108 research outputs found
StateâofâtheâArt Nonprobabilistic Finite Element Analyses
The finite element analysis of a mechanical system is conventionally performed in the context of deterministic inputs. However, uncertainties associated with material properties, geometric dimensions, subjective experiences, boundary conditions, and external loads are ubiquitous in engineering applications. The most popular techniques to handle these uncertain parameters are the probabilistic methods, in which uncertainties are modeled as random variables or stochastic processes based on a large amount of statistical information on each uncertain parameter. Nevertheless, subjective results could be obtained if insufficient information unavailable and nonprobabilistic methods can be alternatively employed, which has led to elegant procedures for the nonprobabilistic finite element analysis. In this chapter, each nonprobabilistic finite element analysis method can be decomposed as two individual parts, i.e., the core algorithm and preprocessing procedure. In this context, four types of algorithms and two typical preprocessing procedures as well as their effectiveness were described in detail, based on which novel hybrid algorithms can be conceived for the specific problems and the future work in this research field can be fostered
Input-output-based genuine value added and genuine productivity in China\u27s industrial sectors (1995-2010)
The rapid growth of China\u27s economy has brought about huge losses of natural capital in the form of natural resource depletion and damages from carbon emissions. This paper recalculates value added, capital formation, capital stock, and related multifactor productivity in China\u27s industrial sectors by further developing the genuine savings method of the World Bank. The sector-level natural capital loss was calculated using China\u27s official inputâoutput table and their extensions for tracing final consumers. The capital output elasticity in the productivity estimation was adjusted based on these tables. The results show that although the loss of natural capital in China\u27s industrial sectors in terms of value added has slowed, the impacts on their productivity during the past decades is still quite clear
Rec4Ad: A Free Lunch to Mitigate Sample Selection Bias for Ads CTR Prediction in Taobao
Click-Through Rate (CTR) prediction serves as a fundamental component in
online advertising. A common practice is to train a CTR model on advertisement
(ad) impressions with user feedback. Since ad impressions are purposely
selected by the model itself, their distribution differs from the inference
distribution and thus exhibits sample selection bias (SSB) that affects model
performance. Existing studies on SSB mainly employ sample re-weighting
techniques which suffer from high variance and poor model calibration. Another
line of work relies on costly uniform data that is inadequate to train
industrial models. Thus mitigating SSB in industrial models with a
uniform-data-free framework is worth exploring. Fortunately, many platforms
display mixed results of organic items (i.e., recommendations) and sponsored
items (i.e., ads) to users, where impressions of ads and recommendations are
selected by different systems but share the same user decision rationales.
Based on the above characteristics, we propose to leverage recommendations
samples as a free lunch to mitigate SSB for ads CTR model (Rec4Ad). After
elaborating data augmentation, Rec4Ad learns disentangled representations with
alignment and decorrelation modules for enhancement. When deployed in Taobao
display advertising system, Rec4Ad achieves substantial gains in key business
metrics, with a lift of up to +6.6\% CTR and +2.9\% RPM
Joint Optimization of Ranking and Calibration with Contextualized Hybrid Model
Despite the development of ranking optimization techniques, pointwise loss
remains the dominating approach for click-through rate prediction. It can be
attributed to the calibration ability of the pointwise loss since the
prediction can be viewed as the click probability. In practice, a CTR
prediction model is also commonly assessed with the ranking ability. To
optimize the ranking ability, ranking loss (e.g., pairwise or listwise loss)
can be adopted as they usually achieve better rankings than pointwise loss.
Previous studies have experimented with a direct combination of the two losses
to obtain the benefit from both losses and observed an improved performance.
