Good Route Research Articles

Dynamic Robot Routing and Destination Assignment Policies for Robotic Sorting Systems

Robotic sorting systems (RSSs) use mobile robots to sort items by destination. An RSS pairs high accuracy and flexible capacity sorting with the advantages of a flexible layout. This is why several express parcel and e-commerce retail companies, who face heavy demand fluctuations, have implemented these systems. To cope with fluctuating demand, temporal robot congestion, and high sorting speed requirements, workload balancing strategies such as dynamic robot routing and destination reassignment may be of benefit. We investigate the effect of a dynamic robot routing policy using a Markov decision process (MDP) model and dynamic destination assignment using a mixed integer programming (MIP) model. To obtain the MDP model parameters, we first model the system as a semiopen queuing network (SOQN) that accounts for robot movement dynamics and network congestion. Then, we construct the MIP model to find a destination reassignment scheme that minimizes the workload imbalance. With inputs from the SOQN and MIP models, the Markov decision process minimizes parcel waiting and postponement costs and helps to find a good heuristic robot routing policy to reduce congestion. We show that the heuristic dynamic routing policy is near optimal in small-scale systems and outperforms benchmark policies in large-scale realistic scenarios. Dynamic destination reassignment also has positive effects on the throughput capacity in highly loaded systems. Together, in our case company, they improve the throughput capacity by 35%. Simultaneously, the effect of dynamic routing exceeds that of dynamic destination reassignment, suggesting that managers should focus more on dynamic robot routing than dynamic destination reassignment to mitigate temporal congestion. Funding: This work was supported by The Fundamental Research Funds for the Central Universities [Grant WK2040000094] and the National Natural Science Foundation of China [Grants 71921001 and 72091215/72091210]. Supplemental Material: The online appendices are available at https://doi.org/10.1287/trsc.2023.0458 .

Research on the Impact of Green Bond Issuance in New Energy Automobile Industry-- Taking BYD Company as an Example

Green bonds are a cutting-edge financial tool that is becoming more and more significant in encouraging green development and investment in the environment. This paper will analyze the operational and financial impact on the company based on the BYD green bond case. From the view of weighted average return on net assets, long-term debt ratio and other indicators, it is found that green bonds can help the company to improve profits, but also bring more debt pressure. Overall green bonds are a good financing route for BYD, creating a diversified development path, broadening the investor base, and improving the green reputation and the company's financial stability. This paper further suggests optimizing the structure of the new energy green bond market, improving the regulatory system and enhancing investor education in order to promote the healthy development of this market.

Comparison of Rigid Pavement Planning Using PD T-14-2003 and NAASRA 1987 Methods in Industrial Areas

As vital infrastructure, roads are a means of transportation access and function as a distribution route for goods and services. Road pavement plays a crucial role in highway construction, necessitating proper planning according to Indonesian standards and planning criteria to ensure smooth land transportation and provide comfort and safety for its users. This study aims to provide information on road conditions, drainage dimensions, and construction costs. Planning is crucial in every road construction design, particularly for rigid pavement, based on survey data collected from the road section. Numerous methods exist for calculating the design value of rigid pavement. We use the Pd T-14-2003 method and the NAASRA 1987 method (National Association of Australian State Road Authorities) to plan rigid pavement thickness in the industrial area of PT. Bukit Muria Jaya Kudus. The Pd T-14-2003 method yielded a JSKN of 4x107 and a CBR of 35% for the subgrade, resulting in a plate thickness of 150 mm. While the Naasra 1987 planning method achieved a JSKN of 6x107 and a CBR of 35% for the base soil, a plate thickness of 160 mm was obtained with a value of K = 80 kPa/mm. The reinforcement planning using the Pd T-14-2003 and Naasra 1987 methods involves longitudinal reinforcement D10 mm at a distance of 150 mm and transverse reinforcement D10 mm at 250 mm. The drainage dimensions at the cross-section location are width x height (1 m x 1 m), and the guard's height is 0.2 m.

