Search Results (18)

Few studies have addressed jack-up substructures with spudcans for offshore wind turbines targeting multi-layer seabed conditions, which are frequently found in the Korean seabed. This study analyzed existing guidelines to establish geotechnical design procedures for a newly proposed jack-up substructure supported by tubular legs with spudcans, as well as to present design cases for a target site. This jack-up spudcan was designed for seabed conditions representative of the Korean southwestern offshore seabed, consisting of a sand–clay–sand layer. Analytical procedures from ISO and InSafeJIP guidelines were adopted to estimate the vertical bearing capacity of the spudcan. The yield envelope was determined based on this estimation, and the spudcan size was selected using structural reaction forces. Predictions from theoretical equations were compared with results from centrifuge tests for verification and discussion. Theoretical vertical capacities according to ISO match well with centrifuge results in sand-over-clay layers, while InSafeJIP shows a similar trend in intermediate clay layers. For clay-over-sand layers, only the vertical capacity formula for a single-sand layer case is available in the guidelines, which tends to overestimate the actual capacity for the underlying sand. However, by applying appropriately selected strength reduction factors, the actual foundation behavior can be reasonably predicted for design, but it is still overestimated, requiring further study. Full article

This research examines the effects of vertical jacking construction on the mechanical behavior of shield tunnels. Model tests simulating vertical jacking were performed utilizing a purpose-built apparatus to quantify the reaction forces generated by the diffusion block during the jacking operation. A systematic analysis was conducted on the mechanical responses of shield tunnel lining segments and their interconnecting joints. Utilizing Particle Flow Code (PFC) methodology, a deformation prediction model specifically tailored for vertical jacking conditions was formulated. Correlating simulation results with experimental measurements quantified the sensitivity of tunnel deformation to grouting reinforcement, enabling the identification of an optimal reinforcement zone. Key findings reveal that the jacking reaction force distribution exhibits pronounced nonlinearity: a substantial increase precedes failure, followed by rapid post-failure reduction and eventual stabilization in advanced jacking stages. Tunnel convergence deformation evolves through four distinct phases: significant growth, rapid attenuation, gradual diminution, and final stabilization. The primary zone of influence encompasses the opening ring and its two adjacent rings. Jacking induces longitudinal bending deformation, with maximum joint opening occurring at the opening ring. Abrupt longitudinal load fluctuations cause dislocation between the opening ring and neighboring rings. Internal segment stresses exhibit initial tensile and compressive increases followed by subsequent relaxation. Externally applied grouting reinforcement effectively attenuates jacking-induced tunnel deformation. An optimal reinforcement range was determined at the 60° position relative to the segment springline, substantially lowering resource consumption and construction risks compared to conventional reinforcement strategies. These outcomes furnish theoretical underpinnings and technical benchmarks for optimizing engineering design and facilitating the implementation of vertical jacking technology. Full article

In long-distance, large-section rectangular pipe jacking operations, machine deviation is an inevitable factor that poses substantial challenges to the accurate prediction of frictional resistance. To address this issue, a novel methodology is proposed to analyze the dynamic interactions at the pipe–soil–slurry interfaces. This approach integrates real-time alignment monitoring with the Winkler elastic foundation theory to enhance predictive accuracy. A comprehensive predictive framework is developed for excavation profiles and pipeline deflection curves under varying thrust distances, enabling the quantification of complex contact states. By applying Newton’s law of friction and the Navier–Stokes fluid mechanics equations, calculation methods for the frictional resistance of pipe–soil contact and pipe–mud contact are systematically derived. Furthermore, a predictive model for the jacking force in long-distance rectangular pipe jacking, accounting for complex contact conditions, is successfully established. The jacking force monitoring data from the 233.6-m utility tunnel pipe jacking project case is utilized to validate the reliability of the proposed theoretical prediction method. Parametric analyses demonstrate that doubling the subgrade reaction coefficient enhances peak resistance by 80%, while deviation amplitude exerts a 70% greater influence on performance compared to cycle parameters. Slurry viscosity emerges as a critical factor governing pipe–slurry interaction resistance, with each doubling of viscosity causing up to a 56% increase in resistance. The developed methodology proves adaptable across five distinct operational phases—machine advancement, initial jacking, stable jacking, deviation accumulation, and final jacking—establishing a robust theoretical framework for the design and precision control of ultra-long pipe jacking projects. Full article

