LONG DISTANCE V.H.F. FIELDS: I. PARTIAL REFLECTION FROM A STANDARD ATMOSPHERE

1955 ◽  
Vol 33 (5) ◽  
pp. 241-256 ◽  
Author(s):  
F. H. Northover
Keyword(s):  
Atmospheric Turbulence ◽  
High Power ◽  
Electromagnetic Waves ◽  
Effective Radius ◽  
The Other ◽  
Optical Range ◽  
Long Distance ◽  
Partial Reflection ◽  
Standard Atmosphere ◽  
Order Of Magnitude

Reliable propagation of V.H.F. waves and microwaves from high power transmitters to distances of several hundred miles beyond optical range has been demonstrated by an ever increasing number of experiments during the last ten years. The fields which have been observed have consistently been many times greater than the field strengths predicted by the "effective radius" theory. The present paper will be published in two parts. In Part I the theory that the phenomenon can be explained solely in terms of "partial internal reflection" from elementary layers of a dielectric distribution where the rate of decrease of (μ – 1) with height is everywhere continuous and of the same order of magnitude as in a "standard" atmosphere is carefully examined and found to be untenable. In Part II, the case where the distribution contains "sharp layers" (i.e., local regions where (μ – 1) changes relatively rapidly with height) is examined and it is found that these could cause the phenomenon. However, in view of the other characteristics of the observed field, it is concluded that the effect in question is probably more usually due to scattering of the electromagnetic waves from atmospheric turbulence.

LONG DISTANCE V.H.F. FIELDS: II. REFRACTIVITY PROFILES CONTAINING "SHARP LAYERS"

1955 ◽  
Vol 33 (6) ◽  
pp. 316-346 ◽  
Author(s):  
F. H. Northover
Keyword(s):  
General Solution ◽  
Experimental Evidence ◽  
Atmospheric Turbulence ◽  
Physical Interpretation ◽  
Long Distance ◽  
Standard Type ◽  
Order Of Magnitude ◽  
Field Formation ◽  
Present Experimental Evidence

In this part the general solution developed in Part I is applied to the case in which the refractivity profile contains sharp layers (i.e. local regions where μ and dμ/dh change very rapidly compared with their rate of variation in a "standard" type atmosphere). It is found that such layers, when well developed, can cause distant fields of the order of magnitude of those which have been observed, but present experimental evidence seems to indicate that scattering from atmospheric turbulence is usually the important factor. An attempt is made to work out a physical interpretation of the field-formation below the elevated layer.

Detection of delamination in composites by using electromagnetic penetrating radar

2014 ◽  
Vol 5 (2) ◽  
pp. 151-156
Author(s):  
Z. Mechbal ◽  
A. Khamlichi
Keyword(s):  
Electromagnetic Wave ◽  
Electromagnetic Waves ◽  
Electromagnetic Wave Propagation ◽  
Wave Reflection ◽  
Image Features ◽  
Partial Reflection ◽  
Straight Path ◽  
Reflected Signal ◽  
Short Time ◽  
Intervening Factors

Composites made from E-glass/epoxy or aramid/epoxy are frequently used in aircraft and aerospace industries. These materials are prone to suffer from the presence of delamination, which can reduce severely the performance of aircrafts and even threaten their safety. Since electric conductivity of these composites is rather small, they can propagate electromagnetic waves. Detection of delamination damage can then be monitored by using an electromagnetic penetrating radar scanner, which consists of emitting waves having the form of short time pulses that are centered on a given work frequency. While propagating, these waves undergo partial reflection when running into an obstacle or a material discontinuity. Habitually, the radar is moved at constant speed along a straight path and the reflected signal is processed as a radargram that gives the reflected energy as function of the two-way time and the antenna position.In this work, modeling of electromagnetic wave propagation in composites made from E-glass/epoxy was performed analytically. The electromagnetic wave reflection from a delamination defect was analyzed as function of key intervening factors which include the defect extent and depth, as well as the work frequency. Various simulations were performed and the obtained results have enabled to correlate the reflection pattern image features to the actual delamination defect characteristics which can provide quantification of delamination.

Comparison of the Potency of 8-L-Arginine, 8-D-Arginine and 8-D-Homoarginine Vasopressin Analogs with Substituted Phenylalanine in Position 2

1994 ◽  
Vol 59 (6) ◽  
pp. 1439-1450 ◽  
Author(s):  
Miroslava Žertová ◽  
Jiřina Slaninová ◽  
Zdenko Procházka
Keyword(s):  
Amino Acid ◽  
Solid Phase Synthesis ◽  
Solid Phase ◽  
Basic Amino Acid ◽  
The Other ◽  
Side Chain ◽  
Inhibitory Potency ◽  
Phase Synthesis ◽  
Other Hand ◽  
Order Of Magnitude

An analysis of the uterotonic potencies of all analogs having substituted L- or D-tyrosine or -phenylalanine in position 2 and L-arginine, D-arginine or D-homoarginine in position 8 was made. The series of analogs already published was completed by the solid phase synthesis of ten new analogs having L- or D-Phe, L- or D-Phe(2-Et), L- or D-Phe(2,4,6-triMe) or D-Tyr(Me) in position 2 and either L- or D-arginine in position 8. All newly synthesized analogs were found to be uterotonic inhibitors. Deamination increases both the agonistic and antagonistic potency. In the case of phenylalanine analogs the change of configuration from L to D in position 2 enhances the uterotonic inhibition for more than 1 order of magnitude. The L to D change in position 8 enhances the inhibitory potency negligibly. Prolongation of the side chain of the D-basic amino acid in position 8 seems to decrease slightly the inhibitory potency if there is L-substituted amino acid in position 2. On the other hand there is a tendency to the increase of the inhibitory potency if there is D-substituted amino acid in position 2.

