Search Results (47)

Christmas tree growers are concerned with improving establishment of their plantations. Here, we report the results of a series of on-farm trials conducted with grower-cooperators in the Pacific Northwest (PNW) and Great Lakes (Michigan—MI) regions to determine the efficacy of treatments at planting on improving tree survival and growth in Christmas tree plantations. Cooperating growers planted species that were typical for each region (Fraser fir in the Great Lakes and Douglas-fir and noble fir in the PNW) and managed the plantings using standard cultural practices, aside from test treatments. Test treatments varied between locations and years but included wood chip mulch, shade blocks, an anti-transpirant, biochar, fertilizers, and various root dips including polymer gels, mycorrhizae, and bio-stimulants. Overall, treatments that directly modified the tree environment (i.e., mulch and shade blocks) provided the most consistent benefit to tree survival and growth. In Michigan, mulching increased survival by 5% on non-irrigated farms and increased second-year shoot growth by ~3 cm. In the PNW trials, mulching increased survival of noble fir seedlings more than Douglas-fir seedlings. Installing controlled release fertilizer packets at planting increased initial growth of Douglas-firs. Application of root dips prior to planting did not improve tree survival or growth relative to dipping tree roots in water (control). Based on our results, we conclude that treatments that conserve soil moisture (mulch) or reduce tree water loss (shade blocks) offer the most direct opportunity for growers to improve initial tree survival and growth. Full article

To address the failure risks associated with long-term service of subsea Christmas tree-wellhead systems under the complex marine environment of the South China Sea, a multi-factor coupled mechanical analysis method is proposed to evaluate the system’s mechanical characteristics and ensure the safety of deepwater oil and gas production. A dynamic model of lateral vibration under seismic loading is established, considering the combined effects of earthquakes, ocean currents, and seabed soil resistance. Based on the actual operating parameters of a well in the Lingshui area of the South China Sea, a three-dimensional finite element model of the subsea Christmas tree-wellhead assembly was developed in ABAQUS 2023. The combined effects of ocean currents, seismic loading, and corrosion over long-term service were simulated to compute and analyze the distributions of stress, bending moment, and associated failure risk. The results indicate that, under a once-in-a-century current combined with seismic waves of intensity V–VI, the system risk remains controllable. However, when the seismic intensity exceeds level VII, the maximum stress and bending moment reach 324.9 MPa and 6.02 MN·m, respectively, surpassing the allowable limits for an X56-grade surface conductor. Considering corrosion effects over a 25-year service life, the extreme stress values increase by 1–5% while the bending moment increases slightly; corrosion significantly amplifies the system’s failure risk. An analysis of the mudline burial height of the subsea wellhead during long-term service shows that, within a range of 1–7 m, variations in system loading are minimal. Based on the mechanical characteristics analysis, it is recommended that the design of subsea Christmas trees and wellheads incorporate regional seismic history, specify X56-grade surface conductors to mitigate corrosion effects, and install leakage-monitoring devices at critical locations to ensure the long-term service safety of the subsea Christmas tree-wellhead system. Full article

During deepwater completion and testing, the platform and riser system are subjected to long-term motions induced by ocean currents, which may cause structural damage and potential failure of the landing string. This study investigates the mechanical and fatigue performance of a subsea Christmas tree and landing string under environmental conditions of the LH11-1 Oilfield in the South China Sea. A global–local simulation framework is used to build a coupled dynamic model of the riser–landing string system and a local model for the landing string, considering load-transfer characteristics, current profiles, periodic features, and two representative environmental conditions (typhoon and non-typhoon). For seventeen typical operating scenarios, the strength of the riser–landing string system is evaluated, and wave-induced and vortex-induced fatigue analyses are performed for the key components. The stress distribution strongly depends on operating conditions, but local strength results confirm that stresses in the primary landing string components remain below allowable limits in all scenarios. Fatigue analysis indicates that the most severe wave-induced damage in the riser occurs at its bottom section, with a fatigue life of about 15.12 years, while in the landing string, it is concentrated near the lower end, with an estimated life of about 52.68 years. The maximum vortex-induced fatigue damage occurs near the riser surface region, with a corresponding fatigue life of about 18.52 years. Full article

