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Influence of pH value and chelating reagent on performance of Li_3V_2(PO_4)3/C cathode material 被引量:2
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作者 向伟 唐艳 +4 位作者 王雁英 钟本和 方为茂 刘恒 郭孝东 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2013年第5期1395-1402,共8页
The Li3V2(PO4)3/C composite cathode material was synthesized via sol-gel method using three different chelating agents (citric acid, salicylic acid and polyacrylic acid) at pH value of 3 or 7. The crystal structur... The Li3V2(PO4)3/C composite cathode material was synthesized via sol-gel method using three different chelating agents (citric acid, salicylic acid and polyacrylic acid) at pH value of 3 or 7. The crystal structure, morphology, specific surface area and electrochemical performance of the prepared samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge test. The results show that the effects of pH value on the performance of the prepared materials are greatly related to the chelating agents. With salicylic acid or polyacrylic acid as the chelating reagent, the structure, morphology and electrochemical performance of the samples are greatly influenced by the pH values. However, the structure of the materials with citric acid as the chelating agent does not change as pH value changes, and the materials own uniform particle size distribution and good electrochemical performance. It delivers an initial discharge capacity of 113.58 mA·h/g at 10C, remaining as high as 108.48 mA·h/g after 900 cycles, with a capacity retention of 95.51%. 展开更多
关键词 Li3v2(PO4)3 cathode material sol-gel method chelating agents pH value
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The value of vegetation ecosystem services:a case of Qinling-Daba Mountains 被引量:20
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作者 REN Zhiyuan,ZHANG Yanfang,LI Jing(College of Tourism and Environment, Shaanxi Normal University, Xi’an 710062, China) 《Journal of Geographical Sciences》 SCIE CSCD 2003年第2期195-200,共6页
According to differences in vegetation types and their coverage, combining the latest research, using theory and method on the value of vegetation ecosystem services, this paper not only calculated goods... According to differences in vegetation types and their coverage, combining the latest research, using theory and method on the value of vegetation ecosystem services, this paper not only calculated goods produced by different types of vegetation but also estimated the value of various vegetation ecosystem services and set up database, GIS and eco-account of vegetation ecosystem. The result was as follows: the value of vegetation's primary productivity, soil and fertility conservation, water conservation, CO 2 fixation and O 2 release was 199.6 billion yuan/a, 22.64 billion yuan/a, 22.66 billion yuan/a, 352.24 billion yuan/a and 374.19 billion yuan/a, respectively. The total value of ecosystem services was 968.33 billion yuan/a. The temperate deciduous broad-leaved forest had the highest contribution rate, accounting for 16.42%. The result of value can reflect regional reality more exactly. 展开更多
关键词 regional vegetation ecosystem services ecological economic value Qinling-Daba mountains CLC number:f062.2 Q948.1
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Prognostic value of interim ^(18)F-FDG PET/CT in diffuse large B-cell lymphoma 被引量:4
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作者 Zhitao Ying Xuejuan Wang +11 位作者 Yuqin Song Wen Zheng Xiaopei Wang Yan Xie Ningjing Lin Meifeng Tu Lingyan Ping Weiping Liu Lijuan Deng Chen Zhang Zhi Yang Jun Zhu 《Chinese Journal of Cancer Research》 SCIE CAS CSCD 2013年第1期95-101,共7页
