Wind Region Research Articles

Power maximization and regulation of the super-large wind turbine system using generalized predictive approach-based torque and pitch control

Power maximization, regulation, and structural load reduction become critical when the wind turbine capacity reaches multi-megawatt levels. Thus a well-designed control system allows for better energy extraction and load alleviation of the large-scale wind energy conversion system (WECS). To do this, a 20MW super-large WECS is first modeled using a permanent magnet synchronous generator (PMSG). Next, the optimal generator torque and rotor pitch angle control are designed based on the generalized predictive control approach. Then, the designed controller predicts the best future control effort by identifying the model using the reaction curve method. Further, the proposed controllers are implemented on the designed super-large PMSG-based WECS to achieve the control objectives from the partial and full-load wind regions. Finally, the suggested controllers are compared with the existing control methods to check their effectiveness using step and unexpectedly varying wind speeds.

Assessment and Prospect of Region Joint Electrolytic Hydrogen Systems Considering Multiple Energy Sources: Wind, Solar, Hydro and Thermal Power

Due to the significantly differentiated electrolytic hydrogen capacity caused by resource characteristics such as wind, solar, hydro, and thermal power in different regions of China, region joint electrolytic hydrogen systems (RJEHS) considering multiple energy sources is proposed to improve this situation. In this framework, a regional decoupling model is established for typical cascade hydropower in Southwest China to simulate the actual operation of it. Moreover, the advantages of RJEHS compared with region separate electrolytic hydrogen systems (RSEHS) in reducing levelized cost of hydrogen (LCOH), carbon emission and the installed capacity of renewable energy power generation are also studied. In addition, differential models considering the power and ramping characteristics of three different types of electrolyzers are established. And the evolution process and development prospect of the planned configuration of the three types of electrolyzers during 2025-2050 are given. The case study verifies the rationality and effectiveness of the proposed framework.

Variations in the intermediate wind region of the blue supergiant 55 Cygni

Context. The quantitative near-infrared (NIR) spectroscopic synthesis is an important technique for determining wind properties of massive stars. The Brα line is an excellent mass-loss tracer and provides valuable information on the physical conditions of intermediate-wind regions. The knowledge of the wind properties gained by studying the NIR lines could provide extra ingredients to the theory of line-driven winds, mainly because the standard theory does not predict observed properties of blue supergiants, such as high values for the β parameter (β> 2), low terminal velocities, and mass-loss variability. Aims. We seek to enhance our understanding of the wind properties of B supergiants. To this end, we propose analysing their NIR spectra over different epochs to study wind variability and its connection with phenomena arising from regions close to the photosphere. Methods. We present the first sets of multi-epoch high-resolution K- and L-band spectra of 55 Cyg acquired with the Gemini Near-InfraRed Spectrograph (GNIRS). We measured line equivalent widths and modelled the Brα line to derive (unclumped) mass-loss rates. Synthetic line profiles were computed for a homogeneous spherical wind by solving the radiative transfer equations in the co-moving frame for a multi-level atom in non-local thermodynamic equilibrium (NLTE). Results. We observe variations in the spectral lines originating in the upper photosphere and the wind. The perturbations, on average, have periods of ~13 and ~23 days; the latter is similar to that found previously from optical data (22.5 days). The NIR lines observed in 2013 are described with the same wind structure used to model a quasi-simultaneous observation in Hα. By contrast, from observations taken in 2015, we derived a higher mean mass-loss rate. Variations in the mass-loss rate are also detected within a few weeks. Interestingly, we find that the profile shape of the Hu14 line sets constraints on the mass loss. Moreover, we find the Mg II doublet in emission, which suggests a tenuous circumstellar gas ring or shell. Conclusions. The variability detected in the NIR H emission lines of 55 Cyg is related to changes in the mass-loss rate, which doubled its value between 2013 and 2015. Furthermore, the short-term variability (within three weeks) in the spectral lines and mass loss supports the hypothesis of strange-mode oscillations. This pilot project demonstrates the importance of comprehensive monitoring of blue supergiants’ variability to deeply understand the physical properties of their stellar winds and the role of pulsations in recurrently enhancing mass loss.

