脉宽调制式电子分析天平的漂移补偿方法研究

温漂和时漂对脉宽调制式电子分析天平示值影响较大且难以区分,分析了永磁体剩磁、动圈长度、恒流源采样电阻、电子元件参数等温漂和时漂影响机理,考虑电磁力平衡传感器各特征位置温度变化及内外温度梯度影响,建立了温漂与温度变化的二次多项式、与温度梯度的近似线性关系以及时漂与时间的指数关系,通过叠加得到示值漂移非线性混合补偿模型,并设计了一种能够同时辨识温漂和时漂模型参数的空载和满载组合漂移实验和数据处理方法,通过大量非均匀温度变化实验得到模型参数,利用该模型对量程220 g、分辨力0.1 mg的电子分析天平进行补偿验证。结果表明,补偿后的天平加载220 g并保持30 min后的示值漂移小于1 mg,零点示值漂移小于0.5 mg,满足国家标准《JJG1036-2008电子天平检定规程》规定的Ⅰ级天平对温漂和时漂性能指标要求。

Cross-section distortion and springback characteristics of double-cavity aluminum profile in force controlled stretch-bending

3D elastic-plastic FE model for simulating the force controlled stretch-bending process of double-cavity aluminum profile was established using hybrid explicit−implicit solvent method.Considering the computational accuracy and efficiency,the optimal choices of numerical parameters and algorithms in FE modelling were determined.The formation mechanisms of cross-section distortion and springback were revealed.The effects of pre-stretching,post-stretching,friction,and the addition of internal fillers on forming quality were investigated.The results show that the stress state of profile in stretch-bending is uniaxial with only a circumferential stress.The stress distribution along the length direction of profile is non-uniform and the maximum tensile stress is located at a certain distance away from the center of profile.As aluminum profile is gradually attached to bending die,the distribution characteristic of cross-section distortion along the length direction of profile changes from V-shape to W-shape.After unloading the forming tools,cross-section distortion decreases obviously due to the stress relaxation,with a maximum distortion difference of 13%before and after unloading.As pre-stretching and post-stretching forces increase,cross-section distortion increases gradually,while springback first decreases and then remains unchanged.With increasing friction between bending die and profile,cross-section distortion slightly decreases,while springback increases.Cross-section distortion decreases by 83%with adding PVC fillers into the cavities of profile,while springback increases by 192.2%.

上海市中运量发展思路研究

近年来,上海市公共交通客运总量增速放缓,地面公交客运总量不断下降。上海市"公交都市"、"十三五"相关规划、"上海市城市总体规划(2017—2035)"均明确提出了发展中运量的要求。上海市发展中运量是常规公交系统转型升级,提升公共交通服务水平,补充和完善轨道交通网络,保障城市运营和社会交通运行稳定性,发展"绿色交通",城市形象更新的需要。根据特征分析、优缺点分析、适应性分析等,针对中心城提出了中运量建设模式和推荐制式,并对未来中运量的发展提出了思考。

反应挤出法制备聚乙丙交酯及其热性能

以双螺杆挤出机为反应器通过乙交酯和L-丙交酯的开环共聚制备了聚乙丙交酯(PGLA),探讨了催化剂用量、聚合温度及螺杆转速等因素对聚合的影响,并采用调制式差示扫描量热分析(MDSC)法详细研究了PGLA在相变过程中的热性能。实验结果表明,在催化剂用量为300×10^-6(w)、聚合温度为200℃、螺杆转速为10 r/min的适宜工艺条件下可获得重均相对分子质量大于1.0×10^5的PGLA,在140℃下真空加热8 h可将残留单体含量降至2%(w)以下,并保持较高的相对分子质量。通过MDSC的不可逆曲线可有效分辨PGLA在熔融过程中发生的微量聚乳酸均聚物的重结晶和PGLA晶体完善等相变;随着升温速率的提高和调制周期的延长,熔融峰分割在可逆曲线上的比例呈逐渐增加的趋势,不可逆曲线上重结晶放热峰的积分面积也逐渐增大。

Role based access control design using Triadic concept analysis

Role based access control is one of the widely used access control models.There are investigations in the literature that use knowledge representation mechanisms such as formal concept analysis(FCA),description logics,and Ontology for representing access control mechanism.However,while using FCA,investigations reported in the literature so far work on the logic that transforms the three dimensional access control matrix into dyadic formal contexts.This transformation is mainly to derive the formal concepts,lattice structure and implications to represent role hierarchy and constraints of RBAC.In this work,we propose a methodology that models RBAC using triadic FCA without transforming the triadic access control matrix into dyadic formal contexts.Our discussion is on two lines of inquiry.We present how triadic FCA can provide a suitable representation of RBAC policy and we demonstrate how this representation follows role hierarchy and constraints of RBAC on sample healthcare network available in the literature.

