Objective Laser-induced breakdown spectroscopy(LIBS)has emerged as a promising technique for rapid,in-situ characterization of rock-core samples owing to minimal sample preparation requirements and simultaneous multi-element detection capability.In geological exploration and resource evaluation,accurate quantification of major elements such as sodium(Na),magnesium(Mg),potassium(K),iron(Fe),calcium(Ca),and aluminum(Al)is essential for assessing mineral composition and economic potential.However,quantitative LIBS analysis of complex geological matrices faces significant challenges:strong pulse-to-pulse intensity fluctuations driven by transient plasma variability,pronounced matrix effects from heterogeneous mineral composition,and microscale surface non-uniformity of pressed powder pellets.Conventional single-shot approaches are susceptible to these disturbances,yielding unstable predictions and limited cross-matrix generalization.The present work aims to develop a practical,hardware-independent approach that exploits repeated-shot statistics to enhance repeatability,accuracy,and dynamic-range coverage of LIBS quantitative models for rock-core analysis. Methods Forty-three certified national reference rock powder samples spanning soils,sediments,and ores were pressed into pellets and measured using a 1064 nm pulsed Nd:YAG LIBS system with a side-axis fiber-coupled spectrometer covering 200-800 nm(Fig.2).For each sample,100 individual laser shots were acquired in a fixed-distance array pattern with 5 mm inter-point spacing;five pre-ablation shots were applied before each sequence to remove surface contamination.Key acquisition parameters are summarized in Tab.1.After outlier rejection,baseline correction,normalization,and z-score standardization,partial least squares(PLS)regression models were independently built for six target elements using 35 training-set samples.A multi-shot fusion strategy was implemented at the prediction stage by arithmetically averaging the 100 per-shot predictions for each test sample,without altering the learned spectrum-to-concentration mapping.To address wide dynamic concentration ranges,a binary high-low modeling scheme was introduced:a low-range sub-model trained in logarithmic concentration space for trace-level sensitivity,a high-range sub-model with concentration-proportional sample weighting for elevated-level robustness,and a tunable Sigmoid gating function for smooth blending of both sub-model outputs(Fig.3). Results and Discussions Single-shot predictions for all six elements exhibited considerable scatter,with large per-sample standard deviations reflecting stochastic plasma fluctuations and local surface non-uniformity(Fig.4(a)).After applying multi-shot fusion,predicted values shifted markedly toward the ideal 1∶1 reference line and residual error bands narrowed substantially across both training and test samples(Fig.4(b)).Quantitatively,test-set root mean square error(RMSE)decreased by 10.5％-66.7％and the coefficient of determination(R2)improved for all six elements(Tab.2).The largest gain was recorded for Fe,whose RMSE dropped from 2.903 wt％to 0.966 wt％(66.7％reduction),consistent with its exceptionally broad concentration span across the sample set;K also benefited markedly,with test-set R2 rising from 0.878 to 0.964 and RMSE falling by 45.8％(Tab.2).These improvements are attributed to statistical averaging of pulse-to-pulse random errors and the broader spatial coverage afforded by the 5 mm-pitch array pattern.For elements whose concentrations span multiple orders of magnitude,the binary high-low PLS framework provided further gains.Taking Fe as the representative example,linear-scale and logarithmic-scale scatter plots confirm that the low-range sub-model systematically underestimates at high concentrations,whereas the high-range sub-model loses precision in the dilute region;the dual-model blend eliminates both deficiencies(Fig.5,Fig.6).Quantitatively,the Sigmoid-gated dual model reduced Fe mean relative error(MRE)from 115.12％(high-range sub-model alone)to 20.11％,while simultaneously lowering RMSE from 0.958 wt％to 0.666 wt％(Tab.3).Consistent MRE and RMSE reductions were observed across all six elements under the binary scheme(Tab.3),confirming that the approach generalizes beyond Fe.The complete inference pipeline processed approximately 1674 spectra per second(0.597 ms per spectrum),confirming real-time suitability for on-site geological deployment. Conclusions A prediction-level multi-shot fusion strategy combined with a binary high-low PLS modeling scheme and a Sigmoid gating mechanism substantially enhances LIBS quantitative stability for complex rock-core matrices.Multi-shot fusion alone reduces RMSE by up to 66.7％,and the binary dual model further suppresses relative errors in the low-concentration region while preserving high-concentration accuracy.Compared with prior approaches based on single-shot spectral normalization or double-pulse hardware enhancement,the proposed framework extracts additional predictive value from repeated-shot data without increasing measurement complexity or hardware cost.Classical PLS regression and statistical aggregation form the sole computational basis,facilitating deployment on portable or industrial LIBS platforms.Millisecond-scale inference satisfies the real-time demands of field geological surveys,resource evaluation,and environmental monitoring.Future research may explore adaptive outlier-aware shot selection,cross-instrument domain adaptation,and more expressive nonlinear regression modules to further improve robustness across extreme matrices and ultra-trace concentration ranges.