Techno-economic assessment of wind power generation feasibility in Sabang

Utilization of renewable energy in Aceh is still limited mainly to small-scale electricity through micro-hydro and solar power plants, accounting for less than 1% of the energy composition. Sabang stands out as a region with significant wind energy potential, boasting a speed of 8 m/s and an average power density of 537 W/m2 for the windiest 10% of the region. Therefore, to explore the viability of harnessing wind energy, a pre-feasibility study is needed. This study aimed to assess the techno-economic feasibility of constructing a wind power plant for electricity generation in Sabang by evaluating the region's wind energy. The statistical method of the Weibull Distribution probability density function was employed to evaluate Wind Power Density (WPD), Wind Turbine Capacity Factor, and Energy Output. Additionally, economic feasibility analysis involved calculating Net Present Value (NPV), Benefit Cost Ratio (BCR), Internal Rate of Return (IRR), Discounted Payback Period (DPP), and Levelized Cost of Energy (LCOE). The results showed that Sabang exhibited favorable[UMN1] wind characteristics with a shape parameter (k) of 1.6, average wind speed (Vm) of 7.9 m/s, and scale parameter (c) of 9 m/s. These features classified Sabang as wind power class 6 with a WPD of 735 watts/m2 at a height of 50 m, and the results were categorized as excellent. The study concluded that constructing a wind power plant in Sabang using the Enercon E-70 turbine at a hub height of 100m was technically feasible. The shape parameter (k) was 1.6, the average wind speed (Vm) was 9.3 m/s, scale parameter (c) was 11 m, and the WPD reached 1213 W/m2, leading to a turbine capacity factor of 0.53 and an annual energy production (AEP) of 64,876,560 kW. The economic analysis yielded promising results for wind power projects. The DPP value was estimated at 5.6 years, the BCR at 1.96, the NPV amounted to USD 14,434,994, the IRR reached 17.9%, and the LCOE was assessed at USD 32.50/MWh. Considering all these economic indicators, it was evident that constructing a wind power plant in Sabang was highly feasible and financially viable

Picoflare jets power the solar wind emerging from a coronal hole on the Sun.

Coronal holes are areas on the Sun with open magnetic field lines. They are a source region of the solar wind, but how the wind emerges from coronal holes is not known. We observed a coronal hole using the Extreme Ultraviolet Imager on the Solar Orbiter spacecraft. We identified jets on scales of a few hundred kilometers, which last 20 to 100 seconds and reach speeds of ~100 kilometers per second. The jets are powered by magnetic reconnection and have kinetic energy in the picoflare range. They are intermittent but widespread within the observed coronal hole. We suggest that such picoflare jets could produce enough high-temperature plasma to sustain the solar wind and that the wind emerges from coronal holes as a highly intermittent outflow at small scales.

Progression of reactive gliosis and astroglial phenotypic changes following stab wound-induced traumatic brain injury in mice.

Astrocytes are the main homeostatic cells in the central nervous system (CNS) and they have an essential role in preserving neuronal physiology. After brain injury, astrocytes become reactive, and that involves a profound change in the astroglial gene expression program as well as intense cytoskeleton remodeling that has been classically shown by the up-regulation of glial fibrillary acidic protein (GFAP), a pan-reactive gene over-expressed in reactive astrocytes, independently of the type of injury. Using the stab wound rodent model of penetrating traumatic injury in the cortex, we here studied the reactive astroglial morphology and reactive microgliosis in detail at 1, 3, 7, 14, and 28 days post-injury (dpi). By combining immunohistochemistry, morphometrical parameters, and Sholl analysis, we segmented the astroglial cell population into clusters of reactive astrocytes that were localized in the core, penumbra, and distal regions of the stab wound. Specifically, highly reactive clusters with more complex morphology, increased C3, decreased aquaporin-4 (AQP4), and glutamine synthetase (GS) expression, were enriched at 7 dpi when behavioral alterations, microgliosis, and neuronal alterations in injured mice were most significant. While pro-inflammatory gain of function with peripheral lipopolysaccharide (LPS) administration immediately after a stab wound expanded these highly reactive astroglial clusters, the treatment with the NF-κB inhibitor sulfasalazine reduced the abundance of this highly reactive cluster. Increased neuronal loss and exacerbated reactive microgliosis at 7 dpi were associated with the expansion of the highly reactive astroglial cluster. We conclude that highly reactive astrocytes found in stab wound injury, but expanded in pro-inflammatory conditions, are a population of astrocytes that become engaged in pathological remodeling with a pro-inflammatory gain of function and loss of homeostatic capacity. Controlling this astroglial population may be a tempting strategy to reduce neuronal loss and neuroinflammation in the injured brain.

