Stress Relief Measurements in Young Adults and Adolescents—A Comparative Pilot Study with Different Relaxation Programs

Background: Chronic stress is a emotional challenge. Constant pressure presents a serious risk of damage to mental and physical health and hence is associated with increased incidence of various diseases. The ability to cope with chronic stress may be a function of psychological resilience including intellectual capacities, but more so of external factors such as life experience and education. Adolescents are more vulnerable to chronic stress than adults. The measures introduced during the COVID-19 pandemic brought up major societal problems. As both children and adolescents lost their life anchors, the prevalence of stress in adolescents increased from 20% to 45%. Chronic psychological stress can impede the normal development of schoolchildren. It may cause anxiety, social withdrawal, interpersonal conflicts and aggression. This applies particularly to those in puberty, with the adolescent already facing unstable social bonds and elevated fear about the future. It is likely that the puberty cohort accounts for the dramatic increase in the prevalence of stress. Since it impacts public health, chronic stress among school-age children is increasingly taking on a socio-political dimension. Non-clinical stress intervention studies can investigate how to achieve stress reduction in school children. Methods: In a small pilot study, we analysed the effects of a training program with four different standard interventions, i.e. mindfulness training, progressive muscle reflection, autogenic training, and sound meditation. We obtained baseline scores of 10 stress-indicators, and re-tested after the interventions were performed. Results: The four applied interventions resulted in a reduction of 8 (out of 10) stress-indicators, such as “feeling stressed” or stress related symptoms (headaches, dizziness, sweating). This positive impact of the interventions significantly reduced “Fears about the future” (p Discussion: School children recognise the positive potential of stress reducing training or interventions. Our results provide evidence in support of integrating the training of relaxation techniques in the school curriculum. We propose that a larger study be undertaken to determine which methods would be most effective.

SIMULATION OF VIBRATION STRESS RELIEF AFTER WELDING BASED ON FEM

A finite element model is developed for the simulation of vibration stress relief （VSR） after welding. For the nonresonant vibration, the reduction in stress strongly depends on the amplitude of vibration. For the resonant vibration, the vibration frequency is the key for stress relief. The vibration frequency should be close to the structure natural frequency for the desired vibration mode. Only small vibration amplitude is required, which will be amplified during vibration. Vibration time does not have a major impact on vibration stress relief. When the amplitude of vibration stress relief is large, the treatment will be more effective.

TECHNOLOGY OF QUANTITATIVE ANALYSIS ON VIBRATORY STRESS RELIEF BASED ON ULTRASONIC TIME-OF-ARRIVAL METHOD

The effect of vibratory stress relief （VSR） is usually evaluated with the indirect method of observing the change of amplitude frequency response characteristics of structures. A new kind of evaluating method of VSR based on the ultrasonic time-of-arrival method （UTM）, which can obtain the residual stress directly through measuring the propagation time of ultrasonic wave in the material, is presented. At first, the principle of the measuring method of residual stress based on UTM is analyzed. Then the measuring system of the method is described, which is in virtue of ultrasonic flaw detector and high-sampling-rate digital oscillograph. And a set of calibration system that contains a piece of standard specimen is also introduced. Experimental results prove the relation between the residual stress and the propagation time of ultrasonic in workpieces. Finally, the measuring and calibration systems are applied in evaluating the effect of VSR. The final test results show that the method is effective.

A Numerical Investigation of the Stress Relief Zones Around a Longwall Face in the Lower Seam for Gas Drainage Considerations

Extraction of a protective coal seam (PVCS)-below or above a coal seam to be mined with the potential of coal andgas outburst risk-plays an important role not only in decreasing the stress field in the surrounding rock mass but alsoin increasing the gas desorption capacity and gas flow permeability in the protected coal seam (PTCS). The PVCSis mined to guarantee the safe mining of the PTCS. This study has numerically evaluated the stress redistributioneffects using FLAC3D model for a longwall face in Shanxi Province. The effects of mining depth, mining height andinter-burden rock mass properties were evaluated using the stress relief angle and stress relief coefficient. Verticalstress distribution, stress relief angle and stress relief coefficient in the PTCS were analyzed as the face advancedin the PVCS. The results showed that the stress relief achieved in different locations of the PTCS varied as the faceadvanced. Sensitivity analyses on the pertinent variables indicate that the stress relief in the PTCS is affected mostby the mining depth followed by the inter-burden lithology and the mining height. Furthermore, the elastic moduliof different layers within the inter-burden rock mass are more important than their uniaxial compressive strength(UCS) and Poisson’s ratio. These observations can guide gas drainage borehole design to minimize the accidentsof coal and gas outbursts.

