Ping Wang

Duke University | DU · Department of Medicine

We construct a two-sector optimal growth model of housing where housing is produced by both land and housing structure/household durables. We explicitly model locational choice. Housing services derive positive utility but are decayed away from the city center. Our model enables a full characterization of the dynamic paths of housing stocks as well...

This paper aims at assessing several fast non-Hertzian methods, coupled with two wear models, based on the wheel–rail rolling contact and wear prediction. Four contact models, namely Kik-Piotrowski's method, Linder's method, Ayasse-Chollet's STRIPES algorithm and Sichani's ANALYN algorithm are employed for comparing the normal contact. For their ta...

During both running and wheel cut operations, wheels of railway vehicles and the friction rollers that support and drive the wheelset on a typical wheel cut lathe are subject to wear and hence are likely to develop out-of-round characteristics after sustained use. The resulting out-of-round wheels can significantly affect the ride quality and can p...

This paper introduces a single-phase five-branch direct ac-ac modular multilevel converter (MMC) with the capability of equal frequency conversion for railway power conditioning applications. By analyzing the branch energy balance mechanism, the basic operating principle of the proposed MMC is clarified and the control strategy is also proposed. Co...

Full-bridge submodule (FBSM) -based modular multilevel converter (FB-MMC) provides an additional freedom for modulation index selection, and it has overwhelming advantages in terms of handling dc short circuit faults and reducing FBSM capacitance. This paper analyzes the impact of reactive power on the FBSM capacitance reduction of the FB-MMC with...

At present, steel-spring floating slabs have been widely used in urban rail transit to reduce the influence of ground vibration caused by vehicle operation on the surrounding environment. As a core part of vibration reduction for floating slab track, the steel-spring vibration isolator may fail in different forms during operation. In order to study...

Heavy metal contamination in aquatic environment has made great adverse impacts on human health and environment. In this work, a label-free electrochemical gold nanoband aptasensor (GNA) was developed using thymine-Hg²⁺-thymine (T-Hg²⁺-T) coordination chemistry for Hg²⁺ detection in drinking water. The gold nanoband sensor contains gold nanoband wo...

Potentiometric plasticizer-free solid-contact Pb2+-selective electrodes based on copolymer methyl methacrylate-n-butyl acrylate (MMA-BA) as membrane matrix and multi-walled carbon nanotubes (MWCNTs) as intermediate ion-to-electron transducing layer have been developed. The disposable electrodes were prepared by drop-casting the copolymer membrane o...

This paper presents a geometric wheel–rail contact algorithm suitable for fault detection in a railway turnout. It employs a dynamic profile sampling method based on the characteristics of the variable section rails in the turnout regions. This algorithm provides a fast and accurate method to identify the wheel–rail contact points in turnouts under...

Developing advanced catalysts ideally requires fundamental knowledge of the chemical and physical transformations occurred in the preparation process of the catalysts. Herein, we report a careful study of the formation mechanism of bimetallic nickel-platinum (Ni-Pt) nanocatalyst supported on ceria (CeO 2 ), which was prepared by co-precipitation me...

In a second-best optimal growth setup with only factor taxes, it is in general optimal to fully replace capital by labor income taxation in the long run. We revisit this important issue by developing a human-capital-based endogenous growth model with frictional labor search, allowing each firm to create multiple vacancies and each worker to determi...

The development of hydrazine monohydrate (N 2 H 4 ·H 2 O) as a viable hydrogen carrier requires high-performance and cost-effective catalysts for selectively promoting its decomposition to generate hydrogen at mild conditions. Herein, we report the synthesis of a non-precious metal nanocatalyst, in both powdery and monolithic forms, using a simple...

We report herein a nanocomposite that has a continuous phase of amorphous calcium carbonate (ACC) filled with fluorescent carbon quantum dots (CD) and undergoes phase transitions triggered by moisture in organic solvents. The phase transitios involve aggregations of the nanocomposite particles and crystallization of the ACC phase. It can be trigger...

The nonlinear and fractional derivative Zener model of viscoelastic material considering Berg’s friction force model is established, which can be used to describe the frequency-dependent and amplitude-dependent behaviour of rubber isolator. The simplified Berg’s friction force scheme was proposed to improve computational efficiency in the frequency...

