按方法、领域与证据探索科学。

Particle-in-Cell Beam Simulation

The Particle-in-Cell (PIC) method is a powerful computational technique for simulating the dynamics of charged particle beams and plasmas in complex electromagnetic field configurations. By tracking individual macroparticles and self-consistently solving Maxwell's equations on a grid, PIC enables study of collective ef

deep learning

PatchTST

PatchTST is a patch-based Transformer architecture for time series forecasting, introduced by Nie and colleagues in 2023, that cuts each series into overlapping patches treated as tokens and processes channels independently. It balances computational efficiency with strong accuracy on long-horizon forecasting.

quantum computing

Path Integral Monte Carlo

Path Integral Monte Carlo (PIMC) is a computational method for calculating thermodynamic and structural properties of quantum systems using Feynman's path integral formulation. Developed rigorously by David Ceperley and colleagues in the 1990s, PIMC treats quantum particles as classical polymers in a higher-dimensional

bioinformatics

Pathway Enrichment Analysis

Pathway enrichment analysis (PEA) is a statistical approach that takes a list of genes or proteins of interest — typically derived from a differential expression or proteomics experiment — and identifies which pre-defined biological pathways or functional gene sets are represented more often than expected by chance. By

civil engineering

Pavement ME Design

The Mechanistic-Empirical Pavement Design Guide (MEPDG or Pavement ME) is a modern method for designing asphalt pavements that predicts performance (rutting, cracking) using mechanistic stress analysis combined with empirical distress models. Developed by AASHTO in 2008 as a successor to the 1993 AASHTO Empirical Guide

particle physics

PDF Fitting

Parton Distribution Function (PDF) fitting is the process of determining the probability distributions of quarks and gluons inside hadrons using high-energy collision data. PDFs are fundamental inputs to all hadron collider phenomenology, essential for predicting cross-sections, designing triggers, and interpreting new

cryptography

Penetration Testing Methodology

Penetration testing is an authorized, controlled simulated attack on systems, networks, and applications to evaluate their security defenses. Unlike vulnerability assessment (which identifies weaknesses), penetration testing actively exploits vulnerabilities to demonstrate real-world impact, confirm exploitability, and

applied physics

Peng-Robinson Equation of State

The Peng-Robinson equation of state is a cubic model that describes the thermodynamic properties of pure fluids and mixtures. Introduced by Ding-Yu Peng and David Bernard Robinson in 1976, it improves upon earlier models (van der Waals, Redlich-Kwong) by better predicting compressibility factors and phase equilibria, e

topology

Persistent Homology

Persistent homology is a method in topological data analysis that quantifies the multi-scale topological structure of data by tracking connected components, loops, and voids as a scale parameter varies. Introduced by Edelsbrunner, Letscher, and Zomorodian in 2002, it encodes topological features through their birth and

applied physics

PFR Model

The PFR (Plug Flow Reactor) model describes the behavior of a tubular reactor in which fluid elements move through as distinct plugs with no axial mixing. Fluid at the inlet is freshly unreacted; as it travels downstream, reactions progress. This idealized model, formalized by Octave Levenspiel alongside CSTR theory, i

bioinformatics

Pharmacophore Modeling

Pharmacophore modeling identifies the spatial arrangement of molecular features (hydrogen bond donors, acceptors, aromatic rings) that are essential for biological activity. Introduced by Gund in 1977, this ligand-based method creates a three-dimensional pattern that can screen chemical libraries and design new active

materials science

Phase-Field Modeling

Phase-Field Modeling (PFM) is a continuum computational method for simulating microstructure evolution, phase transitions, and interfacial dynamics without explicitly tracking moving boundaries. Developed from Cahn-Ginzburg-Landau theory in the 1950s, PFM represents distinct phases through continuous order parameters t

electrical engineering

Phase-Locked Loop

A Phase-Locked Loop (PLL) is a feedback control system that synchronizes an output oscillator to match the phase and frequency of an input signal. Introduced by Gardner in 1966, PLLs are ubiquitous in communications, radar, clock distribution, and power systems. The PLL continuously adjusts its oscillator frequency to

biomechanics

Photoplethysmography

Photoplethysmography (PPG) measures blood volume changes in tissue using light absorption, providing a non-invasive optical window into cardiovascular dynamics. Originally developed by Hertzman in 1937, PPG is now ubiquitous in pulse oximetry, smartwatches, and research applications for monitoring heart rate, blood oxy

bioinformatics

Phylogenetic Analysis

Phylogenetic analysis reconstructs the evolutionary history of organisms, genes, or proteins by comparing molecular sequence data and estimating the branching tree that best explains observed similarities and differences. Rooted in the work of Felsenstein and colleagues from the 1960s onward, it is a cornerstone techni

