external forces
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2022 ◽  
Vol 166 ◽  
pp. 108438
Yichen Yao ◽  
Honglei Sha ◽  
Yixin Su ◽  
Gexue Ren ◽  
Suyuan Yu

Jiuhui Wu ◽  
Shaokun Yang

Abstract In this paper, a novel kind of anti-gravity technology by non-positive equivalent mass of aircraft is presented to try to reveal UFO flying secrets. Starting with a two-degree-of-freedom system, it is found that the system could produce an infinite acceleration under the condition of zero dynamic equivalent mass[1], and also provide a movement opposite to the direction of the external force under the negative equivalent mass[2]. These two cases with non-positive equivalent mass[3] could both be regarded as a novel kind of anti-gravity technology[4,5], which is also verified by a designed dynamic simulation experiment. For any aircraft that can be regarded as a multi-degree-of-freedom system driven by engine or other external forces[6], the non-positive equivalent mass could be designed out once the external input including gravity and engine exciting forces is known[7]. Thus the anti-gravity technology for any aircraft could be realized, which could also be extended to matters related to flight, such as space ships, missiles, airplanes, etc[8].

2022 ◽  
Vol 2 (1) ◽  
pp. 01-06
Zulkarnain ◽  
Irma Indrayani

This study discusses the effect of China's economic revival on Indonesia's foreign policy orientation. Historically, the relationship between China and Indonesia, which had been severed in 1965 due to ideological conflicts and Indonesia's suspicion of China's support for the Indonesian communist party (PKI), has now been re-establish since the 1990s, which began with China's economic growth. Foreign policy is often caused by a combination of unexpected external forces with unfavorable structural factors. The continued stalemate in China-Indonesia bilateral relations has equally serious consequences for China. China's diplomatic failure against Indonesia has cost China, and that loss cannot be offset by the diplomatic gains generated by the opening of new relations with other ASEAN countries. This study tries to discuss this situation in depth using several approaches to find two variables that become the topic of this thesis: the rise of the Chinese economy and its influence on Indonesia's foreign policy. This research found that Indonesia's bilateral relations with China under the leadership of President Susilo Bambang Yudhoyono ran normatively and without significant fluctuations.

Mathematics ◽  
2022 ◽  
Vol 10 (2) ◽  
pp. 224
Paola Rubbioni

In this paper, we study a semilinear integro-differential inclusion in Banach spaces, under the action of infinitely many impulses. We provide the existence of mild solutions on a half-line by means of the so-called extension-with-memory technique, which consists of breaking down the problem in an iterate sequence of non-impulsive Cauchy problems, each of them originated by a solution of the previous one. The key that allows us to employ this method is the definition of suitable auxiliary set-valued functions that imitate the original set-valued nonlinearity at any step of the problem’s iteration. As an example of application, we deduce the controllability of a population dynamics process with distributed delay and impulses. That is, we ensure the existence of a pair trajectory-control, meaning a possible evolution of a population and of a feedback control for a system that undergoes sudden changes caused by external forces and depends on its past with fading memory.

2022 ◽  
Vol 6 ◽  
Phoebe Tay ◽  
Bee Chin Ng

Singapore, a young nation with a colonial past from 1819, has seen drastic changes in the sociolinguistic landscape, which has left indelible marks on the Singapore society and the Singapore deaf community. The country has experienced many political and social transitions from British colonialism to attaining independence in 1965 and thereafter. Since independence, English-based bilingualism has been vigorously promoted as part of nation-building. While the roles of the multiple languages in use in Singapore feature prominently in the discourse on language planning, historical records show no mention of how these impacts on the deaf community. The first documented deaf person in archival documents is a Chinese deaf immigrant from Shanghai who established the first deaf school in Singapore in 1954 teaching Shanghainese Sign Language (SSL) and Mandarin. Since then, the Singapore deaf community has seen many shifts and transitions in education programming for deaf children, which has also been largely influenced by exogeneous factors such as trends in deaf education in the United States A pivotal change that has far-reaching impact on the deaf community today, is the introduction of Signing Exact English (SEE) in 1976. This was in keeping with the statal English-based bilingual narrative. The subsequent decision to replace SSL with SEE has dramatic consequences for the current members of the deaf community resulting in internal divisions and fractiousness with lasting implications for the cohesion of the community. This publication traces the origins of Singapore Sign Language (SgSL) by giving readers (and future scholars) a road map on key issues and moments in this history. Bi- and multi-lingualism in Singapore as well as external forces will also be discussed from a social and historical perspective, along with the interplay of different forms of language ideologies. All the different sign languages and sign systems as well as the written/spoken languages used in Singapore, interact and compete with as well as influence each other. There will be an exploration of how both internal factors (local language ecology) and external factors (international trends and developments in deaf education), impact on how members of the deaf community negotiate their deaf identities.