Examination of the Microvasculature During Wound Process of the Oral Mucosa when Using Dual-Wavelength Photodynamic Therapy: a Pre-Clinical Experimental Randomized Study

Background. Healing of open wounds in the oral cavity is often accompanied by infection and constant traumatization, which lead to impaired blood supply to the tissues, lack of trophic support and low oxygen supply to increasing proliferative processes. Recently, photodynamic therapy has taken its place among the methods for stimulating regeneration of oral mucosal tissues. The authors consider it essential to study the influence of photodynamic treatment on the functional state of the microvasculature in the wound tissues, which determines the transcapillary exchange and the tissue respiration, providing the tissue regeneration.Objective. To study the photodynamic effect of sequential dual-wavelength radiation on the microvasculature in the wound tissues of the oral mucosa in vivo.Methods. The study was carried out on 36 female outbred Wistar rats, weighing 200–250 g. The animals were divided into two groups: control group (n = 18) and experimental group (n = 18). Wound surfaces healed by secondary intention were modeled on the cheek mucosa of the animals. Dual-wavelength photodynamic therapy was performed in the 1st postoperative day in experimental group. The microcirculatory function was assessed by Doppler flowmetry before, and on days 3, 7 and 14 after wounding. The results were processed using IBM SPSS Statistics 26.0.0.1 (IBM Inc., USA).Results. It has been established that dual-wavelength photodynamic therapy has a positive effect on the restoration of the microvasculature of the wound tissues. This therapy facilitated bypassing for microcirculatory flow on the 3rd day of the study, and increased the perfusion of tissues on the 7th. The experimental group did not have congestive-ischaemic phenomena in the wound region; the microcirculatory flow was augmented through the microcirculation regulation by the 14th day.Conclusion. Following the obtained results the use of dual-wavelength photodynamic therapy can be considered as a promising method for restoration of the microvasculature of tissues in the oral mucosal trauma.

Transport and Acceleration of O+ Ions in Upstream Solar Wind Due To Impact of an IMF Discontinuity: 3D Global Hybrid Simulation

AbstractBased on the predictions of global 3D hybrid simulations, we present a new transport/acceleration path for escaped O+ ions in the upstream solar wind region resulting from the impact of a particular IMF tangential discontinuity (TD) with negative (positive) IMF Bz on the discontinuity's anti‐sunward (sunward) side. For O+ ions escaping to the duskside magnetosheath and with gyro‐radii larger than the TD thickness, when they encounter the TD, they can first go sunward into the upstream solar wind. They then gyrate clockwise to the pre‐noon side and get accelerated within the solar wind region and circulate back to the dawnside magnetosphere. These ions may be accelerated to well within the ring current energy range depending on the solar wind electric field strength. This new transport/acceleration path can bring some of the escaped ions into the inner magnetosphere, thus providing a new mechanism for generating an O+ ring current population.

Deciphering the Birth Region, Formation, and Evolution of Ambient and Transient Solar Wind Using Heavy Ion Observations

Deciphering the Birth Region, Formation, and Evolution of Ambient and Transient Solar Wind Using Heavy Ion Observations

Density streams in the disc winds of Classical T Tauri stars

ABSTRACT Spectral and photometric variability of the Classical T Tauri stars RY Tau and SU Aur from 2013 to 2022 is analysed. We find that in SU Aur the H α line’s flux at radial velocity RV = −50 ± 7 km s−1 varies with a period P = 255 ± 5 d. A similar effect previously discovered in RY Tau is confirmed with these new data: P = 21.6 d at RV = −95 ± 5 km s. In both stars, the radial velocity of these variations, the period, and the mass of the star turn out to be related by Kepler’s law, suggesting structural features on the disc plane orbiting at radii of 0.2 au in RY Tau and 0.9 au in SU Aur, respectively. Both stars have a large inclination of the accretion disc to the line of sight – so that the line of sight passes through the region of the disc wind. We propose there is an azimuthal asymmetry in the disc wind, presumably in the form of ‘density streams,’ caused by substructures of the accretion disc surface. These streams cannot dissipate until they go beyond the Alfven surface in the disc’s magnetic field. These findings open up the possibility to learn about the structure of the inner accretion disc of CTTS on scales less than 1 au and to reveal the orbital distances related to the planet’s formation.

