Results 41 to 50 of about 13,084 (117)

关于行列式D≦25的六元恒正二次型

四川大学学报. 自然科学版, 1964
设fn=sum from i‘j=1 to n(asum from n=1 to n(aijxixj)(aij=aji)是一个系数aij均为整数,行列式为Dn=|aij|的n元二次型,如果对xi取任何一组不全为零的实数值时,都使fn取正值,我们称为fn为恒正二次型。两个二次型fn与gn,如果能经行列式等于±1的线性变换可以互相转化的,称为等价。根据等价性将二次型分成若干类,同一类的二次型都等价,不同类的二次型彼此不等价,用hn（Dn）表fn具有行列式为Dn的类数。
柯召, 陈度, 何治国, 余文洲
doaj  

Genetic Confirmations of Dwarf Lemurs Across Madagascar Highlights Complex Biogeographic Patterns 马达加斯加全境鼠狐猴的遗传确认揭示了复杂的生物地理模式

Integrative Conservation, Volume 4, Issue 4, Page 665-674, December 2025.
Using a diagnostic mitochondrial marker gene, we document the presence of furry‐eared dwarf lemurs, a species known from Madagascar's eastern montane rainforests, in several forest fragments across the island's central highlands. These findings raise new questions about when this species colonized these sites, how they tolerate these changing and ...
Marina B. Blanco, Lydia K. Greene, Antonin Andriamahaihavana, Jean‐Basile Andriambeloson, Radosoa Andrianaivoarivelo, Herizo Andrianantenaina, Ando Andriantsalohimisantatra, Landry Bemita, Chris Birkinshaw, Jean Marcellin Dimbilahy, Elaine E. Guevara, Anna Mananjara Mahefaniaina, Manitra F. Rajaonarison, Toky H. Rakotoarinivo, Fenonirina Rakotoarison, Lovasoa Sylviane Rakotozafy, Elodi Rambeloson, Tianjanahary Randriamboavonjy, Yockline Randriamihanta, Hoby A. Rasoanaivo, Rojo N. Ravelojaona, Josia Razafindramanana, Sandratra R. Rakotonomenjanahary, Tahiry V. Rivoharison, Haja R. Tongasoa, Rachel C. Williams, Fanomezana M. Ratsoavina, Anne D. Yoder   +27 more
wiley   +1 more source

Traditional knowledge promotes the protection of large old trees: A case from China's richest biocultural diversity area

People and Nature, Volume 7, Issue 11, Page 2700-2713, November 2025.
Abstract Large old trees are important ecological entities in human settlements, providing cultural values and ecological services that are threatened by current and future changes in global climate, land use and disturbance regimes. Some studies suggest incorporating social and cultural significance into the conservation of large old trees.
Zhuo Cheng, Xiaoping Lu, Yanxiao Fan, Qingjiang Cui, Xian Hu, Chunlin Long   +5 more
wiley   +1 more source

Managing Water Supply Infrastructure in Medium‐Sized Cities to Meet User Demands: A Case Study of Natal, Brazil

World Water Policy, Volume 11, Issue 4, Page 1000-1014, November 2025.
ABSTRACT The article investigates the management of water supply infrastructure in Natal, Brazil, analyzing the alignment between the utility's investments and user demands during the period from 2016 to 2019. Using data from the Customer Service Center (CAU) and official investment information, it was identified that approximately 67% of complaints ...
Loiane Tamara dos Santos Alves Romanato, Neilton Fidelis da Silva, Sheyla Varela Lucena, Leandro Andrei Beser de Deus   +3 more
wiley   +1 more source

关于a（x²+y²）+bz²表数相同的问题

四川大学学报. 自然科学版, 1983
熟知,两个等价的型（即可经行列式为±1之整系数齐次线性变换互变的型）必表数相同。然而其逆不真.1938年,证明,在所有实二元恒正二次型中,除常数因子外,有且仅有一对表数相同但互不等价的型x2+xy+y2与x2+3y2.1963年,给出了三组表数相同但行列式互异（从而互不等价）的三元恒正型.
柯召, 郑德勋
doaj  

Ecological Restoration of Rubber Monocultures: Strategies for Biodiversity and Ecosystem Recovery in Tropical Regions 题目:如何将橡胶林恢复为多样森林？

Integrative Conservation, Volume 4, Issue 3, Page 345-353, September 2025.
Restoration of monoculture in protected and marginal areas can be organized into two phases (1) identification and prioritization of restoration sites based on remote sensing or field survey then assessing degradation level, and (2) implementation of appropriate restoration interventions.
Liang Song, Sujan Balami, Gbadamassi G. O. Dossa, Wei‐Guo Liu, Philippe Thaler, Thomas Cherico Wanger, David P. Edwards, Maria Mei Hua Wang, Yong‐Ping Yang, Rhett D. Harrison   +9 more
wiley   +1 more source

关于Pian-Sumihara杂交应力四边形元的一个等价形式

四川大学学报. 自然科学版, 2009
基于修正的Hellinger-Reissner变分原理,利用Wilson非协调位移和9参完全线性应力模式,作者得到了Pian-Sumihara五参杂交应力四边形元(P-S)的一个等价形式.这一等价性关系使P-S元的三维推广大大简化,然后作者给出了收敛性结果和数值算例.
童蓓蕾, 张世全, 冯印江
doaj  

Z-空间中的连续选择定理及其应用(英文)

四川大学学报. 自然科学版, 1999
在Z 空间的框架下证明了一个连续选择定理 ,推广了Tarafdar的连续选择定理 .作为应用 ,证明了Z 空间中的一个不动点定理及其等价形式 :极大极小定理 ,极大元的存在定理 ,极大极小定理的几何形式 ,并给出了它们的等价性的证明 ,推广了许多已知的结果 .
唐亚勇, 刘亚平
doaj  

在线翻译定价问题

Revista Tradumàtica, 2018
翻译平台、众包和神经机器翻译等信息技术破坏了翻译经济模式。九家全球语言服务公司的定价政策分析表明，向在线商业模式的转变有助于改进基于数量和内容的翻译模式，以提供一系列专注于用户体验的语言服务。
Claire Béatrice Larsonneur
doaj   +1 more source

Equivalent representations of generalized quasi-Sugeno fuzzy integral in supremum forms(广义拟Sugeno模糊积分的确界式等价表示)

Zhejiang Daxue xuebao. Lixue ban, 2014
通过减弱公理化条件给出新拟乘算子，并按照拟乘运算针对实函数正（负）部建立了广义拟Sugeno模糊积分.依据演化的确界概念获得了该积分的3种表达形式，并给出了其等价表示及其证明.最后，通过实例验证了该广义拟Sugeno模糊积分3种等价表示的正确性.
LIYanhong(李艳红)
doaj   +1 more source