Mode Evaluation and Structure Design of Connection between Pole and Base of Roadside Breakaway Sign in China

In order to present reliable mode and structure of connection between pole and base for breakaway sign, mode evaluation and structure design were conducted in this paper. AHP was adopted to evaluate connection modes between sign pole and base. Analytic hierarchy with double criterion layer and corresponding judgment matrix were established. Through qualitative analysis, powers of indexes were given and evaluation results were presented based on standardization process of each evaluation index. It shows that brittle connection mode comes in the first place, the plastic connection mode comes second, and rigid connection mode comes last. Two brittle connection structures were designed through the finite element simulation analysis. By ANSYS software, stress data were given for recessed and hole-type connection design structure. It can be found that maximum tensile stress data of two connection structures are all more than ultimate tensile strength of steel. Thus it can be concluded that two connection structures designed in this paper can be breakaway in collision and protect the safety of vehicle occupants

Divide-and-Approximate: A Novel Constraint Push Strategy for Iceberg Cube Mining

The iceberg cube mining computes all cells v, corresponding to GROUP BY partitions, that satisfy a given constraint on aggregated behaviors of the tuples in a GROUP BY partition. The number of cells often is so large that the result cannot be realistically searched without pushing the constraint into the search. Previous works have pushed antimonotone and monotone constraints. However, many useful constraints are neither antimonotone nor monotone. We consider a general class of aggregate constraints of the form f(v)θσ, where f is an arithmetic function of SQL-like aggregates and θ is one of \u3c, ≤, ≥, \u3e . We propose a novel pushing technique, called Divide-and-Approximate, to push such constraints. The idea is to recursively divide the search space and approximate the given constraint using antimonotone or monotone constraints in subspaces. This technique applies to a class called separable constraints, which properly contains all constraints built by an arithmetic function f of all SQL aggregates

Mechanics and road performance of mudstone modified stabilized gravel subgrade in arid desert areas

This study investigates the feasibility of using mudstone to enhance poorly graded gravel in certain arid regions of the S21 Altay-Urumqi Highway project in Xinjiang. Despite mudstone typically being considered a poor-quality rock, its combination with higher-performance materials like cement, lime, and fly ash can stabilize expansive soils for use as roadbed fill. In the experiments, 30% and 40% mudstone were added to the gravel mixture. The experiments were compared with unmodified K80 and 35% crushed rock mixes. The findings reveal that adding 30% mudstone substantially increased the California Bearing Ratio (CBR) of the gravel mix by over 20%. However, excessive mudstone inclusion could weaken load-bearing capacity. Moreover, mudstone-modified specimens exhibited superior unconfined compressive strength (UCS), splitting strength, compressive resilience modulus (CRM), drying shrinkage resistance, and temperature shrinkage resistance. Under optimum cement dosage, the UCS of mudstone-modified specimens outperformed unmodified specimens, consistently surpassing fly ash-altered groups. Although mixed fly ash initially exhibited lower strength, it gradually approached cement-stabilized strength with an extended curing time. Incorporating crushed stone into the grading curve significantly increased splitting strength due to its high strength and hardness. In contrast, adding mudstone introduced a notable proportion of fine aggregates, resulting in a looser grading skeleton prone to early cracking. This research demonstrates that mudstone enhancement significantly improves roadbed performance, including increased CBR, splitting strength, and crack resistance. The use of mudstone in arid desert areas enhances overall performance while reducing shrinkage coefficients. The suggested approach for semi-rigid pavements in arid deserts recommends specific mineral proportions, various aggregate sizes, an appropriate amount of cement, and 30% mudstone to create dense structures with a higher quantity of coarse aggregate

Piezoelectric sensing method for segmental joint contact stress during shield tunnel construction