Balsam fir is an important specialty horticultural crop in eastern North America and commonly harvested for use as Christmas trees. Postharvest quality is a major challenge for producers, who are particularly concerned about postharvest needle retention. It was hypothesized that pyroligneous acid (PA) would help increase postharvest needle retention in balsam fir when supplied via xylem or foliage. This project first identified foliar spraying as the best application method, then designed a multivariate experiment with two factors. The first factor was foliar treatment (control, water, 1% PA, 2% PA, and 4% PA). The second factor was time, where branches were evaluated for needle abscission at 0, 2, 4, 6, and 8 weeks after harvest. The experiment was replicated 5 times and needle abscission, water uptake, chlorophyll, carotenoids, flavonoids, total phenolics, membrane injury, proline, and H₂O₂ production were all measured in response. Postharvest abscission reached 100% over the 8-week experiment and water uptake decreased by over 80%. Chlorophyll, proline, membrane injury, and H₂O₂ production all increased over time. Although PA did not improve needle retention compared to the control under the tested conditions, 4% PA spray increased proline concentration by 40% while decreasing membrane injury by 26%. Ultimately, PA did not consistently improve needle retention but did induce proline accumulation and membrane protection. Full article

Subsea Christmas trees serve as key technical equipment for subsea oil and gas development, as they regulate the flow of oil and gas at subsea wellheads. Most deep-water subsea Christmas trees deployed in China depend on imports, resulting in high procurement costs. Post-operation, these systems are typically hoisted and recovered using drill pipes and steel wire ropes. However, the harsh and dynamic deep-sea environment complicates the prediction of the tree movement posture in seawater, making safe retrieval an urgent challenge in marine oil and gas resource exploitation. Focusing on 2000 m water depth subsea Christmas tree installation and retrieval, with a specific sea area in the South China Sea as the case study, this paper applies OrcaFlex software version 11.4 to analyze drill pipe stress during retrieval and investigate movement posture changes of the tree body across different stages. Meanwhile, targeting varied operational sea conditions and integrating orthogonal test analysis, this paper quantifies the influence of parameters (wave height, ocean current velocity, and retrieval speed) on the retrieval process. The findings provide theoretical guidance and technical support for China’s deep-water subsea Christmas tree installation and retrieval operations. Full article

Coniferous species are known for their ability to purify air from particulate matter (PM), yet particulates accumulated during cultivation, transport, and outdoor storage may be transferred indoors. This study assesses the particulate load, subsequent retention, and further accumulation/release of PM by commercially available Christmas trees—Norway spruce (Picea abies (L.) H. Karst.) and Caucasian fir (Abies nordmanniana (Steven) Spach). Trees were examined in two commercial forms and maintained in six typical households (three with cut and potted P. abies, three with cut and potted A. nordmanianna) for 30 days. Measurements at four intervals included concentration dynamics of total PM, PM size fractions, as well as surface vs. in-wax PM ratios and epicuticular waxes on needles. Results showed that potted trees carried substantially higher initial PM loads than cut trees, with P. abies exceeding 200 µg·cm⁻², likely due to differences in production and handling. Potted P. abies and cut A. nordmanniana retained large PM fractions more effectively than cut P. abies. In contrast, the fine PM fraction, the most health-relevant, was best accumulated by cut P. abies. Wax-bound PM shares increased time in potted trees and decreased in the cut. Overall, the findings suggest that choosing a Christmas tree is not only an aesthetic preference but a decision with measurable implications for winter indoor air quality. Full article

Produced well flow is controlled through valves placed in the Christmas tree. Being mostly gate-type valves, they isolate the well from the surface when commanded or automatically in an emergency. The reliability of these valves is essential for subsea wells, as maintenance and replacement involve high cost, time, and HSE risks. Their design must withstand harsh conditions such as high temperature, pressure, solid particles, and corrosive environments. However, failures caused by leakage, cold welding, and the erosion of sealing elements are still common. These issues motivated the initial stage of this research, which experimentally showed that replacing the current tungsten carbide (WC) coating with polycrystalline diamond compact (PDC) material reduces friction and wear due to its high hardness and thermal stability. Based on these results, a 3D subsea gate valve model was developed and simulated in Ansys Fluent 2024 R2 under API slurry test conditions using the Oka erosion and Discrete Phase Models. A comparative analysis of WC and PDC coatings for a 5-inch gate valve exposed to a 2% sand slurry (250–400 μm) showed that PDC reduces the erosion depth by 77.6% and extends the valve lifetime by 4.5 times. The findings support the use of PDC for improved erosion resistance in subsea valve applications. Full article

