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电流模PWM降压DC_DC片内补偿电路的设计实现 被引量:8
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作者 代国定 徐洋 +1 位作者 李卫敏 胡波 《电子器件》 CAS 2010年第1期53-57,共5页
对单片电流模降压DC_DC的内部电流环与电压环的稳定性进行了分析研究,分别采用分段线性斜坡补偿与内置频率补偿技术,有效消除环路亚谐波振荡并克服了稳定性对输出负载以及误差放大器增益的依赖,提高了芯片的瞬态响应速度及输出带负载能... 对单片电流模降压DC_DC的内部电流环与电压环的稳定性进行了分析研究,分别采用分段线性斜坡补偿与内置频率补偿技术,有效消除环路亚谐波振荡并克服了稳定性对输出负载以及误差放大器增益的依赖,提高了芯片的瞬态响应速度及输出带负载能力。采用TSMC0.25μmBCD工艺设计实现了一款高电压电流模PWM降压型的DC_DC芯片,spectre仿真结果表明,输出电流可达2A,其线性调整率和负载调整率均小于0.3%,输出电压对负载1A时的阶跃响应时间小于70μs。 展开更多
关键词 降压型DC_DC 电流模PWM 分段线性斜坡补偿 频率补偿 环路增益
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DC_DC变换器使用双因子随机调制技术的系统仿真
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作者 王斌 谢清 王颢雄 《三峡大学学报(自然科学版)》 CAS 2004年第2期120-122,共3页
随机调制技术作为一种新型的控制技术能够改善电磁兼容性.因其开关函数的随机化特性,将引起系统控制的特殊性,需要对电力电子系统采用这种控制技术进行系统仿真研究.提供了DC_DC变换器使用双因子随机调制技术的系统性能的仿真研究及其WE... 随机调制技术作为一种新型的控制技术能够改善电磁兼容性.因其开关函数的随机化特性,将引起系统控制的特殊性,需要对电力电子系统采用这种控制技术进行系统仿真研究.提供了DC_DC变换器使用双因子随机调制技术的系统性能的仿真研究及其WELCH谱估计特性分析,仿真过程通过SIMUUNK实现. 展开更多
关键词 DC_DC变换器 直流变换器 随机调制 计算机仿真
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Proton pump inhibitor step-down therapy for GERD:A multi-center study in Japan
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作者 Takao Tsuzuki Hiroyuki Okada +6 位作者 Yoshiro Kawahara Ryuta Takenaka Junichiro Nasu Hidehiko Ishioka Akiko Fujiwara Fumiya Yoshinaga Kazuhide Yamamoto 《World Journal of Gastroenterology》 SCIE CAS CSCD 2011年第11期1480-1487,共8页
AIM:To investigate the predictors of success in stepdown of proton pump inhibitor and to assess the quality of life(QOL).METHODS:Patients who had heartburn twice a week or more were treated with 20 mg omeprazole(OPZ) ... AIM:To investigate the predictors of success in stepdown of proton pump inhibitor and to assess the quality of life(QOL).METHODS:Patients who had heartburn twice a week or more were treated with 20 mg omeprazole(OPZ) once daily for 8 wk as an initial therapy(study 1).Patients whose heartburn decreased to once a week or less at the end of the initial therapy were enrolled in study 2 and treated with 10 mg OPZ as maintenance therapy for an additional 6 mo(study 2).QOL was in-vestigated using the gastrointestinal symptom rating scale(GSRS)before initial therapy,after both 4 and 8 wk of initial therapy,and at 1,2,3,and 6 mo after starting maintenance therapy.RESULTS:In study 1,108 patients were analyzed.Their characteristics were as follows;median age:63(range: 20-88)years,sex:46 women and 62 men.The success rate of the initial therapy was 76%.In the patients with successful initial therapy,abdominal pain,indigestion and reflux GSRS scores were improved.In study 2,83 patients were analyzed.Seventy of 83 patients completed the study 2 protocol.In the per-protocol analysis,80%of 70 patients were successful for stepdown.On multivariate analysis of baseline demographic data and clinical information,no previous treatment for gastroesophageal reflux disease(GERD)[odds ratio (OR)0.255,95%CI:0.06-0.98]and a lower indigestion score in GSRS at the beginning of step-down therapy(OR 0.214,95%CI:0.06-0.73)were found to be the predictors of successful step-down therapy.The improved GSRS scores by initial therapy were maintained through the step-down therapy.CONCLUSION:OPZ was effective for most GERD patients.However,those who have had previous treatment for GERD and experience dyspepsia before stepdown require particular monitoring for relapse. 展开更多
关键词 Gastroesophageal reflux disease Proton pump inhibitor OMEPRAZOLE step-down therapy Gastrointestinal symptom rating scale
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ARRHENIUS ANALYSIS OF SINGLE-HEATED AND STEP-DOWN HEATED V_(79) AND L CELLSIN VITRO
