期刊文献+
共找到51,633篇文章
< 1 2 250 >
每页显示 20 50 100
Clinical value of precise rehabilitation nursing in management of cerebral infarction 被引量:1
1
作者 Ya-Na Xu Xiu-Zhen Wang Xiao-Rong Zhang 《World Journal of Clinical Cases》 SCIE 2024年第1期24-31,共8页
BACKGROUND Cerebral infarction,previously referred to as cerebral infarction or ischemic stroke,refers to the localized brain tissue experiencing ischemic necrosis or softening due to disorders in brain blood supply,i... BACKGROUND Cerebral infarction,previously referred to as cerebral infarction or ischemic stroke,refers to the localized brain tissue experiencing ischemic necrosis or softening due to disorders in brain blood supply,ischemia,and hypoxia.The precision rehabilitation nursing model for chronic disease management is a continuous,fixed,orderly,and efficient nursing model aimed at standardizing the clinical nursing process,reducing the wastage of medical resources,and improving the quality of medical services.AIM To analyze the value of a precise rehabilitation nursing model for chronic disease management in patients with cerebral infarction.METHODS Patients(n=124)admitted to our hospital with cerebral infarction between November 2019 and November 2021 were enrolled as the study subjects.The random number table method was used to divide them into a conventional nursing intervention group(n=61)and a model nursing intervention group(n=63).Changes in the nursing index for the two groups were compared after conventional nursing intervention and precise rehabilitation intervention nursing for chronic disease management.RESULTS Compared with the conventional intervention group,the model intervention group had a shorter time to clinical symptom relief(P<0.05),lower Hamilton Anxiety Scale and Hamilton Depression Scale scores,a lower incidence of total complications(P<0.05),a higher disease knowledge mastery rate,higher safety and quality,and a higher overall nursing satisfaction rate(P<0.05).CONCLUSION The precision rehabilitation nursing model for chronic disease management improves the clinical symptoms of patients with cerebral infarction,reducing the incidence of total complications and improving the clinical outcome of patients,and is worthy of application in clinical practice. 展开更多
关键词 precise rehabilitation nursing model for chronic disease management Cerebral infarction Knowledge of disease Safety and quality
下载PDF
Comparing Fine-Tuning, Zero and Few-Shot Strategies with Large Language Models in Hate Speech Detection in English
2
作者 Ronghao Pan JoséAntonio García-Díaz Rafael Valencia-García 《Computer Modeling in Engineering & Sciences》 SCIE EI 2024年第9期2849-2868,共20页
Large Language Models(LLMs)are increasingly demonstrating their ability to understand natural language and solve complex tasks,especially through text generation.One of the relevant capabilities is contextual learning... Large Language Models(LLMs)are increasingly demonstrating their ability to understand natural language and solve complex tasks,especially through text generation.One of the relevant capabilities is contextual learning,which involves the ability to receive instructions in natural language or task demonstrations to generate expected outputs for test instances without the need for additional training or gradient updates.In recent years,the popularity of social networking has provided a medium through which some users can engage in offensive and harmful online behavior.In this study,we investigate the ability of different LLMs,ranging from zero-shot and few-shot learning to fine-tuning.Our experiments show that LLMs can identify sexist and hateful online texts using zero-shot and few-shot approaches through information retrieval.Furthermore,it is found that the encoder-decoder model called Zephyr achieves the best results with the fine-tuning approach,scoring 86.811%on the Explainable Detection of Online Sexism(EDOS)test-set and 57.453%on the Multilingual Detection of Hate Speech Against Immigrants and Women in Twitter(HatEval)test-set.Finally,it is confirmed that the evaluated models perform well in hate text detection,as they beat the best result in the HatEval task leaderboard.The error analysis shows that contextual learning had difficulty distinguishing between types of hate speech and figurative language.However,the fine-tuned approach tends to produce many false positives. 展开更多
关键词 Hate speech detection zero-shot few-shot fine-tuning natural language processing
下载PDF
Fish-on-Chips:unveiling neural processing of chemicals in small animals through precise fluidic control
3
