Papers by Hsiao-dong Chiang
IEEE Transactions on Sustainable Energy, Oct 1, 2015
In this paper, the variable wind power is incorporated into the dynamic model for long-term stabi... more In this paper, the variable wind power is incorporated into the dynamic model for long-term stability analysis. A theory-based method is proposed for power systems with wind power to conduct long-term stability analysis, which is able to provide accurate stability assessments with fast simulation speed. Particularly, the theoretical foundation for the proposed approximation approach is presented. The accuracy and efficiency of the method are illustrated by several numerical examples.
arXiv (Cornell University), Nov 26, 2013
In this paper, several numerical examples to illustrate limitations of Quasi Steady-State (QSS) m... more In this paper, several numerical examples to illustrate limitations of Quasi Steady-State (QSS) model in long-term voltage stability analysis are presented. In those cases, the QSS model provided incorrect stability assessment. Causes of failure of the QSS model are explained and analyzed in nonlinear system framework. Sufficient conditions of the QSS model for correct approximation are suggested.
BMC Musculoskeletal Disorders, Oct 14, 2022
Objective Antibiotic-loaded bone cement beads and spacers have been widely used for orthopaedic i... more Objective Antibiotic-loaded bone cement beads and spacers have been widely used for orthopaedic infection. Poor antibiotic elution is not capable of eradicating microbial pathogens and could lead to treatment failure. The elution profiles differ among different cement formulations. Although Simplex P cement has the least release amount, it is widely used due to its ready availability. Previous methods aiming to improve the elution profiles were not translated well to clinical practice. We sought to address this by using easily available materials to improve the elution profile of antibiotics from PMMA, which allows clinicians to implement the method intraoperatively. Methods Vancomycin was mixed with Simplex P cement. We used Vicryl Rapide sutures to fabricate sustainedrelease cement beads by repetitively passing the sutures through the beads and/or mixing suture segments into the cement formulation. Vancomycin elution was measured for 49 days. The mechanism of antibiotic release was observed with gross appearance and scanning electron microscopic images. The antimicrobial activities against MRSA were tested using an agar disk diffusion bioassay. Results Passing Vicryl Rapide sutures through cement beads significantly improved the elution profiles in the 7-week period. The increased ratios were 9.0% on the first day and 118.0% from the 2nd day to the 49th day. Addition of suture segments did not increase release amount. The Vicryl Rapide sutures completely degraded at the periphery and partially degraded at the center. The antibiotic particles were released around the suture, while antibiotic particles kept densely entrapped in the control group. The antimicrobial activities were stronger in passing suture groups.
In this paper, we study numerically the behavior of the closest unstable equilibrium point (UEP) ... more In this paper, we study numerically the behavior of the closest unstable equilibrium point (UEP) on the stability boundary of a stable equilibrium point (SEP) of a post-switching power system along a P-V curve. Using the structure-preserving model of the WSCC 9-bus 3-machine system, we show that along the load curve, the closest UEP can switch to a new UEP. We also show that the stability region of the post-switching SEP can expand and contract as the load moves towards the nose point of the P-V curve. Our numerical results also show the impact of the direction of movement of the closest UEP on the size and shape of the stability region of a SEP.
