The Schwarz primitive triply periodic minimal surface(P-type TPMS)lattice structures are widely used.However,these lattice structures have weak load-bearing capacity compared with other cellular structures.In this pap...The Schwarz primitive triply periodic minimal surface(P-type TPMS)lattice structures are widely used.However,these lattice structures have weak load-bearing capacity compared with other cellular structures.In this paper,an adaptive enhancement design method based on the non-uniform stress distribution in structures with uniform thickness is proposed to design the P-type TPMS lattice structures with higher mechanical properties.Two types of structures are designed by adjusting the adaptive thickness distribution in the TPMS.One keeps the same relative density,and the other keeps the same of non-enhanced region thickness.Compared with the uniform lattice structure,the elastic modulus for the structure with the same relative density increases by more than 17%,and the yield strength increases by more than 10.2%.Three kinds of TPMS lattice structures are fabricated by laser powder bed fusion(L-PBF)with 316L stainless steel to verify the proposed enhanced design.The manufacture-induced geometric deviation between the as-design and as-printed models is measured by micro X-ray computed tomography(μ-CT)scans.The quasi-static compression experimental results of P-type TPMS lattice structures show that the reinforced structures have stronger elastic moduli,ultimate strengths,and energy absorption capabilities than the homogeneous P-TPMS lattice structure.展开更多
In recent scenario of Wireless Sensor Networks(WSNs),there are many application developed for handling sensitive and private data such as military information,surveillance data,tracking,etc.Hence,the sensor nodes of W...In recent scenario of Wireless Sensor Networks(WSNs),there are many application developed for handling sensitive and private data such as military information,surveillance data,tracking,etc.Hence,the sensor nodes of WSNs are distributed in an intimidating region,which is non-rigid to attacks.The recent research domains of WSN deal with models to handle the WSN communications against malicious attacks and threats.In traditional models,the solution has been made for defending the networks,only to specific attacks.However,in real-time applications,the kind of attack that is launched by the adversary is not known.Additionally,on developing a security mechanism for WSN,the resource constraints of sensor nodes are also to be considered.With that note,this paper presents an Enhanced Security Model with Improved Defensive Routing Mechanism(IDRM)for defending the sensor network from various attacks.Moreover,for efficient model design,the work includes the part of feature evaluation of some general attacks of WSNs.The IDRM also includes determination of optimal secure paths and Node security for secure routing operations.The performance of the proposed model is evaluated with respect to several factors;it is found that the model has achieved better security levels and is efficient than other existing models in WSN communications.It is proven that the proposed IDRM produces 74%of PDR in average and a minimized packet drop of 38%when comparing with the existing works.展开更多
Computer-based conceptual design for routine design has made great strides, yet non-routine design has not been given due attention, and it is still poorly automated. Considering that the function-behavior-structure(...Computer-based conceptual design for routine design has made great strides, yet non-routine design has not been given due attention, and it is still poorly automated. Considering that the function-behavior-structure(FBS) model is widely used for modeling the conceptual design process, a computer-based creativity enhanced conceptual design model(CECD) for non-routine design of mechanical systems is presented. In the model, the leaf functions in the FBS model are decomposed into and represented with fine-grain basic operation actions(BOA), and the corresponding BOA set in the function domain is then constructed. Choosing building blocks from the database, and expressing their multiple functions with BOAs, the BOA set in the structure domain is formed. Through rule-based dynamic partition of the BOA set in the function domain, many variants of regenerated functional schemes are generated. For enhancing the capability to introduce new design variables into the conceptual design process, and dig out more innovative physical structure schemes, the indirect function-structure matching strategy based on