Design and fabrication of nitrogen-doped graphene-promoted Na3MnTi(PO4)3@C cathode with three-electron reactions for sodium-ion storage

As a novel cathode material for sodium-ion batteries, Na3MnTi(PO4)3 (denoted as NMTP) has received great attention because of its abundant natural resources, excellent safety, low toxicity as well as three-electron reactions. Unfortunately, the pure NMTP cathode displays a bad conductivity, resulting in an inferior electrochemical performance for sodium energy storage. Herein, we introduce a good route to fabricate the nitrogen-doped graphene-decorated NMTP@C (denoted as NG-NMTP@C) composite with superior rate property and superior cycle stability for the first time. In this fabricated material, the nitrogen-doped graphene nanosheets are dispersed into the NMTP@C particles. Compared to NMTP@C, the prepared NG-NMTP@C cathode possesses better cycle stability and higher capacity. It shows the capacity of 173.1 mAh g−1 at 0.1 C and presents the high capacity retention of around 97.1 % at 10.0 C over 400 cycles. Therefore, this fabricated NG-NMTP@C nanocomposite can be employed as the novel positive electrode in sodium-ion storage.

Yolk-shell MOF-on-MOF hybrid solid-phase microextraction coatings for efficient enrichment and detection of pesticides: Structural regulation cause performance differences

Metal-organic frameworks (MOFs) based composites with different structure-activity relationships have been widely used in the field of organic pollutant adsorption and extraction. Here, two MOF-on-MOF composites with different structures (yolk-shell and core-shell) from homologous sources were prepared by a simple in-situ growth synthesis method and structural regulation. In order to verify the effect of composite structure on the extraction capacity, the adsorption performance of the yolk-shell structure (YS–NH2-UiO-66@CoZn-ZIF) and the core-shell structured (NH2-UiO-66@CoZn-ZIF) material were compared by using them as coating material of direct immersion solid-phase microextraction (DI-SPME) to enrich six pesticides in five matrices. The results showed that because of the unique hollow hierarchical structure, high specific surface area (930.68 m2 g−1), abundant and open active sites, and synergistic and complementary adsorption forces, YS-NH2-UiO-66@CoZn-ZIF composites had the maximum adsorption amount of 36.01–66.31 mg g−1 under the same experiment condition, which was 6.81%–34.26 % higher than that of NH2-UiO-66@CoZn-ZIF. In addition, the adsorption mechanism of the prepared materials was verified and elaborated through theoretical simulations and material characterization. Under the optimized conditions, the YS-NH2-UiO-66@CoZn-ZIF-coated SPME-HPLC-UV method had a wide linear range (0.241–500 μg L−1), a good linear correlation coefficient (R2 > 0.9988), a low detection limits (0.072–0.567 μg L−1, S/N = 3) and low quantification limits (0.241–1.891 μg L−1, S/N = 10). The relative standard deviations of individual fibers and different batches of fibers were 0.47–6.20 % and 0.22–2.48 %, respectively, and individual fibers could be recycled more than 104 times. This work provided a good synthetic route and comparative ideas for exploring the in-situ growth synthesis of yolk-shell composites with reasonable structure-activity relationships.

The influence of debromination and TR on the microstructure and properties of CMSMs

One unique challenging in achieving advanced carbon molecular sieve membranes (CMSMs) is tailoring their gas separation properties from the precursor. To clarify this, we designed two homo-polyimides with a bromine (PI-Br) and a hydroxyl (PI-OH) groups in the ortho position of imide group, and carbonized them into CMSMs at 550 °C (PI-Br-550 and PI-OH-550). There are debromination (510 °C) and carbonization occurred for PI-Br-550 whereas the PI-OH underwent thermally rearrangement (TR, 450 °C) and then pyrolysis to CMSM. After carbonization, both CMSMs showed excellent gas separation properties, with their CO2/CH4 separation performance surpassed the latest 2019 pure-gas and 2018 mixed-gas trade-off curves, additionally, the PI-Br-550 demonstrated a relatively smaller CO2 permeability (12462 vs 14,253 Barrer), lower PCO2 increment ratio (199 vs 1480), and less CO2/CH4 dropping ratio (69.7 to 45.5 vs 87.5 to 36.1) than the PI-OH-550 from their precursors. Their XPS, Raman, and WXRD characterization results indicated that debromination boosts the gas separation performance of CMSM by creating more ultra-micropore “plate” (pyrrolic-N of 36.0 % vs 19.0 %) and smaller d-spacing (3.89 vs 4.15 Å) than the TR precursor, which boosts the permeability of CMSM is due to the high stability of PBO intermediates that retarded the decomposition of the polymer main chian and caused some big pores. The above results provided a good route to get highly efficient CMSM by molecular designing of their precursors.

