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Use of Plastic Correction Formula to Improve Accuracy of Welding Residual Stress Test with Blind-Hole Method 被引量:4
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作者 Qiu Zhao Kongsheng Chen +3 位作者 Meizhong Chen Bruno Briseghella Zhiyong Guo Guotao Yang 《Transactions of Tianjin University》 EI CAS 2018年第5期480-488,共9页
The blind-hole method is the most widely used approach to experimentally determine the distribution of residual stress. This paper aims to improve test accuracy of welding residual stress and conducts an experimental ... The blind-hole method is the most widely used approach to experimentally determine the distribution of residual stress. This paper aims to improve test accuracy of welding residual stress and conducts an experimental study on the strain release factors involved when using the blind-hole method for Q235 and Q345, two steels commonly used in building structures. The ranges of strain release factors A and B in the elastic stage, the effects of strain release factors on residual stress calculated values, and the plastic corrected strain release factors are analyzed considering of the effect of plastic deformation around the blind hole on measurement accuracy. Finally, a simplified calculation formula to determine strain release factors is proposed for use with the blind-hole method. Results show that in the elastic stage, strain release factor A for Q235 and Q345 ranges from-0.399 to-0.525 and strain release factor B from-0.791 to-0.960. Changing the strain release factors A and B shows that calculated residual tensile stress varies in relation to a decrease in both factor values. However, there is a increase in calculated residual compressive stress with a decrease in the strain release factor A value, but there is an decrease with a decrease in strain release factor B value. Calculated residual stress applied to elastic strain release factors is compared with that applied to amended plastic strain release factors for Q235 steel. The maximum deviation between calculated residual stress and test stress is reduced from 21.1 to 1.0%,and for Q345 steel from 26.5 to 1.2%. It is thus evident that the plastic correction formula proposed in this paper can be used in calculations when conducting a residual stress test. 展开更多
关键词 blind-hole method WELDING RESIDUAL stress·Calibration test STRAIN release FACTOR PLASTIC CORRECTION
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ROBUSTNESS OF THE SUBSPACE METHOD FOR BLIND SIGNATURE WAVEFORM ESTIMATION WITH RESPECT TO CHANNEL ORDER IN ASYNCHRONOUS DS-CDMA SYSTEMS 被引量:1
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作者 Cheng Yunpeng Cai Yueming(P. O. Box 106, Mobile Commu. Research Section, Nanjing Inst. of Commun. Eng., Nanjing, 210016) 《Journal of Electronics(China)》 2001年第3期212-216,共5页
The robustness of the subspace method for blind signature waveform estimation with respect to channel order is analyzed in asynchronous DS-CDMA systems theoretically. Theoretical analysis and simulation results show t... The robustness of the subspace method for blind signature waveform estimation with respect to channel order is analyzed in asynchronous DS-CDMA systems theoretically. Theoretical analysis and simulation results show that the overestimating of the channel order will lead to the degradation of the quality of the estimated signature waveform. So we should adopt the channel order as small as possible. 展开更多
关键词 DS-CDMA blind SUBSPACE method ROBUSTNESS
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Blind detection of liquefaction by existing methods for New Zealand M_L6.3 earthquake on Feb. 22,2011 被引量:1