reconstructing the combined structure schemes is adopted. By adjusting the tightness of the partition rules and the granularity of the divided BOA subsets, and making full use of the main function and secondary functions of each basic structure in the process of reconstructing of the physical structures, new design variables and variants are introduced into the physical structure scheme reconstructing process, and a great number of simpler physical structure schemes to accomplish the overall function organically are figured out. The creativity enhanced conceptual design model presented has a dominant capability in introducing new deign variables in function domain and digging out simpler physical structures to accomplish the overall function, therefore it can be utilized to solve non-routine conceptual design problem.展开更多
Osteoarthritis (OA) is a degenerative joint disease and a major cause of pain and disability in older adults. We have previously identified epidermal growth factor receptor (EGFR) signaling as an important regulat...Osteoarthritis (OA) is a degenerative joint disease and a major cause of pain and disability in older adults. We have previously identified epidermal growth factor receptor (EGFR) signaling as an important regulator of cartilage matrix degradation during epiphyseal cartilage development. To study its function in OA progression, we performed surgical destabilization of the medial meniscus (DMM) to induce OA in two mouse models with reduced EGFR activity, one with genetic modification (, was/+ mice) and the other one with pharmacological inhibition (gefitinib treatment). Histological analyses and scoring at 3 months post-surgery revealed increased cartilage destruction and accelerated OA progression in both mouse models. TUNEL staining demonstrated that EGFR signaling protects chondrocytes from OA-induced apoptosis, which was further confirmed in primary chondrocyte culture. Immunohistochemistry showed increased aggrecan degradation in these mouse models, which coincides with elevated amounts of ADAMTS5 and matrix metalloproteinase 13 (MMP13), the principle proteinases responsible for aggrecan degradation, in the articular cartilage after DMM surgery. Furthermore, hypoxia-inducible factor 2α (HIF2α), a critical catabolic transcription factor stimulating MMP13 expression during OA, was also upregulated in mice with reduced EGFR signaling. Taken together, our findings demonstrate a primarily protective role of EGFR during OA progression by regulating chondrocyte survival and cartilage degradation.展开更多
Periodontitis is an inflammatory autoimmune disease. Treatment should alleviate inflammation, regulate the immune reaction and promote periodontal tissue regeneration. Icariin is the main active ingredient of Epimedii...Periodontitis is an inflammatory autoimmune disease. Treatment should alleviate inflammation, regulate the immune reaction and promote periodontal tissue regeneration. Icariin is the main active ingredient of Epimedii Folium, and it is a promising compound for the enhancement of mesenchymal stem cell function, promotion of bone formation, inhibition of bone resorption, alleviation of inflammation and regulation of immunity. The study investigated the effect of icariin on periodontal tissue regeneration in a minipig model of periodontitis. The minipig model of periodontitis was established. Icariin was injected locally. The periodontal clinical assessment index, a computed tomography(CT) scan, histopathology and enzyme-linked immune sorbent assay(ELISA)were used to evaluate the effects of icariin. Quantitative analysis results 12 weeks post-injection demonstrated that probing depth,gingival recession, attachment loss and alveolar bone regeneration values were(3.72 ± 1.18) mm vs.(6.56 ± 1.47) mm,(1.67 ± 0.59)mm vs.(2.38 ± 0.61) mm,(5.56 ± 1.29) mm vs.(8.61 ± 1.72) mm, and(25.65 ± 5.13) mm3 vs.(9.48 ± 1.78) mm3 in the icariin group and0.9% NaCl group, respectively. The clinical assessment, CT scan, and histopathology results demonstrated significant enhancement of periodontal tissue regeneration in the icariin group compared to the 0.9% NaCl group. The ELISA results suggested that the concentration of interleukin-1 beta(IL-1β) in the icariin group was downregulated compared to the 0.9% NaCl group, which indicates that local injection of icariin relieved local inflammation in a minipig model of periodontitis. Local injection of icariin promoted periodontal tissue regeneration and exerted anti-inflammatory and immunomodulatory function. These results support the application of icariin for the clinical treatment of periodontitis.展开更多