Influence of Cultural Alienation on Happiness of Overseas Students: Mediating Role of Stress Relief and Regulating Role of Cultural Intelligence

When the global outbreak of new coronary pneumonia broke out in 2020,online public opinion events triggered by cultural differences among overseas students had come into the public view.To further explore the relationship between the cultural alienation of overseas students and their own happiness,this study takes visualization and analysis of positive,negative sentiment analysis of Weibo netizens’comment data in the“Xu Kexin Incident”as the starting point,on the basis of introducing cultural alienation,stress relief methods,and cultural intelligence,combining gender and social ability,social relations and other individual attributes,designed a questionnaire to investigate 502 overseas students,through the construction and analysis of the adjusted Cox risk ratio intermedi-ary model,comprehensive single factor interference and multi-factor cross-over comprehensive analysis.The results show that the cultural alienation of overseas students has a significant effect on their own well-being.The study concluded as follows:(1)Netizens hold polarized views on the three dimensions of overseas students’mask,safety,and culture;(2)Stress relief methods play an intermediary role between cultural alienation and the happiness of overseas students,among which Negative stress relief methods play a greater role;(3)The level of cultural intelligence regulates the intermediary process of stress relief methods.The higher the level of cultural intelligence,the stronger the regulatory effect.

Evaluation of residual stress relief of aluminum alloy 7050 by using crack compliance method

High strength aluminum alloys of 7xxx series have unacceptable levels of quenching residual stresses from solution heat treatment. The residual stress not only results in machining distortion and dimensional instability, but also increases the possibility of stress corrosion cracks. Therefore, it is necessary to reduce the residual stress to an acceptable level. The crack compliance method was adopted to study the influences of various stress relief methods on residual stress patterns in 7050 aluminum alloy. The results show that 90% residual stress can be eliminated by the cold stretching(Tx51) method. And a lower level of residual stress can be achieved by the uphill quenching(Tx53) method or the cold compression(Tx52). However, there is a very steep residual stress gradient normal to exterior surfaces.

Stress relief and crystal face transition process contribute to the stability of zinc anodes

Zn electrodes are suffering the dendrite growth owing to the enrichment of local space charge, distinct exposed face and residual stress. In this work, we investigated the crystal face properties and stress state of Zn foil through static energy calculations, dynamic crystal growth analysis and finite element simulation of stress states. Then thermal driven is deployed to modify the exposure face and residual stress of Zn foil, aiming for a dendrite-free electrode. The calculation of surface energies and simulation of crystal growth models for different crystal faces indicate that the(0 0 1) face can maintain stability during deposition. Inspired by this mechanism, the(1 0 1) exposed commercial Zn foil is modified by thermal processing. Firstly, the exposure level of the(0 0 1) face increases, though only the peak corresponding to the(0 0 2) crystal face is observed, due to the extinction effect of the densely packed plane(0 0 1) face.Further, the surface morphology becomes smooth and the stress is released with the progresses time.These stress relief and crystal face transition process strengthen the uniformity of ion distribution, and increase the interface stability during the crystal growth, which reduce the defect sites in the deposition.As a result, the Zn electrode exhibits tiny voltage hysteresis and outstanding cycle stability, which reveals improved electrochemical performance. Additionally, Li and Na can also be improved in exposed crystal faces and release strain energy through similar methods to enhance cycling stability.

Theoretical framework for stress relief-support reinforcement cooperative control of rock bursts in deep coal mining

With the increasing depth of coal mining each year,rock burst has emerged as one of the most severe dynamic disasters in deep mining.The research status of rock burst prevention and control theory is summarized.Focused on deep coal mining,the major issues encountered in researching the prevention theory of rock bursts are summarized.Subsequently,the scientific connotation theory of stress relief-support reinforcement cooperative prevention and control of rock bursts in deep coal mines is proposed.Then,the mechanisms underlying the major research directions of the theory of stress relief-support reinforcement coordinated prevention and control and present a preliminarily theoretical framework for stress relief-support reinforcement coordinated prevention and control are outlined.To tackle the key scientific problems in the coordinated prevention and control of rock bursts on relief and support in deep mine,the in-depth research based on the synergetic theory is conducted.This involved exploring the principles of near-field coal mass stress relief,near-field roof andfloor stress relief,and anchor support.Additionally,the stress-energy evolution processes of the roadway near-field surrounding rock structure under various stress relief and anchor support modes be analyzed.Subsequently,a mechanical model for the optimized matching of stress relief surrounding rock and anchor support is established,with the control of the rock burst energy source at its core.Finally,the principle of collaborative prevention and control of deep mining rock burst stress relief and support from the perspectives of structural synergy,strength synergy,and stiffness synergy is elucidated.This insight is expected to provide theoretical support for the research and development of designs and techniques for deep mining rock burst prevention and control.

