This paper reviews foundations for offshore wind energy convertors considering the significant growth of offshore wind energy since the early 2000s. The characteristics of various foundation types ...(i.e., gravity, pile, suction caisson, and float type) and the current status of field application are discussed. Moreover, the mechanical characteristics of soil are described in the sense that these characteristics including modulus, strength, damping, and modulus degradation of soil play critical roles for the design of offshore foundations. By using these mechanical properties of soil, theoretical studies to consider structure-soil interaction are classified (into equivalent spring models, distributed spring models, and continuous element models) and explained. Field and laboratory experiments on the response of structure embedded in soil to static and dynamic loads are discussed. Based on the review of previous studies, directions for future research and study on offshore wind turbine are suggested.
Asiatic acid (AA) is a pleiotropic neuroprotective agent that has been shown to attenuate infarct volume in mouse and rat models of focal ischemia and has a long clinically relevant therapeutic ...time-window. Because in a future trial AA would be administered with tissue-plasminogen activator (t-PA), the only approved acute stroke therapy, we sought to determine the effect of AA when co-administered with t-PA in a rat focal embolic stroke model. Male rats were treated with AA (75 mg/kg) alone, low-dose t-PA (2.5 mg/kg) alone, or a combination of AA and low-dose t-PA at 3 h after inducing embolic stroke. AA significantly reduced infarct volume whereas low-dose t-PA alone did not reduce infarct volume compared with vehicle. Significantly, combination treatment further enhanced reduction of infarct volume versus AA alone. Treatment with AA reduced cytochrome c (CytoC) and apoptosis-inducing factor (AIF) release from brain mitochondria after ischemia. AA was also neuroprotective against L-glutamate-induced toxicity in primary cortical neurons. In summary, combination treatment with AA and low-dose t-PA at 3 h after embolic stroke reduces infarct volume, improves neurological outcome, and provides neuroprotection. The neuroprotective effects of AA were partially associated with reduction of AIF and CytoC release.
As spatial seabed soil variations are stochastic and considerable, it is important to predict the changes in the dynamic behavior of offshore structures for safety. Particularly, if the natural ...frequency of a structure is significantly changed by the soil variations, resonance can cause structural failure; hereafter, this probability is referred to as failure probability. Although several models have been proposed, they require a long computational time to predict failure probabilities. To overcome this limitation, this work proposes a fast method for estimating the failure probability. First, since a very large computation memory is required to construct a finite element model for stochastic soil, block-wise matrix calculations and a dynamic memory allocation technique were adopted. Second, conventional models require a large number of soil samples to calculate the failure probability, which results in heavy computations. A newly developed fast Monte-Carlo (FMC) method is 5.8 times faster than the conventional method with high accuracy (99.41%). This method was applied to offshore wind turbines and successfully predicted various structural characteristics. A noteworthy prediction is that slender and long foundation is more robust to stochastic soil variations than thick and short foundation. The FMC method can be used for preliminary design of offshore structures.
•Failure probability of offshore wind turbine due to spatial variation in soil and resonance is calculated.•Block-wise matrix calculation and dynamic memory allocation are used to generate 3D stochastic soil domains.•A fast Monte-Carlo method significantly reduces computation time to estimate the failure probability.•Model predicted that a long and slender substructure is more reliable than a thick and short one.
As the dynamic stability of a spar-type floating wind turbine (SFWT) must be ensured for a secure and robust operation, tuned mass dampers (TMDs) have been proposed to reduce the vibration of the ...SFWT platform. However, the TMDs in previous studies have several limitations. First, the previously used linear TMDs successfully reduced platform vibration in the absence of wind thrust forces. However, their performance is not satisfactory in the presence of strong winds; if the SFWT structure tilts due to strong winds, the mass of the TMD remains close to the inner wall of the platform. This behavior undermines its vibration reduction performance. To address this issue, a bilinear TMD is introduced in this work. The bilinear TMD significantly reduces vibration even when a strong wind thrust force is applied. Second, previous studies determined the optimized parameters of the TMD based on the free response of the SFWT structure. However, this optimization leads to a low performance TMD when dynamic and stochastic loads were imposed. To address these limitations, this study introduces a bilinear TMD and optimizes its parameters for a variety of operational wind conditions. The bilinear TMD outperforms previous TMDs in every evaluated wind condition by 10%–15%.