Objective: Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous disease. The prognostic factor currently used is not accurate enough to predict the outcomes of patients with DLBCL. The prognostic significance o... Objective: Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous disease. The prognostic factor currently used is not accurate enough to predict the outcomes of patients with DLBCL. The prognostic significance of interim PET/CT in DLBCL remains controversial. The aim of this study is to determine the predictive value of interim 18F-FDG PET/CT after first-line treatment in patients with DLBCL. Methods: Thirty-two patients with DLBCL underwent baseline, interim and post-treatment lSF-FDG PET/CT scans. Imaging results were analyzed for the survival of patients via software SPSS 13.0, retrospectively. Results: Thirty-one of the 32 patients were treated with R-CHOP regimen, and interim 18F-FDG PET/CT of 24 patients was performed after 2 cycles of treatment. After a median follow-up period of 16.7 months, the 2-year progression-free survival (PFS) rates were significantly different between the groups above and below SUVmax CUt-Off value of 2.5 (P=0.039). No significant differences were found in the 2-year PFS rates if SUVm, cut-offvalues were set as 2.0 and 3.0, respectively (P=0.360; P=0.113). Conclusions: Interim PET/CT could predict the prognosis of DLBCL patients with the SUVmax cut-off value of 2.5, but more clinical data should be concluded to confirm this conclusion. 展开更多
关键词 fludeoxy-glucose f18 lyrnphoma large cell DIffUSE PROGNOSIS standard utility value
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Absolute Reference Values of the Real Gas
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作者 Albrecht Elsner 《Engineering(科研)》 2018年第5期270-290,共21页
With his publication in 1873 [1] J. W. Gibbs formulated the thermodynamic theory. It describes almost all macroscopically observed properties of matter and could also describe all phenomena if only the free energy U -... With his publication in 1873 [1] J. W. Gibbs formulated the thermodynamic theory. It describes almost all macroscopically observed properties of matter and could also describe all phenomena if only the free energy U - ST were explicitly known numerically. The thermodynamic uniqueness of the free energy obviously depends on that of the internal energy U and the entropy S, which in both cases Gibbs had been unable to specify. This uncertainty, lasting more than 100 years, was not eliminated either by Nernst’s hypothesis S = 0 at T = 0. This was not achieved till the advent of additional proof of the thermodynamic relation U = 0 at T = Tc. It is noteworthy that from purely thermodynamic consideration of intensive and extensive quantities it is possible to derive both Gibbs’s formulations of entropy and internal energy and their now established absolute reference values. Further proofs of the vanishing value of the internal energy at the critical point emanate from the fact that in the case of the saturated fluid both the internal energy and its phase-specific components can be represented as functions of the evaporation energy. Combining the differential expressions in Gibbs’s equation for the internal energy, d(μ/T)/d(1/T) and d(p/T)/d(1/T), to a new variable d(μ/T)/d(p/T) leads to a volume equation with the lower limit vc as boundary condition. By means of a variable transformation one obtains a functional equation for the sum of two dimensionless variables, each of them being related to an identical form of local interaction forces between fluid particles, but the different particle densities in the vapor and liquid spaces produce different interaction effects. The same functional equation also appears in another context relating to the internal energy. The solution of this equation can be given in analytic form and has been published [2] [3]. Using the solutions emerging in different sets of problems, one can calculate absolutely the internal energy as a function of temperature-dependent, phase-specific volumes and vapor pressure. 展开更多
关键词 ENTROPY REfERENCE value S (M v 0) = 0 INTERNAL Energy REfERENCE value U (M Tc) = 0 ...
