Research on the Collaborative Education Mechanism among In-School Mentors,Enterprise Mentors,and Counselors from the Perspective of Sanquan Education

This study addresses the issues existing in the current cultivation process of outstanding graduate students and explores the collaborative education mechanism among in-school mentors,enterprise mentors,and counselors in the cultivation of outstanding engineers in the mechanical field based on the perspective of Sanquan education(i.e.,holistic,full-course,and all-round education).Through exploring this mechanism,we attempt to construct a more scientific and efficient education model to enhance students’comprehensive quality and practical skills,thereby meeting society’s demand for high-quality talents in the mechanical field.

Effect of Facet Displacement on Radiation Field and Its Application for Panel Adjustment of Large Reflector Antenna

Large reflector antennas are widely used in radars, satellite communication, radio astronomy, and so on. The rapid developments in these fields have created demands for development of better performance and higher surface accuracy. However, low accuracy and low effi- ciency are the common disadvantages for traditional panel alignment and adjustment. In order to improve the surface accuracy of large reflector antenna, a new method is pre- sented to determinate panel adjustment values from far field pattern. Based on the method of Physical Optics （PO）, the effect of panel facet displacement on radiation field value is derived. Then the linear system is constructed between panel adjustment vector and far field pattern. Using the method of Singular Value Decomposition （SVD）, the adjustment value for all panel adjustors are obtained by solving the linear equations. An experiment is conducted on a 3.7 m reflector antenna with 12 segmented panels. The results of simulation and test are similar, which shows that the presented method is feasible. Moreover, thediscussion about validation shows that the method can be used for many cases of reflector shape. The proposed research provides the instruction to adjust surface panels efficiently and accurately.

Characteristics and Formation Mechanism of the Geothermal Field in the North China Downfaulted Basin

The geothermal field is mainly controlled by the regional tectonic framework characterized by alternationsof uplifted and depressed basement. and exhibits a similar zoned distribution of temperatures. In the upliftedarea the geothermal gradient （G） and terrestrial heat flow value（q） of the Cenozoic sedimentary cover are rela-tively high, with G=3.5-5.0℃/100m and q=63-84mW/m;; whereas in the depressions they are rela-tively low, with G=2.7-3.5℃/100m and q=46-59mW/m;. In the whole region, G=3.58℃/100m and q=61.5±13.4nW/m;, indicating a comparatively high geothermal background and the presence of localgeothermal anomalies. A comparison of the results of mathematical simulation of the geothermal field with themeasured values shows a good agrecment between them. The geothermal difference between various tectonicunits is caused chiefly by the lateral and vertical variation of thermal properties of shallow crustal rocks. Thisphenomenon can be regarded as the result of redistribution of relatively uniform heat flows from the deep crustin the surficial part of the crust in the process of their upward conduction.

Thermal evolution of neutron stars with decaying magnetic fields

Rotochemical heating originates in the deviation from beta equilibrium due to spin-down compression, which is closely related to the dipole magnetic field. We numerically calculate the deviation from chemical equilibrium and thermal evolution of neutron stars with decaying magnetic fields. We find that the power-law long term decay of the magnetic field slightly affects the deviation from chemical equilibrium and surface temperature. However, the magnetic decay leads to older neutron stars that could have a different surface temperature with the same magnetic field strength. That is, older neutron stars with a low magnetic field （10^8 G） could have a lower temper- ature even with rotochemical heating in operation, which probably explains the lack of other observations on older millisecond pulsars with higher surface temperature, except millisecond pulsar J0437-4715.

MY WORK IN THE FIELD OF FLUID MECHANICS

I graduated from the National Peiyang University (now called Tianjin University) in 1950, majoring in hydraulic engineering. Starting from 1952, my teaching work was basically in mechanics.My first academic probe was in cybernetics, resulting in the publication of the first Chinese paper concerning optimal control. After 1963, I worked on the theory of hydrodynamic stability. My explorative thrust is at the eigenvalues of the Orr Sommerfeld Equation,a non-self adjoint problem in

Effect of mechanical force field on the electromechanical stability of dielectric elastomers

To study the electromechanical stability of dielectric elastomer subjected to a mechanical force field, we use free energy functions of variable forms to analyze the mechanical performance of dielectric elastomer. The relation among critical nominal electric field, critical true electric field, nominal stress and mechanical force field is derived. These calculations agree well with the experimental results. The results can help us better understand the stability conditions of dielectric elastomers and furthermore guide the design and manufacture of sensors and actuators based on dielectric elastomers.