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作者 Sun Rui Tang Fuhui Chen Longwei 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2011年第4期465-474,共10页
Real-time liquefaction monitoring and warning techniques are new ways to mitigate liquefaction hazard. A key point is to establish a reverse liquefaction detection method based on seismic records. However, the existin... Real-time liquefaction monitoring and warning techniques are new ways to mitigate liquefaction hazard. A key point is to establish a reverse liquefaction detection method based on seismic records. However, the existing methods are quite limited and the reliability requires verification. On Feb. 22, 2011 an earthquake of magnitude 6.3 struck at New Zealand's South Island. Remarkable liquefaction phenomena were reported, which provide an opportunity to verify the existing liquefaction detection methods. 27 acceleration records within 50 km to the epicenter were selected to perform a blind detection by using the existing methods, including Miyajima method, Suzuki method, Kostadinov-Yamazaki method and Yuan-Sun method. The blind detection results indicate that Yuan-Sun method gives correct results for seven confirmed sites, and Suzuki method and Yuan-Sun method yield correct detection for a reported non-liquefied site. Four methods including the Yuan-Sun method give identical detection for four sites and three methods also including the Yuan-Sun method give identical detection for ten sites. Besides, there are five sites, for which the four methods give opposite detection. 展开更多
关键词 New Zealand earthquake LIQUEFACTION detection methods blind detection
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Subspace-Based Blind Channel Estimation Method for MIMO-OFDM Systems
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作者 HOUYong-min RONGMeng-tian 《Wuhan University Journal of Natural Sciences》 EI CAS 2005年第2期413-416,共4页
A subspace-based blind channel estination algo rithm for MIMO-OFDM systems is proposed. This algorithm exploits the cyclostationarity introduced by cyclic prefix of OFDM to estimate the channel parameters. The propose... A subspace-based blind channel estination algo rithm for MIMO-OFDM systems is proposed. This algorithm exploits the cyclostationarity introduced by cyclic prefix of OFDM to estimate the channel parameters. The proposed new algorithm is found to be outperforming the other algorithm with respect to convergence rate and achievable mean square error and robustness to channel order over determination. 展开更多
关键词 MIMO OFDM blind channel estimation subspace method
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Multichannel Blind CT Image Restoration via Variable Splitting and Alternating Direction Method
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作者 孙云山 张立毅 +1 位作者 张海燕 张经宇 《Transactions of Tianjin University》 EI CAS 2015年第6期524-532,共9页
Computed tomography(CT) blurring caused by point spread function leads to errors in quantification and visualization. In this paper, multichannel blind CT image restoration is proposed to overcome the effect of point ... Computed tomography(CT) blurring caused by point spread function leads to errors in quantification and visualization. In this paper, multichannel blind CT image restoration is proposed to overcome the effect of point spread function. The main advantage from multichannel blind CT image restoration is to exploit the diversity and redundancy of information in different acquisitions. The proposed approach is based on a variable splitting to obtain an equivalent constrained optimization formulation, which is addressed with the alternating direction method of multipliers and simply implemented in the Fourier domain. Numerical experiments illustrate that our method obtains a higher average gain value of at least 1.21 d B in terms of Q metric than the other methods, and it requires only 7 iterations of alternating minimization to obtain a fast convergence. 展开更多