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Diagnostic value of lead corrected Vt and V6 in patients with acute pulmonary thromboembolism
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作者 Geng-Xin Sun Juan Wu 《Journal of Hainan Medical University》 2019年第6期42-46,共5页
Objective: To investigate the diagnostic value of lead corrected Vt and V6 in patients with acute pulmonary thromboembolism. Methods: A total of 89 patients with suspected acute PTE were examined in our hospital from ... Objective: To investigate the diagnostic value of lead corrected Vt and V6 in patients with acute pulmonary thromboembolism. Methods: A total of 89 patients with suspected acute PTE were examined in our hospital from January to December 2017. A baseline 12-lead ECG was recorded on admission, with a gain of 10 mm/mV and a paper velocity of 25 mm/s. Results: Of the 89 suspected PTE patients enrolled in this study, 45 patients with acute PTE and 44 patients without PTE were identified by CTA. The chief complaint of most patients in both groups was dyspnea or dyspnea, with no significant difference between the two groups. The levels of d-dimer and high-sensitivity troponin in patients with PTE were significantly higher than those without PTE. QT and QTc in the V1 lead in the PTE group were significantly greater than those in the non-PTE group, but QT and QTc in the V6 lead were not significantly different between the two groups. The QTc difference (V1-V6) in the PTE group was significantly greater than that in the non-PTE group. In the morphological analysis, T wave inversion in lead III of PTE group, T wave inversion of V1 or V1 and V2 was significantly higher than that of non-PTE group. There was no significant difference in the incidence of S1Q3T3 between the two groups. For the prediction of acute PTE, the maximum accuracy of the maximum QTc difference (V1-V6)≥20 ms, the sensitivity was 83.2%, and the specificity and positive predictive value was 100%. T-wave inversion in V1 leads is the most sensitive morphological abnormality associated with PTE with a sensitivity of 80.06% and a specificity of 62.29%. T-wave inversion in lead III is a sub-sensitive predictor with a sensitivity of 51.20%. The specificity is 70.53%. Conclusions: The QTC difference (V1-V6) is a distinct feature of acute PTE, and QTC difference (V1-V6)≥20 ms as an important indicator of acute PTE in emergency settings. 展开更多
关键词 Acute PULMONARY THROMBOEMBOLISM LEADS v1 And v6 Differences In QT Diagnostic value
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STRUCTURES OF VALUES FOR SET GAMES RESTRICTED BY PARTITION SYSTEM