Preparation of highly active and durable electrodes for alkaline water electrolysis by anodizing of commercial FeNi and FeNiCo alloys

Anodizing is gaining popularity as a binder-free fabrication route for obtaining catalyst materials directly on the current collector without using noble metals, binders, or conductive carbon additives. Here, we fabricate promising highly active electrodes for alkaline water electrolysis by anodizing commercial FeNi and FeNiCo alloys (%wt. Fe range between 22 and 63) in an ethylene glycol-based fluoride electrolyte. Anodizing forms metal fluoride coatings, which are converted to OER active compounds (γ-NiOOH:Fe) during potential cycling in an alkaline aqueous solution (1 mol L−1 (M) KOH at 293 K) as a result of leaching of fluoride ions. The morphology, thickness, and number of active sites are influenced by the amount of Fe in the alloy, and the electrode with the highest electrochemical active surface area (Kovar alloy with a 54 %wt. Fe) shows the largest OER activity enhancement by anodizing. The performance evaluation in practical conditions (7 mol L−1 KOH at 343 K) demonstrated a highly active performance with an OER potential as low as 1.52 V at a current density of 600 mA cm−2 even for electrodes obtained in alloys with a low amount of Fe (78-Permalloy with a 22 %wt. Fe), demonstrating that anodizing is an effective way to develop highly active OER electrodes from commercially available alloys. On the other hand, anodizing is a good fluoridation route for transition metals with good results in the formation of F-enriched precursors that efficiently promote active phase formation during the catalytic process, offering the possibility of obtaining catalysts directly on the current collector in a one-step process, easily implemented in industrial applications.

Reactive Traffic Congestion Control by Using a Hierarchical Graph

Traffic management is one of the major factors in growth strategy formulation in urban centers across the globe. The increasing population and, therefore, the increase in the number of vehicles on roads in urban centers cause congested traffic patterns. These patterns typically emerge on intersections in busy city roads at various times during the day, especially during peak hours. A direct consequence of congestion is the increase in commute time and pollution. This paper presents a hierarchical graph-based congestion control (HGCC) method. Congestion values are set and evaluated as a two-level hierarchical graph. The least congestion path algorithm (LCP)is integrated with the HGCC to compute the optimal route between source and destination. The experimental results for a Manhattan-like grid network, together with the paired-sample t-test, show that the proposed method is efficient in achieving good congestion-avoiding routes.

Solving the Palliative Home Health Care Routing and Scheduling Problem with an integer linear programming model

Efficient routing and scheduling are critical for providing patients with quality health care in their homes, and palliative care involves specific requirements. This paper addresses the Palliative Home Health Care Routing and Scheduling Problem (PHHCRSP) through an integrated mathematical model. Key considerations include caregiver skills, care continuity, and a multi-period planning horizon. Special attention is also given to the case of clustered patients. Five formulations with different objective functions are analyzed and solutions reveal that optimizing only for minimum or maximum workload leads to non-efficient routing. The formulation that balances the total workload and the minimum workload emerges as the most effective, as it manages to obtain good routes while distributing the workload evenly among the caregivers. The results of the computational study on a set of well-known benchmark instances show that it is possible to obtain good patient care while keeping good working conditions for the caregivers.

Incorporating photocatalytic fuel cell with dual S-scheme CuBi2O4/Bi2WO6/ZnO NRA photoanode for energy recuperation from municipal wastewater treatment under sunlight