关键词 blind image restoration variable splitting alternating direction method medical CT image
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A Modified Eigenvector Method for Blind Deconvolution of MIMO Systems Using the Matrix Pseudo-Inversion Lemma
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作者 Mitsuru Kawamoto Kiyotaka Kohno +1 位作者 Yujiro Inouye Koichi Kurumatani 《Circuits and Systems》 2011年第1期7-13,共7页
Recently we have developed an eigenvector method (EVM) which can achieve the blind deconvolution (BD) for MIMO systems. One of attractive features of the proposed algorithm is that the BD can be achieved by calculatin... Recently we have developed an eigenvector method (EVM) which can achieve the blind deconvolution (BD) for MIMO systems. One of attractive features of the proposed algorithm is that the BD can be achieved by calculating the eigenvectors of a matrix relevant to it. However, the performance accuracy of the EVM depends highly on computational results of the eigenvectors. In this paper, by modifying the EVM, we propose an algorithm which can achieve the BD without calculating the eigenvectors. Then the pseudo-inverse which is needed to carry out the BD is calculated by our proposed matrix pseudo-inversion lemma. Moreover, using a combination of the conventional EVM and the modified EVM, we will show its performances comparing with each EVM. Simulation results will be presented for showing the effectiveness of the proposed methods. 展开更多
关键词 blind Signal Processing blind Deconvolution EIGENVECTOR methods Super-Exponential Mthods MIMO Systems Matrix Pseudo-Inversion LEMMA
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Single dose dexamethasone prophylaxis of postembolisation syndrome after chemoembolisation in hepatocellular carcinoma patient:A randomised,double-blind,placebo-controlled study 被引量:5
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作者 Panot Sainamthip Chutcharn Kongphanich +1 位作者 Naiyarat Prasongsook Sakkarin Chirapongsathorn 《World Journal of Clinical Cases》 SCIE 2021年第30期9059-9069,共11页
BACKGROUND Even in the immuno-oncology era,transcatheter arterial chemoembolisation(TACE)is the most effective way to treat intermediate stage hepatocellular carcinoma(HCC).Postembolisation syndrome(PES)is the most co... BACKGROUND Even in the immuno-oncology era,transcatheter arterial chemoembolisation(TACE)is the most effective way to treat intermediate stage hepatocellular carcinoma(HCC).Postembolisation syndrome(PES)is the most common side effect from TACE and there is still no standard prevention guideline.AIM To evaluate the efficacy of single dose intravenous dexamethasone regimen to prevent PES after TACE among patients with HCC.METHODS This study enrolled patients with HCC who had eligible indication for TACE without macrovascular invasion/extrahepatic metastasis.Patients were randomly assigned to either an intravenous single dose of dexamethasone 8 mg or placebo one hour before TACE.The primary outcome was a negative result of PES at 48 h after TACE,which was defined as score<2 of Southwest Oncology Group toxicity coding criteria using fever,nausea,vomiting and pain to calculated.And the secondary end point was duration of admission between two groups.RESULTS One hundred patients were randomly assigned 1:1.Under intention-to-treat analysis,49 