Techno-economic Analysis of Distributed Hydrogen Production from Natural Gas

It is well established that hydrogen has the potential to make a significant contribution to the world energy production.In U.S.,majority of hydrogen production plants implement steam methane reforming(SMR) for centralized hydrogen production.However,there is a wide lack of agreement on the nascent stage of using hydrogen as fuel in vehicles industry because of the difficulty in delivery and storage.By performing technological and economic analysis,this work aims to establish the most feasible hydrogen production pathway for automotives in near future.From the evaluation,processes such as thermal cracking of ammonia and centralized hydrogen production followed by bulk delivery are eliminated while on-site steam reforming of methanol and natural gas are the most technologically feasible options.These two processes are further evaluated by comprehensive economic analysis.The results showed that the steam reforming(SR) of natural gas has a shorter payback time and a higher return on investment(ROI) and internal rate of return(IRR).Sensitivity analysis has also been constructed to evaluate the impact of variables like NG feedstock price,capital of investment and operating capacity factor on the overall production cost of hydrogen.Based on this study,natural gas is prompted to be the most economically and technologically available raw material for short-term hydrogen production before the transition to renewable energy source such as solar energy,biomass and wind power.

Three-dimensional finite element analysis on effects of tunnel construction on nearby pile foundation

A three-dimensional finite element simulation was carried out to investigate the effects of tunnel construction on nearby pile foundation.The displacement controlled model (DCM) was used to simulate the tunneling-induced volume loss effects.The numerical model was verified based on the results of a centrifuge test and a set of parametric studies was implemented based on this model.There is good agreement between the trend of the results of the centrifuge test and the present model.The results of parametric studies show that the tunnelling-induced pile internal force and deformation depend mainly on the pile?tunnel distance,the pile length to tunnel depth ratio and the volume loss.Two different zones are separated by a 45° line projected from the tunnel springline.Within the zone of influence,the pile is subjected to tensile force and large settlement;whereas outside the zone of influence,dragload and small settlement are induced.It is also established that the impact of tunnelling on a pile group is substantially smaller as compared with a single pile in the same location with the rear pile in a group,demonstrating a positive pile group effect.

LY294002 potentiates the anti-cancer effect of oxaliplatin for gastric cancer via death receptor pathway

AIM:To examine the effects of combined treatment of oxaliplatin and phosphatidylinositol 3'-kinase inhibitor,2-(4-morpholinyl) -8-phenyl-4H-1-benzopyran-4-one(LY294002) for gastric cancer. METHODS:Cell viability was evaluated by 3-(4,5-dimethylthiazol-2-yl) -2,5-diphenyltetrazolium bromide assay.Apoptotic cells were detected by flow cytometric analysis and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay.Western blotting and immuno-precipitation were used to examine protein expression and recruitment,respectively.Nuclear factorκB(NFκB) binding activities were investigated using electrophoretic mobility shift assay.Nude mice were used to investigate tumor growth. RESULTS:Treatment with combined oxaliplatin and LY294002 resulted in increased cell growth inhibi-tion and cell apoptosis in vitro,and increased tumor growth inhibition and cell death in the tumor mass in vivo.In MKN45 and AGS cells,oxaliplatin treatment promoted both protein kinase B(Akt) and NFκB activation,while pretreatment with LY294002 significantly attenuated oxaliplatin-induced Akt activity and NFκB binding.LY294002 promoted oxaliplatin-induced Fas ligand(FasL) expression,Fas-associated death domain protein recruitment,caspase-8,Bid,and caspase-3 activation,and the short form of cellular caspase-8/FLICEinhibitory protein(c-FLIPS) inhibition.In vivo,LY294002 inhibited oxaliplatin-induced activation of Akt and NFκB,and increased oxaliplatin-induced expression of FasL,inhibition of c-FLIPS,and activation of caspase-8,Bid,and caspase-3. CONCLUSION:Combination of oxaliplatin and LY294002 was therapeutically promising for gastric cancer treatment.The enhanced sensitivity of the combined treatment was associated with the activation of the death receptor pathway.

Design of the University Building Corridor Intelligent Lighting Control System

This paper introduces the traditional lighting control mode and analyzes of defects in three ways, so this paper puts forward four kinds of working mode of intelligent lighting control system. Combined with the working pattern, this paper designs an intelligent lighting control system to analyze the application advantages of intelligent system.