The increasing global demand for renewable energy has resulted in a high interest in wind power, with offshore wind farms offering better performance than onshore installations. Coastal nations are thus, actively developing offshore wind turbines, where monopiles are the predominant foundation type. Despite their widespread use, the effects of monopile installation methods on the overall foundation behaviour are not sufficiently yet understood. This study investigates how different pile installation procedures—jacked and impact-driven—affect the lateral capacity of monopile foundations under both monotonic and dynamic lateral loads, by comparing them with wished-in-place monopiles, the usual assumption in design, for which no soil disturbance due to installation is considered. Three finite element 3D models were employed to simulate these cases, i.e., wished-in-place monopile, jacked, and impact-driven pile, incorporating soil zoning in the latter cases to replicate the effects of the installation methods. Comparisons between all these models, when subject to lateral monotonic and cyclic loads, are presented and discussed in terms of displacements in the soil and horizontal normal stresses. Results reveal that these installation methods significantly influence soil reactions, impacting the lateral performance of monopiles under both monotonic and dynamic conditions. The impact-driven pile demonstrated the most significant influence on the monopile behaviour. These findings highlight the need for engineers to account for installation effects in the design of monopile foundations to enhance performance and reliability, as well as the optimisation of their design. Full article

Hybrid compounds have a significant impact on agriculture as slow macro- and micronutrient administration systems. This study aimed to evaluate the synthesis and effect of the hybrid compound Nd(NO₃)₃@Zn-MOF in different concentrations on the in vitro growth of vanilla (Vanilla planifolia Jacks. ex Andrews). A total of 13 vanilla plantlets per treatment were cultivated in test tubes with semi-solid Murashige and Skoog (MS) medium and without growth regulators and treated with 0, 5, 10, 15, and 30 mg L⁻¹ of Nd(NO₃)₃@Zn-MOF. After 60 days of culture, we evaluated different morphological and biochemical parameters, such as shoot length, root length, the number of roots, the number of leaves, total chlorophyll and carotenoid content, antioxidant capacity, and phenolic compound content. Our results showed that the Nd(NO₃)₃@Zn-MOF at 10 mg L⁻¹ concentration increased plantlet length. Furthermore, we observed an increase in root length and number with the 5 and 10 mg L⁻¹ concentrations, and a decrease in these same parameters with the 15 and 30 mg L⁻¹ Nd(NO₃)₃@Zn-MOF concentrations. There were no significant differences regarding the number of leaves or total chlorophyll content. As for the antioxidant capacity, we observed an increase with 5, 10, and 15 mg L⁻¹ of Nd(NO₃)₃@Zn-MOF and a decrease with the highest concentration. Finally, the phenolic and carotenoid content decreased with the 15 and 30 mg L⁻¹ Nd(NO₃)₃@Zn-MOF concentrations compared to the control. In conclusion, the hybrid compound Nd(NO₃)₃@Zn-MOF showed beneficial effects on the growth, physiology, and biochemistry of V. planifolia in vitro when plants were treated at low concentrations. Additionally, the high concentrations used in this study did not induce toxicity. Our findings suggest that Nd(NO₃)₃@Zn-MOF could be used as a biostimulant in vanilla during its in vitro culture. However, due to the hormetic effect and the possible different reactions of different genotypes, this requires further detailed research. Full article

