Low-Frequency, Open, Sound-Insulation Barrier by Two Oppositely Oriented Helmholtz Resonators

In this work, a low-frequency, open, sound-insulation barrier, composed of a single layer of periodic subwavelength units (with a thickness of λ/28), is demonstrated both numerically and experimentally. Each unit was constructed using two identical, oppositely oriented Helmholtz resonators, which were composed of a central square cavity surrounded by a coiled channel. In the design of the open barrier, the distance between two adjacent units was twice the width of the unit, showing high-performance ventilation, and low-frequency sound insulation. A minimum transmittance of 0.06 could be observed around 121.5 Hz, which arose from both sound reflections and absorptions, created by the coupling of symmetric and asymmetric eigenmodes of the unit, and the absorbed sound energy propagating into the central cavity was greatly reduced by the viscous loss in the channel. Additionally, by introducing a multilayer open barrier, a broadband sound insulation was obtained, and the fractional bandwidth could reach approximately 0.19 with four layers. Finally, the application of the multilayer open barrier in designing a ventilated room was further discussed, and the results presented an omnidirectional, broadband, sound-insulation effect. The proposed open, sound-insulation barrier with the advantages of ultrathin thickness; omnidirectional, low-frequency sound insulation; broad bandwidth; and high-performance ventilation has great potential in architectural acoustics and noise control.

Design and Validation of Thermal Insulation for Deep-sea Fluid Sampler of Jiaolong Human Occupied Vehicle

In this paper, a thermal insulation structure with silica aerogel felt as filler material was designed for the requirements of deep-sea fluid thermal insulation sampling technology for Jiaolong human occupied vehicle. Simulation analysis of thermal insulation performance was carried out and an experimental prototype was developed for the thermal insulation structure. Experimental study on thermal insulation performance was conducted with the variation characteristics of the operation environment for Jiaolong human occupied vehicle being taken into account. Results show that the silica aerogel felt with a thickness of 30 mm filled in the radial space between the inner and outer cylinders can achieve the expected thermal insulation effect during the diving-sampling-transferring process, with maximum temperature rise of 8.5 °C, and can meet the requirements of deep-sea fluid thermal insulation sampling technology.

Heat insulation effect in solar radiation of polyurethane powder coating nanocomposite

This study aims to improve polyurethane-based coating by modified zirconium oxide and aluminum oxide nanoparticles for preparing thin polymeric heat insulation coatings. In the first step, the nanoparticles were chemically modified with the silane coupling agent. Then, three different weight percent of modified nanoparticles (1, 3, and 5% w/w) were mixed with polyurethane, to prepare the nanocomposites, which were coated on metallic plate samples. Then, these plates are used to measure the radiation heat transfer coefficients, absorption coefficient in a region of short wavelengths (UV/VIS/NIR), the emissivity coefficient, and thermography of the samples in a region of long wavelengths (IR). Results showed that by adding the modified nanoparticles to the polyurethane matrix, absorption was decreased and the emissivity coefficient was increased. According to the thermography results, it was observed that the surface temperature of both samples with 3% w/w of nanoparticles had the minimum temperature compare to others. Minimum heat surface observed for 3% w/w of modified nano zirconium oxide.

Characteristics Analysis of Small Insulated Vans Based on Thermoelectric Cooling

In cold chain logistics, refrigerated trucks are used for long-distance transportation across cities, and insulated trucks are used for short-distance delivery within cities. However, the small insulated vans for short-distance transportation like delivering home in urban have heat leakage and no pre-cooling, the transportation time of traffic congestion becomes longer, resulting in poor insulation effect. So, to achieve stable temperature control is difficult, it leads to a big fluctuation in the temperature of the cargo. The thermoelectric cooling technology has the unique advantages of compact structure, flexible layout, no refrigerant, and environmental friendliness, which is very suitable for controlling the temperature of the small insulated vans. In the paper, relationship among COP, working power, and working current of the designed thermoelectric cooler (TEC) is investigated first. And then the best working state of the TEC is obtained. Next, set hot and cold dual temperature zones to ensure the effective use of energy based on thermoelectric cooling characteristics, arranged the cooling device in the insulated van, and revealed the changes in the temperature of the compartment and the cargo through the actual vehicle test. Compared the thermal insulation effect of the compartment with or without thermoelectric cooling technology through CFD. According to the simulation results, the cargo temperature of the insulated van fluctuates between 4 and 6°C within 2.5 h of actual delivery in urban, the insulated van using thermoelectric cooling technology can make the temperature of the cargo fluctuate within 1.5°C. The above proved the good insulated effect of the thermoelectric cooling insulated vans. Finally, the influence of the working time of the thermoelectric refrigeration system on the temperature control effect is also studied. The research results have a certain guiding significance for the application of thermoelectric cooling technology in insulated vans.

A New Type of Hierarchical Honeycomb In-Plane Impact Study

Honeycomb materials have low density, high specific strength and stiffness, impact resistance, and good sound insulation effect, and therefore are widely used in aerospace, automobile, and ship field applications. In this paper, we study the in-plane impact response of a second-order hierarchical honeycomb (SHH) material. Its main structure is a hexagonal honeycomb, and the substructure is composed of an augmented double arrow honeycomb (ADAH) negative Poisson’s ratio unit. Through a finite element simulation, the failure stress of an hierarchical honeycomb in two directions of quasi-static crushing and dynamic crushing was analyzed; the failure stress of the hierarchical honeycomb under different densities, different speeds, and different substructures was discussed; and the theoretical failure stress was verified. The numerical analysis results show that a second-order hierarchical honeycomb (SHH) has better collapse stress than a first-order regular hexagonal honeycomb (FHH) and an augmented double arrow honeycomb (ADAH).

Effects of different thermal insulation methods on the nasopharyngeal temperature in patients undergoing laparoscopic hysterectomy: a prospective randomized controlled trial

Background This study explored the comparison of the thermal insulation effect of incubator to infusion thermometer in laparoscopic hysterectomy. Methods We assigned 75 patients enrolled in the study randomly to three groups: Group A: Used warming blanket; group B: Used warming blanket and infusion thermometer; group C: Used warming blanket and incubator. The nasopharyngeal temperature at different time points during the operation served as the primary outcome. Results The nasopharyngeal temperature of the infusion heating group was significantly higher than that of the incubator group 60 min from the beginning of surgery (T3): 36.10 ± 0.20 vs 35.81 ± 0.20 (P<0.001)90 min from the beginning of surgery (T4): 36.35 ± 0.20 vs 35.85 ± 0.17 (P<0.001). Besides, the nasopharyngeal temperature of the incubator group was significantly higher compared to that of the control group 60 min from the beginning of surgery (T3): 35.81 ± 0.20 vs 35.62 ± 0.18 (P<0.001); 90 min from the beginning of surgery (T4): 35.85 ± 0.17 vs 35.60 ± 0.17 (P<0.001). Regarding the wake-up time, that of the control group was significantly higher compared to the infusion heating group: 24 ± 4 vs 21 ± 4 (P = 0.004) and the incubator group: 24 ± 4 vs 22 ± 4 (P = 0.035). Conclusion Warming blanket (38 °C) combined infusion thermometer (37 °C) provides better perioperative thermal insulation. Hospitals without an infusion thermometer can opt for an incubator as a substitute. Trial registration This trial was registered with ChiCTR2000039162, 20 October 2020.