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Written for beginning learners of the language, this concise introduction to Chinese grammar assumes only a basic knowledge of Chinese, and no knowledge of grammatical terminology and practices. Comparing Chinese grammar patterns and rules with those of English, and illustrated with a wealth of real-life examples, it allows learners to understand the similarities and differences between the two languages. Using engaging and accessible language, it examines the Chinese sound system, writing system, word formation rules, parts of speech, and simple and complex sentences, as well as explaining special constructions that are typically challenging to second language learners. Each chapter begins with clear learning goals and ends with a useful summary highlighting the chapter's main points. To call attention to specific issues, sidebars are interspersed throughout the text, and exercises within the book and online answer keys help students to reinforce learned material and assist with self-study.
Master the principles of structural dynamics with this comprehensive and self-contained textbook, with key theoretical concepts explained through real-world engineering applications. The theory of natural modes of vibration, the finite element method and the dynamic response of structures is balanced with practical applications to give students a thorough contextual understanding of the subject. Enhanced coverage of damping, rotating systems, and parametric excitation provides students with superior understanding of these essential topics. Examples and homework problems, closely linked to real-world applications, enrich and deepen student understanding. Curated mathematical appendices equip students with all the tools necessary to excel, without disrupting coverage of core topics. Containing all the material needed for a one- or two-semester course, and accompanied online by Matlab code, this authoritative textbook is the ideal introduction for graduate students in aerospace, mechanical and civil engineering.
There are various matrices to represent parallel mechanisms. It is essential to design a kind of approach to not only denote the parallel structures but also disclose the joint directions. In this paper, a novel methodology called the kinematic joint matrix (KJM) is proposed. It possesses the mapping relations with parallel manipulators with three kinds of kinematic joints. The size of such matrix is smaller when compared with that of topology matrix. A series of two to six degrees-of-freedom parallel architectures is denoted by the KJM. A convenient approach using a special block diagram is introduced to distinguish various kinds of kinematic joint matrices. In addition, detailed comparisons between KJM and topology matrix are investigated. Three regulations are proposed for the latter to be applicable to parallel mechanisms.
Biped robots with dynamic motion control have shown strong robustness in complex environments. However, many motion planning methods rely on models, which have difficulty dynamically modifying the walking cycle, height, and other gait parameters to cope with environmental changes. In this study, a heuristic model-free gait template planning method with dynamic motion control is proposed. The gait trajectory can be generated by inputting the desired speed, walking cycle, and support height without a model. Then, the stable walking of the biped robot can be realized by foothold adjustment and whole-body dynamics model control. The gait template can be changed in real time to achieve gait flexibility of the biped robot. Finally, the effectiveness of the method is verified by simulations and experiments of the biped robot BHR-B2. The research presented here helps improve the gait transition ability of biped robots in dynamic locomotion.
The effect of sheared E × B flow on the blob dynamics in the scrape-off layer (SOL) of HL-2A tokamak has been studied during the plasma current ramp-up in ohmically heated deuterium plasmas by the combination of poloidal and radial Langmuir probe arrays. The experimental results indicate that the SOL sheared E × B flow is substantially enhanced as the plasma current exceeds a certain value and the strong sheared E × B flow has the ability to slow the blob radial motion via stretching its poloidal correlation length. The locally accumulated blobs are suggested to be responsible for the increase of plasma density just outside the Last Closed Flux Surface (LCFS) observed in this experiment. The results presented here reveal the significant role played by the strong sheared E × B flow on the blob dynamics, which provides a potential method to control the SOL width by modifying the sheared E × B flow in future tokamak plasmas.
The mean velocity follows a logarithmic scaling in the surface layer when normalized by the friction velocity, i.e. a velocity scale derived from the wall-shear stress. The same logarithmic scaling exists for the mean temperature when one normalizes the temperature with the friction temperature, i.e. a scale derived from the wall heat flux. This temperature normalization poses challenges to adiabatic walls, for which the wall heat flux is zero, and the logarithmic temperature scaling becomes singular. This paper aims to establish a temperature transformation that applies to both isothermal walls and adiabatic walls. We show that by accounting for the diffusive flux, both the Van Driest transformation and the semi-local transformation (and other transformations alike) apply to adiabatic walls. We also show that the classic Walz equation works well for adiabatic walls because it models the diffusive flux, albeit in a rather crude way. For validation/testing, we conduct direct numerical simulations of supersonic Couette flows at Mach numbers $M=1$, 3 and 6, and various Reynolds numbers. The two walls are adiabatic, and a source term is included to cancel the aerodynamic heating in the domain. We show that the adiabatic wall data collapse onto the same incompressible logarithmic law of the wall like the isothermal wall data.