The selection of an appropriate slurry ingredient and its percentage ratio is a vital and necessary task for engineers in slurry pipe jacking operations. However, traditional bentonite grouting materials are difficult to degrade because of their single and non-biodegradable composition. Nowadays crosslinked polymers have been widely considered due to their excellent performance and application in engineering practices, which enlighten novel polymer slurry in pipe jacking. This study innovatively proposed using boric acid crosslinked polymers added into polyacrylamide bentonite slurry, which not only solves the shortcomings of traditional grouting materials but also meets the general working performance requirements. The new slurry’s funnel viscosity, filter loss, water dissociation ratio and dynamic shear were tested according to an orthogonal experiment. Single factor range analysis was conducted to identify the optimal mix proportion based on an orthogonal design, and the formation behavior of mineral crystals and microstructure characteristics were evaluated by X-ray diffraction and scanning electron microscopy respectively. According to the results, guar gum and borax form a dense boric acid crosslinked polymer through cross-linking reaction. The internal structure grew tighter and more continuous as the crosslinked polymer concentration grew. It improved the anti-permeability plugging action and viscosity of slurries by 36.1~94.3%. The optimal proportions of sodium bentonite, guar gum, polyacrylamide, borax, and water were 10%, 0.2%, 0.25%, 0.1%, and 89.45% respectively. All these works indicated that the improvement of slurry composition by using boric acid crosslinked polymers was feasible. Full article

The bridge of Shanghai Metro Line 10 over Metro Line 6 is a U-shaped concrete single-box double-cell concrete box beam continuous bridge. A novel method is applied to construct the asymmetric cantilever prefabricated and assembled continuous bridge due to the limited construction space and the complex environment. Four mechanical state control methods are applied during the T-shape structure construction process: tensioning pre-stressed steel strand, jacking by the axial force servo system, adjusting the leg reaction force, and setting the auxiliary leg. Auxiliary measures such as the compressive column, side-span counterweight, and temporary pre-stressing are also taken into consideration. The finite element method simulations are performed to measure effects of the four control methods during the construction process. The front leg force of the bridge erection machine and the deflection of the bridge are then monitored. It was deduced that the simulated and measured values of the cantilever T-shape structure are controlled within the limit range during the construction process. Full article

Urease is an enzyme containing a dinuclear nickel active center responsible for the hydrolysis of urea into carbon dioxide and ammonia. Interestingly, inorganic models of urease are unable to mimic its mechanism despite their similarities to the enzyme active site. The reason behind the discrepancy in urea decomposition mechanisms between inorganic models and urease is still unknown. To evaluate this factor, we synthesized two bis-nickel complexes, [Ni₂L(OAc)] (1) and [Ni₂L(Cl)(Et₃N)₂] (2), based on the Trost bis-Pro-Phenol ligand (L) and encompassing different ligand labilities with coordination geometries similar to the active site of jack bean urease. Both mimetic complexes produced ammonia from urea, (1) and (2), were ten- and four-fold slower than urease, respectively. The presence and importance of several reaction intermediates were evaluated both experimentally and theoretically, indicating the aquo intermediate as a key intermediate, coordinating urea in an outer-sphere manner. Both complexes produced isocyanate, revealing an activated water molecule acting as a base. In addition, the reaction with different substrates indicated the biomimetic complexes were able to hydrolyze isocyanate. Thus, our results indicate that the formation of an outer-sphere complex in the urease analogues might be the reason urease performs a different mechanism. Full article