作者 Samuel K.H.Sy Ho Ko 《Neural Regeneration Research》 SCIE CAS CSCD 2024年第11期2351-2353,共3页
Precise chemical cue presentation alongside advanced brainwide imaging techniques is important to the study of chemosensory processing in animals.Nevertheless,the dynamic nature of chemical-carrying media,such as wate... Precise chemical cue presentation alongside advanced brainwide imaging techniques is important to the study of chemosensory processing in animals.Nevertheless,the dynamic nature of chemical-carrying media,such as water or air,poses a significant challenge for delivering highly-controlled chemical flow to an animal subject.Moreover,contact-based cue manipulation and delivery easily shift the position of the animal subject,which is often undesirable for high-quality brain imaging.Additionally,more advanced interfacing tools that align with the diverse range of body part sizes of an animal,ranging from micrometer-scale neurons to meter-long limbs,are much needed.This is particularly crucial when dealing with dimensions that are beyond the reach of conventional experimental tools. 展开更多
关键词 dealing precise SIZES
下载PDF
Self-consistent and precise measurement of time-dependent radiative albedo of gold based on specially symmetrical triple-cavity Hohlraum
4
作者 Zhiyu Zhang Yang Zhao +19 位作者 Xiaoying Han Liling Li Bo Qing Lifei Hou Yulong Li YuXue Zhang Huan Zhang Xiangming Liu Bo Deng Gang Xiong Min Lv Tuo Zhu Chengwu Huang Tianming Song Yan Zhao Yingjie Li Lu Zhang Xufei Xie Jiyan Zhang Jiamin Yang 《Matter and Radiation at Extremes》 SCIE EI CSCD 2024年第3期57-64,共8页
A self-consistent and precise method to determine the time-dependent radiative albedo,i.e.,the ratio of the reemission flux to the incident flux,for an indirect-drive inertial confinement fusion Hohlraum wall material... A self-consistent and precise method to determine the time-dependent radiative albedo,i.e.,the ratio of the reemission flux to the incident flux,for an indirect-drive inertial confinement fusion Hohlraum wall material is proposed.A specially designed symmetrical triple-cavity gold Hohlraum is used to create approximately constant and near-equilibrium uniform radiation with a peak temperature of 160 eV.The incident flux at the secondary cavity waist is obtained from flux balance analysis and from the shock velocity of a standard sample.The results agree well owing to the symmetrical radiation in the secondary cavity.A self-consistent and precise time-dependent radiative albedo is deduced from the reliable reemission flux and the incident flux,and the result from the shock velocity is found to have a smaller uncertainty than that from the multi-angle flux balance analysis,and also to agree well with the result of a simulation using the HYADES opacity. 展开更多
关键词 precise cavity RADIATIVE
下载PDF
Caliper-based precise positioning of the target(CALIPPOT)for transcranial magnetic stimulation without neuronavigation system
5
作者 Yunsong Hu Rong Zeng +5 位作者 Juan Yue Qiu Ge Hongxiao Wang Zijian Feng Jue Wang Yufeng Zang 《General Psychiatry》 CSCD 2024年第2期311-314,共4页
To the editor:Transcranial magnetic stimulation(TMS)is a non-invasive brain modulation technique.One important usage of TMS is the transient interruption of cognitive brain function(also named virtual lesion)for inves... To the editor:Transcranial magnetic stimulation(TMS)is a non-invasive brain modulation technique.One important usage of TMS is the transient interruption of cognitive brain function(also named virtual lesion)for investigating precisely where and when a specific cortical region contributes to a specific cognitive function.1 A more important usage of TMS is the treatment of brain disorders by repetitive TMS(rTMS). 展开更多
关键词 STIMULATION technique. precise
下载PDF
Fine-tuning electronic structure of N-doped graphitic carbon-supported Co-and Fe-incorporated Mo_(2)C to achieve ultrahigh electrochemical water oxidation activity
6
作者 Md.Selim Arif Sher Shah Hyeonjung Jung +3 位作者 Vinod K.Paidi Kug-Seung Lee Jeong Woo Han Jong Hyeok Park 《Carbon Energy》 SCIE EI CAS CSCD 2024年第7期134-149,共16页
