity. The objective of this article is to propose a selection of materials having a conductivity high enough to make it possible to ensure an air conditioning in summer while limiting, even while removing, the use of energy (electricity or fuel) thanks to walls containing these PCMs. This article consists of two parts: - The first part exposes the problems of the study and specifies the context in which the use of a PCM as a passive air conditioning system fits. - The second part fixes the selection criteria which will allow, in a first approach to choose certain materials.

Parametric study of the dimensionless numbers effects on the thermal behavior of PCM wallboards when it used to store thermal energy in building structures

Thermal energy can be stored as a latent heat in building structures by materials with low phase change temperature called phase change materials (PCM). In this paper, an analytical and mathematical study of the PCM wallboards was done by simulate its thermal behavior, depending on governing heat transfer equations which describe the phase change process of the PCM wallboard.

Thermal analysis of PCM wallboards to be used in building envelopes for energy conservation

In this paper, an analytical and mathematical study of the PCM wallboards was done by simulate its thermal behavior, depending on governing heat transfer equations which describe the phase change process of the PCM wallboard . A mathematical model was done and used to simulate the thermal behavior of several different structures of the wall (single PCM wallboard, PCM wallboard + thermal insulation layer, PCM wallboard + a concrete block).

Influence of Using Phase Change Material (PCM) on the Productivity of the Solar basin Still

The objective of this investigation is to study the influence of application of phase change material (PCM) in solar basin stills for improving its productivity. The experimental results of this investigation showed that using phase change material (paraffin wax) in solar basin still improved its daily productivity, which increased with increasing the mass of phase change material. The highest increase ratio of daily productivity was 26.3[%] when using 3.5[kg] of phase change material in plastic case, and it was 34.74[%] when using 4.5[kg] of phase change material (PCM) in metal case. Also the experimental results of this investigation showed an increase in the period of working basin still provided with phase change material compared with basin still without phase change material. This is owing to the latent heat stored in phase change material, which is emitted to water when solar radiation decreases. This results in longer period of work for the basin still.

Analytical method for determining the temperature of a wall with or without a Phase Change Material (PCM)

When the temperature of the external surface of a wall increases, it is important to predict what the thickness of the wall will be so that the internal surface of the wall does not exceed a limit value. We will study, by an analytical method, the case in which the external surface temperature is linearly varying with time in order to determine the time for which the temperature does not exceed a predetermined limit value at a given depth from the surface. Two cases will be considered: the first one is for a wall made of a homogeneous material (e.g. concrete) and the second one is for a wall made up of concrete and phase-changing material whose melting temperature will be selected according to the desired temperature. The results obtained show that a significant delay to reach this temperature can be obtained between the two cases.