The emergence of curved shield tunnels poses a significant construction challenge. If the quality of the segment assembly is not guaranteed, many segment cracks and damage will result from the stress concentration. Sensing the contact stresses between segmental joints is necessary to improve the quality of segments assembled for shield tunnel construction. Polyvinylidene difluoride (PVDF) piezoelectric material was chosen for the sensor because it can convert contact stresses into electrical signals, allowing the state of the segmental joints to be effectively sensed. It matches the working environment between the segmental joints of the shield tunnel, where flexible structures such as rubber gaskets and force transfer pads are present. This study proposes a piezoelectric sensing method for segmental joints in shield tunnels and conducts laboratory tests, numerical analyses, and field tests to validate the feasibility of the method. The results indicate that the PVDF film sensor can effectively sense the entire compression process of the gasket with different amounts of compression. The piezoelectric cable sensor can effectively sense the joint offset direction of the gasket. For differently shaped sections, the variation in the force sensed by the piezoelectric cable sensors was different, as verified by numerical simulation. Through the field test, it was found that the average contact stress between the segmental joints was in the range of 1.2–1.8 MPa during construction of the curved shield tunnels. The location of the segmental joints and the type of segment affect the contact stress value. The field monitoring results show that piezoelectric sensing technology can be successfully applied during assembly of the segments for effective sensing of the contact stress

Mining Effective Multi-Segment Sliding Window for Pathogen Incidence Rate Prediction

Pathogen incidence rate prediction, which can be considered as time series modeling, is an important task for infectious disease incidence rate prediction and for public health. This paper investigates the application of a genetic computation technique, namely GEP, for pathogen incidence rate prediction. To overcome the shortcomings of traditional sliding windows in GEP-based time series modeling, the paper introduces the problem of mining effective sliding window, for discovering optimal sliding windows for building accurate prediction models. To utilize the periodical characteristic of pathogen incidence rates, a multi-segment sliding window consisting of several segments from different periodical intervals is proposed and used. Since the number of such candidate windows is still very large, a heuristic method is designed for enumerating the candidate effective multi-segment sliding windows. Moreover, methods to find the optimal sliding window and then produce a mathematical model based on that window are proposed. A performance study on real-world datasets shows that the techniques are effective and efficient for pathogen incidence rate prediction

Thermal Cracking of Hydrocarbon Aviation Fuels in Regenerative Cooling Microchannels

Regenerative cooling with hydrocarbon aviation fuels on board is taken as a promising technology for the thermal management system of next-generation aircraft. An improved methodology of an electrically heated tube (1 mm i.d.), i.e., applying the variable reactor tube length to carry on thermal cracking of supercritical hydrocarbon aviation fuels as the electric current heating maintains constant, was proposed to experimentally obtain detailed information on the local concentration and temperature along the microchannels of a heat exchanger. For the first time a series of experimental data on detailed local chemical compositions of cracked hydrocarbon fuel along the cooling microchannels were reported under supercritical conditions (5 MPa, 680–700 °C), and the calculated thermodynamic properties, velocity, and residence times along the tube were also reported. A modified molecular reaction model consisting of 18 species and 24 reactions was developed to predict thermal cracking of hydrocarbon aviation fuels in a wide range of cracking conversion (up to 86%). The work is significant for the design of regenerative cooling structures in predicting the local chemical compositions, estimating thermophysical properties, and coking of the cracked hydrocarbon fuels for heat transfer analysis

Pushing Aggregate Constraints by Divide-and-Approximate

Iceberg-cube mining is to compute the GROUP BY partitions, for all GROUP BY dimension lists, that satisfy a given aggregate constraint. Previous works have pushed anti-monotone constraints into iceberg-cube mining. However, many useful constraints are not anti-monotone. In this paper, we propose a novel strategy for pushing general aggregate constraints, called Divide-and-Approximate. This strategy divides the search space and approximates the constraint in subspaces by a pushable constraint. As the strategy is recursively applied, the approximation approaches the given constraint and the pruning tights up. We show that all constraints defined by SQL aggregates, arithmetic operators and comparison operators can be pushed by Divideand -Approximate. We present an efficient implementation for an important subclass and evaluate it on both synthetic and real life databases