For a fast calculation of vehicle-track dynamics and wheel-rail contact mechanics, wheel-rail contact geometric gap is usually idealised in elliptic or nonelliptic form. These two idealisations deviate from the actual one if the lateral combined curvature within the contact patch is not constant or the yaw angle of wheelset exists. The influence of...

Urolithiasis commonly occurs in kidney and ureteral, and may cause local organ/tissue damage, even kidney failure. The incidence of this disease is increasing worldwide, in which calcium oxalate is the major composition forming the urinary calculus. Therefore, to monitor this disease for the prevention and treatment, measuring the oxalate in the ur...

Heavy-metal pollution has attracted intensive attention from the public because of the severe threats of heavy metals to the ecosystem and human health. Ultralow concentration of heavy metals in aquatic environment leads to the urgent needs of sensitive approaches for heavy-metal detection. Electrochemical DNA biosensors present outstanding superio...

To gain fundamental understanding of how catalyst composition and structure affects catalytic reaction chemistry is of paramount importance in the search of high-performance electrocatalysts for practical applications. Herein, we report an in-depth study of Ni-Mo-O derived electrocatalyst, a promising but less well investigated electrocatalytic mat...

A two-step approach is used to establish a numerical prediction model to study the impact of typical rail corrugation on ground vibration from an underground subway. In the first step, a vehicle-track-tunnel rigid-flexible coupling subsystem is established based on a lumped mass model dynamics and finite element analysis cosimulation method to simu...

Full-bridge submodule (FBSM) capacitance of FBSM based modular multilevel converter (FB-MMC) can achieve a significant reduction with boosted ac voltages, which makes it a promising candidate in voltage-source-converter based high- voltage-direct-current (VSC-HVDC) scenarios in terms of cost reduction and dc short circuit faults tolerance. With con...

This paper conducts a thorough analysis on the circuit dynamics of the single-phase direct ac-ac MMC to address the branch energy divergence problem in the railway power conditioning application scenario. Based on the analysis, a full degree of freedom (DOF) based control scheme is proposed. By controlling all the DOFs in a coordinated manner, exte...

Alzheimer's disease (AD) is a chronic central neurodegenerative disease. The pathological features of AD are the extracellular deposition of senile plaques formed by amyloid-β oligomers (AβOs) and the intracellular accumulation of neurofibrillary tangles. However, due to the lack of effective method and experimental models to study the cognitive de...

We report a simple potentiometric multisensor system for distinguishing the urine samples from the patients with diagnosed prostate cancer and from healthy control group. The sensors of the system are sensitive towards variety of cationic and anionic species in urine, as well as to the presence of RedOx pairs. The response of the system represents...

Significance Intestinal tuft cells are sentinels monitoring the luminal contents and play a critical role in type 2 immunity. In this work, Trichinella spiralis excretion–secretion and extract were shown to directly induce interleukin 25 (IL-25) release from the intestinal villi, evoke calcium responses in tuft cells, and activate Tas2r bitter-tast...

Saxitoxin (STX) is one of the paralytic shellfish poisons (PSP) that endanger people’s health. It is necessary to develop methods for the on-site rapid detection for STX in order to prevent safety accidents. An enzyme-linked immunosorbent assay (ELISA) is timesaving and effective, but it is not suitable for large-scale in-field tests due to the exp...

Drug efficacy and toxicity are key factors of drug development. Conventional 2D cell models or animal models have their limitations for the efficacy or toxicity assessment in preclinical assays, which induce the failure of candidate drugs or withdrawal of approved drugs. Human organs-on-chips (OOCs) emerged to present human-specific properties base...

This paper proposed a novel approach to measure track irregularity by using a multipoint chord reference (MCR) system. In Part I of this study, the theory and methodology were introduced and the performance in the spatial domain were analyzed through theoretical proofs. The current paper analyzes the performance of an MCR system in the wavelength d...

This paper proposes a novel approach to measure track irregularity by using a multipoint chord reference (MCR) system. This paper is the first part presenting the theoretical proofs and methodology for analyzing the system performance in a spatial domain. Part II will study the performance in wavelength domain through numerical approaches. In this...

