Variational capacitance modeling using orthogonal polynomial method

ABSTRACT In this paper, we propose a novel statistical capacitance extraction method for interconnects considering process variations. The new method, called statCap, is based on the spectral stochastic method where orthogonal polynomials are used to represent the statistical processes in a deterministic way. We first show how the variational potential coefficient matrix is represented in a first-order form using Taylor expansion and orthogonal decomposition. Then an augmented potential coefficient matrix, which consists of the coefficients of the polynomials, is derived. After that, corresponding augmented system is solved to obtain the variational capacitance values in the orthogonal polynomial form. Experimental results show that our method is two orders of magnitude faster than the recently proposed statistical capacitance extraction method based on the spectral stochastic collocation approac

Bidirectional regulation of angiogenesis and miR-18a expression by PNS in the mouse model of tumor complicated by myocardial ischemia

BACKGROUND: Panax Notoginseng Saponins (PNS) is the major class of active constituents of notoginseng, a natural product extensively used as a therapeutic agent in China. Tumor when accompanied by cardiovascular disorders poses a greater challenge for clinical management given the paradoxical involvement of angiogenesis, therefore gaining increased research attention. This study aim to investigate effects of PNS and its activity components in the mouse model of tumor complicated with myocardial ischemia. METHODS: Tumor complexed with myocardial ischemia mouse model was first established, which was followed by histological and immunohistochemistry examination to assess the effect of indicated treatments on tumor, myocardial ischemia and tissue specific angiogenesis. MicroRNA (miRNA) profiling was further carried out to identify potential miRNA regulators that might mechanistically underline the therapeutic effects of PNS in this complex model. RESULTS: PNS and its major activity components Rg1, Rb1 and R1 suppressed tumor growth and simultaneously attenuated myocardial ischemia. PNS treatment led to decreased expression of CD34 and vWF in tumor and increased expression of these vascular markers in heart. PNS treatment resulted in reduced expression of miR-18a in tumor and upregulated expression of miR-18a in heart. CONCLUSIONS: Our data demonstrated for the first time that PNS exerts tissue specific regulatory effects on angiogenesis in part through modulating the expression of miR-18a, which could be responsible for its bidirectional effect on complex disease conditions where paradoxical angiogenesis is implicated. Therefore, our study provides experimental evidence warranting evaluation of PNS and related bioactive component as a rational therapy for complex disease conditions including co-manifestation of cancer and ischemic cardiovascular disease

The double inhibition of PDK1 and STAT3-Y705 prevents liver metastasis in colorectal cancer.

As a key glycolysis enzyme, the significance of pyruvate dehydrogenase kinase 1 (PDK1) in the development of colorectal cancer (CRC) remains unknown. This study revealed that the prognosis of CRC patients with high levels of PDK1 was poor, and PDK1 knockdown significantly reduced liver metastasis of CRC in both nude mice and immune competent BALB/C mice. When combined with cryptotanshinone (CPT), an inhibitor of STAT3-p-Y705, the liver metastasis was further inhibited. PDK1 knockdown obviously increased reactive oxygen species level in anoikis conditions and subsequently resulted in an elevated anoikis, but the combination of PDK1 knockdown and CPT showed a reduced effect on anoikis. Based on this discrepancy, the adherence ability of CRC cells to matrix protein fibronectin was further detected. It showed that PDK1 knockdown significantly decreased the adherence of CRC cells to fibronectin when combined with CPT. These results suggest that inhibition of PDK1 can decrease the surviving CRC cells in blood circulation via up-regulation of anoikis, and inhibition of STAT3-p-Y705 can prevent it to settle down on the liver premetastatic niche, which ultimately reduces liver metastasis

SVSI: Fast and Powerful Set-Valued System Identification Approach to Identifying Rare Variants in Sequencing Studies for Ordered Categorical Traits: SVSIfor Genetic Association Studies

For genetic association studies that involve an ordered categorical phenotype, we usually either regroup multiple categories of the phenotype into two categories (“cases” and “controls”) and then apply the standard logistic regression (LG), or apply ordered logistic (oLG) or ordered probit (oPRB) regression which accounts for the ordinal nature of the phenotype. However, these approaches may lose statistical power or may not control type I error rate due to their model assumption and/or instable parameter estimation algorithm when the genetic variant is rare or sample size is limited. Here to solve this problem, we propose a set-valued (SV) system model, which assumes that an underlying continuous phenotype follows a normal distribution, to identify genetic variants associated with an ordinal categorical phenotype. We couple this model with a set-valued system identification algorithm to identify all the key system parameters. Simulations and two real data analyses show that SV and LG accurately controlled the Type I error rate even at a significance level of 10−6 but not oLG and oPRB in some cases. LG had significantly smaller power than the other three methods due to disregarding of the ordinal nature of the phenotype, and SV had similar or greater power than oLG and oPRB. For instance, in a simulation with data generated from an additive SV model with odds ratio of 7.4 for a phenotype with three categories, a single nucleotide polymorphism with minor allele frequency of 0.75% and sample size of 999 (333 per category), the power of SV, oLG and LG models were 70%, 40% and <1%, respectively, at a significance level of 10−6. Thus, SV should be employed in genetic association studies for ordered categorical phenotype

