111 research outputs found
Optimal Auctions vs. Anonymous Pricing: Beyond Linear Utility
The revenue optimal mechanism for selling a single item to agents with
independent but non-identically distributed values is complex for agents with
linear utility (Myerson,1981) and has no closed-form characterization for
agents with non-linear utility (cf. Alaei et al., 2012). Nonetheless, for
linear utility agents satisfying a natural regularity property, Alaei et al.
(2018) showed that simply posting an anonymous price is an e-approximation. We
give a parameterization of the regularity property that extends to agents with
non-linear utility and show that the approximation bound of anonymous pricing
for regular agents approximately extends to agents that satisfy this
approximate regularity property. We apply this approximation framework to prove
that anonymous pricing is a constant approximation to the revenue optimal
single-item auction for agents with public-budget utility, private-budget
utility, and (a special case of) risk-averse utility.Comment: Appeared at EC 201
Simple Mechanisms for Non-linear Agents
We consider agents with non-linear preferences given by private values and
private budgets. We quantify the extent to which posted pricing approximately
optimizes welfare and revenue for a single agent. We give a reduction framework
that extends the approximation of multi-agent pricing-based mechanisms from
linear utility to nonlinear utility. This reduction framework is broadly
applicable as Alaei et al. (2012) have shown that mechanisms for linear agents
can generally be interpreted as pricing-based mechanisms. We give example
applications of the framework to oblivious posted pricing (e.g., Chawla et al.,
2010), sequential posted pricing (e.g., Yan, 2011), and virtual surplus
maximization (Myerson, 1981)
Rationality-Robust Information Design: Bayesian Persuasion under Quantal Response
Classic mechanism/information design imposes the assumption that agents are
fully rational, meaning each of them always selects the action that maximizes
her expected utility. Yet many empirical evidence suggests that human decisions
may deviate from this full rationality assumption. In this work, we attempt to
relax the full rationality assumption with bounded rationality. Specifically,
we formulate the bounded rationality of an agent by adopting the quantal
response model (McKelvey and Palfrey, 1995).
We develop a theory of rationality-robust information design in the canonical
setting of Bayesian persuasion (Kamenica and Gentzkow, 2011) with binary
receiver action. We first identify conditions under which the optimal signaling
scheme structure for a fully rational receiver remains optimal or approximately
optimal for a boundedly rational receiver. In practice, it might be costly for
the designer to estimate the degree of the receiver's bounded rationality
level. Motivated by this practical consideration, we then study the existence
and construction of robust signaling schemes when there is uncertainty about
the receiver's bounded rationality level
Competitive Information Disclosure with Multiple Receivers
This paper analyzes a model of competition in Bayesian persuasion in which
two symmetric senders vie for the patronage of multiple receivers by disclosing
information about the qualities (i.e., binary state -- high or low) of their
respective proposals. Each sender is allowed to commit to a signaling policy
where he sends a private (possibly correlated) signal to every receiver. The
sender's utility is a monotone set function of receivers who make a patron to
this sender.
We characterize the equilibrium structure and show that the equilibrium is
not unique (even for simple utility functions). We then focus on the price of
stability (PoS) in the game of two senders -- the ratio between the best of
senders' welfare (i.e., the sum of two senders' utilities) in one of its
equilibria and that of an optimal outcome. When senders' utility function is
anonymous submodular or anonymous supermodular, we analyze the relation between
PoS with the ex ante qualities (i.e., the probability of high
quality) and submodularity or supermodularity of utility functions. In
particular, in both families of utility function, we show that
when the ex ante quality is weakly smaller than , that is, there
exists equilibrium that can achieve welfare in the optimal outcome. On the
other side, we also prove that when the ex ante quality
is larger than , that is, there exists no equilibrium that can
achieve the welfare in the optimal outcome. We also derive the upper bound of
as a function of and the properties of the value
function. Our analysis indicates that the upper bound becomes worse as the ex
ante quality increases or the utility function becomes more
supermodular (resp.\ submodular)
Enhanced Crystallinity of Triple-Cation Perovskite Film via Doping NH\u3csub\u3e4\u3c/sub\u3eSCN
The trap-state density in perovskite films largely determines the photovoltaic performance of perovskite solar cells (PSCs). Increasing the crystal grain size in perovskite films is an effective method to reduce the trap-state density. Here, we have added NH4SCN into perovskite precursor solution to obtain perovskite films with an increased crystal grain size. The perovskite with increased crystal grain size shows a much lower trap-state density compared with reference perovskite films, resulting in an improved photovoltaic performance in PSCs. The champion photovoltaic device has achieved a power conversion efficiency of 19.36%. The proposed method may also impact other optoelectronic devices based on perovskite films
ZnCuInS/ZnSe/ZnS Quantum Dot-Based Downconversion Light-Emitting Diodes and Their Thermal Effect
The quantum dot-based light-emitting diodes (QD-LEDs) were fabricated using blue GaN chips and red-, yellow-, and green-emitting ZnCuInS/ZnSe/ZnS QDs. The power efficiencies were measured as 14.0 lm/W for red, 47.1 lm/W for yellow, and 62.4 lm/W for green LEDs at 2.6 V. The temperature effect of ZnCuInS/ZnSe/ZnS QDs on these LEDs was investigated using CIE chromaticity coordinates, spectral wavelength, full width at half maximum (FWHM), and power efficiency (PE). The thermal quenching induced by the increased surface temperature of the device was confirmed to be one of the important factors to decrease power efficiencies while the CIE chromaticity coordinates changed little due to the low emission temperature coefficients of 0.022, 0.050, and 0.068 nm/°C for red-, yellow-, and green-emitting ZnCuInS/ZnSe/ZnS QDs. These indicate that ZnCuInS/ZnSe/ZnS QDs are more suitable for downconversion LEDs compared to CdSe QDs
Baichuan 2: Open Large-scale Language Models
Large language models (LLMs) have demonstrated remarkable performance on a
variety of natural language tasks based on just a few examples of natural
language instructions, reducing the need for extensive feature engineering.
However, most powerful LLMs are closed-source or limited in their capability
for languages other than English. In this technical report, we present Baichuan
2, a series of large-scale multilingual language models containing 7 billion
and 13 billion parameters, trained from scratch, on 2.6 trillion tokens.
Baichuan 2 matches or outperforms other open-source models of similar size on
public benchmarks like MMLU, CMMLU, GSM8K, and HumanEval. Furthermore, Baichuan
2 excels in vertical domains such as medicine and law. We will release all
pre-training model checkpoints to benefit the research community in better
understanding the training dynamics of Baichuan 2.Comment: Baichuan 2 technical report. Github:
https://github.com/baichuan-inc/Baichuan
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