International Orthopaedics, May 4, 2020
Purpose Autologous minced cartilage has been used to repair cartilage defects. We have developed ... more Purpose Autologous minced cartilage has been used to repair cartilage defects. We have developed a biphasic cylindrical osteochondral construct for such use in human knees, and report the five year post-operative outcomes. Methods Ten patients with symptomatic osteochondral lesion at femoral condyles were treated by replacing pathological tissue with the osteochondral composites, each consisted a DL-poly-lactide-co-glycolide chondral phase and a DL-poly-lactide-coglycolide/β-tricalcium phosphate osseous phase. A flat chamber between the two phases served as a reservoir to house double-minced (mechanical pulverization and enzymatical dissociation) autologous cartilage graft. The osteochondral lesion was drill-fashioned a pit of identical dimensions as the construct. Graft-laden construct was press fit to the pit. Post-operative outcome was evaluated using Knee Injury and Osteoarthritis Outcome Score (KOOS) up to five years. Regenerated tissue was sampled with arthroscopic needle biopsy for histology at one year, and imaged with magnetic resonance at one, three, and five years to evaluate the neocartilage with MOCART chart. Subchondral bone integration was evaluated with computed tomography at three and five years. Results Nine patients completed the five-year follow-up. Post-operative mean KOOS, except that of the "symptom" subscale, had been significantly higher than pre-operation from one year and maintained to five years. The change of MOCRAT scores of the regenerated cartilage paralleled the change of KOOS. The osseous phase remained mineralized during the five-year period, yet did not fully integrate with the host bone. Conclusions This novel construct for chondrocyte implantation yielded promising mid-term outcome. It repaired the osteochondral lesion with hyaline-like cartilage durable for at least five years.
2019 IEEE Power & Energy Society General Meeting (PESGM), 2019
This paper proposes a partial state estimation of distribution network method based on a nonlinea... more This paper proposes a partial state estimation of distribution network method based on a nonlinear dynamical system approach. The proposed method is globally convergent and can use sparse synchronized phasor measurements without the traditional requirement of network observability. For the application of voltage control or thermal limit control, enhancing the accuracy of the voltage amplitude or the voltage phase angle is required. Under this situation, we propose an enhanced formulation including the voltage amplitude measurement residual constraints and voltage phase angle measurement residual constraints. The IEEE 123-node test feeder, a three-phase unbalanced distribution system, is used to illustrate the effectiveness of the proposed method.
2017 IEEE Power & Energy Society General Meeting, 2017
In this paper we present the dynamic model for transient stability analysis of power systems post... more In this paper we present the dynamic model for transient stability analysis of power systems post transmission switching. We show numerically that the existence of a steady state power flow solution or numerical post-switching stable equilibrium point does not guarantee the dynamic stability of the post-switching power system. Simulations are performed with WSCC 9-bus 3-machine and IEEE 145-bus 50-machine systems.
Regenerative Therapy, 2020
In articular cartilage-repair, grafts usually fuse unsatisfactorily with surrounding host cartila... more In articular cartilage-repair, grafts usually fuse unsatisfactorily with surrounding host cartilage. Enzymatic dissociation of cartilaginous matrix to free chondrocytes may benefit fusion. We tested such a hypothesis with human cartilage in vitro, and with porcine cartilage in vivo. Human articular cartilage was collected from knee surgeries, cut into disc-and-ring sets, and randomly distributed into three groups: disc-and-ring sets in Group 1 were left untreated; in Group 2 only discs, and in Group 3 both discs and rings were treated with enzyme. Each disc-and-ring reassembly was cultured in a perfusion system for 14 days; expression of cartilage marker proteins and genes was evaluated by immunohistochemistry and PCR. Porcine articular cartilage from knees was similarly fashioned into disc-and-ring combinations. Specimens were randomly distributed into a control group without further treatment, and an experimental group with both disc and ring treated with enzyme. Each disc-and-ring reassembly was transplanted into subcutaneous space of a nude mouse for 30 days, and retrieved to examine discring interface. In in vitro study with human cartilage, a visible gap remained at disc-ring interfaces in Group 1, yet became indiscernible in Group 2 and 3. Marker genes, including type II collagen, aggrecan and Sox 9, were well expressed by chondrocytes in all specimens, indicating that chondrocytes' phenotype retained regardless of enzymatic treatment. Similar results were found inin vivo study with porcine cartilage. Enzymatic dissociation of cartilaginous matrix promotes fusion of adjacent cartilage. The clinical relevance may be a novel method to facilitate integration of repaired cartilage in joints.
