Identification of Maximum Road Friction Coefficient and Optimal Slip Ratio Based on Road Type Recognition

The identification of maximum road friction coefficient and optimal slip ratio is crucial to vehicle dynamics and control.However,it is always not easy to identify the maximum road friction coefficient with high robustness and good adaptability to various vehicle operating conditions.The existing investigations on robust identification of maximum road friction coefficient are unsatisfactory.In this paper,an identification approach based on road type recognition is proposed for the robust identification of maximum road friction coefficient and optimal slip ratio.The instantaneous road friction coefficient is estimated through the recursive least square with a forgetting factor method based on the single wheel model,and the estimated road friction coefficient and slip ratio are grouped in a set of samples in a small time interval before the current time,which are updated with time progressing.The current road type is recognized by comparing the samples of the estimated road friction coefficient with the standard road friction coefficient of each typical road,and the minimum statistical error is used as the recognition principle to improve identification robustness.Once the road type is recognized,the maximum road friction coefficient and optimal slip ratio are determined.The numerical simulation tests are conducted on two typical road friction conditions（single-friction and joint-friction）by using CarSim software.The test results show that there is little identification error between the identified maximum road friction coefficient and the pre-set value in CarSim.The proposed identification method has good robustness performance to external disturbances and good adaptability to various vehicle operating conditions and road variations,and the identification results can be used for the adjustment of vehicle active safety control strategies.

Study on inelastic displacement ratio spectra for near-fault pulse-type ground motions

In displacement-based seismic design, inelastic displacement ratio spectra （IDRS） are particularly useful for estimating the maximum lateral inelastic displacement demand of a nonlinear SDOF system from the maximum elastic displacement demand of its counterpart linear elastic SDOF system. In this study, the characteristics of IDRS for near-fault pulse-type ground motions are investigated based on a great number of earthquake ground motions. The influence of site conditions, ratio of peak ground velocity （PGV） to peak ground acceleration （PGA）, the PGV, and the maximum incremental velocity （MIV） on IDRS are also evaluated. The results indicate that the effect of near-fault ground motions on IDRS are significant only at periods between 0.2 s - 1.5 s, where the amplification can approach 20%. The PGV/PGA ratio has the most significant influence on IDRS among the parameters considered. It is also found that site conditions only slightly affect the IDRS.

Separate-Type Estimators for Estimating Population Ratio in Post-Stratified Sampling Using Variable Transformation

The study proposes, along the line of [1], six separate-type estimators for estimating the population ratio of two variables in post-stratified sampling, using variable transformation. Properties of the proposed estimators were obtained up to first order approximations, both for achieved sample configurations (conditional argument) and over repeated samples of fixed size n (unconditional argument). Efficiency conditions, under which the proposed separate-type estimators would perform better than the associated customary separate-type estimators in terms of having smaller mean squared errors, were obtained. Furthermore, conditions under which some of the proposed separate-type estimators would perform better than other proposed separate-type estimators were also obtained. The optimum estimators among the proposed separate-type estimators were obtained and an empirical illustration confirmed the theoretical results.

掺杂反式聚乙炔中Site-type杂质势的唯象模型

利用SSH模型讨论了Site-type杂质势对反式聚乙炔(trans-PA)电子态的影响。具体计算表明:对各向同性情况,Site-fype杂质势破坏了电子能谱的对称性,并使孤子能级发生移动,随着杂质离子与反式聚乙炔链间距的变化,它将引起孤子能级的变动。但不影响孤子局域化程度;而各向异性Site-type杂质势的不均匀性对trans-PA的电子能谱及孤子局域化程度影响较大。

Estimation of Population Ratio in Post-Stratified Sampling Using Variable Transformation

Extending the work carried out by [1], this paper proposes six combined-type estimators of population ratio of two variables in post-stratified sampling scheme, using variable transformation. Properties of the proposed estimators were obtained up to first order approximations,(on–1), both for achieved sample configurations (conditional argument) and over repeated samples of fixed size n (unconditional argument). Efficiency conditions were obtained. Under these conditions the proposed combined-type estimators would perform better than the associated customary combined-type estimator. Furthermore, optimum estimators among the proposed combined-type estimators were obtained both under the conditional and unconditional arguments. An empirical work confirmed the theoretical results.