Mo_(2)C is an excellent electrocatalyst for hydrogen evolution reaction(HER).However,Mo_(2)C is a poor electrocatalyst for oxygen evolution reaction(OER).Herein,two different elements,namely Co and Fe,are incorporated... Mo_(2)C is an excellent electrocatalyst for hydrogen evolution reaction(HER).However,Mo_(2)C is a poor electrocatalyst for oxygen evolution reaction(OER).Herein,two different elements,namely Co and Fe,are incorporated in Mo_(2)C that,therefore,has a finely tuned electronic structure,which is not achievable by incorporation of any one of the metals.Consequently,the resulting electrocatalyst Co_(0.8)Fe_(0.2)-Mo_(2)C-80 displayed excellent OER catalytic performance,which is evidenced by a low overpotential of 214.0(and 246.5)mV to attain a current density of 10(and 50)mA cm^(-2),an ultralow Tafel slope of 38.4 mV dec^(-1),and longterm stability in alkaline medium.Theoretical data demonstrates that Co_(0.8)Fe_(0.2)-Mo_(2)C-80 requires the lowest overpotential(1.00 V)for OER and Co centers to be the active sites.The ultrahigh catalytic performance of the electrocatalyst is attributed to the excellent intrinsic catalytic activity due to high Brunauer-Emmett-Teller specific surface area,large electrochemically active surface area,small Tafel slope,and low chargetransfer resistance. 展开更多
关键词 fine-tuning electronic structures heteronanostructures Mo_(2)C multimetal(Co/Fe) oxygen evolution reaction
下载PDF
Methanol steam reforming for hydrogen production driven by an atomically precise Cu catalyst
7
作者 Weigang Hu Haoqi Liu +7 位作者 Yuankun Zhang Jiawei Ji Guangjun Li Xiao Cai Xu Liu Wen Wu Xu Weiping Ding Yan Zhu 《Green Energy & Environment》 SCIE EI CAS CSCD 2024年第7期1079-1084,共6页
Plasmon-induced hot-electron transfer from metal nanostructures is being intensely pursed in current photocatalytic research,however it remains elusive whether molecular-like metal clusters with excitonic behavior can... Plasmon-induced hot-electron transfer from metal nanostructures is being intensely pursed in current photocatalytic research,however it remains elusive whether molecular-like metal clusters with excitonic behavior can be used as light-harvesting materials in solar energy utilization such as photocatalytic methanol steam reforming.In this work,we report an atomically precise Cu_(13)cluster protected by dual ligands of thiolate and phosphine that can be viewed as the assembly of one top Cu atom and three Cu_(4)tetrahedra.The Cu_(13)H_(10)(SR)_(3)(PR’_(3))_(7)(SR=2,4-dichlorobenzenethiol,PR’_(3)=P(4-FC_(6)H_(4))_(3))cluster can give rise to highly efficient light-driven activity for methanol steam reforming toward H_(2)production. 展开更多
关键词 NANOCLUSTER PHOTOCATALYSIS Methanol steam reforming Atomically precise Copper catalyst
下载PDF
Beidou receiver based on anti-jamming antenna arrays with self-calibration for precise relative positioning
8
作者 AN Yi KANG Ronglei +1 位作者 BAN Yalong YANG Shaoshuai 《Journal of Systems Engineering and Electronics》 SCIE CSCD 2024年第5期1132-1147,共16页
Unmanned aerial vehicles(UAVs)may be subjected to unintentional radio frequency interference(RFI)or hostile jamming attack which will lead to fail to track global navigation satellite system(GNSS)signals.Therefore,the... Unmanned aerial vehicles(UAVs)may be subjected to unintentional radio frequency interference(RFI)or hostile jamming attack which will lead to fail to track global navigation satellite system(GNSS)signals.Therefore,the simultaneous realization of anti-jamming and high-precision carrier phase difference positioning becomes a dilemmatic problem.In this paper,a distortionless phase digital beamforming(DBF)algorithm with self-calibration antenna arrays is proposed,which enables to obtain distortionless carrier phase while suppressing jamming.Additionally,architecture of high precision Beidou receiver based on anti-jamming antenna arrays is proposed.Finally,the performance of the algorithm is evaluated,including antenna calibration accuracy,carrier phase distortionless accuracy,and carrier phase measurement accuracy without jamming.Meanwhile,the maximal jamming to signal ratio(JSR)and real time kinematic(RTK)positioning accuracy under wideband jamming are also investigated.The experimental results based on the real-life Beidou signals show that the proposed method has an excellent performance for precise relative positioning under jamming when compared with other anti-jamming methods. 展开更多
关键词 Beidou receiver antenna array ANTI-JAMMING high precision distortionless carrier phase
下载PDF
Optimizing Enterprise Conversational AI: Accelerating Response Accuracy with Custom Dataset Fine-Tuning
9
作者 Yash Kishore 《Intelligent Information Management》 2024年第2期65-76,共12页