Objective Mid-wavelength infrared band covers a key atmospheric window and contains characteristic absorption lines of numerous gas molecules,driving strong demand fortrace gas analysis,target detection,and free-space optical communication.Developing novel mid-infrared detector materials and heterostructures has become a major focus in optoelectronics.The quantum cascade detector(QCD),a photovoltaic device based on intersubband transitions,employs a multi-quantum-well structure.Electrons in the absorbing well are excited from the ground state to an excited state by infrared photons.Subsequently,through a staircase of subband levels formed by coupled quantum wells with energy spacings matching the longitudinal optical phonon energy,photogenerated carriers are directionally transported via LO phonon scattering.Under zero bias,vertical collection of photogenerated carriers is achieved,offering advantages such as zero-bias operation,low dark current noise,and flexible wavelength tunability.However,the low responsivity of QCD devices is mainly limited by two factors.First,the absorption region adopts a quantum-well structure with a small absorption coefficient,making it difficult to fully utilize the incident photons.Second,the multiperiod cascade structure makes the responsivity inversely proportional to the number of periods,requiring the consumption of multiple photons for each electron collected by the external circuit.In addition,thermal backfilling and scattering losses during photogenerated electron transport further reduce the carrier collection efficiency.This work focuses on the issue of low absorption coefficient and reports a mid-infrared QCD structure and device employing a double-well-coupled structure. Methods A double-well coupled structure was designed to enable multichannel transitions from a strongly coupled ground state to several near-degenerate excited states,and the corresponding device is fabricated.Theoretical calculations validate the feasibility of this structure.The QCD structure is grown on a InP substrate via metal-organic chemical vapor deposition,and device fabrication is completed using lithography and etching.The photocurrent spectrum is measured using a Fourier-transform infrared spectroscopy system.Responsivity is calibrated with a blackbody radiation source and a lock-in amplifier.Dark current and R0A are characterized by an Ⅳ source meter,and the detectivity is subsequently derived. Results and Discussions Theoretical calculations indicate that the device achieves an extraction efficiency of 86.5％,a significantly increased transition matrix element,and an absorption intensity of 1.8％,corresponding to a theoretical peak responsivity of 44.6 mA/W.Experimental results show that the fabricated double-well-coupled mid-infrared quantum cascade detector exhibits a peak response wavelength of 4.9 μm and a peak responsivity of 16 mA/W at 77 K(Fig.3).The R0A value is 6× 105 Ω·cm2,and the peak Johnson-noise-limited detectivity reaches 2×1011 Jones(Fig.5),which is consistent with the theoretical design values.The discrepancy between the experimental and theoretical results is likely attributable to inferior epitaxial growth quality compared with theoretical predictions. Conclusions A double-well-coupled quantum cascade detector with an operating wavelength of 4.9 μm at 77 K was designed.By optimizing the energy level structure,the theoretical responsivity was successfully increased,and the performance improvement was experimentally demonstrated.The detector exhibits high detectivity and responsivity at 77 K,while still maintaining a response at room temperature,indicating that the double-well-coupled structure offers advantages in terms of flexible energy level design and enhanced device performance.In the future,further improvements in epitaxial material quality will be pursued to achieve even higher performance.
