Effects of Stance Width and Barbell Placement on Kinematics, Kinetics, and Myoelectric Activity in Back Squats

Barbell placement and stance width both affect lifting performance in the back squat around the sticking region. However, little is known about how these squat conditions separately could affect the lifting performance. Therefore, this study investigated the effects of stance width and barbell placement upon kinematics, kinetics, and myoelectric activity around the sticking region during a three-repetition maximum back squat. Nine men and nine women (body mass: 76.2 ±11.1, age: 24.9 ± 2.6) performed back squats with four different techniques, such as: high-bar narrow stance (HBNS), high-bar wide stance, low-bar narrow stance, and low-bar wide stance where they lifted 99.2 ± 23.6, 92.9 ± 23.6, 102.5 ± 24.7, and 97.1 ± 25.6 kg, respectively. The main findings were that squatting with a low-bar wide stance condition resulted in larger hip contributions to the total moment than the other squat conditions, whereas squatting with an HBNS resulted in greater knee contributions to the total moment together with higher vastus lateralis and less gluteus maximus myoelectric activity. Our findings suggest that training with an HBNS could be beneficial when targeting the knee extensors and plantar flexors, whereas a low-bar wide stance could be beneficial when targeting the hip extensors.

Relayout on the IKM Krupuk Production Section

This industry, established since 2009, is one of the industries for making raw crackers with various kinds of crackers, which is located in simo angin-angin village, sidoarjo city which produces various kinds of crackers, namely casandra crackers, rose crackers, braid crackers and made with quality flour and fuel. to oven, namely with the steam obtained from the boiler / steam boiler. This study aims to design and suggest improvements to the facility layout properly and the flow of materials smoothly, so that the material travel distance is not too long and can reduce the alternating flow of the production process material in CV Andi Jaya with the Activity Relation Chart method with the application blocplan. One indicator that can determine how good a Layout is is by comparing the total moments in the Layout. From the results of the calculation of total moment efficiency using BLOCPLAN shows better results, where there is an increase of 0.52% from the existing condition or initial layout.

Effects of Valve Disc on Flow Characteristics Inside a Swing Check Valve During Opening and Closing Processes

The check valve is one of the most important devices for safety protection of the piping system in thermal and nuclear power plants. As the key component of the check valve, the valve disc accounts for a major effect on the flow characteristics especially during the opening and closing processes. In this paper, a typical swing check valve is taken as the research object. In order to make a comparative study, three working conditions of 30% THA (Turbine Heat Acceptance), 50% THA and 100% THA are selected. Focusing on the effects of valve disc, how does the valve disc motion interact with the flow field around the valve disc is analyzed with the help of the dynamic mesh technology. The results show that under the combined action of fluid force and gravity, the check valve can be opened and closed quickly. During the opening process, the maximum total moment of the disc appears between 45° ∼ 50° opening angle, and during the closing process the maximum total moment occurs when the disc fully closed. The flow field near the valve disc has similar variation rules with the rotation of the valve disc in the three working conditions, and the pressure near the valve disc reaches the maximum value at the moment of opening and closing. This study can provide some suggestions for the further optimal design of similar swing check valve.

New Insights About the Sticking Region in Back Squats: An Analysis of Kinematics, Kinetics, and Myoelectric Activity

The aim of this study was to investigate barbell, joint kinematics, joint kinetics of hip, knee, and ankle in tandem with myoelectric activity around the sticking region in three-repetition maximum (3-RM) back squats among recreationally trained lifters. Unlike previous literature, this study also investigated the event of first-peak deacceleration, which was expected to be the event with the lowest force output. Twenty-five recreationally trained lifters (body mass: 70.8 ± 10.5, age: 24.6 ± 3.4, height: 172 ± 8.5) were tested in 3-RM back squats. A repeated one-way analysis of variance showed that ground reaction force output decreased at first peak deacceleration compared with the other events. Moreover, torso forward lean, hip moment arm, and hip contribution to total moment increased, whereas the knee moment arms and moment contribution to total moment decreased in the sticking region. Also, stable moment arms and moment contributions to total moment were observed for the ankle in the sticking region. Furthermore, the knee extensors together with the soleus muscle decreased myoelectric activity in the post-sticking region, while the gluteus maximus and biceps femoris increased myoelectric activity in the post-sticking region. Our findings suggest that the large hip moment arms and hip contributions to total moment together with a lower myoelectric activity for the hip extensors contribute to a poor biomechanical region for force output and, thereby, to the sticking region among recreationally trained lifters in 3-RM back squats.

