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Nilspace Factors for General Uniformity Seminorms, Cubic Exchangeability and Limits
We study a class of measure-theoretic objects that we call
eBook
True Colors of Oceanography
Data graphics shape the way science is communicated, and the color schemes we employ can either faithfully represent or tacitly obscure the data a figure is intended to convey (Tufte, 1983). Tasteful use of color can make data graphics visually appealing and can draw viewers in, engaging the audience and encouraging further inspection of a figure. But wherever color is used to represent numerical values, its role transitions from a mere aesthetic nicety to carrying the responsibility of conveying data honestly and accurately. Yet, biases introduced by some common colormaps have gone widely unrecognized within the oceanographic community. Here, we describe the pitfalls of some commonly used colormaps, provide guidelines on effective, accurate colormap selection, and present a suite of perceptually uniform cmocean colormaps that have been designed for oceanographic data display.
Journal Article
The PopuList: A Database of Populist, Far-Left, and Far-Right Parties Using Expert-Informed Qualitative Comparative Classification (EiQCC)
With a proliferation of scholarly work focusing on populist, far-left, and far-right parties, questions have arisen about the correct ways to ideologically classify such parties. To ensure transparency and uniformity in research, the discipline could benefit from a systematic procedure. In this letter, we discuss how we have employed the method of ‘Expert-informed Qualitative Comparative Classification’ (EiQCC) to construct the newest version of The PopuList (3.0) – a database of populist, far-left, and far-right parties in Europe since 1989. This method takes into account the in-depth knowledge of national party experts while allowing for systematic comparative analysis across cases and over time. We also examine how scholars have made use of the previous versions of the dataset, explain how the new version of The PopuList differs from previous ones, and compare it to other data. We conclude with a discussion of the strengths and limitations of The PopuList dataset.
Journal Article
Blend Segregation in Tablets Manufacturing and Its Effect on Drug Content Uniformity—A Review
Content uniformity (CU) of the active pharmaceutical ingredient is a critical quality attribute of tablets as a dosage form, ensuring reproducible drug potency. Failure to meet the accepted uniformity in the final product may be caused either by suboptimal mixing and insufficient initial blend homogeneity, or may result from further particle segregation during storage, transfer or the compression process itself. This review presents the most relevant powder segregation mechanisms in tablet manufacturing and summarizes the currently available, up-to-date research on segregation and uniformity loss at the various stages of production process—the blend transfer from the bulk container to the tablet press, filling and discharge from the feeding hopper, as well as die filling. Formulation and processing factors affecting the occurrence of segregation and tablets’ CU are reviewed and recommendations for minimizing the risk of content uniformity failure in tablets are considered herein, including the perspective of continuous manufacturing.
Journal Article
High‐Uniformity Threshold Switching HfO2‐Based Selectors with Patterned Ag Nanodots
High‐performance selector devices are essential for emerging nonvolatile memories to implement high‐density memory storage and large‐scale neuromorphic computing. Device uniformity is one of the key challenges which limit the practical applications of threshold switching selectors. Here, high‐uniformity threshold switching HfO2‐based selectors are fabricated by using e‐beam lithography to pattern controllable Ag nanodots (NDs) with high order and uniform size in the cross‐point region. The selectors exhibit excellent bidirectional threshold switching performance, including low leakage current (<1 pA), high on/off ratio (>108), high endurance (>108 cycles), and fast switching speed (≈75 ns). The patterned Ag NDs in the selector help control the number of Ag atoms diffusing into HfO2 and confine the positions to form reproducible filaments. According to the statistical analysis, the Ag NDs selectors show much smaller cycle‐to‐cycle and device‐to‐device variations (CV < 10%) compared to control samples with nonpatterned Ag thin film. Furthermore, when integrating the Ag NDs selector with resistive switching memory in one‐selector‐one‐resistor (1S1R) structure, the reduced selector variation helps significantly reduce the bit error rate in 1S1R crossbar array. The high‐uniformity Ag NDs selectors offer great potential in the fabrication of large‐scale 1S1R crossbar arrays for future memory and neuromorphic computing applications. A high‐performance selector is fabricated by patterning highly ordered Ag nanodots to control the formation of reproducible filaments. The selector exhibits low leakage current <1 pA, high on/off ratio >108, high endurance >108 cycles, fast switching speed ≈75 ns, and excellent uniformity with CV < 10%. It is further integrated into one‐selector‐one‐resistor structure to demonstrate the feasibility of large‐scale array operation.