patients were randomly assigned to the dexamethasone and 51 to the placebo groups.Both groups were similar for baseline characteristics.The negative PES rate was significantly higher in the dexamethasone group than in the placebo group(63.3%vs 29.4%;P=0.005).Mean Southwest Oncology Group toxicity coding PES was 2.14(95%CI:1.41-2.8)vs 3.71(95%CI:2.97-4.45)between the dexamethasone and placebo groups,respectively.Cumulative incidence of fever was significantly lower in dexamethasone group with P<0.001,pain,nausea and vomiting were also lower in the dexamethasone group compared with the placebo group(P=0.16,P=0.11,and P=0.49).The dexamethasone regimen was generally well tolerated by patients with HCC patients including those with hepatitis B virus infection and well-controlled diabetes mellitus.CONCLUSION Single dose dexamethasone was effective at preventing PES among patients with HCC treated with TACE.The study showed no adverse events of special interest related to dexamethasone. 展开更多
关键词 Hepatocellular carcinoma CHEMOEMBOLIZATION DEXAMETHASONE Double blind method Prevention Postembolization syndrome
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Evaluation of the effect of acupuncture on hand pain,functional deficits and health-related quality of life in patients with rheumatoid arthritis--A study protocol for a multicenter,double-blind,randomized clinical trial 被引量:14
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作者 Susana Seca Sebastian Kirch +1 位作者 António S.Cabrita Henry J.Greten 《Journal of Integrative Medicine》 SCIE CAS CSCD 2016年第3期219-227,共9页
BACKGROUND: Rheumatoid arthritis(RA) is a systemic inflammatory disease characterized by functional disability and pain. Although acupuncture is widely used, until now Western acupuncture studies on RA have not sho... BACKGROUND: Rheumatoid arthritis(RA) is a systemic inflammatory disease characterized by functional disability and pain. Although acupuncture is widely used, until now Western acupuncture studies on RA have not shown conclusive positive results. Acupuncture is regarded as a reflex therapy that has effects on the human autonomic nervous system. By establishing a traditional Chinese medicine(TCM) diagnosis first, the practitioner is able to choose acupoints according to the state of each individual patient.METHODS/DESIGN: We are interested if acupuncture, using a classical diagnostic procedure to allocate acupoints to the patient according to the Shang Han Lun theory, can be effective in relieving pain, improving hand function and increasing health-related quality of life in RA.The authors intend to harmonize TCM diagnosis according to clinical and genetic profiles. Patients with the TCM diagnosis of a so-called Turning Point syndrome will be followed up in a randomized, prospective, double-blind, placebo-controlled, multicenter and three-armed parallel-group study with a standardized treatment in order to optimize potential therapeutic effects of acupuncture on pain, strength and muscle function of patients with RA as well as the influence on inflammation and quality of life.DISCUSSION: The findings of this study will provide important clinical information about the feasibility and efficacy of acupuncture treatment for RA patients. In addition, it will explore the feasibility of further acupuncture research.TRIAL REGISTRATION NUMBER: Clinical Trials.gov Identifier NCT02553005. 展开更多
关键词 ACUPUNCTURE rheumatoid arthritis quality of life PAIN hand strength study protocol randomized clinical trial double-blind method
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Patient blinding with blunt tip placebo acupuncture needles:comparison between 1 mm and 2 mm skin press 被引量:4