As the realm of enterprise-level conversational AI continues to evolve, it becomes evident that while generalized Large Language Models (LLMs) like GPT-3.5 bring remarkable capabilities, they also bring forth formidab... As the realm of enterprise-level conversational AI continues to evolve, it becomes evident that while generalized Large Language Models (LLMs) like GPT-3.5 bring remarkable capabilities, they also bring forth formidable challenges. These models, honed on vast and diverse datasets, have undoubtedly pushed the boundaries of natural language understanding and generation. However, they often stumble when faced with the intricate demands of nuanced enterprise applications. This research advocates for a strategic paradigm shift, urging enterprises to embrace a fine-tuning approach as a means to optimize conversational AI. While generalized LLMs are linguistic marvels, their inability to cater to the specific needs of businesses across various industries poses a critical challenge. This strategic shift involves empowering enterprises to seamlessly integrate their own datasets into LLMs, a process that extends beyond linguistic enhancement. The core concept of this approach centers on customization, enabling businesses to fine-tune the AI’s functionality to fit precisely within their unique business landscapes. By immersing the LLM in industry-specific documents, customer interaction records, internal reports, and regulatory guidelines, the AI transcends its generic capabilities to become a sophisticated conversational partner aligned with the intricacies of the enterprise’s domain. The transformative potential of this fine-tuning approach cannot be overstated. It enables a transition from a universal AI solution to a highly customizable tool. The AI evolves from being a linguistic powerhouse to a contextually aware, industry-savvy assistant. As a result, it not only responds with linguistic accuracy but also with depth, relevance, and resonance, significantly elevating user experiences and operational efficiency. In the subsequent sections, this paper delves into the intricacies of fine-tuning, exploring the multifaceted challenges and abundant opportunities it presents. It addresses the technical intricacies of data integration, ethical considerations surrounding data usage, and the broader implications for the future of enterprise AI. The journey embarked upon in this research holds the potential to redefine the role of conversational AI in enterprises, ushering in an era where AI becomes a dynamic, deeply relevant, and highly effective tool, empowering businesses to excel in an ever-evolving digital landscape. 展开更多
关键词 fine-tuning DATASET AI CONVERSATIONAL ENTERPRISE LLM
下载PDF
Development and Therapeutic Applications of Precise Gene Editing Technology
10
作者 ZHANG Yi-Meng YANG Xiao +1 位作者 WANG Jian LI Zhen-Hua 《生物化学与生物物理进展》 SCIE CAS CSCD 北大核心 2024年第10期2637-2647,共11页
The advent of gene editing represents one of the most transformative breakthroughs in life science,making genome manipulation more accessible than ever before.While traditional CRISPR/Cas-based gene editing,which invo... The advent of gene editing represents one of the most transformative breakthroughs in life science,making genome manipulation more accessible than ever before.While traditional CRISPR/Cas-based gene editing,which involves double-strand DNA breaks(DSBs),excels at gene disruption,it is less effective for accurate gene modification.The limitation arises because DSBs are primarily repaired via non-homologous end joining(NHEJ),which tends to introduce indels at the break site.While homology directed repair(HDR)can achieve precise editing when a donor DNA template is provided,the reliance on DSBs often results in unintended genome damage.HDR is restricted to specific cell cycle phases,limiting its application.Currently,gene editing has evolved to unprecedented levels of precision without relying on DSB and HDR.The development of innovative systems,such as base editing,prime editing,and CRISPR-associated transposases(CASTs),now allow for precise editing ranging from single nucleotides to large DNA fragments.Base editors(BEs)enable the direct conversion of one nucleotide to another,and prime editors(PEs)further expand gene editing capabilities by allowing for the insertion,deletion,or alteration of small DNA fragments.The CAST system,a recent innovation,allows for the precise insertion of large DNA fragments at specific genomic locations.In recent years,the optimization of these precise gene editing tools has led to significant improvements in editing efficiency,specificity,and versatility,with advancements such as the creation of base editors for nucleotide transversions,enhanced prime editing systems for more efficient and precise modifications,and refined CAST systems for targeted large DNA insertions,expanding the range of applications for these tools.Concurrently,these advances are complemented by significant improvements in in vivo delivery methods,which have paved the way