| 1. |
- Liu, Kun, 1982-, et al.
(författare)
-
Networked Control with a Stochastic Scheduling : a Time-Delay Approach
- 2014
-
Ingår i: The 19th World Congress of IFAC. - : Elsevier BV. - 9783902823625
-
Konferensbidrag (refereegranskat)abstract
- This paper is concerned with the stability analysis of networked control systems with communication constraints, variable delays and variable sampling intervals.The scheduling of sensor communication is defined by a stochastic protocol.The activation probability of each sensor node is a given constant, whereas it is assumed that collisions occur with a certain probability.The resulting closed-loop system is a stochastic impulsive system withdelays in the continuous dynamics and in the reset equations. The system matrices have stochastic parameters with Bernoulli distributions.Sufficient conditions for the exponential mean-square stabilityare derived via a Lyapunov-Krasovskii-based method. The efficiency of the method is illustrated on the examples of a cart-pendulum system and a batch reactor.It is demonstrated how our time-delay approach allows treating network-induced delays larger thanthe sampling intervals.
|
|
| 2. |
- Liu, Kexin, et al.
(författare)
-
One-way surface magnetoplasmon cavity and its application for nonreciprocal devices
- 2016
-
Ingår i: Optics Letters. - : Optical Society of America. - 0146-9592 .- 1539-4794. ; 41:4, s. 800-803
-
Tidskriftsartikel (refereegranskat)abstract
- We theoretically analyze surface magnetoplasmon modes in a compact circular cavity made of magneto-optical material under a static magnetic field. Such a cavity provides two different methods for the surface wave to circulate in a unidirectional manner around the cavity, which offers more freedom, both in the one-way direction and in the frequency range, for designing nonreciprocal photonic components. We also show the interaction between this one-way cavity and waveguides through the example of a circulator, which lays the fundamental groundwork for potential nonreciprocal devices.
|
|
| 3. |
- Liu, Kui, et al.
(författare)
-
Successful ovulation in plasminogen-deficient mice treated with the broad-spectrum matrix metalloproteinase inhibitor galardin.
- 2006
-
Ingår i: Developmental Biology. - New York : Academic P.. - 0012-1606 .- 1095-564X. ; 295:2, s. 615-622
-
Tidskriftsartikel (refereegranskat)abstract
- Many studies have suggested the hypothesis that the plasminogen activator (PA) system and the matrix metalloproteinase (MMP) system, either separately or in combination, may provide the proteolytic activity that is required for rupture of the follicular wall at the time of ovulation. Our recent studies on ovulation in plasminogen (plg)-deficient mice have, however, shown that plasmin is not required for normal ovulation, leading us to the hypothesis that MMPs may be a more important source of proteolysis for this process. To investigate the role of MMPs and also the possibility of a functional overlap or synergy between the MMP and PA systems during ovulation, we have studied ovulation efficiency in wild-type and plg-deficient mice treated with the broad-spectrum MMP inhibitor galardin. We found that in both wild-type mice and heterozygous plg-deficient (plg(+/-)) mice that had been treated with galardin prior to ovulation, there was a mild (18-20%) reduction in ovulation efficiency. Surprisingly, galardin treatment of plg-deficient (plg(-/-)) mice only caused an additional 14% reduction in ovulation efficiency as compared to vehicle-treated plg(-/-) mice. Our data therefore suggest that although MMPs may play a role in degradation of the follicular wall, they may not be obligatory for ovulation. In contrast to previous studies on tissue remodeling during wound heating and placental development, we have demonstrated that there is no obvious functional overlap or synergy between the PA and MMP systems, which has previously been thought to be essential for the ovulatory process.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Liu, Licette C Y, et al.