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作者 Sun Hao 《Applied Mathematics(A Journal of Chinese Universities)》 SCIE CSCD 2006年第1期119-125,共7页
A set game, in which the worth of a coalition is expressed by a set instead of a real number, is a new type of cooperative game. A F-restricted set game is a set game restricted by partition system. The main theorems ... A set game, in which the worth of a coalition is expressed by a set instead of a real number, is a new type of cooperative game. A F-restricted set game is a set game restricted by partition system. The main theorems show the structures of IM-value,OIM-value,SCM-value and ICM-value respectively,and the equivalency of IM value and the OIM-value for monotonic set games restricted by partition system as well. 展开更多
关键词 f-restricted set game partition system value.
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Lattice of Interval-Valued(∈,∈∨q)-Fuzzy LI-Ideals in Lattice Implication Algebras
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作者 Chunhui LIU 《Journal of Mathematical Research with Applications》 CSCD 2016年第4期394-406,共13页
In the present paper, the interval-valued (ε, εv q)-fuzzy LI-ideal theory in lattice implication algebras is further studied. Some new properties of interval-valued (ε, ε v q)-fuzzy LI-ideals are given. Repres... In the present paper, the interval-valued (ε, εv q)-fuzzy LI-ideal theory in lattice implication algebras is further studied. Some new properties of interval-valued (ε, ε v q)-fuzzy LI-ideals are given. Representation theorem of interval-valued (ε, ε v q)-fuzzy LI-ideal which is generated by an interval-valued fuzzy set is established. It is proved that the set consisting of all interval-valued (ε, εv q)-fuzzy LI-ideals in a lattice implication algebra, under the partial order , forms a complete distributive lattice. 展开更多
关键词 lattice-valued logic lattice implication algebra interval-valued (ε ε v q)-fuzzy LI-ideal complete distributive lattice
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JAK2V617F在原发性血小板增多症的表达情况与临床特征分析
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作者 孙兴卫 《临床研究》 2025年第2期88-91,共4页
目的通过对原发性血小板增多症(ET)患者进行JAK2 V617 F突变的检测,研究JAK2 V617 F突变对于ET患者的临床特征以及预后的关系,为ET患者诊断治疗提供帮助。方法按照世界卫生组织(WHO)诊断标准,收集2018年4月至2024年2月确诊的82例ET患者... 目的通过对原发性血小板增多症(ET)患者进行JAK2 V617 F突变的检测,研究JAK2 V617 F突变对于ET患者的临床特征以及预后的关系,为ET患者诊断治疗提供帮助。方法按照世界卫生组织(WHO)诊断标准,收集2018年4月至2024年2月确诊的82例ET患者,通过收集其外周血血小板数、中性粒细胞数、白细胞数、血红蛋白以及纤维蛋白原含量,利用聚合酶链式反应(PCR)技术检测骨髓或外周血中JAK2 V617 F突变的表达。结果(1)本研究收集的82例ET患者中,存在JAK2 V617 F突变的患者有65例,占所有ET患者的79.27%;(2)在ET患者中,JAK2 V617 F基因的表达与性别无关(P=0.947),但是与年龄相关,>50岁组JAK2 V617 F基因突变占比更高,差异具有统计学意义(P=0.020);(3)存在JAK2 V617 F基因的突变的患者血小板数低于阴性患者,差异具有统计学意义(P=0.017),而中性粒细胞数、白细胞数以及纤维蛋白原的检出量则明显较高,差异均有统计学意义(P<0.001);(4)观察患者预后情况,JAK2 V617 F基因的突变会提升血栓以及脾增大风险,差异均有统计学意义(P<0.05)。结论JAK2V617 F突变对原发性血小板增多症的预后产生较大影响,同时可能参与原发性血小板增多症的发病过程。 展开更多