for therapeutic application of precise gene editing tools.Effective delivery systems are critical for the success of gene therapies,and recent developments in both viral and non-viral vectors have improved the efficiency and safety of gene editing.For instance,adeno-associated viruses(AAVs)are widely used due to their high transfection efficiency and low immunogenicity,though challenges such as limited cargo capacity and potential for immune responses remain.Non-viral delivery systems,including lipid nanoparticles(LNPs),offer an alternative with lower immunogenicity and higher payload capacity,although their transfection efficiency can be lower.The therapeutic potential of these precise gene editing technologies is vast,particularly in treating genetic disorders.Preclinical studies have demonstrated the effectiveness of base editing in correcting genetic mutations responsible for diseases such as cardiomyopathy,liver disease,and hereditary hearing loss.These technologies promise to treat symptoms and potentially cure the underlying genetic causes of these conditions.Meanwhile,challenges remain,such as optimizing the safety and specificity of gene editing tools,improving delivery systems,and overcoming off-target effects,all of which are critical for their successful application in clinical settings.In summary,the continuous evolution of precise gene editing technologies,combined with advancements in delivery systems,is driving the field toward new therapeutic applications that can potentially transform the treatment of genetic disorders by targeting their root causes. 展开更多
关键词 precise gene editing CRISPR/Cas system base editing prime editing gene therapy
下载PDF
Performance Evaluation of Low-Cost Dual-Frequency GNSS Receivers for Precise Positioning in Senegal: Issues and Challenges
11
作者 Diogoye Diouf Oustasse Abdoulaye Sall +1 位作者 Ibrahima Khalil Gueye Fatou Ndiaye 《Journal of Analytical Sciences, Methods and Instrumentation》 2024年第2期23-37,共15页
The development of this technology has favored the advances noted in recent years in the field of precise positioning. It has also paved the way for a wide range of research into the evaluation of their performance an... The development of this technology has favored the advances noted in recent years in the field of precise positioning. It has also paved the way for a wide range of research into the evaluation of their performance and reliability, their potential use in different fields, the improvement of performance and combined systems, etc. Single-frequency GNSS receivers, which for a long time remained the only category of low-cost GNSS receivers, often limited by their level of accuracy (metric) mainly due to their single-frequency nature, have been joined in the last decade by dual-frequency GNSS receivers developed by certain manufacturers of positioning equipment. These receivers now offer possible alternatives to the relatively expensive conventional (topographic quality) or geodetic receivers and. In this study, the performance of these low-cost dual-frequency receivers was evaluated in static and real-time kinematic GNSS positioning modes. Static positioning was carried out on three points with sessions of 2 h and 4 h over three days with antenna swapping (CHC i50, Leica GS14 and Emlid Reach RS2+). Real-time observations were carried out on eleven (11) points in open, poorly open and not at all open environments, in order to assess not only performance but also receiver sensitivity in environments with a high risk of multipath. The results obtained showed an average agreement of 2 cm in planimetry between the low-cost Emlid RS2+ receiver and the Leica GS14 and CHC i50 receivers. The differences in altimetry are nevertheless greater (sometimes up to decimetres for certain points). Real-time positioning results provided an average convergence of around 1 cm on the E, N and H components with the results from the low-cost Emlid Reach RS2+ and Ublox ZED-F9P receivers and the CHC i50 receiver. Analysis of the results obtained has enabled us to highlight the various issues and challenges associated with this new generation of GNSS receivers, with a view to enhancing their appropriation and optimal integration in the professional and research worlds. 展开更多
关键词 Low-Cost GNSS NRTK precise Positioning ISSUES CHALLENGES
下载PDF
Empowerment of Precise Ideological and Political Education in Higher Education with Educational Digitalization
12
作者 Yan Dong Yu Yu Ge Yao 《Journal of Contemporary Educational Research》 2024年第4期23-28,共6页