Surface plasmon resonance of noble metal nanoparticles leads to the optical absorption enhancement effects,which have great potential applications in solar cell.By using the general numerical method of discrete dipole...Surface plasmon resonance of noble metal nanoparticles leads to the optical absorption enhancement effects,which have great potential applications in solar cell.By using the general numerical method of discrete dipole approximation (DDA),we study the absorption and scattering properties of two-dimensional square silver nanodisks (2D SSN) arrays on the single crystal silicon solar cell.Based on the effective reflective index model of the single crystal silicon solar cell,we investigate the optical enhancement absorption of light energy by varying the light incident direction,particle size,aspect ratio,and interparticle spacing of the silver nanodisks.The peak values and position of the optical extinction spectra of the 2D square arrays of noble metal nanodisks are obtained with the different array structures.展开更多
Background:The Space Glucose Control (SGC) system is a computer-assisted device combining infusion pumps with the enhanced Model Predictive Control algorithm to achieve the target blood glucose (BG) level safely....Background:The Space Glucose Control (SGC) system is a computer-assisted device combining infusion pumps with the enhanced Model Predictive Control algorithm to achieve the target blood glucose (BG) level safely.The objective of this study was to evaluate the efficacy and safety of glycemic control by SGC with customized BG target range of 5.8-8.9 mmol/L in the critically ill patients.Methods:It is a randomized controlled trial of seventy critically ill patients with mechanical ventilation and hyperglycemia (BG 〉 9.0 mmol/L).Thirty-six patients in the SGC group and 34 in the routine glucose management group were observed for three consecutive days.Target BG for both groups was 5.8-8.9 mmol/L.The primary outcome was the percentage time in the target range.Results:The percentage time within BG target range in the SGC group (69 ± 15%) was significantly higher than in the routine management group (52 ± 24%;P 〈 0.01).No measurement was 〈2.2 mmol/L,and there was only one episode of hypoglycemia (2.3-3.3 mmol/L) in each group.The average BG was significantly lower in the SGC group (7.8 ± 0.7 mmol/L) than in the routine management group (9.1 ± 1.6 mmol/L,P 〈 0.001).Target BG level was reached earlier in the SGC group than routine management group (2.5 ± 2.9 vs.12.1 ± 15.3 h,P =0.001).However,the SGC group performed worse for daily insulin requirement (59.8 ± 39.3 vs.28.4 ± 36.7 U,P =0.001)and sampling interval (2.0 ± 0.5 vs.3.7 ± 0.5 h,P 〈 0.001) than the routine management group did.Multiple linear regression showed that the intervention group remained a significant individual predictor (P 〈 0.001) of the percentage time in target range.Conclusions:The SGC system,with a BG target of 5.8-8.9 mmol/L,resulted in effective and reliable glycemic control with few hypoglycemic episodes in critically ill patients with mechanical ventilation and hyperglycemia.However,the workload was increased.Trial Registration:http://www.clinicaltrials.gov,NCT 02491346;https://www.clinicaltrials.gov/ct2/show/NCT02491346?term=NCT0 2491346&cond=Hyperglycemia&cntry1=ES%3ACN&rank=1.展开更多
Improving simulation performance using activity tracking has attracted attention in the modeling field in recent years.The reference to activity has been successfully used to predict and promote the simulation perform...Improving simulation performance using activity tracking has attracted attention in the modeling field in recent years.The reference to activity has been successfully used to predict and promote the simulation performance.Tracking activity,however,uses only the inherent performance information contained in the models.To extend activity prediction in modeling,we propose the activity enhanced modeling with an activity meta-model at the meta-level.The meta-model provides a set of interfaces to model activity in a specific domain.The activity model transformation in subsequence is devised to deal with the simulation difference due to the heterogeneous activity model.Finally,the resource-aware simulation framework is implemented to integrate the activity models in activity-based simulation.The case study shows the improvement brought on by activity-based simulation using discrete event system specification(DEVS).展开更多