(författare)
-
Vitamin D status and outcomes in heart failure patients
- 2011
-
Ingår i: European Journal of Heart Failure. - : Wiley. - 1388-9842 .- 1879-0844. ; 13:6, s. 619-625
-
Tidskriftsartikel (refereegranskat)abstract
- AIMS: Vitamin D status has been implicated in the pathophysiology of heart failure (HF). The aims of this study were to determine whether a low vitamin D status is associated with prognosis in HF and whether activation of the renin-angiotensin system (RAS) and inflammatory markers could explain this potential association. METHODS AND RESULTS: We measured 25-hydroxy-vitamin D (25(OH)D), plasma renin activity (PRA), interleukin-6 (IL-6), C-reactive protein (CRP), and the incidence of death or HF rehospitalization in 548 patients with HF. Median age was 74 (64-80) years, left ventricular ejection fraction was 30% (23-42), and mean follow-up was 18 months. Low 25(OH)D levels were associated with female gender (P< 0.001), higher age (P= 0.002), and higher N-terminal pro-brain natriuretic peptide (NT-proBNP) levels (P< 0.001). Multivariable linear regression analysis showed that PRA (P= 0.048), and CRP levels (P= 0.006) were independent predictors of 25(OH)D levels. During follow-up, 155 patients died and 142 patients were rehospitalized. Kaplan-Meier analysis showed that lower 25(OH)D concentration was associated with an increased risk for the combined endpoint (all-cause mortality and HF rehospitalization; log rank test P= 0.045) and increased risk for all-cause mortality (log rank test P= 0.014). After adjustment in a multivariable Cox regression analysis, low 25(OH)D concentration remained independently associated with an increased risk for the combined endpoint [hazard ratio (HR) 1.09 per 10 nmol/L decrease; 95% confidence interval (CI) 1.00-1.16; P= 0.040] and all-cause mortality (HR 1.10 per 10 nmol/L decrease; 95% CI 1.00-1.22; P= 0.049). CONCLUSION: A low 25(OH)D concentration is associated with a poor prognosis in HF patients. Activation of the RAS and inflammation may confer the adverse effects of low vitamin D levels.
|
|
| 7. |
- Liu, Linn, et al.
(författare)
-
Comprehensive investigation on energy retrofits in eleven multi-family buildings in Sweden
- 2014
-
Ingår i: Energy and Buildings. - : Elsevier BV. - 0378-7788 .- 1872-6178. ; 84, s. 704-715
-
Tidskriftsartikel (refereegranskat)abstract
- Rapidly growing energy use in the building sector is considered a serious problem by both the European Union (EU) and Sweden. Reducing energy demand in the building sector is important for Sweden in order to reach national energy goals for reduced energy use and CO 2 emissions in the future. This project aims to find energy efficiency potential in multifamily buildings in the Gävleborg region, which is a cold climate region in Sweden. Measurements and simulations have been made on eleven multifamily buildings from the whole region. The results include different energy efficiency measure packages, profitability analysis of individual measures and packages, and primary energy use analysis. The paper also includes CO 2 emissions reduction analysis based on different methods. The project shows that the multifamily buildings in the Gävleborg region have good potential to reduce their energy use by more than 50%, which in turn will contribute to 43% primary energy reduction and 48% CO 2 emissions reduction.
|
|
| 8. |
- Lu, Xuekun, et al.
(författare)
-
Anisotropic crack propagation and deformation in dentin observed by four-dimensional X-ray nano-computed tomography.
- 2019
-
Ingår i: Acta Biomaterialia. - : Elsevier BV. - 1742-7061 .- 1878-7568. ; 96, s. 400-411
-
Tidskriftsartikel (refereegranskat)abstract
- Understanding the cracking behaviour of biological composite materials is of practical importance. This paper presents the first study to track the interplay between crack initiation, microfracture and plastic deformation in three dimensions (3D) as a function of tubule and collagen fibril arrangement in elephant dentin using in situ X-ray nano-computed tomography (nano-CT). A nano-indenter with a conical tip has been used to incrementally indent three test-pieces oriented at 0°, 45° and 70° to the long axis of the tubules (i.e. radial to the tusk). For the 0° sample two significant cracks formed, one of which linked up with microcracks in the axial-radial plane of the tusk originating from the tubules and the other one occurred as a consequence of shear deformation at the tubules. The 70° test-piece was able to bear the greatest loads despite many small cracks forming around the indenter. These were diverted by the microstructure and did not propagate significantly. The 45° test-piece showed intermediate behaviour. In all cases strains obtained by digital volume correlation were well in excess of the yield strain (0.9%), indeed some plastic deformation could even be seen through bending of the tubules. The hoop strains around the conical indenter were anisotropic with the smallest strains correlating with the primary collagen orientation (axial to the tusk) and the largest strains aligned with the hoop direction of the tusk. STATEMENT OF SIGNIFICANCE: This paper presents the first comprehensive study of the anisotropic nature of microfracture, crack propagation and deformation in elephant dentin using time-lapse X-ray nano-computed tomography. To unravel the interplay of collagen fibrils and local deformation, digital volume correlation (DVC) has been applied to map the local strain field while the crack initiation and propagation is tracked in real time. Our results highlight the intrinsic and extrinsic shielding mechanisms and correlate the crack growth behavior in nature to the service requirement of dentin to resist catastrophic fracture. This is of wide interest not just in terms of understanding dentin fracture but also can extend beyond dentin to other anisotropic structural composite biomaterials such as bone, antler and chitin.
|
|
| 9. |
|
|
