OPTIMIZATION RESEARCH FOR A HIGH PRESSURE COMMON RAIL DIESEL ENGINE BASED ON SIMULATION

Y. LIU,Y.-T. ZHANG,T. QIU,X. DING,Q. XIONG 한국자동차공학회 2010 International journal of automotive technology Vol.11 No.5

ABSTRACT−A TP (Temperature Phase) model is presented to carry out optimization calculation for a high-pressure common rail diesel engine. Temperature is the most important parameter in the TP model. For the lower branch (when temperature T < 850 K) of the S-shaped curve (auto-ignition phase), a 6-step ad-hoc model with adjusted rate constants of nheptane is used, referred to steady state assumption. Steady state assumption is based on the observation that, due to very fast chemical processes in combustion problems, many chemical species and reactions are in a quasi-steady state or partial equilibrium. When a species is assumed to be in the steady state, the corresponding differential equation can be replaced by an algebraic relation, which reduces the computational costs. For the middle branch (850 K ≤ T < 1100 K) of the S-shaped curve, a 4-step model is used to calculate the unstable phase. For the upper branch (T≥1100 K) of the S-shaped curve, onestep model is used because the one-step model has widely been used in descriptions of flame stability where it essentially serves as a model that produces a thin flame with strong temperature sensitivity. When zone temperature T<1500 K, only the soot precursors –PAHs (Polycyclic aromatic hydrocarbons) is created and there is no soot emission. When zone temperature T≥1500 K, PAHs and soot source terms (particle inception, surface growth, oxidation, coagulation) are calculated. The TP model is then applied in multidimensional simulations to carry out optimizing, which reduces experiment cost. The results of cylinder pressures, the corresponding heat release rates, NOx and soot with variation of injection time at constant rail pressure, variation of EGR-rate at constant rail pressure and variation of rail pressure at constant EGR-rate between simulation and experimental data are analyzed. The results indicate that the TP model can carry out optimization and CFD (computational fluid dynamics) and can be a tool to calculate for a high-pressure common rail diesel engine.

c-Cbl-Mediated Neddylation Antagonizes Ubiquitination and Degradation of the TGF-β Type II Receptor

Zuo, W.,Huang, F.,Chiang, Y.,Li, M.,Du, J.,Ding, Y.,Zhang, T.,Lee, H.,Jeong, L.,Chen, Y.,Deng, H.,Feng, X.H.,Luo, S.,Gao, C.,Chen, Y.G. Cell Press 2013 Molecular cell Vol.49 No.3

Transforming growth factor β (TGF-β) is a potent antiproliferative factor in multiple types of cells. Deregulation of TGF-β signaling is associated with the development of many cancers, including leukemia, though the molecular mechanisms are largely unclear. Here, we show that Casitas B-lineage lymphoma (c-Cbl), a known proto-oncogene encoding an ubiquitin E3 ligase, promotes TGF-β signaling by neddylating and stabilizing the type II receptor (TβRII). Knockout of c-Cbl decreases the TβRII protein level and desensitizes hematopoietic stem or progenitor cells to TGF-β stimulation, while c-Cbl overexpression stabilizes TβRII and sensitizes leukemia cells to TGF-β. c-Cbl conjugates neural precursor cell-expressed, developmentally downregulated 8 (NEDD8), a ubiquitin-like protein, to TβRII at Lys556 and Lys567. Neddylation of TβRII promotes its endocytosis to EEA1-positive early endosomes while preventing its endocytosis to caveolin-positive compartments, therefore inhibiting TβRII ubiquitination and degradation. We have also identified a neddylation-activity-defective c-Cbl mutation from leukemia patients, implying a link between aberrant TβRII neddylation and leukemia development.

Magnetocaloric and critical behavior in the austenitic phase of Gd-doped Ni₅₀Mn₃₇Sn₁₃ Heusler alloys

Zhang, P.,Phan, T.L.,Dan, N.H.,Thanh, T.D.,Yu, S.C. Elsevier Sequoia 2014 Journal of alloys and compounds Vol.615 No.suppl1

The magnetic phase transition behavior were investigated in detail in Ni<SUB>50-y</SUB>Gd<SUB>y</SUB>Mn<SUB>37</SUB>Sn<SUB>13</SUB> (y=1 and 3) alloys prepared by arc-melting method. The martensite phase was found to be strongly suppressed by a small amount of Gd doping. Based on isothermal magnetization curves around Curie temperature of the austenite (T<SUB>C</SUB><SUP>A</SUP>) phase, critical behavior in the austenite phases of both alloys were determined carefully by the Kouvel-Fisher method. The critical exponents were found to be β=0.473+/-0.020 and γ=1.141+/-0.017 with T<SUB>C</SUB><SUP>A</SUP>=299.0+/-0.2K for y=1, and β=0.469+/-0.068 and γ=1.214+/-0.042 with T<SUB>C</SUB><SUP>A</SUP>=302.9+/-0.7K for y=3, respectively. The values of the critical exponents for the ferromagnetic phase transition in the A phase of two alloys can be basically ascribed in the mean-field model (with β=0.5, γ=1) with slightly deviation, revealing a long-range order of ferromagnetic interactions. Such critical behavior can be attributed to the magnetic inhomogeneities originated from the atomic disorder introduced by Gd doping.

