Longer Tube Research Articles

A comparison of two wave energy converters’ power performance and mooring fatigue characteristics – One WEC vs many WECs in a wave park with interaction effects

The production of renewable energy is key to satisfying the increasing demand for energy without further increasing pollution. Harnessing ocean energy from waves has attracted attention due to its high energy density. This study compares two generations of floating heaving point absorber WEC, WaveEL 3.0 and WaveEL 4.0, regarding their power performance and mooring line fatigue characteristics, which are essential in, e.g., LCoE calculations. The main differences between the two WECs are the principal dimensions and minor differences in their geometries. The DNV software SESAM was used for simulations and analyses of these WECs in terms of buoy heave motion resonances for maximising energy harvesting, motion characteristics, mooring line forces, fatigue of mooring lines, and hydrodynamic power production. The first part of the study presents results from simulations of unit WEC in the frequency domain and in the time domain for regular wave and irregular sea state conditions. A verification of the two WECs’ motion responses and axial mooring line forces is made against measurement data from a full-scale installation. In the second part of the study, the influence of interaction effects is investigated when the WECs are installed in wave parks. The wave park simulations used a fully-coupled non-linear method in SESAM that calculates the motions of the WECs and the mooring line forces simultaneously in the time domain. The amount of fatigue damage accumulated in the mooring lines was calculated using a relative tension-based fatigue analysis method and the rainflow counting method. Several factors that influence the power performance of the wave park and the accumulated fatigue damage of the mooring lines, for example, the WEC distance of the wave park, the sea state conditions, and the direction of incoming waves, are simulated and discussed. The study's main conclusion is that WaveEL 4.0, which has a longer tube than WaveEL 3.0, absorbs more hydrodynamic energy due to larger heave motions and more efficient power production. At the same time, the accumulated fatigue damage in the moorings is lower compared to WaveEL 3.0 if the distance between the WECs in the wave park is not too short. Its motions in the horizontal plane are larger, which may require a larger distance between the WEC units in a wave park to avoid losing efficiency due to hydrodynamic interaction effects.

Transcriptomic Analysis Suggests Auxin Regulation in Dorsal-Ventral Petal Asymmetry of Wild Progenitor Sinningia speciosa.

The establishment of dorsal–ventral (DV) petal asymmetry is accompanied by differential growth of DV petal size, shape, and color differences, which enhance ornamental values. Genes involved in flower symmetry in Sinningia speciosa have been identified as CYCLOIDEA (SsCYC), but which gene regulatory network (GRN) is associated with SsCYC to establish DV petal asymmetry is still unknown. To uncover the GRN of DV petal asymmetry, we identified 630 DV differentially expressed genes (DV-DEGs) from the RNA-Seq of dorsal and ventral petals in the wild progenitor, S. speciosa ‘ES’. Validated by qRT-PCR, genes in the auxin signaling transduction pathway, SsCYC, and a major regulator of anthocyanin biosynthesis were upregulated in dorsal petals. These genes correlated with a higher endogenous auxin level in dorsal petals, with longer tube length growth through cell expansion and a purple dorsal color. Over-expression of SsCYC in Nicotiana reduced petal size by regulating cell growth, suggesting that SsCYC also controls cell expansion. This suggests that auxin and SsCYC both regulate DV petal asymmetry. Transiently over-expressed SsCYC, however, could not activate most major auxin signaling genes, suggesting that SsCYC may not trigger auxin regulation. Whether auxin can activate SsCYC or whether they act independently to regulate DV petal asymmetry remains to be explored in the future.

Numerical Study on Effects of Structure Parameters and Operating Conditions on the Micro-Tubular SOFC Stack Performance