关键词 原发性血小板增多症 JAK2v617 f 临床特征 预后
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JAK2 V617F阳性慢性髓系白血病1例
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作者 张琴 丁慧芳 王椋 《安徽医药》 2025年第12期2504-2507,共4页
目的 为伴JAK2 V617F阳性慢性髓系白血病(CML)的诊疗提供参考。方法 回顾性分析胜利油田中心医院2023年4月22日收治的1例伴JAK2 V617F阳性CML病人的临床资料。结果 该例病人规律应用酪氨酸激酶抑制剂(TKI)6个周期后,疗效良好,达血液学... 目的 为伴JAK2 V617F阳性慢性髓系白血病(CML)的诊疗提供参考。方法 回顾性分析胜利油田中心医院2023年4月22日收治的1例伴JAK2 V617F阳性CML病人的临床资料。结果 该例病人规律应用酪氨酸激酶抑制剂(TKI)6个周期后,疗效良好,达血液学完全缓解。结论 部分伴JAK2 V617F基因突变CML病人,早期使用TKI治疗有效。 展开更多
关键词 慢性髓细胞性白血病 JANUS激酶2 JAK2 v617f突变 BCR-ABL融合基因 酪氨酸激酶抑制剂
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Dibenzo[a,c]phenazin-11-yl(phenyl)methanone(SBLJ23),a novel selective inhibitor targeting JAK2^(V617F)mutation in myeloproliferative neoplasms
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作者 MOHAMMAD ABOHASSAN MESFER MOHAMMAD AL SHAHRANI +1 位作者 SARAH KHALED ALOUDA PRASANNA RAJAGOPALAN 《Oncology Research》 2025年第3期675-685,共11页
Background:The JAK2^(V617F)mutation plays a crucial part in the pathogenesis of myeloproliferative neoplasms(MPN),which includes polycythemia vera(PV),essential thrombocythemia(ET),and primary myelofibrosis(PMF)leadin... Background:The JAK2^(V617F)mutation plays a crucial part in the pathogenesis of myeloproliferative neoplasms(MPN),which includes polycythemia vera(PV),essential thrombocythemia(ET),and primary myelofibrosis(PMF)leading to aberrant proliferation and survival of hematopoietic cells.Alongside the challenges of drug resistance and side effects,identifying novel compounds that selectively target JAK2^(V617F)could provide more effective and safer therapeutic options for patients with MPNs.Materials and Methods:We employed computational approaches like high-throughput virtual screening,molecular dynamics simulations(MDS),and binding free energy calculations to identify inhibitors targeting wild and mutant JAK2 kinases.JAK2^(V617F)positive HEL,wild type JAK2 positive TF-1,and non-cancerous Vero cells were used for in vitro validations.Results:SBLJ23 emerged as a top candidate inhibitor with specificity for JAK2^(V617F).Protein-ligand interaction studies and MDS revealed stable interactions and binding of SBLJ23 over the simulation period,with Root Mean Square Deviation(RMSD)indicating consistent binding after 1t15ns.SBLJ23 displayed a half maximal inhibitory