Effects of Unequal Power on Cooperation in Conflict

1979 ◽  
Vol 44 (1) ◽  
pp. 239-242 ◽  
Author(s):  
Dean Tjosvold ◽  
Morris Okun
Keyword(s):  
Low Power ◽  
High Power ◽  
The Other

Participants were randomly assigned to be high or low power and interacted with another who consistently cooperated, or consistently competed, or alternatively cooperated and competed. Results indicate that low power participants acted more cooperatively, were more attracted to, and wanted to facilitate the other's outcomes to the extent the other had cooperated; the cooperativeness of the high power participants was unaffected by the low power person's actions.

scholarly journals On the 2PN Periastron Precession of the Double Pulsar PSR J0737–3039A/B

Universe ◽  
2021 ◽  
Vol 7 (11) ◽  
pp. 443
Author(s):  
Lorenzo Iorio
Keyword(s):  
General Relativity ◽  
Present Author ◽  
Moment Of Inertia ◽  
The Other ◽  
Orbital Elements ◽  
Binary Pulsars ◽  
Orbital Phase ◽  
Order Of Magnitude ◽  
General Relativistic ◽  
The Moment

One of the post-Keplerian (PK) parameters determined in timing analyses of several binary pulsars is the fractional periastron advance per orbit kPK. Along with other PK parameters, it is used in testing general relativity once it is translated into the periastron precession ω˙PK. It was recently remarked that the periastron ω of PSR J0737–3039A/B may be used to measure/constrain the moment of inertia of A through the extraction of the general relativistic Lense–Thirring precession ω˙LT,A≃−0.00060∘yr−1 from the experimentally determined periastron rate ω˙obs provided that the other post-Newtonian (PN) contributions to ω˙exp can be accurately modeled. Among them, the 2PN seems to be of the same order of magnitude of ω˙LT,A. An analytical expression of the total 2PN periastron precession ω˙2PN in terms of the osculating Keplerian orbital elements, valid not only for binary pulsars, is provided, thereby elucidating the subtleties implied in correctly calculating it from k1PN+k2PN and correcting some past errors by the present author. The formula for ω˙2PN is demonstrated to be equivalent to that obtainable from k1PN+k2PN by Damour and Schäfer expressed in the Damour–Deruelle (DD) parameterization. ω˙2PN actually depends on the initial orbital phase, hidden in the DD picture, so that −0.00080∘yr−1≤ω˙2PN≤−0.00045∘yr−1. A recently released prediction of ω˙2PN for PSR J0737–3039A/B is discussed.

scholarly journals The Acoustic System of the Fendouzhe HOV

Sensors ◽  
2021 ◽  
Vol 21 (22) ◽  
pp. 7478
Author(s):  
Yeyao Liu ◽  
Jingfeng Xue ◽  
Bo Yang ◽  
Min Zhu ◽  
Weizhen Guo ◽  
...  
Keyword(s):  
Electromagnetic Waves ◽  
Underwater Acoustic Communication ◽  
Integrated Navigation ◽  
Acoustic System ◽  
Long Distance ◽  
Radio Communications ◽  
Underwater Acoustic ◽  
Positioning Systems ◽  
Integrated Navigation System ◽  
Manned Submersible

Due to the strong absorption and attenuation of electromagnetic waves by water, radio communications and global positioning systems are lacking in the deep-sea environment. Therefore, underwater long-distance communications, positioning, detection and other functions depend on acoustic technology. In order to realize the above functions, the acoustic system of the Fendouzhe human occupied vehicle (HOV) is composed of eight kinds of sonars and sensors, which is one of the core systems of manned submersible. Based on the Jiaolong/Shenhai Yongshi HOVs, the acoustic system of the Fendouzhe HOV has been developed. Compared with the previous technology, there are many technical improvements and innovations: 10,000-m underwater acoustic communication, 10,000-m underwater acoustic positioning, multi-beam forward-looking imaging sonar, an integrated navigation system, etc. This study introduces the structure of the acoustic system of the Fendouzhe HOV and the technical improvements compared with the Jiaolong/Shenhai Yongshi HOVs. The results of the acoustic system are illustrated by the 10,000-m sea trails in the Mariana Trench from October to December 2020.

scholarly journals Design and Fabrication of Small Vertical-Take-Off-Landing Unmanned Aerial Vehicle

2018 ◽  
Vol 152 ◽  
pp. 02023 ◽  
Author(s):  
Yasir Ashraf Abd Rahman ◽  
Mohammad Taghi Hajibeigy ◽  
Abdulkareem Shafiq Mahdi Al-Obaidi ◽  
Kean How Cheah
Keyword(s):  
Design Methodology ◽  
The Other ◽  
Long Distance ◽  
Open Spaces ◽  
Flight Tests ◽  
Flight Range ◽  
Horizontal Flight ◽  
Vtol Uav ◽  
Aerial Vehicle ◽  
Horizontal Thrust

Modern UAVs available in the market have well-developed to cater to the countless field of application. UAVs have their own limitations in terms of flight range and manoeuvrability. The traditional fixed-wing UAVs can fly for long distance but require runways or wide-open spaces for take-off and landing. On the other hand, the more trending multirotor UAVs are extremely manoeuvrable but cannot be used for long-distance flights because of their slower speeds and relatively higher consumption of energy. This study proposed the implementation of hybrid VTOL UAV which has the manoeuvring advantage of a multirotor UAV while having the ability to travel fast to reach a further distance. The design methodology and fabrication method are discussed extensively which would be followed by a number of flight tests to prove the concept. The proposed UAV would be equipped with quadcopter motors and a horizontal thrust motor for vertical and horizontal flight modes respectively.

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