Search

VSC-HVDC is one of the proven solutions to the transmission problem of offshore wind power and the study of converter is the key technology. Mean value model of converter is introduced. The paper puts forward a method that can simplify the complex converter which is based on IGBT into a mean value model to improve the simulation speed. Through the simulation in Mat lab, the accuracy and high efficiency of simplified model are verified. The results show that the simplified model is feasible.

Programmed Death 1 (PD-1) and T cell Ig and mucin domain-3 protein (Tim-3) are immune checkpoint receptors highly expressed on tumor infiltrating T lymphocytes (TIL). PD-1 inhibits T cell activation and type-1 T cell responses, while Tim-3 is proposed to mark more extensively exhausted cells, although the mechanisms underlying Tim-3 function are not clear. Trials of anti-PD-1 therapy have identified a large subset of non-responder patients, likely due to expression of alternative checkpoint molecules like Tim-3. We investigated the phenotypic and functional characteristics of T cells with differential expression of PD-1 (high/low) and Tim-3 (positive/negative), using TIL directly isolated from head and neck squamous cell carcinomas (HNSCC). Unexpectedly, we found that expression of Tim-3 alone does not necessarily mark TIL as dysfunctional/exhausted. In Tim-3-TIL, PD-1 levels correlate with T cell dysfunction, with a PD-1low/intermed phenotype identifying recently activated and still functional cells, whereas PD-1hiTim-3− T cells are actually exhausted. Nonetheless, PD-1intermed cells are still potently suppressed by PD-L1. PD-1 expression was associated with reduced phosphorylation of ribosomal protein S6 (pS6), whereas Tim-3 expression was associated with increased pS6. Using a novel mouse model for inducible Tim-3 expression, we confirmed that expression of Tim-3 does not necessarily render T cells refractory to further activation. These results suggest the existence of PD-1 and Tim-3 crosstalk in regulating antitumor T cell responses, with important implications for anti-PD-1 immunotherapy.

Al-Ti-C-Y master alloy was prepared by combining SHS technique and melting-casting method. The microstructure of master alloy and its grain-refining effect on AZ31 alloy were investigated by means of OM, XRD, SEM and EDS. Experimental results indicated that the prepared master alloy consisted of α-Al, TiAl 3 , TiC and Al 3 Y phases, and exhibited good grain-refining performance of AZ31 alloy. Morphology of α-Mg changed from coarse dendritic to fine equiaxed and the average grain size of α-Mg matrix reduced from the original 580 to 170 μm after adding 1.0 wt.% master alloy. The grain refining efficiency of Al-Ti-C-Y master alloy on AZ31 alloy was mainly attributed to heterogeneous nucleation of TiC particles and grain growth restriction of Al-Y compound or TiC at grain boundaries.

To improve the strength-toughness and heat-resistance of die cast magnesium alloy, the ZA85 alloy has been prepared by adding proper amount of spherical quasicrystals containing master alloy. The results indicate that the solidification microstructure is inlaid with quasicrystal particles, which is a new phase i(Mg45Zn47Y5Mn3), co-existing with the α-Mg, Φ(Al2Mg5Zn2) phase and τ(Mg32(AlZn)49) phase. Mechanical properties of ZA85 alloys have been dramatically improved owing to the obvious grain refinement of the matrix microstructure. While adding 1.7 wt % spherical quasicrystal containing master alloy, macro-hardness of ZA85 magnesium alloy reaches 75HB; meanwhile, impact toughness reaches the peak value 18.4Jcm-2, which is about 202% of ZA85 base alloy. Due to the pinning effect of quasicrystal particles on grain boundaries, the strengthened ZA85 alloys would have excellent heat-resistance.

Al-Ti-C grain refiners have been prepared by combining self-propagating high-temperature synthesis (SHS) technique and melting-casting method. Effects of Al powder size and C/Ti ratio on the microstructures and grain-refining efficiency of Al-Ti-C grain refiners were studied by OM, XRD, SEM and EDS. The results show that when Al powder size is fine, and C/Ti ratio is 1: 8, SHS reaction among the mixed powders can easily carry on in the melt. As a result, the prepared grain refiner consists of blocky Al3Ti and fine TiC particles distributed in Al matrix, and exhibits excellent grain refining performance on commercially pure Al.