Airflow measurements using averaging Pitot tube under restricted conditions

This paper studies the effect of the air damper placed downstream of an averaging Pitot tube (APT) on the flow measurement in air distribution systems. Experiments are conducted to obtain the characteristic curve of the APT under different damper positions. The analysis of variance (ANOVA) is applied and the results reveals a statistically significant correlation between them. A mathematical model for the pressure coefficient with respect to the damper opening angle is proposed to compensate the systematic error caused by the damper. The model is validated under various Reynolds numbers (Re) varying from 6.38 × 103 to 19.1 × 103 with RMSE < 0.02. By applying the proposed model, the flow measurement errors are reduced below 0.6% for all tested cases, and the highest accuracy (0.02%) is achieved when Re = 9.57 × 103. The proposed model significantly improves the performance of current air flow control stations (AFCS) where the ATP is placed immediately upstream of the air damper. This research can be helpful for manufactures to provide AFCS with higher accuracy and larger operating range.NRF (Natl Research Foundation, S’pore

A 3-stage online distributed cooperative control based air balancing method for air duct systems

The authors have previously proposed a 2-stage online distributed cooperative control-based air balancing (DCC-AB) scheme for air duct systems to realize accurate air balancing and energy saving. However, the practical application shows that the previous 2-stage online DCC-AB scheme may encounter convergence failure when mis-specifying the critical damper. In order to fix this problem, this paper further proposes a 3-stage online DCC-AB method. Unlike the 2-stage online DCC-AB method which selects the critical damper based on an empirical rule, the proposed 3-stage online DCC-AB method introduces a special stage at the beginning of the balancing process to identify the right critical damper to totally eliminate the risk of convergence failure. In addition, the proposed 3-stage online DCC-AB method also introduces a time-varying weighted penalty term to accelerate convergence while ensuring the operation stability. Therefore, the proposed 3-stage online DCC-AB method enjoys the following advantages: a) The convergence failure caused by the misspecification of the critical damper is effectively avoided; b) The convergence rate and the balancing accuracy are further improved compared to the previous 2-stage online DCC-AB method. Finally, the proposed 3-stage online DCC-AB method is validated on a laboratory duct system of 5 terminals under different design flow requirements, no failure cases occur and the absolute relative error of terminal flow is controlled within 7.2% in all test scenarios.Building and Construction Authority (BCA)This work is supported by Building and Construction Authority (BCA) project: On-line Smart Air-Balancing System for Net Zero Energy Buildings (Grant Reference Number: BCA 94.23.1.3, Project WBS number: M4062609.B60)

Research of three dimensional laser scanning coordinate measuring machine

Three dimensional laser scanning coordinate measuring machine is suitable for the measurement of 3D printing products, and its measuring range depends on the three coordinate measuring machine. It is the main 3D printing product measuring instrument [1]. In this paper, the principle of laser scanning three coordinate measuring machine is analyzed. The accuracy and reliability of the calibration system for 3D printing products are verified. According to the newly revised JJF 1064 Calibration specification for coordinate measuring machines [3], it is calibrated

An energy-saving oriented air balancing method for demand controlled ventilation systems with branch and black-box model

This paper proposes an energy-saving oriented air balancing method based on a branch and black-box (B2) model for multi-zone demand controlled ventilation (DCV) systems. The proposed method can achieve accurate air flow control in each zone, which avoids unnecessary energy consumption caused by over-ventilation. The operating procedures of the proposed method are as follows: Building the B2 model for the DCV system → Predicting the terminal static pressures under the given zone design flow values → Determining the damper angles of each zone based on the static pressure predictions. In the proposed air balancing method, the basic modelling unit is the duct branch, instead of the internal fittings in the previous model-based air balancing method. Therefore, the proposed method does not need to know the complicated fitting information (e.g., elbows, transitions, dampers, etc.,) in its modelling process and therefore becomes much simpler. In addition, the complexity of the proposed B2 model is also greatly reduced since it is independent with the fitting numbers and does not need to calculate the fitting loss coefficients. Furthermore, the radial basis function (RBF) kernel is also utilized in the proposed method to guarantee the air balancing accuracy. Compared with the existing air balancing methods, the proposed method is more efficient and effective in practice. In the lab, the proposed air balancing method was validated on a real DCV system of 5 zones under various design flow conditions. The experimental results verified the effectiveness of the proposed method on both the air balancing control accuracy and the energy saving ability

A gradient-based adaptive balancing method for dedicated outdoor air system

This paper presents an online air balancing method applied in dedicated outdoor air systems, named as gradient-based online adaptive balancing (GOAB) method. The GOAB method derives the damper adjustment rule based on the gradient of the objective function that quantifies the discrepancy between actual flow rate and the set point in normalized form. An adaptive mechanism is applied to capture the change of Jacobian matrix during the balancing process. The optimum direction of damper angle increment is determined based on the null space of the gradient vector to speed up the convergence and ensure at least one damper to be fully open. Compared with the existing methods, the proposed GOAB method offers the following advantages:1.) The method can be performed on a duct system in operation, which provides possibility to re-balance the system under dynamic working conditions; 2.) The energy loss on dampers is minimized without compromising the balancing accuracy. Simulations are performed in MATLAB to investigate several model parameters and provide guidance for the parameter design. Experiments are conducted on a 5-ternimal duct system to validate the proposed method under various design flow requirements. The results show that the maximum absolute percentage error can be controlled within 4.3% among all test cases. This method improves the energy efficiency of the duct system and speeds up the convergence rate towards air balance to save time and cost.Ministry of Education (MOE)This work is supported by Tier 1 project: Optimization and Control for Fan Array Based Air Handling Units (Grant Number: 2017-T1-001- 083 (RG 88/17)) by Ministry of Education Singapore