Detection and identification of bitter compounds draw great attention in pharmaceutical and food industry. Several well-known agonists of specific bitter taste receptors have been found to exhibit anti-cancer effects. For example, N-C=S-containing compounds, such as allyl-isothiocyanates, have shown cancer chemo-preventive effects. It is worth noti...

The biological olfactory and gustation system can discriminate thousands of odor and taste substances with high sensitivity and specificity, specific receptor proteins play an important role in this process. This study used the human neuroblastoma SH-SY5Y cell line endogenously expressing the human bitter receptor, T2R16. Meanwhile, an olfactory re...

Dynamic wheel–rail interaction in railway turnouts is more complicated than on ordinary track. In order to evaluate the derailment behaviour of railway wheelsets in railway turnouts, this paper presents a study of dynamic wheel–rail interaction during a wheel flange climbs on the turnout rails, by applying the elasticity positioning wheelset model....

This paper studies the wheel–rail creep curve characteristics and dynamic behaviour in high-speed railway turnouts by considering different wheel–rail surfaces and simulating them using a dynamic functional vehicle–track model with different friction and Kalker’s weight coefficients. The dynamic performance and damage coefficient of CRH2 locomotive...

This paper is concerned with an experimental study of improved slotted stand-off layer rail dampers in reducing railway vibration and noise. To achieve the goal, based on the idea of molecular design, polyurethane/vinyl ester resin interpenetrating polymer network damping materials with high damping properties was developed in the laboratory for th...

γ oscillations (30–120 Hz) are generated intrinsically within local networks in the mammalian olfactory bulb (OB). The OB directly receives peripheral input from olfactory sensory neurons (OSNs) that can respond to nasal airflow, and centrifugal input from neuromodulatory systems whose activities are affected by the behavioral states of animal. How...

Cancer significantly threatens human life, and the chemotherapy drugs are developed and widely used in the cancer treatment. However, the side effects of drugs on heart cause other serious problems. In this study, a dual functional cell-based biosensor integrating interdigitated electrodes (IDEs, monitoring cell viability) and microelectrodes (moni...

Excessive vibration and noise radiation of the track structure can be caused by the operation of high speed trains. Though the track structure is characterized by obvious periodic properties and band gaps, the bandwidth is narrow and the elastic wave attenuation capability within the band gap is weak. In order to effectively control the vibration a...

Turnouts are key line equipment for suspended monorail transit. In order to determine the reasonable line type of the symmetrical suspension monorail turnout, a dynamic model of the multi-degree-of-freedom (MDOF) suspended monorail transit system is established according to the multi-body dynamics theory, and the influence of the radius of the circ...

Turnouts is a key line equipment for suspended monorail transit. In order to analyze the dynamic performance of vehicles passing turnouts, a dynamic model of the multi-degree-of-freedom (MDOF) suspended monorail transit system is established according to the multi-body dynamics theory by taking turnout #5 as an example. The effect of track irregula...

Synthesis of high-performance and cost-effective catalysts towards the hydrogen evolution reaction (HER) is critical in developing electrochemical water-splitting as a viable energy conversion technique. For non-precious metal Co- and Ni-based catalysts, hydroxides were found to form on the surface of the catalysts under alkaline environments and b...

The goal of this study is to develop a vibration-based electromagnetic energy harvesting prototype that provides power to rail-side monitoring equipment and sensors by collecting wheel-rail vibration energy when the train travels. This technology helps power rail–side equipment in off-grid and remote areas. This article introduces the principle, mo...

Compared to the conventional half-bridge sub-module (HBSM) based modular multilevel converter (HB-MMC), the full-bridge SM (FBSM) capacitance of FB-MMC can be reduced significantly with consideration of negative voltage state of the FBSM, which has benefits to cost and size reduction. This paper analyzes the characteristics of the FBSM voltage fund...

This paper analyzes the characteristics of the submodule (SM) voltage fundamental frequency and second-order harmonic ripples with the consideration of negative voltage state of the full-bridge SM (FBSM). The optimal operation point, which minimizes the fundamental frequency ripples, is derived. Both design principle and analytical expressions for...