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作者 Nobuari Takakura Miho Takayama +3 位作者 Morihiro Nasu Masako Nishiwaki Akiko Kawase Hiroyoshi Yajima 《Journal of Integrative Medicine》 CAS CSCD 2018年第3期164-171,共8页
Objective: To investigate the influence of the depth of skin press in blunt tip placebo acupuncture needles on patient blinding and its relationship to needle diameter.Methods: Forty healthy volunteers were enrolled... Objective: To investigate the influence of the depth of skin press in blunt tip placebo acupuncture needles on patient blinding and its relationship to needle diameter.Methods: Forty healthy volunteers were enrolled as subjects for patient blinding. Four acupuncturists applied the following needles randomly at three points in each forearm: 0.18 mm and 0.25 mm diameter penetrating needles inserted to a depth of 5 mm, and 0.18 mm and 0.25 mm diameter skin-touch needles depressing the skin at the acupoint to a depth of 1 mm and 2 mm from the skin surface. The subjects reported their guesses at the nature of needles they received, and rated needle pain and de qi. A blinding index was calculated to define the success of blinding for subjects.Results: The blinding status of subjects for 1 mm press needles of 0.18 mm diameter was "random guess",but "unblinded" for 1 mm press needles of 0.25 mm diameter. For 2 mm press needles of both diameters,the blinding status was "opposite guess" and the blinding status for penetrating needles of both diameters was "unblinded." The percentages of "felt pain" with 2 mm press needles of both diameters were similar to that with penetrating needles, but those were not similar for 1 mm press needles. The frequency of de qi occurrence with 2 mm press needles of 0.18 mm diameter was similar to that of penetrating needles of both diameters.Conclusion: Placebo needles of 2 mm press made more subjects guess that the needles penetrated the skin than 1 mm press needles. The use of small diameter needles increased patient blinding. 展开更多
关键词 Double-blind method Acupuncture PLACEBO SHAM De qi
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一种基于Blind Kriging模型和差分进化的电磁结构优化算法 被引量:2
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作者 陈晓辉 郭欣欣 裴进明 《电子测量与仪器学报》 CSCD 北大核心 2016年第11期1694-1700,共7页
各类电磁结构日趋复杂,设计自由度不断提升.传统优化算法需要对大量的参数组合进行全波仿真试探,设计效率普遍较低。针对这一问题,提出BK(blind Kriging)模型和差分进化相结合的电磁结构优化算法.相比普通Kriging模型,BK模型通过贝叶斯... 各类电磁结构日趋复杂,设计自由度不断提升.传统优化算法需要对大量的参数组合进行全波仿真试探,设计效率普遍较低。针对这一问题,提出BK(blind Kriging)模型和差分进化相结合的电磁结构优化算法.相比普通Kriging模型,BK模型通过贝叶斯参数选择算法将影响性能的主要因子加入回归模型,提高对响应的预测精度;依据BK模型的预测结果从每代差分进化种群中选择最优个体执行电磁仿真。由于优化过程中大量的电磁计算转移到快速的BK模型,优化效率得到显著提升。通过一个圆波导多螺钉极化转换器的优化设计,表明该方法的求解质量和收敛速度优于现有算法。 展开更多
关键词 电磁结构 优化算法 blind KRIGING 差分进化
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航空发动机盲腔螺母精密拧紧技术
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作者 张宗江 李小强 +2 位作者 韩玉杰 李兆宇 张铭铭 《北京航空航天大学学报》 北大核心 2026年第1期260-274,共15页
航空发动机转子狭小盲腔连接质量对转子整体装配质量具有极大的影响,综合国内外现状,由于缺乏盲腔结构高效精准装配工装,导致螺栓连接工艺的精确控制能力不足,进而影响转子盘轴零部件配合表面的连接力学性能,针对某型号盲腔螺母拧紧装... 航空发动机转子狭小盲腔连接质量对转子整体装配质量具有极大的影响,综合国内外现状,由于缺乏盲腔结构高效精准装配工装,导致螺栓连接工艺的精确控制能力不足,进而影响转子盘轴零部件配合表面的连接力学性能,针对某型号盲腔螺母拧紧装配需求,将盲腔螺母拧紧系统分为拧紧力矩传递机构和操作执行机构。在拧紧力矩传递机构设计上,对拧紧工艺扭矩法与扭矩转角法进行比较,确定扭矩转角法作为最终执行工艺,同时,设计力矩传递结构,并对关键部件进行强度和寿命校核,考虑力矩损失建立输入输出力矩模型,确定拧紧工具输入扭矩,实现拧紧力矩的高精度控制;在操作执行机构设计上,对操作执行机构进行机械设计,并对高精度运动部件蜗轮蜗杆进行3DCS仿真,同时,利用MATLAB进行轨迹规划与运动学仿真;基于以上研究开发感知系统及控制系统,进行视觉识别,实现设备的高精度控制,并进行盲腔螺母拧紧技术实验验证,对提高该狭小盘间盲腔螺栓阵列连接质量一致性具有重要意义。 展开更多
关键词 航空发动机 盲腔 扭矩转角法 力矩控制 轨迹规划 偏差分析
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Detecting the signal cycle of the deep Earth’s dynamic processes based on GRACE satellite and CHAOS-7 model data