Principle of in-situ 3D rock stress measurement with borehole wall stress relief method and its preliminary applications to determination of in-situ rock stress orientation and magnitude in Jinping hydropower station

As a main constituent of geological body, the rock masses have distinct differences from other materials, one of which is that rock masses are initially stressed in their natural states. Hence, it is an extremely challenging and significant research project to know the present residual stress of the rock masses in the earth's crust. Although some regularities of distribution of in-situ rock stresses can be deduced, the basic means to study the state of rock stress is in-situ stress measurement. After a brief review of several measuring methods of in-situ 3D rock stress, a new one, borehole wall stress relief method (BWSRM) to determine the in-situ 3D rock stress tensor in a single drilled borehole was proposed. Based on the principle of in-situ rock stress measurement with BWSRM, an original geostress measuring instrument was designed and manufactured. Preliminary experiments for determination of in-situ stress orientation and magnitude were carried out at an experimental tunnel in Jinping Ⅱ hydropower station in China, where the buried depth of overburden was about 2430 m. The results showed that it was feasible to measure the in-situ 3D rock stresses with BWSRM presented in this paper. The BWSRM has a broad prospect for in-situ 3D rock stress measurements in practical rock engineering.

Non-complete relief method for measuring surface stresses in surrounding rocks

The measurement of surface stresses in surrounding rocks with the use of a relief method of annular hole-drilling was studied by numerical analysis. The stress relief process by hole-drilling was then simulated with the use of finite element method. The influences of the borehole diameter(d), the initial stresses and the ratio of the initial principle stresses on the variations of the remained stress and the released stress in function of the relief depth(h) were discussed. The relation between the non-dimensional ratio of the released principle strains and that of the initial principle stresses, and the effect of the elastic modulus and the Poisson ratio of the rock mass on the stress relief curves were studied. The results show that the stress relief behavior formulated with the non-dimensional ratio of the released stress and the ratio of h/d is only sensitive to the ratio of the initial principle stresses and the Poisson ratio. The stresses are completely released when h equals 1.6d, and the tensile stresses take place on the bore core surface in the relief measurement process. Finally, a non-complete relief method of annular hole-drilling for measuring surface stress in surrounding rocks is proposed and the procedure is presented.

Mechanism of Stress Relief Cracking in a Granular Bainitic Steel

Coarse-grained heat-affected zone（CGHAZ） of a low alloyed,granular bainitic steel T24 was simulated in a Gleeble apparatus.The stress relief of the CGHAZ was analyzed by annealing the samples.The morphology and behavior of the microstructure near the grain boundaries during stress relief were investigated by means of focused ion beam,in situ tensile testing,transmission electron microscopy,scanning electron microscopy and electron back-scatter diffraction.It was observed that there were large martensite/austenite islands distributed along the grain boundaries of CGHAZ.During stress relief at elevated temperature,the retained austenite at the grain boundaries decomposed into M3C carbides and a ferrite forming softening zone.Together with the stress relief,piled up of dislocations occurred within the ferrite in the area adjacent to the ferrite/M3C interface,which resulted in high level of stress accumulation and caused crack initiation along the grain boundaries.These results indicate that the stress relief induced the grain boundary crack is controlled by other mechanisms rather than the creep-like grain boundary sliding.

Representation of residual stress symbol in the technical product documentation

A representation of residual stress graphic symbols in technical product documents is studied.The residual stress state of the product can be annotated in the technical product documents such as design drawings,process documents,test reports,papers and monographs.The composition of residual stress and the design of basic symbols,measurement method symbols,relief method symbols and state symbols of residual stress,and the representation of annotation for residual stress in documents are introduced.Residual stress symbol can be used in the design,manufacturing,inspection and service for the residual stress state requirements of the products in the mechanical manufacturing industry,as well as in light industry,daily necessities and other related industries.

