The evolution of virtual fences: A review Umstatter, Christina
Computers and electronics in agriculture,
2011, 2011-1-00, 20110101, Letnik:
75, Številka:
1
Journal Article
Recenzirano
▶ Definition virtual fence: a structure serving as a boundary without a physical barrier. ▶ 1. Category: containing animals in a defined area using animal-borne devices. ▶ 2. Category: containing ...animals without mounting a device onto the animal. ▶ 3. Category: moving fence lines (keeping animals apart or gathering livestock). ▶ Major open questions: energy supply and animal welfare.
A virtual fence can be defined as a structure serving as an enclosure, a barrier, or a boundary without a physical barrier. The concept of virtual fencing occurs increasingly in discussions wherever free-ranging livestock is managed. It is especially interesting because of its potential to initially enhance ecological management, improve management by turning manual labour into cognitive labour as well as improve the life-style of livestock managers. All of these have the potential to reduce costs. Moreover, it opens up the possibility of managing areas that are not manageable at the moment. Therefore, a patent and literature search was conducted to investigate what virtual fencing involves, what opportunities there are for implementing it and what issues still need to be tackled. It was found that there are many different approaches in the development of virtual fencing, which can be split into three categories: first, to contain animals in a defined area or keep them out of a defined area using devices that are animal-borne; second, to contain animals without mounting a device onto the animal; and third, keeping animals apart with a moving fence line or using a virtual fence as a remote gathering device. The first two categories deal with static control of livestock, whereas the third category could be described as a control within moving boundaries. However, despite many patents having been found, only very few products are available on the market.
Two important development areas are the energy use of the device and provision of a system that animals can easily understand, in order to assure welfare standards. The paper critically analyses the wide range of developments to date and points out the advantages and challenges virtual fencing offers. It also provides an indication of how far we are from a marketable product.
•Fencing is more effective than repellent to protect tree sapling in plantations.•The effectiveness of fence is reduced by deeper snow and steeper slope.•Protection methods against deer should be ...selected depending on surrounding conditions.
Population expansion of deer and the damage to planted trees caused by them is becoming a serious conflict between deer and humans. Although there are many methods for tree protection, their effectiveness varies from case to case, and the determinant of effectiveness has rarely been clarified. We investigated the following three specific questions: 1) What factors influence forest managers' choice of protection methods? 2) What factors were important in reducing tree damage by each protection method? 3) Which of the repellents and fences was more effective in reducing tree damage? In 2018, we obtained data of plantation tree damages caused by sika deer (Cervus nippon) and tree protection methods from 1424 plantations in Japan. No protection was chosen at low deer densities, and repellents and fences were chosen at middle and high densities by forest managers. In the case of repellents, the damage rank increased with increasing deer density, tree age, and maximum snow depth, but was not affected by planted tree species (Cryptomeria japonica and Chamaecyparis obtusa). In the case of fences, the damage rank increased with increasing deer density, tree age, maximum snow depth, slope, and decreasing net height. The damage rank also increased with the usage of separable digging prevention net and the net without stainless wire. When the age of planted trees is seven, repellents can suppress the tree damage under 50% only when the deer density is below 10 deer/km2 (no snow) or 6 deer/km2 (snow depth is 16 cm). Fences can suppress tree damage below 50% when deer density was below 38 deer/km2 (snow depth: 0, slope: 35°) or 25 deer/km2 (snow depth: 16, slope: 35°). Deer protection methods should be selected according to environmental conditions such as deer density, snow depth, and slope degree in the case of our treated tree species.
•Highly increased R factor did not trigger a significant increase in soil erosion.•Two consecutive erosive events presented an abnormal erosion behavior.•The second consecutive erosive event ...presented a significant soil erosion decrease.•The use of R factor in consecutive storms involves uncertainties in soil erosion rates.•Highly increased rainfall intensities did not imply high erosion rates.
The research was carried out in one of the most important suburban forests of Greece, after a wildfire (2021). The objectives include the estimation of the annual soil erosion, the effect of extremely intense and consecutive rainfalls on erosion process, the correlation among erosion, rainfall intensity and other factors. To monitor soil erosion in burned and unburned areas, erosion measurements were obtained installing silt fences. The results showed that the main factor affecting annual erosion is the presence or not of vegetation. Rainfall intensity is a major determinant of erosion, especially when it exceeds 6–7 mm/30 min. However, it was revealed that erosion does not increase significantly in burned areas, despite the increase of rainfall intensity. In unburned area the erosion was significantly increased, above a rainfall intensity threshold (>10 mm/30 min). For the first time, it was shown that in cases of two consecutive and very heavy rainfalls, the second and more intense rain caused significantly lower erosion than the first one. A 690 % average increase in R factor during the 2nd storm, showed an average decrease in soil erosion of 20 % (burned and unburned areas). The present study also revealed that the high increase of R factor in the 2nd post-fire year did not trigger a significant increase of soil erosion, since the extreme erosive events occurred very close to each other in time. These findings highlight that the use of R factor in RUSLE, to calculate the annual erosion in burned or unburned areas, detached from the respective field data establishment to validate the model, involves high uncertainties, which could possibly result in wrong erosion rates calculations. Researches and stakeholders, who use the R factor in erosion modeling, should previously examine in detail the exact dates of erosive events, before the implementation of the erosion model.
A compact broadband circularly polarized antenna with novel tilt fences for global navigation satellite system (GNSS) applications is proposed in this letter. The proposed antenna consists of ...Y-shaped feedlines with vacant-quarter rings, parasitic patches, ground, and novel tilt fences. Good impedance matching as well as circular polarization (CP) characteristics are achieved with novel tilt fences. New resonance modes and CP modes are introduced at low frequencies through novel tilt fences, which are equivalent to antenna miniaturization. The proposed antenna with four CP modes is fabricated using simple printed circuit board (PCB) technology and has a compact dimension of 0.29λ 0 ×0.29λ 0 ×0.18λ 0 (λ 0 is the wavelength of the center frequency). Based on the measured results, a wide impedance bandwidth (IBW) and axial-ratio bandwidth (ARBW) are achieved. The −15 dB IBW can cover 1.07-1.98 GHz, and the 3 dB ARBW is 61.5% from 1.07 to 2.02 GHz. In addition, the antenna has a wide overlap bandwidth of 1.07-1.98 GHz (59.7%). This simple and compact CP antenna has good potential in GNSS applications.
Animal migration is one of the most fascinating of all behaviors, links ecosystems and has profound ecological consequences over very large scales. Ungulate migration are among the most imperiled ...ecological phenomena in the world. Substantial populations of migratory ungulates are found in Mongolia's Gobi-Steppe Ecosystem (GSE), which is the largest area of intact steppe in the world and hense is of global importance.