The study of the distribution form and calculation method of the earth pressure on the back wall of a pilot tunnel under a jacking reaction is very important to ensure the safety and smooth construction of the pipe jacking. Based on a metro station in Shenyang, this paper firstly investigates the effects of the changes in the jacking reaction parameters, such as the loading intensity, loading position, and loading area on the earth pressure and the displacement of the back wall in a pilot tunnel through numerical simulation, and then proposes a formula for calculating the soil reaction on the back wall and verifies it by comparison with the FEA (finite element method) results. The results show that the earth pressure distribution pattern of the back wall is similar to the normal distribution curve under the action of the jacking reaction. The horizontal displacement and earth pressure of the back wall will gradually increase with the increase in the jacking reaction. The horizontal displacement of the back wall is greatest when the load is applied to the middle wall, followed by the top wall and the bottom wall. The maximum horizontal displacement is reduced by approximately 24.25% when the loading position changes from the middle to the bottom. As the loading area increases, the maximum horizontal displacement of the back wall decreases, in the order of 11.8% and 14.45% relative to the previous level. The earth pressure of the back wall also decreases, in the order of 17.92% and 22.76% relative to the previous level. The equations presented are applicable to the calculation of the soil reaction in the limit state. Full article

This study aimed to test zona pellucida (ZP) vaccines’ immunocontraceptive efficacy and safety when formulated with non-Freund’s adjuvant (6% Pet Gel A and 500 Μg Poly(I:C)). Twenty-four jennies were randomly assigned to three treatment groups: reZP (n = 7) received three doses of recombinant ZP vaccine; pZP (n = 9) received two doses of native porcine ZP; and Control group (n = 8) received two injections of placebo. Jennies were monitored weekly via transrectal ultrasonography and blood sampling for serum progesterone profiles and anti-pZP antibody titres. In addition, adverse effects were inspected after vaccination. Thirty-five days after the last treatment, jacks were introduced to each group and rotated every 28 days. Vaccination with both pZP and reZP was associated with ovarian shutdown in 44% (4/9) and 71% (4/7) of jennies, 118 ± 33 and 91 ± 20 days after vaccination, respectively (p > 0.05). Vaccination delayed the chances of a jenny becoming pregnant (p = 0.0005; Control, 78 ± 31 days; pZP, 218 ± 69 days; reZP, 244 ± 104 days). Anti-pZP antibody titres were elevated in all vaccinated jennies compared to Control jennies (p < 0.05). In addition, only mild local injection site reactions were observed in the jennies after treatment. In conclusion, ZP vaccines formulated with non-Freund’s adjuvant effectively controlled reproduction in jennies with only minor localised side effects. Full article

Complex microstructures of zircon recrystallisation have been discovered in igneous and metamorphic zircons from the Jack Hills Metasedimentary Belt in Western Australia, and the granitic injection complex of Harris in north-west Scotland. Cathodoluminescence (CL), electron backscatter diffraction (EBSD) and wavelength dispersive spectroscopy (WDS) analysis reveal that recrystallisation in the studied zircons is often characterised by (1) translation, bending and fading of the oscillatory zoning; (2) structural recovery of the zircon; (3) an enrichment in Hf and depletion in Y in recrystallised zircon; and (4) the formation of a recrystallisation interface with a minor (<2°) misorientation. A new, composite recrystallisation model in which trace element and dislocation migration occurs shortly after crystallisation during magmatic cooling and pipe diffusion along dislocation arrays formed by the accumulation of dislocations allows enhanced diffusion to enrich Hf and leach U, Pb and Y. After the recrystallisation event, subsequent metamictization of primary zircon (typically with oscillatory zoning) creates zones that can structurally recover through a diffusion-reaction re-equilibration mechanism, resulting in further trace-element mobility. These mechanisms can create complex microstructures in zircons, suggesting that a detailed understanding of the crystallisation and recrystallisation history of a zircon may be required to accurately interpret its U-Pb ages. Full article

There are a few isolated structures that have been subjected to seismic testing. An isolated structure is incapable of tracking, adjusting, and controlling its dynamic characteristics. As a result, field evaluations of solitary structures’ dynamic characteristics are important. The horizontal initial displacement of a base isolation kindergarten made of 46 isolation bearings is 75 mm. The method for creating the horizontal initial displacement condition is illustrated, as are the primary test findings. Horizontal initial displacement is accomplished with the assistance of a reaction wall, rods, and hydraulic pump system. To begin, we removed the building using hydraulic jacks to produce horizontal displacement of the isolation layer and then attached rods to support the building. The rods were then shot and unloaded, causing the building to shake freely, and its dynamic response and other parameters were tested. The results indicate that the natural vibration period of an isolated structure is much greater than the natural vibration period of a seismic structure. The isolation layer’s hysteretic curve as completely filled; upon unloading, the isolation layer as promptly reset; the dynamic response control effect of each was visible, but the top floor’s acceleration was magnified by approximately 1.27 times. Full article