1 IntroductionLiNbO3 optical modulators have become essential transmission devices for current and future wideband fibre-optic communications for both military and telecommunications applications. For many telecommuni...1 IntroductionLiNbO3 optical modulators have become essential transmission devices for current and future wideband fibre-optic communications for both military and telecommunications applications. For many telecommunications applications, only a narrow bandwidth is required and thus resonantly enhancedMach-Zehndermodulators(RE-MZMs)have been developed to improve modulation efficiency at the expense of bandwidth.展开更多
Optical absorption in thin-film solar cells can be improved by using surface plasmons for guiding and confining the light on the nanoscale.We report theoretical and simulation studies of a-Si thin-film solar cells wit...Optical absorption in thin-film solar cells can be improved by using surface plasmons for guiding and confining the light on the nanoscale.We report theoretical and simulation studies of a-Si thin-film solar cells with silver nanocylinders on the surface.We found that surface plasmons increased the cells' spectral response over almost the entire studied solar spectrum.In the ultraviolet range and at wavelengths close to the Si band gap we observed a significant enhancement of the absorption for both thin-film and wafer-based structures.We also performed optimization studies of particle size,inter-particle distance,and dielectric environment,for obtaining maximal absorption within the substrate.A blue-shift of the resonance wavelength with increasing inter-particle distance was observed in the visible range.Cell performance improved at optimal spacing,which strongly depended on the nanoparticle size.Increasing the nanocylinder size was accompanied by the widening of the plasmon resonance band and a red-shift of the plasmon resonance peaks.A weak red-shift and plasmon peak enhancement were observed in the reflectance curve with increasing refractive index of the dielectric spacer.展开更多
Whispered speech enhancement using auditory masking model in modified Mel- domain and Speech Absence Probability (SAP) was proposed. In light of the phonation char- acteristic of whisper, we modify the Mel-frequency...Whispered speech enhancement using auditory masking model in modified Mel- domain and Speech Absence Probability (SAP) was proposed. In light of the phonation char- acteristic of whisper, we modify the Mel-frequency Scaling model. Whispered speech is filtered by the proposed model. Meanwhile, the value of masking threshold for each frequency band is dynamically determined by speech absence probability. Then whispered speech enhancement is conducted by adaptively rectifying the spectrum subtraction coefficients using different masking threshold values. Results of objective and subjective tests on the enhanced whispered signal show that compared with other methods; the proposed method can enhance whispered signal with better subjective auditory quality and less distortion by reducing the music noise and background noise under the masking threshold value.展开更多
基金supported by the National Natural Science Foundation of China(Nos.12002031,12122202U22B2083)+1 种基金the China Postdoctoral Science Foundation(Nos.BX2021038 and 2021M700428)the National Key Research and Development of China(No.2022YFB4601901)。
文摘The Schwarz primitive triply periodic minimal surface(P-type TPMS)lattice structures are widely used.However,these lattice structures have weak load-bearing capacity compared with other cellular structures.In this paper,an adaptive enhancement design method based on the non-uniform stress distribution in structures with uniform thickness is proposed to design the P-type TPMS lattice structures with higher mechanical properties.Two types of structures are designed by adjusting the adaptive thickness distribution in the TPMS.One keeps the same relative density,and the other keeps the same of non-enhanced region thickness.Compared with the uniform lattice structure,the elastic modulus for the structure with the same relative density increases by more than 17%,and the yield strength increases by more than 10.2%.Three kinds of TPMS lattice structures are fabricated by laser powder bed fusion(L-PBF)with 316L stainless steel to verify the proposed enhanced design.The manufacture-induced geometric deviation between the as-design and as-printed models is measured by micro X-ray computed tomography(μ-CT)scans.The quasi-static compression experimental results of P-type TPMS lattice structures show that the reinforced structures have stronger elastic moduli,ultimate strengths,and energy absorption capabilities than the homogeneous P-TPMS lattice structure.