A Class of Estimators for Population Ratio in Simple Random Sampling Using Variable Transformation

This paper is an extension and generalization of the study carried out by [1] on the estimation of the population ratio (R) of the population means of two variables (y and x) under Simple Random Sampling (SRS) scheme, using a variable transformation of the auxiliary variable, x. All the six estimators proposed by [1] are easily identified as special cases of the proposed class of estimators. Asymptotic properties of the proposed class of estimators are derived theoretically and subsequently verified using empirical illustrations. Some of the proposed estimators are found to have relatively large gains in efficiency over the customary ratio estimator, ?for the given data set.

Statistical Analysis of Variables Influencing Type of Birth in Sri Lanka: A Logistic Regression Approach

Caesarean is a major surgical procedure undertaken in obstetrics and its rate is increasing in Sri Lanka as well as in the world. In Sri Lanka, health statistics show an increase in caesarean rates from 13.3% in 1998 to 30.6% by 2007. Due to its potential serious risks and the burden on the health system, many authorities have recommended reducing the caesarean rate for many years. This motivated us to study the most influential variables on the type of birth in Sri Lanka. In this study, based on the Anuradhapura Teaching Hospital records, entire 805 new born babies’ birth information was considered during the month of May, 2015. The variable “Type of Birth” (Normal/Caesarean) was considered as a binary response variable and age, height, weight of mother and sex, weight, length, shoulder length, head circumference of the baby were treated as explanatory variables. Logistic regression was used to model the data and using stepwise regression;mother’s age, height and weight were identified as the most influential variables on the type of birth. Further, it was observed that the odds of having normal birth is 80% higher for woman who belongs to the age group less than or equal to 30 years compared to woman who belongs to the age group greater than 30 years. Moreover, the Hosmer-Lemeshow goodness of fit test was used to check the adequacy of the fitted model. Results from this study revealed that in future, the type of birth may be predicted by considering these identified influential variables.

Construction and experimental investigation of the R-δf-type welding window

In this study, a new R-δf-type welding window on charge parameters is constructed by determining the boundary conditions of the explosive ratio. The R-δf-type welding window synthetically considers the explosive properties and material properties, and can quickly determine the explosive charge at different welding materials with different thickness. In order to test the practicability and accuracy of the R-δf-type welding window, 410S stainless steel and Q345R low alloy steel plates were explosively welded using 15 mm charge determined by the new window. Microstructures of the bonded sections were examined and then shear tests were carried out on the bonded specimens. Microstructural examination showed the joint interface was transformed from micro wavy to small wavy appearance without microstructure defects. Shear tests results showed inter inacial shear strength was much higher than that of the national first grade standard. So the R-δf-type welding window has strong practicability and accuracy and is helpful to the practical production and application of explosive welding composite materials.

Development of high-aspect-ratio microchannel heat exchanger based on multi-tool milling process

A high-aspect-ratio microchannel heat exchanger based on multi-tool milling process was developed. Several slotting cutters were stacked together for simultaneously machining several high-aspect-ratio microchannels with manifold structures. On the basis of multi-tool milling process, the structural design of the manifold side height, microchannel length, width, number, and interval were analyzed. The heat transfer performances of high-aspect-ratio microchannel heat exchangers with two different manifolds were investigated by experiments, and the influencing factors were analyzed. The results indicate that the magnitude of heat transfer area per unit volume dominates the heat transfer performances of plate-type micro heat exchanger, while the velocity distribution between microchannels has little effects on the heat transfer performances.