Impact of moist wound dressing on wound healing time: A meta-analysis.

Among the assortment of available dressings aimed at promoting wound healing, moist dressings have gained significant popularity because of their ability to create an optimal environment for wound recovery. This meta-analysis seeks to compare the effects of moist dressing versus gauze dressing on wound healing time. A comprehensive literature search was conducted, encompassing publications up until April 1, 2023, across multiple databases including PubMed, Web of Science, China National Knowledge Infrastructure (CNKI), and Cochrane Library. Stringent criteria were used to determine study inclusion and evaluate methodological quality. Statistical analyses were performed utilizing Stata 17.0. A total of 13 articles, encompassing 866 participants, were included in the analysis. The findings indicate that moist dressing surpasses gauze dressing in terms of wound healing time (standard mean difference [SMD] -2.50, 95% confidence interval [CI] -3.35 to -1.66, p < 0.01; I2 = 97.24%), wound site infection rate (odds ratio [OR] 0.30, 95% CI 0.17 to 0.54, p < 0.01; I2 = 39.91%), dressing change times (SMD -3.65, 95% CI -5.34 to -1.97, p < 0.01; I2 = 96.48%), and cost (SMD -2.66, 95% CI -4.24 to -1.09, p < 0.01; I2 = 94.90%). Subgroup analyses revealed possible variations in wound healing time based on wound types and regions. This study underscores the significant advantages associated with the use of moist dressings, including expedited wound healing, reduced infection rates, decreased frequency of dressing changes, and lower overall treatment costs.

The flow in the induction and entrance regions of lab‐scale wind farms

AbstractWith the increasing demand for wind energy, it is important to be able to understand and predict the available wind resources. To that end, the present wind tunnel study addresses the flow in the induction and entrance region of wind farms through particle image velocimetry, with focus on differences between actuator disks and two‐bladed rotating wind turbine models. Both staggered and aligned farm layouts are examined for three different incoming wind directions. For each layout, 69 disks or turbines are used, and the field of view ranges from 12 rotor diameters upstream of the farms to 8 diameters downstream of the first row. The results show that the induction, or blockage effect, is higher for the disks, even though the thrust (or drag) coefficient is the same. In contrast, the wake is stronger downstream of the turbines. The orientation and layout of the farm do not have a major impact on the results. Modal decomposition of the flow shows that the flow structure similarity between the disk and turbines improves downstream of the second row of wake generating objects, indicating that the substitution of wind turbines by actuator disks is more appropriate for wind farms than for the investigation of single wakes.

Design and implementation of a bioclimatic housing prototype for the Bolivian highlands

The Mechanical - Electromechanical Engineering research institute, made up of a multidisciplinary team, designs and implements a bioclimatic housing prototype for the Bolivian highlands, located near the Andes Mountains at an altitude of 3,000 to 4,000 meters above sea level. This project was developed and implemented with financing from the Swiss Cooperation for Bolivia, within the Climate Change Adaptation projects.&#x0D; The design process includes: the sociocultural study of the inhabitants of the region, where direct information is collected from the peasants on the conception of housing in their culture and ancestral construction characteristics of their houses. Subsequently, the climate of the region (temperatures, solar radiation, winds and relative humidity) is characterized with the help of a meteorological station, which provided historical records of 5 years. Those data were sufficient to be able to carry out a reliable characterization, with which the Typical Meteorological Year is determined. Likewise, local construction materials that may be useful in the design are studied, analyzing their thermal and mechanical properties in the laboratory.&#x0D; Finally, with all the information described, an architectural design is carried out taking into account bioclimatic aspects, ways of harnessing solar energy, distribution of the room and a viable construction cost for the economic reality of the region. The developed architectural model is optimized in an energy simulation program (Siter Vs. 1.2), achieving energy savings of 65%. The software used is owned property of the research institute&#x0D; The house has been monitored with temperature sensors for about a year and six months, to date it shows good results, where the correct functioning of the elements and constructive forms is evidenced, reflecting a temperature inside the house of around 10 °C above room temperature 24 hours a day.

