Supervised Knowledge May Hurt Novel Class Discovery Performance

Novel class discovery (NCD) aims to infer novel categories in an unlabeled dataset by leveraging prior knowledge of a labeled set comprising disjoint but related classes. Given that most existing literature focuses primarily on utilizing supervised knowledge from a labeled set at the methodology level, this paper considers the question: Is supervised knowledge always helpful at different levels of semantic relevance? To proceed, we first establish a novel metric, so-called transfer flow, to measure the semantic similarity between labeled/unlabeled datasets. To show the validity of the proposed metric, we build up a large-scale benchmark with various degrees of semantic similarities between labeled/unlabeled datasets on ImageNet by leveraging its hierarchical class structure. The results based on the proposed benchmark show that the proposed transfer flow is in line with the hierarchical class structure; and that NCD performance is consistent with the semantic similarities (measured by the proposed metric). Next, by using the proposed transfer flow, we conduct various empirical experiments with different levels of semantic similarity, yielding that supervised knowledge may hurt NCD performance. Specifically, using supervised information from a low-similarity labeled set may lead to a suboptimal result as compared to using pure self-supervised knowledge. These results reveal the inadequacy of the existing NCD literature which usually assumes that supervised knowledge is beneficial. Finally, we develop a pseudo-version of the transfer flow as a practical reference to decide if supervised knowledge should be used in NCD. Its effectiveness is supported by our empirical studies, which show that the pseudo transfer flow (with or without supervised knowledge) is consistent with the corresponding accuracy based on various datasets. Code is released at https://github.com/J-L-O/SK-Hurt-NCDComment: TMLR 2023 accepted paper. arXiv admin note: substantial text overlap with arXiv:2209.0912

Modulated reflectivity via a symmetrical metal cladding ferrofluids core waveguide chip

We report results of experiments and calculations that help to clarify the underlying physics of the light matter interaction in a symmetrical metal cladding ferrofluids core waveguide chip. Without applying external magnetic field, the observed tunable reflectivity confirms the formation of regular particle aggregates in the ferrofluids under the excited ultrahigh-order modes. A tentative explanation is proposed based on the competition between the optical trapping effect and the Soret effect as the field intensity increases

Simultaneous enhancement of strength and ductility with nano dispersoids in nano and ultrafine grain metals: a brief review

Grain refinement is the most universal and effective method of strengthening metallic materials, which is known as the “Hall-Petch” relationship. However, when grain size is refined to sub-micro regime (Ultrafine Grain, UFG) or even nano regime (Nano Grain, NG), the plasticity of metallic materials becomes poor. Massive studies indicate that the low strain hardening ability resulted from the enhanced dynamic recovery and lack of dislocation accumulation in fine grains is the main reason for low ductility in UFG/NG metals. To resolve this “strength-ductility” conflict, different strategies have been taken, like bimodal/multimodal structure, nanotwins, gradient structure and intragranular nano dispersoids. Among them, the introduction of nano dispersoids into the fine grains attracted lots of attention due to its wide applicability and great success in simultaneously increasing the strength and ductility of the UFG/NG metal. In addition to the enhanced mechanical performance, the introduced second-phase particle may also bring some extraordinary functional properties into the metallic material. In this paper, a brief view of the strategies to improve ductility of the UFG/NG metals and the relevant toughening mechanisms are revealed. Special attentions are paid to the utilization of intragranular nano dispersoids in Aluminum alloys

Not all knowledge is created equal: mutual distillation of confident knowledge

Mutual knowledge distillation (MKD) improves a model by distilling knowledge from another model. However, \textit{not all knowledge is certain and correct}, especially under adverse conditions. For example, label noise usually leads to less reliable models due to undesired memorization \cite{zhang2017understanding,arpit2017closer}. Wrong knowledge misleads the learning rather than helps. This problem can be handled by two aspects: (i) improving the reliability of a model where the knowledge is from (i.e., knowledge source's reliability); (ii) selecting reliable knowledge for distillation. In the literature, making a model more reliable is widely studied while selective MKD receives little attention. Therefore, we focus on studying selective MKD. Concretely, a generic MKD framework, \underline{C}onfident knowledge selection followed by \underline{M}utual \underline{D}istillation (CMD), is designed. The key component of CMD is a generic knowledge selection formulation, making the selection threshold either static (CMD-S) or progressive (CMD-P). Additionally, CMD covers two special cases: zero-knowledge and all knowledge, leading to a unified MKD framework. Extensive experiments are present to demonstrate the effectiveness of CMD and thoroughly justify the design of CMD. For example, CMD-P obtains new state-of-the-art results in robustness against label noise.Comment: NeurIPS 2022 Workshop(Trustworthy and Socially Responsible Machine Learning) pape

