Sustainable Rigid Polyurethane Foam from Wasted Palm Oil and Water Hyacinth Fiber Composite—A Green Sound-Absorbing Material

A novel rigid sound-absorbing material made from used palm oil-based polyurethane foam (PUF) and water hyacinth fiber (WHF) composite was developed in this research. The NCO index was set at 100, while the WHF content was set at 1%wt with mesh sizes ranging from 80 to 20. The mechanical properties, the morphology, the flammability, and the sound absorption coefficient (SAC) of the PUF composite were all investigated. When the WHF size was reduced from 80 to 20, the compression strength of the PUF increased from 0.33 to 0.47 N/mm2. Furthermore, the use of small fiber size resulted in a smaller pore size of the PUF composite and improved the sound absorption and flammability. A feasible sound-absorbing material was a PUF composite with a WHF mesh size of 80 and an SAC value of 0.92. As a result, PUF derived from both water hyacinth and used palm oil could be a promising green alternative material for sound-absorbing applications.

Microwave absorption properties of rare earth alloy Nd2Co17@C/Na2SiO3 composite at elevated temperature (293–723 K) in X band

A variety of new challenges are being faced in the development of high temperature microwave absorbing materials in the X band. Recently, some of the 2:17 phase rare-earth soft magnetic alloys with high permeability and curie temperature have potential to be a novel X band high temperature microwave absorbing material. In this paper, a high temperature microwave absorbing material (Nd2Co17@C/Na2SiO3) is prepared with Nd2Co17 as a raw material. After carbon cladding and Na2SiO3 treatment, the composite can work stably at 723 K. The calculated absorption properties display that the reflection loss (RL) intensity of the composite with a thickness of 1.5 mm is below -6 dB in the whole X band. Moreover, the thermogravimetric (TG) analysis results and static magnetic properties before and after sintering indicate that the material has excellent resistance to oxidation. Rare earth alloy materials provide a new possibility for the research of innovative high temperature absorbing materials.

Comparative Study on Microwave Absorbing Heating Characteristics and Microwave Deicing Performance of Airport Pavement Modified Concrete

In this paper, the airport pavement concrete has been taken as the main research object, three kinds of absorbing materials, namely silicon carbide (SiC), iron oxide (Fe3O4) and graphite, have been respectively mixed into the concrete, and an open microwave testing system has been established. Based on this system, the basic mechanical properties, microwave heating characteristics, microwave deicing effect and its influencing factors of modified concrete are systematically studied. In addition, a comparative analysis of the influence mechanism of different absorbing materials on the strength and absorbing performance of pavement concrete is carried out. The results showed that the addition of SiC, Fe3O4, and graphite could effectively enhance the microwave effect of pavement concrete, and the more the addition, the more obvious the improvement. Furthermore, under the same mixing amount, the degree of improvement of microwave deicing performance of each absorbing material from large to small is graphite, Fe3O4, SiC. However, the addition of graphite will form several weak links in concrete, thereby reducing its overall mechanical properties. SiC can slightly improve the mechanical properties of pavement concrete, but it has no significant effect on the microwave absorption properties. With the addition of Fe3O4, the strength of concrete changes little, and the effect of microwave absorbing heating and microwave deicing is remarkable. In general, the comprehensive performance of microwave deicing of Fe3O4 modified concrete is optimal. This study has high scientific and practical significance, and can be widely applied to deicing projects on airports and high-grade highways.

Fabrication of PDMS@Fe3O4/MS Composite Materials and Its Application for Oil-Water Separation

The discharge of oily wastewater and oil spills at sea are the current difficulties in water pollution control. This problem often leads to terrible disasters. Therefore, the effective realization of oil-water separation is a very challenging problem. Superhydrophobic sponge is a promising oil-absorbing material. In this article, we reported a superhydrophobic sponge with nano-Fe3O4 for oil-water separation. The addition of nano-Fe3O4 allows the sponge to be recycled under the action of magnetic force. The sponge has the advantages of low cost, simple preparation and efficient oil-water separation. This kind of sponge is very worthy of promotion for the treatment of oily wastewater and marine oil spill accidents.