Neurocomputing, 2019
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
IET Generation, Transmission & Distribution, 2018
A coordinated look-ahead reactive power optimisation method is proposed to minimise the required ... more A coordinated look-ahead reactive power optimisation method is proposed to minimise the required number of operating control devices for a time horizon of 24 h. The aim is to determine, via solving a mixed integer non-linear programming (MINLP) problem, optimum value settings of transformer taps, capacitor banks and reactive power output of distributed generators (DGs) based on the day-ahead load demand and active power output of DGs satisfying the engineering and operational constraints. The proposed method employs a three-stage method: assessment stage, time-period-partitioning stage, and coordinated reactive power optimisation stage. The first stage assesses the hourly voltage profile and available delivery capability margin of the system, while the time-period-partitioning stage uses clustering algorithm based on power-flow solution to partition time periods into coherent time durations. The MINLP problem is solved in the proposed coordinated optimisation stage. A modified IEEE13 case and IEEE123 case are used to verify the effectiveness of the proposed three-stage method.
ACS Applied Materials & Interfaces, 2017
In this study, we report a novel, one-step synthesis method to fabricate multilayer graphene (MLG... more In this study, we report a novel, one-step synthesis method to fabricate multilayer graphene (MLG)-wrapped copper nanoparticles (CuNPs) directly on various substrates (e.g., polyimide film (PI), carbon cloth (CC), or Si wafer (Si)). The electrical resistivities of the pristine MLG-CuNPs/PI and MLG-CuNPs/Si were measured 1.7 × 10 −6 and 1.4 × 10 −6 Ω•m, respectively, of which both values are ∼100-fold lower than earlier reports. The MLG shell could remarkably prevent the Cu nanocore from serious damages after MLG-CuNPs being exposed to various harsh conditions. Both MLG-CuNPs/PI and MLG-CuNPs/Si retained almost their conductivities after ambient annealing at 150°C. Furthermore, the flexible MLG-CuNPs/PI exhibits excellent mechanical durability after 1000 bending cycles. We also demonstrate that the MLG-CuNPs/PI can be used as promising source-drain electrodes in fabricating flexible graphene-based field-effect transistor (G-FET) devices. Finally, the MLG-CuNPs/CC was shown to possess high performance and durability toward hydrogen evolution reaction (HER).
IEEE Transactions on Control of Network Systems, 2016
The quasi steady-state (QSS) model based on time-scale decomposition was developed to reduce the ... more The quasi steady-state (QSS) model based on time-scale decomposition was developed to reduce the computational burden for long-term stability analysis. However, it was shown that the QSS model may not provide accurate stability assessments for the complete dynamic model in long-term stability analysis. In this paper, a hybrid QSS model, which serves as a remedy to the QSS model, is proposed. The proposed model can provide accurate approximations for the long-term stability model with much less computational time. The hybrid QSS model proves to be capable of consistently providing accurate approximations for the long-term stability model. In addition, numerical algorithms for the hybrid QSS model are elaborated for practical implementation. Numerical examples show that the hybrid QSS model can quickly screen out stable contingencies and accurately capture unstable contingencies for the long-term stability model in cases where the QSS model fails.
2015 IEEE Power & Energy Society General Meeting, 2015
An on-line line switching method based on a three-stage strategy to effectively relieve overloads... more An on-line line switching method based on a three-stage strategy to effectively relieve overloads in power systems is proposed. The proposed method is designed for on-line applications in the control center environment. To balance the requirements of solution speed and of effectiveness, the proposed three-stage method is composed of screening stage, ranking stage and detailed analysis stage. One distinguishing feature of the proposed method is that it provides multiple high-performance solutions for both single line switching as well as multiple line switching. To evaluate the proposed on-line line witching method, numerical studies are conducted on the IEEE 39-bus and a 2746-bus systems. Simulation studies indicate the proposed method can effectively alleviate overloads in power systems with promising results.
