An impact of moisture content on the air permeability of the fibrous insulation materials

Fibrous materials are characterized by good thermal properties, but are susceptible to air filtration. Effective air and wind protection of the building envelope eliminate the problem of air penetration of fibrous materials, but there are still many buildings where this protection has not been applied. Authors investigated the effect of moisture content on the air permeability of chosen loose fibrous materials: mineral wool, wood wool and cellulose fibers. The presented results may be used to simulate and calculate heat loses in existing buildings.

Determination of the permeability coefficient and airflow resistivity of nonwoven materials

Air penetration behavior plays a vital role in the performance of fibrous material in various industrial applications. Two parameters, the permeability coefficient and airflow resistivity, can describe the air penetration behavior of fibrous material. FX 3300 Textech Tester III and AFD300 AcoustiFlow devices were used to respectively characterize the permeability coefficient and airflow resistivity of nonwoven materials. Nonwoven samples were compressed due to the load from the test head of the FX 3300. Finite element analysis along with the mathematical method were implemented to recover the airflow permeability of samples at the uncompressed state. The effects of pressure drop on the airflow velocity and permeability coefficient were analyzed by the Ergun-type model. The determination of airflow resistivity based on the permeability coefficient is carried out via two approaches, that is, the direct method and the extrapolation method. The results show that the airflow velocity is not linearly related to the pressure drop, which differs from Darcy's law. This non-linear relation is mainly attributed to the influence of frictional loss. By comparing the relative error between assessed and measured airflow resistivity, most of the assessed values of the compressed samples are overestimated. The results also suggest that the direct and extrapolation methods are applicable to assess airflow resistivity on an airflow velocity (or air permeability) test device. Moreover, the Ergun-type model is also applicable to determine the permeability coefficient and airflow resistivity of nonwoven materials.

Computational and experimental determination of waterjet aeration exposure in waves

Object and purpose of research. The object of research was a model of a fast seaworthy boat with discretevariable bottom deadrise and two waterjet propulsors. The purposes of research were to experimentally determine hydrodynamic characteristics of the model in calm water and head regular waves corresponding to the irregular waves of sea states 3 and 4, as well as to determine the possibility of air penetration to waterjet inlets for two variants of their arrangement on model bottom in head-wave conditions, numerical simulation of the full-scale boat movement in oblique irregular waves (sea state 4) for two variants of waterjet arrangement, with an assessment of waterjet duct aeration exposure. Materials and methods. Model hydrodynamics was estimated experimentally by means of towing tests in highspeed seakeeping basin in calm water and head regular waves using standard test equipment; air penetrations were recorded by a GO PRO digital video camera installed on the model above the water inlets. Numerical simulation of the full-scale boat movement was carried out in Star-CCM+ CFD package. Main results. The study yielded the curves of towing resistance, running trim and sinkage versus model speed in calm water and head regular waves of different length for two longitudinal CG positions, as well as the areas of air penetration to waterjet inlets on model bottom. Analysis of the experimental data enabled the estimation of attainable speed for the boat with displacement of 50 and 29 tf in waves for given delivered power. Numerical simulation of the full-scale boat movement in oblique irregular waves for two variants of waterjet arrangement has also been carried out. Conclusion. The results have shown that seakeeping performance of the boat is quite satisfactory and that the most obvious way to mitigate air penetrations is to reduce the speed. Other important factors were shifting the waterjet inlet towards the transom and to the CL, as well as shifting the longitudinal CG forward. The obtained results can be used to select the position of the waterjet inlets on boat bottom in order to increase waterjet efficiency. Using the methods of numerical hydrodynamics, the characteristics of the waterjets have been obtained, the probability and volumes of air penetrations to waterjet ducts (for different variants of waterjet arrangement) at several angles of oblique irregular waves have been estimated.

