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Three-cone bit is the key equipment in the exploration of the oil in offshore drilling and exploration, the bearing system and the seal system are the critical components for the bit. Especially in the offshore drilling environment, the seal design need to be carefully considered. A multi-objective optimization design including orthogonal design method and F-test with finite element analysis for a three-cone bit seal is proposed. Firstly, the calculation method of optimization targets are given, including the minimization of maximum contact pressure and leakage rate analyzed by ANSYS and MATLAB respectively, to maximize seal life and reliability. Then, an orthogonal experiment approach is used to investigate the effects of the eleven parameters on the seal performance, and the influence degrees of the seal factors on the optimization targets have been confirmed by F-test, and the reasonable factors can be determined by the trend of the targets. Finally, in order to validate the analysis results, a new seal was designed and tested on a seal tester compared to the previous seal. In this test, the seal maximum interface temperature that reflects the position of maximum contact pressure can be obtained by using three high precision thermocouples. Both the experiment results and the numerical analyses proved that the maximum contact pressure and leakage rate of the improved seal have been reduced compared to the previous.

In this paper, a closed-form frequency equation of the pipe-in-pipe (PIP) structure with arbitrary boundaries is obtained. The frequency equation is derived from Green's function of the transverse forced vibration of the PIP structure and takes into account the effects of internal two-phase flow and axial pressure. The reliability of the method in this paper is proved by comparison with the published literature. In the numerical discussion part, the PIP structures with clamped-clamped, clamped-free, and elastic boundary conditions are used as examples to discuss. The effects of equivalent stiffness coefficient, internal flow velocity, and gas volume fraction on the stability of PIP structure are studied. The results show that the stability of the PIP structure is better than that of the single-pipe structure, and the greater the equivalent stiffness coefficient of the elastic layer, the higher the critical flow velocity of the structure. In addition, a modal conversion phenomenon existing in the PIP structure is discovered. There are different forms of modal conversion for different boundary conditions, and the modal conversion makes the order of instability of the PIP structure different from that of a single-pipe. The conclusion of this paper has positive significance for the dynamic research of PIP structure. [ABSTRACT FROM AUTHOR]

This paper studies the in-line and cross-flow coupling vibration response characteristics of a marine viscoelastic riser subjected to two-phase internal flow and affected by the combined effects of several parameters including the volume fraction of gas phase, sea water flow velocity, viscoelastic coefficient of the marine riser, axial tension amplitude, and the in-line and cross-flow coupling effect taking into account both the geometric and hydrodynamic nonlinearities. On the base of extended Hamilton's principle for open systems, the dynamic equations of the marine viscoelastic riser subjected to the axial tension and gas-liquid-structure interaction are established. Two distributed and coupled van der Pol wake oscillators are utilized to model the fluctuating lift and drag coefficients, respectively. The finite element method is adopted to directly solve the highly coupled nonlinear fluid-structure interaction equations. Model validations are firstly performed through comparisons with the published experimental data and numerical simulation results, and the characteristic curves of the in-line and cross-flow vibration pattern, the in-line and cross-flow displacement trajectories, the in-line and cross-flow space-time response of displacement, and the in-line and cross-flow space-time response of stress versus different parameters are obtained, respectively. The results show that the volume fraction of gas phase, sea water flow velocity, viscoelastic coefficient of marine riser, axial tension amplitude, the in-line and cross-flow coupling effect, and multiphase internal flow velocity have significant influences on the dynamic response characteristics of the marine viscoelastic riser. Furthermore, the maximum displacements and stresses of the marine viscoelastic riser can be increased or decreased depending on the internal flow velocity, and the critical internal flow velocities result in the increase of mode order for different cross-flow velocities. It is also demonstrated that appropriate viscoelastic coefficients are very important to effectively suppress the maximum displacements and stresses. [ABSTRACT FROM AUTHOR]