A multi-physical field coupled three dimensional model of large-scale micro-tubular solid oxide fuel cell (MTSOFC) stacks was established in this study. The effects of structural parameters and operating conditions, namely configuration of the tube array, diameter, length, distance between tubes, the flow rate and flow path of air, on the stack performance were studied. The triangular array is more compact in space and can achieve higher volume specific power than the square array. However, the more concentrated arrangement also results in a higher local temperature and temperature difference, which is challenging for long-term stability. According to the simulation results, smaller tube diameter and distance between tubes lead to higher volume specific power, with the former having a marginal effect. A longer tube can reduce the axial temperature gradient, which is conducive to long-term operation stability. Increasing the air flow rate of the cathode is the most effective method to reduce the highest temperature. Furthermore, the co-flow arrangement is found to be more helpful to take away the heat generated by the stack than the counter-flow arrangement. Based on the simulation results, the structural parameters and operation conditions suitable for a large-scale micro-tubular SOFC stack are decided, considering the output power, long-term stability, and mechanical strength. The model is demonstrated as a powerful tool for the design and optimization of MTSOFC stacks.Key words: Micro-tubular SOFC Stack; Array Configuration; Structure Parameter; Operation Condition; Volume Specific Power

Ruehssia quirinopolensis (Apocynaceae), a new species from the Cerrado Domain, Brazil

Abstract A new species of Apocynaceae, Ruehssia quirinopolensis, endemic to Serra da Confusão do Rio Preto and Serra da Igrejinha, Quirinópolis, state of Goiás, Brazil, is described and illustrated. It resembles R. rupestris, differing by the white corolla, adaxially villose and with a longer tube, and by its corona lobes with the upper portion lanceolate. Besides a distribution map for the new species, we provide a key to identify the nine species of Ruehssia that occur in Goiás. Ruehssia quirinopolensis is assessed here as Critically Endangered (CR).

Coupling mechanism of natural gas deflagration flame and continuous water in closed pipeline

In order to reveal the propagation characteristics and hazards of a gas explosion in urban drainage pipeline, the dynamic evolution of a methane deflagration in a closed water-containing pipeline was numerically simulated based on Computational Fluid Dynamics (CFD). The interaction mechanism between water oscillation and flame development during the methane deflagration was such revealed. The results show that the presence of water accelerates the flame propagation in the forward accelerating stage. However, the water generally played a significant role in inhibiting the flame propagation because of its cooling and blocking effects. And the flame acceleration may be enhanced with the water present if a longer tube is employed. The shear force generated by the compression wave acting on the stagnant water surface provides the most primitive power for the movement of water, which creates ripples in the calm water. The obstacles and the reciprocating motion of the compression wave make the water ripple and evolve into lifting thin water columns. The shearing effect of high-speed gas flow evolves the water columns into discrete water droplets. This evolution process of the water body increases the contact area between water and flame, thus blocking the transfer of heat and the expansion wave, inhibiting the self-sustained flame propagation, leading to its gradual extinction.

A Third, New Species of Cremosperma (Gesneriaceae) from Panama

A new species of Cremosperma Benth. is described from Panama, bringing the total for the country to three. One species, C. maculatum L. E. Skog, occurs in the province of Chiriquí and also in Colombia and Costa Rica; the second, C. veraguanum Wiehler, occurs in the provinces of Bocas del Toro, Coclé, and Veraguas; and the new species, C. colonense L. E. Skog, Barrie & McPherson, has only been found in the province of Colón and is distinguished from the others by having larger leaves and corollas white with yellow in the throat. The new species is distinguished from C. ecuadoranum L. P. Kvist & L. E. Skog of eastern Ecuador by its branched habit, sericeous peduncles, the corolla white with yellow in the throat and a longer tube, and the usually longer calyx with wider lobes. Based on IUCN criteria, C. colonense is provisionally assessed as Endangered. A key is provided to the Mesoamerican species.

Pouteria citriodora, a New Species of Sapotaceae (Chrysophylloideae) from Brazil

A new species assigned to the genus Pouteria is described and illustrated. Pouteria citriodora is morphologically related to Pouteria procera but differs from itmainly by its axillary and isolated flowers (3–15-flowered in P. procera), calyx aestivation quincuncial (convolute/contorted in P. procera), longer tube corolla (5.0–7.3mmlong vs. 1.75–3.5mmlong in P. procera), and fruits with whitish dots on the surface and a very distinctive Citrus-like smell. Herein environmental, geographic distribution and conservation data for the new species are provided. In addition, a key to species of Pouteria with 5-merous flowers from Bahia state-Brazil is presented.