Microfluidics enables precise manipulation of scarce Traditional Chinese Medicine (TCM) samples while accelerating analysis and enhancing sensitivity. Device-level structures explain these gains: staggered herringbone and serpentine mixers overcome low-Reynolds-number constraints to shorten diffusion distances and reduce incubation time; flow-focusing or T-junction droplet generators create one-droplet–one-reaction compartments that suppress cross-talk and support high-throughput screening; “Christmas-tree” gradient generators deliver quantitative dosing landscapes for mechanism-aware assays; micropillar/weir arrays and nanostructured capture surfaces raise surface-to-volume ratios and probe density, improving capture efficiency and limits of detection; porous-membrane, perfused organ-on-a-chip architectures recreate apical–basolateral transport and physiological shear, enabling metabolism-aware pharmacology and predictive toxicology; wax-patterned paper microfluidics (µPADs) use capillary networks for instrument-free metering in field settings; and lab-on-a-disc radial channels/valves exploit centrifugal pumping for parallelised workflows. Framed by key performance indicators—sensitivity (LOD/LOQ), reliability/reproducibility, time-to-result, throughput, sample volume, and sustainability/cost—this review synthesises how such structures translate into value across TCM quality/safety control, toxicology, pharmacology, screening, and delivery. Emphasis on structure–function relationships clarifies where microfluidics most effectively closes gaps between chemical fingerprints and biological potency and indicates practical routes for standardisation and deployment. Full article

Christmas markets are centres of place and culture, having heritage value through impressive histories and long-running traditions. With their array of congregation spaces, huts, and icons (Christmas trees, nativity scenes, carousels), they represent a cultural landscape en miniature, the structural elements being overlain by multisensorial elements (sounds, smells, tastes). Each of these factors are market-distinctive, as are space and place connections, with each heritage landscape being unique. Collectively, these markets represent a cross-national cultural landscape temporarily unifying communities with different cultural traditions. However, transition examination is limited, and missed experiences or future projections have not yet been addressed. Utilising on-site interviews at five Christmas markets in Germany and UK (Dresden, Mainz, Frankfurt, Offenbach, Birmingham) in 2023, we examine changes over remembered time—what was missed, what has emerged, and what future projections were envisaged. While each market is distinctive, overall trends included a decrease in artisanal products and a concomitant increase in gastronomy, an increase in tourism/commerciality, and diminished traditional experience—with factors including policy/administration control and shifting social demographics. Future projections included diminished ambiance, lessened authenticity, and more commercialisation. Our findings highlight potential conflicts considering transition/development across these cultural landscapes, and issues with respect to heritage and cultural integrity. Full article

This study investigates self-pulsation phenomena in a liquid-centered swirl coaxial injector with a recess length of 4 mm, under varying liquid flow conditions, using numerical simulations. The simulations focused on analyzing spray patterns, pressure oscillations, and dominant frequency characteristics, and the results were compared with previous experimental data. Self-pulsation, observed at liquid flow rates of 60%, 90%, and 100% of nominal values, generated distinctive periodic oscillations in the spray pattern, forming “neck” and “shoulder” breakup structures that resemble a Christmas tree. Surface waves induced by Kelvin-Helmholtz and Rayleigh-Taylor instabilities were identified at the gas-liquid interface, contributing to enhanced atomization and reduced spray breakup length. FFT analysis of the pressure oscillations highlighted a match in trends between simulation and experimental data, although variations in dominant frequency magnitudes arose due to the absence of manifold space in simulations, confining oscillations and slightly elevating dominant frequencies. Regional analysis revealed that interactions between the high-speed gas and liquid film in the recess region drive self-pulsation, leading to amplified pressure oscillations throughout the injector’s internal regions, including the gas annular passage, tangential hole, and gas core. These findings provide insights into the internal flow dynamics of swirl coaxial injectors and inform design optimizations to control instabilities in liquid rocket engines. Full article

Subsea wellheads and Christmas trees are commonly utilized in deepwater oil and gas development. However, the special structure of subsea wellheads makes it difficult to monitor casing–casing annular pressure buildup, which in turn poses a greater risk to the integrity of the wellbore. In order to analyze the effect of changes in the casing-free section and the sealed section on the variation in annulus volume, a new annular pressure buildup model of casing-cement sheath-formation deformation was established and verified according to the elastic deformation theory. Furthermore, the influence of casing deformation on annulus pressure buildup was analyzed. Results indicate that the error of annulus pressure buildup predicted by the multi-string mechanical model proposed in this paper that considers the deformation of the casing sealing section is approximately 13% lower than the one that does not consider this factor. This paper provides guidance for the design of casing strings in deepwater oil and gas wells, ensuring safe production. Full article