A traditional Chinese medicine Huaier triggers G1 cell cycle arrest and apoptosis through cyclins-CDKs-CKIs machinery in MOLT4 cells

Objective: The purpose of the study was to study the effect of Huaier, a traditional Chinese medicine, on the cell cycle adjustment in MOLT4 cells in vitro. Methods: We used MTT assay to test cell viability, flow cytometry to detect cell cycle and apoptosis and western blot to examine the expression of cell-cycle and apoptotic proteins in MOLT4 cells induced by Huaier. Results: Huaier could reduce the viability of MOLT4 cell by inducing G1 arrest and apoptosis. The induction of apoptosis after treatment with Huaier for 24 h was demonstrated in a dose- and time-dependent manner by flow cytometry analysis. G1 arrest induced by Huaier was modulated through the increased expression of Cdki proteins(p21cip/waf1 and p27kip1) with a simultaneous decrease in Cdk2, Cdk4, Cdk6, cyclin D1 and cyclin E expression. Huaier also induced Bax and Bcl-2 expression and activation of Caspase-3. Conclusion: It is firstly demonstrated that Huaier can inhibit proliferation of MOLT4 cells via G1 arrest and apoptosis. These results suggest that Huaier is a cell-cycle anti-cancer drug.

Singularity Analysis of 2-DOF Planar Seven-bar MechanismsUsed in Hybrid Actuators

Based on the Jacobian matrices relating the input speeds with the output speeds of linkages, a general method, which is used for solving the singularities of planar multi-loop multi-DOF linkages, is presented. The four kinds of singularities of 2-DOF planar seven-bar linkages used in hybrid actuators are analyzed in detail by this method. Its five kinds of singular positions whose characteristics are discussed respectively are discovered. Three approaches are proposed on how to avoid the singular positions of planar multi-loop multi-DOF linkages. Based on the assemblability of planar single-loop N-bar chains or linkages, the geometry conditions are investigated and discovered to avoid the singular positions of the linkages. In order to versify aforementioned conclusions, a case is given in which the singular curves are plotted and simulated.

Theoretical Study and Performance Analysis of an Adsorption Chiller

The thermodynamic cycle for an adsorption system is presented inp-T diagram. In order to investigate the performance of the adsorption system, a lumped parameter transient model of the chiller is developed, in order to predict the behaviors of the adsorption chiller system and find the influence of working conditions on its operation. For the working process of the main components of the system, including adsorber, condenser and evaporator, the coupled unsteady equations were set up for each stage. The model was then solved using stable numerical methods from EES （equation engineering solver）, and the performance of the adsorber and condenser/evaporator of the system was analyzed. The condensation, evaporation and adsorber temperature values as well as the adsorption ratio and desorption ratio were obtained as function of operating time. Also, the coefficient of performance was analyzed in function of the heat source temperature and the cooling source temperature.

H_∞ Robust Fault-Tolerant Controller Design for an Autonomous Underwater Vehicle’s Navigation Control System

In order to improve the security and reliability for autonomous underwater vehicle （AUV） navigation, an H∞ robust fault-tolerant controller was designed after analyzing variations in state-feedback gain Operating conditions and the design method were then analyzed so that the control problem could be expressed as a mathematical optimization problem. This permitted the use of linear matrix inequalities （LMI） to solve for the Hv controller for the system. When considering different actuator failures, these conditions were then also mathematically expressed, allowing the H∞ robust controller to solve for these events and thus be fault-tolerant. Finally, simulation results showed that the H∞ robust fault-tolerant controller could provide precise AUV navigation control with strong robustness.

System analysis and path choice for modern agricultural development:a case study of Suzhou

From the view of system theory, modern agriculture in a region embodies elements conformity, structure optimization, multi-functionality and sustainable development. This paper first expounds on the relationship among agricultural elements, structure, function and development theoretically, compartmentalizes agriculture types based on human-land elements matching, and depicts the development path of agricultural multi-functionality. it shows that the matching of human-land elements is a key to agricultural types, and the multi-functionality is an indication of agricultural development stages. At last, as a case study of Suzhou in eastern coastal area, the paper analyzes the evolvement situation and developing mechanism and some typical models of modern agriculture which suit to agriculture system evolvement. The results .show that in Suzhou the agriculture productivity, has improved greatly; And along with the agriculture structure optimizing, agriculture function has translated from ＂production ＂ to ＂non- production and production ＂. With simulation of agricultural trend in Suzhou, it is .found that Suzhou has a LP- dependence （labor productivity） on agricultural element, so Suzhou will has much more potential in land productivity. Based on the above analysis on agricultural system, some typical patterns on modern agriculture in Suzhou are brought up, such as export-oriented agriculture, enterprises-leading agriculture, science and technology, parks agriculture, stereoseopic agriculture, and tourism and sightseeing agriculture.