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作者 张珊文 Eiichi Kano 《Chinese Journal of Cancer Research》 SCIE CAS CSCD 1990年第1期33-44,共12页
The response to single heat treatment and Step-down heat (SDH) treatment in vitro of V79 and L cells was studied. Colony-forming ability was assayed in medium after treatment in vitro. Time-response curves were establ... The response to single heat treatment and Step-down heat (SDH) treatment in vitro of V79 and L cells was studied. Colony-forming ability was assayed in medium after treatment in vitro. Time-response curves were established and subjected to Arrhenius analysis. The Arrhenius curves showed inflection points at 43℃ for V79 cells and at 42℃ for L cells. The activation energies were 145 kcal/mole and 400 kcal/mole above and below 43℃ (P<0.05), respectively, for V79 cells, while 160 kcal/mole and 300 kcal/mole above and below 42℃ (P<0.05), respectively, for L cells. Thermosensitivity of L cells are markedly higher than V79 cells. Both V79 and L cells were sensitized by SDH. The SDH effect was characterized by a reduction in shoulder (an addition effect to sublethal damage), an increase in slope (thermosensitization), and the delay and disappearance of thermotolerant 'tail' for V79 and L cells at 45℃ to 40℃ and 44℃ to 42℃ SDH treatment respectively. Particularly, 42℃ to 39℃ or 42℃ to 40℃ SDH for L cells resulted in thermosensitization effect up to a factor of 7.1 or 2.7, respectively. The effect was quantified by thermorsensitization ratio (TSR), defined as T0 single heated/T0SDH-heated. The relative ratio was much higher for V79 than for L cells. Heat killing with SDH characterized by Arrhenius analysis showed that Step-down heating reduced the activation energy for heat killing more than single heating. The decrease of activation energy for L cells was markedly greater than for V79. These data suggest that greater cellular sensitivity under step-down heating conditions may reflect a different mechanism for cell killing. 展开更多
关键词 OC AND L CELLSIN VITRO ARRHENIUS ANALYSIS OF SINGLE-HEATED AND step-down HEATED V
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Fundamental Study of High Step-down Non-isolated Multicellular DC-DC Converter for Future DC Distribution Systems
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作者 Yusuke Hayashi Yoshikatsu Matsugaki Tamotsu Ninomiya 《Journal of Energy and Power Engineering》 2017年第9期605-613,共9页
A novel high step-down non-isolated DC-DC converter has been proposed. The proposed converter consists of highly efficient non-isolated cell converters using bidirectional semiconductor power devices, and these cell c... A novel high step-down non-isolated DC-DC converter has been proposed. The proposed converter consists of highly efficient non-isolated cell converters using bidirectional semiconductor power devices, and these cell converters are connected in ISOP (input series and output parallel). The non-isolated ISOP converter achieves high step-down ratio of D/N, operating N cell converters under the duty ratio olD. Availability of the proposed converter has been shown by developing the 48 V-12 V laboratory prototype using two 24 V-12 V cell converters. Design consideration for the 48 V-3 V multicellular converter using four 12 V-3 V cell converters has been also conducted, and the potential to approach the efficiency of 97% has been discussed. The proposed topology is suitable for the POL (point of load) converters in the highly efficient next generation DC distribution system for data centers. 展开更多
关键词 DC-DC converter high step-down ratio ISOP GaN (gallium nitride).