文摘In recent scenario of Wireless Sensor Networks(WSNs),there are many application developed for handling sensitive and private data such as military information,surveillance data,tracking,etc.Hence,the sensor nodes of WSNs are distributed in an intimidating region,which is non-rigid to attacks.The recent research domains of WSN deal with models to handle the WSN communications against malicious attacks and threats.In traditional models,the solution has been made for defending the networks,only to specific attacks.However,in real-time applications,the kind of attack that is launched by the adversary is not known.Additionally,on developing a security mechanism for WSN,the resource constraints of sensor nodes are also to be considered.With that note,this paper presents an Enhanced Security Model with Improved Defensive Routing Mechanism(IDRM)for defending the sensor network from various attacks.Moreover,for efficient model design,the work includes the part of feature evaluation of some general attacks of WSNs.The IDRM also includes determination of optimal secure paths and Node security for secure routing operations.The performance of the proposed model is evaluated with respect to several factors;it is found that the model has achieved better security levels and is efficient than other existing models in WSN communications.It is proven that the proposed IDRM produces 74%of PDR in average and a minimized packet drop of 38%when comparing with the existing works.
基金Supported by National Natural Science Foundation of China (Grant Nos.51375496,51205409)
文摘Computer-based conceptual design for routine design has made great strides, yet non-routine design has not been given due attention, and it is still poorly automated. Considering that the function-behavior-structure(FBS) model is widely used for modeling the conceptual design process, a computer-based creativity enhanced conceptual design model(CECD) for non-routine design of mechanical systems is presented. In the model, the leaf functions in the FBS model are decomposed into and represented with fine-grain basic operation actions(BOA), and the corresponding BOA set in the function domain is then constructed. Choosing building blocks from the database, and expressing their multiple functions with BOAs, the BOA set in the structure domain is formed. Through rule-based dynamic partition of the BOA set in the function domain, many variants of regenerated functional schemes are generated. For enhancing the capability to introduce new design variables into the conceptual design process, and dig out more innovative physical structure schemes, the indirect function-structure matching strategy based on reconstructing the combined structure schemes is adopted. By adjusting the tightness of the partition rules and the granularity of the divided BOA subsets, and making full use of the main function and secondary functions of each basic structure in the process of reconstructing of the physical structures, new design variables and variants are introduced into the physical structure scheme reconstructing process, and a great number of simpler physical structure schemes to accomplish the overall function organically are figured out. The creativity enhanced conceptual design model presented has a dominant capability in introducing new deign variables in function domain and digging out simpler physical structures to accomplish the overall function, therefore it can be utilized to solve non-routine conceptual design problem.
基金supported by ASBMR Research Career Enhancement Award (to LQ)NIH grants AR060991 (to LQ)AR062908 (to ME-I)
文摘Osteoarthritis (OA) is a degenerative joint disease and a major cause of pain and disability in older adults. We have previously identified epidermal growth factor receptor (EGFR) signaling as an important regulator of cartilage matrix degradation during epiphyseal cartilage development. To study its function in OA progression, we performed surgical destabilization of the medial meniscus (DMM) to induce OA in two mouse models with reduced EGFR activity, one with genetic modification (, was/+ mice) and the other one with pharmacological inhibition (gefitinib treatment). Histological analyses and scoring at 3 months post-surgery revealed increased cartilage destruction and accelerated OA progression in both mouse models. TUNEL staining demonstrated that EGFR signaling protects chondrocytes from OA-induced apoptosis, which was further confirmed in primary chondrocyte culture. Immunohistochemistry showed increased aggrecan degradation in these mouse models, which coincides with elevated amounts of ADAMTS5 and matrix metalloproteinase 13 (MMP13), the principle proteinases responsible for aggrecan degradation, in the articular cartilage after DMM surgery. Furthermore, hypoxia-inducible factor 2α (HIF2α), a critical catabolic transcription factor stimulating MMP13 expression during OA, was also upregulated in mice with reduced EGFR signaling. Taken together, our findings demonstrate a primarily protective role of EGFR during OA progression by regulating chondrocyte survival and cartilage degradation.