Common ragweed (Ambrosia artemisiifolia L.) is an extremely competitive broadleaved summer annual weed found in Christmas tree production systems within Michigan. Common ragweed has been reported to have resistance to glyphosate, PSII inhibitors, PPO inhibitors, and ALS herbicides. There have been reports from Michigan Christmas tree growers of common ragweed resistance to clopyralid, a synthetic auxin herbicide, in Montcalm County, Michigan. The objective of this study was to test alternative post-emergence herbicide combinations and organic mulch on clopyralid-resistant common ragweed for weed control efficacy. The following two stages of common ragweed were used: stage 1 (6–9 leaves) and stage 2 (12–14 leaves). For common ragweed in stage 1 in 2021 and 2022, as well as stage 2 in 2022, at all evaluation dates, mulch + clopyralid + oxyfluorfen provided the highest level of weed control. For stage 1 in 2022, this treatment combination provided 100% control from 2 weeks after treatment (WAT) and always showed better or equal weed control compared to all the other treatments. The combination of mulch + clopyralid + glyphosate provided 100% control by 2 WAT when plants were treated at stage 2 in 2022. For the plants treated at stage 1 in 2022, many of the treatments reached a fresh weight of 0 g, but in 2021, those same treatments resulted in a fresh weight of around 20 g. Based on fresh weight, the greatest plant growth occurred with glyphosate treatment in 2021 and clopyralid and mulch alone in 2022. This is likely due to common ragweed’s resistance to these herbicides. Full article

A study was conducted to identify balsam fir (Abies balsamea) for use in Christmas tree breeding programs in Northeastern North America. A total of sixty-four phenotypically good trees were identified from a provincial clonal seed orchard in New Brunswick, a multi-aged natural seed production area in Nova Scotia, and an operational plantation in Quebec, Canada. Trees were selected for good growth and form, numbers, and vigour of internodal branches, acceptable crown taper, needle colour, age class, branch angle, needle configuration, and freedom from insects and diseases or deformities, all traits deemed desirable in a Christmas tree. Three branches from each tree were collected at two harvest dates each year, one early and one late during the normal harvesting season in 2020, 2021, and 2022. Qualitative assessments of colour and branch pliability were performed weekly in conjunction with needle loss rub tests. A quantitative assessment of moisture loss was conducted weekly by measuring branch weights. The combination of qualitative and quantitative assessments was used to identify 7 of the 64 trees for which one or more tested branches consistently remained green and pliable, retained the majority of their needles, and lost moisture at a significantly reduced rate in all six testing periods. Grafts of the seven ‘Select’ trees are currently being integrated into seed orchards in the three participating provinces. These second-generation seed orchards are part of breeding programs designed to develop Christmas trees that will perform well under warm fall conditions, an outcome of climate change. The results from this study combined with the progeny testing of the ‘Select’ trees will be used to test for the heritability of needle retention, a key trait for the next generation of Christmas trees in the Northeast. Full article

The subsea jumper has become an essential part of subsea production systems as a gas–liquid mixing pipeline connecting the pipeline end manifold (PLEM) to the Christmas tree. During oil and gas transportation, as a common flow pattern, the alternating flow characteristics of the slug flow easily cause pipeline vibration, resulting in pipeline instability or fatigue damage. The present study investigates experimentally and numerically the slug flow characteristics in the subsea M-shaped jumper and its induced vibrations of the jumper. The flow pattern evolution and slug characteristics of the inner slug flow under different gas–liquid velocities are obtained: the slug frequency and slug velocity, as well as the pressure fluctuation and vibration characteristics caused by the slug flow. The results show that the pressure fluctuations in the front and rear parts of the M-type jumper are obviously different. With the increase in the air–water mixing, the two characteristics, the slug frequency, and the slug velocity also increase. The gas velocity has a greater influence on the slug frequency than the liquid velocity. The slug length decreases as the slug frequency increases. Furthermore, numerical simulations under various experimental conditions are carried out. The results show that the simulation results of the pressure data, the slug characteristics, and the induced vibration amplitude are in good agreement with the experimental data. Full article

Underwater pressure-bearing structures are produced in practice by means of pressure self-enhancement methods in order to improve the stress distribution and enhance the pressure-bearing performance. On the other hand, the pairs equation shows that stress is an important factor influencing the degradation of the structure. In fact, improving the stress distribution will not only improve the pressure-bearing performance, but will have an impact on the life degradation trend. Thus, pressure self-enhancement affects the structural life by changing the stress distribution. With this in mind, this paper considers the effect of pressure self-enhancement on the service time of subsea structures, and a Bayesian network (BN)-based method that can be used to predict the remaining useful life (RUL) of underwater self-enhanced structures is proposed. The method also takes into account the influence of multiple sources of structural factors in order to predict the RUL of the structure more accurately. The life degradation process of an all-electric Christmas tree valve actuator is used as a case study. The prediction results are compared with data in the literature to verify the validity of the method. The results have implications for guidance on the O&M assurance of underwater production systems. Full article