Photocatalytic fuel cell (PFC) utilized the chemical energy contained in the molecules by combining photocatalytic treatment of wastewater with fuel cell electrochemical reaction. Herein, a PFC system with a novel dual S-scheme heterojunction CuBi2O4/Bi2WO6/ZnO nanorod array (CBO/BWO/ZnO NRA) composite photoanode was first constructed for municipal wastewater treatment accompanied with electricity generation under direct sunlight. The introduction of CBO and BWO not only contributed to the narrowing of the band gap which enabled the ZnO NRA to utilize sunlight more efficiently, but also led to the excellent electron-hole segregating capability. The 10% CBO/BWO/ZnO NRA composite photoanode achieved a significantly ameliorated electrical power with maximum power density of 7.707 µW/cm2, which was superior to those pristine ZnO NRA and BWO/ZnO NRA binary materials. The composite photoanode was then tested for its mineralization activity in the municipal wastewater and 98.4% of COD removal was acquired within 90 min. The main attribution that conducive to its spectacular performance in municipal wastewater treatment came from the one-dimensional nanorod array architecture along with the synergistic relation among the three efficient components in the CBO/BWO/ZnO NRA heterojunction that can effectively hinder the charge carrier recombination rate and facilitated a good route for electron transport. The composite photoanode also manifested good stability in five cyclic runs. The dual S-scheme CBO/BWO/ZnO NRA enabled the free active species partook in the photoelectrocatalytic reaction and the working principle of PFC system was also speculated. Additionally, phytotoxicity findings signified that the comprehensive toxicity of municipal wastewater was eliminated after PFC treatment.

Fast, Scalable and Robust Centralized Routing for Data Center Networks

This paper presents a fast and robust centralized data center network (DCN) routing solution, called . For fast routing calculation, uses centralized controllers to collect/disseminate the network’s link-states (LS), and offload the actual routing calculation onto each switch. Observing that the routing changes can be classified into a few fixed patterns in DCNs which have regular topologies, we simplify each switch’s routing calculation into a table-lookup manner, i.e., comparing LS changes with pre-installed base topology and updating routing paths according to predefined rules. As such, the routing calculation time at each switch only needs 10s of us even in a large network topology containing 10K+ switches. For efficient controller fault-tolerance, purposely uses reporter switch to ensure the LS updates successfully delivered to all affected switches. As such, can use multiple stateless controllers and little redundant traffic to tolerate failures, which incurs little overhead under normal case, and keeps 10s of ms fast routing reaction time even under complex data-/control-plane failures. We design, implement and evaluate with extensive experiments on Linux-machine controllers and white-box switches. provides <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim$</tex-math> </inline-formula> 1200x and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim$</tex-math> </inline-formula> 100x shorter convergence time than current distributed protocol BGP and the state-of-the-art centralized routing solution, respectively. Furthermore, Primus maintains good routing controllability/manageability thanks to its centralized architecture, which enables us to build several advanced routing features in our testbed, including routing failure visualization and weighted-cost-multi-path routing.

HPRoP: Hierarchical Privacy-preserving Route Planning for Smart Cities

Route Planning Systems (RPS) are a core component of autonomous personal transport systems essential for safe and efficient navigation of dynamic urban environments with the support of edge-based smart city infrastructure, but they also raise concerns about user route privacy in the context of both privately owned and commercial vehicles. Numerous high-profile data breaches in recent years have fortunately motivated research on privacy-preserving RPS, but most of them are rendered impractical by greatly increased communication and processing overhead. We address this by proposing an approach called Hierarchical Privacy-Preserving Route Planning (HPRoP), which divides and distributes the route-planning task across multiple levels and protects locations along the entire route. This is done by combining Inertial Flow partitioning, Private Information Retrieval (PIR), and Edge Computing techniques with our novel route-planning heuristic algorithm. Normalized metrics were also formulated to quantify the privacy of the source/destination points ( endpoint location privacy ) and the route itself ( route privacy ). Evaluation on a simulated road network showed that HPRoP reliably produces routes differing only by ≤ 20% in length from optimal shortest paths, with completion times within ∼ 25 seconds, which is reasonable for a PIR-based approach. On top of this, more than half of the produced routes achieved near-optimal endpoint location privacy (∼ 1.0) and good route privacy (≥ 0.8).