Parameterization of the collision-coalescence process using series of basis functions: COLNETv1.0.0 model development using a machine learning approach

A parameterization for the collision-coalescence process is presented, based on the methodology of basis functions. The whole drop spectra is depicted as a linear combination of two lognormal distribution functions, in which all distribution parameters are formulated by means of six distribution moments included in a system of equations, thus eliminating the need of fixing any parameters. This basis functions parameterization avoids the classification of drops in artificial categories such as cloud water (cloud droplets) or rain water (raindrops). The total moment tendencies are calculated using a machine learning approach, in which one deep neural network was trained for each of the total moment orders involved. The neural networks were trained using randomly generated data following a uniform distribution, over a wide range of parameters employed by the parameterization. An analysis of the predicted total moment errors was performed, aimed to stablish the accuracy of the parameterization at reproducing the integrated distribution moments representative of physical variables. The applied machine learning approach shows a good accuracy level when compared to the output of an explicit collision-coalescence model.

A common model to explain similarities between injection-induced and natural earthquake swarms

<p>Fluid injections at depth can trigger seismic swarms and aseismic deformations. Similarly, some natural sequences of seismicity occur clustered in time and space, without a distinguishable mainshock. They are usually interpreted as driven by fluid and/or aseismic processes. Those seismic swarms, natural or injection-induced, present similarities in their behavior, such as a seismic front migration. The effective stress drop, defined as a ratio between seismic moment and cluster size, is also weak for all swarms, when compared to usual earthquakes values. However, the physical processes that drive both types of swarms, and that can explain such similarities are still poorly understood. Here, we propose a mechanical model in which the fluid primarily induces an aseismic slip, which then triggers and drives seismicity within and on the edges of the active zone. This model is validated using a global and precise dataset of 16 swarms, from natural or induced origins, in different geological contexts. Consequently, our measurements of the migration velocity of the seismicity front, and of the effective stress drop for our swarms can be related to the seismic-to-aseismic moment. Using our model, we are then able to compute an estimate of the volume of fluids circulating during natural earthquake swarms, assuming the total moment is related to the volume of fluids. Our study highlights common characteristics and novel insights into the physical processes at play during seismic swarms.</p>

Quantum Phase Transition in Spin Dimer Systems

A magnetic moment fluctuates in both longitudinal and transverse directions. The total moment sum rule is a conservation law that can help us resolve data of neutron scattering into the two components.

Determination of the Overturning Torque of the Cutting Forces of the Knife Actuating Device of the Geokhod

The paper considers the relevance of the research, indicated by the authors in the title of the article. As a result of the studies carried out, it was found that the overturning torque of the cutting forces occurs as a result of the imbalance of the system of cutting forces during the destruction of rocks by the actuating device of the geokhod. It was revealed that the value of the critical overturning torque of cutting forces is influenced by two force factors; this is the projection of the resistance of the soil to cutting on a plane perpendicular to the axis of rotation, as well as the total moment of resistance to cutting. As a result of the study, the critical values of the withdrawal force and overturning torque were obtained for specific mining conditions for the development and the specified geometric parameters of the actuating device of the geokhod. The resulting withdrawal force during the destruction of the face rock by the actuating device causes a deviation of the axis of geokhod rotation from the axis of the working’s route. Therefore, it becomes necessary to constantly monitor the deviation of the geokhod rotation axis from the axis of the working’s route, and, if necessary, to correct the geokhod displacement.