Local structure and magnetocaloric effect for La_0.7Sr_0.3Mn_1-xNi_xO₃

Zhang, Y.D.,Phan, T.L.,Yang, D.S.,Yu, S.C. Elsevier 2012 Current Applied Physics Vol.12 No.3

We have prepared polycrystalline La<SUB>0.7</SUB>Sr<SUB>0.3</SUB>Mn<SUB>1-x</SUB>Ni<SUB>x</SUB>O<SUB>3</SUB> (x = 0, 0.01, 0.02, 0.03) samples by conventional solid-state reaction. X-ray absorption studies reveal that Ni dopants in the compounds having an oxidation state of 2+. These Ni<SUP>2+</SUP> ions replace Mn on the octahedral site of the perovskite structure. An increase of the Ni content enhances the concentration of Mn<SUP>4+</SUP> ions. This reduces magnetization, and the ferromagnetic-paramagnetic phase transition temperature (T<SUB>C</SUB>) of La<SUB>0.7</SUB>Sr<SUB>0.3</SUB>Mn<SUB>1-x</SUB>Ni<SUB>x</SUB>O<SUB>3</SUB> from ∼365 K for x = 0 to ∼345 K for x = 0.03. The magnetocaloric effect has also been assessed by means of magnetic-entropy change, which is determined from field dependences of magnetization. We find a large magnetic-entropy change taking place around T<SUB>C</SUB> of the samples. Under an applied field interval of 15 kOe, the maximum magnetic-entropy changes |ΔS<SUB>M</SUB><SUP>max</SUP>| are about 2.33, 2.27, 2.26 and 2.21 J/kg K for x = 0, 0.01, 0.02, and 0.03, respectively. Interestingly, the doping of a small amount of Ni in La<SUB>0.7</SUB>Sr<SUB>0.3</SUB>Mn<SUB>1-x</SUB>Ni<SUB>x</SUB>O<SUB>3</SUB> does not make|ΔS<SUB>M</SUB><SUP>max</SUP>| changed very much, but causes the shift of this value towards room temperature. Such the feature is applicable to control the working temperature range of cooling systems based on the magnetocaloric effect.

T-ray와 텝핑을 이용한 허니콤샌드위치 복합재 결함탐상 평가기법

임광희(K. H. Im),조영태(Y. T. Cho),신승희(S. H. Shin),원재현(J. H Won),정예원(Y. W. Jung),장계림(G. L. Zhang),김선규(S. K. Kim) 한국생산제조학회 2020 한국생산제조시스템학회 학술발표대회 논문집 Vol.2020 No.7

The clonal origins of leukemic progression of myelodysplasia

Kim, T,Tyndel, M S,Kim, H J,Ahn, J-S,Choi, S H,Park, H J,Kim, Y-k,Yang, D-H,Lee, J-J,Jung, S-H,Kim, S Y,Min, Y H,Cheong, J-W,Sohn, S K,Moon, J H,Choi, M,Lee, M,Zhang, Z,Kim, D(D H) Nature Publishing Group 2017 Leukemia Vol.31 No.9

<P>The genetics behind the progression of myelodysplasia to secondary acute myeloid leukemia (sAML) is poorly understood. In this study, we profiled somatic mutations and their dynamics using next generation sequencing on serial samples from a total of 124 patients, consisting of a 31 patient discovery cohort and 93 patients from two validation cohorts. Whole-exome analysis on the discovery cohort revealed that 29 of 31 patients carry mutations related to at least one of eight commonly mutated pathways in AML. Mutations in genes related to DNA methylation and splicing machinery were found in T-cell samples, which expand at the initial diagnosis of the myelodysplasia, suggesting their importance as early disease events. On the other hand, somatic variants associated with signaling pathways arise or their allelic burdens expand significantly during progression. Our results indicate a strong association between mutations in activated signaling pathways and sAML progression. Overall, we demonstrate that distinct categories of genetic lesions play roles at different stages of sAML in a generally fixed order.</P>

Influence of Pr-doping on the magnetic properties and magnetocaloric effect of Ni_50-xPr_xMn₃₇Sn₁₃ alloys

Phan, T.L.,Thanh, P.T.,Dan, N.H.,Zhang, P.,Thanh, T.D.,Phan, M.H.,Yu, S.C. Elsevier Sequoia 2014 JOURNAL OF ALLOYS AND COMPOUNDS Vol.615 No.suppl1