This study is design to explore the association between dietary betaine intake and risk of all-cause and cardiovascular death in patients with CAD. In this cohort study, 1292 patients with CAD were followed-up for a median of 9.2 years. Baseline dietary betaine intake was collected using a paper-based semi-quantitative food frequency questionnaire (FFQ) and assessed according to the US Department of Agriculture (USDA) Database and the data of betaine in common foods. Cox proportional hazards regression models were used to analyze the association between dietary betaine intake and risks of all-cause and cardiovascular mortality. During the follow-up periods, 259 deaths recorded in 1292 participants, of which 167 died of cardiovascular diseases. Patients in the highest tertile of dietary betaine intake had a lower risk of all-cause (P=0.007) and cardiovascular death (P<0.001) than those in the lowest tertile after adjusting for age and sex, traditional cardiovascular risk factors and other potential confounders. After further adjusting for plasma methionine metabolites and vitamins, HRs across tertiles of dietary betaine intake were 1.00, 0.84 and 0.72 for all-cause mortality (P for trend=0.124), and 1.00, 0.77 and 0.55 for cardiovascular mortality (P for trend=0.021). Higher dietary betaine intake was associated with a decreased risk of cardiovascular death after fully adjustment for cardiovascular risk factors, other potential confounders and plasma methionine metabolites and vitamins. However, the association between dietary betaine intake and risk of all-cause mortality was not statistically significant after further adjusting for plasma methionine metabolites and vitamins.
Bicuspid aortic valve is the most common congenital heart malformation and predisposes patients to thoracic aortic aneurysms and aortic dissections. Current peripartum guidelines are extrapolated from other heritable causes of thoracic aortic disease and do not account for unique characteristics of bicuspid aortic valve patients. We therefore evaluated the prevalence of maternal and fetal complications of women with early-onset complications of bicuspid aortic valve disease in the UTHealth Bicuspid Aortic Valve Research Registry. We found that the rate of cardiovascular complications was high and that relatively few women received guideline-recommended care.
We report a systematic experimental study of the mean temperature profile $\theta (\delta z)$ and temperature variance profile $\eta (\delta z)$ across a stable and immiscible liquid–liquid (water–FC770) interface formed in two-layer turbulent Rayleigh–Bénard convection. The measured $\theta (\delta z)$ and $\eta (\delta z)$ as a function of distance $\delta z$ away from the interface for different Rayleigh numbers are found to have the scaling forms $\theta (\delta z/\lambda )$ and $\eta (\delta z/\lambda )$, respectively, with varying thermal boundary layer (BL) thickness $\lambda$. By a careful comparison with the simultaneously measured BL profiles near a solid conducting surface, we find that the measured $\theta (\delta z)$ and $\eta (\delta z)$ near the liquid interface can be well described by the BL equations for a solid wall, so long as a thermal slip length $\ell _T$ is introduced to account for the convective heat flux passing through the liquid interface. Direct numerical simulation results further confirm that the turbulent thermal diffusivity $\kappa _t$ near a stable liquid interface has a complete cubic form, $\kappa _t(\xi )/\kappa \sim (\xi +\xi _0)^3$, where $\kappa$ is the molecular thermal diffusivity of the convecting fluid, $\xi =\delta z/\lambda$ is the normalized distance away from the liquid interface and $\xi _0$ is the normalized slip length associated with $\ell _T$.
Planting patterns have significant effects on rice growth. Nonetheless, little is known about differences in annual crop yield and resource utilization among mechanized rice planting patterns in a rice–wheat cropping system. Field experiments were conducted from 2014 to 2017 using three treatments: pot seedling transplanting for rice and row sowing for wheat (PST-RS), carpet seedling transplanting for rice and row sowing for wheat (CST-RS) and row sowing for both crops (RS-RS). The results showed that, compared with RS-RS, PST-RS and CST-RS prolonged annual crop growth duration by 25–26 and 13–15 days, increased effective accumulated temperature by 399 and 212°C days and increased cumulative solar radiation by 454 and 228 MJ/m2 because of the earlier sowing of rice by 28 and 16 days in PST-RS and CST-RS, respectively. Compared with RS-RS, the annual crop yield of PST-RS and CST-RS increased by 3.1–3.8 and 2.0–2.6 t/ha, respectively, because of the increase in the number of spikelets/kernels per hectare, aboveground biomass, mean leaf area index and grain–leaf ratio. In addition, temperature production efficiency, solar radiation production efficiency and solar radiation use efficiency were higher in PST-RS, followed by CST-RS and RS-RS. These results suggest that mechanized rice planting patterns such as PST-RS increase annual crop production in rice–wheat cropping systems by increasing yield and solar energy utilization.
