China
Africa
Explore chapters and articles related to this topic
State Estimation
Published in M. Necati Özisik, Helcio R. B. Orlande, Inverse Heat Transfer, 2021
M. Necati Özisik, Helcio R. B. Orlande
The use of heat for the treatment of cancer can be aimed at: (i) A mild temperature increase of the tumor, in order to make their cells more susceptible to the effects of other treatments, like radiotherapy or chemotherapy; or (ii) a large temperature increase of the tumor to kill their cells solely by the effects of heat. Within the medical community, these treatments are usually referred to as hyperthermia and thermal ablation, respectively. The hyperthermia treatment of cancer consists in raising tumor tissues to temperatures between 41°C and 47°C during a pre-specified period of time. Among other types of heating, electromagnetic energy sources in the radiofrequency and near-infrared ranges have been used to deliver energy to the target region, due to the biological windows of human tissues that exhibit small absorption. One major problem of the hyperthermia treatment of cancer is the lack of selectivity of the heating procedure. On the other hand, with recent advancements in nanotechnology, nanoparticles have been used as absorbing agents in the near-infrared and in the radiofrequency ranges, in order to provide localized thermal damage to the tumor, with minimal damage to the healthy cells [205–210].
Chemical Sensing with POF
Published in Marcelo Martins Werneck, Regina Célia da Silva Barros Allil, Plastic Optical Fiber Sensors, 2019
Filipa Sequeira, Rogério N. Nogueira, Lúcia Bilro
Absorption is a transfer of energy from the light wave to the atoms or molecules of the medium. Due to the absorption of energy, the electrons that constitute the atoms can be transferred to higher energy states (excited state) and, in the case of molecules, vibration or rotational states can be present. Infrared (IR) radiation is not energetic enough to excite electrons, but this radiation is absorbed generally by all organic molecules causing an excitation in vibrational energies. The IR absorption spectra of compounds are a unique signature of their molecular structure. The IR absorption in specific bands (IR absorptiometry) allow the development of sensors for gases and pollutants (CO2, CH4, SO2, NOx) and other hydrocarbons while the ultraviolet (UV) absorption allow the monitoring of nitrate, nitrite (with absorption bands around 300 and 350 nm, respectively) (Moo, Matjafri, Lim, & Tan, 2016) or PAHs (polycyclic aromatic hydrocarbons) (Axelsson et al., 1995) in water as well as different organic compounds such as potassium hydrogen phthalate (KHP, acidic salt compound) (Kim, Eom, Jung, & Ji, 2016).
Optical Fiber and Its Application in Communication—An Overview
Published in Tarun Kumar Gangopadhyay, Pathik Kumbhakar, Mrinal Kanti Mandal, Photonics and Fiber Optics, 2019
Signal attenuation or loss in optical fiber is caused by a number of processes like absorption, scattering, bending, etc. Signal loss or attenuation depends on the wavelength of light that propagates through the fiber. For a particular wavelength, if Pin is the transmitted optical power at the input of a fiber of length x and Pout is the received power at the other end of the fiber, then according to Beer’s law we get () Pout=Pine−αx
Dielectric properties and electromagnetic wave absorbing performance of granular polysilicon during 2450 MHz microwave smelting
Published in Journal of Microwave Power and Electromagnetic Energy, 2021
Jin Lin, Fucheng Zhang, Yongzhen Bai, Xiaobiao Shang, Ruogu Kang
During the process of microwave heating, when the microwave is radiated from free space to the heating material, only part of the microwave is radiated into the material while another part is reflected, due to a mismatch between the characteristic impedance of free space and the input impedance of the material (the input impedance relates to the characteristic of the material and varies with different materials). The microwave radiated into the material will interact with it, and will be absorbed to be converted into other forms of energy (mainly thermal energy), whereas the unconsumed microwave will either continue to propagate through the material, or be reflected multiple times and then propagate to the surface of the material, where it will form the reflected waves. The microwave absorption of the material is mainly determined by two factors: (1) How much the microwave enters the material, which is the impedance matching characteristic; and (2) How much the microwave enters the material and is consumed, which is the attenuation characteristic (Fang et al. 2019).
Three-stage hybrid osmotic–intermittent microwave–convective drying of apple at low temperature and short time
Published in Drying Technology, 2018
Jalal Dehghannya, Parya Farshad, Maryam Khakbaz Heshmati
Absorption of microwave energy leads to heating of water inside food material and moisture evaporation, which in turn increases the internal pressure and concentration gradient, resulting in an increase in effective moisture diffusion coefficient and accelerated drying.[5] Moreover, the heat generated during microwave radiation causes to an increase in the solubility of pectic materials of the structure, consequently, leading to decreased toughness of the structure and lower resistance of the products against moisture diffusion.[3] During microwave drying, the current of water vapor from internal parts toward products’ surface results in creation of a porous structure. In comparison to hot air-drying, the resulted porosity leads to more water loss, more rehydration, and lower bulk density.[1] In general, the drying curves of all microwave power levels have steep slopes. The initial acceleration observed in microwave drying can be related to faster evaporation of water resulted from structural porosity.[34]
Design, Fabrication and Characteristics of Eco-Friendly Microwave Absorbing Materials: A Review
Published in IETE Technical Review, 2022
Geetika Verma, Kamla Prasan Ray
Electromagnetic radiation-absorbing materials/microwave absorbing materials have been the focus of research since the 1990s due to escalating government norms to monitor and manage the amount of electromagnetic radiation radiated by equipment. The two main necessities of a material to satisfactorily work as an absorber are: High absorption of electromagnetic waves, which depends on the permittivity and permeability of the material used along with the electrical conductivity.Reduced reflections from the absorber air interface.