2022 ◽  
Vol 8 ◽  
Jaemin Lee ◽  
Junhyeok Ahn ◽  
Donghyun Kim ◽  
Seung Hyeon Bang ◽  
Luis Sentis

This paper proposes an online gain adaptation approach to enhance the robustness of whole-body control (WBC) framework for legged robots under unknown external force disturbances. Without properly accounting for external forces, the closed-loop control system incorporating WBC may become unstable, and therefore the desired task goals may not be achievable. To study the effects of external disturbances, we analyze the behavior of our current WBC framework via the use of both full-body and centroidal dynamics. In turn, we propose a way to adapt feedback gains for stabilizing the controlled system automatically. Based on model approximations and stability theory, we propose three conditions to ensure that the adjusted gains are suitable for stabilizing a robot under WBC. The proposed approach has four contributions. We make it possible to estimate the unknown disturbances without force/torque sensors. We then compute adaptive gains based on theoretic stability analysis incorporating the unknown forces at the joint actuation level. We demonstrate that the proposed method reduces task tracking errors under the effect of external forces on the robot. In addition, the proposed method is easy-to-use without further modifications of the controllers and task specifications. The resulting gain adaptation process is able to run in real-time. Finally, we verify the effectiveness of our method both in simulations and experiments using the bipedal robot Draco2 and the humanoid robot Valkyrie.

Cellulose ◽  
2022 ◽  
Eivind Bering ◽  
Jonathan Ø. Torstensen ◽  
Anders Lervik ◽  
Astrid S. de Wijn

Abstract We investigate the dissolution mechanism of cellulose using molecular dynamics simulations in both water and a mixture solvent consisting of water with Na$$^+$$ + , OH$$^-$$ - and urea. As a first computational study of its kind, we apply periodic external forces that mimic agitation of the suspension. Without the agitation, the bundles do not dissolve, neither in water nor solvent. In the solvent mixture the bundle swells with significant amounts of urea entering the bundle, as well as more water than in the bundles subjected to pure water. We also find that the mixture solution stabilizes cellulose sheets, while in water these immediately collapse into bundles. Under agitation the bundles dissolve more easily in the solvent mixture than in water, where sheets of cellulose remain that are bound together through hydrophobic interactions. Our findings highlight the importance of urea in the solvent, as well as the hydrophobic interactions, and are consistent with experimental results. Graphical abstract

2022 ◽  
Vol 13 (1) ◽  
pp. 50
H. A. Mtisi ◽  
K. K. Govender

Although the maize milling industry in South Africa is highly attractive and profitable, new entrants are unsuccessful. Thus, understanding the factors influencing competition is important for developing strategies which can help new entrants to be more resilient and also succeed. A case study of a very successful organization in the industry was conducted using Porters five forces model, to explore the factors influencing competition in the industry. The selected organization employs a differentiation strategy which enables it to constantly improve and introduce new maize meal varieties to serve a wide range of customers. The findings revealed that the selected organization employs resources, capabilities and knowledge in its business processes to sustain its competitive advantage. Thus, it is recommended that firms entering this industry should harmonize internal resources, knowledge, capabilities and external forces to generate a competitive advantage.    Received: 18 November 2021 / Accepted: 30 December 2021 / Published: 5 January 2022

PeerJ ◽  
2022 ◽  
Vol 10 ◽  
pp. e12752
Ryan S. Alcantara ◽  
W. Brent Edwards ◽  
Guillaume Y. Millet ◽  
Alena M. Grabowski

Background Ground reaction forces (GRFs) are important for understanding human movement, but their measurement is generally limited to a laboratory environment. Previous studies have used neural networks to predict GRF waveforms during running from wearable device data, but these predictions are limited to the stance phase of level-ground running. A method of predicting the normal (perpendicular to running surface) GRF waveform using wearable devices across a range of running speeds and slopes could allow researchers and clinicians to predict kinetic and kinematic variables outside the laboratory environment. Purpose We sought to develop a recurrent neural network capable of predicting continuous normal (perpendicular to surface) GRFs across a range of running speeds and slopes from accelerometer data. Methods Nineteen subjects ran on a force-measuring treadmill at five slopes (0°, ±5°, ±10°) and three speeds (2.5, 3.33, 4.17 m/s) per slope with sacral- and shoe-mounted accelerometers. We then trained a recurrent neural network to predict normal GRF waveforms frame-by-frame. The predicted versus measured GRF waveforms had an average ± SD RMSE of 0.16 ± 0.04 BW and relative RMSE of 6.4 ± 1.5% across all conditions and subjects. Results The recurrent neural network predicted continuous normal GRF waveforms across a range of running speeds and slopes with greater accuracy than neural networks implemented in previous studies. This approach may facilitate predictions of biomechanical variables outside the laboratory in near real-time and improves the accuracy of quantifying and monitoring external forces experienced by the body when running.

Water ◽  
2022 ◽  
Vol 14 (1) ◽  
pp. 85
Rong Wang ◽  
John A. Dearing ◽  
Peter G. Langdon

Critical transitions between ecosystem states can be triggered by relatively small external forces or internal perturbations and may show time-lagged or hysteretic recovery. Understanding the precise mechanisms of a transition is important for ecosystem management, but it is hampered by a lack of information about the preceding interactions and associated feedback between different components in an ecosystem. This paper employs a range of data, including paleolimnological, environmental monitoring and documentary sources from lake Erhai and its catchment, to investigate the ecosystem structure and dynamics across multiple trophic levels through the process of eutrophication. A long-term perspective shows the growth and decline of two distinct, but coupled, positive feedback loops: a macrophyte-loop and a phosphorus-recycling-loop. The macrophyte-loop became weaker, and the phosphorus-recycling-loop became stronger during the process of lake eutrophication, indicating that the critical transition was propelled by the interaction of two positive feedback loops with different strengths. For lake restoration, future weakening of the phosphorus-recycling loop or a reduction in external pressures is expected to trigger macrophyte growth and eventually produce clear water conditions, but the speed of recovery will probably depend on the rates of feedback loops and the strength of their coupling.

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