Approximate solution of plastic zone boundary of surrounding rock of circular roadway considering axial stress

In order to study the boundary of plastic zone of surrounding rock of a roadway considering axial stress, based on Mohr-Coulomb criterion, the implicit equation of plastic zone boundary of surrounding rock of circular roadway considering axial stress is derived by introducing Lode angle parameter. The size and shape of plastic zone of surrounding rock under different stress fields are analyzed by changing the horizontal stress σx and axial stress σy of roadway, and the reliability of theoretical analysis is further illustrated by numerical simulation. In addition, the influence of cohesion C, internal friction angle φ, roadway radius R and Poisson’s ratio v on the stability of surrounding rock is studied. The results show that : ① Under the condition of fixed axial lateral pressure while changing horizontal lateral pressure, the size change of plastic zone of surrounding rock can be divided into sensitive zone and insensitive zone, and in the changing process of horizontal lateral pressure, the plastic zone of surrounding rock shows three forms: circular, elliptical and butterfly-shaped. ② Under the condition of fixed horizontal lateral pressure while changing axial lateral pressure, the plastic zone at each position of surrounding rock shows a strong interval effect. By comparing the size of plastic zone under plane strain problem, the region is divided into axial stress-affected zone and axial stress-unaffected zone. In the influence zone of axial stress, the change of axial lateral pressure has great influence on the size of plastic zone of surrounding rock. ③ The failure mode of roadway surrounding rock is determined by the horizontal lateral pressure η1, and the axial lateral pressure η2 has little effect on the shape of plastic zone, but has great influence on the size. ④ The increase of surrounding rock C and φ will reduce the size of plastic zone of roadway surrounding rock to varying degrees, and the increase of R will increase the plastic zone at different positions of surrounding rock in an equal number sequence. In the axial stress-unaffected zone, v has no effect on the size of plastic zone of surrounding rock. In the axial stress-affected zone, the size of plastic zone at the wing corner is not affected by v, and the size of plastic zone at other locations is affected to different degrees

The Design and Research of the Operation Status Detector for Marine Engine Room Power Plant Based on Noise

Designed in this paper, based on the noise of ship engine room power plant running status of detector, is mainly used in the operation of the power plant of acoustic shell size to determine when the machine running state, this device is composed of signal disposal and alarm display adjustment part of two parts. Detector that can show the size of the voice, if exceed the set limit alarm value, the detector can sound an alarm, to remind staff equipment fails, it shall timely inspection maintenance, improve the safety of the operation of the ship

Dynamic Modeling and Motion Control Strategy of Cable-Driven Cleaning Robot for Ship Cargo Hold

Ship cargo-hold cleaning is a low-efficiency and high-risk operation in marine industry, which is generally carried out manually, putting the workers in danger. To improve the efficiency and safety of ship cargo-hold cleaning, a C-DCR is proposed in this article. Most research on the dynamics and control of CDPRs has focused on the scenarios with fixed bases; however, the effect of moving-base excitation on the end-effector is largely ignored. In this article, the dynamic model is established based on Lagrange method considering the ship motion and external disturbance, in which the motor model is considered. On this basis, for the high-speed maneuverability of the C-DCR, a modified PD feedforward tracking controller was proposed. Furthermore, the stability of the controller was proved with the Lyapunov Stability Theory. To keep the cable in tension at all times, the tensions are optimized based on the minimum 2-norm method. The simulation results show that the error mean of position is 0.22 m and the angular error mean is 2.8° under ship motion and external disturbance, indicating that the C-DCR has stable, smooth and bounded tracking performance, which will ensure the accuracy of the cleaning operation

PRINCIPLE AND EXPERIMENT SIMULATION OF THE TELESCOPIC CASING ANTI-SWING DEVICE OF OFFSHORE CRANE

For offshore crane in the operation process at sea,due to the suspension of lifting wire rope belongs to the flexible parts,also wind,wave and ocean environment to inflect the load. These cause the load swing. A new type of offshore crane telescopic sleeve stabilizer was proposed based on the work condition of crane at sea. It uses the casing of the rigid constraints to reduce the swing range of the load,and using the universal torque structure to reduce the stress of the casing. When the casing is moving through the universal torque structure. Rely on the spring dampers to store and release energy. By these methods to reduce the swing of load. The telescopic sleeve device was introduced. A mathematical model of the ship,crane and telescopic sleeve is established. The kinematics analysis of the simulation model is carried out by using Adams. Verify the obvious damping effects of the telescopic sleeve device. At the same time,through constructing the experimental platform for actual experiments,Verifying the telescopic sleeve device in the practical application of also has significant effect of damping

