Wealth Flow Model: Online Portfolio Selection Based on Learning Wealth Flow Matrices

This article proposes a deep learning solution to the online portfolio selection problem based on learning a latent structure directly from a price time series. It introduces a novel wealth flow matrix for representing a latent structure that has special regular conditions to encode the knowledge about the relative strengths of assets in portfolios. Therefore, a wealth flow model (WFM) is proposed to learn wealth flow matrices and maximize portfolio wealth simultaneously. Compared with existing approaches, our work has several distinctive benefits: (1) the learning of wealth flow matrices makes our model more generalizable than models that only predict wealth proportion vectors, and (2) the exploitation of wealth flow matrices and the exploration of wealth growth are integrated into our deep reinforcement algorithm for the WFM. These benefits, in combination, lead to a highly-effective approach for generating reasonable investment behavior, including short-term trend following, the following of a few losers, no self-investment, and sparse portfolios. Extensive experiments on five benchmark datasets from real-world stock markets confirm the theoretical advantage of the WFM, which achieves the Pareto improvements in terms of multiple performance indicators and the steady growth of wealth over the state-of-the-art algorithms.

Multiagent Control of Airplane Wing Stability with “Feathers” under the Flexural Torsional Flutter

This paper proposes a novel method for the unbounded oscillation prevention of an aircraft wing under the flexural torsional flutter, an innovative multiagent attitude to control an aircraft wing with a surface consisting of managed rotating “feathers” (agents). Theoretical evaluation of the method demonstrates its high aptitude to avoid an aircraft wing’s flexural-torsional vibrations via expansion of the model’s ability to dampen the wing oscillations. It potentially allows increasing an aircraft’s speed without misgiving of the flutter. A new way to control an aircraft wing based on the Speed-Gradient methodology is suggested to increase the maximal possible flight speed without a flutter occurrence. Provided experiments demonstrate the theoretical advantage of the multiagent approach to the “feathers” rotation control.

Robust Static Structural System Identification Using Rotations

Deflections are commonly measured in the static structural system identification of structures. Comparatively less attention has been paid to the possibility of measuring rotations for structural system identification purposes, despite the many advantages of using inclinometers, such as a high resolution and being reference free. Although some work using rotations can be found in the literature, this paper, for the very first time, proposes a statistical analysis that justifies the theoretical advantage of measuring rotations. The analytical expressions for the target parameters are obtained via static structural system identification using the constrained observability method first. Combined with the inverse distribution theory, the probability density function of the estimations of the target parameters can be obtained. Comparative studies on a simply supported bridge and a frame structure demonstrate the advantage of measuring rotations regarding the unbiasedness and the extent of variation in the estimations. To achieve robust parameter estimations, four strategies to use redundant rotations are proposed and compared. Numerical verifications on a bridge structure and a high-rise building have shown promising results.

Multidimensional linear cryptanalysis with key difference invariant bias for block ciphers

For block ciphers, Bogdanov et al. found that there are some linear approximations satisfying that their biases are deterministically invariant under key difference. This property is called key difference invariant bias. Based on this property, Bogdanov et al. proposed a related-key statistical distinguisher and turned it into key-recovery attacks on LBlock and TWINE-128. In this paper, we propose a new related-key model by combining multidimensional linear cryptanalysis with key difference invariant bias. The main theoretical advantage is that our new model does not depend on statistical independence of linear approximations. We demonstrate our cryptanalysis technique by performing key recovery attacks on LBlock and TWINE-128. By using the relations of the involved round keys to reduce the number of guessed subkey bits. Moreover, the partial-compression technique is used to reduce the time complexity. We can recover the master key of LBlock up to 25 rounds with about 260.4 distinct known plaintexts, 278.85 time complexity and 261 bytes of memory requirements. Our attack can recover the master key of TWINE-128 up to 28 rounds with about 261.5 distinct known plaintexts, 2126.15 time complexity and 261 bytes of memory requirements. The results are the currently best ones on cryptanalysis of LBlock and TWINE-128.

No Fine-Tuning, No Cry: Robust SVD for Compressing Deep Networks

A common technique for compressing a neural network is to compute the k-rank ℓ2 approximation Ak of the matrix A∈Rn×d via SVD that corresponds to a fully connected layer (or embedding layer). Here, d is the number of input neurons in the layer, n is the number in the next one, and Ak is stored in O((n+d)k) memory instead of O(nd). Then, a fine-tuning step is used to improve this initial compression. However, end users may not have the required computation resources, time, or budget to run this fine-tuning stage. Furthermore, the original training set may not be available. In this paper, we provide an algorithm for compressing neural networks using a similar initial compression time (to common techniques) but without the fine-tuning step. The main idea is replacing the k-rank ℓ2 approximation with ℓp, for p∈[1,2], which is known to be less sensitive to outliers but much harder to compute. Our main technical result is a practical and provable approximation algorithm to compute it for any p≥1, based on modern techniques in computational geometry. Extensive experimental results on the GLUE benchmark for compressing the networks BERT, DistilBERT, XLNet, and RoBERTa confirm this theoretical advantage.

Behandeling van lumbale discushernia: open versus endoscopische discectomie?

