Potential Eruption and Current Activity of Anak Krakatau Volcano, Indonesia

Anak Krakatau Volcano is located in the Sunda Strait known for its paroxysmal eruption in 1883. During the January - November 2019 period, seismicity was dominated by types of quakes which indicated the occurrence of magma supply (VA and VB), near-surface volcanic activity (LF, Hybrid, Harmonic Tremors), and volcanic activity above the volcanic surface (eruptions, emission, and continuous tremors). In the period December 2019 - July 2020, there was an increase in the types of quakes near the surface (LF, Hybrid) and the types of quakes on the surface (emission and continuous tremors). Volcanic deformation monitors changes in tilt over the 2019-2020 period associated with pressure releases before, during and after the eruption. The results of GPS data modeling, the shallow pressure source is at a depth of 0.22 km below sea level. Volcanic activity until July 2020 was dominated by activity near and above the volcanic surface associated with the growth of lava domes. The volcanic system of Anak Krakatau is currently an open system, with the potential for eruptions. Strengthening the early warning system for the eruption of Anak Krakatau is important in mitigating efforts and understanding its eruption potential

An Analysis of the Stress Sources and Coping Styles of the Students Majoring in Pre-school Education in Higher Vocational Colleges

Objectives: Internship is an effective transition for students to enter society and work posts. Through internship, students can be helped to understand their own shortcomings, recognize the forthcoming workplace environment, and make timely preparations. Methods: To strengthen the follow-up inspection and supervision of the internship process, and increase the investment in the internship funds, effectively improve the level of internship guidance. Results: Through a questionnaire survey of pre-school education students in a higher vocational college, the problems of pre-school education students in the process of practice are sorted out and analyzed. The research shows that the pre-school students in vocational education are the research subjects and explore the source of stress in practice. Conclusion: The research shows that the stressors and internship pressure of pre-school teachers are controlled by the work control experience; the interaction pressure source and work control experience have significant interactions in the practice pressure. Students should be prepared for the internship, actively reserve the theoretical knowledge needed, and develop a clear career plan. Successfully completed the internship teaching session.

Self-excited air flow passage changing device for periodic pressurization of soft robot

Recently pneumatic-driven soft robots have been widely developed. Usually, the operating principle of this robot is the inflation and deflation of elastic inflatable chambers by air pressure. Some soft robots need rapid and periodic inflation and deflation of their air chambers to generate continuous motion such as progress motion or rotational motion. However, if the soft robot needs to operate far from the air pressure source, long air tubes are required to supply air pressure to its air chambers. As a result, there is a large delay in supplying air pressure to the air chamber, and the motion of the robot slows down. In this paper, we propose a compact device that changes its airflow passages by self-excited motion generated by a supply of continuous airflow. The diameter and the length of the device are 20 and 50 mm, respectively, and can be driven in a small pipe. Our proposed in-pipe mobile robot is connected to the device and can move in a small pipe by dragging the device into it. To apply the device widely to other soft robots, we also discuss a method of adjusting the output pressure and motion frequency.

Designing of control and expulsion equipment for the pitot-static system of passenger airplanes

The article discusses the issue of automating the serial process of bleeding and control of the pitot- static system of passenger airplanes. A functional diagram and basic design of some parts of the combined equipment are proposed. This equipment makes it possible to alternate the above-mentioned operations with great effectiveness. At the system control stage, the pressure or vacuum in it is created by a pressure-vacuum pneumatic unit. This pneumatic unit consists of a compressor and a set of electromagnetic valves that allow the compressor to be connected to the pumping or scavenging line. The value of the generated pressure is regulated by the flow rate in the pressure/scavenging channel and in the venting channel. Simulation of changes in ambient temperature is achieved due to blowing heated or cooled air over the temperature sensors of the aircraft. Pressure or vacuum in the controlled system is created in turn, in each of its lines. At the expulsion stage, a compressed-nitrogen cylinder acts as the pressure source. The pressurized gas passes through the pitot and is released into the atmosphere, cleaning out the contaminations. No manual operations are required for installing and removing connection hoses after connecting the proposed combined equipment to the pitot-static system. Remote-controlled electromagnetic valves connect the channels of the controlled system to the pressure-vacuum pneumatic unit and the source of compressed nitrogen. This reduces the duration of successive operations for the systems maintenance.

An Energy Efficient Method for Controlling Hydraulic Actuators Using Counterbalance Valves with Adjustable Pilot

Counterbalance valves (CBVs) are widely used in hydraulic machines handling gravitational loads. They are usually adopted in hydraulic circuits that set the flow to the actuator with either metering control strategies or primary control strategies. In these circuits, the CBV does not determine the actuator velocity, but it establishes a proper counterpressure that balances the actuator during overrunning loads. A well-known problem of CBVs is the excessive power consumption introduced into the circuit, which is due to an excessive pressurization of the flow supply. This paper presents a solution for using CBVs to control the actuator velocity while also reducing energy consumption. The method consists in controlling the pilot port of the CBV through an external pressure source (adjustable pilot). The solution is first studied analytically, considering all the possible loading conditions at the actuator. Two different control strategies are presented: the "Smart CBV", where the CBV does not control the actuator velocity but it minimizes the system pressure; and the "Smart System" that uses the CBV to efficiently control the actuator velocity during overrunning load conditions. An experimental validation of the proposed solutions is also provided, taking as reference a truck-mounted hydraulic crane. The results of the proposed solutions are compared to those achieved by the traditional circuit of the reference hydraulic crane which uses standard CBVs. For both cases of "Smart CBV" and "Smart System", a remarkable power saving respectively up to 75% and up to 90% is observed.