Experiment and simulation for the crushing of tailor rolled tubes with various geometric parameters

By properly controlling the parameters of the rolling mill, multiple types of tailor rolled blanks (TRBs) are obtained, which in turn are used to form the tailor rolled tubes (TRTs) with axially varied thickness. Axial-crushing tests have been performed, and the results show that the reaction forces of TRTs show a rising trend with the integrative effect of crushing and repetitive load fluctuations after reaching the relatively low initial loads. Furthermore, investigations of different thickness and lengths are introduced into the TRT structures. It can be concluded that more energy can be absorbed for TRTs when choosing more edge numbers of the polygonal cross-sections. By contrast, the biggest difference in energy absorption is between the triangle and circular section shape, which is about 43.4%. In addition, the energy absorption capacities of TRTs with longer tube or side lengths are improved, but the energy absorption efficiencies are decreased by 21.76% and 8.7%, respectively. Meanwhile, the various distributions of transition zone and layout mode not only alter the characteristics of load curves but also affect the energy absorption capacity and initial resistance. Furthermore, multi-tube structures including TRTs, tailor welded tubes (TWTs) and traditional uniform tubes (UTs) are introduced to carry out the contrast crushing experiments. The initial peak loads of TRTs are the lowest, which are in the range of 43.05–58.28 kN. For the energy absorption, the UT structures can absorb more energy before the moving head reaches about 2/3 of the overall collapse stroke. However, the ability of TRTs to absorb energy is improved significantly in the later stage, making the overall energy absorption greater than in UTs. The reasons for the improved energy absorption efficiency of TRTs are discussed in detail. The corresponding FE models considering the variation of thickness and material properties of TRTs are established and verified with the experiment results. In order to conveniently predict the energy absorption performance of crushing TRTs, mathematical models are adopted.

Fabrication of TiO2 nanotube arrays of different dimension for photocatalytic decomposition of IPA in air streams

TiO2 nanotube arrays (TNTs) were fabricated by anodization under various operational conditions. Dimensions of fabricated TNTs were significantly influenced by the temperature and water content of ethylene glycol-based electrolyte prepared for anodization. TNTs of longer length, larger inner diameter, and thinner wall thickness were fabricated in electrolytes of higher temperatures. For TNTs fabricated in electrolyte containing higher water contents, the relatively fast dissolution of TiO2 led to the formation of TNTs of shorter tube length and larger inner diameter. TNTs were fabricated under different anodization conditions (mainly the water content in ethylene glycol electrolyte and anodization time) to exhibit similar tube length and different inner diameters. Experiments conducted using TNTs of longer tube lengths and smaller inner diameters demonstrated higher photocatalytic decompositions of gaseous isopropyl alcohol (IPA); however, the photocatalytic application of TNTs is limited by the penetration of illumination.

Effect of pipe geometry and material properties on flow characteristics and thermal performance of a conical Hartmann–Sprenger tube

The Hartmann–Sprenger resonance tube is an acoustic device which is the basic part of acoustic igniters with no moving part or electrical spark. In this paper, effects of some design specifications on internal oscillatory flow and thermal performance of a conical Hartmann–Sprenger resonance tube are studied using both experimental and numerical methods. For numerical simulations, an implicit density-based 2D model with second-order upwind scheme is applied. To study the effects of geometrical and material specifications, a set of six different case studies with conical shapes is defined. The conical shape of the tube is selected due to its higher thermal effects and its extreme usage in thermal applications. The parameters to be changed here are pipe material, pipe length, gap distance, and the end wall condition which could be closed or perforated for hot gas extraction. Diagrams of temperature vs.entropy are plotted and compared with each other for all cases in which temperature rise is observed. The results indicated that as the gap distance changes, no oscillatory flow and no sensible temperature rise happens. A tiny hole on the tube end wall reduces the temperature inside the tube, as the shorter tube does. For longer tubes, the frequency of oscillations is proportional to the tube fundamental resonance frequency. Using materials with lower thermal conductivity in the tube wall could produce higher temperatures inside the tube. Here, maximum temperature is achieved in longer closed-end tube with lower thermal conductivity material.

Reassessment of thePsychotria speciosaG. Forst. (Rubiaceae) complex in Tahiti, Society Islands, with a new combination and description of new species,Psychotria paulaeJ.-Y. Meyer, Lorence & J. Florence, sp. nov.