Performance of reinforced lightweight geopolymer composite panels subjected to windborne debris impacts

Lightweight panels have been widely employed as building envelopes in construction. As a result of the rising demand for environmentally friendly building materials, the authors recently developed a lightweight geopolymer composite (LGC) material and investigated the performance of reinforced LGC panels under static loading. Superior performance of LGC panels as compared to conventional panels such as autoclaved aerated concrete (AAC) panels has been observed, demonstrating their potential applications. During strong winds, building envelopes might be subjected to windborne debris impact, which could threaten residents and facilities and lead to structural failure. To explore the application potentials of LGC panels in strong wind regions, in this study, the performances of LGC panels subjected to windborne debris impact were investigated and compared with those of AAC panels by using a pneumatic cannon testing system. The failure modes and damage levels under different impact scenarios of LGC and AAC panels and their impact resistance capacities were obtained, compared and quantified in terms of the projectile residual velocity, penetration length and opening size. The effects of matrix materials, panel thicknesses, impact locations, reinforcement spacings and projectile impact velocities on their impact resistance performance were analyzed. For comparison, the punching shear capacities of the panels were also quasi-statically tested and analyzed subjected to the same projectile employed in the impact tests.

CRYOWRF—Model Evaluation and the Effect of Blowing Snow on the Antarctic Surface Mass Balance

AbstractThe surface mass balance (SMB) of large polar ice sheets and of snow and ice surfaces in general are incompletely understood because of the complexity of processes involved. One such process, drifting and blowing snow, has only been considered in a very simplified way in current meteorological and climatological models. To address this problem, the CRYOWRF model has been developed, a coupled model between the meteorological Weather Research and Forecasting model (WRF) and the snow model SNOWPACK, augmented by a detailed treatment of drifting and blowing snow. Applying CRYOWRF to the SMB of Antarctica, we find that the model reproduces measurements of SMB with similar errors than current models. Drifting and blowing snow and its sublimation play a particularly important role, especially in regions of strong katabatic winds. The CRYOWRF simulations are also in line with satellite estimates of blowing snow frequency. There is a need to further consolidate results by simulations with a higher grid resolution and by including more measurements of SMB contributions from snow fall to transport and sublimation.

MRLC controls apoptotic cell death and functions to regulate epidermal development during planarian regeneration and homeostasis.

Adult stem cells (ASCs) are pluripotent cells with the capacity to self-renew and constantly replace lost cells due to physiological turnover or injury. Understanding the molecular mechanisms of the precise coordination of stem cell proliferation and proper cell fate decision is important to regeneration and organismal homeostasis. The planarian epidermis provides a highly tractable model to study ASC complex dynamic due to the distinct spatiotemporal differentiation stages during lineage development. Here, we identified the myosin regulatory light chain (MRLC) homologue in the Dugesia japonica transcriptome. We found high expression levels of MRLC in wound region during regeneration and also expressed in late epidermal progenitors as an essential regulator of the lineage from neoblasts to mature epidermal cells. We investigated the function of MRLC using in situ hybridization, real-time polymerase chain reactionand double fluorescent and uncovered the potential mechanism. Knockdown of MRLC leads to a remarkable increase in cell death, causes severe abnormalities during regeneration and homeostasis and eventually leads to animal death. The global decrease in epidermal cell in MRLC RNAi animals induces accelerated epidermal proliferation and differentiation. Additionally, we find that MRLC is co-expressed with cdc42 and acts cooperatively to control the epidermal lineage development by affecting cell death. Our results uncover an important role of MRLC, as an inhibitor of apoptosis, involves in epidermal development.

A new perspective on quantitative assessment of photodynamic therapy mediated hydrogel nanocomposite in wound healing using objective biospeckle and morphological local-gradient

Skin wounding is a serious public health issue, especially when considering factors that accelerate tissue recovery. Consequently, the use of photodynamic therapy (PDT) as an effective wound-healing treatment has attracted more scientific attention. Although assessing the wound healing rate is crucial for appropriate monitoring of the probability of wound healing and evaluating the treatment efficiency, the currently used techniques lack the ability to provide such information. Therefore, this study has two aims, first, it contributes to the development of a new image-guided biospeckle system for quantitative monitoring of skin wound healing rate. Second, it evaluates the potential of using a novel synthesized PDT-mediated polyethylene glycol fabric with methylene blue (PEG-MB) hydrogel nanocomposite in accelerating wound healing. The proposed imaging system initially acquires raw biospeckle images from the wound regions of adult healthy albino mice treated with the synthesized hydrogel nanocomposite. Each raw biospeckle image is then converted into maps of morphological local-gradient matrices implemented from the combination of dilation and erosion operations at different radii up to 25 pixels. Subsequently, their intensity histogram statistics are computed, taking central moments as the feature set. Final characterization is achieved via a linear combination of the biospeckle statistics maintaining as much variance as possible using principal component analysis (PCA). The results confirmed by cytokine concentration measurement and histological investigation demonstrate that the innovative biospeckle image-guided system is ideal for investigating wound healing and suggest the potential of the hydrogel nanocomposite as an active dressing.