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益智汤对老年性痴呆模型神经元RNA和Nissl体影响的研究 被引量:4
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作者 陈辉扬 刘志承 《现代预防医学》 CAS 北大核心 2005年第8期949-951,共3页
目的:观察益智汤对老年性痴呆模型神经元RNA和Nissl体的影响。方法:从21月龄昆明种小鼠筛选出自发老年性痴呆鼠,随机分为4组即空白对照组、西药对照组、益智汤给药组、另设老年学习记忆正常组(简称老年正常组,下同)。西药对照组给以Hyde... 目的:观察益智汤对老年性痴呆模型神经元RNA和Nissl体的影响。方法:从21月龄昆明种小鼠筛选出自发老年性痴呆鼠,随机分为4组即空白对照组、西药对照组、益智汤给药组、另设老年学习记忆正常组(简称老年正常组,下同)。西药对照组给以Hydergine0.6mg/kg,益智汤给药组给予益智汤6.80g/kg,连续60d,正常对照和痴呆对照组均灌以等量DW;用跳台实验(step-downtest)检测学习记忆成绩;脑组织冰冻切片,细胞化学方法显示大脑皮质和海马神经元内RNA和Nissl体,全自动显微图象分析系统定量检测相关脑区RNA和Nissl体含量。结果:益智汤能明显增高大脑皮质和海马锥体细胞的RNA和Nissl体含量。结论:益智汤可明显改善自发老年性痴呆模型的学习记忆障碍,并促进调节其大脑皮质和海马的RNA代谢,明显改善学习记忆关键脑区的神经元结构,从而发挥神经元营养和保护作用。 展开更多
关键词 老年性痴呆 益智汤 RNA Nissl体 跳台实验(step-down test)
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一种平均电流控制型开关调节系统的建模 被引量:3
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作者 徐洪韬 《电子设计工程》 2013年第7期112-114,共3页
文中对BUCK型DC_DC变换器进行了系统建模。为了得到包含平均电流调节开关控制方式的双环控制系统的简化模型,提出了一种电流环闭环传递函数的近似函数,并分别对电流控制器,电流补偿网络和功率级进行了建模,采用Mathcad进行仿真,得到系... 文中对BUCK型DC_DC变换器进行了系统建模。为了得到包含平均电流调节开关控制方式的双环控制系统的简化模型,提出了一种电流环闭环传递函数的近似函数,并分别对电流控制器,电流补偿网络和功率级进行了建模,采用Mathcad进行仿真,得到系统相位裕度达到54°的结果。 展开更多
关键词 BUCK型DC—DC 平均电流控制 建模分析 相位裕度
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双直流输入BLDCM驱动系统及其控制
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作者 葛佳隆 张宇翔 +2 位作者 刘金达 李盼菲 郭敏 《微电机》 北大核心 2019年第9期62-67,共6页
提出一种两路直流电源供电的无刷直流电机(BLDCM)驱动电路结构,其中双Buck结构的DC_DC变换器用于稳定母线电压,减小单个输入电源的电压,同时起到升压作用;PWM_ON_PWM调制信号由霍尔传感器信号和反电动势过零点信号相结合产生,用于控制... 提出一种两路直流电源供电的无刷直流电机(BLDCM)驱动电路结构,其中双Buck结构的DC_DC变换器用于稳定母线电压,减小单个输入电源的电压,同时起到升压作用;PWM_ON_PWM调制信号由霍尔传感器信号和反电动势过零点信号相结合产生,用于控制三相桥结构的BLDCM驱动器,能有效减小转矩脉动。使用Simulink仿真工具对双电源输入的DC-DC变换器进行了仿真,验证了DC_DC变换器的可行性,并搭建了整体驱动电路进行实验,生成了标准的PWM_ON_PWM调制信号。 展开更多
关键词 无刷直流电机 DC_DC变换器 霍尔传感器 反电动势 PWM_ON_PWM调制
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电动汽车中基于双能量源的电机驱动与制动研究
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作者 胡超 丁石川 程明 《微电机》 2015年第5期52-56,69,共6页
在分析电动汽车车载条件下,基于双能量源的永磁同步电机系统在驱动与制动能量回收过程中的若干特性。与普通电驱动系统的区别在于,该双能量源系统由超级电容和动力电池组合而成,因此双能源的组成拓扑结构和功率分配方案就直接影响到电... 在分析电动汽车车载条件下,基于双能量源的永磁同步电机系统在驱动与制动能量回收过程中的若干特性。与普通电驱动系统的区别在于,该双能量源系统由超级电容和动力电池组合而成,因此双能源的组成拓扑结构和功率分配方案就直接影响到电机驱动和制动的特性。通过给出的组合方式和控制策略,该系统可有效地实现电动汽车加速与制动时为电机提供加速能量以及高效回收电机制动能量,并能够做到能量在超级电容和动力电池的合理分配。仿真结果验证了该系统的可行性与有效性。 展开更多
关键词 永磁同步电机 能量回收 动力电池 超级电容 双能量源 双向DC_DC电路
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Lithium chloride ameliorates learning and memory ability and inhibits glycogen synthase kinase-3 beta activity in a mouse model of fragile X syndrome 被引量:3
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作者 Shengqiang Chen Xuegang Luo +6 位作者 Quan Yang Weiwen Sun Kaiyi Cao Xi Chen Yueling Huang Lijun Dai Yonghong Yi 《Neural Regeneration Research》 SCIE CAS CSCD 2011年第31期2452-2459,共8页
In the present study,Fmr1 knockout mice (KO mice) were used as the model for fragile X syndrome.The results of step-through and step-down tests demonstrated that Fmr1 KO mice had shorter latencies and more error cou... In the present study,Fmr1 knockout mice (KO mice) were used as the model for fragile X syndrome.The results of step-through and step-down tests demonstrated that Fmr1 KO mice had shorter latencies and more error counts,indicating a learning and memory disorder.After treatment with 30,60,90,120,or 200 mg/kg lithium chloride,the learning and memory abilities of the Fmr1 KO mice were significantly ameliorated,in particular,the 200 mg/kg lithium chloride treatment had the most significant effect.Western blot analysis showed that lithium chloride significantly enhanced the expression of phosphorylated glycogen synthase kinase 3 beta,an inactive form of glycogen synthase kinase 3 beta,in the cerebral cortex and hippocampus of the Fmr1 KO mice.These results indicated that lithium chloride improved learning and memory in the Fmr1 KO mice,possibly by inhibiting glycogen synthase kinase 3 beta activity. 展开更多
