期刊文献+
共找到376篇文章
< 1 2 19 >
每页显示 20 50 100
Effects of Antenna Tilting on Transmitting Power in Mobile Cellular Communication Systems
1
作者 Gbenga E. Aderibigbe Michael O. Kolawole Victor S. A. Adeloye 《International Journal of Communications, Network and System Sciences》 2011年第7期464-467,共4页
Radio resources must be wisely managed, in wireless communication systems, when implementing different multiple access techniques. This perspective is pivotal since the variations in propagation channel are very fast ... Radio resources must be wisely managed, in wireless communication systems, when implementing different multiple access techniques. This perspective is pivotal since the variations in propagation channel are very fast and the system is highly complex due to random and unpredictable movement of mobile users continuously. The complexity in the cellular system periodically contributes to different interference levels, high or low, resulting in the degradation of the system capacity. Transmitter power control is an efficient technique to mitigate the effect of interference under fading conditions, combat the Near-Far problem and conserve the battery life. Several remedial measures—like space diversity, frequency diversity, route diversity, increase in antenna height, antenna tilting, etc.—have been tried by many operators to overcome the debilitating effect of multipath fading in fixed line-of-sight microwave and mobile communication links. Among these remedial measures, diversity techniques have been extensively studied in terms of improvement factor, whereas the concept of antenna tilting is relatively less explored compared with other remedial measures. In this study, the effect of antenna tilting on fixed and mobile communication links is investigated to find out the optimum tilting angles in terms of design parameters, as well as on quality of service (QoS). The paper established that a deviation of more than 1.5o in antenna elevation angle would impact on QoS requirements and seriously affect the quality of signal to be received by the mobile systems. 展开更多
关键词 OPTIMUM tilting Angle QoS Near-Far Effect Mobile STATION Carrier-to-Interference Ratio
下载PDF
Systematic prediction of the gas content, fractures, and brittleness in fractured shale reservoirs with TTI medium
2
作者 Yun Zhao Xiao-Tao Wen +2 位作者 Chen-Long Li Yang Liu Chun-Lan Xie 《Petroleum Science》 SCIE EI CAS CSCD 2024年第5期3202-3221,共20页
The main objective is to optimize the development of shale gas-rich areas by predicting seismic sweet spot parameters in shale reservoirs. We systematically assessed the fracture development, fracture gas content, and... The main objective is to optimize the development of shale gas-rich areas by predicting seismic sweet spot parameters in shale reservoirs. We systematically assessed the fracture development, fracture gas content, and rock brittleness in fractured gas-bearing shale reservoirs. To better characterize gas-bearing shale reservoirs with tilted fractures, we optimized the petrophysical modeling based on the equivalent medium theory. Based on the advantages of shale petrophysical modeling, we not only considered the brittle mineral fraction but also the combined effect of shale porosity, gas saturation, and total organic carbon(TOC) when optimizing the brittleness index. Due to fractures generally functioning as essential channels for fluid storage and movement, fracture density and fracture fluid identification factors are critical geophysical parameters for fractured reservoir prediction. We defined a new fracture gas indication factor(GFI) to detect fracture-effective gas content. A new linear PP-wave reflection coefficient equation for a tilted transversely isotropic(TTI) medium was rederived, realizing the direct prediction of anisotropic fracture parameters and the isotropic elasticity parameters from offset vector tile(OVT)-domain seismic data. Synthetic seismic data experiments demonstrated that the inversion algorithm based on the L_P quasinorm sparsity constraint and the split-component inversion strategy exhibits high stability and noise resistance. Finally, we applied our new prediction method to evaluate fractured gas-bearing shale reservoirs in the Sichuan Basin of China, demonstrating its effectiveness. 展开更多