Association of GA/HbA1c Ratio with Diabetic Retinopathy

Objectives: The aim of this study was to explore the potential correlation between the GA/HbA1c ratio and diabetic retinopathy (DR) in patients with type 2 diabetes (T2D), as the GA/HbA1c ratio serves as a marker for glycemic variability. Methods: A total of 2565 T2D patients were included in this study and grouped into five categories based on the diagnostic criteria for DR. We examined the impact of the GA/HbA1c ratio on the progression of diabetes. Results: The non-DR group exhibited lower GA/HbA1c levels compared to the DR group. Additionally, as the severity of DR increased among the five groups, there was a corresponding increase in the GA/HbA1c ratio. Logistic regression analysis demonstrated that the GA/HbA1c ratio independently elevated the risk of DR occurrence. Conclusions: The GA/HbA1c ratio can independently predict the occurrence and progression of diabetic retinopathy.

Non Degeneration of Fibonacci Series, Pascal’s Elements and Hex Series

Generally Fibonacci series and Lucas series are the same, they converge to golden ratio. After I read Fibonacci series, I thought, is there or are there any series which converges to golden ratio. Because of that I explored the inter relations of Fibonacci series when I was intent on Fibonacci series in my difference parallelogram. In which, I found there is no degeneration on Fibonacci series. In my thought, Pascal triangle seemed like a lower triangular matrix, so I tried to find the inverse for that. In inverse form, there is no change against original form of Pascal elements matrix. One day I played with ring magnets, which forms hexagonal shapes. Number of rings which forms Hexagonal shape gives Hex series. In this paper, I give the general formula for generating various types of Fibonacci series and its non-degeneration, how Pascal elements maintain its identities and which shapes formed by hex numbers by difference and matrices.

Evaluation of Source Rock Potential for Hydrocarbon Generation in Shallow Offshore, Lamu Basin, Kenya

The ever-increasing demand for oil and gas has driven its exploration in rather extreme conditions. In Lamu offshore, which is hitherto underexplored, most of the wells already drilled turned out dry save for a few wells with hydrocarbon shows despite the promising reservoir properties and related geological structures. This, therefore, necessitated a source rock evaluation study in the area to ascertain the presence and potential of the source rock by integrating the geochemical data analysis and petroleum system modeling. The shallow Lamu offshore source rock quantity, quality, and maturity have been estimated through the determination of the total organic carbon (TOC) average values, Kerogen typing, and Rock-Eval pyrolysis measurements respectively. Geochemical data for Kubwa-1, Mbawa-1, Pomboo-1, and Simba-1 were evaluated for determining the source rock potential for hydrocarbon generation. Petroleum system modeling was applied in evaluating geological conditions necessary for a successful charge within a software that integrated geochemical and petrophysical characterization of the sedimentary formations in conjunction with boundary conditions that include basal heat flow, sediment-water interface temperature, and Paleo-water depth. The average TOC of 0.89 wt % in the study area suggests a fair organic richness which seems higher in the late cretaceous (0.98 wt %) than in the Paleocene (0.81 wt %). Vitrinite reflectance and Tmax values in the study area indicate the possible presence of both mature and immature source rocks. Type III Kerogen was the most dominant Kerogen type, and gas shows are the most frequent hydrocarbon encountered in the Lamu Basin with a few cases registering type II/III and type II. The charge properties (i.e. Temperature, transformation ratio, and Vitrinite reflectance) over geologic time at each of the wells have been estimated and their spatial variation mapped as seen from the burial history and depth curves overlaid with temperature, transformation ratio, and Vitrinite reflectance respectively. From the upper cretaceous maturity maps, the results seem to favor near coastal regions where average TOC is about 1.4 wt %, Vitrinite reflectance is more than 0.5%, transformation ratio is more than 10%, and temperatures range from 80°C to 160°C. The results postulate the absence of a definitive effective source rock with a likelihood of having cases of potential and possible source rocks. Moreover, greater uncertainty rests on the source rock’s presence and viability tending toward the deep offshore. Geochemical analysis and petroleum system modeling for hydrocarbon source rock evaluation improved the understanding of the occurrence of the possible and potential source rocks and processes necessary for hydrocarbon generation.