关键词 fragile X syndrome Fmr1 knockout mice step-down test step-through test learning and memory glycogen synthase kinase 3 beta lithium chloride
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Measurement-based approach for identification of static load model of electric power system
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作者 翰林 赵峰 《Journal of Measurement Science and Instrumentation》 CAS CSCD 2016年第3期214-220,共7页
The validity of electric power system simulation or prediction models depends on static load model. Measurement- based approach is the unique method to identify them adequately. The measured power depends on both load... The validity of electric power system simulation or prediction models depends on static load model. Measurement- based approach is the unique method to identify them adequately. The measured power depends on both load reaction to supply voltage alteration and random process of load alteration Basically, there is no any universal method that can single out the inherent static load model from experimental data. The paper offers a proprietary technique which is the particular solution of the task. The technique considers the selection of neighboring measurement pairs with the supply voltage altering significantly be-tween them, the exclusion of selected pairs by load power factor and subsequent selection of the inherent static load model presented as the polynomial load model. The usage of the technique to identify static load model at “Fenster” industrial enterprise (in Borisov city) is presented. The ideas considered in the paper can be used for future development of static load model identification methods with the data obtained during both active experiment and in other operating models of electric power systems. 展开更多
关键词 static load model electric power system load power factor step-down transformer substation
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Chrysophanol attenuates lead exposure-induced injury to hippocampal neurons in neonatal mice 被引量:7
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作者 Ji Zhang Chunlin Yan +3 位作者 Shu Wang Yong Hou Guiping Xue Li Zhang 《Neural Regeneration Research》 SCIE CAS CSCD 2014年第9期924-930,共7页
Previous studies have shown that chrysophanol protects against learning and memory impairments in lead-exposed adult mice. In the present study, we investigated whether chrysophanol can alleviate learning and memory d... Previous studies have shown that chrysophanol protects against learning and memory impairments in lead-exposed adult mice. In the present study, we investigated whether chrysophanol can alleviate learning and memory dysfunction and hippocampal neuronal injury in lead-exposed neonatal mice. At the end of lactation, chrysophanol(0.1, 1.0, 10.0 mg/kg) was administered to the neonatal mice by intraperitoneal injection for 15 days. Chrysophanol significantly alleviated injury to hippocampal neurons and improved learning and memory abilities in the lead-poisoned neonatal mice. Chrysophanol also significantly decreased lead content in blood, brain, heart, spleen, liver and kidney in the lead-exposed neonatal mice. The levels of malondialdehyde in the brain, liver and kidney were significantly reduced, and superoxide dismutase and glutathione peroxidase activities were significantly increased after chrysophanol treatment. Collectively, these findings indicate that chrysophanol can significantly reduce damage to hippocampal neurons in lead-exposed neonatal mice. 展开更多
