ZZZhen Zhang

Zhen Zhang

*This is an algorithmically generated author record based on publicly available information.

Zhen Zhang has a total of 7 co-authors. Here are the top co-authors by number of shared publications:


Latest Publications

  • Open Access

    Reflect-Guard: Enhancing LLM Safeguards Against Adversarial Prompts via Logical Self-Reflection

    by Lixing Lin, Juli You, Yue Li, Luyun Lin, Yiqing Wang, Zhen Zhang, Moxuan Zheng

    LLM safety classifiers such as Llama Guard detect overtly harmful prompts well but remain vulnerable to jailbreaks that disguise intent via role-play, fictional framing, or indirect requests. We present Reflect-Guard: Llama-Guard-3-8B fine-tuned via QLoRA to generate a distilled, GPT-4o-mini-sourced safety rationale before its verdict. Using only 1000training examples and a five-condition ablation, we isolate reflection’s contribution from that of ordinary supervised fine-tuning (SFT). SFT on verdict labels alone already accounts for most of the aggregate gain over the un-fine-tuned baseline (WildGuardTest F1: 0.770 → 0.860; JailbreakBench guard bypass rate: 10.3% → 0.0%). Adding reflection does not improve these aggregate numbers further (F1 falls to 0.842, guard bypass rises to 1.8%) but reallocates performance toward adversarially framed inputs: adversarial-subset recall rises from 0.845 (SFT-only) to 0.921 (+7.6 pp), at a cost of −7.9 pp precision on that subset. The same direction holds across three training seeds (paired t-tests, p=0.018 for overall F1 and p=0.027 for adversarial recall), though we interpret these values cautiously given the small number of seeds. Measured inference latency is 17.9× the baseline’s, driven by ∼92 additional reflection tokens per prompt. The same checkpoint, without additional fine-tuning, shows promising zero-shot transfer to a 329-example financial-harm benchmark (F1: 0.868 → 0.929; recall: 0.767 → 0.867, zero false positives); preliminary two-seed evidence, however, suggests the SFT-only condition may match or exceed this result, so we treat the finance improvement as evidence toward generalization rather than a settled advantage of reflection specifically. Benchmarked against WildGuard, PromptGuard, and a prompted (non-fine-tuned) GPT-4o-mini reasoning classifier on the same sets, WildGuard leads on aggregate WildGuardTest F1 (0.887), while Reflect-Guard achieves higher adversarial-subset recall than every evaluated classifier, including WildGuard (0.921 vs. 0.827) and the prompted teacher (0.636). Overall, supervised fine-tuning drives most of the aggregate gain over an un-fine-tuned classifier, while the generated safety rationale yields a narrower, latency-costly improvement specifically in adversarial-subset recall, a precision–recall tradeoff relevant to safety-critical deployments that prioritize recall over inference speed.

  • Open Access

    Bankruptcy Prediction from 10-K Narratives: Evidence from Interpretable Text Scores and Accounting Baselines

    by Zhen Zhang, Moxuan Zheng, Tongchen Zhang, Luyun Lin, Lixing Lin

    This study examines whether context-validated acute distress disclosures in annual Form 10-K filings improve bankruptcy-risk ranking beyond accounting variables. The analysis links U.S. Securities and Exchange Commission filing data, Item 7 Management’s Discussion and Analysis text, and bankruptcy events from the Florida–UCLA–LoPucki Bankruptcy Research Database for fiscal years 2010–2021. The primary sample contains 21,239 nonfinancial firm-year observations and 159 one-year bankruptcy events. The paper develops a Validated Distress Disclosure (VDD) Dictionary that flags going-concern uncertainty, covenant noncompliance, and lender forbearance or waiver after sentence-level context filtering. In the 2019–2021 holdout test, adding VDD indicators to a six-variable Ohlson-related accounting baseline increases the area under the receiver operating characteristic curve (AUC) from 0.8682 to 0.8827 (Δ=0.0146; 95% confidence interval (CI) [0.0040, 0.0275]) and precision–recall AUC (PR-AUC) from 0.0924 to 0.2060 (Δ=0.1136; 95% CI [0.0458, 0.2132]). Benchmark and decomposition tests indicate that the main signal is concentrated in going-concern disclosures and that VDD is best interpreted as an auditable ranking supplement to accounting variables and broader text models, not as a calibrated probability-of-default model.