The Effect of Grain Orientation of β-Sn on Copper Pillar Solder Joints during Electromigration

The grain orientation of Sn-based solder joints on copper pillars under the combined action of electron wind force and temperature gradient greatly affects their electromigration damage. The copper pillars with Sn-1.8Ag lead-free solder on the top was subjected to a current density of 1.5 × 104 A/cm2 at 125 °C to study the electromigration behaviors. The grain orientation was characterized by scanning electron microscopy (SEM) equipped with electron backscattered diffraction (EBSD) detector. Metal dissolution and voids formation in the cathode as well as massive intermetallic compounds(IMC) accumulation in the anode were observed after electromigration. Closer examination of solder joints revealed that the Sn grain whose c-axis perpendicular to electric current may have retarded Cu diffusion to anode and IMC accumulation. In addition, the newly formed Cu6Sn5 exhibited preferred orientation related to the electric current direction.

Dust Emission from Gobi under Different Dust Content Conditions: A Wind Tunnel Study atop the Mogao Grottoes

Dust emission from the Gobi desert is one of the major sources of global atmospheric aerosols. However, the main factors affecting dust emission from Gobi remain poorly understood. In this paper, field wind tunnel experiments were performed atop the Mogao Grottoes to determine the variation characteristics of the vertical dust flux (F) of particulate matter less than 10 μm (PM10) for Gobi surfaces with different dust content and wind speeds under external sand supply. The results demonstrate that F obeyed a power function with increasing friction velocity (U∗), and increased exponentially with the increasing surface dust content (C). The index of n-value in the formula F∝U∗n is taken in the range of 2.02–2.63 under the surface of 27.3–47.3% dust content (<100 µm), and the dust emission rate was significantly enhanced when the surface dust content exceeded approximately 37%. This study indicates that wind force is the primary dynamic condition affecting Gobi dust emission, and that surface dust content is a significant factor in determining the quantity of dust emission. Furthermore, the contribution of wind force to PM10 emission is greater than the surface dust content, and the higher the height, the greater the weight of friction velocity.

Simulation of Crane Trolley Motion Control to Reduce Load Sway

the work aims to develop a method for controlling a crane trolley, providing a decrease in the swinging of the load on the rope at a given positioning accuracy and minimum time for moving the load. Computer simulation of the trolley controlled movement with a load on a rope was carried out within the "Universal Mechanism" software. The 2D computer model includes a trolley with a pulley, a rope with a hook, and a load. T-force represents the wind force effect. The control system (CS) contains three blocks that ensure the movement of the trolley with limited speed and acceleration, the positioning accuracy of the trolley, limiting the deviation and acceleration of a load. List of requirements for the crane CS comprises six issues. The simulation results illustrate the satisfactory performance of the proposed method. The swing angle and trolley positioning accuracy can be controlled within the acceptable range and the external wind disturbance on the load can be successfully suppressed. The optimal parameters of the proportional-differential corrective control, which ensure the minimum travel time of the trolley with limited oscillation of the load, have been determined. The optimal values of the control parameters depend on the inertial characteristics of the load. The maximum permissible values of speed, acceleration, and positioning errors of the trolley limit from above the optimal values of the control parameters.

Analysis of Wind Load Effect on C-Shape Tall Building with and Without Shear Wall

Since land is scarce in metropolitan locations, it's common for tall building to be erected in C form. With the use of software ETABS 2019, this study examines the features of wind-induced story displacement and story drift operating on tall Cshaped models, with and without shear wall. Also, empirical formulae are used for manual calculations and to obtain the wind force and designed wind pressure on C-shaped tall building using codal provisions of IS 875 (Part 3) : 2015, also its applicability has been validated by a case study. For tall C-shaped buildings, this study gives a comparative result on the effect of wind load on building, with & without shear wall on behalf of maximum story displacement and story drift. Keywords: Plan irregularity, shear wall, wind load, ETABS 19

How the Chaos Theory is Defeated in the Yabu Meteorological Station, Cuba

In this work, 8 weather variables were modeled at the Yabu meteorological station, Cuba, a daily database from the Yabu meteorological station, Cuba, of extreme temperatures, extreme humidity and their average value, precipitation, was used. The force of the wind and the cloudiness corresponding to the period from 1977 to 2021, a linear mathematical model is obtained through the methodology of Regressive Objective Regression (ROR) for each variable that explains their behavior, depending on these 15, 13, 10 and 8 years in advance. It is concluded that these models allow the long-term forecast of the weather, opening a new possibility for the forecast, concluding that the chaos in time can be overcome if this way of predicting is used, the calculation of the mean error regarding the forecast of persistence in temperatures, wind force and cloud cover, while the persistence model is better in humidity, this allows to have valuable information in the long term of the weather in a locality, which results in a better decision making in the different aspects of the economy and society that are impacted by the weather forecast. It is the first time that an ROR model has been applied to the weather forecast processes for a specific day 8, 10, 13 and 15 years in advance.

A Near-Zero Power Triboelectric Wake-Up System for Autonomous Beaufort Scale of Wind Force Monitoring

Beaufort scale of wind force monitoring is the basic content of meteorological monitoring, which is an important means to ensure the safety of production and life by timely warning of natural disasters. As there is a limited battery life for sensors, determining how to reduce power consumption and extend system life is still an urgent problem. In this work, a near-zero power triboelectric wake-up system for autonomous Beaufort scale of wind force monitoring is proposed, in which a rotary TENG is used to convert wind energy into a stored electric energy capacitor. When the capacitor voltage accumulates to the threshold voltage of a transistor, it turns on as an electronic switch and the system wakes up. In active mode, the Beaufort scale of wind force can be judged according to the electric energy and the signal is sent out wirelessly. In standby mode, when there is no wind, the power consumption of the system is only 14 nW. When the wind scale reaches or exceeds light air, the system can switch to active mode within one second and accurately judge the Beaufort scale of wind force within 10 s. This work provided a triboelectric sensor-based wake-up system with ultralow static power consumption, which has great prospects for unattended environmental monitoring, hurricane warning, and big data acquisition.