We examined sensitive questions on political trust and regime support in China using indirect methods. We replicated previous list experiment results confirming that a majority trusts the central government despite overreports. We also conducted novel list experiments on trust in local government and support for removal of the presidential term limit and found evidence of overreporting for both. The point estimate for local government also suggests majority trust, but the central government is both more trusted and feared. However, we did not find evidence of majority support for removing the term limit at the time of the removal, indicating that the public may negatively evaluate government, albeit indirectly, in some circumstances. Last, examining self-monitoring, a personality trait for examining social desirability, we found that it only influenced overreporting trust in the central government. The results reveal meaningful variation in political trust and regime support in the world’s largest authoritarian society.
Although maternal mental illnesses have been found to influence child health and development, little is known about the impact of maternal positive well-being on child health and development. Therefore, this longitudinal study investigated the effects of prenatal subjective well-being on birth outcomes and child development by considering the potential modifier effect of parity.
Pregnant women in early stages of pregnancy were recruited at five selected hospitals in Taipei, Taiwan, during their prenatal appointments since 2011. Self-reported evaluations were conducted at seven time points up to 2 years postpartum. Linear regression and generalized estimating equation models were used for examination.
Higher prenatal eudaimonic well-being was associated with longer gestational length (adjusted beta [aβ] = 0.36, 95% confidence interval [CI] = 0.03, 0.68) and higher birth weight (aβ = 124.71, 95% CI = 35.75, 213.66). Higher positive and negative affect were associated with longer gestational length (aβ = 0.38, 95% CI = 0.06, 0.70) and smaller birth weight (aβ = −93.51, 95% CI = −178.35, −8.67), respectively. For child’s outcomes, we found an association between higher prenatal eudaimonic well-being and decreased risks of suspected developmental delay, particularly for children of multiparous mothers (adjusted odds ratio = 0.18, 95% CI = 0.05, 0.70). Higher levels of prenatal depression and anxiety were significantly associated with increased risks of suspected developmental delay for children of primiparous mothers.
Positive prenatal maternal mental health may benefit birth outcomes and child development, particularly for children of multiparous mothers. Interventions for improving prenatal mental health may be beneficial for child development.
An experimental investigation of the stereocamera's systematic error is carried out to optimize three-dimensional (3-D) dust observation on the HL-2A tokamak. It is found that a larger 3-D region occupied by all calibration points is able to reduce the 3-D reconstruction systematic error of the stereocamera. In addition, the 3-D reconstruction is the most accurate around the region where the calibration points are located. Based on these experimental results, the design of the stereocamera on the HL-2A tokamak is presented, and a set of practical procedures to optimize the 3-D reconstruction accuracy of the stereocamera are proposed.
This article introduces the 2D multilayer Laue lens (MLL) nanofocusing optics recently developed for high-resolution hard X-ray microscopy. The new optics utilized a micro-electro-mechanical-system (MEMS)-based template to accommodate two linear MLL optics in a pre-aligned configuration. Angular misalignment between the two lenses was controlled in tens of millidegrees, and the lateral position error was on a micrometer scale. Using the developed 2D MLLs, an astigmatism-free point focus of approximately 14 nm by 13 nm in horizontal and vertical directions, respectively, at 13.6 keV photon energy was obtained. The success of 2D MLL optics with an approaching 10 nm resolution is a significant step forward for the development of high-resolution hard X-ray microscopy and applications of MLL optics in the hard X-ray community.
Drawing on the job demands-resources model and conservation of resources theory, this study investigates how and when the high-performance work systems (HPWS) influence proactive workforce. Using the data obtained from 204 supervisor-employee dyads in China, we developed and tested a moderated mediation model in which leader-member exchange (LMX) moderates the positive relationship between HPWS and proactive behavior via work engagement. Our results demonstrated that the association between HPWS and proactivity was fully mediated by work engagement. We also found that the indirect effect of HPWS on proactivity was significantly weaker among employees with high-quality LMX. Theoretical and practical implications, as well as directions for future research, are then discussed.
In this paper, a hydraulic soft gripper for underwater applications is designed to provide a solution for improving the gripping force as well as the sensing capability of the soft gripper. The soft gripper is made of silicone and has an integrated semi-circular hydraulic network inside. To enhance the rigidity and grasping performance of the soft gripper, we have integrated a restriction layer consisting of a spring steel plate in the soft gripper. Meanwhile, to enhance the sensing capability of this soft gripper, we have designed a water pressure sensor based on resistance strain gauges and integrated it on the spring steel plate. Before fabrication, we determined the structural parameters of the soft gripper by geometric analysis. Then we experimentally evaluated its pressure-bearing capacity, bending performance, the role of spring steel plates, and the accuracy of the sensor.The experimental results show that the spring steel plate improves the gripping force of the soft gripper, the sensor also has high accuracy, and the built four-finger gripping system has good adaptability to objects of different shapes and weights.Compared with the existing solutions, this solution takes a simpler structural form while improving the gripping force and sensing ability of the soft gripper, and integrates the issues of improving the gripping force and sensing ability. The spring steel plate used in this paper not only improves the gripping force of the soft gripper but also provides a stable and reliable platform for installing sensors.