On the Evolution of, and Hot Gas in, Wind-Blown Bubbles around Massive Stars - Wind Bubbles Are Not Energy-Conserving

The structure and evolution of wind-blown bubbles (WBBs) around massive stars has primarily been investigated using an energy-conserving model of wind-blown bubbles. While this model is useful in explaining the general properties of the evolution, several problems remain, including inconsistencies between observed wind luminosities and those derived using this formulation. Major difficulties include the low X-ray temperature and X-ray luminosity, compared to the model. In this paper, we re-examine the evolution, dynamics, and kinematics of WBBs around massive stars, using published ionization gasdynamic simulations of wind-blown bubbles. We show that WBBs can cool efficiently due to the presence of various instabilities and turbulence within the bubble. The expansion of WBBs is more consistent with a momentum-conserving solution, rather than an energy-conserving solution. This compares well with the dynamics and kinematics of observed wind bubbles. Despite the cooling of the bubble, the shocked wind temperature is not reduced to the observed values. We argue that the X-ray emission arise mainly from clumps and filaments within the hot shocked wind region, with temperatures just above 106 K. The remainder of the plasma can contribute to a lesser extent.

Analysis of the Possibilities of Short-Term Prediction of Geomagnetic Perturbations from Observations of Coronal Mass Ejections at the BSA LPI Radio Telescope

From April 2021 to October 2022, in the monitoring data obtained daily at the Big Scanning Antenna radio telescope (BSA LPI), 11 events were identified for which X-ray flares in the solar corona were followed by magnetic storms on Earth. Interplanetary scintillation monitoring data were considered together with data on solar flare activity and a simple kinematic model of ejection propagation. Based on the estimated ejection velocity between the Sun and the probed region, under the assumption of a constant velocity, the time of arrival of the ejection to the Earth was calculated. Of the 11 events considered, 7 are associated with solitary flares followed by a coronal mass ejection (CME) and 4 are more complex and possibly associated with corotating perturbations or a superposition of corotating and flare perturbations. For the entire set of events, the average time of the real onset of a magnetic storm after the time predicted by the model was 3.6 h and the average time between the onset of scintillation enhancement and the onset of a magnetic storm was 20.1 h. For events associated with solitary flares, the magnetic storm began, on average, 0.8 hours after the predicted time and 15.6 hours after the onset of scintillation enhancement. The delay of magnetic storms with respect to the predicted time is apparently related to the deceleration of the ejection between the probed region of the solar wind and the Earth’s orbit.

The Emergence of a Neutral Wind Region in the Orbital Plane of Symbiotic Binaries during Their Outbursts

Accretion of mass onto a white dwarf (WD) in a binary system can lead to stellar explosions. If a WD accretes from stellar wind of a distant evolved giant in a symbiotic binary, it can undergo occasional outbursts in which it brightens by several magnitudes, produces a low- and high-velocity mass outflow, and, in some cases, ejects bipolar jets. In this paper, we complement the current picture of these outbursts by the transient emergence of a neutral region in the orbital plane of symbiotic binaries consisting of wind from the giant. We prove its presence by determining H0 column densities (N H) in the direction of the WD and at any orbital phase of the binary by modeling the continuum depression around the Lyα line caused by Rayleigh scattering on atomic hydrogen for all suitable objects, i.e., eclipsing symbiotic binaries, for which a well-defined ultraviolet spectrum from an outburst is available. The N H values follow a common course along the orbit with a minimum and maximum of a few times 1022 and 1024 cm−2 around the superior and inferior conjunction of the giant, respectively. Its asymmetry implies an asymmetric density distribution of the wind from the giant in the orbital plane with respect to the binary axis. The neutral wind is observable in the orbital plane owing to the formation of a dense disk-like structure around the WD during outbursts, which blocks ionizing radiation from the central burning WD in the orbital plane.