Al-Ti-C-P master alloy has been successfully fabricated by SHS-melting technology. Microstructures and phase constituent of Al-Ti-C-P master alloy were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and EDS. The results show that Al-Ti-C-P master alloy comprises TiAl3, TiC, AlP and α-Al matrix. After adding 2.0 wt% Al-Ti-C-P master alloy, microstructure and mechanical properties (after T6 treating) of ZL117 alloy has been improved dramatically: The average grain size of primary silicon decreases from 260 to 35 μm, edges and angles of primary silicon are passivated, the morphology of eutectic silicon changes from large needle-like one to fine rod-like or particle-like one, and the microstructures are noticeably refined; Room temperature tensile strength changes from 168 to 260 MPa while elevated temperature tensile strength (at 300) varies from 88 to 125 MPa. Impact toughness and macro-hardness(HB) increases to 17 J/cm2 and 97 from the original 6.5 J/cm2 and 92.

Spherical icosahedral quasicrystalline phase (I-phase) was obtained by introducing Ca, into Mg-Zn-Y alloy under conventional casting conditions. Due to the addition of Ca, Mg45Zn50Y4.5Ca0.5 primary I-phase, which is thermodynamically stable and homogeneously distributed, was generated instead of decahedral quasicrystalline phase during the solidification process; the morphology of primary I-phase in the solidification microstructure changed from petal-like one (60-80μm) to spherical one (≤15μm). When the mass fraction of Ca reaches 0.05%, spherical I-phase with the largest quantity, highest spheroidization rate and highest circular degree can be obtained. Meanwhile, due to the changed morphology and the decreased size of primary I-phase, the hardness of Mg-Zn-Y-Ca master alloy is reduced. The application of spherical I-phase as particulate reinforced phase provides great opportunities for the improvement of strength and toughness of magnesium alloys.

Programmed Death 1 (PD-1) and T cell Ig and mucin domain-3 protein (Tim-3) are immune checkpoint receptors highly expressed on tumor infiltrating T lymphocytes (TIL). PD-1 inhibits T cell activation and type-1 T cell responses, while Tim-3 is proposed to mark more extensively exhausted cells, although the mechanisms underlying Tim-3 function are not clear. Trials of anti-PD-1 therapy have identified a large subset of non-responder patients, likely due to expression of alternative checkpoint molecules like Tim-3. We investigated the phenotypic and functional characteristics of T cells with differential expression of PD-1 (high/low) and Tim-3 (positive/negative), using TIL directly isolated from head and neck squamous cell carcinomas (HNSCC). Unexpectedly, we found that expression of Tim-3 alone does not necessarily mark TIL as dysfunctional/exhausted. In Tim-3-TIL, PD-1 levels correlate with T cell dysfunction, with a PD-1low/intermed phenotype identifying recently activated and still functional ce...

To investigate the influence of co-stimulatory molecules B7-H4 expression on prognosis of gastric cancer patients treated by cytokine-induced killer cells (CIK cells) adoptive immunotherapy.Clinical data of 156 cases of gastric cancer patients were retrospectively analyzed. Patients were divided into chemotherapy group(n=81) and chemotherapy combined with CIK cell therapy group(n=75). B7-H4 expression was detected in the surgical specimens of gastric cancer patients by immunohistochemistry assay. Disease-free survival was compared between the chemotherapy group and the CIK group at different expression levels of B7-H4.The difference was not statistically significant in all clinical and pathological data between the chemotherapy group and the CIK treatment group (P0.05). The postoperative median tumor-free survival in two groups was 18.0 and 45.0 months, respectively, and the difference was statistically significant (chi(2)=11.631, P=0.001). The postoperative median survival time was 27.0 and 49.0 months, respectively, and the difference was statistically significant (chi(2)=10.907, P=0.001). In 86 patients with low B7-H4 expression, the median tumor-free survival time was 32.0 and 62.0 months, respectively, and the difference was statistically significant (chi(2)=4.663,P=0.03). In 70 patients with high B7-H4 expression, the median tumor-free survival time was 11.0 and 18.0 months, respectively, and the difference was statistically significant (chi(2)=11.971, P=0.001).The median tumor-free survival time of patients with gastric cancer may be further improved by chemotherapy combined with CIK cell therapy, regardless of the level of B7-H4 expression.