基金supported by grants from the National Natural Science Foundation of China (grant number 81625005 to Z.F.)High-level Talents of the Beijing Health System (grant number 2014-3-080 to F.Z.)the program for Beijing Science and Technology of Chinese Medicine (grant number JJ2013-11 to F.Z.)
文摘Periodontitis is an inflammatory autoimmune disease. Treatment should alleviate inflammation, regulate the immune reaction and promote periodontal tissue regeneration. Icariin is the main active ingredient of Epimedii Folium, and it is a promising compound for the enhancement of mesenchymal stem cell function, promotion of bone formation, inhibition of bone resorption, alleviation of inflammation and regulation of immunity. The study investigated the effect of icariin on periodontal tissue regeneration in a minipig model of periodontitis. The minipig model of periodontitis was established. Icariin was injected locally. The periodontal clinical assessment index, a computed tomography(CT) scan, histopathology and enzyme-linked immune sorbent assay(ELISA)were used to evaluate the effects of icariin. Quantitative analysis results 12 weeks post-injection demonstrated that probing depth,gingival recession, attachment loss and alveolar bone regeneration values were(3.72 ± 1.18) mm vs.(6.56 ± 1.47) mm,(1.67 ± 0.59)mm vs.(2.38 ± 0.61) mm,(5.56 ± 1.29) mm vs.(8.61 ± 1.72) mm, and(25.65 ± 5.13) mm3 vs.(9.48 ± 1.78) mm3 in the icariin group and0.9% NaCl group, respectively. The clinical assessment, CT scan, and histopathology results demonstrated significant enhancement of periodontal tissue regeneration in the icariin group compared to the 0.9% NaCl group. The ELISA results suggested that the concentration of interleukin-1 beta(IL-1β) in the icariin group was downregulated compared to the 0.9% NaCl group, which indicates that local injection of icariin relieved local inflammation in a minipig model of periodontitis. Local injection of icariin promoted periodontal tissue regeneration and exerted anti-inflammatory and immunomodulatory function. These results support the application of icariin for the clinical treatment of periodontitis.
基金supported by the National Natural Science Foundation of China under Grant No. G050104011004024the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No. A0901040110018512026
文摘Surface plasmon resonance of noble metal nanoparticles leads to the optical absorption enhancement effects,which have great potential applications in solar cell.By using the general numerical method of discrete dipole approximation (DDA),we study the absorption and scattering properties of two-dimensional square silver nanodisks (2D SSN) arrays on the single crystal silicon solar cell.Based on the effective reflective index model of the single crystal silicon solar cell,we investigate the optical enhancement absorption of light energy by varying the light incident direction,particle size,aspect ratio,and interparticle spacing of the silver nanodisks.The peak values and position of the optical extinction spectra of the 2D square arrays of noble metal nanodisks are obtained with the different array structures.
文摘Background:The Space Glucose Control (SGC) system is a computer-assisted device combining infusion pumps with the enhanced Model Predictive Control algorithm to achieve the target blood glucose (BG) level safely.The objective of this study was to evaluate the efficacy and safety of glycemic control by SGC with customized BG target range of 5.8-8.9 mmol/L in the critically ill patients.Methods:It is a randomized controlled trial of seventy critically ill patients with mechanical ventilation and hyperglycemia (BG 〉 9.0 mmol/L).Thirty-six patients in the SGC group and 34 in the routine glucose management group were observed for three consecutive days.Target BG for both groups was 5.8-8.9 mmol/L.The primary outcome was the percentage time in the target range.Results:The percentage time within BG target range in the SGC group (69 ± 15%) was significantly higher than in the routine management group (52 ± 24%;P 〈 0.01).No measurement was 〈2.2 mmol/L,and there was only one episode of hypoglycemia (2.3-3.3 mmol/L) in each group.The average BG was significantly lower in the SGC group (7.8 ± 0.7 mmol/L) than in the routine management group (9.1 ± 1.6 mmol/L,P 〈 0.001).Target BG level was reached earlier in the SGC group than routine management group (2.5 ± 2.9 vs.12.1 ± 15.3 h,P =0.001).However,the SGC group performed worse for daily insulin requirement (59.8 ± 39.3 vs.28.4 ± 36.7 U,P =0.001)and sampling interval (2.0 ± 0.5 vs.3.7 ± 0.5 h,P 〈 0.001) than the routine management group did.Multiple linear regression showed that the intervention group remained a significant individual predictor (P 〈 0.001) of the percentage time in target range.Conclusions:The SGC system,with a BG target of 5.8-8.9 mmol/L,resulted in effective and reliable glycemic control with few hypoglycemic episodes in critically ill patients with mechanical ventilation and hyperglycemia.However,the workload was increased.Trial Registration:http://www.clinicaltrials.gov,NCT 02491346;https://www.clinicaltrials.gov/ct2/show/NCT02491346?term=NCT0 2491346&cond=Hyperglycemia&cntry1=ES%3ACN&rank=1.