However, previous studies break the meaning of output logit as the
click-through rate, which may lead to sub-optimal solutions. To address this
issue, we propose an approach that can Jointly optimize the Ranking and
Calibration abilities (JRC for short). JRC improves the ranking ability by
contrasting the logit value for the sample with different labels and constrains
the predicted probability to be a function of the logit subtraction. We further
show that JRC consolidates the interpretation of logits, where the logits model
the joint distribution. With such an interpretation, we prove that JRC
approximately optimizes the contextualized hybrid discriminative-generative
objective. Experiments on public and industrial datasets and online A/B testing
show that our approach improves both ranking and calibration abilities. Since
May 2022, JRC has been deployed on the display advertising platform of Alibaba
and has obtained significant performance improvements.Comment: Accepted at KDD 202
COPR: Consistency-Oriented Pre-Ranking for Online Advertising
Cascading architecture has been widely adopted in large-scale advertising
systems to balance efficiency and effectiveness. In this architecture, the
pre-ranking model is expected to be a lightweight approximation of the ranking
model, which handles more candidates with strict latency requirements. Due to
the gap in model capacity, the pre-ranking and ranking models usually generate
inconsistent ranked results, thus hurting the overall system effectiveness. The
paradigm of score alignment is proposed to regularize their raw scores to be
consistent. However, it suffers from inevitable alignment errors and error
amplification by bids when applied in online advertising. To this end, we
introduce a consistency-oriented pre-ranking framework for online advertising,
which employs a chunk-based sampling module and a plug-and-play rank alignment
module to explicitly optimize consistency of ECPM-ranked results. A -based weighting mechanism is adopted to better distinguish the importance
of inter-chunk samples in optimization. Both online and offline experiments
have validated the superiority of our framework. When deployed in Taobao
display advertising system, it achieves an improvement of up to +12.3\% CTR and
+5.6\% RPM
Robust Representation Learning for Unified Online Top-K Recommendation
In large-scale industrial e-commerce, the efficiency of an online
recommendation system is crucial in delivering highly relevant item/content
advertising that caters to diverse business scenarios. However, most existing
studies focus solely on item advertising, neglecting the significance of
content advertising. This oversight results in inconsistencies within the
multi-entity structure and unfair retrieval. Furthermore, the challenge of
retrieving top-k advertisements from multi-entity advertisements across
different domains adds to the complexity. Recent research proves that
user-entity behaviors within different domains exhibit characteristics of
differentiation and homogeneity. Therefore, the multi-domain matching models
typically rely on the hybrid-experts framework with domain-invariant and
domain-specific representations. Unfortunately, most approaches primarily focus
on optimizing the combination mode of different experts, failing to address the
inherent difficulty in optimizing the expert modules themselves. The existence
of redundant information across different domains introduces interference and
competition among experts, while the distinct learning objectives of each
domain lead to varying optimization challenges among experts. To tackle these
issues, we propose robust representation learning for the unified online top-k
recommendation. Our approach constructs unified modeling in entity space to
ensure data fairness. The robust representation learning employs domain
adversarial learning and multi-view wasserstein distribution learning to learn
robust representations. Moreover, the proposed method balances conflicting
objectives through the homoscedastic uncertainty weights and orthogonality
constraints. Various experiments validate the effectiveness and rationality of
our proposed method, which has been successfully deployed online to serve real
business scenarios.Comment: 14 pages, 6 figures, submitted to ICD
Volatility of mixed atmospheric humic-like substances and ammonium sulfate particles
The volatility of organic aerosols remains poorly understood due to the complexity of speciation and multiphase processes. In this study, we extracted humic-like substances (HULIS) from four atmospheric aerosol samples collected at the SORPES station in Nanjing, eastern China, and investigated the volatility behavior of particles at different sizes using a Volatility Tandem Differential Mobility Analyzer (VTDMA). In spite of the large differences in particle mass concentrations, the extracted HULIS from the four samples all revealed very high-oxidation states (O : C > 0.95), indicating secondary formation as the major source of HULIS in Yangtze River Delta (YRD). An overall low volatility was identified for the extracted HULIS, with the volume fraction remaining (VFR) higher than 55% for all the regenerated HULIS particles at the temperature of 280 degrees C. A kinetic mass transfer model was applied to the thermodenuder (TD) data to interpret the observed evaporation pattern of HULIS, and to derive the mass fractions of semi-volatile (SVOC), low-volatility (LVOC) and extremely low-volatility components (ELVOC). The results showed that LVOC and ELVOC dominated (more than 80 %) the total volume of HULIS. Atomizing processes led to a size-dependent evaporation of regenerated HULIS particles, and resulted in more ELVOC in smaller particles. In order to understand the role of interaction between inorganic salts and atmospheric organic mixtures in the volatility of an organic aerosol, the evaporation of mixed samples of ammonium sulfate (AS) and HULIS was measured. The results showed a significant but nonlinear influence of ammonium sulfate on the volatility of HULIS. The estimated fraction of ELVOC in the organic part of the largest particles (145 nm) increased from 26 %, in pure HULIS samples, to 93% in 1 : 3 (mass ratio of HULIS : AS) mixed samples, to 45% in 2 : 2 mixed samples, and to 70% in 3 : 1 mixed samples, suggesting that the interaction with ammonium sulfate tends to decrease the volatility of atmospheric organic compounds. Our results demonstrate that HULIS are important low-volatility, or even extremely low-volatility, compounds in the organic-aerosol phase. As important formation pathways of atmospheric HULIS, multiphase processes, including oxidation, oligomerization, polymerization and interaction with inorganic salts, are indicated to be important sources of low-volatility and extremely low-volatility species of organic aerosols.Peer reviewe
Exceptional evolutionary divergence of human muscle and brain metabolomes parallels human cognitive and physical uniqueness
Metabolite concentrations reflect the physiological states of tissues and cells. However, the role of metabolic changes in species evolution is currently unknown. Here, we present a study of metabolome evolution conducted in three brain regions and two non-neural tissues from humans, chimpanzees, macaque monkeys, and mice based on over 10,000 hydrophilic compounds. While chimpanzee, macaque, and mouse metabolomes diverge following the genetic distances among species, we detect remarkable acceleration of metabolome evolution in human prefrontal cortex and skeletal muscle affecting neural and energy metabolism pathways. These metabolic changes could not be attributed to environmental conditions and were confirmed against the expression of their corresponding enzymes. We further conducted muscle strength tests in humans, chimpanzees, and macaques. The results suggest that, while humans are characterized by superior cognition, their muscular performance might be markedly inferior to that of chimpanzees and macaque monkeys.Publisher PDFPeer reviewe
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