Journal Article
Non-Uniformities in Heat Exchangers: A Two-Decade Review of Causes, Effects, and Mitigation Strategies
While extensive research has focused on improving the efficiency and performance of heat exchangers (HXs), identifying the underlying causes of performance degradation remains equally important. Flow and temperature non-uniformities are among the most critical factors affecting performance, often reducing thermo-hydraulic efficiency by approximately 5–10%. These non-uniformities commonly manifest as thermal inconsistencies, airflow maldistribution, and uneven refrigerant distribution. Researchers have observed a notable performance degradation—up to 27%—due to flow maldistribution. Therefore, a clear understanding of their causes and effects is essential for developing effective mitigation strategies to enhance system performance. Despite the notable progress in this area, few studies have systematically classified the dominant non-uniformities associated with specific HX types. This article presents a two-decade review of the causes, impacts, and mitigation approaches related to non-uniformities across different HX configurations. The primary objective is to identify the most critical form of non-uniformity affecting performance in each category. This review specifically examines plate heat exchangers (PHXs), finned and tube heat exchangers (FTHXs), microchannel heat exchangers (MCHXs), and printed circuit heat exchangers (PCHXs). It also discusses mathematical models designed to account for non-uniformities in HXs. This article concludes by identifying key research gaps and outlining future directions to support the development of more reliable and energy-efficient HXs.
Journal Article
Binary quartic forms having bounded invariants, and the boundedness of the average rank of elliptic curves
We prove a theorem giving the asymptotic number of binary quartic forms having bounded invariants; this extends, to the quartic case, the classical results of Gauss and Davenport in the quadratic and cubic cases, respectively. Our techniques are quite general and may be applied to counting integral orbits in other representations of algebraic groups. We use these counting results to prove that the average rank of elliptic curves over ℚ, when ordered by their heights, is bounded. In particular, we show that when elliptic curves are ordered by height, the mean size of the 2-Selmer group is 3. This implies that the limsup of the average rank of elliptic curves is at most 1.5.
Journal Article
Simulation Study of Cylinder-to-Cylinder Variation Phenomena and Key Influencing Factors in a Six-Cylinder Natural Gas Engine
Cylinder-to-cylinder variation (CTCV) is a prevalent issue for natural gas (NG) premixed engines with port fuel injection (PFI), which significantly impacts the engine’s power performance, fuel economy, and reliability. Focusing on this issue, this study established a three-dimensional simulation platform based on a six-cylinder natural gas premixed engine. Quantitative analysis was conducted to discuss the differences in the main boundaries, combustion process, and engine power between cylinders. Additionally, influencing factors of CTCV were explored in terms of mixture uniformity and distribution uniformity. The results indicate that, for the NG premixed engine, many parameters vary significantly between cylinders even under the economical operating condition of 1200 rpm. For example, the difference rate in the peak cylinder pressure and peak phase between cylinder 3 and cylinder 2 can reach 23.5% and 24.3%, respectively. Through the design of simulation cases, it was found that improving the mixture uniformity had a more significant impact on CTCV than improving the distribution uniformity. For example, the relative standard deviation (RSD) of peak pressure decreased by 2.15% through mixture uniformity improvement, while it only decreased by 0.39% through distribution uniformity improvement. At a high speed of 1800 rpm, the influence of distribution uniformity on CTCV increased notably, but the influence of mixture uniformity still remained greater than that of distribution uniformity.
Journal Article