关键词 Petrophysical modeling Brittleness index Fracture gas indication factor(GFI) Tilted transversely isotropic(TTI) Fracture density
下载PDF
Research on Transmission Line Tower Tilting and Foundation State Monitoring Technology Based onMulti-Sensor Cooperative Detection and Correction
3
作者 Guangxin Zhang Minghui Liu +4 位作者 Shichao Cheng Minzhen Wang Changshun Zhao Hongdan Zhao Gaiming Zhong 《Energy Engineering》 EI 2024年第1期169-185,共17页
The transmission line tower will be affected by bad weather and artificial subsidence caused by the foundation and other factors in the power transmission.The tower’s tilt and severe deformation will cause the buildi... The transmission line tower will be affected by bad weather and artificial subsidence caused by the foundation and other factors in the power transmission.The tower’s tilt and severe deformation will cause the building to collapse.Many small changes caused the tower’s collapse,but the early staff often could not intuitively notice the changes in the tower’s state.In the current tower online monitoring system,terminal equipment often needs to replace batteries frequently due to premature exhaustion of power.According to the need for real-time measurement of power line tower,this research designed a real-time monitoring device monitoring the transmission tower attitude tilting and foundation state based on the inertial sensor,the acceleration of 3 axis inertial sensor and angular velocity raw data to pole average filtering pre-processing,and then through the complementary filtering algorithm for comprehensive calculation of tilt angle,the system meets the demand for inclined online monitoring of power line poles and towers regarding measurement accuracy,with low cost and power consumption.The optimization multi-sensor cooperative detection and correction measured tilt angle result relative accuracy can reach 1.03%,which has specific promotion and application value since the system has the advantages of unattended and efficient calculation. 展开更多
关键词 Transmission line tower tilting MULTI-SENSOR foundation state monitoring collaborative detection
下载PDF
Tilt Angle Optimality Criteria for Stand Alone PV Systems
4
作者 Mohammad Abu-Naser 《Journal of Power and Energy Engineering》 2024年第3期1-18,共18页
The conventional approach to optimizing tilt angles for fixed solar panels aims to maximize energy generation over the entire year. However, in the context of a supply controlled electric grid, where solar energy avai... The conventional approach to optimizing tilt angles for fixed solar panels aims to maximize energy generation over the entire year. However, in the context of a supply controlled electric grid, where solar energy availability varies, this criterion may not be optimal. This study explores two alternative optimization criteria focused on maximizing baseload supply potential and minimizing required storage capacity to address seasonality in energy generation. The optimal tilt angles determined for these criteria differed significantly from the standard approach. This research highlights additional factors crucial for designing solar power systems beyond gross energy generation, essential for the global transition towards a fully renewable energy-based electric grid in the future. 展开更多
关键词 Electric Grid Fixed Solar Panels Optimal PV Tilt Angle Seasonal Solar Variability Renewable Energy Supply-Demand Balance
下载PDF
π-凝聚环上的广义Morita对偶及Tilting定理 被引量:1
5
作者 刘敏 李尚莹 《内江师范学院学报》 2002年第4期6-13,共8页
本文建立了 π-凝聚环上有限生成无挠模范畴的 Tilting定理及相关的广义Morita对偶。推广了 Colby有关
关键词 tilting定理 Π-凝聚环 有限生成无挠模 广义Morita对偶 tilting tilting
下载PDF
量子群主Tilting模的张量积及其滤过 被引量:1
6
作者 柏元淮 《数学年刊(A辑)》 CSCD 北大核心 2001年第2期229-236,共8页
A= Z[v]Ω,Ω Z[v]的由-1和奇p生成的理想. U是 A上的量子代数.令 фp是 p次分圆多项式, B= A/(фp),г 是商代数 B关于理想(ζ— 1)的完备化,式中ζ是p次本原根.对人 λ∈ X+, Mг(λ)表首... A= Z[v]Ω,Ω Z[v]的由-1和奇p生成的理想. U是 A上的量子代数.令 фp是 p次分圆多项式, B= A/(фp),г 是商代数 B关于理想(ζ— 1)的完备化,式中ζ是p次本原根.对人 λ∈ X+, Mг(λ)表首权为λ的不可分解 Uг-Tiltins模(称为主 Uг模).本文给出了量子群主 Uг模的张量积定理.对 p≥ 2(h-1),在 p2室中描述了量子群主 Uг模好滤过滤过商之首权的分布状态及其滤过重数作为例子,对秩1型和 A2型的量子群情形给出了 P2室中一般位置室主 Uг模好滤过的分解模式. 展开更多
关键词 量子群 不可分解模 tilting 滤过 张量积定理 理想 分解模式
下载PDF
π-凝聚环上的余*-模和余tilting模
7
作者 刘敏 汪明义 左平 《四川师范大学学报(自然科学版)》 CAS CSCD 2003年第1期33-37,共5页
主要引入了π 凝聚环上的余 模和余tilting模的概念.得到了余 模的3个刻划,并且利用余 模给出了π 凝聚环上余tilting模的特征性质,从而推广了文献(ScienceinChina,1995,39(1):1709~1728.)中的结果.