genetics

Phylogenetic Independent Contrasts

Phylogenetic Independent Contrasts (PIC) is a comparative statistical method that tests for associations between traits across species while accounting for shared evolutionary history. Developed by Joseph Felsenstein in 1985, PIC solves a fundamental problem in comparative biology: related species share traits due to c

oceanography

Phytoplankton Size Class

Phytoplankton size classification is a fundamental framework for organizing plankton communities and understanding their ecological roles and biogeochemical impacts. Developed by Sieburth, Smetacek, and Lenz in 1978, size classes (pico-, nano-, micro-, macro-phytoplankton) define distinct functional groups with differe

applied physics

Pinch Analysis

Pinch analysis is a systematic method for identifying the minimum energy requirements and optimal heat recovery opportunities in chemical processes. Developed by Bodo Linnhoff and John Flower in 1978, it graphically identifies the 'pinch point'—the most constrained part of the process where heating and cooling demands

music information retrieval

Pitch Detection Algorithm

Pitch detection (or fundamental frequency estimation) is the task of automatically determining the perceived pitch of a monophonic (single-source) audio signal at each moment in time. Formalized by de Cheveigné and Kawahara (2002) through the YIN algorithm, it is foundational to music and speech processing. Pitch detec

remote sensing

Pixel-Based Classification

Pixel-based image classification is a fundamental remote-sensing technique that assigns each individual pixel in a satellite or aerial image to a thematic land-cover category based solely on its spectral values across multiple bands. Systematically surveyed and formalized by Lu and Weng (2007), the approach encompasses

civil engineering

Plastic Hinge Analysis

Plastic hinge analysis is a structural engineering method that determines the load-carrying capacity of a structure by tracking the sequential formation of plastic hinges — localised zones where a cross-section has fully yielded — until a kinematic collapse mechanism is formed. Rooted in plastic theory, it provides a m

telecommunications

Polar Codes

Polar codes, introduced by Erdal Arikan in 2009, are the first constructive family of codes proven to achieve the Shannon capacity of symmetric binary-input memoryless channels. They use recursive construction and successive cancellation decoding, a simple greedy algorithm with theoretical guarantees. Polar codes were

machine learning

Policy Gradient

Policy gradient methods are reinforcement-learning algorithms that optimize a parameterized policy directly by gradient ascent on the expected return, rather than learning action-values and acting greedily. Founded on Ronald Williams' 1992 REINFORCE algorithm and the policy gradient theorem of Sutton and colleagues (20

simulation

Policy Scenario Agent-Based Modeling

Policy Scenario Agent-Based Modeling (PS-ABM) is a simulation method that uses agent-based models to evaluate and compare multiple policy scenarios. Heterogeneous autonomous agents interact under different policy regimes, and emergent system-level outcomes are compared across scenarios to inform evidence-based policy d

simulation

Policy Scenario Analysis

Policy Scenario Analysis is a structured method for evaluating how different policy interventions perform across a range of plausible future states. By pairing specific policy levers with alternative scenarios, analysts can assess robustness, trade-offs, and unintended consequences of policy choices before implementati

simulation

Policy Scenario Cellular Automata

Policy Scenario Cellular Automata (PSCA) combines cellular automata simulation with structured scenario analysis to evaluate how alternative policy decisions reshape spatially distributed systems over time. Each scenario encodes a different set of transition rules or constraints, and the model iterates to reveal diverg

simulation

Policy Scenario Discrete-Event Simulation

Policy Scenario Discrete-Event Simulation combines the event-by-event fidelity of Discrete-Event Simulation with systematic policy scenario analysis to evaluate how different interventions, regulations, or resource allocations change system performance. By running multiple well-defined policy scenarios through the same

simulation

Policy Scenario Microsimulation

Policy Scenario Microsimulation applies microsimulation methods to evaluate and compare the distributional and aggregate effects of alternative policy scenarios on a synthetic population. By simulating individual-level behaviour under each policy regime, researchers can measure winners and losers, fiscal costs, and equ

simulation

Policy Scenario Monte Carlo Simulation

Policy Scenario Monte Carlo Simulation combines pre-defined discrete policy scenarios with probabilistic Monte Carlo sampling to quantify uncertainty in outcomes across each scenario. Rather than evaluating a single stochastic model, analysts define two or more policy alternatives and run thousands of Monte Carlo itera