Development of a recreational tour to Momsky Nature park «Aan-Aiylgy» for students

The Arctic region of the Russian Federation is currently attracting much attention. Arctic tourism is becoming increasingly popular. This article considers the concept, features and tourist potential of Momsky district of the Republic of Sakha (Yakutia). One of the modern approaches to the development of the Arctic regions of Yakutia is the effective use of tourist potential, which the Momsky district has. This is a territory with special natural-climatic and tourist-recreational resources. Russia has recently witnessed the growth of domestic tourism due to geopolitical changes, the growth of foreign currencies against the Russian rouble and other factors. This brings high prospects for the development of tourism in the previously unexplored Arctic regions of our country. Theoretical and methodical aspects of the organization of physical recreation for students by means of a tourist camping trip to the Nature Park in the Momsky district «Aan-Aiylgy» are investigated. In the future it is planned to organize camping tours not only for our students, but also for everyone. Exclusive tourist routes will be offered, which, despite their high prices, will be attractive in the current conditions of the global tourist market development. Tourists largely depend on the organizer of the trip. Perhaps it would be better if it was a well-organized travel agency, but unfortunately there is no such agency in the Momsky district. We believe that this is a good opportunity for local entrepreneurs to make money. Tour operators are better at organizing such trips and at arranging meetings with reindeer herders in advance, as well as good route planning. However, if you prefer a private entrepreneur from the representatives of the small indigenous people – Even – as an organizer, the programme will be more interesting: You will visit the camps of their friends or relatives and immerse yourself in the local colourful life. It is also worth mentioning the roads, or rather, their absence, which makes the tourist traffic noticeably less than desired.

How Different Analytical and Stylistics Investigations Can Help in Describing Artefacts Made of Non-coeval Parts: The Imago Pietatis in Breno

ABSTRACT Valcamonica is an Italian Alpine valley that has been the transit route for people and goods in prehistoric, Roman, medieval, and modern times. This led to the presence of artefacts from different eras and/or the occurrence of artefacts made of non-coeval parts. This research reports the characterization of an artefact in the Museum of Breno (Brescia Province). It is surmised that the artwork is made of different and non-coeval parts. The aim of the research is to investigate the natural pigments dyeing the different parts of the artefact, to infer information also on the origin and the dating. The investigation is supported by different analytical techniques (microscopic, spectroscopic, chromatographic, and spectrometric evaluation). The artifact is an Imago Pietatis, with Christ emerging from the tomb with his open arms. Microscopic observation allowed a preliminary evaluation of the colouration and to hypothesize the pigments used. 1H NMR analysis and spectrophotometric analysis suggested the presence of Tyrian purple and logwood (Haematoxylum campechianum) in the background of the sacred image, that was probably a liturgical vestment dismembered and overdyed. It is very likely that the image was in use to a brotherhood of Disciplini, a secular congregation very active in Valcamonica whose activities consisted in praying for the dead and making processions. Our work was important for the narration of this artefact and could be useful for the reconstruction of the object in the original colours, for providing to the local stakeholders a suitable recognition for this historical discovery.

Watt-level and near diffraction-limited Pr3+-doped single-crystal fiber lasers.

Using a CZ-grown a-cut Pr:YLF crystal as laser gain medium after processing it into crystal fiber, we have demonstrated real Pr3+-doped single-crystal fiber lasers for the first time to the best of our knowledge. This Pr3+ crystal fiber has absorbed up to 20.4 W of pump power, which is the highest absorbed power among Pr3+ lasers. For two representative laser emissions at about 639 nm and 607 nm, we have achieved maximum output powers of 5.45 W and 3.04 W, respectively. Output powers of the two lasers show very good linearities, which indicate that the present output powers are only limited by the available pump power. Both laser emissions have exhibited near diffraction-limited beam qualities. This proposal has provided a good and feasible route for the development of compact, high-power, and high-brightness all-solid-state Pr3+ visible lasers via crystal fiber.

Hybrid Dynamic Source Routing Technique and Security Implementation in Adhoc Network Topology

Routing protocols that are developed with the error-prone environment and resource constraints of mobile nodes in mind perform better in wireless Ad Hoc environments. A good and dependable routing method is required to meet the packet transition aim. When the network is small, most existing routing algorithms operate fine, but when the network is large, there is a problem with link breakage in multipath routing algorithms, especially on demand routing algorithms. As a result, we investigated many forms of routing protocols in order to identify all of the existing algorithms' flaws. In this study, we examine existing protocols in terms of network factors such as delay, throughput, energy consumption, control overhead, and so on.