关键词 Π-凝聚环 余*-模 tilting 生成子 有限生成无挠 酋模
下载PDF
Dual pairs of tilting pairs
8
作者 廖贻华 陈建龙 《Journal of Southeast University(English Edition)》 EI CAS 2011年第3期347-350,共4页
A module pair (C, T) over an Artin algebra A is called a tilting pair if both C and T are selforthogonal modules and the conditions T e ada C and C ∈ add T hold. The duality on a tilting pair is investigated to dis... A module pair (C, T) over an Artin algebra A is called a tilting pair if both C and T are selforthogonal modules and the conditions T e ada C and C ∈ add T hold. The duality on a tilting pair is investigated to discuss the condition under which the dual of a tilting pair is also a tilting pair. A necessary and sufficient condition of (D(7), D(C) ) being an n-tilting pair over an Artin algebra for an n-tilting pair ( C, 7) is given. And, a necessary and sufficient condition of ( T^*, C^* ) being an ntilting pair over a selfinjective Artin algebra for an n-tilting pair (C, 7) is also given. 展开更多
关键词 selforthogonal module selfinjective dual module tilting pair
下载PDF
Wakamatsu tilting模的性质
9
作者 邢建民 李秀丽 《科学技术与工程》 2009年第2期360-361,共2页
设Λ为Artin代数,对给定的Wakamatsu tilting模,Wakamatsu tilting cotorsionpair以及相关类的性质。
关键词 Wakamatsu tilting 模核 预覆盖 自正交 cotorsion PAIR
下载PDF
量子群主Tilting模的形式特征标
10
作者 柏元淮 《暨南大学学报(自然科学与医学版)》 CAS CSCD 2001年第5期1-9,共9页
设p≥ 2 (h- 1) ,λ∈X+ 是p2 室中的正则支配权 .证明了主UΨ 模MΨ(λ0 +Pλ1)的形式特征标公式 ;描述了MΨ(λ0 +pλ1)的合成因子的分布状态 .对于A2 型量子群 ,给出了p2 室一般位置室中UΨ 模范畴主UΨ 模MΨ(λ0 +Pλ1)合成因子的... 设p≥ 2 (h- 1) ,λ∈X+ 是p2 室中的正则支配权 .证明了主UΨ 模MΨ(λ0 +Pλ1)的形式特征标公式 ;描述了MΨ(λ0 +pλ1)的合成因子的分布状态 .对于A2 型量子群 ,给出了p2 室一般位置室中UΨ 模范畴主UΨ 模MΨ(λ0 +Pλ1)合成因子的分解模式 . 展开更多
关键词 量子群 不可分解模 tilting 形式特征标 正则支配权 分解模式
下载PDF
Tilting Ratchet肌动蛋白双足运动模型的研究
11
作者 王丹 邓迎春 《湖南城市学院学报(自然科学版)》 CAS 2006年第4期32-35,共4页
针对肌动蛋白两足交替行走的事实提出了Tilting ratchet双足运动模型,并对其运动轨道进行了数学模拟.从而说明所提出的模型能够清楚的描述这种交替行走的运动机制,表明了模型的可行性和有效性.同时还对这种模型中的粒子运动速度和系统... 针对肌动蛋白两足交替行走的事实提出了Tilting ratchet双足运动模型,并对其运动轨道进行了数学模拟.从而说明所提出的模型能够清楚的描述这种交替行走的运动机制,表明了模型的可行性和有效性.同时还对这种模型中的粒子运动速度和系统效率进行了研究,给出了一些数值模拟结果. 展开更多
关键词 分子马达 肌动蛋白 tilting ratchet模型 耦合扩散过程 马达效率
下载PDF
Study on general inverse kinematics of rotating/tilting positioner for robotic arc welding off-line programming 被引量:3
12
作者 田劲松 吴林 戴明 《China Welding》 EI CAS 2001年第1期27-33,共7页
Off line programming provides an essential link between CAD and CAM, whose development will result in greater use of robotic arc welding. An arc welding system with a robot and a rotating/tilting positioner is one of... Off line programming provides an essential link between CAD and CAM, whose development will result in greater use of robotic arc welding. An arc welding system with a robot and a rotating/tilting positioner is one of the most typical workcells. The inverse kinematics of robot and positioner is the foundation of the off line programming system. The previous researchers only focused on a special solution of the positioner inverse kinematics, which is the solution at down hand welding position. In this paper, we introduce a method for representing welding position. Then a general algorithm of rotating/tilting positioner inverse kinematics is presented, and an approach to find the unique solution of the inverse kinematics is discussed. The simulation experiment results show that the general algorithm can improve the ability of robotic arc welding off line programming system to program all types of welding positions. 展开更多
关键词 robotic arc welding off line programming rotating/tilting positioner inverse kinematics
下载PDF
Design of a titl angle measurement system based on ADXL345 sensor 被引量:7
13
作者 SU Yan-ping GONG Mao-fa AN Bin ZHANG Jian-yu ZHAO Xu-jie 《Journal of Measurement Science and Instrumentation》 CAS 2014年第2期19-22,共4页