simulation

Policy Scenario Multi-Objective Optimization

Policy Scenario Multi-Objective Optimization (PS-MOO) integrates explicit policy scenario construction with multi-objective optimization to identify Pareto-optimal policy options across plausible future states. Decision-makers evaluate trade-offs between competing objectives — such as economic efficiency, equity, and e

simulation

Policy Scenario Sensitivity Analysis

Policy Scenario Sensitivity Analysis (PSSA) combines structured scenario planning with formal sensitivity analysis to determine which model inputs and policy parameters most strongly drive outcomes across a set of distinct policy alternatives or future states. It is widely used in public health, climate, energy, and ec

simulation

Policy Scenario System Dynamics

Policy Scenario System Dynamics combines system dynamics modeling with structured scenario analysis to evaluate how different policy interventions affect complex, feedback-driven systems over time. By running multiple policy scenarios through a calibrated stock-and-flow model, analysts can compare long-run outcomes, id

political psychology

Political Tolerance Scale

The Political Tolerance Scale measures willingness to permit unpopular groups to exercise civil liberties and political rights, including free speech, assembly, and voting rights even for groups the respondent strongly opposes. Pioneered by Stouffer (1955) measuring tolerance of communists during McCarthyism and extend

genetics

Polygenic Risk Score

A polygenic risk score (PRS) is a summary measure that aggregates the effects of many genetic variants across the genome to predict an individual's genetic predisposition to disease or other complex traits. Developed initially by Purcell and colleagues in 2007, PRS methods combine genome-wide association study (GWAS) r

control theory

Pontryagin Maximum Principle

The Pontryagin Maximum Principle (PMP) is a fundamental theorem in optimal control theory providing necessary conditions for optimality of a control trajectory. Published by Lev Pontryagin in 1962, PMP generalizes the calculus of variations to control problems with constraints and is the theoretical foundation enabling

text mining

POS Tagging

Part-of-speech tagging assigns a grammatical category label — noun, verb, adjective, and so on — to every word in a text. It is a foundational natural-language-processing task, formalised as a statistical model by Ratnaparkhi (1996) and packaged into widely used toolkits such as Stanford CoreNLP (Manning et al., 2014),

architecture

Post-Occupancy Evaluation

Post-Occupancy Evaluation (POE) is a systematic method for assessing how well a completed building meets the needs and expectations of its occupants, comparing planned performance to actual performance. Formalized by Wolfgang Preiser in the 1980s, POE has become essential for learning what design strategies work, ident

cryptography

Post-Quantum Cryptography (Kyber)

Post-quantum cryptography comprises cryptographic algorithms believed to be secure against both classical and quantum computers. In 2022, NIST standardized post-quantum algorithms including ML-KEM (CRYSTALS-Kyber) for key encapsulation and ML-DSA (CRYSTALS-Dilithium) for signatures. Post-quantum cryptography is essenti

meteorology

Potential Vorticity Inversion

Potential vorticity (PV) inversion is a diagnostic technique that reconstructs atmospheric wind and pressure fields from the spatial distribution of potential vorticity. This method assumes that, in a geostrophically balanced atmosphere, the PV field uniquely determines the balanced circulation around anomalies.

electrical engineering

Power Flow Analysis

Power flow analysis, also called load flow study, is a computational method that determines the steady-state voltage, current, and power distribution across all buses in an electrical power system. Developed by Ward and Hale in 1956, it is fundamental to power system planning, operation, and optimization.

electrical engineering

Power Quality Assessment

Power quality assessment evaluates the suitability of electrical voltage and current waveforms for reliable equipment operation. It measures deviations from ideal sinusoidal waveforms, including voltage sags, swells, harmonics, transients, and imbalance. Comprehensive assessment is critical for ensuring equipment prote

signal processing

Power Spectral Density Estimation

Power Spectral Density (PSD) estimation is a set of methods for determining how the power of a signal is distributed across different frequencies. Proposed by Peter Welch in 1967, PSD estimation techniques are fundamental to frequency domain signal analysis, providing insights into the frequency composition of signals

electrical engineering

Power System State Estimation

Power System State Estimation (PSSE) is a real-time algorithm that estimates the voltage and phase angle at every bus in a power grid from a set of noisy, redundant measurements. Introduced by Schweppe in 1970, it combines measurements (power flows, voltage magnitudes) with the physical power flow model to produce the

bioinformatics

PPI Network Topology

Protein-protein interaction network analysis identifies and characterizes the structural properties of cellular interaction networks. Pioneered by Uetz and colleagues through large-scale yeast two-hybrid screening, this approach reveals topological features like hubs, modules, and motifs that encode functional organiza

model evaluation

Precision

Precision measures the proportion of positive predictions that were actually correct. It answers the question: 'Of all the cases we predicted as positive, how many were truly positive?' Precision is critical in scenarios where false positives are costly.