A mild, green and extra activator‐free synthesis of allylic sulfones from non‐derivatized allylic alcohols and sulfinic acids was developed and only the easily‐available Pd(PPh3)4 was used as the catalyst. This new method could be easily scaled up to gram scale, affording the target allylic sulfones in a nearly quantitative yield with water as the sole by‐product. Mechanism studies both by various NMR techniques and by theoretical calculations suggested two reaction pathways may be involved in the reaction, which are dependent on the reaction media, that is, an eight‐membered ring binding species may be formed in aqueous media between allylic alcohol, sulfinic acid and water, while a six‐membered ring binding species may be formed in common aprotic organic solvent between allylic alcohol and sulfinic acid. Both binding species may be accounted for the efficient activation of allylic alcohols via hydrogen bonding. [ABSTRACT FROM AUTHOR]

In harsh drilling conditions (e.g. abrasive drilling fluid), turbo-drill thrust ball may suffer from raceway surface indentation under the high axial load. The indentation can cause early failure of the bearing components. This paper establishes a micro-scale finite element model (FEM) to discuss the raceway surface indentation resulted from solid particle. For the sake of simplicity, the interaction between steel ball and solid particle as the latter is pressed into the raceway surface was depicted by axial and circumferential displacements. The distribution of stress and strain in solid particle and raceway surface was obtained from the finite element analysis. Through the discussion on solid particle ellipticity and the effect of friction coefficient on indentation features, it is learned that the variation in ellipticity has a slight impact on indentation depth, but a marked effect on raceway surface deformation; the friction coefficient has a significant impact on indentation edge shape and bottom centre of indentation. The simulation results provide a valuable reference for prevention of bearing raceway indentation. [ABSTRACT FROM AUTHOR]

Two large π-conjugated α-cyanostilbene derivatives (2Z,2′Z,4E,4′E)-2,2′-(1,3-phenylene)bis(5-(4-(dimethylamino)phenyl)penta-2,4-dienenitrile) (M-PDC) and (2Z,2′Z,4E,4′E)-2,2′-(1,4-phenylene)bis(5-(4-(dimethylamino)-phenyl)penta-2,4-dienenitrile) (P-PDC) were designed and synthesized through a Knoevenagel condensation reaction between m-phenylenediacetonitrile, p-phenylenediacetonitrile and 4-(dimethylamino)cinnamaldehyde. The two α-cyanostilbene derivatives were isomers, and their optical properties including absorption, emission, quantum yields and lifetime could be tuned by the isomer effect. P-PDC showed an absorption band and an emission peak all at larger wavelengths than M-PDC under the same conditions. Compared to M-PDC, P-PDC exhibited a higher fluorescence quantum yield. Theoretical calculations demonstrated that P-PDC possessed a larger π-conjugated system than M-PDC based on the density functional theory (DFT) method. M-PDC and P-PDC with two dimethyl amine units as proton binding sites showed sensitive naked eye detection ability toward some volatile acids with certain acidity. For example, the limits of detection of solutions of M-PDC and P-PDC in CH2Cl2 were 2.0 and 8.82 nM. Solutions of M-PDC and P-PDC in CH2Cl2 with the addition of TFA could detect some organic amines, and the limits of detection towards TEA were 1.76 and 3.47 nM. Solutions of M-PDC and P-PDC in CH2Cl2 were coated onto a quartz plate and formed a film with different morphologies, which emitted very weak light due to the ACQ effect. But, fortunately, the ACQ effect in the M-PDC and P-PDC films could be overcome via the introduction of CTAB and they exhibited great fluorescence enhancement by 225-fold and 105-fold, respectively. These results enabled a response towards volatile acid gases. The limit of detection of the M-PDC and P-PDC films towards TFA was 17.4 and 2.37 ppm. The M-PDC and P-PDC films showed good reversibility by contacting with volatile acids and organic amine gases in turn. This research will provide a new route for the construction of functional large π-conjugated systems for the detection of gaseous acids and organic amines. [ABSTRACT FROM AUTHOR]