宽高比对煤柱型冲击地压影响规律的实验研究

我国深部煤炭开采日趋复杂,区段煤柱在采动、构造或坚硬顶底板影响下极易诱发煤柱型冲击地压,煤柱型冲击地压的防治已成为煤矿安全高效开采的难题,研究不同宽高比条件下区段煤柱的力学性能及冲击破坏特性对煤柱型冲击地压防治具有积极意义。采用不同宽高比煤样的“岩-煤-岩”组合体进行了单轴压缩实验,通过分析煤岩组合体的冲击倾向性、动态破坏特征、分形维数和声发射特征参数等,研究了宽高比对煤柱冲击破坏的影响规律。结果发现:①煤柱的宽高比对煤岩组合体的冲击倾向性具有显著影响,宽高比不小于2∶1时,其冲击能量指数K_(E)为1.82~2.65,冲击倾向性无明显变化;小于2∶1时冲击倾向性呈先升高后降低的趋势,1∶1时K_(E)最大,达到了15.43。②随宽高比减小,煤岩组合体破坏特征依次表现为:拉压破坏—压剪破坏—拉剪破坏。煤柱宽高比为5∶1~3∶1时,煤岩组合体破坏较为缓慢;宽高比为2∶1时开始出现片状煤屑弹出,冲击破坏剧烈程度较低;宽高比为1∶1和0.75∶1时,具有明显的冲击破坏特性;宽高比为0.5∶1时,煤岩组合体整体稳定性下降,相对0.75∶1煤岩组合体煤柱破坏的剧烈程度降低。③峰后声发射能量释放率与分形维数D变化规律相似,均随宽高比减小呈先升高后降低的趋势。宽高比不小于2∶1时,煤岩组合体破坏过程中能量持续释放时间较长,煤柱破坏平缓;宽高比为1∶1时,能量释放率和D值明显增大,相较宽高比不小于2∶1煤岩组合体的能量释放率增大了约4倍,D值增大了0.18~0.23,煤柱冲击破坏最为剧烈;宽高比0.75∶1煤岩组合体能量释放率与D值分别降低了约10%和0.01,破坏剧烈程度与1∶1煤岩组合体相近;宽高比减小至0.5∶1时,相关参数的降低幅度约为0.75∶1煤岩组合体的6倍,破坏剧烈程度相对较小。研究表明:宽高比对煤柱的冲击破坏具有显著影响,整体上,煤柱冲击破坏剧烈程度随宽高比减小(5∶1~0.5∶1)呈先升高后逐渐降低的趋势;煤柱宽高比大于3∶1时,煤柱冲击危险性相对较小,煤柱宽高比为1∶1和0.75∶1时冲击危险性较大,0.5∶1次之。

蛋白尿与估算肾小球滤过率联合对糖尿病患者新发心血管疾病的影响

目的 观察估算肾小球滤过率(estimated glomerular filtration rate, eGFR)和尿微量白蛋白与肌酐比值(urine albumin-to-creatinine ratio, uACR)评估肾功能的一致性,探讨二者联合对糖尿病患者新发心脑血管疾病(cardia-cerebrovascular disease, CVD)(包括心力衰竭、心肌梗死、脑卒中)的影响。方法 选择参加开滦第5次或第6次健康体检且进行尿微量白蛋白及尿肌酐、血肌酐检测的8 791例2型糖尿病(type 2 diabetes mellitus, T2DM)患者为研究对象。依据基线uACR和eGFR水平分组:正常组(uACR<3 mg/mmol且eGFR≥90 mL·min^(-1)·1.73 m^(-2))、单纯eGFR下降组(uACR<3 mg/mmol且eGFR<90 mL·min^(-1)·1.73 m^(-2))、单纯uACR升高组(uACR≥3 mg/mmol且eGFR≥90 mL·min^(-1)·1.73 m^(-2))和uACR升高合并eGFR下降组(uACR≥3 mg/mmol且eGFR<90 mL·min^(-1)·1.73 m^(-2))。观察eGFR和uACR评估的肾功能是否一致。采用多因素Cox回归模型分析uACR和eGFR联合分组对CVD发病风险的影响。结果 (1)研究对象基线年龄为(60.97±9.99)岁,男性占79.05%,中位uACR为1.68(0.81,4.60)mg/mmol,平均eGFR为(92.14±16.52) mL·min^(-1)·1.73 m^(-2),uACR升高与eGFR下降不一致者占43.59%。(2)中位随访时间为3.83年,共发生CVD事件694例(7.89%),4组总CVD事件的发病密度分别为12.96/1 000人年、19.04/1 000人年、25.65/1 000人年和46.87/1 000人年。(3)与正常组相比,单纯eGFR下降组、单纯uACR升高组和uACR升高合并eGFR下降组新发总CVD事件的风险分别升高1.06(95%CI 0.73~1.55)倍、1.99(95%CI 1.41~2.80)倍和3.00(95%CI 2.12~4.25)倍。结论 eGFR下降和uACR升高所评估的肾功能不一致现象较为常见,二者对CVD发病的影响存在联合作用。