The study explores how educational digitalization enables the precise development of ideological and political education in colleges and universities.Digital transformation enables colleges and universities to accurat... The study explores how educational digitalization enables the precise development of ideological and political education in colleges and universities.Digital transformation enables colleges and universities to accurately define educational objectives,content strategies,effect evaluation,and process management,and realize the precision and intelligence of ideological and political education.The application of big data technology enhances the data-oriented thinking of teachers and students,promotes the accurate application of data,and improves the efficiency of ideological and political education.The research also prospected a new vision of the digital construction of ideological and political courses and clarified the theoretical and practical path of the implementation and evaluation mode of ideological and political courses under digital empowerment.Education digitalization enables precise ideological and political education,which is a key way to promote the innovative development of ideological and political education in colleges and universities and will strongly support the improvement of the overall quality of higher education and the training of excellent talents. 展开更多
关键词 Education digital empowerment precise ideological and political education Improvement of efficiency
下载PDF
医科达Precise直线加速器高压联锁故障维修实例 被引量:3
13
作者 金剑 黄海 +2 位作者 聂娟娟 万里 孟燔 《医疗卫生装备》 CAS 2017年第11期161-163,共3页
0引言医用电子直线加速器是目前最常用的放射治疗设备,其原理是利用微波电场,沿直线加速电子得到较高的能量后对人体病变组织进行照射,以达到治疗肿瘤的目的[1]。熟练掌握加速器的结构和原理,及时排除机器常见故障,不仅可以使临床放疗... 0引言医用电子直线加速器是目前最常用的放射治疗设备,其原理是利用微波电场,沿直线加速电子得到较高的能量后对人体病变组织进行照射,以达到治疗肿瘤的目的[1]。熟练掌握加速器的结构和原理,及时排除机器常见故障,不仅可以使临床放疗工作正常进行,同时对患者较好的治疗也能起到一定的保障作用。现对我院医科达Precise直线加速器常见的一例故障进行简要的分析排除,以供参考。 展开更多
关键词 医科达precise直线加速器 高压联锁 故障维修
下载PDF
Deformation caused by the 2011 eastern Japan great earthquake monitored using the GPS single-epoch precise point positioning technique 被引量:4
14
作者 郭金运 原永东 +2 位作者 孔巧丽 李国伟 王方建 《Applied Geophysics》 SCIE CSCD 2012年第4期483-493,497,共12页
Crustal deformation can provide constraints for studying earthquake rupture and shock wave transmission for the Mw9.0 eastern Japan great earthquake. Using the single- epoch precise point positioning (PPP) method an... Crustal deformation can provide constraints for studying earthquake rupture and shock wave transmission for the Mw9.0 eastern Japan great earthquake. Using the single- epoch precise point positioning (PPP) method and the appropriate positioning flow, we process GPS data from six IGS (International GNSS Service) sites (e.g., MIZU, TSK2, USUD, MTKA, AIRA and KSMV) located in Japan and obtain the positioning results with centimeter scale precision. The displacement time series of the six sites are analyzed using the least squares spectral analysis method to estimate deformations caused by the Mw9.0 mainshock and the Mw7.9 aftershock, and the cumulative displacements after 1 day. Mainshock displacements at station MIZU, the nearest site to the mainshock in the North (N), East (E), and Up (U) directions, are -1.202 m, 2.180 m and -0.104 m, respectively, and the cumulative deformations after 1 day are -1.117 m, 2.071 m and -0.072 m, respectively. The displacements at station KSMV, the nearest site to the Mw7.9 aftershock in the N, E and U directions, are -0.032 m, 0.742 m and -0.345 m, respectively. The other sites obviously experienced eastern movements and subsidence. The deformation vectors indicate that the horizontal displacements caused by the earthquake point to the epicenter and rupture. Elastic bounds evidently took place at all sites. The results indicate that the crustal movements and earthquake were part of a megathrust caused by the Pacific Plate sinking under the North American Plate to the northeast of Japan island arc. 展开更多
关键词 Eastern Japan great earthquake GPS single-epoch precise point positioning crustal deformation
下载PDF
On simulation of precise orbit determination of HY-2 with centimeter precision based on satellite-borne GPS technique 被引量:4
15
作者 郭金运 秦建 +1 位作者 孔巧丽 李国伟 《Applied Geophysics》 SCIE CSCD 2012年第1期95-107,117,共14页