The titl angle measurement system based on the ADXL345 of three-axis acceleration sensor is introduced, and the composition and working principle of the system are described. The MSP430F149 microcontroller of ultra-lo... The titl angle measurement system based on the ADXL345 of three-axis acceleration sensor is introduced, and the composition and working principle of the system are described. The MSP430F149 microcontroller of ultra-low power and high performance is adopted. Firstly, the voltage value which is proportional to the acceleration value is output by ADXL345 when the system is powered. Secondly, the voltage value is converted into the corresponding digital signal by AD converter of the sensor. Thirdly, the digital signal is transformed into the titl angle according to the arithmetic processing of the MSP430F149. Finally, the corresponding angle is displayed on the liquid crystal display (LCD) screen. Experimental results show that the design has high sensitivity and response speed compared with the conventional methods. It is suitable for practical engineering application because of simple structure, low cost and low power consumption. 展开更多
关键词 ADXL345 MSP430F149 tilt angle measurement liquid crystal display (LCD)
下载PDF
STUDY ON THE COUPLED ELECTROMECHANICAL DYNAMICS OF ROTOR SYSTEM EQUIPPED WITH MAGNETIC BEARINGS 被引量:1
14
作者 ZhangGang ZhangJiansheng +5 位作者 LiSongsheng YangXinzhou WuJianfeng WangXiping YuLie XieYoubai 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2004年第1期93-96,共4页
The influences of thrust magnetic bearing and journal tilt on dynamiccharacteristics of rotor system are studied mainly. The Outcome shows that the influences ofcoupling effects of thrust magnetic bearing and tilt of ... The influences of thrust magnetic bearing and journal tilt on dynamiccharacteristics of rotor system are studied mainly. The Outcome shows that the influences ofcoupling effects of thrust magnetic bearing and tilt of journal on critical rotational speeds ofsystem are very large, and the stability of system reduces greatly. That shows it is important thatthe influence of coupling effects of thrust and radial magnetic bearings due to the rotor tiltingmust be considered in the study of rotor-magnetic bearings system dynamic characteristics, and alsoshows it is important that the rotor is mounted and debugged in ideal alignment of magneticbearings. 展开更多
关键词 Thrust magnetic bearing Journal tilt Dynamic characteristics
下载PDF
Optimization and Sizing of a Stand-Alone Photovoltaic System and Assessment of Random Load Fluctuation on Power Supply 被引量:1
15
作者 Leonard Akana Nguimdo Clinton Kum 《Energy and Power Engineering》 2020年第1期28-43,共16页
This study presents an optimization technique and design for a stand-alone photovoltaic (PV) system to provide the required electricity for a single residential household in remote areas. From the basic solar componen... This study presents an optimization technique and design for a stand-alone photovoltaic (PV) system to provide the required electricity for a single residential household in remote areas. From the basic solar components analysis, the irradiance on tilted surface is derived and compared to that on horizontal surface for Furu-Awa locality to infer the appropriate tilt angle (β) that maximizes the collection of solar energy. Seven optimum values of β applicable to the PV network were then derived depending of the period of the year and this simulation resulted that the panels are to be adjusted seven times a year. The optimization technique for load demand based on total apparent power of the household appliances produces an increase of 18% compared to the simple case of the PV components design using active power but leads to the optimum configuration that meets the real load demand of the household. Following the sizing of the station, reliability tests simulations were conducted for a one year corresponding period to infer