Creating concerted active sites composed of noble metals and oxophilic metal hydroxides/oxides has proven an effective approach for improving the performance of the electrocatalysts towards ethanol oxidation. However, the effects of hydroxide morphology on the catalytic property have been very limited attention. Herein, we report the synthesis of a...

The PML‐RARα fusion gene, generated by the t(15;17) chromosome translocation, is regarded as the initiating factor of acute promyelocytic leukaemia (APL). In addition to the well‐known effects on blocking myeloid differentiation at the promyelocytic stage, promyelocytic leukaemia‐retinoic acid receptor α (PML‐RARα) has also been reported to interfe...

Due to the complicated wheel–rail contact relation of railway turnouts, it is necessary to select a reasonable rolling contact model to simulate the vehicle–turnout dynamics and wheel–rail damages. This paper mainly aims to evaluate the calculation accuracy and efficiency of different non-Hertzian modeling approaches in solving normal and tangentia...

To perform the drug screening, planar cultured cell models are commonly applied to test efficacy and toxicity of drugs. However, planar cultured cells are different from the human 3D organs or tissues in vivo. To simulate the human 3D organs or tissues, 3D spheroids are developed by culturing a small aggregate of cells which reside around the extra...

How to obtain sufficient functional olfactory receptors and coupled to transducers with high efficiency are crucial to biomimetic olfactory-based biosensors. In this study, a cell-free expression system was employed to prepare functional olfactory receptors that were utilized as sensitive elements for biomimetic olfactory receptor-based biosensors....

Preclinical efficacy and toxicity assessment of drug candidates plays a significant role in drug discovery and development. Traditional planar cell culture is a common way to perform the preclinical drug test, but it is difficult to correctly predict the drug efficacy and toxicity due to the simple two-dimensional (2D) extracellular microenvironmen...

Surface modification and functionalization of nanomaterials have been adopted widely in devising smart drug delivery systems. This work examines the fabrication of multi-stimuli responsive surfaces on mesoporous silica nanoparticles (MSN) for environmentally sensitive site specific drug delivery with reduced risk of premature drug leakage. Chitosan...

Synthesis of high-performance and cost-effective electrocatalysts towards hydrazine electrooxidation is vital to develop the direct hydrazine fuel cell (DHFC) as a viable energy conversion technology. Herein, we report a combined experimental and theoretical study of nickel phosphides (NixP) as promising catalysts for hydrazine electrooxidation. Ni...

A simple and general approach leading to well-dispersed and surfactant-free multi-walled carbon nanotubes (MWCNT) based single-piece Pb²⁺-selective nanocomposite membrane is proposed. The single-piece solid-contact Pb²⁺-selective electrodes were prepared via one-step drop casting the ultrasonicated suspension mixture on the golden electrodes. The o...

A decentralized control method for power module (PM) capacitor voltage and switching frequency balancing in modular multilevel converter (MMC) is presented in this paper. The proposed method is composed of a central controller, six arm controllers and several group controllers. The group controller is only in charge of the PM capacitor voltage bala...

Platinum (Pt) is well known as the best-performing catalyst for the hydrogen evolution reaction (HER), but its practical application is severely hindered by its prohibitively high cost and problematic performance in alkaline electrolyte. Herein, we report that the issues of intrinsic activity and cost concern of Pt can be simultaneously addressed b...

Lung cancer (LC) is a leading cause of cancer-related morbidity and mortality globally, and exhaled breath test has been considered as a fast, convenient and non-invasive way to diagnose LC in early stage. Volatile organic compounds (VOCs), as markers of LC in exhaled breath, has been widely investigated for cancer diagnosis. However, few study rep...

Okadaic acid (OA) and saxitoxin (STX) are typical toxins of diarrhetic shellfish poisoning (DSP) and paralytic shellfish poisoning (PSP), respectively, which are highly toxic marine toxins threatening human health and environmental safety. OA is a potent inhibitor of serine/threonine protein phosphatases that can cause cellular death, while STX is...