concentration(IC_(50))value of 522.4 nM against the JAK2 enzyme.The compound exhibited inhibition of cell proliferation in HEL and TF-1 cells,with half maximal cell growth inhibitory concentration(GI 50)values of 2.51 and 15.87μM,respectively.Moreover,SBLJ23 induced G 2/M cell cycle arrest in HEL cells to facilitate apoptosis in these cell lines.The compound significantly reduced the percentage of phospho JAK2 and phospho STAT3 in HEL cells.Conclusion:High binding affinity,stable interaction profile,favorable binding free energy,and in vitro validations claim SBLJ23 as a potential lead compound against JAK2^(V617F)and suggest further development and optimization towards clinical application in managing myeloproliferative neoplasms. 展开更多
关键词 JAK2^(v617f)mutation Myeloproliferative neoplasms Kinase inhibitors High-throughput virtual screening Molecular dynamics simulation
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RUNX1::MECOM融合基因合并JAK2 V617F基因突变的原发性骨髓纤维化
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作者 唐永杰 万星煜 +7 位作者 杨武晨 苟阳 李佳 墙星 刘水清 张诚 张曦 彭贤贵 《国际检验医学杂志》 2025年第21期2579-2581,2587,共4页
原发性骨髓纤维化(PMF)是一类以贫血、脾大、骨髓纤维组织增生为主要表现的骨髓增殖性肿瘤(MPN),JAK2 V617F基因突变是其发病的主要驱动基因之一^([1])。RUNX1::MECOM融合基因是由t(3;21)(q26;q22)形成,仅见于约0.2%的髓系肿瘤患者^([2]... 原发性骨髓纤维化(PMF)是一类以贫血、脾大、骨髓纤维组织增生为主要表现的骨髓增殖性肿瘤(MPN),JAK2 V617F基因突变是其发病的主要驱动基因之一^([1])。RUNX1::MECOM融合基因是由t(3;21)(q26;q22)形成,仅见于约0.2%的髓系肿瘤患者^([2])。本文报道了1例罕见的RUNX1::MECOM融合基因合并JAK2 V617F基因突变的PMF患者,现将具体情况介绍如下。 展开更多
关键词 原发性骨髓纤维化 RUNX1::MECOM t(3 21)(q26 q22) JAK2 v617f 急性髓系白血病
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术前BRAFV600E突变丰度、泛免疫炎症值与FDP/FIB比值联合预测甲状腺乳头状癌中央区淋巴结转移的价值
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作者 薛松 韩冬 +2 位作者 罗秀 李红红 谷丽 《临床与病理杂志》 2025年第11期1487-1495,共9页
目的:中央区淋巴结的转移状态是影响甲状腺乳头状癌(papillary thyroid carcinoma,PTC)预后及治疗策略制订的关键因素,建立精准的预测模型以评估PTC患者发生中央区淋巴结转移的风险,具有重要的临床意义。本研究旨在探讨术前V-Raf鼠类肉... 目的:中央区淋巴结的转移状态是影响甲状腺乳头状癌(papillary thyroid carcinoma,PTC)预后及治疗策略制订的关键因素,建立精准的预测模型以评估PTC患者发生中央区淋巴结转移的风险,具有重要的临床意义。本研究旨在探讨术前V-Raf鼠类肉瘤病毒癌基因同源物B1(V-Raf murine sarcoma viral oncogene homolog B1,BRAF)V600E突变丰度、泛免疫炎症值(pan-immune-inflammation value,PIV)、纤维蛋白降解产物(fibrin degradation product,FDP)与纤维蛋白原(fibrinogen,FIB)比值联合检测对预测PTC患者发生中央区淋巴结隐匿性转移的价值,以期为临床术前评估与个体化治疗决策提供参考依据。方法:回顾性分析2020年2月至2025年1月期间于南京市高淳人民医院经手术治疗且术前评估为cN0期的162例PTC患者。根据术后病理证实的中央区淋巴结状态,将162例患者分为转移组与非转移组。术前对所有研究对象进行BRAFV600E突变丰度、血常规和凝血功能检查,其中血常规指标包括血小板计数(platelet count,PLT)、单核细胞计数(monocyte count,MON)、中性粒细胞计数(neutrophil count,NEU)、淋巴细胞计数(lymphocyte count,LYM),凝血功能指标包括FDP和FIB。根据上述指标结果计算PIV(PIV=PLT×NEU×MON/LYM)及FDP/FIB比值。并于术前收集所有研究对象的一般资料。比较转移组与非转移组的BRAFV600E突变丰度、PIV、FDP/FIB比值及其他相关资料。