关键词 nerve regeneration traditional Chinese medicine CHRYSOPHANOL lead poisoning lead MALONDIALDEHYDE superoxide dismutase glutathione peroxidase neurons neonatal mice antioxidant learning and memory Morris water maze step-down test hippocampal neurons ULTRASTRUCTURE Medical Scientific Research Project of Health Bureau of Hebei Province neural regeneration
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一种电流模DC-DC芯片中低延时电流比较器的设计 被引量:1
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作者 吴勃庆 薛晓磊 陈锡明 《通信电源技术》 2017年第4期96-97,共2页
文中设计了一种应用于电流模DC-DC芯片的低延时电流比较器。其主要作用是将电感的峰值电流与所需电流进行比较,输出控制信号,以达到调节输出电压的目的。利用0.35μm BCD工艺HSPICE模型参数对该电流比较器的性能进行仿真模拟,结果表明... 文中设计了一种应用于电流模DC-DC芯片的低延时电流比较器。其主要作用是将电感的峰值电流与所需电流进行比较,输出控制信号,以达到调节输出电压的目的。利用0.35μm BCD工艺HSPICE模型参数对该电流比较器的性能进行仿真模拟,结果表明该电流比较器的功耗为100μW,延迟时间最小为11 ns,满足设计要求,并提高了芯片性能。 展开更多
关键词 DC-DC 电流模 电流比较器
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Basic fibroblast growth factor improves learning and memory functions in chronic stress mice
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作者 Xian Qu Chunying Li +1 位作者 Hongchang Liu Chang Su 《Neural Regeneration Research》 SCIE CAS CSCD 2011年第19期1473-1477,共5页
Four weeks of uncertain stress was used to establish an animal model of chronic stress. Basic fibroblast growth factor was injected daily for 15 days following stress induction. Cell morphology in the hippocampal CA3 ... Four weeks of uncertain stress was used to establish an animal model of chronic stress. Basic fibroblast growth factor was injected daily for 15 days following stress induction. Cell morphology in the hippocampal CA3 region of chronic stress mice revealed cell damage. Nitric oxide content and calcium concentration were significantly increased in the hippocampus, and learning and memory functions were significantly decreased. After basic fibroblast growth factor intervention, Ca2~ overload was decreased and neuronal damage was relieved in hippocampal neurons, which improved learning and memory functions in chronic stress mice. Latency was prolonged and the number of errors was decreased in a passive avoidance test. 展开更多
关键词 basic fibroblast growth factor chronic stress step-down test passive avoidance test learning and memory nitric oxide neural regeneration
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Uncertainty of Clinical Thinking and Patient Safety
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作者 Qian Zhao Zhangshun Shen +1 位作者 Hui Guo Jianguo Li 《International Journal of Clinical Medicine》 2020年第8期474-481,共8页
Clinical thinking have the uncertainty, by which there are not a few mistakes caused. So it is necessary to discuss how to deal with the uncertainty of clinical thinking, which originates from the uncertainty of the o... Clinical thinking have the uncertainty, by which there are not a few mistakes caused. So it is necessary to discuss how to deal with the uncertainty of clinical thinking, which originates from the uncertainty of the objective world, social world and medicine knowledge, and can be seen all over clinical activities;Critical thinking which cautious about the interpretation and prediction of scientific theory is the best practice to explore the uncertainty. The essential purpose of medicine is rescuing people, So it is necessary and scientific to take “excluding life-threatening symptoms first” as the first principle of clinical thinking, which is also the primary method to deal with the uncertainty of clinical thinking;By the limited certainty of clinical thinking, procedural thinking is conducive to building a safer health system that is “easy to do right and difficult to do wrong”. 展开更多