the sensitivity of power supply to initial state of charge, to check the system autonomy and to evaluate the effect of random variation of the load on the smooth functioning of the PV system using a pseudo random number generator. This analysis shows that the minimum capacity of the battery for normal run of the Plan is 22.2% and that with random fluctuation of load, there will be periods of the year where the system experiences power failure depending on how important is the variation. The result of the study may imply a small increase in the cost of the entire plant but improves the stability and flexibility of such a station. 展开更多
关键词 Photovoltaic system OPTIMIZATION APPARENT Power TILT Angle State of Charge Random NUMBERS Generator
下载PDF
A Study on the Characteristics for the Ground Vibration Due to the Travelling Tilting Train 被引量:2
16
作者 Hee Seok Kim 《Engineering(科研)》 2013年第9期729-734,共6页
The development of the tilting train can contribute to solve the economic burden and enhance the transportation means of areas that did not share the benefits of the high speed railway. But the dynamic behavior caused... The development of the tilting train can contribute to solve the economic burden and enhance the transportation means of areas that did not share the benefits of the high speed railway. But the dynamic behavior caused by the interaction between the train and the track as well as the environmental vibrations along the railway should be evaluated to secure the safety of the train and riding comfort. In this paper a study on the characteristics for ground vibration due to the tilting train travelling in the conventional line are carried out. The transmitted load into the ground is computed through a study on the interrelation between the tilting car and the line. This load is applied into the numerical model which is one for the analysis of ground vibration due to the travelling tilting car. The far fields on the numerical model are formed by the absorbing boundary using dashpot, one of the most widely used absorbing boundary in finite element analysis. Using this numerical model, the analysis of the ground vibration characteristics caused by travelling tilting car is performed. From the analysis, it is shown that the transferred load due to the tilting train is larger than that of the conventional train. 展开更多
关键词 GROUND VIBRATION tilting CAR Absorbing BOUNDARY
下载PDF
Post-Acute Sequelae of SARS-Cov-2 Infection Associating Peripheral, Autonomic and Central Nervous System Disturbances: Case Report and Review of the Literature 被引量:1
17
作者 David S. Younger 《World Journal of Neuroscience》 2021年第1期17-21,共5页
<strong>Aim</strong><span><span><span style="font-family:;" "=""><strong>:</strong> To describe post-infectious neurological aspects of COVID-19 in a ... <strong>Aim</strong><span><span><span style="font-family:;" "=""><strong>:</strong> To describe post-infectious neurological aspects of COVID-19 in a patient with progressive post-infectious peripheral (PNS), autonomic (ANS) and central nervous system (CNS) involvement due to SARS-CoV-2 infection. <b>Background</b> <b>and</b> <b><strong>Purpose</strong></b><strong>:</strong> A variety of neurological manifestations have been described in association with Covid-19, however</span></span></span><span><span><span style="font-family:;" "="">,</span></span></span><span><span><span style="font-family:;" "=""> progressive multisystem neurological aspects have not been described. <b><strong>Methods</strong></b><strong>:</strong> A case report detailing the history, examination, and infectious serology associated with SARS-CoV-2, and subsequent neurodiagnostic laboratory testing and treatment. <b><strong>Results</strong></b><strong>:</strong> Neurodiagnostic laboratory studies showed large-fiber demyelinating sensorimotor and painful small fiber sensory polyneuropathy, orthostatic hypotension, and hypometabolism of bilateral anterior and mesial temporal lobes with a possible frontal seizure focus. Treatment was initiated with high-dose immune globulin therapy. <b><strong>Conclusions</strong></b><strong>:</strong> The combination of PNS, ANS <span>and</span> CNS involvement in this patient was associated with post-infectious acquired immunity to SARS-CoV-2.</span></span></span> 展开更多