纤维蛋白原白蛋白比值与糖尿病肾病湿浊证的相关性研究

目的探讨纤维蛋白原白蛋白比值(FAR)与2型糖尿病肾脏病(DKD)湿浊证相关性。方法纳入糖尿病肾脏病231例,湿浊证109例,非湿浊证122例,统计2组FAR及肾功能化验指标,对糖尿病肾脏病湿浊证及FAR等指标采用二项Logistic回归分析及相关性分析,并进行因素校正。结果糖尿病肾脏病患者中,湿浊证发生率47.2%,湿浊证患者FAR高于非湿浊证患者(P<0.05),湿浊证患者空腹血糖(FBG)、血肌酐(serum creatinine,Scr)、尿素氮(BUN)、24h尿蛋白定量(UTP)均高于非湿浊证患者,eGFR低于非湿浊证患者(P<0.05)。随着糖尿病肾脏病进展,湿浊证发生率、FAR水平均逐步上升(P<0.05)。相关性分析发现,FAR与Scr、BUN、UTP、湿浊证比例均呈正相关,FAR与eGFR呈负相关。湿浊证与FAR四分位数二元Logistic回归分析显示,FAR二分位组、三分位组、四分位组患者湿浊证比例OR值分别为1.460、3.285、3.148,模型调整后仍呈现上升趋势(P<0.05)。结论纤维蛋白原白蛋白比值的增加与糖尿病肾脏病湿浊证增加密切相关,高FAR值可能与糖尿病肾病进展有关,是糖尿病肾脏病进展的重要标志物。

输电塔斜材不同节点型式下的受压承载力

为研究节点约束下输电塔斜材受压承载力的计算方法,通过对120根等边角钢的偏心受压承载力试验,分析其最小轴、平行轴布置时的破坏模式、承载力及变形形态,研究不同约束刚度、节点型式对其承载力的影响;结合现行行标公式,针对不同节点连接型式(A、B、C类),提出输电塔斜材受压长细比的计算公式.研究结果表明:长细比小于120时,构件承载力主要受偏心控制,偏心越大,承载力越低;而长细比大于120时,构件承载力主要受约束刚度控制,约束刚度越大,承载力越高;A、C类连接在不同长细比时各具优势,但B类连接的承载力始终低于A、C类连接;国内外规范计算值与试验值均存在较大的偏差,具有一定的局限性,体现在小长细比构件偏心及大长细比构件约束修正不足等方面;所提出长细比修正公式的计算结果与试验结果吻合良好,可用于指导工程设计.