We have studied the magnetic and magnetocaloric (MC) properties of Ni<SUB>50-x</SUB>Pr<SUB>x</SUB>Mn<SUB>37</SUB>Sn<SUB>13</SUB> (x=0, 1, 3, and 5) alloy ingots fabricated by arc-melting. Experimental results revealed a coexistence of the conventional and inverse MC effects in the samples with x=0, 1, and 3. There is a gradual decrease of the magnetization and magnetic-entropy change (ΔS<SUB>m</SUB>) when Pr-doping content increases. However, the Curie temperature of the austenitic phase (T<SUB>C</SUB><SUP>A</SUP>) around room temperature was not changed very much. Particularly, doping a small amount of Pr with x=1 enhances remarkably the linewidth of the peaks in its ΔS<SUB>m</SUB>(T) curves. This increases the relative cooling power (RCP) of Ni<SUB>50-x</SUB>Pr<SUB>x</SUB>Mn<SUB>37</SUB>Sn<SUB>13</SUB> alloys when they are used as coolants in refrigeration devices. For example, under an applied field of H=50 kOe, the RCP increases from 150 for x=0 to ~200J/kg for x=1. Higher Pr contents reduce quickly the MC effect because of the formation of nonmagnetic secondary phases.

Ferromagnetic Order in Rapidly Cooled Nd-Fe-Co-Al Alloy Ribbons

Phan, T. L.,Zhang, Y. D.,Dan, N. H.,Thang, D. D.,Thanh, T. D.,Zhang, P.,Yu, S. C. IEEE 2013 IEEE transactions on magnetics Vol.49 No.7

<P>We have studied the magnetic properties of Nd<SUB>45</SUB>Fe<SUB>30</SUB>Co<SUB>15</SUB>Al<SUB>10</SUB> alloy ribbons with various thicknesses of about 120 (N<SUB>1</SUB>) and 50 μm (N<SUB>2</SUB>) prepared by melt-spinning. Structural analyses based on an X-ray diffractometer and a high-resolution transmission electron microscope revealed an existence of nanocrystals with sizes of 10 ~ 20 nm surrounded by an amorphous host matrix. With decreasing ribbon thickness and nanocrystalline size, magnetic studies upon a vibrating sample magnetometer indicated the decrease of the Curie temperature (T<SUB>C</SUB>), coercive force (H<SUB>c</SUB>), and magnetic entropy change (ΔS<SUB>m</SUB>). In the ferromagnetic region, however, magnetization values determined for N<SUB>2</SUB> are greater than those determined for N<SUB>1</SUB>. These results are related to the differences in the critical exponents of N<SUB>1</SUB> (β=0.418 and γ=1.173), and N<SUB>2</SUB> (β=0.512 and γ=1.077), which are characteristic for the ferromagnetic nature existing in the alloy ribbons with different thicknesses.</P>

Crossover from first-order to second-order phase transitions and magnetocaloric effect in La_0.7Ca_0.3Mn_0.91Ni_0.09O₃

Phan, The-Long,Zhang, P.,Thanh, T. D.,Yu, S. C. American Institute of Physics 2014 Journal of Applied Physics Vol.115 No.17

We have prepared La0.7Ca0.3Mn0.91Ni0.09O3 and then studied its critical behavior and magnetocaloric effect. Analyzing temperature and field dependences of magnetization around the ferromagnetic-paramagnetic transition reveals the sample undergoing the second-order magnetic phase transition with the critical parameters T-C approximate to 199.4K, beta = 0.171 +/- 0.006, and gamma = 0.976 +/- 0.012. A considerable difference of these critical exponents compared with those expected for the standard models is due to the sample exhibiting the crossover property (tricriticality); its exponent values are more close to those expected for the tricritical mean-field theory with beta = 0.25 and gamma = 1. Under the field 40 kOe, the maximum magnetic entropy change (-Delta S-max) around T-C is about 7.1 J center dot kg(-1)center dot K-1, corresponding to a refrigerant capacity RC approximate to 170 J/kg. Particularly, its magnetic-field dependence obeys a power law vertical bar Delta S-max vertical bar infinity H-n, where n = 0.55 is quite far from the value calculated from the relation n = 1 + (beta - 1)/(beta + gamma). (C) 2014 AIP Publishing LLC.

Phase Stability, Band Gap, and Electronic and Magnetic Properties of Quaternary Heusler alloys FeMnScZ (Z = Al, Ga, In)

Y. C. Gao,Y. Zhang,X. T. Wang 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.6

By using the first-principles calculations, we have systematically investigated the phase stability,band gap, and electronic structures and magnetic properties of quaternary Heusler alloys FeMnScZ(Z = Al, Ga, In). We found that FeMnScZ (Z = Al, Ga, In) alloys are half-metallic ferrimagnetsat their equilibrium lattice constants and retain a high spin polarization over a quite wide rangeof lattice distortions. The half-metallic band gap in the FeMnScZ (Z = Al, Ga, In) alloys arisesfrom t1u-t2g splitting but not eu-t1u splitting. The total magnetic moments are 3 μB per unit cellfor FeMnScZ (Z = Al, Ga, In) alloys, following the Slater−Pauling rule with the total number ofvalence electrons minus 18 rather than 24. Moreover, all of these alloys have a negative formationenergy, which implies that they can be synthesized experimentally.