China’s water pricing reforms for irrigation: effectiveness and impact

Irrigation occupies a central position in China’s crop production. However, due to low per capita water resources, much worse, unevenly distributed over regions and time and the rapid increase of water diversions to non-irrigation sectors, irrigation water shortages have become a very serious problem. Without the adoption of effective measures this problem may even threaten China’s food security. Currently, irrigation efficiency is very low in general, irrigation water prices cannot fully recover water supply costs, and irrigation facilities are aging due to the lack of funding for O&M (operation & maintenance). Since water prices are regulated by the government, and not determined by the market, water prices did not work effectively in water allocation. The adoption of more economic incentive measures, such as increasing water prices, has become the main strategy of the Chinese government. Since 1 January 2004, China has carried out a new water pricing regulation. The main objectives of this regulation are that water price should be increased to fully recover water supply cost and that water should be treated as a market good. In non-irrigation sectors, the consensus is that water price could be charged to fully recover water supply cost. However, there is still controversy over the charge of irrigation water pricing. Indeed, increasing water price to fully recover supply cost may seriously affect grain production, and farmers’ income. Past studies in China on these issues mainly focused on the theoretical aspects of the problem, analyzing whether irrigation water price should be increased or not. Little studies have quantified the potential impact of the reforms in China. The following questions need to be elaborated: Are irrigation water pricing reforms effective?; What are the attitudes of the farmers towards the reforms?; How do farmers respond to water pricing reforms?; What comprehensive methods should be adopted to achieve the goals of the reforms? This project is based on the analysis of three case studies (Wudu, Jinghuiqu, and Shijin irrigation districts). Jinghuiqu is located in an arid region, Shijin is located in a semi-arid region and Wudu is located in the more humid Southwest. All the issues mentioned above, have been studied using econometric methods on the basis of the data gathered at the household, field canal, pump, and village level. The study reveals that the farmers’ ability to pay for irrigation water is still low and that the current water prices reflect the farmers’ willingness to pay, which implies that it is in fact very difficult to increase water prices further, let alone fully recover water supply cost. Farmers do not really participate in the irrigation management process, even at the field canal level, which limits the farmers’ willingness to pay. In areas confronted with severe water shortages, such as in the Jinghuiqu and Shijin irrigation districts, it is estimated that the volume of water use significantly affects wheat and maize yields, and the reduction of field water use will lead to the decline of grain production. In such cases, although increasing irrigation water price will encourage farmers to reduce water use, it may also force them to decrease their grain production. These measures affect the farmers’ revenues, which are largely dependent on crop production, thus increasing social inequities. Other policies need to protect weaker groups, such as poor farmers and farmers whose income mainly depends on crops. For instance, water property has still not been initialized and both irrigation bureaus and farmers lack incentives to adopt water-saving technologies. Initiating water property, expanding low-cost water-saving technologies, reforming irrigation management and fostering a water market are all important measures to achieve the policy goals of water-saving. At this point, it is necessary to emphasize that surface water price reforms may deeply affect groundwater resources use, especially in the conjunctive irrigation areas. Without the enhancement of groundwater resources management, saving surface water may lead to more overexploitation of groundwater resources, such was the case in the Jinghuiqu and Shijin irrigation districts. All in all, irrigation water price reforms represent a revolution when compared with traditional irrigation water resource management in China. Comprehensive and integrated policies should be carried out. China being such a large country, reforms cannot be uniform in all areas. Different areas, with different precipitation levels, should adopt different measures. In most parts of South China, volumetric water pricing is not appropriate, since this method requires large infrastructure investments. Collecting water fees on the basis of the farmers’ irrigated area is an alternative policy, although it requires involving farmers in the irrigation management process. Even in the northern regions, the standards of irrigation infrastructure should not be overemphasized and more attention should be paid to the cost-benefits analysis of irrigation investments