Numerical Simulation of the Relationship between the Width of Destressed Zone and Blasthole Depth

Overstress in the surrounding rock of the roadway is a key reason that causes failures of deep roadways. Destressing blasting is one of the promising techniques that could improve the supporting quality. If the depth of the pressure relief blast hole is too shallow, the surrounding rock of the roadway will be broken or even collapsed. If the pressure relief blast hole is too deep, the pressure relief area will be located in the deep part of the surrounding rock of the roadway, which cannot achieve the purpose of releasing the stress in the shallow part of the surrounding rock and cause waste of the blast hole. The width or range of the pressure relief area should just fall in the high stress area of the surrounding rock of the roadway, so the pressure relief blast hole should have a reasonable depth. In order to quantitatively describe the relationship between borehole depth and the width of the stress relief zone, numerical simulations were carried out in ANSYS according to different borehole depths. The results show that the optimal destressing effect is achieved when borehole depth is 4 m. Peak stress of and is significantly reduced by 30.51% and 49.07% after blasting. Meanwhile, the high-stress area shifts about 4.8 m from the roadside to the depth of surrounding rock, thus a 3.8 m wide stress relief zone is formed around the roadside, thus, the aim of quantizing the effects of destress blasting is achieved.

某跨声速风洞用980 高强度钢的去应力热处理工艺研究

热处理是结构件制造的重要环节,与结构件的制造质量和使用性能紧密相关。对某型号跨声速风洞用980高强度钢去应力热处理工艺进行了研究,采用拉伸试验和-20℃低温冲击试验,对比分析了一次、二次去应力退火试验后980高强度钢的强度和韧性。结果表明,当去应力热处理工艺为去应力退火温度为(450±10)℃,保温时间为10~12 h时,跨声速风洞用980高强度钢材料可获得最优的强度和韧性。试验结果对同类材料的去应力热处理具有一定的借鉴意义。

Combined blasting for protection of gob-side roadway with thick and hard roof

The deformation control of surrounding rock in gobside roadway with thick and hard roof poses a significant challenge to the safety and efficiency of coal mining.To address this issue,a novel approach combining directional and non-directional blasting techniques,known as combined blasting,was proposed.This study focuses on the experimental investigation of the proposed method in the 122108 working face in Caojiatan Coal Mine as the engineering background.The initial phase of the study involves physical model experiments to reveal the underlying mechanisms of combined blasting for protecting gob-side roadway with thick and hard roof.The results demonstrate that this approach effectively accelerates the collapse of thick and hard roofs,enhances the fragmentation and expansion coefficient of gangue,facilitates the filling of the goaf with gangue,and provides support to the overlying strata,thus reducing the subsidence of the overlying strata above the goaf.Additionally,the method involves cutting the main roof into shorter beams to decrease the stress and disrupt stress transmission pathways.Subsequent numerical simulations were conducted to corroborate the findings of the physical model experiments,thus validating the accuracy of the experimental results.Furthermore,field engineering experiments were performed,affirming the efficacy of the combined blasting method in mitigating the deformation of surrounding rock and achieving the desired protection of the gob-side roadway.

基于隧道施工阶段地应力实测数据的岩爆判据研究

云南省蔓金高速草果山隧道属于深埋长隧道,隧道围岩坚硬完整且脆性较高,隧道施工阶段面临着岩爆发生的风险。因此,采用应力解除法进行地应力测量,并基于实测数据结合现场岩爆发生情况与国内外不同的强度判据进行对比,并对岩爆判据的适用性进行分析研究。最后,根据岩爆实际发生的情况和位置对岩爆判据进行验证分析,结果表明:岩爆预测标准除应力指标外,还应使用多因素指标进行综合判别;某种岩爆预测方法不能适用所有地下工程,应结合工程的具体情况,进行岩爆危险性评估,为工程提出岩爆防治措施。同时此研究成果为深埋完整硬岩的岩爆灾害分析预测和防控提供了参考依据。

首山一矿深部地应力分布规律及影响因素

为探讨平顶山首山一矿深部地应力分布规律及其影响因素,基于矿井实测地应力数据,运用构造物理学、岩石力学和数值模拟方法,研究了测点地应力类型、大小和方向分布规律,反演了地应力场分布特征,分析了埋深、岩性和地质构造对地应力的影响,确定了影响地应力分布的主控因素。研究表明:多元回归反演分析法获得的地应力计算值与实测值吻合,相对误差小于20%,结果可靠。矿井煤岩体处于三维压应力状态,煤层主应力关系为S_(H)>S_(V)>S_(h),地应力由矿井北部向南部呈现先增大后减小再增大的变化趋势,地应力为28~44 MPa,属于高应力水平,地应力方向为NEE向。埋深影响地应力大小和类型,随埋深增加主应力增大,应力场类型向准静水压力场过渡;岩性与地应力密切相关,从泥岩到砂岩或灰岩,地应力增大,弹性模量越大地应力越大,地层岩性的差异造成地应力大小离散分布、应力方向偏转角不超过10°;矿井地应力与埋深、弹性模量的关系可表示为σ_(H)=0.0350H+0.4681E−8.5513。地质构造是影响首山一矿地应力分布的主控因素,褶皱形态控制地应力的水平应力分布,向斜内弧应力值大于背斜内弧,且褶皱弯曲程度越大,其内弧地应力越大,应力梯度越大;断层带内应力降低、断层尖灭端应力集中,地应力方向沿着断层走向偏转,与断层走向夹角越大,应力方向偏转角越大;断层切割复式褶皱时,断层与向斜构造组合区应力值大于断层与背斜构造组合区,且断褶构造组合造成地应力方向分布紊乱。