The genus Psychotria L. (Rubiaceae) is one of the most diverse in the Pacific, including the islands of French Polynesia with 28 described endemic species. The Psychotria speciosa G. Forst. complex is evaluated, and P. speciosa is lectotypified and an epitype designated. The new combination Psychotria trichocalyx (Drake) Fosberg ex J.-Y. Meyer, Lorence & J. Florence, comb. nov., is made based on Calycosia (Uragoga) trichocalyx. The new species Psychotria paulae J.-Y. Meyer, Lorence & J. Florence, sp. nov., endemic to Tahiti (Society Islands), is described and illustrated. It differs from the closely related Psychotria speciosa by having leaves with longer petioles (up to 5 cm long), flowers fewer per inflorescence (1–3) and with longer pedicels up to 15 mm long, calyx with longer tube and short lobes, a 5–7-lobed corolla, longer fruit pedicels up to 4 cm long, and cylindrical to ovoid fruits 2–3 cm long. The conservation of this extremely rare species, known from only one locality on Tahiti and directly threatened by invasive alien plants (proposed IUCN status: CR), is a priority.

Thermal energy storage characteristics of sand as filler material for solar thermocline tank

The feasibility of sand at various grain sizes as filler material for solar sensible heat thermal energy storage(TES) was investigated. An indirect contact sensible heat TES experiment setup was built. The TES section is a cylindrical tank, which is embedded with 19 stainless tubes arranged like a hexagonal honeycomb. Air was chosen as the heat transfer fluid to flow inside the tubes and carry heat, while the sand in the tank contacts the outside of tubes. Four types of sand: silver sand, medium sand, filter sand and coarse sand, were selected. The results show that voidage is the determining factor for the TES performance rather than density or grain size. Coarse sand is the best among the four types. For materials such as sand whose basic thermal properties only vary a bit, the change of charge temperature can hardly affect the TES performance. When using air as the heat transfer fluid, the TES efficiency is relatively lower. To enhance heat transfer, a lower air velocity or longer tube length is needed. The simplified 2-D simulation results match well with the experimental results and can be used for the prediction of large scale TES tank performance.

Uncertainty analysis: Design of a fouling test device for the liquid-to-refrigerant heat exchangers

Fouling usually builds up on the waterside heat transfer surface of heat exchangers after long-term operation due to the impurity of the working water. Fouling research is important in the HVAC&R and chemical industries in order to develop fouling mitigation strategies and to direct manufacturers and designers for producing better heat exchangers. Fouling thermal resistance was studied using a heat exchanger installed in a testing system, which should have a high accuracy. Many operation parameters could affect the fouling test, thus a thorough design of the testing system is necessary to get reliable and robust data. This paper analyzes the effect of different operating parameters on the uncertainty of the fouling test results (fouling thermal resistance), including the length of the test tube, the surface heat transfer coefficient, the heat flux, the water velocity, and the fouling thermal resistance. Results show that the fouling test on tubes with higher surface heat transfer coefficient has a higher accuracy; Longer tube, higher heat flux, and lower water velocity can reduce the test uncertainty; When the fouling resistance is lower than 1E-5 m2K/W, the uncertainty is very high. The work in this paper is intended to help other fouling researchers to build a reliable test set-up so as to achieve accurate and comparable results.

Guided motion of short carbon nanotube driven by non-uniform electric field

The molecular dynamics simulations are performed to show that in aqueous environments, a short single-walled carbon nanotube (SWCNT) guided by a long SWCNT, either inside or outside the longer tube, is capable of moving along the nanotube axis unidirectionally in an electric field perpendicular to the carbon nanotube (CNT) axis with the linear gradient. The design suggests a new way of molecule transportation or mass delivery. To reveal the mechanism behind this phenomenon, the free energy profiles of the system are calculated by the method of the potential of mean force (PMF).

Magnetic Microstructure of Rolled‐Up Single‐Layer Ferromagnetic Nanomembranes

The magnetic microstructure of rolled-up magnetic nanomembranes is revealed both theoretically and experimentally. Two types of nanomembranes are considered, one with a non-magnetic spacer layer and the other without. Experimentally, by using different materials and tuning the dimensions of the rolled-up nanomembranes, domain patterns consisting of spiral-like and azimuthally magnetized domains are observed, which are in qualitative agreement with the theoretical predictions.