Self-Excited Air Flow Passage Changing Device for Periodic Pressurization of Soft Robot

Recently pneumatic-driven soft robots have been widely developed. Usually, the operating principle of this robot is the inflation and deflation of elastic inflatable chambers by air pressure. Some soft robots need rapid and periodic inflation and deflation of their air chambers to generate continuous motion such as progress motion or rotational motion. However, if the soft robot needs to operate far from the air pressure source, long air tubes are required to supply air pressure to its air chambers. As a result, there is a large delay in supplying air pressure to the air chamber, and the motion of the robot slow down. In this paper, we propose a compact device that changes its airflow passages by self-excited motion generated by a supply of continuous airflow. The diameter and the length of the device are 20 and 50 mm, respectively, and can be driven in a small pipe. Our proposed in-pipe mobile robot is connected to the device and can move in a small pipe by dragging the device into it. To apply the device widely to other soft robots, we also discuss a method of adjusting the output pressure and motion frequency.

The correlation between workers’ working pressure and physical and mental health analyzed by the job demand-resource stress model

BACKGROUND: Under the background of the information society, teachers’ pressure from work and life is increasing. Meanwhile, the working pressure has a potential inevitable connection with the physical and mental health of teachers. OBJECTIVE: To analyze the correlation between working pressure of workers and mental health status, expand the application of the job demand-resource stress (JD-RS) model in the adjustment of working characteristic pressure, and achieve the coordinated development between working pressure and mental health. METHODS: The occupation of the teacher is taken as the research object. First, the pressure source questionnaire and Symptom Check List 90 (SCL-90) are chosen to measure the working pressure and mental health. Also, the reliability and validity of the pressure source questionnaire are tested. Second, the gender, duty, teaching age, and workload of teachers are chosen as the foundation for comparing and analyzing the impact of various dimensions and project factors on teachers’ working pressure and mental health. Finally, based on the method of univariate linear regression analysis, the correlation between teachers’ working pressure and mental health is analyzed and characterized. RESULTS: The measurement tool based on the pressure source questionnaire has good performance reliability and validity. The five dimensions of Cronbach’s coefficients are all greater than 0.8, and the indicators of fitting all meet psychometrics requirements. Significance analysis shows that different genders, duties, teaching ages, and workloads have different levels of significant influence on teachers’ working pressure and mental health. Linear regression analysis shows that teachers’ working pressure has a significant impact on their physical and mental health, which has a predictive effect. Teachers who bear high-intensity pressure have psychological problems. CONCLUSIONS: The research based on the JD-RS model has a positive role in promoting the balanced and coordinated development of working pressure and the physical and mental health of employed workers.

Suppressing the pressure-source instability in modeling deep-draft vessels with low under-keel clearance in FUNWAVE-TVD

This Coastal and Hydraulics Engineering Technical Note (CHETN) documents the development through verification and validation of three instability-suppressing mechanisms in FUNWAVE-TVD, a Boussinesq-type numerical wave model, when modeling deep-draft vessels with a low under-keel clearance (UKC). Many large commercial ports and channels (e.g., Houston Ship Channel, Galveston, US Army Corps of Engineers [USACE]) are traveled and affected by tens of thousands of commercial vessel passages per year. In a series of recent projects undertaken for the Galveston District (USACE), it was discovered that when deep-draft vessels are modeled using pressure-source mechanisms, they can suffer from model instabilities when low UKC is employed (e.g., vessel draft of 12 m¹ in a channel of 15 m or less of depth), rendering a simulation unstable and obsolete. As an increasingly large number of deep-draft vessels are put into service, this problem is becoming more severe. This presents an operational challenge when modeling large container-type vessels in busy shipping channels, as these often will come as close as 1 m to the bottom of the channel, or even touch the bottom. This behavior would subsequently exhibit a numerical discontinuity in a given model and could severely limit the sample size of modeled vessels. This CHETN outlines a robust approach to suppressing such instability without compromising the integrity of the far-field vessel wave/wake solution. The three methods developed in this study aim to suppress high-frequency spikes generated nearfield of a vessel. They are a shock-capturing method, a friction method, and a viscosity method, respectively. The tests show that the combined shock-capturing and friction method is the most effective method to suppress the local high-frequency noises, while not affecting the far-field solution. A strong test, in which the target draft is larger than the channel depth, shows that there are no high-frequency noises generated in the case of ship squat as long as the shock-capturing method is used.