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作者 YongGang Zhang ZhengTao Wang +1 位作者 GangHua Ni and ShiZe Zhang 《Earth and Planetary Physics》 2026年第1期1-12,共12页
The GRACE(Gravity Recovery and Climate Experiment)space mission recorded temporal variation characteristics of the global gravity field at decadal timescales.The gravity data have been shown to capture the dynamics of... The GRACE(Gravity Recovery and Climate Experiment)space mission recorded temporal variation characteristics of the global gravity field at decadal timescales.The gravity data have been shown to capture the dynamics of flows within the outer core and their effects on the core-mantle boundary.We first aim to remove global surface process gravity signals from the GRACE data.We then construct the global core magnetic field according to the CHAOS-7 model.Finally,we apply the blind source separation method to decompose the processed gravity signals and core magnetic signals and compute the power spectral density of the gravity and magnetic field signals by using the Lomb-Scargle periodogram approach.We have discovered a signal cycle(of~6 years)in the principal components of the core magnetic and gravity signals,potentially as a result of deep Earth processes.The main principal components of the core magnetic and gravity signals reveal that the variation trends in the second-order time derivative of the core magnetic field are similar to those in the gravity field.After 2014,the second-order time derivative of the core magnetic field exhibited linear and rapid change characteristics,which were the same as the change in the gravity field and are consistent with existing research results. 展开更多
关键词 GRACE satellite time-variable gravity field core magnetic field mass transport blind source separation method
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Rhus coriaria L. increases serum apolipoprotein-A1 and high-density lipoprotein cholesterol levels: a double-blind placebo-controlled randomized clinical trial
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作者 Zahra Hajmohammadi Mojtaba Heydari +4 位作者 Majid Nimrouzi Pouya Faridi Mohammad Javad Zibaeenezhad Gholamhossein Ranjbar Omrani Mesbah Shams 《Journal of Integrative Medicine》 SCIE CAS CSCD 2018年第1期45-50,共6页
Background: Lipid-lowering effect ofRhus coriaria L. (Rhus) has been investigated in multiple animal stud- ies with promising results. Nonetheless, its clinical efficacy has not been adequately examined. Objective... Background: Lipid-lowering effect ofRhus coriaria L. (Rhus) has been investigated in multiple animal stud- ies with promising results. Nonetheless, its clinical efficacy has not been adequately examined. Objective: The aim of this study was to evaluate the lipid-lowering effects of Rhus among patients with hyperlipidemia. Design, setting, participants and interventions: The study was designed as a two-arm, double-blind placebo-controlled randomized clinical trial, using a parallel design. Eighty patients with primary hyper- lipidemia were randomly assigned to receive Rhus capsules or placebo for 6 weeks. Main outcome measures: The serum lipid levels, apolipoprotein-A1 (Apo-A1) and apolipoprotein-B (Apo-B) were measured. Results: Mean serum high-density lipoprotein cholesterol (HDL-C) and Apo-Al levels were significantly increased in the Rhus group, compared with the placebo group, after 6 weeks of intervention (P= 0.001). The analysis of covariance test including age, gender, body mass index (BMI), and smoking as co-variables revealed that the increase in HDL-C and Apo-A1 levels remained significant, and increases in HDL-C were dependent on the increase in Apo-A1 levels. No significant difference was observed between Rhus and placebo groups in terms of mean reductions in total cholesterol, low-density lipopro- tein cholesterol and triglyceride levels; however, more significant improvement was observed among obese patients (BMI≥ 30 kg/m^2). Conclusion: The study showed significant increases in HDL-C and Apo-Al levels in response to Rhus sup- plementation in patients with hyperlipidemia. Trial registration: ClinicalTrials.gov ID: NCT02295293. 展开更多