聚己内酯热分解机制及其热分解产物

精制后的聚己内酯用三氯甲烷为溶剂制成溶剂膜。以调制式热重分析（TGA）为聚己内酯热裂解的研究方法,并使用核磁共振（NMR）和傅里叶变换红外光谱（FTIR）分析其热裂解后所得的产物。TGA的结果表明,聚己内酯的热裂解过程分为两步,第一步的分解温度为205~295℃,失重率为7.0%;第二步分解温度为311~374℃,失重率为88%,结果同时得到了聚己内酯热分解的活化能、指前因子和速率比等热分解动力学常数,分别为第一步80kJ/mol,5min-1和0.3,第二步分别为146kJ/mol,11min-1和0.47。裂解后的产物经过NMR和FTIR分析,发现不但有高分子的聚己内酯,也有呋喃、取代环丙烷以及不饱和的羧酸等小分子化合物产生。

Inhibitive effect on apoptosis in splenic lymphocytes of mice pretreated with Lingzhi (GanodermaLucidum) spores

OBJECTIVE： To investigate how the pretreatment of mice with Ganoderma spores affected the apop- tosis of their splenic lymphocytes induced by dexa- methasone after 19 days treatment. METHODS： Sixty Kunming mice were randomly di- vided into six groups： blank control groupdrenched with normal saline; a drug control group drenched with 150 mg/mL Ganoderma spores; a model group treated with saline; a low dose group with S0 mg/mL Ganoderma spores; a moderate dose group with 100 mg/mL Ganoderma spores; and a high dose group with 150 mg/mL Ganoderma spores. The effect of Ganoderma spores on apoptosis in spleen lymphocytes was analyzed. All groups were treated for 19 days. On day 20, the model group and the 3 treatment groups were intraperitoneally injected dexamethasone to induce apoptosis. Splenic index and apoptosis indes were employed to measure cell apoptosis RESULTS： The results showed that Ganoderma spores reduced the splenic index to different de- grees in each group and the best effect was seen in the high dose group （P〈0.05）. Terminal dexynucleo- tidyl transferase （TdT）-mediated 2＇-Deoxyuridine 5＇-Triphosphate nick end labeling staining revealed that the apoptotic index in all groups administered Ganoderma spores differed significantly from the model group, and a dose-response was observed. Flow cytometric analysis indicated that spleen lym- phocyte apoptosis in the model group was exten- sive. Each dose of Ganoderma spores inhibited dexamethasone-induced apoptosis in spleen lym- phocytes, and a dose-response was observed as well. The highest dose of Ganoderma spores de- creased Malondialdehyde content in serum in- duced by dexamethasone （P〈0.05）. CONCLUSION： The findings imply that the pretreat- ment of the mice with Ganoderma spores could re- duce the apoptosis rate induced by dexametha- sone in their splenic lymphocytes.

Experimental investigation on control of vortex shedding mode of a circular cylinder using synthetic jets placed at stagnation points

Control of flow around a circular cylinder by synthetic jets has been experimentally investigated in a water tunnel with particle image velocimetry(PIV) technique.The synthetic jets are positioned at both the front and rear stagnation points.With power spectrum analysis,proper orthogonal decomposition(POD) method and other techniques for data processing,particular attention is paid to the control of vortical structures around the circular cylinder,in which the excitation frequency f e is one to three times of the natural frequency f0 and the cylinder Reynolds number and the excitation amplitude are fixed.The influenced-scope of the synthetic jet enlarges as the excitation frequency increases,and thus the synthetic jet dominates the global flow field gradually.For the natural case and the control case at fe/f0=1,the distributions of the first two POD modes and the power spectra for their POD coefficients all exhibit the characteristics of the natural shedding with antisymmetric mode.For fe/f0=2 and fe/f0=3,the variations in the third and fourth POD modes and the corresponding power spectra indicate that the wake vortex shedding mode changes and the dominant frequency becomes the excitation frequency.For fe/f0=2,the wake vortex sheds downstream with either the antisymmetric or the symmetric mode;for fe/f0=3,the synthetic jet vortex pair interacts with the near wake shear layers from both sides to induce a pair of the symmetric wake vortices,which is gradually converted into an antisymmetric mode when shedding downstream.

An Equilibrium Analysis of a Contest Model

Based on the assumption that the value of the prize to two contestants increases in their effort levels, a new type of contest model is established. A necessary and weak sufficient condition for a Cournot-Nash equilibrium of the contest model are given.