A new fluorescent supramolecular self-assembly gelator (1) based on naphthalimide derivative with a tetrazole group was designed and synthesized, which could form a stable gel in acetone/H2O (1/1, v/v). The self-assembly process of gelator 1 was studied through SEM, UV-Vis absorption, fluorescence emission, XRD, and water contact angle. The microbelt structure was observed for the self-assembly system with its hydrophobic surface with the contacting angle of 143°. J-type aggregation mode was employed in the gel state, whose fluorescence emission showed a large red-shift of 153 nm compared with that for the solution state. This self-assembly system could selectively detect Cu2+ and K+, and their corresponding limit of detection was 5.65 × 10−7 M and 1.73 × 10−7 M, respectively. it's the fluorescence emission and color changed during the detection process of K+. This self-assembly was immune to acid although it has a tetrazole group. Interestingly, this self-assembly system could continuously respond to the organic amine and gaseous acid in three different states such as solution, gel, and xerogel. The limit of detection in the solution state for TEA and TFA was 7.66 × 10−5 M and 2.01 × 10−7 M, respectively. The limit of detection of the xerogel film towards TEA was 0.19 ppm. This research will provide a new way for the construction of multifunctional self-assembly systems for the detection of metal ions or organic amines and gaseous acids. [ABSTRACT FROM AUTHOR]

A new gelator (1) was designed and synthesized through a Knoevenagel condensation reaction between 4-dimethylaminocinnamaldehyde and a gallic acid derivative containing a carbanion. This gelator could form stable organogels in hexane, petroleum ether, DMSO and acetonitrile. The self-assembly processes of 1 in four solvents were carefully investigated via UV-vis absorption, fluorescence, FTIR, XRD, water contact angles and field emission scanning electron microscopy (FESEM). Nanofibre and microsphere structures were observed in their self-assembly systems. The xerogel 1 film surfaces exhibited different hydrophobicities with water contact angles of 113.5–155°. The J-type aggregation mode was employed in the self-assembly process, and hydrogen bonding and π–π stacking were the main driving forces for organogel formation. Fluorescence emission of organogel 1 from acetonitrile was shifted from 558 nm of its corresponding diluted acetonitrile solution to 601 nm with a red-shift of 43 nm. Interestingly, compound 1 could sensitively respond to volatile acid, and further to organic amine gases along with obvious color changes. The detection limit for trifluoroacetic acid (TFA) by solution 1 in acetonitrile was 1.03 × 10−8 M with a corresponding association constant (K) of 6.85 × 104 M−1. The detection limit for triethylamine (TEA) by solution 1 in acetonitrile with 1.8 eq. of TFA was 1.27 × 10−8 M with a corresponding association constant (K) of 4.027 × 104 M−1. The yellow color of solution 1 could be reversibly changed to colorless in the titration process. At the same time, xerogel 1 exhibited sensitive response abilities for volatile acids and organic amines. The fluorescence of xerogel 1 could be quenched when in contact with a volatile acid within 7 s and recovered under further contact with a volatile amine within 15 s. The detection limit of xerogel film 1 towards trifluoroacetic acid (TFA) gases was 3.2 ppb. Organogel 1 exhibited sensitive response abilities towards TFA and TEA, and then rapidly expressed fluorescence, a gel state and a color change. This research would provide a new window into fast and sensitive detection of volatile acids and organic amines. [ABSTRACT FROM AUTHOR]

