Since Monday the 2nd, GDACS has been carrying warnings about a new Tropical Cyclone in the North West Pacific, with a name that will resonate well with radio amateurs.
Tropical Storm YAGI arose on the 1st, over the northern islands of Philippines, and then started moving towards China. Later on the 2nd, a RED alert level for Philippines and China was issued, with expected high wind speeds of 210km/h.
By Wednesday the Vietnamese border with China was included in the warning as well as Laos, and estimated maximum wind speeds of 241km/h were forecast. Nearly 14 million people were in the path of 120km/h winds.
On Saturday the GDACS newsletter said that, following YAGI’s passage over northern and eastern Philippines in combination with the south-west monsoon, 16 people had died, 13 others had been injured and 17 were still missing. Moreover, almost 550,000 people had been affected and almost 48,000 displaced across eight regions of the country.
YAGI was expected to continue westward over the South China Sea on 4-6 September, further strengthening, and to make landfall between northern Hainan Island and south-eastern Guangdong province, south-eastern China on 6 September, with maximum sustained winds up to 240 km/h. It was expected yesterday to cross the coast of Northern Vietnam in the Hanoi region as well, with maximum sustained wind speeds of 185km/h.
In the same report Brian Jacobs ZS6YZ sent to me last week, he reported on an agreement that has been signed with the Brakpan Aero Club which manages the Brakpan Airport (FABB) on behalf of the City of Ekurhuleni. The agreement allows HAMNET Gauteng full access to the Airport facilities. This allows the HAMNET container with their cache of equipment to be moved to Brakpan Airfield. A space has been allocated for the container and Ekurhuleni Disaster Management has also requested that their logo be added to the HAMNET container.
HAMNET also has permission to use the extensive area on the airport for training. The first training event on 14 September will be a fox hunt with a twist, amongst the hangers, so that the members who have not yet been involved in a PLB or ELT recovery can get some practice in an environment where reflections of the signal can cause confusion while hunting for the device.
Very good news, that, Brian, and I’m glad the HAMNET container has been centralized to a place where it will always be accessible.
The City of Cape Town’s Disaster Risk Management Centre (DRMC) says that volunteers play a critical role in disaster mitigation efforts.
DRMC has relied heavily on its crop of volunteers in the past year to amplify its response to fires, floods and other public safety risks in Cape Town. The metro has experienced a surge in severe weather conditions in the past two years, including damaging winds and record high rainfall, that has resulted in flooding and property damage, and accelerated the extent of both wildfires and structural fires.
This has resulted in an increased demand on the services of the Disaster Risk Management Centre, and its dedicated crop of volunteers, to help those in need.
DRMC has 419 registered volunteers, working in teams in various parts of the metropole. They are activated through the Disaster Operations Centre via their unit coordinators to assist officials in affected communities for the duration of an incident or event.
During the period April to June this year, volunteers spent 18 471 hours assisting DRMC officials – this equates to more than 769 days of voluntary service.
The appointment of volunteers is entrenched in the Disaster Management Volunteer Regulations Framework, which allows the City to establish volunteer units and by doing so, empower communities effectively to respond to disaster relief efforts.
Thanks to iol.co.za for this report.
HAMNET Western Cape has signed a memorandum of understanding with the DRMC, and has a dedicated radio station (ZS1DCC) at the Goodwood Headquarters, with UHF, VHF, APRS, HF, Winlink, VarAC, and Echolink, as well as Marine monitoring capability, and a 5 GHz microwave link directly with a similar station (ZS1DZ) at the Provincial Emergency Management Centre at Tygerberg Hospital, which manages provincial disasters and their communications. The 5 GHz link is independent of all other means of communications between ZS1DCC and ZS1DZ, and completely private.
Here’s something with applications in amateur radio. Phys.org reports that researchers at ETH Zurich have managed to make sound waves travel only in one direction. In the future, this method could also be used in technical applications with electromagnetic waves.
Water, light and sound waves usually propagate in the same way forward as in a backward direction. As a consequence, when we are speaking to someone standing some distance away from us, that person can hear us as well as we can hear them. Ten years ago, researchers succeeded in suppressing sound wave propagation in the backward direction; however, this also attenuated the waves traveling forwards.
A team of researchers at ETH Zurich led by Nicolas Noiray, professor for Combustion, Acoustics and Flow Physics, in collaboration with Romain Fleury at EPFL, has now developed a method for preventing sound waves from traveling backward without deteriorating their propagation in the forward direction.
In the future, this method, which has recently been published in Nature Communications, could also be applied to electromagnetic waves.
Among other things, Noiray studies how self-sustaining thermo-acoustic oscillations can arise from the interplay between sound waves and flames in the combustion chamber of an aircraft engine, which can lead to dangerous vibrations. In the worst case, these vibrations can destroy the engine.
Noiray had the idea to use harmless self-sustaining aero-acoustic oscillations in order to allow sound waves to pass only in one direction and without any losses through a so-called circulator. In his scheme, the unavoidable attenuation of the sound waves is compensated by the self-oscillations in the circulator synchronizing with the incoming waves, which allows them to gain energy from those oscillations.
The circulator itself was supposed to consist of a disk-shaped cavity through which swirling air is blown from one side through an opening in its centre. For a specific combination of blowing speed and intensity of the swirl, a whistling sound is thus created in the cavity.
“In contrast to ordinary whistles, in which sound is created by a standing wave in the cavity, in this new whistle it results from a spinning wave,” explains Tiemo Pedergnana, a former doctoral student in Noiray’s group and lead author of the study.
From the idea to the experiment, it took a while. First, Noiray and his co-workers investigated the fluid mechanics of the spinning wave whistle, and then added three acoustic waveguides to it, which are arranged in a triangular shape along the edge of the circulator.
Sound waves that are fed in through the first waveguide can leave the circulator through the second waveguide. However, a wave entering through the second waveguide cannot exit “backwards” through the first waveguide, but can do so through the third waveguide.
“This concept of loss-compensated non-reciprocal wave propagation is, in our view, an important result that can also be transferred to other systems,” says Noiray. He sees his sound wave circulator mainly as a powerful toy model for the general approach of wave manipulation using synchronized self-oscillations that can, for instance, be applied to metamaterials for electromagnetic waves.
In this way, microwaves in radar systems could be guided better, and so-called topological circuits could be realized, with which signals can be routed in future communications systems.
Hmm – wonder whether this technology could be used in a flaming argument with your Significant Other, in which neither of you can hear what the other is saying! It might defuse the situation very quickly.
To be honest, radio aficionados have been using circulators for a long time. I wonder why it took so long to apply the process to sound.
This is Dave Reece ZS1DFR reporting for HAMNET in South Africa.