Objective Semiconductor packaged devices often require failure diagnosis under the constraints of noncontact measurement,no package opening,and rapid hotspot localization.In practice,defect induced thermal signatures can be weak and may be obscured by direct current background radiation,slow temperature drift,and asynchronous disturbances.In addition,thermal diffusion in multilayer package structures reduces spatial contrast,which limits localization robustness.This work proposes an electrically excited infrared thermography method that uses internal Joule heating as a defect related heat source,enabling hotspot enhancement and localization without decapsulation. Methods A unipolar sinusoidal electrical excitation with a direct current bias is applied to the specimen,so that defect related conductive paths generate a periodically modulated Joule heating component at the fundamental excitation frequency.An infrared camera records the surface temperature sequence.Pixelwise dual channel orthogonal coherent demodulation is performed by discrete correlation with in phase and quadrature reference signals over an integer number of excitation periods,and the fundamental frequency amplitude plot and phase plot are reconstructed(Fig.1).This demodulation suppresses the direct current background,slow drift,and asynchronous noise.For objective comparison across different excitation conditions,a peak gradient based self calibrated spatial partition is introduced to determine a characteristic hotspot scale,and a coupled metric that jointly reflects peak significance and spatial focusing is constructed for parameter selection;the defect cluster center is obtained using a lightweight unsupervised clustering step(Fig.5,Fig.6). Results and Discussions Experiments were conducted on an electrically overstressed Microcontroller Unit(MCU)specimen in a quad flat package,and the reconstructed amplitude plots exhibit a single peak distribution that is close to Gaussian around the defect;the peak position remains consistent across excitation conditions,demonstrating stable localization(Fig.4).Frequency sweep results show that increasing the frequency markedly reduces the core hotspot area,indicating enhanced spatial focusing(Fig.7(a)),while the peak significance decreases at higher frequencies(Fig.7(c)).Nevertheless,the coupled metric increases overall with frequency(Fig.7(b)),indicating that the gain from spatial focusing exceeds the loss in peak magnitude under the tested conditions.Voltage sweep results indicate that the core area varies weakly with the excitation amplitude and shows larger scatter(Fig.8(a)),whereas the coupled metric exhibits a clear nonlinear trend across the tested range(Fig.8(b)),consistent with the combined influence of peak magnitude and spatial diffusion(Fig.8(c)).Phase plots show a stable phase anomaly region across multiple frequencies(Fig.9).The phase increases with frequency in a nonlinear manner and tends to saturate at higher frequencies(Fig.10),and phase profiles provide repeatable extrema that can serve as an auxiliary and more robust cue for localization(Fig.11,Fig.12).Decapsulation inspection,bare die observation,and emission microscopy(EMMI)comparison confirm that the localized infrared hotspot corresponds to the electrically abnormal region(Fig.13). Conclusions An electrically excited infrared thermography approach combined with orthogonal coherent demodulation is developed for hotspot localization in semiconductor packaged devices without decapsulation.Joint amplitude and phase analysis supports objective parameter selection and improves localization robustness.Under the experimental conditions of this work,a lock in frequency range of 0.5 Hz to 1.25 Hz and an excitation amplitude range of 1.0 V to 1.4 V are more favorable for stable defect detection and localization.
Objective The time delay integration(TDI)CMOS image sensor improves the signal-to-noise ratio(SNR)by accumulating the same image signal over multiple exposures,making it widely applicable in high-SNR-demanding fields such as aerospace,satellite imaging,and semiconductor testing.To further enhance the circuit's SNR,the number of accumulation levels in the analog domain accumulators is increased.However,parasitic capacitance and circuit noise also increase with the higher accumulation stages,which limits the improvement of SNR.Traditional analog accumulators can no longer meet the requirements of such applications.To reduce the impact of parasitic effects on accumulation accuracy,a compensation method utilizing polarity inversion switches and adaptive positive feedback capacitors is introduced.Furthermore,in response to the core technical bottleneck caused by front-end circuit noise,which limits SNR enhancement in high-stage analog accumulators,an innovative architecture for the TDI CMOS image sensor's analog domain accumulator based on fully parallel correlated multi-sampling(CMS)technology is proposed. Methods CMS technology is integrated with the analog domain accumulator using shared capacitors,resulting in a fully parallel CMS-based architecture for the analog domain accumulator(Fig.4)and its circuit timing sequence(Fig.5).This architecture allows the input signal to be sampled and averaged multiple times while enabling signal transfer and accumulation based on its structural characteristics,without the need for additional buffers.The architecture is designed to effectively suppress circuit noise within a more compact chip area,while ensuring that the TDI accumulation line rate remains unaffected,thereby enhancing the SNR performance of the TDI CMOS image sensor analog domain accumulator.By abstracting the mathematical model of CMS technology(Fig.2)and deeply coupling it with the TDI SNR model,the circuit's SNR enhancement is optimized,and a systematic performance evaluation is conducted. Results and Discussions To evaluate the SNR improvement of the proposed architecture after its actual design,an analog domain accumulator