Coal pillar mechanics of violent failure in U.S. Mines

This paper seeks to enhance the understanding that the horizontal stresses build up and release during coal pillar loading and unloading(post-failure) drawing upon three decades of observations, geomechanical monitoring and numerical modeling in bump-prone U.S. mines. The focus is on induced horizontal stress in mine pillars and surrounding strata as highly stressed pillars punch into the roof and floor, causing shear failure and buckling of strata; under stiff stratigraphic units of some western US mines, these events could be accompanied by violent failure of pillar cores. Pillar punching eventually results in tensile stresses at the base of the pillar, facilitating transition into the post-failure regime; this transition will be nonviolent if certain conditions are met, notably the presence of interbedded mudstones with low shear strength properties and proper mine designs for controlling seismicity and dynamic loads. The study clearly shows high confining stress build-up in coal pillars resulting in up to twice higher peak vertical stress and high strain energy accumulations in some western US mines in comparison with peak stresses predicted using common empirical pillar design methods. It is the unstable release of this strain energy that can cause significant damage resulting from pillar dilation and ground movements. These forces are much greater than the capacity of most common internal support systems, resulting in horizontal stressinduced roof falls locally, in mines under unremarkable far-field horizontal stress. Attention should be placed on pillar designs as increasing support density may prove to be ineffective. This mechanism is analyzed using field measurements and generic finite-difference stress analyses. The study confirms the higher load carrying capacity of confinement-controlled coal seams in comparison with structurally controlled coal seams. Such significant differences in confining stresses are not taken into account when estimating peak pillar strength using most common empirical techniques such as those proposed by Bieniawski and Salamon. While using lower pillar strength estimates may be considered conservative,it underestimates the actual capacity of pillars in accumulating much higher stress and strain energies,misleading the designer and inadvertently diminishing mine safety. The role of induced horizontal stress in mine pillars and surrounding strata is emphasized in coal pillar mechanics of violent failure. The triggering mechanism for the violent events is sudden loss of pillar confinement due to dynamic loading resulting from failure of overlying stiff and strong strata. Evidence of such mechanism is noted in the field by observed red-dust at the coal-rock interfaces at the location of coal bumps and irregular, periodic caving in room-and-pillar mines quantified through direct pressure measurements in the gob.

Moment tensor inversion for focal mechanism of the Beibuwan earthquakes

Two earthquakes of Ms=6.0 and Ms=6. 1 consecutively occurred on December 31, 1994 and January 10, 1995 in Beibuwan region, China. By using the generalized reflection-transmission coefficient matrix and the discrete slowness integration method in the calculation of Green's functions, we obtained the focal mechanisms of these earthquakes using long-period waveforms of regional body waves recorded by the China Digital Seismograph Network (CDSN) by means of moment tensor inversion method in frequency domain. The results inverted indicate that the focal mechanisms of these two earthquakes were similar to each other. Their principal compressional stresses are in NW-SE direction and principal tensional stresses are in NE-SW direction. It turns out that the occurrence of the two earthquakes was controlled by the same tectonic environment related to the collision of the Philippine Plate and the Eurasian Plates. On the other hand, the results imply that the stress field in the seismogenic region has a significant change after the Ms=6.0 earthquake. It may be proposed that the occurrence of the Ms=6. 1 earthquake could be related to the stress field adjustment caused by the Ms=6.0 earthquake.

Diffusion Mechanism of Energy Flow in Multi-heat-source Synthesis of SiC

Through the experiments and the numerical simulation of temperature field in multi-heatsource synthesis Si C furnace, in order to research the feature point in multi-heat-source synthesis furnace, the variation law of heat fl ux was studied and the multi-directional energy fl ow diffusion mechanism was revealed. The results show that, due to the shielding action between the heat-source and the superposition effect of thermal fields, the insulating effect is best in multi-heat-source synthesis furnace. The heat emission effect is good outside the common area between heat-sources, but the heat storage is poor. Compared with the synthesis furnace that heat source is parallelly arranged, the furnace of stereoscopic arrangement has a more obvious heat stacking effect and better heat preservation effect, but the air permeability of heat source connecting regions is worse. In the case with the same ingredients, the resistance to thermal diffusion and mass diffusion is higher in heat source connecting regions.

Numerical simulation of spatial-temporal evolution characteristics of subsurface fluid based on strong body seismogenic model$$$$

Using finite element technique of the plane-strain problem in solid-liquid two-phase medium, we Studied the char acteristics of 'field precursors' and 'focus precursors' of subsurface fluid and their spatial-temporal evolution in case of dip-slip earthquake. The results show that: ① the change of ground fluid is slow and the anomaly is not prominent in the early period which is of elastic accumulation and non-linear; ② dilatancy emerges and anomalyfocus mainly in the source region in the moderate period which is hardening and of local dilatancy. In the period the focus precursors emerge earlier than the field precursors; ③ anomalies spreed continuously in the source area and new regions with big anomaly emerge out of the source region in the middle-short period which is of large scale dilatancy.

Mechanism of Gravity Impulse

It is well known that energy-momentum is the source of gravitational field. For a long time, it is generally believed that only stars with huge masses can generate strong gravitational field. Based on the unified theory of gravitational interactions and electromagnetic interactions, a new mechanism of the generation of gravitational field is studied. According to this mechanism, in some special conditions, electromagnetic energy can be directly converted into gravitational energy, and strong gravitational field can be generated without massive stars. Gravity impulse found in experiments is generated by this mechanism.

Modeling the rail surface unevenness of a high-precision radio telescope

This study proposed a coarse-fine mixed model for describing the rail surface unevenness of an ultra-large fully steerable radio telescope （Qi Tai Telescope） with a diameter of 110 meters. The rail surface unevenness includes information on error arising from two different scales, i.e., the long-period- short-change and the short-period-long-change. Consequently, in this study an idea of a mixed model was proposed, in which trigonometric and fractal functions were, respectively, used to describe infor- mation on error from two scales. Key parameters were determined by using the least squares method and the wavelet transform method, and finally, a specific mathematical expression of the model was obtained by optimization. To validate the effectiveness of the new modeling method, the mixed model was then used to describe the rails of the Green Bank Telescope, the Large Millimeter Telescope, and a radio telescope in Miyun, Beijing. A comparative study revealed that the maximum error was less than 15 %, thus the result was superior to those of existing modeling methods.