A new gelator 1, containing a quinoline group, was designed, synthesized, and fully characterized. It was found that a stable organogel of 1 could be obtained in some solvents, including ethanol, acetonitrile, n-hexane, petroleum ether, and DMSO. It is worth mentioning that a supragel was formed in hexane and petroleum ether with critical gel concentrations of 0.16% and 0.17%, respectively. The self-assembly process of gelator 1 in the above five solvents was carefully investigated by FESEM, UV-vis, FL, FTIR, XRD, and water contact angle experiments. It was found that gelator molecule 1 could self-assemble into different self-assembly structures with different surface wettabilities – from super-hydrophilicity to super-hydrophobicity – in the self-assembly process. The organogel of 1 that was formed in acetonitrile could emit strong light when compared with that emitted by organogel 1 in the other four solvents under the stimulation of 365 nm light. At the same time, the fluorescence emission of the organogel state had a red-shift of 70 nm when compared with that of the solution state. The fluorescence emission of molecule 1 in solution and its gel state was further and well verified via theoretical calculations. The fluorescence emission of the acetonitrile solution of gelator 1 could reversibly respond to TFA and TEA, along with a change in the maximum emission wavelength between 382 nm and 458 nm, in turn. The xerogel of 1 formed in acetonitrile exhibited a sensitive responsive ability towards TFA and TEA. More interesting are the different changes in behavior of the fluorescence emission of molecule 1 in solution and the xerogel state in response to TFA and TEA. This research will provide a new way to design multi-functional soft matter materials that show a response to volatile acid and organic amine vapors. [ABSTRACT FROM AUTHOR]

In this paper, the static buckling and post buckling dynamic characteristics of functionally graded pipeline with geometric imperfections on Pasternak foundation are studied. The functional gradient material is modeled based on the modified power law distribution, and the pores generated in the material during manufacturing are described based on the Voigt model. Based on the Euler-Bernoulli beam theory, considering Pasternak foundation and von-Kaman nonlinearity, the control equation is derived by using Hamilton principle. The closed solution of nonlinear stability is given. The effects of maximum defect amplitude, porosity, power law index and Pasternak foundation on the static buckling and vibration characteristics near the first-order buckling configuration are discussed. The numerical results show that the maximum defect amplitude and Pasternak foundation have significant effects on the critical buckling load, post-buckling structure and natural frequency of the pipeline. • The buckling and post-buckling characteristics of pipeline with defects on complex ground have not been studied. • The research on buckling and post-buckling characteristics of functionally graded curved pipeline is very limited. • The free vibration around the buckling position of the elbow structure caused by the coriolis effect is considered. • Porosity and initial defect effects are considered as important research factors. • The research on static buckling stability and dynamic response of pipeline around Pasternak foundation is still blank. [ABSTRACT FROM AUTHOR]

The study of thermal post-buckling characteristics of functionally graded pipelines is of great significance for promoting the application of functionally graded materials in spacecraft thermal protection design and marine pipelines. In this study, the static buckling of functionally graded pipes with porosity and the pseudo-linear vibration near the first buckling position of post-buckling are studied. Based on the modified power-law distribution, it is assumed that the material properties of porous FGM pipes change continuously and smoothly along the radial direction. For porosity, it generally occurs in the manufacturing process of functionally graded materials, so the classical Voigt model is selected to describe the material properties of functionally graded material pipelines with pores. Based on Hamilton principle, the nonlinear control equations and corresponding boundary conditions of the pipeline are derived. Firstly, the Routh-Hurwitz criterion is used to discuss the influence of temperature and porosity volume fraction on the critical flow velocity of instability, and then the post-buckling structure of the pipeline and the dynamic characteristics of post-buckling are discussed. The numerical results discussed the influence of important parameters such as power law index, porosity volume fraction and temperature on the buckling and post-buckling behaviors of the system. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • No use of any catalyst. • No external oxidant and additive. • Reaction in aqueous media. • Gram-scale synthesis. Abstract A convenient and precise nitration and oximation of alkenes with tert -butyl nitrite has been reported, yielding α-nitro ketoximes in satisfactory yields with broad substrate generality and excellent stereoselectivity under mild conditions. Experiments indicate that tert -butyl nitrite serves as both NO and NO 2 sources and water plays a key role in this difunctionalization reaction. [ABSTRACT FROM AUTHOR]