Towards the Compilation of the Global Twilight Pattern

This paper summarizes ISRN’s 3-years research on the occurrence of dawn and dusk to mark the timings of the Fajr and Isha prayers. We acquired the astronomical data not only in Indonesia but also in Malaysia, the US, Egypt, and Turkey. It will be an attempt to compile a global twilight pattern in the future. The main instrument used is a Sky Quality Meter (SQM) that records the sky brightness data. For quality assurance, ISRN-UHAMKA employed dozens of imaging sensors ranging from an All Sky Camera, different types of DSLR, and gadget cameras. From hundreds of astronomical data, we have collected; it seems that the occurrence of the real twilight to mark the Fajr prayer throughout the world is the same. That is when the sun is at its depression angle of around 120-130. Likewise, the dusk to mark the end of the Maghrib prayer also occurs when the sun is at a solar depression angle around 120-130. Meanwhile, Muslims in the world use different solar depression angles ranging from -150 to -200.fields.

Dynamic Analysis of Shearer Traction Unit Considering the Longitudinal Swing

Shearer traction failure occurs frequently, which seriously restricts the safe and efficient mining of coal. However, the influence of the shearer’s posture on traction has not been fully considered in the existing research. To improve traction reliability: the dynamic model of the traction unit is established considering longitudinal swing; the walking characteristics of the shearer and the dynamics of the traction unit are analyzed; and the influences of traction velocity, drum load cutting arm angle, and depression angle are discussed. The results show that the longitudinal swing is reciprocating and the positive swing is more serious. With the increase of the traction velocity, the walking stability of the shearer decreases while the contact force increases, especially the support slipper. The longitudinal swing increases with the increase of lateral load, but the supporting force of the support slipper decreases with the increase of cutting load. The forces of the walking wheel and the support slipper show an increasing trend with the increase of cutting arm angle. When the depression angle is 5–10°, the load distribution of the contact components of the traction unit is more balanced. The results provide a reference for the structure optimization of the shearer and the layout of coalface.

Corrigendum to the Reply to ‘Critical review on the paper: The earliest datable noctilucent cloud observation (Parma, Italy AD 1840)’

The first aim of this corrigendum is to point out and correct calculation errors on solar depression angle and azimuth angle in Bertolin and Domínguez-Castro (2020a, 2020b). The second aim is to recognize that these calculations are correct in Dalin (2020). The third aim is to analyze the chances of Antonio Colla to observe the noctilucent cloud (NLC) taking into account the correct calculations of the twilight sky arc determining the illuminated area of an NLC and the uncertainties in the Colla’s observation report.

Reply to the ‘Critical review on the paper: The earliest datable noctilucent cloud observation (Parma, Italy AD 1840)’

In this reply, the aim of the authors is to correct the calculation errors on solar depression angle and azimuth angle as recognized by Dr. Dalin in his critical review. However, these updated and corrected calculations do not affect the possibility for Antonio Colla of having observed the Noctilucent Cloud (NLC) plausible both in the direction and for the duration he described in his observations. In this reply, the authors offer two different interpretations in this regard.

Compensation of Contour Distortion in Stretch-Flanging Metal Sheets

Stretch-flanging commonly appears at the concave edge of the panel part. Sheet thickness tends to decrease at the center of flange attributed to the outflow of metal flow, and hence causes a radial shrinking of the material. This shrinking pulls the ends of the flange and makes the adjacent surface overcrown. In this paper the effect of punch profiles on a laboratory scale profile, which assimilates the front fender part adjoining the head light, was investigated for the stretch-flanging process. Both the concave and convex punch profiles were considered. SUS 304 stainless steel sheet of 0.6 mm thick was used as the model metal sheet. DynaForm software was used in simulating the stretch flanging process and followed by experimental verification. The results show that a depression angle of 4.4° and an elevation angle 2.6° can produce lowest crown-contour for the concave and convex punches, respectively. The concave punch also causes less thinning at the flange center which makes it a favorable solution than that of the convex punch.

SAR ATR of Ground Vehicles Based on ESENet

In recent studies, synthetic aperture radar (SAR) automatic target recognition (ATR) algorithms that are based on the convolutional neural network (CNN) have achieved high recognition rates in the moving and stationary target acquisition and recognition (MSTAR) dataset. However, in a SAR ATR task, the feature maps with little information automatically learned by CNN will disturb the classifier. We design a new enhanced squeeze and excitation (enhanced-SE) module to solve this problem, and then propose a new SAR ATR network, i.e., the enhanced squeeze and excitation network (ESENet). When compared to the available CNN structures that are designed for SAR ATR, the ESENet can extract more effective features from SAR images and obtain better generalization performance. In the MSTAR dataset containing pure targets, the proposed method achieves a recognition rate of 97.32% and it exceeds the available CNN-based SAR ATR algorithms. Additionally, it has shown robustness to large depression angle variation, configuration variants, and version variants.

Study of Loading and Running Characteristic of Hydraulic Support in Underhand Mining Face

According to complex geological conditions of working face E1108 in Xin-ji mine #2, loading and running characteristic of hydraulic support, influence of depression angle on mining pressure behaviors, as well as relation between advancing speed and the support loading were measured and analyzed. The results indicate that depression angle is inversely proportional to support resistance, in other words, larger depression angle area coincides with lower support resistance area. Moreover, support resistance is generally high when working face advancing speed is slow. Technologies for controlling hydraulic support stability such as improving advancing speed properly, controlling mining height and increasing support resistance are put forward based on research.