关键词 COVID-19 SARS-CoV-2 Long Hauler Long Covid Peripheral Neuropathy DYSAUTONOMIA ENCEPHALOPATHY ENCEPHALITIS EMG NCS Tilt Table Test Epidermal Nerve Fibers PET/MRI
下载PDF
Realization of Tip Tilting By 8-Step Line Tilting
18
作者 CHEN Ying-Tian ZHANG Yang +3 位作者 HU Sen HO Tso-Hsiu Boon Ham Lim Chen Sin Lim 《Communications in Theoretical Physics》 SCIE CAS CSCD 2009年第9期549-554,共6页
By direct calculation of rotation matrices of SO(3),we show how certain specific sequence of eight consecutiverotations of digital angles can yield a tilting of a facet mirror.We also design a detailed program specifi... By direct calculation of rotation matrices of SO(3),we show how certain specific sequence of eight consecutiverotations of digital angles can yield a tilting of a facet mirror.We also design a detailed program specifically to tiltan array of mirrors from planar orientation to the required focusing orientation.We describe how to use the 8-step torealize the focusing of the mirror array.We have found,in our designed program,an important feature of row-sharingduring the rotations for the columns and similarly the column-sharing during the rotations for the row.This feature cansave a lot of operating time during the actual realization of the mechanical movements. 展开更多
关键词 rotational group solar energy optical device tip tilting line tilting
下载PDF
STUDY ON DYNAMIC CURVING BEHAVIOR OF TILTING PASSENGER CARS
19
作者 Liu Hongyou Zeng Jing National Traction Power Laboratory, Southwest Jiaotong University, Chengdu 610031, China 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2002年第4期360-365,371,共7页
By using tilting carbodies, train can negotiate at a higher speed withoutreducing the passenger's ride quality. This is a good method to allow a significant increase inspeed at existing track to improve the railwa... By using tilting carbodies, train can negotiate at a higher speed withoutreducing the passenger's ride quality. This is a good method to allow a significant increase inspeed at existing track to improve the railway transportation capability, and to enhance thecompetition ability of railways with other transportation systems. With the increase of the curvenegotiation speed, the wheel-rail lateral forces and wheel-rail wear of the tilting train willincrease. The self-steering radial bogie is an effective way to solve the problem. The dynamic modelof the tilting passenger car with self-steering bogies is established in detail, and the curvingperformance of the car is investigated. 展开更多
关键词 tilting passenger car self-steering bogie dynamic curving behavior wheel-rail interaction
下载PDF
Realization of Fine Tip Tilting by 16-Step Line Tilting
20
作者 丁璐 陈应天 +1 位作者 胡森 张杨 《Communications in Theoretical Physics》 SCIE CAS CSCD 2010年第7期175-180,共6页
Following Chen's method [Commun. Theor. Phys. 52 (2009) 549] to use &step line tilting to realize tip tilting, to achieve finer rotation, it is discovered that a 16-step line tilting method may realize a rotation ... Following Chen's method [Commun. Theor. Phys. 52 (2009) 549] to use &step line tilting to realize tip tilting, to achieve finer rotation, it is discovered that a 16-step line tilting method may realize a rotation two order smaller than that achieved by &step. 展开更多
关键词 rotation group tip tilting line tilting
下载PDF
上一页 1 2 19 下一页 到第
使用帮助 返回顶部