对PTC患者发生中央区淋巴结转移的相关危险因素进行二元Logistic回归分析。绘制受试者操作特征(receiver operating characteristic,ROC)曲线,分析术前BRAFV600E突变丰度、PIV联合FDP/FIB比值对PTC患者发生中央区淋巴结转移的预测价值。结果:转移组58例,非转移组104例。与非转移组比较,转移组男性、年龄<45岁、病灶多发、侵犯被膜的占比更高,肿瘤最大径更大,2组比较差异均有统计学意义(均P<0.05);体重指数(body mass index,BMI)、病灶分布等其他指标,2组间的差异均无统计学意义(均P>0.05)。转移组术前BRAFV600E突变丰度、PIV、FDP/FIB比值均显著高于非转移组(均P<0.05);2组BRAFV600E突变率的差异无统计学意义(P>0.05)。二元Logistic回归分析结果显示,年龄<45岁、较大的肿瘤最大径、侵犯被膜,以及较高的BRAFV600E突变丰度、PIV、FDP/FIB比值均为PTC患者发生中央区淋巴结转移的危险因素(均P<0.05)。术前BRAFV600E突变丰度、PIV、FDP/FIB比值预测PTC患者发生中央区淋巴结转移的截断值分别为33.16%、202.74、1.53 mg/g,曲线下面积(area under the curve,AUC)分别为0.738、0.780、0.699;三者联合预测PTC患者发生中央区淋巴结转移的AUC为0.863;三者联合的AUC明显优于BRAFV600E突变丰度(Z=3.135,P=0.002)、PIV(Z=2.155,P=0.031)和FDP/FIB比值(Z=4.113,P<0.001)单独预测的AUC。结论:术前BRAFV600E突变丰度、PIV、FDP/FIB比值均为PTC发生中央区淋巴结转移的独立危险因素,三者联合检测对PTC中央区淋巴结转移具有更好的预测价值。 展开更多
关键词 甲状腺乳头状癌 淋巴结转移 v-Raf鼠类肉瘤病毒癌基因同源物B1 突变丰度 泛免疫炎症值 纤维蛋白降解产物/纤维蛋白原 预后
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大禹节水基于“C+F+EPC+O”模式的战略演进与价值重构研究
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作者 郭龙 《价值工程》 2026年第6期67-70,共4页
本研究以商业模式演进理论为基础,聚焦大禹节水集团股份有限公司从传统节水设备制造商向“三农三水”综合服务商的战略转型过程,系统剖析其“C+F+EPC+O”(咨询+融资+设计采购施工+运营)商业模式的构建与实践路径。通过解析“元谋模式”... 本研究以商业模式演进理论为基础,聚焦大禹节水集团股份有限公司从传统节水设备制造商向“三农三水”综合服务商的战略转型过程,系统剖析其“C+F+EPC+O”(咨询+融资+设计采购施工+运营)商业模式的构建与实践路径。通过解析“元谋模式”“武清模式”等典型案例,揭示了企业从“交付产品”到“投资价值”的战略演进逻辑,以及在此过程中实现的价值主张、价值创造方式和价值获取机制的三维系统性重构。研究发现,该模式推动大禹节水完成了从“工程承包商”向“产业合伙人”的角色跃迁,并通过数字技术赋能与生态协同,形成了可持续的综合服务能力。本文不仅从理论层面丰富了工程企业转型与价值重构的研究视角,也为同类企业向高质量综合服务商转型提供了可借鉴的实践框架与实施路径。 展开更多
关键词 C+f+EPC+O 战略演进 价值重构 大禹节水 商业模式创新 投融建营一体化
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新型感应电机V/F控制系统稳定性方法 被引量:13
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作者 陈伟 杨荣峰 +2 位作者 于泳 徐壮 徐殿国 《电机与控制学报》 EI CSCD 北大核心 2009年第A01期11-14,共4页
针对感应电机V/F控制系统在空载或轻裁时存在一个持续振荡的稳定性问题,提出一种改善感应电机V/F控制系统稳定性的方法。根据感应电机的数学模型,研究了系统振荡与无功电流波动之间的关系。并基于定子电压定向对电流进行分解,通过... 针对感应电机V/F控制系统在空载或轻裁时存在一个持续振荡的稳定性问题,提出一种改善感应电机V/F控制系统稳定性的方法。根据感应电机的数学模型,研究了系统振荡与无功电流波动之间的关系。并基于定子电压定向对电流进行分解,通过控制无功电流恒定调节输出电压来抑制电机振荡,提高系统的稳定性。实验结果表明:该方法不依赖电机参数,鲁棒性高,使系统在0~50Hz内都能平稳运行,电机的振荡得到了抑制,有效地提高了系统的稳定性。 展开更多
关键词 振荡抑制 无功电流 定子电压定向 v/f控制
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一种改善VVVF变频调速系统稳定性方法 被引量:12
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作者 王庆义 尹泉 +1 位作者 赵金 万淑芸 《电机与控制学报》 EI CSCD 北大核心 2007年第2期138-142,152,共6页
针对异步电机运行在V/f控制方式下空载或者轻载时容易出现电流畸变振荡甚至系统不稳定现象,在功率控制原理基础上,提出了一种改善V/f控制交流传动系统稳定性的控制方法。通过深入分析系统不稳定时电机输入功率和电流之间的变换关系,... 针对异步电机运行在V/f控制方式下空载或者轻载时容易出现电流畸变振荡甚至系统不稳定现象,在功率控制原理基础上,提出了一种改善V/f控制交流传动系统稳定性的控制方法。通过深入分析系统不稳定时电机输入功率和电流之间的变换关系,在定子电压矢量定向坐标系中采用了一个频率补偿器的方法来动态调整频率,以达到抑制电流振荡的目的,保持系统的稳定性。该方法在通用的变频调速装置上仅仅由软件实现,不需要额外的硬件成本。仿真和试验结果表明,该控制方法能有效抑制电流和速度振荡,明显改善系统的稳定性。 展开更多