关键词 Clinical Thinking UNCERTAINTY Critical Thinking step-down Thinking Procedural Thinking
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一种宽供电范围开关电源变换器设计
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作者 陈修林 王富光 张顺彪 《机车电传动》 北大核心 2015年第3期23-25,34,共4页
为了满足宽供电范围需求,开发设计了一种电感耦合式Step-down CUK变换器开关电源,对该变换器的输入输出电流进行了稳态分析,表明变换器具有的电流连续特性,有利于提升变换器的功率密度;提出了一种变频控制策略及其实现方法,解决了变换... 为了满足宽供电范围需求,开发设计了一种电感耦合式Step-down CUK变换器开关电源,对该变换器的输入输出电流进行了稳态分析,表明变换器具有的电流连续特性,有利于提升变换器的功率密度;提出了一种变频控制策略及其实现方法,解决了变换器的稳定性问题。试验验证及批量装车考核表明该设计具有实用性。 展开更多
关键词 step-down CUK BUCK BOOST 变频控制 开关电源 宽供电范围 中央控制单元
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3D阶梯模板在SMT特殊制程及器件上的应用技术
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作者 杨根林 《现代表面贴装资讯》 2012年第4期37-46,共10页
在当前的SMT生产制程中,由于某些电子产品SMD凹腔电路板(CarityPCB)设计、元器件高密度组装与特殊构造需要,以及通孔回流焊(Through—HoleReflow)器件、混合制程器件(HybridProcessComponent)、正反表面焊接连接器(DoubleSurfa... 在当前的SMT生产制程中,由于某些电子产品SMD凹腔电路板(CarityPCB)设计、元器件高密度组装与特殊构造需要,以及通孔回流焊(Through—HoleReflow)器件、混合制程器件(HybridProcessComponent)、正反表面焊接连接器(DoubleSurfaceReflowSolderingDevice)等问题,令焊锡膏或胶的印刷与涂覆工艺,变得日益复杂与多样化。而一直来最具主流的普通平面型印刷模板(2DScreenStencil),便难以满足日新月异复杂工艺需求,于是非共面性阶梯模板(3DStencil)应运而生,它为解决SMT特殊制程及异型器件的焊锡或胶的印刷涂覆问题,正发挥着日益重要的作用。3DStencil的设计多种多样且用途广泛,它适宜各种较为复杂的PCBA组装工艺需求,可用在各种较为前端的特殊而复杂的工艺产品上。传统的非共面性3D模板,通常有局部减薄模板(Step—downstencil)、局部加厚模板(Step—upstencil)或两种工艺同时在一块模板上应用,模板的局部加厚或减薄的阶梯高度,通常需依据PCB板面的凹陷或凸起高度以及元器件的特点灵活应对,且加厚或减薄的阶梯既可放在模板装锡膏的印刷面,也可放在模板的底面。而时下的精密特制3D阶梯型模板,其模板钢片厚度与普通2D模板无异,但阶梯高度可达N20mm它足以避让底部多数己组装的SMD器件或AI器件剪脚后的高度。这种模板通常称之为VectorGuard3DStencil,由于它能够对己贴片组件展示出全方位的立体屏蔽保护而得名。3D阶梯模板在设计制作过程中,需重点关注其脱模性能与模板的使用寿命,力求使其既有良好的印刷效果又能经久耐用。在各种模板的制作工艺中,电铸成形模板和激光切割/电抛光模板的印刷性能较好,而以激光切割加电抛旋光性价比最高;对于印刷工艺的优化,模板的设计是关键的一环。为了使焊锡膏的脱模性能达到最好,模板上的开孔尺寸比率以及开孔性能应当按照行业标准设计,其开口的宽厚比、面积比、开孔梯度、开口侧壁的光洁度等方面都有严格要求。多半情况下,通过3D阶梯模板能够解决的SMT特殊制程及器件的工艺难题,也能通过非接触式喷印(JetPrinting)或针头点涂(Dispenser)的工艺方式解决。不过机器喷印或点涂的方式,不仅前期设备投资巨大,而且它们对于高密度设计的PCB和精细间距器件(FinePitchTechnology),在组装精度、质量和效率等诸多方面都还受到限制,很多时候还不及3D模板实用有效。 展开更多
关键词 非共面性模板(3D Stencil) 凹陷电路板(cavity PCB) AI印胶模板(AI Stencil) 双面回焊器件(Double Side REFLOW Solde ring Device) 混合制程器件(Hybrid P rocess Component) 通孔回流焊(Th rough—HoleReflow) 喷印锡工艺(Jet Printing) 局部减薄模板(step-down STENCIL 局部加厚模板(Step—up stencil) 脱模性能(Release pe rfo rmance)
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Research of Step-down Stress Accelerated Degradation Data Assessment Method of a Certain Type of Missile Tank 被引量:7
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作者 YAO Jun XU Mingge ZHONG Weiqiang 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2012年第6期917-924,共8页