Template Assisted Fabrication of TiO<sub>2</sub> and BaTiO<sub>3</sub> Nanotubes

This paper discussed fabrication of TiO2 and BaTiO3 nanotubes by sol-gel method and used anodic aluminum oxide (AAO) as template. The mechanical properties of TiO2 or BaTiO3 NTs are not great, so a longer tube can crack easily, leading to the peeling off of the NTs film from the Ti substrate. Therefore, we propose to use AAO as a template, followed by deposition of TiO2 and BaTiO3 NT inside AAO to make a working electrode for further electronic devices.

Length-controlled few-walled carbon nanotubes and their effect on the electrical property of flexible transparent conductive films

We investigated the effect of the length of carbon nanotubes (CNTs) on the electrical property of CNT-based flexible, transparent, and conductive films (TCFs). We grew vertically aligned CNTs with controlled lengths, dispersed them in ethanol by ultrasonication, and spray coated them onto polyethylene terephthalate (PET) sheets. We focused on the variation in the sheet resistance and transmittance of the above-mentioned films as a function of the CNT length, and we found that the optimum CNT length was 200 μm. We concluded that the CNT length should be carefully optimized because a shorter tube affords the advantage of efficient dispersion, while a longer tube helps in reducing the number of contact points between tubes along the electrical conduction path.

Effects of geometric and crystal structures on the photoelectrical properties of highly ordered TiO2 nanotube arrays

Abstract

Evolution of kaolinite subgroup minerals and mixed-layer illite/smectite in the Paleogene Damintun Depression in Liaohe Basin of China and its implication for paleotemperature

The oil-rich Damintun Depression is located in the Liaohe Basin, Northeast China, and was formed during the Paleogene. The major oil-producing strata in the depression are mudstone and shale. To explore the burial diagenetic history of the basin and the formation thresholds of hydrocarbons, the characters of the kaolinite subgroup minerals and mixed-layer illite/smectite in the mudstone and the shale are studied by using X-ray diffraction, electron probe, scanning electron microscope, and Fourier infrared spectrum. The kaolinite subgroup consists of kaolinite and halloysite. The kaolinite is flake-like or vermiform-like. The halloysite is in long tubular shape and its length is related to its iron content. A longer tube has lower iron content. The crystallinity of kaolinite is 0.40 °2θ, and its degree of order increases from 0.03 to 1.17 with the burial depth. Kaolinite is in disorder when the buried depth is less than or equal to 2479 m , and it is partially ordered when the buried depth is greater than 2479 m. Kaolinite is supposed to turn into dickite when the depth is greater than 2550 m, but low penetrability and low porosity of the shale and mudstone prevent such a change. The mixed-layer illite/smectite changes from disorder to order continually as the buried depth increases. Its disorder (R0I/S), as defined by illite layer content (I%), is smaller than 50% at depths less than 2550.25 m. Based on Hoffman & Hower’s model, the paleo-geothermal gradients of 3.37–3.76°C/100 m (3.57°C /100 m on average) can be derived in the Paleocene Damintun Depression, which is significantly higher than the present geothermal gradient (2.9°C/100 m). The threshold depth of the oil formation in the depression is about 2550 m. Damintun Depression, Paleogene, kaolinite, halloysite, mixed-layer illite/smectite, mixed-layer illite/smectite geothermometer, paleo-geothermal gradient

Estudios sobre Rubiáceas Mexicanas XXVI.ParadeppeaBorhidi sectio nova del génerodeppeaSchltdl. Et Cham. (Hamelieae) y dos especies Nuevas de Oeste de Oaxaca

Two new species of the genus Deppea . Schltdl. et Cham. were collected in the Putla district of Oaxaca state, near to the Oaxaca-Guerrero border near to the southern end of the eastern wing of the Sierra Madre Occidental, both species belong to the group characterised by flowers of funnel-shaped corolla with longer tube than the corolla lobes, short filaments and included anthers in the throat, features different from those of the type species D. erythrorhiza and related species with rotated flowers with short tube and long corolla lobes, long exerted filaments and anthers. Based on the mentioned floral-morphological differences — similar to those detected formerly in the genus Edithea Standl. — a new section is established for a group of five species under the name Paradeppea .