底板动压巷道压裂弱结构体应力转移控制技术

为了满足煤矿安全生产的需要,许多巷道都会布置在煤层底板中,如部分运输大巷、排水巷道、瓦斯抽采巷道等。采动应力容易造成底板巷道围岩应力升高,加剧底板巷道围岩变形,造成支护永久失效、顶板下沉、巷道底鼓、两帮收敛等破坏。针对此,提出了在应力传递路径上实施水力压裂,在指定的区域制造出一定空间形态的水压裂缝网,形成压裂弱结构体,实现区域范围内的应力转移,从而降低巷道区域范围内的应力,控制巷道的围岩稳定性的控制技术,并通过理论分析及现场工程验证等方式,揭示了底板动压巷道压裂弱结构体应力转移的力学机制,建立了相应的力学模型,对压裂弱结构体的合理位置、范围等影响因素进行了求解。得出:(1)压裂弱结构体使局部应力场发生明显变化,出现应力升高区和应力降低区,应力降低区主要分布在弱结构体与采动应力连线的方向上,主要集中在一个拱形的范围内;由于膨胀效应,在与应力来源垂直的方向上产生应力集中,出现应力升高区。(2)最大主应力变化幅度与压裂弱结构体的长轴长L、短轴长H、到巷道的距离P、与巷道连线的水平夹角β、压裂层的强度C及内摩擦角α、压裂的损伤变量D等有关。其中到巷道的距离P对卸压效果影响最大,损伤变量D对卸压效果影响最小。(3)采用提出的计算方法设计了淮北矿业集团袁店一矿的103运输集中巷的卸压方案,工程应用结果表明,底板动压巷道变形速率明显减缓,验证了底板强动压巷道压裂弱结构体应力转移模型的合理性。

松软煤层底板爆破致裂增透模拟试验研究及应用

针对松软煤层爆破增透钻孔施工困难,爆破增透产生的裂隙不发育且易于重新压实的问题,提出在底板岩层开展爆破作业,达到松软煤层增透进而增加瓦斯有效抽采时间的目的。为了监测跨界面应力波传播规律及煤层损伤状况,在实验室构建了物理模型并开展了煤层底板爆破相似模拟试验。同时使用数值模拟的研究方法对煤层底板爆破过程中煤、岩体内部的损伤及裂隙的演化过程进行补充。结果表明:松软煤层底板爆破裂纹沿爆破孔向四周岩体扩展,爆破孔位置和底板煤岩交界面以及煤层内部的破坏较为严重,产生跨界面损伤裂纹。爆炸应力波从松软煤层底板岩层传播到松软煤层时,岩体和松软煤体的交界面产生透射压缩应力波和反射拉伸应力波,透射波作用于松软煤体,使煤层裂隙增加;反射波反作用于岩体,在煤岩交界面形成交叉裂纹,使底板岩层裂隙和松软煤层裂隙贯通,有利于松软煤层的瓦斯垂向运移流动和卸压瓦斯抽采。潘一东煤矿现场应用表明,煤层底板爆破增透后瓦斯抽采纯量及其浓度快速上升,抽采纯量从0.06 m^(3)/min提高到1.46 m^(3)/min,增加了23.33倍;瓦斯浓度从爆破前的10.46%上升到45.50%左右,增加了3.34倍,并且长时间维持在较高水平。研究成果可为深部松软煤层瓦斯高效抽采提供理论基础和技术支持。

飞机结构梁多轴铣削加工程序与工艺优化研究

为解决飞机结构梁铣削加工过程中容易产生变形的问题。针对飞机结构梁类的薄壁腔体难加工零件进行了加工工艺分析和流程设计,此类零件的毛坯残余应力是影响零件加工变形的重要因素,有效的应力释放可以提高零件的加工质量。对此利用UGNX软件进行了数控编程,并利用VERICUT软件进行仿真,以最大切削厚度为目标进行了切削参数优化,优化后的程序能够有效的提高加工效率,并且探讨了以保证加工质量目标的刀轨编程策略和方法,有效的解决了飞机结构梁铣削加工过程中产生变形的问题。