Assessment of different machine learning techniques in predicting the compressive strength of self-compacting concrete

The compressive strength of self-compacting concrete (SCC) needs to be determined during the construction design process. This paper shows that the compressive strength of SCC (CS of SCC) can be successfully predicted from mix design and curing age by a machine learning (ML) technique named the Extreme Gradient Boosting (XGB) algorithm, including non-hybrid and hybrid models. Nine ML techniques, such as Linear regression (LR), K-Nearest Neighbors (KNN), Support Vector Machine (SVM), Decision Trees (DTR), Random Forest (RF), Gradient Boosting (GB), and Artificial Neural Network using two training algorithms LBFGS and SGD (denoted as ANN_LBFGS and ANN_SGD), are also compared with the XGB model. Moreover, the hybrid models of eight ML techniques and Particle Swarm Optimization (PSO) are constructed to highlight the reliability and accuracy of SCC compressive strength prediction by the XGB_PSO hybrid model. The highest number of SCC samples available in the literature is collected for building the ML techniques. Compared with previously published works’ performance, the proposed XGB method, both hybrid and non-hybrid models, is the most reliable and robust of the examined techniques, and is more accurate than existing ML methods (R² = 0.9644, RMSE = 4.7801, and MAE = 3.4832). Therefore, the XGB model can be used as a practical tool for engineers in predicting the CS of SCC.     

Purification and properties of a low-molecular-weight phytase from Cladosporium sp. FP-1

A fungus producing high levels of phytase was isolated from air and identified as Cladosporium sp. The phytase production was stimulated by phytate in the medium used. The maximum production of phytase (108 U/ml) occurred in a medium containing 1.0 g of phytate per 100 ml. The phytase was purified to electrophoretic homogeneity by ion-exchange chromatography and gel filtration. Based on SDS-PAGE analysis, the molecular weight of the purified phytase was calculated to be approximately 32.6 kDa, and the narrow protein band indicated that this phytase is not glycosylated. The phytase has an optimum pH of 3.5, and an optimum temperature of 40 degrees C. The phytase activity was stimulated by 2-mercaptoethanol and dithiothreitol, and inhibited by Ba2+, Pb2+, iodoacetate, p-chloromercuribenzoate and phenylmethylsulfonyl fluoride. The phytase displayed high affinity for phytate and the Km was 15.2+/-3.1 microM. NMR analyses (1D and 2D) indicated that the end hydrolysis product of phytate was myo-inositol 1,2,5-triphosphate.     

Piezoelectric pump with flexible venous valves for active cell transmission

The development of organ-on-a-chip systems demands high requirements for adequate micro-pump performance, which needs excellent performance and effective transport of active cells. In this study, we designed a piezoelectric pump with a flexible venous valve inspired by that of humans. Performance test of the proposed pump with deionized water as the transmission medium shows a maximum output flow rate of 14.95 mL/min when the input voltage is 100 V, and the pump can transfer aqueous solutions of glycerol with a viscosity of 10.8 mPa·s. Cell survival rate can reach 97.22% with a yeast cell culture solution as the transmission medium. A computational model of the electric-solid-liquid multi-physical field coupling of the piezoelectric pump with a flexible venous valve is established, and simulation results are consistent with experimental results. The proposed pump can help to construct the circulating organ-on-a-chip system, and the simple structure and portable application can enrich the design of microfluidic systems. In addition, the multi-physical field coupling computational model established for the proposed piezoelectric pump can provide an in-depth study of the characteristics of the flow field, facilitating the optimal design of the micro-pump and providing a reference for the further study of active cell transport in organ-on-a-chip systems.     

大型轴流工水轮机叶片的大面积喷焊

针对大型轴流式水轮机叶片的空间几何形状要求高和大面积喷焊受热极易产生变形等问题，采用由外向内、由薄到厚、由点到面、对称喷焊工艺和叶片刚性网架固定等技术措施，得到了表面平整、内在质量优良的涂层，叶片喷焊后经组合样板检测变形量很小，无需进行修理即可组装运行，并获得了优良的耐空蚀和泥砂磨损的性能，延长了水轮机的使用寿命。     

陶瓷散热片用铜浆玻璃相的制备

厚膜陶瓷散热片的制备工艺一般为丝网印刷铜浆、烧结、化学镀镍3部分。目前印刷在散热片上的铜浆，经化学镀镍工艺后附着力下降，因此研究制备导电性好、导热性优和附着力高的铜浆是制备陶瓷散热片的关键。通过对铜浆玻璃相的制备、玻璃软化温度的测定和玻璃釉在化学镀镍液中的耐蚀性测试，得到了耐蚀性较好的玻璃釉，其玻璃相成分为40％si0...     

膨胀土强度影响因素探讨

膨胀土地区的工程灾害防治问题日益突出，其本质问题是土体强度的变化。研究表明，膨胀土的强度是内因和外因等多种因素综合作用的表现，影响膨胀土强度的内在因素主要有膨胀土自身的物理特性、结构特征、矿物成分及含量，外在因素主要有取土样及试样制作过程中的扰动对土体结构性的破坏程度、试验条件及方法等。     

Radioimmunoassay of pepsinogens I and II in human serum

ＲａｄｉｏｉｍｍｕｎｏａｓａｙｏｆｐｅｐｓｉｎｏｇｅｎｓＩａｎｄＩｉｎｈｕｍａｎｓｅｒｕｍＸｉａｏＺｈｉＪｉａｎ，ＪｉａｎｇＭｅｎｇＪｕｎａｎｄＨｕａｎｇＸｕＱｕａｎ（ＪｉａｎｇｓｕＩｎｓｔｉｔｕｔｅｏｆＮｕｃｌｅａｒＭｅｄｉｃｉｎｅ，Ｓｔａ...     

合理调整主扇运行 提高经济效益

泉沟煤矿原生产能力 0 .2 1Mt α ,1973年开始改扩建 ,1978年正式投产 ,生产水平为 - 115水平。井田面积 8.4m2 ,共有可采煤层七层 ,矿井瓦斯相对涌出量为 4 .4 2 5m3 t,属低瓦斯矿井 ;所有可采煤层均属有爆炸危险煤层 ,煤尘爆炸指数在35～ 4 5 %之间。经过 4 0年的开采 ,矿井煤炭资源逐渐枯竭 ,自 1997年开始矿井进入收缩时期 ,主要以寻找经济煤量为主 ,对边角块段煤柱进行回收。随着采场的不断改变 ,矿井通风系统也不断的变化 ,原有的矿井通风能力不适用矿井生产。先后进行了几次大的通风系统改造 ,取得了较好的经济效益。1　原有矿井通…