1. Background: Urea is the main product of the nitrogenous breakdown of protein metabolism in mammals. In this study, process intensification for enzymatic hydrolysis of urea by urease enzyme (jack bean urease) was examined in a membrane reactor. 2. Methods: Batch and continuous enzymatic hydrolysis reactions were performed at different substrate concentrations to determine the digestibility and affinity of the substrate with that of the enzyme. The hydrolysate samples were obtained by an optimized continuous enzyme membrane reactor (EMR) coupled with an ultra-filtration membrane (250 kDa). Feed concentration varied from 100 to 500 mg/L. Laboratory experiments were conducted at room temperature (20 ± 1 °C), with a flow rate of 20 mL/min, urease concentration of 0.067 g/L, ionic strength (I = 0, 0.01, 0.05), and ammonium nitrogen addition of (0, 100 mg/L, 200 mg/L, 500 mg/L). Moreover, the effect of ionic strength, ammonium nitrogen concentration, feed concentration, and enzyme concentration on urea hydrolysis was examined. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDAX) analysis were used to identify the physicochemical properties as well as the elemental composition of the Ultra-Filtration membrane used in this study. 3. Results: The study revealed that higher ionic strength and higher concentrations of NH₄SO₂ and ammonium nitrogen (NH₃-N) inhibithydrolysis of urea by reducing the urease enzyme activity in the system over time. 4. Conclusions: Herein, a sustainable alternative for the conversion of urea to ammonia by utilizing urease in an EMR was demonstrated. Full article

Sporosarcina pasteurii (S. pasteurii) is bacterium notable for its highly efficient urea degradation ability. Due to its high urease activity, S. pasteurii has been successfully utilized in applications including solidifying soil or sand, termed “bio-concrete”. In addition to calcium carbonate precipitation, urease isolated from the jack bean plant was recently demonstrated to induce the formation of magnetic iron oxide particles from soluble ferrous ion in a designed reaction. However, it remained unknown if a similar magnetic material could be formed using whole cells with high urease activity under biocompatible conditions. Here, we demonstrated that magnetic iron oxide with a highly ordered structure could be formed on the surface of S. pasteurii cells with a theoretical product of 1.17 mg in a 2-mL reaction. Moreover, the cells surrounded by the precipitated magnetic iron oxide maintained their viability. Due to the simple cultivation of S. pasteurii, the process developed in this study could be useful for the green synthesis of magnetic iron oxide, basic research on the mechanism of magnetic microbial-induced precipitation (MIP), and related engineering applications. Full article

A set of 6- to 24-valent clusters was constructed with terminal deoxynojirimycin (DNJ) inhibitory heads through C6 or C9 linkers by way of Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reactions between mono- or trivalent azido-armed iminosugars and calix[8]arene scaffolds differing in their valency and their rigidity but not in their size. The power of multivalency to upgrade the inhibition potency of the weak DNJ inhibitor (monovalent DNJ K_i being at 322 and 188 µM for C6 or C9 linkers, respectively) was evaluated on the model glycosidase Jack Bean α-mannosidase (JBα-man). Although for the clusters with the shorter C6 linker the rigidity of the scaffold was essential, these parameters had no influence for clusters with C9 chains: all of them showed rather good relative affinity enhancements per inhibitory epitopes between 70 and 160 highlighting the sound combination of the calix[8]arene core and the long alkyl arms. Preliminary docking studies were performed to get insights into the preferred binding modes. Full article