The performance degradation rates of the missile tank are generally time-varying functions uneasily evaluated by general classical evaluation methods. This paper develops a segmented nonlinear accelerated degradation ... The performance degradation rates of the missile tank are generally time-varying functions uneasily evaluated by general classical evaluation methods. This paper develops a segmented nonlinear accelerated degradation model (SNADM) based on the equivalent method of accumulative damage theory, which tackles the problem that product life is difficult to be determined with degradation rate being a function of the variable of time. A segmented expression of the function of population accumulative degradation is derived. And combined with nonlinear function, an accelerated degradation function, i.e., SNADM is obtained. The parameters of the SNADM are identified by numerical iteration, and the statistical function of degradation track is extrapolated. The reliability function is determined through the type of random process of the degradation distribution. Then an evaluation of product storage life is undertaken by combining the statistical function of degradation track, reliability function and threshold. An example of a missile tank undergoes a step-down stress accelerated degradation test (SDSADT), in which the results with the SNADM and the classical method are evaluated and compared. The technology introduced is validated with the resultant coincidence of both evaluated and field storage lives. 展开更多
关键词 reliability accelerated degradation model step-down stress testing life assessment cumulative damage
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Process performance and quality attributes of temperature and step-down relative humidity controlled hot air drying of Panax notoginseng roots 被引量:3
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作者 Dalong Jiang Congcong Li +4 位作者 Sara Zielinska Yanhong Liu Zhenjiang Gao Rongyan Wang Zhi’an Zheng 《International Journal of Agricultural and Biological Engineering》 SCIE EI CAS 2021年第6期244-257,共14页
The effects of temperature and step-down relative humidity controlled hot-air drying(THC-HAD)on the drying kinetics,energy efficiency and quality,i.e.,rehydration ratio(RR),color parameters(L*,a*,b*),total color diffe... The effects of temperature and step-down relative humidity controlled hot-air drying(THC-HAD)on the drying kinetics,energy efficiency and quality,i.e.,rehydration ratio(RR),color parameters(L*,a*,b*),total color difference(ΔE*),Panax notoginseng saponins(PNS)content,and ginsenosides content(R1,Rg1,Re,Rd,Rb1)of Panax notoginseng roots were evaluated.The drying time was significantly affected by the drying temperature followed by the relative humidity(RH)of the drying air.Special combination of drying conditions,i.e.,drying temperature of 50°C,relative humidity of 40%for 3 h and then continuous dehumidification from 40%to 8%allowed to shorten the drying time by 25%compared to drying at the same temperature and continuous dehumidification.The longer was the drying time under constant high RH of drying air,the lower was the RR of dried samples.The step-down RH strategy contributed to the formation of a porous structure,enhancement of drying efficiency and quality improvement.Generally,the ginsenosides content increased with the increase in temperature,while no obvious trend was recorded for ginsenoside R1.The contents of the ginsenoside R1,Rg1,Rb1 and PNS decreased with the increase in the drying time under constant high RH.Taking into account the drying time,energy consumption and quality attributes,drying at the temperature of 50°C,constant RH of 40%for 3 h and then step-down RH from 40%to 8%was proposed as the most favorable combination of drying conditions for dehydration of whole Panax notoginseng roots. 展开更多
关键词 Panax notoginseng(Burk.)F.H.Chen(Araliaceae)roots step-down relative humidity hot air drying process performance quality attribute
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