黄土地基阶梯型截面桩承载模型试验与计算

为研究黄土地基阶梯型截面桩的荷载传递机理,通过室内模型试验与有限元计算,分析阶梯型截面桩竖向静荷载下的桩身轴力、桩侧摩阻力、桩顶沉降和桩身不同深度荷载分担比,并探索了变径比对其工作性能的影响,并对其进行优化设计。结果表明:在相同荷载下,阶梯型截面桩的桩顶沉降明显小于等截面桩,当变径比在0.8~0.9时,沉降控制效果最佳,其材料利用率最高;若二者极限承载力相同时,阶梯型截面桩的最高材料利用率为等截面桩的1.06倍。阶梯型截面桩为摩擦型桩,变截面位置土体对桩体具有支承作用,其变径处底面土体能承担部分桩顶荷载。桩侧能够分担更多桩顶荷载,减轻桩端土体承载,当变径比在0.8~0.9时,侧摩阻力发挥程度更高。在桩体用料相同时,与等截面桩相比,阶梯型截面桩能大幅度提高承载能力。

透水丁坝孔型对坝体附近水流特性影响研究

为深入探讨透水丁坝透水孔型对其附近水流特性的影响,通过室内高精度水槽试验,采用三维声学多普勒流速仪对矩形、方圆形和椭圆形三种透水孔型下丁坝附近水流流速进行测量,获得不同透水孔型影响下的丁坝附近水流流速和紊动强度分布特征。结果表明,坝后水流流速波动和紊动强度明显大于坝前,透水丁坝对近坝区水流影响较大,距丁坝越远,流速均匀性越好,紊动强度越小。透水丁坝的缓流效果与透水孔型密切相关,矩形透水孔的坝后缓流率为35.4%,缓流效果较好,方圆形透水孔次之,椭圆形最小,研究结果可为丁坝的透水孔型选择提供指导和参考。

Genetic types and geochemicai characteristics of natural gases in the Jiyang Depression,China

Natural gases were widely distributed in the Jiyang Depression with complicated component composition, and it is difficult to identify their genesis. Based on investigation of gas composition, carbon isotope ratios, light hydrocarbon properties, as well as geological analysis, natural gases in the Jiyang Depression are classified into two types, one is organic gas and the other is abiogenic gas. Abiogenic gas is mainly magmatogenic or mantlederived CO2. Organic gases are further divided into coaltype gas, oil-type gas, and biogas according to their kero- gen types and formation mechanisms. The oil-type gases are divided into mature oil-type gas （oil-associated gas） and highly mature oil-type gas. The highly mature oil-type gases can be subdivided into oil-cracking gas and kerogen thermal degradation gas. Identification factors for each kind of hydrocarbon gas were summarized. Based on genesis analysis results, the genetic types of gases buried in different depths were discussed. Results showed that shallow gases （〈1,500 m） are mainly mature oil-type gases, biogas, or secondary gases. Secondary gases are rich in methane because of chromatographic separation during migration and secondary biodegradation. Secondary biodegradation leads to richness of heavy carbon isotope ratios in methane and propane. Genesis of middle depth gases （1,500-3,500 m） is dominated by mature oil-type gases.Deep gases （3,500-5,500 m） are mainly kerogen thermal degradation gas, oil-cracking gas, and coal-type gas.

Numerical computation of anti-liquefaction effect of lattice-type cement-mixed soil countermeasure

Continuous soil-cement wall confinement method to resist liquefaction is a new kind of process. However, whether it also has a good effect on anti-liquefaction or not needs to be urgently answered for earthquake engineering. Quiet boundary is adopted on the lateral face while free field boundary is employed at the bottom. Byrne model on dynamic pore water pressure generation is accepted and natural seismic wave EI Centro whose peak acceleration is adjusted to 0.2 g in proportion is used for input. A double-layer foundation with sandy soil in the upper portion while clay soil in the lower part is chosen as the calculation model, which is 30 m in length and 20 m in width. The groundwater level is on the ground surface. Excess pore water pressure rate is considered as a liquefaction index in the three-dimensional non-linear earthquake response computation. The anti-liquefaction effectiveness and its influencing factors, such as confinement element area are studied. For the natural double-layer foundation, it is liquefied when the excess pore water pressure rate reaches 1.0 under the seismic load. Under the same earthquake load, the peak excess pore water pressure reduces to 0.56 after adopting reinforcement of the continuous soil-cement wall, which is 46% lower than before. It indicates that continuous soil-cement wall confinement method can attain the purpose of anti-liquefaction. Accordingly, it can be a sort of engineering measure to carry on the anti-liquefaction foundation treatment.