Invisible mercury ion is an extremely poisonous environmental pollutant, therefore, a fast and highly sensitive detection method is of significant importance. In this study, a liquid-gated graphene field-effect transistor (GFET) array biosensor (6 × 6 GFETs on the chip) was fabricated and applied for Hg²⁺ quantitate detection based on single-strand...

Conventional chemical surfactants attach on blots randomly, accompanied with health and environmental issues. To address this, a surfactant peptide was designed to mimic chemical surfactants with an affinity binding peptide as a hydrophobic tail for the cleanup of biofilm contaminations. The micelle forming and structural changes of the peptide in...

In order to enable the vehicle to change among the tracks, the stock and switch rails are separated and provided with different rail resilience levels on the baseplate in the railway turnout switch panel. Therefore, there will be vertical relative motion between stock/switch rails under wheel loads, and the relative motion will change the combined...

Okadaic acid (OA), a representative diarrhetic shellfish poisoning toxin, mainly produced by toxigenic dinoflagellates, has significant hazard to public health. Traditional methods for detection of OA can not give the consideration to the need of rapid, high sensitive, quantitative and in-situ detection at the same time. Herein, a new effective det...

Wave propagation in the ordered and randomly disordered periodic track structure in high-speed railways are investigated theoretically and experimentally. Taking the CRTS-I double-block ballastless track structure in China as the research object, a theoretical model of periodic track structure is established. The rail is modelled as a Timoshenko be...

Railway vibration energy harvesting technology is to recover the energy generated by the track vibration when a train passes by,to provide power to the rail-side devices for railway condition monitoring in off-grid and remote areas.However,the requirements for track vibration parameters of existing track vibration harvesting method do not conform t...

This article presents a prototype of wireless rechargeable sensor nodes for the health monitoring of urban rail corrugation. The proposed system includes a local energy generator constructed based on the electromagnetic-induction principle, a DC–DC booster converter, wireless sensor nodes, and an analysis interface using Littlewood–Paley wavelet tr...

Vascular cell functionality is critical to blood vessel homeostasis. Constitutive NF-κB activation in vascular cells results in chronic vascular inflammation, leading to various cardiovascular diseases. However, how NF-κB regulates human blood vessel homeostasis remains largely elusive. Here, using CRISPR/Cas9-mediated gene editing, we generated Re...

The technology of continuously welded rails (CWRs) is important in modern railway track structures. To measure rail stress, resistance strain gauges are preferred due to their good stability, sensitivity, and resistance to external interference. Based on the bi-directional strain method, we present a new method for measuring longitudinal rail stres...

Hydrous hydrazine (N2H4·H2O) is considered as a promising hydrogen carrier. In the development of N2H4·H2O-based hydrogen generation system, monolithic catalysts are highly desirable owing to their reusability, ready controllability of reaction and simple design of hydrogen generator. Herein, we report the synthesis of a monolithic catalyst compose...

Multi-stimulation responsive nanomaterial-based drug delivery systems promise enhanced therapeutic efficacy in cancer therapy. This work examines a smart pH/GSH dual-responsive drug delivery system by using dialdehyde dextrin (DAD) end-capped mesoporous silica nanoparticles (MSNs). Specifically, DAD was applied as a “gatekeeper polymer” agent to se...

Chromium(VI) has been known as a toxic heavy metal ion that can cause adverse effects to human health, including carcinogenic effects. An approach that can detect chromium(VI) in a rapid, sensitive and portable manner is of great importance. This paper presents a miniaturized portable electrochemical system for chromium(VI) determination based on a...

Cardiac issues are always one of major health problems that attract wide attention by the public. It is urgent to explore a preclinical strategy to efficiently prevent the life-threatening arrhythmias by precisely assessing the cardiac excitation-contraction behavior. Conventional label-free asynchronous strategies are difficult to synchronously re...

Objective: To present a original technique of robotic-assisted urethra-sparing simple prostatectomy (RAUSP) for treating patients with benign prostatic hyperplasia (BPH). Materials and methods: From Apr 2015 to Dec 2016, 27 patients underwent RAUSP via an extraperitoneal approach. Baseline patient characteristics, perioperative outcomes, patholo...