•The vibration reduction by a linear TMD can be insignificant due to the collision between the TMD and the platform wall.•A bilinear TMD is proposed to reduce the vibration by suppressing the collision.•The parameter values of bilinear TMD are optimized by considering the average wind speed.•In a wide range of wind speed, the bilinear TMD is more efficient than a linear TMD by 10%–15%.
Early mobilization is an integral part of an enhanced recovery program after colorectal cancer surgery. The safety and efficacy of postoperative inpatient exercise are not well known. The primary ...objective was to determine the efficacy of a postoperative exercise program on postsurgical recovery of stage I-III colorectal cancer patients.
We randomly allocated participants to postoperative exercise or usual care (1:1 ratio). The postoperative exercise intervention consisted of 15 min of supervised exercise two times per day for the duration of their hospital stay. The primary outcome was the length of stay (LOS) at the tertiary care center. Secondary outcomes included patient-perceived readiness for hospital discharge, anthropometrics (e.g., muscle mass), and physical function (e.g., balance, strength).
A total of 52 (83%) participants (mean SD age, 56.6 8.9 years; 23 44% male) completed the trial. The median LOS was 6.0 days (interquartile range; IQR 5-7 days) in the exercise group and 6.5 days (IQR 6-7 days) in the usual-care group (P = 0.021). The exercise group met the targeted LOS 64% of the time, while 36% of the usual care group met the targeted LOS (colon cancer, 5 days; rectal cancer, 7 days). Participants in the exercise group felt greater readiness for discharge from the hospital than those in the usual care group (Adjusted group difference = 14.4; 95% CI, 6.2 to 22.6; P < 0.01). We observed a small but statistically significant increase in muscle mass in the exercise group compared to usual care (Adjusted group difference = 0.63 kg; 95% CI, 0.16 to 1.1; P = 0.03).
Postsurgical inpatient exercise may promote faster recovery and discharge after curative-intent colorectal cancer surgery.
The study was registered at WHO International Clinical Trials Registry Platform (ICTRP; URL http://apps.who.int/trialsearch ); Trial number: KCT0003920 .
This paper presents the method of reducing torque ripple of brushless direct current (BLDC) motor. In the BLDC motor, the torque ripple is decided by the back-electromotive force (EMF) and current ...waveform. If the back-EMF is constant in the conduction region of current, the torque ripple depends on the current ripple. The period of freewheeling region in the conduction region can be acquired by circuit analysis using the Laplace transformation and the torque ripple can be also reduced by varying input voltage to reduce the current ripple. The suggested method to reduce the torque ripple is confirmed by the dynamic simulation with the parameters of 500W BLDC motor
•Dynamics of the battery pack are characterized for various operational conditions.•Statistical structural variations are analyzed using an order reduction technique.•Proper design of the spacers can ...eliminate concerns on high modal density.•Fixed-boundary modes are sensitive to the evolution of structural dynamics.•Probabilistic analysis defines sensitive locations for monitoring a battery pack.
The dynamic responses of a Li-ion battery pack deployed on hybrid electric vehicles are studied with a high fidelity finite element model and a parametric reduced-order model. The effects of microstructure transformation in the electrode materials caused by lithium-ion intercalation/deintercalation on the evolution of dynamic responses are investigated including the effects of the state of charge, aging, and cell-to-cell variations. The dynamic responses obtained from a finite element analysis show two interesting phenomena. First, the high modal density is controllable with the design modification of a pack component. Second, dynamic responses, especially the evolution of the natural frequencies of the fixed-boundary modes, of a Li-ion battery pack provide useful information to estimate the dynamic states or health states of the battery. A probabilistic analysis is also carried out considering stochastic operational conditions of hybrid electric vehicles with a parametric reduced-order model. The probabilistic analysis not only suggests appropriate modes and locations for monitoring its dynamic responses, but also determines the maximum response level of every cell in the battery pack. The proposed modeling approach can improve the safety and reliability of the structural design of battery cells and packs. Furthermore, it can be useful for the identification of the battery states during the operation.