Use of radon barriers to reach an acceptable radon level

A method is presented for theoretically estimating the necessary airtightness of a radon barrier. Radon barriers are used to balance the indoor radon concentration. To balance radon at an acceptable level, for a given ventilation rate for indoor air, a barrier must fulfil the requirements for airtightness and the indoor-air radon penetration from the soil, which is determined by the radon concentration in the soil gas. The method identifies the optimal radon barrier for a building. Ten different radon barriers are evaluated. Barriers include system solutions based on materials such as bitumen-based radon blockers, wet-room membranes, reinforced fix mortar pastes, and polyethylene membranes. The barriers are tested using a modified version of the test method NBI 167/02 radon membrane: test of airtightness. The radon barriers are evaluated for a typical building construction for a single-family house with radon exposure from the ground. An acceptable radon concentration of 100 Bq/m3 in indoor air is used in combination with a number of higher radon levels. The different radon barriers are evaluated in accordance with their ability to prevent air penetration from the ground. Furthermore, how mounting a barrier can affect the durability of a building is discussed, as the measures may create a far more vulnerable building.

Information technology in the study of the quality of concrete work

The article presents the results of using information technologies in the study of changes of concrete characteristics at different hardening conditions. The use of the developed temperature measurement complexes made it possible to control the conditions of hardening of monolithic concrete structures directly under production conditions. The results by means of using regression analysis are obtained, regression models of the dependence of the compressive strength of concrete on time and hardening temperature are determined. A significant decrease in compressive strength and resistance to air penetration of concrete samples during their storage under conditions of significant temperature fluctuations has been established.

Reasons for Triple-Funding of the Jet-Engine-Industry to Meet 2020–2040 6th-Gen-Challenge: Counter-Air Penetration, CAP

I often open my lectures with a question: Do you agree that as speed goes down in any landing, the vertical tail fails to orient the nose back to the runway under strong side winds while ONLY side deflecting jet-engine-steering (JES) can safely re-orient it to safe landing? Just facts, less opinions; And if you do, you accept the 1ST-element of jetonautics defined by 12 figures below, text and references 1 to 48.

Reasons for triple-funding of the jet-engine-industry to meet 2020-2040 6TH-Gen-Challenge: Counter-Air Penetration, CAP

The forthcoming 2020-2040 6TH-Generation is characterized by a host of debated and confused CASLAP-strategies, doctrines, tactics, mission definitions, jetonautic-funding, systems-of-systems technologies vis-à-vis AOOF-based-prop-swarm-technologies and almost symmetric jetonautics at both sides, [Part-A references 5,10,11,17,20,24,26,32,36,48,49]. CASLAP offensive-defensive options for each country vary with jetonautics, location, time, scientific and technological education, economics, geopolitics and stealth/super-agility/armament/AI of its fighter aircraft, UCAVs, JES-UCAV, prop-drones or USV, LCS, ULV, each with a different control-communication and various propulsion systems ranging from $100/unit in prop-drone-swarms to $10+ million per jet engine unit with spares, parts, maintenance, etc. It therefore deems timely to introduce an initial degree of order and classification to prevent today future misunderstanding/errors in designs, funding and encounters – the central aim and scope of these editorials.

Katabatically Driven Cold Air Intrusions into a Basin Atmosphere

The interactions between a katabatic flow on a plain and a circular basin cut into the plain and surrounded by an elevated rim were examined during a 5-h steady-state period during the Second Meteor Crater Experiment (METCRAX II) to explain observed disturbances to the nocturnal basin atmosphere. The approaching katabatic flow split horizontally around Arizona’s Meteor Crater below a dividing streamline while, above the dividing streamline, an ~50-m-deep stable layer on the plain was carried over the 30–50-m rim of the basin. A flow bifurcation occurred over or just upwind of the rim, with the lowest portion of the stable layer having negative buoyancy relative to the air within the crater pouring continuously over the crater’s upwind rim and accelerating down the inner sidewall. The cold air intrusion was deepest and coldest over the direct upwind crater rim. Cold air penetration depths varied around the inner sidewall depending on the temperature deficit of the inflow relative to the ambient environment inside the crater. A shallow but extremely stable cold pool on the crater floor could not generally be penetrated by the inflow and a hydraulic jump–like feature formed on the lower sidewall as the flow approached the cold pool. The upper nonnegatively buoyant portion of the stable layer was carried horizontally over the crater, forming a neutrally stratified, low–wind speed cavity or wake in the lee of the upwind rim that extended downward into the crater over the upwind sidewall.