基金Project supported by the National Natural Science Foundation of China(Nos.71303252 and 91024030)
文摘Improving simulation performance using activity tracking has attracted attention in the modeling field in recent years.The reference to activity has been successfully used to predict and promote the simulation performance.Tracking activity,however,uses only the inherent performance information contained in the models.To extend activity prediction in modeling,we propose the activity enhanced modeling with an activity meta-model at the meta-level.The meta-model provides a set of interfaces to model activity in a specific domain.The activity model transformation in subsequence is devised to deal with the simulation difference due to the heterogeneous activity model.Finally,the resource-aware simulation framework is implemented to integrate the activity models in activity-based simulation.The case study shows the improvement brought on by activity-based simulation using discrete event system specification(DEVS).
文摘1 IntroductionLiNbO3 optical modulators have become essential transmission devices for current and future wideband fibre-optic communications for both military and telecommunications applications. For many telecommunications applications, only a narrow bandwidth is required and thus resonantly enhancedMach-Zehndermodulators(RE-MZMs)have been developed to improve modulation efficiency at the expense of bandwidth.
文摘Optical absorption in thin-film solar cells can be improved by using surface plasmons for guiding and confining the light on the nanoscale.We report theoretical and simulation studies of a-Si thin-film solar cells with silver nanocylinders on the surface.We found that surface plasmons increased the cells' spectral response over almost the entire studied solar spectrum.In the ultraviolet range and at wavelengths close to the Si band gap we observed a significant enhancement of the absorption for both thin-film and wafer-based structures.We also performed optimization studies of particle size,inter-particle distance,and dielectric environment,for obtaining maximal absorption within the substrate.A blue-shift of the resonance wavelength with increasing inter-particle distance was observed in the visible range.Cell performance improved at optimal spacing,which strongly depended on the nanoparticle size.Increasing the nanocylinder size was accompanied by the widening of the plasmon resonance band and a red-shift of the plasmon resonance peaks.A weak red-shift and plasmon peak enhancement were observed in the reflectance curve with increasing refractive index of the dielectric spacer.
基金supported by the National Natural Science Foundation of China(61071215)the University Natural Science Research Project of Jiangsu Province(05KJB510113)
文摘Whispered speech enhancement using auditory masking model in modified Mel- domain and Speech Absence Probability (SAP) was proposed. In light of the phonation char- acteristic of whisper, we modify the Mel-frequency Scaling model. Whispered speech is filtered by the proposed model. Meanwhile, the value of masking threshold for each frequency band is dynamically determined by speech absence probability. Then whispered speech enhancement is conducted by adaptively rectifying the spectrum subtraction coefficients using different masking threshold values. Results of objective and subjective tests on the enhanced whispered signal show that compared with other methods; the proposed method can enhance whispered signal with better subjective auditory quality and less distortion by reducing the music noise and background noise under the masking threshold value.