Inflammation, diabetes, and even malignancies are pharmacological effects connected by antioxidant capacity and free radicals. Many antioxidants scavenge free radicals originating from dietary ...sources such as fruits, vegetables, and teas. To identify the bioactive components of
Ligularia stenocephala
, an effective method combining HPLC-QTOF-MS and bioactivity evaluation was investigated for the first time. Antioxidant agents were isolated from
L. stenocephala
, a folk medicine used for edema and scrofula in Korea, Japan, and China. The phytochemical investigation of the aerial parts of
L. stenocephala
resulted in the separation and determination of six compounds (
1
–
6
). In particular, the chemical structures were identified as hyperoside (
1
), 3,5-dicaffeoylquinic acid (
2
), 3,5-dicaffeoylquinic acid methyl ester (
3
), trifolin (
4
), rutin (
5
), and 3,4-dicaffeoylquinic acid (
6
). Their structures were identified using 1D and 2D NMR spectroscopy and high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) data analysis. The results showed that phenolic components were responsible for the antioxidant inhibitory activity of
L. stenocephala
. Additionally, to understand the mechanisms of the antioxidant inhibitory activity of
L. stenocephala
, a docking simulation study was performed to support the in vitro results. Taken together, this new method is rapid, inexpensive, and can be applied to identify the active components of medicinal herbs without separation.
The effect of subclinical thyroid dysfunction on vascular atherosclerosis remains uncertain. The objective of this study was to elucidate the association between sustained subclinical thyroid ...dysfunction and carotid plaques, which are an early surrogate marker of systemic atherosclerosis.
The study included 21,342 adults with consistent thyroid hormonal status on serial thyroid function tests (TFTs) and carotid artery duplex ultrasonography at a health screening center between 2007 and 2014. The effect of subclinical thyroid dysfunction on baseline carotid plaques and newly developed carotid plaques during 5-year follow-up was determined by logistic regression analyses and GEE (Generalized Estimating Equations), respectively.
Carotid plaques were more common in the subclinical hypothyroidism (55.6%) than the euthyroidism (47.8%) at baseline. However, in multivariable analysis, thyroid status was not a significant risk for the carotid plaques at baseline. Instead, traditional cardiovascular risk factors, such as age (P <0.001), systolic blood pressure (P = 0.023), fasting blood glucose (P = 0.030), and creatinine (P = 0.012) were associated with baseline carotid plaques in subclinical hypothyroidism. In longitudinal analyses of subjects who were followed up for more than 5 years, there was no significant difference in the cumulative incidence of new carotid plaques according to time between subjects with subclinical hypothyroidism and those with euthyroidism (P = 0.392).
Sustained subclinical thyroid dysfunction did not affect the baseline or development of carotid plaques in healthy individuals.
•Dynamic response of wind turbines is considerably changed due to soil degradation.•The spectral density of stress of soil is studied for offshore wind turbines.•The stochastic behavior of soil ...stress for offshore wind turbines is investigated.•A novel method is proposed to calculate the long-term soil degradation.•The potential of the proposed method for robust design is shown with case studies.
Novel methods combined with an integrated simulation platform are suggested for the design of offshore wind turbines (OWTs) and substructures that ensure a 20-year lifespan. These methods enable one to estimate the long-term evolution of the dynamic responses of OWTs due to the degradation of the soil modulus of the foundation under stochastic loading conditions. The results of this study show that random fluctuations of the soil stress caused by stochastic loads (i.e., aerodynamic and hydrodynamic loads acting on OWTs) can be described by a Rayleigh distribution and a Gaussian distribution. By using these probabilistic characteristics, the stochastic fluctuations in the soil stress can be rapidly calculated without using Monte Carlo simulations. Moreover, a new method based on the derivatives of the degradation functions and on the inverse of these functions is also suggested to calculate the mean degradation index. These methods significantly decrease the computational effort, thus overcoming a critical drawback of existing methods. Case studies demonstrate that the dimensions of the substructures significantly affect the evolution of the dynamic response. This suggests that the evolution of the dynamic response should be considered in the design process to secure the serviceability of OWTs and substructures.
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