关键词 Dyslipidemias Rhus coriaria LLipids Dietary supplements Plants Apolipoproteins A Randomized controlled trial Double-blind method
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Safety and efficacy of Tongkuaixiao ointment in reliving cancer-induced pain: a multicenter double-blind placebo-controlled randomized trial
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作者 Tan Huangying Zhu Shijie +9 位作者 Li Tong Feng Li Zhang Xia Li Yuan Lou Yanni Liu Meng Wan Donggui Li Peiwen Jia Liqun Deng Bo 《Journal of Traditional Chinese Medicine》 SCIE CAS CSCD 2016年第6期695-700,共6页
OBJECTIVE: To evaluate the safety and efficacy of Tongkuaixiao ointment(TKXO) in treating moderate-to-severe cancer induced somatalgia.METHODS: Totally 130 patients with moderateto-severe cancer induced somatalgia wer... OBJECTIVE: To evaluate the safety and efficacy of Tongkuaixiao ointment(TKXO) in treating moderate-to-severe cancer induced somatalgia.METHODS: Totally 130 patients with moderateto-severe cancer induced somatalgia were randomly divided into a TKXO group and a control group.The patients were treated with either TKXO applied externally or placebo, with opioid analgesics orally at the same time. Observation parameters were included numerical rating scale(NRS) scores,analgesic efficacy, initiation effective time, persistent analgesic time, equivalent morphine dose,National Comprehensive Cancer Network(NCCN)grade in Impact of Pain Measurement Scores, and safety and satisfaction extent investigation.RESULTS: NRS scores and NCCN grade in Impact of Pain Measurement Scores decreased significantly after 5-days' treatment in the two groups(P <0.0001). Compared to the control group, initiation effective time was significantly shorter(P < 0.05)and persistent analgesic time was significantly longer(P < 0.01), equivalent oral morphine doses of the first day and the whole treatment course were significantly decreased in the TKXO treatment group(P < 0.01 or P < 0.05). No obvious adverse effects were found in the TKXO group.CONCLUSION: TKXO combined with opioid analgesics possesses the advantages of high efficacy,fast action, long persistent action, safety and convenience in use, and it can reduce the dose of opioid. 展开更多
关键词 Cancer pain External therapies Randomized controlled trail Double-blinded method
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钢桥面板嵌补段U肋对接焊缝残余应力与变形研究 被引量:2
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作者 李枝军 刘千军 +2 位作者 谢长进 张菁 徐秀丽 《桥梁建设》 北大核心 2025年第2期58-65,共8页
为研究钢桥面板嵌补段U肋对接焊缝的残余应力分布和变形规律,以苏州某新建内河航道桥为背景,开展现场原位试验及有限元数值模拟分析。首先利用盲孔法对现场原位焊接试件表面残余应力进行测试,然后基于Goldak双椭球热源模型编写焊接模拟... 为研究钢桥面板嵌补段U肋对接焊缝的残余应力分布和变形规律,以苏州某新建内河航道桥为背景,开展现场原位试验及有限元数值模拟分析。首先利用盲孔法对现场原位焊接试件表面残余应力进行测试,然后基于Goldak双椭球热源模型编写焊接模拟子程序,采用顺序耦合法和热弹塑性法对温度场和力学场进行数值模拟。结果表明:残余应力集中在距离焊缝中心20 mm的热影响区域内;纵向和横向残余应力呈现出由中间往两端递减的分布规律,在焊缝路径中间应力大小分布均匀;纵向残余应力在整个焊缝路径上都为拉应力,在中间部位最大达400 MPa;横向残余应力在焊缝路径中间为拉应力(最大约为160 MPa),而在路径两端则表现为较大的压应力(最大达350 MPa);弧形段的应力分布规律与直线段基本一致。U肋对接焊试件变形呈现向内侧凹陷的面外特征,最大变形出现在焊缝起始位置,达2.06 mm,变形量随着与焊缝距离的增加而减小且在远离焊缝区域呈线性变化,同时试件产生下凹的纵向弯曲变形。 展开更多
关键词 钢桥面板 U肋对接焊缝 残余应力 变形 原位试验 盲孔法 有限元法
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X80高钢级管道焊接残余应力测试研究 被引量:2