ANALYSIS OF THE EFFICIENCY OF ACOUSTIC SCREENS OF DIFFERENT DESIGNS

Various sources of noise in cities and ways to combat them are considered. The effi ciency of two types of acoustic screens is analyzed: single-layer and two-and three-layer. The positive and negative characteristics of various designs of existing acoustic screens are listed. A fundamentally new design of the acoustic screen is described: the panels have a ridge profi le, they are located along the vertical axis of the frame with a step at which the panels above the located ridge cover the top of the lower ridge, the outer surfaces of the panels and their end parts are made of a material that has sound-refl ecting properties, and the inner surfaces of the panels are made of sound-absorbing material. Such an acoustic screen is devoid of the disadvantages inherent in acoustic screens of other structures and is more effi cient. The considered invention allows due to the use of the ridge shape of acoustic panels: prevent the refl ection of sound energy in the direction of noise sources (a small part will be directed upwards); provide almost complete absorption of sound energy as it passes through the channels formed by the ridge panels; provide the same effective protection against noise sources located on both sides of the screen; prevent the formation of snow and ice crust on sound-absorbing surfaces, which ensures the constant eff ectiveness of the screen in diff erent seasons of the year; reduce metal consumption, which will reduce the weight of the structure without reducing its effi ciency and reduce the cost of acoustic screens.

Kajian pemantauan dosis neutron terhadap pekerja radiasi pada pengoperasian Linac dengan energi foton ≥ 10 MV

The use of Linac for radiotherapy is starting to use a lot of high-energy photons of 10 MV; in addition, some use 15 MV for patient therapy in routine use, there is also the use of 6 MV. The purpose of this study is to obtain an overview and information of the neutron dose that has the potential to provide additional doses for radiation workers operating the Linac 10 MV aircraft. Based on the Regulation of the Head of BAPETEN No. 3 of 2013, Article 48 paragraph (2) states that in the operation of Linac with X-ray photon energies above 10 MV, must coat the shield wall with a neutron-absorbing material. The statement follows the IAEA-TecDoc 1891 that neutrons will have the potential to have a significant radiological impact on workers if routinely operated at energies above 10 MV, so must consider protection for workers. The results of a survey from 27 hospitals, obtained information through filling out questionnaires and discussions and validated with B@LIS Pendora, it found that the trend of annual doses received by each profession in the operation of Linac 6 MV, 10 MV, and 15 MV was less than one mSv, only partially small worker dose that is above one mSv (above the 90th percentile). This study concluded that the presence of neutrons in Linacs up to 10 MV was deemed not to have a significant radiological impact on workers. The recommended criteria/mechanism for monitoring worker neutron doses in Linacs up to 10 MV could be based on if the safety study results obtained a dose received by workers 1.5 mSv/year. Then, there is no need to monitor the neutron dose. If the measurement results of exposure to neutron and gama radiation around the Linac space are 7.5 microSv/hour, there is no need for neutron monitoring. In Linacs above 10 MV, if the annual effective dose is 1.5 mSv/year, there is no need to monitor the dose of special neutron personnel. Still, routine radiation exposure monitoring may be considered every two years. Keywords: Neutron Dose, Radiation Worker, Linac, Dose Monitoring.

Research on space microwave energy reception technology based on electromagnetic-thermal-DC conversion

A new microwave energy reception method is proposed for the wireless energy transmission needs of lunar rovers combined with the lunar environment, i.e. collecting thermal energy through microwave absorbing materials, and then converting thermal energy into direct current by using temperature difference power generation devices. The article analyses the two conversion processes, microwave-thermal and thermal-DC, separately. Under the approximate condition that the temperature at both ends of the absorbing material is regarded as equal, the two conversion processes are linked by energy conservation, which theoretically leads to the temperature and total efficiency of the system at steady state. The temperature and total efficiency of the system are initially obtained by numerical simulation with respect to the thickness of the absorbing material, the receiving area and the input power density by selecting the parameters of the carbon and iron composite material at 10 GHz. The results show that there is an optimum thickness of absorbing material for a certain input power density and receiving area, which results in the highest system efficiency. The larger the receiving area and input power density in a certain range, the higher the efficiency, but beyond a certain range the system efficiency shows a decreasing trend. Also the theory and the actual will produce a large deviation when temperature is high. The article concludes that this energy receiving method has great potential for application in the space environment based on the excellent wave absorbing materials and thermoelectric components but further research is needed.