Relationship between internationalization and financial performance: Evidence from ENR-Listed Chinese firms

Since the financial crisis in 2008, the international construction market has shown a relatively weak state of development. Along with China's "Belt and Road Initiative," an increasing number of Chinese construction firms have swarmed to explore the global market and expect to improve their financial performance via internationalization. However, few studies have addressed how and to what extent the internationalization strategy contributes to financial performance. This paper therefore proposes three sets of assumptions on this issue and establishes four regression models. Through multiple regression analysis of 32 Chinese construction firms listed in the Engineering News-Record (ENR) during the 2010-2017 period, the study described here explored the relationship between a construction firm's degree of internationalization and its financial performance as well as the moderating effect of business diversification and three types of macroenvironmental risk. The results reveal that (1) there is a U-shaped relationship between degree of internationalization of construction firms and their financial performance - when the degree of internationalization is less than 52%, the relationship is negative and when it is greater than 52%, the relationship is positive; (2) business diversification acts as a positive moderator in the relationship between internationalization and financial performance; and (3) both economic risks and social risks play a positive moderating role in the relationship between internationalization and financial performance, whereas financial risks play a negative moderating role. This study contributes to the engineering management literature not only by broadening understanding of how internationalization strategy influences financial performance but also by guiding business layout and risk management during the internationalization process. The findings of this study are limited to the sample data from a single country (i.e., China). Similar research might be conducted in the future using sample data from different countries for comparative analysis to draw more generalizable and meaningful conclusions.</p

Assessing Cultivated Land–Use Transition in the Major Grain-Producing Areas of China Based on an Integrated Framework

The cultivated land-use transition (CLUT) is the morphological result of changes in the cultivated land-use mode over time, and the result of the interaction and mutual restriction of the human land system. This paper applies a “spatial–functional” integrated framework to understand the structure and functioning of CLUTs, and quantitatively evaluates and visualizes CLUTs in the major grain-producing area in southern China. The results show that (1) the comprehensive CLUT index in the middle and lower reaches of the Yangtze River changed from 0.0480 to 0.0711 from 2001 to 2019 and indicated significant differences in the transition index between different regions. (2) The CLUT identified a positive aggregation effect under a 5% significance during the period, and the agglomeration degree of the spatial and functional transitions strengthened, which increased from 0.3776 to 0.4673 and from 0.2127 to 0.2952, respectively. (3) The gravity center of the CLUT demonstrated a pattern of migration from the southwest to the northeast, and the migration speed of the gravity center decreased from 2.9401 km/year to 1.2370 km/year. The migration direction of the gravity center for the spatial transition is opposite to the functional transition, and the migration speed of the gravity center for the spatial and functional transitions decreased from 8.3573 km/year to 1.0814 km/year, and from 3.2398 km/year to 1.0254 km/year, respectively. To address this transition, policymakers should formulate differentiated policies to promote the sustainable use of cultivated land through the spatial and functional transition of major grain-producing areas

Assessing Cultivated Land&ndash;Use Transition in the Major Grain-Producing Areas of China Based on an Integrated Framework

The cultivated land-use transition (CLUT) is the morphological result of changes in the cultivated land-use mode over time, and the result of the interaction and mutual restriction of the human land system. This paper applies a &ldquo;spatial&ndash;functional&rdquo; integrated framework to understand the structure and functioning of CLUTs, and quantitatively evaluates and visualizes CLUTs in the major grain-producing area in southern China. The results show that (1) the comprehensive CLUT index in the middle and lower reaches of the Yangtze River changed from 0.0480 to 0.0711 from 2001 to 2019 and indicated significant differences in the transition index between different regions. (2) The CLUT identified a positive aggregation effect under a 5% significance during the period, and the agglomeration degree of the spatial and functional transitions strengthened, which increased from 0.3776 to 0.4673 and from 0.2127 to 0.2952, respectively. (3) The gravity center of the CLUT demonstrated a pattern of migration from the southwest to the northeast, and the migration speed of the gravity center decreased from 2.9401 km/year to 1.2370 km/year. The migration direction of the gravity center for the spatial transition is opposite to the functional transition, and the migration speed of the gravity center for the spatial and functional transitions decreased from 8.3573 km/year to 1.0814 km/year, and from 3.2398 km/year to 1.0254 km/year, respectively. To address this transition, policymakers should formulate differentiated policies to promote the sustainable use of cultivated land through the spatial and functional transition of major grain-producing areas