Design of a New Propulsion Mechanism of Imitating Duck’s Webbed-feet

With the wide application of the underwater vehicle in ocean exploration, bionics propulsion aroused intensive interest among researchers. Bionic locomotion of aquatic animals has the advantages of highly maneuver, power-efficient endurance and so on. In the paper the mechanism of duck’s swimming is studied and a novel bionics propulsion mechanism is designed and analyzed. The mechanics of underwater vehicle is investigated by ADAMS. Dynamics response of the system is analyzed by using numerical method. The simulation results suggest that the designed propulsion mechanism can imitate the movement modes of the duck’s webbed feet, and implement the motion of vehicle in fluid environment. DOI: http://dx.doi.org/10.11591/telkomnika.v11i8.313

SparseCL: Sparse Contrastive Learning for Contradiction Retrieval

Contradiction retrieval refers to identifying and extracting documents that explicitly disagree with or refute the content of a query, which is important to many downstream applications like fact checking and data cleaning. To retrieve contradiction argument to the query from large document corpora, existing methods such as similarity search and crossencoder models exhibit significant limitations. The former struggles to capture the essence of contradiction due to its inherent nature of favoring similarity, while the latter suffers from computational inefficiency, especially when the size of corpora is large. To address these challenges, we introduce a novel approach: SparseCL that leverages specially trained sentence embeddings designed to preserve subtle, contradictory nuances between sentences. Our method utilizes a combined metric of cosine similarity and a sparsity function to efficiently identify and retrieve documents that contradict a given query. This approach dramatically enhances the speed of contradiction detection by reducing the need for exhaustive document comparisons to simple vector calculations. We validate our model using the Arguana dataset, a benchmark dataset specifically geared towards contradiction retrieval, as well as synthetic contradictions generated from the MSMARCO and HotpotQA datasets using GPT-4. Our experiments demonstrate the efficacy of our approach not only in contradiction retrieval with more than 30% accuracy improvements on MSMARCO and HotpotQA across different model architectures but also in applications such as cleaning corrupted corpora to restore high-quality QA retrieval. This paper outlines a promising direction for improving the accuracy and efficiency of contradiction retrieval in large-scale text corpora

Survey of Bias In Text-to-Image Generation: Definition, Evaluation, and Mitigation

The recent advancement of large and powerful models with Text-to-Image (T2I) generation abilities -- such as OpenAI's DALLE-3 and Google's Gemini -- enables users to generate high-quality images from textual prompts. However, it has become increasingly evident that even simple prompts could cause T2I models to exhibit conspicuous social bias in generated images. Such bias might lead to both allocational and representational harms in society, further marginalizing minority groups. Noting this problem, a large body of recent works has been dedicated to investigating different dimensions of bias in T2I systems. However, an extensive review of these studies is lacking, hindering a systematic understanding of current progress and research gaps. We present the first extensive survey on bias in T2I generative models. In this survey, we review prior studies on dimensions of bias: Gender, Skintone, and Geo-Culture. Specifically, we discuss how these works define, evaluate, and mitigate different aspects of bias. We found that: (1) while gender and skintone biases are widely studied, geo-cultural bias remains under-explored; (2) most works on gender and skintone bias investigated occupational association, while other aspects are less frequently studied; (3) almost all gender bias works overlook non-binary identities in their studies; (4) evaluation datasets and metrics are scattered, with no unified framework for measuring biases; and (5) current mitigation methods fail to resolve biases comprehensively. Based on current limitations, we point out future research directions that contribute to human-centric definitions, evaluations, and mitigation of biases. We hope to highlight the importance of studying biases in T2I systems, as well as encourage future efforts to holistically understand and tackle biases, building fair and trustworthy T2I technologies for everyone

Successful transplantation of guinea pig gut microbiota in mice and its effect on pneumonic plague sensitivity

Microbiota-driven variations in the inflammatory response are predicted to regulate host responses to infection. Increasing evidence indicates that the gastrointestinal and respiratory tracts have an intimate relationship with each other. Gut microbiota can influence lung immunity whereby gut-derived injurious factors can reach the lungs and systemic circulation via the intestinal lymphatics. The intestinal microbiota’s ability to resist colonization can be extended to systemic infections or to pathogens infecting distant sites such as the lungs. Unlike the situation with large mammals, the microtus Yersinia pestis 201 strain exhibits strong virulence in mice, but nearly no virulence to large mammals (such as guinea pigs). Hence, to assess whether the intestinal microbiota from guinea pigs was able to affect the sensitivity of mice to challenge infection with the Y. pestis 201 strain, we fed mice with guinea pig diets for two months, after which they were administered 0.5 ml of guinea pig fecal suspension for 30 days by oral gavage. The stools from each mouse were collected on days 0, 15, and 30, DNA was extracted from them, and 16S rRNA sequencing was performed to assess the diversity and composition of the gut microbiota. We found that the intestinal microbiota transplants from the guinea pigs were able to colonize the mouse intestines. The mice were then infected with Yersinia pestis 201 by lung invasion, but no statistical difference was found in the survival rates of the mice that were colonized with the guinea pig’s gut microbiota and the control mice. This indicates that the intestinal microbiota transplantation from the guinea pigs did not affect the sensitivity of the mice to pneumonic plague