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作者 古松 蒋广 +3 位作者 顾颖 陈祥斌 孔超 张豫 《精密成形工程》 北大核心 2025年第1期127-133,共7页
目的获得X80高钢级管道环焊缝焊接残余应力大小与分布模式。方法首先采用盲孔法对X80高钢级管道的环焊缝焊接残余应力进行了测试,然后将测试结果与X80管道焊接残余应力的相关文献试验数据以及国家标准《在用含缺陷压力容器安全评定》GB/... 目的获得X80高钢级管道环焊缝焊接残余应力大小与分布模式。方法首先采用盲孔法对X80高钢级管道的环焊缝焊接残余应力进行了测试,然后将测试结果与X80管道焊接残余应力的相关文献试验数据以及国家标准《在用含缺陷压力容器安全评定》GB/T 19624—2019所规定的内容进行了对比分析,最后根据测试数据提出了X80高钢级管道环焊缝焊接残余应力σ_(R)与距焊缝中心距离x之间的函数关系式,进一步得到了X80管道环焊缝沿环向与轴向的焊接残余应力计算公式。结果X80管道环焊缝沿环向区域存在较大的残余拉应力,焊接残余应力在焊趾区域达到峰值,表现为随着距焊缝中心距离的增加,环向残余应力由拉应力小幅度增加达到峰值567 MPa后迅速转变为压应力,随后缓慢转变为拉应力并趋近于0。随着距焊缝中心距离的增加,轴向残余应力由压应力迅速转变为拉应力,其中压应力峰值为92 MPa,发生在焊缝熔合线位置,拉应力峰值为188 MPa,出现在远离熔合线16 mm位置。结论根据试验结果提出了适用于X80管道环焊缝沿环向与轴向的焊接残余应力分布模式,为含缺陷X80管道的安全评定及修复提供理论参考。 展开更多
关键词 X80管道 焊接残余应力 盲孔法 环焊缝 试验研究
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地下结构排水盲沟减压抗浮简化设计方法 被引量:1
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作者 潘泓 刘荣照 +2 位作者 骆冠勇 彭斯格 曹洪 《岩土工程学报》 北大核心 2025年第4期685-694,共10页
目前,排水盲沟减压抗浮系统中排水盲沟设计主要采用数值法分析计算,尚无简单实用的简化计算方法。基于盲沟为等水头边界及入渗量均布于盲沟单元等假定,建立排水盲沟网格简化模型,得到平面布置为矩形的盲沟单元水头分布解析解,给出入渗... 目前,排水盲沟减压抗浮系统中排水盲沟设计主要采用数值法分析计算,尚无简单实用的简化计算方法。基于盲沟为等水头边界及入渗量均布于盲沟单元等假定,建立排水盲沟网格简化模型,得到平面布置为矩形的盲沟单元水头分布解析解,给出入渗量、单元几何尺寸等参数即可算得盲沟单元内水头分布。提出均匀入渗和非均匀入渗情况下底板入渗量分布的计算模式。通过算例验证,简化方法适用前提为盲沟及结构底板底部布置有渗透性远大于土体的疏水层,简化算法与有限元结果的相对误差较小且结果偏于保守,可用于盲沟布置的设计。对典型土层算例对比发现:若底板下部地层为弱透水层中夹有一层强透水层,底板入渗量会均匀分布,盲沟可等间距均匀布置;若下部地层无强透水层,入渗量大部分集中在距帷幕1倍~1.5倍坑底含水层厚度范围内,盲沟间距应在该范围内减小,在底板中部增大。 展开更多
关键词 抗浮 排水减压 排水盲沟 渗流 简化方法
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多谱自适应小波和盲源分离耦合的生理信号降噪方法 被引量:1
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作者 王振宇 向泽锐 +2 位作者 支锦亦 丁铁成 邹瑞 《北京航空航天大学学报》 北大核心 2025年第3期910-921,共12页
为提高生理信号的质量和可靠性,将盲源分离和小波阈值方法进行耦合研究,提出了多谱自适应小波信号增强方法并与改进的盲源分离方法相结合进行降噪处理。为评估所提方法的有效性,使用小波变换中软阈值、硬阈值、自适应阈值3种方法计算信... 为提高生理信号的质量和可靠性,将盲源分离和小波阈值方法进行耦合研究,提出了多谱自适应小波信号增强方法并与改进的盲源分离方法相结合进行降噪处理。为评估所提方法的有效性,使用小波变换中软阈值、硬阈值、自适应阈值3种方法计算信噪比(SNR)和均方根误差(RMSE)。结果表明:所提方法在软阈值下具有较强的适用性,增强后的信号软阈值相比硬阈值,SNR提升约44.2%,RMSE下降约28.8%,处理时间减少约1.4%。软阈值相比自适应阈值,SNR提升约706%,RMSE下降约16.7%,处理时间减少约3.0%。为对比软阈值下各参数差异,使用软阈值对原始信号、加噪信号和增强信号进行对比分析及归一化处理。结果显示增强后的信号具有较好的SNR、较低的RMSE和较短的处理时间,软阈值下增强后的信号与原始信号相比,SNR提升约0.12%,RMSE下降约2.5%,处理时间减少约3.9%,进一步验证了所提方法的有效性,并提高了信号质量。 展开更多
关键词 多谱自适应小波 盲源分离 小波变换 降噪方法 生理信号
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突出结构联合L0先验的模糊图像盲复原方法
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作者 高如新 朱新柳 +1 位作者 郭凤云 李雪颖 《计算机应用与软件》 北大核心 2025年第3期190-195,共6页
为了解决结构类模糊图像在边缘模糊核估计方法中复原效果较差这一问题,提出突出结构联合L0先验的模糊图像盲复原方法。利用模糊图像的突出结构估计图像边缘,根据模糊核估计的数学模型来恢复中间潜像并代替模糊图像作为新的输入,结合L0... 为了解决结构类模糊图像在边缘模糊核估计方法中复原效果较差这一问题,提出突出结构联合L0先验的模糊图像盲复原方法。利用模糊图像的突出结构估计图像边缘,根据模糊核估计的数学模型来恢复中间潜像并代替模糊图像作为新的输入,结合L0正则化先验约束模型求解得到模糊核和清晰图像。实验结果表明,提出的方法可较好地复原结构类模糊图像和大尺度模糊核运动模糊图像,抑制振铃效果显著,在复原效果上优于其他方法。 展开更多
关键词 盲复原方法 突出结构 L0先验 数学模型 模糊核
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对接焊缝残余应力的分布规律及对疲劳寿命的影响
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作者 蔺鹏臻 于博 何志刚 《湖南大学学报(自然科学版)》 北大核心 2025年第9期150-162,共13页
为了研究钢桥对接焊接接头温度场、残余应力场和变形场的分布规律,利用有限元软件建立16 mm厚桥钢板对接焊缝三维有限元模型,并通过盲孔法试验实测数据对模型的正确性加以验证.基于此,进一步分析了焊件温度场、残余应力场和变形场的分... 为了研究钢桥对接焊接接头温度场、残余应力场和变形场的分布规律,利用有限元软件建立16 mm厚桥钢板对接焊缝三维有限元模型,并通过盲孔法试验实测数据对模型的正确性加以验证.基于此,进一步分析了焊件温度场、残余应力场和变形场的分布规律,并在焊件中引入初始裂缝,探讨了初始缺陷和焊接残余应力对焊缝疲劳寿命的影响.研究结果表明:沿垂直焊缝方向,纵向残余应力呈现拉-压分布状态,焊缝附近60 mm的热影响区内,主要为拉应力,峰值达415 MPa,超过材料的屈服强度,当远离热影响区时,纵向残余拉应力转变为压应力.横向残余应力在焊趾处达到峰值205 MPa.在无约束条件下,焊接引起的变形为典型的平面外角变形,随着与焊缝中心的距离增加,各测点的变形呈线性增长,最大变形出现在焊件外边缘,为14.58 mm.即使是较小的残余应力,无论其状态如何,均会影响疲劳寿命.3%和8%的残余拉-压应力分别导致疲劳寿命降低16.7%和提高68.4%;残余拉应力随着应力的增大导致疲劳寿命降低,但降低速率逐渐衰减.当拉/压应力数值相近时,压应力对疲劳寿命的影响远大于拉应力.在实际构件的预制过程中,应通过预变形等方法来控制焊件的变形;焊后通过表面处理技术控制残余拉应力,以提高材料的疲劳寿命和延长结构的使用寿命. 展开更多
关键词 盲孔法检测 残余应力 热力耦合分析 数值模型 疲劳裂纹扩展
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