The HY-2 satellite carrying a satellite-borne GPS receiver is the first Chinese radar altimeter satellite, whose radial orbit determination precision must reach the centimeter level. Now HY-2 is in the test phase so t... The HY-2 satellite carrying a satellite-borne GPS receiver is the first Chinese radar altimeter satellite, whose radial orbit determination precision must reach the centimeter level. Now HY-2 is in the test phase so that the observations are not openly released. In order to study the precise orbit determination precision and procedure for HY-2 based on the satellite- borne GPS technique, the satellite-borne GPS data are simulated in this paper. The HY-2 satellite-borne GPS antenna can receive at least seven GPS satellites each epoch, which can validate the GPS receiver and antenna design. What's more, the precise orbit determination processing flow is given and precise orbit determination experiments are conducted using the HY-2-borne GPS data with both the reduced-dynamic method and the kinematic geometry method. With the 1 and 3 mm phase data random errors, the radial orbit determination precision can achieve the centimeter level using these two methods and the kinematic orbit accuracy is slightly lower than that of the reduced-dynamic orbit. The earth gravity field model is an important factor which seriously affects the precise orbit determination of altimeter satellites. The reduced-dynamic orbit determination experiments are made with different earth gravity field models, such as EIGEN2, EGM96, TEG4, and GEMT3. Using a large number of high precision satellite-bome GPS data, the HY-2 precise orbit determination can reach the centimeter level with commonly used earth gravity field models up to above 50 degrees and orders. 展开更多
关键词 HY-2 satellite satellite-borne GPS technique precise orbit determination reduced-dynamic method kinematic geometry method
下载PDF
Modified algorithm of combined GPS/GLONASS precise point positioning for applications in open-pit mines 被引量:2
16
作者 蔡昌盛 罗小敏 朱建军 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2014年第5期1547-1553,共7页
A modified algorithm of combined GPS/GLONASS precise point positioning (GG-PPP) was developed by decreasing the number of unknowns to be estimated so that accurate position solutions can be achieved in the case of l... A modified algorithm of combined GPS/GLONASS precise point positioning (GG-PPP) was developed by decreasing the number of unknowns to be estimated so that accurate position solutions can be achieved in the case of less number of visible satellites. The system time difference between GPS and GLONASS (STDGG) and zenith tropospheric delay (ZTD) values were firstly estimated in an open sky condition using the traditional GG-PPP algorithm. Then, they were used as a priori known values in the modified algorithm instead of estimating them as unknowns. The proposed algorithm was tested using observations collected at BJFS station in a simulated open-pit mine environment. The results show that the position filter converges much faster to a stable value in all three coordinate components using the modified algorithm than using the traditional algorithm. The modified algorithm achieves higher positioning accuracy as well. The accuracy improvement in the horizontal direction and vertical direction reaches 69% and 95% at a satellite elevation mask angle of 50°, respectively. 展开更多
关键词 GPS GLONASS precise point positioning elevation mask angle open-pit mine
下载PDF
医科达Precise直线加速器iViewGT系统故障分析及维修 被引量:13
17
作者 陈浩 林丹凤 +1 位作者 李玉琼 严潭 《中国医学装备》 2015年第9期132-133,共2页
瑞典医科达公司的Precise直线加速器是一款设计精细、全数字化控制的加速器,配备40对MLC(多叶光阑)[1]。其中利用i View GT电子影像验证系统,可开展普通放射治疗、立体定向放射治疗及适形调强放射治疗(intensity modulated radiation... 瑞典医科达公司的Precise直线加速器是一款设计精细、全数字化控制的加速器,配备40对MLC(多叶光阑)[1]。其中利用i View GT电子影像验证系统,可开展普通放射治疗、立体定向放射治疗及适形调强放射治疗(intensity modulated radiation therapy,IMRT),高分辨率的影像质量保证了投照剂量得到实时验证,以满足不同患者的治疗需要[2]。 展开更多
关键词 医科达 直线加速器 precise iViewGT 放射治疗 影像质量 MODULATED 系统故障分析 验证系统 全数字化控制
下载PDF
Precise加速器脉冲控制电路疑难故障检修一例 被引量:2
18
作者 乔桦 孟晓东 《医疗卫生装备》 CAS 2004年第8期83-83,共1页
关键词 precise加速器 脉冲控制电路 疑难故障 故障检修 故障现象
下载PDF
医科达Precise直线加速器无高压故障检修 被引量:5
19
作者 王俐 《第三军医大学学报》 CAS CSCD 北大核心 2004年第14期1290-1290,1294,共2页
关键词 precise直线加速器 故障检修 高压电路
下载PDF
The Precise Order and Singular Directions of Meromorphic Functions 被引量:2
20
作者 张学莲 《Journal of Beijing Institute of Technology》 EI CAS 1997年第1期14-18,共5页
The rnemmorphic functions of positive order(both finite positive order and infinite order) are discussed.First,the precise order and type function are given by using the characteristic function.Then some singular dire... The rnemmorphic functions of positive order(both finite positive order and infinite order) are discussed.First,the precise order and type function are given by using the characteristic function.Then some singular directions are defined and their existence is proved. 展开更多
关键词 metamorphic function singular direction precise order
下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部