model evaluation

Precision-Recall AUC

The Precision-Recall Area Under the Curve (PR AUC) is the area under the curve formed by plotting recall on the x-axis and precision on the y-axis. It is particularly useful for evaluating classifiers on imbalanced datasets, where it is often more informative than ROC AUC.

marketing management

Price Fairness Scale

The Price Fairness Scale (PFS), developed by Xia, Monroe, and Cox (2004), measures customer perception of whether a charged price is fair and reasonable relative to value received and market comparison. Price fairness assessment differs from absolute price satisfaction: customers may perceive a price as high but fair i

machine learning

Principal Component Analysis

Principal Component Analysis (PCA) is an unsupervised dimensionality-reduction method — given its modern textbook treatment by Ian Jolliffe (2002) — that compresses high-dimensional data into fewer dimensions while preserving the maximum possible variance. It re-expresses correlated variables as a small set of uncorrel

machine learning

Principal Components Regression

Principal components regression first compresses a set of correlated predictors into a few principal components — the directions of greatest variance — and then regresses the response on those components. By discarding low-variance directions, PCR stabilizes estimation in the presence of multicollinearity and high dime

control theory

Probabilistic Roadmap

The Probabilistic Roadmap (PRM) method is a motion planning algorithm that builds a pre-computed graph (roadmap) of feasible paths through the configuration space by sampling random configurations and connecting them if collision-free. Introduced by Kavraki et al. in 1996, PRM is powerful for multi-query planning scena

civil engineering

Probabilistic Seismic Hazard Analysis

Probabilistic Seismic Hazard Analysis (PSHA) is a quantitative engineering framework used in civil and geotechnical engineering to estimate the likelihood that ground shaking will exceed a specified intensity level at a site within a given time window. By combining earthquake source geometry, recurrence statistics, and

process mining

Process Mining

Process Mining is a data-driven discipline that extracts knowledge about real-world processes from event logs recorded by information systems. Introduced systematically by Wil van der Aalst, with foundational workflow mining formalized in 2004 and consolidated in the 2016 textbook, the technique bridges data science an

reliability engineering

Prognostics and Remaining Useful Life

Prognostics and Health Management (PHM) is a methodology for predicting the remaining useful life (RUL) of equipment by monitoring its condition and extrapolating degradation trends. Unlike reactive maintenance (wait for failure) or preventive maintenance (fixed schedules), prognostics enable predictive maintenance: ac

text mining

Prompt Engineering

Prompt engineering is the practice of crafting structured natural-language instructions — prompts — to elicit targeted outputs from large language models (LLMs). Formalised by Brown et al. (2020) in the context of GPT-3 and extended by Wei et al. (2022) with chain-of-thought prompting, it encompasses four main strategi

text mining

Propaganda Detection

Propaganda detection is a natural-language-processing task that automatically identifies and labels persuasion and manipulation techniques in text — such as loaded language, oversimplified solutions, bandwagon appeals, and glittering generalities. It builds on the fine-grained propaganda analysis introduced by Da San M

aerospace

Propeller Lifting Line

Propeller lifting line theory is a mathematical framework for analyzing and designing ship propellers by modeling each blade as a lifting line with circulation distribution. Developed by Sydney Goldstein in 1929 and refined by Kerwin and others, the method accounts for blade loading, wake effects, and propeller interac

aerospace

Proportional Navigation

Proportional Navigation (PN) is a guidance law that generates command accelerations proportional to the rate of change of the line-of-sight angle between a pursuer and target. Introduced by Lin-Hsiung Chu in the 1950s, it became the foundation of modern missile guidance systems. PN solves the pursuit-evasion problem by

electrical engineering

Protection Relay Coordination

Protection relay coordination ensures that when a fault occurs, the relay nearest to the fault operates first, isolating only the faulted section while keeping healthy portions of the network energized. This selective clearing strategy minimizes service disruption and is achieved by carefully coordinating pickup curren

bioinformatics

Proteomics Analysis

Proteomics analysis is a systematic pipeline for identifying and quantifying proteins in biological samples using mass spectrometry. Starting from raw spectral data, the workflow searches protein sequence databases, estimates abundance across conditions, applies statistical tests for differential expression, and maps f

linguistics

Prototype Theory

Prototype Theory is a framework for understanding how humans categorize concepts, proposing that categories are organized around prototypes—the most typical or central members. Developed by Eleanor Rosch in 1973, the theory challenges classical logic's view that categories have fixed boundaries defined by necessary-and