based on fully parallel CMS technology was implemented in a 2048×128 TDI CMOS image sensor using a 55 nm CMOS process.Simulations comparing the ideal(Fig.9)and actual(Fig.10)SNR improvements show that the actual SNR improvement closely matches the ideal values,demonstrating a significant enhancement in the circuit's SNR.Simulation of the circuit's effective accumulation order(Fig.11)reveals that the proposed circuit achieves a 128-order accumulation effect,equivalent to the 625.461-order effective accumulation result of the circuit in[10],significantly enhancing the circuit's effective accumulation order.The circuit's quality factor calculation indicates that it performs excellently in terms of power consumption,SNR,and line frequency(Tab.1).Additionally,image processing tests confirm that the circuit effectively suppresses low-frequency noise from the front-end circuit,leading to a noticeable improvement in SNR.This results in fewer imaging noise spots and clearer image quality. Conclusions An analog domain accumulator architecture based on fully parallel correlated multi-sampling technology is designed,utilizing shared capacitors to synchronize correlated multi-sampling and analog accumulation.This approach effectively suppresses circuit noise while maintaining the TDI accumulator's line frequency,achieving a significant improvement in circuit SNR and enabling a higher effective accumulation stage with a more compact chip area.The proposed method,implemented using a 55 nm standard CMOS process,is successfully applied in a 2048-column,128-stage TDI image sensor.Post-layout simulation results show that,at a line frequency of 10.85 kHz,the SNR of the 128-stage accumulation improves by 27.962 dB.Of this,the polarity inversion switch and adaptive positive feedback capacitor method contribute 20.9 dB,while the CMS technology provides an additional 7.062 dB.The power consumption per column is 301 μW,with an area of 0.361 mm2 for the 128-stage accumulator per column.The CMS circuit reduces the area by more than 40％compared to traditional designs,reducing the area of each column of the proposed accumulator to 98.5％.The circuit effectively reduces noise and enhances the SNR,significantly improving imaging accuracy under low-light conditions.
Objective The planning of lunar bases,represented by the International Lunar Research Station,is advancing lunar exploration into a new phase of"long-term utilization and in-situ resource transformation".In-situ resource utilization(ISRU)of lunar regolith is crucial for constructing sustainable lunar habitats.However,the extreme lunar environment and manufacturing processes may introduce internal defects into regolith-based components,posing risks to structural integrity.Thus,developing in-situ non-destructive detection techniques is imperative.While infrared thermography offers significant advantages,its conventional excitation sources(e.g.,halogen lamps,lasers)rely on external power supplies,presenting limitations for long-term lunar surface operations.To address this problem,this study proposes and investigates a novel in-situ infrared thermographic inspection method utilizing concentrated solar energy as the excitation source. Methods A three-dimensional finite element model coupling optical excitation with transient heat transfer was established.Four groups of lunar regolith simulant specimens with standardized dimensions(20 mm× 15 mm× 5 mm)were designed,each containing an array of flat-bottom hole defects at their surface center.These defects varied systematically in diameter(1-4 mm)and burial depth(0.2-0.5 mm).Numerical simulations were conducted under three characteristic scenarios:earth ambient temperature,lunar high-temperature,and lunar low-temperature environment.First,the detection process of a specimen with 1-mm diameter defects was simulated and compared across all three environments.Subsequently,the influence of defect size was analyzed by simulating specimens with defect diameters of 2-4 mm under the lunar low-temperature condition,using a pulsed heating protocol. Results and Discussions From the temperature distribution at typical times in earth ambient temperature scenario(Fig.5),lunar high-temperature scenario(Fig.6),lunar low-temperature scenario(Fig.7),it can be seen that the optimal detection window universally occurs during the late heating to early cooling phases across all scenarios,as the thermal excitation is sufficiently established while background thermal noise remains non-uniform,maximizing the temperature contrast between defects and the substrate.In the lunar high-temperature scenario,the elevated initial temperature combined with intense heating accelerates thermal diffusion,allowing deeper defects to manifest earlier.However,this advantage is offset by a significantly reduced thermal contrast due to the overall high background temperature,which compromises defect contour clarity and identifiable duration.As shown in temperature distribution of specimens with different defect diameters at typical times(Fig.8),under identical excitation conditions,larger defects produce thermal signals with greater robustness and a longer observable time window. Conclusions This study establishes a coupled"optical-thermal"3D finite element simulation model,systematically demonstrating the feasibility of using concentrated solar excited infrared thermography for in-situ defect detection of lunar regolith molten structures.The temperature field evolution trends are generally similar across the three scenarios,with the optimal detection window commonly appearing during the late heating phase to the early cooling phase.The distinction lies in the lunar high-temperature environment,where deeper defects manifest earlier but the excessively high background temperature reduces the recognizability of defect contours.Under identical excitation conditions,larger-sized defects produce thermal signals with stronger robustness and a longer observable time window.