Three-Dimensional Optimal Guidance with Lyapunov Redesign for UAV Interception

Three-dimensional guidance laws are designed to intercept non-maneuvering targets and maneuvering targets in this paper. An optimal control approach with constant or time-variant feedback gain is proposed for interception. The cost function is designed with considerations on energy-efficiency and time-efficiency in the transient process. Lyapunov redesign method is applied to treat the target acceleration, where the precise information of target accelerations is not necessarily required. Efficacy of the proposed guidance laws is proved theoretically and verified by simulation results. </jats:p

Study on vibration energy harvesting of offshore platform by energy harvester based on nonlinear energy sink

Under the impacts of waves and other marine environment, the jacket offshore platform has an obvious vibration and generates lots of energy. Meanwhile, the platform may suffer fatigue damage. The vibration energy harvesting of a jacket offshore platform under random waves with a nonlinear energy sink (NES) was investigated, and a NES-Energy harvester (NES-EH) was then designed by combining an electromagnetic linear generator with the NES. Moreover, the dynamic model of the NES-EH-offshore platform was built, and the electromagnetic damping and stiffness of the energy harvester were optimized by analyzing the energy capture efficiency and root mean square reduction of the platform displacement. The effects of NES nonlinear stiffness and damping, peak period and effective wave height of irregular waves on the capture power and width of the NES-EH were also analyzed. The results show that nonlinear stiffness and damping of the NES impact the energy capturing efficiency of the NES-EH; the smaller the damping and nonlinear stiffness, the higher the power captured by electromagnetic damping in the NES-EH. Compared with NES, the NES-EH system has a better effect on the vibration control of the platform and can better capture considerable vibration energy. </jats:p

Research on new technology for offshore heavy oil thermal recovery with rod pumping

Abstract The high-efficient development of heavy oil is difficult for offshore oil field. Based on the mature technology of onshore heavy oil thermal recovery, a new rod pumping technology of “heavy oil steam stimulation along with conventional sucker rod pumping system” is proposed. According to the structure space of aimed offshore platform, we designed one new kind of miniature hydraulic pumping unit with long-stroke, low pumping speed and compact structure. The paper also studies the offshore heavy oil thermal recovery well safety technology, establishes a leakage model of wellhead sealing and a mechanical model of sealed rubber sleeve on downhole nonlinear large deformation. The study shows that a series of equipment for offshore rod pumping oil recovery and the key technology of well safety lay a solid foundation for carrying out rod pumping of offshore heavy oil thermal recovery

Nonlinear Dynamics Behavior of Tethered Submerged Buoy under Wave Loadings

Abstract Tethered submerged buoy is used extensively in the field of marine engineering. In this paper considering the effect of wave, the nonlinear dynamics behavior of tethered submerged buoy is debated under wave loadings. According to Newton’s second law, the dynamic of the system is built. The coupling factor of the system is neglected, the natural frequency is calculated. The dynamic responses of the system are analyzed using Runge–Kutta method. Considering the variety of the steepness kA, the phenomenon of dynamic behavior can be periodic, double periodic and quasi-periodic and so on. The bifurcation diagram and the largest Lyapunov exponent are applied to judge the nonlinear characteristic. It is helpful to understand the dynamic behavior of tethered submerged buoy and design the mooring line of tethered submerge buoy.</jats:p

ANALYSIS OF ENERGY ABSORBING DEVICE BASED ON DAMPED DYNAMIC VIBRATION ABSORBER

Vibrations exist widely in tall buildings, vehicle systems, and ocean platform suffering from environmental loading such as wind, wave or earthquake. With the global concern on energy and environmental issues, energy absorbing from large-scale vibrations becomes a research frontier. A type of damped dynamics vibration energy absorber is built and analyzed in this paper, in which an added mass is connected to the vibration system with the electromagnetic transducer and spring. The relationships between electrical damping ratio, excitation frequency ratio and dimensionless power are analyzed in frequency domain. The optimal parameters for maximizing the power output are discussed in analytical form while taking the inherent mechanical damping of the system into account. The results indicate that when the system has suitable optimal excitation frequency ratio and damping ratio and so on, more power can be obtained. It is helpful for the design of energy absorber devices. </jats:p