Open (micro) discectomie is a routine treatment for patients with a lumbar disc hernia and incapacitating sciatica, resistant to conservative treatment. Alternatively, the full-endoscopic discectomy has been increasingly performed over the past years. While the surgical instrumentation for this approach has improved and the necessary specialized training is widely available, the technique remains challenging for the surgeon and the assumed/theoretical advantage regarding patient morbidity is still unproven. When compared to open (micro) discectomie, the existing literature fails to attribute significant decreases in length of hospital stay or complication rates to the full-endoscopic approach, therefore making the cost-benefit analysis uninteresting due to the higher associated cost. The structural lack of financing of Belgian hospitals leads to intrinsic budgetary limitations which are emphasized if the hospitals have to carry the extra costs related to endoscopic disc surgery themselves.

Dislocation of rotating-hinge total knee arthroplasty

The number of rotating-hinge total knee arthroplasties (RH-TKAs) is increasing. As a result, the number of complications related to these procedures will also increase. RH-TKAs have the theoretical advantage of reducing bone implant stresses and early aseptic loosening. However, these implants also have complication rates that cannot be ignored. If complications occur, the options for revision of these implants are limited. Dislocation of RH-TKAs is rare, with an incidence between 0.7% and 4.4%. If it occurs, this complication must be accurately diagnosed and treated quickly due to the high incidence of neurovascular complications. If the circulatory and neurological systems are not properly assessed or if treatment is delayed, limb ischemia, soft tissue death, and the need for amputation can occur. Dislocation of a RH-TKA is often a difficult problem to treat. A closed reduction should not be attempted, because it is unlikely to be satisfactory. In addition, in patients with dislocation of a RH-TKA, the possibility of component failure or breakage must be considered. Open reduction of the dislocation should be performed urgently, and provision should be made for revision (that is, the necessary instrumentation should be available) of the RH-TKA, if it proves necessary. The mobile part that allows rotation can have various shapes and lengths. This variance in design could explain why the reported outcomes vary and why there is a probability of tibiofemoral dislocation. Cite this article: EFORT Open Rev 2021;6:107-112. DOI: 10.1302/2058-5241.6.200093

Relativism and the Metaphysics of Value: A Comment on Daan Evers

Daan Evers argues that relativists about aesthetic and other types of evaluative language face some distinctive and largely overlooked metaphysical difficulties concerning the nature of the states of affairs that such statements are intended to be about. These difficulties, as Evers notes, all rest on the assumption that evaluative language is representational. Evers takes it that it is only on this assumption that evaluative relativism is distinguished from expressivism. I argue that this is incorrect and that, without falling into some form of expressivism, relativists can and must drop the representational assumption, but that the resulting position is one in which relativism no longer offers any distinctive dialectical or theoretical advantage.

An Assessment of Bayesian Model-Averaged Logistic Regression for Intensive-Care Prognosis

SUMMARYLogistic regression is the standard method for developing prognostic models for intensive care, but this approach does not take into account the uncertainty in the model selected and the uncertainty in its regression coefficients. This weakness can be addressed by adopting a Bayesian model-averaged approach to logistic regression; however, with respect to the dataset used for our study, we found maximum likelihood to be as effective as the more elaborate Bayesian approach, and an implementation of model averaging did not improve performance. Nevertheless, the Bayesian approach has the theoretical advantage that it can exploit prior knowledge about regression coefficient and model probabilities.

Femtolaser Assisted Cataract Surgeryand Toric Lenses in Patients with Astigmatism. Review

The presence of concomitant corneal astigmatism is the most common cause of low visual functions in patients with surgical treatment of cataracts. The implantation of toric intraocular lenses is procedure of choice in the correction of corneal astigmatism from 1.0 DPT and more in patients with cataracts. Successful results depend on several factors, the most important of which: the correct and stable position of the intraocular lens (IOL) in the capsule bag, the absence of residual astigmatism, the choice of the implanted IOL’s model, taking into account material and design of lens elements. Deviation of the cylindrical component by 10 degrees reduces visual acuity up to 35 %. Repeated intervention for the purpose of toric lens reposition, according to the literature, varies from 0,65 to 9 % and is carried out with the rotation of IOL more than 10°. Femtolaser-assisted phacoemulsification allows partially automate the surgical process, making it more efficient and safe, creating a theoretical advantage over manual techniques of surgery. In practice, the capsulorexis formed by the femtolaser is characterized by a regular rounded shape with a given diameter and provides a coating of optical part of IOL for 360°, which, according to various sources, contributes to a lesser degree of decentralization and tilt of the lens in the capsule bag and can be considered as one of the reasons for obtaining a more accurate refractive result and, as a consequence, higher visual functions. The review presents the results of clinical studies of corneal astigmatism correction during standard and femtolaser-assisted phacoemulsification with implantation of various models of toric IOLs: visual acuity, rotational stability, residual astigmatism percentage, wave front change. Researchers continue to discuss the advantages and disadvantages of modern technologies. However, the problem of increasing the predictability of the surgical outcome in order to obtain a higher refractive result both in the early and in the long-term postoperative period remains unquestionable.