IET Generation, Transmission & Distribution, 2016
Many existing short-circuit calculation (SCC) methods may encounter the issue of divergence in so... more Many existing short-circuit calculation (SCC) methods may encounter the issue of divergence in solving distribution systems with distributed generators (DGs) and ZIP (constant power, constant current, and constant impedance) loads. To address this problem, this study presents a robust homotopy-enhanced numerical SCC method for general distribution networks with non-linear loads. Numerical studies reveal that the difference of SCC results between ZIP loads and constant impedance loads can be as large as 37.9% for the IEEE 8500-node test system, highlighting the importance of load modelling in calculating short-circuit currents. To demonstrate its robustness and effectiveness, the proposed method is evaluated on the IEEE 13-bus network and the IEEE 8500-node test system. The evaluation results are very promising. One distinguished feature of the proposed method is that it can assist several existing SSC methods to solve the short-circuit equations of distribution networks with DGs and ZIP loads.
2014 IEEE PES T&D Conference and Exposition, 2014
The widespread use of distributed generators (DGs) in utility distribution feeders brings about s... more The widespread use of distributed generators (DGs) in utility distribution feeders brings about several challenges to the operation, planning, and design of general distribution networks. In this paper, the task of accurate determination of available delivery capability (ADC) subject to thermal limits, voltage limits, and voltage stability limit is formulated. A rigorous numerical method to calculate the ADC of large-scale distribution networks with renewables is presented. This numerical method computes three critical points which are the saddle-node bifurcation point or structure-induced bifurcation point, voltage violation point, and thermal-limit violation point. To gain the speed and robustness for the proposed method, the continuation method is integrated into the proposed numerical method. For illustrative purposes, the proposed method is applied to the IEEE 14-bus test feeder and the IEEE 8500-node test system.
2013 IEEE Power & Energy Society General Meeting, 2013
Reconfiguration technique has been used to reduce networks losses, balance user loads and restore... more Reconfiguration technique has been used to reduce networks losses, balance user loads and restore power supply after a power outage in a distribution system. With a large amount of uncontrollable distributed generation (DG) added into the distribution system, reconfiguration technique is also applied to deal with the interconnection capability of DG in a network. This paper aims to obtain the maximum DG power injection into the system, while satisfying current, voltage constraints and large enough load margin. A method based on reconfiguration technique to solve the issue aforementioned is presented. The Binary Particle Swarm Optimization (BPSO) is employed to solve the discrete nonlinear optimization problem. IEEE123 case, an unbalance three-phase distribution system, is used to verify the availability of the proposed methodology and the results from the simulation demonstrate the method proposed efficiency.
Journal of Orthopaedic & Sports Physical Therapy, 2015
STEM CELLS, 2003
Stem cell-based therapies for degenerative disorders and injuries are promising in the new era. M... more Stem cell-based therapies for degenerative disorders and injuries are promising in the new era. Multipotential mesenchymal stem cells (MSCs) from bone marrow (BM) are on the leading edge because they are easy to expand in culture while maintaining their multilineage potential. In vitro assessment of the chondrogenic and osteogenic potentials of cultured MSCs has been established, and the BM used in those experiments was exclusively from healthy donors via iliac crest aspiration. It is unknown whether human marrow obtained from femurs also contains these multipotential MSCs. We collected marrow from proximal femurs of two patients undergoing total hip replacement surgery for femoral head osteonecrosis and isolated and culture expanded MSCs to about 20 population doublings. These cells were homogeneously positive for β β1 1-integrin. When pelleted into aggregates and cultured in a medium containing transforming growth factor-β β3 for 14 days, the cells began to express mRNA for aggrecan and collagen type II and to deposit immunoreactive collagen type II and sulfated proteoglycans in the matrix, hallmarks of chondrogenic differentiation. These MSCs could also be differentiated into osteocytic lineage in vitro, as shown by increased expression of alkaline phosphatase activity and deposition of mineral content onto culture plates. These results indicate that femoral BM obtained during hip surgeries also contained multipotential MSCs. These data imply that direct replacement therapy using MSCs from in situ marrow may be possible in the future and that an MSC bank may be established by using marrow from this approach, bypassing the necessity for iliac marrow aspiration from healthy donors. Stem
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Papers by Hsiao-dong Chiang