Enhanced load transfer by designing mechanical interfacial bonding in carbon nanotube reinforced aluminum composites

International audienc

Controlling the emission from semiconductor quantum dots using ultra-small tunable optical microcavities

We report the control of spontaneous emission from CdSe/ZnS core-shell quantum dots coupled to novel open-access optical microcavities. The cavities are fabricated by focused ion beam milling and provide mode volumes less than a cubic micrometre. The quantum dot emission spectrum, spatial modes and lifetime are all modified substantially by the presence of the cavity, and can be tuned by actively varying the cavity length. An increase in emission rate of 75% is achieved at room temperature, attributed to the Purcell effect in the 'bad emitter' regime. We demonstrate a high degree of control over the emission from the dots, including near single-mode operation and the ability to detect strong emission from individual nanocrystals. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft

Large two-photon absorption of terpyridine-based quadrupolar derivatives : towards their applications in optical limiting and biological imaging

Developing organic chromophores with large two-photon absorption (TPA) in both organic solvents and aqueous media is crucial owing to their applications in solid-state photonic devices and biological imaging. Herein, a series of novel terpyridine-based quadrupolar derivatives have been synthesized. The influences of electron-donating group, type of conjugated bridge, as well as solvent polarity on the molecular TPA properties have been investigated in detail. In contrast to the case in organic solvents, bis(thienyl)-benzothiadiazole as a rigid conjugated bridge will completely quench molecular two-photon emission in aqueous media. However, the combination of alkylcarbazole as the donor and bis(styryl)benzene as a conjugation bridge can enlarge molecular TPA cross-sections in both organic solvent and aqueous media. The reasonable two-photon emission brightness for the organic nanoparticles of chromophores 3–5 in the aqueous media, prepared by the reprecipitation method, enables them to be used as probes for in vivo biological imaging

Genetic analysis of a large Han Chinese family line with schizoaffective psychosis

To locate the specific susceptibility genes of a high incidence of schizoaffective disease (SAD) with autonomic dominant inheritance, we recruited a family group from Henan Province with a high incidence of SAD, including 19 individuals sampled from five generations.We used a genome-wide high-density SNP chip to perform genotype detection. The LINKAGE package and MENDEL programs were used for. The two-point and multipoint analyses were calculated by Merlin and SimWalk2 software to obtain the nonparametric linkage (NPL) value, corresponding P value, and parameter linkage limit of detection (LOD) value.Genome-wide linkage analysis yielded a significant linkage signal located on the short arm of chromosome 19. In the dominant genetic model, the LOD of the multipoint parametric analysis was 2.5, and the nonparametric analysis was 19.4 (P < 0.00001). Further haploid genotype analysis localized the candidate region in the 19p13.3–13.2 region, beginning at rs178414 and ending at rs11668751 with a physical length of approximately 4.9 Mb. We believe that the genes responsible for SAD are in this region

Power Batteries Health Monitoring: A Magnetic Imaging Method Based on Magnetoelectric Sensors

With the popularity of electric vehicles, the ever-increasing demand for high-capacity batteries highlights the need for monitoring the health status of batteries. In this article, we proposed a magnetic imaging technique (MIT) to investigate the health status of power batteries nondestructively. This technique is based on a magnetic sensor array, which consists of a 16-channel high-performance magnetoelectric sensor, and the noise equivalent magnetic induction (NEB) of each channel reaches 3–5 pT/Hz1/2@10 Hz. The distribution of the magnetic field is imaged by scanning the magnetic field variation of different positions on the surface. Therefore, the areas of magnetic anomalies are identified by distinguishing different magnetic field abnormal results. and it may be possible to classify the battery failure, so as to put forward suggestions on the use of the battery. This magnetic imaging method expands the application field of this high-performance magnetoelectric sensor and contributes to the battery’s safety monitoring. Meanwhile, it may also act as an important role in other nondestructive testing fields