关键词 频率补偿器 振荡抑制 稳定 v/f控制
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异步电机V/F控制系统起动和某频段振荡问题 被引量:11
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作者 李洪亮 姜建国 周中正 《电机与控制学报》 EI CSCD 北大核心 2017年第1期90-97,共8页
针对传统预励磁之后预励磁电流衰减快,导致电机起动电流过大的缺陷,提出一种比较有效的降低异步电机起动电流的方法。通过解耦算法分别闭环控制d、q轴电流进行电机起动,起动平稳之后由闭环控制状态,通过提出的逼近算法平滑切换到异步电... 针对传统预励磁之后预励磁电流衰减快,导致电机起动电流过大的缺陷,提出一种比较有效的降低异步电机起动电流的方法。通过解耦算法分别闭环控制d、q轴电流进行电机起动,起动平稳之后由闭环控制状态,通过提出的逼近算法平滑切换到异步电机的V/F控制。该方法可有效解决电机起动电流过大的问题。针对电机某频率段出现持续低频振荡的问题,在定子电压上叠加一个抑制电流振荡的电压分量,可有效解决传统V/F控制算法在某频率段系统持续低频振荡的问题。采用提出的算法,达到了降低电机起动电流和抑制系统振荡的目的。仿真和实验结果都证明了算法的正确性和有效性。 展开更多
关键词 v/f控制 起动电流 抑制振荡 预励磁 异步电机
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线聚焦无镜头式聚偏氟乙烯超声探头的研制及V(f,z)分析法在表面波波速测量中的应用 被引量:7
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作者 何存富 吕炎 +2 位作者 宋国荣 吴斌 李永春 《机械工程学报》 EI CAS CSCD 北大核心 2011年第24期1-7,共7页
线聚焦式超声材料性质表征系统可以对水浸试样漏表面波或类漏表面波的相速度进行精确的测量,但鉴于传统超声显微镜镜头的材料昂贵且制作困难,采用厚度为40?m的聚偏氟乙烯(Polyvinylidene fluoride,PVDF)压电薄膜作为激励/接收元件,设计... 线聚焦式超声材料性质表征系统可以对水浸试样漏表面波或类漏表面波的相速度进行精确的测量,但鉴于传统超声显微镜镜头的材料昂贵且制作困难,采用厚度为40?m的聚偏氟乙烯(Polyvinylidene fluoride,PVDF)压电薄膜作为激励/接收元件,设计、制作两个应用于声学显微系统的线聚焦无镜头式PVDF超声换能器,其中心频率分别为5 MHz和11 MHz。区别于传统超声显微镜高昂的设备费用与利用单频V(z)曲线测量空间振荡周期?z的方法,基于二维傅里叶变换开发出一种改进的适用于宽频的V(f,z)分析法,并发展建立一套成本较低的用于测量材料漏表面波波速的散焦试验系统。为测试换能器、算法和整体系统的性能,对抛光熔融石英进行非接触式水浸超声试验,利用V(f,z)分析法提取出表面波波速,并将试验结果与理论值进行对比,两者吻合较好。 展开更多
关键词 超声显微镜 线聚焦 聚偏氟乙烯超声探头 v(f z)分析法
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基于SPMC75F2413A的感应电机开环V/F控制 被引量:6
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作者 孔祥洪 顾滨 +1 位作者 董昌春 王令群 《实验室研究与探索》 CAS 2008年第4期31-35,共5页
给出了一种基于SPMC75F2413A的感应电机开环V/F控制的一种实现方法。SPMC75F2413A接收来自键盘或是PC机通信接口的控制信息产生相应的SPWM驱动信号,实现AC变频马达的V/F开环变频驱动功能。
关键词 SPMC75f2413A 感应电机 v/f控制
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异步电机V/f调速轻载振荡抑制方法研究 被引量:5
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作者 王天雷 张京玲 +2 位作者 贺跃帮 王柱 颜健毅 《微特电机》 北大核心 2017年第1期73-76,共4页
针对异步电机V/f控制在空载及轻载状态出现的电流振荡现象,分析得出振荡原因在于定子无功电流分量振荡造成的电机定子磁链及电磁转矩振荡。在定子电压矢量定向坐标系中,对定子无功电流分量进行振荡抑制,电流和转速得以稳定。该方法在通... 针对异步电机V/f控制在空载及轻载状态出现的电流振荡现象,分析得出振荡原因在于定子无功电流分量振荡造成的电机定子磁链及电磁转矩振荡。在定子电压矢量定向坐标系中,对定子无功电流分量进行振荡抑制,电流和转速得以稳定。该方法在通用变频调速装置上由软件实现,不需要额外的硬件成本。实验结果验证所述方法的有效性,目前已应用于通用变频器产品中,取得了良好的经济效益。 展开更多
关键词 异步电机 v/f控制 振荡抑制
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一种用于高压测量系统的V/F转换电路的设计 被引量:7
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作者 方志 邱毓昌 赵中原 《电测与仪表》 北大核心 2002年第2期30-32,共3页
设计了一种通过VCO实现的V/F转换电路,介绍了这个电路在罗柯夫斯基线圈组成的大电流测量系统中的应用,实验结果表明这种V/F转换电路具有良好的实用性。
关键词 v/f转换 频率调制 电压控制振荡器 罗柯夫斯基线圈
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