A Design and Challenges in Energy Optimizing CR-Wireless Sensor Networks

Background: The progress of the Cognitive Radio-Wireless Sensor Network is being influenced by advancements in wireless sensor networks (WSNs), which significantly have unique features of cognitive radio technology (CR-WSN). Enhancing the network lifespan of any network requires better utilization of the available spectrum as well as the selection of a good routing mechanism for transmitting informational data to the base station from the sensor node without data conflict. Aims: Cognitive radio methods play a significant part in achieving this, and when paired with WSNs, the above-mentioned objectives can be met to a large extent. Methods:: A unique energy-saving Distance- Based Multi-hop Clustering and Routing (DBMCR) methodology in association with spectrum allocation is proposed as a heterogeneous CR-WSN model. The supplied heterogeneous CR-wireless sensor networks are separated into areas and assigned a different spectrum depending on the distance. Information is sent over a multi-hop connection after dynamic clustering using distance computation. Results: The findings show that the suggested method achieves higher stability and ensures the energy-optimizing CR-WSN. The enhanced scalability can be seen in the First Node Death (FND). Additionally, the improved throughput helps to preserve the residual energy of the network which helps to address the issue of load balancing across nodes. Conclusions: Thus, the result acquired from the above findings shows that the proposed heterogeneous model achieves the enhanced network lifetime and ensures the energy optimizing CR-WSN.

Assessment of the Attractiveness and Passage Efficiency of Different Fish Passage Solutions at a Hydropower Plant by Combining Fine Scale 2D-Telemetry and Hydraulic Numerical Modelling

Mitigation measures for downstream-migrating Atlantic salmon smolts (Salmo salar L.) are commonly insufficiently attractive to enable safe entrance and passage with no delay. Combining 2D telemetry with hydrodynamic modelling has been shown to be a good tool to better understand the influence of hydrodynamic factors on the migration route choice of fishes. In this study, we investigated the smolt downstream migration at a hydropower plant in Belgium that offers five migration routes, including two Archimedes screws and one nature-like fishway. At the hydropower plant, the Archimedes screws were the most used migration routes, due to higher discharges and more important water depths at their entrance. The weir and the canal intake were less used by the smolts. The nature-like fishway turned out to be less used, with 23% of the smolts. Its associated crossing time was significantly longer, probably due to shallow water depths and high flow velocities. The nature-like fishway had the potential to become a good migration route for salmon smolts after improvements to increase attractiveness and passage efficiency. Moreover, the Archimedes screws were not detrimental to the smolts and did not cause any significant delays to the crossing time.

Conductance is responsible for the power conversion efficiency of solar cell

Many attempts were made in solar energy to find advanced solar energy technology for solar cell which is with high power conversion efficiency; calculation output current by output voltage using a model of solar cells is very useful for this major aim. Although there are many models can be used to estimate current via voltage from solar cells, no one parameter in the models is a correlation to power conversion efficiency. One simplification of single diode model is proposed in this paper. Not only this model is in form of explicit function, but also one parameter as parallel conductance is correlation to power conversion efficiency. The accuracy of the proposed model is evaluated using thirty experimental data. It was found that in all experimental cases, very good match between measured and calculated is reached. The first important result indicates that power conversion efficiency independent on solar cell connection in series due to parallel conductance independent on solar cell connection in series. The major contribution is that the mathematical relationship between power conversion efficiency and parallel conductance is found in this paper. It is envisaged that the proposed methodology can be a very good route for researchers to discover advanced solar cell.

An Overview of Retrosynthesis Analysisa Synthetic Approach

Retrosynthesis analysis is a key skill in synthetic chemistry. Learning retrosynthesis can help scholars to have a deeper understanding in the reactivity and structure of chemical molecules. However, most high school students lack the understanding in this field. As to solve this problem, this work aims to give an introductory overview of retrosynthesis. In this paper, several key principles and typical strategies of retrosynthesis are introduced. The Principles part includes the basic terms of retrosynthesis, types of disconnections (one-group disconnection, two-group disconnection, pericyclic disconnection, illogical disconnection and fine tuning) and characteristics of a good disconnection. The Strategies part includes (1, y) Dioxygenation pattern, the common atom approach how to exploit symmetry. Two examples are also illustrated as applications of retrosynthesis analysis. This work will help students to be able to use basic retrosynthesis analysis skills to disconnect certain molecules. Specifically, to recognize good disconnections and design reasonable synthetic routes for the target molecules.